Blood-derived lysophospholipid sustains hepatic phospholipids and fat storage necessary for hepatoprotection in overnutrition

The liver has a high demand for phosphatidylcholine (PC) particularly in overnutrition where reduced phospholipid levels have been implicated in the development of non-alcoholic fatty liver disease (NAFLD). Whether other pathways exist in addition to de novo PC synthesis that contribute to hepatic PC pools remains unknown. Here, we identified the lysophosphatidylcholine (LPC) transporter Mfsd2a as critical for maintaining hepatic phospholipid pools. Hepatic Mfsd2a expression was induced in patients having NAFLD and in mice in response to dietary fat via glucocorticoid receptor action. Mfsd2a liver-specific deficiency in mice (L2aKO) led to a robust NASH-like phenotype within just two weeks of dietary fat challenge associated with reduced hepatic phospholipids containing linoleic acid. Reducing dietary choline intake in L2aKO mice exacerbated liver pathology and deficiency of liver phospholipids containing polyunsaturated fatty acids (PUFA). Treating hepatocytes with LPC containing oleate and linoleate, two abundant blood-derived LPCs, specifically induced lipid droplet biogenesis and contributed to phospholipid pools, while LPC containing the omega-3 fatty acid DHA promoted lipid droplet formation and suppressed lipogenesis. This study revealed that PUFA containing LPCs drive both hepatic lipid droplet formation, suppress lipogenesis and sustain hepatic phospholipid pools--processes that are critical for protecting the liver from excess dietary fat.