The systolic–diastolic difference in carotid stiffness is increased in type 2 diabetes: The Maastricht Study

The Putative Role of Methylglyoxal in Arterial Stiffening: A Review

BACKGROUND

Arterial stiffening is a hallmark of vascular ageing and a consequence of many diseases including diabetes mellitus. Methylglyoxal (MGO), a highly reactive α-dicarbonyl mainly formed during glycolysis, has emerged as a potential contributor to the development of arterial stiffness. MGO reacts with arginine and lysine residues in proteins to form stable advanced glycation endproducts (AGEs). AGEs may contribute to arterial stiffening by increased cross-linking of collagen within the extracellular matrix (ECM), by altering the vascular structure, and by triggering inflammatory and oxidative pathways. Although arterial stiffness is mainly determined by ECM and vascular smooth muscle cell function, the effects of MGO and MGO-derived AGEs on these structures have not been thoroughly reviewed to date.

METHODS AND RESULTS

We conducted a PubMed search without filtering for publication date which resulted in 16 experimental and 22 clinical studies eligible for inclusion. Remarkably, none of the experimental and only three of the clinical studies specifically mentioned MGO-derived AGEs. Almost all studies reported an association between arterial stiffness and AGE accumulation in the arterial wall or increased plasma AGEs. Other studies report reduced arterial stiffness in experimental models upon administration of AGE-breakers.

CONCLUSIONS

No papers published to date directly show an association between MGO or MGO-derived AGEs and arterial stiffening. The relevance of the various underlying mechanisms is not yet clear, which is particularly due to methodological challenges in the detection of MGO and MGO-derived AGEs at the molecular, intra- and pericellular, and structural levels, as well as in challenges in the assessment of intrinsic arterial wall properties at ECM- and tissue levels.

Measures of Left Ventricular Diastolic Function and Cardiorespiratory Fitness According to Glucose Metabolism Status: The Maastricht Study

Background

This cross‐sectional study evaluated associations between structural and functional measures of left ventricular diastolic function and cardiorespiratory fitness (CRF) in a well‐characterized population‐based cohort stratified according to glucose metabolism status.

Methods and Results

Six hundred seventy‐two participants from The Maastricht Study (mean±SD age, 61±9 years; 17.4% prediabetes and 25.4% type 2 diabetes mellitus) underwent both echocardiography to determine left atrial volume index, left ventricular mass index, maximum tricuspid flow regurgitation, average e′ and E/e′ ratio; and submaximal cycle ergometer test to determine CRF as maximum power output per kilogram body mass. Associations were examined with linear regression adjusted for cardiovascular risk and lifestyle factors, and interaction terms. After adjustment, in normal glucose metabolism but not (pre)diabetes, higher left atrial volume index (per 1 mL/m²), left ventricular mass index (per 1 g/m^2.7), maximum tricuspid regurgitation flow (per 1 m/s) were associated with higher CRF (maximum power output per kilogram body mass; β in normal glucose metabolism 0.015 [0.008–0.023], P_interaction (pre)diabetes <0.10; 0.007 [−0.001 to 0.015], P_interaction type 2 diabetes mellitus <0.10; 0.129 [0.011–0.246], P_interaction >0.10; for left atrial volume index, left ventricular mass index, maximum tricuspid regurgitation flow, respectively). Furthermore, after adjustment, in all individuals, higher average E/e′ ratio (per unit), but not average e′, was associated with lower CRF (normal glucose metabolism −0.044 [−0.071 to −0.016]), P_interaction >0.10).

Conclusions

In this population‐based study, structural and functional measures of left ventricular diastolic function were independently differentially associated with CRF over the strata of glucose metabolism status. This suggests that deteriorating left ventricular diastolic function, although of small effect, may contribute to the pathophysiological process of impaired CRF in the general population. Moreover, the differential effects in these structural measures may be the consequence of cardiac structural adaptation to effectively increase CRF in normal glucose metabolism, which is absent in (pre)diabetes.

Type 2 Diabetes Mellitus Is Independently Associated With Decreased Neural Baroreflex Sensitivity: The Paris Prospective Study III

OBJECTIVE

Impaired baroreflex function is an early indicator of cardiovascular autonomic imbalance. Patients with type 2 diabetes mellitus (T2D) have decreased baroreflex sensitivity (BRS), however, whether the neural BRS (nBRS) and mechanical component of the BRS is altered in those with high metabolic risk (HMR, impaired fasting glucose and metabolic syndrome) or with overt T2D, is unknown. We examined this in a community-based observational study, the Paris Prospective Study III (PPS3). Approach and Results: In 7626 adults aged 50 to 75 years, resting nBRS (estimated by low-frequency gain, from carotid distension rate and RR [time elapsed between two successive R waves] intervals) and mechanical BRS were measured by high-precision carotid echotracking. The associations between overt T2D or HMR as compared with subjects with normal glucose metabolism and nBRS or mechanical BRS were quantified using multivariable linear regression analysis. There were 319 subjects with T2D (61±6 years, 77% male), 1450 subjects with HMR (60±6 years, 72% male), and 5857 subjects with normal glucose metabolism (59±6 years, 57% male). Compared with normal glucose metabolism, nBRS was significantly lower in HMR subjects (β=-0.07 [95% CI, -0.12 to -0.01]; P=0.029) and in subjects with T2D (β=-0.18 [95% CI, -0.29 to -0.07]; P=0.002) after adjustment for confounding and mediating factors. Subgroup analysis suggests significant and independent alteration in mechanical BRS only among HMR patients who had both impaired fasting glucose and metabolic syndrome.

CONCLUSIONS

In this community-based study of individuals aged 50 to 75, a graded decrease in nBRS was observed in HMR subjects and patients with overt T2D as compared with normal glucose metabolism subjects.

Constitutive interpretation of arterial stiffness in clinical studies: a methodological review

Clinical assessment of arterial stiffness relies on noninvasive measurements of regional pulse wave velocity or local distensibility. However, arterial stiffness measures do not discriminate underlying changes in arterial wall constituent properties (e.g., in collagen, elastin, or smooth muscle), which is highly relevant for development and monitoring of treatment. In arterial stiffness in recent clinical-epidemiological studies, we systematically review clinical-epidemiological studies (2012–) that interpreted arterial stiffness changes in terms of changes in arterial wall constituent properties (63 studies included of 514 studies found). Most studies that did so were association studies (52 of 63 studies) providing limited causal evidence. Intervention studies (11 of 63 studies) addressed changes in arterial stiffness through the modulation of extracellular matrix integrity (5 of 11 studies) or smooth muscle tone (6 of 11 studies). A handful of studies (3 of 63 studies) used mathematical modeling to discriminate between extracellular matrix components. Overall, there exists a notable gap in the mechanistic interpretation of stiffness findings. In constitutive model-based interpretation, we first introduce constitutive-based modeling and use it to illustrate the relationship between constituent properties and stiffness measurements (“forward” approach). We then review all literature on modeling approaches for the constitutive interpretation of clinical arterial stiffness data (“inverse” approach), which are aimed at estimation of constitutive properties from arterial stiffness measurements to benefit treatment development and monitoring. Importantly, any modeling approach requires a tradeoff between model complexity and measurable data. Therefore, the feasibility of changing in vivo the biaxial mechanics and/or vascular smooth muscle tone should be explored. The effectiveness of modeling approaches should be confirmed using uncertainty quantification and sensitivity analysis. Taken together, constitutive modeling can significantly improve clinical interpretation of arterial stiffness findings.