Research Interests

Synoposis:
Insulin Resistance; Obesity; Diabetes; Cardiovascular disease.
Description:
The primary focus of my research is to enhance our understanding of the relationship between obesity and insulin resistance and subsequent Type 2 diabetes. Towards this goal, my research efforts have included studies aimed at examining the effects of diet-induced obesity in animal models and of recent, determining mechanisms that may predispose African Americans to diabetes.

Endocannabinoid system, obesity and insulin resistance: The endocannabinoid system (ECS) has garnered a great deal of attention as a potential therapeutic target in combating obesity as well as its associated metabolic abnormalities. We have demonstrated that chronic blockade of the ECS with a receptor antagonist corrects the deleterious effects of diet-induced obesity by restoring insulin sensitivity and normalizing fat cell size. These findings were found to be in part, independent of its suppressive actions on food intake. Taken together, these data warrant further investigation into the role of the ECS and obesity-associated abnormalities, strongly suggesting that chronic endocannabinoid activation may contribute to obesity and the sequela of its associated diseases. Thus, our findings have led us to hypothesize that dysregulation of the ECS, manifested as overactivation, may serve as a critical link between obesity and its co-morbidities.

Ethnic differences in the pathogenesis of diabetes: African Americans have a high prevalence of Type 2 diabetes and cardiovascular disease compared to their white counterparts. Traditionally, certain metabolic risk factors are included in the development of these two disease processes, such as obesity, in particular increased visceral or central adiposity, elevated fasting free fatty acids (FFA) and decreased HDL-cholesterol. While African Americans may exhibit a high prevalence of obesity, their central fat mass has been shown to be lower, including lower fasting FFA and higher HDL cholesterol Hence, different mechanisms are operative in the pathogenesis of insulin resistance and subsequent Type 2 diabetes and cardiovascular disease in AA than other ethnic groups. We aim to examine nighttime alterations in key metabolic determinants of insulin sensitivity that may predispose African Americans to be disproportionately affected by cardio-metabolic diseases.

HISTORY & EDUCATION

Degrees
  • Wayne State University, PHD, 1991

PUBLICATIONS

  • Bergman RN, Kim SP, Ellmerer M, Hucking K, Getty L, Kabir M, Ionut V, Richey J, Mittelman S, Van Citters G and Ader M. Physiological basis of the metabolic syndrome. In: Progress in Obesity Research. Medeiro-Netos G, Halpern A and Bouchard C. (eds.), John Libbey Eurotext Ltd, 2003, 653-656.
  • Richey JM, Kabir M, Woolcott OO, Kim SP, Harrison LN, Stefanovski D, Hsu IR, Zheng D, Lottati M, Kolka C, Ionut V, Catalano KJ, Chiu JD and RN Bergman. Insulin sensitivity and visceral adiposity: effects of rimonabant. In: Despres JP & Di Marzo V. Abdominal obesity and the endocannabinoid system: from basic aspects to clinical management of cardiometabolic risk. New York, Informa Healthcare USA Inc. 2009; 81-88.
  • Richey JM, Woolcott OO, Stefanovski D, Harrison LN, Zheng D, Lottati M, Hsu IR, Kim SP, Kabir M, Catalano KJ, Chiu JD, Ionut V, Kolka C, Mooradian V and RN Bergman. Rimonabant prevents additional accumulation of visceral and abdominal subcutaneous fat induced by high-fat diet in dogs. Am J Physiol Endocrinol Metab. 2009; 296:E1311-1318.
  • Spruijt-Metz D, Belcher B, Anderson D, Lane CJ, Chou C-P, Salter D, Davis JN, Hsu YW, Neuhouser ML, Richey JM, McKenzie T L, Goran MI and Weigensberg M. A high-sugar/low-fiber meal compared with a low-sugar/high-fiber meal leads to higher leptin and physical activity in overweight Latina females. J Am Diet Assoc. 2009 Jun;109(6):1058-63. PMCID: PMC2768570
  • Emken, AB, Richey J, Belcher B, Hsu YW and Spruijt-Metz D. Physical activity is negatively associated with adiponectin in minority girls. International Journal of Pediatrics, 2010, Article ID 846070.

Direct link to profile: http://keck.usc.edu/profiles?facid=965