Hypoxic induction of vascular endothelial growth factor is markedly decreased in diabetic individuals who do not develop retinopathy

Genetic Variability in VEGFA Gene Influences the Effectiveness of Tennis Elbow Therapy with PRP: A Two-Year Prospective Cohort Study

Vascular endothelial growth factor (VEGF) is implicated in both the etiology of tendinopathy and its healing process. Polymorphic variants of the VEGFA gene exhibit varied expression, which can influence the phenotype and treatment effectiveness. The aim of the present study was to analyze the influence of VEGFA gene variants on the effectiveness of tennis elbow therapy using platelet-rich plasma (PRP), measured through common patient-reported outcome measures (PROMs). A cohort of 107 patients (132 elbows) with tennis elbow was prospectively analyzed, with a two-year follow-up (at weeks 2, 4, 8, 12, 24, 52, and 104 after PRP injection). PROMs values were compared between variants of five VEGFA gene polymorphisms (rs699947 A>C, rs2010963 C>G, rs1413711 C>T, rs3024998 C>T and rs3025021 C>T) at each follow-up point. Patients with genotypes GG (rs2010963) and CC (rs3024998) had better response to PRP therapy (significantly fewer symptoms and limitations in the upper limb compared to carriers of alleles C and T, respectively). Polymorphisms influenced also selected hematological parameters. VEGFA gene polymorphisms (rs2010963 and rs3024998) appear to be significant treatment modifiers for tendinopathy, and their genotyping may serve as an effective tool for personalized patient selection for PRP therapy.

Genetic polymorphisms in VEGFA and VEGFR2 genes associated with coronary heart disease susceptibility and severity

BACKGROUND

​Vascular endothelial growth factor A (VEGFA) is well acknowledged as a powerful angiogenesis-promoting agent mainly through its receptor VEGFR2. Ischemia stimulates VEGFA/VEGFR2 signaling pathway and elevated serum levels of VEGFA were detected in coronary heart disease (CHD) patients. The goal of the current study is to determine how four SNPs in the genes for VEGFA (rs3025039 and rs699947) and VEGFR2 (rs2305948 and rs1870377) contribute to the development of CHD. We also wanted to use the Gensini score to confirm if these four SNPs have an effect on the severity of coronary lesions.

METHODS

In this case-control research, we used the restriction fragment length polymorphism of the polymerase chain reaction to genotype 239 CHD patients and 200 controls. Age, sex, smoking behavior, and obesity were taken into account in the statistical analysis.

RESULTS

Two VEGFA/VEFGR2 signaling pathway SNPs (rs699947 and rs1870377) were found to be associated with CHD (C vs. A, P = 0.002; OR = 1.47 (1.12-1.93); A vs. T, P = 0.001; OR = 1.58 (1.17-2.13) respectively). The rs2305948 showed no allelic associations with CHD susceptibility, although we noticed a slight association under the recessive model of rs3025039 TT genotype (p = 0.023; OR = 6.41 (1.14-36.12)) only under adjusted analyses. In addition, both VEGFA SNPs (rs699947and rs3025039) were found to be associated with high Gensini score (p < 0.001).

CONCLUSIONS

Our research helps to shed further light on the pathophysiology of CHD. The VEGFA/VEGFR2 signaling pathway may have been downregulated, increasing CHD susceptibility and risk.

Vascular Endothelial Growth Factor Single Nucleotide Polymorphism +405 G/C (rs2010963) is associated with Levels, Infection Severity, and Amputation among South Indian Diabetic Foot Ulcer Patients

Background

The regulation of vascular endothelial growth factor (VEGF) by genetic factors in T2DM and DFU still requires thorough investigation. Hence, the present study aimed to investigate the association of VEGF +405 G/C in DFU subjects and correlate it with its circulatory levels, infection severity, and amputation rate.

Materials and Methods

This study registered a total of 754 participants of which group I: healthy controls (n = 297), group II: T2DM subjects (n = 242), and group III: DFU subjects (n = 215). Genotyping and levels of rs2010963 were analyzed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and ELISA, respectively.

Results

Results of the current study showed a clear decline in circulatory VEGF-A levels in DFU subjects. VEGF-A was decreased in DFU subjects with the mutant "CC" genotype. The mutant "CC" of VEGF +405G/C was also found to be more susceptible to ulcer grade (III and IV) and major amputations.

Conclusion

VEGF +405G/C SNP is associated with levels, infection severity, and amputation amongst South Indian DFU patients.

Studies of the retinal microcirculation using human donor eyes and high-resolution clinical imaging: Insights gained to guide future research in diabetic retinopathy

The microcirculation plays a key role in delivering oxygen to and removing metabolic wastes from energy-intensive retinal neurons. Microvascular changes are a hallmark feature of diabetic retinopathy (DR), a major cause of irreversible vision loss globally. Early investigators have performed landmark studies characterising the pathologic manifestations of DR. Previous works have collectively informed us of the clinical stages of DR and the retinal manifestations associated with devastating vision loss. Since these reports, major advancements in histologic techniques coupled with three-dimensional image processing has facilitated a deeper understanding of the structural characteristics in the healthy and diseased retinal circulation. Furthermore, breakthroughs in high-resolution retinal imaging have facilitated clinical translation of histologic knowledge to detect and monitor progression of microcirculatory disturbances with greater precision. Isolated perfusion techniques have been applied to human donor eyes to further our understanding of the cytoarchitectural characteristics of the normal human retinal circulation as well as provide novel insights into the pathophysiology of DR. Histology has been used to validate emerging in vivo retinal imaging techniques such as optical coherence tomography angiography. This report provides an overview of our research on the human retinal microcirculation in the context of the current ophthalmic literature. We commence by proposing a standardised histologic lexicon for characterising the human retinal microcirculation and subsequently discuss the pathophysiologic mechanisms underlying key manifestations of DR, with a focus on microaneurysms and retinal ischaemia. The advantages and limitations of current retinal imaging modalities as determined using histologic validation are also presented. We conclude with an overview of the implications of our research and provide a perspective on future directions in DR research.

Differentiating Microaneurysm Pathophysiology in Diabetic Retinopathy Through Objective Analysis of Capillary Nonperfusion, Inflammation, and Pericytes

Microaneurysms are biomarkers of microvascular injury in diabetic retinopathy (DR). Impaired retinal capillary perfusion is a critical pathogenic mechanism in the development of microvascular abnormalities. Targeting fundamental molecular disturbances resulting from capillary nonperfusion, such as increased vascular endothelial growth factor expression, does not always reverse the anatomic complications of DR, suggesting that other pathogenic mechanisms independent of perfusion also play a role. We stratify the effects of capillary nonperfusion, inflammation, and pericyte loss on microaneurysm size and leakage in DR through three-dimensional analysis of 636 microaneurysms using high-resolution confocal scanning laser microscopy. Capillary nonperfusion, pericyte loss, and inflammatory cells were found to be independent predictors of microaneurysm size. Nonperfusion alone without pericyte loss or inflammation was not a significant predictor of microaneurysm leakage. Microaneurysms found in regions without nonperfusion were significantly smaller than those found in regions with nonperfusion, and their size was not associated with pericyte loss or inflammation. In addition, microaneurysm size was a significant predictor of leakage in regions with nonperfusion only. This report refines our understanding of the disparate pathophysiologic mechanisms in DR and provides a histologic rationale for understanding treatment failure for microvascular complications in DR.

A study of the genotyping and vascular endothelial growth factor polymorphism differences in diabetic and diabetic retinopathy patients

Background

Retinopathy is one of the major causes of visual impairment which is the most severe microvascular complication of diabetes mellitus (DM). The aim of this study was to evaluate the association between diabetic retinopathy (DR) and two SNPs (− 152G > A and − 165C > T) located in the promoter region of the vascular endothelial growth factor (VEGF) gene in a small sample from Egyptian population. One hundred diabetic patients without retinopathy (DWR) and two hundred diabetic patients with retinopathy were included in this study. Genotype analysis for the two SNPs (− 152G > A and − 165C > T) was assessed by using the PCR–RFLP technique. In addition, the serum protein level of VEGF was measured by ELISA assay.

Results

The results showed a significant relationship between − 152G > A (rs13207351) polymorphism and both proliferative and non-proliferative retinopathy in genotypes (GG, GA, AA). The risk factor increment in the mutant heterozygous genotype (GA) was significantly increased in NPDR compared to PDR (OR = 16.3, 95%CI = 0.80–331.7); (OR = 20.4, 95%CI = 1.08–385.3), respectively. There was no significance between VEGF − 165C > T (rs79469752) gene polymorphism and retinopathy. Moreover, the serum protein level of VEGF showed a highly significant increase (P = 0.0001) in PDR (Mean ± SD = 3691 ± 124.9) when compared to both DWR (Mean ± SD = 497.3 ± 18.51) and NPDR (Mean ± SD = 1674.5 ± 771.7). These results were supported by the increased level of VEGF in serum protein which is positively correlated with the severity of retinopathy. Measuring VEGF protein level in DR patients would help as a biomarker in early diagnosis.

Conclusion

The increase in the mutant heterogeneous GA genotype in VEGF − 152G > A SNP could be a risk factor for the progression of severe retinopathy in diabetic patients.

Discoveries from the study of longstanding type 1 diabetes

Award programmes that acknowledge the remarkable accomplishments of long-term survivors with type 1 diabetes have naturally evolved into research programmes to determine the factors associated with survivorship and resistance to chronic complications. In this review, we present an overview of the methodological sources of selection bias inherent in survivorship research (selection of those with early-onset diabetes, incidence-prevalence bias and bias from losses to follow-up in cohort studies) and the breadth and depth of literature focusing on this special study population. We focus on the learnings from the study of longstanding type 1 diabetes on discoveries about the natural history of insulin production loss and microvascular complications, and mechanisms associated with them that may in future offer therapeutic targets. We detail descriptive findings about the prevalence of preserved insulin production and resistance to complications, and the putative mechanisms associated with such resistance. To date, findings imply that the following mechanisms exist: strategies to maintain or recover beta cells and their function; activation of specific glycolytic enzymes such as pyruvate kinase M2; modification of AGE production and processing; novel mechanisms for modification of renin-angiotensin-aldosterone system activation, in particular those that may normalise afferent rather than efferent renal arteriolar resistance; and activation and modification of processes such as retinol binding and DNA damage checkpoint proteins. Among the many clinical and public health insights, research into this special study population has identified putative mechanisms that may in future serve as therapeutic targets, knowledge that likely could not have been gained without studying long-term survivors.

VEGF Promoter Region 18-bp Insertion-Deletion Polymorphism in Sickle Cell Disease Patients with Microalbuminuria: A Pilot Study

Purpose

Vascular endothelial growth factor (VEGF) is a potent inducer of micro vascular permeability thus leading to nephropathy. Insertion/deletion (I/D) polymorphism of 18 bp at - 2549 position in VEGF gene causes increased transcription leading to increased production of VEGF. Thus, we aimed to associate I/D polymorphism of the 18 bp fragment at - 2549 position of the promoter region of VEGF gene with sickle cell nephropathy (SCN).

Methods

This observational analytical case control study included 30 subjects each of SCN, sickle cell disease (SCD) without nephropathy and the control group. The subjects were assessed for various hematological and biochemical parameters. Further, 18 bp I/D polymorphism of VEGF gene in all three study groups was assessed by polymerase chain reaction followed by electrophoresis and compared.

Result

Though increased frequency of both DD genotype and D allele was found in SCN compared to SCD and control, only frequency of D allele was found to be significantly higher (p = 0.04). D allele posed marginal risk of microalbuminuria in SCD subjects compared to controls (OR = 2.11) as well as to SCD without MA subjects (OR = 1.84).

Conclusion

D allele in I/D polymorphism in the promoter region of VEGF gene may be associated with marginal increase in risk of susceptibility to sickle cell nephropathy.

Association between VEGF genetic variants and diabetic foot ulcer in Chinese Han population: A case-control study

The aim of this study was to investigate the association of vascular endothelial growth factor (VEGF) gene polymorphisms with diabetic foot ulcer (DFU) susceptibility in a Chinese Han population.Around 88 type 2 diabetes mellitus (T2DM) patients without DFU and 97 T2DM patients with DFU were enrolled in this study. A total of 103 age and gender matched healthy individuals were recruited as healthy control. VEGF gene polymorphisms rs699947 and rs13207351 were analyzed by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) method. Odds ratio (OR) with 95% confidence interval (CI) was calculated to assess the association between VEGF gene polymorphisms and DFU risk.The frequency of AA and AC genotypes of rs699947 were lower in DFU patients than that in healthy controls (P = .020, P = .031), suggesting that AC and AA genotypes were negatively associated with DFU risk originating from healthy individuals (OR = 0.496, 95%CI = 0.274-0.899; OR = 0.130, 95%CI = 0.015-1.112). Significantly decreased trend of rs699947 A allele was observed in DFU patients when compared to the controls (P = .004), suggesting A allele was distinctly correlated with decreased DFU risk (OR = 0.490, 95%CI = 0.298-0.804). But no significant differences were detected in rs13207351 genotype and allele distributions between patients and control groups (P > .05).Individuals carrying VEGF rs699947 A allele show low susceptibility to DFU in the Chinese Han population.

Vascular endothelial growth factor A polymorphisms are associated with increased risk of coronary heart disease: a meta-analysis

Coronary heart disease (CHD) is a common complex disease resulting from the interaction of multiple environmental and genetic factors. To assess the potential relationship of vascular endothelial growth factor (VEGFA) rs699947 C>A, rs3025039 C>T and rs2010963 G>C polymorphisms with CHD risk, a comprehensive meta-analysis was conducted. A systematic search of EMBASE and PubMed online database for publications on VEGFA polymorphisms and risk of CHD was carried out. Crude Odds ratios (ORs) with their 95% confidence intervals (CIs) were calculated to determine the association. A total of ten publications including 22 trails involving 2097 cases and 2867 controls were included in our pooled analysis. Overall, results of the present meta-analysis demonstrated a significant association between VEGFA rs699947 C>A polymorphism and an increased risk of CHD. After stratifying by ethnicity and CHD type, the association was also obtained. A significant association between VEGFA rs3025039 C>T polymorphism and risk of CHD was also found. For VEGFA rs2010963 G>C polymorphism, the polymorphism was associated with MI risk. In conclusion, our findings suggest that VEGFA rs699947 C>A, rs3025039 C>T and rs2010963 G>C polymorphisms are risk factors for CHD. In the future, large sample size and well-designed epidemiologic studies are needed to confirm these conclusions.

Fighting diabetic foot ulcers-The diabetologist: A king maker of the fight

Diabetic foot ulcer is a costly and serious complication of diabetes mellitus and is the major cause of non-traumatic limb amputations worldwide. Its development is primarily the result of diabetic neuropathy and/or peripheral arterial disease with accompanied bone abnormalities and is complicated by invasive infection. The management of this clinical condition focuses on identification of the "at-risk" foot, treatment of the ulcerated foot, and prevention of further complications. As diabetic foot ulcer represents the sum of multiple etiologies, its treatment requires a multidisciplinary team, which can result in a significant reduction in the incidence of ulcers, infections and amputations. The team should include a diabetologist, a podiatrist, an orthoptist, an educator and a plaster technician, in close collaboration with a vascular surgeon, an orthopedic/podiatric surgeon and a dermatologist. It is recommended that a diabetologist be the multidisciplinary team leader, as diabetic foot ulcer is a complication of diabetes and chronic hyperglycemia represents the main cause for its development. The appropriate composition of professionals involved in the team is institution-dependent and may vary worldwide, depending on the diabetic population. The concept of establishing a diabetic foot care team is recommended by all National and International Diabetes Scientific Societies and Associations.

Hypoxia and Dark Adaptation in Diabetic Retinopathy: Interactions, Consequences, and Therapy

In diabetes, retinal blood flow is compromised, and retinal hypoxia is likely to be further intensified during periods of darkness. During dark adaptation, rod photoreceptors in the outer retina are maximally depolarized and continuously release large amounts of the neurotransmitter glutamate-an energetically demanding process that requires the highest oxygen consumption per unit volume of any tissue of the body. In complete darkness, even more oxygen is consumed by the outer retina, producing a steep fall in the retinal oxygen tension curve which reaches a nadir at the depth of the mitochondrial-rich rod inner segments. In contrast to the normal retina, the diabetic retina cannot meet the added metabolic load imposed by the dark-adapted rod photoreceptors; this exacerbates retinal hypoxia and stimulates the overproduction of vascular endothelial growth factor (VEGF). The use of nocturnal illumination to prevent dark adaptation, specifically reducing the rod photoreceptor dark current, should ameliorate diabetic retinopathy.

The Role of VEGF in the Diabetic Patients Undergoing Endovascular Therapy of Symptomatic Aortic Valve Stenosis

The aim of this study was to explore changes in plasma vascular endothelial growth factor (VEGF) in aged patients who undergone transcatheter aortic valve implantation or balloon angioplasty for the treatment of aortic stenosis. Plasma VEGF was measured in subjects with diabetes mellitus type 2 (DM) (n=21, age 79.2±1.6 years) and in non-diabetic subjects (non-DM) (n=23, age 84.4±0.7 years), using an ELISA kit. Before the procedure plasma levels of VEGF were significantly lower in DM than in non-DM patients (P<0.05). Plasma VEGF significantly increased in both groups (DM and non-DM) 24 h (387±64 vs. 440±30 pg/ml, P<0.05) and 72 h (323±69 vs. 489±47 pg/ml, P<0.05) after the endovascular procedure. However, the VEGF in DM patients was significantly lower compared to non-DM subjects up to one month after the endovascular procedure (283±47 vs. 386±38 pg/ml, P<0.05). We conclude that increased plasma VEGF in aged patients associates with atherosclerotic aortic valve stenosis. In spite of that plasma VEGF in DM was constantly significantly lower than in non diabetic patients, both before and after the endovascular procedure, possibly reflecting a disturbance of angiogenic/anti-angiogenic balance in diabetes.

Further evidence for the contribution of the vascular endothelial growth factor gene in coronary artery disease susceptibility

Coronary artery disease (CAD) receives intensive attentions in the research of cardiovascular diseases, due to its high incidence and severe impact on the quality of life vascular endothelial growth factor (VEGF), a potent angiogenic and vascular permeability factor, has been strongly implicated in the pathogenesis of CAD. Genetic markers in different regions of the VEGF gene have a plausible role in modulating the risk of CAD. To identify the markers contributing to the genetic susceptibility to CAD, we examined the potential association between CAD and 10 single nucleotide polymorphisms (SNPs, rs699947, rs1570360, rs2010963, rs833068, rs3024997, rs3025000, rs3025010, rs3025020, rs3025030, rs3025039) of the VEGF gene using the MassARRAY system. Participants included 242 CAD patients and 253 healthy controls from a Chinese Han Population (He'nan Province, China). The allelic or genotypic frequencies of the rs699947 (5' untranslated regions, 5'UTR) and rs2010963 (5'UTR) polymorphisms in the CAD patients were significantly different from those in the healthy controls. The CAD patients had significantly higher frequency of the rs699947 A allele (χ(2)=11.141, P=0.001, OR=1.665, 95% CI=1.232-2.250) and rs2010963 C allele (χ(2)=13.593, P=0.0002, OR=1.611, 95% CI=1.249-2.077). Strong linkage disequilibrium was observed in the rs699947-rs1570360-rs2010963 haplotype block (D'>0.9). Significantly more C-G-C haplotypes (P=0.040) and significantly fewer C-G-G haplotypes (P=0.0004) were found in the CAD patients. The possible association of rs699947 and rs2010963 with CAD risks warrant confirmation in independent case-control studies and may be informative for future investigations on the pathogenesis of CAD.

The pathogenesis of early retinal changes of diabetic retinopathy

Recent successful trials of antibodies to vascular endothelial growth factor (VEGF) in diabetic retinopathy implicate this cytokine as a major cause of diabetic retinopathy (DR) and diabetic macular oedema (DME). The mechanisms which cause VEGF to be over-expressed to cause the vasculopathy are not entirely clear. This review explores the earliest changes to the retina in DR and the factors that predispose or prevent DR, including sleep apnoea, receptor degenerations laser treatment and VEGF polymorphism. The review also presents the evidence that retinal hypoxia, existing in the earliest stages, causes DR. This hypoxia is much increased by dark adaptation, indicating a new and possibly superior therapy.

VEGF gene mRNA expression in patients with coronary artery disease

To assess the expression of vascular endothelium growth factor (VEGF) mRNA in unstimulated peripheral blood mononuclear cells of patients with and without coronary artery disease (CAD). We also studied whether the functional VEGF -2,578C/A polymorphism may influence the level of VEGF mRNA expression in individuals undergoing coronary angiography because chest pain. We assessed 50 consecutive patients with angiographically confirmed CAD (CAD+). Also, 50 consecutive individuals with normal coronary studies were included in the study for comparison. VEGF mRNA expression was examined using quantitative real-time PCR and genotyping for VEGF -2,578C/A was performed using ARMS-PCR technique. VEGF mRNA expression was significantly decreased in CAD+ patients when compared to CAD- individuals (p = 0.01). The frequency of VEGF -2578 allele C and genotype CC was increased in CAD+ patients. In this regard, homozygosity for the CC genotype was more commonly observed in CAD+ (30 %) than in those without CAD disease (18 %). However, the difference was slightly out of the range of significance (p = 0.1). In addition, a trend for reduction in the expression of VEGF mRNA was observed when patients carrying the VEGF -2,578AA genotype were compared with those VEGF -2,578AC heterozygous or those homozygous for the VEGF -2,578CC genotype. VEGF gene expression is decreased in individuals with CAD+ disease. The VEGF -2,578C/A polymorphism may influences the expression of VEGF.

VEGF gene polymorphism association with diabetic foot ulcer

OBJECTIVE

Functional polymorphisms within vascular endothelial growth factor (VEGF) gene have shown association with various conditions including diabetic neuropathy and retinopathy. In this study we have performed a candidate gene association study in order to examine VEGF gene polymorphism association with diabetic foot ulcer (DFU).

METHODS

The study group comprised of type 2 diabetes patients with (N=247) and without (N=241) DFU. Healthy control subjects (N=98) were also recruited from the same area. The ARMS-PCR technique was applied for genotyping of VEGF gene SNPs at positions -7*C/T and -2578*C/A.

RESULTS

The frequency of genotype AA was significantly decreased in patients with DFU compared with diabetic subjects without DFU (AA vs CA+CC, p=0.003, OR=0.44, CI=0.24-0.80). Also there was a significant decrease in frequency of A allele in patients with DFU compared to the controls (p=0.02, OR=0.68, CI=0.48-0.96).

CONCLUSION

It seems that lower frequency of A allele in patients with DFU is conferring a protective effect which might be as a result of increased angiogenesis in patients carrying this allele.

Variations within oxygen-regulated gene expression in humans

The effects of hypoxia on gene transcription are mainly mediated by a transcription factor complex termed hypoxia-inducible factor (HIF). Genetic manipulation of animals and studies of humans with rare hereditary disease have shown that modifying the HIF pathway affects systems-level physiological responses to hypoxia. It is, however, an open question whether variations in systems-level responses to hypoxia between individuals could arise from variations within the HIF system. This study sought to determine whether variations in the responsiveness of the HIF system at the cellular level could be detected between normal individuals. Peripheral blood lymphocytes (PBL) were isolated on three separate occasions from each of 10 healthy volunteers. After exposure of PBL to eight different oxygen tensions ranging from 20% to 0.1%, the expression levels of four HIF-regulated transcripts involved in different biological pathways were measured. The profile of expression of all four transcripts in PBL was related to oxygen tension in a curvilinear manner. Double logarithmic transformation of these data resulted in a linear relationship that allowed the response to be parameterized through a gradient and intercept. Analysis of variance (ANOVA) on these parameters showed that the level of between-subject variation in the gradients of the responses that was common across all four HIF-regulated transcripts was significant (P = 0.008). We conclude that statistically significant variation within the cellular response to hypoxia can be detected between normal humans. The common nature of the variability across all four HIF-regulated genes suggests that the source of this variation resides within the HIF system itself.

Hypoxia-inducible factor as a physiological regulator

Hypoxia-inducible factor (HIF) is a transcription complex which responds to changes in oxygen, providing cells with a master regulator that coordinates changes in gene transcription. HIF operates in all mammalian cell types and is ancient in evolutionary terms, being conserved in C. elegans and D. melanogaster. This review summarizes recent insights into the molecular events that link reduced oxygenation to HIF activation and emerging insights into the extensive role of HIF in a broad range of physiological processes.

Spare the rod and spoil the eye

This review presents a new unified view of the pathogenesis of three common causes of acquired retinal degenerative disease-diabetic retinopathy, age related macular degeneration, and retinopathy of prematurity. In these three conditions, angiogenesis has a predominant role in the development of sight threatening pathology. Angiogenesis is controlled by among other factors the expression of vascular endothelial growth factor (VEGF), which in turn is regulated by absolute and relative lack of oxygen. The severe pathological manifestations of these three conditions are not part of a general underlying disease process because they are peculiar to the eye, and the profound hypoxia that develops in normal retina during dark adaptation (rod driven hypoxia) is an adequate and elegant additional factor to explain their pathogenesis. A large number of experimental reports support this conclusion, although rod driven anoxia is not generally considered as a causal factor in ocular disease. However, the hypothesis can be critically tested, and also suggests novel methods of treatment and prevention of these conditions that may be simpler and more inexpensive than current therapies and that have a smaller potential for adverse effects.

Longitudinal MRI tracking of the angiogenic response to hind limb ischemic injury in the mouse

Ischemic injury and revascularization are frequently associated with hyperpermeability. Although extravasation of plasma proteins may promote tissue recovery through the generation of the provisional matrix that supports angiogenesis, edema may also result in progressive damage to the muscle. The aim of this research was to determine the time course of hyperpermeability associated with the angiogenic response induced by ligation of the femoral artery at the right posterior limb in mice. Hyperpermeability was followed noninvasively by MRI using an in-house-built permanent polyethylene catheter that enabled daily intravenous administration of biotin-BSA-Gd-DTPA. The mice were scanned once prior to ligation and five times during the week post-ligation. The MRI data, along with histopathology, indicated that the early hemodynamic compensation over loss of arterial blood supply occurred by angiogenesis and dilation of vessels in the skin and subcutaneous fat, and was accompanied by vascular hyperpermeability around the site of ligation. Functional recovery of the ischemic limb (i.e., regaining the ability to step on the limb), and the color and shape of the toes correlated with regeneration as shown by histopathology and MRI analysis. Thus, MRI provided valuable information on the transient hyperpermeability induced during the early stages of angiogenesis, and its subsequent resolution along with functional recovery from acute hind limb ischemia in mice.

Erythropoietin therapy in predialysis patients

Introduction Anemia is recognized as a very important non-traditional risk factor for cardiovascular morbidity and mortality in patients with uremia. Despite many advantages of erythropoietin therapy, the number of patients treated with this drug is modest, particularly during the pre-end stage renal disease. Patients with chronic renal failure are at risk to develop coronary artery disease, left ventricular hypertrophy and chronic heart failure when hemoglobin concentration falls below 10 g/dl and creatinine clearance under 60 ml/min. Erythropoietin therapy Early erythropoietin treatment prevents not only cardiovascular morbidity and mortality, but also progression of renal failure towards end-stage renal disease. Anti-oxidant, anti-hypoxic and anti-apoptotic effects of erythropoietin prevent tubular lesions and interstitial fibrosis. There still remains a confusion regarding the optimum target hemoglobin concentration in the pre-dialysis phase. Guidelines in Europe and US are probably not appropriate for all patients and it is important that renal anemia patients are considered as individuals. It may be appropriate to normalize hemoglobin concentration in young patients who have active lifestyles and no severe co-morbidity. In contrast, partial correction is more appropriate for the elderly with significant co-morbidities. Special attention should be paid to patients with diabetes, where anemia starts earlier and is more profound than in other renal patients. There is no risk of early anemia treatment using erythropoietin and this regime does not increase the total cost of treatment. Conclusion Early referral to a nephrologist is the key how to define underlying renal disease, slow down the progression of renal failure, prevent co-morbid conditions and to prepare patients for end-stage renal disease treatment.

Plasma brain natriuretic peptide levels in normotensive Type 2 diabetic patients without cardiac disease and macroalbuminuria

To clarify the relationship of the plasma brain natriuretic peptide (BNP) levels to diabetic complications, we studied plasma BNP levels in 100 normotensive diabetic patients without clinical cardiac disease and macroalbuminuria. The values of plasma BNP levels were not significantly different between patients with microalbuminuria and those with normoalbuminuria (12.2 +/- 2.0 vs. 12.3 +/- 1.3 pg/ml, means +/- S.E.M.), and neither were the BNP levels of patients with and without retinopathy significantly different (15.7 +/- 3.4 vs. 11.4 +/- 1.0 pg/ml). BNP levels of the subjects with cerebral vascular disease (CVD) were not statistically different from those of subjects without CVD (17.5 +/- 5.5 vs. 11.7 +/- 1.0 pg/ml), although mean BNP value of subjects with CVD was higher than that of subjects without it. With regard to peripheral vascular disease (PVD), BNP levels of the subjects with PVD were not statistically different from those of subjects without PVD (13.5 +/- 2.3 vs. 12.1 +/- 1.2 pg/ml). We also studied radial arterial oxygen tension of 45 patients and compared these levels between those with and without diabetic complications. However, we could not find statistical differences between them. In conclusion, our study suggests that BNP and arterial oxygen tension levels will not be affected by retinopathy, microalbuminuria, CVD, and PVD in normotensive diabetic patients without clinical cardiac disease and macroalbuminuria. Therefore, when normotensive diabetic patients without macroalbuminuria show increased plasma level of BNP, we should examine their cardiac function in detail, considering subclinical cardiac disease.

Regulation of VEGF in diabetic patients with critical limb ischemia

Diabetic patients are at a 10- to 20-fold increased risk for the development of critical limb ischemia. Vascular endothelial growth factor (VEGF) is critical for the development of collateral blood vessels, which can effectively bypass peripheral arterial occlusions. We therefore set out to determine if the regulation of VEGF in patients with peripheral vascular disease differs in diabetic and nondiabetic patients. Diabetic and nondiabetic patients with peripheral vascular disease were divided into those with or without critical limb ischemia as defined by clinical criteria (rest pain, nonhealing ulcer). Monocytes from peripheral blood were isolated from all patients and the hypoxic induction of VEGF was determined in vitro. In patients without diabetes, we found that there was no significant difference in the hypoxic induction of VEGF between patients with or without critical limb ischemia. However, in diabetic patients we found that patients with critical limb ischemia produced significantly more VEGF than patients without critical limb ischemia (6.3 +/- 1.3 vs. 2.1 +/- 0.3, p < 0.015). We conclude that diabetic patients with critical limb ischemia do not have an impairment in the ability to produce VEGF with hypoxia. Contrary to current dogma, treatment paradigms directed at increasing VEGF production in the diabetic patient with critical limb ischemia might not be beneficial.