Gut-directed supplements partially shield mice from chemotherapy intestinal injury

Melphalan, a drug used at high doses to prepare patients with multiple myeloma for autologous stem-cell transplantation, frequently damages the intestinal lining, triggering mucositis, diarrhea, and an elevated risk of infection.

The researchers first built a mouse model of melphalan-induced intestinal toxicity. In a dose-optimization phase, C57BL/6 mice received oral melphalan at doses ranging from 10 to 60 milligrams per kilogram. Doses of 30 milligrams per kilogram and above killed animals within two to four days, and a validation run at 20 milligrams per kilogram also proved lethal by day four. Only the 10 milligram per kilogram dose produced measurable toxicity—body-weight loss and reduced feed intake—without any mortality, so it was selected for the main experiment. For context, the authors note that high-dose melphalan conditioning in patients corresponds numerically to roughly 3.6 to 5.2 milligrams per kilogram for a 70-kilogram adult, though they stress this is not a direct cross-species conversion because simple weight scaling ignores differences in drug metabolism and exposure.

In the main study, 30 mice of both sexes were randomly split into five groups of six: a vehicle control, melphalan alone, and three melphalan-plus-intervention arms. Each intervention was given orally once daily for three days before and three days after a single oral dose of melphalan. The researchers then measured body weight, small-intestinal length, plasma biomarkers, intestinal protein expression, and a targeted panel of gut metabolites.

Melphalan alone left a clear signature of intestinal damage. Treated mice lost body weight and showed significant shortening of the small intestine. Their plasma citrulline—a biomarker that reflects functional enterocyte mass and is widely used to gauge epithelial injury after intensive chemotherapy—dropped, while circulating lipopolysaccharide (LPS), a component of bacterial membranes that should normally be confined to the gut lumen, rose. Plasma occludin, an exploratory indicator of epithelial tight-junction disruption, also increased. Together, these changes point to enterocyte loss and a leakier intestinal barrier, allowing luminal bacterial products to slip into the bloodstream. Histopathology confirmed the picture: melphalan-only animals showed lamina propria inflammation, mucosal ulceration, and occasional villous shortening compared with largely normal vehicle-control tissue.

The metabolic consequences were equally broad. Using a targeted liquid chromatography–tandem mass spectrometry method developed in-house, the team quantified short-chain fatty acids (SCFAs), bile acids, and indole-derived tryptophan metabolites in cecal contents. Compared with vehicle controls, melphalan-treated mice had significantly lower levels of the bile acids deoxycholic acid, taurocholate, and lithocholic acid, and significantly lower levels of all four measured tryptophan-derived metabolites: indole-3-propionic acid, indole-3-acetic acid, indole-3-aldehyde, and tryptamine. Among SCFAs, valerate, isovalerate, acetate, propionate, and iso-butyrate all fell significantly, while the drop in butyrate did not reach statistical significance. These metabolite classes matter because they participate in epithelial energy metabolism, immune regulation, and maintenance of the mucosal barrier, so their depletion describes an intestinal environment less supportive of tissue repair.

All three interventions partially attenuated the physiological and barrier-related damage. FOS, the probiotic preparation, and chlorophyllin each reduced body-weight loss and restored small-intestinal length and plasma-marker levels toward vehicle-control values, though the magnitude and statistical significance varied. In the repeated-measures analysis of body weight, Dunnett-adjusted comparisons found significantly less weight loss with FOS on day three relative to melphalan alone, while chlorophyllin was actually associated with greater weight loss on day one. Small-intestinal length was significantly preserved in the FOS and probiotic groups, but the chlorophyllin comparison was not significant. On the plasma side, all three interventions generally raised citrulline and lowered LPS and occludin relative to melphalan alone, with the probiotic group showing the lowest mean LPS concentration among the intervention arms.

The metabolite recovery patterns were strikingly intervention-specific. FOS and the probiotic preparation significantly increased deoxycholic acid and lithocholic acid, and both significantly raised taurocholate, as did chlorophyllin—making taurocholate the one bile acid lifted by all three treatments. None of the interventions changed cholic acid significantly. In the SCFA panel, FOS and the probiotic preparation significantly increased valerate, acetate, and propionate; FOS additionally raised isovalerate, and the probiotic alone raised iso-butyrate. Chlorophyllin produced no significant changes in any of the six measured SCFAs. In the tryptophan-derived panel, the probiotic preparation and chlorophyllin significantly increased indole-3-propionic acid and indole-3-acetic acid, while FOS did not. Indole-3-aldehyde and tryptamine rose descriptively in the intervention groups but never reached significance.

The team also looked for links between gut chemistry and barrier integrity. Pooling individual animals across all five groups, they found a significant inverse Spearman correlation between plasma citrulline and circulating LPS (rs = −0.5493, p = 0.002), meaning animals with lower citrulline tended to have higher LPS. The authors caution that this pooled association may partly reflect differences between treatment groups and does not establish causation. Descriptively, group-level changes in acetate, butyrate, and indole-3-acetic acid paralleled changes in citrulline across treatments, but these patterns were not used for inferential testing. Western blotting on small-intestinal tissue, with three biological samples per group, suggested that melphalan increased TLR2 and SOD1 expression and reduced claudin-1, with partial reversal under chlorophyllin—though these findings were descriptive rather than statistically tested.

Several important caveats temper the findings. After cecal samples under 50 milligrams were excluded by a pre-set criterion, the metabolomic analysis rested on just three biological samples per group, which the authors acknowledge limits statistical power and precision; they explicitly label the metabolite results exploratory and in need of confirmation in larger studies. Multiple-comparison adjustment was applied within each metabolite but not across metabolites. Histopathological abnormalities, including crypt loss, persisted in all intervention groups at day three without consistent normalization, meaning the interventions improved physiological and plasma markers even as structural injury remained visible; later time points would be needed to track recovery. Microbial composition was not directly assessed, so the metabolite shifts cannot be tied to specific microbiome changes, and because the probiotic was given as a commercial fermented-milk product, the contributions of the Shirota strain and the milk matrix itself cannot be separated.

Even with those limits, the study adds a useful layer to a growing literature on managing chemotherapy-induced gastrointestinal toxicity. It shows that melphalan injury in mice is accompanied by coordinated, measurable disruption of the gut’s SCFA, bile-acid, and tryptophan-metabolite pools, and that nutritionally distinct interventions can partially restore different slices of that chemistry while easing barrier dysfunction. The authors position the work as a rationale for further investigation of gut-directed nutritional strategies to mitigate chemotherapy-associated intestinal injury—not as evidence for clinical use.

Subject of Research: Effects of prebiotic, probiotic, and chlorophyllin interventions on melphalan-induced intestinal injury and gut metabolite profiles in mice

Article Title: Prebiotic, probiotic, and chlorophyllin interventions differentially attenuate melphalan-induced intestinal injury and modulate gut metabolite profiles

Article References: Redhu, A. K., Puia, S., Chavan, N., Ali, R., Das, A., Kodolikar, K., Das, G., Kadam, S., Pal, K., & Gota, V. (2026). Prebiotic, probiotic, and chlorophyllin interventions differentially attenuate melphalan-induced intestinal injury and modulate gut metabolite profiles. Frontiers in Microbiology, 17, 2003316. https://doi.org/10.3389/fmicb.2026.2003316

Image Credits: AI Generated

DOI: 10.3389/fmicb.2026.2003316

Keywords: melphalan, intestinal mucositis, fructo-oligosaccharides, probiotics, Lacticaseibacillus paracasei Shirota, chlorophyllin, short-chain fatty acids, bile acids, indole derivatives, gut barrier, plasma citrulline, chemotherapy toxicity