Bisphenol A disturbs metabolism of primary rat adipocytes without affecting adipokine secretion

Integrated In-Silico and In Vitro analysis to Decipher the contribution of bisphenol-A in cervical cancer

Bisphenol A (BPA) is a synthetic chemical widely used as a monomer for producing polycarbonate plastics. The present investigation employed an in-silico approach to identify BPA-responsive genes and comprehend the biological functions affected using in vitro studies. A Comparative Toxicogenomics Database search identified 29 BPA-responsive genes in cervical cancer (CC). Twenty-nine genes were screened using published datasets, and thirteen of those showed differential expression between normal and CC samples. Protein-Protein Interaction Networks (PPIN) analysis identified BIRC5, CASP8, CCND1, EGFR, FGFR3, MTOR, VEGFA, DOC2B, WNT5A, and YY1 as hub genes. KM-based survival analysis identified that CCND, EGFR, VEGFA, FGFR3, DOC2B, and YY1 might affect CC patient survival. SiHa and CaSki cell proliferation, migration, and invasion were all considerably accelerated by BPA exposure. Changes in cell morphology, remodeling of the actin cytoskeleton, increased number and length of filopodia, elevated intracellular reactive oxygen species and calcium, and lipid droplet accumulation were noted upon BPA exposure. BPA treatment upregulated the expression of epithelial to mesenchymal transition pathway members and enhanced the nuclear translocation of CTNNB1. We showed that the enhanced migration and nuclear translocation of CTNNB1 upon BPA exposure is a calcium-dependent process. The present study identified potential BPA-responsive genes and provided novel insights into the biological effects and mechanisms affected by BPA in CC. Our study raises concern over the use of BPA.

Bombesin-like receptor 3 expression induced by bisphenol A is likely associated with reduced cell proliferation by inhibiting DNA synthesis and inducing inflammation in liver cells

BACKGROUND

Bisphenol A (BPA) is an exogenous endocrine disruptor mimicking hormones closely associated with health complications, such as cancer progression. BPA is also related to an increase in the prevalence of obesity-related diseases due to its obesogenic action. Bombesin-like receptor 3 (BRS3) is an important factor that should be considered in the adipogenic gene network, as depletion of this gene alters adiposity.

METHODS

Therefore, the present study aimed to investigate the messenger ribonucleic acid (mRNA) expression of BRS3 in human liver THLE-2 cells post-BPA treatment by real-time polymerase chain reaction. The effects of BPA on the levels of pro-inflammatory proteins, interleukin 6 (IL6) and CC motif chemokine ligand 2 (CCL2), in conditioned media of BPA-treated THLE-2 cells and deoxyribonucleic acid (DNA) synthesis in replicating BPA-treated THLE-2 cells during the cell cycle were also examined by enzyme-linked immunosorbent assay (ELISA) and flow cytometry, respectively.

RESULTS

The study found that the mRNA expression of BRS3 was increased in THLE-2 cells treated with BPA. The study also showed that the expression levels of IL6 and CCL2 reached an optimum level in the conditioned media of BPA-treated THLE-2 cells after 48 h of treatment. Subsequently, the DNA synthesis analysis showed that bromodeoxyuridine/propidium iodide (BrdU/PI) stained positive cells were decreased in BPA-treated THLE-2 cells at 72 h of treatment.

CONCLUSION

The study demonstrates that BRS3 expression induced by BPA is likely associated with reduced cell proliferation by inhibiting DNA synthesis and inducing cellular inflammation in liver cells.

[Synthetic phenolic compounds perturb lipid metabolism and induce obesogenic effects]

Given continuous development in society and the economy, obesity has become a global epidemic, arousing great concern. In addition to genetic and dietary factors, exposure to environmental chemicals is associated with the occurrence and development of obesity. Current research has indicated that some chemicals with endocrine-disrupting effects can affect lipid metabolism in vivo, causing elevated lipid storage. These chemicals are called "environmental obesogens". Synthetic phenolic compounds (SPCs) are widely used in industrial and daily products, such as plastic products, disinfectants, pesticides, food additives, and so on. The exposure routes of SPCs to the human body may include food and water consumption, direct skin contact, etc. Their unintended exposure could cause harmful effects on human health. As a type of endocrine disruptor, SPCs interfere with adipogenesis and lipid metabolism, exhibiting the characteristics of environmental obesogens. Because SPCs have similar phenolic structures, gathering information on their influences on lipid metabolism would be helpful to understand their structure-related effects. In this review, three commonly used research methods for screening environmental obesogens, including in vitro testing for molecular interactions, cell adipogenic differentiation models, and in vivo studies on lipid metabolism, are summarized, and the advantages and disadvantages of these methods are compared and discussed. Based on both in vitro and in vivo data, three types of SPCs, including bisphenol A (BPA) and its analogues, alkylphenols (APs), and synthetic phenolic antioxidants (SPAs), are systematically discussed in terms of their ability to disrupt adipogenesis and lipid metabolism by focusing on adipose and hepatic tissues, among others. Common findings on the effects of these SPCs on adipocyte differentiation, lipid storage, hepatic lipid accumulation, and liver steatosis are described. The underlying toxicological mechanisms are also discussed from the aspects of nuclear receptor transactivation, inflammation and oxidative stress regulation, intestinal microenvironment alteration, epigenetic modification, and some other signaling pathways. Future research to increase public knowledge on the obesogenic effects of emerging chemicals of concern is encouraged.

A Rare Olive Compound Oleacein Improves Lipid and Glucose Metabolism, and Inflammatory Functions: A Comprehensive Whole-Genome Transcriptomics Analysis in Adipocytes Differentiated from Healthy and Diabetic Adipose Stem Cells

Oleacein (OLE), a rare natural compound found in unfiltered extra virgin olive oil, has been shown to have anti-inflammatory and anti-obesity properties. However, little is known regarding the mechanisms by which OLE influences metabolic processes linked to disease targets, particularly in the context of lipid metabolism. In the present study, we conducted whole-genome DNA microarray analyses in adipocytes differentiated from human adipose-derived stem cells (hASCs) and diabetic hASCs (d-hASCs) to examine the effects of OLE on modulating metabolic pathways. We found that OLE significantly inhibited lipid formation in adipocytes differentiated from both sources. In addition, microarray analysis demonstrated that OLE treatment could significantly downregulate lipid-metabolism-related genes and modulate glucose metabolism in both adipocyte groups. Transcription factor enrichment and protein-protein interaction (PPI) analyses identified potential regulatory gene targets. We also found that OLE treatment enhanced the anti-inflammatory properties in adipocytes. Our study findings suggest that OLE exhibits potential benefits in improving lipid and glucose metabolism, thus holding promise for its application in the management of metabolic disorders.

Impact of combined chronic exposure to low-dose bisphenol A and fructose on serum adipocytokines and the energy target metabolome in white adipose tissue

Background: Adipose tissue is a dynamic endocrine organ that plays a key role in regulating metabolic homeostasis. Previous studies confirmed that bisphenol A (BPA) or fructose can interfere with the function of adipose tissue. Nonetheless, knowledge on how exposure to BPA and fructose impacts energy metabolism in adipose tissue remains limited.Purpose: To determine impact of combined chronic exposure to low-dose bisphenol A and fructose on serum adipocytokines and the energy target metabolome in white adipose tissue.Method: 57 energy metabolic intermediates in adipose tissue and 7 adipocytokines in serum from Sprague Dawley rats were examined after combined exposure to two levels of BPA (lower dose: 0.25, and higher dose: 25 μg/kg every other day) and 5% fructose for 6 months.Results: combined exposure to lower-dose BPA and fructose significantly increased omentin-1, pyruvic acid, adenosine triphosphate (ATP), adenosine monophosphate (AMP), inosine monophosphate (IMP), inosine, and l-lactate; however, these parameters were not significantly affected by higher-dose BPA combined with fructose. Interestingly, the level of succinate (an intermediate of the citric acid cycle) increased dose-dependently in adipose tissue, and the level of apelin 13 (a versatile adipocytokine) decreased dose-dependently in serum after combined exposure to BPA and fructose. Phosphoenolpyruvic acid, phenyl-lactate, and ornithine were significantly correlated with asprosin, omentin-1, apelin, apelin 13, and adiponectin, while l-tyrosine was significantly correlated with irisin and a-FABP under combined exposure to BPA and fructose.Conclusions: these findings indicated that lower-dose BPA combined with fructose could amplify the impact on glycolysis, energy storage, and purine nucleotide biosynthesis in adipose tissue, and adipocytokines, such as omentin-1 and apelin 13, may be related to metabolic interference induced by BPA and fructose exposure.

Association of serum bisphenol A levels with incident overweight and obesity risk and the mediating effect of adiponectin

BACKGROUND

Existing cross-sectional studies indicated a positive association of bisphenol A (BPA) with overweight and obesity. However, the relationship and potential mechanisms underlying this association remain to be elucidated in prospective studies.

OBJECTIVE

This study was designed to investigate whether serum BPA is associated with incident overweight and obesity risk, and to further explore whether adiponectin plays a mediating role in the association.

METHODS

We measured blood BPA and adiponectin in Chinese populations. The association of serum BPA with overweight and obesity risk was evaluated using multivariable logistic regression models. We further examined the mediating effect of adiponectin by causal mediation analysis.

RESULTS

Among 796 participants free of overweight and obesity at baseline, 133 individuals developed overweight and obesity during the follow-up period. Compared with those in the lowest quartile of serum BPA, those in the second and third quartiles were positively associated with incident overweight and obesity risk adjusting for covariates (all P-values < 0.05), whereas this association was not observed in the fourth quartile. Further spline analysis showed an inverted U-shaped dose-response relationship (P_non-linear = 0.04). Furthermore, each unit of serum log₁₀-transformed BPA levels was associated with higher changes in waist-to-height ratio and body roundness index (all P-values < 0.05). Mediation analysis indicated significant indirect effects of adiponectin on the associations of BPA with overweight and obesity prevalence (mediation proportion: 46.08%; P = 0.02), and BMI levels (mediation proportion: 30.32%; P = 0.03).

CONCLUSION

Serum BPA displayed a positive association with incident overweight and obesity risk in a non-monotonic pattern, and adiponectin might mediate the association. Further mechanistic studies are warranted.

Regulatory Effects of Metformin, an Antidiabetic Biguanide Drug, on the Metabolism of Primary Rat Adipocytes

Metformin is a biguanide compound commonly applied in humans with type 2 diabetes. The drug affects different tissues, including fat tissue. The direct influence of metformin on cells of fat tissue, i.e., adipocytes, is poorly elucidated. In the present study, the short-term (4-h) effects of metformin on lipogenesis, glucose transport, lipolysis, and lactate release in primary rat adipocytes were explored. It was demonstrated that metformin reduced insulin-induced lipogenesis and increased glucose transport into adipocytes. The tested compound also decreased lactate release from fat cells. It was shown that metformin substantially limited lipolysis stimulated by epinephrine (adrenergic receptor agonist) and dibutyryl-cAMP (direct activator of protein kinase A). Moreover, metformin decreased the lipolytic process triggered by DPCPX (adenosine A1 receptor antagonist). In the case of each lipolytic stimulator, the drug evoked a similar inhibitory effect in the presence of 3 and 12 mM glucose. The lipolytic response of adipocytes to epinephrine was also found to be reduced by metformin when glucose was replaced by alanine. It was demonstrated that the tested compound limits the release of both glycerol and fatty acids from fat cells. The results of the present study provided evidence that metformin significantly affects the metabolism of primary rat adipocytes. Its action covers processes related to lipid accumulation and release and occurs after relatively short-term exposure.

Hyperinsulinemia: beneficial or harmful or both on glucose homeostasis

Insulin, a principal anabolic hormone produced by pancreatic β-cells, has a primary function of storage of nutrients following excessive energy intake. Pre- or early type 2 diabetes stages present hyperinsulinemia (β-cell dysfunction) and insulin resistance. Initiation of hyperinsulinemia is triggered by a loss of first-phase glucose-stimulated insulin secretion with altered membrane ion channel distribution. More factors, including insulin resistance and excessive proliferation of β-cells, deteriorate the hyperinsulinemia, whereas the hyperinsulinemia contributes to further development of insulin resistance and type 2 diabetes; to develop eventually late-stage diabetes with absolute insulin deficiency. In this mini-review, the major focus was put on the causes and pathophysiology of hyperinsulinemia, and the metabolic consequences and current treatment of hyperinsulinemia were discussed. The data used in this narrative review were collected mainly from relevant discoveries in the past 3 years.

Triglyceride profiles are associated with subacute exposure to bisphenol A in healthy young adults

Conflicted results from previous epidemiological studies call for mechanistic evidence to associate exposure to bisphenol A (BPA) with cardiometabolic diseases. In this natural experiment among healthy travelers from Los Angeles (LA) to Beijing, we collected paired urine and blood samples before their departure, 6-8 weeks after their arrival to Beijing, and 4-7 weeks after their return to LA for the assessment of urinary BPA and lipidome in the serum fraction of blood, to study the effects of drastically changed BPA exposure on the lipid metabolism in relation to the development of cardiometabolic disorders. We used linear mixed-effects models with random intercepts for participant and phase to examine the associations between urinary BPA and serum lipidome. Among 744 lipid species from seven classes, triglyceride (TGs) species showed the strongest associations with BPA exposure. The elevation in BPA exposure was associated with increases in TGs with short carbon chains or few double bonds, and decreases in TGs with long carbon chains or many double bonds. A significant linear relationship was observed between BPA-associated TG changes and the number of carbons and double-bonds in the acyl chain. No modification effects of gender but of body mass index (BMI) were observed on the associations between BPA exposure and TGs. This interdisciplinary environmental research substantiated the cardiometabolic effects of BPA according to the perturbations of TG profiling.

Hemin attenuates response of primary rat adipocytes to adrenergic stimulation

Hemin is an activator of heme oxygenase-1 (HO-1), an enzyme catalyzing heme degradation. Up-regulation of HO-1 is observed in response to various pathological conditions. Moreover, pharmacological activation of HO-1 is associated with numerous beneficial effects in the organism. Hemin was shown to exert, among other, anti-diabetic and anti-obesity properties. These effects are strongly linked with adipose tissue. However, the direct influence of hemin on metabolism of the fat cells have not been explored. The present study aimed to determine the short-term effects of hemin on metabolism of the primary rat adipocytes. We focused on processes directly related to lipid accumulation, such as lipogenesis and lipolysis. For this purpose, the isolated cells were subjected for 2 h to 40 µM hemin, and effects of this compound on insulin-stimulated glucose conversion to lipids, lactate release, lipolysis induced by various stimuli, and also on the antilipolytic action of insulin were determined. It was shown that hemin did not affect insulin-induced lipogenesis and lactate release. However, hemin significantly decreased lipolysis stimulated by epinephrine. The inhibitory effect of hemin on epinephrine-induced lipolysis was not abolished in the presence of SnMP, an inhibitor of HO-1, which suggests hemin action irrespective of this enzyme. Similar inhibitory effects on epinephrine-induced lipolysis were observed in the presence of 3 and 12 mM glucose. Moreover, hemin was shown to reduce epinephrine-induced lipolysis also when glucose was replaced by alanine or by succinate. Apart from changes in epinephrine action, it was found that the lipolytic response of the adipocytes to isoproterenol was also diminished by hemin. However, hemin failed to affect lipolysis stimulated by dibutyryl-cAMP (a direct activator of protein kinase A), forskolin (an activator of adenylate cyclase), and also by DPCPX (an adenosine A₁ receptor antagonist). Additionally, epinephrine-induced lipolysis was shown to be decreased by insulin, and this effect was deepened in the presence of hemin. These results indicate that short-term exposure of the adipocytes to hemin does not affect processes related to glucose metabolism, such as lipogenesis and lactate release. However, hemin was found to decrease the lipolytic response to adrenergic stimulation, which is associated with reduced lipid release from adipocytes. Moreover, our results indicate that hemin is also capable of diminishing the exaggerated lipolysis, which occurs in the presence of supraphysiological concentrations of glucose.