Study of Ligament Ossification and Abnormal Glucose Tolerance in the Zucker Fatty Rat
Significant expression of insulin-sensitive cells and the IGF-I-binding protein CTGF was observed in the cellular hyperplasia areas of the spinal ligament sites and Achilles tendon ectopic ossifi cation sites of Zucker fatty rats. We prepared MSG-treated rats, which exhibit hyperleptinemia and hyperinsulinemia from 6 months of age onward, as in ZFRs; however, as in other rats with dietary obesity, no ligament ossifi cation changes were seen at the spinal ligament sites.
Moreover, significantly more expression of IRS-1 was observed in the hypertrophic chondrocytes and juvenile osteoblasts in the cell hyperplasia areas of the spinal ligaments of the ZFRs, and there was little expression of IRS-2 in the ZFRs compared to the other groups. Therefore, a difference in sensitivity between the insulin receptor substrates (i.e., a decrease in IRS-2 and a corresponding increase in IRS-1) due to hyperinsulinemia and hyperleptinemia is thought to be involved, suggesting that an increase in bone metabolism mediated by IRS-1 is the cause of the ossifi cation at the spinal ligament sites in ZFRs.
KeywordsBone Mineral Density Connective Tissue Growth Factor Toluidine Blue Abnormal Glucose Tolerance Spinal Ligament
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