Intramyocellular lipid is associated with visceral adiposity, markers of insulin resistance, and cardiovascular risk in prepubertal children: the EPOCH study

Fat as a Friend or Foe of the Bone

PURPOSE OF REVIEW

The objective of this review is to summarize the literature on the prevalence and diagnosis of obesity and its metabolic profile, including bone metabolism, focusing on the main inflammatory and turnover bone mediators that better characterize metabolically healthy obesity phenotype, and to summarize the therapeutic interventions for obesity with their effects on bone health.

RECENT FINDINGS

Osteoporosis and fracture risk not only increase with age and menopause but also with metabolic diseases, such as diabetes mellitus. Thus, patients with high BMI may have a higher bone fragility and fracture risk. However, some obese individuals with healthy metabolic profiles seem to be less at risk of bone fracture. Obesity has become an alarming disease with growing prevalence and multiple metabolic comorbidities, resulting in a significant burden on healthcare and increased mortality. The imbalance between increased food ingestion and decreased energy expenditure leads to pathological adipose tissue distribution and function, with increased secretion of proinflammatory markers and harmful consequences for body tissues, including bone tissue. However, some obese individuals seem to have a healthy metabolic profile and may not develop cardiometabolic disease during their lives. This healthy metabolic profile also benefits bone turnover and is associated with lower fracture risk.

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.

Epigenetic age acceleration is associated with speed of pubertal growth but not age of pubertal onset

Using data from a longitudinal cohort of children, we examined whether epigenetic age acceleration (EAA) was associated with pubertal growth and whether these associations were mediated by adiposity. We examined associations between EAA at approximately 10 years of age with pubertal growth metrics, including age at peak height velocity (PHV), PHV, and sex steroid levels and whether these associations were mediated by measures of adiposity including body mass index (BMI) and MRI-assessed visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT). Children (n = 135) with accelerated EAA had higher PHV (β 0.018, p = 0.0008) although the effect size was small. The association between EAA and age at PHV was not significant (β  - 0.0022, p = 0.067). Although EAA was associated with higher BMI (β 0.16, p = 0.0041), VAT (β 0.50, p = 0.037), and SAT (β 3.47, p = 0.0076), BMI and VAT did not mediate associations between EAA and PHV, while SAT explained 8.4% of the association. Boys with higher EAA had lower total testosterone (β  - 12.03, p = 0.0014), but associations between EAA and other sex steroids were not significant, and EAA was not associated with sex steroid levels in girls. We conclude that EAA did not have strong associations with either age at onset of puberty or pubertal growth speed, although associations with growth speed were statistically significant. Studies with larger sample sizes are needed to confirm this pattern of associations.

The association of dietary insulin load and dietary insulin index with body composition among professional soccer players and referees

BACKGROUND

There has been limited research undertaken about the association of dietary insulin load (DIL) and dietary insulin index (DII) with body composition in non-athletic adults, however, to the best of our knowledge No previous study has investigated such an association in an athletic population.

PURPOSE

The aim of this study was to explore the association of DII and DIL with body compositions in male and female soccer players and referees.

METHODS

The cross-sectional study was conducted on 199 professional male and female soccer players and referees. A 147-item semi-quantitative food frequency questionnaire (FFQ) was adopted to congregate the participants' dietary data. Body composition was measured using InBody to gain a detailed understanding of fat mass, percent body fat (PBF), lean mass, percent muscle mass (PMM), and bone mineral content (BMC). Waist circumference (WC), hip circumference (HC), waist-to-hip ratio (WHR), and waist-to-height ratio (WHtR) were obtained from all participants. Other body composition parameters include a body shape index (ABSI), abdominal volume index (AVI), body adiposity index (BAI), body roundness index (BRI), conicity index (CI), weight-adjusted waist index (WWI) and waist-to-hip-to-height ratio (WHHR) were calculated using a particular defined formula.

RESULTS

Results of multiple linear regression revealed that there is a significant association between DIL and BMI (P = 0.04) in < 18 male soccer players, CI (P = 0.04) and WWI (P = 0.03) in ≥ 18 female soccer players, PBF (P = 0.02), PMM (P = 0.01) and WWI (P = 0.01) in ≥ 18 female soccer players. Nevertheless, no significant associations between DIL and body composition parameters were found in the referees. Additionally, there is a significant association between DII and BMC (P = 0.02) in male soccer referees, however, no significant associations were found in young soccer players and female athletes.

CONCLUSION

This study demonstrates that DIL is positively associated with BMI, CI, and WWI in male soccer players and PBF, and WWI in female soccer players. Although, there was an observed negative association between DIL and PMM in females. In addition, a significant negative association between DII and BMC was observed in male soccer players.

Gestational diabetes mellitus, epigenetic age and offspring metabolism

AIMS

No reports examine the relationship between in-utero exposure to gestational diabetes mellitus (GDM), offspring epigenetic age acceleration (EAA), and offspring insulin sensitivity.

METHODS

Using data from a cohort study, we examined associations between GDM in-utero exposure and offspring EAA at approximately 10 years of age, using separate regression models adjusting for offspring chronological age and sex. We also examined associations between EAA with updated homeostasis model assessment of insulin sensitivity and secretion (HOMA2-S and HOMA2-β) measured at approximately 10 and 16 years of age, using mixed linear regression models accounting for repeated measures after adjustment for offspring chronological age and sex.

RESULTS

Compared to unexposed offspring (n = 91), offspring exposed to GDM (n = 88) had greater EAA or older extrinsic age compared to chronological age (β-coefficient 2.00, 95% confidence interval [0.71, 3.28], p = 0.0025), but not greater intrinsic EAA (β-coefficient -0.07, 95% CI [-0.71, 0.57], p = 0.93). Extrinsic EAA was associated with lower insulin sensitivity (β-coefficient -0.018, 95% CI [-0.035, -0.002], p = 0.03) and greater insulin secretion (β-coefficient 0.018, 95% CI [0.006, 0.03], p = 0.003), and these associations persisted after further adjustment for measures of maternal and child adiposity. No associations were observed between intrinsic EAA and insulin sensitivity and secretion, before or after adjustment for measures of maternal and child adiposity.

CONCLUSIONS

In this study, children exposed to GDM experience greater extrinsic EAA, which is associated with lower insulin sensitivity and greater insulin secretion. Further studies are needed to determine the directionality of these associations.

Simultaneous monitoring of mouse grip strength, force profile, and cumulative force profile distinguishes muscle physiology following surgical, pharmacologic and diet interventions

Grip strength is a valuable preclinical assay to study muscle physiology in disease and aging by directly determining changes in muscle force generation in active laboratory mice. Existing methods to statistically evaluate grip strength, however, have limitations in the power and scope of the physiological features that are assessed. We therefore designed a microcontroller whose serial measure of resistance-based force enables the simultaneous readout of (1) peak grip strength, (2) force profile (the non-linear progress of force exerted throughout a standard grip strength trial), and (3) cumulative force profile (the integral of force with respect to time of a single grip strength trial). We hypothesized that muscle pathologies of different etiologies have distinct effects on these parameters. To test this, we used our apparatus to assess the three muscle parameters in mice with impaired muscle function resulting from surgically induced peripheral pain, genetic peripheral neuropathy, adverse muscle effects induced by statin drug, and metabolic alterations induced by a high-fat diet. Both surgically induced peripheral nerve injury and statin-associated muscle damage diminished grip strength and force profile, without affecting cumulative force profile. Conversely, genetic peripheral neuropathy resulting from lipin 1 deficiency led to a marked reduction to all three parameters. A chronic high-fat diet led to reduced grip strength and force profile when normalized to body weight. In high-fat fed mice that were exerted aerobically and allowed to recover for 30 min, male mice exhibited impaired force profile parameters, which female mice were more resilient. Thus, simultaneous analysis of peak grip strength, force profile and cumulative force profile distinguishes the muscle impairments that result from distinct perturbations and may reflect distinct motor unit recruitment strategies.

Longitudinal characterization of determinants associated with obesogenic growth patterns in early childhood

BACKGROUND

Longitudinal assessment of the determinants of obesogenic growth trajectories in childhood can suggest appropriate developmental windows for intervention.

METHODS

Latent class growth mixture modelling was used to identify body mass index (BMI) z-score trajectories from birth to age 6 years in 994 children from a prospective mother-offspring cohort (Chinese, Indian and Malay ethnicities) based in Singapore. We evaluated the early-life determinants of the trajectories as well as their associations with cardiometabolic risk markers at age 6 years.

RESULTS

Five BMI z-score trajectory patterns were identified, three within the healthy weight range, alongside early-acceleration and late-acceleration obesogenic trajectories. The early-acceleration pattern was characterized by elevated fetal abdominal circumference growth velocity, BMI acceleration immediately after birth and crossing of the obesity threshold by age 2 years. The late-acceleration pattern had normal fetal growth and BMI acceleration after infancy, and approached the obesity threshold by age 6 years. Abdominal fat, liver fat, insulin resistance and odds of pre-hypertension/hypertension were elevated in both groups. Indian ethnicity, high pre-pregnancy BMI, high polygenic risk scores for obesity and shorter breastfeeding duration were common risk factors for both groups. Malay ethnicity and low maternal educational attainment were uniquely associated with early BMI acceleration, whereas nulliparity and obesogenic eating behaviours in early childhood were uniquely associated with late BMI acceleration.

CONCLUSION

BMI acceleration starting immediately after birth or after infancy were both linked to early cardiometabolic alterations. The determinants of these trajectories may be useful for developing early risk stratification and intervention approaches to counteract metabolic adversities linked to childhood obesity.

Moderating effect of bone maturation on the relationship between body fat and insulin resistance

OBJECTIVES

The aim of the present study was to analyze the moderating effect of maturation on the relationship between body fat and insulin resistance, in children from 9 to 12 years.

METHODS

Maturity offset, homeostasis model assessment index of insulin resistance (HOMA-IR), and body fat percentage (BF%) were estimated in 127 children. Skeletal maturation indicator (SMI) was estimated in 105 participants. A moderation analysis based on a linear regression and on Johnson-Neyman technique was performed using a 95% confidence level.

RESULTS

BF%, insulin levels, and HOMA-IR values were lower in late maturers than on-time maturers (p<0.05). SMI moderated the relationship between BF% and HOMA-IR index in 11.1% of boys and in 32.5% of girls (p<0.05). Also, the highest values of HOMA-IR index were observed at -1 year to achieve the peak height velocity, in girls (p<0.05).

CONCLUSIONS

Maturation process has a moderation effect on the relationship BF% and insulin resistance, particularly in early maturers; furthermore, it was independently associated with HOMA-IR.

Sex steroids and adiposity in a prospective observational cohort of youth

OBJECTIVE

Adiposity, particularly visceral adipose tissue (VAT), predicts adverse cardiovascular risk factor profiles in children as well as adults. Although endogenous sex steroids likely influence VAT in adults, such an association has not been established in youth. The association between childhood and adolescent sex steroids with adiposity, specifically VAT, was examined before and after adjustment for other hormone changes.

METHODS

These analyses examined longitudinal associations between sex steroids (testosterone, estradiol, dehydroepiandrosterone [DHEA]) and magnetic resonance imaging assessments of VAT in 418 children, 49% of whom were non-White, at approximately 10 years old at Visit 1 (V1) and 17 years old at Visit 2 (V2). Linear mixed effects models adjusted for maternal education, household income, child caloric intake, physical activity, fasting insulin and leptin, and hepatic fat fraction. Differences in associations by race and pubertal stage were also assessed.

RESULTS

At V1, mean body mass index (BMI) for boys was 19.1 (4.7) kg/m2 and for girls was 18.5 (4.1) kg/m2. At V2, mean BMI for boys was 23.7 (5.5) kg/m2 and for girls was 23.6 (5.7) kg/m2. For each ng/dl (0.035 nmol/L) increase in testosterone at V1, there was a 0.25 cm2 increase in concurrent and future VAT in non-White (p = 0.04) but not White girls (p = 0.78). Higher levels of testosterone and DHEA at V1 were associated with greater concurrent and future VAT at V2. These associations were consistent regardless of pubertal stage. In boys, higher testosterone predicted higher future VAT but lower concurrent VAT. Estradiol and DHEA did not predict future VAT in boys. In girls, DHEA predicted future subcutaneous adipose tissue (SAT), and no sex steroids predicted future SAT in boys.

CONCLUSIONS

Testosterone levels predict VAT in boys and girls, and DHEA predicts VAT in girls, even after adjustment for other hormone changes.

Contribution of Intramyocellular Lipids to Decreased Computed Tomography Muscle Density With Age

Skeletal muscle density, as determined by computed tomography (CT), has been shown to decline with age, resulting in increased frailty and morbidity. However, the mechanism underlying this decrease in muscle density remains elusive. We sought to investigate the role of intramyocellular lipid (IMCL) accumulation in the age-related decline in muscle density. Muscle density was measured using computerized tomography (CT), and IMCL content was quantified using in vivo proton magnetic resonance spectroscopy (¹H-MRS). The study population consisted of 314 healthy participants (142 men, 32–98 years) of the Baltimore Longitudinal Study of Aging (BLSA). In addition to IMCL quantification, obesity-related covariates were measured, including body mass index (BMI), waist circumference, and circulating triglyceride concentration. Higher IMCL concentrations were significantly correlated with lower muscle density in older individuals, independent of age, sex, race, and the obesity-associated covariates (p < 0.01). Lower muscle density was also significantly associated with greater age-adjusted IMCL, a variable we constructed using LOESS regression (p < 0.05). Our results suggest that the accumulation of IMCL may be associated with a decrease in muscle density. This may serve to define a potential therapeutic target for treatment of age-associated decreased muscle function.

Cardiometabolic Profile of Different Body Composition Phenotypes in Children

CONTEXT

Cardiometabolic profiles of different body composition phenotypes are poorly characterized in young children, where it is well established that high adiposity is unfavorable, but the role of lean mass is unclear.

OBJECTIVE

We hypothesized that higher lean mass attenuates cardiometabolic risk in children with high fat mass.

METHODS

In 6-year-old children (n = 377) from the Growing Up in Singapore Towards healthy Outcomes (GUSTO) prospective birth cohort, whole-body composition was measured by quantitative magnetic resonance, a novel validated technology. Based on fat mass index (FMI) and lean mass index (LMI), 4 body composition phenotypes were derived: low FMI-low LMI (LF-LL), low FMI-high LMI (LF-HL), high FMI-low LMI (HF-LL), high FMI-high LMI (HF-HL).

MAIN OUTCOME MEASURES

Body mass index (BMI) z-score, fasting plasma glucose, insulin resistance, metabolic syndrome risk score, fatty liver index, and blood pressure.

RESULTS

Compared with the LF-HL group, children in both high FMI groups had increased BMI z-score (HF-HL: 1.43 units 95% CI [1.11,1.76]; HF-LL: 0.61 units [0.25,0.96]) and metabolic syndrome risk score (HF-HL: 1.64 [0.77,2.50]; HF-LL: 1.28 [0.34,2.21]). The HF-HL group also had increased fatty liver index (1.15 [0.54,1.77]). Girls in HF-HL group had lower fasting plasma glucose (-0.29 mmol/L [-0.55,-0.04]) and diastolic blood pressure (-3.22 mmHg [-6.03,-0.41]) than girls in the HF-LL group. No similar associations were observed in boys.

CONCLUSION

In a multi-ethnic Asian cohort, lean mass seemed to protect against some cardiometabolic risk markers linked with adiposity, but only in girls. The FMI seemed more important than lean mass index in relation to cardiometabolic profiles of young children.

Branched-Chain Amino Acid Supplementation Does Not Preserve Lean Mass or Affect Metabolic Profile in Adults with Overweight or Obesity in a Randomized Controlled Weight Loss Intervention

BACKGROUND

Branched-chain amino acid (BCAA) supplementation has been shown to increase muscle mass or prevent muscle loss during weight loss.

OBJECTIVE

We aimed to investigate the effects of a BCAA-supplemented hypocaloric diet on lean mass preservation and insulin sensitivity.

METHODS

A total of 132 Chinese adults (63 men and 69 women aged 21-45 y, BMI 25-36 kg/m2) were block randomly assigned by gender and BMI into 3 hypocaloric diet (deficit of 500 kcal/d) groups: standard-protein (14%) with placebo (control, CT) or BCAA supplements at 0.1 g · kg-1 body weight · d-1 (BCAA) or high-protein (27%) with placebo (HP). The subjects underwent 16 wk of dietary intervention with provision of meals and supplements, followed by 8 wk of weight maintenance with provision of supplements only. One-way ANOVA analysis was conducted to analyze the primary (lean mass and insulin sensitivity) and secondary outcomes (anthropometric and metabolic parameters) among the 3 groups. Paired t-test was used to analyze the change in each group.

RESULTS

The 3 groups demonstrated similar significant reductions in body weight (7.97%), fat mass (13.8%), and waist circumference (7.27%) after 16 wk of energy deficit. Lean mass loss in BCAA (4.39%) tended to be lower than in CT (5.39%) and higher compared with HP (3.67%) (P = 0.06). Calf muscle volume increased 3.4% in BCAA and intramyocellular lipids (IMCLs) decreased in BCAA (17%) and HP (18%) (P < 0.05) over 16 wk. During the 8 wk weight maintenance period, lean mass gain in BCAA (1.03%) tended to be lower compared with CT (1.58%) and higher than in HP (-0.002%) (P = 0.04). Lean mass gain differed significantly between CT and HP (P = 0.03). Insulin sensitivity and metabolic profiles did not differ among the groups throughout the study period.

CONCLUSIONS

BCAA supplementation does not preserve lean mass or affect insulin sensitivity in overweight and obese adults during weight loss. A higher protein diet may be more advantageous for lean mass preservation.

Mismatch between poor fetal growth and rapid postnatal weight gain in the first 2 years of life is associated with higher blood pressure and insulin resistance without increased adiposity in childhood: the GUSTO cohort study

BACKGROUND

Using longitudinal ultrasounds as an improved fetal growth marker, we aimed to investigate if fetal growth deceleration followed by rapid postnatal weight gain is associated with childhood cardiometabolic risk biomarkers in a contemporary well-nourished population.

METHODS

We defined fetal growth deceleration (FGD) as ultrasound-measured 2nd-3rd-trimester abdominal circumference decrease by ≥0.67 standard deviation score (SDS) and rapid postnatal weight gain (RPWG) as 0-2-year-old weight increase by ≥0.67 SDS. In the GUSTO mother-offspring cohort, we grouped 797 children into four groups of FGD-only (14.2%), RPWG-only (23.3%), both (mismatch, 10.7%) or neither (reference, 51.8%). Adjusting for confounders and comparing with the reference group, we tested associations of these growth groups with childhood cardiometabolic biomarkers: magnetic resonance imaging (MRI)-measured abdominal fat (n = 262), liver fat (n = 216), intramyocellular lipids (n = 227), quantitative magnetic resonance-measured overall body fat % (BF%) (n = 310), homeostasis model assessment of insulin resistance (HOMA-IR) (n = 323), arterial wall thickness (n = 422) and stiffness (n = 443), and blood pressure trajectories (ages 3-6 years).

RESULTS

Mean±SD birthweights were: FGD-only (3.11 ± 0.38 kg), RPWG-only (3.03 ± 0.37 kg), mismatch (2.87 ± 0.31 kg), reference (3.30 ± 0.36 kg). FGD-only children had elevated blood pressure trajectories without correspondingly increased BF%. RPWG-only children had altered body fat partitioning, higher BF% [BF = 4.26%, 95% confidence interval (CI) (2.34, 6.19)], HOMA-IR 0.28 units (0.11, 0.45)] and elevated blood pressure trajectories. Mismatch children did not have increased adiposity, but had elevated ectopic fat, elevated HOMA-IR [0.29 units (0.04,0.55)] and the highest blood pressure trajectories. Associations remained even after excluding small-for-gestational-age infants from analyses.

CONCLUSIONS

Fetal growth deceleration coupled with rapid postnatal weight gain was associated with elevated childhood cardiometabolic risk biomarkers without correspondingly increased BF%.

21st Century Advances in Multimodality Imaging of Obesity for Care of the Cardiovascular Patient

Although obesity is typically defined by body mass index criteria, this does not differentiate true body fatness, as this includes both body fat and muscle. Therefore, other fat depots may better define cardiometabolic and cardiovascular disease (CVD) risk imposed by obesity. Data from translational, epidemiological, and clinical studies over the past 3 decades have clearly demonstrated that accumulation of adiposity in the abdominal viscera and within tissue depots lacking physiological adipose tissue storage capacity (termed "ectopic fat") is strongly associated with the development of a clinical syndrome characterized by atherogenic dyslipidemia, hyperinsulinemia/glucose intolerance/type 2 diabetes mellitus, hypertension, atherosclerosis, and abnormal cardiac remodeling and heart failure. This state-of-the-art paper discusses the impact of various body fat depots on cardiometabolic parameters and CVD risk. Specifically, it reviews novel and emerging imaging techniques to evaluate adiposity and the risk of cardiometabolic diseases and CVD.

Non-invasive Quantification of Fat Deposits in Skeletal Muscle Predicts Cardiovascular Outcome in Kidney Failure

Fat accumulation in skeletal muscle was recently established as a major risk factor for cardiovascular disease (CVD) in the general population, but its relevance for patients with kidney failure is unknown. Here we examined the potential association between muscle radiation attenuation (MRA), a non-invasive indicator of fat deposits in muscle, and cardiovascular events in patients with kidney failure treated with peritoneal dialysis (PD) and investigated dynamic changes and determinants of MRA in this population. We retrospectively assessed MRA on computed tomography images collected yearly in 101 incident patients with kidney failure starting PD between January 2006 and December 2015. After a median of 21 months on dialysis, 34 patients had 58 non-fatal cardiovascular events, and 22 patients had died. Baseline MRA was associated with cardiovascular events during time on dialysis, and patients with higher MRA (reflecting lower amounts of fat in muscle) showed a reduced incidence of CVD, independently of traditional risk factors (adjusted HR, 0.91; 95% CI, 0.86-0.97, P = 0.006). Multivariate regression analysis identified old age, female gender, visceral fat area, and low residual urine volume as independent determinants of MRA. As compared with reference values from a healthy population, patients with kidney failure had lower MRA (i.e., increased fat accumulation), independently of age, gender, and body-mass index. The subset of patients who underwent kidney transplantation showed a significant increase in MRA after restoration of kidney function. These observations expand the association between ectopic fat accumulation and CVD to the population on dialysis, and suggest that kidney failure is reversibly associated with fatty muscle infiltration.

Role of Metabolic Stress and Exercise in Regulating Fibro/Adipogenic Progenitors

Obesity is a major public health concern and is associated with decreased muscle quality (i.e., strength, metabolism). Muscle from obese adults is characterized by increases in fatty, fibrotic tissue that decreases the force producing capacity of muscle and impairs glucose disposal. Fibro/adipogenic progenitors (FAPs) are muscle resident, multipotent stromal cells that are responsible for muscle fibro/fatty tissue accumulation. Additionally, they are indirectly involved in muscle adaptation through their promotion of myogenic (muscle-forming) satellite cell proliferation and differentiation. In conditions similar to obesity that are characterized by chronic muscle degeneration, FAP dysfunction has been shown to be responsible for increased fibro/fatty tissue accumulation in skeletal muscle, and impaired satellite cell function. The role of metabolic stress in regulating FAP differentiation and paracrine function in skeletal muscle is just beginning to be unraveled. Thus, the present review aims to summarize the recent literature on the role of metabolic stress in regulating FAP differentiation and paracrine function in skeletal muscle, and the mechanisms responsible for these effects. Furthermore, we will review the role of physical activity in reversing or ameliorating the detrimental effects of obesity on FAP function.

Childhood adiposity and adolescent sex steroids in the Exploring Perinatal Outcomes among Children study

OBJECTIVE

It is unclear how childhood adipose tissue deposition influences sex hormone profiles in later adolescence.

DESIGN

Prospective cohort study.

PARTICIPANTS

Children (n = 418) with a mean age of 10.5 (1.5) years at visit 1 and 16.7 (1.2) at visit 2 in the Exploring Perinatal Outcomes among Children (EPOCH) Study.

MEASUREMENTS

We used reverse-scale Cox proportional hazard models to assess associations between pubertal dehydroepiandrosterone (DHEA), testosterone (T), and oestradiol (E2) and childhood-to-puberty rate of change in visceral (VAT) and subcutaneous adipose tissue (SAT). Models stratified by sex and adjusted for childhood adiposity, maternal factors, birthweight and pubertal onset, and then further adjusted for insulin, luteinizing hormone (LH), leptin and hepatic fat fraction.

RESULTS

Among boys, more rapid accumulation of either VAT or SAT was associated with lower testosterone at visit 2 (HR 0.86, and .96, respectively, both P < .0001), independently of race/ethnicity, LH, leptin and hepatic fat fraction. Among boys, more childhood VAT was associated with lower testosterone in adolescence (HR 0.98, P = .003), but this association did not persist after adjustment for leptin or insulin. No associations were observed between either fat measure and oestradiol or DHEA in boys. In girls, no associations between childhood fat or fat accumulation and sex hormones were observed.

CONCLUSIONS

More rapid accumulation of fat is associated with lower testosterone in boys. These associations suggest that fat growth influences androgen profiles in adolescent boys. Since fat accumulation is a modifiable risk factor, the study results provide a possible intervention target and time period for improving adult health.

Determinants of intramyocellular lipid accumulation in early childhood

Background/Objectives

Accumulation of lipid droplets inside skeletal muscle fibers (intramyocellular lipids or IMCL) with increasing obesity has been linked to skeletal muscle insulin resistance and risk of type 2 diabetes in both adults and prepubertal children. We aimed to evaluate the associations of race, genotype, prenatal factors, and postnatal factors with IMCL in early childhood.

Subjects/Methods

This study was a secondary analysis performed on the GUSTO birth cohort. Soleus muscle IMCL of 392 children at 4.5 years of age was measured by magnetic resonance spectroscopy, of which usable imaging data were obtained from 277 children (137 Chinese, 87 Malays, and 53 Indians). Metabolic assessments (fasting glucose, insulin, and HOMA-IR) were performed at age 6.

Results

The mean IMCL level at 4.5 years was 0.481 ± 0.279% of water resonance (mean ± sd). Corroborating with results from adults, Indian children had the highest IMCL levels compared with Malay and Chinese children. Among the prenatal factors, the rate of gestational weight gain (GWG rate) was associated with offspring IMCL (B = 0.396 (0.069, 0.724); p = 0.018). Both race and GWG rate continued to be associated with offspring IMCL even after accounting for current offspring BMI. Postnatally, IMCL was associated with shorter breastfeeding duration (B = 0.065 (0.001, 0.128); p = 0.045) and conditional relative weight gain between ages 2 and 3 (B = 0.052 (0.012, 0.093); p = 0.012). The associations with postnatal factors were attenuated after adjusting for current offspring BMI. IMCL was positively associated with offspring BMI (B = 0.028 (0.012, 0.044); p = 0.001). IMCL levels were not associated with fasting glucose, fasting insulin, and HOMA-IR at age 6.

Conclusion

This study provides evidence that IMCL accumulation occurs in early childhood and that developmental factors and race are associated with it. We also show that early childhood IMCL accumulation is well tolerated, suggesting that the adverse associations between IMCL and insulin resistance may emerge at older ages.

Iron in Micronutrient Powder Promotes an Unfavorable Gut Microbiota in Kenyan Infants

Iron supplementation may have adverse health effects in infants, probably through manipulation of the gut microbiome. Previous research in low-resource settings have focused primarily on anemic infants. This was a double blind, randomized, controlled trial of home fortification comparing multiple micronutrient powder (MNP) with and without iron. Six-month-old, non- or mildly anemic, predominantly-breastfed Kenyan infants in a rural malaria-endemic area were randomized to consume: (1) MNP containing 12.5 mg iron (MNP+Fe, n = 13); (2) MNP containing no iron (MNP−Fe, n = 13); or (3) Placebo (CONTROL, n = 7), from 6–9 months of age. Fecal microbiota were profiled by high-throughput bacterial 16S rRNA gene sequencing. Markers of inflammation in serum and stool samples were also measured. At baseline, the most abundant phylum was Proteobacteria (37.6% of rRNA sequences). The proteobacterial genus Escherichia was the most abundant genus across all phyla (30.1% of sequences). At the end of the intervention, the relative abundance of Escherichia significantly decreased in MNP−Fe (−16.05 ± 6.9%, p = 0.05) and CONTROL (−19.75 ± 4.5%, p = 0.01), but not in the MNP+Fe group (−6.23 ± 9%, p = 0.41). The second most abundant genus at baseline was Bifidobacterium (17.3%), the relative abundance of which significantly decreased in MNP+Fe (−6.38 ± 2.5%, p = 0.02) and CONTROL (−8.05 ± 1.46%, p = 0.01), but not in MNP-Fe (−4.27 ± 5%, p = 0.4445). Clostridium increased in MNP-Fe only (1.9 ± 0.5%, p = 0.02). No significant differences were observed in inflammation markers, except for IL-8, which decreased in CONTROL. MNP fortification over three months in non- or mildly anemic Kenyan infants can potentially alter the gut microbiome. Consistent with previous research, addition of iron to the MNP may adversely affect the colonization of potential beneficial microbes and attenuate the decrease of potential pathogens.

The Obesity Epidemic and Consequences for Rheumatoid Arthritis Care

With the prevalence of obesity increasing dramatically worldwide over the past several decades, an increasing body of literature has examined the impact of obesity in the context of rheumatoid arthritis (RA). Epidemiologic studies suggest that obesity may be associated with a modestly increased risk for the development of RA, although these studies have shown conflicting results. Among patients with established RA, obesity has been observed to be associated with greater subjective measures of disease activity and poor treatment response, but also with a decreased risk of joint damage and lower mortality. A comprehensive evaluation of the influence of obesity on the measurement of disease, response to therapies, and long-term prognosis is critical in order to understand these observations. This review therefore focuses on recent observations, potential explanations for these findings, and implications for clinicians and investigators caring for and studying patients with RA.

Multidisciplinary care of obese children and adolescents for one year reduces ectopic fat content in liver and skeletal muscle

Background

Ectopic fat deposition in liver and skeletal muscle tissue is related to cardiovascular disease risk and is a common metabolic complication in obese children. We evaluated the hypotheses of ectopic fat in these organs could be diminished following 1 year of multidisciplinary care specialized in childhood obesity, and whether this reduction would associate with changes in other markers of metabolic function.

Methods

This observational longitudinal study evaluated 40 overweight children and adolescents enrolled in a multidisciplinary treatment protocol at the Children’s Obesity Clinic, Holbæk, Denmark. The participants were assessed by anthropometry, fasting blood samples (HbA1c, glucose, insulin, lipids, and biochemical variables of liver function), and liver and muscle fat content assessed by magnetic resonance spectroscopy at enrollment and following an average of 12.2 months of care. Univariate linear regression models adjusted for age, sex, treatment duration, baseline degree of obesity, and pubertal developmental stage were used for investigating possible associations.

Results

The standard deviation score (SDS) of baseline median body mass index (BMI) was 2.80 (range: 1.49–3.85) and the median age was 14 years (10–17). At the end of the observational period, the 40 children and adolescents (21 girls) significantly decreased their BMI SDS, liver fat, muscle fat, and visceral adipose tissue volume. The prevalence of hepatic steatosis changed from 28 to 20 % (p = 0.26) and the prevalence of muscular steatosis decreased from 75 to 45 % (p = 0.007).

Changes in liver and muscle fat were independent of changes in BMI SDS, baseline degree of obesity, duration of treatment, age, sex, and pubertal developmental stage.

Conclusions

A 1-year multidisciplinary intervention program in the setting of a childhood obesity outpatient clinic confers a biologically important reduction in liver and muscle fat; metabolic improvements that are independent of the magnitude of concurrent weight loss.

Trial registration

ClinicalTrials.gov registration number: NCT00928473, the Danish Childhood Obesity Biobank. Registered June 25, 2009.

Electronic supplementary material

The online version of this article (doi:10.1186/s12887-015-0513-6) contains supplementary material, which is available to authorized users.

Skeletal muscle and pediatric bone development

PURPOSE OF REVIEW

The purpose of this review is to summarize the recent clinical findings surrounding the muscle-bone relationships in children, while considering muscle adiposity, endocrine factors, and lifestyle influences (i.e., diet and exercise) involved in pediatric musculoskeletal development.

RECENT FINDINGS

Positive relationships between cortical bone geometry and muscle mass, size and function have been reported. Prospective studies in particular have helped clarify some of the inconsistent relationships between muscle and cortical bone volumetric density. Muscle fat is associated with impaired glucose handling and muscular functionality, which may in turn have a downstream effect on cortical bone growth during adolescence. Lifestyle factors such as healthful diets and higher impact physical activities can promote optimal skeletal development by improving the muscular phenotype and endocrine profile.

SUMMARY

Muscle and bone are two intricately-related tissue types; however, factors such as sex, maturation, study design, and outcome measures studied can modify this relationship. Further research is warranted to understand the impact of muscle adiposity on cardiometabolic health, muscle function and, subsequently, pediatric musculoskeletal development and fracture risk. Following age-specific diet and physical activity recommendations should be a major focus in obtaining optimal muscle and bone development throughout maturation.

1H-MRS Measured Ectopic Fat in Liver and Muscle in Danish Lean and Obese Children and Adolescents

Objectives

This cross sectional study aims to investigate the associations between ectopic lipid accumulation in liver and skeletal muscle and biochemical measures, estimates of insulin resistance, anthropometry, and blood pressure in lean and overweight/obese children.

Methods

Fasting plasma glucose, serum lipids, serum insulin, and expressions of insulin resistance, anthropometry, blood pressure, and magnetic resonance spectroscopy of liver and muscle fat were obtained in 327 Danish children and adolescents aged 8–18 years.

Results

In 287 overweight/obese children, the prevalences of hepatic and muscular steatosis were 31% and 68%, respectively, whereas the prevalences in 40 lean children were 3% and 10%, respectively. A multiple regression analysis adjusted for age, sex, body mass index z-score (BMI SDS), and pubertal development showed that the OR of exhibiting dyslipidemia was 4.2 (95%CI: [1.8; 10.2], p = 0.0009) when hepatic steatosis was present. Comparing the simultaneous presence of hepatic and muscular steatosis with no presence of steatosis, the OR of exhibiting dyslipidemia was 5.8 (95%CI: [2.0; 18.6], p = 0.002). No significant associations between muscle fat and dyslipidemia, impaired fasting glucose, or blood pressure were observed.

Liver and muscle fat, adjusted for age, sex, BMI SDS, and pubertal development, associated to BMI SDS and glycosylated hemoglobin, while only liver fat associated to visceral and subcutaneous adipose tissue and intramyocellular lipid associated inversely to high density lipoprotein cholesterol.

Conclusion

Hepatic steatosis is associated with dyslipidemia and liver and muscle fat depositions are linked to obesity-related metabolic dysfunctions, especially glycosylated hemoglobin, in children and adolescents, which suggest an increased cardiovascular disease risk.

Metabolic basis of ethnic differences in diabetes risk in overweight and obese youth

The global pandemic of childhood obesity has led to increased risk for prediabetes and type 2 diabetes mellitus (T2DM). Studies have shown decreased insulin sensitivity and/or secretion with increasing adiposity and consistently observed greater risk for T2DM in obese, non-Caucasian youth. In the current review we describe recent advances in understanding how obesity and metabolic status in children and adolescents confers various risk profiles for T2DM among Latinos, African Americans, Caucasians, Asians, and Native Americans. These possible determinants include ectopic fat distribution, adipose tissue inflammation and fibrosis, and elevated plasma levels of nonesterified free fatty acids. Future work should aim to elucidate the ethnic-specific pathophysiology of T2DM in order to develop and implement appropriate prevention and treatment strategies based on different ethnic profiles of diabetes risk.

Cardiovascular disorders in the context of non-alcoholic Fatty liver disease: a literature review

Non-alcoholic fatty liver disease (NAFLD) is the leading cause of chronic liver disease in the United States and other industrialized countries, and the reported prevalence in the developing countries is also rather high. This disease is associated with a high rate of morbidity and mortality and damage to the other organs. The cardiovascular system is, perhaps, the most vulnerable organ to NAFLD adverse effects to the extent that most mortality associated with this disease is reportedly from the cardiovascular system rather than from the liver itself. In this article, we review the significant aspects of cardiovascular disorders associated with NAFLD, including the epidemiology of cardiovascular diseases in NAFLD patients, factors that interfere in this relationship like hypertension, severity of NAFLD, and age of the patients, and finally preventive strategies whose employment could significantly improve the outcome.

Geometric and architectural contributions to hamstring musculotendinous stiffness

BACKGROUND

Greater hamstring musculotendinous stiffness is associated with lesser anterior cruciate ligament loading mechanisms during both controlled joint perturbations and dynamic tasks, suggesting a potential protective mechanism. Additionally, lesser hamstring stiffness has been reported in females, potentially contributing to their greater risk of anterior cruciate ligament injury. However, the factors which contribute to high vs. low stiffness are unclear. Muscle geometry and architecture influence force production and may, therefore, influence stiffness. The purpose of this investigation was to evaluate the contributions of geometric and architectural muscle characteristics to hamstring stiffness.

METHODS

Thirty healthy individuals (15 males, 15 females) volunteered for participation. Biceps femoris long head cross-sectional area, pennation angle, fiber length, tendon stiffness, and posterior thigh fat thickness were assessed via ultrasound imaging, and strength was measured via isometric contraction. Stiffness was assessed via the damped oscillatory technique.

FINDINGS

Following normalization to anthropometric factors, only strength (r=0.535) and posterior thigh fat thickness (Spearman ρ=-0.305) were correlated with stiffness. Normalized tendon stiffness (0.06 vs. 0.10N/m·kg(-1)) and strength (7.1 vs. 10.0N·kg(-1)) were greater in males, while posterior thigh fat thickness (10.4 vs. 5.0mm) was greater in females.

INTERPRETATION

Greater posterior thigh fat thickness may influence stiffness by contributing to greater intramuscular fat and shank segment mass, and lesser muscle per unit mass in the thigh segment. These findings suggest that training designed to increase hamstring strength and decrease fat mass may be beneficial for anterior cruciate ligament injury prevention.

Bone Remodeling and Energy Metabolism: New Perspectives

Bone mineral, adipose tissue and energy metabolism are interconnected by a complex and multilevel series of networks. Calcium and phosphorus are utilized for insulin secretion and synthesis of high energy compounds. Adipose tissue store lipids and cholecalciferol, which, in turn, can influence calcium balance and energy expenditure. Hormones long-thought to solely modulate energy and mineral homeostasis may influence adipocytic function. Osteoblasts are a target of insulin action in bone. Moreover, endocrine mediators, such as osteocalcin, are synthesized in the skeleton but regulate carbohydrate disposal and insulin secretion. Finally, osteoblasts and adipocytes originate from the same mesenchymal progenitor. The mutual crosstalk between osteoblasts and adipocytes within the bone marrow microenvironment plays a crucial role in bone remodeling. In the present review we provide an overview of the reciprocal control between bone and energy metabolism and its clinical implications.

Body composition analysis in the pediatric population

Body composition analysis has become a useful tool in both clinical and research settings. Its use in the pediatric population is complicated by the rapid periods of growth and physical development that are characteristic of infancy, childhood, and adolescence. A thorough understanding of the changing nature of body composition during this time is essential for choosing the most appropriate measurement technique for a given individual, population, or clinical question. Growing evidence suggests that tissues such as fat, muscle, and bone are intimately involved in the regulation of whole body energy metabolism. This knowledge, when coupled with advancements in imaging techniques such as MRI and PET-CT, offers the possibility of developing new models of "functional" body composition. These models may prove to be especially important when assessing malnutrition and metabolic risk in patients with chronic disease.