Differential Effects of Palmitate and Palmitoleate on Insulin Action and Glucose Utilization in Rat L6 Skeletal Muscle Cells

Biochem J. 2006 Nov 1;399(3):473-81. doi: 10.1042/BJ20060244.

Abstract

An increase in circulating levels of specific NEFAs (non-esterified fatty acids) has been implicated in the pathogenesis of insulin resistance and impaired glucose disposal in skeletal muscle. In particular, elevation of SFAs (saturated fatty acids), such as palmitate, has been correlated with reduced insulin sensitivity, whereas an increase in certain MUFAs and PUFAs (mono- and poly-unsaturated fatty acids respectively) has been suggested to improve glycaemic control, although the underlying mechanisms remain unclear. In the present study, we compare the effects of palmitoleate (a MUFA) and palmitate (a SFA) on insulin action and glucose utilization in rat L6 skeletal muscle cells. Basal glucose uptake was enhanced approx. 2-fold following treatment of cells with palmitoleate. The MUFA-induced increase in glucose transport led to an associated rise in glucose oxidation and glycogen synthesis, which could not be attributed to activation of signalling proteins normally modulated by stimuli such as insulin, nutrients or cell stress. Moreover, although the MUFA-induced increase in glucose uptake was slow in onset, it was not dependent upon protein synthesis, but did, nevertheless, involve an increase in the plasma membrane abundance of GLUT1 and GLUT4. In contrast, palmitate caused a substantial reduction in insulin signalling and insulin-stimulated glucose transport, but was unable to antagonize the increase in transport elicited by palmitoleate. Our findings indicate that SFAs and MUFAs exert distinct effects upon insulin signalling and glucose uptake in L6 muscle cells and suggest that a diet enriched with MUFAs may facilitate uptake and utilization of glucose in normal and insulin-resistant skeletal muscle.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Transport Systems / metabolism
  • Amino Acids / metabolism
  • Aminoisobutyric Acids / metabolism
  • Animals
  • Biological Transport / drug effects
  • Cell Membrane / metabolism
  • Cells, Cultured / drug effects
  • Cells, Cultured / metabolism
  • Culture Media, Serum-Free
  • Cycloheximide / pharmacology
  • Enzyme Inhibitors / pharmacology
  • Fatty Acids, Monounsaturated / pharmacology*
  • Glucose / metabolism*
  • Glucose Transporter Type 1 / metabolism
  • Glucose Transporter Type 4 / metabolism
  • Glycogen / biosynthesis
  • Glycogen Synthase Kinase 3 / antagonists & inhibitors
  • Glycogen Synthase Kinase 3 / metabolism
  • Insulin / pharmacology
  • Insulin Resistance
  • Models, Biological
  • Muscle Cells / drug effects*
  • Muscle Cells / metabolism
  • Muscle Proteins / biosynthesis
  • Oleic Acid / metabolism
  • Oxidation-Reduction / drug effects
  • Palmitic Acid / pharmacology*
  • Phosphorylation / drug effects
  • Protein Synthesis Inhibitors / pharmacology
  • Protein Transport / drug effects
  • Proto-Oncogene Proteins c-akt / antagonists & inhibitors
  • Proto-Oncogene Proteins c-akt / metabolism
  • Rats
  • Ribosomal Protein S6 Kinases, 70-kDa / antagonists & inhibitors
  • Ribosomal Protein S6 Kinases, 70-kDa / metabolism

Substances

  • Amino Acid Transport Systems
  • Amino Acids
  • Aminoisobutyric Acids
  • Culture Media, Serum-Free
  • Enzyme Inhibitors
  • Fatty Acids, Monounsaturated
  • Glucose Transporter Type 1
  • Glucose Transporter Type 4
  • Insulin
  • Muscle Proteins
  • Protein Synthesis Inhibitors
  • SNAT2 protein, rat
  • Slc2a1 protein, rat
  • Slc2a4 protein, rat
  • palmitoleic acid
  • 2-(methylamino)isobutyric acid
  • Oleic Acid
  • Palmitic Acid
  • Glycogen
  • Cycloheximide
  • Proto-Oncogene Proteins c-akt
  • Ribosomal Protein S6 Kinases, 70-kDa
  • Glycogen Synthase Kinase 3
  • Glucose