Twenty-three healthy subjects [11 male, 12 female; [mean ± SEM] age: 26 ± 0.2 y [range: 18-33 y]; body mass index: 21.8 ± 0.1 kg/m2 [range: 17.0-25.9 kg/m2] without symptoms or a history of gastrointestinal disease, abdominal surgery or diabetes mellitus, were included in this observational study. The mean waist:hip ratio for the women was 0.74 ± 0.02 and for the men 0.87 ± 0.01. The subjects had no connective tissue disease or cerebrovascular or endocrine disease, and none was taking any medication, except four women who were taking oral contraceptives. All subjects were in sinus rhythm. Three men were snuff users, and one was a smoker. Two women were snuff users. All subjects were recruited from the population of southern Sweden.
The subjects were examined between 7.30 and 11.00 am after an 8-h fast. Smoking and snuff-taking were prohibited 8 h prior to and during the test. The fasting blood glucose concentration of each subject was checked on the day of the examination to ensure that it was normal. If the subjects reported gastrointestinal symptoms (diarrhea or constipation) on the day of the study, the examination was postponed. The test meal consisted of 300 g rice pudding (Goda Gröten Risgrynsgröt; Lantmännen AXA, Järna, Sweden). The total caloric value of the meal was 330 kcal: 10% from protein (9 g), 58% from carbohydrates (48 g) and 32% from fat (12 g). The meal was ingested within 5 min.
The gastric emptying rate (GER) was estimated using an ultrasound method described in detail previously [18
]. The sonographic examination was performed with a 3.5 MHz abdominal transducer (Acuson Sequioa 512, Mountain View, CA), and an imaging system (Siemens Elegra, Siemens Medical Solutions, Mountain View, CA). Measurements of the gastric antrum were performed by a single observer. The abdominal aorta and the left lobe of the liver were used as internal landmarks in each measurement of the gastric antrum. The subjects were examined in the supine position, and not allowed to sit up between examinations. Measurements were made 15 and 90 min after the meal had been consumed, and the GER was expressed as the percentage change in the antral cross-sectional area between these two measurements. At each examination, the longitudinal and anteroposterior diameters were measured three times, and the mean values were used to calculate the cross-sectional area of the gastric antrum. The GER (%) was calculated using the following equation:
Transthoracic echocardiography examinations were performed with a Sonos 5500 ultrasound system (Philips, Andover, MA, USA) in the left lateral position, after 15 minutes' rest. On the day of the study, an initial examination was performed to rule out any cardiac dysfunction. A single observer performed all echocardiography measurements three times on separate cardiac cycles, and the mean values were used in the analyses. TDI of the septal (s) and lateral (l) mitral annulus was obtained from the apical four-chamber view, in accordance with current guidelines . Peak systolic (S'), early (E') and late (A') mitral annular diastolic velocities were measured. The LV SV was measured, and the LV CO was calculated according to current guidelines [20, 21]. All TDI measurements were performed under respiratory arrest after an end-expiration. The blood pressure and echocardiogram were measured before the meal (0 min) and 30, and 110 min after the start of the meal.
Venous blood samples were taken before and 15, 30, 45, 60, 90, and 120 min after the start of the meal to measure blood glucose and plasma insulin levels. Blood glucose concentrations were measured with the HemoCue Glucose system (HemoCue AB, Ängelholm, Sweden). The precision of the HemoCue Glucose system was better than 0.3 SD from 0 mmol/L to 22.2 mmol/L. Insulin concentrations were measured using an immunoassay with an alkaline phosphatase conjugate (Access Ultrasensitive Insulin, Beckman-Coulter AB, Bromma, Sweden). The sensitivity of the insulin immunoassay was 0.03 mUnit/L (mU/L), and the intra-assay coefficient of variation was below 10% from 0.03 mU min/L to 300 mU/L.
A validated satiety scoring scale was used according to the method of Hauber et al., based on a scoring system from -10 (extreme hunger) to +10 (extreme satiety) . Satiety scores were estimated before the meal (0 min) and 15, 30, 45, 60, 90 and 120 min after the start of the meal.
All subjects gave their written informed consent. The study was approved by the Ethics Committee of Lund University, and performed according to the Helsinki Declaration. The trial is registered in the US National Library of Medicine with the trial registration number NCT01027507.
Results are given as mean values and the SEM unless otherwise stated. The areas under the curves (AUCs) were calculated for blood glucose and insulin concentrations, satiety, CO, HR, SV, systolic and diastolic blood pressure, S's, S'l, E's, E'l, A's, and A'l in each subject using GraphPad Prism software (version 4; GraphPad, San Diego, CA). All other statistical calculations were performed in SPSS for Windows version 14.0, 2005 (SPSS Inc., Chicago IL, USA). The changes in levels of blood glucose, plasma insulin and satiety were calculated as the difference between levels before the meal (fasting value) and 30 and 120 min after the start of the meal. The changes in HR, SV, CO, systolic and diastolic blood pressure, S's, S'l, E's, E'l, A's, and A'l were calculated as the difference between levels before the meal (fasting value) and 30 and 110 min after the start of the meal. To determine whether the meal affected a given parameter, the baseline value was compared with the 30 min and 120 min postprandial value using the Wilcoxon t-test. The postprandial values at 30 min and 120 min were also compared using the Wilcoxon t-test. Possible correlations between CO, HR, SV, systolic blood pressure, diastolic blood pressure, S's, S'l, E's, E'l, A's, A'l, blood glucose level, plasma insulin level, GER, and satiety were analyzed with Pearson's correlation. Values of P < 0.05 were considered significant.