Nanoanalytical analysis of bisphosphonate-driven alterations of microcalcifications using a 3D hydrogel system and in vivo mouse model.

Vascular calcification predicts atherosclerotic plaque rupture and cardiovascular events. Retrospective studies of women taking bisphosphonates (BiPs), a proposed therapy for vascular calcification, showed that BiPs paradoxically increased morbidity in patients with prior acute cardiovascular events but decreased mortality in event-free patients. Calcifying extracellular vesicles (EVs), released by cells within atherosclerotic plaques, aggregate and nucleate calcification. We hypothesized that BiPs block EV aggregation and modify existing mineral growth, potentially altering microcalcification morphology and the risk of plaque rupture. Three-dimensional (3D) collagen hydrogels incubated with calcifying EVs were used to mimic fibrous cap calcification in vitro, while an ApoE-/- mouse was used as a model of atherosclerosis in vivo. EV aggregation and formation of stress-inducing microcalcifications was imaged via scanning electron microscopy (SEM) and atomic force microscopy (AFM). In both models, BiP (ibandronate) treatment resulted in time-dependent changes in microcalcification size and mineral morphology, dependent on whether BiP treatment was initiated before or after the expected onset of microcalcification formation. Following BiP treatment at any time, microcalcifications formed in vitro were predicted to have an associated threefold decrease in fibrous cap tensile stress compared to untreated controls, estimated using finite element analysis (FEA). These findings support our hypothesis that BiPs alter EV-driven calcification. The study also confirmed that our 3D hydrogel is a viable platform to study EV-mediated mineral nucleation and evaluate potential therapies for cardiovascular calcification.

Zooming in on the genesis of atherosclerotic plaque microcalcifications.

Epidemiological evidence conclusively demonstrates that calcium burden is a significant predictor of cardiovascular morbidity and mortality; however, the underlying mechanisms remain largely unknown. These observations have challenged the previously held notion that calcification serves to stabilize the atherosclerotic plaque. Recent studies have shown that microcalcifications that form within the fibrous cap of the plaques lead to the accrual of plaque-destabilizing mechanical stress. Given the association between calcification morphology and cardiovascular outcomes, it is important to understand the mechanisms leading to calcific mineral deposition and growth from the earliest stages. We highlight the open questions in the field of cardiovascular calcification and include a review of the proposed mechanisms involved in extracellular vesicle-mediated mineral deposition.

Genesis and growth of extracellular-vesicle-derived microcalcification in atherosclerotic plaques.

Clinical evidence links arterial calcification and cardiovascular risk. Finite-element modelling of the stress distribution within atherosclerotic plaques has suggested that subcellular microcalcifications in the fibrous cap may promote material failure of the plaque, but that large calcifications can stabilize it. Yet the physicochemical mechanisms underlying such mineral formation and growth in atheromata remain unknown. Here, by using three-dimensional collagen hydrogels that mimic structural features of the atherosclerotic fibrous cap, and high-resolution microscopic and spectroscopic analyses of both the hydrogels and of calcified human plaques, we demonstrate that calcific mineral formation and maturation results from a series of events involving the aggregation of calcifying extracellular vesicles, and the formation of microcalcifications and ultimately large calcification areas. We also show that calcification morphology and the plaque's collagen content-two determinants of atherosclerotic plaque stability-are interlinked.

Cardiovascular calcification: current controversies and novel concepts.

Cardiovascular calcification is a commonly observed but incompletely understood mechanism of increased atherosclerotic plaque instability and accelerated aortic valve stenosis. Traditional histological staining and imaging techniques are nonspecific for the type of mineral present in calcified tissues, information that is critical for proper validation of in vitro and in vivo models. This review highlights current gaps in our understanding of the biophysical implications and the cellular mechanisms of valvular and vascular calcification and how they may differ between the two tissue types. We also address the hindrances of current cell culture systems, discussing novel platforms and important considerations for future studies of cardiovascular calcification.

Effect of insulin feedback on closed-loop glucose control: a crossover study.

BACKGROUND: Closed-loop (CL) insulin delivery systems utilizing proportional-integral-derivative (PID) controllers have demonstrated susceptibility to late postprandial hypoglycemia because of delays between insulin delivery and blood glucose (BG) response. An insulin feedback (IFB) modification to the PID algorithm has been introduced to mitigate this risk. We examined the effect of IFB on CL BG control. METHODS: Using the Medtronic ePID CL system, four subjects were studied for 24 h on PID control and 24 h during a separate admission with the IFB modification (PID + IFB). Target glucose was 120 mg/dl; meals were served at 8:00 AM, 1:00 PM, and 6:00 PM and were identical for both admissions. No premeal manual boluses were given. Reference BG excursions, defined as incremental glucose rise from premeal to peak, and postprandial BG area under the curve (AUC; 0-5 h) were compared. Results are reported as mean ± standard deviation. RESULTS: The PID + IFB control resulted in higher mean BG levels compared with PID alone (153 ± 54 versus 133 ± 56 mg/dl; p < .0001). Postmeal BG excursions (114 ± 28 versus 114 ± 47 mg/dl) and AUCs (285 ± 102 versus 255 ± 129 mg/dl/h) were similar under both conditions. Total insulin delivery averaged 57 ± 20 U with PID versus 45 ± 13 U with PID + IFB (p = .18). Notably, eight hypoglycemic events (BG < 60 mg/dl) occurred during PID control versus none during PID + IFB. CONCLUSIONS: Addition of IFB to the PID controller markedly reduced the occurrence of hypoglycemia without increasing meal-related glucose excursions. Higher average BG levels may be attributable to differences in the determination of system gain (Kp) in this study. The prevention of postprandial hypoglycemia suggests that the PID + IFB algorithm may allow for lower target glucose selection and improved overall glycemic control.

Effect of pramlintide on prandial glycemic excursions during closed-loop control in adolescents and young adults with type 1 diabetes.

OBJECTIVE: Even under closed-loop (CL) conditions, meal-related blood glucose (BG) excursions frequently exceed target levels as a result of delays in absorption of insulin from the subcutaneous site of infusion. We hypothesized that delaying gastric emptying with preprandial injections of pramlintide would improve postprandial glycemia by allowing a better match between carbohydrate and insulin absorptions. RESEARCH DESIGN AND METHODS: Eight subjects (4 female; age, 15-28 years; A1C, 7.5 ± 0.7%) were studied for 48 h on a CL insulin-delivery system with a proportional integral derivative algorithm with insulin feedback: 24 h on CL control alone (CL) and 24 h on CL control plus 30-µg premeal injections of pramlintide (CLP). Target glucose was set at 120 mg/dL; timing and contents of meals were identical on both study days. No premeal manual boluses were given. Differences in reference BG excursions, defined as the incremental glucose rise from premeal to peak, were compared between conditions for each meal. RESULTS: CLP was associated with overall delayed time to peak BG (2.5 ± 0.9 vs. 1.5 ± 0.5 h; P < 0.0001) and reduced magnitude of glycemic excursion (88 ± 42 vs. 113 ± 32 mg/dL; P = 0.006) compared with CL alone. Pramlintide effects on glycemic excursions were particularly evident at lunch and dinner, in association with higher premeal insulin concentrations at those mealtimes. CONCLUSIONS: Pramlintide delayed the time to peak postprandial BG and reduced the magnitude of prandial BG excursions. Beneficial effects of pramlintide on CL may in part be related to higher premeal insulin levels at lunch and dinner compared with breakfast.

Influenza vaccination rates among pharmacists.

OBJECTIVES: To quantify influenza vaccination rates and determine perceived barriers to influenza vaccination among U.S. pharmacists from various practice settings. DESIGN: Prospective study. SETTING: United States in 2008. PARTICIPANTS: 1,028 respondents, including 895 pharmacists. INTERVENTION: A survey request was distributed manually at the 2008 National Community Pharmacists Association annual meeting, and an initial e-mail was sent with two follow-up e-mails to all pharmacists who receive e-mails via Pharmacist e-link. MAIN OUTCOME MEASURES: Vaccination rates and barriers to vaccination among pharmacists. RESULTS: Pharmacists reported an influenza vaccination rate of 78%, with coverage varying across practice settings: hospital (88%), academia (86%), clinic (83%), and community (75%). Employers infrequently required the influenza vaccine as a condition of employment (7%), and slightly more than one-half (58%) compensated pharmacists for being vaccinated; both of these were significantly associated with higher influenza vaccination rates (P < 0.001 for both). One-quarter of pharmacists (26%) expressed at least one issue regarding the influenza vaccine. Pharmacists were significantly less likely to be vaccinated if they expressed a concern (91% vs. 43%, P < 0.0001). Community pharmacists were significantly less likely to be compensated for receiving the influenza vaccination and significantly more likely to express one or more concerns than pharmacists from any other practice setting. CONCLUSION: Pharmacists reported high influenza vaccination rates overall, with slight variability among practice settings. Although employers infrequently required influenza vaccination, approximately one-half of employers compensated their pharmacists for being vaccinated. Employer incentives and pharmacist attitudes were highly correlated with influenza vaccination.

Guideline-concordant antibiotic use and survival among patients with community-acquired pneumonia admitted to the intensive care unit.

OBJECTIVE: This study evaluated the survival benefit of US community-acquired pneumonia (CAP) practice guidelines in the intensive care unit (ICU) setting. METHODS: We conducted a retrospective cohort study of adult patients with CAP who were admitted to 5 community hospital ICUs between November 1, 1999, and April 30, 2000. The guidelines for antibiotic prescriptions were the 2007 Infectious Diseases Society of America/American Thoracic Society guidelines. Guideline-concordant antimicrobial therapy was defined as a beta-lactam plus fluoroquinolone or macrolide, antipseudomonal beta-lactam plus fluoroquinolone, or antipseudomonal beta-lactam plus aminoglycoside plus fluoroquinolone or macrolide. Patients with a documented beta-lactam allergy were considered to have received guideline-concordant therapy if they received a fluoroquinolone with or without clindamycin, or aztreonam plus fluoroquinolone with or without aminoglycoside. All other antibiotic regimens were considered to be guideline discordant. Time to clinical stability, time to oral antibiotics, length of hospital stay, and in-hospital mortality were evaluated with regression models that included the outcome as the dependent variable, guideline-concordant antibiotic therapy as the independent variable, and the Pneumonia Severity Index (PSI) score and facility as covariates. RESULTS: The median age of the 129 patients included in the study was 71 years (interquartile range, 60-79 years). Sixty-two of 129 patients (48%) were male. Comorbidities included liver dysfunction (7 patients [5%]), heart failure (62 [48%]), renal dysfunction (39 [30%]), cerebrovascular disease (21 [16%]), and cancer (14 [11%]). The median (25th-75th percentile) PSI score was 119 (98-142), and overall mortality was 19% (25 patients). Patient demographics were similar between groups. Fifty-three patients (41%) received guideline-endorsed therapies. Guideline-discordant therapy was associated with an increase in inpatient mortality (25% vs 11%; odds ratio = 2.99 [95% CI, 1.08-9.54]). Receipt of guideline-concordant antibiotics was not associated with reductions in time to clinical stability, time to oral antibiotics, or length of hospital stay when patients who died were excluded from the analysis. CONCLUSION: Guideline-concordant empiric antibiotic therapy was associated with improved survival among these patients with CAP who were admitted to 5 ICUs.