Michael D. Jensen, M.D.

Fatty Acid Metabolism in Humans

Our research interests are in the effects of obesity and how body fat and body-fat distribution influence health. Adipose tissue stores > 95% of all fatty acids in the body, and the regulated uptake, storage and release of fatty acids plays a major role in determining the health effects of body fat. Ongoing studies involve the measurement of systemic and regional free fatty acid uptake and release, attempting to relate these measures to organ and tissue function. We also measure the uptake of fatty acids into muscle, liver and adipose tissue in order to determine whether preferential uptake of fat can predispose to obesity or a specific body fat distribution. We measure the cellular fate(s) of fatty acids and the cell processes responsible for these steps. Our long-term goal is to understand the regulation of body fat and body fat distribution in hopes of developing novel approaches to improve the health of humans affected by obesity/excess fat.

Our human studies involve the following: long-term feeding experiments; the use of isotope dilution techniques to measure free fatty acid, glycerol and triglyceride fatty acid turnover; blood flow measurements; body composition measurements using dual energy X-ray absorptiometry, total body water, and CT scanning; exercise studies; indirect calorimetry to measure energy expenditure and substrate oxidation; doubly labeled water; ELIZA, Western blotting, real-time PCR and tissue enzyme activity measures to understand tissue function. To gain tissue for the latter measurements we routinely perform adipose tissue and muscle biopsies. We have recently developed PET tracers to study fatty acid metabolism in humans.

We have investigated the effects of obesity and hormonal factors on body-fat distribution, protein, lipoprotein, and glucose metabolism. Also, we have explored fuel metabolism during low- and high-intensity exercise, and how humans deal with excess energy intake and energy deficits.