Analysis of the Human Proteome in Subcutaneous and Visceral Fat Depots in Diabetic and Non-diabetic Patients with Morbid Obesity

Abstract

No longer regarded as simply a storage depot, fat is a dynamic organ acting locally and systemically to modulate energy homeostasis, glucose sensitivity, insulin resistance, and inflammatory pathways. Here, mass spectrometry was used to survey the proteome of patient matched subcutaneous fat and visceral fat in 20 diabetic vs 22 nondiabetic patients with morbid obesity. A similar number of proteins (~600) were identified in each tissue type. When stratified by diabetic status, 19 and 41 proteins were found to be differentially abundant in subcutaneous fat and omentum, respectively. These proteins represent pathways known to be involved in metabolism. Five of these proteins were differentially abundant in both fat depots: moesin, 78 kDa glucose-regulated protein, protein cordon-bleu, zinc finger protein 611, and cytochrome c oxidase subunit 6B1. Three proteins, decorin, cytochrome c oxidase subunit 6B1, and 78 kDa glucose-regulated protein, were further tested for validation by western blot analysis. Investigation of the proteins reported here is expected to expand on the current knowledge of adipose tissue driven biochemistry in diabetes and obesity, with the ultimate goal of identifying clinical targets for the development of novel therapeutic interventions in the treatment of type 2 diabetes mellitus. To our knowledge, this study is the first to survey the global proteome derived from each subcutaneous and visceral adipose tissue obtained from the same patient in the clinical setting of morbid obesity, with and without diabetes. It is also the largest study of diabetic vs nondiabetic patients with 42 patients surveyed.

The human type 2 diabetes-specific visceral adipose tissue proteome and transcriptome in obesity

“…Proteomic studies of human adipose tissues provide an understanding of aberrant signaling pathways associated with DM 6 – 9 . Kim et al performed nano-liquid chromatography-mass spectrometry (LC–MS)/mass spectrometry (MS) analysis of human VAT and generated data suggesting cross-talk among VAT cells associated with early DM pathogenesis 7 .…”

Proteome analysis of human adipocytes identifies depot-specific heterogeneity at metabolic control points

“…There are currently no studies comparing the transcriptomes of paired human VAT, ASAT, and GFAT to better understand the differences in the molecular mechanisms between upper-and lower-body adipose tissues. Previous data-dependent proteomic analyses of whole adipose tissue detected between 17 and 600 proteins and showed that proteins involved in the extracellular matrix (29), glucose metabolism, lipid metabolism, lipid transport, response to stress, and inflammation are differentially expressed between VAT and ASAT (28,30). Proteins involved in metabolic processes such as CES, ALDH1A1, GSTP1, and FABP5 that are also associated with insulin resistance and metabolic syndrome are upregulated in VAT when compared with ASAT (28,30).…”

“…Others have profiled the whole transcriptome of human adipose tissues obtained from visceral and subcutaneous locations (25)(26)(27), which indicated that the genes involved in cellular and embryonic development, connective tissues disorders, cell morphology, lipid droplet formation and mobilization, and angiogenesis-related pathways were differentially regulated between these adipose sites. Cross-sectional analysis of the proteomes from whole VAT and ASAT (28)(29)(30) indicates that proteins associated with glucose and lipid metabolism, lipid transport, response to stress and inflammation, and nuclear receptor activation pathways were differentially regulated, whereas a recent study (31) reported few differences between the ASAT and GFAT proteomes. However, adipose tissue is composed of many cell types, including mature adipocytes, adipocyte precursors (i.e., preadipocytes), immune cells, endothelial cells, and fibroblasts (32), hence analyzing the whole adipose tissue proteome does not accurately represent the proteome of adipocytes.…”

Quantitative proteomic analysis of murine white adipose tissue for peritoneal cancer metastasis

“…Fang et al performed immune-depletion of albumin proteins after delipidation. They identified 637 protein groups in subcutaneous fat and 604 protein groups in omental fat via in-solution digests and single LC-MS runs on an LTQ-XL mass spectrometer [20]. Gomez-Serrano et al .…”

“…Proteomic analysis of adipose tissue has focused almost exclusively on human subjects and animal models of diabetes and other metabolic diseases [19]. The main tissue groups used for analysis in proteomic studies are subcutaneous and omental (visceral) fat depots, which are heavily affected in metabolic diseases [1, 20]. However, adipose tissue function affects several other medical conditions, including inflammatory diseases, parasitic infections, immune responses, and cancer [8, 21–23].…”