Association between diabetic-autonomic-C-fibre-neuropathy and medial wall calcification and the significance in the outcome of trophic foot lesions

Peripheral Arterial Disease and the Diabetic Foot Syndrome: Neuropathy Makes the Difference! A Narrative Review

Background: In vascular medicine, peripheral arterial disease (PAD) and diabetic foot syndrome (DFS) are often considered synonymous with respect to the need for revascularization. In PAD patients, clinical symptoms reflect the degree of atherosclerotic disease, since peripheral innervation, including pain sensation, is not usually compromised. In DFS patients, however, symptoms of relevant foot ischemia are often absent and progression of ischemia goes unnoticed owing to diabetic polyneuropathy, the loss of nociception being the main trigger for foot ulcers. This review analyzes the fundamental differences between PAD and DFS against the background of polyneuropathy. Methods: The literature research for the 2014 revision of the German evidence-based S3-PAD-guidelines was extended to 2023. Results: Vascular examination is imperative for both, PAD and DFS. Stage-dependent revascularization is of utmost importance in PAD patients, especially those suffering from critical limb-threatening ischemia (CLTI). Successful therapy of DFS goes further, including infection and metabolic control, wound management, offloading the foot and lifelong prophylaxis in the course of a multidisciplinary treatment concept. Revascularization is not needed in all cases of DFS. Conclusions: There are fundamental differences between PAD and DFS with respect to pathophysiology, the anatomical distribution of arterial occlusive processes, the clinical symptoms, the value of diagnostic tools such as the ankle-brachial index, and classification. Also, therapeutic concepts differ substantially between the two patient populations.

Paradoxical Changes of Cutaneous Microcirculation and Sympathetic Fibers of Rat Hind Limbs after Sciatic Nerve Compression

BACKGROUND

Recent studies show evidence that surgical nerve decompression could improve cutaneous blood flow (CBF), which might benefit ulcer healing. However, the change of CBF and sympathetic fibers after nerve compression is poorly understood. In the current study, a unilateral sciatic nerve compression model was created in Sprague-Dawley rats.

METHODS

A laser Doppler imaging system was applied to assess the CBF of the regions below the ankles. Immunohistochemistry and transmission electron microscopy were used to investigate the histopathologic changes of sympathetic fibers in sciatic nerve samples.

RESULTS

Laser Doppler imaging revealed decreased CBF of both the lesional limb and the contralesional limb, which occurred earlier in the lesional side, indicating an enhanced sympathetic tone on vasomotor function. Intraneural density of sympathetic fibers decreased on both sides and the ultrastructure of unmyelinated fibers of both sides degenerated in a nonsynchronized manner.

CONCLUSIONS

The study revealed nonsynchronized reduced CBF of bilateral hind limbs with paradoxically degenerated and diminished sympathetic fibers in bilateral sciatic nerves after unilateral sciatic nerve compression. These results may validate the importance of and broaden the indications for surgical nerve decompression in preventing or treating foot ulcers.

[Diabetic foot syndrome-Part 1 : Definition, pathophysiology, diagnostics and classification]

There are ca. 8 million persons with diabetes mellitus living in Germany. A late sequelae of diabetes is the diabetic foot syndrome (DFS), the prevalence of which is greatly increasing. It comprises all alterations of the foot as a result of diabetic polyneuropathy as well as microvascular and macrovascular (peripheral arterial occlusive disease, PAOD) alterations. Many of the ca. 250,000 newly diagnosed diabetic foot ulcers per year become chronic wounds. Despite intensive efforts for prevention, early diagnosis and adequate wound care, ca. 13,000 persons with diabetes undergo major limb amputation in Germany every year. With consistent treatment in interdisciplinary centers and by exhausting all possible methods of wound treatment, pressure relief as well as arterial revascularization, the major amputation rate in patients with diabetic foot problems can be reduced by 80%. With a suitable strategy of prevention, the recurrence rate of foot ulcers would be reduced.

Factors associated with sclerostin levels - A calcification inhibitor - In individuals with type 2 diabetes mellitus; Is autonomic neuropathy the missing link?

BACKGROUND

Sclerostin inhibits bone formation and its expression is upregulated in the vasculature during the arterial calcification process as a counterregulatory mechanism preventing further calcification. Lower extremity arterial calcification (LEAC) is common in neuropathic patients with type 2 diabetes (T2DM). Herein, we investigated for associations between plasma sclerostin levels and diabetic neuropathy as well as LEAC in subjects with T2DM.

METHODS

A total of 74 individuals with and 76 without T2DMwere recruited. Plasma sclerostin levels were measured by ELISA. Diagnosis of cardiac autonomic neuropathy (CAN) was based on the battery of the four autonomic tests, while of somatosensory peripheral neuropathy (DPN) on neuropathy symptom score and neuropathy disability score. LEAC was assessed with conventional ankle and foot x-rays.

RESULTS

Plasma sclerostin levels were higher in participants with LEAC vs. those without LEAC in both diabetes and non-diabetes cohorts (p = 0.035 and p = 0.003, respectively). In the diabetes cohort, patients with CAN, but not with DPN, had higher sclerostin levels when compared with those without CAN (p < 0.001). Multivariate analysis in the diabetes cohort demonstrated that sclerostin levels were associated positively with CAN and LEAC, while in the non-diabetes cohort there was a trend for a positive association with male gender and presence of LEAC.

CONCLUSION

Plasma sclerostin levels are increased in individuals with LEAC irrespectively of diabetes status. In addition, plasma sclerostin concentrations are associated independently with LEAC and CAN in people with T2DM.

Vascular disease in the lower limb in type 1 diabetes

This review considers peripheral arterial disease (PAD) in the diabetic ischaemic lower limb including both macrovascular and microvascular aspects. The presentation of PAD is probably not significantly different in type 1 compared with type 2 diabetes. PAD in diabetic patients is diffuse and located distally being most severe in the crural and also the foot arteries. It is associated with arterial calcification and occlusion of the arteries rather than stenosis. Compared with the nondiabetic patient, PAD develops at a younger age, and women are equally affected as men. It is not known whether the presentation of ischaemic lower limb disease in diabetes can be explained by one disease, namely, atherosclerosis, which has particular features peculiar to diabetes such as distal arterial involvement, or by the occurrence of two separate diseases: first, classical atherosclerosis and, second, a diabetic macroangiopathy, a term for nonatherosclerotic arterial disease in diabetes that is characterized by medial arterial calcification. Furthermore, there is controversy with regard to the significance of structural changes in the microcirculation of the diabetic foot.

Improving major amputation rates in the multicomplex diabetic foot patient: focus on the severity of peripheral arterial disease

OBJECTIVE

Peripheral arterial disease (PAD), as well as diabetic neuropathy, is a risk factor for the development of diabetic foot ulcers. The aim of this study was to evaluate differences and predictors of outcome parameters in patients with diabetic foot by stratifying these subjects according to the severity of PAD.

RESEARCH DESIGN AND METHODS

In a prospective study, patients with new diabetic foot ulcers have been treated and investigated by structured healthcare. Subjects were recruited between 1 January 2000 and 31 December 2007. All study participants underwent a 2-year follow-up observation period. The patients underwent a standardized examination and classification of their foot ulcers according to a modification of the University of Texas Wound Classification System. The severity of PAD was estimated by measurement of the ankle brachial index (ABI) and the continuous wave Doppler flow curve into undisturbed perfusion (0.9 < ABI < 1.3), compensated perfusion (0.5 < ABI < 0.9), decompensated perfusion (ABI < 0.5) and medial arterial calcification.

RESULTS

A total of 678 patients with diabetic foot were consecutively included into the study (69% male, mean age 66.3 ± 11.0 years, mean diabetes duration 15.8 ± 10.2 years). Major amputations (above the ankle) were performed in 4.7% of the patients. 22.1% of these subjects had decompensated PAD. These subjects had delayed ulcer healing, higher risk for major amputation [odds ratio (OR) 7.7, 95% confidence interval (CI) 2.8-21.2, p < 0.001] and mortality (OR 4.9, 95 % CI 1.1-22.1, p < 0.05).

CONCLUSION

This prospective study shows that the severity of PAD significantly influences the outcome of diabetic foot ulcers regarding to wound healing, major amputation and mortality.

Medial arterial calcification in diabetes and its relationship to neuropathy

Calcification of the media of arterial walls is common in diabetes and is particularly associated with distal symmetrical neuropathy. Arterial calcification also complicates chronic kidney disease and is an independent risk factor for cardiovascular and all-cause mortality. The term calcification is not strictly accurate because the morphological changes incorporate those of new bone formation, i.e. ossification. The processes are complex, but are closely related to those involved in bone homeostasis, and it is relevant that calcification of the arterial wall and osteopenia often co-exist. One particular factor linked to the development of arterial calcification is distal symmetrical neuropathy; indeed, it has been suggested that neuropathy explains the distal distribution of arterial calcification in diabetes. It has also been suggested that the link with neuropathy results from loss of neuropeptides, such as calcitonin gene-related peptide, which are inherently protective. The association between distal symmetrical neuropathy and calcification of the arterial wall highlights the fact that neuropathy may be an independent risk factor for cardiovascular mortality.

Vascular calcifications seen on mammography: an independent factor indicating coronary artery disease

PURPOSE

Establish a relationship between vascular calcifications seen via mammography and coronary artery disease, estimate the risk ratios, and investigate the interrelationships between vascular calcification and other risk factors for coronary artery disease.

MATERIALS AND METHODS

This was a case-control study consisting of 40 women with coronary artery disease in the case group and 40 women without any history of coronary artery disease in the control group who were matched according to age. The study was approved by the Institution's Research Ethics Committee (consent statement was obtained). Odds ratios and confidence intervals were calculated using univariate analysis. Interrelationships among other risk factors, such as arterial hypertension, dyslipidemia, smoking and diabetes mellitus, were calculated using multivariate analysis. A p <0.05 was considered to be significant for statistical analysis.

RESULTS

The mean ages for the case and control groups were 64.65 years and 63.88 years, respectively. In multivariate analysis, the only variables related to coronary artery disease were Vascular calcification [OR 4.71 (CI 1.36-16.33) p=0.014], family history [OR 5.76 (CI 1.58-21.03) p=0.008] and arterial hypertension [OR 15.92 (CI 3.12-81.14) p=0.001]. Although smoking and diabetes are important variables in the pathogenesis of coronary artery disease, these factors did not show statistically significant associations in this sample.

CONCLUSION

The presence of vascular calcifications seen via mammography was an independent risk factor for coronary artery disease, as were hypertension and a family history of coronary artery disease.

Medial artery calcification as an indicator of diabetic peripheral vascular disease

BACKGROUND

Mönckeberg sclerosis or medial artery calcification (MAC) is a well-known phenomenon associated with diabetic and other arterial disease. However, its consequence within the foot, and specifically the first dorsal metatarsal artery, has not previously been studied.

MATERIALS AND METHODS

Nearly 1,000 foot x-rays were studied over a 9-month period in a busy hospital to identify the prevalence of first dorsal metatarsal artery calcification. The electronic medical notes for all the patients were reviewed to confirm which patients were known to be diabetic. The patients with positive findings were then identified and their HbA1c, creatinine, and previous foot interventions recorded.

RESULTS

Of the population studied, 1.4% had medial artery calcification of the 1st dorsal metatarsal artery: 93% were known diabetics and 100% had impaired glucose tolerance (a glucose plasma concentration of greater than 7.8 mmol/l 2-hours post-glucose loading). Seventy-nine percent had required previous podiatric care for foot ulceration and 64% had required surgical intervention for their diabetic feet. MAC has a high positive predictive value (92.9% (95% CI 69.2 to 98.7)) for diabetes, with a good specificity (99.9% (95%CI 99.4 to 100)) and low false positive rate (0.1% (05%CI 0.0 to 0.6)).

CONCLUSION

Medial artery calcification in the first dorsal metatarsal artery is characteristic of impaired glucose metabolism, and if seen on routine x-ray should be an indication for screening of the patient. It should also be considered as a foot-at-risk sign in the established diabetic due to the high incidence of foot ulceration and need for surgical intervention in this group.

Effects of diabetes on the vascular system: current research evidence and best practice recommendations

Diabetes mellitus has been referred to as a vascular disease because of its effect on the vascular endothelial wall. In recent years, research has identified specific effects of hyperglycemia and insulin resistance on the vasculature of the diabetic patient. Atherosclerosis is known to develop earlier in the diabetic patient and is more aggressive due to the metabolic effects of hyperglycemia and insulin resistance. The results of many large, randomized, prospective trials have provided practice changes in the management of the patient with diabetes. Trials such as the Framingham Study identified risk factors associated with atherosclerosis. Additional studies, such as the Diabetes Control and Complications Trial and the United Kingdom Prospective Diabetes Study, provided information about risk factors for diabetes and contributed to treatment recommendations for the person with type 1 or type 2 diabetes. Results of these and many other trials continue to change the recommendations for the person with diabetes to reduce mortality and prevent coronary heart disease, blindness, renal failure, and amputation. This paper will identify the effects of diabetes on the vascular system and outline best practice recommendations on the basis of clinical trials.

Aortic distensibility is reduced in subjects with type 2 diabetes and cardiac autonomic neuropathy

BACKGROUND

Reduced aortic distensibility predicts cardiovascular mortality in patients with type 2 diabetes and impaired glucose tolerance. Cardiac autonomic neuropathy is common in subjects with diabetes. However, the relationship between the elastic properties of the aorta and autonomic neuropathy has not been studied to date in subjects with type 2 diabetes.

MATERIALS AND METHODS

In this cross-sectional study, a total of 87 subjects with type 2 diabetes (27 with and 60 without cardiac autonomic neuropathy) as well as 60 healthy individuals, matched for age and sex with the diabetic subjects, were examined. Cardiac autonomic neuropathy was diagnosed on the basis of the battery of the classic cardiovascular autonomic function tests. Aortic distensibility was assessed by high-resolution ultrasonography.

RESULTS

Diabetic patients had reduced aortic distensibility in comparison with the control subjects: 1.81 +/- 0.58 vs. 2.53 +/- 0.34 10-6 cm2 dyn-1, respectively (P < 0.0001). In addition, diabetic individuals with cardiac autonomic neuropathy had reduced aortic distensibility as compared with patients without this complication: 1.60 +/- 0.72 vs. 1.90 +/- 0.48 10-6 cm2 dyn-1, respectively (P = 0.02). Multivariate linear regression analysis in the diabetic group, after controlling for a number of confounding factors such as age, systolic and diastolic blood pressure, duration of diabetes and presence as well as severity of cardiac autonomic neuropathy, demonstrated a significant and independent association between duration of diabetes [B = -0.02, SE(B) = 0.01, P = 0.01] and presence of cardiac autonomic neuropathy [B = -0.29, SE(B) = 0.14, P = 0.03] with aortic distensibility.

CONCLUSION

Type 2 diabetes is associated with a significant reduction in the elastic properties of the aorta. In addition, known duration of diabetes and presence of cardiac autonomic neuropathy are the main predictors of aortic distensibility in subjects with type 2 diabetes.

Cartilaginous metaplasia in calcified diabetic peripheral vascular disease: morphologic evidence of enchondral ossification

The mechanism of arterial calcification is not clear. We examined histological sections of major arteries from lower extremities of two patients with longstanding type II (or non-insulin-dependent) diabetes mellitus, and found morphological evidence of cartilaginous metaplasia and ectopic ossification with associated severe medial arterial calcification and atherosclerosis. Hematoxylin and eosin, alcian blue, and toluidine blue stains were applied for the demonstration of cartilage cells and their specific matrix proteins, and immunohistochemical studies for type II collagen. To our knowledge, cartilaginous metaplasia has not previously been described in medium-sized human muscular arteries. This observation supports the hypothesis that active enchondral ossification may be a pathway leading to arterial calcification in diabetic obstructive peripheral vascular disease.

Effects of preventative footwear on foot pressure as determined by pedobarography in diabetic patients: a prospective study

AIMS

This study analysed the effects of specially manufactured insoles on foot pressures in diabetic patients during a 1-year prospective observation period.

METHODS

We studied 81 type 2 diabetic patients without foot lesions. Using pedobarography three different regions of interest were examined: maximum peak pressure (MPP) of the total foot area, heel region and head of metatarsal bone I-III. Eighteen patients with high risk pressure (MPP of total foot 474 +/- 183 kPa; heel region 278 +/- 147 kPa, metatarsal 389 +/- 222 kPa) received optimal insole support. Sixty-three patients as a control group (MMP of total foot 367.7 +/- 157 kPa; heel 263.1 +/- 127 kPa, metatarsal 339.9 +/- 171 kPa) received conventional footwear.

RESULTS

After insole support a 30% pressure reduction of total foot MMP (474 +/- 183 kPa vs. 290 +/- 106 kPa) was achieved in the treatment group. After 6 months (324 +/- 127 kPa) and 1 year (380 +/- 190 kPa) a pressure reduction was found. Between the 6- and 12-month controls plantar pressures again increased. In the control group a significant increase of all peak pressures occurred.

CONCLUSIONS

Early insole support is successful in reducing plantar pressure. A repeated adjustment should be performed every 6 months to prevent foot pressure increases. The comparison of foot pressure development between the two groups showed constant levels in the treatment group. In the control group a marked increase of the pressure values was found. Identification and subsequent support of patients with high ulceration risk may help to reduce the high amputation rate.

Comparison of the microvascular response to transcutaneous electrical nerve stimulation and postocclusive ischemia in the diabetic foot

Neurogenic inflammation, mediated by unmyelinated C-nerve fibers, is part of the acute neurovascular response to injury. Laser doppler flowmetry was used to measure the flare response to transcutaneous electrical nerve stimulation (TENS) and to compare this axon reflex vasodilatation with postischemic hyperemia in the skin of the foot in diabetic and nondiabetic subjects. Twenty-one control subjects and 57 diabetic patients (25 type I; 32 type II; 14 without complications; 14 with neuropathy and without retinopathy; 8 with retinopathy and without neuropathy; 21 with neuropathy and retinopathy) were enrolled in the study. Following TENS, an increase in skin blood flow was found at the dorsum of the foot without any significant difference between the different groups. Compared to the control group, axon reflex vasodilatation was significantly reduced in the group of patients with diabetic neuropathy and in the group of patients with diabetic neuropathy and retinopathy at the pulp of the hallux (61 +/- 15 versus -6 +/- 16; versus 23 +/- 5; p < 0.05, respectively). All investigated groups exhibited a significant increase in skin blood flow after arterial occlusion without any significant difference between the groups. A good association was observed between postocclusive and TENS-induced hyperemia at the dorsum of the foot (r = 0.39; p = 0.0002), but only a weak association was found at the pulp of the hallux (r = 0.24; p = 0.03). TENS-induced hyperemia was associated with a diminished sweat response (p = 0.03), but not with pathological cardiovascular function tests (p = 0.07). Electrical axon reflex vasodilatation is diminished in diabetic patients suffering from peripheral autonomic C-fiber injury, especially in skin rich in thermoregulatory blood flow. The diminished neurovascular response is independent of vascular alterations in diabetes mellitus.