Adipose Tissue Levels of DDT as Risk Factor for Obesity and Type 2 Diabetes Mellitus

The epidemiology of cryptorchidism and potential risk factors, including endocrine disrupting chemicals

Congenital cryptorchidism, also known as undescended testis, is the condition where one or both testes are not in place in the scrotum at birth and is one of the most common birth defects in boys. Temporal trends and geographic variation in the prevalence of cryptorchidism from 1% to 9% have been reported in prospective cohort studies. The testes develop in the abdominal cavity and descend to the scrotum in two phases, which should be completed by gestational week 35. Thus, the risk of cryptorchidism is higher in preterm boys. In many cases a spontaneous descent occurs during the first months of life during the surge of gonadotropins and testosterone. If not, the testis is usually brought down to the scrotum, typically by surgery, to increase future fertility chances and facilitate cancer surveillance. The increasing frequency of impaired semen quality and testicular cancer, with which cryptorchidism is associated, represents a concern for male reproductive health in general and a need to understand its risk factors. The risk of cryptorchidism is closely related to gestational factors (preterm birth, low birth weight and intrauterine growth restriction), and especially maternal smoking seems to be a risk factor. Evidence is accumulating that the increasing prevalence of cryptorchidism is also related to prenatal exposure to environmental chemicals, including endocrine disrupting compounds. This association has been corroborated in rodents and supported by ecological studies. Conducting human studies to assess the effect of endocrine disrupting chemicals and their interactions is, however, challenged by the widespread concomitant exposure of all humans to a wide range of chemicals, the combined effect of which and their interactions are highly complex.

DDT exposure induces tremor-like behavior and neurotoxicity in developmental stages of embryonic zebrafish

Dichlorodiphenyltrichloroethane (DDT) is a broad-spectrum insecticide, widely detected in environments due to its high stability characteristic and long natural half-life period. The adverse impact of DDT exposure on organisms and humans has attracted great concern worldwide. The current study explored the developmental and neurobehavioral toxicity response of DDT in embryonic zebrafish. The embryos were treated with DDT (0, 0.1, 1, 2.5 and 5 µM) during 6 h post fertilization (hpf) to 144 hpf. Our result indicated that DDT exposures increased the embryo hatching rate at 48 and 60 hpf, the larval malformation rate at 120 hpf and mortality rate at 144 hpf. The manifested malformations included uninflated swim bladder, bent spine and tail, deformed liver, and pericardial edema. The 120 hpf larval organs size of the gut and swim bladder was decreased in higher exposed concentration groups. Besides, DDT exposure resulted in hyperactivity for the embryo spontaneous movement at 24 hpf and tremor like movement measured by the free larval activity at 72 hpf, as well as the larval activity at 96 hpf under light-dark transition stimulus. Mechanistic examinations at 120 hpf revealed DDT exposure elevated oxidative stress through MDA formation increase, ATP level decrease as well as antioxidant enzyme genes (sod1 and gpx1a) expression decrease. DDT exposure induced abnormal neurotransmitters expression with DA level increase, 5-HT and NOS level decrease. DDT exposure suppressed the gene expressions involved in axon development (rab33a and nrxn2a) and potassium channel (kcnq2 and kcnq3). Our results suggest that the hyperactivity and tremor like movement in DDT-exposed embryos/larvae may result from oxidative stress involved with neuronal damage.

Pesticides and insulin resistance-related metabolic diseases: Evidences and mechanisms

The use of pesticides in the past century has lot helped humankind in improving crops' field and general hygiene level. Nevertheless, there has been countless evidences on the toxic effects of pesticides on the living systems. The link of exposure to pesticides with different human chronic diseases in the context of carcinogenicity, neurotoxicity, developmental toxicity, etc., have been evaluated in various types of studies. There are also some evidences on the link of exposure to pesticides with higher incidence of metabolic diseases associated with insulin resistance like diabetes, obesity, metabolic syndrome, hypertension, polycystic ovary syndrome and chronic kidney diseases. Physiologically, weakening intracellular insulin signaling is considered as a compensatory mechanism for cells to cope with cellular stresses like xenobiotic effects, oxidative stress and inflammatory responses, but it can pathologically lead to a defective cycle with lowered sensitivity of the cells to insulin which happens in metabolic disorders. In this work, the data related to metabolic toxicity of pesticides categorized in the mentioned metabolic diseases with a focus on the effects of pesticides on insulin signaling pathway and the mechanisms of development of insulin resistance will be systematically reviewed and presented.

Inherited Epigenetic Hallmarks of Childhood Obesity Derived from Prenatal Exposure to Obesogens

Childhood obesity has reached epidemic levels in developed countries and is becoming a major cause for concern in the developing world. The causes of childhood obesity are complex and multifactorial, involving the interaction between individual genetics and environmental and developmental factors. Among the environmental factors, there is a growing interest in understanding the possible relationship between the so-called environmental obesogens and the development of obesity in children. Exposure to these obesogens such as phthalates, bisphenol A, or parabens, has been identified as a promoter of obesity through different mechanisms such as the alteration of adipocyte development from mesenchymal progenitors, the interference with hormone receptors, and induced inflammation. However, less attention has been paid to the inheritance of epigenetic modifications due to maternal exposure to these compounds during pregnancy. Thus, the aim of this review is to summarize the current knowledge of epigenetic modifications due to maternal exposure to those obesogens during pregnancy as well as their potential implication on long-term obesity development in the offspring and transgenerational inheritance of epiphenotypes.

Pesticides as endocrine disruptors: programming for obesity and diabetes

PURPOSE

Exposure to pesticides has been associated with obesity and diabetes in humans and experimental models mainly due to endocrine disruptor effects. First contact with environmental pesticides occurs during critical phases of life, such as gestation and lactation, which can lead to damage in central and peripheral tissues and subsequently programming disorders early and later in life.

METHODS

We reviewed epidemiological and experimental studies that associated pesticide exposure during gestation and lactation with programming obesity and diabetes in progeny.

RESULTS

Maternal exposure to organochlorine, organophosphate and neonicotinoids, which represent important pesticide groups, is related to reproductive and behavioral dysfunctions in offspring; however, few studies have focused on glucose metabolism and obesity as outcomes.

CONCLUSION

We provide an update regarding the use and metabolic impact of early pesticide exposure. Considering their bioaccumulation in soil, water, and food and through the food chain, pesticides should be considered a great risk factor for several diseases. Thus, it is urgent to reformulate regulatory actions to reduce the impact of pesticides on the health of future generations.

Application of In Vitro Models for Studying the Mechanisms Underlying the Obesogenic Action of Endocrine-Disrupting Chemicals (EDCs) as Food Contaminants-A Review

Obesogenic endocrine-disrupting chemicals (EDCs) belong to the group of environmental contaminants, which can adversely affect human health. A growing body of evidence supports that chronic exposure to EDCs can contribute to a rapid increase in obesity among adults and children, especially in wealthy industrialized countries with a high production of widely used industrial chemicals such as plasticizers (bisphenols and phthalates), parabens, flame retardants, and pesticides. The main source of human exposure to obesogenic EDCs is through diet, particularly with the consumption of contaminated food such as meat, fish, fruit, vegetables, milk, and dairy products. EDCs can promote obesity by stimulating adipo- and lipogenesis of target cells such as adipocytes and hepatocytes, disrupting glucose metabolism and insulin secretion, and impacting hormonal appetite/satiety regulation. In vitro models still play an essential role in investigating potential environmental obesogens. The review aimed to provide information on currently available two-dimensional (2D) in vitro animal and human cell models applied for studying the mechanisms of obesogenic action of various industrial chemicals such as food contaminants. The advantages and limitations of in vitro models representing the crucial endocrine tissue (adipose tissue) and organs (liver and pancreas) involved in the etiology of obesity and metabolic diseases, which are applied to evaluate the effects of obesogenic EDCs and their disruption activity, were thoroughly and critically discussed.

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.

Association of Organochlorine Pesticides With Genetic Markers of Endoplasmic Reticulum Stress in Type 2 Diabetes Mellitus: A Case-Control Study Among the North-Indian Population

BACKGROUND

Organochlorine pesticides (OCPs) have been long linked to type 2 diabetes mellitus (T2DM); however, this relation at the molecular level has not been explored yet. Endoplasmic reticulum (ER) stress and pro-inflammatory pathways are considered vital ones in the pathogenesis of T2DM. We aimed to investigate the existence of any association between OCPs, ER stress, and pro-inflammatory pathways in subjects with known T2DM.

METHODS

Seventy subjects each with T2DM and normal glucose tolerance were recruited from the surgery department. Their visceral adipose tissue was collected intraoperatively. OCP concentration, ER stress, and pro-inflammatory markers were analyzed and compared between two study groups.

RESULTS

We found 18 OCPs and their metabolites in visceral adipose tissue samples of study participants. The levels of δ-HCH, heptachlor, endrin, and p,p'DDT were significantly higher in the T2DM group and were also positively correlated with fasting and postprandial plasma glucose levels (p < 0.01). We observed a positive association of δ-HCH (p < 0.01), heptachlor (p < 0.05), and endrin (p < 0.05) with central adiposity and ER stress markers. However, we failed to establish the correlation of OCPs with any of the pro-inflammatory markers.

CONCLUSION

The existence and simultaneous complex correlation of OCPs with ER stress may explain their role in the pathogenesis of T2DM, revealing the persistence of the gene-environment interaction in the etiology of T2DM.