Vascular complications are a leading cause of morbidity and mortality in both men and women with type 1 (T1DM) or type 2 (T2DM) diabetes mellitus, however the prevalence, progression and pathophysiology of both microvascular (nephropathy, neuropathy and retinopathy) and macrovascular [coronary heart disease (CHD), myocardial infarction, peripheral arterial disease (PAD) and stroke] disease are different in the two sexes. In general, men appear to be at a higher risk for diabetic microvascular complications, while the consequences of macrovascular complications may be greater in women. Interestingly, in the absence of diabetes, women have a far lower risk of either micro- or macro-vascular disease compared with men for much of their lifespan. Thus, the presence of diabetes confers greater risk for vascular complications in women compared with men and some of the potential reasons, including contribution of sex hormones and sex-specific risk factors are discussed in this review. There is a growing body of evidence that sex hormones play an important role in the regulation of cardiovascular function. While estrogens are generally considered to be cardioprotective and androgens detrimental to cardiovascular health, recent findings challenge these assumptions and demonstrate diversity and complexity of sex hormone action on target tissues, especially in the setting of diabetes. While some progress has been made toward understanding the underlying mechanisms of sex differences in the pathophysiology of diabetic vascular complications, many questions and controversies remain. Future research leading to understanding of these mechanisms may contribute to personalized- and sex-specific treatment for diabetic micro- and macro-vascular disease.

Elevated protein kinase C activity has been linked to the vascular and neural complications of diabetes. The aim of the present study was to examine the involvement of the β-isoform of protein kinase C in abnormalities of neuronal function, neural tissue perfusion and endothelium-dependent vasodilation in diabetes, by treatment with the selective inhibitor LY333531 (10mg·kg -1 ·day -1 ). Diabetes was induced in rats by streptozotocin; the duration of diabetes was 8 weeks. Nerve conduction velocity was monitored, and responses to noxious mechanical and thermal stimuli were estimated by the Randall–Sellito and Hargreaves tests respectively. Sciatic nerve and superior cervical ganglion blood flow were measured by microelectrode polarography and hydrogen clearance. Vascular responses were examined using the in vitro mesenteric bed preparation. An 8-week period of diabetes caused deficits in sciatic motor (20%) and saphenous nerve sensory (16%) conduction velocity, which were reversed by LY333531. Diabetic rats had mechanical and thermal hyperalgesia. LY333531 treatment did not affect mechanical thresholds, but corrected thermal hyperalgesia. Sciatic nerve and superior cervical ganglion blood flow were both reduced by 50% by diabetes; this was almost completely corrected by 2 weeks of LY333531 treatment. Diabetes caused a 32% reduction in vasodilation of the mesenteric vascular bed in response to acetylcholine, mediated by nitric oxide and endothelium-derived hyperpolarizing factor. When the former was abolished during nitric oxide synthase inhibition, an 80% diabetic deficit in the remaining relaxation was noted. LY333531 treatment attenuated the development of these defects by 64% and 53% respectively. Thus protein kinase Cβ contributes to the neural and vascular complications of experimental diabetes; LY333531 is a candidate for further study in clinical trials of diabetic neuropathy and vasculopathy.

1. In the feet of patients with diabetic neuropathy, total skin blood flow is increased due to an increased shunt flow. The question is, does this increased anastomotic shunt flow lead to either under- or overperfused nutritive capillaries. 2. To solve this question, skin microcirculation tests of the left big toe were performed in 20 healthy control subjects and in 40 insulin-dependent diabetic patients without macroangiopathy, 20 without and 20 with neuropathy. Skin temperature measurements and laser Doppler fluxmetry were performed to record mainly shunt flow and capillaroscopy to study nailfold capillary blood flow. 3. The insulin-dependent diabetic patients with neuropathy had a higher baseline skin temperature (mean ± SEM; 30.0 ± 0.6°C) and laser Doppler fluxmetry [26.2 ± 2.2 perfusion units (pu)] than patients without neuropathy (27.2 ± 0.8°C, P < 0.01; 16.1 ± 2.0 pu, P < 0.01) and healthy control subjects (27.9 ± 0.7°C, P < 0.05; 18.6 ± 2.8 pu, P < 0.05). Sympathetic stimulation (inspiratory gasp) resulted in a smaller laser Doppler fluxmetry decrease in the neuropathic patients (31.4 ± 4.6%) compared with non-neuropathic patients (48.2 ± 5.1%, P < 0.05) and control subjects (49.0 ± 3.8%, P < 0.05), while no difference between the three groups was seen in the laser Doppler fluxmetry decrease during a postural vasoconstriction test. The number of visible capillaries was highest in the neuropathic patients (10.2 ± 0.6/0.5 mm 2 ), when compared with non-neuropathic patients (8.7 ± 1.2/0.5 mm 2 , P < 0.05) and control subjects (8.3 ± 0.3/0.5 mm 2 , P < 0.001). Capillary blood-cell velocity was significantly higher in the neuropathic patients (0.32 ± 0.05 mm/s) compared with non-neuropathic patients (0.23 ± 0.03 mm/s, P < 0.05) and control subjects (0.23 ± 0.02 mm/s, P < 0.01). 4. We conclude that there is an overperfused nutritive capillary circulation in the feet of patients with diabetic neuropathy. This is in contradiction to the capillary steal phenomenon and favours the hyperdynamic hypothesis to explain the decreased healing potential in diabetic neuropathic foot ulceration.

1. Flow motion is the cyclical variation in blood flow owing to the rhythmical opening and closing of arterioles. Previous studies have suggested that cutaneous flow motion may be altered in diabetic neuropathy but have not been consistent in their findings. 2. In order to assess the effect of diabetic peripheral neuropathy on flow motion, we have examined the frequency and amplitude of flow motion in 12 patients with diabetic peripheral neuropathy, 10 age-matched diabetic patients without peripheral neuropathy and 10 age-matched non-diabetic controls. 3. Peripheral neuropathy was diagnosed by a history of foot ulceration or chronic painful neuropathy, clinical examination and abnormal peroneal nerve conduction velocities. Blood flow, using laser Doppler flowmetry, was measured at four sites on the dorsum of both hands and feet. Flow motion was analysed using fast Fourier transform analysis, between 0.05 and 0.2 Hz, and displayed on a power spectral density graph. Predominant frequency and relative amplitude of flow motion were calculated. 4. Relative amplitude and frequency of flow motion were similar in the hands of all three groups, as was the frequency in the feet of the three groups. Relative amplitude was significantly smaller in the feet of diabetic patients with neuropathy (median 7.2%, 95% confidence interval 4.9–9.4%) than in diabetic patients without neuropathy (median 13.5%, 95% confidence interval 6.3–21.5%, P < 0.02) or in non-diabetic control subjects (median 10.3%, 95% confidence interval 6.9–27.4%, P < 0.02). 5. Flow motion amplitude is reduced in diabetic peripheral neuropathy. The control of flow motion amplitude appears to be at least partly under neurological control.

1. Neurogenic inflammation, mediated by nociceptor C fibres, is part of the acute neurovascular response to injury producing the axon reflex flare. Laser Doppler flowmetry was used to measure the flare response induced by the electrophoresis, at various current strengths, of a ring of acetylcholine solution into dorsal foot skin. 2. Nineteen control subjects and 52 long-duration insulin-dependent (Type 1) diabetic patients of similar age (20 without complications; 19 with laser-treated retinopathy; 13 with reduced vibration perception and retinopathy) were studied in order to investigate the possible attenuation of this defence mechanism in diabetes. 3. The maximal (1 mA) flare response [control median (interquartile range): 1.55 (1.16–2.06) arbitrary units] was reduced greatly in neuropathic patients [0.37 (0.24–0.66) arbitrary units; P ≤ 0.001 with respect to all other groups], especially those with a previous history of foot ulceration. The flare was also reduced in some patients with retinopathy alone [1.06 (0.56–1.27) arbitrary units; P < 0.005 with respect to control subjects]. 4. No rightward shift of the curve of hyperaemic response plotted against current strength was found, suggesting that the abnormal response was due to axonal loss rather than to dysfunction. 5. Neurogenic inflammation, mediated by small pain fibres, was markedly impaired in a group of diabetic patients at risk of foot ulceration. Furthermore, impairment of this nociceptor C fibre response can develop before clinical large-fibre neuropathy and could itself predispose to foot complications.

1. The diabetic neuropathic foot exhibits excess arteriovenous anastomotic shunt flow due to a reduced sympathetic vasoconstrictor tone. Local axon reflexes (mediating postural vasoconstriction, for example) are preserved even in severe diabetic neuropathy. This excess shunt flow and its local neurogenic control may be important in the development of complications of the neuropathic limb. 2. The response of arteriovenous anastomoses to local heating was assessed in 13 diabetic patients with neuropathy (12 insulin-dependent), 10 diabetic control patients (seven insulin-dependent) and 10 normal control subjects. The aim was to study the local reflex control of arteriovenous flow when central sympathetic tone had been largely removed. 3. The change in skin blood flow on local heating to 44°C was measured by using a laser Doppler flowmeter in standard environmental conditions with the foot at heart level. Two sites were assessed: (i) the plantar surface of the great toe (a site in which skin blood flow is dominated by arteriovenous shunt flow) and (ii) the dorsum of the foot (a site without anastomotic flow). 4. It was found that when heat was applied to the plantar surface of the great toe in the diabetic patients with neuropathy a paradoxical decrease in flow through arteriovenous anastomoses occurred, flow declining to 65% ( P < 0.05) of its resting value. This could be compared with an increase in flow over the same time period of 262% and 228% ( P < 0.01) in diabetic control patients and normal subjects, respectively. When the foot dorsum was heated flow increased in a similar fashion in all patient groups, and a decline in flow was not observed. 5. Peak flow at the great toe was significantly lower in the diabetic patients with neuropathy compared with both the diabetic control patients and the normal subjects [23.68 (44.64) flow units versus 57.0 (43.92) flow units and 76.32 (40.88) flow units, respectively, medians and interquartile ranges, P < 0.02]. 6. Thus we have demonstrated that in the presence of neuropathy local heating of the toe pulp may produce (i) a paradoxical fall in skin blood flow and (ii) a greatly reduced peak skin blood flow. The importance of this abnormal vascular control in the pathogenesis of complications of the neuropathic limb has now to be determined.

1. Low intracellular concentrations of myo -inositol in diabetic cells may contribute to the development of tissue damage. The cause of these low levels is unknown, but inhibition of a putative myo -inositol transporter by high concentrations of glucose has been proposed. We have developed a triple-isotope method for estimating myo -inositol influx into human leucocytes and so investigated both the kinetics of this uptake in normal volunteers and the effect of glucose upon it. 2. Uptake was composed of a passive component with a rate constant of 2.4 ± 0.3 × 10 −2 min −1 and a saturable component with a K m of 61 ± 23 μmol/l and a V max. of 11.3 ± 4.5 × 10 −4 mmol min −1 l −1 . Ouabain and low extracellular concentrations of sodium partly inhibited influx. Uptake was predominantly into the cytosolic fraction of the cell with 12% entering the membrane-associated fraction at both 5 and 10 min. 3. myo -inositol influx was significantly inhibited by both d - and l -glucose but not by sucrose. Neither cytochalasin B nor ethyl isopropyl amiloride significantly inhibited uptake. 4. It is concluded that a myo -inositol transporter exists in human leucocytes which is similar to that found in other species and tissues. Our technique allows myo inositol influx in diabetic subjects to be related to varying glycaemic control and tissue damage.

1. Immunohistochemical, immunoblotting and release experiments were performed on ileum from control rats, from 8-week streptozotocin-diabetic rats and from diabetic rats after acute application of insulin in vitro . 2. There was an increase in vasoactive-intestinal-polypeptide-like and a decrease in calcitonin-gene-related-peptide-like immunoreactivity in the myenteric plexus of the diabetic rat ileum, although electrically evoked release of both peptides from enteric nerves was defective. Acute application of insulin in vitro reversed the defective release and changes in immunoreactivity of vasoactive intestinal polypeptide and calcitonin-gene-related peptide seen in the enteric nerves of streptozotocin-diabetic rat ileum. 3. In addition, using a monoclonal neurofilament antibody RT 97 that recognizes a phosphorylated neurofilament epitope present in normal enteric nerves, it was shown that this phosphorylated neurofilament epitope was absent in diabetic nerves, even though a polyclonal neurofilament antibody revealed that neurofilaments were present in both axons and cell bodies of the myenteric plexus of diabetic rat ileum. After only 2 h of insulin incubation in vitro , the phosphorylated neurofilament epitope was again present in the nerves. 4. It is suggested that the abnormal distribution of phosphorylated neurofilaments and defective storage and release of vasoactive intestinal polypeptide and calcitonin-gene-related peptide in the present study may be a more general feature of diabetes. The restoration of these abnormalities by continuous acute insulin application in vitro shown here suggests that the availability of a steady level of insulin might prevent some of the changes which occur in early stages of diabetes. If so, this could influence the use of insulin in the treatment of diabetes, particularly in view of the recent report that short-term continuous subcutaneous insulin infusion restores the function of the autonomic and peripheral nerves in type I diabetic patients [Krönert, K., Hülsen, J., Luft, D., Stetter, T. & Eggstein, M. (1987) Journal of Clinical Endocrinology and Metabolism , 64 , 1219–1223].

1. Plasma pancreatic polypeptide (PP), vasoactive intestinal polypeptide (VIP), substance P (SP), neurotensin (NT) and noradrenaline (NA) were measured in eight healthy subjects and 12 long-term insulin-dependent diabetic patients with and without autonomic neuropathy, before and after intravenous infusion of the ganglionic blocking agent trimethaphan camsylate, in order to determine the influence of the autonomic nervous system on the baseline values of the substances. 2. The basal levels of the measured substances were not significantly different in healthy subjects and patients with or without diabetic autonomic neuropathy. 3. In healthy subjects, the ganglionic blockade induced a significant decrease in PP (80%) ( P < 0.02), NA (58%) ( P <0.05), NT (27%) ( P < 0.05) and a significant increase in SP (30%) ( P < 0.05), while the VIP concentration remained unchanged. 4. The diabetic patients had nearly the same significant decrease in PP (68%) ( P < 0.01), NA (50%) ( P < 0.01), NT (22%) ( P < 0.02), VIP (21%) ( P < 0.05) and increase in SP (73%) ( P < 0.01). No relationship was found between the autonomic neuropathy and changes of the substances during ganglionic blockade. 5. The results indicate that the postganglionic part of the autonomic nervous system participates in the maintenance of a normal baseline level of PP, NT and NA, but not of VIP. The regulation of VIP may be disturbed in long-term diabetic subjects.