Daidzein improves insulin resistance in ovariectomized rats

To determine whether daidzein improves insulin resistance by modifying weight gain, visceral fat accumulation, blood lipids and serum cytokines levels in ovariectomized Sprague-Dawley rats.

Twenty-eight 12-week-old female rats were divided into three groups: the sham-operated group (SHAM) (n =10), the ovariectomized group receiving daidzein therapy (DAID) (n =10), and the ovariectomized control group (Control) (n =8). The rats in the DAID group received 50 mg/kg daidzein via gavage daily. Weight and food intake were recorded every 2 weeks. All of the animals were euthanized 12 weeks after ovariectomy, after which their fasting insulin, glucose, blood lipids, estradiol, interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), adiponectin and leptin levels were measured.

After 12 weeks, the ovariectomized rats demonstrated an increase in their body weight and visceral fat; compared to the SHAM rats, the ovariectomized rats also experienced a significant increase in their serum IL-6 levels and insulin resistance, which was calculated using the homeostatic model assessment of insulin resistance (HOMA-IR) (p <0.05). Daidzein therapy decreased weight gain, visceral fat, the HOMA-IR index and IL-6 levels that were induced by ovariectomy. Rats which had received daidzein therapy had lower levels of TNF-α, leptin and blood lipids (except for high density lipoprotein cholesterol) than the other two groups. IL-6 levels positively correlated with the HOMA-IR index in all of the rats after adjustment for body weight (r =0.495; p =0.016).

We conclude that daidzein can improve insulin resistance induced by ovariectomy by decreasing weight gain, visceral fat accumulation, blood lipids, TNF-α, leptin and IL-6 levels.