Body Composition Profiling in the UK Biobank Imaging Study

Beyond body mass index: exploring the role of visceral adipose tissue in intensive care unit outcomes

Obesity is a worldwide health crisis and poses significant challenges in critical care. Many studies suggest an 'obesity paradox', in which obesity, defined by body mass index (BMI), is associated with better outcomes. However, the inability of BMI to discriminate between fat and muscle or between visceral adipose tissue and subcutaneous adipose tissue, limits its prediction of metabolic ill health. We suggest that the 'obesity paradox' may be more reflective of the limitations of BMI than the protective effect of obesity. We explore the biological processes leading to visceral fat accumulation, and the evidence linking it to outcomes in critical illness. In the 'spillover' hypothesis of adipose tissue expansion, caloric excess and impaired expansion of storage capacity in the subcutaneous adipose tissue lead to accumulation of visceral adipose tissue. This is associated with a chronic inflammatory state, which is integral to the link between visceral adiposity, type 2 diabetes mellitus, and ischaemic heart disease. We review the current evidence on visceral adiposity and critical illness outcomes. In COVID-19, increased visceral adipose tissue, irrespective of BMI, is associated with more severe disease. This is mirrored in acute pancreatitis, suggesting visceral adiposity is linked to poorer outcomes in some hyperinflammatory conditions. We suggest that visceral adiposity's chronic inflammatory state may potentiate acute inflammation in conditions such as COVID-19 and acute pancreatitis. Further work is required to investigate other critical illnesses, especially sepsis and acute respiratory distress syndrome, in which current evidence is scarce. This may give further insights into pathophysiology and inform tailored treatment and nutrition strategies based on body fat distribution.

MRI Measures of Fat Distribution and Risk of Cancer

BACKGROUND

Excess adiposity has been associated with an increased risk of several types of cancer. The relationship between fat tissue distribution in the body and these outcomes is less well known. Using data from the UK Biobank imaging substudy, we evaluated the prospective relationship between MRI-derived measurements of adipose tissue distribution and the risk of the major site-specific cancers associated with obesity.

METHODS

Between 2014 and 2023, MRI measurements on adipose tissue distribution and volume were obtained from 49,044 (52.2% women) cancer-free UK Biobank participants. Quantitative MRI data included volumes of visceral adipose tissue (VAT) and abdominal subcutaneous adipose tissue (ASAT), total abdominal fat/height squared (TAT/h2), and muscle fat infiltration (MFI). Cox proportional hazard models adjusted for cancer-specific risk factors were used to generate HRs and 95% confidence intervals.

RESULTS

Incident cancer cases of the breast (N = 179), endometrium (n = 30), colorectum (n = 145), and kidney (n = 50) were ascertained over a median follow-up of 4.5 years. In women, VAT, TAT/h2, and MFI were positively associated with a risk of postmenopausal breast cancer, and ASAT was associated with an increased risk of endometrial cancer. In men, VAT and TAT/h2 were positively associated with a risk of colorectal cancer, whereas ASAT was associated with an increased risk of kidney cancer.

CONCLUSIONS

The present study showed that increasing volumes of VAT, ASAT, and MFI were associated with cancers at specific organ sites, indicating a potential role for adipose tissue distribution in influencing cancer risk.

IMPACT

Both visceral and subcutaneous fat may have an impact on the risk of certain cancers.

Sarcopenia and the management of spinal disease in the elderly

Sarcopenia, generally defined by the loss of skeletal mass and function, may disproportionately affect elderly individuals and heavily influence spinal disease. Muscle atrophy is associated with myriad clinical problems, including thoracic kyphosis, increased sagittal vertical axis (SVA), spinal implant failures, and postoperative complications. As such, the aim of this narrative review is to synthesize pertinent literature detailing the intersection between sarcopenia and the impact of sarcopenia on the management of spine disease. Specifically, we focus on the domains of etiology, diagnosis and assessment, impact on the cervical and lumbar spine, spinal augmentation procedures, neoplastic disease, whiplash injury, and recovery/prevention. A narrative review was conducted by searching the PubMed and Google Scholar databases from inception to July 12, 2024, for any cohort studies, systematic reviews, or randomized controlled trials. Case studies and conference abstracts were excluded. Diagnosis of sarcopenia relies on the assessment of muscle strength and quantity/quality. Strength may be assessed using clinical tools such as gait speed, timed up and go (TUG) test, or hand grip strength, whereas muscle quantity/quality may be assessed via computed tomography (CT scan), magnetic resonance imaging (MRI), and dual-energy X-ray absorptiometry (DXA scan). Sarcopenia has a generally negative impact on the clinical course of those undergoing cervical and lumbar surgery, and may be predictive of mortality in those with neoplastic spinal disease. In addition, severe acceleration-deceleration (whiplash) injuries may result in cervical extensor muscle atrophy. Intervention and recovery measures include nutrition or exercise therapy, although the evidence for nutritional intervention is lacking. Sarcopenia is a widely prevalent pathology in the advanced-age population, in which the diagnostic criteria, impact on spinal pathology, and recovery/prevention measures remain understudied. However, further understanding of this therapeutically challenging pathology is paramount, as surgical outcome may be heavily influenced by sarcopenia status.

Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD) Impacts Long-Term Outcomes After Curative-Intent Surgery for Hepatocellular Carcinoma

BACKGROUND

Curative surgery for hepatocellular carcinoma (HCC) includes liver resection (LR) and orthotopic liver transplantation (OLT). Due to the obesity epidemic, metabolic dysfunction-associated steatotic liver disease (MASLD) is a frequent HCC aetiology that often coincides with increased alcohol consumption, termed MetALD, or even alcohol-associated liver disease (ALD).

METHODS

Patients undergoing LR or OLT for HCC at Charité-Universitätsmedizin Berlin (2010-2020) were included in this retrospective cohort study investigating disease aetiology, time to recurrence (TTR), overall survival (OS) and CT-based body composition.

RESULTS

Out of 579 patients with HCC, 417 underwent LR and 162 OLT. Tumour aetiologies were viral n = 191 (33.0%), MASLD n = 158 (27.3%), MetALD n = 51 (8.8%), ALD n = 68 (11.7%) and other/cryptogenic n = 111 (19.2%). Patients with MASLD and MetALD had more intramuscular (p < 0.001, p = 0.015) and visceral fat (both p < 0.001) than patients with non-metabolic dysfunction aetiologies. Patients with MASLD-HCC had comparable TTR (median 26 months, [95% CI: 23-31] vs. 30 months [95% CI: 4-57], p = 0.425) but shorter OS than patients with other HCC aetiologies (63 months [95% CI: 42-84] vs. 80 months [95% CI: 60-100], hazard ratio: 1.53 [95% CI: 1.050-2.229], p = 0.026) after LR. Multivariate analysis confirmed MASLD aetiology, portal vein thrombosis and MELD score ≥ 10 as independent prognostic factors for OS in LR (adjusted p = 0.021,p < 0.001,p = 0.003), even after excluding in-hospital mortality (adjusted p = 0.016,p = 0.002,p = 0.002). Causes of death were similar in MASLD and non-MASLD aetiology.

CONCLUSIONS

Patients with HCC undergoing LR and meeting the new MASLD criteria have significantly shorter OS. This study provides empirical prognostic evidence for the novel MASLD/MetALD classification in a large European cohort of patients undergoing curative-intent HCC therapy.

Refining visceral adipose tissue quantification: Influence of sex, age, and BMI on single slice estimation in 3D MRI of the German National Cohort

OBJECTIVES

High prevalence of visceral obesity and its associated complications underscore the importance of accurately quantifying visceral adipose tissue (VAT) depots. While whole-body MRI offers comprehensive insights into adipose tissue distribution, it is resource-intensive. Alternatively, evaluation of defined single slices provides an efficient approach for estimation of total VAT volume. This study investigates the influence of sex-, age-, and BMI on VAT distribution along the craniocaudal axis and total VAT volume obtained from single slice versus volumetric assessment in 3D MRI and aims to identify age-independent locations for accurate estimation of VAT volume from single slice assessment.

MATERIALS AND METHODS

This secondary analysis of the prospective population-based German National Cohort (NAKO) included 3D VIBE Dixon MRI from 11,191 participants (screened between May 2014 and December 2016). VAT and spine segmentations were automatically generated using fat-selective images. Standardized craniocaudal VAT profiles were generated. Axial percentage of total VAT was used for identification of reference locations for volume estimation of VAT from a single slice.

RESULTS

Data from 11,036 participants (mean age, 52 ± 11 years, 5681 men) were analyzed. Craniocaudal VAT distribution differed qualitatively between men/women and with respect to age/BMI. Age-independent single slice VAT estimates demonstrated strong correlations with reference VAT volumes. Anatomical locations for accurate VAT estimation varied with sex/BMI.

CONCLUSIONS

The selection of reference locations should be different depending on BMI groups, with a preference for caudal shifts in location with increasing BMI. For women with obesity (BMI >30 kg/m2), the L1 level emerges as the optimal reference location.

Low creatinine to cystatin C ratio is associated with lower muscle volumes and poorer gait speeds in the longitudinal Integrated Women's Health Program cohort

OBJECTIVE

Little is known about the longitudinal associations between creatinine-cystatin C ratios (CCR) with muscle volume and function during the menopausal transition. We investigated the longitudinal relationship of baseline CCR, with muscle volumes measured by magnetic resonance imaging (MRI), and objectively measured muscle strength and physical performance after 6.6-year follow-up.

METHODS

Participants from the Integrated Women's Health Programme (IWHP) cohort (n = 891, baseline mean age 56.2 ± 6.0) who attended both baseline and follow-up visits underwent objectively measured muscle strength and physical performance assessments and MRI. Creatinine to cystatin C ratio was calculated as (creatinine [mg/dL] / cystatin C [mg/L]) and low CCR were those in the lowest tertile (CCR < 8.16). Multivariable regression analyses were used to determine the associations of baseline CCR with muscle volumes and function 6.6 years later.

RESULTS

Baseline low CCR was associated with lower MRI-measured muscle volumes and poorer physical function 6.6 years later. Compared to high CCR group, mean fat-free thigh muscle volume of the low CCR group was 0.350 L lower (95% CI, 0.183-0.518) after adjustment for covariates. Similarly, the low CCR group was associated with 0.029 m/s slower (95% CI, 0.006-0.053) slower mean usual gait and 0.049 m/s slower (95% CI, 0.020-0.078) mean narrow gait speeds. CCR was not associated with handgrip strength and repeated chair stands and one-leg stand tests.

CONCLUSION

Low CCR at baseline was associated with lower fat-free muscle volumes and poorer gait speeds 6.6 years later. The potential of CCR as a predictive biomarker for adverse events related to sarcopenia in midlife women merits further investigation.

Body Shapes of Multiple Anthropometric Traits and All-cause and Cause-specific Mortality in the UK Biobank

BACKGROUND

Individual traditional anthropometric measures such as body mass index and waist circumference may not fully capture the relation of adiposity to mortality. Investigating multitrait body shapes could overcome this limitation, deepening insights into adiposity and mortality.

METHODS

Using UK Biobank data from 462,301 adults (40-69 years at baseline: 2006-2010), we derived four body shapes from principal component analysis on body mass index, height, weight, waist and hip circumference, and waist-to-hip ratio. We then used multivariable-adjusted Cox proportional hazard models to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for associations between body shapes and mortality for principal component scores of +1 and -1.

RESULTS

During 6,114,399 person-years of follow-up, 28,807 deaths occurred. A generally obese body shape exhibited a U-shaped mortality association. A tall and centrally obese body shape showed increased mortality risk in a dose-response manner (comparing a score of +1 and 0: HR = 1.16, 95% CI = 1.14, 1.18). Conversely, tall and lean or athletic body shapes displayed no increased mortality risks when comparing a score of +1 and 0, with positive relations for the comparison between a score of -1 and 0 in these shapes (short and stout shape: HR = 1.12, 95% CI = 1.10, 1.14; nonathletic shape: HR = 1.15, 95% CI = 1.13, 1.17).

CONCLUSION

Four distinct body shapes, reflecting heterogeneous expressions of obesity, were differentially associated with all-cause and cause-specific mortality. Multitrait body shapes may refine our insights into the associations between different adiposity subtypes and mortality.

Subphenotypes of body composition and their association with cardiometabolic risk - Magnetic resonance imaging in a population-based sample

BACKGROUND

For characterizing health states, fat distribution is more informative than overall body size. We used population-based whole-body magnetic resonance imaging (MRI) to identify distinct body composition subphenotypes and characterize associations with cardiovascular disease (CVD) risk.

METHODS

Bone marrow, visceral, subcutaneous, cardiac, renal, hepatic, skeletal muscle and pancreatic adipose tissue were measured by MRI in n = 299 individuals from the population-based KORA cohort. Body composition subphenotypes were identified by data-driven k-means clustering. CVD risk was calculated by established scores.

RESULTS

We identified five body composition subphenotypes, which differed substantially in CVD risk factor distribution and CVD risk. Compared to reference subphenotype I with favorable risk profile, two high-risk phenotypes, III&V, had a 3.8-fold increased CVD risk. High-risk subphenotype III had increased bone marrow and skeletal muscle fat (26.3 % vs 11.4 % in subphenotype I), indicating ageing effects, whereas subphenotype V showed overall high fat contents, and particularly elevated pancreatic fat (25.0 % vs 3.7 % in subphenotype I), indicating metabolic impairment. Subphenotype II had a 2.7-fold increased CVD risk, and an unfavorable fat distribution, probably smoking-related, while BMI was only slightly elevated. Subphenotype IV had a 2.8-fold increased CVD risk with comparably young individuals, who showed high blood pressure and hepatic fat (17.7 % vs 3.0 % in subphenotype I).

CONCLUSIONS

Whole-body MRI can identify distinct body composition subphenotypes associated with different degrees of cardiometabolic risk. Body composition profiling may enable a more comprehensive risk assessment than individual fat compartments, with potential benefits for individualized prevention.

Frailty and risk of metabolic dysfunction-associated steatotic liver disease and other chronic liver diseases

BACKGROUND & AIMS

Frailty is associated with multiple morbidities. However, its effect on chronic liver diseases remains largely unexplored. This study evaluated the association of frailty with the risk of incident metabolic dysfunction-associated steatotic liver disease (MASLD), cirrhosis, liver cancer, and liver-related mortality.

METHODS

A total of 339,298 participants without prior liver diseases from the UK Biobank were included. Baseline frailty was assessed by physical frailty and the frailty index, categorizing participants as non-frail, prefrail, or frail. The primary outcome was MASLD, with secondary outcomes, including cirrhosis, liver cancer, and liver-related mortality, confirmed through hospital admission records and death registries.

RESULTS

During a median follow-up of 11.6 years, 4,667 MASLD, 1,636 cirrhosis, 257 liver cancer, and 646 liver-related mortality cases were identified. After multivariable adjustment, the risk of MASLD was found to be higher in participants with prefrailty (physical frailty: hazard ratio [HR] 1.66, 95% CI 1.40-1.97; frailty index: HR 2.01, 95% CI 1.67-2.42) and frailty (physical frailty: HR 3.32, 95% CI 2.54-4.34; frailty index: HR 4.54, 95% CI 3.65-5.66) than in those with non-frailty. Similar results were also observed for cirrhosis, liver cancer, and liver-related mortality. Additionally, the frail groups had a higher risk of MASLD, which was defined as MRI-derived liver proton density fat fraction >5%, than the non-frail group (physical frailty: odds ratio 1.64, 95% CI 1.32-2.04; frailty index: odds ratio 1.48, 95% CI 1.30-1.68).

CONCLUSIONS

Frailty was associated with an increased risk of chronic liver diseases. Public health strategies should target reducing chronic liver disease risk in frail individuals.

IMPACT AND IMPLICATIONS

While frailty is common and associated with a poor prognosis in people with MASLD (metabolic dysfunction-associated steatotic liver disease) and advanced chronic liver diseases, its impact on the subsequent risk of these outcomes remains largely unexplored. Our study showed that frailty was associated with increased risks of MASLD, cirrhosis, liver cancer, and liver-related mortality. This finding suggests that assessing frailty may help identify a high-risk population vulnerable to developing chronic liver diseases. Implementing strategies that target frailty could have major public health benefits for liver-related disease prevention.

Higher Aircraft Noise Exposure Is Linked to Worse Heart Structure and Function by Cardiovascular MRI

BACKGROUND

Aircraft noise is a growing concern for communities living near airports.

OBJECTIVES

This study aimed to explore the impact of aircraft noise on heart structure and function.

METHODS

Nighttime aircraft noise levels (Lnight) and weighted 24-hour day-evening-night aircraft noise levels (Lden) were provided by the UK Civil Aviation Authority for 2011. Health data came from UK Biobank (UKB) participants living near 4 UK major airports (London Heathrow, London Gatwick, Manchester, and Birmingham) who had cardiovascular magnetic resonance (CMR) imaging starting from 2014 and self-reported no hearing difficulties. Generalized linear models investigated the associations between aircraft noise exposure and CMR metrics (derived using a validated convolutional neural network to ensure consistent image segmentations), after adjustment for demographic, socioeconomic, lifestyle, and environmental confounders. Mediation by cardiovascular risk factors was also explored. Downstream associations between CMR metrics and major adverse cardiac events (MACE) were tested in a separate prospective UKB subcohort (n = 21,360), to understand the potential clinical impact of any noise-associated heart remodeling.

RESULTS

Of the 3,635 UKB participants included, 3% experienced higher Lnight (≥45 dB) and 8% higher Lden (≥50 dB). Participants exposed to higher Lnight had 7% (95% CI: 4%-10%) greater left ventricular (LV) mass and 4% (95% CI: 2%-5%) thicker LV walls with a normal septal-to-lateral wall thickness ratio. This concentric LV remodeling is relevant because a 7% greater LV mass associates with a 32% greater risk of MACE. They also had worse LV myocardial dynamics (eg, an 8% [95% CI: 4%-12%] lower global circumferential strain which associates with a 27% higher risk of MACE). Overall, a hypothetical individual experiencing the typical CMR abnormalities associated with a higher Lnight exposure may have a 4 times higher risk of MACE. Findings were clearest for Lnight but were broadly similar in analyses using Lden. Body mass index and hypertension appeared to mediate 10% to 50% of the observed associations. Participants who did not move home during follow-up and were continuously exposed to higher aircraft noise levels had the worst CMR phenotype.

CONCLUSIONS

Higher aircraft noise exposure associates with adverse LV remodeling, potentially due to noise increasing the risk of obesity and hypertension. Findings are consistent with the existing literature on aircraft noise and cardiovascular disease, and need to be considered by policymakers and the aviation industry.

PennPRS: a centralized cloud computing platform for efficient polygenic risk score training in precision medicine

Polygenic risk scores (PRS) are becoming increasingly vital for risk prediction and stratification in precision medicine. However, PRS model training presents significant challenges for broader adoption of PRS, including limited access to computational resources, difficulties in implementing advanced PRS methods, and availability and privacy concerns over individual-level genetic data. Cloud computing provides a promising solution with centralized computing and data resources. Here we introduce PennPRS (https://pennprs.org), a scalable cloud computing platform for online PRS model training in precision medicine. We developed novel pseudo-training algorithms for multiple PRS methods and ensemble approaches, enabling model training without requiring individual-level data. These methods were rigorously validated through extensive simulations and large-scale real data analyses involving over 6,000 phenotypes across various data sources. PennPRS supports online single- and multi-ancestry PRS training with seven methods, allowing users to upload their own data or query from more than 27,000 datasets in the GWAS Catalog, submit jobs, and download trained PRS models. Additionally, we applied our pseudo-training pipeline to train PRS models for over 8,000 phenotypes and made their PRS weights publicly accessible. In summary, PennPRS provides a novel cloud computing solution to improve the accessibility of PRS applications and reduce disparities in computational resources for the global PRS research community.

The association between android-to-gynoid lean mass ratio and all-cause and specific-cause mortality in US adults: A prospective study

OBJECTIVE

The associations of lean mass distribution with mortality risk are not fully elucidated. We aimed to evaluate the effects of a new lean mass distribution indicator-android/gynoid lean mass ratio (AGLR) evaluated by dual-energy x-ray absorptiometry (DXA) on the risk of all-cause and specific-cause mortality in a NHANES cohort.

METHODS

This was a population-based cohort study, which included 18 542 subjects aged 20 years and older from the US National Health and Nutrition Examination Survey (US NHANES, 2003-2006 and 2011-2018). The primary outcomes of our study were all-cause mortality, cardiovascular (CVD) mortality and cancer mortality, which were obtained from the linkage to registries. Cox proportional hazard regression models were used to investigate the association between lean mass distribution and mortality risk among the US NHANES general population. Restricted cubic spline nested in Cox regression was also used to test whether there was a non-linear association of AGLR as a continuous variable with the risk of mortality.

RESULTS

During a median follow-up of 6.9 years, 1412 participants died, of whom 435 were due to CVD and 340 were due to cancer. The multivariable-adjusted (Model 4) hazard ratios (HRs) for each SD increase in AGLR were 1.53 (95% confidence interval [CI] 1.40-1.67) for all-cause mortality, 1.56 (95% CI 1.30-1.87) for cancer mortality and 1.64 (95% CI 1.47-1.84) for CVD mortality. The associations were robust in sensitivity analyses and present in most subgroups.

CONCLUSIONS

AGLR evaluated by DXA was associated with a higher risk of all-cause and specific-cause mortality among the general population from the US NHANES cohort.

Advances in body composition: a 100-year journey

Knowledge of human body composition at the dawn of the twentieth century was based largely on cadaver studies and chemical analyses of isolated organs and tissues. Matters soon changed by the nineteen twenties when the Czech anthropologist Jindřich Matiegka introduced an influential new anthropometric method of fractionating body mass into subcutaneous adipose tissue and other major body components. Today, one century later, investigators can not only quantify every major body component in vivo at the atomic, molecular, cellular, tissue-organ, and whole-body organizational levels, but go far beyond to organ and tissue-specific composition and metabolite estimates. These advances are leading to an improved understanding of adiposity structure-function relations, discovery of new obesity phenotypes, and a mechanistic basis of some weight-related pathophysiological processes and adverse clinical outcomes. What factors over the past one hundred years combined to generate these profound new body composition measurement capabilities in living humans? This perspective tracks the origins of these scientific innovations with the aim of providing insights on current methodology gaps and future research needs.

Fat-Free Mass: Friend or Foe to Metabolic Health?

BACKGROUND

Fat mass (FM) and fat-free mass (FFM) are body composition estimates commonly reported in research studies and clinical settings. Recently, fat-free mass indexed to height (fat-free mass index; FFMI) has been shown to be positively associated with impaired insulin sensitivity or insulin resistance. Consequently, hypertrophic resistance training which can increase FFM was also questioned. This paper sets out to evaluate these propositions.

METHODS

In this narrative review, we discuss possible reasons that link FFMI to adverse metabolic health outcomes including the limitations of the body composition model that utilizes FFM. The safety of resistance training is also briefly discussed.

RESULTS

Approximately 50% of FFM is comprised of skeletal muscle (SM), with the other 50% being viscera, skin, and bone; FFM and SM cannot be conflated. FFM and fat mass (FM) can both rise with increasing body weight and adiposity, indicating a positive correlation between the two compartments. Risk assessment models not adequately adjusting for this correlation may cause erroneous conclusions, however which way FM and FFM are indexed. Adipose tissue accumulation with weight gain, measured by dual-energy X-ray absorptiometry or bioelectrical impedance, can inflate FFM estimates owing to increased connective tissue. Increased adiposity can also result in fat deposition within skeletal muscle disrupting metabolic health. Importantly, non-skeletal muscle components of the FFM, i.e., the liver and pancreas, both critical in metabolic health, can also be negatively affected by the same lifestyle factors that impact SM. The most frequently used body composition techniques used to estimate FM and FFM cannot detect muscle, liver or pancreas fat infiltration. Prospective evidence demonstrates that resistance training is a safe and effective exercise modality across all ages, especially in older adults experiencing age- or disease-related declines in muscle health.

CONCLUSIONS

The association between FFM and insulin resistance is largely an artefact driven by inadequate assessment of skeletal muscle. If FM and FFM are used, at the minimum, they need to be evaluated in context with one another. Body composition methods, such as magnetic resonance imaging, which measures skeletal muscle rather than fat-free mass, and adipose tissue as well as muscle ectopic fat, are preferred methods. Resistance training is important in achieving and maintaining good health across the lifespan. While strength and power are critical components of resistance training, the reduction of skeletal mass through ageing or disease may require hypertrophic training to mitigate and slow down the progression of this often-inevitable process.

The association between the healthy lifestyle index and MRI-derived body composition measurements in the UK Biobank study

A high healthy lifestyle index (HLI) score, which reflects an adequate amount of sleep, no alcohol consumption, no smoking, a moderate to high physical activity level, a high quality diet, and a normal body mass index (BMI), has been associated with reduced risk of morbidity and mortality. We examined the relationship between the HLI and measurements of adipose and lean tissue volumes measured using magnetic resonance imaging (MRI). We studied 33,002 participants in the UK Biobank study, aged 40-69 years at enrolment. Information on lifestyle components was obtained at the baseline examination (2006-2010), while MRI was performed at a later exam (2014-2020). A multilevel HLI score, constructed by assigning individual scores to each HLI component, was categorized into quartiles in multivariable linear regression analyses. Higher HLI levels were associated with lower levels of body composition parameters (visceral and subcutaneous adipose tissue, total adipose tissue, total lean tissue, muscle fat infiltration, abdominal fat ratio, weight to muscle ratio) in a dose-dependent manner (tests-for-trend p-value < 0.001 for all parameters). When BMI was excluded from the HLI score and included separately in the model, a direct association between HLI score and total lean tissue volume was observed. Higher HLI scores were associated with a better body composition profile.

Visceral and subcutaneous adiposity and cardiovascular disease: Unravelling associations and prognostic value

AIM

The distribution pattern of abdominal adiposity may help determine cardiovascular disease (CVD). Waist circumference (WC) is the most common but imprecise method for measuring abdominal adiposity, as it fails to differentiate between visceral adipose tissue (VAT) and abdominal subcutaneous adipose tissue (ASAT). This study aimed to determine whether elevated VAT or ASAT provides greater prognostic value for CVD events compared to elevated WC in the general population using data from the UK Biobank.

MATERIALS AND METHODS

In this secondary analysis of UK Biobank study, 24 265 participants with available abdominal magnetic resonance imaging data were included. The primary outcome of the study was coronary heart disease (CHD), and secondary outcomes included stroke, heart failure (HF) and atrial fibrillation (AF). Cox regressions for VAT, ASAT and WC were examined in relation to the predefined outcomes on continuous scales using standard deviation (SD) changes and by categories of concordant and discordant values defined by medians.

RESULTS

During a mean follow-up period of 12.9 ± 1.8 years, 2641 participants developed CVD events (1296 CHD, 165 stroke, 286 HF and 894 AF) Each 1 SD increase in VAT yielded a hazard ratio (HR) of 1.15 (95% confidence interval [CI]: 1.09-1.22) for CHD risk, whereas ASAT had a HR of 1.10 (95% CI: 1.04-1.18). Further adjustment for WC eliminated the association between ASAT and CHD risk, in contrast to the association between VAT and CHD risk, which remained almost unaffected. Discordant VAT above the median with WC below presented a HR of 1.43 (95% CI: 1.15-1.78) for CHD, compared with concordant VAT and WC below the median. Similar results were found for discordant WC above the median with VAT below, with a HR of 1.46 (95% CI: 1.18-1.81). In contrast, discordant ASAT above the median with WC below was not associated with an increased risk of CHD. Similarly, discordant ASAT above the median with VAT below was not associated with an increased risk of CHD. Additionally, there was no observed association between VAT or ASAT and the risks of stroke, HF or AF after further adjustment for WC. Additionally, there was no observed association between VAT or ASAT and the risks of stroke, HF or AF after further adjustment for WC.

CONCLUSION

Incorporating VAT measurements alongside WC data improved the ability to identify individuals at high risk for CHD compared to using WC alone. Both VAT and WC proved to be more accurate indicators of CHD risk than ASAT. However, VAT alone did not fully account for the CHD risk associated with elevated WC levels. Neither VAT nor ASAT showed an association with the risk of stroke, HF and AF.

A validated estimate of visceral adipose tissue volume in relation to cancer risk

BACKGROUND

Despite the recognized role of visceral adipose tissue in carcinogenesis, its independent association with cancer risk beyond traditional obesity measures remains unknown because of limited availability of imaging data.

METHODS

We developed an estimation equation for visceral adipose tissue volume using elastic net regression based on demographic and anthropometric data in a subcohort of participants in the UK Biobank (UKB; n = 23 148) with abdominal magnetic resonance imaging scans. This equation was externally validated in 2713 participants from the 2017-2018 National Health and Nutrition Examination Survey according to sex, age, and race groups. We then applied the equation to the overall UKB cohort of 461 665 participants to evaluate the prospective association between estimated visceral adipose tissue and cancer risk using Cox proportional hazards models. We also calculated the population attributable risk of cancer associated with estimated visceral adipose tissue and body mass index (BMI).

RESULTS

Estimated visceral adipose tissue showed a high correlation with measured visceral adipose tissue in internal and external validations (r = 0.81-0.86). During a median 12-year follow-up in the UKB, we documented 37 397 incident cancer cases; estimated visceral adipose tissue was statistically significantly associated with elevated risk of obesity-related and individual cancers, independent of BMI and waist circumference. Population attributable risk for total cancer associated with high (quartiles 2-4 vs 1) estimated visceral adipose tissue (9.0% for men, 11.6% for women) was higher than high BMI (quartiles 2-4 vs 1 = 5.0% for men, 8.2% for women).

CONCLUSIONS

Estimated visceral adipose tissue showed robust performance in UKB and National Health and Nutrition Examination Survey and was associated with cancer risk independent of BMI and waist circumference. This study provides a potential clinical tool for visceral adipose tissue estimation and underscores that visceral adipose tissue can be an important target for cancer prevention.

Cardiovascular risk and obesity impact loss of grey matter volume earlier in males than females

BACKGROUND

It remains imperative to discover the time course that cardiovascular risk factors influence neurodegeneration in males and females and decipher whether the apolipoprotein (APOE) genotype mediates this relationship. Here we perform a large-scale evaluation of the influence of cardiovascular risk and obesity on brain volume in males and females in different age groups.

METHODS

34 425 participants between the ages of 45 and 82 years were recruited from the UK Biobank database https://www.ukbiobank.ac.uk. T1-weighted structural MR images (n=34 425) were downloaded locally for all participants, and voxel-based morphometry was performed to characterise the volumetric changes of the whole brain. The influence of Framingham cardiovascular risk (general cardiovascular risk), abdominal subcutaneous adipose tissue, and visceral adipose tissue volume (obesity) on cortical grey matter volume across different decades of life was evaluated with voxel-wise analysis.

RESULTS

In males, cardiovascular risk and obesity demonstrated the greatest influence on lower grey matter volume between 55-64 years of age. Female participants showed the greatest effect on lower grey matter volume between 65-74 years of age. Associations remained significant in APOE ε4 carriers and APOE ε4 non-carriers when evaluated separately.

CONCLUSIONS

The strongest influence of cardiovascular risk and obesity on reduced brain volume was between 55-64 years of age in males, whereas women were most susceptible to the detrimental effects of cardiovascular risk a decade later between 65-74 years of age. Here we elucidate the timing that targeting cardiovascular risk factors and obesity should be implemented in males and females to prevent neurodegeneration and Alzheimer's disease development.

Body composition and muscle composition phenotypes in patients on waitlist and shortly after liver transplant - results from a pilot study

BACKGROUND

Sarcopenia is common in end-stage liver disease and negatively impacts patients awaiting or undergoing liver transplantation (LT). Magnetic resonance imaging (MRI) may be used to measure body composition and sarcopenia. We aimed to evaluate the feasibility of MRI-based LT body composition profiling, describe waitlist body composition, and assess the natural rate of change in body composition while on the waitlist and post-LT.

METHODS

This prospective pilot study recruited adults listed for LT at an urban, tertiary care facility. Eighteen participants were scanned at time of waitlisting and 15 had follow-up MRIs (waitlist and/or post-LT). An 8-min MRI was used to measure body composition (AMRA® Researcher) including thigh fat-free muscle volume (FFMV) and fat infiltration (MFI), visceral (VAT) and abdominal subcutaneous (ASAT) adipose tissue volumes, and liver fat. A sex- and BMI invariant FFMV z-score (z-FFMV) was calculated, and muscle composition (MC) phenotypes were defined using the muscle assessment score (consisting of the FFMV z-score and sex-adjusted MFI). Rate of body composition change was calculated using mixed-effect modelling and is presented as rate per 30 days.

RESULTS

At time of waitlisting, 73% of the 18 participants had high MFI and 39% had the adverse MC (low FFMV z-score and high MFI) phenotype. Seven participants received an LT. Post-LT serial MRIs, at a median of 147 days apart within the first 200 days post-LT, demonstrated increased z-FFMV 0.22 SDs/(30 days) (p = 0.002), VAT 0.23 (p < 0.001), and ASAT 0.52 (p = 0.001) L/(30 days), but no change in MFI (p = 0.200) nor liver fat (p = 0.232).

CONCLUSION

MRI-based body composition profiling is feasible in LT patients and shortly after LT. This can be amended to routine clinical scans and may help in early identification of patients who may benefit from interventions to improve body composition. In addition, body composition changes significantly over time after LT.

Artificial intelligence driven definition of food preference endotypes in UK Biobank volunteers is associated with distinctive health outcomes and blood based metabolomic and proteomic profiles

BACKGROUND

Specific food preferences can determine an individual's dietary patterns and therefore, may be associated with certain health risks and benefits.

METHODS

Using food preference questionnaire (FPQ) data from a subset comprising over 180,000 UK Biobank participants, we employed Latent Profile Analysis (LPA) approach to identify the main patterns or profiles among participants. blood biochemistry across groups/profiles was compared using the non-parametric Kruskal-Wallis test. We applied the Limma algorithm for differential abundance analysis on 168 metabolites and 2923 proteins, and utilized the Database for Annotation, Visualization and Integrated Discovery (DAVID) to identify enriched biological processes and pathways. Relative risks (RR) were calculated for chronic diseases and mental conditions per group, adjusting for sociodemographic factors.

RESULTS

Based on their food preferences, three profiles were termed: the putative Health-conscious group (low preference for animal-based or sweet foods, and high preference for vegetables and fruits), the Omnivore group (high preference for all foods), and the putative Sweet-tooth group (high preference for sweet foods and sweetened beverages). The Health-conscious group exhibited lower risk of heart failure (RR = 0.86, 95%CI 0.79-0.93) and chronic kidney disease (RR = 0.69, 95%CI 0.65-0.74) compared to the two other groups. The Sweet-tooth group had greater risk of depression (RR = 1.27, 95%CI 1.21-1.34), diabetes (RR = 1.15, 95%CI 1.01-1.31), and stroke (RR = 1.22, 95%CI 1.15-1.31) compared to the other two groups. Cancer (overall) relative risk showed little difference across the Health-conscious, Omnivore, and Sweet-tooth groups with RR of 0.98 (95%CI 0.96-1.01), 1.00 (95%CI 0.98-1.03), and 1.01 (95%CI 0.98-1.04), respectively. The Health-conscious group was associated with lower levels of inflammatory biomarkers (e.g., C-reactive Protein) which are also known to be elevated in those with common metabolic diseases (e.g., cardiovascular disease). Other markers modulated in the Health-conscious group, ketone bodies, insulin-like growth factor-binding protein (IGFBP), and Growth Hormone 1 were more abundant, while leptin was less abundant. Further, the IGFBP pathway, which influences IGF1 activity, may be significantly enhanced by dietary choices.

CONCLUSIONS

These observations align with previous findings from studies focusing on weight loss interventions, which include a reduction in leptin levels. Overall, the Health-conscious group, with preference to healthier food options, has better health outcomes, compared to Sweet-tooth and Omnivore groups.

Poor muscle health and cardiometabolic risks associated with antidepressant treatment

OBJECTIVE

This study aims to investigate whether antidepressant users display differences in fat distribution and muscle composition relative to non-users and to explore risk factors for developing cardiovascular disease (CVD) and type 2 diabetes.

METHODS

The study used quantitative adipose and muscle tissue measures derived from magnetic resonance imaging data from UK Biobank (N = 40,174). Fat distribution and muscle composition of selective serotonin reuptake inhibitor (SSRI) and tricyclic antidepressant (TCA) users were compared with sex-, age-, and BMI-matched control individuals. Cox regression models were used to test for increased risk of developing CVD and type 2 diabetes.

RESULTS

SSRI users had more visceral fat, smaller muscle volume, and higher muscle fat infiltration compared with matched control individuals. Female users showed a larger increase in BMI over time compared with male users. However, male users displayed an unhealthier body composition profile. Male SSRI users also had an increased risk of developing CVD. Both male and female TCA users showed lower muscle volume and an increased risk of developing type 2 diabetes.

CONCLUSIONS

Adverse changes in body composition of antidepressant users are not captured by tracking the body weight or the BMI of the patients. These changes may lead to a worsened cardiometabolic risk profile.

Liver transplant recipients have worse metabolic body phenotype compared with matched non-transplant controls

Background and Aim

Quantification of body compartments, particularly the interaction between adipose tissue and skeletal muscle, is emerging as novel a biomarker of metabolic health. The present study evaluated the impact of liver transplant (LT) on body compartments.

Methods

Totally 66 adult LT recipients were enrolled in whom body compartments including visceral adipose tissue (VAT), abdominal subcutaneous adipose tissue (ASAT), muscle fat infiltration (MFI), fat-free muscle volume (FFMV), and liver fat (LF) were quantified via whole body magnetic resonance imaging (MRI). To provide non-LT comparison, each LT recipient was matched to at least 150 non-LT controls for same sex, age, and body mass index (BMI) from the UK Biobank registry.

Results

LT recipients (vs matched non-LT controls) had significantly higher subcutaneous (13.82 ± 5.47 vs 12.10 ± 5.10 L, P < 0.001) and visceral fat (7.59 ± 3.75 vs 6.72 ± 3.06 L, P = 0.003) and lower LF (5.88 ± 7.14 vs 8.75 ± 6.50%, P < 0.001) and muscle volume (11.69 ± 2.95 vs 12.12 ± 2.90 L, P = 0.027). In subgroup analysis, patients transplanted for metabolic dysfunction-associated steatohepatitis (MASH) cirrhosis (vs non-MASH cirrhosis) had higher ASAT, VAT, and MFI. A trend toward higher LF content was noted; however, this did not reach statistical significance (6.90 ± 7.35 vs 4.04 ± 6.23%, P = 0.189). Finally, compared with matched non-LT controls, patients transplanted for MASH cirrhosis had higher ASAT and VAT; however, FFMV and MFI were similar.

Conclusion

Using non-LT controls, the current study established the higher-than-expected adiposity burden among LT recipients, which is even higher among patients transplanted for MASH cirrhosis. These findings provide data needed to design future studies developing radiomics-based risk-stratification strategies in LT recipients.

Identification of novel genes whose expression in adipose tissue affects body fat mass and distribution: an RNA-Seq and Mendelian Randomization study

Many studies have shown that abdominal adiposity is more strongly related to health risks than peripheral adiposity. However, the underlying pathways are still poorly understood. In this cross-sectional study using data from RNA-sequencing experiments and whole-body MRI scans of 200 participants in the EPIC-Potsdam cohort, our aim was to identify novel genes whose gene expression in subcutaneous adipose tissue has an effect on body fat mass (BFM) and body fat distribution (BFD). The analysis identified 625 genes associated with adiposity, of which 531 encode a known protein and 487 are novel candidate genes for obesity. Enrichment analyses indicated that BFM-associated genes were characterized by their higher than expected involvement in cellular, regulatory and immune system processes, and BFD-associated genes by their involvement in cellular, metabolic, and regulatory processes. Mendelian Randomization analyses suggested that the gene expression of 69 genes was causally related to BFM and BFD. Six genes were replicated in UK Biobank. In this study, we identified novel genes for BFM and BFD that are BFM- and BFD-specific, involved in different molecular processes, and whose up-/downregulated gene expression may causally contribute to obesity.

Weight gain leads to greater adverse metabolic responses in South Asian compared with white European men: the GlasVEGAS study

South Asians (SAs) develop type 2 diabetes at lower body mass index values than white Europeans (WEs). This basic human experimental study aimed to compare the metabolic consequences of weight gain in SA and WE men without overweight or obesity. Fourteen SAs and 21 WEs had assessments of body composition, metabolic responses to mixed-meal ingestion, cardiorespiratory fitness and physical activity, and a subcutaneous abdominal adipose tissue biopsy, before and after 4-6 weeks of overfeeding to induce 5-7% weight gain. Here we show that body mass index and whole-body adipose tissue volume increases similarly between ethnic groups, but SAs gain less lean tissue. SAs experience a substantially greater decrease in insulin sensitivity compared with WEs (38% versus 7% decrease, P = 0.009), have fewer small (37.1% versus 60.0%, P = 0.003) and more large (26.2% versus 9.1%, P = 0.005) adipocytes at baseline and have a smaller decrease in very small adipocytes with weight gain (-0.1% versus -1.9%, P < 0.0001). Ethnic differences in adipocyte morphology are associated with SA's greater adverse metabolic changes with weight gain. ClinicalTrials.gov registration: NCT02399423 .

Linearity and bias of proton density fat fraction across the full dynamic range of 0-100%: a multiplatform, multivendor phantom study using 1.5T and 3T MRI at two sites

OBJECTIVE

Performance assessments of quantitative determinations of proton density fat fraction (PDFF) have largely focused on the range between 0 and 50%. We evaluate PDFF in a two-site phantom study across the full 0-100% PDFF range.

MATERIALS AND METHODS

We used commercially available 3D chemical-shift-encoded water-fat MRI sequences from three MRI system vendors at 1.5T and 3T and conducted the study across two sites. A spherical phantom housing 18 vials spanning the full 0-100% PDFF range was used. Data at each site were acquired using default parameters to determine same-day and different-day intra-scanner repeatability, and inter-system and inter-site reproducibility, in addition to linear regression between reference and measured PDFF values.

RESULTS

Across all systems, results demonstrated strong linearity and minimal bias. For 1.5T systems, a pooled slope of 0.99 with a 95% confidence interval (CI) of 0.981-0.997 and a pooled intercept of 0.61% PDFF with a 95% CI of 0.17-1.04 were obtained. Results for pooled 3T data included a slope of 1.00 (95% CI 0.995-1.005) and an intercept of 0.69% PDFF (95% CI 0.39-0.97). Inter-site and inter-system reproducibility coefficients ranged from 2.9 to 6.2 (in units of PDFF), while intra-scanner same-day and different-day repeatability ranged from 0.6 to 7.8.

DISCUSSION

PDFF across the 0-100% range can be reliably estimated using current commercial offerings at 1.5T and 3T.

Central Lean Mass Distribution and the Risks of All-Cause and Cause-Specific Mortality in 40,283 UK Biobank Participants

INTRODUCTION

The purpose of this study was to investigate the association of central lean mass distribution with the risk of mortality.

METHODS

This cohort study included 40,283 UK Biobank participants. Cox proportional hazards regression models were used to estimate the association of central lean mass distribution, i.e., trunk-to-leg lean mass ratio, assessed by dual-energy X-ray absorptiometry, with the risk of mortality.

RESULTS

The median age of the participants was 65 years, and 52% were women. During a median follow-up of 4.18 years, 674 participants died, of whom 366 were due to cancer and 126 were due to cardiovascular causes. Compared with the lowest tertile of a trunk-to-leg lean mass ratio, the multivariable-adjusted (age, sex, ethnicity, lifestyle, comorbidities, body mass index, and appendicular muscle mass index) hazards ratios of the highest tertile of trunk-to-leg lean mass ratio were 1.55 (95% CI: 1.23-1.94), 1.69 (95% CI: 1.26-2.26), and 1.14 (95% CI: 0.72-1.80) for all-cause, cancer, and cardiovascular mortality, respectively. Neutrophil-to-lymphocyte ratio mediated 9.3% (95% CI: 3.3%-40.4%) of the association of trunk-to-leg lean mass ratio with all-cause mortality. There was evidence for additive interactions of trunk-to-leg lean mass ratio with older age and poor diet quality for all-cause mortality.

CONCLUSION

Trunk-to-leg lean mass ratio, assessed by dual-energy X-ray absorptiometry, was positively associated with the risks of all-cause and cancer mortality, independent of general obesity and central obesity, in UK middle-aged and older adults. Central lean mass distribution may interact synergistically with aging and poor diet quality to further increase the risk of death.

Evaluating Sex-specific Differences in Abdominal Fat Volume and Proton Density Fat Fraction at MRI Using Automated nnU-Net-based Segmentation

Sex-specific abdominal organ volume and proton density fat fraction (PDFF) in people with obesity during a weight loss intervention was assessed with automated multiorgan segmentation of quantitative water-fat MRI. An nnU-Net architecture was employed for automatic segmentation of abdominal organs, including visceral and subcutaneous adipose tissue, liver, and psoas and erector spinae muscle, based on quantitative chemical shift-encoded MRI and using ground truth labels generated from participants of the Lifestyle Intervention (LION) study. Each organ's volume and fat content were examined in 127 participants (73 female and 54 male participants; body mass index, 30-39.9 kg/m2) and in 81 (54 female and 32 male participants) of these participants after an 8-week formula-based low-calorie diet. Dice scores ranging from 0.91 to 0.97 were achieved for the automatic segmentation. PDFF was found to be lower in visceral adipose tissue compared with subcutaneous adipose tissue in both male and female participants. Before intervention, female participants exhibited higher PDFF in subcutaneous adipose tissue (90.6% vs 89.7%; P < .001) and lower PDFF in liver (8.6% vs 13.3%; P < .001) and visceral adipose tissue (76.4% vs 81.3%; P < .001) compared with male participants. This relation persisted after intervention. As a response to caloric restriction, male participants lost significantly more visceral adipose tissue volume (1.76 L vs 0.91 L; P < .001) and showed a higher decrease in subcutaneous adipose tissue PDFF (2.7% vs 1.5%; P < .001) than female participants. Automated body composition analysis on quantitative water-fat MRI data provides new insights for understanding sex-specific metabolic response to caloric restriction and weight loss in people with obesity. Keywords: Obesity, Chemical Shift-encoded MRI, Abdominal Fat Volume, Proton Density Fat Fraction, nnU-Net ClinicalTrials.gov registration no. NCT04023942 Supplemental material is available for this article. Published under a CC BY 4.0 license.

Automated abdominal adipose tissue segmentation and volume quantification on longitudinal MRI using 3D convolutional neural networks with multi-contrast inputs

OBJECTIVE

Increased subcutaneous and visceral adipose tissue (SAT/VAT) volume is associated with risk for cardiometabolic diseases. This work aimed to develop and evaluate automated abdominal SAT/VAT segmentation on longitudinal MRI in adults with overweight/obesity using attention-based competitive dense (ACD) 3D U-Net and 3D nnU-Net with full field-of-view volumetric multi-contrast inputs.

MATERIALS AND METHODS

920 adults with overweight/obesity were scanned twice at multiple 3 T MRI scanners and institutions. The first scan was divided into training/validation/testing sets (n = 646/92/182). The second scan from the subjects in the testing set was used to evaluate the generalizability for longitudinal analysis. Segmentation performance was assessed by measuring Dice scores (DICE-SAT, DICE-VAT), false negatives (FN), and false positives (FP). Volume agreement was assessed using the intraclass correlation coefficient (ICC).

RESULTS

ACD 3D U-Net achieved rapid (< 4.8 s/subject) segmentation with high DICE-SAT (median ≥ 0.994) and DICE-VAT (median ≥ 0.976), small FN (median ≤ 0.7%), and FP (median ≤ 1.1%). 3D nnU-Net yielded rapid (< 2.5 s/subject) segmentation with similar DICE-SAT (median ≥ 0.992), DICE-VAT (median ≥ 0.979), FN (median ≤ 1.1%) and FP (median ≤ 1.2%). Both models yielded excellent agreement in SAT/VAT volume versus reference measurements (ICC > 0.997) in longitudinal analysis.

DISCUSSION

ACD 3D U-Net and 3D nnU-Net can be automated tools to quantify abdominal SAT/VAT volume rapidly, accurately, and longitudinally in adults with overweight/obesity.

Utilizing a novel MRI technique to identify adverse muscle composition in end-stage liver disease: A pilot study

INTRODUCTION AND OBJECTIVES

Sarcopenia is a common complication of end-stage liver disease (ESLD), but its exact relationship to myosteatosis and frailty remains unclear. In this pilot study, we tested the feasibility of a specialized MRI protocol and automated image analysis in patients with ESLD.

MATERIALS AND METHODS

In a single-center prospective study, adult liver transplant candidates with ESLD underwent assessment of muscle composition between 3/2022 and 6/2022 using the AMRA® MAsS Scan. The primary outcome of interest was feasibility of the novel MRI technique in patients with ESLD. We also tested if thigh muscle composition correlated with validated measures of frailty and sarcopenia.

RESULTS

Eighteen subjects (71 % male, mean age 59 years) were enrolled. The most common etiologies of cirrhosis were alcohol-related liver disease (44 %) and non-alcohol-associated fatty liver disease (33 %), with a mean MELD-Na of 13 (± 4). The mean time needed to complete the MRI protocol was 14.9 min and only one patient could not complete it due to metal hardware in both knees. Forty-one percent of patients had adverse muscle composition (high thigh fat infiltration and low-fat free muscle volume) and these patients were more likely to have undergone a recent large volume paracentesis (43 % vs. 0 %, p < 0.02). The adverse muscle composition group performed significantly worse on the 6-minute walk test compared to the remainder of the cohort (379 vs 470 m, p < 0.01).

CONCLUSIONS

The AMRA® MAsS Scan is feasible to perform in patients with ESLD and can be used to quantify myosteatosis, a marker of muscle quality and potentially muscle functionality in ESLD.

Multi-organ imaging-derived polygenic indexes for brain and body health

The UK Biobank (UKB) imaging project is a crucial resource for biomedical research, but is limited to 100,000 participants due to cost and accessibility barriers. Here we used genetic data to predict heritable imaging-derived phenotypes (IDPs) for a larger cohort. We developed and evaluated 4,375 IDP genetic scores (IGS) derived from UKB brain and body images. When applied to UKB participants who were not imaged, IGS revealed links to numerous phenotypes and stratified participants at increased risk for both brain and somatic diseases. For example, IGS identified individuals at higher risk for Alzheimer's disease and multiple sclerosis, offering additional insights beyond traditional polygenic risk scores of these diseases. When applied to independent external cohorts, IGS also stratified those at high disease risk in the All of Us Research Program and the Alzheimer's Disease Neuroimaging Initiative study. Our results demonstrate that, while the UKB imaging cohort is largely healthy and may not be the most enriched for disease risk management, it holds immense potential for stratifying the risk of various brain and body diseases in broader external genetic cohorts.

Effect of tirzepatide on body fat distribution pattern in people with type 2 diabetes

AIMS

To describe the overall fat distribution patterns independent of body mass index (BMI) in participants with type 2 diabetes (T2D) in the SURPASS-3 MRI substudy by comparison with sex- and BMI-matched virtual control groups (VCGs) derived from the UK Biobank imaging study at baseline and Week 52.

METHODS

For each study participant at baseline and Week 52 (N = 296), a VCG of ≥150 participants with the same sex and similar BMI was identified from the UK Biobank imaging study (N = 40 172). Average visceral adipose tissue (VAT), abdominal subcutaneous adipose tissue (aSAT) and liver fat (LF) levels and the observed standard deviations (SDs; standardized normal z-scores: z-VAT, z-aSAT and z-LF) were calculated based on the matched VCGs. Differences in z-scores between baseline and Week 52 were calculated to describe potential shifts in fat distribution pattern independent of weight change.

RESULTS

Baseline fat distribution patterns were similar across pooled tirzepatide (5, 10 and 15 mg) and insulin degludec (IDeg) arms. Compared with matched VCGs, SURPASS-3 participants had higher baseline VAT (mean [SD] z-VAT +0.42 [1.23]; p < 0.001) and LF (z-LF +1.24 [0.92]; p < 0.001) but similar aSAT (z-aSAT -0.13 [1.11]; p = 0.083). Tirzepatide-treated participants had significant decreases in z-VAT (-0.18 [0.58]; p < 0.001) and z-LF (-0.54 [0.84]; p < 0.001) but increased z-aSAT (+0.11 [0.50]; p = 0.012). Participants treated with IDeg had a significant change in z-LF only (-0.46 [0.90]; p = 0.001), while no significant changes were observed for z-VAT (+0.13 [0.52]; p = 0.096) and z-aSAT (+0.09 [0.61]; p = 0.303).

CONCLUSION

In this exploratory analysis, treatment with tirzepatide in people with T2D resulted in a significant reduction of z-VAT and z-LF, while z-aSAT was increased from an initially negative value, suggesting a possible treatment-related shift towards a more balanced fat distribution pattern with prominent VAT and LF loss.

Expression of mitochondrial oxidative stress response genes in muscle is associated with mitochondrial respiration, physical performance, and muscle mass in the Study of Muscle, Mobility, and Aging

Gene expression in skeletal muscle of older individuals may reflect compensatory adaptations in response to oxidative damage that preserve tissue integrity and maintain function. Identifying associations between oxidative stress response gene expression patterns and mitochondrial function, physical performance, and muscle mass in older individuals would further our knowledge of mechanisms related to managing molecular damage that may be targeted to preserve physical resilience. To characterize expression patterns of genes responsible for the oxidative stress response, RNA was extracted and sequenced from skeletal muscle biopsies collected from 575 participants (≥70 years old) from the Study of Muscle, Mobility, and Aging. Expression levels of 21 protein-coding RNAs related to the oxidative stress response were analyzed in relation to six phenotypic measures, including maximal mitochondrial respiration from muscle biopsies (Max OXPHOS), physical performance (VO2 peak, 400-m walking speed, and leg strength), and muscle size (thigh muscle volume and whole-body D3Cr muscle mass). The mRNA level of the oxidative stress response genes most consistently associated across outcomes are preferentially expressed within the mitochondria. Higher expression of mRNAs that encode generally mitochondria located proteins SOD2, TRX2, PRX3, PRX5, and GRX2 were associated with higher levels of mitochondrial respiration and VO2 peak. In addition, greater SOD2, PRX3, and GRX2 expression was associated with higher physical performance and muscle size. Identifying specific mechanisms associated with high functioning across multiple performance and physical domains may lead to targeted antioxidant interventions with greater impacts on mobility and independence.

Higher expression of denervation-responsive genes is negatively associated with muscle volume and performance traits in the study of muscle, mobility, and aging (SOMMA)

With aging skeletal muscle fibers undergo repeating cycles of denervation and reinnervation. In approximately the 8th decade of life reinnervation no longer keeps pace, resulting in the accumulation of persistently denervated muscle fibers that in turn cause an acceleration of muscle dysfunction. The significance of denervation in important clinical outcomes with aging is poorly studied. The Study of Muscle, Mobility, and Aging (SOMMA) is a large cohort study with the primary objective to assess how aging muscle biology impacts clinically important traits. Using transcriptomics data from vastus lateralis muscle biopsies in 575 participants we have selected 49 denervation-responsive genes to provide insights to the burden of denervation in SOMMA, to test the hypothesis that greater expression of denervation-responsive genes negatively associates with SOMMA participant traits that included time to walk 400 meters, fitness (VO2peak), maximal mitochondrial respiration, muscle mass and volume, and leg muscle strength and power. Consistent with our hypothesis, increased transcript levels of: a calciumdependent intercellular adhesion glycoprotein (CDH15), acetylcholine receptor subunits (CHRNA1, CHRND, CHRNE), a glycoprotein promoting reinnervation (NCAM1), a transcription factor regulating aspects of muscle organization (RUNX1), and a sodium channel (SCN5A) were each negatively associated with at least 3 of these traits. VO2peak and maximal respiration had the strongest negative associations with 15 and 19 denervation-responsive genes, respectively. In conclusion, the abundance of denervationresponsive gene transcripts is a significant determinant of muscle and mobility outcomes in aging humans, supporting the imperative to identify new treatment strategies to restore innervation in advanced age.

Approximation of bone mineral density and subcutaneous adiposity using T1-weighted images of the human head

Bones and brain are intricately connected and scientific interest in their interaction is growing. This has become particularly evident in the framework of clinical applications for various medical conditions, such as obesity and osteoporosis. The adverse effects of obesity on brain health have long been recognised, but few brain imaging studies provide sophisticated body composition measures. Here we propose to extract the following bone- and adiposity-related measures from T1-weighted MR images of the head: an approximation of skull bone mineral density (BMD), skull bone thickness, and two approximations of subcutaneous fat (i.e., the intensity and thickness of soft non-brain head tissue). The measures pertaining to skull BMD, skull bone thickness, and intensi-ty-based adiposity proxy proved to be reliable ( r =.93/.83/.74, p <.001) and valid, with high correlations to DXA-de-rived head BMD values (rho=.70, p <.001) and MRI-derived abdominal subcutaneous adipose volume (rho=.62, p <.001). Thickness-based adiposity proxy had only a low retest reliability ( r =.58, p <.001).The outcomes of this study constitute an important step towards extracting relevant non-brain features from available brain scans.

Risk stratification using magnetic resonance imaging-derived, personalized z-scores of visceral adipose tissue, subcutaneous adipose tissue, and liver fat in persons with obesity

BACKGROUND

Individual patterns of fat accumulation (visceral, subcutaneous, and/or liver fat) can determine cardiometabolic risk profile.

OBJECTIVE

To investigate risk stratification using personalized fat z-scores in persons with a body mass index (BMI) of 30-40 kg/m2 from the UK Biobank imaging study.

SETTING

Population-based study.

METHODS

Whole-body magnetic resonance (MR) images of 40,174 participants from the UK Biobank imaging study were analyzed for visceral adipose tissue (VAT), abdominal subcutaneous adipose tissue (aSAT), and liver fat (LF) and used to calculate sex- and body size-invariant fat z-scores (VATz, aSATz, LFz). Associations between z-scores and later incident cardiovascular disease (CVD) and type 2 diabetes (T2D) were investigated using Cox proportional hazards modeling and Kaplan-Meier curves in participants with BMI 30-40 kg/m2.

RESULTS

A total of 6716 participants had BMI 30-40 kg/m2 and within this group, CVD was positively associated with VATz (crude hazard ratio (cHR) [95% CI]: 1.30 [1.20-1.40], P < .001) and negatively associated with aSATz and LFz (cHR: 0.91 [0.85-0.99], P = .028, and 0.88 [0.82-0.95], P = .002). All z-scores remained significant after adjustment for sex, BMI, and age, but only VATz was significant when previous CVD was added. T2D was positively associated with VATz and LFz (cHR: 1.53 [1.40-1.67], P < .001, and 1.35 [1.23-148], P < .001) and negatively associated with aSATz (cHR: 0.90 [0.81-0.99], P = .026). All z-scores remained significant after adjustment for sex, BMI, and age.

CONCLUSIONS

Personalized MR-derived fat z-scores can identify phenotypes of obesity with specific cardiometabolic risk profiles regardless of BMI. Current guidelines for bariatric surgery based on BMI exclude some of these high-risk patients.

Spleen volume is independently associated with non-alcoholic fatty liver disease, liver volume and liver fibrosis

Non-alcoholic fatty liver disease (NAFLD) can lead to irreversible liver damage manifesting in systemic effects (e.g., elevated portal vein pressure and splenomegaly) with increased risk of deadly outcomes. However, the association of spleen volume with NAFLD and related type 2-diabetes (T2D) is not fully understood. The UK Biobank contains comprehensive health-data of 500,000 participants, including clinical data and MR images of >40,000 individuals. The present study estimated the spleen volume of 37,066 participants through automated deep learning-based image segmentation of neck-to-knee MR images. The aim was to investigate the associations of spleen volume with NAFLD, T2D and liver fibrosis, while adjusting for natural confounders. The recent redefinition and new designation of NAFLD to metabolic dysfunction-associated steatotic liver disease (MASLD), promoted by major organisations of studies on liver disease, was not employed as introduced after the conduct of this study. The results showed that spleen volume decreased with age, correlated positively with body size and was smaller in females compared to males. Larger spleens were observed in subjects with NAFLD and T2D compared to controls. Spleen volume was also positively and independently associated with liver fat fraction, liver volume and the fibrosis-4 score, with notable volumetric increases already at low liver fat fractions and volumes, but not independently associated with T2D. These results suggest a link between spleen volume and NAFLD already at an early stage of the disease, potentially due to initial rise in portal vein pressure.

Dissecting unique and common variance across body and brain health indicators using age prediction

Ageing is a heterogeneous multisystem process involving different rates of decline in physiological integrity across biological systems. The current study dissects the unique and common variance across body and brain health indicators and parses inter-individual heterogeneity in the multisystem ageing process. Using machine-learning regression models on the UK Biobank data set (N = 32,593, age range 44.6-82.3, mean age 64.1 years), we first estimated tissue-specific brain age for white and gray matter based on diffusion and T1-weighted magnetic resonance imaging (MRI) data, respectively. Next, bodily health traits, including cardiometabolic, anthropometric, and body composition measures of adipose and muscle tissue from bioimpedance and body MRI, were combined to predict 'body age'. The results showed that the body age model demonstrated comparable age prediction accuracy to models trained solely on brain MRI data. The correlation between body age and brain age predictions was 0.62 for the T1 and 0.64 for the diffusion-based model, indicating a degree of unique variance in brain and bodily ageing processes. Bayesian multilevel modelling carried out to quantify the associations between health traits and predicted age discrepancies showed that higher systolic blood pressure and higher muscle-fat infiltration were related to older-appearing body age compared to brain age. Conversely, higher hand-grip strength and muscle volume were related to a younger-appearing body age. Our findings corroborate the common notion of a close connection between somatic and brain health. However, they also suggest that health traits may differentially influence age predictions beyond what is captured by the brain imaging data, potentially contributing to heterogeneous ageing rates across biological systems and individuals.

Body composition and body fat distribution in tissue-specific insulin resistance and in response to a 12-week isocaloric dietary macronutrient intervention

BACKGROUND

Body composition and body fat distribution are important predictors of cardiometabolic diseases. The etiology of cardiometabolic diseases is heterogenous, and partly driven by inter-individual differences in tissue-specific insulin sensitivity.

OBJECTIVES

To investigate (1) the associations between body composition and whole-body, liver and muscle insulin sensitivity, and (2) changes in body composition and insulin sensitivity and their relationship after a 12-week isocaloric diet high in mono-unsaturated fatty acids (HMUFA) or a low-fat, high-protein, high-fiber (LFHP) diet.

METHODS

This subcohort analysis of the PERSON study includes 93 individuals (53% women, BMI 25-40 kg/m2, 40-75 years) who participated in this randomized intervention study. At baseline and after 12 weeks of following the LFHP, or HMUFA diet, we performed a 7-point oral glucose tolerance test to assess whole-body, liver, and muscle insulin sensitivity, and whole-body magnetic resonance imaging to determine body composition and body fat distribution. Both diets are within the guidelines of healthy nutrition.

RESULTS

At baseline, liver fat content was associated with worse liver insulin sensitivity (β [95%CI]; 0.12 [0.01; 0.22]). Only in women, thigh muscle fat content was inversely related to muscle insulin sensitivity (-0.27 [-0.48; -0.05]). Visceral adipose tissue (VAT) was inversely associated with whole-body, liver, and muscle insulin sensitivity. Both diets decreased VAT, abdominal subcutaneous adipose tissue (aSAT), and liver fat, but not whole-body and tissue-specific insulin sensitivity with no differences between diets. Waist circumference, however, decreased more following the LFHP diet as compared to the HMUFA diet (-3.0 vs. -0.5 cm, respectively). After the LFHP but not HMUFA diet, improvements in body composition were positively associated with improvements in whole-body and liver insulin sensitivity.

CONCLUSIONS

Liver and muscle insulin sensitivity are distinctly associated with liver and muscle fat accumulation. Although both LFHP and HMUFA diets improved in body fat, VAT, aSAT, and liver fat, only LFHP-induced improvements in body composition are associated with improved insulin sensitivity.

TRIAL REGISTRATION

NCT03708419 (clinicaltrials.gov).

Energetics and clinical factors for the time required to walk 400 m: The Study of Muscle, Mobility and Aging (SOMMA)

BACKGROUND

Walking slows with aging often leading to mobility disability. Mitochondrial energetics has been found to be associated with gait speed over short distances. Additionally, walking is a complex activity but few clinical factors that may be associated with walk time have been studied.

METHODS

We examined 879 participants ≥70 years and measured the time to walk 400 m. We tested the hypothesis that decreased mitochondrial energetics by respirometry in muscle biopsies and magnetic resonance spectroscopy in the thigh and is associated with longer time to walk 400 m. We also used cardiopulmonary exercise testing to assess the energetic costs of walking: maximum oxygen consumption (VO2peak) and energy cost-capacity (the ratio of VO2, at a slow speed to VO2peak). In addition, we tested the hypothesis that selected clinical factors would also be associated with 400-m walk time.

RESULTS

Lower Max OXPHOS was associated with longer walk time, and the association was explained by the energetic costs of walking, leg power, and weight. Additionally, a multivariate model revealed that longer walk time was also significantly associated with lower VO2peak, greater cost-capacity ratio, weaker leg power, heavier weight, hip and knee stiffness, peripheral neuropathy, greater perceived exertion while walking slowly, greater physical fatigability, less moderate-to-vigorous exercise, less sedentary time, and anemia. Significant associations between age, sex, muscle mass, and peripheral artery disease with 400-m walk time were explained by other clinical and physiologic factors.

CONCLUSIONS

Lower mitochondrial energetics is associated with needing more time to walk 400 m. This supports the value of developing interventions to improve mitochondrial energetics. Additionally, doing more moderate-to-vigorous exercise, increasing leg power, reducing weight, treating hip and knee stiffness, and screening for and treating anemia may reduce the time required to walk 400 m and reduce the risk of mobility disability.

Linking sarcopenia, brain structure and cognitive performance: a large-scale UK Biobank study

Sarcopenia refers to age-related loss of muscle mass and function and is related to impaired somatic and brain health, including cognitive decline and Alzheimer's disease. However, the relationships between sarcopenia, brain structure and cognition are poorly understood. Here, we investigate the associations between sarcopenic traits, brain structure and cognitive performance. We included 33 709 UK Biobank participants (54.2% female; age range 44-82 years) with structural and diffusion magnetic resonance imaging, thigh muscle fat infiltration (n = 30 561) from whole-body magnetic resonance imaging (muscle quality indicator) and general cognitive performance as indicated by the first principal component of a principal component analysis across multiple cognitive tests (n = 22 530). Of these, 1703 participants qualified for probable sarcopenia based on low handgrip strength, and we assigned the remaining 32 006 participants to the non-sarcopenia group. We used multiple linear regression to test how sarcopenic traits (probable sarcopenia versus non-sarcopenia and percentage of thigh muscle fat infiltration) relate to cognitive performance and brain structure (cortical thickness and area, white matter fractional anisotropy and deep and lower brain volumes). Next, we used structural equation modelling to test whether brain structure mediated the association between sarcopenic and cognitive traits. We adjusted all statistical analyses for confounders. We show that sarcopenic traits (probable sarcopenia versus non-sarcopenia and muscle fat infiltration) are significantly associated with lower cognitive performance and various brain magnetic resonance imaging measures. In probable sarcopenia, for the included brain regions, we observed widespread significant lower white matter fractional anisotropy (77.1% of tracts), predominantly lower regional brain volumes (61.3% of volumes) and thinner cortical thickness (37.9% of parcellations), with |r| effect sizes in (0.02, 0.06) and P-values in (0.0002, 4.2e-29). In contrast, we observed significant associations between higher muscle fat infiltration and widespread thinner cortical thickness (76.5% of parcellations), lower white matter fractional anisotropy (62.5% of tracts) and predominantly lower brain volumes (35.5% of volumes), with |r| effect sizes in (0.02, 0.07) and P-values in (0.0002, 1.9e-31). The regions showing the most significant effect sizes across the cortex, white matter and volumes were of the sensorimotor system. Structural equation modelling analysis revealed that sensorimotor brain regions mediate the link between sarcopenic and cognitive traits [probable sarcopenia: P-values in (0.0001, 1.0e-11); muscle fat infiltration: P-values in (7.7e-05, 1.7e-12)]. Our findings show significant associations between sarcopenic traits, brain structure and cognitive performance in a middle-aged and older adult population. Mediation analyses suggest that regional brain structure mediates the association between sarcopenic and cognitive traits, with potential implications for dementia development and prevention.

Multimodality Imaging in Metabolic Syndrome: State-of-the-Art Review

Metabolic syndrome comprises a set of risk factors that include abdominal obesity, impaired glucose tolerance, hypertriglyceridemia, low high-density lipoprotein levels, and high blood pressure, at least three of which must be fulfilled for diagnosis. Metabolic syndrome has been linked to an increased risk of cardiovascular disease and type 2 diabetes mellitus. Multimodality imaging plays an important role in metabolic syndrome, including diagnosis, risk stratification, and assessment of complications. CT and MRI are the primary tools for quantification of excess fat, including subcutaneous and visceral adipose tissue, as well as fat around organs, which are associated with increased cardiovascular risk. PET has been shown to detect signs of insulin resistance and may detect ectopic sites of brown fat. Cardiovascular disease is an important complication of metabolic syndrome, resulting in subclinical or symptomatic coronary artery disease, alterations in cardiac structure and function with potential progression to heart failure, and systemic vascular disease. CT angiography provides comprehensive evaluation of the coronary and systemic arteries, while cardiac MRI assesses cardiac structure, function, myocardial ischemia, and infarction. Liver damage results from a spectrum of nonalcoholic fatty liver disease ranging from steatosis to fibrosis and possible cirrhosis. US, CT, and MRI are useful in assessing steatosis and can be performed to detect and grade hepatic fibrosis, particularly using elastography techniques. Metabolic syndrome also has deleterious effects on the pancreas, kidney, gastrointestinal tract, and ovaries, including increased risk for several malignancies. Metabolic syndrome is associated with cerebral infarcts, best evaluated with MRI, and has been linked with cognitive decline. ©RSNA, 2024 Test Your Knowledge questions for this article are available in the supplemental material. See the invited commentary by Pickhardt in this issue.

Skewness in Body fat Distribution Pattern Links to Specific Cardiometabolic Disease Risk Profiles

OBJECTIVE

Fat distribution pattern could help determine cardiometabolic risk profile. This study aimed to evaluate the association of balance/imbalance between visceral adipose tissue (VAT), abdominal subcutaneous adipose tissue (aSAT), and liver fat (LF) with incident type 2 diabetes (T2D) and cardiovascular disease (CVD) in the UK Biobank prospective cohort study.

METHODS

Magnetic resonance images of 40 174 participants were analyzed for VAT, aSAT, and LF using AMRA® Researcher. To assess fat distribution patterns independent of body mass index (BMI), fat z-scores (z-VAT, z-aSAT, z-LF) were calculated. Participants without prevalent T2D/CVD (N = 35 138) were partitioned based on balance between (1) z-VAT and z-LF (z-scores = 0 as cut-points for high/low), (2) z-VAT and z-aSAT, and (3) z-LF and z-aSAT. Associations with T2D/CVD were investigated using Cox regression (crude and adjusted for sex, age, BMI, lifestyle, arterial hypertension, statin treatment).

RESULTS

T2D was significantly associated with z-LF (hazard ratio, [95% CI] 1.74 [1.52-1.98], P < .001) and z-VAT (1.70 [1.49-1.95], P < .001). Both remained significant after full adjustment. For z-scores balance, strongest associations with T2D were z-VAT > 0 and z-LF > 0 (4.61 [2.98-7.12]), z-VAT > 0 and z-aSAT < 0 (4.48 [2.85-7.06]), and z-LF > 0 and z-aSAT < 0 (2.69 [1.76-4.12]), all P < .001. CVD was most strongly associated with z-VAT (1.22 [1.16-1.28], P < .001) which remained significant after adjustment for sex, age, BMI, and lifestyle. For z-scores balance, strongest associations with CVD were z-VAT > 0 and z-LF < 0 (1.53 [1.34-1.76], P < .001) and z-VAT > 0 and z-aSAT < 0 (1.54 [1.34-1.76], P < .001). When adjusted for sex, age, and BMI, only z-VAT > 0 and z-LF < 0 remained significant.

CONCLUSION

High VAT in relation to BMI (z-VAT > 0) was consistently linked to both T2D and CVD; z-LF > 0 was linked to T2D only. Skewed fat distribution patterns showed elevated risk for CVD (z-VAT > 0 and z-LF < 0 and z-VAT > 0 and z-aSAT < 0) and T2D (z-VAT > 0 and z-aSAT < 0).

Association of Visceral Obesity Indices With Incident Diabetic Retinopathy in Patients With Diabetes: Prospective Cohort Study

BACKGROUND

Visceral adipose tissue plays an active role in the pathogenesis of type 2 diabetes and vascular dysfunction. The lipid accumulation product (LAP), visceral adiposity index (VAI), and Chinese VAI (CVAI) have been proposed as simple and validated surrogate indices for measuring visceral adipose tissue. However, the evidence from prospective studies on the associations between these novel indices of visceral obesity and diabetic retinopathy (DR) remains scant.

OBJECTIVE

This study aimed to investigate the longitudinal associations of LAP, VAI, and CVAI with incident DR in Chinese patients with diabetes.

METHODS

This was a prospective cohort study conducted in Guangzhou in southern China. We collected baseline data between November 2017 and July 2020, while on-site follow-up visits were conducted annually until January 2022. The study participants consisted of 1403 patients with a clinical diagnosis of diabetes, referred from primary care, who were free of DR at baseline. The LAP, VAI, and CVAI levels were calculated by sex-specific equations based on anthropometric and biochemical parameters. DR was assessed using 7-field color stereoscopic fundus photographs and graded according to the modified Airlie House Classification scheme. Time-dependent Cox proportional hazard models were constructed to estimate the hazard ratios with 95% CIs. Restricted cubic spline curves were fitted to examine the dose-response relationship between the 3 indices of visceral obesity and new-onset DR. Subgroup analyses were performed to investigate the potential effect modifiers.

RESULTS

The mean age of study participants was 64.5 (SD 7.6) years, and over half (816/1403, 58.2%) were female. During a median follow-up of 2.13 years, 406 DR events were observed. A 1-SD increment in LAP, VAI, or CVAI was consistently associated with increased risk for new-onset DR, with a multivariable‑adjusted hazard ratio of 1.24 (95% CI 1.09-1.41; P=.001), 1.22 (95% CI 1.09-1.36; P<.001), and 1.48 (95% CI 1.19-1.85; P=.001), respectively. Similar patterns were observed across tertiles in LAP (P for trend=.001), VAI (P for trend<.001), and CVAI (P for trend=.009). Patients in the highest tertile of LAP, VAI, and CVAI had an 84%, 86%, and 82% higher hazard of DR, respectively, compared to those in the lowest tertile. A nonlinear dose-response relationship with incident DR was noted for LAP and VAI (both P for nonlinearity<.05), but not for CVAI (P for nonlinearity=.51). We did not detect the presence of effect modification by age, sex, duration of diabetes, BMI, or comorbidity (all P for interaction>.10).

CONCLUSIONS

Visceral obesity, as measured by LAP, VAI, or CVAI, is independently associated with increased risk for new-onset DR in Chinese patients with diabetes. Our findings may suggest the necessity of incorporating regular monitoring of visceral obesity indices into routine clinical practice to enhance population-based prevention for DR.

Body composition, lifestyle, and depression: a prospective study in the UK biobank

BACKGROUND

Obesity has been related to depression and adhering healthy lifestyle was beneficial to lower the risk of depression; however, little is known about the relationship between body composition and fat distribution with depression risk and the influence of body composition and fat distribution on the association of lifestyle and depression. Therefore, we aimed to investigate whether body composition and fat distribution were associated with the adverse events of depression and the relationship between lifestyle and depression.

METHODS

We included 330,131 participants without depression at baseline in the UK Biobank (mean age, 56.9 years; 53.83% females). The assessment of depression was sourced from health outcomes across self-report, primary care, hospital inpatient data, and death data. Body composition was determined by bioelectrical impedance. Seven lifestyles (no current smoking, moderate alcohol consumption, regular physical activity, healthy diet, less sedentary behavior, healthy sleep pattern, and appropriate social connection) were used to generate a lifestyle score.

RESULTS

During a median of 11.7 years of follow-up, 7576 incident depression occurred. All the body composition measures were positively associated with depression risk, with the Hazard ratios (HR) for the uppermost tertile (T3) versus the lowest tertile (T1) ranging from 1.26 (95% CI: 1.15-1.39) for trunk fat-free mass (TFFM) to 1.78 (1.62-1.97) for leg fat percentage (LFP). In addition, we found significant interactions between fat mass-related indices, especially leg fat mass (LFM) (p = 1.65 × 10-9), and lifestyle score on the risk of depression, for which the beneficial associations of a healthy lifestyle with the risk of depression were more evident among participants with low body fat measurement.

CONCLUSIONS

High levels of body composition measures were associated with an increased depression risk. Adverse body composition measures may weaken the link between a healthy lifestyle and a reduced risk of depression.

Precision MRI phenotyping of muscle volume and quality at a population scale

Introduction: Magnetic resonance imaging (MRI) enables direct measurements of muscle volume and quality, allowing for an in-depth understanding of their associations with anthropometric traits, and health conditions. However, it is unclear which muscle volume measurements: total muscle volume, regional measurements, measurements of muscle quality: intermuscular adipose tissue (IMAT) or proton density fat fraction (PDFF), are most informative and associate with relevant health conditions such as dynapenia and frailty. Methods: We have measured image-derived phenotypes (IDPs) including total and regional muscle volumes and measures of muscle quality, derived from the neck-to-knee Dixon images in 44,520 UK Biobank participants. We further segmented paraspinal muscle from 2D quantitative MRI to quantify muscle PDFF and iron concentration. We defined dynapenia based on grip strength below sex-specific cut-off points and frailty based on five criteria (weight loss, exhaustion, grip strength, low physical activity and slow walking pace). We used logistic regression to investigate the association between muscle volume and quality measurements and dynapenia and frailty. Results: Muscle volumes were significantly higher in male compared with female participants, even after correcting for height while, IMAT (corrected for muscle volume) and paraspinal muscle PDFF were significantly higher in female compared with male participants. From the overall cohort, 7.6% (N = 3,261) were identified with dynapenia, and 1.1% (N = 455) with frailty. Dynapenia and frailty were positively associated with age and negatively associated with physical activity levels. Additionally, reduced muscle volume and quality measurements were associated with both dynapenia and frailty. In dynapenia, muscle volume IDPs were most informative, particularly total muscle exhibiting odds ratios (OR) of 0.392, while for frailty, muscle quality was found to be most informative, in particular thigh IMAT volume indexed to height squared (OR = 1.396), both with p-values below the Bonferroni-corrected threshold (p < 8.8 × 10 - 5 ). Conclusion: Our fully automated method enables the quantification of muscle volumes and quality suitable for large population-based studies. For dynapenia, muscle volumes particularly those including greater body coverage such as total muscle are the most informative, whilst, for frailty, markers of muscle quality were the most informative IDPs. These results suggest that different measurements may have varying diagnostic values for different health conditions.

Reduced metabolic flexibility is a predictor of weight gain among liver transplant recipients

Metabolic flexibility is the ability to match biofuel availability to utilization and is inversely associated with increased metabolic burden among liver transplant (LT) recipients. The present study evaluated the impact of metabolic flexibility on weight gain following LT. LT recipients were enrolled prospectively (n = 47) and followed for 6 months. Metabolic flexibility was measured using whole-room calorimetry and is expressed as a respiratory quotient (RQ). Peak RQ represents maximal carbohydrate metabolism and occurs in the post-prandial state, while trough RQ represents maximal fatty acid metabolism occurring in the fasted state. The clinical, metabolic, and laboratory characteristics of the study cohort of lost weight (n = 14) and gained weight (n = 33) were similar at baseline. Patients who lost weight were more likely to reach maximal RQ (maximal carbohydrate oxidation) early and rapidly transitioned to trough RQ (maximal fatty acid oxidation). In contrast, patients who gained weight had delayed time to peak RQ and trough RQ. In multivariate modeling, time to peak RQ (β-coefficient 0.509, p = 0.01), time from peak RQ to trough RQ (β-coefficient 0.634, p = 0.006), and interaction between time to peak RQ to trough RQ and fasting RQ (β-coefficient 0.447, p = 0.02) directly correlated with the severity of weight gain. No statistically significant relationship between peak RQ, trough RQ, and weight change was demonstrated. Inefficient transition between biofuels (carbohydrates and fatty acids) is associated with weight gain in LT recipients that is independent of clinical metabolic risk. These data offer novel insight into the physiology of obesity after LT with the potential to develop new diagnostics and therapeutics.

Pain and the biochemistry of fibromyalgia: patterns of peripheral cytokines and chemokines contribute to the differentiation between fibromyalgia and controls and are associated with pain, fat infiltration and content

Objectives

This explorative study analyses interrelationships between peripheral compounds in saliva, plasma, and muscles together with body composition variables in healthy subjects and in fibromyalgia patients (FM). There is a need to better understand the extent cytokines and chemokines are associated with body composition and which cytokines and chemokines differentiate FM from healthy controls.

Methods

Here, 32 female FM patients and 30 age-matched female healthy controls underwent a clinical examination that included blood sample, saliva samples, and pain threshold tests. In addition, the subjects completed a health questionnaire. From these blood and saliva samples, a panel of 68 mainly cytokines and chemokines were determined. Microdialysis of trapezius and erector spinae muscles, phosphorus-31 magnetic resonance spectroscopy of erector spinae muscle, and whole-body magnetic resonance imaging for determination of body composition (BC)-i.e., muscle volume, fat content and infiltration-were also performed.

Results

After standardizing BC measurements to remove the confounding effect of Body Mass Index, fat infiltration and content are generally increased, and fat-free muscle volume is decreased in FM. Mainly saliva proteins differentiated FM from controls. When including all investigated compounds and BC variables, fat infiltration and content variables were most important, followed by muscle compounds and cytokines and chemokines from saliva and plasma. Various plasma proteins correlated positively with pain intensity in FM and negatively with pain thresholds in all subjects taken together. A mix of increased plasma cytokines and chemokines correlated with an index covering fat infiltration and content in different tissues. When muscle compounds were included in the analysis, several of these were identified as the most important regressors, although many plasma and saliva proteins remained significant.

Discussion

Peripheral factors were important for group differentiation between FM and controls. In saliva (but not plasma), cytokines and chemokines were significantly associated with group membership as saliva compounds were increased in FM. The importance of peripheral factors for group differentiation increased when muscle compounds and body composition variables were also included. Plasma proteins were important for pain intensity and sensitivity. Cytokines and chemokines mainly from plasma were also significantly and positively associated with a fat infiltration and content index.

Conclusion

Our findings of associations between cytokines and chemokines and fat infiltration and content in different tissues confirm that inflammation and immune factors are secreted from adipose tissue. FM is clearly characterized by complex interactions between peripheral tissues and the peripheral and central nervous systems, including nociceptive, immune, and neuroendocrine processes.

Lumbar Disc Degeneration Is Linked to Dorsal Subcutaneous Fat Thickness at the L1-L2 Intervertebral Disc Level Measured by MRI

BACKGROUND

Obese individuals have a higher risk of degenerative disc disease (DDD). Currently, body mass index is not sensitive enough to differentiate between muscle and fat distribution, and obesity-related health issues are linked to the way body fat is distributed. Therefore, this study aims to investigate the association between the dorsal subcutaneous fat thickness (DSFT) of the lumbar spine, an alternative measurement tool of body fat distribution, and DDD.

METHODS

A total of 301 patients with DDD and 123 participants without the disease were recruited. Using length functions of magnetic resonance imaging (MRI) console, the DSFT of L1 to S1 intervertebral disc levels was measured in mid-sagittal spin-echo T2 weighted image. The Mann-Whitney U test and Chi-squared test (X2) were utilized to examine any variations between the case and control groups. Logistic regression models were built to explore the association of the DSFT with DDD.

RESULTS

The logistical regression model showed a positive association between DDD and DSFT [OR: 1.30, 95% CI: 1.02-1.64, p = 0.03]. In the stratified logistic regression analysis, a positive association was found between DDD and DSFT among younger participants and females [OR young: 1.48; 95% CI (1.02-2.20); p = 0.04-OR female: 1.37; 95% CI (1-1.88); p = 0.05].

CONCLUSIONS

Younger females with thicker DSFT at the L1-L2 level are more likely to develop DDD. This suggests that increased DSFT may be a contributing factor to DDD.

A rapid, non-invasive, clinical surveillance for CachExia, sarcopenia, portal hypertension, and hepatocellular carcinoma in end-stage liver disease: the ACCESS-ESLD study protocol

BACKGROUND

Liver cirrhosis, the advanced stage of many chronic liver diseases, is associated with escalated risks of liver-related complications like decompensation and hepatocellular carcinoma (HCC). Morbidity and mortality in cirrhosis patients are linked to portal hypertension, sarcopenia, and hepatocellular carcinoma. Although conventional cirrhosis management centered on treating complications, contemporary approaches prioritize preemptive measures. This study aims to formulate novel blood- and imaging-centric methodologies for monitoring liver cirrhosis patients.

METHODS

In this prospective study, 150 liver cirrhosis patients will be enrolled from three Swedish liver clinics. Their conditions will be assessed through extensive blood-based markers and magnetic resonance imaging (MRI). The MRI protocol encompasses body composition profile with Muscle Assement Score, portal flow assessment, magnet resonance elastography, and a abbreviated MRI for HCC screening. Evaluation of lifestyle, muscular strength, physical performance, body composition, and quality of life will be conducted. Additionally, DNA, serum, and plasma biobanking will facilitate future investigations.

DISCUSSION

The anticipated outcomes involve the identification and validation of non-invasive blood- and imaging-oriented biomarkers, enhancing the care paradigm for liver cirrhosis patients. Notably, the temporal evolution of these biomarkers will be crucial for understanding dynamic changes.

TRIAL REGISTRATION

Clinicaltrials.gov, registration identifier NCT05502198. Registered on 16 August 2022. Link: https://classic.

CLINICALTRIALS

gov/ct2/show/NCT05502198 .

Body Composition Evaluation and Clinical Markers of Cardiometabolic Risk in Patients with Phenylketonuria

Cardiovascular diseases are the main cause of mortality worldwide. Patients with phenylketonuria (PKU) may be at increased cardiovascular risk. This review provides an overview of clinical and metabolic cardiovascular risk factors, explores the connections between body composition (including fat mass and ectopic fat) and cardiovascular risk, and examines various methods for evaluating body composition. It particularly focuses on nutritional ultrasound, given its emerging availability and practical utility in clinical settings. Possible causes of increased cardiometabolic risk in PKU are also explored, including an increased intake of carbohydrates, chronic exposure to amino acids, and characteristics of microbiota. It is important to evaluate cardiovascular risk factors and body composition in patients with PKU. We suggest systematic monitoring of body composition to develop nutritional management and hydration strategies to optimize performance within the limits of nutritional therapy.