Influence of serum ferritin combined with blood cadmium concentrations on blood pressure and hypertension: From the Korean National Health and Nutrition Examination Survey

Cadmium exposure and risk of hypertension: A systematic review and dose-response meta-analysis

BACKGROUND

Exposure to environmental toxic metals represents a significant global public health concern. Many studies have reported that cadmium (Cd) exposure increases the risk of hypertension. Since the shape of such relation has not been well characterized, we assessed it by performing a systematic review and dose-response meta-analysis of human studies.

METHODS

We searched the literature through September 5, 2024 to identify papers related to Cd, hypertension, and blood pressure. Inclusion criteria were: observational design, adult population, assessment of exposure using Cd biomarkers, and availability of exposure category-specific risk estimates for hypertension. We performed a dose-response meta-analysis of the results from included studies.

RESULTS

Of the 18 studies published between 2006 and 2024, most had a cross-sectional design. Cd was measured in whole blood and/or urine in almost all studies, whereas only two studies measured Cd in serum. The dose-response meta-analysis indicated an almost linear relation between urinary Cd concentrations and hypertension risk with RR = 1.18, 95% CI 1.02-1.37 at 2.0 μg/g creatinine compared with no exposure. In contrast, the association between blood Cd concentrations and hypertension risk was non-linear: there was a steep monotonic increase in risk for Cd concentrations below 2 μg/L, reaching a RR of 1.48 (95% CI 1.17-1.86) at 2.0 μg/L, after which a plateau seemed reached. We found similar trends when restricting to studies of Asian population, while when considering North American studies, hypertension risk increased above 1.0 μg/g creatinine.

CONCLUSIONS

In this dose-response meta-analysis, risk of hypertension showed a non-linear positive association with blood Cd concentrations and a linear positive association with urinary Cd concentrations. Inconsistency in the shape of associations could relate to the different timing of exposure assessed by the biomarkers or the alteration Cd excretion at increasing exposure levels. Mitigation of Cd exposure is confirmed as a public health priority for chronic disease prevention.

Factors moderating cadmium bioavailability: Key considerations for comparing blood cadmium levels between groups

Cadmium (Cd) is recognized as a significant hazard to human health, with exposure linked to a variety of adverse outcomes including various cancers, cardiovascular diseases, chronic kidney disease, and osteoporosis. Residing in areas contaminated with Cd is undoubtedly a risk factor for developing the aforementioned conditions. However, the risk of developing Cd-related disorders is not uniform among individuals. Deficiencies in iron, zinc, and calcium, along with iron deficiency anemia, decreased lung function often seen in chronic obstructive pulmonary disease (COPD), and low circulating levels of parathyroid hormone (PTH), may enhance Cd intestinal absorption. Conversely, chronic liver disorders can lead to the progressive loss of hepatocytes and the release of free Cd into the circulation, resulting in elevated Cd blood levels. Moreover, studies comparing Cd blood levels between different regions within a country or between two groups of individuals, for example, those with and without osteoporosis, should consider all variables that may impact Cd levels. These include age, sex, alcohol consumption, blood levels of iron, calcium, and zinc, the presence of anemia, COPD, PTH levels, and the presence of liver or kidney disease. In this review, we delve into all factors that could influence Cd blood levels, providing a comprehensive analysis.

Environmental Cadmium Exposure Induces an Increase in Systolic Blood Pressure by Its Effect on GFR

Chronic exposure to the nephrotoxic metal pollutant, cadmium (Cd), has been associated with hypertension, but the mechanism by which it raises blood pressure is not understood. We hypothesize that exposure to Cd reduces the glomerular filtration rate (GFR), which in turn causes a rise in blood pressure. Data were collected from 447 Thai subjects with a mean age of 51.1 years, of which 48.8% had hypertension, 15.4% had diabetes, and 6.9% had an estimated GFR (eGFR) below 60 mL/min/1.73 m2 (low eGFR). More than half (58.8%) and 23.9% had moderate and severe tubular proteinuria, respectively. The mean blood and urinary Cd concentrations were 2.75 and 4.23 µg/L, respectively. Doubling of body burden of Cd increased the prevalence odds ratios (POR) for low eGFR and severe tubular proteinuria 41% and 48%, respectively. The POR for hypertension rose twofold in those with blood Cd levels of 0.61–1.69 µg/L or urinary Cd excretion levels ≥ 0.98 µg/g creatinine. In the hypertensive group, the eGFR was inversely associated with age (β = −0.517), the Cd excretion rate (β = −0.177), and diabetes (β = −0.175). By mediation analysis, an increase in SBP was attributable totally to the effect of Cd on GFR. Thus, blood pressure appeared to rise as GFR fell. This finding is consistent with the well-known role of the kidney in long-term blood pressure regulation, and explains a universally high prevalence of hypertension among patients with low eGFR.

Urinary cadmium was linearly and positively associated with cardiac infarction/injury score and subclinical myocardial injury in the general population without cardiovascular diseases and chronic kidney disease

PURPOSE

The study was to investigate the association between urinary cadmium with cardiac infarction/injury score (CIIS) and subclinical myocardial injury (SC-MI) in the general population without cardiovascular diseases (CVDs) and chronic kidney disease (CKD).

METHODS

In this large-scale cross-sectional study, we enrolled 4492 individuals without CVDs and CKD from the third National Health and Nutrition Examination Survey. Logistic regression models, linear regression models, subgroup analyses, and restricted cubic spline (RCS) were performed to assess the association between urinary cadmium with CIIS and SC-MI.

RESULTS

Participants with SC-MI had higher levels of urinary cadmium compared with those without SC-MI (P < 0.001). In multivariate regression analyses adjusting for all confounding variables, higher levels of urinary cadmium were strongly associated not only with higher risk of SC-MI but also with higher CIIS (P < 0.05). Further subgroup analyses showed that the association between urinary cadmium and SC-MI remained significant in the subgroups of ≥ 50 years, men, smokers, and those without diabetes or hypertension (P < 0.05). Additionally, RCS analysis showed that after adjusting for all confounding factors, urinary cadmium was linearly and positively associated with CIIS and SC-MI (P overall < 0.05, P for nonlinearity > 0.05).

CONCLUSION

Urinary cadmium was linearly and positively associated with CIIS and SC-MI in the general population without CVDs and CKD.

Prenatal cadmium exposure impairs neural tube closure via inducing excessive apoptosis in neuroepithelium

Birth defects have become a public health concern. The hazardous environmental factors exposure to embryos could increase the risk of birth defects. Cadmium, a toxic environmental factor, can cross the placental barrier during pregnancy. Pregnant woman may be subjected to cadmium before taking precautionary protective actions. However, the link between birth defects and cadmium remains obscure. Cadmium exposure can induce excessive apoptosis in neuroepithelium during embryonic development progresses. Cadmium exposure activated the p53 via enhancing the adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) and reactive oxygen species' (ROS) level. And cadmium decreases the level of Paired box 3 (Pax3) and murine double minute 2 (Mdm2), disrupting the process of p53 ubiquitylation. And p53 accumulation induced excessive apoptosis in neuroepithelium during embryonic development progresses. Excessive apoptosis led to the failure of neural tube closure. The study emphasizes that environmental materials may increase the health risk for embryos. Cadmium caused the failure of neural tube closure during early embryotic day. Pregnant women may be exposed by cadmium before taking precautionary protective actions, because of cadmium concentration-containing foods and environmental tobacco smoking. This suggests that prenatal cadmium exposure is a threatening risk factor for birth defects.

Blood Cadmium and Abdominal Aortic Calcification in Population with Different Weight Statuses: a Population-Based Study

The aim of our study was to assess the effect of blood cadmium levels (B-Cd) on abdominal aortic calcification (AAC). We used the data from the 2013-2014 NHANES database. A total of 1530 participants were included in our study, with a mean AAC score of 1.40 ± 0.10, and a prevalence of severe AAC of 7.98%. Participants with higher B-Cd quartiles showed a higher prevalence of severe AAC. B-Cd was positively associated with higher AAC scores and increased risk of severe AAC. In the obese population, blood cadmium levels showed a positive association with the risk of severe AAC. There may be a positive correlation between B-Cd levels and AAC scores and risk of severe AAC, and this correlation is more pronounced in the obese population. Therefore, the cadmium load in AAC patients in the obese population should be considered in clinical work.

Estimation of the Cadmium Nephrotoxicity Threshold from Loss of Glomerular Filtration Rate and Albuminuria

Cadmium (Cd) is a pervasive, toxic environmental pollutant that preferentially accumulates in the tubular epithelium of the kidney. Current evidence suggests that the cumulative burden of Cd here leads to the progressive loss of the glomerular filtration rate (GFR). In this study, we have quantified changes in estimated GFR (eGFR) and albumin excretion (Ealb) according to the levels of blood Cd ([Cd]b) and excretion of Cd (ECd) after adjustment for confounders. ECd and Ealb were normalized to creatinine clearance (Ccr) as ECd/Ccr and Ealb/Ccr. Among 482 residents of Cd-polluted and non-polluted regions of Thailand, 8.1% had low eGFR and 16.9% had albuminuria (Ealb/Ccr) × 100 ≥ 20 mg/L filtrate. In the low Cd burden group, (ECd/Ccr) × 100 < 1.44 µg/L filtrate, eGFR did not correlate with ECd/Ccr (β = 0.007) while an inverse association with ECd/Ccr was found in the medium (β = -0.230) and high burden groups (β = -0.349). Prevalence odds ratios (POR) for low eGFR were increased in the medium (POR 8.26) and high Cd burden groups (POR 3.64). Also, eGFR explained a significant proportion of Ealb/Ccr variation among those with middle (η2 0.093) and high [Cd]b tertiles (η2 0.132) but did not with low tertiles (η2 0.001). With an adjustment of eGFR, age and BMI, the POR values for albuminuria were increased in the middle (POR 2.36) and high [Cd]b tertiles (POR 2.74) and those with diabetes (POR 6.02) and hypertension (2.05). These data indicate that (ECd/Ccr) × 100 of 1.44 µg/L filtrate (0.01-0.02 µg/g creatinine) may serve as a Cd threshold level based on which protective exposure guidelines should be formulated.

Evidence Linking Cadmium Exposure and β2-Microglobulin to Increased Risk of Hypertension in Diabetes Type 2

The most common causes of chronic kidney disease, diabetes, and hypertension are significant public health issues worldwide. Exposure to the heavy metal pollutant, cadmium (Cd), which is particularly damaging to the kidney, has been associated with both risk factors. Increased levels of urinary β₂-microglobulin (β₂M) have been used to signify Cd-induced kidney damage and circulating levels have been linked to blood pressure control. In this study we investigated the pressor effects of Cd and β₂M in 88 diabetics and 88 non-diabetic controls, matched by age, gender and locality. The overall mean serum β₂M was 5.98 mg/L, while mean blood Cd and Cd excretion normalized to creatinine clearance (C_cr) as E_Cd/C_cr were 0.59 µg/L and 0.0084 µg/L of filtrate (0.95 µg/g creatinine), respectively. The prevalence odds ratio for hypertension rose by 79% per every ten-fold increase in blood Cd concentration. In all subjects, systolic blood pressure (SBP) showed positive associations with age (β = 0.247), serum β₂M (β = 0.230), and E_Cd/C_cr (β = 0.167). In subgroup analysis, SBP showed a strong positive association with E_Cd/C_cr (β = 0.303) only in the diabetic group. The covariate-adjusted mean SBP in the diabetics of the highest E_Cd/C_cr tertile was 13.8 mmHg higher, compared to the lowest tertile (p = 0.027). An increase in SBP associated with Cd exposure was insignificant in non-diabetics. Thus, for the first time, we have demonstrated an independent effect of Cd and β₂M on blood pressure, thereby implicating both Cd exposure and β₂M in the development of hypertension, especially in diabetics.

The association between serum ferritin and blood pressure in adult women: a large cross-sectional study

BACKGROUND

Studies on the relationships between ferritin and blood pressure remain limited, especially in adult women. The aim of the present study was to investigate the associations between serum ferritin and blood pressure among adult women.

METHODS

Using the National Health and Nutrition Examination Survey, a cross-sectional study, including 5521 adult women, was performed. Weighted multivariate regressions, subgroup analyses, threshold effect analyses, and sensitivity analysis were used.

RESULTS

The authors found that serum ferritin was independently and positively correlated to diastolic blood pressure (DBP), and this positive correlation kept present among women who are 26-30 years old, non-pregnant women, Mexican American women, and women of other races in the subgroup analyses. Additionally, no significant association was found between serum ferritin and systolic blood pressure (SBP), except in women aged 26-30, Mexican American women, and women of other races. In pregnant women, the association between serum ferritin and SBP was an inverted U-shaped curve with an inflection point at 39.5 ng/mL.

CONCLUSIONS

The authors demonstrated that serum ferritin was positively correlated to DBP in adult women, which may provide a novel reference for clinical management.