Non-alcoholic Fatty Liver Disease (NAFLD) is the most common form of liver disease and is associated with metabolic dysregulation. Although G protein-coupled receptor 84 (GPR84) has been associated with inflammation, its role in metabolic regulation remains elusive. The aim of our study was to evaluate the potential of PBI-4547 for the treatment of NAFLD and to validate the role of its main target receptor, GPR84. We report that PBI-4547 is a fatty acid mimetic, acting concomitantly as a GPR84 antagonist and GPR40/GPR120 agonist. In a mouse model of diet-induced obesity, PBI-4547 treatment improved metabolic dysregulation, reduced hepatic steatosis, ballooning and NAFLD score. PBI-4547 stimulated fatty acid oxidation and induced gene expression of mitochondrial uncoupling proteins in the liver. Liver metabolomics revealed that PBI-4547 improved metabolic dysregulation induced by a high-fat diet regimen. In Gpr84 −/− mice, PBI-4547 treatment failed to improve various key NAFLD-associated parameters, as was observed in wildtype littermates. Taken together, these results highlight a detrimental role for the GPR84 receptor in the context of meta-inflammation and suggest that GPR84 antagonism via PBI-4547 may reflect a novel treatment approach for NAFLD and its related complications. Non-Alcoholic Fatty Liver Disease (NAFLD) is the most prevalent chronic liver disease worldwide and is among the top three causes of liver transplantation in the US. NAFLD represents the pathological hepatic manifestation of metabolic dysregulation including fatty acid (FA) metabolism, not caused by excessive alcohol consumption, pro-steatogenic drugs or hereditary disorders and is defined by the presence of steatosis in the liver, due to triglyceride accumulation in hepatocytes (> 5% of total fat content) 1. Pathological signs range from steatosis to non-alcoholic steatohepatitis (NASH), which represents the most severe condition. Although the precise molecular mechanisms underlying the progression from simple steatosis to NASH remain elusive, several key risk factors are known to be intimately involved including inflammation, diet and infectious agents. The most important risk factor for NAFLD/NASH is type-II diabetes mellitus and remains a strong predictor for development of adverse clinical outcomes including advanced liver fibrosis and death. Other aggravating factors, such

PBI-4050 (3-pentylbenzenacetic acid sodium salt), a novel first-in-class orally active compound that has completed clinical Phases Ib and II in subjects with chronic kidney disease (CKD) and metabolic syndrome respectively, exerts antifibrotic effects in several organs via a novel mechanism of action, partly through activation of the G protein receptor 40 (GPR40) receptor. Here we evaluate the effects of PBI-4050 in both WT and Gpr40−/− mice on adenine-induced tubulointerstitial injury, anemia and activation of the unfolded protein response (UPR) pathway. Adenine-induced CKD was achieved in 8-week-old C57BL/6 mice fed a diet supplemented with 0.25% adenine. After 1 week, PBI-4050 or vehicle was administered daily by oral-gavage for 3 weeks. Gpr40−/− mice were also subjected to adenine-feeding, with or without PBI-4050 treatment. PBI-4050 improved renal function and urine concentrating ability. Anemia was present in adenine-fed mice, while PBI-4050 blunted these effects and led to significantly higher plasma erythropoietin (EPO) levels. Adenine-induced renal fibrosis, endoplasmic reticulum (ER) stress and apoptosis were significantly decreased by PBI-4050. In parallel, Gpr40−/− mice were more susceptible to adenine-induced fibrosis, renal function impairment, anemia and ER stress compared with WT mice. Importantly, PBI-4050 treatment in Gpr40−/− mice failed to reduce renal injury in this model. Taken together, PBI-4050 prevented adenine-induced renal injury while these beneficial effects were lost upon Gpr40 deletion. These data reinforce PBI-4050’s use as a renoprotective therapy and identify GPR40 as a crucial mediator of its beneficial effects.

Chronic kidney disease (CKD) is a worldwide health burden with increases risk of end-stage renal function if left untreated. CKD induced in the context of metabolic syndrome (MS) increases risks of hypertension, hyperglycemia, excess body fat and dyslipidemia. To test if combining a high-fat diet (HFD) regimen onto the hypertensive/ diabetic phenotype would mimic features of MS induced-CKD in mice, hyperglycemia was induced in genetically hypertensive mice (Lin), followed by HFD regimen. For that, 8-week-old male were subjected to streptozotocin (STZ) intraperitoneal (i.p.) injections (50 mg/kg, 5 days consecutive). LinSTZ were fed a 60% kCal HFD for 8 weeks. Lin mice treated with STZ developed polydipsia, became hypertensive and hyperglycemic. HFD induced weight gain, protected against glomerular hypertrophy, scarring, and albuminuria at endpoint compared to regular diet fed LinSTZ. On the other hand, HFD induced steatosis, liver fibrosis, inflammation, and increase in AST/ALT ratio, characteristics of non-alcoholic liver disease. Taken together, our results show that LinSTZ mice fed a HFD did not lead to a more robust model of MS-induced CKD, protected against kidney injury, but inducing liver damage. More studies are necessary to understand the kidney protective mechanisms of HFD when superimposed with hypertension and type 1 diabetes.

Background and Aims Fatty acid receptors have recently been implicated in the progression of fibrotic disorders. GPR40 deletion predisposes to AKI and CKD-induced fibrosis, while deletion of the pro-inflammatory GPR84 receptor was beneficial in this context. PBI-4050, a novel therapeutic compound with excellent safety and efficacy profiles in both experimental and clinical settings, is a dual GPR40 agonist and GPR84 antagonist. In this study, we sought to determine which of these receptors had a predominant effect in adenine-induced CKD. Method Ten-week-old male GPR40/84 double knockout mice (40/84ko) and age/strain matched WT C57BL/6 mice were subjected to a regular or adenine-supplemented diet (0.25%) for 4 weeks (n=10 per group). Plasma samples were collected on a weekly basis for hematocrit assessment. At endpoint, mice were placed in metabolic cages for 24 hours for urine collection. Plasma minerals and electrolytes, urinalysis and a comprehensive blood count were performed at endpoint. Results Adenine feeding led to early and sustained weight-loss, which was significantly worse in WT mice compared to 40/84ko mice. At day 14, Hct was significantly decreased in adenine-fed WT mice, while unaffected in the 40/84ko group. Adenine-induced reductions in hemoglobin and red blood cells counts were also greatly improved in 40/84ko mice. Adenine-feeding led to increased circulating neutrophils and decreased lymphocyte in WT mice, which was not seen in 40/84ko mice. Importantly, renal function assessed by plasma creatinine, urea and creatinine-clearance and renal hypertrophy were significantly improved in Ad-fed 40/84ko mice. Moreover, fractional excretion for sodium, potassium and calcium were increased by adenine-feeding in WT, but not in 40/84ko mice. Conclusion Overall, the loss of both GPR40 and GPR84 led to major improvements in several key renal functional abnormalities associated with adenine-induced CKD including weight-loss, anemia and renal functional decline. These studies, along with our previous work highlight the potential of targeting fatty-acid GPCR’s, notably GPR84, for the treatment of inflammation/fibrosis related kidney diseases.