Effects of vitamin D2 or D3 supplementation on glycaemic control and cardiometabolic risk among people at risk of type 2 diabetes: results of a randomized double-blind placebo-controlled trial.

AIMS: To investigate the effect of short-term vitamin D supplementation on cardiometabolic outcomes among individuals with an elevated risk of diabetes. METHODS: In a double-blind placebo-controlled randomized trial, 340 adults who had an elevated risk of type 2 diabetes (non-diabetic hyperglycaemia or positive diabetes risk score) were randomized to either placebo, 100,000 IU vitamin D2 (ergocalciferol) or 100,000 IU vitamin D3 (cholecalciferol), orally administered monthly for 4 months. The primary outcome was change in glycated haemoglobin (HbA1c) between baseline and 4 months, adjusted for baseline. Secondary outcomes included: blood pressure; lipid levels; apolipoprotein levels; C-reactive protein levels; pulse wave velocity (PWV); anthropometric measures; and safety of the supplementation. RESULTS: The mean [standard deviation (s.d.)] 25-hydroxyvitamin D [25(OH)D]2 concentration increased from 5.2 (4.1) to 53.9 (18.5) nmol/l in the D2 group, and the mean (s.d.) 25(OH)D3 concentration increased from 45.8 (22.6) to 83.8 (22.7) nmol/l in the D3 group. There was no effect of vitamin D supplementation on HbA1c: D2 versus placebo: -0.05% [95% confidence interval (CI) -0.11, 0.02] or -0.51 mmol/mol (95% CI -1.16, 0.14; p = 0.13); D3 versus placebo: 0.02% (95% CI -0.04, 0.08) or 0.19 mmol/mol (95% CI -0.46, 0.83; p = 0.57). There were no clinically meaningful effects on secondary outcomes, except PWV [D2 versus placebo: -0.68 m/s (95% CI -1.31, -0.05); D3 versus placebo -0.73 m/s (95% CI -1.42, -0.03)]. No important safety issues were identified. CONCLUSIONS: Short-term supplementation with vitamin D2 or D3 had no effect on HbA1c. The modest reduction in PWV with both D2 and D3 relative to placebo suggests that vitamin D supplementation has a beneficial effect on arterial stiffness.

Cardiac function in 10-year-old twins following different fetal therapies for twin-twin transfusion syndrome.

OBJECTIVES: To compare cardiac function at 10 years of age in four groups of monochorionic diamniotic (MCDA) twin pairs: uncomplicated MCDA twins (n = 6) (Group 1); twins that had had twin-twin transfusion syndrome (TTTS) managed by amnioreduction (TTTS-amnio, n = 9) (Group 2) or laser photocoagulation (TTTS-laser, n = 10) (Group 3); and dichorionic diamniotic controls (DCDA, n = 6) (Group 4). METHODS: Echocardiograms optimizing apical four-chamber and short-axis left ventricular views were stored for offline speckle-tracking analysis, blinded to twin type. Myocardial long-axis shortening and lengthening velocities were measured using pulsed Doppler ultrasound at the cardiac base. M-mode measurements of fractional shortening (short axis) and maximal excursion of the atrioventricular annulus (four-chamber) were recorded. Syngo Vector Velocity Imaging software tracked left ventricular myocardial motion offline to produce free wall strain, strain rate and rotation. Intertwin pair and group differences were investigated using ANOVA. RESULTS: Cardiac measurements were within the normal ranges for 10-year-olds. No significant within-twin-pair and intergroup differences were found in current size, heart rates, strain or strain rate. Compared to DCDA controls, TTTS twins showed less cardiac rotation (TTTS-laser, P < 0.001 and TTTS-amnio, P = 0.054) with significant intertwin reduction in the ex-recipient (TTTS-amnio, P = 0.006) and larger MCDA twins (P = 0.027) compared with their cotwins. A similar pattern was seen in left ventricular early diastolic mitral valve tissue velocity (MVE') in all monochorionic groups, but only achieving significance in TTTS-amnio twins (P = 0.037). Intrapair differences in rotation and MVE' were significantly different following treatment at Quintero stages III or IV. CONCLUSIONS: Within-twin-pair patterns of left ventricular rotation and diastolic function differ at 10 years of age in ex-recipients of TTTS twins treated with amnioreduction compared with those treated by laser photocoagulation and controls. .

Morbid anatomy in neonates with Ebstein's anomaly of the tricuspid valve: pathophysiologic and clinical implications.

The hearts of six neonates with Ebstein's anomaly of the tricuspid valve who died in the 1st month of life were compared with hearts of six age- and size-matched control neonates. All six hearts had morphologically severe disease with gross right atrial dilation and marked apical displacement of the tricuspid valve. All had a secundum atrial septal defect and four had additional cardiac lesions (pulmonary atresia in two, ventricular septal defect in two). There was significant thinning of the right ventricular free wall distal to the tricuspid valve (3 +/- 0.2 mm vs. control 4.2 +/- 0.2, p less than 0.01) and right ventricular fiber diameter was reduced (7.2 +/- 0.3 microns vs. control 11.4 +/- 0.6, p less than 0.001). The fibrous tissue content of both right and left ventricular free walls was increased (right, 29.3 +/- 2.6% vs. control 8.7 +/- 1.1, p less than 0.001; left, 23.2 +/- 1.5% vs. control 8.5 +/- 0.7%, p less than 0.001). Although the right ventricular abnormalities might be explained by hemodynamic stress in utero, abnormalities of the left ventricular free wall suggest that either genetic or nonhemodynamic environmental factors are involved in the morphogenesis of this condition. Increased right and left ventricular fibrosis may contribute to the poor early outcome in this group and may predispose to late complications, such as subnormal exercise performance, hemodynamic deterioration or late sudden death that may occur in patients with Ebstein's anomaly who survive the neonatal period.

Static mechanical properties and chemical composition of the aorta of spontaneously hypertensive rats: a comparison with the effects of induced hypertension.

The static elastic properties and medial scleroprotein content of the aorta have been examined in spontaneously hypertensive rats (AS strain) aged 6 and 20 weeks (group SH). The results are compared with data from two previous studies on normal (group N) and induced hypertensive animals (group H). Spontaneous hypertension is associated with a relative increase in elastin and decrease in collagen when compared with the normal aorta. These changes are similar to, although smaller in magnitude than, those associated with induced hypertension. Elasticity measurements show that the functional stiffness (incremental strain) of the aorta in group SH is greater than normal. However, this difference diminishes with age, suggesting an adaptive response which tends to maintain the functional stiffness near to normal levels.

Effects of hypertension on the static mechanical properties and chemical composition of the rat aorta.

The contributions of the relative radius, relative wall thickness, incremental strain, incremental elastic modulus, and medial scleroprotein content to the static elastic properties of the rat aortic wall have been examined in three groups of rats. Controls, rats made hypertensive at four weeks of age, and rats whose blood pressure was lowered after 6 weeks hypertension, were studied. The results show evidence of adaptive changes in the aorta of hypertensive animals, and that irreversible alterations in the mechanical properties of the wall may be induced by a brief period of hypertension. A direct relationship between aortic medial scleroprotein content and the elastic properties of the wall is demonstrated.

Effect of beta-aminopropionitrile on the static elastic properties and blood pressure of spontaneously hypertensive rats.

The static elastic properties of the aorta ad systolic blood pressure in the caudal artery have been measured in 55 spontaneously hypertensive rats of the AS strain. Animals were divided into five groups and treated from the age of 4 to 12 weeks as follows: (1) 0.25 mm silver clip positioned around the right renal artery; (2) renal artery clipped as group (1) followed by daily injection of beta-aminopropionitrile fumarate (beta-APN); (3) daly injection of beta-APN without clipping; (4) daily injection of 0.09% saline; (5) untreated. Mean systolic blood pressures at 12 weeks of age were Group (1) 21.8; Group (2) 16.2; Group (3) 17.0; Group (4) 18.0; Group (5) 17.5 (units kPa). Thus, administration of beta-APN prevents the development of renal hypertension in clipped animals while producing no significant alteration in animals with intact renal arteries. At pressures within the physiological range the functional distensibility of all the treated animals was greater than that of the controls (pressure strain elastic modulus significantly lower). Similar changes were observed in the variation of structural distensibility (incremental elastic modulus) with pressure. At any level of total strain greater than 0.7 the incremental elastic modulus of both groups of animals treated with beta-APN was significantly less than control values. These observations are consistent with reports in the literature that administration of beta-APN causes a reduction in either the amount of cross-linked or normal scleroprotein in the aorta.

An in vivo study of the total occlusion method for the analysis of forward and backward pressure waves.

The arterial pressure wave, Pm, is composed of a forward travelling wave, Pf, and a backward travelling wave, Pb, resulting from partial reflection of PI at the peripheral beds. The magnitude of Pb depends on the degree of vasoconstriction. Total occlusion of the vessel distal to the pressure measurement site results in a wave which is equal to 2Pf. Subtraction of the derived Pf wave from Pm gives Pb, provided there is no re-reflection of Pb by proximal discontinuities. To test the validity of this total occlusion method for the determination of the components of Pm, measurements were carried out in an anaesthetised dog and the results compared with the method of Westerhof et al., (1972). The measurements were made at three arterial sites: 1. in the aorta just proximal to the junction of the renal artery; 2. at the termination of the aorta; and 3. in the femoral artery. The magnitude of Pb was varied by the infusion of vasoactive drugs. There was good agreement between the two methods at site 1 but at the other two sites the agreement was less good. It is shown that this is the result of re-reflection of the backward travelling waves produced by the occlusion at the aortic termination and the renal artery junction.

Effect of smooth muscle activity on the static and dynamic elastic properties of the rabbit carotid artery.

The variation of radius with pressure was measured in vitro in the carotid artery of ten rabbits. Experiments were performed without prior conditioning of the vessel, over an inflation-deflation cycle at pressures in the range 0 to 24 kPa during treatment with, and in the absence of noradrenaline (referred to as active and passive conditions). The effect of a step change in pressure (2.7 kPa) on the radius of the vessel was investigated on a further three specimens. Under passive conditions, the variation of the static and the real part of the dynamic incremental elastic modulus with pressure and stress was similar during both inflation and deflation. Under active conditions a large degree of pressure-radius hysteresis was observed. At physiological pressures smooth muscle activity was associated with a decrease in elastic modulus when compared to passive values at the same pressure or stress. At a stress above 2 x 10(5) N.m-2 yield of the constricted vessels was observed and on further inflation and subsequent deflation the pressure radius curve was identical to that obtained under passive conditions. We suggest that conditioning a vessel, by means of repeated inflation to a high pressure and deflation to zero pressure, before measuring its elastic properties may give misleading results when applied to the vessels of living animals.

Changes in the distensibility of the intrapulmonary arteries in the normal newborn and growing pig.

The static elastic properties and structure of the intra-pulmonary arteries have been studied in pigs from fetal life to 4 months old, by radiographic and histological methods. During this period the average radius of the vessels examined varied from approximately equal to 0.9 mm at birth to 3.3 mm at the age of 4 months. The form of the pressure radius curves was similar to that observed in the systemic circulation and was characteristic of the gradual recruitment of collagen fibres with increasing pressure. In vessels near the hilum, wall thickness decreased from approximately equal to 180 microns to 100 microns during the first 2 weeks and thereafter increased to approximately equal to 250 microns. Throughout the lung and in all age groups there was a linear relationship between the logarithm of pressure strain elastic modulus (used as a measure of functional stiffness) and pressure. In contrast to the systemic arteries there was little change in functional stiffness towards the periphery, although the incremental elastic modulus (structural stiffness) did increase at sites further removed from the heart. During the first two weeks of life there was little change in functional stiffness (Ep approximately equal to 1.1 X 10(4) Nm2) although by 4 months Ep had increased by a factor of three. During this period despite fluctuations with age, an overall increase in structural stiffness was also observed (EINC approximately equal to 1 X 10(5) at 4 to 6 h to 2 X 10(5) Nm-2 at 4 months). The observations suggest that the changes in elasticity observed in early life are a consequence of the adaptation of the circulation to the lower pulmonary arterial pressure of extra-uterine life.

Impulse propagation in normal and stenosed vessels.

The propagation of a transient pressure impulse in a viscoelastic medium was investigated by experiments using water-filled latex rubber tubing and the aorta of anaesthetised dogs. A 5 ms pressure impulse was produced by the impact of a solenoid driven hammer. The propagation characteristics of the impulse (attenuation and propagation velocity) along the vessel were determined by means of a catheter-tip pressure manometer placed at various distances distal to the impulse generator. The presence of stenoses of varying degrees of severity resulted in reflection of the impulse and the appearance of reflected pulses whose magnitude depended on the stenotic severity. The experiments suggest that for the technique to be used in the detection of local reflecting sites such as might result from vascular occlusive disease, the lesions should occlude at least 70% of the lumen and should be no more than 0.20 m distal to the impulse generator.

Static mechanical properties of the developing and mature rat aorta.

The static mechanical properties of the aorta have been examined in rats, aged between 4 weeks and 2 years. Internal radius, relative wall thickness, circumferential incremental strain, and circumferential incremental elastic modulus have been measured at pressures between 1.33 and 33.3 kPa (10 and 250 mm Hg). The results show that the value of the incremental elastic modulus does not change after 12 weeks. Changes observed in younger animals are related to alterations in relative wall thickness. The findings correlate with previously observed chemical and morphological changes. Studies of muscle function indicate that the smooth muscle of the media does not contribute significantly to the static elastic properties of the vessel wall.

Pulmonary vascular input impedance in the newborn and infant pig.

The input impedance of the main pulmonary artery in 26 pigs aged from 1 h to 2 weeks has been calculated from measurements of pressure and flow. From these data we have derived estimates of the hydraulic power output of the right heart. The impedance spectra were similar in form to those in many other studies and were consistent with the presence of a single reflection site within the lung. The frequency of the (single) minimum decreased steadily with increasing age as did the corresponding zero crossing point on the phase curve. From estimates of propagation velocity the position of this "reflection site" was found to coincide with the position of the lung periphery in each age group. An overall fall in characteristic impedance with increasing age was found to be due to the increasing diameter of the pulmonary artery rather than to changes in its elasticity. The total power output/body weight of the right heart fell from 10.4 to 4.8 mW X kg-1 from birth to 4 weeks of age. During this period the ratio of pulsatile to steady power fell from 0.5 to 0.31. We conclude that this fall is related to a reduction in the effective reflection of pressure and flow waves within the lung due to increasing attenuation and possibly to a reduction in the magnitude of the lumped reflection coefficient itself.

Characterisation of Elastic and Acoustic Properties of an Agar-Based Tissue Mimicking Material.

As a first step towards an acoustic localisation device for coronary stenosis to provide a non-invasive means of diagnosing arterial disease, measurements are reported for an agar-based tissue mimicking material (TMM) of the shear wave propagation velocity, attenuation and viscoelastic constants, together with one dimensional quasi-static elastic moduli and Poisson's ratio. Phase velocity and attenuation coefficients, determined by generating and detecting shear waves piezo-electrically in the range 300 Hz-2 kHz, were 3.2-7.5 ms(-1) and 320 dBm(-1). Quasi-static Young's modulus, shear modulus and Poisson's ratio, obtained by compressive or shear loading of cylindrical specimens were 150-160 kPa; 54-56 kPa and 0.37-0.44. The dynamic Young's and shear moduli, derived from fitting viscoelastic internal variables by an iterative statistical inverse solver to freely oscillating specimens were 230 and 33 kPa and the corresponding relaxation times, 0.046 and 0.036 s. The results were self-consistent, repeatable and provide baseline data required for the computational modelling of wave propagation in a phantom.

Desmin expression in rhabdomyosarcoma: influence of the desmin clone and immunohistochemical method.

AIM: To determine which, if any, of five commercially available desmin clones is most reliable at labelling desmin filaments and whether the enhanced polymer one step (EPOS) method of labelling is of any advantage in the routine diagnostic laboratory. METHODS: Thirty four rhabdomyosarcomas from the files at The Hospital for Sick Children, Great Ormond Street, London, were studied. Four different desmin clones, DE-R-11, D33, DE-U-10, and PDE, were applied to each using the conventional extravidin biotin peroxidase method. The D33 clone was also applied using the EPOS method. RESULTS: The EPOS method incorporating D33 persistently scored more cells as desmin positive and was positive in four cases which were negative on staining with the other clones. CONCLUSIONS: The D33 desmin clone used with the EPOS method is more reliable for identifying desmin filaments in tumours than other desmin antibodies tested. Different desmin clones using a routine technique label different rhabdomyosarcoma cells and therefore it is justifiable to use more than one clone.

Coronary vasodilatation induced by calcitonin gene-related peptide in the anaesthetised pig.

The ability of CGRP to increase blood flow in the coronary circulation of the anaesthetized pig was studied in a constant pressure perfusion model. Human alpha-CGRP, when infused close-arterially into the left anterior descending coronary artery perfused at constant pressure, produced a marked and prolonged dose-related increase in coronary flow, at doses above 10 pmol min-1. The gradient of the flow/pressure curves at each dose increased with an increase in pressure, indicating a drop in the resistance of the coronary bed. No significant change was observed in heart rate, left ventricle pressure, mean arterial pressure or cardiac output.

Actions of cysteinyl leukotrienes in coronary, femoral and carotid vessels of the pig.

Coronary, femoral and carotid vascular beds of anaesthetised pigs were perfused with heparinised arterial blood using an extracorporeal perfusion system. Blood flow was measured in each vascular bed. Leukotriene (LT) D4 caused a dose-related reduction in flow in the left anterior descending (LAD) artery. LTs C4 and D4, angiotensin and noradrenaline caused dose-related reductions in flow in femoral and carotid vascular beds. High doses of LTD4 caused total cessation of blood flow in the LAD and femoral beds. In the femoral and carotid beds LTC4 but not LTD4 caused an initial increase followed by a prolonged reduction in flow. Indomethacin (1.4 X 10(-5) mol kg-1, i.v.) did not affect the vasoconstrictor action of LTs.

Residual strains in conduit arteries.

Residual strains and stresses are those that exist in a body when all external loads are removed. Residual strains in arteries can be characterized by the opening angle of the sector-like cross-section which arises when an unloaded ring segment is radially cut. A review of experimental methods for measuring residual strains and the main results about the variation of the opening angle with arterial localization, age, smooth muscle activity, mechanical environment and certain vascular pathologies are presented and discussed. It is shown that, in addition to their well-established ability to homogenize the stress field in the arterial wall, residual strains make arteries more compliant and thereby improve their performance as elastic reservoirs and ensure more effective local control of the arterial lumen by smooth muscle cells. Finally, evidence that, in some cases, residual strains remain in arteries even after they have been cut radially is discussed.

High frequency characteristics of the arterial system.

Pressure, flow and diameter were measured in the abdominal aorta of five anesthetized dogs during normal heart beats and heart beats with a superimposed impulse (generated by rapidly injecting a small volume of saline into the system). From Fourier analysis it was found that the impulse enhanced the amplitudes of the higher harmonics so that frequencies up to 80 Hz could be studied. Both the input impedance and apparent phase velocity above 20 Hz were independent of frequency and their average values were designated as characteristic impedance and true phase velocity. Average characteristic impedance for all five animals was 2.0 +/- 0.1 X 10(8) Nsm-5 and average phase velocity was 8.3 +/- 0.6 ms-1. Phase velocities calculated from characteristic impedance (1.76-2.39 X 10(8) Nsm-5) and from the slope of the pressure-diameter relation (0.102-0.25 X 10(-8) Nm-3) were similar to the true phase velocity as defined above (6.79-9.85 ms-1). It may be concluded that the input impedance converges to characteristic impedance and apparent phase velocity converges to phase velocity for high frequencies.

Comparison of different methods for the determination of the true wave propagation coefficient, in rubber tubes and the canine thoracic aorta.

The results from studies of wave propagation in large arteries carried out over the last 25 years have shown that there is a good agreement among values of the imaginary part of the complex propagation coefficient, as expressed by pressure or flow-rate wave propagation velocity. However, there is considerable disparity among estimations of the degree of wave attenuation, the real part of the propagation coefficient. In order to determine whether this disparity is due to differences inherent in the various methods used to measure true wave propagation coefficients or whether it is caused by differences in experimental conditions, we have compared three techniques for determining true pulse wave propagation coefficients the three-point method, the occlusion method and a recently described iterative procedure. In addition, the results were compared to apparent propagation coefficients calculated without accounting for reflections. Measurements were carried out using each method in turn on a rubber tube of known transmission characteristics in which the magnitude of reflections was small. The iterative procedure and the three-point method were also compared under conditions of strong reflection. In the tube, the values of propagation velocity and attenuation coefficient determined by each method were similar. Although some discrepancies were noted, they did not amount to a systematic trend. The iterative procedure and the occlusion method were also used to analyse measurements on the thoracic aorta of three anaesthetized greyhounds. In the animal experiments, in spite of increased scatter, partly due to the variation between dogs, the two methods for determining true pulse-wave propagation yielded similar results. Since the differences between our estimates of propagation coefficients obtained by the methods tested are small with respect to those found when comparing the results from several reports in the literature, we conclude that any discrepancies between studies cannot be due to problems associated with the methods themselves but must have been caused by variations in experimental conditions or by other unknown artefacts.

Analysis of the strain and stress distribution in the wall of the developing and mature rat aorta.

The variation of wall stress distribution with age in the thoracic and abdominal aortas of normotensive rats was studied. Dimensions of the zero-stress configurations were measured at the ages of 4, 8, 12, 20, and 52 weeks. Using data from previously published inflation tests, the circumferential stress-strain relationship was obtained in each age group. The calculated stress distribution showed that the average circumferential stress remained practically constant after the age of 20 weeks. The circumferential stress at the innermost part of the arterial wall was greater than the stress at the outermost part, but the difference was maintained at a moderate level with adjustments in the zero-stress configuration. It is speculated that, after the age of 20 weeks, changes in arterial geometry and rheological properties tend to maintain a constant stress distribution under varying conditions of loading. This distribution was achieved by enhanced growth at the inner part of the media in comparison with the growth at its outer margins and suggests that during development and maturity, the growth of the aorta is modulated by circumferential stress.