Regulation of Gpr173 expression, a putative phoenixin receptor, by saturated fatty acid palmitate and endocrine-disrupting chemical bisphenol A through a p38-mediated mechanism in immortalized hypothalamic neurons.

GPR173 is a highly conserved G protein coupled receptor associated with the hypothalamic-pituitary-gonadal reproductive axis. It is expressed in the brain and ovaries, however considerable knowledge about its function remains unknown. One putative ligand for this receptor is phoenixin (PNX), a newly identified reproductive peptide involved in hypothalamic coordination of the estrous cycle. In order to characterize GPR173, it is vital to determine how Gpr173 is regulated in the hypothalamus. Since the hypothalamus senses compounds from the blood, such as nutrients and chemicals, we examined the effect of palmitate, a saturated fatty acid, and bisphenol A (BPA), an endocrine disrupting chemical, on Gpr173 gene expression. Immortalized hypothalamic neurons were treated with palmitate or BPA for 2-24 h and Gpr173 mRNA levels were assessed with RT-qPCR. Palmitate and BPA both reduced Gpr173 mRNA levels, in part through the mitogen-activated protein kinase (MAPK), p38. Pre-treatment with palmitate for 24 h blocked the PNX-induction of phosphorylated cAMP response element-binding protein (CREB) levels. In conclusion, nutrition levels and environmental chemicals may influence reproductive function through modulation of Gpr173 expression, which may prove to be a future therapeutic target in reproductive health.

Palmitate-induced insulin resistance is attenuated by Pioglitazone and EGCG through reducing the gluconeogenic key enzymes expression in HepG2 cells.

HYPOTHESIS: Palmitate causes insulin resistance (IR) in insulin target tissue. Pioglitazone (an anti-hyperglycemic agent) and epigallocatechin gallate (EGCG, a dietary supplement) can be used for the treatment of type 2 diabetes. However, their molecular effects on gluconeogenesis remain unclear. OBJECTIVE: Hence, we aimed to investigate the simultaneous effect of these anti-hyperglycemic agents on gluconeogenesis through in vitro experiments. METHODS: HepG2 cells were treated with 0.5 mM palmitate, 10 µM pioglitazone, and 40 µM epigallocatechin gallate (EGCG). Gene expression assay was used to investigate the underlying mechanism. Glucose production assay was applied in culture medium to evaluate the activity of gluconeogenesis pathway. RESULTS: Palmitate induced IR could significantly increase G6Pase and PEPCK gene expressions by 58 and 30%, respectively, compared to the control. EGCG reduced the expression of PEPCK and G6Pase by 53 and 67%, respectively. Pioglitazone reduced the mRNA level of PEPCK and G6Pase by 58 and 62% respectively. Combined treatment of insulin-resistant cells with EGCG and pioglitazone significantly decreased the mRNA level of PEPCK and G6Pase by 73 and 80%, respectively. Treatment with palmitate increased glucose production by 50% in HepG2 cells. When the insulin resistant HepG2 cells were treated alone with EGCG and pioglitazone, the glucose production reduced by 50 and 55%, respectively. The combined treatment with EGCG and pioglitazone resulted in 69% reduction in glucose production compared to the palmitate treated HepG2 cells. CONCLUSIONS: These data suggest the additive inhibitory effect of co-treatment with pioglitazone and EGCG on the gluconeogenesis pathway in palmitate-induced insulin resistance HepG2 cells.

Timosaponin B-II Ameliorates Palmitate-Induced Insulin Resistance and Inflammation via IRS-1/PI3K/Akt and IKK/NF-[Formula: see text]B Pathways.

This study aimed to investigate the effect of timosaponin B-II (TB-II) on palmitate (PA)-induced insulin resistance and inflammation in HepG2 cells, and probe the potential mechanisms. TB-II, a main ingredient of the traditional Chinese medicine Anemarrhena asphodeloides Bunge, notably ameliorated PA-induced insulin resistance and inflammation, and significantly improved cell viability, decreased PA-induced production of tumor necrosis factor-[Formula: see text] (TNF-[Formula: see text]) and interleukin-6 (IL-6) levels. Further, TB-II treatment notably decreased malondialdehyde (MDA) and lactate dehydrogenase (LDH) levels, and improved superoxide dismutase (SOD) and nitric oxide (NO). TB-II also reduced HepG2 cells apoptosis. Insulin receptor substrate-1 (IRS1)/phosphatidylinositol 3-kinase (PI3K)/Akt and inhibitor of nuclear factor [Formula: see text]-B kinase (IKK)/NF-[Formula: see text]B pathways-related proteins, and IKK[Formula: see text], p65 phosphorylation, serine phosphorylation of insulin receptor substrate-1 (IRS-1) at S307, tyrosine phosphorylation of IRS-1, and Akt activation were determined by Western blot. Compared to model group, TB-II significantly downregulated the expression of p-NF-[Formula: see text]Bp65, p-IKK[Formula: see text], p-IRS-1, p-PI3K and p-Akt. TB-II is a promising potential agent for the management of palmitate-induced insulin resistance and inflammation, which might be via IR/IRS-1/PI3K/Akt and IKK/NF-[Formula: see text]B pathways.

ß-Caryophyllene attenuates palmitate-induced lipid accumulation through AMPK signaling by activating CB2 receptor in human HepG2 hepatocytes.

SCOPE: Nonalcoholic fatty liver disease is currently the most common chronic liver disease worldwide, characterized by excessive hepatic lipid accumulation without significant ethanol consumption. We have performed a screening for medicinal foods that inhibit hepatocytic lipid accumulation through activation of AMP-activated protein kinase (AMPK), which is a critical regulator of the hepatic lipid metabolism. METHODS AND RESULTS: We found that clove (Syzygium aromaticum), which is commonly used as a spice, markedly inhibits palmitate-inducible lipid accumulation in human HepG2 hepatocytes. Analyses of the clove extracts found that ß-caryophyllene, an orally-active cannabinoid, is the principal suppressor of the lipid accumulation, and stimulates the phosphorylation of AMPK and acetyl-CoA carboxylase 1 (ACC1). Our data also showed that ß-caryophyllene prevents the translocation of sterol regulatory element-binding protein-1c (SREBP-1c) into the nucleus and forkhead box protein O1 (FoxO1) into the cytoplasm through AMPK signaling, and consequently, induces a significant downregulation of fatty acid synthase (FAS) and upregulation of adipose triglyceride lipase, respectively. Moreover, we demonstrated that the ß-caryophyllene-induced activation of AMPK could be mediated by the cannabinoid type 2 receptor-dependent Ca2+ signaling pathway. CONCLUSION: Our results suggest that ß-caryophyllene has the potential efficacy in preventing and ameliorating nonalcoholic fatty liver disease and its associated metabolic disorders.

Crude Saponins of Panax notoginseng Have Neuroprotective Effects To Inhibit Palmitate-Triggered Endoplasmic Reticulum Stress-Associated Apoptosis and Loss of Postsynaptic Proteins in Staurosporine Differentiated RGC-5 Retinal Ganglion Cells.

Increased apoptosis of retinal ganglion cells (RGCs) contributes to the gradual loss of retinal neurons at the early phase of diabetic retinopathy (DR). There is an urgent need to search for drugs with neuroprotective effects against apoptosis of RGCs for the early treatment of DR. This study aimed to investigate the neuroprotective effects of saponins extracted from Panax notoginseng, a traditional Chinese medicine, on apoptosis of RGCs stimulated by palmitate, a metabolic factor for the development of diabetes and its complications, and to explore the potential molecular mechanism. We showed that crude saponins of P. notoginseng (CSPN) inhibited the increased apoptosis and loss of postsynaptic protein PSD-95 by palmitate in staurosporine-differentiated RGC-5 cells. Moreover, CSPN suppressed palmitate-induced reactive oxygen species generation and endoplasmic reticulum stress-associated eIF2α/ATF4/CHOP and caspase 12 pathways. Thus, our findings address the potential therapeutic significance of CSPN for the early stage of DR.

Curcumin protects hearts from FFA-induced injury by activating Nrf2 and inactivating NF-κB both in vitro and in vivo.

Obesity and increased free fatty acid (FFA) level are tightly linked, leading to the development of cardiovascular disorders. Curcumin is a natural product from Curcuma longa with multiple bioactivities and is known to have cardioprotective effects in several cellular and animal models. The current study was designed to evaluate the cardioprotective effects of curcumin and demonstrate the underlying mechanism in FFA-induced cardiac injury. Using cell culture studies and high fat in vivo model, we explored the mechanistic basis of anti-inflammatory and antioxidant activities of curcumin. We observed that palmitate (PA) treatment in cardiac derived H9C2 cells induced a marked increase in reactive oxygen species, inflammation, apoptosis and hypertrophy. All of these changes were effectively suppressed by curcumin treatment. In addition, oral administration of curcumin at 50mg/kg completely suppressed high fat diet-induced oxidative stress, inflammation, apoptosis, fibrosis, hypertrophy and tissue remodeling in mice. The beneficial actions of curcumin are closely associated with its ability to increase Nrf2 expression and inhibit NF-κB activation. Thus, both in vitro and in vivo studies showed a promising role of curcumin as a cardioprotective agent against palmitate and high fat diet mediated cardiac dysfunction. We indicated the regulatory roles of Nrf2 and NF-κB in obesity-induced heart injury, and suggested that they may be important therapeutic targets in the treatment of obesity-related disorders.