Impaired fatty acid oxidation in muscle of aging rats perfused under basal conditions

Department of Kinesiology and Diabetes Research Center, University of Southern California, Los Angeles, California 90089 The purpose of the present study was to examine the utilization of fatty acids (FA) and muscle substrates by skeletal muscle in young, middle-aged, and old adult rats under conditions of euglycemia with low insulin levels. Male Fischer 344 × Brown Norway rats aged 5, 15, or 24 mo underwent hindlimb perfusion with a medium of 8 mM glucose, 1 mM palmitate, 25 µU/ml insulin, [1- 14 C]palmitate, and [3- 3 H]glucose. Glucose and palmitate uptake were similar among age groups. The percent and total palmitate oxidized (nmol · min 1 · g 1 ) were 30-36 and 41-49% lower ( P