The Estrogenic Effects of the Soy Phytoestrogen Genistein on the Liver and Bone of Chickens

Abstract

Commercial chickens are known to develop various estrogen dependent diseases, including liver steatosis and osteoporosis. Studies involving both humans and animals have indicated that consuming soy protein may reduce the incidence of both these diseases. Soy phytoestrogens have been shown to reduce lipid accumulation in the liver and increase bone mineral content and bone density in humans. No previous research has been performed on the effects of genistein in the liver or bone of chickens. Abnormal liver lipid accumulation, known as fatty liver or hepatosteatosis, is associated with many factors including plasma estrogen levels, excessive alcohol consumption, metabolic derangements, and obesity. Research evidence suggests that soy phytoestrogens may have a protective effect against liver lipid accumulation induced by estrogens in mammals. A series of studies was performed to determine if genistein would have a protective effect against liver lipid accumulation induced by exogenous estrogen in the chicken. Three experiments were performed using different types and ages of chickens; aged hens, mature hens, and male broiler chicks. Genistein doses were given by a daily oral gavage for fourteen days. Estrogen doses were given by injection in the subcutaneous tissue in the back of the neck three times during each experiment. There were no significant differences in most of the items measured. Exogenous estrogen was used to induce heavy liver lipid accumulation, but failed to induce this accumulation in all of the experiments. Because of this, it was difficult to determine if genistein had a protective effect on the liver. Research has suggested that the primary soy phytoestrogen, genistein, may help alleviate osteoporosis in women by increasing bone density through its estrogenic action. It is unknown whether genistein may improve bone density in aging laying hens or actually contribute to the problem through negative interactions with the hen’s endocrine system. The objective of this study was to characterize and quantify the effects of the genistein on bone physiology in aged hens. Sixty White Leghorn laying hens, which were 3 years old and had never been through an induced molting process, were randomly selected and divided into 4 treatments: Sham Control, Low Genistein, Medium Genistein, and High Genistien. Doses were given by subcutaneous injection in the back of the neck every other day for 8 weeks. There were significant differences between femurs belonging to birds in the High Genistein and Medium Genistein treatments for all of the bone parameters measured. Neither the Low Genistein treatment (10 mg/kg body weight) nor the Medium Genistein treatment (15 mg/kg body weight) showed a significant positive effect on the bone as compared to the Sham Control. The results of this study suggest that the High Genistein treatment (20 mg/kg body weight) has a beneficial effect on femur quality of aged laying hens.