Effect of macronutrient composition of the diet on the regulation of lipolysis in adipose tissue at rest and during exercise: microdialysis study.

The aim of the present study was to elucidate, using a microdialysis technique, whether modifications in the proportion of fat in the diet influence lipid mobilization from adipose tissue in situ. Nine healthy volunteers (age, 23.4 +/- 0.2 years; body mas index [BMI], 23.5 +/- 1.6 kg/m(2)) were fed, in random order, with a high-fat diet (HFD) (65% of energy content fat, 15% protein, 20% carbohydrate) or a high-carbohydrate diet (HCD) (70% carbohydrate, 15% protein, 15% fat) for 5 days, with a washout period of 10 days between the diets. Subjects were studied in the fasting state on the morning following days 4 and 5 of each diet. We measured the concentration of extracellular glycerol (EGC) in adipose tissue in response to (1) pharmacologic stimulation with isoprenaline (1 and 10 micromol/L) in situ, (2) stimulation with intravenous infusion of epinephrine (0.0375 microg/min/kg body weight), and (3) submaximal aerobic exercise (50% V*O2max, 60-minute duration). No effect of the diet composition was found in the increases of EGC in response to isoprenaline (area under the curve [AUC]: HFD, 1,534 +/- 370 micromol/90 min; HCD, 1,108 +/- 465 micromol/90 min; not significant [NS]) or epinephrine stimulations (AUC: HFD, 190 +/- 92 micromol/30 min; HCD, 251 +/- 298 micromol/30 min; NS). The exercise-induced increase in EGC was higher during the HFD (AUC: HFD, 1,641 +/- 181 micromol/60 min; HCD, 963 +/- 156 micromol/60 min; P <.05) and was associated with a higher exercise-induced response of norepinephrine (P <.05) and epinephrine (P =.056) and lower insulinemia during exercise. The results suggest that macronutrient composition of diet does not affect the beta-adrenergic responsiveness of adipose tissue to catecholamine action at rest. During exercise, the HFD promotes higher lipolysis in adipose tissue and this is associated with a higher catecholamine response and lower insulinemia.