[PhD defence] 17/12/2024 - Léna PETIT: "Association of two species of microalgae: Nutritional interest and potential impact on cardiometabolic risk" (UPR LAPEC)

Léna PETIT will be submitting her thesis on 17 December 2024 on the subject of "Combining two species of microalgae: nutritional benefits and potential impact on cardiometabolic risk".

Laboratory

UPR 4278 LAPEC - Laboratory of Cardiovascular Experimental Physiology

Composition of the jury

Mr Cyril REBOUL	Avignon University	Thesis co-director
Mr Grégory MEYER	Avignon University	Thesis co-director
Mr Guillaume WALTHER	Avignon University	Examiner
Mr Jean-François LANDRIER	Aix Marseille University	Examiner
Ms Khadija OUGUERRAM	University of Nantes	Rapporteur
Mr Sébastien MARZE	INRAE Nantes	Rapporteur
Mr Jean-Paul CADORET	ALGAMA company	Thesis co-supervisor

Summary

Cardiovascular disease is a major public health issue. The Western diet, with its associated nutritional imbalances, is a major risk factor in the development of cardiometabolic diseases. In addition, it is both a source of highly oxidisable fatty acids such as n-6, and of iron, which initiates oxidation. During digestion, these fatty acids are oxidised, generating highly reactive compounds such as 4-HNE, which are then absorbed and contribute to the development of cardiovascular pathologies. Microalgae are organisms with a wide biological diversity. Among them, Spirulina is renowned for its high protein content and antioxidant activity, as well as for its usefulness in preventing certain metabolic disorders. Nannochloropsis is particularly rich in EPA, an n-3 fatty acid important in cardiovascular prevention. In this context, the first objective of this thesis was to assess the nutritional relevance of combining these two species.

In the second part of this work, we wanted to evaluate the effect of combining these 2 algae on the bioaccessibility of compounds recognised for their beneficial effects on cardiovascular health, and also on the antioxidant activity of these microalgae during digestion, particularly in a context favouring lipid oxidation, such as in a Western diet. In addition, as the resistance of the cell walls of certain species of microalgae can limit their digestibility, the impact of an extraction process on these different parameters was also a key element of this thesis work. We were able to show that the mix of Spirulina and Nannochloropsis is a qualitative source of protein, n-3 fatty acids and certain vitamins and minerals. In addition, using an in-vitro digestion model, we have shown that the prior application of an extraction process improves the bioaccessibility of cardioprotective compounds such as EPA, and antioxidants such as carotenoids for the group combining the two species of microalgae. Finally, we report in this work that this extract mix effectively limits the formation of oxidation products following in-vitro digestion of a pro-oxidant meal mimicking the Western diet. It would subsequently be interesting to confirm these data in vivo or in humans.

Keywords Microalgae, Nutrition, Extraction, Cardiovascular health, Oxidative stress