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Obesity, Metabolic Syndrome, and Type 2 Diabetes

Lecture Overview

  • Title: Lecture 10: Obesity, metabolic syndrome, and type 2 diabetes

  • Course: KHPM324 Chronic Diseases of Modern Society

  • Instructor: Hannah Oh, ScD, Division of Health Policy & Management, College of Health Sciences, Korea University

Announcements

  • Reading Assignment #2: Due by midnight on 10/14 (Wednesday)

  • No Class: On 10/6 and 10/8 due to National Holiday

    • Recorded lecture video (part I CVD review) will be posted on the course website

    • Attendance will be recorded via view history

  • Deadline for other assignments: Friday 10/17

Midterm Exam Information

  • Date and Time: 10/22, 1:30 PM - 2:45 PM (in-person)

  • Coverage: Introduction, Part 1, and Part 2 of the course content

  • Study Guide: Will be posted on the course website

  • Exam Format:

    • Multiple-choice

    • True/False

    • Short answer questions

  • Location: Room B128

Insulin

  • Definition: A hormone made by the pancreas that facilitates the entry of glucose from the blood into body cells for energy utilization.

  • Consequences of Deficiency: Inability to produce insulin or effectively utilize it results in elevated blood glucose levels.

  • Functions:

    • Signals the liver, muscle, and fat cells to absorb glucose from the blood.

  • Regulatory Mechanism:

    • Lower insulin levels prompt the liver to release stored glucose (gluconeogenesis) to maintain energy availability.

Normal Insulin Action

  • Mechanism of Action:

    • Liver: Takes up glucose, converting it to glycogen for storage (glycogen synthesis).

    • Fat Cells:

    • Absorb glucose to be stored as triglycerides.

    • Inhibit fat breakdown.

    • Glucose Utilization: Promotes glucose uptake for energy.

  • Energy Availability: When insulin levels drop, the liver releases glucose to ensure energy supply is consistent.

Insulin Resistance

  • Process:

    1. Increased blood sugar levels enter the bloodstream.

    2. Pancreas produces more insulin to facilitate glucose uptake.

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

    4. Pancreas compensates by increasing insulin production.

    5. Eventually, the pancreas fails to keep up with demand; insulin production decreases, and blood sugar levels continue to rise, leading to prediabetes or diabetes.

Metabolic Syndrome

  • Definition: A combination of metabolic disorders, characterized by:

    • Dyslipidemia

    • Obesity

    • Glucose intolerance

    • Hypertension

  • Prevalence: Significantly more common in patients with cardiovascular diseases and type 2 diabetes.

  • Body Composition: Notable for distinctive body type, particularly increased abdominal circumference.

Diagnosis of Metabolic Syndrome

  • Criteria:

    • Insulin resistance is a primary indicator.

    • There is a consensus that excess adiposity, especially central obesity, is a pivotal factor in metabolic syndrome, despite ongoing debates regarding exact definitions.

Risk Factors for Coronary Heart Disease (CHD)

  • Links: Metabolic syndrome correlates with an increased risk of CHD.

  • Adjust Hazard Ratio Findings (Ballantyne et al. 2008):

    • Women: 0.7

    • Men: 1

    • Additional increases in risk for each additional component of metabolic syndrome:

    • 2: 3

    • 3: 4

    • 4+: Further increased risk.

Components of Metabolic Syndrome and Diabetes Risk

  • Risk Components:

    • High LDL cholesterol

    • Central obesity

    • High triglycerides (TG), low HDL

    • High blood pressure

    • Elevated blood glucose levels

  • Associations: Metabolic syndrome and type 2 diabetes linked to an increase in CHD risk.

Adipose Tissue as an Endocrine Organ

  • Functions and Dysfunctions:

    • Increased Factors:

    • Lipoprotein lipase

    • Inflammation indicators (e.g., Interleukin-6)

    • Angiotensinogen

    • Various proteins (C-reactive protein, tumor necrosis factor-alpha, adipsin, resistin, leptin)

    • Free fatty acids (FFA)

    • Lactate

    • Decreased Factors:

    • Adiponectin

  • Consequences of Imbalance: Contributes to complications like hypertension, atherosclerosis, thrombosis, and insulin resistance.

Abdominal vs. Overall Obesity

  • Research Findings (Wang et al. AJCN 2005):

    • High waist circumference (WC) is a significant risk factor for type 2 diabetes (Relative Risk [RR] = 20.4), more pronounced than Body Mass Index (BMI) (RR = 16.5).

    • Notable that fat distribution plays a crucial role in health outcomes.

  • Metrics of Risk: Relation of baseline waist circumference (WC), waist-to-hip ratio (WHR), and BMI deciles to type 2 diabetes risk.

Joint Effects of Obesity on Diabetes Risk

  • Study Insights (Wang et al. AJCN 2005):

    • Both BMI and WC (or WHR) serve as independent predictors of type 2 diabetes risk.

BMI vs. Physical Activity

  • Analysis of Diabetes Risk:

    • Multivariable Relative Risk (RR) of type 2 diabetes is influenced by categories of BMI and levels of physical activity.

    • Obesity and lack of physical activity both contribute to diabetes development, but the influence of obesity is significantly greater.

    • Increasing physical activity proves beneficial for diabetes prevention, but cannot fully mitigate the negative impacts of obesity.

  • Citing Study (Rana et al. 2007): Emphasizes the importance of considering both BMI and physical activity in diabetes prevention strategies.

Summary

  • Core Insights:

    • Excess adiposity, particularly central obesity, is the fundamental cause of metabolic syndrome and type 2 diabetes.

    • Insulin resistance is a widely accepted unifying mechanism for obesity-related metabolic disorders, with inflammation instigated by adipose tissue also playing a significant role in the onset of insulin resistance and subsequent metabolic disturbances.

    • Relationship Sequence: Obesity → Inflammation → Insulin Resistance → Diabetes.

  • Measurement Importance:

    • Both BMI and fat distribution (i.e., waist circumference) are critical metrics for predicting various metabolic disorders.

    • Certain ethnic groups, notably Asians, demonstrate heightened vulnerability to the detrimental effects of excess body fat.