SUMMARY Obesity-related leptin resistance manifests in loss of leptin’s ability to reduce appetite and increase energy expenditure. Obesity is also associated with increased activity of the endocannabinoid system, and CB1 receptor (CB1R) inverse agonists reduce body weight and the associated metabolic complications, although adverse neuropsychiatric effects halted their therapeutic development. Here we show that in mice with diet-induced obesity (DIO), the peripherally restricted CB1R inverse agonist JD5037 is equieffective with its brain-penetrant parent compound in reducing appetite, body weight, hepatic steatosis, and insulin resistance, even though it does not occupy central CB1R or induce related behaviors. Appetite and weight reduction by JD5037 are mediated by resensitizing DIO mice to endogenous leptin through reversing the hyperleptinemia by decreasing leptin expression and secretion by adipocytes and increasing leptin clearance via the kidney. Thus, inverse agonism at peripheral CB1R not only improves cardiometabolic risk in obesity but has antiobesity effects by reversing leptin resistance.

Type 2 diabetes mellitus (T2DM) progresses from compensated insulin resistance to beta ceil failure resulting in uncompensated hyperglycemia, a process replicated in the Zucker diabetic fatty (ZDF) rat. The Nlrp3 inflammasome has been implicated in obesity-induced insulin resistance and beta cell failure. Endocannabinoids contribute to insuiin resistance through activation of peripheral CB1 receptors (CB1Rs) and also promote beta cell failure. Here we show that beta cell failure in adult ZDF rats is not associated with CB1R signaling in beta ceils, but rather in M1 macrophages infiltrating into pancreatic islets, and that this leads to activation of the Nlrp3-ASC inflammasome in the macrophages. These effects are replicated in vitro by incubating wild-type human or rodent macrophages, but not macrophages from CB1R-deficient [Cnr1−/−) or Nlrp3−/− mice, with the endocannabinoid anandamide. Peripheral CB1R blockade, in vivo depletion of macrophages or macrophage-specific knockdown of CB1R reverses or prevents these changes and restores normoglycemia and glucose-induced insulin secretion. These findings implicate endocannabinoids and inflammasome activation in beta cell failure and identify macrophage-expressed CB1R as a therapeutic target in T2DM.

Diabetic nephropathy is a major cause of end-stage kidney disease, and overactivity of the endocannabinoid/cannabinoid 1 receptor (CB 1 R) system contributes to diabetes and its complications. Zucker diabetic fatty (ZDF) rats develop type 2 diabetic nephropathy with albuminuria, reduced glomerular filtration, activation of the reninangiotensin system (RAS), oxidative/nitrative stress, podocyte loss, and increased CB 1 R expression in glomeruli. Peripheral CB 1 R blockade initiated in the prediabetic stage prevented these changes or reversed them when animals with fully developed diabetic nephropathy were treated. Treatment of diabetic ZDF rats with losartan, an angiotensin II receptor-1 (Agtr1) antagonist, attenuated the development of nephropathy and down-regulated renal cortical CB 1 R expression, without affecting the marked hyperglycemia. In cultured human podocytes, CB 1 R and desmin gene expression were increased and podocin and nephrin content were decreased by either the CB 1 R agonist arachydonoyl-2′-chloroethylamide, angiotensin II, or high glucose, and the effects of all three were antagonized by CB 1 R blockade or siRNA-mediated knockdown of CNR1 (the cannabinoid type 1 receptor gene). We conclude that increased CB 1 R signaling in podocytes contributes to the development of diabetic nephropathy and represents a common pathway through which both hyperglycemia and increased RAS activity exert their deleterious effects, highlighting the therapeutic potential of peripheral CB 1 R blockade.iabetic nephropathy, a highly prevalent and serious complication of both type 1 and type 2 diabetes mellitus and a leading cause of renal failure, is characterized by albuminuria, decreased glomerular filtration rate (GFR), mesangial expansion, thickening of the glomerular basement membrane, and glomerular sclerosis (1). Multiple mechanisms have been implicated in the development of diabetic nephropathy, including activation of the renin-angiotensin system (RAS) (2), increase in oxidative (3) and nitrosative/nitrative stress (4), as well as an increase in local inflammation (5).The endocannabinoid system plays a well-documented role in obesity and its metabolic complications, including insulin resistance and type 2 diabetes (T2DM). Globally acting cannabinoid 1 receptor (CB 1 R) antagonists/inverse agonists improve obesity-related insulin resistance, dyslipidemia, fatty liver, and β-cell loss, and attenuate obesity-related inflammatory changes both in preclinical models of diet-induced or genetic obesity and in clinical trials in overweight subjects with metabolic syndrome (reviewed in refs. 6 and 7). Global CB 1 R blockade also has beneficial effects in mouse models of type 1 and type 2 diabetic nephropathy (8-11). However, the therapeutic development of this class of compounds has been halted because of adverse neuropsychiatric side effects in a small proportion of treated subjects (12). Recent studies in rodent models have demonstrated that peripherally restricted CB 1 R antagonists are as effective as globally acti...