Bezafibrate enhances proliferation and differentiation of osteoblastic MC3T3-E1 cells via AMPK and eNOS activation.

AIM: To investigate the effects of bezafibrate on the proliferation and differentiation of osteoblastic MC3T3-E1 cells, and to determine the signaling pathway underlying the effects. METHODS: MC3T3-E1 cells, a mouse osteoblastic cell line, were used. Cell viability and proliferation were examined using MTT assay and colorimetric BrdU incorporation assay, respectively. NO production was evaluated using the Griess reagent. The mRNA expression of ALP, collagen I, osteocalcin, BMP-2, and Runx-2 was measured using real-time PCR. Western blot analysis was used to detect the expression of AMPK and eNOS proteins. RESULTS: Bezafibrate increased the viability and proliferation of MC3T3-E1 cells in a dose- and time-dependent manner. Bezafibrate (100 µmol/L) significantly enhanced osteoblastic mineralization and expression of the differentiation markers ALP, collagen I and osteocalcin. Bezafibrate (100 µmol/L) increased phosphorylation of AMPK and eNOS, which led to an increase of NO production by 4.08-fold, and upregulating BMP-2 and Runx-2 mRNA expression. These effects could be blocked by AMPK inhibitor compound C (5 µmol/L), or the PPARß inhibitor GSK0660 (0.5 µmol/L), but not by the PPARα inhibitor MK886 (10 µmol/L). Furthermore, GSK0660, compound C, or N(G)-nitro-L-arginine methyl ester hydrochloride (L-NAME, 1 mmol/L) could reverse the stimulatory effects of bezafibrate (100 µmol/L) on osteoblast proliferation and differentiation, whereas MK886 only inhibited bezafibrate-induced osteoblast proliferation. CONCLUSION: Bezafibrate stimulates proliferation and differentiation of MC3T3-E1 cells, mainly via a PPARß-dependent mechanism. The drug might be beneficial for osteoporosis by promoting bone formation.

Altered nuclear factor-kappaB inducing kinase expression in insulin-resistant mice.

BACKGROUND: Insulin resistance is an underlying feature of both type 2 diabetes and metabolic syndrome. Currently, it is unclear whether nuclear factor (NF)-κB inducing kinase (NIK) plays a role in the development of insulin resistance. The present in vivo study investigated the roles of NIK and IκB kinase α (IKKα) in obesity-induced insulin resistance using animal models. METHODS: NIK expression was evaluated by Western blotting in male Lep(ob) mice and C57BL/6J mice fed a high-fat diet (HFD) (45% fat). After metformin and sulfasalazine treatment, NIK expression was investigated during the improvement of insulin resistance. RESULTS: NIK was increased by about 1-fold in the renal tissues of Lep(ob) mice and C57BL/6J mice fed a HFD for 12 weeks. After 1 and 3 weeks of high-fat feeding, we observed an almost 50% decrease in NIK and IKKα expression in the liver and renal tissues of C57BL/6J mice. NIK expression was significantly lower in the liver and renal tissues of HFD-fed mice that were treated with insulin sensitizers, metformin and sulfasalazine. However, IKKα expression was increased after metformin treatment in both tissues. CONCLUSION: These results suggest a possible role of NIK in the liver and renal tissues of insulin-resistant mice.

[Three single nucleotide polymorphisms of porphobilinogen deaminase gene related to a Chinese patient with acute intermittent porphyria].

OBJECTIVE: To analyzed the role of genetic factors in pathogenesis of acute intermittent porphyria (AIP). METHODS: Peripheral blood sample was collected from a Chinese female AIP patients, aged 36, to undergo direct sequencing to analyze all the exons and flanking introns of the porphobilinogen deaminase (PBGD) and protoporphyrinogen oxidase (PPOX) genes. The sequencing results were compared with the established human PBGD and PPOX sequences (GenBank Accession No. M95623; NC_000001.9). RESULTS: Direct sequencing showed three kinds of single nucleotide polymorphism (SNP) in the PBGD gene. No mutation was found in the coding regions of either PBGD or PPOX gene. CONCLUSION: The three SNPs may underlie the genetic defects of AIP in Chinese. SNP may serve as genetic markers for linkage analysis to track presymptomatic carriers in AIP families.

Beta-cell dysfunction is the primary contributor to the early postpartum diabetes among Chinese women with history of gestational diabetes mellitus.

BACKGROUND: Women with a history of gestational diabetes mellitus (GDM) are at higher risk of future development of diabetes. This study investigated the risk factors associated with early postpartum abnormal glucose regulation (AGR) among Chinese women with a history of GDM. METHODS: A total of 186 women with a history of GDM were screened for early postpartum AGR at 6-8 weeks after delivery. Those with AGR were given lifestyle intervention therapy and reevaluated in 6-12 months. The demographic, anthropometric, prenatal and delivery data were recorded. The plasma high-sensitivity C-reactive protein (HsCRP) and lipid concentration were measured, and insulin secretion were analyzed. Insulinogenic index Deltains30'/DeltaBG30', the homeostasis model assessment index (HOMA)-B, and HOMA-IR were calculated. Multiple regression analysis was performed to identify the risk factors. RESULTS: Of the GDM women 28.0% (52/186) had AGR at 6-8 weeks after delivery; 45.2% (17/40) of these AGR women reminded abnormal after 6-12 month lifestyle intervention. Compared to the women who reverted to normal, women with consistent AGR showed significantly lower fasting insulin concentration, lower Deltains30'/DeltaBG30' as well as lower HOMA-B. No significant differences in age, body mass index (BMI), waist circumference, blood pressure, lipid level, HsCRP and HOMA-IR were observed between the two groups. Pre-pregnancy BMI = 25 kg/m(2), fasting glucose level = 5.6 mmol/L and/or 75 g oral glucose tolerance test (OGTT) 2 hours glucose level = 11.1 mmol/L during pregnancy were predictors for the AGR at 6-8 weeks after delivery. Deltains30'/DeltaBG30 = 1.05 was a significant risk contributor to the consistent early postpartum AGR. CONCLUSION: There is a high incidence of early postpartum AGR among Chinese woman with prior GDM. Beta-cell dysfunction, rather than insulin resistance or inflammation, is the predominant contributor to the early onset and consistent AGR after delivery.

[Etiological dissection in common anti-islet autoantibody-negative patients with type 1 diabetes].

OBJECTIVE: To explore the immunological and genetic factors of common anti-islet autoantibody-negative patients with type 1 diabetes. METHODS: Specimens of peripheral blood were collected from 33 common autoantibody (GAD-Ab, IA2-Ab, IAA, TGA and TPO-Ab) negative diabetic patients with new-onset of unprovoked ketosis (or ketoacidosis), and genome DNA was extracted. The antibodies to carboxypeptide-H (CPH) and SOX13 (ICA12) were detected by radioligand assay. The gene mutations of MODY3 (HNF-1alpha) and MODY6 (NeuroD1/Beta2) were detected by PCR-SSCP sequencing. Mitochondrial gene mutations were analyzed with PCR-RFLP. RESULTS: Two (6%) of the patients were SOX13-Ab positive, while none of them was positive for CPH-Ab. Gene mutation detection found one case of a new mutation, R321H (CGC-->CAC) in the exon 5 of HNF-1alpha gene and one case with ND1 mt3316 G-->A mutation in mitochondrial DNA. In addition to the diabetes-associated mutations described above, seven polymorphisms of HNF-1alpha gene, including L17L, I27L, L459L, S487N, IVS5 + 9 C > G, IVS6-42 G > T, and IVS7 + 7 G > A, and one NeuroD1/Beta2 gene polymorphic variant Ala45Thr, were found. CONCLUSION: Autoimmunity and gene mutations (such as MODY3 and mitochondrial genes mutations) may be etiological in a few cases initially diagnosed as autoantibody-negative type 1 diabetes. Autoimmunity and MODY and mitochondrial diabetes should be excluded if idiopathic type 1 (type 1B) diabetes is diagnosed.

[Additive effects of the variants in the beta(3)-adrenergic receptor and uncoupling protein-2 genes on obesity in Chinese].

OBJECTIVE: To investigate the additive effects of uncoupling protein 2 (UCP2) gene Ala55Val variation and ADR beta(3) gene Trp64Arg variation on the obesity in Chinese Han population. METHODS: The UCP2 gene Ala55Val variation and ADR beta(3) gene Trp64Arg variation were examined by polymerase chain reaction-restriction fragment length polymorphism(PCR-RFLP) in 119 obese subject with mean BMI (27.9+/-2.98)kg/m(2) and in 177 control subjects with mean BMI(21.9+/-1.9)kg/m(2). The additive effects of the two gene mutations were analyzed. RESULTS: (1) The frequency of ADR beta(3) gene Trp64Arg variation in obese subjects was not significantly different from that in control subjects. In control subjects, the Trp64Arg variation carriers had higher fasting glucose level and 2-hour-post-prandial glucose level than did non-carriers. (2) The frequency of homozygote of UCP2 gene Ala55Val variation in obese subjects was higher than that in the control subjects (OR=3.71, P=0.001). In control subjects the Ala55Val variation carriers had higher BMI. (3) When there was only UCP2 gene or ADR beta(3) gene mutation, the frequency of gene mutation in obese subjects was not significantly different from that in control subjects (P>0.05). But when there were simultaneously two gene mutations, the frequency of gene mutations was higher in obese subjects than in control subjects (OR=2.57, P=0.009). (4) The genotype carriers with Val/Val+ Trp/Arg were the greatest relation to obese obesity (OR=8.58, P=0.002). CONCLUSION: The homozygote of UCP2 gene Ala55Val mutation increases the risk of obesity. Though the UCP2 gene mutation alone or the ADR beta(3) gene mutation alone is not associated with obesity, the possible additive effects of the two micro-genes increase the occurring of obesity.

[Common variants in beta 3-adrenergic-receptor and uncoupling protein-2 genes are associated with type 2 diabetes and obesity].

OBJECTIVE: To investigate the effects of uncoupling protein-2 (UCP2) gene Ala55Val variation and beta(3)-adrenergic-receptor (beta(3)-AR) gene Trp64Arg variation on type 2 diabetes and obesity, as well as the combined effects between the two variations. METHODS: The peripheral blood samples of 173 type 2 diabetics, 119 obese persons, and 177 control subjects were collected. PCR-RFLP was used to detect the UCP2 gene Ala55Val variation and beta(3)-AR gene Trp64Arg variation. The haplotype and allele frequency distributions among the three groups were analyzed. The combined effect of the two gene mutations was analyzed too. RESULTS: (1) The frequencies of homozygote of UCP2 gene Ala55Val variation in the diabetes and obesity patients were both significantly higher than that in the control subjects (OR = 4.62, P = 0.001; OR = 3.71, P = 0.001). The Ala55Val variation carriers had higher BMI in the control subjects. (2) The gene frequency of homozygote of beta(3)-AR gene Trp64Arg variation was significantly higher in the diabetes patients than in the control subjects. The Trp64Arg variation carriers had higher fasting and 2-hour postgrandual glucose levels than the non-carriers in the control subjects. (3) When there was only UCP2 gene mutation or beta(3)-AR gene mutation, their frequencies in diabetes and obesity patients were not significantly different from that in the control subjects (both P > 0.05). However, the frequencies of the combined mutations of these two genes in either the diabetes patients or in the obesity patients were both significantly higher than in the control subjects (OR = 3.69, P = 0.000; OR = 2.57, P = 0.009). (4) The Val/Val + Trp/Arg carriers had the greatest relation with diabetes (OR = 10.43, P = 0.000) and obesity (OR = 8.58, P = 0.002). CONCLUSION: The homozygote of UCP2 gene Ala55Val mutation significantly enhances the risks of diabetes and obesity. The homozygote of beta(3)-AR gene Trp64Arg mutation is related with diabetes. The accumulation of the effects of two micro-genes creates obvious phenotypic effects.