title: High sucrose diet and exercise: effects on insulin-receptor function of 12- and 24-mo-old Sprague-Dawley rats.
abstract: The purpose of this study was to evaluate the effect of aging (12 vs. 24 mo) on skeletal muscle insulin receptor function of male Sprague-Dawley rats fed either a 33% sucrose (wt/wt) or sucrose-free diet. The effect of exercise in combination with the sucrose diet was also evaluated by exercising half of the sucrose-fed group on a motorized treadmill. Insulin-receptor function was assessed in vitro by measuring the binding capacity of [125I]-insulin to partially purified receptors of the biceps femoris and vastus lateralis. Tyrosine kinase activity was measured as an index of postreceptor function. Insulin-receptor number was significantly decreased in 24-mo-old sucrose-fed rats compared to 12-mo-old rats fed the sucrose or sucrose-free diets. The affinity of insulin for the receptor did not significantly differ among groups. Maximal tyrosine kinase activity in vastus lateralis was significantly decreased in 12-mo-old sucrose-fed rats compared with sedentary 24-mo-old rats fed the sucrose-free diet or 24-mo-old rats fed the sucrose diet in combination with exercise. Exercise prevented the decrease in receptor function in both 12- and 24-mo-old sucrose-fed rats as measured by insulin binding and tyrosine kinase activity. These data suggest that diet and/or exercise rather than aging per se has a greater influence on insulin-receptor function.
authors.affiliation: Department of Nutrition, University of California, Davis 95616.
authors.forename: K C
authors.initials: KC
authors.lastname: Eiffert
authors.forename: R B
authors.initials: RB
authors.lastname: McDonald
authors.forename: J S
authors.initials: JS
authors.lastname: Stern
mesh_terms: D000375:Aging / Q000378:metabolism*; D000818:Animals; D001786:Blood Glucose; D004040:Dietary Carbohydrates / Q000008:administration & dosage*; D007328:Insulin / Q000097:blood / Q000378:metabolism*; D008297:Male; D009132:Muscles / Q000187:drug effects / Q000378:metabolism*; D005082:Physical Exertion; D051381:Rats; D011919:Rats, Inbred Strains; D011972:Receptor, Insulin / Q000187:drug effects* / Q000378:metabolism; D013395:Sucrose / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D001786:Blood Glucose; D004040:Dietary Carbohydrates; D007328:Insulin; D013395:Sucrose; D011972:Receptor, Insulin