ABSTRACT
During adipogenesis, preadipocytes' cytoskeleton reorganizes in parallel with lipid accumulation. Failure to do so may impact the ability of adipose tissue (AT) to shift between lipid ...storage and mobilization. Here, we identify cytoskeletal transgelin 2 (TAGLN2) as a protein expressed in AT and associated with obesity and inflammation, being normalized upon weight loss. TAGLN2 was primarily found in the adipose stromovascular cell fraction, but inflammation, TGF‐β, and estradiol also prompted increased expression in human adipocytes. Tagln2 knockdown revealed a key functional role, being required for proliferation and differentiation of fat cells, whereas transgenic mice overexpressing Tagln2 using the adipocyte protein 2 promoter disclosed remarkable sex‐dependent variations, in which females displayed “healthy” obesity and hypertrophied adipocytes but preserved insulin sensitivity, and males exhibited physiologic changes suggestive of defective AT expandability, including increased number of small adipocytes, activation of immune cells, mitochondrial dysfunction, and impaired metabolism together with decreased insulin sensitivity. The metabolic relevance and sexual dimorphism of TAGLN2 was also outlined by genetic variants that may modulate its expression and are associated with obesity and the risk of ischemic heart disease in men. Collectively, current findings highlight the contribution of cytoskeletal TAGLN2 to the obese phenotype in a gender‐dependent manner.—Ortega, F. J., Moreno‐Navarrete, J. M., Mercader, J. M., Gómez‐Serrano, M., García‐Santos, E., Latorre, J., Lluch, A., Sabater, M., Caballano‐Infantes, E., Guzmán, R., Macías‐González, M., Buxo, M., Gironés, J., Vilallonga, R., Naon, D., Botas, P., Delgado, E., Corella, D., Burcelin, R., Frühbeck, G., Ricart, W., Simó, R., Castrillon‐Rodríguez, I., Tinahones, F. J., Bosch, F., Vidal‐Puig, A., Malagón, M. M., Peral, B., Zorzano, A., Fernández‐Real, J. M. Cytoskeletal transgelin 2 contributes to gender‐dependent adipose tissue expandability and immune function. FASEB J. 33, 9656–9671 (2019). www.fasebj.org
Human age-related diseases, including obesity and type 2 diabetes (T2DM), have long been associated to mitochondrial dysfunction; however, the role for adipose tissue mitochondria in these conditions ...remains unknown. We have tackled the impact of aging and T2DM on adipocyte mitochondria from obese patients by quantitating not only the corresponding abundance changes of proteins, but also the redox alterations undergone by Cys residues thereof. For that, we have resorted to a high-throughput proteomic approach based on isobaric labeling, liquid chromatography and mass spectrometry. The alterations undergone by the mitochondrial proteome revealed aging- and T2DM-specific hallmarks. Thus, while a global decrease of oxidative phosphorylation (OXPHOS) subunits was found in aging, the diabetic patients exhibited a reduction of specific OXPHOS complexes as well as an up-regulation of the anti-oxidant response. Under both conditions, evidence is shown for the first time of a link between increased thiol protein oxidation and decreased protein abundance in adipose tissue mitochondria. This association was stronger in T2DM, where OXPHOS mitochondrial- vs. nuclear-encoded protein modules were found altered, suggesting impaired mitochondrial protein translocation and complex assembly. The marked down-regulation of OXPHOS oxidized proteins and the alteration of oxidized Cys residues related to protein import through the redox-active MIA (Mitochondrial Intermembrane space Assembly) pathway support that defects in protein translocation to the mitochondria may be an important underlying mechanism for mitochondrial dysfunction in T2DM and physiological aging. The present draft of redox targets together with the quantification of protein and oxidative changes may help to better understand the role of oxidative stress in both a physiological process like aging and a pathological condition like T2DM.
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•First high-throughput redox proteomic analysis of human adipocyte mitochondria.•Thiol protein oxidation is inversely correlated to protein levels in adipocyte mitochondria.•OXPHOS Mitochondrial- vs. nuclear-encoded protein modules are altered in T2DM.•Redox proteomics highlights defects in protein import through the MIA pathway in aging and T2DM.•Complex IV emerges as a common target of oxidative modifications connecting aging and T2DM.
Obesity is increasing exponentially in developed countries and constitutes a public health problem by enhancing the risk for metabolic disorder and cardiovascular disease. Differences in gene ...expression profiles and in metabolic and biochemical properties have been well-described between omental and subcutaneous adipose tissue in humans. Because omental adipose tissue has been strongly associated with the development of insulin resistance, type 2 diabetes and cardiovascular disease, we searched for proteins differentially expressed in these two fat depots using two-dimensional fluorescence difference gel electrophoresis (2D-DIGE) and mass spectrometry (MS). In this analysis, we found 43 proteins, several of which were validated by immunoblotting and immunostaining analyses. Results demonstrated tissue-specific molecular differences in the protein makeup of the two analyzed fat depots mainly related to metabolic processes such as glucose and lipid metabolism, lipid transport, protein synthesis, protein folding, response to stress and inflammation. This suggests higher metabolic activity as well as increased cell stress in the omental compared to the subcutaneous fat. These findings provide some insights into the role of omental fat in abdominal obesity-associated co-morbidities.
Alternative macrophages (M2) express the cluster differentiation (CD) 206 (MCR1) at high levels. Decreased M2 in adipose tissue is known to be associated with obesity and inflammation-related ...metabolic disturbances. Here we aimed to investigate MCR1 relative to CD68 (total macrophages) gene expression in association with adipogenic and mitochondrial genes, which were measured in human visceral VWAT, n = 147 and subcutaneous adipose tissue SWAT, n = 76 and in rectus abdominis muscle (n = 23). The effects of surgery-induced weight loss were also longitudinally evaluated (n = 6).
MCR1 and CD68 gene expression levels were similar in VWAT and SWAT. A higher proportion of CD206 relative to total CD68 was present in subjects with less body fat and lower fasting glucose concentrations. The ratio MCR1/CD68was positively associated with IRS1gene expression and with the expression of lipogenic genes such as ACACA, FASN and THRSP, even after adjusting for BMI. The ratio MCR1/CD68 in SWAT increased significantly after the surgery-induced weight loss (+44.7%; p = 0.005) in parallel to the expression of adipogenic genes. In addition, SWAT MCR1/CD68ratio was significantly associated with muscle mitochondrial gene expression (PPARGC1A, TFAM and MT-CO3). AT CD206 was confirmed by immunohistochemistry to be specific of macrophages, especially abundant in crown-like structures.
A decreased ratio MCR1/CD68 is linked to adipose tissue and muscle mitochondrial dysfunction at least at the level of expression of adipogenic and mitochondrial genes.
Protein expression studies based on the two major intra-abdominal human fat depots, the subcutaneous and the omental fat, can shed light into the mechanisms involved in obesity and its ...co-morbidities. Here we address, for the first time, the identification and validation of reference proteins for data standardization, which are essential for accurate comparison of protein levels in expression studies based on fat from obese and non-obese individuals.
To uncover adipose tissue proteins equally expressed either in omental and subcutaneous fat depots (study 1) or in omental fat from non-obese and obese individuals (study 2), we have reanalyzed our previously published data based on two-dimensional fluorescence difference gel electrophoresis. Twenty-four proteins (12 in study 1 and 12 in study 2) with similar expression levels in all conditions tested were selected and identified by mass spectrometry. Immunoblotting analysis was used to confirm in adipose tissue the expression pattern of the potential reference proteins and three proteins were validated: PARK7, ENOA and FAA. Western Blot analysis was also used to test customary loading control proteins. ENOA, PARK7 and the customary loading control protein Beta-actin showed steady expression profiles in fat from non-obese and obese individuals, whilst FAA maintained steady expression levels across paired omental and subcutaneous fat samples.
ENOA, PARK7 and Beta-actin are proper reference standards in obesity studies based on omental fat, whilst FAA is the best loading control for the comparative analysis of omental and subcutaneous adipose tissues either in obese and non-obese subjects. Neither customary loading control proteins GAPDH and TBB5 nor CALX are adequate standards in differential expression studies on adipose tissue. The use of the proposed reference proteins will facilitate the adequate analysis of proteins differentially expressed in the context of obesity, an aim difficult to achieve before this study.
Expression and activity of the main lipogenic enzymes is paradoxically decreased in obesity, but the mechanisms behind these findings are poorly known. Breast Cancer 1 (BrCa1) interacts with ...acetyl-CoA carboxylase (ACC) reducing the rate of fatty acid biosynthesis. In this study, we aimed to evaluate BrCa1 in human adipose tissue according to obesity and insulin resistance, and in vitro cultured adipocytes.
BrCa1 gene expression, total and phosphorylated (P-) BrCa1, and ACC were analyzed in adipose tissue samples obtained from a total sample of 133 subjects. BrCa1 expression was also evaluated during in vitro differentiation of human adipocytes and 3T3-L1 cells.
BrCa1 gene expression was significantly up-regulated in both omental (OM; 1.36-fold, p = 0.002) and subcutaneous (SC; 1.49-fold, p = 0.001) adipose tissue from obese subjects. In parallel with increased BrCa1 mRNA, P-ACC was also up-regulated in SC (p = 0.007) as well as in OM (p = 0.010) fat from obese subjects. Consistent with its role limiting fatty acid biosynthesis, both BrCa1 mRNA (3.5-fold, p<0.0001) and protein (1.2-fold, p = 0.001) were increased in pre-adipocytes, and decreased during in vitro adipogenesis, while P-ACC decreased during differentiation of human adipocytes (p = 0.005) allowing lipid biosynthesis. Interestingly, BrCa1 gene expression in mature adipocytes was restored by inflammatory stimuli (macrophage conditioned medium), whereas lipogenic genes significantly decreased.
The specular findings of BrCa1 and lipogenic enzymes in adipose tissue and adipocytes reported here suggest that BrCa1 might help to control fatty acid biosynthesis in adipocytes and adipose tissue from obese subjects.
Objective:
This study aimed to define the potential role of PTHrP on adipogenic regulation and to analyze its relationship with obesity and insulin resistance.
Design:
This was a cross-sectional ...study in which visceral (VAT) and subcutaneous (SAT) adipose tissue were extracted from 19 morbidly obese, 10 obese, and 10 lean subjects. PTHrP mRNA levels were measured in VAT and SAT. VAT mesenchymal stem cells and 3T3-L1 cells were differentiated into adipocytes in presence or absence of PTHrP siRNA. PTHrP mRNA and protein levels as well as adipogenic markers were evaluated by Western blotting or qPCR. Immunohistochemistry and immunofluorescence procedures were used for PTHrP intracellular localization.
Results:
Both human VAT and SAT express PTHrP protein mainly in the nucleolar compartment of stromal vascular fraction cells. The highest levels of PTHrP mRNA and protein expression were detected in undifferentiated mesenchymal cells and progressively decreased during adipogenesis. Remarkably, adipogenic differentiation in human mesenchymal stem cells (A-hMSC) was significantly impaired in a pthrp knockdown. PTHrP seems to be related to obesity-associated insulin resistance (IR), given that we found that PTHrP mRNA expression was higher in VAT from morbidly obese with a low IR degree (MO-L-IR) subjects than those from morbidly obese with a high IR degree (MO-H-IR) and lean subjects, and correlated positively with body mass index and hip circumference. We also found that A-hMSC from MO-L-IRs displayed higher adipogenic capacity than those from both MO-H-IRs and leans. In addition, adipogenesis was impaired in VAT from MO-H-IRs, given that mRNA expression levels of key adipogenic regulators were lower than those from MO-L-IR subjects.
Conclusions:
PTHrP could be a potential new therapeutic target for the reprograming of adipogenesis and adipose tissue expansion, thus possibly ameliorating the metabolic syndrome in obese subjects.
Obesity is a main global health issue and an outstanding cause of morbidity and mortality predisposing to type 2 diabetes (T2DM) and cardiovascular diseases. Huge research efforts focused on gene ...expression, cellular signalling and metabolism in obesity have improved our understanding of these disorders; nevertheless, to bridge the gap between the regulation of gene expression and changes in signalling/metabolism, protein levels must be assessed. We have extensively analysed visceral adipose tissue from age-, T2DM- and gender-matched obese patients using high-throughput proteomics and systems biology methods to identify new biomarkers for the onset of T2DM in obesity, as well as to gain insight into the influence of aging and gender in these disorders. About 250 proteins showed significant abundance differences in the age, T2DM and gender comparisons. In diabetic patients, remarkable gender-specific hallmarks were discovered regarding redox status, immune response and adipose tissue accumulation. Both aging and T2DM processes were associated with mitochondrial remodelling, albeit through well-differentiated proteome changes. Systems biology analysis highlighted mitochondrial proteins that could play a key role in the age-dependent pathophysiology of T2DM. Our findings could serve as a framework for future research in Translational Medicine directed at improving the quality of life of obese patients.
Obesity is recognized as an epidemic health problem worldwide. In humans, the accumulation of omental rather than subcutaneous fat appears to be tightly linked to insulin resistance, type 2 diabetes ...and cardiovascular disease. Differences in gene expression profiles in the adipose tissue comparing non-obese and obese subjects have been well documented. However, to date, no comparative proteomic studies based on omental fat have investigated the influence of obesity in protein expression. In this work, we searched for proteins differentially expressed in the omental fat of non-obese and obese subjects using 2D-DIGE and MS. Forty-four proteins, several of which were further studied by immunoblotting and immunostaining analyses, showed significant differences in the expression levels in the two groups of subjects. Our findings reveal a clearly distinctive proteomic profile between obese and non-obese subjects which emphasizes: i) reduced metabolic activity in the obese fat, since most down-regulated proteins were engaged in metabolic pathways; and ii) morphological and structural cell changes in the obese fat, as revealed by the functions exerted by most up-regulated proteins. Interestingly, transketolase and aminoacylase-1 represent newly described molecules involved in the pathophysiology of obesity, thus opening up new possibilities in the study of obesity.
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► 2D-DIGE was used for the first time to study obesity based on omental fat. ► Twenty proteins were up-regulated and 24 down-regulated in response to obesity. ► Diminished metabolism is a hallmark of obesity. ► The up-regulated proteins evidence morphological changes in the obese adipocytes. ► TKT and ACY-1 are newly described proteins with an important role in obesity.
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