Diabetes, lower extremity amputation, loss of protective sensation, and neuronal nitric oxide synthase associated protein in the chronic renal insufficiency cohort study

Assessment of potential genetic markers for diabetic foot ulcer among Moscow residents

PURPOSE

Diabetic foot ulcer (DFU) is one of the most severe complications of type 2 diabetes, which is manifested in chronic skin ulcers of lower extremities. DFU treatment remains complex and expensive despite the availability of well-established protocols. Early prediction of potential DFU development at the onset of type 2 diabetes can greatly improve the aftermath of this complication.

METHODS

To assess potential genetic markers for DFU, a group of diabetic patients from Moscow region with and without DFU was genotyped for a number of SNPs previously reported to be associated with the DFU.

RESULTS

Obtained results did not confirm previously claimed association of rs1024611, rs3918242, rs2073618, rs1800629, rs4986790, rs179998, rs1963645 and rs11549465 (respectively, in MCP1, MMP9, TNFRSF11B, TNFα, TLR4, eNOS, NOS1AP and HIF1α genes) with the DFU. Surprisingly, the t allele of rs7903146 in the TCF7l2 gene known as one of the most prominent risk factors for type 2 diabetes has shown a protective effect on DFU with OR(95%) = 0.68(0.48-0.96).

CONCLUSION

Non-replication of previously published SNP associations with DFU suggests that the role of genetic factors in the DFU onset is either highly variable in different populations or is not as significant as the role of non-genetic factors.

Improvement in Protective Sensation: Clinical Evidence From a Randomized Controlled Trial for Treatment of Painful Diabetic Neuropathy With 10 kHz Spinal Cord Stimulation

BACKGROUND

Painful diabetic neuropathy (PDN) can result in the loss of protective sensation, in which people are at twice the likelihood of foot ulceration and three times the risk of lower extremity amputation. Here, we evaluated the long-term effects of high-frequency (10 kHz) paresthesia-independent spinal cord stimulation (SCS) on protective sensation in the feet and the associated risk of foot ulceration for individuals with PDN.

METHODS

The SENZA-PDN clinical study was a randomized, controlled trial in which 216 participants with PDN were randomized to receive either conventional medical management (CMM) alone or 10 kHz SCS plus CMM, with optional treatment crossover after 6 months. At study visits (baseline through 24 months), 10-g monofilament sensory assessments were conducted at 10 locations per foot. Two published methods were used to evaluate protective sensation via classifying risk of foot ulceration.

RESULTS

Participants in the 10 kHz SCS group reported increased numbers of sensate locations as compared to CMM alone (P < .001) and to preimplantation (P < .01) and were significantly more likely to be at low risk of foot ulceration using both classification methods. The proportion of low-risk participants approximately doubled from preimplantation to 3 months postimplantation and remained stable through 24 months (P ≤ .01).

CONCLUSIONS

Significant improvements were observed in protective sensation from preimplantation to 24 months postimplantation for the 10 kHz SCS group. With this unique, disease-modifying improvement in sensory function, 10 kHz SCS provides the potential to reduce ulceration, amputation, and other severe sequelae of PDN.

TRIAL REGISTRATION

The SENZA-PDN study is registered on ClinicalTrials.gov with identifier NCT03228420.

Circulating endothelial precursor cells are associated with a healed diabetic foot ulcer evaluated in a prospective cohort study

The goal of this multicentre study was to evaluate whether circulating endothelial precursor cells and microparticles can predict diabetic foot ulcer healing by the 16th week of care. We enrolled 207 subjects, and 40.0% (28.4, 41.5) healed by the 16th week of care. Using flow cytometry analysis, several circulating endothelial precursor cells measured at the first week of care were associated with healing after adjustment for wound area and wound duration. For example, CD34+ CD45dim , the univariate odds ratio was 1.19 (95% confidence interval: 0.88, 1.61) and after adjustment for wound area and wound duration, the odds ratio was (1.67 (1.16, 2.42) p = 0.006). A prognostic model using CD34+ CD45dim , wound area, and wound duration had an area under the curve of 0.75 (0.67, 0.82) and CD34+ CD45dim per initial wound area, an area under the curve of 0.72 (0.64, 0.79). Microparticles were not associated with a healed wound. Previous studies have indicated that circulating endothelial precursor cells measured at the first office visit are associated with a healed diabetic foot ulcer. In this multicentred prospective study, we confirm this finding, show the importance of adjusting circulating endothelial precursor cells measurements by wound area, and show circulating endothelial precursor cells per wound area is highly predictive of a healed diabetic foot ulcer by 16th week of care.

Blood-Borne Microparticles Are an Inflammatory Stimulus in Type 2 Diabetes Mellitus

The proinflammatory state associated with diabetes mellitus (DM) remains poorly understood. We found patients with DM have 3- to 14-fold elevations of blood-borne microparticles (MPs) that bind phalloidin (Ph; Ph positive [+] MPs), indicating the presence of F-actin on their surface. We hypothesized that F-actin-coated MPs were an unrecognized cause for DM-associated proinflammatory status. Ph+MPs, but not Ph-negative MPs, activate human and murine (Mus musculus) neutrophils through biophysical attributes of F-actin and membrane expression of phosphatidylserine (PS). Neutrophils respond to Ph+MPs via a linked membrane array, including the receptor for advanced glycation end products and CD36, PS-binding membrane receptors. These proteins in conjunction with TLR4 are coupled to NO synthase 1 adaptor protein (NOS1AP). Neutrophil activation occurs because of Ph+MPs causing elevations of NF-κB and Src kinase (SrcK) via a concurrent increased association of NO synthase 2 and SrcK with NOS1AP, resulting in SrcK S-nitrosylation. We conclude that NOS1AP links PS-binding receptors with intracellular regulatory proteins. Ph+MPs are alarmins present in normal human plasma and are increased in those with DM and especially those with DM and a lower-extremity ulcer.

Neutrophil microparticle production and inflammasome activation by hyperglycemia due to cytoskeletal instability

Microparticles are lipid bilayer-enclosed vesicles produced by cells under oxidative stress. MP production is elevated in patients with diabetes, but the underlying cellular mechanisms are poorly understood. We hypothesized that raising glucose above the physiological level of 5.5 mm would stimulate leukocytes to produce MPs and activate the nucleotide-binding domain, leucine-rich repeat pyrin domain-containing 3 (NLRP3) inflammasome. We found that when incubated in buffer with up to 20 mm glucose, human and murine neutrophils, but not monocytes, generate progressively more MPs with high interleukin (IL)-1β content. Enhanced MP production required generation of reactive chemical species by mitochondria, NADPH oxidase, and type 2 nitric-oxide synthase (NOS-2) and resulted in S-nitrosylation of actin. Depleting cells of capon (C-terminal PDZ ligand of neuronal nitric-oxide synthase protein), apoptosis-associated speck-like protein containing C-terminal caspase recruitment domain (ASC), or pro-IL-1β prevented the hyperglycemia-induced enhancement of reactive species production, MP generation, and IL-1β synthesis. Additional components required for these responses included inositol 1,3,5-triphosphate receptors, PKC, and enhancement of filamentous-actin turnover. Numerous proteins become localized to short filamentous actin in response to S-nitrosylation, including vasodilator-stimulated phosphoprotein, focal adhesion kinase, the membrane phospholipid translocation enzymes flippase and floppase, capon, NLRP3, and ASC. We conclude that an interdependent oxidative stress response to hyperglycemia perturbs neutrophil cytoskeletal stability leading to MP production and IL-1β synthesis.

NOS1AP genetic variation is associated with impaired healing of diabetic foot ulcers and diminished response to healing of circulating stem/progenitor cells

It is unclear why many with diabetes develop foot ulcers (DFU) and why some do not heal. It could be associated with genetic variation. We have previously shown that NOS1AP variation is associated with lower extremity amputation in those with diabetes and that circulating stem progenitor cell concentration (SPC) is associated with impaired foot ulcer healing in those with diabetes. The goal of this study was to determine if NOS1AP variation is associated with impaired wound healing and with SPC mobilization in those with DFU. In longitudinal cohort study we demonstrate that NOS1AP variants rs16849113 and rs19649113 are associated with impaired wound healing and with SPC mobilization in those with DFU. We believe that further study of NOS1AP is merited and that it NOS1AP might be associated with a functional impairment.

Relationship between amputation and risk factors in individuals with diabetes mellitus: A study with Brazilian patients

Individuals with diabetes develop lower extremity amputation for several reasons. Investigations into pathways to the development of complications are important both for treatment and prevention.

AIM

To evaluate the relationship between amputation and risk factors in people with diabetes mellitus.

MATERIALS AND METHOD

All participants included in this study (n=165) were recruited from the Diabetic Foot Program, developed in a Brazilian University, over seven years (2007-2014) and all information for this study was extracted from their clinical records.

RESULTS

The prevalence of amputation in patients with diabetes with four risk factors was up to 20% higher when compared to those with only one risk factor. The main predictive risk factors for amputation in this population were the presence of an ulcer and smoking.

CONCLUSION

The risk factors for amputation can be predicted for people with diabetes mellitus and, in the present study, the main factors were the presence of an ulcer and the smoking habit.

Variants in genes belonging to the fibroblast growth factor family are associated with lower extremity amputation in non-Hispanic whites: Findings from the chronic renal insufficiency cohort study

Diabetes is the major risk factor for nontraumatic lower extremity amputation (LEA). The role of genetic polymorphisms in predisposing diabetics to impaired wound healing leading to LEA has not been sufficiently explored. We investigated the association between a set of genes belonging to the angiogenesis/wound repair pathway with LEA in the Chronic Renal Insufficiency Cohort, a study of adults with chronic kidney disease (CKD) that includes a subgroup with diabetes. This study was performed on 3,772 Chronic Renal Insufficiency Cohort participants who were genotyped on the ITMAT-Broad-CARe array chip. A total of 1,017 single-nucleotide polymorphisms (SNPs) in 22 genes belonging to the angiogenesis/would repair pathway were investigated. LEA was determined from patient self-report. The association between genetic variants and LEA status was examined using logistic regression and additive genetic models after stratifying the cohort by race/ethnicity and diabetic status. Unadjusted analyses as well as analyses adjusted for age, sex, estimated glomerular filtration rate, body mass index, peripheral vascular disease, hemoglobin A1c, and population stratification were performed. In non-Hispanic white participants with diabetes, rs11938826 and rs1960669, both intronic SNPs in the gene basic fibroblast growth factor-2 (FGF2), were significantly associated with LEA in covariate-adjusted analysis (OR: 2.83 (95% CI: 1.73, 4.62); p-value: 0.000034; Bonferroni adjusted p-value: 0.0006) and (OR: 2.61 (95% CI: 1.48, 4.61); p-value: 0.00095; Bonferroni adjusted p-value: 0.02). In the same subgroup, rs10883688, an FGF8 SNP of unknown functional effect, was also associated with LEA (OR: 1.72 (95% Confidence Interval: 1.14, 2.6); p-value: 0.00999; Bonferroni adjusted p-value: 0.04). No statistically significant associations were identified in the other ethnic groups. In conclusion, variant/s in FGF2 and FGF8 may predispose diabetics with CKD to LEA. Dysregulation of the FGF2 gene represents an opportunity to understand further, and possibly intervene upon, mechanisms of wound healing in diabetics with CKD.

Identifying Common Genetic Risk Factors of Diabetic Neuropathies

Type 2 diabetes mellitus (T2DM) is a global public health problem of epidemic proportions, with 60-70% of affected individuals suffering from associated neurovascular complications that act on multiple organ systems. The most common and clinically significant neuropathies of T2DM include uremic neuropathy, peripheral neuropathy, and cardiac autonomic neuropathy. These conditions seriously impact an individual's quality of life and significantly increase the risk of morbidity and mortality. Although advances in gene sequencing technologies have identified several genetic variants that may regulate the development and progression of T2DM, little is known about whether or not the variants are involved in disease progression and how these genetic variants are associated with diabetic neuropathy specifically. Significant missing heritability data and complex disease etiologies remain to be explained. This article is the first to provide a review of the genetic risk variants implicated in the diabetic neuropathies and to highlight potential commonalities. We thereby aim to contribute to the creation of a genetic-metabolic model that will help to elucidate the cause of diabetic neuropathies, evaluate a patient's risk profile, and ultimately facilitate preventative and targeted treatment for the individual.

Genetic risk factors for hypertrophic scar development

Hypertrophic scars (HTSs) occur in 30 to 72% patients after thermal injury. Risk factors include skin color, female sex, young age, burn site, and burn severity. Recent correlations between genetic variations and clinical conditions suggest that single-nucleotide polymorphisms (SNPs) may be associated with HTS formation. The authors hypothesized that an SNP in the p27 gene (rs36228499) previously associated with decreased restenosis after coronary stenting would be associated with lower Vancouver Scar Scale (VSS) measurements and decreased itching. Patient and injury characteristics were collected from adults with thermal burns. VSS scores were calculated at 4 to 9 months after injury. Genotyping was performed using real-time polymerase chain reaction. Logistic regression was used to determine risk factors for HTS as measured by a VSS score >7. Three hundred subjects had a median age of 39 years (range, 18-91); 69% were male and median burn size was 7% TBSA (range, 0.25-80). Consistent with literature, the p27 variant SNP had an allele frequency of 40%, but was not associated with reduced HTS formation or lower itch scores in any genetic model. HTS formation was associated with American Indian/Alaskan Native race (odds ratio [OR], 12.2; P = .02), facial burns (OR, 9.4; P = .04), and burn size ≥20% TBSA (OR, 1.99; P = .03). Although the p27 SNP may protect against vascular fibroproliferation, the effect cannot be generalized to cutaneous scars. This study suggests that American Indian/Alaskan Native race, facial burns, and higher %TBSA are independent risk factors for HTS. The American Indian/Alaskan Native association suggests that there are potentially yet-to-be-identified genetic variants.

Digital imaging analysis to assess scar phenotype

In order to understand the link between the genetic background of patients and wound clinical outcomes, it is critical to have a reliable method to assess the phenotypic characteristics of healed wounds. In this study, we present a novel imaging method that provides reproducible, sensitive, and unbiased assessments of postsurgical scarring. We used this approach to investigate the possibility that genetic variants in orofacial clefting genes are associated with suboptimal healing. Red-green-blue digital images of postsurgical scars of 68 patients, following unilateral cleft lip repair, were captured using the 3dMD imaging system. Morphometric and colorimetric data of repaired regions of the philtrum and upper lip were acquired using ImageJ software, and the unaffected contralateral regions were used as patient-specific controls. Repeatability of the method was high with intraclass correlation coefficient score > 0.8. This method detected a very significant difference in all three colors, and for all patients, between the scarred and the contralateral unaffected philtrum (p ranging from 1.20(-05) to 1.95(-14) ). Physicians' clinical outcome ratings from the same images showed high interobserver variability (overall Pearson coefficient = 0.49) as well as low correlation with digital image analysis results. Finally, we identified genetic variants in TGFB3 and ARHGAP29 associated with suboptimal healing outcome.

Epidemiology of foot ulceration and amputation: can global variation be explained?

Amputation is a treatment, and not simply part of the natural history of foot disease. However, assessment of amputation incidence is the measure most frequently used to document an outcome reflecting the management of diabetic foot disease, mainly because the data are already captured in most health care systems. Nevertheless, interpretation of the results requires great care. Many centers have recorded decreases in the incidence of amputation in recent years and have concluded that this reflects improvement in clinical care. Although improvement in clinical care is clearly of a priority, it is important not to underestimate the extent to which the at-risk population (those with diabetes) may have changed as a result of changing criteria for the diagnosis of diabetes, as well as the increasing implementation of systematic and opportunistic screening. The incidence of amputation can be calculated and expressed in many ways, with different groups using different criteria for deciding both the numerator and the denominator, and studying populations that may differ in several different ways. Given that the incidence of amputation can also be influenced by a wide variety of clinical and social factors, it is not surprising that considerable variation exists between published studies from different countries. For these reasons it is currently difficult to make meaningful comparisons between data from different countries. On the other hand, the demonstration of wide variation within a single country or between countries or communities that have very similar populations, health care systems, and procedures for documenting amputation incidence is of greater interest. When 8- to 10-fold variation exists within similar health care systems, a risk as large as any published risk factor for amputation, it is essential that the reasons are explored. While race and social deprivation both make an important contribution to variation, another is likely to relate to aspects of the structure of care, including the training and beliefs of individual clinicians, patients’ access to care, preferences of patients, and the ability of a patient to understand the need for care and execute a care plan. This area of study requires further investigation.