Phytosterol additive boosts adrenal response to ACTH in male Japanese quail (Coturnix coturnix japonica)

Sea cucumbers-derived sterol sulfate alleviates insulin resistance and inflammation in high-fat-high-fructose diet-induced obese mice

Sea cucumbers are widely consumed in traditional medicine and food. Sea cucumbers-derived sulfated sterol exhibits a sulfate group at C-3 position, which is different from phytosterol with a hydroxyl group. However, the effect of sterol sulfate on metabolic syndrome remains unknown. The purpose of the present study is to investigate the alleviation of sterol sulfate on high-fat-high-fructose diet (HFFD)-induced insulin resistance and inflammation. After 2 weeks feeding with HFFD, male C57BL/6J mice were continuously fed with HFFD plus 0.4 % (w/w) sterol sulfate or phytosterol for 6 weeks. The OGTT was carried out at 7 weeks. At the end of the experimental period, the changes of glycogen, circulating glucose, insulin, pro-inflammatory cytokine and adiponectin were measured. H&E staining was used to observe the morphological changes in adipose tissue. Furthermore, the underlying molecular mechanisms were investigated. Dietary sterol sulfate was superior to phytosterol in reducing body weight gain, adipocyte hypertrophy, and levels of circulating glucose and insulin, as well as increasing the glycogen content of tissues. Furthermore, sterol sulfate ameliorated insulin resistance mainly due to the inhibition of gluconeogenesis, the promotion of glycogen synthesis and GLUT4 translocation by activating PI3K/Akt signaling pathway. Additionally, sterol sulfate effectively attenuated inflammation by increasing serum adiponectin and reducing pro-inflammatory cytokine release. Sterol sulfate exhibited a more significant effect than phytosterol in alleviating HFFD -induced insulin resistance and inflammation, which might be closely related to the sulfate group. The results might provide insights into the prevention and alleviation of metabolic syndrome.

Enhancement of Galloylation Efficacy of Stigmasterol and β-Sitosterol Followed by Evaluation of Cholesterol-Reducing Activity

In this study, incorporation of gallic acid into typical phytosterols (β-sitosterol and stigmasterol) through Steglich esterification was optimized employing the protection and deprotection strategy. A novel mechanism leading to side esterification was discovered. Complication of the phenolic hydroxyl groups and side reactions were successfully reduced under the optimized conditions. The structural identity and purity of galloyl stigmasterol and galloyl β-sitosterol were confirmed by NMR, FT-IR, and HPLC-MS. Evaluation of galloyl β-sitosterol and galloyl stigmasterol revealed their excellent antioxidant and cholesterol-reducing activities. Significant enhancement of cholesterol-reducing activity by galloylation was unveiled especially for β-sitosterol. Galloyl β-sitosterol had slightly better antioxidant activity at ambient temperature and better cholesterol-reducing activity. Molecular modeling suggested that a subtle difference of galloyl β-sitosterol and galloyl stigmasterol in activities could be attributed to variation of molecular rigidity and conformation. The excellent properties of galloyl β-sitosterol and galloyl stigmasterol suggested their great potential application in the food industry.

The effects of phytosterols on the sexual behavior and reproductive function in the Japanese quail (Coturnix coturnix japonica)

Phytosterols (PS) are plant origin sterols naturally found in many foods and added as food additives. Since 1950, PS have attracted considerable attention due to their ability to lower serum cholesterol and inhibit cardiovascular disease (CVD). However, recent studies have found that PS act as endocrine-disrupting chemicals in laboratory animals. Therefore, this study was aimed at finding the mechanism(s) for PS effects on the sexual behaviors and reproductive functions in male Japanese quails (Coturnix coturnix japonica). At 15 d of age, 30 male Japanese quails were randomly assigned to 3 groups for the chronic in-vivo experiment. Animals were gavaged daily with single dose of PS suspension (PS dissolved in medium chain triglyceride [MCT]) into the crop sac from 15-100 d of age. Following maturation, a sexual behavior test, semen collection, and test of fertilization ability were performed. Blood was collected by cervical dislocation at 100 day of age for hormones analysis. To observe the direct effects of PS on the testis, interstitial cells of the normal testes were cultured for 24 h. Ovine-LH (O-LH) was used for half of each group to stimulate interstitial cells for testosterone production. The results showed that chronic doses of PS reduced (P < 0.01) mount and copulation behavior in male quails (primarily in the group receiving 800 mg/kg BW). Both acute in vitro and chronic in vivo experiments revealed a reduction in testosterone (P < 0.05) after PS treatments; concomitantly, Leydig cell numbers were also low (P < 0.05) at a dose of 800 mg/kg BW. Real-time PCR results showed lower expression of 17β-hydroxysteroid dehydrogenase (17β-HSD) at the same dose. The results suggested that feeding large amounts of PS reduced testosterone levels and sexual behavior by affecting Leydig cell proliferation, and cholesterol trafficking, 17β-HSD expression in the testes of male Japanese quail.

Effects of Phytosterols as Food Additives on Adrenal and Reproductive Endocrine Function during Sexual Maturation in Male Japanese Quail (Coturnix coturnix japonica)

Varying amounts of phytosterols (PS) occur naturally in several foods of plant origin. PS, which are structurally and functionally similar to cholesterol, have been shown to reduce plasma total cholesterol (TC) and low-density lipoprotein-cholesterol (LDL-C) levels. Moreover, PS disrupts endocrine function in certain animals. In the present study, we investigated the effects of high doses of PS on adrenal and reproductive endocrine function during sexual maturation in Japanese male quails. Two experiments were conducted; in the first experiment, quail chicks were subjected to long-term chronic feeding of PS (8, 80, and 800 mg/kg body weight [BW]) and the chemicals were gavaged into the crop sac from 7-50 days post-hatching. From the forty-fourth day, half of the animals in each group were subjected to a 6-day adrenocorticotropic hormone (ACTH) challenge for artificial stimulation of the adrenal gland and evaluation of long-term PS effects; in the second experiment, single doses of PS were subcutaneously injected (SC) into adult males (10-weeks-old) to assess the acute direct effect. Results indicated that chronically PS-fed animals showed a better adrenal response to ACTH challenge, and the corticosterone levels were higher (P<0.05) than those of the controls. Moreover, corticosterone levels were also high (P<0.05) 3 h after SC injection of PS. In contrast, testosterone levels and the testes weights were significantly lower (P<0.05) in the groups chronically administered with PS. No differences were observed in the testosterone levels in the acute experiment or luteinizing hormone (LH) levels in either experiment. In conclusion, the differential effects of PS on the adrenal gland and testis might be due to preferential use of different lipoprotein-cholesterol forms for steroid production. In addition, PS might locally perturb testosterone production by its accumulation or delay in testicular maturation.