Mediating role of TYG-BMI in vitamin D and nonalcoholic fatty liver disease

Abstract:

Objective To analyze the correlation between the serum vitamin D and triglyceride glucose-body mass index（TYG-BMI） of type 2 diabetes mellitus（T2DM） patients complicated with nonalcoholic fatty liver disease（NAFLD），and to explore the roles played by TYG-BMI in the vitamin D deficiency of T2DM living with NAFLD.Methods A total of 434 patients with T2DM hospitalized at Department of Endocrinology，Hebei General Hospital were included in the study. These patients’ demographics and clinical data were collected. Abdominal ultrasonography was performed to diagnose NAFLD. Vitamin D deficiency was defined as that 25-hydroxyvitamin D［25（OH）D］ vitamin levels were less than 20 ng/mL. Spearman correlation was used to test for an association among 25（OH）D，TYG-BMI and risk factors of NAFLD in T2DM. Multiple logistic regression was used to determine the association in 25（OH）D，TYG-BMI and NAFLD. Mediation analysis was used to explore whether TYG-BMI mediated the association between 25（OH）D and NAFLD.Results ①In all included T2DM patients，the 25（OH）D level in patients with NAFLD was significantly lower［15.89（12.33，19.94） vs. 18.27（14.05，24.63），P<0.05］ and TYG-BMI was significantly higher［213.59（191.92，237.60） vs. 176.91（159.55，196.86），P<0.05］ compared with those without NAFLD. The data showed the same trends for males and females（P<0.05）. ②According to different 25（OH）D levels，the prevalence of NAFLD in the vitamin D deficiency group（60.1%） was higher than that in the vitamin D insufficiency group（45.4%） and the vitamin D sufficiency group（23.3%），and the difference was statistically significant（P<0.05）. ③Serum 25（OH）D level was negatively correlated with TYG-BMI， both in women and in men（men： r=-0.215，P<0.001；women： r=-0.271，P<0.001）. ④After adjusting for confounding factors，multivariate logistic regression analysis revealed that Vitamin D deficiency was a risk factor for NAFLD in T2DM patients（Model 1 OR=2.347，95%CI=1.423-3.871，P=0.001；Model 2 OR=2.478，95%CI=1.472-4.172，P=0.001；Model 3 OR=2.057，95%CI=1.172–3.610，P=0.012）. Gender-specific subgroup logistic regression analyses showed vitamin D deficiency was an independent risk factor for NAFLD in T2DM for women（Model 1 OR=5.52，95%CI=2.008-15.177，P=0.001；Model 2 OR=5.342，95%CI=1.776-16.061，P=0.003；Model 3 OR=3.734，95%CI=1.108-12.578，P=0.034）. ⑤TYG-BMI was positively correlated with the prevalence of NAFLD in all T2DM patients，male patients and female patients（P<0.05）. ⑥Mediation analysis indicated that TYG-BMI partly mediated the indirect effect of 25（OH）D on NAFLD incidence（percentage of mediation： 58.66% of all patients，and 38.07% of female patients）.Conclusion Vitamin D deficiency is associated with an increased incidence of NAFLD only in female subjects with T2DM. The association between vitamin D deficiency and higher prevalence of NAFLD in T2DM may be at least partially mediated by TYG-BMI.