Insulin-Mediated Glucose Uptake and Organ Perfusion Assessed by Total-Body PET During GIP and GLP-1 Infusion

This study investigates how the naturally occurring gut hormones GIP and GLP-1 influence whole-body glucose uptake and organ perfusion in humans. Using a state-of-the-art total-body PET-CT scanner, the study measures dynamic uptake of the glucose analogue 18F-FDG and blood flow using H₂¹⁵O across multiple organs during controlled elevations of plasma glucose and endogenous insulin secretion. The project consists of two sub-studies. Sub-study 1 includes healthy individuals who undergo three experimental visits with infusions of GIP, GLP-1, or saline (placebo) during a hyperglycemic clamp followed by FDG PET-CT scanning. Sub-study 2 includes healthy individuals and participants with type 2 diabetes who undergo two experimental visits with saline followed by either GIP or GLP-1 during a hyperglycemic clamp, combined with repeated H₂¹⁵O PET-CT measurements of perfusion. The primary aims are to quantify insulin-mediated skeletal muscle glucose uptake (sub-study 1) and skeletal muscle perfusion (sub-study 2). Secondary aims include assessment of glucose uptake and perfusion across adipose tissue, liver, and additional organs. The results will provide novel physiological insight into postprandial glucose metabolism and serve as reference data for future whole-body PET research.