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ObjectiveHuman white adipose tissue (AT) is a metabolically active organ with distinct depot-specific functions. Despite their locations close to the gastrointestinal tract, mesenteric AT and epiploic AT (epiAT) have only scarcely been investigated. Here, we aim to characterise these ATs in-depth and estimate their contribution to alterations in whole-body metabolism.DesignMesenteric, epiploic, omental and abdominal subcutaneous ATs were collected from 70 patients with obesity undergoing Roux-en-Y gastric bypass surgery. The metabolically well-characterised cohort included nine subjects with insulin sensitive (IS) obesity, whose AT samples were analysed in a multiomics approach, including methylome, transcriptome and proteome along with samples from subjects with insulin resistance (IR) matched for age, sex and body mass index (n=9). Findings implying differences between AT depots in these subgroups were validated in the entire cohort (n=70) by quantitative real-time PCR.ResultsWhile mesenteric AT exhibited signatures similar to those found in the omental depot, epiAT was distinct from all other studied fat depots. Multiomics allowed clear discrimination between the IS and IR states in all tissues. The highest discriminatory power between IS and IR was seen in epiAT, where profound differences in the regulation of developmental, metabolic and inflammatory pathways were observed. Gene expression levels of key molecules involved in AT function, metabolic homeostasis and inflammation revealed significant depot-specific differences with epiAT showing the highest expression levels.ConclusionMulti-omics epiAT signatures reflect systemic IR and obesity subphenotypes distinct from other fat depots. Our data suggest a previously unrecognised role of human epiploic fat in the context of obesity, impaired insulin sensitivity and related diseases.

Most information on molecular processes accompanying and driving adipocyte differentiation are derived from rodent models. Here, a comprehensive analysis of combined transcriptomic and proteomic alterations during adipocyte differentiation in Simpson–Golabi–Behmel Syndrome (SGBS) cells is provided. The SGBS cells are a well‐established and the most widely applied cell model to study human adipocyte differentiation and cell biology. However, the molecular alterations during human adipocyte differentiation in SGBS cells have not yet been described in a combined analysis of proteome and transcriptome. Here a global proteomic and transcriptomic data set comprising relative quantification of a total of 14372 mRNA transcripts and 2641 intracellular and secreted proteins is presented. 1153 proteins and 313 genes are determined as differentially expressed between preadipocytes and the fully differentiated cells including adiponectin, lipoprotein lipase, fatty acid binding protein 4, fatty acid synthase, stearoyl‐CoA desaturase, and apolipoprotein E and many other proteins from the fatty acid synthesis, amino acid synthesis as well as glucose and lipid metabolic pathways. Preadipocyte markers, such as latexin, GATA6, and CXCL6, are found to be significantly downregulated at the protein and transcript level. This multi‐omics data set provides a deep molecular profile of adipogenesis and will support future studies to understand adipocyte function.

Scope Thermal processing of soy milk kills pathogens and denatures anti‐nutrition factors warranting microbiological safety, better digestibility, and longer storage. Additionally, Maillard reactions are triggered, yielding glycated proteins (Amadori/Heyns products) and a heterogeneous group of advanced glycation end‐products (AGEs). These modifications alter the nutritional value, antigenicity, and digestibility of proteins. They also raise concerns about potentially toxic effects. This study aims at characterizing these modifications in proteins from different soy milk products. Methods and results Here, glycation and AGE‐modification sites in the proteome of ultrahigh‐temperature‐treated natural soy milk, soy milk sweetened with hexose (fructose)‐containing sweeteners (SSM), and sucrose as well as soy‐based infant formulas (SIFs) from different manufacturers are reported for the first time. A bottom‐up proteomic approach based on nano reversed‐phase high‐perfomance liquid chromatography‐electrospray ionization‐tandem mass spectrometry (nanoRP‐HPLC‐ESI‐MS/MS) (collision‐induced dissociation (CID) and electron transfer dissociation modes) identified 229 glycated peptides and 128 AGE‐modified peptides resembling 53 proteins. The glycation sites are mainly derived from hexoses, whereas Nδ‐carboxyethylarginine and methylglyoxal‐derived hydroimidazolone are the main AGEs in soy milk. Conclusion The qualitative and quantitative data obtained here indicate that early glycation increases with harsher processing conditions (SIFs) and the addition of hexose‐containing sweeteners (SSMs), whereas the latter sweeteners (but not the harsher processing) triggered more AGE modifications.

Adipokines and apolipoproteins are key regulators and potential biomarkers in obesity and associated diseases and their quantitative assessment is crucial for functional analyses to understand disease mechanisms. Compared to routinely used ELISAs, multiple reaction monitoring (MRM)-based mass spectrometry allows multiplexing and detection of proteins for which antibodies are not available. Thus, we established an MRM method to quantify 9 adipokines and 10 apolipoproteins in human serum. We optimized sample preparation by depleting the two most abundant serum proteins for improved detectability of low abundant proteins. Intra-day and inter-day imprecision were below 16.5%, demonstrating a high accuracy. In 50 serum samples from participants with either normal weight or obesity, we quantified 8 adipokines and 10 apolipoproteins. Significantly different abundances were observed for five adipokines (adipsin, adiponectin, chemerin, leptin, vaspin) and four apolipoproteins (apo-B100/-C2/-C4/-D) between the body mass index (BMI) groups. Additionally, we applied our MRM assay to serum samples from normal weight children and human adipocyte cell culture supernatants to proof the feasibility for large cohort studies and distinct biological matrices. In summary, this multiplexed assay facilitated the investigation of relationships between adipokines or apolipoproteins and phenotypes or clinical parameters in large cohorts, which may contribute to disease prediction approaches in the future.

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