Adiponectin concentration in plasma is associated with muscle fiber size in healthy middle-aged men

Abstract

Obesity and ectopic fat deposition are major risk factors for many diseases ranging from insulin resistance to type 2 diabetes and atherosclerosis. In obese individuals, the size of muscle fibers is increased mainly because of the ectopic fat present in skeletal muscle. The aim of the study was to investigate if adipokines would associate with muscle fiber characteristics and if muscle fiber characteristics and expression of the skeletal muscle adiponectin receptor (ADIPOR) would be associated with overweight and other components of the metabolic syndrome. This is a population-based, epidemiological cross-sectional study where normotensive, non-smoking men with normal OGTT provided a muscle biopsy (N = 54). Body mass index was higher in the group with the largest muscle fiber size (p for trend <0.05) compared to medium (p <0.05) or small (p <0.05) muscle fiber size. Plasma adiponectin level (p < 0.05) was negatively and concentrations of leptin (p < 0.05) and hs-CRP (p <0.05) positively associated with muscle fiber size before adjustments. The inverse association between the plasma adiponectin level and muscle fiber size tertile remained significant (p < 0.05) when adjusted for age and total adiposity. No associations were observed between the expression of muscle adiponectin receptors (ADIPOR) and features of the metabolic syndrome. Skeletal muscle fiber characteristics are related to overweight. In addition, a correlation was observed between low adiponectin and large muscle fiber size and this was not dependent on the amount of total fatness.

Key Words::

• Overweight
• metabolic syndrome
• adipokines
• ectopic fat
• skeletal muscle

Acknowledgements

The authors thank Ms Saija Kortetjärvi, Ms Liisa Mannermaa, Ms Sirpa Rannikko, and Ms Leena Ukkola for their excellent technical assistance.

Funding sources: This study was supported by the Research Council for Health of the Academy of Finland 2001–2003 grant number: 73162, 2004–2006 grant number 205963.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.