Relationships between fat deposition in the liver and skeletal muscle and insulin sensitivity in Japanese individuals: a pilot study

Abstract

Purpose

To evaluate the relationships between insulin sensitivity (IS), body fat accumulation, and aerobic capacity in middle- to older-aged Japanese participants with visceral adiposity.

Participants and methods

Aerobic capacity was measured during an incremental ramp exercise test. Computed tomography was used to measure visceral (VFA) and subcutaneous (SFA) fat area, the fat in liver-to-spleen ratio (L/S), and low-density skeletal muscle area (LDMA). IS was assessed using euglycemic-hyperinsulinemic clamps.

Results

A total of 11 males and 9 females, age 58 ± 9 years (mean ± standard deviation), body mass index 29 ±4.1 kg/m², and VFA 190 ±53 cm² participated in this study. In unadjusted models, VFA, LDMA, and L/S were significantly correlated with IS, which remained in adjusted models for LDMA and L/S, but not for VFA. In multiple stepwise regression analysis including sex, age, body fat, VFA, SFA, alcohol consumption, and aerobic capacity (oxygen uptake at the lactate threshold), L/S, and LDMA accounted for 70% of the total variance in IS. Percentage body fat and SFA, but not VFA, were significantly correlated with high molecular-weight adiponectin levels (r = 0.58, P < 0.01 and r = 0.54, P < 0.05, respectively). IS and L/S were significantly and negatively correlated with tumor necrosis factor-α (r = −0.67 and −0.63, respectively; both P < 0.01) and plasminogen activator inhibitor-1 (r = −0.58, P < 0.01 and −0.52, P < 0.05, respectively), whereas LDMA was not.

Conclusion

These findings indicate that ectopic fat deposition in the liver and skeletal muscle may be associated with peripheral IS independently of body fat accumulation and aerobic capacity in middle- to older-aged Japanese individuals with visceral adiposity. Because of the small sample size, additional larger studies are needed to provide further insight into these preliminary findings.

Keywords:

• aerobic capacity
• fat in liver
• lipid-rich skeletal muscle
• visceral fat
• subcutaneous fat
• peripheral insulin sensitivity

Acknowledgments

We gratefully acknowledge the members of the Laboratory of Exercise Physiology, Fukuoka University, particularly Ms Yoko Sakai and Dr Takuro Matsuda, for their help with data evaluation. We also thank Dr Kyogo Kurita, Dr Hiroaki Sato, and Dr Koji Midorikawa of Fukuseikai Hospital, Fukuoka, Japan for their technical assistance with CT examinations. The authors are grateful to the study participants as well. This study was carried out with the support of the Fukuoka University Institute for Physical Activity, a Technology Scientific Research Budget Basic Research Grant (A19200049 Strategic Research Infrastructure) from the Japanese Government’s Ministry of Education, Culture, Sports, Science and Technology, and a Global FU Program grant from Fukuoka University.

Disclosure

The authors report no conflicts of interest in this work.