Smartphone-Based High-Throughput Fluorimetric Assay for Histidine Quantification in Human Urine Using 96-Well Plates.

A high-throughput fluorimetric assay for histidine was developed, using a 96-well plates platform. The analyte reacts selectively with o-phthalaldehyde under mild alkaline conditions to form a stable derivative. Instrumental-free detection was carried out using a smartphone after illumination under UV light (365 nm). The method was proved to be linear up to 100 µM histidine, with an LLOQ (lower limit of quantification) of 10 µM. The assay was only prone to interference from glutathione and histamine that exist in the urine samples at levels that are orders of magnitude lower compared to histidine. Human urine samples were analyzed following minimum treatment and were found to contain histidine in the range of 280 to 1540 µM. The results were in good agreement with an HPLC corroborative method.

Macro- and microvascular reactivity during repetitive exposure to shortened sleep: sex differences.

Epidemiological studies have reported strong association between sleep loss and hypertension with unknown mechanisms. This study investigated macrovascular and microcirculation changes and inflammatory markers during repetitive sleep restriction. Sex differences were also explored. Forty-five participants completed a 22-day in-hospital protocol. Participants were assigned to, (1) eight-hour sleep per night (control), or (2) sleep restriction (SR) condition: participants slept from 0300 to 0700 h for three nights followed by a recovery night of 8-h sleep, repeated four times. Macrocirculation assessed by flow mediated dilation (FMD) and microcirculation reactivity tests were performed at baseline, last day of each experimental block and during recovery at the end. Cell adhesion molecules and inflammatory marker levels were measured in blood samples. No duration of deprivation (SR block) by condition interaction effects were found for FMD, microcirculation, norepinephrine, cell adhesion molecules, IL-6 or IL-8. However, when men and women were analyzed separately, there was a statistical trend (p = 0.08) for increased IL-6 across SR blocks in women, but not in men. Interestingly, men showed a significant progressive (dose dependent) increase in skin vasodilatation (p = 0.02). A novel and unexpected finding was that during the recovery period, men that had been exposed to repeated SR blocks had elevated IL-8 and decreased norepinephrine. Macrocirculation, microcirculation, cell adhesion molecules, and markers of inflammation appeared to be resistant to this model of short-term repetitive exposures to the blocks of shortened sleep in healthy sleepers. However, men and women responded differently, with women showing mild inflammatory response and men showing more vascular system sensitivity to the repetitive SR.

Integrated Skin Transcriptomics and Serum Multiplex Assays Reveal Novel Mechanisms of Wound Healing in Diabetic Foot Ulcers.

Nonhealing diabetic foot ulcers (DFUs) are characterized by low-grade chronic inflammation, both locally and systemically. We prospectively followed a group of patients who either healed or developed nonhealing chronic DFUs. Serum and forearm skin analysis, both at the protein expression and the transcriptomic level, indicated that increased expression of factors such as interferon-γ (IFN-γ), vascular endothelial growth factor, and soluble vascular cell adhesion molecule-1 were associated with DFU healing. Furthermore, foot skin single-cell RNA sequencing analysis showed multiple fibroblast cell clusters and increased inflammation in the dorsal skin of patients with diabetes mellitus (DM) and DFU specimens compared with control subjects. In addition, in myeloid cell DM and DFU upstream regulator analysis, we observed inhibition of interleukin-13 and IFN-γ and dysregulation of biological processes that included cell movement of monocytes, migration of dendritic cells, and chemotaxis of antigen-presenting cells pointing to an impaired migratory profile of immune cells in DM skin. The SLCO2A1 and CYP1A1 genes, which were upregulated at the forearm of nonhealers, were mainly expressed by the vascular endothelial cell cluster almost exclusively in DFU, indicating a potential important role in wound healing. These results from integrated protein and transcriptome analyses identified individual genes and pathways that can potentially be targeted for enhancing DFU healing.

The Effect of Continuous Positive Airway Pressure on Vascular Function and Cardiac Structure in Diabetes and Sleep Apnea. A Randomized Controlled Trial.

Rationale: Although both type 2 diabetes mellitus (T2DM) and obstructive sleep apnea (OSA) are independently recognized as risk factors for cardiovascular disease, little is known about their interaction.Objectives: We hypothesized that T2DM and OSA act synergistically to increase vascular risk, and that treatment of OSA would improve vascular reactivity in patients with T2DM plus OSA.Methods: Cross-sectional study of 141 adults with T2DM, OSA, T2DM plus OSA, and control subjects, followed by a 3-month, parallel-arm, randomized, placebo-controlled trial comparing active and sham continuous positive airway pressure (CPAP) in 53 adults with T2DM plus OSA. Endothelium-dependent macro- and microvascular reactivity (flow-mediated dilation [FMD] of the brachial artery and acetylcholine-induced dilation of forearm microvasculature, respectively) and cardiovascular magnetic resonance to assess left- and right-ventricular mass/volume.Results: Mean (±SD) FMD was 6.1 (±4.0)%, 7.3 (±3.6)%, 6.8 (±4.5)%, and 4.8 (±2.9)% in control subjects, T2DM only, OSA only, and T2DM plus OSA, respectively. We observed a significant T2DM × OSA interaction on FMD, such that the mean effect of OSA in those with T2DM was 3.1% (95% confidence interval [CI], 0.6 to 5.6) greater than the effect of OSA in those without T2DM. A total of 3 months of CPAP resulted in a mean absolute increase in FMD of 0.3% (95% CI, -1.9 to 2.5; primary endpoint), with a net improvement of 1.1% (95% CI, -1.4 to 3.6) among those with adherence of 4 h/night or greater. A significant T2DM × OSA interaction was found for both left ventricular (LV) and right ventricular end-diastolic volume, such that OSA was associated with a 22.4 ml (95% CI, 3.2 to 41.6) greater LV end-diastolic volume and 23.2 ml (95% CI, 2.6 to 43.8) greater right ventricular end-diastolic volume in those with T2DM compared with the impact of OSA in those without T2DM. We observed a net improvement in LV end-diastolic volume of 8.7 ml (95% CI, -7.0 to 24.4).Conclusions: The combination of T2DM plus OSA is associated with macrovascular endothelial dysfunction beyond that observed with either disease alone. CPAP for 3 months did not significantly improve macrovascular endothelial function in the intent-to-treat analysis; however, cardiovascular magnetic resonance results suggest that there may be a beneficial effect of CPAP on LV diastolic volume.Clinical trial registered with www.clinicaltrials.gov (NCT01629862).

Assessment of telomerase activity in leukocytes of type 2 diabetes mellitus patients having or not foot ulcer: Possible correlation with other clinical parameters.

Telomerase is the enzyme that maintains telomere length by adding telomeric repeats after each cell division. Numerous metabolic factors such as obesity, insulin resistance or physical inactivity have been associated with shortened telomeres. In the present study, we assessed telomerase activity in diabetic patients having or not foot ulcer. A total of 90 adult patients with type 2 diabetes mellitus (T2DM) were studied. Patients were allocated into two groups according to the absence or presence of active foot ulcers as follows: Νon-ulcer group (N=58) and ulcer group (N=32). Our data revealed that the patients with diabetic ulcers had significantly greater waist circumference and neuropathy disability score, while exhibiting lower telomerase activity, indicating the possible existence of a common clinical profile among ulcer-bearing diabetic patients. Validation of our findings by extending the study in larger patient groups may contribute to the understanding of T2DM pathophysiology and its main clinical implications.

Effect of Linagliptin on Vascular Function: A Randomized, Placebo-controlled Study.

CONTEXT: The dipeptidyl peptidase-4 inhibitor, linagliptin, possesses pleiotropic vasodilatory, antioxidant, and anti-inflammatory properties in animals, independent of its glucose-lowering properties. Although large, randomized clinical trials are being conducted to better evaluate the efficacy and safety of linagliptin on cardiovascular outcomes, little is known about its effects on vascular function in humans. OBJECTIVE: This study sought to evaluate the effect of linagliptin on surrogates of vascular and mitochondrial function. DESIGN AND SETTING: This was a randomized, double-blind, placebo-controlled trial at a tertiary care center with a large type 2 diabetes referral base. PATIENTS AND INTERVENTION: Forty participants with type 2 diabetes were included in a 12-wk treatment of either linagliptin 5mg/d or placebo. MAIN OUTCOME MEASURES: Micro- and macrovascular functions were assessed using laser Doppler coupled with iontophoresis and with brachial flow-mediated dilation, respectively. Mitochondrial function was assessed by phosphorus-31 metabolites changes in the calf muscle measured by magnetic resonance spectroscopy. Circulating endothelial progenitor cells, as well as inflammatory cytokines, growth factors, and biomarkers of endothelial function were also quantified. RESULTS: Linagliptin was associated with an increase in axon reflex-dependent vasodilation, a marker of neurovascular function (P = .05). A trend indicating increased endothelium-dependent microvascular reactivity was observed (P = .07). These were associated with decreases in concentrations of IFNγ (P < .05), IL-6 (P = .03), IL-12 (P < .03), and MIP-1 (P < .04) following linagliptin treatment when compared with placebo. CONCLUSIONS: This study demonstrates that linagliptin tends to improve endothelial and neurovascular microvascular function and is associated with decreased markers of inflammation in patients with type 2 diabetes. There was no significant effect of linagliptin on mitochondrial function, macrovascular function, or endothelial progenitor cells.

Diabetic Peripheral Neuropathy as a Predictor of Asymptomatic Myocardial Ischemia in Type 2 Diabetes Mellitus: A Cross-Sectional Study.

INTRODUCTION: Diabetic peripheral neuropathy (DPN) is one of the most common complications of diabetes and has been associated with cardiovascular disease, the leading cause of mortality in diabetes. As asymptomatic myocardial ischemia (MI) is frequent in diabetes, we hypothesized that DPN may be associated with MI in patients with type 2 diabetes mellitus and no history of cardiovascular events. METHODS: Eighty-two patients with DPN (n = 41) or without DPN (n = 41) were included. Among the DPN group, 15 had active foot ulcers. All subjects underwent Technetium-99 m sestamibi single-photon emission computed tomographic imaging for the estimation of myocardial ischemia, expressed as Summed Stress Score (SSS). The Neuropathy Disability Score (NDS) was used to quantify DPN and abnormal ratio of the longest electrocardiographic RR interval between the 28th and 32nd beats, after standing to the shortest interval between the 13th and 17th beats (RR ratio) was used as an index of cardiovascular autonomic neuropathy (CAN). RESULTS: Abnormal SSS was observed in 9.8% of patients without DPN and in 46.3% of patients with DPN (p < 0.001). In the multivariate analysis, NDS was the strongest predictor for SSS (ß = 0.32, p = 0.003). When excluding patients with abnormal RR ratio (ß = 0.32, p = 0.003) or with foot ulcers (ß = 0.24, p = 0.04), this association remained significant. The RR ratio was also significantly associated with SSS in univariate (ρ = -0.30, p = 0.005) and multiple regressions (ß = 0.24, p = 0.02). CONCLUSIONS: MI was strongly associated with DPN, and this association remained significant in patients with normal RR ratio. These results suggest that DPN assessment could help in identifying patients at risk of cardiovascular disease (CVD).

Endothelial Dysfunction as a Link Between Cardiovascular Risk Factors and Peripheral Neuropathy in Diabetes.

CONTEXT: Cardiovascular risk factors are well-known predictors of the development of diabetic peripheral neuropathy (DPN), which has traditionally been considered as a manifestation of diabetes-associated microangiopathy. Because endothelial dysfunction is strongly associated with all cardiovascular risk factors, we hypothesized that it may be a link between cardiovascular risk factors and DPN. OBJECTIVE: The primary objective of this study was to test whether endothelial dysfunction is a predictor of DPN. DESIGN AND SETTING: This is a cross-sectional analysis of a cohort composed of patients followed at the Microcirculatory Laboratory, Beth Israel Deaconess Medical Center. PATIENTS: Participants with diabetes without DPN (n = 192) and with DPN (n = 166), subjects with prediabetes (n = 75), and nondiabetic controls (n = 59) were included. INTERVENTIONS: Endothelial function was assessed with flow-mediated dilation (FMD) of the brachial artery. Inflammatory cytokines and biomarkers of endothelial function (soluble intercellular and vascular cell adhesion molecules) were quantified using a multiplex bead-based immunoassay. Neurological assessment included the neuropathy disability score (NDS). MAIN OUTCOME MEASURE: The relationship between FMD and NDS assessed using multiple linear regression. RESULTS: In addition to already known risk factors of DPN, FMD was strongly associated with NDS (ß = -0.24; P < .001). Sensitivity analysis that removed FMD from the model provided similar results for soluble intercellular cell adhesion molecule-1, another biomarker of endothelial function. Confirmatory factor analysis further showed that endothelial dysfunction is a significant mediator between glycosylated hemoglobin and diabetes duration and diabetic complications. CONCLUSIONS: This study shows that endothelial dysfunction occurs early in the pathophysiology of diabetes and is a link between cardiovascular risk factors and DPN.

Obstructive Sleep Apnea and Vascular Diseases.

Obstructive sleep apnea (OSA) affects a large proportion of adults, and is as an independent risk factor for cerebrovascular and cardiovascular disease. The repetitive airway obstruction that characterizes OSA results in intermittent hypoxia, intrathoracic pressure swings, and sleep fragmentation, which in turn lead to sympathetic activation, oxidative stress, inflammation, and endothelial dysfunction. This review outlines the associations between OSA and vascular diseases and describes basic mechanisms that may be responsible for this association, in both the micro- and macrocirculation. It also reports on interventional studies that aim to ameliorate OSA and thereby reduce vascular disease burden. © 2016 American Physiological Society. Compr Physiol 6:1519-1528, 2016.

Mast Cells Regulate Wound Healing in Diabetes.

Diabetic foot ulceration is a severe complication of diabetes that lacks effective treatment. Mast cells (MCs) contribute to wound healing, but their role in diabetes skin complications is poorly understood. Here we show that the number of degranulated MCs is increased in unwounded forearm and foot skin of patients with diabetes and in unwounded dorsal skin of diabetic mice (P < 0.05). Conversely, postwounding MC degranulation increases in nondiabetic mice, but not in diabetic mice. Pretreatment with the MC degranulation inhibitor disodium cromoglycate rescues diabetes-associated wound-healing impairment in mice and shifts macrophages to the regenerative M2 phenotype (P < 0.05). Nevertheless, nondiabetic and diabetic mice deficient in MCs have delayed wound healing compared with their wild-type (WT) controls, implying that some MC mediator is needed for proper healing. MCs are a major source of vascular endothelial growth factor (VEGF) in mouse skin, but the level of VEGF is reduced in diabetic mouse skin, and its release from human MCs is reduced in hyperglycemic conditions. Topical treatment with the MC trigger substance P does not affect wound healing in MC-deficient mice, but improves it in WT mice. In conclusion, the presence of nondegranulated MCs in unwounded skin is required for proper wound healing, and therapies inhibiting MC degranulation could improve wound healing in diabetes.

MRI assessment of regional differences in phosphorus-31 metabolism and morphological abnormalities of the foot muscles in diabetes.

PURPOSE: To assess differences in the phosphorus-31 (31 P) metabolism and morphology in multiple muscle regions in the forefoot of diabetic patients and normal subjects. MATERIALS AND METHODS: Fifteen diabetic patients and 15 normal subjects were assessed for muscle atrophy by 1 H magnetic resonance imaging (MRI) at 3T to grade the flexor hallucis, adductor hallucis, interosseous regions, and entire foot cross-section. Each region and the entire foot were also quantitatively evaluated for metabolic function using 31 P imaging for spatial mapping of the inorganic phosphate (Pi) to phosphocreatine (PCr) ratio (Pi/PCr). The ratio of viable muscle area to the predefined region areas (31 P/1 H) was calculated. The variability of each method was assessed by its coefficient of variation (CV). RESULTS: Muscle atrophy was significantly more severe in diabetic compared to normal subjects in all regions (P < 0.01). The 31 P/1 H area ratio was significantly larger in the adductor hallucis than in the other two regions (P < 0.05). The Pi/PCr ratio was significantly different between the two groups in the flexor hallucis and interosseous regions (P < 0.05) but not adductor hallucis region. The CV for Pi/PCr ranged from 10.13 to 55.84, while it ranged from 73.40 to 263.90 for qualitative grading. CONCLUSION: Changes in atrophy and metabolism appear to occur unequally between different regions of the forefoot in diabetes. The adductor hallucis region appears more capable of maintaining structural and metabolic integrity than the flexor hallucis or interosseous regions. The CV analysis suggests that the quantitative 31 P methods have less variability than the qualitative grading. J. Magn. Reson. Imaging 2016;44:1132-1142.

Obese Patients with Type 2 Diabetes on Conventional Versus Intensive Insulin Therapy: Efficacy of Low-Calorie Dietary Intervention.

INTRODUCTION: The aim of this prospective study was to assess the results of a standard low-calorie dietary intervention (7.5 MJ/day) on body weight (BW) and the metabolic profile of obese patients with type 2 diabetes mellitus (T2DM) on intensive insulin therapy (IIT: 4 insulin injections/day) versus conventional insulin therapy (CIT: 2/3 insulin injections/day). METHODS: A total of 60 patients (n = 60, 23 males and 37 postmenopausal females) were recruited and categorized into two groups according to the scheme of insulin treatment. Thirty were on IIT (13 males and 17 females) and an equal number on CIT (10 males and 20 females). BW, body mass index (BMI), HbA1c, and metabolic parameters were compared at 6 and 12 months after baseline. RESULTS: Significant reductions were observed in the BW, BMI, HbA1c (p ≤ 0.001 for all) and cholesterol (p ≤ 0.05) at 6 months post-intervention. At 1 year, median BW reduction was 4.5 kg (3.3, 5.8) for patients on IIT and 4.8 kg (3.6, 7.0) for those on CIT. The 12-month dietary intervention increased prevalence of normoglycemia in the IIT group and reduced the prevalence of obesity prevalence among the CIT participants (all p < 0.001). CIT patients with BW reduction ≥5.0% demonstrated 11-fold greater chances of being normoglycemic (odds ratio 11.3, 95% CI 1.1-110.5). BW reduction ≥7.0% was associated with CIT, being overweight, and having normal HDLc, LDLc, and cholesterol levels. A reduction in BW between 5.0% and 6.9% was associated with IIT, normoglycemia, and obesity. CONCLUSION: A 12-month 1800-kcal dietary intervention achieved significant BW and HbA1c reductions irrespectively of insulin regimen. CIT was associated with BW reduction greater than 8.0%, whereas IIT was associated with higher rates of normoglycemia.

Pathogenesis and treatment of impaired wound healing in diabetes mellitus: new insights.

Diabetic foot ulcers (DFUs) are one of the most common and serious complications of diabetes mellitus, as wound healing is impaired in the diabetic foot. Wound healing is a dynamic and complex biological process that can be divided into four partly overlapping phases: hemostasis, inflammation, proliferative and remodeling. These phases involve a large number of cell types, extracellular components, growth factors and cytokines. Diabetes mellitus causes impaired wound healing by affecting one or more biological mechanisms of these processes. Most often, it is triggered by hyperglycemia, chronic inflammation, micro- and macro-circulatory dysfunction, hypoxia, autonomic and sensory neuropathy, and impaired neuropeptide signaling. Research focused on thoroughly understanding these mechanisms would allow for specifically targeted treatment of diabetic foot ulcers. The main principles for DFU treatment are wound debridement, pressure off-loading, revascularization and infection management. New treatment options such as bioengineered skin substitutes, extracellular matrix proteins, growth factors, and negative pressure wound therapy, have emerged as adjunctive therapies for ulcers. Future treatment strategies include stem cell-based therapies, delivery of gene encoding growth factors, application of angiotensin receptors analogs and neuropeptides like substance P, as well as inhibition of inflammatory cytokines. This review provides an outlook of the pathophysiology in diabetic wound healing and summarizes the established and adjunctive treatment strategies, as well as the future therapeutic options for the treatment of DFUs.