Effects of Maresin 1, an omega-3 fatty acid-derived lipid mediator, on adipose tissue and liver function in obesity

This research demonstrated the ability of the n-3 PUFA EPA to increase mitochondrial content, and to activate master regulators of mitochondrial biogenesis and to promote the expression of genes that typify beige adipocytes in cultured fully differentiated human subcutaneous adipocytes from overweight subjects. Moreover, EPA up-regulated genes involved in fatty acid oxidation while down-regulated lipogenic genes. These data suggest that EPA promotes a remodelling of adipocyte metabolism which could be in part responsible for EPA beneficial effects in obesity. Moreover, this research revealed for the first time that MaR1 inhibits TNF-a-induced lipolysis. This effect seems to be associated to MaR1 ability to prevent the reduction of perilipin and ATGL-inhibitor G0S2 protein expression induced by the cytokine. MaR1 also reversed the decrease on total hormone sensitive lipase (total HSL), and the ratio of phosphoHSL at Ser-565/total HSL, while preventing the increased ratio of phosphoHSL at Ser-660/total HSL as well as the phosphorylation of ERK1/2 induced by TNF-a. Moreover, MaR1 counteracted the cytokine-induced decrease of p62 protein content, and also prevented the induction of LC3II/LC3I ratio. These data point out that MaR1 ameliorate TNF-a-induced alterations on lipolysis and autophagy in adipocytes, which may contribute to the beneficial actions of MaR1 on adipose tissue inflammation and insulin sensitivity. The current study also demonstrated that MaR1 reverses obesity-related liver steatosis in two different models of obesity (ob/ob and diet-induced obese (DIO) mice) and characterized the mechanisms involved. Remarkably, oral gavage of MaR1 decreased serum transaminases, reduced liver weight and TG content. MaR1-treated mice exhibited reduced hepatic lipogenic enzymes content (FAS) or activation (by phosphorylation of ACC), accompanied by upregulation of genes involved in fatty acid oxidation (Cpt1a and Acox1) and autophagy (Atg 5 and Atg7), along with increased number of autophagic vacuoles and reduced p62 protein levels. MaR1 also induced AMPK phosphorylation in DIO mice and in primary hepatocytes, and preincubation of hepatocytes with the AMPK inhibitor Compound C reversed MaR1 effects on Cpt1a, Acox1, Atg5 and Atg7 expression, suggesting the implication of AMPK in MaR1 actions. The present study also reported that MaR1 treatment by oral gavage to DIO mice increased brown adipose tissue (BAT) UCP1 levels and upregulated other thermogenic-related genes along with an increase in the mRNA levels of glucose transporters and fatty acid oxidation-related genes. Indeed, in cultured brown adipocytes MaR1 also promoted glucose uptake and fatty acid utilization, in parallel with the upregulation of thermogenic genes and oxygen consumption rates. Interestingly, microPET studies with 18F-FDG revealed that acute treatment with MaR1 potentiates cold-induced BAT activation in mice. Furthermore, MaR1 induced beige adipocyte markers (Ucp1, Pgc-1a, Tmem26 and Tbx1) in subcutaneous white adipose tissue (WAT) of DIO mice as well as in human mesenchymal cells (hMSC)-derived adipocytes treated with MaR1 along the differentiation process. The fact that this effect was not observed when MaR1 treatment was tested on mature adipocytes, point toward that MaR1 exerts its browning effect via recruiting brite adipocytes and not by promoting transdifferentiation from mature white to beige adipocytes. Nevertheless, mature white adipocytes treated acutely with MaR1 exhibited higher fatty acid oxidation rates. These data reveal MaR1 as a novel agent able to promote BAT activation and WAT browning, which could also contribute to its insulin-sensitizing properties in obesity. In summary, the outcomes of the current project regarding the metabolic actions of MaR1 have uncover that MaR1 might constitutes a novel therapeutic candidate to tackle obesity comorbidities such as insulin resistance, type 2 diabetes and non-alcoholic fatty liver disease

Effects of Maresin 1, an omega-3 fatty acid-derived lipid mediator, on adipose tissue and liver function in obesity

This research demonstrated the ability of the n-3 PUFA EPA to increase mitochondrial content, and to activate master regulators of mitochondrial biogenesis and to promote the expression of genes that typify beige adipocytes in cultured fully differentiated human subcutaneous adipocytes from overweight subjects. Moreover, EPA up-regulated genes involved in fatty acid oxidation while down-regulated lipogenic genes. These data suggest that EPA promotes a remodelling of adipocyte metabolism which could be in part responsible for EPA beneficial effects in obesity. Moreover, this research revealed for the first time that MaR1 inhibits TNF-a-induced lipolysis. This effect seems to be associated to MaR1 ability to prevent the reduction of perilipin and ATGL-inhibitor G0S2 protein expression induced by the cytokine. MaR1 also reversed the decrease on total hormone sensitive lipase (total HSL), and the ratio of phosphoHSL at Ser-565/total HSL, while preventing the increased ratio of phosphoHSL at Ser-660/total HSL as well as the phosphorylation of ERK1/2 induced by TNF-a. Moreover, MaR1 counteracted the cytokine-induced decrease of p62 protein content, and also prevented the induction of LC3II/LC3I ratio. These data point out that MaR1 ameliorate TNF-a-induced alterations on lipolysis and autophagy in adipocytes, which may contribute to the beneficial actions of MaR1 on adipose tissue inflammation and insulin sensitivity. The current study also demonstrated that MaR1 reverses obesity-related liver steatosis in two different models of obesity (ob/ob and diet-induced obese (DIO) mice) and characterized the mechanisms involved. Remarkably, oral gavage of MaR1 decreased serum transaminases, reduced liver weight and TG content. MaR1-treated mice exhibited reduced hepatic lipogenic enzymes content (FAS) or activation (by phosphorylation of ACC), accompanied by upregulation of genes involved in fatty acid oxidation (Cpt1a and Acox1) and autophagy (Atg 5 and Atg7), along with increased number of autophagic vacuoles and reduced p62 protein levels. MaR1 also induced AMPK phosphorylation in DIO mice and in primary hepatocytes, and preincubation of hepatocytes with the AMPK inhibitor Compound C reversed MaR1 effects on Cpt1a, Acox1, Atg5 and Atg7 expression, suggesting the implication of AMPK in MaR1 actions. The present study also reported that MaR1 treatment by oral gavage to DIO mice increased brown adipose tissue (BAT) UCP1 levels and upregulated other thermogenic-related genes along with an increase in the mRNA levels of glucose transporters and fatty acid oxidation-related genes. Indeed, in cultured brown adipocytes MaR1 also promoted glucose uptake and fatty acid utilization, in parallel with the upregulation of thermogenic genes and oxygen consumption rates. Interestingly, microPET studies with 18F-FDG revealed that acute treatment with MaR1 potentiates cold-induced BAT activation in mice. Furthermore, MaR1 induced beige adipocyte markers (Ucp1, Pgc-1a, Tmem26 and Tbx1) in subcutaneous white adipose tissue (WAT) of DIO mice as well as in human mesenchymal cells (hMSC)-derived adipocytes treated with MaR1 along the differentiation process. The fact that this effect was not observed when MaR1 treatment was tested on mature adipocytes, point toward that MaR1 exerts its browning effect via recruiting brite adipocytes and not by promoting transdifferentiation from mature white to beige adipocytes. Nevertheless, mature white adipocytes treated acutely with MaR1 exhibited higher fatty acid oxidation rates. These data reveal MaR1 as a novel agent able to promote BAT activation and WAT browning, which could also contribute to its insulin-sensitizing properties in obesity. In summary, the outcomes of the current project regarding the metabolic actions of MaR1 have uncover that MaR1 might constitutes a novel therapeutic candidate to tackle obesity comorbidities such as insulin resistance, type 2 diabetes and non-alcoholic fatty liver disease

Dual role of protein tyrosine phosphatase 1B in the progression and reversion of non-alcoholic steatohepatitis

Objectives: Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease in Western countries. Protein tyrosine phosphatase 1B (PTP1B), a negative modulator of insulin and cytokine signaling, is a therapeutic target for type 2 diabetes and obesity. We investigated the impact of PTP1B deficiency during NAFLD, particularly in non-alcoholic steatohepatitis (NASH). Methods: NASH features were evaluated in livers from wild-type (PTP1BWT) and PTP1B-deficient (PTP1BKO) mice fed methionine/cholinedeficient diet (MCD) for 8 weeks. A recovery model was established by replacing MCD to chow diet (CHD) for 2e7 days. Non-parenchymal liver cells (NPCs) were analyzed by flow cytometry. Oval cells markers were measured in human and mouse livers with NASH, and in oval cells from PTP1BWT and PTP1BKO mice. Results: PTP1BWT mice fed MCD for 8 weeks exhibited NASH, NPCs infiltration, and elevated Fgf21, Il6 and Il1b mRNAs. These parameters decreased after switching to CHD. PTP1B deficiency accelerated MCD-induced NASH. Conversely, after switching to CHD, PTP1BKO mice rapidly reverted NASH compared to PTP1BWT mice in parallel to the normalization of serum triglycerides (TG) levels. Among NPCs, a drop in cytotoxic natural killer T (NKT) subpopulation was detected in PTP1BKO livers during recovery, and in these conditions M2 macrophage markers were upregulated. Oval cells markers (EpCAM and cytokeratin 19) significantly increased during NASH only in PTP1B-deficient livers. HGF-mediated signaling and proliferative capacity were enhanced in PTP1BKO oval cells. In NASH patients, oval cells markers were also elevated. Conclusions: PTP1B elicits a dual role in NASH progression and reversion. Additionally, our results support a new role for PTP1B in oval cell proliferation during NAFLD

Maresin 1 activates brown adipose tissue and promotes browning of white adipose tissue in mice

Objective: Maresin 1 (MaR1) is a docosahexaenoic acid-derived proresolving lipid mediator with insulin-sensitizing and anti-steatosis properties. Here, we aim to unravel MaR1 actions on brown adipose tissue (BAT) activation and white adipose tissue (WAT) browning. Methods: MaR1 actions were tested in cultured murine brown adipocytes and in human mesenchymal stem cells (hMSC)-derived adipocytes. In vivo effects of MaR1 were tested in diet-induced obese (DIO) mice and lean WT and Il6 knockout (Il6 / ) mice. Results: In cultured differentiated murine brown adipocytes, MaR1 reduces the expression of inflammatory genes, while stimulates glucose uptake, fatty acid utilization and oxygen consumption rate, along with the upregulation of mitochondrial mass and genes involved in mitochondrial biogenesis and function and the thermogenic program. In Leucine Rich Repeat Containing G Protein-Coupled Receptor 6 (LGR6)-depleted brown adipocytes using siRNA, the stimulatory effect of MaR1 on thermogenic genes was abrogated. In DIO mice, MaR1 promotes BAT remodeling, characterized by higher expression of genes encoding for master regulators of mitochondrial biogenesis and function and iBAT thermogenic activation, together with increased M2 macrophage markers. In addition, MaR1-treated DIO mice exhibit a better response to cold-induced BAT activation. Moreover, MaR1 induces a beige adipocyte signature in inguinal WAT of DIO mice and in hMSC-derived adipocytes. MaR1 potentiates Il6 expression in brown adipocytes and BAT of cold exposed lean WT mice. Interestingly, the thermogenic properties of MaR1 were abrogated in Il6 / mice. Conclusions: These data reveal MaR1 as a novel agent that promotes BAT activation and WAT browning by regulating thermogenic program in adipocytes and M2 polarization of macrophages. Moreover, our data suggest that LGR6 receptor is mediating MaR1 actions on brown adipocytes, and that IL-6 is required for the thermogenic effects of MaR1