Early life nutrition influences thymic growth in male mice that may be related to the regulation of longevity
Résumé
Nutrition and growth rate during early life can influence later health and lifespan. We previously demonstrated that low birth weight resulting from maternal protein restriction during pregnancy followed by catch-up growth in rodents was associated with shortened lifespan whereas protein restriction and slow growth during lactation increased lifespan. The underlying mechanisms by which these differences arise are unknown. Here we report that maternal protein restriction in mice influences thymic growth in early adult life. Offspring of dams fed a low protein diet during lactation (PLP offspring) showed significant thymic growth from 21 days to 12 weeks of age whereas this was not observed in control mice or offspring of dams fed a low protein diet during pregnancy (recuperated offspring). PCNA and SIRT1 protein levels at 21 days of age were significantly higher in thymus from both PLP (P < 0.001 and P < 0.05 respectively) and recuperated mice (P < 0.001 and P < 0.01 respectively) compared to controls. At 12 weeks PLP maintained a higher SIRT1 level whereas PCNA was decreased in thymus from recuperated offspring. This suggests that mitotic activity was initially enhanced in thymus of both PLP and recuperated offspring but remained sustained into adulthood only in PLP mice. The differential mitotic activity in thymus of PLP and recuperated animals appeared to be influenced by changes in sex hormone concentrations and expression of p53, p16, the androgen receptor, IL-7 and the IL-7 receptor. The differential thymic growth may contribute to the regulation of longevity by maternal diet.
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