Effects of Equol Supplementation on Growth Performance, Redox Status, Intestinal Health and Skeletal Muscle Development of Weanling Piglets with Intrauterine Growth Retardation

Abstract

Animals with intrauterine growth retardation (IUGR) usually undergo injured postnatal growth and development during the early period after birth. Equol (Eq), an isoflavan produced by gut bacteria in response to daidzein intake, has various health benefits. Therefore, the objective of this study was to evaluate whether Eq supplementation can influence the growth performance, redox status, intestinal health and skeletal muscle development of weanling piglets with IUGR. A total of 10 normal-birth-weight (NBW) newborn female piglets and 20 newborn female piglets with IUGR were selected. After weaning at the age of 21 d, 10 NBW piglets and 10 IUGR piglets were allocated to the NBW group and IUGR group, respectively, and offered a basal diet. The other 10 IUGR piglets were allocated to the IUGR + Eq group and offered a basal diet with 50 mg of Eq per kg of diet. The whole trial lasted for 21 d. At the end of the feeding trial, all piglets were sacrificed for the collection of serum, intestinal tissues and skeletal muscles. Supplementation with Eq increased the average daily gain (ADG), average daily feed intake (ADFI), duodenal villus height to crypt depth ratio (V/C), jejunal villus height and V/C, but reduced the duodenal crypt depth in neonatal piglets with IUGR. Meanwhile, Eq supplementation elevated the activities of superoxide dismutase (SOD) and catalase (CAT) in the serum and duodenum and the activity of SOD in the jejunum, but lowered malondialdehyde (MDA) content in the serum, jejunum and ileum of piglets with IUGR. In addition, supplementation with Eq reduced diamine oxidase (DAO) activity and the levels of D-lactate and endotoxin in serum, and the tumor necrosis factor-α (TNF-α) level in jejunum and ileum, whereas the concentration of serum immunoglobulin G (IgG) and the mRNA levels of intestinal barrier-related markers in jejunum and ileum of IUGR piglets were increased. Furthermore, supplementation with Eq elevated the percentage of fast-fibers and was accompanied with higher mRNA expression of myosin heavy chain IIb (MyHC IIb) and lower mRNA levels in MyHC I in the longissimus thoracis (LT) muscle of IUGR piglets. In summary, Eq supplementation can promote antioxidant capacity, maintain intestinal health and facilitate skeletal muscle development, thus resulting in the higher growth performance of IUGR piglets.

Keywords: equol; intestinal health; intrauterine growth retardation; piglets; redox status; skeletal muscle development.

Figure 1

Effects of Eq supplementation on the mRNA level of ZO1, ZO2, CLDN1, CLDN2, OCLN, MUC2, MUC20 and TFF3 in jejunum (A) and ileum (B) of weanling piglets with IUGR. β-actin was considered as an internal reference gene. Data were exhibited as the means ± SD, n = 10/group. NBW group: NBW piglets were offered a basal diet; IUGR group: IUGR piglets were offered a basal diet; IUGR + Eq: IUGR piglets were offered a basal diet supplemented with 50 mg of Eq per kg of diet. ZO1, zona occludens 1; ZO2, zona occludens 2; CLDN1, claudin 1; CLDN2, claudin 2; OCLN, occluding; MUC1, mucin 1; MUC2, mucin 2; TFF3, trefoil factor family 3. The different letters indicate significant differences among treatments (p < 0.05).

Figure 2

Effects of Eq supplementation on skeletal muscle fiber type in the LT muscle of weanling piglets with IUGR. (A) The ATPase staining of LT muscles. Fast-fibers stain dark gray. Original magnification, ×100. Bars: 100 μm. (B) The percentage of fast-twitch fibers was analyzed based on the ATPase staining. (C) Relative mRNA expressions of four MyHC isoforms in LT muscles. β-actin was used as an internal reference gene. Data were exhibited as the means ± SD, n = 10/group. NBW group: NBW piglets were offered a basal diet; IUGR group: IUGR piglets were offered a basal diet; IUGR + Eq: IUGR piglets were offered a basal diet supplemented with 50 mg of Eq per kg of diet. MyHC, myosin heavy chain. The different letters indicate significant differences among treatments (p < 0.05).