Associations of CKD risk factors and longitudinal changes in urine biomarkers of kidney tubules among women living with HIV.

BACKGROUND: Novel urine biomarkers have enabled the characterization of kidney tubular dysfunction and injury among persons living with HIV, a population at an increased risk of kidney disease. Even though several urine biomarkers predict progressive kidney function decline, antiretroviral toxicity, and mortality in the setting of HIV infection, the relationships among the risk factors for chronic kidney disease (CKD) and urine biomarkers are unclear. METHODS: We assessed traditional and infection-related CKD risk factors and measured 14 urine biomarkers at baseline and at follow-up among women living with HIV in the Women's Interagency Health Study (WIHS). We then used simultaneously adjusted multivariable linear regression models to evaluate the associations of CKD risk factors with longitudinal changes in biomarker levels. RESULTS: Of the 647 women living with HIV in this analysis, the majority (67%) were Black, the median age was 45 years and median follow-up time was 2.5 years. Each traditional and infection-related CKD risk factor was associated with a unique set of changes in urine biomarkers. For example, baseline hemoglobin a1c was associated with worse tubular injury (higher interleukin [IL]-18), proximal tubular reabsorptive dysfunction (higher α1-microglobulin), tubular reserve (lower uromodulin) and immune response to injury (higher chitinase-3-like protein-1 [YKL-40]). Furthermore, increasing hemoglobin a1c at follow-up was associated with further worsening of tubular injury (higher kidney injury molecule-1 [KIM-1] and IL-18), as well as higher YKL-40. HCV co-infection was associated with worsening proximal tubular reabsorptive dysfunction (higher ß2-microglobulin [ß2m]), and higher YKL-40, whereas HIV viremia was associated with worsening markers of tubular and glomerular injury (higher KIM-1 and albuminuria, respectively). CONCLUSIONS: CKD risk factors are associated with unique patterns of biomarker changes among women living with HIV, suggesting that serial measurements of multiple biomarkers may help in detecting and monitoring kidney disease in this setting.

A kinematic model-based analysis framework for 3D Cine-DENSE-validation with an axially compressed gel phantom and application in sheep before and after antero-apical myocardial infarction.

PURPOSE: Myocardial strain is increasingly used to assess left ventricular (LV) function. Incorporation of LV deformation into finite element (FE) modeling environment with subsequent strain calculation will allow analysis to reach its full potential. We describe a new kinematic model-based analysis framework (KMAF) to calculate strain from 3D cine-DENSE (displacement encoding with stimulated echoes) MRI. METHODS: Cine-DENSE allows measurement of 3D myocardial displacement with high spatial accuracy. The KMAF framework uses cine cardiovascular magnetic resonance (CMR) to facilitate cine-DENSE segmentation, interpolates cine-DENSE displacement, and kinematically deforms an FE model to calculate strain. This framework was validated in an axially compressed gel phantom and applied in 10 healthy sheep and 5 sheep after myocardial infarction (MI). RESULTS: Excellent Bland-Altman agreement of peak circumferential (Ecc ) and longitudinal (Ell ) strain (mean difference = 0.021 ± 0.04 and -0.006 ± 0.03, respectively), was found between KMAF estimates and idealized FE simulation. Err had a mean difference of -0.014 but larger variation (±0.12). Cine-DENSE estimated end-systolic (ES) Ecc , Ell and Err exhibited significant spatial variation for healthy sheep. Displacement magnitude was reduced on average by 27%, 42%, and 56% after MI in the remote, adjacent and MI regions, respectively. CONCLUSIONS: The KMAF framework allows accurate calculation of 3D LV Ecc and Ell from cine-DENSE.

Urine Biomarkers of Kidney Tubule Health and Incident CKD Stage 3 in Women Living With HIV: A Repeated Measures Study.

RATIONALE & OBJECTIVE: Single measurements of urinary biomarkers reflecting kidney tubule health are associated with chronic kidney disease (CKD) risk in HIV infection, but the prognostic value of repeat measurements over time is unknown. STUDY DESIGN: Cohort study. SETTING & PARTICIPANTS: 647 women living with HIV infection enrolled in the Women's Interagency Health Study. EXPOSURES: 14 urinary biomarkers of kidney tubule health measured at 2 visits over a 3-year period. OUTCOME: Incident CKD, defined as estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73 m2 at two 6-month visits and an average eGFR decline ≥ 3% per year. ANALYTICAL APPROACH: We used multivariable generalized estimating equations adjusting for CKD risk factors to evaluate baseline, time-updated, and change-over-time biomarker associations with incident CKD. We compared CKD discrimination between models with and without a parsimoniously selected set of biomarkers. RESULTS: During a median 7 years of follow-up, 9.7% (63/647) developed CKD. In multivariable-adjusted analyses, 3 of 14 baseline biomarkers associated with incident CKD. In contrast, 10 of 14 time-updated biomarkers and 9 of 14 biomarkers modeled as change over time associated with incident CKD. Urinary epidermal growth factor (EGF), α1-microglobulin (A1M), and albumin were selected using penalized regression methods. In the time-updated model, lower urinary EGF (risk ratio [RR] per 2-fold higher time-updated biomarker levels, 0.69; 95% CI, 0.58-0.81), higher urinary A1M (RR, 1.47; 95% CI, 1.25-1.73), and higher urinary albumin excretion (RR, 1.21; 95% CI, 1.03-1.42) were jointly associated with increased risk for CKD. Compared with a base model (C statistic, 0.75), CKD discrimination improved after adding urinary EGF, A1M, and albumin values across baseline (C = 0.81), time-updated (C = 0.83), and change-over-time (C = 0.83) models (P < 0.01 for all). LIMITATIONS: Observational design, incident CKD definition limited to eGFR. CONCLUSIONS: Repeat urinary biomarker measurements for kidney tubule health have stronger associations with incident CKD compared with baseline measurements and moderately improve CKD discrimination in women living with HIV infection.

Follow-Up Rates at a Free Ophthalmology Clinic at a Homeless Shelter.

Objective Eye health among the homeless community is important, as poor vision makes this population vulnerable and adds significantly to the social and health burden. There is limited knowledge on patient follow-up rates for their eye conditions and barriers to accessing care in this population. The purpose of this retrospective chart review study is to examine follow-up rates and barriers to care for patients referred from a free, medical-student run ophthalmology clinic at a homeless shelter. Methods All patients evaluated at a free ophthalmology clinic from September 2017 to September 2018 were included; no patients were excluded. If indicated, patients were referred for advanced ophthalmologic care at a local county hospital and free eyeglasses at a nonprofit organization. Primary outcomes were follow-up rates at the county hospital and nonprofit organization. Secondary outcomes included prespecified baseline variables hypothesized to be associated with follow-up rates. These categorical variables were compared with Chi-square testing to determine their association with follow-up rates. The hypothesis being tested was formulated before data collection. Results Of the 68 patients, 84% were males with a mean age of 50 years. Overall, 40 patients were referred for free eyeglasses and 17 to the county hospital. Of those referred, 14 patients presented for free eyeglasses and 7 presented to the county hospital. About 79% of patients with a pre-established primary care provider presented to their appointment compared with 20% of those without one ( p = 0.03). The 44% of patients with a high school diploma presented while all patients without a high school diploma failed to present ( p = 0.04). Vision-threatening conditions identified at the shelter clinic did not affect follow-up rates ( p = 0.79). Conclusion Less than half of referred patients in our study presented to their appointments. Barriers to presentation included no primary care provider and lower educational status, with no improvement in follow-up rates among those referred for vision-threatening conditions. Interventions such as health coaching with particular attention to educating patients on the effects of vision-threatening conditions may be warranted, particularly for those not looped into the health care system and those of lower educational attainment.

Left ventricular geometry during unloading and the end-systolic pressure volume relationship: Measurement with a modified real-time MRI-based method in normal sheep.

The left ventricular (LV) end-systolic (ES) pressure volume relationship (ESPVR) is the cornerstone of systolic LV function analysis. We describe a 2D real-time (RT) MRI-based method (RTPVR) with separate software tools for 1) semi-automatic level set-based shape prior method (LSSPM) of the LV, 2) generation of synchronized pressure area loops and 3) calculation of the ESPVR. We used the RTPVR method to measure ventricular geometry, ES pressure area relationship (ESPAR) and ESPVR during vena cava occlusion (VCO) in normal sheep. 14 adult sheep were anesthetized and underwent measurement of LV systolic function. Ten of the 14 sheep underwent RTMRI and eight of the 14 underwent measurement with conductance catheter; 4 had both RTMRI and conductance measurements. 2D cross sectional RTMRI were performed at apex, mid-ventricle and base levels during separate VCOs. The Dice similarity coefficient was used to compare LSSPM and manual image segmentation and thus determine LSSPM accuracy. LV cross-sectional area, major and minor axis length, axis ratio, major axis orientation angle and ESPAR were measured at each LV level. ESPVR was calculated with a trapezoidal rule. The Dice similarity coefficient between LSSPM and manual segmentation by two readers was 87.31±2.51% and 88.13±3.43%. All cross sections became more elliptical during VCO. The major axis orientation shifted during VCO but remained in the septo-lateral direction. LV chamber obliteration at the apical level occurred during VCO in 7 of 10 sheep that underwent RTMRI. ESPAR was non-linear at all levels. Finally, ESPVR was non-linear because of apical collapse. ESPVR measured by conductance catheter (EES,Index = 2.23±0.66 mmHg/ml/m2) and RT (EES,Index = 2.31±0.31 mmHg/ml/m2) was not significantly different. LSSPM segmentation of 2D RT MRI images is accurate and allows calculation of LV geometry, ESPAR and ESPVR during VCO. In the future, RTPVR will facilitate determination of regional systolic material parameters underlying ESPVR.

Myocardial injection of a thermoresponsive hydrogel with reactive oxygen species scavenger properties improves border zone contractility.

The decrease in contractility in myocardium adjacent (border zone; BZ) to a myocardial infarction (MI) is correlated with an increase in reactive oxygen species (ROS). We hypothesized that injection of a thermoresponsive hydrogel, with ROS scavenging properties, into the MI would decrease ROS and improve BZ function. Fourteen sheep underwent antero-apical MI. Seven sheep had a comb-like copolymer synthesized from N-isopropyl acrylamide (NIPAAm) and 1500 MW methoxy poly(ethylene glycol) methacrylate, (NIPAAm-PEG1500), injected (20 × 0.5 mL) into the MI zone 40 min after MI (MI + NIPAAm-PEG1500) and seven sheep were MI controls. Cardiac MRI was performed 2 weeks before and 6 weeks after MI + NIPAAm-PEG1500. BZ wall thickness at end systole was significantly higher for MI + NIPAAm-PEG1500 (12.32 ± 0.51 mm/m2 MI + NIPAAm-PEG1500 vs. 9.88 ± 0.30 MI; p = .023). Demembranated muscle force development for BZ myocardium 6 weeks after MI was significantly higher for MI + NIPAAm-PEG1500 (67.67 ± 2.61 mN/m2 MI + NIPAAm-PEG1500 vs. 40.53 ± 1.04 MI; p < .0001) but not significantly different from remote myocardium or BZ or non-operated controls. Levels of ROS in BZ tissue were significantly lower in the MI + NIPAAm-PEG1500 treatment group (hydroxyl p = .0031; superoxide p = .0182). We conclude that infarct injection of the NIPAAm-PEG1500 hydrogel with ROS scavenging properties decreased ROS and improved contractile protein function in the border zone 6 weeks after MI.

HIV preexposure prophylaxis with tenofovir disoproxil fumarate/emtricitabine and changes in kidney function and tubular health.

OBJECTIVE: To evaluate the effects of HIV preexposure prophylaxis (PrEP) with tenofovir disoproxial fumurate (TDF)/emtricitabine (FTC) on kidney function and kidney tubular health. DESIGN: The Iniciativa Profilaxis Pre-Exposicion open-label extension (iPrEx-OLE) study enrolled former PrEP trial participants to receive open-label TDF/FTC. This study included 123 iPrEx-OLE participants who demonstrated PrEP adherence. METHODS: We compared estimated glomerular filtration rate calculated using serum creatinine (eGFRcr), serum cystatin C (eGFRcys), and in combination (eGFRcr-cys), and a panel of 14 urine biomarkers reflecting kidney tubular health before and 6 months after PrEP initiation. RESULTS: At baseline, mean eGFRcr, eGFRcys, and eGFRcr-cys were 108.3, 107.0, and 111.1 ml/min per 1.73 m, respectively. Six months after PrEP initiation, eGFRcr declined by -4% (95% CI: -5.7 to -2.4%), eGFRcys declined by -3.3% (95% CI: -8.3 to 1.9%), and eGFRcr-cys declined by -4.1% (95% CI: -7.5 to -0.7%). From the urine biomarker panel, α1-microglobulin and ß2-microglobulin increased by 22.7% (95% CI: 11.8--34.7%) and 14.1% (95% CI: -6.1 to 38.6%), whereas chitinase-3-like 1 protein and monocyte chemoattractant protein-1 decreased by -37.7% (95% CI: -53.0 to -17.3%) and -15.6% (95% CI: -31.6 to 4.2%), respectively. Ten of the 14 urine biomarkers, including albumin, had estimated changes of less than 12% with wide confidence intervals. CONCLUSION: Six months of PrEP with TDF/FTC was associated with decreases in eGFRcr and eGFRcys. We also observed for the first time changes in flour of 14 urine biomarkers reflecting kidney tubular health. These findings demonstrate that PrEP has direct effects on eGFR and the proximal tubule.

Peripheral Artery Disease Is Associated with a Deficiency of Erythrocyte Membrane n-3 Polyunsaturated Fatty Acids.

Population-based data suggest that individuals who consume large dietary amounts of n-3 polyunsaturated fatty acids (PUFA) have lower odds of peripheral artery disease (PAD); however, clinical studies examining n-3 PUFA levels in patients with PAD are sparse. The objective of this study is to compare erythrocyte membrane fatty acid (FA) content between patients with PAD and controls. We conducted a cross-sectional study of 179 vascular surgery outpatients (controls, 34; PAD, 145). A blood sample was drawn and the erythrocyte FA content was assayed using capillary gas chromatography. We calculated the ratio of the n-3 PUFA eicosapentaenoic acid (EPA) to the n-6 PUFA arachidonic acid (ARA) as well as the omega-3 index (O3I), a measure of erythrocyte content of the n-3 PUFA, EPA, and docosahexaenoic acid (DHA), expressed as a percentage of total erythrocyte FA. Compared with controls, patients with PAD smoked more and were more likely to have hypertension and hyperlipidemia (p < 0.05). Patients with PAD had a lower mean O3I (5.0 ± 1.7% vs 6.0 ± 1.6%, p < 0.001) and EPA:ARA ratio (0.04 ± 0.02 vs 0.05 ± 0.05, p < 0.001), but greater mean total saturated fats (39.5 ± 2.5% vs 38.5 ± 2.6%, p = 0.01). After adjusting for several patient characteristics, comorbidities, and medications, an absolute decrease of 1% in the O3I was associated with 39% greater odds of PAD (odds ratio [OR] 1.39, 95% confidence interval [CI] 1.03-1.86, and p = 0.03). PAD was associated with a deficiency of erythrocyte n-3 PUFA, a lower EPA:ARA ratio, and greater mean total saturated fats. These alterations in FA content may be involved in the pathogenesis or development of poor outcomes in PAD.

Leptinemia is Associated With Peripheral Artery Disease.

BACKGROUND: Leptin, adiponectin, and resistin are in a class of hormones called adipokines that are produced by adipocytes and have been implicated in the causal pathway of atherosclerosis. We examined the association between adipokine levels and peripheral artery disease (PAD), hypothesizing that after adjusting for fat mass, leptin and resistin would be higher, whereas adiponectin would be lower, in patients with PAD. METHODS: A cross-sectional sample of 179 predominately male (97%) vascular surgery outpatients was recruited from the San Francisco Veterans Affairs Medical Center (SFVAMC). PAD was defined as either an ankle-brachial index < 0.9 plus symptoms of claudication or prior revascularization for symptomatic PAD (n = 141). Controls had an ankle-brachial index ≥0.9 and no history of atherosclerotic disease (n = 38). Adipokines were assayed using commercially available ELISA kits and values were log-transformed. Fat mass was measured using bioelectrical impedance. RESULTS: In an analysis adjusting for body mass index (BMI) and atherosclerotic risk factors, higher serum leptin was associated with PAD (OR 2.54, 95% CI 1.07-6.01, P = 0.03), whereas high molecular weight adiponectin was inversely associated, though not significantly (OR 0.60, 95% CI 0.33-1.08, P = 0.09). Resistin was not associated with PAD. Sensitivity analyses using fat mass/height2 rather than BMI yielded similar results. CONCLUSIONS: These results indicate that after adjusting for BMI or fat mass, serum leptin levels are positively and independently associated with PAD, whereas high molecular weight adiponectin might be inversely associated. Using a more representative, nonveteran sample, further investigations should focus on the potential role of adipokines in the pathophysiology of PAD as well as determine whether leptin levels have clinical utility in predicting PAD outcomes.

Radial Artery Tonometry is Associated With Major Adverse Cardiac Events in Patients With Peripheral Artery Disease.

BACKGROUND: Peripheral artery disease (PAD) is associated with increased arterial stiffness, as measured by an increasing radial artery augmentation index (AIX). However, it has not yet been clearly demonstrated whether AIX is associated with adverse cardiovascular outcomes in a PAD population. MATERIALS AND METHODS: Seventy-two patients with PAD were recruited between 2011 and 2016. Radial artery applanation tonometry was performed at a baseline visit, and the central AIX, normalized to 75 beats/min, and the peripheral AIX were calculated using pulse wave analysis. Incident major adverse cardiac events (MACEs) were identified by subsequent chart review. RESULTS: Study subjects had comorbidities commonly associated with PAD including a high prevalence of hypertension (93%), hyperlipidemia (85%), coronary artery disease (39%), and diabetes mellitus (39%). During a median follow-up period of 34 mo (interquartile range 29-38), 14 patients experienced a MACE. In a univariate Cox proportional hazards model, a 10-unit increase in the peripheral AIX was significantly associated with a 54% increased rate of MACE (hazard ratio [HR] 1.54, 95% confidence interval [CI] 1.06-2.22, P = 0.02), but central AIX, normalized to 75 beats/min, was not (HR 1.33, 95% CI 0.71-2.47, P = 0.37). In a multivariable model adjusted for coronary artery disease, age, and Rutherford category the peripheral AIX remained significantly associated with MACE (HR 1.70, 95% CI 1.10-2.62, P = 0.02). CONCLUSIONS: Increased arterial stiffness, as measured by the peripheral AIX, was independently associated with an increased rate of MACE in patients with PAD. The use of radial artery tonometry should be contemplated as a tool for risk stratification in patients with PAD.

Serum resistin is associated with impaired endothelial function and a higher rate of adverse cardiac events in patients with peripheral artery disease.

OBJECTIVE: Resistin is a hormone that has been associated with metabolic syndrome and cardiovascular disease. The role of resistin in patients with peripheral artery disease (PAD) has not been fully explored. This study seeks to understand the relationship between serum resistin, vascular function, and cardiovascular outcomes in patients with PAD. METHODS: There were 106 patients with PAD who were recruited between 2011 and 2016. Patients attended a baseline visit during which a comprehensive vascular physiology assessment including medical and surgical history, radial artery tonometry, and flow mediated-vasodilation (FMD) was completed. A blood sample was drawn, and serum resistin was assayed using enzyme-linked immunosorbent assay kits. Using the time of study enrollment as the time of origin, incident major adverse cardiac events (MACEs) were identified by subsequent chart review and defined as a composite end point of myocardial infarction, coronary revascularization, transient ischemic attack, stroke, or death from a cardiac cause. RESULTS: Patients had a mean age of 68 ± 8 years, were largely white (75%), and had comorbidities commonly associated with PAD including hypertension (92%), hyperlipidemia (87%), coronary artery disease (37%), and diabetes mellitus (38%). After stratification by resistin quartile, higher resistin quartiles were significantly associated with an older age, a greater number of pack-years smoked, and a lower estimated glomerular filtration rate. Despite similar comorbidities and medication use, endothelial function, as measured by FMD, was significantly lower with increasing resistin quartile (I, 9.1% ± 3.3%; II, 7.1% ± 3.5%; III, 5.8% ± 4.0%; IV, 5.6% ± 3.5%; P = .002). In multivariable linear regression, higher resistin quartiles (III and IV) were associated with lower FMD relative to quartile I after adjusting for several patient characteristics, medications, and comorbidities (III, -2.26 [95% confidence interval (CI), -4.51 to -0.01; P = .05]; IV, -2.53 [95% CI, -4.87 to -0.20; P = .03]). During a median follow-up period of 36 months (interquartile range, 29-45 months), 21 patients experienced the primary end point. In a Cox proportional hazards model adjusted for smoking status, coronary artery disease, and age, each 1 ng/mL increase in resistin was associated with a 10% increased risk of MACEs (hazard ratio, 1.10; 95% CI, 1.00-1.20; P = .04). CONCLUSIONS: In patients with PAD, higher levels of resistin were associated with impaired endothelial function and an increased rate of MACEs. These results suggest that resistin may be a marker or effector of impaired vascular physiology and adverse cardiac outcomes in patients with PAD. Further research is needed to determine the potential mechanisms by which resistin may impair endothelial function and increase MACEs in this population.

Depression severity is associated with increased inflammation in veterans with peripheral artery disease.

The present study examines the association between depressive symptoms and inflammatory markers in peripheral artery disease (PAD) to better understand the mechanistic relationship between depression and PAD. A cross-sectional sample of 117 patients with PAD (97% male, 76% Caucasian) was recruited from the San Francisco Veterans Affairs Medical Center. Patients were categorized into three subgroups based upon current depressive symptom severity, as defined by Patient Health Questionnaire-8 scores: no symptoms (score of 0-4, n = 62), mild symptoms (score of 5-9, n = 33), and moderate/severe symptoms (score ≥ 10, n = 22). Serum levels of high-sensitivity C-reactive protein (hs-CRP), interleukin-6 (IL-6), soluble intercellular adhesion molecule-1 (ICAM-1), and tumor necrosis factor-alpha (TNF-α) were assayed and log-transformed for multivariable analysis. To decrease the possibility of Type 1 errors, inflammatory markers were standardized and summed to create a total inflammatory score. In a multivariable analysis controlling for demographics, PAD severity, and atherosclerotic risk factors, mild and moderate/severe depressive symptoms were predictive of a higher total inflammatory score when compared to the group with no symptoms (mild symptoms p = 0.04, moderate/severe symptoms p = 0.007). Exploratory multivariable analyses of individual inflammatory markers found IL-6 levels were significantly higher in the moderate/severe symptoms group ( p = 0.006) than in the no symptoms group. Moreover, hs-CRP and ICAM-1 trended upwards with increasing depression severity. TNF-α was not associated with depression severity. We conclude that depressive symptom severity was independently associated with greater inflammation in PAD. Future research should examine the strength and directionality of this association through larger prospective cohort studies, as well as investigate the pathophysiological mechanisms responsible.

Characterizing the relationship between flow-mediated vasodilation and radial artery tonometry in peripheral artery disease.

BACKGROUND: Arterial stiffness, measured by the augmentation index (AIX) from radial artery tonometry, and endothelial dysfunction, measured by brachial-artery flow-mediated vasodilation (FMD), have each been associated with increased risk of cardiovascular events. However, their interrelationship in peripheral artery disease (PAD) patients is poorly understood. MATERIALS AND METHODS: In a cross-sectional analysis of 123 vascular surgery outpatients, the association between FMD and AIX was examined in controls with atherosclerotic risk factors (n = 32) and patients with PAD (n = 91). PAD was defined as claudication symptoms with an ankle-brachial index of <0.9 or a history of revascularization for symptomatic PAD. Controls had an ankle-brachial index ≥0.9 and no history of atherosclerotic vascular disease. RESULTS: Compared to controls, patients with PAD had lower FMD (6.3 ± 3.8 versus 8.4 ± 3.7, P = 0.008), while central AIX normalized to 75 beats per minute (25.5 ± 9.0 versus 19.3 ± 8.6, P = 0.001) and peripheral AIX (91.3 ± 14.5 versus 81.3 ± 11.4, P = 0.001) were higher. FMD was not significantly correlated with either central or peripheral AIX (central AIX: P = 0.58; peripheral AIX: P = 0.89) across the entire cohort, or in either the patients with PAD (central AIX: P = 0.48; peripheral AIX: P = 0.23) or controls (central AIX: P = 0.43; peripheral AIX: P = 0.92). In a multivariate model including FMD, higher AIX remained independently associated with PAD. CONCLUSIONS: In an analysis of vascular surgery outpatients, no correlation between FMD and AIX was detected. Larger prospective studies are needed to determine whether the inclusion of both parameters improves predictive models for the early identification and potential risk stratification of PAD patients.

Short term doxycycline treatment induces sustained improvement in myocardial infarction border zone contractility.

Decreased contractility in the non-ischemic border zone surrounding a MI is in part due to degradation of cardiomyocyte sarcomeric components by intracellular matrix metalloproteinase-2 (MMP-2). We recently reported that MMP-2 levels were increased in the border zone after a MI and that treatment with doxycycline for two weeks after MI was associated with normalization of MMP-2 levels and improvement in ex-vivo contractile protein developed force in the myocardial border zone. The purpose of the current study was to determine if there is a sustained effect of short term treatment with doxycycline (Dox) on border zone function in a large animal model of antero-apical myocardial infarction (MI). Antero-apical MI was created in 14 sheep. Seven sheep received doxycycline 0.8 mg/kg/hr IV for two weeks. Cardiac MRI was performed two weeks before, and then two and six weeks after MI. Two sheep died prior to MRI at six weeks from surgical/anesthesia-related causes. The remaining 12 sheep completed the protocol. Doxycycline induced a sustained reduction in intracellular MMP-2 by Western blot (3649±643 MI+Dox vs 9236±114 MI relative intensity; p = 0.0009), an improvement in ex-vivo contractility (65.3±2.0 MI+Dox vs 39.7±0.8 MI mN/mm2; p<0.0001) and an increase in ventricular wall thickness at end-systole 1.0 cm from the infarct edge (12.4±0.6 MI+Dox vs 10.0±0.5 MI mm; p = 0.0095). Administration of doxycycline for a limited two week period is associated with a sustained improvement in ex-vivo contractility and an increase in wall thickness at end-systole in the border zone six weeks after MI. These findings were associated with a reduction in intracellular MMP-2 activity.

Association between arterial stiffness and peripheral artery disease as measured by radial artery tonometry.

OBJECTIVE: Arterial stiffness and peripheral artery disease (PAD) are both associated with an elevated risk of major adverse cardiac events; however, the association between arterial stiffness and PAD is less well characterized. The goal of this study was to examine the association between parameters of radial artery tonometry, a noninvasive measure of arterial stiffness, and PAD. METHODS: We conducted a cross-sectional study of 134 vascular surgery outpatients (controls, 33; PAD, 101) using arterial applanation tonometry. Central augmentation index (AIX) normalized to 75 beats/min and peripheral AIX were measured using radial artery pulse wave analysis. Pulse wave velocity was recorded at the carotid and femoral arteries. PAD was defined as symptomatic claudication with an ankle-brachial index of <0.9 or a history of peripheral revascularization. Controls had no history of atherosclerotic vascular disease and an ankle-brachial index ≥0.9. RESULTS: Among the 126 participants with high-quality tonometry data, compared with controls (n = 33), patients with PAD (n = 93) were older, with higher rates of hypertension, hyperlipidemia, diabetes, and smoking (P < .05). Patients with PAD also had greater arterial stiffness as measured by central AIX, peripheral AIX, and pulse wave velocity (P < .05). In a multivariable model, a significantly increased odds of PAD was associated with each 10-unit increase in central AIX (odds ratio, 2.1; 95% confidence interval, 1.1-3.9; P = .03) and peripheral AIX (odds ratio, 1.9; 95% confidence interval, 1.2-3.2; P = .01). In addition, central and peripheral AIX were highly correlated (r120 = 0.76; P < .001). CONCLUSIONS: In a cross-sectional analysis, arterial stiffness as measured by the AIX is independently associated with PAD, even when adjusting for several atherosclerotic risk factors. Further prospective data are needed to establish whether radial artery tonometry could be a tool for risk stratification in the PAD population.

Two Distinct Isoforms of Matrix Metalloproteinase-2 Are Associated with Human Delayed Kidney Graft Function.

Delayed graft function (DGF) is a frequent complication of renal transplantation, particularly in the setting of transplantation of kidneys derived from deceased donors and expanded-criteria donors. DGF results from tubular epithelial cell injury and has immediate and long term consequences. These include requirement for post-transplantation dialysis, increased incidence of acute rejection, and poorer long-term outcomes. DGF represents one of the clearest clinical examples of renal acute ischemia/reperfusion injury. Experimental studies have demonstrated that ischemia/reperfusion injury induces the synthesis of the full length secreted isoform of matrix metalloproteinase-2 (FL-MMP-2), as well as an intracellular N-terminal truncated MMP-2 isoform (NTT-MMP-2) that initiates an innate immune response. We hypothesized that the two MMP-2 isoforms mediate tubular epithelial cell injury in DGF. Archival renal biopsy sections from 10 protocol biopsy controls and 41 cases with a clinical diagnosis of DGF were analyzed for the extent of tubular injury, expression of the FL-MMP-2 and NTT-MMP-2 isoforms by immunohistochemistry (IHC), in situ hybridization, and qPCR to determine isoform abundance. Differences in transcript abundance were related to tubular injury score. Markers of MMP-2-mediated injury included TUNEL staining and assessment of peritubular capillary density. There was a clear relationship between tubular epithelial cell expression of both FL-MMP-2 and NTT-MMP-2 IHC with the extent of tubular injury. The MMP-2 isoforms were detected in the same tubular segments and were present at sites of tubular injury. qPCR demonstrated highly significant increases in both the FL-MMP-2 and NTT-MMP-2 transcripts. Statistical analysis revealed highly significant associations between FL-MMP-2 and NTT-MMP-2 transcript abundance and the extent of tubular injury, with NTT-MMP-2 having the strongest association. We conclude that two distinct MMP-2 isoforms are associated with tubular injury in DGF and offer novel therapeutic targets for the prevention of this disorder.

Myofilament dysfunction contributes to impaired myocardial contraction in the infarct border zone.

After myocardial infarction, a poorly contracting nonischemic border zone forms adjacent to the infarct. The cause of border zone dysfunction is unclear. The goal of this study was to determine the myofilament mechanisms involved in postinfarction border zone dysfunction. Two weeks after anteroapical infarction of sheep hearts, we studied in vitro isometric and isotonic contractions of demembranated myocardium from the infarct border zone and a zone remote from the infarct. Maximal force development (Fmax) of the border zone myocardium was reduced by 31 ± 2% versus the remote zone myocardium (n = 6/group, P < 0.0001). Decreased border zone Fmax was not due to a reduced content of contractile material, as assessed histologically, and from myosin content. Furthermore, decreased border zone Fmax did not involve altered cross-bridge kinetics, as assessed by muscle shortening velocity and force development kinetics. Decreased border zone Fmax was associated with decreased cross-bridge formation, as assessed from muscle stiffness in the absence of ATP where cross-bridge formation should be maximized (rigor stiffness was reduced 34 ± 6%, n = 5, P = 0.011 vs. the remote zone). Furthermore, the border zone myocardium had significantly reduced phosphorylation of myosin essential light chain (ELC; 41 ± 10%, n = 4, P < 0.05). However, for animals treated with doxycycline, an inhibitor of matrix metalloproteinases, rigor stiffness and ELC phosphorylation were not reduced in the border zone myocardium, suggesting that doxycycline had a protective effect. In conclusion, myofilament dysfunction contributes to postinfarction border zone dysfunction, myofilament dysfunction involves impaired cross-bridge formation and decreased ELC phosphorylation, and matrix metalloproteinase inhibition may be beneficial for limiting postinfarct border zone dysfunction.