Effect of hydroxycitrate on respiratory quotient, energy expenditure, and glucose tolerance in male rats after a period of restrictive feeding

Objective Recently we demonstrated that hydroxycitrate (HCA) suppresses food intake and body weight regain in male rats after substantial body weight loss. However, it is not known whether HCA also affects the respiration quotient (RQ), energy expenditure (EE), and glucose tolerance in this animal model. Methods Twenty-four male rats (initial body weight, 378 ± 3 g) were fed restrictively (10 g/d) for 10 d and then given ad libitum access to a high-glucose diet supplemented with 3% HCA for 6 d. Controls received the same diet without the supplement. RQ and EE were measured during ad libitum days 1, 2, and 6. An oral glucose tolerance test was performed on ad libitum day 4 or 5. Results HCA decreased RQ and EE during ad libitum days 1 and 2. In all probability, these findings reflect a decrease in de novo lipogenesis. On ad libitum day 6, RQ and EE did not differ between treatment groups. HCA suppressed food intake during the first 3 d ad libitum, but overall body weight regain was not decreased in the HCA group. The oral glucose tolerance test showed that HCA significantly decreased the increase in plasma glucose from baseline (Δglucose) and tended to decrease the area under the curve for glucose. Δinsulin and area under the curve for insulin did not differ between groups. Conclusions These results indicate that, in this animal model, HCA suppresses de novo lipogenesis. Moreover, HCA may improve glucose tolerance.