Gastrointestinal Appetite Hormones Change With Maternal Adaptations to Pregnancy and Lactation in the Rat

Johnson, Michelle Lucy (2015). Gastrointestinal Appetite Hormones Change With Maternal Adaptations to Pregnancy and Lactation in the Rat. PhD thesis The Open University.



As obesity is becoming more prevalent, there is concern for maternal health during pregnancy, parturition and beyond, alongside the impact that maternal obesity has on offspring health. Appetite regulation by gut hormones is one target for obesity ‘treatment’, although little is known about this fundamental system during different female reproductive stages. The main aims of this thesis were to study the orexigenic stomach-secreted hormone ghrelin and the anorexigenic colon-secreted hormones peptide-YY (PYY) and glucagonlike peptide-1 (GLP-1) in female rats during their oestrous cycle, pregnancy and lactation. Changes in gut dimensions during pregnancy and lactation were also studied. In addition, lactation litter sizes were adjusted to explore the effects of different nutritional demands on both the dams and their male and female pups.

Reduced food intake has been reported during oestrus in rats. Here, significantly reduced fasted stomach contents leading into oestrus occurred with significantly increased circulating GLP-1 during proestrus. Ghrelin-positive stomach cells were significantly higher after parturition compared with non-pregnant and pregnant dams; this change may initiate and sustain lactation-associated hyperphagia, with significantly increased plasma ghrelin evident by late lactation. Paradoxical high levels of PYY and GLP-1 were found early in lactation when food intake was high, which may be related to a significant increase in gut growth from early to late lactation. Maternal gut size was significantly increased by late lactation and lactation litter size appeared to influence these changes. Only male offspring had altered satiety hormones, with significantly decreased descending colon PYY and GLP-1 levels when raised in large litters.

In conclusion, gut hormones and gastrointestinal modifications were altered during different reproductive states in females and in their male offspring at weaning. Further study is required to elucidate whether these changes may persist, influencing future health status, and whether they can be reliably modified for therapeutic purposes.

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