Background: Obesity is an established risk factor for higher SARS-CoV-2 viral loads, severe COVID-pneumonia requiring hospitalization, and worse outcomes. However, the underlying mechanisms for the increased risk are not well understood. SARS-CoV-2 is a respiratory virus with the primary route of entry through lungs, where the Spike protein of SARS-CoV-2 binds to ACE2 receptor on pneumocytes. Lung surfactant produced by type II pneumocytes plays a major role in respiratory defense against infections. Surfactant predominantly contains lipids especially phosphatidylcholines (PC) and obesity is characterized by aberrant lipid metabolism. We hypothesized that altered lipid composition in lung surfactant in obesity may promote SARS-CoV-2 infection, leading to severe COVID-disease.
Methods: Lipidomic analysis of lung tissue and bronchoalveolar lavage fluid (BALF) was performed using LC-MS/MS. The effects of PCs on SARS-CoV-2 pseudovirus infection were studied in HEK293T cells with ACE2 overexpression and in Vero-E6 cells with endogenous ACE2 expression.
Results: Lipidomic analysis revealed that myristic acid containing dimyristoyl-PC (DMPC) and palmitoylmirystoyl-PC (PMPC) were commonly reduced in lung tissue and BALF from high fat diet-induced obese mice. DMPC and PMPC markedly inhibited wild type and D614G mutant SARS-CoV-2 infection in HEK293T-ACE2 and Vero-E6 cells. Feeding obese mice with trimyristin, the triglycerides of myristic acid, increased DMPC and PMPC in lung surfactant. Lipid extract from BALF of trimyristin-treated obese mice reduced wild type and D614G mutant SARS-CoV-2 infection. The inhibitory effects of DMPC and PMPC on SARS-CoV-2 infection were reversed by cholesterol.
Conclusions: The reduced DMPC and PMPC in lung surfactant contributes to the increased SARS-CoV-2 infection. Increasing DMPC and PMPC in lung surfactant may be an innovative strategy for preventing and treating severe COVID-disease in obesity.
K.Du: None. L.Sun: None. Z.Luo: None. Y.Cao: None. J.Shan: None. Q.Yang: None.
National Institutes of Health (R01DK121146) ;Pacific Life Foundation Fellowship to UC Irvine Diabetes Center;Chinese National Natural Science Foundation (No.81774156)