The 2017 Banting Memorial Lecture The diabetic lower limb - a forty year journey: from clinical observation to clinical science

Longitudinal physiological remoulding of lower limb skin as a cause of diabetic foot ulcer: a histopathological examination

OBJECTIVE

Diabetic foot ulcer (DFU) is recognised as a severe complication in patients with type 2 diabetes. With the increasing incidence of diabetes, it represents a major medical challenge. Several models have been proposed to explain its aetiology; however, they have never been assessed by longitudinal histopathological examination, which this study aims to address.

METHOD

Multiplex-immunofluorescence analysis was carried out with lengthwise serial skin specimens obtained from the medial thigh, lower leg, ankle, dorsum of foot and acrotarsium close to the DFU region of a patient with type 2 diabetes receiving above the knee amputation.

RESULTS

Proximal-to-distal gradual loss of peripheral nerve was demonstrated, accompanied by compromised capillaries in the superficial papillary plexus and distended CD31-positive capillaries in the dorsum of foot. Neural fibres and capillaries were also significantly compromised in the sweat gland acinus in the ankle and dorsum of foot. Injuries in the superficial papillary plexus, sweat gland acinus, and sweat gland-associated adipose tissues were accompanied by significant infiltration of macrophages. These results indicated that longitudinal impairment of local blood circulation could be the cause of peripheral neuropathy, which initiated ulcer formation. Resultant chronic inflammation, involving sweat gland-associated adipose tissue, gave rise to impairment of wound healing, and thus DFU formation.

CONCLUSION

Longitudinal histopathological examination demonstrated that impairment of local microvascular circulation (rather than the systemic complication caused by type 2 diabetes) was considered the primary cause of peripheral neuropathy, which initiated ulceration. Together with chronic inflammation in the superficial papillary plexus and sweat gland-associated adipose tissue, it resulted in the development of a DFU. Although this is a study of just one individual's limb, our study provided a unique observation, contributing mechanistic insights into developing novel intervening strategies to prevent and treat DFUs.

Gustatory sweating in people with type 1 and type 2 diabetes mellitus: Prevalence and risk factors

Objective

Gustatory sweating (GS) is characterized by profuse sweating during or immediately after ingestion of food and is known as a complication of diabetes mellitus (DM). This study aimed to determine the prevalence of GS and to characterize the sweating in a cohort of patients with type 1 and type 2 diabetes mellitus (T1DM and T2DM) as compared with a control group.

Methods

In a cross‐sectional study, 665 outpatients with T1DM and 505 outpatients with T2DM filled in an 8‐point questionnaire about GS. Answers were paired with medical data from the electronic patient records to explore associations with DM complications. The control group consisted of 1158 persons without DM answering the same questionnaire in an online version.

Results

In people with T1DM and T2DM, the prevalence of GS was 10% (95% CI 7%–12%) and 13% (95% CI 10%–16%), respectively. In the control group, the prevalence of GS was 5% (95% CI 3%–6%). Most commonly, people sweat on the face and/or head and upper body with a duration of 10–30 min albeit in the control group <10 min. In patients with T1DM, increased HbA1c was associated with GS (OR 1.3 [95% CI 1.05–1.6], p = .016), and in T2DM, younger age (OR 0.95 [95% CI 0.92–0.99), p = .006), presence of severe peripheral neuropathy (OR 2.33 [95% CI 1.04–5.2], p = .039) and absence of proliferative retinopathy were associated with GS (OR 0.22 [95% CI 0.07–0.71], p = .011).

Conclusion

We found the prevalence of gustatory sweating of 11% in a hospital‐based cohort of patients with T1DM and T2DM. This was twice as high as in non‐diabetic control persons. Associations between GS and known diabetes complications could only be demonstrated in T2DM. Compared with a control group without DM, odds for GS are higher in people with DM and age >45.

Impaired dermal microvascular reactivity and implications for diabetic wound formation and healing: an evidence review

Diabetic foot ulcers (DFUs) are among the most consequential and costly complications faced by patients with diabetes and the global healthcare system. Acknowledged risk factors for DFUs include diabetic peripheral neuropathy (DPN), peripheral arterial disease (PAD), microtrauma and foot deformities. Research on additional risk factors for DFUs has recently focused on dysregulated, autonomic vasomotor control in the skin of patients with DPN. In particular, impaired dermal microvascular reactivity (IDMR) with its attendant reduction in nutritive capillary blood flow has been identified as an emerging risk factor. This especially relates to refractory wounds noted in patients without overt PAD signs. In this paper, evidence will be reviewed supporting the evolving understanding of IDMR and its impact on DFU formation and healing. Advances in diagnostic instrumentation driving this research along with the most promising potential therapies aimed at improving microvascular function in the diabetic foot will be discussed in brief.

Skin AGEs and diabetic neuropathy

Advanced glycation end-products (AGEs) are heterogeneous molecules produced by the non-enzymatic glycation of proteins, lipids, or nucleic acids during hyperglycaemia. Accumulation of AGEs in the peripheral nerves has recently been proposed as an additional risk factor for the development of diabetic neuropathy (DN). The gold standard for measurement of tissue-bound AGEs is tissue biopsy. However, their assessment with the newer, fast and simple method of skin autofluorescence (sAF) has recently gained special interest by virtue of its non-invasive, highly reproducible nature and its acceptable correlation with the reference method of skin biopsy. Accumulation of tissue AGEs evaluated by sAF has been shown to independently correlate with DN. Importantly, increasing evidence underscores their potential value as early biomarkers of the latter. Further important associations include diabetic nephropathy, diabetic retinopathy and cardiovascular autonomic neuropathy. However, the value of the implementation of screening with skin AGEs for DN remains unclear. The aim of the present review is to critically summarise current evidence on the association between skin AGEs and diabetic microvascular complications, with a particular emphasis on diabetic neuropathy, and to note the most important limitations of existing knowledge. Longer follow-up studies are also highly anticipated to clarify its role and provide data on patient selection and cost-effectiveness.

Saving the Diabetic Foot During the COVID-19 Pandemic: A Tale of Two Cities

Of all the late complications of diabetes, those involving the foot have traditionally required more face-to-face patient visits to clinics to treat wounds by debridement, offloading, and many other treatment modalities. The advent of the coronavirus disease 2019 (COVID-19) pandemic has resulted not only in the closing of most outpatient clinics for face-to-face consultations but also in the inability to perform most laboratory and imaging investigations. This has resulted in a paradigm shift in the delivery of care for those with diabetic foot ulcers. The approaches to this challenge in two centers with an interest in diabetic foot disease, including virtual consultations using physician-to-patient and physician-to-home nurse telemedicine as well as home podiatry visits, are described in this review and are illustrated by several case vignettes. The outcomes from these two centers suggest that we may be witnessing new possibilities in models of care for the diabetic foot.