Esma Karkeni

Vitamin D protects against diet-induced obesity by enhancing fatty acid oxidation

Prospective studies reported an inverse correlation between 25-hydroxyvitamin D [25(OH)D] plasma levels and prevalence of obesity and type 2 diabetes. In addition, 25(OH)D status may be a determinant of obesity onset. However, the causality between these observations is not yet established. We studied the preventive effect of vitamin D3 (VD3) supplementation (15,000 IU/kg of food for 10 weeks) on onset of obesity in a diet-induced obesity mouse model. We showed that the VD3 supplementation limited weight gain induced by high-fat diet, which paralleled with an improvement of glucose homeostasis. The limitation of weight gain could further be explained by an increased lipid oxidation, possibly due to an up-regulation of genes involved in fatty acid oxidation and mitochondrial metabolism, leading to increased energy expenditure. Altogether, these data show that VD3 regulates energy expenditure and suggest that VD3 supplementation may represent a strategy of preventive nutrition to fight the onset of obesity and associated metabolic disorders.

Vitamin D limits chemokine expression in adipocytes and macrophage migration in vitro and in male mice.

Vitamin D (VD) displays immunoregulatory effects and reduces adipocyte inflammation, which may participate to a reduction of adipose tissue macrophage infiltration in the context of obesity-associated low-grade inflammation. These observations have been described mainly in vitro, through the evaluation of a limited number of inflammatory markers. Here, we studied the effects of 1,25 dihydroxy-VD on chemokine network expression in adipocytes (by transcriptomic approach), and we confirm the physiological relevance of these data in vivo, by demonstrating the effect of VD on cytokine and chemokine gene expression as well as on macrophage infiltration in adipose tissue. 1,25 dihydroxy-VD down-regulated (-1.3- to -10.8-fold) the mRNA expression of 29 chemokines and limited macrophage migration in TNFα-conditioned adipocyte medium (1.5-fold; P < .05). This effect was associated with a reduction in p65 and IκB (nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor, alpha) phosphorylation (2-fold compared with TNFα; P < .05). The effects of VD were confirmed in mice injected ip with lipopolysaccharide (acute inflammation) and diet-induced obese mice (metabolic inflammation), where the levels of mRNA encoding proinflammatory cytokines and chemokines (∼2-fold) were reduced in adipocytes (acute and metabolic inflammation) and adipose tissue and that macrophage infiltration was also inhibited in the adipose tissue of obese mice (metabolic inflammation). Altogether, these results showed that VD displayed a global immunoregulatory impact on adipocytes, notably via the inhibition of chemokine expression and macrophage infiltration in inflamed adipose tissue.

Lycopene and tomato powder supplementation similarly inhibit high‐fat diet induced obesity, inflammatory response, and associated metabolic disorders

SCOPE Several studies have linked the high intake of lycopene or tomatoes products with lower risk for metabolic diseases. The aim of the present study was to evaluate and to compare the effect of lycopene and tomato powder on obesity-associated disorders. METHODS AND RESULTS Male C57BL/J6 mice were assigned into four groups to receive: control diet (CD), high fat diet (HFD), high fat diet supplemented with lycopene or with tomato powder (TP) for 12 weeks. In HFD condition, lycopene and TP supplementation significantly reduced adiposity index, organ, and relative organ weights, serum triglycerides, free fatty acids, 8-iso-prostaglandin GF2α and improved glucose homeostasis, but did not affect total body weight. Lycopene and TP supplementation prevented HFD-induced hepatosteatosis and hypertrophy of adipocytes. Lycopene and TP decreased HFD-induced proinflammatory cytokine mRNA expression in the liver and in the epididymal adipose tissue. The anti-inflammatory effect of lycopene and TP was related to a reduction in the phosphorylation levels of IκB, and p65, and resulted in a decrease of inflammatory proteins in adipose tissue. CONCLUSION These results suggest that lycopene or TP supplementation display similar beneficial health effects that could be particularly relevant in the context of nutritional approaches to fight obesity-associated pathologies.

All-trans-retinoic acid represses chemokine expression in adipocytes and adipose tissue by inhibiting NF-κB signaling ☆

An effect of the Vitamin A metabolite all-trans-retinoic acid (ATRA) on body weight regulation and adiposity has been described, but little is known about its impact on obesity-associated inflammation. Our objective was to evaluate the overall impact of this metabolite on inflammatory response in human and mouse adipocytes, using high-throughput methods, and to confirm its effects in a mouse model. ATRA (2 μM for 24 h) down-regulated the mRNA expression of 17 chemokines in human adipocytes, and limited macrophage migration in a TNFα-conditioned 3 T3-L1 adipocyte medium (73.7%, P<.05). These effects were confirmed in mice (n=6-9 per group) subjected to oral gavage of ATRA (5 mg/kg of body weight) and subsequently injected intraperitoneally with lipopolysaccharide. In this model, both systemic and adipose levels of inflammatory markers were reduced. The antiinflammatory effect of ATRA was associated with a reduction in the phosphorylation levels of IκB and p65 (~50%, P<.05), two subunits of the NF-κB pathway, probably mediated by PGC1α, in 3 T3-L1 adipocytes. Taken together, these results show a significant overall antiinflammatory effect of ATRA on proinflammatory cytokine and chemokine production in adipocyte and adipose tissue and suggest that ATRA supplementation may represent a strategy of preventive nutrition to fight against obesity and its complications.

Vitamin D limits inflammation-linked microRNA expression in adipocytes in vitro and in vivo: A new mechanism for the regulation of inflammation by vitamin D.

ABSTRACT Inflammation of adipose tissue is believed to be a contributing factor to many chronic diseases associated with obesity. Vitamin D (VD) is now known to limit this metabolic inflammation by decreasing inflammatory marker expression and leukocyte infiltration in adipose tissue. In this study, we investigated the impact of VD on microRNA (miR) expression in inflammatory conditions in human and mouse adipocytes, using high-throughput methodology (miRNA PCR arrays). Firstly, we identified three miRs (miR-146a, miR-150, and miR-155) positively regulated by TNFα in human adipocytes. Interestingly, the expression of these miRs was strongly prevented by 1,25(OH)2D preincubation. These results were partly confirmed in 3T3-L1 adipocytes (for miR-146a and miR-150). The ability of VD to control the expression of these miRs was confirmed in diet-induced obese mice: the levels of the three miRs were increased following high fat (HF) diet in epididymal white adipose tissue and reduced in HF diet fed mice supplemented with VD. The involvement of NF-κB signaling in the induction of these miRs was confirmed in vitro and in vivo using aP2-p65 transgenic mice. Finally, the ability of VD to deactivate NF-κB signaling, via p65 and IκB phosphorylation inhibition in murine adipocyte, was observed and could constitute a driving molecular mechanism. This study demonstrated for the first time that VD modulates the expression of miRs in adipocytes in vitro and in adipose tissue in vivo through its impact on NF-κB signaling pathway, which could represent a new mechanism of regulation of inflammation by VD.

Gene Expression Pattern in Response to Cholecalciferol Supplementation Highlights Cubilin as a Major Protein of 25(OH)D Uptake in Adipocytes and Male Mice White Adipose Tissue

It is well established that the active form of vitamin D (i.e., 1,25-dihydroxyvitamin D [1,25(OH)2D]) regulates the expression of genes involved in its own metabolism and transport in the kidney and possibly in the liver. However, little is known about the transcriptional impact of cholecalciferol supplementation on white adipose tissue (WAT) and adipocytes, which are a major site of vitamin D and 25-hydroxyvitamin D [25(OH)D] storage in the organism. To fill this gap, we investigated the impact of cholecalciferol supplementation in WAT via a panel of genes coding for enzymes and proteins involved in vitamin D metabolism and uptake. Mice supplemented with cholecalciferol (15,000 IU/kg of body weight per day) for 4 days showed decreased messenger RNA (mRNA) levels of proteins involved in cholecalciferol metabolism (Cyp24a1, Cyp27a1) and decreased cubilin mRNA levels in WAT. These data were partly confirmed in 3T3-L1 adipocytes incubated with 1,25(OH)2D. The downregulation of cubilin mRNA observed in WAT and in 3T3-L1 was confirmed at the protein level in WAT and at the mRNA level in human primary adipocytes. Vitamin D receptor (VDR) agonist (EB1089) and RNA interference approaches demonstrated that VDR was involved in this regulation. Furthermore, chemical inhibitor and RNA inference analysis demonstrated that cubilin was involved in 25(OH)D uptake by adipocytes. This study established an overall snapshot of the genes regulated by cholecalciferol in mouse WAT and cell-autonomously in adipocytes. We highlighted that the regulation of cubilin expression was mediated by a VDR-dependent mechanism, and we demonstrated that cubilin was involved in 25(OH)D uptake by adipocytes.

Diet induced obesity modifies vitamin D metabolism and adipose tissue storage in mice

Low circulating levels of total and free 25-hydroxyvitamin D (25(OH)D) indicative of vitamin D status have been associated with obesity in humans. Moreover, obesity is thought to play a causal role in the reduction of 25(OH)D levels, and several theories have been put forward to explain this relationship. Here we tested the hypothesis that obesity disrupts vitamin D homeostasis in key organs of vitamin D metabolism. Male C57BL6 mice were fed for 7 or 11 weeks on either a control diet (control, 10% energy from fat) or a high-fat diet (HF, 60% energy from fat) formulated to provide equivalent vitamin D3 intake in both groups. After 7 weeks, there was a transient increase of total 25(OH)D together with a significant decrease of plasma vitamin D3 that could be related to the induction of hepatic genes involved in 25-hydroxylation. After 11 weeks, there was no change in total 25(OH)D but a significant decrease of free 25(OH)D and plasma vitamin D3 levels. We also quantified an increase of 25(OH)D in adipose tissue that was inversely correlated to the free 25(OH)D. Interestingly, this accumulation of 25(OH)D in adipose tissue was highly correlated to the induction of Cyp2r1, which could actively participate in vitamin D3 trapping and subsequent conversion to 25(OH)D in adipose tissue. Taken together, our data strongly suggest that the enzymes involved in vitamin D metabolism, notably in adipose tissue, are transcriptionally modified under high-fat diet, thus contributing to the obesity-related reduction of free 25(OH)D.

Microparticle miRNAs as Biomarkers of Vascular Function and Inflammation Response to Aerobic Exercise in Obesity?: Exercise and Microparticles/microRNAs in Obesity

This study aimed to explore the role of nine microRNAs (miRNAs) in microparticles (MPs) on the efficacy of aerobic exercise in the regulation of inflammation and vascular function in obesity.

0311 : Physical exercise regulates angiogenesis in adipose tissue of dietinduced obese mice thru ECSCR/Akt pathways

Reduced capillary density in adipose tissue is associated with obesity and results in decrease perfusion, decreased oxygen consumption and insulin resistance. Pro- (VEGF-A) and anti-angiogenic (TSP-1) factors expression is central determinant of angiogenesis, with greater VEGF-A/TSP-1 ratio promoting angiogenesis. Since endothelial cells are involved in the pathogenesis of insulin resistance through their role in insulin delivery and adipose tissue angiogenesis, we investigated the role of ECSCR (endothelial cell surface expressed chemotaxis and apoptosis regulator) – Akt axis. In this context, we studied effects of voluntary exercise in mice fed with a high fat diet (HFD) on the AT vascularization. We have demonstrated that 7 weeks-exercise training reduced epididymal and subcutaneous white adipose tissue (eWAT) and (sWAT) mass by 33% and 45% respectively compared to sedentary HFD mice and stimulated capillary growth in AT with a significant increased of capillaries/ adipocyte ratio on eWAT and sWAT (+16% and 28% respectively), associated with a significant VEGF-A/TSP-1 expression ratio increase. Furthermore, while ECSCR protein expression was decreased and associated to a lower ratio of PhosphoAkt/Akt in eWAT and sWAT of HFD mice in comparison to control mice, 7 weeks-exercise training led to a significant increase of ECSCR protein expression associated to the raise of PhosphoAkt/Akt ratio in both eWAT and sWAT. In addition, eWAT and sWAT thermogenic and metabolic activities were stimulated by 7 weeks-exercise training, with increased PGC-1α, Sirt-3 and PPARα in comparison to eWAT and sWAT from sedentary HFD mice. In conclusion, our results indicate that physical exercise acts as a pro-angiogenic stimulus in AT in favor of capillary growth, and that ECSCR – Akt axis as well as VEGF-A/TSP-1 play central role in angioadaptation of AT. The author hereby declares no conflict of interest

0229 : Aerobic exercise training modulates microparticles miRNAs: link to improved endothelial function and regulation of inflammation?

Exercise training is known to stimulate vascular function and remodeling in a shear stress and inflammation dependent manner. Microparticles (MPs) released from vascular cells in response to shear stress, play a role in cell-cell crosstalk through carrying bioactive molecules such as miRNAs. Thus, the aim of our study was to explore whether exercise training impacts vascular wall cells and contributes to vascular function improvement through the modulation of inflammation molecules release. Therefore, we investigated the presence in MPs of 9 inflammation-regulatory miRNAs. A group of sedentary women (n=6, BMI The author hereby declares no conflict of interest