Reduction of serum lipids by soy protein and soluble fiber is not associated with the ABCG5/G8, apolipoprotein E, and apolipoprotein A1 polymorphisms in a group of hyperlipidemic Mexican subjects.

Several studies have evaluated the effect of soy protein or soluble fiber on serum cholesterol in hypercholesterolemic subjects, with different results. We hypothesized that this response is associated with the presence of polymorphisms in genes encoding proteins involved in lipoprotein metabolism or reverse cholesterol transport. Thus, the aims of the present work were to study the effectiveness of a dietary portfolio consisting of a combination of soy protein and soluble fiber integrated in a low saturated fat (LSF) diet on blood lipids in a Mexican group with hyperlipidemia and to determine the association between responsiveness to the diet and the frequency of apolipoprotein (Apo) E and ApoA1 and ABCG5/8 polymorphisms. Forty-three hyperlipidemic subjects (20 men and 23 women) were given an LSF diet for 1 month, followed by an LSF diet that included 25 g of soy protein and 15 g of soluble fiber daily for 2 months. After the 3-month dietary intervention, serum total cholesterol (TC) significantly decreased by 20.6%, and serum triglycerides (TGs) decreased by 40.4%. Fifty-one percent of the subjects had a reduction more than 20% in serum TC, and 77% of the subjects had a reduction more than 20% in serum TG (hyperresponders). Approximately 14% of the hypercholesterolemic subjects had the ABCG8 (52 G/C) polymorphism, 65% had the ABCG5 (1950 C/G and G/G) polymorphism, 53.5% had the ApoA1 (-75 G/A and A/A) polymorphism, and 23.3% had the ApoE (3/4) polymorphism. Independently of genotype, the combination of cholesterol-lowering foods in an LSF diet significantly reduced serum TC and TG in Mexican hypercholesterolemic subjects.

Soy protein ameliorates metabolic abnormalities in liver and adipose tissue of rats fed a high fat diet.

Chronic consumption of high-fat or -carbohydrate diets is associated with the development of obesity; however, it is not well established whether dietary protein plays a role in the development of abnormalities of lipid metabolism that occur during obesity. To determine the effect of different types of protein during diet-induced obesity on hepatic and adipocyte lipid metabolism, rats were fed casein (CAS) or soy (SOY) protein diets with 5% fat or high-fat diets with 25% fat (HF-CAS and HF-SOY) for 180 d. Rats fed soy diets had lower hepatic sterol regulatory element binding protein-1 (SREBP-1) expression and higher SREBP-2 expression than those fed casein diets, leading to less hepatic lipid deposition. On the other hand, long-term HF-SOY consumption prevented hyperleptinemia in comparison with rats fed HF-CAS. Rats fed soy protein diet showed higher adipocyte perilipin mRNA expression and smaller adipocyte area than those fed casein diets, which was associated with a lower body fat content. Furthermore, the lipid droplet area in brown adipose tissue was significantly lower in rats fed soy diets than in those fed casein diets and it was associated with higher uncoupling protein-1 (UCP-1) expression. As a result, rats fed the soy diets gained less weight than those fed the casein diets, in part due to an increase in the thermogenic capacity mediated by UCP-1. These results suggest that the type of protein consumed and the presence of fat in the diet modulate lipid metabolism in adipose tissue and liver.