Type 1 vs Type 2

Types of Diabetes Mellitus

• Two clinically distinct forms were emphasized.

  • Type 1 ("juvenile" / autoimmune) diabetes

  • Immune system destroys the pancreatic β-cells that synthesize insulin.

  • Result ⇒ complete absence of endogenous insulin.

  • Patients are totally dependent on exogenous insulin therapy for survival.

  • Type 2 (insulin-resistant) diabetes

  • Pancreas continues to secrete insulin, but target cells fail to respond.

  • Primary mechanism mentioned ⇒ ↓ number or functionality of insulin receptors on the cell membrane.

    • Speaker’s own experiments: high-stress situations correlate with a measurable loss of surface insulin receptors.

  • Despite differing etiology from Type 1, the downstream metabolic consequences mirror those of absolute insulin deficiency.

Shared Pathophysiological Endpoint

• Whether insulin is absent (Type 1) or ineffective (Type 2), the body acts as if insulin is not present at all.

• The core defect ⇒ inability to move glucose from blood into insulin-dependent tissues.

Immediate Metabolic Result: Hyperglycemia

• Definition: sustained elevation of blood glucose.

• Marked on diagram in yellow by the lecturer.

• Represents the starting point for a cascade of signs & symptoms.

Clinical Manifestations & Mechanistic Links

• Polyphagia (excessive hunger)

  • Even with abundant circulating glucose, cells are starving for usable fuel.

  • CNS interprets this intracellular energy deficit as "hungry" → stimulates appetite.

  • Eating episodes further spike plasma glucose, aggravating hyperglycemia.

• Enhanced Risk of Infection

  • Elevated glucose diffuses into interstitial fluid → nutrient-rich medium for bacteria.

  • Frequently compounded by:

  • Poor peripheral blood flow → sluggish delivery of immune cells.

  • Diabetic neuropathy → diminished pain perception; infections go unnoticed until severe.

  • Clinical endpoint may include chronic ulcers and limb amputations (toes, feet, legs).

• Renal Glucosuria

  • Kidneys normally reclaim filtered glucose via carrier-mediated transport.

  • At high loads, carriers become saturated ("transport maximum" concept from earlier lectures).

  • Excess glucose remains in the filtrate → appears in urine.

• Polyuria (excessive urination)

  • Glucose in tubular fluid acts osmotically; water follows to maintain solution balance.

  • Large obligatory water loss accompanies glucosuria.

• Polydipsia (excessive thirst)

  • Water depletion → plasma osmolarity rises → hypothalamic thirst centers activated.

  • Patients drink copiously to compensate for urinary water loss.

Earlier Course Concepts Reinforced

• Saturation Kinetics

  • Reabsorption of substances in the nephron obeys carrier-limited transport.

  • When $[Glucose]<em>{filtrate} \gg T</em>{max}$, reabsorption plateaus and spillover occurs.

• Osmosis

  • Water movement is dictated by solute gradients; hence water "follows" unreclaimed glucose in the nephron.

Practical / Real-World Considerations

• Glucose monitoring and receptor sensitivity are both critical therapeutic targets.

• Prompt treatment of minor skin injuries is essential in diabetics to prevent limb-threatening infections.

• Stress management may indirectly influence insulin receptor density in Type 2 patients (per lecturer’s experimental findings).

Ethical & Public-Health Angle

• Awareness campaigns often focus on Type 2, but recognizing Type 1’s autoimmune nature prevents stigmatizing patients for "lifestyle" causes.

• Limb amputation prevalence underscores socioeconomic and quality-of-life implications of inadequate diabetes control.