Amino Acid Digestibility of Whey and Zein Proteins
Condition: Amino Acid
Study type: Interventional

Summary: 
      The main goal of the study is to determine true ileal amino acid digestibility of whey
      protein isolate (WPI) and zein proteins in healthy subjects equipped with naso-ileal tube.
      The endogenous losses of proteins and amino acids will be determined by collecting digesta
      samples after a protein-free diet in a third group of subjects.
    

Detailed description: 
      True ileal amino acid digestibility of whey protein isolate (WPI) and zein proteins will be
      determined in healthy subjects. The endogenous losses of proteins and amino acids will be
      determined by collecting digesta samples after a protein-free test-meal in a different group
      of subjects.

      24 volunteers will be included in the study (men and women; aged 18-65 y; BMI 18-30 kg/m2)
      and tested at AgroParisTech (Human Nutrition Research Centre of Avicenne Hospital). Due to
      the invasive procedure of intubation, each volunteer will test only one test-meal (n=8 /
      test-meal).

      One week before the experiment, the volunteers will follow a standard diet adapted to their
      body weight to control their protein intake (1.3 g protein/kg body weight). The volunteers
      will arrive at the hospital the morning before the day of the experiment and will be equipped
      with a double lumen intestinal tube that will be allowed to progress through the intestinal
      tract for 24h. On the day of the experiment, the position of the tube will be checked by
      radiography to verify its location at the terminal ileum. A catheter will be inserted in the
      forearm vein for blood sampling. A perfusion of the non-absorbable marker polyethylene glycol
      -4000 will start to estimate the intestinal flow and the basal ileal sample will be collected
      during 30 min. Basal plasma sample will be collected. Then, at t=0, the volunteer will drink
      the test-meal. Until t=9h, intestinal content will be continuously collected by aspiration
      and pooled every 30 minutes. Blood will be sampled every 30 minutes during 4h and hourly
      thereafter.

      The test meal will consist of a protein-free biscuit (160 g) and a drink (500 ml) with the
      test protein as the sole source of protein or no protein for the protein-free group. Celite
      will be added to the protein-free biscuit and inulin labelled with carbon 13 will be added to
      the drink as indigestible markers of the meal to allow correction for incomplete collection
      of digesta. The test proteins will be WPI or zein.

      The total nitrogen will be measured in meal and digesta samples by the coupling of Elemental
      Analysis with stable Isotope Ratio Mass Spectrometry (EA-IRMS) and the amino acid
      concentration in meal, digesta and plasma samples will be measured by High Performance Liquid
      Chromatography (HPLC) in order to determine the ileal bioavailability of amino acid of zein
      and whey protein. Plasma hormonal profile will also be determined to evaluate the effect of
      each protein sources on metabolic hormones such as insulin, glucagon, leptin, etc.
    

Intervention name(s): Whey Protein Isolate 894 Fonterra; Zein Sigma-Aldrich W555025; Protein-free test-meal
Intervention type(s): Other; Other; Other
Intervention description(s): 30 g of protein powder diluted in water; 30 g of protein powder diluted in water; No protein included in the drink made of water and flavour/sugar
Allocation: Randomized
Intervention model: Parallel Assignment
Intervention model description: 3 groups, one for each protein sources (zein and whey) and one for determination of endogenous amino acid losses (protein-free meal)
Masking: Single (Outcomes Assessor)
Primary purpose: Basic Science
Keywords: digestibility; whey protein; zein; bioavailability