Discovery of AdipoRon analogues as novel AMPK activators without inhibiting mitochondrial complex I

Adiponectin receptor agonist adipoRon alleviates imiquimod-induced murine psoriasis

Psoriasis is a chronic inflammatory skin disease involving inflammation, immune responses and keratinocytes proliferation. It has been suggested that adiponectin/adiponectin receptor 1 (AdipoR1) signaling plays a role in regulating psoriatic skin inflammation. AdipoRon is a small molecule agonist of AdipoR1 and AdipoR2. The effect of adipoRon on psoriasis has not been elucidated. In this study, using a GEO database, we found that the expression of adiponectin was substantially decreased in skin lesions of psoriasis patients. This reduction was also validated in an imiquimod-induced psoriasis mouse model. Interestingly, we found that topical administration of adipoRon significantly ameliorated skin lesions induced by imiquimod. The critical pro-inflammatory cytokines (IL-6, IL-17A and IL-23) and the infiltration of macrophages, especially M1 macrophages were dramatically decreased while the infiltration of M2 macrophages were slightly increased in the skin lesions upon adipoRon treatment. Mechanistically, adipoRon inhibited macrophage inflammation and keratinocytes proliferation via activation of AMPK signaling pathway. Collectively, our study demonstrates that adipoRon displayed anti-inflammatory activity and anti-proliferation of keratinocytes, and attenuated psoriatic response. Activating AdipoR1 signaling pathway by adipoRon or others may represent a novel therapeutic approach to psoriasis.

Visceral obesity and HFpEF: targets and therapeutic opportunities

The effectiveness of weight-loss drugs in heart failure (HF) with preserved ejection fraction (HFpEF) highlights the link between obesity (adipose tissue) and HF (the heart). Recent guidelines incorporating the waist:height ratio for diagnosing and treating obesity reflect the growing recognition of the significance of visceral adiposity. However, its unique impact on HFpEF and their complex relationship remain underexplored. With limited treatment options for obesity-related HFpEF, novel disease-modifying treatments are urgently needed. Here, we clarify the relationship between visceral obesity and HFpEF, introducing the concept of the visceral adipose tissue-heart axis to explore its mechanisms and therapeutic potential. We also discuss promising strategies targeting visceral obesity in HFpEF and propose directions for future research.

Oral Administration of the Adiponectin Receptor 1 Agonistic Dipeptide Tyr-Pro Prevents Hyperglycemia in Spontaneously Diabetic Torii Rats

The dipeptide Tyr-Pro, a novel natural agonist of adiponectin receptor 1 (AdipoR1), promotes glucose uptake in skeletal muscle cells. This study investigated the antidiabetic effect of orally administered Tyr-Pro in spontaneously diabetic Torii (SDT) rats. Oral administration of Tyr-Pro (1 mg/kg/day) improved glucose intolerance in SDT rats at 22 weeks of prediabetic age. By 29 weeks of age, fasting blood glucose levels (BGLs) increased to 142 ± 14 mg/dL in the control group, whereas those in the Tyr-Pro group remained within the normal range (80-99 mg/dL), demonstrating a novel antidiabetic effect in vivo. Substantially increased levels of AdipoR1 and p-AMPK/AMPK were observed in the skeletal muscle of Tyr-Pro-administrated SDT rats. The intake of Tyr-Pro also enhanced insulin secretion and inhibited p-IRS-1(Ser) in skeletal muscle. These findings demonstrate that Tyr-Pro prevented the onset of diabetes and improved impaired insulin signaling pathways in SDT rats by inducing AdipoR1-mediated AMPK activation.

Selectively targeting the AdipoR2-CaM-CaMKII-NOS3 axis by SCM-198 as a rapid-acting therapy for advanced acute liver failure

Acute liver failure (ALF) is a hepatology emergency with rapid hepatic destruction, multiple organ failures, and high mortality. Despite decades of research, established ALF has minimal therapeutic options. Here, we report that the small bioactive compound SCM-198 increases the survival of male ALF mice to 100%, even administered 24 hours after ALF establishment. We identify adiponectin receptor 2 (AdipoR2) as a selective target of SCM-198, with the AdipoR2 R335 residue being critical for the binding and signaling of SCM-198-AdipoR2 and AdipoR2 Y274 residue serving as a molecular switch for Ca2+ influx. SCM-198-AdipoR2 binding causes Ca2+ influx and elevates the phosphorylation levels of CaMKII and NOS3 in the AdipoR2-CaM-CaMKII-NOS3 complex identified in this study, rapidly inducing nitric oxide production for liver protection in murine ALF. SCM-198 also protects human ESC-derived liver organoids from APAP/TAA injuries. Thus, selectively targeting the AdipoR2-CaM-CaMKII-NOS3 axis by SCM-198 is a rapid-acting therapeutic strategy for advanced ALF.

AdipoRon improves mitochondrial homeostasis and protects dopaminergic neurons through activation of the AMPK signaling pathway in the 6-OHDA-lesioned rats

The progressive decline of dopaminergic neurons in Parkinson's disease (PD) has been linked to an imbalance in energy and the failure of mitochondrial function. AMP-activated protein kinase (AMPK), the major intracellular energy sensor, regulates energy balance, and damage to nigral dopaminergic neurons induced by 6-hydroxydopamine (6-OHDA) is exacerbated in the absence of AMPK activity. This study aimed to examine the potential therapeutic advantages of AdipoRon, an AMPK activator, on motor function and mitochondrial homeostasis in a 6-OHDA-induced PD model. Male Wistar rats were subjected to unilateral injection of 6-OHDA (10 μg) into the left medial forebrain bundle at two points, and after 7 days, they were treated with intranasal AdipoRon (0.1, 1, and 10 μg) or Levodopa (10 mg/kg, p. o.) for 21 successive days. Following the last treatment day, motor behavior was evaluated through the Murprogo's test, bar test, beam walking test, and apomorphine-induced rotation test. After euthanasia, the left substantia nigra (SN) was separated for evaluation of ATP, mitochondrial membrane potential (MMP), and protein expressions of AMPK, p-AMPK, and mitochondrial dynamics markers (Mfn-2 and Drp-1). Moreover, the number of tyrosine hydroxylase-positive (TH+) cells was quantified in the left substantia nigra. Intranasal AdipoRon effectively reversed muscle rigidity, akinesia, bradykinesia, and rotation caused by 6-OHDA. Moreover, AdipoRon increased the phospho-AMPK/AMPK ratio, mitigated mitochondrial dysfunction, and improved mitochondrial dynamics in the SN. Furthermore, AdipoRon increased the number of TH+ cells in the SN of PD animals. These findings suggest that AdipoRon could protect dopaminergic neurons by activating the AMPK pathway and improving mitochondrial dysfunction.

Identification of AdipoRon analogues as novel activators of AMPK for the treatment of type 2 diabetes

The activation of AMPK has emerged as a promising therapeutic approach for the treatment of metabolic diseases. AdipoRon, an agonist of the adiponectin receptor, has been identified as a compound capable of activating AMPK via the adiponectin receptor. To identify novel AdipoRon analogues with AMPK activation potential, a total of 17 analogues were designed, synthesized, and subjected to biological evaluation. Among these analogues, X-12 was discovered to exhibit potent activation of AMPK. In experimental studies, X-12 demonstrated dose-dependent improvements in glucose tolerance in normal mice. Furthermore, it significantly reduced fasting blood glucose levels and ameliorated insulin resistance in db/db diabetic mice. These findings highlight the therapeutic potential of X-12 as a novel class of AMPK activators for the treatment of metabolic diseases.

Identification of a novel adiponectin receptor and opioid receptor dual acting agonist as a potential treatment for diabetic neuropathy

Diabetic neuropathy (DN) is a long-term complication of diabetes mellitus, affecting different periphery nerve systems including sensory and motor neurons. Hyperglycemia is the major cause of DN with symptoms such as weakness of balance or coordination, insensitivity to sensation, weakness of the muscles as well as numbness and pain in limbs Analgesic drug such as opioids can be effective to relief neuropathy pain but there is no effective treatment. Adiponectin is an anti-diabetic adipokine, which possesses insulin-sensitizing and neuroprotective effects. In this project, we aim to identify an agent which is dual acting to opioid and adiponectin receptors. Within a virtual screening repositioning campaign, a large collection of compounds with different structures comprehensive of adipoRon-like piperidine derivatives was screened by docking. Recently developed opioid receptor benzomorphanic agonists finally emerged as good ligands to adiponectin receptors showing some 2D and 3D structural similarities with AdipoRon. Particularly, we have identified (+)-MML1017, which has high affinity to the same binding domain of AdipoR1 and AdipoR2 as AdipoRon. Our western blot results indicate (+)-MML1017 activates AMPK phosphorylation through both adipoR1 and adipoR2 in neuronal cell line. Moreover, pretreatment of (+)-MML1017 can improve the cell viability with motor neurons under hyperglycermic conditions. The (+)-MML1017 also activates μ-opioid receptor cells in a concentration-dependent manner. Our study identified a novel compound having dual activity on opioid receptors and adiponectin receptors that may have analgesic effects and neuroprotective effects to treat diabetic neuropathy.

AdipoRon Inhibits Neuroinflammation Induced by Deep Hypothermic Circulatory Arrest Involving the AMPK/NF-κB Pathway in Rats

Deep hypothermic circulatory arrest (DHCA) can induce systemic inflammatory response syndrome, including neuroinflammation. Finding suitable compounds is necessary for attenuating neuroinflammation and avoiding cerebral complications following DHCA. In the present study, we established DHCA rat models and monitored the vital signs during the surgical process. After surgery, we found significantly increased proinflammatory cytokines (IL-6, IL-1β, and TNF-α) in DHCA rats. Quantitative proteomics analysis was performed for exploring the differentially expressed proteins in hippocampus of DHCA rats and the data showed the adiponectin receptor 1 protein was upregulated. More importantly, administration of AdipoRon, a small-molecule adiponectin receptor agonist, could improve the basic vital signs and attenuate the increased IL-6, IL-1β, and TNF-α in DHCA rats. Furthermore, AdipoRon inhibits the activation of microglia (M1 state) and promotes their transition to an anti-inflammatory state, via promoting the phosphorylation of adenosine monophosphate-activated protein kinase (AMPK), and downregulating nuclear factor kappa B (NF-κB) in DHCA rats. Consistently, we used LPS-treated BV2 cells to mimic the neuroinflammatory condition and found that AdipoRon dose-dependently decreased cytokines, along with increased phosphorylation of AMPK and downregulated NF-κB. In conclusion, our present data supported that AdipoRon inhibited DHCA-induced neuroinflammation via activating the hippocampal AMPK/NF-κB pathway.

Terminal Phenoxy Group as a Privileged Moiety of the Drug Scaffold-A Short Review of Most Recent Studies 2013-2022

The terminal phenoxy group is a moiety of many drugs in use today. Numerous literature reports indicated its crucial importance for biological activity; thus, it is a privileged scaffold in medicinal chemistry. This review focuses on the latest achievements in the field of novel potential agents bearing a terminal phenoxy group in 2013-2022. The article provided information on neurological, anticancer, potential lymphoma agent, anti-HIV, antimicrobial, antiparasitic, analgesic, anti-diabetic as well as larvicidal, cholesterol esterase inhibitors, and antithrombotic or agonistic activities towards the adrenergic receptor. Additionally, for selected agents, the Structure-Activity-Relationship (SAR) is also discussed. Thus, this study may help the readers to better understand the nature of the phenoxy group, which will translate into rational drug design and the development of a more efficient drug. To the best of our knowledge, this is the first review devoted to an in-depth analysis of the various activities of compounds bearing terminal phenoxy moiety.

A spotlight on underlying the mechanism of AMPK in diabetes complications

OBJECTIVE

Type 2 diabetes (T2D) is one of the centenarian metabolic disorders and is considered as a stellar and leading health issue worldwide. According to the International Diabetes Federation (IDF) Diabetes Atlas and National Diabetes Statistics, the number of diabetic patients will increase at an exponential rate from 463 to 700 million by the year 2045. Thus, there is a great need for therapies targeting functions that can help in maintaining the homeostasis of glucose levels and improving insulin sensitivity. 5' adenosine monophosphate-activated protein kinase (AMPK) activation, by various direct and indirect factors, might help to overcome the hurdles (like insulin resistance) associated with the conventional approach.

MATERIALS AND RESULTS

A thorough review and analysis was conducted using various database including MEDLINE and EMBASE databases, with Google scholar using various keywords. This extensive review concluded that various drugs (plant-based, synthetic indirect/direct activators) are available, showing tremendous potential in maintaining the homeostasis of glucose and lipid metabolism, without causing insulin resistance, and improving insulin sensitivity. Moreover, these drugs have an effect against diabetes and are therapeutically beneficial in the treatment of diabetes-associated complications (neuropathy and nephropathy) via mechanism involving inhibition of nuclear translocation of SMAD4 (SMAD family member) expression and association with peripheral nociceptive neurons mediated by AMPK.

CONCLUSION

From the available information, it may be concluded that various indirect/direct activators show tremendous potential in maintaining the homeostasis of glucose and lipid metabolism, without resulting in insulin resistance, and may improve insulin sensitivity, as well. Therefore, in a nut shell, it may be concluded that the regulation of APMK functions by various direct/indirect activators may bring promising results. These activators may emerge as a novel therapy in diabetes and its associated complications.

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.