Dioxins, furans and dioxin-like PCBs in human blood: causes or consequences of diabetic nephropathy?

Prospective study on the joint effect of persistent organic pollutants and glucose metabolism on chronic kidney disease: Modifying effects of lifestyle interventions

There is no evidence on the associations between persistent organic pollutants (POPs) and the incidence of chronic kidney disease (CKD) in the Chinese rural population. We aimed to investigate the individual and mixed effects of 22 POPs on the prevalence and incidence of CKD, and the joint effects of POPs and abnormal glucose metabolism as well as the modification effects of healthy lifestyle on these associations. A total of 2775 subjects, including 925 subjects with normal plasma glucose (NPG) and 925 subjects with prediabetes (PDM) and type 2 diabetes mellitus (T2DM), were enrolled from the Henan Rural Cohort Study. Logistic regression and quantile g-computation were performed to assess the individual and mixed effects of POPs on the risk of CKD. Joint effects of POPs and abnormal glucose metabolism status, as well as the modification effects of lifestyle on CKD were assessed. After 3-year follow-up, an increment of ln-o,p'-DDT was related to an elevated risk of CKD prevalence. Positive associations of p,p'-DDE and β-BHC with CKD incidence were observed (P < 0.05). In addition, participants with high levels of ∑POPs were associated elevated incidence risk of CKD (OR: 1.217, 95%CI: 1.008-1.469). One quartile increase in POPs mixture was associated with the increased incidence of CKD among T2DM patients (P < 0.05). Further, a higher risk of CKD was observed among PDM and T2DM patients with high levels of o,p'-DDT, p,p'-DDE, β-BHC, and ∑POPs than NPG subjects with low levels of pollutants. In addition, interactive effects of ∑POPs and lifestyle score on CKD incidence were found. Individual and mixed exposure to POPs increased the prevalence and incidence of CKD, and glucose metabolic status exacerbated the risk of CKD resulting from such exposures. Further, the modifying effects of lifestyle were observed, highlighting the importance of precision prevention for high-risk CKD population and healthy lifestyle intervention measures.

Metformin attenuates PM2.5-induced oxidative stress by inhibiting the AhR/CYP1A1 pathway in proximal renal tubular epithelial cells

The harmful effects of PM2.5 on human health, including an increased risk of chronic kidney disease (CKD), have raised a lot of attention, but the underlying mechanisms are unclear. We used the Shanghai Meteorological and Environmental Animal Exposure System (Shanghai-METAS) to simulate the inhalation of PM2.5 in the real environment and established an animal model by exposing C57BL/6 mice to filtered air (FA) and Particulate Matter (PM2.5) for 8 weeks. PM2.5 impaired the renal function of the mice, and the renal tubules underwent destructive changes. Analysis of NHANES data showed a correlation between reduced kidney function and higher blood levels of PM2.5 components, polychlorinated biphenyls (PCBs) and dioxins, which are Aryl hydrocarbon Receptor (AhR) ligands. PM2.5 exposure induced higher levels of AhR and CYP1A1 and oxidative stress as evidenced by the higher levels of ROS, MDA, and GSSG in kidneys of mice. PM2.5 exposure led to AhR overexpression and nuclear translocation in proximal renal tubular epithelial cells. Inhibition of AhR reduced CYP1A1 expression and PM2.5-increased levels of ROS, MDA and GSSG. Our study suggested metformin can mitigate PM2.5-induced oxidative stress by inhibiting the AhR/CYP1A1 pathway. These findings illuminated the role of AhR/CYP1A1 pathway in PM2.5-induced kidney injury and the protective effect of metformin on PM2.5-induced cellular damage, offering new insights for air pollution-related renal diseases.

Exposure to several polychlorinated biphenyls (PCBs) is associated with chronic kidney disease among general adults: Korean National Environmental Health Survey (KoNEHS) 2015-2017

We investigated the association between major persistent organic pollutants (POPs) exposure and chronic kidney disease (CKD) among general adult population of Korea. For this purpose, a subset of the adult population (n = 1276) participated in Korean National Environmental Health Survey (KoNEHS) Cycle 3 (2015-2017) were analyzed for twenty-four POPs in serum, including organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs), and were derived for estimated glomerular filtration rate (eGFR) and urinary albumin-to-creatinine ratio (uACR). Multivariable linear regression was conducted to assess the association between POPs exposure and CKD-related parameters including eGFR and uACR. As sensitivity analyses, principal component analysis was conducted. Moreover, the U.S. National Health and Nutrition Examination Survey (NHANES) 1999-2004 data were chosen to compare with the observations of the Korean adults. Approximately 7.7% of the Korean adult population possessed CKD based on either eGFR (<60 ml/min/1.73 m²) or uACR (≥30 mg/g) criteria. Among the POPs that were detected in ≥70% of the subjects, PCB153 (β = -1.61, 95% CI: -2.55, -0.67, P = 0.001) and PCB180 (β = -1.47, 95% CI: -2.53, -0.40, P = 0.007) exhibited significant associations with decreased eGFR, especially in females. In male participants, hexachlorobenzene (HCB) was associated with eGFR (β = -0.79, 95% CI: -1.53, -0.04, P = 0.040). Sex-dependent associations with eGFR were also shown in the PCA model. Moreover, the sex-dependent associations of PCBs were similarly observed in the adult populations of the US NHANES. However, POPs exposure was not associated with uACR, regardless of association model or population. The observed associations of PCBs are supported by several experimental studies reported elsewhere. To our knowledge, it is the first report that suggests significant associations of PCBs and HCB with eGFR among general population, and further validations in other populations are warranted.

Trends in concentrations of selected dioxins and furans across various stages of kidney function for US adults

Exposure to dioxins and furans has the potential to affect kidney function and could be associated with chronic kidney disease. Data for US adults aged ≥ 20 years from the National Health and Nutrition Examination Survey for 1999-2004 (N = 4433) were analyzed to study trends in adjusted concentrations (AGM) of 1,2,3,7,8-pentachlorodibenzo-p-dioxin, 1,2,3,6,7,8-hexachlorodibenzo-p-dioxin, 1,2,3,4,6,7,8-heptachlororodibenzo-p-dioxin, 1,2,3,4,6,7,8,9-octachlorodibenzo-p-dioxin, 2,3,4,7,8-pentachlorodibenzofuran, 1,2,3,4,7,8-hexachlorodibenzofuran, 1,2,3,6,7,8-hexachlorodibenzofuran, and 1,2,3,4,6,7,8-heptachlorodibenzofuran across the stages of kidney function (KF). Stages of KF were defined based on estimated glomerular filtration rate or eGFR expressed in mL/min/1.73 m2. For KF-1, eGFR was > 90, between 60 and 90 for KF-2, between 45 and 60 for KF-3A, and between 15 and 45 for KF-3B/4. AGMs for 1,2,3,7,8-pentachlorodibenzo-p-dioxin and 1,2,3,6,7,8-hexachlorodibenzo-p-dioxin increased consistently across the full spectrum of kidney function. For example, AGMs for the total population for 1,2,3,7,8-pentachlorodibenzo-p-dioxin were 2.5, 4.5, 9.3, and 14.9 fg/g lipid for KF-1, KF-2, KF-3A, and KF-3B/4, respectively. For other six dioxins/furans, AGMs increased over KF-1 through KF-3A but then decreased for KF-3B/4, for example, 1,2,3,4,6,7,8-heptachlorodibenzofuran for males, and AGMs for KF-1, KF-2, KF-3A, and KF-3B/4 were 7.9, 8.4, 10.7, and 7.5 fg/g lipid, respectively. For 1,2,3,4,6,7,8-heptachlorodibenzo-p-dioxin and 1,2,3,6,7,8-hexachlorodibenzofuran, smokers were found to have lower AGMs than nonsmokers. For example, for 1,2,3,4,6,7,8-heptaachlorodibenzo-p-dioxin, smoker-nonsmoker AGMs were 22.2 vs. 39.4 fg/g lipid at KF-1, 29.5 vs. 51.4 fg/g lipid at KF-2, 61.6 vs. 72.8 fg/g lipid at KF-3A, and 34.9 vs. 66.4 fg/g lipid at KF-3B/4. The reverse more often than not, was, however, observed for other six dioxins/furans. Smoker-nonsmoker AGMs for 1,2,3,7,8-pentachlorodibenzo-p-dioxin were 2.4 vs. 2.6 fg/g lipid at KF-1, 5.1 vs. 4.0 fg/g lipid at KF-2, 12.7 vs. 6.7 fg/g lipid at KF-3A, and 18.6 vs. 11.9 fg/g lipid at KF-3B/4. In conclusion, lipid-adjusted serum concentrations of dioxins and furans continue increasing as kidney function keeps deteriorating until KF-3A. However, these increases in serum concentrations until KF-3A may be followed by substantial decreases for selected dioxins/furans during KF-3B/4.

Environment-Wide Association Study of CKD

BACKGROUND AND OBJECTIVES

Exposure to environmental chemicals has been recognized as one of the possible contributors to CKD. We aimed to identify environmental chemicals that are associated with CKD.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We analyzed the data obtained from a total of 46,748 adults who participated in the National Health and Nutrition Examination Survey (1999-2016). Associations of chemicals measured in urine or blood (n=262) with albuminuria (urine albumin-to-creatinine ratio ≥30 mg/g), reduced eGFR (<60 ml/min per 1.73 m²), and a composite of albuminuria or reduced eGFR were tested and validated using the environment-wide association study approach.

RESULTS

Among 262 environmental chemicals, seven (3%) chemicals showed significant associations with increased risk of albuminuria, reduced eGFR, or the composite outcome. These chemicals included metals and other chemicals that have not previously been associated with CKD. Serum and urine cotinines, blood 2,5-dimethylfuran (a volatile organic compound), and blood cadmium were associated with albuminuria. Blood lead and cadmium were associated with reduced eGFR. Blood cadmium and lead and three volatile compounds (blood 2,5-dimethylfuran, blood furan, and urinary phenylglyoxylic acid) were associated with the composite outcome. A total of 23 chemicals, including serum perfluorooctanoic acid, seven urinary metals, three urinary arsenics, urinary nitrate and thiocyanate, three urinary polycyclic aromatic hydrocarbons, and seven volatile organic compounds, were associated with lower risks of one or more manifestations of CKD.

CONCLUSIONS

A number of chemicals were identified as potential risk factors for CKD among the general population.

The role of pollutants in type 2 diabetes mellitus (T2DM) and their prospective impact on phytomedicinal treatment strategies

Type 2 diabetes mellitus (T2DM) is the most common form of diabetes and it is characterized by high blood sugar and abnormal sera lipid levels. Although the specific reasons for the development of these abnormalities are still not well understood, traditionally, genetic and lifestyle behavior have been reported as the leading causes of this disease. In the last three decades, the number of diabetic patients has drastically increased worldwide, with current statistics suggesting the number is to double in the next two decades. To combat this incurable ailment, orthodox medicines, to which economically disadvantaged patients have minimal access to, have been used. Thus, a considerable amalgamation of medicinal plants has recently been proven to possess therapeutic capabilities to manage T2DM, and this has prompted studies primarily focusing on the healing aspect of these plants, and ultimately, their commercialization. Hence, this review aims to highlight the potential threat of pollutants, i.e., polyfluoroalkyl compounds (PFCs), endocrine disrupting chemicals (EDCs) and heavy metals, to medicinal plants, and their prospective impact on the phytomedicinal therapy strategies for T2DM. It is further suggested that auxiliary research be undertaken to better comprehend the factors that influence the uptake of these compounds by these plants. This should include a comprehensive risk assessment of phytomedicinal products destined for the treatment of T2DM. Regulations that control the use of PFC-precursors in certain developing countries are also long overdue.

Association of dioxins, furans and dioxin-like PCBs in human blood with nephropathy among US teens and young adults

We assessed the association of three chlorinated dibenzo-p-dioxins, a chlorinated dibenzofuran, and four dioxin-like polychlorinated biphenyls (PCBs) in human blood with nephropathy (microalbuminuria or macroalbuminuria) among teens and young adults (12-30 years old) having normal glycohemoglobin (A1c <5.7%). The data were derived from the 1999-2004 National Health and Nutrition Examination Survey (unweighted n=1504, population estimate=38,806,338). In this paper, nephropathy refers to normal A1c with nephropathy. In an all-adult sample (Everett CJ, Thompson OM. Dioxins, furans and dioxin-like PCBs in human blood: causes or consequences of diabetic nephropathy? Environ Res 2014;132:126-31), the cut-offs for these chemicals being considered elevated, were defined as the 75th percentile. Using these same cut-offs again, the proportion of those with one or more of the eight dioxin-like compounds elevated was 9.9%. The four chemicals associated with nephropathy were 1,2,3,6,7,8-hexachlorodibenzo-p-dioxin, PCB 126, PCB 169, and PCB 156. The proportion with one or more of these four dioxin-like chemicals elevated was 3.9% (unweighted n=46) and the odds ratio (OR) for nephropathy was 7.1 [95% confidence interval (CI) 1.8-28.1]. The association was strong among females (OR 17.4, 95% CI 3.4-88.6), but among males there were no cases of nephropathy when one or more of the four dioxin-like chemicals were elevated, and therefore no association. In a separate analysis, elevated toxic equivalency, defined using the eight dioxin-like chemicals (TEQ8), was associated with nephropathy. TEQ8 ≥50.12 fg/g included 2.6% of the sample (unweighted n=28) and had an OR of 5.8 (95% 1.3-25.9) for nephropathy. As found in the analysis of one or more of four dioxin-like chemicals elevated, TEQ8 ≥50.12 fg/g was associated with nephropathy among females (OR 11.9, 95% CI 1.6-87.2), but not males. Trends for least-squares means also differed by gender, but there were no significant differences in mean TEQ8 between normal subjects and those having nephropathy in either males or females. We also evaluated pre-diabetes (A1c 5.7-6.4%) without nephropathy and found no associations when one or more of four dioxin-like compounds were elevated, or when TEQ8 was ≥50.12 fg/g. In this study, associations of dioxin-like chemicals with nephropathy were found among females at an early age. Prospective studies are needed to determine if dioxin-like compounds cause nephropathy, or if these relationships are cases of reverse causation.

Absorption of PCB126 by upper airways impairs G protein-coupled receptor-mediated immune response

PCB126 is a dioxin-like polychlorinated biphenyl (PCB) environmental pollutant with a significant impact on human health, as it bioaccumulates and causes severe toxicity. PCB126-induced immune toxicity has been described, although the mechanisms have not been fully elucidated. In this study, an in vivo protocol of PCB126 intoxication into male Wistar rats by intranasal route was used, which has not yet been described. The intoxication was characterised by PCB126 accumulation in the lungs and liver, and enhanced aryl hydrocarbon receptor expression in the liver, lungs, kidneys, and adipose tissues. Moreover, an innate immune deficiency was characterised by impairment of adhesion receptors on blood leukocytes and by reduced blood neutrophil locomotion and oxidative burst activation elicited by ex vivo G protein-coupled receptor (GPCR) activation. Specificity of PCB126 actions on the GPCR pathway was shown by normal burst oxidative activation evoked by Toll-like receptor 4 and protein kinase C direct activation. Moreover, in vivo PCB180 intoxication did not alter adhesion receptors on blood leukocytes either blood neutrophil locomotion, and only partially reduced the GPCR-induced burst oxidative activation on neutrophils. Therefore, a novel mechanism of in vivo PCB126 toxicity is described which impairs a pivotal inflammatory pathway to the host defence against infections.

The effects of environmental chemicals on renal function

The global incidence of chronic kidney disease (CKD) is increasing among individuals of all ages. Despite advances in proteomics, genomics and metabolomics, there remains a lack of safe and effective drugs to reverse or stabilize renal function in patients with glomerular or tubulointerstitial causes of CKD. Consequently, modifiable risk factors that are associated with a progressive decline in kidney function need to be identified. Numerous reports have documented the adverse effects that occur in response to graded exposure to a wide range of environmental chemicals. This Review summarizes the effects of such chemicals on four aspects of cardiorenal function: albuminuria, glomerular filtration rate, blood pressure and serum uric acid concentration. We focus on compounds that individuals are likely to be exposed to as a consequence of normal consumer activities or medical treatment, namely phthalates, bisphenol A, polyfluorinated alkyl acids, dioxins and furans, polycyclic aromatic hydrocarbons and polychlorinated biphenyls. Environmental exposure to these chemicals during everyday life could have adverse consequences on renal function and might contribute to progressive cumulative renal injury over a lifetime. Regulatory efforts should be made to limit individual exposure to environmental chemicals in an attempt to reduce the incidence of cardiorenal disease.