Impaired fatty acid oxidation in muscle of aging rats perfused under basal conditions.
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 x Brown Norway rats aged 5, 15, or 24 mo underwent hindlimb perfusion with a medium of 8 mM glucose, 1 mM palmitate, 25 microU/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 < 0.05) in 15-mo- and 24-mo-old than in 5-mo-old animals. Compared with 5-mo- and 15-mo-old animals, pre- and postperfusion muscle triglyceride (TG) levels were significantly (P < 0.05) elevated 91-305% in red and 118-219% in white muscles of 24-mo-old animals. Fatty acid-binding protein content was 40-64% higher (P < 0.05) in 24-mo- than in 5-mo- or 15-mo-old animals. In red muscle, hormone-sensitive lipase (HSL) content was 28% lower (P < 0.05) in 24-mo- than in 5-mo-old animals. These results indicate that, under euglycemic conditions in the presence of low insulin levels, the reduction in FA disposal to oxidation and the decrease in HSL content may contribute to the accumulation of TG in muscle of old animals.
Tucker
Michelle Z
MZ
Department of Kinesiology and Diabetes Research Center, University of Southern California, Los Angeles, California 90089, USA.
Turcotte
Lorraine P
LP
D000375:Aging / Q000378:metabolism*; D000818:Animals; D002250:Carbon Radioisotopes; D002352:Carrier Proteins / Q000378:metabolism; D002950:Citrate (si)-Synthase / Q000378:metabolism; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D005947:Glucose / Q000493:pharmacokinetics; D006003:Glycogen / Q000378:metabolism; D006868:Hydrolysis; D014905:Independent State of Samoa; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism*; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D010084:Oxidation-Reduction; D010100:Oxygen / Q000493:pharmacokinetics; D010168:Palmitates / Q000493:pharmacokinetics*; D010477:Perfusion; D051381:Rats; D011914:Rats, Inbred BN; D011916:Rats, Inbred F344; D002787:Sterol Esterase / Q000378:metabolism; D014280:Triglycerides / Q000378:metabolism; D014316:Tritium
D002250:Carbon Radioisotopes; D002352:Carrier Proteins; C490174:Fabp7 protein, rat; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D010168:Palmitates; D014280:Triglycerides; D014316:Tritium; D006003:Glycogen; D002950:Citrate (si)-Synthase; D002787:Sterol Esterase; D005947:Glucose; D010100:Oxygen