A blueberry-enriched diet counteracts the effects of estrogen deficiency in mice on bone, skeletal muscle, and peripheral fat, and alters the gut microbiome.

Abstract

Diets containing natural plant products exhibit protective effects on the adult skeleton by unclear mechanisms. We previously identified a blueberry cultivar (Montgomery= Mont) that protects from ovariectomy (OVX)-induced bone loss, when 10% lyophilized (freeze dried) berry was incorporated into a control diet (AIN-93M) and fed for 6 wks to sham/OVX 4 mo mice. We report here that bones from Mont-fed mice exhibited increased endogenous antioxidant response (EAR), assessed by phase-II detoxifying/antioxidant enzyme gene expression. In contrast, EAR was not increased in bones from mice fed 2 other berry-containing diets that did not protect from OVX-induced bone loss. Mont did not prevent OVX-induced reduction in the expression of C3, an estrogen receptor ERE-containing responsive gene. Thus, Mont diet specifically counteracted the harmful oxidative actions of OVX by increasing EAR, without activating canonical estrogenic actions in bone. Mont-fed mice were also protected from OVX-induced decreased BV/TV, TbTh, and TbN, assessed by micro-CT, and the increase in resorption (CTX). In addition, OVX induced skeletal muscle loss in control-fed mice, quantified by gastrocnemius weight, whereas Mont-fed mice were protected. Further, OVX control-fed mice exhibited increased body weight and peripheral fat mass, quantified by DEXA; and mice fed with Mont, but not with the 2 other berries, did not gain weight or peripheral fat upon OVX. We next examined potential effects of OVX and the Mont diet on the gut microbiome, known to affect homeostasis of several tissues. Fecal bacterial DNA was analyzed using 16S rRNA gene sequences from high throughput paired end MiSeq technology. We found that OVX did not induce significant changes in the microbiome regardless of the diet. In contrast, Mont-fed mice exhibited a statistically significant alteration of the microbiome compared with control- fed mice (axis1=54.4% per MANOVA, p=0.001). Further, analysis of the phylogenetic diversity detected higher prevalence of the bacterial communities Alloprevotella, Ruminococcus (starch fermenters), and an unclassified taxon Coriobacteriales Incertae in Mont-fed mice. In contrast, control-fed mice exhibited higher prevalence of Bifidobacterium and Coriobacteriaceae UCG-002 communities. These findings highlight the impact of nutrition on musculoskeletal tissue maintenance and the gut microbiome, and suggest alternative interventions to prevent the harmful effects of estrogen deficiency.