Rsearchers from Zhejiang and Qingdao Universities say their study provides evidence that n-3 PUFA supplementation significantly reduces the alanine aminotransferase (ALT), aspartate aminotransferase (AST) and triglyceride (TAG) concentrations, and marginally reduces liver fat content.
“We believe that the results will have significant implications for treatment of NAFLD,” they wrote in the journal Clinical Nutrition.
Previously, they said blood and/or liver fatty acid contents of healthy subjects and non-alcoholic fatty liver disease (NAFLD) patients had shown inconsistent associations.
The same applied to the results of randomized controlled trials (RCTs) in relation to the effects of PUFA supplementation on ALT, AST and TAG, they said.
Therefore, their study aimed to investigate the differences of fatty acid content in the blood and/or liver tissue between healthy subjects and NAFLD patients, and to quantify the benefits of n-3 PUFA therapy in NAFLD patients.
A systematic literature search was performed up to November 2016 using PubMed and Scopus databases.
“The differences of fatty acid content between cases and controls were calculated as weighted mean differences (WMD) by using a random-effects model. The intervention effects of RCTs were calculated as WMD for net changes in ALT, AST, liver fat, TAG and fasting glucose levels, respectively.
“Meta-regression with restricted maximum likelihood estimation was used to evaluate a potential linear relationship between confounding factors and effect sizes. Generalized least square was performed for dose-response analysis.”
Ten eligible case-control studies and 11 RCTs were included. The pooled estimates showed that blood and/or liver DHA content was significantly higher in the controls compared with the cases.
“The meta-analysis of case-control studies was the first to investigate the differences of blood and/or liver fatty acid content between cases and controls,” they wrote.
“The pooled effects suggested a hypothesis that n-3 PUFA supplementation, especially DHA, might be beneficial for treatment of NAFLD. Second, there were a total of 11 RCTs with a considerably large sample-size, which provided a powerful statistical power to evaluate the pooled estimates.
“Furthermore, sensitivity analysis showed that the pooled estimates were not driven substantially with exclusion of any one trial at a time, suggesting the stability of the pooled effects.”
The researchers suggested three possible mechanisms through which n-3 PUFA supplementation improves NAFLD.
They said it may increase TAG synthesis and accelerate lipid oxidation in the liver, have a beneficial effect on the fluidity of cell membranes to reduce NAFLD risk, while its anti-inflammatory activities may stem the progression of the disease.
The study concluded that well-designed RCTs with a large sample-size should now be conducted to obtain the optimal dose and duration of n-3 PUFA supplementation for NAFLD therapy.
“Since EPA, DPA and DHA may have independent and shared effects for health benefits, the use of animal models with highly purified EPA, DPA and DHA treatment should be performed to investigate the molecular mechanisms of action for treatment of NAFLD,” they added.
Source: Clinical Nutrition
“Fatty acid and non-alcoholic fatty liver disease: Meta-analyses of case-control and randomized controlled trials”
Authors: Xiao-fei Guo et al.