title: AMPK activation is not critical in the regulation of muscle FA uptake and oxidation during low-intensity muscle contraction.
abstract: To determine the role of AMP-activated protein kinase (AMPK) activation on the regulation of fatty acid (FA) uptake and oxidation, we perfused rat hindquarters with 6 mM glucose, 10 microU/ml insulin, 550 microM palmitate, and [14C]palmitate during rest (R) or electrical stimulation (ES), inducing low-intensity (0.1 Hz) muscle contraction either with or without 2 mM 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside (AICAR). AICAR treatment significantly increased glucose and FA uptake during R (P < 0.05) but had no effect on either variable during ES (P > 0.05). AICAR treatment significantly increased total FA oxidation (P < 0.05) during both R (0.38 +/- 0.11 vs. 0.89 +/- 0.1 nmol x min(-1) x g(-1)) and ES (0.73 +/- 0.11 vs. 2.01 +/- 0.1 nmol x min(-1) x g(-1)), which was paralleled in both conditions by a significant increase and significant decrease in AMPK and acetyl-CoA carboxylase (ACC) activity, respectively (P < 0.05). Low-intensity muscle contraction increased glucose uptake, FA uptake, and total FA oxidation (P < 0.05) despite no change in AMPK (950.5 +/- 35.9 vs. 1,067.7 +/- 58.8 nmol x min(-1) x g(-1)) or ACC (51.2 +/- 6.7 vs. 55.7 +/- 2.0 nmol x min(-1) x g(-1)) activity from R to ES (P > 0.05). When contraction and AICAR treatment were combined, the AICAR-induced increase in AMPK activity (34%) did not account for the synergistic increase in FA oxidation (175%) observed under similar conditions. These results suggest that while AMPK-dependent mechanisms may regulate FA uptake and FA oxidation at rest, AMPK-independent mechanisms predominate during low-intensity muscle contraction.
authors.affiliation: Dept. of Kinesiology and Biological Sciences, Diabetes Research Center, Univ. of Southern California, 3560 Watt Way, PED 107, Los Angeles, CA 90089-0652, USA.
authors.forename: Marcella A
authors.initials: MA
authors.lastname: Raney
authors.forename: Alice J
authors.initials: AJ
authors.lastname: Yee
authors.forename: Mark K
authors.initials: MK
authors.lastname: Todd
authors.forename: Lorraine P
authors.initials: LP
authors.lastname: Turcotte
mesh_terms: D055372:AMP-Activated Protein Kinases; D000103:Acetyl-CoA Carboxylase / Q000378:metabolism; D000620:Aminoimidazole Carboxamide / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D004558:Electric Stimulation; D004789:Enzyme Activation; D005227:Fatty Acids / Q000378:metabolism* / Q000493:pharmacokinetics; D005947:Glucose / Q000378:metabolism / Q000494:pharmacology; D007004:Hypoglycemic Agents / Q000494:pharmacology; D019344:Lactic Acid / Q000378:metabolism / Q000494:pharmacology; D008297:Male; D008316:Malonyl Coenzyme A / Q000378:metabolism; D009097:Multienzyme Complexes / Q000378:metabolism*; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D010084:Oxidation-Reduction; D010101:Oxygen Consumption / Q000502:physiology; D019308:Palmitic Acid / Q000378:metabolism / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D012265:Ribonucleotides / Q000494:pharmacology
chemical_list: D005227:Fatty Acids; D007004:Hypoglycemic Agents; D009097:Multienzyme Complexes; D012265:Ribonucleotides; D019308:Palmitic Acid; D019344:Lactic Acid; D000620:Aminoimidazole Carboxamide; D008316:Malonyl Coenzyme A; D017346:Protein Serine-Threonine Kinases; D055372:AMP-Activated Protein Kinases; D000103:Acetyl-CoA Carboxylase; C031143:AICA ribonucleotide; D005947:Glucose