Interaction of macro- and microvascular function underlies brachial artery flow-mediated dilation in humans.

Brachial artery flow-mediated dilation (BAFMD) is induced by hyperemic wall shear rate (WSR) following forearm ischemia. In older adults, there appears to be a reduced brachial hyperemic WSR and altered stimulus-response relationship compared with young adults. However, it is unclear if an altered forearm microvascular response to ischemia influences brachial hyperemic WSR in older adults. We determined associations between brachial hyperemic WSR and forearm skeletal muscle oxygen saturation in young and older adults. Healthy young (n = 17, 29 ± 7 yr) and older (n = 32, 65 ± 4 yr) adults participated in the study. BAFMD by a multigate spectral Doppler system and forearm skeletal muscle oxygen saturation by near-infrared spectroscopy were concurrently measured. When compared with the young, older adults showed reduced oxygen extraction kinetics (OE, 0.15 [0.12-0.17] vs. 0.09 [0.05-0.12]%s-1) and magnitude (So2deficit, 3,810 ± 1,420 vs. 2,723 ± 1,240%s) during ischemia, as well as oxygen resaturation kinetics (So2slope, 2.5 ± 0.7 vs. 1.7 ± 0.7%s-1) upon reperfusion (all P < 0.05). When OE in the young and So2slope in older adults were stratified by their median values, young adults with OE above the median had greater hyperemic WSR parameters compared with those below the median (P < 0.05), but So2slope in older adults did not show clear differences in hyperemic WSR parameters between those above/below the median. This study demonstrates that, in addition to a reduced microvascular response to ischemia, there may be a dissociation between microvascular response to ischemia and brachial hyperemic WSR in older adults, which may result in a further impairment of BAFMD in this cohort.NEW & NOTEWORTHY Microvascular response to ischemia and subsequent reperfusion is diminished in older adults compared with the young. Furthermore, there appears to be a dissociation between the microvascular response to ischemia and brachial hyperemic WSR in older adults, which may further disturb the BAFMD process in this cohort. A reduced BAFMD in older adults may be a result of multiple alterations occurring both at macro- and microcirculation.

Assessing electronic device use behaviours in healthy adults: development and evaluation of a novel tool.

BACKGROUND: Chronic exposure of the macula to blue light from electronic devices has been identified as a potential macular health concern. The impacts remain poorly investigated as no validated methods to capture usual device use behaviours exist. PURPOSE: The aim of this study was to develop and validate the Electronic Device Use Questionnaire (EDUQ) against multiple 24-h electronic device use diaries in healthy Australian and United Kingdom adults. METHODS: The EDUQ and diaries were developed to capture device use across categories (television, computer and handheld devices). Over eight weeks 56 Australian and 24 United Kingdom participants completed three questionnaires and eight diaries via online platforms. Tool validity was determined through Bland-Altman plot analysis of mean daily hours of device use between the tools. RESULTS: The EDUQ demonstrated poor validity in both cohorts with poor agreement when compared with the diaries. When the device categories were combined, a mean difference between the tools of 1.54 h/day, and 95% limits of agreement between -2.72 h/day and 5.80 h/day was observed in the Australian cohort. Across both cohorts and all device categories the mean differences indicated individuals were more likely to report higher device use through the questionnaire rather than diaries. CONCLUSIONS: The EDUQ is a novel tool and demonstrated the difficulty for participants of accurately recalling usual behaviour of device use. Poor agreement in reported device use occurred across all device categories. The poor agreement may be related to factors such as memory recall bias, and the number of diaries captured not being reflective of usual use. Future studies should look to address these factors to improve validity of device use capture.

Microstructural Characterization of Resistance Artery Remodelling in Diabetes Mellitus.

INTRODUCTION: Microvascular remodelling is a symptom of cardiovascular disease. Despite the mechanical environment being recognized as a major contributor to the remodelling process, it is currently only understood in a rudimentary way. OBJECTIVE: A morphological and mechanical evaluation of the resistance vasculature in health and diabetes mellitus. METHODS: The cells and extracellular matrix of human subcutaneous resistance arteries from abdominal fat biopsies were imaged using two-photon fluorescence and second harmonic generation at varying transmural pressure. The results informed a two-layer mechanical model. RESULTS: Diabetic resistance arteries reduced in wall area as pressure was increased. This was attributed to the presence of thick, straight collagen fibre bundles that braced the outer wall. The abnormal mechanical environment caused the internal elastic lamina and endothelial and vascular smooth muscle cell arrangements to twist. CONCLUSIONS: Our results suggest diabetic microvascular remodelling is likely to be stress-driven, comprising at least 2 stages: (1) Laying down of adventitial bracing fibres that limit outward distension, and (2) Deposition of additional collagen in the media, likely due to the significantly altered mechanical environment. This work represents a step towards elucidating the local stress environment of cells, which is crucial to build accurate models of mechanotransduction in disease.

Treatment of myocardial ischaemia-reperfusion injury in patients with ST-segment elevation myocardial infarction: promise, disappointment, and hope.

Acute myocardial infarction (AMI) is a major cause of morbidity and mortality worldwide. Timely reperfusion with primary percutaneous coronary intervention (PPCI) remains the gold standard in patients presenting with ST-segment elevation myocardial infarction (STEMI), limiting infarct size, preserving left ventricular ejection fraction (LVEF), and improving clinical outcomes. Despite this, a significant proportion of STEMI patients develop post-infarct heart failure. We review the current understanding and up-to-date evidence base for therapeutic intervention of ischaemia-reperfusion injury (IRI), a combination of myocardial ischaemia secondary to acute coronary occlusion and reperfusion injury leading to further myocardial injury and cell death. Multiple treatment modalities have been shown to be cardioprotective and reduce IRI in experimental animal models. Recent phase II/III randomised controlled trials (RCT) have assessed multiple cardioprotective strategies ranging from ischaemic conditioning, therapeutic hypothermia and hyperoxaemia to pharmacological therapies. While several therapies have been shown to reduce infarct size in animal models or proof-of-concept studies, many larger scale trial results have proven inconsistent and disappointing. Hard clinical outcomes remain elusive. We discuss potential reasons for the difficulties in translation to clinical practice.

Cross-cultural adaptation of the Spanish MINICHAL instrument into English for use in the United Kingdom.

BACKGROUND: Hypertension is a highly prevalent condition, with optimal treatment to BP targets conferring significant gains in terms of cardiovascular outcomes. Understanding why some patients do not achieve BP targets would be enhanced through greater understanding of their health-related quality of life (HRQoL). However, the only English language disease-specific instruments for measurement of HRQoL in hypertension have not been validated in accordance with accepted standards. It is proposed that the Spanish MINICHAL instrument for the assessment of HRQoL in hypertension could be translated, adapted and validated for use in the United Kingdom. The aim of the study was therefore to complete this process. METHODS: The MINICHAL authors were contacted and the original instrument obtained. This was then translated into English by two independent English-speakers, with these versions then reconciled, before back-translation and subsequent production of a 2nd reconciled version. Thereafter, a final version was produced after cognitive debriefing, for administration and psychometric analysis in the target population of patients living in the Exeter area (Southwest UK) aged 18-80 years with treatment-naïve grade II-III hypertension, before, during and after 18 weeks' intensive treatment. RESULTS: The English-language instrument was administered to 30 individuals (median age: 58.5 years, 53% male). Psychometric analysis demonstrated a floor effect, though no ceiling effect. Internal consistency for both state of mind (StM) and somatic manifestations (SM) dimensions of the instrument were acceptable (Cronbach's alpha = 0.81 and 0.75), as was test-retest reliability (ICC = 0.717 and 0.961) and construct validity, which was measured through co-administration with the EQ-5D-5L and Bulpitt-Fletcher instruments. No significant associations were found between scores and patient characteristics known to affect HRQoL. The EQ-5D-5L instrument found an improvement in HRQoL following treatment, with the StM and SM dimensions of the English language MINICHAL trending to support this (d = 0.32 and 0.02 respectively). CONCLUSIONS: The present study details the successful English translation and validation of the MINICHAL instrument for use in individuals with hypertension. The data reported also supports an improvement in HRQoL with rapid treatment of grade II-III hypertension, a strategy which has been recommended by contemporaneous European guidelines. Trial registration ISRCTN registry number: 57475376 (assigned 25/06/2015).

A genome-wide association study implicates multiple mechanisms influencing raised urinary albumin-creatinine ratio.

Raised albumin-creatinine ratio (ACR) is an indicator of microvascular damage and renal disease. We aimed to identify genetic variants associated with raised ACR and study the implications of carrying multiple ACR-raising alleles with metabolic and vascular-related disease. We performed a genome-wide association study of ACR using 437 027 individuals from the UK Biobank in the discovery phase, 54 527 more than previous studies, and followed up our findings in independent studies. We identified 62 independent associations with ACR across 56 loci (P < 5 × 10-8), of which 20 were not previously reported. Pathway analyses and the identification of 20 of the 62 variants (at r2 > 0.8) coinciding with signals for at least 16 related metabolic and vascular traits, suggested multiple pathways leading to raised ACR levels. After excluding variants at the CUBN locus, known to alter ACR via effects on renal absorption, an ACR genetic risk score was associated with a higher risk of hypertension, and less strongly, type 2 diabetes and stroke. For some rare genotype combinations at the CUBN locus, most individuals had ACR levels above the microalbuminuria clinical threshold. Contrary to our hypothesis, individuals carrying more CUBN ACR-raising alleles, and above the clinical threshold, had a higher frequency of vascular disease. The CUBN allele effects on ACR were twice as strong in people with diabetes-a result robust to an optimization-algorithm approach to simulating interactions, validating previously reported gene-diabetes interactions (P ≤ 4 × 10-5). In conclusion, a variety of genetic mechanisms and traits contribute to variation in ACR.

Effects of exenatide on microvascular reactivity in patients with type 2 diabetes and coronary artery disease: A randomized controlled study.

OBJECTIVE: We studied the effect of the GLP-1RA exenatide on skin microvascular function in patients with T2DM and CAD. METHODS: Thirty-five patients with T2DM, CAD, and HbA1C 42-86 mmol/mol were randomized to treatment with exenatide or conventional non-GLP-1-based therapy for 12 weeks. Skin microvascular function was examined in the forearm by LDF and iontophoretic application of acetyl choline and SNP, and by PORH at baseline and after 12 weeks. Blood samples for fasting plasma glucose, HbA1C, and lipid profile were collected. RESULTS: At 12 weeks, patients on exenatide showed reductions in HbA1C (from 63.5 ± 13 to 60.7 ± 14 mmol/mol, p = .065), body weight (from 92.6 ± 16 to 89 ± 16 kg, p < .001), and systolic blood pressure (from 141 ± 13 to 134 ± 16 mm Hg, p < .05) as compared to the conventionally treated group. There were no significant changes in skin microvascular function between or within the two groups at follow-up. CONCLUSIONS: Three months' daily treatment with the GLP-1RA exenatide in T2DM patients with CAD showed no significant effects on skin microvascular function or blood glucose control, while this study confirms a reduction in body weight and blood pressure by exenatide, as compared to conventional antidiabetic drug treatment.

Morphological and functional cardiac consequences of rapid hypertension treatment: a cohort study.

BACKGROUND: Left ventricular (LV) hypertrophy (LVH) in uncontrolled hypertension is an independent predictor of mortality, though its regression with treatment improves outcomes. Retrospective data suggest that early control of hypertension provides a prognostic advantage and this strategy is included in the 2018 European guidelines, which recommend treating grade II/III hypertension to target blood pressure (BP) within 3 months. The earliest LVH regression to date was demonstrated by echocardiography at 24 weeks. The effect of a rapid guideline-based treatment protocol on LV remodelling, with very early BP control by 18 weeks remains controversial and previously unreported. We aimed to determine whether such rapid hypertension treatment is associated with improvements in LV structure and function through paired cardiovascular magnetic resonance (CMR) scanning at baseline and 18 weeks, utilising CMR mass and feature tracking analysis. METHODS: We recruited participants with never-treated grade II/III hypertension, initiating a guideline-based treatment protocol which aimed to achieve BP control within 18 weeks. CMR and feature tracking were used to assess myocardial morphology and function immediately before and after treatment. RESULTS: We acquired complete pre- and 18-week post-treatment data for 41 participants. During the interval, LV mass index reduced significantly (43.5 ± 9.8 to 37.6 ± 8.3 g/m2, p < 0.001) following treatment, accompanied by reductions in LV ejection fraction (65.6 ± 6.8 to 63.4 ± 7.1%, p = 0.03), global radial strain (46.1 ± 9.7 to 39.1 ± 10.9, p < 0.001), mid-circumferential strain (- 20.8 ± 4.9 to - 19.1 ± 3.7, p = 0.02), apical circumferential strain (- 26.0 ± 5.3 to - 23.4 ± 4.2, p = 0.003) and apical rotation (9.8 ± 5.0 to 7.5 ± 4.5, p = 0.003). CONCLUSIONS: LVH regresses following just 18 weeks of intensive antihypertensive treatment in subjects with newly-diagnosed grade II/III hypertension. This is accompanied by potentially advantageous functional changes within the myocardium and supports the hypothesis that rapid treatment of hypertension could improve clinical outcomes. TRIAL REGISTRATION: ISRCTN registry number: 57475376 (assigned 25/06/2015).

Weight change and sulfonylurea therapy are related to 3 year change in microvascular function in people with type 2 diabetes.

AIMS/HYPOTHESIS: Although cardiovascular disease is the biggest cause of death in people with diabetes, microvascular complications have a significant impact on quality of life and financial burden of the disease. Little is known about the progression of microvascular dysfunction in the early stages of type 2 diabetes before the occurrence of clinically apparent complications. We aimed to explore the determinants of endothelial-dependent and -independent microvascular function progression over a 3 year period, in people with and without both diabetes and few clinical microvascular complications. METHODS: Demographics were collected in 154 participants with type 2 diabetes and in a further 99 participants without type 2 diabetes. Skin microvascular endothelium-dependent response to iontophoresis of acetylcholine and endothelium-independent responses to sodium nitroprusside were measured using laser Doppler fluximetry. All assessments were repeated 3 years later. RESULTS: People with type 2 diabetes had impaired endothelial-dependent microvascular response compared with those without (AUC 93.9 [95% CI 88.1, 99.4] vs 111.9 [102.3, 121.4] arbitrary units [AU] × min, p < 0.001, for those with vs without diabetes, respectively). Similarly, endothelial-independent responses were attenuated in those with diabetes (63.2 [59.2, 67.2] vs 75.1 [67.8, 82.4] AU × min, respectively, p = 0.002). Mean microvascular function declined over 3 years in both groups to a similar degree (pinteraction 0.74 for response to acetylcholine and 0.69 for response to sodium nitroprusside). In those with diabetes, use of sulfonylurea was associated with greater decline (p = 0.022 after adjustment for co-prescriptions, change in HbA1c and weight), whereas improving glycaemic control was associated with less decline of endothelial-dependent microvascular function (p = 0.03). Otherwise, the determinants of microvascular decline were similar in those with and without diabetes. The principal determinant of change in microvascular function in the whole population was weight change over 3 years, such that those that lost ≥5% weight had very little decline in either endothelial-dependent or -independent function compared with those that were weight stable, whereas those who gained weight had a greater decline in function (change in endothelial-dependent function was 1.2 [95% CI -13.2, 15.7] AU × min in those who lost weight; -15.8 [-10.5, -21.0] AU × min in those with stable weight; and -37.8 [-19.4, -56.2] AU × min in those with weight gain; ptrend < 0.001). This association of weight change with change in endothelial function was driven by people with diabetes; in people without diabetes, the relationship was nonsignificant. CONCLUSIONS/INTERPRETATION: Over 3 years, physiological change in weight was the greatest predictor of change in microvascular function.

The systemic microcirculation in dialysis populations.

In a rapidly expanding population of patients with chronic kidney disease, including 2 million people requiring renal replacement therapy, cardiovascular mortality is 15 times greater than the general population. In addition to traditional cardiovascular risk factors, more poorly defined risks related to uremia and its treatments appear to contribute to this exaggerated risk. In this context, the microcirculation may play an important early role in cardiovascular disease associated with chronic kidney disease. Experimentally, the uremic environment and dialysis have been linked to multiple pathways causing microvascular dysfunction. Coronary microvascular dysfunction is reflected in remote and more easily studied vascular beds such as the skin. There is increasing evidence for a correlation between systemic microvascular dysfunction and adverse cardiovascular outcomes. Systemic microcirculatory changes have not been extensively investigated across the spectrum of chronic kidney disease. Recent advances in non-invasive techniques studying the microcirculation in vivo in man are increasing the data available particularly in patients on hemodialysis. Here, we review current knowledge of the systemic microcirculation in dialysis populations, explore whether non-invasive techniques to study its function could be used to detect early stage cardiovascular disease, address challenges faced in studying this patient cohort and identify potential future avenues for research.

Urinary nitrate concentration as a marker for kidney transplant rejection.

BACKGROUND: Early identification and treatment of kidney transplant rejection episodes is vital to limit loss of function and prolong the life of the transplanted kidney and recipient. Current practice depends on detecting a creatinine rise. A biomarker to diagnose transplant rejection at an earlier time point than current practice, or to inform earlier decision making to biopsy, could be transformative. It has previously been shown that urinary nitrate concentration is elevated in renal transplant rejection. Nitrate is a nitric oxide (NO) oxidation product. Transplant rejection upregulates NO synthesis via inducible nitric oxide synthase leading to elevations in urinary nitrate concentration. We have recently validated a urinary nitrate concentration assay which could provide results in a clinically relevant timeframe. Our aim was to determine whether urinary nitrate concentration is a useful tool to predict renal transplant rejection in the context of contemporary clinical practice. METHODS: We conducted a prospective observational study, recruiting renal transplant participants over an 18-month period. We made no alterations to the patients' clinical care including medications, immunosuppression, diet and frequency of visits. We collected urine samples from every clinical attendance. We assessed the urinary nitrate to creatinine ratio (uNCR) between patient groups: routine attendances, biopsy proven rejection, biopsy proven no rejection and other call backs. uNCR was examined over time for those with biopsy proven transplant rejection. These four groups were compared using an ANOVA test. RESULTS: A total of 2656 samples were collected. uNCR during biopsy proven rejection, n = 15 (median 49 µmol/mmol, IQR 23-61) was not significantly different from that of routine samples, n = 164 (median 55 µmol/mmol, IQR 37-82) (p = 0.55), or biopsy proven no rejection, n = 12 (median 39 µmol/mmol, IQR 21-89) (P = 0.77). Overall uNCR was highly variable with no diagnostic threshold for kidney transplant rejection. Furthermore, within-patient uNCR was highly variable over time, and thus it was not possible to produce individualised patient thresholds to identify rejection. The total taking Tacrolimus was 204 patients, with no statistical difference between the uNCR of all those on Tacrolimus, against those not, p = 0.18. CONCLUSION: The urinary nitrate to creatinine ratio is not a useful biomarker for renal transplant rejection.

Prognostic imaging biomarkers for diabetic kidney disease (iBEAt): study protocol.

BACKGROUND: Diabetic kidney disease (DKD) remains one of the leading causes of premature death in diabetes. DKD is classified on albuminuria and reduced kidney function (estimated glomerular filtration rate (eGFR)) but these have modest value for predicting future renal status. There is an unmet need for biomarkers that can be used in clinical settings which also improve prediction of renal decline on top of routinely available data, particularly in the early stages. The iBEAt study of the BEAt-DKD project aims to determine whether renal imaging biomarkers (magnetic resonance imaging (MRI) and ultrasound (US)) provide insight into the pathogenesis and heterogeneity of DKD (primary aim) and whether they have potential as prognostic biomarkers in DKD (secondary aim). METHODS: iBEAt is a prospective multi-centre observational cohort study recruiting 500 patients with type 2 diabetes (T2D) and eGFR ≥30 ml/min/1.73m2. At baseline, blood and urine will be collected, clinical examinations will be performed, and medical history will be obtained. These assessments will be repeated annually for 3 years. At baseline each participant will also undergo quantitative renal MRI and US with central processing of MRI images. Biological samples will be stored in a central laboratory for biomarker and validation studies, and data in a central data depository. Data analysis will explore the potential associations between imaging biomarkers and renal function, and whether the imaging biomarkers improve the prediction of DKD progression. Ancillary substudies will: (1) validate imaging biomarkers against renal histopathology; (2) validate MRI based renal blood flow measurements against H2O15 positron-emission tomography (PET); (3) validate methods for (semi-)automated processing of renal MRI; (4) examine longitudinal changes in imaging biomarkers; (5) examine whether glycocalyx and microvascular measures are associated with imaging biomarkers and eGFR decline; (6) explore whether the findings in T2D can be extrapolated to type 1 diabetes. DISCUSSION: iBEAt is the largest DKD imaging study to date and will provide valuable insights into the progression and heterogeneity of DKD. The results may contribute to a more personalised approach to DKD management in patients with T2D. TRIAL REGISTRATION: Clinicaltrials.gov ( NCT03716401 ).

Locally delivered GLP-1 analogues liraglutide and exenatide enhance microvascular perfusion in individuals with and without type 2 diabetes.

AIMS/HYPOTHESIS: Glucagon-like peptide-1 (GLP-1) analogues reduce the risk of macrovascular disease in diabetes; however, little is known about their microvascular effects. This research examined the microvascular actions of the GLP-1 analogues liraglutide and exenatide in individuals with and without type 2 diabetes (study 1). It also explored the involvement of the GLP-1 receptor (study 2) and the nitric oxide pathway in mediating the microvascular effects of the analogues. METHODS: Trial design: Studies 1 and 2 had a randomised, controlled, double-blind study design. Study 1 participants, intervention and methods: three participant groups were recruited: individuals with well-controlled type 2 diabetes, and obese and lean individuals without diabetes (21 participants per group). Liraglutide (0.06 mg), exenatide (0.5 µg) and saline (154 mmol/l NaCl; 0.9%) control were microinjected into separate sites in the dermis (forearm) in a randomised order, blinded to operator and participant. Skin microvascular perfusion was assessed by laser Doppler perfusion imaging. Outcomes were stabilised response (mean skin perfusion between 7.5 and 10 min post microinjection) and total response (AUC, normalised for baseline perfusion). Perfusion response to GLP-1 analogues was compared with saline within each group as well as between groups. Study 2 participants, intervention and methods: in healthy individuals (N = 16), liraglutide (0.06 mg) and saline microinjected sites were pretreated with saline or the GLP-1 receptor blocker, exendin-(9,39), in a randomised order, blinded to participant and operator. Outcomes were as above (stabilised response and total perfusion response). Perfusion response to liraglutide was compared between the saline and the exendin-(9,39) pretreated sites. In vitro study: the effects of liraglutide and exenatide on nitrate levels and endothelial nitric oxide synthase phosphorylation (activation) were examined using human microvascular endothelial cells. RESULTS: Study 1 results: both analogues increased skin perfusion (stabilised response and total response) in all groups (n = 21 per group, p < 0.001), with the microvascular responses similar across groups (p ≥ 0.389). Study 2 results: liraglutide response (stabilised response and total response) was not influenced by pretreatment with exendin-(9,39) (70 nmol/l) (N = 15, one dataset excluded) (p ≥ 0.609). Liraglutide and exenatide increased nitrate production and endothelial nitric oxide synthase (eNOS) phosphorylation (p ≤ 0.020). CONCLUSIONS/INTERPRETATION: Liraglutide and exenatide increased skin microvascular perfusion in individuals with and without well-controlled diabetes, potentially mediated, at least in part, by NO. TRIAL REGISTRATION: ClinicalTrials.gov NCT01677104. FUNDING: This work was supported by Diabetes UK (grant numbers: 09/0003955 and 12/0004600 [RW and JM Collins Legacy, Funded Studentship]).

Arterial wall shear rate response to reactive hyperaemia is markedly different between young and older humans.

KEY POINTS: The vasodilatory response to reactive hyperaemia is impaired with advancing age, but it is unclear whether this is because of an altered wall shear rate (WSR) stimulus or an altered flow-mediated dilatation (FMD) response. Using new technology that allows detailed WSR measurement, we assessed the WSR-FMD response in healthy older people. Our data show that older people have a markedly altered and diminished WSR response to reactive hyperaemia compared to young people, but reduced WSR alone does not fully explain reduced FMD. In young people, WSR appears to be coupled to FMD but, by age ∼65 years, the arterial vasodilatory response has begun to uncouple from the WSR stimulus. These findings point to the importance and utility of comprehensively characterizing the WSR-FMD response when using reactive hyperaemia to assess vascular function, as well as giving new insight into the age-related alteration in vascular function. ABSTRACT: The vasodilatory response to reactive hyperaemia is impaired with age, but it is unknown whether this is because of an altered wall shear rate (WSR) stimulus or an altered flow-mediated dilatation (FMD) response to the WSR stimulus. Inherent difficulties in measuring blood flow velocity close to the arterial wall have prevented detailed assessment of the WSR-FMD response. Using an enhanced multigate spectral Doppler ultrasound system (ultrasound advanced open platform), we aimed to produce new data on the WSR-FMD relationship in healthy older adults. Sixty healthy people, comprising 28 young (27.5 ± 5.5 years) and 32 older (64.9 ± 3.7 years) individuals, underwent FMD assessment. Raw data were post-processed using custom-designed software to obtain WSR and diameter parameters. The data revealed that older people have a much altered and diminished WSR response to reactive hyperaemia compared to younger people [e.g. WSR peak: 622 (571-673) vs. 443 (396-491) 1/s in young and older respectively; P < 0.05]. However, reduced WSR alone does not appear to fully explain the reduced FMD response in older people because associations between WSR and FMD were few and weak. This was in contrast to young adults, where associations were strong. We conclude that WSR during FMD is much altered and diminished in older people, and there appears to be an 'uncoupling' of WSR from FMD in older people that may reflect a loss of precision in the reactive hyperaemia stimulus-response relationship. These findings also point to the importance and utility of comprehensively characterizing the WSR-FMD response when using reactive hyperaemia to assess vascular function.

Metformin is the key factor in elevated plasma growth differentiation factor-15 levels in type 2 diabetes: A nested, case-control study.

Produced as a tissue defence response to hypoxia and inflammation, growth differentiation factor-15 (GDF-15) is elevated in people receiving metformin treatment. To gain insight into the relationship of GDF-15 with metformin and major cardiovascular risk factors, we analysed the data from the SUMMIT cohort (n = 1438), a four-centre, nested, case-control study aimed at verifying whether biomarkers of atherosclerosis differ according to the presence of type 2 diabetes and cardiovascular disease. While in univariate analysis, major cardiovascular risk factors, with the exception of gender and cholesterol, increased similarly and linearly across GDF-15 quartiles, the independent variables associated with GDF-15, both in participants with and without diabetes, were age, plasma creatinine, N-terminal pro-brain natriuretic peptide, diuretic use, smoking exposure and glycated haemoglobin. In participants with diabetes, metformin treatment was associated with a 40% rise in GDF-15 level, which was independent of the other major factors, and largely explained their elevated GDF-15 levels. The relatively high GDF-15 bioavailability might partly explain the protective cardiovascular effects of metformin.

Raman spectroscopy for rapid intra-operative margin analysis of surgically excised tumour specimens.

Raman spectroscopy, a form of vibrational spectroscopy, has the ability to provide sensitive and specific biochemical analysis of tissue. This review article provides an in-depth analysis of the suitability of different Raman spectroscopy techniques in providing intra-operative margin analysis in a range of solid tumour pathologies. Surgical excision remains the primary treatment of a number of solid organ cancers. Incomplete excision of a tumour and positive margins on histopathological analysis is associated with a worse prognosis, the need for adjuvant therapies with significant side effects and a resulting financial burden. The provision of intra-operative margin analysis of surgically excised tumour specimens would be beneficial for a number of pathologies, as there are no widely adopted and accurate methods of margin analysis, beyond histopathology. The limitations of Raman spectroscopic studies to date are discussed and future work necessary to enable translation to clinical use is identified. We conclude that, although there remain a number of challenges in translating current techniques into a clinically effective tool, studies so far demonstrate that Raman Spectroscopy has the attributes to successfully perform highly accurate intra-operative margin analysis in a clinically relevant environment.

Red Blood Cell Susceptibility to Pneumolysin: CORRELATION WITH MEMBRANE BIOCHEMICAL AND PHYSICAL PROPERTIES.

This study investigated the effect of the biochemical and biophysical properties of the plasma membrane as well as membrane morphology on the susceptibility of human red blood cells to the cholesterol-dependent cytolysin pneumolysin, a key virulence factor of Streptococcus pneumoniae, using single cell studies. We show a correlation between the physical properties of the membrane (bending rigidity and surface and dipole electrostatic potentials) and the susceptibility of red blood cells to pneumolysin-induced hemolysis. We demonstrate that biochemical modifications of the membrane induced by oxidative stress, lipid scrambling, and artificial cell aging modulate the cell response to the toxin. We provide evidence that the diversity of response to pneumolysin in diabetic red blood cells correlates with levels of glycated hemoglobin and that the mechanical properties of the red blood cell plasma membrane are altered in diabetes. Finally, we show that diabetic red blood cells are more resistant to pneumolysin and the related toxin perfringolysin O relative to healthy red blood cells. Taken together, these studies indicate that the diversity of cell response to pneumolysin within a population of human red blood cells is influenced by the biophysical and biochemical status of the plasma membrane and the chemical and/or oxidative stress pre-history of the cell.

GLP-1 analogue-induced weight loss does not improve obesity-induced AT dysfunction.

Glucagon-like peptide-1 (GLP-1) analogues aid weight loss that improves obesity-associated adipose tissue (AT) dysfunction. GLP-1 treatment may however also directly influence AT that expresses the GLP-1 receptor (GLP-1R). The present study aimed to assess the impact of GLP-1 analogue treatment on subcutaneous AT (SCAT) inflammatory and fibrotic responses, compared with weight loss by calorie reduction (control). Among the 39 participants with Type 2 diabetes recruited, 30 age-matched participants were randomized to 4 months treatment with Liraglutide (n=22) or calorie restriction based on dietetic counselling (n=8). Assessments included clinical characteristics and repeated subcutaneous abdominal AT biopsies. Liraglutide resulted in weight loss in most participants (-3.12±1.72 kg, P=0.007) and significant reduction in visceral AT (VAT). It was more effective in lowering fasting glucose, in comparison with weight loss by dieting. However, tumour necrosis factor-α (TNFA) AT-expression (P=0.0005), macrophage chemoattractant protein-1 (MCP-1) expression (P=0.027) and its serum levels (P=0.048) increased with Liraglutide, suggestive of an inflammatory response unlike in the diet arm in which a trend of lower cluster of differentiation 14 (CD14) expression (P=0.09) was found. Liraglutide treatment also increased expression of factors involved in extracellular matrix (ECM) deposition, transforming growth factor-ß (TGFB) and collagen type 1 alpha 1 chain (COL1A1) (TGFB1: before 0.73±0.09 arbitrary units (AU), after 1.00±0.13 AU, P=0.006; COL1A1: 0.84±0.09 AU compared with 1.49±0.26 AU, P=0.026). Liraglutide thus appears to induce an inflammatory response in AT and influences ECM remodelling. Despite its superior effect on glycaemia, Liraglutide does not improve obesity-associated AT dysfunction in subcutaneous tissue. It is yet unclear whether this limits AT storage capacity for lipids. This may be of importance in patients being re-exposed to positive energy balance such as post GLP-1 discontinuation.

Raman spectroscopy and multivariate analysis for the non invasive diagnosis of clinically inconclusive vulval lichen sclerosus.

Vulval lichen sclerosus (LS) is a common inflammatory condition associated with an increased risk of developing vulval carcinoma. Diagnosis is usually clinical although biopsy is necessary if the diagnosis is uncertain or if there is a failure to respond to adequate initial treatment. Raman spectroscopy has the potential to be applied in vivo for near real time objective non-invasive optical diagnosis, avoiding the need for invasive tissue biopsies. The aim of this study was to evaluate the diagnostic performance of Raman spectroscopy for differentiating LS from other vulval conditions in fresh vulval biopsies. Biopsies were analysed from 27 women with suspected LS in whom the attending gynaecologist could not establish the diagnosis on clinical presentation alone. Spectral variance was explored using principal component analysis and in conjunction with the histological diagnoses was used to develop and test a multivariate linear discriminant classification model. This model was validated with leave one sample out cross validation and the diagnostic performance of the technique assessed in comparison with the pathology gold standard. After cross validation the technique was able to correctly differentiate LS from other inflammatory vulval conditions with a sensitivity of 91% and specificity of 80%. This study demonstrates Raman spectroscopy has potential as a technique for in vivo non-invasive diagnosis of vulval skin conditions. Applied in the clinical setting this technique may reduce the need for invasive tissue biopsy. Further in vivo study is needed to assess the ability of Raman spectroscopy to diagnose other vulval conditions before clinical application.