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BACKGROUND: Male Kunming mice were divided into the normal diet group (control group) and the high-fat diet group (HF group, 185 g·kg-1 protein, 600 g·kg-1 fat and 205 g·kg-1 carbohydrate). After eight weeks' feeding, the behavioral and biochemical indicators in serum were determined. The double bottle preference experiment was used to study the preference of mice for five sweeteners. The contents of monoamine neurotransmitters and genes expression related to dopamine (DA) and opioid receptor were also determined. RESULTS: The body weight of the mice in HF group increased significantly (p < 0.05) after 36 days compared with the control group. While the feed intake of HF group increased sharply in the first 12 days, and then it became basically unchanged. The preference of the HF group for all the five sweeteners was very significantly lower (p < 0.01) than that of the control group. The depression-related behavior was observed in the HF group mice. The contents of TG, TC and LDLC in the HF group were extremely higher (p < 0.01) than that of the control group. The genes expression related to DA and opioid receptor in the HF group was significantly lower than that of the control group, except for the preproenkephalin (PENK). CONCLUSIONS: In summary, this study suggested that a long-term high-fat diet could result in the decrease of the preference for sweeteners on mice due to the long-term consumption of high-fat diet could result in a state of reward hypofunction on mice. This article is protected by copyright. All rights reserved.

This study focused on the effect of short-term intake of sweeteners on feed intake, solution consumption and neurotransmitters release on mice. The results showed that the free drinking of 10 mM sucralose solution, 100 mM maltose solution, 3 mM saccharin solution and 3 g/L stevioside solution for 32 days will not affect the normal development of the body weight and feed intake of the mice. The consumption of maltose solution was significantly higher than that of the other sweeteners. The leptin and insulin levels increased significantly after the short-term intake of these four sweeteners. The dopamine (DA) content in the whole brain of the mice increased significantly only in the maltose group. These results indicate that the short-term intake of the preferred concentrations of maltose, stevioside, sucralose and saccharin will not affect the body weight and feed intake of the mice. Mice prefer maltose solution to other sweeteners solutions. The 100 mM maltose solution and 3 mM saccharin solution could result in the oxidative stress on mice after 32 days’ short-term intake. Compared with other sweeteners, only sugars that could be broken down into small molecules of glucose might have a positive effect on dopamine levels.

The effect of short-term intake of high- and low-concentrations of sucrose solution on the neurochemistry of male and female mice was studied. The body weight, feed intake, sucrose solution consumption and brain monoamine neurotransmitters were determined after 34 days' intake of 1% and 8% sucrose solutions. The gene expression and protein levels related to dopamine and opioids were also determined. The results showed that the intake of 1% and 8% sucrose solution for 34 days did not cause significant changes in the weight development of both male and female mice. The preference for sucrose varies with sex. Both males and females had greater preference for the high concentration sucrose solution than the low concentration sucrose solution. The continuous intake of sucrose stimulated the release of monoamine neurotransmitters (DA, 5-HT, NE) in the brains of mice, and the reward effect of 8% sucrose solution is significantly higher than that of 1% sucrose solution. The sex of mice did not affect the release of neurotransmitters. The gene expressions of D1 and D2 were up-regulated in the 1% sucrose group of male mice, while the OPRM1 gene expression was down-regulated. The expression of these three genes in the 8% sucrose group of male mice was all down-regulated, while the gene expressions of D1 and D2 in the 1% and 8% sucrose group (p < 0.05) of female mice were both up-regulated.

Four natural sweeteners (sucrose, stevioside, maltose and xylitol) and six artificial sweeteners (acesulfame, sucralose, aspartame, cyclamate, saccharin and neotame) were used to study the effects of different sweeteners on the behavior and neurotransmitter release of mice with two-bottle preference experiments. The results showed that very significant preference behavior for 8% sucrose solution, 0.3% stevioside solution, 10 mM acesulfame, 10 mM sucralose and 10 mM aspartame solutions (p