Stan Kubow

Routes of formation and toxic consequences of lipid oxidation products in foods.

Lipid oxidation in foods is initiated by free radical and/or singlet oxygen mechanisms which generate a series of autocatalytic free radical reactions. These autoxidation reactions lead to the breakdown of lipid and to the formation of a wide array of oxidation products. The nature and proportion of these products can vary widely between foods and depend on the composition of the food as well as numerous environmental factors. The toxicological significance of lipid oxidation in foods is complicated by interactions of secondary lipid oxidation products with other food components. These interactions could either form complexes that limit the bioavailability of lipid breakdown products or can lead to the formation of toxic products derived from non-lipid sources. A lack of gross pathological consequences has generally been observed in animals fed oxidized fats. On the other hand, secondary products of lipid autoxidation can be absorbed and may cause an increase in oxidative stress and deleterious changes in lipoprotein and platelet metabolism. The presence of reactive lipid oxidation products in foods needs more systematic research in terms of complexities of food component interactions and the metabolic processing of these compounds.

Potatoes and human health.

The potato (Solanum tuberosum L.) tuber follows only rice and wheat in world importance as a food crop for human consumption. Cultivated potatoes have spread from the Andes of South America where they originated to 160 countries around the world. Consumption of fresh potatoes has declined while processed products have increased in popularity. As the potato becomes a staple in the diets of an increasing number of humans, small differences in potato nutritional composition will have major impacts on population health. The potato is a carbohydrate-rich, energy-providing food with little fat. Potato protein content is fairly low but has an excellent biological value of 90–100. Potatoes are particularly high in vitamin C and are a good source of several B vitamins and potassium. The skins provide substantial dietary fiber. Many compounds in potatoes contribute to antioxidant activity and interest in cultivars with pigmented flesh is growing. This review will examine the nutrient and bioactive compounds in potatoes and their impact on human health.

Toxicity of dietary lipid peroxidation products

Abstract Humans are exposed to oxidized fats in the diet from fatty fish and fish oils, deep fat frying and powdered foods. Air-oxidized fish oils can induce toxic symptoms by stressing the vitamin E antioxidant system. Although primary hydroperoxides and lipid polymers produced from thermally stressed oils are not toxicologically important, toxic effects may be induced by secondary lipid peroxides. Recent studies indicate that thermally stressed oils may have a role in the acceleration of atherosclerosis. There is increasing evidence that cholesterol oxides found in some deep fat fried and dehydrated foods can exert atherogenic effects. Weak mutagenic activity has also been detected in deep-fried fats, although the toxicological significance is unclear.

The influence of positional distribution of fatty acids in native, interesterified and structure-specific lipids on lipoprotein metabolism and atherogenesis

Abstract The arrangement of fatty acids (FA) on the glycerol backbone of triacylglycerols (TAG) among natural fats has been indicated to be responsible for specific effects on lipoprotein metabolism and atherogenesis which may not be predicted from the unsaturated index alone. Typically, hypercholesterolemic animal fats such as bovine milk fat and lard contain mainly saturated FA on the sn-2 position. In contrast, in most vegetable oils such as cocoa butter unsaturated FA occupy the sn-2 position and saturated FA are usually located in the sn-1 and sn-3 positions. Human and animal feeding studies are discussed in which the TAG stereospecific composition of the fed fats has been altered via chemical or enzymatic interesterification. These processes either rearrange FA in each TAG position to one third of its total content within a fat, or generate novel synthetic fats from the interchange of FA between discrete TAG molecules from different fat sources. Such studies have shown effects of interesterification of milk fat, lard, and peanut oil on fat absorption, plasma cholesterol, and TAG concentrations and atherogenesis. Kinetic rat studies using radiolabeled FA and cholesterol have indicated a slowed chylomicron metabolism in structure-specific TAG containing a saturated FA at the sn-2 position. On the other hand, negligible effects of TAG structure on chylomicron and lipoprotein metabolism have been observed in recent humans and animal studies from the feeding of interesterified forms of palm oil in which palmitic acid is enriched at the sn-2 position. Metabolic parameters not measured in these investigations, however, such as alterations in platelet aggregation activity and in free cholesterol concentrations at the level of serum and liver have been noted from other interesterified palm oil feeding studies pointing to the need for further research. The role of TAG structure in natural, interesterified, and structure-specific fats on FA and cholesterol absorption, chylomicron clearance, and lipoprotein metabolism is discussed as well as the confounding aspects that need consideration in terms of these studies.

Microwave-Assisted Extraction of Phenolic Antioxidants from Potato Peels

A response surface method was used to optimize the microwave-assisted extraction parameters such as extraction time (t) (min), solvent (methanol) concentration (S) (v/v) and microwave power level (MP) for extraction of antioxidants from potato peels. Max. total phenolics content of 3.94 mg g−1 dry weight (dw) was obtained at S of 67.33%, t of 15 min and a MP of 14.67%. For ascorbic acid (1.44 mg g−1 dw), caffeic acid (1.33 mg g−1 dw), ferulic acid (0.50 mg g−1 dw) max contents were obtained at S of 100%, t of 15 min, and MP of 10%, while the max chlorogenic acid content (1.35 mg g−1 dw) was obtained at S of 100%, t of 5 min, and MP of 10%. The radical scavenging activity of the extract was evaluated by using the DPPH assay and optimum antioxidant activity was obtained at S of 100%, t of 5 min, and MP of 10%.

Oxysterol as a Marker of Atherogenic Dyslipidemia in Adolescence

CONTEXT Oxysterols represent potentially important oxidative stress biomarkers in adolescence. OBJECTIVE The objective of the study was to examine the relationship between the concentrations of serum enzymatically and nonenzymatically generated oxysterols, measures of obesity, and metabolic components including insulin resistance and levels of blood pressure and serum lipids. DESIGN This was a cross-sectional study. SETTING All subjects were examined between 2003 and 2005 at a hospital, a part of a follow-up evaluation mother-daughter pairs representing pregnancies affected or unaffected by gestational diabetes that resulted in the deliveries in 1989-1991. SUBJECTS Subjects included a subset (n=89) of the total study population of 189 adolescent girls with a mean age of 15.32+/-0.65 yr and body mass index of 22.54+/-3.98 kg/m2. MAIN OUTCOME MEASURES Measures included serum levels of the oxysterols 7alpha-hydroxy-cholesterol, 7beta-hydroxycholesterol, and 7-ketocholesterol; and body mass index, homeostasis model assessment insulin resistance index, fasting insulin, fasting glucose, blood pressure, total cholesterol, non-high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglycerides, and apolipoprotein B (ApoB). RESULTS Serum oxysterol concentrations in the adolescent cohort correlated positively with insulin (P<0.05), total cholesterol (P<0.05), non-high-density lipoprotein cholesterol (P<0.05), low-density lipoprotein cholesterol (P<0.05), and ApoB (P<0.01). ApoB and fasting insulin were found to be the major determinants of serum oxysterols after adjustment for body mass index. Being a daughter of gestational diabetes pregnancy alone did not seem to be a predisposing factor to increased oxidative stress in our cohort. CONCLUSION Serum oxysterol concentrations increase with obesity, insulin, and ApoB, which are established derangements associated with the metabolic syndrome.

Lipid components of traditional inuit foods and diets of Baffin Island

Abstract Traditional wildlife foods harvested and consumed by the Inuit resident on the east coast of Baffin Island were analyzed for fat and fatty acid contents. While values for these components in caribou and various species of seals have been reported earlier, this is the first comprehensive report of the major fatty acids in the spectrum of foods consumed by a population resident in the high Arctic. This is the first report of fat and fatty acid contents of several of these foods derived from animal population species. Summary data are also presented on fats, energy, and total fatty acid contents in the average annual diet of adult males and females who consume both traditional Inuit and market foods. It was found that while market foods contribute more total energy, total fat, and saturated and polyunsaturated fats, the total energy as saturated fat is less than 10%. The very low ω-6 to ω-3 fatty acid ratios in the Inuit food dietary profile of 0.26 (women) and 0.29 (men) are the reverse of recently proposed ratios for optimal health. However, since the traditional Inuit diet supported a healthy population supposedly free of cardiovascular disease, the low ω-6 to ω-3 dietary fat intakes may be appropriate for the Inuit.

The association of desaturase 9 and plasma fatty acid composition with insulin resistance-associated factors in female adolescents.

Desaturase 9 (Delta 9), which converts saturated fatty acids (SFAs) into monounsaturated fatty acids, is an important component in leptin-mediated energy homeostasis in rodent models. Few human studies, however, have been performed regarding the clinical relevance of Delta 9, particularly whether Delta 9 is involved in the relationship between blood fatty acid profiles and insulin resistance-associated factors. The aim of the present study was to examine fatty acid data from 178 apparently healthy female adolescents and determine whether (a) Delta 9 has independent associations with adiposity, insulin resistance level, and fasting plasma polyunsaturated fatty acids (PUFAs); (b) Delta 9 is a predictor of fasting blood lipid profile; and (c) the associations between fasting plasma fatty acid component and insulin resistance level are independent of abdominal obesity level. Desaturase 9-16 (surrogate of Delta 9 as calculated by plasma ratio C16:1 n-7/C16:0) correlated with waist girth (r = .160, P < .05), homeostasis model assessment of insulin resistance (HOMA-IR) (r = .201, P < .01), plasma PUFAs (eg, C20:4 n-6 [r = -.269, P < .001], C22:6 n-3 [r = -.274, P < .001]). After adjustment for dietary SFAs, Delta 9-16 had stronger correlation with waist (r = .227, P < .01) and significant correlation with PUFAs, whereas it had a nonsignificant correlation with HOMA-IR. The same pattern was observed with Delta 9-18 (surrogate of Delta 9 as calculated by plasma ratio C18:1 n-9/C18:0). After adjustment for dietary SFAs, waist, and HOMA-IR, Delta 9-16 and Delta 9-18 were still positive predictors of triglyceride (both P < .001) and apolipoprotein B (Delta 9-18, P < .001; Delta 9-16, P = .052). After adjustment for waist, HOMA-IR only remained a positive determinant of medium-chain SFAs (C14:0, P < .001; C16:0, P < .05); but it emerged to be inversely related to C20:4 n-6 (P < 0.1). The positive and independent associations of medium-chain SFAs with insulin resistance level suggest their vital roles in diabetes pathogenesis, whereas certain PUFAs such as C20:4 n-6 appear to be protective. The observed associations of Delta 9 with adiposity and plasma lipid profile in these apparently healthy female adolescents support the concept derived from rodent models that Delta 9 activity is independently reflective of higher body mass index and higher circulatory triglyceride levels.

High hydrostatic pressure pre-treatment of whey proteins enhances whey protein hydrolysate inhibition of oxidative stress and IL-8 secretion in intestinal epithelial cells

Background High hyperbaric pressure treatment of whey protein isolate (WPI) causes changes in the protein structure that enhances the anti-oxidant and anti-inflammatory effects of WPI. Objective The aim of this study was to compare the anti-oxidant and anti-inflammatory effects of pressurized whey protein isolate (pWPI) vs. native WPI (nWPI) hydrolysates in Caco-2 cells exposed to hydrogen peroxide (H2O2). Design Cells were cultured with different concentrations of pWPI or nWPI hydrolysates either 1 h before or 1 h after H2O2. Cell viability, IL-8 secretion, intracellular reactive oxygen species (ROS), and the medium anti-oxidant capacity (FRAP assay) were measured. Results Prior to and after H2O2 exposure, pWPI and nWPI hydrolysates inhibited IL-8 secretion and ROS generation, and increased FRAP activity in a dose-dependent manner. The maximal inhibition of H2O2-induced IL-8 secretion was greater with 2000 µg mL−1 of pWPI (50%) vs. nWPI (30%) hydrolysates. At the latter concentration, inhibition of H2O2-induced ROS formation reached 76% for pWPI, which was greater than for nWPI hydrolysates (32.5%). Conclusions These results suggest that WPI hydrolysates can alleviate inflammation and oxidative stress in intestinal cells exposed to oxidative injury, which is further enhanced by hyperbaric pressure pre-treatment of WPI.

Whey protein hydrolysates decrease IL-8 secretion in lipopolysaccharide (LPS)-stimulated respiratory epithelial cells by affecting LPS binding to Toll-like receptor 4

UNLABELLED Whey proteins (WP) exert anti-inflammatory and antioxidant effects. Hyperbaric pressurisation of whey increases its digestibility and changes the spectrum of peptides released during digestion. We have shown that dietary supplementation with pressurised whey improves nutritional status and systemic inflammation in patients with cystic fibrosis (CF). Both clinical indices are largely affected by airway processes, to which respiratory epithelial cells actively contribute. Here, we tested whether peptides released from the digestion of pressurised whey can attenuate the inflammatory responses of CF respiratory epithelial cells. Hydrolysates of pressurised WP (pWP) and native WP (nWP, control) were generated in vitro and tested for anti-inflammatory properties judged by the suppression of IL-8 production in CF and non-CF respiratory epithelial cell lines (CFTE29o- and 1HAEo-, respectively). We observed that, in both cell lines, pWP hydrolysate suppressed IL-8 production stimulated by lipopolysaccharide (LPS) to a greater magnitude compared with nWP hydrolysate. Neither hydrolysate suppressed IL-8 production induced by TNF-α or IL-1β, suggesting an effect on the Toll-like receptor (TLR) 4 pathway, the cellular sensor for LPS. Further, neither hydrolysate affected TLR4 expression or neutralised LPS. Both pWP and nWP hydrolysates similarly reduced LPS binding to surface TLR4, while pWP tended to more potently increase extracellular antioxidant capacity. IN CONCLUSION (1) anti-inflammatory properties of whey are enhanced by pressurisation; (2) suppression of IL-8 production may contribute to the clinical effects of pressurised whey supplementation on CF; (3) this effect may be partly explained by a combination of reduced LPS binding to TLR4 and enhanced extracellular antioxidant capacity.