Olive oil-fried sardines in the prevention of dietary hypercholesterolemia in rats. Effects on some serum lipids and cell-damage marker enzymes

Calcium and phosphorus bioavailability in rats consuming oil from either raw sardines or sardines fried in olive oil Biodisponibilidad de calcio y fósforo en ratas alimentadas con grasa de sardina cruda o frita con aceite de oliva

Three diets were prepared containing 8% olive oil (OO), fresh sardine ( Clupea pilchardus) oil (SO), and oil from sardines fried in olive oil (FSO), respectively. After in vitro digestion, soluble (dialyzed and nondialyzed) and insoluble Ca and P fractions were determined. In vitro Ca availability tended to be higher with SO, and even more so with FSO, than with OO, while that of P increased only slightly with FSO. Growing rats consumed the diets for 28 days. Food intake and body weight increased with FSO more than with OO, but decreased markedly with SO, due to an imbalance in the n-3/n-6 fatty acid ratio. Absorption efficiencies of Ca and P were higher with SO than with the other diets during days 5-12. Because urinary Ca excretion was also greater with SO, apparent retention of both Ca and P was lower with this diet. With SO, carcass content of Ca and P was low but their concentrations were high. Apparent retention of these minerals and their carcass content were similar or higher with FSO than with OO. Therefore, although availability of Ca and P from raw and fried sardine oil diets was sufficient in vitro, consumption of raw sardine oil as the only dietary fat produced changes in calcium and phosphorus bioavailability, an effect of sardine oil which disappeared after frying in olive oil.

Comparative Effects of the Fat Extracted from Raw and Fried Sardines Upon Rat Growth and Zinc Bioavailability

Three diets containing 8% olive oil, fresh sardine (Clupea pilchardus) oil and oil from sardines fried in olive oil were prepared. After in vitro digestion, soluble (dialysed and non-dialysed) and insoluble zinc fractions were determined. Fresh sardine oil and oil from sardines fried in olive oil provided more dialysed zinc and less insoluble zinc than 8% olive oil. Three groups of growing rats consumed the diets for 28 days. Food intake and body weight values of rats fed 8% olive oil were significantly higher than those fed fresh sardine oil and slightly lower than those fed oil from sardines fried in olive oil. Animals fed fresh sardine oil exhibited the lowest apparent zinc retention during days 5-12, but absorption efficiency increased during days 21-28 and all groups had similar final zinc absorption and retention values. Animals fed oil from sardines fried in olive oil displayed higher (days 5-12) or similar (days 21-28) apparent zinc absorption and retention values than rats fed 8% olive oil and fresh sardine oil. Hepatic zinc concentrations were higher in rats fed oil from sardines fried in olive oil than fed fresh sardine oil, while all groups showed similar spleenic concentrations. Zinc accumulation in skin was significantly higher in animals fed fresh sardine oil than in those fed oil from sardines fried in olive oil, and their total erythrocyte zinc concentrations were also higher than in rats fed oil from sardines fried in olive oil or on 8% olive oil. In conclusion, a diet high in raw sardine fatty acids can cause excessive zinc accumulation in skin and erythrocytes. However, these negative effects of sardine oil disappear after frying in olive oil.

Effect of Olive Oil-Fried Sardine Consumption on Liver Lipid Composition and Fatty Acid Cholesterol Esterification in Hypercholesterolemic Rats

PUFA n-3 diets have hypolipemic and cardiovascular protection properties, however their effects on liver lipids are not well established. This work aimed to find out the acceptability and effects of diets containing olive oil-fried sardines on serum cholesterol, liver lipid and fatty acids profile in hypercholesterolemic growing Wistar rats. Hypercholesterolemia was induced for three weeks by a casein plus DL-methionine, olive oil and cholesterol plus bovine bileas cholesterol-raising agent. Rats were later transferred for three weeks to semisynthetic diets containing casein plus DL-methionine and olive oil (CO), casein plus DLmethionine, olive oil and the cholesterol-raising agent (COC), sardines fried in olive oil (S), and sardines friedin olive oil and the cholesterol-raising agent (SC). SC or S diets were well accepted by the rats. The SC-diet markedly blocked and reversed the hypercholesterolemic induction of the cholesterol-raising agent. The cholesterol withdrawal decreased serum cholesterol in CO and S dietsby decreasing the serum non-HDL-cholesterol content but the S-diet totally normalised the serum cholesterol. Fried sardines did not change the triacylglycerol, free, esterified and total cholesterol contents of liver. Although long PUFA n-6 and PUFA n-3 were decreased by the dietary cholesterol, olive oil-fried sardine consumption maintained the docosahexaenoic acid and thedocosahexaenoic acid/linolenic acid ratio in liver and cholesterol ester fraction at a high level. Olive oil fried sardines blocked the hypercholesterolemic effect of the diet containing cholesterol and help normalising lipoprotein profile in a rather short period. The oleic acid esterification of cholesterol was kept high in all experimental diets as a mechanism to maintain the liver cholesterol ester/free cholesterol ratio as high as possible. The fat in the oliveoil-fried sardines was used similarly to the oleic acid by the liver of hypercholesterolemic rats but increased its PUFA n-3 content in the total liver and its cholesterol ester fraction.

Thermal Oxidation of Olive Oil, Sunflower Oil and a Mix of Both Oils during Forty Discontinuous Domestic Fryings of Different Foods

Changes in sunflower oil (SO), olive oil (OO) of 0.4º acidity value and a mixture (1:1) of both oils (MO) were studied during forty domestic discontinuous deep-fat frying of various foodstuffs, mostly frozen foods. The replenishment of the oil in the fryer with fresh oil was performed after every ten uses to maintain the oil volume in the fryer. Alteration of oils was evaluated by measuring polar content (PC) and compounds related to thermoxidative and hydrolytic changes. PC increased with different rates in the three oils, thus after twenty fryings, PC was 25.3 g/100 g oil for SO, 22.4 g/100 g oil forMOand 19.7 g/100 g oil for OO. At the fortieth frying, the three oils surpassed the critical level for PC of 25 g/100 g oil, but SO andMOwere abused oils with a PC value = 30 g/100 g oil. Oxidized triacylglycerols (OTG), triacylglycerol dimers (TD) and triacylglycerol polymers (TP) increased after forty fryings 6.1, 34.5 and 260 times, respectively, in SO; 7.8, 50.9 and 115.8 times, respectively, in MO and 19.5, 70 and 149 times, respectively, in OO. The TP+TD/OTG ratio was used to assess the more predominant alteration through frying in the three oils. This ratio increased after forty fryings more in SO followed by MO, and then by OO, showing that oils rich in linoleic acid became more polymerized in frying than those rich in oleic acid. According to PC and the thermoxidative changes, MO behaved as a mix of OO and SO. Data indicated that during the first twenty fryings, olive oil of 0.4 º acidity value and the oil mix performed more satisfactorily than sunflower oil in repeated fryings of frozen foods, however, differences in frying oil behavior decreased during the last twenty fryings.

Effects of seaweed-restructured pork diets enriched or not with cholesterol on rat cholesterolaemia and liver damage

Seaweed enriched-restructured pork (RP) is a potential functional food. However, indications of adverse effects associated with herbal medications, which include among others liver failure, toxic hepatitis, and death have been reported. Cholesterol feeding produces hepatomegalia and fat liver infiltration. The effect of seaweed-RP diet, cholesterol-enriched or not, on plasma cholesterol, liver damage markers, structure, and cytochrome CYP4A-1 were evaluated after 5 wk. Eight rat groups were fed a mix of 85% AIN-93M rodent-diet plus 15% RP. The Cholesterol-control (CC), Cholesterol-Wakame (CW), Cholesterol-Nori (CN) and Cholesterol-Sea Spaghetti (CS) groups respectively consumed similar diets to control (C), Wakame (W), Nori (N), and Sea Spaghetti (S) but as part of hypercholesterolaemic diets. CN and CS significantly blocked the hypercholesterolaemic effect observed in CC group. After 5-wk, N and S diets increased the CYP4A-1 expression. However, seaweed-RPs were unable to reduce the histological liver alterations observed in CC group. Larger and more abundant hepatocellular alterations were found in CS and CN rats suggesting that the hypocholesterolaemic effects of these seaweed-RPs seem to be a two-edged sword as they increased liver damage. Future studies are needed to understand the involved mechanisms.

Wakame and Nori in restructured meats included in cholesterol-enriched diets affect the antioxidant enzyme gene expressions and activities in Wistar rats

The effects of diets including restructured meats (RM) containing Wakame or Nori on total liver glutathione status, and several antioxidant enzyme gene expressions and activities were tested. Six groups of ten male growing Wistar rats each were fed a mix of 85% AIN-93 M diet and 15% freeze-dried RM for 35 days. The control group (C) consumed control RM, the Wakame (W) and the Nori (N) groups, RM with 5% Wakame and 5% Nori, respectively. Animals on added cholesterol diets (CC, CW, and CN) consumed their corresponding basal diets added with cholesterol (2%) and cholic acid (0.4%). Alga and dietary cholesterol significantly interact (P < 0.002) influencing all enzyme expressions but not activities. The cholesterol supplement decreased most enzyme expression and activity. W-RM vs. C-RM increased (P < 0.05) expression of GPx, GR, Mn-SOD, and Cu,Zn-SOD and decreased that of catalase. N-RM vs. C-RM increased (P < 0.05) expression of catalase and Mn-SOD. GR activity increased in W-RM rats while SOD activity increased, but that of Se-GPx decreased in N animals. W-RM increased total and reduced glutathione and decreased the redox index. CN diet induced significantly lower plasma cholesterol levels (P < 0.001) than the CW diet. In conclusion, Nori-RM is a hypocholesterolemic food while Wakame-RM is an antioxidant food. This should be taken into account when including this kind of RM as potential functional foods in human.

Characteristics and nutritional and cardiovascular-health properties of seaweeds

While marine algae have traditionally formed part of the Oriental diet, their major use in Western countries has been in the phytocolloid industry. Only a few coastal communities outside Asia have customarily used seaweeds as components of special dishes. Of late, however, seaweeds have gained importance as foodstuffs in Western countries and most recently as components of functional foods because of their high dietary fiber, mineral, vitamin, and phytochemical content, low energy levels, and high concentrations of certain polyunsaturated fatty acids. The present paper reviews the available data for some of the components of the major edible algae and studies several factors that can affect their physiochemical properties (e.g., hydration, water and oil-holding capacity, fermentability, binding capacity, etc.) and, in turn, their nutritional importance. The effects of marine alga consumption on growth and body weight, mineral availability, lipid metabolism, blood pressure, and antioxidant properties are reviewed, together with preliminary data on the effects of some functional foods containing seaweeds on lipid metabolism and gene expression of enzymes engaged in antioxidant protection. This review concludes with some remarks regarding the danger of the improper use of seaweeds in herbal medications. In addition, as the properties of algae are highly dependent on their individual composition, any generalization regarding these properties may be considered misleading and scientifically inappropriate.

A Nori but not a Konbu, dietary supplement decreases the cholesterolaemia, liver fat infiltration and mineral bioavailability in hypercholesterolaemic growing Wistar rats

The nutritional consequences of algae consumption in young populations consuming hypercholesterolaemic diets have hardly been investigated. This study tests the effect of algae supplementation of cholesterol-enriched balanced diets on growth, dietary efficiency ratio, mineral intake and absorption, organ weight and structure and cholesterolaemia in growing Wistar rats. Three groups of ten rats each were fed for 3 weeks with experimental diets containing 93 % casein-soyabean oil base with 2.4 % cholesterol-raising agent and 7 % supplement. The control group received cellulose (35 %), group 2 consumed Nori (33.8 % fibre) and group 3 consumed Konbu (36.1 % fibre). Food intake and body weight gain were not significantly affected. Algae groups presented significantly higher dietary efficiency ratio values than control rats. Apparent absorption of several minerals appeared significantly affected, mainly in Nori-fed rats, with a significant decrease in the ratio of Zn and Cu intakes and apparent absorption. Nori diet significantly decreased plasma cholesterol. Algae supplement did not significantly affect organ size and structure. Control and Konbu rats showed severe liver fat infiltration, while Nori rats exhibited a significantly lower degree of lipid-like hepatocyte vacuolization but light to moderate leukocyte infiltration. Light to moderate scaling off of the epithelium and moderate submucosa oedema was observed in all groups. Although long-term studies are needed to check the possible extrapolation of these data to human subjects, it can be concluded that a Nori, but not a Konbu, dietary supplement reverses the negative effect of dietary cholesterol intake and also appears to be related to mineral availability in growing subjects.

Differential effects of konbu and nori seaweed dietary supplementation on liver glutathione status in normo- and hypercholesterolaemic growing rats

The effects of six balanced diets for 3 weeks on dietary intake, growth, liver weight and fat, plasma cholesterol, total antioxidant capacity, liver glutathione status and antioxidant enzymes in growing male Wistar rats were studied. Ten rats per group were fed casein- and soyabean-based diets with or without 2.4 % cholesterol-raising agent. Seven percent of the diet consisted of a cellulose-wheat starch mix (35:65; control diets), freeze-dried nori (nori diets) or konbu (konbu diets). The 7 % dietary supplement of seaweeds was well accepted and induced normal growth rates in rats. Except for food intake, total and reduced glutathione and total antioxidant capacity, dietary cholesterol addition significantly affected (at least P<0.05) all parameters studied. Alga consumption affected total and reduced glutathione, glutathione reductase activity, plasma cholesterol, and total and cholesterol-adjusted total antioxidant capacity (at least P<0.05). A significant cholesterol-alga interaction was found for liver weight, total glutathione peroxidase (GSH-Px) and the Se-dependent GSH-Px:total GSH-Px ratio (at least P<0.05). GSH-Px activity increased in cholesterol-fed nori rats mainly as Se-dependent GSH-Px, while in konbu and control groups the GSH-Px activity was related to increases in both non-Se-dependent and Se-dependent GSH-Px activities. The decrease in the antioxidant status of konbu rats was related to the high As content of this alga, which led to a compensatory increase in glutathione reductase activity in these animals. In conclusion, although some antioxidant compounds are present in algae, other dietary compounds, such as As, induced poor antioxidant status in rats.

Effect of Olive Oil-Fried Sardine Consumption on Cholesterol Content in the Serum, Lipoproteins, Spleen and Adipose Tissue of Hypercholesterolemic Rats

BACKGROUND

The information about the effect of fried-oily fish consumption on cholesterol metabolism is rather scarce.

AIM

To test the effect of olive oil-fried sardine consumption on cholesterol content in the serum, lipoproteins, spleen and adipose tissue of hypercholesterolemic rats.

METHODS

Hypercholesterolemia was induced for 3 weeks by a casein + olive diet containing cholesterol and bovine bile (COC). Rats were later switched for 2 weeks to diets containing casein + olive oil (CO), olive oil-fried sardines (S), and olive oil-fried sardines-cholesterol-bovine bile (SC) while one rat group continued on the COC diet. Cholesterol was determined in serum, lipoproteins, adipose tissue and spleen.

RESULTS

The SC diet markedly blocked the hypercholesterolemic induction of the cholesterol-raising agents. Dietary cholesterol withdrawal decreased serum cholesterol levels, with the S diet inducing the highest decrease in serum and VLDL + LDL-cholesterol levels. Cholesterol withdrawal decreased spleen total cholesterol content and weight but the S diet was unable to reduce spleen cholesterol content (micromol/g) more than CO diet. Adipose tissue of S rats displayed the lowest cholesterol values. Cholesterol (mmol/g) of adipose tissue correlated very significantly with total serum cholesterol (r = 0.9225, p < 0.0001) and VLDL + LDL-cholesterol (r = 0.9313, p < 0.0001).

CONCLUSIONS

Cholesterol in adipose tissue was very sensitive to variations in plasma cholesterol. Consumption of fried sardines interacts with cholesterol withdrawal, accelerating serum cholesterol normalization and reduction of cholesterol levels in adipose tissue.

Fat and protein from olive oil-fried sardines interact to normalize serum lipoproteins and reduce liver lipids in hypercholesterolemic rats

Fatty fish consumption has been recommended due to its high (n-3) PUFA content. However, an effect of its protein on serum lipids and lipoproteins has also been suggested. The present study was designed to determine the acceptability of diets containing sardines fried in olive oil or the fat extracted from those sardines and the normalization of serum lipids and lipoproteins, the hepatic lipid profile, and the fatty acid composition of the liver of growing Wistar rats fed these diets after dietary loading of cholesterol. Hypercholesterolemia was induced for 3 wk by feeding rats a casein/olive oil/cholesterol diet. Rats were then switched for 2 wk to cholesterol-free purified diets containing casein plus olive oil (CO), sardines fried in olive oil (S) and casein plus the fat extracted from sardines fried in olive oil (CSF). The S and CSF diets were well accepted by the rats. Withdrawal of dietary cholesterol markedly reduced (P < 0.05) serum cholesterol level in all of the groups, but the S group had the greatest decrease and the CO group the smallest decrease. The S group had a more normal lipoprotein profile, in which HDL was the major lipid carrier, whereas rats of the CO group still had beta-VLDL particles. CSF-fed rats had an intermediate profile. Liver fat and total, free and esterified cholesterol levels were lower (P < 0,05) in the S group than in the other two groups. The S and CSF diets increased (P < 0.05) the (n-3) PUFA content in hepatic triacylglyceride, cholesterol ester and phospholipid fractions. The liver fatty acid profile of the S group was more normalized than those of the other two groups. These findings suggest that the inclusion in the diet of whole sardines fried in olive oil normalizes cholesterol metabolism in hypercholesterolemic rats more quickly than consumption of their extracted fat.