Investigating the effects of persistent organic pollutants (POPs) on insulin-like growth factor 1 (IGF-1) in grey seals

Abstract

Young animals may be vulnerable to disruption of hormones due to chemical exposure, as they are still actively growing and developing. Scientific evidence shows that a class of toxic organic chemicals known as persistent organic pollutants (POPs) are a cause of increasing rates of endocrine and developmental disorders, such as Laron syndrome and could also disrupt other pathways important to health. POPs are introduced into the environment by human processes and are notable for their resistance to various forms of degradation. Insulin-like growth factor 1 (IGF-1) is a hormone produced by the liver which is important to numerous processes including metabolism, growth and development, disruption to any of these processes could severely impact survival and reproductive success.

Grey seals (Halichoerus grypus) are a useful sentinel species to study POPs due to their high fat content, the lipophilic nature of POPs and the high trophic level of the food chain they occupy. Plasma samples from grey seal pups were obtained before the beginning of this project by Kimberley Bennett, plasma samples were taken from pups during suckling and again during fasting and blubber explants were sampled to determine POP concentrations of each pup.

A scoping review was conducted to establish a consensus on the existing scientific literature investigating the effects of POPs on IGF-1 and related hormones, which showed that there is a lack of replicated data examining this topic which should be addressed in the future to confirm the effects of POPs on IGF-1.

The next aim of this project was to investigate if IGF-1, in the plasma of grey seal pups, is disrupted by exposure to POPs. To do this a western blot protocol was optimised to ensure the optimum concentrations of protein, primary antibody and secondary antibody were used during analysis of the seal plasma samples. Ultimately, western blotting and densitometry found no association between the levels of circulatory IGF-1 in the plasma samples and the concentration of POPs in the blubber of the seals.

The results of this project indicate that IGF-1 is not disrupted by exposure to POPs but there is still significant work to be done investigating this subject before we can be confident in this conclusion. Further research should be done on this subject utilising larger sample sizes or using samples which are more concentrated with POPs to help identify the effects of POPs on IGF-1.

Date of Award	18 Jun 2025
Original language	English
Awarding Institution	Abertay University
Supervisor	Kimberley Bennett (Supervisor) & Anne Savage (Supervisor)