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.