Author response to Letter to the Editor: Potential implications of COVID-19 in non-alcoholic fatty liver disease.

Dear Editor,

We are grateful to Grietje H. Prins et al for their interest in our recent article regarding the characteristics and mechanisms of liver damage caused by three highly pathogenic coronavirus infections and for their valuable insights on the liver injury among COVID‐19. ,

Grietje H. Prins et al came up with a link between non‐alcoholic fatty liver diseases (NAFLD) and COVID‐19. Ji et al analysed 202 consecutive COVID‐19 patients and found that the patients with NAFLD had higher likelihood of abnormal liver function, longer viral shedding time, and a higher risk of disease progression to severe COVID‐19 compared with non‐NAFLD patients. On the other hand, progressive severe COVID‐19 patients had higher body mass index (BMI) and percentage of comorbidity including hypertension, diabetes and cardiovascular disease. A large cohort study also confirmed that COVID‐19 patients with abnormal liver function test results had a higher BMI and tended to have pre‐existing liver diseases, including NAFLD. The high prevalence of NAFLD has been fuelled by unhealthy lifestyles worldwide; a large population might be at risk of severe COVID‐19.

The role of NAFLD involving in severity of COVID‐19 remains unclear. NAFLD has been associated with increased production of inflammatory cytokines which might contribute to severe clinical outcomes of COVID‐19, further study is warranted. The usage of angiotensin‐converting enzyme inhibitors (ACE‐Is) in hypertension patients has been considered to increase the expression of ACE2 receptor in the liver and promoting SARS‐COV‐2 susceptibility and disease severity of COVID‐19. However, the results from Cai's study showed that the hypertension patients treated with ACE‐Is/angiotensin receptor blockers (ARBs) drugs were not increased the incidence of progressing to severe COVID‐19 compared to the patients taking other antihypertensive drugs.

It is worth noting that NAFLD was renamed as metabolic (dysfunction)‐associated fatty liver disease (MAFLD) recently. The diagnosis criteria of MAFLD are independent of the amount of alcohol consumed and based on evidence of hepatic steatosis, in addition to one of the following criteria, overweight/obesity, the presence of type 2 diabetes mellitus or evidence of metabolic dysregulation. For establishing reliable cohort studies to investigate the role of MAFLD in COVID‐19, it is strongly recommended to evaluate the hepatic steatosis with abdominal ultrasound or computed tomography examination when patients admitted to hospital.

CONFLICT OF INTEREST

The authors disclose no conflict of interest.

AUTHOR CONTRIBUTIONS

Xin Zheng designed and planned the work, and revised the manuscript. Ling Xu and Jia Liu performed the literature search and interpretation, and manuscript drafting. Mengji Lu and Dongliang Yang helped revise the manuscript.