Retinal microvascular function and incidence and trajectories of clinically relevant depressive symptoms: the Maastricht Study

BACKGROUND

Cerebral microvascular dysfunction may contribute to depression via disruption of brain structures involved in mood regulation, but evidence is limited. We investigated the association of retinal microvascular function, a proxy for microvascular function in the brain, with incidence and trajectories of clinically relevant depressive symptoms.

METHODS

Longitudinal data are from The Maastricht Study of 5952 participants (59.9 ± 8.5 years/49.7% women) without clinically relevant depressive symptoms at baseline (2010-2017). Central retinal arteriolar equivalent and central retinal venular equivalent (CRAE and CRVE) and a composite score of flicker light-induced retinal arteriolar and venular dilation were assessed at baseline. We assessed incidence and trajectories of clinically relevant depressive symptoms (9-item Patient Health Questionnaire score ⩾10). Trajectories included continuously low prevalence (low, n = 5225 [87.8%]); early increasing, then chronic high prevalence (early-chronic, n = 157 [2.6%]); low, then increasing prevalence (late-increasing, n = 247 [4.2%]); and remitting prevalence (remitting, n = 323 [5.4%]).

RESULTS

After a median follow-up of 7.0 years (range 1.0-11.0), 806 (13.5%) individuals had incident clinically relevant depressive symptoms. After full adjustment, a larger CRAE and CRVE were each associated with a lower risk of clinically relevant depressive symptoms (hazard ratios [HRs] per standard deviation [s.d.]: 0.89 [95% confidence interval (CI) 0.83-0.96] and 0.93 [0.86-0.99], respectively), while a lower flicker light-induced retinal dilation was associated with a higher risk of clinically relevant depressive symptoms (HR per s.d.: 1.10 [1.01-1.20]). Compared to the low trajectory, a larger CRAE was associated with lower odds of belonging to the early-chronic trajectory (OR: 0.83 [0.69-0.99]) and a lower flicker light-induced retinal dilation was associated with higher odds of belonging to the remitting trajectory (OR: 1.23 [1.07-1.43]).

CONCLUSIONS

These findings support the hypothesis that cerebral microvascular dysfunction contributes to the development of depressive symptoms.

Capillary rarefaction: a missing link in renal and cardiovascular disease?

Patients with chronic kidney disease (CKD) have an increased risk for cardiovascular morbidity and mortality. Capillary rarefaction may be both one of the causes as well as a consequence of CKD and cardiovascular disease. We reviewed the published literature on human biopsy studies and conclude that renal capillary rarefaction occurs independently of the cause of renal function decline. Moreover, glomerular hypertrophy may be an early sign of generalized endothelial dysfunction, while peritubular capillary loss occurs in advanced renal disease. Recent studies with non-invasive measurements show that capillary rarefaction is detected systemically (e.g., in the skin) in individuals with albuminuria, as sign of early CKD and/or generalized endothelial dysfunction. Decreased capillary density is found in omental fat, muscle and heart biopsies of patients with advanced CKD as well as in skin, fat, muscle, brain and heart biopsies of individuals with cardiovascular risk factors. No biopsy studies have yet been performed on capillary rarefaction in individuals with early CKD. At present it is unknown whether individuals with CKD and cardiovascular disease merely share the same risk factors for capillary rarefaction, or whether there is a causal relationship between rarefaction in renal and systemic capillaries. Further studies on renal and systemic capillary rarefaction, including their temporal relationship and underlying mechanisms are needed. This review stresses the importance of preserving and maintaining capillary integrity and homeostasis in the prevention and management of renal and cardiovascular disease.

Elevated blood pressure accelerates white matter brain aging among late middle-aged women: a Mendelian Randomization study in the UK Biobank

BACKGROUND

Elevated blood pressure (BP) is a modifiable risk factor associated with cognitive impairment and cerebrovascular diseases. However, the causal effect of BP on white matter brain aging remains unclear.

METHODS

In this study, we focused on N  = 228 473 individuals of European ancestry who had genotype data and clinical BP measurements available (103 929 men and 124 544 women, mean age = 56.49, including 16 901 participants with neuroimaging data available) collected from UK Biobank (UKB). We first established a machine learning model to compute the outcome variable brain age gap (BAG) based on white matter microstructure integrity measured by fractional anisotropy derived from diffusion tensor imaging data. We then performed a two-sample Mendelian randomization analysis to estimate the causal effect of BP on white matter BAG in the whole population and subgroups stratified by sex and age brackets using two nonoverlapping data sets.

RESULTS

The hypertension group is on average 0.31 years (95% CI = 0.13-0.49; P  < 0.0001) older in white matter brain age than the nonhypertension group. Women are on average 0.81 years (95% CI = 0.68-0.95; P  < 0.0001) younger in white matter brain age than men. The Mendelian randomization analyses showed an overall significant positive causal effect of DBP on white matter BAG (0.37 years/10 mmHg, 95% CI 0.034-0.71, P  = 0.0311). In stratified analysis, the causal effect was found most prominent among women aged 50-59 and aged 60-69.

CONCLUSION

High BP can accelerate white matter brain aging among late middle-aged women, providing insights on planning effective control of BP for women in this age group.

Habitual intake of advanced glycation endproducts is not associated with worse insulin sensitivity, worse beta cell function, or presence of prediabetes or type 2 diabetes: The Maastricht Study

BACKGROUND & AIMS

A diet high in advanced glycation endproducts (AGEs) is a potential risk factor for insulin resistance, beta cell dysfunction, and ultimately type 2 diabetes. We investigated associations between habitual intake of dietary AGEs and glucose metabolism in a population-based setting.

METHODS

In 6275 participants of The Maastricht Study (mean ± SD age: 60 ± 9, 15.1% prediabetes and 23.2% type 2 diabetes), we estimated habitual intake of dietary AGEs N^ε-(carboxymethyl)lysine (CML), N^ε-(1-carboxyethyl)lysine (CEL), and N^δ-(5-hydro-5-methyl-4-imidazolon-2-yl)-ornithine (MG-H1) by combining a validated food frequency questionnaire (FFQ) with our mass-spectrometry dietary AGE database. We determined insulin sensitivity (Matsuda- and HOMA-IR index), beta cell function (C-peptidogenic index, glucose sensitivity, potentiation factor, and rate sensitivity), glucose metabolism status, fasting glucose, HbA1c, post-OGTT glucose, and OGTT glucose incremental area under the curve. Cross-sectional associations between habitual AGE intake and these outcomes were investigated using a combination of multiple linear regression and multinomial logistic regression adjusting for several potential confounders (demographic, cardiovascular, and lifestyle factors).

RESULTS

Generally, higher habitual intake of AGEs was not associated with worse indices of glucose metabolism, nor with increased presence of prediabetes or type 2 diabetes. Higher dietary MG-H1 was associated with better beta cell glucose sensitivity.

CONCLUSIONS

The present study does not support an association of dietary AGEs with impaired glucose metabolism. Whether higher intake of dietary AGEs translates to increased incidence of prediabetes or type 2 diabetes on the long term should be investigated in large prospective cohort studies.

Alcohol consumption and microvascular dysfunction: a J-shaped association: The Maastricht Study

BACKGROUND

Microvascular dysfunction (MVD) is an important contributor to major clinical disease such as stroke, dementia, depression, retinopathy, and chronic kidney disease. Alcohol consumption may be a determinant of MVD.

OBJECTIVE

Main objectives were (1) to study whether alcohol consumption was associated with MVD as assessed in the brain, retina, skin, kidney and in the blood; and (2) to investigate whether associations differed by history of cardiovascular disease or sex.

DESIGN

We used cross-sectional data from The Maastricht Study (N = 3,120 participants, 50.9% men, mean age 60 years, and 27.5% with type 2 diabetes [the latter oversampled by design]). We used regression analyses to study the association between total alcohol (per unit and in the categories, i.e. none, light, moderate, high) and MVD, where all measures of MVD were combined into a total MVD composite score (expressed in SD). We adjusted all associations for potential confounders; and tested for interaction by sex, and history of cardiovascular disease. Additionally we tested for interaction with glucose metabolism status.

RESULTS

The association between total alcohol consumption and MVD was non-linear, i.e. J-shaped. Moderate versus light total alcohol consumption was significantly associated with less MVD, after full adjustment (beta [95% confidence interval], -0.10 [-0.19; -0.01]). The shape of the curve differed with sex (P_interaction = 0.03), history of cardiovascular disease (P_interaction < 0.001), and glucose metabolism status (P_interaction = 0.02).

CONCLUSIONS

The present cross-sectional, population-based study found evidence that alcohol consumption may have an effect on MVD. Hence, although increasing alcohol consumption cannot be recommended as a policy, this study suggests that prevention of MVD may be possible through dietary interventions.

Pyridoxamine reduces methylglyoxal and markers of glycation and endothelial dysfunction, but does not improve insulin sensitivity or vascular function in abdominally obese individuals: A randomized double-blind placebo-controlled trial

AIM

To investigate the effects of pyridoxamine (PM), a B6 vitamer and dicarbonyl scavenger, on glycation and a large panel of metabolic and vascular measurements in a randomized double-blind placebo-controlled trial in abdominally obese individuals.

MATERIALS AND METHODS

Individuals (54% female; mean age 50 years; mean body mass index 32 kg/m² ) were randomized to an 8-week intervention with either placebo (n = 36), 25 mg PM (n = 36) or 200 mg PM (n = 36). We assessed insulin sensitivity, β-cell function, insulin-mediated microvascular recruitment, skin microvascular function, flow-mediated dilation, and plasma inflammation and endothelial function markers. PM metabolites, dicarbonyls and advanced glycation endproducts (AGEs) were measured using ultra-performance liquid chromatography tandem mass spectrometry. Treatment effects were evaluated by one-way ANCOVA.

RESULTS

In the high PM dose group, we found a reduction of plasma methylglyoxal (MGO) and protein-bound Nδ-(5-hydro-5-methyl-4-imidazolon-2-yl)-ornithine (MG-H1), as compared to placebo. We found a reduction of the endothelial dysfunction marker soluble vascular cell adhesion molecule-1 (sVCAM-1) in the low and high PM dose group and of soluble intercellular adhesion molecule-1 (sICAM-1) in the high PM dose, as compared to placebo. We found no treatment effects on insulin sensitivity, vascular function or other functional outcome measurements.

CONCLUSIONS

This study shows that PM is metabolically active and reduces MGO, AGEs, sVCAM-1 and sICAM-1, but does not affect insulin sensitivity and vascular function in abdominally obese individuals. The reduction in adhesion markers is promising because these are important in the pathogenesis of endothelial damage and atherosclerosis.

Habitual intake of dietary methylglyoxal is associated with less low-grade inflammation: the Maastricht Study

BACKGROUND

Dicarbonyls are major reactive precursors of advanced glycation endproducts (AGEs). Dicarbonyls are formed endogenously and also during food processing. Circulating dicarbonyls and AGEs are associated with inflammation and microvascular complications of diabetes, but for dicarbonyls from the diet these associations are currently unknown.

OBJECTIVES

We sought to examine the associations of dietary dicarbonyl intake with low-grade inflammation and microvascular function.

METHODS

In 2792 participants (mean ± SD age: 60 ± 8 y; 50% men; 26% type 2 diabetes) of the population-based cohort the Maastricht Study, we estimated the habitual intake of the dicarbonyls methylglyoxal (MGO), glyoxal (GO), and 3-deoxyglucosone (3-DG) by linking FFQ outcome data to our food composition database of the MGO, GO, and 3-DG content of >200 foods. Low-grade inflammation was assessed as six plasma biomarkers, which were compiled in a z score. Microvascular function was assessed as four plasma biomarkers, compiled in a zscore; as diameters and flicker light-induced dilation in retinal microvessels; as heat-induced skin hyperemic response; and as urinary albumin excretion. Cross-sectional associations of dietary dicarbonyls with low-grade inflammation and microvascular function were investigated using linear regression with adjustments for age, sex, potential confounders related to cardiometabolic risk factors, and lifestyle and dietary factors.

RESULTS

Fully adjusted analyses revealed that higher intake of MGO was associated with a lower z score for inflammation [standardized β coefficient (STD β): -0.05; 95% CI: -0.09 to -0.01, with strongest inverse associations for hsCRP and TNF-α: both -0.05; -0.10 to -0.01]. In contrast, higher dietary MGO intake was associated with impaired retinal venular dilation after full adjustment (STD β: -0.07; 95% CI: -0.12 to -0.01), but not with the other features of microvascular function. GO and 3-DG intakes were not consistently associated with any of the outcomes.

CONCLUSION

Higher habitual intake of MGO was associated with less low-grade inflammation. This novel, presumably beneficial, association is the first observation of an association between MGO intake and health outcomes in humans and warrants further investigation.

Effect of iron deficiency on skeletal muscle metabolism in heart failure with preserved ejection fraction

Background

Iron deficiency (ID) is suggested to be one of the key comorbidities contributing to heart failure with preserved ejection fraction (HFpEF) and concomitant exercise intolerance, possibly by inducing systemic inflammation and microvascular dysfunction (MVD). ID is associated with poorer prognosis in HFpEF, but its exact impact on exercise capacity in HFpEF patients remains to be further investigated.

Purpose

To evaluate the effect of ID on exercise capacity in HFpEF patients by assessing skeletal muscle metabolism. Additionally, to assess the association between ID and MVD in HFpEF patients.

Methods

This prospective study included patients diagnosed with HFpEF according to the ESC Heart Failure 2016 guidelines between January 2018 and May 2021. Patients were excluded if they were of childbearing potential, had any iron supplementation 6 months or chemotherapy 1 year prior to inclusion, were known with significant peripheral artery disease, or had any contraindication for phosphorus-magnetic resonance spectroscopy (31P-MRS). Iron status was defined as absolute ID (serum ferritin &lt;100μg/L), relative ID (serum ferritin 100–299μg/L and transferrin saturation &lt;20%), and no ID. Skeletal muscle oxidative capacity of the upper leg was evaluated by determining phosphocreatine (PCr) recovery kinetics with 31P-MRS in the vastus lateralis muscle after isometric knee extension exercise. Microvascular function was assessed as heat-induced skin hyperemia using laser-Doppler flowmetry. Clinical data up to 6 months prior to or after inclusion was used.

Results

Twenty-four HFpEF patients without ID and 18 with ID were included, including 14 patients with absolute ID. Clinical characteristics of patients without ID and with ID were comparable: median age 74 [69–79] vs. 77 [69–81] years, 13 (54%) vs. 14 (78%) were females, and 20 (83%) vs. 16 (89%) had a history of hypertension (Table 1). Both groups showed similar halftime of PCr recovery after exercise (29.2 [22.8–33.2] vs. 27.0 [21.1–31.4] seconds, p=0.416), and similar skin hyperaemic flow increase (1142 [576–2247] vs. 1023 [574–1511] %, p=0.554). These measures of skeletal muscle metabolism and microvascular function were not correlated. In a subset of patients (11 without ID and 13 with ID), elevated high-sensitive C-reactive protein (hsCRP) was correlated with PCr recovery halftime in those with ID (R2 0.565, p=0.003). This correlation was not found in patients without ID (R2 0.119, p=0.300) in the original data (Figure 1), but was found after removal of a prominent outlier (R2 0.654, p=0.005).

Conclusion

HFpEF patients without ID showed comparable skeletal muscle oxidative capacity and microvascular skin hyperaemia compared to HFpEF patients with ID. Post-hoc analysis suggests that inflammation affects skeletal muscle metabolism in HFpEF patients, possibly regardless of ID. Future studies on the effects of ID and inflammation on cellular metabolism could suggest therapeutic targets in HFpEF.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): This study was funded by Vifor Pharma. The funder had no influence on the study results.

A randomized diet-induced weight-loss intervention reduces plasma complement C3: Possible implication for endothelial dysfunction

OBJECTIVE

Complement C3 and other components of the alternative pathway are higher in individuals with obesity. Moreover, C3 has been identified as a risk factor for cardiovascular disease. This study investigated whether, and how, a weight-loss intervention reduced plasma C3, activated C3 (C3a), and factor D and explored potential biological effects of such a reduction.

METHODS

The study measured plasma C3, C3a, and factor D by ELISA and measured visceral adipose tissue, subcutaneous adipose tissue, and intrahepatic lipid by magnetic resonance imaging in lean men (n = 25) and men with abdominal obesity (n = 52). The men with obesity were randomized to habitual diet or an 8-week dietary weight-loss intervention.

RESULTS

The intervention significantly reduced C3 (-0.15 g/L [95% CI: -0.23 to -0.07]), but not C3a or factor D. The C3 reduction was mainly explained by reduction in visceral adipose tissue but not subcutaneous adipose tissue or intrahepatic lipid. This reduction in C3 explained a part of the weight-loss-induced improvement of markers of endothelial dysfunction, particularly the reduction in soluble endothelial selectin and soluble intercellular adhesion molecule.

CONCLUSIONS

Diet-induced weight loss in men with abdominal obesity could be a way to lower plasma C3 and thereby improve endothelial dysfunction. C3 reduction may be part of the mechanism via which diet-induced weight loss could ameliorate the risk of cardiovascular disease in men with abdominal obesity.

Renal Clearance of Fibroblast Growth Factor-23 (FGF23) and its Fragments in Humans

Relative abundance of fibroblast growth factor-23 (FGF23) measured by the C-terminal (cFGF23, which measures both intact FGF23 and C-terminal fragments) versus intact (iFGF23, measures only intact hormone) assays varies by kidney function in humans. Differential kidney clearance may explain this finding. We measured cFGF23 and iFGF23 in the aorta and bilateral renal veins of 162 patients with essential hypertension undergoing renal angiography. Using multivariable linear regression, we examined factors associated with aorta to renal vein reduction of FGF23 using both assays. Similar parameters and with addition of urine concentrations of cFGF23 and iFGF23 were measured in six Wistar rats. Mean ± standard deviation (SD) age was 54 ± 12 years, 54% were women, and mean creatinine clearance was 72 ± 48 mL/min/100 g. The human kidney reduced the concentrations of both cFGF23 (16% ± 12%) and iFGF23 (21% ± 16%), but reduction was higher for iFGF23. Greater kidney creatinine and PTH reductions were each independently associated with greater reductions of both cFGF23 and iFGF23. The greater kidney reduction of iFGF23 compared to cFGF23 appeared stable and consistent across the range of creatinine clearance evaluated. Kidney clearance was similar, and urine concentrations of both assays were low in the rat models, suggesting kidney metabolism of both cFGF23 and iFGF23. Renal reduction of iFGF23 is higher than that of creatinine and cFGF23. Our data suggest that FGF23 is metabolized by the kidney. However, the major cell types involved in metabolization of FGF23 requires future study. Kidney clearance of FGF23 does not explain differences in C-terminal and intact moieties across the range of kidney function. © 2022 American Society for Bone and Mineral Research (ASBMR).

Effects of Diet-Induced Weight Loss on Plasma Markers for Cholesterol Absorption and Synthesis: Secondary Analysis of a Randomized Trial in Abdominally Obese Men

Cross-sectional studies have shown that obesity is associated with lower intestinal cholesterol absorption and higher endogenous cholesterol synthesis. These metabolic characteristics have also been observed in patients with type 2 diabetes, metabolic syndrome, steatosis or cholestasis. The number of intervention studies evaluating the effect of weight loss on these metabolic characteristics is, however, limited, while the role of the different fat compartments has not been studied into detail. In a randomized trial, abdominally obese men (N = 54) followed a 6-week very low caloric (VLCD) diet, followed by a 2 week weight-maintenance period. Non-cholesterol sterols were measured at baseline and after 8 weeks, and compared to levels in lean participants (N = 25). After weight loss, total cholesterol (TC)-standardized cholestanol levels increased by 0.18 µmol/mmol (p < 0.001), while those of campesterol and lathosterol decreased by 0.25 µmol/mmol (p < 0.05) and 0.39 µmol/mmol (p < 0.001), respectively. Moreover, after weight loss, TC-standardized lathosterol and cholestanol levels were comparable to those of lean men. Increases in TC-standardized cholestanol after weight loss were significantly associated with changes in waist circumference (p < 0.01), weight (p < 0.001), BMI (p < 0.001) and visceral fat (p < 0.01), but not with subcutaneous and intrahepatic lipids. In addition, cross-sectional analysis showed that visceral fat fully mediated the association between BMI and TC-standardized cholestanol levels. Intrahepatic lipid content was a partial mediator for the association between BMI and TC-standardized lathosterol levels. In conclusion, diet-induced weight loss decreased cholesterol synthesis and increased cholesterol absorption. The increase in TC-standardized cholestanol levels was not only related to weight loss, but also to a decrease in visceral fat volume. Whether these metabolic changes ameliorate other metabolic risk factors needs further study.

The Role of Systemic Microvascular Dysfunction in Heart Failure with Preserved Ejection Fraction

Heart failure with preserved ejection fraction (HFpEF) is a condition with increasing incidence, leading to a health care problem of epidemic proportions for which no curative treatments exist. Consequently, an urge exists to better understand the pathophysiology of HFpEF. Accumulating evidence suggests a key pathophysiological role for coronary microvascular dysfunction (MVD), with an underlying mechanism of low-grade pro-inflammatory state caused by systemic comorbidities. The systemic entity of comorbidities and inflammation in HFpEF imply that patients develop HFpEF due to systemic mechanisms causing coronary MVD, or systemic MVD. The absence or presence of peripheral MVD in HFpEF would reflect HFpEF being predominantly a cardiac or a systemic disease. Here, we will review the current state of the art of cardiac and systemic microvascular dysfunction in HFpEF (Graphical Abstract), resulting in future perspectives on new diagnostic modalities and therapeutic strategies.

Extracerebral microvascular dysfunction is related to brain MRI markers of cerebral small vessel disease: The Maastricht Study

BACKGROUND

Cerebral small vessel disease (cSVD) is a late consequence of cerebral microvascular dysfunction (MVD). MVD is hard to measure in the brain due to its limited accessibility. Extracerebral MVD (eMVD) measures can give insights in the etiology of cerebral MVD, as MVD may be a systemic process. We aim to investigate whether a compound score consisting of several eMVD measures is associated with structural cSVD MRI markers.

METHODS

Cross-sectional data of the population-based Maastricht Study was used (n = 1872, mean age 59 ± 8 years, 49% women). Measures of eMVD included flicker light-induced retinal arteriolar and venular dilation response (retina), albuminuria and glomerular filtration rate (kidney), heat-induced skin hyperemia (skin), and plasma biomarkers of endothelial dysfunction (sICAM-1, sVCAM-1, sE-selectin, and von Willebrand factor). These measures were standardized into z scores and summarized into a compound score. Linear and logistic regression analyses were used to investigate the associations between the compound score and white matter hyperintensity (WMH) volume, and the presence of lacunes and microbleeds, as measured by brain MRI.

RESULTS

The eMVD compound score was associated with WMH volume independent of age, sex, and cardiovascular risk factors (St β 0.057 [95% CI 0.010-0.081], p value 0.01), but not with the presence of lacunes (OR 1.011 [95% CI 0.803-1.273], p value 0.92) or microbleeds (OR 1.055 [95% CI 0.896-1.242], p value 0.52).

CONCLUSION

A compound score of eMVD is associated with WMH volume. Further research is needed to expand the knowledge about the role of systemic MVD in the pathophysiology of cSVD.

Habitual intake of dietary advanced glycation end products is not associated with generalized microvascular function-the Maastricht Study

BACKGROUND

Endogenously formed advanced glycation end products (AGEs) may be important drivers of microvascular dysfunction and the microvascular complications of diabetes. AGEs are also formed in food products, especially during preparation methods involving dry heat.

OBJECTIVES

We aimed to assess cross-sectional associations between dietary AGE intake and generalized microvascular function in a population-based cohort.

METHODS

In 3144 participants of the Maastricht Study (mean ± SD age: 60 ± 8 y, 51% men) the dietary AGEs Nε-(carboxymethyl)lysine (CML), Nε-(1-carboxyethyl)lysine (CEL), and Nδ-(5-hydro-5-methyl-4-imidazolon-2-yl)-ornithine (MG-H1) were estimated using the combination of our ultra-performance LC-tandem MS dietary AGE database and an FFQ. Microvascular function was determined in the retina as flicker light-induced arteriolar and venular dilation and as central retinal arteriolar and venular equivalents, in plasma as a z score of endothelial dysfunction biomarkers (soluble vascular adhesion molecule 1 and soluble intracellular adhesion molecule 1, soluble E-selectin, and von Willebrand factor), in skin as the heat-induced skin hyperemic response, and in urine as 24-h albuminuria. Associations were evaluated using multiple linear regression adjusting for demographic, cardiovascular, lifestyle, and dietary factors.

RESULTS

Overall, intakes of CML, CEL, and MG-H1 were not associated with the microvascular outcomes. Although higher intake of CEL was associated with higher flicker light-induced venular dilation (β percentage change over baseline: 0.14; 95% CI: 0.02, 0.26) and lower plasma biomarker z score (β: -0.04 SD; 95% CI: -0.08, -0.00 SD), the effect sizes were small and their biological relevance can be questioned.

CONCLUSIONS

We did not show any strong association between habitual intake of dietary AGEs and generalized microvascular function. The contribution of dietary AGEs to generalized microvascular function should be further assessed in randomized controlled trials using specifically designed dietary interventions.

Sex differences in the association of prediabetes and type 2 diabetes with microvascular complications and function: The Maastricht Study

BACKGROUND

Women with type 2 diabetes are disproportionally affected by macrovascular complications; we here investigated whether this is also the case for microvascular complications and retinal microvascular measures.

METHODS

In a population-based cohort study of individuals aged 40-75 years (n = 3410; 49% women, 29% type 2 diabetes (oversampled by design)), we estimated sex-specific associations, and differences therein, of (pre)diabetes (reference: normal glucose metabolism), and of continuous measures of glycemia with microvascular complications and retinal measures (nephropathy, sensory neuropathy, and retinal arteriolar and venular diameters and dilatation). Sex differences were analyzed using regression models with interaction terms (i.e. sex-by- (pre)diabetes and sex-by-glycemia) and were adjusted for potential confounders.

RESULTS

Men with type 2 diabetes (but not those with prediabetes) compared to men with normal glucose metabolism, (and men with higher levels of glycemia), had significantly higher prevalences of nephropathy (odds ratio: 1.58 95% CI (1.01;2.46)) and sensory neuropathy (odds ratio: 2.46 (1.67;3.63)), larger retinal arteriolar diameters (difference: 4.29 µm (1.22;7.36)) and less retinal arteriolar dilatation (difference: - 0.74% (- 1.22; - 0.25)). In women, these associations were numerically in the same direction, but generally not statistically significant (odds ratios: 1.71 (0.90;3.25) and 1.22 (0.75;1.98); differences: 0.29 µm (- 3.50;4.07) and: - 0.52% (- 1.11;0.08), respectively). Interaction analyses revealed no consistent pattern of sex differences in the associations of either prediabetes or type 2 diabetes or glycemia with microvascular complications or retinal measures. The prevalence of advanced-stage complications was too low for evaluation.

CONCLUSIONS

Our findings show that women with type 2 diabetes are not disproportionately affected by early microvascular complications.

Carotid stiffness is associated with retinal microvascular dysfunction-The Maastricht study

Objective

This study investigated whether arterial stiffening is a determinant of subtle retinal microvascular changes that precede diabetic retinopathy.

Research design and methods

This study used cross‐sectional data from the Maastricht Study, a type 2 diabetes‐enriched population‐based cohort study. We used multivariable linear regression analysis to investigate, in individuals without and with type 2 diabetes, the associations of carotid distensibility coefficient and carotid‐femoral pulse wave velocity with retinal microvascular diameters and flicker light‐induced dilation and adjusted for cardiovascular and lifestyle risk factors.

Results

The retinal microvascular diameter study population consisted of N = 2434 participants (51.4% men, mean ± SD age 59.8 ± 8.1 years, and 28.1% type 2 diabetes). No measures of arterial stiffness were significantly associated with microvascular diameters. Greater carotid distensibility coefficient (i.e., lower carotid stiffness) was significantly associated with greater retinal arteriolar flicker light‐induced dilation (per standard deviation, standardized beta [95% CI] 0.06 [0.00; 0.12]) and non‐significantly, but directionally similarly, associated with greater retinal venular flicker light‐induced dilation (0.04 [−0.02; 0.10]). Carotid‐femoral pulse wave velocity (i.e., aortic stiffness) was not associated with retinal microvascular flicker light‐induced dilation. The associations between carotid distensibility coefficient and retinal arteriolar and venular flicker light‐induced dilation were two‐ to threefold stronger in individuals with type 2 diabetes than in those without.

Conclusion

In this population‐based study greater carotid, but not aortic, stiffness was associated with worse retinal flicker light‐induced dilation and this association was stronger in individuals with type 2 diabetes. Hence, carotid stiffness may be a determinant of retinal microvascular dysfunction.

Diet-induced weight loss reduces postprandial dicarbonyl stress in abdominally obese men: Secondary analysis of a randomized controlled trial

AIMS

Dicarbonyl compounds contribute to the formation of advanced glycation endproducts (AGEs) and the development of insulin resistance and vascular complications. Dicarbonyl stress may already be detrimental in obesity. We evaluated whether diet-induced weight loss can effectively reverse dicarbonyl stress in abdominally obese men.

MATERIALS AND METHODS

Plasma samples were collected from lean (n = 25) and abdominally obese men (n = 52) in the fasting state, and during a mixed meal test (MMT). Abdominally obese men were randomized to 8 weeks of dietary weight loss or habitual diet, followed by a second MMT. The α-dicarbonyls methylglyoxal (MGO), glyoxal (GO) and 3-deoxyglucosone (3-DG) and AGEs were measured by UPLC-MS/MS. Skin autofluorescence (SAF) was measured using the AGE reader. T-tests were used for the cross-sectional analysis and ANCOVA to assess the treatment effect.

RESULTS

Postprandial glucose, MGO and 3-DG concentrations were higher in obese men as compared to lean men (p < 0.05 for all). Fasting dicarbonyls, AGEs, and SAF were not different between lean and obese men. After the weight loss intervention, fasting MGO levels tended to decrease by 25 nmol/L (95%-CI: -51-0.5; p = 0.054). Postprandial dicarbonyls were decreased after weight loss as compared to the control group: iAUC of MGO decreased by 57% (5280 nmol/L∙min; 95%-CI: 33-10526; p = 0.049), of GO by 66% (11,329 nmol/L∙min; 95%-CI: 495-22162; p = 0.041), and of 3-DG by 45% (20,175 nmol/L∙min; 95%-CI: 5351-35000; p = 0.009). AGEs and SAF did not change significantly after weight loss.

CONCLUSION

Abdominal obesity is characterized by increased postprandial dicarbonyl stress, which can be reduced by a weight loss intervention. Registered under ClinicalTrials.gov Identifier no. NCT01675401.

Intact and C-Terminal FGF23 Assays-Do Kidney Function, Inflammation, and Low Iron Influence Relationships With Outcomes?

CONTEXT

Higher fibroblast growth factor-23 (FGF23) concentrations are associated with heart failure and mortality in diverse populations, but the strengths of associations differ markedly depending up on which assay is used.

OBJECTIVE

We sought to evaluate whether iron deficiency, inflammation, or kidney function account for differences in the strengths of associations between these 2 FGF23 assays with clinical outcomes.

DESIGN

Case cohort study from the Cardiovascular Health Study.

SETTING

A total of 844 community-dwelling individuals aged 65 years or older with and without chronic kidney disease were followed for 10 years.

OUTCOMES

Outcomes included death, incident heart failure (HF), and incident myocardial infarction (MI). Exposure was baseline intact and C-terminal FGF23. Using modified Cox models, adjusting sequentially we tested whether observed associations of each assay with outcomes were attenuated by iron status, inflammation, kidney function, or their combinations.

RESULTS

FGF23 measured by either assay was associated with mortality in unadjusted analysis (intact FGF23 hazard ratio [HR] per 2-fold higher 1.45; 95% CI, 1.25-1.68; C-terminal FGF23 HR 1.38; 95% CI, 1.26-1.50). Adjustment for kidney function completely attenuated associations of intact FGF23 with mortality (HR 1.00; 95% CI, 0.85-1.17), but had much less influence on the association of C-terminal FGF23, for which results remained significant after adjustment (HR 1.15; 95% CI, 1.04-1.28). Attenuation was much less with adjustment for iron status or inflammation. Results were similar for the HF end point. Neither C-terminal or intact FGF23 was associated with MI risk.

CONCLUSIONS

The relationship of FGF23 with clinical end points is markedly different depending on the type of FGF23 assay used. The associations of biologically active FGF23 with clinical end points may be confounded by kidney disease, and thus much weaker than previously thought.

Microvascular Phenotyping in the Maastricht Study: Design and Main Findings, 2010-2018

Microvascular dysfunction (MVD) is a common pathophysiological change that occurs in various diseases, such as type 2 diabetes mellitus (T2DM), heart failure, dementia, and depression. Recent technical advances have enabled noninvasive measurement and quantification of microvascular changes in humans. In this paper, we describe the protocols of the microvascular measurements applied in the Maastricht Study, an ongoing prospective, population-based cohort study of persons aged 40–75 years being carried out in the southern part of the Netherlands (baseline data assessment, November 2010–January 2020). The study includes a variety of noninvasive measurements in skin, retina, brain, and sublingual tissue, as well as plasma and urine biomarker assessments. Following this, we summarize our main findings involving these microvascular measurements through the end of 2018. Finally, we provide a brief perspective on future microvascular investigations within the framework of the Maastricht Study.

Type 2 diabetes and HbA1c are independently associated with wider retinal arterioles: the Maastricht study

AIMS/HYPOTHESIS

Retinal microvascular diameters are biomarkers of cardio-metabolic risk. However, the association of (pre)diabetes with retinal microvascular diameters remains unclear. We aimed to investigate the association of prediabetes (impaired fasting glucose or impaired glucose tolerance) and type 2 diabetes with retinal microvascular diameters in a predominantly white population.

METHODS

In a population-based cohort study with oversampling of type 2 diabetes (N = 2876; n = 1630 normal glucose metabolism [NGM], n = 433 prediabetes and n = 813 type 2 diabetes, 51.2% men, aged 59.8 ± 8.2 years; 98.6% white), we determined retinal microvascular diameters (measurement unit as measured by retinal health information and notification system [RHINO] software) and glucose metabolism status (using OGTT). Associations were assessed with multivariable regression analyses adjusted for age, sex, waist circumference, smoking, systolic blood pressure, lipid profile and the use of lipid-modifying and/or antihypertensive medication.

RESULTS

Multivariable regression analyses showed a significant association for type 2 diabetes but not for prediabetes with arteriolar width (vs NGM; prediabetes: β = 0.62 [95%CI -1.58, 2.83]; type 2 diabetes: 2.89 [0.69, 5.08]; measurement unit); however, there was a linear trend for the arteriolar width across glucose metabolism status (p for trend = 0.013). The association with wider venules was not statistically significant (prediabetes: 2.40 [-1.03, 5.84]; type 2 diabetes: 2.87 [-0.55, 6.29], p for trend = 0.083; measurement unit). Higher HbA_1c levels were associated with wider retinal arterioles (standardised β = 0.043 [95% CI 0.00002, 0.085]; p = 0.050) but the association with wider venules did not reach statistical significance (0.037 [-0.006, 0.080]; p = 0.092) after adjustment for potential confounders.

CONCLUSIONS/INTERPRETATION

Type 2 diabetes, higher levels of HbA_1c and, possibly, prediabetes, are independently associated with wider retinal arterioles in a predominantly white population. These findings indicate that microvascular dysfunction is an early phenomenon in impaired glucose metabolism.

Higher levels of daily physical activity are associated with better skin microvascular function in type 2 diabetes-The Maastricht Study

Objective

Physical activity may provide a means for the prevention of cardiovascular disease via improving microvascular function. Therefore, this study investigated whether physical activity is associated with skin and retinal microvascular function.

Methods

In The Maastricht Study, a population‐based cohort study enriched with type 2 diabetes (n = 1298, 47.3% women, aged 60.2 ± 8.1 years, 29.5% type 2 diabetes), we studied whether accelerometer‐assessed physical activity and sedentary time associate with skin and retinal microvascular function. Associations were studied by linear regression and adjusted for major cardiovascular risk factors. In addition, we investigated whether associations were stronger in type 2 diabetes.

Results

In individuals with type 2 diabetes, total physical activity and higher‐intensity physical activity were independently associated with greater heat‐induced skin hyperemia (regression coefficients per hour), respectively, 10 (95% CI: 1; 18) and 36 perfusion units (14; 58). In individuals without type 2 diabetes, total physical activity and higher‐intensity physical activity were not associated with heat‐induced skin hyperemia. No associations with retinal arteriolar %‐dilation were identified.

Conclusion

Higher levels of total and higher‐intensity physical activity were associated with greater skin microvascular vasodilation in individuals with, but not in those without, type 2 diabetes.

Fasting and post-oral-glucose-load levels of methylglyoxal are associated with microvascular, but not macrovascular, disease in individuals with and without (pre)diabetes: The Maastricht Study

AIMS

Reactive dicarbonyl compounds, such as methylglyoxal (MGO), rise during an oral glucose tolerance test (OGTT), particularly in (pre)diabetes. Fasting MGO levels are associated with chronic kidney disease (CKD) and cardiovascular disease (CVD) in patients with poorly controlled type 2 diabetes mellitus (T2DM). Yet, whether fasting or post-OGTT plasma MGO levels are associated with vascular disease in people with (pre)diabetes is unknown.

METHODS

Subjects with normal glucose metabolism (n=1796; age: 57.9±8.2 years; 43.3% men), prediabetes (n=478; age: 61.6±7.6 years; 54.0% men) and T2DM (n=669; age: 63.0±7.5 years; 67.0% men) from the Maastricht Study underwent OGTTs. Plasma MGO levels were measured at baseline and 2h after OGTT by mass spectrometry. Prior CVD was established via questionnaire. CKD was reflected by estimated glomerular filtration rate (eGFR) and albuminuria; retinopathy was assessed using retinal photographs. Data were analyzed using logistic regression adjusted for gender, age, smoking, systolic blood pressure, total-to-HDL cholesterol ratio, triglycerides, HbA_1c, BMI and medication use. Odd ratios (ORs) were expressed per standard deviation of LN-transformed MGO.

RESULTS

Fasting and post-OGTT MGO levels were associated with higher ORs for albuminuria ≥30mg/24h [fasting: 1.12 (95% CI: 0.97-1.29); post-OGTT: 1.19 (1.01-1.41)], eGFR<60mL/min/1.73 m² [fasting: 1.58 (95% CI: 1.38-1.82), post-OGTT: 1.57 (1.34-1.83)] and retinopathy [fasting: 1.59 (95% CI: 1.01-2.53), post-OGTT: 1.38 (0.77-2.48)]. No associations with prior CVD were found.

CONCLUSION

Fasting and post-OGTT MGO levels were associated with microvascular disease, but not prior CVD. Thus, therapeutic strategies directed at lowering MGO levels may prevent microvascular disease.

Microcirculatory assessment of vascular diseases

The term "microcirculation" refers to the terminal vascular network of the body, which includes arterioles, capillaries, venules as well as initial lymphatic vessels. Additionally, it insinuates to their unique function in thermoregulation, fluid balance, maintenance of cellular exchange, and metabolism. Disturbances of microvascular function were identified to precede macrovascular involvement in the presence of cardiovascular risk factors and is the hallmark of terminal disease stages like critical limb or acral ischemia. Nevertheless, despite its obvious significance in vascular medicine assessment of microvascular function became increasingly neglected in the clinical institutions during the last decades and seems to play a subordinary role in medical education. We therefore provide an overview over relevant and clinically practicable methods to assess microcirculation in vascular medicine with critical estimations of their pros and cons and their perspectives in the future.

Effects of diet-induced weight loss on postprandial vascular function after consumption of a mixed meal: Results of a randomized controlled trial with abdominally obese men

BACKGROUND

Effects of weight loss on postprandial vascular function have not been studied so far. We therefore examined (i) effects of diet-induced weight loss on postprandial changes in various vascular function markers after consumption of a mixed meal and (ii) differences between normal-weight and abdominally obese men of comparable age at baseline and after weight loss.

METHODS

Fifty-four apparently healthy abdominally obese (waist circumference: 102-110 cm) and 25 normal-weight men (waist circumference: <94 cm) participated. The abdominally obese men were randomly allocated to a diet-induced weight-loss program or a no-weight loss control group. Men assigned to the weight-loss program followed a calorie-restricted diet for six weeks targeting a waist circumference of less than 102 cm, followed by a weight-maintenance period for two weeks. The control group maintained their habitual diet and physical activity levels. Measurements were performed before and two hours after consumption of the test meal consisting of two muffins (containing 56.6 g fat) and 300 mL low-fat milk.

RESULTS

The mean weight loss was 10.3 kg in the weight-loss compared with the control group. The postprandial change in flow-mediated vasodilation of the brachial artery (FMD) was significantly higher at baseline in normal-weight as compared with the postprandial change in abdominally obese men (1.89 ± 2.52 versus 0.48 ± 2.50 percentage points; P = 0.027). However, no differences in postprandial changes were observed in the abdominally obese men after weight loss compared with the control treatment. Also, weight reduction did not affect postprandial changes in carotid-to-femoral pulse wave velocity, retinal microvascular caliber properties, or plasma markers of microvascular endothelial function. Even though postprandial increases in triacylglycerol (P = 0.028), insulin (P = 0.029) and C-peptide concentrations (P < 0.001) were reduced in the abdominally obese men following weight loss, postprandial changes in FMD at the end of the weight-loss treatment were still more unfavorable as compared with those observed in normal-weight individuals.

CONCLUSION

In this trial with abdominally obese men, we did not find effects of diet-induced weight loss on postprandial changes in vascular endothelial function, arterial stiffness and markers of microvascular function. This trial was registered on ClinicalTrials.gov under study number NCT01675401.

The oral glucose tolerance test-derived incremental glucose peak is associated with greater arterial stiffness and maladaptive arterial remodeling: The Maastricht Study

Background

Daily glucose variability may contribute to vascular complication development irrespective of mean glucose values. The incremental glucose peak (IGP) during an oral glucose tolerance test (OGTT) can be used as a proxy of glucose variability. We investigated the association of IGP with arterial stiffness, arterial remodeling, and microvascular function, independent of HbA_1c and other confounders.

Methods

IGP was calculated as the peak minus baseline plasma glucose value during a seven-point OGTT in 2758 participants (age: 60 ± 8 years; 48% women) of The Maastricht Study, an observational population-based cohort. We assessed the cross-sectional associations between IGP and arterial stiffness (carotid-femoral pulse wave velocity [cf-PWV], carotid distensibility coefficient [carDC]), arterial remodeling (carotid intima-media thickness [cIMT]; mean [CWS_mean] and pulsatile [CWS_puls] circumferential wall stress), and microvascular function (retinal arteriolar average dilatation; heat-induced skin hyperemia) via multiple linear regression with adjustment for age, sex, HbA_1c, cardiovascular risk factors, lifestyle factors, and medication use.

Results

Higher IGP was independently associated with higher cf-PWV (regression coefficient [B]: 0.054 m/s [0.020; 0.089]) and with higher CWS_mean (B: 0.227 kPa [0.008; 0.446]). IGP was not independently associated with carDC (B: − 0.026 10⁻³/kPa [− 0.112; 0.060]), cIMT (B: − 2.745 µm [− 5.736; 0.245]), CWS_puls (B: 0.108 kPa [− 0.054; 0.270]), retinal arteriolar average dilatation (B: − 0.022% [− 0.087; 0.043]), or heat-induced skin hyperemia (B: − 1.380% [− 22.273; 19.513]).

Conclusions

IGP was independently associated with aortic stiffness and maladaptive carotid remodeling, but not with carotid stiffness, cIMT, and microvascular function measures. Future studies should investigate whether glucose variability is associated with cardiovascular disease.

Serum Phosphate and Microvascular Function in a Population-Based Cohort

BACKGROUND AND OBJECTIVES

Higher serum phosphate is associated with cardiovascular events and all-cause mortality. Explanations of this association have focused on large vessel calcification and stiffness. Studies suggest that a higher serum phosphate induces microvascular dysfunction, but relationships in humans with direct measures of microvascular function are lacking.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We performed a cross-sectional analysis of 3189 community-living participants that underwent skin capillaroscopy, laser-Doppler flowmetry, and flicker light-induced retinal vessel responses. We used linear regression to assess the association between serum phosphate and each microvascular outcome. The primary outcome was skin capillary recruitment during postocclusive peak reactive hyperemia by capillaroscopy. Secondary outcomes included capillary recruitment during venous congestion, heat-induced skin hyperemic response, flicker light-induced retinal arteriolar, and venular dilation.

RESULTS

The mean age of the cohort was 59±8 years, 48% were women, 7% had an eGFR <60 ml/min per 1.73 m², and the mean serum phosphate concentration was 3.2±0.5 mg/dl. A 1 mg/dl higher serum phosphate was independently associated with a 5.0% lower postocclusive capillary recruitment (95% CI, -10.0% to -0.1%). Results were similar for capillary recruitment with venous congestion (-4.5%; 95% CI, -9.8% to 0.7%). A 1 mg/dl higher serum phosphate was also independently associated with a 0.23% lower retinal venular dilation in response to flicker light (95% CI, -0.44% to -0.02%). A higher serum phosphate was not associated with change in flicker light-induced retinal arteriolar dilation or heat-induced skin hyperemic response, however a higher serum phosphate was associated with a lower heat-induced skin hyperemic response among men (-149% [95% CI, -260 to -38] per 1 mg/dl higher serum phosphate) but not women (P interaction, 0.01).

CONCLUSIONS

Higher serum phosphate concentrations, even within the normal range, are associated with microvascular dysfunction in community-living individuals.

PODCAST

This article contains a podcast at https://www.asn-online.org/media/podcast/CJASN/2019_09_20_CJN02610319.mp3.

Contribution of Liver Fat to Weight Loss-Induced Changes in Serum Hepatokines: A Randomized Controlled Trial

CONTEXT

Hepatokines have emerged as potential mediators of obesity-associated comorbidities, such as type 2 diabetes, cardiovascular disease, fractures, and central hypogonadism.

OBJECTIVE

To assess whether weight loss-induced changes in hepatokines are mediated by intrahepatic triglyceride (IHTG) content.

DESIGN

Cross-sectional study and randomized controlled trial.

SETTING

General community.

PARTICIPANTS

Metabolically healthy, lean men (waist <94 cm; n = 25) and men with abdominal obesity (waist 102 to 110 cm; n = 52).

INTERVENTION

Men with abdominal obesity were randomized to 8-week dietary weight loss or no weight loss.

MAIN OUTCOME MEASURES

IHTG and serum hepatokines, that is, serum IGF1, IGF binding protein 1 (IGFBP1), SHBG, fibroblast growth factor 21 (FGF21), fetuin A, and plasma fetuin B.

RESULTS

All hepatokines, except for fetuin B, were significantly different between lean men and men with obesity. After the weight-loss intervention (-10.3 kg; 95% CI, -11.4 to-9.2), serum IGF1, IGFBP1, SHBG, and fetuin A approached the values observed in lean men. Cross-sectional associations were observed between IHTG and IGF1 (β = -0.51; 95% CI, -0.82 to -0.20), IGFBP1 (β = -4.2; 95% CI, -7.7 to -0.7), and FGF21 (β = 2.1; 95% CI, 1.3 to 2.9) in lean men and men with abdominal obesity combined. Weight loss resulted in a reduction of IHTG (treatment effect, -2.2%; 95% CI, -3.4% to -1.2%) that was associated with a change in IGF1 (β = -0.9; 95% CI, -1.3 to -0.4), IGFBP1 (β = -0.17; 95% CI, -0.31 to -0.03), and SHBG levels (β = -0.18; 95% CI, -0.29 to -0.07). Mediation analyses showed that only the weight loss-induced change in serum IGF1 was mediated by IHTG (mediated effect, 32.7%; 95% CI, 4.6% to 79.2%).

CONCLUSIONS

Dietary weight loss has differential effects on hepatokines. This study shows that the change in serum IGF1 levels after dietary weight loss is mediated by the change in IHTG content.

Prediabetes Is Associated With Structural Brain Abnormalities: The Maastricht Study

OBJECTIVE

Structural brain abnormalities are key risk factors for brain diseases, such as dementia, stroke, and depression, in type 2 diabetes. It is unknown whether structural brain abnormalities already occur in prediabetes. Therefore, we investigated whether both prediabetes and type 2 diabetes are associated with lacunar infarcts (LIs), white matter hyperintensities (WMHs), cerebral microbleeds (CMBs), and brain atrophy.

RESEARCH DESIGN AND METHODS

We used data from 2,228 participants (1,373 with normal glucose metabolism [NGM], 347 with prediabetes, and 508 with type 2 diabetes (oversampled); mean age 59.2 ± 8.2 years; 48.3% women) of the Maastricht Study, a population-based cohort study. Diabetes status was determined with an oral glucose tolerance test. Brain imaging was performed with 3 Tesla MRI. Results were analyzed with multivariable logistic and linear regression analyses.

RESULTS

Prediabetes and type 2 diabetes were associated with the presence of LIs (odds ratio 1.61 [95% CI 0.98-2.63] and 1.67 [1.04-2.68], respectively; P _trend = 0.027), larger WMH (β 0.07 log10-transformed mL [log-mL] [95% CI 0.00-0.15] and 0.21 log-mL [0.14-0.28], respectively; P _trend <0.001), and smaller white matter volumes (β -4.0 mL [-7.3 to -0.6] and -7.2 mL [-10.4 to -4.0], respectively; P _trend <0.001) compared with NGM. Prediabetes was not associated with gray matter volumes or the presence of CMBs.

CONCLUSIONS

Prediabetes is associated with structural brain abnormalities, with further deterioration in type 2 diabetes. These results indicate that, in middle-aged populations, structural brain abnormalities already occur in prediabetes, which may suggest that the treatment of early dysglycemia may contribute to the prevention of brain diseases.

The association between diabetes status, HbA1c, diabetes duration, microvascular disease, and bone quality of the distal radius and tibia as measured with high-resolution peripheral quantitative computed tomography-The Maastricht Study

In this small cross-sectional study of predominantly well-treated participants with relatively short-term type 2 diabetes duration, HbA1c > 7% (53 mmol/mol) was associated with lower cortical density and thickness and higher cortical porosity at the distal radius, lower trabecular thickness at the distal tibia, and higher trabecular number at both sites.

INTRODUCTION

To examine the association between diabetes status and volumetric bone mineral density (vBMD), bone microarchitecture and strength of the distal radius and tibia as assessed with HR-pQCT. Additionally-in participants with type 2 diabetes (T2DM), to examine the association between HbA1c, diabetes duration, and microvascular disease (MVD) and bone parameters.

METHODS

Cross-sectional data from 410 (radius) and 198 (tibia) participants of The Maastricht Study (mean age 58 year, 51% female). Diabetes status (normal glucose metabolism, prediabetes, or T2DM) was based on an oral glucose tolerance test and medication history.

RESULTS

After full adjustment, prediabetes and T2DM were not associated with vBMD, bone microarchitecture, and strength of the radius and tibia, except for lower trabecular number (Tb.N) of the tibia (- 4%) in prediabetes and smaller cross-sectional area of the tibia (- 7%) in T2DM. In T2DM, HbA1c > 7% was associated with lower cortical vBMD (- 5%), cortical thickness (- 16%), higher cortical porosity (+ 20%) and Tb.N (+ 9%) of the radius, and higher Tb.N (+ 9%) and lower trabecular thickness (- 13%) of the tibia. Diabetes duration > 5 years was associated with higher Tb.N (+ 6%) of the radius. The presence of MVD was not associated with any bone parameters.

CONCLUSIONS

In this study with predominantly well-treated T2DM participants with relatively short-term diabetes duration, inadequate blood glucose control was negatively associated with cortical bone measures of the radius. In contrast, trabecular number was increased at both sites. Studies of larger sample size are warranted for more detailed investigations of bone density and bone quality in patients with T2DM.

Muscle fiber capillarization as determining factor on indices of insulin sensitivity in humans

To investigate the association between muscle fiber capillarization and indices of insulin sensitivity in healthy older adults. A skeletal muscle biopsy was taken from the m. vastus lateralis of 22 healthy (nondiabetic) male older adults. In addition, all participants underwent an Oral Glucose Tolerance Test (OGTT). Muscle fiber capillarization was assessed by immunohistochemistry. Participants were divided into a group with relatively low (LOW) or high (HIGH) muscle fiber capillarization (capillary‐to‐fiber perimeter exchange (CFPE) index), based on the median value for the entire group. All participants were healthy, nonobese, and had a normal glucose tolerance, according to the individual OGTT results. Whereas no differences in blood glucose concentrations were observed between groups during the OGTT, the postprandial increase in plasma insulin concentrations was significantly greater in the LOW compared to the HIGH muscle fiber capillarization group (P < 0.05). Skeletal muscle fiber capillarization may determine insulin sensitivity in humans.

Aldosterone Is Not Associated With Metabolic and Microvascular Insulin Sensitivity in Abdominally Obese Men

CONTEXT

Impaired insulin-mediated muscle microvascular recruitment (IMMR) may add to the development of insulin resistance and hypertension. Increased aldosterone levels have been linked to these obesity-related complications in severely to morbidly obese individuals and to impaired microvascular function in experimental studies.

OBJECTIVES

To investigate whether aldosterone levels are associated with IMMR, insulin sensitivity, and blood pressure in lean and moderately abdominally obese men, and to study the effect of weight loss.

DESIGN, SETTING, PARTICIPANTS, INTERVENTION, MAIN OUTCOME MEASURES

In 25 lean and 53 abdominally obese men, 24-hour blood pressure measurement was performed, and aldosterone levels were measured using ultra-performance liquid chromatography tandem mass spectrometry. Insulin sensitivity was assessed by determining whole-body glucose disposal during a hyperinsulinemic clamp. IMMR in forearm skeletal muscle was measured with contrast-enhanced ultrasonography. These assessments were repeated in the abdominally obese men following an 8-week weight loss or weight stable period.

RESULTS

Sodium excretion and aldosterone levels were similar in lean and abdominally obese participants, but sodium excretion was inversely associated with aldosterone concentration only in the lean individuals [lean, β/100 mmol sodium excretion (adjusted for age and urinary potassium excretion) = -0.481 (95% confidence interval, -0.949 to -0.013); abdominally obese, β/100 mmol sodium excretion = -0.081 (95% confidence interval, -0.433 to 0.271); P for interaction = 0.02]. Aldosterone was not associated with IMMR, insulin sensitivity, or blood pressure and was unaffected by weight loss.

CONCLUSION

In moderately abdominally obese men, the inverse relationship between sodium excretion and aldosterone concentration is less than that in lean men but does not translate into higher aldosterone levels. The absolute aldosterone level does not explain differences in microvascular and metabolic insulin sensitivity and blood pressure between lean and moderately abdominally obese men.

Cardiovascular risk factors as determinants of retinal and skin microvascular function: The Maastricht Study

Objective

Microvascular dysfunction is an important underlying mechanism of microvascular diseases. Determinants (age, sex, hypertension, dyslipidemia, hyperglycemia, obesity, and smoking) of macrovascular diseases affect large-artery endothelial function. These risk factors also associate with microvascular diseases. We hypothesized that they are also determinants of microvascular (endothelial) function.

Methods

In The Maastricht Study, a type 2 diabetes-enriched population-based cohort study (n = 1991, 51% men, aged 59.7±8.2 years), we determined microvascular function as flicker light-induced retinal arteriolar %-dilation and heat-induced skin %-hyperemia. Multiple linear regression analyses were used to assess the associations of cardiovascular risk factors (age, sex, waist circumference, total-to-high-density lipoprotein (HDL) cholesterol ratio, fasting plasma glucose (FPG), 24-h systolic blood pressure, and cigarette smoking) with retinal and skin microvascular function.

Results

In multivariate analyses, age and FPG were inversely associated with retinal and skin microvascular function (regression coefficients per standard deviation (SD) were -0.11SD (95%CI: -0.15;-0.06) and -0.12SD (-0.17;-0.07) for retinal arteriolar %-dilation and -0.10SD (-0.16;-0.05) and -0.11SD (-0.17;-0.06) for skin %-hyperemia, respectively. Men and current smokers had -0.43SD (-0.58;-0.27) and -0.32SD (-0.49;-0.15) lower skin %-hyperemia, respectively. 24-h systolic blood pressure, waist circumference, and total-to-HDL cholesterol ratio were not statistically significantly associated with these microvascular functions.

Conclusions

Associations between cardiovascular risk factors and retinal and skin microvascular function show a pattern that is partly similar to the associations between cardiovascular risk factors and macrovascular function. Impairment of microvascular function may constitute a pathway through which an adverse cardiovascular risk factor pattern may increase risk of diseases that are partly or wholly of microvascular origin.

Assessing Microvascular Function in Humans from a Chronic Disease Perspective

Microvascular dysfunction (MVD) is considered a crucial pathway in the development and progression of cardiometabolic and renal disease and is associated with increased cardiovascular mortality. MVD often coexists with or even precedes macrovascular disease, possibly due to shared mechanisms of vascular damage, such as inflammatory processes and oxidative stress. One of the first events in MVD is endothelial dysfunction. With the use of different physiologic or pharmacologic stimuli, endothelium-dependent (micro)vascular reactivity can be studied. This reactivity depends on the balance between various mediators, including nitric oxide, endothelin, and prostanoids, among others. The measurement of microvascular (endothelial) function is important to understand the pathophysiologic mechanisms that contribute to MVD and the role of MVD in the development and progression of cardiometabolic/renal disease. Here, we review a selection of direct, noninvasive techniques for measuring human microcirculation, with a focus on methods, interpretation, and limitations from the perspective of chronic cardiometabolic and renal disease.

Association of Microvascular Dysfunction With Late-Life Depression: A Systematic Review and Meta-analysis

Importance

The etiologic factors of late-life depression are still poorly understood. Recent evidence suggests that microvascular dysfunction is associated with depression, which may have implications for prevention and treatment. However, this association has not been systematically reviewed.

Objective

To examine the associations of peripheral and cerebral microvascular dysfunction with late-life depression.

Data Sources

A systematic literature search was conducted in MEDLINE and EMBASE for and longitudinal studies published since inception to October 16, 2016, that assessed the associations between microvascular dysfunction and depression.

Study Selection

Three independent researchers performed the study selection based on consensus. Inclusion criteria were a study population 40 years of age or older, a validated method of detecting depression, and validated measures of microvascular function.

Data Extraction and Synthesis

This systematic review and meta-analysis has been registered at PROSPERO (CRD42016049158) and is reported in accordance with the PRISMA and MOOSE guidelines. Data extraction was performed by an independent researcher.

Main Outcomes and Measures

The following 5 estimates of microvascular dysfunction were considered in participants with or without depression: plasma markers of endothelial function, albuminuria, measurements of skin and muscle microcirculation, retinal arteriolar and venular diameter, and markers for cerebral small vessel disease. Data are reported as pooled odds ratios (ORs) by use of the generic inverse variance method with the use of random-effects models.

Results

A total of 712 studies were identified; 48 were included in the meta-analysis, of which 8 described longitudinal data. Data from 43 600 participants, 9203 individuals with depression, and 72 441 person-years (mean follow-up, 3.7 years) were available. Higher levels of plasma endothelial biomarkers (soluble intercellular adhesion molecule-1: OR, 1.58; 95% CI, 1.28-1.96), white matter hyperintensities (OR, 1.29; 95% CI, 1.19-1.39), cerebral microbleeds (OR, 1.18; 95% CI, 1.03-1.34), and cerebral (micro)infarctions (OR, 1.30; 95% CI, 1.21-1.39) were associated with depression. Among the studies available, no significant associations of albuminuria and retinal vessel diameters with depression were reported. Longitudinal data showed a significant association of white matter hyperintensities with incident depression (OR, 1.19; 95% CI, 1.09-1.30).

Conclusions and Relevance

This meta-analysis shows that both the peripheral and cerebral forms of microvascular dysfunction are associated with higher odds of (incident) late-life depression. This finding may have clinical implications because microvascular dysfunction might provide a potential target for the prevention and treatment of depression.

The Link Between Adipose Tissue Renin-Angiotensin-Aldosterone System Signaling and Obesity-Associated Hypertension

Obese individuals frequently develop hypertension, which is for an important part attributable to renin-angiotensin-aldosterone system (RAAS) overactivity. This review summarizes preclinical and clinical evidence on the involvement of dysfunctional adipose tissue in RAAS activation and on the renal, central, and vascular mechanisms linking RAAS components to obesity-associated hypertension.

CD4+CD28null T Cells are related to previous cytomegalovirus infection but not to accelerated atherosclerosis in ANCA-associated vasculitis

Previous studies have suggested an increased risk for cardiovascular events in antineutrophil cytoplasmic antibodies (ANCA)-associated vasculitis (AAV). We analyzed the presence of atherosclerotic damage in patients with AAV in relation to the presence of CD4⁺CD28^null T cells and antibodies against cytomegalovirus (CMV) and human Heat-Shock Protein 60 (hHSP60). In this cross-sectional study, patients with inactive AAV were compared with healthy controls (HC). Carotid intima-media thickness (IMT) and aortic pulse-wave velocity (PWV) were measured. In addition, CD4⁺CD28^null T cells, anti-CMV, and anti-hHSP60 levels were determined. Forty patients with AAV were included. Patients’ spouses were recruited as HC (N = 38). CD4⁺CD28^null T cells are present in patients with AAV in a higher percentage (median 3.1, range 0.01–85) than in HC (0.28, 0–36, P < 0.0001). No significant difference in IMT (mm) between patients and controls was detected (mean 0.77 ± standard deviation 0.15 and 0.73 ± 0.11, respectively, P = 0.20). PWV standardized for MAP was increased in AAV patients (9.80 ± 2.50 m/s, compared to 8.72 ± 1.68 in HC, P = 0.04). There was a strong association between a previous CMV infection and the presence and percentage of CD4⁺CD28^null T cells (0.33 vs 13.8, P < 0.001). There was no relationship between CD4⁺CD28^null T cells and/or a previous CMV infection and IMT or PWV. There was no relation between anti-hHSP60 and CD4⁺CD28^null T cells. Increased PWV values suggest atherosclerotic damage in patients with AAV. Plaque size, as determined by IMT, did not differ. CD4⁺CD28^null T cells are increased in AAV and related to the previous CMV infection.

Physical Activity Is Associated With Glucose Tolerance Independent of Microvascular Function: The Maastricht Study

CONTEXT AND OBJECTIVE

Moderate-to-vigorous physical activity (MVPA) and physical fitness (PF) are positively associated with glucose tolerance. Such associations may be partly conditioned by microvascular function, which is a common correlate to MVPA, PF, and glucose tolerance. To test this hypothesis, the present study sought to investigate independent associations of MVPA and PF with glucose tolerance and to what extent these associations are mediated by microvascular function. Design, Setting, Participants, and Outcome Measures: Data from The Maastricht Study were used (n = 512 for MVPA and n = 488 for PF analyses; mean age, 59 [SD = 9] y, 52 % men). Glucose tolerance was assessed by 2-hour postload plasma glucose levels (2hPG). The total number of weekly hours of MVPA was estimated with the Community Healthy Activities Model Program for Seniors questionnaire. Walking speed during the 6-minute walk test was used to evaluate PF. Microvascular function was determined by postocclusive capillary recruitment and flowmotion with capillaroscopy and laser Doppler flowmetry in skin microcirculation.

RESULTS

In univariate analyses, MVPA, PF, and microvascular function variables were associated with 2hPG. MVPA (n = 512, β = -0.056, P = .019) and PF (n = 488, β = -0.368, P = .006) remained associated with 2hPG after adjustment for established cardio-metabolic risk factors and history of cardiovascular disease; addition of microvascular function variables as potential mediators did not materially change the associations of MVPA (β = -0.054, P = .024) and PF (β = -0.364, P = .006) with 2hPG. No mediation effects of microvascular function variables were detected.

CONCLUSIONS

MVPA and PF were independently associated with 2hPG, irrespective of established risk factors and generalized microvascular function. The possibility that specific microvascular functions, eg, insulin-mediated vasodilation, influence the association of MVPA and PF with 2hPG needs further investigation.

Capillary Rarefaction Associates with Albuminuria: The Maastricht Study

Albuminuria may be a biomarker of generalized (i.e., microvascular and macrovascular) endothelial dysfunction. According to this concept, endothelial dysfunction of the renal microcirculation causes albuminuria by increasing glomerular capillary wall permeability and intraglomerular pressure, the latter eventually leading to glomerular capillary dropout (rarefaction) and further increases in intraglomerular pressure. However, direct evidence for an association between capillary rarefaction and albuminuria is lacking. Therefore, we examined the cross-sectional association between the recruitment of capillaries after arterial occlusion (capillary density during postocclusive peak reactive hyperemia) and during venous occlusion (venous congestion), as assessed with skin capillaroscopy, and albuminuria in 741 participants of the Maastricht Study, including 211 participants with type 2 diabetes. Overall, 57 participants had albuminuria, which was defined as a urinary albumin excretion ≥30 mg/24 h. After adjustment for potential confounders, participants in the lowest tertile of skin capillary recruitment during postocclusive peak reactive hyperemia had an odds ratio for albuminuria of 2.27 (95% confidence interval, 1.07 to 4.80) compared with those in the highest tertile. Similarly, a comparison between the lowest and the highest tertiles of capillary recruitment during venous congestion yielded an odds ratio of 2.89 (95% confidence interval, 1.27 to 6.61) for participants in the lowest tertile. In conclusion, lower capillary density of the skin microcirculation independently associated with albuminuria, providing direct support for a role of capillary rarefaction in the pathogenesis of albuminuria.

Growth and endothelial function in the first 2 years of life

OBJECTIVE

To test the hypothesis that the inverse association between infant growth and endothelial function at 6 months would persist to 24 months and that accelerated growth would lead to an increased percent body fat, which would, in turn, impact negatively on endothelial function.

STUDY DESIGN

In a prospective observational study, 104 healthy term newborns underwent anthropometry and measurements of vascular vasodilation at 0, 6, 12, and 24 months. We recorded maximum vasodilation in response to acetylcholine (endothelium-dependent) and nitroprusside (endothelium-independent) by use of laser-Doppler vascular perfusion monitoring of the forearm skin vasculature. Additional anthropometry at 1 and 3 months was collected from child welfare centers. The data were analyzed by multilevel linear regression.

RESULTS

Weight gain from 0-1 month was associated inversely with maximum perfusion in response to acetylcholine at the age of 2 years (b = -8.28 perfusion units [PU] per Δ z-score, P = .03). Weight gain from 0-1 month was related positively to maximum perfusion in response to nitroprusside (b = 10.12 PU per Δ z-score, P = .04), as was birth weight (b = 8.02 PU per z-score, P = .02). Body fat percentage did not have a significant effect in any of the perfusion models and was not related to maximum perfusion at 2 years.

CONCLUSION

Infant weight gain from 0-1 month is inversely related to endothelial function in healthy term infants, at least to the age of 2 years. This relationship was not explained by an increased percentage body fat.

Microvascular dysfunction as a link between obesity, insulin resistance and hypertension

Impaired microvascular dilatation from any cause and impaired insulin-mediated capillary recruitment in particular result in suboptimal delivery of glucose and insulin to skeletal muscle, and subsequently impairment of glucose disposal (insulin resistance). In addition, microvascular dysfunction, through functional and/or structural arteriolar and capillary drop-out, and arteriolar constriction, increases peripheral resistance and thus blood pressure. Microvascular dysfunction may thus constitute a pathway that links insulin resistance and hypertension. Overweight and obesity may be an important cause of microvascular dysfunction. Mechanisms linking overweight and obesity to microvascular dysfunction include changes in the secretion of adipokines leading to increased levels of free fatty acids and inflammatory mediators, and decreased levels of adiponectin all of which may impair endothelial insulin signaling. Microvascular dysfunction may thus constitute a new treatment target in the prevention of type 2 diabetes mellitus and hypertension.

Effect of antioxidant vitamin supplementation on endothelial function in type 2 diabetes mellitus: a systematic review and meta-analysis of randomized controlled trials

Controversy exists among trials assessing whether prolonged antioxidant vitamin supplementation improves endothelial function in type 2 diabetes mellitus (T2DM) subjects. The aim of this study was to systematically review and quantify the effect of antioxidant vitamin supplementation on endothelial function in T2DM subjects. MEDLINE, Cochrane, Scopus and Web of Science were searched up to February 2013 for randomized controlled trials assessing the effect of antioxidant vitamin E and/or C supplementation on endothelial function in T2DM subjects. Ten randomized controlled trials comparing antioxidant vitamin-supplemented and control groups (overall n = 296) met the inclusion criteria. Post-intervention standardized mean difference (SMD) in endothelial function did not reach statistical significance between groups (0.35; 95% confidence interval = -0.17, 0.88; P = 0.18). In subgroup analysis, post-intervention endothelial function was significantly improved by antioxidant vitamin supplementation in T2DM subgroups with body mass index (BMI) ≤ 29.45 kg m(-2) (SMD = 1.02; P < 0.05), but not in T2DM subgroups with BMI > 29.45 kg m(-2) (SMD = -0.07; P = 0.70). In meta-regression, an inverse association was found between BMI and post-intervention SMD in endothelial function (B = -0.024, P = 0.02). Prolonged antioxidant vitamin E and/or C supplementation could be effective to improve endothelial function in non-obese T2DM subjects.

Genetic, maternal and placental factors in the association between birth weight and physical fitness: a longitudinal twin study

Background

Adult cardiorespiratory fitness and muscle strength are related to all-cause and cardiovascular mortality. Both are possibly related to birth weight, but it is unclear what the importance is of genetic, maternal and placental factors in these associations.

Design

Peak oxygen uptake and measures of strength, flexibility and balance were obtained yearly during adolescence (10–18 years) in 114 twin pairs in the Leuven Longitudinal Twin Study. Their birth weights had been collected prospectively within the East Flanders Prospective Twin Survey.

Results

We identified linear associations between birth weight and adolescent vertical jump (b = 1.96 cm per kg birth weight, P = 0.02), arm pull (b = 1.85 kg per kg birth weight P = 0.03) and flamingo balance (b = −1.82 attempts to stand one minute per kg birth weight, P = 0.03). Maximum oxygen uptake appeared to have a U-shaped association with birth weight (the smallest and largest children had the lowest uptake, P = 0.01), but this association was no longer significant after adjustment for parental BMI. Using the individual twin’s deviation from his own twin pair’s average birth weight, we found positive associations between birth weight and adolescent vertical jump (b = 3.49, P = 0.0007) and arm pull (b = 3.44, P = 0.02). Δ scores were calculated within the twin pairs as first born twin minus second born twin. Δ birth weight was associated with Δ vertical jump within MZ twin pairs only (b = 2.63, P = 0.009), which indicates importance of placental factors.

Conclusions

We found evidence for an association between adolescent physical performance (strength, balance and possibly peak oxygen uptake) and birth weight. The associations with vertical jump and arm pull were likely based on individual, more specifically placental (in the case of vertical jump) factors. Our results should be viewed as hypothesis-generating and need confirmation, but potentially support preventive strategies to optimize birth weight, for example via placental function, to target later fitness and health.

Genetic and environmental factors in associations between infant growth and adult cardiometabolic risk profile in twins

BACKGROUND

Accelerated infant growth is associated with an altered, mostly adverse adult cardiometabolic risk profile. The importance of genetic and environmental factors to these associations is unclear.

OBJECTIVE

The objective was to examine the importance of genetic and environmental factors in the associations between infant growth and adult cardiometabolic risk factors (anthropometric characteristics, lipids, insulin sensitivity, leptin, blood pressure, and fibrinogen) in twins.

DESIGN

Cardiometabolic risk factors were assessed in 240 twin pairs (aged 18-34 y) from the East Flanders Prospective Twin Survey. Infant growth was defined as change in weight z score. We regressed intrapair differences in growth during 4 growth windows (0-1, 1-6, 6-12, and 12-24 mo) against intrapair differences in the risk factors in monozygotic and dizygotic twins separately.

RESULTS

Within monozygotic twin pairs only, associations between infant growth and most adult lipids, glucose, leptin, and blood pressure (eg, systolic blood pressure: b = 5.95 mm Hg per change in z score, P = 0.01 in monozygotic twins; b = -1.64, P = 0.82 in dizygotic twins from 12 to 24 mo) were found. Within dizygotic twin pairs only, associations between growth and triglycerides and fibrinogen (eg, fibrinogen: b = 0.07 ln mg/dL per change in z score, P = 0.31 in monozygotic twins; b = 0.79, P = 0.01 in dizygotic twins from 0 to 1 mo) were identified. Most associations showed a detrimental effect of accelerated growth, but beneficial associations were also identified (eg, total-to-high-density-lipoprotein cholesterol ratio: b = -0.22 per change in z score from 1 to 6 mo, P = 0.008 in monozygotic twins).

CONCLUSION

Our data showed that environmental factors play a role in the associations between infant growth and most adult lipids, glucose, leptin, and blood pressure, whereas genetic factors are involved regarding triglycerides and fibrinogen.

Semi-automatic assessment of skin capillary density: proof of principle and validation

BACKGROUND

Skin capillary density and recruitment have been proven to be relevant measures of microvascular function. Unfortunately, the assessment of skin capillary density from movie files is very time-consuming, since this is done manually. This impedes the use of this technique in large-scale studies. We aimed to develop a (semi-) automated assessment of skin capillary density.

METHODS

CapiAna (Capillary Analysis) is a newly developed semi-automatic image analysis application. The technique involves four steps: 1) movement correction, 2) selection of the frame range and positioning of the region of interest (ROI), 3) automatic detection of capillaries, and 4) manual correction of detected capillaries. To gain insight into the performance of the technique, skin capillary density was measured in twenty participants (ten women; mean age 56.2 [42-72] years). To investigate the agreement between CapiAna and the classic manual counting procedure, we used weighted Deming regression and Bland-Altman analyses. In addition, intra- and inter-observer coefficients of variation (CVs), and differences in analysis time were assessed.

RESULTS

We found a good agreement between CapiAna and the classic manual method, with a Pearson's correlation coefficient (r) of 0.95 (P<0.001) and a Deming regression coefficient of 1.01 (95%CI: 0.91; 1.10). In addition, we found no significant differences between the two methods, with an intercept of the Deming regression of 1.75 (-6.04; 9.54), while the Bland-Altman analysis showed a mean difference (bias) of 2.0 (-13.5; 18.4) capillaries/mm(2). The intra- and inter-observer CVs of CapiAna were 2.5% and 5.6% respectively, while for the classic manual counting procedure these were 3.2% and 7.2%, respectively. Finally, the analysis time for CapiAna ranged between 25 and 35min versus 80 and 95min for the manual counting procedure.

CONCLUSION

We have developed a semi-automatic image analysis application (CapiAna) for the assessment of skin capillary density, which agrees well with the classic manual counting procedure, is time-saving, and has a better reproducibility as compared to the classic manual counting procedure. As a result, the use of skin capillaroscopy is feasible in large-scale studies, which importantly extends the possibilities to perform microcirculation research in humans.

Angiotensin-(1-7)-induced renal vasodilation in hypertensive humans is attenuated by low sodium intake and angiotensin II co-infusion

Current evidence suggests that angiotensin-(1-7) plays an important role in the regulation of tissue blood flow. This evidence, however, is restricted to studies in animals and human forearm. Therefore, we studied the effects of intrarenal angiotensin-(1-7) infusion on renal blood flow in hypertensive humans. To assess the influence of renin-angiotensin system activity, sodium intake was varied and co-infusion with angiotensin II was performed in a subgroup. In 57 hypertensive patients who were scheduled for renal angiography, renal blood flow was measured ((133)Xenon washout method) before and during intrarenal infusion of angiotensin-(1-7) (3 incremental doses: 0.27, 0.9, and 2.7 ng/kg per minute). Patients were randomized into low or high sodium intake. These 2 groups of patients received angiotensin-(1-7), with or without intrarenal co-infusion of angiotensin II (0.3 ng/kg per minute). Angiotensin-(1-7) infusion resulted in intrarenal vasodilation in patients adhering to a sodium-rich diet. This vasodilatory effect of angiotensin-(1-7) was clearly attenuated by low sodium intake, angiotensin II co-infusion, or both. Regression analyses showed that the prevailing renin concentration was the only independent predictor of angiotensin-(1-7)-induced renal vasodilation. In conclusion, angiotensin-(1-7) induces renal vasodilation in hypertensive humans, but the effect of angiotensin-(1-7) is clearly attenuated by low sodium intake and co-infusion of angiotensin II. This supports the hypothesis that angiotensin-(1-7) induced renal vasodilation depends on the degree of renin-angiotensin-system activation.