Changes Of Glucose Tolerance And Dietary Regulation Mechanism Induced By Artificial Sweetener In Mice

More than 20 kinds of artificial sweeteners with characteristics of metabolic inertia have been widely used in food and pharmaceutical industries in different countries and regions.But their impacts on the organism remain controversial in recent years.The consumption of non-nutritive sweetener even sugar substitute of diabetics,largely in the form of food additives,has been associated in epidemiological studies with numerous adverse metabolic outcomes,including weight gain,the metabolic syndrome,and diabetes.However,there are still many controversies about the effects of long-term use of sweeteners on dietary behavior and glucose metabolism,and the mechanism causing the above phenomenon is not fully understood.At the same time,it is not clear whether the abnormal glucose metabolism can be changed by dietary regulation.Therefore,in this paper,C57BL/6 mice,ICR mice,sweet taste receptor Tas1r3 knockout mice and germ-free mice were used as experimental animals.Animal behavior,Western blot,real-time fluorescence PCR and ELISA methods were used to analyze the effects of long-term exposure of artificial sweeteners on the food intake,drink consumption,body weight and glucose tolerance of mice.Secondly,the effects of sucralose exposure on intestinal sweetness receptors and glucose transporters were analyzed to explore the possible molecular mechanism of impaired glucose tolerance based on sweet-sensing signaling pathway.Finally,we explored whether reducing the amount of digestible starch in the diet could improve the negative effects of artificial sweeteners.The results of the studies are listed as follows: 1.Artificial sweeteners induced impaired glucose tolerance in mice through the sweet signaling pathwaySucralose(SUC),acesulfame potassium(AK)and saccharin(SAC)were exposed to male C57BL/6 mice for 12-18 weeks with different sweetness(8,10,12,14,16 and 18).Mice exposed to purified water were treated as the blank control group.The results showed that in the process of sweetener exposure,compared with the control group,the long-term exposure of artificial sweetener induced significantly increased blood glucose and impaired glucose tolerance in mice,and the degree of increase and impaired glucose tolerance were positively correlated with the exposure time.Further 12 weeks of exposure to Tas1r3 knockout mice and germ-free mice exposed to sucralose with a sweetness of 8-14 showed that the sweetener exposure had the same impaired glucose tolerance as the wild-type mice,but the sweetener had no effect on the glucose tolerance of Tas1r3 knockout mice.These results suggest that the sweetness signaling pathway is a potential target for glucose intolerance induced by long-term exposure to artificial sweeteners.2.Long-term exposure of artificial sweeteners upregulated the expression abundance of sweet receptors and glucose transportersSucralose was exposed to wild-type mice with different sweetness(8-18).The expression of sweet taste receptor genes(Tas1r2,Tas1r3)and glucose transporter genes(Sglt-1,Glut2)in different segments of the small intestine(including duodenum,proximal jejunum,middle jejunum,distal jejunum and ileum)was detected by fluorescence quantitative PCR.The results showed that the sweetness receptors and glucose transporters were up-regulated in 5 intestinal segments after artificial sweetness exposure.In addition,the up-regulation of Tas1r2 and Tas1r3 was positively correlated with the sweetness of sucralose,while the expression of Sglt-1 and Glut2 first increased and then decreased with the increase of the sweetness of sucralose,and reached the highest level when the sweetness of sucralose was 12.These results suggest that the addition of sweeteners may modulate glucose transporter expression by enhancing the sweetness signal,thereby achieving the regulation of glucose tolerance.3.The decrease of digestible starch content in diet improved the glucose metabolism disorder induced by artificial sweetener in miceThe digestible starch content(55%,44% and 33%)of the diets and sucralose with sweetness of 12 were exposed to male ICR mice.Mice exposed to the digestible starch content of 66% of the diet and sucralose with sweetness of 12 were treated as the control group,and mice exposed to the digestible starch content of 66% of the diet and purified water were treated as the blank control group.The results showed that sucralose exposure resulted in dysfunction of glucose metabolism,including the increase of glucose,insulin resistance,sweet receptors,glucose transporters and carbohydrate absorption.Through the positive regulation of the above indexes,the digestible starch content in the diet was reduced to improve the glucose metabolism disorder induced by artificial sweeteners in mice,and the digestible starch content of 33% of diet had the most significant effect.Further 66% digestible starch content of the diet,different sweeteners with different sweetness(acesulfame potassium with sweetness of 10,saccharin with sweetness of 8)were exposed to male C57BL/6 mice for 6 weeks,and then mice were exposed to the digestible starch content of 33% of the diet for next 6 weeks.The results showed that the digestible starch content of 33% of the diet could significantly improve the glucose metabolism disorder induced by artificial sweeteners in mice by positively regulating the glucose,insulin resistance,sweet receptors,glucose transporters and carbohydrate absorption.The above results indicate that diet regulates glucose transporter expression,regulates glucose tolerance and improves glucose metabolism abnormalities by enhancing sweet taste signal.In conclusion,the above results demonstrate that the sweetness signaling pathway is a potential target for impaired glucose tolerance induced by artificial sweeteners.Reducing the digestible starch content in the diet can greatly improve the glucose metabolism disorder induced by artificial sweeteners.The mechanism of impaired glucose tolerance and dietary regulation induced by artificial sweeteners is explained.These results may provide support for the identification of the mechanism of impaired glucose tolerance induced by artificial sweeteners and lay the foundation for the alleviation of glucose metabolism disorders.