Insulin action in black Americans with NIDDM

Area of Science:

• Endocrinology
• Metabolic Diseases
• Clinical Research

Background:

• Non-insulin-dependent diabetes mellitus (NIDDM) is a complex metabolic disorder.
• Understanding factors influencing insulin action is crucial for managing NIDDM, particularly in diverse populations.
• Obesity and hyperglycemia are known contributors to insulin resistance.

Purpose of the Study:

• To investigate the impact of obesity and hyperglycemia on insulin action in black patients with NIDDM.
• To explore the relationship between Body Mass Index (BMI) and insulin sensitivity/resistance in this population.
• To determine how acute hyperglycemia affects insulin action in NIDDM patients with varying obesity levels.

Main Methods:

• Euglycemic insulin clamp technique with D-[3-3H]glucose infusion to assess insulin action.
• Measurement of Body Mass Index (BMI) to quantify obesity.
• Study of 39 black NIDDM patients with normal glycemic control initially.
• Re-evaluation of insulin action in 9 patients who developed hyperglycemia.

Main Results:

• Insulin sensitivity was linked to BMI extremes: 87.5% of lean patients (BMI < 24.0 kg/m2) were insulin sensitive, while 88.9% of obese patients (BMI > 28.5 kg/m2) were insulin resistant.
• A bimodal distribution of insulin action was observed in the midrange BMI group, with approximately 50% insulin sensitive and 50% insulin resistant.
• Hyperglycemia decreased insulin action in insulin-sensitive patients, independent of obesity, but did not affect insulin-resistant patients.

Conclusions:

• Approximately 50% of black NIDDM patients exhibit insulin resistance.
• The relationship between obesity and insulin resistance in this group is complex and not linear.
• Two hypotheses are proposed: either insulin resistance is acquired and modulated by hyperglycemia, or NIDDM presents as variants with primary insulin resistance or normal sensitivity.