Both water extract of rice bran (RBW) and rice bran oil (RBO) were previously shown to reduce fat deposition and area under the glucose-clearance curve in Sprague-Dawley rats fed with high-fat diet (65% of total calories) for four weeks [1]. To elucidate the effect on pancreatic islets, the study on the histology of these rat tissues was conducted. Rats in group 2 to 9 were high-fat fed. Group 3 to 6 were separately either co-treated daily with three doses (22.05, 220.5, 2205mg/kg) of RBW or 9.55mg/kg of metformin, twice daily. The high-fat feed in group 7 to 9 contained 20, 40 and 50% of total calories as cold pressed RBO, respectively. After four weeks of treatment, the insulin staining showed significant amount of vacuoles within beta cells (arrow head) as well as the dilated blood vessel (arrow) in tissues of rat fed with high-fat diet alone. RBW at the minimum daily dose of 220.5mg/kg, metformin and cold pressed RBO (group 8 and 9) were able to abolish these abnormalities. There was no positive Ki-67 staining in any tissue indicating no cell proliferative effect. It was concluded that rice bran extract ameliorates insulin resistance partly by protecting beta-cell function [3, 4].