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[Effects of chlorogenic acid on glucose tolerance and its curve characteristics in high-fat diet-induced obesity rats].

OBJECTIVE
To observe the effect of chlorogenic acid (chlorogenic acid, CGA) on the glucose tolerance and its curve characteristics in high fat diet-induced obesity (diet-induced-obesity, DIO) rats, so as to provide scientific grounds for the development and utilization of CGA in early prevention and reversal of prediabetes.


METHODS
Eight of forty-six male Sprague-Dawley rats were randomly selected as the normal diet group (CON group), and the rest were fed with high-fat diet. After 4 weeks, 24 high-fat-induced obese rats were screened according to the criteria and then randomly divided into high fat diet group (HFD group), 50% CGA group and 98% CGA group. The CGA groups received intragastric administrations of 50% CGA and 98% CGA orally via a gavage needle once a day for 8 weeks, respectively, while the CON and HFD groups received a carrier solution (phosphate buffer saline, PBS). Their body weights were measured weekly and oral glucose tolerance test (OGTT) was performed every 4 weeks. Fasting insulin and insulin release were measured at the end of the study. Meanwhile, HOMA-IR and visceral fat percentage were calculated. Histopathological examination by hematoxylin and eosin staining method were evaluated in the pancreatic tissues.


RESULTS
Before the intervention of chlorogenic acid, blood glucose levels 120 min after glucose loading (P<0.05) and AUC-G (P<0.05) were increased in the HFD group when compared with the CON group, and the time to glucose peak was delayed after 4 weeks of chlorogenic acid intervention (P<0.05). After 8 weeks of intervention, the HOMA-IR index, the insulin levels at 0 min, 30 min, 60 min, and 120 min after glucose loading and AUC-I increased (P<0.05), and the histopathological examination showed obvious hyperplasia of pancreatic islets (P<0.05). Compared with the HFD group, there was no significant change in glucose tolerance and glucose peak time in 50%CGA and 98%CGA groups at the end of 4 weeks of intervention. However, after 8 weeks of intervention, OGTT-60min,OGTT-120min blood glucose (P<0.05) were lower, HOMA-IR index and OGTT-0min, OGTT-120min serum insulin level decreased (P<0.05), the time to glucose peak shifted to an earlier timepoint (P<0.05), abnormal islet hyperplasia attenuated (P<0.05) in 50% CGA and 98% CGA groups. Also, the OGTT-30min serum insulin level was decreased (P<0.05) in 50% CGA group.


CONCLUSION
Delay in time to glucose peak during the OGTT was one of the manifestations of impaired glucose tolerance in DIO rats, and 50% and 98% CGA could improve the glucose tolerance and delay in glucose peak time.