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This Article Full Text Full Text (PDF) All Versions of this Article: 107/3/824    most recent 91382.2008v1 Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Høeg, L. Articles by Kiens, B. PubMed PubMed Citation Articles by Høeg, L. Articles by Kiens, B.

Higher intramuscular triacylglycerol in women does not impair insulin sensitivity and proximal insulin signaling

The Copenhagen Muscle Research Centre, Molecular Physiology Group, Section of Human Physiology, Department of Exercise and Sport Sciences, University of Copenhagen, Copenhagen, Denmark

Submitted 18 October 2008 ; accepted in final form 29 June 2009

Women have been shown to have higher muscle triacylglycerol (IMTG) levels than men and could therefore be expected to have lower insulin sensitivity than men, since previous studies have linked high IMTG to decreased insulin sensitivity. Therefore, insulin sensitivity of whole body and leg glucose uptake was studied in 9 women in the follicular phase and 8 men on a controlled diet and matched for maximal oxygen uptake per kilogram of lean body mass and habitual activity level. A 47% higher (P < 0.05) IMTG level was found in women than in men, and, at the same time, women also displayed 22% higher whole body insulin sensitivity (P < 0.05) and 29% higher insulin-stimulated leg glucose uptake (P = 0.05) during an euglycemic-hyperinsulinemic (70 µU/ml) clamp compared with matched male subjects. The higher insulin sensitivity in women could not be explained by higher expression of muscle glucose transporter GLUT4, insulin receptor, or Akt expression or by the ability of insulin to stimulate Akt Thr³⁰⁸ or Akt Ser⁴⁷³ phosphorylation. However, a 30% higher (P < 0.05) capillary density and 31% more type 1 muscle fiber expressed per area in the vastus lateralis muscle were noted in women than in matched men. It is concluded that despite 47% higher IMTG levels in women in the follicular phase, whole body as well as leg insulin sensitivity are higher than in matched men. This was not explained by sex differences in proximal insulin signaling in women. In women, it seems that a high capillary density and type 1 muscle fiber expression may be important for insulin action.

muscle triacylglycerol; sex paradox; insulin action