Determinants of intramyocellular lipid accumulation in early childhood

Associations of cord plasma per- and polyfluoroakyl substances (PFAS) with neonatal and child body composition and adiposity: The GUSTO study

BACKGROUND

The influence of prenatal exposure to per- and poly- fluoroalkyl substances (PFAS) on birth size and offspring adiposity is unclear, especially for the newer, shorter-chained replacement PFAS.

METHODS

In the GUSTO multi-ethnic Singaporean mother-offspring cohort, 12 PFAS were measured in 783 cord plasma samples using ultra-performance-liquid chromatography-tandem-mass-spectrometer (UPLC-MS/MS). Outcomes included offspring anthropometry, other indicators of body composition/metabolic health, and MRI-derived abdominal adiposity (subset) at birth and 6 years of age. PFAS were modeled individually, in categories of long-chain and short-chain PFAS, and as scores of three principal components (PC) derived using PC analysis (PC1, PC2, and PC3 reflect predominant exposure patterns to "very-long-PFAS", "long-PFAS", and "short-PFAS", respectively). Associations with outcomes were assessed using multivariable linear regressions, adjusted for important covariates such as maternal sociodemographic and lifestyle factors.

RESULTS

Overall, cord PFAS levels showed either no or positive associations (mostly for long-chain PFAS) with birth weight, length and head circumference. In general, PFAS were associated with higher neonatal abdominal adiposity, driven by shorter-chain PFAS. Perfluoroheptanoic acid (PFHpA) was associated with higher volumes of superficial subcutaneous adipose tissue (sSAT) (3.75 [1.13, 6.37] mL per SD increase in PFAS) and internal adipose tissue (IAT) (1.39 [0.41, 2.38] mL). Higher levels of perfluorobutanesulfonic acid (PFBS), short-chain PFAS, and PC3 were associated with higher IAT volume (β range 1.22-1.41 mL/SD, all P < 0.02), especially in girls. Higher PC3 score was additionally associated with higher sSAT (3.12 [0.45, 5.80] mL) volume. At age 6 years, most observed associations did not persist. No consistent associations were observed between PFAS and whole-body adiposity measures.

CONCLUSIONS

Fetal exposure to emerging short-chain PFAS was associated with higher abdominal adiposity at birth but not at age 6 years. Further research is needed to replicate the findings and to determine if these effects may reappear beyond early childhood. Population exposure to newer PFAS and consequent health impact must be monitored.

Prevalence and Mechanisms of Skeletal Muscle Atrophy in Metabolic Conditions

Skeletal muscle atrophy is prevalent in a myriad of pathological conditions, such as diabetes, denervation, long-term immobility, malnutrition, sarcopenia, obesity, Alzheimer's disease, and cachexia. This is a critically important topic that has significance in the health of the current society, particularly older adults. The most damaging effect of muscle atrophy is the decreased quality of life from functional disability, increased risk of fractures, decreased basal metabolic rate, and reduced bone mineral density. Most skeletal muscle in humans contains slow oxidative, fast oxidative, and fast glycolytic muscle fiber types. Depending on the pathological condition, either oxidative or glycolytic muscle type may be affected to a greater extent. This review article discusses the prevalence of skeletal muscle atrophy and several mechanisms, with an emphasis on high-fat, high-sugar diet patterns, obesity, and diabetes, but including other conditions such as sarcopenia, Alzheimer's disease, cancer cachexia, and heart failure.

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.

Molecular Mechanisms Underlying the Elevated Expression of a Potentially Type 2 Diabetes Mellitus Associated SCD1 Variant

Disturbances in lipid metabolism related to excessive food intake and sedentary lifestyle are among major risk of various metabolic disorders. Stearoyl-CoA desaturase-1 (SCD1) has an essential role in these diseases, as it catalyzes the synthesis of unsaturated fatty acids, both supplying for fat storage and contributing to cellular defense against saturated fatty acid toxicity. Recent studies show that increased activity or over-expression of SCD1 is one of the contributing factors for type 2 diabetes mellitus (T2DM). We aimed to investigate the impact of the common missense rs2234970 (M224L) polymorphism on SCD1 function in transfected cells. We found a higher expression of the minor Leu224 variant, which can be attributed to a combination of mRNA and protein stabilization. The latter was further enhanced by various fatty acids. The increased level of Leu224 variant resulted in an elevated unsaturated: saturated fatty acid ratio, due to higher oleate and palmitoleate contents. Accumulation of Leu224 variant was found in a T2DM patient group, however, the difference was statistically not significant. In conclusion, the minor variant of rs2234970 polymorphism might contribute to the development of obesity-related metabolic disorders, including T2DM, through an increased intracellular level of SCD1.

The Kynurenine Pathway Metabolites in Cord Blood Positively Correlate With Early Childhood Adiposity

CONTEXT

The kynurenine pathway generates metabolites integral to energy metabolism, neurotransmission, and immune function. Circulating kynurenine metabolites positively correlate with adiposity in children and adults, yet it is not known whether this relationship is present already at birth.

OBJECTIVE

In this prospective longitudinal study, we investigate the relationship between cord blood kynurenine metabolites and measures of adiposity from birth to 4.5 years.

METHODS

Liquid chromatography-tandem mass spectrometry was used to quantify cord blood kynurenine metabolites in 812 neonates from the Growing Up in Singapore Towards healthy Outcomes (GUSTO) study. Fat percentage was measured by air displacement plethysmography and abdominal adipose tissue compartment volumes; superficial (sSAT) and deep subcutaneous (dSAT) and internal adipose tissue were quantified by magnetic resonance imaging at early infancy in a smaller subset of neonates, and again at 4 to 4.5 years of age.

RESULTS

Cord blood kynurenine metabolites appeared to be higher in female newborns, higher in Indian newborns compared with Chinese newborns, and higher in infants born by cesarean section compared with vaginal delivery. Kynurenine, xanthurenic acid, and quinolinic acid were positively associated with birthweight, but not with subsequent weight during infancy and childhood. Quinolinic acid was positively associated with sSAT at birth. Kynurenic acid and quinolinic acid were positively associated with fat percentage at 4 years.

CONCLUSION

Several cord blood kynurenine metabolite concentrations were positively associated with birthweight, with higher kynurenic acid and quinolinic acid correlating to higher percentage body fat in childhood, suggesting these cord blood metabolites as biomarkers of early childhood adiposity.

Brown Adipose Tissue, Adiposity, and Metabolic Profile in Preschool Children

CONTEXT

An inverse relationship between brown adipose tissue (BAT) and obesity has previously been reported in older children and adults but is unknown in young children.

OBJECTIVE

We investigated the influence of BAT in thermoneutral condition on adiposity and metabolic profile in Asian preschool children.

DESIGN, SETTING, AND PARTICIPANTS

A total of 198 children aged 4.5 years from a prospective birth cohort study, Growing Up in Singapore Towards Healthy Outcomes (GUSTO) were successfully studied with water-fat magnetic resonance imaging of the supraclavicular and axillary fat depot (FDSA). Regions within FDSA with fat-signal-fraction between 20% and 80% were considered BAT, and percentage BAT (%BAT; 100*BAT volume/ FDSA volume) was calculated.

MAIN OUTCOME MEASURES

Abdominal adipose tissue compartment volumes, ectopic fat in the soleus muscle and liver, fatty liver index, metabolic syndrome scores, and markers of insulin sensitivity.

RESULTS

A 1% unit increase in %BAT was associated with lower body mass index, difference (95% CI), -0.08 (-0.10, -0.06) kg/m2 and smaller abdominal adipose tissue compartment volumes. Ethnicity and sex modified these associations. In addition, each unit increase in %BAT was associated with lower ectopic fat at 4.5 years in the liver, -0.008% (-0.013%, -0.003%); soleus muscle, -0.003% (-0.006%, -0.001%) of water content and lower fatty liver index at 6 years.

CONCLUSIONS

Higher %BAT is associated with a more favorable metabolic profile. BAT may thus play a role in the pathophysiology of obesity and related metabolic disorders. The observed ethnic and sex differences imply that the protective effect of BAT may vary among different groups.

Seeing the fetus from a DOHaD perspective: discussion paper from the advanced imaging techniques of DOHaD applications workshop held at the 2019 DOHaD World Congress

Advanced imaging techniques are enhancing research capacity focussed on the developmental origins of adult health and disease (DOHaD) hypothesis, and consequently increasing awareness of future health risks across various subareas of DOHaD research themes. Understanding how these advanced imaging techniques in animal models and human population studies can be both additively and synergistically used alongside traditional techniques in DOHaD-focussed laboratories is therefore of great interest. Global experts in advanced imaging techniques congregated at the advanced imaging workshop at the 2019 DOHaD World Congress in Melbourne, Australia. This review summarizes the presentations of new imaging modalities and novel applications to DOHaD research and discussions had by DOHaD researchers that are currently utilizing advanced imaging techniques including MRI, hyperpolarized MRI, ultrasound, and synchrotron-based techniques to aid their DOHaD research focus.

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%.