Metabolomics in human SGBS cells as new approach method for studying adipogenic effects: Analysis of the effects of DINCH and MINCH on central carbon metabolism

Growing evidence suggests that exposure to certain metabolism-disrupting chemicals (MDCs), such as the phthalate plasticizer DEHP, might promote obesity in humans, contributing to the spread of this global health problem. Due to the restriction on the use of phthalates, there has been a shift to safer declared substitutes, including the plasticizer diisononyl-cyclohexane-1,2-dicarboxylate (DINCH). Notwithstanding, recent studies suggest that the primary metabolite monoisononyl-cyclohexane-1,2-dicarboxylic acid ester (MINCH), induces differentiation of human adipocytes and affects enzyme levels of key metabolic pathways. Given the lack of methods for assessing metabolism-disrupting effects of chemicals on adipose tissue, we used metabolomics to analyze human SGSB cells exposed to DINCH or MINCH. Concentration analysis of DINCH and MINCH revealed that uptake of MINCH in preadipocytes was associated with increased lipid accumulation during adipogenesis. Although we also observed intracellular uptake for DINCH, the solubility of DINCH in cell culture medium was limited, hampering the analysis of possible effects in the μM concentration range. Metabolomics revealed that MINCH induces lipid accumulation similar to peroxisome proliferator-activated receptor gamma (PPARG)-agonist rosiglitazone through upregulation of the pyruvate cycle, which was recently identified as a key driver of de novo lipogenesis. Analysis of the metabolome in the presence of the PPARG-inhibitor GW9662 indicated that the effect of MINCH on metabolism was mediated at least partly by a PPARG-independent mechanism. However, all effects of MINCH were only observed at high concentrations of 10 μM, which are three orders of magnitudes higher than the current concentrations of plasticizers in human serum. Overall, the assessment of the effects of DINCH and MINCH on SGBS cells by metabolomics revealed no adipogenic potential at physiologically relevant concentrations. This finding aligns with previous in vivo studies and supports the potential of our method as a New Approach Method (NAM) for the assessment of adipogenic effects of environmental chemicals.

Transforming growth factor beta superfamily regulation of adipose tissue biology in obesity

Accumulation of dysfunctional white adipose tissues increases risks for cardiometabolic diseases in obesity. In addition to white, brown or brite adipose tissues are also present in adult humans and increasing their amount may be protective. Therefore, understanding factors regulating the amount and function of each adipose depot is crucial for developing therapeutic targets for obesity and its associated metabolic diseases. The transforming growth factor beta (TGFβ) superfamily, which consists of TGFβ, BMPs, GDFs, and activins, controls multiple aspects of adipose biology. This review focuses on the recent development in understanding the role of TGFβ superfamily in the regulation of white, brite and brown adipocyte differentiation, adipose tissue fibrosis, and adipocyte metabolic and endocrine functions. TGFβ family and their antagonists are produced locally within adipose tissues and their expression levels are altered in obesity. We also discuss their potential contribution to adipose tissue dysfunction in obesity.

Exposure to chronic early-life stress lastingly alters the adipose tissue, the leptin system and changes the vulnerability to western-style diet later in life in mice

Early-life stress (ES) increases the vulnerability to develop psychopathologies and cognitive decline in adulthood. Interestingly, this is often comorbid with metabolic disorders, such as obesity. However, it is unclear whether ES leads to lasting metabolic changes and to what extent this is associated with the ES-induced cognitive impairments. Here, we used an established chronic ES mouse model (from postnatal day (P) 2 to P9) to investigate the short- and long-term effects of ES exposure on parameters of the adipose tissue and the leptin system (i.e. circulating levels and gene expression of leptin and its receptor) in both sexes. Immediately following ES, the offspring exhibited reductions in white adipose tissue (WAT) mass, plasma leptin levels and in leptin mRNA expression in WAT. Furthermore, ES exposure led to increased brown adipose tissue and browning of WAT, which was evident by a drastic increase in uncoupling protein 1 mRNA expression in the inguinal WAT at P9. Notably, the ES-induced reductions in WAT mass, plasma leptin and leptin expression in WAT were sustained into adulthood and were accompanied by changes in body fat distribution, such as a higher ratio between mesenteric WAT and other WATs. Interestingly, while ES exposure increased leptin receptor mRNA expression in the choroid plexus, it was unaltered in the hippocampus. This suggests an adaptation to maintain central leptin homeostasis following ES exposure. In addition, chronic ES exposure resulted in the well-established cognitive impairment in object recognition performance during adulthood, which correlated positively with reductions in WAT mass observed in male, but not in female mice. Finally, to assess if ES leads to a different metabolic phenotype in a moderate obesogenic environment, we measured body fat accumulation of control and ES-exposed mice in response to a moderate western-style diet (WSD) that was provided during adulthood. ES-exposed mice subjected to WSD exhibit a higher increase in adiposity when compared to controls, suggesting that ES exposure might result in a higher vulnerability to develop obesity in a moderate obesogenic environment. To conclude, chronic ES exposure alters parameters of the adipose tissue, leads to central adaptations in leptin regulation and results in higher fat accumulations when exposed to a WSD challenge later in life. A better understanding of these metabolic effects induced by ES might open up new avenues for therapeutic (e.g. nutritional) interventions.

Effects of fermented rooibos (Aspalathus linearis) on adipocyte differentiation

Rooibos (Aspalathus linearis) contains a rich complement of polyphenols, including flavonoids, considered to be largely responsible for its health promoting effects, including combatting obesity. The purpose of this study was to examine the effect of fermented rooibos hot water soluble solids on in vitro adipocyte differentiation by using differentiating 3T3-L1 adipocytes. Hot water soluble solids were obtained when preparing an infusion of fermented rooibos at "cup-of-tea" strength. The major phenolic compounds (>5 mg/g) were isoorientin, orientin, quercetin-3-O-robinobioside and enolic phenylpyruvic acid-2-O-β-D-glucoside. Treatment of 3T3-L1 adipocytes with 10 μg/ml and 100 μg/ml of the rooibos soluble solids inhibited intracellular lipid accumulation by 22% (p<0.01) and 15% (p<0.05), respectively. Inhibition of adipogenesis was accompanied by decreased messenger RNA (mRNA) expression of PPARγ, PPARα, SREBF1 and FASN. Western blot analysis exhibited decreased PPARα, SREBF1 and AMPK protein expression. Impeded glycerol release into the culture medium was observed after rooibos treatment. None of the concentrations of rooibos hot water soluble solids was cytotoxic, in terms of ATP content. Interestingly, the higher concentration of hot water soluble solids increased ATP concentrations which were associated with increased basal glucose uptake. Decreased leptin secretion was observed after rooibos treatment. Our data show that hot water soluble solids from fermented rooibos inhibit adipogenesis and affect adipocyte metabolism, suggesting its potential in preventing obesity.