Final Report Summary - BIOSEAFOOD (Bioactive compounds from seafood byproducts)
The overall aim of this project was to link together several key groups of research questions as a strategy to optimise biological effects of three categories of marine extracts and understand what happens to them under simulated digestion. These three extracts contain well-established or potential bioactive compounds: cod liver oil (containing n-3 PUFA), fish protein hydrolysates (containing peptides) and seaweed extracts (containing polyphenols). In this project these marine bioactive compounds have been followed from the raw material source to active cellular site to optimise their activity. The research questions this project aimed at linking together were:
- stability and stabilising effects of marine extracts in a food matrix;
- understanding of the stability of marine extracts against oxidative degradation during gastrointestinal (GI) digestion;
- understanding of effects from the digested marine extracts on the cell proteome and metabolism as well as cellular oxidative stress and inflammation.
The project aims were met by the following actions:
- demonstrating that high quality, high activity and stable marine bioactive extracts were produced. Also demonstrating that the seaweed extract was an excellent antioxidant against hemoglobin (Hb) mediated oxidation in a fish model system, both with and without the addition of cod liver oil. The cod protein hydrolysate was on the other hand a very effective antioxidant in an iron-fortified cod liver oil emulsion due to its strong metal chelating properties. Re-extraction of the seaweed extract and hydrolysate from the food models showed that their antioxidant capacity remained the same after seven days of storage, demonstrating their strong activity and stability in the food system.
- demonstrating that cod liver oil is subjected to significant lipid oxidation in the gastric and intestinal phases of a static in vitro gastrointestinal (GI) model. Among contributing factors were the liberation of free fatty acids from the oil, build up of trace elements and presence of bile acids. Results showed that the seaweed extract was able to inhibit / reduce GI-induced lipid oxidation while no effects were seen from protein hydrolysates.
- demonstrating that in vitro GI-digested cod liver oil, cod hydrolysate as well as a water soluble seaweed extract had significant effects on changes in protein expression in a yeast cell model. For the seaweed extract and hydrolysate, effects were stronger than for the non-digested counterparts. The yeast model exposed to digested protein hydrolysates showed inhibition of proteins which are over-expressed in various tumours and which are highly conserved in humans.
- demonstrating that digested cod liver oil stimulated reactive oxygen species (ROS) formation in yeast cell models while digested seaweed extract and protein hydrolysate were antioxidative and thus reduced ROS-formation. Additionally, results in both Caco-2 cells and HepG2 cells showed antioxidative effects from seaweed extracts and protein hydrolysates. All three cell systems showed that the extracts had good cellular antioxidant activity.
- demonstrating an increased interleukin 10 (IL-10) secretion by dendritic cells that were matured in the presence of a digested seaweed extract, which suggests these extracts have an immunostimulating effects. Hydrolysates on the other hand did not have the same effect.
This project has led to significant advances in our knowledge how marine components with biological activity may be affected during digestion, negatively or positively. The outcome of the project will provide guidelines on foods containing these bioactive components to protect and optimise the biological activity of the components upon consumption. Producers and end-users of marine bioactive compounds such as those studied in this project are expected to gain from the findings of this project, understanding better how their extracts function.
The finding that protein hydrolysates can be very efficient antioxidants in food emulsions could be important for those developing and producing these products. Additionally, the findings that there are certain ROS-inhibiting properties of hydrolysates on a cellular level, and also indications that hydrolysates can down-regulate expression of proteins which are over-expressed in various tumours and which are highly conserved in humans should be of high relevance. The protein hydrolysate results should stimulate the fish processing industry to make better uses of their by-products which can be excellent raw materials for making protein hydrolysates in the way described in this project. Such value adding would also have a direct environmental impact. The strong antioxidant properties seen in the seaweed extracts both in muscle foods and on a cellular level should stimulate entrepreneurs to start commercial production of seaweed extracts for the food industry. There exists a significant opportunity for new natural food extracts to established themselves on the market.
The finding that omega-3 PUFAs are oxidised in the stomach and intestine upon simulated digestion is of great scientific and social significance. Omega-3 PUFAs are known to be highly beneficial but are at the same time inherently unstable. The findings underline the importance of stabilising the omega-3 PUFAs in the foods so they are protected during digestion. This information should be of interest for fish oil producers and end-users of fish oil, as this project has produced new knowledge on how such oils can be protected against oxidation with help from other marine ingredients. To stabilise oil both during food storage and during GI-conditions, it appears like combinations of antioxidant functions are needed.
The results may also aid toxicologists in developing biomarkers to evaluate safety of bioactive compounds and also nutritionists and regulatory governmental agencies in designing and establishing appropriate dietary guidelines and recommendations. In addition, the results of this project are of course of interest for the scientific community since many new finding have come out of this project. For example, the fact that highly reactive oxidation products (aldehydes) can form during GI-digestion from fish oil may very well have contributed to discrepancies in the literature on health effects from n-3 PUFA.
- stability and stabilising effects of marine extracts in a food matrix;
- understanding of the stability of marine extracts against oxidative degradation during gastrointestinal (GI) digestion;
- understanding of effects from the digested marine extracts on the cell proteome and metabolism as well as cellular oxidative stress and inflammation.
The project aims were met by the following actions:
- demonstrating that high quality, high activity and stable marine bioactive extracts were produced. Also demonstrating that the seaweed extract was an excellent antioxidant against hemoglobin (Hb) mediated oxidation in a fish model system, both with and without the addition of cod liver oil. The cod protein hydrolysate was on the other hand a very effective antioxidant in an iron-fortified cod liver oil emulsion due to its strong metal chelating properties. Re-extraction of the seaweed extract and hydrolysate from the food models showed that their antioxidant capacity remained the same after seven days of storage, demonstrating their strong activity and stability in the food system.
- demonstrating that cod liver oil is subjected to significant lipid oxidation in the gastric and intestinal phases of a static in vitro gastrointestinal (GI) model. Among contributing factors were the liberation of free fatty acids from the oil, build up of trace elements and presence of bile acids. Results showed that the seaweed extract was able to inhibit / reduce GI-induced lipid oxidation while no effects were seen from protein hydrolysates.
- demonstrating that in vitro GI-digested cod liver oil, cod hydrolysate as well as a water soluble seaweed extract had significant effects on changes in protein expression in a yeast cell model. For the seaweed extract and hydrolysate, effects were stronger than for the non-digested counterparts. The yeast model exposed to digested protein hydrolysates showed inhibition of proteins which are over-expressed in various tumours and which are highly conserved in humans.
- demonstrating that digested cod liver oil stimulated reactive oxygen species (ROS) formation in yeast cell models while digested seaweed extract and protein hydrolysate were antioxidative and thus reduced ROS-formation. Additionally, results in both Caco-2 cells and HepG2 cells showed antioxidative effects from seaweed extracts and protein hydrolysates. All three cell systems showed that the extracts had good cellular antioxidant activity.
- demonstrating an increased interleukin 10 (IL-10) secretion by dendritic cells that were matured in the presence of a digested seaweed extract, which suggests these extracts have an immunostimulating effects. Hydrolysates on the other hand did not have the same effect.
This project has led to significant advances in our knowledge how marine components with biological activity may be affected during digestion, negatively or positively. The outcome of the project will provide guidelines on foods containing these bioactive components to protect and optimise the biological activity of the components upon consumption. Producers and end-users of marine bioactive compounds such as those studied in this project are expected to gain from the findings of this project, understanding better how their extracts function.
The finding that protein hydrolysates can be very efficient antioxidants in food emulsions could be important for those developing and producing these products. Additionally, the findings that there are certain ROS-inhibiting properties of hydrolysates on a cellular level, and also indications that hydrolysates can down-regulate expression of proteins which are over-expressed in various tumours and which are highly conserved in humans should be of high relevance. The protein hydrolysate results should stimulate the fish processing industry to make better uses of their by-products which can be excellent raw materials for making protein hydrolysates in the way described in this project. Such value adding would also have a direct environmental impact. The strong antioxidant properties seen in the seaweed extracts both in muscle foods and on a cellular level should stimulate entrepreneurs to start commercial production of seaweed extracts for the food industry. There exists a significant opportunity for new natural food extracts to established themselves on the market.
The finding that omega-3 PUFAs are oxidised in the stomach and intestine upon simulated digestion is of great scientific and social significance. Omega-3 PUFAs are known to be highly beneficial but are at the same time inherently unstable. The findings underline the importance of stabilising the omega-3 PUFAs in the foods so they are protected during digestion. This information should be of interest for fish oil producers and end-users of fish oil, as this project has produced new knowledge on how such oils can be protected against oxidation with help from other marine ingredients. To stabilise oil both during food storage and during GI-conditions, it appears like combinations of antioxidant functions are needed.
The results may also aid toxicologists in developing biomarkers to evaluate safety of bioactive compounds and also nutritionists and regulatory governmental agencies in designing and establishing appropriate dietary guidelines and recommendations. In addition, the results of this project are of course of interest for the scientific community since many new finding have come out of this project. For example, the fact that highly reactive oxidation products (aldehydes) can form during GI-digestion from fish oil may very well have contributed to discrepancies in the literature on health effects from n-3 PUFA.