Free fatty acid and glucose metabolism in human aging: evidence for operation of the Randle cycle.
We assessed insulin effects on plasma free fatty acid (FFA) and glucose metabolism in seven elderly (71 +/- 2 yr) and in seven younger (21 +/- 1 yr) subjects matched for body weight and body mass index but not for percent body fat (32.4 +/- 3.8% in elderly vs. 20.4 +/- 3.5% in young, P < 0.05), by performing sequential euglycemic clamps at five insulin doses (0.6, 1.5, 3, 6, and 15 pmol.min-1.kg-1) in combination with indirect calorimetry and [1-14C]palmitate plus [3-3H]glucose infusion. At baseline, plasma FFA concentration, turnover infusion. At baseline, plasma FFA concentration, turnover and oxidation, and total lipid oxidation were all increased in the elderly (897 +/- 107 vs. 412 +/- 50 mumol/l and 11.2 +/- 1.4 vs. 5.14 +/- 0.86, 3.45 +/- 0.65 vs. 1.37 +/- 0.25, and 4.63 +/- 0.72 vs. 3.01 +/- 0.33 mumol.min-1.kg-1 lean body mass, P < 0.05 for all comparisons), whereas glucose turnover was similar as a result of decreased glucose oxidation (8.2 +/- 1.4 vs. 13 +/- 1.9 mumol.min-1.kg-1 lean body mass, P < 0.05) and increased glucose storage (6.6 +/- 1.4 vs. 1.7 +/- 1.3 mmol.min-1.kg-1 lean body mass, P < 0.05). At all insulin infusions, plasma FFA concentration, turnover and oxidation, and total lipid oxidation were higher in the elderly than in the younger group (P < 0.05). However, if normalized per fat mass, all FFA and lipid metabolic fluxes, both in the postabsorptive state and during hyperinsulinemia, were comparable in the two groups.(ABSTRACT TRUNCATED AT 250 WORDS)
Bonadonna
R C
RC
Metabolism Unit, University of Pisa, Italy.
Groop
L C
LC
Simonson
D C
DC
DeFronzo
R A
RA
D000328:Adult; D000368:Aged; D000375:Aging / Q000378:metabolism*; D001786:Blood Glucose / Q000378:metabolism; D001823:Body Composition; D005230:Fatty Acids, Nonesterified / Q000378:metabolism*; D005260:Female; D005947:Glucose / Q000378:metabolism*; D006801:Humans; D007328:Insulin / Q000097:blood; D050356:Lipid Metabolism; D008297:Male; D009994:Osmolar Concentration; D010084:Oxidation-Reduction
D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D005947:Glucose