Macronutrient Distribution and Plasma Metabolites to Model Meals Composition
Condition: Glucose Metabolism
Study type: Observational

Summary: 
      Continuous glucose monitors (CGMs) measure plasma glucose concentration continually and thus
      they are a key tool in the management of diabetes, including type 2 diabetes (T2D). A key
      factor in diabetes management is a reduction of dietary carbohydrates (CHO) and/or exchanging
      high glycemic index (GI) CHO with low GI CHO. However, the protein and fat content of the
      meal can have a significant impact on the glucose readings obtained from a CGM as there is no
      enough data available on their sensitivity during meals.
    

Detailed description: 
      The study involves 1 screening visit of approximately 1 hour and 9 study days of
      approximately 8 hours. Subjects will be asked to arrive in the fasted state on all study
      days. Fasting prior to screening is not required. On the screening day, body weight, height,
      and body composition by Dual-energy X-ray absorptiometry (DXA) will be measured. In addition,
      habitual dietary intake, physical activity level (PASE), and quality of life (SGRQ-C) will be
      assessed.

      To test the relation between plasma amino acid, triglycerides, and glucose concentration
      measured by standard methods (such as finger stick) and continuous wearable devices, a
      premarket FDA-approved continuous glucose monitor (CGM) from Abbott (FreeStyle Libre Pro)
      that monitors glucose concentrations every 15 min is used. The single-use sensors are placed
      on the upper arm and contain a very tiny 5 mm filament (<0.4 mm diameter) that is introduced
      into the skin when the sensor is placed. On the first study day, the CGM will be placed to
      monitor glucose concentrations until the last study day. At least every 14 days, sensors will
      be replaced by new ones. On each study day, body weight and height will be measured and the
      glucose concentration data will be downloaded from the sensor onto the reader device. A
      catheter will be inserted in a peripheral vein of the lower arm or hand to enable blood
      sampling. The arm will be put in a hot box to allow collecting arterialized venous blood
      samples. After taking a baseline blood sample, the predefined meal will be consumed within 10
      min. Small arterialized venous blood samples (5 ml) will subsequently be drawn at times: 15,
      30, 45, 60, 90, 120, 180, 240, 300, 360, 420, and 480 minutes (13 blood samples, total blood
      approx 65 ml). Samples will be collected in predefined tubes, plasma/serum separated,
      aliquoted, and stored at -80 deg. Celsius for later assays and/or send to a local accredited
      laboratory for the concentrations of amino acids and other parameters (including fatty acids,
      glucose, insulin).
    

Intervention name(s): Predefined meal
Intervention type(s): Combination Product
Intervention description(s): Nine predefined meals are administered in a randomized fashion, one meal per one study day, 2-3 study days per week. Meals have a form of drinks with different compositions of protein, carbohydrates and fat in relation to the US diet
Observational model: Other
Time perspective: Prospective
Sampling method: Probability Sample
Study population: 
        Healthy older adults (60-85y; equal gender) with a BMI between 25 and 35 will be recruited
        from an existing database of CTRAL. In addition, we will recruit older adults that respond
        to distributed flyers and advertisements in the newspaper and to radio announcements in the
        community of the College Station/Bryan area. Informed consent will be obtained on the
        screening day before any study-related procedures will be performed. If inclusion/exclusion
        criteria are met, subjects are invited to take part in the study.
      
Biospecimen description: 
      Plasma samples
    
Keywords: response to food; plasma glucose; continuous glucose monitor