Evaluation of Biomarkers for Predicting Macronutrient Intake

On each study day, body weight and height will be measured. An in-dwelling 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 multiple times. 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 amino acids, fatty acids, glucose, insulin).

In the opposite limb, a commercially available microdialysis catheter will be placed in the forearm following standard operating procedures developed by the European Academy of Allergy & Clinical Immunology Task Force on Skin Microdialysis. Dialysate will be collected in 30-minute aliquots in microvials for the duration of the study day. Microvials will be weighed before and after sample collection. A syringe filled with perfusate containing mixture of stable tracer-labelled amino acids and glucose will be infused through the syringe pump at a controlled rate.

On each of the study days, subjects will consume two meals with defined composition of macronutrients eight hours apart.

Inclusion criteria

• Ability to walk, sit down and stand up independently
• Age 50-75 years old
• Ability to lie in supine or slightly elevated position for approximately 13 hours
• BMI between 25 and 35
• Willingness and ability to comply with the protocol

Exclusion criteria

• Established diagnosis of malignancy
• Established diagnosis of Insulin or non-Insulin Dependent Diabetes Mellitus
• History of untreated metabolic diseases including hepatic or renal disorder
• Currently on anticoagulants (i.e., warfarin, factor X inhibitors or direct thrombin inhibitors)
• History of deep vein thrombosis, pulmonary embolisms, or known clotting disorders
• Presence of acute illness or metabolically unstable chronic illness
• Recent myocardial infarction (less than 1 year)
• Known allergy or intolerance to any of the meal components
• Any other condition according to the PI or nurse that was found during the screening visit, that would interfere with the study or safety of the patient
• Failure to give informed consent or Investigator's uncertainty about the willingness or ability of the participant to comply with the protocol requirements