Neuromodulation by soy diets or equol: Anti-depressive & anti-obesity-like influences, age- & hormone-dependent effects

Abstract

BackgroundSoy-derived isoflavones potentially protect against obesity and depression. In five different studies we examined the influence of soy-containing diets or equol injections on depression, serotonin levels, body weight gain (BW) and white adipose tissue (WAT) deposition in female Long-Evans rats at various stages of life [rats were intact, ovariectomized or experienced natural ovarian failure (NOF)].ResultsIn general, animals fed a soy-rich diet (Phyto-600) and/or administered equol (@ 5 mg/kg/day) displayed significant decreases in BW and WAT compared to a low-soy diet. When equol was injected alone (5 mg/kg/day), experiments 1, 4, and 5 demonstrated that body weight was significantly decreased. Equol has body weight control effects in females that are dependent on ovarian status and/or age of diet initiation. Experiments 1-4 all displayed no significant differences in depressive-related behavior as measured by the Prosolt forced swim test (PFST) when soy-rich (Phyto-600) or low-soy diets (Phyto-low) or equol treatments (5 mg/kg/day) were tested in female rats at various ages or hormonal status. Results of all the experiments are not presented here due to space limitations, but data from experiment 5 are presented. From conception female rats were exposed to either: a) a soy-rich (Phyto-600) or b) low-soy diet (Phyto-low). After 290 days all rats experienced NOF. At 330 days-old the animals were examined in the Porsolt forced swim test (PFST). One month later a second PFST was performed [after Phyto-low fed animals were injected with equol (5 mg/kg/day) for one week prior to the second PFST]. At the first PFST, serotonin and mobility levels were significantly decreased in the Phyto-low fed animals compared to animals that consumed the Phyto-600 diet. After equol injections at the second PFST, mobility and serotonin levels significantly increased in aged NOF rats fed the Phyto-low diet (to levels comparable to Phyto-600 fed animals).ConclusionsConsumption of dietary isoflavones or equol exposure in rats has body weight controlling effects and equol specifically may have antidepressant potential dependent upon diet initiation and/or dosage of treatments. The current study demonstrates that equol is able to decrease body weight, abdominal WAT, and depressive-related behavior. While other factors and mechanisms may play a role, in part, the present results provide a greater understanding of how isoflavonoid molecules modulate the brain's influence on behavior.

Noble Rats Display Decreased Weight Gain and Visceral Adiposity via Lifelong Exposure to an Isoflavone-Rich Diet

“…The present results were similar to previous findings where feeding Long-Evans rats significantly reduced VAT weights when fed a High-Iso vs. a Low-Iso diet [20,29]. While genistein has been shown to have weight reducing and diabetic protecting properties [30], it is interesting to note that equol represents the major circulating isoflavonoid in the present study that has been shown to have beneficial weight and VAT reducing actions [19,31].…”

Tissue- and Organ-Specific Promoters for Expression of Heterologous Genes in Transgenic Cassava (Manihot Esculenta Crantz) Plants

“…As highlighted by the reports by Setchell and Clerici, Lund et al, and Blake et al, equol has recently caught the interest of researchers because of its powerful antioxidant activity and its unique molecular and biochemical messenger properties with implications in treating age-related diseases [22][23][24]. Of particular interest, equol has an affinity for estrogen receptor beta, which is abundant in keratinocytes of the epidermis and fibroblasts in the dermis, as reported by several investigators [14,[25][26][27].…”

Use of Phytoestrogens for the Treatment of Psychiatric Symptoms Associated with Menopause Transition

“…Authors showed that soy diet rich in phytoestrogens and equol produced antidepressant-like efects at the same time that induces a reduction of body weight and white adipose tissue in all endocrine conditions. After the soy-rich diet, high plasmatic levels of genistein, daidzein and equol were detected in those animals that received the highest dose [65]. Unfortunately, the authors did not evaluate anxiety-like behaviors.…”

“…After that, several doses of a diet rich in phytoestrogens (200 or 600 ppm of phytoestrogens in diet) and equol injections (5 mg/kg) were evaluated in the forced swimming test in rats under diferent endocrine conditions: intact, ovariectomized and aged rats with natural ovarian failure [65]. Interestingly, the later group resembles an animal model of "natural menopause" because rats are acyclic, and it is the only report, as far as we know, that evaluate the efect of the isolavones under this condition.…”