To Estimate the Correlation between Serum Sialic Acid Levels with Microalbuminuria and Glycated Hemoglobin in Diabetic Nephropathy Patients

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DISSERTATION ON

TO ESTIMATE THE CORRELATION BETWEEN

SERUM SIALIC ACID LEVELS WITH

MICROALBUMINURIA AND GLYCATED HEMOGLOBIN

IN DIABETIC NEPHROPATHY PATIENTS

Dissertation submitted to

TAMILNADU Dr.M.G.R MEDICAL UNIVERSITY

In partial fulfillment of the requirement

for the award of degree of

MD BRANCH -XIII

IN

BIO-CHEMISTRY

KARPAGA VINAYAGA INSTITUTE OF MEDICAL SCIENCES

AND RESEARCH CENTRE

MADHURANTHAGAM.

THE TAMIL NADU DR. M.G.R. MEDICAL UNIVERSITY, CHENNAI,

TAMILNADU.

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CERTIFICATE

This is to certify that Dr.K.PIRUTHIVIRAJAN, a Post Graduate student

in the Department of Bio-Chemistry has carried out the work titled “TO

ESTIMATE THE CORRELATION BETWEEN SERUM SIALIC ACID

LEVELS WITH MICROALBUMINURIA AND GLYCATED

HEMOGLOBIN IN DIABETIC NEPHROPATHY PATIENTS” under the

guidance of Dr.ARUNA KUMARI, Professor and Head, Dept. of

Bio-Chemistry, towards the partial fulfilment of regulations laid down by the

Tamilnadu Dr.M.G.R Medical University, Chennai, Tamilnadu, India, for the

award of Doctor of Medicine (M.D.,) in Bio-Chemistry.

Dr .A.R. Chakravarthy.MD, DGO,

Dean,

Karpaga Vinayaga Institute of Medical Sciences and Research Centre

Madurantagam Tk,

Kancheepuram Dist-603308 Tamilnadu, India.

Prof. Dr.ARUNA KUMARI.,M.D., PROFESSOR AND HEAD

DEPARTMENT OF BIO-CHEMISTRY Karpaga Vinayaga Institute of Medical Sciencesand Research Centre

Madurantagam Tk,

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DECLARATION

I declare that the dissertation entitled “TO ESTIMATE THE

CORRELATION BETWEEN SERUM SIALIC ACID LEVELS WITH

MICROALBUMINURIA AND GLYCATED HEMOGLOBIN IN

DIABETIC NEPHROPATHY PATIENTS” submitted by me for the Degree

of M.D is the record work carried out by me during the period of January 2014

to March 2015 under the guidance of Dr.ARUNA KUMARI.M.D.,

PROFESSOR and H.O.D of Bio-Chemistry, Karpaga Vinayaga Institute of

Medical Sciences and Research Centre and has not formed the basis of any

Degree ,Diploma, Fellowship, titles in this or any other University or other

similar Institutions of Higher learning.

Signature of the candidate

Place: Dr.K.PIRUTHIVIRAJAN

Date:

Signature of the guide

Dr.ARUNA KUMARI.MD.,

H.O.D & Professor

Karpaga Vinayaga Institute of medical Sciences and Research Centre,

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ACKNOWLEDGEMENT

My heartfelt gratitude and sincere thanks to

Dr. R. Annamalai.MS.MCh.,(Ortho) Managing Director, Karpaga Vinayaga

Institute of Medical Sciences for his valuable support and guidance in helping

me with all available resources..

I wish to thank Dr.A.R.Chakravarthy.MD.DGO., Dean Karpaga

Vinayaga Institute of Medical Sciences and Research Centre for providing me all

the facilities to conduct this study.

I express my sincere thanks to my esteemed guide Dr.ARUNA

KUMARI,M.D., Professor and Head in the Department of Bio-Chemistry,

Karpaga Vinayaga Institute of Medical Sciences and Research Centre for her

encouragement and valuable guidance in the topic given from time to time for

the successful completion of this study.

I am also thankful to Dr.D.PREM KUMAR.MS., Medical

Superintendent, Dr.S.SWETHA,M.D., and Dr.KATHEEJA,M.D., Assistant

Professors in the Department of Bio-Chemistry, Karpaga Vinayaga Institute of

Medical Sciences and Research Centre for their kind guidance and

encouragement during the course of this study.

I am extremely thankful to Mr.Saravanan.,M.Sc., Department of

Bio-Chemistry, Karpaga Vinagaya Institute of Medical Sciences and Research

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I convey my valuable thanks to all the Post Graduate colleagues of

Department of Bio-Chemistry for their greatest support and co-operation in

completing my dissertation.

I also thank my technical staffs and nontechnical staffs of department of

Bio-Chemistry and the Central Lab for their excellent help in laboratory work.

Finally, I am deeply indebted to my parents, my wife Dr.P.KALAI

SELVI , my daughter NIVEDHITHA PIRUTHIVIRAJAN and my son

K.P.ESHWAANTH KEERTHI for their support, encouragement and sacrifice

during the study period.

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TABLE OF CONTENTS

S.

NO.

TITLE

PAGE

NO.

1. INTRODUCTION 01

2. AIMS AND OBJECTIVES 04

3. REVIEW OF LITERATURE 05

4. MATERIALS AND METHODS 46

5. RESULTS 52

6. DISCUSSION 67

7. SUMMARY 72

8. CONCLUSION 75

9. ANNEXURES

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INTRODUCTION

“Diabetes mellitus” is the major healthcare problem occurring all over the

world. “Diabetes mellitus”, the most common endocrine disease is represented

by “metabolic abnormalities” due to relative or absolute deficiency of insulin and

or insulin resistance resulting in “hyperglycemia” and associated with “micro

and macrovascular complications”.1

Diabetes is not an epidemic anymore but has turned into pandemic for the

whole world.2 The universal survey reported that diabetes is disturbing nearly

10% of the inhabitants.3 According to the “World Health Organization (WHO)”

projections, the predominance of diabetes is likely to augment by 35% by the

year 2025.4 India has a elevated predominance of diabetes and the numbers are

increasing.5

Diabetes mellitus” presents with characteristic symptoms such as

“polydipsia, polyuria, polyphagia, weight loss and the long-term effects include

progressive development of microvascular complications, particularly in the eye

and kidney, and an increased frequency of macrovascular disease such as

peripheral vascular and coronary heart disease”.6 “Diabetes mellitus” is the most

important reason of “End Stage Renal Disease (ESRD)”. It is responsible for

30-40 % of all ESRD. Even though “Type 1 and Type 2 DM” lead to ESRD, most

of the patients are those with “Type 2 DM”7

Diabetic renal disease” is categorized by an augment in the “flow of

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pressure” and decrease in the rate of filtration in the “glomerulus” most

important ultimately to “End Stage Renal Disease”.7 “Reactive oxygen species

(ROS)” increase is caused by “Hyperglycemia”. “Poly ADP-ribose polymerase

(PARP)” is activated by stand breaks in DNA. Decreased

“glyceraldhyde-3-phosphate dehydrogenase (GAPDH)”, activity causes augmented “polyol

pathway flux, intracellular advanced glycation end product formation, activation

of protein kinase C and hexosamine pathway flux”.8,9 These pathways in

combination, finally results in high renal albumin permeability and extracellular

matrix growth, resulting in “proteinuria, glomerulosclerosis and tubular

interstitial fibrosis”.10

“Serum sialic acid” is a recently recognized possible risk factor for the

rise of “macro and microvascular complications of diabetes”.11 “Serum sialic

acid” is a part of “glycoprotein” such as acute phase proteins which are increased

in diabetes. The possible mechanism linked with the function of sialic acid is to

maintain the “negative charge of renal glomerular basement membrane”. Due to

increased “vascular permeability” there is shedding of “vascular endothelial

sialic acid into circulation”.12

“Microalbuminuria” is the earliest manifestation of “diabetic

nephropathy” and it is the predictor of incipient nephropathy in diabetic patients.

“Glycated haemoglobin” is a standard measure of severity of diabetes mellitus

and gives an idea about long term “glycemic control”. “Microalbuminuria” arise

from the amplified passage of albumin throughout the “glomerular filtration”

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due to “renal disease” is more frequent in diabetics than in non diabetics.7 If

obvious nephropathy is present, progression cannot be stopped, only delayed.

Susceptible tests for “microalbuminuria” are needed to avoid the initial

stages of injury by forceful control of “hyperglycemia and hypertension”.

Several studies have demonstrated increased “serum sialic acid levels in diabetic

nephropathy patients” when compared to controls.11

Thus, the present study was intended to explore the role of “serum sialic

acid” as a dangerous factor in the progress of “diabetic nephropathy” and to

associate the clinical relationship of “serum sialic acid with glycated

haemoglobin and the indicator of diabetic nephropathy such as

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AIM OF THE STUDY

-

To estimate the serum sialic acid levels in diabetic nephropathy

patients.

-

To know the correlation between serum sialic acid and

microalbuminuria in diabetic nephropathy patients.

-

To know the correlation between serum sialic acid and glycated

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REVIEW OF LITERATURE

HISTORICAL REVIEW OF DIABETES MELLITUS:

The clinical characteristics of diabetes were depicted 3000 years prior by

the customary Egyptians. The expression "diabetes" was first authored by

Araetus of Cappodocia (81-133 AD). “United Nations organization” presented a

“clinical portrayal of the infection”, detecting the “increased urine flow, thirst,

appetite and weight reduction”, highlights which are immediately identifiable

now a days.The sweet taste of urine in “polyuric diabetics”, which congregated

ants was observed during the 5th and 6th century AD by “ancient Indians (Susruta

and Charuka)” and these descriptions even mention 2 varieties of diabetes, one in

older (adult onset), obese individuals and another in thin and younger subjects

and this division predated the modem classification into “type 2 and type 1

diabetes”. Later, Thomas Willis rediscovered the sweetness of diabetic urine in

1675.14

In 1776, Matthew Dobson in the UK made the vital scrutiny, confirmed

that the sweetness in both urine and serum was due to sugar, and suggested that

diabetes is a common disease. “Cotunnius, who described the parting of a clot in

heated diabetic urine, first discovered the presence of proteinuria in a diabetic

patient in 1764”.15

In 1797, an effort at treatment began on the “origin of glycosuria and

polyuria”, John Rollo executed a detailed metabolic study of a “plump diabetic”,

and he showed that the degree of “glycosuria” depended upon the type of food

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presumably those in an advanced stage of type 1 diabetes and he also observed

cataracts in diabetics”.15

In 1857, “an important milestone in the history of diabetes was the

establishment of the role of the liver in glycogenesis and the concept that

diabetes was due to excess glucose production,” which was discovered by

Claude Bernard, and he also demonstrated links between the central nervous

system dysfunction and the diabetic state.16

In 1869, Paul Langerhans was the first to describe, pancreatic clusters of

cells in teased preparations of pancreas which are now known as the "Islets of

Langerhans" and “the role of the pancreas in the pathogenesis of diabetes” was

confirmed by Mering and Minkowski in1889. Consequently, this discovery

constituted the basis of insulin isolation and its clinical use by Banting and Best

in 1921.

The difficulties of diabetes influencing the eyes, to be specific “Diabetic

retinopathy”, had been depicted before the revelation of insulin but it was a rarity

because few diabetics lived long enough to develop “retinopathy and

glomerulosclerosis”, which gradually progressed to “renal failure and death and

this condition” was named the "Kimmelstiel-Wilson" nodules after its American

and British co-discoverers in 1936. Moreover, with longer survival of diabetic

subjects, consequences influencing the peripheral and later the autonomic,

“sensory system and gestational diabetes were portrayed”. On the other hand, at

present, “diabetes mellitus” contains a “heterogeneous” gathering of complex

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“varied consequences and hyperglycaemia” which is the cardinal element of

these conditions and has accordingly been utilized to characterize diabetes .16

“Diabetes mellitus (DM)” is a collection of “metabolic syndrome with

hyperglycemia”. “It is associated with abnormalities in carbohydrate, fat, and

protein metabolism and results in chronic complications including

micro-vascular, macro-micro-vascular, and neuropathic disorders”.

The economic burden of DM, including direct restorative and treatment

costs and additionally backhanded expenses ascribed to inability and mortality

have expanded considerably. “DM is the leading cause of blindness in adults

aged 20 to 74 years, and the leading contributor to development of end stage

renal disease”. It likewise represents roughly 82,000 lower limb removals

annually.17 “The cardiovascular event is responsible for two-thirds of deaths in

individuals with type 2 DM. Although efforts to control hyperglycemia and

associated symptoms are important, the major challenges in optimally managing

the patient with DM are targeted at reducing or preventing complications, and

improving life expectancy and quality of life.”

Research and drug advancement endeavours in the course of recent

decades have given significant data that applies specifically to enhance the

results in patients with DM and have expanded the “therapeutic

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Characterization of Diabetes:

Diabetes is a metabolic disorder characterized by resistance to the action

of insulin, insufficient insulin secretion, or both.18 The clinical indication of these

issue is “hyperglycemia”. The dominant part of diabetic patients are

characterized into one of two general classifications: “type 1 diabetes caused by

an absolute deficiency of insulin, or type 2 diabetes defined by the presence of

insulin resistance with an inadequate compensatory increase in insulin

secretion”. Females who generate diabetes due to the “stress of pregnancy” are

classified as having “gestational diabetes”. Finally, uncommon types of diabetes

“caused by infections, drugs, endocrinopathies, pancreatic destruction, and

known genetic defects”.

Type 1 Diabetes:

Occurs due to autoimmune destruction of the β-cells of the pancreas.

Markers of “immune destruction of the B-cell” are available at the time of

diagnosis in 90% of people and “incorporate islet cell antibodies, antibodies to

glutamic acid decarboxylase and antibodies to insulin”. In spite of the fact that

this type of diabetes normally happens in children and adolescents, it can happen

at any age. More young people ordinarily have a “rapid rate of β-cell destruction

and present with ketoacidosis”, whereas “adults often maintain sufficient insulin

secretion to prevent ketoacidosis for many years, which is often referred to as

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Type 2 Diabetes:

It is described by insulin resistance and a relative absence of insulin

secretion, with progressive lower insulin secretion after some time. Most people

with “type 2 diabetes” show abdominal obesity, which itself cause insulin

resistance. Furthermore, “hypertension, dyslipidemia and increased Plasminogen

Activator Inhibitor Type 1 (PAI-1) levels” are regularly present in these people.

This “clustering of abnormalities” is referred to as the “insulin resistance

syndrome or the metabolic syndrome”. Because of these abnormalities, “patients

with type 2 diabetes” are at increased risk of “developing macrovascular

complications”. “Type 2 diabetes” has a strong “genetic predisposition” and is

more common in all ethnic groups other than those of “European ancestry”. At

this point the genetic cause of most cases of “type 2 diabetes” is not well

defined.20

Gestational diabetes mellitus: (GDM)

“GDM is characterized as glucose intolerance first recognized during

pregnancy. Gestational diabetes complicates approximately 7% of all

pregnancies.”

Other particular types of diabetes (Genetic imperfections):

“Maturity-onset diabetes” of youth is described by impaired insulin

secretion with minimal or no insulin resistance. Patients typically exhibit “mild

hyperglycemia” at an early age. The ailment is acquired in an “autosomal

dominant pattern” with no less than six distinctive loci recognized to date.

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hyperglycemia” and is acquired in an autosomal dominant pattern. Also, the

generation of mutant insulin molecules has been distinguished in a couple of

families and results in gentle “glucose intolerance”. A few hereditary changes

have been portrayed in the “insulin receptor” and are connected with “insulin

resistance”.

“Type A insulin resistance” alludes to the “clinical disorder of acanthosis

nigricans, virilization in ladies, polycystic ovaries, and hyperinsulinemia”.

Conversely, “type B insulin resistance” is brought on via auto antibodies to the

insulin receptor.

“Leprechaunism is a pediatric syndrome” with specific facial features and

severe insulin resistance because of a defect in the insulin receptor gene. 21

Prevalence:

The worldwide commonness of diabetes in 2008 was assessed to be 10%

in grown-ups matured >25 years. The predominance of diabetes was most

noteworthy in “Eastern Mediterranean Region and the Region of Americas (11%

for both genders)”. The lower economic nations over the world demonstrated

predominance of 8%.

In India, the results of prevalence showed that 37.7 million people of

diabetes were present among which 21.4 were in urban area and 16.3 in rural

area. The total mortality due to diabetes was 1.09 lakh and around 2.2 million

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Epidemiology:

Typical “type 1 DM is an autoimmune disorder” developing in childhood

or early adulthood, although some latent forms do occur. “Type 1 DM” accounts

for 5% to 10% of all cases of DM and is likely initiated by the exposure of a

genetically susceptible individual to an environmental agent.23 “Candidate genes

and environmental factors” are reportedly prevalent in the general population,

but “development of B-cell autoimmunity” occurs in less than 10% of the

“genetically susceptible population” and progresses to “type 1 DM” in less than

1% of the population.24

The pervasiveness of “type 2 DM” is expanding. There is likely one

individual undiscovered for each three persons as of now determined to have the

sickness. “Multiple risk factors” for the advancement of “type 2 DM” have been

recognized, including family history (i.e., folks or kin with diabetes); over

weight (i.e., ≥20% over perfect body weight, or body mass list [BMI] ≥25

kg/m2); “habitual physical inactivity; race or ethnicity; previously identified

impaired glucose tolerance or impaired fasting glucose, hypertension (≥140/90

mm Hg in adults); high-density lipoprotein (HDL) cholesterol ≤35 mg/dL and/or

a triglyceride level ≥250 mg/dL; history of gestational DM or delivery of a baby

weighing >4 kg (9 lb); history of vascular disease; presence of acanthosis

nigricans and polycystic ovary disease”.25

Most instances of “type 2 DM” do not have an understood reason.

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in the United States.27 Most females will come back to “normoglycemia”, yet

30% of them tend to have “type 2 DM” later in their life.

Pathogenesis of Type 1 Diabetes Mellitus:

Type 1 DM is portrayed by a lack of pancreatic β-cell function. What is

clear are four primary components: “(1) a long preclinical period marked by the

presence of immune markers when β-cell destruction is thought to occur; (2)

hyperglycemia when 80% to 90% of β-cells are destroyed; (3) transient

remission (the so-called honeymoon phase); and (4) established disease with

associated risks for complications and death. Unknown is whether there is one or

more inciting factors (e.g., cow’s milk, or viral, dietary, or other environmental

exposure) that initiate the autoimmune process”.20

The immune system procedure is interceded by “macrophages” and “T

lymphocytes” with “auto antibodies to different β-cell antigens” that circulate in

the body. The most normally recognized immune response connected with “type

1 DM” is the islet cell counter acting agent. The test for islet “cell immune

response”, is hard to institutionalize crosswise over research facilities. Other all

the more promptly measured circulating antibodies incorporate insulin auto

antibodies, antibodies coordinated against “glutamic acid decarboxylase”, insulin

antibodies against islet “tyrosine phosphatise”, and a few others. More than 90%

of recently determined persons to have “type 1 DM” have some of these

antibodies, as will 3.5% to 4% of unaffected first-degree relatives. “Preclinical

β-cell autoimmunity” goes before the determination of “type 1 DM” by up to 9 to

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persons”, or can advance to failure of the “B-cells” in others. These antibodies

are by and large considered as markers of sickness instead of “β-cell

destruction”. They have been utilized to recognize people at risk for “type 1

DM” in assessing illness avoidance strategies.

Other non pancreatic immune system issue are connected with “type 1

DM”, most often “Hashimoto's thyroiditis”, yet the degree of organ contribution

can extend from no different organs to “polyglandular failure”.28 Other applicant

quality areas have been recognized on a few different chromosomes also. Since

twin studies don't demonstrate 100% concordance, ecological agents like

infection, chemicals, and diet are more likely to contribute to the disease.

“Annihilation of pancreatic β-cell function causes hyperglycemia” in view of an

outright lack of “both insulin and amylin”.29 Insulin brings down blood glucose

by a mixture of components including: incitement of tissue glucose uptake,

concealment of glucose generation by the liver, and decrease of free unsaturated

fat discharge from fat cells.30

The decrease of free unsaturated fats assumes a critical part in glucose

homeostasis. Enhanced levels of free unsaturated fats restrain the uptake of

glucose by muscle and induces hepatic gluconeogenesis.31 Amylin, a

glucoregulatory peptide hormone co-discharged with insulin, assumes a part in

slowing so as to “bring down blood glucose gastric emptying, supressing

glucagon yield cells, and expanding satiety from pancreatic β-cell.”32 In type 1

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Pathogenesis of Type 2 Diabetes Mellitus:

Normal Insulin Action:

During Fasting, 75% of aggregate “body glucose transfer happens in non–

insulin dependent tissues: the cerebrum and splanchnic tissues (liver and

gastrointestinal tissues)”.33 Actually, brain glucose uptake happens at the same

rate amid bolstered and fasting periods and is not modified in type 2 diabetes.

The rest of the 25% of glucose uptake happens in muscle, which is reliant on

insulin.34 In the fasting state more or less 85% of glucose is received from the

liver, and the remaining sum is delivered by the kidney.33-35

Glucagon, delivered by pancreatic β-cells, is discharged in the fasting

state to restrict the activity of insulin and invigorate hepatic glucose creation. In

this way, glucagons forestall hypoglycemia or restores normoglycemia if

hypoglycemia has occurred.36

In the fed state, starch ingestion builds the plasma glucose focus and

invigorates insulin discharge from the pancreatic β-cells. The resultant

hyperinsulinemia decreases hepatic glucose and increases glucose uptake by the

tissues in the periphery.37 “The majority (~80%–85%) of glucose that is taken up

by peripheral tissues is disposed in muscle, with only a small amount (~4%–5%)

being metabolized by adipocytes. In the fed state, glucagon is suppressed. 36”

“Although fat tissue is responsible for only a small amount of total body

glucose disposal, it plays a very important role in the maintenance of total body

glucose homeostasis. Small increments in the plasma insulin concentration exert

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fatty acid (FFA) level. The decline in plasma FFA concentration results in

increased glucose uptake in muscle38 and reduces hepatic glucose production.39

Thus a decrease in the plasma FFA concentration lowers plasma glucose by both

decreasing its production and enhancing the uptake in muscle.40,41”

“Type 2 diabetic individuals are characterized by (a) defects in insulin

secretion; and (b) insulin resistance involving muscle, liver, and the adipocyte.

Insulin resistance is present even in lean type 2 diabetic individuals.”

(a)Impaired insulin secretion:

“The pancreas in people with a cell is able to adjust its secretion of insulin to

maintain normal functioning β- normal glucose tolerance. Thus, in non-diabetic

individuals, insulin is increased in proportion to the severity of the insulin

resistance, and glucose tolerance remains normal.”

“Impaired insulin secretion is a uniform finding in type 2 diabetic patients

and the evolution of β-cell dysfunction has been well characterized in diverse

ethnic populations. As the FPG concentration increases from 80 to 140 mg/dl,

the fasting plasma insulin concentration increases progressively, peaking at a

value that is 2- to 2.5- fold greater than in normal weight nondiabetic controls.

When the FPG cell is unable to maintain its elevated concentration exceeds 140

mg/dL, the β- rate of insulin secretion, and the fasting insulin concentration

declines precipitously. This decrease in fasting insulin leads to an increase in

hepatic glucose production overnight, which results in an elevated FPG

concentration.42 In the type 2 diabetic patient, decreased postprandial insulin

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stimulus for insulin secretion from gut hormones. The role gut hormones play in

insulin secretion is best shown by comparing the insulin response to an oral

glucose load versus an isoglycemic intravenous glucose infusion.”43

“In nondiabetic control individuals, 73% more insulin is released in response

to an oral glucose load compared to the same amount of glucose given

intravenously. This increased insulin secretion in response to an oral glucose

stimulus is referred to as the incretin effect and suggests that gut derived

hormones when stimulated by glucose lead to an increase in pancreatic insulin

secretion. In type 2 diabetic patients this incretin effect is blunted, with the

increase in insulin secretion to only 50% of that seen in nondiabetic control

individuals.43 It is now known that two hormones, glucagon-like peptide-1

(GLP-1) and glucose-dependent insulin-releasing peptide (GIP), are responsible for

more than 90% of the increased insulin secretion seen in response to an oral

glucose load. In patients with type 2 diabetes GLP- 1 levels are reduced whereas

GIP levels are increased.44 GLP-1 is secreted from the L-cells in the distal

intestinal mucosa in response to mixed meals. Because GLP-1 levels increase

within minutes of food ingestion, neural signals initiated by food entry in the

proximal gastrointestinal tract must simulate GLP-1 secretion.45 The

insulinotropic action of GLP-1 is glucose-dependent, and for GLP-1 to enhance

insulin secretion, glucose concentrations must be higher than 90 mg/dL.”44

“In addition to stimulating insulin secretion, GLP-1 suppresses glucagon

secretion, slows gastric emptying and reduces food intake by increasing satiety.

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secreted by K-cells in the intestine and like GLP, increase insulin secretion. 46

However, GIP has no effect on glucagon secretion, gastric motility, or satiety.” 47

(a)Site of insulin resistance in type 2 diabetes:

Liver:

“In type 2 diabetic subjects with mild to moderate fasting hyperglycemia

(140 to 200 mg/dl, 7.8 to 11.1 mmol/l) basal hepatic glucose production is

increased by ~0.5 mg/kg per minute. Consequently, during the overnight

sleeping hours the liver of an 80-kg diabetic individual with modest fasting

hyperglycemia adds an additional 35 g of glucose to the systemic circulation.

This increase in fasting hepatic glucose production is the cause of fasting

hyperglycemia.”33

“Following glucose ingestion, insulin is secreted into the portal vein and

carried to the liver, where it suppresses glucagon secretion and reduces hepatic

glucose output. Type 2 diabetic patients fail to suppress glucagon in response to

a meal and can even have a paradoxical rise in glucagon levels.48,49 Thus, hepatic

insulin resistance and hyperglucagonemia result in continued production of

glucose by the liver. Therefore, type 2 diabetic patients have two sources of

glucose in the postprandial state, one from the diet and one from continued

glucose production from the liver. These sources of glucose in combination with

a shortened gastric emptying time can result in marked hyperglycemia.”

Peripheral (Muscle):

“Muscle is the major site of glucose disposal in man, and approximately

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physiologic increase in plasma insulin concentration, muscle glucose uptake

increases linearly, reaching a plateau value of 10 mg/kg per minute. In contrast,

in lean type 2 diabetic subjects, the onset of insulin action is delayed for ~40

minutes, and the ability of insulin to stimulate leg glucose uptake is reduced by

50%. Therefore the primary site of insulin resistance in type 2 diabetic subjects

resides in muscle tissue.”33

Peripheral (Adipocyte):

In obese nondiabetic and diabetic humans, basal plasma FFA levels are

increased and fail to suppress normally after glucose ingestion. FFAs are stored

as triglycerides in adipocytes and serve as an important energy source during

conditions of fasting. Insulin is a potent inhibitor of lipolysis, and restrains the

release of FFAs from the adipocyte by inhibiting the hormone-sensitive lipase

enzyme. It is now recognized that chronically elevated plasma FFA

concentrations can lead to insulin resistance in muscle and liver, 33,38,40,50 and

impair insulin secretion.51,52 In addition to FFAs that circulate in plasma in

increased amounts, type 2 diabetic and obese nondiabetic individuals have

increased stores of triglycerides in muscle53,54 and liver 55,56 and the increased fat

content correlates closely with the presence of insulin resistance in these tissues.

In summary, insulin resistance involving both muscle and liver are characteristic

features of the glucose intolerance in type 2 diabetic individuals. In the basal

state, the liver represents a major site of insulin resistance, and this is reflected

by overproduction of glucose. This accelerated rate of hepatic glucose output is

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individuals. In the fed state, both decreased muscle glucose uptake and impaired

suppression of hepatic glucose production contribute to the insulin resistance. In

obese individuals and in the majority (>80%) of type 2 diabetic subjects, there is

an expanded fat cell mass, and the adipocytes are resistant to the antilipolytic

effects of insulin. Most obese and diabetic individuals are characterized by

expanded visceral adiposity, which is especially refractory to insulin effects and

results in a high lipolytic rate. Not surprisingly, both type 2 diabetes and obesity

are characterized by an elevation in the mean 24-hour plasma FFA concentration.

Elevated plasma FFA levels, as well as increased triglyceride/fatty acyl

coenzyme A (CoA) content in muscle, liver, and β- cells, lead to the

development of muscle/hepatic insulin resistance and impaired insulin secretion.

Cellular Mechanisms of Insulin Resistance:

“Weight gain leads to insulin resistance, and obese nondiabetic

individuals have the same degree of insulin resistance as lean type 2 diabetic

patients.57 In 1,146 nondiabetic, normotensive individuals, Ferrannini and

associates showed a progressive loss of insulin sensitivity when the BMI

increased from 18 kg/m2 to 38 kg/m2.58 The increase in insulin resistance with

weight gain is directly related to the amount of visceral adipose tissue.59,60 The

term visceral adipose tissue (VAT) refers to fat cells located within the

abdominal cavity and includes omental, mesenteric, retroperitoneal, and

perinephric adipose tissue. Visceral adipose tissue represents 20% of fat in men

and 6% of fat in women. This fat tissue has been shown to have a higher rate of

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These fatty acids are released into the portal circulation and drain into the liver,

where they stimulate the production of very low density lipoproteins and

decrease insulin sensitivity in peripheral tissues.59 VAT also produces a number

of cytokines that cause insulin resistance. These factors drain into the portal

circulation and reduce insulin sensitivity in peripheral tissues.61 The fat cell also

has the capability of producing at least one hormone that improves insulin

sensitivity: adiponectin. This factor is made in decreasing amounts as an

individual becomes more obese.62,63 In animal models, adiponectin decreases

hepatic glucose production and increases fatty acid oxidation in muscle.”64,65

SIGNS AND SYMPTOMS:

“The classical symptoms of diabetes are polyuria (frequent urination),

polydipsia (increased thirst) and polyphagia (increased hunger).66 Symptoms

may develop rapidly (weeks or months) in type 1 diabetes while in type 2

diabetes they usually develop much more slowly and may be subtle or absent.

Prolonged high blood glucose can cause glucose absorption in the lens of the

eye, which leads to changes in its shape, resulting in vision changes. Blurred

vision is a common complaint leading to a diabetes diagnosis; type 1 should

always be suspected in cases of rapid vision change, whereas with type 2

changes is generally more gradual, but should still be suspected. A number of

skin rashes can occur in diabetes that is collectively known as diabetic

(27)

27

COMPLICATIONS:

“All forms of diabetes increase the risk of long-term complications. These

typically develop after many years (10–20 years), but may be the first symptom

in those who have otherwise not received a diagnosis before that time. The major

long-term complications relate to damage to blood vessels. Diabetes doubles the

risk of cardiovascular disease.”67

The main "macrovascular" diseases (related to atherosclerosis of larger

arteries) are ischemic heart disease (angina and myocardial infarction), stroke

and peripheral vascular disease. “Diabetes also causes "microvascular"

complications - damage to the small blood vessels.68 Diabetic retinopathy, which

affects blood vessel formation in the retina of the eye, can lead to visual

symptoms, reduced vision, and potentially blindness. Diabetic nephropathy, the

impact of diabetes on the kidneys, can lead to scarring changes in the kidney

tissue, loss of small or progressively larger amounts of protein in the urine, and

eventually chronic kidney disease requiring dialysis. Diabetic neuropathy is the

impact of diabetes on the nervous system, most commonly causing numbness,

tingling and pain in the feet and also increasing the risk of skin damage due to

altered sensation. Together with vascular disease in the legs, neuropathy

contributes to the risk of diabetes-related foot problems (such as diabetic foot

ulcers) that can be difficult to treat and occasionally require amputation.”69

DIABETIC NEPHROPATHY

“The commonest of the systemic disease involving the kidney is diabetes

(28)

28

with diabetes nephropathy has proved to be an important consequence of

mortality. Diabetic nephropathy plays a significant role as one cause of end stage

renal failure in the western world.”

“Diabetic nephropathy is a clinical syndrome characterized by persistent

albuminuria, arterial blood pressure elevation, a relentless decline in glomerular

filtration rate (GFR), and an associated high risk of cardiovascular morbidity and

mortality.70 This major life-threatening complication develops in approximately

35% of subjects with type 1 diabetes. The prevalence in type 2 diabetes is higher

than type 1; this form of diabetes now contributes to at least 50% of those with

diabetic nephropathy who develop end stage renal disease (ESRD) and requires

dialysis or transplantation for survival.”71

Natural history of Diabetic Nephropathy:

“The natural history of diabetic nephropathy has been relatively well

defined in type 1 diabetics. In type 2 diabetics, the process remains unclear with

regard to the time of onset of disease or the presence of other factors such as

hypertension, age or race. However, clinical investigators have been able to

classify the development of ESRD based on the onset and duration of the

disease.”

“The classifications of ESRD were introduced by Mogensen et al, (1993) and

divided into five stages as described below. 72

 Stage 1, at the onset of the diabetes, there is glomerular hyperfiltration

(29)

29

hypertension associated with high blood glucose concentrations. At this

stage urinary albumin excretion may be normal or slightly elevated.

 Stage II is a silent phase that follows hyperfiltration and is associated with

subtle morphological changes including thickening of the glomerular

basement membrane (GBM), glomerular hypertrophy, mesangial

expansion, and modest expansion of the tubulointerstitium.

 Stage III develops after 7-15 years, with diabetic patients or incipient

nephropathy this can be detected clinically by the presence of

microalbuminuria. Abnormal urinary albumin excretion cannot be

detected by conventional or dipstick methods (semi-quantitative) but are

measurable using sensitive techniques such as quantitative immunoassay.

 Stage IV is characterised by the presence of overt nephropathy, with

dipstick-positive proteinuria. GFR falls steadily, by about 12ml/min. year,

and clinically, measurement of plasma creatinine and microalbuminuria

are used to monitor renal function and to indicate the decline of GFR.

Hypertension when present in patients at this stage is usually associated

with the presence of >500 mg urinary total protein/24 h. However,

histological glomerular lesions, found in most long-term diabetics with

nephropathy, may include thickened glomerular capillaries, mesangial

expansion, intercapillary nodules of glomerulosclerosis of the afferent and

efferent arterioles and the presence of glomerular microanueurysms. The

mesangial cells of one or more of the glomerular segments produce

(30)

30

as Kimmelstiel-Wilson nodules. The development of oedema is one of the

earliest clinical features of renal impairment, often associated with

anaemia and a rather non-specific decline in general health.

 Stage V is end stage renal failure, with the presence of severe mesangial

expansion, uraemia, hypertension, and serum creatinine concentration of

more than 400 gmol/1.”

STRUCTURAL, FUNCTIONAL, BIOCHEMICAL AND

PHYSIOLOGICAL ASPECTS OF THE KIDNEY:

“The kidneys play a major role in the homeostatic mechanisms of the

human body and reduced renal function strongly correlates with increasing

patient’s morbidity and motility. The kidneys form a paired organ system,

located in the retroperitoneal space, and demonstrate exquisite heterogeneity

which consist of three main areas namely the cortex, the medulla and the inner

medulla or papilla. The kidneys have both sympathetic and parasympathetic

nervous supply whose function appears to be predominantly associated with

vasomotor activity. Each kidney receives its blood supply from a single renal

artery derived from the abdominal aorta, with the venous return along a renal

vein that emerges into the vena cava. The renal artery divides into posterior and

anterior elements, which then divide into interlobar, arcuate, interlobular, and

ultimately into the afferent arterioles, which expand into the highly specialised

capillary bed that form the glomerulus. These capillaries then rejoin to form the

afferent arteriole, which then forms the capillary plexuses as well as the

(31)

31

of the nephron, the proximal and distal tubules, the loop of Henle, and collecting

duct, providing oxygen and nutrients and removing ions, molecules, and water

which are reabsorbed by the nephron.”

NEPHRON:

“The functional unit of the kidney is the nephron and each kidney has

been reported to contain between I and 1.5 million nephrons. There are at least

three types of nephrons, which include the superficial, midcortical and

juxtamedullary types. Each nephron consists of a glomerulus and Bowman's

capsule, which is next to the proximal tubule (PT) and the following section is

the loop of Henle, which leads into the renal medulla.”

At the junction of the inner and outer medulla, the loop becomes thicker

before leading to the distal tubule (DT) and collecting tubule (CT). This section

of the nephron then merges with those of other nephrons to form the renal pelvis

and ultimately the ureter.

GLOMERULUS:

“The glomerulus consists of a turft of blood capillaries, which is in close

contact with Bowmans's capsule. This close alliance enables the ultrafiltration of

plasma through three layers of cells which together act as a selective permeable

barrier. Glomerular structure and permeability are maintained by the glomerular

mesangial cells, thereby altering the glomerular capillary surface area available

for filtration. The glomerular basement membrane (GBM) is approximately 300

nm thick in adult humans and consists of three distinct electron-dense layers such

(32)

32

lamina densa consists of mainly type IV collagen embedded in a matrix of

glucoprotein and proteoglycans. This forms the main size discriminant barrier to

protein passage into the tubular lumen. The other two layers of the GBM are rich

in negatively charged polyanionic glucoprotein such as heparin sulphate

proteoglycans (HSP). The epithelial cells lining Bowmans's capsule are known

as podocytes and have a large number of extensions or foot processes that are

embedded in the GBM. The foot processes from adjacent podocytes are

interdigitated to form filtration slits, which are covered by highly hydrated

anionic mucopolysaccharide that is rich in sialic acid.”

“Consequently, the resulting structure is relatively impermeable to most

proteins above 60 kD, but passage of proteins is also modulated by their charge

and shape i.e. charge and size selectivity. The final cellular component of the

glomerulus is the mesangial cells (MC), which are embedded in an extra cellular

matrix (ECM) between the capillaries and play a critical role in the modulation

of glomerular blood flow and filtration by contraction and relaxation. MC are of

mesenchymal origin and contain contractile elements which express receptors to

many different hormones and cytokines, including angiotensin II, insulin-like

growth factor 1 (IGF-1), tumour necrosis factor, inteleukin-1, transforming

growth factor beta (TGF-ß) and advanced glycation end products (AGES). The

mesangial matrix, although developmentally and morphologically distinct from

the GBM, is composed of essentially the same components, i. e. collagen type

(33)

33

PROXIMAL TUBULE (PT)

“The proximal tubular region of the nephron consists of the proximal

convoluted tubule, and a straight segment, also known as the pars recta. Three

distinct cell types from the epithelial lining of these proximal structures and the

S1, S2 and S3 regions are separated on the basis of their morphological and

functional characteristics. The S1 segment, composed of S1-type cells, makes up

the beginning and middle portion of the convoluted proximal tubule and are

generally columnar with abundant microvilli on the luminal surface, thereby

increasing the surface area for reabsorption from tubular fluid by 40 fold. A well

developed phagolysosomal system, a large endocytotic apparatus of numerous

apical vacuoles and numerous mitochondria are also present in this segment. The

S2 segment forms the remaining portion of the proximal convoluted tubule and

the initial portion of the straight segment. S2 cells have fewer microvilli and

mitochondria than Si cells and they also contain the majority of the PT

lysosomes. Finally, the remaining portion of the pars recta is the S3 segment

which consists of the end of the straight portion and the beginning of the thin

descending loop Henle. Cells in this region have few microvilli and

mitochondria. The Si and S2 segments perform the majority of the solute and

fluid reabsorption coupled largely to sodium reabsorption. Large basolateral

membrane (BLM) interdigitations are found within the PT providing a large

surface area for Na+/K+ transport, which maintains the osmotic gradients

(34)

34

LOOP OF HENLE AND DISTAL TUBULE (DT)

“The loop of Henle is divided into the descending and ascending limbs.

These limbs form a hairpin loop, which either extend deeply into

(juxtramedullary) or reach only just into the medulla (cortical). The terminal

segment of the distal tubule is the convoluted part. Each segment of the loop of

Henle and the subsequent distal section has different permeability properties,

allowing the production of concentrated urine, as well as controlling intra and

extracellular osmolality and pH. Part of the distal tubule is especially close to the

glomerulus and the afferent and the efferent arterioles. Specialised cells, called

the macula densa, which are in this area respond to the sodium and chloride

composition of tubular fluid in order to maintain water and electrolyte

homeostasis (i.e. tubuloglomerulo feed back).”

FILTRATION, REABSORPTION AND SECRETION:

Glomerular filtration is a passive process dependent on the pressure

within the glomerular capillary network which in turn depends on the surface

area and intrinsic permeability of the glomerulus. The hydrostatic and oncotic

pressure gradients across the capillary walls are determined by both flow and

resistance. In the normally functioning kidney, molecules of > 50 A° are not

filtered due to size, shape or charge, whilst molecules < 40 A° are freely

permeable. These include glucose, amino acids, urea, Na+ and K+ ions. The

filtrate entering the nephron is isotonic with, and of similar composition to,

plasma except for the presence of large molecular weight proteins, which remain

(35)

35

Approximately 60-70% of the filtrate volume (water, sodium, and urea) is

reabsorbed in the PT whilst some ions and molecules are actively secreted

further down the nephron to maintain blood ionic concentration and volume. The

sodium concentration in the PT cell effects levels of energy generation and Na+

ions enter passively down an electrical gradient (-70mV) and are then actively

transported across the BLM via Na+-K+- ATPase and Na+-H+-ATPase activity

which allows the reabsorption and secretion of other solutes such as Cl", K+, H+

ions, to balance the Na+ ion movement.

RENAL BLOOD FLOW (RBF) AND GLOMERULAR FILTRATION

RATE (GFR)

“According to the myogenic theory, increased tension of the afferent

arterioles, brought about by an increase in perfusion pressure, causes automatic

contraction of the smooth muscle fibres in the vessel wall, thereby increasing the

resistance to flow and so keeping the flow constant in spite of the increase in

perfusion pressure. Tubulo-glomerular feedback (TGF) mechanisms are also

involved in supporting this process. TGF is a mechanism in which changes in DT

fluid composition are detected by the macula densa and, as a consequence, alter

the vascular elements of the glomeruli, thereby affecting single nephron GFR,

RBF and GFR are also under hormonal and nervous control. An intact renin

angiotensin aldosterone system (RAAS) is required for the normal regulation of

(36)

36

Measurement of GFR

“GFR is considered to be the most reliable measure of the glomerular

functional capacity of the kidneys and is often thought of as indicative of the

number of functioning nephrons. An estimate of the GFR can be made by

measuring the urinary excretion of a substance which is completely filtered from

the blood by the glomeruli and which is not secreted, reabsorbed or metabolised

by the renal tubules. Experimentally, inulin has been found to meet these

requirements. However, measurement of creatinine clearance is commonly used

method for estimation of the GFR in the routine clinical laboratory.”

U= urinary creatinine concentration (μmol/1),

V= urine flow rate [ml/min or (1/24 h)/1.44m2)]

P= plasma creatinine concentration (µmol/1)

Structural and functional changes in diabetic kidney

Nephromegaly was first described in diabetes more than a century ago

and is an early feature of both experimental and human diabetes.73 In animals,

nephromegaly occurs within four days of diabetes onset and most type 1

diabetics have large kidneys at diagnosis. Consequently, this enlargement is

mostly due to a combination of tubular hypertrophy and hyperplasia and

interstitial expansion, and is probably a response to increased glucose and fluid

(37)

37

1% of total kidney volume, so their contribution to whole organ enlargement is

significant.74

Glomerular enlargement has been a recognised feature of diabetes, and is

present both in early and later stages of the disease.75 Early glomerular

enlargement in experimental diabetes is the result of an increase in capillary

filtration surface area caused by an increase in capillary length, or number, or

both. In experimental diabetes, early glomerular enlargement coincides with

increased glomerular filtration.76 This, so-called hyperfiltration has been

proposed as an important pathophysiological factor for diabetic

glomerulopathy.77 Glomerular enlargement has therefore been considered as a

factor predisposing the subject to progression of glomerulopathy, perhaps by an

increase in capillary wall radius in response to raised intraglomerular pressure,

thus leading to increased capillary wall tension.74

Furthermore, the end result of diabetic glomerulopathy is a globally

sclerosed, non-functioning glomerulus. Such glomeruli can appear either as

relatively acellular, eosinophilic globes, which ultimately hyalinize and become

reabsorbed or as collapsed structures with an irregular crenated basement

membrane. The former appearance is consistent with an internal glomerular

obliteration by mesangial expansion, the latter more with ischaemia. These

interpretations are supported by reported positive correlations of percentage of

globally sclerosed glomeruli with mesangial expansion and afferent arteriolar

(38)

38

GBM thickening can be demonstrated in most diabetic subjects,

irrespective of the severity of their nephropathy, although those with heavier

proteinuria tend to have thicker membranes. It is thus not as specific a sign of

renal complication as the diffuse mesangial lesion, although those subjects with

nephropathy tend to have thicker GBMs than age and diabetes duration matched

subjects with normal renal function. Most of the increase in matrix is due to type

IV collagen accumulation. There is, however, a net loss of proteoglycan, which

is also dispersed throughout the thicker membranes. This loss is probably to

result in a loss of negative electrostatic charge and thus permit the passage of

positively charged proteins such as albumin.74

The Kimmelstiel-Wilson nodule is more specific for diabetic

nephropathy but occurs in only 20-70% of diabetics who demonstrate the diffuse

lesion. Furthermore, there are no obvious changes in endothelial or epithelial

cells in glomerulopathy, except that there is a widening of podocyte foot

processes. This development may be a ubiquitous response to increased protein

passage across the GBM, as its observed in other proteinuric states.74

A tubulo-interstitium compartment is also a major feature of diabetic

nephropathy and an important predictor of renal dysfunction. Renal enlargement

in diabetic animals is due to an initial tubular cell hyperplasia and subsequently

to cell hypertrophy. These changes are associated with alteration in expression of

growth factors such as TGF-ß and can be prevented by appropriate insulin

therapy. Tubular basement membrane (TBM) probably has a similar composition

(39)

39

has still not been widely studied. Diabetics develop TBM thickening about two

to three times the value observed in their non-diabetic siblings.79 Furthermore,

macromolecular penetration of the interstitial space may activate fibrosis and

would be further facilitated by disruption of the TBM. AGES also have been

demonstrated to increase pore size in bovine TBM, which may also result in

increased protein permeation.80

Clinical and biochemical aspects of diabetic nephropathy

Diagnosis of diabetic nephropathy

“The diagnosis of diabetic nephropathy is only definitively made by renal

biopsy, but this is rarely necessary clinically where the diagnosis is based on

both the clinical and biochemical abnormalities demonstrated the kidney, such as

the presence of proteinuria, development of a progressive rise in blood pressure,

and a progressive and relentless decline in renal function towards end stage renal

failure. Elevations of urinary albumin excretion are used to define both the

diagnosis of diabetic nephropathy and it progression. An increase in albumin

excretion is taken as the hallmark of diabetic nephropathy.”81

MICROALBUMINURIA

“Microalbuminuria is one of the earliest signs of renal insult in diabetes

and is currently the main focus of attention, as it is also associated with increased

risk of morbidity and premature death from cardiovascular disease.82 The

presence of microproteinuria in general, or microalbuminuria in particular,

reflects loss of charge selectivity and an increase in capillary permeability in the

(40)

40

failure (overt nephropathy) in diabetes mellitus; its presence here is termed

incipient nephropathy.”

Microalbuminuria, defined as an increased urinary albumin excretion

detectable only by sensitive immunoassay expressed either by time or with

reference to creatinine concentration, has been used for many years as a predictor

of incipient nephropathy in diabetics.81 The gold standard of microalbuminuria

measurement is based on the excretion rate of albumin in a timed urine

collection, while for more rapid estimations the urinary albumin concentration in

an early morning mid stream specimen of urine may be used. In order to correct

for variations in body fluid balance, the latter is normally referenced against the

(41)

41

Table: 1 Classification of Albuminuria:74

Normalbuminuria

Microalbuminuri

a

Macroalbuminuri

a

Albumin excretion rate

(mg/24h)

< 30 30-300 >300

Albumin excretion rate

(μg/min)

< 20 20-200 >200

Albumin concentration

(mg/L)

< 20 20-200 >200

ACR(mg/g creatinine) < 30 30-300 >300

ACR(mg/mmol

creatinine)

<3.5 3.5-35 >35

“Microalbuminuria may initially be transient in nature, but may become

persistent and result in the patient progressing to end stage renal failure if left

untreated. Indeed, microalbuminuria may progress to ESRD in 7-10 years after

onset of diabetes.83 In subjects with type 1 diabetes, about 80% of who develop

persistent microalbuminuria if left untreated, develop overt nephropathy within

10-15 years, accompanied by hypertension. This may eventually lead to end

stage renal failure within a further 10-20 years without appropriate therapeutic

(42)

42

develop microalbuminuria and overt nephropathy shortly after the diagnosis of

diabetes is probably because diabetes has been present for many years before the

diagnosis was made. However, overall 20-40% of type 2 diabetics with

microalbuminuria progress to overt nephropathy which ultimately may lead to

ESRD.”84

Pathophsiyology

“The intimate relationship between low-level albumin excretion and

vascular permeability makes UAE highly sensitivity to the presence of any

inflammatory process, including cardiovascular disease.82 Almost all filtered

albumin is reabsorbed by the proximal tubule via a high-affinity, low-capacity

endocytotic mechanism. Since tubular mechanisms for albumin reabsorption are

near saturation, urinary albumin excretion would increase following any increase

in tubular load. Glomerular permeability to albumin is dependent on endothelial

charge selectivity as well as size selectivity. The negative charge conferred on

the glomerular membrane by its constituent glycoproteins plays a role in

restricting the permeability of anionic proteins. Loss of glomerular charge

selectivity has been found in both diabetic and non-diabetic subjects with

microalbuminuria. However, the mechanisms underlying microalbuminuria still

remain to be fully elucidated.”85

SCREENING

“Annual screening for microalbuminuria will allow the identification of

those diabetics with either nephropathy or at risk of developing nephropathy. A

(43)

43

diabetes. Conversely, microalbuminuria rarely occurs with short duration of type

1 diabetes or before puberty and therefore, screening should begin with puberty

and after 5 years disease duration. If the urinalysis is positive for protein, a

quantitative measure is frequently helpful in the development of a treatment

regime.”

Screening for microalbuminuria can be performed by three methods: 1)

measurement of the albumin to creatinine ratio in a random spot urine collection;

2) 24h collection with creatinine, allowing the simultaneous measurement of

creatinine clearance; and 3) timed (e. g. 4h or overnight) collection.83

TREATMENT OF DIABETIC NEPHROPATHY

Effective of glycemic control

The DCCT, the UKPDS, the Stockholm and Intervention Study have

demonstrated definitively that intensive diabetes therapy can significantly reduce

the risk of the development of microalbuminuria and overt nephropathy in

subjects with diabetes. However, an improvement in renal function, which is

already restricted, can be attained by limiting maintaining blood glucose

concentrations close to reference values (mean HbA1c 6.5%) and intensified

blood pressure treatment.

Control of blood pressure and antihypertensive agent

Both systolic and diastolic hypertension significantly accelerates the

progression of diabetic nephropathy, and aggressive antihypertensive

management is able to greatly decrease the rate of decline of GFR. According to

(44)

44

Prevention, Detection, Evaluation, and Treatment of High Blood Pressure, blood

pressure levels above 135/85 mm Hg in a diabetic is abnormal. Treatment should

be directed at lowering the systolic level to about 100 to 110 mm Hg. The

positive response to antihypertensive treatment coupled with the concept that

often there is a progressive deterioration of renal function regardless of the

underlying etiology gave rise to the idea that haemodynamic factors may be

critical in furthering the depletion in GFR. In this hypothesis, damage to

glomeruli causes changes in the microcirculation that result in hyperfiltration

occurring in the remaining glomuruli with increased intraglomerular pressure

and increased sensitivity to angiotension II; the single nephron hyperfiltration

with intraglomerular hypertension is in itself damaging. Initially, Angiotensin

Converting Enzyme (ACE) inhibitors can reduce the degree of microalbuminuria

and can reduce the rate of progression of diabetic nephropathy to a greater

degree in both type 1 and type 2 diabetics. 75,83

Protein Restriction

“Dietary protein restriction has been demonstrated to decrease

albuminuria and reduce the rate of deterioration glomerular function in various

renal diseases. Both animal and human studies have demonstrated that restriction

of dietary protein intake also reduces diabetic intraglomerular pressure and

retards the progression of renal disease and diabetic nephropathy. The consensus

is to prescribe a protein intake of approximately the adult recommended dietary

allowance (RDA) of 0.8 g/kg/day (approximately 10% of daily calories) in the

(45)

45

GFR begins to decline, further restriction to 0.6 g/kg/day may prove useful in

slowing any further decline of GFR.”83

Renal replacement therapy (RRT)

“RRT consists of haemodialysis, continuous ambulatory peritoneal

dialysis (CAPD) and renal transplantation. Renal transplantation is the treatment

of choice for those under 60 years of age and should be considered when the

serum creatinine concentration reaches about 500-800 μmol/l.”74

SIALIC ACID

“Sialic acids are small aminosaccharides. They consist of a neuraminic

acid backbone with one or multiple O- or N-linked side chains, the most

abundant derivative in humans being Nacetylneuraminic acid (Figure 1).”

N- acetylneuraminic acid

“Sialic acids are numerous in many human tissues and fluids. In serum,

sialic acids are mostly bound to the carbohydrate chains of glycoproteins and

glycolipids.86 Sialic acid residues are located in the terminal ends of

carbohydrate chains of many glycoproteins, for instance immunoglobulins

and peptide hormones, and when the terminal sialic acid is removed by

neuraminidase of the vascular endothelium, a galactose molecule is

revealed. Specific receptors on hepatocytes recognize these asialoglyco-proteins

Figure

Table: 1 Classification of Albuminuria:74
Table: 1 Classification of Albuminuria:74 p.41
Table 1) Age distribution among study groups:

Table 1)

Age distribution among study groups: p.58
Table 2) Sex distribution among study groups:

Table 2)

Sex distribution among study groups: p.59
Figure 2 Sex distribution among study groups

Figure 2

Sex distribution among study groups p.59
Table 3) Comparison of blood sugar levels among studied groups:

Table 3)

Comparison of blood sugar levels among studied groups: p.60
Figure 3 Blood sugar levels among studied groups

Figure 3

Blood sugar levels among studied groups p.60
Figure 4 Glycated Haemoglobin among studied groups

Figure 4

Glycated Haemoglobin among studied groups p.61
Table 4) Comparison of Glycated Haemoglobin among studied groups:

Table 4)

Comparison of Glycated Haemoglobin among studied groups: p.61
Figure 5 Blood urea and Serum creatinine among studied groups

Figure 5

Blood urea and Serum creatinine among studied groups p.62
Figure 6 Serum sialic acid among studied groups

Figure 6

Serum sialic acid among studied groups p.63
Figure 7 Microalbuminuria among studied groups

Figure 7

Microalbuminuria among studied groups p.64
Table 7) Comparison of Microalbuminuria among studied groups:

Table 7)

Comparison of Microalbuminuria among studied groups: p.64
Table 8) Correlation of Serum sialic acid and blood sugar levels in cases and controls:

Table 8)

Correlation of Serum sialic acid and blood sugar levels in cases and controls: p.65
Figure 8 Correlation of Serum sialic acid and blood sugar levels among cases

Figure 8

Correlation of Serum sialic acid and blood sugar levels among cases p.66
Table 9) Correlation of Serum Sialic acid and glycated haemoglobin in cases and controls:

Table 9)

Correlation of Serum Sialic acid and glycated haemoglobin in cases and controls: p.67
Figure 9 Correlation of Serum Sialic acid and glycated haemoglobin in cases

Figure 9

Correlation of Serum Sialic acid and glycated haemoglobin in cases p.68
Table 10) Correlation of Serum Sialic acid and serum creatinine in cases and controls:

Table 10)

Correlation of Serum Sialic acid and serum creatinine in cases and controls: p.69
Figure 10 Correlation of Serum sialic acid and serum creatinine in cases

Figure 10

Correlation of Serum sialic acid and serum creatinine in cases p.70
Table 11) Correlation of Serum Sialic acid and microalbuminuria in cases and controls:

Table 11)

Correlation of Serum Sialic acid and microalbuminuria in cases and controls: p.71
Figure 11 Correlation of Serum Sialic acid and microalbuminuria in cases

Figure 11

Correlation of Serum Sialic acid and microalbuminuria in cases p.72

References

Related subjects :