Untargeted Metabolomics Analysis of Chlorogenic Acid Using Rat Models with 5/6 Nephrectomy and Hyperuricemia

Abstract

Background: The mechanisms underlying the uric acid-lowering effect of chlorogenic acid (CGA) remain unclear. In this study, the therapeutic effects of CGA on rats were investigated using a 5/6 nephrectomy and hyperuricemia model and the related mechanisms were explored. Methods: The rat model with 5/6 nephrectomy and hyperuricemia was established. A total of 40 Sprague–Dawley rats were categorized into five groups, namely, control group, M group (no treatment), FT group (treatment with febuxostat), and LT group (treatment with CGA). Moreover, rats with 5/6 nephrectomy were categorized as the chronic kidney disease (CKD) group (n = 8). Blood biochemical indices; changes in renal and bone histomorphology; plasma metabolomics and changes in the metabolic spectrum; expression levels of toll-like receptor 4 (TLR4), intercellular adhesion molecule-1 (ICAM-1), fibronectin (FN1), and Beclin-1 (BECN1) in kidneys; expression levels of TLR4, ICAM-1, BECN1, and microtubule-associated proteins 1A/1B light chain 3B (LC3B) in the kidney tissue; and expression levels of matrix GLA protein (MGP) and TLR4 in the femur were evaluated. Results: Compared with the CKD group, serum levels of uric acid, creatinine, urea nitrogen, urinary protein, tartrate-resistant acid phosphatase (TRACP-5B), and β-CrossLaps (β-CTX); renal mRNA levels of ICAM-1 and FN1; and renal expression level of ICAM-1 were increased. However, the levels of 25-hydroxy vitamin D, blood calcium, and osteocalcin; renal mRNA levels of Beclin-1 and TLR4; and renal expression levels of LC3B, Beclin-1, and TLR4 were reduced in the M group. These changes were significantly alleviated using febuxostat or CGA (p < 0.05). In total, 903 metabolites were identified in the four groups in both positive and negative ion modes, and differential metabolites were mainly enriched in protein digestion and absorption, central carbon metabolism in carcinomas, ATP-binding cassette transporters, pyrimidine metabolism, mineral absorption, and amino acid biosynthesis. In the M group, febuxostat or CGA improved the renal and bone pathological changes and femoral expression levels of MGP and TLR4. Conclusions: This study is the first to show improvement in renal tubulointerstitial fibrosis and osteoporosis using CGA, which may be associated with autophagy activation regulated by TLR4. Untargeted metabolomics analysis revealed differential serum metabolites and metabolic pathways, thus providing a basis for using CGA to treat hyperuricemia in CKD.