Excessive zinc intake increases systemic blood pressure and reduces renal blood flow via kidney angiotensin II in rats

Plasma metals, genetic risk, and rapid kidney function decline among type 2 diabetes

BACKGROUND

Rapid kidney function decline (RKFD) is a main clinical feature of early chronic kidney disease (CKD) in type 2 diabetes (T2D). Environmental and genetic factors influencing RKFD remain inadequately elucidated.

OBJECTIVES

This study aimed to examine the associations of metals with RKFD among T2D and to further investigate the effect of metal mixtures on RKFD with the modifying effect of genetic susceptibility.

METHODS

This study included 2209 people with T2D (1942 had genotyping data) free of CKD at baseline from the Dongfeng-Tongji cohort. We used inductively coupled plasma-mass spectrometry (ICP-MS) to measure 23 metals in baseline plasma. Using elastic net (ENET), multivariate logistic regression, and Bayesian kernel machine regression (BKMR) model, we examined independent associations of multiple metals with RKFD. We calculated the environmental risk score (ERS) to assess the effects of metal mixtures on RKFD and the genetic risk score (GRS) to assess genetic susceptibility. RKFD was defined as estimated glomerular filtration rate (eGFR) loss > 3 mL/min/1.73 m2/year.

RESULTS

During a median of 9.8 years follow-up, 262 participants developed RKFD. Aluminum, vanadium, zinc, selenium, rubidium, tin, barium, and tungsten were screened from ENET. In multivariate logistic models, vanadium, selenium, and tungsten were negatively associated with RKFD, while zinc, tin, and rubidium were positively associated. The BKMR showed a nonlinear association of vanadium and rubidium with RKFD and interactions between metals (barium‑vanadium, barium‑rubidium). The ERS was positive associated with RKFD (per SD increase in ERS, OR = 1.94, 95% CI: 1.66, 2.27). No significant interaction between ERS and GRS was observed on RKFD, however, participants in the highest ERS and GRS group had the highest RKFD risk.

CONCLUSION

Vanadium and rubidium were associated with RKFD in T2D. Metal mixtures was associated with an increased risk of RKFD in T2D, particularly in those at high genetic risk.

Effects of zinc in podocytes and cortical collecting duct in vitro and Dahl Salt-Sensitive rats in vivo

Zinc is one of the essential divalent cations in the human body and a fundamental microelement involved in the regulation of many cellular and subcellular functions. Experimental studies reported that zinc deficiency is associated with renal damage and could increase blood pressure. It was proposed that zinc dietary supplementation plays a renoprotective role. Our study aimed to investigate the effects of zinc on intracellular signaling in renal cells and explore the correlation between dietary zinc and the progression of salt-induced hypertension. The impact of extracellular zinc concentrations on two different kidney epithelial cell types - podocytes and principal cells of the cortical collecting duct (CCD), was tested. In podocytes, a rise in extracellular zinc promotes TRPC6 channel-mediated calcium entry but not altered intracellular zinc levels. However, we observe the opposite effect in CCD cells with no alteration in calcium levels and steady-state elevation in intracellular zinc. Moreover, prolonged extracellular zinc exposure leads to cytotoxic insults in CCD cells but not in podocytes, characterized by increased cell death and disrupted cytoskeletal organization. Next, we tested if dietary zinc plays a role in the development of hypertension in Dahl salt-sensitive rats. Neither zinc-rich nor deficient diets impact the regular development of salt-sensitive hypertension. These results suggest specialized roles for zinc in renal function, implicating its involvement in proliferation and apoptosis in CCD cells and calcium signaling and cytoskeletal dynamics modulation in podocytes. Further research is required to elucidate the detailed mechanisms of zinc action and its implications in renal health and disease.

Contribution of serum elements to blood pressure during pregnancy by impacting gut microbiota: A prospective cohort study

Exposure to environmental elements can alter gut microbiota, further affecting host health. Exploring the interrelationships among element exposure, gut microbiota and blood pressure (BP) during pregnancy, as well as the mediating roles of gut microbiota, is warranted, which holds implications for maternal and offspring health. In a prospective cohort study between 2017-2018, 733 pregnant women were included. The serum elements and gut microbiota during the second trimester were assessed, and BP was collected during the second and third trimester and before delivery. Fourteen associations were identified between serum elements and BP, including positive associations of zinc (Zn) and thallium (Tl) with systolic BP during the second trimester. Rubidium (Rb) showed a positive association with Pielou's evenness. Serum elements, such as Tl and Rb, were significantly associated with the relative abundance of bacteria and co-abundance groups (CAGs). Alpha diversity was negatively associated with BP levels and trajectories. Moreover, 15 associations between gut microbiota and BP were shown. Finally, mediation analysis confirmed that CAG2 and Pielou's evenness mediated the associations of Tl and Rb with BP, respectively. We concluded that serum elements can contribute to BP changes during pregnancy through gut microbiota, suggesting gut microbiota-targeted approach as a potential intervention.

The association between urinary metals/metalloids and chronic kidney disease among general adults in Wuhan, China

The relation between exposure to single metal/metalloid and the risk of chronic kidney disease (CKD) remains unclear. We aimed to determine the single and mixed associations of 21 heavy metals/metalloids exposure and the risk of CKD. We performed a cross-sectional study that recruited 4055 participants. Multivariate logistic regression, linear regression and weighted quantile sum (WQS) regression were conducted to explore the possible effects of single and mixed metals/metalloids exposure on the risk of CKD, the risk of albuminuria and changes in the estimated glomerular filtration rate (eGFR). In single-metal models, Cu, Fe, and Zn were positively associated with increased risks of CKD (P-trend < 0.05). Compared to the lowest level, the highest quartiles of Cu (OR = 2.94; 95% CI: 1.70, 5.11; P-trend < 0.05), Fe (OR = 2.39; 95% CI: 1.42, 4.02; P-trend < 0.05), and Zn (OR = 2.35; 95% CI: 1.31, 4.24; P-trend < 0.05) were associated with an increased risk of CKD. After multi-metal adjustment, the association with the risk of CKD remained robust for Cu (P < 0.05). Weighted quantile sum regression revealed a positive association between mixed metals/metalloids and the risk of CKD, and the association was largely driven by Cu (43.7%). Specifically, the mixture of urinary metals/metalloids was positively associated with the risk of albuminuria and negatively associated with eGFR.

Association between urinary metal concentrations and abnormal estimated glomerular filtration rate in Chinese community-dwelling elderly: Exploring the mediating effect of triglycerides

BACKGROUND

Environmental metal exposure is associated with elevated triglycerides (TG) and the development of chronic kidney disease (CKD). However, the relationship between metal exposure and glomerular filtration rate (GFR) remains uncertain, and the mediating effect of TG between the two is unclear.

METHODS

This study measured the concentrations of 14 metals in urine samples from 3752 elderly people in the community. The most relevant metals were screened by least absolute shrinkage and selection operator (LASSO) regression. The relationship between combined exposure to multiple metals and abnormal estimated glomerular filtration rate (eGFR) was explored using multivariate logistic regression analysis and Bayesian kernel machine regression (BKMR) analysis. Generalized linear regression models and the Karlson-Holm-Green (KHB) method were used to assess the mediating effects of TG.

RESULTS

In the single-metal model, calcium (Ca), iron (Fe), selenium (Se), strontium (Sr), and thallium (Tl) showed significant negative correlations with the prevalence of abnormal eGFR (all P < 0.05). In the multi-metals model, Ca, Se, and Tl continued to show significant negative correlations, while vanadium (V) and zinc (Zn) showed significant positive correlations with abnormal eGFR (all P < 0.05). The BKMR model showed a negative joint effect of the mixture of Ca, V, Zn, Se, and Tl on the prevalence of abnormal eGFR. The generalized linear regression model showed a significant positive correlation between the concentrations of Ca (β = 0.07), Zn (β = 0.07), Se (β = 0.09), and TG levels (all P < 0.05). In the mediation analysis, TG masked a 4.30% and 5.21% correlation between Ca and Se and the prevalence of eGFR abnormalities, respectively.

CONCLUSIONS

Urinary concentration of multiple metals is significantly associated with eGFR abnormalities, and Ca, and Se may be among the potential protective factors. TG masked some of the protective effects of Ca and Se.

Associations of multiple plasma metals with chronic kidney disease in patients with diabetes

As common contaminants, metals are non-negligible risk factors for diabetes and chronic kidney disease. However, whether there is an association between multiple metals exposure and incident chronic kidney disease (CKD) risk in patients with diabetes is unclear. We conducted a prospective study to evaluate these associations. In total, 3071 diabetics with baseline estimated glomerular filtration rate (eGFR) ≥ 60 mL/min/1.73 m² from the Dongfeng-Tongji cohort were included. We measured baseline plasma concentrations of 23 metals and investigated the associations between plasma metal concentrations and CKD in diabetics using logistic regression, the least absolute shrinkage and selection operator (LASSO), and the Bayesian Kernel Machine Regression (BKMR) models. During average 4.6 years of follow-up, 457 diabetics developed CKD (14.9 %). The three models consistently found plasma levels of zinc, arsenic, and rubidium had a positive association with incident CKD risk in patients with diabetes, while titanium, cadmium, and lead had an inverse correlation. The results of BKMR showed a significant and positive overall effect of 23 metals on the risk of CKD, when all of the metals were above the 50th percentile as compared to the median value. In addition, potential interactions of zinc and arsenic, zinc and cadmium, zinc and lead, titanium and arsenic, and cadmium and lead on CKD risk were observed. In summary, we found significant associations of plasma titanium, zinc, arsenic, rubidium, cadmium, and lead with CKD in diabetes and interactions between these metals except for rubidium. Co-exposure to multiple metals was associated with increased CKD risk in diabetics.

Exposure to zinc induces lysosomal-mitochondrial axis-mediated apoptosis in PK-15 cells

Zinc (Zn), a kind of metallic element, can cause poisonous effects on host physiology when its excess exposure. Lysosomes and mitochondria are the toxic targets of heavy metals, and the lysosomal-mitochondrial axis is also verified to take part in apoptosis, but the related underlying mechanisms in Zn-induced cytotoxicity remain undefined. Here, we identified that excess Zn could cause cell damage in PK-15 cells accompanied by the lysosomal and mitochondrial dysfunction, with the evidence by the elevated levels of cathepsin B/D (CTSB/CTSD) in cytoplasm and decrease of Lyso-Tracker Red signal, red fluorescence intensity of AO staining, mitochondrial complex enzyme activities and ATP production. Additionally, the number of Annexin V⁺/PI^--stained cells, apoptosis-related genes (Bax, Bid, Bak1, Caspase-9, and Caspase-3) and proteins levels of Bax, Bak1, Caspase-9, cleaved Caspase-3 and cytoplasmic Cyt C were signally elevated under Zn exposure, while the protein levels of Bcl2 and mitochondrial Cyt C were observably decreased. Importantly, Pepstatin A (the activity inhibitor of CTSD) and RNA interference of CTSD (si-CTSD) was used to reduce the release of lysosomal CTSD to the cytoplasm, which could signally alleviated Zn-induced mitochondrial damage and apoptosis. In summary, these results suggested that Zn could induced lysosomal and mitochondrial dysfunction in PK-15 cells, and the CTSD played an important role in Zn-induced lysosomal-mitochondrial axis-mediated apoptosis. Our results provided a new insight in Zn-induced toxicology, which for protecting the ecological environment and public health.

Associations of plasma metal concentrations with the decline in kidney function: A longitudinal study of Chinese adults

Metals are widespread pollutants in the environment which have been reported to be associated with kidney dysfunction in many existing epidemiological studies. However, most of the studies are cross-sectional design and mainly focus on several toxic metals including arsenic, lead and cadmium. Therefore, we conducted this prospective study within the Dongfeng-Tongji cohort to evaluate the associations of plasma multiple metals with the decline in kidney function among Chinese middle-aged and elderly. In total, 1434 participants free of chronic diseases at baseline were included in analysis. We measured baseline plasma concentrations of 23 metals and calculated estimated glomerular filtration rate (eGFR) using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation based on serum creatinine, age, sex and ethnicity. Bonferroni correction was used for multiple testing to reduce the probability of a type I error. Principal component analysis was conducted to evaluate the combined effect of multiple metal co-exposure. Most of the plasma metal concentrations were within the literature reported reference values, whereas the concentration of lead and nickel exceeded the guideline value. We found that plasma concentrations of aluminum, arsenic, barium, lead, molybdenum, rubidium, strontium, vanadium and zinc were significantly associated with the decline in kidney function measured by annual eGFR decline, rapid renal function decline (defined as an annual decline in eGFR ≥ 5 mL/min/1.73 m²) or incident eGFR < 60 mL/min/1.73 m², with the adjusted beta coefficients (95% CI) for annual eGFR decline 0.50 (0.30, 0.69), 0.98 (0.74, 1.23), 0.56 (0.32, 0.79), 0.21 (0.03, 0.39), 0.35 (0.16, 0.54), 0.94 (0.71, 1.17), 0.37 (0.15, 0.60), 0.78 (0.54, 1.02), and 0.74 (0.57, 0.91), respectively. The metals exposures were linked with increased risks of impaired kidney function. Associations of principal components representing these metals with the decline in kidney function were significant and suggest a possible additional health risk by co-exposure. Participants engaged in manufacturing had higher plasma levels of several metals compared with those who had been involved in management- or administration-related work. Our findings suggest that exposure to multiple metals contribute to the decline in kidney function among the middle-aged and elderly. Co-exposure to multiple metals may have synergetic effect on the kidney function. Further studies are warranted to confirm our findings and clarify the potential mechanisms.

Selenium, copper, zinc and hypertension: an analysis of the National Health and Nutrition Examination Survey (2011-2016)

BACKGROUND

Hypertension is a major cardiovascular illness worldwide with many underlying causes. The role of trace elements selenium, copper, and zinc in hypertension is uncertain. The objective of this study was to evaluate the role of these trace elements in hypertension.

METHOD

Data from 6683 National Health and Nutrition Examination Survey (NHANES) participants from 2011 to 2016 were analyzed using Statistical Analytical System (SAS, version 9.4) software for the role of trace elements in hypertension in age range 8 to 80 years, irrespective of the antihypertensive medication taken. Recent American Heart Association guidelines and pediatric practice guidelines for hypertension were used.

RESULTS

Findings showed a significant positive association between serum selenium levels and hypertension but not serum zinc and copper. At optimal levels for transport and distribution, serum selenium levels of 120 μg/L or higher (reference level 70-150 μg/L) were significantly associated with hypertension (OR = 1.46, 95% CI = 1.29-1.66) after adjusting for confounding factors. At serum selenium level greater than 150 μg/L, the association with hypertension strengthened (OR = 1.69, 95% CI = 1.32-2.17).

CONCLUSION

A positive association was found between serum selenium and hypertension, irrespective of age or anti-hypertensive medications intake. These findings also suggest that the reference levels of serum levels in healthy individuals may need to be re-determined, if supported by additional studies. If validated, patients with hypertension may also need to be cautioned about selenium intake.

Maternal cadmium exposure in the mouse leads to increased heart weight at birth and programs susceptibility to hypertension in adulthood

Cadmium (Cd) is a toxic heavy metal ubiquitous in the environment. Maternal exposure to Cd is associated with fetal growth restriction, trace element deficiencies, and congenital malformations. Cd exposure during adulthood is associated with cardiovascular disease (CVD); however, the effects of maternal Cd exposure on offspring cardiovascular development and disease are not well-understood. Utilizing a mouse model of maternal Cd exposure, we show that offspring born to Cd-exposed mothers have increased heart weights at birth and susceptibility to hypertension during adulthood. Despite inefficient maternal-fetal transfer of Cd, maternal Cd alters fetal levels of essential trace elements including a deficiency in iron, which is required for cardiovascular system development, oxygen homeostasis, and cellular metabolism. RNA-seq on newborn hearts identifies differentially expressed genes associated with maternal Cd exposure that are enriched for functions in CVD, hypertension, enlarged hearts, cellular energy, and hypoxic stress. We propose that a maternal Cd exposure-induced iron deficiency leads to altered cellular metabolic pathways and hypoxic conditions during fetal development; this stress may contribute to increased heart weight at birth and the programming of susceptibility to hypertension in adulthood. These studies will give insights into potential mechanisms through which maternal Cd exposure impacts cardiovascular development and disease.

Zinc deficiency induces hypertension by promoting renal Na+ reabsorption

Zn²⁺ deficiency (ZnD) is a common comorbidity of many chronic diseases. In these settings, ZnD exacerbates hypertension. Whether ZnD alone is sufficient to alter blood pressure (BP) is unknown. To explore the role of Zn²⁺ in BP regulation, adult mice were fed a Zn²⁺-adequate (ZnA) or a Zn²⁺-deficient (ZnD) diet. A subset of ZnD mice were either returned to the ZnA diet or treated with hydrochlorothiazide (HCTZ), a Na⁺-Cl^- cotransporter (NCC) inhibitor. To reduce intracellular Zn²⁺ in vitro, mouse distal convoluted tubule cells were cultured in N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN, a Zn²⁺ chelator)- or vehicle (DMSO)-containing medium. To replete intracellular Zn²⁺, TPEN-exposed cells were then cultured in Zn²⁺-supplemented medium. ZnD promoted a biphasic BP response, characterized by episodes of high BP. BP increases were accompanied by reduced renal Na⁺ excretion and NCC upregulation. These effects were reversed in Zn²⁺-replete mice. Likewise, HCTZ stimulated natriuresis and reversed BP increases. In vitro, Zn²⁺ depletion increased NCC expression. Furthermore, TPEN promoted NCC surface localization and Na⁺ uptake activity. Zn²⁺ repletion reversed TPEN effects on NCC. These data indicate that 1) Zn²⁺ contributes to BP regulation via modulation of renal Na⁺ transport, 2) renal NCC mediates ZnD-induced hypertension, and 3) NCC is a Zn²⁺-regulated transporter that is upregulated with ZnD. This study links dysregulated renal Na⁺ handling to ZnD-induced hypertension. Furthermore, NCC is identified as a novel mechanism by which Zn²⁺ regulates BP. Understanding the mechanisms of ZnD-induced BP dysregulation may have an important therapeutic impact on hypertension.

Effect of hypotensive therapy combined with modified diet or zinc supplementation on biochemical parameters and mineral status in hypertensive patients

BACKGROUND

Hypotensive therapy leads to a number of trace elements metabolism disturbances. Zinc balance is frequently affected by antihypertensive treatment.

AIM

To evaluate the effect of a hypotensive treatment, modified diet and zinc supplementation on mineral status and selected biochemical parameters in newly diagnosed hypertensive patients on monotherapy.

METHODS

In the first stage, arterial hypertension in ninety-eight human subjects was diagnosed. In the second stage, antihypertensive monopharmacotherapy was implemented. In the third stage, patients were randomized into three groups and continued antihypertensive monotherapy: group D received an optimal-mineral-content diet, group S received zinc supplementation, and group C had no changes in diet or zinc supplementation. Iron, zinc, and copper concentrations in serum, erythrocytes, urine, and hair were determined. Lipids, glucose, ceruloplasmin, ferritin, albumin, C-reactive protein (CRP), tumor necrosis factor α (TNF-α), nitric oxide (NO), superoxide dismutase (SOD) and catalase (CAT) were assayed in serum.

RESULTS

Antihypertensive monotherapy decreased zinc concentration in serum and erythrocytes and increased the level of zinc in urine, decreased CAT and SOD activity, TNF-α concentration in serum, and increased the level of NO in the serum. Zinc supply led to an increase in zinc concentration in serum, erythrocytes, and hair (in group S only). In the groups with higher zinc intake, decreased glucose concentration in the serum was observed. Significant correlation was seen between the zinc and glucose serum concentrations.

CONCLUSION

Hypotensive drugs disturb zinc status in newly diagnosed hypertensive patients. Antihypertensive monotherapy combined with increased zinc supply in the diet or supplementation favorably modify zinc homeostasis and regulate glucose status without blood pressure affecting in patients with hypertension.

Association between serum zinc and later development of metabolic syndrome in middle aged and older men: The Kuopio Ischaemic Heart Disease Risk Factor Study

OBJECTIVE

The aim of this study was to investigate associations of serum zinc with incident metabolic syndrome and its components in middle-aged and older Finnish men.

METHODS

An 11-y prospective follow-up study conducted among 683 men from the Kuopio Ischaemic Heart Disease Risk Factor Study who were 42 to 60 y old at baseline in 1984 to 1989. The main outcome was incident metabolic syndrome, defined by the National Cholesterol Education Program (NCEP) criteria. Other outcomes were the individual components of the NCEP metabolic syndrome: Fasting blood glucose, serum triacylglycerols, serum high-density lipoprotein (HDL) cholesterol, hypertension, and waist circumference.

RESULTS

During the average follow-up of 11 y, 139 men (20.4%) developed metabolic syndrome. Those in the highest tertile of serum zinc had 84% higher risk (95% confidence interval 12 to 201%, P trend across tertiles = 0.015) to develop metabolic syndrome compared with those in the lowest tertile, after adjustment for several potential confounders. The association between serum zinc and incident metabolic syndrome was attenuated by adjustment for waist circumference, serum HDL cholesterol, or hypertension. Serum zinc was also directly associated with higher waist circumference and hypertension and inversely associated with HDL cholesterol at the 11 y examinations.

CONCLUSIONS

We found a direct association between serum zinc and incidence of metabolic syndrome in middle-aged and older eastern Finnish men. Further studies are warranted to explore the mechanisms.

Zinc delays the progression of obesity-related glomerulopathy in mice via down-regulating P38 MAPK-mediated inflammation

OBJECTIVE

Obesity, particularly child obesity, is one of the most common public health problems in the world and raises the risk of end-stage renal disease. Zinc (Zn) is essential for multiple organs in terms of normal structure and function; however, effects of Zn deficiency or supplementation among young individuals with obesity have not been well studied.

METHODS

Weaned mice were fed high-fat diets (HFD) with varied contents of Zn (Zn deficient, adequate, and supplemented) for 3 or 6 months. This study examined associations between renal pathogenesis and dietary Zn levels, specifically assessing inflammatory pathways by utilizing P38 MAPK inhibitor SB203580.

RESULTS

HFD feeding induced typical syndromes of obesity-related renal disorders, which worsened by Zn marginal deficiency. The progression of obesity-related renal disorders was delayed by Zn supplementation. HFD induced renal inflammation, reflected by increased P38 MAPK phosphorylation along with increases of inflammatory cytokines MCP-1, IL-1β, IL-6, and TNF-α. P38 MAPK inhibition prevented renal pathological changes in mice fed with HFD and HFD/Zn deficiency.

CONCLUSIONS

P38 MAPK mediated the renal inflammatory responses, which played a central role in the pathogenesis of HFD-induced renal disorders. Zn could delay the progression of obesity-related kidney disease by down-regulating P38 MAPK-mediated inflammation.

The implications of angiotensin-converting enzymes and their modulators in neurodegenerative disorders: current and future perspectives

Angiotensin converting enzyme (ACE) is a dipeptidyl peptidase transmembrane bound enzyme. Generally, ACE inhibitors are used for the cardiovascular disorders. ACE inhibitors are primary agents for the management of hypertension, so these cannot be avoided for further use. The present Review focuses on the implications of angiotensin converting enzyme inhibitors in neurodegenerative disorders such as dementia, Alzheimer's disease, Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis, stroke, and diabetic neuropathy. ACE inhibitors such as ramipril, captopril, perindopril, quinapril, lisinopril, enalapril, and trandolapril have been documented to ameliorate the above neurodegenerative disorders. Neurodegeneration occurs not only by angiotensin II, but also by other endogenous factors, such as the formation of free radicals, amyloid beta, immune reactions, and activation of calcium dependent enzymes. ACE inhibitors interact with the above cellular mechanisms. Thus, these may act as a promising factor for future medicine for neurological disorders beyond the cardiovascular actions. Central acting ACE inhibitors can be useful in the future for the management of neuropathic pain due to following actions: (i) ACE-2 converts angiotensinogen to angiotensin(1-7) (hepatapeptide) which produces neuroprotective action; (ii) ACE inhibitors downregulate kinin B1 receptors in the peripheral nervous system which is responsible for neuropathic pain. However, more extensive research is required in the field of neuropathic pain for the utilization of ACE inhibitors in human.

Zinc-Excess Intake Causes the Deterioration of Renal Function Accompanied by an Elevation in Systemic Blood Pressure Primarily Through Superoxide Radical-Induced Oxidative Stress

Using rats fed 22 g/d of a control diet containing 0.005% zinc (Zn) or 2 Zn-excess diets containing 0.05% or 0.2% Zn for 4 weeks, we examined the mechanisms involved in the deterioration of renal function induced by Zn-excess intake. An increase in Zn intake elevated mean blood pressure (BP) and reduced renal blood flow (RBF) and inulin clearance in a dose-dependent manner. This decline in inulin clearance may be derived from a fall in RBF. Administration of the nitric oxide (NO) synthase inhibitor, Nω-nitro-l-arginine methyl ester, markedly increased mean BP and significantly decreased RBF in the 3 groups of rats. Administration of the exogenous superoxide radical (OO−) scavenger, tempol, significantly decreased mean BP and substantially increased RBF in all groups of rats. These observations suggest that both an elevation in systemic BP and a reduction in RBF seen in the 2 Zn-excess diet groups result from a decrease in the action of the vasodilator, NO, through the formation of peroxynitrite based on the nonenzymatic reaction of NO and increased OO−. Indeed, the activity of the endogenous OO− scavenger, copper/Zn-superoxide dismutase, was significantly reduced in the vessel wall of rats fed 2 Zn-excess diets versus a control diet. 8-Hydroxy-2′-deoxyguanosine formation caused by OO− generation was notably elevated in the kidneys of rats fed 2 Zn-excess diets relatively to rats fed a control diet. Thus, Zn-excess intake leads to the aggravation of renal function concomitantly with an increase in systemic BP predominantly through the oxidative stress caused by OO−.

Gender differences in the relationship between serum zinc concentration and metabolic syndrome

BACKGROUND

Zinc, a co-factor of antioxidant enzymes, may be involved in the pathophysiology of metabolic syndrome (MetS).

AIM

To determine the association between serum zinc concentration and MetS in a population-based study.

SUBJECTS AND METHODS

In the Tehran Lipid and Glucose Study, serum zinc concentration was measured by flame atomic absorption spectrometry in 2626 adult participants. After removal of outliers, usable data was available for 2401 participants. Dietary zinc was assessed by a validated semi-quantitative food frequency questionnaire.

RESULTS

Compared to those without the MetS, serum zinc concentration was significantly higher in men with syndrome (17.1 ± 4.9 vs 16.5 ± 4.6 μmol/L, p = 0.035); however, values were comparable in females (16.1 ± 4.8 vs 15.8 ± 4.4, p = 0.460). Men in tertile 3 of serum zinc had significantly higher chances of having MetS, even after multivariate adjustment (OR = 1.48, 95% confidence interval (CI) = 1.07-2.06, p = 0.020). Women in tertile 2 of serum zinc had significantly lower chances of having MetS, which remained significant after multivariate adjustment (OR = 0.68, 95% CI = 0.47-0.99, p = 0.046).

CONCLUSION

This study observed a gender difference between serum zinc and MetS, with higher levels being positively associated with MetS in men and having a protective effect in women. Further studies are needed to elucidate the role of zinc status in the development of MetS.