Ghrelin as a Potential Biomarker for Obesity in African-American Adolescents
Obesity has become a global epidemic. The literature confirms that obesity results from various environmental factors superimposed on a genetic background. There are current interventions in place; however, they have not proven to be as effective as speculated. Exploring molecular pathways involved in energy metabolism could lead to the identification of novel therapies and biomarkers for obesity. Ghrelin is a novel orexigenic hormone that plays pivotal roles in a number of biologically important processes, including food consumption and long-term energy balance. Ghrelin is a gastric hormone that is increased during states of negative energy balance and decreased in states of positive energy balance. Leptin, which antagonizes orexigenic peptides like ghrelin, is an adipocyte-specific hormone that suppresses appetite. The level of serum leptin correlates with body fat mass. Targeting this and other physiological markers could unveil the molecular mechanisms involved in the development of obesity. The purpose of this study was to determine the serum ghrelin concentration of obese African-American adolescents with a family history of diabetes in a parent or grandparent. This study also aimed to identify the possible relationship of ghrelin, leptin, and insulin during a glucose tolerance test on obese African-American adolescents.
The plasma ghrelin concentration was measured using commercially available radioimmunoassay kits to identify the concentration of both total and active ghrelin. Total ghrelin is predominantly found in circulation. This study focuses on identifying total ghrelin concentration in both obese and non-obese African-American adolescents. The average plasma ghrelin concentration was higher in non-obese African-American adolescents (223 ± 17.6 pM) and lower in obese African-American adolescents (181 ± 17 pM). When ghrelin concentration was compared to BMI, individuals with higher BMIs were found to have lower concentrations of ghrelin in a fasted state. During a glucose tolerance test, the plasma ghrelin concentration varied from patient to patient. However, there was an overall decrease in plasma ghrelin during the glucose tolerance test on obese African-American adolescents.
Total ghrelin concentration was then compared to leptin and insulin data collected during a previous study on vitamin-D deficiency and insulin resistance. When comparing the data, ghrelin exhibited a negative relationship with both insulin (r= -0.71) and leptin (r= -0.56) during a glucose tolerance test. Therefore, high levels of insulin are associated with lower levels of ghrelin and high levels of ghrelin are associated with lower levels of leptin. Interestingly, in comparing these three hormones, we found that both leptin and ghrelin exhibited little change during the glucose tolerance test. These findings suggest that obese adolescents in this study have developed a resistance to the action of both ghrelin and leptin. These findings add to the current understanding of various hormones involved in obesity and create potential avenues to explore in both obesity and diabetes research.
0307: Molecular biology
0325: Black studies