Effect of Vitamin E on Clinical Outcomes in Patients With Non-alcoholic Fatty Liver Disease: A Meta-Analysis

Vitamin E for people with non-alcoholic fatty liver disease

RATIONALE

Non-alcoholic fatty liver disease (NAFLD), recently renamed metabolic dysfunction-associated steatotic liver disease (MASLD), is the most common liver disease worldwide, affecting an estimated 3 in 10 people. The available treatment is far from optimal. Diet and lifestyle changes to promote weight loss and weight loss maintenance are the basic management of NAFLD, but these are difficult to achieve and maintain. Vitamin E has shown beneficial effects on oxidative stress, which plays a major role in the pathogenesis of NAFLD. However, there is uncertainty about the effects of vitamin E for people with NAFLD.

OBJECTIVES

To evaluate the beneficial and harmful effects of vitamin E alone, or vitamin E in combination with other vitamins or minerals, versus placebo or no intervention in people with NAFLD.

SEARCH METHODS

We used recommended Cochrane search methods. The latest search was performed on 2 February 2024.

ELIGIBILITY CRITERIA

We included randomised clinical trials that compared vitamin E alone, or in combination with other vitamins or minerals, at any dose, duration, and route of administration, versus placebo or no intervention, in people with NAFLD of any age, sex, or ethnic origin. We included participants with imaging techniques or histology-proven NAFLD and minimal alcohol intake, and participants with steatohepatitis who had liver biopsies.

OUTCOMES

Our critical outcomes were all-cause mortality, liver-related mortality, and serious adverse events. Our important outcomes were liver-related morbidity, health-related quality of life, non-serious adverse events, biochemical response, and imaging assessment of the degree of fatty liver.

RISK OF BIAS

We used Cochrane's RoB 2 tool to assess risk of bias for each of the predefined outcomes.

SYNTHESIS METHODS

We used standard Cochrane methods. We used GRADE to assess the certainty of evidence.

INCLUDED STUDIES

We included 16 randomised clinical trials involving 1066 paediatric and adult participants with NAFLD. Experimental groups received vitamin E alone (14 trials) or vitamin E in combination with vitamin C (2 trials). Control groups received placebo in 13 trials and no intervention in three trials. Daily dosages of oral vitamin E ranged from 298 international units (IU) to 1000 IU. Co-interventions were lifestyle and low-calorie diet interventions in 13 trials, ursodeoxycholic acid in one trial, unchanged diet and physical activity in one trial, and baseline treatments for type 2 diabetes in one trial. Nine trials had more than two intervention groups, but we used only the groups in which vitamin E alone or vitamin E in combination with vitamin C were compared with placebo or no intervention. In total, 7.9% (84/1066) of participants dropped out. Follow-up ranged from 2 months to 24 months.

SYNTHESIS OF RESULTS

Vitamin E versus placebo or no intervention The effects of vitamin E versus placebo or no intervention on all-cause mortality (risk ratio (RR) 3.45, 95% confidence interval (CI) 0.57 to 20.86; 3 trials, 351 participants; very low certainty evidence) and serious adverse events (RR 1.91, 95% CI 0.30 to 12.01; 2 trials, 283 participants; very low certainty evidence) are very uncertain. There were no data on liver-related mortality or liver-related morbidity. The effects of vitamin E versus placebo or no intervention on physical health-related quality of life (mean difference (MD) 0.74, 95% CI -0.52 to 2.01; 2 trials, 251 participants; higher scores indicate better quality of life; very low certainty evidence); psychosocial health-related quality of life (MD -0.57, 95% CI -4.11 to 2.97; 2 trials, 251 participants; higher scores indicate better quality of life; very low certainty evidence); and non-serious adverse events (RR 0.86, 95% CI 0.64 to 1.17; 2 trials, 283 participants; very low certainty evidence) are also very uncertain. There were no data on proportion of participants without a decrease in liver enzymes. Vitamin E likely slightly reduces serum alanine transaminase (ALT) (MD -9.29, 95% CI -13.69 to -4.89; 11 trials, 708 participants; moderate certainty evidence) and aspartate aminotransferase (AST) (MD -4.90, 95% CI -7.24 to -2.57; 11 trials, 695 participants; moderate certainty evidence) levels compared with placebo or no intervention. Vitamin E may slightly reduce serum alkaline phosphatase (ALP) levels (MD -5.21, 95% CI -9.88 to -0.54; 5 trials, 416 participants; very low certainty evidence), but the evidence is very uncertain. Vitamin E plus vitamin C versus placebo There were no data on all-cause mortality, liver-related mortality, serious adverse events, liver-related morbidity, health-related quality of life, and non-serious adverse events. The effects of vitamin E plus vitamin C on reducing serum ALT (MD -0.50, 95% CI -4.58 to 3.58; 2 trials, 133 participants; very low certainty evidence), AST (MD 0.09, 95% CI -3.39 to 3.57; 1 trial, 88 participants; very low certainty evidence), and gamma-glutamyl transferase (GGT) levels (MD 1.58, 95% CI -3.22 to 6.38; 1 trial, 88 participants; very low certainty evidence) are very uncertain. We identified three ongoing trials, and six trials are awaiting classification.

AUTHORS' CONCLUSIONS

Given the very low certainty evidence, we do not know if long-term treatment (18 months to 24 months) with vitamin E administered alone affects all-cause mortality, serious adverse events, quality of life, or non-serious adverse events in people with NAFLD when compared with placebo or no intervention. We found no data on liver-related mortality, liver-related morbidity, or proportion of participants without a decrease in liver enzymes. Vitamin E likely reduces ALT and AST slightly when compared with placebo, but whether this has any impact on the clinical course in people with NAFLD is unknown. The trials on vitamin E plus vitamin C did not report on all-cause mortality, liver-related mortality, serious adverse events, liver-related morbidity, health-related quality of life, or non-serious adverse events. Given the very low certainty evidence, we do not know the effects of vitamin E plus vitamin C on liver enzymes in people with NAFLD when compared with placebo.

FUNDING

Three trials disclosed no external funding. Five trials were industry funded. Five trials were funded by organisations with no vested interests. Three trials did not provide any information on clinical trial support or sponsorship.

REGISTRATION

Protocol: doi.org/10.1002/14651858.CD015033.

The Interplay between Liver and Adipose Tissue in the Onset of Liver Diseases: Exploring the Role of Vitamin Deficiency

The deficiency of vitamins, a condition known as "hidden hunger", causes comprehensive pathological states. Research over the years has identified a relationship between liver diseases and hypovitaminosis or defects in vitamin metabolism. The exact mechanisms remain elusive; however, the crucial involvement of specific vitamins in metabolic functions, alongside the reclassification of liver disease as metabolic dysfunction-associated steatotic liver disease (MASLD), has prompted researchers to investigate the potential cause-effect dynamics between vitamin deficiency and liver disease. Moreover, scientists are increasingly investigating how the deficiency of vitamins might disrupt specific organ crosstalk, potentially contributing to liver disease. Although the concept of a dysmetabolic circuit linking adipose tissue and the liver, leading to liver disease, has been discussed, the possible involvement of vitamin deficiency in this axis is a relatively recent area of study, with numerous critical aspects yet to be fully understood. In this review, we examine research from 2019 to July 2024 focusing on the possible link between liver-adipose tissue crosstalk and vitamin deficiency involved in the onset and progression of non-alcoholic fatty liver disease (NAFLD). Studies report that vitamin deficiency can affect the liver-adipose tissue axis, mainly affecting the regulation of systemic energy balance and inflammation.

Diet, exercise, and supplements: what is their role in the management of the metabolic dysfunction-associated steatotic liver disease in children?

Metabolic dysfunction-associated steatotic liver disease (MASLD), previously known as nonalcoholic fatty liver disease (NAFLD), is the main cause of chronic liver disease in children and adolescents. Indeed, epidemiological studies have shown that MASLD affects up to 40% of children with obesity. Despite the recent approval of medications that target weight loss in adolescents that could have benefits on pediatric MASLD, lifestyle interventions, such as diet and exercise, remain the mainstay of our therapeutic approach. More specifically, studies on diet alone have focused on the possible role of carbohydrate or fat restriction, albeit without a definite answer on the best approach. Weight loss after dietary intervention in children with obesity and MASLD has a beneficial effect, regardless of the diet used. In relation to the role of exercise in MASLD reversal, indirect evidence comes from studies showing that a sedentary lifestyle leading to poor fitness, and low muscle mass is associated with MASLD. However, research on the direct effect of exercise on MASLD in children is scarce. A combination of diet and exercise seems to be beneficial with several studies showing improvement in surrogate markers of MASLD, such as serum alanine aminotransferase and hepatic fat fraction, the latter evaluated with imaging studies. Several dietary supplements, such as vitamin E, probiotics, and omega-3 fatty acid supplements have also been studied in children and adolescents with MASLD, but with equivocal results. This review aims to critically present available data on the effects of lifestyle interventions, including diet, exercise, and dietary supplements, on pediatric MASLD, thus suggesting a frame for future research that could enhance our knowledge on pediatric MASLD management and optimize clinicians' approach to this vexing medical condition.

A Narrative Review of Oxidative Stress and Liver Disease in Pregnancy: The Role of Antioxidants

Pregnancy brings numerous physiological changes to the body of the pregnant woman. Liver diseases in pregnancy contribute to increased oxidative stress, disrupting the delicate balance between reactive oxygen species and antioxidant defence. Antioxidant supplementation may have potential benefits in addressing pregnancy-related liver disorders, such as HELLP (haemolysis, elevated liver enzymes, low platelet count) and preeclampsia-associated liver dysfunction in pregnancy. The purpose of this narrative review is to review the evidence regarding oxidative stress in liver disorders during pregnancy and the role of antioxidants in alleviating oxidative stress and its effect on maternal and foetal outcomes. A narrative review study design involved a comprehensive search across three scientific databases: PubMed, Embase, and MEDLINE, published in the last 20 years. The searches were performed up to January 2024. Thirty-two studies were included in the narrative review. The most studied antioxidants were vitamins (vitamin C and E) for their role in clinical treatment, prophylaxis, and clearing surrogate oxidative stress markers. The majority of studies were on preeclampsia. Though the existing literature is not robust, available evidence suggests that antioxidant supplementation may have potential benefits in addressing pregnancy-related liver disorders, such as HELLP and preeclampsia-associated liver dysfunction in pregnancy. However, there is a need to establish consistent protocols, ethical standards, and well-designed clinical trials to clarify the timing and dosage of antioxidants in pregnancy. Antioxidants may alleviate the oxidative stress in various liver disorders during pregnancy, which still needs to be studied further for their clinical relevance.

Study on the mechanism of vitamin E alleviating non-alcoholic fatty liver function based on non-targeted metabolomics analysis in rats

Non-alcoholic fatty liver disease (NAFLD) is a hepatic manifestation of metabolic syndrome. Vitamin E (VE) has antioxidant properties and can mediate lipid metabolism. Non-targeted metabolomics technology was employed to uncover comprehensively the metabolome of VE in NAFLD rats. NAFLD model was created with a high-fat and high-cholesterol diet (HFD) in rats. NAFLD rats in the VE group were given 75 mg/(kg day) VE. The metabolites in the serum of rats were identified via UPLC and Q-TOF/MS analysis. KEGG was applied for the pathway enrichment. VE improved the liver function, lipid metabolism, and oxidative stress in NAFLD rats induced by HFD. Based on the metabolite profile data, 132 differential metabolites were identified between VE group and the HFD group, mainly including pyridoxamine, betaine, and bretylium. According to the KEGG results, biosynthesis of cofactors was a key metabolic pathway of VE in NAFLD rats. VE can alleviate NAFLD induced by HFD, and the underlying mechanism is associated with the biosynthesis of cofactors, mainly including pyridoxine and betaine.