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Background Several computational methods have been developed that integrate transcriptomics data with genome-scale metabolic reconstructions to increase accuracy of inferences of intracellular metabolic flux distributions. Even though existing methods use transcript abundances as a proxy for enzyme activity, each method uses a different hypothesis and assumptions. Most methods implicitly assume a proportionality between transcript levels and flux through the corresponding function, although these proportionality constant(s) are often not explicitly mentioned nor discussed in any of the published methods. E-Flux is one such method and, in this algorithm, flux bounds are related to expression data, so that reactions associated with highly expressed genes are allowed to carry higher flux values. Results Here, we extended E-Flux and systematically evaluated the impact of an assumed proportionality constant on model predictions. We used data from published experiments with Escherichia coli and Saccharomyces cerevisiae and we compared the predictions of the algorithm to measured extracellular and intracellular fluxes. Conclusion We showed that detailed modelling using a proportionality constant can greatly impact the outcome of the analysis. This increases accuracy and allows for extraction of better physiological information., Background Several computational methods have been developed that integrate transcriptomics data with genome-scale metabolic reconstructions to increase accuracy of inferences of intracellular metabolic flux distributions. Even though existing methods use transcript abundances as a proxy for enzyme activity, each method uses a different hypothesis and assumptions. Most methods implicitly assume a proportionality between transcript levels and flux through the corresponding function, although these proportionality constant(s) are often not explicitly mentioned nor discussed in any of the published methods. E-Flux is one such method and, in this algorithm, flux bounds are related to expression data, so that reactions associated with highly expressed genes are allowed to carry higher flux values. Results Here, we extended E-Flux and systematically evaluated the impact of an assumed proportionality constant on model predictions. We used data from published experiments with Escherichia coli and Saccharomyces cerevisiae and we compared the predictions of the algorithm to measured extracellular and intracellular fluxes. Conclusion We showed that detailed modelling using a proportionality constant can greatly impact the outcome of the analysis. This increases accuracy and allows for extraction of better physiological information.

Nutrition in early life can have lasting effects on metabolism: nutritional programming. Pregnancy and lactation are well established critical periods of development impacting lifelong health, but development continues after these periods. Therefore, nutrition in later periods, such as the weaning and (early) post-weaning period, may also induce lasting metabolic effects. After lactation, when an infant relies solely on milk for nutrition, the weaning period commences. In this phase, solid foods are gradually introduced; it is a period of great diversification of the diet. The transition to solid foods introduces a major change in carbohydrate exposure. The main carbohydrate in the lactation period is lactose, a dimer of glucose and galactose. Gradually, a variety of di- and polysaccharides are introduced that are mainly glucose based, but can also contain fructose.Whether or not exposure to different types of monosaccharides at weaning has lasting effects on metabolism and metabolic health is not known. The aim of this thesis was to establish whether the post-weaning period is a critical developmental period in which exposure to different types of monosaccharides can lead to programming of adult metabolic health. We were particularly interested in galactose and fructose. Our interest in galactose was because this sugar almost disappears from the diet after weaning. Our interest in fructose was because it appears in the diet at weaning, and is suggested to be more detrimental to health compared to glucose, which is always present and is taken as a reference. Thus we compared effects of the dietary monosaccharides fructose and galactose, to those of glucose. Analyses were focussed on body composition and metabolic health. A mouse model for nutritional programming was used. In this model, newly weaned C57BL/6JRccHsd mice were fed with diets differing in monosaccharide content for three weeks. Afterwards, all mice were fed an obesogenic high-fat diet (HFD) for nine wee

Indirect calorimetry (InCa) is an essential tool for human and animal studies of energy metabolism. InCa measures the metabolic gases consumed (oxygen, O2) and produced (carbon dioxide, CO2) by the organism to calculate energy expenditure (EE). The ratio of CO2 produced to O2 consumed, or the respiratory exchange ratio (RER), indicates substrate utilisation (carbohydrate, fat, and protein) at the whole body level. Significant improvements in commercial InCa systems for rodents have increased its accuracy and resolution, yet there have been few attempts to extend the technique by measuring other physiological gases. These gases can be of microbial origin, like hydrogen (H2) and methane (CH4), which result from fermentation by the gut microbiome. Furthermore, conventional InCa cannot distinguish between the oxidation of exogenous (e.g. dietary) and endogenous (stored in the body) substrates. Stable isotopic tracers, like 13C-enriched nutrients, make this distinction possible by analysis of the ratio of 13CO2/12CO2 in expired air. These gases (H2, CH4, 13CO2, 12CO2) are rarely measured in mouse studies and, when they are, they need expensive equipment and considerable time and effort. Dietary starches can be lowly or highly digestible. Lowly digestible starches generally produce lower glycaemic responses, provide fermentative substrates for the intestinal microbiota, and are thought to prevent excessive adiposity and favour metabolic health. There are some indications that starch digestibility has different metabolic effects in females and males. The evidence for this is very limited and, where both sexes have been studied, little attention has been paid to other aspects of carbohydrate metabolism, besides oral glucose tolerance tests and static tests for glycaemia. Moreover, despite the potential of starches to impact metabolism, there are no evidence-based recommendations for starch intake for young children. This is important because early life nutrition has the pow

Male ferrets, aged 3 months, were divided into two group: one group remained at 22 degrees Celsius, while the other group was acclimatized to 4 degrees Celsius for one week. After sacrification, inguinal and periaortic white adipose tissues were dissected, and used for RNA isolation and subsequent global gene expression profiling using custom Agilent ferret-specific 2x400K microarrays. Data analysis indicated that while the cold exposure induces an increase on metabolism in inguinal white adopose tissue, in periaortic white adipose tissue this stimulus induces a reduction on expression of genes involved in cell cycle and in immune response

Background: Excessive white adipose tissue (WAT) expansion as in obesity is generally associated with chronic inflammation of WAT, which contributes to obesity associated complications. Low oxygen availability in WAT is hypothesized to be the initiator of this inflammatory response. Hypothesis: We examined the hypothesis that local tissue hypoxia is responsible for the initiation of inflammation in WAT. Research design and methods: Diet-induced obese male C57BL/6JOlaHsd mice, housed at thermoneutrality, were exposed to mild environmental oxygen restriction (OxR, to 13% oxygen) for five days and compared with mice kept at normoxia, after which WAT and serum were collected. Body composition, systemic metabolic parameters, WAT macrophage infiltration (as marker for tissue inflammation) and whole genome microarray analysis, and circulating adipokines were measured. Results: Five days OxR decreased body weight and fat mass, and increased blood levels of haemoglobin and haematocrit, as well as lactate to glucose ratio, which indicated systemic hypoxia. No difference in adipose tissue inflammation was found, which was supported by down regulation of inflammation-associated transcript levels of S100a8, Saa1, and Saa3. Serum metabolomics revealed an increase of branched chain amino acid Valine and propionylcarnitine. Adipokines CCDC3, CCK, and Adiponectin are reduced by OxR on transcript (Cck) or serum protein level (Adiponectin), or both (CCDC3). Conclusions: Mild oxygen restriction does not increase white adipose tissue inflammation in obese mice. However, a systemic adaptation together with a metabolic response in WAT was observed

Antral follicle size might be a valuable additive predictive marker for IVF outcome. However, while some studies show positive relations between follicle size and reproductive outcome, others have not been successful in establishing this relation. To better understand consequences of antral follicle size for reproductive outcome, we aimed to obtain insight in follicle size-related granulosa cell processes, as granulosa cells play an essential role in follicular development via the production of growth factors, steroids and metabolic intermediates, needed for follicular growth and oocyte development. Using pigs as a model, we compared gene and protein expression in granulosa cells of smaller and larger follicles in the healthy antral follicle pool at the start of the follicular phase of the estrous cycle. In sows, the early antral follicle pool is very heterogeneous when e.g. size and steroid content of the follicular fluid are considered. To which extent this variety contributes to the developmental competence of the follicles is not clear. Therefore, sows with high variation in antral follicle size (HighVAR) as well as sows with low variation in antral follicle size (LowVAR) were used. Granulosa cells of smaller antral follicles in the healthy antral follicle pool show increased cell proliferation, which was accompanied by a metabolic shift towards aerobic glycolysis (i.e. the Warburg effect), similar to other highly proliferating cells. High granulosa cell proliferation rates in smaller follicles might be regulated via increased granulosa cell expression of AR and EGFR which are activated in response to locally produced mitogens. While granulosa cells of smaller follicles in the pool were more proliferative, indicative of higher follicular growth, granulosa cells of larger follicles in the pool showed less proliferation and were more differentiated, as they showed a higher expression of follicular maturation marker IGF1 and ANGPT1. Our results imply that the inclu

Male ferrets, aged 3 months, were divided into two group: one group remained at 22 degrees Celsius, while the other group was acclimatized to 4 degrees Celsius for one week. After sacrification, inguinal white adipose tissues were dissected, and used for RNA isolation and subsequent global gene expression profiling using custom Agilent ferret-specific 2x400K microarrays. Data analysis indicated that mainly metabolism is significantly upregulated. When we focus on the top 50 significantly upregulated transcripts we identified: 7 genes involved in the structure and actin metabolism; 2 genes involved in lipid metabolism and 5 genes involved in electron transport chain in mitochondria and oxidative phosphorylation, suggesting an increased fatty acid catabolism; 4 genes involved in skeletal muscle or muscle contraction and 6 genes involved in skeletal development and 1 gene involved in brown and white adipose differentiation, suggesting a transformation of the cell population; 6 genes involved in amino acid catabolism; and 19 others genes involved in other processes

Antral follicle size might be a valuable additive predictive marker for IVF outcome. To better understand consequences of antral follicle size as a marker for reproductive outcome, we aimed to obtain insight in follicle size-related granulosa cell processes, as granulosa cells play an essential role in follicular development via the production of growth factors, steroids and metabolic intermediates. Using the pig as a model, we compared gene expression in granulosa cells of smaller and larger follicles in the healthy antral follicle pool of sows which had a high variation versus low variation in follicle size. Selected gene expression was confirmed at the protein level. Granulosa cells of smaller antral follicles showed increased cell proliferation, which was accompanied by a metabolic shift towards aerobic glycolysis (i.e. the Warburg effect), similar to other highly proliferating cells. High granulosa cell proliferation rates in smaller follicles might be regulated via increased granulosa cell expression of the androgen receptor and the epidermal growth factor receptor, which are activated in response to locally produced mitogens. While granulosa cells of smaller follicles in the pool are more proliferative, granulosa cells of larger follicles express more maturation markers such as insulin-like growth factor 1 (IGF1) and angiopoietin 1 (ANGPT1) and are therefore more differentiated. As both higher IGF1 and ANGPT1 have been associated with better IVF outcomes, the results of our study imply that including smaller follicles for oocyte aspiration might have negative consequences for IVF outcome.

Distinct markers for early, mild vitamin B3 deficiency are lacking. To identify these, we examined the molecular responses of white adipose tissue to vitamin B3 withdrawal. We performed a dietary intervention in male C57Bl/6JRcc mice. A diet with a low but adequate level of tryptophan without nicotinamide riboside (NR) was compared to the same diet with NR at the recommended vitamin B3 (30 mg NR per kg diet). Physiological and circulating parameters were determined and global transcriptomics, qRT-PCR and histology of epididymal white adipose tissue (eWAT) were done. We observed a decreased insulin sensitivity and a shift from carbohydrate to fatty acid oxidation. This was consistent with molecular changes in eWAT, where we observed an altered MEK/ERK signalling, a lowering of glucose utilization markers and an increase in makers of fatty acid catabolism, which may be related to the consistent reduction of mitochondrial OXPHOS Complex I (mRNAs and protein). The synthesis pathway of tetrahydropteridine (BH4), an essential cofactor for neurotransmitter synthesis, was found to be increased. Based on our results, we propose the technically validated downregulation of Anp32a, Tnk2 and the upregulation of Mapk1, Map2k1, Mthfs, Mthfsl and Qdpr as a WAT transcriptional signature marker for mild vitamin B3 deficiency

This SuperSeries is composed of the SubSeries listed below. Overall design: Refer to individual Series, This SuperSeries is composed of the SubSeries listed below. Overall design: Refer to individual Series

Maternal high-fat consumption has negative effects on the offspring’s obesity/diabetes susceptibility and we hypothesize that epigenetic modifications in the skeletal muscle are partly responsible for this phenotype. To detect genes affected by maternal nutrition, offspring of low-fat (LF) and high-fat (HF) diet fed dams (C57BL/6 mice) received LF diet upon weaning and were sacrificed at an age of 6 or 25 weeks. M. quadriceps gene expression was investigated by microarray analysis revealing upregulation of the nuclear receptor Nr4a1 by maternal HF feeding. This was accompanied by promoter hypomethylation of CpG‑1408 which correlated with higher Nr4a1 gene expression at both ages. Offspring voluntary exercise training normalized Nr4a1 methylation/expression and ameliorated the negative effects of maternal HF feeding on insulin sensitivity. Overall, Nr4a1 expression correlated with higher insulin levels during oral glucose tolerance test and could, therefore, be involved in the programming offspring’s diabetes susceptibility.

The gut microbiome interacts continuously with the host and its diet. Studying these interactions and their evolution in vivo as soon as they happen have been impossible. Here we develop a method to study microbiota-host-diet interactions continuously, non-invasively, and in real time, by measuring hydrogen (H2) and methane (CH4) production in mice housed in indirect calorimetry chambers., The gut microbiome interacts continuously with the host and its diet. Studying these interactions and their evolution in vivo as soon as they happen have been impossible. Here we develop a method to study microbiota-host-diet interactions continuously, non-invasively, and in real time, by measuring hydrogen (H2) and methane (CH4) production in mice housed in indirect calorimetry chambers.

Selenium is an essential micronutrient. Its recommended daily allowance is not attained by a significant proportion of the population in many countries and its intake has been suggested to affect colorectal carcinogenesis. Therefore, microarrays were used to determine how both selenoprotein and global gene expression patterns in the mouse colon were affected by marginal selenium deficiency comparable to variations in human dietary intakes. Two groups of 12 mice each were fed a selenium-deficient (0.086mg Se/kg) or a selenium-adequate (0.15mg Se/kg) diet. After 6wk, plasma selenium level, liver, and colon glutathione peroxidase (GPx) activity in the deficient group was 12, 34, and 50%, respectively, of that of the adequate group. Differential gene expression was analysed with mouse 44K whole genome microarrays. Pathway analysis by GenMAPP identified the protein biosynthesis pathway as most significantly affected, followed by inflammation, Delta-Notch and Wnt pathways. Selected gene expression changes were confirmed by quantitative real-time PCR. GPx1 and the selenoproteins W, H, and M, responded significantly to selenium intake making them candidates as biomarkers for selenium status. Thus, feeding a marginal selenium-deficient diet resulted in distinct changes in global gene expression in the mouse colon. Modulation of cancer-related pathways may contribute to the higher susceptibility to colon carcinogenesis in low selenium status.

van Schothorst EM, Bunschoten A, Verlinde E, Schrauwen P, Keijer J. Glycemic index differences of high-fat diets modulate primarily lipid metabolism in murine adipose tissue. Physiol Genomics 43: 942-949, 2011. First published June 14, 2011; doi: 10.1152/physiolgenomics.00042.2011.-A low vs. high glycemic index of a high-fat (HF) diet (LGI and HGI, respectively) significantly retarded adverse health effects in adult male C57BL/6J mice, as shown recently (Van Schothorst EM, Bunschoten A, Schrauwen P, Mensink RP, Keijer J. FASEB J 23: 1092-1101, 2009). The LGI diet enhanced whole body insulin sensitivity and repressed HF diet-induced body and white adipose tissue (WAT) weight gain, resulting in significantly reduced serum leptin and resistin levels and increased adiponectin levels. We questioned how WAT is modulated and characterized the molecular mechanisms underlying the glycemic index-mediated effects using whole genome microarrays. This showed that the LGI diet mainly exerts its beneficial effects via substrate metabolism, especially fatty acid metabolism. In addition, cell adhesion and cytoskeleton remodeling showed reduced expression, in line with lower WAT mass. An important transcription factor showing enhanced expression is PPAR-gamma. Furthermore, serum levels of triglycerides, total cholesterol, and HDL- and LDL-cholesterol were all significantly reduced by LGI diet, and simultaneously muscle insulin sensitivity was significantly increased as analyzed by protein kinase B/Akt phosphorylation. Cumulatively, even though these mice were fed an HF diet, the LGI diet induced significantly favorable changes in metabolism in WAT. These effects suggest a partial overlap with pharmacological approaches by thiazolidinediones to treat insulin resistance and statins for hypercholesterolemia. It is therefore tempting to speculate that such a dietary approach might beneficially support pharmacological treatment of insulin resistance or hypercholesterolemia in humans.

This SuperSeries is composed of the SubSeries listed below.

Background: Body weight (BW) cycling, the yo-yo effect, is generally thought to have adverse effects on human metabolic health. However, human and animal experiments are limited in number and do not provide clear answers, partly due to large variations in experimental design, parameters measured, and definitions of BW cycling. Here, we examined the effect of repetitive BW cycling versus single- and non-cycling control groups, without alterations in diet composition, on steady state BW and metabolic parameters. Methods: We induced well-defined BW cycles on a semi-purified high fat diet in C57BL/6J mice, a well-described animal model for diet-induced obesity, and measured energy expenditure and relevant metabolic parameters. Results: Our setup indeed resulted in the intended BW changes and always reached a stage of energy balance. A history of weight cycling did not result in increased BW or fat mass compared with the control group, nor in deteriorated serum concentrations of glucose, adipokines and serum triglyceride and free fatty acid (FFA) concentrations. If anything, BW tended to be reduced, presumably because of a reduced overall energy intake in BW cycling animals. Conclusion: Repeated cycling in BW without changes in diet composition does not lead to impaired metabolic health nor increased BW (gain).

AB - Beneficial effects of low glycemic index (GI) diets in rodents have been studied using healthy low-fat diets, while the effects might be different on high-fat diets inducing progression of insulin resistance. We fed C57BL/6J male mice high-fat low/high-GI (LGI/HGI) diets for 13 wk. Glucose and insulin tolerance and serum substrates, including adipokines, were measured longitudinally. The LGI group showed a significantly higher glucose tolerance from wk 2 onwards, which was supported by lower serum insulin and free fatty acids levels at 8 wk, and a tendency for lower leptin levels, while resistin levels remained similar. At 11 wk, when differences in serum resistin started to increase, differences in serum insulin were diminished. Although food intake was similar throughout the study, body weights and epididymal adipose tissue mass became significantly lower in the LGI group at necropsy. Several serum substrates and adipose tissue leptin mRNA levels, as analyzed by Q-PCR, were, again, significantly lower, whereas adiponectin mRNA levels were higher. Taken together, an LGI high-fat diet maintains higher glucose tolerance and insulin sensitivity via adipose tissue modulation solely because of a difference in the type of carbohydrate, supporting a nutritional approach in the fight against insulin resistance.-Van Schothorst, E. M., Bunschoten, A., Schrauwen, P., Mensink, R. P., Keijer, J. Effects of a high-fat, low versus high glycemic index diet: retardation of insulin resistance involves adipose tissue modulation

Objective: Fibroblast growth factor 21 (FGF21) was recently discovered as stress-induced myokine during mitochondrial disease and proposed as key metabolic mediator of the integrated stress response (ISR) presumably causing systemic metabolic improvements. Curiously, the precise cell-non-autonomous and cell-autonomous relevance of endogenous FGF21 action remained poorly understood. Methods: We made use of the established UCP1 transgenic (TG) mouse, a model of metabolic perturbations made by a specific decrease in muscle mitochondrial efficiency through increased respiratory uncoupling and robust metabolic adaptation and muscle ISR-driven FGF21 induction. In a cross of TG with Fgf21-knockout (FGF21-/-) mice, we determined the functional role of FGF21 as a muscle stress-induced myokine under low and high fat feeding conditions. Results: Here we uncovered that FGF21 signaling is dispensable for metabolic improvements evoked by compromised mitochondrial function in skeletal muscle. Strikingly, genetic ablation of FGF21 fully counteracted the cell-non-autonomous metabolic remodeling and browning of subcutaneous white adipose tissue (WAT), together with the reduction of circulating triglycerides and cholesterol. Brown adipose tissue activity was similar in all groups. Remarkably, we found that FGF21 played a negligible role in muscle mitochondrial stress-related improved obesity resistance, glycemic control and hepatic lipid homeostasis. Furthermore, the protective cell-autonomous muscle mitohormesis and metabolic stress adaptation, including an increased muscle proteostasis via mitochondrial unfolded protein response (UPRmt) and amino acid biosynthetic pathways did not require the presence of FGF21. Conclusions: Here we demonstrate that although FGF21 drives WAT remodeling, the adaptive pseudo-starvation response under elevated muscle mitochondrial stress conditions operates independently of both WAT browning and FGF21 action. Thus, our findings challenge FGF21 as key me

Optimal health is maintained by interaction of multiple intrinsic and environmental factors at different levels of complexity-from molecular, to physiological, to social. Understanding and quantification of these interactions will aid design of successful health interventions. We introduce the reference network concept as a platform for multi-level exploration of biological relations relevant for metabolic health, by integration and mining of biological interactions derived from public resources and context-specific experimental data. A White Adipose Tissue Health Reference Network (WATRefNet) was constructed as a resource for discovery and prioritization of mechanism-based biomarkers for white adipose tissue (WAT) health status and the effect of food and drug compounds on WAT health status. The WATRefNet (6,797 nodes and 32,171 edges) is based on (1) experimental data obtained from 10 studies addressing different adiposity states, (2) seven public knowledge bases of molecular interactions, (3) expert's definitions of five physiologically relevant processes key to WAT health, namely WAT expandability, Oxidative capacity, Metabolic state, Oxidative stress and Tissue inflammation, and (4) a collection of relevant biomarkers of these processes identified by BIOCLAIMS ( http://bioclaims.uib.es ). The WATRefNet comprehends multiple layers of biological complexity as it contains various types of nodes and edges that represent different biological levels and interactions. We have validated the reference network by showing overrepresentation with anti-obesity drug targets, pathology-associated genes and differentially expressed genes from an external disease model dataset. The resulting network has been used to extract subnetworks specific to the above-mentioned expert-defined physiological processes. Each of these process-specific signatures represents a mechanistically supported composite biomarker for assessing and quantifying the effect of interventions on a physiologic

Indirect calorimetry (InCa) can potentially be used to noninvasively assess metabolic and age-related flexibility. To assess the use of InCa for this purpose, we tested the sensitivity and response stability over time of three InCa-based treatments in old versus adult mice. Diurnal patterns of respiratory exchange ratio were followed for 24 hours under standard conditions (Treatment 1), but the results were not stable between test periods. As a challenge, fasted mice received glucose to test switch-effectiveness from fat to glucose oxidation (Treatment 2). No differences between groups were observed, although old mice showed higher adiposity and lower white adipose tissue (WAT) mitochondrial density, indicative of age-impaired metabolic health. Lastly, adaptation to a challenge of oxygen restriction (OxR, 14.5% O2) was assessed as a novel approach (Treatment 3). This treatment stably detected significant differences: old mice did not maintain reduced oxygen consumption under OxR during both test periods, whereas adult mice did. Further biochemical and gene expression analyses showed that OxR affected glucose and lactate homeostasis in liver and WAT of adult mice, supporting the observed differences in oxygen consumption. In conclusion, InCa analysis of the response to OxR in mice is a sensitive and reproducible treatment to noninvasively measure age-impaired metabolic health.

This SuperSeries is composed of the following subset Series: GSE45991: Amino acid deprivation due to overexpression of UCP1 in skeletal muscle: signalling via FGF-21 GSE45992: Transgenic overexpression of UCP1 in skeletal muscle in mice fed a HFD: signalling via FGF-21 Skeletal muscle FGF21 secretion: part of a novel metabolic rescue cycle Susanne Keipert, Mario Ost, Janine Dokas, Evert M. van Schothorst, Mariona Jove, Reinald Pamplona, Manuel Portero-Otin, Jaap Keijer, Susanne Klaus

Given the positive results of quercetin in in vitro genotoxicity studies, the in vivo genotoxic properties of this important dietary flavonoid warrant testing, especially considering possible high intake via widely available food supplements. Here, this was done by transcriptome analyses of the most relevant tissues, liver and small intestine, of quercetin supplemented mice. Quercetin (0.33%) supplemented to a high-fat diet was administered to mice during 12 weeks. Serum alanine aminotransferase and aspartate aminotransferase levels revealed no indications for hepatotoxicity. Microarray pathway analysis of liver and small intestine showed no regulation of genotoxicity related pathways. Analysis of DNA damage related genes also did not point at genotoxicity. Furthermore, a published classifier set of transcripts for identifying genotoxic compounds did not indicate genotoxicity. Only two transcripts of the classifier set were regulated, but in the opposite direction compared with the genotoxic compounds 2-acetylaminofluorene (2-AAF) and aflatoxin B1 (AFB1). Based on the weight of evidence of three different types of analysis, we conclude that supplementation with quercetin at ~350 mg/kg bw/day for 12 weeks in mice showed no up-regulation of genotoxicity related pathways in liver and small intestine.

Health is influenced by interplay of molecular, physiological and environmental factors. To effectively maintain health and prevent disease, health-relevant relations need to be understood at multiple levels of biological complexity. Network-based methods provide a powerful platform for integration and mining of data and knowledge characterizing different aspects of health. Previously, we have reported physiological and gene expression changes associated with adaptation of murine epididymal white adipose tissue (eWAT) to 5 days and 12 weeks of high-fat diet (HFD) and low-fat diet feeding (Voigt et al. in Mol Nutr Food Res 57:1423–1434, 2013. doi:10.1002/mnfr.201200671). In the current study, we apply network analysis on this dataset to comprehensively characterize mechanisms driving the short- and long-term adaptation of eWAT to HFD across multiple levels of complexity. We built a three-layered interaction network comprising enriched biological processes, their transcriptional regulators and associated changes in physiological parameters. The multi-layered network model reveals that early eWAT adaptation to HFD feeding involves major changes at a molecular level, including activation of TGF-ß signalling pathway, immune and stress response and downregulation of mitochondrial functioning. Upon prolonged HFD intake, initial transcriptional response tails off, mitochondrial functioning is even further diminished, and in turn the relation between eWAT gene expression and physiological changes becomes more prominent. In particular, eWAT weight and total energy intake negatively correlate with cellular respiration process, revealing mitochondrial dysfunction as a hallmark of late eWAT adaptation to HFD. Apart from global understanding of the time-resolved adaptation to HFD, the multi-layered network model allows several novel mechanistic hypotheses to emerge: (1) early activation of TGF-ß signalling as a trigger for structural and morphological changes in mitochondrial org

Poly-unsaturated fatty acids (PUFAs) are considered to be healthier than saturated fatty acids (SFAs), but others postulate that especially the ratio of omega-6 to omega-3 PUFAs (n6/n3 ratio) determines health. Health can be determined with biomarkers, but functional health status is likely better reflected by challenge tests that assess metabolic flexibility. The aim of this study was to determine the effect of high-fat diets with different fatty acid compositions, but similar n6/n3 ratio, on metabolic flexibility. Therefore, adult male mice received isocaloric high-fat diets with either predominantly PUFAs (HFpu diet) or predominantly SFAs (HFs diet) but similar n6/n3 ratio for six months, during and after which several biomarkers for health were measured. Metabolic flexibility was assessed by the response to an oral glucose tolerance test, a fasting and re-feeding test and an oxygen restriction test (OxR; normobaric hypoxia). The latter two are non-invasive, indirect calorimetry-based tests that measure the adaptive capacity of the body as a whole. We found that the HFs diet, compared to the HFpu diet, increased mean adipocyte size, liver damage, and ectopic lipid storage in liver and muscle; although, we did not find differences in body weight, total adiposity, adipose tissue health, serum adipokines, whole body energy balance, or circadian rhythm between HFs and HFpu mice. HFs mice were, furthermore, less flexible in their response to both fasting- re-feeding and OxR, while glucose tolerance was indistinguishable. To conclude, the HFs versus the HFpu diet increased ectopic fat storage, liver damage, and mean adipocyte size and reduced metabolic flexibility in male mice. This study underscores the physiological relevance of indirect calorimetry-based challenge tests.

Dietary flavonoid intake is associated with reduced risk of cardiovascular diseases, possibly by affecting metabolic health. The relative potency of different flavonoids in causing beneficial effects on energy and lipid metabolism has not been investigated. Effects of quercetin, hesperetin, epicatechin, apigenin and anthocyanins in mice fed a high-fat diet (HF) for 12 weeks were compared, relative to normal-fat diet. HF-induced body weight gain was significantly lowered by all flavonoids (17–29 %), but most by quercetin. Quercetin significantly lowered HF-induced hepatic lipid accumulation (71 %). Mesenteric adipose tissue weight and serum leptin levels were significantly lowered by quercetin, hesperetin and anthocyanins. Adipocyte cell size and adipose tissue inflammation were not affected. The effect on body weight and composition could not be explained by individual significant effects on energy intake, energy expenditure or activity. Lipid metabolism was not changed as measured by indirect calorimetry or expression of known lipid metabolic genes in liver and white adipose tissue. Hepatic expression of Cyp2b9 was strongly downregulated by all flavonoids. In conclusion, all flavonoids lowered parameters of HF-induced adiposity, with quercetin being most effective.

Dietary triglycerides are hydrolyzed in the small intestine principally by pancreatic lipase. Following uptake by enterocytes and secretion as chylomicrons, dietary lipids are cleared from the bloodstream via lipoprotein lipase. Whereas lipoprotein lipase is inhibited by several proteins including Angiopoietin-like 4 (Angptl4), no endogenous regulator of pancreatic lipase has yet been identified. Here we present evidence that Angptl4 is an endogenous inhibitor of dietary lipid digestion. Angptl4-/- mice were heavier compared to their wild-type counterparts without any difference in food intake, energy expenditure or locomotor activity. However, Angptl4-/- mice showed decreased lipid content in the stools and increased accumulation of dietary triglycerides in the small intestine, which coincided with elevated luminal lipase activity in Angptl4-/- mice. Furthermore, recombinant Angptl4 reduced the activity of pancreatic lipase as well as the lipase activity in human ileostomy output. In conclusion, our data suggest that Angptl4 is an endogenous inhibitor of intestinal lipase activity.

Body weight stability may imply active regulation towards a certain physiological condition, a body weight setpoint. This interpretation is ill at odds with the world-wide increase in overweight and obesity. Until now, a body weight setpoint has remained elusive and the setpoint theory did not provide practical clues for body weight reduction interventions. For this an alternative theoretical model is necessary, which is available as the settling point model. The settling point model postulates that there is little active regulation towards a predefined body weight, but that body weight settles based on the resultant of a number of contributors, represented by the individual’s genetic predisposition, in interaction with environmental and socioeconomic factors, such as diet and lifestyle. This review refines the settling point model and argues that by taking body weight regulation from a settling point perspective, the road will be opened to careful dissection of the various contributors to establishment of body weight and its regulation. This is both necessary and useful. Nutrigenomic technologies may help to delineate contributors to body weight settling. Understanding how and to which extent the different contributors influence body weight will allow the design of weight loss and weight maintenance interventions, which hopefully are more successful than those that are currently available.

Background & Aims: Non-alcoholic fatty liver disease accompanies obesity and is independently associated with cardiovascular disease. Omega-3 fatty acids, such as docosahexaenoic (DHA) and eicosapentaenoic (EPA) acid, reduce the risk of cardiovascular disease due to their anti-inflammatory and hypolipidemic effects. Recent data suggested that metabolic effects of EPA/DHA as marine phospholipids could be stronger than triglycerides (fish oil). We characterised the mechanisms underlying beneficial effects of EPA/DHA phospholipids alone or in combination with antidiabetic drugs on hepatosteatosis in dietary obese mice. Methods: Male C57BL/6N mice were fed for 7 weeks a corn oil-based high-fat diet (cHF) or subjected to cHF-based interventions: (i) cHF with DHA/EPA as phosphatidylcholine-rich concentrate replacing ~10 % of dietary lipids (PC); ii) cHF with a low-dose of thiazolidinedione rosiglitazone (10 mg/kg diet), which retains some of the beneficial effects but also potentiates hepatic lipid accumulation (R); and iii) PC+R. Metabolic profiling together with hepatic gene expression and lipidomic analyses were performed. Results: PC and PC+R prevented weight gain and glucose intolerance induced by cHF, while all interventions reduced abdominal fat and plasma triglycerides. In contrast to R, PC and PC+R lowered hepatic and plasma cholesterol and eliminated hepatosteatosis. Hepatic microarray analysis primarily revealed a complex downregulation of lipogenic and cholesterol biosynthesis pathways by PC. Lipidomic analysis identified arachidonic acid, DHA and EPA in hepatic phosphatidylcholine and phosphatidylethanolamine fractions as the most important variables. Importantly, down-regulation of genes within these pathways was enlarged by phospholipid versus triglyceride forms of EPA/DHA in an independent experiment. Conclusions: Obesity-associated hepatosteatosis and hypercholesterolemia were ameliorated by marine phospholipids in association with a complex inhibition of

Dietary flavonoids may protect against cardiovascular diseases (CVD). Increased circulating lipid levels and hepatic lipid accumulation are known risk factors for CVD. The aim of this study was to investigate the effects and underlying molecular mechanisms of the flavonoid quercetin on hepatic lipid metabolism in mice with high-fat diet induced body weight gain and hepatic lipid accumulation. Adult male mice received a 40 energy% high-fat diet without or with supplementation of 0.33 % (w/w) quercetin for 12 weeks. Body weight gain was 29 % lower in quercetin fed mice (p < 0.01), while the energy intake was not significantly different. Quercetin supplementation lowered hepatic lipid accumulation to 29 % of the amount present in the control mice (p < 0.01). 1H nuclear magnetic resonance serum lipid profiling revealed that the supplementation significantly lowered serum lipid levels. Global gene expression profiling of liver showed that cytochrome P450 2b (Cyp2b) genes, key target genes of the transcription factor constitutive androstane receptor (Car; official symbol Nr1i3), were downregulated. Quercetin decreased high-fat diet induced body weight gain, hepatic lipid accumulation and serum lipid levels. This was accompanied by regulation of cytochrome P450 2b genes in liver, which are possibly under transcriptional control of CAR. The quercetin effects are likely dependent on the fat content of the diet.

Elevated circulating lipid levels are known risk factors for cardiovascular diseases (CVD). In order to examine the effects of quercetin on lipid metabolism, mice received a mild-high-fat diet without (control) or with supplementation of 0.33% (w/w) quercetin for 12 weeks. Gas chromatography and 1H nuclear magnetic resonance were used to quantitatively measure serum lipid profiles. Whole genome microarray analysis of liver tissue was used to identify possible mechanisms underlying altered circulating lipid levels. Body weight, energy intake and hepatic lipid accumulation did not differ significantly between the quercetin and the control group. In serum of quercetin-fed mice, triglycerides (TG) were decreased with 14% (p

Using standardized, semipurified diets is a crucial factor for reproducibility of experimental nutritional studies. For the purpose of comparability and integration of research, two European consortia, Mitofood and BIOCLAIMS, proposed an AIN-93-based standard reference diet, the standardized BIOCLAIMS low-fat diet (LFD) as well as a high-fat diet (HFD). In order to evaluate the BIOCLAIMS LFD and HFD, we performed short-term (5 days) and long-term (12 weeks) feeding experiments using male C57BL/6 mice. The HFD has the same composition as the LFD except the fat content is increased to 40% energy in exchange for carbohydrates. Both diets were accepted by the animals and proof of principle was given that the BIOCLAIMS HFD increases body weight and body fat and affects glucose homeostasis. Short-term feeding trials (5 days) were performed in order to identify metabolic and molecular parameters which can serve as acute predictors for metabolic disorders due to high-fat diet-induced obesity. We analyzed gene expression in gonadal white adipose tissue of short- and long-term fed animals with whole genome microarrays. The BIOCLAIMS HFD strongly influenced gene expression in white adipose tissue after short- and long-term intervention. A total number of 973 and 4678 transcripts were significantly different between both diets after 5 days feeding and 12 weeks feeding, respectively. A total number of 764 transcripts encoding 549 genes were significantly differentially regulated between LF and HF animals after 12 weeks feeding as well as after 5 days feeding. Of these 549 overlapping genes, a substantial number (434 genes) were expressed at a lower level and 115 genes were expressed at a higher level in the HF mice compared to the LF mice. Without exception, all genes were regulated equally. Pathway analysis revealed a prominent role for genes involved in lipid metabolism, carbohydrate metabolism and oxidative phosphorylation. This was confirmed by quantitative real-time reverse

Elevated circulating lipid levels are known risk factors for cardiovascular diseases (CVD). In order to examine the effects of quercetin on hepatic lipid metabolism and detailed serum lipid profiles, mice received a mild-high-fat diet without (control) or with supplementation of 0.33% (w/w) quercetin for 12 weeks. Gas chromatography and 1H nuclear magnetic resonance were used to measure quantitatively serum lipid profiles and whole genome microarray analysis was used to identify the responsible mechanisms in liver. There were no significant differences found in mean body weight, energy intake and hepatic lipid accumulation between the quercetin and control group. In serum of quercetin-fed mice, TG levels were decreased with 15%, poly unsaturated fatty acids (PUFA) were increased with 14% and saturated fatty acids were decreased. Palmitic acid, oleic acid, and linoleic acid were all decreased in quercetin-fed mice by 9-15%. Both palmitic acid and oleic acid can be oxidized by omega-oxidation. Indeed, gene expression profiling showed that quercetin increased hepatic lipid metabolism, especially omega-oxidation. At the gene level, this was reflected by the up regulation of cytochrome P450 (Cyp) 4a10, Cyp4a14, Cyp4a31 and Acyl-CoA thioesterase 3 (Acot3). Two relevant regulators, Cytochrome P450 oxidoreductase (Por, rate limiting for cytochrome P450s) and the transcription factor Constitutive androstane receptor (Car; official symbol Nr1i3) were also up regulated in the quercetin-fed mice. We conclude that quercetin intake increased hepatic lipid omega-oxidation and lowered corresponding circulating lipid levels, a process that may involve Por and Car, and results in a potential beneficial CVD preventive effect.

Moderate selenium deficiency may lead to an impaired capacity to cope with health challenges. Functional effects of suboptimal selenium intake are not fully known, and biomarkers for an insufficient selenium supply are inadequate. We therefore fed mice diets of moderately deficient or adequate selenium intake for 6 weeks. Changes in global gene expression were monitored by microarray analysis in splenic leukocytes. Genes for four selenoproteins, Sepw1, Gpx1, Selh and Sep15, were the most significantly down-regulated in moderate selenium deficiency, and this was confirmed by quantitative polymerase chain reaction (qPCR). Classification of significantly affected genes revealed that processes related to inflammation, heme biosynthesis, DNA replication and transcription, cell cycle and transport were affected by selenium restriction. Down-regulation by moderate selenium deficiency of specific genes involved in inflammation and heme biosynthesis was confirmed by qPCR. Myeloperoxidase and lysozyme activities were decreased in selenium-restricted leukocytes, providing evidence for functional consequences. Genes for 31 nuclear factor (NF)-kappaB targets were down-regulated in moderate selenium deficiency, indicating an impaired NF-kappaB signaling. Together, the observed changes point to a disturbance in inflammatory response. The selenoproteins found here to be sensitive to selenium intake in murine leukocytes might also be useful as biomarkers for a moderate selenium deficiency in humans.

Flavonoids are bioactive food compounds with potential lipid-lowering effects. Commercially available enzymatic assays are widely used to determine free fatty acid (FFA) and triglyceride (TG) levels both in vivo in plasma or serum and in vitro in cell culture medium or cell lysate. However, we have observed that various flavonoids interfere with peroxidases used in these enzymatic assays, resulting in incorrect lower FFA and TG levels than actually present. Furthermore, addition of isorhamnetin or the major metabolite of the flavonoid quercetin in human and rat plasma, quercetin-3-O-glucuronide, to murine serum also resulted in a significant reduction of the detected TG levels, while a trend was seen for FFA levels. It is concluded that when applying these assays, vigilance is needed and alternative analytical methods, directly assessing FFA or TG levels, should be used for studying the biological effects of flavonoids on FFA and TG levels.

Insulin resistance, the key defect in type 2 diabetes (T2D), is associated with a low capacity to adapt fuel oxidation to fuel availability, i.e., metabolic inflexibility. This, in turn, contributes to a further damage of insulin signaling. Effectiveness of T2D treatment depends in large part on the improvement of insulin sensitivity and metabolic adaptability of the muscle, the main site of whole-body glucose utilization. We have shown previously in mice fed an obesogenic high-fat diet that a combined use of n-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA) and thiazolidinediones (TZDs), anti-diabetic drugs, preserved metabolic health and synergistically improved muscle insulin sensitivity. We investigated here whether n-3 LC-PUFA could elicit additive beneficial effects on metabolic flexibility when combined with a TZD drug rosiglitazone. Adult male C57BL/6N mice were fed an obesogenic corn oil-based high-fat diet (cHF) for 8 weeks, or randomly assigned to various interventions: cHF with n-3 LC-PUFA concentrate replacing 15% of dietary lipids (cHF+F), cHF with 10 mg rosiglitazone/kg diet (cHF+ROSI), cHF+F+ROSI, or chow-fed. Indirect calorimetry demonstrated superior preservation of metabolic flexibility to carbohydrates in response to the combined intervention. Metabolomic and gene expression analyses in the muscle suggested distinct and complementary effects of the interventions, with n-3 LC-PUFA supporting complete oxidation of fatty acids in mitochondria and the combination with n-3 LC-PUFA and rosiglitazone augmenting insulin sensitivity by the modulation of branched-chain amino acid metabolism. These beneficial metabolic effects were associated with the activation of the switch between glycolytic and oxidative muscle fibers, especially in the cHF+F+ROSI mice. Our results further support the idea that the combined use of n-3 LC-PUFA and TZDs could improve the efficacy of the therapy of obese and diabetic patients.

Experimental replication is fundamental for practicing science. To reduce variability, it is essential to control sources of variation as much as possible. Diet is an important factor that can influence many processes and functional outcomes in studies performed with rodent models. This is especially true for, but not limited to, nutritional studies. To compare functional effects of different nutrients, it is important to use standardized, semi-purified diets. Here, we propose and describe a standard reference diet, the BIOCLAIMS standard diet. The diet is AIN-93 based, but further defined with dietary and experimental requirements taken into account that allow for experiments with bioactive food components and natural (non-expensive) labeling. This diet will be implemented by two European research consortia, Mitofood and BIOCLAIMS, to ensure inter-laboratory comparability.

This SuperSeries is composed of the SubSeries listed below.

Impaired resistance to insulin, the key defect in type 2 diabetes (T2D), is associated with a low capacity to adapt fuel oxidation to fuel availability, i.e., metabolic inflexibility. The hampered metabolic adaptability triggers a further damage of insulin signaling. Since skeletal muscle is the main site of glucose uptake, effectiveness of T2D treatment depends in large on the improvement of insulin sensitivity and metabolic adaptability of the muscle. We have shown previously in mice fed an obesogenic high-fat diet that a combination treatment using n-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA) and thiazolidinedione (TZD) anti-diabetic drugs preserved metabolic health and synergistically improved muscle insulin sensitivity. We investigated here whether TZD rosiglitazone could elicit the additive beneficial effects on metabolic flexibility when combined with n-3 LC-PUFA. Adult male C57BL/6N mice were fed an obesogenic corn oil-based high-fat diet (cHF) for 8 weeks, or randomly assigned to various dietary treatments: (i) cHF+F, cHF with n-3 LC-PUFA concentrate replacing 15% of dietary lipids; (ii) cHF+ROSI, cHF with 10 mg rosiglitazone/kg diet; and (iii) cHF+F+ROSI, or chow-fed. Indirect calorimetry demonstrated superior preservation of metabolic flexibility to carbohydrates in response to the combination treatment. Metabolomic and gene expression analyses in the muscle suggested distinct and complementary effects of the single treatments, with rosiglitazone augmenting insulin sensitivity by the modulation of branched-chain amino acid metabolism, and n-3 LC PUFA supporting complete oxidation of fatty acids in mitochondria. These beneficial metabolic effects were associated with the activation of the switch between glycolytic and oxidative muscle fibers, especially in the cHF+F+ROSI mice. Our results further support the idea that the combination treatment using n-3 LC-PUFA and TZDs could improve the efficacy of the treatment of obese and diabetic patients.