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Abstract
Background
Studies for the regulation of fatty acid metabolism are deficient relatively in skeletal muscle and heart. The investigations in pathological conditions for malonyl-CoA decarboxylase (MCD) and for the relation of MCD and PPAR-α·-γ agonists are insufficient in particular.
Methods
In the current study, fully differentiated H9c2 muscle cells were exposed to pathological conditions such as hyperlipidemic (0.1 mM Palmitate) and hyperglycemic (16.5 mM Glucose) condition with 5 uM PPAR-γ agonist (rosiglitazone) and 10 uM PPAR-α agonist (WY14,643) and then experiments such as MCD activity assay, MCD real-time RT-PCR, MCD reporter gene assay, MCD Western blotting, PPAR-α Western blotting, and palmitate oxidation test were carried out.
Results
Only PPAR-α agonist increased MCD activity. In the result of real-time RT-PCR, both PPAR-α and PPAR-γ agonists elevated MCD mRNA expression in hyperlipidemic condition. MCD protein expression was decreased in hyperlipidemic condition, however, increased in rosiglitazone, or WY14,643 treated conditions. Rosiglitazone, and WY14,643 treated groups showed incresed MCD protein expression in hyperglycemic condition.
Hyperlipidemic control group and PPAR-α·-γ agonists treated groups presented about 3.8 times more increased palmitate oxidation level than normolipidemic control group in hyperlipidemic condition.
PPAR-α agonist treated group showed 49% more increased palmitate oxidation rate than hyperlipidemic control group in primary cultured rat skeletal muscle cells. The amount of palmitate oxidation from differentiated H9c2 muscle cells that had overexpressed PPAR-α structural genes was more increased than control group.
Conclusion
This study suggests that PPAR-α agonist ameliorates the defects induced by hyperlipidemic condition through the regulation of MCD.
In summary, a closely reciprocal relation among PPAR-α agonist, MCD, and fatty acid oxidation existed distinctly in hyperlipidemic condition, but not in hyperglycemic condition.
Figures and Tables
Fig. 1
The alteration of MCD activities in hyperglycemic (A) and hyperlipidemic (B) conditions. Fully differentiated myotubes were treated with 5 uM rosiglitazone and 10 uM WY14,643 in hyperglycemic condition and in hyperlipidemic condition. Only WY-14,643 increased MCD enzyme activity in hyperglycemic and hyperlipidemic conditions.
*P < 0.05
Fig. 2
The alteration of MCD mRNA expressions in hyperglycemic (A) and hyperlipidemic (B) conditions. The elevation of MCD mRNA expression by PPAR agonists was observed in hyperlipidemic condition, however, not in hyperglycemic condition.
*P < 0.05
Fig. 3
The result of MCD promoter gene assay in hyperglycemic and hyperlipidemic conditions. The expression rate of MCD promoter gene was increased by PPAR agonists in hyperlipidemic condition, however, not in hyperglycemic condition.
*P < 0.05
Fig. 4
The alteration of MCD protein expressions in hyperglycemic (A) and hyperlipidemic (B) conditions. MCD protein expression that was decreased in hyperlipidemic condition was increased by treatments of PPAR agonists. In hyperglycemic condition PPAR agonists increased MCD protein expression.
*P < 0.05
Fig. 5
The effects of PPAR agonists on palmitate oxidations from H9c2 cells (A, B) in hyperglycemic (A) and hyperlipidemic (B) conditions, and from HepG2 cells (C) in hyperlipidemic condition. Palmitate oxidation was increased in only hyperlipidemic condition.
The increase of palmitate oxidation from H9c2 cells occurred only in hyperlipidemic condition, but palmitate oxidation rates among hyperlipidemic control group and PPAR agonists treated groups were not different. HepG2 cells in hyperlipidemic condition was like to the palmitate oxidation aspect of H9c2 cells in same condition.
*P < 0.05
Fig. 6
The effects of PPAR agonists on palmitate oxidations from primary cultured rat skeletal muscle cell in hyperglycemic (A) and hyperlipidemic (B) conditions. There was no differences among experimental groups in hyperglycemic condition. But in hyperlipidemic condition the palmitate oxidation rates of hyperlipidemic control group and PPAR-α agonist treated group were more increased than normolipidemic control group and hyperlipidemic control group respectively, however, the palmitate oxidation rate of PPAR-γ agonist treated group was decreased in comparison with hyperlipidemic control group.
*P < 0.05
Fig. 7
The alteration of PPAR-α protein expression in hyperlipidemic condition
In hyperlipidemic condition, only protein expression of WY14,643 treated group was increased.
*P < 0.05.
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