Effects of parenteral nutrition supplemented with beta‐hydroxy‐beta‐methylbutyrate on gut‐associated lymphoid tissue and morphology in mice

Background Parenteral nutrition (PN) without enteral nutrition (EN) leads to marked atrophy of gut‐associated lymphoid tissue (GALT), causing mucosal defense failure in both the gut and the extraintestinal mucosal system. We evaluated the effects of beta‐hydroxy‐beta‐methylbutyrate (HMB) on GALT and gut morphology in PN‐fed mice. Methods Experiment 1: male Institute of Cancer Research mice were assigned to the Chow (n = 12), Control (standard PN: n = 10), or H600 and H2000 (PN containing 600 mg/kg or H2000 mg/kg body weight of Ca‐HMB: n = 12 and 10, respectively) groups. After 5 days of dietary manipulation, all mice were killed and the whole small intestine was harvested. GALT lymphocyte cell numbers and phenotypes of Peyer patch (PP), intraepithelial space, and lamina propria lymphocytes were evaluated. Experiment 2: 47 mice (Chow: n = 12; Control: n = 14; H600: n = 11; and H2000: n = 10) were fed for 5 days as in experiment 1. Proliferation and apoptosis of gut immune cells and mucosa, and protein expressions (mammalian target of rapamycin [mTOR], caspase‐3, and Bcl2) were evaluated in the small intestine. Results Compared with the Controls, the Chow and HMB groups showed significantly higher PP cell numbers, prevented gut mucosal atrophy, inhibited apoptosis of gut cells, and increased their proliferation in association with increased mTOR activity and Bcl2 expression. Conclusion HMB‐supplemented PN is a potentially novel method of preserving GALT mass and gut morphology in the absence of EN.