The isoflavones genistein and daidzein increase hepatic concentration of thyroid hormones and affect cholesterol metabolism in middle-aged male rats.

We examined whether isoflavones interfere with thyroid homeostasis, increase hepatic thyroid hormone concentrations and affect cholesterol metabolism in middle-aged (MA) male rats. Thirteen-month-old Wistar rats were injected subcutaneously with 35 mg/kg b.w./day of genistein, daidzein or vehicle (controls) for four weeks. Hepatic Dio1 gene expression was up-regulated by 70% (p < 0.001 for both) and Dio1 enzyme activity increased by 64% after genistein (p < 0.001) and 73% after daidzein treatment (p < 0.0001). Hepatic T3 was 75% higher (p < 0.05 for both), while T4 increased only after genistein treatment. Serum T4 concentrations were 31% lower in genistein- and 49% lower in dadzein-treated rats (p < 0.001 for both) compared with controls. Hepatic Cyp7a1 gene expression was up-regulated by 40% after genistein and 32% after daidzein treatment (p < 0.05 for both), in agreement with a 7α-hydroxycholesterol increase of 50% (p < 0.01) and 88% (p < 0.001), respectively. Serum 24- and 27-hydroxycholesterol were 30% lower (p < 0.05 for both), while only 24-hydroxycholesterol was decreased in the liver by 45% after genistein (p < 0.05) and 39% (p < 0.01) after dadzein treatment. Serum concentration of the cholesterol precursor desmosterol was 32% (p < 0.05) lower only after dadzein treatment alone, while both isoflavones elevated this parameter in the liver by 45% (p < 0.01). In conclusion, isoflavones increased T3 availability in the liver of MA males, despite decreasing serum T4. Hepatic increase of T3 possibly contributes to activation of the neutral pathway of cholesterol degradation into bile acids in the liver. While isoflavones obviously have the potential to trigger multiple mechanisms involved in cholesterol metabolism and oxysterol production, they failed to induce any hypocholesterolemic effect.

Testosterone and estradiol treatments differently affect pituitary-thyroid axis and liver deiodinase 1 activity in orchidectomized middle-aged rats.

We previously reported that orchidectomy (Orx) of middle-aged rats (15-16-month-old; MA) slightly affected pituitary-thyroid axis, but decreased liver deiodinase (Dio) type 1 and pituitary Dio2 enzyme activities. At present, we examined the effects of subsequent testosterone-propionate treatment (5mg/kg; Orx+T), and compared the effects of testosterone with the effects of estradiol-dipropionate (0.06mg/kg; Orx+E) treatment. Hormones were subcutaneously administered, daily, for three weeks, while Orx and sham-operated (SO) controls received only the vehicle. The applied dose of T did not alter serum TSH, T4 and T3 concentrations in Orx- MA, though it increased TSH when administrated to Orx young adults (2.5-month-old; Orx-YA). However, pituitaries of Orx-MA+T rats had higher relative intensity of immunofluorescence (RIF) for TSHß; in their thyroids we found increased volume and height of follicular epithelium, decreased volume of the colloid and higher RIF for T4-bound to thyroglobulin (Tg-T4). Liver Dio1 activity was increased. E-treatment did not affect serum hormone levels, pituitary RIF for TSHß, or liver Dio1 activity in Orx-MA rats. Thyroids had decreased relative volume and height of follicular epithelium, increased relative volume of the colloid, decreased volume of sodium-iodide symporter-immunopositive epithelium and lower RIF for Tg-T4. Detected changes were statistically significant. In conclusion, androgenization enhanced pituitary TSHß RIF, thyroid activation and liver Dio1 enzyme activity in Orx-MA, without elevating serum TSH as in Orx-YA rats. Estrogenization induced pituitary enlargement with no effect on pituitary TSHß RIF, serum TSH or liver Dio1 activity. E also induced alterations in thyroid histology that indicate mild suppression of its functioning, and contributed to thyroid blood vessel enlargement in Orx-MA rats.

Genistein affects parathyroid gland and NaPi 2a cotransporter in an animal model of the andropause.

This study aimed to examine the effects of genistein on the structural and functional changes in parathyroid glands (PTG) and sodium phosphate cotransporter 2a (NaPi 2a) in orchidectomized rats. Sixteen-month-old Wistar rats were divided into sham-operated (SO), orchidectomized (Orx) and genistein-treated orchidectomized (Orx+G) groups. Genistein (30 mg/kg/day) was administered subcutaneously for 3 weeks, while the controls received vehicle alone. PTG was analyzed histomorphometrically, while the expressions of NaPi 2a mRNA/protein levels from kidneys were determined by real time PCR and Western blots. Serum and urine parameters were determined biochemically. The PTG volume in Orx rats was increased by 30% (p<0.05), compared to the SO group. Orx+G treatment increased the PTG volume by 35% and 75% (p<0.05) respectively, comparing to Orx and SO animals. Orchidectomy led to increment of serum PTH by 27% (p<0.05) compared to the SO group, Orx+G decreased it by 18% (p<0.05) comparing to Orx animals. NaPi 2a expression in Orx animals was reduced in regards to its abundance in SO animals, although it was increased in Orx+G group compared to the Orx. Phosphorus urine content of Orx animals was raised by 12% (p<0.05) compared to that for the SO group, while Orx+G induced a 17% reduction (p<0.05) in regards to Orx animals. Our study shows that Orx increases PTG volume and serum PTH level, while protein expression of NaPi 2a is reduced. Application of genistein attenuates the orchidectomy-induced changes in serum PTH level, stimulates the expression of NaPi 2a and reduces urinary Pi excretion, implying potential beneficial effects on andropausal symptoms.

Daidzein effects on ACTH cells: immunohistomorphometric and hormonal study in an animal model of the andropause.

Daidzein is a potential natural alternative to estradiol during therapy of some malignancies in men. Besides weak inhibition of tyrosine kinase activity, daidzein has a sizeable inhibitory effect on calcium channels. The aim of this study was to examine the effects of daidzein on the immunohistomorphometric features of pituitary adrenocorticotropes (ACTH cells) and circulating levels of ACTH and corticosterone, in comparison with estradiol, in an animal model of the andropause. Sixteen-month-old Wistar rats were divided into sham operated (SO), orchidectomized (Orx), estradiol treated orchidectomized (Orx+E) and daidzein treated orchidectomized (Orx+D) groups. Estradiol (0.625 mg/kg/day) and daidzein (30 mg/kg/day) were administered subcutaneously for three weeks, while the SO and Orx groups received the vehicle alone. ACTH cells were identified by the peroxidase-antiperoxidase (PAP) immunohistochemical procedure. Peripheral circulating concentrations of ACTH and corticosterone were measured by immunoassay. Orchidectomy reduced (p<0.05) the cell volume and volume density of adrenocorticotropes by 11% and 16%, respectively, in comparison to SO rats. In Orx+E rats, the volume density of ACTH cells decreased (p<0.05) by 25%, but the circulating level of ACTH increased (p<0.05) by 29%, compared to Orx rats. Daidzein treatment significantly decreased (p<0.05): volume density of ACTH cells, circulating ACTH and corticosterone by 24%, 48% and 33%, respectively, compared to the Orx group. In conclusion, this study revealed that daidzein negatively modulated the immunohistomorphometric features of ACTH cells and, unlike estradiol, decreased ACTH and corticosterone secretion, in an animal model of the andropause.

Daidzein administration positively affects thyroid C cells and bone structure in orchidectomized middle-aged rats.

SUMMARY: Thyroid C cells hormone, calcitonine, inhibits bone resorption. We have demonstrated that daidzein treatment of orchidectomized rats (model for osteoporosis) stimulated C cells and increased trabecular bone mass. These results suggest that, besides direct action, daidzein may also affect bone structure indirectly through enhancement of thyroid C cell activity. INTRODUCTION: Thyroid C cells produce calcitonin (CT) which acts as an inhibitor of bone resorption. In this study, the influence of daidzein treatment on thyroid C cells, bone structure, and bone function in orchidectomized (Orx) middle-aged rats was investigated. METHODS: Sixteen-month-old Wistar rats were divided into Orx and sham-operated (SO) groups. Half the Orx rats were given subcutaneous injections of daidzein (30 mg/kg b.w./day) for 3 weeks. CT-immunopositive thyroid C cells were morphometrically analyzed. The metaphyseal region of the proximal tibia was measured histomorphometrically, and cancellous bone area (B.Ar), trabecular thickness (Tb.Th), trabecular number (Tb.N), and trabecular separation (Tb.Sp) were calculated. Serum samples were analyzed for CT and osteocalcin (OC), calcium (Ca) and phosphorus concentrations, and urine samples for Ca levels. RESULTS: Treatment of Orx animals with daidzein significantly increased volume of C cells compared to the Orx rats. Daidzein also enhanced B.Ar, Tb.Th, and Tb.N and reduced Tb.Sp. The serum OC and urinary Ca concentrations decreased significantly in comparison with the Orx group. CONCLUSIONS: These findings indicate that daidzein treatment stimulates thyroid C cells, increase trabecular bone mass, and decrease bone turnover in Orx middle-aged rats, which is the model of male osteoporosis.

Multiple treatments with SRIH-14 or octreotide affect adrenal zona glomerulosa in adult male rats.

Somatostatin analogues are currently used to treat various disorders such as hypersecretion and different neuroendocrine tumors. In this study we examined the effects on the adrenal cortex of somatostatin (SRIH-14) and octreotide administered subcutaneously twice daily for 5 days to adult male rats. Control rats received saline under the same regime. After sacrifice, the adrenal glands were removed and examined morphometrically using the M(42) multipurpose test system. Blood samples were prepared for biochemical tests. Both SRIH-14 and octreotide induced morphofunctional changes in adrenal zona glomerulosa. We found significant decreases (p < 0.05) in the absolute cell and nuclear volumes of zona glomerulosa in both experimental groups in comparison to the control. The serum aldosterone level was 11% lower (p < 0.05) in the SRIH-14 and 13% (p < 0.05) lower in the octreotide-treated group in comparison with the control group. Morphometric parameters of zona fasciculata and zona reticulata and corticosterone levels were not altered significantly (p > 0.05) in either treated group. It may therefore be concluded that both SRIH-14 and octreotide affected zona glomerulosa in the same manner by decreasing morphofunctional characteristics.

The effects of chronic SRIH-14 and octreotide administration on the pituitary-adrenal axis in adult male rats.

The effects of chronic treatments with SRIH-14 and octreotide on pituitary corticotropes (ACTH cells) and on the adrenal cortex of male Wistar rats were examined. Adult males received two daily s.c. injections of 20 microg/100 g of body weight of either SRIH-14 or octreotide for 28 consecutive days. ACTH cells were studied using a peroxidase-antiperoxidase immunocytochemical procedure. Morpho-metry was used to evaluate the changes in cell and nuclear volumes (microm3) and volume densities (%) of ACTH-immunoreactive cells. The adrenal cortex was analyzed by histological and morphometric methods. A significant (p<0.05) decrease in body weight and in the absolute weights of the pituitary and adrenal glands was observed in both treated groups. Morphometric parameters of ACTH cells in both treated groups were not significantly (p>0.05) different than in control rats. The absolute volumes of the adrenal gland and adrenal cortex were significantly (p<0.05) decreased in both treated groups. The absolute and relative volumes of the zona glomerulosa (ZG), as well as the cellular and nuclear volumes of the ZG were significantly (p<0.05) decreased in the both treated groups. In rats treated with SRIH-14 and octreotide, the absolute and relative volumes of the zona fasciculata (ZF) and zona reticularis (ZR), as well as their stereological parameters, did not change significantly (p>0.05). The aldosterone levels in the SRIH-14 and ocreotide-treated groups were significantly (p<0.05) decreased - by 13% and 19%, respectively. The concentration of ACTH and corticosterone did not change significantly. Together, these findings show that SRIH-14 and octreotide administration affected the morphological characteristics of the adrenal ZG in a similar manner, and brought about a decrease in plasma aldosterone concentration. These treatments did not affect pituitary ACTH cells or adrenal ZF and ZR functioning.

Central effects of ghrelin on serum growth hormone and morphology of pituitary somatotropes in rats.

Ghrelin, an endogenous ligand for the growth hormone (GH) secretagogue receptor, was originally purified from rat stomach; subsequently, ghrelin neurons were found in the arcuate nuclei of rats. Central effects of the peptide on GH release, however, remain to be clarified. The aim of the present study was to determine the morphologic features of GH-producing pituicytes and serum GH concentration after central administration of ghrelin. Five injections of rat ghrelin or phosphate-buffered saline (PBS; n = 10 rats/group) were given every 24 hrs (1 microg of ghrelin in 5 microl of PBS) into the lateral cerebral ventricle of male rats. Significant (P < 0.05) increases in absolute and relative pituitary weights occurred in ghrelin-treated rats versus controls (58% and 41%, respectively). Morphometric parameters (i.e., the volume of GH cells, volume of their nuclei, and volume density) all significantly (P < 0.05) increased by 17%, 18%, and 19%, respectively, in the ghrelin-treated group versus controls. Terminal serum concentration of GH was significantly (P < 0.05) increased by 15% with ghrelin treatment. The results clearly document that daily nanomolar doses of ghrelin into the lateral cerebral ventricle stimulate GH cell proliferation and promote GH release. Thus, achieving pharmacologic control of central ghrelin receptors is a promising modality to modulate the actions of GH.