Within-sibship genome-wide association analyses decrease bias in estimates of direct genetic effects.

Estimates from genome-wide association studies (GWAS) of unrelated individuals capture effects of inherited variation (direct effects), demography (population stratification, assortative mating) and relatives (indirect genetic effects). Family-based GWAS designs can control for demographic and indirect genetic effects, but large-scale family datasets have been lacking. We combined data from 178,086 siblings from 19 cohorts to generate population (between-family) and within-sibship (within-family) GWAS estimates for 25 phenotypes. Within-sibship GWAS estimates were smaller than population estimates for height, educational attainment, age at first birth, number of children, cognitive ability, depressive symptoms and smoking. Some differences were observed in downstream SNP heritability, genetic correlations and Mendelian randomization analyses. For example, the within-sibship genetic correlation between educational attainment and body mass index attenuated towards zero. In contrast, analyses of most molecular phenotypes (for example, low-density lipoprotein-cholesterol) were generally consistent. We also found within-sibship evidence of polygenic adaptation on taller height. Here, we illustrate the importance of family-based GWAS data for phenotypes influenced by demographic and indirect genetic effects.

Applying Mendelian randomization to appraise causality in relationships between nutrition and cancer.

Dietary factors are assumed to play an important role in cancer risk, apparent in consensus recommendations for cancer prevention that promote nutritional changes. However, the evidence in this field has been generated predominantly through observational studies, which may result in biased effect estimates because of confounding, exposure misclassification, and reverse causality. With major geographical differences and rapid changes in cancer incidence over time, it is crucial to establish which of the observational associations reflect causality and to identify novel risk factors as these may be modified to prevent the onset of cancer and reduce its progression. Mendelian randomization (MR) uses the special properties of germline genetic variation to strengthen causal inference regarding potentially modifiable exposures and disease risk. MR can be implemented through instrumental variable (IV) analysis and, when robustly performed, is generally less prone to confounding, reverse causation and measurement error than conventional observational methods and has different sources of bias (discussed in detail below). It is increasingly used to facilitate causal inference in epidemiology and provides an opportunity to explore the effects of nutritional exposures on cancer incidence and progression in a cost-effective and timely manner. Here, we introduce the concept of MR and discuss its current application in understanding the impact of nutritional factors (e.g., any measure of diet and nutritional intake, circulating biomarkers, patterns, preference or behaviour) on cancer aetiology and, thus, opportunities for MR to contribute to the development of nutritional recommendations and policies for cancer prevention. We provide applied examples of MR studies examining the role of nutritional factors in cancer to illustrate how this method can be used to help prioritise or deprioritise the evaluation of specific nutritional factors as intervention targets in randomised controlled trials. We describe possible biases when using MR, and methodological developments aimed at investigating and potentially overcoming these biases when present. Lastly, we consider the use of MR in identifying causally relevant nutritional risk factors for various cancers in different regions across the world, given notable geographical differences in some cancers. We also discuss how MR results could be translated into further research and policy. We conclude that findings from MR studies, which corroborate those from other well-conducted studies with different and orthogonal biases, are poised to substantially improve our understanding of nutritional influences on cancer. For such corroboration, there is a requirement for an interdisciplinary and collaborative approach to investigate risk factors for cancer incidence and progression.

Household Food Insecurity Is Associated with Adverse Mental Health Indicators and Lower Quality of Life among Koreans: Results from the Korea National Health and Nutrition Examination Survey 2012-2013.

Food insecurity is an ongoing public health issue and contributes to mental health status. We investigated whether food insecurity is associated with inadequate nutrient intake and whether it affects mental health indicators (perceived stress/experience of depressive symptom/suicidal ideation) and quality of life (QOL) among Koreans (n = 5862, 20-64 years) using data from the Korea National Health and Nutritional Examination Survey (2012-2013). Household food security status was categorized as "food-secure household", "food-insecure household without hunger", and "food-insecure household with hunger". Data on food insecurity, sociodemographic factors, nutrient intake, mental health indicators, and QOL were used. A logistic regression model was conducted to determine odds ratios (ORs) for psychological health. A greater proportion of food-insecure participants were nutritionally deficient compared with expectations of the 2015 Korean Dietary Reference Intakes. These deficiencies were generally higher in both "food-insecure household" groups. Both "food-insecure household" groups, particularly the "food-insecure household with hunger" group showed significantly adverse mental health status (ORs: 1.52-3.83) and lower QOL (ORs: 1.49-3.92) than did the "food-secure household" group before and after adjusting for sex, age, education, household income, smoking/alcohol consumption, physical activity, marital status, and receiving food assistance. In conclusion, food insecurity may be significantly associated with adverse mental health indicators and decreased QOL in young/middle-aged Koreans.

Arginase inhibition ameliorates hepatic metabolic abnormalities in obese mice.

OBJECTIVES: We examined whether arginase inhibition influences hepatic metabolic pathways and whole body adiposity in diet-induced obesity. METHODS AND RESULTS: After obesity induction by a high fat diet (HFD), mice were fed either the HFD or the HFD with an arginase inhibitor, Nω-hydroxy-nor-L-arginine (nor-NOHA). Nor-NOHA significantly prevented HFD-induced increases in body, liver, and visceral fat tissue weight, and ameliorated abnormal lipid profiles. Furthermore, nor-NOHA treatment reduced lipid accumulation in oleic acid-induced hepatic steatosis in vitro. Arginase inhibition increased hepatic nitric oxide (NO) in HFD-fed mice and HepG2 cells, and reversed the elevated mRNA expression of hepatic genes in lipid metabolism. Expression of phosphorylated 5' AMPK-activated protein kinase α was increased by arginase inhibition in the mouse livers and HepG2 cells. CONCLUSIONS: Arginase inhibition ameliorated obesity-induced hepatic lipid abnormalities and whole body adiposity, possibly as a result of increased hepatic NO production and subsequent activation of metabolic pathways involved in hepatic triglyceride metabolism and mitochondrial function.

Hypocholesterolemic effect of daily fisetin supplementation in high fat fed Sprague-Dawley rats.

We aimed to test whether fisetin could modulate cholesterol homeostasis in rats with diet-induced hypercholesterolemia, and further investigated the underlying mechanisms by which fisetin exerts its cholesterol lowering effect. Blood lipid profile, hepatic cholesterol content, as well as gene expressions in cholesterol metabolism were examined. Elevated levels of total cholesterol and LDL-cholesterol, along with hepatic cholesterol content in a high fat group were found to be significantly reduced by fisetin. The high fat diet significantly decreased hepatic mRNA levels of LDLR, SREBP2, HMGCR and PCSK9 in comparison to the control diet, however, fisetin did not further elicit any changes in mRNA levels of the same genes. The high fat diet dramatically increased the transcript levels of CYP7A1, which was subsequently reversed by the fisetin. In HepG2 cells, fisetin was found to increase the levels of a nuclear form of SREBP2 and LDLR. In conclusion, fisetin supplementation displayed hypocholesterolemic effects by modulating the expression of genes associated with cholesterol and bile acid metabolism.

Quercetin up-regulates expressions of peroxisome proliferator-activated receptor γ, liver X receptor α, and ATP binding cassette transporter A1 genes and increases cholesterol efflux in human macrophage cell line.

Cholesterol-laden macrophages trigger accumulation of foam cells and increase the risk of developing atherosclerosis. We hypothesized that quercetin could lower the content of cholesterol in macrophages by regulating the expression of the ATP binding cassette transporter A1 (ABCA1) gene in differentiated human acute monocyte leukemia cell line (THP-1) cells and thereby reducing the chance of forming foam cells. Quercetin, in concentrations up to 30 µM, was not cytotoxic to differentiated THP-1 cells. Quercetin up-regulated both ABCA1 messenger RNA and protein expression in differentiated THP-1 cells, and its maximum effects were demonstrated at 0.3 µM for 4 to 8 hours in incubation. In addition, quercetin increased protein levels of peroxisome proliferator-activated receptor γ (PPARγ) and liver X receptor α (LXRα) within 2 hours of treatment. Because PPARγ and LXRα are important transcriptional factors for ABCA1, quercetin-induced up-regulation of ABCA1 may be mediated by increased expression levels of the PPARγ and LXRα genes. Furthermore, quercetin-enhanced cholesterol efflux from differentiated THP-1 cells to both high-density lipoprotein (HDL) and apolipoprotein A1. Quercetin at the dose of 0.15 µM elevated the cholesterol efflux only for HDL. At the dose of 0.3 µM, quercetin demonstrated effects both on HDL and apolipoprotein A1. Our data demonstrated that quercetin increased the expressions of PPARγ, LXRα, and ABCA1 genes and cholesterol efflux from THP-1 macrophages. Quercetin-induced expression of PPARγ and LXRα might subsequently affect up-regulation of their target gene ABCA1. Taken together, ingestion of quercetin or quercetin-rich foods could be an effective way to improve cholesterol efflux from macrophages, which would contribute to lowering the risk of atherosclerosis.

Quercetin up-regulates LDL receptor expression in HepG2 cells.

Quercetin, an abundant flavonol found in fruits and vegetable, has been implicated in lowering the risk of cardiovascular disease that is often associated with high plasma levels of low density lipoprotein (LDL) cholesterol. Here we investigated whether quercetin could modulate the expression of LDL receptors (LDLR) in HepG2 cells and the possible underlying mechanisms to exert quercetin's effects. We found that quercetin was able to induce LDLR expression with at least a 75 µ m concentration, which was accompanied by an increase in nuclear sterol regulatory element binding protein 2 (SREBP2). This effect was mediated by activation of c-jun-N-terminal kinase (JNK) and extracellular signal-regulated kinase (ERK) signalling pathways as implicated by experiments using chemical inhibitors of each pathway. When cells were challenged with protein synthesis inhibitors in quercetin-activated LDLR transcription, LDL mRNA levels were not significantly affected by cycloheximide but puromycin abolished quercetin-induced LDLR transcription. Taken together, we conclude that quercetin can initiate LDLR transcription by enhancing SREBP2 processing, but new protein synthesis might be necessary to exert a maximum effect of quercetin in the up-regulation of the LDLR gene. Our findings demonstrate that quercetin strongly up-regulated LDLR gene expression, which might elicit hypolipidemic effects by increasing the clearance of circulating LDL cholesterol levels from the blood.