Protective effects of adiponectin on uncoupling of glomerular VEGF-NO axis in early streptozotocin-induced type 2 diabetic rats

Association between life's essential 8 and diabetic kidney disease: a population-based study

BACKGROUND AND AIMS

Diabetic patients are highly susceptible to cardiovascular and renal diseases. As a newly updated comprehensive index for assessing cardiovascular health (CVH), Life's essential 8 (LE8) has the potential to serve as a practical tool for evaluating the risk of diabetic kidney disease (DKD). We are committed to exploring the relationship between LE8 and its subscales with DKD in diabetic patients, aiming to provide preliminary evidence for the formulation of clinical strategies.

METHODS AND RESULTS

A total of 3,715 NHANES participants were included in this study, representing 18.9 million non-institutionalized residents of the United States. The mean age of all subjects was 59.72 years, and the weighted prevalence of DKD among diabetic patients was 36.39%. After adjusting for potential confounding factors, it was found that compared to the low LE8 group, the risk of developing DKD was significantly lower in the moderate LE8 group (OR: 0.54, 95% CI: 0.43-0.66) and the high LE8 group (OR: 0.18, 95% CI: 0.08-0.42). A similar trend was observed across the subscales of the LE8 score. The results of the fully adjusted restricted cubic spline regression analysis revealed a linear relationship between LE8 and its subscales with DKD. The findings remained consistent in subgroup and sensitivity analyses, with no significant interactions observed between subgroups.

CONCLUSION

Higher scores on the LE8 and its subscales were associated with a lower risk of developing DKD. However, the long-term causal relationship between LE8 and DKD risk necessitates further validation and exploration through large-scale, rigorously designed prospective studies.

Unveiling mechanisms underlying kidney function changes during sex hormone therapy

BACKGROUNDMen with chronic kidney disease (CKD) experience faster kidney function decline than women. Studies in individuals undergoing sex hormone therapy suggest a role for sex hormones, as estimated glomerular filtration rate (eGFR) increases with feminizing therapy and decreases with masculinizing therapy. However, effects on measured GFR (mGFR), glomerular and tubular function, and involved molecular mechanisms remain unexplored.METHODSThis prospective, observational study included individuals initiating feminizing (estradiol and antiandrogens; n = 23) or masculinizing (testosterone; n = 21) therapy. Baseline and 3-month assessments included mGFR (iohexol clearance), kidney perfusion (para-aminohippuric acid clearance), tubular injury biomarkers, and plasma proteomics.RESULTSDuring feminizing therapy, mGFR and kidney perfusion increased (+3.6% and +9.1%, respectively; P < 0.05) without increased glomerular pressure. Tubular injury biomarkers, including urine neutrophil gelatinase-associated lipocalin, epidermal growth factor (EGF), monocyte chemoattractant protein-1, and chitinase 3-like protein 1 (YKL-40), decreased significantly (-53%, -42%, -45%, and -58%, respectively). During masculinizing therapy, mGFR and kidney perfusion remained unchanged, but urine YKL-40 and plasma tumor necrosis factor receptor 1 (TNFR-1) increased (+134% and +8%, respectively; P < 0.05). Proteomic analysis revealed differential expression of 49 proteins during feminizing and 356 proteins during masculinizing therapy. Many kidney-protective proteins were positively associated with estradiol and negatively associated with testosterone, including proteins involved in endothelial function (SFRP4, SOD3), inflammation reduction (TSG-6), and maintaining kidney tissue structure (agrin).CONCLUSIONSex hormones influence kidney physiology, with estradiol showing protective effects on glomerular and tubular function, while testosterone predominantly exerts opposing effects. These findings emphasize the role of sex hormones in sexual dimorphism observed in kidney function and physiology and suggest new approaches for sex-specific precision medicine.TRIAL REGISTRATIONDutch Trial Register (ID: NL9517); ClinicalTrials.gov (ID: NCT04482920).

Transplantation of Human Amniotic Mesenchymal Stem Cells Up-Regulates Angiogenic Factor Expression to Attenuate Diabetic Kidney Disease in Rats

BACKGROUND AND AIMS

Diabetic kidney disease (DKD) is a prevalent and intractable microvascular complication of diabetes mellitus (DM), the process of which is closely related to abnormal expression of angiogenesis-regulating factors (ARFs). Stem cell transplantation might be a novel strategy for treating DKD. This study aims to explore the effect of transplantation of human amniotic mesenchymal stem cells (hAMSCs) on renal microangiopathy in a type 1 DKD rat model (T1DRM).

METHODS

Seventy-two rats were randomly divided into three groups, including normal control group, DKD group, and hAMSCs transplantation group. T1DRM was established using a rat tail vein injection of streptozotocin (STZ) (55 mg/kg). hAMSCs were obtained from placental amniotic membranes during cesarean delivery and transplanted at 3 and 4 weeks through penile veins. At 6, 8, and 12 weeks following transplantation, blood glucose levels, renal function, pathological kidney alterations, and the expressions of ARFs' mRNA and protein were analyzed.

RESULTS

In T1DRM, transplanted hAMSCs that were homed at the injured site of kidneys increased ARFs' expression and decreased blood glucose levels. Compared to the DKD group, the levels of 24-h urinary protein, serum creatinine, urea, and kidney injury molecule-1 (KIM-1) were reduced in hAMSCs transplantation group. In terms of renal pathology such as the degree of basement membrane thickening, hAMSCs transplantation was also less severe than the DKD group, thereby alleviating kidney injury.

CONCLUSION

hAMSCs transplantation might ameliorate STZ-induced chronic kidney injury through increasing ARFs' expression in kidneys and lowering blood glucose levels.

Biological Activity of c-Peptide in Microvascular Complications of Type 1 Diabetes-Time for Translational Studies or Back to the Basics?

People with type 1 diabetes have an increased risk of developing microvascular complications, which have a negative impact on the quality of life and reduce life expectancy. Numerous studies in animals with experimental diabetes show that c-peptide supplementation exerts beneficial effects on diabetes-induced damage in peripheral nerves and kidneys. There is substantial evidence that c-peptide counteracts the detrimental changes caused by hyperglycemia at the cellular level, such as decreased activation of endothelial nitric oxide synthase and sodium potassium ATPase, and increase in formation of pro-inflammatory molecules mediated by nuclear factor kappa-light-chain-enhancer of activated B cells: cytokines, chemokines, cell adhesion molecules, vascular endothelial growth factor, and transforming growth factor beta. However, despite positive results from cell and animal studies, no successful c-peptide replacement therapies have been developed so far. Therefore, it is important to improve our understanding of the impact of c-peptide on the pathophysiology of microvascular complications to develop novel c-peptide-based treatments. This article aims to review current knowledge on the impact of c-peptide on diabetic neuro- and nephropathy and to evaluate its potential therapeutic role.

Liraglutide improves obesity-induced renal injury by alleviating uncoupling of the glomerular VEGF-NO axis in obese mice

Obesity-related kidney disease is associated with generalized endothelial dysfunction. Liraglutide, a glucagon-like peptide-1 agonist, has cardiovascular-renal protective effects in patients with diabetes. In this study, the ability of liraglutide to reduce urinary albumin excretion by alleviating glomerular vascular endothelial growth factor-nitric oxide (VEGF-NO) axis uncoupling was assessed in high fat diet-induced obese mice. C57BL/6J mice were divided into control and obesity groups, treated with or without liraglutide (200 μg/kg/day). Blood biochemistry and urinary albumin excretion were measured. Glomerular VEGF and the AMPK-endothelial nitric oxide synthase (eNOS) pathway were assayed by western blotting. Glomerular NO, renal haeme oxygenase-1 activity, and malondialdehyde levels were also measured. Treatment of obese mice with liraglutide led to significant reductions in body weight gain (46 ± 1 g vs 55 ± 1 g, P < .0001), visceral fat (8.9 ± 0.6 g vs 14.5 ± 0.6 g, P < .0001), perirenal fat (2.9 ± 0.2 g vs 5.4 ± 0.3 g, P < .0001), and free fatty acid (1.71 ± 0.12 mmol/L vs 1.02 ± 0.08 mmol/L, P < .0001). Liraglutide significantly improved glucose homeostasis, which was impaired in obese mice. Liraglutide reduced urinary albumin excretion and glomerular hypertrophy in obese mice. Additionally, liraglutide significantly decreased VEGF and increased glomerular NO production in glomeruli, indicating restoration of the glomerular VEGF-NO axis. Furthermore, liraglutide activated the glomerular AMPK-eNOS pathway in obese mice, upregulated renal haeme oxygenase-1 activity, and reduced the renal malondialdehyde levels in obese mice. In conclusion, liraglutide reduced microalbuminuria and ameliorated renal injury by alleviating the uncoupling of the glomerular VEGF-NO axis.

Role of VEGF-A and LRG1 in Abnormal Angiogenesis Associated With Diabetic Nephropathy

Diabetic nephropathy (DN) is an important public health concern of increasing proportions and the leading cause of end-stage renal disease (ESRD) in diabetic patients. It is one of the most common long-term microvascular complications of diabetes mellitus that is characterized by proteinuria and glomerular structural changes. Angiogenesis has long been considered to contribute to the pathogenesis of DN, whereas the molecular mechanisms of which are barely known. Angiogenic factors associated with angiogenesis are the major candidates to explain the microvascular and pathologic finds of DN. Vascular endothelial growth factor A (VEGF-A), leucine-rich α-2-glycoprotein 1, angiopoietins and vasohibin family signal between the podocytes, endothelium, and mesangium have important roles in the maintenance of renal functions. An appropriate amount of VEGF-A is beneficial to maintaining glomerular structure, while excessive VEGF-A can lead to abnormal angiogenesis. LRG1 is a novel pro-angiogenic factors involved in the abnormal angiogenesis and renal fibrosis in DN. The imbalance of Ang1/Ang2 ratio has a role in leading to glomerular disease. Vasohibin-2 is recently shown to be in diabetes-induced glomerular alterations. This review will focus on current understanding of these angiogenic factors in angiogenesis and pathogenesis associated with the development of DN, with the aim of evaluating the potential of anti-angiogenesis therapy in patients with DN.

Novel insight into perirenal adipose tissue: A neglected adipose depot linking cardiovascular and chronic kidney disease

Obesity is associated with adverse metabolic diseases including cardiovascular disease (CVD) and chronic kidney disease (CKD). These obesity-related diseases are highly associated with excess fat accumulation in adipose tissue. However, emerging evidence indicates that visceral adiposity associates more with metabolic and cardiovascular risk factors. Perirenal adipose tissue, surrounding the kidney, is originally thought to provides only mechanical support for kidney. However, more studies demonstrated perirenal adipose tissue have a closer association with renal disease than other visceral fat deposits in obesity. Additionally, perirenal adipose tissue is also an independent risk factor for CKD and even associated more with CVD. Thus, perirenal adipose tissue may be a connection of CVD with CKD. Here, we will provide an overview of the perirenal adipose tissue, a neglected visceral adipose tissue, and the roles of perirenal adipose tissue linking with CVD and CKD and highlight the perirenal adipose tissue as a potential strategy for future therapeutics against obesity-related disease.

Adiponectin for the treatment of diabetic nephropathy

The metabolic burden caused by hyperglycemia can result in direct and immediate metabolic injuries, such as oxidative stress and tissue inflammation, in the kidney. Furthermore, chronic hyperglycemia can lead to substantial structural changes such as formation of advanced glycation end-products, glomerular and tubular hypertrophy, and tissue fibrosis. Glomerular hypertrophy renders podocytes vulnerable to increased glomerular filtration, leading to podocyte instability and loss. Thus, prevention of glomerular hypertrophy and attenuation of glomerular hyperfiltration may have therapeutic potential for diabetic nephropathy (DN). Adiponectin is an adipokine that improves insulin sensitivity in obesity-related metabolic disorders, including diabetes, but its efficacy is unknown. Moreover, the recently developed adiponectin receptor agonist, AdipoRon, shows therapeutic potential for DN. In this review, we focus on the role of glomerular hypertrophy in the pathogenesis of DN and discuss the role of adiponectin in its prevention.

C1q/TNF-related protein 9 improves the anti-contractile effects of perivascular adipose tissue via the AMPK-eNOS pathway in diet-induced obese mice

The anti-contractile property of perivascular adipose tissue (PVAT) is abolished through an endothelium-dependent pathway in obesity. C1q/tumor necrosis factor-related protein (CTRP)9 improved endothelial function by promoting endothelium-dependent vasodilatation. The aims of this study were to investigate whether CTRP9 improves the anti-contractile effect of PVAT and protects against PVAT dysfunction in obese mice. The mice were treated with a high-fat diet with or without CTRP9 treatment. Thoracic aortas with or without PVAT (PVAT+ or PVAT-) were prepared, and concentration-dependent responses to phenylephrine were measured. Obese mice showed a significantly increased contractile response, which was suppressed by CTRP9 treatment both with and without PVAT. PVAT significantly reduced the anti-contractile effect in obese mice, which was partially restored by CTRP9 treatment. Treatment of the aortic rings (PVAT+) with inhibitors of AMP protein kinase (AMPK), Akt and endothelial nitric oxide synthase (eNOS) attenuated the beneficial effect of CTRP9 on PVAT. Similar results were observed when we pretreated the aortic rings with CTRP9 ex vivo. CTRP9 significantly enhanced the phosphorylation levels of AMPK, Akt and eNOS, and reduced superoxide production and TNF-α levels in PVAT from obese mice. Our study suggests that CTRP9 enhanced the anti-contractile effect of PVAT and improved PVAT function by activating the AMPK-eNOS pathway in obese mice.

Macro- and microvascular endothelial dysfunction in diabetes

Endothelial cells, as well as their major products nitric oxide (NO) and prostacyclin, play a key role in the regulation of vascular homeostasis. Diabetes mellitus is an important risk factor for cardiovascular disease. Diabetes-induced endothelial dysfunction is a critical and initiating factor in the genesis of diabetic vascular complications. The present review focuses on both large blood vessels and the microvasculature. The endothelial dysfunction in diabetic macrovascular complications is characterized by reduced NO bioavailability, poorly compensated for by increased production of prostacyclin and/or endothelium-dependent hyperpolarizations, and increased production or action of endothelium-derived vasoconstrictors. The endothelial dysfunction of microvascular complications is primarily characterized by decreased release of NO, enhanced oxidative stress, increased production of inflammatory factors, abnormal angiogenesis, and impaired endothelial repair. In addition, non-coding RNAs (microRNAs) have emerged as participating in numerous cellular processes. Thus, this reviews pays special attention to microRNAs and their modulatory role in diabetes-induced vascular dysfunction. Some therapeutic strategies for preventing and restoring diabetic endothelial dysfunction are also highlighted.

Therapeutic angiogenesis by vascular endothelial growth factor supplementation for treatment of renal disease

PURPOSE OF REVIEW

Vascular endothelial growth factors (VEGFs) influence renal function through angiogenesis, with VEGF-A being the most potent inducer of vascular formation. In the normal glomerulus, tight homeostatic balance is maintained between the levels of VEGF-A isoforms produced by podocyte cells, and the VEGF receptors (VEGFRs) expressed by glomerular endothelial, mesangial, and podocyte cells. Renal disease occurs when this homeostatic balance is lost, manifesting in the abnormal autocrine and paracrine VEGF-A/VEGFR signaling, ultrastructural glomerular and tubular damage, and impaired filtration.

RECENT FINDINGS

Preclinical disease models of ischemic renal injury, including acute ischemia/reperfusion, thrombotic microangiopathy, and chronic renovascular disease, treated with exogenous VEGF supplementation demonstrated therapeutic efficacy. These results suggest a therapeutic VEGF-A paracrine effect on endothelial cells in the context of acute or chronic obstructive ischemia. Conversely, renal dysfunction in diabetic nephropathy appears to occur through an upregulated VEGF autocrine effect on podocyte cells, which is exacerbated by hyperglycemia. Therefore, VEGF supplementation therapy may be contraindicated for treatment of diabetic nephropathy, but specific results will depend on dose and on the specific site of VEGF delivery. A drug delivery system that demonstrates cell specificity for glomerular or peritubular capillaries could be employed to restore balance to VEGF-A/VEGFR2 signaling, and by doing so, prevent the progression to end-stage renal disease.

SUMMARY

The review discusses the preclinical data available for VEGF supplementation therapy in models of renal disease.

Resveratrol increases AdipoR1 and AdipoR2 expression in type 2 diabetic nephropathy

BACKGROUND

Adiponectin has multiple functions including insulin sensitization, anti-inflammation and antiatherogenesis in various organs. Adiponectin activates 5'-adenosine monophosphate-activated protein kinase (AMPK) and peroxisome proliferator-activated receptor (PPAR)α via the adiponectin receptor (AdipoR) 1 and 2, which are critical for regulating lipids and glucose homeostasis and for controlling oxidative stress. We investigated whether resveratrol can inhibit renal damage in type 2 diabetic db/db mice and the underlying mechanisms of its effects.

METHODS

Four groups of male C57 BLKS/J db/m and db/db mice and human glomerular endothelial cells (HGECs) were used. Resveratrol was administered to diabetic and nondiabetic mice by oral gavage for 12 weeks starting at 8 weeks of age.

RESULTS

In db/db mice, resveratrol increased serum adiponectin levels and decreased albuminuria, glomerular matrix expansion, inflammation and apoptosis in the glomerulus. Resveratrol increased the phosphorylation of AMPK and silent information regulator T1 (SIRT1), and decreased phosphorylation of downstream effectors class O forkhead box (FoxO)1 and FoxO3a via increasing AdipoR1 and AdipoR2 in the renal cortex. Furthermore, resveratrol increased expression of PPARγ coactivator (PGC)-1α, estrogen-related receptor-1α, and phosphorylated acetyl-CoA carboxylase and decreased sterol regulatory element-binding protein 1. This effect lowered the content of nonesterified fatty acid and triacylglycerol in the kidneys, decreasing apoptosis, oxidative stress and activating endothelial nitric oxide synthase. Resveratrol prevented cultured HGECs from undergoing high-glucose-induced oxidative stress and apoptosis by activating the AMPK-SIRT1-PGC-1α axis and PPARα through increases in AdipoR1 and AdipoR2 expression.

CONCLUSIONS

These results suggest that resveratrol prevents diabetic nephropathy by ameliorating lipotoxicity, oxidative stress, apoptosis and endothelial dysfunction via increasing AdipoR1 and AdipoR2 expression.

Relationship of adiponectin to markers of oxidative stress in type 2 diabetic patients: influence of incipient diabetes-associated kidney disease

PURPOSE

Adiponectin may be beneficial in incipient chronic kidney disease by antagonizing oxidative stress. We evaluated adiponectin, malondialdehyde (MDA), and superoxide dismutase (SOD), in type 2 diabetes mellitus patients (T2DP) with and without incipient nephropathy.

METHODS

T2DP with glomerular filtration rate (GFR) >30 ml/min were compared with 20 healthy controls. Clinical and laboratory evaluations, levels of MDA (fluorimetric thiobarbituric test), SOD (cytochrome reduction method) and adiponectin (ELISA) were obtained.

RESULTS

Sixty-four patients (GFR 91.44 ± 38.50 ml/min, urinary albumin-to-creatinine ratio [UACR] 20.81 [4.64-72.88 mg/g]) were included. MDA was higher in T2DP than in controls: 3.97 (2.43-4.59) versus 1.35 (1.16-1.81) nmol/ml, p < 0.0001. MDA correlated with glycated hemoglobin (r = 0.40, p = 0.001), adiponectin (r = -0.28, p = 0.03), systolic blood pressure (r = -0.28, p = 0.03) and SOD (r = -0.35, p = 0.005); adiponectin (p = 0.01) and glycated hemoglobin (p = 0.02) remained significant predictors of MDA in multiple regression analysis. SOD was negatively correlated with glycemia (r = -0.71, p < 0.0001) and glycated hemoglobin (r = -0.5, p < 0.0001). When patients were divided according to a ROC-derived adiponectin cutoff of 8.9 µg/ml, patients with higher adiponectin had lower MDA, [2.55 (2.35-3.60) vs. 4.10 (2.89-5.31) nmol/ml, p = 0.005] but similar SOD levels. In T2DP with nephropathy (GFR < 60 ml/min or UACR > 30 mg/g), the correlation of adiponectin with MDA was stronger, (r = -0.51, p = 0.004) confirmed in multiple regression analysis (p = 0.03). Adiponectin was not correlated with MDA, and SOD was inversely related to MDA in patients without nephropathy.

CONCLUSION

Adiponectin is a significant predictor of MDA in early diabetic nephropathy, whereas SOD strongly depends only on glycemic control and is not directly related to adiponectin.