Role for Retinoic Acid-Related Orphan Receptor Alpha (RORα) Expressing Macrophages in Diet-Induced Obesity

Association Between RORA Polymorphisms and Obesity

RORα is a transcription factor encoded by RORA gene. This protein is involved in several metabolic conditions, including obesity. We assessed association between two polymorphisms within this gene (namely rs11639084 and rs4774388) and severe obesity in Iranian population. Both SNPs were associated with obesity in all models (P < 0.0001) except for over-dominant model. T allele of rs11639084 was associated with this trait with OR (95% CI) of 16.85 (13.11-21.67) and was considered as the risk allele. Allelic model best fit the data, since the AIC value for this model was the highest (AIC = 28.82). In the co-dominant model, TT genotype was associated with obesity with OR (95% CI) of 301.6 (137.4-662.1). This genotype was shown to be the risk genotype in the recessive model when compared with TC+CC (OR (95% CI) = 60.54 (30.35-120.7)). The C allele of rs4774388 was shown to be the risk allele with OR (95% CI) of 4.61 (3.72-5.71). In the recessive model, the CC genotype was associated with the mentioned trait with OR (95% CI) of 9.92 (6.62-14.8). This model best fit the data (AIC = 37.08). Cumulatively, the current study suggests contribution of RORα to the pathogenesis of obesity.

Targeting RORα in macrophages to boost diabetic bone regeneration

Diabetes mellitus (DM) has become a serious threat to human health. Bone regeneration deficiency and nonunion caused by DM is perceived as a worldwide epidemic, with a very high socioeconomic impact on public health. Here, we find that targeted activation of retinoic acid-related orphan receptor α (RORα) by SR1078 in the early stage of bone defect repair can significantly promote in situ bone regeneration of DM rats. Bone regeneration relies on the activation of macrophage RORα in the early bone repair, but RORα of DM rats fails to upregulation as hyperglycemic inflammatory microenvironment induced IGF1-AMPK signalling deficiency. Mechanistic investigations suggest that RORα is vital for macrophage-induced migration and proliferation of bone mesenchymal stem cells (BMSCs) via a CCL3/IL-6 depending manner. In summary, our study identifies RORα expressed in macrophages during the early stage of bone defect repair is crucial for in situ bone regeneration, and offers a novel strategy for bone regeneration therapy and fracture repair in DM patients.

Retinoic Acid-Related Orphan Receptor α Is Required for Generation of Th2 Cells in Type 2 Pulmonary Inflammation

The transcription factor retinoic acid-related orphan receptor α (RORα) is important in regulating several physiological functions, such as cellular development, circadian rhythm, metabolism, and immunity. In two in vivo animal models of type 2 lung inflammation, Nippostrongylus brasiliensis infection and house dust mite (HDM) sensitization, we show a role for Rora in Th2 cellular development during pulmonary inflammation. N. brasiliensis infection and HDM challenge induced an increase in frequency of Rora-expressing GATA3+CD4 T cells in the lung. Using staggerer mice, which have a ubiquitous deletion of functional RORα, we generated bone marrow chimera mice, and we observed a delayed worm expulsion and reduced frequency in the expansion of Th2 cells and innate lymphoid type 2 cells (ILC2s) in the lungs after N. brasiliensis infection. ILC2-deficient mouse (Rorafl/flIl7raCre) also had delayed worm expulsion with associated reduced frequency of Th2 cells and ILC2s in the lungs after N. brasiliensis infection. To further define the role for Rora-expressing Th2 cells, we used a CD4-specific Rora-deficient mouse (Rorafl/flCD4Cre), with significantly reduced frequency of lung Th2 cells, but not ILC2, after N. brasiliensis infection and HDM challenge. Interestingly, despite the reduction in pulmonary Th2 cells in Rorafl/flCD4Cre mice, this did not impact the expulsion of N. brasiliensis after primary and secondary infection, or the generation of lung inflammation after HDM challenge. This study demonstrates a role for RORα in Th2 cellular development during pulmonary inflammation that could be relevant to the range of inflammatory diseases in which RORα is implicated.

Identification and characterization of the long non-coding RNA NFIA-AS2 as a novel locus for body mass index in American Indians

BACKGROUND

Genome-wide association studies have shown that body mass index (BMI), an estimate of obesity, is highly polygenic. Individual variants typically have small effect sizes, making it challenging to identify unique loci in under-represented ethnic groups which lack statistical power due to their small sample size. Yet obesity is a major health disparity and is particularly prevalent in southwestern American Indians. Here, we identify and characterize a new locus for BMI that was detected by analyzing moderate associations with BMI obtained in a population-based sample of southwestern American Indians together with the well-powered GIANT dataset.

METHODS

Genotypes for 10.5 million variants were tested for association with BMI in 5870 American Indians and 2600 variants that showed an association P < 10^-3 in the American Indian sample were combined in a meta-analysis with the BMI data reported in GIANT (N = 240,608). The newly identified gene, NFIA-AS2 was functionally characterized, and the impact of its lead associated variant rs1777538 was studied both in-silico and in-vitro.

RESULTS

Rs1777538 (T/C; C allele frequency = 0.16 in American Indians and 0.04 in GIANT, meta-analysis P = 5.0 × 10^-7) exhibited a large effect in American Indians (1 kg/m² decrease in BMI per copy of C allele). NFIA-AS2 was found to be a nuclear localized long non-coding RNA expressed in tissues pertinent to human obesity. Analysis of this variant in human brown preadipocytes showed that NFIA-AS2 transcripts carrying the C allele had increased RNA degradation compared to the T allele transcripts (half-lives = 9 h, 13 h respectively). During brown adipogenesis, NFIA-AS2 featured a stage-specific regulation of nearby gene expression where rs1777538 demonstrated an allelic difference in regulation in the mature adipocytes (the strongest difference was observed for L1TD1, P = 0.007).

CONCLUSION

Our findings support a role for NFIA-AS2 in regulating pathways that impact BMI.

von Willebrand factor links primary hemostasis to innate immunity

The plasma multimeric glycoprotein von Willebrand factor (VWF) plays a critical role in primary hemostasis by tethering platelets to exposed collagen at sites of vascular injury. Recent studies have identified additional biological roles for VWF, and in particular suggest that VWF may play an important role in regulating inflammatory responses. However, the molecular mechanisms through which VWF exerts its immuno-modulatory effects remain poorly understood. In this study, we report that VWF binding to macrophages triggers downstream MAP kinase signaling, NF-κB activation and production of pro-inflammatory cytokines and chemokines. In addition, VWF binding also drives macrophage M1 polarization and shifts macrophage metabolism towards glycolysis in a p38-dependent manner. Cumulatively, our findings define an important biological role for VWF in modulating macrophage function, and thereby establish a novel link between primary hemostasis and innate immunity.

Nuclear Receptor RORα/γ: Exciting Modulators in Metabolic Syndrome and Related Disorders

Under the influences of modern lifestyle, metabolic syndromes (MetS), including insulin resistance, obesity, and fatty liver, featuring a worldwide chronic disease, greatly raise the risk of type 2 diabetes, heart disease, and stroke. However, its pathogenesis is still unclear, and there are limited drugs with strong clinical efficacy and specificity. Given the close connection between impaired lipid metabolism and MetS onset, modulating the lipid metabolic genes may provide potential prospects in the development of MetS therapeutics. Nuclear receptors are such druggable transcription factors that translate physiological signals into gene regulation via DNA binding upon ligand activation. Recent studies reveal vital functions of the NRs retinoic acid's receptor-related orphan receptors (RORs), including RORα and RORγ, in the gene regulation in lipid metabolism and MetS. This review focuses on the latest developments in their actions on MetS and related metabolic disorders, which would benefit future clinically therapeutic applications.

Rora Regulates Neutrophil Migration and Activation in Zebrafish

Neutrophil migration and activation are essential for defense against pathogens. However, this process may also lead to collateral tissue injury. We used microRNA overexpression as a platform and discovered protein-coding genes that regulate neutrophil migration. Here we show that miR-99 decreased the chemotaxis of zebrafish neutrophils and human neutrophil-like cells. In zebrafish neutrophils, miR-99 directly targets the transcriptional factor RAR-related orphan receptor alpha (roraa). Inhibiting RORα, but not the closely related RORγ, reduced chemotaxis of zebrafish and primary human neutrophils without causing cell death, and increased susceptibility of zebrafish to bacterial infection. Expressing a dominant-negative form of Rorα or disrupting the roraa locus specifically in zebrafish neutrophils reduced cell migration. At the transcriptional level, RORα regulates transmembrane signaling receptor activity and protein phosphorylation pathways. Our results, therefore, reveal previously unknown functions of miR-99 and RORα in regulating neutrophil migration and anti-microbial defense.

Maternal diabetes-mediated RORA suppression contributes to gastrointestinal symptoms in autism-like mouse offspring

BACKGROUND

Retinoic acid-related orphan receptor alpha (RORA) has been reported to be suppressed in autistic patients and is associated with autism spectrum disorders (ASD), although the potential role and mechanism of RORA on gastrointestinal (GI) symptoms in ASD patients is still not reported. In this study, we aim to investigate the contribution of RORA to GI symptoms through a maternal diabetes-mediated autism-like mouse model.

RESULTS

Male offspring of diabetic dams were treated with either superoxide dismutase (SOD) mimetic MnTBAP or RORA agonist SR1078, or were crossbred with intestine epithelial cells (IEC)-specific RORA knockout (RORA^-/-) mouse. Gene expression, oxidative stress and inflammation were measured in brain tissues, peripheral blood mononuclear cells (PBMC) and IEC, and GI symptoms were evaluated. Our results showed that SOD mimetic MnTBAP completely, while RORA agonist SR1078 partly, reversed maternal diabetes-mediated oxidative stress and inflammation in the brain, PBMC and IEC, as well as GI symptoms, including intestine permeability and altered gut microbiota compositions. IEC-specific RORA deficiency either mimicked or worsened maternal diabetes-mediated GI symptoms as well as oxidative stress and inflammation in IEC, while there was little effect on maternal diabetes-mediated autism-like behaviors.

CONCLUSIONS

We conclude that RORA suppression contributes to maternal diabetes-mediated GI symptoms in autism-like mouse offspring, this study provides a potential therapeutical target for maternal diabetes-mediated GI symptoms in offspring through RORA activation.

AKR1C2 and AKR1C3 expression in adipose tissue: Association with body fat distribution and regulatory variants

BACKGROUND

Changes in androgen dynamics within adipose tissue have been proposed as modulators of body fat accumulation. In this context, AKR1C2 likely plays a significant role by inactivating 5α-dihydrotestosterone.

AIM

To characterize AKR1C2 expression patterns across adipose depots and cell populations and to provide insight into the link with body fat distribution and genetic regulation.

METHODS

We used RNA sequencing data from severely obese patients to assess patterns of AKR1C2 and AKR1C3 expression in abdominal adipose tissue depots and cell fractions. We additionally used data from 856 women to assess AKR1C2 heritability and to link its expression in adipose tissue with body fat distribution. Further, we used public resources to study AKR1C2 genetic regulation as well as reference epigenome data for regulatory element profiling and functional interpretation of genetic data.

RESULTS

We found that mature adipocytes and adipocyte-committed adipocyte progenitor cells (APCs) had enriched expression of AKR1C2. We found adipose tissue AKR1C2 and AKR1C3 expression to be significantly and positively associated with percentage trunk fat mass in women. We identified strong genetic regulation of AKR1C2 by rs28571848 and rs34477787 located on the binding sites of two nuclear transcription factors, namely retinoid acid-related orphan receptor alpha and the glucocorticoid receptor.

CONCLUSION

We confirm the link between AKR1C2, adipogenic differentiation and adipose tissue distribution. We provide insight into genetic regulation of AKR1C2 by identifying regulatory variants mapping to binding sites for the glucocorticoid receptor and retinoid acid-related orphan receptor alpha which may in part mediate the effect of AKR1C2 expression on body fat distribution.

Functions for Retinoic Acid-Related Orphan Receptor Alpha (RORα) in the Activation of Macrophages During Lipopolysaccharide-Induced Septic Shock

The transcription factor Related Orphan Receptor Alpha (RORα) plays an important role in regulating circadian rhythm, inflammation, metabolism and cellular development. Herein we show that in the absence of functional RORα in mice there is reduced susceptibility to LPS-induced endotoxic shock, with selective decreases in release of pro-inflammatory cytokines. Treatment of mice with a RORα selective synthetic inhibitor also reduced the severity of LPS-induced endotoxemia. The reduction in responses in Rora deficient mice was associated with an alterations in metabolic and pro-inflammatory functions of macrophages, both in vivo peritoneal macrophages and in vitro generated bone marrow derived macrophages. Using LysM^CreRora^fl/sg mice the reduced susceptibility to LPS was shown to be specific to Rora expression in the macrophages. This study identifies that Rora-mediated regulation of macrophages impacts on the pro-inflammatory responses elicited by LPS.

Aging with rhythmicity. Is it possible? Physical exercise as a pacemaker

Aging is associated with gradual decline in numerous physiological processes, including a reduction in metabolic functions and immunological system. The circadian rhythm plays a vital role in health, and prolonged clock disruptions are associated with chronic diseases. The relationships between clock genes, aging, and immunosenescence are not well understood. Inflammation is an immune response triggered in living organisms in response to the danger associated with pathogens and injury. The term 'inflammaging' has been used to describe the chronic low-grade-inflammation that develops with advancing age and predicts susceptibility to age-related pathologies. Equilibrium between pro-and anti-inflammatory cytokines is needed for healthy aging and longevity. Sedentary and poor nutrition style life indices a disruption in circadian rhythm promoting an increase in pro-inflammatory factors or leads for chronic low-grade inflammation. Moreover, signals mediated by pro-inflammatory cytokines, such as tumor necrosis factor-alpha and interleukin-6, might accentuate of the muscle loss during aging. Circadian clock is important to maintain the physiological functions, as maintenance of immune system. A strategy for imposes rhythmicity in the physiological systems may be adopted of exercise training routine. The lifelong regular practice of physical exercise decelerates the processes of aging, providing better quality and prolongation of life. Thus, in this review, we will focus on how aging affects circadian rhythms and its relationship to inflammatory processes (inflammaging), as well as the role of physical exercise as a regulator of the circadian rhythm, promoting aging with rhythmicity.