Early kidney injury in patients with non-alcoholic fatty liver disease: a cross-sectional study

Objective To investigate early kidney injury in the patients with non-alcoholic fatty liver disease (NAFLD) without hypertension, diabetes and history of kidney diseases, as so to provide evidence for preventing early kidney injury in patients with NAFLD. Methods From December 2014 to January 2016, 169 subjects visiting Sichuan Provincial People′s Hospital were recruited. Among them, 104 cases were in NAFLD group, 31 cases were in simple obesity group (overweight or obesity), and 34 subjects were in the healthy control group. The general data, biochemical indexes, metabolic indexes, biochemical indexes of kidney, and early kidney injury makers, including serum β2-microglobulin, urinary albumin and creatinine ratio (ACR) and estimated glomerular filtration rate (eGFR), were detected. Least significant difference-t test, chi-square test and Spearman correlation analysis were performed for statistical analysis. Results Compared with simple obesity group, alanine aminotransferase (ALT), aspartate aminotransferase (AST), γ-glutamyl transpeptadase (GGT), fasting insulin level, homeostasis model assessment-insulin resistance (HOMA-IR), serum creatinine, ACR and β2 microglobulin were higher in NAFLD group ((21.13±8.14) U/L vs. (66.20±44.34) U/L, (24.80±9.57) U/L vs. (49.78±25.41) U/L, (19.26±7.88) U/L vs. (66.53±56.34) U/L, (7.03±1.52) mU/L vs. (9.55±5.41) mU/L, 1.22±0.38 vs. 2.23±2.01, (62.90±10.01) μmol/L vs. (71.75±10.80) μmol/L, (4.41±1.16) μg/mg vs. (13.76±9.56) μg/mg, (1.46±0.26) mg/L vs. (2.01±0.53) mg/L); however the eGFR was lower (112.46±11.90) mL·min-1·(1.73 m2)-1 vs. (101.09±17.17) mL·min-1·(1.73 m2)-1). The differences were statistically significant (t=9.825, 8.250, 8.288, 4.229, 4.121, 4.007, 9.732, 7.792 and -3.443, all P 0.05). Compared with healthy control group, the renal injury indexes serum creatinine, ACR and β2 microglobulin of NAFLD group were higher((58.78±7.77) μmol/L vs. (71.75±10.80) μmol/L, (1.01±0.32) μg/mg vs. (13.76±9.56) μg/mg, (1.12±0.15) mg/L vs. (2.01±0.53) mg/L), and the eGFR was lower ((115.10±12.59) mL·min-1·(1.73 m2)-1 vs. (101.09±17.17) mL·min-1·(1.73 m2)-1). The differences were statistically significant (t=7.621, 13.591, 15.126 and -5.120, all P<0.01). Compared with healthy control group, the renal injury indexes ACR and β2 microglobulin of simple obesity group were higher ((1.01±0.32) μg/mg vs. (4.41±1.16) μg/mg, (1.12±0.15) mg/L vs. (1.46±0.26) mg/L), and the differences were statistically significant (t=9.732 and 7.792, both P<0.01). ACR of NAFLD patients was positively correlated with body mass index, waist circumference, triglyceride level, total cholesterol level, low density lipoprotein level, fasting blood glucose level, two-hour postprandial blood glucose, fasting insulin level and HOMA-IR (r=0.554, 0.327, 0.314, 0.353, 0.176, 0.195, 0.552, 0.364 and 0.987, all P<0.05), and was negatively correlated with high density lipoprotein (r=-0.330, P<0.01). Conclusions NAFLD is closely related with chronic kidney disease at same baseline of gender, age, blood glucose, blood lipids, and blood pressure. Abnormal metabolism of glycolipids, obesity and insulin resistance may be the mechanisms of early kidney injury in NAFLD patients. Combination of ACR and β2 microglobulin are more sensitive than serum creatinine and eGFR in detecting early renal injury in NAFLD patients. Key words: Nonalcoholic fatty liver disease; Obesity; Chronic kidney disease; Early kidney injury