Postprandial Lipid Tracer and Exercise in Spinal Cord Injury

Spinal cord injury (SCI) results in dysregulation of fat metabolism that increases the risk of morbidity and mortality from cardioendocrine disease. Excessive accumulation of visceral fat after SCI is a serious risk component for cardioendocrine disease and results in part from pronounced hypertriglyceridemia following ingestion of fat-containing meals (i.e., exaggerated postprandial lipemia; PPL). Although exaggerated PPL is well documented in persons with SCI, its etiology is unknown. Specifically, it remains to be determined to what extent exaggerated PPL in those with SCI results from impairments in the use of exogenous (dietary) and/or endogenous (stored) fats. Additionally, it is not known if exercise improves postprandial fat use in a manner that alleviates the exaggerated PPL in this population and reduces the risk of cardioendocrine disease. The objective of the this study is to examine the mechanisms of exaggerated PPL in those with SCI and the effects of an acute pre-meal exercise bout by employing novel stable isotope tracer techniques. In persons without SCI, it is well established that pre-meal exercise lowers PPL in part by improving the use of exogenous and endogenous fats. While muscle atrophy and blunted sublesional sympathetic activity following SCI may hinder fat use, preliminary data indicate that fat use is increased during recovery from exercise in the postabsorptive (fasted) state in this population. Thus, the investigators hypothesize that decreased use of exogenous and endogenous fats contributes to exaggerated PPL in SCI, and that pre-meal exercise will reduce PPL due to increased use of both fat sources.