Gene transfer of an engineered transcription factor promoting expression of VEGF-A protects against experimental diabetic neuropathy

Tocotrienol-Rich Vitamin E (Tocovid) Improved Nerve Conduction Velocity in Type 2 Diabetes Mellitus Patients in a Phase II Double-Blind, Randomized Controlled Clinical Trial

Diabetic peripheral neuropathy (DPN) is the most common microvascular complication of diabetes that affects approximately half of the diabetic population. Up to 53% of DPN patients experience neuropathic pain, which leads to a reduction in the quality of life and work productivity. Tocotrienols have been shown to possess antioxidant, anti-inflammatory, and neuroprotective properties in preclinical and clinical studies. This study aimed to investigate the effects of tocotrienol-rich vitamin E (Tocovid Suprabio^TM) on nerve conduction parameters and serum biomarkers among patients with type 2 diabetes mellitus (T2DM). A total of 88 patients were randomized to receive 200 mg of Tocovid twice daily, or a matching placebo for 12 months. Fasting blood samples were collected for measurements of HbA1c, renal profile, lipid profile, and biomarkers. A nerve conduction study (NCS) was performed on all patients at baseline and subsequently at 2, 6, 12 months. Patients were reassessed after 6 months of washout. After 12 months of supplementation, patients in the Tocovid group exhibited highly significant improvements in conduction velocity (CV) of both median and sural sensory nerves as compared to those in the placebo group. The between-intervention-group differences (treatment effects) in CV were 1.60 m/s (95% CI: 0.70, 2.40) for the median nerve and 2.10 m/s (95% CI: 1.50, 2.90) for the sural nerve. A significant difference in peak velocity (PV) was also observed in the sural nerve (2.10 m/s; 95% CI: 1.00, 3.20) after 12 months. Significant improvements in CV were only observed up to 6 months in the tibial motor nerve, 1.30 m/s (95% CI: 0.60, 2.20). There were no significant changes in serum biomarkers, transforming growth factor beta-1 (TGFβ-1), or vascular endothelial growth factor A (VEGF-A). After 6 months of washout, there were no significant differences from baseline between groups in nerve conduction parameters of all three nerves. Tocovid at 400 mg/day significantly improve tibial motor nerve CV up to 6 months, but median and sural sensory nerve CV in up to 12 months of supplementation. All improvements diminished after 6 months of washout.

Transplantation of human dental pulp stem cells ameliorates diabetic polyneuropathy in streptozotocin-induced diabetic nude mice: the role of angiogenic and neurotrophic factors

BACKGROUND

Dental pulp stem cells (DPSCs) have high proliferation and multi-differentiation capabilities that maintain their functionality after cryopreservation. In our previous study, we demonstrated that cryopreserved rat DPSCs improved diabetic polyneuropathy and that the efficacy of cryopreserved rat DPSCs was equivalent to that of freshly isolated rat DPSCs. The present study was conducted to evaluate whether transplantation of cryopreserved human DPSCs (hDPSCs) is also effective for the treatment of diabetic polyneuropathy.

METHODS

hDPSCs were isolated from human impacted third molars being extracted for orthodontic reasons. Eight weeks after the induction of diabetes in nude mice, hDPSCs (1 × 10⁵/limb) were unilaterally transplanted into the hindlimb skeletal muscle, and vehicle (saline) was injected into the opposite side as a control. The effects of hDPSCs were analyzed at 4 weeks after transplantation.

RESULTS

hDPSC transplantation significantly ameliorated reduced sensory perception thresholds, delayed nerve conduction velocity, and decreased the blood flow to the sciatic nerve in diabetic mice 4 weeks post-transplantation. Cultured hDPSCs secreted the vascular endothelial growth factor (VEGF) and nerve growth factor (NGF) proteins. A subset of the transplanted hDPSCs was localized around the muscle bundles and expressed the human VEGF and NGF genes at the transplanted site. The capillary/muscle bundle ratio was significantly increased on the hDPSC-transplanted side of the gastrocnemius muscles in diabetic mice. Neutralizing antibodies against VEGF and NGF negated the effects of hDPSC transplantation on the nerve conduction velocity in diabetic mice, suggesting that VEGF and NGF may play roles in the effects of hDPSC transplantation on diabetic polyneuropathy.

CONCLUSIONS

These results suggest that stem cell transplantation with hDPSCs may be efficacious in treating diabetic polyneuropathy via the angiogenic and neurotrophic mechanisms of hDPSC-secreted factors.

Spermine oxidase: A promising therapeutic target for neurodegeneration in diabetic retinopathy

Diabetic Retinopathy (DR), is a significant public health issue and the leading cause of blindness in working-aged adults worldwide. The vision loss associated with DR affects patients' quality of life and has negative social and psychological effects. In the past, diabetic retinopathy was considered as a vascular disease; however, it is now recognized to be a neuro-vascular disease of the retina. Current therapies for DR, such as laser photocoagulation and anti-VEGF therapy, treat advanced stages of the disease, particularly the vasculopathy and have adverse side effects. Unavailability of effective treatments to prevent the incidence or progression of DR is a major clinical problem. There is a great need for therapeutic interventions capable of preventing retinal damage in DR patients. A growing body of evidence shows that neurodegeneration is an early event in DR pathogenesis. Therefore, studies of the underlying mechanisms that lead to neurodegeneration are essential for identifying new therapeutic targets in the early stages of DR. Deregulation of the polyamine metabolism is implicated in various neurodegenerative diseases, cancer, renal failure, and diabetes. Spermine Oxidase (SMOX) is a highly inducible enzyme, and its dysregulation can alter polyamine homeostasis. The oxidative products of polyamine metabolism are capable of inducing cell damage and death. The current review provides insight into the SMOX-regulated molecular mechanisms of cellular damage and dysfunction, and its potential as a therapeutic target for diabetic retinopathy. Structural and functional changes in the diabetic retina and the mechanisms leading to neuronal damage (excitotoxicity, loss of neurotrophic factors, oxidative stress, mitochondrial dysfunction etc.) are also summarized in this review. Furthermore, existing therapies and new approaches to neuroprotection are discussed.

VEGF-B promotes recovery of corneal innervations and trophic functions in diabetic mice

Vascular endothelial growth factor (VEGF)-B possesses the capacity of promoting injured peripheral nerve regeneration and restore their sensory and trophic functions. However, the contribution and mechanism of VEGF-B in diabetic peripheral neuropathy remains unclear. In the present study, we investigated the expression and role of VEGF-B in diabetic corneal neuropathy by using type 1 diabetic mice and cultured trigeminal ganglion (TG) neurons. Hyperglycemia attenuated the endogenous expression of VEGF-B in regenerated diabetic corneal epithelium, but not that of VEGF receptors in diabetic TG neurons and axons. Exogenous VEGF-B promoted diabetic corneal nerve fiber regeneration through the reactivation of PI-3K/Akt-GSK3β-mTOR signaling and the attenuation of neuronal mitochondria dysfunction via the VEGF receptor-1 and neuropilin-1. Moreover, VEGF-B improved corneal sensation and epithelial regeneration in both normal and diabetic mice, accompanied with the elevated corneal content of pigment epithelial-derived factor (PEDF). PEDF blockade partially abolished trophic function of VEGF-B in diabetic corneal re-innervation. In conclusion, hyperglycemia suppressed endogenous VEGF-B expression in regenerated corneal epithelium of diabetic mice, while exogenous VEGF-B promoted recovery of corneal innervations and trophic functions through reactivating PI-3K/Akt-GSK-3β-mTOR signaling, attenuating neuronal oxidative stress and elevating PEDF expression.

Directing an artificial zinc finger protein to new targets by fusion to a non-DNA-binding domain

Transcription factors are often regarded as having two separable components: a DNA-binding domain (DBD) and a functional domain (FD), with the DBD thought to determine target gene recognition. While this holds true for DNA binding in vitro, it appears that in vivo FDs can also influence genomic targeting. We fused the FD from the well-characterized transcription factor Krüppel-like Factor 3 (KLF3) to an artificial zinc finger (AZF) protein originally designed to target the Vascular Endothelial Growth Factor-A (VEGF-A) gene promoter. We compared genome-wide occupancy of the KLF3FD-AZF fusion to that observed with AZF. AZF bound to the VEGF-A promoter as predicted, but was also found to occupy approximately 25 000 other sites, a large number of which contained the expected AZF recognition sequence, GCTGGGGGC. Interestingly, addition of the KLF3 FD re-distributes the fusion protein to new sites, with total DNA occupancy detected at around 50 000 sites. A portion of these sites correspond to known KLF3-bound regions, while others contained sequences similar but not identical to the expected AZF recognition sequence. These results show that FDs can influence and may be useful in directing AZF DNA-binding proteins to specific targets and provide insights into how natural transcription factors operate.

Vascular endothelial growth factor-A165b prevents diabetic neuropathic pain and sensory neuronal degeneration

Diabetic peripheral neuropathy affects up to half of diabetic patients. This neuronal damage leads to sensory disturbances, including allodynia and hyperalgesia. Many growth factors have been suggested as useful treatments for prevention of neurodegeneration, including the vascular endothelial growth factor (VEGF) family. VEGF-A is generated as two alternative splice variant families. The most widely studied isoform, VEGF-A165a is both pro-angiogenic and neuroprotective, but pro-nociceptive and increases vascular permeability in animal models. Streptozotocin (STZ)-induced diabetic rats develop both hyperglycaemia and many of the resulting diabetic complications seen in patients, including peripheral neuropathy. In the present study, we show that the anti-angiogenic VEGF-A splice variant, VEGF-A165b, is also a potential therapeutic for diabetic neuropathy. Seven weeks of VEGF-A165b treatment in diabetic rats reversed enhanced pain behaviour in multiple behavioural paradigms and was neuroprotective, reducing hyperglycaemia-induced activated caspase 3 (AC3) levels in sensory neuronal subsets, epidermal sensory nerve fibre loss and aberrant sciatic nerve morphology. Furthermore, VEGF-A165b inhibited a STZ-induced increase in Evans Blue extravasation in dorsal root ganglia (DRG), saphenous nerve and plantar skin of the hind paw. Increased transient receptor potential ankyrin 1 (TRPA1) channel activity is associated with the onset of diabetic neuropathy. VEGF-A165b also prevented hyperglycaemia-enhanced TRPA1 activity in an in vitro sensory neuronal cell line indicating a novel direct neuronal mechanism that could underlie the anti-nociceptive effect observed in vivo. These results demonstrate that in a model of Type I diabetes VEGF-A165b attenuates altered pain behaviour and prevents neuronal stress, possibly through an effect on TRPA1 activity.

Enhanced MyoD-induced transdifferentiation to a myogenic lineage by fusion to a potent transactivation domain

Genetic reprogramming holds great potential for disease modeling, drug screening, and regenerative medicine. Genetic reprogramming of mammalian cells is typically achieved by forced expression of natural transcription factors that control master gene networks and cell lineage specification. However, in many instances, the natural transcription factors do not induce a sufficiently robust response to completely reprogram cell phenotype. In this study, we demonstrate that protein engineering of the master transcription factor MyoD can enhance the conversion of human dermal fibroblasts and adult stem cells to a skeletal myocyte phenotype. Fusion of potent transcriptional activation domains to MyoD led to increased myogenic gene expression, myofiber formation, cell fusion, and global reprogramming of the myogenic gene network. This work supports a general strategy for synthetically enhancing the direct conversion between cell types that can be applied in both synthetic biology and regenerative medicine.

Engineering synthetic TALE and CRISPR/Cas9 transcription factors for regulating gene expression

Engineered DNA-binding proteins that can be targeted to specific sites in the genome to manipulate gene expression have enabled many advances in biomedical research. This includes generating tools to study fundamental aspects of gene regulation and the development of a new class of gene therapies that alter the expression of endogenous genes. Designed transcription factors have entered clinical trials for the treatment of human diseases and others are in preclinical development. High-throughput and user-friendly platforms for designing synthetic DNA-binding proteins present innovative methods for deciphering cell biology and designing custom synthetic gene circuits. We review two platforms for designing synthetic transcription factors for manipulating gene expression: Transcription activator-like effectors (TALEs) and the RNA-guided clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 system. We present an overview of each technology and a guide for designing and assembling custom TALE- and CRISPR/Cas9-based transcription factors. We also discuss characteristics of each platform that are best suited for different applications.

Mechanism of diabetic neuropathy: Where are we now and where to go?

Neuropathy is the most common complication of diabetes. As a consequence of longstanding hyperglycemia, a downstream metabolic cascade leads to peripheral nerve injury through an increased flux of the polyol pathway, enhanced advanced glycation end‐products formation, excessive release of cytokines, activation of protein kinase C and exaggerated oxidative stress, as well as other confounding factors. Although these metabolic aberrations are deemed as the main stream for the pathogenesis of diabetic microvascular complications, organ‐specific histological and biochemical characteristics constitute distinct mechanistic processes of neuropathy different from retinopathy or nephropathy. Extremely long axons originating in the small neuronal body are vulnerable on the most distal side as a result of malnutritional axonal support or environmental insults. Sparse vascular supply with impaired autoregulation is likely to cause hypoxic damage in the nerve. Such dual influences exerted by long‐term hyperglycemia are critical for peripheral nerve damage, resulting in distal‐predominant nerve fiber degeneration. More recently, cellular factors derived from the bone marrow also appear to have a strong impact on the development of peripheral nerve pathology. As evident from such complicated processes, inhibition of single metabolic factors might not be sufficient for the treatment of neuropathy, but a combination of several inhibitors might be a promising approach to overcome this serious disorder. (J Diabetes Invest, doi: 10.1111/j.2040‐1124.2010.00070.x, 2010)

Delayed administration of a bio-engineered zinc-finger VEGF-A gene therapy is neuroprotective and attenuates allodynia following traumatic spinal cord injury

Following spinal cord injury (SCI) there are drastic changes that occur in the spinal microvasculature, including ischemia, hemorrhage, endothelial cell death and blood-spinal cord barrier disruption. Vascular endothelial growth factor-A (VEGF-A) is a pleiotropic factor recognized for its pro-angiogenic properties; however, VEGF has recently been shown to provide neuroprotection. We hypothesized that delivery of AdV-ZFP-VEGF--an adenovirally delivered bio-engineered zinc-finger transcription factor that promotes endogenous VEGF-A expression--would result in angiogenesis, neuroprotection and functional recovery following SCI. This novel VEGF gene therapy induces the endogenous production of multiple VEGF-A isoforms; a critical factor for proper vascular development and repair. Briefly, female Wistar rats--under cyclosporin immunosuppression--received a 35 g clip-compression injury and were administered AdV-ZFP-VEGF or AdV-eGFP at 24 hours post-SCI. qRT-PCR and Western Blot analysis of VEGF-A mRNA and protein, showed significant increases in VEGF-A expression in AdV-ZFP-VEGF treated animals (p<0.001 and p<0.05, respectively). Analysis of NF200, TUNEL, and RECA-1 indicated that AdV-ZFP-VEGF increased axonal preservation (p<0.05), reduced cell death (p<0.01), and increased blood vessels (p<0.01), respectively. Moreover, AdV-ZFP-VEGF resulted in a 10% increase in blood vessel proliferation (p<0.001). Catwalk™ analysis showed AdV-ZFP-VEGF treatment dramatically improves hindlimb weight support (p<0.05) and increases hindlimb swing speed (p<0.02) when compared to control animals. Finally, AdV-ZFP-VEGF administration provided a significant reduction in allodynia (p<0.01). Overall, the results of this study indicate that AdV-ZFP-VEGF administration can be delivered in a clinically relevant time-window following SCI (24 hours) and provide significant molecular and functional benefits.

Effect of high-fat diet on peripheral neuropathy in C57BL/6 mice

Objective. Dyslipidemia may contribute to the development of peripheral neuropathy, even in prediabetics; however, few studies have evaluated vascular dysfunction and oxidative stress in patients with peripheral neuropathy. Methods. Using high-fat diet- (HFD-) induced prediabetic C57BL/6 mice, we assessed motor and sensory nerve conduction velocity (NCV) using a BIOPAC System and thermal algesia with a Plantar Test (Hargreaves' method) Analgesia Meter. Intraepidermal nerve fiber density and mean dendrite length were tested following standard protocols. Vascular endothelial growth factor-A (VEGF-A) and 12/15-lipoxygenase (12/15-LOX) were evaluated by immunohistochemistry and Western blot, respectively. Results. HFD-fed mice showed deficits in motor and sensory NCV, thermal hyperalgesia, reduced mean dendrite length, and VEGF-A expression in the plantar skin and increased 12/15-LOX in the sciatic nerve (P < 0.05 compared with controls). Conclusion. HFD may cause large myelinated nerve and small sensory nerve fiber damage, thus leading to neuropathy. The mean dendrite length may be a more sensitive marker for early detection of peripheral neuropathy. Reduced blood supply to the nerves and increased oxidative stress may contribute to the development and severity of peripheral neuropathy.

Therapeutic effects of 15 Hz pulsed electromagnetic field on diabetic peripheral neuropathy in streptozotocin-treated rats

Although numerous clinical studies have reported that pulsed electromagnetic fields (PEMF) have a neuroprotective role in patients with diabetic peripheral neuropathy (DPN), the application of PEMF for clinic is still controversial. The present study was designed to investigate whether PEMF has therapeutic potential in relieving peripheral neuropathic symptoms in streptozotocin (STZ)-induced diabetic rats. Adult male Sprague-Dawley rats were randomly divided into three weight-matched groups (eight in each group): the non-diabetic control group (Control), diabetes mellitus with 15 Hz PEMF exposure group (DM+PEMF) which were subjected to daily 8-h PEMF exposure for 7 weeks and diabetes mellitus with sham PEMF exposure group (DM). Signs and symptoms of DPN in STZ-treated rats were investigated by using behavioral assays. Meanwhile, ultrastructural examination and immunohistochemical study for vascular endothelial growth factor (VEGF) of sciatic nerve were also performed. During a 7-week experimental observation, we found that PEMF stimulation did not alter hyperglycemia and weight loss in STZ-treated rats with DPN. However, PEMF stimulation attenuated the development of the abnormalities observed in STZ-treated rats with DPN, which were demonstrated by increased hind paw withdrawal threshold to mechanical and thermal stimuli, slighter demyelination and axon enlargement and less VEGF immunostaining of sciatic nerve compared to those of the DM group. The current study demonstrates that treatment with PEMF might prevent the development of abnormalities observed in animal models for DPN. It is suggested that PEMF might have direct corrective effects on injured nerves and would be a potentially promising non-invasive therapeutic tool for the treatment of DPN.

Diabetes Mellitus: New Challenges and Innovative Therapies

Diabetes is a common chronic disease affecting an estimated 285 million adults worldwide. The rising incidence of diabetes, metabolic syndrome, and subsequent vascular diseases is a major public health problem in industrialized countries. This chapter summarizes current pharmacological approaches to treat diabetes mellitus and focuses on novel therapies for diabetes mellitus that are under development.

There is great potential for developing a new generation of therapeutics that offer better control of diabetes, its co-morbidities and its complications. Preclinical results are discussed for new approaches including AMPK activation, the FGF21 target, cell therapy approaches, adiponectin mimetics and novel insulin formulations. Gene-based therapies are among the most promising emerging alternatives to conventional treatments. Therapies based on gene silencing using vector systems to deliver interference RNA to cells (i.e. against VEGF in diabetic retinopathy) are also a promising therapeutic option for the treatment of several diabetic complications.

In conclusion, treatment of diabetes faces now a new era that is characterized by a variety of innovative therapeutic approaches that will improve quality of life in the near future.

Treatment of traumatic brain injury using zinc-finger protein gene therapy targeting VEGF-A

Vascular endothelial growth factor (VEGF) plays a role in angiogenesis and has been shown to be neuroprotective following central nervous system trauma. In the present study we evaluated the pro-angiogenic and neuroprotective effects of an engineered zinc-finger protein transcription factor transactivator targeting the vascular endothelial growth factor A (VEGF-ZFP). We used two virus delivery systems, adeno-virus and adeno-associated virus, to examine the effects of early and delayed VEGF-A upregulation after brain trauma, respectively. Male Sprague-Dawley rats were subject to a unilateral fluid percussion injury (FPI) of moderate severity (2.2-2.5 atm) followed by intracerebral microinjection of either adenovirus vector (Adv) or an adeno-associated vector (AAV) carrying the VEGF-ZFP construct. Adv-VEGF-ZFP-treated animals had significantly fewer TUNEL positive cells in the injured penumbra of the cortex (p<0.001) and hippocampus (p=0.001) relative to untreated rats at 72 h post-injury. Adv-VEGF-ZFP treatment significantly improved fEPSP values (p=0.007) in the CA1 region relative to injury alone. Treatment with AAV2-VEGF-ZFP resulted in improved post-injury microvascular diameter and improved functional recovery on the balance beam and rotarod task at 30 days post-injury. Collectively, the results provide supportive evidence for the concept of acute and delayed treatment following TBI using VEGF-ZFP to induce angiogenesis, reduce cell death, and enhance functional recovery.

Angiotensin-converting enzyme gene single polymorphism as a genetic biomarker of diabetic peripheral neuropathy: longitudinal prospective study

BACKGROUND

Identifying patients at risk of developing diabetic peripheral neuropathy (DPN) is of paramount importance in those with type 2 diabetes mellitus (T2DM) to provide and anticipate secondary prevention measures as well as intensify action on risk factors, particularly so in primary care. Noteworthy, the incidence of DPN remains unknown in our environment.

AIMS

(i) To analyze a single angiotensin-converting enzyme (ACE) gene polymorphism (D/I) as a genetic marker of risk of developing DPN, and (ii) to determine the incidence of DPN in our environment.

RESEARCH DESIGN AND METHODS

Longitudinal study with annual follow-up for 3years involving a group of T2DM (N=283) randomly selected. ACE gene polymorphism distribution (I=insertion; D=deletion) was determined. DPN was diagnosed using clinical and neurophysiology evaluation.

RESULTS

Baseline DPN prevalence was 28.97% (95% CI, 23.65-34.20). ACE polymorphism heterozygous genotype D/I presence was 60.77% (95% CI, 55.05-66.5) and was independently associated with a decreased risk of DPN (RR, 0.51; 95% CI, 0.30-0.86). DPN correlated with age (P<0.001) but not with gender (P=0.466) or time of evolution of T2DM (P=0.555). Regarding end point, DPN prevalence was 36.4% (95% CI, 30.76-42.04), and accumulated incidence was 10.4% 3years thereafter. In the final Poisson regression analysis, the presence of heterozygous genotype remained independently associated with a decreased risk of DPN (RR, 0.71; (95% CI, 0.53-0.96). DPN presence remained correlated with age (P=0.002), but not with gender (P=0.490) or time of evolution (P=0.630).

CONCLUSIONS

In our series, heterozygous ACE polymorphism (D/I) stands as a protective factor for DPN development. Accumulated incidence of DPN was relevant. Further prospective studies are warranted.

Intramuscular administration of a VEGF zinc finger transcription factor activator (VEGF-ZFP-TF) improves functional outcomes in SOD1 rats

Amyotrophic lateral sclerosis (ALS) is characterized by motor neuron loss leading to paralysis and death. Vascular endothelial growth factor (VEGF) has angiogenic, neurotrophic, and neuroprotective properties, and has preserved neuromuscular function and protected motor neurons in rats engineered to overexpress the human gene coding the mutated G93A form of the superoxide dismutase-1 (SOD1). We assessed the effects of intramuscular administration of a plasmid that encodes a zinc finger protein transcription factor (ZFP-TF) engineered to induce VEGF expression in the SOD1 rat model of ALS. Weekly injections of the plasmid preserved ipsilateral hindlimb grip strength and markedly improved rotarod performance in SOD1 rats compared to the vehicle-treated group. The number of motor neurons and the proportion of innervated neuromuscular junctions were similar in both groups. In conclusion, our data suggest that administration of the VEGF-ZFP-TF may be neuroprotective and has potential as a safe and practical approach for the management of motor disability in ALS.

Regulation of hypoxia-inducible factor 1 and the loss of the cellular response to hypoxia in diabetes

Diabetes is frequently associated with hypoxia and is known to impair ischaemia-induced neovascularisation and other forms of adaptive cell and tissue responses to low oxygen levels. Hyperglycaemia appears to be the driving force of such deregulation. Recent data indicate that destabilisation of hypoxia-inducible factor 1 (HIF-1) is most likely the event that transduces hyperglycaemia into the loss of the cellular response to hypoxia in most diabetic complications. HIF-1 is a critical transcription factor involved in oxygen homeostasis that regulates a variety of adaptive responses to hypoxia, including angiogenesis, metabolic reprogramming and survival. Thus, destabilisation of HIF-1 is likely to have a negative impact on cell and tissue adaptation to low oxygen. Indeed, destabilisation of HIF-1 by high glucose levels has serious consequences in various organs and tissues, including myocardial collateralisation, wound healing, renal, neural and retinal function, as a result of poor cell and tissue responses to low oxygen. This review aims to integrate and summarise some of the most recent developments, including new proposed molecular models, on this research topic, particularly in terms of their implications for potential therapeutic approaches for the prevention or treatment of some of the diabetic complications characterised by impaired cellular and tissue responses to hypoxia.

Regulation of hypoxia-inducible factor 1 and the loss of the cellular response to hypoxia in diabetes

Diabetes is frequently associated with hypoxia and is known to impair ischaemia-induced neovascularisation and other forms of adaptive cell and tissue responses to low oxygen levels. Hyperglycaemia appears to be the driving force of such deregulation. Recent data indicate that destabilisation of hypoxia-inducible factor 1 (HIF-1) is most likely the event that transduces hyperglycaemia into the loss of the cellular response to hypoxia in most diabetic complications. HIF-1 is a critical transcription factor involved in oxygen homeostasis that regulates a variety of adaptive responses to hypoxia, including angiogenesis, metabolic reprogramming and survival. Thus, destabilisation of HIF-1 is likely to have a negative impact on cell and tissue adaptation to low oxygen. Indeed, destabilisation of HIF-1 by high glucose levels has serious consequences in various organs and tissues, including myocardial collateralisation, wound healing, renal, neural and retinal function, as a result of poor cell and tissue responses to low oxygen. This review aims to integrate and summarise some of the most recent developments, including new proposed molecular models, on this research topic, particularly in terms of their implications for potential therapeutic approaches for the prevention or treatment of some of the diabetic complications characterised by impaired cellular and tissue responses to hypoxia.

Novel insights on diagnosis, cause and treatment of diabetic neuropathy: focus on painful diabetic neuropathy

Diabetic neuropathy is common, under or misdiagnosed, and causes substantial morbidity with increased mortality. Defining and developing sensitive diagnostic tests for diabetic neuropathy is not only key to implementing earlier interventions but also to ensure that the most appropriate endpoints are employed in clinical intervention trials. This is critical as many potentially effective therapies may never progress to the clinic, not due to a lack of therapeutic effect, but because the endpoints were not sufficiently sensitive or robust to identify benefit. Apart from improving glycaemic control, there is no licensed treatment for diabetic neuropathy, however, a number of pathogenetic pathways remain under active study. Painful diabetic neuropathy is a cause of considerable morbidity and whilst many pharmacological and nonpharmacological interventions are currently used, only two are approved by the US Food and Drug Administration. We address the important issue of the 'placebo effect' and also consider potential new pharmacological therapies as well as nonpharmacological interventions in the treatment of painful diabetic neuropathy.

Diabetes mellitus: new challenges and innovative therapies

Diabetes mellitus is a widespread disease prevalence and incidence of which increases worldwide. The introduction of insulin therapy represented a major breakthrough in type 1 diabetes; however, frequent hyper- and hypoglycemia seriously affects the quality of life of these patients. New therapeutic approaches, such as whole pancreas transplant or pancreatic islet transplant, stem cell, gene therapy and islets encapsulation are discussed in this review. Regarding type 2 diabetes, therapy has been based on drugs that stimulate insulin secretion (sulphonylureas and rapid-acting secretagogues), reduce hepatic glucose production (biguanides), delay digestion and absorption of intestinal carbohydrate (alpha-glucosidase inhibitors) or improve insulin action (thiazolidinediones). This review is also focused on the newer therapeutically approaches such as incretin-based therapies, bariatric surgery, stem cells and other emerging therapies that promise to further extend the options available. Gene-based therapies are among the most promising emerging alternatives to conventional treatments. Some of these therapies rely on genetic modification of non-differentiated cells to express pancreatic endocrine developmental factors, promoting differentiation of non-endocrine cells into β-cells, enabling synthesis and secretion of insulin in a glucose-regulated manner. Alternative therapies based on gene silencing using vector systems to deliver interference RNA to cells (i.e. against VEGF in diabetic retinopathy) are also a promising therapeutic option for the treatment of several diabetic complications. In conclusion, treatment of diabetes faces now a new era that is characterized by a variety of innovative therapeutic approaches that will improve quality-life and allow personalized therapy-planning in the near future.

Engineered zinc finger protein-mediated VEGF-a activation restores deficient VEGF-a in sensory neurons in experimental diabetes

OBJECTIVE

The objectives of the study were to evaluate retrograde axonal transport of vascular endothelial growth factor A (VEGF-A) protein to sensory neurons after intramuscular administration of an engineered zinc finger protein activator of endogenous VEGF-A (VZ+434) in an experimental model of diabetes, and to characterize the VEGF-A target neurons.

RESEARCH DESIGN AND METHODS

We compared the expression of VEGF-A in lumbar (L)4/5 dorsal root ganglia (DRG) of control rats and VZ+434-treated and untreated streptozotocin (STZ)-induced diabetic rats. In addition, axonal transport of VEGF-A, activation of signal transduction pathways in the DRG, and mechanical sensitivity were assessed.

RESULTS

VEGF-A immunoreactivity (IR) was detected in small- to medium-diameter neurons in DRG of control rats. Fewer VEGF-A-IR neurons were observed in DRG from STZ-induced diabetic rats; this decrease was confirmed and quantified by Western blotting. VZ+434 administration resulted in a significant increase in VEGF-A protein expression in ipsilateral DRG, 24 h after injection. VEGF-A was axonally transported to the DRG via the sciatic nerve. VZ+434 administration resulted in significant activation of AKT in the ipsilateral DRG by 48 h that was sustained for 1 week after injection. VZ+434 protected against mechanical allodynia 8 weeks after STZ injection.

CONCLUSIONS

Intramuscular administration of VZ+434 increases VEGF-A protein levels in L4/5 DRG, correcting the deficit observed after induction of diabetes, and protects against mechanical allodynia. Elevated VEGF-A levels result from retrograde axonal transport and are associated with altered signal transduction, via the phosphatidylinositol 3'-kinase pathway. These data support a neuroprotective role for VEGF-A in the therapeutic actions of VZ+434 and suggest a mechanism by which VEGF-A exerts this activity.

Diabetes and failure of axon regeneration in peripheral neurons

Peripheral neurons are targeted by a 'double hit' during diabetes mellitus. First, they are damaged directly; diabetic polyneuropathy is a progressive neurodegenerative disorder that involves sensory, autonomic and eventually motor neurons. The second 'hit' involves a profound impairment in the ability of peripheral axons to regenerate. This is important because the impairment impacts on how patients may recover from polyneuropathy. Moreover, diabetic patients also develop direct focal injures of peripheral nerves, such as carpal tunnel syndrome and ulnar neuropathy at the elbow. Their response to the treatment of these selective injuries is also impaired. Regeneration of peripheral neurons is normally a complex process that involves axon sprouting, upregulation of molecular regeneration programs, clearance of pathways for axon regrowth, maturation of new axons and reconnection to their targets. Schwann cells and perineuronal glial cells provide support during many of these processes. However, in diabetes mellitus a number of these steps may be independently impaired. In this brief article, we discuss evidence for several of these mechanisms of regenerative failure in diabetes.

The generation of zinc finger proteins by modular assembly

The modular assembly (MA) method of generating engineered zinc finger proteins (ZFPs) was the first practical method for creating custom DNA-binding proteins. As such, MA has enabled a vast exploration of sequence-specific methods and reagents, ushering in the modern era of zinc finger-based applications that are described in this volume. The first zinc finger nuclease to cleave an endogenous site was created using MA, as was the first artificial transcription factor to enter phase II clinical trials. In recent years, other excellent methods have been developed that improved the affinity and specificity of the engineered ZFPs. However, MA is still used widely for many applications. This chapter will describe methods and give guidance for the creation of ZFPs using MA. Such ZFPs might be useful as starting materials to perform other methods described in this volume. Here, we also describe a single-strand annealing recombination assay for the initial testing of zinc finger nucleases.

Neuroprotection using gene therapy to induce vascular endothelial growth factor-A expression

Engineered zinc-finger protein (ZFP) transcription factors induce the expression of endogenous genes and can be remotely delivered using adenoviral vectors. One such factor, Ad-32Ep65-Flag (Ad-p65), targets and induces expression of vascular endothelial growth factor (VEGF; also called VEGF-A) splice variants in their normal biological stoichiometry. We show that Ad-p65 transfection of primary motor neurons results in VEGF variant expression and a significant increase in axon outgrowth in these cells. Given the neuroprotective effects of VEGF and its ability to increase neurite outgrowth, we examined the efficacy of Ad-p65 to enhance motor neuron regeneration in vivo using rats that have undergone recurrent laryngeal nerve (RLN)-crush injury. Injection of Ad-p65 after RLN crush accelerated the return of vocal fold mobility and the percentage of nerve-endplate contacts in the thyroarytenoid muscle. Overall, adenoviral delivery of an engineered ZFP transcription factor inducing VEGF-A splice variant expression enhances nerve regeneration. ZFP transcription factor gene therapy to increase expression of the full complement of VEGF-A splice variants is a promising avenue for the treatment of nerve injury and neurodegeneration.

Reinstate the damaged VEGF signaling pathway with VEGF-activating transcription factor

OBJECTIVE

To investigate the role of vascular endothelial growth factor-activating transcriptional factor (VEGF-ATF) on the VEGF signaling pathway in diabetes mellitus.

METHODS

Totally, 20 C57BL/6 mice fed with high fat diet was induced into diabetes mellitus. Ten diabetes mellitus mice received a lower limb muscle injection with VEGF-ATF plasmid, and another ten were as control. VEGF-ATF is an engineered transcription factor designed to increase VEGF expression. Three days later, mice were sacrificed and the injected gastrocnemius was used for analysis. VEGF mRNA and protein expressions were examined by real-time PCR and ELISA respectively. VEGF receptor 2 mRNA expression was tested with RT-PCR. Phosphorylated Akt, Akt, endothelial nitric oxide synthase (eNOS), and phosphorylated eNOS were assessed by western blot.

RESULTS

At 3 days post-injection, in mice with diabetes mellitus, VEGF gene transfer increased VEGF mRNA copies and VEGF protein expression in injected muscles compared with control; and reinstated the impaired VEGF signaling pathway with increasing the ratios of phosphorylated Akt/Akt and phosphorylated eNOS/eNOS. However, it did not affect the expression of VEGF receptor 2 mRNA.

CONCLUSION

Gene transfer with VEGF-ATF is able to reinstate the impaired VEGF downstream pathway, and potentially promote therapeutic angiogenesis in mice with diabetes mellitus.

Vascular endothelial growth factor-A: a multifunctional molecular player in diabetic retinopathy

Vascular endothelial growth factor-A (VEGF-A), first described as "vascular permeability factor", is a critical molecule in the pathogenesis of diabetic retinopathy at several levels. Previous studies have outlined the importance of VEGF-A in mediating vascular pathology in both experimental models and clinical diabetic retinopathy, which are characterized by retinal vascular leakage, preretinal neovascularisation and neuronal degeneration. Paradoxically, recent reports have emphasized the potential neurotrophic effects of VEGF-A on the quiescent vasculature, as well as its direct and indirect protective effects on retinal neurons. VEGF-A has also been identified as an important signalling regulator in the normal central nervous system. Consequently, anti-VEGF therapy for diabetic retinopathy has become a controversal issue. This review outlines recently developed concepts relating to the role of VEGF-A in the pathogenesis of diabetic retinopathy, with particular emphasis on its implications for clinical practice.

Zinc-finger-based artificial transcription factors and their applications

Artificial transcription factors (ATFs) are potentially a powerful molecular tool to modulate endogenous target gene expression in living cells and organisms. To date, many DNA-binding molecules have been developed as the DNA-binding domains for ATFs. Among them, ATFs comprising Cys(2)His(2)-type zinc-finger proteins (ZFPs) as the DNA-binding domain have been extensively explored. The zinc-finger-based ATFs specifically recognize targeting sites in chromosomes and effectively up- and downregulate expression of their target genes not only in vitro, but also in vivo. In this review, after briefly introducing Cys(2)His(2)-type ZFPs, I will review the studies of endogenous human gene regulation by zinc-finger-based ATFs and other applications as well.

Role and therapeutic potential of VEGF in the nervous system

The development of the nervous and vascular systems constitutes primary events in the evolution of the animal kingdom; the former provides electrical stimuli and coordination, while the latter supplies oxygen and nutrients. Both systems have more in common than originally anticipated. Perhaps the most striking observation is that angiogenic factors, when deregulated, contribute to various neurological disorders, such as neurodegeneration, and might be useful for the treatment of some of these pathologies. The prototypic example of this cross-talk between nerves and vessels is the vascular endothelial growth factor or VEGF. Although originally described as a key angiogenic factor, it is now well established that VEGF also plays a crucial role in the nervous system. We describe the molecular properties of VEGF and its receptors and review the current knowledge of its different functions and therapeutic potential in the nervous system during development, health, disease and in medicine.

Vascular endothelial growth factor gene transfer for diabetic polyneuropathy: a randomized, double-blinded trial

OBJECTIVE

Randomized, blinded trial of intramuscular gene transfer using plasmid vascular endothelial growth factor (VEGF) to treat diabetic polyneuropathy.

METHODS

Diabetic patients with polyneuropathy were randomized to receive a VEGF-to-placebo ratio of 3:1. Three sets of injections were given at eight standardized sites adjacent to the sciatic, peroneal, and tibial nerves of one leg. Primary outcomes were change in symptom score at 6 months and a prespecified overall clinical and electrophysiological improvement score. Secondary outcomes were differences in symptoms, examination scores, visual analog pain scale, nerve conduction, and quantitative sensory testing.

RESULTS

Thirty-nine patients received plasmid VEGF and 11 received placebo. Mean symptom score improved in both legs at 6 months, favoring VEGF over placebo (-1.2 +/- 0.5 vs -0.9 +/- 0.5; p < 0.01 after adjustment for change in the untreated leg) and compared with the untreated leg (-0.7 +/- 0.5; p = 0.02). The region of sensory loss and visual analog pain scale improved in the treated group (-1.5 vs -0.5; p = 0.01). Twelve of 39 VEGF versus 2 of 11 placebo patients met criterion for overall improvement. Other measures including nerve conduction potentials did not improve. There were 84 adverse events in VEGF patients, and 22 were serious; there were 51 events in placebo patients, and 2 were serious.

INTERPRETATION

Intramuscular plasmid VEGF gene transfer improved diabetic neuropathic symptoms, meeting primary end-point criteria for efficacy but not affecting most secondary measures. Treatment was associated with more serious adverse events that did not reach statistical significance. These results are not conclusive but may justify further clinical study.

Therapies for hyperglycaemia-induced diabetic complications: from animal models to clinical trials

Diabetic complications — the long-term damage to various organ systems — are a great cause of mortality and morbidity in both type 1 and type 2 diabetes. There are currently few therapeutic options to prevent or ameliorate these complications.

High blood glucose levels and the subsequent metabolic consequences of hyperglycaemia are widely considered the primary event that initiates diabetic complications, although there is accumulating evidence that impaired insulin signalling arising from insulin deficiency and insulin resistance may also have a pathogenic role.

Vascular dysfunction is a prominent complication of diabetes that is widely held to underlie damage to organ systems such as the macrovasculature, kidneys, eyes and nerves. Other consequences of diabetes, such as dyslipidaemia and hypertension, are key modifiers of vascular injury and act as accelerators of diabetic complications.

Numerous pathogenic mechanisms, including increased polyol pathway flux and mitochondrial activity, activation of protein kinase C and NADPH oxidase and signalling through the receptor for advanced glycation end products (RAGE) pathway, seem to form a central pathogenic axis that is common to most, if not all, of the complications of diabetes. These disorders all promote excess production of pro-oxidative molecules. Organ-specific mechanisms, such as diminished growth factor support and repair pathway activation, must also be considered.

Few animal models of diabetic complications faithfully reflect the advanced stages of organ pathology seen in humans. Current models can be viewed as potentially illustrating early biochemical and functional disorders of diabetes that ultimately lead to advanced pathology. New animal models are being developed using both a reductionist approach for examining specific gene products of interest and also by combining diverse molecular and physiological risk factors.

Control of blood glucose levels and lipids remains the most meaningful approach for preventing diabetic complications. This strategy is likely to be complemented by a diverse range of more focused therapeutics that have emerged from mechanistic studies in animal models and which are currently in clinical development. Some of these, such as those targeting cardiovascular disease, have the potential to affect several diabetic complications, whereas others focus on intervening in organ-specific pathogenic mechanisms. It is probable that combination therapies aimed at the hyperglycaemia-driven pathogenic axis and also at organ-specific disorders will provide the most effective approach to treating the diverse complications of diabetes.

Long-term diabetes increases the likelihood of developing complications such as macrovascular disease, nephropathy, retinopathy and neuropathy. This Review highlights the range of pathologies that are precipitated by hyperglycaemia and discusses recent developments in preclinical and clinical research for each of these complications.

Long-term diabetes increases the likelihood of developing secondary damage to numerous systems, and these complications represent a substantial cause of morbidity and mortality. Establishing the causes of diabetes remains the key step towards eradicating the disease, but the prevention and amelioration of diabetic complications is equally important for the millions of individuals who already have the disease or are likely to develop it before prophylaxis or a cure become routinely available. In this Review, we focus on four common complications of diabetes, discuss the range of pathologies that are precipitated by hyperglycaemia and highlight emerging targets for therapeutic intervention.

Clinical screening and diagnosis of diabetic polyneuropathy: the North Catalonia Diabetes Study

BACKGROUND

To evaluate the prevalence of diabetic polyneuropathy (DPN) and develop a simple and accurate method for the evaluation of DPN risk in primary care settings.

MATERIALS AND METHODS

Cross-sectional descriptive study in a random sample (N = 307) of type 2 diabetes mellitus participants. DPN was diagnosed by both clinical neurological examination and simplified DPN Selection Method in each patient. Correlation between the two methods was obtained.

RESULTS

Prevalence of DPN was 23.13% (confidence interval,18.38-27.87) according to clinical neurological examination. Noteworthy, clinical neurological evaluation scores were related to nerve conduction studies (r = 0.882; P < 0.0005). DPN presence was positively related to age, metabolic control (HbA1c levels), known duration of diabetes, diabetic retinopathy, cardiovascular disease, peripheral ischemia and systolic and diastolic blood pressure, but was negatively related to current high-density lipoprotein cholesterol (HDL-C) levels (P < 0.0001). The sensitivity and specificity of our DPN Selection Method (using four clinical parameters: age, retinopathy, HbA1c and HDL-C plasma levels) for diagnosis of DPN was 74.20% and 74.90%, respectively.

CONCLUSIONS

The expected prevalence of DPN was observed. The sensitivity of the DPN Selection Method correlated well with formal clinical neurological exam in detection of the condition. We therefore conclude the DPN Selection Method is a useful tool in primary care settings in the evaluation and diagnosis of DPN.

Serum VEGF increases in diabetic polyneuropathy, particularly in the neurologically active symptomatic stage

AIM

To identify the relationship between vascular endothelial growth factor (VEGF) and diabetic polyneuropathy (DPN).

METHODS

Two hundred and twenty diabetic patients participated, 113 with DPN and 107 without DPN. All patients were also classified according to the four stages of DPN (no neuropathy: stage 0; asymptomatic neuropathy: stage 1; symptomatic neuropathy: stage 2; disabling neuropathy: stage 3). Serum VEGF concentration was measured using an enzyme-linked immunosorbent assay (ELISA) and levels between the patients with and without DPN and also between the different stages of DPN, were compared.

RESULTS

The mean serum VEGF level in all patients was 264.6 +/- 218.8 pg/ml. The mean serum VEGF level was higher in patients with DPN (310.1 +/- 224.3 pg/ml) than in the patients without DPN (216.5 +/- 204.0 pg/ml, P = 0.0014). Serum VEGF was higher in the 'symptomatic' stage (stage 2, 364.8 +/- 225.9 pg/ml) in comparison with the 'asymptomatic' (stage 1, 256.7 +/- 224.4 pg/ml, P = 0.015) and 'disabling' (stage 3, 180.3 +/- 109.4 pg/ml, P = 0.042) stages. The mean serum VEGF level in patients with diabetic retinopathy (261.1 +/- 210.6 pg/ml) and in patients with diabetic nephropathy (241.5 +/- 185.7 pg/ml) was not increased.

CONCLUSIONS

The serum VEGF level is increased in patients with DPN, particularly in patients in the neurologically active 'symptomatic' stage.

The therapeutic potential of VEGF inhibition in diabetic microvascular complications

During the last few years, the incidence of microvascular complications in diabetes mellitus has rapidly increased as a consequence of both an increase in incidence of type 2 and type 1 diabetes mellitus. The pathogenesis of diabetic microvascular complications is still largely unknown. Among the many hypotheses, a dysfunction in angiogenesis has been suggested as a common origin for retinopathy, nephropathy, and neuropathy. Based on this hypothesis, inhibition of vascular endothelial growth factor (VEGF) has been tested as a potential therapeutic approach to prevent and cure diabetic microvascular complications. Several VEGF inhibitors are currently under evaluation or are approved for the treatment of wet age-related macular degeneration and macular edema. These include inhibitors of intracellular transcription of VEGF (e.g. bevasiranib), inhibitors of extracellular VEGF (e.g. pegaptanib), inhibitors of VEGF receptor expression (e.g. aflibercept [VEGF-TRAP]) and inhibitors of the intracellular signaling cascade activating VEGF (e.g. midostaurin). According to the existing evidence base, although inhibition of VEGF results in a better outcome in the case of diabetic retinopathy and also, despite some discrepant results, in the case of diabetic nephropathy, there is no final confirmation that VEGF inhibition is a valid approach for diabetic neuropathy. The latter complication actually, in line with other chronic neuropathies, seems to improve with stimulation of angiogenesis through increased expression of VEGF.

Reduced vascular endothelial growth factor expression and intra-epidermal nerve fiber loss in human diabetic neuropathy

OBJECTIVE

To assess the relevance of vascular endothelial growth factor (VEGF) in the maintenance of peripheral nerve integrity in diabetic neuropathy we have assessed the expression of VEGF and intra-epidermal nerve fiber density (IENFD) in skin biopsy samples from diabetic patients.

RESEARCH DESIGN AND METHODS

Fifty-three diabetic patients and 12 nondiabetic control subjects underwent neurological evaluation, electrophysiology, quantitative sensory, and autonomic function testing. Dermal blood flow responses were evaluated with laser Doppler flowmetry. Skin biopsies were performed on the dorsum of the foot, and IENFD was quantified and compared with the expression of vascular endothelial growth factor A (VEGF-A), its receptor vascular endothelial growth factor receptor 2 (VEGFR-2), hypoxia-inducible factor 1alpha (HIF-1alpha), and microvessel density.

RESULTS

IENFD decreased progressively with increasing severity of diabetic neuropathy (P < 0.001). The dermal blood flow response to acetylcholine was reduced in diabetic patients with mild and moderate neuropathy (P < 0.01), and the intensity of staining for epidermal VEGF-A was significantly reduced in diabetic patients compared with control subjects (P < 0.01). Epidermal HIF-1alpha and VEGFR-2 expression did not differ between groups.

CONCLUSIONS

Progressive endothelial dysfunction, a reduction in VEGF expression, and loss of intra-epidermal nerve fibers occurs in the foot skin of diabetic patients with increasing neuropathic severity.

Regulation of endogenous gene expression using small molecule-controlled engineered zinc-finger protein transcription factors

Small-molecule-regulated gene expression offers the promise of titrating the dose and duration of action of DNA-based therapies. To this end, we show that engineered zinc-finger protein transcription factors (ZFP TFs) can be coupled with a drug-inducible regulatory domain to permit small-molecule control of endogenous gene transcription. We constructed a drug-responsive ZFP TF via the fusion of a ZFP DNA-binding domain (DBD) targeting the human VEGF-A gene and an effector domain containing a truncated progesterone receptor ligand-binding domain linked to the NFkappaB p65 activation domain. Introduction of this engineered ZFP TF into human or murine cells allowed expression of the chromosomal VEGF-A gene to be induced upon addition of mifepristone, a synthetic steroid analog. Mifepristone-dependent VEGF-A induction was rapid, dose-dependent and reversible. Moreover, stable lines expressing the drug-responsive ZFP TF could be maintained in a state of continuous induction for at least 30 days without loss of viability. Potent VEGF-A induction was demonstrated using different engineered ZFP DBDs, thus this approach may represent a general solution to small-molecule regulation of targeted endogenous genes.

In mice with type 2 diabetes, a vascular endothelial growth factor (VEGF)-activating transcription factor modulates VEGF signaling and induces therapeutic angiogenesis after hindlimb ischemia

Peripheral arterial disease is a major complication of diabetes. The ability to promote therapeutic angiogenesis may be limited in diabetes. Type 2 diabetes was induced by high-fat feeding C57BL/6 mice (n = 60). Normal chow-fed mice (n = 20) had no diabetes. Mice underwent unilateral femoral artery ligation and excision. A plasmid DNA encoded an engineered transcription factor designed to increase vascular endothelial growth factor expression (ZFP-VEGF). On day 10 after the operation, the ischemic limbs received 125 microg ZFP-VEGF plasmid or control. Mice were killed 3, 10, or 20 days after injection (n = 10/group, at each time point). Limb blood flow was measured by laser Doppler perfusion imaging. VEGF mRNA expression was examined by real-time PCR. VEGF, Akt, and phospho-Akt protein were measured by enzyme-linked immunosorbent assay. Capillary density, proliferation, and apoptosis were assessed histologically. Compared with normal mice, mice with diabetes had greater VEGF protein, reduced phospho-Akt-to-Akt ratio before ligation, and an impaired perfusion recovery after ligation. At 3 and 10 days after injection, in mice with diabetes, gene transfer increased VEGF expression and signaling. At later time points, gene transfer resulted in better perfusion recovery. Gene transfer with ZFP-VEGF was able to promote therapeutic angiogenesis mice with type 2 diabetes.

Isolated Use of Vibration Perception Thresholds and Semmes-Weinstein Monofilament in Diagnosing Diabetic Polyneuropathy: “The North Catalonia Diabetes Study”

Several systems are used for the diagnosis of diabeticpolyneuropathy (DPN). We analyzed the isolated use of vibration perception thresholds (VPTs) or monofilament (MF) for the diagnosis of DPN. A group of 400 patients who had type 2 diabetes was selected from the North Catalonia Study Group. A clinical neurologic evaluation was performed based on three categories of the San Antonio Consensus. Neurothesiometer and quantitative tuning fork explored VPT, and MF was assessed by Olmos and Michigan Diabetic Neuropathy Score (MDNS) criteria. The use of VPT and MF showed a high specificity and low sensitivity. MF, by MDNS criteria, was more sensitive and specific, and showed more accurate positive and negative predictive values. The predicted probability of DPN diagnosis was higher with a tuning fork evaluation.

Targeting the human genome

In recent years, some useful nucleic-acid-based tools including antisense oligonucleotides, aptamers, ribozymes, and small interfering RNA have been developed to alter the expression of a given gene. To date, however, these methods have proven to be generally insufficient for many applications and typically have not demonstrated high delivery efficiency or high target specificity in vivo. Emerging technologies that employ artificially designed transcription factors could offer an alternative solution, as they can recognize target DNA sequences with high specificity. In addition, these artificial proteins can be used not only as transcriptional regulators but also as genome modifiers that cleave and stimulate mutations at desired positions in the genome. These nucleotide-targeting molecules must be delivered efficiently to the target cells to promote their therapeutic activity and several delivery technologies have been developed for this purpose.