Feasibility of MR-Based Body Composition Analysis in Large Scale Population Studies

Introduction Quantitative and accurate measurements of fat and muscle in the body are important for prevention and diagnosis of diseases related to obesity and muscle degeneration. Manually segmenting muscle and fat compartments in MR body-images is laborious and time-consuming, hindering implementation in large cohorts. In the present study, the feasibility and success-rate of a Dixon-based MR scan followed by an intensity-normalised, non-rigid, multi-atlas based segmentation was investigated in a cohort of 3,000 subjects. Materials and Methods 3,000 participants in the in-depth phenotyping arm of the UK Biobank imaging study underwent a comprehensive MR examination. All subjects were scanned using a 1.5 T MR-scanner with the dual-echo Dixon Vibe protocol, covering neck to knees. Subjects were scanned with six slabs in supine position, without localizer. Automated body composition analysis was performed using the AMRA Profiler™ system, to segment and quantify visceral adipose tissue (VAT), abdominal subcutaneous adipose tissue (ASAT) and thigh muscles. Technical quality assurance was performed and a standard set of acceptance/rejection criteria was established. Descriptive statistics were calculated for all volume measurements and quality assurance metrics. Results Of the 3,000 subjects, 2,995 (99.83%) were analysable for body fat, 2,828 (94.27%) were analysable when body fat and one thigh was included, and 2,775 (92.50%) were fully analysable for body fat and both thigh muscles. Reasons for not being able to analyse datasets were mainly due to missing slabs in the acquisition, or patient positioned so that large parts of the volume was outside of the field-of-view. Discussion and Conclusions In conclusion, this study showed that the rapid UK Biobank MR-protocol was well tolerated by most subjects and sufficiently robust to achieve very high success-rate for body composition analysis. This research has been conducted using the UK Biobank Resource

A follow-up study for left ventricular mass on chromosome 12p11 identifies potential candidate genes

<p>Abstract</p> <p>Background</p> <p>Left ventricular mass (LVM) is an important risk factor for cardiovascular disease. Previously we found evidence for linkage to chromosome 12p11 in Dominican families, with a significant increase in a subset of families with high average waist circumference (WC). In the present study, we use association analysis to further study the genetic effect on LVM.</p> <p>Methods</p> <p>Association analysis with LVM was done in the one LOD critical region of the linkage peak in an independent sample of 897 Caribbean Hispanics. Genotype data were available on 7085 SNPs from 23 to 53 MB on chromosome 12p11. Adjustment was made for vascular risk factors and population substructure using an additive genetic model. Subset analysis by WC was performed to test for a difference in genetic effects between the high and low WC subsets.</p> <p>Results</p> <p>In the overall analysis, the most significant association was found to rs10743465, downstream of the <it>SOX5 </it>gene (p = 1.27E-05). Also, 19 additional SNPs had nominal p < 0.001. In the subset analysis, the most significant difference in genetic effect between those with high and low WC occurred with rs1157480 (p = 1.37E-04 for the difference in β coefficients), located upstream of <it>TMTC1</it>. Twelve additional SNPs in or near 6 genes had p < 0.001.</p> <p>Conclusions</p> <p>The current study supports previously identified evidence by linkage for a genetic effect on LVM on chromosome 12p11 using association analysis in population-based Caribbean Hispanic cohort. <it>SOX5 </it>may play an important role in the regulation of LVM. An interaction of <it>TMTC1 </it>with abdominal obesity may contribute to phenotypic variation of LVM.</p

Cardiac rehabilitation and exercise therapy in the elderly: Should we invest in the aged?

Coronary heart disease (CHD) is the leading cause of death worldwide and becomes increasingly prevalent among patients aged 65 years and older. Elderly patients are at a higher risk for complications and accelerated physical deconditioning after a cardiovascular event, especially compared to their younger counterparts. The last few decades were privy to multiple studies that demonstrated the beneficial effects of cardiac rehabilitation (CR) and exercise therapy on mortality, exercise capacity, psychological risk factors, inflammation, and obesity among patients with CHD. Unfortunately, a significant portion of the available data in this field pertains to younger patients. A viable explanation is that older patients are grossly underrepresented in these programs for multiple reasons starting with the patient and extending to the physician. In this article, we will review the benefits of CR programs among the elderly, as well as some of the barriers that hinder their participation