UCP1 In Brown Adipose Tissue Research Articles

Cyanidin-3-O-glucoside Regulates the Expression of Ucp1 in Brown Adipose Tissue by Activating Prdm16 Gene.

(1) Background: Brown adipose tissue (BAT) burns energy to produce heat. Cyanidin-3-O-glucoside (C3G) can then enhance the thermogenic ability of BAT in vivo. However, the mechanism by which C3G regulates Ucp1 protein expression remains unclear. (2) Methods: In this study, C3H10T12 brown adipose cells and db/db mice and mice with high-fat, high-fructose, diet-induced obesity were used as the model to explore the effect of C3G on the expression of the Ucp1 gene. Furthermore, the 293T cell line was used for an in vitro cell transgene, a double luciferase reporting system, and yeast single hybridization to explore the mechanism of C3G in regulating Ucp1 protein. (3) Results: we identified that, under the influence of C3G, Prdm16 directly binds to the −500 to −150 bp promoter region of Ucp1 to activate its transcription and, thus, facilitate BAT programming. (4) Conclusions: This study clarified the mechanism by which C3G regulates the expression of the Ucp1 gene of brown fat to a certain extent.

MiR-409-3p targets a MAP4K3-ZEB1-PLGF signaling axis and controls brown adipose tissue angiogenesis and insulin resistance.

Endothelial cells (ECs) within the microvasculature of brown adipose tissue (BAT) are important in regulating the plasticity of adipocytes in response to increased metabolic demand by modulating the angiogenic response. However, the mechanism of EC-adipocyte crosstalk during this process is not completely understood. We used RNA sequencing to profile microRNAs derived from BAT ECs of obese mice and identified an anti-angiogenic microRNA, miR-409-3p. MiR-409-3p overexpression inhibited EC angiogenic properties; whereas, its inhibition had the opposite effects. Mechanistic studies revealed that miR-409-3p targets ZEB1 and MAP4K3. Knockdown of ZEB1/MAP4K3 phenocopied the angiogenic effects of miR-409-3p. Adipocytes co-cultured with conditioned media from ECs deficient in miR-409-3p showed increased expression of BAT markers, UCP1 and CIDEA. We identified a pro-angiogenic growth factor, placental growth factor (PLGF), released from ECs in response to miR-409-3p inhibition. Deficiency of ZEB1 or MAP4K3 blocked the release of PLGF from ECs and PLGF stimulation of 3T3-L1 adipocytes increased UCP1 expression in a miR-409-3p dependent manner. MiR-409-3p neutralization improved BAT angiogenesis, glucose and insulin tolerance, and energy expenditure in mice with diet-induced obesity. These findings establish miR-409-3p as a critical regulator of EC-BAT crosstalk by modulating a ZEB1-MAP4K3-PLGF signaling axis, providing new insights for therapeutic intervention in obesity.

Caloric Restriction and Hypothalamic Leptin Gene Therapy Have Differential Effects on Energy Partitioning in Adult Female Rats.

Dieting is a common but often ineffective long-term strategy for preventing weight gain. Similar to humans, adult rats exhibit progressive weight gain. The adipokine leptin regulates appetite and energy expenditure but hyperleptinemia is associated with leptin resistance. Here, we compared the effects of increasing leptin levels in the hypothalamus using gene therapy with conventional caloric restriction on weight gain, food consumption, serum leptin and adiponectin levels, white adipose tissue, marrow adipose tissue, and bone in nine-month-old female Sprague-Dawley rats. Rats (n = 16) were implanted with a cannula in the 3rd ventricle of the hypothalamus and injected with a recombinant adeno-associated virus, encoding the rat gene for leptin (rAAV-Lep), and maintained on standard rat chow for 18 weeks. A second group (n = 15) was calorically-restricted to match the weight of the rAAV-Lep group. Both approaches prevented weight gain, and no differences in bone were detected. However, calorically-restricted rats consumed 15% less food and had lower brown adipose tissue Ucp-1 mRNA expression than rAAV-Lep rats. Additionally, calorically-restricted rats had higher abdominal white adipose tissue mass, higher serum leptin and adiponectin levels, and higher marrow adiposity. Caloric restriction and hypothalamic leptin gene therapy, while equally effective in preventing weight gain, differ in their effects on energy intake, energy expenditure, adipokine levels, and body composition.

Hypothalamic Leptin Gene Therapy and Caloric Restriction Have Differential Effects on Energy Intake and Energy Partitioning in Adult Female Rats

ObjectivesWeight gain during middle age is associated with several chronic diseases. Dieting is a common but often ineffective long-term strategy for stabilizing body weight at optimal levels for health. Similar to humans, middle-aged rats exhibit progressive weight gain and are a useful model for evaluating strategies for controlling weight. The adipokine leptin is an important regulator of appetite and energy expenditure but peripheral hyperleptinemia is associated with leptin resistance and may contribute to chronic inflammation. Here we compared the effects of increasing leptin levels selectively in the hypothalamus using gene therapy with conventional caloric restriction (CR) on weight gain, food consumption, serum leptin, abdominal white adipose tissue, and bone marrow adipose tissue in nine-month-old female rats. MethodsRats (n = 16) were implanted with a cannula in the 3rd ventricle of the hypothalamus and injected with adeno-associated virus encoding a recombinant rat gene for leptin (rAAV-lep) and maintained on standard rat chow for 18 weeks. A control group (n = 15) was calorically restricted (CR) to match the weight of the rAAV-lep group. ResultsBoth approaches were effective in preventing weight gain. However, rAAV-lep rats consumed 16% more food and had higher brown adipose tissue Ucp-1 mRNA expression than CR rats. Additionally, compared to CR rats, rAAV-lep rats had lower abdominal white adipose tissue mass, lower serum leptin levels, and lower bone marrow adiposity. ConclusionsHypothalamic leptin gene therapy and CR, while equally effective in preventing weight gain, differ in their effects on energy intake, expenditure and body composition. Our findings suggest that increasing hypothalamic leptin levels has advantages (e.g., desirable body composition and unrestricted food intake) over conventional CR as a strategy for preventing age-related weight gain. Funding SourcesNIH AR060913.

Fish Oil Increases Diet-Induced Thermogenesis in Mice.

Increasing energy expenditure (EE) is beneficial for preventing obesity. Diet-induced thermogenesis (DIT) is one of the components of total EE. Therefore, increasing DIT is effective against obesity. We examined how much fish oil (FO) increased DIT by measuring absolute values of DIT in mice. C57BL/6J male mice were given diets of 30 energy% fat consisting of FO or safflower oil plus butter as control oil (Con). After administration for 9 days, respiration in mice was monitored, and then the data were used to calculate DIT and EE. DIT increased significantly by 1.2-fold in the FO-fed mice compared with the Con-fed mice. Body weight gain was significantly lower in the FO-fed mice. FO increased the levels of uncoupling protein 1 (Ucp1) mRNA and UCP1 protein in brown adipose tissue (BAT) by 1.5- and 1.2-fold, respectively. In subcutaneous white adipose tissue (subWAT), the levels of Ucp1 mRNA and UCP1 protein were increased by 6.3- and 2.7-fold, respectively, by FO administration. FO also significantly increased the expression of markers of browning in subWAT such as fibroblast growth factor 21 and cell death-inducing DNA fragmentation factor α-like effector a. Thus, dietary FO seems to increase DIT in mice via the increased expressions of Ucp1 in BAT and induced browning of subWAT. FO might be a promising dietary fat in the prevention of obesity by upregulation of energy metabolism.

The Acute Effects of Swimming Exercise on PGC-1α-FNDC5/Irisin-UCP1 Expression in Male C57BL/6J Mice

Irisin is a myokine primarily secreted by skeletal muscles and is known as an exercise-induced hormone. The purpose of this study was to determine whether the PGC-1α -FNDC5 /Irisin-UCP1 expression which is an irisin-related signaling pathway, is activated by an acute swimming exercise. Fourteen to sixteen weeks old male C57BL/6J mice (n = 20) were divided into control (CON, n = 10) and swimming exercise groups (SEG, n = 10). The SEG mice performed 90 min of acute swimming exercise, while control (non-exercised) mice were exposed to shallow water (2 cm of depth) for 90 min. The mRNA and protein expression of PGC-1α, FNDC5 and browning markers including UCP1 were evaluated by quantitative real-time PCR and western blotting. Serum irisin concentration was measured by enzyme-linked immunosorbent assay. An acute swimming exercise did not lead to alterations in the mRNA and protein expression of PGC-1α in both soleus and gastrocnemius muscles, the mRNA and protein expression of UCP1 in brown adipose tissue, mRNA browning markers in visceral adipose tissue and circulating irisin when compared with the control group. On the other hand, an acute swimming exercise led to increases in the mRNA and protein expressions of FNDC5 in the soleus muscle, the protein expression of FNDC5 in the gastrocnemius muscles and the protein expression of UCP1 in subcutaneous adipose tissue.

CD38 downregulation modulates NAD+ and NADP(H) levels in thermogenic adipose tissues

Different strategies to boost NAD+ levels are considered promising means to promote healthy aging and ameliorate dysfunctional metabolism. CD38 is a NAD+-dependent enzyme involved in the regulation of different cell functions. In the context of systemic energy metabolism, it has been demonstrated that brown adipocytes, the parenchymal cells of brown adipose tissue (BAT) as well as beige adipocytes that emerge in white adipose tissue (WAT) depots in response to catabolic conditions, are important to maintain metabolic homeostasis. In this study we aim to understand the functional relevance of CD38 for NAD+ and energy metabolism in BAT and WAT, also using a CD38−/− mouse model.During cold exposure, an increase in NAD+ levels occurred in BAT of wild type mice, together with a marked downregulation of CD38, as detected at the mRNA and protein level. CD38 downregulation was observed also in WAT of cold-exposed mice, where it was accompanied by a strong increase in NADP(H) levels. Accordingly, NAD kinase and glucose-6-phosphate dehydrogenase activities were enhanced in WAT (but not in BAT). Increased NAD+ levels were observed in BAT/WAT from CD38−/− compared with wild type mice, in line with CD38 being a major NAD+-consumer in AT. CD38−/− mice kept at 6 °C had higher levels of Ucp1 and Pgc-1α in BAT and WAT, and increased levels of phosphorylated hormone-sensitive lipase in BAT, compared with wild type mice.These results demonstrate that CD38, by modulating cellular NAD(P)+ levels, is involved in the regulation of thermogenic responses in cold-activated BAT and WAT.

Chronic stress inhibits hypothalamus-pituitary-thyroid axis and brown adipose tissue responses to acute cold exposure in male rats.

Cold exposure activates the hypothalamus-pituitary-thyroid (HPT) axis, response blunted by previous acute stress or corticosterone administration. Chronic stressors can decrease serum T3 concentration, and thyrotropin-releasing hormone (Trh) expression in the paraventricular nucleus (PVN), but impact onthe response to cold is unknown; this was studied in rats submitted to daily repeated restraint (rRes) that causes habituation of hypothalamus-pituitary-adrenal (HPA) axis response, or to chronic variable stress (CVS) that causes sensitization and hyperreactivity. Wistar male adult rats were submitted to rRes 30min/day, or to CVS twice a day, for 15 days. On day 16, rats were exposed 1h to either 5 or 21°C. Parameters of HPT and HPA axes activity and of brown adipose tissue (BAT) cold response were measured; gene expression in PVN and BAT, by RT-PCR; serum hormone concentration by radioimmunoassay or ELISA. Compared to naïve animals, Crh and corticosterone concentrations were attenuated at the end of rRes, but increased at the end of CVS treatments. Cold exposure increased mRNA levels of Crh, Trh, and serum concentration of thyrotropin in naïve, but not in rRes or CVS rats; corticosterone increased in all groups. Cold induced expression of thermogenic genes in BAT (Dio2 and Ucp1) in naïve but not in stressed rats; Adrb3 expression was differentially regulated. Both types of chronic stress blunted HPT and BAT responses to cold. Long-term stress effects on noradrenergic and/or hormonal signaling are likely responsible for HPT dysfunction and not the type of chronic stressor.

NOD1 deficiency promotes an imbalance of thyroid hormones and microbiota homeostasis in mice fed high fat diet

The contribution of the nucleotide-binding oligomerization domain protein NOD1 to obesity has been investigated in mice fed a high fat diet (HFD). Absence of NOD1 accelerates obesity as early as 2 weeks after feeding a HFD. The obesity was due to increases in abdominal and inguinal adipose tissues. Analysis of the resting energy expenditure showed an impaired function in NOD1-deficient animals, compatible with an alteration in thyroid hormone homeostasis. Interestingly, free thyroidal T4 increased in NOD1-deficient mice fed a HFD and the expression levels of UCP1 in brown adipose tissue were significantly lower in NOD1-deficient mice than in the wild type animals eating a HFD, thus contributing to the observed adiposity in NOD1-deficient mice. Feeding a HFD resulted in an alteration of the proinflammatory profile of these animals, with an increase in the infiltration of inflammatory cells in the liver and in the white adipose tissue, and an elevation of the circulating levels of TNF-α. In addition, alterations in the gut microbiota in NOD1-deficient mice correlate with increased vulnerability of their ecosystem to the HFD challenge and affect the immune-metabolic phenotype of obese mice. Together, the data are compatible with a protective function of NOD1 against low-grade inflammation and obesity under nutritional conditions enriched in saturated lipids. Moreover, one of the key players of this early obesity onset is a dysregulation in the metabolism and release of thyroid hormones leading to reduced energy expenditure, which represents a new role for these hormones in the metabolic actions controlled by NOD1.

Dietary Supplementation with Dunaliella Tertiolecta Prevents Whitening of Brown Fat and Controls Diet-Induced Obesity at Thermoneutrality in Mice.

We investigated the effect of evodiamine-containing microalga Dunaliella tertiolecta (DT) on the prevention of diet-induced obesity in a thermoneutral C57BL/6J male (30 °C). It attenuates the activity of brown adipose tissue (BAT), which accelerates diet-induced obesity. Nine-week-old mice were fed a high-fat diet supplemented with 10 g (Low group) or 25 g (High group) DT powder per kg food for 12 weeks. Compared to control mice without DT supplementation, body weight gain was significantly reduced in the High group with no difference in food intake. Tissue analyses indicated maintenance of multilocular morphology in BAT and reduced fat deposition in liver in DT-supplemented mice. Molecular analysis showed a significant decrease in mammalian target of rapamycin−ribosomal S6 protein kinase signaling pathway in white adipose tissue and upregulation in mRNA expression of brown fat-associated genes including fibroblast growth factor-21 (Fgf21) and uncoupling protein 1 (Ucp1) in BAT in the High group compared to the control. In the experiments using C3H10T1/2 adipocytes, DT extract upregulated mRNA expression of brown fat-associated genes in dose-dependent and time-dependent manners, accompanied by a significant increase in secreted FGF21 levels. Our data show the ability of DT as a nutraceutical to prevent brown fat attenuation and diet-induced obesity in vivo.

1964-P: Slug Epigenetically Represses Adipose Thermogenic Programs

Thermogenic fat, such as brown adipose tissue (BAT) and beige fat, gains increasing attention due to its ability to protect against obesity and type 2 diabetes. Brown adipocytes and beige adipocytes contain dense mitochondria that burn glucose and free fatty acids to produce heat, and mitochondrial Ucp1 mediates heat production. Coactivator PGC1α is a master regulator of mitochondrial biogenesis and Ucp1 expression, and profoundly influences the energy expenditure capability of thermogenic fat. We attempted to delineate transcriptional regulators that govern thermogenic fat activity through PGC1α, and identified transcriptional repressor Slug. Both human and mouse PGC1α promoters contain multiple Slug binding motifs. Slug potently suppressed the activity of PGC1α promoter luciferase reporters but not mutant PGC1α promoters lacking Slug motifs. Consistently, Slug physically bound to the PGC1α promoter and decreased the levels of PGC1α promoter H3K9 acetylation, a transcriptionally-active epigenetic mark, presumably by recruiting HDAC1/2 to the promoter. In line with this notion, treatment with HDAC1/2 inhibitor trichostatin A abrogated the ability of Slug to suppress PGC1α promoter luciferase reporters. Remarkably, deletion of Slug substantially increased expression of PGC1α and Ucp1 in both BAT and inguinal fat in mice, and increased H3K9 acetylation levels on the PGC1α promoter in BAT. Slug-deficient BAT had increased O2 consumption rates and thermogenesis capability. Slug knockout mice were resistant to high fat diet-induced obesity, insulin resistance, glucose intolerance, and fatty liver disease. Likewise, adipocyte-specific deletion of Slug also ameliorated HFD-induced glucose intolerance. Unlike global Slug knockout mice, adipocyte-specific Slug knockout mice displayed mild metabolic phenotypes. In conclusion, our data suggest that Slug regulates thermogenic fat energy expenditure at least in part by epigenetically suppressing the PGCα-mitochondria axis. Disclosure Q. Kang: None. L. Jiang: None. L. Rui: None.

42-OR: The Impact of GSNOR-Mediated Nitroso-Redox Signaling on Immuno-Metabolic Interaction in the Brown Adipose Tissue

The thermogenic function of brown adipose tissue (BAT) is tightly regulated by cellular redox status, however, the molecular mechanism underlying this regulation is largely unknown. S-nitrosoglutathione reductase (GSNOR, Adh5) is a major denitrosylase that balances intracellular nitroso-redox status. Although GSNOR dysregulation has been implicated in the pathogenesis of many chronic diseases, the pathophysiological role of GSNOR in the BAT is completely unknown. We found cold exposure increased murine BAT GSNOR while diet-induced obesity (DIO) suppressed it, indicating a potential role for GSNOR in metabolic adaptation in the BAT. Mechanistically, we found that the transcription factor heat shock factor 1 (HSF1) occupies the Adh5 promoter activating Adh5 expression, while DIO inhibited the HSF1-GSNOR axis in the BAT. Notably, administration of a HSF1 enhancer to mice with DIO significantly improved glucose intolerance and BAT mitochondrial dysfunciton. Furthermore, GSNOR deletion in the BAT (GSNORBKO) suppressed UCP1-dependent respiration under both thermoneutral and cold acclimation conditions, as well as elevated immune cell infiltration in the BAT. This was in part mediated by increased BAT nitrosative stress and UCP1 S-nitrosylation induced by GSNOR deletion. Moreover, GSNORBKO mice have worsened DIO-induced glucose intolerance and decreased UCP1-mediated oxygen consumption. In contrast, gain-of GSNOR function in the BAT improved DIO-associated glucose intolerance, increased UCP1-dependent oxygen consumption and decreased DIO-induced inflammation. These data provide novel evidence that GSNOR plays a protective role in BAT against metabolic stressors. Ultimately, insights into the mechanisms by which dysregulation of nitroso-redox signaling impairs BAT metabolic homoestasis and drives the pathologies associated with obesity are expected to accelerate the development of novel therapeutic targets for metabolic diseases. Disclosure S. Sebag: None. Q. Qian: None. Z. Zhang: None. M. Li: None. V.A. Lira: None. M.J. Potthoff: None. L. Yang: None. Funding American Diabetes Association (1-18-IBS-149 to L.Y.)

Thermoneutrality Exacerbates Nonalcoholic Steatohepatitis in Mice

Abstract Objectives Nonalcoholic Steatohepatitis (NASH), the aggressive subtype of nonalcoholic fatty liver disease, affects about 1.5–6.45% of population in the world. Understanding the pathophysiology of NASH is critical to develop a therapeutic strategy for NASH. In this study, we investigated whether thermoneutrality can modulate the progression of NASH. Methods Male C57BL/6 J mice were randomly assigned to 2 groups (16 mice/group), and fed with either a control chow diet (CHD) (Picolab rodent diet 20, LabDiet) with a regular drinking water or an “fast food” diet (FFD) (Research Diets, D12079B) plus fructose 23.1 g/L and glucose 18.9 g/L added to the drinking water for 20 weeks. Half of mice in each group were housed at the standard temperature (ST) (22°C), and the other half of mice were housed at the thermoneutral temperature (TT) (27°C). Body weight, food intake, and body composition were measured weekly. Histological assessments, including H&E staining, trichrome staining, and Picro Sirius Red staining, were used to examine lipid accumulation and collagen formation in liver. In addition, Real-time PCR was performed to study gene expression in the liver and brown adipose tissue (BAT). Results In the FFD group, mice under TT compared to ST had significantly higher body weight gain, total fat mass, higher plasma levels of aspartate aminotransferase, alanine aminotransferase, total cholesterol, and low-density lipoprotein cholesterol. Moreover, FFD mice under TT demonstrated more pronounced lipid accumulation and presence of collagen, higher expression of several genes involved in lipid synthesis (Fasn, Acc1, and Serbp1c) and collagen formation (Col1a1), and significantly higher expression of inflammation markers including Ccl5, Nos2, Mcp1, and Il12b in the liver. As expected, TT housing significantly inhibited expression of thermogenesis markers, such as Ucp1, Elov3, and Cidea in BAT regardless of diets. Mice fed CHD did not present NASH even they were exposed to TT. Conclusions Thermoneutrality exacerbated the progression of NASH in mice. Further studies are warranted to investigate how brown fat activity regulates the development of NASH. Funding Sources The College of Human Sciences of Texas Tech University; the National Center for Complementary & Integrative Health (Grant R15AT008733).

Taurine Stimulates Thermoregulatory Genes in Brown Fat Tissue and Muscle without an Influence on Inguinal White Fat Tissue in a High-Fat Diet-Induced Obese Mouse Model.

This study was conducted to investigate if taurine supplementation stimulates the induction of thermogenic genes in fat tissues and muscles and decipher the mechanism by which taurine exerts its anti-obesity effect in a mildly obese ICR (CD-1®) mouse model. Three groups of ICR mice were fed a normal chow diet, a high-fat diet (HFD), or HFD supplemented with 2% taurine in drinking water for 28 weeks. The expression profiles of various genes were analyzed by real time PCR in interscapular brown adipose tissue (BAT), inguinal white adipose tissue (iWAT), and the quadriceps muscles of the experimental groups. Genes that are known to regulate thermogenesis like PGC-1α, UCP-1, Cox7a1, Cox8b, CIDE-A, and β1-, β2-, and β3-adrenergic receptors (β-ARs) were found to be differentially expressed in the three tissues. These genes were expressed at a very low level in iWAT as compared to BAT and muscle. Whereas, HFD increased the expression of these genes. Taurine supplementation stimulated the expression of UCP-1, Cox7a1, and Cox8b in BAT and only Cox7a1 in muscle, while there was a decrease in iWAT. In contrast, fat deposition-related genes, monoamine oxidases (MAO)-A, and -B, and lipin-1, were decreased by taurine supplementation only in iWAT and not in BAT or muscle. In conclusion, the potential anti-obesity effects of taurine may be partly due to upregulated thermogenesis in BAT, energy metabolism of muscle, and downregulated fat deposition in iWAT.

OR04-06 G Protein GSα in Muscle Is Essential for Survival During Cold Adaptation in the Absence of Thermogenesis of Brown Adipose Tissue

Adaptive thermogenesis is important for the control of body temperature (Tb) and maintenance of body weight, and it is primarily regulated by sympathetically-driven brown adipose tissue (BAT). Studies indicate that muscle is also involved in thermogenic regulation. Gsα couples to ligands and receptors, including β-adrenergic receptors, to increase intracellular cAMP. Our previous studies have showed that mice with adipose-specific Gsα deficiency had inactive BAT and impaired cold tolerance. To determine whether Gsα/cAMP signaling in skeletal muscle compensates for loss of BAT thermogenesis, we generated mice with Gsα deficiency in adipocyte tissue alone (AdipGsKO), in skeletal muscle alone (SkMGsKO) or in both (AdipSkMGsKO). Compared to control mice, AdipGsKO and SkMGsKO mice had normal body weight, while AdipSkMGsKO showed reduced body weight with normal food intake and energy expenditure. Both AdipGsKO and AdipSkMGsKO mice had elevated fasting glucose levels, but similar glucose tolerance to control or SkMGsKO mice. SkMGsKO mice displayed reduced insulin sensitivity. When acutely exposed to 6oC for 3 hours, AdipGsKO and AdipSkMGsKO mice rapidly decreased their Tb, indicating that they are sensitive to acute cold exposure, consistent with their inactive BAT. To assess adaptation to chronic cold, mice were exposed to gradually declining ambient temperature from 22oC to 6oC with a daily decrease of 2oC and were then kept at 6oC for 5 days. As expected, both AdipGsKO and AdipSkMGsKO mice failed to stimulate BAT UCP1 by cold adaptation. Unexpectedly, AdipGsKO mice maintained normal Tb similar to control and SkMGsKO mice. However, AdipSkMGsKO mice started to rapidly drop their Tb when ambient temperature declined to 14oC and 85% of SkMGsKO mice (11/13) died before the end of experiment. These results suggest that when there is a lack of BAT function, Gsα/cAMP signaling in muscle plays an essential role for mice to survive in response to chronic cold challenge.

A dysregulated bile acid-gut microbiota axis contributes to obesity susceptibility

BackgroundThe composition of the bile acid (BA) pool is closely associated with obesity and is modified by gut microbiota. Perturbations of gut microbiota shape the BA composition, which, in turn, may alter important BA signaling and affect host metabolism. MethodsWe investigated BA composition of high BMI subjects from a human cohort study and a high fat diet (HFD) obesity prone (HF-OP) / HFD obesity resistant (HF-OR) mice model. Gut microbiota was analysed by metagenomics sequencing. GLP-1 secretion and gene regulation studies involved ELISA, qPCR, Western blot, Immunohistochemistry, and Immunofluorescence staining. FindingsWe found that the proportion of non-12-OH BAs was significantly decreased in the unhealthy high BMI subjects. The HF-OR mice had an enhanced level of non-12-OH BAs. Non-12-OH BAs including ursodeoxycholate (UDCA), chenodeoxycholate (CDCA), and lithocholate (LCA) were decreased in the HF-OP mice and associated with altered gut microbiota. Clostridium scindens was decreased in HF-OP mice and had a positive correlation with UDCA and LCA. Gavage of Clostridium scindens in mice increased the levels of hepatic non-12-OH BAs, accompanied by elevated serum 7α-hydroxy-4-cholesten-3-one (C4) levels. In HF-OP mice, altered BA composition was associated with significantly downregulated expression of GLP-1 in ileum and PGC1α, UCP1 in brown adipose tissue. In addition, we identified that UDCA attenuated the high fat diet-induced obesity via enhancing levels of non-12-OH BAs. InterpretationOur study highlights that dysregulated BA signaling mediated by gut microbiota contributes to obesity susceptibility, suggesting modulation of BAs could be a promising strategy for obesity therapy.

Investigating Anti-Obesity Effects by Oral Administration of Aloe vera Gel Extract (AVGE): Possible Involvement in Activation of Brown Adipose Tissue (BAT).

The aim of this study is to investigate the mechanism of anti-obesity effects of Aloe vera gel extract (AVGE) containing Aloe sterols. Previously, we reported that oral intake of Aloe vera components has an anti-diabetic and anti-obesity effect. This study was designed to assess the role of brown adipose tissue (BAT) in the anti-obesity effect of AVGE. Six-week-old male mice were divided into three groups; STD (standard diet), HFD (60% high fat diet) and AVGE (60% high fat diet with AVGE treatment). During 11 wk of AVGE administration, body weight has been monitored. Tissue samples were obtained to be measured the weight and evaluated the gene expressions. Mice treated with AVGE had suppressed body weight, and liver and fat weight gain. To investigate BAT activation, we measured the expression of mRNA related to BAT thermogenesis. Mice in the AVGE group had higher expression of Ucp1, Adrb3, and Cidea in BAT compared to HFD. Next, to investigate the possibility that AVGE induced hepatic FGF21, which is an important factor for nutrient and energy homeostasis including BAT regulation, in vitro study was conducted. HepG2 cell stimulated by AVGE were highly expressed FGF21. These results suggested that BAT activation partially contributes to mechanism of anti-obesity effect of Aloe sterols in diet-induced obesity (DIO) models. However, further study is needed to determine the predominant mechanism.

AMPK activation ameliorates fine particulate matter-induced hepatic injury.

Both the epidemiological and animal experimental studies have reported the association between PM2.5 and respiratory, cardiovascular, and metabolic diseases. However, the study linking PM2.5 and hepatic injury is few, and the relative mechanism has not been fully elucidated. Thirty-two 6-week-old male C57BL/6 mice were exposed to filtered air (FA) or concentrated PM2.5 for 12weeks using Shanghai Meteorological and Environmental Animal Exposure System ("Shanghai-METAS"), respectively. At week 11, the mice began to be treated with intraperitoneal injection of normal 0.9% saline or AMPK activator (AICAR). The mRNA levels of IL-6 and TNF-α, and protein expressions of AMPK, GLUT4, NF-κB, p38MAPK, ERK, and JNK in the liver and UCP-1 in brown adipose tissue (BAT) were measured. Meanwhile, histopathological examination both in the liver and BAT was performed to evaluate the histopathological changes. PM2.5 exposure induced steatosis, hepatocyte ballooning, lobular and portal inflammation in the liver, and the brown adipocyte swelling in BAT. The results found that PM mice displayed higher IL-6, TNF-α, NF-κB, and JNK expression and lower AMPK, GLUT4, and UCP-1 when compared with FA mice. The AICAR injection upregulated the expressions of GLUT4 in the liver of PM-AIC mice when compared with the PM mice. However, there were no significant effects of AICAR on histopathological condition. The current study showed that ambient PM2.5 exposure might induce the hepatic injury along with the lipid metabolism disorder in BAT. AMPK activation can ameliorate most of the harmful effects and might become the potential target for treating PM2.5-induced hepatic injury.

Eicosapentaenoic Acid Reduces Hepatic Steatosis Independently of UCP1

Hepatic steatosis is characterized by excessive accumulation of triglyceride (TG). Mitochondrial membrane uncoupling proteins (UCPs) are potential targets for obesity treatment, given their ability to dissipate energy as heat. Previous studies in our lab have indicated that the omega‐3 polyunsaturated fatty acid, eicosapentaenoic acid (EPA), reduced obesity, inflammation and hepatic steatosis, and upregulated brown adipose tissue UCP1 protein in high fat (HF) fed mice housed at ambient temperature (22–23°C). However, EPA‐mediated improvements were attenuated and were independent of UCP1 when mice were housed in a thermoneutral environment (28–30°C). Thus, the objective of this work is to determine mechanisms of EPA‐mediated improvements in liver steatosis in UCP1 Knockout (KO) mice. Wild type (WT) and UCP1‐KO B6 mice were fed a HF diet with 36 g/kg AlaskOmega, 800mg/g fish oil of EPA (WT‐EPA, KO‐EPA) or without EPA (WT‐HF, KO‐HF) for 14 weeks. Mice were metabolically phenotyped during the feeding period, and histology and molecular analyses were performed in the liver after euthanasia. The KO‐HF group were highest in body weight, while KO‐HF, WT‐HF and WT‐EPA were comparable. Surprisingly, EPA attenuated weight gain in the KO‐EPA group compared to KO‐HF. Further, liver TG levels were significantly reduced in the KO‐EPA group compared to the KO‐HF. Consistent with this finding, EPA upregulated fatty acid beta‐oxidation markers only in the KO‐EPA group, indicated by significant increases in peroxisome proliferator activated receptor‐alpha (Ppara) and carnitine palmitoyltransferase (Cpt) 1a compared to KO‐HF. In conclusion, EPA rescued the detrimental effects of UCP1 deficiency in the livers of HF fed mice in a thermoneutral environment. Further studies are ongoing to dissect mechanistic basis for UCP1‐independent beneficial effects of EPA in liver steatosis. Our promising findings warrant further EPA supplementation studies in humans with obesity, given the limited activity of brown adipose tissue and downregulation of UCP1 in this population.Support or Funding InformationFunded by NIH/NCCIH grant #R15AT008879‐01A1 (N.M.M.)

Ambient fine particulate matter exposure perturbed circadian rhythm and oscillations of lipid metabolism in adipose tissues

Emerging evidence indicated that disruption of circadian rhythm (CR) induced metabolic disorders, including dysregulation of energy homeostasis and lipid dysfunction, which was associated with ambient fine particulate matter (PM2.5) as well. However, the role and mechanism of CR in PM2.5-mediated metabolic disorder remain unknown. In the present study, we investigated circadian rhythmic characteristics and explored the effect of PM2.5 on oscillating clock of lipid function and metabolism in white adipose tissue (WAT) and brown adipose tissue (BAT). C57BL/6 mice were exposed to PM2.5 in a whole-body inhalational exposure system. After 10 weeks, the expression of clock-related genes exhibits more robust CR in BAT than WAT, with the acrophase of PER2 in both types of adipose tissue being significantly decreased at ZT12 and Bmal1 increased at ZT0/24 in WAT in response to PM2.5 exposure. In addition, both CR pattern and expression levels of Sirt1 got significantly inhibited by PM2.5 exposure in WAT, accompanied with adipose dysfunction evidenced by inhibited pattern and expression levels of adipokines at the same ZT time points. Finally, a similar phase right shift from ZT4 to ZT12 in both Sirt3 and Ucp1 in BAT was induced by PM2.5 exposure. These findings indicate that disruption of the CR in adipose tissues could be an important way by which PM2.5 exposure induces metabolic disorder and provide potential targets for further investigation.