Haptoglobin deficiency determines changes in adipocyte size and adipogenesis

Expression of obesity- and type-2 diabetes-associated genes in omental adipose tissue of individuals with obesity

AIMS

Obesity and type 2 diabetes mellitus are two pathologies that share metabolic abnormalities in most of the cases; however, there are differences as well. Some studies have reported that approximately 30% of obese patients have normal glucose and lipid levels in blood despite an accumulation of abdominal adipose tissue. Here, we compare the gene expression in adipose tissue of several genes associated with obesity and/or diabetes between obese patients without T2D and obese patients with T2D.

METHODS

Omental adipose tissue was collected during the patients elective bariatric surgery. Gene expression was determined by real-time PCR. Phenotypic variables were correlated with gene expression and 2^^-ΔΔCt relative expression analysis between groups was performed.

RESULTS

The stronger correlations in the obese without T2D or reference group was between ICAM1 and HbA1c; HP and TC and LDL while in the obese with diabetes or case group the correlation occurred between CSF1 and BMI. A correlation between HP and TC was found in the case group as well. The expression of VEGFA, CCND2, IL1R1 and PTEN was downregulated in the obese with T2D group.

CONCLUSIONS

This study identified genes whose expression is different between obese subjects with and without diabetes. Those genes are related to inflammation, cholesterol transport, adipocyte differentiation/expansion and browning.

Protein Expression of AEBP1, MCM4, and FABP4 Differentiate Osteogenic, Adipogenic, and Mesenchymal Stromal Stem Cells

Mesenchymal stem cells (MSCs) gain an increasing focus in the field of regenerative medicine due to their differentiation abilities into chondrocytes, adipocytes, and osteoblastic cells. However, it is apparent that the transformation processes are extremely complex and cause cellular heterogeneity. The study aimed to characterize differences between MSCs and cells after adipogenic (AD) or osteoblastic (OB) differentiation at the proteome level. Comparative proteomic profiling was performed using tandem mass spectrometry in data-independent acquisition mode. Proteins were quantified by deep neural networks in library-free mode and correlated to the Molecular Signature Database (MSigDB) hallmark gene set collections for functional annotation. We analyzed 4108 proteins across all samples, which revealed a distinct clustering between MSCs and cell differentiation states. Protein expression profiling identified activation of the Peroxisome proliferator-activated receptors (PPARs) signaling pathway after AD. In addition, two distinct protein marker panels could be defined for osteoblastic and adipocytic cell lineages. Hereby, overexpression of AEBP1 and MCM4 for OB as well as of FABP4 for AD was detected as the most promising molecular markers. Combination of deep neural network and machine-learning algorithms with data-independent mass spectrometry distinguish MSCs and cell lineages after adipogenic or osteoblastic differentiation. We identified specific proteins as the molecular basis for bone formation, which could be used for regenerative medicine in the future.

Causal Association of Haptoglobin With Obesity in Mexican Children: A Mendelian Randomization Study

CONTEXT

Little is known about the association between haptoglobin level and cardiometabolic traits. A previous genome-wide association study identified rs2000999 in the HP gene as the stronger genetic contributor to serum haptoglobin level in European populations.

OBJECTIVE AND DESIGN

We investigated the association of HP rs2000999 with serum haptoglobin and childhood and adult obesity in up to 540/697 and 592/691 Mexican cases and controls, respectively. Anthropometric and biochemical data were collected. Serum haptoglobin was measured by an immunoturbidimetry assay. HP rs2000999 was genotyped using the TaqMan technology. Mendelian randomization analysis was performed using the Wald and inverse variance weighting methods.

RESULTS

Haptoglobin level was positively associated with childhood and adult obesity. HP rs2000999 G allele was positively associated with haptoglobin level in children and adults. HP rs2000999 G allele was positively associated with childhood but not adult obesity. The association between HP rs2000999 and childhood obesity was removed after adjusting for haptoglobin level. In a Mendelian randomization analysis, haptoglobin level genetically predicted by HP rs2000999 showed a significant causal effect on childhood obesity by the Wald and inverse variance weighting methods.

CONCLUSION

Our data provide evidence for the first time for a causal positive association between serum haptoglobin level and childhood obesity in the Mexican population. Our study contributes to the genetic elucidation of childhood obesity and proposes haptoglobin as an important biomarker and treatment target for obesity.

Sick fat: the good and the bad of old and new circulating markers of adipose tissue inflammation

Adipose tissue (AT) is one of the largest endocrine organs contributing to metabolic homeostasis. The functional pleiotropism of AT depends on its ability to secrete a large number of hormones, cytokines, extracellular matrix proteins and growth factors, all influencing many local and systemic physiological and pathophysiological processes. In condition of chronic positive energy balance, adipocyte expansion, hypoxia, apoptosis and stress all lead to AT inflammation and dysfunction, and it has been demonstrated that this sick fat is a main risk factor for many metabolic disorders, such as type 2 diabetes mellitus, fatty liver, cardiovascular disease and cancer. AT dysfunction is tightly associated with aberrant secretion of bioactive peptides, the adipocytokines, and their blood concentrations often reflect the expression in the AT. Despite the existence of an association between AT dysfunction and systemic pro-inflammatory state, most of the circulating molecules detectable in obese and dysmetabolic individuals do not identify specifically the condition of sick fat. Based on this premise, this review provides a concise overview of "classic" and novel promising adipocytokines associated with AT inflammation and discusses possible critical approaches to their interpretation in clinical practice.

Influence of Obesity on Serum Concentrations of Acute-Phase Proteins in Horses

Obesity in human and veterinary medicine is one of the most complex challenges within emerging diseases in the context of health. The problem of obesity in horses results in severe comorbidities; therefore, acute-phase proteins should be investigated for fluctuations increasing or decreasing by at least 25% in response to inflammation; these are candidates for future biomarkers and might provide new perspectives on early diagnosis and prognosis. Serum samples were analyzed in nine healthy animals (C) and nine obese animals (O). The proteins were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and the concentrations determined by computerized densitometry; matrix assisted laser desorption ionization time of flight mass spectrometry/TOF mass spectrometry was performed to identify the proteins, and the results obtained were compared to the Equidae and Metazoa taxon protein database deposited in UNIPROT using the MASCOT application. Three proteins presented a difference between the groups; ceruloplasmin (Cp), α₁-antitrypsin (α₁-antitryp), and haptoglobin (Hp). The behavior of the Cp and Hp proteins was compatible with the available literature for obesity in other species. The α₁-antitryp protein was positively correlated with leptin, demonstrating the need for further investigations. The initial study of these proteins was important due to the lack of information available on the influence of obesity on inflammatory biomarkers in horses in Brazil; therefore, we sought to verify a possible association between overweight and changes in the studied variables.

Sympathetic inputs regulate adaptive thermogenesis in brown adipose tissue through cAMP-Salt inducible kinase axis

Various physiological stimuli, such as cold environment, diet, and hormones, trigger brown adipose tissue (BAT) to produce heat through sympathetic nervous system (SNS)- and β-adrenergic receptors (βARs). The βAR stimulation increases intracellular cAMP levels through heterotrimeric G proteins and adenylate cyclases, but the processes by which cAMP modulates brown adipocyte function are not fully understood. Here we described that specific ablation of cAMP production in brown adipocytes led to reduced lipolysis, mitochondrial biogenesis, uncoupling protein 1 (Ucp1) expression, and consequently defective adaptive thermogenesis. Elevated cAMP signaling by sympathetic activation inhibited Salt-inducible kinase 2 (Sik2) through protein kinase A (PKA)-mediated phosphorylation in brown adipose tissue. Inhibition of SIKs enhanced Ucp1 expression in differentiated brown adipocytes and Sik2 knockout mice exhibited enhanced adaptive thermogenesis at thermoneutrality in an Ucp1-dependent manner. Taken together, our data indicate that suppressing Sik2 by PKA-mediated phosphorylation is a requisite for SNS-induced Ucp1 expression and adaptive thermogenesis in BAT, and targeting Sik2 may present a novel therapeutic strategy to ramp up BAT thermogenic activity in humans.

Comprehensive Myocardial Proteogenomics Profiling Reveals C/EBPα as the Key Factor in the Lipid Storage of ARVC

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is hereditary cardiomyopathy characterized by the fibro-fatty replacement of the myocardium. A small number of noncomprehensive profiling studies based on human cardiac tissues have been conducted and reported; consequently, ARVC's gene expression pattern characteristics remain largely undocumented. Our study applies large-scaled, quantitative proteomics based on TMT-labeled LC-MS/MS to analyze the left and right ventricular myocardium of four ARVC and four DCM explanted hearts to compare them with normal hearts. Our objective is to reveal the characteristic proteome pattern in ARVC compared with DCM as well as nondiseased heart. We also conducted the RNA sequencing of 10 right ventricles from ARVC hearts paired with four nondiseased donor hearts to validate the proteome results. In a manner similar to that of the well-defined DCM heart failure model, the ARVC model demonstrates the downregulation of mitochondrial function proteins and the effects of many heart failure regulators such as TGFB, RICTOR, and KDM5A. In addition, the inflammatory signaling, especially the complement system, was activated much more severely in ARVC than in DCM. Our most significant discovery was the lipid metabolism reprogramming of both ARVC ventricles in accordance with the upregulation of lipogenesis factors such as FABP4 and FASN. We identified the key upstream regulator of lipogenesis as C/EBPα. Transcriptome profiling verified the consistency with proteome alterations. This comprehensive proteogenomics profiling study reveals that an activation of C/EBPα, along with the upregulation of its lipogenesis targets, accounts for lipid storage and acts as a hallmark of ARVC.

The Multifaceted Haptoglobin in the Context of Adipose Tissue and Metabolism

Obesity is a low chronic inflammatory state because several inflammatory factors are increased in obese subjects, this having important implications for the onset of obesity-associated complications. The source of most of these inflammatory molecules is white adipose tissue (WAT), which upon excessive weight gain, becomes infiltrated with macrophages and lymphocytes and undergoes important changes in its gene expression. Haptoglobin (Hp), a typical marker of inflammation in clinical practice, main carrier of free hemoglobin, and long known to be part of the hepatic acute phase response, perfectly sits in the intersection between obesity and inflammation: it is expressed by adipocytes and its abundance in WAT and in plasma positively relates to the degree of adiposity. In the present review, we will analyze causes and consequences of Hp expression and regulation in WAT and how these relate to the obesity/inflammation paradigm and comorbidities.

Dynamic and extensive metabolic state-dependent regulation of cytokine expression and circulating levels

Cytokines play diverse and critical roles in innate and acquired immunity, and several function within the central nervous system and in peripheral tissues to modulate energy metabolism. The extent to which changes in energy balance impact the expression and circulating levels of cytokines (many of which have pleiotropic functions) has not been systematically examined. To investigate metabolism-related changes in cytokine profiles, we used a multiplex approach to assess changes in 71 circulating mouse cytokines in response to acute (fasting and refeeding) and chronic (high-fat feeding) alterations in whole body metabolism. Refeeding significantly decreased serum levels of IL-22, IL-1α, soluble (s)IL-2Rα, and soluble vascular endothelial growth factor receptor 3 (VEGFR3), but markedly increased granulocyte colony-stimulating factor (G-CSF), IL-1β, chemokine (C-C motif) ligand (CCL2), sIL-1RI, lipocalin-2, pentraxin-3, tissue inhibitor of metalloproteinase (TIMP-1), and serum amyloid protein (SAP) relative to the fasted state. Interestingly, only a few of these changes paralleled the alterations in expression of their corresponding mRNAs. Functional studies demonstrated that central delivery of G-CSF increased, whereas IL-22 decreased, food intake. Changes in food intake were not accompanied by acute alterations in orexigenic (Npy and Agrp) and anorexigenic (Pomc and Cart) neuropeptide gene expression in the hypothalamus. In the context of chronic high-fat feeding, circulating levels of chemokine (C-X-C) ligand (CXCL1), serum amyloid protein A3 (SAA3), TIMP-1, α1-acid glycoprotein (AGP), and A2M were increased, whereas IL-12p40, CCL4, sCD30, soluble receptor for advanced glycation end products (sRAGE), CCL12, CCL20, CX3CL1, IL-16, IL-22, and haptoglobin were decreased relative to mice fed a control low-fat diet. These results demonstrate that both short- and long-term changes in whole body metabolism extensively alter cytokine expression and circulating levels, thus providing a foundation and framework for further investigations to ascertain the metabolic roles for these molecules in physiological and pathological states.

Haptoglobin is required to prevent oxidative stress and muscle atrophy

BACKGROUND

Oxidative stress (OS) plays a major role on tissue function. Several catabolic or stress conditions exacerbate OS, inducing organ deterioration. Haptoglobin (Hp) is a circulating acute phase protein, produced by liver and adipose tissue, and has an important anti-oxidant function. Hp is induced in pro-oxidative conditions such as systemic inflammation or obesity. The role of systemic factors that modulate oxidative stress inside muscle cells is still poorly investigated.

RESULTS

We used Hp knockout mice (Hp-/-) to determine the role of this protein and therefore, of systemic OS in maintenance of muscle mass and function. Absence of Hp caused muscle atrophy and weakness due to activation of an atrophy program. When animals were stressed by acute exercise or by high fat diet (HFD), OS, muscle atrophy and force drop were exacerbated in Hp-/-. Depending from the stress condition, autophagy-lysosome and ubiquitin-proteasome systems were differently induced.

CONCLUSIONS

Hp is required to prevent OS and the activation of pathways leading to muscle atrophy and weakness in normal condition and upon metabolic challenges.