ABSTRACT
OBJECTIVE@#To investigate the effect CD36 deficiency on muscle insulin signaling in mice fed a normal-fat diet and explore the possible mechanism.@*METHODS@#Wild-type (WT) mice and systemic CD36 knockout (CD36-/-) mice with normal feeding for 14 weeks (n=12) were subjected to insulin tolerance test (ITT) after intraperitoneal injection with insulin (1 U/kg). Real-time PCR was used to detect the mRNA expressions of insulin receptor (IR), insulin receptor substrate 1/2 (IRS1/2) and protein tyrosine phosphatase 1B (PTP1B), and Western blotting was performed to detect the protein expressions of AKT, IR, IRS1/2 and PTP1B in the muscle tissues of the mice. Tyrosine phosphorylation of IR and IRS1 and histone acetylation of PTP1B promoter in muscle tissues were detected using co-immunoprecipitation (Co-IP) and chromatin immunoprecipitation (ChIP), respectively.@*RESULTS@#CD36-/- mice showed significantly lowered insulin sensitivity with obviously decreased area under the insulin tolerance curve in comparison with the WT mice (P < 0.05). CD36-/- mice also had significantly higher serum insulin concentration and HOMA-IR than WT mice (P < 0.05). Western blotting showed that the p-AKT/AKT ratio in the muscle tissues was significantly decreased in CD36-/- mice as compared with the WT mice (P < 0.01). No significant differences were found in mRNA and protein levels of IR, IRS1 and IRS2 in the muscle tissues between WT and CD36-/- mice (P>0.05). In the muscle tissue of CD36-/- mice, tyrosine phosphorylation levels of IR and IRS1 were significantly decreased (P < 0.05), and the mRNA and protein levels of PTP1B (P < 0.05) and histone acetylation level of PTP1B promoters (P < 0.01) were significantly increased as compared with those in the WT mice. Intraperitoneal injection of claramine, a PTP1B inhibitor, effectively improved the impairment of insulin sensitivity in CD36-/- mice.@*CONCLUSION@#CD36 is essential for maintaining muscle insulin sensitivity under physiological conditions, and CD36 gene deletion in mice causes impaired insulin sensitivity by up-regulating muscle PTP1B expression, which results in detyrosine phosphorylation of IR and IRS1.
Subject(s)
Animals , Mice , Gene Deletion , Histones/genetics , Insulin , Insulin Receptor Substrate Proteins/metabolism , Insulin Resistance/genetics , Membrane Cofactor Protein/genetics , Mice, Knockout , Muscles/metabolism , Phosphoric Monoester Hydrolases/metabolism , Protein Tyrosine Phosphatase, Non-Receptor Type 1/metabolism , Proto-Oncogene Proteins c-akt/metabolism , RNA, Messenger/metabolism , Receptor, Insulin/metabolism , Tyrosine/genetics , Up-RegulationABSTRACT
Background. CD46 is a complement regulatory glycoprotein. Certain polymorphic forms of the CD46 gene have been associated with recurrent pregnancy loss in the Caucasian population. We assessed the role of CD46 polymorphism in recurrent spontaneous abortion in our setting, as this has not been done on Indian subjects till date. Methods. Polymerase chain reaction–restriction fragment length polymorphism (PCR–RFLP) was carried out on 44 samples each from women with recurrent spontaneous abortion and normal pregnancy. Genotyping of the CD46 gene was done using 2.5% agarose gel. Statistical analysis was done using the TFPGA software. Results. The absence of CD46H*1 homozygosity was more pronounced in women with recurrent spontaneous abortion in the Indian population. Of recurrent aborters, 9% had the H*1/*1 genotype as compared to 30% of normal pregnant women. Conclusion. Although our data did not fit the Hardy– Weinberg equilibrium, this pilot study indicates that further increasing the sample size might clarify whether polymorphism in the first intron of the CD46 gene can be regarded as a risk factor for recurrent spontaneous abortion.