diabetes mellitus dr. meg-angela christi amores. diabetes mellitus refers to a group of common...
TRANSCRIPT
Diabetes Mellitus
• refers to a group of common metabolic disorders that share the phenotype of hyperglycemia
• Factors: – reduced insulin secretion– decreased glucose utilization– increased glucose production
Diagnosis
• Criteria for the diagnosis of DM– Symptoms of diabetes plus random blood glucose
concentration > 200 mg/dL– Fasting plasma glucose > 126 mg/dL– Two-hour plasma glucose > 200 mg/dL during an
oral glucose tolerance test
– FPG is the most reliable and convenient test for identifying DM in asymptomatic individuals
Risk Factors for Type 2 DM
• Family history of diabetes (i.e., parent or sibling with type 2 diabetes)
• Obesity (BMI 25 kg/m2) • Habitual physical inactivity Race/ethnicity • Previously identified IFG or IGT • History of GDM or delivery of baby >4 kg (>9 lb) • Hypertension (blood pressure 140/90 mmHg) • HDL cholesterol level <35 mg/dL (0.90 mmol/L) and/or a
triglyceride level >250 mg/dL (2.82 mmol/L) • Polycystic ovary syndrome or acanthosis nigricans • History of vascular disease
Insulin biosynthesis, Secretion, Action
• produced in the beta cells of the pancreatic islets• PREPROINSULIN• PROINSULIN• A or B chains of INSULUN
Secretion
• Glucose is the key regulator of insulin secretion by the pancreatic beta cell
• Glucose levels > 70 mg/dL stimulate insulin synthesis
• transport into the beta cell by the GLUT2 glucose transporter
• phosphorylation by glucokinase – rate-limiting step that controls
glucose-regulated insulin secretion
• metabolism of glucose-6-phosphate via glycolysis generates ATP
• inhibits the activity of an ATP-sensitive K+ channel
• opens voltage-dependent calcium channels
• stimulates insulin secretion
Action
• Once insulin is secreted into the portal venous system, ~50% is degraded by the liver
• Unextracted insulin enters the systemic circulation where it binds to receptors in target sites
• initiate a complex cascade of phosphorylation and dephosphorylation reactions
• resulting in the widespread metabolic and mitogenic effects of insulin
Action
• Glucose homeostasis reflects a balance between hepatic glucose production and peripheral glucose uptake and utilization
• Insulin is the most important regulator of this metabolic equilibrium
Type I DM
• the result of interactions of genetic, environmental, and immunologic factors that ultimately lead to the destruction of the pancreatic beta cells and insulin deficiency
• rate of decline in beta cell mass varies widely among individuals, with some patients progressing rapidly to clinical diabetes and others evolving more slowly
Type I DM
• Features of diabetes do not become evident until a majority of beta cells are destroyed (~80%)
Type II DM
• Insulin resistance and abnormal insulin secretion are central to the development of type 2 DM
• has a strong genetic component• polygenic and multifactorial since in addition
to genetic susceptibility, environmental factors (such as obesity, nutrition, and physical activity) modulate the phenotype
Type II DM
• Obesity, particularly visceral or central (as evidenced by the hip-waist ratio), is very common
• In the early stages of the disorder, glucose tolerance is normal, pancreatic beta cells compensate by increasing insulin output
Approach to patient
• HISTORY– DM-relevant aspects such as weight, family history
of DM and its complications, risk factors for cardiovascular disease, exercise, smoking, and ethanol use
– Symptoms of hyperglycemia:• polyuria, polydipsia, weight loss, fatigue, weakness,
blurry vision, frequent superficial infections (vaginitis, fungal skin infections), and slow healing of skin lesions after minor trauma
– Blurred vision
Approach to patient
• PHYSICAL EXAMINATION– weight or BMI, retinal examination, orthostatic
blood pressure, foot examination, peripheral pulses, and insulin injection sites
– Blood pressure > 130/80 mmHg is considered hypertension
– peripheral neuropathy, calluses, superficial fungal infections, nail disease, ankle reflexes, and foot deformities
Treatment
Overall goals of therapy• (1) eliminate symptoms related to hyperglycemia• (2) reduce or eliminate the long-term microvascular
and macrovascular complications of DM• (3) allow the patient to achieve as normal a lifestyle
as possible
Treatment
• Patient education– nutrition, exercise, care of diabetes during illness,
and medications– fruits, vegetables, fiber-containing foods, and low-
fat milk is advised– Consumption of foods with a low glycemic index– Reduced calorie and nonnutritive sweeteners are
useful