Obesity if known to be associated with brain insulin resistance in humans and evidence is rapidly accumulating that brain insulin resistance influences peripheral metabolism, eating behavior and cognition. A reduced insulin response in the brain is found mainly in people with a metabolically unfavorable fat distribution - high visceral fat. Visceral fat produces inflammatory mediators and elevated inflammatory levels are closely linked to insulin resistance. Inflammation of the brain (i.e., neuroinflammation) has been proposed as a possible cause of brain insulin resistance. Interestingly, rodent models of a high calorie diet show that these inflammatory mechanisms occur rapidly in the brain, even prior to weight gain of the animals. Among other things, it has been shown in humans that a short-term increase in calories, especially carbohydrates and fats, reduces insulin sensitivity in the body and increases inflammatory parameters in the blood. Whether a high-calorie diet triggers insulin resistance or inflammation in the human brain is currently unknown. Aim of study: The aim of the study is to investigate the effects of a five-day high calorie diet in healthy young male volunteers on peripheral and brain insulin sensitivity as well as on eating behavior, mood and cognition. Brain insulin sensitivity, peripheral metabolism and different behavioral assessments will be evaluated before, 1 week and 2 weeks after high caloric diet.
Study Type
INTERVENTIONAL
Allocation
NON_RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
NONE
Enrollment
32
After dietary counseling, subjects will receive high caloric snacks for five days.
University of Tuebingen, Department of Internal Medicine IV
Tübingen, Germany
Change in brain insulin sensitivity
fMRI measurement will be performed before and after administration of 160 U of human insulin as nasal spray. Changes in regional activity will be quantified to assess regional brain insulin sensitivity.
Time frame: Outcome measurements will be assessed at baseline (t0). Then, the 5-day high caloric diet or control dietwill start 5 to 30 days after t0. Outcome measurements will again be assessed on the 6th-7th day and on the 10th-15th day after start of diet.
Change in quantitative proton density
The inflammatory processes in the brain will be measured through the quantification of the water content by means of proton density imaging.
Time frame: Outcome measurements will be assessed at baseline (t0). Then, the 5-day high caloric diet or control dietwill start 5 to 30 days after t0. Outcome measurements will again be assessed on the 6th-7th day and on the 10th-15th day after start of diet.
Change in brain metabolites
The inflammatory processes in the brain will be measured through the determination of brain metabolites by MR spectroscopy
Time frame: Outcome measurements will be assessed at baseline (t0). Then, the 5-day high caloric diet or control dietwill start 5 to 30 days after t0. Outcome measurements will again be assessed on the 6th-7th day and on the 10th-15th day after start of diet.
Change in whole-body insulin sensitivity
Insulin sensitivity will be estimated from a frequent-sampling 75 g oral glucose tolerance test using the Matsuda formula.
Time frame: Outcome measurements will be assessed at baseline (t0). Then, the 5-day high caloric diet or control diet will start 5 to 30 days after t0. Outcome measurements will again be assessed on the 6th-7th day and on the 10th-15th day after start of diet.
Change in body fat distribution
Body composition will be addressed by whole-body MRI and liver MRS.
Time frame: Outcome measurements will be assessed at baseline (t0). Then, the 5-day high caloric diet or control dietwill start 5 to 30 days after t0. Outcome measurements will again be assessed on the 6th-7th day and on the 10th-15th day after start of diet.
Behavioral assessment
Memory function, food reward behavior and mood will be assessed by questionnaires, neuropsychological testing and a snack test.
Time frame: Outcome measurements will be assessed at baseline (t0). Then, the 5-day high caloric diet or control dietwill start 5 to 30 days after t0. Outcome measurements will again be assessed on the 6th-7th day and on the 10th-15th day after start of diet.
Change in insulin secretion
Insulin secretion will be estimated from a frequent-sampling 75 g oral glucose tolerance test.
Time frame: Outcome measurements will be assessed at baseline (t0). Then, the 5-day high caloric diet or control dietwill start 5 to 30 days after t0. Outcome measurements will again be assessed on the 6th-7th day and on the 10th-15th day after start of diet.
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