The consumption of vegetable oils and their possible participation as a neuroprotector

Introduction

Reactive oxygen species (ROS) and free radicals generated through biological systems can cause the oxidation of cellular proteins and lipids, leading to the development of premature aging. The human body possesses defense mechanisms against ROS, such as specific enzymes (catalase, superoxide dismutase, and glutathione peroxidase) and thiol antioxidants. Plant foods included in the daily diet provide bioactive components with multiple functions, such as protection against lipid peroxidation and antioxidant activity [1].

Oxidative stress and neurodegenerative diseases

The brain has an oxidative metabolism and high cortisol concentration, which leads to damage to brain cells and accelerates neurodegenerative disorders, causing a decrease in growth factors due to the release of proinflammatory cytokines, resulting in the generation of oxidative stress [2]. At least 80% of the constituent lipids of the brain are unsaturated fatty acids, resulting in susceptibility to lipoperoxidation as well as to the formation of secondary compounds (isoprostanes, malondialdehyde, and acrolein) [3]. The formation of lipoperoxidation causes cellular dysfunction, alterations in protein structures that favor the development of neurodegenerative diseases, thereby decreasing the concentration of antioxidant enzymes [4]. Central nervous system cell-derived ROS production occurs through microglia cells, which release O²⁻, H₂O₂⁻ and cytokines, the latter of which induce continuous ROS production and expression of the enzyme inducible nitric oxide synthase (iNOS), responsible for the generation of reactive nitrogen-derived species [5]. Neurodegenerative conditions cause alterations in consciousness by causing severe damage to neuronal cells; these pathologies are gradual and progressive [6]. Neurodegenerative diseases are classified according to the Diagnostic and Statistical Manual of Mental Disorders (DSM-V), including Alzheimer’s disease (AD), dementia, Amyotrophic lateral sclerosis (ALS), Parkinson’s disease (PD), and Huntington’s disease (HD) [7].

Bioactive components of vegetable oils and neuroprotection

Vegetable oils are a rich source of nutraceuticals, which play important roles in human health, such as linoleic acid, linolenic acid, monounsaturated fatty acids, phenolic compounds, vitamins, carotenoids, tocopherols and tocotrienols [8]. Linoleic acid (LA), an essential fatty acid in mammals due to the inability to synthesize it, accounts for more than 50% of the lipid content in many vegetable oils. Adequate LA intake reduces plasma low-density lipoprotein cholesterol (LDL-c), and dietary intervention studies show that replacing 5% of dietary energy derived from saturated fatty acids with ω6-type polyunsaturated fatty acids reduces LDL-c by up to 10% [9]. Linolenic acid (ALA) is another essential fatty acid in mammals, after its absorption, it is catabolized into a longer chain and more unsaturated free fatty acids, such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), although its endogenous production is low, it can be considered as an alternative. Nonenzymatic oxidation of ALA gives rise to isoprostane analogues called phytoprostanes, which possess anti-inflammatory activities. The ALA-enriched diet reduces oxidative stress and inflammation during myocardial infarction while increasing the formation of phytoprostane [1]. The most abundant monounsaturated fatty acid is oleic acid, which has been associated with a significant reduction in mortality risk from cardiovascular events and stroke [10]. The phenolic content of vegetable oils has been associated with beneficial effects on serum lipids, free radical scavenging, antioxidant and anti-inflammatory activity, and modulation of the immune response [11]. Vitamin E and carotenoids are lipophilic antioxidants in vegetable oils, which function to lower serum LDL levels and prevent oxidation [1]. Román (2019) indicates that the inclusion of nutritional components in the Mediterranean diet can reduce age-related cognitive decline and AD. Polyphenols and flavonoids from cereals, vegetables, fruits, olive oil, and beverages such as red wine, tea, chocolate, and coffee are important components of the diet because of their antioxidant and anti-inflammatory properties, which are beneficial for cardiovascular diseases, stroke, and cancer prevention. Fruit and vegetable polyphenols modulate tau hyperphosphorylation and beta-amyloid aggregation in animal models of Alzheimer’s disease [12]. Although the protective role played by the components of vegetable oils has been emphasized, it should be mentioned that lipid peroxidation is the main effect of free radicals on the lipids that make up cell membranes. Due to this process, the damage induced by free radicals through the reaction products of these molecules on membrane lipids, such as malondialdehyde (MDA), 4-hydroxy-2,3-nonenal (4-HNE) and 4-hydroxy-2,3-alkenal, where the concentration of these reaction products is proportional to the oxidative damage generated. Lipid peroxidation produces these electrophiles (MDA or 4-HNE), which modify essential proteins, resulting in loss of protein function and cellular homeostasis [13]. Vegetable oils should be consumed as an accompaniment to salads and as a dressing, always avoiding heating. Therefore, it is necessary to mention that the consumption of food is not enough to treat or prevent a pathology.

Still, a much healthier lifestyle is required, in addition to the physical activity corresponding to the age range of each of us.

Final considerations

In conclusion, we can say that the consumption of vegetable oils is recommended due to their functional properties (free of cholesterol, trans fats and non-interaction with other nutrients) as well as their greater availability to the population at a lower cost and not with the risk of contamination by methylmercury present in the main animal source of ω3 polyunsaturated fatty acid. They are an option for the prevention and treatment of neurodegenerative conditions in the control and regulation of oxidative stress; however, there are still situations that should be considered as relevant aspects in future research. The mechanism of action of the nutraceutical components of vegetable oils (dosage of administration, duration of treatment, and tissue specificity) has not been fully understood, and the amount of energy they contain and contribute to the normal diet must be considered.