AMPK stimulation increases LCFA but not glucose clearance in cardiac muscle in vivo.

Shearer J, Fueger PT, Rottman JN, Bracy DP, Martin PH, Wasserman DH
Am J Physiol Endocrinol Metab. 2004 287 (5): E871-7

PMID: 15265760 · DOI:10.1152/ajpendo.00125.2004

AMP-activated protein kinase (AMPK) independently increases glucose and long-chain fatty acid (LCFA) utilization in isolated cardiac muscle preparations. Recent studies indicate this may be due to AMPK-induced phosphorylation and activation of nitric oxide synthase (NOS). Given this, the aim of the present study was to assess the effects of AMPK stimulation by 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside (AICAR; 10 mg.kg(-1).min(-1)) on glucose and LCFA utilization in cardiac muscle and to determine the NOS dependence of any observed effects. Catheters were chronically implanted in a carotid artery and jugular vein of Sprague-Dawley rats. After 4 days of recovery, conscious, unrestrained rats were given either water or water containing 1 mg/ml nitro-L-arginine methyl ester (L-NAME) for 2.5 days. After an overnight fast, rats underwent one of four protocols: saline, AICAR, AICAR + L-NAME, or AICAR + Intralipid (20%, 0.02 ml.kg(-1).min(-1)). Glucose was clamped at approximately 6.5 mM in all groups, and an intravenous bolus of 2-deoxy-[(3)H]glucose and [(125)I]-15-(p-iodophenyl)-3-R,S-methylpentadecanoic acid was administered to obtain indexes of glucose and LCFA uptake and clearance. Despite AMPK activation, as evidenced by acetyl-CoA carboxylase (Ser(221)) and AMPK phosphorylation (Thr(172)), AICAR increased cardiac LCFA but not glucose clearance. L-NAME + AICAR established that this effect was not due to NOS activation, and AICAR + Intralipid showed that increased cardiac LCFA clearance was not LCFA-concentration dependent. These results demonstrate that, in vivo, AMPK stimulation increases LCFA but not glucose clearance by a NOS-independent mechanism.

MeSH Terms (19)

Aminoimidazole Carboxamide AMP-Activated Protein Kinases Animals Enzyme Activation Enzyme Inhibitors Fat Emulsions, Intravenous Fatty Acids Glucose Hypoglycemic Agents Male Multienzyme Complexes Myocardium NG-Nitroarginine Methyl Ester Nitric Oxide Nitric Oxide Synthase Protein-Serine-Threonine Kinases Rats Rats, Sprague-Dawley Ribonucleotides

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