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

Abstract

Eiichi Yoshimura1,2, Hideaki Kumahara3, Takuro Tobina4, Sakiko Matono1, Akira Kiyonaga4, Miyuki Kimura5, Hiroshi Tsukikawa6, Shinya Kono6, Takashi Etou5, Shin Irie5, Keizo Anzai7, Hiroaki Tanaka41Graduate School of Sports and Health Science, Fukuoka University, Fukuoka, Japan; 2Faculty of Medicine, Fukuoka University, Fukuoka, Japan; 3Faculty of Nutrition Sciences, Nakamura Gakuen University, Fukuoka, Japan; 4Faculty of Sports and Health Science, Fukuoka University, Fukuoka, Japan; 5Kyushu Clinical Pharmacology Research Clinic, Fukuoka, Japan; 6PS Clinic, Fukuoka, Japan; 7Saga University Hospital, Saga, JapanPurpose: 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