Liver X receptors and fat cell metabolism

Genomic Convergence in Hibernating Mammals Elucidates the Genetics of Metabolic Regulation in the Hypothalamus

Elucidating the genetic basis of mammalian metabolism could help define mechanisms central to health and disease. Here, we define conserved cis-regulatory elements (CREs) and programs for mammalian metabolic control. We delineate gene expression and chromatin responses in the mouse hypothalamus for 7 steps of the Fed-to-Fasted-to-Refed (FFR) response process. Comparative genomics of hibernating versus non-hibernating lineages then illuminates cis-elements showing convergent changes in hibernators. Hibernators accumulated loss-of-function effects for specific CREs regulating hypothalamic FFR responses. Multi-omics approaches pinpoint key CREs, genes, regulatory programs, and cell types in the divergence of hibernating and homeothermic lineages. The refeeding period after extended fasting is revealed as one critical period of chromatin remodeling with convergent genomic changes. This genetic framework is a step toward harnessing hibernator adaptations in medicine.

Adipocyte Mitochondria: Deciphering Energetic Functions across Fat Depots in Obesity and Type 2 Diabetes

Adipose tissue, a central player in energy balance, exhibits significant metabolic flexibility that is often compromised in obesity and type 2 diabetes (T2D). Mitochondrial dysfunction within adipocytes leads to inefficient lipid handling and increased oxidative stress, which together promote systemic metabolic disruptions central to obesity and its complications. This review explores the pivotal role that mitochondria play in altering the metabolic functions of the primary adipocyte types, white, brown, and beige, within the context of obesity and T2D. Specifically, in white adipocytes, these dysfunctions contribute to impaired lipid processing and an increased burden of oxidative stress, worsening metabolic disturbances. Conversely, compromised mitochondrial function undermines their thermogenic capabilities, reducing the capacity for optimal energy expenditure in brown adipocytes. Beige adipocytes uniquely combine the functional properties of white and brown adipocytes, maintaining morphological similarities to white adipocytes while possessing the capability to transform into mitochondria-rich, energy-burning cells under appropriate stimuli. Each type of adipocyte displays unique metabolic characteristics, governed by the mitochondrial dynamics specific to each cell type. These distinct mitochondrial metabolic phenotypes are regulated by specialized networks comprising transcription factors, co-activators, and enzymes, which together ensure the precise control of cellular energy processes. Strong evidence has shown impaired adipocyte mitochondrial metabolism and faulty upstream regulators in a causal relationship with obesity-induced T2D. Targeted interventions aimed at improving mitochondrial function in adipocytes offer a promising therapeutic avenue for enhancing systemic macronutrient oxidation, thereby potentially mitigating obesity. Advances in understanding mitochondrial function within adipocytes underscore a pivotal shift in approach to combating obesity and associated comorbidities. Reigniting the burning of calories in adipose tissues, and other important metabolic organs such as the muscle and liver, is crucial given the extensive role of adipose tissue in energy storage and release.

Environmental chemicals change extracellular lipidome of mature human white adipocytes

Certain environmental chemicals affect the body's energy balance and are known as metabolism disrupting chemicals (MDCs). MDCs have been implicated in the development of metabolic diseases, such as obesity and type 2 diabetes. In contrast to their well-known impact on developing adipocytes, MDC effects leading to altered energy balance and development of insulin resistance in mature white adipocytes, constituents of adult adipose tissue, are largely unclear. Here, we investigated the effects of six well-established environmental MDCs (bisphenol A (BPA), perfluorooctanoic acid (PFOA), triclosan (TCS), p,p-dichlorodiphenyl-dichloroethylene (ppDDE), tributyltin chloride (TBT) and triphenyl phosphate (TPP)) on mature human white adipocytes derived from mesenchymal stem cells in vitro. We aimed to identify biomarkers and sensitive endpoints of their metabolism disrupting effects. While most of the tested exposures had no effect on adipocyte glucose consumption, lipid storage and assessed gene expression endpoints, the highest concentration of triclosan affected the total lipid storage and adipocyte size, as well as glucose consumption and mRNA expression of the glucose transporter GLUT1, leptin and adiponectin. Additionally, an increased expression of adiponectin was observed with TPP and the positive control PPARγ agonist rosiglitazone. In contrast, the lipidomic analysis of the cell culture medium after a 3-day exposure was extremely sensitive and revealed concentration-dependent changes in the extracellular lipidome of adipocytes exposed to nearly all studied chemicals. While some of the extracellular lipidome changes were specific for the MDC used, some effects were found common to several tested chemicals and included increases in lysophosphatidylcholines, glycerophospholipids and ceramides and a decrease in fatty acids, with possible implications in inflammation, lipid and glucose uptake. This study points to early signs of metabolic disruption and likely systemic effects of mature adipocyte exposure to environmental chemicals, as well as to the need to include lipidomic endpoints in the assessment of adverse effects of MDCs.

ASGR1 deficiency diverts lipids toward adipose tissue but results in liver damage during obesity

BACKGROUND

Asialoglycoprotein receptor 1 (ASGR1), primarily expressed on hepatocytes, promotes the clearance and the degradation of glycoproteins, including lipoproteins, from the circulation. In humans, loss-of-function variants of ASGR1 are associated with a favorable metabolic profile and reduced incidence of cardiovascular diseases. The molecular mechanisms by which ASGR1 could affect the onset of metabolic syndrome and obesity are unclear. Therefore, here we investigated the contribution of ASGR1 in the development of metabolic syndrome and obesity.

METHODS

ASGR1 deficient mice (ASGR1-/-) were subjected to a high-fat diet (45% Kcal from fat) for 20 weeks. The systemic metabolic profile, hepatic and visceral adipose tissue were characterized for metabolic and structural alterations, as well as for immune cells infiltration.

RESULTS

ASGR1-/- mice present a hypertrophic adipose tissue with 41% increase in fat accumulation in visceral adipose tissue (VAT), alongside with alteration in lipid metabolic pathways. Intriguingly, ASGR1-/- mice exhibit a comparable response to an acute glucose and insulin challenge in circulation, coupled with notably decreased in circulating cholesterol levels. Although the liver of ASGR1-/- have similar lipid accumulation to the WT mice, they present elevated levels of liver inflammation and a decrease in mitochondrial function.

CONCLUSION

ASGR1 deficiency impacts energetic homeostasis during obesity leading to improved plasma lipid levels but increased VAT lipid accumulation and liver damage.

The fat accumulation promotion effects of dihydrxytetraphenylmethane and its underlying mechanisms via transcriptome analysis

Dihydrxytetraphenylmethane, also known as Bisphenol BP (BPBP), has been increasingly used in industrial production and more frequently detected in the environment as an alternative plasticizer of BPA. However, there are no reports about BPBP in food safety or its effects on cellular lipogenesis. The purpose of this research was to investigate the influence and potential mechanisms of BPBP on adipogenesis in 3T3-L1 cells. Cells were treated with 4 concentrations (0.01, 0.1, 1, and 10 μM) of BPBP and the results showed that treatment with at low concentrations (0.01 μM) promoted cell fat differentiation and triglyceride accumulation. RNA-seq data showed that a total of 370 differentially expressed genes between control and the low-dose BPBP-treated group were determined, including 227 upregulated genes and 143 downregulated genes. Some key genes related to adipocyte differentiation and adipogenesis were significantly enriched after BPBP treatment, including PPAR-γ, Adipoq, Nr1h3 and Plin1. Pathway analyses suggest that the activation of PPAR-γ signaling pathway may be key for BPBP to promote adipocyte differentiation and fat accumulation. Our work provides evidence for the potential obesogenic effect of BPBP and may call for further research on the safety of the chemical in food products.

Principal component analysis of adipose tissue gene expression of lipogenic and adipogenic factors in obesity

OBJECTIVE

A better understanding of mechanisms regulating lipogenesis and adipogenesis is needed to overcome the obesity pandemic. We aimed to study the relationship of the transcript levels of peroxisome proliferator activator receptor γ (PPARγ), CCAAT/enhancer-binding protein alpha (C/EBP-α), liver X receptor (LXR), sterol regulatory element-binding protein-1c (SREBP-1c), fatty acid synthase (FAS), and acetyl-CoA carboxylase (ACC) in subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) from obese and normal-weight women with a variety of anthropometric indices, metabolic and biochemical parameters, and insulin resistance.

METHODS

Real-time PCR was done to evaluate the transcript levels of the above-mentioned genes in VAT and SAT from all participants.

RESULTS

Using principal component analysis (PCA) results, two significant principal components were identified for adipogenic and lipogenic genes in SAT (SPC1 and SPC2) and VAT (VPC1 and VPC2). SPC1 was characterized by relatively high transcript levels of SREBP1c, PPARγ, FAS, and ACC. However, the second pattern (SPC2) was associated with C/EBPα and LXR α mRNA expression. VPC1 was characterized by transcript levels of SREBP1c, FAS, and ACC. However, the VPC2 was characterized by transcript levels of C/EBPα, LXR α, and PPARγ. Pearson's correlation analysis showed that unlike SPC2, which disclosed an inverse correlation with body mass index, waist and hip circumference, waist to height ratio, visceral adiposity index, HOMA-IR, conicity index, lipid accumulation product, and weight-adjusted waist index, the VPC1 was positively correlated with above-mentioned obesity indices.

CONCLUSION

This study provided valuable data on multiple patterns for adipogenic and lipogenic genes in adipose tissues in association with a variety of anthropometric indices in obese subjects predicting adipose tissue dysfunction and lipid accumulation.

The Role of Solute Carrier Transporters in Efficient Anticancer Drug Delivery and Therapy

Transporter-mediated drug resistance is a major obstacle in anticancer drug delivery and a key reason for cancer drug therapy failure. Membrane solute carrier (SLC) transporters play a crucial role in the cellular uptake of drugs. The expression and function of the SLC transporters can be down-regulated in cancer cells, which limits the uptake of drugs into the tumor cells, resulting in the inefficiency of the drug therapy. In this review, we summarize the current understanding of low-SLC-transporter-expression-mediated drug resistance in different types of cancers. Recent advances in SLC-transporter-targeting strategies include the development of transporter-utilizing prodrugs and nanocarriers and the modulation of SLC transporter expression in cancer cells. These strategies will play an important role in the future development of anticancer drug therapies by enabling the efficient delivery of drugs into cancer cells.

Short communication: Photoperiod impacts ovarian extracellular matrix and metabolic gene expression in Siberian hamsters

Ovarian cyclicity is variable in adult Siberian hamsters (Phodopus sungorus), who respond to long breeding season photoperiods with follicle development and ovulation, while short photoperiods typical of the non-breeding season induce gonadal atrophy. Recent RNAseq results identified ovarian matrix components and regulators of metabolism as differentially regulated by photoperiod; however, the impact of photoperiod across a full cycle of ovarian regression and recrudescence had not been explored for additional regulators of ovarian metabolism and extracellular matrix components. We hypothesized that matrix and metabolism-related genes would be expressed differentially across photoperiods that mimic breeding and non-breeding season daylengths. Hamsters were housed in one of four photoperiod groups: long day (16 h of light per day: 8 h of dark; LD, controls), short day regressed (8 L:16D; SD, regressed), and females exposed to SD then transferred to LD to stimulate return of ovarian function for 2 (early recrudescence), or 8 (late recrudescence) weeks. Plasma leptin concentrations along with expression of ovarian versican and liver-receptor homolog-1/Nr582 mRNA decreased in SD compared to LD and late recrudescence, while vimentin mRNA expression peaked in early and late recrudescence. Ovarian expression of fibronectin and extracellular matrix protein-1 was low in LD ovaries and increased in regressed and recrudescing groups. Expression of hyaluronidase-2, nectin-2, liver-X receptors-α and-β, and adiponectin mRNA peaked in late recrudescence, with no changes noted for adiponectin receptor-1 and -2. The results offer a first look at the parallels between expression of these genes and the dynamic remodeling that occurs during ovarian regression and recrudescence.

Novel insights into the regulation of cellular catabolic metabolism in macrophages through nuclear receptors

Regulation of cellular catabolic metabolism in immune cells has recently become a major concept for resolution of inflammation. Nuclear receptors (NRs), including peroxisome proliferator activator receptors (PPARs), 1,25-dihydroxyvitamin D(3) receptor (VDR), liver X receptors (LXRs), glucocorticoid receptors (GRs), estrogen-related receptor α (ERRα) and Nur77, have been identified as major modulators of inflammation, affecting innate immune cells, such as macrophages. Evidence emerges on how NRs regulate cellular metabolism in macrophages during inflammatory processes and contribute to the resolution of inflammation. This could have new implications for our understanding of how NRs shape immune responses and inform anti-inflammatory drug design. This review will highlight the recent developments about NRs and their role in cellular metabolism in macrophages.

Methanolic fruit extract of Myrica nagi protects the hypothalamus and attenuates inflammation associated with gold thioglucose- and high-fat diet-induced obesity via various adipokines

BACKGROUND

Myrica nagi is popular in unani and ayurveda. Chemical constituents like myricetin isolated from its fruit has been shown to exert beneficial effects against cardiovascular disease, cancer, inflammatory conditions, and metabolic disorders.

OBJECTIVES

This study aimed to elucidate the anti-obesity effect of the methanolic extract of M. nagi (MEMN) using in vivo animal models of obesity induced by gold thioglucose or a high-fat diet.

MATERIALS AND METHODS

The obese mice were treated or untreated with MEMN for 8 weeks. Thereafter, feed intake, Lee index, and body mass index (BMI); biochemical parameters such as lipid profile, liver enzymes and specific biomarkers of obesity, including insulin, leptin, adiponectin, free fatty acids (FFA), monocyte chemoattractant protein (MCP)-1, and resistin, were recorded. The weight and histopathology of organs and fat tissue were examined to validate the effectiveness of the extract.

RESULTS

MEMN administration at various doses significantly reduced the induced weight gain, feed intake, BMI, and Lee index. Adipose tissue decreased as the MEMN dose increased. MEMN attenuated liver enzyme activity, decreased lipid, leptin, MCP-1, resistin, and FFA levels, and increased adiponectin levels. It also increased protection of liver cells and decreased accumulation of mesenteric fat.

CONCLUSIONS

MEMN supplementation decreased weight and improved obesity serum/plasma lipid biomarker, insulin, leptin, adiponectin, MCP-1, and resistin levels. The weight-reducing activity of MEMN may be mediated by decreased gastrointestinal fat absorption and modulation of inflammation associated signaling pathways, leading to reduced adipose inflammation associated with energy expenditure.

LXR agonist modifies neuronal lipid homeostasis and decreases PGD2 in the dorsal root ganglia in western diet-fed mice

The prevalence of peripheral neuropathy is high in diabetic and overweight populations. Chronic neuropathic pain, a symptom of peripheral neuropathy, is a major disabling symptom that leads to a poor quality of life. Glucose management for diabetic and prediabetic individuals often fail to reduce or improve pain symptoms, therefore, exploring other mechanisms is necessary to identify effective treatments. A large body of evidence suggest that lipid signaling may be a viable target for management of peripheral neuropathy in obese individuals. The nuclear transcription factors, Liver X Receptors (LXR), are known regulators of lipid homeostasis, phospholipid remodeling, and inflammation. Notably, the activation of LXR using the synthetic agonist GW3965, delayed western diet (WD)-induced allodynia in rodents. To further understand the neurobiology underlying the effect of LXR, we used translating ribosome affinity purification and evaluated translatomic changes in the sensory neurons of WD-fed mice treated with the LXR agonist GW3965. We also observed that GW3965 decreased prostaglandin levels and decreased free fatty acid content, while increasing lysophosphatidylcholine, phosphatidylcholine, and cholesterol ester species in the sensory neurons of the dorsal root ganglia (DRG). These data suggest novel downstream interplaying mechanisms that modifies DRG neuronal lipid following GW3965 treatment.

FTO gene expression in diet-induced obesity is downregulated by Solanum fruit supplementation

The Fat Mass and Obesity-associated (FTO) gene has been shown to play an important role in developing obesity, manifesting in traits such as increased body mass index, increased waist-to-hip ratio, and the distribution of adipose tissues, which increases the susceptibility to various metabolic syndromes. In this study, we evaluated the impact of fruit-based diets of Solanum melongena (SMF) and Solanum aethiopicum fruits (SAF) on the FTO gene expression levels in a high-fat diet (HFD)-induced obese animals. Our results showed that the mRNA level of the FTO gene was downregulated in the hypothalamus, and white and brown adipose tissue following three and six weeks of treatment with SMF- and SAF-based diets in the HFD-induced obese animals. Additionally, the Solanum fruit supplementation exhibited a curative effect on obesity-associated abrasions on the white adipose tissue (WAT), hypothalamus, and liver. Our findings collectively suggest the anti-obesity potential of SMF and SAF via the downregulation of the FTO gene.

Genome-wide analysis of cis-regulatory changes underlying metabolic adaptation of cavefish

Cis-regulatory changes are key drivers of adaptative evolution. However, their contribution to the metabolic adaptation of organisms is not well understood. Here, we used a unique vertebrate model, Astyanax mexicanus-different morphotypes of which survive in nutrient-rich surface and nutrient-deprived cave waters-to uncover gene regulatory networks underlying metabolic adaptation. We performed genome-wide epigenetic profiling in the liver tissues of Astyanax and found that many of the identified cis-regulatory elements (CREs) have genetically diverged and have differential chromatin features between surface and cave morphotypes, while retaining remarkably similar regulatory signatures between independently derived cave populations. One such CRE in the hpdb gene harbors a genomic deletion in cavefish that abolishes IRF2 repressor binding and derepresses enhancer activity in reporter assays. Selection of this mutation in multiple independent cave populations supports its importance in cave adaptation, and provides novel molecular insights into the evolutionary trade-off between loss of pigmentation and adaptation to food-deprived caves.

Multiple myeloma cells induce lipolysis in adipocytes and uptake fatty acids through fatty acid transporter proteins

Adipocytes occupy 70% of the cellular volume within the bone marrow (BM) wherein multiple myeloma (MM) originates and resides. However, the nature of the interaction between MM cells and adipocytes remains unclear. Cancer-associated adipocytes support tumor cells through various mechanisms, including metabolic reprogramming of cancer cells. We hypothesized that metabolic interactions mediate the dependence of MM cells on BM adipocytes. Here we show that BM aspirates from precursor states of MM, including monoclonal gammopathy of undetermined significance and smoldering MM, exhibit significant upregulation of adipogenic commitment compared with healthy donors. In vitro coculture assays revealed an adipocyte-induced increase in MM cell proliferation in monoclonal gammopathy of undetermined significance/smoldering MM compared with newly diagnosed MM. Using murine MM cell/BM adipocyte coculture assays, we describe MM-induced lipolysis in adipocytes via activation of the lipolysis pathway. Upregulation of fatty acid transporters 1 and 4 on MM cells mediated the uptake of secreted free fatty acids (FFAs) by adjacent MM cells. The effect of FFAs on MM cells was dose dependent and revealed increased proliferation at lower concentrations vs induction of lipotoxicity at higher concentrations. Lipotoxicity occurred via the ferroptosis pathway. Exogenous treatment with arachidonic acid, a very-long-chain FFA, in a murine plasmacytoma model displayed a reduction in tumor burden. Taken together, our data reveal a novel pathway involving MM cell-induced lipolysis in BM adipocytes and suggest prevention of FFA uptake by MM cells as a potential target for myeloma therapeutics.

Elucidating Drug-Like Compounds and Potential Mechanisms of Corn Silk (Stigma Maydis) against Obesity: A Network Pharmacology Study

Corn silk (Stigma Maydis) has been utilized as an important herb against obesity by Chinese, Korean, and Native Americans, but its phytochemicals and mechanisms(s) against obesity have not been deciphered completely. This study aimed to identify promising bioactive constituents and mechanism of action(s) of corn silk (CS) against obesity via network pharmacology. The compounds from CS were identified using Gas Chromatography Mass Spectrometry (GC-MS) and were confirmed ultimately by Lipinski's rule via SwissADME. The relationships of the compound-targets or obesity-related targets were confirmed by public bioinformatics. The signaling pathways related to obesity, protein-protein interaction (PPI), and signaling pathways-targets-bioactives (STB) were constructed, visualized, and analyzed by RPackage. Lastly, Molecular Docking Test (MDT) was performed to validate affinity between ligand(s) and protein(s) on key signaling pathway(s). We identified a total of 36 compounds from CS via GC-MS, all accepted by Lipinski's rule. The number of 36 compounds linked to 154 targets, 85 among 154 targets related directly to obesity-targets (3028 targets). Of the final 85 targets, we showed that the PPI network (79 edges, 357 edges), 12 signaling pathways on a bubble chart, and STB network (67 edges, 239 edges) are considered as therapeutic components. The MDT confirmed that two key activators (β-Amyrone, β-Stigmasterol) bound most stably to PPARA, PPARD, PPARG, FABP3, FABP4, and NR1H3 on the PPAR signaling pathway, also, three key inhibitors (Neotocopherol, Xanthosine, and β-Amyrone) bound most tightly to AKT1, IL6, FGF2, and PHLPP1 on the PI3K-Akt signaling pathway. Overall, we provided promising key signaling pathways, targets, and bioactives of CS against obesity, suggesting crucial pharmacological evidence for further clinical testing.

Protective effects of a unique combination of nutritionally active ingredients on risk factors and gene expression associated with atherosclerosis in C57BL/6J mice fed a high fat diet

Atherosclerosis, an inflammatory disorder of the vasculature and the underlying cause of cardiovascular disease, is responsible for one in three global deaths. Consumption of active food ingredients such as omega-3 polyunsaturated fatty acids, flavanols and phytosterols has many beneficial effects on cardiovascular disease. However, their combined actions on the risk factors for atherosclerosis remains poorly understood. We have previously shown that a formulation containing each of these active components at physiologically relevant doses modulated several monocyte/macrophage processes associated with atherosclerosis in vitro, including inhibition of cytokine-induced pro-inflammatory gene expression, chemokine-driven monocyte migration, expression of M1 phenotype markers, and promotion of cholesterol efflux. The objectives of the present study were to investigate whether the protective actions of the formulation extended in vivo and to delineate the potential underlying mechanisms. The formulation produced several favourable changes, including higher plasma levels of HDL and reduced levels of macrophages and myeloid-derived suppressor cells in the bone marrow. The mRNA expression of liver-X-receptor-α, peroxisome proliferator-activated receptor-γ and superoxide dismutase-1 was induced in the liver and that of interferon-γ and the chemokine (C-X-C motif) ligand 1 decreased, thereby suggesting the potential mechanisms for many beneficial effects. Other changes were also observed such as increased plasma levels of triglycerides and lipid peroxidation that may reflect potential activation of brown fat. This study provides new insights into the protective actions and the potential underlying mechanisms of the formulation in vivo, particularly in relation to risk factors together with changes in systemic inflammation and hepatic lipid alterations associated with atherosclerosis and metabolic syndrome, and supports further assessments in human trials.

Low Molecular Weight Fucoidan Can Inhibit the Fibrosis of Diabetic Kidneys by Regulating the Kidney Lipid Metabolism

In this study, a diabetic kidney disease model was established by placing the test rats on a high-sugar/high-fat diet combined with streptozotocin induction. Histopathological examination (H&E, Masson, and PASM stain) showed pathological changes in the diabetic rat kidneys, in addition to fibrotic symptoms and collagen deposition. Immunohistochemistry and western blot analyses indicated that the diabetic condition significantly increased the expressions of fibrotic markers including collagen, α-SMA, and fibronectin. The levels of cholesterol, triglyceride, and low-density lipoprotein were also increased in diabetic kidney disease (DKD) rat blood, while the level of high-density lipoprotein was decreased. The results of Oil red O staining experiments indicated that the kidneys of diabetic rats exhibited appreciable fat deposition, with high contents of triglyceride and cholesterol. To inhibit fibrosis and reduce fat deposition, low molecular weight fucoidan (LMWF) may be used. Based on PCR and western blot analyses, LMWF can regulate the expression levels of important lipid metabolism regulators, thereby impeding the development of kidney fibrosis. Through the vitro model, it also be indicated that LMWF could inhibit fibrosis process through regulating lipid metabolism which induced by palmitic acid.

Increased Risk of High Body Fat and Altered Lipid Metabolism Associated to Suboptimal Consumption of Vitamin A Is Modulated by Genetic Variants rs5888 (SCARB1), rs1800629 (UCP1) and rs659366 (UCP2)

Obesity is characterized by an excessive body fat percentage (BF%). Animal and cell studies have shown benefits of vitamin A (VA) on BF% and lipid metabolism, but it is still controversial in humans. Furthermore, although some genetic variants may explain heterogeneity in VA plasma levels, their role in VA metabolic response is still scarcely characterized. This study was designed as a combination of an observational study involving 158 male subjects followed by a study with a well-balanced genotype-phenotype protocol, including in the design an ex vivo intervention study performed on isolated peripheral blood mononuclear cells (PBMCs) of the 41 former males. This is a strategy to accurately identify the delivery of Precision Nutrition recommendations to targeted subjects. The study assesses the influence of rs5888 (SCARB1), rs659366 (UCP2), and rs1800629 (UCP1) variants on higher BF% associated with suboptimal VA consumption and underlines the cellular mechanisms involved by analyzing basal and retinoic acid (RA) response on PBMC gene expression. Data show that male carriers with the major allele combinations and following suboptimal-VA diet show higher BF% (adjusted ANOVA test p-value = 0.006). Genotype-BF% interaction is observed on oxidative/inflammatory gene expression and also influences lipid related gene expression in response to RA. Data indicate that under suboptimal consumption of VA, carriers of VA responsive variants and with high-BF% show a gene expression profile consistent with an impaired basal metabolic state. The results show the relevance of consuming VA within the required amounts, its impact on metabolism and energy balance, and consequently, on men's adiposity with a clear influence of genetic variants SCARB1, UCP2 and UCP1.

The regulation of Niemann-Pick C1-Like 1 (NPC1L1) gene expression in opposite direction by Bacteroides spp. and related outer membrane vesicles in Caco-2 cell line

Purpose

The intestine has substantial role in cholesterol homeostasis due to the presence of various cholesterol transporters and gut microbiota. Bacteroides spp. are important members of gut microbiota that employ outer membrane vesicles (OMVs) to interact with host. In this regard, we evaluated the effect of Bacteroides fragilis, Bacteroides thetaiotaomicron and related OMVs on the gene expression of important cholesterol transporters, Niemann-Pick C1-Like 1 (NPC1L1), ATP-binding cassette (ABCA1), and liver X receptors (LXRs) in Caco-2 cells.

Methods

OMVs were isolated from overnight brain heart infusion (BHI) broth of bacterial standard strains using deoxycholate and assessed by Scanning electron microscopy (SEM). The relative change in genes expression was assessed by Quantitative reverse transcription PCR (RT-qPCR) based on SYBR Green and 2^-∆∆ct method in Caco-2 cells that were treated with bacteria and OMVs. Data were statistically analyzed with GraphPad Prism software. Finally, pathway enrichment based on the studied genes was performed using Cytoscape plugin ClueGO.

Results

B. fragilis (P value = 0.002) and B. thetaiotaomicron (P value = 0.001) significantly reduced NPC1L1 gene expression in Caco-2 cells. Interestingly, NPC1L1 transcripts were significantly increased by both OMVs(P value = 0.04) (P value = 0.01). Also, LXRβ was significantly down regulated by B. thetaiotaomicron (P value = 0.02). ClueGO analysis on the studied genes demonstrated several functional groups which involve in lipid and cholesterol metabolism.

Conclusion

The opposite effect of B. fragilis, B. thetaiotaomicron and related OMVs on the NPC1L1 gene expression was observed in Caco-2 cells. Interestingly, these effects partially were in line with the alternation of LXRs expression. However, based on pathway enrichment analysis, further molecular investigations are required to elaborate in details the specific association between Bacteroides spp. and OMVs with regulation of cholesterol signaling pathways including cholesterol transport, lipid storage, lipid homeostasis and cholesterol homeostasis.

Apolipoprotein M: Research Progress and Clinical Perspective

Apolipoprotein M (apoM) was first identified and characterized to the apolipoprotein family in 1999. Human apoM gene is located in a highly conserved segment in the major histocompatibility complex (MHC) class III locus on chromosome 6 and codes for an about 23 kDa protein that structurally belongs to the lipocalin superfamily. ApoM is selectively expressed in hepatocytes and in the tubular epithelium of kidney. In human plasma, apoM is mainly confined to the high-density lipoprotein (HDL) particles, but it may also occur in other lipoprotein classes, such as in the triglyceride-rich particles after fat intake. It has been demonstrated that apoM is critical for the formation of HDL, notably pre-beta HDL1. The antiatherogenic function of HDL is well established, and its ability to promote cholesterol efflux from foam cells in the atherosclerotic lesions is generally regarded as one of the key mechanisms behind this protective function. However, HDL could also display a variety of properties that may affect the complex atherosclerotic processes by other mechanisms, thus being involved in processes related to antioxidant defense, immune system, and systemic effects in septicemia, which may be partly contributed via its apolipoproteins and/or phospholipids. Moreover, it has been demonstrated that apoM functions as a natural carrier of sphingosin-1-phosphate (S1P) in vivo which may be related to its antiatherosclerotic and protective effects on endothelial cell barrier and anti-inflammatory properties. These may also provide a link between the diverse effects of HDL.

High-Fat Diets and LXRs Expression in Rat Liver and Hypothalamus

Disturbances on lipid metabolism are associated with health disorders. High-fat diets (HFDs) consumption promotes cardiovascular and neurodegenerative diseases where cholesterol plays an important role. Among regulators of this steroid homeostasis, the liver X receptors (LXRs) induce genes that protect cells from cholesterol overload. We previously described how both hypothalamic LXRα and LXRβ are sensitive to a high-fructose diet, suggesting that these receptors trigger responses related to control of energy and food intake. The present work's main objective was to study the effect of different HFDs on LXRs expression (in hypothalamus and liver), and lipid profile. Male rats received control diet (CD), HFD1 (CD + bovine fat (BF)), HFD2 (CD + BF + cholic acid (CA)), HFD3 (CD + BF + cholesterol), or HFD4 (CD + BF + CA + cholesterol) for different time periods. Hypothalamic LXRβ, both hepatic LXRs subtypes, and total cholesterol (TC) raised after 2 weeks of HFDs. Four and 8 weeks of HFD3 and HFD4 increased the LXRs subtypes in both tissues and TC levels. Only HFD4 reduced triglycerides (TG) levels after 2 and 8 weeks. The TC and TG values correlated significantly with LXRs expression only in rats fed with HFD4. These data add relevant information about how diet composition can produce different scales of hypercholesterolemia states accompanied with central and peripheral changes in the LXRs expression.

Breed, Diet, and Interaction Effects on Adipose Tissue Transcriptome in Iberian and Duroc Pigs Fed Different Energy Sources

In this study, we analyzed the effects of breed, diet energy source, and their interaction on adipose tissue transcriptome in growing Iberian and Duroc pigs. The study comprised 29 Iberian and 19 Duroc males, which were kept under identical management conditions except the nutritional treatment. Two isoenergetic diets were used with 6% high oleic sunflower oil (HO) or carbohydrates (CH) as energy sources. All animals were slaughtered after 47 days of treatment at an average live weight of 51.2 kg. Twelve animals from each breed (six fed each diet) were employed for ham subcutaneous adipose tissue RNA-Seq analysis. The data analysis was performed using two different bioinformatic pipelines. We detected 837 and 1456 differentially expressed genes (DEGs) according to breed, depending on the pipeline. Due to the strong effect of breed on transcriptome, the effect of the diet was separately evaluated in the two breeds. We identified 207 and 57 DEGs depending on diet in Iberian and Duroc pigs, respectively. A joint analysis of both effects allowed the detection of some breed–diet interactions on transcriptome, which were inferred from RNA-Seq and quantitative PCR data. The functional analysis showed the enrichment of functions related to growth and tissue development, inflammatory response, immune cell trafficking, and carbohydrate and lipid metabolism, and allowed the identification of potential regulators. The results indicate different effects of diet on adipose tissue gene expression between breeds, affecting relevant biological pathways.

The chromatin remodeling protein BRG1 links ELOVL3 trans-activation to prostate cancer metastasis

Prostate cancer malignancies are intimately correlated with deregulated fatty acid metabolism. The underlying epigenetic mechanism is not fully understood. In the present study we investigated the mechanism whereby the chromatin remodeling protein BRG1 regulates the transcription of long-chain fatty acid elongase 3 (Elovl3) in prostate cancer cells. We report that in response to pro-metastatic cues (androgen and TGF-β) BRG1 expression was up-regulated along with Elvol3 in prostate cancer cells. BRG1 over-expression potentiated whereas BRG1 knockdown attenuated prostate cancer cell migration and invasion. Coincidently, Elovl3 was up-regulated following BRG1 over-expression and down-regulated after BRG1 knockdown in prostate cancer cells. Further analysis revealed that BRG1 interacted with and was recruited by retinoic acid receptor-related orphan receptor (RORγ) to the Elovl3 promoter to activate transcription. Chromatin immunoprecipitation (ChIP) profiling demonstrated that BRG1 interacted with histone acetyltransferase p300 to activate Elovl3 transcription. Depletion of p300 by siRNA or inhibition of p300 by curcumin attenuated Elovl3 trans-activation in prostate cancer cells. Together, our data identify a novel epigenetic pathway that links Elovl3 transcription to prostate cancer cell migration and invasion.

Serum proteome changes and accelerated reduction of fat mass after laparoscopic gastric plication in morbidly obese patients

Laparoscopic Gastric Plication (LGP) is a relatively new bariatric surgical procedure which no part of the stomach is removed. It is not clearly understood how LGP leads to fatty tissue reduction. We aimed to investigate the impact of LGP on serum proteome and understand molecular mechanisms of LGP-induced weight loss post-surgery. A Prospective observational study of 16 obese individuals who underwent LGP was performed. A Label-free quantitative shotgun proteomics approach was used to compare serum proteome of subjects before surgery with serum of the same individuals 1 to 2 months post-surgery (T1) and 4 to 5 months post-surgery (T2). The proteome analysis revealed that 48 proteins were differentially regulated between pre-surgery and T1, and seven proteins between pre-surgery and T2 of which six proteins were shared between the two timepoints. Among differentially regulated proteins, four proteins (SRGN, FETUB, LCP1 and CFP) have not previously been described in the context of BMI/weight loss. Despite few differences following LGP, most regulated serum proteins are in accordance with alternative weight loss procedures. Pathway analysis revealed changes to lipid- and inflammatory pathways, including PPARα/RXRα, LXR/RXR and FXR/RXR activation, especially at T1. At T2, the pathways related to inflammation and immune system are most affected. SIGNIFICANCE: Among the available clinical therapies for morbid obesity, bariatric surgery is considered as the most effective approach to achieve long-term weight loss, alongside a significant improvement in metabolic syndrome. However, very little is known about the underlying mechanism associated with significant weight loss post-surgery. Understanding such mechanisms could lead to development of safer non-surgical weight loss approaches. We here present the first analysis of the impact of LGP on the serum proteome, to bring new insights into the underlying molecular mechanism. Our findings indicate that LGP has a comprehensive systemic effect based on the blood serum proteome profile which might account for accelerated reduction of fat mass after surgery, thus, food restriction is not the only reason for weight loss following this unique surgical approach. As secretory regions of the stomach are preserved in LGP and it is associated with minimal physiological and anatomical changes, the findings are of high importance in the field of bariatric surgery and weight loss.

The Antagonist Effect of Arachidonic Acid on GLUT4 Gene Expression by Nuclear Receptor Type II Regulation

OBJECTIVES

Obesity is a complex disease that has a strong association with diet and lifestyle. Dietary factors can influence the expression of key genes connected to insulin resistance, lipid metabolism, and adipose tissue composition. In this study, our objective was to determine gene expression and fatty acid (FA) profiles in visceral adipose tissue (VAT) from lean and morbidly obese individuals. We also aimed to study the agonist effect of dietary factors on glucose metabolism.

DESIGN AND METHODS

Lean and low and high insulin resistance morbidly obese subjects (LIR-MO and HIR-MO) were included in this study. The gene expression of liver X receptor type alpha (LXR-α) and glucose transporter type 4 (GLUT4) and the FA profiles in VAT were determined. Additionally, the in vivo and in vitro agonist effects of oleic acid (OA), linoleic acid (LA), and arachidonic acid (AA) by peroxisome proliferator-activated receptor type gamma 2 (PPAR-γ2) on the activity of GLUT4 were studied.

RESULTS

Our results showed a dysregulation of GLUT4 and LXR-α in VAT of morbidly obese subjects. In addition, a specific FA profile for morbidly obese individuals was found. Finally, AA was an PPAR-γ2 agonist that activates the expression of GLUT4.

CONCLUSIONS

Our study suggests a dysregulation of LXR-α and GLUT4 expression in VAT of morbidly obese individuals. FA profiles in VAT could elucidate their possible role in lipolysis and adipogenesis. Finally, AA binds to PPAR-γ2 to activate the expression of GLUT4 in the HepG2 cell line, showing an alternative insulin-independent activation of GLUT4.

Comparative Proteomic Analysis of Visceral Adipose Tissue in Morbidly Obese and Normal Weight Chinese Women

OBJECTIVE

Visceral adipose tissue (VAT) plays a central role in the balance of energy metabolism. The objective of this study was to investigate the differentially expressed proteins in VAT between morbidly obese (BMI >35 kg/m²) and normal weight Chinese women.

METHOD

Nine morbidly obese women and 8 normal weight women as controls were enrolled. Abdominal VAT was excised and analyzed by label-free one-dimensional liquid chromatography tandem mass spectrometry (1D-LC-MS/MS). Differentially expressed VAT proteins were further analyzed with Gene Ontology (GO) analysis and Ingenuity Pathway Analysis (IPA). Masson's trichrome staining and CD68 immunohistochemical staining of VAT were conducted in all subjects.

RESULT

A total of 124 differentially expressed proteins were found with a ≥2-fold difference. Forty-one proteins were upregulated, and 83 proteins were downregulated in obese individuals. These altered VAT proteins were involved in the attenuation of the liver X receptor/retinoid X receptor (LXR/RXR) signaling pathway and the activation of the acute-phase response process. Three proteins (ACSL1, HADH, and UCHL1) were validated by western blotting using the same set of VAT samples from 6 morbidly obese and 7 normal weight patients, and the results indicated that the magnitude and direction of the protein changes were in accordance with the proteomic analysis. Masson's trichrome staining and CD68 immunohistochemical staining demonstrated that there was much more collagen fiber deposition and CD68-positive macrophages in the VAT of morbidly obese patients, suggesting extensive fiber deposition and macrophage infiltration.

CONCLUSION

A number of differentially expressed proteins were identified in VAT between morbidly obese and normal weight Chinese females. These differential proteins could be potential candidates in addressing the role of VAT in the development of obesity.

LXR/RXR pathway signaling associated with triple-negative breast cancer in African American women

Background

Triple-negative breast cancer (TNBC) is more prevalent in African and African American (AA) women compared to European American (EA) women. African and AA women diagnosed with TNBC experience high frequencies of metastases and less favorable outcomes. Emerging evidence indicates that this disparity may in fact be the result of the uniquely aggressive biology of African and AA disease.

Purpose

To understand the reasons for TNBC in AA aggressive biology, we designed the present study to examine the proteomic profiles of TNBC and luminal A (LA) breast cancer within and across patients’ racial demographic groups in order to identify proteins or molecular pathways altered in TNBC that offer some explanation for its aggressiveness and potential targets for treatment.

Materials and methods

Proteomic profiles of TNBC, LA tumors, and their adjacent normal tissues from AA and EA women were obtained using 2-dimensional gel electrophoresis and bioinformatics, and differentially expressed proteins were validated by Western blot and immunohistochemistry. Our data showed that a number of proteins have significantly altered in expression in LA tumors compared to TNBC, both within and across patients’ racial demographic groups. The differentially overexpressed proteins in TNBC (compared to LA) of AA samples were distinct from those in TNBC (compared to LA) of EA women samples. Among the signaling pathways altered in AA TNBC compared to EA TNBC are innate immune signaling, calpain protease, and pyrimidine de novo synthesis pathways. Furthermore, liver LXR/RXR signaling pathway was altered between LA and TNBC in AA women and may be due to the deficiency of the CYP7B1 enzyme responsible for cholesterol degradation.

Conclusion

These findings suggest that TNBC in AA women enriched in signaling pathways that are different from TNBC in EA women. Our study draws a link between LXR/RXR expression, cholesterol, obesity, and the TNBC in AA women.

A critical role for ABC transporters in persistent lung inflammation in the development of emphysema after smoke exposure

Macrophage infiltration is common to both emphysema and atherosclerosis, and cigarette smoke down-regulates the macrophage cholesterol efflux transporter ATP binding cassette (ABC)A1. This decreased cholesterol efflux results in lipid-laden macrophages. We hypothesize that cigarette smoke adversely affects cholesterol transport via an ABCA1-dependent mechanism in macrophages, enhancing TLR4/myeloid differentiation primary response gene 88 (Myd88) signaling and resulting in matrix metalloproteinase (MMP) up-regulation and exacerbation of pulmonary inflammation. ABCA1 is significantly down-regulated in the lung upon smoke exposure conditions. Macrophages exposed to cigarette smoke in vivo and in vitro exhibit impaired cholesterol efflux correlating with significantly decreased ABCA1 expression, up-regulation of the TLR4/Myd88 pathway, and downstream MMP-9 and MMP-13 expression. Treatment with liver X receptor (LXR) agonist restores ABCA1 expression after short-term smoke exposure and attenuates the inflammatory response; after long-term smoke exposure, there is also attenuated physiologic and morphologic changes of emphysema. In vitro, treatment with LXR agonist decreases macrophage inflammatory activation in wild-type but not ABCA1 knockout mice, suggesting an ABCA1-dependent mechanism of action. These studies demonstrate an important association between cigarette smoke exposure and cholesterol-mediated pathways in the macrophage inflammatory response. Modulation of these pathways through manipulation of ABCA1 activity effectively blocks cigarette smoke-induced inflammation and provides a potential novel therapeutic approach for the treatment of chronic obstructive pulmonary disease.-Sonett, J., Goldklang, M., Sklepkiewicz, P., Gerber, A., Trischler, J., Zelonina, T., Westerterp, M., Lemaître, V., Okada, V., D'Armiento, J. A critical role for ABC transporters in persistent lung inflammation in the development of emphysema after smoke exposure.

In Vitro Cocktail Effects of PCB-DL (PCB118) and Bulky PCB (PCB153) with BaP on Adipogenesis and on Expression of Genes Involved in the Establishment of a Pro-Inflammatory State

(1) Objective: Highlight the in vitro effects of 3T3-L1 cell exposure to polychlorinated biphenyls (PCB118 and 153) or benzo(a)pyrene (BaP) alone or as a cocktail on adipogenesis (ADG) by focusing on changes in lipid metabolism and inflammatory-related genes expression (INFG) and ADG-related genes expression (ADGG); (2) Results: Treatment from the early stage of cell differentiation by BaP alone or in combination with PCBs decreased the expression of some of the ADGG (PPARγGlut-4, FAS, Lipin-1a, Leptin, and Adiponectin). BaP enhanced the INFG, especially MCP-1 and TNFα. Co-exposure to BaP and PCB153 showed a synergistic effect on TNFα and IL6 expression. Treatment with BaP and PCBs during only the maturation period up-regulated the INFG (IL6, TNFα, CXCL-10 & MCP-1). PCB118 alone also enhanced TNFα, CXCL-10, and PAI-1 expression. The change in MCP-1 protein expression was in agreement with that of the gene. Finally, the BaP-induced up-regulation of the xenobiotic responsive element (XRE)-controlled luciferase activity was impaired by PCB153 but not by PCB118; (3) Conclusion: BaP and PCBs down-regulate a part of ADGG and enhance INFG. The direct regulatory effect of PCBs on both ADGG and INFG is usually rather lower than that of BaP and synergistic or antagonistic cocktail effects are clearly observed.

Small heterodimer partner 1 directly interacts with NS5A viral protein and has a key role in HCV related liver cell transformation

HCV life cycle is strictly correlated with the hepatocyte lipid metabolism; moreover, the progression of HCV chronic hepatitis is accelerated by the presence of liver steatosis. Among the steatogenic genes deregulated during the HCV infection one of the most attractive is the Small Heterodimer Protein 1 (SHP1; NR0B2), that is involved in a remarkable number of metabolic functions. HCV NS5A is an essential and integral component of the HCV membranous-web replicon complex (RC) and plays an essential role to transfer the viral genome from the RCs to the surface of the lipid droplets (LDs) that, in turn, play a key function during HCV life cycle.

With the help of a HCV infection model, we demonstrate a functional interaction between SHP1 and HCV NS5A protein. SHP1 silencing (siSHP1) reversed the pro-oncogenic effects of HCV infection, inducing a significant decrease in liver lipid accumulation and in NS5A protein expression. Moreover, siSHP1 causes a strong modulation of some genes involved in HCV-related EMT, such as: HNF4, a central regulators of hepatocyte differentiation, E-Cadherin, SNAILs.

Our data suggest that SHP1 results not only to be strictly connected to the pathogenesis of HCV-related liver steatosis, but also to its progression towards the liver transformation.

Perilipin 5 and liver fatty acid binding protein function to restore quiescence in mouse hepatic stellate cells

Hepatic stellate cell (HSC) activation occurs along with decreased Perilipin5 (Plin5) and liver fatty acid-binding protein (L-Fabp) expression and coincident lipid droplet (LD) depletion. Conversely, the activated phenotype is reversible in WT HSCs upon forced expression of Plin5. Here, we asked if L-Fabp expression is required for Plin5-mediated rescue of the quiescent phenotype. Lentiviral Plin5 transduction of passaged L-Fabp^-/- HSCs failed to reverse activation markers or restore lipogenic gene expression and LD formation. However, adenoviral L-Fabp infection of lentiviral Plin5 transduced L-Fabp^-/- HSCs restored both the quiescent phenotype and LD formation, an effect also mediated by adenoviral intestine-Fabp or adipocyte-Fabp. Expression of exogenous Plin5 in activated WT HSCs induced a transcriptional program of lipogenic gene expression including endogenous L-Fabp, but none of the other FABPs. We further demonstrated that selective, small molecule inhibition of endogenous L-Fabp also eliminated the ability of exogenous Plin5 to rescue LD formation and reverse activation of WT HSCs. This functional coordination of L-Fabp with Plin5 was 5'-AMP-activated protein kinase (AMPK)-dependent and was eliminated by AMPK inhibition. Taken together, our results indicate that L-Fabp is required for Plin5 to activate a transcriptional program that restores LD formation and reverses HSC activation.

LXRα and LXRβ Nuclear Receptors Evolved in the Common Ancestor of Gnathostomes

Nuclear receptors (NRs) regulate numerous aspects of the endocrine system. They mediate endogenous and exogenous cues, ensuring a homeostatic control of development and metabolism. Gene duplication, loss and mutation have shaped the repertoire and function of NRs in metazoans. Here, we examine the evolution of a pivotal orchestrator of cholesterol metabolism in vertebrates, the liver X receptors (LXRs). Previous studies suggested that LXRα and LXRβ genes emerged in the mammalian ancestor. However, we show through genome analysis and functional assay that bona fide LXRα and LXRβ orthologues are present in reptiles, coelacanth and chondrichthyans but not in cyclostomes. These findings show that LXR duplicated before gnathostome radiation, followed by asymmetric paralogue loss in some lineages. We suggest that a tighter control of cholesterol levels in vertebrates was achieved through the exploitation of a wider range of oxysterols, an ability contingent on ligand-binding pocket remodeling.

Morin, a novel liver X receptor α/β dual antagonist, has potent therapeutic efficacy for nonalcoholic fatty liver diseases

BACKGROUND AND PURPOSE

Morin is a natural occurring flavonoid in many dietary plants and has a wide range of beneficial effects on metabolism; however, the mechanism underlying its action remains elusive.

EXPERIMENTAL APPROACH

A reporter assay and the time-resolved FRET assay were used to identify morin as a dual antagonist of liver X receptor (LXR)-α and -β. Morin (100 mg^. 100 g^-1 diet) was administered to high-fat diet-induced obese or LXRβ^-/- mice. The pharmacological effects and mechanism of action of morin were evaluated by Western blot and RT-PCR analyses.

KEY RESULTS

From the in vitro assays, morin was shown to be a dual antagonist of LXRα and LXRβ. In vivo, morin blunted the development of liver hepatic steatosis, reduced body weight gains, lowered triglyceride levels and improved glucose and insulin tolerance in mice fed a high-fat diet. Mechanistically, morin inhibited 3T3-L1 adipocyte differentiation and lipid formation in human hepatic HepG2 cells and suppressed the mRNA expression of genes downstream of LXR. Consistently, the effects of morin on metabolic disorders were attenuated in LXRβ^-/- mice.

CONCLUSION AND IMPLICATIONS

Our data reveal that morin is a dual antagonist of LXRα and LXRβ and suggest that morin may alleviate hepatic steatosis and other associated metabolic disorders via the suppression of LXR signalling and, therefore, shows promise as a novel therapy or nutraceutical for nonalcoholic fatty liver disease.

Impaired adipose expansion caused by liver X receptor activation is associated with insulin resistance in mice fed a high-fat diet

Liver X receptors (LXR) are deemed as potential drug targets for atherosclerosis, whereas a role in adipose tissue expansion and its relation to insulin sensitivity remains unclear. To assess the metabolic effects of LXR activation by the dual LXRα/β agonist T0901317, C57BL/6 mice fed a high-fat diet (HFD) were treated with T0901317 (30 mg/kg once daily by intraperitoneal injection) for 3 weeks. Differentiated 3T3-L1 adipocytes were used for analysing the effect of T0901317 on glucose uptake. The following results were obtained from this study. T0901317 reduced fat mass, accompanied by a massive fatty liver and lower serum adipokine levels in HFD mice. Increased adipocyte apoptosis was found in epididymal fat of T0901317-treated HFD mice. In addition, T0901317 treatment promoted basal lipolysis, but blunted the anti-lipolytic action of insulin. Furthermore, LXR activation antagonised PPARγ target genes in epididymal fat and PPARγ-PPRE-binding activity in 3T3-L1 adipocytes. Although the glucose tolerance was comparable to that in HFD mice, the insulin response during IPGTT was significantly higher and the insulin tolerance was significantly impaired in T0901317-treated HFD mice, indicating decreased insulin sensitivity by T0901317 administration, and which was further supported by impaired insulin signalling found in epididymal fat and decreased insulin-induced glucose uptake in 3T3-L1 adipocytes by T0901317 administration. In conclusion, these findings reveal that LXR activation impairs adipose expansion by increasing adipocyte apoptosis, lipolysis and antagonising PPARγ-mediated transcriptional activity, which contributes to decreased insulin sensitivity in whole body. The potential of LXR activation being a therapeutic target for atherosclerosis might be limited by the possibility of exacerbating insulin resistance.

[Regulation of ABCA1 and ABCG1 gene expression in the intraabdominal adipose tissue]

Tissue specific expression of genes encoding cholesterol transporters ABCA1 and ABCG1 as well as genes encoding the most important transcriptional regulators of adipogenesis - LXRa, LXRb, PPARg and RORa has been investigated in intraabdominal adipose tissue (IAT) samples.A direct correlation between the content of ABCA1 and ABCG1 proteins with RORa protein level (r=0.480, p<0.05; r=0.435, p<0.05, respectively) suggests the role of the transcription factor RORa in the regulation of IAT ABCA1 and ABCG1 protein levels. ABCA1 and ABCG1 gene expression positively correlated with obesity indicators such as body mass index (BMI) (r=0.522, p=0.004; r=0.594, p=0.001, respectively) and waist circumference (r=0.403, p=0.033; r=0.474, p=0.013, respectively). The development of obesity is associated with decreased IAT levels of RORa and LXRb mRNA (p=0.016 and p=0.002, respectively). These data suggest that the nuclear factor RORa can play a significant role in the regulation of cholesterol metabolism and control IAT expression of ABCA1 and ABCG1, while the level of IAT LXRb gene expression may be an important factor associated with the development of obesity.

A-FABP mediates adaptive thermogenesis by promoting intracellular activation of thyroid hormones in brown adipocytes

The adipokine adipocyte fatty acid-binding protein (A-FABP) has been implicated in obesity-related cardio-metabolic complications. Here we show that A-FABP increases thermogenesis by promoting the conversion of T4 to T3 in brown adipocytes. We find that A-FABP levels are increased in both white (WAT) and brown (BAT) adipose tissues and the bloodstream in response to thermogenic stimuli. A-FABP knockout mice have reduced thermogenesis and whole-body energy expenditure after cold stress or after feeding a high-fat diet, which can be reversed by infusion of recombinant A-FABP. Mechanistically, A-FABP induces the expression of type-II iodothyronine deiodinase in BAT via inhibition of the nuclear receptor liver X receptor α, thereby leading to the conversion of thyroid hormone from its inactive form T4 to active T3. The thermogenic responses to T4 are abrogated in A-FABP KO mice, but enhanced by A-FABP. Thus, A-FABP acts as a physiological stimulator of BAT-mediated adaptive thermogenesis.

Geranylgeranyl pyrophosphate performs as an endogenous regulator of adipocyte function via suppressing the LXR pathway

Isoprenoids such as geranylgeranyl pyrophosphate (GGPP) influence various biological processes. Here we show that GGPP inhibits adipocyte differentiation via the liver X receptors (LXRs) pathway. Intracellular GGPP levels and GGPP synthase (Ggps) mRNA expression increases during adipocyte differentiation. Ggps expression also increases in white adipose tissue of obese mice. GGPP addition reduces the expression of adipogenic marker genes such as adipocyte fatty acid binding protein, peroxisome proliferator-activated receptor γ, and insulin-stimulated glucose uptake. Similarly, over-expressing Ggps inhibits adipocyte differentiation. In contrast, Ggps knockdown promotes adipocyte differentiation. Inhibition of adipocyte differentiation by GGPP was partially reduced by LXR agonist T0901317. Furthermore, Ggps knockdown up-regulates LXR target genes during adipocyte differentiation. These results suggest that GGPP may act as an endogenous regulator of adipocyte differentiation and maturation through a mechanism partially dependent on the LXR pathway.

ALOX5AP Overexpression in Adipose Tissue Leads to LXA4 Production and Protection Against Diet-Induced Obesity and Insulin Resistance

Eicosanoids, such as leukotriene B4 (LTB4) and lipoxin A4 (LXA4), may play a key role during obesity. While LTB4 is involved in adipose tissue inflammation and insulin resistance, LXA4 may exert anti-inflammatory effects and alleviate hepatic steatosis. Both lipid mediators derive from the same pathway, in which arachidonate 5-lipoxygenase (ALOX5) and its partner, arachidonate 5-lipoxygenase-activating protein (ALOX5AP), are involved. ALOX5 and ALOX5AP expression is increased in humans and rodents with obesity and insulin resistance. We found that transgenic mice overexpressing ALOX5AP in adipose tissue had higher LXA4 rather than higher LTB4 levels, were leaner, and showed increased energy expenditure, partly due to browning of white adipose tissue (WAT). Upregulation of hepatic LXR and Cyp7a1 led to higher bile acid synthesis, which may have contributed to increased thermogenesis. In addition, transgenic mice were protected against diet-induced obesity, insulin resistance, and inflammation. Finally, treatment of C57BL/6J mice with LXA4, which showed browning of WAT, strongly suggests that LXA4 is responsible for the transgenic mice phenotype. Thus, our data support that LXA4 may hold great potential for the future development of therapeutic strategies for obesity and related diseases.

Liver X receptor and STAT1 cooperate downstream of Gas6/Mer to induce anti-inflammatory arginase 2 expression in macrophages

Mer signaling increases the transcriptional activity of liver X receptor (LXR) to promote the resolution of acute sterile inflammation. Here, we aimed to understand the pathway downstream of Mer signaling after growth arrest-specific protein 6 (Gas6) treatment that leads to LXR expression and transcriptional activity in mouse bone-marrow derived macrophages (BMDM). Gas6-induced increases in LXRα and LXRβ and expression of their target genes were inhibited in BMDM from STAT1^−/− mice or by the STAT1-specific inhibitor fludarabine. Gas6-induced STAT1 phosphorylation, LXR activation, and LXR target gene expression were inhibited in BMDM from Mer^−/− mice or by inhibition of PI3K or Akt. Gas6-induced Akt phosphorylation was inhibited in BMDM from STAT1^−/− mice or in the presence of fludarabine. Gas6-induced LXR activity was enhanced through an interaction between LXRα and STAT1 on the DNA promoter of Arg2. Additionally, we found that Gas6 inhibited lipopolysaccharide (LPS)-induced nitrite production in a STAT1 and LXR pathway-dependent manner in BMDM. Additionally, Mer-neutralizing antibody reduced LXR and Arg2 expression in lung tissue and enhanced NO production in bronchoalveolar lavage fluid in LPS-induced acute lung injury. Our data suggest the possibility that the Gas6-Mer-PI3K/Akt-STAT1-LXR-Arg2 pathway plays an essential role for resolving inflammatory response in acute lung injury.

The Flavone Luteolin Inhibits Liver X Receptor Activation

Luteolin is a dietary flavonoid with medicinal properties including antioxidant, antimicrobial, anticancer, antiallergic, and anti-inflammatory. However, the effect of luteolin on liver X receptors (LXRs), oxysterol sensors that regulate cholesterol homeostasis, lipogenesis, and inflammation, has yet to be studied. To unveil the potential of luteolin as an LXRα/β modulator, we investigated by real-time RT-PCR the expression of LXR-target genes, namely, sterol regulatory element binding protein 1c (SREBP-1c) in hepatocytes and ATP-binding cassette transporter (ABC)A1 in macrophages. The lipid content of hepatocytes was evaluated by Oil Red staining. The results demonstrated, for the first time, that luteolin abrogated the LXRα/β agonist-induced LXRα/β transcriptional activity and, consequently, inhibited SREBP-1c expression, lipid accumulation, and ABCA1 expression. Therefore, luteolin could abrogate hypertriglyceridemia associated with LXR activation, thus presenting putative therapeutic effects in diseases associated with deregulated lipid metabolism, such as hepatic steatosis, cardiovascular diseases, and diabetes.

27-Hydroxycholesterol suppresses lipid accumulation by down-regulating lipogenic and adipogenic gene expression in 3T3-L1 cells

Cholesterol oxidation products (oxycholesterols) are produced from cholesterol by automatic and/or enzymatic oxidation of the steroidal backbone and side-chain. Oxycholesterols are present in plasma and serum, suggesting that oxycholesterols are related to the development and progression of various diseases. However, limited information is available about the absolute amounts of oxycholesterols in organs and tissues, and the physiological significance of oxycholesterols in the body. In the present study, we quantified the levels of 13 oxycholesterols in white adipose tissue (WAT) of mice and then evaluated correlations between each oxycholesterol level and WAT weight. The sum of the levels of 13 oxycholesterols in WAT (white adipose tissue) was 15.9 ± 3.4 μg/g of WAT weight and approximately 1 % of cholesterol level. Among oxycholesterols, the levels of 27-hydroxycholesterol (27-OH), an endogenous oxycholesterol produced by enzymatic oxidation, and the relative WAT weights were significantly negatively correlated. Next, we evaluated the effects of 27-OH on lipogenesis and adipogenesis in 3T3-L1 cells. TO901317 (TO), a potent and selective agonist for LXRα, significantly increased intracellular TAG contents, while 27-OH significantly reduced the contents to half when compared with control (DMSO) and completely abolished the effect of TO. In addition, 27-OH significantly reduced the mRNA levels of lipogenic (LXRα and FAS) and adipogenic genes (PPARγ and aP2) during adipocyte maturation of 3T3-L1 cells. In conclusion, our results indicate that 27-OH suppresses lipid accumulation by down-regulating lipogenic and adipogenic gene expression in 3T3-L1 cells.

Dietary licorice root supplementation reduces diet-induced weight gain, lipid deposition, and hepatic steatosis in ovariectomized mice without stimulating reproductive tissues and mammary gland

SCOPE

We studied the impact of dietary supplementation with licorice root components on diet-induced obesity, fat accumulation, and hepatic steatosis in ovariectomized C57BL/6 mice as a menopause model.

MATERIALS AND METHODS

We evaluated the molecular and physiological effects of dietary licorice root administered to ovariectomized C57BL/6 mice as root powder (LRP), extracts (LRE), or isolated isoliquiritigenin (ILQ) on reproductive (uterus and mammary gland) and nonreproductive tissues important in regulating metabolism (liver, perigonadal, perirenal, mesenteric, and subcutaneous fat). Quantitative outcome measures including body weight, fat distribution (magnetic resonance imaging), food consumption, bone density and weight (Dual-energy X-ray absorptiometry), and gene expression were assessed by the degree of restoration to the preovariectomized health state. We characterized histological (H&E and oil red O staining) and molecular properties (expression of certain disease markers) of these tissues, and correlated these with metabolic phenotype as well as blood levels of bioactives.

CONCLUSION

Although LRE and ILQ provided some benefit, LRP was the most effective in reducing body weight gain, overall fat deposition, liver steatosis, and expression of hepatic lipid synthesis genes following ovariectomy. Our data demonstrate that licorice root provided improvement of multiple metabolic parameters under conditions of low estrogen and high-fat diets without stimulating reproductive tissues.

Steroid biosynthesis in adipose tissue

Tissue-specific expression of steroidogenic enzymes allows the modulation of active steroid levels in a local manner. Thus, the measurement of local steroid concentrations, rather than the circulating levels, has been recognized as a more accurate indicator of the steroid action within a specific tissue. Adipose tissue, one of the largest endocrine tissues in the human body, has been established as an important site for steroid storage and metabolism. Locally produced steroids, through the enzymatic conversion from steroid precursors delivered to adipose tissue, have been proven to either functionally regulate adipose tissue metabolism, or quantitatively contribute to the whole body's steroid levels. Most recently, it has been suggested that adipose tissue may contain the steroidogenic machinery necessary for the initiation of steroid biosynthesis de novo from cholesterol. This review summarizes the evidence indicating the presence of the entire steroidogenic apparatus in adipose tissue and discusses the potential roles of local steroid products in modulating adipose tissue activity and other metabolic parameters.

The HIV matrix protein p17 induces hepatic lipid accumulation via modulation of nuclear receptor transcriptoma

Liver disease is the second most common cause of mortality in HIV-infected persons. Exactly how HIV infection per se affects liver disease progression is unknown. Here we have investigated mRNA expression of 49 nuclear hormone receptors (NRs) and 35 transcriptional coregulators in HepG2 cells upon stimulation with the HIV matrix protein p17. This viral protein regulated mRNA expression of some NRs among which LXRα and its transcriptional co-activator MED1 were highly induced at mRNA level. Dissection of p17 downstream intracellular pathway demonstrated that p17 mediated activation of Jak/STAT signaling is responsible for the promoter dependent activation of LXR. The treatment of both HepG2 as well as primary hepatocytes with HIV p17 results in the transcriptional activation of LXR target genes (SREBP1c and FAS) and lipid accumulation. These effects are lost in HepG2 cells pre-incubated with a serum from HIV positive person who underwent a vaccination with a p17 peptide as well as in HepG2 cells pre-incubated with the natural LXR antagonist gymnestrogenin. These results suggest that HIV p17 affects NRs and their related signal transduction thus contributing to the progression of liver disease in HIV infected patients.

Many obesity-associated SNPs strongly associate with DNA methylation changes at proximal promoters and enhancers

BACKGROUND

The mechanisms by which genetic variants, such as single nucleotide polymorphisms (SNPs), identified in genome-wide association studies act to influence body mass remain unknown for most of these SNPs, which continue to puzzle the scientific community. Recent evidence points to the epigenetic and chromatin states of the genome as having important roles.

METHODS

We genotyped 355 healthy young individuals for 52 known obesity-associated SNPs and obtained DNA methylation levels in their blood using the Illumina 450 K BeadChip. Associations between alleles and methylation at proximal cytosine residues were tested using a linear model adjusted for age, sex, weight category, and a proxy for blood cell type counts. For replication in other tissues, we used two open-access datasets (skin fibroblasts, n = 62; four brain regions, n = 121-133) and an additional dataset in subcutaneous and visceral fat (n = 149).

RESULTS

We found that alleles at 28 of these obesity-associated SNPs associate with methylation levels at 107 proximal CpG sites. Out of 107 CpG sites, 38 are located in gene promoters, including genes strongly implicated in obesity (MIR148A, BDNF, PTPMT1, NR1H3, MGAT1, SCGB3A1, HOXC12, PMAIP1, PSIP1, RPS10-NUDT3, RPS10, SKOR1, MAP2K5, SIX5, AGRN, IMMP1L, ELP4, ITIH4, SEMA3G, POMC, ADCY3, SSPN, LGR4, TUFM, MIR4721, SULT1A1, SULT1A2, APOBR, CLN3, SPNS1, SH2B1, ATXN2L, and IL27). Interestingly, the associated SNPs are in known eQTLs for some of these genes. We also found that the 107 CpGs are enriched in enhancers in peripheral blood mononuclear cells. Finally, our results indicate that some of these associations are not blood-specific as we successfully replicated four associations in skin fibroblasts.

CONCLUSIONS

Our results strongly suggest that many obesity-associated SNPs are associated with proximal gene regulation, which was reflected by association of obesity risk allele genotypes with differential DNA methylation. This study highlights the importance of DNA methylation and other chromatin marks as a way to understand the molecular basis of genetic variants associated with human diseases and traits.

Targeting fatty acid metabolism to improve glucose metabolism

Disturbances in fatty acid metabolism in adipose tissue, liver, skeletal muscle, gut and pancreas play an important role in the development of insulin resistance, impaired glucose metabolism and type 2 diabetes mellitus. Alterations in diet composition may contribute to prevent and/or reverse these disturbances through modulation of fatty acid metabolism. Besides an increased fat mass, adipose tissue dysfunction, characterized by an altered capacity to store lipids and an altered secretion of adipokines, may result in lipid overflow, systemic inflammation and excessive lipid accumulation in non-adipose tissues like liver, skeletal muscle and the pancreas. These impairments together promote the development of impaired glucose metabolism, insulin resistance and type 2 diabetes mellitus. Furthermore, intrinsic functional impairments in either of these organs may contribute to lipotoxicity and insulin resistance. The present review provides an overview of fatty acid metabolism-related pathways in adipose tissue, liver, skeletal muscle, pancreas and gut, which can be targeted by diet or food components, thereby improving glucose metabolism.