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BACKGROUND: South Asians generally have an unfavourable metabolic phenotype compared with white Caucasians, including central obesity and insulin resistance. The Wnt protein family interacts with insulin signaling, and impaired Wnt signaling is associated with adiposity and type 2 diabetes mellitus. We aimed to investigate Wnt signaling in relation to insulin signaling in South Asians compared with white Caucasians.METHODS: Ten Dutch South Asian men with prediabetes and overweight or obesity and 10 matched Dutch white Caucasians were included. Blood samples were assayed for the Wnt inhibitor sclerostin. Subcutaneous white adipose tissue (WAT) and skeletal muscle biopsies were assayed for Wnt and insulin signaling gene expression with quantitative reverse transcription polymerase chain reaction (Clinicaltrials.gov NCT02291458).RESULTS: Plasma sclerostin was markedly higher in South Asians compared with white Caucasians (+65%, PCONCLUSION: South Asian men with overweight or obesity and prediabetes have higher plasma sclerostin and lower Wnt signaling gene expression in WAT compared with white Caucasians. We interpret that reduced Wnt signaling could contribute to impaired insulin signaling in South Asians.

Introduction Non-coding genetic variation at TCF7L2 is the strongest genetic determinant of type 2 diabetes (T2D) risk in humans. TCF7L2 encodes a transcription factor mediating the nuclear effects of WNT signaling in adipose tissue (AT). In vivo studies in transgenic mice have highlighted important roles for TCF7L2 in adipose tissue biology and systemic metabolism. Objective To map the expression of TCF7L2 in human AT, examine its role in human adipose cell biology in vitro, and investigate the effects of the fine-mapped T2D-risk allele at rs7903146 on AT morphology and TCF7L2 expression. Methods Ex vivo gene expression studies of TCF7L2 in whole and fractionated human AT. In vitro TCF7L2 gain- and/or loss-of-function studies in primary and immortalized human adipose progenitor cells (APCs) and mature adipocytes (mADs). AT phenotyping of rs7903146 T2D-risk variant carriers and matched controls. Results Adipose progenitors (APs) exhibited the highest TCF7L2 mRNA abundance compared to mature adipocytes and adipose-derived endothelial cells. Obesity was associated with reduced TCF7L2 transcript levels in whole subcutaneous abdominal AT but paradoxically increased expression in APs. In functional studies, TCF7L2 knockdown (KD) in abdominal APs led to dose-dependent activation of WNT/β-catenin signaling, impaired proliferation and dose-dependent effects on adipogenesis. Whilst partial KD enhanced adipocyte differentiation, near-total KD impaired lipid accumulation and adipogenic gene expression. Over-expression of TCF7L2 accelerated adipogenesis. In contrast, TCF7L2-KD in gluteal APs dose-dependently enhanced lipid accumulation. Transcriptome-wide profiling revealed that TCF7L2 might modulate multiple aspects of AP biology including extracellular matrix secretion, immune signaling and apoptosis. The T2D-risk allele at rs7903146 was associated with reduced AP TCF7L2 expression and enhanced AT insulin sensitivity. Conclusions TCF7L2 plays a complex role in AP biology and has both dose- and depot-dependent effects on adipogenesis. In addition to regulating pancreatic insulin secretion, genetic variation at TCF7L2 might also influence T2D risk by modulating AP function.

Brown adipose tissue (BAT) is a potential target to treat cardiometabolic disorders because of its capacity to combust glucose and fatty acids for thermoregulation. Its cellular and molecular investigation in humans is hampered by the limited availability of cell material and the heterogeneity of BAT between and within individuals. In this study, monoclonal lines of conditionally immortalized brown preadipocytes (iBPAs) of mouse and human origin were generated. Conditional immortalization was achieved by doxycycline-controlled expression of simian virus 40 large tumor antigen (LT) with a repressor-based Tet-On system. In the presence of doxycycline, both the murine and human cell lines showed long-term proliferation capacity with a population doubling time of similar to 28 h. After switching off LT expression by doxycycline removal and exposure to adipogenic differentiation medium, cells from both species acquired brown adipocyte properties. This was evidenced by the accumulation of multilocular lipid droplets, the upregulation of brown adipocyte markers including uncoupling protein 1 and an increase in lipolysis and oxygen consumption following adrenergic stimulation. Switching off LT expression before the onset of adipogenic differentiation was only critical for inducing adipogenesis in the human iBPAs, while their murine counterparts showed adipogenesis upon exposure to the adipogenic differentiation cocktail regardless of LT expression. When switched to proliferation medium, cultures of adipogenically differentiated human iBPAs de-differentiated and resumed cell division without losing their adipogenic capacity. We suggest that iBPAs represent an easy-to-use model for fundamental and applied research into BAT offering unique experimental opportunities due to their capacity to switch between proliferative and differentiated states.

Brown adipose tissue (BAT) activation stimulates energy expenditure in human adults, which makes it an attractive target to combat obesity and related disorders. Recent studies demonstrated a role for G protein‐coupled receptor 120 (GPR120) in BAT thermogenesis. Here, we investigated the therapeutic potential of GPR120 agonism and addressed GPR120‐mediated signaling in BAT. We found that activation of GPR120 by the selective agonist TUG‐891 acutely increases fat oxidation and reduces body weight and fat mass in C57Bl/6J mice. These effects coincided with decreased brown adipocyte lipid content and increased nutrient uptake by BAT, confirming increased BAT activity. Consistent with these observations, GPR120 deficiency reduced expression of genes involved in nutrient handling in BAT. Stimulation of brown adipocytes in vitro with TUG‐891 acutely induced O 2 consumption, through GPR120‐dependent and GPR120‐independent mechanisms. TUG‐891 not only stimulated GPR120 signaling resulting in intracellular calcium release, mitochondrial depolarization, and mitochondrial fission, but also activated UCP1. Collectively, these data suggest that activation of brown adipocytes with the GPR120 agonist TUG‐891 is a promising strategy to increase lipid combustion and reduce obesity.

Obesity and dyslipidemia are major risk factors for the development of cardiovascular diseases (CVD). Quercetin, a natural flavonoid, lowers plasma triglycerides (TG) in human intervention studies, and its intake is associated with lower CVD risk. The aim of this study was to elucidate the mechanism by which quercetin lowers plasma TG levels in diet-induced obesity. C57Bl/6J mice received a high-fat diet (45% of calories derived from fat) with or without quercetin (0.1% w/w) for 12 weeks. Quercetin decreased plasma TG levels from nine weeks onwards (&minus, 19%, p &lt, 0.05), without affecting food intake, body composition, or energy expenditure. Mechanistically, quercetin did not reduce intestinal fatty acid (FA) absorption. Rather, quercetin induced a slight reduction in liver Apob expression (&minus, 13%, p &lt, 0.05), which suggests decreased very-low density lipoprotein-TG production. Interestingly, quercetin also markedly increased the uptake of [3H]oleate, which was derived from glycerol tri[3H]oleate-labeled lipoprotein-like particles by subcutaneous white adipose tissue (sWAT, +60%, p &lt, 0.05). Furthermore, quercetin also markedly increased mRNA expression of Ucp1 (+229%, p &lt, 0.05) and Elovl3 (+138%, p &lt, 0.05), specifically in sWAT. Accordingly, only quercetin-treated animals showed uncoupling protein-1 protein-positive cells in sWAT, which is fully compatible with increased browning. Taken together, the TG-lowering effect of quercetin may, at least in part, be due to increased TG-derived FA uptake by sWAT as a consequence of browning.

Obesity is a well-established risk factor for atherosclerosis. However, the mechanistic link between accumulation of adipose tissue and development of atherosclerosis is not clear. Adipose tissue comprises various depots including white adipose tissue (WAT), brown adipose tissue (BAT) and thoracic and abdominal perivascular adipose tissue (PVAT). The phenotype of thoracic PVAT resembles BAT, whereas abdominal PVAT is more like WAT. Here, we review the distinct roles of the adipose tissue depots in the development of atherosclerosis with the ultimate aim to understand how these can be targeted to reduce atherosclerosis. In obesity, increased fatty acid release by WAT and decreased lipid combustion by BAT and thoracic PVAT lead to hyperlipidaemia, which contributes to atherosclerosis development. Besides, obese WAT and abdominal PVAT release pro-inflammatory factors that further promote atherosclerosis. To discourage atherosclerosis development, strategies that reduce the release of pro-inflammatory factors and fatty acids from WAT and abdominal PVAT, or increase combustion of fatty acids by activation of BAT and thoracic PVAT and beiging of WAT are probably most efficient. Possible therapies could include anti-inflammatory compounds such as adiponectin and salicylates to lower inflammation, and β3-adrenergic receptor activators to increase fatty acid combustion. Additional and more specific strategies to promote fatty acid combustion are currently subject of investigation. In conclusion, different adipose depots differentially affect atherosclerosis development, in which atherosclerosis is promoted by energy-storing adipose depots and attenuated by energy-combusting adipose tissue. In obesity, combining therapies that reduce inflammation and increase combustion of lipids are most conceivable to restrain atherogenesis.

Objective Pathogenic immunoglobulins are produced during the development of obesity and contribute to the development of insulin resistance (IR). However, the mechanisms by which these antibodies affect IR are largely unknown. This study investigated whether Fc-receptors contribute to the development of diet-induced obesity and IR by studying FcRγ−/− mice that lack the γ-subunit necessary for signaling and cell surface expression of FcγR and FceRI. Methods FcRγ−/− and wild-type (WT) mice were fed a high-fat diet (HFD) to induce obesity. At 4 and 11 weeks, body weight and insulin sensitivity were measured, and adipose tissue (AT) inflammation was determined. Furthermore, intestinal triglyceride (TG) uptake and plasma TG clearance were determined, and gut microbiota composition was analyzed. Results FcRγ−/− mice gained less weight after 11 weeks of HFD. They had reduced adiposity, adipose tissue inflammation, and IR. Interestingly, FcRγ−/− mice had higher lean mass compared to WT mice, which was associated with increased energy expenditure. Intestinal TG absorption was increased whereas plasma TG clearance was not affected in FcRγ−/− mice. Gut microbial composition differed significantly and might therefore have added to the observed phenotype. Conclusions FcRγ-chain deficiency reduces the development of diet-induced obesity, as well as associated AT inflammation and IR at 11 weeks of HFD.

BACKGROUND AND PURPOSE: Salsalate (salicylsalicylic acid) is an anti-inflammatory drug that was recently found to exert beneficial metabolic effects on glucose and lipid metabolism. Although its utility in the prevention and management of a wide range of vascular disorders, including type 2 diabetes and metabolic syndrome has been suggested before, the potential of salsalate to protect against non-alcoholic steatohepatitis (NASH) remains unclear. The aim of the present study was therefore to ascertain the effects of salsalate on the development of NASH. EXPERIMENTAL APPROACH: Transgenic APOE*3Leiden.CETP mice were fed a high-fat and high-cholesterol diet with or without salsalate for 12 and 20 weeks. The effects on body weight, plasma biochemical variables, liver histology and hepatic gene expression were assessed. KEY RESULTS: Salsalate prevented weight gain, improved dyslipidemia and insulin resistance and ameliorated diet-induced NASH, as shown by decreased hepatic microvesicular and macrovesicular steatosis, reduced hepatic inflammation and reduced development of fibrosis. Salsalate affected lipid metabolism by increasing β-oxidation and decreasing lipogenesis, as shown by the activation of PPAR-α, PPAR-γ co-activator 1β, RXR-α and inhibition of genes controlled by the transcription factor MLXIPL/ChREBP. Inflammation was reduced by down-regulation of the NF-κB pathway, and fibrosis development was prevented by down-regulation of TGF-β signalling. CONCLUSIONS AND IMPLICATIONS: Salsalate exerted a preventive effect on the development of NASH and progression to fibrosis. These data suggest a clinical application of salsalate in preventing NASH. Chemicals/CAS: alanine aminotransferase, 9000-86-6, 9014-30-6; aspartate aminotransferase, 9000-97-9; glucose, 50-99-7, 84778-64-3; insulin, 9004-10-8; peroxisome proliferator activated receptor alpha, 147258-70-6; salsalate, 552-94-3

Brown adipose tissue (BAT) activation and white adipose tissue (WAT) beiging can increase energy expenditure and have the potential to reduce obesity and associated diseases. The immune system is a potential target in mediating brown and beige adipocyte activation. Type 2 and anti-inflammatory immune cells contribute to metabolic homeostasis within lean WAT, with a prominent role for eosinophils and interleukin (IL)-4-induced anti-inflammatory macrophages. We determined eosinophil numbers in epididymal WAT (EpAT), subcutaneous WAT (ScAT) and BAT after 1 day, 3 days or 1 week of high-fat diet (HFD) feeding in C57Bl/6 mice. One day of HFD resulted in a rapid drop in eosinophil numbers in EpAT and BAT, and after 3 days, in ScAT. In an attempt to restore this HFD-induced drop in adipose tissue eosinophils, we treated 1-week HFD-fed mice with helminth antigens from Schistosoma mansoni or Trichuris suis and evaluated whether the well-known protective metabolic effects of helminth antigens involves BAT activation or beiging. Indeed, antigens of both helminth species induced high numbers of eosinophils in EpAT, but failed to induce beiging. In ScAT, Schistosoma mansoni antigens induced mild eosinophilia, which was accompanied by slightly more beiging. No effects were observed in BAT. To study type 2 responses on brown adipocytes directly, T37i cells were stimulated with IL-4. This increased Ucp1 expression and strongly induced the production of eosinophil chemoattractant CCL11 (+26-fold), revealing that brown adipocytes themselves can attract eosinophils. Our findings indicate that helminth antigen-induced eosinophilia fails to induce profound beiging of white adipocytes.

Obesity is associated with a variety of medical conditions such as type 2 diabetes and cardiovascular diseases and is therefore responsible for high morbidity and mortality rates. Increasing energy expenditure by brown adipose tissue (BAT) is a current novel strategy to reduce the excessive energy stores in obesity. Brown adipocytes burn energy to generate heat and are mainly activated upon cold exposure. As prolonged cold exposure is not a realistic therapy, researchers worldwide are searching for novel ways to activate BAT and/or induce beiging of white adipose tissue. Recently, the contribution of immune cells in the regulation of brown adipocyte activity and beiging of white adipose tissue has gained increased attention, with a prominent role for eosinophils and alternatively activated macrophages. This review discusses the rediscovery of BAT, presents an overview of modes of activation and differentiation of beige and brown adipocytes, and describes the recently discovered immunological pathways that are key in mediating brown/beige adipocyte development and function. Interventions in immunological pathways harbor the potential to provide novel strategies to increase beige and brown adipose tissue activity as a therapeutic target for obesity.

Background and aims: Activation of brown adipose tissue (BAT) reduces both hyperlipidemia and atherosclerosis by increasing the uptake of triglyceride-derived fatty acids by BAT, accompanied by formation and clearance of lipoprotein remnants. We tested the hypothesis that the hepatic uptake of lipoprotein remnants generated by BAT activation would be accelerated by concomitant statin treatment, thereby further reducing hypercholesterolemia and atherosclerosis. Methods: APOE*3-Leiden. CETP mice were fed a Western-type diet and treated without or with the selective beta 3-adrenergic receptor (AR) agonist CL316,243 that activates BAT, atorvastatin (statin) or both. Results: beta 3-AR agonism increased energy expenditure as a result of an increased fat oxidation by activated BAT, which was not further enhanced by statin addition. Accordingly, statin treatment neither influenced the increased uptake of triglyceride-derived fatty acids from triglyceride-rich lipoprotein-like particles by BAT nor further lowered plasma triglyceride levels induced by beta 3-AR agonism. Statin treatment increased the hepatic uptake of the formed cholesterol-enriched remnants generated by beta 3-AR agonism. Consequently, statin treatment further lowered plasma cholesterol levels. Importantly, statin, in addition to beta 3-AR agonism, also further reduced the atherosclerotic lesion size as compared to beta 3-AR agonism alone, without altering lesion severity and composition. Conclusions: Statin treatment accelerates the hepatic uptake of remnants generated by BAT activation, thereby increasing the lipid-lowering and anti-atherogenic effects of BAT activation in an additive fashion. We postulate that, in clinical practice, combining statin treatment with BAT activation is a promising new avenue to combat hyperlipidemia and cardiovascular disease. (C) 2017 Elsevier B.V. All rights reserved

The endocannabinoid system is an important player in energy metabolism by regulating appetite, lipolysis, and energy expenditure. Chronic blockade of the cannabinoid 1 receptor (CB1R) leads to long-term maintenance of weight loss and reduction of dyslipidemia in experimental and human obesity. The molecular mechanism by which CB1R blockade reverses dyslipidemia in obesity has not yet been clarified. In this study, we showed that CB1R blockade with the systemic CB1R blocker rimonabant enhanced whole-body energy expenditure and activated brown adipose tissue (BAT), indicated by increased expression of genes involved in BAT thermogenesis and decreased lipid droplet size in BAT. This was accompanied by selectively increased triglyceride (TG) uptake by BAT and lower plasma TG levels. Interestingly, the effects on BAT activation were still present at thermoneutrality and could be recapitulated by using the strictly peripheral CB1R antagonist AM6545, indicating direct peripheral activation of BAT. Indeed, CB1R blockade directly activated T37i brown adipocytes, resulting in enhanced uncoupled respiration, most likely via enhancing cAMP/PKA signaling via the adrenergic receptor pathway. Our data indicate that selective targeting of the peripheral CB1R in BAT has therapeutic potential in attenuating dyslipidemia and obesity.

Introduction: Brown adipose tissue (BAT) produces heat by burning triglyceride (TG)-derived fatty acids. As a result, BAT accelerates the formation and hepatic clearance of cholesterol-enriched lipoprotein remnants via the apoE-LDL receptor (LDLR) pathway, thereby alleviating hypercholesterolemia. Since statins upregulate hepatic LDLR expression, the aim of this study was to investigate whether BAT activation and statin treatment cooperate in lowering hyperlipidemia and atherosclerosis. Methods and Results: APOE*3-Leiden.CETP mice were fed a Western-type diet and treated with the selective β3-AR agonist CL316243 that activates BAT (CL, 20 μg/day; s.c.), atorvastatin (statin, 0.0036% w/w, in diet) or both. BAT activation alone and combined with statin treatment increased energy expenditure (+15%) as a result of increased fat oxidation (+50%). Furthermore, BAT activation decreased the lipid droplet content within BAT (-50%) and induced browning of subcutaneous white adipose tissue. BAT activation alone and combined with statin treatment also lowered plasma TG levels (-60%). In addition, plasma cholesterol was lowered by both BAT activation (-29%) and statin (-31%), but even further by the combination (-44%). The uptake of TG-derived fatty acids from glycerol tri[3H]oleate and [14C]cholesteryl oleate-labeled VLDL-mimicking particles into BAT was enhanced by BAT activation (+234%) and on top of statin (+220%), but not by statin alone. The hepatic uptake of the cholesterol-enriched remnants tended to be increased by BAT activation (+18%) or statin (+22%), and was markedly increased by the combination of BAT activation and statin treatment (+70%). Hepatic cholesterol levels were reduced by statin alone and the combination (-41%). Importantly, atherosclerosis development was decreased by BAT activation (-42%) and statin (-50%) alone and further decreased by the combination (-70%). Conclusions: BAT activation enhances the lipid-lowering and anti-atherogenic effect of statin treatment. We postulate that combining statin treatment with BAT activation is a promising new avenue to combat hyperlipidemia and cardiovascular diseases.

Contains fulltext : 172003.pdf (Publisher’s version ) (Open Access) BACKGROUND AND AIMS: Bacille-Calmette-Guerin (BCG), prepared from attenuated live Mycobacterium bovis, modulates atherosclerosis development as currently explained by immunomodulatory mechanisms. However, whether BCG is pro- or anti-atherogenic remains inconclusive as the effect of BCG on cholesterol metabolism, the main driver of atherosclerosis development, has remained underexposed in previous studies. Therefore, we aimed to elucidate the effect of BCG on cholesterol metabolism in addition to inflammation and atherosclerosis development in APOE*3-Leiden.CETP mice, a well-established model of human-like lipoprotein metabolism. METHODS: Hyperlipidemic APOE*3-Leiden.CETP mice were fed a Western-type diet containing 0.1% cholesterol and were terminated 6 weeks after a single intravenous injection with BCG (0.75 mg; 5 x 10(6) CFU). RESULTS: BCG-treated mice exhibited hepatic mycobacterial infection and hepatomegaly. The enlarged liver (+53%, p = 0.001) coincided with severe immune cell infiltration and a higher cholesterol content (+31%, p = 0.03). Moreover, BCG reduced plasma total cholesterol levels (-34%, p = 0.003), which was confined to reduced nonHDL-cholesterol levels (-36%, p = 0.002). This was due to accelerated plasma clearance of cholesterol from intravenously injected [(14)C]cholesteryl oleate-labelled VLDL-like particles (t(1/2) -41%, p = 0.002) as a result of elevated hepatic uptake (+25%, p = 0.05) as well as reduced intestinal cholestanol and plant sterol absorption (up to -37%, p = 0.003). Ultimately, BCG decreased foam cell formation of peritoneal macrophages (-18%, p = 0.02) and delayed atherosclerotic lesion progression in the aortic root of the heart. BCG tended to decrease atherosclerotic lesion area (-59%, p = 0.08) and reduced lesion severity. CONCLUSIONS: BCG reduces plasma nonHDL-cholesterol levels and delays atherosclerotic lesion formation in hyperlipidemic mice.

Novel strategies are needed to reduce the obesity epidemic. One promising strategy is activation of brown adipose tissue (BAT), either via the brain or directly, which increases energy expenditure by combustion of fatty acids (FAs) into heat. The enzyme complex AMP-activated protein kinase (AMPK) is crucially involved in energy metabolism and is highly expressed in both brain and BAT, regulating thermogenesis. As a general rule, BAT activity and energy expenditure are increased either by suppression of AMPK activity in the brain, resulting in enhanced sympathetic outflow towards BAT, or by activation of AMPK in BAT. Targeting AMPK may thus hold therapeutic potential for the treatment of obesity and related disorders.

Pathogenic immunoglobulins are produced during the development of obesity and contribute to the development of insulin resistance (IR). However, the mechanisms by which these antibodies affect IR are largely unknown. This study investigated whether Fc-receptors contribute to the development of diet-induced obesity and IR by studying FcRγ(-/-) mice that lack the γ-subunit necessary for signaling and cell surface expression of FcγR and FcεRI.FcRγ(-/-) and wild-type (WT) mice were fed a high-fat diet (HFD) to induce obesity. At 4 and 11 weeks, body weight and insulin sensitivity were measured, and adipose tissue (AT) inflammation was determined. Furthermore, intestinal triglyceride (TG) uptake and plasma TG clearance were determined, and gut microbiota composition was analyzed.FcRγ(-/-) mice gained less weight after 11 weeks of HFD. They had reduced adiposity, adipose tissue inflammation, and IR. Interestingly, FcRγ(-/-) mice had higher lean mass compared to WT mice, which was associated with increased energy expenditure. Intestinal TG absorption was increased whereas plasma TG clearance was not affected in FcRγ(-/-) mice. Gut microbial composition differed significantly and might therefore have added to the observed phenotype.FcRγ-chain deficiency reduces the development of diet-induced obesity, as well as associated AT inflammation and IR at 11 weeks of HFD.

Salsalate (salicylsalicylic acid) is an anti-inflammatory drug that was recently found to exert beneficial metabolic effects on glucose and lipid metabolism. Although its utility in the prevention and management of a wide range of vascular disorders, including type 2 diabetes and metabolic syndrome has been suggested before, the potential of salsalate to protect against non-alcoholic steatohepatitis (NASH) remains unclear. The aim of the present study was therefore to ascertain the effects of salsalate on the development of NASH.Transgenic APOE*3Leiden.CETP mice were fed a high-fat and high-cholesterol diet with or without salsalate for 12 and 20 weeks. The effects on body weight, plasma biochemical variables, liver histology and hepatic gene expression were assessed.Salsalate prevented weight gain, improved dyslipidemia and insulin resistance and ameliorated diet-induced NASH, as shown by decreased hepatic microvesicular and macrovesicular steatosis, reduced hepatic inflammation and reduced development of fibrosis. Salsalate affected lipid metabolism by increasing β-oxidation and decreasing lipogenesis, as shown by the activation of PPAR-α, PPAR-γ co-activator 1β, RXR-α and inhibition of genes controlled by the transcription factor MLXIPL/ChREBP. Inflammation was reduced by down-regulation of the NF-κB pathway, and fibrosis development was prevented by down-regulation of TGF-β signalling.Salsalate exerted a preventive effect on the development of NASH and progression to fibrosis. These data suggest a clinical application of salsalate in preventing NASH.

Contains fulltext : 152584.pdf (Publisher’s version ) (Closed access) The role of Kupffer cells (KCs) in the pathophysiology of the liver has been firmly established. Nevertheless, KCs have been underexplored as a target for diagnosis and treatment of liver diseases owing to the lack of noninvasive diagnostic tests. We addressed the hypothesis that cholesteryl ester transfer protein (CETP) is mainly derived from KCs and may predict KC content. Microarray analysis of liver and adipose tissue biopsies, obtained from 93 obese subjects who underwent elective bariatric surgery, showed that expression of CETP is markedly higher in liver than adipose tissue. Hepatic expression of CETP correlated strongly with that of KC markers, and CETP messenger RNA and protein colocalized specifically with KCs in human liver sections. Hepatic KC content as well as hepatic CETP expression correlated strongly with plasma CETP concentration. Mechanistic and intervention studies on the role of KCs in determining the plasma CETP concentration were performed in a transgenic (Tg) mouse model expressing human CETP. Selective elimination of KCs from the liver in CETP Tg mice virtually abolished hepatic CETP expression and largely reduced plasma CETP concentration, consequently improving the lipoprotein profile. Conversely, augmentation of KCs after Bacille-Calemette-Guerin vaccination largely increased hepatic CETP expression and plasma CETP. Also, lipid-lowering drugs fenofibrate and niacin reduced liver KC content, accompanied by reduced plasma CETP concentration. CONCLUSIONS: Plasma CETP is predominantly derived from KCs, and plasma CETP level predicts hepatic KC content in humans.(Hepatology 2015;62:1710-1722).

Objectives: The endocannabinoid system is an important player in energy metabolism by regulating appetite, lipolysis and energy expenditure. Chronic blockade of the cannabinoid 1 receptor (CB1R) leads to long-term maintained weight loss and reduction of dyslipidemia in experimental and human obesity. Brown adipose tissue (BAT) that burns lipids towards heat using UCP1, recently emerged as a major player in lipoprotein metabolism and is present and active in human adults. The aim of the present study was to elucidate the mechanism by which CB1R blockade reverses dyslipidemia and obesity, with special focus on BAT. Methods and results: Diet-induced obese APOE*3-Leiden.CETP transgenic mice, a well-established model for human-like lipoprotein metabolism, were treated with the systemic CB1R blocker rimonabant (10 mg/kg/day) for 4 weeks. Rimonabant persistently decreased body weight (-25%, pin vitro blockade of the CB1R in cultured brown adipocytes resulted in 2.5-fold upregulation of UCP1. Importantly, the in vivo results could be fully recapitulated using the strictly peripheral CB1R antagonist AM6545 (10 mg/kg/day) that does not induce hypophagia. Conclusion: CB1R blockade reduces dyslipidemia and obesity by peripheral activation of BAT. Selective targeting of peripheral CB1R in BAT has thus great therapeutic potential in decreasing dyslipidemia and obesity and ultimately cardiovascular diseases.

Aims/hypothesis White adipose tissue (WAT) consists of various depots with different adipocyte functionality and immune cell composition. Knowledge of WAT-depot-specific differences in expandability and immune cell influx during the development of obesity is limited, therefore we aimed to characterise different WAT depots during the development of obesity in mice. Methods Gonadal WAT (gWAT), subcutaneous WAT (sWAT) and mesenteric WAT (mWAT) were isolated from male C57Bl/6J mice with different body weights (approximately 25–60 g) and analysed. Linear and non-linear regression models were used to describe the extent of WAT depot expandability and immune cell composition as a function of body weight. Results Whereas mouse sWAT and mWAT continued to expand with body weight, gWAT expanded mainly during the initial phase of body weight gain. The expansion diminished after the mice reached a body weight of around 40 g. From this point on, gWAT crown-like structure formation, liver steatosis and insulin resistance occurred. Mouse WAT depots showed major differences in immune cell composition: gWAT consisted mainly of macrophages, whereas sWAT and mWAT primarily contained lymphocytes. Conclusions/interpretation Marked inter-depot differences exist in WAT immune cell composition and expandability. The limited storage capacity of gWAT seems to direct the development of metabolic disorders in male C57Bl/6J mice. Electronic supplementary material The online version of this article (doi:10.1007/s00125-015-3594-8) contains peer-reviewed but unedited supplementary material, which is available to authorised users.