Effects of maternal nutrient restriction and melatonin supplementation on vascularity in ovine maternal and fetal jejunum

Abstract Text:

Mounting evidence from previous studies suggests that melatonin, a neurohormone secreted by the pineal gland, likely plays a role in regulating nutrient delivery by regulating blood flow and improving vascular development. Therefore, this study was conducted to investigate the effect of maternal nutrient restriction and melatonin supplementation on vascular development of maternal and fetal small intestine in sheep. Thirty one primiparous ewes were randomly assigned to receive 5 mg of melatonin per day (MEL) or no melatonin (CON) and 100% (adequate fed; ADQ) or 60% (restricted; RES) of nutrient recommendations from d 50 to 130 of gestation. At d 130 of gestation, ewes were euthanized and small intestinal (jejunal) tissues were collected from the dam and fetus. Intestinal capillaries were stained using Anti-CD31 (Abcam) followed by fluorescently labelled, goat anti-rabbit secondary antibody (Alexa Fluor 633; Abcam). A DAPI stain was used to counterstain cell nuclei. Z-stacks of 15-µm deep, optical sections of jejunal tissues including intact villi were obtained using a confocal laser-scanning microscope (Zeiss AxioObserver Z1 with LSM700). Rendered 3D images were analyzed for capillary volume, which was expressed as a percentage of the total villous volume by using Imaris 7 software (Bitplane, South Windsor, CT). Data were analyzed as a completely randomized design, with a 2 × 2 factorial arrangement of treatments. In the maternal jejunum, there was no effect of maternal melatonin treatment or nutritional level on capillary volume density (P > 0.59); however, due to the large decrease in jejunal mass (RES only 0.69 of ADQ; P < 0.001) total jejunal vascularity was decreased (P = 0.02) in RES vs. ADQ ewes. For the fetal intestine, neither capillary volume density nor total intestinal vascularity were affected by MEL supplementation or nutritional level, and a melatonin × nutrition interaction was not observed. Our data suggest that nutritional level affects maternal jejunal mass and total vascularity. However, neither melatonin supplementation nor nutritional level affected capillary volume density of maternal jejunum, or capillary volume density or total vascularity of fetal intestine. Future research is needed to investigate whether maternal melatonin supplementation or nutritional level, or both, affect vascularity of the intestine postnatally.

Keywords: intestine, maternal melatonin treatment, vascularity