Microarray evidences the role of pathologic adipose tissue in insulin resistance and their clinical implications

Effects of long-term exercise on plasma adipokine levels and inflammation-related gene expression in subcutaneous adipose tissue in sedentary dysglycaemic, overweight men and sedentary normoglycaemic men of healthy weight

AIMS/HYPOTHESIS

Obesity and insulin resistance may be associated with altered expression and secretion of adipokines. Physical activity can markedly improve insulin sensitivity, but the association with adipokines remains largely unknown. In this study, we examined the effects of physical activity on the subcutaneous white adipose tissue (scWAT) secretome and its relationship to insulin sensitivity.

METHODS

As reported previously, we enrolled 26 sedentary, middle-aged men (13 dysglycaemic and overweight; 13 normoglycaemic and of healthy weight) into a 12 week, supervised, intensive physical exercise intervention that included two endurance and two resistance sessions each week. Insulin sensitivity was measured as the glucose infusion rate from a euglycaemic-hyperinsulinaemic clamp. In our previous study, we measured maximum oxygen uptake, upper- and lower-body strength and a range of circulating biomarkers, and quantified adipose tissue depots using MRI and magnetic resonance spectroscopy. We have now performed global mRNA sequencing, microarrays and RT-PCR of scWAT and skeletal muscle biopsies, and quantified selected plasma adipokines by ELISA.

RESULTS

Insulin sensitivity increased similarly in both dysglycaemic (45%) and normoglycaemic (38%) men after 12 weeks of exercise, as reported previously. mRNA sequencing of scWAT revealed 90 transcripts that responded to exercise in dysglycaemic men, whereas only marginal changes were observed in normoglycaemic men. These results were validated using microarrays and RT-PCR. A total of 62 out of 90 transcripts encoded secreted proteins. Overall, 17 transcripts were upregulated and 73 transcripts were downregulated. Downregulated transcripts included several macrophage markers, and were associated with inflammatory and immune-related pathways. Levels of these immune-related transcripts were enhanced in dysglycaemic men vs normoglycaemic men at baseline, but were normalised after the exercise intervention. Principal component and correlation analyses revealed inverse correlations between levels of these immune-related transcripts and insulin sensitivity at baseline, after the intervention, and for the change between baseline and after the intervention. In addition, levels of these transcripts at baseline could predict exercise-induced improvements in insulin sensitivity. Adipokine levels in scWAT (but not in skeletal muscle) were significantly correlated with corresponding plasma adipokine concentrations, as exemplified by leptin, high-molecular-weight adiponectin and secreted frizzled-related protein 4 (SFRP4). SFRP4 mRNA was the most exercise-responsive transcript in scWAT from dysglycaemic men, and plasma SFRP4 concentrations were reduced in dysglycaemic men, but not in normoglycaemic men, after 12 weeks of exercise.

CONCLUSIONS/INTERPRETATION

This study indicates that scWAT may be an important mediator of exercise-induced improvements in insulin sensitivity, especially in overweight dysglycaemic individuals at increased risk of developing type 2 diabetes.

A Network Biology Approach for Assessing the Role of Pathologic Adipose Tissues in Insulin Resistance Using Meta-analysis of Microarray Datasets

Background

The role of adipose tissue in Insulin resistance (IR) and Type 2 Diabetes (T2D) has well been received in the biomedical community; being a precursor of T2D, identification of the molecular basis of IR is therefore, vital to elucidate T2D- pathogenesis and meta-analysis of previously conducted microarray studies provides an inexpensive approach to achieve this end.

Methods

In this study, we have carried out a statistical meta-analysis of 157 microarray datasets from five independent studies and identified a meta-signature of 1,511 genes; their functional meaning was elucidated by integrated pathways-analysis. Further, a protein-protein interaction network was constructed and key genes along with their high confidence transcriptional- and epigenetic-mediators were identified using a network biology approach.

Results

Various inflammation- and immune system-related pathways such as TGF-β signaling, IL7 signaling, Neutrophil degranulation, and Chemokine signaling etc. were enriched in sick adipose tissues; identified transcription factors, and microRNAs were also found to regulate processes relevant to IR/T2D pathophysiology.

Conclusion

This study endorses the development of effective bioinformatics workflow and further grants an indication for the acceptance of adiposopathy as the root mechanistic pathology that poses risk for development of type 2 diabetes; concept of adipospathy in place of metabolic syndrome will open the possibility to design drugs, those will ameliorate adipose functions and hence proved to be more effective against Type 2 Diabetes.

System Level Meta-analysis of Microarray Datasets for Elucidation of Diabetes Mellitus Pathobiology

BACKGROUND

Type 2 diabetes (T2D) is a common multi-factorial disease that is primarily ac-counted to ineffective insulin action in lowering blood glucose level and later escalates to impaired insu-lin secretion by pancreatic β cells. Deregulation in insulin signaling to its target organs is attributed to this disease phenotype. Various genome-wide microarray studies from multiple insulin responsive tis-sues have been conducted in past but due to inherent noise in microarray data and heterogeneity in dis-ease etiology; reproduction of prioritized pathways/genes is very low across various studies.

OBJECTIVE

In this study, we aim to identify consensus signaling and metabolic pathways through system level meta-analysis of multiple expression-sets to elucidate T2D pathobiology.

METHOD

We used 'R', an open source statistical environment, which is routinely used for Microarray data analysis particularly using special sets of packages available at Bioconductor. We primarily focused on gene-set analysis methods to elucidate various aspects of T2D.

RESULT

Literature-based evidences have shown the success of our approach in exploring various known aspects of diabetes pathophysiology.

CONCLUSION

Our study stressed the need to develop novel bioinformatics workflows to advance our understanding further in insulin signaling.

Characterization of visceral and subcutaneous adipose tissue transcriptome in pregnant women with and without spontaneous labor at term: implication of alternative splicing in the metabolic adaptations of adipose tissue to parturition

OBJECTIVE

The aim of this study was to determine gene expression and splicing changes associated with parturition and regions (visceral vs. subcutaneous) of the adipose tissue of pregnant women.

STUDY DESIGN

The transcriptome of visceral and abdominal subcutaneous adipose tissue from pregnant women at term with (n=15) and without (n=25) spontaneous labor was profiled with the Affymetrix GeneChip Human Exon 1.0 ST array. Overall gene expression changes and the differential exon usage rate were compared between patient groups (unpaired analyses) and adipose tissue regions (paired analyses). Selected genes were tested by quantitative reverse transcription-polymerase chain reaction.

RESULTS

Four hundred and eighty-two genes were differentially expressed between visceral and subcutaneous fat of pregnant women with spontaneous labor at term (q-value <0.1; fold change >1.5). Biological processes enriched in this comparison included tissue and vasculature development as well as inflammatory and metabolic pathways. Differential splicing was found for 42 genes [q-value <0.1; differences in Finding Isoforms using Robust Multichip Analysis scores >2] between adipose tissue regions of women not in labor. Differential exon usage associated with parturition was found for three genes (LIMS1, HSPA5, and GSTK1) in subcutaneous tissues.

CONCLUSION

We show for the first time evidence of implication of mRNA splicing and processing machinery in the subcutaneous adipose tissue of women in labor compared to those without labor.

4-Hydroxynonenal Regulates TNF-α Gene Transcription Indirectly via ETS1 and microRNA-29b in Human Adipocytes Induced From Adipose Tissue-Derived Stromal Cells

Obesity is characterized by an accumulation of excessive body fat and can be diagnosed by a variety of measures, such as BMI. However, in some obese individuals, oxidative stress is also thought to be an important pathogenic mechanism of obesity-associated metabolic syndrome. Oxidative stress increases the lipid peroxidation product, 4-hydroxynonenal (4-HNE), which is one of the most abundant and active lipid peroxides. Within the adipose tissue, adipocytes are derived from adipose tissue-derived stromal cells (ADSCs), which play a key role in the generation and metabolism of adipose tissue. Additionally, obesity is associated with low-grade inflammation. Specific microRNAs (miRNAs) that regulate obesity-associated inflammation are largely dysregulated in metabolic syndrome (MS). In this study, we aim to confirm whether 4-HNE and miRNAs play a role in the regulation of TNF-α gene transcription. We enrolled six obese individuals who were referred to Harbin Medical University (Heilongjiang, China) and six nonobese control participants. Plasma 4-HNE levels of the 12 subjects were determined by ELISA. Using qRT-PCR, we measured ETS1, miR-29b, SP1, and TNF-α levels in subcutaneous white adipose tissue (WAT). Furthermore, we examined the relationship between ETS1 and TNF-α using a luciferase reporter assay and a ChIP assay. Our results suggest that ETS1 promotes TNF-α gene transcription in adipocytes. In addition, we demonstrated that 4-HNE promotes TNF-α gene transcription through the inhibition of the miR-29b → SP1 → TNF-α pathway and promotion of the ETS1 → TNF-α pathway. Anat Rec, 299:1145-1152, 2016. © 2016 Wiley Periodicals, Inc.

MicroRNA-29b promotes the adipogenic differentiation of human adipose tissue-derived stromal cells

OBJECTIVE

Obesity is primarily characterized by the accumulation of large amounts of fat in adipose tissue. Within the adipose tissue, adipocytes are derived from adipose tissue-derived stromal cells (ADSCs) via a specialized cell lineage differentiation process, and ADSCs play a key role in the generation and metabolism of adipose tissue. This study investigated whether microRNAs (miRNAs) play a role in adipocyte differentiation.

METHODS

Using luciferase reporter and ChIP assays, the relationship between miR-29b, SP1, and TNF-α was examined.

RESULTS

During the normal adipogenic differentiation of ADSCs, up-regulation of miR-29b promoted adipogenesis by enhancing SP1-mediated inhibition of TNF-α.

CONCLUSIONS

This study investigated the regulatory role of miR-29b during the adipogenic differentiation of ADSCs and found that miR-29b is an effective positive regulator of adipogenesis.

Characterization of Visceral and Subcutaneous Adipose Tissue Transcriptome and Biological Pathways in Pregnant and Non-Pregnant Women: Evidence for Pregnancy-Related Regional-Specific Differences in Adipose Tissue

Objective

The purpose of this study was to compare the transcriptome of visceral and subcutaneous adipose tissues between pregnant and non-pregnant women.

Study Design

The transcriptome of paired visceral and abdominal subcutaneous adipose tissues from pregnant women at term and matched non-pregnant women (n = 11) was profiled with the Affymetrix Human Exon 1.0 ST array. Differential expression of selected genes was validated with the use of quantitative reverse transcription–polymerase chain reaction.

Results

Six hundred forty-four transcripts from 633 known genes were differentially expressed (false discovery rate (FDR) <0.1; fold-change >1.5), while 42 exons from 36 genes showed differential usage (difference in FIRMA scores >2 and FDR<0.1) between the visceral and subcutaneous fat of pregnant women. Fifty-six known genes were differentially expressed between pregnant and non-pregnant subcutaneous fat and three genes in the visceral fat. Enriched biological processes in the subcutaneous adipose tissue of pregnant women were mostly related to inflammation.

Conclusion

The transcriptome of visceral and subcutaneous fat depots reveals pregnancy-related gene expression and splicing differences in both visceral and subcutaneous adipose tissue. Furthermore, for the first time, alternative splicing in adipose tissue has been associated with regional differences and human parturition.

Adipogenic transcriptome profiling using high throughput technologies

The recent technological innovations in the area of functional genomics, gene expression/transcriptomic profiling can provide new insights to understand the molecular basis of adipogenesis. The focus of this review is to highlight the recent advances in our understanding of the complex interplay of gene expression events and the regulatory mechanisms of adipogenesis in mouse cell lines, humans and farm animals. All these studies have employed the availability of constantly evolving high throughput 'omics' technologies including microarrays, RNA-Seq, chromatin immunoprecipitation, next generation sequencing, RNAi, miRNA profiling and quantitative PCR arrays.

Dysregulated inflammation as a risk factor for pneumonia in the elderly

Advances in modern medicine have led to an increase in the median life span and an expansion of the world's population over the age of 65. With increasing numbers of the population surviving to the extreme of age, those at risk for the development of pneumonia will approach 2 billion by the year 2050. Numerous age-related changes in the lung likely contribute to the enhanced occurrence of pneumonia in the elderly. Inflammation in the elderly has been shown to increase risk prior to infection; age-associated inflammation enhances bacterial ligand expression in the lungs which increases the ability of bacteria to attach and invade host cells. Conversely, the elaboration of the acute inflammatory response during early infection has been found to decrease with age resulting in a delayed immune response and diminished bacterial killing. Finally, the resolution of the inflammatory response during the convalescent stage back to "baseline" is often prolonged in the elderly and associated with negative outcomes, such as adverse cardiac events. The focus of this review will be to discuss our current understanding of the potential mechanisms by which dysregulated inflammation (both prior to and following an infectious insult) enhances susceptibility to and severity of community acquired pneumonia (CAP) in the elderly with an emphasis on pneumococcal pneumonia, the leading cause of CAP.