Adiponectin attenuates high glucose-induced apoptosis through the AMPK/p38 MAPK signaling pathway in NRK-52E cells

Lipid and glucose metabolism in senescence

Senescence is an inevitable biological process. Disturbances in glucose and lipid metabolism are essential features of cellular senescence. Given the important roles of these types of metabolism, we review the evidence for how key metabolic enzymes influence senescence and how senescence-related secretory phenotypes, autophagy, apoptosis, insulin signaling pathways, and environmental factors modulate glucose and lipid homeostasis. We also discuss the metabolic alterations in abnormal senescence diseases and anti-cancer therapies that target senescence through metabolic interventions. Our work offers insights for developing pharmacological strategies to combat senescence and cancer.

Akkila S, S. Ibrahim M. Adiponectin and the expression of BAX and caspase 3 in high-fructose - induced testicular injury in albino mice

Introduction and Aim: The increase in the prevalence of obesity and metabolic syndrome in recent decades has been correlated with high consumption of high-fructose and high-fat diets and has been associated with increased rates of male infertility. The aim of this study was to investigate how high fructose diet exerts its effect upon testicular morphology in addition to examine the potential effects of adiponectin treatment in restoring the architecture of seminiferous tubules through the expression of immunohistochemical markers BAX and caspase-3. Materials and Methods: Twenty-five adult albino mice were divided into three groups: In Group 1, mice fed with diet contained high concentration of fructose followed by adiponectin injection, Group 2, the mice fed with high concentration of fructose diet and received a saline placebo injection, and Group 3 (control) was nourished a regular food for 8 weeks. The parameters studied included changes in animal body weight, testicular spermatogenesis index, spermatogonia count, apoptotic index, exfoliative epithelium percentage and immunohistochemical scores for testicular BAX and caspase-3 expression. Results: Animals on high fructose diet showed increase in body weight which was markedly reduced by adiponectin treatment. High fructose diet also resulted in reduced spermatogenesis index and spermatogonia count with increased apoptotic and epithelial exfoliation indices. High fructose diet was also associated with high-fructose induced obesity and significantly associated with increased BAX and caspase-3 expression alleviated by adiponectin treatment. Conclusion: High-fructose intake induces obesity and obesity-related reduction in male fertility by reducing spermatogenesis and enhancing testicular cell apoptosis via different pathophysiological mechanisms. Such effects and mechanism can be reversed and corrected with adiponectin treatment.

The potential molecular implications of adiponectin in the evolution of SARS-CoV-2: Inbuilt tendency

Adiponectin (APN) is an adipokine concerned in the regulation of glucose metabolism, insulin sensitivity and fatty acid oxidation. APN plays a critical role in viral infections by regulating the immune response through its anti-inflammatory/pro-inflammatory axis. Reduction of APN may augment the severity of viral infections because APN inhibits immune cells’ response via suppression of inflammatory signaling pathways and stimulation of adenosine monophosphate protein kinase (AMPK). Moreover, APN inhibits the stimulation of nuclear factor kappa B (NF-κB) and regulates the release of pro-inflammatory cytokines, such as tumor necrosis factor alpha (TNF-α) and interleukins (IL-18, IL-6). In COVID-19, abnormalities of the fatty tissue due to oxidative stress (OS) and hyperinflammation may inhibit the production and release of APN. APN has lung-protective effect and can prevent SARS-CoV-2-induced acute lung injury (ALI) through the amelioration of endoplasmic reticulum (ER) stress, endothelial dysfunction (ED) and stimulation of peroxisome proliferator-activated receptor-alpha (PPAR-α). It has been established that there is a potential correlation between inflammatory signal transduction pathways and APN that contributes to the development of SARS-CoV-2 infections. Deregulation of these molecular pathways affects the expression of APN and vice versa. In addition, the reduction of APN effect in SARS-CoV-2 infection could be a potential cause of the exacerbation of pro-inflammatory effects which are associated with the disease severity. In this context, exploratory, developmental, and extensive prospective studies are necessary.

Camu-Camu Fruit Extract Inhibits Oxidative Stress and Inflammatory Responses by Regulating NFAT and Nrf2 Signaling Pathways in High Glucose-Induced Human Keratinocytes

Myrciaria dubia (HBK) McVaugh (camu-camu) belongs to the family Myrtaceae. Although camu-camu has received a great deal of attention for its potential pharmacological activities, there is little information on the anti-oxidative stress and anti-inflammatory effects of camu-camu fruit in skin diseases. In the present study, we investigated the preventative effect of 70% ethanol camu-camu fruit extract against high glucose-induced human keratinocytes. High glucose-induced overproduction of reactive oxygen species (ROS) was inhibited by camu-camu fruit treatment. In response to ROS reduction, camu-camu fruit modulated the mitogen-activated protein kinases (MAPK)/activator protein-1 (AP-1), nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), and nuclear factor of activated T cells (NFAT) signaling pathways related to inflammation by downregulating the expression of proinflammatory cytokines and chemokines. Furthermore, camu-camu fruit treatment activated the expression of nuclear factor E2-related factor 2 (Nrf2) and subsequently increased the NAD(P)H:quinone oxidoreductase1 (NQO1) expression to protect keratinocytes against high-glucose-induced oxidative stress. These results indicate that camu-camu fruit is a promising material for preventing oxidative stress and skin inflammation induced by high glucose level.

Adiponectin Synthesis, Secretion and Extravasation from Circulation to Interstitial Space

Adiponectin, an adipokine that circulates as multiple multimeric complexes at high levels in serum, has antidiabetic, anti-inflammatory, antiatherogenic, and cardioprotective properties. Understanding the mechanisms regulating adiponectin's physiological effects is likely to provide critical insight into the development of adiponectin-based therapeutics to treat various metabolic-related diseases. In this review, we summarize our current understanding on adiponectin action in its various target tissues and in cellular models. We also focus on recent advances in two particular regulatory aspects; namely, the regulation of adiponectin gene expression, multimerization, and secretion, as well as extravasation of circulating adiponectin to the interstitial space and its degradation. Finally, we discuss some potential therapeutic approaches using adiponectin as a target and the current challenges facing adiponectin-based therapeutic interventions.

Adiponectin-Transfected Endothelial Progenitor Cells Have Protective Effects After 2-Hour Middle-Cerebral Artery Occlusion in Rats With Type 2 Diabetes Mellitus

Objectives: This present study aimed to examine the effects of adiponectin-transfected endothelial progenitor cells (LV-APN-EPCs) on cerebral ischemia-reperfusion injury in rats with type 2 diabetes mellitus (T2DM) and to explore the underlying mechanisms. Methods: Seventy male Sprague-Dawley rats with T2DM were randomly divided into sham, phosphate-buffered saline (PBS), LV-APN-EPCs, LV-EPCs, and EPCs groups. Transient middle cerebral artery occlusion (MCAO) was induced by the intraluminal suture method. After 1 h of reperfusion, the five interventions were performed by tail-vein injections. The modified neurological severity score (mNSS) was used to assess neurological function before and on days 1, 7, and 14 after MCAO. After 14 days, magnetic resonance imaging scanning, hematoxylin and eosin staining, terminal dUTP nick-end labeling staining, Western blotting analysis, cluster of differentiation (CD) 31 immunofluorescence, and enzyme-linked immunosorbent assay were used to evaluate infarct rate, morphological damage, cell apoptosis, and microvessel density. Results: Compared with PBS, LV-EPCs, and EPCs groups, the LV-APN-EPCs group showed significantly lower mNSS score, lower infarct rate, and less morphological damage (all P < 0.05). In addition, compared with other groups, the LV-APN-EPCs group had significantly increased levels of B cell lymphoma/leukemia-2 (Bcl-2) protein, CD31+ microvessels, endothelial nitric oxide synthase, and vascular endothelial growth factor, and decreased levels of Bcl-2-associated X protein and neuronal apoptosis in the peri-infarct cortex (all P < 0.05). Conclusion: These results suggest that LV-APN-EPCs exert protective effects against cerebral ischemia-reperfusion injury in T2DM rats by increasing angiogenesis.

Bromodomain-containing protein 4 and its role in cardiovascular diseases

Bromodomain-containing protein 4 (BRD4), a chromatin-binding protein, is involved in the development of various tumors. Recent evidence suggests that BRD4 also plays a significant role in cardiovascular diseases, such as ischemic heart disease, hypertension, and cardiac hypertrophy. This review summarizes the roles of BRD4 as a potential regulator of various pathophysiological processes in cardiovascular diseases, implicating that BRD4 may be a new therapeutic target for cardiovascular diseases in the future.

Potent Inhibitory Effect of BJ-3105, a 6-Alkoxypyridin-3-ol Derivative, on Murine Colitis Is Mediated by Activating AMPK and Inhibiting NOX

Inflammatory bowel disease (IBD) is a chronic relapsing inflammation in the gastrointestinal tract. Biological therapeutics and orally available small molecules like tofacitinib (a JAK inhibitor) have been developed to treat IBD, but half of the patients treated with these drugs fail to achieve sustained remission. In the present study, we compared the therapeutic effects of BJ-3105 (a 6-alkoxypyridin-3-ol derivative) and tofacitinib in IBD. BJ-3105 induced activation of AMP-activated protein kinase (AMPK) in the kinase activity measurement and recovery from cytokine-induced AMPK deactivation in HT-29 human colonic epithelial cells. Similar to tofacitinib and D942 (an AMPK activator), BJ-3105 inhibited IL-6-induced JAK2/STAT3 phosphorylation and TNF-α-stimulated activation of IKK/NF-κB, and consequently, stimulus-induced upregulations of inflammatory cytokines and inflammasome components. In addition, unlike tofacitinib or D942, BJ-3105 inhibited NADPH oxidase (NOX) activation and consequent superoxide production induced by activators (mevalonate and geranylgeranyl pyrophosphate) of the NOX cytosolic component Rac. In mice, oral administration with BJ-3105 ameliorated dextran sulfate sodium (DSS)-induced colitis and azoxymethane/DSS-induced colitis-associated tumor formation (CAT) much more potently than that with tofacitinib. Moreover, BJ-3105 suppressed the more severe form of colitis and CAT formation in mice with AMPK knocked-out in macrophages (AMPKα^fl/fl-Lyz2-Cre mice) with much greater efficacy than tofacitinib. Taken together, our findings suggest BJ-3105, which exerted a much better anti-colitis effect than tofacitinib through AMPK activation and NOX inhibition, is a promising candidate for the treatment of IBD.

Adiponectin and Cognitive Decline

Adiponectin (ADPN) is a plasma protein secreted by adipose tissue showing pleiotropic effects with anti-diabetic, anti-atherogenic, and anti-inflammatory properties. Initially, it was thought that the main role was only the metabolism control. Later, ADPN receptors were also found in the central nervous system (CNS). In fact, the receptors AdipoR1 and AdipoR2 are expressed in various areas of the brain, including the hypothalamus, hippocampus, and cortex. While AdipoR1 regulates insulin sensitivity through the activation of the AMP-activated protein kinase (AMPK) pathway, AdipoR2 stimulates the neural plasticity through the activation of the peroxisome proliferator-activated receptor alpha (PPARα) pathway that inhibits inflammation and oxidative stress. Overall, based on its central and peripheral actions, ADPN appears to have neuroprotective effects by reducing inflammatory markers, such as C-reactive protein (PCR), interleukin 6 (IL6), and Tumor Necrosis Factor a (TNFa). Conversely, high levels of inflammatory cascade factors appear to inhibit the production of ADPN, suggesting bidirectional modulation. In addition, ADPN appears to have insulin-sensitizing action. It is known that a reduction in insulin signaling is associated with cognitive impairment. Based on this, it is of great interest to investigate the mechanism of restoration of the insulin signal in the brain as an action of ADPN, because it is useful for testing a possible pharmacological treatment for the improvement of cognitive decline. Anyway, if ADPN regulates neuronal functioning and cognitive performances by the glycemic metabolic system remains poorly explored. Moreover, although the mechanism is still unclear, women compared to men have a doubled risk of developing cognitive decline. Several studies have also supported that during the menopausal transition, the estrogen reduction can adversely affect the brain, in particular, verbal memory and verbal fluency. During the postmenopausal period, in obese and insulin-resistant individuals, ADPN serum levels are significantly reduced. Our recent study has evaluated the relationship between plasma ADPN levels and cognitive performances in menopausal women. Thus, the aim of this review is to summarize both the mechanisms and the effects of ADPN in the central nervous system and the relationship between plasma ADPN levels and cognitive performances, also in menopausal women.

Estrogenic Compounds or Adiponectin Inhibit Cyclic AMP Response to Human Luteinizing Hormone in Mouse Leydig Tumor Cells

Mouse Leydig Tumor cells (mLTC), transiently expressing cAMP-dependent luciferase, were used to study the influence of sexual steroids and of adiponectin (ADPN) on the cAMP response to luteinizing hormones (LH). While testosterone and progesterone had no significant effect, several molecules with estrogenic activity (17β-estradiol, ethynylestradiol, and bisphenol A) provoked a decrease in intracellular cyclic AMP accumulation under 0.7 nM human LH stimulation. Adiponectin exhibited a bimodal dose-effect on LH response: synergistic between 2–125 ng/mL and inhibitory between 0.5–5 µg/mL. In brief, our data indicate that estrogens and ADPN separately exert rapid (<1 h) inhibitory and/or synergistic effects on cAMP response to LH in mLTC-1 cells. As the inhibitory effect of each estrogenic molecule was observed after only 1-h preincubation, it might be mediated through the G protein-coupled estrogen receptor (GPER) membrane receptor, but this remains to be demonstrated. The synergistic effect with low concentrations of ADPN with human Luteinizing Hormone (hLH) was observed with both fresh and frozen/thawed ADPN. In contrast, the inhibitory effect with high concentrations of ADPN was lost with frozen/thawed ADPN, suggesting deterioration of its polymeric structure.

Prevention of kidney cell damage in hyperglycaemia condition by adiponectin

Adiponectin (APN) is an adipocytokine, secreted from adipose tissue and has anti-inflammatory, anti-ageing, and antidiabetic properties. Hyperglycaemia can damage the renal cells, and mammalian target of rapamycin (mTOR), along with Sirtuin 1 (SIRT1), have an important role in kidney cell response to hyperglycaemia. Therefore, understanding the relationship between adiponectin, mTOR, and SIRT1 proteins is beneficial for deciphering the mechanism of adiponectin function. In this study, Human Embryonic Kidney-293 (HEK-293) cells were cultured under normal and high-glucose condition, with and without APN (1, 10, and 100 ng/mL) for 48 hours. mTOR protein expression was evaluated by western blot analysis, and SIRT1 protein was assessed using ELISA method. To evaluate hyperglycaemia-mediated cytotoxicity, cell viability was determined using MTT assay. Data showed that APN in high dose (100 ng/mL) significantly reduced the expression of mTOR and p-mTOR, increased SIRT1 protein, and also improved cell viability compared with the control high glucose (p ≤ 0.05). According to this results, APN can be useful in preventing renal cell damage, by affecting on the expression of mTOR and SIRT1 proteins, as well as increasing the survival of kidney cells in hyperglycaemia conditions. SIGNIFICANCE OF THE STUDY: Adiponectin triggered mTOR/p-mTOR/SIRT1 pathway and decreased cell death in human kidney cells. Our findings provide preliminary experimental data that support further studies on the potential therapeutic role of adiponectin in diabetes and diabetic-induced metabolic complications.

Erianin protects against high glucose-induced oxidative injury in renal tubular epithelial cells

Erianin is the major bibenzyl compound found in Dendrobium chrysotoxum Lindl. The current study was designed to investigate the protective effects of erianin on high glucose-induced injury in cultured renal tubular epithelial cells (NRK-52E cells) and determine the possible mechanisms for its effects. NRK-52E cells were pretreated with erianin (5, 10, 25 or 50 nmol/L) for 1 h followed by further exposure to high glucose (30 mmol/L, HG) for 48 h. Erianin concentration dependently enhanced cell viability followed by HG treatment in NRK-52E cells. HG induced reactive oxygen species (ROS) generation, malondialdehyde production, and glutathione deficiency were recovered in NRK-52E cells pretreated with erianin. HG triggered cell apoptosis via the loss of mitochondrial membrane potential, depletion of adenosine triphosphate, upregulation of caspases 9 and 3, enhancement of cytochrome c release, and subsequent interruption of the Bax/Bcl-2 balance. These detrimental effects were ameliorated by erianin. HG also induced activation of p53, JNK, p38 mitogen-activated protein kinase (MAPK) and nuclear factor-κB (NF-κB) in NRK-52E cells, which were blocked by erianin. The results suggest that treatment NRK-52E cells with erianin halts HG-induced renal dysfunction through the suppression of the ROS/MAPK/NF-κB signaling pathways. Our findings provide novel therapeutic targets for diabetic nephropathy.

Function of BRD4 in the pathogenesis of high glucose‑induced cardiac hypertrophy

Diabetic cardiomyopathy is one of the major complications of diabetes, and due to the increasing number of patients with diabetes it is a growing concern. Diabetes-induced cardiomyopathy has a complex pathogenesis and histone deacetylase-mediated epigenetic processes are of prominent importance. The olfactory bromodomain-containing protein 4 (BRD4) is a protein that recognizes and binds acetylated lysine. It has been reported that the high expression of BRD4 is involved in the process of cardiac hypertrophy. The aim of the present study was to investigate the function of BRD4 in the process of high glucose (HG)-induced cardiac hypertrophy, and to clarify whether epigenetic regulation involving BRD4 is an important mechanism. It was revealed that BRD4 expression levels were increased in H9C2 cells following 48 h of HG stimulation. This result was also observed in a diabetic rat model. Furthermore, HG stimulation resulted in the upregulation of the myocardial hypertrophy marker, atrial natriuretic peptide, the cytoskeletal protein α-actin and fibrosis-associated genes including transforming growth factor-β, SMAD family member 3, connective tissue growth factor and collagen, type 1, α1. However, administration of the specific BRD4 inhibitor JQ1 (250 nM) for 48 h reversed this phenomenon. Furthermore, protein kinase B (AKT) phosphorylation was activated by HG stimulation and suppressed by JQ1. In conclusion, BRD4 serves an important role in the pathogenesis of HG-induced cardiomyocyte hypertrophy through the AKT pathway.

TAK1 mediates apoptosis via p38 involve in ischemia-induced renal fibrosis

Renal fibrosis is a common and characteristic symptom of chronic kidney disease (CKD). However, the molecular mechanisms of renal fibrosis remain elusive. Ischemia injury, as a major cause of AKI, deserves more attention in order to improve the knowledge of AKI-induced fibrosis. Transforming growth factor-β (TGF-β)-activated kinase 1 (TAK1) interacts directly with TGF-β, which play a critical role in the progression of fibrosis. Therefore, the present study aimed to investigate the role of TAK1 in the pathogenesis of ischemia-induced renal fibrosis. Compared with mice in the vehicle group, mice intraperitoneally injected with TAK1 inhibitor were found to have lower serum creatinine, less tubular damage and more mild fibrosis following ischemia-induced AKI. Furthermore, inhibition of TAK1 reduced p38 phosphorylation, decreased expression of Bax and caspase 3 and apoptosis cells in kidneys of mice treated with IR-induced AKI. Compared with vehicle-treated renal tubular epithelial cells, TAK1 overexpression cells were found to have a higher apoptosis and fibrosis index level and p38 phosphorylation following hypoxia/reoxygenation (H/R) treatment. Furthermore, the p38 inhibitor combined with TAK1 overexpression verified the role of TAK1/p38 signaling pathway in apoptosis and fibrosis index level of renal tubular epithelial cells treated with H/R. Thus, our results show that TAK1 plays an important role in the pathogenesis of ischemia-induced renal fibrosis and may mediate p38-regulated cell apoptosis.

Adiponectin and its receptors are involved in hypertensive vascular injury

Adipocyte-derived adiponectin (APN) is involved in the protection against cardiovascular disease, but the endogenous APN and its receptor expression in the perivascular adipocytes and their role in hypertensive vascular injury remain unclear. The present study aimed to detect endogenous APN and its receptor expression and their protective effects against hypertensive vascular injury. APN was mainly expressed in the perivascular adipocytes, while its receptors AdipoR1 and AdipoR2 were ubiquitously expressed in the blood vessels. Angiotensin II (Ang II)-induced hypertension resulted in a significant decrease of APN and AdipoR1 and AdipoR2 in the perivascular adipocytes and vascular cells. The migration assay used demonstrated that APN attenuated Ang II-induced vascular smooth muscle cells migration and p38 phosphorylation Furthermore, the in vivo study demonstrated that APN receptor agonist AdipoRon attenuated Ang II-induced hypertensive vascular hypertrophy and fibrosis. Taken together, the present study indicated that perivascular adipocytes-derived APN attenuated hypertensive vascular injury possibly via its receptor-mediated inhibition of p38 signaling pathway.

Correction: Adiponectin attenuates high glucose-induced apoptosis through the AMPK/p38 MAPK signaling pathway in NRK-52E cells

[This corrects the article DOI: 10.1371/journal.pone.0178215.].