Dendrobium officinalis six nostrum ameliorates urate under-excretion and protects renal dysfunction in lipid emulsion-induced hyperuricemic rats

Abstract

Aim: Hyperuricemia (HUA) is a metabolic disease caused by the overproduction or underexcretion of uric acid (UA). Our previous study found that treatment with Dendrobium officinalis six nostrum (DOS) led to a significant reduction in serum UA (SUA) by inhibiting UA production and promoting UA excretion in a rat model of HUA induced by potassium oxonate (PO) and high-fat sorghum feed. In this study, we aimed to further investigate the effects of DOS on UA excretion by the kidney and intestine to explore whether DOS protects against histopathological changes, and to elucidate its possible mechanisms of action in a lipid emulsion (LE)-induced rat model of HUA.

Methods: The main chemical constituents of DOS were determined to be acteoside and astilbin by high-performance liquid chromatography (HPLC). Three different doses of DOS (3.3, 6.6, and 13.2 g/kg/day) were given to rats daily after induction of HUA by oral administration of LE for 8 weeks. The levels of creatinine (Cr) in serum and urine and UA in serum, urine, and feces were measured by an automatic biochemical analyzer. The expression of TLR4, NF-κB and urate transport-related transporters (URAT1, ABCG2, and PDZK1) in kidney was measured by Western blot (WB). Intestinal urate transporters (ABCG2 and GLUT9) expression was assayed by IHC and WB. Serum LPS and renal inflammatory factors (IL-6, IL-8 and TNF-α) levels were measured using enzyme-linked immunosorbent assay (ELISA) kits. Hematoxylin and eosin (H&E) staining was used to assess renal histological changes.

Results: DOS treatment significantly reduced the SUA and SCr levels by increasing urine volume, 24 h urine uric acid (UUA), fecal UA (FUA), urine creatinine (UCr), and fractional excretion of UA (FEUA) levels in hyperuricemic rats. Moreover, DOS effectively regulated URAT1, PDZK1, and ABCG2 protein levels in the kidney, as well as restored protein levels of GLUT9 and ABCG2 in the intestine. DOS markedly reduced serum LPS anddown-regulated renal TLR4 and NF-κB protein levels to suppress IL-6, IL-8, and TNF-α secretion. It also improved renal inflammation in hyperuricemic rats. In addition, DOS attenuated histopathological changes in the kidneys of LE-induced rats. HPLC analysis showed levels of acteoside and astilbin of 1.39 mg/g and 0.72 mg/g in DOS, respectively.

Conclusion: DOS has anti-hyperuricemic and anti-inflammatory effects in a rat model of HUA. The molecular mechanism appears to involve the regulation of urate transport-related transporters including renal ABCG2, URAT1, and PDZK1, and intestinal GLUT9 and ABCG2, as well as the inhibition of the LPS/TLR4/NF-κB signaling to reduce IL-6, IL-8, and TNF-α secretion in hyperuricemic rats.

Keywords: Dendrobium officinalis six nostrum; Hyperuricemia; Renal inflammation; Urate transporter.