title: Effects of tumor necrosis factor-alpha on glucose metabolism in cultured human muscle cells from nondiabetic and type 2 diabetic subjects.
abstract: The effects of tumor necrosis factor-alpha (TNF alpha) on glucose uptake and glycogen synthase (GS) activity were studied in human skeletal muscle cell cultures from nondiabetic and type 2 diabetic subjects. In nondiabetic muscle cells, acute (90-min) exposure to TNF alpha (5 ng/ml) stimulated glucose uptake (73 +/- 14% increase) to a greater extent than insulin (37 +/- 4%; P < 0.02). The acute uptake response to TNF alpha in diabetic cells (51 +/- 6% increase) was also greater than that to insulin (31 +/- 3%; P < 0.05). Prolonged (24-h) exposure of nondiabetic muscle cells to TNF alpha resulted in a further stimulation of uptake (152 +/- 31%; P < 0.05), whereas the increase in cells from type 2 diabetics was not significant compared with that in cells receiving acute treatment. After TNF alpha treatment, the level of glucose transporter-1 protein was elevated in nondiabetic (4.6-fold increase) and type 2 (1.7-fold) cells. Acute TNF alpha treatment had no effect on the fractional velocity of GS in either nondiabetic or type 2 cells. Prolonged exposure reduced the GS fractional velocity in both nondiabetic and diabetic cells. In summary, both acute and prolonged treatment with TNF alpha up-regulate glucose uptake activity in cultured human muscle cells, but reduce GS activity. Increased skeletal muscle glucose uptake in conditions of TNF alpha excess may serve as a compensatory mechanism in the insulin resistance of type 2 diabetes.
authors.affiliation: Veterans Affairs Medical Center and Department of Medicine, University of California-San Diego, La Jolla, California 92093, USA. tciaraldi@ucsd.edu
authors.forename: T P
authors.initials: TP
authors.lastname: Ciaraldi
authors.forename: L
authors.initials: L
authors.lastname: Carter
authors.forename: S
authors.initials: S
authors.lastname: Mudaliar
authors.forename: P A
authors.initials: PA
authors.lastname: Kern
authors.forename: R R
authors.initials: RR
authors.lastname: Henry
mesh_terms: D000328:Adult; D002478:Cells, Cultured; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism* / Q000473:pathology; D005947:Glucose / Q000378:metabolism*; D006003:Glycogen / Q000096:biosynthesis; D006006:Glycogen Synthase / Q000378:metabolism; D006801:Humans; D008875:Middle Aged; D009004:Monosaccharide Transport Proteins / Q000378:metabolism; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000378:metabolism* / Q000473:pathology; D012016:Reference Values; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: D009004:Monosaccharide Transport Proteins; D014409:Tumor Necrosis Factor-alpha; D006003:Glycogen; D006006:Glycogen Synthase; D005947:Glucose