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| Author(s): |
Simone Mendonça
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Faculdade de Saúde Pública (FSP/CIR) |
| Defense date: | 2006-03-09 |
| Examining board members: |
Jose Alfredo Gomes Areas;
Nágila Raquel Teixeira Damasceno;
Ursula Maria Lanfer Marquez;
Paulo Hilario Nascimento Saldiva;
Raul Dias dos Santos Filho
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| Advisor: | Jose Alfredo Gomes Areas |
| Abstract | |
Objective. Amaranth has been considered a functional food because its consumption can lower blood cholesterol levels. In the present work the effect of amaranth protein on this property was investigated in hamsters. A possible component in amaranth grain that would respond for this effect is the protein fraction. Methods. In this study the amaranth protein was isolated by its alkaline solubilization at pH 11 and acid precipitation at pH 5.7. The isolate thus produced was defatted and resulted in a protein content of about 96%. This product was introduced in experimental diets to fed hamsters that previously had their blood cholesterol increased by a diet containing 30% casein and 0.05% cholesterol during 3 weeks Animals were then, divided in 3 groups (n = 11/group) were fed diets containing (g/100 g diet): (A) 20 casein (control), (B) 20 purified amaranths protein (group replacement), (C) 20 casein + 10 purified amaranths protein (group supplementation) for 4 wks. Results. The results showed that when amaranth was the sole protein source (at 20% level) or it was admixed with casein (20% casein +10% of amaranth protein), the hypercholesterolemized hamsters had a significant (P < 0.05) reduction in cholesterol levels (51 and 30%, respectively) as compared 7% reduction of the control group (20% casein). In the first week of diet the decrease was already observed. The lowering was mainly in LDL fraction. The mecanisms involved in lowering plasma cholesterol were investigated. Digestibility of amaranth protein was as high. The bile acids excretion was inversely proportional to plasma cholesterol lowering, while cholesterol excretion in feces was directly proportional. When free amino acids simulating the amaranth protein were used as the only nitrogen source of diet the cholesterol reduction was about 11%. Casein supplemented with arginine to bring the lysine/arginine ratio to 0.5, as observed in amaranth protein, was had deleterious effects to hamsters cholesterol levels. The bile acid and cholesterol excretion of this trial were equal to all groups. Conclusions. Amaranth´s protein reduces plasma cholesterol. Digestibility and bile acid excretion are not related to hypocholesterolemic effect of amaranths protein. The proportion between lysine/argine is a partial explanation for this effect, but the presence of whole protein is necessary for the higher cholesterol excretion in feces. The full understanding of mechanisms involved in cholesterol reduction in these experiments is not fully elucidated, suggesting further research on the direct action in lipid metabolism by peptides originated from the incomplete digestion of amaranth protein. (AU) | |