The role of exercise in limiting progression from liver inflammation and fibrosis to cirrhosis and carcinoma: a systematic review with meta-analysis of human and animal studies

BackgroundExercise may prevent the progression of liver disease and protect against liver cancer. This review with meta-analysis synthesised the evidence from both human and animal studies to better understand whether exercise has the capacity to (i) promote regression of early fibrosis; (ii) decrease and/or delay progression to cirrhosis; and (iii) progression to carcinoma. MethodsA systematic search was performed to identify studies comprising of humans and animals with liver disease that compared exercise to an inactive or less active control. Outcomes included liver disease regression and progression, and markers of liver function and damage. ResultsWe found 18 human and 29 animal studies. A single study provided direct evidence that exercise can reverse NAFLD and decrease progression to cirrhosis. Meta-analysis of human studies identified decreases in liver enzymes; ALT (SMD = -0.28, 95%CI = -0.53, -0.03), AST (SMD = -0.12, 95%CI = -0.32, 0.07), GGT (SMD = -0.23, 95%CI = -0.36, -0.10), as well as a small increase in ALP (SMD = 0.23, 95%CI = -0.13, 0.59), and liver triglycerides (SMD = -0.24, 95%CI = -0.66, 0.18). Meta-analysis of animal studies identified decreases in liver enzymes; ALT (SMD = -2.85, 95%CI = -4.55, -1.14), AST (SMD = -2.85, 95%CI = -4.55, -1.14), and liver triglycerides (SMD = -1.36, 95%CI = -2.08, -0.65), liver weight (SMD = -1.94, 95%CI = -2.78, - 1.10), and the NAFLD activity score (SMD = -1.36, 95%CI = -2.08, -0.65). ConclusionOnly one study provided direct evidence that exercise has the capacity to regress early fibrosis, as well as delay the progression to cirrhosis. Several studies, however, indicate that exercise intervention reduce markers of liver function and damage.