Lipoprotein(a) and dietary proteins: casein lowers lipoprotein(a) concentrations as compared with soy protein.
(1/910)
BACKGROUND: Substitution of soy protein for casein in the diet decreases LDL cholesterol and increases HDL cholesterol. How the 2 proteins affect lipoprotein(a) [Lp(a)], an independent risk factor for coronary artery disease, is unknown. OBJECTIVE: We compared the effects of dietary soy protein and casein on plasma Lp(a) concentrations. DESIGN: Nine normolipidemic men were studied initially while consuming their habitual, self-selected diets, and then, in a crossover design, while consuming 2 liquid-formula diets containing either casein or soy protein. The dietary periods lasted 45 d (n = 7) or 33 d (n = 2). Fasting total cholesterol, LDL-cholesterol, HDL-cholesterol, triacylglycerol, and Lp(a) concentrations were measured throughout. RESULTS: After 30 d of each diet, the mean concentration of Lp(a) was not significantly different after the soy-protein and self-selected diets. However, Lp(a) decreased by an average of 50% (P < 0.001) after the casein diet as compared with concentrations after both the soy-protein and self-selected diets. Two weeks after subjects switched from the self-selected to the soy-protein diet, Lp(a) increased by 20% (P = 0.065), but subsequently decreased to baseline. In contrast, the switch to the casein diet did not cause an increase in Lp(a), but instead a continuing decrease in mean concentrations to 65% below baseline (P < 0.0002). Total cholesterol, LDL cholesterol, and HDL cholesterol were significantly lower > or =30 d after both the casein and soy-protein diets than after the self-selected diet (P < 0.001). HDL cholesterol was 11% higher after the soy-protein diet than after the casein diet (P < 0.002), but LDL cholesterol, total cholesterol, and triacylglycerol were not significantly different after the casein and soy-protein diets. CONCLUSION: These findings indicate that soy protein may have an Lp(a)-raising effect, potentially detrimental to its use in antiatherogenic diets. (+info)
Effect of reducing the phytate content and of partially hydrolyzing the protein in soy formula on zinc and copper absorption and status in infant rhesus monkeys and rat pups.
(2/910)
BACKGROUND: Although soy formulas have been designed to meet the nutrient requirements of human infants, they also contain phytate, which may negatively affect trace element absorption. OBJECTIVE: We evaluated the effect of removing phytate on zinc and copper absorption and status in infant rhesus monkeys and suckling rat pups and evaluated differences between intact and partially hydrolyzed soy protein. DESIGN: In monkeys, regular and low-phytate soy formulas were fed exclusively for 4 mo and whole-body absorption and retention of 65Zn, 67Cu, 59Fe, 54Mn, and 47Ca were determined at different time points with a whole-body counter. Subsequently, zinc and copper absorption from several human infant formulas and the effect of phytate concentration were evaluated in suckling rat pups by using 65Zn and 64Cu. Finally, infant rhesus monkeys were fed low-phytate formulas with intact or hydrolyzed soy protein for 4 mo and plasma zinc and copper were measured monthly. RESULTS: In the first monkey study, zinc absorption at 1 mo was higher from low-phytate soy formula (36%) than from regular soy formula (22%), whereas there was no significant difference between groups in the absorption of other minerals. Plasma copper was significantly lower in monkeys fed low-phytate soy formula from 2 to 4 mo. In rat pups, zinc absorption was significantly higher from low-phytate soy formula (78%) than from regular soy formula (51%) and hydrolysis of the protein had no significant effect. Phytate content or protein hydrolysis did not significantly affect copper absorption. In the second monkey study, plasma copper concentrations were highest in monkeys fed the low-phytate, hydrolyzed-protein soy formula. CONCLUSION: Reducing the phytate content and partially hydrolyzing the protein in soy formula had a beneficial effect on zinc and copper absorption and status in infant rhesus monkeys. (+info)
Quality and safety evaluation of genetically engineered rice with soybean glycinin: analyses of the grain composition and digestibility of glycinin in transgenic rice.
(3/910)
The composition of nutritionally and physiologically important molecules in transgenic rice with the soybean glycinin gene was determined and compared with that of a non-transgenic control. Except for the levels of protein, amino acids and moisture, no marked differences were found between the two kinds of rice. The protein content of the transgenic rice was about 20% higher than the control (control, 6.5 g/100 g; transgenic, 8.0 g/100 g) with a concomitantly lower moisture content. This increased protein content mainly resulted from the increased glycinin expressed in the transgenic rice, and the protein was susceptible to gastric and intestinal digestion juices. In parallel with the increased protein content, some important amino acids lacking in quantity in normal rice were replenished. (+info)
Dietary soy protein effects on inherited polycystic kidney disease are influenced by gender and protein level.
(4/910)
The effects of dietary soy protein compared to casein were examined in male and female CD1-pcy/pcy (pcy) mice with polycystic kidney disease. Animals 10 wk of age were fed purified diets containing either soy protein isolate or casein given at a level of 17.4 or 6% protein. After 13 wk on the diets, body weights and serum concentrations of albumin and protein indicated that protein nutrition was adequate on all diets. Overall, animals fed soy protein versus casein had 28% lower (P = 0.0037) relative kidney weights (g/100 g body wt), 37% lower (P = 0.0089) cyst scores (% cyst area x relative kidney weight), and 25% less (P = 0.0144) kidney water (g). Dietary protein reduction resulted in 30% lower (P = 0.0010) relative kidney weights, 25% lower (P = 0.0327) cyst scores, and 35% less (P = 0.0001) kidney water. Analysis of interactions between main effects revealed that the effects of soy protein on kidney size were significant only in females, and that effects of soy protein on cyst score were significant only in animals on the low protein diets. In addition, differences in kidney weights and cyst score due to protein reduction were significant in animals fed soy protein, but not in those fed casein as the protein source. These results show that both dietary protein source and level significantly affect polycystic kidney disease in pcy animals, with the effects of dietary soy protein being most pronounced in female animals fed the low protein diets and the effects of protein reduction being most pronounced in animals fed soy protein-based diets. (+info)
Isolation of peptides from an enzymatic hydrolysate of food proteins and characterization of their taste properties.
(5/910)
Soybean protein, casein, bonito protein and chicken protein, each as foodstuff protein, were hydrolyzed with four proteinases; namely, pepsin, trypsin, alpha-chymotrypsin and bromelain. Since the chicken protein hydrolysate with bromelain possessed the most favorable umami taste, eleven peptides were isolated from the chicken protein hydrolysate by successive chromatography on ODS, Amberlite IR-120B, Amberlite IRA-410 and AG-50W; their structures were Asp-Ala, Asp-Val, Glu-Glu, Glu-Val, Ala-Asp-Glu, Ala-Glu-Asp, Asp-Glu-Glu, Asp-Glu-Ser, Glu-Glu-Asn, Ser-Pro-Glu, and Glu-Pro-Ala-Asp. Many of them did not show any umami taste by themselves, but Glu-Glu, Glu-Val, Ala-Asp-Glu, Ala-Glu-Asp, Asp-Glu-Glu, and Ser-Pro-Glu were recognized to enhance the umami taste of 0.02% 5'-inosine monophosphate (IMP). A combination of these peptides, especially 0.5% each of Glu-Glu, Glu-Val, Asp-Glu-Glu and Glu-Glu-Asn, with 0.02% IMP produced a delicious "full" umami taste. (+info)
Topological and functional characterization of the N-glycans of soybean (Glycine max) agglutinin.
(6/910)
Soybean agglutinin (SBA), is a noncovalently bound tetramer comprised of four identical subunits having a single N-glycan chain, Man9GlcNAc2, that is known to be essential for regeneration of the functional tetrameric structure from unfolded subunits. In this study, SBA was found to have strong affinity for concanavalin A, indicating that the N-glycans are extensively solvent-exposed. The susceptibilities of the N-glycans to alpha-mannosidase and endo-beta-N-acetylglucosaminidase revealed that their distal areas have nonreducing ends embedded among the subunits, whereas their proximal regions are solvent-exposed. Endo-beta-N-acetylglucosaminidase-digested SBA was unable to retain its conformation and gradually unfolded. Periodate-oxidized SBA, whose N-glycans closely correspond to the invariant pentasaccharide core, tended to dissociate into the subunits, but permitted to stay as folded monomers. This SBA species was capable of refolding from unfolded subunits but unable to form the functional tetramer. It seems probable that the proximal regions of the N-glycans function in the formation and stabilization of the subunit conformation, whereas the branches outside the invariant cores stabilize the tetrameric structure. (+info)
Sequencing and characterization of the citrus weevil, Diaprepes abbreviatus, trypsin cDNA. Effect of Aedes trypsin modulating oostatic factor on trypsin biosynthesis.
(7/910)
Trypsin mRNA from the citrus weevil, Diaprepes abbreviatus, was reverse transcribed and amplified by PCR. A cDNA species of 513 bp was cloned and sequenced. The 3' and 5' ends of the gene (262 bp and 237 bp, respectively) were amplified by rapid amplification of cDNA ends, cloned and sequenced. The deduced sequence of the trypsin cDNA (860 bp) encodes for 250 amino acids including 11 amino acids of activation and signal peptides and exhibited 16.8% identity to trypsin genes of selected Lepidoptera and Diptera. A three-dimensional model of Diaprepes trypsin contained two domains of beta-barrel sheets as has been found in Drosophila and Neobellieria. The catalytic active site is composed of the canonical triad of His41, Asp92 and Ser185 and a specificity pocket occupied by Asp179 with maximal activity at pH 10.4. Southern blot analysis indicated that at least two copies of the gene are encoded by Diaprepes midgut. Northern blot analysis detected a single RNA band below 1.35 kb at different larval ages (28-100 days old). The message increased with age and was most abundant at 100 days. Trypsin activity, on the other hand, reached a peak at 50 days and fell rapidly afterwards indicating that the trypsin message is probably regulated translationally. Feeding of soybean trypsin inhibitor and Aedes aegypti trypsin modulating oostatic factor affected trypsin activity and trypsin biosynthesis, respectively. These results indicate that Diaprepes regulates trypsin biosynthesis with a trypsin modulating oostatic factor-like signal. (+info)
Intact dietary soy protein, but not adding an isoflavone-rich soy extract to casein, improves plasma lipids in ovariectomized cynomolgus monkeys.
(8/910)
The dietary consumption of soy protein has been linked to a reduction in coronary heart disease and improvements in a number of related risk factors. Recent investigations have focused on isoflavone components of soy protein. The purpose of this study was to examine plasma lipids and lipoproteins, particularly LDL, with the intake of intact soy protein or casein-lactalbumin diets with and without a semipurified extract of soy, rich in isoflavones. Sixty ovariectomized cynomolgus monkeys were assigned to one of three groups fed diets containing the following: 1) casein-lactalbumin as the protein source (CAS; n = 20); 2) CAS plus a semipurified extract of soy, rich in isoflavones (ISO; n = 20); or 3) intact soy protein (SOY; n = 20) for 12 wk. Lipoproteins were fractionated by combined ultracentrifugation and HPLC. Isolated LDL particles were further subfractionated by dividing the LDL peak into three fractions for compositional analyses. The SOY group had significantly lower plasma total cholesterol, VLDL plus IDL cholesterol and LDL cholesterol, and significantly less HDL cholesterol than the CAS group. LDL particles from the SOY group had a significantly less cholesteryl ester than the CAS group. The semipurified extract of soy, rich in isoflavones, added to casein-lactalbumin protein did not have the same effects as intact soy protein on plasma lipids and lipoproteins. Other components of soy protein, either alone or in combination with isoflavones, may be involved in the effects seen in this study. (+info)