β3-adrenoceptor-mediated increased circulating transaminase levels in mice treated with its agonist BRL 37344

In silico identification of a biarylamine acting as agonist at human β3 adrenoceptors and exerting BRL37344-like effects on mouse metabolism

Human β3-adrenoceptor (β3AR) agonists were considered potential agents for the treatment of metabolic disorders. However, compounds tested as β3AR ligands have shown marked differences in pharmacological profile in rodent and human species, although these compounds remain attractive as they were successfully repurposed for the therapy of urinary incontinence. In this work, some biarylamine compounds were designed and tested in silico as potential β3AR agonists on 3-D models of mouse or human β3ARs. Based on the theoretical results, we identified, synthesized and tested a biarylamine compound (polibegron). In CHO-K1 cells expressing the human β3AR, polibegron and the β3AR agonist BRL 37344 were partial agonists for stimulating cAMP accumulation (50 and 57% of the response to isoproterenol, respectively). The potency of polibegron was 1.71- and 4.5-fold higher than that of isoproterenol and BRL37344, respectively. These results indicate that polibegron acts as a potent, but partial, agonist at human β3ARs. In C57BL/6N mice with obesity induced by a high-fat diet, similar effects of the equimolar intraperitoneal administration of polibegron and BRL37344 were observed on weight, visceral fat and plasma levels of glucose, cholesterol and triglycerides. Similarities and differences between species related to ligand-receptor interactions can be useful for drug designing.

[Investigation of Predisposition Biomarkers to Identify Risk Factors for Drug-induced Liver Injury in Humans: Analyses of Endogenous Metabolites in an Animal Model Mimicking Human Responders to APAP-induced Hepatotoxicity]

Drug-induced liver injury is a main reason of regulatory action pertaining to drugs, including restrictions to clinical indications and withdrawal from the marketplace. Acetaminophen (APAP) is a commonly used and effective analgesic/antipyretic agent and relatively safe drug even in long-term treatment. However, it is known that APAP at therapeutic doses may cause hepatotoxicity in some individuals. Hence great efforts have been made to identify risk factors for APAP-induced chronic hepatotoxicity. We investigated the contribution of undernourishment to susceptibility to APAP-induced chronic hepatotoxicity using an animal model. We employed daytime restricted fed (RF) rats as a modified-nutritional state model for human APAP-induced hepatotoxicity. RF and ad libitum fed (ALF) rats were given APAP at 0, 300, and 500 mg/kg for 3 months. Plasma and urinary glutathione-related metabolomes and liver function parameters were measured during the dosing period. Endogenous metabolites forming at different levels between the RF and ALF rats could be potential predisposition biomarkers for APAP-induced hepatotoxicity. In addition, RF rats were considered a useful model to estimate the contribution of nutritional state of patients to APAP-induced chronic hepatotoxicity. In this article we report our current research focusing on nutritional state as risk factor for APAP-induced chronic hepatotoxicity and our findings of hepatotoxicity biomarkers.

Antihypernociceptive activity of anethole in experimental inflammatory pain

Anethole has been reported to have antioxidant, antibacterial, antifungal, antiinflammatory, and anesthetic properties. In the present study, we evaluated the effects of anethole in two pain models of inflammatory origin: acute inflammation induced by carrageenan and persistent inflammation induced by Complete Freund's adjuvant. We evaluated the effects of anethole (125, 250, and 500 mg/kg) on the development of paw oedema and mechanical hypernociception. The liver was collected for histological analysis. Paw skin was collected to determine the levels of the cytokines tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), interleukin-17 (IL-17), and myeloperoxidase activity. Blood was collected to assess alanine transaminase (ALT) and aspartate transaminase (AST). The chemical composition of star anise oil was determined by gas chromatography/mass spectrometry (GC/MS), showing a presence of anethole of 98.1%. Oral pretreatment with anethole in mice inhibited paw oedema, mechanical pernociception, myelopewroxidase activity, TNF-α, IL-1β and IL-17 levels in acute and persistent inflammation models. Additionally, anethole treatment did not alter prostaglandin E2-induced mechanical hypernociception. Possible side effects were also examined. Seven-day anethole treatment did not alter plasma AST and ALT levels, and the histological profile of liver tissue was normal. The present study provides evidence of the antiinflammatory and analgesic activities of anethole in acute and persistent inflammation models.

Effects of Citrus aurantium (bitter orange) fruit extracts and p-synephrine on metabolic fluxes in the rat liver

The fruit extracts of Citrus aurantium (bitter orange) are traditionally used as weight-loss products and as appetite supressants. An important fruit component is p-synephrine, which is structurally similar to the adrenergic agents. Weight-loss and adrenergic actions are always related to metabolic changes and this work was designed to investigate a possible action of the C. aurantium extract on liver metabolism. The isolated perfused rat liver was used to measure catabolic and anabolic pathways, including oxygen uptake and perfusion pressure. The C. aurantium extract and p-synephrine increased glycogenolysis, glycolysis, oxygen uptake and perfusion pressure. These changes were partly sensitive to α- and β-adrenergic antagonists. p-Synephrine (200 μM) produced an increase in glucose output that was only 15% smaller than the increment caused by the extract containing 196 μM p-synephrine. At low concentrations the C. aurantium extract tended to increase gluconeogenesis, but at high concentrations it was inhibitory, opposite to what happened with p-synephrine. The action of the C. aurantium extract on liver metabolism is similar to the well known actions of adrenergic agents and can be partly attributed to its content in p-synephrine. Many of these actions are catabolic and compatible with the weight-loss effects usually attributed to C. aurantium.