Isomer-specific actions of conjugated linoleic acid on muscle glucose transport in the obese Zucker rat

Erik J Henriksen, Mary K. Teachey, Zachary C. Taylor, Stephan Jacob, Arne Ptock, Klaus Krämer, Oliver Hasselwander

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Abstract

The fatty acid-conjugated linoleic acid (CLA) enhances glucose tolerance and insulin action on skeletal muscle glucose transport in rodent models of insulin resistance. However, no study has directly compared the metabolic effects of the two primary CLA isomers, cis-9, trans-11-CLA (c9,t11-CLA) and trans-10,cis-12-CLA (t10,c12-CLA). Therefore, we assessed the effects of a 50:50 mixture of these two CLA isomers (M-CLA) and of preparations enriched in either c9,t11-CLA (76% enriched) or t10,c12-CLA (90% enriched) on glucose tolerance and insulin-stimulated glucose transport in skeletal muscle of the insulin-resistant obese Zucker (fa/fa) rat. Animals were treated daily by gavage with either vehicle (corn oil), M-CLA, c9,t11-CLA, or t10,c12-CLA (all CLA treatments at 1.5 g total CLA/kg body wt) for 21 consecutive days. During an oral glucose tolerance test, glucose responses were reduced (P < 0.05) by 10 and 16%, respectively, in the M-CLA and t10,c12-CLA animals, respectively, whereas insulin responses were diminished by 21 and 19% in these same groups. There were no significant alterations in these responses in the c9,t11-CLA group. Insulin-mediated glucose transport activity was enhanced by M-CLA treatment in both type I soleus (32%) and type IIb epitrochlearis (58%) muscles and by 36 and 48%, respectively, with t10,c12-CLA. In the soleus, these increases were associated with decreases in protein carbonyls (index of oxidative stress, r = -0.616, P = 0.0038) and intramuscular triglycerides (r = -0.631, P = 0.0028). Treatment with c9,t11-CLA was without effect on these variables. These results suggest that the ability of CLA treatment to improve glucose tolerance and insulin-stimulated glucose transport activity in insulin-resistant skeletal muscle of the obese Zucker rat are associated with a reduction in oxidative stress and muscle lipid levels and can be specifically ascribed to the actions of the t10,c12 isomer. In the obese Zucker rat, the c9,t11 isomer of CLA is metabolically neutral.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Endocrinology and Metabolism
Volume285
Issue number1 48-1
StatePublished - Jul 1 2003

Fingerprint

Conjugated Linoleic Acids
Zucker Rats
Isomers
Muscle
Rats
Glucose
Muscles
Insulin
Oxidative stress
Skeletal Muscle
Animals
Oxidative Stress
Linoleic acid
Corn Oil
Glucose Tolerance Test
Triglycerides
Fatty Acids
Insulin Resistance
Rodentia
Lipids

Keywords

  • Conjugated fatty acids
  • Epitrochlearis
  • Insulin resistance
  • Lipids
  • Soleus

ASJC Scopus subject areas

  • Physiology
  • Endocrinology
  • Biochemistry

Cite this

Isomer-specific actions of conjugated linoleic acid on muscle glucose transport in the obese Zucker rat. / Henriksen, Erik J; Teachey, Mary K.; Taylor, Zachary C.; Jacob, Stephan; Ptock, Arne; Krämer, Klaus; Hasselwander, Oliver.

In: American Journal of Physiology - Endocrinology and Metabolism, Vol. 285, No. 1 48-1, 01.07.2003.

Research output: Contribution to journalArticle

Henriksen, Erik J ; Teachey, Mary K. ; Taylor, Zachary C. ; Jacob, Stephan ; Ptock, Arne ; Krämer, Klaus ; Hasselwander, Oliver. / Isomer-specific actions of conjugated linoleic acid on muscle glucose transport in the obese Zucker rat. In: American Journal of Physiology - Endocrinology and Metabolism. 2003 ; Vol. 285, No. 1 48-1.
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N2 - The fatty acid-conjugated linoleic acid (CLA) enhances glucose tolerance and insulin action on skeletal muscle glucose transport in rodent models of insulin resistance. However, no study has directly compared the metabolic effects of the two primary CLA isomers, cis-9, trans-11-CLA (c9,t11-CLA) and trans-10,cis-12-CLA (t10,c12-CLA). Therefore, we assessed the effects of a 50:50 mixture of these two CLA isomers (M-CLA) and of preparations enriched in either c9,t11-CLA (76% enriched) or t10,c12-CLA (90% enriched) on glucose tolerance and insulin-stimulated glucose transport in skeletal muscle of the insulin-resistant obese Zucker (fa/fa) rat. Animals were treated daily by gavage with either vehicle (corn oil), M-CLA, c9,t11-CLA, or t10,c12-CLA (all CLA treatments at 1.5 g total CLA/kg body wt) for 21 consecutive days. During an oral glucose tolerance test, glucose responses were reduced (P < 0.05) by 10 and 16%, respectively, in the M-CLA and t10,c12-CLA animals, respectively, whereas insulin responses were diminished by 21 and 19% in these same groups. There were no significant alterations in these responses in the c9,t11-CLA group. Insulin-mediated glucose transport activity was enhanced by M-CLA treatment in both type I soleus (32%) and type IIb epitrochlearis (58%) muscles and by 36 and 48%, respectively, with t10,c12-CLA. In the soleus, these increases were associated with decreases in protein carbonyls (index of oxidative stress, r = -0.616, P = 0.0038) and intramuscular triglycerides (r = -0.631, P = 0.0028). Treatment with c9,t11-CLA was without effect on these variables. These results suggest that the ability of CLA treatment to improve glucose tolerance and insulin-stimulated glucose transport activity in insulin-resistant skeletal muscle of the obese Zucker rat are associated with a reduction in oxidative stress and muscle lipid levels and can be specifically ascribed to the actions of the t10,c12 isomer. In the obese Zucker rat, the c9,t11 isomer of CLA is metabolically neutral.

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