Impact of flaxseed and soy nuts as dietary supplements on lipid profile, insulin sensitivity and GLUT4 expression in ovariectomized rats.

Key Findings

The most widely researched phytoestrogens are soy isoflavones (genistein, daidzein and glycitein) and flaxseed lignans (secoisolariciresinol). Potential benefits include anticarcinogenic effect, cardioprotection, and reversal of some menopausal symptoms or deleterious effects of genotoxicity.   The literature is not consistent with regard to the association between estrogen deprivation and changes in the glucose transporter type 4 (GLUT4). This study aimed to examine the effects of flaxseed or soy nuts versus estradiol on lipid profile, blood pressure, insulin sensitivity, and GLUT4 expression in ovariectomized female rats. This study showed in an animal model of hypoestrogenism that soy nuts and flaxseed phytoestrogens may have health benefits by reducing cholesterol and triglycerides with no effects on body weight, BP and insulin sensitivity. These effects were accompanied by increased GLUT4 expression at cardiac and adipose tissue level mostly in the plasma membrane. Soy nuts and flaxseed intake had no effect on BP possibly because the rats in this experiment were young and normotensive, or even because they were administered different amounts from those that have been associated with BP effects in rats. The authors concluded that flaxseed and soy nuts as dietary supplements may improve lipid profile. Flaxseed and soy nuts increased GLUT4 expression, particularly in adipose tissue, which may be associated with a tendency to improve insulin resistance. Thus, these dietary supplements, used in an animal model of menopause, may have health benefits with potential clinical implications by improving lipid profile and increasing GLUT4 expression in insulin-sensitive tissues with no harmful estrogen-like effects on both reproductive and cardiovascular systems.

ABSTRACT

We assessed the effects of a diet with flaxseed or soy nuts versus estradiol on lipid profile, insulin sensitivity, and GLUT4 expression in ovariectomized female rats. Forty-four Wistar female rats (90-days old) underwent ovariectomy were divided: C (standard diet); E (standard diet+subcutaneous 17β-estradiol pellets); L (standard diet+flaxseed+subcutaneous placebo pellets); and S (standard diet+soy nuts+subcutaneous placebo pellets). Customized diets and the insertion of pellets were started 21 days after ovariectomy, and maintained for another 21 days. We measured body weight, insulin tolerance, total cholesterol, LDL-cholesterol, HDL-cholesterol, triglycerides, and GLUT4 (cardiac and adipose tissues). We found lower body weight and Lee index in group E; a trend for improved insulin sensitivity in S (p=0.066). Groups L and S showed lower lipid profile vs. C. Microsomal GLUT4 increased in L (cardiac and adipose tissues); plasma membrane GLUT4 increased in E, L and S (both tissues). We conclude that flaxseed and soy nuts as dietary supplements improve lipid profile and they increased GLUT4 expression.