Liver mitochondrial DNA damage and genetic variability of Cytochrome b - a key component of the respirasome - drive the severity of fatty liver disease.

BACKGROUND AND AIMS: The progression of nonalcoholic fatty liver disease (NAFLD) into severe histological forms (steatohepatitis - NASH) is paralleled by the occurrence of complex molecular processes. Mitochondrial dysfunction is a hallmark feature of advanced disease. Mitochondrially encoded cytochrome B (cytochrome b, MT-CYB), a member of the oxidative phosphorylation system, is a key component of the respirasome supercomplex. Here, we hypothesized that NAFLD severity is associated with liver tissue cytochrome b mutations and damaged mitochondrial DNA (mtDNA). METHODS: We included 252 liver specimens of NAFLD patients - in whom histological disease ranged from mild to severe - which were linked to clinical and biochemical information. Tissue molecular explorations included MT-CYB sequencing and analysis of differential mtDNA damage. Profiling of circulating Krebs cycle metabolites and global liver transcriptome was performed in a subsample of patients. Tissue levels of 4-hydroxynonenal - a product of lipid peroxidation and 8-hydroxy-2'-deoxyguanosine, a marker of oxidative damage - were measured. RESULTS: Compared to simple steatosis, NASH is associated with a higher level of MT-CYB variance, 12.1 vs. 15.6 substitutions per 103  bp (P = 5.5e-10). The burden of variants was associated with increased levels of 2-hydroxyglutarate, branched-chain amino acids, and glutamate, and changes in the global liver transcriptome. Liver mtDNA damage was associated with advanced disease and inflammation. NAFLD severity was associated with increased tissue levels of DNA oxidative adducts and lipid peroxyl radicals. CONCLUSION: NASH is associated with genetic alterations of the liver cellular respirasome, including high cytochrome b variation and mtDNA damage, which may result in broad cellular effects.

Mendelian randomisation suggests no beneficial effect of moderate alcohol consumption on the severity of nonalcoholic fatty liver disease.

BACKGROUND: Previous epidemiological studies suggest that patients diagnosed with nonalcoholic fatty liver disease (NAFLD) who drink light to moderate amounts of alcohol (up to ~30 g per day) have less severe histological lesions compared with nondrinkers. However, while the cross-sectional nature of current evidence precludes assessment of causality, cumulative lifetime-exposure of moderate alcohol consumption on histological outcomes has never been evaluated. AIM: To overcome these limitations, a Mendelian randomisation study was performed using a validated genetic variant (rs1229984 A;G) in the alcohol dehydrogenase (ADH1B) gene as a proxy of long-term alcohol exposure. METHODS: We first assessed whether the instrumental variant (rs1229984) was associated with the amount of alcohol consumption in our cohort. We further explored the association between the variant and histological outcomes; a sample of 466 individuals, including 266 patients with NAFLD confirmed by liver biopsy, was studied. RESULTS: We found that carriers of the A-allele consumed significantly lower amounts of alcohol compared with noncarriers (2.3 ± 5.3 vs. 8.18 ± 21 g per day, mean ± s.d., P = 0.03). The analysis of association with the disease severity showed that carriers of the A-allele had lower degree of histological steatosis (1.76 ± 0.83 vs. 2.19 ± 0.78, P = 0.03) and lower scores of lobular inflammation (0.54 ± 0.65 vs. 0.95 ± 0.92, P = 0.02) and NAFLD-Activity Score (2.9 ± 1.4 vs. 3.7 ± 1.4, P = 0.015) compared with noncarriers. CONCLUSION: Mendelian randomisation analysis suggests no beneficial effect of moderate alcohol consumption on NAFLD disease severity.

Obesity, metabolic profile, and inhibition failure: Young women under scrutiny.

BACKGROUND: The prevalence of obesity, as well as evidence about this pathology as a risk factor for cognitive decline and dementia in the elderly, is increasing worldwide. Executive functions have been found to be compromised in most studies, although the specific results are dissimilar. Obese young women constitute an interesting study and intervention group, having been found to be unaffected by age and hormonal negative effects on cognition and considering that their health problems affect not only themselves but their families and offspring. The objective of the present study was to compare the executive performance of obese young women with that of a healthy control group. METHODS: A cross-sectional study was done among premenopausal women from a public hospital in Buenos Aires. The sample comprised 113 participants (32 healthy controls and 81 obese women), who were evaluated for depressive and anxiety symptoms (Beck Depression Inventory-II and State-Trait Anxiety Inventory) and executive functioning (Trail-Making Test B, Stroop Color and Word Test, Wisconsin Card Sorting Test, and verbal fluency test). Statistical analysis was done by using the SPSS version 20.0 software. RESULTS: Among executive functions, a significant difference was found between groups in inhibition (p<0.01). No correlation was found between psychopathologic measures and Stroop Test Interference results. We found slight correlations between Stroop Test Interference results, waist circumference, fat mass and HDL-cholesterol. In obese group, there was a negative slightly correlation between this cognitive test and 2h post-load glucose level. CONCLUSIONS: Inhibition was decreased in our obese young women group, and glucose/lipid metabolism may be involved in this association. The cognitive impairment is comparable with that described in addictive conditions. Our conclusions support the concept of multidisciplinary management of obese patients from the time of diagnosis. Detecting and understanding cognitive dysfunction in this population is essential to providing appropriate treatment.