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Pathogenesis and Classification of Glycemic Disorders. Hyperglycemia The Defining Feature of Diabetes. Excessive glucose production. Impaired glucose clearance. Hyperglycemia. Tissue injury. 1. Hyperglycemia Damages Tissues. Effects of hyperglycemia
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HyperglycemiaThe Defining Feature of Diabetes Excessive glucose production Impaired glucose clearance Hyperglycemia Tissue injury 1
Hyperglycemia Damages Tissues • Effects of hyperglycemia • Glycation of proteins (eg, hemoglobin, collagen) • Accumulation of sorbitol and fructose (eg, in nerves, lens) • Activation of protein kinase C (eg, on vascular cells) • Tissue changes • Altered protein function and turnover, cytokine activation • Osmotic and oxidative stress • Reduced motor and sensory nerve conduction velocity • Increased glomerular filtration rate and renal plasma flow 2
Medical Complications of Hyperglycemia • Retinopathy, nephropathy, neuropathy • Cardiovascular disorders • Infections, cataracts, connective tissue disorders 3
Two Mechanisms of Tissue Injury by Hyperglycemia Hyperglycemia Glycation pathway Sorbitol pathway Advanced glycation end products (AGEs) Glycated proteins (eg, A1C) Sorbitol and fructose Altered function or turnover Receptor-mediated cytokine effects Osmotic effects Oxidative effects Brownlee M. Metabolism. 2000;49(suppl 1):9-13; Greene DA et al. N Engl J Med. 1987;316:599-606; Sheetz MJ, King GL. JAMA. 2002;288:2579-2588 4