Pregnancy and Lactation in Sprague-Dawley Rats Result in Permanent Reductions of Tibia Trabecular Bone Mineral Density and Structure but Consumption of Red Rooibos Herbal Tea Supports the Partial Recovery

Abstract

During pregnancy and lactation, maternal bone mineral density (BMD) is reduced as calcium is mobilized to support offspring bone development. In humans, BMD returns to pre-pregnancy levels shortly after delivery, shifting from a high rate of bone resorption during pregnancy and lactation, into a rapid phase of bone formation post-lactation. This rapid change in bone turnover may provide an opportunity to stimulate a greater gain in BMD and stronger trabecular and cortical structure than present pre-pregnancy. Providing polyphenols present in red rooibos herbal tea may promote such an effect. In vitro, red rooibos polyphenols stimulate osteoblast activity, reduce osteoclastic resorption, and increase mineral production. The study objective was to determine if consuming red rooibos from pre-pregnancy through to 4 months post-lactation resulted in a higher BMD and improved trabecular and cortical bone structure in a commonly used rat model. Female Sprague-Dawley rats (n = 42) were randomized to one of the following groups: PREG TEA (pregnant, received supplemental level of red rooibos in water: ~2.6 g /kg body weight/day in water), PREG WATER (pregnant, received water), or NONPREG CON (age-matched, non-pregnant control, received water) from 2 weeks pre-pregnancy (age 8 weeks) through to 4 months post-lactation. Rats were fed AIN-93G (pre-pregnancy through to the end of lactation) and AIN-93M (post-lactation onwards). BMD and trabecular structure (bone volume fraction, trabecular number, trabecular separation) were improved (p < 0.05) by 1- or 2-months post-lactation when comparing PREG TEA to PREG CON, though neither group recovered to the level of NONPREG CON. Cortical outcomes (cortical area fraction, cortical thickness, tissue mineral density) for PREG TEA and PREG CON were reduced (p < 0.05) following lactation but returned to the level of NONPREG CON by 2-months post-lactation, with the exception of cortical thickness. The lack of recovery of BMD and key outcomes of trabecular bone structure was unexpected. While consumption of red rooibos did not result in stronger bone post-lactation, red rooibos did support the partial recovery of trabecular BMD and bone structure following pregnancy and lactation. The findings also provide insight into the timing and dose of polyphenols to study in future interventions.

Maternal Exposure to Red Rooibos Does Not Alter Bone Development in Male or Female Sprague-Dawley Rat Offspring

“…This study was approved by the Animal Care Committee at Brock University, St. Catharines, Canada (Animal Use Protocol #18-03-02), and performed in accordance with the Canadian Council of Animal Care. Male and female Sprague-Dawley rats were the offspring of the mothers previously reported [ 9 ] and the study design is described here in brief: 5-week-old female Sprague-Dawley rats were acclimatized to the controlled environment for 1 week and then randomly assigned to receive 1 of 2 interventions ( n = 14 rats/group): control water with 0 mg RR tea/kg body weight/d (CON) or water with 2600 mg RR tea/kg body weight/day. After 3 wk of receiving CON or RR, rats were mated and followed until 4 mo after lactation.…”

“…The statistical power analysis (d = 1.64, alpha = 0.05, power = 0.80) was conducted a priori for a larger maternal study [ 9 ]. As previously described, one male and one female offspring from each litter were selected for analysis ( n CON = 13 offspring per sex because one mother did not become pregnant; n RR = 14 males and n RR = 13 females because one litter had only male offspring).…”

“…Like ovariectomy, pregnancy and lactation also challenge the rodent skeleton. Using the Sprague-Dawley rat model, we previously studied if RR consumption supported recovery of mother’s BMD and bone structure after pregnancy and lactation [ 9 ]. In vivo microcomputed tomography was used to assess these outcomes before mating, at the end of lactation, and at monthly intervals until 4 mo after lactation (endpoint).…”

“…Intervention with RR supported a partial recovery of BMD and trabecular bone structure at 2- and 3-mo after lactation. However, full recovery of these bone outcomes, as suggested by a level similar to the growth control, was not observed by the study endpoint [ 9 ]. The present study was an extension of this larger study in mothers, with a focus on offspring bone health.…”

“…The objectives of this study were to determine whether maternal consumption of RR throughout pregnancy and lactation improved bone development and strength in male and female offspring at young adulthood, and to determine potential sex-specific responses. RR was selected because of the demonstrated stimulation of bone mineralization in vitro, possibly because of antioxidant activity [ [9] , [10] , [11] , [12] ], and for its lack of caffeine content—an important consideration for fetal health.…”