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Context Visceral fat (VF), more than fat elsewhere in the body [mostly subcutaneous fat (SF)], promotes systemic inflammation and related disease. The mechanisms of preferentially visceral accumulation of body fat are largely unknown. Objective To identify genetic loci and mechanistic pathways of preferential accumulation of VF and associated low-grade systemic inflammation. Design Genome-wide association study (GWAS). Setting and Participants Population-based cohort of 1586 adolescents (aged 12 to 19 years) and adults (aged 36 to 65 years). Main Outcome Measures Abdominal VF and SF were measured with MRI, total body fat (TBF) was assessed with bioimpedance, and low-grade systemic inflammation was examined by serum C-reactive protein (CRP) measurement. Results This GWAS of preferential accumulation of VF identified a significant locus on chromosome 6 at rs803522 (P = 1.1 × 10−9 or 4.3 × 10−10 for VF adjusted for SF or TBF, respectively). The major allele was associated with more VF; the association was similar in adolescents and adults. The allele was also associated with higher CRP level, but this association was stronger in adults than adolescents (P for interaction = 4.5 × 10−3). In adults, VF was a significant mediator (P = 1.9× 10−4) in the association between the locus and CRP, explaining 30% of the mediation. The locus was near ATG5, encoding an autophagy molecule reported to modulate adipocyte size and macrophage polarization. Conclusion A genetic locus near ATG5 regulates preferential accumulation of VF (vs SF) in youth and adulthood and contributes to the development of systemic inflammation in adulthood.

Perturbations in fatty acid (FA) metabolism as well as thinning of the cerebral cortex have been associated with cognitive decline in the elderly. Predominant FAs in the brain are docosahexaenoic acid (DHA) and arachidonic acid (ARA). Approximately 2–8% of esterified DHA and 3–5% of esterified ARA in the brain are replaced daily. DHA and ARA are derivatives of 18-carbon essential FAs, α-linolenic acid and linoleic acid, that must be imported into the brain from the circulation. In blood, FAs are primarily transported in triacylglycerols (TAGs) from which they can be released at the blood–brain-barrier and transported inside the brain. We show that circulating levels of TAGs carrying 18-carbon FAs are positively associated with cortical thickness in middle-aged adults. These associations are stronger in cortical regions with higher expression of genes regulating long-chain FA metabolism and cellular membranes, and cortical thickness in the same regions may be related to cognitive performance., Eeva Sliz et al. show an association between triacylglycerols species carrying 18-carbon unsaturated fatty acids and cortical thickness by combining serum lipidomics and brain imaging data. This association is more pronounced in cortical regions with higher expression of genes regulating fatty acid metabolism and cellular membranes.

Many traits of the brain and body show marked sex differences, but the distributions of their values overlap substantially between the two sexes. To investigate variations associated with biological sex, beyond binary differences, we create continuous sex scores capturing the inter-individual variability in phenotypes. In an adolescent cohort (n = 1,029; 533 females), we have generated three sex scores based on brain-body traits: 'overall' (48 traits), 'pubertal' (26 traits) and 'non-pubertal' (22 traits). We then conducted sex-stratified multiple linear regressions (adjusting for age) using sex scores to test associations with sex hormones, personality traits and internalizing-externalizing behaviour. Higher sex scores (that is, greater 'femaleness') were associated with lower testosterone in males only, as well as lower extraversion, higher internalizing and lower externalizing in both sexes. The associations with testosterone, internalizing and externalizing were driven by pubertal sex scores, underscoring the importance of adolescence in shaping within-sex individual variability.

Life-long maintenance of brain health is important for the prevention of cognitive impairment in older age. Low-grade peripheral inflammation associated with excess visceral fat (VF) may influence brain structure and function. Here we examined (i) if this type of inflammation is associated with altered white-matter (WM) microstructure and lower cognitive functioning in adolescents, and (ii) if recently identified circulating glycerophosphocholines (GPCs) can index this type of inflammation and associated variations in WM microstructure and cognitive functioning. We studied a community-based sample of 872 adolescents (12–18 years, 48% males) in whom we assessed VF and WM microstructure with magnetic resonance imaging, processing speed with cognitive testing, serum C-reactive protein (CRP, a common marker of peripheral inflammation) with a high-sensitivity assay, and serum levels of a panel of 64 GPCs with advanced mass spectrometry. VF was associated with CRP, and CRP in turn was associated with “altered” WM microstructure and lower processing speed (all p

Resting‐state functional magnetic resonance imaging (rs‐fMRI) is frequently used to study brain function; but, it is unclear whether BOLD‐signal fluctuation amplitude and functional connectivity are associated with vascular factors, and how vascular‐health factors are reflected in rs‐fMRI metrics in the healthy population. As arterial stiffening is a known age‐related cardiovascular risk factor, we investigated the associations between aortic stiffening (as measured using pulse‐wave velocity [PWV]) and rs‐fMRI metrics. We used cardiac MRI to measure aortic PWV (an established indicator of whole‐body vascular stiffness), as well as dual‐echo pseudo‐continuous arterial‐spin labeling to measure BOLD and CBF dynamics simultaneously in a group of generally healthy adults. We found that: (1) higher aortic PWV is associated with lower variance in the resting‐state BOLD signal; (2) higher PWV is also associated with lower BOLD‐based resting‐state functional connectivity; (3) regions showing lower connectivity do not fully overlap with those showing lower BOLD variance with higher PWV; (4) CBF signal variance is a significant mediator of the above findings, only when averaged across regions‐of‐interest. Furthermore, we found no significant association between BOLD signal variance and systolic blood pressure, which is also a known predictor of vascular stiffness. Age‐related vascular stiffness, as measured by PWV, provides a unique scenario to demonstrate the extent of vascular bias in rs‐fMRI signal fluctuations and functional connectivity. These findings suggest that a substantial portion of age‐related rs‐fMRI differences may be driven by vascular effects rather than directly by brain function.

Background: Glycerophosphocholine (GPC) metabolites modulate atherosclerosis and thus risk for cardiovascular disease (CVD). Preclinical CVD may start during adolescence. Here, we used targeted serum lipidomics to identify a new panel of GPCs, and tested whether any of these GPCs are associated, in adolescence, with classical risk factors of CVD, namely excess visceral fat (VF), elevated blood pressure, insulin resistance, and atherogenic dyslipidemia. Methods: We studied a population-based sample of 990 adolescents (12–18 years, 48% male), as part of the Saguenay Youth Study. Using liquid chromatography-electrospray ionization-mass spectrometry, we identified 69 serum GPCs within the 450 to 680 m / z range. We measured VF with MRI. Results: We identified several novel GPCs that were associated with multiple CVD risk factors. Most significantly, PC16:0/2:0 was negatively associated with VF ( P =1.4×10 –19 ), blood pressure ( P =7.7×10 –5 ), and fasting triacylglycerols ( P =9.0×10 –5 ), and PC14:1/0:0 was positively associated with VF ( P =3.0×10 –7 ), fasting insulin ( P =5.4×10 –32 ), and triacylglycerols ( P =1.4×10 –29 ). The Sobel test of mediation revealed that both GPCs mediated their respective relations between VF (as a potential primary exposure) and CVD risk factors (as outcomes, P values–3 ). Furthermore, a GPC shown recently to predict incident coronary heart disease in older adults, PC18:2/0:0, was associated with several CVD risk factors in adolescents; these associations were less strong than those with the newly identified GPCs. Conclusions: We identified novel GPCs strongly associated with multiple CVD risk factors in adolescents. These GPCs may be sensitive indicators of obesity-related risk for CVD outcomes in adults, and may improve biological understanding of CVD risk.

This Mini-Review describes sex differences in 66 quantitative characteristics of the brain and body measured in a community-based sample of 1,024 adolescents 12-18 years of age, members of the Saguenay Youth Study. Using an extensive phenotyping protocol, we have obtained measures in a number of domains, including brain structure, cognition, mental health, substance use, body composition, metabolism, cardiovascular reactivity, and life style. For each measure, we provide estimates of effect size (Cohen's d) and sex-specific correlations with age (Pearson R). In total 59 of the 66 characteristics showed sex differences (at a nominal P

Summary Cerebrovascular alterations are a key feature of Alzheimer’s disease (AD) pathogenesis. However, whether vascular damage contributes to synaptic dysfunction and how it synergizes with amyloid pathology to cause neuroinflammation and cognitive decline remain poorly understood. Here, we show that the blood protein fibrinogen induces spine elimination and promotes cognitive deficits mediated by CD11b-CD18 microglia activation. 3D molecular labeling in cleared mouse and human AD brains combined with repetitive in vivo two-photon imaging showed focal fibrinogen deposits associated with loss of dendritic spines independent of amyloid plaques. Fibrinogen-induced spine elimination was prevented by inhibiting reactive oxygen species (ROS) generation or genetic ablation of CD11b. Genetic elimination of the fibrinogen binding motif to CD11b reduced neuroinflammation, synaptic deficits, and cognitive decline in the 5XFAD mouse model of AD. Thus, fibrinogen-induced spine elimination and cognitive decline via CD11b link cerebrovascular damage with immune-mediated neurodegeneration and may have important implications in AD and related conditions.

Background Obesity is associated with cardiometabolic disturbances, which may have significant implications for musculoskeletal health and exercise tolerance. Objective We sought to determine the association between muscle structure, function, and metabolism in adolescents across the weight spectrum. Methods This cross-sectional case–control study included overweight and obese participants (n = 24) 8–18 years of age with a body mass index (BMI) ≥ 85th percentile for age and gender, and non-obese participants (n = 24) with a BMI

Obesity is associated with an increased risk of depression. The aim of the present study was to investigate whether obesity is a causative factor for the development of depression and what is the molecular pathway(s) that link these two disorders. Using lipidomic and transcriptomic methods we identified a mechanism that links exposure to a high-fat diet (HFD) in mice with alterations in hypothalamic function that lead to depression. Consumption of an HFD selectively induced accumulation of palmitic acid in the hypothalamus, suppressed the 3´, 5´-cyclic AMP (cAMP)/protein kinase A (PKA) signaling pathway, and increased the concentration of free-fatty acid receptor 1 (FFAR1). Deficiency of phosphodiesterase 4A (PDE4A), an enzyme that degrades cAMP and modulates stimulatory regulative G-protein (Gs)-coupled G protein-coupled receptor signaling, protected animals either from genetic- or dietary induced depression phenotype. These findings suggest that dietary intake of saturated fats disrupts hypothalamic functions by suppressing cAMP/PKA signaling through activation of PDE4A. FFAR1 inhibition and/or an increase of cAMP signaling in the hypothalamus could offer potential therapeutic targets to counteract the effects of dietary or genetically induced obesity on depression.

© 2017 Elsevier Inc. Blood-brain barrier (BBB) disruption alters the composition of the brain microenvironment by allowing blood proteins into the CNS. However, whether blood-derived molecules serve as extrinsic inhibitors of remyelination is unknown. Here we show that the coagulation factor fibrinogen activates the bone morphogenetic protein (BMP) signaling pathway in oligodendrocyte progenitor cells (OPCs) and suppresses remyelination. Fibrinogen induces phosphorylation of Smad 1/5/8 and inhibits OPC differentiation into myelinating oligodendrocytes (OLs) while promoting an astrocytic fate in vitro. Fibrinogen effects are rescued by BMP type I receptor inhibition using dorsomorphin homolog 1 (DMH1) or CRISPR/Cas9 activin A receptor type I (ACVR1) knockout in OPCs. Fibrinogen and the BMP target Id2 are increased in demyelinated multiple sclerosis (MS) lesions. Therapeutic depletion of fibrinogen decreases BMP signaling and enhances remyelination in vivo. Targeting fibrinogen may be an upstream therapeutic strategy to promote the regenerative potential of CNS progenitors in diseases with remyelination failure. Extrinsic inhibitors contribute to remyelination failure in neurological diseases. Petersen et al. identify the blood coagulation factor fibrinogen as an activator of BMP receptor signaling in oligodendrocyte progenitor cells that may be targeted therapeutically to promote remyelination.

Activation of innate immunity and deposition of blood-derived fibrin in the central nervous system (CNS) occur in autoimmune and neurodegenerative diseases, including multiple sclerosis (MS) and Alzheimer's disease (AD). However, the mechanisms that link disruption of the blood-brain barrier (BBB) to neurodegeneration are poorly understood, and exploration of fibrin as a therapeutic target has been limited by its beneficial clotting functions. Here we report the generation of monoclonal antibody 5B8, targeted against the cryptic fibrin epitope γ377-395, to selectively inhibit fibrin-induced inflammation and oxidative stress without interfering with clotting. 5B8 suppressed fibrin-induced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activation and the expression of proinflammatory genes. In animal models of MS and AD, 5B8 entered the CNS and bound to parenchymal fibrin, and its therapeutic administration reduced the activation of innate immunity and neurodegeneration. Thus, fibrin-targeting immunotherapy inhibited autoimmunity- and amyloid-driven neurotoxicity and might have clinical benefit without globally suppressing innate immunity or interfering with coagulation in diverse neurological diseases.

Objective To study the relationships between parameters of glucose and insulin metabolism and visceral and abdominal ectopic fat in youth. Methods A cross sectional study of 50 children (24 females), 8-18 years old. Anthropometrics, body composition, blood-work and visceral and ectopic fat by magnetic resonance imaging were assessed. Insulin secretion, insulin sensitivity and beta cell function were calculated from an oral glucose tolerance test. Results BMI z-scores ranged between −1.3 and 4.5. The hepatic fat fraction (HFF) ranged between 0 and 36% and pancreatic fat fraction (PFF) between 0 and 14%. Visceral fat, HFF and PFF were associated with clinical and biochemical metabolic abnormalities, and correlated with markers of insulin sensitivity (r = −0.60, P

Background Obesity, a major risk factor for cardiometabolic disease, is associated with lower cognitive performance from childhood to senescence, especially on tasks of executive function. In the cardiovascular domain, fat stored viscerally rather than elsewhere in the body carries particularly high risk. It is unknown whether this is also true in case of obesity-cognition relationships. The aim of this study is to assess the cross-sectional relationship between visceral fat (VF) and cognitive performance in a community sample of healthy adolescents. Methods In a community-based sample of 983 adolescents (12–18 years old, 480 males), VF was quantified using magnetic resonance imaging, total body fat was measured using a multifrequency bioimpedance and cognitive performance was assessed using a battery of cognitive tests measuring executive function and memory. Results We found that larger volumes of VF were associated with lower performance on six measures of executive function (p=0.0001 to 0.02). We also found that the association of VF with executive function was moderated by sex for a subset of measures, such that relationship was present mainly in females and not in males (sex-by-VF interaction: p=0.001 to 0.04). These relationships were independent of the quantity of total body fat and a number of potential confounders, including age, puberty stage and household income. Conclusions Our results suggest that the adverse association between obesity and executive function may be attributed to fat stored viscerally and not to fat stored elsewhere in the body. They also suggest that females compared with males may be more sensitive to the potentially detrimental effects of VF on cognition.

This Mini-Review describes sex differences in 66 quantitative characteristics of the brain and body measured in a community-based sample of 1,024 adolescents 12-18 years of age, members of the Saguenay Youth Study. Using an extensive phenotyping protocol, we have obtained measures in a number of domains, including brain structure, cognition, mental health, substance use, body composition, metabolism, cardiovascular reactivity, and life style. For each measure, we provide estimates of effect size (Cohen's d) and sex-specific correlations with age (Pearson R). In total 59 of the 66 characteristics showed sex differences (at a nominal P 0.05), with small (32), medium-sized (13), and large (11) effects. Some, but not all, of these sex differences increase during adolescence; this appears to be the case mostly for anatomical and physiological measures. © 2016 Wiley Periodicals, Inc.

Hypertension, typically considered a disorder of adulthood, is now emerging in adolescence. This is mainly due to the growing prevalence of obesity and the fact that excess body fat increases blood pressure (BP).The objective of the study was to investigate whether genome-wide identified gene loci of obesity are associated with elevated BP in adolescence.This was a genotype-phenotype association study.The study was conducted in a French-Canadian founder population.Participants included 598 adolescents, aged 12-18 yr.Testing associations between 530,011 single-nucleotide polymorphisms (SNP; Human610W-Quad BeadChip) and obesity measures and between identified SNP and BP.Total fat mass (TFM) was assessed with bioelectrical impedance, and body mass index (BMI) was determined with anthropometry. BP was measured beat by beat during an hour-long protocol.The genome-wide association studies of TFM and BMI revealed two novel and several previously identified loci of obesity. The former were PAX5 (rs16933812, TFM: P = 9.3 × 10(-9)) and MRPS22 (rs7638110, BMI: P = 4.6 × 10(-8)), and the top ones among the latter (P5 × 10(-4)) were MC4R (rs17773430, BMI: P = 5.8 × 10(-6)), FTO (rs9930333, BMI: P = 1.9 × 10(-4)), and MTCH2 (rs7120548, BMI: P = 1.9 × 10(-4)). From these five, only the PAX5, MRPS22, and FTO were also associated with BP; their minor allele homozygotes vs. major allele homozygotes showed greater TFM by 2.9-8.0 kg and higher BP by 3.3-6.7 mm Hg.Genome-wide association studies conducted in an adolescent founder population revealed two new and a number of previously identified loci of obesity and demonstrated that several but not all of these loci are also associated with elevated BP. These results begin to reveal the genetic architecture of obesity-induced hypertension.

In industrialized countries, prenatal exposure to maternal cigarette smoking (PEMCS) is the most common environmental insult to the fetus. Here, we tested the hypothesis that PEMCS amplifies accumulation of abdominal fat during the accelerated weight gain occurring in late puberty. This hypothesis was tested in 508 adolescents (12-18 years, 237 exposed prenatally to maternal cigarette smoking) in whom subcutaneous and intra-abdominal fat were quantified with magnetic resonance imaging (MRI). We found that, in early puberty, exposed and nonexposed adolescents did not differ in MRI-based measures of adiposity. In late puberty, on the other hand, exposed compared with nonexposed adolescents demonstrated markedly higher quantities of both subcutaneous fat (by 26%, P = 0.004) and intra-abdominal fat (by 33%, P = 0.001). These group differences remained virtually unchanged after adjusting for sex and potential confounders, including birth weight and breastfeeding. As such, our results suggest that PEMCS may represent a major risk factor for the development of abdominal obesity at the later stages of puberty.

Intra-abdominal accumulation of fat is a hallmark of male body-fat distribution and a major risk factor for hypertension. Sympathoactivation may be one of the mechanisms linking intra-abdominal obesity to hypertension. The aim of the present study was to investigate whether a functional variation in the androgen-receptor gene ( AR , a variable number of CAG repeats in exon 1) is associated with intra-abdominal adiposity, sympathetic modulation of vasomotor tone, and blood pressure in adolescent boys but not girls. We studied 223 boys and 259 girls (age 12 to 18 years) from a French-Canadian founder population. Intra-abdominal fat and subcutaneous-abdominal fat were quantified with an MRI. Blood pressure was recorded beat-to-beat during an hour-long protocol including physical and mental challenges, and these blood pressure time series were used to assess sympathetic modulation of vasomotor tone by power spectral analysis. The results showed that boys with a “low” versus “intermediate” or “high” CAG-repeat number in AR demonstrated higher intra-abdominal fat (by 28% and 48%, respectively) but not subcutaneous-abdominal fat. These intra-abdominal fat differences remained significant after adjusting for serum levels of sex hormones and subcutaneous-abdominal fat. Furthermore, boys with low versus intermediate or high CAG-repeat numbers also showed higher blood pressure, with the differences being most pronounced during mental stress (8.0 and 8.5 mm Hg, respectively) and higher sympathetic modulation of vasomotor tone. As expected, no such differences were seen among girls. In adolescent boys, low CAG-repeat numbers in AR may be a genetic risk factor for intra-abdominal obesity and hypertension; sympathoactivation may be an underlying link between the 2 conditions.

Background— FTO is the first gene established as contributing to common forms of obesity. The gene is highly expressed in the hypothalamus and is thought to mediate this effect through its influence on energy homeostasis. The hypothalamus, however, also regulates blood pressure (BP). Therefore, we investigated whether the FTO -risk variant is associated not only with increased adiposity but also with elevated BP and whether the latter may be mediated, in part, by increased sympathetic modulation of vasomotor tone. Methods and Results— The primary study was carried out in 485 adolescents recruited from a French Canadian founder population who underwent detailed body-composition and cardiovascular phenotyping. Body fat was examined with MRI, bioimpedance, and anthropometry. BP was recorded beat to beat at rest and during physical and mental challenges. Sympathetic modulation of vasomotor tone was assessed with power spectral analysis of BP. We found that individuals with the FTO- risk genotype compared with those without it demonstrate greater adiposity, including the amount of intra-abdominal fat (by 38%). They also showed higher systolic BP throughout the entire protocol, with a maximum difference during a mental stress (6.4 [1.5 to 11.3] mm Hg). The difference in BP was accompanied by elevated index of sympathetic modulation of vasomotor tone. A replication in an independent sample of adults from the same founder population confirmed the association between FTO and BP. Conclusions— These results suggest that, in a French Canadian founder population, FTO may increase not only risk for obesity, as demonstrated in other populations, but also for hypertension. The latter may be related, at least in part, to the regulation of sympathetic vasomotor tone.

Obesity is associated with cardiometabolic disturbances, which may have significant implications for musculoskeletal health and exercise tolerance.We sought to determine the association between muscle structure, function, and metabolism in adolescents across the weight spectrum.This cross-sectional case-control study included overweight and obese participants (n = 24) 8-18 years of age with a body mass index (BMI) ≥ 85th percentile for age and gender, and non-obese participants (n = 24) with a BMI 85bese and overweight patients had similar age, height, and physical activity to non-obese controls, but obese and overweight participants exhibited higher insulin resistance. Obese and overweight participants had longer PCr recovery than non-obese controls following 5x30s of moderate-intensity exercise (51.2 ± 20.1 s vs. 23.9 ± 7.5 s, p = 0.004). In univariate correlation analysis, impaired PCr recovery was associated with a higher BMI z-score (rA slower phosphocreatine recovery following aerobic exercise is strongly associated with increasing adiposity. A slower metabolic recovery following aerobic exercise stress suggests that endurance exercise training in obese adolescents may be an optimal strategy to target exercise intolerance in this cohort.

Despite numerous reports indicating HIF-1α expression in glia, neurons, and inflammatory cells in the CNS of MS patients, the cell-specific contribution of HIF-1α to disease pathogenesis remains unclear. Here we show that although HIF-1α is dramatically upregulated in astrocytes and myeloid cells in EAE, cell-specific depletion of HIF-1α in these two cell types surprisingly does not affect the development of neuroinflammatory disease., Hypoxia-like tissue alterations, characterized by the upregulation of hypoxia-inducible factor-1α (HIF-1α), have been described in the normal appearing white matter and pre-demyelinating lesions of multiple sclerosis (MS) patients. As HIF-1α regulates the transcription of a wide set of genes involved in neuroprotection and neuroinflammation, HIF-1α expression may contribute to the pathogenesis of inflammatory demyelination. To test this hypothesis, we analyzed the effect of cell-specific genetic ablation or overexpression of HIF-1α on the onset and progression of experimental autoimmune encephalomyelitis (EAE), a mouse model for MS. HIF-1α was mainly expressed in astrocytes and microglia/macrophages in the mouse spinal cord at the peak of EAE. However, genetic ablation of HIF-1α in astrocytes and/or myeloid cells did not ameliorate clinical symptoms. Furthermore, conditional knock-out of Von Hippel Lindau, a negative regulator of HIF-1α stabilization, failed to exacerbate the clinical course of EAE. In accordance with clinical symptoms, genetic ablation or overexpression of HIF-1α did not change the extent of spinal cord inflammation and demyelination. Overall, our data indicate that despite dramatic upregulation of HIF-1α in astrocytes and myeloid cells in EAE, HIF-1α expression in these two cell types is not required for the development of inflammatory demyelination. Despite numerous reports indicating HIF-1α expression in glia, neurons, and inflammatory cells in the CNS of MS patients, the cell-specific contribution of HIF-1α to disease pathogenesis remains unclear. Here we show that although HIF-1α is dramatically upregulated in astrocytes and myeloid cells in EAE, cell-specific depletion of HIF-1α in these two cell types surprisingly does not affect the development of neuroinflammatory disease. Together with two recently published studies showing a role for oligodendrocyte-specific HIF-1α in myelination and T-cell-specific HIF-1α in EAE, our results demonstrate a tightly regulated cellular specificity for HIF-1α contribution in nervous system pathogenesis.

To study the relationships between parameters of glucose and insulin metabolism and visceral and abdominal ectopic fat in youth.A cross sectional study of 50 children (24 females), 8-18 years old. Anthropometrics, body composition, blood-work and visceral and ectopic fat by magnetic resonance imaging were assessed. Insulin secretion, insulin sensitivity and beta cell function were calculated from an oral glucose tolerance test.BMI z-scores ranged between -1.3 and 4.5. The hepatic fat fraction (HFF) ranged between 0 and 36% and pancreatic fat fraction (PFF) between 0 and 14%. Visceral fat, HFF and PFF were associated with clinical and biochemical metabolic abnormalities, and correlated with markers of insulin sensitivity (r = -0.60, P0.01; r = -0.64, P0.01; r = -0.48, P0.01, respectively) insulin secretion (r = 0.55, P0.01; r = 0.57, P0.01; r = 0.41, P0.01, respectively), and beta cell function (r = -0.49, P0.01; r = -0.59, P0.01; r = -0.39, P0.01, respectively).Accumulations of pancreatic and hepatic fat have complementary clinical consequences in youth. While visceral and hepatic fat demonstrated a dominant effect, even relatively small degrees of pancreatic fat deposition may contribute to metabolic alterations.

Objective : Visceral fat (VF) increases cardiometabolic risk more than fat stored subcutaneously. Here, we investigated how well routine clinical measures of adiposity, namely body mass index (BMI) and waist circumference (waist), predict VF and subcutaneous fat (SF) in a large population-based sample of adolescents. As body-fat distribution differs between males and females, we performed these analyses separately in each sex. Design and Methods : VF and SF were measured by magnetic resonance imaging in 1,002 adolescents (482 males, age 12–18 years). Relationships of BMI and waist with VF and SF were tested in multivariable analyses, which adjusted for potentially confounding effects of age and height. Results : In both males and females, BMI and waist were highly correlated with VF and SF, and explained 55–76% of their total variance. When VF was adjusted for SF, however, BMI and waist explained, respectively, only 0% and 4% of VF variance in males, and 4% and 11% of VF variance in females. In contrast, when SF was adjusted for VF, BMI and waist explained, respectively, 36% and 21% of SF variance in males, and 48% and 23% of SF variance in females. These relationships were similar during early and late puberty. Conclusions and Relevance : During adolescence, routine clinical measures of adiposity predict well SF but not VF. This holds for both sexes and throughout puberty. Further longitudinal studies are required to assess how well these measures predict changes of VF and SF over time. Given the clinical importance of VF, development of cost-effective imaging techniques and/or robust biomarkers of VF accumulation that would be suitable in everyday clinical practice is warranted.

ObjectiveDysregulation of the autonomic nervous system is thought to be involved in craniopharyngioma-related hypothalamic obesity (CRHO). Increased parasympathetic activity and decreased sympathetic activity have been suggested. We aimed to study autonomic activity using heart rate variability (HRV) and biochemical measures in youth with CRHO compared with controls and to explore relationships between obesity and autonomic indices.DesignA cross-sectional study of 16 youth with CRHO and 16 controls matched for sex, age, and BMI.MethodsAnthropometrics, fasting blood-work, resting energy expenditure (REE), 24-h HRV, and 24-h urine catecholamines were assessed. Quality of life, sleepiness, and autonomic symptoms were evaluated. Power spectral analysis of the HRV was performed.ResultsHRV power spectral analysis parameters of both parasympathetic activity (mean high frequency (HF (ms2)) 611±504 vs 459±336,P=0.325) and sympathetic activity (median low frequency/HF 1.62 (1.37, 2.41) vs 1.89 (1.44, 2.99),P=0.650) did not differ between the groups. Parasympathetic activity negatively correlated with central adiposity in both groups (r=−0.53,P=0.034 andr=−0.54,P=0.029) and sympathetic activity positively correlated with central adiposity in CRHO (r=0.51,P=0.043). Youth with CRHO had significantly lower REE; lower health and activity scores in the quality of life questionnaires, and higher sleepiness scores.ConclusionsAutonomic activity was similar in CRHO and control subjects. The degree of central adiposity correlated negatively with parasympathetic activity and positively with sympathetic activity in children with CRHO. These results provide a new perspective regarding autonomic balance in this unique patient population.

Greater blood pressure (BP) reactivity and slower BP recovery from physical and mental challenges predict future hypertension. Males exhibit higher BP than females throughout their reproductive age and, as such, have a higher prevalence of hypertension. Excess body-fat is a major risk factor for hypertension in both males and females. We investigated whether BP reactivity and recovery from physical and mental challenges differ between adolescent males and females, and whether these hemodynamic parameters are associated with resting BP and are influenced by excess body-fat in a sex-specific manner. In 285 male and 311 female adolescents (age 12-18 years), we quantified visceral fat (VF) with magnetic resonance imaging and total body fat (TBF) with bioimpedance and measured systolic BP (SBP) beat-by-beat at rest and during physical (10-min standing) and mental (2-min math test) challenges. Our results showed that in both sexes, BP reactivity and BP recovery for both challenges (adjusted for age, height and initial BP) correlated closely with resting BP (0.03 ≤ r2 ≤ 0.34). In addition, for both physical and mental challenges, males versus females showed greater BP reactivity (by 3.5 mm Hg, p

Individuals who exhibit exaggerated blood pressure (BP) reactivity to physical and mental challenges at a young age are at increased risk of developing hypertension in adulthood. Hypertension is a complex genetic trait that is more prevalent in men than women during reproductive age. CYP17A1 is one of the best-established gene loci of hypertension. It encodes a key enzyme in the steroidogenic pathway that produces mineralocorticoids, glucocorticoids, androgens, and estrogens; as such, it may influence BP reactivity in a sex-specific manner. Here, we investigated whether CYP17A1 is associated with BP reactivity to physical and mental challenges in adolescence. In 285 male and 311 female adolescents (age 12-18 years), we measured systolic BP (SBP) and diastolic BP (DBP) beat-by-beat during a 52-minute protocol, which included a physical (10-min standing) and mental (2-min math test) challenge and we genotyped 8 tagging single nucleotide polymorphisms (SNPs) that covered the entire region of CYP17A1. Genotype-phenotype association tests were performed separately in males and females, while adjusting for age, height and initial BP. Our results showed that 6 SNPs were associated with higher SBP and DBP reactivity (p=0.003-0.0001), but only in response to mental stress and only in boys. At rs619824 , minor allele homozygotes differed from major allele homozygotes by 8.7 mm Hg of SBP (p=3x10-4) and 4.8 mm Hg of DBP (p=1x10-4) in boys, and the two groups varied only by 2.0 mm Hg of SBP (p=0.31) and 0.9 mm Hg of DBP (p=0.42) in girls. These results suggest that CYP17A1 may contribute to the development of hypertension through the regulation of the stress response and that, at least in adolescence, this effect appears to be present in males but not in females.

SummaryBackground and Objectives Turner syndrome (TS) confers increased lifetime risk of type 2 diabetes mellitus and cardiovascular disease. We compared cardiometabolic risk factors and measures of subcutaneous, visceral adipose tissue and intra-myocellular lipid between young TS girls and an age- and BMI-standard deviation scores (SDS)-matched healthy female cohort. Patients and Methods A cross-sectional cohort study was conducted at the Hospital for Sick Children, Toronto. Nineteen TS and 17 control girls (13·7 ± 2·5 vs 12·7 ± 3·4 years of age, respectively, P = 0·30). Multiple-sample oral glucose tolerance test with measurement of fasting insulin, LDL, HDL, triglycerides, adiponectin and highly sensitive C-reactive protein (hsCRP) was performed. Subcutaneous adipose tissue, visceral adipose tissue intramyocellular lipid levels evaluated by magnetic resonance techniques. Insulin secretion (IS), sensitivity (Si) and the insulin secretion–sensitivity index (ISSI-2) were calculated from oral glucose tolerance test data. Results Five TS and no controls had impaired fasting glucose or impaired glucose tolerance; none had type 2 diabetes mellitus. Insulin sensitivity and insulin secretion were similar between groups; ISSI-2 was lower in TS (923·5 ± 307·3 vs 659·1 ± 387·3; P = 0·03). TS girls had higher blood pressure (82·5 ± 13·6 vs 73·5 ± 5·5 mmHg; P = 0·0146), waist circumference (76·0 ±11·8 vs 65·9 ± 9·7; P = 0·0087) and subcutaneous adipose tissue (135·6 ± 88·6 vs 69·3 ± 59·9; P = 0·01) than controls. Visceral adipose tissue, intramyocellular lipid levels and adiponectin were not different between groups. TS girls also had higher triglycerides (1·1 ± 0·6 vs 0·7 ± 0·3; P = 0·003), total cholesterol (4·4 ± 0·7 vs 3·9 ± 0·4; P = 0·02) and hsCRP (2·0 ± 1·9 vs 0·8 ± 0·3; P = 0·01). Conclusions TS girls exhibit more cardiometabolic risk factors and reduced beta cell function compared with age- and BMI-SDS-matched girls. Increased awareness of early risk of type 2 diabetes mellitus and hypertension in TS girls is needed.

Objectives To investigate during adolescence (1) sex differences in blood pressure (BP) and hemodynamic factors at rest and during physical and mental challenges and (2) whether these differences are mediated by body composition and glucose and lipid metabolism. Design Cross-sectional study of a population-based cohort. Setting Saguenay Youth Study, Quebec, Canada, from November 2003 to June 2007. Participants A total of 425 adolescents (225 girls aged 12-18 years). Outcome Measures Systolic and diastolic BP measured using a Finometer. Secondary outcome measures were (1) hemodynamic parameters also measured with a Finometer, (2) body composition assessed with magnetic resonance imaging, bioimpedance, and anthropometry, and (3) metabolic indices determined from a fasting blood sample. Results Girls vs boys demonstrated lower systolic and diastolic BP at rest and during challenges, with the differences being greatest during a math-stress test (adjusted difference, 7 mm Hg; 95% confidence interval [CI], 4-10 mm Hg and adjusted difference, 6 mm Hg; 95% CI, 4-8 mm Hg, respectively). The differences were mainly due to girls vs boys having lower stroke volume while lying down, standing (adjusted difference, 4 mL; 95% CI, 1-7 mL), and sitting, and lower total peripheral resistance during the math-stress test (adjusted difference, 0.14 mm Hg · s/mL; 95% CI, 0.09-0.21 mm Hg · s/mL). Intra-abdominal fat was positively associated with BP, but less in girls than in boys, and fat-free mass, fat mass, and insulin resistance were also positively associated with BP, similarly in boys and girls. Conclusions In adolescence, BP is lower in girls than boys, with the difference being determined mainly by lower stroke volume during physical challenges and by lower total peripheral resistance during mental challenges. Body composition and insulin resistance contribute to these differences.

To investigate the association between intra-abdominal adiposity and individual components of the metabolic syndrome (MS) in adolescent males and females.Cross-sectional study of a population-based cohort.Saguenay Youth Study, Quebec, Canada.A total of 324 adolescents, aged 12 to 18 years.Measures were compared between males and females with "high" or "low" intra-abdominal fat (IAF).Intra-abdominal fat was quantified with magnetic resonance imaging. Primary outcome measures were blood pressure (BP) and fasting serum glucose, insulin, lipids, and C-reactive protein levels. Secondary mechanistic measures were cardiovascular variability indexes of autonomic nervous system function, pubertal development, and serum levels of cortisol, leptin, and sex hormones.The MS was completely absent in adolescents with low IAF and was present in 13.8% of males and 8.3% of females with high IAF. Excess IAF was associated with a higher homeostasis model assessment index (0.5 [95% confidence interval (CI), 0.3 to 0.8]; P.001) and triglycerides level (17.7 mg/dL [to convert to millimoles per liter, multiply by 0.0113] [95% CI, 9.7 to 25.7 mg/dL]; P.001), lower high-density lipoprotein cholesterol level (-3.9 mg/dL [to convert to millimoles per liter, multiply by 0.0259] [95% CI, -6.2 to -1.5 mg/dL]; P = .003), and higher C-reactive protein level (0.03 mg/L [to convert to nanomoles per liter, multiply by 9.524] [95% CI, 0.01 to 0.05 mg/L]; P = .003). High IAF was associated with elevations of BP and sympathetic activity in males only (higher systolic BP, 6 mm Hg [95% CI, 1 to 11 mm Hg]; P = .02 and low-frequency power of diastolic BP, 629 mm Hg2 [95% CI, 37 to 1222 mm Hg2]; P = .04).Our results suggest that, already in adolescence, accumulation of IAF may promote development of the MS, affecting the metabolic and inflammatory components similarly in both sexes but influencing BP adversely only in males. The latter may be attributed, in part, to the augmentation of sympathetic activity also seen only in males.

The search for genes of complex traits is aided by the availability of multiple quantitative phenotypes collected in geographically isolated populations. Here we provide rationale for a large-scale study of gene-environment interactions influencing brain and behavior and cardiovascular and metabolic health in adolescence, namely the Saguenay Youth Study (SYS). The SYS is a retrospective study of long-term consequences of prenatal exposure to maternal cigarette smoking (PEMCS) in which multiple quantitative phenotypes are acquired over five sessions (telephone interview, home, hospital, laboratory, and school). To facilitate the search for genes that modify an individual's response to an in utero environment (i.e. PEMCS), the study is family-based (adolescent sibships) and is carried out in a relatively geographically isolated population of the Saguenay Lac-Saint-Jean (SLSJ) region in Quebec, Canada. DNA is acquired in both biological parents and in adolescent siblings. A genome-wide scan will be carried out with sib-pair linkage analyses, and fine mapping of identified loci will be done with family-based association analyses. Adolescent sibships (12-18 years of age; two or more siblings per family) are recruited in high schools throughout the SLSJ region; only children of French-Canadian origin are included. Based on a telephone interview, potential participants are classified as exposed or nonexposed prenatally to maternal cigarette smoking; the two groups are matched for the level of maternal education and the attended school. A total of 500 adolescent participants in each group will be recruited and phenotyped. The following types of datasets are collected in all adolescent participants: (1) magnetic resonance images of brain, abdominal fat, and kidneys, (2) standardized and computer-based neuropsychological tests, (3) hospital-based cardiovascular, body-composition and metabolic assessments, and (4) questionnaire-derived measures (e.g. life habits such as eating and physical activity; drug, alcohol use and delinquency; psychiatric symptoms; personality; home and school environment; academic and vocational attitudes). Parents complete a medical questionnaire, home-environment questionnaire, a handedness questionnaire, and a questionnaire about their current alcohol and drug use, depression, anxiety, and current and past antisocial behavior. To date, we have fully phenotyped a total of 408 adolescent participants. Here we provide the description of the SYS and, using the initial sample, we present information on ascertainment, demographics of the exposed and nonexposed adolescents and their parents, and the initial MRI-based assessment of familiality in the brain size and the volumes of grey and white matter.

Hypoxia-like tissue alterations, characterized by the upregulation of hypoxia-inducible factor-1α (HIF-1α), have been described in the normal appearing white matter and pre-demyelinating lesions of multiple sclerosis (MS) patients. As HIF-1α regulates the transcription of a wide set of genes involved in neuroprotection and neuroinflammation, HIF-1α expression may contribute to the pathogenesis of inflammatory demyelination. To test this hypothesis, we analyzed the effect of cell-specific genetic ablation or overexpression of HIF-1α on the onset and progression of experimental autoimmune encephalomyelitis (EAE), a mouse model for MS. HIF-1α was mainly expressed in astrocytes and microglia/macrophages in the mouse spinal cord at the peak of EAE. However, genetic ablation of HIF-1α in astrocytes and/or myeloid cells did not ameliorate clinical symptoms. Furthermore, conditional knock-out of Von Hippel Lindau, a negative regulator of HIF-1α stabilization, failed to exacerbate the clinical course of EAE. In accordance with clinical symptoms, genetic ablation or overexpression of HIF-1α did not change the extent of spinal cord inflammation and demyelination. Overall, our data indicate that despite dramatic upregulation of HIF-1α in astrocytes and myeloid cells in EAE, HIF-1α expression in these two cell types is not required for the development of inflammatory demyelination. Despite numerous reports indicating HIF-1α expression in glia, neurons, and inflammatory cells in the CNS of MS patients, the cell-specific contribution of HIF-1α to disease pathogenesis remains unclear. Here we show that although HIF-1α is dramatically upregulated in astrocytes and myeloid cells in EAE, cell-specific depletion of HIF-1α in these two cell types surprisingly does not affect the development of neuroinflammatory disease. Together with two recently published studies showing a role for oligodendrocyte-specific HIF-1α in myelination and T-cell-specific HIF-1α in EAE, our results demonstrate a tightly regulated cellular specificity for HIF-1α contribution in nervous system pathogenesis.

Objective. To assess the effect of combined diazoxide-metformin therapy in obese adolescents treated for craniopharyngioma. Design. A prospective open-label 6-month pilot treatment trial in 9 obese subjects with craniopharyngioma. Diazoxide (2 mg/kg divided b.i.d., maximum 200 mg/day) and metformin (1000 mg b.i.d.). Whole body insulin sensitivity index (WBISI) and area-under-the-curve insulin (AUCins) were calculated. Results. Seven subjects completed: 4M/3F, mean ± SD age years, weight kg, BMI kg/m2, and BMI SDS . Two were withdrawn due to vomiting and peripheral edema. Of participants completing the study, the mean ± SD weight gain, BMI, and BMI SDS during the 6 months were reduced compared to the 6 months prestudy ( versus kg, ; versus kg/m2, ; versus , , resp.). AUCins correlated with weight loss (, ) and BMI decrease (, ). Conclusion. Combined diazoxide-metformin therapy was associated with reduced weight gain in patients with hypothalamic obesity. AUCins at study commencement predicted effectiveness of the treatment.