INTRAMUSCULAR TRIGLYCERIDE TURNOVER AND INSULIN SENSITIVITY

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Our overall objective is to elucidate the relationship between intramuscular triglyceride (IMTG) turnover and insulin sensitivity during rest, exercise, and recovery. We are proposing to study insulin sensitive (endurance trained athletes) and insensitive individuals (Type II diabetics). We aim to better understand the paradox where high concentrations of IMTG are negatively associated with insulin sensitivity in Type II diabetes, yet positively associated with insulin sensitivity in endurance athletes. This study will also address potential differences in IMTG utilization between genders, and determine if IMTG is an important fuel source during exercise in trained individuals. We hypothesize IMTG turnover and utilization will be increased in athletes compared to Type II diabetics at rest, during, and after exercise. We postulate that increased IMTG turnover protects against the decreased insulin action commonly observed with increased IMTG stores in Type II diabetics. To evaluate our hypothesis we will recruit men and women who are either endurance trained athletes or Type II diabetics. Insulin action will first be determined via a frequently sampled intravenous glucose tolerance test. Subjects will then perform one metabolic study with an infusion of a stable isotope of palmitate and muscle biopsies during rest, 1.5 hours of exercise at 50% VO2max, and then during 2 hours of recovery. IMTG turnover will then be calculated using fractional incorporation rates of tracer into the IMTG pool.