Medical Student Research Fellowship for Summer 2010

Mentor: Vincent Aguirre
Department: Internal Medicine
Room number: K5.140C
Mail Code: 9151
Phone number: 8-0201
E-mail: Vincent.aguirre@utsouthwestern.edu
Project title: The effect of gastric bypass in mice on peripheral insulin signaling

Animal subjects IRB approved project number (where applicable): APN 2009-0062

Project Type animal-based research

Brief Description of Project: Gastric bypass is the most efficacious and durable treatment for severe obesity. Due to its associated risk and cost, however, it is only available to the severely obese. Less-invasive therapies are needed for the large population of patients at risk for obesity-related disease who do not meet the current weight criteria for bariatric surgery. The Aguirre lab has developed a model of Roux-en-Y gastric bypass (RYGB) in mice. RYGB in mice with diet-induced obesity and diabetes induces substantial and sustained weight loss. RYGB also improves fasting glycemia, glucose tolerance, and insulin tolerance. To investigate the mechanisms underlying the effect of RYGB on peripheral insulin action, Stephen will evaluate insulin-signaling in the liver and skeletal muscle of insulin-stimulated mice after RYGB. He will do so by performing western blot analysis using liver and skeletal muscle extracts from insulin-stimulated, RYGB and sham-treated mice. After SDS-PAGE using whole cell lysate, he will perform immunoblot analysis using well-characterized phospho-specific antibodies that recognize activated forms of key regulatory molecules in the insulin signaling pathway, including the b-subunit of the insulin receptor, IRS family members, and AKT. Gel-loading will be controlled using total protein analysis (colorimetric) and immunoblot analysis with polyclonal anti-sera to the entire molecule of interest (non-phospho-specific). Data will be detected and quantified by densitometry. This experiment will directly address the impact of RYGB on components of the insulin-signaling pathway in its effect on peripheral insulin action. Stephen will perform this work in its entirety under the direct supervision of my technician, Juliet Fong, and myself. If times allows, Stephen will also quantify glycogen in the same samples as a physiologic assay of insulin action in these peripheral tissues after RYGB. This will be performed by acid precipitation and colorimetric analysis, controlled as amount of tissue subjected to extraction. Data will be quantified and normalized to tissue mass.

Previous Research Activities or Publications with Medical Students:
Jason Cano spent last summer in my laboratory when he quantified enteroendocrine (EE) cell number in ileal sections obtained from rats after ileal transposition and RYGB - two animal surgical models with profound effects on measures of diabetes. He did so by immunoflourescent analysis on paraffin sections with anti-serum specific for peptide Y-Y, a secreted product from EE cells. Consistent with the increase in incretin levels (secreted products from EE cells) we see after these procedures, Jason found a statistically significant increase in EE cell number after RYGB and ileal transposition. This data has been incorporated in a manuscript currently in preparation.