Metabolic effects of orally administered small-molecule agonists of GPR55 and GPR119 in multiple low-dose streptozotocin-induced diabetic and incretin-receptor-knockout mice

Positive interplay between FFAR4/GPR120, DPP-IV inhibition and GLP-1 in beta cell proliferation and glucose homeostasis in obese high fat fed mice

G-protein coupled receptor-120 (GPR120; FFAR4) is a free fatty acid receptor, widely researched for its glucoregulatory and insulin release activities. This study aimed to investigate the metabolic advantage of FFAR4/GPR120 activation using combination therapy. C57BL/6 mice, fed a High Fat Diet (HFD) for 120 days to induce obesity-diabetes, were subsequently treated with a single daily oral dose of FFAR4/GPR120 agonist Compound A (CpdA) (0.1μmol/kg) alone or in combination with sitagliptin (50 mg/kg) for 21 days. After 21-days, glucose homeostasis, islet morphology, plasma hormones and lipids, tissue genes (qPCR) and protein expression (immunocytochemistry) were assessed. Oral administration of CpdA improved glucose tolerance (34% p<0.001) and increased circulating insulin (38% p<0.001). Addition of CpdA with the dipeptidyl peptidase-IV (DPP-IV) inhibitor, sitagliptin, further improved insulin release (44%) compared to sitagliptin alone and reduced fat mass (p<0.05). CpdA alone (50%) and in combination with sitagliptin (89%) induced marked reductions in LDL-cholesterol, with greater effects in combination (p<0.05). All treatment regimens restored pancreatic islet and beta-cell area and mass, complemented with significantly elevated beta-cell proliferation rates. A marked increase in circulating GLP-1 (53%) was observed, with further increases in combination (38%). With treatment, mice presented with increased Gcg (proglucagon) gene expression in the jejunum (130% increase) and ileum (120% increase), indicative of GLP-1 synthesis and secretion. These data highlight the therapeutic promise of FFAR4/GPR120 activation and the potential for combined benefit with incretin enhancing DPP-IV inhibitors in the regulation of beta cell proliferation and diabetes.

GPR119 agonists for type 2 diabetes: past failures and future hopes for preclinical and early phase candidates

INTRODUCTION

Type 2 diabetes (T2D) is metabolic disorder associated with a decrease in insulin activity and/or secretion from the β-cells of the pancreas, leading to elevated circulating glucose. Current management practices for T2D are complex with varying long-term effectiveness. Agonism of the G protein-coupled receptor GPR119 has received a lot of recent interest as a potential T2D therapeutic.

AREAS COVERED

This article reviews studies focused on GPR119 agonism in animal models of T2D and in patients with T2D.

EXPERT OPINION

GPR119 agonists in vitro and in vivo can potentially regulate incretin hormone release from the gut, then pancreatic insulin release which regulates blood glucose concentrations. However, the success in controlling glucose homeostasis in rodent models of T2D and obesity, failed to translate to early-stage clinical trials in patients with T2D. However, in more recent studies, acute and chronic dosing with the GPR119 agonist DS-8500a had increased efficacy, although this compound was discontinued for further development. New trials on GPR119 agonists are needed, however it may be that the future of GPR119 agonists lie in the development of combination therapy with other T2D therapeutics.

Δ9-Tetrahydrocannabinol Treatment Modifies Insulin Secretion in Pancreatic Islets from Prediabetic Mice Under Hypercaloric Diet

Background: The endocannabinoid system over-activation is associated with type-2 diabetes mellitus onset, involving physiological, metabolic, and genetic alterations in pancreatic islets. The use of Δ9-Tetrahydrocannabinol (THC) as treatment is still controversial since its effects and mechanisms on insulin secretion are unclear. The aim of this study was to evaluate the effects of THC treatment in pancreatic islets from prediabetic mice. Methods: Prediabetes was induced in mice by hypercaloric diet, and then treated with THC for 3 weeks. Blood glucose and body weight were determined, after behavior tests. Histological changes were evaluated in whole pancreas; in isolated islets we analyzed the effect of THC exposure in glucose-stimulated insulin secretion (GSIS), gene expression, intracellular cyclic adenosine monophosphate (cAMP), and cytosolic calcium changes. Results: THC treatment in prediabetic mice enhanced anxiety and antidepressive behavior without changes in food ingestion, decreased oral-glucose tolerance test, plasma insulin and weight, with small alterations on pancreatic histology. In isolated islets from healthy mice THC increased GSIS, cAMP, and CB1 receptor (CB1r) expression, meanwhile calcium release was diminished. Small changes were observed in islets from prediabetic mice. Conclusions: THC treatment improves some clinical parameters in prediabetic mice, however, in isolated islets, modifies GSIS, intracellular calcium and gene expression, suggesting specific effects related to diabetes evolution.

Antidiabetic actions of GPR55 agonist Abn-CBD and sitagliptin in obese-diabetic high fat fed mice

GPR55 has been recognized as a novel anti-diabetic target exerting positive effects on beta cell function and mass. This study evaluated the metabolic actions and therapeutic efficacy of GPR55 agonist abnormal cannabidiol (Abn-CBD) administered alone and in combination with sitagliptin in diet-induced obese-diabetic mice. Chronic effects of 21-day oral administration of Abn-CBD (0.1 µmol/kg BW) monotherapy and in combination with sitagliptin (50 mg/kg BW) were assessed in obese-diabetic HFF mice (n = 8). Assessments of plasma glucose, circulating insulin, DPP-IV activity, CRP, amylase, lipids, body weight and food intake were undertaken. Glucose tolerance, insulin sensitivity, DEXA scanning and islet morphology analysis were performed at 21-days. Sitagliptin, Abn-CBD alone and in combination with sitagliptin attenuated plasma glucose by 37-53 % (p < 0.01 - p < 0.001) and enhanced circulating insulin concentrations by 23-31 % (p < 0.001). Abn-CBD alone and with sitagliptin reduced bodyweight by 9-10 % (p < 0.05). After 21-days, Abn-CBD in combination with sitagliptin (44 %; p < 0.01) improved glucose tolerance, whilst enhancing insulin sensitivity by 79 % (p < 0.01). Abn-CBD increased islet area (86 %; p < 0.05), beta cell mass (p < 0.05) and beta cell proliferation (164 %; p < 0.001), whilst in combination with sitagliptin islet area was decreased (50 %; p < 0.01). Abn-CBD alone, in combination with sitagliptin or sitagliptin alone decreased triglycerides by 34-65 % (p < 0.001) and total cholesterol concentrations by 15-25 % (p < 0.001). In addition, Abn-CBD in combination with sitagliptin reduced fat mass by 19 % (p < 0.05) and reduced CRP concentrations (39 %; p < 0.05). These findings advocate Abn-CBD monotherapy and in combination with sitagliptin as a novel and effective approach for bodyweight control and the treatment of glucose intolerance and dyslipidaemia in type-2-diabetes.

A Phase I Randomized, Double-blind, Placebo-controlled Study on Efficacy and Safety Profile of a Sublingually Administered Cannabidiol /Delta 9-tetrahydrocannabidiol (10: 1) Regimen in Diabetes Type 2 Patients

The current study aimed to evaluate the safety profile and efficacy of a cannabis-based sublingual spray, CBDEX10^® (containing 100 µg cannabidiol and 10 µg Δ⁹-tetrahydrocannabinol per puff; CBD/Δ⁹-THC 10:1), in improving lipid profile and glycemic state of the diabetic patients. Fifty diabetic patients were randomly allocated to the treatment (n = 25; receiving two puffs of CBDEX10^® twice daily) or the control groups (n = 25; receiving two puffs of placebo). The primary endpoint of the study was to evaluate the efficacy of the CBDEX10^® adjunctive therapy in improving the lipid profile and glycemic state of diabetic patients; the secondary endpoint was to assess the safety profile and tolerability of the spray. A statistically significant decline in total cholesterol [estimated treatment difference (ETD) = -19.73 mg/dL; P < 0.05], triglyceride (ETD = -27.84 mg/dL; P < 0.01), LDL-C (ETD = -5.37 mg/dL; P < 0.01), FBS (ETD = -12 mg/dL; P < 0.01), Hb A1C (ETD = -0.21 mg/dL; P < 0.01) and insulin secretion (ETD = -5.21 mIU/L; P < 0.01) was observable in the patients treated with CBDEX10^® at the end of the 8-week treatment period. Regarding safety, the mentioned adjunctive regimen was well, and there were no serious or severe adverse effects. Overall, CBDEX1^® sublingual spray could be a new therapeutic agent for lipid and glycemic control in diabetic patients.

Novel Noninvasive Approaches to the Treatment of Obesity: From Pharmacotherapy to Gene Therapy

Recent insights into the pathophysiologic underlying mechanisms of obesity have led to the discovery of several promising drug targets and novel therapeutic strategies to address the global obesity epidemic and its comorbidities. Current pharmacologic options for obesity management are largely limited in number and of modest efficacy/safety profile. Therefore, the need for safe and more efficacious new agents is urgent. Drugs that are currently under investigation modulate targets across a broad range of systems and tissues, including the central nervous system, gastrointestinal hormones, adipose tissue, kidney, liver, and skeletal muscle. Beyond pharmacotherapeutics, other potential antiobesity strategies are being explored, including novel drug delivery systems, vaccines, modulation of the gut microbiome, and gene therapy. The present review summarizes the pathophysiology of energy homeostasis and highlights pathways being explored in the effort to develop novel antiobesity medications and interventions but does not cover devices and bariatric methods. Emerging pharmacologic agents and alternative approaches targeting these pathways and relevant research in both animals and humans are presented in detail. Special emphasis is given to treatment options at the end of the development pipeline and closer to the clinic (ie, compounds that have a higher chance to be added to our therapeutic armamentarium in the near future). Ultimately, advancements in our understanding of the pathophysiology and interindividual variation of obesity may lead to multimodal and personalized approaches to obesity treatment that will result in safe, effective, and sustainable weight loss until the root causes of the problem are identified and addressed.

GPR55 and GPR119 Receptors Contribute to the Processing of Neuropathic Pain in Rats

Orphan G-protein-coupled receptors (GPCR) comprise a large number of receptors which are widely distributed in the nervous system and represent an opportunity to identify new molecular targets in pain medicine. GPR55 and GPR119 are two orphan GPCR receptors whose physiological function is unclear. The aim was to explore the participation of spinal GPR55 and GPR119 in the processing of neuropathic pain in rats. Mechanical allodynia was evaluated using von Frey filaments. Protein localization and modulation were measured by immunohistochemistry and western blotting, respectively. Intrathecal administration of CID16020046 (selective GPR55 antagonist) or AS1269574 (selective GPR119 agonist) produced a dose-dependent antiallodynic effect, whereas O1062 (GPR55 agonist) and G-protein antagonist peptide dose-dependently prevented the antiallodynic effect of CID16020046 and AS1269574, respectively. Both GPR55 and GPR119 receptors were expressed in spinal cord, dorsal root ganglia and sciatic nerve, but only GPR119 was downregulated after 14 days of spinal nerve ligation. Data suggest that GPR55 and GPR119 participate in the processing of neuropathic pain and could be useful targets to manage neuropathic pain disorders.

Abnormal cannabidiol ameliorates inflammation preserving pancreatic beta cells in mouse models of experimental type 1 diabetes and beta cell damage

The atypical cannabinoid Abn-CBD improves the inflammatory status in preclinical models of several pathologies, including autoimmune diseases. However, its potential for modulating inflammation in autoimmune type 1 diabetes (T1D) is unknown. Herein we investigate whether Abn-CBD can modulate the inflammatory response during T1D onset using a mouse model of T1D (non-obese diabetic- (NOD)-mice) and of beta cell damage (streptozotocin (STZ)-injected mice). Six-week-old female NOD mice were treated with Abn-CBD (0.1-1 mg/kg) or vehicle during 12 weeks and then euthanized. Eight-to-ten-week-old male C57Bl6/J mice were pre-treated with Abn-CBD (1 mg/kg of body weight) or vehicle for 1 week, following STZ challenge, and euthanized 1 week later. Blood, pancreas, pancreatic lymph nodes (PLNs) and T cells were collected and processed for analysis. Glycemia was also monitored. In NOD mice, treatment with Abn-CBD significantly reduced the severity of insulitis and reduced the pro-inflammatory profile of CD4⁺ T cells compared to vehicle. Concomitantly, Abn-CBD significantly reduced islet cell apoptosis and improved glucose tolerance. In STZ-injected mice, Abn-CBD decreased circulating proinflammatory cytokines and ameliorated islet inflammation reducing intra-islet phospho-NF-κB and TXNIP. Abn-CBD significantly reduced 2 folds intra-islet CD8⁺ T cells and reduced Th1/non-Th1 ratio in PLNs of STZ-injected mice. Islet cell apoptosis and intra-islet fibrosis were also significantly reduced in Abn-CBD pre-treated mice compared to vehicle. Altogether, Abn-CBD reduces circulating and intra-islet inflammation, preserving islets, thus delaying the progression of insulitis. Hence, Abn-CBD and related compounds emerge as new candidates to develop pharmacological strategies to treat the early stages of T1D.

A molecular explanation of cardiovascular protection through abnormal cannabidiol: Involving the dysfunctional β-adrenergic and ATP-sensitive K+ channel activity in cardiovascular compromised preterm infants

Growing cannabis efficacy, usage frequency, legal supply, and declining awareness of danger recently led to expanded United States cannabis exposure. In turn, cannabis use among elderly people over 50 has more than tripled in a decade and has contributed toward a positive association of cannabis use with pathological conditions, which include type II diabetes, metabolic syndrome, neurovascular and cardiovascular disease. Remarkably, all these outcome results are mediated by the involvement of the ATP-sensitive K+ channel. Cardiovascular compromise is a common syndrome in preterm infants that leads to incidence and death and has been distinguished by poor systemic flow or hypotension. Conditions of cardiovascular compromise include vasodysregulation and myocardial malfunction through dysfunctional β-adrenergic activity. To avoid organ hypoperfusion progressing to tissue hypoxia-ischemia, inotropic drugs are used. Many premature children, however, respond insufficiently to inotropic activity with adrenergic agonists. The clinical disturbance including myocardial dysfunction through the activation of the ATP-sensitive K+ channel is often involved and the comparative efficacy of the nonpsychotropic cannabinoid, abnormal cannabidiol (Abn-CBD) is not yet known. Therefore, our primary aim was to investigate the molecular exploration of the cannabinoid system specifically Abn-CBD in cardiovascular protection involving dysregulated KATP.

GPR119 agonists: Novel therapeutic agents for type 2 diabetes mellitus

Diabetes mellitus type 2 (T2D) is a group of genetically heterogeneous metabolic disorders whose frequency has gradually risen worldwide. Diabetes mellitus Type 2 (T2D) has started to achieve a pandemic level, and it is estimated that within the next decade, cases of diabetes might get double due to increase in aging population. Diabetes is rightly called the 'silent killer' because it has emerged to be one of the major causes, leading to renal failure, loss of vision; besides cardiac arrest in India. Thus, a clinical requirement for the oral drug molecules monitoring glucose homeostasis appears to be unmet. GPR119 agonist, a family of G-protein coupled receptors, usually noticed in β-cells of pancreatic as well as intestinal L cells, drew considerable interest for type 2 diabetes mellitus (T2D). GPR119 monitors physiological mechanisms that enhance homeostasis of glucose, such as glucose-like peptide-1, gastrointestinal incretin hormone levels, pancreatic beta cell-dependent insulin secretion and glucose-dependent insulinotropic peptide (GIP). In this manuscript, we have reviewed the work done in the last five years (2015-2020) which gives an approach to design, synthesize, evaluate and study the structural activity relationship of novel GPR119 agonist-based lead compounds. Our article would help the researchers and guide their endeavours in the direction of strategy and development of innovative, effective GPR119 agonist-based compounds for the management of diabetes mellitus type 2.

Targeting lipid GPCRs to treat type 2 diabetes mellitus - progress and challenges

Therapeutic approaches to the treatment of type 2 diabetes mellitus that are designed to increase insulin secretion either directly target β-cells or indirectly target gastrointestinal enteroendocrine cells (EECs), which release hormones that modulate insulin secretion (for example, incretins). Given that β-cells and EECs both express a large array of G protein-coupled receptors (GPCRs) that modulate insulin secretion, considerable research and development efforts have been undertaken to design therapeutic drugs targeting these GPCRs. Among them are GPCRs specific for free fatty acid ligands (lipid GPCRs), including free fatty acid receptor 1 (FFA1, otherwise known as GPR40), FFA2 (GPR43), FFA3 (GPR41) and FFA4 (GPR120), as well as the lipid metabolite binding glucose-dependent insulinotropic receptor (GPR119). These lipid GPCRs have demonstrated important roles in the control of islet and gut hormone secretion. Advances in lipid GPCR pharmacology have led to the identification of a number of synthetic agonists that exert beneficial effects on glucose homeostasis in preclinical studies. Yet, translation of these promising results to the clinic has so far been disappointing. In this Review, we present the physiological roles, pharmacology and clinical studies of these lipid receptors and discuss the challenges associated with their clinical development for the treatment of type 2 diabetes mellitus.

Satellite glia as a critical component of diabetic neuropathy: Role of lipocalin-2 and pyruvate dehydrogenase kinase-2 axis in the dorsal root ganglion

Diabetic peripheral neuropathy (DPN) is a common complication of uncontrolled diabetes. The pathogenesis of DPN is associated with chronic inflammation in dorsal root ganglion (DRG), eventually causing structural and functional changes. Studies on DPN have primarily focused on neuronal component, and there is limited knowledge about the role of satellite glial cells (SGCs), although they completely enclose neuronal soma in DRG. Lipocalin-2 (LCN2) is a pro-inflammatory acute-phase protein found in high levels in diverse neuroinflammatory and metabolic disorders. In diabetic DRG, the expression of LCN2 was increased exclusively in the SGCs. This upregulation of LCN2 in SGCs correlated with increased inflammatory responses in DRG and sciatic nerve. Furthermore, diabetes-induced inflammation and morphological changes in DRG, as well as sciatic nerve, were attenuated in Lcn2 knockout (KO) mice. Lcn2 gene ablation also ameliorated neuropathy phenotype as determined by nerve conduction velocity and intraepidermal nerve fiber density. Mechanistically, studies using specific gene KO mice, adenovirus-mediated gene overexpression strategy, and primary cultures of DRG SGCs and neurons have demonstrated that LCN2 enhances the expression of mitochondrial gate-keeping regulator pyruvate dehydrogenase kinase-2 (PDK2) through PPARβ/δ, thereby inhibiting pyruvate dehydrogenase activity and increasing production of glycolytic end product lactic acid in DRG SGCs and neurons of diabetic mice. Collectively, our findings reveal a crucial role of glial LCN2-PPARβ/δ-PDK2-lactic acid axis in progression of DPN. Our results establish a link between pro-inflammatory LCN2 and glycolytic PDK2 in DRG SGCs and neurons and propose a novel glia-based mechanism and drug target for therapy of DPN. MAIN POINTS: Diabetes upregulates LCN2 in satellite glia, which in turn increases pyruvate dehydrogenase kinase-2 (PDK2) expression and lactic acid production in dorsal root ganglia (DRG). Glial LCN2-PDK2-lactic acid axis in DRG plays a crucial role in the pathogenesis of diabetic neuropathy.

The Effects of Cannabidiol, a Non-Intoxicating Compound of Cannabis, on the Cardiovascular System in Health and Disease

Cannabidiol (CBD) is a non-intoxicating and generally well-tolerated constituent of cannabis which exhibits potential beneficial properties in a wide range of diseases, including cardiovascular disorders. Due to its complex mechanism of action, CBD may affect the cardiovascular system in different ways. Thus, we reviewed the influence of CBD on this system in health and disease to determine the potential risk of cardiovascular side effects during CBD use for medical and wellness purposes and to elucidate its therapeutic potential in cardiovascular diseases. Administration of CBD to healthy volunteers or animals usually does not markedly affect hemodynamic parameters. Although CBD has been found to exhibit vasodilatory and antioxidant properties in hypertension, it has not affected blood pressure in hypertensive animals. Hypotensive action of CBD has been mainly revealed under stress conditions. Many positive effects of CBD have been observed in experimental models of heart diseases (myocardial infarction, cardiomyopathy, myocarditis), stroke, neonatal hypoxic ischemic encephalopathy, sepsis-related encephalitis, cardiovascular complications of diabetes, and ischemia/reperfusion injures of liver and kidneys. In these pathological conditions CBD decreased organ damage and dysfunction, oxidative and nitrative stress, inflammatory processes and apoptosis, among others. Nevertheless, further clinical research is needed to recommend the use of CBD in the treatment of cardiovascular diseases.

Formation of βTC3 and MIN6 Pseudoislets Changes the Expression Pattern of Gpr40, Gpr55, and Gpr119 Receptors and Improves Lysophosphatidylcholines-Potentiated Glucose-Stimulated Insulin Secretion

The impaired spatial arrangement and connections between cells creating islets of Langerhans as well as altered expression of G protein-coupled receptors (GPCRs) often lead to dysfunction of insulin-secreting pancreatic β cells and can significantly contribute to the development of diabetes. Differences in glucose-stimulated insulin secretion (GSIS) are noticeable not only in diabetic individuals but also in model pancreatic β cells, e.g., βTC3 and MIN6 β cell lines with impaired and normal insulin secretion, respectively. Now, we compare the ability of GPCR agonists (lysophosphatidylcholines bearing fatty acid chains of different lengths) to potentiate GSIS in βTC3 and MIN6 β cell models, cultured as adherent monolayers and in a form of pseudoislets (PIs) with pancreatic MS1 endothelial cells. Our aim was also to investigate differences in expression of the GPCRs responsive to LPCs in these experimental systems. Aggregation of β cells into islet-like structures greatly enhanced the expression of Gpr40, Gpr55, and Gpr119 receptors. In contrast, the co-culture of βTC3 cells with endothelial cells converted the GPCR expression pattern closer to the pattern observed in MIN6 cells. Additionally, the efficiencies of various LPC species in βTC3-MS1 PIs also shifted toward the MIN6 cell model.

Oleoylethanolamide Exhibits GPR119-Dependent Inhibition of Osteoclast Function and GPR119-Independent Promotion of Osteoclast Apoptosis

Oleoylethanolamide (OEA), a bioactive lipid in bone, is known as an endogenous ligand for G protein-coupled receptor 119 (GPR119). Here, we explored the effects of OEA on osteoclast differentiation, function, and survival. While OEA inhibits osteoclast resorptive function by disrupting actin cytoskeleton, it does not affect receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclast differentiation. OEA attenuates osteoclast spreading, blocks actin ring formation, and eventually impairs bone resorption. Mechanistically, OEA inhibits Rac activation in response to macrophage colony-stimulating factor (M-CSF), but not RANKL. Furthermore, the OEA-mediated cytoskeletal disorganization is abrogated by GPR119 knockdown using small hairpin RNA (shRNA), indicating that GPR119 is pivotal for osteoclast cytoskeletal organization. In addition, OEA induces apoptosis in both control and GPR119 shRNAtransduced osteoclasts, suggesting that GPR119 is not required for osteoclast apoptosis. Collectively, our findings reveal that OEA has inhibitory effects on osteoclast function and survival of mature osteoclasts via GPR119-dependent and GPR119-independent pathways, respectively.

CRISPR/Cas9 gene editing demonstrates metabolic importance of GPR55 in the modulation of GIP release and pancreatic beta cell function

G-protein coupled receptor-55 (GPR55), an endocannabinoid receptor, is a novel anti-diabetic target. This study aimed to assess the metabolic functionality of GPR55 ligands using CRISPR/Cas9 gene editing to determine their regulatory role in beta cell function and incretin-secreting enteroendocrine cells. A clonal Gpr55 knockout beta cell line was generated by CRISPR/Cas9 gene editing to investigate insulin secretion and Gpr55 signalling. Acute effects of GPR55 agonists were investigated in high fat fed (HFD) diabetic HsdOla:TO (Swiss TO) mice. Atypical and endogenous endocannabinoid ligands (10^-7-10^-4M) stimulated insulin secretion (p < 0.05-0.001) in rodent (BRIN-BD11) and human (1.1B4) beta cells, with 2-2.7-fold (p < 0.001) increase demonstrated in BRIN-BD11 cells (10^-4M). The insulinotropic effect of Abn-CBD (42 %), AM251 (30 %) and PEA (53 %) were impaired (p < 0.05) in Gpr55 knockout BRIN-BD11 cells, with the secretory effect of O-1602 completely abolished (p < 0.001). Gpr55 ablation abolished the release of intracellular Ca²⁺ upon treatment with O-1602, Abn-CBD and PEA. Upregulation of insulin mRNA by Abn-CBD and AM251 (1.7-3-fold; p < 0.01) was greatly diminished (p < 0.001) in Gpr55 null cells. Orally administered Abn-CBD and AM251 (0.1 μmol/kgBW) improved GIP (p < 0.05-p < 0.01), GLP-1 (p < 0.05-p < 0.001), glucose tolerance (p < 0.001) and circulating insulin (p < 0.05-p < 0.001) in HFD diabetic mice. Abn-CBD in combination therapy with DPP-IV inhibitor (Sitagliptin) resulted in greater improvement in glucose tolerance (p < 0.05) and insulin release (p < 0.05). Antagonism of Gpr55 in-vivo attenuated the glucoregulatory effects of Abn-CBD (p < 0.05). Conclusively, GPR55 agonists enhance insulin, GIP and GLP-1 release, thereby promoting GPR55 agonist monotherapy and combinational therapy as a novel approach for the treatment of type-2-diabetes.

Potential metabolic and behavioural roles of the putative endocannabinoid receptors GPR18, GPR55 and GPR119 in feeding

Endocannabinoids are ancient biomolecules involved in several cellular (e.g., metabolism) and physiological (e.g., eating behaviour) functions. Indeed, eating behaviour alterations in marijuana users have led to investigate the orexigen-ic/anorexigenic effects of cannabinoids in animal/human models. This increasing body of research suggests that the endo-cannabinoid system plays an important role in feeding control. Accordingly, within the endocannabinoid system, canna-binoid receptors, enzymes and genes represent potential therapeutic targets for dealing with multiple metabolic and behav-ioural dysfunctions (e.g., obesity, anorexia, etc.). Paradoxically, our understanding on the endocannabinoid system as a cel-lular mediator is yet limited. For example: (i) only two cannabinoid receptors have been classified, but they are not enough to explain the pharmacological profile of several experimental effects induced by cannabinoids; and (ii) several orphan G pro-tein-coupled receptors (GPCRs) interact with cannabinoids and we do not know how to classify them (e.g., GPR18, GPR55 and GPR119; amongst others).

On this basis, the present review attempts to summarize the lines of evidence supporting the potential role of GPR18, GPR55 and GPR119 in metabolism and feeding control that may explain some of the divergent effects and puzzling data re-lated to cannabinoid research. Moreover, their therapeutic potential in feeding behaviour alterations will be considered.

The Atypical Cannabinoid Abn-CBD Reduces Inflammation and Protects Liver, Pancreas, and Adipose Tissue in a Mouse Model of Prediabetes and Non-alcoholic Fatty Liver Disease

Background and Aims: The synthetic atypical cannabinoid Abn-CBD, a cannabidiol (CBD) derivative, has been recently shown to modulate the immune system in different organs, but its impact in obesity-related meta-inflammation remains unstudied. We investigated the effects of Abn-CBD on metabolic and inflammatory parameters utilizing a diet-induced obese (DIO) mouse model of prediabetes and non-alcoholic fatty liver disease (NAFLD). Materials and Methods: Ten-week-old C57Bl/6J mice were fed a high-fat diet for 15 weeks, following a 2-week treatment of daily intraperitoneal injections with Abn-CBD or vehicle. At week 15 mice were obese, prediabetic and developed NAFLD. Body weight and glucose homeostasis were monitored. Mice were euthanized and blood, liver, adipose tissue and pancreas were collected and processed for metabolic and inflammatory analysis. Results: Body weight and triglycerides profiles in blood and liver were comparable between vehicle- and Abn-CBD-treated DIO mice. However, treatment with Abn-CBD reduced hyperinsulinemia and markers of systemic low-grade inflammation in plasma and fat, also promoting white adipose tissue browning. Pancreatic islets from Abn-CBD-treated mice showed lower apoptosis, inflammation and oxidative stress than vehicle-treated DIO mice, and beta cell proliferation was induced. Furthermore, Abn-CBD lowered hepatic fibrosis, inflammation and macrophage infiltration in the liver when compared to vehicle-treated DIO mice. Importantly, the balance between hepatocyte proliferation and apoptosis was improved in Abn-CBD-treated compared to vehicle-treated DIO mice. Conclusions: These results suggest that Abn-CBD exerts beneficial immunomodulatory actions in the liver, pancreas and adipose tissue of DIO prediabetic mice with NAFLD, thus protecting tissues. Therefore, Abn-CBD and related compounds could represent novel pharmacological strategies for managing obesity-related metabolic disorders.

Rapid and Concomitant Gut Microbiota and Endocannabinoidome Response to Diet-Induced Obesity in Mice

The intestinal microbiota and the expanded endocannabinoid system, or endocannabinoidome, have both been implicated in diet-induced obesity and dysmetabolism. This study aims at identifying the potential interactions between these two fundamental systems—which form the gut microbiota-endocannabinoidome axis—and their involvement in the establishment of diet-induced obesity and related metabolic complications. We report here time- and segment-specific microbiome disturbances as well as modifications of intestinal and circulating endocannabinoidome mediators during high-fat, high-sucrose diet-induced glucose intolerance and subsequent obesity and hyperinsulinemia. This highlights the involvement of, and the interaction between, the gut microbiota and the endocannabinoidome during metabolic adaptation to high-fat and high-sucrose feeding. These results will help identifying actionable gut microbiome members and/or endocannabinoidome mediators to improve metabolic health.

The intestinal microbiota and the expanded endocannabinoid (eCB) system, or endocannabinoidome (eCBome), have both been implicated in diet-induced obesity and dysmetabolism. These systems were recently suggested to interact during the development of obesity. We aimed at identifying the potential interactions between gut microbiota composition and the eCBome during the establishment of diet-induced obesity and metabolic complications. Male mice were fed a high-fat, high-sucrose (HFHS) diet for 56 days to assess jejunum, ileum, and cecum microbiomes by 16S rRNA gene metataxonomics as well as ileum and plasma eCBome by targeted liquid chromatography-tandem mass spectrometry (LC-MS/MS). The HFHS diet induced early (3 days) and persistent glucose intolerance followed by weight gain and hyperinsulinemia. Concomitantly, it induced the elevation of the two eCBs, anandamide, in both ileum and plasma, and 2-arachidonoyl-glycerol, in plasma, as well as alterations in several other N-acylethanolamines and 2-acylglycerols. It also promoted segment-specific changes in the relative abundance of several genera in intestinal microbiota, some of which were observed as early as 3 days following HFHS diet. Weight-independent correlations were found between the relative abundances of, among others, Barnesiella, Eubacterium, Adlercreutzia, Parasutterella, Propionibacterium, Enterococcus, and Methylobacterium and the concentrations of anandamide and the anti-inflammatory eCBome mediator N-docosahexaenoyl-ethanolamine. This study highlights for the first time the existence of potential interactions between the eCBome, an endogenous system of multifunctional signaling lipids, and several intestinal genera during early and late HFHS-induced dysmetabolic events, with potential impact on the host capability of adapting to increased intake of fat and sucrose.

IMPORTANCE The intestinal microbiota and the expanded endocannabinoid system, or endocannabinoidome, have both been implicated in diet-induced obesity and dysmetabolism. This study aims at identifying the potential interactions between these two fundamental systems—which form the gut microbiota-endocannabinoidome axis—and their involvement in the establishment of diet-induced obesity and related metabolic complications. We report here time- and segment-specific microbiome disturbances as well as modifications of intestinal and circulating endocannabinoidome mediators during high-fat, high-sucrose diet-induced glucose intolerance and subsequent obesity and hyperinsulinemia. This highlights the involvement of, and the interaction between, the gut microbiota and the endocannabinoidome during metabolic adaptation to high-fat and high-sucrose feeding. These results will help identifying actionable gut microbiome members and/or endocannabinoidome mediators to improve metabolic health.

The Expanded Endocannabinoid System/Endocannabinoidome as a Potential Target for Treating Diabetes Mellitus

PURPOSE OF REVIEW

The endocannabinoid (eCB) system, i.e. the receptors that respond to the psychoactive component of cannabis, their endogenous ligands and the ligand metabolic enzymes, is part of a larger family of lipid signals termed the endocannabinoidome (eCBome). We summarize recent discoveries of the roles that the eCBome plays within peripheral tissues in diabetes, and how it is being targeted, in an effort to develop novel therapeutics for the treatment of this increasingly prevalent disease.

RECENT FINDINGS

As with the eCB system, many eCBome members regulate several physiological processes, including energy intake and storage, glucose and lipid metabolism and pancreatic health, which contribute to the development of type 2 diabetes (T2D). Preclinical studies increasingly support the notion that targeting the eCBome may beneficially affect T2D. The eCBome is implicated in T2D at several levels and in a variety of tissues, making this complex lipid signaling system a potential source of many potential therapeutics for the treatments for T2D.

Pharmacological potential of novel agonists for FFAR4 on islet and enteroendocrine cell function and glucose homeostasis

BACKGROUND

To investigate the metabolic effects of FFAR4-selective agonists on islet and enteroendocrine cell hormone release and the combined therapeutic effectiveness with DPP-IV inhibitors.

METHODS

Insulinotropic activity and specificity of FFAR4 agonists were determined in clonal pancreatic BRIN-BD11 cells. Expression of FFAR4 was assessed by qPCR and western blotting following agonist treatment in BRIN-BD11 cells and by immunohistochemistry in mouse islets. Acute in-vivo effects of agonists was investigated after intraperitoneal (i.p.) or oral administration in lean and HFF-obese diabetic mice.

RESULTS

GSK137647 (10^-11-10^-4 M) and Compound-A (10^-10-10^-4 M) stimulated insulin secretion at 5.6 mM (p < 0.05-p < 0.001) and 16.7 mM (p < 0.05-p < 0.001) glucose in BRIN-BD11 cells, with no cytotoxicity effects as assessed by MTT. FFAR4 antagonist (AH-7614) abolished the insulintropic effect of GSK137647 (p < 0.05-p < 0.001), whilst FFAR1 antagonist (GW1100) had no effect. Incubation of BRIN-BD11 cells with GSK137647 and Compound-A increased FFAR4 (p < 0.01) gene expression at 16.7 mM glucose, with a corresponding increase in FFAR4 (p < 0.01) protein concentrations. FFAR4 upregulation was attenuated under normoglycaemic conditions. Immunohistochemistry demonstrated co-localisation of FFAR4 and insulin in mouse islets. Orally administered GSK137647 or Compound-A (0.1 µmol/kgBW) improved glucose tolerance (p < 0.001), increased plasma insulin (p < 0.001), GLP-1 (p < 0.05), GIP (p < 0.05) and induced satiety (p < 0.001) in HFF mice, with glucose-lowering effects enhanced in combination with DPP-IV inhibitor (Sitagliptin) (p < 0.05).

CONCLUSIONS

Specific FFAR4 agonism improves glucose tolerance through insulin and incretin secretion, with enhanced DPP-IV inhibition in combination with Sitagliptin.

GENERAL SIGNIFICANCE

These findings have for the first time demonstrated that selective FFAR4 activation regulates both islet and enteroendocrine hormone function with agonist combinational therapy, presenting a promising strategy for the treatment of type-2-diabetes.

Cannabidiol improves metabolic dysfunction in middle-aged diabetic rats submitted to a chronic cerebral hypoperfusion

Cannabidiol (CBD), a compound obtained from Cannabis sativa, has wide range of therapeutic properties, including mitigation of diabetes and neurodegeneration. Cerebral ischemia and consequent learning disabilities are aggravated in elderly diabetic subjects. However, there are no studies showing the effect of CBD treatment in elderly diabetes patients suffering cerebral ischemia. The present work tested the hypothesis that CBD treatment improves metabolic dysfunctions in middle-aged diabetic rats submitted to chronic cerebral hypoperfusion. In this work, 350-day-old male Wistar streptozotocin-induced diabetic rats were used. To induce cerebral ischemia was used a chronic cerebral hypoperfusion (CCH), surgically, via the four-vessel occlusion/internal carotid artery (4-VO/ICA). Four diabetic groups were established: Non-CCH Treated Diabetic (DNT), CCH Treated Diabetic (DCT), Non-CCH Vehicle Diabetic (DNV), and CCH Vehicle Diabetic (DCV). Vehicle groups were not treated with CBD. The animals were treated during 30 days with 10 mg CBD/Kg bw/day. After treatment, the animals were euthanized, and blood levels of glucose, insulin, total cholesterol, high density lipoprotein (HDL), low density lipoprotein (LDL), triglycerides, fructosamine, aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were evaluated. DCT group presented reduction of hyperglycemia and an increase of insulinemia. Also was observed lower fructosamine, LDL, HDL, triglycerides and total cholesterol levels. AST and ALT concentration were reduced in CBD treated groups. CBD may be used as therapeutic tool to protect metabolism against injuries from diabetes aggravated by cerebral ischemia.

Targeting GPCRs Activated by Fatty Acid-Derived Lipids in Type 2 Diabetes

G protein-coupled receptors (GPCRs) are the most intensively studied drug targets, because of their diversity, cell-specific expression, and druggable sites accessible at the cell surface. Preclinical and clinical studies suggest that targeting GPCRs activated by fatty acid-derived lipids may have potential to improve glucose homeostasis and reduce complications in patients with type 2 diabetes (T2D). Despite the discontinued development of fasiglifam (TAK-875), the first FFA1 agonist to reach late-stage clinical trials, lipid-sensing receptors remain a viable target, albeit with a need for further characterization of their binding mode, intracellular signaling, and toxicity. Herein, we analyze general discovery trends, various signaling pathways, as well as possible challenges following activation of GPCRs that have been validated clinically to control blood glucose levels.

The Bile Acid TUDCA Improves Beta-Cell Mass and Reduces Insulin Degradation in Mice With Early-Stage of Type-1 Diabetes

Type 1 diabetes (T1D) is characterized by impairment in beta-cell mass and insulin levels, resulting in hyperglycemia and diabetic complications. Since diagnosis, appropriate control of glycaemia in T1D requires insulin administration, which can result in side effects, such as hypoglycemia. In this sense, some bile acids have emerged as new therapeutic targets to treat T1D and T2D, as well as metabolic diseases. The taurine conjugated bile acid, tauroursodeoxycholic (TUDCA) reduces the incidence of T1D development and improves glucose homeostasis in obese and T2D mice. However, its effects in early-stage of T1D have not been well explored. Therefore, we have assessed the effects of TUDCA on the glycemic control of mice with early-stage T1D. To achieve this, C57BL/6 mice received intraperitoneal administration of streptozotocin (STZ, 40 mg/kg) for 5 days. Once diabetes was confirmed in the STZ mice, they received TUDCA treatment (300 mg/kg) or phosphate buffered saline (PBS) for 24 days. After 15 days of treatment, the STZ+TUDCA mice showed a 43% reduction in blood glucose, compared with the STZ group. This reduction was likely due to an increase in insulinemia. This increase in insulinemia may be explained, at least in part, by a reduction in hepatic IDE activity and, consequently, reduction on insulin clearance, as well as an increase in beta-cell mass and a higher beta-cell number per islet. Also, the groups did not present any alterations in insulin sensitivity. All together, these effects contributed to the improvement of glucose metabolism in T1D mice, pointing TUDCA as a potential therapeutic agent for the glycemic control in early-stage of T1D.

Atypical cannabinoid ligands O-1602 and O-1918 administered chronically in diet-induced obesity

Atypical cannabinoid compounds O-1602 and O-1918 are ligands for the putative cannabinoid receptors G protein-coupled receptor 55 and G protein-coupled receptor 18. The role of O-1602 and O-1918 in attenuating obesity and obesity-related pathologies is unknown. Therefore, we aimed to determine the role that either compound had on body weight and body composition, renal and hepatic function in diet-induced obesity. Male Sprague-Dawley rats were fed a high-fat diet (40% digestible energy from lipids) or a standard chow diet for 10 weeks. In a separate cohort, male Sprague-Dawley rats were fed a high-fat diet for 9 weeks and then injected daily with 5 mg/kg O-1602, 1 mg/kg O-1918 or vehicle (0.9% saline/0.75% Tween 80) for a further 6 weeks. Our data demonstrated that high-fat feeding upregulates whole kidney G protein receptor 55 expression. In diet-induced obesity, we also demonstrated O-1602 reduces body weight, body fat and improves albuminuria. Despite this, treatment with O-1602 resulted in gross morphological changes in the liver and kidney. Treatment with O-1918 improved albuminuria, but did not alter body weight or fat composition. In addition, treatment with O-1918 also upregulated circulation of pro-inflammatory cytokines including IL-1α, IL-2, IL-17α, IL-18 and RANTES as well as plasma AST. Thus O-1602 and O-1918 appear not to be suitable treatments for obesity and related comorbidities, due to their effects on organ morphology and pro-inflammatory signaling in obesity.

Role of Hippocampal Lipocalin-2 in Experimental Diabetic Encephalopathy

Diabetic encephalopathy is a severe diabetes-related complication in the central nervous system (CNS) that is characterized by degenerative neurochemical and structural changes leading to impaired cognitive function. While the exact pathophysiology of diabetic encephalopathy is not well-understood, it is likely that neuroinflammation is one of the key pathogenic mechanisms that cause this complication. Lipocalin-2 (LCN2) is an acute phase protein known to promote neuroinflammation via the recruitment and activation of immune cells and glia, particularly microglia and astrocytes, thereby inducing proinflammatory mediators in a range of neurological disorders. In this study, we investigated the role of LCN2 in multiple aspects of diabetic encephalopathy in mouse models of diabetes. Here, we show that induction of diabetes increased the expression of both Lcn2 mRNA and protein in the hippocampus. Genetic deficiency of Lcn2 significantly reduced gliosis, recruitment of macrophages, and production of inflammatory cytokines in the diabetic mice. Further, diabetes-induced hippocampal toxicity and cognitive decline were both lower in Lcn2 knockout mice than in the wild-type animals. Taken together, our findings highlight the critical role of LCN2 in the pathogenesis of diabetic encephalopathy.

Effects of Cannabidiol on Diabetes Outcomes and Chronic Cerebral Hypoperfusion Comorbidities in Middle-Aged Rats

Diabetes and aging are risk factors for cognitive impairments after chronic cerebral hypoperfusion (CCH). Cannabidiol (CBD) is a phytocannabinoid present in the Cannabis sativa plant. It has beneficial effects on both cerebral ischemic diseases and diabetes. We have recently reported that diabetes interacted synergistically with aging to increase neuroinflammation and memory deficits in rats subjected to CCH. The present study investigated whether CBD would alleviate cognitive decline and affect markers of inflammation and neuroplasticity in the hippocampus in middle-aged diabetic rats submitted to CCH. Diabetes was induced in middle-aged rats (14 months old) by intravenous streptozotocin (SZT) administration. Thirty days later, the diabetic animals were subjected to sham or CCH surgeries and treated with CBD (10 mg/kg, once a day) during 30 days. Diabetes exacerbated cognitive deficits induced by CCH in middle-aged rats. Repeated CBD treatment decreased body weight in both sham- and CCH-operated animals. Cannabidiol improved memory performance and reduced hippocampal levels of inflammation markers (inducible nitric oxide synthase, ionized calcium-binding adapter molecule 1, glial fibrillary acidic protein, and arginase 1). Cannabidiol attenuated the decrease in hippocampal levels of brain-derived neurotrophic factor induced by CCH in diabetic animals, but it did not affect the levels of neuroplasticity markers (growth-associated protein-43 and synaptophysin) in middle-aged diabetic rats. These results suggest that the neuroprotective effects of CBD in middle-aged diabetic rats subjected to CCH are related to a reduction in neuroinflammation. However, they seemed to occur independently of hippocampal neuroplasticity changes.

Generation and Biological Characteristics of a Mouse Model of Breast Cancer that Copresents with Diabetes Mellitus

Both diabetes and breast cancer are common diseases worldwide, and diabetes is also linked to higher rates of breast cancer. Epidemiological data also indicate that diabetes may be one of the risk factors for breast cancer. However, the effect of diabetes on breast cancer progression in vivo is rarely reported. We established an ideal animal model of breast cancer using transgenic MMTV-PyMT mice, which spontaneously developed breast cancer. In this model, the animals copresented with diabetes mellitus, which allowed us to study the effect of high glucose on breast cancer. Compared with MMTV-PyMT mice without diabetes, MMTV-PyMT mice with diabetes developed heavier tumors and exhibited greater tumor volumes. Furthermore, high glucose promoted the invasiveness and metastasis of breast cancer in MMTV-PyMT mice. This breast cancer model in which mice copresented with diabetes provides a useful tool to study the effect of diabetes on breast cancer. Anat Rec, 302:269-277, 2019. © 2018 Wiley Periodicals, Inc.

Endocannabinoids in the Islets of Langerhans: the ugly, the bad, and the good facts

The endocannabinoid system (ECS) regulates cellular homeostasis and whole-body metabolism. There is an autonomous ECS in the endocrine pancreas, including the cannabinoid 1 receptor (CB₁R) that is present in β-cells. Here, we discuss conflicts that have arisen with regard to the function(s) of the ECs in the endocrine pancreas and that have caused confusion when defining the role of the ECS in islets of Langerhans, especially the role(s) of CB₁R in β-cells. We also discuss the latest data published concerning the ECS in islets. CB₁R in particular is not simply a negative modulator of insulin secretion as it is also involved in intra-islet inflammation during high fat-high sugar intake and it is a negative regulator of β-cell viability and turnover. We also discuss the feasibility of using CB₁R as a target for the treatment of diabetes.

LH-21 and abnormal cannabidiol improve β-cell function in isolated human and mouse islets through GPR55-dependent and -independent signalling

AIMS

To examine the effects of Abn-CBD (GPR55 agonist) and LH-21 (CB1 antagonist) on human and mouse islet function, and to determine signalling via GPR55 using islets from GPR55^-/- mice.

MATERIALS AND METHODS

Islets isolated from human organ donors and mice were incubated in the absence or presence of Abn-CBD or LH-21, and insulin secretion, [Ca²⁺ ]_i, cAMP_, apoptosis, β-cell proliferation and CREB and AKT phosphorylation were examined using standard techniques.

RESULTS

Abn-CBD potentiated glucose-stimulated insulin secretion and elevated [Ca²⁺ ]_i in human islets and islets from both GPR55^+/+ and GPR55^-/- mice. LH-21 also increased insulin secretion and [Ca²⁺ ]_i in human islets and GPR55^+/+ mouse islets, but concentrations of LH-21 up to 0.1 μM were ineffective in islets from GPR55^-/- mice. Neither ligand affected basal insulin secretion or islet cAMP levels. Abn-CBD and LH-21 reduced cytokine-induced apoptosis in human islets and GPR55^+/+ mouse islets, and these effects were suppressed after GPR55 deletion. They also increased β-cell proliferation: the effects of Abn-CBD were preserved in islets from GPR55^-/- mice, while those of LH-21 were abolished. Abn-CBD and LH-21 increased AKT phosphorylation in mouse and human islets.

CONCLUSIONS

This study showed that Abn-CBD and LH-21 improve human and mouse islet β-cell function and viability. Use of islets from GPR55^-/- mice suggests that designation of Abn-CBD and LH-21 as a GPR55 agonist and a CB1 antagonist, should be revised.

Lysophosphatidylinositols, from Cell Membrane Constituents to GPR55 Ligands

Lysophosphatidylinositols (LPIs) are membrane constituents that alter the properties of said membranes. However, recent data showing that the once orphan receptor, GPR55, can act as a receptor for LPIs has sparked a renewed interest in LPIs as bioactive lipids. As evidence supporting the importance of LPIs and/or GPR55 is continuously accumulating and because LPI levels are altered in a number of pathologies such as obesity and cancer, the coming years should bring new, exciting discoveries to this field. In this review, we discuss the recent work on LPIs and on their molecular target, the GPR55 receptor. First, we summarize the metabolism of LPIs before outlining the cellular pathways activated by GPR55. Then, we review the actions of LPIs and GPR55 that could have potential pharmacological or therapeutic applications in several pathophysiological settings, such as cancer, obesity, pain, and inflammation.

GPR55: A therapeutic target for Parkinson's disease?

The GPR55 receptor is expressed abundantly in the brain, especially in the striatum, suggesting it might fulfill a role in motor function. Indeed, motor behavior is impaired in mice lacking GPR55, which also display dampened inflammatory responses. Abnormal-cannabidiol (Abn-CBD), a synthetic cannabidiol (CBD) isomer, is a GPR55 agonist that may serve as a therapeutic agent in the treatment of inflammatory diseases. In this study, we explored whether modulating GPR55 could also represent a therapeutic approach for the treatment of Parkinson's disease (PD). The distribution of GPR55 mRNA was first analyzed by in situ hybridization, localizing GPR55 transcripts to neurons in brain nuclei related to movement control, striatum, globus pallidus, subthalamic nucleus, substantia nigra and cortex. Striatal expression of GPR55 was downregulated in parkinsonian conditions. When Abn-CBD and CBD (5 mg/kg) were chronically administered to mice treated over 5 weeks with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine and probenecid (MPTPp), Abn-CBD but not CBD prevented MPTPp induced motor impairment. Although Abn-CBD protected dopaminergic cell bodies, it failed to prevent degeneration of the terminals or preserve dopamine levels in the striatum. Both compounds induced morphological changes in microglia that were compatible with an anti-inflammatory phenotype that did not correlate with a neuroprotective activity. The symptomatic relief of Abn-CBD was further studied in the haloperidol-induced catalepsy mouse model. Abn-CBD had an anti-cataleptic effect that was reversed by CBD and PSB1216, a newly synthesized GPR55 antagonist, and indeed, two other GPR55 agonists also displayed anti-cataleptic effects (CID1792197 and CID2440433). These results demonstrate for the first time that activation of GPR55 might be beneficial in combating PD.

An Overview on Medicinal Chemistry of Synthetic and Natural Derivatives of Cannabidiol

Cannabidiol (CBD) has been traditionally used in Cannabis-based preparation, however historically, it has received far less interest as a single drug than the other components of Cannabis. Currently, CBD generates considerable interest due to its beneficial neuroprotective, antiepileptic, anxiolytic, antipsychotic, and anti-inflammatory properties. Therefore, the CBD scaffold becomes of increasing interest for medicinal chemists. This review provides an overview of the chemical structure of natural and synthetic CBD derivatives including the molecular targets associated with these compounds. A clear identification of their biological targets has been shown to be still very challenging.

GPR55 and the regulation of glucose homeostasis

Pathophysiological conditions such as obesity and type 2 diabetes (T2D) are reportedly associated to over-activation of the endocannabinoid system (ECS). Therefore, modulation of the ECS offers potential therapeutic benefits on those diseases. GPR55, the receptor for L-α-lysophosphatidylinositol (LPI) that has also affinity for various cannabinoid ligands, is distributed at the central and peripheral level and it is involved in several physiological processes. This review summarizes the localization and role of GPR55 in tissues that are crucial for the regulation of glucose metabolism, and provides an update on its contribution in obesity and insulin resistance. Finally, the therapeutic potential of targeting the GPR55 receptor is also discussed.

GPR55: a new promising target for metabolism?

GPR55 is a G-protein-coupled receptor (GPCR) that has been identified as a new cannabinoid receptor. Given the wide localization of GPR55 in brain and peripheral tissues, this receptor has emerged as a regulator of multiple biological actions. Lysophosphatidylinositol (LPI) is generally accepted as the endogenous ligand of GPR55. In this review, we will focus on the role of GPR55 in energy balance and glucose metabolism. We will summarize its actions on feeding, nutrient partitioning, gastrointestinal motility and insulin secretion in preclinical models and the scarce data available in humans. The potential of GPR55 to become a new pharmaceutical target to treat obesity and type 2 diabetes, as well as the foreseeing difficulties are also discussed.