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[The study on mechanism of appetite regulation in diet-induced obesity resistant rats].

OBJECTIVE
To explore the cause of decreasing intake food of diet-induced obesity resistant (DIO-R) rats.


METHODS
Fifty male Sprague-dawley (SD) rats were randomly divided into control group and high-fat group and they were fed with basic diet and high-fat diet respectively for 13 weeks. DIO-R and diet-induced obesity (DIO) rats were selected according to their body weight and the quantity of energy intake, then observing the changes of the total food intake, the level of serum leptin and plasma NPY were determined by radioimmunoassay and the contents of the melanocortin receptor-4 (MCR-4) in brain were determined by Western Blot.


RESULTS
The total food intake of DIO-R rats was (1 679.1 +/- 146.8) g. The total food intake of DIO rats was (1 818.4 +/- 148.9) g. The total food intake of DIO-R rats was lower than that of DIO rats (P < 0.05). The level of plasma NPY of DIO-R rats was (795.24 +/- 83.59) ng/L. The level of plasma NPY of DIO rats was (1 007.14 +/- 172.83) ng/L. The level of plasma NPY of DIO-R rats was lower than that of the DIO rats (P < 0.05). The levels of serum leptin of basic, DIO-R and DIO rats was (4.80 +/- 0.75) microg/L, (9.17 +/- 1.19) microg/L and (9.32 +/- 1.04) microg/L. The level of serum leptin of rats in high-fat diet group was increased as compared with the rats in basic diet group, but there was no significant difference between DIO-R and DIO rats (P > 0.05). The levels of brain MCR-4 of basic, DIO-R and DIO rats were (342 +/- 31) mm2, (455 +/- 33) mm2, (355 +/- 30) mm2. High fat diets increased the content of brain MCR-4 in DIO-R rats.


CONCLUSION
DIO-R rats decreased appetite by increasing expression of ob gene to reduce activity of NPY pathway and activate the MCR-4 pathway, and thus inhibit the increase body of weight.