The quantity and quality of cardiovascular fat at mid-life and future cognitive performance among women: The SWAN cardiovascular fat ancillary study

INTRODUCTION

Cardiovascular fat is a novel risk factor that may link to dementia. Fat volume and radiodensity are measurements of fat quantity and quality, respectively. Importantly, high fat radiodensity could indicate healthy or adverse metabolic processes.

METHODS

The associations of cardiovascular fat (including epicardial, paracardial, and thoracic perivascular adipose tissue [PVAT]) quantity and quality assessed at mean age of 51 with subsequent cognitive performance measured repeatedly over 16 years of follow-up were examined using mixed models among 531 women.

RESULTS

Higher thoracic PVAT volume was associated with a higher future episodic memory (β[standard error (SE)] = 0.08 [0.04], P = 0.033), while higher thoracic PVAT radiodensity with lower future episodic (β[SE] = -0.06 [0.03], P = 0.045) and working (β[SE] = -0.24 [0.08], P = 0.003) memories. The latter association is prominent at higher volume of thoracic PVAT.

DISCUSSION

Mid-life thoracic PVAT may have a distinct contribution to future cognition possibly due to its distinct adipose tissue type (brown fat) and anatomical proximity to the brain circulation.

HIGHLIGHTS

Higher mid-life thoracic perivascular adipose tissue (thoracic PVAT) volume is related to a better future episodic memory in women. Higher mid-life thoracic PVAT radiodensity is related to worse future working and episodic memories. Negative association of high thoracic PVAT radiodensity with working memory is prominent at higher thoracic PVAT volume. Mid-life thoracic PVAT is linked to future memory loss, an early sign of Alzheimer's disease. Mid-life women's epicardial and paracardial fat are not related to future cognition.

Learning Clinical Concepts for Predicting Risk of Progression to Severe COVID-19

With COVID-19 now pervasive, identification of high-risk individuals is crucial. Using data from a major healthcare provider in Southwestern Pennsylvania, we develop survival models predicting severe COVID-19 progression. In this endeavor, we face a tradeoff between more accurate models relying on many features and less accurate models relying on a few features aligned with clinician intuition. Complicating matters, many EHR features tend to be under-coded degrading the accuracy of smaller models. In this study we develop two sets of high-performance risk scores: (i) an unconstrained model built from all available features; and (ii) a pipeline that learns a small set of clinical concepts before training a risk predictor. Learned concepts boost performance over the corresponding features (C-index 0.858 vs. 0.844) and demonstrate improvements over (i) when evaluated out-of-sample (subsequent time periods). Our models outperform previous works (C-index 0.844-0.872 vs. 0.598-0.810).

Association of Hydroxychloroquine Use With Decreased Incident Atrial Fibrillation in Systemic Lupus Erythematosus

OBJECTIVE

To study the relationship between hydroxychloroquine (HCQ) use and new-onset atrial fibrillation in patients with systemic lupus erythematosus (SLE).

METHODS

A retrospective cohort of adult patients with SLE was constructed from December 1, 2014 to May 30, 2017. Patients were categorized as either HCQ users or nonusers. The primary outcome was incident atrial fibrillation. Secondary outcomes included incident ventricular arrhythmias (composite of ventricular tachycardia, ventricular fibrillation, or torsades de pointes). Outcomes were adjudicated by review of the electronic health record. Statistical analyses included simple and multivariable logistic regression tests to estimate the association between HCQ use and incident atrial fibrillation after adjusting for relevant confounders. Propensity score matching analysis was completed.

RESULTS

Our study included 1,647 patients with SLE, of which 917 were HCQ users and 730 were nonusers. A total of 23 atrial fibrillation events occurred, including 3 in HCQ users and 20 in nonusers. Logistic regression analysis showed an odds ratio (OR) of 0.12 (95% confidence interval [95% CI] 0.034-0.39, P = 0.0005) for incident atrial fibrillation and 2.39 (95% CI 0.25-23.0, P = 0.45) for ventricular arrhythmias. Results remained significant in the fully adjusted and propensity score-matched models.

CONCLUSION

In this exploratory study, HCQ use was associated with an 88% decrease in the risk of incident atrial fibrillation in patients with SLE. Considering the increased cardiovascular risk in SLE, incorporation of HCQ into the regimen may be beneficial for both disease manifestations and reducing the risk of atrial fibrillation. Further studies would be needed to confirm the antifibrillatory benefit of this relatively safe and low-cost medication.

Dual plate fixation results in improved union rates in comminuted distal femur fractures compared to single plate fixation

Purpose

The treatment of distal femur fractures with extensive metaphyseal comminution is frequently complicated by high rates of nonunion and varus collapse. Dual plating with lateral and medial locking plates for these types of fractures has shown promising results in the recent literature. We hypothesize that dual plating of comminuted distal femur fractures leads to higher union rates and lower revision rates compared to an isolated lateral locking plate.

Methods

A retrospective medical chart review between January 2015 and December 2017 was conducted. Inclusion criteria included patients 18 years of age and older who sustained a complex distal femur fracture (AO/OTA 33-C2/33-C3 or periprosthetic fracture with significant metaphyseal comminution) and at least 6 months of follow up. Patients with simple fracture patterns, alternative fixation methods, and inadequate follow up were excluded. All patients in the single plating group were treated with a lateral distal femoral locking plate using a lateral approach. In the patients treated with dual plating, an extensile parapatellar approach was utilized for fracture reduction and placement of an adjunctive medial plate. Demographic information, fracture types, injury severity score (ISS), medical comorbidities, type of surgical fixation, union rates, complications, knee range of motion, time to follow up, and need for revision surgery were extrapolated from the medical charts for analysis.

Results

Twenty-one patients were included in the study. Thirteen patients underwent single plate fixation and 8 underwent dual plate fixation. There were no significant differences in demographics, number of co-morbidities, fracture classification, or ISS between single and dual plate groups (p > 0.05 for all). There was a statistically significant difference in union rates between the single plate group (6 nonunions, 4 unions, and 3 delayed unions) and the dual plate group, with no nonunions or delayed unions (p = 0.0049). Although not statistically significant, 4 patients treated with single plating underwent revision ORIF, compared to none in the dual plating group (p = 0.13). There were no significant differences in time to follow up, time to full weight bearing, or infection rates (p > 0.1 for all).

Conclusion

Based on these results, the medial and lateral locked plating technique demonstrates a higher union rate, with possible lower rates of revision surgery, compared to a single lateral plate in highly comminuted distal femur fractures.

Level of evidence

Level 3. Retrospective Cohort Study.

Associations of cardiovascular fat radiodensity and vascular calcification in midlife women: The SWAN cardiovascular fat ancillary study

BACKGROUND AND AIMS

Fat radiodensity, measured via CT Hounsfield units (HU), is a potential marker of fat quality. We sought to determine the cross-sectional associations of total heart fat (TAT) and aortic perivascular fat (PVAT) radiodensity with cardiovascular risk factors, coronary artery calcification (CAC), and aortic calcification (AC) in midlife women.

METHODS

Fat radiodensity, CAC, and AC were quantified using CT scans. A total of 528 women (mean age: 50.9 ± 2.9 years; 37% Black) were included in analyses.

RESULTS

Women in the lowest TAT radiodensity tertile were more likely to have adverse cardiovascular risk factors. Independent of cardiovascular risk factors, women in the middle and high TAT radiodensity tertiles were less likely to have CAC (OR (95% CI): 0.32 (0.18, 0.59); 0.43 (0.24, 0.78), respectively) compared with women in the lowest TAT radiodensity tertile. Although adjusting for BMI attenuated the overall association, women in the middle TAT radiodensity tertile remained at significantly lower odds of CAC when compared to the low radiodensity tertile, 0.47 (0.24, 0.93), p=0.03. No significant associations were found for PVAT radiodensity and calcification measures in multivariable analysis.

CONCLUSIONS

Lower TAT radiodensity was associated with a less favorable cardiometabolic profile. Women with mid-range TAT radiodensity values had a lower odds of CAC presence, independent of CVD risk factors and BMI. More research is necessary to understand radiodensity as a surrogate marker of fat quality in midlife women.

3D MicroCT spatial and temporal characterization of thoracic aorta perivascular adipose tissue and plaque volumes in the ApoE-/- mouse model

Perivascular adipose tissue (PVAT) influences vascular function and pathology. We present a protocol using micro-computed tomography (microCT), a novel imaging technique typically used for hard biological tissue, to characterize the temporal and spatial development of aorta PVAT and luminal plaque soft tissue. Apolipoprotein E deficient (ApoE) and C57Bl/6J (control) mice were fed a high fat western diet up to 30 weeks. 3D microCT reconstructions were used to quantify: 1) vascular wall volume, a surrogate measure of remodeling, was greater in ApoE, 2) aorta PVAT volume was reduced in ApoE, 3) plaque volumes increased over time in ApoE, 4) plaque development co-localized with luminal ostia, origins of branching arteries, which traveled through areas of greatest PVAT volume, 5) qualitatively, the same arteries showed evidence of increased tortuosity in ApoE. This study reflects the potential of microCT analyses to assess vascular wall, PVAT and arterial trajectory modifications in relevant animal models. Abbreviations: PVAT: perivascular adipose tissue; ApoE: apolipoprotein E deficient mouse strain; Control: C57Bl/6J mouse strain; PTA: 0.3% phosphotungstic acid; microCT: micro-computed tomography; CV: cardiovascular; CVD: cardiovascular disease; IQR: interquartile range; PPARγ: peroxisome proliferator activated receptor - gamma; VV: vasa vasorum; 3D: three dimensional.

In vivo Endocrine Secretion of Prostacyclin Following Expression of a Cyclooxygenase-1/Prostacyclin Fusion Protein in the Salivary Glands of Rats Via Nonviral Gene Therapy

Pulmonary arterial hypertension (PAH) is a progressive disease that culminates in right heart failure and death. Prostacyclin (PGI2) and its derivatives are effective treatments for PAH when administered as continuous parenteral infusions. This treatment paradigm requires medical sophistication, and patients are at risk for complications from an indewelling catheter; drug interruptions may result in rebound pulmonary hypertension and death. We hypothesized that the salivary gland can be repurposed into an endogenous production site for circulating PGI2 through the expression of a fusion protein embodying cyclooxygenase-1 (Cox1) and prostacyclin synthase (PGIS) domains. We utilized ultrasound-assisted gene transfer, a nonviral gene transfer strategy that achieves robust gene transfer to the salivary gland. We initially found that Cox1-PGIS expression in livers of mice using an adenoviral vector dramatically increased circulating PGI2 relative to untreated rats or rats treated with PGIS alone. We then utilized ultrasound-assisted gene transfer to express Cox1-PGIS in the submandibular glands of rats and showed a significant elevation of circulating PGI2 that corresponded to approximately 30% of that seen in humans undergoing intravenous infusion therapy for PAH. These results suggest the feasibility of gene therapy to drive endogenous biosynthesis of PGI2 as a therapeutic strategy for the treatment of PAH.

MicroCT analysis of vascular morphometry: a comparison of right lung lobes in the SUGEN/hypoxic rat model of pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a rare disease characterized by significant vascular remodeling within the lung. Clinical computed tomography (CT) scans are routinely used to aid in PAH diagnosis. Animal models, including the Sugen-hypoxic rat model (SU/hyp), of PAH closely mimic human PAH development. We have previously used micro-computed tomography (microCT) to find extensive right lung vascular remodeling in the SU/hyp. We hypothesized that the individual right lung lobes may not contribute equally to overall lung vascular remodeling. Sprague-Dawley rats were subjected to a subcutaneous injection of vascular endothelial growth factor receptor blocker (Sugen 5416) and subsequently exposed to chronic hypoxic conditions (10% O₂) for three weeks. Following perfusion of the lung vasculature with an opaque resin (Microfil), the right lung lobes were microCT-imaged with a 10-µm voxel resolution and 3D morphometry analysis was performed separately on each lobe. As expected, we found a significantly lower ratio of vascular volume to total lobe volume in the SU/hyp compared with the control, but only in the distal lobes (inferior: 0.23 [0.21–0.30] versus 0.35 [0.27–0.43], P = 0.02; accessory: 0.27 [0.25–0.33] versus 0.37 [0.29–0.43], P = 0.06). Overall, we observed significantly fewer continuous blood vessels and reduced vascular density while having greater vascular lumen diameters in the distal lobes of both groups (P < 0.05). In addition, the vascular separation within the SU/hyp lobes and the vascular surface area to volume ratio were significantly greater in the SU/hyp lobes compared with controls (P < 0.03). Results for the examined parameters support the overall extensive vascular remodeling in the SU/hyp model and suggest this may be lobe-dependent.

Plasma complement and vascular complement deposition in patients with coronary artery disease with and without inflammatory rheumatic diseases

PURPOSE

Inflammatory rheumatic diseases (IRD) are associated with accelerated coronary artery disease (CAD), which may result from both systemic and vascular wall inflammation. There are indications that complement may be involved in the pathogenesis of CAD in Systemic Lupus Erythematosus (SLE) and Rheumatoid Arthritis (RA). This study aimed to evaluate the associations between circulating complement and complement activation products with mononuclear cell infiltrates (MCI, surrogate marker of vascular inflammation) in the aortic media and adventitia in IRDCAD and non-IRDCAD patients undergoing coronary artery bypass grafting (CABG). Furthermore, we compared complement activation product deposition patterns in rare aorta adventitial and medial biopsies from SLE, RA and non-IRD patients.

METHODS

We examined plasma C3 (p-C3) and terminal complement complexes (p-TCC) in 28 IRDCAD (SLE = 3; RA = 25), 52 non-IRDCAD patients, and 32 IRDNo CAD (RA = 32) from the Feiring Heart Biopsy Study. Aortic biopsies taken from the CAD only patients during CABG were previously evaluated for adventitial MCIs. The rare aortic biopsies from 3 SLE, 3 RA and 3 non-IRDCAD were assessed for the presence of C3 and C3d using immunohistochemistry.

RESULTS

IRDCAD patients had higher p-TCC than non-IRDCAD or IRDNo CAD patients (p<0.0001), but a similar p-C3 level (p = 0.42). Circulating C3 was associated with IRD duration (ρ, p-value: 0.46, 0.03). In multiple logistic regression analysis, IRD remained significantly related to the presence and size of MCI (p<0.05). C3 was present in all tissue samples. C3d was detected in the media of all patients and only in the adventitia of IRD patients (diffuse in all SLE and focal in one RA).

CONCLUSION

The independent association of IRD status with MCI and the observed C3d deposition supports the unique relationship between rheumatic disease, and, in particular, SLE with the complement system. Exaggerated systemic and vascular complement activation may accelerate CVD, serve as a CVD biomarker, and represent a target for new therapies.

Postmenopausal Women With Greater Paracardial Fat Have More Coronary Artery Calcification Than Premenopausal Women: The Study of Women's Health Across the Nation (SWAN) Cardiovascular Fat Ancillary Study

Background

Volumes of paracardial adipose tissue (PAT) and epicardial adipose tissue (EAT) are greater after menopause. Interestingly, PAT but not EAT is associated with estradiol decline, suggesting a potential role of menopause in PAT accumulation. We assessed whether volumes of heart fat depot (EAT and PAT) were associated with coronary artery calcification (CAC) in women at midlife and whether these associations were modified by menopausal status and estradiol levels.

Methods and Results

EAT and PAT volumes and CAC were measured using electron beam computed tomography scans. CAC was evaluated as (1) the presence of CAC (CAC Agatston score ≥10) and (2) the extent of any CAC (log CAC Agatston score >0). The study included 478 women aged 50.9 years (58% pre‐ or early perimenopausal, 10% late perimenopausal, and 32% postmenopausal). EAT was significantly associated with CAC measures, and these associations were not modified by menopausal status or estradiol. In contrast, associations between PAT and CAC measures were modified by menopausal status (interaction‐P≤0.01). Independent of study covariates including other adiposity measures, each 1‐SD unit increase in log PAT was associated with 102% higher risk of CAC presence (P=0.04) and an 80% increase in CAC extent (P=0.008) in postmenopausal women compared with pre‐ or early perimenopausal women. Additional adjustment for estradiol and hormone therapy attenuated these differences. Moreover, the association between PAT and CAC extent was stronger in women with lower estradiol levels (interaction P=0.004).

Conclusions

The findings suggest that PAT is a potential menopause‐specific coronary artery disease risk marker, supporting the need to monitor and target this fat depot for intervention in women at midlife.

Three-dimensional micro computed tomography analysis of the lung vasculature and differential adipose proteomics in the Sugen/hypoxia rat model of pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a rare disease characterized by significant vascular remodeling. The obesity epidemic has produced great interest in the relationship between small visceral adipose tissue depots producing localized inflammatory conditions, which may link metabolism, innate immunity, and vascular remodeling. This study used novel micro computed tomography (microCT) three-dimensional modeling to investigate the degree of remodeling of the lung vasculature and differential proteomics to determine small visceral adipose dysfunction in rats with severe PAH. Sprague-Dawley rats were subjected to a subcutaneous injection of vascular endothelial growth factor receptor blocker (Sugen 5416) with subsequent hypoxia exposure for 3 weeks (SU/hyp). At 12 weeks after hypoxia, microCT analysis showed a decrease in the ratio of vascular to total tissue volume within the SU/hyp group (mean ± standard deviation: 0.27 ± 0.066; P = 0.02) with increased vascular separation (0.37 ± 0.062 mm; P = 0.02) when compared with the control (0.34 ± 0.084 and 0.30 ± 0.072 mm). Differential proteomics detected an up-regulation of complement protein 3 (C3; SU/hyp∶control ratio = 2.86) and the adipose tissue-specific fatty acid binding protein-4 (FABP4, 2.66) in the heart adipose of the SU/hyp. Significant remodeling of the lung vasculature validates the efficacy of the SU/hyp rat for modeling human PAH. The upregulation of C3 and FABP4 within the heart adipose implicates small visceral adipose dysfunction. C3 has been associated with vascular stiffness, and FABP4 suppresses peroxisome proliferator-activated receptor, which is a major regulator of adipose function and known to be downregulated in PAH. These findings reveal that small visceral adipose tissue within the SU/hyp model provides mechanistic links for vascular remodeling and adipose dysfunction in the pathophysiology of PAH.

In situ expression of Bcl-2 in pulmonary artery endothelial cells associates with pulmonary arterial hypertension relative to heart failure with preserved ejection fraction

We have previously reported that pulmonary artery endothelial cells (PAECs) can be harvested from the tips of discarded Swan-Ganz catheters after right heart catheterization (RHC). In this study, we tested the hypothesis that the existence of an antiapoptotic phenotype in PAECs obtained during RHC is a distinctive feature of pulmonary arterial hypertension (PAH; World Health Organization group 1) and might be used to differentiate PAH from other etiologies of pulmonary hypertension. Specifically, we developed a flow cytometry-based measure of Bcl-2 activity, referred to as the normalized endothelial Bcl-2 index (NEBI). We report that higher NEBI values are associated with PAH to the exclusion of heart failure with preserved ejection fraction (HFpEF) and that this simple diagnostic measurement is capable of differentiating PAH from HFpEF without presenting addition risk to the patient. If validated in a larger, multicenter study, the NEBI has the potential to assist physicians in the selection of appropriate therapeutic interventions in the common and dangerous scenario wherein patients present a clinical and hemodynamic phenotype that makes it difficult to confidently differentiate between PAH and HFpEF.

Cardiovascular Fat, Menopause, and Sex Hormones in Women: The SWAN Cardiovascular Fat Ancillary Study

CONTEXT

Cardiovascular risk increases in women after menopause. Mounting evidence demonstrates a role of cardiovascular fat (CF) in the pathogenesis of coronary heart disease, but no research has examined CF in relation to sex hormones or menopausal status in women.

OBJECTIVE

The objective was to determine the relationship between CF depots, menopausal status, and endogenous sex hormones.

DESIGN

Cross-sectional and longitudinal study designs were used.

SETTING

The setting included the Study of Women's Health Across the Nation (SWAN) Heart and Cardiovascular Fat Ancillary Study.

PARTICIPANTS

A total of 456 women (mean age, 50.75 y); 62% premenopausal/early perimenopausal, and 38% late peri-/postmenopausal.

INTERVENTION

Menopausal status, endogenous sex hormones measured simultaneously with CF volumes, and circulating estradiol available 4.80 years (median) before CF measures.

MAIN OUTCOME MEASURES

Volumes of CF (epicardial adipose tissue [EAT], paracardial adipose tissue [PAT], total heart adipose tissue [TAT = EAT + PAT], and aortic perivascular adipose tissue [PVAT]).

RESULTS

In final models, late peri-/postmenopausal women had 9.88% more EAT, 20.72% more PAT, and 11.69% more TAT volumes than pre-/early perimenopausal women (P < .05). PVAT was not associated with menopausal status. In final models, lower estradiol concentrations were associated with greater volumes of PAT and TAT (P < .05). Women with the greatest reduction in estradiol since baseline had greater volumes of PAT compared to women with the least reduction (P = .02).

CONCLUSIONS

Late peri-/postmenopausal women have greater volumes of heart fat compared with pre-/early perimenopausal women independent of age, obesity, and other covariates. Endogenous sex hormones are associated with CF. Perhaps CF plays a role in the higher risk of coronary heart disease reported in women after menopause.

Complement protein C3 and coronary artery calcium in middle-aged women with polycystic ovary syndrome and controls

Circulating complement protein C3 (C3) levels have been associated with coronary artery calcification (CAC) in women with systemic lupus erythematosus, but have yet to be evaluated in women with polycystic ovary syndrome (PCOS). We aimed to determine whether C3 levels were elevated in women with PCOS compared to controls and to quantify the association of C3 with cardiovascular disease (CVD) risk factors and CAC and if PCOS modified this association. This cross-sectional analysis included 132 women with PCOS and 155 controls, 35-62 years old, from the third visit of a case-control study. CAC was measured during the study visit, and circulating C3 was measured in stored sera. The presence of CAC and CAC categories (Agatston score 0, 1-9.9 and ≥ 10) were used for logistic and ordinal regression analysis, respectively. C3 levels were not significantly different between women with PCOS and controls. Among all women, C3 was associated with the presence of CAC and increasing CAC groups after adjusting for age, PCOS status and insulin or body mass index (BMI), all p<0.05. In addition, C3 was associated with the presence of CAC after adjusting for age, PCOS status, BMI, insulin and African American race, p=0.049. PCOS status did not modify these associations. In conclusion, circulating C3 levels may prove beneficial in identifying women at risk of CVD in women with PCOS and the general population.

Menopause, complement, and hemostatic markers in women at midlife: the Study of Women's Health Across the Nation

OBJECTIVE

To evaluate whether higher circulating levels of complement proteins C3 and C4 are associated with menopausal status and with hemostatic/thrombus formation markers (circulating factor VII (factor VIIc), fibrinogen, plasminogen activator inhibitor-1 (PAI-1) and tissue plasminogen activator antigen (tPA-ag)) in a sample of midlife women.

METHODS AND RESULTS

A total of 100 women (50 late peri-/postmenopausal and 50 pre-/early peri- menopausal women) from the Study of Women's Health Across the Nation (SWAN) Pittsburgh site were included in the present analysis. Factor VIIc and PAI-1 were log transformed. Linear regression was used for analysis. The mean age of the study participants was 50.5 ± 2.6 years with 73% were Caucasian and 27% were African American. C3 but not C4 was significantly higher in postmenopausal women compared to premenopausal women (P value = 0.03), adjusting for age, race and BMI. In final model (adjusting for age, race, BMI and menopausal status), C3 was associated with higher levels of log PAI-1 (P value = 0.0009) and tPA-ag (P value = 0.0003), while C4 was associated with higher levels of log factor VIIc (P value = 0.04) and fibrinogen (P value = 0.005).

CONCLUSIONS

These data suggest that C3 and C4 may be related to blood clots via their associations with hemostatic markers and that C3 is related to menopausal status. Complement proteins C3 and C4 could be possible pathways by which postmenopausal women are at higher risk of atherosclerosis and cardiovascular related events. It is important to replicate these findings in a larger sample size.

Perivascular adipose tissue of the descending thoracic aorta is associated with systemic lupus erythematosus and vascular calcification in women

OBJECTIVE

Women with systemic lupus erythematosus (SLE) have an increased risk of cardiovascular disease (CVD). Traditional CVD and SLE-disease related risk factors do not fully account for this increased risk. Perivascular adipose tissue (PVAT) is a visceral adipose depot in close proximity to blood vessels possibly influencing CVD. We hypothesized that women with SLE have an increased volume of descending thoracic aortic PVAT (aPVAT) associated with increased vascular calcification.

METHODS

Using electron beam computed tomography, we quantified the aPVAT in clinically CVD-free SLE women (n = 135) and age-/race-matched healthy controls (HC, n = 152). Coronary artery calcification (CAC) and aortic calcification (AC) were quantified using Agatston scores and the aPVAT was quantified using standard Hounsfield Units (HU) for adipose tissue.

RESULTS

Women with SLE had greater median aPVAT (32.2 cm(3) vs HC aPVAT 28.6 cm(3), p = 0.0071) and greater median AC (26.0 vs HC AC 6.0, p = 0.0013) than the healthy control women. Total aPVAT (per 25 cm(3)) remained significantly associated with SLE after adjusting for CVD risk factors (Odds Ratio 1.74 [95% Confidence Interval: 1.04-2.9], p = 0.034), but was attenuated when adjusting for circulating inflammatory markers (p = 0.34). In a logistic regression analysis, SLE aPVAT (per 25 cm(3)) was associated with AC (6.78 [2.0-23], p = 0.0019), which remained significant after adjusting for circulating inflammatory markers (p = 0.0074), and CAC (2.66 [1.4-5.0], p = 0.0028).

CONCLUSIONS

Total aPVAT is greater in clinically CVD-free SLE women than in age-/race-matched controls and is associated with calcification in different vascular beds.

Effects of an intensive behavioral weight loss intervention consisting of caloric restriction with or without physical activity on common carotid artery remodeling in severely obese adults

OBJECTIVE

Obesity increases cardiovascular disease risk and adversely affects vascular structure and function. Few studies have evaluated the vascular effects of non-surgical weight reduction in the severely obese. We hypothesized that weight loss and improvements in cardiometabolic factors would reduce common carotid artery intima-media thickness (CIMT) and inter-adventitial diameter (AD) in severely obese adults.

METHODS

We performed carotid ultrasound and measured cardiometabolic factors in 90 severely obese participants (body mass index (BMI)≥35 kg/m(2), age 30-55) at baseline and 6 months in a randomized clinical trial of dietary intervention with (n=45) or without (n=45) physical activity.

RESULTS

The achieved weight loss (mean=8%) did not differ significantly by intervention group (P=0.10) and resulted in a 0.07 mm mean decrease in AD (P=0.001). AD change was positively correlated with changes in BMI, waist circumference, abdominal visceral and subcutaneous fat, and body fat mass, and AD decreased more in men (P<0.05 for all). After multivariable adjustment, changes in BMI (P=0.03) and abdominal subcutaneous fat (P=0.04) were significant determinants of AD change. Although CIMT did not decrease significantly overall (-0.008 mm, P=0.16), individuals who lost at least 5% of their body weight experienced a significant mean reduction in CIMT of 0.02 mm (P=0.002). CIMT change was positively correlated with changes in BMI, waist circumference, fat-free mass, leptin, and insulin (P<0.05 for all). After multivariable adjustment, insulin reduction remained a significant determinant of CIMT decrease (P=0.03).

CONCLUSION

A 6 month intensive behavioral intervention can significantly reverse metabolic and vascular abnormalities in severely obese adults.

Complement proteins C3 and C4 bind to collagen and elastin in the vascular wall: a potential role in vascular stiffness and atherosclerosis

Circulating inflammatory mediators including complement activation products participate in the pathogenesis of cardiovascular diseases. As such, previous reports demonstrating the presence of complement proteins within atherosclerotic plaque and on the luminal surface would be anticipated. In contrast, we have recently made the unexpected observation that complement proteins also deposit along the external elastic lamina of mouse aortas in the absence of luminal deposition or plaque development. This suggests that complement activation may play a critical role in the pathogenesis of vascular stiffness and atherosclerosis through a mechanism initiated within the adventitia rather than on the endothelial surface. This hypothesis was tested in the current study by ultrastructural identification of the C3- and C4-binding targets within the adventitia of the mouse aorta. The results demonstrate extensive binding of C3 and C4 to both collagen and elastin fibers within the adventitia in both ApoE(-/-) and C57Bl/6J control mice, as well as the presence of C3 and C4 within perivascular adipose tissue. These observations suggest a potential "outside-in" mechanism of vascular stiffness during which perivascular adipose may produce C3 and C4 that bind to collagen and elastin fibers within the adventitia through covalent thiolester bonds, leading to increased vascular stiffness.

Biomechanical and Biotribological Correlation of Induced Wear on Bovine Femoral Condyles

Characterizing the biomechanical and biotribological properties for articular surfaces in healthy, damaged, and repaired states will both elucidate the understanding of mechanical degradation and lubricating phenomena and enhance the development of functional tissue engineered cartilage and surgical repair techniques. In recent work, a new methodology involving concomitant linear translational and oscillating rotational motion was developed to determine the frictional and wear characteristics of articular cartilage. The impetus of this work was to further characterize the biomechanical characteristics from stress relaxation and dynamic cyclical indentation testing of normal and damaged articular cartilage and to correlate the biotribological characteristic findings with the biomechanical data. Quasilinear viscoelastic (QLV) theory was used to curve fit the stress-relaxation data, while the dynamic data were used both to determine the dynamic properties through fast Fourier transform analysis and to validate the dynamic behavior based on the properties obtained from the QLV theory. Comparisons of the curve-fit parameters showed a significant decrease in pre- versus postwear elastic response, A(p<0.04), and viscous response, c(p<0.01). In addition, the short term relaxation time, τ1(p<0.0062), showed a significant decrease between surfaces with and without a defect. The magnitude of the complex modulus from dynamic tests revealed a decrease due to wear, lGlpostwear∕lGlprewear<1(p<0.05). The loss factor, tanδ, was generally greater while lGl was less for those specimens experiencing rotation. A linear regression analysis was performed to correlate μstatic and μinitial with the curve-fit QLV parameters, A, B, c, τ1, and τ2. Increasing coefficients of friction correlated with decreases in the elastic response, A, viscous response, c, and the short term relaxation time constant, τ1, while B became increasingly nonlinear and τ2 became shorter postwear. Qualitatively, scanning electron microscopy photographs revealed the mechanical degradation of the tissue surface due to wear. Surfaces with a defect had an increased amount of wear debris, which ultimately contributed to third body wear. Surfaces without a defect had preferentially aligned abrasions, while those surfaces not within the wear path showed no signs of wear. The efficacy of various repair techniques and innovative repair tissue models in comparison to normal and worn articular surface tissue can be determined through experimental designs involving both biomechanical and biotribological parameter characterizations. The development of this comprehensive testing scenario involving both biotribological and biomechanical characteristics is essential to the continued development of potential articular repair tissue.

In vivo response of polylactic acid-alginate scaffolds and bone marrow-derived cells for cartilage tissue engineering

Successful application of tissue-engineering techniques to damaged biological structures is determined by functional performance in vivo. This study evaluated the in vivo response of a tissue-engineered construct composed of a polylactic acid-alginate amalgam seeded with bone marrow-derived mesenchymal stem cells and stimulated in vitro with transforming growth factor beta for cartilage tissue engineering. Constructs were placed in cylindrical osteochondral defects in the canine femoral condyle and examined 6 weeks postoperatively by gross, histological, immunohistochemical, and biomechanical analyses. In the course of 6 weeks in vivo, the defects filled with a cartilaginous tissue regardless of whether cell-seeded (experimental) or cell-free (control) constructs were implanted; however, the quality of the tissue differed between the experimental and control defects. Cell-seeded experimental defects showed more cartilage-like matrix quality, cell distribution, and proteoglycan staining. Biomechanically, experimental and control specimens exhibited similar behavior; however, both tissues were still immature compared with normal cartilage. The evidence accumulated in this study showed a modest acceleration of the in vivo healing of cell-seeded constructs but also demonstrated a reparative response of cell-free constructs. This finding suggests that the constructs prepared from the PLA-alginate amalgam may serve as a means for host cell attachment.

Mechanical Properties and Cellular Proliferation of Electrospun Collagen Type II

A suitable technique for articular cartilage repair and replacement is necessitated by inadequacies of current methods. Electrospinning has potential in cartilage repair by producing scaffolds with fiber diameters in the range of native extracellular matrix. Chondrocytes seeded onto such scaffolds may prefer this environment for differentiation and proliferation, thus approaching functional cartilage replacement tissue. Scaffolds of collagen type II were created by an electrospinning technique. Individual scaffold specimens were prepared and evaluated as uncross-linked, cross-linked, or crosslinked/seeded. Uncross-linked scaffolds contained a minimum and average fiber diameter of 70 and 496 nm, respectively, whereas cross-linked scaffolds possessed diameters of 140 nm and 1.46 microm. The average thickness for uncross-linked scaffolds was 0.20 +/- 0.02 mm and 0.52 +/- 0.07 mm for cross-linked scaffolds. Uniaxial tensile tests of uncross-linked scaffolds revealed an average tangent modulus, ultimate tensile strength, and ultimate strain of 172.5 +/- 36.1 MPa, 3.3 +/- 0.3 MPa, and 0.026 +/- 0.005 mm/mm, respectively. Scanning electron microscopy of cross-linked scaffolds cultured with chondrocytes demonstrated the ability of the cells to infiltrate the scaffold surface and interior. Electrospun collagen type II scaffolds produce a suitable environment for chondrocyte growth, which potentially establishes the foundation for the development of articular cartilage repair.

MR imaging of normal and matrix-depleted cartilage: correlation with biomechanical function and biochemical composition

PURPOSE

To correlate articular cartilage function, as reflected in biomechanical properties and biochemical composition, with magnetic resonance (MR) imaging parameters of normal articular cartilage and cartilage partially depleted of matrix components.

MATERIALS AND METHODS

Normal articular cartilage from 12 porcine patellae was evaluated biomechanically, biochemically, and with MR imaging (with and without gadolinium enhancement). The patellae were then enzymatically treated to deplete the matrix of either collagen or proteoglycan and then reevaluated biomechanically, biochemically, and with MR imaging. Correlations between cartilaginous tissue function and MR imaging parameters were made. Analysis of variance was performed to assess the effect of enzymatic treatment on measured parameters. Linear correlations among the MR imaging, biochemical, and biomechanical parameters were performed to determine the strengths of the relationships. P <.05 indicated statistically significant differences.

RESULTS

Biochemical, biomechanical, and MR analyses enabled detection of changes caused by matrix depletion (P <.05). T2 was the most useful MR imaging parameter for distinguishing proteoglycan loss from collagen loss. T2 correlated significantly with both biomechanical modulus (indicative of cartilage stiffness; P <.001, R2 = 0.51) and biochemical proteoglycan content (P <.001, R2 = 0.44). Differentiation between proteoglycan loss and collagen loss in terms of T1 improved with gadolinium enhancement. With gadolinium enhancement, proteoglycan depletion was associated with a greater decrease in T1 than collagen depletion (P <.05).

CONCLUSION

An association between biochemical and biomechanical functional status and MR imaging parameters of articular cartilage was demonstrated. Linear correlations existed between modulus and proteoglycan content in terms of T2. Additionally, proteoglycan loss and collagen loss had differing effects on gadolinium-enhanced T1 when it was expressed as the ratio of T1 after gadolinium enhancement/T1 before gadolinium enhancement.