Influence of Different Degrees of Food Restriction on Immune Function and Gut Microbiota in Brandt's Voles

Small mammals in temperate areas frequently face fluctuations in food resources, and food shortage is a key factor affecting their immune function. In order to understand whether immune function and gut microbiota change under food shortage, adult male Brandt's voles (Lasiopodomys brandtii) were used and divided into Fed (Fed, n = 8), 80% food restriction (80% FR, n = 10) and 60% food restriction (60% FR, n = 9) groups. The experimental course lasted for 35 days. Food restriction reduced body mass (p < 0.001) but did not affect total fat mass (p = 0.532) or blood glucose levels (p = 0.777) compared with the Fed voles. Immunological parameters-including wet masses of thymus and spleen, phytohemagglutinin (PHA) responses at 6 h, 12 h, 24 h, and 48 h post PHA injection, interleukin-4 (IL-4) levels (p = 0.700), the counts of white blood cells (p = 0.864), lymphocytes (p = 0.692), and neutrophils (p = 0.729)-were not influenced by food restriction, indicating that voles could maintain stable immune function under food shortage. Similarly, leptin (p = 0.219) and corticosterone (CORT) (p = 0.282) levels were also not impacted by food restriction, and no correlation existed between these two hormones and the above immunological indices. However, interferon-γ (IFN-γ) (p < 0.001) levels in the 80% FR group were the highest among the three groups. Food restriction had no effect on alpha (α)-diversity of the gut microbiota, indicating that food restriction does not affect their diversity or richness. Food restriction did not affect relative abundance at the phylum or genus levels, nor at most family levels, but reduced Erysipelotrichaceae at the family level. In summary, Brandt's voles could maintain stable energy status, leptin and corticosterone levels, and the diversity and richness of the gut microbiota under food restriction, which may help us to understand this species' ability to survive well in times of food shortage.