Palmitate acutely raises glycogen synthesis in rat soleus muscle by a mechanism that requires its metabolization (Randle cycle)

FEBS Lett. 2003 Apr 24;541(1-3):109-14. doi: 10.1016/s0014-5793(03)00316-8.

Abstract

The acute effect of palmitate on glucose metabolism in rat skeletal muscle was examined. Soleus muscles from Wistar male rats were incubated in Krebs-Ringer bicarbonate buffer, for 1 h, in the absence or presence of 10 mU/ml insulin and 0, 50 or 100 microM palmitate. Palmitate increased the insulin-stimulated [(14)C]glycogen synthesis, decreased lactate production, and did not alter D-[U-(14)C]glucose decarboxylation and 2-deoxy-D-[2,6-(3)H]glucose uptake. This fatty acid decreased the conversion of pyruvate to lactate and [1-(14)C]pyruvate decarboxylation and increased (14)CO(2) produced from [2-(14)C]pyruvate. Palmitate reduced insulin-stimulated phosphorylation of insulin receptor substrate-1/2, Akt, and p44/42 mitogen-activated protein kinases. Bromopalmitate, a non-metabolizable analogue of palmitate, reduced [(14)C]glycogen synthesis. A strong correlation was found between [U-(14)C]palmitate decarboxylation and [(14)C]glycogen synthesis (r=0.99). Also, palmitate increased intracellular content of glucose 6-phosphate in the presence of insulin. These results led us to postulate that palmitate acutely potentiates insulin-stimulated glycogen synthesis by a mechanism that requires its metabolization (Randle cycle). The inhibitory effect of palmitate on insulin-stimulated protein phosphorylation might play an important role for the development of insulin resistance in conditions of chronic exposure to high levels of fatty acids.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Culture Techniques
  • Glucose / metabolism
  • Glycogen / biosynthesis*
  • Glycogen / metabolism
  • Insulin / pharmacology
  • Insulin Receptor Substrate Proteins
  • Intracellular Signaling Peptides and Proteins
  • Male
  • Mitogen-Activated Protein Kinases / metabolism
  • Muscle, Skeletal / drug effects
  • Muscle, Skeletal / metabolism*
  • Palmitates / metabolism
  • Palmitates / pharmacology*
  • Phosphoproteins / metabolism
  • Protein-Serine-Threonine Kinases*
  • Proto-Oncogene Proteins / metabolism
  • Proto-Oncogene Proteins c-akt
  • Rats
  • Rats, Wistar

Substances

  • Insulin
  • Insulin Receptor Substrate Proteins
  • Intracellular Signaling Peptides and Proteins
  • Irs1 protein, rat
  • Irs2 protein, rat
  • Palmitates
  • Phosphoproteins
  • Proto-Oncogene Proteins
  • Glycogen
  • Akt1 protein, rat
  • Protein-Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-akt
  • Mitogen-Activated Protein Kinases
  • Glucose