Beneficial effects of inorganic nitrate in non-alcoholic fatty liver disease

The association between serum and urinary nitric oxide metabolites and fatty liver index: a population-based study

BACKGROUND AND AIM

We investigated the association between fasting serum and urinary nitric oxide metabolite (NOx) levels and fatty liver index (FLI), a non-invasive surrogate of non-alcoholic fatty liver disease (NAFLD) and liver steatosis.

METHOD

This cross-sectional study included 598 adults (aged≥18 years, 48.6% men) who participated in the Tehran Lipid and Glucose Study (2015-2017). Serum and urine NOx concentrations were quantified using a spectrophotometric method following the Griess reaction. FLI values were calculated using γ-glutamyl transferase, triglycerides, body mass index, and waist circumference. The associations between urinary and serum NOx-to-creatinine (Cr) ratio [either as a categorical variable, i.e., tertiles, or as a continuous variable, i.e., per 1 SD) with NAFLD (i.e., FLI≥60) were assessed using multivariable-adjusted binary logistic regression.

RESULTS

The study participants' mean (SD) age was 42.5±14.6 y. The mean (SD) of serum and urinary NOx was 37.5±16.7 and 1310±751 μmol/L, respectively. The mean (SD) of FLI was 43.3±30.2, and the prevalence of NAFLD was 32.4%. Serum NOx-to-Cr ratio was not associated with the chance of having NAFLD (OR=1.66, 95% CI=0.98-2.82; P value=0.058). Higher urinary NOx-to-Cr ratio was significantly associated with a reduced probability of NAFLD (OR=0.61, 95% CI=0.38-0.95, and OR=0.54, 95% CI=0.34-0.87, in the second and third tertiles).

CONCLUSION

Higher dietary nitrate (NO3) intake, indicated by increased urinary NOx-to-Cr ratio, is associated with a reduced probability of NAFLD, highlighting the potential role of dietary NO3 in liver health.

Liver sinusoidal endothelial cells: Friend or foe in metabolic dysfunction- associated steatotic liver disease/metabolic dysfunction-associated steatohepatitis

Metabolic dysfunction-associated steatotic liver disease (MASLD) is the predominant liver disease and is becoming the paramount contributor to end-stage liver disease and liver-related deaths. Liver sinusoidal endothelial cells (LSECs) located between the hepatic parenchyma and blood from viscera and gastrointestinal tract are the gatekeepers for the hepatic microenvironment and normal function. In normal physiological conditions, LSECs govern the substance exchange between hepatic parenchyma and blood through dynamic regulation of fenestration and maintain the quiescent state of Kupffer cells (KCs) and hepatic stellate cells. In MASLD, lipotoxicity, insulin resistance, gastrointestinal microbiota dysbiosis, and mechanical compression caused by fat-laden hepatocytes result in LSECs capillarization and dysfunction. The altered LSECs progressively shift from healer to injurer, exacerbating liver inflammation and advancing liver fibrosis. This review focuses on the deteriorative roles of LSECs and related molecular mechanisms involved in MASLD and their contribution to metabolic dysfunction-associated steatohepatitis (MASH) and liver fibrosis development and progression. Furthermore, in this review, we propose that targeting LSECs dysfunction is a prospective therapeutic strategy to restore the physiological function of LSECs and mitigate MASLD progression.

Associations between intake of different types of vegetables and metabolic dysfunction-associated fatty liver disease: a population-based study

BACKGROUND

Metabolic dysfunction-associated fatty liver disease (MAFLD) presently poses a threat to approximately 24% of the global population. The consumption of healthy diets rich in an abundant assortment of vegetables has been scientifically validated to mitigate the progression of MAFLD. However, it remains uncertain whether all categories of vegetables confer benefits for MAFLD. The objective of this study is to investigate the impact of different types of vegetables on MAFLD, aiming to provide a scientific basis for developing more appropriate dietary recommendations for individuals at high risk of MAFLD.

METHODS

We investigated the associations between various types of vegetable consumption and the risk of MAFLD, utilizing data sourced from the National Health and Nutrition Examination Survey (NHANES) 2017-2018 cycle. Employing multiple logistic regression and subgroup analyses, we estimated odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

Our analysis encompassed a total of 3162 participants. Remarkably, heightened intake of dark green vegetables demonstrated an innovative association with reduced odds of MAFLD (OR = 0.54; 95% CI: 0.36-0.81; p-value = 0.01), while other kinds of vegetable shown no significant association with MAFLD in the full adjusted model (all p-vale > 0.05). In the subgroup analysis, a prominent inverse correlation between the consumption of dark green vegetables and MAFLD was discerned among female and non-Hispanic white people with higher educational attainment.

CONCLUSIONS

Our study conclusively demonstrates that a heightened intake of dark green vegetables is linked to diminished odds of MAFLD.

An Analysis of the Gut Microbiota and Related Metabolites following PCSK9 Inhibition in Statin-Treated Patients with Elevated Levels of Lipoprotein(a)

BACKGROUND

Atherosclerotic cardiovascular disease (ASCVD) is a leading cause of global mortality, often associated with high blood levels of LDL cholesterol (LDL-c). Medications like statins and PCSK9 inhibitors, are used to manage LDL-c levels and reduce ASCVD risk. Recent findings connect the gut microbiota and its metabolites to ASCVD development. We showed that statins modulate the gut microbiota including the production of microbial metabolites involved in the regulation of cholesterol metabolism such as short chain fatty acids (SCFAs) and bile acids (BAs). Whether this pleiotropic effect of statins is associated with their antimicrobial properties or it is secondary to the modulation of cholesterol metabolism in the host is unknown. In this observational study, we evaluated whether alirocumab, a PCSK9 inhibitor administered subcutaneously, alters the stool-associated microbiota and the profiles of SCFAs and BAs.

METHODS

We used stool and plasma collected from patients enrolled in a single-sequence study using alirocumab. Microbial DNA was extracted from stool, and the bacterial component of the gut microbiota profiled following an amplicon sequencing strategy targeting the V3-V4 region of the 16S rRNA gene. Bile acids and SCFAs were profiled and quantified in stool and plasma using mass spectrometry.

RESULTS

Treatment with alirocumab did not alter bacterial alpha (Shannon index, p = 0.74) or beta diversity (PERMANOVA, p = 0.89) in feces. Similarly, circulating levels of SCFAs (mean difference (95% confidence interval (CI)), 8.12 [-7.15-23.36] µM, p = 0.25) and BAs (mean difference (95% CI), 0.04 [-0.11-0.19] log10(nmol mg-1 feces), p = 0.56) were equivalent regardless of PCSK9 inhibition. Alirocumab therapy was associated with increased concentration of BAs in feces (mean difference (95% CI), 0.20 [0.05-0.34] log10(nmol mg-1 feces), p = 0.01).

CONCLUSION

In statin-treated patients, the use of alirocumab to inhibit PCSK9 leads to elevated levels of fecal BAs without altering the bacterial population of the gut microbiota. The association of alirocumab with increased fecal BA concentration suggests an additional mechanism for the cholesterol-lowering effect of PCSK9 inhibition.

Long-term dietary nitrate supplementation slows the progression of established atherosclerosis in ApoE-/- mice fed a high fat diet

BACKGROUND AND AIMS

Atherosclerosis is associated with a reduction in the bioavailability and/or bioactivity of endogenous nitric oxide (NO). Dietary nitrate has been proposed as an alternate source when endogenous NO production is reduced. Our previous study demonstrated a protective effect of dietary nitrate on the development of atherosclerosis in the apoE-/- mouse model. However most patients do not present clinically until well after the disease is established. The aims of this study were to determine whether chronic dietary nitrate supplementation can prevent or reverse the progression of atherosclerosis after disease is already established, as well as to explore the underlying mechanism of these cardiovascular protective effects.

METHODS

60 apoE-/- mice were given a high fat diet (HFD) for 12 weeks to allow for the development of atherosclerosis. The mice were then randomized to (i) control group (HFD + 1 mmol/kg/day NaCl), (ii) moderate-dose group (HFD +1 mmol/kg/day NaNO3), or (iii) high-dose group (HFD + 10 mmol/kg/day NaNO3) (20/group) for a further 12 weeks. A group of apoE-/- mice (n = 20) consumed a normal laboratory chow diet for 24 weeks and were included as a reference group.

RESULTS

Long-term supplementation with high dose nitrate resulted in ~ 50% reduction in plaque lesion area. Collagen expression and smooth muscle accumulation were increased, and lipid deposition and macrophage accumulation were reduced within atherosclerotic plaques of mice supplemented with high dose nitrate. These changes were associated with an increase in nitrite reductase as well as activation of the endogenous eNOS-NO pathway.

CONCLUSION

Long-term high dose nitrate significantly attenuated the progression of established atherosclerosis in the apoE-/- mice fed a HFD. This appears to be mediated in part through a XOR-dependent reduction of nitrate to NO, as well as enhanced eNOS activation via increased Akt and eNOS phosphorylation.

Analysis of environmental chemical mixtures and nonalcoholic fatty liver disease: NHANES 1999-2014

We aimed to investigate the associations between chemical mixtures and the risk of nonalcoholic fatty liver disease (NAFLD) in this study. A total of 127 exposure analytes within 13 chemical mixture groups were included in the current analysis. Associations between chemical mixture exposure and prevalence of NAFLD were examined using weighted quantile sum (WQS) regressions. NAFLD was diagnosed by hepatic steatosis index (HSI) and US fatty liver index (USFLI). In USFLI-NAFLD cohort, chemical mixtures positively associated with NAFLD development included urinary metals (OR: 1.10, 95% CI: 1.04-1.16), urinary perchlorate, nitrate and thiocyanate (OR: 1.06, 95% CI: 1.02-1.11), urinary pesticides (OR: 1.24, 95% CI: 1.09-1.40), urinary phthalates (OR: 1.18, 95% CI: 1.09-1.28), urinary polyaromatic hydrocarbons (PAHs) (OR: 1.08, 95% CI: 1.03-1.14), and urinary pyrethroids, herbicides, and organophosphate pesticides metabolites (OR: 1.32, 95% CI: 1.15-1.51). All of the above mixtures were also statistically significant in WQS regressions in the HSI-NAFLD cohort. Besides, some chemical mixtures were only significant in HSI-NAFLD cohort including urinary arsenics (OR: 1.07, 95% CI: 1.02-1.12), urinary phenols (OR: 1.10, 95% CI: 1.02-1.19) and blood polychlorinated dibenzo-p-dioxins (OR: 1.10, 95% CI: 1.03-1.17). Three types of chemical mixtures only showed significant associations in the healthy lifestyle score (HLS) of 3-4 subgroup, including urinary perchlorate, nitrate and thiocyanate, urinary PAHs and blood polychlorinated dibenzo-p-dioxins. In conclusion, the exposure of specific types of chemical mixtures were associated with elevated NAFLD risk, and the effects of some chemical mixtures on NAFLD development exhibited differences in participants with different lifestyles.

Nitrate exposure reprograms hepatic amino acid and nutrient sensing pathways prior to exercise: A metabolomic and transcriptomic investigation in zebrafish (Danio rerio)

Scope: Nitrate supplementation is a popular ergogenic aid that improves exercise performance by reducing oxygen consumption during exercise. We investigated the effect of nitrate exposure and exercise on metabolic pathways in zebrafish liver.

Materials and methods: Fish were exposed to sodium nitrate (606.9 mg/L), or control water, for 21 days and analyzed at intervals during an exercise test. We utilized untargeted liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis and measured gene expression of 24 genes central to energy metabolism and redox signaling.

Results: We observed a greater abundance of metabolites involved in endogenous nitric oxide (NO) metabolism and amino acid metabolism in nitrate-treated liver at rest, compared to rested controls. In the absence of exercise, nitrate treatment upregulated expression of genes central to nutrient sensing (pgc1a), protein synthesis (mtor) and purine metabolism (pnp5a and ampd1) and downregulated expression of genes involved in mitochondrial fat oxidation (acaca and cpt2).

Conclusion: Our data support a role for sub-chronic nitrate treatment in the improvement of exercise performance, in part, by improving NO bioavailability, sparing arginine, and modulating hepatic gluconeogenesis and glycolytic capacity in the liver.

Associations between intake of starchy and non-starchy vegetables and risk of hepatic steatosis and fibrosis

BACKGROUND

Current dietary guidelines generally treat all types of vegetables the same. However, whether specific vegetables are more beneficial or deleterious for preventing chronic liver disease (CLD) remains uncertain.

METHODS

We investigated the associations between starchy and non-starchy vegetables and the odds of hepatic steatosis and fibrosis in a US nationwide cross-sectional study. Diet was assessed by the 24-h dietary recalls. Hepatic steatosis and fibrosis were defined based on vibration-controlled transient elastography (TE). Multiple logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

Among 4170 participants with reliable TE test, 1436 were diagnosed with steatosis, 255 with advanced fibrosis. Increased intake of total starchy vegetables was associated with higher odds of steatosis (OR per 1-SD increment 1.11, 95% CI 1.01-1.24) and advanced fibrosis (OR = 1.39, 95% CI 1.15-1.69). Similar positive associations were observed for potatoes. Conversely, intakes of total non-starchy (OR = 0.82, 95% CI 0.71-0.95) and dark-green vegetables (OR = 0.89, 95% CI 0.82-0.97) were inversely associated with steatosis prevalence. Replacing 5% of energy from starchy vegetables (OR = 0.65, 95% CI 0.44-0.97) or potatoes (OR = 0.65, 95% CI 0.43-0.97) with equivalent energy from dark-green vegetables was associated with lower odds of steatosis.

CONCLUSIONS

These findings support the recommendation to limit starchy vegetable intake and increase non-starchy vegetable intake in CLD prevention, and provide evidence for the potential health benefit from dietary substitution of non-starchy vegetables for starchy vegetables.

Beneficial Effects of Dietary Nitrite on a Model of Nonalcoholic Steatohepatitis Induced by High-Fat/High-Cholesterol Diets in SHRSP5/Dmcr Rats: A Preliminary Study

Nonalcoholic steatohepatitis (NASH) is a chronic liver disease that leads to liver cirrhosis and hepatocellular carcinoma. Endothelial dysfunction caused by hepatic lipotoxicity is an underlying NASH pathology observed in the liver and the cardiovascular system. Here, we evaluated the effect of dietary nitrite on a rat NASH model. Stroke-prone, spontaneously hypertensive 5/Dmcr rats were fed a high-fat/high-cholesterol diet to develop the NASH model, with nitrite or captopril (100 mg/L, each) supplementation in drinking water for 8 weeks. The effects of nitrite and captopril were evaluated using immunohistochemical analyses of the liver and heart tissues. Dietary nitrite suppressed liver fibrosis in the rats by reducing oxidative stress, as measured using the protein levels of nicotinamide adenine dinucleotide phosphate oxidase components and inflammatory cell accumulation in the liver. Nitrite lowered the blood pressure in hypertensive NASH rats and suppressed left ventricular chamber enlargement. Similar therapeutic effects were observed in a captopril-treated rat NASH model, suggesting the possibility of a common signaling pathway through which nitrite and captopril improve NASH pathology. In conclusion, dietary nitrite attenuates the development of NASH with cardiovascular involvement in rats and provides an alternative NASH therapeutic strategy.