title: Effects of glucose or fructose feeding on glycogen repletion in muscle and liver after exercise or fasting.
abstract: In athletics, muscle and liver glycogen content is critical to endurance. This study compared the effectiveness of glucose and fructose feeding on restoring glycogen content after glycogen was decreased by exercise (90-min swim) or fasting (24 h). After 2 h of recovery from either exercise or fasting there was no measurable glycogen repletion in red vastus lateralis muscle in response to fructose. In contrast, glucose feeding induced a similar and significant carbohydrate storage after both depletion treatments (8.44 mumol X g-1 X 2 h-1). In the liver, following 2 h of recovery, the rates of glycogen storage were similar after either glucose or fructose ingestion, but fasting caused a greater rate of repletion (83 mumol X g-1 X 2 h-1) than exercise (50 mumol X g-1 X 2 h-1). After 4 h of recovery fructose-fed exercised animals had the highest glycogen concentration (165 mumol X g-1) followed by the glucose-fed exercised group (119 mumol X g-1). These values were 50 and 36%, respectively, of that measured in the normal-fed liver (327 mumol X g-1). In contrast, liver glycogen values in the fasted group decreased between the 2nd and 4th hour of recovery in response to both feeding regimens. From these results we conclude that fructose is a poor nutritional precursor for rapid glycogen restoration in muscle after exercise, but that both glucose and fructose promote rapid accumulation of glycogen in the liver.
mesh_terms: D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D004040:Dietary Carbohydrates / Q000378:metabolism*; D005215:Fasting; D005632:Fructose / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism*; D006003:Glycogen / Q000378:metabolism*; D008112:Liver Glycogen / Q000378:metabolism*; D009132:Muscles / Q000378:metabolism*; D005082:Physical Exertion; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D001786:Blood Glucose; D004040:Dietary Carbohydrates; D008112:Liver Glycogen; D005632:Fructose; D006003:Glycogen; D005947:Glucose