Mammographic density mediates the protective effect of early-life body size on breast cancer risk.

The unexplained protective effect of childhood adiposity on breast cancer risk may be mediated via mammographic density (MD). Here, we investigate a complex relationship between adiposity in childhood and adulthood, puberty onset, MD phenotypes (dense area (DA), non-dense area (NDA), percent density (PD)), and their effects on breast cancer. We use Mendelian randomization (MR) and multivariable MR to estimate the total and direct effects of adiposity and age at menarche on MD phenotypes. Childhood adiposity has a decreasing effect on DA, while adulthood adiposity increases NDA. Later menarche increases DA/PD, but when accounting for childhood adiposity, this effect is attenuated. Next, we examine the effect of MD on breast cancer risk. DA/PD have a risk-increasing effect on breast cancer across all subtypes. The MD SNPs estimates are heterogeneous, and additional analyses suggest that different mechanisms may be linking MD and breast cancer. Finally, we evaluate the role of MD in the protective effect of childhood adiposity on breast cancer. Mediation MR analysis shows that 56% (95% CIs [32%-79%]) of this effect is mediated via DA. Our finding suggests that higher childhood adiposity decreases mammographic DA, subsequently reducing breast cancer risk. Understanding this mechanism is important for identifying potential intervention targets.

Physical activity alters the effect of genetic determinants of adiposity on hypertension among individuals of European ancestry in the UKB.

Hypertension is a leading risk factor for cardiovascular disease and is modulated by genetic variants. This study aimed to assess the effect of obesity genetic liability and physical activity on hypertension among European and African ancestry individuals within the UK Biobank (UKB). Participants were 230 115 individuals of European ancestry and 3239 individuals of African ancestry from UKB. Genetic liability for obesity were estimated using previously published data including genetic variants and effect sizes for body mass index (BMI), waist-hip ratio (WHR) and waist circumference (WC) using Plink software. The outcome was defined as stage 2 hypertension (systolic blood pressure ≥ 140 mmHg, diastolic blood pressure ≥90 mmHg, or the use of anti-hypertensive medications). The association between obesity genetic liability and the outcome was assessed across categories of self-reported physical activity using logistic regression. Among European ancestry participants, there was up to a 1.2 greater odds of hypertension in individuals with high genetic liability and low physical activity compared to individuals with low genetic liability and high physical activity (p < 0.001). In individuals engaging in low levels of physical activity compared with moderate/high physical activity, the effect of BMI genetic liability on hypertension was greater (p interaction = 0.04). There was no evidence of an association between obesity genetic liability and hypertension in individuals of African ancestry in the whole sample or within separate physical activity groups (p > 0.05). This study suggests that higher physical activity levels are associated with lower odds of stage 2 hypertension among European ancestry individuals who carry high genetic liability for obesity. This cannot be inferred for individuals of African ancestry, possibly due to the low African ancestry sample size within the UKB.

Overexpression of Slc22a18 facilitates fat accumulation in mice.

We previously reported that solute carrier family 22 member 18 (Slc22a18) regulates lipid accumulation in 3T3-L1 adipocytes. Here, we provide additional evidence derived from experiments with adenoviral vector expression and genetic manipulation of mice. In primary cultured rat hepatocytes, adenoviral overexpression of mouse Slc22a18 increased triglyceride accumulation and triglyceride synthetic activity, which was decreased in an adenoviral knockdown experiment. Adenoviral overexpression of mouse Slc22a18 in vivo caused massive fatty liver in mice, even under normal dietary conditions. Conversely, adenoviral knockdown of mouse Slc22a18 reduced hepatic lipid accumulation induced by a high-glucose and high-sucrose diet. We created Slc22a18 knockout mice, which grew normally and showed no obvious spontaneous phenotypes. However, compared with control littermates, the knockout mice exhibited decreased hepatic triglyceride content under refeeding conditions, significantly reduced epididymal fat mass, and tended to have lower liver weight in conjunction with leptin deficiency. Finally, we created transgenic mice overexpressing rat Slc22a18 in an adipose-specific manner, which had increased body weight and epididymal fat mass primarily because of increased adipocyte cell volume. In these transgenic mice, a positive correlation was observed between adiposity and the expression levels of the rat Slc22a18 transgene. Taken together, these results indicate that Slc22a18 has positive effects on lipid accumulation in vivo.

Clinically relevant plasma proteome for adiposity depots: evidence from systematic mendelian randomization and colocalization analyses.

BACKGROUND: The accumulation of visceral and ectopic fat comprise a major cause of cardiometabolic diseases. However, novel drug targets for reducing unnecessary visceral and ectopic fat are still limited. Our study aims to provide a comprehensive investigation of the causal effects of the plasma proteome on visceral and ectopic fat using Mendelian randomization (MR) approach. METHODS: We performed two-sample MR analyses based on five large genome-wide association study (GWAS) summary statistics of 2656 plasma proteins, to screen for causal associations of these proteins with traits of visceral and ectopic fat in over 30,000 participants of European ancestry, as well as to assess mediation effects by risk factors of outcomes. The colocalization analysis was conducted to examine whether the identified proteins and outcomes shared casual variants. RESULTS: Genetically predicted levels of 14 circulating proteins were associated with visceral and ectopic fat (P < 4.99 × 10- 5, at a Bonferroni-corrected threshold). Colocalization analysis prioritized ten protein targets that showed effect on outcomes, including FST, SIRT2, DNAJB9, IL6R, CTSA, RGMB, PNLIPRP1, FLT4, PPY and IL6ST. MR analyses revealed seven risk factors for visceral and ectopic fat (P < 0.0024). Furthermore, the associations of CTSA, DNAJB9 and IGFBP1 with primary outcomes were mediated by HDL-C and SHBG. Sensitivity analyses showed little evidence of pleiotropy. CONCLUSIONS: Our study identified candidate proteins showing putative causal effects as potential therapeutic targets for visceral and ectopic fat accumulation and outlined causal pathways for further prevention of downstream cardiometabolic diseases.

Inverse associations of cord blood mitochondrial DNA copy number with childhood adiposity.

OBJECTIVE: The objective of this study was to examine associations between umbilical cord mitochondrial DNA copy number (mtDNAcn) and adiposity across childhood. METHODS: In a prospective birth cohort of Dominican and African American children from New York City, New York (1998-2006), mtDNAcn was measured in cord blood. Children (N = 336) were evaluated for their height, weight, and bioimpedance at age 5, 7, 9, and 11 years. We used linear mixed-effects models to assess associations of mtDNAcn tertiles in cord blood with child BMI, BMI z scores, fat mass index, and body fat percentage. Latent class growth models and interactions between mtDNAcn and child age or child age2 were used to assess associations between age and adiposity trajectories. RESULTS: BMI was, on average, 1.5 kg/m2 higher (95% CI: 0.58, 2.5) in individuals with mtDNAcn in the low- compared with the middle-mtDNAcn tertile. Results were similar for BMI z score, fat mass index, and body fat percentage. Moreover, children in the low-mtDNAcn group had increased odds of being in an "increasing" or "high-stable" adiposity class. CONCLUSIONS: Lower mtDNAcn at birth may predict greater childhood adiposity, highlighting the potential key role of perinatal mitochondrial function in adiposity during development.

Characterizing the Causal Pathway From Childhood Adiposity to Right Heart Physiology and Pulmonary Circulation Using Lifecourse Mendelian Randomization.

BACKGROUND: Observational epidemiological studies have reported an association between childhood adiposity and altered cardiac morphology and function in later life. However, whether this is due to a direct consequence of being overweight during childhood has been difficult to establish, particularly as accounting for other measures of body composition throughout the lifecourse can be exceptionally challenging. METHODS AND RESULTS: In this study, we used human genetics to investigate this using a causal inference technique known as lifecourse Mendelian randomization. This approach allowed us to evaluate the effect of childhood body size on 11 measures of right heart and pulmonary circulation independent of other anthropometric traits at various stages in the lifecourse. We found strong evidence that childhood body size has a direct effect on an enlarged right heart structure in later life (eg, right ventricular end-diastolic volume: ß=0.24 [95% CI, 0.15-0.33]; P=3×10-7) independent of adulthood body size. In contrast, childhood body size effects on maximum ascending aorta diameter attenuated upon accounting for body size in adulthood, suggesting that this effect is likely attributed to individuals remaining overweight into later life. Effects of childhood body size on pulmonary artery traits and measures of right atrial function became weaker upon accounting for adulthood fat-free mass and childhood height, respectively. CONCLUSIONS: Our findings suggest that, although childhood body size has a long-term influence on an enlarged heart structure in adulthood, associations with the other structural components of the cardiovascular system and their function may be largely attributed to body composition at other stages in the lifecourse.

Cardiovascular Significance and Genetics of Epicardial and Pericardial Adiposity.

Importance: Epicardial and pericardial adipose tissue (EPAT) has been associated with cardiovascular diseases such as atrial fibrillation or flutter (AF) and coronary artery disease (CAD), but studies have been limited in sample size or drawn from selected populations. It has been suggested that the association between EPAT and cardiovascular disease could be mediated by local or paracrine effects. Objective: To evaluate the association of EPAT with prevalent and incident cardiovascular disease and to elucidate the genetic basis of EPAT in a large population cohort. Design, Setting, and Participants: A deep learning model was trained to quantify EPAT area from 4-chamber magnetic resonance images using semantic segmentation. Cross-sectional and prospective cardiovascular disease associations were evaluated, controlling for sex and age. Prospective associations were additionally controlled for abdominal visceral adipose tissue (VAT) volumes. A genome-wide association study was performed, and a polygenic score (PGS) for EPAT was examined in independent FinnGen cohort study participants. Data analyses were conducted from March 2022 to December 2023. Exposures: The primary exposures were magnetic resonance imaging-derived continuous measurements of epicardial and pericardial adipose tissue area and visceral adipose tissue volume. Main Outcomes and Measures: Prevalent and incident CAD, AF, heart failure (HF), stroke, and type 2 diabetes (T2D). Results: After exclusions, this study included 44 475 participants (mean [SD] age, 64.1 [7.7] years; 22 972 female [51.7%]) from the UK Biobank. Cross-sectional and prospective cardiovascular disease associations were evaluated for a mean (SD) of 3.2 (1.5) years of follow-up. Prospective associations were additionally controlled for abdominal VAT volumes for 38 527 participants. A PGS for EPAT was examined in 453 733 independent FinnGen cohort study participants. EPAT was positively associated with male sex (ß = +0.78 SD in EPAT; P < 3 × 10-324), age (Pearson r = 0.15; P = 9.3 × 10-229), body mass index (Pearson r = 0.47; P < 3 × 10-324), and VAT (Pearson r = 0.72; P < 3 × 10-324). EPAT was more elevated in prevalent HF (ß = +0.46 SD units) and T2D (ß = +0.56) than in CAD (ß = +0.23) or AF (ß = +0.18). EPAT was associated with incident HF (hazard ratio [HR], 1.29 per +1 SD in EPAT; 95% CI, 1.17-1.43), T2D (HR, 1.63; 95% CI, 1.51-1.76), and CAD (HR, 1.19; 95% CI, 1.11-1.28). However, the associations were no longer significant when controlling for VAT. Seven genetic loci were identified for EPAT, implicating transcriptional regulators of adipocyte morphology and brown adipogenesis (EBF1, EBF2, and CEBPA) and regulators of visceral adiposity (WARS2 and TRIB2). The EPAT PGS was associated with T2D (odds ratio [OR], 1.06; 95% CI, 1.05-1.07; P =3.6 × 10-44), HF (OR, 1.05; 95% CI, 1.04-1.06; P =4.8 × 10-15), CAD (OR, 1.04; 95% CI, 1.03-1.05; P =1.4 × 10-17), AF (OR, 1.04; 95% CI, 1.03-1.06; P =7.6 × 10-12), and stroke in FinnGen (OR, 1.02; 95% CI, 1.01-1.03; P =3.5 × 10-3) per 1 SD in PGS. Conclusions and Relevance: Results of this cohort study suggest that epicardial and pericardial adiposity was associated with incident cardiovascular diseases, but this may largely reflect a metabolically unhealthy adiposity phenotype similar to abdominal visceral adiposity.

Genetic Evidence for Distinct Biological Mechanisms That Link Adiposity to Type 2 Diabetes: Toward Precision Medicine.

We aimed to unravel the mechanisms connecting adiposity to type 2 diabetes. We used MR-Clust to cluster independent genetic variants associated with body fat percentage (388 variants) and BMI (540 variants) based on their impact on type 2 diabetes. We identified five clusters of adiposity-increasing alleles associated with higher type 2 diabetes risk (unfavorable adiposity) and three clusters associated with lower risk (favorable adiposity). We then characterized each cluster based on various biomarkers, metabolites, and MRI-based measures of fat distribution and muscle quality. Analyzing the metabolic signatures of these clusters revealed two primary mechanisms connecting higher adiposity to reduced type 2 diabetes risk. The first involves higher adiposity in subcutaneous tissues (abdomen and thigh), lower liver fat, improved insulin sensitivity, and decreased risk of cardiometabolic diseases and diabetes complications. The second mechanism is characterized by increased body size and enhanced muscle quality, with no impact on cardiometabolic outcomes. Furthermore, our findings unveil diverse mechanisms linking higher adiposity to higher disease risk, such as cholesterol pathways or inflammation. These results reinforce the existence of adiposity-related mechanisms that may act as protective factors against type 2 diabetes and its complications, especially when accompanied by reduced ectopic liver fat.

Independent association of general and central adiposity with risk of gallstone disease: observational and genetic analyses.

Background: General obesity is a well-established risk factor for gallstone disease (GSD), but whether central obesity contributes additional independent risk remains controversial. We aimed to comprehensively clarify the effect of body fat distribution on GSD. Methods: We first investigated the observational association of central adiposity, characterized by waist-to-hip ratio (WHR), with GSD risk using data from UK Biobank (N=472,050). We then explored the genetic relationship using summary statistics from the largest genome-wide association study of GSD (ncase=43,639, ncontrol=506,798) as well as WHR, with and without adjusting for body mass index (BMI) (WHR: n=697,734; WHRadjBMI: n=694,649). Results: Observational analysis demonstrated an increased risk of GSD with one unit increase in WHR (HR=1.18, 95%CI=1.14-1.21). A positive WHR-GSD genetic correlation (rg =0.41, P=1.42×10-52) was observed, driven by yet independent of BMI (WHRadjBMI: rg =0.19, P=6.89×10-16). Cross-trait meta-analysis identified four novel pleiotropic loci underlying WHR and GSD with biological mechanisms outside of BMI. Mendelian randomization confirmed a robust WHR-GSD causal relationship (OR=1.50, 95%CI=1.35-1.65) which attenuated yet remained significant after adjusting for BMI (OR=1.17, 95%CI=1.09-1.26). Furthermore, observational analysis confirmed a positive association between general obesity and GSD, corroborated by a shared genetic basis (rg =0.40, P=2.16×10-43), multiple novel pleiotropic loci (N=11) and a causal relationship (OR=1.67, 95%CI=1.56-1.78). Conclusion: Both observational and genetic analyses consistently provide evidence on an association of central obesity with an increased risk of GSD, independent of general obesity. Our work highlights the need of considering both general and central obesity in the clinical management of GSD.

Separating the effects of life course adiposity on diabetic nephropathy: a comprehensive multivariable Mendelian randomization study.

Aims: Previous Mendelian randomization (MR) of obesity and diabetic nephropathy (DN) risk used small sample sizes or focused on a single adiposity metric. We explored the independent causal connection between obesity-related factors and DN risk using the most extensive GWAS summary data available, considering the distribution of adiposity across childhood and adulthood. Methods: To evaluate the overall effect of each obesity-related exposure on DN (Ncase = 3,676, Ncontrol = 283,456), a two-sample univariate MR (UVMR) analysis was performed. The independent causal influence of each obesity-related feature on DN was estimated using multivariable MR (MVMR) when accounting for confounding variables. It was also used to examine the independent effects of adult and pediatric obesity, adjusting for their interrelationships. We used data from genome-wide association studies, including overall general (body mass index, BMI) and abdominal obesity (waist-to-hip ratio with and without adjustment for BMI, i.e., WHR and WHRadjBMI), along with childhood obesity (childhood BMI). Results: UVMR revealed a significant association between adult BMI (OR=1.24, 95%CI=1.03-1.49, P=2.06×10-2) and pediatric BMI (OR=1.97, 95%CI=1.59-2.45, P=8.55×10-10) with DN risk. At the same time, adult WHR showed a marginally significant increase in DN (OR =1.27, 95%CI = 1.01-1.60, P=3.80×10-2). However, the outcomes were adverse when the influence of BMI was taken out of the WHR (WHRadjBMI). After adjusting for childhood BMI, the causal effects of adult BMI and adult abdominal obesity (WHR) on DN were significantly attenuated and became nonsignificant in MVMR models. In contrast, childhood BMI had a constant and robust independent effect on DN risk(adjusted for adult BMI: IVW, OR=1.90, 95% CI=1.60-2.25, P=2.03×10-13; LASSO, OR=1.91, 95% CI=1.65-2.21, P=3.80×10-18; adjusted for adult WHR: IVW, OR=1.80, 95% CI=1.40-2.31, P=4.20×10-6; LASSO, OR=1.90, 95% CI=1.56-2.32, P=2.76×10-10). Interpretation: Our comprehensive analysis illustrated the hazard effect of obesity-related exposures for DN. In addition, we showed that childhood obesity plays a separate function in influencing the risk of DN and that the adverse effects of adult obesity (adult BMI and adult WHR) can be substantially attributed to it. Thus, several obesity-related traits deserve more attention and may become a new target for the prevention and treatment of DN and warrant further clinical investigation, especially in childhood obesity.

A causal relationship between appendicular lean mass and atrial fibrillation: A two sample Mendelian randomization study.

BACKGROUND AND AIM: The relationship between appendicular lean mass (ALM) and most cardiovascular events has been established, but the direct association between ALM and atrial fibrillation (AF) remains uncertain. METHODS AND RESULTS: Herein, we identified 494 single-nucleotide polymorphisms (SNPs) strongly associated with ALM as instrumental variables (P < 5E-8) based on a genome-wide association study (GWAS) with 450,243 European participants. Then, we employed five Mendelian randomization (MR) analysis methods to investigate the causal relationship between ALM and AF. All results indicated a causal relationship between ALM and AF, among Inverse variance weighted (P = 8.44E-15, odds ratio [OR]: 1.16, 95 % confidence interval [CI]: 1.114-1.198). Furthermore, we performed a sensitivity analysis, which revealed no evidence of pleiotropy (egger_intercept = 0.000089, P = 0.965) or heterogeneity (MR Egger, Q Value = 0.980; Inverse variance weighted, Q Value = 0.927). The leave-one-out method demonstrates that individual SNPs have no driven impact on the whole causal relationship. Multivariable MR analysis indicates that, after excluding the influence of hypertension and coronary heart disease, a causal relationship between ALM and AF still exists (P = 7.74E-40, OR 95 %CI: 1.389 (1.323-1.458)). Importantly, the Radial MR framework analysis and Robust Adjusted Profile Score (RAPS) further exhibit the robustness of this causal relationship. CONCLUSION: A strong association between ALM and AF was confirmed, and high ALM is a risk factor for AF.

Human Genetic Variation at rs10071329 Correlates With Adiposity-Related Traits, Modulates PPARGC1B Expression, and Alters Brown Adipocyte Function.

Human genetic variation in PPARGC1B has been associated with adiposity, but the genetic variants that affect PPARGC1B expression have not been experimentally determined. Here, guided by previous observational data, we used clustered regularly interspaced short palindromic repeats/CRISPR associated protein 9 (CRISPR/Cas9) to scarlessly edit the alleles of the candidate causal genetic variant rs10071329 in a human brown adipocyte cell line. Switching the rs10071329 genotype from A/A to G/G enhanced PPARGC1B expression throughout the adipogenic differentiation, identifying rs10071329 as a cis-expression quantitative trait loci (eQTL). The higher PPARGC1B expression in G/G cells coincided with greater accumulation of triglycerides and higher expression of mitochondria-encoded genes, but without significant effects on adipogenic marker expression. Furthermore, G/G cells had improved basal- and norepinephrine-stimulated mitochondrial respiration, possibly relating to enhanced mitochondrial gene expression. The G/G cells also exhibited increased norepinephrine-stimulated glycerol release, indicating improved lipolysis. Altogether, our results showed that rs10071329 is a cis-eQTL, with the G/G genotype conferring enhanced PPARGC1B expression, with consequent improved mitochondrial function and response to norepinephrine in brown adipocytes. This genetic variant, and as yet undetermined eQTLs, at PPARGC1B could prove useful in genotype-based precision medicine for obesity treatment.

Adiposity and Functional Outcome After Ischemic Stroke: A Mendelian Randomization Study

BACKGROUND AND OBJECTIVES: To investigate the causal relationships of abdominal adiposity (waist-to-hip ratio [WHR]) and overall adiposity (body mass index [BMI]) with functional outcome after ischemic stroke using Mendelian randomization. METHODS: Genetic instruments for WHR and BMI were obtained from the largest available genome-wide association studies meta-analysis of the Genetic Investigation of ANthropometric Traits consortium and the UK Biobank (N max = 806,834). Functional outcome after ischemic stroke was assessed using the modified Rankin Scale (mRS) score at 3-month after stroke onset, with mRS >2 (mRS 3-6) defined as an unfavorable functional outcome. Corresponding genetic estimates for an unfavorable functional outcome were extracted from the Genetics of Ischemic Stroke Functional Outcome network (N = 6,021). We applied a random-effects inverse variance weighted method as our main analysis. RESULTS: Genetically predicted higher WHR (per 0.09 ratio units) was associated with unfavorable functional outcome after ischemic stroke (mRS 3-6, OR = 1.48; 95% CI = 1.03-2.13; p = 0.033). The results remained directionally consistent in sensitivity analyses. Conversely, genetically predicted BMI (per 4.8 kg/m2) was not associated with unfavorable functional outcome after ischemic stroke (OR = 1.01; 95% CI = 0.75-1.36; p = 0.937). DISCUSSION: This study provides genetic evidence supporting the hypothesis that abdominal adiposity has a detrimental effect on functional recovery after ischemic stroke.

The interaction between MALAT1 and TUG1 with dietary fatty acid quality indices on visceral adiposity index and body adiposity index.

We aimed to investigate the interaction between the transcript levels of taurine-upregulated gene 1 (TUG1) and metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) and the Cholesterol-Saturated Fat Index (CSI) in relation to the visceral adiposity index (VAI) and body adiposity index (BAI). This cross-sectional study involved 346 women classified as obese and overweight, aged between 18 and 48 years. Dietary intake and the quality of dietary fat were assessed using a validated and reliable 147-item semi-quantitative food frequency questionnaire, with the Cholesterol-Saturated Fat Index (CSI) used as an indicator. Transcription levels of MALAT1 and TUG1 were evaluated through real-time polymerase chain reaction following the criteria outlined in the Minimum Information for Publication of Quantitative standards. Serum profiles were measured using standard protocols. We observed a positive association between transcription level of MALAT1 and VAI in both crude (ß = 3.646, 95% CI 1.950-5.341, p < 0.001) and adjusted (ß = 8.338, 95% CI 6.110-10.566, p < 0.001) models. Furthermore, after adjusting for confounders, a significant positive interaction was noted between MALAT1 expression and CSI on BAI (ß: 0.130, 95% CI 0.019, 0.240, p = 0.022), with a marginal positive interaction observed on VAI (ß: 0.718, 95% CI - 0.028, 1.463, p = 0.059). It seems that there may be a positive interaction between MALAT1 transcription level and CSI on VAI and BAI among overweight and obese women. However, no associations were seen between TUG1 mRNA level and the above-mentioned outcomes. Further functional studies are still required to elucidate this concept.

Neonatal adiposity is associated with microRNAs in adipocyte-derived extracellular vesicles in maternal and cord blood, a discovery analysis.

BACKGROUND: Maternal body size, nutrition, and hyperglycemia contribute to neonatal body size and composition. There is little information on maternal-fetal transmission of messages which influence fetal growth. We analyzed adipocyte-derived small extracellular vesicular (ADsEV) microRNAs in maternal and cord blood to explore their adipogenic potential. METHODS: There were 279 mother-neonate pairs with all phenotypic data (normal glucose tolerant NGT = 148, gestational diabetes mellitus GDM = 131). Neonates with adiposity were those in the highest tertile (T3) of sex-specific sum of skinfolds and those without adiposity (lean) in the lowest tertile T1 of NGT pregnancies. We studied ADsEV miRNAs in 76 and 51 neonates with and without adiposity respectively and their mothers based on power calculations (68 NGT and 59 GDM pregnancies). ADsEV miRNAs from maternal and cord blood plasma samples were profiled on Agilent 8*60 K microarray. Differential expression (DE) of ADsEV miRNAs in adipose vs. lean groups was studied before and after adjustment for maternal GDM, adiposity, and vitamin B12-folate status. RESULTS: Multiple miRNAs were common in maternal and cord blood and positively correlated. We identified 24 maternal and 5 cord blood miRNAs differentially expressed (discovery p ≤ 0.1) in the adipose group in unadjusted, and 19 and 26, respectively, in the adjusted analyses. Even though DE miRNAs were different in maternal and cord blood, they targeted similar adipogenic pathways (e.g., the forkhead box O (FOXO) family of transcription factors, mitogen­activated protein kinase (MAPK) pathway, transforming growth factor beta (TGF-ß) pathway). Maternal GDM and adiposity were associated with many DE ADsEV miRNAs. CONCLUSION: Our results suggest that the ADsEV miRNAs in mothers are potential regulators of fetal adiposity. The expression and functionality of miRNAs appear to be influenced by maternal adiposity, hyperglycemia, and micronutrient status during pregnancy.

Vaspin: A Novel Biomarker Linking Gluteofemoral Body Fat and Type 2 Diabetes Risk.

OBJECTIVE: To determine whether adiposity depots modulate vaspin levels and whether vaspin predicts type 2 diabetes (T2D) risk, through epidemiological and genetic analyses. RESEARCH DESIGN AND METHODS: We assessed the relationship of plasma vaspin concentration with incident and prevalent T2D and adiposity-related variables in 1) the Prospective Urban and Rural Epidemiology (PURE) biomarker substudy (N = 10,052) and 2) the Outcome Reduction with Initial Glargine Intervention (ORIGIN) trial (N = 7,840), using regression models. We then assessed whether vaspin is causally associated with T2D and whether genetic variants associated with MRI-measured adiposity depots modulate vaspin levels, using two-sample Mendelian randomization (MR). RESULTS: A 1-SD increase in circulating vaspin levels was associated with a 16% increase in incident T2D in the PURE cohort (hazard ratio 1.16; 95% CI 1.09-1.23; P = 4.26 × 10-7) and prevalent T2D in the ORIGIN cohort (odds ratio [OR] 1.16; 95% CI 1.07-1.25; P = 2.17 × 10-4). A 1-unit increase in BMI and triglyceride levels was associated with a 0.08-SD (95% CI 0.06-0.10; P = 2.04 × 10-15) and 0.06-SD (95% CI 0.04-0.08; P = 4.08 × 10-13) increase, respectively, in vaspin in the PURE group. Consistent associations were observed in the ORIGIN cohort. MR results reinforced the association between vaspin and BMI-adjusted T2D risk (OR 1.01 per 1-SD increase in vaspin level; 95% CI 1.00-1.02; P = 2.86 × 10-2) and showed that vaspin was increased by 0.10 SD per 1-SD decrease in genetically determined gluteofemoral adiposity (95% CI 0.02-0.18; P = 2.01 × 10-2). No relationships were found between subcutaneous or visceral adiposity and vaspin. CONCLUSIONS: These findings support that higher vaspin levels are related to increased T2D risk and reduced gluteofemoral adiposity, positioning vaspin as a promising clinical predictor for T2D.

Observational and genetic associations of adiposity with cardiopulmonary multimorbidity: Linear and nonlinear Mendelian randomization analysis.

OBJECTIVE: Whether adiposity traits are causal risk factors for cardiopulmonary multimorbidity (CP-MM) remains largely unknown. The aim of this study was to examine the causal role of adiposity traits in the development of CP-MM. METHODS: This study involved 408,886 participants from the UK Biobank who had complete phenotypic and genetic data. Cox regression and Mendelian randomization (MR) analyses were conducted separately for observational and causal associations. RESULTS: During a median follow-up of 8.7 years, 1492 incident CP-MM were ascertained. In observational analysis, individuals with obesity had a hazard ratio (HR) of 1.51 (95% confidence intervals [CI]: 1.30-1.75) for developing CP-MM, compared with those with normal body mass index (BMI). Restricted cubic spline analyses showed a U-shaped relationship between continuous BMI and CP-MM (p < 0.001), whereas WHRadjBMI exhibited a linear relationship (p = 0.828). Joint analysis revealed that maintaining ideal waist-hip ratio (WHR) in adults with overweight is still effective in preventing CP-MM. In linear MR analysis, 1 kg/m2 increase in genetically predicted BMI and per 1% higher in genetically predicted WHRadjBMI was associated with 9% and 10% higher risk for incident CP-MM, respectively. Nonlinear MR analyses demonstrated linearity between genetically predicted BMI or WHRadjBMI and CP-MM. CONCLUSIONS: Adiposity may play a causal role in CP-MM development and represent a promising approach for multimorbidity prevention.

Skeletal muscle myostatin mRNA expression is upregulated in aged human adults with excess adiposity but is not associated with insulin resistance and ageing.

Myostatin negatively regulates skeletal muscle growth and appears upregulated in human obesity and associated with insulin resistance. However, observations are confounded by ageing, and the mechanisms responsible are unknown. The aim of this study was to delineate between the effects of excess adiposity, insulin resistance and ageing on myostatin mRNA expression in human skeletal muscle and to investigate causative factors using in vitro models. An in vivo cross-sectional analysis of human skeletal muscle was undertaken to isolate effects of excess adiposity and ageing per se on myostatin expression. In vitro studies employed human primary myotubes to investigate the potential involvement of cross-talk between subcutaneous adipose tissue (SAT) and skeletal muscle, and lipid-induced insulin resistance. Skeletal muscle myostatin mRNA expression was greater in aged adults with excess adiposity than age-matched adults with normal adiposity (2.0-fold higher; P < 0.05) and occurred concurrently with altered expression of genes involved in the maintenance of muscle mass but did not differ between younger and aged adults with normal adiposity. Neither chronic exposure to obese SAT secretome nor acute elevation of fatty acid availability (which induced insulin resistance) replicated the obesity-mediated upregulation of myostatin mRNA expression in vitro. In conclusion, skeletal muscle myostatin mRNA expression is uniquely upregulated in aged adults with excess adiposity and insulin resistance but not by ageing alone. This does not appear to be mediated by the SAT secretome or by lipid-induced insulin resistance. Thus, factors intrinsic to skeletal muscle may be responsible for the obesity-mediated upregulation of myostatin, and future work to establish causality is required.

Causal effects of life course adiposity on temporomandibular disorders: A Mendelian randomization study.

BACKGROUND: Previous studies investigated the associations between obesity and temporomandibular disorders (TMDs), but the evidence for the causal inferences was unclear. OBJECTIVE: We aimed to investigate the causal link between life course adiposity and TMDs. METHODS: Mendelian randomization (MR) studies were performed using genetic instruments for birth weight (BW) (N = 261 932), childhood body mass index (BMI) (N = 39 620), childhood body size (N = 454 718), adult BMI (N = 99 998), body fat percentage (N = 454 633) and TMDs (N = 211 023). We assessed the overall effect of each life course adiposity factor via inverse-variance weighted (IVW), weighted median, and MR-Egger methods and performed extensive sensitivity analyses. Additionally, multivariable MR was conducted to evaluate the direct and indirect effects of childhood BMI on TMDs while accounting for BW and adult BMI, and vice versa. RESULTS: Univariable MR analyses revealed a causal effect of low childhood adiposity on an increased risk of TMDs (childhood BMI: IVW OR: 0.65, 95% CI: 0.54-0.78, p < .001; childhood body size: IVW OR: 0.56, 95% CI: 0.43-0.73, p < .001). No causal association existed between genetically predicted BW, adult BMI, or body fat percentage and TMDs. In the multivariable MR analyses, the effects of childhood BMI on TMDs occurrence remained significant and direct, even after adjusting for BW and adult BMI (multivariable IVW OR: 0.78, 95% CI: 0.61-0.99, p = .048). No pleiotropy and heterogeneity were detected (p > .05). CONCLUSION: Low childhood BMI might causally increase the risk of TMDs through a direct pathway.

Cord blood DNA methylation of immune and lipid metabolism genes is associated with maternal triglycerides and child adiposity.

OBJECTIVE: Fetal exposures may impact offspring epigenetic signatures and adiposity. The authors hypothesized that maternal metabolic traits associate with cord blood DNA methylation, which, in turn, associates with child adiposity. METHODS: Fasting serum was obtained in 588 pregnant women (27-34 weeks' gestation), and insulin, glucose, high-density lipoprotein cholesterol, triglycerides, and free fatty acids were measured. Cord blood DNA methylation and child adiposity were measured at birth, 4-6 months, and 4-6 years. The association of maternal metabolic traits with DNA methylation (429,246 CpGs) for differentially methylated probes (DMPs) and regions (DMRs) was tested. The association of the first principal component of each DMR with child adiposity was tested, and mediation analysis was performed. RESULTS: Maternal triglycerides were associated with the most DMPs and DMRs of all traits tested (261 and 198, respectively, false discovery rate < 0.05). DMRs were near genes involved in immune function and lipid metabolism. Triglyceride-associated CpGs were associated with child adiposity at 4-6 months (32 CpGs) and 4-6 years (2 CpGs). One, near CD226, was observed at both timepoints, mediating 10% and 22% of the relationship between maternal triglycerides and child adiposity at 4-6 months and 4-6 years, respectively. CONCLUSIONS: DNA methylation may play a role in the association of maternal triglycerides and child adiposity.