Basal and insulin-regulated free fatty acid and glucose metabolism in humans.
These studies were done to examine the effects of body composition, resting energy expenditure (REE), sex, and fitness on basal and insulin-regulated FFA and glucose metabolism. We performed 137 experiments in 101 nondiabetic, premenopausal women and men, ranging from low normal weight to class III obese (BMI 18.0-40.5 kg/m2). Glucose flux was measured using [6-(2)H2]glucose and FFA kinetics with [9,10-(3)H]oleate under either basal (74 experiments) or euglycemic hyperinsulinemic (1.0 mU.kg FFM(-1).min(-1)) clamp conditions (63 experiments). Consistent with our previous findings, REE and sex independently predicted basal FFA flux, whereas fat-free mass was the best predictor of basal glucose flux; in addition, percent body fat was independently and positively associated with basal glucose flux (total r2 = 0.52, P < 0.0001). Insulin-suppressed lipolysis remained significantly associated with REE (r = 0.25, P < 0.05), but percent body fat also contributed (total adjusted r2 = 0.36, P < 0.0001), whereas sex was not significantly related to insulin-suppressed FFA flux. Glucose disposal during hyperinsulinemia was independently associated with peak VO2, percent body fat, and FFA concentrations (total r2 = 0.63, P < 0.0001) but not with sex. We conclude that basal glucose production is independently related to both FFM and body fatness. In addition, hyperinsulinemia obscures the sex differences in FFA release relative to REE, but brings out the effects of fatness on lipolysis.
Shadid
Samyah
S
Endocrine Research Unit, 5-194 Joseph, Mayo Clinic, Rochester, MN 55905, USA.
Kanaley
Jill A
JA
Sheehan
Michael T
MT
Jensen
Michael D
MD
D000273:Adipose Tissue / Q000033:anatomy & histology; D000328:Adult; D001823:Body Composition; D002940:Circadian Rhythm; D004734:Energy Metabolism; D005230:Fatty Acids, Nonesterified / Q000378:metabolism*; D005260:Female; D005947:Glucose / Q000378:metabolism*; D015309:Glucose Clamp Technique; D006801:Humans; D006946:Hyperinsulinism / Q000378:metabolism; D007328:Insulin / Q000378:metabolism*; D008066:Lipolysis; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000378:metabolism; D010101:Oxygen Consumption; D010809:Physical Fitness; D012146:Rest; D012737:Sex Factors
D005230:Fatty Acids, Nonesterified; D007328:Insulin; D005947:Glucose