fatty liver disease occurs frequently in the setting of metabolic syndrome, but the factors leading to nonalcoholic steatohepatitis (NASH) are not fully understood. This study investigated Toll-like receptor 4 (TLR4) signaling in human liver with the goal of delineating whether activation of this pathway segregates those with nonalcoholic fatty liver from those with NASH. Experiments were performed using liver biopsy tissue obtained from class III obese subjects undergoing bariatric surgery, and extended to an immortalized human hepatocyte HepaRG cell line and primary human hepatocytes. The bacterial endotoxin lipopolysaccharide (LPS) and total free fatty acid levels were significantly increased in plasma of NASH patients. TLR4 mRNA levels were significantly increased in subjects with NASH compared with NAFL as was interferon regulatory factor (IRF) 3 in the myeloid differentiation factor 88-independent signaling pathway. In HepaRG cells, nuclear factor-B (NF-B) nuclear translocation and functional activity increased following treatment with the fatty acid, palmitate, and following exposure to LPS compared with hepatocytes stimulated with a lipogenic treatment that induced de novo lipogenesis. Palmitate and LPS induction of NF-B activity was partially attenuated by chemical-or small-interfering RNA-mediated inhibition of TLR4. Expression of TLR4 and its downstream mediators was upregulated with palmitate and LPS. Similar results were observed using primary human hepatocytes from a lean donor. Interestingly, NF-B activity assays showed obese donor hepatocytes were resistant to chemical TLR4 inhibition. In conclusion, TLR4 expression is upregulated in a large cohort of NASH patients, compared with those with NAFL, and this occurs within the setting of increased LPS and fatty acids. nonalcoholic steatohepatitis; palmitate; Toll-like receptor 4; nuclear factor-

Abbreviations used in this paper: AUC, area under the curve; Ex-9, exendin-9; Fxr D/E , farnesoid X receptor null mice; GB-IL, bile diversion to the ileum; GLP-1, glucagon-like polypeptide 1; GLP-1r, glucagon-like polypeptide 1 receptor; Glp-1r L/L , glucagon-like 1 receptor deficient mice; HFD, high-fat diet; OGTT, oral glucose tolerance test; RYGB, Rouxen-Y gastric bypass; Tgr5 L/L , Takeda G protein-coupled bile acid receptor-1 null mice; T2D, type 2 diabetes; VSG, vertical sleeve gastrectomy. Most current article

The aim of this study is to test whether the Cyp2c44 epoxygenase dependent metabolism of arachidonic acid (AA) prevents the hypertensive effect of a high K intake (HK) by inhibiting the ENaC activity. A HK intake elevated Cyp2c44 mRNA expression and 11,12-epoxyeicosatrienoic acid (11,12-EET) levels in the cortical collecting duct (CCD) in Cyp2c44(+/+) mice(wt). However, a HK intake failed to increase 11,12-EET formation in the CCDs of Cyp2c44(-/-) mice. Moreover, increasing K intake enhanced AA-induced inhibition of ENaC in the wt but not in Cyp2c44(-/-) mice. In contrast, 11,12-EET, a Cyp2c44 metabolite, inhibited ENaC in the wt and Cyp2c44(-/-) mice. The notion that Cyp2c44 is the epoxygenase responsible for mediating the inhibitory effects of AA on ENaC is further suggested by the observation that inhibiting Cyp-epoxygenase increased the whole-cell Na currents in principal cells of wt but not in Cyp2c44(-/-) mice. Feeding mice with a HK diet raised the systemic blood pressures of Cyp2c44(-/-) mice but was without an effect on wt mice. Moreover, application of amiloride abolished the HK-induced hypertension in Cyp2c44(-/-) mice. The HK-induced hypertension of Cyp2c44(-/-) mice was accompanied by decreasing 24-hr urinary Na excretion and increasing the plasma Na concentration, the effects were absent in wt mice. In contrast, disruption of the Cyp2c44 gene did not alter K excretion. We conclude that Cyp2c44 epoxygenase mediates the inhibitory effect of AA on ENaC and that Cyp2c44 functions as a HK-inducible anti-hypertensive enzyme responsible for inhibiting ENaC activity and Na absorption in the aldosterone-sensitive distal nephron (ASDN).

The regulation of the human liver-specific cytochrome P450 4F3B (CYP4F3B) isoform, a splice variant of the CYP4F3 gene with strong substrate specificity for long chain fatty acids, is yet an unsolved question. This report provides the first evidence that CYP4F3B is uniquely induced by prostaglandin A 1 (PGA 1 ) in human hepatocyte-like

CYP4A11, the major fatty acid x-hydroxylase in human liver is involved in the balance of lipids, but its role and regulation are both poorly understood. We studied the effects of retinoids on the regulation of CYP4A11 in the human hepatoma cell line HepaRG. Treatment of HepaRG cells with all-trans-retinoic acid resulted in a strong decrease in CYP4A11 gene expression and apoprotein content and, furthermore, was associated with a 50% decrease in the microsomal lauric acid hydroxylation activity. Such a strong suppression of CYP4A11 expression by retinoids could have a major impact on fatty acid metabolism in the liver.

Aims Ghrelin is a gastric-derived hormone that stimulates growth hormone (GH) secretion and has a multi-faceted role in the regulation of energy homeostasis, including glucose metabolism. Circulating ghrelin concentrations are modulated in response to nutritional status, but responses to ghrelin in altered metabolic states are poorly understood. We investigated the metabolic effects of ghrelin in obesity and early after Roux-en-Y gastric bypass (RYGB). Materials and Methods We assessed central and peripheral metabolic responses to acyl ghrelin infusion (1 pmol kg−1 min−1) in healthy, lean subjects (n=9) and non-diabetic, obese subjects (n=9) before and two weeks after RYGB. Central responses were assessed by GH and pancreatic polypeptide (surrogate for vagal activity) secretion. Peripheral responses were assessed by hepatic and skeletal muscle insulin sensitivity during a hyperinsulinemic-euglycemic clamp. Results Ghrelin-stimulated GH secretion was attenuated in obese subjects, but was restored by RYGB to a response similar to lean subjects. The heightened pancreatic polypeptide response to ghrelin infusion in the obese was attenuated after RYGB. Hepatic glucose production and hepatic insulin sensitivity were not altered by ghrelin infusion in the RYGB subjects. Skeletal muscle insulin sensitivity was impaired to a similar degree in the lean, obese, and post-RYGB in response to ghrelin infusion. Conclusions These data suggest that obesity is characterized by abnormal central, but not peripheral, responsiveness to ghrelin that can be restored early after RYGB before significant weight loss. Further work is necessary to fully elucidate the role of ghrelin in the metabolic changes that occur in obesity and after RYGB.

No abstract

ABSTRACT:Fatty acid microsomal -oxidation involves cytochrome P450 enzymes. Some of them belonging to the CYP4F3 family are mainly expressed in the liver, making this organ a major player in energy homeostasis and lipid metabolism. To study this important regulation pathway, we used HepaRG cells, which gradually undergo a complete differentiation process. Even at the early stage of the differentiation process, CYP4F3B generated by alternative splicing of the CYP4F3 gene represented the prevalent isoform in HepaRG cells as in the liver. Its increasing expression associated with hepatocyte differentiation status suggested a hepatic-specific control of this isoform. As in liver microsomes, the catalytic hydroxylation of the CYP4F3B substrate [1-