Acute Exercise Bout Effects on GH and IGF1 in Prediabetic and Healthy African Americans

The incidence of pre-diabetes (PD) and Type-2 Diabetes Mellitus (T2D) is a worldwide epidemic. African American (AA) individuals are disproportionately more likely to become diabetic than other ethnic groups. Over the long-term, metabolic complications related to diabetes result in significant alterations in growth hormone (GH) and insulin-like growth factor-1 (IGF-1). Considering the limited exercise-related studies in the area of gene expression changes with disease progression, the objective of this study was to examine differences in exercise-induced gene expression related to the GH and IGF-1 pathways in peripheral blood mononuclear cells (PBMCs) of healthy (CON) and PD AA individuals. Design: Ten subjects [5 PD (age=35±9.3 yr, BMI=32.1±4.0, FBG=101.8±1.3 mg/dl) and 5 CON (age=31±9.4 yr, BMI=29.4±5.2, FBG=82.8±9.7 mg/dl)] had blood drawn for RNA isolation prior to exercise (Pre), immediately following acute moderate intensity exercise on a treadmill (Post-1), 6-hours post (Post-6), and 24-hours post (Post-24). Isolation of mRNA from PBMCs was performed using ficoll separation, while the profiling of mRNA expression was performed using beadchip arrays that were scanned and analyzed by a gene expression module. Scan results were statistically analyzed for a specific list of genes related to GH and IGF-1. GH and IGF-1 protein levels were also assessed in each sample. To address issues of normality, all GH and IGF-1 data were log-transformed prior to analysis. Statistical significance was set at p<0.05. Results: Group differences for GH2 variant 2 (p=0.070) and GH2 variant 3 (p=0.059) were coupled with significant alterations in IGF-1 mRNA over time (p=0.024). A significant interaction between group and time was observed for GHRH mRNA (p=0.008). No group differences were observed in GH AUC (p=0.649), ∆GH (p=0.331), GHrec (p=0.294), or IGF-1 AUC (p=0.865), representing a similar exercise-induced GH and IGF-1 response for both groups. Conclusions: Analysis of GH and IGF-1 related-gene expression indicates that mild elevations in fasting blood glucose and exercise-induced alterations in gene expression are impacted by the prediabetic state.