Dietary Genistein is Protective Against X-ray Cataract in the Rat

Abstract

Abstract: : Background: Genistein inhibits diabetic cataract in the streptozotocin rat model, presumably due to its aldose reductase inhibitor (ARI) activity. Genistein is also a known anti-oxidant. We sought to assess the impact of oral genistein on gamma ray-induced cataract in the rat, in order to distinguish between ARI and other potential anti-cataract properties of genistein. Methods: Six-week old Sprague-Dawley rats were divided into the following groups: 20 rats received a gamma ray dose of 20 Gy from a Cesium 127 source to the right lens and a standard diet containing soy and thus genistein (RSD), 20 rats received radiation plus a special soy-free control diet containing virtually no genistein (RCD), 20 rats received radiation plus a standard diet supplemented with150 mg/kg/day genistein (R/150G), 21 rats received radiation plus 300 mg/kg/day genistein (R/300G), and 20 control animals received no radiation nor genistein (C). Retroillumination photographs of the irradiated eye were taken at 2, 6, 12, 18 and 24 weeks. The photographs were graded on a 0-4 scale with reference to photographic standards by a single, experienced, masked observer. An HPLC assay was carried out to measure lens and plasma-free genistein in 4 R/150G, 4 R/300G, 4 RSD and 10 RCD animals. Results: Mean cataract grade was significantly higher among the RCD animals than among all groups receiving genistein (P < 0.0001). Mean grades at 12 weeks were: RSD 0.6 +/- 1.19; RCD 3.8 +/- 0.8; R/150G 0.35 +/- 1.1; R/300G 0.38 +/- 1.1) Grade 4 opacities were also significantly more common in the RCD animals (P < 0.0001). Non-radiated eyes of the RCD animals remained clear. Genistein levels in the plasma, radiated and irradiated lens were significantly (P < 0.05) lower for the RCD animals than the genistein-treated animals, but were not lower for the RSD animals. (Table) Conclusions: Orally-absorbed genistein is present in the crystalline lens in measurable concentrations. Genistein protects against radiation cataract formation in this rat model, whether delivered through supplementation or dietary soy.  

Keywords: antioxidants • cataract • animal model