The Fasting Study - Unraveling the Mechanistic Effects of Prolonged Fasting in Humans.
Condition: Fasting; Adipose Tissue; Clinical Trial; Lipid Metabolism
Study type: Interventional

Summary: 
      Elevated levels of plasma triglycerides are increasingly recognized as an important causal
      risk factor for cardiovascular disease and associated pathologies. Lowering plasma
      triglycerides may therefore be a therapeutic target to lower cardiovascular disease risk.
      With this study the investigators want to examine the effects of fasting on adipose tissue
      metabolism in humans.
    

Detailed description: 
      Rationale: Elevated levels of plasma triglycerides are increasingly recognized as an
      important causal risk factor for cardiovascular disease and associated pathologies. Lowering
      plasma triglycerides may therefore be a therapeutic target to lower cardiovascular disease
      risk. Lipoprotein lipase (LPL) is the enzyme that catalyzes the hydrolysis of plasma
      triglycerides into fatty acids on the capillary endothelium, thereby lowering plasma
      triglycerides and stimulating the uptake of these fatty acids into cells. Angiopoietin-like 4
      (ANGPTL4) is produced by fat cells and promotes the unfolding and inactivation of LPL,
      leading to decreased hydrolysis of plasma triglycerides. The role of ANGPTL4 in regulating
      LPL is especially important during fasting. However, as most studies are performed in animal
      models, little is known about the effects of fasting on adipose tissue metabolism in humans,
      and specifically on ANGPTL4 and its relationship with LPL.

      Objectives: The key objective of this study is to determine the effect of a prolonged fast on
      ANGPTL4 gene and protein expression in subcutaneous adipose tissue, the key organ involved in
      lipid metabolism. Additionally, the effect of a prolonged fast on LPL gene expression, LPL
      protein expression, and on LPL activity in subcutaneous adipose tissue will be examined. To
      explore the systemic effects of a prolonged fast, the investigators will also measure ANGPTL4
      levels in plasma, and ANGPTL4 and LPL gene expression in circulating immune cells (PBMCs).
      The secondary objective of this study is to obtain a more holistic view on the changes
      occurring upon a prolonged fast, by examining the effects of fasting on whole genome
      expression, post-transcriptional changes, and on markers of metabolic status. The combined
      results of all measurements will ultimately lead to a better understanding of the mechanistic
      effects of a prolonged fast and the metabolic functioning in humans.

      Study design: The Fasting Study is a single arm intervention study in healthy men and women.
      The investigators will examine the effects of a fed state, which is 2 hours after the last
      food intake, versus a prolonged fasted state, which is 26 hours after the last food intake.
      Adipose tissue biopsies and blood samples will be taken 2 hours after the last meal and 26
      hours after the last meal. The 24 hours between sampling points are chosen to prevent effects
      of the circadian rhythm.

      Study population: The study population will consist of 24, 40-70 years old men and women with
      a BMI of 22-30 kg/m2, selected from the surroundings of Wageningen through the mailing list
      for potential study research subjects of the division of Human Nutrition and health of
      Wageningen University. If needed, additional recruitment of research subjects will take place
      by flyers and posters, or advertisements in local newspapers.

      Intervention: All research subjects will start with the consumption of a standardized meal
      (ad libitum). Directly thereafter the intervention begins, which is a fasting period of
      twenty-six-hours, during which research subjects are not allowed to eat or drink anything
      except for water, which the research subjects may consume ad libitum. The investigators will
      take the first blood samples and adipose tissue biopsies two hours after the consumption of
      the standardized meal. This is the fed state: the point in time where the body is
      physiologically fed, based on the average time for plasma free fatty acids to drop.
      Twenty-four hours after the "fed state", research subjects are in the prolonged fasted state,
      and the investigators will take the final blood samples and adipose tissue biopsies. The time
      period of twenty-four-hours between sampling points is chosen to prevent the effects of
      circadian related changes on our outcome measures.
    

Intervention name(s): Fasting for 26-hours
Intervention type(s): Other
Intervention description(s): All research subjects will have to fast for 26 hours in total.
All research subjects start with a standardized meal. Two hours after the standardized meal the samples in the fed state will be taken. Research participants are not allowed to eat anything after the consumption of the standardized meal until the second measurements on day 2, 26-hours later. There are 24 hours between the two measurement points.
Other intervention name(s): Prolonged fasting
Intervention model: Single Group Assignment
Intervention model description: Research subjects are measured in the fed state and in the prolonged fasted state.
Masking: None (Open Label)
Primary purpose: Basic Science
Keywords: Physiology; Humans