The venoarteriolar response in diabetics

Type 2 diabetes impairs vascular responsiveness to nitric oxide, but not the venoarteriolar reflex or post-occlusive reactive hyperaemia in forearm skin

The venoarteriolar reflex (VAR) is a local mechanism by which vasoconstriction is mediated in response to venous congestion. This response may minimize tissue overperfusion, preventing capillary damage and oedema. Post-occlusive reactive hyperaemia (PORH) is used to assess microvascular function by performing a brief local arterial occlusion resulting in a subsequent rapid transient vasodilation. In the current study, we hypothesized that type 2 diabetes (T2D) attenuates VAR and PORH responses in forearm skin in vivo. In 11 healthy older adults (Control, 58 ± 8 years) and 13 older adults with controlled T2D (62 ± 10 years), cutaneous blood flow measured by laser-Doppler flowmetry was monitored following a 3-min venous occlusion of 45 mm Hg that elicited the VAR, followed by a 3-min recovery period and then a 5-min arterial occlusion of 240 mm Hg that induced PORH. Finally, sodium nitroprusside, a nitric oxide donor, was administered to induce maximum vasodilation. VAR and PORH variables were similar between groups. By contrast, maximal cutaneous blood flow induced by sodium nitroprusside was lower in the T2D group. Taken together, our observations indicate that T2D impairs vascular smooth muscle responsiveness to nitric oxide, but not VAR and PORH in forearm skin.

Mechanisms of Venoarteriolar Reflex in Type 2 Diabetes with or without Peripheral Neuropathy

Simple Summary

Postural changes induce arteriolar vasoconstriction in response to an increase in venous pressure in the limbs known as the venoarteriolar reflex (VAR). Previous studies reported that skin blood perfusion is impaired during the VAR in persons with type 2 diabetes mellitus (T2DM) with or without peripheral neuropathy, compared to control subjects. The aim of this study is to investigate the underlying mechanisms of the VAR in T2DM, with and without peripheral neuropathy. This study provides evidence that confirmed neuropathy alters the VAR by an alteration of the neurogenic response to leg dependency.

Abstract

The aim of this study is to investigate the underlying mechanisms of the venoarteriolar reflex (VAR) in type 2 diabetes mellitus (T2DM), with and without peripheral neuropathy. Laser Doppler flowmetry (LDF) recordings were performed on the medial malleus and dorsal foot skin, before and during leg dependency in healthy controls, in persons with obesity, in those with T2DM, in those with T2DM and subclinical neuropathy, and in those with T2DM and confirmed neuropathy. LDF recordings were analyzed with the wavelet transform to evaluate the mechanisms controlling the flowmotion (i.e., endothelial nitric oxide-independent and -dependent, neurogenic, myogenic, respiratory and cardiac mechanisms). Skin blood perfusion decreased throughout leg dependency at both sites. The decrease was blunted in persons with confirmed neuropathy compared to those with T2DM alone and the controls. During leg dependency, total spectral power increased in all groups compared to rest. The relative contribution of the endothelial bands increased and of the myogenic band decreased, without differences between groups. Neurogenic contribution decreased in controls, in persons with obesity and in those with T2DM, whereas it increased in subclinical- and confirmed neuropathy. In conclusion, this study provides evidence that confirmed diabetic neuropathy alters the VAR through the neurogenic response to leg dependency.

Neck cooling induces blood pressure increase and peripheral vasoconstriction in healthy persons

Introduction

Noninvasive temperature modulation by localized neck cooling might be desirable in the prehospital phase of acute hypoxic brain injuries. While combined head and neck cooling induces significant discomfort, peripheral vasoconstriction, and blood pressure increase, localized neck cooling more selectively targets blood vessels that supply the brain, spares thermal receptors of the face and skull, and might therefore cause less discomfort cardiovascular side effects compared to head- and neck cooling. The purpose of this study is to assess the effects of noninvasive selective neck cooling on cardiovascular parameters and cerebral blood flow velocity (CBFV).

Methods

Eleven healthy persons (6 women, mean age 42 ± 11 years) underwent 90 min of localized dorsal and frontal neck cooling (EMCOOLS Brain.Pad™) without sedation. Before and after cooling onset, and after every 10 min of cooling, we determined rectal, tympanic, and neck skin temperatures. Before and after cooling onset, after 60- and 90-min cooling, we monitored RR intervals (RRI), systolic, diastolic blood pressures (BPsys, BPdia), laser Doppler skin blood flow (SBF) at the index finger pulp, and CBFV at the proximal middle cerebral artery (MCA). We compared values before and during cooling by analysis of variance for repeated measurements with post hoc analysis (significance: p < 0.05).

Results

Neck skin temperature dropped significantly by 9.2 ± 4.5 °C (minimum after 40 min), while tympanic temperature decreased by only 0.8 ± 0.4 °C (minimum after 50 min), and rectal temperature by only 0.2 ± 0.3 °C (minimum after 60 min of cooling). Index finger SBF decreased (by 83.4 ± 126.0 PU), BPsys and BPdia increased (by 11.2 ± 13.1 mmHg and 8.0 ± 10.1 mmHg), and heart rate slowed significantly while MCA-CBFV remained unchanged during cooling.

Conclusions

While localized neck cooling prominently lowered neck skin temperature, it had little effect on tympanic temperature but significantly increased BP which may have detrimental effects in patients with acute brain injuries.

Microangiopathy: Is it relevant to wound healing in diabetic foot disease?

Chronic diabetic complications - both microvascular and macrovascular - have become serious health issues with their increasing prevalence paralleling the dramatic rise of the diabetic population worldwide. Of these complications, foot disease is a major cause of morbidity and mortality, consuming more health care resource than all other complications combined. Diabetic polyneuropathy and peripheral vascular disease constitute the two main risk factors, with trauma and foot infection being the most important initiating factors and contributors to delayed healing. Intracellular oxidative stress mediated by hyperglycaemia along with hypertension, dyslipidaemia and smoking constitute the main pathological processes in the aetiology of both macrovascular and microvascular disease. Whilst the former remains the major cause of overall mortality in diabetes, the role of microangiopathy in the pathogenesis of diabetes foot disease and its contribution to delayed wound healing in diabetes has yet to be fully understood and indeed continues to be debated. This article will review the key findings to date on structural and functional microvascular abnormalities in the diabetic foot skin and consider their contribution to impaired would healing.

KCa and KV channels modulate the venoarteriolar reflex in non-glabrous human skin with no roles of KATP channels, NOS, and COX

The venoarteriolar reflex is a local mechanism that induces vasoconstriction during venous congestion in various tissues, including skin. This response is thought to play a critical role in minimizing capillary damage or edema resulting from overperfusion, though factors that modulate this response remain largely unknown. Here, we hypothesized that nitric oxide synthase (NOS), cyclooxygenase (COX), and Ca²⁺-activated, ATP-sensitive, and voltage-gated K⁺ channels (K_Ca, K_ATP, and K_V channels, respectively) modulate the venoarteriolar reflex in human skin. Cutaneous blood flow (laser-Doppler flowmetry) was monitored during a 3-min pre-occlusion baseline and following a 3-min venous occlusion of 45 mmHg, the latter maneuver was used to induce the venoarteriolar reflex. The venoarteriolar reflex was assessed at the following forearm skin sites: Experiment 1 (n = 11): 1) lactated Ringer solution (Control), 2) 10 mM N^ω-nitro-_L-arginine (NOS inhibitor), 3) 10 mM ketorolac (COX inhibitor), and 4) combined NOS + COX inhibition; Experiment 2 (n = 15): 1) lactated Ringer solution (Control), 2) 50 mM tetraethylammonium (K_Ca channel blocker), 3) 5 mM glybenclamide (K_ATP channel blocker), and 4) 10 mM 4-aminopyridine (K_V channel blocker). Separate and combined NOS and COX inhibition as well as K_ATP channel blocker had no effect on venoarteriolar reflex. Conversely, venoarteriolar reflex was attenuated by K_Ca channel blockade (36-38%) and augmented by K_V channel blockade (38-55%). We showed that K_Ca and K_V channels modulate the venoarteriolar reflex with minimum roles of NOS, COX, and K_ATP channels in human non-glabrous forearm skin in vivo. Thus, cutaneous venoarteriolar reflex changes could reflect altered K⁺ channel function.

Total Triterpenic Fraction of Centella asiatica in Chronic Venous Insufficiency and in High-Perfusion Microangiopathy

Total triterpenic fraction of Centella asiatica (TTFCA) is effective in improving venous wall alterations in chronic venous hypertension and in protecting the venous endothelium. TTFCA is active on connective tissue modulation, improves the synthesis of collagen and other tissue proteins by modulating the action of fibroblasts in the vein wall, and stimulates collagen remodeling in and around the venous wall. This is due to the modulating action of TTFCA on fibroblasts as shown by experiments on the growth of human embryonal fibroblasts. TTFCA has a moderate in-vitro and in-vivo stimulating effect on collagen synthesis and, at higher dosages, an inhibition on the synthesis of collagen and acid mucopolysaccharides. Studies have indicated the role of TTFCA on the synthesis of specific venous wail elements by cell cultures of human embryonal fibroblasts. The tissue-stimulating action is shown by the increased collagen production independent from the stimulation of cell proliferation (this differentiates the action of TTFCA from cell growth factors). TTFCA is active on the microcirculation in venous and diabetic microangiopathy. Signs and symptoms of venous hypertension and edema are improved by treatment. The remodeling on collagen synthesis could be one of the possible mechanisms of actions of TTFCA in the remodeling of echolucent (soft; therefore, with risk of thrombosis and embolization) plaques at the carotid and femoral bifurcation. This compound is safe and well tolerated. In conclusion, several actions of TTFCA in vascular diseases makes the use of this compound very interesting in venous and arterial problems.

Capillary Filtration in Venous Hypertension: Evaluation with the Vacuum Suction Chamber Device and Strain-Gauge Plethysmography

The aim of this study was to evaluate local capillary filtration with the vacuum suction chamber (VSC) and the rate of ankle swelling (RAS) in patients with ankle edema due to venous hypertension before and after treatment with oral TTFCA (60 mg tablets twice daily) for 4 weeks. Strain-gauge plethysmography (SGP) was used to assess RAS and local capillary filtration was studied with the VSC (applied on the perimalleolar region); the disappearance of the weal was measured (minutes). Fifty patients with chronic venous insufficiency and edema were included (M:F = 25:25) after informed consent and randomized into a treatment (mean age 43; SD 7) and a control (mean age 44; SD 8) group. Compliance was very good (100% completed the 4-week trial); no side effects were observed. The two groups were comparable for age/sex distribution. Values of RAS and VSC time were comparable in the two groups, at inclusion. After 4 weeks there were no changes in the control group. A significant reduction was observed in the treatment (RAS decreased to 34% of the initial value; the VSC time decreased 48%; p<0.02). Treatment with TTFCA in chronic venous insufficiency is useful as soon as edema is detected to control the progressive alterations leading to ulcerations. This action is produced by complex actions on the microcirculation reducing and controlling edema and modulating collagen synthesis. This results in an improvement of the microcirculation, skin and subcutaneous tissue perfusion and functions.

Simultaneous Changes in Leg Arterial Pulsatile Blood Flow and Toe Laser-Doppler Perfusion Accompanying Graded Thigh Compression

Previous findings showed that regional ankle cuff compression and below-knee compression bandaging cause significant decreases in skin blood perfusion distal to the compressed regions. Contrastingly, with compression bandaging, as is commonly used in the treatment of venous ulcers and other conditions, an increase in leg pulsatile blood flow in compressed regions has been reported without corresponding decreases in sub-bandage skin blood perfusion. The explanation for these differential effects is unclear in part because of the fact that foot-to-knee compression bandaging has both direct sub-bandage tissue effects and effects on distal and sub-bandage venous hemodynamics. To help clarify this issue, the present study was done to determine the role of compression-induced changes in venous pressure per se on both skin microvascular and calf pulsatile blood flow. This was done using graded thigh cuff compression up to 50 mm Hg to modify lower extremity venous pressure. During these compressions mid-calf pulsatile blood flow via magnetic resonance flowmetry and toe-skin laser-Doppler blood perfusion

Heat-washout - an objective method for diagnosing neuropathy and atherosclerosis in diabetic patients

BACKGROUND

The heat-washout method is an objective method that measures cutaneous blood flow rate (BFR) in ml (100 g. min)(-1), previously found useful for measuring toe BFR in non-diabetic patients with claudication.

AIM

The method is used for evaluating the presence of a veno-arteriolar reflex (VAR) in the forefoot and signs of atherosclerosis in the first toe in type 2 diabetics.

METHODS

Nine type 2 diabetics for +10 years, peripheral neuropathy, median age 62, and 9 healthy subjects without diabetes, median age 52 were examined for the presence of a VAR in the forefoot. A VAR was present when BFR decreased 25% or more with the foot 50 cm below heart level. Examinations for atherosclerosis were made in the pulp of the first toe. An increase in BFR of 50% or more with the foot 50 cm below heart level indicated the presence of atherosclerosis.

RESULTS

The VAR was significantly attenuated in type 2 diabetics with neuropathy compared to controls, (P<0·01). Only one patient with known neuropathy and diabetes showed a reflex compared to eight out of nine controls (P<0·01). The VAR was correlated to the vibration perception threshold measured with biothesiometry (r = -0·661, P = 0·0003). Two patients with type 2 diabetes and neuropathy without clinical sign of peripheral artery disease (PAD) had an abnormal response similar to that seen in subjects with intermittent claudication.

CONCLUSION

The heat-washout method seems useful as and objective method for evaluating as well the presence of a VAR as atherosclerosis in type 2 diabetics.

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.

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.

Blood flow in the skin of type 1 diabetic patients before and after combined pancreas/kidney transplantation

BACKGROUND

To analyze effects of long-term glucose normalization after pancreas transplantation, different parameters of skin microcirculation were assessed by laser Doppler fluxmetry.

METHODS

Forty-two type 1 diabetic patients after successful simultaneous pancreas/kidney transplantation (Group A, median 32.3 months posttransplant), 28 patients with functioning kidney grafts, but insulin therapy (Group B, median 64.9 months posttransplant) and 13 diabetic pretransplant patients (Group C, median 14.2 months on dialysis) were compared with 33 healthy subjects (Group D). Resting blood flow, postocclusive hyperemia, venoarteriolar response on the right foot and decrease in blood flow during cold pressure test on the left finger was assessed.

RESULTS

Postocclusive hyperemia, decrease in blood flow during cold pressure test and venoarteriolar response were higher in Group D than in all patient groups. Resting blood flow in Group A was significantly lower than in Groups B and C (following values as median): 3.6 perfusion units (PU) versus 7.4 PU in Group B, p < 0.01 and 12.1 PU in Group C, p < 0.001, respectively, and was not significantly different to controls (Group D, 5.2 PU). Postocclusive hyperemia was higher in Group A than in Groups B and C (266.7% vs 160.0%, p < 0.05 and 79.4% n.s., respectively), but significantly less than in Group D (563.5%). The microangiopathy index-high values reflecting less or no microangiopathy-was significantly higher in Group A than in Groups B and C (11.0 vs 4.3, p < 0.001 and 4.7, p < 0.05, respectively), and was very much comparable to the values in healthy controls (Group D, 10,3). The decrease in blood flow during cold pressure test was higher in Group A compared to Groups B and C (25.2% vs 21.1% and 13.8%, n.s., respectively), but much less than in Group D (65,7%).

CONCLUSION

These data suggest an improvement without complete normalization of skin microcirculation by long-term blood glucose normalization achieved by pancreas transplantation.

Effect of local heating and vasodilation on the cutaneous venoarteriolar response

The cutaneous venoarteriolar response (CVAR) is a local non-adrenergic vasoconstrictor reflex that is engaged via increases in local transmural pressure. The purpose of this study was to determine if local temperature alters the vasoconstrictor ability of the CVAR. Twelve (5 male, 7 female) subjects performed a CVAR maneuver at local temperatures of 30+/-1, 34, 38, and 42 degrees C. CVAR was also engaged after vasodilation via intradermal perfusion of sodium nitroprusside or the attenuation of local heating-induced vasodilation via intradermal perfusion of N(G)-nitro-L: -arginine methyl ester (L: -NAME) in five subjects (2 male, 3 female). CVAR was elicited by rapid cuff inflation to 45mmHg proximal to two dorsal forearm sites for 2 min in both protocols. Local heating caused a progressive increase in skin blood flow (8+/-1, 18+/-4, 43+/-11, and 78+/-2% maximal skin blood flow for 30+/-1, 34, 38, and 42 degrees C, respectively). Engagement of the CVAR decreased skin blood flow by 53+/-2, 57+/-3, and 51+/-4%, for 30+/-1, 34, and 38 degrees C, respectively. In contrast, local heating to 42 degrees C significantly attenuated the CVAR (16+/-11 %). Local administration of sodium nitroprusside during neutral temperature and L: -NAME during local heating also significantly attenuated the vasoconstrictor response of the CVAR by 27+/-8 and 38+/-4%, respectively. These data indicate that CVAR is attenuated at high (42 degrees C) local skin temperatures and that this attenuation is likely due to an effect of both local heating-induced vasodilation and a direct temperature effect.

Microcirculation in insulin resistance and diabetes: more than just a complication

The microvascular bed is an anatomical entity which is governed by specific, highly regulated mechanisms which are closely adapted to the specific function of each vascular segment. Among those, small arteriolar vasomotion and capacity of small vessels to constrict in response to physical and humoral stimuli play a major role. Other processes of importance for the adequacy of nutritive perfusion are haemorheological properties of whole blood and red cells, adhesiveness of leukocytes and capillary permeability. This review provides some description of these phenomena, how they impact on organ function and how they appear in diabetes. Metformin, as a unique example among the drug arsenal, exerts various effects preferentially at the level of smallest vessels (arterioles, capillaries, venules). This review summarises our actual knowledge and includes several new data showing its high potential for reducing microvascular dysfunction. Most of these unique properties have also been demonstrated in non-diabetic animals or humans, suggesting they are intrinsic to the drug and not secondary to diabetic metabolic improvement. A particular focus is put on the relevance of metformin's capacity to stimulate slow wave arteriolar vasomotion and improve functional capillary density, whereby nutritive flow can be re-established. Finally, the implication of microcirculation in other aspects of insulin resistance and diabetes, such as macroangiopathy and metabolic control, is discussed and strengthens the concept of a broad involvement of microvascular dysfunction in these diseases as well as the potential interest of introducing adapted treatment early in the history of a patient's diabetes.

Posturally induced leg vasoconstrictive responses: relationship to standing duration, impedance and volume changes

Shifting legs to a gravity-dependent position provokes a physiological vasoconstrictive response that forms the basis of several diagnostic tests based on initial (< 5 min) blood perfusion decreases. However, it is not known if responses are maintained over longer duration and if they depend on the volume shifted to the limb during the manoeuvre. These issues were investigated by measurements of blood perfusion changes on foot and ankle (laser Doppler) and below-knee volume and impedance changes induced by 30 min of standing in 10 healthy volunteers. Initial perfusion decreases were 66.4% +/- 2.6% and 49.3% +/- 3.8% for ankle and foot dorsum, respectively, and were fully maintained during sustained standing without evidence of 'vasodilator escape'. Response magnitudes were not dependent on leg volume changes using geometric or impedance measures. A close correlation (r2 = 0.78) between impedance and volume changes suggests the former as a useful way of assessing dynamic limb volume changes. Sustained vasoconstrictive responses make it unlikely that extending the duration of such tests would offer more, diagnostic information than is currently available.

Diabetes: the use of color Doppler sonography for the assessment of vascular complications

The use of color Doppler sonography (CDS) in the assessment of diabetic vascular complications is not yet well established. Among the complications of the disease, retinopathy, nephropathy and peripheral arteriopathy are classically due to a vascular attack, either a micro or a macroangiopathy. The results of CDS in the assessment of retinopathy and nephropathy are correlated with the degree of the disease and the biological findings, but the diagnostic and prognostic benefit of these results remains unclear compared to the conventional tests. Doppler sonography is more helpful in peripheral arteriopathy assessment; it may take the place of arteriography in the most clinical situations. The technique is particularly useful in case of proximal atheromatous-like arteriopathy. When the arteriopathy is distal, mediacalcinosis, specific to diabetes, may interfere with the functional test like the ankle/arm pressure index measurement.

Comparative assessment of peripheral sympathetic function by postural vasoconstriction arteriolar reflex and sympathetic skin response in NIDDM patients

PURPOSE

The aim of the study was to compare peripheral sympathetic adrenergic and cholinergic nerve function in NIDDM (non-insulin-dependent diabetes mellitus) patients with various degrees of diabetic neuropathy and neuropathic foot ulceration. The parameters used were postural vasoconstriction arteriolar reflex (VAR) and sympathetic skin response (SSR), respectively.

PATIENTS AND METHODS

Forty-seven NIDDM patients were studied. No patients had clinically significant peripheral vascular disease. They were divided according to peripheral somatic neuropathy, assessed by clinical score and vibration perception threshold (VPT). Twenty-two patients showed no significant evidence of peripheral neuropathy and normal VPT (DN-); 15 had signs and symptoms of neuropathy and VPT alteration (DN+); 10 had diabetic neuropathy and foot ulceration (DNU). Twenty-two normal subjects were also examined as a control group. Resting arteriovenous shunt skin blood flow, measured using laser-Doppler flowmetry, and the VAR of the big toe on lowering the foot were studied. Sympathetic skin response was assessed by an EMG apparatus. Autonomic function was also investigated by using standard cardiovascular reflex tests.

RESULTS

Resting blood flow values were similar in the three NIDDM groups and in the control group. VAR to foot lowering was significantly impaired in all NIDDM groups by comparison with controls (72.8 +/- 2.1%, mean +/- SEM), this impairment being progressively more pronounced in DN- (58.8 +/- 2.3%, P < 0.001), DN+ (33.3 +/- 3.0%, P < 0.001 versus DN-) and DNU (8.6 +/- 2.7%, P < 0.001 versus DN+). Sympathetic skin response was assessed in 28 patients and was significantly impaired in DN-compared with the control group (2.53 +/- 0.04 versus 2.71 +/- 0.04 log mcV, P < 0.01). This impairment was severe in the DNU compared with the DN+ group (1.36 +/- 0.05 versus 2.26 +/- 0.04 log mcV, P < 0.005). A positive correlation was found between VAR values and SSR (P < 0.001), and these measurements were also closely correlated with several parameters of central autonomic and somatic neuropathy.

CONCLUSION

These results indicate that peripheral sympathetic adrenergic and cholinergic fibers simultaneously undergo early alterations in diabetic patients, even when there is no clinical neuropathy. Our data also show almost complete abolition of peripheral sympathetic activity in NIDDM patients with foot ulceration.

Impairment of the postural venoarteriolar response in young type 1 diabetic patients. A study by laser doppler flowmetry

The skin blood flow and venoarteriolar response (VAR) in the feet of the young type 1 diabetic patients were studied with laser Doppler flowmetery. The findings were correlated with diabetic microangiopathy in 24 young patients without neuropathy--14 with diabetic microangiopathy, 10 without--and 10 healthy controls. In type 1 diabetic patients and skin blood flow, after lowering of the leg, was significantly higher in the microangiopathic patients than in the healthy controls, 5.3 +/- 1.4 vs 3 +/- 1.5, (P < 0.01). The VAR index was significantly lower in both groups of diabetics as compared with controls. In conclusions laser Doppler flowmetry is an easy and reliable noninvasive technique to evaluate skin blood flow abnormalities in the the feet of young type 1 diabetic patients, including those without neuropathy. The VAR has been found abnormal in the feet of young diabetic patients with and without microangiopathy, regardless of the presence of peripheral neuropathy.