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Background: Non-alcoholic fatty liver disease (NAFLD) has been increasing in association with the epidemic of obesity and diabetes. Peroxisomes are single membrane-enclosed organelles that play a role in the metabolism of lipid and reactive oxygen species. The present study examined the role of peroxisomes in high-fat diet (HFD)-induced NAFLD using fenofibrate, a peroxisome proliferator-activated receptor α (PPARα) agonist.Methods: Eight-week-old male C57BL/6J mice were fed either a normal diet or HFD for 12 weeks, and fenofibrate (50 mg/kg/day) was orally administered along with the initiation of HFD.Results: HFD-induced liver injury as measured by increased alanine aminotransferase, inflammation, oxidative stress, and lipid accumulation was effectively prevented by fenofibrate. Fenofibrate significantly increased the expression of peroxisomal genes and proteins involved in peroxisomal biogenesis and function. HFD-induced attenuation of peroxisomal fatty acid oxidation was also significantly restored by fenofibrate, demonstrating the functional significance of peroxisomal fatty acid oxidation. In Ppara deficient mice, fenofibrate failed to maintain peroxisomal biogenesis and function in HFD-induced liver injury.Conclusion: The present data highlight the importance of PPARα-mediated peroxisomal fitness in the protective effect of fenofibrate against NAFLD.

Rationale: Vascular remodeling, including smooth muscle cell hypertrophy and proliferation, is the key pathological feature of pulmonary arterial hypertension (PAH). Prostaglandin I2 analogs (beraprost, iloprost, and treprostinil) are effective in the treatment of PAH. Of note, the clinically favorable effects of treprostinil in severe PAH may be attributable to concomitant activation of DP1 (D prostanoid receptor subtype 1).Objectives: To study the role of DP1 in the progression of PAH and its underlying mechanism.Methods: DP1 levels were examined in pulmonary arteries of patients and animals with PAH. Multiple genetic and pharmacologic approaches were used to investigate DP1-mediated signaling in PAH.Measurements and Main Results: DP1 expression was downregulated in hypoxia-treated pulmonary artery smooth muscle cells and in pulmonary arteries from rodent PAH models and patients with idiopathic PAH. DP1 deletion exacerbated pulmonary artery remodeling in hypoxia-induced PAH, whereas pharmacological activation or forced expression of the DP1 receptor had the opposite effect in different rodent models. DP1 deficiency promoted pulmonary artery smooth muscle cell hypertrophy and proliferation in response to hypoxia via induction of mTORC1 (mammalian target of rapamycin complex 1) activity. Rapamycin, an inhibitor of mTORC1, alleviated the hypoxia-induced exacerbation of PAH in DP1-knockout mice. DP1 activation facilitated raptor dissociation from mTORC1 and suppressed mTORC1 activity through PKA (protein kinase A)-dependent phosphorylation of raptor at Ser791. Moreover, treprostinil treatment blocked the progression of hypoxia-induced PAH in mice in part by targeting the DP1 receptor.Conclusions: DP1 activation attenuates hypoxia-induced pulmonary artery remodeling and PAH through PKA-mediated dissociation of raptor from mTORC1. These results suggest that the DP1 receptor may serve as a therapeutic target for the management of PAH.

Irisin is an exercise-induced myokine, suggested to exert beneficial effects on metabolism. However, the studies on the regulation of irisin secretion and the expression of its precursor FNDC5 have shown conflicting data. The discrepancies among previous correlation studies in humans are related to the heterogeneity of the study population. The fact that irisin is not only a myokine but also an adipokine leads to the further complexity of the role of irisin in metabolic regulation. In this study, we examined the regulation of FNDC5 expression and irisin in circulation in both type 1 and type 2 diabetic mice, and their potential relationships with metabolic parameters. In streptozotocin (STZ)-induced type 1 diabetic mice, high-fat diet (HFD)-induced obese mice and db/db mice, the circulating irisin as well as FNDC5 gene expression in subcutaneous fat was downregulated. Muscle FNDC5 expression was only significantly lower in STZ mice, and epididymal fat FNDC5 expression was unaltered. It is interesting to note that plasma irisin levels correlated positively with subcutaneous fat FNDC5 expression, but not epididymal fat or muscle. Moreover, both irisin levels and subcutaneous fat FNDC5 correlated negatively with markers of insulin resistance. These results suggest a regulatory role for subcutaneous fat-derived FNDC5/irisin in metabolic disease.

Mechanical insults, such as stent implantation, can induce endothelial injury, vascular inflammation, and ultimately lead to vascular neointimal hyperplasia. Resolvin E1 (RvE1), derived from the ω3 fatty acid eicosapentaenoic acid, can facilitate the resolution of inflammation in many settings. We therefore aimed to determine if there was a role for RvE1 in preventing neointimal formation after arterial injury and to understand the underlying mechanisms. Vascular inflammation and neointimal hyperplasia were induced by wire injury in the femoral arteries of mice. Administration of exogenous RvE1 and endogenously generated RvE1 via dietary supplementation with eicosapentaenoic acid and aspirin markedly reduced vascular neointima formation in this model. Mechanistically, RvE1 was found to inhibit vascular neutrophil infiltration, promote macrophage polarization toward an M2-like phenotype, suppress T-cell trafficking by reducing RANTES secretion from vascular smooth muscle cells, and inhibit vascular smooth muscle cell migration. In summary, RvE1 demonstrated a protective role against vascular inflammation and remodeling in response to mechanical injury, suggesting that it may serve as an adjuvant therapeutic agent for percutaneous coronary interventions, such as stent implantation.-Liu, G., Gong, Y., Zhang, R., Piao, L., Li, X., Liu, Q., Yan, S., Shen, Y., Guo, S., Zhu, M., Yin, H., Funk, C. D., Zhang, J., Yu, Y. Resolvin E1 attenuates injury-induced vascular neointimal formation by inhibition of inflammatory responses and vascular smooth muscle cell migration.

8-Hydroxy-2-deoxyguanosine (8-OHdG), a marker of oxidative DNA damage, has been recently shown to exert anti-inflammatory effects through inhibition of Rac1. Inflammation in adipose tissue is a hallmark of obesity-induced insulin resistance, but the therapeutic potential of 8-OHdG in treatment of metabolic diseases has not been fully elucidated. The aim of this study was to examine the effect of exogenously administered 8-OHdG on adipose tissue and whole body metabolism. In cultured adipocytes, 8-OHdG inhibited adipogenesis and reversed TNFα-induced insulin resistance. In high-fat diet (HFD)-induced obese mice, 8-OHdG administration blunted the rise in body weight and fat mass. The decrease in adipose tissue mass by 8-OHdG was due to reduced adipocyte hypertrophy through induction of adipose triglyceride lipase and inhibition of fatty acid synthase expression. 8-OHdG also inhibited the infiltration of macrophages, resulting in amelioration of adipose tissue inflammation and adipokine dysregulation. Moreover, 8-OHdG administration ameliorated adipocyte as well as systemic insulin sensitivity. Both in vivo and in vitro results showed that 8-OHdG induces AMPK activation and reduces JNK activation in adipocytes. In conclusion, our results show that orally administered 8-OHdG protects against HFD-induced metabolic disorders by regulating adipocyte metabolism.

Aims: Peroxisome is a critical organelle for fatty acid oxidation (FAO) and metabolism of reactive oxygen species (ROS). Increased oxidative stress in adipose tissue contributes to the development of insulin resistance and metabolic syndrome in obesity. This study aimed to investigate the role of peroxisomal fitness in maintaining adipocyte function, which has been under-rated in the obesity research area. Results: Reduced peroxisomal gene expressions in white adipose tissue (WAT) of obese mice suggested a close correlation between peroxisomes and obesity. Peroxisomal biogenesis factor 5 siRNA increased cellular ROS and inflammatory mediators in 3T3-L1 adipocytes. On the contrary, hydrogen peroxide or tumor necrosis factor-α treatment significantly decreased biogenesis- and function-related peroxisomal proteins, suggesting a positive feedback loop of ROS/inflammation and peroxisomal dysfunction. Correspondingly, catalase (a major peroxisomal antioxidant)-knockout mice fed with high-fat diet (HFD) exhibited suppressed peroxisomal proteins along with increased oxidative stress and accelerated obesity. In response to fenofibrate (a peroxisomal proliferator) treatment, WAT of HFD-fed wild-type mice showed not only increases in peroxisomal biogenesis and FAO but also attenuated features of adipocyte dysfunction and obesity. However, these results were not observed in peroxisome proliferator-activated receptor-alpha null obese mice. Innovation: Impaired peroxisomal fitness enhanced oxidative stress and inflammation in adipocytes, which exacerbates obesity. Conclusion: Adipose tissue peroxisomal homeostasis plays an important role in attenuating the features of obesity, and it can be a potential therapeutic target of obesity.

Pulmonary arterial hypertension (PAH) is commonly associated with chronic hypoxemia in disorders such as chronic obstructive pulmonary disease (COPD). Prostacyclin analogs are widely used in the management of PAH patients; however, clinical efficacy and long-term tolerability of some prostacyclin analogs may be compromised by concomitant activation of the E-prostanoid 3 (EP3) receptor. Here, we found that EP3 expression is upregulated in pulmonary arterial smooth muscle cells (PASMCs) and human distal pulmonary arteries (PAs) in response to hypoxia. Either pharmacological inhibition of EP3 or Ep3 deletion attenuated both hypoxia and monocrotaline-induced pulmonary hypertension and restrained extracellular matrix accumulation in PAs in rodent models. In a murine PAH model, Ep3 deletion in SMCs, but not endothelial cells, retarded PA medial thickness. Knockdown of EP3α and EP3β, but not EP3γ, isoforms diminished hypoxia-induced TGF-β1 activation. Expression of either EP3α or EP3β in EP3-deficient PASMCs restored TGF-β1 activation in response to hypoxia. EP3α/β activation in PASMCs increased RhoA-dependent membrane type 1 extracellular matrix metalloproteinase (MMP) translocation to the cell surface, subsequently activating pro–MMP-2 and promoting TGF-β1 signaling. Activation or disruption of EP3 did not influence PASMC proliferation. Together, our results indicate that EP3 activation facilitates hypoxia-induced vascular remodeling and pulmonary hypertension in mice and suggest EP3 inhibition as a potential therapeutic strategy for pulmonary hypertension.

Macrophages are important components of adipose tissue inflammation, which results in metabolic diseases such as insulin resistance. Notably, obesity induces a proinflammatory phenotypic switch in adipose tissue macrophages, and oxidative stress facilitates this switch. Thus, we examined the role of endogenous catalase, a key regulator of oxidative stress, in the activity of adipose tissue macrophages in obese mice. Catalase knockout (CKO) exacerbated insulin resistance, amplified oxidative stress, and accelerated macrophage infiltration into epididymal white adipose tissue in mice on normal or high-fat diet. Interestingly, catalase deficiency also enhanced classical macrophage activation (M1) and inflammation but suppressed alternative activation (M2) regardless of diet. Similarly, pharmacological inhibition of catalase activity using 3-aminotriazole induced the same phenotypic switch and inflammatory response in RAW264.7 macrophages. Finally, the same phenotypic switch and inflammatory responses were observed in primary bone marrow-derived macrophages from CKO mice. Taken together, the data indicate that endogenous catalase regulates the polarization of adipose tissue macrophages and thereby inhibits inflammation and insulin resistance.