Bile acids have been shown to be important hormones during the feed/fast cycle, allowing the liver to coordinately regulate nutrient metabolism. How they accomplish this has not been fully elucidated. Conjugated bile acids have been shown to activate both the ERK1/2 and AKT signaling pathways via S1PR2 in rodent hepatocytes and in vivo. Here, we report that feeding mice a high fat diet, infusion of taurocholate into the chronic bile fistula rat, or overexpression of the gene encoding S1PR2 in mouse hepatocytes significantly up-regulated hepatic SphK2, but not SphK1. Key genes encoding nuclear receptors/enzymes involved in nutrient metabolism were significantly down-regulated in livers of S1PR2−/− and SphK2−/− mice. In contrast, overexpression of the gene encoding S1PR2 in primary mouse hepatocytes differentially increased SphK2, but not SphK1, and mRNA levels of key genes involved in nutrient metabolism. Nuclear levels of S1P, an endogenous inhibitor of HDAC 1/2, as well as the acetylation of H3K9, H4K5 and H2BK12, were significantly decreased in hepatocytes prepared from S1PR2−/− and SphK2−/− mice. Both S1PR2−/− and SphK2−/− mice rapidly developed fatty livers on a high fat diet suggesting the importance of conjugated bile acids, S1PR2 and SphK2 in regulating hepatic lipid metabolism.

Hyperglycemia-induced inflammation and apoptosis have important roles in the pathogenesis of diabetic cardiomyopathy. We recently found that a novel curcumin derivative, C66, is able to reduce the high glucose (HG)-induced inflammatory response. This study was designed to investigate the protective effects on diabetic cardiomyopathy and its underlying mechanisms. Pretreatment with C66 significantly reduced HG-induced overexpression of inflammatory cytokines via inactivation of nuclear factor-κB in both H9c2 cells and neonatal cardiomyocytes. Furthermore, we showed that the inhibition of Jun NH2-terminal kinase (JNK) phosphorylation contributed to the protection of C66 from inflammation and cell apoptosis, which was validated by the use of SP600125 and dominant-negative JNK. The molecular docking and kinase activity assay confirmed direct binding of C66 to and inhibition of JNK. In mice with type 1 diabetes, the administration of C66 or SP600125 at 5 mg/kg significantly decreased the levels of plasma and cardiac tumor necrosis factor-α, accompanied by decreasing cardiac apoptosis, and, finally, improved histological abnormalities, fibrosis, and cardiac dysfunction without affecting hyperglycemia. Thus, this work demonstrated the therapeutic potential of the JNK-targeting compound C66 for the treatment of diabetic cardiomyopathy. Importantly, we indicated a critical role of JNK in diabetic heart injury, and suggested that JNK inhibition may be a feasible strategy for treating diabetic cardiomyopathy.

Bile duct obstruction is a potent stimulus for cholangiocyte proliferation, especially for large cholangiocytes. Our previous studies reported that conjugated bile acids (CBAs) activate the AKT and ERK1/2 signaling pathways via the sphingosine 1-phosphate receptor 2 (S1PR2) in hepatocytes and cholangiocarcinoma cells. It also has been reported that taurocholate (TCA) promotes large cholangiocyte proliferation and protects cholangiocytes from bile duct ligation (BDL)-induced apoptosis. However, the role of S1PR2 in bile acid-mediated cholangiocyte proliferation and cholestatic liver injury has not been elucidated. Here we report that S1PR2 is the predominant S1PR expressed in cholangiocytes. Both TCA- and S1P-induced activation of ERK1/2 and AKT were inhibited by JTE-013, a specific antagonist of S1PR2, in cholangiocytes. In addition, TCA- and S1P-induced cell proliferation and migration were inhibited by JTE-013 and a specific shRNA of S1PR2 as well as chemical inhibitors of ERK1/2 and AKT in mouse cholangiocytes. In BDL mice, the expression of S1PR2 was upregulated in whole liver and cholangiocytes. S1PR2 deficiency significantly reduced BDL-induced cholangiocyte proliferation and cholestatic injury as indicated by significant reduction of inflammation and liver fibrosis in S1PR2−/− mice. Treatment of BDL mice with JTE-013 significantly reduced total bile acid levels in the serum and cholestatic liver injury. This study suggests that the CBA-induced activation of S1PR2-mediated signaling pathways plays a critical role in obstructive cholestasis and may represent a novel therapeutic target for cholestatic liver diseases.

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High aerobic glycolysis not only provides energy to cancer cells, but also supports their anabolic growth. JMJD1A, a histone demethylase that specifically demethylates H3K9me1/2, is overexpressed in multiple cancers, including urinary bladder cancer (UBC). It is unclear whether JMJD1A could promote cancer cell growth through enhancing glycolysis. In this study, we found that downregulation of JMJD1A decreased UBC cell proliferation, colony formation and xenograft tumor growth. Knockdown of JMJD1A inhibited glycolysis by decreasing the expression of genes participated in glucose metabolism, including GLUT1, HK2, PGK1, PGM, LDHA and MCT4. Mechanistically, JMJD1A cooperated with hypoxia inducible factor 1α (HIF1α), an important transcription factor for glucose metabolism, to induce the glycolytic gene expression. JMJD1A was recruited to the promoter of glycolytic gene PGK1 to demethylate H3K9me2. However, the JMJD1A (H1120Y) mutant, which loses the demethylase activity, failed to cooperate with HIF1α to induce the glycolytic gene expression, and failed to demethylate H3K9me2 on PGK1 promoter, suggesting that the demethylase activity of JMJD1A is essential for its coactivation function for HIF1α. Inhibition of glycolysis through knocking down HIF1α or PGK1 decelerated JMJD1A-enhanced UBC cell growth. Consistent with these results, a positive correlation between JMJD1A and several key glycolytic genes in human UBC samples was established by analyzing a microarray-based gene expression profile. In conclusion, our study demonstrates that JMJD1A promotes UBC progression by enhancing glycolysis through coactivation of HIF1α, implicating that JMJD1A is a potential molecular target for UBC treatment.