Moderate intake of aspartame and sucralose with meals, but not fructose, does not exacerbate energy and glucose metabolism in estrogen-deficient rats

Abstract

Both nutritive and non-nutritive sweeteners may influence energy and glucose metabolism differently. The hypothesis that sucrose, fructose, aspartame, and sucralose intake differently modulate energy and glucose metabolism was tested in an estrogen-deficient animal model. At 30 min after giving aspartame and sucralose (10 mg/kg body weight), an oral glucose tolerance test (OGTT) was conducted with glucose, sucrose, and fructose in ovariectomized (OVX) rats. After OGTT, they were continuously fed high fat diets including either 10% corn starch (Control), 10% sucrose (Sucrose), 10% fructose (Fructose), 0.05% aspartame + 9.95% starch (Aspartame) or 0.05% sucralose + 9.95% starch (Sucralose) for 8 week. During 30 min after acute administration of aspartame and sucralose, serum glucose concentrations increased despite slightly increased serum insulin levels before glucose infusion. However, glucose tolerance was not significantly different among the groups. In chronic study, serum glucose concentrations were lowest and insulin highest at the overnight-fasted state in Aspartame and Sucralose. Postprandial serum glucagon-like peptide-1 (GLP-1) and insulin levels were higher in Aspartame and Sucralose than Control. Hepatic insulin signaling (pAkt → pGSK-3β) and phosphoenolpyruvate carboxykinase (PEPCK) expression were lower in Sucralose and Aspartame than the Fructose. Serum acetate levels produced by gut microbiota were higher were lower in the fructose group than Aspartame and Sucralose groups. In conclusion, aspartame and sucralose with a meal might be preferable sweeteners to fructose and sucrose in estrogen deficient rats, and possibly post-menopausal women; however, this needs to be confirmed in human studies.

Keywords: GLP-1; fructose; glucose; insulin signaling; non-nutritive sweeteners.

Fig. 1

Serum glucose and insulin levels after oral infusion of glucose, sucrose or fructose prior to the oral intake of distilled water, aspartame, or sucralose. Rats had 10 mg aspartame, sucralose or distilled water per kg body weight and at 30 min later, the rats had 2 g glucose, fructose or sucrose per kg body weight. Rats in the Aspartame and Sucralose groups had glucose and those in the Sucrose and Fructose had sucrose and fructose, respectively. Serum glucose levels were measured every 10 min after giving aspartame, sucralose and distilled water (−30 min) (A). Area under the curve (AUC) of serum glucose levels was calculated in 3 parts (B): prior to oral glucose infusion (−30–0 min), 1st part after glucose infusion (0–40 min) and 2nd part after glucose infusion (40–120 min). Serum insulin levels were measured at −30, 0, 20, 40, and 90 min (C). AUC of serum insulin levels were assayed in the 1st part after glucose infusion (0–20 min) and 2nd part after glucose infusion (20–40 min) (D). The dots and bars represent means ± SD (n = 12). *Significantly different among all groups in one-way ANOVA at p<0.05, ** at p<0.01, *** at p<0.001. ^a,b,cThe different letters on the bars represent significant differences among the groups by Tukey’s test at p<0.05.

Fig. 2

The changes of serum glucose levels and areas under the curve of glucose and insulin during the oral glucose tolerance test (OGTT) after 7 week consumption of the assigned sweeteners. The ovariectomized (OVX) rats were provided with a 45% fat diet with 10% starch, sucrose, fructose, aspartame + starch and sucralose + starch for 8 weeks. At the 7th week, 2 g of glucose/kg body weight was orally administered and the serum glucose and insulin levels were measured at the indicated times. The changes in the serum glucose (A) and insulin (B) levels were measured during the OGTT. The average of the area under the curve (AUC) of glucose (C) and insulin (D) during the first part (0–40 min) and second part (40–120 min) of the OGTT. The dots and bars represent means ± SD (n = 12). *Significantly different among all groups in one-way ANOVA at p<0.05, ** at p<0.01. ^a,b,cThe different letters on the bars represent significant differences among the groups by Tukey’s test at p<0.05.

Fig. 3

Serum GLP-1 levels at 30 min after assigned meal intake. After 7 weeks of feeding with a 45% fat diet with 10% starch, sucrose, fructose, aspartame + starch and sucralose + starch in the ovariectomized (OVX) rats, the rats had blood collection in overnight fasting state and 1 h food provision. Serum GLP-1 levels were measured from the blood. The bars represent means ± SD (n = 12). ^a,b,cThe different letters on the bars represent significant differences among the groups by Tukey’s test at p<0.05.

Fig. 4

Hepatic insulin signaling at the end of experiment. The ovariectomized (OVX) rats were provided with a 45% fat diet with 10% starch, sucrose, fructose, aspartame + starch and sucralose + starch for 8 weeks. After 16 h fasting, regular human insulin (5 U/kg body weight) was injected through their inferior vena cava. Hepatic deposition of glycogen and triglyceride was measured (A). The hepatic insulin signaling were measured with immunoblotting (B). The band intensity was measured with image analyzer (C). The bars represent means ± SD (n = 6). ^a,b,cThe different letters on the bars represent significant differences among the groups by Tukey’s test at p<0.05.