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Kurs: MCAT > Rozdział 2

Lekcja 1: Biological sciences practice passage questions

Do artificial sweeteners increase diabetes risk?

Zadanie

The effect of non-caloric artificial sweeteners (NAS) on human metabolism is controversial. Some suggest that NAS may short circuit metabolic pathways resulting in catastrophic consequences that range from increased obesity rates to higher cancer incidence. Recently, scientists performed 3 experiments to verify the effects of NAS on blood glucose levels and glycemic index - a number that indicates the total rise in a person's blood after ingesting food - and how the host’s intestinal microbes may modulate this effect.
Experiment 1: Scientists compared the blood glucose levels of groups of mice that were fed a oral solution with 3 types of NAS (saccharin, sucralose, or aspartame) with 3 control groups of mice that fed on water, glucose, or sucrose. Their results show that mice that received a type of NAS had significantly different blood glucose levels than the control groups (Figure 1).
Experiment 2: After 11 weeks, scientists repeated the same experiment, but this time prior to measuring the blood glucose levels, they treated the mice with 2 broad-spectrum antibiotic regimens (designated antibiotics A and B). This time blood glucose levels of the mice that received a type of NAS were similar to blood glucose levels of the control groups. Results of experiments 1 and 2 are shown on Figure 1.
Experiment 3: Because saccharin had the highest effect on blood glucose levels, the scientists then performed an additional experiment with 2 groups of mice. One group of mice received an intestinal microbiota transplantation from donor mice that drank a saccharin solution. A second group received an intestinal microbiota transplantation from donor mice that drank water only. The results of this experiment also showed significantly different blood glucose levels between the two groups of mice (Figure 2).
Figure 1. Blood glucose levels for mice fed with water, sucrose, glucose, saccharin, sucralose, aspartame for 11 weeks and then administered antibiotics: ciprofloxacin and metronidazole (‘antibiotics A’) or vancomycin (‘antibiotics B’). *** Indicates that blue lines are significantly different from others.
Figure 2. Blood glucose levels for mice that were never exposed to NAS following transplant of microbiota from saccharin- and water-fed mice. * Indicates that curves are significantly different from each other.
Assuming that their results reflect what would be observed in humans similar in humans, what is the effect of saccharin exposure on blood glucose levels and complications associated with diabetes mellitus risk?
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