Exploring Adiponectin in Autosomal Dominant Kidney Disease: Insight and Implications.

Autosomal Dominant Polycystic Kidney Disease (ADPKD) is a common monogenic disorder characterized by renal cysts and progressive renal failure. In kidney diseases, adipose tissue undergoes functional changes that have been associated with increased inflammation and insulin resistance mediated by release of adipokines. Adiponectin is involved in various cellular processes, such as energy and inflammatory and oxidative processes. However, it remains to be determined whether adiponectin is involved in the concomitant metabolic dysfunctions present in PKD. In this scenario, we aimed to analyze: (a) PPARγ, ADIPOQ, ADIPOR1 and ADIPOR2 gene variations in 92 ADPKD patients through PCR-Sanger sequencing; and (b) adiponectin levels and its oligomerization state by ELISA and Western Blot. Our results indicated that: (a) 14 patients carried the PPARγ SNP, 29 patients carried the ADIPOQ SNP rs1501299, and 25 patients carried the analyzed ADIPOR1 SNPs. Finally, 82 patients carried ADIPOR2 SNPs; and (b) Adiponectin is statistically lower in ADPKD patients compared to controls, and further statistically lower in ESRD than in non-ESRD patients. An inverse relationship between adiponectin and albumin and between adiponectin and creatinine and a direct relationship between adiponectin and eGFR were found. Interestingly, significantly lower levels of adiponectin were found in patients bearing the ADIPOQ rs1501299 SNP and associated with low levels of eGFR. In conclusion, adiponectin levels and the presence of ADIPOQ rs1501299 genotype are significantly associated with a worse ADPKD phenotype, indicating that both could potentially provide important insights into the disease. Further studies are warranted to understand the pathophysiological role of adiponectin in ADPKD patients.

The effect of plasma cytokines on the expression of adiponectin and its receptors in the synovial membrane of joints and the infrapatellar fat pad in patients with rheumatoid arthritis and osteoarthritis.

BACKGROUND: Rheumatoid arthritis (RA) is an autoimmune inflammatory disease that leads to joint destruction. Numerous pro-inflammatory mediators, including adipokines, play an important role in the pathogenesis of RA. OBJECTIVE: The aim of the study was to investigate the relationships between selected plasma cytokines and expression of adiponectin and its receptors in the synovium and the infrapatellar fat pad in patients with RA and osteoarthritis (OA). METHODS: Blood, synovium and fat pad samples from 18 patients with RA and 18 with OA were collected during joint replacement surgery. Spearman rank correlations between plasma concentrations of selected cytokines (IL-1ß, IL-2, IL-4, IL-6, IL-7, IL-8, IL-10, IL-12 p40, IL-13, IL-17, G-CSF and GM-CSF) and the expression of adiponectin and its receptors were determined. Plasma levels of cytokines were determined using a magnetic bead-based multiplex assay, mRNA expression of adiponectin and its receptors were determined by real-time PCR. RESULTS: In OA patients, there were significant positive correlations between adiponectin expression in the synovial membrane and plasma levels of IL-1ß, IL-4, G-CSF and GM-CSF, as well as a significant positive correlation between adiponectin expression in the fat pad and plasma levels of GM-CSF. In addition, OA patients showed significant negative correlations between AdipoR1 and AdipoR2 expression in the synovial membrane and plasma IL-6 levels, as well as between AdipoR2 expression in the synovial membrane and plasma MCP-1 and TNF-α levels. In patients with RA, there were no significant correlations between adiponectin expression in the synovial membrane and infrapatellar fat pad and plasma levels of the cytokines studied. In addition, RA patients showed a statistically significant negative correlation between AdipoR1 expression in the synovial membrane and plasma levels of TNF-α, IL-7, IL-12 and IL-13, and a significant negative correlation between AdipoR1 expression in the infrapatellar fat pad and plasma levels of IL-1ß. CONCLUSIONS: Adiponectin and its receptors showed the correlations with several plasma cytokines, however, a thorough understanding of the role of adiponectin in RA and OA requires further investigation.

The slow-release adiponectin analog ALY688-SR modifies early-stage disease development in the D2.mdx mouse model of Duchenne muscular dystrophy.

Fibrosis is associated with respiratory and limb muscle atrophy in Duchenne muscular dystrophy (DMD). Current standard of care partially delays the progression of this myopathy but there remains an unmet need to develop additional therapies. Adiponectin receptor agonism has emerged as a possible therapeutic target to lower inflammation and improve metabolism in mdx mouse models of DMD but the degree to which fibrosis and atrophy are prevented remain unknown. Here, we demonstrate that the recently developed slow-release peptidomimetic adiponectin analog, ALY688-SR, remodels the diaphragm of murine model of DMD on DBA background (D2.mdx) mice treated from days 7-28 of age during early stages of disease. ALY688-SR also lowered interleukin-6 (IL-6) mRNA but increased IL-6 and transforming growth factor-ß1 (TGF-ß1) protein contents in diaphragm, suggesting dynamic inflammatory remodeling. ALY688-SR alleviated mitochondrial redox stress by decreasing complex I-stimulated H2O2 emission. Treatment also attenuated fibrosis, fiber type-specific atrophy, and in vitro diaphragm force production in diaphragm suggesting a complex relationship between adiponectin receptor activity, muscle remodeling, and force-generating properties during the very early stages of disease progression in murine model of DMD on DBA background (D2.mdx) mice. In tibialis anterior, the modest fibrosis at this young age was not altered by treatment, and atrophy was not apparent at this young age. These results demonstrate that short-term treatment of ALY688-SR in young D2.mdx mice partially prevents fibrosis and fiber type-specific atrophy and lowers force production in the more disease-apparent diaphragm in relation to lower mitochondrial redox stress and heterogeneous responses in certain inflammatory markers. These diverse muscle responses to adiponectin receptor agonism in early stages of DMD serve as a foundation for further mechanistic investigations.NEW & NOTEWORTHY There are limited therapies for the treatment of Duchenne muscular dystrophy. As fibrosis involves an accumulation of collagen that replaces muscle fibers, antifibrotics may help preserve muscle function. We report that the novel adiponectin receptor agonist ALY688-SR prevents fibrosis in the diaphragm of D2.mdx mice with short-term treatment early in disease progression. These responses were related to altered inflammation and mitochondrial functions and serve as a foundation for the development of this class of therapy.

Overexpression of salusin­ß downregulates adipoR1 expression to prevent fatty acid oxidation in HepG2 cells.

Salusin­ß and adiponectin receptor 1 (adipoR1) serve important roles in the development of certain cardiovascular diseases and lipid metabolism. However, to the best of our knowledge, the relationship between salusin­ß and adipoR1, and their underlying mechanisms of action, currently remain unclear. In the present study, lentiviral vectors designed to overexpress salusin­ß or knock down salusin­ß expression were used in 293T and HepG2 cells. Semi­quantitative PCR was performed to investigate the relationship between salusin­ß and adipoR1 mRNA expression in 293T cells. Western blotting was used to assess the protein expression levels of adipoR1, adenosine monophosphate­activated protein kinase (AMPK), acetyl­CoA carboxylase (ACC) and carnitine palmitoyl transferase 1A (CPT­1A) in transfected HepG2 cells. Simultaneously, HepG2 cells were treated with an adipoR1 inhibitor (thapsigargin) or agonist (AdipoRon) and the resultant changes in the expression levels of the aforementioned proteins were observed. Oil Red O staining and measurements of cellular triglyceride levels were performed to assess the extent of lipid accumulation in HepG2 cells. The results demonstrated that salusin­ß overexpression downregulated adipoR1 expression and inhibited the phosphorylation of AMPK and ACC, which led to decreased CPT­1A protein expression. By contrast, salusin­ß knockdown increased adipoR1 expression and promoted the phosphorylation of AMPK and ACC, which conversely enhanced CPT­1A protein expression. Treatment with adipoR1 agonist, AdipoRon, reversed the effects of salusin­ß overexpression. In addition, salusin­ß overexpression enhanced intracellular lipid accumulation in HepG2 cells induced by free fatty acid treatment. These findings highlighted the potential regulatory role of salusin­ß in adipoR1­mediated signaling pathways. To conclude, the present study provided insights into the regulation of fatty acid metabolism by the liver. In particular, salusin­ß may serve as a potential target for the therapeutic intervention of metabolic disorders of lipids.

[AdipoRon Effect on Expression of Lipid Metabolism Genes in Cultured Human Primary Macrophages].

Atherosclerosis is characterized by excessive uptake of cholesterol-rich low-density lipoprotein (LDL) by vascular wall macrophages. The macrophages are transformed into foam cells, lipids accumulate in the intima of arteries, atherosclerotic plaques arise, and cardiovascular diseases develop. Adiponectin is an adipose tissue adipokine and possess anti-atherogenic and anti-inflammatory activities, which are mediated by adiponectin binding to its receptors AdipoR1 and AdipoR2. To exert its anti-atherogenic effect, adiponectin may regulate the reverse cholesterol transport and prevent foam cells formation. The small-molecule adiponectin receptor agonist AdipoRon was assumed to modulate expression of reverse cholesterol transport and inflammation genes in human macrophages. Several AdipoRon concentrations (0, 5, 10, and 20 µM) were tested for effect on expression of the lipid metabolism genes ABCA1, ABCG1, APOA1, NR1H3 (LXRα), NR1H2 (LXRß), PPARG, and ACAT1 and the inflammation genes IL6, TNFA, and TLR4 in cultured human primary macrophages and the THP-1 macrophage cell line. Cell viability was measured using the MTS assay. ABCA1, ABCG1, APOA1, NR1H3, NR1H2, PPARG, ACAT1, IL6, TNFA, and TLR4 mRNA levels in human primary macrophages were assessed by real-time PCR. The PPARG and ABCA1 relative mRNA levels were found to increase in human primary macrophages treated with 5 or 10 µM AdipoRon for 24 h. A higher AdipoRon concentration (20 µM) was cytotoxic to macrophages, especially THP-1 cells. The effect of AdipoRon on human macrophages and potential adiponectin receptor agonists are of interest to study in view of the need to develop new approaches to atherosclerosis prevention and treatment.

Sex-Specific Associations between Adiponectin and Leptin Signaling and Pancreatic Cancer Survival.

BACKGROUND: Circulating adiponectin and leptin have been associated with risk of pancreatic cancer. However, the relationship between long-term exposure to these adipokines in the prediagnostic period with patient survival has not been investigated. METHODS: Adipokine levels were measured in prospectively collected samples from 472 patients with pancreatic cancer. Because of sex-specific differences in adipokine levels, associations were evaluated separately for men and women. In a subset of 415 patients, we genotyped 23 SNPs in adiponectin receptor genes (ADIPOR1 and ADIPOR2) and 30 SNPs in the leptin receptor gene (LEPR). RESULTS: Adiponectin levels were inversely associated with survival in women [HR, 1.71; 95% confidence interval (CI), 1.15-2.54]; comparing top with bottom quartile but not in men (HR, 0.89; 95% CI, 0.46-1.70). The SNPs rs10753929 and rs1418445 in ADIPOR1 were associated with survival in the combined population (per minor allele HR, 0.66; 95% CI, 0.51-0.84, and HR, 1.33; 95% CI, 1.12-1.58, respectively). Among SNPs in LEPR, rs12025906, rs3790431, and rs17127601 were associated with survival in the combined population [HRs, 1.54 (95% CI, 1.25-1.90), 0.72 (95% CI, 0.59-0.88), and 0.70 (95% CI, 0.56-0.89), respectively], whereas rs11585329 was associated with survival in men only (HR, 0.39; 95% CI, 0.23-0.66; Pinteraction = 0.0002). CONCLUSIONS: High levels of adiponectin in the prediagnostic period were associated with shorter survival among women, but not among men with pancreatic cancer. Several polymorphisms in ADIPOR1 and LEPR are associated with patient survival. IMPACT: Our findings reveal the association between adipokine signaling and pancreatic cancer survival and demonstrate the importance of examining obesity-associated pathways in relation to pancreatic cancer in a sex-specific manner.

Emerging Role of Adiponectin/AdipoRs Signaling in Choroidal Neovascularization, Age-Related Macular Degeneration, and Diabetic Retinopathy.

Age-related macular degeneration (AMD), a leading cause of irreversible blindness in adults, may result in poor central vision, making it difficult to see, read, and drive. AMD is generally classified in either dry or wet types. Milder cases of dry AMD may progress to geographic atrophy (GA), leading to significant visual disability; wet, or neovascular AMD, which involves choroidal neovascularization (CNV), can lead to complete loss of central vision. Adiponectin (APN) discovery in the mid-1990's and, subsequently, its two cognate receptors (AdipoRs) in the early 2000s have led to a remarkable progress in better understanding metabolic disorders, as well as metabolism-associated ocular pathology. APN/AdipoRs signaling plays a central role in a variety of molecular and cellular physiological events, including glucose and lipid metabolism, whole-body energy regulation, immune and inflammation responses, insulin sensitivity and retinal cell biological functions. This review is an amalgamation of recent information related to APN/AdipoRs in the pathophysiology of retinal diseases and furthers its association with AMD and diabetic retinopathy. Additionally, we present our original research, where we designed control peptide and CNV inhibitory peptide from the globular region of APN to see the effect of these peptides on the mouse model of laser-induced CNV. The inhibitory peptide (APN1) inhibited CNV by more than 75% while the control peptide did not inhibit CNV.

Physical exercise attenuates age-related muscle atrophy and exhibits anti-ageing effects via the adiponectin receptor 1 signalling.

BACKGROUND: Although the adiponectin signalling exerts exercise-mimicking effects, whether this pathway contributes to the anti-ageing benefits of physical exercise has not been established yet. METHODS: Swim exercise training and wheel running were used to measure lifespan in the nematode Caenorhabditis elegans and skeletal muscle quality in mice, respectively. Muscle weight, muscle fibre cross-sectional area (CSA) and myonuclei number were used to evaluate muscle mass. RNA sequencing (RNA-Seq) analysis of skeletal muscle in exercised mice was used to study the underlying mechanisms. Western blot and immunofluorescence were performed to explore autophagy- and senescence-related markers. RESULTS: The C. elegans adiponectin receptor PAQR-1/AdipoR1, but not PAQR-2/AdipoR2, was activated (3.55-fold and 3.48-fold increases in p-AMPK on Days 1 and 6, respectively, P < 0.001), which was involved in lifespan extension in exercised worms. Exercise training increased skeletal muscle mass index (1.29-fold, P < 0.01), muscle weight (1.75-fold, P < 0.001), myonuclei number (1.33-fold, P < 0.05), muscle fibre CSA (1.39-fold, P < 0.05) and capillary abundance (2.19-fold, P < 0.001 for capillary density; 1.58-fold, P < 0.01 for capillary number) in aged mice. Physical exercise reduced protein (2.94-fold, P < 0.001) and mRNA levels (1.70-fold, P < 0.001) of p16INK4a , a marker for cellular senescence, in skeletal muscle of aged mice. These beneficial effects of exercise on skeletal muscle of mice were dependent on AdipoR1. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis for differentially expressed genes in skeletal muscle between exercised mice with and without AdipoR1 knockdown by RNA-Seq analysis revealed that several KEGG pathways, such as 'AMPK signalling pathway' (P < 0.001), 'FOXO signalling pathway' (P < 0.001) and 'autophagy' (P < 0.001) were overrepresented. Knockdown of FoxO3a inhibited exercise-mediated beneficial effects on skeletal muscle quality of mice by inhibiting autophagy/mitophagy (3.81-fold reduction in LC3-II protein, P < 0.001; 1.53-fold reduction in BNIP3 protein, P < 0.05). Knockdown of daf-16, the FoxO homologue in C. elegans, reduced autophagy (2.77-fold and 2.06-fold reduction in GFP::LGG-1 puncta in seam cells and the intestine, respectively, P < 0.05) and blocked lifespan extension by exercise in worms. CONCLUSIONS: Our findings provide insights into how the AdipoR1 pathway has an impact on the anti-ageing benefits of exercise and implicate that activation of the AdipoR1 signalling may represent a potential therapeutic strategy for reducing age-related loss of skeletal muscle.

Distinct roles of ADIPOR1 and ADIPOR2: A pan-cancer analysis.

Introduction: AdipoR1 and AdipoR2 proteins, encoded by ADIPOR1 and ADIPOR2 genes respectively, are the receptors of adiponectin secrected by adipose tissue. Increasing studies have identified the vital role of adipose tissue in various diseases, including cancers. Hence, there is an urgent need to explore the roles of AdipoR1 and AdipoR2 in cancers. Methods: We conducted a comprehensive pan-cancer analysis for the roles of AdipoR1 and AdipoR2 via several public databases, including expression differences, prognostic value, and the correlations with tumor microenvironment, epigenetic modification, and drug sensitivity. Results: Both ADIPOR1 and ADIPOR2 genes are dysregulated in most cancers, but their genomic alteration frequencies are low. In addition, they are also correlated with the prognosis of some cancers. Although they are not strongly correlated with tumor mutation burden (TMB) or microsatellite instability (MSI), ADIPOR1/2 genes display a significant association with cancer stemness, tumor immune microenvironment, immune checkpoint genes (especially CD274 and NRP1), and drug sensitivity. Discussion: ADIPOR1 and ADIPOR2 play critical roles in diverse cancers, and it is a potential strategy to treat tumors through targeting ADIPOR1 and ADIPOR2.

The Mef2c/AdipoR1 axis is responsible for myogenic differentiation and is regulated by resistin in skeletal muscles.

Previous studies have shown that accumulated lipid and insulin resistance emerges in skeletal muscle after the onset of obesity and diabetes. We have previously shown that resistin significantly increases lipid contents in C2C12 cells. However, studies evaluating the effects of resistin on skeletal muscle cells and tissues are limited; despite that, an understanding of resistin action and function on lipid alteration in skeletal muscle tissues is critical for understanding obesity-related diseases. In this study, we document that resistin increases lipid deposition both in vitro and in vivo. Further, resistin promotes fiber type transformation, decreases enzyme activities, inhibits myogenic differentiation, and decreases muscle grip and excise endurance. In addition, adiponectin signaling is activated during myocyte differentiation, but it is inhibited at elevated resistin concentrations. Mechanistic investigation revealed that mef2c is responsible for adiponectin signaling pathway inhibition by inhibiting adipoR1 expression at the transcriptional level. In conclusion, this is the first study to document that resistin increases ectopic lipid deposition in skeletal muscles via a mef2c-adipoR1 signaling pathway, which reveals for the first time the presence of crosstalk between resistin and adiponectin in skeletal muscles.

The adiponectin receptor agonist, AdipoRon, promotes reproductive hormone secretion and gonadal development via the hypothalamic-pituitary-gonadal axis in chickens.

Adiponectin is a key hormone secreted by fat tissues that has multiple biological functions, including regulating the energy balance and reproductive system by binding to its receptors AdipoR1 and AdipoR2. This study investigated the correlation between the levels of adiponectin and reproductive hormones in the hypothalamic-pituitary-ovarian (HPO) axis of laying hens at 4 different developmental stages (15, 20, 30, and 68 wk) and explored the effects of AdipoRon (an activator of adiponectin receptors) on the hypothalamic-pituitary-gonadal (HPG) axis and follicle and testicular Leydig cells in vitro and in vivo. The results demonstrated that the adiponectin level was significantly correlated with that of reproductive hormones in the HPO axis (e.g., GnRH, FSH, LH, and E2) in laying hens at 4 different ages. Moreover, AdipoRon could promote the expression of AdipoR1 and AdipoR2 and the secretion of reproductive hormones in the HPG axis, including GnRH, FSH, LH, P4, and T. AdipoRon could also upregulate the expression of genes related to follicular steroidogenesis (STAR, CYP19A1, CYP17A1, and CYP11A1), hepatic lipid synthesis (OVR, MTP), follicular lipid uptake (PPAR-g), and follicular angiogenesis (VEGFA1, VEGFA2, VEGFR1, ANGPT1, ANGPT2, TEK) in the oviposition period, and all of these findings were consistent with the results obtained from in vitro experiments after the transfection of small white follicles (SWFs) with AdipoRon. Furthermore, the results suggest that AdipoRon increases the diameter of testicular seminiferous tubules, the number of spermatogenic cells and sperm production in vivo and enhances the expression of AdipoR1, AdipoR2 and steroid hormones in vitro. Collectively, the findings suggest that AdipoRon could facilitate the expression and secretion of reproductive hormones in the HPG axis by activating its receptors and then improve the growth and development of follicles and testes in chickens.

Adiponectin Stimulates Apolipoprotein A-1 Gene Expression in HepG2 Cells via AMPK, PPARα, and LXRs Signaling Mechanisms.

Adiponectin is an adipose tissue hormone, participating in energy metabolism and involved in atherogenesis. Previously, it was found that adiponectin increases expression of the APOA1 (apolipoprotein A-1) gene in hepatocytes, but the mechanisms of this effect remained unexplored. Our aim was to investigate the role of adiponectin receptors AdipoR1/R2, AMP-activated protein kinase (AMPK), nuclear peroxisome proliferator-activated receptor alpha (PPARα) and liver X receptors (LXRs) in mediating the action of adiponectin on hepatic APOA1 expression in human hepatoma HepG2 cells. The level of APOA1 expression was determined by RT-qPCR and ELISA. We showed that the siRNA-mediated knockdown of genes coding for AdipoR1, AdipoR2, AMPK, PPARα, and LXRα and ß prevented adiponectin-induced APOA1 expression in HepG2 cells and demonstrated that interaction of PPARα and LXRs with the APOA1 gene hepatic enhancer is important for the adiponectin-dependent APOA1 transcription. The results of this study point out to the involvement of both types of adiponectin receptors, AMPK, PPARα, and LXRs in the adiponectin-dependent upregulation of the APOA1 expression.

Effects of Cilostazol on Angiogenesis in Diabetes through Adiponectin/Adiponectin Receptors/Sirtuin1 Signaling Pathway.

Cilostazol is an antiplatelet agent with vasodilating effects that functions by increasing the intracellular concentration of cyclic adenosine monophosphate. We have previously shown that cilostazol has favorable effects on angiogenesis. However, there is no study to evaluate the effects of cilostazol on adiponectin. We investigated the effects of cilostazol on angiogenesis in diabetes in vitro and in vivo through adiponectin/adiponectin receptors (adipoRs) and the sirtuin 1 (SIRT1)/AMP-activated protein kinase (AMPK) signaling pathway. Human umbilical vein endothelial cells (HUVECs) and human aortic smooth muscle cells (HASMCs) were cocultured under high glucose (HG) conditions. Adiponectin concentrations in the supernatants were significantly increased when HASMCs were treated with cilostazol but not significantly changed when only HUVECs were treated with cilostazol. Cilostazol treatment enhanced the expression of SIRT1 and upregulated the phosphorylation of AMPK in HG-treated HUVECs. By sequential knockdown of adipoRs, SIRT1, and AMPK, our data demonstrated that cilostazol prevented apoptosis and stimulated proliferation, chemotactic motility, and capillary-like tube formation in HG-treated HUVECs through the adipoRs/SIRT1/AMPK signaling pathway. The phosphorylation of downstream signaling molecules, including acetyl-CoA carboxylase (ACC) and endothelial nitric oxide synthase (eNOS), was downregulated when HUVECs were treated with a SIRT1 inhibitor. In streptozotocin-induced diabetic mice, cilostazol treatment could improve blood flow recovery 21-28 days after inducing hindlimb ischemia as well as increase the circulating of CD34+CD45dim cells 14-21 days after operation; moreover, these effects were significantly attenuated by the knockdown of adipoR1 but not adipoR2. The expression of SIRT1 and phosphorylation of AMPK/ACC and Akt/eNOS in ischemic muscles were significantly attenuated by the gene knockdown of adipoRs. Cilostazol improves HG-induced endothelial dysfunction in vascular endothelial cells and enhances angiogenesis in diabetic mice by upregulating the expression of adiponectin/adipoRs and its SIRT1/AMPK downstream signaling pathway.

Association of Adiponectin Receptors with Metabolic and Immune Homeostasis Parameters in Colorectal Cancer: In Silico Analysis and Observational Findings.

Adiponectin (ADIPOQ) as both a regulator of metabolic homeostasis and a protein involved in immune response might be of particular interest to contemporary laboratory medicine, especially in terms of minimally invasive diagnostics. The diverse roles of ADIPOQ with regard to the immune and metabolic aspects of colorectal carcinogenesis have been proposed. However, the expression of its receptors ADIPOR1 and ADIPOR2 is scarcely explored in peripheral blood mononuclear cells (PBMCs). Moreover, ADIPORs' relationships with the immune response mediator TNF-α have not been previously investigated in the PBMCs of CRC patients. This study used both in silico and observational case-control analyses with the aim of exploring the association of ADIPOR gene expression and ADIPOQ single nucleotide polymorphisms (SNPs) with the inflammatory marker TNF-α and lipid status parameters in patients with CRC. Publicly available transcriptomic datasets (GSE47756, GSE44076) obtained from analyses of monocytes and CRC tissue samples were employed for the in silico evaluation of ADIPORs' specific genetic traits. GSE47756 and GSE44076 datasets were processed with GSEA software to provide a genetic fingertip of different signaling pathways associated with ADIPORs' mRNA levels. The case-control aspect of the study included the PBMC samples of 73 patients diagnosed with CRC and 80 healthy volunteers. The PCR method was carried out for the PBMC gene expression analysis (ADIPOR1, ADIPOR2, TNF-α mRNA levels) and for the subjects' genotyping (ADIPOQ rs266729, ADIPOR1 rs7539542). GSEA showed significant associations of ADIPOR mRNA expression with gene sets related to metabolic and immune homeostasis in both datasets. The case-control study revealed the association of ADIPOR1 rs7539542 with reduced lipid status parameters in CRC. In addition, PBMC ADIPOR1 mRNA levels decreased in CRC (p < 0.001), whereas ADIPOR2 mRNA did not differ between the groups (p = 0.442). A reduction in PBMC TNF-α mRNA levels was noted in CRC (p < 0.05). Our results indicate that ADIPOR1 and ADIPOR2 play a significant role in the alteration of both metabolic and immune homeostasis during the progression of CRC. For the first time, ADIPOR1 is shown to be a specific receptor for mediating ADIPOQ's effects in the PBMCs of CRC patients.

miRNA-323a-3p promoted intracranial, aneurysm-induced inflammation via AMPK/NF-κB signaling pathway by AdipoR1.

BACKGROUND: An intracranial arterial wall which locally protrudes outward, typically in the capsule and fusiform, is called an intracranial aneurysm (IA). Among these aneurysms, 1-2% might spontaneously rupture before treatment. Anterior and posterior communicating aneurysms are more likely to rupture than other aneurysms, and an anterior communicating aneurysm is more likely to rupture than a posterior communicating aneurysm. OBJECTIVES: To identify the effects of miRNA-323a-3p expression in intracranial aneurysms and its potential regulatory mechanism. MATERIAL AND METHODS: Patients with IA and healthy volunteers were enrolled, and their serum samples were extracted for the detection of tumor necrosis factor alpha (TNF-α), interleukin 1ß (IL-1ß), IL-6, IL-18, and miRNA-323a-3p. Then, the regulatory effects of miRNA-323a-3p on the above inflammatory factors and AdipoR1/AMPK/NF-kb signaling were also detected in vitro. RESULTS: The downregulation of miRNA-323a-3p reduced the expression of inflammatory factors (TNF-α, IL-1ß, IL-6, and IL-18) in an in vitro model in comparison with the control group. The overexpression of miRNA-323a-3p suppressed the protein expression of adiponectin receptor R1 (AdipoR1) and p-AMPK, and induced NF-κB-p65 protein expression in an in vitro model. CONCLUSIONS: We showed that AdipoR1 plasmid, AMPK activator 1 or si-NF-κB reduced the pro-inflammatory effects of miRNA-323a-3p in an in vitro model. The miRNA-323a-3p exacerbated the inflammatory reaction in IA through AMPK/NF-κB signaling by AdipoR1. Our findings suggest that miRNA-323a-3p targeting AdipoR1 is promising in further anti-inflammatory treatment of IAs.

Role of Adiponectin Peptide I (APNp1) in Age-Related Macular Degeneration.

Age-related macular degeneration (AMD) is an eye disease that can cause central vision loss, particularly in the elderly population. There are 2 classes of AMD, wet-type and dry-type. Wet-type involves excess angiogenesis around the macula, referred to as choroidal neovascularization (CNV). This can result in leaky vessels, often causing more severe vision loss than dry-type AMD. Adiponectin peptide 1 (APNp1) has been shown to slow the progression of CNV. Here, we used a mouse model and FITC-labeled APNp1 to determine if APNp1 could be delivered effectively as an eye drop. Our experiment revealed that topically applied FITC-APNp1 could reach the macula of the eye, which is crucial for treating wet-type AMD. We also tested delivery of APNp1 via injection of an adeno-associated virus (AAV) vector in a mouse model of CNV. AAV is a harmless virus easy to manipulate and is very often used for protein or peptide deliveries. Results revealed an increase in the expression of APNp1 in the retina and choroid over a 28-day period. Finally, we investigated the mechanism by which APNp1 affects CNV by examining the expression of adiponectin receptor 1 (AdipoR1) and proliferating cell nuclear antigen (PCNA) in the retinal and choroidal tissue of the mouse eyes. AdipoR1 and PCNA were overexpressed in these tissues in mice with laser-induced CNV compared to naïve mice. Based on our data shown here, we think it will enhance our understanding of APNp1 as a therapeutic agent for wet-type AMD and possible treatment alternatives that could be more beneficial for patients.

AdipoR1 Regulates Ionizing Radiation-Induced Ferroptosis in HCC cells through Nrf2/xCT Pathway.

Radiotherapy has been used for decades in the treatment of liver cancer. We previously found that adiponectin receptor (AdipoR1) is a prognostic biomarker for hepatoma carcinoma (HCC) after stereotactic body radiation therapy (SBRT) and blocking AdipoR1 enhances radiation sensitivity in hepatoma carcinoma cells. In the current study, we aimed to elucidate the roles of AdipoR1 in ionizing radiation- (IR-) induced radiosensitivity by activating ferroptosis pathway in HCC cells. We found that IR upregulated the expression of AdipoR1 and furthermore promoted the protein stability of transcription factor Nrf2, Nrf2 binded to the xCT promoter and increased xCT transcription and expression, and this directly contributed to the protective function in the early stage of radiation in HCC cells. AdipoR1 knockdown significantly inhibited expression of Nrf2 and xCT and, furthermore, increased both IR- and erastin-induced ferroptosis, which could be abolished by the rescue of Nrf2 and xCT. For the first time, we found that radiation-induced ferroptosis was mediated by AdipoR1-Nrf2-xCT pathway in HCC cells. These results provide new insights to the development and application of novel therapeutic strategies for hepatoma carcinoma.

Adiponectin receptors sustain haematopoietic stem cells throughout adulthood by protecting them from inflammation.

How are haematopoietic stem cells (HSCs) protected from inflammation, which increases with age and can deplete HSCs? Adiponectin, an anti-inflammatory factor that is not required for HSC function or haematopoiesis, promotes stem/progenitor cell proliferation after bacterial infection and myeloablation. Adiponectin binds two receptors, AdipoR1 and AdipoR2, which have ceramidase activity that increases upon adiponectin binding. Here we found that adiponectin receptors are non-cell-autonomously required in haematopoietic cells to promote HSC quiescence and self-renewal. Adiponectin receptor signalling suppresses inflammatory cytokine expression by myeloid cells and T cells, including interferon-γ and tumour necrosis factor. Without adiponectin receptors, the levels of these factors increase, chronically activating HSCs, reducing their self-renewal potential and depleting them during ageing. Pathogen infection accelerates this loss of HSC self-renewal potential. Blocking interferon-γ or tumour necrosis factor signalling partially rescues these effects. Adiponectin receptors are thus required in immune cells to sustain HSC quiescence and to prevent premature HSC depletion by reducing inflammation.

A small molecule screen for paqr-2 suppressors identifies Tyloxapol as a membrane fluidizer for C. elegans and mammalian cells.

Defects in cell membrane homeostasis are implicated in numerous disorders, including cancer, neurodegeneration and diabetes. There is therefore a need for a powerful model to study membrane homeostasis and to identify eventual therapeutic routes. The C. elegans gene paqr-2 encodes a homolog of the mammalian AdipoR1 and AdipoR2 proteins that, when mutated, causes a membrane homeostasis defect accompanied by multiple phenotypes such as intolerance to dietary saturated fatty acids, intolerance to cold and a characteristic tail tip morphology defect. We screened a compound library to identify molecules that can suppress the paqr-2 phenotypes. A single positive hit, Tyloxapol, was found that very effectively suppresses multiple paqr-2 phenotypes. Tyloxapol is a non-ionic detergent currently in use clinically as an expectorant. Importantly, we examined the potential of Tyloxapol as a fluidizer in human cells and found that it improves the viability and membrane fluidity of AdipoR2-deficient human cells challenged with palmitic acid, a membrane-rigidifying saturated fatty acid.

Estradiol overcomes adiponectin-resistance in diabetic mice by regulating skeletal muscle adiponectin receptor 1 expression.

Adiponectin and insulin resistance creates a vicious cycle that exacerbates type 2 diabetes. Earlier, we observed that female leptin receptor-deficient BLKS mice (BKS-db/db) were more sensitive to an adiponectin mimetic GTDF than males, which led us to explore if E2 plays a crucial role in modulation of adiponectin-sensitivity. Male but not female BKS-db/db mice were resistant to metabolic effects of globular adiponectin treatment. Male BKS-db/db displayed reduced skeletal muscle AdipoR1 protein expression, which was consequent to elevated polypyrimidine tract binding protein 1 (PTB) and miR-221. E2 treatment in male BKS-db/db, and ovariectomized BALB/c mice rescued AdipoR1 protein expression via downregulation of PTB and miR-221, and also directly increased AdipoR1 mRNA by its classical nuclear receptors. Estrogen receptor regulation via dietary or pharmacological interventions may improve adiponectin resistance and consequently ameliorate insulin resistance in type 2 diabetes.