The WHO reports suggest that DM is one of the most Non communicable disease and is 5th leading cause of death in most of the developed countries. In India that prevalance is increasing year by year . It is estimated that by 2025, 75% of pop with diabets will reside in developing countrieswith 57.1 million
Fasting state and feed state
Kidney , blood vessels, peripheral nerve ,
PMN leukocyte function is depressed, particularly when acidosis is also present. Leukocyte adherence, chemotaxis, and phagocytosis may be affected. Antioxidant systems involved in bactericidal activity may also be impaired.
Increased Polyol - sorbitol Pathway fluxIncreased AGES formationActivation of protein kinase CIncreased Hexosamine pathway flux
Prolonged exposure to elevated glucose concentrations damages tissues by causing either acute, reversible metabolic changes (mostly related to increased polyolpolyol pathway activity and glycosylation of proteins) or cumulative irreversible changes in longlived molecules (formation of advanced glycosylation end products /AGE/ on matrix proteins such as collagen and on nucleic acids and nucleoproteins).
The AGEs induce irreversible cross-links between molecules and thus alter their chemical and biological properties
Glucose, in its aldehyde form, reacts with the amino groups of protein to form a Schiff base which rearranges to a stable ketoamine adduct This process, non-enzymatic glycation of protein, occurs naturally in the body. Glycation not only affects the structure and function of protein, but also initiates a series of Maillard or browning reactions that eventually lead to cross-linking and denaturation of proteins.
This type of reaction is somewhat slower in an organism. The sugar-protein complex is able to initiate a chain reaction that ends in forming reversible intermediate substances in a few days. These substances dehydrate, condense and reorganize themselves after a few weeks and become the irreversible components of AGEs.
Amadori modified histones were identified in liver cells of diabetes patients whereas Amadori albumin was associated with early nephropathy and with retinopathy in type 1 diabetes patients .Increased level of Amadori-glycated collagen was found in type 1 diabetic patient with or without retinopathy and it was also independently associated with retinopathy .It is reported that Amadori products of glycated serum proteins contribute to diabetic nephropathy and elevated concentrations of Amadori albumin in animals were linked with diabetic retinopathy. Fructosamine levels of purified immunoglobulins (IgG, IgA, IgM) were higher in both type 1 and 2 diabetes patients with nephropathy as compared to those without any complications. A number of Amadori-modified plasma proteins such as immunoglobulin (Ig) heavy-chain constant regions and Ig light chains were found in type 2 diabetes patients with the help of Amadori-antibody (1-deoxyfructosyl lysine) .Amadoriglycated albumin and lipoproteins were associated with increased atherosclerosis in diabetes A detailed
Glycation of proteins is implicated in diabetes (7). Glucose and other saccharides are important glycating agents, but the most reactive glycating agents are the a -oxoaldehydes (8). Early glycation adducts (Schiff’s base, fructosamine) and advanced glycation adducts (AGEs) are formed glucosefructosegalactose
Ag (10,11). e-corrected levels of glycoxidation products in collagen correlate with the severity of diabetic complications
At least four different AGE receptors have been described, two of which belong to the group of receptor scavengers. One of them is very similar, if not identical, to the receptor which internalizes altered LDL particles. Receptors on endothelial cells are different.
Vascular tissue AGE accumulation cause protein crosslinking & oxidative damage Increased vascular matrix thickening and narrowing of lumen Increased endothelial cell permeability and procoagulant activity thrombosis Mononuclear cell chemotaxis/activation cytokine and growth factor release Increased macrophage uptake of AGE-LDL ® atheroma
WORLD-WIDE ESTIMATED NUMBER
OF ADULTS WITH DIABETES BY AGE
GROUP AND YEAR
is a group of metabolic diseases characterized by
• defects in insulin secretion,
• defects in insulin action
• or both.
long-term damage, dysfunction, and
failure of various organs, especially the
Pancreas beta cells
INSULIN ACTIONS: A REVIEW
TYPES AND CAUSES OF
Type 1 ( was called “insulin- dependent DM”/ juvenile type of DM) ( 5-10%)
Type 2 (was called “non insulin- dependent DM” /adult onset DM ) (90-95%)
The “pre-diabetic stage” (impaired glucose tolerance)
Gestational DM -any degree of glucose intolerance with onset or first
recognition during pregnancy [in 2-5% of all pregnancies]
Other specific types (1% - 2%)
– genetic syndromes (affecting insulin secretion or action)
– endocrinopathies (Acromegaly, Cushing’s syndrome, glucagonoma,
– diseases of pancreas (chronic pancreatitis, cancer)
– drug- or chemical-induced (corticosteroids, beta-blockers, thiazide
– infections (viral)
The main focus of this plenary
• Metabolic complications of low blood glucose levels
(hypoglycaemia) and of high blood glucose levels (hyperglycaemia).
– e.g. diabetic symptoms(3P’s ), infections, Diabetic coma
• Chronic complications:
peripheral vascular disease
COMPLICATIONS OF DIABETES MELLITUS
CLINICAL FEATURES OF DM DUE TO LACK OF INSULIN : MC
Starvation in the
midst of plenty
Muscle protein breakdown
CHRONIC COMPLICATIONS OF
Microvascular And consequently, macrovascular
complications are specific to diabetes and do not occur
without longstanding hyperglycaemia.
Other metabolic, environmental and genetic factors are
undoubtedly involved in their pathogenesis.
Both T1DM and T2DM are susceptible to microvascular
complications, although patients with T2DM are older at
presentation and may die of macrovascular disease before
microvascular disease is advanced.
Prolonged exposure to elevated glucose concentrations
damages tissues by causing either acute, reversible
metabolic changes (mostly related to increased polyol
polyol pathway activity and glycosylation of proteins)
or cumulative irreversible changes in longlived
molecules (formation of advanced glycosylation end
products /AGE/ on matrix proteins such as collagen and
on nucleic acids and nucleoproteins).
Nonenzymatic glycation is a process by which glucose
is chemically bound to amino groups of proteins but
without the help of enzymes.
It is a classical covalent reaction in which, by means of N-
glycoside bonding, the sugar-protein complex is formed
through a series of chemical reactions described by a chemist
Maillard reactions are complex and multilayer, and
can be analyzed in three steps.
1) The sugar-protein complex is formed first (Amadori
rearrangement). It is an early product of
nonenzymatic glycation, an intermediary which is a
precursor of all later compounds.
2) The formation of numerous intermediary products,
some of which are very reactive and continue with
3) Polymerization reaction of the complex products
formed in the second step, whereby
heterogeneous structures named advanced
glycation endproducts (AGE) are formed.
Other processes that contribute to the formation of
AGES are summarised in Figure .
Schematic presentation of potential pathway
leading to AGE formation
1.AGE arise from decomposition of Amadori products
2.fragmentation products of polyol pathway
3.as glycooxidative products,
which all react with amino groups of protein
GLO=glyoxal; MGO=methylglyoxal; 3-DG=3deoxyglucosone;
Glycation of proteins take place at ε-amino groups of lysine
or hydroxylysine residues as well as at α-amino groups of
amino terminal residues .
Specific lysine residues in hemoglobin, human serum
albumin and α-crystallins have been identified as preferential
sites of glycation.
Other lysine-rich proteins, IgG and IgM, were found to be
glycated in diabetes patients.
Glycation also takes place on arginine residues and that
of histidine, tryptophan and cysteine residues
Endogenous glycations occur mainly in the bloodstream
to a small proportion of the absorbed simple sugars:
Glucose , fructose, and galactose .
It appears that fructose and galactose have approximately
ten times the glycation activity of glucose, the primary body
Cross-linking potency is variable among the sugars, with a
rank order of glucose < fructose < ribose, and phosphorylated
sugars being more potent than their unphosphorylated
In spite of the fact that sugars are the main
precursors of AGE compounds, numerous intermediary
metabolites, i.e. a -oxoaldehydes, , glyoxal,
methylglyoxal and 3-deoxyglucosone also creatively
participate in nonenzymatic glycation reactions.
Such intermediary products are generated during
glycolysis (methylglyoxal) or along the polyolic
pathway, and can also be formed by autooxidation of
Alpha-oxoaldehydes modify AGEs surprisingly fast,
in contrast to classical Maillard reactions,
which are very slow.
GLYCATION HAS BOTH PHYSIOLOGICAL AND
In physiological conditions, glycation can be detected in the
process of aging, and the reactions are significantly faster
and more intensive, with frequently increased glucose
concentrations , such as in diabetes.
In diabetology, the importance of these processes
manifests in two essential issues:
1) effect of protein glycation on the change of their structure
and function, and
2) use of glycated protein level as a parameter of integrated
A classical example of nonenzymatic glycation is the
a) Formation of glycated hemoglobin, HbA1c.
As the life of Hgb is 120 days, HbA1c,reflects the status of
glucose in diabetes over a long time.
b) Fructosamine a glycated product,depicts short term
status as short half life
The excessive cleavage of glucose, especially with
important protein amino groups, can affect cell function
and structure and create an imbalance which leads to cell
This condition seems to target organs and tissues that
are not dependent on insulin for their absorption of glucose.
Kidneys, blood vessels, peripheral nerves and lenses of
the eye are more susceptible to damage from periods of
hyperglycemia than other organs due to their
lack of insulin dependence.
Due to glycation there is change in the structure and function of a
protein that can be studied by;
ADVANCED GLYCATION ENDPRODUCTS (AGES)
During the process of glycation, early glycation products are
formed first, which subsequently rearrange into final AGE
structures through a series of very complex chemical
Protein modification with AGE is irreversible, as there are no
enzymes in the body that would be able to hydrolyze AGE
These structures then accumulate during the lifespan of the
protein on which they have been formed. Examples include all
types of collagen , albumin, basic myelin protein, eye lens
proteins,lipoproteins, and nucleic acid.
So, AGE is the result of years of accumulated glycated
damage to molecules that are not replaced regularly, but
have a low turnover rate.
The major biological effects of excessive glycation
1) Inhibition of regulatory molecule binding
2) Crosslinking of glycated proteins
3) Trapping of soluble proteins by glycated extracellular
4) Decreased susceptibility to proteolysis
5) Inactivation of enzymes
6) Abnormalities of nucleic acid function
7) Increased immunogenicity in relation to immune
It has been well documented that AGEs progressively accumulate on
tissues and organs developing chronic complications of diabetes mellitus,
i.e. retinopathy, nephropathy, neuropathy, and progressive
Age-corrected levels of glycoxidation products in collagen
correlate with the severity of diabetic complications
Also, cross-linking of collagen proteins, for example,
contributes both to the rigidity and the loss of elasticity of
tissues, and to the thickening of capillary walls observed in
diabetes and during the aging process.
This protein modification is also responsible for crystalline
lenses becoming opaque in cataracts, a degenerative
disease that is also frequent in diabetic or aged persons.
Also glycation substances may be involved in the
pathogenesis of Alzheimer's disease, since an accumulation
of these substances is observed at the sites of neuronal
degeneration during the course of this disease
In addition to the cross-linking of long-lived molecules,
AGE are able to stick the rapidly renewable plasma
Molecules together, whether albumin, antibodies,
or LDL cholesterol.
The body does have a defense against
The immune system has macrophages
with special receptors for AGEs.
The macrophages engulf AGEs and
Eventually the products are excreted in
The level of AGE proteins reflects kinetic balance of two opposite
processes: the rate of AGE compound formation,
and the rate of their degradation by means of receptors.
AGE receptors participate in the elimination and change of
aged, reticular and denatured molecules of extracellular matrix as
well as of other AGE molecules.
However, in diabetes mellitus AGE protein accumulation
may exceed the ability of their elimination due to chronic
hyperglycemia and excessive glycation process.
AGE protein binding to macrophage receptors causes a
cascade of events in the homeostasis of blood vessel walls
and their milieu by mediation of cytokines and tissue growth
These are sites on cell membranes that bind AGE ligands.
The abbreviation used to denote them in the literature is
RAGE, they belong to immunoglobulin receptor family, and
predominate in tissues.
Can variations in AGE level explain differences in the
susceptibility to development of complications?
It is not known, however, theoretical reflections indicate
that gene diversity in AGE receptors could offer an
Glycotoxins (AGE peptides)
Tissue macrophages with AGE receptors represent the major
pathway of tissue AGE alteration and cell degradation.
In this process, AGE peptides are released as degradation
products, which partly occurs through proteolysis of the matrix
Component, commonly named glycotoxins.
Glycotoxins (AGE peptides) are very reactive on entering
In case they have not been eliminated through the kidneys,
recirculating AGE peptides can generate new AGE products
that react with other plasma or tissue components.
At this stage, glycation becomes an autonomic process which
significantly accelerates the progress of the complication
CLINICAL SIGNIFICANCE OF ADVANCED GLYCATION
A variety of human tissues interact with the products of
advanced glycation during normal homeostasis.
Clinical implications of the phenomenon of advanced
glycation are discussed below.;
Role of AGEs and AGE receptors in the
pathogenesis of diabetic complications
AGEs in diabetic vasculopathy and atherosclerosis
Atherosclerotic cardiovascular disease is the major cause of
morbidity and mortality in diabetes.
The mechanisms by which diabetes so dramatically increases
atherosclerosis are yet poorly understood.
AGEs also play a significant role in atherosclerosis.
For instance, reticulated and irreversible LDL from the
circulation binds to AGE-modified collagen of the blood vessel
walls. (Vascular tissue AGE accumulation cause protein
crosslinking & oxidative damage)
Increased endothelial cell permeability and procoagulant
Mononuclear cell chemotaxis/activation cytokine and
growth factor release
In the majority of blood vessels, reticular binding delays
normal outflow of LDL particles that have penetrated the
vessel wall, thus enhancing cholesterol deposition in the
intima.(Increased vascular matrix thickening and narrowing
Such AGE reticulation increases lipoprotein deposition
regardless of the plasma LDL level.( Increased macrophage
uptake of AGE-LDL atheroma)
This is followed by an
accelerated development of
This lead to High Blood
The presence of many AGE compounds in the atheroma
has been demonstrated by immunohistochemistry
It has been well documented that lipids and lipoproteins are
deeply involved in the atherogenic process.
AGEs and renal failure
Persistent hyperglycemia has a central role in the development
of diabetic nephropathy that is clinically manifested by
proteinuria progressing to renal insufficiency, and
histopathologically by mesangial expansion and glomerular
basement membrane thickening.
A possible link between elevated glucose level and diabetic
nephropathy resides in the glycation process producing AGEs.
This modification may impair the original function of either
protein and may affect normal processes of turnover and
AGEs can induce an excess crosslinking of collagen
molecules in the glomerular plasma membrane affecting the
assembly and architecture of the
glomerular basement membrane
and mesangial matrix, and can
potentially act on mesangial cells
via growth factors, causing cells to
synthesize more extracellular
All these processes may lead to
enhanced deposition of
extracellular matrix proteins in the
mesangium, interfere with the
mesangial clearance of
macromolecules, and alter macrophage function, thus
contributing to mesangial expansion and glomerular occlusion.
Circulating serum AGE level is markedly increased in
patients with diabetes and renal insufficiency.
Serum AGEs include both serum proteins that have been
modified by advanced glycation and low molecular weight
Using specific immunoassay, serum AGE peptide levels
have been found to correlate with renal function.
In fact, close correlation has been demonstrated between
serum AGE levels and creatinine clearance.
In normal controls, AGE peptide clearance has been
estimated to 0.72 ml/min.
Diabetic persons with normal glomerular filtration rate can
clear AGE peptides at the same rate.
However, progressive loss of renal function is associated
with increasing circulating AGE peptide levels.
Current renal replacement therapies, hemodialysis or
peritoneal dialysis, are relatively inefficient in removing AGEs
from the serum of diabetic patients.
In these patients, AGE peptides persist at up to 8-fold normal
Diabetic patients with renal failure are known to be particularly
susceptible to cardiovascular complications due to accelerated
AGES AND DIABETIC RETINA
Histologic features of early diabetic retinopathy are
characterized by acellular capillaries and resultant areas of
These microvascular alterations are associated with the
accumulation of AGEs of long-lived extracellular matrix
Such structural abnormalities are detectable by specific
autofluorescence and by anti-AGE antibodies.
In an experimental animal model, treatment with
aminoguanidine, an ihibitor of AGE formation, was shown to
reduce the formation of acellular capillaries and to prevent
proliferation of endothelial cells, suggesting that AGE may
play a major role in the pathogenesis of diabetic retinopathy.
It was also demonstrated that AGE-modified albumin co-
localizes with the component of AGE receptors in the retinal
vasculature of both diabetic rats and AGE-infused rats,
suggesting that progressive accumulation of AGE may well be
the underlying mechanism for the loss of pericytes and
endothelial cells in early diabetic retinopathy.
This is supported by the finding that AGE receptor is
localized in human and rat retinal microvessels.
AGES IN DIABETIC NEUROPATHY
The major causative link between clinical diabetic
and peripheral nerve changes is hyperglycemia.
One of the important biochemical pathways involved, with a
potential role in diabetic neuropathy, is glycation leading to
AGE modification of nerve proteins.
AGEs have been stained in the endoneurium, particularly
on the axons, endoneurial capillaries, and perineurium of
diabetic patients with neuropathy.
Axonal cytoskeletal proteins have essential roles in axonal
structure and function.
Nonenzymatic glycation of axonal proteins causes
alteration in structure and transport, leading to axonal atrophy
Additionally, studies have shown that glycation of myelin
occurs in both peripheral nerve and brain.
To more precisely define the role of nonenzymatic glycation
in diabetic neuropathy, it is important to identify exactly which
proteins are being glycated.
Their localization is also of immense value in determining
the relative contribution of these glycated proteins to
The main aim of the studies is to contribute to open new
lines for basic research on the compelling issue of
establishing a common molecular basis for the mechanisms
of diabetic complications.
This, in turn, should pave the way for clinical investigation
& looking for appropriate targets for a therapeutic
counteraction aiming to retard the formation chronic