title: The effects of aging on glucose metabolism in adipocytes from Fischer rats.
abstract: We have studied glucose metabolism in adipocytes from younger (6 months) and older (24 months) Fischer rats. Insulin binding was similar in both groups, expressed per cell number (2.67 +/- 0.41% vs. 2.96 +/- 0.38%) or per cell surface area (4.59 +/- 0.70% vs. 4.15 +/- 0.53%) in the 6- and 24-month-old animals, respectively. Maximal insulin-stimulated 3-O-methylglucose transport was decreased by 40% in the older group (0.234 +/- 0.032) compared with that in the younger group (0.411 +/- 0.031 pmol/2 X 10(9) micron 2 X sec (P less than 0.01), with no change in basal rates of transport. The decrease in glucose transport was due to a 36% reduction in the maximum velocity (91 pmol/sec in the younger vs. 59 pmol/sec in the older group), with no change in the Km. Postglucose transport steps of glucose metabolism, including CO2 oxidation, triglyceride synthesis, and lactate production, were measured at a higher glucose concentration (2 mM), where glucose transport is not rate limiting. Overall maximal insulin-stimulated glucose metabolism was decreased by 45% in the older group (15.6 nmol) compared with that in the younger group (28.6 nmol/10(5) cells X h; P less than 0.05). Glucose oxidation was decreased by 42% (2.9 vs. 5.0 nmol/10(5) cells X h; P less than 0.05), triglyceride synthesis by 40% (5.9 vs. 9.8 nmol/10(5) cells X h; P less than 0.05), and lactate production by 47% (6.3 vs. 11.8 nmol/10(5) cells X h; P less than 0.05). We conclude that in adipocytes from aged Fischer rats, cellular insulin resistance is due to multiple post-binding defects involving the glucose transport system and more distal intracellular processes.
mesh_terms: D000273:Adipose Tissue / Q000166:cytology / Q000378:metabolism*; D000375:Aging; D000818:Animals; D001692:Biological Transport; D002952:Citric Acid Cycle; D005215:Fasting; D005947:Glucose / Q000378:metabolism*; D006600:Hexosephosphates / Q000378:metabolism; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance; D007773:Lactates / Q000378:metabolism; D008297:Male; D008757:Methylglucosides / Q000378:metabolism; D051381:Rats; D011972:Receptor, Insulin / Q000378:metabolism; D014280:Triglycerides / Q000096:biosynthesis
chemical_list: D006600:Hexosephosphates; D007328:Insulin; D007773:Lactates; D008757:Methylglucosides; D014280:Triglycerides; D011972:Receptor, Insulin; D005947:Glucose