title: Direct measurement of change in muscle glycogen concentration after a mixed meal in normal subjects.
abstract: Postprandial storage of carbohydrate as glycogen in muscle was quantitated in normal subjects (n = 8) by natural abundance 13C-nuclear magnetic resonance spectroscopy with proton decoupling in a 4.7-tesla magnet. After an overnight fast three basal measurements of gastrocnemius muscle glycogen were made and a mixed meal was given. Muscle glycogen concentration rose from 83.3 +/- 5.2 to a maximum of 100.2 +/- 6.7 mmol/l muscle at 4.9 h (P < 0.01) and fell thereafter to 90.6 +/- 5.9 mmol/l muscle at 7 h postprandially (P < 0.006). The meal brought about an increase in plasma glucose from 5.4 +/- 0.2 to 7.3 +/- 0.4 mmol/l at 30 min but this was followed by a rapid fall to 6.2 +/- 0.4 mmol/l at 75 min. Plasma insulin rose from 62.4 +/- 11.4 to 900 +/- 216 pmol/l at 30 min and declined steadily thereafter. It was calculated from total muscle mass measurements and estimation of carbohydrate absorption rates that at peak muscle glycogen concentrations between 26 and 35% of the absorbed carbohydrate was stored as muscle glycogen. These data quantitate the role of skeletal muscle glycogen synthesis in postprandial carbohydrate storage and demonstrate that this tissue acts as a dynamic buffer to maintain glucose homeostasis during postprandial substrate storage.
authors.affiliation: Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut 06511.
authors.forename: R
authors.initials: R
authors.lastname: Taylor
authors.forename: T B
authors.initials: TB
authors.lastname: Price
authors.forename: L D
authors.initials: LD
authors.lastname: Katz
authors.forename: R G
authors.initials: RG
authors.lastname: Shulman
authors.forename: G I
authors.initials: GI
authors.lastname: Shulman
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000032:analysis; D004435:Eating; D005260:Female; D006003:Glycogen / Q000378:metabolism*; D006801:Humans; D007328:Insulin / Q000097:blood; D007773:Lactates / Q000097:blood; D019344:Lactic Acid; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D009132:Muscles / Q000378:metabolism*; D009994:Osmolar Concentration; D012016:Reference Values; D014280:Triglycerides / Q000097:blood
chemical_list: D001786:Blood Glucose; D007328:Insulin; D007773:Lactates; D014280:Triglycerides; D019344:Lactic Acid; D006003:Glycogen