Alginate oligosaccharides attenuate obesity-associated kidney injury through modulation of the intestinal environment with renoprotection transferable by small intestinal contents.

Background: High-fat diet (HFD)-induced obesity is closely associated with metabolic imbalance and kidney injury. Alginate oligosaccharides (AOS) are considered promising dietary bioactive compounds; however, whether they protect against obesity-associated renal damage has not been fully clarified. In this study, we investigated whether AOS ameliorates renal injury in HFD-fed mice and further used transplantation of small intestinal contents to explore the possible involvement of gut-derived factors. Methods: After AOS treatment, metabolic parameters, renal function, kidney histopathology, and related pathological alterations were evaluated. For the transplantation experiment, small intestinal contents collected from control or AOS-treated donor mice were administered to HFD-fed recipient mice, after which renal and metabolic phenotypes were assessed. Results: AOS improved HFD-induced metabolic disorders and alleviated renal injury. Mice treated with AOS showed lower serum blood urea nitrogen and creatinine levels, reduced renal lipid accumulation, and attenuated inflammatory and oxidative stress-related changes. Notably, recipient mice receiving small intestinal contents from AOS-treated donors also exhibited partial improvement in these abnormalities, whereas contents from control donors showed weaker or less consistent effects. These findings suggest that AOS-associated alterations in small intestinal contents may contribute to the observed renoprotective effects. Conclusion: AOS attenuated obesity-associated renal injury in HFD-fed mice, and this effect was at least partially transferable through transplantation of small intestinal contents. This study provides supportive evidence that gut-derived factors are involved, at least in part, in the renoprotective effects associated with AOS.