Defective myogenic response of retinal vessels is associated with accelerated onset of retinopathy in type 1 diabetic individuals

PURPOSE: We seek to identify pathogenic mechanisms for diabetic retinopathy that can become therapeutic targets beyond hyperglycemia and hypertension. We investigated if a defective myogenic response of retinal arteries to increased perfusion pressure, which exposes capillaries to increased pressure and flow, is associated with the onset of clinical retinopathy. METHODS: We examined prospectively the incidence of retinopathy in type 1 diabetic individuals tested 4 years earlier for the retinal arterial myogenic response, and in a cross-sectional study the prevalence of defective myogenic response in type 1 patients who had diabetic retinopathy. Among these, we contrasted early-onset (after 15 \ub1 2 years of diabetes, E-DR; n = 5) to late-onset (after 26 \ub1 3 years of diabetes, L-DR; n = 7) retinopathy. We measured the myogenic response using a laser Doppler blood flowmeter after a change in posture from sitting to reclining, which increases retinal perfusion pressure. RESULTS: Five of seven participants who 4 years prior had a defective myogenic response had now developed clinical retinopathy; as compared with only one of six participants who 4 years prior had a normal response (P = 0.10). In the cross-sectional study, all participants had normal retinal hemodynamics at steady state. In response to the postural change, only the E-DR group showed defective myogenic response (P = 0.005 versus controls, P = 0.02 versus L-DR) and abnormally high retinal blood flow (P = 0.016 versus controls). CONCLUSIONS: In type 1 diabetic patients, a defective myogenic response of retinal arteries to pressure is not required for the development of clinical retinopathy, but is prominently associated with an accelerated onset of retinopathy

Mechanisms involved in the development and healing of diabetic foot ulceration

We examined the role of vascular function and inflammation in the development and failure to heal diabetic foot ulcers (DFUs). We followed 104 diabetic patients for a period of 18.4 \ub1 10.8 months. At the beginning of the study, we evaluated vascular reactivity and serum inflammatory cytokines and growth factors. DFUs developed in 30 (29%) patients. DFU patients had more severe neuropathy, higher white blood cell count, and lower endothelium-dependent and -independent vasodilation in the macrocirculation. Complete ulcer healing was achieved in 16 (53%) patients, whereas 13 (47%) patients did not heal. There were no differences in the above parameters between the two groups, but patients whose ulcers failed to heal had higher tumor necrosis factor-\u3b1, monocyte chemoattractant protein-1, matrix metallopeptidase 9 (MMP-9), and fibroblast growth factor 2 serum levels when compared with those who healed. Skin biopsy analysis showed that compared with control subjects, diabetic patients had increased immune cell infiltration, expression of MMP-9, and protein tyrosine phosphatase-1B (PTP1B), which negatively regulates the signaling of insulin, leptin, and growth factors. We conclude that increased inflammation, expression of MMP-9, PTP1B, and aberrant growth factor levels are the main factors associated with failure to heal DFUs. Targeting these factors may prove helpful in the management of DFUs

Mechanisms Involved in the Development and Healing of Diabetic Foot Ulceration

We examined the role of vascular function and inflammation in the development and failure to heal diabetic foot ulcers (DFUs). We followed 104 diabetic patients for a period of 18.4 ± 10.8 months. At the beginning of the study, we evaluated vascular reactivity and serum inflammatory cytokines and growth factors. DFUs developed in 30 (29%) patients. DFU patients had more severe neuropathy, higher white blood cell count, and lower endothelium-dependent and -independent vasodilation in the macrocirculation. Complete ulcer healing was achieved in 16 (53%) patients, whereas 13 (47%) patients did not heal. There were no differences in the above parameters between the two groups, but patients whose ulcers failed to heal had higher tumor necrosis factor-α, monocyte chemoattractant protein-1, matrix metallopeptidase 9 (MMP-9), and fibroblast growth factor 2 serum levels when compared with those who healed. Skin biopsy analysis showed that compared with control subjects, diabetic patients had increased immune cell infiltration, expression of MMP-9, and protein tyrosine phosphatase-1B (PTP1B), which negatively regulates the signaling of insulin, leptin, and growth factors. We conclude that increased inflammation, expression of MMP-9, PTP1B, and aberrant growth factor levels are the main factors associated with failure to heal DFUs. Targeting these factors may prove helpful in the management of DFUs

Role of Endothelial Progenitor Cells and Inflammatory Cytokines in Healing of Diabetic Foot Ulcers

Background: To evaluate changes in endothelial progenitor cells (EPCs) and cytokines in patients with diabetic foot ulceration (DFU) in association with wound healing. Methods: We studied healthy subjects, diabetic patients not at risk of DFU, at risk of DFU and with active DFU. We prospectively followed the DFU patients over a 12-week period. We also investigated similar changes in diabetic rabbit and mouse models of wound healing. Results: All EPC phenotypes except the kinase insert domain receptor (KDR)+CD133+ were reduced in the at risk and the DFU groups compared to the controls. There were no major EPC differences between the control and not at risk group, and between the at risk and DFU groups. Serum stromal-cell derived factor-1 (SDF-1) and stem cell factor (SCF) were increased in DFU patients. DFU patients who healed their ulcers had lower CD34+KDR+ count at visits 3 and 4, serum c-reactive protein (CRP) and granulocyte-macrophage colony-stimulating factor (GM-CSF) at visit 1, interleukin-1 (IL-1) at visits 1 and 4. EPCs tended to be higher in both diabetic animal models when compared to their non-diabetic counterparts both before and ten days after wounding. Conclusions: Uncomplicated diabetes does not affect EPCs. EPCs are reduced in patients at risk or with DFU while complete wound healing is associated with CD34+KDR+ reduction, suggesting possible increased homing. Low baseline CRP, IL-1α and GM-CSF serum levels were associated with complete wound healing and may potentially serve as prognostic markers of DFU healing. No animal model alone is representative of the human condition, indicating the need for multiple experimental models

Molecular Biomarkers of Vascular Dysfunction in Obstructive Sleep Apnea

Untreated and long-lasting obstructive sleep apnea (OSA) may lead to important vascular abnormalities, including endothelial cell (EC) dysfunction, hypertension, and atherosclerosis. We observed a correlation between microcirculatory reactivity and endothelium-dependent release of nitric oxide in OSA patients. Therefore, we hypothesized that OSA affects (micro)vasculature and we aimed to identify vascular gene targets of OSA that could possibly serve as reliable biomarkers of severity of the disease and possibly of vascular risk. Using quantitative RT-PCR, we evaluated gene expression in skin biopsies of OSA patients, mouse aortas from animals exposed to 4-week intermittent hypoxia (IH; rapid oscillations in oxygen desaturation and reoxygenation), and human dermal microvascular (HMVEC) and coronary artery endothelial cells (HCAEC) cultured under IH. We demonstrate a significant upregulation of endothelial nitric oxide synthase (eNOS), tumor necrosis factor-alpha-induced protein 3 (TNFAIP3; A20), hypoxia-inducible factor 1 alpha (HIF-1α?? and vascular endothelial growth factor (VEGF) expression in skin biopsies obtained from OSA patients with severe nocturnal hypoxemia (nadir saturated oxygen levels [SaO2]<75%) compared to mildly hypoxemic OSA patients (SaO2 75%–90%) and a significant upregulation of vascular cell adhesion molecule 1 (VCAM-1) expression compared to control subjects. Gene expression profile in aortas of mice exposed to IH demonstrated a significant upregulation of eNOS and VEGF. In an in vitro model of OSA, IH increased expression of A20 and decreased eNOS and HIF-1α expression in HMVEC, while increased A20, VCAM-1 and HIF-1αexpression in HCAEC, indicating that EC in culture originating from distinct vascular beds respond differently to IH stress. We conclude that gene expression profiles in skin of OSA patients may correlate with disease severity and, if validated by further studies, could possibly predict vascular risk in OSA patients

Role of Patrolling Monocytes in Diabetic Retinopathy in an animal model of Type 1 Diabetes

Based on their functional and morphological characteristics, monocytes can be divided in inflammatory (CD115+, Ly6C+ in mice; CD14+ CD16\u2013 in humans), intermediate (CD115+Ly6Cint in mice; CD14+ CD16+ in humans), and patrolling monocytes (PMo) (CD115+Ly6C\u2013 in mice; CD14dimCD16+ in humans). PMo survey blood vessels and have housekeeping functions for the endothelium. We wished to learn how PMo react to diabetes; whether PMo contribute to leukostasis; and whether diabetes alters the functionality of PMo. To test whether diabetes affects PMo in the macrocirculation, we performed flowcytometric analysis on circulating blood of diabetic and non-diabetic mice. We found that diabetes reduced the number of circulating leukocytes, and that this decrease was driven by a decrease in lymphocytes, while granulocytes and total monocytes were unaltered. Diabetes induced a rearrangement of the monocyte subpopulations: PMo decreased, intermediate increased, inflammatory were unchanged. To test whether diabetes affects PMo in the microcirculation, we performed immunofluorescence of whole retinas from intracardially perfused mice. Diabetes induced a ~4-fold increase in the absolute number of PMo. We next tested whether the absence of PMo would affect leukostasis, by taking advantage of an animal model of absence of PMo, the NR4A1-/- mouse. Diabetic NR4A1-/- mice did not show the increase present in wild-type mice, supporting the finding that PMo are key elements in diabetic leukostasis. Next, we assessed retinal microvascular damage in NR4A1-/- mice, by determining the number of acellular capillaries in retinal trypsin digests. We found that healthy aging and 4-months duration of diabetes did not induce any increase in retinal microangiopathy in NR4A1-/- mice. Conversely, we found that 6-month duration of diabetes induced in NR4A1-/- mice more retinal microangiopathy. Notably, we found no difference in vascular permeability between WT or Nr4a1-/- mice, with and without diabetes, indicating that the blood-retinal barrier is intact in Nr4a1-/- mice. These findings led us to inquire whether diabetes induces changes in the transcriptome of PMo by Next Generation Sequencing. We studied wild-type mice with 5 months duration of diabetes, based on the previous observation that diabetic NR4A1-/- mice showed increased retinal microangiopathy after 6, but not 4, months of diabetes. Analyzing the signature of the differentially expressed genes, we found that 5 months of diabetes induced in PMo a comprehensive anti-inflammatory, anti-apoptotic, pro-adhesive/pro-migratory, and vasculo-protective signature. On these data we performed Gene Set Enrichment Analysis, Ingenuity Pathway Analysis, and STRING analysis. Based on their results, we planned the real-time qPCR on PMo sorted from WT mice after 3, 5, and 7 months of diabetes duration. We found that a protective program is activated in mice as early as after 3 months of diabetes, and up to 7 months of diabetes duration. However, CXCR4 is upregulated in mice with 3 and 5 months \u336 but not 7 months \u336 of diabetes duration. This finding, together with the morphological observation that microangiopathy was not apparent before 6 months of diabetes, suggests that CXCR4 may be critical for the delivery of protective/healing activities by PMo on retinal vessels. The first novel concept is the discovery of mechanisms that protect and repair retinal microvessels, thereby indicating that diabetic retinal microangiopathy reflects the balance of damage and repair. The second novel concept is that leukostasis represents an attempt to bring healing influences to damaged microvessels, rather than a pro-inflammatory event as currently proposed, thereby changing the meaning of this phenomenon. The results of this work have the potential to change the clinical management of retinopathy, by fostering the development on the one hand of a biomarker of risk of retinopathy, and on the other hand new interventions

\ufeff\ufeff\ufeff\ufeff\ufeff\ufeff\ufeffCutaneous alterations in diabetes mellitus

\ufeff\ufeff\ufeff\ufeff\ufeff\ufeff Dermatological problems occur with increased frequency in individuals with diabetes mellitus (DM). Cutaneous manifestations may be the first presenting sign of DM or even precede the diagnosis by many years. The main changes in the skin are due to alterations of microcirculation, the nervous system, and collagen. The most common skin problems in DM are acanthosis nigricans, necrobiosis lipoidica, diabetic dermopathy, scleredema, and granuloma anulare. The purpose of this review is to describe the molecular and anatomopathological alterations occurring at the skin during DM, and to illustrate the most important and common clinical skin manifestations in patients with DM. \ufeff\ufeff\ufeff

Treating diabetic ulcers

Diabetic foot ulceration is a serious secondary complication of diabetes mellitus and the most common cause of hospitalization in diabetic patients. The etiology of diabetic foot ulcerations is complex due to their multifactorial nature. Thus, addressing all of the factors involved remains instrumental in wound healing. AREAS COVERED: The first part of this review focuses on the pathophysiology of diabetic foot ulceration and wound-healing impairment. The second part reviews the standard treatments, including advanced wound-care products and new therapeutic approaches currently under investigation. The reader will understand the most up-to-date research regarding the unique pathophysiology of diabetic foot ulceration along with the basic cornerstones of current recommended standard therapy. EXPERT OPINION: Diabetic foot ulceration is a serious complication that can lead--potentially--to devastating lower-extremity amputations. Proper adherence to standard treatment strategies can potentially prevent the need for amputatio

The Increased Transforming Growth Factor-\u3b2 Signaling Induced by Diabetes Protects Retinal Vessels

The roles of transforming growth factor (TGF)-\u3b2 in extracellular matrix production and vascular remodeling, coupled with increased TGF-\u3b2 expression and signaling in diabetes, suggest TGF-\u3b2 as an important contributor to the microangiopathy of diabetic retinopathy and nephropathy. To investigate whether increased TGF-\u3b2 signaling could be a therapeutic target for preventing retinopathy, we used a pharmacologic approach (SM16, a selective inhibitor of the type 1 TGF-\u3b2 receptor activin receptor-like kinase 5, orally active) to inhibit the increased, but not the basal, Tgf-\u3b2 signaling in retinal vessels of diabetic rats. At the level of vascular gene expression, 3.5 months' diabetes induced minimal changes. Diabetes + SM16 for 3 weeks caused widespread changes in gene expression poised to enhance vascular inflammation, thrombosis, leakage, and wall instability; these changes were not observed in control rats given SM16. The synergy of diabetes and SM16 in altering gene expression was not observed in the lung. At the level of vascular network morphology, 7 months' diabetes induced no detectable changes. Diabetes + SM16 for 3 weeks caused instead distorted morphology and decreased density. Thus, in diabetes, retinal vessels become dependent on a small increase in TGF-\u3b2 signaling via activin receptor-like kinase 5 to maintain early integrity. The increased TGF-\u3b2 signaling may protect against rapid retinopathy progression and should not be a target of inhibitory interventions