Asymmetric dimethylarginine positively modulates Calcium-Sensing Receptor signalling to promote lipid accumulation and adiposity

Irreversible methylation of arginine residues generates asymmetric dimethylarginine (ADMA). ADMA is a competitive inhibitor of nitric oxide (NO) synthase and an independent risk factor for cardiovascular disease. Plasma ADMA concentrations increase with obesity and fall following weight loss. Here, we demonstrate that ADMA drives lipid accumulation through a newly identified NO-independent pathway via the amino-acid sensitive calcium-sensing receptor (CaSR). ADMA treatment of 3T3-L1 and HepG2 cells activates mTOR signalling and upregulates a suite of lipogenic genes with an associated increase in triglyceride content. Pharmacological blockade of CaSR inhibits ADMA driven lipid accumulation and ADMA treatment potentiates CaSR signalling via both Gq and Gi/o pathways. Impairment of ADMA metabolism in adipocytes in vivo , by dimethylamine dimethylaminohydrolase-1 (DDAH1) deletion, increases visceral adiposity and adipocyte hypertrophy. This study identifies a signalling mechanism for ADMA as an endogenous ligand of the G protein-coupled receptor CaSR that potentially contributes to the impact of ADMA in cardiometabolic disease. ### Competing Interest Statement JL is a founder, director and shareholder in Critical Pressure Ltd. Critical Pressure owns patents relating to small molecule inhibitors of enzymes that metabolise ADMA (dimethylarginine dimethylaminohydrolases, DDAH).