Role of the eNOS-NO system in regulating the antiproteinuric effects of VEGF receptor 2 inhibition in diabetes

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.

Glomerular cell cross talk in diabetic kidney diseases

Diabetic kidney disease (DKD) is a severe microvascular complication of diabetes mellitus. It is the leading inducement of end-stage renal disease (ESRD), and its global incidence has been increasing at an alarming rate. The strict control of blood pressure and blood glucose can delay the progression of DKD, but intensive treatment is challenging to maintain. Studies to date have failed to find a complete cure. The glomerulus's alterations and injuries play a pivotal role in the initiation and development of DKD. A wealth of data indicates that the interdependent relationship between resident cells in the glomerulus will provide clues to the mechanism of DKD and new ways for therapeutic intervention. This review summarizes the significant findings of glomerular cell cross talk in DKD, focusing on cellular signaling pathways, regulators, and potential novel avenues for treating progressive DKD.

Metformin prevents p-tau and amyloid plaque deposition and memory impairment in diabetic mice

Insulin deficiency or resistance can promote dementia and hallmarks of Alzheimer's disease (AD). The formation of neurofibrillary tangles of p-TAU protein, extracellular Aβ plaques, and neuronal loss is related to the switching off insulin signaling in cognition brain areas. Metformin is a biguanide antihyperglycemic drug used worldwide for the treatment of type 2 diabetes. Some studies have demonstrated that metformin exerts neuroprotective, anti-inflammatory, anti-oxidant, and nootropic effects. This study aimed to evaluate metformin's effects on long-term memory and p-Tau and amyloid β modulation, which are hallmarks of AD in diabetic mice. Swiss Webster mice were distributed in the following experimental groups: control; treated with streptozotocin (STZ) that is an agent toxic to the insulin-producing beta cells; STZ + metformin 200 mg/kg (M200). STZ mice showed significant augmentation of time spent to reach the target box in the Barnes maze, while M200 mice showed a significant time reduction. Moreover, the M200 group showed reduced GFAP immunoreactivity in hippocampal dentate gyrus and CA1 compared with the STZ group. STZ mice showed high p-Tau levels, reduced p-CREB, and accumulation of β-amyloid (Aβ) plaque in hippocampal areas and corpus callosum. In contrast, all these changes were reversed in the M200 group. Protein expressions of p-Tau, p-ERK, pGSK3, iNOS, nNOS, PARP, Cytochrome c, caspase 3, and GluN2A were increased in the parietal cortex of STZ mice and significantly counteracted in M200 mice. Moreover, M200 mice also showed significantly high levels of eNOS, AMPK, and p-AKT expression. In conclusion, metformin improved spatial memory in diabetic mice, which can be associated with reducing p-Tau and β-amyloid (Aβ) plaque load and inhibition of neuronal death.

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.

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.

VEGF and the diabetic kidney: More than too much of a good thing

Over a decade and a half has passed since the publication of early reports hinting at a pathogenetic role for vascular endothelial growth factor ("VEGF") in the development of diabetic kidney disease. In diabetic rats, renal mRNA levels of the VEGF-A isoform were upregulated and administration of a VEGF-A neutralizing antibody attenuated albuminuria: VEGF was "bad" in diabetic nephropathy. Since that time, our understanding of the complexity of the renal VEGF system has advanced. Unlike its experimental counterpart, human diabetic nephropathy is associated with diminished VEGF-A levels and experience in the oncological setting has taught us that VEGF blocking therapy can cause adverse renal effects in patients. Correspondingly, investigational studies in cultured cells and rodent models have demonstrated that the biological effects of the VEGF system are dependent not only on the amount of VEGF, but also the type of VEGF, its sites of action and the prevailing milieu. Here we reflect back on the discoveries that have been made since those initial reports that shone the spotlight on the importance of the VEGF system in the diabetic kidney and we consider that the role of VEGF in diabetic nephropathy extends well beyond being "too much of a good thing".

Vascular endothelial growth factor signaling is necessary for expansion of medullary microvessels during postnatal kidney development

Postnatal inhibition or deletion of angiotensin II (ANG II) AT1 receptors impairs renal medullary mircrovascular development through a mechanism that may include vascular endothelial growth factor (VEGF). The present study was designed to test if VEGF/VEGF receptor signaling is necessary for the development of the renal medullary microcirculation. Endothelial cell-specific immunolabeling of kidney sections from rats showed immature vascular bundles at postnatal day (P) 10 with subsequent expansion of bundles until P21. Medullary VEGF protein abundance coincided with vasa recta bundle formation. In human fetal kidney tissue, immature vascular bundles appeared early in the third trimester (GA27-28) and expanded in size until term. Rat pups treated with the VEGF receptor-2 (VEGFR2) inhibitor vandetanib (100 mg·kg−1·day−1) from P7 to P12 or P10 to P16 displayed growth retardation and proteinuria. Stereological quantification showed a significant reduction in total length (386 ± 13 vs. 219 ± 16 m), surface area, and volume of medullary microvessels. Vascular bundle architecture was unaffected. ANG II-AT1A/1B−/− mice kidneys displayed poorly defined vasa recta bundles whereas mice with collecting duct principal cell-specific AT1A deletion displayed no medullary microvascular phenotype. In conclusion, VEGFR2 signaling during postnatal development is necessary for expansion of the renal medullary microcirculation but not structural patterning of the vasa recta bundles, which occurs through an AT1-mediated mechanism.

The angiogenic effect of dracorhodin perchlorate on human umbilical vein endothelial cells and its potential mechanism of action

Hyperglycemia is the key clinical feature of diabetes, and may induce refractory wound lesions and impaired angiogenesis. Dracorhodin perchlorate (Dra) is the major ingredient of dragon's blood and it has been used as a medicine to treat chronic wounds, such as diabetic foot, since ancient times in many cultures. The current study aimed to investigate the effect of Dra on human umbilical vein endothelial cells (HUVECs) under high‑glucose (HG) stimulation and its potential mechanism. Dra was observed to increase the multiplication capacity of HUVECs both under low glucose (LG) and HG concentrations. Additionally, migration and tube formation in HUVECs was facilitated by Dra. The expression levels of Ras, mitogen‑activated protein kinase (MAPK) and vascular endothelial growth factor, which are key components of the Ras/MAPK pathway, were upregulated following Dra treatment. The present study is the first report, to the best of our knowledge, of the effects of Dra on wound healing, and the association with the Ras/MAPK signaling pathway.

The Puerarin improves renal function in STZ-induced diabetic rats by attenuating eNOS expression

Diabetic nephropathy (DN) is a serious complication and it leads to kidney failure. The endothelial nitric oxide synthases (eNOS) seems to be involved in the development and progression of DN. The Puerarin is a well-known Chinese traditional formula, which is widely used in clinical practice for the treatment of kidney disease. The present study was designed to investigate the renal protective effects of Puerarin on streptozotocin (STZ)-induced diabetic rats. Thirty Sprague-Dawley (SD) male rats were divided into three groups at random. The diabetic group and the Puerarin-treated group were intraperitoneally injected with STZ 65 mg/kg and the Puerarin-treated rats were intraperitoneally injected Puerarin 100 mg/kg/day for 4 weeks. The results showed the Puerarin could improve body weight, blood sugar, BUN and SCr levels, and reduce ultrastructural changes of kidney in diabetic rats. It also attenuated eNOS expression in glomerular endothelial cells and tubular cells of diabetic rats with Puerarin treatment (p < 0.05). The Puerarin had significant renal-protective effects for the diabetic nephropathy, possibly through regulating eNOS expression, and it may be used as a potential therapeutic reagent.

Vascular endothelial growth factor and the kidney: something of the marvellous

PURPOSE OF REVIEW

The vascular endothelial growth factor (VEGF) system is a multifarious network and an exemplar of an intraglomerular signalling pathway. Here, we review recent advances that highlight the subtle nature of the renal VEGF system and its influencers.

RECENT FINDINGS

The VEGF system is no longer considered as a simple paracrine, ligand-receptor interaction under the regulatory control of a soluble 'decoy', soluble fms-like tyrosine kinase-1 (sFLT1). Rather, the abundantly expressed, podocyte-derived VEGF isoform, VEGF-A, is now recognized to mediate both paracrine effects across the filtration barrier and autocrine actions, functioning to preserve the integrity of the cells from which it arises. Autocrine actions of the podocyte VEGF system extend beyond those of the VEGF-A isoform, however, with sFLT1 itself now appreciated as regulating podocyte morphology by binding to lipid microdomains. These and other functions of the VEGF system are profoundly affected by the presence, nature and abundance of influencers both intrinsic and extrinsic to the pathway, the latter most readily exemplified by the role of the cytokine in the diabetic kidney.

SUMMARY

The glomerular VEGF system plays a delicate, yet critical, role in preserving renal homeostasis. It may be intricate, but 'in all things of nature there is something of the marvellous'.