Investigating Susceptibility to Diabetes Using Features of the Adipose Tissue in Response to In Utero Polycyclic Aromatic Hydrocarbons Exposure

The Association between Urinary Polycyclic Aromatic Hydrocarbons Metabolites and Type 2 Diabetes Mellitus

Polycyclic aromatic hydrocarbons (PAHs) are considered to be endocrine disruptors. In this study, the evidence on the association between PAHs and diabetes was systematically reviewed. PubMed, EMBASE, and ISI Web of Science were systematically searched for studies reporting the association between PAHs and diabetes. Of the 698 articles identified through the search, nine cross-sectional studies were included. Seven were conducted in the general population and two in coke oven workers. Fixed-effects and random-effects models were used to calculate the total effect. Subgroup analysis was further carried out according to the types of PAH metabolites. The results showed that the odds of diabetes were significantly higher for the highest category of urinary naphthalene (NAP), fluorine (FLU), phenanthrene (PHEN), and total mono-hydroxylated (OH-PAH) metabolites compared to the lowest category. The pooled odds ratios (OR) and 95% confidence intervals (CI) were 1.52 (95%CI: 1.19, 1.94), 1.53 (95%CI: 1.36, 1.71), 1.43 (95%CI: 1.28, 1.60), and 1.49 (95%CI: 1.07, 2.08), respectively. In coke oven workers, 4-hydroxyphenanthrene (4-OHPh) was significantly correlated with an increased risk of diabetes. Exposure measurements, outcome definitions, and adjustment for confounders were heterogeneous between studies. The results of the current study demonstrate a potentially adverse effect of PAHs on diabetes. Further mechanistic studies and longitudinal studies are needed to confirm whether PAH metabolite levels are causative, and hence associative, with increased diabetes incidences.

The Role of Persistent Organic Pollutants in Obesity: A Review of Laboratory and Epidemiological Studies

Persistent organic pollutants (POPs) are considered as potential obesogens that may affect adipose tissue development and functioning, thus promoting obesity. However, various POPs may have different mechanisms of action. The objective of the present review is to discuss the key mechanisms linking exposure to POPs to adipose tissue dysfunction and obesity. Laboratory data clearly demonstrate that the mechanisms associated with the interference of exposure to POPs with obesity include: (a) dysregulation of adipogenesis regulators (PPARγ and C/EBPα); (b) affinity and binding to nuclear receptors; (c) epigenetic effects; and/or (d) proinflammatory activity. Although in vivo data are generally corroborative of the in vitro results, studies in living organisms have shown that the impact of POPs on adipogenesis is affected by biological factors such as sex, age, and period of exposure. Epidemiological data demonstrate a significant association between exposure to POPs and obesity and obesity-associated metabolic disturbances (e.g., type 2 diabetes mellitus and metabolic syndrome), although the existing data are considered insufficient. In conclusion, both laboratory and epidemiological data underline the significant role of POPs as environmental obesogens. However, further studies are required to better characterize both the mechanisms and the dose/concentration-response effects of exposure to POPs in the development of obesity and other metabolic diseases.

Dietary ingestion of 2-aminoanthracene (2AA) and the risk for type-1 diabetes (T1D)

Type 1 diabetes (T1D) is an autoimmune disorder caused by the destruction of insulin-secreting β-cells.T1D is on the rise around the world. Exposure to polycyclic aromatic hydrocarbons (PAHs) including 2-aminoanthracene (2AA) is considered a contributor to TID increase. The contribution of the ingestion of 2AA toward T1D vulnerability is examined. 2AA is found in a variety of household products. Juvenile male Sprague Dawley rats ingested various amounts of 2AA contaminated diet for 12 weeks. Results showed marginal reduction in body weight gain for the 100 mg/kg treated animals. Glucose tolerance test (GTT) indicated no changes at six weeks. However, at week 12, both treated groups had higher levels of blood glucose than the control group. Serum insulin concentration was elevated in the 50 mg/kg group while reduced in the 100 mg/kg animals. Serum lactate dehydrogenase activity was elevated in treated groups. Evaluation of pancreatic inflammatory cytokines revealed overexpression of IL-1B, IL-6, and IL-7. Apoptotic genes in the pancreas of exposed rats were overly expressed. Histopathology and insulin immunohistochemistry data showed the presence of mesenteric vessels surrounded by lymphocyte and enlarged size of islet cells respectively in the high dose group. These results suggest 2AA ingestion may enhance T1D development.

The hepatic effects in dams that ingested 2-aminoanthracene during gestation and lactation

Diabetes mellitus has been on a continual rise as one of the top chronic diseases to affect individuals worldwide. The goal of this study was to determine how exposure from a well-known toxicant, a polycyclic aromatic hydrocarbon called 2-aminoanthracene (2AA), could potentially lead to diabetes, damage the liver, and have negative effects to the offspring. Humans are exposed to 2AA from foods cooked in high heat and tobacco smoke, among others. To analyze the effects of 2AA, three groups of Sprague Dawley dams consumed an adulterated 2AA diet from gestation to their postnatal period. Timed-pregnant dams ingested 0 mg/kg (control group (C)), 50 mg/kg (low dose group (LD)), and 100 mg/kg (high dose group (HD)) 2AA. Hepatic gene expressions of Adam8, Bax, Ccng1, CD68, CD93, Cdkn1c, and Ddit4 indicated a significant overexpression of Bax, Ccng1, CD68, CD93, and Cdkn1c in treated groups. Although there was no significant difference in the damage to the liver architecture by 2AA, the positively stained CD68+ cells were slightly increased in treated rats. Significant decreases in the albumin and aspartate aminotransferase levels might indicate an inflammatory response from 2AA exposure in dams. Immunoglobulin A (IgA) concentration was also decreased, in contrast to studies of liver cirrhosis that reported increased serum IgA concentration. Overexpression of genes Ddit4, Cdkn1c, Ccng1, Bax, CD93, and CD68 point to hepatic inflammation and apoptosis. Overall results suggest a link between environmental 2AA exposure and adverse liver effects, which has potential to increase susceptibility to type 2 diabetes and other diseases.

Association of the IL6 Gene Polymorphism with Component Features of Metabolic Syndrome in Obese Subjects

Metabolic syndrome (MetS) is a risk factor for type 2 diabetes mellitus and cardiovascular disease. Obesity is a component of the metabolic syndrome. Several genetic variants are reported to be associated with obesity and hypo adiponectinemia, including ars1800796 polymorphism of the interleukin-6 (IL-6) gene. Since obesity is associated with inflammatory factors, the aim of this study was to investigate the association between this polymorphism and MetS and its related features. Obese patients with body mass index (BMI) ≥ 30 (n = 182) were recruited into this study and divided into two groups; 110 patients with MetS, based on the International Diabetes Federation (IDF) criteria, and 72 subjects without MetS. The anthropometric and biochemical data for the groups were compared. Genotyping was carried out using RT-PCR. The association of the genetic polymorphism with MetS and its components were assessed using univariate and multivariate analyzes. There was an association between the presence of the rs1800796polymorphism of the IL-6 gene, with BMI (P = 0.031), high-density lipoprotein (HDL) (P = 0.010) and low-density lipoprotein (LDL) (P = 0.037), while this genetic variant did not show any significant association with the presence of MetS as defined by the IDF. We demonstrate an association between the rs1800796 genetic variant of the IL-6 gene with components of MetS including BMI, and HDL-cholesterol, but not the MetS itself. Therefore, supporting further studies are warranted to investigate this point in a larger population.