Arthur L. Weltman

Multifactorial Determinants of Functional Capacity in Peripheral Arterial Disease: Uncoupling of Calf Muscle Perfusion and Metabolism

OBJECTIVES We aimed to investigate the pathophysiology of peripheral arterial disease (PAD) by examining magnetic resonance imaging (MRI) and spectroscopic (MRS) correlates of functional capacity. BACKGROUND Despite the high prevalence, morbidity, and cost of PAD, its pathophysiology is incompletely understood. METHODS Eighty-five patients (age 68 +/- 10 years) with mild-to-moderate PAD (ankle-brachial index 0.69 +/- 0.14) had their most symptomatic leg studied by MRI/MRS. Percent wall volume in the superficial femoral artery was measured with black blood MRI. First-pass contrast-enhanced MRI calf muscle perfusion and (31)P MRS phosphocreatine recovery time constant (PCr) were measured at peak exercise in calf muscle. All patients underwent magnetic resonance angiography (MRA), treadmill testing with maximal oxygen consumption measurement, and a 6-min walk test. RESULTS Mean MRA index of number and severity of stenoses was 0.84 +/- 0.68 (normal 0), % wall volume 74 +/- 11% (normal 46 +/- 7%), tissue perfusion 0.039 +/- 0.015 s(-1) (normal 0.065 +/- 0.013 s(-1)), and PCr 87 +/- 54 s (normal 34 +/- 16 s). MRA index, % wall volume, and ankle-brachial index correlated with most functional measures. PCr was the best correlate of treadmill exercise time, whereas calf muscle perfusion was the best correlate of 6-min walk distance. No correlation was noted between PCr and tissue perfusion. CONCLUSIONS Functional limitations in PAD are multifactorial. As measured by MRI and spectroscopy, atherosclerotic plaque burden, stenosis severity, tissue perfusion, and energetics all play a role. However, cellular metabolism is uncoupled from tissue perfusion. These findings suggest a potential role for therapies that regress plaque, increase tissue perfusion, and/or improve cellular metabolism. (Comprehensive Magnetic Resonance of Peripheral Arterial Disease; NCT00587678).

Effects of n-3 fish oil on metabolic and histological parameters in NASH: A double-blind, randomized, placebo-controlled trial

BACKGROUND & AIMS This studys aim was to assess the histological and metabolic effects of n-3 polyunsaturated fatty acids (PUFAs) vs. placebo while adjusting for the impact of age and weight change in NASH patients. (ClinicalTrials.gov: NCT00681408). METHODS Forty-one subjects with non-cirrhotic NASH were enrolled, and 34 completed the study. 17 received n-3 fish oil 3000 mg/day and 17 received placebo daily for 1 year with typical counselling on caloric intake and physical activity for all subjects. RESULTS N-3- and placebo-treated groups showed no significant difference for the primary end point of NASH activity score (NAS) reduction ⩾ 2 points without fibrosis progression after adjustment for known covariates (n-3, 4/17 (23.5%); placebo, 3/17, (17.6%), p = 0.99). Among subjects with increased or stable weight, n-3 subjects showed a larger decrease in liver fat content by MRI than placebo-treated subjects (p = 0.014 for 2nd quartile, p = 0.003 for 3rd quartile of weight change). N-3 treatment showed significant fat reduction on the paired analysis of image-assisted fat morphometry regardless of weight loss or gain. Exercise capacity remained markedly reduced in all subjects. No independent effects on markers of hepatocyte injury or insulin sensitivity indices were observed. CONCLUSION N-3 PUFAs at 3000 mg/day for one year did not lead to an improvement in the primary outcome of histological activity in NASH patients (⩾ 2 point NAS reduction). N-3 led to reduced liver fat by multiple measures. Other metabolic effects were not seen, although no detrimental effects were apparent. Whether longer duration, higher dose, or different composition of n-3 therapy would lead to additional benefits is uncertain.

Calf Muscle Perfusion at Peak Exercise in Peripheral Arterial Disease: Measurement by First-Pass Contrast-Enhanced Magnetic Resonance Imaging

To develop a contrast‐enhanced magnetic resonance (MR) technique to measure skeletal muscle perfusion in peripheral arterial disease (PAD).

Antioxidant supplementation lowers exercise-induced oxidative stress in young overweight adults

Objective: To determine whether antioxidant (AOX) supplementation attenuates post‐exercise oxidative stress and contributors to oxidative stress (inflammation, blood lipids) in overweight young adults.

Effects of antioxidant supplementation on insulin sensitivity, endothelial adhesion molecules, and oxidative stress in normal-weight and overweight young adults

The objective of the study was to determine whether short-term antioxidant (AOX) supplementation affects insulin sensitivity, endothelial adhesion molecule levels, and oxidative stress in overweight young adults. A randomized, double-blind, controlled study tested the effects of AOXs on measures of insulin sensitivity (homeostasis model assessment [HOMA]) and quantitative insulin sensitivity check index), endothelial adhesion molecules (soluble intercellular adhesion molecule-1, vascular adhesion molecule, and endothelial-leukocyte adhesion molecule-1), adiponectin, and oxidative stress (lipid hydroperoxides) in overweight and normal-weight individuals (N = 48, 18-30 years). Participants received either AOX (vitamin E, 800 IU; vitamin C, 500 mg; beta-carotene, 10 mg) or placebo for 8 weeks. The HOMA values were initially higher in the overweight subjects and were lowered with AOX by week 8 (15% reduction, P = .02). Adiponectin increased in both AOX groups. Soluble intercellular adhesion molecule-1 and endothelial-leukocyte adhesion molecule-1 decreased in overweight AOX-treated groups by 6% and 13%, respectively (P < .05). Plasma lipid hydroperoxides were reduced by 0.31 and 0.70 nmol/mL in the normal-weight and overweight AOX-treated groups, respectively, by week 8 (P < .05). Antioxidant supplementation moderately lowers HOMA and endothelial adhesion molecule levels in overweight young adults. A potential mechanism to explain this finding is the reduction in oxidative stress by AOX. Long-term studies are needed to determine whether AOXs are effective in suppressing diabetes or vascular activation over time.

Low-Density Lipoprotein Lowering Does Not Improve Calf Muscle Perfusion, Energetics, or Exercise Performance in Peripheral Arterial Disease

OBJECTIVES We hypothesized that low-density lipoprotein (LDL) reduction regardless of mechanism would improve calf muscle perfusion, energetics, or walking performance in peripheral arterial disease (PAD) as measured by magnetic resonance imaging and magnetic resonance spectroscopy. BACKGROUND Statins improve cardiovascular outcome in PAD, and some studies suggest improved walking performance. METHODS Sixty-eight patients with mild to moderate symptomatic PAD (age 65 ± 11 years; ankle-brachial index [ABI] 0.69 ± 0.14) were studied at baseline and annually for 2 years after beginning simvastatin 40 mg (n = 20) or simvastatin 40 mg/ezetimibe 10 mg (n = 18) if statin naïve, or ezetimibe 10 mg (n = 30) if taking a statin. Phosphocreatine recovery time was measured by (31)P magnetic resonance spectroscopy immediately after symptom-limited calf exercise on a 1.5-T scanner. Calf perfusion was measured using first-pass contrast-enhanced magnetic resonance imaging with 0.1 mM/kg gadolinium at peak exercise. Gadolinium-enhanced magnetic resonance angiography was graded. A 6-min walk and a standardized graded Skinner-Gardner exercise treadmill test with peak Vo(2) were performed. A repeated-measures model compared changes over time. RESULTS LDL reduction from baseline to year 2 was greater in the simvastatin 40 mg/ezetimibe 10 mg group (116 ± 42 mg/dl to 56 ± 21 mg/dl) than in the simvastatin 40 mg group (129 ± 40 mg/dl to 90 ± 30 mg/dl, p < 0.01). LDL also decreased in the ezetimibe 10 mg group (102 ± 28 mg/dl to 79 ± 27 mg/dl, p < 0.01). Despite this, there was no difference in perfusion, metabolism, or exercise parameters between groups or over time. Resting ABI did improve over time in the ezetimibe 10 mg group and the entire study group of patients. CONCLUSIONS Despite effective LDL reduction in PAD, neither tissue perfusion, metabolism, nor exercise parameters improved, although rest ABI did. Thus, LDL lowering does not improve calf muscle physiology or functional capacity in PAD. (Comprehensive Magnetic Resonance of Peripheral Arterial Disease; NCT00587678).

Jogging Biomechanics after Exercise in Individuals with ACL-Reconstructed Knees.

PURPOSE Return to recreational activity is a common goal for the clinician and patient after ACL reconstruction (ACLR) and structured rehabilitation. Decreased peak knee flexion angle and external knee flexion moment during walking and jogging have been indicated as significant contributors to cartilage degeneration over time after knee joint injury. The purpose of this investigation was to measure the effects of 30 min of exercise on knee joint kinetics and kinematics in participants with a history of ACLR. METHODS ACLR participants (n = 20, 9 females and 11 males) and healthy controls (n = 23, 11 females and 12 males) participated in an observational laboratory study. Gait analysis was performed on all subjects before and after a 30-min exercise protocol. Sagittal and frontal plane kinematics and kinetics were measured in the involved limb in the ACLR group and compared with healthy control participants across the gait cycle using 90% confidence intervals. Significant differences between groups were established as a consecutive 3% of the gait cycle in which 90% confidence interval did not overlap. RESULTS Preexercise, ACLR participants were more hip flexed with higher magnitude external hip flexion moments and lower magnitude external knee flexion moments during the stance phase compared with healthy controls. ACLR participants experienced preexercise to postexercise declines in hip flexion angle and external hip flexion moment along with increases in external knee flexion moment when compared with healthy controls. CONCLUSIONS Exercise-related adaptations in hip and knee biomechanics are different in individuals with a history ACLR when compared with healthy controls despite a return to recreational activity. The biomechanical response to fatiguing exercise observed in this investigation may provide insight into one potential source of elevated knee injury risk and reduced long-term knee joint health after ACLR.

The effect of exercise intensity on endothelial function in physically inactive lean and obese adults.

Purpose To examine the effects of exercise intensity on acute changes in endothelial function in lean and obese adults. Methods Sixteen lean (BMI <25, age 23±3 yr) and 10 obese (BMI >30, age 26±6 yr) physically inactive adults were studied during 3 randomized admissions [control (C, no exercise), moderate-intensity exercise (M, @ lactate threshold (LT)) and high-intensity exercise (H, midway between LT and VO2peak) (30 min)]. Endothelial function was assessed by flow-mediated dilation (FMD) at baseline and 1, 2, and 4 h post-exercise. Results RM ANCOVA revealed significant main effects for group, time, and group x condition interaction (p<0.05). A diurnal increase in FMD was observed in lean but not obese subjects. Lean subjects exhibited greater increases in FMD than obese subjects (p = 0.0005). In the obese group a trend was observed for increases in FMD at 2- and 4-hr after M (p = 0.08). For lean subjects, FMD was significantly elevated at all time points after H. The increase in FMD after H in lean subjects (3.2±0.5%) was greater than after both C (1.7±0.4%, p = 0.015) and M (1.4±0.4%, p = 0.002). FMD responses of lean and obese subjects significantly differed after C and H, but not after M. Conclusion In lean young adults, high-intensity exercise acutely enhances endothelial function, while moderate-intensity exercise has no significant effect above that seen in the absence of exercise. The FMD response of obese adults is blunted compared to lean adults. Diurnal variation should be considered when examining the effects of acute exercise on FMD.

Reproducibility of rest and exercise stress contrast-enhanced calf perfusion magnetic resonance imaging in peripheral arterial disease.

BackgroundThe purpose was to determine the reproducibility and utility of rest, exercise, and perfusion reserve (PR) measures by contrast-enhanced (CE) calf perfusion magnetic resonance imaging (MRI) of the calf in normal subjects (NL) and patients with peripheral arterial disease (PAD).MethodsEleven PAD patients with claudication (ankle-brachial index 0.67 ±0.14) and 16 age-matched NL underwent symptom-limited CE-MRI using a pedal ergometer. Tissue perfusion and arterial input were measured at rest and peak exercise after injection of 0.1 mM/kg of gadolinium-diethylnetriamine pentaacetic acid (Gd-DTPA). Tissue function (TF) and arterial input function (AIF) measurements were made from the slope of time-intensity curves in muscle and artery, respectively, and normalized to proton density signal to correct for coil inhomogeneity. Perfusion index (PI) = TF/AIF. Perfusion reserve (PR) = exercise TF/ rest TF. Intraclass correlation coefficient (ICC) was calculated from 11 NL and 10 PAD with repeated MRI on a different day.ResultsResting TF was low in NL and PAD (mean ± SD 0.25 ± 0.18 vs 0.35 ± 0.71, p = 0.59) but reproducible (ICC 0.76). Exercise TF was higher in NL than PAD (5.5 ± 3.2 vs. 3.4 ± 1.6, p = 0.04). Perfusion reserve was similar between groups and highly variable (28.6 ± 19.8 vs. 42.6 ± 41.0, p = 0.26). Exercise TF and PI were reproducible measures (ICC 0.63 and 0.60, respectively).ConclusionAlthough rest measures are reproducible, they are quite low, do not distinguish NL from PAD, and lead to variability in perfusion reserve measures. Exercise TF and PI are the most reproducible MRI perfusion measures in PAD for use in clinical trials.

Morbidly obese women with and without endometrial cancer: are there differences in measured physical fitness, body composition, or hormones?

OBJECTIVE Exercise is potentially protective against cancer for obese women. The objectives were to examine differences in activity, body composition, and hormones in overweight/obese women with and without endometrial cancer. METHODS Women ≥ 50 years old with a body mass index (BMI) ≥ 25 kg/m(2) scheduled for abdominal hysterectomy were enrolled. Demographics, physical activity, and quality of life (QOL) data were collected. Body composition/fitness was evaluated using Air Displacement Plethysmography (BodPod) and a standardized treadmill. Adiponectin, androstenedione, leptin, estradiol, estrone, progesterone, sex hormone binding globulin, insulin and glucose were measured. RESULTS Thirty-eight women enrolled in this pilot study; 22 had endometrial cancer. Mean age was 58.3 years, mean BMI, fat weight and percent body fat were 41.3 kg/m(2), 55 kg and 51% respectively. Fitness levels were poor; 90% of women had peak oxygen uptakes below the 10th percentile of population normals yet 80% still rated their fitness level as equivalent to other women. Women with and without cancer did not differ in age, BMI, co-morbidities, energy expenditures, body composition, hormones or QOL although glucose levels were higher in women with cancer (119.5 vs. 90.7 mg/dl; p=0.049). Cancer subjects scored worse on every fitness measurement, reaching statistical significance for VO(2 peak) (15.0 vs. 17.9 ml/kg/min; p=0.033). Current exercisers had a lower BMI (p=0.039), decreased fat weight (p=0.024), decreased waist circumference (p=0.05) and improved vitality compared to non-exercisers. CONCLUSION Physical fitness levels were abysmal in these morbidly obese subjects and worse for cancer patients. Exercise correlated with improved body composition and vitality.