The effect of meals rich in carbohydrate and fat on metabolism and inflammation

Meals: High carbohydrate High fat Mixed high carbohydrate and high fat Meal composition: High carbohydrate: 130 g of Heinz canned spaghetti in tomato sauce and cheese, 140 g of white bread, 40 g toasted Muesly, 30 g jam, 40 ml of cordial concentrate in 250 ml water, 150 g plain fat free yoghurt, 5 g sugar (950 kcal, 12.6 g fat, 158 g carbohydrate, 51 g protein). High fat meal: 100 g eggs fried in 15 ml canola oil, 30 g Ryvita crisp-bread, 10 g butter, 52.5 cheddar cheese, 30 g mixed nuts, 125 g strawberries, 40 g whipping cream, 4 g sugar (1066 kcal, 81 g fat, 25 g carbohydrate, 59 g protein). High carbohydrate high fat meal: 100 g eggs fried in 15 ml canola oil, 160 g bagel, 7 g butter, 40 g jam, 21 g cheddar cheese, 20 g mixed nuts (1169 kcal, 75 g fat, 79 g carbohydrate, 45 g protein). Research Plan and procedures: Each subject attends the Clinical Research unit in the morning after an overnight fast (10-12 hours) for five visits: Screening Visit (visit 1): Detailed information, informed consent. Medical history, clinical check, blood pressure, weight, height, oral glucose tolerance test (OGTT). At the end of screening, if eligible to participate in the study, the clamp visit (visit 2) and meal visits (visits 3-5) will be scheduled. The clamp visit will be booked 7-14 days after the screening visit and the first meal visit (visit 3) will be scheduled 14 days after visit 2. Clamp visit (visit 2): Fasting blood samples Indirect calorimetry Heart rate variability at resting and during the intravenous glucose tolerance test (IVGTT) and hyperinsulinaemic euglycaemic clamp (see detailed procedure below). Dual X-ray absorptiometry (DXA) and computerized tomography (CT). Visit 3,4 and 5 are identical and performed 7-14 days apart: Baseline (fasting) indirect calorimetry, heart rate variability Test meal 1/2/3 in a randomized order. Specifically, the subjects will be randomized for the first meal and will then have the 2 other meal types in a randomized order. Blood samples are taken before and 30, 60, 120, 180 and 240 min after the meal for measuring cytokines, glucose, insulin, hormones, triglyceride. Indirect calorimetry is repeated at 3.5-4.0 hours to evaluate postprandial fat and carbohydrate oxidation. Heart rate variability at 30-min intervals in the postprandial state. Subjects undergo the following procedures: Oral Glucose Tolerance Test (OGTT)- A 75g glucose drink is given and blood glucose is measured at -10, 0, 30, 60, 90 and 120 minutes. Intravenous Glucose Tolerance Test (IVGTT) is performed to assess B-cell function and the heart rate variability response to endogenous insulin. Blood is drawn at -10, 0, 1, 2, 3, 4, 5, 6, 8, 10, 20, 30, 40, 50, 60 min after infusion of 0.3 g/kg dextrose 25% (maximum 25 g or 100 ml). Hyperinsulinaemic euglycaemic clamp is performed to assess whole-body insulin sensitivity and heart rate variability response to supra-physiological hyperinsulinaemia. Insulin is infused intravenously at 60 mU/m2 body surface area/min. Glucose is infused at a rate sufficient to maintain blood glucose at about 5 mmol/L (euglycaemia). The steady state glucose infusion rate (GIR) is defined as the average rate of glucose delivery during the last 30 min period of the clamp. Two venous cannulae will be needed, one at each forearm. The antecubital vein is usually used. Before the insertion of the cannulae the usual antiseptic procedures are applied. Blood is drawn every 10 minutes during the clamp. Indirect calorimetry will be performed fasting and at clamp steady stae (from 90-120 min) or at 3.5-4 h post meal. This technique is used to evaluate resting energy expenditure and the carbohydrate and fat oxidation rate. A transparent plastic hood is connected to the measuring device and placed over the subjects head for a 30 min period. Calculations of O2 consumption and CO2 production are done by continuous measurements of inspired and expired air diluted in a constant air flow. Subjects will be asked to remain motionless and awake. Dual X-ray absorptiometry (DXA) is performed to quantify body fat, central fat and lean body mass. Lunar Prodigy (Lunar Radiation Corporation, software version 7.51) whole body scanner at St Vincent’s Hospital is used. The scanner emits low energy X-rays. The scan takes about 5 minutes and the radiation dose is less than 1 mrem (equal to about 12 h background radiation). CT scan - Cross-sectional CT slices (at L2/3 and L4/5) to evaluate visceral and subcutaneous abdominal fat. Liver fat content will also be evaluated (1 slice).