Establishment of High-Fat Diet–Induced Obesity Rat Model

The obesity rat model was established based on the method described by Levin and Dunnmeynell12 and Wang et al.13 Sixty male Sprague-Dawley rats (180 ± 10 g) were housed on a 12-hour light-dark cycle and fed a standard chow diet (69% carbohydrate, 20% protein, and 5% fat) for 1 week to adapt to the diet. Then, 45 rats were randomly switched to a high-fat diet (HFD; 59% carbohydrate, 20% protein, and 15% fat, which is from the recipe of the American Institute of Nutrition and the Association of Official Analytical Chemists, with slight modification). According to the method described by Levin and Dunnmeynell, after 12 weeks, 15 obese rats with the greatest body weight gain were obtained. Apomorphine (APO) was used to estimate penile erectile function in control and obese rats. Epididymal, peritoneal, and mesenteric fat weights of six rats from each group were tested randomly for additional obesity estimates. Triglyceride, total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, fasting blood glucose, hemoglobin A_1c, serum insulin, and testosterone levels from six rats from each group were measured to determine metabolic profiles.