1999 Fiscal Year Final Research Report Summary
Factor of suppression of tissue protein degradation after feeding and its mechanism
| Project/Area Number |
09660126
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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 |
食品科学・栄養科学
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| Research Institution | IWATE UNIVERSITY |
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Principal Investigator |
NAGASAWA Takashi Faculty of Agriculture, Department of Bioscience and Technology, Associate Professor, 農学部, 助教授 (80189117)
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| Project Period (FY) |
1997 – 1999
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| Keywords | Dietary protein / Myofibrillar protein / Protein degradation / Protein synthesis / Leucine / 3-Methylhistidine / p70S6 kinase |
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| Research Abstract |
After feeding of 20% casein diet for 1h, the rate of myofibrillar protein degradation measured by the serum concentration of 3-methyl-histidine (MeHis) and the release rate of MeHis from the isolated muscle significantly decreased, although they did not change when rats fed protein free diet. The suppression was increased with content of dietary protein content and it was not changed when feeding protein content was constant but energy was decreased. These results strongly suggest that dietary protein directly regulate myofibrillar protein degradation after feeding. Leu in dietary protein mainly affect the suppression, since these change was also seen in rats fed on Leu diet or force fed on Leu suspension.
Mechanism of suppression of degradation after feeding was analyzed by proteolysis inhibitors. When lysosome and calcium-dependent proteolytic systems were inhibited, the suppression was not seen, indicating that calpain may key enzyme. However, when ATP-dependent proteolytic system was inhibited, the suppression of myofibrillar protein degradation after feeding was demonstrated.
Phosphorylation of p70S6 kinase which correlates with protein synthesis was immediately activated by protein and Leu feeding. Therefore, protein synthesis may be activated more rapidly than protein degradation by feeding.
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