Diabetes Mel itus
WHO
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? Diabetes mellitus is a chronic disease caused by inherited and/oracquired deficiency in production of insulin by the pancreas, or by the
ineffectiveness of the insulin produced.
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? results in increased concentrations of glucose in the blood, which in
turn damage the blood vessels and nerves.
? Diabetes mellitus is a group of metabolic disorders sharing the
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common feature of hyperglycemia
Classification
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? two principle forms of diabetes:1. Type 1 diabetes (formerly known as insulin-dependent)
2. Type 2 diabetes (formerly named non-insulin-dependent)
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ETIO-PATHOGENESIS? PATHOGENESIS OF TYPE 1 DM. destruction of -cel mass, usual y leading
to absolute insulin deficiency.
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1. Genetic susceptibility- HLA gene cluster on chromosome 6p21, which
according to some estimates contributes as much as 50% of the genetic
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susceptibility to type 1 diabetes.? Al ele-HLA-DR3-DR4
2.Autoimmune factors: fundamental immune abnormality in type 1 diabetes
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is a failure of self-tolerance in T cel s specific for islet antigens
? islet cel antibodies
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? insulitis? Selective destruction of -cel s
? TH1 cells secrete-IFN- and TNF
? Islet autoantigens- cell enzyme glutamic acid decarboxylase (GAD),
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and islet cell autoantigen 512(ICA512)
? cell-mediated autoimmunity
? Associated with other autoimmune diseases
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3.Environmental factors
? viral infections
? Chemicals-alloxan, streptozotocin and pentamidine.
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Etiopathogenesis in DM type2
PATHOGENESIS OF TYPE 2 DM.
complex disease that involves an interplay of genetic and
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environmental factors and a proinflammatory state.
1-Genetic Factors-first-degree relatives have 5- to 10-fold higher risk
2-Environmental Factors-Obesity, sedentary lifestyle
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3-Insulin resistance-Mechanism of hyperglycaemia in these cases is explained as under:
i) impairs glucose utilisation and hence hyperglycaemia.
ii) There is increased hepatic synthesis of glucose.
iii) Hyperglycaemia in obesity is related to high levels of free fatty acids
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and cytokines
4-Current consideration-
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? Polymorphism in various post-receptor intracellular signal pathwaymolecules.
? Elevated free fatty acids
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-Cell DysfunctionSeveral mechanisms have been implicated in promoting -cell
dysfunction in type 2 diabetes, including:
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? Excess free fatty acids that compromise cell function and attenuateinsulin release ("lipotoxicity")
? impact of chronic hyperglycemia ("glucotoxicity")
? An abnormal "incretin effect," leading to reduced secretion of GIP
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and GLP-1, hormones that promote insulin release
? Amyloid deposition within islets 90% of diabetic islets cell in long
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standing? genetic predisposition
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Obesity and Insulin Resistance
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vFree fatty acids (FFAs)-? accumulation of cytoplasmic intermediates like diacylglycerol (DAG)
? DAG compete with glucose for substrate oxidation
vAdipokines- Adiponectin levels are reduced in obesity, thus
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contributing to insulin resistancevInflammation
Inflammation:
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? FFA & Beta cell
? Inflammasome
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? Cytokines IL-1, IL-1? promote insulin resistance
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Metabolic actions of insulin in striated muscle, adipose tissue,and liver.
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Pathophysiological basis of common signs and symptoms due to uncontrol edhyperglycaemia in diabetes mel itus
? Morphologic Features ?
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1. Pancreatic Islets2. Diabetic Macrovascular Disease
3. Diabetic Microangiopathy
4. Diabetic Nephropathy
5. Diabetic Ocular Complications
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6. Diabetic neuropathyMorphologic Features
Pancreatic Islets-
1-Insulitis:
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? In type 1 DM-?lymphocytic infiltrate,macrophage and few polymorphs
? In type 2 DM-
?variable degree of fibrous tissue in the islets
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2-Islet cell mass:? Type-1- loss of pancreatic -cells and its hyalinisation
? In type 2 DM-hyperplasia and hypertrophy of islets
3-Amyloidosis:
? type 1 DM- absent
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? Type-2DM-around the capillaries of the islets causing compressionand atrophy of islet tissue
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? Diabetic Macrovascular Disease-?hallmark of diabetic macrovascular disease is accelerated
atherosclerosis involving the aorta and large- and medium-sized
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arteries?Myocardial infarction
?Gangrene of the lower extremities
?Hyaline arteriolosclerosis
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renal hyaline arteriolosclerosis
? Diabetic Microangiopathy- diffuse thickening of basement
membranes.
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?capillaries of the skin, skeletal muscle, retina, renal glomeruli, and
renal medulla
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? leaky? Diabetic Nephropathy-
Three lesions are encountered:
(1) glomerular lesions
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(2) renal vascular lesions(3) pyelonephritis, including necrotizing papillitis
? Glomerular lesion-
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?Capillary Basement Membrane?Diffuse Mesangial Sclerosis- consists of diffuse increase in mesangial
matrix.
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?Nodular Glomerulosclerosis- also known as intercapillary
glomerulosclerosis or Kimmelstiel-Wilson disease.
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Diffuse and nodular diabetic glomerulosclerosis (PAS
stain).
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? nodular lesions are frequently accompanied by prominentaccumulations of hyaline material in capillary loops ("fibrin caps") or
adherent to Bowman capsules ("capsular drops").
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Nephrosclerosis
?Renal atherosclerosis and arteriolosclerosis-
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Hyaline arteriolosclerosis affects not only the afferent but also theefferent arteriole
?Pyelonephritis is an acute or chronic inflammation of the kidneys that
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usually begins in the interstitial tissue and then spreads to affect thetubules
? necrotizing papillitis
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Diabetic Ocular Complications-
Histologically,
? Non proliferative (non-proliferative)
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? proliferative retinopathyBackground (non-proliferative) retinopathy. initial retinal capillary
microangiopathy
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? i ) Friability of neo vascularization results in vitreous haemorrhages.
? i i) Proliferation of astrocytes and fibrous tissue around the new blood
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vessels.? iv) Fibrovascular and gliotic tissue contracts to cause retinal detachment
and blindness.
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? Diabetic Neuropathy-duration of the disease; up to 50% of diabetics overall have peripheral
neuropathy
Activation of PKC and polyol pathway
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Accumulation of fructose and sorbitol in nerveNonenzymatic glycosylation of structural nerve protein
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Four distinct mechanisms1-Formation of Advanced Glycation End Products. Advanced glycation
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end products (AGEs) are formed as intracellularglucose derived dicarbonyl precursors+ amino groups
advanced glycation end product(AGEs)
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(glyoxal, methylglyoxal, and 3-deoxyglucosone)? AGEs bind to a specific receptor (RAGE) that is expressed on
inflammatory cells (macrophages and T cells), endothelium, and
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vascular smooth muscle.
AGE-RAGE signal ing axis
? TGF-excess basement membrane material
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? vascular endothelial growth factor (VEGF)- neovasculerization? reactive oxygen species (ROS) in endothelial cells
? procoagulant activity
? Enhanced proliferation of vascular smooth muscle cells and synthesis
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of extracellular matrix2-Activation of Protein Kinase C.
second messenger diacyl glycerol (DAG) is an important signal
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transduction pathway.Intracellular hyperglycemia--- de novo synthesis of DAG--excessive
PKC activation- vascular permeability and angiogenesis
3-Oxidative Stress and Disturbances in Polyol Pathways
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? Sustained hyperglycemia---- aldol reductase-- progressive depletion of
intracellular NADPH -- decreased rgeneration of reduced
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glutathione(GSH) - increasing cellular susceptibility to oxidativestress
? Responsible for diabetic neuropathy
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4-Hexosamine Pathways and Generation of Fructose-6- Phosphate
Hyperglycemia ---increases intracellular levels of fructose-6-
phosphate via HM- excess proteoglycans - abnormal
expression of TGF or PAI-1--- exacerbate the end-organ damage
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Complications of Diabetes-
I.Acute metabolic complications:
? diabetic ketoacidosis
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? hyperosmolar nonketotic coma? hypoglycaemia
I . Late systemic complications:
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? atherosclerosis? diabetic microangiopathy
? diabetic nephropathy
? diabetic neuropathy
? diabetic retinopathy and infections
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1.Diabetic ketoacidosis (DKA), complication of type 1 DM.
Lack of insulin
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LypolysisFree fatty acid in plasma
FFA+acetyl co enzyme A--liver Ketone body
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2.Hyperosmolar hyperglycaemic nonketotic coma (HHS)-
High Blood sugar
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High plasma osmolality
Hyperglycemic diuresis
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DehydrartionCNS complication
3.Hypoglycaemia-
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? patients of type 1 DM.? Excessive administration of insulin, missing a meal, or due to stress
I .LATE SYSTEMIC COMPLICATIONS-
1.Atherosclerosis-
? hyperlipidaemia,
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? reduced HDL levels,? nonenzymatic glycosylation,
? increased platelet adhesiveness,
? obesity
? hypertension
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2.Diabetic microangiopathy
3. Diabetic nephropathy
4. Diabetic neuropathy
5. Diabetic retinopathy
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6. Infections-?impaired leucocyte functions
? reduced cellular immunity
?poor blood supply
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