A Brief Communication

Abstract

Nutritional supplements containing soybean phytoestrogens, the isoflavones genistein (G) and daidzein (D), are increasingly used as alternative therapy for osteoporosis, cancer, and cardiovascular and other diseases with a frequency that increases with advancing age. In this study we examined the effects of subcutaneous administration of either G or D on serum lipid levels in orchidectomized (Orx) and intact (IA) middle-aged male rats, which are experimental models of andropause. Sixteen-month-old Wistar rats were treated with 10 mg/kg and 30 mg/kg of either G or D. The control groups received testosterone, estradiol, or vehicle for 3 weeks, after which the total serum cholesterol (TC), low-density lipoprotein (LDL-C), high-density lipoprotein (HDL-C), and total triglycerides (TT) were measured. Compared with the matching vehicle-treated controls, the higher doses of G and D and testosterone treatment significantly (P < 0.05) lowered the TC and lipoprotein cholesterol levels. The greatest effect was observed regarding LDL-C in both Orx and IA males after G and D treatments, in which LDL-C decreased by more than 30%. The lower isoflavone doses induced a significant cholesterol-lowering effect (P < 0.05) only in the Orx group. Like the estradiol treatment, the higher doses of G and D increased the TT levels in both rat models by more than 50% (P < 0.05). The lower doses of isoflavones increased TT only in the Orx group. In male middle-aged rats, injections of higher doses of G and D decreased the serum cholesterol levels, as did testosterone injection, and brought about an increase in serum triglycerides similar to that observed after estradiol treatment.

Somatopause, weaknesses of the therapeutic approaches and the cautious optimism based on experimental ageing studies with soy isoflavones

“…Our animal model of severe andropause (orchidectomized middle-aged male rats; the central regulation of endocrine processes is disturbed) was characterized by almost 10 % decrease in the mean body mass, when compared to the same parameter in sham-operated middle-aged rats (Ajdžanović et al, 2014[ 8 ]). Orchidectomy-caused testosterone elimination from the hormonal millieu of this model did not affect on TSH and thyroxine circulating levels, but significantly increased cholesterol (total, LDL and HDL) blood concentrations (Šošić-Jurjević et al, 2007[ 126 ], 2012[ 128 ]). While the average absolute pituitary weight was not significantly changed in the orchidectomized model males, the average relative pituitary weight was significantly (p<0.05) increased by 13.6 %, in comparison with the sham-operated controls.…”

“…and high (30 mg/kg b.m.) genistein or daidzein application to orchidectomized middle-aged rats (Šošić-Jurjević et al, 2007[ 126 ]). Appearance of the somatotropic system and the related biochemical/physiological parameters, reflecting the soy isoflavone application in the animal model of severe andropause, are not all in the perfect coherence when it comes to the potential benefit of the substances' supplementation.…”

“…Representative studies have shown that some positive outcome could be noticed in soy isoflavone treatment of breast and prostate cancer, osteoporosis, coronary heart disease, as well as ageing-related psychological symptoms (Casini et al, 2006[ 34 ]; Messina, 2010[ 93 ]; Messina et al, 2010[ 94 ]; Andres et al, 2011[ 20 ]). The research experience that qualifies us for an credible opinion related to soy isoflavone effects during ageing is based on a multi-year exploitation of different rat models of andropause and menopause, in the context of these compounds application (Ajdžanović et al, 2009[ 10 ][ 11 ], 2011[ 12 ], 2012[ 9 ], 2014[ 8 ][ 6 ]; Milošević et al, 2009[ 99 ]; Filipović et al, 2007[ 52 ], 2010[ 50 ]; Šošić-Jurjević et al, 2007[ 126 ], 2010[ 127 ], 2012[ 128 ], 2014[ 129 ]; Pantelić et al, 2013[ 112 ]; Trifunović, 2012[ 137 ]; Trifunović et al, 2012[ 134 ], 2014[ 135 ][ 133 ], 2016[ 136 ]; Medigović et al, 2015[ 92 ]). The general scarcity of data concerning the soy isoflavone effects in somatopause, together with the fact that our ageing rat models, besides numerous neuroendocrine axes disturbancies, manifest the somatopausal symptoms also, highlight the reported soy isoflavone role in their, at least partly, alleviation (Trifunović, 2012[ 137 ]; Ajdžanović et al, 2014[ 8 ]; Trifunović et al, 2014[ 133 ], 2016[ 136 ]).…”