Inhibition of Intestinal Bile Acid Transporter Slc10a2 Improves Triglyceride Metabolism and Normalizes Elevated Plasma Glucose Levels in Mice

Interruption of the enterohepatic circulation of bile acids increases cholesterol catabolism, thereby stimulating hepatic cholesterol synthesis from acetate. We hypothesized that such treatment should lower the hepatic acetate pool which may alter triglyceride and glucose metabolism. We explored this using mice deficient of the ileal sodium-dependent BA transporter (Slc10a2) and ob/ob mice treated with a specific inhibitor of Slc10a2. Plasma TG levels were reduced in Slc10a2-deficient mice, and when challenged with a sucrose-rich diet, they displayed a reduced response in hepatic TG production as observed from the mRNA levels of several key enzymes in fatty acid synthesis. This effect was paralleled by a diminished induction of mature sterol regulatory element-binding protein 1c (Srebp1c). Unexpectedly, the SR-diet induced intestinal fibroblast growth factor (FGF) 15 mRNA and normalized bile acid synthesis in Slc10a2−/− mice. Pharmacologic inhibition of Slc10a2 in diabetic ob/ob mice reduced serum glucose, insulin and TGs, as well as hepatic mRNA levels of Srebp1c and its target genes. These responses are contrary to those reported following treatment of mice with a bile acid binding resin. Moreover, when key metabolic signal transduction pathways in the liver were investigated, those of Mek1/2 - Erk1/2 and Akt were blunted after treatment of ob/ob mice with the Slc10a2 inhibitor. It is concluded that abrogation of Slc10a2 reduces hepatic Srebp1c activity and serum TGs, and in the diabetic ob/ob model it also reduces glucose and insulin levels. Hence, targeting of Slc10a2 may be a promising strategy to treat hypertriglyceridemia and diabetes

Diversity and Community Trust in Swedish Local Communities

This article analyses the effect of immigration-related diversity on different forms of trust through the hierarchical analysis of three levels of approximately 5,000 respondents nested in over 800 neighbourhoods and 33 municipalities. The data set is based on a unique survey that was specially designed to measure different forms of trust and to test the effects of context. Building on previous findings about the effect of diversity on various forms of trust in Sweden, we discuss three mechanisms through which diversity may drive down community trust in diverse settings – dissimilarity, perceptions of unfairness and asymmetry of information and norms – and explore these empirically. In particular, we examine under which conditions asymmetry of information and norms and perceptions of unfairness affect community trust, and how it interacts with diversity. Our analysis reveals that norm asymmetry and perceptions of unfairness affect community trust negatively but the negative effects are more pronounced in the most diverse local communities.acceptedVersio

Control of Steroid 21-oic Acid Synthesis by Peroxisome Proliferator-activated Receptor α and Role of the Hypothalamic-Pituitary-Adrenal Axis*

A previous study identified the peroxisome proliferator-activated receptor α (PPARα) activation biomarkers 21-steroid carboxylic acids 11β-hydroxy-3,20-dioxopregn-4-en-21-oic acid (HDOPA) and 11β,20-dihydroxy-3-oxo-pregn-4-en-21-oic acid (DHOPA). In the present study, the molecular mechanism and the metabolic pathway of their production were determined. The PPARα-specific time-dependent increases in HDOPA and 20α-DHOPA paralleled the development of adrenal cortex hyperplasia, hypercortisolism, and spleen atrophy, which was attenuated in adrenalectomized mice. Wy-14,643 activation of PPARα induced hepatic FGF21, which caused increased neuropeptide Y and agouti-related protein mRNAs in the hypothalamus, stimulation of the agouti-related protein/neuropeptide Y neurons, and activation of the hypothalamic-pituitary-adrenal (HPA) axis, resulting in increased adrenal cortex hyperplasia and corticosterone production, revealing a link between PPARα and the HPA axis in controlling energy homeostasis and immune regulation. Corticosterone was demonstrated as the precursor of 21-carboxylic acids both in vivo and in vitro. Under PPARα activation, the classic reductive metabolic pathway of corticosterone was suppressed, whereas an alternative oxidative pathway was uncovered that leads to the sequential oxidation on carbon 21 resulting in HDOPA. The latter was then reduced to the end product 20α-DHOPA. Hepatic cytochromes P450, aldehyde dehydrogenase (ALDH3A2), and 21-hydroxysteroid dehydrogenase (AKR1C18) were found to be involved in this pathway. Activation of PPARα resulted in the induction of Aldh3a2 and Akr1c18, both of which were confirmed as target genes through introduction of promoter luciferase reporter constructs into mouse livers in vivo. This study underscores the power of mass spectrometry-based metabolomics combined with genomic and physiologic analyses in identifying downstream metabolic biomarkers and the corresponding upstream molecular mechanisms

Fibroblast Growth Factor-21 Regulates PPAR gamma Activity and the Antidiabetic Actions of Thiazolidinediones

Fibroblast growth factor-21 (FGF21) is a circulating hepatokine that beneficially affects carbohydrate and lipid metabolism. Here, we report that FGF21 is also an inducible, fed-state autocrine factor in adipose tissue that functions in a feed-forward loop to regulate the activity of peroxisome proliferator-activated receptor gamma (PPAR gamma), a master transcriptional regulator of adipogenesis. FGF21 knockout (KO) mice display defects in PPARg signaling including decreased body fat and attenuation of PPAR gamma-dependent gene expression. Moreover, FGF21-KO mice are refractory to both the beneficial insulin-sensitizing effects and the detrimental weight gain and edema side effects of the PPAR gamma agonist rosiglitazone. This loss of function in FGF21-KO mice is coincident with a marked increase in the sumoylation of PPAR gamma, which reduces its transcriptional activity. Adding back FGF21 prevents sumoylation and restores PPAR gamma activity. Collectively, these results reveal FGF21 as a key mediator of the physiologic and pharmacologic actions of PPAR gamma.close11810