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

Diabetes, Metabolic Syndrome and Obesity: Targets and Therapy Dovepress open access to scientific and medical research o r i g i n al r e s e a r c h Diabetes, Metabolic Syndrome and Obesity: Targets and Therapy downloaded from https://www.dovepress.com/ by 213.32.48.132 on 12-Jul-2018 For personal use only. Open Access Full Text Article Relationships between fat deposition in the liver and skeletal muscle and insulin sensitivity in Japanese individuals: a pilot study This article was published in the following Dove Press journal: Diabetes, Metabolic Syndrome and Obesity: Targets and Therapy 19 January 2011 Number of times this article has been viewed Eiichi Yoshimura 1,2 Hideaki Kumahara 3 Takuro Tobina 4 Sakiko Matono 1 Akira Kiyonaga 4 Miyuki Kimura 5 Hiroshi Tsukikawa 6 Shinya Kono 6 Takashi Etou 5 Shin Irie 5 Keizo Anzai 7 Hiroaki Tanaka 4 1 Graduate School of Sports and Health Science, Fukuoka University, Fukuoka, Japan; 2Faculty of Medicine, Fukuoka University, Fukuoka, Japan; 3 Faculty 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, Japan Introduction Correspondence: Hiroaki Tanaka Faculty of Sports and Health Science, Fukuoka University, 8-19-1 Nanakuma, Jonan-ku, Fukuoka 814-0180, Japan Tel +81 92 871 6631 (ext 6767) Fax +81 92 862 3033 Email submit your manuscript | www.dovepress.com Dovepress DOI: 10.2147/DMSO.S16175 Powered by TCPDF (www.tcpdf.org) 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 Recent studies have shown that ectopic fat deposition in the liver1–3 and skeletal muscle4,5 is negatively correlated with insulin sensitivity (IS), even in relatively lean individuals. Obese patients often exhibit fat accumulation in the liver and skeletal muscle, regardless of visceral fat (VF) accumulation.1,6 This suggests that ectopic fat in either organ may be involved in the pathogenesis of declining IS. Decreased aerobic capacity is correlated with metabolic risk7 and declining IS,8 independently of VF and subcutaneous fat (SF). Similarly, a correlation between aerobic capacity and liver fat has also been reported.6,9 These findings suggest that VF, fat accumulation in the liver and skeletal muscle, and aerobic capacity each exert specific effects on the decline in IS. Diabetes, Metabolic Syndrome and Obesity: Targets and Therapy 2011:4 35–43 35 © 2011 Yoshimura et al, publisher and licensee Dove Medical Press Ltd. This is an Open Access article which permits unrestricted noncommercial use, provided the original work is properly cited. Dovepress Diabetes, Metabolic Syndrome and Obesity: Targets and Therapy downloaded from https://www.dovepress.com/ by 213.32.48.132 on 12-Jul-2018 For personal use only. Yoshimura et al To evaluate the strength of the correlation between these parameters and IS, it is necessary to measure all of the parameters in the same participants. To our knowledge, only one study has measured IS in relation to VF, SF, liver fat, intramyocellular fat, and aerobic capacity.10 That study of Finnish subjects showed that liver fat was strongly correlated with IS rather than with intramyocellular fat. Furthermore, patients with metabolic syndrome had significantly higher liver fat content than did those without metabolic syndrome, whereas there was no significant difference in intramyocellular fat between these groups. However, such information has been lacking with regard to the Japanese population. Such information is needed because Japanese individuals show a higher risk for type 2 diabetes at lower levels of obesity as compared with Caucasian individuals. For example, Kadowaki et al reported that Japanese individuals had greater VF area (VFA) than did Caucasians. 11 Furthermore, the incidence of fatty liver was higher, despite the lower body mass index (BMI), in Japanese individuals than in Caucasians.12 Thus, these data suggest there are ethnic differences in fat distribution between Asians (Japanese) and Caucasians. Despite these findings, the relationship between ectopic fat deposition in the liver or skeletal muscle and IS in Japanese individuals is still unclear. Therefore, in an attempt to address this limited knowledge, we performed this preliminary study to explore the relationship between peripheral IS, body fat accumulation, and aerobic capacity in middle- to older-aged Japanese participants with visceral adiposity. Participants and methods Participants Participants were Japanese individuals .40 years old with a waist circumference .85 cm (males) or .90 cm (females) according to the Japanese diagnostic criteria for metabolic syndrome in adults, and VFA . 100 cm2 according to the Japanese clinical criteria for visceral adiposity. The subjects who were enrolled in this study were not taking any medications affecting IS. Furthermore, individuals who were taking (...truncated)