In vivo absorption, metabolism, and urinary excretion of alpha,beta-unsaturated aldehydes in experimental animals. Relevance to the development of cardiovascular diseases by the dietary ingestion of thermally stressed polyunsaturate-rich culinary oils.

Abstract

Thermal stressing of polyunsaturated fatty acid (PUFA)- rich culinary oils according to routine frying or cooking practices generates high levels of cytotoxic aldehydic products (predominantly trans-2-alkenals, trans,trans-alka-2,4-dienals, cis,trans-alka-2, 4-dienals, and n-alkanals), species arising from the fragmentation of conjugated hydroperoxydiene precursors. In this investigation we demonstrate that typical trans-2-alkenal compounds known to be produced from the thermally induced autoxidation of PUFAs are readily absorbed from the gut into the systemic circulation in vivo, metabolized (primarily via the addition of glutathione across their electrophilic carbon-carbon double bonds), and excreted in the urine as C-3 mercapturate conjugates in rats. Since such aldehydic products are damaging to human health, the results obtained from our investigations indicate that the dietary ingestion of thermally, autoxidatively stressed PUFA-rich culinary oils promotes the induction, development, and progression of cardiovascular diseases.

Reduced Postprandial Serum Paraoxonase Activity After a Meal Rich in Used Cooking Fat

“…The current postprandial changes in HDL lipid composition including increased triglyceride and phospholipid content and decreased cholesteryl ester content after the meals were generally in line with the corresponding postprandial changes reported previously. 49 Animal studies suggest that secondary lipid oxidation products, including low molecular weight carbonyl compounds, are absorbed from the gut, 20,24,25 inhibit enzyme activities, 25 and form conjugates with glutathione, 24 a thiol containing compound. Derivatisation of cysteine thiol groups on paraoxonase inhibits its activity.…”

“…Detoxification by a glutathione peroxidase cycle in the gut 23 may severely limit absorption of dietary lipid hydroperoxides. However, secondary lipid oxidation products are more readily absorbed 20,24 and can inhibit hepatic enzymes in animals. 25 In mice that are susceptible to arterial lesion development, an atherogenic diet and injection of mildly oxidized LDL and oxidized lipids into the circulation reduces serum paraoxonase activity.…”

The effect of meals rich in thermally stressed olive and safflower oils on postprandial serum paraoxonase activity in patients with diabetes

“…LDL enriched with monounsaturated fatty acids (MUFA) are more resistant to potentially atherogenic oxidative modification (Reaven et al, 1993). Furthermore, cooking with vegetable oils rich in MUFA would be expected to result in lower levels of lipid oxidation products compared with oils rich in PUFA (Grootveld et al, 1998;Kritchevsky & Tepper, 1967). Vegetable oils rich in PUFA are vulnerable to oxidation during heating in air and diets rich in oxidised PUFA increase levels of lipid oxidation products in human chylomicrons (Staprans et al, 1999) and accelerate the development of experimental atherosclerosis (Staprans et al, 1996).…”

Keloid of ear lobes: nature's ear rings

“…Inclusion of vitamin E to frying oil was found to render polyunsaturated fatty acids more resistant to oxidation (7). During frying, lipids especially polyunsaturated fatty acids (PUFA) undergo oxidation, hydrolysis and polymerization which lead to the production of volatile and non-volatile degradation products (8,9).…”