Principles of Human Physiology: Diabetes Mellitus
Principles of Human Physiology: Chapter 24a - Diabetes Mellitus
Chapter Outline
- 24.1 Classification of Diabetes Mellitus
- 24.2 Acute Effects of Diabetes Mellitus
Learning Outcomes
- Identify the different causes of type 1 and type 2 diabetes.
- Describe the initial manifestations of diabetes mellitus.
- Identify the causes and effects of ketoacidosis.
- Describe the different mechanisms through which diabetes may lead to a coma.
Classification of Diabetes Mellitus
- Type 2 Diabetes Mellitus (Type 2 DM)
- Definition: Target cells have a decreased response to insulin.
- Other Names:
- Insulin-independent diabetes mellitus (IIDM)
- Non-insulin-dependent diabetes mellitus (NIDDM)
- Adult-onset diabetes mellitus
- Prevalence: Accounts for 90-95% of diabetes cases in the United States.
Effects of Diabetes on Organs Throughout the Body
- Brain: lethargy, coma
- Eye: retinopathy
- Heart: cardiomyopathy
- Kidneys: nephropathy, proteinuria, polyuria
- Gastrointestinal Tract: polyphagia
- Gonads: impotency
- Blood Vessels: microvascular damage, macrovascular damage, atherosclerosis
- Peripheral Nerves: neuropathy
- Feet: foot ulcers
Comparison of Type 1 and Type 2 Diabetes Mellitus
| Feature | Type 1 Diabetes Mellitus | Type 2 Diabetes Mellitus |
|---|---|---|
| Prevalence | 5%-10% | 90%-95% |
| Previous Nomenclature | Insulin-dependent diabetes mellitus (IDDM), Juvenile-onset diabetes mellitus | Insulin-independent diabetes mellitus (IIDM), Adult-onset diabetes mellitus, Non-insulin-dependent diabetes mellitus (NIDDM) |
| Pathology | Autoimmune disease of pancreatic beta cells causing insufficient release of insulin into blood | Tissue resistance to insulin |
| Age of Onset | Adolescence to young adulthood | Adulthood, but occurrence in children is increasing |
| Clinical Diagnostics | Decreased blood insulin, elevated blood glucose, impaired glucose tolerance, elevated hemoglobin A1c, presence of antibodies to beta cell components | Normal or elevated blood insulin (may decrease as the disease progresses), elevated blood glucose, impaired glucose tolerance, elevated hemoglobin A1c, no antibodies to beta cells |
| Familial | 30%-50% concordance in identical twins, family history in 10% | 60%-80% concordance in identical twins, family history in more than 50% |
| Complications | Hyperglycemia leading to increased glycosylation of proteins, ketoacidosis is common | Hyperglycemia leading to increased glycosylation of proteins, ketoacidosis is rare |
| Management | Insulin is mandatory in all cases, diet, exercise | Insulin is used occasionally, diet, exercise |
Diabetic Ketoacidosis
- Common Complication of Type 1 DM
- Mechanism: Glucose is unavailable to cells due to lack of insulin.
- Consequences:
- Lipolysis occurs; oxidation results in liver production of ketones.
- Increased levels of ketones in blood.
Delayed Wound Healing Related to Diabetes
- Overview: The process of wound healing can be impaired in diabetes mellitus.
Phases of Wound Healing
Phase 1: Inflammation
- Stimuli: Inflammatory process stimulated by macrophages.
- Processes: Secretion of additional cytokines and growth factors.
- Fibroblast Activity: Basic fibroblast growth factor attracts fibroblasts.
Phase 2: Tissue Formation
- Process: Involves the formation of new functional tissue and repair mechanisms.
Phase 3: Remodeling
- Process: Fibroblasts lay down organized collagen, cells fill in the wound area.
Problems Associated with Diabetes in Wound Healing
- Loss of Erythrocyte Flexibility: Decreases oxygen delivery which prolongs remodeling phase.
- Decreased Secretion of Messengers: Lower levels of cytokines and growth factors leading to decreased collagen production by fibroblasts.
Diabetic Foot Ulcers
- Commonality: Diabetic foot ulcers are prevalent in diabetics due to neuropathy resulting in less pain sensation.
- Complications: Can progress leading to serious consequences, including leg amputation.
- Statistics: 84% of leg amputations originated from foot ulcers.