AdipoRon reduces TGFß1-mediated collagen deposition in vitro and alleviates knee stiffness in vivo.

Arthrofibrosis, which causes joint motion restrictions, is a common complication following total knee arthroplasty (TKA). Key features associated with arthrofibrosis include myofibroblast activation, knee stiffness, and excessive scar tissue formation. We previously demonstrated that adiponectin levels are suppressed within the knee tissues of patients affected by arthrofibrosis and showed that AdipoRon, an adiponectin receptor agonist, exhibited anti-fibrotic properties in human mesenchymal stem cells. In this study, the therapeutic potential of AdipoRon was evaluated on TGFß1-mediated myofibroblast differentiation of primary human knee fibroblasts and in a mouse model of knee stiffness. Picrosirius red staining revealed that AdipoRon reduced TGFß1-induced collagen deposition in primary knee fibroblasts derived from patients undergoing primary TKA and revision TKA for arthrofibrosis. AdipoRon also reduced mRNA and protein levels of ACTA2, a key myofibroblast marker. RNA-seq analysis corroborated the anti-myofibrogenic effects of AdipoRon. In our knee stiffness mouse model, 6 weeks of knee immobilization, to induce a knee contracture, in conjunction with daily vehicle (DMSO) or AdipoRon (1, 5, and 25 mg/kg) via intraperitoneal injections were well tolerated based on animal behavior and weight measurements. Biomechanical testing demonstrated that passive extension angles (PEAs) of experimental knees were similar between vehicle and AdipoRon treatment groups in mice evaluated immediately following immobilization. Interestingly, relative to vehicle-treated mice, 5 mg/kg AdipoRon therapy improved the PEA of the experimental knees in mice that underwent 4 weeks of knee remobilization following the immobilization and therapy. Together, these studies revealed that AdipoRon may be an effective therapeutic modality for arthrofibrosis.

Small-molecule agonist AdipoRon alleviates diabetic retinopathy through the AdipoR1/AMPK/EGR4 pathway.

BACKGROUND: Diabetes mellitus (DM) is a progressive disease that involves multiple organs due to increased blood glucose, and diabetic retinopathy (DR) is the main complication of DM in the eyes and causes irreversible vision loss. In the pathogenesis of diabetic vascular disease, oxidative stress caused by hyperglycemia plays an important role in Müller cell impairment. In recent years, AdipoRon, an adiponectin analog that demonstrated important physiological functions in obesity, diabetes, inflammation, and cardiovascular diseases, demonstrated cellular protection from apoptosis and reduced inflammatory damage through a receptor-dependent mechanism. Here, we investigated how AdipoRon reduced oxidative stress and apoptosis in Müller glia in a high glucose environment. RESULTS: By binding to adiponectin receptor 1 on Müller glia, AdipoRon activated 5' adenosine monophosphate-activated protein kinase (AMPK)/acetyl-CoA carboxylase phosphorylation downstream, thereby alleviating oxidative stress and eventual apoptosis of cells and tissues. Transcriptome sequencing revealed that AdipoRon promoted the synthesis and expression of early growth response factor 4 (EGR4) and inhibited the cellular protective effects of AdipoRon in a high-glucose environment by reducing the expression of EGR4. This indicated that AdipoRon played a protective role through the EGR4 and classical AMPK pathways. CONCLUSIONS: This provides a new target for the early treatment of DR.

Intranasal AdipoRon Mitigated Anxiety and Depression-Like Behaviors in 6-OHDA-Induced Parkinson 's Disease Rat Model: Going Beyond Motor Symptoms.

Depression and anxiety are prevalent neuropsychiatric conditions among patients with Parkinson's disease (PD), which may manifest prior to motor symptoms. As levodopa, a prominent treatment for PD motor symptoms, provides few benefits for mood-related abnormalities, tackling non-motor symptoms is particularly important. AdipoRon (Ad), an adiponectin agonist, has demonstrated neuroprotective effects by suppressing neuroinflammatory responses and activating the AMPK/Sirt-1 signaling pathway. This study looked at the potential advantages and underlying mechanisms of intranasal Ad in a rat model of PD induced by 6-hydroxydopamine (6-OHDA). We found that Ad at doses of 1 and 10 µg for 21 days exhibited anxiolytic- and antidepressant effects in the open field (OF) test, elevated plus maze (EPM), sucrose splash test, and forced swimming test in a PD model caused by a unilateral 6-OHDA injection into the medial forebrain bundle (MFB). The Ad also lowered the levels of corticosterone in the blood, decreased inflammasome components (NLRP3, caspase 1, and IL-1ß), and increased Sirt-1 protein levels in the prefrontal cortex (PFC) of PD rats. We conclude that Ad ameliorates anxious and depressive-like behaviors in the PD rat model through stimulating the AMPK/Sirt-1 signaling and blocking the NLRP3 inflammasome pathways in the PFC.

AdipoRon Ameliorates Synaptic Dysfunction and Inhibits tau Hyperphosphorylation through the AdipoR/AMPK/mTOR Pathway in T2DM Mice.

There is growing evidence showing that adiponectin (APN) can improve Alzheimer's disease(AD)-like pathological changes by improving insulin resistance. However, the role of AdipoRon (an Adiponectin receptor agonist) on synaptic plasticity and cognitive dysfunction in the early stages of type 2 diabetes mellitus(T2DM) remains unknown. In this study, we investigated the neuroprotective effect and the molecular mechanism underlying the effect of AdipoRon in T2DM mice. We found that AdipoRon significantly restored the cognitive deficits in T2DM mice, including shorter escape latency, more crossing times, increased distances, and percentage of time in the target quadrant. In addition, AdipoRon treatment up-regulated synaptic proteins (PSD95, SYN, GAP43, and SYP), increased the number of hippocampal synapses and attenuated synaptic damage, including the length, the number and the density of dendritic spines in CA1 and DG regions. Furthermore, AdipoRon attenuated Tau phosphorylation at multiple AD-related sites (p-tau 205, p-tau 396, p-tau 404) by promoting AdipoR expression and activating the AMPK/mTOR pathway. Our data suggests that AdipoRon exerts neuroprotective effects on the T2DM mice, which may be mediated by the activation of the AdipoR/AMPK/mTOR signaling pathway.

AdipoRon exerts opposing effects on insulin sensitivity via fibroblast growth factor 21-mediated time-dependent mechanisms.

Increasing evidence has shown that AdipoRon, a synthetic adiponectin receptor agonist, is involved in the regulation of whole-body insulin sensitivity and energy homeostasis. However, the mechanisms underlying these alterations remain unclear. Here, using hyperinsulinemic-euglycemic clamp and isotopic tracing techniques, we show that short-term (10 days) AdipoRon administration indirectly inhibits lipolysis in white adipose tissue via increasing circulating levels of fibroblast growth factor 21 in mice fed a high-fat diet. This led to reduced plasma-free fatty acid concentrations and improved lipid-induced whole-body insulin resistance. In contrast, we found that long-term (20 days) AdipoRon administration directly exacerbated white adipose tissue lipolysis, increased hepatic gluconeogenesis, and impaired the tricarboxylic acid cycle in the skeletal muscle, resulting in aggravated whole-body insulin resistance. Together, these data provide new insights into the comprehensive understanding of multifaceted functional complexity of AdipoRon.

Adiponectin deficiency promotes endometrial carcinoma pathogenesis and development via activation of mitogen-activated protein kinase.

Obesity is one of the major risk factors for cancer. Clinical studies have demonstrated that circulating levels of adiponectin are inversely correlated, not only with the extent of adiposity, but also with the incidence of several types of cancer, particularly endometrial cancer (EC). However, thus far, adiponectin remains a correlative factor, without definitive evidence to show a causal effect in EC and the potential mechanism(s) involved. To address this issue, we introduced an Apn-null mutation into Pten haploid-deficient (Pten+/- ) mice. The Pten heterozygous mutation alone led to the development of EC in less than 30% of female mice; however, when combined with the Apn-null mutation, the incidence of endometrial lesions rose to at least two-thirds. Although Apn deficiency did not further potentiate the Akt activation caused by the Pten mutation, it elevated the phosphorylation of mitogen-activated protein kinase (MAPK) p42/44, indicating activation of the MAPK signaling pathway. Treatment of Apn-/- ;Pten+/- mice with a MEK inhibitor blocked the development of EC. Finally, xenografts of a PTEN-proficient human EC cell line grew faster in Apn-deficient mice, whereas an adiponectin receptor agonist reduced xenograft growth of a PTEN-deficient human EC cell line. Thus, reduction of adiponectin activity promotes EC development, at least in the context of Pten mutation, by activating MAPK. © 2022 The Pathological Society of Great Britain and Ireland.

Adiponectin receptor agonist AdipoRon modulates human and mouse platelet function.

Adiponectin, an adipokine secreted by adipocytes, has anti-atherosclerotic and antithrombotic activities. AdipoRon is synthetic small molecule adiponectin receptor agonist. In this study, we investigated the effect of AdipoRon on platelet activation and thrombus formation. Washed human platelets were prepared from the peripheral blood of healthy donors. In a series of in vitro platelet functional assays, pre-treatment with AdipoRon (10, 20, 40 µg/mL) dose-dependently inhibited the aggregation, granule secretion and spreading of washed human platelets. We showed that AdipoRon (20, 40 µg/mL) significantly inhibited AMPK, Syk, PLCγ2, PI3K, Akt, p38-MAPK and ERK1/2 signalling pathways in washed human platelets. In addition, we demonstrated that the phosphorylation of CKII at Tyr255 was an important mechanism of the integrin αIIbß3-mediated platelet activation. Meanwhile, AdipoR1 deficiency impaired the inhibitory effect of AdipoRon on mouse platelets. In ferric chloride-induced carotid injury model, injection of AdipoRon (5 or 12.5 mg/kg, iv) significantly attenuated arterial thrombosis. In conclusion, AdipoRon attenuates platelet function via the AdipoR1/AMPK/CKII/PI3K/AKT signalling pathways, while exerting a protective effect against arterial thrombosis. This study offers new insights into the fields of cardiovascular disease and antiplatelet drug discovery.Schematic model of AdipoRon regulating platelet activation. (BioRender.com).

AdipoRon alleviates fatty acid-induced lipid accumulation and mitochondrial dysfunction in bovine hepatocytes by promoting autophagy.

During the transition period in dairy cows, high circulating concentrations of nonesterified fatty acids (NEFA) increase hepatic lipid deposits and are considered a major pathological factor for liver damage. We investigated whether AdipoRon, a synthetic small-molecule agonist of adiponectin receptors 1 and 2 shown to prevent liver lipid accumulation in nonruminants, could alleviate NEFA-induced lipid accumulation and mitochondrial dysfunction. Bovine hepatocytes were isolated from 5 healthy Holstein female newborn calves (1 d of age, 30-40 kg, fasting), and independently isolated hepatocytes from at least 3 different calves were used for each subsequent experiment. The composition and concentration of NEFA used in this study were selected according to hematological criteria of dairy cows with fatty liver or ketosis. First, hepatocytes were cultured with various concentrations of NEFA (0, 0.6, 1.2, or 2.4 mM) for 12 h. In a second experiment, hepatocytes were treated with AdipoRon at different concentrations (0, 5, 25, or 50 µM for 12 h) and times (25 µM for 0, 6, 12, or 24 h) with or without NEFA (1.2 mM) treatment. In the last experiment, hepatocytes were treated with AdipoRon (25 µM), NEFA (1.2 mM), or both for 12 h after treatment with or without the autophagy inhibitor chloroquine. Hepatocytes treated with NEFA had increased protein abundance of sterol regulatory element-binding protein 1c (SREBP-1c) and mRNA abundance of acetyl-CoA carboxylase 1 (ACACA), and decreased protein abundance of peroxisome proliferator-activated receptor α (PPARA), proliferator-activated receptor gamma coactivator-1 α (PGC-1α), mitofusin 2 (MFN2), cytochrome c oxidase subunit IV (COX IV), and mRNA abundance of carnitine palmitoyltransferase 1A (CPT1A), along with lower ATP concentrations. AdipoRon treatment reversed these effects, suggesting this compound had a positive effect on lipid metabolism and mitochondrial dysfunction during the NEFA challenge. In addition, upregulated expression of microtubule-associated protein 1 light chain 3-II (LC3-II, encoded by MAP1LC3) and downregulated expression of sequestosome-1 (SQSTM1, also called p62) indicated that AdipoRon enhanced autophagic activity in hepatocytes. The fact that chloroquine impeded the beneficial effects of AdipoRon on lipid accumulation and mitochondrial dysfunction suggested a direct role for autophagy during NEFA challenge. Our results suggest that autophagy is an important cellular mechanism to prevent NEFA-induced lipid accumulation and mitochondrial dysfunction in bovine hepatocytes, which is consistent with other studies. Overall, AdipoRon may represent a promising therapeutic agent to maintain hepatic lipid homeostasis and mitochondrial function in dairy cows during the transition period.

The effects of AdipoRon on cytochrome P450-related gene expression, acute steroidogenic regulatory protein, and structure of ovary in polycystic ovary syndrome model.

PURPOSE: One of the most common causes of infertility in adult women is polycystic ovary syndrome (PCOS) which has been identified with symptoms such as chronic hyperandrogenism, anovulation, and polycystic ovaries. Adiponectin modulates steroidogenesis and the expression of ovulation-related genes. Herein, we assessed the effect of AdipoRon (adiponectin agonist) in the PCOS model mice. METHODS: The PCOS model was induced with letrozole in the adult female mice and the animals received intraperitoneal injection of AdipoRon (5 mg/kg) for 10 days. Expression of CYP11A, CYP17A, and CYP19A genes, StAR protein, and histomorphology of the ovary were evaluated using real-time RT-PCR, western blotting, and histochemistry methods, respectively. RESULTS: Although administration of letrozole caused an increase in the expression of CYP11A, CYP17A, and StAR and a decrease in the CYP19A1 expression, injection of AdipoRon reversed these changes. Moreover, AdipoRon treatment resulted in an improvement of folliculogenesis and a reduction of cysts compared to the letrozole-treated mice. CONCLUSION: It is likely that AdipoRon has protective effects on the PCOS through modulation of cytochrome P450-related genes and steroidogenesis but needs further study to be sure.

Adiponectin Enhances Fatty Acid Signaling in Human Taste Cells by Increasing Surface Expression of CD36.

Adiponectin, a key metabolic hormone, is secreted into the circulation by fat cells where it enhances insulin sensitivity and stimulates glucose and fatty acid metabolism. Adiponectin receptors are highly expressed in the taste system; however, their effects and mechanisms of action in the modulation of gustatory function remain unclear. We utilized an immortalized human fungiform taste cell line (HuFF) to investigate the effect of AdipoRon, an adiponectin receptor agonist, on fatty acid-induced calcium responses. We showed that the fat taste receptors (CD36 and GPR120) and taste signaling molecules (Gα-gust, PLCß2, and TRPM5) were expressed in HuFF cells. Calcium imaging studies showed that linoleic acid induced a dose-dependent calcium response in HuFF cells, and it was significantly reduced by the antagonists of CD36, GPR120, PLCß2, and TRPM5. AdipoRon administration enhanced HuFF cell responses to fatty acids but not to a mixture of sweet, bitter, and umami tastants. This enhancement was inhibited by an irreversible CD36 antagonist and by an AMPK inhibitor but was not affected by a GPR120 antagonist. AdipoRon increased the phosphorylation of AMPK and the translocation of CD36 to the cell surface, which was eliminated by blocking AMPK. These results indicate that AdipoRon acts to increase cell surface CD36 in HuFF cells to selectively enhance their responses to fatty acids. This, in turn, is consistent with the ability of adiponectin receptor activity to alter taste cues associated with dietary fat intake.

Anti-Inflammatory Effects of Adiponectin Receptor Agonist AdipoRon against Intervertebral Disc Degeneration.

Adiponectin, a hormone secreted by adipocytes, has anti-inflammatory effects and is involved in various physiological and pathological processes such as obesity, inflammatory diseases, and cartilage diseases. However, the function of adiponectin in intervertebral disc (IVD) degeneration is not well understood. This study aimed to elucidate the effects of AdipoRon, an agonist of adiponectin receptor, on human IVD nucleus pulposus (NP) cells, using a three-dimensional in vitro culturing system. This study also aimed to elucidate the effects of AdipoRon on rat tail IVD tissues using an in vivo puncture-induced IVD degeneration model. Analysis using quantitative polymerase chain reaction demonstrated the downregulation of gene expression of proinflammatory and catabolic factors by interleukin (IL)-1ß (10 ng/mL) in human IVD NP cells treated with AdipoRon (2 µM). Furthermore, western blotting showed AdipoRon-induced suppression of p65 phosphorylation (p < 0.01) under IL-1ß stimulation in the adenosine monophosphate-activated protein kinase (AMPK) pathway. Intradiscal administration of AdipoRon was effective in alleviating the radiologic height loss induced by annular puncture of rat tail IVD, histomorphological degeneration, production of extracellular matrix catabolic factors, and expression of proinflammatory cytokines. Therefore, AdipoRon could be a new therapeutic candidate for alleviating the early stage of IVD degeneration.

[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.

Adiponectin suppresses tumor growth of nasopharyngeal carcinoma through activating AMPK signaling pathway.

BACKGROUND: Adiponectin is an adipocyte-secreted cytokine that enhances insulin sensitivity and attenuates inflammation. Although circulating adiponectin level is often inversely associated with several malignancies, its role in the development of nasopharyngeal carcinoma (NPC) remains unclear. Here, we investigated the clinical association between circulating adiponectin level and NPC, and examined the impact of adiponectin, as well as the underlying mechanisms, on NPC growth both in vitro and in vivo. METHODS: The association between circulating adiponectin level and the risk of developing NPC was assessed in two different cohorts, including a hospital-based case-control study with 152 cases and 132 controls, and a nested case-control study with 71 cases and 142 controls within a community-based NPC screening cohort. Tumor xenograft model, cell proliferation and cycle assays were applied to confirm the effects of adiponectin on NPC growth in cultured cells and in xenograft models. We also investigated the underlying signaling mechanisms with various specific pharmacological inhibitors and biochemistry analysis. RESULTS: High adiponectin levels were associated with a monotonic decreased trend of NPC risk among males in both the hospital-based case-control study and a nested case-control study. In vitro, recombinant human full-length adiponectin significantly inhibited NPC cell growth and arrested cell cycle, which were dependent on AMPK signaling pathway. The growth of xenograft of NPC tumor was sharply accelerated in the nude mice carrying genetic adiponectin deficiency. An adiponectin receptor agonist, AdipoRon, displayed strong anti-tumor activity in human xenograft models. CONCLUSIONS: These findings demonstrated for the first time that circulating adiponectin is not only inversely associated with NPC, but also controls the development of NPC via AMPK signaling pathway. Stimulation of adiponectin function may become a novel therapeutic modality for NPC.

Targeting Ceramides and Adiponectin Receptors in the Islet of Langerhans for Treating Diabetes.

Ceramides belong to the sphingolipid family and represent the central hub of the sphingolipid network. In obesity, oversupply of saturated fatty acids including palmitate raises ceramide levels which can be detrimental to cells. Elevated ceramides can cause insulin resistance, endoplasmic reticulum stress, and mitochondrial dysfunction. Studies over the last few decades have highlighted the role played by ceramides in pancreatic islet ß-cell apoptosis, especially under glucolipotoxic and inflammatory conditions. This review focuses on ceramides and adiponectin receptor signaling, summarizing recent advancements in our understanding of their roles in islet ß-cells and the discovery of zinc-dependent lipid hydrolase (ceramidase) activity of adiponectin receptors. The therapeutic potential of targeting these events to prevent islet ß-cell loss for treating diabetes is discussed.

Adiponectin receptor agonist AdipoRon ameliorates renal inflammation in diet-induced obese mice and endotoxin-treated human glomeruli ex vivo.

AIMS/HYPOTHESIS: Chronic low-grade inflammation with local upregulation of proinflammatory molecules plays a role in the progression of obesity-related renal injury. Reduced serum concentration of anti-inflammatory adiponectin may promote chronic inflammation. Here, we investigated the potential anti-inflammatory and renoprotective effects and mechanisms of action of AdipoRon, an adiponectin receptor agonist. METHODS: Wild-type DBA/2J mice were fed with high-fat diet (HFD) supplemented or not with AdipoRon to model obesity-induced metabolic endotoxaemia and chronic low-grade inflammation and we assessed changes in the glomerular morphology and expression of proinflammatory markers. We also treated human glomeruli ex vivo and human podocytes in vitro with AdipoRon and bacterial lipopolysaccharide (LPS), an endotoxin upregulated in obesity and diabetes, and analysed the secretion of inflammatory cytokines, activation of inflammatory signal transduction pathways, apoptosis and migration. RESULTS: In HFD-fed mice, AdipoRon attenuated renal inflammation, as demonstrated by reduced expression of glomerular activated NF-κB p65 subunit (NF-κB-p65) (70%, p < 0.001), TNFα (48%, p < 0.01), IL-1ß (51%, p < 0.001) and TGFß (46%, p < 0.001), renal IL-6 and IL-4 (21% and 20%, p < 0.05), and lowered glomerular F4/80-positive macrophage infiltration (31%, p < 0.001). In addition, AdipoRon ameliorated HFD-induced glomerular hypertrophy (12%, p < 0.001), fibronectin accumulation (50%, p < 0.01) and podocyte loss (12%, p < 0.001), and reduced podocyte foot process effacement (15%, p < 0.001) and thickening of the glomerular basement membrane (18%, p < 0.001). In cultured podocytes, AdipoRon attenuated the LPS-induced activation of the central inflammatory signalling pathways NF-κB-p65, c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (p38-MAPK) (30%, 36% and 22%, respectively, p < 0.001), reduced the secretion of TNFα (32%, p < 0.01), and protected against podocyte apoptosis and migration. In human glomeruli ex vivo, AdipoRon reduced the LPS-induced secretion of inflammatory cytokines IL-1ß, IL-18, IL-6 and IL-10. CONCLUSIONS/INTERPRETATION: AdipoRon attenuated the renal expression of proinflammatory cytokines in HFD-fed mice and LPS-stimulated human glomeruli, which apparently contributed to the amelioration of glomerular inflammation and injury. Mechanistically, based on assays on cultured podocytes, AdipoRon reduced LPS-induced activation of the NF-κB-p65, JNK and p38-MAPK pathways, thereby impelling the decrease in apoptosis, migration and secretion of TNFα. We conclude that the activation of the adiponectin receptor by AdipoRon is a potent strategy to attenuate endotoxaemia-associated renal inflammation.

AdipoRon promotes diabetic fracture repair through endochondral ossification-based bone repair by enhancing survival and differentiation of chondrocytes.

Diabetic bone defects may exhibit impaired endochondral ossification (ECO) leading to delayed bone repair. AdipoRon, a receptor agonist of adiponectin polymers, can ameliorate diabetes and related complications, as well as overcome the disadvantages of the unstable structure of artificial adiponectin polymers. Here, the effects of AdipoRon on the survival and differentiation of chondrocytes in a diabetic environment were explored focusing on related mechanisms in gene and protein levels. In vivo, AdipoRon was applied to diet-induced-obesity (DIO) mice, a model of obesity and type 2 diabetes, with femoral fracture. Sequential histological evaluations and micro-CT were examined for further verification. We found that AdipoRon could ameliorate cell viability, apoptosis, and reactive oxygen species (ROS) production and promote mRNA expression of chondrogenic markers and cartilaginous matrix production of ATDC5 cells in high glucose medium via activating ERK1/2 pathway. Additionally, DIO mice with intragastric AdipoRon administration had more neocartilage and accelerated new bone formation. These data suggest that AdipoRon could stimulate bone regeneration via ECO in diabetes.

AdipoRon and Other Adiponectin Receptor Agonists as Potential Candidates in Cancer Treatments.

The high mortality rate together with an ever-growing number of annual cases have defined neoplastic disorders as "the real 21st-century disease". Its dubious distinction also results from conventional therapy failure, which has made cancer an orphan disease. Therefore, innovative and alternative therapeutic strategies are mandatory. The ability to leverage human naturally occurring anti-tumor defenses has always represented a fascinating perspective, and the immuno blockage approval in cancer treatment represents in timeline the latest success. As a multifunctional organ, adipose tissue releases a large amount of adipokines having both carcinogenic and antitumor properties. The negative correlation between serum levels and risk for developing malignancies, as well as the huge number of existing preclinical studies, have identified adiponectin as a potential anticancer adipokine. Nevertheless, its usage in clinical has constantly clashed with the inability to reproduce a mimic synthetic compound. Between 2011 and 2013, two distinct adiponectin receptor agonists were recognized, opening new scenarios even in cancer. Here, we review the first orally active adiponectin receptor agonists AdipoRon, from the discovery to the anticancer evidence. Including our latest findings in osteosarcoma models, we summarize AdipoRon and other existing agonists state-of-art, questioning about the feasibility assessment of this strategy in cancer treatment.

Adiponectin and Leptin Exert Antagonizing Effects on HUVEC Tube Formation and Migration Modulating the Expression of CXCL1, VEGF, MMP-2 and MMP-9.

Adiponectin and leptin are two abundant adipokines with different properties but both described such as potent factors regulating angiogenesis. AdipoRon is a small-molecule that, binding to AdipoRs receptors, acts as an adiponectin agonist. Here, we investigated the effects of AdipoRon and leptin on viability, migration and tube formation on a human in vitro model, the human umbilical vein endothelial cells (HUVEC) focusing on the expression of the main endothelial angiogenic factors: hypoxia-inducible factor 1-alpha (HIF-1α), C-X-C motif chemokine ligand 1 (CXCL1), vascular endothelial growth factor A (VEGF-A), matrix metallopeptidase 2 (MMP-2) and matrix metallopeptidase 9 (MMP-9). Treatments with VEGF-A were used as positive control. Our data revealed that, at 24 h treatment, proliferation of HUVEC endothelial cells was not influenced by AdipoRon or leptin administration; after 48 h longer exposure time, the viability was negatively influenced by AdipoRon while leptin treatment and the combination of AdipoRon+leptin produced no effects. In addition, AdipoRon induced a significant increase in complete tubular structures together with induction of cell migration while, on the contrary, leptin did not induce tube formation and inhibited cell migration; interestingly, the co-treatment with both AdipoRon and leptin determined a significant decrease of the tubular structures and cell migration indicating that leptin antagonizes AdipoRon effects. Finally, we found that the effects induced by AdipoRon administration are accompanied by an increase in the expression of CXCL1, VEGF-A, MMP-2 and MMP-9. In conclusion, our data sustain the active role of adiponectin and leptin in linking adipose tissue with the vascular endothelium encouraging the further deepening of the role of adipokines in new vessel's formation, to candidate them as therapeutic targets.

AdipoRon Treatment Induces a Dose-Dependent Response in Adult Hippocampal Neurogenesis.

AdipoRon, an adiponectin receptor agonist, elicits similar antidiabetic, anti-atherogenic, and anti-inflammatory effects on mouse models as adiponectin does. Since AdipoRon can cross the blood-brain barrier, its chronic effects on regulating hippocampal function are yet to be examined. This study investigated whether AdipoRon treatment promotes hippocampal neurogenesis and spatial recognition memory in a dose-dependent manner. Adolescent male C57BL/6J mice received continuous treatment of either 20 mg/kg (low dose) or 50 mg/kg (high dose) AdipoRon or vehicle intraperitoneally for 14 days, followed by the open field test to examine anxiety and locomotor activity, and the Y maze test to examine hippocampal-dependent spatial recognition memory. Immunopositive cell markers of neural progenitor cells, immature neurons, and newborn cells in the hippocampal dentate gyrus were quantified. Immunosorbent assays were used to measure the serum levels of factors that can regulate hippocampal neurogenesis, including adiponectin, brain-derived neurotrophic factor (BDNF), and corticosterone. Our results showed that 20 mg/kg AdipoRon treatment significantly promoted hippocampal cell proliferation and increased serum levels of adiponectin and BDNF, though there were no effects on spatial recognition memory and locomotor activity. On the contrary, 50 mg/kg AdipoRon treatment impaired spatial recognition memory, suppressed cell proliferation, neuronal differentiation, and cell survival associated with reduced serum levels of BDNF and adiponectin. The results suggest that a low-dose AdipoRon treatment promotes hippocampal cell proliferation, while a high-dose AdipoRon treatment is detrimental to the hippocampus function.

AdipoRon, an Orally Active, Synthetic Agonist of AdipoR1 and AdipoR2 Receptors Has Gastroprotective Effect in Experimentally Induced Gastric Ulcers in Mice.

INTRODUCTION: Adiponectin is a hormone secreted by adipocytes, which exhibits insulin-sensitizing and anti-inflammatory properties and acts through adiponectin receptors: AdipoR1 and AdipoR2. The aim of the study was to evaluate whether activation of adiponectin receptors AdipoR1 and AdipoR2 with an orally active agonist AdipoRon has gastroprotective effect and to investigate the possible underlying mechanism. METHODS: We used two well-established mouse models of gastric ulcer (GU) induced by oral administration of EtOH (80% solution in water) or diclofenac (30 mg/kg, p.o.). Gastroprotective effect of AdipoRon (dose 5 and 50 mg /kg p.o) was compared to omeprazole (20 mg/kg p.o.) or 5% DMSO solution (control). Clinical parameters of gastroprotection were assessed using macroscopic (gastric lesion area) and microscopic (evaluation of the gastric mucosa damage) scoring. To establish the molecular mechanism, we measured: myeloperoxidase (MPO), superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPX) activities; glutathione (GSH) level; and IL-1ß, adenosine monophosphate-activated protein kinase (AMPK), and phosphorylated AMPK expression in gastric tissue. RESULTS: AdipoRon produced a gastroprotective effect in both GU mouse models as evidenced by significantly lower macroscopic and microscopic damage scores. AdipoRon exhibited anti-inflammatory effect by reduction in MPO activity and IL-1ß expression in the gastric tissue. Moreover, AdipoRon induced antioxidative action, as demonstrated with higher GSH levels, and increased SOD and GPX activity. CONCLUSIONS: Activation of AdipoR1 and AdipoR2 using AdipoRon reduced gastric lesions and enhanced cell response to oxidative stress. Our data suggest that AdipoR1 and AdipoR2 activation may be an attractive therapeutic strategy to inhibit development of gastric ulcers.