BackgroundIntervention strategies for obesity are global issues that require immediate attention. One approach is to exploit the growing consensus that beneficial gut microbiota could be of use in intervention regimes. Our objective was to determine the mechanism by which the probiotic bacteria Lactobacillus paracasei ssp paracasei F19 (F19) could alter fat storage. Angiopoietin-like 4 (ANGPTL4) is a circulating lipoprotein lipase (LPL) inhibitor that controls triglyceride deposition into adipocytes and has been reported to be regulated by gut microbes.Methodology/Principal FindingsA diet intervention study of mice fed high-fat chow supplemented with F19 was carried out to study potential mechanistic effects on fat storage. Mice given F19 displayed significantly less body fat, as assessed by magnetic resonance imaging, and a changed lipoprotein profile. Given that previous studies on fat storage have identified ANGPTL4 as an effector, we also investigated circulating levels of ANGPTL4, which proved to be higher in the F19-treated group. This increase, together with total body fat and triglyceride levels told a story of inhibited LPL action through ANGPTL4 leading to decreased fat storage. Co-culture experiments of colonic cell lines and F19 were set up in order to monitor any ensuing alterations in ANGPTL4 expression by qPCR. We observed that potentially secreted factors from F19 can induce ANGPTL4 gene expression, acting in part through the peroxisome proliferator activated receptors alpha and gamma. To prove validity of in vitro findings, germ-free mice were monocolonized with F19. Here we again found changes in serum triglycerides as well as ANGPTL4 in response to F19.Conclusions/SignificanceOur results provide an interesting mechanism whereby modifying ANGPTL4, a central player in fat storage regulation, through manipulating gut flora could be an important gateway upon which intervention trials of weight management can be based.

Growth/differentiation factor 3 (GDF3) is highly expressed in adipose tissue, and previous overexpression experiments in mice have suggested that it may act as an adipogenic factor under conditions of high lipid load. GDF3 has been shown to signal via the activin receptor ALK4 during embryogenesis, but functional receptors in adipose tissue are unknown. In this study, we show that Gdf3 ؊/؊ mutant mice accumulate less adipose tissue than WT animals and show partial resistance to high-fat diet-induced obesity despite similar food intake. We also demonstrate that GDF3 can signal via the ALK4-homolog ALK7 and the coreceptor Cripto, both of which are expressed in adipose tissue. In agreement with a role for ALK7 in GDF3 signaling in vivo, mutant mice lacking ALK7 also showed reduced fat accumulation and partial resistance to diet-induced obesity. We propose that GDF3 regulates adiposetissue homeostasis and energy balance under nutrient overload in part by signaling through the ALK7 receptor.high-fat diet ͉ metabolism ͉ TGF-␤ ͉ energy balance ͉ insulinemia

The two liver X receptors (LXRs), LXRalpha and LXRbeta, are transcriptional regulators of cholesterol, lipid, and glucose metabolism and are both activated by oxysterols. Impaired metabolism is linked with obesity, insulin resistance, and type 2-diabetes (T2D). In the present study, we aimed to delineate the specific roles of LXRalpha and -beta in metabolic processes. C57Bl/6 female mice were fed a normal or a high-fat diet (HFD) and metabolic responses in wild-type, LXRalpha(-/-), LXRbeta(-/-), and LXRalphabeta(-/-) mice were analyzed. Whole body fat and intramyocellular lipid contents were measured by nuclear magnetic resonance. Energy expenditure was measured in individual metabolic cages. Glucose, insulin, and pyruvate tolerance tests were performed and gene expression profiles analyzed by qPCR. We found that both LXRbeta(-/-) and LXRalphabeta(-/-) mice are resistant to HFD-induced obesity independently of the presence of high cholesterol. Using tolerance tests, we found that, on an HFD, LXRbeta(-/-) mice enhanced their endogenous glucose production and became highly insulin resistant, whereas LXRalpha(-/-) and LXRalphabeta(-/-) mice remained glucose tolerant and insulin sensitive. Gene expression profiling confirmed that LXRbeta is the regulator of lipogenic genes in visceral white adipose tissue (WAT) and muscle tissue and, surprisingly, that Ucp1 and Dio2 are not responsible for the protection against diet-induced obesity observed in LXRbeta(-/-) and LXRalphabeta(-/-) mice. LXRalpha is required for the control of cholesterol metabolism in the liver, while LXRbeta appears to be a major regulator of glucose homeostasis and energy utilization and of fat storage in muscle and WAT. We conclude that selective LXRbeta agonists would be novel pharmaceuticals in the treatment of T2D.

Although the starch in parboiled rice is less susceptible to digestion in vitro, exogenous glucose availability was not significantly different after ingestion of large amounts of polished or parboiled rice. Glucose absorption remains incomplete 8 h after ingestion of both types of rice.

Prolonged exposure to elevated glucocorticoid levels is known to produce insulin resistance (IR), a hallmark of diabetes mellitus. Although not fully elucidated, the underlying molecular mechanisms by which glucocorticoids induce IR may provide potential targets for pharmacological interventions. Here we characterized muscle lipid metabolism in a dexamethasone-aggravated diet-induced obesity murine model of IR. Male C57BL/6 mice on a high-fat diet for 2 months when challenged with dexamethasone showed elevated food consumption and weight gain relative to age and diet-matched animals dosed with saline only. Dexamethasone treatment impaired glucose tolerance and significantly increased the intramyocellular lipid content in the tibialis anterior muscle (TA). A good correlation (r = 0.76, P < 0.01) was found between accumulation in intramyocellular lipid content in the TA and visceral adiposity. The linoleic acid (18:2) to polyunsaturated acid ratio was increased in the dexamethasone-treated animals (+29%; P < 0.01), suggesting a possible increase in stearoyl-CoA desaturase 2 activity, as reported in Sertoli cells. The treatment was also accompanied by a reduction in the percent fraction of omega-3 and long-chain polyunsaturated fatty acids in the TA. Analysis of the low-molecular-weight metabolites from muscle extracts showed that there was no dysregulation of muscle amino acids, as has been associated with dexamethasone-induced muscle proteolysis. In conclusion, dexamethasone-induced insulin resistance in diet-induced obese mice is associated with a profound perturbation of lipid metabolism. This is particularly true in the muscle, in which an increased uptake of circulating lipids along with a conversion into diabetogenic lipids can be observed.

Brown adipocytes are multilocular lipid storage cells that play a crucial role in nonshivering thermogenesis. Uncoupling protein 1 (UCP1) is a unique feature of brown fat cells that allows heat generation on sympathetic nervous system stimulation. As conventional transcriptional factors that are activated in various signaling pathways, liver-X receptors (LXRs) play important roles in many physiological processes. The role of LXRs in the regulation of energy homeostasis remains unclear, however. Female WT, LXRαβ −/− , LXRα −/− , and LXRβ −/− mice were fed with either a normal diet (ND) or a high-carbohydrate diet (HCD) supplemented with or without GW3965-LXR agonist. LXRαβ −/− mice exhibited higher energy expenditure (EE) as well as higher UCP1 expression in brown adipose tissue (BAT) compared with WT mice on the HCD. In addition, long-term treatment of WT mice with GW3965 showed lower EE at thermoneutrality (30°C) and lower Ucp1 expression level in BAT. Furthermore, H&E staining of the BAT of LXRαβ −/− mice exhibited decreased lipid droplet size compared with WT mice on the HCD associated with a more intense UCP1-positive reaction. Quantification of triglyceride (TG) content in BAT showed lower TG accumulation in LXRβ −/− mice compared with WT mice. Surprisingly, GW3965 treatment increased TG content (twofold) in the BAT of WT and LXRα −/− mice but not in LXRβ −/− mice. Furthermore, glucose transporter (GLUT4) in the BAT of LXRα −/− and LXRβ −/− mice was sixfold and fourfold increased, respectively, compared with WT mice on the ND. These findings suggest that LXRα as well as LXRβ could play a crucial role in the regulation of energy homeostasis in female mice and may be a potential target for the treatment of obesity and energy regulation.

High visceral adiposity and intramyocellular lipid levels (IMCL) are both associated with the development of type 2 diabetes. The relationship between visceral adiposity and IMCL levels was explored in diet- and glucocorticoid-induced models of insulin resistance. In the diet-induced model, lean and fa/fa Zucker rats were fed either normal or high-fat (HF) chow over 4 wk. Fat distribution, IMCL content in the tibialis anterior (TA) muscle (IMCL(TA)), and whole body insulin resistance were measured before and after the 4-wk period. The HF diet-induced increase in IMCL(TA) was strongly correlated with visceral fat accumulation and greater glucose intolerance in both groups. The increase in IMCL(TA) to visceral fat accumulation was threefold greater for fa/fa rats. In the glucocorticoid-induced model, insulin sensitivity was impaired with dexamethasone. In vivo adiposity and IMCL(TA) content measurements were combined with ex vivo analysis of plasma and muscle tissue. Dexamethasone treatment had minimal effects on visceral fat accumulation while increasing IMCL(TA) levels approximately 30% (P < 0.05) compared with controls. Dexamethasone increased plasma glucose by twofold and increased the saturated fatty acid content of plasma lipids [fatty acid (CH2)n/omegaCH3 ratio +15%, P < 0.05]. The lipid composition of the TA muscle was unchanged by dexamethasone treatment, indicating that the relative increase in IMCL(TA) observed in vivo resulted from a decrease in lipid oxidation. Visceral adiposity may influence IMCL accumulation in the context of dietary manipulations; however, a "causal" relationship still remains to be determined. Dexamethasone-induced insulin resistance likely operates under a different mechanism, i.e., independently of visceral adiposity.

The liver X receptors (LXRs) play a key role in cholesterol and bile acid metabolism but are also important regulators of glucose metabolism. Recently, LXRs have been proposed as a glucose sensor affecting LXR-dependent gene expression. We challenged wild-type (WT) and LXR␣␤ Ϫ/Ϫ mice with a normal diet (ND) or a high-carbohydrate diet (HCD). Magnetic resonance imaging showed different fat distribution between WT and LXR␣␤ Ϫ/Ϫ mice. Surprisingly, gonadal (GL) adipocyte volume decreased on HCD compared with ND in WT mice, whereas it slightly increased in LXR␣␤ Ϫ/Ϫ mice. Interestingly, insulin-stimulated lipogenesis of isolated GL fat cells was reduced on HCD compared with ND in LXR␣␤ Ϫ/Ϫ mice, whereas no changes were observed in WT mice. Net de novo lipogenesis (DNL) calculated from V O2 and V CO2 was significantly higher in LXR␣␤ Ϫ/Ϫ than in WT mice on HCD. Histology of HCD-fed livers showed hepatic steatosis in WT mice but not in LXR␣␤ Ϫ/Ϫ mice. Glucose tolerance was not different between groups, but insulin sensitivity was decreased by the HCD in WT but not in LXR␣␤ Ϫ/Ϫ mice. Finally, gene expression analysis of adipose tissue showed induced expression of genes involved in DNL in LXR␣␤ Ϫ/Ϫ mice compared with WT animals as opposed to the liver, where expression of DNL genes was repressed in LXR␣␤ Ϫ/Ϫ mice. We thus conclude that absence of LXRs stimulates DNL in adipose tissue, but suppresses DNL in the liver, demonstrating opposite roles of LXR in DNL regulation in these two tissues. These results show tissue-specific regulation of LXR activity, a crucial finding for drug development. high carbohydrate; energy regulation; metabolism; insulin resistance OBESITY AND ASSOCIATED COMPLICATIONS such as cardiovascular diseases and diabetes represent a major health problem in Western countries. The molecular mechanisms behind metabolic disorders are poorly understood but typically involve deregulation of cholesterol, lipid, and carbohydrate metabolism as well as impaired insulin signaling. The principal function of insulin is to maintain blood glucose and nonesterified fatty acid (NEFA) concentrations nearly constant despite the fluctuations during dietary intake of carbohydrates and lipids. De novo lipogenesis (DNL), i.e., the synthesis of fatty acids from nonlipid substrates, mainly carbohydrates, is nutritionally regulated. Both glucose and insulin signaling pathways are engaged in response to dietary carbohydrates to synergistically induce expression of glycolytic and lipogenic genes in the liver (12).Liver and adipose tissue are the two main sites of DNL in mice (32, 46). In humans, DNL capacity of adipose tissue remains controversial. Diraison et al. (14) found that a highcarbohydrate diet (HCD) in humans does not upregulate DNL or expression of lipogenic genes in adipocytes, whereas hepatic DNL is increased two-to threefold. Letexier et al. (32) concluded that DNL is reduced in human adipose tissue compared with rodents due to a lower abundance of sterol-responsive element-binding protein-1c (SREBP-1c) protein (...