The effects of dietary galactooligosaccharides (GOS) on the murine immune system were examined. BALB/c mice were orally administered GOS, and the intestinal mucosal immune responses were measured. Fecal total IgA in the GOS group was significantly increased at 2 weeks after the start of administration and returned to the same level as the control group 3 weeks later. Four weeks later, the mice were sacrificed. Total IgA in supernatants of Peyer’s patch cell cultures and colon tissue extracts from the GOS group were higher than in those from the control group. BALB/c mice were intraperitoneally immunized with ovalbumin (OVA). Total IgE and OVA-specific IgG1 in serum and total IgE, OVA-specific IgG1 and IL-4 secreted by splenocytes in vitro in the GOS diet group were significantly lower than those in the control diet group. The effects of GOS on experimental allergic rhinitis were then investigated. GOS significantly inhibited antigen-induced sneezing and tended to decrease nasal rubbing in sensitized BALB/c mice. These results indicate that GOS possesses immunostimulatory activity and anti-allergic effects. GOS did not augment proliferation of splenocytes from control mice and did not influence immunoglobulin production by splenocytes and Peyer's patch cells in vitro. On the other hand, cecal tissue weight and cecal content weight were significantly increased and the pH of the cecal content was decreased by GOS intake. We suggest that the effects of GOS on the murine immune system appear to be mediated by intestinal microflora.

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To investigate why groups of pups nursed by dams fed a low-fat diet (LFD) or a high-fat diet (HFD) show a preference for HFD after weaning, Studies 1 and 2 were conducted using HFD-1 and HFD-2, respectively, with cellulose added to maintain the same energy concentration as a low-fat diet (LFD). Study 1: Two groups of pregnant rats were fed either LFD or HFD-1 during pregnancy and lactation. When their pups were placed on a self-selection regimen of LFD and HFD-1 for 2 weeks after weaning, the ratio of HFD-1 intake (HFD-1 intake/total intake) by pups nursed by dams fed LFD and HFD-1 was 82% and 88%, respectively. Study 2: The same experiment as that in Study 1 was conducted using LFD and HFD-2. Although the ratio of HFD-2 intake by pups nursed by dams fed LFD decreased from 80% to 20% at the end of 2 weeks after weaning, that by pups nursed by dams fed HFD-2 was 71% throughout the self-selection period. These results indicate that (1) preferential high-fat diet intake by weaning pups is linked to dietery high energy density (kcal/g), and (2) low energy density high-fat diet-feeding during pregnancy and lactation affects the fat intake preference of pups and guards against fat overfeeding when pups are nursed by dams fed LFD.

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