Extraction, characterisation, and exploitation of marine derived bioactive peptides for enhancing health

  • Shaun Sharkey

Student thesis: Doctoral Thesis


Dietary proteins are under increasing investigation as a source of bioactive peptides for management of type-2 diabetes (T2DM) and obesity. Both conditions are increasing exponentially in the global population, and although there are many pharmaceutical options available for diabetes management, the same is not true for obesity. Furthermore, effective nutritional intervention could potentially reduce the amount of pharmaceutical dependence in T2DM management. Fish protein hydrolysates, and in particular blue whiting, are an attractive protein source in an Irish context due to its abundance in Irish Atlantic coastal waters, representing a possible high-quality dietary protein from a relatively sustainable source.

The aim of this study was to characterise the effect of various proteolytic enzyme combinations on blue whiting protein. Initially, this was carried out by comparison of physicochemical properties, amino acid profile, in vitro DPP-4 inhibition, insulin secretion, and GLP-1 secretion. Eleven laboratory-scale blue
whiting protein hydrolysates (BWPH) were generated, and some exhibited potent anti-diabetic bioactivity, thus 6 industrial-scale BWPH were generated, four of which were replicates of laboratory-scale hydrolysates and two of which were of interest to industrial partners. Once again, BWPH showed potent bioactivity in vitro, and although bioactivity was impacted by simulated gastro-intestinal digestion in most cases, BW-SPH-A and BW-SPH-C had increased bioactivity indicating promise for future in vivo studies.

This prompted further investigation in vivo through use of feeding studies and oral glucose tolerance tests in healthy mice. BW-SPH-A elicited a potent reduction in food intake, while BW-SPH-C induced a considerable change in postprandial blood glucose excursion. Both hydrolysates induced a concomitant increase in plasma insulin response. BW-SPH-A also induced an increase in total PYY, presenting a likely mechanism of action for the reduction in food intake. Mice were also administered BWPH 2 h prior to experimentation, however limited effect was observed indicating a short half-life of the bioactive peptides present.

To further investigate the bioactive effects, BWPH were administered twice-daily for 28 days via oral gavage to both HFF and HFF/STZ mice. However, the findings with HFF mice did not correlate with those from acute in vivo studies. Further, while there were some promising changes in blood glucose in HFF/STZ mice, there was considerable variability in diabetes progression in the mice which hampered statistical significance. Interestingly however, in both studies BW-SPH-C elicited positive changes in pancreatic islet architecture, and further investigation of its role in diabetes management is altogether warranted.

When considered as a whole, these data form a solid foundation of research into the characterisation of BWPH for T2DM and obesity management, however much further research is required to identify individual bioactive peptides, further assess the effects of BWPH in vivo in more reliable animal models of disease, and to understand the sensory acceptability of the BWPH in human intervention trials.
Date of AwardApr 2022
Original languageEnglish
SponsorsDepartment of Education
SupervisorFinbarr O'Harte (Supervisor), Philip Allsopp (Supervisor) & Lynsey Elizabeth Hollywood (Supervisor)


  • Diabetes
  • Obesity
  • Fish protein hydrolysate

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