Impacts of linseed meal and estradiol-17beta on mass, cellularity, angiogenic factors, and vascularity of the jejunum

To evaluate the estrogenic potential of the phytoestrogen secoisolariciresinol diglycoside (SDG) found in linseed meal (LSM) on jejunal mass, cellular proliferation, vascularity, and expression of angiogenic factors and their receptors, 48 ovariectomized ewes (54.6 +/- 1.1 kg) were fed a diet containing 12.5% LSM for 0, 1, 7, or 14 d and implanted with estradiol-17beta (E(2)) for 0, 6, or 24 h before tissue collection. Angiogenic factors and receptors measured included vascular endothelial growth factor (VEGF), VEGF receptor-1 (FLT), VEGF receptor-2 (KDR), fibroblast growth factor (FGF), FGF receptor 2 IIIc (FGFR), angiopoietin (ANG)-1, ANG-2, ANG receptor (Tie-2), endothelial nitric oxide synthase (eNOS), and soluble guanylate cyclase (sGC). There was a LSM x E(2) interaction (P = 0.003) on the jejunal cellular proliferation index. Jejunal cellular proliferation increased (P < 0.002) in ewes not fed LSM and implanted with E(2) for 6 or 24 h compared with ewes implanted for 0 h but did not increase when LSM was fed for 1, 7, or 14 d. Neither feeding LSM nor implanting ewes with E(2) altered vascular area density (P > 0.75) or vascular surface area (P > 0.29) of the jejunal villi. Expression of mRNA for the angiogenic factors VEGF, FGF, FGFR, ANG-1, ANG-2, and Tie-2 were not altered (P > 0.33) by feeding LSM or implanting ewes with E(2). Implanting ewes with E(2) for 6 h increased (P = 0.04) eNOS expression compared with ewes implanted for 0 h. Feeding LSM and implanting ewes with E(2) interacted to alter mRNA expression of FLT (P = 0.04), KDR (P < 0.001), and sGC (P = 0.04). When LSM was fed for 1, but not 0, 7, or 14 d, expression of FLT mRNA decreased (P < 0.03) when ewes were implanted with E(2) for 24 h compared with ewes implanted for 0 or 6 h. Expression of KDR mRNA was suppressed in ewes fed LSM for 1 (P = 0.03) or 7 d (P = 0.0007) and implanted with E(2) for 24 h compared with ewes implanted for 0 h. When LSM was fed for 14 d, implanting ewes for 6 h increased (P = 0.04) KDR expression compared with ewes implanted for 0 h. Ewes fed LSM for 0 and 1 d experienced an increase in sGC mRNA expression when implanted for 6 h (P = 0.001) compared with ewes implanted for 0 h. When implanted for 24 h, levels were similar (P = 0.80) to those observed when ewes were implanted for 0 h. Expression of sGC was not altered by E(2) when LSM was fed for 1, 7, or 14 d (P > 0.11). The impacts of E(2) and LSM on nutrient uptake and growth during physiologically important time points are unknown.