Physiological, mitochondrial, and oxidative stress differences in the presence or absence of lactation in rats

BACKGROUND: Human epidemiological data show that breastfeeding reduces the mother’s probability of developing several disease conditions, including obesity and type II diabetes compared to mothers that give birth but do not breastfeed. The goal of this investigation was to characterize how lactation changes a rat’s body composition, metabolism, mitochondrial function, and oxidative stress. METHODS: Ten-week old female Sprague-Dawley rats were divided into three groups (n = 8 per group): 1) non-reproductive (NR), 2) those that were allowed to mate and give birth, but were not allowed to suckle their pups (PP), and 3) those that were allowed to mate and give birth, and suckled their young until weaning at 21 days (PL). All animals were sacrificed at a time corresponding to 7 days following the weaning of pups (i.e., day 28 postpartum). RESULTS: The body mass of PL rats was similar to NR rats, but the body mass of PP rats was higher than NR rats. Importantly, PL rats had lower retroperitoneal white adipose tissue mass compared to both NR and PP rats. The difference in fat mass was accompanied by higher protein levels of PPARδ, SOD2, and reduced oxidative damage. Furthermore, the liver of PL rats had higher mitochondrial function with NADH-linked substrates, and higher expression of PGC-1α, PPARδ, and SOD2. CONCLUSIONS: These acute differences observed between female rats that did and did not suckle their young could be used as the foundation for future research investigating the prolonged and sustained benefits of lactation.