Protective effects of adiponectin against renal ischemia-reperfusion injury via prostacyclin-PPARα-heme oxygenase-1 signaling pathway

The Role of Adipose Tissue and Nutrition in the Regulation of Adiponectin

Adipose tissue (AT), composed mainly of adipocytes, plays a critical role in lipid control, metabolism, and energy storage. Once considered metabolically inert, AT is now recognized as a dynamic endocrine organ that regulates food intake, energy homeostasis, insulin sensitivity, thermoregulation, and immune responses. This review examines the multifaceted role of adiponectin, a predominant adipokine released by AT, in glucose and fatty acid metabolism. We explore the regulatory mechanisms of adiponectin, its physiological effects and its potential as a therapeutic target for metabolic diseases such as type 2 diabetes, cardiovascular disease and fatty liver disease. Furthermore, we analyze the impact of various dietary patterns, specific nutrients, and physical activities on adiponectin levels, highlighting strategies to improve metabolic health. Our comprehensive review provides insights into the critical functions of adiponectin and its importance in maintaining systemic metabolic homeostasis.

Prostacyclin in trauma patients with hemorrhagic shock: A randomized clinical trial

BACKGROUND

A main cause of trauma morbidity and mortality is multiple-organ failure, and endotheliopathy has been implicated. Pilot studies indicate that low-dose prostacyclin improves endothelial functionality in critically ill patients, suggesting that this intervention may improve trauma patient outcome.

METHODS

We conducted a multicenter, randomized, blinded, clinical investigator-initiated trial in 229 trauma patients with hemorrhagic shock who were randomized 1:1 to 72 hours infusion of the prostacyclin analog iloprost (1 ng/kg/min) or placebo. The primary outcome was the number of intensive care unit (ICU)-free days alive within 28 days of admission. Secondary outcomes included 28-day all-cause mortality and hospital length of stay.

RESULTS

The mean number of ICU-free days alive within 28 days was 15.64 days in the iloprost group versus 13.99 days in the placebo group (adjusted mean difference, -1.63 days [95% confidence interval (CI), -4.64 to 1.38 days]; p = 0.28). The 28-day mortality was 18.8% in the iloprost group versus 19.6% in the placebo group (odds ratio, 1.01 [95% CI, 0.51-2.0]; p = 0.97). The mean hospital length of stay was 19.96 days in the iloprost group versus 27.32 days in the placebo group (adjusted mean difference, 7.84 days [95% CI, 1.66-14.02 days], p = 0.01).

CONCLUSION

Iloprost did not result in a statistically significant increase in the number of ICU-free days alive within 28 days of admission, whereas it was safe and a statistically significant reduction in hospital length of stay was observed. Further research on prostacyclin in shocked trauma patients is warranted.

LEVEL OF EVIDENCE

Therapeutic/Care Management; Level II.

Endocrinological disorders in acute kidney injury: an often overlooked field of clinical research

Acute kidney injury (AKI) is a common comorbidity, affecting approximately one in five hospitalized adults. The kidney is the site for the production, metabolism or excretion of most hormones, including the production of erythropoietin (EPO), the active form of vitamin D, renin, thrombopoietin, and the excretion of insulin, catecholamines, gastrin and many other hormones. Therefore, it is reasonable to say that AKI can have a considerable impact on the endocrine system. Although the effects of AKI on various parameters, including cardiovascular parameters, serum electrolytes and acid-base disorders, neuro-humoral mechanisms and neurological outcomes have been extensively studied, the endocrinological consequences of AKI are understudied. Thyroid dysfunction, mainly euthyroid sick syndrome, hypo/hyperglycemia, bone mineral disorders, changes in EPO and atrial natriuretic peptide (ANP) levels are commonly found in AKI. EPO, thyroxine and ANP administration have been evaluated as potential tools to prevent or treat AKI with varying success, while the effects of AKI on some key hormones, including cortisol and insulin, have never been studied. Aim of this narrative review is to illustrate what is known and what is not known about the endocrinological outcomes of AKI. Few clinical trials are ongoing: however, there is a clear need for large-scale randomized controlled trials investigating the endocrinological consequences of AKI.

Adiponectin gene therapy prevents islet loss after transplantation

Significant pancreatic islet dysfunction and loss shortly after transplantation to the liver limit the widespread implementation of this procedure in the clinic. Nonimmune factors such as reactive oxygen species and inflammation have been considered as the primary driving force for graft failure. The adipokine adiponectin plays potent roles against inflammation and oxidative stress. Previous studies have demonstrated that systemic administration of adiponectin significantly prevented islet loss and enhanced islet function at post‐transplantation period. In vitro studies indicate that adiponectin protects islets from hypoxia/reoxygenation injury, oxidative stress as well as TNF‐α‐induced injury. By applying adenovirus mediated transfection, we now engineered islet cells to express exogenous adiponectin gene prior to islet transplantation. Adenovirus‐mediated adiponectin transfer to a syngeneic suboptimal islet graft transplanted under kidney capsule markedly prevented inflammation, preserved islet graft mass and improved islet transplant outcomes. These results suggest that adenovirus‐mediated adiponectin gene therapy would be a beneficial clinical engineering approach for islet preservation in islet transplantation.

The effect of prostacyclin infusion on markers of endothelial activation and damage in mechanically ventilated patients with SARS-CoV-2 infection

Background

In a pilot study, we found a significant reduction in mean daily sequential organ failure assessment score in mechanically ventilated patients with COVID-19 who received prostacyclin, compared to placebo. We here investigate the effect on biomarkers of endothelial activation and damage.

Methods

Post-hoc study of a randomized controlled trial in adult patients with confirmed SARS-CoV-2 infection, mechanically ventilated, with soluble thrombomodulin (sTM) plasma levels >4 ng/mL. Patients received prostacyclin infusion (1 ng/kg/min) or placebo. Blood samples were collected at baseline and 24 h.

Results

Eighty patients were randomized (41 prostacyclin, 39 placebo). The median changes in syndecan-1 plasma levels at 24 h were −3.95 (IQR: −21.1 to 2.71) ng/mL in the prostacyclin group vs. 3.06 (IQR: −8.73 to 20.5) ng/mL in the placebo group (difference of the medians: -7.01 [95% CI: −22.3 to −0.231] ng/mL, corresponding to −3% [95% CI: −11% to 0%], p = 0.04). Changes in plasma levels of sTM, PECAM-1, p-selectin, and CD40L did not differ significantly between groups.

Conclusions

Prostacyclin infusion, compared to placebo, resulted in a measurable decrease in endothelial glycocalyx shedding (syndecan-1) at 24 h, suggesting a protective effect on the endothelium, which may be related to the observed reduction in organ failure.

The Endothelium and COVID-19: An Increasingly Clear Link Brief Title: Endotheliopathy in COVID-19

The endothelium has a fundamental role in the cardiovascular complications of coronavirus disease 2019 (COVID-19). Infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) particularly affects endothelial cells. The virus binds to the angiotensin-converting enzyme 2 (ACE-2) receptor (present on type 2 alveolar cells, bronchial epithelial cells, and endothelial cells), and induces a cytokine storm. The cytokines tumor necrosis factor alpha, interleukin-1 beta, and interleukin-6 have particular effects on endothelial cells-leading to endothelial dysfunction, endothelial cell death, changes in tight junctions, and vascular hyperpermeability. Under normal conditions, apoptotic endothelial cells are removed into the bloodstream. During COVID-19, however, endothelial cells are detached more rapidly, and do not regenerate as effectively as usual. The loss of the endothelium on the luminal surface abolishes all of the vascular responses mediated by the endothelium and nitric oxide production in particular, which results in greater contractility. Moreover, circulating endothelial cells infected with SARS-CoV-2 act as vectors for viral dissemination by forming clusters that migrate into the circulation and reach distant organs. The cell clusters and the endothelial dysfunction might contribute to the various thromboembolic pathologies observed in COVID-19 by inducing the formation of intravascular microthrombi, as well as by triggering disseminated intravascular coagulation. Here, we review the contributions of endotheliopathy and endothelial-cell-derived extracellular vesicles to the pathogenesis of COVID-19, and discuss therapeutic strategies that target the endothelium in patients with COVID-19.

Transcriptomic Analysis Revealed an Important Role of Peroxisome-Proliferator-Activated Receptor Alpha Signaling in Src Homology Region 2 Domain-Containing Phosphatase-1 Insufficiency Leading to the Development of Renal Ischemia-Reperfusion Injury

In kidney transplantation, the donor kidney inevitably undergoes ischemia-reperfusion injury (IRI). It is of great importance to study the pathogenesis of IRI and find effective measures to attenuate acute injury of renal tubules after ischemia-reperfusion. Our previous study found that Src homology region 2 domain-containing phosphatase-1 (SHP-1) insufficiency aggravates renal IRI. In this study, we systematically analyzed differences in the expression profiles of SHP-1 (encoded by Ptpn6)-insufficient mice and wild-type mice by RNA-seq. We found that a total of 161 genes showed at least a twofold change, with a false discovery rate <0.05 in Ptpn6 +/mev mice after IRI and 42 genes showing more than a fourfold change. Of the eight genes encoding proteins with immunoreceptor tyrosine-based inhibitory motifs (ITIMs) that bind to Ptpn6, three were upregulated, and five were downregulated. We found that for the differentially expressed genes (DEGs) with a fold change >2, the most significantly enriched Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways were the cell division pathway and peroxisome-proliferator activated receptor PPARα signaling pathways. Furthermore, the downregulated genes of the PPARα signaling pathway were mainly related to fatty acid absorption and degradation. Using an agonist of the PPARα signaling pathway, fenofibrate, we found that renal IRI was significantly attenuated in Ptpn6 +/mev mice. In summary, our results show that insufficiency of SHP-1 inhibits the expression of genes in the PPARα signaling pathway, thereby leading to increased reactive oxygen species (ROS) and exacerbating the renal IRI. The PPARα signaling agonist fenofibrate partially attenuates renal IRI induced by SHP-1 insufficiency.

The effect of body mass index on the development of acute kidney injury and mortality in intensive care unit: is obesity paradox valid?

BACKGROUND

The conflicting results of studies on intensive care unit (ICU) mortality of obese patients and obese patients with acute kidney injury (AKI) reveal a paradox within a paradox. The aim of this study was to determine the effects of body mass index and obesity on AKI development and ICU mortality.

METHODS

The 4,459 patients treated between January 2015 and December 2019 in the ICU at a Tertiary Care Center in Turkey were analyzed retrospectively.

RESULTS

AKI developed more in obese patients with 69.8% (620). AKI development rates were similar in normal-weight (65.1%; 1172) and overweight patients (64.9%; 1149). The development of AKI in patients who presented with cerebrovascular diseases was higher in obese patients (81; 76.4%) than in normal-weight (158; 62.7%) and overweight (174; 60.8%) patients (p < 0.05). The risk of developing AKI was approximately 1.4 times (CI 95% = 1.177-1.662) higher in obese patients than in normal-weight patients. Dialysis was used more frequently in obese patients (24.3%, p < 0.001), who stayed longer in the ICU (p < 0.05). It was determined that the development of AKI in normal-weight and overweight patients increased mortality (p < 0.001) and that there was not a difference in mortality rates between obese patients with and without AKI.

CONCLUSION

The risk of AKI development was higher in obese patients but not in those who were in serious conditions. Another paradox was that the development of AKI was associated with a higher mortality rate in normal-weight and overweight patients, but not in obese patients. Cerebrovascular diseases as a cause of admission pose additional risks for AKI.

Prostacyclin in Mechanically Ventilated Patients with COVID-19 and Severe Endotheliopathy: A Multicenter, Randomized, Clinical Trial

Rationale

The mortality in patients infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) who require mechanical ventilation remains high, and endotheliopathy has been implicated.

Objectives

To determine the effect of prostacyclin infusion in mechanically ventilated patients infected with SARS-CoV-2 with severe endotheliopathy.

Methods

We conducted a multicenter, randomized clinical trial in adults infected with coronavirus disease (COVID-19) who required mechanical ventilation and had a plasma level of thrombomodulin >4 ng/ml; patients were randomized to 72-hour infusion of prostacyclin 1 ng/kg/min or placebo.

Measurements and Main Results

The main outcome was the number of days alive and without mechanical ventilation within 28 days. Key secondary outcomes were 28-day mortality and serious adverse events within 7 days. Eighty patients were randomized (41 prostacyclin and 39 placebo). The median number of days alive without mechanical ventilation at 28 days was 16.0 days (SD, 12) versus 5.0 days (SD, 10) (difference of the medians, 10.96 days; 95% confidence interval [CI], −5 to 21; P = 0.07) in the prostacyclin and the placebo groups, respectively. The 28-day mortality was 21.9% versus 43.6% in the prostacyclin and the placebo groups, respectively (risk ratio, 0.50; 95% CI, 0.24 to 0.96; P = 0.06). The incidence of serious adverse events within 7 days was 2.4% versus 12.8% (risk ratio, 0.19; 95% CI, 0.001 to 1.11; P = 0.10) in the prostacyclin and the placebo groups, respectively.

Conclusions

Prostacyclin was not associated with a significant reduction in the number of days alive and without mechanical ventilation within 28 days. The point estimates, however, favored the prostacyclin group in all analyses, including 28-day mortality, warranting further investigation in larger trials.

Clinical trial registered with www.clinicaltrials.gov (NCT 04420741); EudraCT Identifier: 2020-001296-33.

Peroxisome Proliferator-Activated Receptors (PPARs) and Oxidative Stress in Physiological Conditions and in Cancer

Peroxisome proliferator-activated receptors (PPARs) belong to the nuclear hormone receptor superfamily. Originally described as “orphan nuclear receptors”, they can bind both natural and synthetic ligands acting as agonists or antagonists. In humans three subtypes, PPARα, β/δ, γ, are encoded by different genes, show tissue-specific expression patterns, and contribute to the regulation of lipid and carbohydrate metabolisms, of different cell functions, including proliferation, death, differentiation, and of processes, as inflammation, angiogenesis, immune response. The PPAR ability in increasing the expression of various antioxidant genes and decreasing the synthesis of pro-inflammatory mediators, makes them be considered among the most important regulators of the cellular response to oxidative stress conditions. Based on the multiplicity of physiological effects, PPAR involvement in cancer development and progression has attracted great scientific interest with the aim to describe changes occurring in their expression in cancer cells, and to investigate the correlation with some characteristics of cancer phenotype, including increased proliferation, decreased susceptibility to apoptosis, malignancy degree and onset of resistance to anticancer drugs. This review focuses on mechanisms underlying the antioxidant and anti-inflammatory properties of PPARs in physiological conditions, and on the reported beneficial effects of PPAR activation in cancer.

Perilipin 2 Impacts Acute Kidney Injury via Regulation of PPARα

Renal ischemia-reperfusion (I/R) can induce oxidative stress and injury via the generation of reactive oxygen species (ROS). Renal proximal tubular cells are susceptible to oxidative stress, and the dysregulation of renal proximal tubular cellular homeostasis can damage cells via apoptotic pathways. A recent study showed that the generation of ROS can increase perilipin 2 (Plin2) expression in HepG2 cells. Some evidence has also demonstrated the association between Plin2 expression and renal tumors. However, the underlying mechanism of Plin2 in I/R-induced acute kidney injury (AKI) remains elusive. Here, using a mouse model of I/R-induced AKI, we found that ROS generation was increased and the expression of Plin2 was significantly upregulated. An in vitro study further revealed that the expression of Plin2, and the generation of ROS were significantly upregulated in primary tubular cells treated with hydrogen peroxide. Accordingly, Plin2 knockdown decreased apoptosis in renal proximal tubular epithelial cells treated with hydrogen peroxide, which depended on the activation of peroxisome proliferator-activated receptor α (PPARα). Overall, the present study demonstrated that Plin2 is involved in AKI; knockdown of this marker might limit apoptosis via the activation of PPARα. Consequently, the downregulation of Plin2 could be a novel therapeutic strategy for AKI.

Sanziguben polysaccharides inhibit diabetic nephropathy through NF-κB-mediated anti-inflammation

Background

Sanziguben polysaccharides (SZP) are large amounts of classical Chinese medicines from Sanziguben (SZGB). Moreover, SZGB is a widely applied compound prescription for diabetic nephropathy (DN) treatment, but the role is still unclear. This study initially explores the mechanism of SZP in the treatment of DN.

Methods

The high-fat diet plus streptozotocin injections were used to replicate the DN models in male C57BL/6 mice. DN mice were divided into five groups: DN mice, DN mice treated with SZP(1.01 or 2.02 g/kg), DN mice treated with SZGB decoction(4.7 g/kg), and DN mice treated with metformin (300 mg/kg). HG and LPS plus TNFα stimulated human tubule epithelial (HK-2) cells to establish an in vitro model and treated with SZP (100 or 200 μg/mL).

Results

SZP was found to comprise sugar, protein, and uronic acid. Furthermore, SZP alleviated the progression of inflammation in vivo and in vitro by inhibiting the expression of NF-κB.

Conclusions

NF-κB plays a critical role in the development of DN induced by STZ and HG. Furthermore, SZP can attenuate the NF-κB‐mediated progression of diabetic nephropathy, improve DN through anti-inflammation.

Efficacy and safety of iloprost in trauma patients with haemorrhagic shock-induced endotheliopathy-Protocol for the multicentre randomized, placebo-controlled, blinded, investigator-initiated shine-trauma trial

BACKGROUND

Traumatic injury accounts for 800 000 deaths in the European Union annually. The main causes of deaths in trauma patients are exsanguination and multiple organ failure (MOF). We have studied >1000 trauma patients and identified shock-induced endotheliopathy (SHINE), the pathophysiological mechanism responsible for MOF and high mortality. Pilot studies indicate that low-dose iloprost (1 ng/kg/min) improves endothelial functionality in critically ill patients suggesting this intervention may improve patient outcome in traumatic SHINE.

MATERIAL AND METHODS

This is a multicentre, randomized, blinded clinical investigator-initiated phase 2B trial in trauma patients with haemorrhagic shock-induced endotheliopathy. Patients are randomized 1:1 to 72 hours infusion of iloprost 1 ng/kg/min or Placebo (equal volume of saline). A total of 220 trauma patients will be included. The primary endpoint is the number of intensive care unit (ICU)-free days, within 28 days of admission. Secondary endpoints include 28- and 90-day all-cause mortality, hospital length of stay, vasopressor-free days in the intensive care unit (ICU) within 28 days, ventilator-free days in the ICU within 28 days, renal replacement-free days in the ICU within 28 days, number of serious adverse reactions and serious adverse events within the first 4 days of admission.

DISCUSSION

This trial will test the safety and efficacy of administration of iloprost vs placebo for 72 hours in trauma patients with haemorrhagic shock-induced endotheliopathy. Trial endpoints focus on the potential effect of iloprost to reduce the need for ICU stay secondary to mitigation of organ failure.

TRIAL REGISTRATION

SHINE-TRAUMA trial-EudraCT no. 2019-000936-24-Clinicaltrials.gov: NCT03903939 Ethics Committee no. H-19014482.

Heme Oxygenase 1: A Defensive Mediator in Kidney Diseases

The incidence of kidney disease is rising, constituting a significant burden on the healthcare system and making identification of new therapeutic targets increasingly urgent. The heme oxygenase (HO) system performs an important function in the regulation of oxidative stress and inflammation and, via these mechanisms, is thought to play a role in the prevention of non-specific injuries following acute renal failure or resulting from chronic kidney disease. The expression of HO-1 is strongly inducible by a wide range of stimuli in the kidney, consequent to the kidney's filtration role which means HO-1 is exposed to a wide range of endogenous and exogenous molecules, and it has been shown to be protective in a variety of nephropathological animal models. Interestingly, the positive effect of HO-1 occurs in both hemolysis- and rhabdomyolysis-dominated diseases, where the kidney is extensively exposed to heme (a major HO-1 inducer), as well as in non-heme-dependent diseases such as hypertension, diabetic nephropathy or progression to end-stage renal disease. This highlights the complexity of HO-1's functions, which is also illustrated by the fact that, despite the abundance of preclinical data, no drug targeting HO-1 has so far been translated into clinical use. The objective of this review is to assess current knowledge relating HO-1's role in the kidney and its potential interest as a nephroprotection agent. The potential therapeutic openings will be presented, in particular through the identification of clinical trials targeting this enzyme or its products.

Increased vascular permeability and severe renal tubular damage after ischemia-reperfusion injury in mice lacking adiponectin or T-cadherin

Adiponectin (APN) is a circulating protein specifically produced by adipocytes. Native APN specifically binds to T-cadherin, a glycosylphosphatidylinositol-anchored protein, mediating the exosome-stimulating effects of APN in endothelial, muscle, and mesenchymal stem cells. It was previously reported that APN has beneficial effects on kidney diseases, but the role of T-cadherin has not been clarified yet. Here, our immunofluorescence study indicated the existence of both T-cadherin and APN protein in pericytes, subsets of tissue-resident mesenchymal stem/progenitor cells positive for platelet-derived growth factor receptor β (PDGFRβ), surrounding peritubular capillaries. In an acute renal ischemia-reperfusion (I/R) model, T-cadherin-knockout (Tcad-KO) mice, similar to APN-KO mice, exhibited the more progressive phenotype of renal tubular damage and increased vascular permeability than wild-type mice. In addition, in response to I/R-injury, the renal PDGFRβ-positive cell area increased in wild-type mice, but opposingly decreased in both Tcad-KO and APN-KO mice, suggesting severe pericyte loss. Mouse primary pericytes also expressed T-cadherin. APN promoted exosome secretion in a T-cadherin-dependent manner. Such exosome production from pericytes may play an important role in maintaining the capillary network and APN-mediated inhibition of renal tubular injury. In summary, our study suggested that APN protected the kidney in an acute renal injury model by binding to T-cadherin.NEW & NOTEWORTHY In the kidney, T-cadherin-associated adiponectin protein existed on peritubular capillary pericytes. In an acute renal ischemia-reperfusion model, deficiency of adiponectin or T-cadherin exhibited the more progressive phenotype of renal tubular damage and increased vascular permeability, accompanied by severe pericyte loss. In vitro, adiponectin promoted exosome secretion from mouse primary pericytes in a T-cadherin-dependent manner. Adiponectin plays an important role in maintaining the capillary network and amelioration of renal tubular injury by binding to T-cadherin.

Heme Degradation in Pathophysiology of and Countermeasures to Inflammation-Associated Disease

The class of tetrapyrrol "coordination complexes" called hemes are prosthetic group components of metalloproteins including hemoglobin, which provide functionality to these physiologically essential macromolecules by reversibly binding diatomic gasses, notably O₂, which complexes to ferrous (reduced/Fe(II)) iron within the heme porphyrin ring of hemoglobin in a pH- and PCO₂-dependent manner-thus allowing their transport and delivery to anatomic sites of their function. Here, pathologies associated with aberrant heme degradation are explored in the context of their underlying mechanisms and emerging medical countermeasures developed using heme oxygenase (HO), its major degradative enzyme and bioactive metabolites produced by HO activity. Tissue deposits of heme accumulate as a result of the removal of senescent or damaged erythrocytes from circulation by splenic macrophages, which destroy the cells and internal proteins, including hemoglobin, leaving free heme to accumulate, posing a significant toxicogenic challenge. In humans, HO uses NADPH as a reducing agent, along with molecular oxygen, to degrade heme into carbon monoxide (CO), free ferrous iron (FeII), which is sequestered by ferritin protein, and biliverdin, subsequently metabolized to bilirubin, a potent inhibitor of oxidative stress-mediated tissue damage. CO acts as a cellular messenger and augments vasodilation. Nevertheless, disease- or trauma-associated oxidative stressors sufficiently intense to overwhelm HO may trigger or exacerbate a wide range of diseases, including cardiovascular and neurologic syndromes. Here, strategies are described for counteracting the effects of aberrant heme degradation, with a particular focus on "bioflavonoids" as HO inducers, shown to cause amelioration of severe inflammatory diseases.

OX-HDL: A Starring Role in Cardiorenal Syndrome and the Effects of Heme Oxygenase-1 Intervention

In this review, we will evaluate how high-density lipoprotein (HDL) and the reverse cholesterol transport (RCT) pathway are critical for proper cardiovascular-renal physiology. We will begin by reviewing the basic concepts of HDL cholesterol synthesis and pathway regulation, followed by cardiorenal syndrome (CRS) pathophysiology. After explaining how the HDL and RCT pathways become dysfunctional through oxidative processes, we will elaborate on the potential role of HDL dysfunction in CRS. We will then present findings on how HDL function and the inducible antioxidant gene heme oxygenase-1 (HO-1) are interconnected and how induction of HO-1 is protective against HDL dysfunction and important for the proper functioning of the cardiovascular-renal system. This will substantiate the proposal of HO-1 as a novel therapeutic target to prevent HDL dysfunction and, consequently, cardiovascular disease, renal dysfunction, and the onset of CRS.

The Yin and Yang of Alarmins in Regulation of Acute Kidney Injury

Acute kidney injury (AKI) is a major clinical burden affecting 20 to 50% of hospitalized and intensive care patients. Irrespective of the initiating factors, the immune system plays a major role in amplifying the disease pathogenesis with certain immune cells contributing to renal damage, whereas others offer protection and facilitate recovery. Alarmins are small molecules and proteins that include granulysins, high-mobility group box 1 protein, interleukin (IL)-1α, IL-16, IL-33, heat shock proteins, the Ca++ binding S100 proteins, adenosine triphosphate, and uric acid. Alarmins are mostly intracellular molecules, and their release to the extracellular milieu signals cellular stress or damage, generally leading to the recruitment of the cells of the immune system. Early studies indicated a pro-inflammatory role for the alarmins by contributing to immune-system dysregulation and worsening of AKI. However, recent developments demonstrate anti-inflammatory mechanisms of certain alarmins or alarmin-sensing receptors, which may participate in the prevention, resolution, and repair of AKI. This dual function of alarmins is intriguing and has confounded the role of alarmins in AKI. In this study, we review the contribution of various alarmins to the pathogenesis of AKI in experimental and clinical studies. We also analyze the approaches for the therapeutic utilization of alarmins for AKI.

Efficacy and safety of iloprost in patients with septic shock-induced endotheliopathy-Protocol for the multicenter randomized, placebo-controlled, blinded, investigator-initiated trial

BACKGROUND

In Europe 700.000 new cases of sepsis occur annually and more than 100.000 of these patients die due to multiorgan failure (MOF). We have identified shock-induced endotheliopathy (SHINE) to be associated with development of MOF and mortality. Furthermore, in patients with septic shock those with circulating levels of thrombomodulin (TM) above 10 ng/mL have twice the mortality (56% vs 28%) than those with levels below this level. Pilot studies indicate that infusion of iloprost (1 ng/kg/min) is associated with improved endothelial function in patients with septic shock.

MATERIAL AND METHODS

This is a multicenter, randomized, blinded, investigator-initiated, adaptive phase 2B trial in up to 384 patients with septic shock-induced endotheliopathy defined by TM > 10 ng/mL who are allocated 1:1 to 72 hours continuous infusion of iloprost 1 ng/kg/min or placebo (equal volume of saline). The primary outcome is the mean daily modified Sequential Organ Failure Assessment (SOFA) score in the ICU up to day 90. Secondary outcomes include 28- and 90-day all-cause mortality, days alive without vasopressor in the ICU within 90 days, days alive without mechanical ventilation in the ICU within 90 days, days alive without renal replacement therapy in the ICU within 90 days, numbers of serious adverse reactions, and the number of serious adverse events within the first 7 days.

DISCUSSION

This trial tests the safety and efficacy of iloprost vs placebo for 72 hours in patients with septic shock and SHINE. The outcome measures focus on the potential effect of the intervention to mitigate organ failure.

TRIAL REGISTRATION

COMBAT-SHINE trial-EudraCT no. 2019-001131-31-Clinicaltrials.gov: NCT04123444-Ethics Committee no. H-19018258.

Adiponectin in renal fibrosis

Renal fibrosis is an inevitable consequence of parenchymal scarring and is the common final pathway that mediates almost all progressive renal diseases. Adiponectin, a hormone produced by adipose tissue, possesses potent anti-insulin, anti-inflammatory, and anti-fibrotic properties. Reportedly, adiponectin serves as an important messenger that facilitates complex interactions between adipose tissue and other metabolically related organs. In recent years, a growing body of evidence supports adiponectin involvement in renal fibrosis. These studies provide a deeper understanding of the molecular mechanism of action of adiponectin in renal fibrosis and also offer a potential preventive and therapeutic target for renal fibrosis. In this review, the physiological role of adiponectin is briefly introduced, and then the mechanism of adiponectin-mediated renal fibrosis and the related signaling pathways are described. Finally, we summarize the findings regarding the clinical value of adiponectin in renal fibrotic diseases and prospected its application potential.

Physiological role of adiponectin in different tissues: a review

Adiponectin is the most important adipokine secreted by the adipose tissue. It carries out an important role in setting up the metabolism and improving the function of various organs. Adiponectin in the kidneys prevents degradation of the renal arteries, reduces protein excretion, and improves filtration. This role is accomplished by regulating anabolic pathways and reducing oxidative stress in the renal tissue. This hormone in the liver prevents the accumulation of fat and free radicals that cause damage to liver cells and tissue. This adipokine, by preventing inflammatory processes, oxidative stress, obesity and insulin resistance, improves vascular function and prevents the development of atherosclerosis. It seems that adiponectin can also be a therapeutic target for many metabolic diseases. This study aims to clarify the adipose tissue discharge. Here, the diverse physiological actions of adiponectin were reviewed to provide an overview of its therapeutic potential in different metabolic disorders.

[Research progress in adipose tissue promoted wound healing]

OBJECTIVE

To summarize recent progress in adipose tissue acting as a more efficient and ideal therapy to facilitate wound repair and evaluate the therapeutic values of adipose tissue.

METHODS

The related literature about adipose tissue for wound healing in recent years was reviewed and analyzed.

RESULTS

Enormous studies focus on the capacity of adipose tissue to accelerate wound healing including cellular components, extracellular matrix, and paracrine signaling have been investigated.

CONCLUSION

Adipose tissue has generated great interest in recent years because of unique advantages such as abundant and accessible source, thriven potential to enhance the regeneration and repair of damaged tissue. However, there is still a need to explore the mechanism that adipose tissue regulates cellular function and tissue regeneration in order to facilitate clinical application of adipose tissue in wound healing.

Biomarkers of cadmium, lead and mercury exposure in relation with early biomarkers of renal dysfunction and diabetes: Results from a pilot study among aging Canadians

Cadmium (Cd), lead (Pb) and mercury (Hg) are known nephrotoxicants that have been associated with the risk of developing type-2 diabetes (T2D). The aim of this pilot study was to explore relations between biomarkers of Cd, Pb and Hg exposure, early urinary biomarkers of renal dysfunction (kidney-injured molecule-1 (KIM-1), N-acetylglucosaminidase and retinol-binding protein (RBP)) and plasma biomarkers deemed predictive of the risk of developing T2D (adiponectin, leptin, branched-chain and aromatic amino acids), among 70 participants (age range: (46-87 yrs)) from the Canadian Longitudinal Study on Aging (CLSA) with normal glycemic control (glycated haemoglobin ≤ 6.5%) in all but four of them. Significant (p < 0.05) Spearman correlation coefficients were obtained between: plasma adiponectin and RBP (r = 0.42), urinary Cd (r = 0.32), blood Cd (r = 0.36); KIM-1 and CdU (r = 0.33) as well as HgU (r = 0.37); RBP and isoleucine (r = -0.28), leucine (r = -0.33), tyrosine (r = -0.3) and valine (r = -0.44); CdU and isoleucine and valine (r = -0.27 for both). Multiple linear regression analyses showed that some T2D-related biomarkers are confounders of associations between RBP and Hg or Cd biomarkers. Path analyses support a mediating effect of adiponectin on the relation between urinary Cd and RBP. Concluding, this pilot study originally investigated a comprehensive set of biomarkers on complex interactions between toxic metal exposure, renal function and T2D in a group of aging Canadians. Its findings warrant further investigation of longitudinal data in a greater number of participants.

Differential Signature of Obesity in the Relationship with Acute Kidney Injury and Mortality after Coronary Artery Bypass Grafting

BACKGROUND

Obesity is related to several comorbidities and mortality, but its relationship with acute kidney injury (AKI) and long-term mortality remain undetermined in patients undergoing coronary artery bypass grafting.

METHODS

Data from 3,018 patients (age ≥ 18 years) who underwent coronary artery bypass graft surgery from two tertiary referral centers were retrospectively reviewed between 2004 and 2015. Obesity was defined using the body mass index, according to the World Health Organization's recommendation. The odds and hazard ratios in post-surgical, AKI, and all-cause mortality were calculated after adjustment for multiple covariates. Patients were followed for 90 ± 40.9 months (maximum: 13 years).

RESULTS

Among the cohort, 37.4%, 2.4%, 21.1%, 35.1%, and 4.0% of patients were classified as normal weight, underweight, overweight-at-risk, obese I, and obese II, respectively. Post-surgical AKI developed in 799 patients (26.5%). Patients in the obese groups (overweight-at-risk to obese II) had a higher risk of AKI than did those in the normal-weight group. During the follow-up period, 787 patients (26.1%) died. Underweight patients had a higher risk of mortality than did normal-weight patients, whereas overweight-at-risk, obese I, and obese II patients showed better survival rates.

CONCLUSION

After coronary artery bypass graft surgery, obese patients encountered a high risk of AKI, and underweight patients exhibited a low chance of survival. Awareness of both obese and underweight statuses should be raised in these patients.

Ablation of soluble epoxide hydrolase reprogram white fat to beige-like fat through an increase in mitochondrial integrity, HO-1-adiponectin in vitro and in vivo

We have shown that epoxyeicosatrienoic acids (EETs), specifically 11,12- and 14,15-EETs, reduce adipogenesis in human mesenchymal stem cells and mouse preadipocytes (3T-3L1). In this study, we explore the effects of soluble epoxide hydrolase (sEH) deletion on various aspects of adipocyte-function, including programing for white vs. beige-like fat, and mitochondrial and thermogenic gene-expressions. We further hypothesize that EETs and heme-oxygenase 1 (HO-1) form a synergistic, functional module whose effects on adipocyte and vascular function is greater than the effects of sEH deletion alone. In in vitro studies, we examined the effect of sEH inhibitors on MSC-derived adipocytes. MSC-derived adipocytes exposed to AUDA, an inhibitor of sEH, exhibit an increased number of small and healthy adipocytes, an effect reproduced by siRNA for sEH. in vivo studies indicate that sEH deletion results in a significant decrease in adipocyte size, inflammatory adipokines NOV, TNFα, while increasing adiponectin (p < 0.05). These findings are associated with a decrease in body weight (p < 0.05), and visceral fat (p < 0.05). Importantly, sEH deletion was associated with a significant increase in Mfn1, COX 1, UCP1 and adiponectin (p < 0.03). sEH deletion was manifested by a significant increase in EETs isomers 5,6-EET, 8,9-EET, 11,12-EET, and 14,15-EET and an increased EETs/DHETEs ratio. Notably, activation of HO-1 gene expression further increased the levels of EETs, suggesting that the antioxidant HO-1 system protects EETs from degradation by ROS. These results are novel in that sEH deletion, while increasing EET levels, resulted in reprograming of white fat to express mitochondrial and thermogenic genes, a phenotype characteristic of beige-fat. Thus, EETs agonist(s) and sEH inhibitors may have therapeutic potential in the treatment of metabolic syndrome and obesity.

Adiponectin and Its Isoforms in Pathophysiology

Adiponectin circulates in blood in multiple isoforms. High molecular weight (HMW) adiponectin is thought to be most biologically active and promotes glucose uptake, insulin sensitivity, and fatty acid oxidation. In obesity, adiponectin isoform formation is disrupted, leading to an inverse association between metabolic disease and HMW and total adiponectin. Adiponectin isoforms also function as acute-phase reactants influencing inflammation in acute and chronic disease. Interestingly, adiponectin and mortality have a U-shaped association. Unfortunately, data concerning adiponectin and its pathophysiologic function conflict. This is predominantly due to difficulties in adequate measurement of adiponectin isoforms and lack of a gold standard. In this review we provide a general overview of the formation and function of adiponectin and its isoforms under physiologic conditions. We highlight the ways adiponectin isoform formation is disrupted in obesity and its ensuing pathologic conditions. Furthermore, we will elaborate on the role of adiponectin isoforms as inflammatory proteins with respect to cardiac and kidney disease and discuss the association of adiponectin with mortality. Finally, we will provide a historical perspective on the measurement of adiponectin isoforms, current limitations, and future challenges.

Roles of lipocalin 2 and adiponectin in iron overload cardiomyopathy

Thalassemia is among the most common genetic diseases worldwide. Ineffective erythropoiesis, chronic hemolysis, and regular blood transfusion in thalassemia patients lead to increased iron burden. Iron overload cardiomyopathy is the most severe co-morbidity and most common cause of mortality in thalassemia patients. Although its associated mechanisms are still not completely understood, cellular iron mishandling, chronic inflammation, and oxidative stress appear to be the key processes involved. In order to acquire a more comprehensive insight of the impact of cardiac iron overload, these alterations need to be intensively investigated. This comprehensive mini-review focuses on two emergent molecules which have been shown to potentially play significant roles in iron overload cardiomyopathy. These two molecules are an iron-transporting protein, lipocalin 2, and an anti-inflammatory adipokine, adiponectin. Reports from in vitro and in vivo studies are comprehensively summarized. Clinical studies examining the roles of these molecules in thalassemia patients are also presented and discussed.

Heat shock proteins and kidney disease: perspectives of HSP therapy

Heat shock proteins (HSPs) mediate a diverse range of cellular functions, prominently including folding and regulatory processes of cellular repair. A major property of these remarkable proteins, dependent on intracellular or extracellular location, is their capacity for immunoregulation that optimizes immune activity while avoiding hyperactivated inflammation. In this review, recent investigations are described, which examine roles of HSPs in protection of kidney tissue from various traumatic influences and demonstrate their potential for clinical management of nephritic disease. The HSP70 class is particularly attractive in this respect due to its multiple protective effects. The review also summarizes current understanding of HSP bioactivity in the pathophysiology of various kidney diseases, including acute kidney injury, diabetic nephropathy, chronic glomerulonephritis, and lupus nephritis-along with other promising strategies for their remediation, such as DNA vaccination.

Heme Oxygenase 1 as a Therapeutic Target in Acute Kidney Injury

A common clinical condition, acute kidney injury (AKI) significantly influences morbidity and mortality, particularly in critically ill patients. The pathophysiology of AKI is complex and involves multiple pathways, including inflammation, autophagy, cell-cycle progression, and oxidative stress. Recent evidence suggests that a single insult to the kidney significantly enhances the propensity to develop chronic kidney disease. Therefore, the generation of effective therapies against AKI is timely. In this context, the cytoprotective effects of heme oxygenase 1 (HO-1) in animal models of AKI are well documented. HO-1 modulates oxidative stress, autophagy, and inflammation and regulates the progression of cell cycle via direct and indirect mechanisms. These beneficial effects of HO-1 induction during AKI are mediated in part by the by-products of the HO reaction (iron, carbon monoxide, and bile pigments). This review highlights recent advances in the molecular mechanisms of HO-1-mediated cytoprotection and discusses the translational potential of HO-1 induction in AKI.

BML-111 Attenuates Renal Ischemia/Reperfusion Injury Via Peroxisome Proliferator-Activated Receptor-α-Regulated Heme Oxygenase-1

We examine whether BML-111, a lipoxin receptor agonist, inhibits renal ischemia/reperfusion (I/R) injury, and whether peroxisome proliferator-activated receptor-α (PPARα) or heme oxygenase-1 (HO-1) is involved in protective effects of BML-111 on kidney against I/R injury. Rats subjected to renal I/R injury were treated with or without BML-111. Renal histological and immunohistochemical studies were performed. Expressions of phosphorylated p38 mitogen-activated protein kinase (pp38 MAPK), phosphorylated PPARα (pPPARα), and HO-1 were assessed in NRK-52E cells exposed to BML-111. The binding activity of PPARα to peroxisome proliferator-responsive element (PPRE) on HO-1 promoter in the cells was determined. BML-111 treatment resulted in a marked reduction in the severity of histological features of renal I/R injury, and attenuated the rise in renal myeloperoxidase and malondialdehyde, blood urea nitrogen and creatinine, urinary N-acetyl-β-glucosaminidase, and leucine aminopeptidase levels caused by I/R injury. BML-111 stimulated the renal expressions of pPPARα and HO-1, and cellular messenger RNA (mRNA) and protein expressions of pPPARα and HO-1 which were both blocked by GW6471, a selective PPARα antagonist, and ZnPP-IX, a specific inhibitor of HO-1 pretreatment. The pp38 MAPK inhibitor SB203580 blocked the BML-111-induced expressions of pp38 MAPK, pPPARα, and HO-1 in NRK-52E cells. The binding activity of PPARα to PPRE in nuclear extracts of NRK-52E cells was enhanced by treatment of the cells with BML-111, and was suppressed by GW6471 and SB203580. BML-111 protects the kidney against I/R injury via activation of p38 MAPK/PPARα/HO-1 pathway.

Renoprotective effect of a combination of garlic and telmisartan against ischemia/reperfusion-induced kidney injury in obese rats

Obesity enhances the frequency and severity of acute kidney injury (AKI). Telmisartan pre-treatment was used experimentally in the amelioration of ischemia/reperfusion (IR)-induced AKI. However, there is a lack of evidence regarding its beneficial effects on AKI in obese animals. The present study, therefore, aimed to explore the protective effects of garlic and/or telmisartan against renal damage induced by unilateral IR in obese rats. Meloxicam was used as a standard anti-inflammatory agent. Prophylactic oral administration of meloxicam (3 mg kg(-1)), garlic (500 mg kg(-1)) and/or telmisartan (5 and 10 mg kg(-1)) for 4 wk protected against renal function deterioration induced by IR in obese rats. Both doses of telmisartan significantly reduced serum total cholesterol and triacyglycerol levels as well as peri-renal adipocytes size and renal fibrosis. Renal nuclear factor-kappa B immunoreactivity, tumor necrosis factor-alpha content as well as interleukin-10, adiponectin receptor 1 and macrophages (M1, M2) polarization markers (CD11c, CD206) mRNA expressions were down-regulated in ischemic kidney tissues and white adipose tissues around them by all treatments. Moreover, garlic, telmisartan and their combinations significantly suppressed oxidative stress in renal ischemic tissues. Histological picture was also improved by these treatments. Interestingly, the combinations provided a greater protection than their monotherapy in a dose-dependent manner. We suppose that this combination may be a promising prophylactic regimen for managing AKI in case of obesity. Thus, future experimental and clinical large-scale studies are necessary.

Heme Oxygenase-1 in Kidney Health and Disease

SIGNIFICANCE

Acute kidney injury (AKI) and chronic kidney disease (CKD) represent a considerable burden in healthcare. The heme oxygenase (HO) system plays an important role in regulating oxidative stress and is protective in a variety of human and animal models of kidney disease. Preclinical studies of the HO system have led to the development of several clinical trials targeting the enzyme or its products.

RECENT ADVANCES

Connection of HO, ferritin, and other proteins involved in iron regulation has provided important insight into mechanisms of damage in AKI. Also, HO-1 expression is important in the pathogenesis of hypertension, diabetic kidney disease, and progression to end-stage renal disease.

CRITICAL ISSUES

Despite intriguing discoveries, no drugs targeting the HO system have been translated to the clinic. Meanwhile, treatments for AKI and CKD are urgently needed. Many factors have likely contributed to challenges in clinical translation, including variation in animal models, difficulties in obtaining human tissue, and complexity of the disease processes being studied.

FUTURE DIRECTIONS

The HO system represents a promising avenue of investigation that may lead to targeted therapeutics. Tissue-specific gene modulation, widening the scope of animal studies, and continued clinical research will provide valuable insight into the role HO plays in kidney homeostasis and disease. Antioxid. Redox Signal. 25, 165-183.

Obesity, Acute Kidney Injury, and Mortality in Critical Illness

OBJECTIVES

Although obesity is associated with risk for chronic kidney disease and improved survival, less is known about the associations of obesity with risk of acute kidney injury and post acute kidney injury mortality.

DESIGN

In a single-center inception cohort of almost 15,000 critically ill patients, we evaluated the association of obesity with acute kidney injury and acute kidney injury severity, as well as in-hospital and 1-year survival. Acute kidney injury was defined using the Kidney Disease Outcome Quality Initiative criteria.

MEASUREMENTS AND MAIN RESULTS

The acute kidney injury prevalence rates for normal, overweight, class I, II, and III obesity were 18.6%, 20.6%, 22.5%, 24.3%, and 24.0%, respectively, and the adjusted odds ratios of acute kidney injury were 1.18 (95% CI, 1.06-1.31), 1.35 (1.19-1.53), 1.47 (1.25-1.73), and 1.59 (1.31-1.87) when compared with normal weight, respectively. Each 5-kg/m² increase in body mass index was associated with a 10% risk (95% CI, 1.06-1.24; p < 0.001) of more severe acute kidney injury. Within-hospital and 1-year survival rates associated with the acute kidney injury episodes were similar across body mass index categories.

CONCLUSION

Obesity is a risk factor for acute kidney injury, which is associated with increased short- and long-term mortality.

Protective role of adiponectin in a rat model of intestinal ischemia reperfusion injury

AIM: To determine the potential protective role of adiponectin in intestinal ischemia reperfusion (I/R) injury.

METHODS: A rat model of intestinal I/R injury was established. The serum level of adiponectin in rats with intestinal I/R injury was determined by enzyme-linked immunosorbent assay (ELISA). The serum levels of interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α were also measured by ELISA. Apoptosis of intestinal cells was detected using the terminal deoxynucleotidyl transferase dUTP nick end labeling assay. The production of malondialdehyde (MDA) and superoxide dismutase (SOD) and villous injury scores were also measured.

RESULTS: Adiponectin was downregulated in the serum of rats with intestinal I/R injury compared with sham rats. No significant changes in the expression of adiponectin receptor 1 and adiponectin receptor 2 were found between sham and I/R rats. Pre-treatment with recombinant adiponectin attenuated intestinal I/R injury. The production of pro-inflammatory cytokines, including IL-6, IL-1β, and TNF-α, in rats with intestinal I/R injury was reduced by adiponectin pre-treatment. The production of MDA was inhibited, and the release of SOD was restored by adiponectin pre-treatment in rats with intestinal I/R injury. Adiponectin pre-treatment also inhibited cell apoptosis in these rats. Treatment with the AMP-activated protein kinase (AMPK) signaling pathway inhibitor, compound C, or the heme oxygenase 1 (HO-1) inhibitor, Snpp, attenuated the protective effects of adiponectin against intestinal I/R injury.

CONCLUSION: Adiponectin exhibits protective effects against intestinal I/R injury, which may involve the AMPK/HO-1 pathway.

Adiponectin secreted by tubular renal cells during LPS exposure worsens the cellular inflammatory damage

The pathogenetic role of adiponectin (ADPN) in kidney failure is not yet elucidated, since in vitro and in vivo studies have demonstrated that ADPN exerts both anti-inflammatory and pro-inflammatory effects. Starting from our previous findings demonstrating that HK-2 cells express and secrete ADPN, in this study we investigated the autocrine role of ADPN in tubular inflammatory damage induced by lipopolysaccharide (LPS) and the underlying molecular mechanisms. Firstly, we observed that short-term exposure to LPS enhanced ADPN protein expression as well as the adiponectin receptor ADIPOR1 mRNA content together with its signaling pathway downstream, pAMPK/pERK/pJNK, whose up-regulation status was reversed when ADPN gene knockdown occurred. Interestingly, in the same experimental conditions, we observed that ADPN mediated the nuclear translocation of the transcription factors nuclear factor kappa B (NFkB) and pcFos/pcJun (activator protein 1, AP-1), both induced by the pJNK pathway and involved in tumor necrosis factor (TNF)-α transactivation. Indeed, by transient transfection assay, we observed that the LPS-induced increase of TNF-α promoter activity was abrogated in cells pretreated with the inhibitors of NFkB and AP-1. Collectively our results suggest that in HK-2 cells, ADPN produced upon LPS stimulus could worsen the inflammatory damage in an autocrine-dependent manner.

Renal protective effects of induction of haem oxygenase-1 combined with increased adiponectin on the glomerular vascular endothelial growth factor-nitric oxide axis in obese rats

What is the central question of this study? This study aimed to investigate whether induction of haem oxygenase-1 (HO-1) can protect the kidneys of obese rats by regulating the glomerular vascular endothelial growth factor-nitric oxide (VEGF-NO) axis by increasing the adiponectin concentrations. What is the main finding and its importance? Induction of HO-1 reduces the degree of microalbuminuria and has renal protective effects by improving endothelial function and regulating the uncoupled glomerular VEGF-NO axis in diet-induced obese rats. The mechanism may be related to increased activation of the HO-1-adiponectin axis. The glomerular vascular endothelial growth factor-nitric oxide (VEGF-NO) axis plays a critical role in maintenance of normal kidney function in obesity. Induction of haem oxygenase-1 (HO-1) may result in a parallel increase in adiponectin secretion. The aim of this study was to investigate whether induction of HO-1 could protect the kidneys of obese rats by regulating the glomerular VEGF-NO axis by increasing adiponectin levels. Rats received high-fat diets and were injected with either cobalt protoporphyrin to induce HO-1 or stannous protoporphyrin to inhibit HO-1. Blood and urine samples were collected. Endothelial function was determined by measuring the endothelium-dependent vasodilatation of the aorta. Renal tissues were collected for CD34 immunohistochemistry. The glomerular VEGF-NO axis and the AMP kinase-phosphoinositide 3-kinase (PI3K)/Akt-endothelial nitric oxide synthase pathway were measured. Induction of HO-1 by cobalt protoporphyrin decreased microalbuminuria, plasma free fatty acids, serum high-sensitivity C-reactive protein and malondialdehyde levels and increased serum adiponectin levels compared with the untreated obese rats. Severe impairment of endothelium-dependent vasodilatation was observed in the obese rats, which was improved to some extent by HO-1 induction. Induction of HO-1 reduced glomerular CD34 expression and production of reactive oxygen species in obese rats. Obese rats showed increased glomerular VEGF expression and reduced NO levels. This uncoupling of the glomerular VEGF-NO axis was improved to some extent by induction of HO-1, with enhancement of p-AMP kinase, p-Akt and phospho-endothelial nitric oxide synthase in obese rats. These results indicate that induction of HO-1 with cobalt protoporphyrin reduces the degree of microalbuminuria and has renal protective effects by improving endothelial dysfunction and regulating the glomerular VEGF-NO axis in diet-induced obese rats by increasing adiponectin levels.

Deletion of the gene for adiponectin accelerates diabetic nephropathy in the Ins2 (+/C96Y) mouse

AIMS/HYPOTHESIS

Diabetic nephropathy is one of the most common forms of chronic kidney disease. The role of adiponectin in the development of diabetic nephropathy has not been elucidated, and the aim of the present study was to investigate the hypothesis that deletion of the gene for adiponectin would accelerate diabetic nephropathy in the Akita mouse.

METHODS

We followed four groups of mice from 4 weeks to 16 weeks of age (n ≥ 10 in each group): wild-type (WT) (Ins2 (+/+) Adipoq(+/+)) mice; APN(-/-) (Ins2(+/+) Adipoq(-/-)) mice; Akita (Ins2(+/C96Y) Adipoq(+/+)) mice and Akita/APN(-/-) (Ins2(+/C96Y) Adipoq(-/-)) mice. The mice were then killed and diabetic kidney injury was assessed. In vitro experiments were performed in primary mesangial cells.

RESULTS

Mice from both diabetic groups exhibited increased glomerular adiponectin receptor 1 (adipoR1) expression, kidney hypertrophy, glomerular enlargement, increased albuminuria and tissue oxidative stress compared with the WT control. Deletion of the adiponectin gene had no effect on glycaemia. However, Akita/APN(-/-) mice exhibited a greater extent of renal hypertrophy. In vitro, adiponectin attenuated high-glucose-induced phosphorylation of mammalian target of rapamycin (mTOR) and ribosomal protein S6 kinase (S6K). A higher level of fibrosis was observed in the tubulointerstitial and glomerular compartments of the Akita/APN(-/-) mice and adiponectin was found to inhibit TGFβ-induced Smad2 and Smad3 phosphorylation in vitro. There was an exaggerated inflammatory response in the Akita/APN(-/-) mice. Adiponectin also inhibited high-glucose-induced activation of nuclear factor κB (NFκB) in mesangial cells.

CONCLUSIONS/INTERPRETATION

Our data suggest that adiponectin is an important determinant of the kidney response to high glucose in vivo and in vitro.

Chikusetsu Saponin IVa Ameliorates Cerebral Ischemia Reperfusion Injury in Diabetic Mice via Adiponectin-Mediated AMPK/GSK-3β Pathway In Vivo and In Vitro

Diabetes mellitus substantially increases the risk of stroke and enhances brain's vulnerability to ischemia insult. In a previous study, Chikusetsu saponin IVa (CHS) pretreatment was proved to protect the brain from cerebral ischemic in normal stroke models. Whether CHS could attenuate cerebral ischemia/reperfusion (I/R) injury in diabetic mice and the possible underlying mechanism are still unrevealed. Male C57BL/6 mice were injected streptozotocin to induce diabetes. After that, the mice were pretreated with CHS for 1 month, and then, focal cerebral ischemia was induced following 24-h reperfusion. The neurobehavioral scores, infarction volumes, and some cytokines in the brain were measured. Apoptosis was analyzed by caspase-3, Bax, and Bcl-2 expression. Downstream molecules of adiponectin (APN) were investigated by Western blotting. The results showed that CHS reduced infarct size, improved neurological outcomes, and inhibited cell injury after I/R. In addition, CHS pretreatment increased APN level and enhanced neuronal AdipoR1, adenosine monophosphate-activated protein kinase (AMPK), and glycogen synthase kinase 3 beta (GSK-3β) expression in a concentration-dependent manner in diabetic mice, and these effects were abolished by APN knockout (KO). In vitro test, CHS treatment also alleviated PC12 cell injury and apoptosis, evidenced by reduced tumor necrosis factor alpha (TNF-α), malondialdehyde (MDA) and caspase-3 expression, and Bax/Bcl-2 ratio in I/R injured cells. Moreover, CHS enhanced AdipoR1, AMPK, and GSK-3β expression in a concentration-dependent manner. Likewise, short interfering RNA (sinRNA) knockdown of liver kinase B1 (LKB1), an upstream kinase of AMPK, reduced the ability of CHS in protecting cells from I/R injury. Furthermore, this LKB1-dependent cellular protection resulted from AdipoR1 and APN activation, as supported by the experiment using sinRNA knockdown of AdipoR1 and APN. Thus, CHS protected brain I/R in diabetes through AMPK-mediated phosphorylation of GSK-3β downstream of APN-LKB1 pathway.

Obesity, oxidative stress, and fibrosis in chronic kidney disease

Obesity in combination with diabetes and hypertension likely is contributing to the increasing incidence of chronic kidney disease (CKD) in the 21st century worldwide and requires novel insights and strategies for treatment. There is an increasing recognition that the kidney has an important role in the complex inter-organ communication that occurs with the development of inflammation and fibrosis with obesity. Inhibition of the adiponectin-AMPK pathway has now become established as a critical pathway regulating both inflammation and pro-fibrotic pathways for both obesity-related kidney disease and diabetic kidney disease. AMPK regulates NFκB activation and is a potent regulator of NADPH oxidases. Nox4 in particular has emerged as a key contribtor to the early inflammation of diabetic kidney disease. AMPK also regulates several transcription factors that contribute to stimulation of the transforming growth factor-beta (TGF-β) system. Another key aspect of AMPK regulation is its control of mammalian target of rapamycin (mTOR) and mitochondrial biogenesis. Inhibition of PGC-1α, the transcriptional co-activator of mitochondrial biogenesis is being recognized as a key pathway that is inhibited in diabetic kidney disease and may be linked to inhibition of mitochondrial function. Translation of this concept is emerging via the field of urine metabolomics, as several metabolites linked to mitochondria are consistently downregulated in human diabetic kidney disease. Further studies to explore the role of AMPK and related energy-sensing pathways will likely lead to a more comprehensive understanding of why the kidney is affected early on and in a progressive manner with obesity and diabetes.

Obesity in kidney disease: A heavyweight opponent

Obesity is an important worldwide challenge that must be faced in most developed and developing countries because of unhealthy nutritional habits. The consequences of obesity and being overweight are observed in different organs, but the kidney is one of the most affected. Excess adipose tissue causes hemodynamic alterations in the kidney that can result in renal disease. However, obesity is also commonly associated with other comorbidities such as chronic inflammation, hypertension and diabetes. This association of several aggravating factors is still a matter of concern in clinical and basic research because the pathophysiologic mechanisms surrounding chronic kidney disease development in obese patients remain unclear. This review will discuss the consequences of obesity in the context of renal injury.

Heme oxygenase-1 and acute kidney injury

PURPOSE OF REVIEW

Heme oxygenase activity, possessed by an inducible heme oxygenase-1 (HO-1) and a constitutive isoform (HO-2), catalyzes the conversion of heme to biliverdin, liberates iron, and generates carbon monoxide. First shown in acute kidney injury (AKI), HO-1 is now recognized as a protectant against diverse insults in assorted tissues. This review summarizes recent contributions to the field of HO-1 and AKI.

RECENT FINDINGS

Recent findings elucidate the following: the transcriptional regulation and significance of human HO-1 in AKI; the protective effects of HO-1 in age-dependent and sepsis-related AKI, cardiorenal syndromes, and acute vascular rejection in renal xenografts; the role of heme oxygenase in tubuloglomerular feedback and renal resistance to injury; the basis for cytoprotection by HO-1; the protective properties of ferritin and carbon monoxide; HO-1 and the AKI-chronic kidney disease transition; HO-1 as a biomarker in AKI; the role of HO-1 in mediating the protective effects of specific cytokines, stem cells, and therapeutic agents in AKI; and HO-2 as a protectant in AKI.

SUMMARY

Recent contributions support, and elucidate the basis for, the induction of HO-1 as a protectant against AKI. Translating such therapeutic potential into a therapeutic reality requires well tolerated and effective modalities for upregulating HO-1 and/or administering its products, which, optimally, should be salutary even when AKI is already established.

PPARα: A Master Regulator of Bilirubin Homeostasis

Hypolipidemic fibrates activate the peroxisome proliferator-activated receptor (PPAR) α to modulate lipid oxidation and metabolism. The present study aimed at evaluating how 3 PPARα agonists, namely, fenofibrate, gemfibrozil, and Wy14,643, affect bilirubin synthesis and metabolism. Human umbilical vein epithelial cells (HUVEC) and coronary artery smooth muscle cells (CASMC) were cultured in the absence or presence of the 3 activators, and mRNA, protein, and/or activity levels of the bilirubin synthesizing heme oxygenase- (HO-) 1 and biliverdin reductase (BVR) enzymes were determined. Human hepatocytes (HH) and HepG2 cells sustained similar treatments, except that the expression of the bilirubin conjugating UDP-glucuronosyltransferase (UGT) 1A1 enzyme and multidrug resistance-associated protein (MRP) 2 transporter was analyzed. In HUVECs, gemfibrozil, fenofibrate, and Wy14,643 upregulated HO-1 mRNA expression without affecting BVR. Wy14,643 and fenofibrate also caused HO-1 protein accumulation, while gemfibrozil and fenofibrate favored the secretion of bilirubin in cell media. Similar positive regulations were also observed with the 3 PPARα ligands in CASMCs where HO-1 mRNA and protein levels were increased. In HH and HepG2 cells, both UGT1A1 and MRP2 transcripts were also accumulating. These observations indicate that PPARα ligands activate bilirubin synthesis in vascular cells and metabolism in liver cells. The clinical implications of these regulatory events are discussed.

Prostacyclin analogue beraprost inhibits cardiac fibroblast proliferation depending on prostacyclin receptor activation through a TGF β-Smad signal pathway

Previous studies showed that prostacyclin inhibited fibrosis. However, both receptors of prostacyclin, prostacyclin receptor (IP) and peroxisome proliferator-activated receptor (PPAR), are abundant in cardiac fibroblasts. Here we investigated which receptor was vital in the anti-fibrosis effect of prostacyclin. In addition, the possible mechanism involved in protective effects of prostacyclin against cardiac fibrosis was also studied. We found that beraprost, a prostacyclin analogue, inhibited angiotensin II (Ang II)-induced neonatal rat cardiac fibroblast proliferation in a concentration-dependent and time-dependent manner. Beraprost also suppressed Ang II-induced collagen I mRNA expression and protein synthesis in cardiac fibroblasts. After IP expression was knocked down by siRNA, Ang II-induced proliferation and collagen I synthesis could no longer be rescued by beraprost. However, treating cells with different specific inhibitors of PPAR subtypes prior to beraprost and Ang II stimulation, all of the above attenuating effects of beraprost were still available. Moreover, beraprost significantly blocked transforming growth factor β (TGF β) expression as well as Smad2 phosphorylation and reduced Smad-DNA binding activity. Beraprost also increased phosphorylation of cAMP response element binding protein (CREB) at Ser133 in the nucleus. Co-immunoprecipitation analysis revealed that beraprost increased CREB but decreased Smad2 binding to CREB-binding protein (CBP) in nucleus. In conclusion, beraprost inhibits cardiac fibroblast proliferation by activating IP and suppressing TGF β-Smad signal pathway.

The role of adiponectin in renal physiology and development of albuminuria

Adiponectin is secreted by the adipose tissue and is downregulated in states of obesity and insulin resistance. There is a growing body of evidence indicating that adiponectin has renoprotective effects and protects against the development of albuminuria in rodent experiments. Adiponectin crossing the glomerular filtration barrier possibly inhibits inflammation, fibrosis and oxidative stress in kidneys through activation of AMP-activated protein kinase. Moreover, microalbuminuria is a well established early sign of progressive cardiovascular and renal disease, even in subjects with preserved glomerular filtration rate. Studies investigating the relationship between serum adiponectin levels and urinary albumin excretion rate (UAE) have yielded conflicting data and the mechanisms underlying the interplay between adiponectin and albuminuria remain to be elucidated. This article constitutes a critical review attempting to clarify any remaining confusion about this matter. Furthermore, this article examines the clinical significance of adiponectin-albuminuria interplay, suggesting that adiponectin is possibly involved in the development of albuminuria that is associated with obesity, diabetes and cardiovascular disease and may mediate, at least in part, the actions of medical treatments that influence UAE, such as angiotensin-converting-enzyme inhibitors, angiotensin II receptor blockers, thiazolidinediones, fenofibrate and diet. Further studies to investigate more thoroughly the renoprotective role of adiponectin in the human setting should be carefully planned, focusing on causality and the possible influence of adiponectin on the development of albuminuria in specific clinical settings.

Peroxisome proliferator-activated receptor agonists in a battle against the aging kidney

As aging is a complex phenomenon characterized by intraindividual and interindividual diversities in the maintenance of the homeostatic condition of cells and tissues, changes in renal function are not uniform and depend on associated diseases and environmental factors. Multiple studies have investigated the possible underlying mechanisms of age-related decline in kidney function. Evolutionary, molecular, cellular and systemic theories have been postulated to explain the primary disease independent age-related changes and adaptive responses. As peroxisome proliferator-activated receptors (PPARs) are involved in a broad spectrum of biological processes, PPAR activation might have an effect on the prevention of cell senescence. In this review, we will focus on the experimental and clinical evidence of PPAR agonists in a battle against the aging kidney.

The obesity paradox and acute kidney injury: beneficial effects of hyper-inflammation?

In the general population, obesity is associated with an increased mortality risk, whereas several epidemiological studies demonstrated a protective effect of obesity in critically ill patients. In this context, Sleeman and colleagues investigated the effects of obesity on kidney function in a well-established porcine model of cardiopulmonary bypass. The authors confirm literature data that obesity per se is associated with a chronic hyper-inflammatory status. Nevertheless, obese swine undergoing the surgical procedure presented with attenuated kidney dysfunction and tissue apoptosis. The authors suggest that the chronic inflammation causes pre-conditioning against excessive acute hyper-inflammation. The authors have to be commended for using a long-term, clinically relevant model that, moreover, addresses a variety of putative mechanisms. The study is discussed in the context of the controversial findings that, in contrast to the existing literature on improved survival, most studies available suggest a higher incidence and severity of acute kidney injury in obese patients when compared with lean controls.