Abstract
The role of seed proteins, especially soyabean 7S globulins, in controlling dyslipidaemia is widely acknowledged. Amino acid sequence homology among the proteins of this family could reflect similar biological functions in other species. The aim of the present study was to unveil a hypolipidaemic effect of the 7S globulins from cowpeas (7S-C) and adzuki beans (7S-A), administered orally to rats fed a hypercholesterolaemic (HC; high cholesterol and TAG) diet for 28 d. A total of forty-five rats were divided into five groups (nine rats per group): (1) standard (STD) diet; (2) HC diet; (3) HC diet+7S-C (300mg/kg per d); (4) HC diet+7S-A (300mg/kg per d); and (5) HC diet+simvastatin (SVT; 50mg/kg per d), as a control. Significant decreases in food intake and final body weight of rats receiving HC+7S-C and HC+7S-A diets compared with groups fed the HC and STD diets were observed. Significant decreases in serum total and non-HDL-cholesterol of 7S-C, 7S-A and SVT groups were also observed. HDL-cholesterol levels increased in the 7S-C, 7S-A and SVT groups, while hepatic cholesterol and TAG concentrations were significantly lower than in the HC diet group for the 7S-C-supplemented group only. Faecal excretions of fat and cholesterol in HC diet groups were considerably higher in animals consuming the 7S globulins. The results show that cowpea and adzuki bean 7S globulins promote cholesterol-decreasing effects in hypercholesterolaemic rats even at low dosages, as already observed for other legume seed storage proteins of this family. This main effect is discussed in relation to the possible mechanisms of action.
Highlights
Dietary interventions have been used to control serum TAG and cholesterol, contributing to prevent CHD; in particular, diets containing soyabean and other legumes seeds have been associated with a reduction in the number of risk factors associated with these illnesses[1,2,3,4]
Isolation of cowpea and adzuki bean 7S globulins for animal trials In the present study, two novel isolation procedures of cowpea and adzuki bean main protein fractions, i.e. the 7S globulins, were used to generate sufficient amounts of proteins for animal trials
Effects of the daily administration of 7S globulins from cowpeas (7S-C), adzuki bean 7S globulin (7S-A) and simvastatin on food consumption, weight gain, feeding efficiency ratio and faecal excretion in the animals of all groups, fed the diets for 28 d, are shown in Table 2. 7S-A and simvastatin produced a decrease of about 12 % on the final body weight of the animals, with a reduction on the average body-weight gain of 23 % with respect to the HC diet-fed animal group. 7S-C was effective too, though to a lesser extent
Summary
Dietary interventions have been used to control serum TAG and cholesterol, contributing to prevent CHD; in particular, diets containing soyabean and other legumes seeds have been associated with a reduction in the number of risk factors associated with these illnesses[1,2,3,4]. The 7S globulins of most leguminous seeds are composed of a subunit assortment yielding a molecular mass of approximately 150–220 kDa; the constituent subunits may vary in size and number within and among species[18]. Despite these differences, a considerable degree of sequence homology, when comparing partial and complete nucleotide sequences of genes and mRNA encoding for them, has been observed[19]. In the search of the biological activity of never-investigated species, we undertook the present study to monitor the effects of isolated 7S globulins from cowpeas and adzuki beans (7S-C and 7S-A, respectively), compared with simvastatin, on lipid parameters of rats fed a hyperlipidaemic and cholesterolaemic diet
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