[Induced differentiation and signaling factor PTEN expression of 3T3-L1 adipocytes].

OBJECTIVE: To optimize the condition for inducing the differentiation of 3T3-L1 preadipocytes into adipocytes and study the expression of PTEN tumor suppression gene in this process, aiming to understand the regulatory role of PTEN in normal adipocyte differentiation and collect laboratory evidence for developing drugs targeting PTEN. METHODS: The differentiation of 3T3-L1 preadipocytes cultured in high-glucose DMEM were induced according to 2 protocols with different combinations of dexamethasone, isobutylmethylxanthine (IBMX) and insulin, and the resultant adipocytes were identified by oil red O staining. The total proteins of 3T3-L1 were extracted and analyzed by Western blotting, and PTEN homology between mice and human was analyzed by bioinformatic method. RESULTS: For optimized 3T3-L1 differentiation, 3T3-L1 cells were initially induced with the combination of 1 micromol/L dexamethasone, 0.5 mmol/L IBMX and 5 microg/ml insulin for 48 h, followed by treatment with 5 microg/ml insulin in 4.5 g/L glucose DMEM for 48 h, which resulted in high differentiation rate of 3T3-L1 cells (up to 90% on the 10th day) with unified morphology and size. PTEN expression varied quantitatively in the process of differentiation, especially low on the 12th day as compared with those measured on days 4, 6 and 9. The mice PTEN mRNA shared 96% homology and PTEN amino acid 100% homology with their human counterparts. CONCLUSION: Endogenous PTEN expression is down-regulated during 3T3-L1 differentiation, suggesting that PTEN may enhance insulin sensitivity and promote adipogenesis under physiological conditions.

[Relationship of collagen type I alpha 1 and alpha 2 gene polymorphisms with bone mineral density].

OBJECTIVE: To investigate collagen type I alpha 1 (COL1A1) and alpha 2 (COL1A2) gene polymorphisms in Chinese and their relationship with bone mineral density. METHODS: Totalling 628 residents of Han nationality in Guangzhou aged 53.4-15.9 (range 20-79) years were surveyed for COL1A1 and COL1A2 gene genotypes by polymerase chain reaction-restriction fragment length polymorphism. Bone mineral density of the lumbar vertebrae, greater trochanter, femur neck and Ward's triangle was measured by dual-energy X-ray absorptiometry. RESULTS: COL1A1 Sp1 polymorphism was not found in these subjects, and the genotype of all samples were type SS. COL1A2 genotyping revealed the distribution of EE genotype in 49.7%, Ee in 40.9% and ee in 9.4% of the subjects. The frequency distribution of EcoR1 alleles followed the Hardy-Weinberg equilibrium. The mean bone mineral density did no significantly differ among these genotype groups (P>0.05 by analysis of variance). CONCLUSION: COL1A1 Sp1 binding site polymorphism is absent and COL1A2 EcoR1 site polymorphism is not associated with bone mineral density in Chinese of Han nationality.