Postprandial study protocol and assessment of insulin sensitivity
Cohort 2 subjects attended our Clinical Research Facility at 09:00 hours
after an overnight fast. The standard OFTT meal comprised fresh cream
with 40% (weight by volume; w/v) fat emulsion
(polyunsaturated:saturated fat ratio of 0.10) that contained 0.001%
(w/v) cholesterol and 3% (w/v) carbohydrates, and had a total energy
content of 3700 Kcal/L13. The fresh cream was given at
a dose of 50g fat and 3.75g glucose/m2 body surface
(approximately 200ml). Subjects were allowed up to 10 minutes to consume
the meal. During the test, participants remained supine and were only
allowed to drink mineral water. Blood samples were obtained at 0
(fasting baseline), 30, 60, 120, 180 and 240 minutes after consuming the
meal, collected into sodium EDTA (2 mg/mL) then centrifuged immediately
for 15 min at 800 × g at 4 °C. Plasma was separated and stored in
aliquots at −80 °C until analysis. The areas under the curves (AUC) for
triglycerides and complement components were calculated using the
trapezoid method.
On a separate day, after an overnight fast, subjects in cohort 2
underwent basal sampling for measurement of lipids and testosterone.
Subjects subsequently underwent a standard 75g oral glucose tolerance
test (OGTT). Glucose and insulin were measured at 0, 30, 60, 90 and 120
minutes. The AUCs for insulin and glucose were calculated using the
trapezoid method. The homeostatic model assessment method was also used
to estimate insulin resistance (HOMA-IR).