Activation of GPR81 by lactate drives tumour-induced cachexia.

Cachexia affects 50-80% of patients with cancer and accounts for 20% of cancer-related death, but the underlying mechanism driving cachexia remains elusive. Here we show that circulating lactate levels positively correlate with the degree of body weight loss in male and female patients suffering from cancer cachexia, as well as in clinically relevant mouse models. Lactate infusion per se is sufficient to trigger a cachectic phenotype in tumour-free mice in a dose-dependent manner. Furthermore, we demonstrate that adipose-specific G-protein-coupled receptor (GPR)81 ablation, similarly to global GPR81 deficiency, ameliorates lactate-induced or tumour-induced adipose and muscle wasting in male mice, revealing adipose GPR81 as the major mediator of the catabolic effects of lactate. Mechanistically, lactate/GPR81-induced cachexia occurs independently of the well-established protein kinase A catabolic pathway, but it is mediated by a signalling cascade sequentially activating Gi-Gßγ-RhoA/ROCK1-p38. These findings highlight the therapeutic potential of targeting GPR81 for the treatment of this life-threatening complication of cancer.

Higenamine, a Dual Agonist for ß 1- and ß 2-Adrenergic Receptors Identified by Screening a Traditional Chinese Medicine Library.

Chronic heart failure is the terminal stage of various cardiovascular diseases. Despite the availability of several classes of drugs, there is still an unmet need for effective treatment. Based on bench work during the past two decades, we have proposed that enhancement of ß 2-adrenergic receptor signaling in combination with the presently preferred ß 1-adrenergic receptor blockade would be a promising strategy. Chinese herbal medicines have been shown to be effective in the treatment of heart failure, although the mechanisms largely remain unknown. In the present study, we screened an herbal medicine compound/extract library for ß-adrenergic receptor ligands to determine the target of certain effective botanical remedies and seek a leading compound(s) for chronic heart failure treatment. Using a high-throughput screening assay, we identified higenamine, which has a long history in chronic heart failure treatment in traditional Chinese medicine, to be a potent ß-adrenergic receptor agonist. Further experiments using specific inhibitors showed that higenamine activated both ß 1-adrenergic receptor and ß 2-adrenergic receptor. Inhibition of its action by pertussis toxin (a Gi inhibitor) indicated that it is a ß 2-adrenergic receptor Gs/Gi dual agonist. Contractility experiments demonstrated a positive inotropic effect of higenamine. In conclusion, we found an herbal compound, higenamine, to be a dual agonist for ß 1/ß 2-adrenergic receptors with no preference in stimulating the Gs and Gi pathways in ß 2-adrenergic receptor signaling. Our results elucidated not only the target of higenamine to explain its pharmacological effect in treating chronic heart failure, but also the mechanisms of its cardiac toxicity.