Effects Of Tea Polyphenols On Lactation Performance In Rats

Objective: In order to increase milk production of rats, the effect of tea polyphenols onlactation performance, blood biochemical parameters, antioxidant capacity and immunefunction in maternal rats, and the impact on blood biochemical parameters, antioxidantfunction, immune function in nursing pups have been studied and analyzed. The regulatorymechanisms of tea polyphenols on lactation performance of maternal rats have also beeninvestigated through the effect of the rat prolactin receptor and estrogen receptor geneexpression.Methods: Forty SPF healthy pregnant SD rats, weighing280~320g, were selected. Theywere randomly divided into four groups after three-days’ pre-feeding with10in each group.Four kinds of diets were designed by2×2Latin square experiment: high-energy diet group(HE), low-energy diet group (LE), high-energy diet+500mg polyphenols/kg diet group(HE-TP), low-energy diet+500mg polyphenols/kg diet group (LE-TP). The whole trialperiod was40days. From the first day of delivery, weight was recorded every other day. Onthe21th day of lactation period, blood were collected from the heart. Samples of breast, liver,spleen and thymus were collected after the rats were slaughtered. Blood lipid and redoxstate-related indicators in plasma and tissues were measured. Levels of PRL, E2, IgA, IgM,IgG in plasma were assayed using ELISA kits; genes expression of PRLR, ERα, ERβ in breast,hypothalamus and liver were detected through RT-PCR.Results:(1) Tea polyphenols significantly improved the thymus index, spleen index oflactating rats and their pups, while liver index was significantly decreased; maternal lactationwas significantly improved by11.6%, and levels of prolactin (PRL) and estrogen (E2) inplasma and breast tissues were significantly increased (P<0.05);(2) Fed high-energy dietswas easy to cause oxidative stress, lipid levels were significantly increased and antioxidantcapacity was decreased; while adding tea polyphenols could help to improve blood lipidmetabolism and antioxidant levels in lactating rats and their pups, T-AOC, SOD, CAT activitywere significantly increased (P<0.05), MDA levels were significantly reduced (P<0.05);(3)Tea polyphenols could significantly improve the levels of IgA, IgM, IgG in plasma oflactating rats and their pups (P<0.05), and were increased by22.4%,27.1%,27.2%respectively, which contributed to enhancing immunity;(4) The gene expression of PRLR andERα in mammary gland, hypothalamus and liver of lactating rats were significantlyup-regulated by the effect of tea polyphenols (P<0.05), meanwhile, ERβ expression level inhypothalamus and liver tissue up-regulated, but showed no significant difference (P>0.05).But there was barely significant change of ERβ expression in breast tissue during lactation. By up-regulating the gene expression of prolactin receptor and estrogen receptor, the lactationof maternal rats was significantly improved.Conclusion: That improving the level of dietary energy intake could effectively increasethe lactation of maternal rats. However, fed high-energy diets would change the redox state,and cause oxidative damage, leading to elevated levels of blood lipids and decreasingantioxidant capacity. Adding tea polyphenols into the diet could reverse the imbalance of theredox state, contribute to improving the antioxidant capacity of lactating rats and their pups,enhancing immune function and improving the blood lipid metabolism to some extent. Theprobable mechanism may be related to the fact that tea polyphenols adjust hormone levels byregulating the expression of related-genes, resulting in the enhanced lactation performance ofmaternal rats.