The Effects Of Chromium And Fish Oil On Rats Made Obese By High-fat Diet And Its Mechanism

In this paper, the effects and mechanisms of chromium and fish oil were studied in obese ratsand developing obese induced by high-fat diet. Developing obese rats were fed a high-fat dietsupplemented with chromium and fish oil. Obese rats were induced successfully by a basicalhigh-fat diet, and then, fed a high-fat diet with chromium and fish oil. We studied the effects ofhigh fat diet alone or with either or both chromium or fish oil in male wistar rats. Threeexperiments were carried out.In experiment one, 5 groups were studied for 5 weeks: a group given high-fat diet, a groupgiven high-fat diet and chromium, a group given high-fat diet and fish oil, a group given high-fatdiet+fish oil +chromium, and a control group given basic diet. At weekly intervals, tail blood wastaken after 12 hours'fasting, and the blood glucose, insulin and leptin were measured at the end ofthe study. Results show that developing obese rats have a high blood leptin level and high insulinlevel, after being fed a high-fat diet for five weeks. It suggests that, insulin and leptin resistancewere induced, with leptin resistance earlier than insulin resistance in the rats during the developingof obesity. Both chromium, fish oil alone or in combination prevented the developing of obesityand delayed the development of insulin resistance and leptin resistance.In experiment two, rats were fed a high-fat diet for 8 weeks. Some became obese, theDiet-induced obesity (DIO) rats; the others did not become obese and were called diet-inducedobesity resistance (DIO-R) rats. DIO rats were divided into four groups. All groups were fed ahigh-fat diet continuously and three groups were given chromium and/or fish oil for another sixweeks. The results showed that chromium and fish oil increased the blood levels of testosterone,growth hormone, free thyroxin 3 and decreased blood cholesterol, triglycerides, glucose, leptin,insulin and free thyroxine in DIO rats. Chromium and fish oil therefore played an important role inhormone levels.In order to study the mechanism of the effects of chromium and fish oil on DIO rats, wemeasured the blood neuropeptide Y using the RIA Kit; brain melanocortin-4 receptor using thewestern blot; uncoupling protein 2 mRNA of white fat tissue using the reverse transcriptpolymerase chain reaction. Compared with the animals in the control group, DIO rats had higherlevels of blood NPY and brain Orexin A. Chromium and fish oil group had low levels of brainOrexin A. Results indicated that DIO rats had greater appetite compared with control group andthat chromium and fish oil can depress high appetite of DIO rats. Expression of UCP2 mRNA ofwhite fat tissue of DIO rats was higher than that of the control group. Chromium can increase theexpression of UCP2 mRNA of white fat tissue of DIO rats.Obese rats had lipid and carbohydrate metabolism disorders. Chromium and/or fish oilprevented the development of obese rats and controlled the energy metabolism. These results maybe useful in the prevention of obesity in humans.