Adiponectin is an important adipose-specific protein, which possesses insulin (INS)-sensitizing, antiinflammatory, and antiatherosclerotic functions. However, its regulation remains largely unknown. In this study, we identified that ryanodine receptor (RyR)3 plays an important role in the regulation of adiponectin expression. RyR3 was expressed in 3T3-L1 preadipocytes, and its level was decreased upon adipogenesis. Silencing of RyR3 expression in 3T3-L1 preadipocytes resulted in up-regulated adiponectin promoter activity, enhanced adiponectin mRNA expression, and more adiponectin protein secreted into the medium. An inverse relation between RyR3 and adiponectin mRNA levels was also observed in adipose tissues of db/db mice. In addition, knockdown of RyR3 with small interfering RNA (siRNA) in db/db mice and high-fat diet-fed obese mice increased serum adiponectin level, improved INS sensitivity, and lowered fasting glucose levels. These effects were in parallel with decreased mitochondrial Ca(2+), increased mitochondrial mass, and reduced activating transcription factor 3 (atf3) expression. Overexpression of atf3 in 3T3-L1 preadipocytes blocked the effect of RyR3 silencing on adiponectin expression, indicating that an atf3-dependent pathway mediates the effect downstream of RyR3 silencing. Our data suggest that RyR3 may be a new therapeutic target for improving INS sensitivity and related metabolic disorders.
Various prostanoids and peroxisome proliferator-activated receptor γ (PPARγ) ligands play an important role in gastric cancer. Previously, we demonstrated that prostaglandin reductase 2 (PTGR2) catalyzes the reduction of the PPARγ ligand 15-keto-PGE(2) into 13,14-dihydro-15-keto-PGE(2). Here, we present functional data and clinical relevance for the role of PTGR2 in gastric cancer. Using lentiviral technology in AGS and SNU-16 gastric cancer cell lines, we either down-regulated or overexpressed PTGR2. In vitro analysis showed that PTGR2 knockdown resulted in decreased proliferation rate and colony formation, and in vivo xenograft models showed slower growth of tumors. Mechanistically, PTGR2 knockdown induced cell death, altered mitochondrial function, and increased reactive oxygen species production, which led to activation of ERK1/2 and caspase 3, with increased Bcl-2 and suppressed Bax expression. PTGR2 overexpression showed the opposite outcomes. Clinically, immunopathological staining showed strong PTGR2 expression in the gastric tumor portion, relative to nearby nontumor portions, and its expression negatively correlated with survival of patients with intestinal-type gastric cancer. Finally, in contrast to PTGR2-overexpressing cells, PTGR2-knockdown cells were more sensitive to cisplatin and 5-fluorouracil. Taken together, our findings not only provide functional and mechanistic evidence of the involvement of PTGR2 in gastric cancer, but also provide clinical observations affirming the significance of PTGR2 in gastric cancer and suggesting that PTGR2-target based therapy is worth further evaluation.
Prostaglandins are potent modulators of insulin sensitivity. We systemically evaluated the association of 61 tag single-nucleotide polymorphisms (SNP) in 14 genes involved in prostaglandin metabolism with type 2 diabetes. Among all genotyped SNPs, rs10483032 in the CBR3 (carbonyl reductase 3) gene, which encodes for an enzyme converting prostaglandin E(2) to prostaglandin F2(α), was associated with type 2 diabetes in 760 type 2 diabetic cases and 760 controls (stage-1 study) (P = 2.0 × 10(-4)). The association was validated in 1,615 cases and 1,162 controls (stage-2 study) (P = 0.009). The A allele at rs10483032 was associated with increased risk of type 2 diabetes (odds ratio = 1.29; 95% confidence interval = 1.14-1.47; combined P < 0.0001). The association was externally validated in the Finland-United States Investigation of NIDDM Genetics (FUSION) study (P = 3.7 × 10(-4)). The risk A allele was associated with higher homeostasis model assessment of insulin resistance (HOMA-IR) in 1,012 non-diabetic controls and 1,138 non-diabetic subjects from the Stanford Asia-Pacific Program for Hypertension and Insulin Resistance (SAPPHIRe) family study. CBR3 gene expression in human abdominal adipose tissue was negatively associated with fasting insulin and HOMA-IR. CBR3 gene expression increased during differentiation of 3T3-L1 preadipocytes into adipocytes. Knockdown of CBR3 in 3T3-L1 preadipocytes enhanced adipogenesis and peroxisome proliferator-activator receptor-γ response element reporter activity. Our results indicated that genetic polymorphism in the CBR3 gene conferred risk of type 2 diabetes and insulin resistance in Chinese. The association was probably mediated through modulation of adipogenesis.
This study analyzes how regional public transport facilities and medical services affect the efficiency of international tourist hotels (ITHs). First, we adopt data envelopment analysis (DEA) to measure the cost efficiency of international tourist hotels in Taiwan during 1998 to 2009. Next, we use the truncated regression to estimate the effect of traffic convenience and medical services on cost efficiency. The distance to international airports and distance to MRT station have significantly negative effects on cost efficiency of international tourist hotels, while the distance to the freeway exit, distance to bus station, and pickup service, chain system, and shorter operating year have significantly positive impacts on their cost efficiency. The shorter distance to the hospital and more hospitals in a region significantly improve cost efficiency of ITHs in Taiwan.
Peroxisome proliferators-activated receptor gamma (PPARγ) receptor is a transcription factor that is located in and functions primarily in the nucleus. PPARγ is exported from the nucleus upon mitogen and ligand stimulation under certain circumstances. However, a cytoplasmic PPARγ interacting protein and its function have not been previously identified. Here, we report for the first time that cytosolic PPARγ interacts directly with cytoskeletal vimentin. We performed PPARγ immunoprecipitation followed by mass spectrometry to identify the vimentin-PPARγ complex. This interaction was confirmed by reciprocal vimentin and PPARγ immunoprecipitation and co-immunofluorescence examination. We demonstrated that PPARγ colocalized with vimentin in certain organelles that is golgi, mitochondria, and endoplasmic reticulum. In cells depleted of vimentin, PPARγ was ubiquitinated and targeted to a proteasomal degradation pathway. Together, these findings indicate a direct interaction of PPARγ with vimentin in the cytosolic compartment, in which vimentin appears to play a role in regulating the turnover rate of PPARγ, which may further regulate genomic or non-genomic activities through the regulation of PPARγ protein degradation.
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