Impact of Maternal Intermittent Fasting During Pregnancy on Fetal Growth and the System L Amino Acid Transporter in a Rat Model

Abstract

Maternal undernutrition during pregnancy may programme the fetus to undergo altered metabolic and physiological responses, accompanied by long-lasting effects such as an increased risk of disease later on in life, including cardio-renal dysfunction. Fasting during the Islamic festival of Ramadan is an obligatory religious requirement and a period during which the intake of food and fluids are forbidden from sunrise until sunset. Many Muslim pregnant women fast, despite being exempt from this requirement, to satisfy their religious beliefs. Fasting during pregnancy has been observed to have a negative effect on maternal and fetal health which may last into adulthood. The aims of this study were to investigate the effect of different patterns of maternal intermittent fasting (MIF) during pregnancy on maternal and fetal development and to examine sex-specific differences. A rat model was used to investigate the effects of MIF, mimicking the repeated daily pattern of Ramadan fasting, on 1) maternal physiology; 2) fetal development; 3) branched chain amino acid (BCAA) concentrations; 4) placenta (Pl) and yolk sac (YS) development and system L amino acid transporter (AAT) activity and expression; 5) mTOR signalling activity. The differential expression of LAT subtypes of system L AAT in Pl and YS was also determined in control rats. Methods: Control (C) pregnant rats had free access to food, and three groups of rats were subjected either to MIF during the first three days of pregnancy (early fasted; EF); which is approximately equal to the first month of pregnancy in humans or throughout the period of pregnancy (full fasted; FF); and a pair fed (PF) group which had access to the same quantity of food as the EF group for only the first three days of pregnancy. Food was withdrawn from FF and EF rats at 5 pm and returned at 9 am. All rats had free access to water throughout pregnancy. Observations were made at gestational day 21 (GD 21) and were separated according to fetal sex, to determine sexual dimorphic responses to maternal dietary regimen. Results: EF and PF had no effect on maternal physiology or fetal development but were associated with some changes in system L AAT expression; Pl gene expression of Slc43a2 (LAT4) was higher in the EF group compared to C, but this was not mirrored by a protein expression change or in matched YS. Pl LAT2 protein expression was higher in male fetuses of the EF group compared to C. PF group showed a higher expression of Slc7a5 (LAT1) in matched Pl and YS compared to C, whereas Slc7a8 (LAT2) was reduced in YS of the PF group compared to C, with no change in this gene in the matched Pl. FF rats consumed less food and water, which was associated with a reduction in maternal weight gain. At GD 21, fetal weight in the FF group was lower, associated with shorter length and smaller abdominal circumference in male fetuses only. FF group also showed an increase in fetal brain/liver weight ratio and a reduction in maternal and fetal plasma isoleucine concentration, associated with a reduction in maternal valine concentration. Although placental efficiency (fetal: Pl weight ratio) was reduced in both sexes of this group, the FF model did not affect Pl or YS weight, Pl junctional (JZ) and labyrinth zone (LZ) weights, total BCAA concentrations,14C-leucine accumulation and 4E-BP1 protein expression in Pl zones and YS. In C groups, Slc7a5 (LAT1), Slc7a8 (LAT2), Slc3a2 (CD98) and Slc43a2 (LAT4) were identified in rat Pl and YS with similar expression patterns between sexes, but different across tissues. Slc7a5 gene and LAT1 protein expression was significantly higher in Pl than YS; associated with a higher concentration of total BCAA concentrations. Conversely, Slc7a8 and Slc43a2 gene expression and LAT2 and LAT4 protein expression was significantly higher in YS than Pl. Slc3a2 gene expression was significantly higher in Pl than YS, but CD98 protein expression was comparable between tissues. By immunohistochemis

Date of Award	1 Aug 2020
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Nicholas Ashton (Supervisor) & Jocelyn Glazier (Supervisor)