Effect of stevia and fructose consumption on food intake, body weight gain and metabolic parameters in rat

A relationship has been suggested between the increase in the consumption of sweetened beverages with high concentrations of sugars such as fructose and the increase in the prevalence of obesity and diabetes mellitus type 2 (Figlewicz et al., 2009; Nakagawa et al., 2006). In addition, industrial fructose has been produced in the last decades as a food and beverage sweetener, either fructose alone or as a component of a product called high fructose corn syrup (White, 2008). With the increase of the production of fructose its intake has increased; thus, increasing daily caloric intake (Douard and Ferraris, 2012; Nakagawa et al., 2006) and according to what was published by Martinez et al., (2018) exposure to an environment rich in palatable foods may contribute to overfeeding. As an alternative solution has been promoted the consumption of non-caloric sweeteners such as Stevia rebaudiana, which has been used for centuries to sweeten drinks and make tea (Tandel, 2011). Stevia is a South American plant native of Paraguay. The sweet-tasting components of stevia are called steviol glycosides that are naturally present in the stevia leaf. There are 11 steviol glycosides of which rebaudioside A and stevioside are the most abundant (Ashwell, 2015). The benefits attributed to stevia are due to its content of essential vitamins, minerals and antioxidants (Tondare and Hembade, 2019). Its positive effect on glycemic control is due to a decrease in the absorption of glucose in the duodenum, glycogenolysis and gluconeogenesis (Ahmad and Ahmad, 2018). Studies conducted in both humans and animals have evaluated the toxicity of stevia and support the safety of its consumption. No cases of intoxication due to stevia consumption or allergic type reactions have been reported (Ashwell, 2015; Purohit and Mishra, 2018; Tandel, 2011). The Food and Drug Administration has not questioned the GRAS status (generally recognized as safe) of certain high purity steviol glycosides for use in food (FDA, 2018). Studies in animal models have reported that stevia consumption for 8 weeks has reduced glucose levels in diabetic rats (Ahmad and Ahmad, 2018; Sharma et al., 2012), has decreased food intake, body weight (Elnaga et al., 2016) and triglyceride levels (Ahmad et al., 2018). However, Figlewicz et al., (2009) has not found differences in the body weight gain of rats that consumed stevia, hoodia, agave and fructose for 10 weeks; while Rosales et al., (2018) have reported an increase in body weight and insulin resistance in mice after 12 weeks of stevia consumption compared to the intake of sucrose and sucralose. Although the latter has been linked to hepatotoxic and nephrotoxic effects in the murine model (Sharma et al., 2007). The objective of this study was to compare the effect of stevia and fructose consumption on food intake, body weight gains and metabolic profile in Wistar rats.

Thirty-six 2-month-old male Wistar rats that were divided into three groups: control group (CG, n = 12), stevia group (SG, n = 12) and fructose group (FG, n = 12). All groups were provided with free access to water and food for 13 weeks. In addition, the SG group was provided with 0.2% stevia solution (high purity liquid extract) and the FG group with a 15% fructose solution (pure fructose). Subjects were housed in individual boxes and kept in 12-hour light-dark cycles (7:00 a.m. - 7:00 p.m.); with 22±1°C of ambient temperature. All procedures were carried out in accordance with the provisions of the Official Mexican Standard for the care, management and use of laboratory animals (NOM-062-200-1999) and approved by the Institutional Committee on Animal Ethics of the Behavioural Research Institute Food and Nutrition. The consumption of water, food and sweetened solutions has been recorded daily, while body weight has been registered weekly. Once the 13 weeks of experimentation was completed, the subjects were sacrificed and a blood sample was taken from each of them. The serum obtained was separated by centrifugation and kept at -70°C. Subsequently, the spectrophotometry technique was used to determine the amount of triglycerides, cholesterol and glucose (Linear Chemicals, Spain). Insulin levels were quantified by a Micro ELISA test using a standardized procedure based on the DSL-10-1600 Active™ insulin kit (Diagnostic Systems Laboratories, Webster, TX, USA) and the BIO reading kit -ELISA. Statistical analysis was conducted using one-way analysis of variance (ANOVA) and Bonferroni post hoc multiple comparison test using STATA/SE 12.0. The values of P<0.05 were considered as statistically significant.

The average values of food consumption, water, solutions and body weight are shown in Table 1. The FG has recorded a lower food intake compared to the other two groups. The SG has reported a lower feed intake than the CG with a statistically significant difference. These results coincide with those published by Ahmad et al., (2018) who provided stevia to rats at different concentrations for 8 weeks and found that the higher the dose of stevia, the less food was consumed. This may suggest that the consumption of stevia does not stimulate the appetite or cause a positive energy balance that leads to an increase in body weight (Ahmad and Ahmad, 2018). The fructose group showed a statistically significant increase in body weight (p<0.05) with respect to the stevia and control groups due to the caloric intake of fructose and its poor satiating effect (Havel, 2001; Tappy and Le, 2010). Of the total fluid consumption, the FG showed the highest intake with respect to the rest of the groups (p<0.05), while the CG showed the highest water intake (p<0.05). In the consumption of the sweetened solutions, the FG showed the highest consumption with respect to the SG (p<0.05). This result does not coincide with those reported by Figlewicz et al., (2009) who reported that the intake of drink sweetened with stevia produced an increase in fluid intake compared to a drink sweetened with fructose. However, Rosales et al., (2018) reported that the age of the subjects can intervene in the amount of sweetened solution consumed. In their study, they showed that subjects with younger age (4 and 9 weeks old) showed a lower stevia consumption compared to sucralose, whereas in subjects of 15 weeks of age the result is inverted.



Fig 1 shows the results of the metabolic parameters at the end of the 13 weeks of the experiment. The FG showed the highest serum glucose levels compared to the other groups (p<0.005). In insulin levels (panel B), the group with the highest serum levels was FG, showing a statistically significant difference with respect to stevia (p=0.022). The consumption of stevia showed better ability to regulate glucose and insulin levels compared to the group that consumed fructose. This is probably due to a decrease in the hepatic expression of the enzyme phosphoenolpyruvate carboxykinase (PEPCK). PEPCK is a key enzyme in the secretion of insulin and gluconeogenesis that contribute to the regulation of glycaemia and insulin sensitivity (Ahmad and Ahmad, 2018; Chen et al., 2005; Elnaga et al., 2016; Stark and Kibbey, 2014). It is important to perform additional studies to corroborate the possible molecular mechanisms that explain the effects of stevia consumption. For triglyceride levels (panel C), FC showed the highest levels compared to the CG and SG (p=0.002). The decrease in the levels of triglycerides in the SG as compared to the FG may be due to the fact that the stevia compounds (steviosides) improve the activity of the hepatic lipase that results in the catabolism of the lipids (Ahmad et al., 2018). For cholesterol (panel D), the FG group showed higher levels than the CG (p=0.001) and the SG (p=0.000). The SG group showed lower cholesterol levels than the CG (p=0.018). This is probably due to the ability of stevia to increase the excretion of bile acids and interrupt the formation of bile acid micelles, preventing the absorption of cholesterol in the small intestine (Ahmad et al., 2018). Later in the colon, stevia binds to bile or dietary cholesterol and increases the fecal excretion of bile acids by activating cholesterol 7α hydroxylase, thus reducing cholesterol levels. This indicates that stevia has an antihy perc hole sterolemic effect (Brijesh and Kamath, 2016; Elnaga et al., 2016; Hossain et al., 2011).

The present study indicates that the consumption of stevia showed no toxic effects and could be useful to reduce food intake, reduce cholesterol levels and contribute to better glycemic control in a rat animal model.

All authors declare that there is no conflict of interest.