Diabetes Mellitus Overview

Diabetes Mellitus

• Metabolic disease characterized by elevated blood glucose due to defects in insulin secretion, insulin action, or both.

Diabetes Mellitus Classification

• Type 1 (IDDM): 5-10% of all diabetes cases
  • Occurs in childhood and adolescence
  • Abrupt onset
  • Insulin dependence
  • Tendency towards ketosis
  • Absence of insulin with excess glucagon
  • β-Cell destruction leading to absolute insulin deficiency
  • Autoantibodies
• Type 2 (NIDDM): 90% of all diabetes cases
  • Adult onset
  • Insulin resistance with secretory defect
  • Relative insulin deficiency (hyperinsulinemia)
  • Increased with age, obesity, and lack of exercise
  • Glucagon secretion is attenuated
  • Non-insulin dependent
  • Ketosis tendency is rare
  • Higher tendency to develop hyperosmolar states

Diabetes Mellitus Symptoms

• Polydipsia (increased thirst)
• Polyuria (increased urination)
• Polyphagia (increased hunger)

Diabetes Mellitus Laboratory Findings

• Increased glucose in plasma and urine
• Increased urine specific gravity
• Increased serum and urine osmolality
• Ketones in serum and urine (ketonemia and ketonuria)
• Decreased blood pH and urine pH (acidosis)
• Electrolyte imbalance (decreased Na, increased K)

Diabetes Mellitus Diagnostic Criteria

• Random plasma glucose ≥200 mg/dL with symptoms of diabetes
• Fasting plasma glucose ≥126 mg/dL
• 2-hour plasma glucose ≥200 mg/dL during an oral glucose tolerance test (OGTT)

Categories of Fasting Plasma Glucose (FPG)

• Provisional diabetes diagnosis: FPG ≤126 mg/dL
• Impaired fasting glucose: FBG 100-125 mg/dL
• Normal fasting glucose: FBG ≤99 mg/dL

Regulation of Glucose Metabolism

• Insulin (hypoglycemic agent)
  • Primary hormone for decreasing blood glucose
  • Synthesized by β cells in the islets of Langerhans (pancreas)
  • Increases glycogenesis, glycolysis, and lipogenesis; decreases glycogenolysis
• Glucagon (hyperglycemic agent)
  • Primary hormone responsible for increasing blood glucose
  • Synthesized by α cells in the islets of Langerhans (pancreas)
  • Increases glycogenolysis and gluconeogenesis
• Epinephrine
  • Produced by the adrenal medulla; increases blood glucose
  • Released during stress
  • Inhibits insulin secretion; increases glycogenolysis and lipolysis
• Cortisol (glucocorticoids)
  • Produced by the adrenal cortex; increases plasma glucose
  • Decreases intestinal glucose entry into cells; increases gluconeogenesis, glycogenolysis, and lipolysis
• Growth hormone
  • Produced by the anterior pituitary gland; increases plasma glucose
  • Decreases glucose entry into cells; increases glycolysis
• Thyroxine
  • Produced by the thyroid gland; increases plasma glucose
  • Increases glycogenolysis, gluconeogenesis, and glucose intestinal absorption
• Somatostatin
  • Produced by the delta cells of the islets of Langerhans in the pancreas and hypothalamus.
  • Increases plasma glucose by inhibiting insulin, glucagon, growth hormone, etc.

Hyperglycemia

• Increase in plasma glucose leads to insulin secretion by β cells in the pancreatic islets.

Glucose Metabolism

• Glycolysis (Embden-Meyerhof Pathway): Glucose is converted into ATP, lactate, and pyruvate; insulin-dependent
• Gluconeogenesis: Formation of glucose-6-phosphate from non-carbohydrate sources (like fats and proteins); yields glucose and ketone bodies.
• Glycogenolysis: Breakdown of glycogen into glucose for energy; glucagon-dependent
• Glycogenesis: Conversion of glucose into glycogen for storage; insulin-dependent
• Lipogenesis: Conversion of carbohydrates into fatty acids
• Lipolysis: Decomposition of fat

This quiz covers the essentials of Diabetes Mellitus, including its classification into Type 1 and Type 2 diabetes, their onset, symptoms, and underlying mechanisms. Test your knowledge on metabolic diseases and understand the differences between these two common types of diabetes.