MB

Insulin Resistance and Type 2 Diabetes

Lecture Overview

  • Lecture 8: Insulin Resistance and Type 2 Diabetes

    • Course: KHPM324 Chronic Diseases of Modern Society

    • Lecturer: Hannah Oh, ScD

    • Institution: Division of Health Policy & Management, College of Health Sciences, Korea University

Understanding Diabetes

  • Definition of Diabetes

    • A metabolic disorder characterized by the inability of the pancreas to make insulin or the body's ineffective use of insulin.

    • Insulin:

    • A hormone produced by the pancreas that facilitates the entry of glucose from the bloodstream into the body's cells for energy utilization.

    • Insufficient insulin production or ineffective usage leads to elevated glucose levels in the blood, which, over time, can damage the body and cause failure of various organs.

Types of Diabetes

Type 1 Diabetes

  • Characteristics:

    • Rapid onset of symptoms.

    • Requires insulin therapy for survival.

Type 2 Diabetes

  • Prevalence:

    • Accounts for at least 90% of all diabetes cases.

  • Age of Onset:

    • Can occur at any age but is often adult-onset.

  • Pathophysiology:

    • Characterized by insulin resistance and/or relative insulin deficiency.

    • Often associated with overweight or obesity.

    • Initially manageable through non-pharmacological means like exercise and diet; however, most individuals eventually require oral medications or insulin.

Normal Body Function in Glucose Metabolism

  • Process:

    1. Food is digested and broken down into blood sugar.

    2. Blood sugar enters the bloodstream, signaling the pancreas to release insulin.

    3. Insulin facilitates the uptake of blood sugar by cells for energy.

    4. Insulin prompts the liver to store excess blood sugar for later use.

    5. As blood sugar levels decrease in the bloodstream, insulin levels are also reduced.

    6. Lower insulin levels signal the liver to release stored blood sugar, ensuring energy availability even during periods of fasting.

Insulin Resistance Mechanism

  • Process:

    1. A higher amount of blood sugar accumulates in the bloodstream.

    2. The pancreas produces more insulin to help the cells absorb blood sugar.

    3. Over time, cells become less responsive to insulin, causing insulin resistance.

    4. The pancreas continues to produce insulin in an attempt to overcome the resistance.

    5. Eventually, the pancreas can no longer sustain insulin production, leading to rising blood sugar levels and setting the stage for prediabetes or diabetes.

Consequences of Insulin Resistance

  • Health Implications:

    • Persistent high glucose levels in the blood can lead to various health problems including hunger, cravings, and potential damage to organs over time.

    • Increased insulin demand can result in cells being deprived of energy despite elevated insulin levels.

Symptoms and Diagnosis of Type 2 Diabetes

  • Symptomatic Pathway:

    1. Consumption of carbohydrates leads to glucose entering the bloodstream.

    2. The pancreas may either not release enough insulin, or the body may resist insulin’s effects.

    3. Excess glucose builds up in the blood.

    4. The body attempts to eliminate excess glucose, resulting in frequent urination and other symptoms.

    5. Common symptoms include weight loss, tiredness, and excessive thirst.

Diabetic Complications

  • Diabetic Retinopathy:

    • A condition where tiny blood vessels leak fluid into the retina, compromising vision.

Diagnosis Criteria for Diabetes

  • Testing Methods:

    • Fasting Plasma Glucose Test (FPG):

    • Normal: <100 mg/dL

    • Pre-diabetes: 100-125 mg/dL

    • Diabetes: ≥126 mg/dL

    • 2-Hour Oral Glucose Tolerance Test (OGTT):

    • Normal: <140 mg/dL

    • Pre-diabetes: 140-199 mg/dL

    • Diabetes: ≥200 mg/dL

    • A1C Test:

    • Average blood glucose over the past 3 months.

    • Pre-diabetes: HbA1c 5.7-6.4%

    • Diabetes: HbA1c ≥ 6.5%

Risk Factors for Insulin Resistance

  • Major Risk Factors:

    • Obesity (especially abdominal and visceral fat).

    • High sugar and processed foods diet.

    • Physical inactivity.

    • Chronic inflammation.

    • Poor sleep habits and conditions like sleep apnea.

    • Genetic predisposition.

Obesity and Diabetes Correlation

  • Studies:

    • Chan et al. 1994 and Colditz et al. 1995 emphasize obesity as the single most important risk factor for diabetes.

Impact of Physical Activity

  • Diabetes Risk:

    • Physical activity significantly reduces diabetes risk, with changes in activity levels reflecting percentage changes in diabetes risk.

    • Different activities have varying impact based on duration and intensity.

Dietary Implications for Type 2 Diabetes Management

  • Diet Influence:

    • Direct correlation between diet, obesity, insulin resistance, and type 2 diabetes.

Glycemic Index (GI)

  • Definition:

    • A numerical value assigned to carbohydrate-containing foods based on how quickly they raise blood glucose levels.

  • Low GI Foods:

    • Release glucose slowly, aiding in good glucose control for individuals with diabetes.

  • High GI Foods:

    • Release glucose rapidly; beneficial for energy recovery post-exercise or addressing hypoglycemia.

Glycemic Load (GL)

  • Formula:

    • Glycemic Load (GL) = GI × (Carbohydrate (g) content per serving) / 100.

  • Significance:

    • Combines both the quantity and quality of carbohydrates.

    • Example: Watermelon has a high GI (80) but a low GL (5) due to its low carbohydrate content.

Relative Risk in Diet and Type 2 Diabetes

  • Various dietary factors correlate to relative risk for developing type 2 diabetes, showing significant trends based on quintile intakes of certain nutrients.

Sugar-Sweetened Beverage Consumption

  • Impact:

    • Sugar-sweetened soft drink consumption is associated with increased risk for developing type 2 diabetes, observed with significant trends in reported studies.

Type 2 Diabetes in Asia

  • Phenomenon:

    • Asians may develop diabetes at a lower BMI due to the “metabolically obese” phenotype.

    • This results from a combination of rapid nutritional transition and genetic factors that influence metabolic efficiency.

Complications Arising from Diabetes

  • Serious health risks associated with diabetes include:

    • Kidney disease

    • Increased risks for heart disease, stroke, and cancer

    • Nerve damage and impaired circulation

    • Weakened immune system

    • Inflammation and mortality risk

Treatment Options for Diabetes

  • Insulin Therapy

    • Crucial for managing Type 1 diabetes.

  • Metformin

    • Most commonly prescribed medication for Type 2 diabetes, lowers blood sugar levels.

  • Alternative Medications

    • SGLT2 inhibitors (which reduce renal glucose reabsorption) and weight loss medications.

  • Lifestyle Changes

    • Emphasis on healthy eating and regular exercise as vital components in managing diabetes.