SKELETAL MUSCLEAS A ETIOLOGY OF OBESITY AND INSULIN RESISTANCE : INVESTIGATION BY USING FAST-TWITCH FIBER DOMINANT MODEL RATS (FFDR)
| Project/Area Number |
10680037
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
体育学
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| Research Institution | KYUSHU UNIVERSITY |
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Principal Investigator |
KUMAGAI Shuzo Institute of Health Science, Kyushu University, Associate Professor, 健康科学センター, 助教授 (80145193)
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| Co-Investigator(Kenkyū-buntansha) |
NAKAMURA Tomohiro Department of General Education, Osaka Institute of Technology, Lecturer, 一般教育科, 講師 (30217872)
KATSUTA Shigeru Institute of Health and Sports Sciences, University of Tsukuba, Professor, 体育科学系, 教授 (70038446)
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| Project Period (FY) |
1998 – 1999
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| Project Status |
Completed (Fiscal Year 1999)
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| Budget Amount *help |
¥2,700,000 (Direct Cost: ¥2,700,000)
Fiscal Year 1999: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1998: ¥1,700,000 (Direct Cost: ¥1,700,000)
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| Keywords | FAST-TWITCH FIBER DOMINANT MODEL RAT (FFDR) / HIGH-FAT DIET / MUSCLE FIBER COMPOSITION / FAT ACCUMULATION / OXIDATIVE ENZYME ACTIVITY / 速筋優位モデルラット / インスリン感受性 / 肥満 / 筋繊維組成 / 毛細血管 / 自発運動量 |
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| Research Abstract |
Recent studies reported skeletal muscle characteristics to be related to abdominal obesity, insulin resistance, and hyper tension. There is some evidences that the percentage of fast-twitch (%FT) fibers in human muscle is inversely associated with insulin resistance and is also positively related with body fat accumulation. However, it has yet to be elucidated as to whether rats with genetically higher levels of %FT fibers developed by Suwa et al (Am. J. Physiol., 271 : R432 - R436, 1996) had lower levels of insulin sensitivity than control rats. The FT% fiber in both the M. gastrocnemius and soleus in FT fiber dominant model rat (FFDR) were demonstrated to be significantly higher than in control rats (CR). The main purposes of present study was to investigate the levels of insulin sensitivity, some muscle characteristics including fiber composition and capillary density, and the distance for voluntary wheel running between FFDR and CR. FFDR (n=6) and CR(n=8) aged from 8 to 9 weeks wer
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e used in this study. Insulin sensitivity was evaluated by the euglycemic hyper insulinemic clamp for 90min and was calculated as the mean glucose infusion rate (GIR ; mg/ kg/ min) from 60 to 90 min. The mean plasma insulin concentration in both groups during this period showed no significant differences. Neither the body weight, fat contents, and individual muscle weight of FFDR were observed to be significantly different from CR, except for higher the weight of M. soleus in FFDR. A significantly lower levels of percentage of slow-twitch (%ST) fibers in the deep portion of the M. gastrocnemius and soleus, and higher levels of %FTb fibers in the deep portion of M. gastrocnemius and %FTa fibers in M. soleus were observed in FFDR when compared with CR. On the other hand, no significant differences between FFDR and CR were observed regarding the capillary density, capillary to fiber ratio, and the mean number of capillaries around the muscle fiber. The GIR in FFDR (4.9mg/kg/min) was not significantly lower than that in CR (4.6mg/kg/min). Distance covered by wheel running in FFDR at aged from 8 to 9 weeks was also significantly longer than that in CR. From these results, the muscle fiber composition is thus suggested to not be the single determinant of the whole-body glucose uptake in young male rats. The second purpose of present study was to investigate the effect of high-fat diet on abdominal fat accumulation, and histochemical and biochemical muscle characteristics between FFDR and CR after low- and high-fat diet. The FFDR with low-fat diet (FL ; n=8), FFDR with high-fat diet (FH ; n=9), CR with low-fat diet (CL ; n=7) and CR with high-fat diet (CH ; n=7) were used in this study. Each diet were started at age of 8 weeks and were maintained for 6 weeks. Increasing in body weight and abdominal fat accumulation in CH were significantly higher than in FL and FH. No significant Difference was observed in energy intake among 4 groups. Although weight of M. gastrocnemius in CH was higher than in FL and FH, no significant difference were observed in the weight of M. soleus and M. plantaris among 4 groups. The %type1 fibers in M. gastrocnemius in FFDR was significantly lower than in CR, but %type 2DX fibers in FFDR was significantly higher than that in FFDR. In the deep portion of M. gastrocnemius, succinate dehydrogenase (SDH) activity in type 2A and type 2DX fibers is significantly higher than that in type1 fibers in each group. From these results, it is suggested that the difference in fat accumulation after high-fat diet between CR and FFDR is dependent on difference in oxidative capacity of each fiber type but not in the muscles volume. Less
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Report
(3 results)
Research Products
(6 results)
