The role of MRI in understanding the underlying mechanisms in obesity associated diseases

Non-invasive mapping of brown adipose tissue activity with magnetic resonance imaging

Thermogenic brown adipose tissue (BAT) has a positive impact on whole-body metabolism. However, in vivo mapping of BAT activity typically relies on techniques involving ionizing radiation, such as [18F]fluorodeoxyglucose ([18F]FDG) positron emission tomography (PET) and computed tomography (CT). Here we report a noninvasive metabolic magnetic resonance imaging (MRI) approach based on creatine chemical exchange saturation transfer (Cr-CEST) contrast to assess in vivo BAT activity in rodents and humans. In male rats, a single dose of the β3-adrenoceptor agonist (CL 316,243) or norepinephrine, as well as cold exposure, triggered a robust elevation of the Cr-CEST MRI signal, which was consistent with the [18F]FDG PET and CT data and 1H nuclear magnetic resonance measurements of creatine concentration in BAT. We further show that Cr-CEST MRI detects cold-stimulated BAT activation in humans (both males and females) using a 3T clinical scanner, with data-matching results from [18F]FDG PET and CT measurements. This study establishes Cr-CEST MRI as a promising noninvasive and radiation-free approach for in vivo mapping of BAT activity.

Measurement of subcutaneous fat tissue: reliability and comparison of caliper and ultrasound via systematic body mapping

Caliper and ultrasound (US) are used to measure subcutaneous fat tissue depth (SFT) and then to calculate total body fat. There is no evidence-based recommendation as to whether caliper or US are equally accurate. The aim of this paper was therefore to compare reliability of both methods. In this methodical study, 54 participants (BMI: 24.8 ± 3.5 kg/m²; Age: 43.2 ± 21.7 years) were included. Using systematic body mapping, the SFT of 56 areas was measured. We also analyzed 4 body sites via MRI. A comparison between caliper and US detected clear differences in mean SFT of all areas (0.83 ± 0.33 cm vs. 1.14 ± 0.54 cm; p < 0.001) showing moderate reliability (ICC 0.669, 95%CI: 0.625–0.712). US and MRI revealed in the abdominal area a SFT twice as thick as caliper (2.43 ± 1.36 cm vs. 2.26 ± 1.32 cm vs. 1.15 ± 0.66 cm; respectively). Caliper and US revealed excellent intrarater (ICC caliper: 0.944, 95%CI: 0.926–0.963; US: 0.934, 95%CI: 0.924–0.944) and good interrater reliability (ICC caliper: 0.794, 95%CI: 0.754–0.835; US: 0.825, 95%CI: 0.794–0.857). Despite the high reliability in measuring SFT that caliper and US show, our comparison of the two methods yielded clear differences in SFT, particularly in the abdominal area. In accuracy terms, US is preferable for most mapping areas.

3T-MRI-based age, sex and site-specific markers of musculoskeletal health in healthy children and young adults

Objective

The aim of this study is to investigate the role of 3T-MRI in assessing musculoskeletal health in children and young people.

Design

Bone, muscle and bone marrow imaging was performed in 161 healthy participants with a median age of 15.0 years (range, 8.0, 30.0).

Methods

Detailed assessment of bone microarchitecture (constructive interference in the steady state (CISS) sequence, voxel size 0.2 × 0.2 × 0.4 mm3), bone geometry (T1-weighted turbo spin echo (TSE) sequence, voxel size 0.4 × 0.4 × 2 mm3) and bone marrow (1H-MRS, point resolved spectroscopy sequence (PRESS) (single voxel size 20 × 20 × 20 mm3) size and muscle adiposity (Dixon, voxel size 1.1 × 1.1 × 2 mm3).

Results

There was an inverse association of apparent bone volume/total volume (appBV/TV) with age (r = -0.5, P < 0.0005). Cortical area, endosteal and periosteal circumferences and muscle cross-sectional area showed a positive association to age (r > 0.49, P < 0.0001). In those over 17 years of age, these parameters were also higher in males than females (P < 0.05). This sex difference was also evident for appBV/TV and bone marrow adiposity (BMA) in the older participants (P < 0.05). AppBV/TV showed a negative correlation with BMA (r = -0.22, P = 0.01) which also showed an association with muscle adiposity (r = 0.24, P = 0.04). Cortical geometric parameters were highly correlated with muscle area (r > 0.57, P < 0.01).

Conclusions

In addition to providing deep insight into the normal relationships between bone, fat and muscle in young people, these novel data emphasize the role of MRI as a non-invasive method for performing a comprehensive and integrated assessment of musculoskeletal health in the growing skeleton.

Associations of the BDNF Val66Met Polymorphism With Body Composition, Cardiometabolic Risk Factors, and Energy Intake in Youth With Obesity: Findings From the HEARTY Study

The brain-derived neurotrophic factor (BDNF) Val66Met polymorphism is functionally related to BDNF, and is associated with obesity and metabolic complications in adults, but limited research exists among adolescents. This study comparatively examined carriers and non-carriers of the BDNF Val66Met polymorphism on body composition, energy intake, and cardiometabolic profile among adolescents with obesity. The sample consisted of 187 adolescents with obesity; 99 were carriers of the homozygous Val (G/G) alleles and 88 were carriers of the Val/Met (G/A) or Met (A/A) alleles. Cardiometabolic profile and DNA were quantified from fasted blood samples. Body composition was assessed by magnetic resonance imaging (MRI). Compared to carriers of the homozygous Val (G/G) allele, carriers of the Val/Met (G/A) or Met/Met (A/A) variants exhibited significantly higher protein (p = 0.01) and fat (p = 0.05) intake, C-Reactive protein (p = 0.05), and a trend toward higher overall energy intake (p = 0.07), fat-free mass (p = 0.07), and lower HDL-C (p = 0.07) Results showed for the first time that among youth with obesity, carriers of the Val66Met BDNF Met-alleles exhibited significantly higher C-reactive protein and energy intake in the form of fat and protein compared to Val-allele carriers, thereby providing support for the possible role of BDNF in appetite, weight, and metabolic regulation during adolescence. Clinical Trial Registration: http://clinicaltrials.gov/, identifier NCT00195858.

Mothers' cafeteria diet induced sex-specific changes in fat content, metabolic profiles, and inflammation outcomes in rat offspring

“Western diet” containing high concentrations of sugar and fat consumed during pregnancy contributes to development of obesity and diabetes type 2 in offspring. To mimic effects of this diet in animals, a cafeteria (CAF) diet is used. We hypothesized that CAF diet given to rats before, and during pregnancy and lactation differently influences fat content, metabolic and inflammation profiles in offspring. Females were exposed to CAF or control diets before pregnancy, during pregnancy and lactation. At postnatal day 25 (PND 25), body composition, fat contents were measured, and blood was collected for assessment of metabolic and inflammation profiles. We have found that CAF diet lead to sex-specific alterations in offspring. At PND25, CAF offspring had: (1) higher percentage of fat content, and were lighter; (2) sex-specific differences in levels of glucose; (3) higher levels of interleukin 6 (IL-6), interleukin-10 (IL-10) and tumor necrosis factor (TNF-α); (4) sex-specific differences in concentration of IL-6 and TNF-α, with an increase in CAF females; (5) higher level of IL-10 in both sexes, with a more pronounced increase in females. We concluded that maternal CAF diet affects fat content, metabolic profiles, and inflammation parameters in offspring. Above effects are sex-specific, with female offspring being more susceptible to the diet.

Magnetic resonance imaging of obesity and metabolic disorders: Summary from the 2019 ISMRM Workshop

More than 100 attendees from Australia, Austria, Belgium, Canada, China, Germany, Hong Kong, Indonesia, Japan, Malaysia, the Netherlands, the Philippines, Republic of Korea, Singapore, Sweden, Switzerland, the United Kingdom, and the United States convened in Singapore for the 2019 ISMRM-sponsored workshop on MRI of Obesity and Metabolic Disorders. The scientific program brought together a multidisciplinary group of researchers, trainees, and clinicians and included sessions in diabetes and insulin resistance; an update on recent advances in water-fat MRI acquisition and reconstruction methods; with applications in skeletal muscle, bone marrow, and adipose tissue quantification; a summary of recent findings in brown adipose tissue; new developments in imaging fat in the fetus, placenta, and neonates; the utility of liver elastography in obesity studies; and the emerging role of radiomics in population-based "big data" studies. The workshop featured keynote presentations on nutrition, epidemiology, genetics, and exercise physiology. Forty-four proffered scientific abstracts were also presented, covering the topics of brown adipose tissue, quantitative liver analysis from multiparametric data, disease prevalence and population health, technical and methodological developments in data acquisition and reconstruction, newfound applications of machine learning and neural networks, standardization of proton density fat fraction measurements, and X-nuclei applications. The purpose of this article is to summarize the scientific highlights from the workshop and identify future directions of work.

Associations of plasma CD36 and body fat distribution

CONTEXT

CD36 is a class B scavenger-receptor involved in the uptake of fatty acids in liver and adipose tissue. It is unknown whether plasma CD36 levels are related to liver fat content or adipose tissue in the general population.

METHODS

We measured plasma CD36 from 575 participants of the community-based PopGen-cohort who underwent magnetic resonance imaging (MRI) to quantify visceral (VAT) and subcutaneous (SAT) adipose tissue and liver signal intensity (LSI), a proxy for liver fat content. Non-alcoholic fatty liver disease (NAFLD) was defined as LSI ≥3.0 in the absence of high alcohol intake. The relations between plasma CD36 and body mass index (BMI), VAT, SAT, LSI, and NAFLD were evaluated using multivariable-adjusted linear and logistic regression analysis.

RESULTS

Plasma CD36 concentrations were correlated with BMI (r=0.11; P=0.01), SAT (r=0.16; P<0.001), and VAT (r=0.15, P<0.001), but not with LSI (P=0.44). In multivariable-adjusted regression models, mean BMI values rose across CD36-quartiles (Q1: 27.8 kg/m2; Q4: 28.9 kg/m2; P-trend=0.013). Similarly, VAT (Q1: 4.13 dm3; Q4: 4.71 dm3; P-trend<0.001) and SAT (Q1: 7.61 dm3; Q4: 8.74 dm3; P-trend<0.001) rose across CD36 quartiles. Plasma CD36 concentrations were unrelated to LSI (P-trend=0.36), and NAFLD (P-trend=0.64). Participants with NAFLD and elevated alanine aminotransferase (ALT), a marker for liver damage, had higher CD36 compared to NAFLD participants with normal ALT.

CONCLUSIONS

Higher plasma concentrations of CD36 were associated with greater general and abdominal adiposity, but not with liver fat content or NAFLD in this community-based sample. However, plasma CD36 may reflect more severe liver damage in NAFLD.

Associations of Fetal and Infant Weight Change With General, Visceral, and Organ Adiposity at School Age

IMPORTANCE

Both fetal and infant growth influence obesity later in life. The association of longitudinal fetal and infant growth patterns with organ fat is unknown.

OBJECTIVE

To examine the associations of fetal and infant weight change with general, visceral, and organ adiposity at school age.

DESIGN, SETTING, AND PARTICIPANTS

This cohort study was embedded in the Generation R Study, a population-based prospective cohort study in Rotterdam, the Netherlands. Pregnant women with a delivery date between April 2002 and January 2006 were eligible to participate. Follow-up measurements were performed for 3205 children. Data analysis of this population was performed from July 26, 2018, to February 7, 2019.

EXPOSURES

Fetal weight was estimated in the second and third trimester of pregnancy. Infant weight was measured at 6, 12, and 24 months. Fetal and infant weight acceleration or deceleration were defined as a change in standard deviation scores greater than 0.67 between 2 ages.

MAIN OUTCOMES AND MEASURES

Visceral fat index, pericardial fat index, and liver fat fraction were measured by magnetic resonance imaging.

RESULTS

The sample consisted of 3205 children (1632 girls [50.9%]; mean [SD] age, 9.8 [0.3] years). Children born small for gestational age had the lowest median body mass index compared with children born appropriate for gestational age and large for gestational age (16.4 [90% range, 14.1-23.6] vs 16.9 [90% range, 14.4-22.8] vs 17.4 [90% range, 14.9-22.7]). Compared with children with normal fetal and infant growth (533 of 2370 [22.5%]), those with fetal weight deceleration followed by infant weight acceleration (263 of 2370 [11.1%]) had the highest visceral fat index (standard deviation scores, 0.18; 95% CI, 0.03-0.33; P = .02) and liver fat fraction (standard deviation scores, 0.34; 95% CI, 0.20-0.48; P < .001).

CONCLUSIONS AND RELEVANCE

Fetal and infant weight change patterns were both associated with childhood body fat, but weight change patterns in infancy tended to have larger effects. Fetal growth restriction followed by infant growth acceleration was associated with increased visceral and liver fat.

Subcutaneous fat mass in infancy and abdominal, pericardial and liver fat assessed by Magnetic Resonance Imaging at the age of 10 years

BACKGROUND/OBJECTIVES

Fat mass development in infancy contributes to later adiposity, but its relation to ectopic fat depots is unknown. We examined the associations of infant subcutaneous fat with childhood general and organ-specific fat.

SUBJECTS/METHODS

Among 593 children from a population-based prospective cohort study, we obtained total subcutaneous fat mass (as sum of biceps, triceps, suprailiacal, and subscapular skinfolds thickness), central-to-total subcutaneous fat ratio (sum of suprailiacal and subscapular skinfold thickness/total subcutaneous fat) at 1.5, 6 and 24 months of age. At 10 years, we assessed BMI, fat mass index (FMI) based on total body fat by dual-energy X-ray absorptiometry, and abdominal subcutaneous, visceral and pericardial fat mass indices, and liver fat fraction by Magnetic Resonance Imaging.

RESULTS

A higher central-to-total subcutaneous fat ratio at 1.5 months only and higher total subcutaneous fat at 6 and 24 months were associated with higher BMI, FMI and subcutaneous fat mass index at 10 years. The observed associations were the strongest between total subcutaneous fat at 24 months and these childhood outcomes (difference per 1-SDS increase in total subcutaneous fat: 0.15 SDS (95% Confidence Interval (CI) 0.08, 0.23), 0.17 SDS (95% CI 0.10, 0.24), 0.16 SDS (95% CI 0.08, 0.23) for BMI, FMI and childhood subcutaneous fat mass index, respectively). Infant subcutaneous fat measures at any time point were not associated with visceral and pericardial fat mass indices, and liver fat fraction at 10 years.

CONCLUSIONS

Our results suggest that infant subcutaneous fat is associated with later childhood abdominal subcutaneous fat and general adiposity, but not with other organ-specific fat depots.

Infant breastfeeding and childhood general, visceral, liver, and pericardial fat measures assessed by magnetic resonance imaging

Background

Although a longer duration of breastfeeding has been associated with a lower risk of childhood obesity, the impact on specific organ fat depots is largely unknown.

Objective

We examined the associations of any breastfeeding, duration and exclusiveness of breastfeeding, and of age at introduction of solid foods with measures of general, visceral, and organ adiposity at 10 y.

Design

In a population-based prospective cohort study in 4444 children, we obtained information on infant feeding by questionnaires. At the mean age of 9.8 y, we estimated body mass index from height and weight; fat mass index and fat-free mass index by dual-energy X-ray absorptiometry; and visceral fat index, pericardial fat index, and liver fat fraction by MRI. MRI scans were performed in a subgroup of 2646 children.

Results

After adjustment for age and sex, we observed associations of infant feeding with all general, visceral, and organ fat outcomes, except for pericardial fat index, at the age of 10 y. After further adjustment for family-based sociodemographic, maternal lifestyle-related, and childhood factors, only the associations of shorter breastfeeding duration and nonexclusive breastfeeding with a lower fat-free mass index remained significant (P < 0.05). The associations of infant feeding with visceral fat index and liver fat fraction were attenuated to nonsignificant. Maternal education was found to be the strongest confounder.

Conclusion

Our results suggest that the assoiations of any breastfeeding, duration and exclusiveness of breastfeeding, and age at the introduction of solid foods with general, visceral, and organ fat measures at the age of 10 y are largely explained by family-based sociodemographic factors.

Associations of adult genetic risk scores for adiposity with childhood abdominal, liver and pericardial fat assessed by magnetic resonance imaging

Background

Genome-wide association studies (GWAS) identified single nucleotide polymorphisms (SNPs) involved in adult fat distribution. Whether these SNPs also affect abdominal and organ-specific fat accumulation in children is unknown.

Methods

In a population-based prospective cohort study among 1 995 children (median age: 9.8 years, 95% range 9.4;10.8), We tested the associations of six genetic risk scores based on previously identified SNPs for childhood BMI, adult BMI, liver fat, WHR, pericardial fat mass, visceral- and subcutaneous adipose tissue ratio (VAT/SAT ratio), and four individual SAT and VAT associated SNPs, for association with SAT (N=1 746), VAT (N=1 742), VAT/SAT ratio (N=1 738), liver fat fraction (N=1 950), and pericardial fat mass (N=1 803) measured by Magnetic Resonance Imaging.

Results

Per additional risk allele in the childhood BMI genetic risk score, SAT increased 0.020 standard deviation scores (SDS), (95% confidence interval (CI) 0.009;0.031, p-value:3.28*10^-4) and VAT increased 0.021 SDS, 95% CI:0.009;0.032, p-value:4.68*10^-4). The adult BMI risk score was positively associated with SAT (0.022 SDS increase, CI:0.015;0.029, p-value:1.33*10^-9), VAT (0.017 SDS increase, CI:0.010;0.025, p-value:7.00*10^-6), and negatively with VAT/SAT ratio (-0.012 SDS decrease, CI:-0.019;-0.006, p-value:2.88*10^-4). The liver fat risk score was associated with liver fat fraction (0.121 SDS, CI:0.086;0.157, p-value:2.65*10^-11). Rs7185735 (SAT), was associated with SAT (0.151 SDS, CI:0.087;0.214, p-value:3.00*10^-6) and VAT/SAT ratio (-0.126 SDS, CI:-0.186;-0.065, p-value:4.70*10^-5). After stratification by sex the associations of the adult BMI risk score with SAT and VAT and of the liver fat risk score with liver fat fraction remained in both sexes. Associations of the childhood BMI risk score with SAT, and the adult BMI risk score with VAT/SAT ratio were present among boys only, whereas the association of the pericardial fat risk score with pericardial fat was present among girls only.

Conclusion

Genetic variants associated with BMI, body fat distribution, liver and pericardial fat already affect body fat distribution in childhood.