# In Vivo Absorption of Iron Complexes of Chondroitin Sulfates with Different Molecular Weights and Their Anti-Inflammation and Metabolism Regulation Effects on LPS-Induced Macrophages

## TL;DR

This study shows that low-molecular-weight chondroitin sulfate-iron complexes are better absorbed and more effective at reducing inflammation than standard forms.

## Contribution

The study demonstrates that molecular weight reduction and iron chelation enhance the bioavailability and anti-inflammatory effects of chondroitin sulfate.

## Key findings

- Low-molecular-weight chondroitin sulfate-iron complexes (LCS-Fe) showed higher blood absorption and liver accumulation than standard forms.
- CS-Fe and LCS-Fe more effectively inhibited inflammation markers like NO, COX-2, and IL-1β in LPS-induced macrophages.
- All tested compounds reversed about a quarter of LPS-induced metabolic changes, particularly affecting branched-chain amino acid biosynthesis.

## Abstract

The present study investigated the effects of hierarchical molecular weights and iron chelation on the in vivo absorption and the inflammatory bioactivity of chondroitin sulfate (CS). Firstly, CS, chondroitin sulfate-iron complex (CS-Fe), and low-molecular-weight chondroitin sulfate-iron complex (LCS-Fe) were fluorescently labeled and characterized. Then, the plasma concentration–time profiles and fluorescence imaging results demonstrated that LCS-Fe was more efficiently absorbed into the bloodstream and showed a higher Cmax (415.16 ± 109.50 μg/mL) than CS-Fe (376.60 ± 214.10 μg/mL) and CS (135.27 ± 236.82 μg/mL), and it clearly accumulated in the liver. Furthermore, the anti-inflammatory effect of CS-Fe and LCS-Fe was assayed in LPS-induced macrophages, and LCS-Fe and CS-Fe both showed a better inhibitory effect on NO production, COX-2 and IL-1β gene expression levels compared to CS. Additionally, targeted metabolic analysis of macrophages using LC-MS/MS revealed that CS, CS-Fe, and LCS-Fe could reverse approximately one quarter of the LPS-induced differential metabolites, and the biosynthesis of valine, leucine, and isoleucine was the most significantly involved metabolic pathway. Notably, the molecular weight reduction and iron chelation could both enhance the bioavailability and anti-inflammatory efficacy of CS.