Increases in insulin sensitivity among obese youth are associated with gene expression changes in whole blood.

OBJECTIVE: Lifestyle intervention can improve insulin sensitivity in obese youth, yet few studies have examined the molecular signatures associated with these improvements. Therefore, the purpose of this study was to explore gene expression changes in whole blood that are associated with intervention-induced improvements in insulin sensitivity. METHODS: Fifteen (7M/8F) overweight/obese (BMI percentile = 96.3 ± 1.1) Latino adolescents (15.0 ± 0.9 years) completed a 12-week lifestyle intervention that included weekly nutrition education and 180 minutes of moderate-vigorous exercise per week. Insulin sensitivity was estimated by an oral glucose tolerance test and the Matsuda Index. Global microarray analysis profiling from whole blood was performed to examine changes in gene expression and to explore biological pathways that were significantly changed in response to the intervention. RESULTS: A total of 1,459 probes corresponding to mRNA transcripts (717 up, 742 down) were differentially expressed with a fold change ≥1.2. These genes were mapped within eight significant pathways identified, including insulin signaling, type 1 diabetes, and glycerophospholipid metabolism. Participants with increased insulin sensitivity exhibited five times the number of significant genes altered compared with nonresponders (1,144 vs. 230). CONCLUSIONS: These findings suggest that molecular signatures from whole blood are associated with lifestyle-induced health improvements among high-risk Latino youth.

Identification of a role for CLASP2 in insulin action.

Insulin stimulates the mobilization of glucose transporter 4 (GLUT4) storage vesicles to the plasma membrane, resulting in an influx of glucose into target tissues such as muscle and fat. We present evidence that CLIP-associating protein 2 (CLASP2), a protein previously unassociated with insulin action, is responsive to insulin stimulation. Using mass spectrometry-based protein identification combined with phosphoantibody immunoprecipitation in L6 myotubes, we detected a 4.8-fold increase of CLASP2 in the anti-phosphoserine immunoprecipitates upon insulin stimulation. Western blotting of CLASP2 immunoprecipitates with the phosphoantibody confirmed the finding that CLASP2 undergoes insulin-stimulated phosphorylation, and a number of novel phosphorylation sites were identified. Confocal imaging of L6 myotubes revealed that CLASP2 colocalizes with GLUT4 at the plasma membrane within areas of insulin-mediated cortical actin remodeling. CLASP2 is responsible for directing the distal end of microtubules to the cell cortex, and it has been shown that GLUT4 travels along microtubule tracks. In support of the concept that CLASP2 plays a role in the trafficking of GLUT4 at the cell periphery, CLASP2 knockdown by siRNA in L6 myotubes interfered with insulin-stimulated GLUT4 localization to the plasma membrane. Furthermore, siRNA mediated knockdown of CLASP2 in 3T3-L1 adipocytes inhibited insulin-stimulated glucose transport. We therefore propose a new model for CLASP2 in insulin action, where CLASP2 directs the delivery of GLUT4 to cell cortex landing zones important for insulin action.