Diabetic neuropathy and the microcirculation

Therapeutic potential of 4-hexylresorcinol in reducing sarcopenia in diabetic masseter muscle

BACKGROUND

This study aimed to evaluate the effects of 4-hexylresorcinol (4HR), a synthetic compound with antioxidant and stress-modulating properties, on diabetic sarcopenia in the masseter muscle.

METHODS

A controlled, parallel-arm study was conducted using 38 Sprague-Dawley rats divided into diabetic and non-diabetic groups. Diabetes was induced with streptozotocin (STZ), and the groups were further subdivided to receive weekly subcutaneous injections of either 4HR or saline. Muscle volume was assessed using micro-computed tomography (μCT), and glycogen storage and protein expression were analyzed using periodic acid-Schiff (PAS) staining and immunohistochemistry.

RESULTS

μCT analysis revealed that diabetic rats exhibited significantly reduced masseter muscle volume compared to non-diabetic rats. However, 4HR treatment partially mitigated muscle volume loss in diabetic animals. Histological analysis showed higher PAS staining intensity in the diabetic group treated with 4HR compared to the untreated diabetic group, suggesting improved glycogen storage. Immunohistochemistry demonstrated that 4HR treatment significantly increased Glut4 and phosphorylated AMPKα (p-AMPKα) expression in diabetic muscle, indicating enhanced glucose uptake and metabolic activity.

CONCLUSIONS

4HR effectively alleviates diabetes-induced sarcopenia by preserving muscle volume, enhancing glycogen storage, and upregulating Glut4 and p-AMPKα expression. These findings suggest that 4HR holds potential as a therapeutic agent for combating muscle wasting in diabetes.

Distinguishing pain profiles among individuals with long COVID

Background

For many people with long COVID (LC), new-onset pain is a debilitating consequence. This study examined the nature of new-onset pain and concomitant symptoms in patients with LC to infer mechanisms of pain from the relationships between pain and health-related factors.

Methods

Pain and other symptoms were evaluated in 153 individuals with LC using the Self-Administered Leeds Assessment of Neuropathic Symptoms and Signs, EuroQoL Visual Analog Scale, and Quality of Life in Neurological Disorders. The relationships between pain and patient factors were analyzed using Chi Square and independent t-tests.

Results

20.3% of individuals who reported new-onset pain had neuropathic pain, which was associated with lower quality of life and higher rates of cognitive dysfunction compared to those with non-neuropathic pain. Other symptoms were similar between groups, however heart-related symptoms were more prevalent in individuals with neuropathic pain and mood swings were more prevalent for individuals with non-neuropathic pain.

Conclusions

Characterizing the relationships between NP and quality of life in individuals with LC can aid in developing better clinical management strategies. Understanding the associations between NP and cognitive dysfunction provides the imperative foundation for future studies further examining the pathophysiological mechanisms underlying pain development in LC.

Dynamic Microcirculation Characteristics of Plantar Skin Under Metatarsal Head of Human Foot in Response to Life-Like Pressure Stimulus

OBJECTIVE

Diabetic foot ulcer (DFU) is a severe complication with high mortality. High plantar pressure and poor microcirculation are considered main causes of DFU. The specific aims were to provide a novel technique for real-time measurement of plantar skin blood flow (SBF) under walking-like pressure stimulus and delineate the first plantar metatarsal head dynamic microcirculation characteristics because of life-like loading conditions in healthy individuals.

METHODS

Twenty young healthy participants (14 male and 6 female) were recruited. The baseline (i.e., unloaded) SBF of soft tissue under the first metatarsal head were measured using laser Doppler flowmetry (LDF). A custom-made machine was utilized to replicate daily walking pressure exertion for 5 min. The exerted plantar force was adjusted from 10 N (127.3 kPa) to 40 N (509.3 kPa) at an increase of 5 N (63.7 kPa). Real-time SBF was acquired using the LDF. After each pressure exertion, postload SBF was measured for comparative purposes. Statistical analysis was performed using the R software.

RESULTS

All levels of immediate-load and postload SBF increased significantly compared with baseline values. As the exerted load increased, the postload and immediate-load SBF tended to increase until the exerted load reached 35 N (445.6 kPa). However, in immediate-load data, the increasing trend tended to level off as the exerted pressure increased from 15 N (191.0 kPa) to 25 N (318.3 kPa). For postload and immediate-load SBF, they both peaked at 35 N (445.6 kPa). However, when the exerted force exceeds 35 N (445.6 kPa), both the immediate-load and postload SBF values started to decrease.

CONCLUSIONS

Our study offered a novel real-time plantar soft tissue microcirculation measurement technique under dynamic conditions. For the first metatarsal head of healthy people, 20 N (254.6 kPa)-plantar pressure has a fair microcirculation stimulus compared with higher pressure. There might be a pressure threshold at 35 N (445.6 kPa) for the first metatarsal head, and soft tissue microcirculation may decrease when local pressure exceeds it.

Skin microcirculatory responses: A potential marker for early diabetic neuropathy assessment using a low-cost portable diffuse optical spectrometry device

Diffuse optical measurement is an evolving optical modality providing a fast and portable solution for microcirculation assessment. Diffuse optics in static and dynamic modalities are combined here in a system to assess hemodynamics in skin tissues of control and diabetic subjects. The in-house developed system consists of a laser source, fiber optic probe, a low-cost avalanche photodiode, a finite element model (FEM) derived static optical property estimator, and a software correlator for continuous flow monitoring through microvasculature. The studies demonstrated that the system quantifies the changes in blood flow rate in the immediate skin subsurface. The system is calibrated with in vitro flow models and a proof-of-concept was demonstrated on a limited number of subjects in a clinical environment. The flow changes in response to vasoconstrictive and vasodilative stimuli were analyzed and used to classify different stages of diabetes, including diabetic neuropathy.

Risk factors predicting hospital-acquired pressure injury in adult patients: An overview of reviews

BACKGROUND

Hospital-acquired pressure injuries remain a significant patient safety threat. Current well-known pressure injury risk assessment tools have many limitations and therefore do not accurately predict the risk of pressure injury development over diverse populations. A contemporary understanding of the risk factors predicting pressure injury in adult hospitalised patients will inform pressure injury prevention and future researchers considering risk assessment tool development may benefit from our summary and synthesis of risk factors.

OBJECTIVE

To summarise and synthesise systematic reviews that identify risk factors for hospital-acquired pressure injury development in adult patients.

DESIGN

An overview of systematic reviews.

METHODS

Cochrane and the Joanna Briggs Institute methodologies guided this overview. The Cochrane library, CINAHL, MEDLINE, and Embase databases were searched for relevant articles published in English from January 2008 to September 2022. Two researchers independently screened articles against the predefined inclusion and exclusion criteria, extracted data and assessed the quality of the included reviews using "a measurement tool to assess systematic reviews" (AMSTAR version 2). Data were categorised using an inductive approach and synthesised according to the recent pressure injury conceptual frameworks.

RESULTS

From 11 eligible reviews, 37 risk factors were categorised inductively into 14 groups of risk factors. From these, six groups were classified into two domains: four to mechanical boundary conditions and two to susceptibility and tolerance of the individual. The remaining eight groups were evident across both domains. Four main risk factors, including diabetes, length of surgery or intensive care unit stay, vasopressor use, and low haemoglobin level were synthesised. The overall quality of the included reviews was low in five studies (45 %) and critically low in six studies (55 %).

CONCLUSIONS

Our findings highlighted the limitations in the methodological quality of the included reviews that may have influenced our results regarding risk factors. Current risk assessment tools and conceptual frameworks do not fully explain the complex and changing interactions amongst risk factors. This may warrant the need for more high-quality research, such as cohort studies, focussing on predicting hospital-acquired pressure injury in adult patients, to reconsider these risk factors we synthesised.

REGISTRATION

This overview was registered with the PROSPERO (CRD42022362218) on 27 September 2022.

Assessment of revascularization impact on microvascular oxygenation and perfusion using spatial frequency domain imaging

The microvasculature (with vessels <100 μm in diameter) plays a crucial role in tissue oxygenation, perfusion and wound healing in the lower limb. While this holds clinical significance, microvasculature evaluation in the limbs is not a standard practice. Surgical interventions focus on reestablishing blood flow in larger vessels affected by the peripheral artery disease (PAD). Nevertheless, the impact of revascularization on tissue oxygenation and perfusion in severe microvascular disease (MVD) is still unknown. We present the cases of two patients who underwent surgical revascularization for peripheral blood flow with different outcomes. Patient A had PAD, while B had PAD, severe MVD and a non-healing wound. Although both showed improvements in ankle-brachial index post-op, spatial frequency domain imaging metrics (which measure microvascular oxygenation and perfusion) remained unchanged in B, indicating a potential gap in assessing the surgical efficacy in MVD using ankle brachial index and emphasizing microcirculation evaluation in optimizing wound healing outcomes.

The relationship between common risk factors and the pathology of pressure ulcer development: a systematic review

OBJECTIVE

The aim of this systematic review was to examine the associations and relationship between commonly cited risk factors and the pathology of pressure ulcer (PU) development.

METHOD

Using systematic review methodology, original research studies, prospective design and human studies written in English were included. The search was conducted in March 2018, using Ovid, Ovid EMBASE and CINAHL databases. Data were extracted using a pre-designed extraction tool and all included studies were quality appraised using the evidence-based librarianship critical appraisal.

RESULTS

A total of 382 records were identified, of which five met the inclusion criteria. The studies were conducted between 1994 and 2017. Most studies were conducted in hospital and geriatric wards. The mean sample size was 96±145.7 participants. Ischaemia, recovery of blood flow and pathological impact of pressure and shear was mainly found as the cited risk factor and PU aetiology.

CONCLUSION

This review systematically analysed five papers exploring the relationship between risk factors for PU development and aetiology. It identified many risk factors and underlying pathological mechanisms that interact in the development of PU including ischaemia, stress, recovery of blood flow, tissue hypoxia and the pathological impact of pressure and shear. There are several pathways in which these pathological mechanisms contribute to PU development and identifying these could establish potential ways of preventing or treating the development of PU for patients.

Outcome of distal lower leg reconstruction with the propeller perforator flap in diabetic patients

In diabetic foot patients, wound coverage options are quite limited due to vascular abnormalities. However, even though significant atherosclerotic changes are found in major vessels of the lower leg in diabetic foot patients, perforating vessels, which are used as the vascular pedicle of propeller perforator flaps, are often spared from atherosclerosis. Therefore, the propeller perforator flap could be an alternative option for diabetic foot patients. The purpose of this study was to compare the outcome of the propeller perforator flap between diabetic and nondiabetic patients in reconstruction of the distal lower leg. We retrospectively included all patients who underwent reconstruction of the distal lower leg with a propeller flap between 2014 and 2018. Thirty-five propeller perforator flaps in 20 diabetic patients and 15 nondiabetic patients were included. Of the 35 patients, 21 showed complete healing, and 14 showed flap complications. The rate of complications in diabetic patients was approximately 85.7%. Sex (p = .002), diabetes (p = .007), chronic renal failure (p < .001), and diabetic neuropathy (p = .011) were associated with flap complications. Crude regression analysis showed that the female sex (p = .002), diabetes (p = .01), and diabetic neuropathy (p = .012) were significant risk factors for the occurrence of any complications, but the significance of diabetes and diabetic neuropathy was not maintained in the adjusted models. Therefore, the propeller perforator flap might not be effective for reconstructing diabetic foot ulcers.

Association between blood pressure variability, cardiovascular disease and mortality in type 2 diabetes: A systematic review and meta-analysis

AIM

To investigate the associations of blood pressure variability (BPV), expressed as long-term (visit-to-visit) and short-term (ambulatory blood pressure monitoring [ABPM] and home blood pressure monitoring [HBPM]) and all-cause mortality, major adverse cardiovascular events (MACEs), extended MACEs, microvascular complications (MiCs) and hypertension-mediated organ damage (HMOD) in adult patients with type 2 diabetes.

MATERIALS AND METHODS

PubMed, Medline, Embase, Cinahl, Web of Science, ClinicalTrials.gov and grey literature databases were searched for studies including patients with type 2 diabetes, at least one variable of BPV (visit-to-visit, HBPM, ABPM) and evaluation of the incidence of at least one of the following outcomes: all-cause mortality, MACEs, extended MACEs and/or MiCs and/or HMOD. The extracted information was analyzed using random effects meta-analysis and meta-regression.

RESULTS

Data from a total of 377 305 patients were analyzed. Systolic blood pressure (SBP) variability was associated with a significantly increased risk of all-cause mortality (HR 1.12, 95% CI 1.04-1.21), MACEs (HR 1.01, 95% CI 1.04-1.17), extended MACEs (HR 1.07, 95% CI 1.03-1.11) and MiCs (HR 1. 12, 95% CI 1.01-1.24), while diastolic blood pressure was not. Associations were mainly driven from studies on long-term SBP variability. Qualitative analysis showed that BPV was associated with the presence of HMOD expressed as carotid intima-media thickness, pulse wave velocity and left ventricular hypertrophy. Results were independent of mean blood pressure, glycaemic control and serum creatinine levels.

CONCLUSIONS

Our results suggest that BPV might provide additional information rather than mean blood pressure on the risk of cardiovascular disease in patients with type 2 diabetes.

Prostaglandin E1 plus methylcobalamin combination therapy versus prostaglandin E1 monotherapy for patients with diabetic peripheral neuropathy: A meta-analysis of randomized controlled trials

BACKGROUND

Prostaglandin E1 (P) or methylcobalamin (M) treatment has been suggested as a therapeutic approach for diabetic peripheral neuropathy (DPN) in many clinical trial reports. However, the combined effects of 2 drugs still remain dubious.

OBJECTIVE

The aim of this report was to evaluate the efficacy of M plus P (M + P) for the treatment of DPN compared with that of P monotherapy, in order to provide a reference resource for rational drug use.

METHODS

Randomized controlled trials (RCTs) of M + P for DPN published up to September 2017 were searched. Risk ratio (RR), mean difference (MD), and 95% confidence interval (CI) were calculated and heterogeneity was assessed with the I test. Subgroup and sensitivity analyses were also performed. The outcomes measured were as follows: the clinical efficacy, median motor nerve conduction velocities (MNCV), median sensory nerve conduction velocity (SNCV), peroneal MNCV, peroneal SNCV, and adverse effects.

RESULTS

Sixteen RCTs with 1136 participants were included. Clinical efficacy of M + P combination therapy was significantly better than P monotherapy (fifteen trials; RR 1.25, 95% CI 1.18-1.32, P < .00001, I = 27%). Compared with P monotherapy, the pooled effects of M + P combination therapy on nerve conduction velocity were (MD 6.29, 95% CI 4.63-7.94, P < .00001, I = 90%) for median MNCV, (MD 5.68, 95% CI 3.53-7.83, P < .00001, I = 94%) for median SNCV, (MD 5.36, 95% CI 3.86-6.87, P < .00001, I = 92%) for peroneal MNCV, (MD 4.62, 95% CI 3.48-5.75, P < .00001, I = 86%) for peroneal SNCV. There were no serious adverse events associated with drug intervention.

CONCLUSIONS

M + P combination therapy was superior to P monotherapy for improvement of neuropathic symptoms and NCVs in DPN patients. Moreover, no serious adverse events occur in combination therapy.

The identification of higher forefoot temperatures associated with peripheral arterial disease in type 2 diabetes mellitus as detected by thermography

AIMS

The purpose of this study was to investigate whether heat emitted from the feet of patients with type 2 diabetes (DM) and peripheral arterial disease (PAD) differed from those with type 2 diabetes without complications (DM).

METHODS

A non-experimental, comparative prospective study design was employed in a tertiary referral hospital. Out of 223 randomly selected participants (430 limbs) who were initially tested, 62 limbs were categorized as DM+PAD and 22 limbs as DM without PAD. Subjects with evidence of peripheral neuropathy were excluded. Participants underwent thermographic imaging. Automatic segmentation of regions of interest extracted the temperature data.

RESULTS

A significant difference in temperature in all the toes between the two groups was found (p=0.005, p=0.033, p=0.015, p=0.038 and p=0.02 for toes 1-5 respectively). The mean forefoot temperature in DM+PAD was significantly higher than that in DM (p=.019), with DM+PAD having a higher mean temperature (28.3°C) compared to DM (26.2°C). Similarly, the toes of subjects with DM+PAD were significantly warmer than those of subjects with DM only.

CONCLUSIONS

Contrary to expectations the mean toe and forefoot temperatures in DM patients with PAD is higher than in those with DM only. This unexpected result could be attributed to disruption of noradrenergic vasoconstrictor thermoregulatory mechanisms with resulting increased flow through cutaneous vessels and subsequent increased heat emissivity. These results demonstrate that thermography may have potential in detecting PAD and associated temperature differences.

Blood flow characteristics of diabetic patients with complications detected by optical measurement

Background

Diabetes mellitus (DM) is one of the most common diseases worldwide. Uncontrolled and prolonged hyperglycemia can cause diabetic complications, which reduce the quality of life of patients. Diabetic complications are common in DM patients. Because it is impossible to completely recover from diabetic complications, it is important for early detection. In this study, we suggest a novel method of determining blood flow characteristics based on fluorescence image analysis with indocyanine green and report that diabetic complications have unique blood flow characteristics.

Methods

We analyzed time-series fluorescence images obtained from controls, DM patients, and DM patients with complications. The images were segmented into the digits and the dorsum of the feet and hands, and each part has been considered as arterial and capillary flow. We compared the blood flow parameters in each region among the three groups.

Results

The DM patients with complications showed similar blood flow parameters to the controls, except the area under the curve and the maximum intensity, which indicate the blood flow volume. These parameters were significantly decreased in DM patients with complications. Although some blood flow parameters in the feet of DM patients with complications were close to normal blood flow, the vascular response of the macrovessels and microvessels to stimulation of the hands was significantly reduced, which indicates less reactivity in DM patients with complications.

Conclusions

Our results suggest that DM patients, and DM patients with complications, have unique peripheral blood flow characteristics.

Testing the sympathetic nervous system of the foot has a high predictive value for early amputation in patients with diabetes with a neuroischemic ulcer

OBJECTIVE

There is evidence from the literature that dysfunctionality of the sympathetic nervous system of the foot with subsequent loss of local autoregulation could be a predictor of early amputation in patients with diabetes with a neuroischemic ulcer. To confirm this we tested the functionality of the sympathetic nervous system in the foot in a consecutive group of 31 patients with diabetes with critical limb ischemia and non-healing neuroischemic ulcer.

RESEARCH DESIGN AND METHODS

Prospective cohort with retrospective analysis after 12 months of routinely acquired clinical data. All patients in the study group underwent angiography of the foot as part of a routine angioplasty procedure. Primary study endpoint was lower extremity amputation-free survival at 12 months. Because of the study design no other endpoints could be analyzed. The functionality of the sympathetic nervous system was tested with perfusion angiography.

RESULTS

Thirty-one patients were followed for 12 months. The Capillary Resistance Index (CRI) was used to measure the response of the sympathetic nervous system. CRI≥0.9 is the cut-off point for a non-responsive sympathetic nervous system. All patients (n=11) with a CRI≥0.9 underwent a major amputation before 12 months. Of all patients with a CRI only 15% underwent major amputation. The positive predictive value for major amputation before 12 months for patients with a CRI ≥ 0.9 was 100%.

CONCLUSIONS

A non-responsive sympathetic nervous system of the foot is a strong predictor of early major amputation (log rank p<0.001; HR 14.22; 95% CI 3.64 to 55.51).

Pulsed electromagnetic field therapy promotes healing and microcirculation of chronic diabetic foot ulcers: a pilot study

OBJECTIVE

To examine the effects of pulsed electromagnetic field (PEMF) therapy on promoting the healing and microcirculation of chronic diabetic foot ulcers.

DESIGN

A randomized, double-blind, placebo-controlled clinical trial on a homogenous subset of chronic diabetic foot ulcers.

SETTING

Hospital and university.

PATIENTS

Thirteen subjects (7 in the PEMF group and 6 in the control group) diagnosed with type 2 diabetes and had unsatisfactory healing of ulcer(s) in the preceding 4 weeks were recruited.

INTERVENTIONS

Subjects were randomly allocated to receive either active PEMF therapy (duration: 60 minutes; frequency: 12 Hz; intensity: 12 Gauss) or nonactive PEMF for 14 sessions within 3 weeks.

MAIN OUTCOME MEASURES

Assessment on wound closure, wound depth, and microcirculation were performed at the baseline, end of the treatment period, and 1-month follow-up.

MAIN RESULTS

By the end of the treatment period, there was an 18% decrease in wound size in the active PEMF group as compared with a 10% decrease in the control group. The PEMF group demonstrated significant cumulative increase in cutaneous capillary blood velocity (by 28%) and 14% increase in capillary diameter. In contrast, the control group showed a decrease in both capillary blood velocity and diameter.

CONCLUSION

In this study, PEMF therapy seemed to accelerate wound healing and improve microcirculation.

Microvascular Changes in the Diabetic Foot

Impairment of the microcirculation of diabetic patients may contribute to secondary complications in the lower extremity, such as foot infections and ulcerations. These microcirculatory changes, which are mainly functional rather than structural, are responsible for the impaired ability of the microvasculature to vasodilate in response to injury. Dysfunction of vascular endothelial cells and vascular smooth muscle cells both contribute to the reduction in vasodilation that is observed in diabetic patients. Nerve-axon reflex related microvascular vasodilation is also impaired in the diabetic population, and there is a growing belief that both the failure of the vessels to dilate and the impairment of the nerve axon reflex are major causes for impaired wound healing in diabetic patients. Further studies are necessary to clarify the precise etiology of endothelial and smooth muscle dysfunction in diabetic patients so that potential therapeutic interventions may be identified.

Noninvasive Measurement Techniques for Monitoring of Microvascular Function in the Diabetic Foot

There are, currently, 3 established clinical techniques routinely employed to determine the risk of ulceration in the diabetic foot. These are assessment of the circulation, the nervous control of sensation, and foot sensitivity to loading. Macrovascular measurements are used to assess sufficiency of the arterial supply to the foot. Evaluation of somatic neuropathy provides an indication of loss of plantar sensation. Skin pressure measurements indicate abnormalities in plantar loading. This combined approach is effective in allowing preventative measures to be applied prior to the onset of ulceration. In contrast, clinical measurement of microvascular function in the diabetic foot is uncommon. Indeed, there remains uncertainty regarding the importance of micro-vascular complications in the development of foot ulcers. This is in part due to the difficulty of making in vivo measurements of microvascular function. This article evaluates 3 noninvasive measurement techniques for routine micro-vascular assessment of the diabetic foot: transcutaneous oxygen tension, laser Doppler flowmetry, and near-infrared spectroscopy. These techniques can be used to obtain useful parameters of microvascular function including surface oxygen, blood flow, intracellular oxygenation, and cellular respiration. In principle, such measurements can be related to underlying pathophysiology, for example, microangiopathy or autonomic neuropathy. This article considers how these general techniques can be adapted to support routine clinical measurement of microvascular function, particularly in the neuropathic diabetic foot.

Transcutaneous oxygen pressure (TcPO₂): a novel diagnostic tool for peripheral neuropathy in type 2 diabetes patients

AIMS

The assessment of transcutaneous oxygen pressure (TcPO2) may serve as a non-invasive and lower-cost alternative to nerve conduction studies (NCSs) for the diagnosis of diabetic peripheral neuropathy (DPN). The aim of this study was to determine whether the measurement of TcPO2 is useful for evaluating DPN.

METHODS

We performed a cross-sectional study of 381 consecutive hospitalized diabetic patients classified by clinical examination and NCS as having DPN. Anthropometric and metabolic parameters were assessed. The TcPO2 examination was performed in both supine and sitting positions.

RESULTS

Three hundred and one patients had DPN. The TcPO2 in both the supine and sitting positions was highest in the Non-DPN group and lower in the confirmed DPN group than the other three groups (p<0.001). The Non-DPN group had the lowest sitting-supine position difference in TcPO2 among the groups (p<0.001). The risk factors strongly associated with DPN included sitting-supine position difference in TcPO2 (OR=4.971, p<0.001), diabetic retinopathy (DR) (odds ratio [OR]=3.794, p=0.002), and HbA1c (OR=1.534, p=0.033). The area under the curve (AUC) of the sitting-supine position difference in TcPO2 was 0.722 and revealed an optimal cut-off point for the identification of DPN (19.5 mmHg) that had a sensitivity of 0.611 and a specificity of 0.738 based on AUC analysis.

CONCLUSIONS

This large study of diabetic patients confirms that the sitting-supine position difference in TcPO2 is higher in DPN patients than control subjects, indicating that TcPO2 examination is a promising valuable diagnostic tool for DPN.

Microcirculatory vasomotor changes are associated with severity of peripheral neuropathy in patients with type 2 diabetes

Systemic microvascular complications are related to the presence of diabetic neuropathy. This study investigated the associations of blood flow oscillations with peripheral neuropathy in 25 controls and 3 diabetic groups including clinical (24), subclinical (27) and without neuropathy (26). Laser Doppler skin perfusion was transformed into three low-frequency subintervals corresponding to endothelial, neurogenic and myogenic vasomotor controls. The average vasomotion was significantly reduced in clinical neuropathy group and characterized by endothelial and neural but not smooth muscle-related changes. The normalized spectrums revealed a relative increase of myogenic and decrease of neurogenic activity in subclinical neuropathy group. The myogenic component showed a statistically inverse correlation with postural fall in systolic blood pressure (r = -0.32, p < 0.01). The diabetic patients with decreased low-frequency vasomotor responses were associated with increased odds ratio of peripheral neuropathy [odds ratio = 3.51 (95% confidence interval = 1.19-10.31), p = 0.02]. This study elucidated possible interaction between impaired microvascular flow motion and diabetic peripheral neuropathy. The vasomotor changes of skin microcirculation could be detected even in the absence of overt cardiovascular dysfunction.

Streptozotocin-induced diabetes differentially affects sympathetic innervation and control of plantar metatarsal and mesenteric arteries in the rat

In humans neural control of arterial vessels supplying skin in the extremities is particularly vulnerable to the effects of diabetes. Here the streptozotocin (STZ) rat model of type 1 diabetes was used to compare effects on neurovascular function in plantar metatarsal arteries (PMAs), which supply blood to skin of hind paw digits, with those in mesenteric arteries (MAs). Twelve weeks after STZ (60 mg/kg ip), wire myography was used to assess vascular function. In PMAs, lumen dimensions were unchanged but both nerve-evoked contractions and sensitivity to α(1) (phenylephrine, methoxamine)- and α(2) (clonidine)-adrenoceptor agonists were reduced. The density of perivascular nerve fibers was also reduced by ~25%. These changes were not observed in PMAs from STZ-treated rats receiving either a low dose of insulin that did not greatly reduce blood glucose levels or a high dose of insulin that markedly reduced blood glucose levels. In MAs from STZ-treated rats, nerve-evoked increases in force did not differ from control but, because lumen dimensions were ~20% larger, nerve-evoked increases in effective transmural pressure were smaller. Increases in effective transmural pressure produced by phenylephrine or α,β-methylene ATP in MAs from STZ-treated rats were not smaller than control, but the density of perivascular nerve fibers was reduced by ~10%. In MAs, the increase in vascular dimensions is primarily responsible for reducing effectiveness of nerve-evoked constrictions. By contrast, in PMAs decreases in both the density of perivascular nerve fibers and the reactivity of the vascular muscle appear to explain impairment of neurovascular transmission.

Changes of skin temperature of parts of the body and serum asymmetric dimethylarginine (ADMA) in type-2 diabetes mellitus Indian patients

In India, number of people with type 2 Diabetes Mellitus (DM) would be 87 million by the year 2030. DM disturbs autonomic regulation of skin micro-circulation, and causes decrease in resting blood flows through the skin. The skin blood flow has a major effect on its temperature. The aim of the study was to evaluate changes of skin temperature of all parts of the body and serum asymmetric dimethylarginine, ADMA (μmol/L) in type-2 DM Indian patients. Group-I: Normal (n = 17; M/F: 10/15, mean ± SD = 43.2 ± 9.4 years); Group-II: Type-2 DM without cardiovascular (CV) complications (n = 15; M/F: 10/7, mean ± SD = 46.3 ± 14.0 years); Thermograms of all parts of the body were acquired using a non-contact infrared (IR) thermography camera (ThermaCAM T400, FLIR Systems, Sweden). Blood parameters and thyroid hormone were measured biochemically. Indian diabetic risk score (IDRS) was calculated for each subject. In type-2 DM patients without CV group (n = 15), there was a statistically significant (p = 0.01) negative correlations between HbA(1c) and skin temperature of eye and nose (r = -0.57 and r = -0.55 respectively). ADMA was correlated significantly (p = 0.01) with HbA(1c) (r = 0.65) and estimated average glucose, eAG (r = 0.63). In normal subjects, mean minimum and maximum values of skin temperatures were observed at posterior side of sole (26.89 °C) and ear (36.85 °C) respectively. In type-2 DM without CV, mean values of skin temperature in different parts of the body from head to toe were lesser than those values in control group; but this decreases were statistically significant in nose (32.66 Vs 33.99 °C, p = 0.024) as well as in tibia (32.78 Vs 33.13 °C, p = 0.036) regions.

The association between skin blood flow and edema on epidermal thickness in the diabetic foot

BACKGROUND

Skin blood flow plays an important role in maintaining the health of the skin. The development of interstitial edema may impede oxygen diffusion to the skin. The aim of this study was to evaluate the association of skin blood flow and edema and epidermal thickness in the feet of people with and without diabetic neuropathy compared with a healthy control group.

SUBJECTS AND METHODS

Eighty-seven subjects (19 people with diabetic neuropathy and foot ulceration, 35 people with diabetes but without neuropathy, and 33 healthy controls without diabetes) participated in the study. High-frequency ultrasonography was used to measure the epidermal thickness and edema in papillary skin at the big toe as reflected by the thickness of the subepidermal low echogenic band (SLEB). The capillary nutritive blood flow was measured by the use of video capillaroscopy, and skin blood flux was monitored by laser Doppler flowmetry.

RESULTS

There was a 7.2% increase in epidermal thickness in those with diabetes but without neuropathy and a 16.5% decrease in people with diabetic neuropathy and foot ulceration compared with the healthy controls (all P<0.05). The SLEB thickness increased in all subjects with diabetes to a greater degree in those with neuropathy and ulceration than in those without (64.7% vs. 11.8%, P<0.001). Skin blood flux was shown to be higher in the diabetes groups than in the controls (all P<0.05), but no significant differences were found in the resting nutritive capillary blood flow (P>0.05). A significant negative correlation (P=0.002, r=-0.366) was demonstrated between the SLEB and epidermal thickness at the pulp of the big toe, whereas no significant correlation was demonstrated between skin blood flow and epidermal thickness (all P>0.05).

CONCLUSIONS

An increase in subepidermal edema was demonstrated in people with diabetic neuropathy and ulceration, which may partly contribute to reduced epidermal thickness at the pulp of the big toe. This may subsequently lead to the breaking down of skin in the diabetic foot.

The diabetes-induced functional and distributional changes of the alpha 1-adrenoceptor of the abdominal aorta and distal mesenteric artery from streptozotocin-induced diabetic rats

Background

The aim of this study was to evaluate the effect of diabetes on the function and distribution of vascular α₁-adrenoceptors in the abdominal aorta and distal mesenteric artery from streptozotocin (STZ)-induced diabetic rats at the level of the α₁-adrenoceptor subtypes.

Methods

Diabetes was induced by a single intravenous injection of STZ (60 mg/kg) in 8 week-old male Sprague-Dawley rats (n = 11). Age-matched normal rats (n = 14) were used as a control group. Four weeks after STZ injection, the tilting-induced change of the mean arterial pressure was recorded. The α₁-adrenoceptor subtypes mediating the contractions of the distal mesenteric artery and abdominal aorta were investigated using the agonist phenylephrine and subtype-selective antagonists that included prazocin, 5-methylurapidil and BMY 7378. The expressions of the α₁-adrenoceptor subtypes of each artery were examined by immunofluorescence staining using the subtype selective antibodies.

Results

The recovery of the mean arterial pressure was delayed after positional change in the diabetic rats. Compared with that of the normal rats, the contractile response to phenylephrine was increased in the abdominal aortas and it was decreased in the distal mesenteric arteries in the diabetic rats. In addition, compared with the normal rats, the fluorescent intensity of all the α₁-adrenoceptor subtypes was increased in the abdominal aortas and it was decreased in the mesenteric arteries of the diabetic rats.

Conclusions

Diabetes increased the contractility of the abdominal aorta in response to phenylephrine, yet diabetes decreased that of the mesenteric arteries in the STZ-induced diabetic rats. Those results are mainly based on the overall change of the α₁-adrenoceptor, and not on the change of the specific α₁-adrenoceptor subtypes.

Effect of rimonabant, the cannabinoid CB1 receptor antagonist, on peripheral nerve in streptozotocin-induced diabetic rat

The aim of this study is to investigate the effect of rimonabant, which has antiatherosclerotic and antiinflammatory properties, on peripheral neuropathy in a diabetic rat. Diabetic rat models were induced by treatment with streptozotocin and then either normal or diabetic rats were treated with an oral dose of 10mg/kg/day rimonabant or placebo for 24 weeks. We quantified the densities of intraepidermal (PGP9.5+) nerve fiber and total skin (RECA-1+) capillary length. We also measured the current perception threshold, as defined by the intensity of sine-wave stimulus, skin blood flow after treadmill running and TNF-alpha level in spinal cord tissue or plasma. After 24 weeks, rimonabant reduced the body weight and food intake in both diabetic and normal rats, but it had no effect on blood sugar levels. In addition, rimonabant treatment significantly improved the decreased intraepidermal nerve fiber density (5.53+/-0.12 vs. 4.36+/-0.27/mm, P<0.05) and alleviated the increased current perception threshold in rimonabant-treated versus control diabetic rats. These responses were closely associated with the attenuation of skin capillary loss (1.98+/-0.07 vs. 1.67+/-0.10 mm/mm(2), P<0.05), increase in skin blood flow (14.93+/-1.08 vs. 12.07+/-0.87 TPU, P<0.05) and reduction in TNF-alpha level in tissue (70.10+/-4.99 vs. 91.18+/-3.34 pg/mg, P<0.05) in rimonabant-treated diabetic rats compared with placebo. These findings suggest that rimonabant can be beneficial for treatment of diabetic peripheral neuropathy, possibly due to its potential role in micro- and macrovessel protection and its anti-inflammatory properties.

Microvascular dysfunction in diabetic foot disease and ulceration

Diabetic foot disease and ulceration is a major complication that may lead to the amputation of the lower limbs. Microangiopathy may play a significant role in the pathogenesis of tissue breakdown in the diabetic foot. However, the precise mechanisms of this process remain unclear and poorly understood. Microvasculature in the skin is comprised of nutritive capillaries and thermoregulatory arteriovenous shunt flow. It is regulated through the complex interaction of neurogenic and neurovascular control. The interplay among endothelial dysfunction, impaired nerve axon reflex activities, and microvascular regulation in the diabetic patient results in the poor healing of wounds. Skin microvasculature undergoes both morphologic changes as well as functional deficits when parts of the body come under stress or injury. Two important theories that have been put forward to explain the abnormalities that have been observed are the haemodynamic hypothesis and capillary steal syndrome. With advances in medical technology, microvasculature can now be measured quantitatively. This article reviews the development of microvascular dysfunction in the diabetic foot and discusses how it may relate to the pathogenesis of diabetic foot problems and ulceration. Common methods for measuring skin microcirculation are also discussed.

Relationship between skin resistance level and static balance in type II diabetic subjects

Diabetes mellitus is major cause leading to pathological changes in skin foot plantar area (SFPA) and affected the static standing balance duration (SSBD). Skin resistance level (SRL) is related to skin conductance which changes in the presence of sweat. This study aims to find out the relationship between the SRL and SSBD in type II diabetic patients. Sixty-eight voluntary students, 30 type II diabetic patients and 30 healthy non-diabetic subjects, were participated to the study. The SSBD was measured on dominant and non-dominant legs. SRLs were recorded with two surface electrodes over the metatarsus heads and heel. The SSBD of the healthy young group was found to be higher than the other groups (P<0.001). The SRL values of the non-dominant leg in the diabetic group was found to be lower than the others (P=0.014). For dominant and non-dominant legs within each group, only the healthy young group has statistically difference (P=0.012). A significant correlation was seen to be between the SRL and SSBD for only healthy non-diabetic group for the non-dominant leg. The relation between the SRL and SSBD is poor but very promising. Measurement of the SRL can be used in evaluating the inflammation of the diabetic foot.

Warm immersion recovery test in assessment of diabetic neuropathy--a proof of concept study

The aim of this article was to present results of warm immersion recovery test in the diabetic foot with neuropathy using a liquid crystal-based contact thermography system. It is intended to provide a 'proof of concept' for promoting the role of supplementary thermal assessment techniques and evidence-based diagnosis of diabetic neuropathy. A total of 81 subjects from the outpatient department of MV Hospital for Diabetes, India, were assessed using a liquid crystal thermography system. Each subject was assigned to one of three study groups, that is diabetic neuropathy, diabetic non neuropathy and non diabetic healthy. The room temperature and humidity were consistently maintained at 24 degrees C and less than 50%, respectively, with air conditioning. The right foot for each subject was located on the measurement platform after warm immersion in water at 37 degrees C. Whole-field thermal images of the plantar foot were recorded for 10 minutes. Local measurements at the most prevalent sites of ulceration, that is metatarsal heads, great toe and heel, show highest temperature deficit after recovery for diabetic neuropathy group. The findings of the current study support the ones of a previous study by the authors, which used cold immersion recovery test for the neuropathic assessment of the diabetic foot. A temperature deficit between the recovery and the baseline temperature for the neuropathic group suggests degeneration of thermoreceptors. Thermal stimulus tests can be useful to validate the nutritional deficits' (during plantar loading and thermal stimulus) contribution in foot ulceration.

Cold immersion recovery responses in the diabetic foot with neuropathy

The aim of this article was to investigate the effectiveness of testing cold immersion recovery responses in the diabetic foot with neuropathy using a contact thermography system based on thermochromic liquid crystals. A total of 81 subjects with no history of diabetic foot ulceration were assigned to neuropathy, non neuropathy and healthy groups. Each group received prior verbal and written description of the test objectives and subsequently underwent a comprehensive foot care examination. The room temperature and humidity were consistently maintained at 24 degrees C and less than 50%, respectively, with air conditioning. The right foot for each subject was located on the measurement platform after cold immersion in water at 18-20 degrees C. Whole-field thermal images of the plantar foot were recorded for 10 minutes. Patients with diabetes with neuropathy show the highest 'delta temperature', that is difference between the temperature after 10-minute recovery period and baseline temperature measured independently at all the three sites tested, that is first metatarsal head (MTH), second MTH and heel. This clinical study showed for the first time the evidence of poor recovery times for the diabetic foot with neuropathy when assessing the foot under load. A temperature deficit (because of poor recovery to baseline temperature) suggests degeneration of thermoreceptors, leading to diminished hypothalamus-mediated activity in the diabetic neuropathic group.

Neurovascular control and neurogenic inflammation in diabetes

Loss of pain perception is currently seen as a key factor in the development of diabetic foot ulcers. However, recent studies suggest that nerves play a central role in tissue homeostasis and can orchestrate complex reparative as well as destructive processes in the feet. Evidence is presented that suggests that denervation can result in altered capillary blood flow (in patients with type 2 diabetes), oxygen delivery, fluid filtration, and inflammatory responses. These processes could render the feet of diabetic patients with neuropathy more susceptible to tissue damage, infection and perhaps, in a subset of patients, to the development of acute Charcot neuro-osteoarthropathy (CN).

Endothelial and neural regulation of skin microvascular blood flow in patients with diabetic peripheral neuropathy: effect of treatment with the isoform-specific protein kinase C beta inhibitor, ruboxistaurin

PURPOSE

This article aims to study the effects of ruboxistaurin (RBX) on skin microvascular blood flow (SkBF) and evaluate the relationship between endothelial and neural control of SkBF in patients with diabetic peripheral neuropathy (DPN).

METHODS

We studied 11 placebo- and 9 RBX (32 mg/day)-treated patients who participated in a 1-year, double-masked, randomized, Phase 3 study of RBX for treatment of DPN sensory symptoms. Patients had type 1 or type 2 diabetes, a detectable sural sensory nerve action potential, and Neuropathy Total Symptom Score-6 (NTSS-6) >6 points. SkBF was measured by laser Doppler velocimetry, combined with iontophoresis of acetylcholine and sodium nitroprusside, at baseline, 3 months, and 1 year. Sensory symptoms and electrophysiology were also evaluated during the study. The relationship between endothelial and neural control of SkBF at baseline was assessed using linear regression.

RESULTS

No significant differences (RBX vs. placebo) were demonstrable for post-iontophoresis SkBF [fold increase from basal state (1 year): endothelium-dependent, 3.6 vs. 8.6; endothelium-independent, 3.7 vs. 2.0; C fiber-mediated, 1.7 vs. 2.0; P>.05] or sensory symptoms [NTSS-6 total score (1 year): 7.7 vs. 6.0 points; P=.4]. There were also no significant between-group differences in nerve conduction parameters, except for placebo peroneal nerve conduction velocity, which demonstrated a statistically significant improvement of unknown clinical importance (Z=2.1; P=.034). At baseline, C fiber-mediated vasodilatation correlated well with endothelium-dependent vasodilation (r=.7, P<.01) but not with endothelium-independent vasodilatation (r=-.1, P=.7).

CONCLUSIONS

RBX demonstrated no effect on SkBF or sensory symptoms after 1 year in this cohort. The correlation between C fiber-mediated and endothelium-dependent SkBF at baseline suggests that improving endothelial function could affect the microcirculation not only locally but also via the neurovascular arcade.

Neurovascular factors in wound healing in the foot skin of type 2 diabetic subjects

OBJECTIVE

Delayed wound healing in diabetic patients without large-vessel disease has been attributed to microvascular dysfunction, neuropathy, and abnormal cellular and inflammatory responses. The role of these abnormalities has mainly been examined in animal models. Few studies have been undertaken in diabetic patients, and those that have are limited due to analysis in wounds from chronic ulcers. In this study, we quantified the rate of wound healing in relation to skin neurovascular function and structure following a dorsal foot skin biopsy in type 2 diabetes.

RESEARCH DESIGN AND METHODS

Twelve healthy control subjects and 12 type 2 diabetic subjects with neuropathy but without macrovascular disease were studied. We quantified rate of wound healing and related it to skin microvascular function (laser Doppler imager [LDI](max)), blood vessel density, small nerve fiber function (LDI(flare)) and nerve fiber density, vascular endothelial growth factor (VEGF) and its receptor (FLK1), and hypoxia-inducible factor (HIF)-1alpha expression.

RESULTS

The rate of wound closure was identical between control subjects and diabetic patients despite a significant reduction in maximum hyperemia (LDI(max)), epidermal and dermal VEGF-A, and epidermal and dermal blood vessel VEGFR-2 expression as well as the neurogenic flare response (LDI(flare)) and dermal nerve fiber density. There was no significant difference in HIF-1alpha and dermal blood vessel density between control subjects and diabetic patients.

CONCLUSIONS

In conclusion, the results of this study suggest that wound closure in subjects with type 2 diabetes is not delayed despite significant alterations in neurovascular function and structure.

Thermography and thermometry in the assessment of diabetic neuropathic foot: a case for furthering the role of thermal techniques

There are currently 3 established techniques employed routinely to determine the risk of foot ulceration in the patient with diabetes mellitus. These are the assessment of circulation, neuropathy, and foot pressure. These assessments are widely used clinically as well as in the research domain with an aim to prevent the onset of foot ulceration. Routine neuropathic evaluation includes the assessment of sensory loss in the plantar skin of the foot using both the Semmes Weinstein monofilament and the biothesiometer. Thermological measurements of the foot to assess responses to thermal stimuli and cutaneous thermal discrimination threshold are relatively uncommon. Indeed, there remains uncertainty regarding the importance of thermal changes in the development of foot ulcers. Applications of thermography and thermometry in lower extremity wounds, vascular complications, and neuropathic complications have progressed as a result of improved imaging software and transducer technology. However, the uncertainty associated with the specific thermal modality, the costs, and processing times render its adaptation to the clinic. Therefore, wider adoption of thermological measurements has been limited. This article reviews thermal measurement techniques specific to diabetic foot such as electrical contact thermometry, cutaneous thermal discrimination thresholds, infrared thermography, and liquid crystal thermography.

Relationship of skin temperature to sympathetic dysfunction in diabetic at-risk feet

The relationship of plantar skin temperature to diabetic neuropathy was studied using clinical, nerve conduction and autonomic evaluations. The sympathetic skin response (SSR) was found present in both feet of 25 control subjects and 29 (out of 69) diabetic patients (SSR+ group). For those diabetic patients absent with the SSR in both feet, 18 patients (at-risk group) had preulcerative skin lesions (dry and fissured skin) and 22 did not (SSR- group). The at-risk group showed significantly higher mean foot temperature (30.2+/-1.3 degrees Celsius) than the SSR- (27.9+/-1.7 degrees Celsius), the SSR+ (27.1+/-2.0 degrees Celsius) and the control group (26.8+/-1.8 degrees Celsius). The SSR- group had smaller temperature differences (7.2+/-1.7 degrees Celsius versus 8.6+/-1.6 degrees Celsius, p<0.05) and smaller normalized temperature (referencing to the forehead temperature) (0.19 versus 0.24, p<0.01) than the SSR+ group. Although the three diabetic groups had no significant differences in clinical and cardiovascular abnormalities, the at-risk group showed more nerve conduction abnormalities than the SSR- and SSR+ groups (55% versus 23% and 14%, p<0.02). This study indicated that the thermoregulatory sweating abnormality signified early sympathetic damage in diabetic feet. Assessing skin conditions and sudomotor activities should help identify small fiber neuropathy in diabetic patients with at-risk feet conditions.

Normocytic normochromic anemia due to automatic neuropathy in type 2 diabetic patients without severe nephropathy: a possible role of microangiopathy

We describe here four male patients with long-term and poorly controlled type 2 diabetes mellitus. They shared many common characteristic complications, such as severe autonomic neuropathy, proliferative retinopathy and normocytic normochromic anemia without progressive renal failure and macroangiopathy. They also showed normal levels of erythropoietin and reticulocyte, which was considered relatively low. The coefficient of variation of R-R, a useful method to estimate autonomic failure, showed markedly advanced autonomic neuropathy in all four patients. Coronary angiography did not reveal stenosis, anomaly or collateral vessels, but left ventriclography showed diffuse or partial hypokinesis. Massive proteinuria, high urinary levels of N-acetyl-beta-D-glucosamidase (NAG) and beta2-microglobulin (beta2M) were detected, though creatinine clearance (Ccr) was not so deteriorated. Treatment with recombinant erythropoietin increased their hemoglobin and hematocrit levels. These common points have a possibility to be brought about by tubulointerstitial damage and microangiopathy may be involved in it.

Foot temperature in diabetic polyneuropathy: innocent bystander or unrecognized accomplice?

AIM

To explore mechanisms by which temperature could influence the pathogenesis and symptoms of diabetic polyneuropathy.

METHODS

We conducted a literature review attempting to identify mechanisms by which diabetic polyneuropathy could be affected by temperature.

RESULTS

Cooling can theoretically hasten the progression of diabetic polyneuropathy through several different mechanisms. Specifically, cooling can enhance neuronal ischaemia, increase formation of reactive oxygen species, slow axonal transport, increase protein kinase C activity, and interfere with immune function. Short-term temperature fluctuations (both warming and cooling) can initiate and exacerbate neuropathic pain by causing neuronal hyperexcitability and functional deafferentation. Although normal fluctuations of distal extremity temperature may be sufficient for these effects, impaired thermoregulation may make the distal extremities more susceptible to temperature extremes. Eventually, a 'vicious cycle' may ensue, resulting in neuronal deterioration with further disruption of temperature regulation. Limited epidemiological data suggest a higher prevalence of diabetic polyneuropathy in populations living in colder locations, supporting our hypothesis.

CONCLUSIONS

Variations in foot temperature may play an important but as yet unrecognized role in the development and symptoms of diabetic polyneuropathy. Further basic and clinical research exploring this concept could help elucidate the natural history of diabetic polyneuropathy and lead to novel therapeutic strategies.

Impaired microvascular function related to poor metabolic control in young patients with diabetes

The purpose of the present study was to identify whether young patients with type 1 diabetes using modern multiple insulin injection therapy (MIT) have signs of microvascular dysfunction and to elucidate possible correlations with various disease parameters. Skin blood flow on the dorsum of the foot was measured with laser Doppler perfusion imaging in 37 patients (age 10-21 years, disease duration 6.0-16 years) and 10 healthy controls. Measurements were performed at rest, after change in posture (the leg was lowered below heart level) and during postocclusive hyperaemia. Following a change in posture blood flow increased instead of decreased in a majority of the study subjects. Patients with acute HbA1c >7.5% (n = 22) had an increase in skin blood flow at rest and a significantly reduced blood flow when the leg was lowered below heart level as compared with patients with HbA1c <7.5% (0.26 V versus 0.17 V, P<0.01 and 0.12 V versus 0.23 V, P<0.05, respectively) and healthy controls. Following occlusion of the macrocirculation for 3 min a small non-significant decrease in the hyperaemic response was seen in the patients. The postocclusive hyperaemic response and the venoarteriolar reflex were not correlated to duration of disease, long-term metabolic control or electrophysiological signs of peripheral nerve dysfunction. It is concluded that signs of microvascular dysfunction related to poor metabolic control are present in young patients with MIT treatment and rather well-controlled diabetes. Low resting blood flow levels are suggested to contribute to the absence of postural vasoconstrictor response.

Loss of pain perception in diabetes is dependent on a receptor of the immunoglobulin superfamily

Molecular events that result in loss of pain perception are poorly understood in diabetic neuropathy. Our results show that the receptor for advanced glycation end products (RAGE), a receptor associated with sustained NF-kappaB activation in the diabetic microenvironment, has a central role in sensory neuronal dysfunction. In sural nerve biopsies, ligands of RAGE, the receptor itself, activated NF-kappaBp65, and IL-6 colocalized in the microvasculature of patients with diabetic neuropathy. Activation of NF-kappaB and NF-kappaB-dependent gene expression was upregulated in peripheral nerves of diabetic mice, induced by advanced glycation end products, and prevented by RAGE blockade. NF-kappaB activation was blunted in RAGE-null (RAGE(-/-)) mice compared with robust enhancement in strain-matched controls, even 6 months after diabetes induction. Loss of pain perception, indicative of long-standing diabetic neuropathy, was reversed in WT mice treated with soluble RAGE. Most importantly, loss of pain perception was largely prevented in RAGE(-/-) mice, although they were not protected from diabetes-induced loss of PGP9.5-positive plantar nerve fibers. These data demonstrate, for the first time to our knowledge, that the RAGE-NF-kappaB axis operates in diabetic neuropathy, by mediating functional sensory deficits, and that its inhibition may provide new therapeutic approaches.

Skin Blood Flow in the Upper and Lower Extremities of Diabetic Patients with and without Autonomic Neuropathy

BACKGROUND

Microvascular blood flow in the human skin is subject to rhythmic variations reflecting the influence of heartbeat, respiration, intrinsic myogenic activity, neurogenic factors and endothelial activity. The aim of our study was to test the hypothesis that basal skin blood flow (BSBF) and its dynamic components differ (1) among diabetic patients without autonomic neuropathy and with it and healthy control subjects, and (2) among the upper and lower extremities.

PATIENTS AND METHODS

BSBF at four recording sites with predominantly nutritive capillary circulation (right and left caput ulnae, right and left medial malleolus) was measured by laser Doppler flowmetry in 25 diabetic patients without cardiovascular autonomic neuropathy (D), 18 neuropathic diabetic patients (DAN) and 36 healthy controls (C). Wavelet transform was applied to the laser Doppler signal.

RESULTS

In absolute terms, mean flow, mean amplitude of the total spectrum and mean amplitudes at all frequency intervals were highest in C, followed by DAN and lowest in D. However, these differences were statistically significant only in the left arm. Within all three groups, mean flow and spectral amplitudes were significantly higher in the arms than in the legs, besides there was a significant difference between the two arms in D.

CONCLUSION

We have confirmed the differences in BSBF among D, DAN and C, and demonstrated differences among the four recording sites which have not been previously described. The latter indicates an uneven progression of autonomic neuropathy and allows for speculation that the left arm is the latest to be affected.

Advances in the treatment of the diabetic foot: Is there a role for adjunctive hyperbaric oxygen therapy?

There have been many advances in the treatment of wounds made in the last decade. Innovative techniques of wound closure, topical agents, aggressive vascular repair, focused wound care management, and adjunctive hyperbaric oxygen therapy are but a few of these improvements. The vital role of oxygen in wound healing is becoming better understood, in no small part, due to Dr. T. K. Hunt and his colleagues at the Wound Healing Laboratory at the University of California, San Francisco. Elements of that contribution will be examined in this article. How these elements may be applied to improve wound healing will be explained and the possible role of adjunctive hyperbaric oxygen therapy based on sound science in the management of the difficult diabetic foot wound, will be highlighted.

Comparative roles of microvascular and nerve function in foot ulceration in type 2 diabetes

OBJECTIVE

To determine the relative roles of different modalities of sensory nerve function (large and small fiber) and the role of microvascular dysfunction in foot ulceration in type 2 diabetic subjects.

RESEARCH DESIGN AND METHODS

A total of 20 control subjects and 18 type 2 diabetic subjects with foot ulceration and 20 without were studied. None of the subjects had clinical features of peripheral vascular disease. The Computer-Aided Sensory Evaluator IV (CASE IV) was used to determine vibration detection threshold (VDT), cold detection threshold (CDT), warm detection threshold (WDT), and heat pain onset threshold (HPO). Vibration perception threshold (VPT) was also assessed by a neurothesiometer. Microvascular function (maximum hyperemia to skin heating to 44 degrees C) was assessed using laser Doppler flowmetry (mean maximum hyperemia using laser Doppler flowmeter [LDF(max)]), laser Doppler imaging (mean maximum hyperemia using laser Doppler imager [LDI(max)]), and skin oxygenation with transcutaneous oxygen tension (TcpO(2)).

RESULTS

VPT, VDT, CDT, and HPO were all significantly higher in individuals with ulceration than in those without (VPT and VDT: P < 0.0001) (CDT and HPO: P = 0.01). LDF(max), LDI(max), and TcpO(2) were significantly lower in the two diabetic groups than in the control subjects, but there was no difference between individuals with and without ulceration. Univariate logistic regression analysis revealed similar odds ratios for foot ulceration for VDT, CDT, HPO, and VPT (OR 1.97 [95% CI 1.30-2.98], 1.58 [1.20-2.08], 2.30 [1.21-4.37], and 1.24 [1.08-1.42], respectively). None of the microvascular parameters yielded significant odds ratios for ulceration.

CONCLUSIONS

This study found that there was no additional value in measuring small-fiber function with the CASE IV over measuring vibration by either CASE IV or the inexpensive neurothesiometer in discriminating between individuals with and without ulceration. Furthermore, none of the tests of microvascular function including the TcpO(2) were able to discriminate between individuals with and without ulceration, suggesting that such tests may not be of benefit in identifying subjects at greater risk of foot ulceration.

Early endothelial dysfunction severely impairs skin blood flow response to local pressure application in streptozotocin-induced diabetic mice

Pressure-induced vasodilation (PIV) is a mechanism whereby skin blood flow increases in response to progressive locally applied pressure. Skin blood flow in response to applied pressure decreased early in diabetic patients as a result of vascular and/or neural impairment. This study was designed to determine the effect of vascular changes on PIV in 1-week streptozotocin-induced diabetic mice. We assessed cutaneous microvascular response to local increasing pressure application measured by laser Doppler flowmetry (LDF) and endothelium-dependent and -independent vasodilation by iontophoretic delivery of acetylcholine and sodium nitroprusside and sciatic motor nerve conduction velocity and morphometry. In control mice, LDF increased 34% from baseline to 0.2 kPa external pressure, showing PIV response. In contrast, diabetic mice had no LDF increase in response to progressive external pressure. Moreover, after iontophoretic delivery of acetylcholine, endothelium-dependent vasodilation was largely attenuated in diabetic mice (25%) compared with control mice (81%), whereas vasodilation to sodium nitroprusside was not different between groups. Nerve function as assessed by sciatic nerve conduction velocity and morphometry did not differ between groups. These findings suggest that endothelial impairment is sufficient to severely alter PIV response, which seems to be highly sensitive to endothelial nitric oxide levels. PIV suppression could favor diabetes complications such as diabetic foot ulcers.