Obesity is associated with increased activity of two lipid signaling systems (endocannabinoids [ECs] and ceramides), with both being implicated in insulin resistance. Cannabinoid-1 receptor (CB1R) antagonists reverse obesity and insulin resistance, but have psychiatric side effects. Here we analyzed the role of ceramide in CB1R-mediated insulin resistance in C57Bl6/J mice with high-fat diet-induced obesity (DIO), using JD5037, a peripherally restricted CB1R inverse agonist. Chronic JD5037 treatment of DIO mice reduced body weight and steatosis and improved glucose tolerance and insulin sensitivity. Peripheral CB1R blockade also attenuated the diet-induced increase in C14:0, C16:0, C18:0, and C20:0 ceramide species with either C16 or C18 sphingosine-base in the liver. Decreased ceramide levels reflected their reduced de novo synthesis, due to inhibition of the activity of serine-palmitoyl transferase (SPT) and the expression of its SPTLC3 catalytic subunit, as well as reduced ceramide synthase (CerS) activity related to reduced expression of CerS1 and CerS6. JD5037 treatment also increased ceramide degradation due to increased expression of ceramidases. In primary cultured mouse hepatocytes and HepG2 cells, the EC anandamide increased ceramide synthesis in an eIF2α-dependent manner, and inhibited insulin-induced akt phosphorylation by increased serine phosphorylation of IRS1 and increased expression of the serine/threonine phosphatase Phlpp1. These effects were abrogated by JD5037 or the SPT inhibitor myriocin. Chronic treatment of DIO mice with myriocin or JD5037 similarly reversed hepatic insulin resistance, as verified using a euglycemic/hyperinsulinemic clamp. Conclusion : ECs induce CB1R-mediated, endoplasmic reticulum stress-dependent synthesis of specific ceramide subspecies in the liver, which plays a key role in obesity-related hepatic insulin resistance.

OBJECTIVE: The beneficial effects of the inactivation of endocannabinoid system (ECS) by administration of antagonists of the cannabinoid receptor (CB) 1 on several pathological features associated with obesity is well demonstrated, but the relative contribution of central versus peripheral mechanisms is unclear. We examined the impact of CB1 antagonism on liver and adipose tissue lipid metabolism in a mouse model of diet-induced obesity. RESEARCH DESIGN AND METHODS: Mice were fed either with a standard diet or a high-sucrose high-fat (HSHF) diet for 19 weeks and then treated with the CB1-specific antagonist SR141716 (10 mg · kg−1 · day−1) for 6 weeks. RESULTS: Treatment with SR141716 reduced fat mass, insulin levels, and liver triglycerides primarily increased by HSHF feeding. Serum adiponectin levels were restored after being reduced in HSHF mice. Gene expression of scavenger receptor class B type I and hepatic lipase was induced by CB1 blockade and associated with an increase in HDL-cholesteryl ether uptake. Concomitantly, the expression of CB1, which was strongly increased in the liver and adipose tissue of HSHF mice, was totally normalized by the treatment. Interestingly, in visceral but not subcutaneous fat, genes involved in transport, synthesis, oxidation, and release of fatty acids were upregulated by HSHF feeding, while this effect was counteracted by CB1 antagonism. CONCLUSIONS: A reduction in the CB1-mediated ECS activity in visceral fat is associated with a normalization of adipocyte metabolism, which may be a determining factor in the reversion of liver steatosis induced by treatment with SR141716.

Significance: Diabetic nephropathy is the leading cause of chronic kidney disease in the United States, and one of the most significant long-term complications of both type 1 and type 2 diabetes, which currently lack fully effective therapy. Hyperglycemia and activation of the renin-angiotensin system (RAS) are thought to be the two main drivers of this pathology. We have recently shown that selective blockade of peripheral cannabinoid receptor-1 (CB ₁ R) delayed and attenuated the development of type 2 diabetes in a rat model. Here we show that the nephropathy-inducing effects of both hyperglycemia and activation of the RAS involve CB ₁ R activation in glomerular podocytes, and that antagonism of peripheral CB ₁ R could represent a novel, effective, and rational approach to both prevent and reverse diabetic nephropathy.

Idiopathic pulmonary fibrosis (IPF) is a life-threatening disease without effective treatment, highlighting the need for identifying new targets and treatment modalities. The pathogenesis of IPF is complex, and engaging multiple targets simultaneously might improve therapeutic efficacy. To assess the role of the endocannabinoid/cannabinoid receptor 1 (endocannabinoid/CB ₁ R) system in IPF and its interaction with inducible nitric oxide synthase (iNOS) as dual therapeutic targets, we analyzed lung fibrosis and the status of the endocannabinoid/CB ₁ R system and iNOS in mice with bleomycin-induced pulmonary fibrosis (PF) and in lung tissue and bronchoalveolar lavage fluid (BALF) from patients with IPF, as well as controls. In addition, we investigated the antifibrotic efficacy in the mouse PF model of an orally bioavailable and peripherally restricted CB ₁ R/iNOS hybrid inhibitor. We report that increased activity of the endocannabinoid/CB ₁ R system parallels disease progression in the lungs of patients with idiopathic PF and in mice with bleomycin-induced PF and is associated with increased tissue levels of interferon regulatory factor-5. Furthermore, we demonstrate that simultaneous engagement of the secondary target iNOS by the hybrid CB ₁ R/iNOS inhibitor has greater antifibrotic efficacy than inhibition of CB ₁ R alone. This hybrid antagonist also arrests the progression of established fibrosis in mice, thus making it a viable candidate for future translational studies in IPF.