EFFECT OF ELEVATED [FFA] ON GLUCOSE UPTAKE AND LACTATE EFFLUX DURING SUBMAXIMAL EXERCISE IN MAN 9

Abstract

The present investigation examined the effect of enhanced plasma free fatty acid availability on leg glucose uptake and lactate efflux during prolonged submaximal cycling exercise. Seven males cycled for 70 min (10 min at 40% and 60 min at 65% VO2max) while infused with either Intralipid (100 ml) and heparin (2000 U) (INTRA) or saline (CON). At the onset of exercise, plasma arterial [FFA] was 0.70 ± 0.03 mM (INTRA) vs. 0.22 ± 0.01 mM(CON). Arterial and femoral venous catheters were inserted and blood samples and expired gases were collected simultaneously at rest and at 8, 18, 34, 50 and 68 min of exercise. Blood flow was estimated from pulmonary O2 uptake and the leg a-v (O2) difference. No difference existed in VO2 or blood flow between trials, while average pulmonary RER was higher in CON (0.94 ± 0.01) compared to INTRA (0.91 ± 0.01)(p<0.05). Mean leg FFA uptake was higher in INTRA (0.16 ± 0.03 mmol/min) vs. CON (0.04 ± 0.01 mmol/min) during exercise (p<0.01). There was a significant decrease in lactate efflux during INTRA (1.55 ± 0.36 mmol/min) compared to CON (3.07 ± 0.47 mmol/min) (p<0.05). Leg glucose uptake was not different at any time point between trials. In conclusion, enhanced FFA availability leads to a decrease in lactate efflux and no change in glucose uptake. Therefore, if carbohydrate sparing occurs at these workloads, it must be a function of reduced glycogenolysis.