Mahmoud Bouziane

Changes in fatty acid compositions of total serum and lipoprotein particles, in growing rats given protein-deficient diets with either hydrogenated coconut or salmon oils as fat sources

The present study examines the effects of dietary saturated (hydrogenated coconut oil) and polyunsaturated (salmon oil) fats on the composition and metabolism of lipoproteins in growing rats fed on protein-deficient diets. Four groups of rats were fed on the following diets for 28 d: 200 g casein + 50 g coconut oil (COC)/kg, 20 g casein + 50 g coconut oil (COd)/kg, 200 g casein + 50 g salmon oil (SAC)/kg, 20 g casein + 50 g salmon oil (SAd)/kg. Both protein-deficient groups exhibited low concentrations of protein and triacylglycerol (in serum, very-low-density lipoprotein (VLDL), low-density lipoprotein-high-density lipoprotein, (LDL-HDL1) and HDL2-3), of cholesterol (in LDL-HDL1) and of phospholipids (in VLDL). Furthermore, serum and VLDL cholesterol concentrations were also reduced in the SAd group. Compared with rats given 200 g casein/kg diets, those fed on low-protein diets presented lower linoleic and arachidonic acid levels, in serum phospholipids and a dramatic decrease in the polyunsaturated: saturated fatty acid value. Relative amounts of linoleic and arachidonic acids in phospholipids of VLDL and HDL2-3 were also lowered in the COd group but not in the SAd group. However, proportions of 22:5n-6 and 22:6n-3 in VLDL and HDL2-3 phospholipid fractions were enhanced in the COd and SAd groups respectively. The most affected apolipoproteins (apo) were apo B100 and apo B48 in rats fed on protein-deficient diets, apo AI and apo E in the COd group, and apo AIV in the SAd group. Compared with rats fed hydrogenated coconut oil diets, those fed salmon oil diets had enhanced LDL-HDL1 and HDL2-3 but lower VLDL total apolipoproteins (mainly due to a fall in apo B100 and apo B48). Arachidonic and eicosapentaenoic acids, which are impaired by protein deficiency, are the precursors of prostaglandins, thromboxanes and leukotrienes which are implicated in a number of regulatory processes. Our results demonstrate that protein malnutrition is associated with impaired metabolism of arachidonic and eicosapentaenoic acids. Protein malnutrition and essential fatty acid (EFA) deficiency are characterized by many common clinical features and the link between the two may be an impaired production of eicosanoids, since arachidonic and eicosapentaenoic acids are the precursors of these important metabolic regulators. Because of the apparent involvement of EFA deficiency in the aetiology of protein malnutrition, it may be prudent to include adequate amounts of EFA in diets of infants suffering from kwashiorkor.

Relationship between rat liver microsomal Δ6 and Δ5 desaturase activities and fatty acid composition: comparative effects of coconut and salmon oils during protein restriction

Abstract The aim of this work was to compare the effects of coconut and salmon oils on rat liver microsomal Δ6 and Δ5 desaturations, during protein restriction. A higher Δ6 desaturase activity was noted in rats fed the low-protein coconut oil diet, in comparison with that occurring in rats fed either a low-protein or normal-protein salmon oil diet. No variation was observed in Δ5 desaturase activity or in 20:4n-6/ 18:2n-6 ratio. The fatty acid composition of liver microsomal phospholipids provided evidence of higher levels of 20:5n-3 and 22:6n-3 in the normal-protein salmon oil group, when compared with the low-protein salmon oil group. No influence of experimental diets on the total n-3 and total n-6 fatty acids could be demonstrated. Aside from investigating the effects of protein restriction on the liver microsomal desaturases, this work shows that there is no correlation between microsomal desaturation rates and microsomal phospholipid profiles even when diets are rich in polyunsaturated fatty acids (salmon oil).

Dietary protein deficiency affects n-3 and n-6 polyunsaturated fatty acids hepatic storage and very low density lipoprotein transport in rats on different diets.

Fatty livers and the similarity between the skin lesions in kwashiorkor and those described in experimental essential fatty acid (EFA) deficiency have led to the hypothesis that protein and EFA deficiencies may both occur in chronic malnutrition. The relationship between serum very low density lipoprotein (VLDL) and hepatic lipid composition was studied after 28 d of protein depletion to determine the interactions between dietary protein levels and EFA availability. Rats were fed purified diets containing 20 or 2% casein and 5% fat as either soybean oil rich in EFA, or salmon oil rich in eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids, or hydrogenated coconut, oil poor in EFA. Animals were divided into six groups, SOC (20% casein +5% soybean oil), SOd (2% casein +5% soybean oil), COC (20% casein +5% hydrogenated coconut oil), COd (2% casein + 5% hydrogenated coconut oil), SAC (20% casein +5% salmon oil) and SAd (2% casein +5% salmon oil). After 28 d, liver steatosis and reduced VLDL-phospholipid contents (P<0.001) were observed in protein-deficient rats. In protein deficiency, triacylglycerol and phospholipid fatty acid compositions in both liver and VLDL showed a decreased polyunsaturated-to-saturated fatty acid ratio. This ratio was higher with the salmon oil diets and lower with the hydrogenated coconut oil diets. Furthermore, independent of the oil in the diet, protein deficiency decreased linoleic and arachidonic acids in VLDL phospholipids. Conversely, despite decreased proportions of EPA at low protein levels, DHA levels remained higher in rats fed salmon oil diets. While in rats fed the hydrogenated coconut oil-fed diets the amount of 22∶5n−6 was lower in liver, it was higher in VLDL lipids at low protein levels. Both EPA and arachidonic acid are precursors of eicosanoids and their diminution may be related to certain clinical symptoms seen in infants suffering from kwashiorkor.

Unsaturated fatty acid bioavailability in growing rats fed low or adequate protein diets with sunflower or soybean oils

Abstract The relationship of serum very low density lipoproteins (VLDL) to hepatic lipid composition was studied after 28 days of protein depletion to determine the interactions between dietary protein levels and the essential fatty acid (EFA) availability. This was examined in rats using a dietary combination of 20% or 2% casein with 5% vegetable oils, variable in their n-6:n-3 fatty acid ratios. Rats were divided into four groups, SFC (20% casein + 5% sunflower oil ); SFd (2% casein + 5% sunflower oil ); SC (20% casein + 5% soybean oil ); Sd (2% casein + 5% soybean oil ). Dietary protein depletion decreased phospholipid and protein concentrations in liver and VLDL, whereas triacylglycerol amounts were enhanced in liver, but lowered in VLDL. Dietary protein depletion strongly depressed VLDL apolipoproteins. Protein-deficient groups (SFd and Sd) exhibited, in both liver and VLDL, decreased linoleic acid in triacylglycerol fractions and depressed both arachidonic and linoleic acids in phospholipid fractions. In spite of short periods of dietary treatment, protein depletion involved an impairment in EFA availability. Total n-6 polyunsaturated fatty acids contents were diminished in liver and VLDL lipids, while total n-3 polyunsaturated fatty acids contents were diminished in only VLDL triacylglycerol and phospholipid. Furthermore, sunflower oil amplified this impairment, and the lack of α-linolenic acid involved a greater diminution in n-3 polyunsaturated fatty acids and enhanced 20:3 n-9 and 22:5 n-6, especially in phospholipid fractions. In this experiment, in spite of a short period of dietary treatment, protein depletion strongly impairs EFA metabolism and accentuates the α-linolenic acid deficiency.

Influence of protein intake associated with coconut or salmon oil on serum, VLDL, LDL and HDL proteins and lipids in the rat

Fish oils contain high quantities of eicosapentaenoic acid (EPA = 20:5 m3) and docosahexaenoic acid (22:6 m3). These m3 polyunsaturated fatty acids (PUFA) have a protective effects against atherosclerosis by lowering serum triacylglyerols (TG) and cholesterol levels. Protein malnutrition increases essential fatty acid (EFA) requirements. The effects of protein depletion associated with salmon (rich in w3 PUFA) or coconut oil (poor in EFA) on various serum parameters (proteins, triacylglycerols, phospholipids and total cholesterol were studied in young Wistar rats.