Formation of malondialdehyde (MDA), 4-hydroxy-2-hexenal (HHE) and 4-hydroxy-2-nonenal (HNE) in fish and fish oil during dynamic gastrointestinal in vitro digestion

Abstract

Marine lipids contain a high proportion of polyunsaturated fatty acids (PUFA), including the characteristic long chain (LC) n-3 PUFA. Upon peroxidation these lipids generate reactive products, such as malondialdehyde (MDA), 4-hydroxy-2-hexenal (HHE) and 4-hydroxy-2-nonenal (HNE), which can form covalent adducts with biomolecules and thus are regarded as genotoxic and cytotoxic. PUFA peroxidation can occur both before and after ingestion. The aim of this study was to determine what levels of MDA, HHE and HNE can evolve in the gastric and intestinal lumen after ingesting meals containing fish or fish oil using a dynamic gastrointestinal (GI) model (TIM). The impact of the fish muscle matrix, lipid content, fish species, and oven baking on GI oxidation was evaluated. MDA and HHE concentrations in gastric lumen increased for all meals during digestion, with the highest level found with herring mince; ∼ 25 μM MDA and ∼ 850 nM HHE. Aldehyde concentrations reached in intestinal lumen during digestion of fish containing meals were generally lower than in gastric lumen, while isolated herring oils (bulk and emulsified) generated higher MDA and HHE values in intestinal lumen compared to gastric lumen. Based on aldehyde levels in gastric lumen, meals containing herring lipids were ranked: raw herring (17% lipid) = baked herring (4% lipid) > raw herring (4% lipid) ≫ herring oil emulsion > herring oil. Herring developed higher concentrations of MDA and HHE during gastric digestion compared to salmon, which initially contained lower levels of oxidation products. Cooked salmon generated higher MDA concentrations during digestion than raw salmon. Low levels of HNE were observed during digestion of all test meals, in accordance with the low content of n-6 PUFA in fish lipids.

Long‐Chain n‐3 PUFA Content and n‐6/n‐3 PUFA Ratio in Mammal, Poultry, and Fish Muscles Largely Explain Differential Protein and Lipid Oxidation Profiles Following In Vitro Gastrointestinal Digestion

“…Indeed, highly significant and strong correlations were found among 4‐HHE, PROP, and TBARS in digests, and LC n‐3 PUFAs in muscle foods (all r between 0.838 and 0.975, all p < 0.001), but not with ALA, the most dominantly present n‐3 PUFA in mammal and poultry muscles ( Table ). Previous studies also reported the formation of 4‐HHE and MDA during the digestion of herring, salmon, and various fish oils, accompanied by relatively low 4‐HNE formation . In agreement to our results, Steppeler et al .…”

“…Muscle foods from different animal origin vary widely in concentrations of heme‐Fe, n‐3 , and n‐6 PUFAs, and endogenous antioxidants such as vitamin E, carnosine, and anserine, all compounds with the ability to influence oxidative reactions during digestion. Yet, the variation in the sensitivity to oxidation during digestion of muscles originating from various animal species is only scarcely explored . Muscle foods are classified according to their mammal, avian, or aquatic origin, or as “white meat” or “red meat,” referring to their low and high heme‐Fe contents, respectively.…”

“…In the present study, we aimed to elucidate which intrinsic factors (heme‐Fe, PUFAs, endogenous antioxidants) of cooked muscle foods of avian, mammal, or aquatic origin explain the extent and type of oxidation product formation during digestion, since this species variation has been only scarcely explored . Therefore, 21 muscles belonging to 18 different animal species (seven mammals, seven poultry, and four fish), were digested in vitro.…”

Amounts of malondialdehyde do not accurately represent the real oxidative level of all vegetable oils: a kinetic study of malondialdehyde formation

“…Obviously, the higher PUFA contents of vegetable oil, the greater MDA‐generating potential it may exhibit. Previous literature reported that aldehydes derived from the oxidative decomposition of PUFA hydroperoxides (Larsson et al ., ). So LO, containing the highest amount of PUFA, showed the greatest MDA‐generating ability, which also explained why MDA content of LO was the highest in our experiment (Fig.…”

Everything Should Be as Simple as It Can Be. But Not Simpler. Does Food Lipid Oxidation Require an Omics Approach?

“…Only in the last few years have some research groups started to bridge this gap by investigating the levels of reactive aldehydes and epoxidation products during oil digestion …”