Expression profiling by high throughput sequencing
Summary
Low-calorie sweetener (LCS) consumption in children has increased dramatically due to widespread presence in the food environment and efforts to mitigate obesity through sugar replacement. However, mechanistic studies on the long-term impact of early-life LCS consumption on cognitive function and physiological processes are lacking. Here, we developed a rodent model to evaluate the effects of daily LCS consumption (acesulfame potassium, saccharin, or stevia) during adolescence on adult metabolic, behavioral, gut microbiome, and brain transcriptomic outcomes. Results reveal that habitual early-life LCS consumption impacts normal post-oral glucose handling and impairs hippocampal-dependent memory in the absence of weight gain. Furthermore, adolescent LCS consumption yielded long-term reductions in lingual sweet taste receptor expression and alterations in sugar-motivated appetitive and consummatory responses. While early life LCS consumption did not produce robust changes in the gut microbiome, brain region-specific RNA sequencing analyses reveal LCS-induced changes in collagen- and synaptic signaling-related gene pathways in the hippocampus and nucleus accumbens, respectively, in a sex-dependent manner. Collectively, these results reveal that habitual early-life LCS consumption has long lasting implications for glucoregulation, sugar-motivated behavior, and hippocampal-dependent memory in rats, which may be based in part on changes in nutrient transporter, sweet taste receptor, and central gene pathway expression.
Overall design
Male and female Sprague Dawley rats (Envigo, Indianapolis, IN, USA; postnatal day (PN) 25; 50-70g) were housed individually in a climate controlled (22–24 °C) environment with a 12:12 light/dark cycle (lights off at 6pm). Rats were maintained on standard chow (Lab Diet 5001; PMI Nutrition International, Brentwood, MO, USA; 29.8% kcal from protein, 13.4% kcal from fat, 56.7% kcal from carbohydrate) and water. All experiments were performed during the light cycle. At PN 26, rats were randomized into groups of comparable weights and provided with their experimental diets. Body weights were measured daily whereas water consumption and chow intake were measured 3 times per week. Female estrus phase was not manipulated nor tracked in any of the experiments. Diet. Juvenile male and female rats (n=8 per sex) were provided with the maximum acceptable daily intake (ADI) in mg/kg body weight, as recommended by the U.S. FDA, for acesulfame potassium (ACE-K; catalog # A2815, Spectrum Chemical, Gardena, CA, USA; 0.1% weight/volume (w/v) in reverse osmosis (RO) water; ~15 mg/kg). The volume required for delivery of ACE-K was calculated based on body weight daily and injected into a rodent sipper tube with a vinyl cap, and placed on the wire rack of the home cage adjacent to the rat’s ad libitum standard chow and water bottle. Voluntary consumption of the entire sweetener ration was verified daily by inspecting the tube for all animals. Rats in the control group (CTL; n=8 per sex) were provided a sipper tube filled with RO water at an equivalent volume/body weight as the ACE-K and group. Sweetener access ceased at PN 80.
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