OBJECTIVETo explore the expression changes of mRNA and protein of uncoupling protein 2 (UCP2) in adipose tissues and uncoupling protein 3 (UCP3) in muscle tissues of rats which were treated with repeated fasting/refeeding and followed by fed with high-fat diet, and their possible mechanism on lipid metabolism.

METHODSThe model of repeating fasting/refeeding rats (repeated cycles of 1-day fasting and 1-day refeeding for 6 weeks fed with common-fat diet, RFR) was designed. At the end of the 6th week, the RFR rats were switched to high-fat diet every day (RFR-CF/HF). Moreover, the control rats were randomly divided into two groups and then fed with high-fat diet (HF) and common-fat diet (CF) respectively for 6 weeks. All rats were killed at the end of the 6th and the 12th week, serum and plasma samples were taken from abdominal aorta, and then the concentration of serum lipids, glucose, free fatty acid (FFA), and plasma insulin were measured. The histomorphological changes of liver tissues were observed by HE staining. The expression level of mRNA and protein of UCP2 in adipose tissues and UCP3 in muscle tissues was respectively measured by RT-PCR and Western blot.

RESULTS(1) The concentration of serum glucose in RFR group was significantly lower than that in control group (P < 0.05), while the concentration of serum FFA, expression level of UCP2 mRNA, UCP3 mRNA and protein were significantly higher than those in control group (P < 0.05). (2) The concentration of serum total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), and plasma insulin in RFR-CF/HF group was significantly lower than that in HF group, but significantly higher than that in CF group (P < 0.05). The concentration of serum FFA was significantly lower than that of HF and CF groups (P < 0.01). The expression level in UCP2, UCP3 mRNA and protein was significantly higher than that of HF group, but significantly lower than that of CF group (P < 0.05).

CONCLUSIONThe feeding pattern of repeated fasting/refeeding can decrease the obese degree induced by high-fat diet, increase the mRNA and protein expression of UCP2 in adipose tissues and UCP3 in muscle tissues, up-regulate the proton leak caused by obesity, and improve the rate of basic energy metabolism in rats.