Azahara I. Rupérez

Cell Models and Their Application for Studying Adipogenic Differentiation in Relation to Obesity: A Review

Over the last several years, the increasing prevalence of obesity has favored an intense study of adipose tissue biology and the precise mechanisms involved in adipocyte differentiation and adipogenesis. Adipocyte commitment and differentiation are complex processes, which can be investigated thanks to the development of diverse in vitro cell models and molecular biology techniques that allow for a better understanding of adipogenesis and adipocyte dysfunction associated with obesity. The aim of the present work was to update the different animal and human cell culture models available for studying the in vitro adipogenic differentiation process related to obesity and its co-morbidities. The main characteristics, new protocols, and applications of the cell models used to study the adipogenesis in the last five years have been extensively revised. Moreover, we depict co-cultures and three-dimensional cultures, given their utility to understand the connections between adipocytes and their surrounding cells in adipose tissue.

Genetics of Oxidative Stress in Obesity

Obesity is a multifactorial disease characterized by the excessive accumulation of fat in adipose tissue and peripheral organs. Its derived metabolic complications are mediated by the associated oxidative stress, inflammation and hypoxia. Oxidative stress is due to the excessive production of reactive oxygen species or diminished antioxidant defenses. Genetic variants, such as single nucleotide polymorphisms in antioxidant defense system genes, could alter the efficacy of these enzymes and, ultimately, the risk of obesity; thus, studies investigating the role of genetic variations in genes related to oxidative stress could be useful for better understanding the etiology of obesity and its metabolic complications. The lack of existing literature reviews in this field encouraged us to gather the findings from studies focusing on the impact of single nucleotide polymorphisms in antioxidant enzymes, oxidative stress-producing systems and transcription factor genes concerning their association with obesity risk and its phenotypes. In the future, the characterization of these single nucleotide polymorphisms (SNPs) in obese patients could contribute to the development of controlled antioxidant therapies potentially beneficial for the treatment of obesity-derived metabolic complications.

Influence of variants in the NPY gene on obesity and metabolic syndrome features in Spanish children

Variants in the neuropeptide Y (NPY) gene have been associated with obesity and its traits. The objective of the present study was to evaluate the association of single nucleotide polymorphisms (SNPs) in the NPY gene with obesity, metabolic syndrome features, and inflammatory and cardiovascular disease (CVD) risk biomarkers in Spanish children. We recruited 292 obese children and 242 normal-body mass index (BMI) children. Height, weight, BMI, waist circumference, clinical and metabolic markers, adipokines, and inflammatory (PCR, IL-6, IL-8 and TNF-α) and CVD risk biomarkers (MPO, MMP-9, sE-selectin, sVCAM, sICAM, and PAI-1) were analyzed. Seven SNPs in the NPY gene were genotyped. The results of our study indicate that anthropometric measurements, clinical and metabolic markers, adipokines (leptin and resistin), and inflammatory and CVD risk biomarkers were generally elevated in the obese group. The exceptions to this finding included cholesterol, HDL-c, and adiponectin, which were lower in the obese group, and glucose, LDL-c, and MMP-9, which did not differ between the groups. Both rs16147 and rs16131 were associated with the risk of obesity, and the latter was also associated with insulin resistance, triacylglycerols, leptin, and HDL-c. Thus, we confirm the association of rs16147 with obesity, and we demonstrate for the first time the association of rs16131 with obesity and its possible impact on the early onset of metabolic syndrome features, mainly triacylglycerols, in children.

Paraoxonase 1 activities and genetic variation in childhood obesity.

Changes in paraoxonase 1 (PON1) activities have been observed in a variety of diseases involving oxidative stress, such as CVD. However, its role in obesity has not been fully established. In the present study, we aimed (1) to genotype sixteen PON1 SNP, (2) to measure serum PON1 activities and (3) to correlate these findings with the incidence of childhood obesity and related traits. We conducted a case-control study of 189 normal-weight and 179 obese prepubertal children, and we measured four different PON1 activities: lactonase; paraoxonase; arylesterase; diazoxonase. Although none of these activities was significantly different between the obese and normal-weight children, lactonase activity was found to be positively correlated with HDL-cholesterol and ApoA1 levels and negatively correlated with myeloperoxidase and fatty acid-binding protein 4 levels. Among the sixteen genotyped PON1 SNP, only the intronic SNP rs854566 exhibited a significant association with obesity (OR 0·61, 95 % CI 0·41, 0·91; P= 0·016). This genetic variant was also associated with increased diazoxonase, lactonase and arylesterase activities and decreased paraoxonase activity. Other genetic variants exhibited different association patterns with serum activities based on their location within the PON1 gene, and SNP that were located within the promoter were strongly associated with lactonase, arylesterase and diazoxonase activities. The functional variant Q192R exhibited the greatest effect on paraoxonase activity (P= 5·88 × 10(-42)). In conclusion, SNP rs854566 was negatively associated with childhood obesity and with increased serum PON1 activities in prepubertal children. We determined that lactonase is a reliable indicator of PON1 activities and should be included in future studies of PON1 function.

Influence of FTO variants on obesity, inflammation and cardiovascular disease risk biomarkers in Spanish children: a case-control multicentre study.

BackgroundVariants in the FTO gene have been associated with obesity in children, but this association has not been shown with other biomarkers. We assessed the association of 52 FTO polymorphisms, spanning the whole gene, with obesity and estimated the influence of these polymorphisms on anthropometric, clinical and metabolic parameters as well as inflammation and cardiovascular disease (CVD) risk biomarkers among Spanish children.MethodsA multicentre case–control study was conducted in 534 children (292 obese and 242 with normal-BMI). Anthropometric, clinical, metabolic, inflammation and CVD risk markers were compared using the Student’s t-test for unpaired samples. The genotype relative risk was assessed by comparing the obese and normal-BMI group, calculating the odds ratio. The association of each SNP with phenotypic parameters was analysed using either logistic or linear regression analysis.ResultsAll anthropometric, clinical and metabolic factors as well as inflammatory and CVD risk biomarkers were higher in the obese than in the normal-BMI group, except adiponectin and HDL-c that were lower, and glucose, LDL-c, and metalloproteinase-9 that did not show difference. Four polymorphisms (rs9935401, rs9939609, rs9928094 and rs9930333) were positively associated with obesity and in linkage disequilibrium between each other; the haplotype including the risk alleles of these polymorphisms showed a high risk for obesity. The rs8061518 was negatively associated with obesity and the haplotype including this SNP and rs3826169, rs17818902 and rs7190053 showed a decreased risk for obesity. Additionally, the rs8061518 was associated with weight, diastolic blood pressure, insulin, homeostatic model assessment of insulin resistance, leptin, and active plasminogen inhibitor activator-1 after sex and age adjustment; however, after an additional BMI adjustment, this polymorphism remained associated only with leptin.ConclusionsWe validated the previous reported association of genetic variability in intron 1 of the FTO gene with the risk of obesity and found no association with other related traits in this region of the gene. We have observed strong statistical evidence for an association of rs8061518 in intron 3 of the gene with decreased risk of obesity and low concentration of leptin.

Association of Genetic Polymorphisms for Glutathione Peroxidase Genes with Obesity in Spanish Children

Background/Aims: Altered expression and activity of the antioxidant enzymes glutathione peroxidases (GPXs) have been observed in obesity in human and animal studies. We aimed to study 59 single nucleotide polymorphisms (SNPs) for GPX1-7 genes and to characterize their association with prepubertal childhood obesity and its associated biomarkers. Methods: This case-control study included 193 obese and 191 normal-weight prepubertal Spanish children, in whom anthropometry, biochemical parameters, adipokines, antioxidant enzyme erythrocyte activities and biomarkers of oxidative stress, inflammation and cardiovascular risk were measured. The genotype analysis was performed in the Illumina platform. PLINK and SPSS were used for statistical analyses. Results: We found SNPs rs757228 and rs8103188 (GPX4) to be negatively associated and rs445870 (GPX5) and rs406113 (GPX6) to be positively associated with obesity in children. The variant rs2074451 (GPX4) increased GPX activity in erythrocytes. Although we did not find significant differences in erythrocyte GPX activity between obese and normal-weight children, GPX activity was found to be positively and significantly correlated with blood pressure, adipocyte fatty acid-binding protein and high-sensitivity C-reactive protein. Conclusions: The GPX variants rs757228, rs8103188, rs445870 and rs406113 were associated with prepubertal childhood obesity. However, erythrocyte GPX activity was not altered in obese prepubertal Spanish children.

Impact of 3-Amino-1,2,4-Triazole (3-AT)-Derived Increase in Hydrogen Peroxide Levels on Inflammation and Metabolism in Human Differentiated Adipocytes.

Obesity is characterized by an excessive accumulation of fat in adipose tissue, which is associated with oxidative stress and chronic inflammation. Excessive H2O2 levels are degraded by catalase (CAT), the activity of which is decreased in obesity. We investigated the effects of inhibition of catalase activity on metabolism and inflammation by incubating human differentiated adipocytes with 10 mM 3-amino-1,2,4-triazole (3-AT) for 24 h. As expected, the treatment decreased CAT activity and increased intracellular H2O2 levels significantly. Glutathione peroxidase (GPX) activity was also reduced, and the gene expression levels of the antioxidant enzymes GPX4 and peroxiredoxins (1, 3 and 5) were inhibited. Interestingly, this occurred along with lower mRNA levels of the transcription factors nuclear factor (erythroid 2-like 2) and forkhead box O, which are involved in redox homeostasis. However, superoxide dismutase activity and expression were increased. Moreover, 3-AT led to nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) activation and increased tumor necrosis alpha and interleukin 6 protein and gene expression levels, while lowering peroxisome proliferator-activated receptor gamma (PPARγ) mRNA and protein levels. These alterations were accompanied by an altered glucose and lipid metabolism. Indeed, adipocytes treated with 3-AT showed reduced basal glucose uptake, reduced glucose transporter type 4 gene and protein expression, reduced lipolysis, reduced AMP-activated protein kinase activation and reduced gene expression of lipases. Our results indicate that increased H2O2 levels caused by 3-AT treatment impair the antioxidant defense system, lower PPARγ expression and initiate inflammation, thus affecting glucose and lipid metabolism in human differentiated adipocytes.

Leptin Receptor Gene Variant rs11804091 Is Associated with BMI and Insulin Resistance in Spanish Female Obese Children: A Case-Control Study

Leptin is an endocrine hormone that has a critical role in body weight homoeostasis and mediates its effects via the leptin receptor (LEPR). Common polymorphisms in the genes coding leptin receptors have been associated with metabolic abnormalities. We assessed the association of 28 LEPR polymorphisms with body mass index (BMI) and their relationship with obesity-related phenotypes, inflammation and cardiovascular disease risk biomarkers. A multicentre case-control study was conducted in 522 children (286 with obesity and 236 with normal-BMI). All anthropometric, metabolic factors and biomarkers were higher in children with obesity except apolipoprotein (Apo)-AI, cholesterol, high-density lipoprotein cholesterol (HDL-c), and adiponectin, which were lower in the obesity group; and glucose, low-density lipoprotein cholesterol (LDL-c), and matrix metalloproteinase-9 that did not differ between groups. We identified the associations between rs11208659, rs11804091, rs10157275, rs9436303 and rs1627238, and BMI in the whole population, as well as the association of rs11804091, rs10157275, and rs1327118 with BMI in the female group, although only the rs11804091 remained associated after Bonferroni correction (p = 0.038). This single nucleotide polymorphisms (SNP) was also associated with insulin (p = 0.004), homeostasis model assessment for insulin resistance (HOMA-IR) (p = 0.006), quantitative insulin sensitivity check index (QUICKI) (p = 0.005) and adiponectin (p = 0.046) after adjusting for age, Tanner stage and BMI. Our results show a sex-specific association between the rs11804091 and obesity suggesting an influence of this SNP on insulin resistance.

Changes in Oxidative Stress and Inflammatory Biomarkers in Fragile Adults over Fifty Years of Age and in Elderly People Exclusively Fed Enteral Nutrition.

We aim to evaluate whether exclusive feeding of an enteral formula enriched with n-3 long chain polyunsaturated fatty acids (n-3 LC-PUFA) affects oxidative stress and the antioxidant defence system and may improve the levels of some relevant inflammatory, and cardiovascular biomarkers in frail adults over fifty years of age and in elderly subjects. Fifty-five patients were divided into two groups and were exclusively fed a newly designed normoproteic and isocaloric enteral formula enriched with eicosapentaenoic (98 mg/d) and docosahexaenoic acids (46 mg/d) (n = 26) or a reference enteral diet (n = 29). Oxidative, inflammatory and cardiovascular risk biomarkers and red blood cell fatty acid profiles were determined at the beginning and after 90 and 180 days of feeding. The n-3 LC-PUFA percentage tended to be higher (P = 0.053) in the experimental group than in the reference group. Administration of the n-3 LC-PUFA diet did not increase oxidative stress or modify plasma antioxidant capacity but decreased antioxidant enzymatic activities. MMP-9 plasma concentration decreased with both formulae, whereas tPAI-1 tended to decrease (P = 0.116) with the administration of the experimental formula. In conclusion, administration of the new n-3 LC-PUFA-enriched product for 6 months did not negatively alter the oxidative status and improved some cardiovascular risk biomarkers.