Development Of Diabetic Microvascular Complications Research Articles

Diabetic microvascular complications and associated factors in patients with type 2 diabetes in Southern Ethiopia.

Microvascular complications are long-term complications that affect small blood vessels, usually developed in diabetes, and are primary causes of end-stage renal disease, several painful neuropathies, and blindness. Thus, this study aimed to determine diabetic microvascular complications and factors associated with them among patients with type 2 diabetes. An institution-based cross-sectional study was conducted among 378 type 2 diabetes patients. The presence of at least one diabetic microvascular complications diagnosed by physicians and found on the record was considered to have microvascular complications. The data was collected by reviewing the medical records of T2DM patients who were on follow-up from January 1, 2012, to December 31, 2021. The collected data was entered into EpiData version 3.1 and analyzed by Stata version 14. Bivariate and multivariable logistic regression were used to identify statistically significant risk factors for diabetic microvascular complications at p-value < 0.05. Patients with type 2 diabetes mellitus had a prevalence of diabetic microvascular complications of 26.5% (95% CI: 22.0%, 30.9%). Diabetic neuropathy was the highest (13.2%), followed by diabetic nephropathy (12.4%), and diabetic retinopathy (6.4%). Increasing age, poor glycemic control, hypertension comorbidity, anemia, positive proteinuria, a longer duration of type 2 diabetes mellitus, and hypercholesterolemia were significantly associated factors with diabetic microvascular complications. Diabetic microvascular complications were highly prevalent. Therefore, the study suggests that interventional strategies should be taken for poor glycemic control, hypertension comorbidity, anemia, positive proteinuria, and hypercholesterolemia to control the development of diabetic microvascular complications in patients with type 2 diabetes.

Virtual screening for chemical analogues similar to phytochemicals that inhibit aldose reductase in the development of diabetic microvascular complications

Background: The polyol pathway contributes to the development of diabetic complications but can be inhibited by plant phytochemicals. This study aimed at assessing analogs of specific flavonoids that delay onset of microvascular complications with better pharmacokinetic and toxicology profiles. Methods: An in silico study design was employed. The phytochemicals luteolin and quercetin were selected. Analogs were obtained from ZINC database and prepared using Avogadro software. Docking analysis was done using AutoDock Vina embedded in Chimera. Ligand enzyme interaction was carried out using Biovia Discovery studio. Pharmacokinetic and toxicological profiling was carried out using SWISSADME and protox server. A total of 40 analogues were analyzed. Sulindac was used as the comparator besides original phytochemicals. Results: Docking analysis showed both luteolin and quercetin (-9.7) had a slightly stronger affinity for inhibiting aldose reductase compared with sulindac (-9.6). Eight analogues of luteolin and 14 analogues of quercetin showed stronger affinity with the highest registered at -10.6. Both luteolin and quercetin did not violate the Lipinski rule, had high GI absorption, did not cross the blood brain barrier nor were p-glycoprotein substrates, and inhibited CYP1A2, CYP2D6 and CYP3A4. The LD50 of luteolin (3,919 mg/kg) was high indicating excellent safety profile. Quercetin had a low LD50 (159 mg/kg). All 22 analogues exhibited similar pharmacokinetic profiles to their respective phytochemical. However, they did differ in terms of docking strength and toxicology analysis. Six out of the eight luteolin analogues had LD50=3,919 mg/kg, while the remaining had LD50=159 mg/kg. Five quercetin analogues had LD50 of 159 mg/kg, another five had LD50=3,919 mg/kg and the rest had LD50=4,000 mg/kg, while the other two had a LD50 of 5,000 mg/kg. Conclusions: In conclusion, six ZINC compounds similar to luteolin and nine similar to quercetin had stronger binding affinity for aldose reductase and superior toxicological profile compared to parent phytochemicals.

The role of protein kinase C in diabetic microvascular complications.

Protein kinase C (PKC) is a family of serine/threonine protein kinases, the activation of which plays an important role in the development of diabetic microvascular complications. The activation of PKC under high-glucose conditions stimulates redox reactions and leads to an accumulation of redox stress. As a result, various types of cells in the microvasculature are influenced, leading to changes in blood flow, microvascular permeability, extracellular matrix accumulation, basement thickening and angiogenesis. Structural and functional disorders further exacerbate diabetic microvascular complications. Here, we review the roles of PKC in the development of diabetic microvascular complications, presenting evidence from experiments and clinical trials.

The Emerging Role of Continuous Glucose Monitoring in the Management of Diabetic Peripheral Neuropathy: A Narrative Review.

The aim of this narrative review is to present data on the role of continuous glucose monitoring (CGM) in the management of peripheral diabetic neuropathy (DPN) among individuals with type 1 and type 2 diabetes mellitus. Adequate glycaemic control is crucial to prevent the development or progression of DPN. CGM systems are valuable tools for improving glycaemic control and reducing glycaemic variability (GV). Chronic hyperglycaemia is known to be a risk factor for the development of diabetic microvascular complications, including DPN. In addition, there is now evidence that GV, evaluated by mean amplitude of glycaemic excursions, may be a novel factor in the pathogenesis of diabetic complications. Increased GV appears to be an independent risk factor for DPN and correlates with painful neuropathy. Similarly, time-in-range correlates positively with peripheral nerve function and negatively with sudomotor dysfunction. However, relevant studies are rather limited in scope, and the vast majority are cross-sectional and use different methodologies for the assessment of DPN. Therefore, the causal relationship between CGM-derived data and the development of DPN cannot be firmly established at the present time. It also remains to be elucidated whether CGM measures can be considered the new therapeutic targets for DPN management.

Adiponectin accumulation in the retinal vascular endothelium and its possible role in preventing early diabetic microvascular damage

Adiponectin (APN), a protein abundantly secreted from adipocytes, has been reported to possess beneficial effects on cardiovascular diseases in association with its accumulation on target organs and cells by binding to T-cadherin. However, little is known about the role of APN in the development of diabetic microvascular complications, such as diabetic retinopathy (DR). Here we investigated the impact of APN on the progression of early retinal vascular damage using a streptozotocin (STZ)-induced diabetic mouse model. Our immunofluorescence results clearly showed T-cadherin-dependent localization of APN in the vascular endothelium of retinal arterioles, which was progressively decreased during the course of diabetes. Such reduction of retinal APN accompanied the early features of DR, represented by increased vascular permeability, and was prevented by glucose-lowering therapy with dapagliflozin, a selective sodium-glucose co-transporter 2 inhibitor. In addition, APN deficiency resulted in severe vascular permeability under relatively short-term hyperglycemia, together with a significant increase in vascular cellular adhesion molecule-1 (VCAM-1) and a reduction in claudin-5 in the retinal endothelium. The present study demonstrated a possible protective role of APN against the development of DR.

Leukocytic dysregulation in children with type 1 diabetes: relation to diabetic vascular complications.

Growing evidences highlight the role of the innate immune response in the pathogenesis of type 1 diabetes (T1D) vascular complications. Neutrophil lymphocytic ratio (NLR) and platelet lymphocytic ratio (PLR) are inexpensive but novel markers of chronic inflammation might have prognostic value in children with T1D. To study NLR and PLR levels in children with T1D in comparison to matched controls and correlate them with fraction-C of glycosylated hemoglobin (HbA1C) and micro-vascular complications. Hundred children with T1D were compared to 100 matched healthy controls. History included diabetes duration, insulin dose and frequency of hypoglycemic attacks. Fundus examination and the simple rapid neuropathy disability score were done. HbA1C, fasting lipids, urinary albumin excretion and complete blood count were measured with assessment of NLR and PLR. NLR was significantly higher (p = 0.008) and PLR was significantly lower (p = 0.007) in children with T1D than controls. NLR was positively correlated while PLR was negatively correlated with HbA1C, diabetes duration, fasting cholesterol, triglycerides and LDL. NLR was significantly higher (p < 0.001) and PLR was significantly lower (p = 0.005) in children with microvascular complications than those without. Moreover, multivariate logistic regression revealed that microvascular complications were independently associated with NLR (p = 0.013) and PLR (p = 0.004). Children with T1D had significantly higher NLR and lower PLR compared to controls. These changes were more evident in those with diabetic microvascular complications than those without. Furthermore, NLR was positively correlated and PLR was negatively correlated to HbA1C, diabetes duration and hyperlipidemia. Hence, NLR and PLR can be a potential indicator for the risk of development of diabetic microvascular complications in children with T1D.

Advanced glycation end products induce endothelial hyperpermeability via β-catenin phosphorylation and subsequent up-regulation of ADAM10.

Endothelial hyperpermeability is the initial event in the development of diabetic microvascular complications, and advanced glycation end products (AGEs) are suggested to cause much of the endothelial hyperpermeability associated with diabetes mellitus, but the molecular mechanism remains to be characterized. β‐catenin reportedly plays dual functions in maintaining normal endothelial permeability by serving both as an adhesive component and a signal transduction component. Here, we found that AGEs induced the phosphorylation of β‐catenin at residues Y654 and Y142 and the endothelial hyperpermeability was reversed when the two residues were blocked. In mechanism, phosphorylation of Y654 was blocked by Src inactivation, whereas phosphorylation of Y142 was reduced by a focal adhesion kinase inhibitor. β‐catenin Y654 phosphorylation induced by AGEs facilitated the dissociation of vascular endothelial (VE)‐cadherin/β‐catenin and the impairment of adherens junctions (AJs), whereas β‐catenin Y142 phosphorylation favoured the dissociation of β‐catenin and α‐catenin. Further investigation revealed that β‐catenin Y142 phosphorylation was required for AGEs‐mediated β‐catenin nuclear translocation, and this nuclear‐located β‐catenin subsequently activated the TCF/LEF pathway. This pathway promotes the transcription of the Wnt target, ADAM10 (a disintegrin and metalloprotease 10), which mediates VE‐cadherin shedding and leads to further impairment of AJs. In summary, our study showed the role of β‐catenin Y654 and Y142 phosphorylation in AGEs‐mediated endothelial hyperpermeability through VE‐cadherin/β‐catenin/α‐catenin dissociation and up‐regulation of ADAM10, thereby advancing our understanding of the underlying mechanisms of AGEs‐induced microvascular hyperpermeability.

The role of protein oxidation in the development of diabetic microvascular complications

OBJECTIVE:The role of protein oxidation in the development of diabetic microvascular complications was investigated.METHODS:In total, 266 participants were split into five groups: Group 1; diabetes mellitus for at least 10 years without any complications, Group 2; diabetic nephropathy, Group 3; diabetic neuropathy, Group 4; diabetic retinopathy, and Group 5; control group. Thiol, disulfide, ferroxidase, and ischemia-modified albumin (IMA) levels were analyzed in the serum.RESULTS:Native thiol, total thiol, and native thiol/total thiol were lower in Group 4 than Groups 1, 3, and 5 (p<0.001). However, disulfide/native thiol and disulfide/total thiol were higher in Group 4 than all other groups (p<0.001). IMA was higher in Groups 3 and 4 than all other groups (p<0.001). Ferroxidase was lower in Groups 3 and 4 than Group 2 (p<0.001).CONCLUSION:Thiol-disulfide homeostasis impairment in favor of disulfide may have a function in the progress of diabetic retinopathy. Furthermore, the disruptions of IMA and ferroxidase levels involve in the development of diabetic retinopathy and neuropathy.

TLR2 knockout protects against diabetes-mediated changes in cerebral perfusion and cognitive deficits.

The risk of cognitive decline in diabetes (Type 1 and Type 2) is significantly greater compared with normoglycemic patients, and the risk of developing dementia in diabetic patients is doubled. The etiology for this is likely multifactorial, but one mechanism that has gained increasing attention is decreased cerebral perfusion as a result of cerebrovascular dysfunction. The innate immune system has been shown to play a role in diabetic vascular complications, notably through the Toll-like receptor (TLR)-stimulated release of proinflammatory cytokines and chemokines that lead to vascular damage. TLR2 has been implicated in playing a crucial role in the development of diabetic microvascular complications, such as nephropathy, and thus, we hypothesized that TLR2-mediated cerebrovascular dysfunction leads to decreased cerebral blood flow (CBF) and cognitive impairment in diabetes. Knockout of TLR2 conferred protection from impaired CBF in early-stage diabetes and from hyperperfusion in long-term diabetes, prevented the development of endothelium-dependent vascular dysfunction in diabetes, created a hyperactive and anxiolytic phenotype, and protected against diabetes-induced impairment of long-term hippocampal and prefrontal cortex-mediated fear learning. In conclusion, these findings support the involvement of TLR2 in the pathogenesis of diabetic vascular disease and cognitive impairment.

C-peptide antioxidant adaptive pathways in β cells and diabetes.

In this review, we present findings that support autocrine cell protection by C-peptide in the context of clinical studies of type 1 diabetes (T1D), which universally measure C-peptide serum levels as a surrogate for β cell functional mass. Over the last decade, evidence has accumulated that supports models in which C-peptide, cosecreted with insulin by pancreatic β cells, acts on peripheral targets including the vascular endothelium to reduce oxidative stress and apoptosis subsequent to exposure to diabetic insults. In parallel, as assays have become more sensitive, C-peptide has been detected in the circulation of most subjects with T1D where higher C-peptide levels are associated with fewer and slower development of diabetic microvascular complications, consistent with antioxidant protection by C-peptide. Clinical trials investigating C-peptide-replacement therapy effects have demonstrated amelioration of T1D nephropathy and neuropathy. Recently, the antioxidant action of C-peptide was extended to the β cells secreting it, that is an autocrine mechanism. Autocrine protection has major implications for the treatment of diabetes because the more C-peptide secreted, the more protection provided to the same β cells resulting in a slower decay in β cell functional mass over the time course of disease. Why β cells evolved to cosecrete an antioxidant C-peptide hormone together with the glycaemia-lowering insulin hormone is explored in the context of proposed evolutionary advantages of physiologically transient oxidative stress and insulin resistance as an adaptation for survival through times of fuel scarcity. The importance of recognizing autocrine C-peptide protection of functional β cell mass in observational clinical studies, and its therapeutic implications in interventional C-peptide-replacement studies, will be discussed.

Fenofibrate suppresses cellular metabolic memory of high glucose in diabetic retinopathy via a sirtuin 1-dependent signalling pathway.

Inflammation is a major contributing factor in the development of diabetic microvascular complications, regardless of whether improved glycaemic control is achieved. Studies have increasingly indicated that fenofibrate, a lipid‑lowering therapeutic agent in clinical use, exerts a potential anti‑inflammatory effect, which is mediated by sirtuin 1 (SIRT1; an NAD+‑dependent deacetylase) in endothelial cells. The aim of the present study was to investigate the inhibitory effect of fenofibrate on metabolic memory (via the regulation of SIRT1), and inflammatory responses in cell and animal models of diabetic retinopathy (DR). The data demonstrated that high glucose treatment in human retinal endothelial cells (HRECs) inhibited the expression and deacetylase activity of SIRT1. The reduction of SIRT1 expression and deacetylase activity persisted following a return to normal glucose levels. Furthermore, nuclear factor‑κB expression was observed to be negatively correlated with SIRT1 expression and activity in HRECs under high glucose levels and the subsequent return to normal glucose levels. Fenofibrate treatment abrogated these changes. Knockdown of SIRT1 attenuated the effect of fenofibrate on high glucose‑induced NF‑κB expression. In addition, fenofibrate upregulated SIRT1 expression through peroxisome proliferator‑activated receptor α in high glucose‑induced metabolic memory. These findings indicate that fenofibrate is important in anti‑inflammatory processes and suppresses the cellular metabolic memory of high glucose‑induced stress via the SIRT1‑dependent signalling pathway. Thus, treatment with fenofibrate may offer a promising therapeutic strategy for halting the development of DR and other complications of diabetes.

Genetics and diabetic microangiopathy

Human vital organ systems may be affected by diabetic microvascular complications (DMC), lead to public health difficulty. Recent evidence shows genetic factors provide to the genetic and structural variants, and/or variability in disease severity play important roles in the development of DMC among the patients with similar risk factors. Several genetic loci have discovered that figure the risk of DMC as detected by genetic linkage studies. Genetic variants demonstrate for susceptibility to DMC as detected by genetic association studies. Copy number variation and interactions of gene Χ environment have been discovered by compelling analysis of structural variants. Mitochondrial DNA also acts a definite role in the development of DMC. Sequencing technologies have light important horizon on detecting rare and common genetic loci. This review focuses on the common science of the genetic context of DMC. Finally, recognition of genes or genetic loci and structural variants providing to risk of or guarding from DMC will help intuition the underlying mechanism of DMC, with conclusive suggestions for the evolvement of new medicine for diabetes mellitus complications.

Diabetes Mellitus: Novel Insights, Analysis and Interpretation of Pathophysiology and Complications Management with Imidazole-Containing Peptidomimetic Antioxidants

Patients suffering from the severe complications associated with both insulin- (IDDM) and non-insulin-dependent diabetes mellitus (NIDDM): nephropathy, retinopathy, neuropathy, and atherosclerosis are still largely left without a prospect of an efficient treatment. Chronic hyperglycaemia, the primary clinical manifestation of diabetes, is associated with development of certain of the diabetic complications. The accelerated formation of advanced glycation end-products (AGEs) due to elevated glycemia has repeatedly been reported as a central pathogenic factor in the development of diabetic microvascular complications. Glucose and α-dicarbonyl compounds chemically attach to proteins and nucleic acids without the aid of enzymes. Initially, chemically reversible Schiff base and Amadori product adducts form in proportion to glucose concentration. The major biological effects of excessive nonenzymatic glycosylation are leading to increased free radical production and compromised free radical inhibitory and scavenger systems, inactivation of enzymes; inhibition of regulatory molecule binding; crosslinking of glycosylated proteins and trapping of soluble proteins by glycosylated extracellular matrix (both may progress in the absence of glucose); decreased susceptibility to proteolysis; abnormalities of nucleic acid function; altered macromolecular recognition and endocytosis; and increased immunogenicity. The discovery of chemical agents that can inhibit deleterious glycation reactions is potentially of great therapeutic benefit to all diabetes-associated pathologies. This study demonstrates the progress in development of patented carnosine mimetics resistant in formulations to enzymatic hydrolysis with human carnosinases that are acting as a universal form of antioxidant, deglycating and transglycating agents that inhibit sugar-mediated protein cross-linking, chelate or inactivate a number of transition metal ions (including ferrous and copper ions), possess lipid peroxidase type of activity and protection of antioxidant enzymes from inactivation (such as in a case of superoxide dismutase). Carnosine biological mimetics react with methylglyoxal and they are described in this study as a glyoxalase mimetics. The imidazole-containing carnosine biological mimetics can react with a number of deleterious aldehydic products of lipid peroxidation and thereby suppress their toxicity. Carnosine and carcinine can also react with glycated proteins and inhibit advanced glycation end product formation. These studies indicate a therapeutic role for imidazole-containing antioxidants (non-hydrolized carnosine, carcinine, D-carnosine, ophthalmic prodrug N-acetylcarnosine, leucyl-histidylhidrazide and patented formulations thereof) in therapeutic management strategies for Type 2 Diabetes.

Circulation Research Thematic Synopsis Diabetes and Obesity

<i>Circulation Research</i> Thematic Synopsis Diabetes and Obesity

Redox Mediating Epigenetic Changes Confer Metabolic Memories

It's not always the case that it's easy to forgive and forget, particularly when it comes to past memories. The concept of the legacy effect or hyperglycemic memory describes the deferred consequence of antecedent glycemic status on the development of diabetic complications. Anyone researching chronic hyperglycemia appreciates that glucose is still considered the major risk factor implicated in the development and progression of diabetic vascular complications. Now, the same can be concluded for transient hyperglycemia. Large clinical studies have demonstrated that prior glycemic control has a sustained benefit in reducing subsequent diabetic complications.1–4 The Diabetes Control and Complications Trial (DCCT) and the follow-up study, Epidemiology of Diabetes Interventions and Complications (EDIC) have determined that episodes of poor glycemic control can lead many years later to the long-term complications of diabetes.5,6 The DCCT study was designed to compare intensive versus conventional approaches to improve glycemic control and determine the effects of these regimens on the development and progression of vascular complications in patients with type-1 diabetes. Because the development of diabetic microvascular complications and cardiovascular disease takes time, the follow-up EDIC study was designed to investigate the long-lasting effects of intensive and conventional therapies. The findings of these extended studies show that early intensive intervention was more effective in slowing the development of diabetic complications and this was clearly evidenced with the benefit of 6.5 years of intensive therapy during the DCCT phase being sustained, the benefits continuing for at least 10 years after return to usual glycemic control. When taken together, these studies in type 1 diabetes as well as the more recent findings from the follow up of the United Kingdom Prospective Diabetes Study emphasize that prior periods of intensive glycemic control significantly reduces the major burden of diabetes, its vascular complications.7 …

A Polymorphism within the Fructosamine-3-kinase Gene is Associated with HbA1c Levels and the Onset of Type 2 Diabetes Mellitus

Non-enzymatic glycation is a process, which leads to the formation of advanced glycation endproducts. These compounds are involved in the development of diabetic microvascular complications. Fructosamine-3-kinase (FN3K) is an intracellular enzyme that phosphorylates fructosamines resulting in fructosamine-3-phosphate, which subsequently decomposes to inorganic phosphate, 3-deoxyglucasone and the unmodified amine. Recently, the G900C (rs1056534) single nucleotide polymorpism (SNP) of the FN3K gene was found to be associated with the enzyme activity. The aim of the study was to investigate the impact of the SNP on clinical and biochemical features and microvascular complications of type 2 diabetes. A total of 859 type 2 diabetic subjects and 265 healthy controls were enrolled in the study and were genotyped with PCR-RFLP method. Genotype frequencies were as follows, CC: 5%, GC: 54%, GG: 41% in subjects with type 2 diabetes and CC: 6%, GC: 51%, GG: 43% in the controls. Diabetic subjects with the CC variant had lower HbA (1c) levels compared with the others (CC: 6.48+/-0.05%; GC: 7.66+/-0.09%; GG: 7.68+/-0.09%; p<0.001). Furthermore, in case of the CC allelic variant type 2 diabetes was diagnosed at a later age than in case of GC or GG variants (CC: 56.0+/-1.90 years; GC: 52.0+/-0.62 years; GG: 50.1+/-0.71 years; p<0.05). Logistic regression analysis did not reveal association between CC genotype and diabetic complications, such as diabetic nephropathy, neuropathy and retinopathy (OR=1.036, CI 95% 0.652-1.647, p=0.880; OR=0.985, CI 95% 0.564-1.721 p=0.958; OR=1.213, CI 95% 0.470-3.132, p=0.690, respectively). We conclude that the G900C polymorphism associates with the level of HbA (1c) and the onset of the disease, but not with either of the diabetic microvascular complications.

Methyltetrahydrofolate reductase C677T gene mutation and hyperhomocysteinemia as a novel risk factor for diabetic nephropathy

Hyperhomocysteinemia is a well-defined risk factor for endothelial dysfunction and atherosclerosis. A point mutation (677 C-T) of MTHFR gene results in a significant increase at plasma homocysteine levels. In this study we aimed to evaluate the effects of MTHFR gene mutation and consequent hyperhomocysteinemia on the development of diabetic microvascular complications in comparison with the other defined risk factors. Diabetic patients without a history of macrovascular complication or overt nephropathy enrolled into the study. The presence of MTHFR 677 C-T point mutation was evaluated by Real-Time PCR technique by using a LightCycler. MTHFR heterozygous mutation was present in 24 patients over 52. Patients with diabetes were divided into two groups according to the presence of MTHFR gene mutation. Both groups were well matched regarding age and diabetes duration. Metabolic parameters, plasma homocysteine, microalbuminuria, folic acid, and vitamin B12 levels were also studied. Presence of neuropathy and retinopathy were evaluated by specific tests. Duration of diabetes, BMI, systolic and diastolic blood pressure, plasma CRP, HbA1c, and lipid levels were not different between the two groups. Plasma homocysteine (12.89 +/- 1.74 and 8.98 +/- 1.91 micromol/l; P < 0.0001) and microalbuminuria levels (73.40 +/- 98.15 and 29.53 +/- 5.08 mg/day; P = 0.021) were significantly higher in the group with MTHFR gene mutation while creatinine clearance levels (101.1 +/- 42.6 and 136.21 +/- 51.50 ml/min; P = 0.008) were significantly lower. Sixteen over 22 (73%) of the patients with diabetic nephropathy had MTHFR gene mutation, while this was only 27% (8 over 30) in normoalbuminuric patients (P = 0.017). There was a significant correlation of plasma homocysteine level with microalbuminuria (r = 0.54; P = 0.031) in the patients with diabetic nephropathy who had C677T polymorphism. We did not find any specific association of MTHFR gene mutation and hyperhomocysteinemia with retinopathy or neuropathy.

C-Peptide and its Intracellular Signaling

Although long believed to be inert, C-peptide has now been shown to have definite biological effects both in vitro and in vivo in diabetic animals and in patients with type 1 diabetes. These effects point to a protective action of C-peptide against the development of diabetic microvascular complications. Underpinning these observations is undisputed evidence of C-peptide binding to a variety of cell types at physiologically relevant concentrations, and the downstream stimulation of multiple cell signaling pathways and gene transcription via the activation of numerous transcription factors. These pathways affect such fundamental cellular processes as re-absorptive and/or secretory phenotype, migration, growth, and survival. Whilst the receptor remains to be identified, experimental data points strongly to the existence of a specific G-protein-coupled receptor for C-peptide. Of the cell types studied so far, kidney tubular cells express the highest number of C-peptide binding sites. Accordingly, C-peptide exerts major effects on the function of these cells, and in the context of diabetic nephropathy appears to antagonise the pathophysiological effects of major disease mediators such as TGFbeta1 and TNFalpha. Therefore, based on its cellular activity profile C-peptide appears well positioned for development as a therapeutic tool to treat microvascular complications in type 1 diabetes.

Cytoprotective effects of phenolic acids on methylglyoxal‐induced apoptosis in Neuro‐2A cells

In the process of glycation, methylglyoxal is a reactive dicarbonyl compound physiologically generated as an intermediate of glycolysis, and is found in high levels in blood or tissue of diabetic models. Biological glycation has been commonly implicated in the development of diabetic microvascular complications of neuropathy. Increasing evidence suggests that neuronal cell cycle regulatory failure followed by apoptosis is an important mechanism in the development of diabetic neuropathy complication. Naturally occurring antioxidants, especially phenolic acids have been recommended as the major bioactive compounds to prevent chronic diseases and promote health benefits. The objective of this study was to investigate the inhibitory abilities of phenolic acids (chlorogenic acid, syringic acid and vanillic acid) on methylglyoxal-induced mouse Neuro-2A neuroblastoma (Neuro-2A) cell apoptosis in the progression of diabetic neuropathy. The data indicated that methylglyoxal induced mouse Neuro-2A neuroblastoma (Neuro-2A) cell apoptosis via alternation of mitochondria membrane potential and Bax/Bcl-2 ratio, activation of caspase-3, and cleavage of poly (ADP-ribose) polymerase. Furthermore, the results demonstrated that activation of mitogen-activated protein kinase signal pathways (JNK and p38) participated in the methylglyoxal-induced Neuro-2A cell apoptosis process. Treatment of Neuro-2A cells with phenolic acids markedly suppresses cell apoptosis induced by methylglyoxal, suggesting that phenolic acids possess cytoprotective ability in the prevention of diabetic neuropathy complication.

Autosomal inheritance of diabetes in two families characterized by obesity and a novel H241Q mutation inNEUROD1

The aim of the study was to search for mutations in the NEUROD1 and IPF-1 genes in patients with clinical characteristics of maturity-onset diabetes of the young (MODY) but with no mutations in the HNF-4A (MODY1), GCK (MODY2) and TCF1 (MODY3) genes. We studied 30 unrelated Czech probands with a clinical diagnosis of MODY (median age at testing, 18 yr; median age at the recognition of hyperglycaemia, 16 yr). The promoter, exons and exon/intron boundaries of the NEUROD1 and IPF-1 genes were examined by polymerase chain reaction-denaturing high performance liquid chromatography and direct sequencing. While no mutations were found in the IPF-1 gene, a novel H241Q substitution of NEUROD1 gene was identified in two unrelated families. In the first proband, the H241Q mutation led to early diagnosed (20 yr) hyperglycaemia followed by development of diabetic microvascular complications by the age of 32 yr. The second proband suffered from slowly progressing hyperglycaemia detected at the age of 30 yr. Affected members of both families were obese. The overall prevalence of the variant among the general population was 4 of 13 568 chromosomes. We report a novel disease-associated variant in NEUROD1 identified among a set of MODYX families. The variant seems to precipitate type-2-like diabetes in excessively obese individuals.