Vascular compliance in diabetes

A retinal imaging system for combined measurement of optic nerve head vascular pulsation and stimulated vasodilation in humans

Vascular pulsation at the optic nerve head (ONH) reflects vessel properties. Reduction in the stimulated retinal vasodilatory capacity has been reported in diabetes, but its relation with vascular pulsation is unknown. Here we report a new retinal imaging system for correlative assessment of ONH vascular pulsation and stimulated retinal vasodilation. Retinal reflectance images were acquired before and during light flicker stimulation to quantify arterial and venous vasodilation (DAR, DVR) in subjects with and without diabetic retinopathy (N = 25). ONH vascular pulsation amplitude and frequency (PA, PF), were quantified by curve fitting of periodic intensity waveforms acquired in retinal vasculature (RV) and ONH tissue (ONHT) regions. The relationships between pulsation metrics, heart rate (HR), intraocular pressure (IOP), and vasodilatory responses were evaluated. Pulsation metrics were not significantly different between regions (p ≥ 0.70). In RV, inter-image variabilities of PA and PF were 10% and 6%, whereas inter-observer variabilities were 7% and 2% respectively. In both regions, PF was correlated with HR (p ≤ 0.001). PA was associated with DAR in both regions (p ≤ 0.03), but only with DVR in RV (p ≤ 0.05). Overall, ONH vascular pulsation was associated with stimulated retinal vasodilation, suggesting diabetes may have concomitant effects on retinal vasculature compliance and neurovascular coupling.

Basement membrane proteins in various arterial beds from individuals with and without type 2 diabetes mellitus: a proteome study

BACKGROUND

Basement membrane (BM) accumulation is a hallmark of micro-vessel disease in diabetes mellitus (DM). We previously reported marked upregulation of BM components in internal thoracic arteries (ITAs) from type 2 DM (T2DM) patients by mass spectrometry. Here, we first sought to determine if BM accumulation is a common feature of different arteries in T2DM, and second, to identify other effects of T2DM on the arterial proteome.

METHODS

Human arterial samples collected during heart and vascular surgery from well-characterized patients and stored in the Odense Artery Biobank were analysed by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). We included ascending thoracic aortas (ATA) (n = 10 (type 2 DM, T2DM) and n = 10 (non-DM)); laser capture micro-dissected plaque- and media compartments from carotid plaques (n = 10 (T2DM) and n = 9 (non-DM)); and media- and adventitia compartments from ITAs (n = 9 (T2DM) and n = 7 (non-DM)).

RESULTS

We first extended our previous finding of BM accumulation in arteries from T2DM patients, as 7 of 12 pre-defined BM proteins were significantly upregulated in bulk ATAs consisting of > 90% media. Although less pronounced, BM components tended to be upregulated in the media of ITAs from T2DM patients, but not in the neighbouring adventitia. Overall, we did not detect effects on BM proteins in carotid plaques or in the plaque-associated media. Instead, complement factors, an RNA-binding protein and fibrinogens appeared to be regulated in these tissues from T2DM patients.

CONCLUSION

Our results suggest that accumulation of BM proteins is a general phenomenon in the medial layer of non-atherosclerotic arteries in patients with T2DM. Moreover, we identify additional T2DM-associated effects on the arterial proteome, which requires validation in future studies.

Measurement of normal retinal vascular pulse wave attenuation using modified photoplethysmography

Pulse wave attenuation characteristics reflect compliance and resistance properties of the vessel wall as well as initial pulse generation factors. Recently, it has become possible to measure and map the retinal vessel wall pulse wave amplitudes. Predictable pulse wave amplitude distribution may allow inferences to be made concerning vascular compliance and resistance. Twenty-eight eyes from sixteen subjects (8 male and 8 female) were examined using modified retinal photoplethysmography with simultaneous ophthalmodynamometry. This allowed the assessment of vessel wall pulsation amplitudes under a dynamic range of intraocular pressures. Pulse amplitudes were calculated using harmonic regression analysis. The pulse wave attenuation was measured under different ranges of ophthalmodynamometric force (ODF) as a function of distance along the vessel (V_Dist), which in turn was calculated in disc diameters (DD) from the center of the optic disc. A linear mixed-effects model with randomized slopes and intercepts was used to estimate the correlations between the logarithmically transformed harmonic regression wave amplitude (HRW_a) and the Fourier trigonometric coefficients with the predictors (V_Dist and ODF). The retinal venous harmonic regression wave attenuation (coefficient value±standard error) -0.40±0.065/DD, (p-value < 0.00001, 95% confidence interval (CI) -0.53 to -0.27), which was approximately twice that of the arterial -0.17±0.048/DD, (p-value < 0.0004, 95% CI = -0.27 to -0.08). There was a positive correlation between attenuation of the harmonic regression wave and ophthalmodynamometric force in both vascular systems. The attenuation of all but the sine coefficient of the second Fourier harmonic (b_n2) achieved statistical significance in the correlation with V_Dist. The cosine coefficient of the first Fourier harmonic a_n1 was the only coefficient to achieve statistical significance in the correlation with the predictors V_Dist and ODF in both vascular systems. The a_n1 coefficient value in the correlation with V_Dist was -3.79±0.78 and -1.269±0.37 (p < 0.0006), while this coefficient value in the correlation with ODF was 0.026±0.0099 and 0.009±0.04 (p < 0.01) in both the retinal veins and arteries respectively. The predictable attenuation characteristics in normal subjects suggest that this technique may allow the non-invasive quantification of retinal vascular compliance and other hemodynamic parameters.

Vascular compliance in women with polycystic ovary syndrome treated with spironolactone

Polycystic ovary syndrome (PCOS) is the most common endocrine disorder in women of reproductive age in the United States and has been associated with several diseases including cardiovascular disease, obesity, and glucose intolerance. In this study, systolic blood pressure, diastolic blood pressure, pulse pressure (vascular compliance), large artery elasticity, systemic vascular resistance (SVR), total vascular impedance (TVI), and body mass index (BMI) were measured before and after treatment with spironolactone in 10 women with PCOS. Systolic BP, diastolic BP, and BMI were similar prior to treatment and after treatment. Pulse pressure decreased slightly post-treatment compared to pretreatment but not to significance (P = 0.07). The results show that after treatment with spironolactone, there was a statistically significant increase in large artery elasticity (P = 0.047), while there was a statistically significant decrease in SVR and TVI (P = 0.0005 and P = 0.03). This study indicates that treatment with spironolactone improves large artery elasticity and reduces systemic vascular resistance without any change in small artery elasticity.

Reduced Regional Cerebral Blood Flow Relates to Poorer Cognition in Older Adults With Type 2 Diabetes

Type 2 diabetes mellitus (T2DM) increases risk for dementia, including Alzheimer's disease (AD). Many previous studies of brain changes underlying cognitive impairment in T2DM have applied conventional structural magnetic resonance imaging (MRI) to detect macrostructural changes associated with cerebrovascular disease such as white matter hyperintensities or infarcts. However, such pathology likely reflects end-stage manifestations of chronic decrements in cerebral blood flow (CBF). MRI techniques that measure CBF may (1) elucidate mechanisms that precede irreversible parenchymal damage and (2) serve as a marker of risk for cognitive decline. CBF measured with arterial spin labeling (ASL) MRI may be a useful marker of perfusion deficits in T2DM and related conditions. We examined associations among T2DM, CBF, and cognition in a sample of 49 well-characterized nondemented older adults. Along with a standard T1-weighted scan, a pseudocontinuous ASL sequence optimized for older adults (by increasing post-labeling delays to allow more time for the blood to reach brain tissue) was obtained on a 3T GE scanner to measure regional CBF in FreeSurfer derived regions of interest. Participants also completed a neuropsychological assessment. Results showed no significant differences between individuals with and without T2DM in terms of cortical thickness or regional brain volume. However, adjusting for age, sex, comorbid vascular risk factors, and reference CBF (postcentral gyrus) older adults with T2DM demonstrated reduced CBF in the hippocampus, and inferior temporal, inferior parietal, and frontal cortices. Lower CBF was associated with poorer memory and executive function/processing speed. When adjusting for diabetes, the significant associations between lower regional CBF and poorer executive function/processing speed remained. Results demonstrate that CBF is reduced in older adults with T2DM, and suggest that CBF alterations likely precede volumetric changes. Notably, relative to nondiabetic control participants, those with T2DM showed lower CBF in predilection sites for AD pathology (medial temporal lobe and inferior parietal regions). Findings augment recent research suggesting that perfusion deficits may underlie cognitive decrements frequently observed among older adults with T2DM. Results also suggest that CBF measured with ASL MRI may reflect an early and important marker of risk of cognitive impairment in T2DM and related conditions.

Vascular compliance in lean, obese, and diabetic children and adolescents: a cross-sectional study in a minority population

BACKGROUND

In adults, both obesity and type 2 diabetes mellitus (T2DM) are positively correlated with cardiovascular disease mortality and arterial stiffness. Several studies of adults have shown that both obesity and T2DM are independently associated with increased arterial stiffness. However, little is known about the relationship between arterial compliance and cardiovascular disease risk in children. We assessed whether large and small arterial compliance is impaired in obese and diabetic pubertal children.

METHODS

One hundred children of African-Caribbean ethnicity, aged 14-16 years, including 21 lean children (between the 25th and 75th percentile), 40 obese children (>95th percentile), and 39 children with T2DM diagnosed by American Diabetes Association criteria were studied. Arterial compliance of the large (C1) and small (C2) vessels was measured using radial arterial diastolic pulse wave contour analysis.

RESULTS

C1 did not differ significantly between lean, obese, and T2DM subjects. C2 was significantly greater in obese and T2DM subjects (10.9 ± 1 and 10.4 ± 0.7 ml/mm Hg × 100 ml, respectively) compared to lean subjects (7.8 ± 0.8 ml/mm Hg × 100 ml; p < 0.05). C2 was also significantly greater in T2DM subjects receiving antihypertensive drug therapy than in diabetic subjects not on antihypertensive treatment.

CONCLUSION

Increased compliance in diabetic and obese children compared to lean subjects could be secondary to premature maturation of the vascular system; whether this early maturation can translate into a subsequent rise in the incidence of cardiovascular events related to diabetes and obesity can only be determined by long-term follow-up of these patients.

Time-dependent alterations in rat macrovessels with type 1 diabetes

Vascular complications are associated with the progressive severity of diabetes, resulting in significant morbidity and mortality. This study quantifies functional vascular parameters and macrovascular structure in a rat model of type 1 diabetes. While there was no difference in the systemic arterial elastance (Ea) with 50 days of diabetes, changes were noted in the aorta and femoral artery including increased tunica media extracellular matrix content, decreased width of both the media and individual smooth muscle cell layers, and increased incidence of damaged mitochondria. Extracellular matrix proteins and elastin levels were significantly greater in the aorta of diabetic animals. These differences correlated with diminished matrix metalloprotease activity in the aorta of the diabetic animals. In conclusion, diabetes significantly altered the structure and ultrastructure of the aorta and femoral artery before systemic changes in arterial elastance could be detected.

Atrioventricular conduction in the hypertensive patient: influence of aging, pulse pressure, and arterial stiffness

Atrioventricular (AV) conduction time (PR interval) lengthens with age. Hypertension is often presented as an accelerated aging of the heart and arteries. The principal marker of arterial aging is an increase in arterial stiffness and pulse pressure. We were interested to find out whether parameters of blood pressure and arterial stiffness were related to the PR interval and whether they influenced its long-term progression. We examined factors linked to the PR interval at baseline in a cohort of untreated hypertensive patients including office and 24-hr blood pressure and arterial stiffness (QKD(100-60)). Long-term evolution of the PR interval and related factors were obtained during follow-up of this population. Baseline data were obtained in 1,034 untreated hypertensive patients. At baseline, four variables emerged as significantly and independently correlated with PR interval: Gender, age, weight, and heart rate. During follow-up (137 ± 78 months), 328 of these patients were re-examined. In this group, PR increased from 159 ± 20 to 167 ± 25 msec (p<0.001), a mean alteration of 8 ± 19 msec. This change was correlated with the baseline 24 hr PP (r=0.17, p=0.004) and with the duration of follow-up (r=0.13, p=0.02). In the group with baseline evaluation of arterial stiffness (n=141), QKD(100-60) was correlated with the change in PR interval (r= -0.33, p<0.0001) along with the duration of follow-up (r=0.22, p=0.005). This study shows a link between baseline increased pulse pressure or arterial stiffness with the prolongation of the PR interval with aging. Because this link was observed during follow-up, it is possible that increased arterial stiffness favors the increase in the PR interval with age.

Cardiovascular rehabilitation increase arterial compliance in type 2 diabetic patients with coronary artery disease

AIMS

The effect of a cardiovascular rehabilitation program on arterial compliance in type 2 diabetes mellitus with coronary disease was studied.

METHODS

Hemodynamic data and arterial compliance were measured with a tonometer (HDI/Pulse wave CR-2000) in coronary artery disease patients with (n=32) and without (n=24) type 2 diabetes before and after a 6-week multidisciplinary cardiac rehabilitation program.

RESULTS

A decrease in heart rate and an increase in stroke volume without significant change in resting cardiac output were obtained in diabetic patients. Arterial compliance of both small and large arteries was significantly increased. In 10 diabetic patients, this increase could be related to an increase in the anti-hypertensive treatment and to the decreased blood pressure. In the 22 remainders, the small artery compliance was significantly increased independently of blood pressure change.

CONCLUSIONS

Exercise training as well as optimization of diabetes and dyslipidemia treatment could explain the improvement of arterial compliance. If these changes are long-lasting and if they improve prognosis remains to be evaluated.

Effect of Fixed‐Dose ACE‐Inhibitor/Calcium Channel Blocker Combination Therapy vs. ACE‐Inhibitor Monotherapy on Arterial Compliance in Hypertensive Patients With Type 2 Diabetes

Assessment of vascular compliance may be a useful measurement of the clinical effects of antihypertensive treatment. Both angiotensin-converting enzyme (ACE) inhibitors and calcium channel blockers are known to improve vascular elasticity. A study was performed to test the hypothesis that combined therapy with an ACE inhibitor and a calcium channel blocker would have additive benefits on vascular compliance at similar levels of blood pressure (BP), as compared with monotherapy with an ACE inhibitor. This 12-week, double-blind study was a substudy of a larger clinical hypertension study conducted in patients with hypertension and type 2 diabetes. Subjects (N = 20) were randomized to either a fixed-dose combination of amlodipine besylate/benazepril HCl or to enalapril monotherapy. BP, heart rate, large- and small-vessel compliance, systemic vascular resistance, and urinary microalbumin excretion were assessed at baseline and after treatment. Both treatments were similarly effective in lowering BP, reducing systemic vascular resistance, and decreasing urinary microalbumin excretion. Improvement in large-vessel compliance was significantly greater among subjects who received ACE-inhibitor/calcium channel blocker combination therapy (52%) as compared with those who received ACE-inhibitor monotherapy (32%; p < 0.05). No significant change in small-vessel compliance was observed with either treatment. Greater improvement in large-vessel compliance with combination therapy was independent of BP lowering.

Vascular Compliance in Women With Polycystic Ovary Syndrome and Healthy Women

Polycystic ovary syndrome (PCOS), one of the most common endocrine disorders in women of reproductive age, has been associated with the cardiometabolic syndrome and increased risk for cardiovascular diseases. Large (C1) and small (C2) vessel compliance and fasting lipids were measured in 45 healthy women and 36 women with PCOS. There were no differences in vacular compliance (C1, C2) between the 2 groups. Systolic blood pressure (116.8 vs 124.3 mm Hg; P=.01), mean arterial pressure (82.5 vs 87 mm Hg; P=.03), and low-density lipoprotein cholesterol (98.1 vs 119 mg/dL; P=.001) were significantly higher in the PCOS group. This difference was not significant after adjusting for age and body mass index. High-density lipoprotein levels in subjects with PCOS were significantly lower than in healthy women (60.2 vs 48.9 mg/dL, P=.02) even after adjusting for age and body mass index. The study indicates that obesity and low high-density lipoprotein are the major contributing factors to cardiovascular changes in PCOS.

Insulin and insulin resistance: impact on blood pressure and cardiovascular disease

Cardiovascular disease is a major cause of mortality in individuals with diabetes. Many factors, including hypertension, contribute to the high prevalence of CVD in this population. Hypertension occurs approximately twice as frequently in patients with diabetes compared with patients without diabetes. Conversely, recent data suggest that hypertensive persons are more likely to develop diabetes than normotensive persons. In addition, up to 75% of CVD in patients with diabetes may be attributed to hypertension, leading to recommendations for more aggressive blood pressure control (ie, < 130/85 mm Hg) in persons with coexistent diabetes and hypertension. Increasing obesity further contributes to both diabetes and hypertension and significantly increases CVD morbidity and mortality. Other important risk factors for CVD in these patients include atherosclerosis, dyslipidemia, microalbuminuria, endothelial dysfunction, platelet hyperaggregability, coagulation abnormalities, and diabetic cardiomyopathy. The current knowledge regarding these risk factors has been reviewed, placing special emphasis on the metabolic syndrome, hypertension, microalbuminuria, and the role of obesity in these disorders. Although not discussed in detail, it is acknowledged that both hygienic measures (weight loss and aerobic exercise) and treatment strategies that include aspirin, statins, INS sensitizers, and antihypertensive agents that reduce renin-angiotensin-aldosterone system activity have been shown to reduce inflammation, coagulation abnormalities, endothelial function, proteinuria, and in some cases reduce CVD and renal disease progression. Additional therapeutic agents are currently being developed specifically to improve INS sensitivity and other CVD risk factors that are components of the cardiometabolic syndrome.