Resting-state Imaging and Chronic Consumption of Non-Nutritive SweetenerS

Condition(s) studied

Investigational drug(s) / intervention(s)

administration of questionnaires: During this visit, the investigator will again explain the study objectives and procedure. Once these explanations have been provided, healthy volunteers will be able to give their informed consent to participate. After signing the consent form, the following will be conducted during this visit: * A medical examination. * An electronic questionnaire including two consumption frequency assessment tools, adapted in French, to measure daily sugar and artificial sweetener intake. * Five tests assess the level of dependence on alcohol, drugs (cannabis, solvents, tranquilizers, barbiturates, cocaine, stimulants, hallucinogens, or narcotics), gambling, video games, and possible eating disorders. Volunteers with a score deemed above the norm for at least one of these six tests will be excluded from this study. * A urine screening test for drug use (cannabis, opiates, amphetamines, cannabinoids, benzodiazepines, cocaine) will be performed during this visit.

carrying out a MRI scan: A functional exploration using resting-state fMRI and microstructural tissue organization using DTI will take place in the days following the inclusion visit, depending on the availability of "research" slots in the Department of Radiology and Imaging, Clermont-Ferrand University Hospital.

Can distribution visit for subjects in the "non/low" sweetener consumption group: During this visit, scheduled following the MRI, subjects will go to the PIC/CIC where they will be given cans for the 5 weeks of the nutritional intervention (660 ml of sweetened beverage, or 2 cans per day). Subjects will be advised to arrive by car if possible and to park in the PIC/CIC parking lot at the foot of the building. Drinks will be provided to the subject in one or two batches (with an additional visit to the center to pick up any missing drinks) at the subject's convenience. They will also receive instructions for completing the electronic questionnaire to assess daily sugar and sweetener consumption. Subjects will complete this questionnaire weekly, which they will receive by email. Their email address will be collected during this visit.

carrying out a MRI scan: A functional exploration using resting-state fMRI and microstructural tissue organization using DTI, post-nutritional intervention (5 weeks) in non- and low-sugar consumers: this exploration will take place depending on the availability of "research" slots at the Department of Radiology and Imaging, Clermont-Ferrand University Hospital.

Study summary

Non-nutritive sweeteners are used as a substitute for simple sugars to improve the palatability of food products without increasing their sugar and calorie content. They represent a global market of 7 billion euros, with an annual growth of 5%. Reducing their consumption therefore seems to be excluded. Some studies have focused on the impacts of these substances on brain activity. According to a recent study, continuous consumption of low doses of saccharin in adult mice significantly decreases the level of dopamine in the prefrontal cortex and significantly increases striatal dopamine, which modifies decision-making strategies. Resting-state functional Magnetic Resonance Imaging (r-fMRI) studies in humans have also shown that an increase in striatal dopaminergic activity modifies the resting-state functional connectivity of brain regions linked to the reward circuit. r-fMRI allows the characterization of brain networks and the strength of correlations between brain regions, without any specific task being required. It is a rapid, non-invasive technique that can measure changes in brain functional connectivity.

In addition to r-fMRI, diffusion tensor imaging (DTI) is able to assess white matter microstructure and the integrity or otherwise of fiber tracts. Several parameters such as the fractional anisotropy (FA), coefficient of white matter, mean diffusivity, and radial diffusivity can be modified in the event of changes in functional connectivity, reflecting axonal rearrangements, not visible on conventional MRI sequences. Based on previous research, investigators hypothesize that (1) chronic consumption of non-nutritive artificial sweeteners increases striatal dopaminergic activity. (2) This modification is accompanied by changes in resting-state functional connectivity in brain regions of interest associated with the reward circuit in healthy young adults.

Then, the primary objective of this study is to compare, in the resting state, the differences in functional connectivity of brain regions of interest between "non/low consumers" and "high consumers" of sweeteners at the start of the study using r-fMRI.

The key secondary objective of this study is to assess changes in brain connectivity using r-fMRI in non- and low-consuming subjects before and after a transient increase in their sweetener consumption over 5 weeks.

The secondary objectives include assessing daily sugar consumption (5-week follow-up), daily consumption of non-energy-rich artificial sweeteners (5-week follow-up), Body Mass Index (BMI), physical activity level, and white matter microstructure and fibrous tract integrity using a diffusion-weighted MRI (DTI) sequence.

Eligibility

Primary outcome measure(s)

• 1. At rest, functional connectivity between brain areas in healthy subjects, non/low consumers and high consumers of sweetener — High sweetner consumers: within 4 weeks after enrollment. Low or no sweetner consumer: within 4 weeks after enrollment and immediately after completion of the 5-weeks nutritional intervention.
  Resting-state functional magnetic resonance imaging (rs-fMRI) is a method that studies the connectivity of different regions of the nervous system. Based on the acquisition of the BOLD (Bond Oxygen Level Dependent) signal, this method focuses more specifically on the study of low-frequency fluctuations (\<0.1 Hz) of this signal. The goal of resting-state imaging is to identify the synchronous activation of different regions of the brain and brainstem, in the absence of a stimulus or a task being performed. This activation can be observed between physically connected regions, or not, and demonstrates the involvement of these regions in a common network called the "Resting State Network" (RSN), which brings together different brain regions involved in common functions; this is referred to as "functional connectivity" between these regions. Areas of interest involved in the reward circuit (amygdala, nucleus accumbens, anterior insula, striatum, the prefrontal cortex, hypothalamus).

Trial sites (1)

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