BACKGROUND & AIMS:Some patients with SARS-CoV-2 infection have abnormal liver function. We aimed to clarify the features of COVID-19-related liver damage to provide references for clinical treatment. METHODS:We performed a retrospective, single-center study of 148 consecutive patients with confirmed COVID-19 (73 female, 75 male; mean age, 50 years) at the Shanghai Public Health Clinical Center from January 20 through January 31, 2020. Patient outcomes were followed until February 19, 2020. Patients were analyzed for clinical features, laboratory parameters (including liver function tests), medications, and length of hospital stay. Abnormal liver function was defined as increased levels of alanine and aspartate aminotransferase, gamma glutamyltransferase, alkaline phosphatase, and total bilirubin. RESULTS:Fifty-five patients (37.2%) had abnormal liver function at hospital admission; 14.5% of these patients had high fever (14.5%), compared with 4.3% of patients with normal liver function (P [ .027). Patients with abnormal liver function were more likely to be male, and had higher levels of procalcitonin and C-reactive protein. There was no statistical difference between groups in medications taken before hospitalization; a significantly higher proportion of patients with abnormal liver function (57.8%) had received lopinavir/ritonavir after admission compared to patients with normal liver function (31.3%). Patients with abnormal liver function had longer mean hospital stays (15.09 -4.79 days) than patients with normal liver function (12.76 -4.14 days) (P [ .021). CONCLUSIONS:More than one third of patients admitted to the hospital with SARS-CoV-2 infection have abnormal liver function, and this is associated with longer hospital stay. A significantly higher proportion of patients with abnormal liver function had received lopinavir/ritonavir after admission; these drugs should be given with caution.

Gut microbiota has been well recognized in regulation of intestinal homeostasis and pathogenesis of inflammatory bowel diseases. However, the mechanisms involved are still not completely understood. Further, the components of the microbiota which are critically responsible for such effects are also largely unknown. Accumulating evidence suggests that, in addition to pathogen-associated molecular patterns (PAMP), nutrition and bacterial metabolites might greatly impact the immune response in the gut and beyond. Short-chain fatty acids (SCFA), which are metabolized by gut bacteria from otherwise indigestible fiber-rich diets, have been shown to ameliorate diseases in animal models of inflammatory bowel diseases (IBD) and allergic asthma. Although the exact mechanisms for the action of SCFA are still not completely clear, most notable among the SCFA targets is the mammalian G protein-coupled receptor pair of GPR41 and GPR43. In addition to the well-documented inhibition of histone deacetylases (HDAC) activity mainly by butyrate and propionate, which causes anti-inflammatory activities on IEC, macrophages, and dendritic cells, SCFA has recently been implicated in promoting development of Treg cells and possibly other T cells. In addition to animal models, the beneficial effects have also been reported from the clinical studies that used SCFA therapeutically in controlled trial settings in inflammatory disease, in that application of SCFA improved indices of IBD and therapeutic efficacy was demonstrated in acute radiation proctitis. In this review article, we will summarize recent progresses of SCFA in regulation of intestinal homeostasis as well as in pathogenesis of IBD.

Innate lymphoid cells (ILCs) and CD4+ T cells produce IL-22, which is critical for intestinal immunity. The microbiota is central to IL-22 production in the intestines; however, the factors that regulate IL-22 production by CD4+ T cells and ILCs are not clear. Here, we show that microbiota-derived short-chain fatty acids (SCFAs) promote IL-22 production by CD4+ T cells and ILCs through G-protein receptor 41 (GPR41) and inhibiting histone deacetylase (HDAC). SCFAs upregulate IL-22 production by promoting aryl hydrocarbon receptor (AhR) and hypoxia-inducible factor 1α (HIF1α) expression, which are differentially regulated by mTOR and Stat3. HIF1α binds directly to the Il22 promoter, and SCFAs increase HIF1α binding to the Il22 promoter through histone modification. SCFA supplementation enhances IL-22 production, which protects intestines from inflammation. SCFAs promote human CD4+ T cell IL-22 production. These findings establish the roles of SCFAs in inducing IL-22 production in CD4+ T cells and ILCs to maintain intestinal homeostasis.