Chemokines in human obesity.

Obesity and type 2 diabetes have been shown to be associated with chronic inflammation. Despite extensive evidence for inflammatory mediators in the obese patients and multiple clinical trials, the outcome has been disappointing. In murine models recruitment of immune cells during inflammation has been shown to contribute to the chronic inflammation. Clearcut evidence for the differential expression of chemokines that mediate this recruitment is not available. In this short review we discuss the observations on CCL2 and CCL5 in human obesity.

Metabolic endotoxemia promotes adipose dysfunction and inflammation in human obesity.

Impaired adipose tissue (AT) lipid handling and inflammation is associated with obesity-related metabolic diseases. Circulating lipopolysaccharides (LPSs) from gut microbiota (metabolic endotoxemia), proposed as a triggering factor for the low-grade inflammation in obesity, might also be responsible for AT dysfunction. Nevertheless, this hypothesis has not been explored in human obesity. To analyze the relationship between metabolic endotoxemia and AT markers for lipogenesis, lipid handling, and inflammation in human obesity, 33 patients with obesity scheduled for surgery were recruited and classified according to their LPS levels. Visceral and subcutaneous AT gene and protein expression were analyzed and adipocyte and AT in vitro assays performed. Subjects with obesity with a high degree of metabolic endotoxemia had lower expression of key genes for AT function and lipogenesis ( SREBP1, FABP4, FASN, and LEP) but higher expression of inflammatory genes in visceral and subcutaneous AT than subjects with low LPS levels. In vitro experiments corroborated that LPS are responsible for adipocyte and AT inflammation and downregulation of PPARG, SCD, FABP4, and LEP expression and LEP secretion. Thus, metabolic endotoxemia influences AT physiology in human obesity by decreasing the expression of factors involved in AT lipid handling and function as well as by increasing inflammation.

Omega-3 fatty acid supplementation influences the whole blood transcriptome in women with obesity, associated with pro-resolving lipid mediator production.

The n-3 polyunsaturated fatty acids (PUFAs) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) may reduce low-grade inflammation associated with obesity. The relationship between therapeutic response to n-3 PUFAs and modification of the transcriptome in obesity or metabolic syndrome remains to be explored. Blood samples were obtained from women with obesity before and after three-months supplementation with a moderate dose of n-3 PUFAs (1.8g EPA+DHA per day) or from controls. n-3 PUFAs (GC) and plasma concentrations of lipoxins, resolvins, protectin X (GC-MS/MS) and inflammatory markers (ELISA) were measured. Whole blood transcriptome was assayed using microarray. Women supplemented with n-3 PUFAs for 3months had significantly higher levels of EPA and DHA in plasma phosphatidylcholine. n-3 PUFA supplementation, in contrast to placebo, significantly decreased the concentrations of several inflammatory markers (SELE, MCP-1, sVCAM-1, sPECAM-1, and hsCRP), fasting triglycerides and insulin and increased the concentrations of pro-resolving DHA derivatives in plasma. The microarray data demonstrated effects of n-3 PUFAs on PPAR-α, NRF2 and NF-κB target genes. N-3 PUFAs increased DHA-derived pro-resolving mediators in women with obesity. Elevated resolvins and up-regulation of the resolvin receptor occurred in parallel with activation of PPAR-α target genes related to lipid metabolism and of NRF2 up-regulated antioxidant enzymes.

[The genetics of obesity - pathogenetic, clinical and diagnostic aspects].

Due to its prevalence and its health-related, economic and social consequences, childhood and adult obesity is a complex, medical and civilizational problem, which has been on the increase in the last decade. The results of multi-center investigations reveal that genetic factors play an essential role in the etiopathogenesis of obesity, particularly in the case of extreme cases with very early onset. The Body Mass Index (BMI) is one of the most frequently used indicators of obesity and shows a strong genetic component with a 40-70% degree of heritability. The three types of genetically conditioned obesity are: (1) isolated (nonsyndromic) monogenic obesity, (2) syndromic monogenic obesity associated with dysmorphic features and/or congenital defects, caused by mutations in specific gene(s), (3) chromosomal aberrations, including submicroscopic changes. The most prevalent common (complex) obesity is linked to the presence of various changes in different genomic loci, which are subject to interactions and modifications by environmental (ethnic, dietary, lifestyle, bacterial flora, oxidative stress), as well as epigenetic (i.e., associated with DNA methylation, histone modification) and epistatic (gene-gene interaction) factors. Recent investigations using the modern methods of genome-wide association studies (GWAS), bioinformatics and proteomics, have made it possible to elucidate 8 key genes among the 97 genes most likely to play significant roles in the metabolic effects of obesity. The results of investigations on the pathogenesis of complex obesity do not as yet clarify the potential pathogenic significance of these genomic changes in humans. This article discusses the neuro-endocrinological regulation of the sensation of hunger and thirst, the clinical consequences of mutations in genes associated with the melanocortin pathway, and the features of the most common obesity syndromes, including syndromes conditioned by genomic imprinting. A diagnostic algorithm for cases of suspected syndromic obesity is proposed.

Human adipocyte function is impacted by mechanical cues.

Fibrosis is a hallmark of human white adipose tissue (WAT) during obesity-induced chronic inflammation. The functional impact of increased interstitial fibrosis (peri-adipocyte fibrosis) on adjacent adipocytes remains unknown. Here we developed a novel in vitro 3D culture system in which human adipocytes and decellularized material of adipose tissue (dMAT) from obese subjects are embedded in a peptide hydrogel. When cultured with dMAT, adipocytes showed decreased lipolysis and adipokine secretion and increased expression/production of cytokines (IL-6, G-CSF) and fibrotic mediators (LOXL2 and the matricellular proteins THSB2 and CTGF). Moreover, some alterations including lipolytic activity and fibro-inflammation also occurred when the adipocyte/hydrogel culture was mechanically compressed. Notably, CTGF expression levels correlated with the amount of peri-adipocyte fibrosis in WAT from obese individuals. Moreover, dMAT-dependent CTGF promoter activity, which depends on ß1-integrin/cytoskeleton pathways, was enhanced in the presence of YAP, a mechanosensitive co-activator of TEAD transcription factors. Mutation of TEAD binding sites abolished the dMAT-induced promoter activity. In conclusion, fibrosis may negatively affect human adipocyte function via mechanosensitive molecules, in part stimulated by cell deformation.

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.

Duodenal Metatranscriptomics to Define Human and Microbial Functional Alterations Associated with Severe Obesity: A Pilot Study.

Obesity is a multifactorial disorder, and the gut microbiome has been suggested to contribute to its onset. In order to better clarify the role of the microbiome in obesity, we evaluated the metatranscriptome in duodenal biopsies from a cohort of 23 adult severely obese and lean control subjects using next generation sequencing. Our aim was to provide a general picture of the duodenal metatranscriptome associated with severe obesity. We found altered expressions of human and microbial genes in the obese compared to lean subjects, with most of the gene alterations being present in the carbohydrate, protein, and lipid metabolic pathways. Defects were also present in several human genes involved in epithelial intestinal cells differentiation and function, as well as in the immunity/inflammation pathways. Moreover, the microbial taxa abundance inferred by our transcriptomic data differed in part from the data that we previously evaluated by 16S rRNA in 13/23 individuals of our cohort, particularly concerning the Firmicutes and Proteobacteria phyla abundances. In conclusion, our pilot study provides the first taxonomic and functional characterization of duodenal microbiota in severely obese subjects and lean controls. Our findings suggest that duodenal microbiome and human genes both play a role in deregulating metabolic pathways, likely affecting energy metabolism and thus contributing to the obese phenotype.

Inflammation in human adipose tissues-Shades of gray, rather than white and brown.

Chronic inflammation in adipose tissues has been associated with obesity and metabolic syndrome over the years. Various studies using animal models have contributed to our knowledge on the pro- and anti- inflammatory mediators that regulate obesity. Analyses of cytokine profiles in humans have not revealed a clear scenario. Likewise, treatments targeting inflammation to control obesity and insulin resistance has not yielded promising results. In this review we summarize the data available in human obesity and discuss the possible reasons that could explain the difficulties in treating obesity and insulin resistance by targeting pro-inflammatory cytokines.

Caloric Restriction and Diet-Induced Weight Loss Do Not Induce Browning of Human Subcutaneous White Adipose Tissue in Women and Men with Obesity.

Caloric restriction (CR) is standard lifestyle therapy in obesity management. CR-induced weight loss improves the metabolic profile of individuals with obesity. In mice, occurrence of beige fat cells in white fat depots favors a metabolically healthy phenotype, and CR promotes browning of white adipose tissue (WAT). Here, human subcutaneous abdominal WAT samples were analyzed in 289 individuals with obesity following a two-phase dietary intervention consisting of an 8 week very low calorie diet and a 6-month weight-maintenance phase. Before the intervention, we show sex differences and seasonal variation, with higher expression of brown and beige markers in women with obesity and during winter, respectively. The very low calorie diet resulted in decreased browning of subcutaneous abdominal WAT. During the whole dietary intervention, evolution of body fat and insulin resistance was independent of changes in brown and beige fat markers. These data suggest that diet-induced effects on body fat and insulin resistance are independent of subcutaneous abdominal WAT browning in people with obesity.

Challenges in simulating the human gut for understanding the role of the microbiota in obesity.

There is an elevated incidence of cases of obesity worldwide. Therefore, the development of strategies to tackle this condition is of vital importance. This review focuses on the necessity of optimising in vitro systems to model human colonic fermentation in obese subjects. This may allow to increase the resolution and the physiological relevance of the information obtained from this type of studies when evaluating the potential role that the human gut microbiota plays in obesity. In light of the parameters that are currently used for the in vitro simulation of the human gut (which are mostly based on information derived from healthy subjects) and the possible difference with an obese condition, we propose to revise and improve specific standard operating procedures.

Using molecular functional networks to manifest connections between obesity and obesity-related diseases.

Obesity is a primary risk factor for many diseases such as certain cancers. In this study, we have developed three algorithms including a random-walk based method OBNet, a shortest-path based method OBsp and a direct-overlap method OBoverlap, to reveal obesity-disease connections at protein-interaction subnetworks corresponding to thousands of biological functions and pathways. Through literature mining, we also curated an obesity-associated disease list, by which we compared the methods. As a result, OBNet outperforms other two methods. OBNet can predict whether a disease is obesity-related based on its associated genes. Meanwhile, OBNet identifies extensive connections between obesity genes and genes associated with a few diseases at various functional modules and pathways. Using breast cancer and Type 2 diabetes as two examples, OBNet identifies meaningful genes that may play key roles in connecting obesity and the two diseases. For example, TGFB1 and VEGFA are inferred to be the top two key genes mediating obesity-breast cancer connection in modules associated with brain development. Finally, the top modules identified by OBNet in breast cancer significantly overlap with modules identified from TCGA breast cancer gene expression study, revealing the power of OBNet in identifying biological processes involved in the disease.

Investigation of common and rare genetic variation in the BAMBI genomic region in light of human obesity.

The aim of this study was to confirm the previously identified link between BAMBI and human obesity by means of a genetic and functional analysis. We performed both a mutation analysis, using high-resolution melting curve analysis, and a genetic association study, including 8 common tagSNPs in the BAMBI gene region. Three of the identified genetic variants (R151W, H201R, and C229R) were evaluated for their Wnt signaling enhancing capacity in a Wnt luciferase reporter assay. Mutation screening of the BAMBI coding region and exon-intron boundaries on our population of 677 obese children and adolescents and 529 lean control subjects resulted in the identification of 18 variants, 10 of which were not previously reported and 12 of which were exclusively found in obese individuals. The difference in variant frequency, not taking into account common polymorphisms, between obese (3.1 %) and lean (0.9 %) subjects was statistically significant (p = 0.004). Our Wnt luciferase assay, using WT and mutant BAMBI constructs, showed a significantly reduced activity for all of the investigated variants. Logistic and linear regression analysis on our Caucasian population of 1022 obese individuals and 606 lean controls, did not identify associations with obesity parameters (p values >0.05). We found several rare genetic variations, which represent the first naturally occurring missense variants of BAMBI in obese patients. Three variants (R151W, H201R, and C229R) were shown to reduce Wnt signaling enhancing capacity of BAMBI and we believe this result should encourage further study of this gene in other obese populations. In addition, we did not find evidence for the involvement of BAMBI common variation in human obesity in our population.

Neuropeptide Y gene-by-psychosocial stress interaction effect is associated with obesity in a Korean population.

BACKGROUND: Chronic psychosocial stress is a crucial risk factor in the development of many diseases including obesity. Neuropeptide Y (NPY), distributed throughout the peripheral and central nervous system, is believed to pay a role in the pathophysiologic relationship between stress and obesity. Although several animal studies have investigated the impact on obesity of interactions between NPY single nucleotide polymorphisms (SNPs) and stress, the same remains to be analyzed in humans. METHODS: To identify NPY gene-by-stress interaction effects on human obesity, we analyzed the interaction between four NPY SNPs and stress with obesity-related traits, including visceral adipose tissue (VAT). A total of 1468 adult subjects were included for this analysis. RESULTS: In a SNP-only model without interaction with stress, no significant SNPs were found (pSNP>0.05). However, NPY SNPs-by-stress interaction effects were significantly linked to body mass index (BMI), waist circumference, and VAT (pint<0.05), even though a significant interaction effect for rs16135 on BMI was not identified. These significant interaction effects were also detected in interaction results for the binary traits of obesity. Among the obesity traits, mean changes of VAT by increased stress levels in homozygous risk allele carriers were the greatest (range of mean increases for four SNPs (min-max)=12.57cm(2)-29.86cm(2)). CONCLUSIONS: This study suggests that common polymorphisms for NPY were associated with human obesity by interacting with psychosocial stress, emphasizing the need for stress management in obesity prevention.

Ghrelin Receptor Mutations and Human Obesity.

Growth hormone secretagogue receptor (GHSR) was originally identified as an orphan receptor in porcine and rat anterior pituitary membranes. In 1999, GHSR was deorphanized and shown to be a receptor for ghrelin, a peptide hormone secreted from the stomach. Therefore, GHSR is also called ghrelin receptor. In addition to regulating growth hormone secretion, ghrelin receptor regulates various physiological processes, including food intake and energy expenditure, glucose metabolism, cardiovascular functions, gastric acid secretion and motility, and immune function. Several human genetic studies conducted in populations originated from Europe, Africa, South America, and East Asia identified rare mutations and single nucleotide polymorphisms that might be associated with human obesity and short stature. Functional analyses of mutant GHSRs reveal multiple defects, including cell surface expression, ligand binding, and basal and stimulated signaling. With growing understanding in the functionality of naturally occurring GHSR mutations, potential therapeutic strategies including pharmacological chaperones and novel ligands could be used to correct the GHSR mutants.

A tale with a Twist: a developmental gene with potential relevance for metabolic dysfunction and inflammation in adipose tissue.

The Twist proteins (Twist-1 and -2) are highly conserved developmental proteins with key roles for the transcriptional regulation in mesenchymal cell lineages. They belong to the super-family of bHLH proteins and exhibit bi-functional roles as both activators and repressors of gene transcription. The Twist proteins are expressed at low levels in adult tissues but may become abundantly re-expressed in cells undergoing malignant transformation. This observation prompted extensive research on the roles of Twist proteins in cancer progression and metastasis. Very recent studies indicate a novel role for Twist-1 as a potential regulator of adipose tissue (AT) remodeling and inflammation. Several studies suggested that developmental genes are important determinants of obesity, fat distribution and remodeling capacity of different adipose depots. Twist-1 is abundantly and selectively expressed in the adult AT and its constitutive expression is significantly higher in subcutaneous (SAT) vs. visceral (VAT) fat in both mice and humans. Moreover, Twist1 expression is strongly correlated with BMI and insulin resistance in humans. However, the functional roles and transcriptional downstream targets of Twist1 in AT are largely unexplored. The purpose of this review is to highlight the major findings related to Twist1 expression in different fat depots and cellular components of AT and to discuss the potential mechanisms suggesting a role for Twist1 in AT metabolism, inflammation and remodeling.

An age structured model for obesity prevalence dynamics in populations

Objective. Modeling the correlation of the development of obesity in a population with age and time and predict the dynamics of the correlation of the development of obesity in a population with age and time under different scenarios in Valencia (Spain). Materials and methods. An age structured mathematical model is used to describe the future dynamics of obesity prevalence for different ages in human population with excess weight. Simulation of the model with parameters estimated using the Health Survey of the Region of Valencia 2000 (4.319 interviews) and Health Survey of the Region of Valencia 2005 (4.012 interviews). The model considers only overweight and obese populations since these subpopulations are the most relevant on obesity health concern. Results. The model allows predicting and studying the prevalence of obesity for each age. Results showed an increasing trend of obesity in the following years in well accordance with the trend observed in several countries. Conclusions. Based on the numerical simulations it is possible to conclude that the age structured mathematical model is suitable to forecast the obesity epidemic in each age group in different countries. Additionally, this type of models may be applied to study other characteristics of other populations such animal populations.