Cardiovascular morbidity and mortality related to non-alcoholic fatty liver disease: a systematic review and meta-analysis of prospective studies

Background

Whether non-alcoholic fatty liver disease (NAFLD) is a risk factor for cardiovascular (CV) events is still debated. Currently available evidence derives from non-homogeneous studies yielding conflicting results.

Purpose

We set out to assess the relationship between NAFLD and CV morbidity and mortality by pooling results of previous studies.

Methods

We performed a systematic review and meta-analysis of prospective observational studies published from 1966 through 2021 reporting summary-level outcome data in subjects with and without NAFLD. Adjusted risk ratios (RRs) and 95% confidence intervals (CIs) for all-cause mortality, CV mortality, myocardial infarction (MI), stroke, major adverse cerebrocardiovascular events (MACCE) and atrial fibrillation (AF) were pooled through inverse variance random-effect meta-analysis to compute the summary effect size. We performed post-hoc subgroup analysis stratified by geographical region and univariate mixed-effect model meta-regression analysis to address statistical heterogeneity.

Results

We identified a total of 29 studies pooling an overall population of 5,626,573 middle-aged individuals (mean age 56±8; male sex 53%; NAFLD 5.8%, n=326,389). Mean follow-up was 10±6 years. Compared with control population, presence of NAFLD was associated with similar risk of all-cause death (RR 1.17; 95% CI 0.89–1.52) and CV death (RR 0.84; 95% CI 0.64–1.10). When analysed by geographic location, pooled estimates of RR (95% CI) for all-cause death were 1.57 (1.00–2.48) for Western countries, and 0.81 (0.52–1.1.26) for Eastern countries (test for subgroup difference, P=0.04). Meta-regression analysis showed a stronger relationship between NAFLD and all-cause mortality proportional to increasing body mass index (P=0.048). NAFLD was associated with increased risk of myocardial infarction (RR 1.35; 95% CI 1.09–1.68), stroke (RR 1.20; 95% CI 1.06–1.35), MACCE (RR 2.09; 95% CI 1.57–2.78) and atrial fibrillation (RR 1.37; 95% CI 1.05–1.78).

Conclusion

NAFLD portends excess all-cause mortality but only in Western countries. CV mortality was similar in NAFLD and non-NAFLD groups. NAFLD is associated with increased risk of incident MI, stroke, MACCE and AF.

Funding Acknowledgement

Type of funding sources: None. Figure 1Figure 2

Effects of phosphatidylcholine and sodium deoxycholate on human primary adipocytes and fresh human adipose tissue

Recent studies introduced the novel concept of chemical lipolysis where phosphatidylcholine (PC), an active component of commercial preparations, plays a pivotal role. Other studies suggested that sodium deoxycholate (DOC), an excipient contained in medical preparations, could be the real active component performing an adipocytolytic action. We investigated the effects of PC and DOC on human primary adipocyte cultures and on human fresh adipose tissue. Human adipocytes isolated by Rodbell's method, were cultured onto type I collagen-coated glass coverslips, placed into 24-well tissue culture plates. Cells were incubated with or without DOC (5-7-9%), PC (5%) or DOC/PC mixture and observed under phase contrast microscope. After incubation, cells were stained with Oil Red-O and with acridine orange/ethidium bromide to observe necrotic cells with phase contrast microscope and fluorescent microscope, respectively. Histological specimens from adipose tissue biopsies were observed with phase contrast microscopy and with scanning electron microscopy. To investigate the lipid pattern variability in the different experimental conditions, culture medium obtained from the different treatments was subjected to lipid extraction and subsequently to thin layer chromatography (TLC). Microscopic observation of adipocytes showed that DOC treatment led to a detrimental morphological effect in a dose-dependent manner. PC treatment did not significantly affect adipocyte viability. On the contrary, results from experiments aimed to analyze the effects of PC/DOC combined treatment suggested a PC protective role against the DOC harmful effects on adipocytes. Results indicated that clinical effects, observed in local treatment with pharmaceutical preparation, could be due only to DOC, a detergent inducing nonspecific lysis of cell membranes following adipocyte necrosis. On the other hand, PC could likely be incorporated in the lipid bilayer, thus strongly reducing the disruptive DOC effects.

Lipid Metabolism Impairment in Human Gliomas: Expression of Peroxisomal Proteins in Human Gliomas at Different Grades of Malignancy

Gliomas are histologically graded by cellularity, cytological atypia, necrosis, mitotic figures, and vascular proliferation, features associated with biologically aggressive behaviour. However, abundant evidence suggests the presence of unrecognized, clinically relevant subclasses of the diffuse gliomas, both in respect to their underlying molecular phenotype and their clinical response to therapy. It is well-known that patient prognosis and therapeutic decisions rely on accurate pathological grading. Recently, it was reported that human gliomas accumulate lipid droplets during progression, suggesting a lipid metabolism impairment. Considering the crucial role of peroxisomes in lipid metabolism, in the present work we studied the expression profiles of proteins either exclusively localized to peroxisomes, such as peroxin14 (PEX14), peroxisomal membrane protein 70Kda (PMP70), acyl-CoA oxidase, thiolase, or partially associated to peroxisomes such as Hydroxymethylglutaryl-CoA reductase (HMGCoA-red) and peroxisomal-related proteins, namely PPARa, in human glioma specimens at different grades of malignancy. Moreover, Nile red staining of lipid droplets, thin layer chromatography (TLC) and proton nuclear magnetic resonance spectroscopy (NMR) were carried out in order to correlate the biochemical results with the lipid content of tumor tissues. The results obtained indicate that correlating the malignancy grade with the expression of peroxisomal genes and proteins, may constitute a sensitive tool to highlight possible subtypes not recognized by the classical histological techniques.