Physiologic and Endocrine Correlates of Overweightness in African Americans and Caucasians

摘要

Obesity has reached epidemic levels and the incidence continues to rise. The current study was seeking to examine the hypothesis that obesity may reflect dysfunctioning of the hypothalamic-pituitary-adrenal (HPA) axis in response to stressors. African American persons are at greatest risk, but reasons for this difference are unknown. We studied 126 healthy men and women of Caucasian (CA) and African American (AA) ethnicity and examined their responses to physiologic stressors: exercise and ingestion of a meal. Methods: The HPA axis was studied by using two stress paradigms and two steroid regimens: hydrocortisone (HCO) and dexamethasone (DEX). We were able to detect subtle differences in HPA axis reactivity in obese individuals that might contribute to morbidity and perhaps even make individuals resistant to therapeutic interventions. Results: AA, particularly those who are obese by percent body fat, are highly sensitive to glucocorticoids. This was noted during exercise under conditions of DEX and in response to a meal, under all conditions but to a greater extent under conditions for DEX. Importantly, AA had significantly lower cardiovascular fitness than CA. Fitness was inversely related to obesity, insulin resistance, and glucocorticoid sensitivity. Lastly, lipid profiles of AA are more favorable that age-matched, healthy CA. Using either triglycerides or HDLcholesterol as indicators of cardiovascular disease would indicate minimal risk. Conclusions: Over the past five years, we achieved all goals for this project. Notably, we enrolled 160 participants and completed testing on 126.