A causal link between oxidative stress and inflammation in cardiovascular and renal complications of diabetes

Nephroprotective Effects of Synthetic Flavonoid Hidrosmin in Experimental Diabetic Nephropathy

Diabetes mellitus (DM) is a high-impact disease commonly characterized by hyperglycemia, inflammation, and oxidative stress. Diabetic nephropathy (DN) is a common diabetic microvascular complication and the leading cause of chronic kidney disease worldwide. This study investigates the protective effects of the synthetic flavonoid hidrosmin (5-O-(beta-hydroxyethyl) diosmin) in experimental DN induced by streptozotocin injection in apolipoprotein E deficient mice. Oral administration of hidrosmin (300 mg/kg/day, n = 11) to diabetic mice for 7 weeks markedly reduced albuminuria (albumin-to-creatinine ratio: 47 ± 11% vs. control) and ameliorated renal pathological damage and expression of kidney injury markers. Kidneys of hidrosmin-treated mice exhibited lower content of macrophages and T cells, reduced expression of cytokines and chemokines, and attenuated inflammatory signaling pathways. Hidrosmin treatment improved the redox balance by reducing prooxidant enzymes and enhancing antioxidant genes, and also decreased senescence markers in diabetic kidneys. In vitro, hidrosmin dose-dependently reduced the expression of inflammatory and oxidative genes in tubuloepithelial cells exposed to either high-glucose or cytokines, with no evidence of cytotoxicity at effective concentrations. In conclusion, the synthetic flavonoid hidrosmin exerts a beneficial effect against DN by reducing inflammation, oxidative stress, and senescence pathways. Hidrosmin could have a potential role as a coadjutant therapy for the chronic complications of DM.

The Protective Effect of Ethyl Acetate and n-Butanol Fractions of Wine-Steamed Ligustri Lucidi Fructus on Diabetic Nephropathy in Rats

Ligustri Lucidi Fructus (LLF), the dry and ripe fruit of Ligustrum lucidum W. T. Aiton (Oleaceae), is a traditional Chinese medicine for nourishing the liver and kidney in clinics for thousands of years. Wine-steamed Ligustri Lucidi Fructus (WLL) can alleviate coolness and smoothness of LLF and enhance the function of nourishing the liver and kidney, so ancient and modern medicine usually used it in clinics. First of all, we prepared the extracts of different polar fractions of WLL to explore the effective fractions and potential mechanisms of WLL in the treatment of diabetic nephropathy (DN). Then, HPLC method was used to determine the contents of 12 active components in WLL and its different polar components. Finally, the potential relationship between 12 active components and physicochemical parameters of DN rats was explored. The pharmacological experiments showed that WLL, ethyl acetate (EtOAc), and n-butanol (n-BuOH) extracts not only significantly alleviated the clinical symptoms and kidney damage of DN rats but also had obvious anti-inflammatory and antioxidant effects. In addition, the results of HPLC analysis showed that the 12 active components of WLL mainly existed in the extracts of EtOAc and n-BuOH. The Pearson correlation analysis showed 12 active components and physicochemical parameters had different degrees of correlation. In conclusion, we proved that the extracts of EtOAc and n-BuOH were the effective fractions of WLL in treating DN in rats, and they could regulate the levels of inflammatory cytokines and decrease oxidation stress, which provides a basis for further research on the mechanism of WLL in treating DN and provides a pharmacological and chemical foundation for the development of new anti-DN drugs.

Targeting NLRP3 Inflammasome in the Treatment Of Diabetes and Diabetic Complications: Role of Natural Compounds from Herbal Medicine

Diabetes, a common metabolic disease with various complications, is becoming a serious global health pandemic. So far there are many approaches in the management of diabetes; however, it still remains irreversible due to its complicated pathogenesis. Recent studies have revealed that nucleotide-binding and oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome plays a vital role in the progression of diabetes and many of its complications, making it a promising therapeutic target in pharmaceutical design. Natural derived herbal medicine, known for its utilization of natural products such as herbs or its bioactive ingredients, is shown to be able to ameliorate hyperglycemia-associated symptoms and to postpone the progression of diabetic complications due to its anti-inflammatory and anti-oxidative properties. In this review, we summarized the role of NLRP3 inflammasome in diabetes and several diabetic complications, as well as 31 active compounds that exert therapeutic effect on diabetic complications via inhibiting NLRP3 inflammasome. Improving our understanding of these promising candidates from natural compounds in herbal medicine targeting NLRP3 inflammasome inspires us the relationship between inflammation and metabolic disorders, and also sheds light on searching potential agents or therapies in the treatment of diabetes and diabetic complications.

Effects of the SGLT2 inhibitor canagliflozin on plasma biomarkers TNFR-1, TNFR-2 and KIM-1 in the CANVAS trial

AIMS/HYPOTHESIS

Higher plasma concentrations of tumour necrosis factor receptor (TNFR)-1, TNFR-2 and kidney injury molecule-1 (KIM-1) have been found to be associated with higher risk of kidney failure in individuals with type 2 diabetes in previous studies. Whether drugs can reduce these biomarkers is not well established. We measured these biomarkers in samples of the CANVAS study and examined the effect of the sodium-glucose cotransporter 2 inhibitor canagliflozin on these biomarkers and assessed whether the early change in these biomarkers predict cardiovascular and kidney outcomes in individuals with type 2 diabetes in the CANagliflozin cardioVascular Assessment Study (CANVAS).

METHODS

Biomarkers were measured with immunoassays (proprietary multiplex assay performed by RenalytixAI, New York, NY, USA) at baseline and years 1, 3 and 6. Mixed-effects models for repeated measures assessed the effect of canagliflozin vs placebo on the biomarkers. Associations of baseline levels and the early change (baseline to year 1) for each biomarker with the kidney outcome were assessed using multivariable-adjusted Cox regression.

RESULTS

In total, 3523/4330 (81.4%) of the CANVAS participants had available samples at baseline. Each doubling in baseline TNFR-1, TNFR-2 and KIM-1 was associated with a higher risk of kidney outcomes, with corresponding HRs of 3.7 (95% CI 2.3, 6.1; p < 0.01), 2.7 (95% CI 2.0, 3.6; p < 0.01) and 1.5 (95% CI 1.2, 1.8; p < 0.01), respectively. Canagliflozin reduced the level of the plasma biomarkers with differences in TNFR-1, TNFR-2 and KIM-1 between canagliflozin and placebo during follow-up of 2.8% (95% CI 3.4%, 1.3%; p < 0.01), 1.9% (95% CI 3.5%, 0.2%; p = 0.03) and 26.7% (95% CI 30.7%, 22.7%; p < 0.01), respectively. Within the canagliflozin treatment group, each 10% reduction in TNFR-1 and TNFR-2 at year 1 was associated with a lower risk of the kidney outcome (HR 0.8 [95% CI 0.7, 1.0; p = 0.02] and 0.9 [95% CI 0.9, 1.0; p < 0.01] respectively), independent of other patient characteristics. The baseline and 1 year change in biomarkers did not associate with cardiovascular or heart failure outcomes.

CONCLUSIONS/INTERPRETATION

Canagliflozin decreased KIM-1 and modestly reduced TNFR-1 and TNFR-2 compared with placebo in individuals with type 2 diabetes in CANVAS. Early decreases in TNFR-1 and TNFR-2 during canagliflozin treatment were independently associated with a lower risk of kidney disease progression, suggesting that TNFR-1 and TNFR-2 have the potential to be pharmacodynamic markers of response to canagliflozin.

Effects of valsartan combined with α-lipoic acid on renal function in patients with diabetic nephropathy: a systematic review and meta-analysis

BACKGROUND

Diabetic nephropathy (DN) is one of the most serious microvascular complications of diabetes, valsartan and α-lipoic acid alone or in combination has been used for the treatment of patients with DN. However, some results in these clinical reports were still controversial. The purpose of this study was to evaluate the efficacy of valsartan combined with α-lipoic acid on renal function in patients with DN.

METHODS

We searched the electronic databases including PubMed, Sciencedirect, EMBASE, Cochrane library, Chinese national knowledge infrastructure (CNKI) and Wanfang databases, and the publication deadline was limited to January 2020. Randomized controlled trials (RCTs) evaluating the effects of valsartan combined with α-lipoic acid in DN patients were included. Pooled estimates were conducted using a fixed or random effect model. The outcomes included urinary albumin excretion rate (UAER), and the level of urinary albumin, β₂-microglobulin (β₂-MG), hypersensitive C-reactive protein (hs-CRP) and oxidative stress.

RESULTS

11 studies with 1294 participants were included in this study. The pooled analysis indicated that α-lipoic acid combined with valsartan could remarkably reduce UAER (P < 0.00001, SMD = -1.95, 95%CI = -2.55 to - 1.20; P = 0.03, SMD = -0.85, 95%CI = -1.59 to - 0.1) and the level of urinary albumin (P = 0.001, SMD = -1.48, 95%CI = - 2.38 to - 0.58; P = 0.01, SMD = -1.67, 95%CI = -3.00 to - 0.33), β₂-MG (P < 0.001,SMD = - 2.59, 95%CI = -3.78 to - 1.40; P = 0.03, SMD = -0.48, 95%CI = -0.93 to - 0.04) when compared with valsartan or lipoic acid monotherapy in patients with DN. However, there was no significant difference in the level of hs-CRP among the three therapies (P = 0.06, SMD = -2.80, 95%CI = -5.67 to 0.07; P = 0.10, SMD = -0.42, 95%CI = - 0.92 to 0.08). In addition, α-lipoic acid combined with valsartan markedly increased the level of SOD (P = 0.03, SMD = 1.24, 95%CI = 0.32 to 1.03; P = 0.0002, SMD = 0.68, 95%CI = 0.32 to 1.03) and T-AOC (P < 0.00001, SMD = 0.89, 95%CI = 0.62 to 1.16; P = 0.02, SMD = 0.58, 95%CI = 0.10 to1.07), and reduced the level of MDA(P = 0.0002, SMD = -1.99, 95%CI = -3.02 to - 0.96; P = 0.0001, SMD = -0.69, 95%CI = -1.04 to - 0.34).

CONCLUSIONS

α-lipoic acid combined with valsartan could significantly reduce the level of urinary albumin and oxidative stress, increase antioxidant capacity and alleviate renal function damage in patients with DN, and this will provide a reference for the selection of treatment drugs for DN.

Regression Modeling of the Antioxidant-to-Nephroprotective Relation Shows the Pivotal Role of Oxidative Stress in Cisplatin Nephrotoxicity

The clinical utility of the chemotherapeutic drug cisplatin is significantly limited by its nephrotoxicity, which is characterized by electrolytic disorders, glomerular filtration rate decline, and azotemia. These alterations are consequences of a primary tubulopathy causing injury to proximal and distal epithelial cells, and thus tubular dysfunction. Oxidative stress plays a role in cisplatin nephrotoxicity and cytotoxicity, but its relative contribution to overall toxicity remains unknown. We studied the relation between the degree of oxidative reduction (provided by antioxidant treatment) and the extent of nephrotoxicity amelioration (i.e., nephroprotection) by means of a regression analysis of studies in animal models. Our results indicate that a linear relation exists between these two parameters, and that this relation very nearly crosses the value of maximal nephroprotection at maximal antioxidant effect, suggesting that oxidative stress seems to be a pivotal and mandatory mechanism of cisplatin nephrotoxicity, and, hence, an interesting, rationale-based target for clinical use. Our model also serves to identify antioxidants with enhanced effectiveness by comparing their actual nephroprotective power with that predicted by their antioxidant effect. Among those, this study identified nanoceria, erythropoietin, and maltol as highly effective candidates affording more nephroprotection than expected from their antioxidant effect for prospective clinical development.

Naringenin alleviates myocardial ischemia reperfusion injury by enhancing the myocardial miR-126-PI3K/AKT axis in streptozotocin-induced diabetic rats

Ischemic heart disease (IHD) is a leading cause of death in patients with type 1 diabetes. The key to treating IHD is to restore blood supply to the ischemic myocardium, which inevitably causes myocardial ischemia reperfusion (MI/R) injury. Although naringenin (Nar) prevents MI/R injury, the role of Nar in diabetic MI/R (D-MI/R) injury remains to be elucidated. The PI3K/AKT signaling pathway and microRNA (miR)-126 have previously been shown to serve anti-MI/R injury roles. The present study aimed to investigate the protection of Nar against D-MI/R injury and the role of the miR-126-PI3K/AKT axis. Diabetic rats were treated distilled water or Nar (25 or 50 mg/kg, orally) for 30 days and then exposed to MI/R. The present results revealed that Nar alleviated MI/R injury in streptozotocin (STZ)-induced diabetic rats, as shown below: the reduction myocardial enzymes levels was measured using spectrophotometry, the increase of cardiac viability was detected by MTT assay, the inhibition of myocardial oxidative stress was measured using spectrophotometry and the enhancement of cardiac function were recorded using a hemodynamic monitoring system. Furthermore, Nar upregulated the myocardial miR-126-PI3K/AKT axis in D-MI/R rats. These results indicated that Nar alleviated MI/R injury through upregulating the myocardial miR-126-PI3K/AKT axis in STZ-induced diabetic rats. The current findings revealed that Nar, as an effective agent against D-MI/R injury, may provide an effective approach in the management of diabetic IHD.

Coordinated Contribution of NADPH Oxidase- and Mitochondria-Derived Reactive Oxygen Species in Metabolic Syndrome and Its Implication in Renal Dysfunction

Metabolic syndrome (MetS), a complex of interrelated risk factors for cardiovascular disease and diabetes, is comprised of central obesity (increased waist circumference), hyperglycemia, dyslipidemia (high triglyceride blood levels, low high-density lipoprotein blood levels), and increased blood pressure. Oxidative stress, caused by the imbalance between pro-oxidant and endogenous antioxidant systems, is the primary pathological basis of MetS. The major sources of reactive oxygen species (ROS) associated with MetS are nicotinamide-adenine dinucleotide phosphate (NADPH) oxidases and mitochondria. In this review, we summarize the current knowledge regarding the generation of ROS from NADPH oxidases and mitochondria, discuss the NADPH oxidase- and mitochondria-derived ROS signaling and pathophysiological effects, and the interplay between these two major sources of ROS, which leads to chronic inflammation, adipocyte proliferation, insulin resistance, and other metabolic abnormalities. The mechanisms linking MetS and chronic kidney disease are not well known. The role of NADPH oxidases and mitochondria in renal injury in the setting of MetS, particularly the influence of the pyruvate dehydrogenase complex in oxidative stress, inflammation, and subsequent renal injury, is highlighted. Understanding the molecular mechanism(s) underlying MetS may lead to novel therapeutic approaches by targeting the pyruvate dehydrogenase complex in MetS and prevent its sequelae of chronic cardiovascular and renal diseases.

Identification and Characterization of Novel Antioxidant Protein Hydrolysates from Kiwicha (Amaranthus caudatus L.)

Kiwicha (Amaranthus caudatus) is considered one of the few multipurpose pseudocereals for its potential use not only as a source of nutrients and fiber but also for its bioactive compounds. In recent years, antioxidant peptides are commonly used as functional ingredient of food. Herein, a kiwicha protein isolate (KPI), obtained from kiwicha defatted flour (KDF), was hydrolyzed by Bioprotease LA 660, a food-grade endoprotease, under specific conditions. The resulting kiwicha protein hydrolysates (KPHs) were chemically characterized and their digestibility and antioxidant capacity were evaluated by in vitro cell-free experiments owing to their measure of capacity to sequester DPPH free radical and reducing power. KPHs showed higher digestibility and antioxidant capacity than intact proteins into KPI. Therefore, the results shown in this study indicate that KPHs could serve as an adequate source of antioxidant peptides, representing an effective alternative to the generation of functional food.

Oxidative stress in vascular calcification

Vascular calcification (VC), which is closely associated with significant mortality in cardiovascular disease, chronic kidney disease (CKD), and/or diabetes mellitus, is characterized by abnormal deposits of hydroxyapatite minerals in the arterial wall. The impact of oxidative stress (OS) on the onset and progression of VC has not been well described. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidases, xanthine oxidases, myeloperoxidase (MPO), nitric oxide synthases (NOSs), superoxide dismutase (SOD) and paraoxonases (PONs) are relevant factors that influence the production of reactive oxygen species (ROS). Furthermore, excess ROS-induced OS has emerged as a critical mediator promoting VC through several mechanisms, including phosphate balance, differentiation of vascular smooth muscle cells (VSMCs), inflammation, DNA damage, and extracellular matrix remodeling. Because OS is a significant regulator of VC, antioxidants may be considered as novel treatment options.

Effect of Hydrolyzed Bird's Nest on β-Cell Function and Insulin Signaling in Type 2 Diabetic Mice

Type 2 diabetes mellitus is characterized by both resistance to the action of insulin and defects in insulin secretion. Bird’s nest, which is derived from the saliva of swiftlets are well known to possess multiple health benefits dating back to Imperial China. However, it’s effect on diabetes mellitus and influence on the actions of insulin action remains to be investigated. In the present study, the effect of standardized aqueous extract of hydrolyzed edible bird nest (HBN) on metabolic characteristics and insulin signaling pathway in pancreas, liver and skeletal muscle of db/db, a type 2 diabetic mice model was investigated. Male db/db diabetic and its euglycemic control, C57BL/6J mice were administered HBN (75 and 150 mg/kg) or glibenclamide (1 mg/kg) orally for 28 days. Metabolic parameters were evaluated by measuring fasting blood glucose, serum insulin and oral glucose tolerance test (OGTT). Insulin signaling and activation of inflammatory pathways in liver, adipose, pancreas and muscle tissue were evaluated by Western blotting and immunohistochemistry. Pro-inflammatory cytokines were measured in the serum at the end of the treatment. The results showed that db/db mice treated with HBN significantly reversed the elevated fasting blood glucose, serum insulin, serum pro-inflammatory cytokines levels and the impaired OGTT without affecting the body weight of the mice in all groups. Furthermore, HBN treatment significantly ameliorated pathological changes and increased the protein expression of insulin, and glucose transporters in the pancreatic islets (GLUT-2), liver and skeletal muscle (GLUT-4). Likewise, the Western blots analysis denotes improved insulin signaling and antioxidant enzyme, decreased reactive oxygen species producing enzymes and inflammatory molecules in the liver and adipose tissues of HBN treated diabetic mice. These results suggest that HBN improves β-cell function and insulin signaling by attenuation of oxidative stress mediated chronic inflammation in the type 2 diabetic mice.

Abnormal Crosstalk between Endothelial Cells and Podocytes Mediates Tyrosine Kinase Inhibitor (TKI)-Induced Nephrotoxicity

Vascular endothelial growth factor A (VEGFA) and its receptor VEGFR2 are the main targets of antiangiogenic therapies, and proteinuria is one of the common adverse events associated with the inhibition of the VEGFA/VEGFR2 pathway. The proteinuric kidney damage induced by VEGFR2 tyrosine kinase inhibitors (TKIs) is characterized by podocyte foot process effacement. TKI therapy promotes the formation of abnormal endothelial‒podocyte crosstalk, which plays a key role in TKI-induced podocyte injury and proteinuric nephropathy. This review article summarizes the underlying mechanism by which the abnormal endothelial‒podocyte crosstalk mediates podocyte injury and discusses the possible molecules and signal pathways involved in abnormal endothelial‒podocyte crosstalk. What is more, we highlight the molecules involved in podocyte injury and determine the essential roles of Rac1 and Cdc42; this provides evidence for exploring the abnormal endothelial‒podocyte crosstalk in TKI-induced nephrotoxicity.

Association of Type 2 Diabetes Mellitus and Glycemic Control With Intracranial Plaque Characteristics in Patients With Acute Ischemic Stroke

BACKGROUND

Type 2 diabetes mellitus (T2DM) has shown to be associated with carotid plaque vulnerability. However, the impact of T2DM on intracranial artery atherosclerosis is not well-understood.

PURPOSE

To evaluate the association of diabetes and glycemic control with intracranial atherosclerotic plaque characteristics identified by three-dimensional contrast enhanced MR vessel wall imaging in patients after acute ischemic stroke.

STUDY TYPE

Prospective.

POPULATION

Two hundred and eighty-eight symptomatic patients with acute ischemic stroke due to intracranial atherosclerotic plaque.

FIELD STRENGTH/SEQUENCE

T₁ WI volume isotropic turbo spin-echo acquisition sequence at 3.0 T.

ASSESSMENT

Clinical profiles, blood biomarkers, the number of intracranial plaques, plaque enhanced score, and the features (location, luminal stenotic rate, intraplaque hemorrhage, length, burden, enhancement grade, and ratio) of culprit plaque (defined as the most stenotic lesion ipsilateral to the ischemic event) and nonculprit plaque were analyzed by three radiologists.

STATISTICAL TESTS

Analysis of variance (ANOVA), Shapiro-Wilk normality test, Levene's test, ANOVA with Bonferroni post-hoc test, Kruskal Wallis H test with subsequent pairwise comparisons, chi-square with Bonferroni post-hoc test, generalized linear regression, Pearson correlation test, Kendall's W and intra-class correlation coefficient.

RESULTS

Two hundred and twenty-five participants (age 60 ± 10 years, 58.7% male) with 958 intracranial plaques were included. More intracranial plaques were found in the T2DM group than the non-T2DM group (4.80 ± 2.22 vs. 3.60 ± 1.78, P < 0.05). Patients with poorly-controlled T2DM exhibited higher culprit plaque enhancement ratio than patients with well-controlled T2DM and non-T2DM (2.32 ± 0.61 vs. 1.60 ± 0.62 and 1.39 ± 0.39; respectively, P < 0.05). After adjusting for other clinical variables, T2DM was independently associated with increased intracranial plaque number (β = 0.269, P < 0.05), and HbA1c level was independently associated with culprit plaque enhancement ratio (β = 0.641, P < 0.05) in multivariate analysis.

DATA CONCLUSION

T2DM is associated with an increased intracranial plaque number. Higher HbA1c is associated with stronger plaque enhancement. 3D contrast enhanced MR vessel wall imaging may help better understand the association of T2DM and glycemic control with intracranial plaque.

LEVEL OF EVIDENCE

1 TECHNICAL EFFICACY STAGE: 3.

Activation of soluble guanylyl cyclase signalling with cinaciguat improves impaired kidney function in diabetic mice

BACKGROUND AND PURPOSE

Diabetic nephropathy is the leading cause for end-stage renal disease worldwide. Until now, there is no specific therapy available. Standard treatment with inhibitors of the renin-angiotensin system just slows down progression. However, targeting the NO/sGC/cGMP pathway using sGC activators does prevent kidney damage. Thus, we investigated if the sGC activator cinaciguat was beneficial in a mouse model of diabetic nephropathy, and we analysed how mesangial cells (MCs) were affected by related conditions in cell culture.

EXPERIMENTAL APPROACH

Type 1 diabetes was induced with streptozotocin in wild-type and endothelial NOS knockout (eNOS KO) mice for 8 or 12 weeks.. Half of these mice received cinaciguat in their chow for the last 4 weeks. Kidneys from the diabetic mice were analysed with histochemical assays and by RT-PCR and western blotting. . Additionally, primary murine MCs under diabetic conditions were stimulated with 8-Br-cGMP or cinaciguat to activate the sGC/cGMP pathway.

KEY RESULTS

The diabetic eNOS KO mice developed most characteristics of diabetic nephropathy, most marked at 12 weeks. Treatment with cinaciguat markedly improved GFR, serum creatinine, mesangial expansion and kidney fibrosis in these animals. We determined expression levels of related signalling proteins. Thrombospondin 1, a key mediator in kidney diseases, was strongly up-regulated under diabetic conditions and this increase was suppressed by activation of sGC/cGMP signalling.

CONCLUSION AND IMPLICATIONS

Activation of the NO/sGC/PKG pathway with cinaciguat was beneficial in a model of diabetic nephropathy. Activators of sGC might be an appropriate therapy option in patients with Type 1 diabetes.

Homoarginine ameliorates diabetic nephropathy independent of nitric oxide synthase-3

Recently we showed that homoarginine supplementation confers kidney protection in diabetic mouse models. In this study we tested whether the protective effect of homoarginine is nitric oxide synthase-3 (NOS3)-independent in diabetic nephropathy (DN). Experiments were conducted in NOS3 deficient (NOS3-/- ) mice and their wild type littermate using multiple low doses of vehicle or streptozotocin and treated with homoarginine via drinking water for 24 weeks. Homoarginine supplementation for 24 weeks in diabetic NOS3-/- mice significantly attenuated albuminuria, increased blood urea nitrogen, histopathological changes and kidney fibrosis, kidney fibrotic markers, and kidney macrophage recruitment compared with vehicle-treated diabetic NOS3-/- mice. Furthermore, homoarginine supplementation restored kidney mitochondrial function following diabetes. Importantly, there were no significant changes in kidney NOS1 or NOS2 mRNA expression between all groups. In addition, homoarginine supplementation improved cardiac function and reduced cardiac fibrosis following diabetes. These data demonstrate that the protective effect of homoarginine is independent of NOS3, which will ultimately change our understanding of the mechanism(s) by which homoarginine induce renal and cardiac protection in DN. Homoarginine protective effect in DN could be mediated via improving mitochondrial function.

Effects of long-term vitamin D and n-3 fatty acid supplementation on inflammatory and cardiac biomarkers in patients with type 2 diabetes: secondary analyses from a randomised controlled trial

AIMS/HYPOTHESIS

Interventions that reduce inflammation may delay progression of microvascular and macrovascular complications in diabetes. We examined the effects of vitamin D₃ and/or n-3 fatty acid supplementation vs placebo on 5 year changes in serum inflammatory and cardiac biomarkers in adults with type 2 diabetes.

METHODS

This study reports pre-specified secondary outcomes of the Vitamin D and Omega-3 Trial to Prevent and Treat Diabetic Kidney Disease, in which 1312 US adults with type 2 diabetes and without known cardiovascular disease, malignancy, or end-stage kidney disease were randomised using computer-generated random numbers in blocks of eight to vitamin D₃ (2000 IU/day) vs placebo and n-3 fatty acids (eicosapentaenoic acid [EPA] and docosahexaenoic acid [DHA]; 1 g/day) vs placebo in a 2 × 2 factorial design. Participants, examiners, and researchers assessing outcomes were blinded to intervention assignment. We measured serum IL-6, high-sensitivity C-reactive protein (hsCRP) and N-terminal pro-B-type natriuretic peptide (NT-proBNP) at baseline and after 2 and 5 years.

RESULTS

A total of 333 participants were randomised to vitamin D₃ and placebo n-3 fatty acids, 289 to n-3 fatty acids and placebo vitamin D₃, 370 to vitamin D₃ and n-3 fatty acids, and 320 to 2 placebos; 989 (75%) and 934 (71%) participants returned blood samples at 2 and 5 years, respectively. Participants had a mean age of 67.6 years (46% women). Overall, baseline geometric means of IL-6, hsCRP and NT-proBNP were 1.2 pg/ml, 1.9 mg/l and 262 ng/l, respectively. After 5 years, mean IL-6 and hsCRP remained within 6% of their baseline values while mean NT-proBNP increased by 55% overall. Compared with placebo, participants assigned to vitamin D₃ had a 1.24-fold greater increase in NT-proBNP over 5 years (95% CI 1.09, 1.41; p = 0.003), while IL-6 and hsCRP did not have a significant difference in change. Comparing n-3 fatty acids with placebo, there was no significant difference in change in IL-6, hsCRP or NT-proBNP. No heterogeneity was observed in subgroup analyses accounting for baseline eGFR, urine albumin to creatinine ratio, initial biomarker concentration, 25-hydroxyvitamin D level or EPA+DHA index.

CONCLUSIONS/INTERPRETATION

Among adults with type 2 diabetes, supplementation with vitamin D₃ or n-3 fatty acids did not reduce IL-6, hsCRP or NT-proBNP over 5 years.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01684722 FUNDING: The study was funded by grant R01DK088762 from the National Institute of Diabetes and Digestive and Kidney Diseases. Graphical abstract.

Association Between Lipoprotein (A) and Diabetic Nephropathy in Patients With Type 2 Diabetes Mellitus: A Meta-Analysis

BACKGROUND

Lipoprotein (a) [Lp (a)] has been well recognized as a risk factor of cardiovascular disease. However, the association between serum Lp (a) and diabetic nephropathy in patients with type 2 diabetes mellitus (T2DM) remains unknown. We performed a meta-analysis to comprehensively evaluate the above association.

METHODS

Observational studies aiming to evaluate the independent association between serum Lp (a) and diabetic nephropathy in T2DM patients were identified by systematic search of PubMed and Embase databases. A random-effect model which incorporated the potential intra-study heterogeneity was used for the meta-analysis.

RESULTS

Eleven observational studies with 9304 T2DM patients were included. Results showed that compared to those with the lowest Lp (a), patients with the highest Lp (a) level had higher odds of diabetic nephropathy (adjusted odds ratio [OR]: 1.63, 95% confidence interval [CI]: 1.25-2.14, I² = 54%, P < 0.001). Meta-analysis of studies in which Lp (a) was presented as continuous variables showed consistent result (adjusted OR: 1.13 for 1 mg/dl increment of Lp (a), 95% CI: 1.03-1.24, I2 = 36%, P = 0.008). Subgroup analyses showed that study characteristics such as definitions of diabetic nephropathy and study design did not significantly affect the association (P for subgroup difference all > 0.05).

CONCLUSIONS

Higher serum Lp (a) in patients with T2DM is independently associated with higher odds of diabetic nephropathy. Large scale prospective cohort studies are needed to validate this finding. Moreover, the potential influence of Lp (a) lowering on renal function in T2DM patients may be further investigated.

Hepatic Knockdown of Endothelin Type A Receptor (ETAR) Ameliorates Hepatic Insulin Resistance and Hyperglycemia Through Suppressing p66Shc-Mediated Mitochondrial Fragmentation in High-Fat Diet-Fed Mice

BACKGROUND

Emerging evidence from animal studies and clinical trials indicates that systemic inhibition of endothelin1 (ET1) signaling by endothelin receptor antagonists improves pathological features of diabetes and its complications. It is indicated that endothelin type A receptor (ETAR) plays a major role in ET1-mediated pathophysiological actions including diabetic pathology. However, the effects as well as the mechanistic targets of hepatic ET1/ETAR signaling inhibition on the pathology of metabolic diseases remain unclear. This study aimed to investigate the beneficial effects as well as the underlying mechanisms of hepatic ETAR knockdown on metabolism abnormalities in high-fat diet (HFD)-fed mice.

METHODS

Mice were fed a HFD to induce insulin resistance and metabolism abnormalities. L02 cells were treated with ET1 to assess the action of ET1/ETAR signaling in vitro. Liver-selective knockdown of ETAR was achieved by tail vein injection of adeno-associated virus 8 (AAV8). Systemic and peripheral metabolism abnormalities were determined in vivo and in vitro. Mitochondrial fragmentation was observed by transmission electron microscope (TEM) and mitoTracker red staining.

RESULTS

Here we provided in vivo and in vitro evidence to demonstrate that liver-selective knockdown of ETAR effectively ameliorated hepatic insulin resistance and hyperglycemia in HFD-fed mice. Mechanistically, hepatic ETAR knockdown alleviated mitochondrial fragmentation and dysfunction via inactivating 66-kDa Src homology 2 domain-containing protein (p66Shc) to recover mitochondrial dynamics, which was mediated by inhibiting protein kinase Cδ (PKCδ), in the livers of HFD-fed mice. Ultimately, hepatic ETAR knockdown attenuated mitochondria-derived oxidative stress and related liver injuries in HFD-fed mice. These ETAR knockdown-mediated actions were confirmed in ET1-treated L02 cells.

CONCLUSION

This study defined an ameliorative role of hepatic ETAR knockdown in HFD-induced metabolism abnormalities by alleviating p66Shc-mediated mitochondrial fragmentation and consequent oxidative stress-related disorders and indicated that hepatic ETAR knockdown may be a promising therapeutic strategy for metabolic diseases.

Intestinal fatty acid-binding protein, a biomarker of intestinal barrier dysfunction, increases with the progression of type 2 diabetes

OBJECTIVE

To investigate serum intestinal fatty acid-binding protein (I-FABP) in two groups of patients with different duration of hyperglycemia in a cross-sectional study.

MATERIALS AND METHODS

In the present study, a total of 280 individuals (158 outpatients and 122 inpatients) suffering from hyperglycemia were recruited between May and September 2019. The clinical information of all participants was collected from the hospital information system, including the duration of hyperglycemia, age, gender, hemoglobin A1c (HbA1c), 75-g oral glucose tolerance test including fasting plasma glucose (FPG), 2-hour plasma glucose (2hPG), fasting C-peptide (FC-pep), 2-hour C-peptide (2hC-pep), fasting insulin (FIns), and 2-hour insulin (2hIns). In addition, the morbidity of diabetic complications (retinopathy, neuropathy, and nephropathy) in the inpatient group was determined. Furthermore, the difference between 2hPG and FPG (ΔPG), the difference between 2hC-pep and FC-pep (ΔC-pep), and the difference between 2hIns and FIns (ΔIns) were calculated. The level of serum I-FABP, a biomarker of intestinal barrier (IB) dysfunction, was estimated by an enzyme-linked immunosorbent assay.

RESULTS

For the outpatient group, the median duration of hyperglycemia was less than a year; the serum I-FABP level was positively correlated with age (R = 0.299, P < 0.001). For the inpatient group, the median duration of hyperglycemia was ten years; correlation analysis showed that the serum I-FABP level was positively associated with age and ΔPG (R = 0.286, P = 0.001; R = 0.250, P = 0.006, respectively) while negatively associated with FC-pep and 2hC-pep (R =  - 0.304, P = 0.001; R =  - 0.241, P = 0.008, respectively); multiple linear regression analysis showed that the serum I-FABP level was positively associated with the duration of hyperglycemia (β = 0.362, P < 0.001); moreover, patients with retinopathy had a significantly higher I-FABP level than those without retinopathy (P = 0.001).

CONCLUSIONS

In the outpatients whose duration of hyperglycemia was less than a year, the serum I-FABP level was positively associated with age. In the inpatients with different courses of diabetes, the serum I-FABP level was positively associated with the duration of hyperglycemia and glycemic variability but negatively associated with islet beta-cell function; moreover, the serum I-FABP level was higher in patients with retinopathy than in those without retinopathy, suggesting that the IB dysfunction got worse with the progression of diabetes.

Molecular Mechanisms and Functions of lncRNAs in the Inflammatory Reaction of Diabetes Mellitus

Diabetes is a chronic inflammatory state, and several studies have shown that the mechanisms of insulin resistance and abnormal islet β-cell function in diabetes are closely related to inflammatory reactions. Inflammation plays a critical role in diabetic complications. Long noncoding RNAs (lncRNAs), a new area of genomic research for gene regulation, have complex biological functions in various aspects of cellular biological activity. Recent studies have shown that lncRNAs are associated with the regulation of inflammatory responses in various ways, including at the epigenetic, transcriptional, and posttranscriptional levels. This paper presents a brief review of studies on the mechanisms of lncRNAs in diabetic inflammation. The purpose of this article is to determine the role of lncRNAs in the process of diabetic inflammation and to provide new strategies for the use of lncRNAs in the treatments for diabetic inflammation.

Oxidative Stress and Inflammation in Renal and Cardiovascular Complications of Diabetes

Simple Summary

The progressive nature of type 2 diabetes mellitus (T2DM) leads to micro- and macro-vascular complications, including renal and cardiovascular disease. These alone, or in combination, are a major cause of premature morbidity and mortality in diabetic patients. Despite advances in glucose lowering treatments, these diabetic complications are still inadequately prevented or reversed. This ongoing cardiovascular–renal burden in diabetes poses a heavy cost on the health care system. Therefore, there is an urgent need to develop more effective treatments. In this review, we discuss how oxidative stress and inflammation induce and perpetuate the renal and cardiovascular complications of diabetes. It is particularly important to understand these driving mechanisms in order to elucidate pharmacological targets and mechanism-based future drug therapies.

Abstract

Oxidative stress and inflammation are considered major drivers in the pathogenesis of diabetic complications, including renal and cardiovascular disease. A symbiotic relationship also appears to exist between oxidative stress and inflammation. Several emerging therapies target these crucial pathways, to alleviate the burden of the aforementioned diseases. Oxidative stress refers to an imbalance between reactive oxygen species (ROS) and antioxidant defenses, a pathological state which not only leads to direct cellular damage but also an inflammatory cascade that further perpetuates tissue injury. Emerging therapeutic strategies tackle these pathways in a variety of ways, from increasing antioxidant defenses (antioxidants and Nrf2 activators) to reducing ROS production (NADPH oxidase inhibitors and XO inhibitors) or inhibiting the associated inflammatory pathways (NLRP3 inflammasome inhibitors, lipoxins, GLP-1 receptor agonists, and AT-1 receptor antagonists). This review summarizes the mechanisms by which oxidative stress and inflammation contribute to and perpetuate diabetes associated renal and cardiovascular disease along with the therapeutic strategies which target these pathways to provide reno and cardiovascular protection in the setting of diabetes.

Differential Regulation of mTOR Complexes with miR-302a Attenuates Myocardial Reperfusion Injury in Diabetes

Persistent activation of mTOR (mammalian target of rapamycin) in diabetes increases the vulnerability of the heart to ischemia/reperfusion (I/R) injury. We show here that infusion of rapamycin (mTOR inhibitor) at reperfusion following ischemia reduced myocardial infarct size and apoptosis with restoration of cardiac function in type 1 diabetic rabbits. Likewise, treatment with rapamycin protected hyperglycemic human-pluripotent-stem-cells-derived cardiomyocytes (HG-hiPSC-CMs) following simulated ischemia (SI) and reoxygenation (RO). Phosphorylation of S6 (mTORC1 marker) was increased, whereas AKT phosphorylation (mTORC2 marker) and microRNA-302a were reduced with concomitant increase of its target, PTEN, following I/R injury in diabetic heart and HG-hiPSC-CMs. Rapamycin inhibited mTORC1 and PTEN, but augmented mTORC2 with restoration of miRNA-302a under diabetic conditions. Inhibition of miRNA-302a blocked mTORC2 and abolished rapamycin-induced protection against SI/RO injury in HG-hiPSC-CMs. We conclude that rapamycin attenuates reperfusion injury in diabetic heart through inhibition of PTEN and mTORC1 with restoration of miR-302a-mTORC2 signaling.

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miR-302a and AKT phosphorylation are suppressed in post-ischemic diabetic heart

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Negative regulator of insulin signaling, PTEN, is induced after ischemia reperfusion

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miRNA-302a-mimic abolishes ischemic injury in hyperglycemic human iPS cardiocytes

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Rapamycin treatment restores miR-302a-mTORC2 cardioprotective signaling in diabetes

Association of Long-Term Air Pollution with Prevalence and Incidence of Distal Sensorimotor Polyneuropathy: KORA F4/FF4 Study

BACKGROUND

Air pollution contributes to type 2 diabetes and cardiovascular diseases, but its relevance for other complications of diabetes, in particular distal sensorimotor polyneuropathy (DSPN), is unclear. Recent studies have indicated that DSPN is also increasingly prevalent in obesity.

OBJECTIVES

We aimed to assess associations of air pollutants with prevalent and incident DSPN in a population-based study of older individuals with high rates of type 2 diabetes and obesity.

METHODS

Cross-sectional analyses on prevalent DSPN were based on 1,075 individuals 62-81 years of age from the German Cooperative Health Research in the Region of Augsburg (KORA) F4 survey (2006-2008). Analyses on incident DSPN included 424 individuals without DSPN at baseline (KORA F4), of whom 188 had developed DSPN by the KORA FF4 survey (2013-2014). Associations of annual average air pollutant concentrations at participants' residences with prevalent and incident DSPN were estimated using Poisson regression models with a robust error variance adjusting for multiple confounders.

RESULTS

Higher particle number concentrations (PNCs) were associated with higher prevalence [risk ratio (RR) per interquartile range (IQR) increase=1.10 (95% CI: 1.01, 1.20)] and incidence [1.11 (95% CI: 0.99, 1.24)] of DSPN. In subgroup analyses, particulate (PNC, PM10, PMcoarse, PM2.5, and PM2.5abs) and gaseous (NOx, NO2) pollutants were positively associated with prevalent DSPN in obese participants, whereas corresponding estimates for nonobese participants were close to the null [e.g., for an IQR increase in PNC, RR=1.17 (95% CI: 1.05, 1.31) vs. 1.06 (95% CI: 0.95, 1.19); pinteraction=0.22]. With the exception of PM2.5abs, corresponding associations with incident DSPN were positive in obese participants but null or inverse for nonobese participants, with pinteraction≤0.13 [e.g., for PNC, RR=1.28 (95% CI: 1.08, 1.51) vs. 1.03 (95% CI: 0.90, 1.18); pinteraction=0.03].

DISCUSSION

Both particulate and gaseous air pollutants were positively associated with prevalent and incident DSPN in obese individuals. Obesity and air pollution may have synergistic effects on the development of DSPN. https://doi.org/10.1289/EHP7311.

Polysulfide-mediated sulfhydration of SIRT1 prevents diabetic nephropathy by suppressing phosphorylation and acetylation of p65 NF-κB and STAT3

Diabetic kidney disease is known as a major cause of chronic kidney disease and end stage renal disease. Polysulfides, a class of chemical agents with a chain of sulfur atoms, are found to confer renal protective effects in acute kidney injury. However, whether a polysulfide donor, sodium tetrasulfide (Na₂S₄), confers protective effects against diabetic nephropathy remains unclear. Our results showed that Na₂S₄ treatment ameliorated renal dysfunctional and histological damage in diabetic kidneys through inhibiting the overproduction of inflammation cytokine and reactive oxygen species (ROS), as well as attenuating renal fibrosis and renal cell apoptosis. Additionally, the upregulated phosphorylation and acetylation levels of p65 nuclear factor κB (p65 NF-κB) and signal transducer and activator of transcription 3 (STAT3) in diabetic nephropathy were abrogated by Na₂S₄ in a sirtuin-1 (SIRT1)-dependent manner. In renal tubular epithelial cells, Na₂S₄ directly sulfhydrated SIRT1 at two conserved CXXC domains (Cys371/374; Cys395/398), then induced dephosphorylation and deacetylation of its targeted proteins including p65 NF-κB and STAT3, thereby reducing high glucose (HG)-caused oxidative stress, cell apoptosis, inflammation response and epithelial-to-mesenchymal transition (EMT) progression. Most importantly, inactivation of SIRT1 by a specific inhibitor EX-527, small interfering RNA (siRNA), a de-sulfhydration reagent dithiothreitol (DTT), or mutation of Cys371/374 and Cys395/398 sites at SIRT1 abolished the protective effects of Na₂S₄ on diabetic kidney insulting. These results reveal that polysulfides may attenuate diabetic renal lesions via inactivation of p65 NF-κB and STAT3 phosphorylation/acetylation through sulfhydrating SIRT1.

The Interplay between Oxidative Stress, Exercise, and Pain in Health and Disease: Potential Role of Autonomic Regulation and Epigenetic Mechanisms

Oxidative stress can be induced by various stimuli and altered in certain conditions, including exercise and pain. Although many studies have investigated oxidative stress in relation to either exercise or pain, the literature presents conflicting results. Therefore, this review critically discusses existing literature about this topic, aiming to provide a clear overview of known interactions between oxidative stress, exercise, and pain in healthy people as well as in people with chronic pain, and to highlight possible confounding factors to keep in mind when reflecting on these interactions. In addition, autonomic regulation and epigenetic mechanisms are proposed as potential mechanisms of action underlying the interplay between oxidative stress, exercise, and pain. This review highlights that the relation between oxidative stress, exercise, and pain is poorly understood and not straightforward, as it is dependent on the characteristics of exercise, but also on which population is investigated. To be able to compare studies on this topic, strict guidelines should be developed to limit the effect of several confounding factors. This way, the true interplay between oxidative stress, exercise, and pain, and the underlying mechanisms of action can be revealed and validated via independent studies.

Mechanism of progression of diabetic kidney disease mediated by podocyte mitochondrial injury

Diabetic kidney disease (DKD) is an important diabetic microvascular complication, which has become the main cause of end-stage renal disease (ESRD) all over the world. It is of great significance to find effective therapeutic targets and improve the prognosis of the disease. Traditionally, it is believed that the activation of the renin-angiotensin-aldosterone system (RAAS) is the main reason for the progression of DKD, but with the progress of research, it is known that the production of proteinuria in patients with DKD is also related to podocyte injury and loss. Many studies have shown that mitochondrial dysfunction in podocytes plays an important role in the occurrence and development of DKD, and oxidative stress is also the main pathway and common hub of diabetes to the occurrence and development of microvascular and macrovascular complications. Thus, the occurrence and progression of DKD is correlated with not only the activation of the RAAS, but also the damage of mitochondria, oxidative stress, and inflammatory mediators. Besides, diabetes-related metabolic disorders can also cause abnormalities in mitochondrial dynamics, autophagy and cellular signal transduction, which are intertwined in a complex way. Therefore, in this review, we mainly explore the mechanism and the latest research progress of podocyte mitochondria in DKD and summarize the main signal pathways involved in them. Thus, it provides feasible clinical application and future research suggestions for the prevention and treatment of DKD, which has important practical significance for the later treatment of patients with DKD.

Vitamin D Protects against Oxidative Stress and Inflammation in Human Retinal Cells

Diabetic retinopathy is a vision-threatening microvascular complication of diabetes and is one of the leading causes of blindness. Oxidative stress and inflammation play a major role in its pathogenesis, and new therapies counteracting these contributors could be of great interest. In the current study, we investigated the role of vitamin D against oxidative stress and inflammation in human retinal pigment epithelium (RPE) and human retinal endothelial cell lines. We demonstrate that vitamin D effectively counteracts the oxidative stress induced by hydrogen peroxide (H₂O₂). In addition, the increased levels of proinflammatory proteins such as Interleukin (IL)-6, IL-8, Monocyte chemoattractant protein (MCP)-1, Interferon (IFN)-γ, and tumor necrosis factor (TNF)-α triggered by lipopolysaccharide (LPS) exposure were significantly decreased by vitamin D addition. Interestingly, the increased IL-18 only decreased by vitamin D addition in endothelial cells but not in RPE cells, suggesting a main antiangiogenic role under inflammatory conditions. Moreover, H₂O₂ and LPS induced the alteration and morphological damage of tight junctions in adult retinal pigment epithelium (ARPE-19) cells that were restored under oxidative and inflammatory conditions by the addition of vitamin D to the media. In conclusion, our data suggest that vitamin D could protect the retina by enhancing antioxidant defense and through exhibiting anti-inflammatory properties.

NOX4-dependent regulation of ENaC in hypertension and diabetic kidney disease

NADPH oxidase 4 (NOX4) is the most abundant NOX isoform in the kidney; however, its importance for renal function has only recently emerged. The NOX4-dependent pathway regulates many factors essential for proper sodium handling in the distal nephron. However, the functional significance of this pathway in the control of sodium reabsorption during the initiation of chronic kidney disease is not established. The goal of this study was to test Nox4-dependent ENaC regulation in two models: SS hypertension and STZ-induced type 1 diabetes. First, we showed that genetic ablation of Nox4 in Dahl salt-sensitive (SS) rat attenuated a high-salt (HS)-induced increase in epithelial Na⁺ channel (ENaC) activity in the cortical collecting duct. We also found that H₂ O₂ upregulated ENaC activity, and H₂ O₂ production was reduced in both the renal cortex and medulla in SS^Nox4-/- rats fed an HS diet. Second, in the streptozotocin model of hyperglycemia-induced renal injury ENaC activity in hyperglycemic animals was elevated in SS but not SS^Nox4-/- rats. NaCl cotransporter (NCC) expression was increased compared to healthy controls, while expression values between SS and SS^Nox4-/- groups were similar. These data emphasize a critical contribution of the NOX4-mediated pathway in maladaptive upregulation of ENaC-mediated sodium reabsorption in the distal nephron in the conditions of HS- and hyperglycemia-induced kidney injury.

Lentiviral gene therapy vectors encoding VIP suppressed diabetes-related inflammation and augmented pancreatic beta-cell proliferation

Type 1 diabetes (T1DM) is an autoimmune condition in which the immune system attacks and destroys insulin-producing beta cells in the pancreas leading to hyperglycemia. Vasoactive intestinal peptide (VIP) manifests insulinotropic and anti-inflammatory properties, which are useful for the treatment of diabetes. Because of its limited half-life due to DPP-4-mediated degradation, constant infusions or multiple injections are needed to observe any therapeutic benefit. Since gene therapy has the potential to treat genetic diseases, an HIV-based lentiviral vector carrying VIP gene (LentiVIP) was generated to provide a stable VIP gene expression in vivo. The therapeutic efficacy of LentiVIP was tested in a multiple low-dose STZ-induced animal model of T1DM. LentiVIP delivery into diabetic animals reduced hyperglycemia, improved glucose tolerance, and prevented weight loss. Also, a decrease in serum CRP levels, and serum oxidant capacity, but an increase in antioxidant capacity were observed in LentiVIP-treated animals. Restoration of islet cell mass was correlated with an increase in pancreatic beta-cell proliferation. These beneficial results suggest the therapeutic effect of LentiVIP is due to the repression of diabetes-induced inflammation, its insulinotropic properties, and VIP-induced beta-cell proliferation.

UPLC-MS-based urine nontargeted metabolic profiling identifies dysregulation of pantothenate and CoA biosynthesis pathway in diabetic kidney disease

AIMS

Diabetic kidney disease (DKD) is a major prevalent chronic microvascular complication of type 2 diabetes (T2D). However, the present diagnostic indicators have limitations in the early diagnosis of DKD. This study concentrated on the sensitive and specific biomarkers in early diagnosis of DKD by metabolomics.

MATERIALS AND METHODS

In this cross-sectional study, we performed a UPLC-MS based nontargeted metabolomics assay to profile the urinary metabolites in patients with DKD. Principal Component Analysis (PCA) and orthogonal partial least square discriminant analysis (OPLS-DA) were used for screening out the metabolomic variables.

KEY FINDINGS

A total of 147 urinary metabolites were identified and 5 metabolic pathways were correlated with DKD pathophysiology. Pantothenate and coenzyme A biosynthesis pathway alteration was found the most prominent in DKD subjects. 4 metabolites, including dihydrouracil, ureidopropionic acid, pantothenic acid (PA), and adenosine 3',5'-diphosphate involved in pantothenate and CoA biosynthesis were significantly down-regulated.

SIGNIFICANCE

Our finding indicates that PA would be served as a novel predictive biomarker associated with DKD development and progression. Furthermore, our results provide a promising prospect that PA and CoA biosynthesis pathway can be potential therapeutic targets for DKD treatment.

Immune Dysfunction in Uremia 2020

Cardiovascular disease and infections are major causes for the high incidence of morbidity and mortality of patients with chronic kidney disease. Both complications are directly or indirectly associated with disturbed functions or altered apoptotic rates of polymorphonuclear leukocytes, monocytes, lymphocytes, and dendritic cells. Normal responses of immune cells can be reduced, leading to infectious diseases or pre-activated/primed, giving rise to inflammation and subsequently to cardiovascular disease. This review summarizes the impact of kidney dysfunction on the immune system. Renal failure results in disturbed renal metabolic activities with reduced renin, erythropoietin, and vitamin D production, which adversely affects the immune system. Decreased kidney function also leads to reduced glomerular filtration and the retention of uremic toxins. A large number of uremic toxins with detrimental effects on immune cells have been identified. Besides small water-soluble and protein-bound compounds originating from the intestinal microbiome, several molecules in the middle molecular range, e.g., immunoglobulin light chains, retinol-binding protein, the neuropeptides Met-enkephalin and neuropeptide Y, endothelin-1, and the adipokines leptin and resistin, adversely affect immune cells. Posttranslational modifications such as carbamoylation, advanced glycation products, and oxidative modifications contribute to uremic toxicity. Furthermore, high-density lipoprotein from uremic patients has an altered protein profile and thereby loses its anti-inflammatory properties.

Upregulation of long non-coding RNA MEG3 in type 2 diabetes mellitus complicated with vascular disease: a case-control study

Previous studies have indicated that long non-coding RNAs (lncRNAs) were closely related to diabetes. In this study, we aimed to explore the possible role and mechanism of lncRNA MEG3 in the occurrence and development of type 2 diabetes mellitus (T2DM) and its vascular complications. A case-control study involving 115 subjects was conducted, including 53 T2DM patients (37 patients with vascular complication and 16 patients without vascular complications) and 62 healthy subjects. We performed real-time polymerase chain reaction (RT-PCR) analysis of the lncRNA MEG3 and miR-146a levels in peripheral blood mononuclear cells (PBMCs) in the 115 samples. We found that the expression of lncRNA MEG3 was upregulated in the T2DM patients with vascular complication (DC group) compared with T2DM patients without vascular complication (D group) (P < 0.05) and the control group (P < 0.01). miR-146a levels in DC group were significantly lower compared with control group. There was a significant positive correlation between the expression of lncRNA MEG3 and glucose (GLU) (r = 0.301, P = 0.0011) and hemoglobin A1C (HbA1c) (r = 0.477, P = 0.0006). Our study suggests MEG3 may play as an important role in progression of diabetes-related vascular complications, contributing to a novel understanding of pathogenesis and prognosis for diabetes and its complications.

Stimulation of ORAI1 expression, store-operated Ca2+ entry, and osteogenic signaling by high glucose exposure of human aortic smooth muscle cells

Diabetes and chronic kidney disease (CKD) both trigger vascular osteogenic signaling and calcification leading to early death by cardiovascular events. Osteogenic signaling involves upregulation of the transcription factors CBFA1, MSX2, and SOX9, as well as alkaline phosphatase (ALP), an enzyme fostering calcification by degrading the calcification inhibitor pyrophosphate. In CKD, osteogenic signaling is triggered by hyperphosphatemia, which upregulates the serum and glucocorticoid-inducible kinase SGK1, a strong stimulator of the Ca²⁺-channel ORAI1. The channel is activated by STIM1 and accomplishes store-operated Ca²⁺-entry (SOCE). The present study explored whether exposure of human aortic smooth muscle cells (HAoSMCs) to high extracellular glucose concentrations similarly upregulates ORAI1 and/or STIM1 expression, SOCE, and osteogenic signaling. To this end, HAoSMCs were exposed to high extracellular glucose concentrations (15 mM, 24 h) without or with additional exposure to the phosphate donor ß-glycerophosphate. Transcript levels were estimated using qRT-PCR, protein abundance using Western blotting, ALP activity using a colorimetric assay kit, calcium deposits utilizing Alizarin red staining, cytosolic Ca²⁺-concentration ([Ca²⁺]_i) by Fura-2-fluorescence, and SOCE from increase of [Ca²⁺]_i following re-addition of extracellular Ca²⁺ after store depletion with thapsigargin (1 μM). As a result, glucose enhanced the transcript levels of SGK1 and ORAI1, ORAI2, and STIM2, protein abundance of ORAI1, SOCE, the transcript levels of CBFA1, MSX2, SOX9, and ALPL, as well as calcium deposits. Moreover, glucose significantly augmented the stimulating effect of ß-glycerophosphate on transcript levels of SGK1 and ORAI1, SOCE, the transcript levels of osteogenic markers, as well as calcium deposits. ORAI1 inhibitor MRS1845 (10 μM) significantly blunted the glucose-induced upregulation of the CBFA1 and MSX2 transcript levels. In conclusion, the hyperglycemia of diabetes stimulates expression of SGK1 and ORAI1, thus, augmenting store-operated Ca²⁺-entry and osteogenic signaling in HAoSMCs.

ROS-associated immune response and metabolism: a mechanistic approach with implication of various diseases

The immune system plays a pivotal role in maintaining the defense mechanism against external agents and also internal danger signals. Metabolic programming of immune cells is required for functioning of different subsets of immune cells under different physiological conditions. The field of immunometabolism has gained ground because of its immense importance in coordination and balance of immune responses. Metabolism is very much related with production of energy and certain by-products. Reactive oxygen species (ROS) are generated as one of the by-products of various metabolic pathways. The amount, localization of ROS and redox status determine transcription of genes, and also influences the metabolism of immune cells. This review discusses ROS, metabolism of immune cells at different cellular conditions and sheds some light on how ROS might regulate immunometabolism.

Chronic obstructive pulmonary disease, lung function and risk of type 2 diabetes: a systematic review and meta-analysis of cohort studies

Background

The association between chronic obstructive pulmonary disease (COPD), lung function and risk of type 2 diabetes mellitus (T2DM) remains controversial. We performed a meta-analysis to clarify this issue.

Methods

The PubMed and EMBASE databases were searched. Cohort studies on COPD, lung function and risk of T2DM in adults were included. A random effects model was adopted to calculate the summary risk ratio (RR) and 95% confidence interval (CI). Dose-response analysis was conducted where possible.

Results

A total of 13 eligible cohort studies involving 307,335 incident T2DM cases and 7,683,784 individuals were included. The risk of T2DM was significantly higher in patients with COPD than those without COPD (RR = 1.25, 95% CI 1.16–1.34). Compared to the highest category of percentage forced vital capacity (FVC%), the lowest category of FVC% was associated with a higher risk of T2DM (RR = 1.43, 95% CI 1.33–1.53). Similarly, the summary RR of T2DM for the lowest versus highest category of percentage forced expiratory volume in 1 s (FEV1%) was 1.49 (95% CI 1.39–1.60). Significant linear associations of FVC% and FEV1% with risk of T2DM were found (P_{non-linearity} > 0.05); the RR of T2DM was 0.88 (95% CI 0.82–0.95) and 0.87 (95% CI 0.81–0.94) per 10% increase in FVC% and FEV1%, respectively. There was a non-significant relationship between the FEV1/FVC ratio and the risk of T2DM.

Conclusions

Both COPD and impaired lung function, especially restricted ventilation dysfunction, could increase the risk of T2DM. However, these findings should be interpreted with caution due to the limited number of studies, and need to be validated by future studies.

Circulating TNF receptors and risk of renal disease progression, cardiovascular disease events and mortality in patients with diabetes: a systematic review and meta-analysis

PURPOSE

Inflammation plays an important role in the pathogenesis of diabetes complications. This study aims to assess the association between circulating inflammatory biomarkers TNF receptors (TNFRs) and the risk of renal disease progression, cardiovascular disease (CVD) events, and mortality in patients with diabetes.

METHODS

PubMed and Embase databases were comprehensively searched up to March 2019. Data were extracted independently by two reviewers. A random effects model was performed for the pooled analyses.

RESULTS

Five studies in 3316 subjects assessed TNFRs with renal disease in patients with type 1 diabetes and showed both TNFR-1 and TNFR-2 were consistently associated with the renal outcomes. Fourteen studies in 7696 subjects evaluated TNFRs in patients with type 2 diabetes. The pooled risk ratio per doubling increase in TNFR-1 and TNFR-2 for renal disease progression was more than two (2.64 [1.98, 3.52] and 2.23 [1.69, 2.94]). The subgroup analyses and sensitivity analyses further illustrated these results of renal outcome and its robustness. Moreover, higher TNFR-1 and TNFR-2 was also significantly associated with CVD events and mortality in patients with type 2 diabetes.

CONCLUSIONS

Circulating TNFR-1 and TNFR-2 are independently associated with higher risk of renal disease progression, CVD events, and mortality in patients with diabetes and might contribute to the clinical risk assessment in the future.

Ginsenoside Rg1 ameliorates glomerular fibrosis during kidney aging by inhibiting NOX4 and NLRP3 inflammasome activation in SAMP8 mice

Aging is closely related to the progress of renal fibrosis, which eventually results in renal dysfunction. Ginsenoside Rg1 (Rg1) has been reported to have an extensive anti-aging effect. However, the role and mechanism of Rg1 in aging-related renal fibrosis remain unclear. The present study aimed to evaluate the protective effect and mechanism of Rg1 in renal fibrosis during kidney aging in a model of SAMP8 mice. Taking SAMR1 mice as the control group, SAMP8 mice were administered Apocynin (50 mg/kg), Tempol (50 mg/kg), or Rg1 (5, 10 mg/kg) intragastrically for 9 weeks as treatment groups. The results showed that the elevated levels of blood urea nitrogen, serum creatinine and senescence-associated β-galactosidase (β-Gal) were markedly decreased, the glomerular mesangial proliferation was significantly alleviated and the increased levels of collagen IV and TGF-β1 were significantly downregulated by Rg1 in SAMP8 mice. In addition, the generation of ROS and the expression of NADHP oxidase 4 (NOX4) in the renal cortex were significantly reduced by Rg1 treatment. The expression levels of NLRP3 inflammasome-related proteins and the inflammation-related cytokine IL-1β were also inhibited by Rg1 treatment in the SAMP8 mice. These results suggested that Rg1 could delay kidney aging and inhibit aging-related glomerular fibrosis by reducing NOX4-derived ROS generation and downregulating NLRP3 inflammasome expression.

Highlights from the 2019 International Aspirin Foundation Scientific Conference, Rome, 28 June 2019: benefits and risks of antithrombotic therapy for cardiovascular disease prevention

At the 2019 International Aspirin Foundation Scientific Conference 'Benefits and Risks of Antithrombotic Therapy for Cardiovascular Disease Prevention', held in Rome, Italy, international experts sought to discuss and debate the optimal antithrombotic strategy for the secondary prevention of cardiovascular disease (CVD) and to seek agreement around dosing and target populations for aspirin use in primary disease prevention. Getting the best evidence to support real-life decisions in the clinic can be complex, and individualising management in order to balance both the risks and benefits of different disease prevention strategies appears to be the best approach. It is hoped that future decision-making tools and biomarkers will help direct treatments at those most likely to benefit.

Activation of ALDH2 attenuates high glucose induced rat cardiomyocyte fibrosis and necroptosis

Necroptosis is one of a regulated programmed death mode, fibrosis is closely related with cell death. It has been reported that inhibition of necroptosis can play the protective role in cardiac ischemia and reperfusion injury, stroke and other diseases, but the mechanisms of aldehyde dehydrogenases 2 (ALDH2) against high glucose induced neonatal rat ventricular primary cardiomyocytes fibrosis and necroptosis had not been elucidated clearly. This study was to observe the effect of ALDH2 on high glucose (HG) induced myocardial fibrosis and necroptosis in primary rat cardiomyocytes model. In contrast to normal glucose group, in HG group, with the decreases of ALDH2 activity, mRNA and protein levels, the cardiomyocytes viability was decreased, reactive oxygen species (ROS), the inflammation factors - tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), interleukin-1β (IL-1β) levels, collagen I (col I) and col III mRNA expressions and tissue inhibitors of matrix metalloproteinase 4 (TIMP4) protein expression were increased, while matrix metalloproteinase 14 (MMP14) protein level, the ratio of MMP14/TIMP4 were decreased, and the necroptosis key factors - the receptor interacting protein 1 (RIP1), RIP3 and mixed lineage kinase domain-like protein (MLKL) at mRNA and protein expressions were increased, the inflammasome core proteins - NLRP3 and ASC protein expressions were also increased, the apoptosis rate and necrosis rate were also increased. When the cardiomyocytes were treated with Alda-1 (the ALDH2 agonist) in HG intervention, the cell viability, ALDH2 activity, mRNA and protein levels, MMP14 protein level, the ratio of MMP14/TIMP4 were higher, ROS and TNF-α, IL-6, IL-1β levels, RIP1, RIP3, MLKL, NLRP3 and ASC expressions, col I and col III, TIMP4 expressions, the apoptosis rate and necrosis rate were lower than in HG group. Daidzin, the antagonist of ALDH2 abolished the role of Alda-1. In summary, ALDH2 maybe is a key regulator in high glucose induced cardiomyocytes injury. Activation of ALDH2 prevented the happening of fibrosis, apoptosis and necroptosis in high glucose induced primary cardiomyocytes injury model, the protective effects were related to the inhibiting of oxidative stress and inflammation, changing of MMP14 and TIMP4, then inhibiting the happening of fibrosis, apoptosis and necroptosis. These findings advance our understanding of the intensive mechanisms of ALDH2's cardioprotection, and provide the targeted basis for clinical diabetes treatment.

Evaluation of lipoprotein-associated phospholipase A2 as a marker for renal microvasculopathy in adolescents with Type 1 diabetes

AIM

To assess the relevance of lipoprotein-associated phospholipase A2 activity as a diagnostic and prognostic marker for renal microvascular diseases.

METHODS

We analysed lipoprotein-associated phospholipase A2 activity and lysophosphatidylcholine levels (as a surrogate marker of oxidative stress) in 165 adolescents (aged 17.0 ± 2.3 years) with a history of Type 1 diabetes greater than 10 years. Clinical data were obtained from the German/Austrian nationwide Diabetes-Patients Follow-up (DPV) registry at blood collection and on average 2.4 ± 1.3 years later at follow-up. Relationships between lipoprotein-associated phospholipase A2 activity and clinical, demographic and laboratory variables, lysophosphatidylcholine levels and presence of albuminuria were evaluated by multivariable linear and logistic regression.

RESULTS

Lipoprotein-associated phospholipase A2 activity was higher in male than female adolescents (P = 0.002). Albuminuria was present in 14% (22/158) of participants at baseline, and 5% (4/86) of participants without albuminuria at baseline developed albuminuria until follow-up. Lipoprotein-associated phospholipase A2 activity was associated neither with present nor with incident albuminuria. Lysophosphatidylcholine did not correlate with lipoprotein-associated phospholipase A2 activity. Cross-sectional bivariate correlation as well as multivariable linear regression analysis revealed a negative correlation of lipoprotein-associated phospholipase A2 activity with HbA_1c and HDL-cholesterol.

CONCLUSIONS

Lipoprotein-associated phospholipase activity was not associated with surrogate markers for oxidative stress and early diabetic nephropathy. The association of decreased lipoprotein-associated phospholipase A2 activity with poor glucose control might limit its function as a predictor of micro- and macrovascular diseases in Type 1 diabetes.

Advanced Glycation End Products: Potential Mechanism and Therapeutic Target in Cardiovascular Complications under Diabetes

The occurrence and development of cardiovascular complications are predominantly responsible for the increased morbidity and mortality observed in patients with diabetes. Oxidative stress under hyperglycemia is currently considered the initial link to diabetic cardiovascular complications and a key node for the prevention and treatment of diabetes-related fatal cardiovascular events. Numerous studies have indicated that the common upstream pathway in the context of oxidative stress in the cardiovascular system under diabetic conditions is the interaction of advanced glycation end products (AGEs) with their receptors (RAGEs). Therefore, a further understanding of the relationship between oxidative stress and AGEs is of great significance for the prevention and treatment of cardiovascular complications in patients with diabetes. In this review, we will briefly summarize the recent research advances in diabetes with an emphasis on oxidative stress and its association with AGEs in diabetic cardiovascular complications.

Effects of Propolis Extract and Propolis-Derived Compounds on Obesity and Diabetes: Knowledge from Cellular and Animal Models

Propolis is a natural product resulting from the mixing of bee secretions with botanical exudates. Since propolis is rich in flavonoids and cinnamic acid derivatives, the application of propolis extracts has been tried in therapies against cancer, inflammation, and metabolic diseases. As metabolic diseases develop relatively slowly in patients, the therapeutic effects of propolis in humans should be evaluated over long periods of time. Moreover, several factors such as medical history, genetic inheritance, and living environment should be taken into consideration in human studies. Animal models, especially mice and rats, have some advantages, as genetic and microbiological variables can be controlled. On the other hand, cellular models allow the investigation of detailed molecular events evoked by propolis and derivative compounds. Taking advantage of animal and cellular models, accumulating evidence suggests that propolis extracts have therapeutic effects on obesity by controlling adipogenesis, adipokine secretion, food intake, and energy expenditure. Studies in animal and cellular models have also indicated that propolis modulates oxidative stress, the accumulation of advanced glycation end products (AGEs), and adipose tissue inflammation, all of which contribute to insulin resistance or defects in insulin secretion. Consequently, propolis treatment may mitigate diabetic complications such as nephropathy, retinopathy, foot ulcers, and non-alcoholic fatty liver disease. This review describes the beneficial effects of propolis on metabolic disorders.

Serum Albumin, but not Bilirubin, is Associated with Diabetic Chronic Vascular Complications in a Chinese Type 2 Diabetic Population

To identify the factors associated with serum total bilirubin (STB) and determine whether STB is independently associated with diabetic retinopathy (DR) or diabetic kidney disease (DKD), 1,665 Chinese patients with type 2 diabetes (T2DM) (248 outpatients newly diagnosed with T2DM [NDM] and 1,417 inpatients previously diagnosed with T2DM [PDM]) were studied. Clinical and biochemical information was collected, and a single nucleotide polymorphism (rs6704078) of the UGT1A1 gene was genotyped in 1,059 individuals. Multiple linear regression showed that STB was associated with haemoglobin concentration, platelet count, and serum triglyceride concentration in NDM and PDM patients, and with serum albumin, duration of diabetes, and smoking in PDM patients. In patients with PDM, multiple logistic regression revealed that serum albumin was associated with DR (odds ratio [OR] = 0.92, 95% confidence interval [CI]: 0.87-0.96, p = 0.001) and DKD (OR = 0.93, 95% CI: 0.88-0.98, p = 0.005) after adjustment for STB, STB-related factors, and risk factors for DR and DKD. In addition, patients with the T allele of rs6704078 had higher STB (13.2 [10.4-17.9] μmol/L versus 11.8 (9.4-14.8) μmol/L; p < 0.001) and similar risks of DR or DKD to those without the T allele. Thus, serum albumin, but not STB, is associated with DR and DKD.

Mesenchymal Stem Cells Reverse Diabetic Nephropathy Disease via Lipoxin A4 by Targeting Transforming Growth Factor β (TGF-β)/smad Pathway and Pro-Inflammatory Cytokines

BACKGROUND Diabetic nephropathy (DN) is the leading cause of end-stage renal disease. Mesenchymal stem cells (MSCs) treatment has been proved to be effective in DN models by protecting renal function and preventing fibrosis. However, the underlying mechanism is unclear. Previous research indicated diabetes and associated complications may be attributed to failed resolution of inflammation, which is deliberately regulated by pro-resolving lipids, including lipoxins (LXs), resolvins (Rv) D and E series, protectins, and maresins. In this study, we monitored pro-resolving mediators in a DN model to explore the mechanism of MSCs treatment. MATERIAL AND METHODS The DN model was induced by STZ injection in SD rats. UPLC-MS/MS was performed to determine pro-resolving lipids in kidney tissue and serum of DN model before and after MSCs treatment, as well as in supernatants of HBZY-1-MSCs co-culture. RESULTS LXA4 was highly accumulated in renal tissue of DN rats with MSCs treatment; ex vivo, LXA4 was significantly increased in the supernatants of HBZY-1 cells co-cultured with MSCs in a high-glucose (HG) medium. Western blot analysis indicated that ALX/FPR2, the receptor of LXA4, was markedly expressed in renal tissue of the DN-MSC group and HBZY-1 after incubating with MSCs in HG. Intraperitoneal injection of LXA4 inhibited renal fibrosis by targeting TGF-ß/Smad signaling and downregulated serum TNF-alpha, IL-6, IL-8, and IFN-γ in DN rats. Notably, all the protective effects induced by MSCs or LXA4 were abolished by ALX/FRP2 blocking. CONCLUSIONS Our results demonstrate that MSCs intervention prevented DN procession via the LXA4-ALX/FPR2 axis, which inhibited glomerulosclerosis and pro-inflammatory cytokines, eventually contributing to kidney homeostasis.