Extensive weight loss reveals distinct gene expression changes in human subcutaneous and visceral adipose tissue

The serine protease KLK7 promotes immune cell infiltration in visceral adipose tissue in obesity

Obesity is a major health problem associated with global metabolic dysfunction and increased inflammation. It is thus critical to identify the mechanisms underlying the crosstalk between immune cells and adipose tissue that drive cardiovascular and metabolic dysfunction in obesity. Expression of the kallikrein-related serine protease 7 (KLK7) in adipose tissue is linked to inflammation and insulin resistance in high fat diet (HFD)-fed mice. Here, we engineered mice with a macrophage-specific KLK7 knockout (KLK7MKO) to investigate how KLK7 loss impacts immune cell function and obesity-related pathology. Compared to control mice, we observed lower levels of systemic inflammation, with less infiltration and activation of inflammatory macrophages in HFD-fed KLK7MKO mice, particularly in the epididymal adipose tissue. Mechanistically, we uncover that Klk7 deficiency reduces pro-inflammatory gene expression in macrophages and restricts their migration through higher cell adhesion, hallmark features of macrophages in obese conditions. Importantly, through analyses of 1143 human visceral adipose tissue samples, we uncover that KLK7 expression is associated with pathways controlling cellular migration and inflammatory gene expression. In addition, serum KLK7 levels were strongly correlated with circulating inflammatory markers in a second cohort of 60 patients with obesity and diabetes. Our work uncovers the pro-inflammatory role of KLK7 in controlling inflammatory macrophage polarization and infiltration in visceral obesity, thereby contributing to metabolic disease. Thus, targeting KLK7 to control immune cell activation may dissociate adipose dysfunction from obesity, thereby representing an alternative obesity therapy.

Subcutaneous adipose tissue and skeletal muscle mitochondria following weight loss

Obesity is a major global health issue with various metabolic complications. Both bariatric surgery and dieting achieve weight loss and improve whole-body metabolism, but vary in their ability to maintain these improvements over time. Adipose tissue and skeletal muscle metabolism are crucial in weight regulation, and obesity is linked to mitochondrial dysfunction in both tissues. The impact of bariatric surgery versus dieting on adipose tissue and skeletal muscle mitochondrial metabolism remains to be elucidated. Understanding the molecular pathways that modulate tissue metabolism following weight loss holds potential for identifying novel therapeutic targets in obesity management. This narrative review summarizes current knowledge on mitochondrial metabolism following bariatric surgery and diet-induced weight loss in adipose tissue and skeletal muscle, and sheds light on their respective effects.

Chromatin landscape in paired human visceral and subcutaneous adipose tissue and its impact on clinical variables in obesity

BACKGROUND

Obesity is a global health challenge and adipose tissue exhibits distinct depot-specific characteristics impacting differentially on the risk of metabolic comorbidities.

METHODS

Here, we integrate chromatin accessibility (ATAC-seq) and gene expression (RNA-seq) data from intra-individually paired human subcutaneous (SAT) and omental visceral adipose tissue (OVAT) samples to unveil depot-specific regulatory mechanisms.

FINDINGS

We identified twice as many depot-specific differentially accessible regions (DARs) in OVAT compared to SAT. SAT-specific regions showed enrichment for adipose tissue enhancers involving genes controlling extracellular matrix organization and metabolic processes. In contrast, OVAT-specific regions showed enrichment in promoters linked to genes associated with cardiomyopathies. Moreover, OVAT-specific regions were enriched for bivalent transcription start site and repressive chromatin states, suggesting a "lingering" regulatory state. Motif analysis identified CTCF and BACH1 as most significantly enriched motifs in SAT and OVAT-specific DARs, respectively. Distinct gene sets correlated with important clinical variables of obesity, fat distribution measures, as well as insulin, glucose, and lipid metabolism.

INTERPRETATION

We provide an integrated analysis of chromatin accessibility and transcriptional profiles in paired human SAT and OVAT samples, offering new insights into the regulatory landscape of adipose tissue and highlighting depot-specific mechanisms in obesity pathogenesis.

FUNDING

SS received EU-Scientia postdoctoral Fellowship and project funding from the European Union's Horizon 2020 Research and Innovation program under the Marie Skłodowska-Curie Grant, (agreement No. 801133). LlCP and TR were supported by Helse Sør-Øst grants to Y.B (ID 2017079, ID 278908). MB received funding from grants from the DFG (German Research Foundation)-Projekt number 209933838-SFB 1052 (project B1) and by Deutsches Zentrum für Diabetesforschung (DZD, Grant: 82DZD00601).

Association of Lifestyle-Induced Weight Loss With Gene Expression in Subcutaneous Adipose Tissue in Metabolic Syndrome

AIMS

Lifestyle-induced weight loss (LIWL) is considered an effective therapy for the treatment of metabolic syndrome (MetS). The role of differentially expressed genes (DEGs) in adipose tissue function and in the success of LIWL in MetS is still unclear. We investigated the effect of 6 months of LIWL on transcriptional regulation in subcutaneous adipose tissue (SAT). Aiming to identify a LIWL-associated "gene signature" in SAT, DEGs were fitted into a linear regression model.

MATERIALS AND METHODS

The study is embedded in a prospective, two-arm, controlled, monocentric, randomized, 6-month interventional trial in individuals with MetS following LIWL. The trial included 43 nonsmoking, nondiabetic men aged 45-55 years with MetS.

RESULTS

In total, we identified 642 DEGs in SAT after 6 months of LIWL. The identified DEGs were validated in two cross-sectional cohorts analyzing SAT from individuals with and without obesity. Gene enrichment analysis of the DEGs revealed the strongest association with cholesterol metabolic processes. Accordingly, DEGs were correlated with the lipid parameters HDL cholesterol, LDL cholesterol, and triglycerides in corresponding serum samples. We identified 3 genes with an AUC of 0.963 (95% CI: 0.906-1.0) associated with a loss of more than 10% of initial body weight that was maintained for at least 12 months after LIWL, namely SUMO3 (Small ubiquitin-related modifier 3), PRKG2 (Protein Kinase CGMP-Dependent 2), and ADAP2 (ArfGAP with Dual PH Domains 2).

CONCLUSION

In summary, we have identified DEGs in SAT after LIWL, which may play an important role in metabolic functions. In particular, altered gene expression in SAT may predict sustained weight loss.

Proteomic profiling reveals alterations in metabolic and cellular pathways in severe obesity and following metabolic bariatric surgery

In this study, we investigated the impact of bariatric surgery on the adipose proteome to better understand the metabolic and cellular mechanisms underlying weight loss following the procedure. A total of 46 patients with severe obesity were included, with samples collected both before and after bariatric surgery. In addition, 15 healthy individuals without obesity who did not undergo surgery served as controls and were studied once. We utilized quantitative liquid chromatography-tandem mass spectrometry analysis to conduct a large-scale proteomic study on abdominal subcutaneous biopsies obtained from the study participants. Our proteomic profiling revealed that among the 2,254 compared proteins, 46 were upregulated and 34 were downregulated 6 months post surgery compared with baseline [false discovery rate (FDR) < 0.01]. We observed a downregulation of proteins associated with mitochondrial integrity, amino acid catabolism, and lipid metabolism in the patients with severe obesity compared with the controls. Bariatric surgery was associated with an upregulation in pathways related to mitochondrial function, protein synthesis, folding and trafficking, actin cytoskeleton regulation, and DNA binding and repair. These findings emphasize the significant changes in metabolic and cellular pathways following bariatric surgery, highlighting the potential mechanisms underlying the observed health improvements postbariatric surgery. The data provided alongside this paper will serve as a valuable resource for the development of targeted therapeutic strategies for obesity and related metabolic complications. ClinicalTrials.gov registration numbers: NCT00793143 (registered on 19 November 2008) (https://clinicaltrials.gov/ct2/show/NCT00793143) and NCT01373892 (registered on 15 June 2011) (https://clinicaltrials.gov/ct2/show/NCT01373892).NEW & NOTEWORTHY Our study investigates the effects of metabolic bariatric surgery on adipose tissue proteins, highlighting the mechanisms driving weight loss postsurgery. Through extensive proteomic analysis of adipose biopsies from patients with severe obesity pre- and postsurgery, alongside healthy subjects without obesity, we identified significant alterations in metabolic pathways. These findings provide insights into potential therapeutic targets for obesity-related complications.

Sex-specific role of epigenetic modification of a leptin upstream enhancer in adipose tissue

OBJECTIVE

Maternal hormonal status can have long-term effects on offspring metabolic health and is likely regulated via epigenetic mechanisms. We elucidated the effects of maternal thyroid hormones on the epigenetic regulation of leptin (Lep) transcription in adipose tissue (AT) and subsequently investigated the role of DNA methylation at a Lep upstream enhancer (UE) in adipocyte biology.

RESULTS

Pregnant mice treated with triiodothyronine (T3) produced offspring with reduced body weight, total fat mass, and gonadal white adipose tissue (gWAT) mass at 6 months of age (treatment: N = 8; control: N = 12). Compared with control offspring, exclusively female offspring of T3-treated mothers presented lower Lep mRNA levels and higher Lep UE methylation in gWAT. In murine preadipocytes, targeted demethylation of the Lep UE via a dCas9-SunTag-TET1 system reduced methylation by ~ 20%, but this effect was insufficient to alter Lep expression or lipid accumulation after differentiation. In human omental visceral AT (OVAT) samples from the Leipzig Obesity BioBank (LOBB, N = 52), LEP UE methylation was associated with body fat percentage, and mediation analysis indicated that leptin serum levels partially mediate this association exclusively in females.

CONCLUSION

Findings from the animal model suggest that maternal thyroid hormones influence offspring gWAT Lep expression in a sex-specific manner, potentially through changes in Lep UE methylation. However, in vitro experiments indicate that Lep UE methylation alone is not sufficient to regulate Lep expression or adipocyte lipid accumulation. In humans with obesity, LEP UE methylation is associated with body fat percentage, with leptin serum levels potentially acting as a mediator exclusively in females.

Understanding Adipose Tissue Dysfunction

Diseases affecting adipose tissue (AT) function include obesity, lipodystrophy, and lipedema, among others. Both a lack of and excess AT are associated with increased risk for developing diseases including type 2 diabetes mellitus, hypertension, obstructive sleep apnea, and some types of cancer. However, individual risk of developing cardiometabolic and other 'obesity-related' diseases is not entirely determined by fat mass. Rather than excess fat accumulation, AT dysfunction may represent the mechanistic link between obesity and comorbid diseases. There are people who remain metabolically healthy despite obesity, whereas people with normal weight or very low subcutaneous AT mass may develop typically obesity-related diseases. AT dysfunction is characterized by adipocyte hypertrophy, impaired subcutaneous AT expandability (ectopic fat deposition), hypoxia, a variety of stress, inflammatory processes, and the release of proinflammatory, diabetogenic, and atherogenic signals. Genetic and environmental factors might contribute to AT heterogeneity either alone or via interaction with intrinsic biological factors. However, many questions remain regarding the mechanisms of AT dysfunction initiation and whether and how it could be reversed. Do AT signatures define clinically relevant subtypes of obesity? Is the cellular composition of AT associated with variation in obesity phenotypes? What roles do environmental compounds play in the manifestation of AT dysfunction? Answers to these and other questions may explain AT disease mechanisms and help to define strategies for improving AT health. This review focuses on recent advances in our understanding of AT biology.

Thyroid hormones are required for thermogenesis of beige adipocytes induced by Zfp423 inactivation

The significance of thyroid hormones (THs) in beige adipocyte thermogenesis remains incompletely understood. We previously reported that THs directly regulate the expression of zinc-finger protein 423 (ZFP423), an anti-thermogenic factor, in adipose tissue. This study investigates the interaction between THs and adrenergic signaling in regulating thermogenic capacity and activation of beige adipocytes formed in response to Zfp423 deletion. We demonstrate that THs are indispensable for uncoupling protein 1 (UCP1)-dependent thermogenesis, leading to increased energy expenditure in mice with adipocyte-specific Zfp423 knockout. Targeted activation of the thyroid receptor isoform TRβ, which plays a central role in the inguinal depot, is sufficient to enhance energy expenditure in hypothyroid Zfp423iAKO mice. Mechanistically, THs and ZFP423 pathways cooperate to regulate early B cell factor 2 (EBF2)-mediated activation of the Ucp1 gene. RNA sequencing (RNA-seq) analysis of human adipose tissue samples supports the relevance of this regulatory network for human adipose tissue plasticity.

Expression of Intelectin-1, also known as Omentin-1, is related to clinical phenotypes such as overweight, obesity, insulin resistance, and changes after bariatric surgery

Intelectin-1 (ITLN1; also Omentin-1, OMNT1) is secreted by adipose tissue (AT) and plays an important role in glucose metabolism regulation, with links to obesity-associated diseases. ITLN1 activity so far has rarely been investigated using RNA-sequencing and in larger cohorts. We evaluated ITLN1 expression among three clinical cohorts of the Leipzig Obesity BioBank-a cross-sectional cohort comprising of 1480 people, a cohort of people with metabolically healthy or unhealthy obesity (31 insulin-sensitive, 42 insulin-resistant individuals with obesity), and a longitudinal two-step bariatric surgery cohort (n = 65). We hypothesized that AT ITLN1 expression is associated with serum omentin-1, clinical parameters associated with obesity, and with weight loss after bariatric surgery. We also investigated the correlation of AT ITLN1 expression with genes related to inflammatory response, lipid metabolism, obesity, and regulation of energy balance. Likewise, we inspected gene group expression and metabolic pathways associated with ITLN1 expression using gene set enrichment and gene correlation analysis. We show that ITLN1 expression differs in VAT and SAT, and should therefore be analyzed separately. Furthermore, ITLN1 expression increases with VAT tissue mass, but is negatively affected by AT tissue dysfunction among individuals with unhealthy obesity, corroborated by interplay with genes related to tissue inflammation. Gene set enrichment and gene correlation analysis of ITLN1 expression suggest that AT ITLN1 expression is related to local inflammatory processes in AT, but also in processes such as regulation of appetite, energy balance, and maintenance of body weight.

Slit3 Fragments Orchestrate Neurovascular Expansion and Thermogenesis in Brown Adipose Tissue

Brown adipose tissue (BAT) represents an evolutionary innovation enabling placental mammals to regulate body temperature through adaptive thermogenesis. Brown adipocytes are surrounded by a dense network of blood vessels and sympathetic nerves that support their development and thermogenic function. Cold exposure stimulates BAT thermogenesis through the coordinated induction of brown adipogenesis, angiogenesis, and sympathetic innervation. However, how these distinct processes are coordinated remains unclear. Here, we identify Slit guidance ligand 3 (Slit3) as a new niche factor that mediates the crosstalk among adipocyte progenitors, endothelial cells, and sympathetic nerves. We show that adipocyte progenitors secrete Slit3 which regulates both angiogenesis and sympathetic innervation in BAT and is essential for BAT thermogenesis in vivo. Proteolytic cleavage of Slit3 generates secreted Slit3-N and Slit3-C fragments, which activate distinct receptors to stimulate angiogenesis and sympathetic innervation, respectively. Moreover, we introduce bone morphogenetic protein-1 (Bmp1) as the first Slit protease identified in vertebrates. In summary, this study underscores the essential role of Slit3-mediated neurovascular network expansion in enabling cold-induced BAT adaptation. The co-regulation of neurovascular expansion by Slit3 fragments provides a bifurcated yet harmonized approach to ensure a synchronized response of BAT to environmental challenges. This study presents the first evidence that adipocyte progenitors regulate tissue innervation, revealing a previously unrecognized dimension of cellular interaction within adipose tissue.

Consequences of COVID-19 on Adipose Tissue Signatures

Since the emergence of coronavirus disease-19 (COVID-19) in 2019, it has been crucial to investigate the causes of severe cases, particularly the higher rates of hospitalization and mortality in individuals with obesity. Previous findings suggest that adipocytes may play a role in adverse COVID-19 outcomes in people with obesity. The impact of COVID-19 vaccination and infection on adipose tissue (AT) is currently unclear. We therefore analyzed 27 paired biopsies of visceral and subcutaneous AT from donors of the Leipzig Obesity BioBank that have been categorized into three groups (1: no infection/no vaccination; 2: no infection but vaccinated; 3: infected and vaccinated) based on COVID-19 antibodies to spike (indicating vaccination) and/or nucleocapsid proteins. We provide additional insights into the impact of COVID-19 on AT biology through a comprehensive histological transcriptome and serum proteome analysis. This study demonstrates that COVID-19 infection is associated with smaller average adipocyte size. The impact of infection on gene expression was significantly more pronounced in subcutaneous than in visceral AT and mainly due to immune system-related processes. Serum proteome analysis revealed the effects of the infection on circulating adiponectin, interleukin 6 (IL-6), and carbonic anhydrase 5A (CA5A), which are all related to obesity and blood glucose abnormalities.

Transcriptional and epigenetic changes after dietary and surgical weight loss interventions in an animal model of obesity

BACKGROUND

Identifying determinants that can predict response to weight loss interventions is imperative for optimizing therapeutic benefit. We aimed to identify changes in DNA methylation and mRNA expression of a subset of target genes following dietary and surgical interventions in high-fat-diet (HFD)-induced obese rats.

METHODS

Forty-two adult Wistar Han male rats were divided into two groups: control rats (n = 7) and obese rats (n = 28), fed a HFD for 10 weeks (t10). Obese rats were randomly subdivided into five intervention groups (seven animals per group): (i) HFD; (ii) very-low-calorie diet (VLCD); (iii) sham surgery, and (iv) sleeve gastrectomy (SG). At week sixteen (t16), animals were sacrificed and tissue samples were collected to analyze changes in DNA methylation and mRNA expression of the selected genes.

RESULTS

By type of intervention, the surgical procedures led to the greatest weight loss. Changes in methylation and/or expression of candidate genes occurred proportionally to the effectiveness of the weight loss interventions. Leptin expression, increased sixfold in the visceral fat of the obese rats, was partially normalized after all interventions. The expression of fatty acid synthase (FASN) and monocyte chemoattractant protein 1 (MCP-1) genes, which was reduced 0.5- and 0.15-fold, respectively, in the liver tissue of obese rats, were completely normalized after weight loss interventions, particularly after surgical interventions. The upregulation of FASN and MCP-1 gene expression was accompanied by a significant reduction in promoter methylation, up to 0.5-fold decrease in the case of the FASN (all intervention groups) and a 0.8-fold decrease in the case of the MCP-1 (SG group).

CONCLUSIONS

Changes in tissue expression of specific genes involved in the pathophysiological mechanisms of obesity can be significantly attenuated following weight loss interventions, particularly surgery. Some of these genes are regulated by epigenetic mechanisms.

Transcriptome Changes and Metabolic Outcomes After Bariatric Surgery in Adults With Obesity and Type 2 Diabetes

Context

Bariatric surgery has been shown to be effective in inducing complete remission of type 2 diabetes in adults with obesity. However, its efficacy in achieving complete diabetes remission remains variable and difficult to predict before surgery.

Objective

We aimed to characterize bariatric surgery-induced transcriptome changes associated with diabetes remission and the predictive role of the baseline transcriptome.

Methods

We performed a whole-genome microarray in peripheral mononuclear cells at baseline (before surgery) and 2 and 12 months after bariatric surgery in a prospective cohort of 26 adults with obesity and type 2 diabetes. We applied machine learning to the baseline transcriptome to identify genes that predict metabolic outcomes. We validated the microarray expression profile using a real-time polymerase chain reaction.

Results

Sixteen patients entered diabetes remission at 12 months and 10 did not. The gene-expression analysis showed similarities and differences between responders and nonresponders. The difference included the expression of critical genes (SKT4, SIRT1, and TNF superfamily), metabolic and signaling pathways (Hippo, Sirtuin, ARE-mediated messenger RNA degradation, MSP-RON, and Huntington), and predicted biological functions (β-cell growth and proliferation, insulin and glucose metabolism, energy balance, inflammation, and neurodegeneration). Modeling the baseline transcriptome identified 10 genes that could hypothetically predict the metabolic outcome before bariatric surgery.

Conclusion

The changes in the transcriptome after bariatric surgery distinguish patients in whom diabetes enters complete remission from those who do not. The baseline transcriptome can contribute to the prediction of bariatric surgery-induced diabetes remission preoperatively.

The Role of Phosphatidylethanolamine N-Methyltransferase (PEMT) and Its Waist-Hip-Ratio-Associated Locus rs4646404 in Obesity-Related Metabolic Traits and Liver Disease

In previous genome-wide association studies (GWAS), genetic loci associated with obesity and impaired fat distribution (FD) have been identified. In the present study, we elucidated the role of the PEMT gene, including the waist-hip-ratio-associated single nucleotide polymorphism rs4646404, and its influence on obesity-related metabolic traits. DNA from 2926 metabolically well-characterized subjects was used for genotyping. PEMT expression was analyzed in paired visceral (vis) and subcutaneous (sc) adipose tissue (AT) from a subset of 574 individuals. Additionally, PEMT expression was examined in vis, sc AT and liver tissue in a separate cohort of 64 patients with morbid obesity and liver disease. An in vitro Pemt knockdown was conducted in murine epididymal and inguinal adipocytes. Our findings highlight tissue-specific variations in PEMT mRNA expression across the three studied tissues. Specifically, vis PEMT mRNA levels correlated significantly with T2D and were implicated in the progression of non-alcoholic steatohepatitis (NASH), in contrast to liver tissue, where no significant associations were found. Moreover, sc PEMT expression showed significant correlations with several anthropometric- and metabolic-related parameters. The rs4646404 was associated with vis AT PEMT expression and also with diabetes-related traits. Our in vitro experiments supported the influence of PEMT on adipogenesis, emphasizing its role in AT biology. In summary, our data suggest that PEMT plays a role in regulating FD and has implications in metabolic diseases.

Laminin α4 Expression in Human Adipose Tissue Depots and Its Association with Obesity and Obesity Related Traits

Laminin α4 (LAMA4) is one of the main structural adipocyte basement membrane (BM) components that is upregulated during adipogenesis and related to obesity in mice and humans. We conducted RNA-seq-based gene expression analysis of LAMA4 in abdominal subcutaneous (SC) and visceral (VIS) adipose tissue (AT) depots across three human sub-cohorts of the Leipzig Obesity BioBank (LOBB) to explore the relationship between LAMA4 expression and obesity (N = 1479) in the context of weight loss (N = 65) and metabolic health (N = 42). We found significant associations of LAMA4 with body fat mass (p < 0.001) in VIS AT; higher expression in VIS AT compared to SC AT; and significant relation to metabolic health parameters e.g., body fat in VIS AT, waist (p = 0.009) and interleukin 6 (p = 0.002) in male VIS AT, and hemoglobin A1c (p = 0.008) in male SC AT. AT LAMA4 expression was not significantly different between subjects with or without obesity, metabolically healthy versus unhealthy, and obesity before versus after short-term weight loss. Our results support significant associations between obesity related clinical parameters and elevated LAMA4 expression in humans. Our work offers one of the first references for understanding the meaning of LAMA4 expression specifically in relation to obesity based on large-scale RNA-seq data.

The Role of NAD+ in Metabolic Regulation of Adipose Tissue: Implications for Obesity-Induced Insulin Resistance

Obesity-induced insulin resistance is among the key factors in the development of type 2 diabetes, atherogenic dyslipidemia and cardiovascular disease. Adipose tissue plays a key role in the regulation of whole-body metabolism and insulin sensitivity. In obesity, adipose tissue becomes inflamed and dysfunctional, exhibiting a modified biochemical signature and adipokine secretion pattern that promotes insulin resistance in peripheral tissues. An important hallmark of dysfunctional obese adipose tissue is impaired NAD+/sirtuin signaling. In this chapter, we summarize the evidence for impairment of the NAD+/sirtuin pathway in obesity, not only in white adipose tissue but also in brown adipose tissue and during the process of beiging, together with correlative evidence from human studies. We also describe the role of PARPs and CD38 as important NAD+ consumers and discuss findings from experimental studies that investigated potential NAD+ boosting strategies and their efficacy in restoring impaired NAD+ metabolism in dysfunctional obese adipose tissue. In sum, these studies suggest a critical role of NAD+ metabolism in adipose biology and provide a basis for the potential development of strategies to restore metabolic health in obesity.

Changes in Branched-Chain Amino Acids One Year after Sleeve Gastrectomy in Youth with Obesity and Their Association with Changes in Insulin Resistance

Adults with obesity have a reduction in branched-chain amino acid (BCAA) levels following metabolic and bariatric surgery (MBS), which is hypothesized to contribute to the metabolic advantages of MBS. We examined this relationship in 62 youth 13-24 years old with severe obesity (47 female) over 12 months. Thirty had sleeve gastrectomy (SG) and 32 were non-surgical controls (NS). We measured fasting insulin, glucose, glycated hemoglobin (HbA1c), isoleucine, leucine, and valine concentrations, and post-prandial insulin and glucose, following a mixed meal tolerance test. Twenty-four-hour food recalls were collected. At baseline, groups did not differ in the intake or the serum levels of BCAAs, HbA1C, HOMA-IR, Matsuda index, insulinogenic index, or oral Disposition index (oDI). Over 12 months, SG vs. NS had greater reductions in serum BCAAs, and SG had significant reductions in BCAA intake. SG vs. NS had greater reductions in HbA1c and HOMA-IR, with increases in the Matsuda index and oDI. In SG, baseline leucine and total BCAA concentrations were negatively correlated with the baseline Matsuda index. Reductions in serum leucine were positively associated with the reductions in HOMA-IR over 12 months. These associations suggest a potential role of BCAA in regulating metabolic health. Reducing dietary intake and serum BCAA concentrations may reduce insulin resistance.

Sex-Specific Effects of the Genetic Variant rs10487505 Upstream of leptin in the Development of Obesity

The SNP rs10487505 in the promotor region of the leptin gene was reported to be associated with decreased circulating leptin and increased body mass index (BMI). However, the phenotypic outcomes affected by rs10487505 in the leptin regulatory pathway have not been systematically studied. Therefore, the aim of this study was to elucidate the influence of rs10487505 on leptin mRNA expression and obesity-related parameters. We genotyped rs10487505 in DNA samples from 1665 patients with obesity and lean controls and measured leptin gene expression in paired samples of adipose tissue (AT, N = 310), as well as circulating leptin levels. We confirm the leptin-lowering effect of rs10487505 in women. In contrast to the previously reported data from population-based studies, in this mainly obese cohort, we describe a lower mean BMI in women carrying the C allele of rs10487505. However, no association of rs10487505 with AT leptin mRNA expression was found. Our data suggest that reduced circulating leptin levels are not a result of the direct silencing of leptin mRNA expression. Furthermore, leptin reduction by rs10487505 does not associate with BMI in a linear manner. Instead, the decreasing effect on BMI might be dependent on the severity of obesity.

Combined genetic deletion of GDF15 and FGF21 has modest effects on body weight, hepatic steatosis and insulin resistance in high fat fed mice

OBJECTIVES

Obesity in humans and mice is associated with elevated levels of two hormones responsive to cellular stress, namely GDF15 and FGF21. Over-expression of each of these is associated with weight loss and beneficial metabolic changes but where they are secreted from and what they are required for physiologically in the context of overfeeding remains unclear.

METHODS

Here we used tissue selective knockout mouse models and human transcriptomics to determine the source of circulating GDF15 in obesity. We then generated and characterized the metabolic phenotypes of GDF15/FGF21 double knockout mice.

RESULTS

Circulating GDF15 and FGF21 are both largely derived from the liver, rather than adipose tissue or skeletal muscle, in obese states. Combined whole body deletion of FGF21 and GDF15 does not result in any additional weight gain in response to high fat feeding but it does result in significantly greater hepatic steatosis and insulin resistance than that seen in GDF15 single knockout mice.

CONCLUSIONS

Collectively the data suggest that overfeeding activates a stress response in the liver which is the major source of systemic rises in GDF15 and FGF21. These hormones then activate pathways which reduce this metabolic stress.

Metabolic Effects of the Waist-To-Hip Ratio Associated Locus GRB14/COBLL1 Are Related to GRB14 Expression in Adipose Tissue

GRB14/COBLL1 locus has been shown to be associated with body fat distribution (FD), but neither the causal gene nor its role in metabolic diseases has been elucidated. We hypothesize that GRB14/COBLL1 may act as the causal genes for FD-related SNPs (rs10195252 and rs6738627), and that they may be regulated by SNP to effect obesity-related metabolic traits. We genotyped rs10195252 and rs6738627 in 2860 subjects with metabolic phenotypes. In a subgroup of 560 subjects, we analyzed GRB14/COBLL1 gene expression in paired visceral and subcutaneous adipose tissue (AT) samples. Mediation analyses were used to determine the causal relationship between SNPs, AT GRB14/COBLL1 mRNA expression, and obesity-related traits. In vitro gene knockdown of Grb14/Cobll1 was used to test their role in adipogenesis. Both gene expressions in AT are correlated with waist circumference. Visceral GRB14 mRNA expression is associated with FPG and HbA1c. Both SNPs are associated with triglycerides, FPG, and leptin levels. Rs10195252 is associated with HbA1c and seems to be mediated by visceral AT GRB14 mRNA expression. Our data support the role of the GRB14/COBLL1 gene expression in body FD and its locus in metabolic sequelae: in particular, lipid metabolism and glucose homeostasis, which is likely mediated by AT GRB14 transcript levels.

Remission of obesity and insulin resistance is not sufficient to restore mitochondrial homeostasis in visceral adipose tissue

Metabolic plasticity is the ability of a biological system to adapt its metabolic phenotype to different environmental stressors. We used a whole-body and tissue-specific phenotypic, functional, proteomic, metabolomic and transcriptomic approach to systematically assess metabolic plasticity in diet-induced obese mice after a combined nutritional and exercise intervention. Although most obesity and overnutrition-related pathological features were successfully reverted, we observed a high degree of metabolic dysfunction in visceral white adipose tissue, characterized by abnormal mitochondrial morphology and functionality. Despite two sequential therapeutic interventions and an apparent global healthy phenotype, obesity triggered a cascade of events in visceral adipose tissue progressing from mitochondrial metabolic and proteostatic alterations to widespread cellular stress, which compromises its biosynthetic and recycling capacity. In humans, weight loss after bariatric surgery showed a transcriptional signature in visceral adipose tissue similar to our mouse model of obesity reversion. Overall, our data indicate that obesity prompts a lasting metabolic fingerprint that leads to a progressive breakdown of metabolic plasticity in visceral adipose tissue.

Adipsin Serum Concentrations and Adipose Tissue Expression in People with Obesity and Type 2 Diabetes

(1) Adipsin is an adipokine that may link increased fat mass and adipose tissue dysfunction to obesity-related cardiometabolic diseases. Here, we investigated whether adipsin serum concentrations and adipose tissue (AT) adipsin mRNA expression are related to parameters of AT function, obesity and type 2 diabetes (T2D). (2) Methods: A cohort of 637 individuals with a wide range of age and body weight (Age: 18–85 years; BMI: 19–70 kg/m2) with (n = 237) or without (n = 400) T2D was analyzed for serum adipsin concentrations by ELISA and visceral (VAT) and subcutaneous (SAT) adipsin mRNA expression by RT-PCR. (3) Results: Adipsin serum concentrations were significantly higher in patients with T2D compared to normoglycemic individuals. We found significant positive univariate relationships of adipsin serum concentrations with age (r = 0.282, p < 0.001), body weight (r = 0.264, p < 0.001), fasting plasma glucose (r = 0.136, p = 0.006) and leptin serum concentrations (r = 0.362, p < 0.001). Neither VAT nor SAT adipsin mRNA expression correlated with adipsin serum concentrations after adjusting for age, sex and BMI. Independent of T2D status, we found significantly higher adipsin expression in SAT compared to VAT (4) Conclusions: Our data suggest that adipsin serum concentrations are strongly related to obesity and age. However, neither circulating adipsin nor adipsin AT expression reflects parameters of impaired glucose or lipid metabolism in patients with obesity with or without T2D.

Impact of Bariatric Surgery on Adipose Tissue Biology

Bariatric surgery (BS) procedures are actually the most effective intervention to help subjects with severe obesity achieve significant and sustained weight loss. White adipose tissue (WAT) is increasingly recognized as the largest endocrine organ. Unhealthy WAT expansion through adipocyte hypertrophy has pleiotropic effects on adipocyte function and promotes obesity-associated metabolic complications. WAT dysfunction in obesity encompasses an altered adipokine secretome, unresolved inflammation, dysregulated autophagy, inappropriate extracellular matrix remodeling and insufficient angiogenic potential. In the last 10 years, accumulating evidence suggests that BS can improve the WAT function beyond reducing the fat depot sizes. The causal relationships between improved WAT function and the health benefits of BS merits further investigation. This review summarizes the current knowledge on the short-, medium- and long-term outcomes of BS on the WAT composition and function.

Loss of lymphocyte cytosolic protein 1 (LCP1) induces browning in 3T3-L1 adipocytes via β3-AR and the ERK-independent signaling pathway

Increased browning of white adipocytes (beiging) is considered a promising therapeutic strategy to fight obesity and its associated metabolic complications. However, the molecular mechanism modulating brown and beige fat-mediated thermogenesis is not fully elucidated. Here, we identified the lymphocyte cytosolic protein 1 (LCP1) as a factor that obstructs fat browning in white adipocytes. LCP1 plays a vital role in non-hematopoietic malignancies, and is also a well-known tumor biomarker; however, evidence regarding its function in adipocytes remains to be elucidated. The current study explores the physiological role of LCP1 in cultured 3T3-L1 white adipocytes, by applying the loss-of-function study using siRNA. Induction of fat browning by LCP1 depletion was evidenced by evaluating the gene and protein expression levels of brown fat-associated markers through real-time qRT-PCR and immunoblot analysis, respectively. We observed that deficiency of LCP1 promotes mitochondrial biogenesis, and significantly enhances expressions of the core brown fat-specific genes (Cd137, Cidea, Cited1, Tbx1, and Tmem26) and proteins (PGC-1α, PRDM16, and UCP1). In addition, deficiency of LCP1 promotes lipid catabolism as well as suppresses adipogenesis and lipogenesis. Loss of LCP1 also ameliorates cellular stress by downregulating JNK and c-JUN in adipocytes, and stimulates apoptosis. A mechanistic study revealed that deficiency of LCP1 induces browning in white adipocytes, independently via β3-AR and the ERK signaling pathway. The current data reveals a previously unknown mechanism of LCP1 in browning of white adipocytes, and highlights the potential of LCP1 as a pharmacotherapeutic target for treating obesity and other metabolic disorders.

Molecular Aspects of Lifestyle and Environmental Effects in Patients With Diabetes: JACC Focus Seminar

Diabetes is characterized as an integrated condition of dysregulated metabolism across multiple tissues, with well-established consequences on the cardiovascular system. Recent advances in precision phenotyping in biofluids and tissues in large human observational and interventional studies have afforded a unique opportunity to translate seminal findings in models and cellular systems to patients at risk for diabetes and its complications. Specifically, techniques to assay metabolites, proteins, and transcripts, alongside more recent assessment of the gut microbiome, underscore the complexity of diabetes in patients, suggesting avenues for precision phenotyping of risk, response to intervention, and potentially novel therapies. In addition, the influence of external factors and inputs (eg, activity, diet, medical therapies) on each domain of molecular characterization has gained prominence toward better understanding their role in prevention. Here, the authors provide a broad overview of the role of several of these molecular domains in human translational investigation in diabetes.

Cholesterol-binding translocator protein TSPO regulates steatosis and bile acid synthesis in nonalcoholic fatty liver disease

Translocator protein (TSPO, 18 kDa) levels increase in parallel with the evolution of simple steatosis (SS) to nonalcoholic steatohepatitis (NASH) in nonalcoholic fatty liver disease (NAFLD). However, TSPO function in SS and NASH is unknown. Loss of TSPO in hepatocytes in vitro downregulated acetyl-CoA acetyltransferase 2 and increased free cholesterol (FC). FC accumulation induced endoplasmic reticulum stress via IRE1A and protein kinase RNA-like ER kinase/ATF4/CCAAT-enhancer-binding protein homologous protein pathways and autophagy. TSPO deficiency activated cellular adaptive antioxidant protection; this adaptation was lost upon excessive FC accumulation. A TSPO ligand 19-Atriol blocked cholesterol binding and recapitulated many of the alterations seen in TSPO-deficient cells. These data suggest that TSPO deficiency accelerated the progression of SS. In NASH, however, loss of TSPO ameliorated liver fibrosis through downregulation of bile acid synthesis by reducing CYP7A1 and CYP27A1 levels and increasing farnesoid X receptor expression. These studies indicate a dynamic and complex role for TSPO in the evolution of NAFLD.

Differential Mitochondrial Gene Expression in Adipose Tissue Following Weight Loss Induced by Diet or Bariatric Surgery

CONTEXT

Mitochondria are essential for cellular energy homeostasis, yet their role in subcutaneous adipose tissue (SAT) during different types of weight-loss interventions remains unknown.

OBJECTIVE

To investigate how SAT mitochondria change following diet-induced and bariatric surgery-induced weight-loss interventions in 4 independent weight-loss studies.

METHODS

The DiOGenes study is a European multicenter dietary intervention with an 8-week low caloric diet (LCD; 800 kcal/d; n = 261) and 6-month weight-maintenance (n = 121) period. The Kuopio Obesity Surgery study (KOBS) is a Roux-en-Y gastric bypass (RYGB) surgery study (n = 172) with a 1-year follow-up. We associated weight-loss percentage with global and 2210 mitochondria-related RNA transcripts in linear regression analysis adjusted for age and sex. We repeated these analyses in 2 studies. The Finnish CRYO study has a 6-week LCD (800-1000 kcal/d; n = 19) and a 10.5-month follow-up. The Swedish DEOSH study is a RYGB surgery study with a 2-year (n = 49) and 5-year (n = 37) follow-up.

RESULTS

Diet-induced weight loss led to a significant transcriptional downregulation of oxidative phosphorylation (DiOGenes; ingenuity pathway analysis [IPA] z-scores: -8.7 following LCD, -4.4 following weight maintenance; CRYO: IPA z-score: -5.6, all P < 0.001), while upregulation followed surgery-induced weight loss (KOBS: IPA z-score: 1.8, P < 0.001; in DEOSH: IPA z-scores: 4.0 following 2 years, 0.0 following 5 years). We confirmed an upregulated oxidative phosphorylation at the proteomics level following surgery (IPA z-score: 3.2, P < 0.001).

CONCLUSIONS

Differentially regulated SAT mitochondria-related gene expressions suggest qualitative alterations between weight-loss interventions, providing insights into the potential molecular mechanistic targets for weight-loss success.

Vertical sleeve gastrectomy induces distinctive transcriptomic responses in liver, fat and muscle

Vertical sleeve gastrectomy (VSG) is the most commonly performed bariatric/metabolic surgery, exhibiting a high rate of diabetes remission in humans. To elucidate the molecular mechanisms of VSG, we performed transcriptomic analysis of the liver, fat, and muscle in VSG mice. C57BL/6 mice fed a high-fat diet were randomly assigned to sham or VSG surgery. The sham-operated mice were fed ad libitum (sham group) or pair-fed (sham-PF group) matching their food intake to the VSG-operated mice. Comparative transcriptomic analysis of the liver, fat, and muscle using RNA sequencing was performed. VSG reduced body weight and improved glucose tolerance compared to the sham group, but not more than the sham-PF group. Improvement in fatty liver and adipose tissue inflammation was comparable between VSG and sham-PF. However, global gene expression profiles showed distinctive changes in the liver, fat, and muscle of the VSG group compared to both the sham or sham-PF groups. The liver showed the most prominent gene expression changes. Immune response-related pathways were commonly upregulated in the three organs of the VSG group compared to the sham or sham-PF. VSG induces organ-specific gene expression changes in the liver, fat, and muscle, which may play critical roles in metabolic improvements after VSG.

Effects of Gut Metabolites and Microbiota in Healthy and Marginal Livers Submitted to Surgery

Microbiota is defined as the collection of microorganisms within the gastrointestinal ecosystem. These microbes are strongly implicated in the stimulation of immune responses. An unbalanced microbiota, termed dysbiosis, is related to the development of several liver diseases. The bidirectional relationship between the gut, its microbiota and the liver is referred to as the gut-liver axis. The translocation of bacterial products from the intestine to the liver induces inflammation in different cell types such as Kupffer cells, and a fibrotic response in hepatic stellate cells, resulting in deleterious effects on hepatocytes. Moreover, ischemia-reperfusion injury, a consequence of liver surgery, alters the microbiota profile, affecting inflammation, the immune response and even liver regeneration. Microbiota also seems to play an important role in post-operative outcomes (i.e., liver transplantation or liver resection). Nonetheless, studies to determine changes in the gut microbial populations produced during and after surgery, and affecting liver function and regeneration are scarce. In the present review we analyze and discuss the preclinical and clinical studies reported in the literature focused on the evaluation of alterations in microbiota and its products as well as their effects on post-operative outcomes in hepatic surgery.

Branched-Chain Amino Acid Oxidation Is Elevated in Adults with Morbid Obesity and Decreases Significantly after Sleeve Gastrectomy

BACKGROUND

Plasma concentrations of branched-chain amino acids (BCAAs) are elevated in obese individuals with insulin resistance (IR) and decrease after bariatric surgery. However, the metabolic mechanisms are unclear.

OBJECTIVES

Our objectives are to compare leucine kinetics between morbidly obese and healthy-weight individuals cross-sectionally, and to prospectively evaluate changes in the morbidly obese after sleeve gastrectomy. We hypothesized that leucine oxidation is slower in obese individuals and increases after surgery.

METHODS

Ten morbidly obese [BMI (in kg/m2) ≥32.5, age 21-50 y] and 10 healthy-weight participants (BMI <25), matched for age (median ∼30 y) but not gender, were infused with [U-13C6] leucine and [2H5] glycerol to quantify leucine and glycerol kinetics. Morbidly obese participants were studied again 6 mo postsurgery. Primary outcomes were kinetic parameters related to BCAA metabolism. Data were analyzed by nonparametric methods and presented as median (IQR).

RESULTS

Participants with obesity had IR with an HOMA-IR (4.89; 4.36-8.76) greater than that of healthy-weight participants (1.32; 0.99-1.49; P < 0.001) and had significantly faster leucine flux [218; 196-259 compared with 145; 138-149 μmol · kg fat-free mass (FFM)-1 · h-1], oxidation (24.0; 17.9-29.8 compared with 16.1; 14.3-18.5 μmol · kg FFM-1 · h-1), and nonoxidative disposal (204; 190-247 compared with 138; 129-140 μmol · kg FFM-1 · h-1) (P < 0.017 for all). After surgery, the morbidly obese had a marked improvement in IR (3.54; 3.06-6.08; P = 0.008) and significant reductions in BCAA concentrations (113; 95-157 μmol/L) and leucine oxidation (9.37; 6.85-15.2 μmol · kg FFM-1 · h-1) (P = 0.017 for both). Further, leucine flux in this group correlated significantly with IR (r = 0.78, P < 0.001).

CONCLUSIONS

BCAA oxidation is not impaired but elevated in individuals with morbid obesity. Plasma BCAA concentrations are lowered after surgery owing to slower breakdown of body proteins as insulin's ability to suppress proteolysis is restored. These findings suggest that IR is the underlying cause and not the consequence of elevated BCAAs in obesity.

Putative positive role of inflammatory genes in fat deposition supported by altered gene expression in purified human adipocytes and preadipocytes from lean and obese adipose tissues

Background

Obesity is a chronic low-grade inflammatory disease that is generally characterized by enhanced inflammation in obese adipose tissue (AT). Here, we investigated alterations in gene expression between lean and obese conditions using mRNA-Seq data derived from human purified adipocytes (ACs) and preadipocytes (preACs).

Results

Total mRNA-seq data were generated with 27 AC and 21 preAC samples purified from human visceral AT collected during resection surgery in cancer patients, where the samples were classified into lean and obese categories by BMI > 25 kg/m². We defined four classes of differentially expressed genes (DEGs) by comparing gene expression between (1) lean and obese ACs, (2) lean and obese preACs, (3) lean ACs and lean preACs, and 4) obese ACs and obese preACs. Based on an analysis of comparison 1, numerous canonical obesity-related genes, particularly inflammatory genes including IL-6, TNF-α and IL-1β, i.e., the genes that are expected to be upregulated in obesity conditions, were found to be expressed at significantly lower levels in obese ACs than in lean ACs. In contrast, some inflammatory genes were found to be expressed at higher levels in obese preACs than lean preACs in the analysis of comparison 2. The analysis of comparisons 3 and 4 showed that inflammatory gene classes were expressed at higher levels in differentiated ACs than undifferentiated preACs under both lean and obese conditions; however, the degree of upregulation was significantly greater for lean than for obese conditions. We validated our observations using previously published microarray transcriptome data deposited in the GEO database (GSE80654).

Conclusions

Taken together, our analyses suggest that inflammatory genes are expressed at lower levels in obese ACs than in lean ACs because lean adipogenesis involves even greater enhancement of inflammatory responses than does obese adipogenesis.

Long-term changes in adipose tissue gene expression following bariatric surgery

OBJECTIVE

Patients undergoing bariatric surgery present long-term metabolic improvements and reduced type 2 diabetes risk, despite long-term weight regain. We hypothesized that part of these protective effects could be linked to altered gene expression in white adipose tissue (WAT).

METHODS

Transcriptomic profiling by gene microarray was performed in abdominal subcutaneous WAT from women before (n = 50) and two (n = 49) and five (n = 38) years after Roux-en-Y gastric bypass (RYGB) surgery as well as in 28 age-matched nonoperated women.

RESULTS

In the obese women, the average body weight decrease was 38 kg 2 years postsurgery followed by an 8 kg weight regain between 2 and 5 years. Most of the long-term changes in WAT gene expression occurred during the first 2 years. However, a subset of genes encoding proteins involved in inflammation displayed a continued decrease between baseline, 2 and 5 years, respectively; that is an expression pattern independent of body weight regain. Expression of 71 of these genes correlated with measurements of adipocyte morphology or serum adipokine levels.

CONCLUSION

The continuous improvement in WAT inflammatory gene expression, despite body weight relapse, may contribute to the sustained effects on adipose morphology after bariatric surgery.

The omentum of obese girls harbors small adipocytes and browning transcripts

Severe obesity (SO) affects about 6% of youth in the United States, augmenting the risks for cardiovascular disease and type 2 diabetes. Herein, we obtained paired omental adipose tissue (omVAT) and abdominal subcutaneous adipose tissue (SAT) biopsies from girls with SO undergoing sleeve gastrectomy (SG), to test whether differences in cellular and transcriptomic profiles between omVAT and SAT depots affect insulin sensitivity differently. Following weight loss, these analyses were repeated in a subgroup of subjects having a second SAT biopsy. We found that omVAT displayed smaller adipocytes compared with SAT, increased lipolysis through adipose triglyceride lipase phosphorylation, reduced inflammation, and increased expression of browning/beiging markers. Contrary to omVAT, SAT adipocyte diameter correlated with insulin resistance. Following SG, both weight and insulin sensitivity improved markedly in all subjects. SAT adipocytes' size became smaller, showing increased lipolysis through perilipin 1 phosphorylation, decreased inflammation, and increased expression in browning/beiging markers. In summary, in adolescent girls with SO, both omVAT and SAT depots showed distinct cellular and transcriptomic profiles. Following weight loss, the SAT depot changed its cellular morphology and transcriptomic profiles into more favorable ones. These changes in the SAT depot may play a fundamental role in the resolution of insulin resistance.

FAM13A affects body fat distribution and adipocyte function

Genetic variation in the FAM13A (Family with Sequence Similarity 13 Member A) locus has been associated with several glycemic and metabolic traits in genome-wide association studies (GWAS). Here, we demonstrate that in humans, FAM13A alleles are associated with increased FAM13A expression in subcutaneous adipose tissue (SAT) and an insulin resistance-related phenotype (e.g. higher waist-to-hip ratio and fasting insulin levels, but lower body fat). In human adipocyte models, knockdown of FAM13A in preadipocytes accelerates adipocyte differentiation. In mice, Fam13a knockout (KO) have a lower visceral to subcutaneous fat (VAT/SAT) ratio after high-fat diet challenge, in comparison to their wild-type counterparts. Subcutaneous adipocytes in KO mice show a size distribution shift toward an increased number of smaller adipocytes, along with an improved adipogenic potential. Our results indicate that GWAS-associated variants within the FAM13A locus alter adipose FAM13A expression, which in turn, regulates adipocyte differentiation and contribute to changes in body fat distribution.

Changes in adipose tissue lipolysis gene expression and insulin sensitivity after weight loss

OBJECTIVE

Insulin resistance is a major pathophysiological link between obesity and its metabolic complications. Weight loss (WL) is an effective tool to prevent obesity-related diseases; however, the mechanisms of an improvement in insulin sensitivity (IS) after weight-reducing interventions are not completely understood. The aim of the present study was to analyze the relationships between IS and adipose tissue (AT) expression of the genes involved in the regulation of lipolysis in obese subjects after WL.

METHODS

Fifty-two obese subjects underwent weight-reducing dietary intervention program. The control group comprised 20 normal-weight subjects, examined at baseline only. Hyperinsulinemic-euglycemic clamp and s.c. AT biopsy with subsequent gene expression analysis were performed before and after the program.

RESULTS

AT expression of genes encoding lipases (PNPLA2, LIPE and MGLL) and lipid-droplet proteins enhancing (ABHD5) and inhibiting lipolysis (PLIN1 and CIDEA) were decreased in obese individuals in comparison with normal-weight individuals. The group of 38 obese participants completed dietary intervention program and clamp studies, which resulted in a significant WL and an improvement in mean IS. However, in nine subjects from this group IS did not improve in response to WL. AT expression of PNPLA2, LIPE and PLIN1 increased only in the group without IS improvement.

CONCLUSIONS

Excessive lipolysis may prevent an improvement in IS during WL. The change in AT PNPLA2 and LIPE expression was a negative predictor of the change in IS after WL.

Relationships between computed tomography-assessed density, abdominal fat volume, and glucose metabolism after sleeve gastrectomy in Japanese patients with obesity

In this study, we investigated the relationships between body weight (BW), computed tomography (CT)-assessed abdominal adipose tissue, and the glycemic metabolic profile in obese Japanese patients following laparoscopic sleeve gastrectomy (LSG). This study analyzed adipose tissue compartments using CT methods before and 1 year after LSG. Thirty obese patients were studied, and variables measured included visceral adipose tissue (VAT), subcutaneous adipose tissue (SAT), density of VAT (VAT-D), and density of SAT (SAT-D). We also examined the parameters in patients according to whether they had type-2 diabetes (T2DM). LSG induced significant losses in BW, SAT, and VAT after LSG. Additionally, SAT-D and VAT-D both increased and fasting plasma glucose (FPG) and HbA1c, but not C-peptide, decreased after surgery. ΔSAT and ΔVAT were positively related, and ΔSAT-D and ΔVAT-D were negatively related to ΔBW and/or FPG. Furthermore, a multivariate regression model showed that total BW loss (TBWL) was closely related to ΔSAT (β = 0.84; p < 0.001) and ΔVAT-D (β = -0.45; p < 0.05) and improvement of FPG was related to ΔVAT (β = 0.61; p < 0.05) after LSG. Finally, ΔFPG was correlated with ΔVAT in 16 T2DM patients (r = 0.58; p < 0.05) but not in non-T2DM patients. TBWL was related to ΔSAT and ΔVAT-D, and improvement of FPG was related to ΔVAT in obese Japanese patients after LSG.

The Potential Use of Metabolic Cofactors in Treatment of NAFLD

Non-alcoholic fatty liver disease (NAFLD) is caused by the imbalance between lipid deposition and lipid removal from the liver, and its global prevalence continues to increase dramatically. NAFLD encompasses a spectrum of pathological conditions including simple steatosis and non-alcoholic steatohepatitis (NASH), which can progress to cirrhosis and liver cancer. Even though there is a multi-disciplinary effort for development of a treatment strategy for NAFLD, there is not an approved effective medication available. Single or combined metabolic cofactors can be supplemented to boost the metabolic processes altered in NAFLD. Here, we review the dosage and usage of metabolic cofactors including l-carnitine, Nicotinamide riboside (NR), l-serine, and N-acetyl-l-cysteine (NAC) in human clinical studies to improve the altered biological functions associated with different human diseases. We also discuss the potential use of these substances in treatment of NAFLD and other metabolic diseases including neurodegenerative and cardiovascular diseases of which pathogenesis is linked to mitochondrial dysfunction.

Serum proteome changes and accelerated reduction of fat mass after laparoscopic gastric plication in morbidly obese patients

Laparoscopic Gastric Plication (LGP) is a relatively new bariatric surgical procedure which no part of the stomach is removed. It is not clearly understood how LGP leads to fatty tissue reduction. We aimed to investigate the impact of LGP on serum proteome and understand molecular mechanisms of LGP-induced weight loss post-surgery. A Prospective observational study of 16 obese individuals who underwent LGP was performed. A Label-free quantitative shotgun proteomics approach was used to compare serum proteome of subjects before surgery with serum of the same individuals 1 to 2 months post-surgery (T1) and 4 to 5 months post-surgery (T2). The proteome analysis revealed that 48 proteins were differentially regulated between pre-surgery and T1, and seven proteins between pre-surgery and T2 of which six proteins were shared between the two timepoints. Among differentially regulated proteins, four proteins (SRGN, FETUB, LCP1 and CFP) have not previously been described in the context of BMI/weight loss. Despite few differences following LGP, most regulated serum proteins are in accordance with alternative weight loss procedures. Pathway analysis revealed changes to lipid- and inflammatory pathways, including PPARα/RXRα, LXR/RXR and FXR/RXR activation, especially at T1. At T2, the pathways related to inflammation and immune system are most affected. SIGNIFICANCE: Among the available clinical therapies for morbid obesity, bariatric surgery is considered as the most effective approach to achieve long-term weight loss, alongside a significant improvement in metabolic syndrome. However, very little is known about the underlying mechanism associated with significant weight loss post-surgery. Understanding such mechanisms could lead to development of safer non-surgical weight loss approaches. We here present the first analysis of the impact of LGP on the serum proteome, to bring new insights into the underlying molecular mechanism. Our findings indicate that LGP has a comprehensive systemic effect based on the blood serum proteome profile which might account for accelerated reduction of fat mass after surgery, thus, food restriction is not the only reason for weight loss following this unique surgical approach. As secretory regions of the stomach are preserved in LGP and it is associated with minimal physiological and anatomical changes, the findings are of high importance in the field of bariatric surgery and weight loss.

Key Genes of Lipid Metabolism and WNT-Signaling Are Downregulated in Subcutaneous Adipose Tissue with Moderate Weight Loss

Smaller cross-sectional studies and bariatric surgery trials suggest that weight loss may change the expression of genes in adipose tissue that have been implicated in the development of metabolic diseases, but well-powered intervention trials are lacking. In post hoc analyses of data from a 12-week dietary intervention trial initially designed to compare metabolic effects of intermittent vs. continuous calorie restriction, we analyzed the effects of overall weight loss on the subcutaneous adipose tissue (SAT) transcriptome. Changes in the transcriptome were measured by microarray using SAT samples of 138 overweight or obese individuals (age range: 35–65 years, BMI range: 25–40, non-smokers, non-diabetics). Participants were grouped post hoc according to the degree of their weight loss by quartiles (average weight loss in quartiles 1 to 4: 0%, −3.2%, −5.9%, and −10.7%). Candidate genes showing differential expression with weight loss according to microarray analyses were validated by reverse transcription quantitative polymerase chain reaction (RT-qPCR), and fold changes (FCs) were calculated to quantify differences in gene expression. A comparison of individuals in the highest vs. the lowest weight loss quartile revealed 681 genes to be differentially expressed (corrected p < 0.05), with 40 showing FCs of at least 0.4. Out of these, expression changes in secreted frizzled-related protein 2 (SFRP2, FC = 0.65, p = 0.006), stearoyl-CoA desaturase (SCD, FC = −1.00, p < 0.001), and hypoxia inducible lipid droplet-associated (HILPDA, FC = −0.45, p = 0.001) with weight loss were confirmed by RT-qPCR. Dietary weight loss induces significant changes in the expression of genes implicated in lipid metabolism (SCD and HILPDA) and WNT-signaling (SFRP2) in SAT.

Saturated Fatty Acid Activates T Cell Inflammation Through a Nicotinamide Nucleotide Transhydrogenase (NNT)-Dependent Mechanism

Circulating fatty acids (FAs) increase with obesity and can drive mitochondrial damage and inflammation. Nicotinamide nucleotide transhydrogenase (NNT) is a mitochondrial protein that positively regulates nicotinamide adenine dinucleotide phosphate (NADPH), a key mediator of energy transduction and redox homeostasis. The role that NNT-regulated bioenergetics play in the inflammatory response of immune cells in obesity is untested. Our objective was to determine how free fatty acids (FFAs) regulate inflammation through impacts on mitochondria and redox homeostasis of peripheral blood mononuclear cells (PBMCs). PBMCs from lean subjects were activated with a T cell-specific stimulus in the presence or absence of generally pro-inflammatory palmitate and/or non-inflammatory oleate. Palmitate decreased immune cell expression of NNT, NADPH, and anti-oxidant glutathione, but increased reactive oxygen and proinflammatory Th17 cytokines. Oleate had no effect on these outcomes. Genetic inhibition of NNT recapitulated the effects of palmitate. PBMCs from obese (BMI >30) compared to lean subjects had lower NNT and glutathione expression, and higher Th17 cytokine expression, none of which were changed by exogenous palmitate. Our data identify NNT as a palmitate-regulated rheostat of redox balance that regulates immune cell function in obesity and suggest that dietary or therapeutic strategies aimed at increasing NNT expression may restore redox balance to ameliorate obesity-associated inflammation.

Role or Synergistic Interaction of Adenosine and Vitamin D3 Alongside High-Intensity Interval Training and Isocaloric Moderate Intensity Training on Metabolic Parameters: Protocol for an Experimental Study

BACKGROUND

Obesity is known as one of the major causes of epidemiologic diseases worldwide; therefore, the introduction of treatment strategies by medical professionals, such as the use of various medicines and exercise programs to reduce fat or prevent obesity, is on the rise. Recently, researchers have shown special interest in assessing the effect of lipolytic adenosine and vitamin D deficiency, as well as the effect of exercise, on decreasing body fat percentage.

OBJECTIVE

This study has been designed to examine the effect of adenosine and vitamin D3 injections, in conjunction with high-intensity interval training and isocaloric moderate-intensity training, on the metabolic parameters of obesity induced by a high-fat diet.

METHODS

This is an experimental study using 92 Wistar rats. At 6 weeks of age, the rats' weights will be recorded, after which they will have 1 week to adapt to their new environment before being divided into 12 groups. The rats will participate in a 2-stage experimental intervention, including a 13-week fattening diet phase followed by a 12-week exercise training phase consisting of an exercise program and the injection of adenosine and vitamin D3. Groups 1 and 2 will have a normal diet, and the other groups will have a diet of 40% fat, with free access to food and water up to the second half of the second stage of the study (end of the sixth week of training). After termination of the interventions, tissue collection and molecular assessments (blood for biochemical, tissues for gene expression analyses, and anthropometrical indexes) will be performed.

RESULTS

The project was initiated in April 2017 and completed in December 2017. Data analysis is under way, and the first results are expected to be submitted for publication in November 2018.

CONCLUSIONS

We hypothesize that weight loss-induced molecular changes and upregulation will be observed in line with an increase in lipolysis and beta oxidation in muscle and fat tissue as a result of performing isocaloric training in drug-receiving rats and groups on a high-fat diet.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

RR1-10.2196/10753.

Alterations in branched-chain amino acid kinetics in nonobese but insulin-resistant Asian men

Background

Branched-chain amino acids (BCAAs) are elevated in the insulin-resistant (IR) state. The reasons for this increase remain unclear, but it may be related to abnormalities in BCAA metabolism and free fatty acid (FFA) metabolism.

Objective

In this study, we quantified BCAA and FFA kinetics of IR and insulin-sensitive (IS) nonobese Asian men with the use of stable-isotope tracers. We hypothesized that in addition to greater substrate flux, the BCAA oxidative pathway is also impaired to account for the higher plasma BCAA concentration in the IR state.

Design

We recruited 12 IR and 14 IS nonobese and healthy Asian men. Oral-glucose-tolerance tests (OGTTs) were performed to quantify insulin sensitivity, and subjects underwent 2 stable-isotope infusion studies. [U-13C6]Leucine was infused to measure leucine flux and oxidation as indexes of BCAA metabolism, whereas [U-13C16]palmitate was infused to measure palmitate flux and oxidation to represent FFA metabolism, The 2H2O dilution method was used to estimate body composition.

Results

IR subjects had greater adiposity and significantly higher fasting and post-OGTT glucose and insulin concentrations compared with the IS group. However, none of the subjects were diabetic. Despite similar dietary protein intake, IR subjects had a significantly higher plasma BCAA concentration and greater leucine flux. Leucine oxidation was also greater in the IR group, but the relation between leucine oxidation and flux was significantly weaker in the IR group than in the IS group (r = 0.530 compared with 0.695, P < 0.0388 for differences between slope). FFA oxidation was, however, unaffected despite higher FFA flux in the IR group.

Conclusion

The higher plasma BCAA concentration in healthy nonobese individuals with IR is associated with a weaker relation between BCAA oxidation and BCAA flux and this occurs in the presence of accelerated FFA flux and oxidation.

Timing of eating in adults across the weight spectrum: Metabolic factors and potential circadian mechanisms

Timing of eating is recognized as a significant contributor to body weight regulation. Disruption of sleep-wake cycles from a predominantly diurnal (daytime) to a delayed (evening) lifestyle leads to altered circadian rhythms and metabolic dysfunction. This article reviews current evidence for timed and delayed eating in individuals of normal weight and those with overweight or obesity: although some findings indicate a benefit of eating earlier in the daytime on weight and/or metabolic outcomes, results have not been uniformly consistent, and more rigorous and longer-duration studies are needed. We also review potential circadian mechanisms underlying the metabolic- and weight-related changes resulting from timed and delayed eating. Further identification of such mechanisms using deep phenotyping is required to determine targets for medical interventions for obesity and for prevention of metabolic syndrome and diabetes, and to inform clinical guidelines regarding eating schedules for management of weight and metabolic disease.

Integrating Extracellular Flux Measurements and Genome-Scale Modeling Reveals Differences between Brown and White Adipocytes

White adipocytes are specialized for energy storage, whereas brown adipocytes are specialized for energy expenditure. Explicating this difference can help identify therapeutic targets for obesity. A common tool to assess metabolic differences between such cells is the Seahorse Extracellular Flux (XF) Analyzer, which measures oxygen consumption and media acidification in the presence of different substrates and perturbagens. Here, we integrate the Analyzer's metabolic profile from human white and brown adipocytes with a genome-scale metabolic model to predict flux differences across the metabolic map. Predictions matched experimental data for the metabolite 4-aminobutyrate, the protein ABAT, and the fluxes for glucose, glutamine, and palmitate. We also uncovered a difference in how adipocytes dispose of nitrogenous waste, with brown adipocytes secreting less ammonia and more urea than white adipocytes. Thus, the method and software we developed allow for broader metabolic phenotyping and provide a distinct approach to uncovering metabolic differences.

Adipose tissue depots and inflammation: effects on plasticity and resident mesenchymal stem cell function

Adipose tissue (AT) is a highly heterogeneous organ. Beside the heterogeneity associated to different tissue types (white, brown, and 'brite') and its location-related heterogeneity (subcutaneous, visceral, epicardial, and perivascular, etc.), AT composition, structure, and functionality are highly dependent on individual-associated factors. As such, the pro-inflammatory state associated to the presence of obesity and other cardiovascular risk factors (CVRFs) directly affects AT metabolism. Furthermore, the adipose-derived stem cells (ASCs) that reside in the stromal vascular fraction of AT, besides being responsible for most of the plasticity attributed to AT, is an additional source of heterogeneity. Thus, ASCs directly contribute to AT homeostasis, cell renewal, and spontaneous repair. These ASCs share many properties with the bone-marrow mesenchymal stem cells (i.e. potential to differentiate towards multiple tissue lineages, and angiogenic, antiapoptotic, and immunomodulatory properties). Moreover, ASCs show clear advantages in terms of accessibility and quantity of available sample, their easy in vitro expansion, and the possibility of having an autologous source. All these properties point out towards a potential use of ASCs in regenerative medicine. However, the presence of obesity and other CVRFs induces a pro-inflammatory state that directly impacts ASCs proliferation and differentiation capacities affecting their regenerative abilities. The focus of this review is to summarize how inflammation affects the different AT depots and the mechanisms by which these changes further enhance the obesity-associated metabolic disturbances. Furthermore, we highlight the impact of obesity-induced inflammation on ASCs properties and how those effects impair their plasticity.

Emerging perspectives on branched-chain amino acid metabolism during adipocyte differentiation

PURPOSE OF REVIEW

Adipogenesis has been extensively studied in the context of carbohydrate and lipid metabolism. However, little information exists on the role of amino acid metabolism during adipocyte differentiation. Here, we review how branched-chain amino acid (BCAA) metabolism is modified during adipogenesis and, due to the limited information in the area, address questions that remain to be answered with further research.

RECENT FINDINGS

BCAAs are rapidly consumed during adipocyte differentiation and are indispensable for this process. Furthermore, we describe how BCAA catabolic enzymes and the metabolic fate of BCAAs are modified during adipogenesis.

SUMMARY

Obesity is a chronic disease characterized by increased adipose tissue due to either an increase in the size (hypertrophy) and/or number of adipocytes (hyperplasia). Hyperplasia is determined by the rate of adipogenesis. Therefore, understanding the mechanism that modulates adipogenesis in the context of amino acid metabolism will help to establish pharmacological and dietary interventions involving the type and amount of dietary protein for the treatment of obesity and its associated comorbidities.Video abstract http://links.lww.com/COCN/A11.

Changes in Global Transcriptional Profiling of Women Following Obesity Surgery Bypass

BACKGROUND

Differential gene expression in peripheral blood mononuclear cells (PBMCs) after Roux-en-Y gastric bypass (RYGB) is poorly characterized. Markers of these processes may provide a deeper understanding of the mechanisms that underlie these events. The main goal of this study was to identify changes in PBMC gene expression in women with obesity before and 6 months after RYGB-induced weight loss.

METHODS

The ribonucleic acid (RNA) of PBMCs from 13 obese women was analyzed before and 6 months after RYGB; the RNA of PBMCs from nine healthy women served as control. The gene expression levels were determined by microarray analysis. Significant differences in gene expression were validated by real-time quantitative polymerase chain reaction (RT-qPCR).

RESULTS

Microarray analysis for comparison of the pre- and postoperative periods showed that 1366 genes were differentially expressed genes (DEGs). The main pathways were related to gene transcription; lipid, energy, and glycide metabolism; inflammatory and immunological response; cell differentiation; oxidative stress regulation; response to endogenous and exogenous stimuli; substrate oxidation; mTOR signaling pathway; interferon signaling; mitogen-activated protein kinases (MAPK), cAMP response element binding protein (CREB1), heat shock factor 1 (HSF1), and sterol regulatory element binding protein 1c (SREBP-1c) gene expression; adipocyte differentiation; and methylation.

CONCLUSIONS

Six months after bariatric surgery and significant weight loss, many molecular pathways involved in obesity and metabolic diseases change. These findings are an important tool to identify potential targets for therapeutic intervention and clinical practice of nutritional genomics in obesity.

Effects of Weight Loss on Glutathione Peroxidase 3 Serum Concentrations and Adipose Tissue Expression in Human Obesity

BACKGROUND/AIMS

Altered expression and circulating levels of glutathione peroxidase 3 (GPX3) have been observed in obesity and type 2 diabetes (T2D) across species. Here, we investigate whether GPX3 serum concentrations and adipose tissue (AT) GPX3 mRNA expression are related to obesity and weight loss.

METHODS

GPX3 serum concentration was measured in 630 individuals, including a subgroup (n = 293) for which omental and subcutaneous (SC) GPX3 mRNA expression has been analyzed. GPX3 analyses include three interventions: 6 months after bariatric surgery (n = 80) or combined exercise/hypocaloric diet (n = 20) or two-step bariatric surgery (n = 24) studies.

RESULTS

Bariatric surgery-induced weight loss (-25.8 ± 8.4%), but not a moderate weight reduction of -8.8 ± 6.5% was associated with significantly reduced GPX3 serum concentrations. GPX3 mRNA is significantly higher expressed in AT from individuals with normal glucose metabolism compared to T2D patients. SC AT GPX3 expression is significantly higher in lean compared to obese as well as in insulin-sensitive compared insulin-resistant individuals with obesity. Weight loss after bariatric surgery causes a significant increase in SC AT GPX3 expression. AT GPX3 expression significantly correlates with age, BMI, fat distribution, insulin sensitivity (only SC AT), but not with circulating GPX3.

CONCLUSION

Our data support the notion that SC AT GPX3 expression is associated with obesity, fat distribution and related to whole body insulin resistance.

Development of multivariable models to predict change in Body Mass Index within a clinical trial population of psychotic individuals

Many antipsychotics promote weight gain, which can lead to non-compliance and relapse of psychosis. By developing models that accurately identify individuals at greater risk of weight gain, clinicians can make informed treatment decisions and target intervention measures. We examined clinical, genetic and expression data for 284 individuals with psychosis derived from a previously published randomised controlled trial (IMPACT). These data were used to develop regression and classification models predicting change in Body Mass Index (BMI) over one year. Clinical predictors included demographics, anthropometrics, cardiac and blood measures, diet and exercise, physical and mental health, medication and BMI outcome measures. We included genetic polygenic risk scores (PRS) for schizophrenia, bipolar disorder, BMI, waist-hip-ratio, insulin resistance and height, as well as gene co-expression modules generated by Weighted Gene Co-expression Network Analysis (WGCNA). The best performing predictive models for BMI and BMI gain after one year used clinical data only, which suggests expression and genetic data do not improve prediction in this cohort.