Effects of L-selenomethylselenocysteine-fortified milk powder on immune homeostasis, intestinal integrity, and gut microbiota in immunosuppressed mice.
Immunosuppression is strongly associated with impaired intestinal health and perturbations in gut microbial composition. This study aimed to evaluate the regulatory effects of L-selenomethylselenocysteine (L-SeMC) fortified milk powder on immune function and gut microbiota in cyclophosphamide (CTX)-induced immunosuppressed mice, and to compare its efficacy with selenium-enriched yeast (SY) and sodium selenite (Na2SeO3). The results demonstrated that L-SeMC intervention significantly mitigated CTX-induced weight loss and markedly enhanced thymus and spleen indices. L-SeMC effectively boosted splenic lymphocyte proliferation and significantly reduced the serum levels of pro-inflammatory cytokines compared with the model group. Histologically, L-SeMC alleviated pathological damage in the spleen, liver, and intestine, notably restoring jejunal villus height and the villus-to-crypt (V/C) ratio. Moreover, L-SeMC significantly increased gut microbial diversity and was associated with changes in the relative abundance of several taxa, including Odoribacter, Bacteroides, Lachnospiraceae, and Roseburia. L-SeMC exhibited superior efficacy in regulating immune function and alleviating intestinal injury compared with SY and Na2SeO3. These findings suggested that L-SeMC-fortified milk powder may help alleviate CTX-induced immunosuppression and is associated with changes in gut microbial composition under the present experimental conditions, providing preliminary evidence for its potential application in functional dairy products.