fMRI of Hypothalamic Responses to Glucose, Fructose, Sucrose and Sucralose

The hypothalamus is known to be important for control of feeding behaviour as well as the regulation of temperature. Functional magnetic resonance imaging (fMRI) is a non-invasive method, which detects transient haemodynamic changes in the brain, using blood oxygen level dependent (BOLD) signal differences.

In order to investigate the role of hypothalamic neural activity in response to different sweeteners, fMRI will be performed before, during and after ingestion of 300 ml plain water or 300 ml water containing 50 g glucose, 50 g fructose, 50 g sucrose or 0.33 g sucralose (high intensity sweetener not providing energy). All beverages will be consumed at 22 °C.

The study uses a randomized cross-over design in 16 healthy male subjects with a normal body weight. There will be an interval of at least one week between the five occasions.

Blood Oxygen Level Dependent signal intensity of the hypothalamus will be continuously measured for 21 minutes (5 minutes baseline, 4 minutes during drinking and 12 minutes after drinking).

Inclusion criteria

• Signed informed consent
• Age between 18 and 25 years
• BMI between 20 and 24 kg/m2
• Length between 170 and 190 centimetres

Exclusion criteria

• Diabetes or history of other disturbances of glucose metabolism (eg impaired glucose tolerance, hypoglycaemia).
• Any genetic or psychiatric disease (e.g. fragile X syndrome, major depression) affecting brain
• Any significant chronic disease
• Renal or hepatic disease
• Recent weight changes or attempts to lose weight (> 3 kg weight gain or loss, within the last 3 months)
• Smoking (current or last 6 months)
• Alcohol consumption of more than 21 units per week or use of recreational drugs at present or in the last year
• Recent blood donation (within the last 2 months)
• Recent participation in other biomedical research projects (within the last 3 months), participation in 3 or more biomedical research projects in one year
• Contra-indication to MRI scanning:

• Claustrophobia
• Pacemakers and defibrillators
• Nerve stimulators
• Intracranial clips
• Intraorbital or intraocular metallic fragments
• Cochlear implants
• Ferromagnetic implants