Cadmium exposure, intercellular adhesion molecule-1 and peripheral artery disease: a cohort and an experimental study

OBJECTIVES

Cadmium exposure has been found to be associated with atherosclerotic plaques in the carotid arteries and with circulating levels of the proatherogenic intercellular adhesion molecule-1 (ICAM-1). The research questions were (1) if blood and urinary cadmium levels are associated with low ankle-brachial index (ABI) as a measure of peripheral artery disease in a longitudinal study and (2) if ICAM-1 mediates proatherogenic effects of cadmium exposure.

DESIGN

A prospective, observational cohort study with a 5-year follow-up and an experimental study of cultured human aortic endothelial cells exposed to cadmium.

SETTING

Research unit at a university hospital.

PARTICIPANTS

A cohort of 64-year-old women (n=489) recruited by stratified sampling of similarly sized groups with normal, impaired and diabetic glucose tolerance as assessed in a population-based screening examination.

PRIMARY AND SECONDARY OUTCOME MEASURES

ABI (ratio of the systolic blood pressures in the tibial and brachial arteries ≤0.9 in any artery) in relation to cadmium exposure; ICAM-1 concentrations in the cell culture medium after cadmium incubation.

RESULTS

High (tertile 3 vs 1) concentrations of blood (B-Cd) or creatine-adjusted urinary cadmium (U-Cd) at baseline were found to predict low ABI after adjustment for smoking and other cardiovascular risk factors at baseline. For U-Cd the OR was 2.5 (95% CI 1.1 to 5.8). After exclusion of participants with ultrasound-assessed femoral atherosclerosis at baseline the OR for U-Cd was unchanged, and for B-Cd it was 3.7 (95% CI 1.05 to 13.3). Inclusion of serum ICAM-1 levels did not affect the cadmium-related ORs in multivariate analyses. The experimental study did not show any cadmium-induced increase of the production of ICAM-1 from human endothelial cells.

CONCLUSIONS

Cadmium exposure was associated with future peripheral artery disease, supporting the concept that cadmium exposure in the population has proatherogenic effects, although ICAM-1 mediated effects do not seem to be involved.

The relationship between sex hormones, sex hormone binding globulin and peripheral artery disease in older persons

OBJECTIVE

The prevalence of peripheral artery disease (PAD) increases with aging and is higher in persons with metabolic syndrome and diabetes. PAD is associated with adverse outcomes, including frailty and disability. The protective effect of testosterone and sex hormone binding globulin (SHBG) for diabetes in men suggests that the biological activity of sex hormones may affect PAD, especially in older populations.

METHODS

Nine hundred and twenty-one elderly subjects with data on SHBG, testosterone (T), estradiol (E2) were selected from InCHIANTI study. PAD was defined as an Ankle-Brachial Index (ABI) < 0.90. Logistic regression models adjusted for age (Model 1), age, BMI, insulin, interleukin-6, physical activity, smoking, chronic diseases including metabolic syndrome (Model 2), and a final model including also sex hormones (Model 3) were performed to test the relationship between SHBG, sex hormones and PAD.

RESULTS

The mean age (±SD) of the 419 men and 502 women was 75.0 ± 6.8 years. Sixty two participants (41 men, 21 women) had ABI < 0.90. Men with PAD had SHBG levels lower than men without PAD (p = 0.03). SHBG was negatively and independently associated with PAD in men (p = 0.028) but not in women. The relationship was however attenuated after adjusting for sex hormones (p = 0.07). The E2 was not significantly associated with PAD in both men and women. In women, but not in men, T was positively associated with PAD, even after adjusting for multiple confounders, including E2 (p = 0.01).

CONCLUSIONS

Low SHBG and high T levels are significantly and independently associated with the presence of PAD in older men and women, respectively.

Automated photoplethysmography-based determination of ankle-brachial index: a validation study against Doppler sonography

INTRODUCTION

Determination of ankle-brachial-index (ABI) by manual Doppler is well established to screen for lower extremity arterial disease (LEAD) and to predict cardiovascular risk. A new generation of digital-controlled devices promises automated ABI determination. The aim of this study was to determine comparability of automated photoplethysmography (PPG)-derived ABI calculation with the Doppler-ABI algorithm commonly used in cohort studies.

METHODS

Automated PPG-based ABI measurements [Vascular Explorer (VE) and Vicorder (VI)] were recorded from 112 limbs of healthy subjects and 22 limbs of patients with confirmed LEAD. Validity was evaluated on the basis of receiver-operating characteristic (ROC) analysis of clinical status and concordance with Doppler-ABI. Differences between cuff inflation [inf]- and deflation [def]-based method were studied in VE.

RESULTS

PPG-based ABI values were higher compared to Doppler-ABI (VI +0.06, VEinf +0.15, VEdef +0.09, p < 0.001, respectively). The difference was pronounced in pathological (<0.9), borderline (0.9-0.99) and low normal (1.0-1.09) ABI, but less in ABI ≥1.1. However, ROC analysis revealed excellent diagnostic value for LEAD (sensitivity/specificity) and comparable area under the curve at method-adapted ABI thresholds for all methods: Doppler (95/90 %, 0.95), VI (75/96 %, 0.91), VEinf (85/89 %, 0.93) and VEdef (80/98 %, 0.94).

CONCLUSIONS

Digital-controlled PPG-based ABI determination is a useful diagnostic application for LEAD. However, the systematic higher ABI in PPG-based measurement compared to Doppler and remarkable differences between the deflationary and inflationary method are critical for the interpretation of borderline and low normal ABI values where precise reading is essential to detect mild LEAD and subclinical disease and to predict cardiovascular risk.