WDTC1, the ortholog of Drosophila adipose gene, associates with human obesity, modulated by MUFA intake

A high-sugar diet, but not obesity, reduces female fertility in Drosophila melanogaster

Obesity is linked to reduced fertility in various species, from Drosophila to humans. Considering that obesity is often induced by changes in diet or eating behavior, it remains unclear whether obesity, diet, or both reduce fertility. Here, we show that Drosophila females on a high-sugar diet become rapidly obese and less fertile as a result of increased death of early germline cysts and vitellogenic egg chambers (or follicles). They also have high glycogen, glucose and trehalose levels and develop insulin resistance in their fat bodies (but not ovaries). By contrast, females with adipocyte-specific knockdown of the anti-obesity genes brummer or adipose are obese but have normal fertility. Remarkably, females on a high-sugar diet supplemented with a separate source of water have mostly normal fertility and glucose levels, despite persistent obesity, high glycogen and trehalose levels, and fat body insulin resistance. These findings demonstrate that a high-sugar diet affects specific processes in oogenesis independently of insulin resistance, that high glucose levels correlate with reduced fertility on a high-sugar diet, and that obesity alone does not impair fertility.

TRiC/CCT chaperonin is required for the folding and inhibitory effect of WDTC1 on adipogenesis

Obesity has become a global pandemic. WDTC1 is a WD40-containing protein that functions as an anti-obesity factor. WDTC1 inhibits adipogenesis by working as an adaptor of the CUL4-DDB1 E3 ligase complex. It remains unclear about how WDTC1 is regulated. Here, we show that the TRiC/CCT functions as a chaperone to facilitate the protein folding of WDTC1 and proper function in adipogenesis. Through tandem purification, we identified the molecular chaperone TRiC/CCT as WDTC1-interacting proteins. WDTC1 bound the TRiC/CCT through its ADP domain, and the TRiC/CCT recognized WDTC1 through the CCT5 subunit. Disruption of the TRiC/CCT by knocking down CCT1 or CCT5 led to misfolding and lysosomal degradation of WDTC1. Furthermore, the knockdown of CCT1 or CCT5 eliminated the inhibitory effect of WDTC1 on adipogenesis. Our studies uncovered a critical role of the TRiC/CCT in the folding of WDTC1 and expanded our knowledge on the regulation of adipogenesis.

LncRNA HCP5 acts as a miR-128-3p sponge to promote the progression of multiple myeloma through activating Wnt/β-catenin/cyclin D1 signaling via PLAGL2

BACKGROUND

Although long non-coding RNA (lncRNA) HCP plays essential roles in human cancers, its function and mechanism in multiple myeloma (MM) have not crystallized.

METHODS

HCP5 level in MM was assessed through qRT-PCR. A series of functional investigations were conducted to evaluate the influences of HCP5 on proliferation and apoptosis. Bioinformatics analysis and RIP/RNA pull-down assays were carried out to determine the relationships among HCP5, miR-128-3p, and PLAGL2. Relative protein level was determined through Western blot. A xenograft tumor model was applied for validating the roles of HCP5/miR-128-3p/PLAGL2 axis in vivo.

RESULTS

HCP5 was significantly increased in MM. HCP5 knockdown effectively thwarted the proliferative rate and cell cycle of MM cell lines and suppressed tumor growth. HCP5 regulated PLAGL2 expression by sponging miR-128-3p. PLAGL2 overexpression effectively rescued cells from influences by sh-HCP5 on cell proliferative and apoptotic rates. Additionally, HCP5 knockdown significantly inhibited Wnt/β-catenin/cyclin D1 signaling, and these effects were eliminated by PLAGL2 overexpression.

CONCLUSION

Our study revealed that HCP5/miR-128-3p/PLAGL2 is closely correlated to MM development by modulating Wnt/β-catenin/cyclin D1 signaling. HCP5 promoted cell proliferation and tumor formation of MM cells by activating the Wnt/β-catenin/CCND1 signaling pathway by sponging miR-128-3p to increase PLAGL2 expression.

Insect Models in Nutrition Research

Insects are the most diverse organisms on earth, accounting for ~80% of all animals. They are valuable as model organisms, particularly in the context of genetics, development, behavior, neurobiology and evolutionary biology. Compared to other laboratory animals, insects are advantageous because they are inexpensive to house and breed in large numbers, making them suitable for high-throughput testing. They also have a short life cycle, facilitating the analysis of generational effects, and they fulfil the 3R principle (replacement, reduction and refinement). Many insect genomes have now been sequenced, highlighting their genetic and physiological similarities with humans. These factors also make insects favorable as whole-animal high-throughput models in nutritional research. In this review, we discuss the impact of insect models in nutritional science, focusing on studies investigating the role of nutrition in metabolic diseases and aging/longevity. We also consider food toxicology and the use of insects to study the gut microbiome. The benefits of insects as models to study the relationship between nutrition and biological markers of fitness and longevity can be exploited to improve human health.

The putative oncogenic role of WDTC1 in colorectal cancer

Microsatellite instability (MSI) is detected in approximately 15% of colorectal cancers (CRCs). WD40 and tetratricopeptide repeats 1 (WDTC1) is frequently mutated in MSI CRC, indicating that it may contribute to CRC development. However, the functional evidence of the role of WDTC1 in CRC development remains unknown. Herein, we conducted in vitro assays to examine the function of WDTC1 using knockdown experiments in three CRC cell lines, SW480, CACO2, and LoVo. We provided strong evidence that silencing WDTC1 significantly suppressed cell proliferation, migration, and invasion consistently in all three CRC cell lines. To evaluate the potential role of WDTC1 in regulating CRC-related genes, we conducted RNA sequencing after 24 and 48 h in SW480 cells after treating WDTC1-siRNA and its vehicle control cells. Differential gene expression analysis identified 44 (42 downregulated and 2 upregulated) and 16 (all downregulated) genes, at time points of 24 and 48 h, respectively, whereas 15 downregulated genes were commonly detected at both time points. The ingenuity pathways analysis suggested that the most significant enrichments associated with cancer function and upstream regulator ATM/ATR were observed for these commonly observed genes. We further verified differential gene expression of eight cancer-related genes, ARHGEF12, GSTP1, FNDC3A, TMTC3, RTN4, RRM2, UHMK1, and PTPRF, using RT-PCR in all three cell lines. Our findings provided additional insight into the oncogenic role of WDTC1 in CRC development.

Identification of candidate biomarkers and pathways associated with type 1 diabetes mellitus using bioinformatics analysis

Type 1 diabetes mellitus (T1DM) is a metabolic disorder for which the underlying molecular mechanisms remain largely unclear. This investigation aimed to elucidate essential candidate genes and pathways in T1DM by integrated bioinformatics analysis. In this study, differentially expressed genes (DEGs) were analyzed using DESeq2 of R package from GSE162689 of the Gene Expression Omnibus (GEO). Gene ontology (GO) enrichment analysis, REACTOME pathway enrichment analysis, and construction and analysis of protein–protein interaction (PPI) network, modules, miRNA-hub gene regulatory network and TF-hub gene regulatory network, and validation of hub genes were performed. A total of 952 DEGs (477 up regulated and 475 down regulated genes) were identified in T1DM. GO and REACTOME enrichment result results showed that DEGs mainly enriched in multicellular organism development, detection of stimulus, diseases of signal transduction by growth factor receptors and second messengers, and olfactory signaling pathway. The top hub genes such as MYC, EGFR, LNX1, YBX1, HSP90AA1, ESR1, FN1, TK1, ANLN and SMAD9 were screened out as the critical genes among the DEGs from the PPI network, modules, miRNA-hub gene regulatory network and TF-hub gene regulatory network. Receiver operating characteristic curve (ROC) analysis confirmed that these genes were significantly associated with T1DM. In conclusion, the identified DEGs, particularly the hub genes, strengthen the understanding of the advancement and progression of T1DM, and certain genes might be used as candidate target molecules to diagnose, monitor and treat T1DM.

Phenotyping of Drosophila melanogaster—A Nutritional Perspective

The model organism Drosophila melanogaster was increasingly applied in nutrition research in recent years. A range of methods are available for the phenotyping of D. melanogaster, which are outlined in the first part of this review. The methods include determinations of body weight, body composition, food intake, lifespan, locomotor activity, reproductive capacity and stress tolerance. In the second part, the practical application of the phenotyping of flies is demonstrated via a discussion of obese phenotypes in response to high-sugar diet (HSD) and high-fat diet (HFD) feeding. HSD feeding and HFD feeding are dietary interventions that lead to an increase in fat storage and affect carbohydrate-insulin homeostasis, lifespan, locomotor activity, reproductive capacity and stress tolerance. Furthermore, studies regarding the impacts of HSD and HFD on the transcriptome and metabolome of D. melanogaster are important for relating phenotypic changes to underlying molecular mechanisms. Overall, D. melanogaster was demonstrated to be a valuable model organism with which to examine the pathogeneses and underlying molecular mechanisms of common chronic metabolic diseases in a nutritional context.

Construction of the gene expression subgroups of patients with coronary artery disease through bioinformatics approach

Coronary artery disease (CAD) is a heterogeneous disease that has placed a heavy burden on public health due to its considerable morbidity, mortality and high costs. Better understanding of the genetic drivers and gene expression clustering behind CAD will be helpful for the development of genetic diagnosis of CAD patients. The transcriptome of 352 CAD patients and 263 normal controls were obtained from the Gene Expression Omnibus (GEO) database. We performed a modified unsupervised machine learning algorithm to group CAD patients. The relationship between gene modules obtained through weighted gene co-expression network analysis (WGCNA) and clinical features was identified by the Pearson correlation analysis. The annotation of gene modules and subgroups was done by the gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis. Three gene expression subgroups with the clustering score of greater than 0.75 were constructed. Subgroup I may experience coronary artery disease of an in-creased severity, while subgroup III is milder. Subgroup I was found to be closely related to the upregulation of the mitochondrial autophagy pathway, whereas the genes of subgroup II were shown to be related to the upregulation of the ribosome pathway. The high expression of APOE, NOS1 and NOS3 in the subgroup I suggested that the patients had more severe coronary artery disease. The construction of genetic subgroups of CAD patients has enabled clinicians to improve their understanding of CAD pathogenesis and provides potential tools for disease diagnosis, classification and assessment of prognosis.

The Mediator subunit MED20 organizes the early adipogenic complex to promote development of adipose tissues and diet-induced obesity

MED20 is a non-essential subunit of the transcriptional coactivator Mediator complex, but its physiological function remains largely unknown. Here, we identify MED20 as a substrate of the anti-obesity CRL4-WDTC1 E3 ubiquitin ligase complex through affinity purification and candidate screening. Overexpression of WDTC1 leads to degradation of MED20, whereas depletion of WDTC1 or CUL4A/B causes accumulation of MED20. Depleting MED20 inhibits adipogenesis, and a non-degradable MED20 mutant restores adipogenesis in WDTC1-overexpressing cells. Furthermore, knockout of Med20 in preadipocytes abolishes development of brown adipose tissues. Removing one allele of Med20 in preadipocytes protects mice from diet-induced obesity and reverses weight gain in Cul4a- or Cul4b-depleted mice. Chromatin immunoprecipitation sequencing (ChIP-seq) analysis reveals that MED20 organizes the early adipogenic complex by bridging C/EBPβ and RNA polymerase II to promote transcription of the central adipogenic factor, PPARγ. Our findings have thus uncovered a critical role of MED20 in promoting adipogenesis, development of adipose tissue and diet-induced obesity.

Lipidome remodeling in aging normal and genetically obese Drosophila males

Lipid homeostasis is essential for insects to maintain phospholipid (PL)-based membrane integrity and to provide on-demand energy supply throughout life. Triacylglycerol (TAG) is the major lipid class used for energy production and is stored in lipid droplets, the universal cellular fat storage organelles. Accumulation and mobilization of TAG are strictly regulated since excessive accumulation of TAG leads to obesity and has been correlated with adverse effects on health- and lifespan across phyla. Little is known, however, about when during adult life and why excessive storage lipid accumulation restricts lifespan. We here used genetically obese Drosophila mutant males, which were all shown to be short-lived compared to control males and applied single fly mass spectrometry-based lipidomics to profile TAG, diacylglycerol and major membrane lipid signatures throughout adult fly life from eclosion to death. Our comparative approach revealed distinct phases of lipidome remodeling throughout aging. Quantitative and qualitative compositional changes of TAG and PL species, which are characterized by the length and saturation of their constituent fatty acids, were pronounced during young adult life. In contrast, lipid signatures of adult and senescent flies were remarkably stable. Genetically obese flies displayed both quantitative and qualitative changes in TAG species composition, while PL signatures were almost unaltered compared to normal flies at all ages. Collectively, this suggests a tight control of membrane composition throughout lifetime largely uncoupled from storage lipid metabolism. Finally, we present first evidence for a characteristic lipid signature of moribund flies, likely generated by a rapid and selective storage lipid depletion close to death. Of note, the analytical power to monitor lipid species profiles combined with high sensitivity of this single fly lipidomics approach is universally applicable to address developmental or behavioral lipid signature modulations of importance for insect life.

A DNA repair disorder caused by de novo monoallelic DDB1 variants is associated with a neurodevelopmental syndrome

The DNA damage-binding protein 1 (DDB1) is part of the CUL4-DDB1 ubiquitin E3 ligase complex (CRL4), which is essential for DNA repair, chromatin remodeling, DNA replication, and signal transduction. Loss-of-function variants in genes encoding the complex components CUL4 and PHIP have been reported to cause syndromic intellectual disability with hypotonia and obesity, but no phenotype has been reported in association with DDB1 variants. Here, we report eight unrelated individuals, identified through Matchmaker Exchange, with de novo monoallelic variants in DDB1, including one recurrent variant in four individuals. The affected individuals have a consistent phenotype of hypotonia, mild to moderate intellectual disability, and similar facies, including horizontal or slightly bowed eyebrows, deep-set eyes, full cheeks, a short nose, and large, fleshy and forward-facing earlobes, demonstrated in the composite face generated from the cohort. Digital anomalies, including brachydactyly and syndactyly, were common. Three older individuals have obesity. We show that cells derived from affected individuals have altered DDB1 function resulting in abnormal DNA damage signatures and histone methylation following UV-induced DNA damage. Overall, our study adds to the growing family of neurodevelopmental phenotypes mediated by disruption of the CRL4 ubiquitin ligase pathway and begins to delineate the phenotypic and molecular effects of DDB1 misregulation.

In silico Analysis Excavates A Novel Competing Endogenous RNA Subnetwork in Adolescent Idiopathic Scoliosis

Background and Objective: Adolescent idiopathic scoliosis (AIS) is a complex three-dimensional deformity of the spine. Mesenchymal stem cells (MSCs) regulate bone mass homeostasis in AIS, which might be related to the pathogenesis of AIS. However, the mRNA–miRNA–lncRNA network linked to the regulation of the genetic pathogenesis of MSCs remains unknown.

Methods: We conducted an exhaustive literature search of PubMed, EMBASE, and the Gene Expression Omnibus database to find differentially expressed genes (DEGs), differentially expressed miRNAs (DE miRNAs), and differentially expressed lncRNAs (DE lncRNAs). Functional enrichment analysis was performed through Enrichr database. Protein–protein interaction (PPI) network was constructed using STRING database, and hub genes were identified by CytoHubba. Potential regulatory miRNAs and lncRNAs of mRNAs were predicted by miRTarBase and RNA22, respectively.

Results: We identified 551 upregulated and 476 downregulated genes, 42 upregulated and 12 downregulated miRNAs, and 345 upregulated and 313 downregulated lncRNAs as DEGs, DE miRNAs, and DE lncRNAs, respectively. Functional enrichment analysis revealed that they were significantly enriched in protein deglutamylation and regulation of endoplasmic reticulum unfolded protein response. According to node degree, one upregulated hub gene and eight downregulated hub genes were identified. After drawing the Venn diagrams and matching to Cytoscape, an mRNA–miRNA–lncRNA network linked to the pathogenesis of MSCs in AIS was constructed.

Conclusion: We established a novel triple regulatory network of mRNA–miRNA–lncRNA ceRNA, among which all RNAs may be utilized as the pathogenesis biomarker of MSCs in AIS.

Drosophila as a model to study obesity and metabolic disease

Excess adipose fat accumulation, or obesity, is a growing problem worldwide in terms of both the rate of incidence and the severity of obesity-associated metabolic disease. Adipose tissue evolved in animals as a specialized dynamic lipid storage depot: adipose cells synthesize fat (a process called lipogenesis) when energy is plentiful and mobilize stored fat (a process called lipolysis) when energy is needed. When a disruption of lipid homeostasis favors increased fat synthesis and storage with little turnover owing to genetic predisposition, overnutrition or sedentary living, complications such as diabetes and cardiovascular disease are more likely to arise. The vinegar fly Drosophila melanogaster (Diptera: Drosophilidae) is used as a model to better understand the mechanisms governing fat metabolism and distribution. Flies offer a wealth of paradigms with which to study the regulation and physiological effects of fat accumulation. Obese flies accumulate triacylglycerols in the fat body, an organ similar to mammalian adipose tissue, which specializes in lipid storage and catabolism. Discoveries in Drosophila have ranged from endocrine hormones that control obesity to subcellular mechanisms that regulate lipogenesis and lipolysis, many of which are evolutionarily conserved. Furthermore, obese flies exhibit pathophysiological complications, including hyperglycemia, reduced longevity and cardiovascular function - similar to those observed in obese humans. Here, we review some of the salient features of the fly that enable researchers to study the contributions of feeding, absorption, distribution and the metabolism of lipids to systemic physiology.

Remarkable Evolutionary Conservation of Antiobesity ADIPOSE/WDTC1 Homologs in Animals and Plants

ASG2 (Altered Seed Germination 2) is a prenylated protein in Arabidopsis thaliana that participates to abscisic acid signaling and is proposed to act as a substrate adaptor for the DDB1 (DNA damage-binding protein 1)-CUL4 (Cullin 4) E3 ubiquitin ligase complex. ASG2 harbors WD40 and TetratricoPeptide Repeat (TPR) domains, and resembles the well-conserved animal gene called ADP (antiobesity factor ADIPOSE) in fly and WDTC1 (WD40 and TPR 1) in humans. Loss of function of WDTC1 results in an increase in adipocytes, fat accumulation, and obesity. Antiadipogenic functions of WDTC1 involve regulation of fat-related gene transcription, notably through its binding to histone deacetylases (HDACs). Our sequence and phylogenetic analysis reveals that ASG2 belongs to the ADP/WDTC1 cluster. ASG2 and WDTC1 share a highly conserved organization that encompasses structural and functional motifs: seven WD40 domains and WD40 hotspot-related residues, three TPR protein-protein interaction domains, DDB1-binding elements [H-box and DWD (DDB1-binding WD40 protein)-box], and a prenylatable C-terminus. Furthermore, ASG2 involvement in fat metabolism was confirmed by reverse genetic approaches using asg2 knockout Arabidopsis plants. Under limited irradiance, asg2 mutants produce "obese" seeds characterized by increased weight, oil body density, and higher fatty acid contents. In addition, considering some ASG2- and WDTC1-peculiar properties, we show that the WDTC1 C-terminus is prenylated in vitro and HDAC-binding capability is conserved in ASG2, suggesting that the regulation mechanism and targets of ADP/WDTC1-like proteins may be conserved features. Our findings reveal the remarkable evolutionary conservation of the structure and the physiological role of ADIPOSE homologs in animals and plants.

Discovering New Genes in the Pathways of Common Sporadic Neurodegenerative Diseases: A Bioinformatics Approach

Late onset Alzheimer's disease (AD) and Parkinson's disease (PD) are mostly "sporadic" age-related neurodegenerative disorders, but with a clear genetic component. However, their genetic architecture is complex and heterogeneous, largely remaining a conundrum, with only a handful of well-established genetic risk factors consistently associated with these diseases. It is possible that numerous, yet undiscovered, AD and PD related genes might exist. We focused on the 'gene' as a mediator to find new potential genes that might have a relationship with both disorders using bio-literature mining techniques. Based on Entrez Gene, we extracted the genes and directional gene-gene relation in the entire MEDLINE records and then constructed a directional gene-gene network. We identified common genes associated with two different but related diseases by performing shortest path analysis on the network. With our approach, we were able to identify and map already known genes that have a direct relationship with PD and AD. In addition, we identified 7 genes previously unknown to be a bridge between these two disorders. We confirmed 4 genes, ROS1, FMN1, ATP8A2, and SNORD12C, by biomedical literature and further checked 3 genes, ERVK-10, PRS, and C7orf49, that might have a high possibility to be related with both diseases. Additional experiments were performed to demonstrate the effectiveness of our proposed method. Comparing to the co-occurrence approach, our approach detected 25% more candidate genes and verified 10% more genes that have the relationship between both diseases than the co-occurrence approach did.

The antiobesity factor WDTC1 suppresses adipogenesis via the CRL4WDTC1 E3 ligase

WDTC1/Adp encodes an evolutionarily conserved suppressor of lipid accumulation. While reduced WDTC1 expression is associated with obesity in mice and humans, its cellular function is unknown. Here, we demonstrate that WDTC1 is a component of a DDB1-CUL4-ROC1 (CRL4) E3 ligase. Using 3T3-L1 cell culture model of adipogenesis, we show that disrupting the interaction between WDTC1 and DDB1 leads to a loss of adipogenic suppression by WDTC1, increased triglyceride accumulation and adipogenic gene expression. We show that the CRL4(WDTC) (1) complex promotes histone H2AK119 monoubiquitylation, thus suggesting a role for this complex in transcriptional repression during adipogenesis. Our results identify a biochemical role for WDTC1 and extend the functional range of the CRL4 complex to the suppression of fat accumulation.

Quantitative Genetics of Food Intake in Drosophila melanogaster

Food intake is an essential animal activity, regulated by neural circuits that motivate food localization, evaluate nutritional content and acceptance or rejection responses through the gustatory system, and regulate neuroendocrine feedback loops that maintain energy homeostasis. Excess food consumption in people is associated with obesity and metabolic and cardiovascular disorders. However, little is known about the genetic basis of natural variation in food consumption. To gain insights in evolutionarily conserved genetic principles that regulate food intake, we took advantage of a model system, Drosophila melanogaster, in which food intake, environmental conditions and genetic background can be controlled precisely. We quantified variation in food intake among 182 inbred, sequenced lines of the Drosophila melanogaster Genetic Reference Panel (DGRP). We found significant genetic variation in the mean and within-line environmental variance of food consumption and observed sexual dimorphism and genetic variation in sexual dimorphism for both food intake traits (mean and variance). We performed genome wide association (GWA) analyses for mean food intake and environmental variance of food intake (using the coefficient of environmental variation, CV_E, as the metric for environmental variance) and identified molecular polymorphisms associated with both traits. Validation experiments using RNAi-knockdown confirmed 24 of 31 (77%) candidate genes affecting food intake and/or variance of food intake, and a test cross between selected DGRP lines confirmed a SNP affecting mean food intake identified in the GWA analysis. The majority of the validated candidate genes were novel with respect to feeding behavior, and many had mammalian orthologs implicated in metabolic diseases.

Adipose tissue expression of adipose (WDTC1) gene is associated with lower fat mass and enhanced insulin sensitivity in humans

OBJECTIVE

The overexpression of the adipose gene (adp/WDTC1) in mice inhibits lipid accumulation and improves the metabolic profile. Subcutaneous fat adp expression in humans and its relation to metabolic parameters was evaluated.

DESIGN AND METHODS

Abdominal subcutaneous fat adp expression, insulin sensitivity (clamp), and respiratory quotient (RQ; indirect calorimetry) were assessed in: 36 obese and 56 BMI-, race-, and sex-matched type 2 diabetic volunteers (Look AHEAD Adipose Ancillary Study); 37 nondiabetic Pima Indians including obese (n = 18) and nonobese (n = 19) subjects and; 62 nonobese nondiabetic subjects at the Pennington Center in the ADAPT study.

RESULTS

In the Look AHEAD Study, adp expression normalized for cyclophilin B was higher in males versus females (1.27 ± 0.06 vs. 1.11 ± 0.04; P < 0.01) but not after controlling for body fat. Adp expression was not influenced by the presence of diabetes but was related to body fat (r = -0.23; P = 0.03), insulin sensitivity (r = 0.23; P = 0.03) and fasting/insulin-stimulated RQ (r = 0.31 and 0.33; P < 0.01). In Pima Indians, adp expression was also higher in males versus females (1.00 ± 0.05 vs. 0.77 ± 0.05; P = 0.02) and higher in nonobese versus obese (1.02 ± 0.05 vs. 0.80 ± 0.06; P = 0.03). In the ADAPT study, there was no difference in adp expression between males and females.

CONCLUSION

Consistent with animal studies, our results suggest that high adp expression in human adipose tissue is associated with lower adiposity and enhanced glucose utilization.

Molecular cloning and characterization of the anti-obesity gene adipose in pig

Obesity has become an epidemic health problem characterized by aberrant energy metabolism. As the major player in energy homeostasis, adipose tissue has a decisive role in the development of obesity. Many genes involved in adipogenesis are also correlated with obesity. Adipose (Adp) has been established as an anti-obesity gene to repress adipogenesis and fat accumulation in mice, which inhibits the transcriptional activity of PPARγ by forming a chromatin remodeling complex with histones and HDAC3. Here, we reported the cloning and characterization of the pig Adp gene. Pig Adp cDNA had an ORF of 2034 nucleotides and was highly conserved among various species. Genomic sequence analysis indicated that pig Adp gene contains 16 exons and 15 introns, spanning more than 60kb on chromosome 6q21-24. The expression of pig Adp was high in testis, lung, kidney and adipose tissues, and relatively low in skeletal muscle. Bioinformatic analysis of 5'-flanking region of Adp has identified several potential binding sites for pivotal transcriptional factors related to both adipocyte differentiation and inflammation, highlighting the significance of Adp in energy metabolism. We have confirmed that KLF6, a positive regulator of adipogenesis, can enhance the promoter activity of Adp and up-regulate its mRNA expression. Taken together, our results would be helpful for further study of Adp regulation in the process of fat accumulation.

Adaptive genetic variation and population differences

Since the expansion of modern humans (Homo sapiens) from Africa to the rest of the world between 50,000 and 100,000 years ago, the human genome has been shaped not only by demographic history but also by adaptation to local environments, including regional climate, landscape, food sources, culture, and pathogens. Genetic differences among populations interact with environmental factors, such as diet and lifestyle, leading to differences in nutrient metabolism, which translate into differences in susceptibility to a variety of diseases. Individuals from different populations sharing the same environments can exhibit differences in disease risk, as do individuals from the same population living in various regions of the globe. Therefore, it is important to understand how adaptive genetic variations interact with environments to influence health. This knowledge will provide a broad foundation for designing experiments and approaches in nutrigenomics research and strengthening the knowledge base for dietary recommendations for disease prevention. The objectives of this chapter are to (1) understand the methodology employed in examining adaptive genetic variation across populations, (2) establish the importance of adaptive genetic variation to human health, and (3) discuss the implications for nutrigenomics research and disease prevention.

Candidate driver genes in microsatellite-unstable colorectal cancer

Defects in the mismatch repair system lead to microsatellite instability (MSI), a feature observed in ∼ 15% of all colorectal cancers (CRCs). Microsatellite mutations that drive tumourigenesis, typically inactivation of tumour suppressors, are selected for and are frequently detected in MSI cancers. Here, we evaluated somatic mutations in microsatellite repeats of 790 genes chosen based on reduced expression in MSI CRC and existence of a coding mononucleotide repeat of 6-10 bp in length. All the repeats were initially sequenced in 30 primary MSI CRC samples and whenever frameshift mutations were identified in >20%, additional 70 samples were sequenced. To distinguish driver mutations from passengers, we similarly analyzed the occurrence of frameshift mutations in 121 intronic control repeats and utilized a statistical regression model to determine cut-off mutation frequencies for repeats of all types (A/T and C/G, 6-10 bp). Along with several know target genes, including TGFBR2, ACVR2, and MSH3, six novel candidate driver genes emerged that harbored significantly more mutations than identical control repeats. The mutation frequencies in 100 MSI CRC samples were 51% in G8 of GLYR1, 47% in T9 of ABCC5, 43% in G8 of WDTC1, 33% in A8 of ROCK1, 30% in T8 of OR51E2, and 28% in A8 of TCEB3. Immunohistochemical staining of GLYR1 revealed defective protein expression in tumors carrying biallelic mutations, supporting a loss of function hypothesis. This is a large scale, unbiased effort to identify genes that when mutated are likely to contribute to MSI CRC development.

Effects of Panicum miliaceum L. extract on adipogenic transcription factors and fatty acid accumulation in 3T3-L1 adipocytes

The dietary intake of whole grains is known to reduce the incidence of chronic diseases such as obesity, diabetes, cardiovascular disease, and cancer. To investigate whether there are anti-adipogenic activities in various Korean cereals, we assessed water extracts of nine cereals. The results showed that treatment of 3T3-L1 adipocytes with Sorghum bicolor L. Moench, Setaria italica Beauvois, or Panicum miliaceum L. extract significantly inhibited adipocyte differentiation, as determined by measuring oil red-O staining, triglyceride accumulation, and glycerol 3-phosphate dehydrogenase activity. Among the nine cereals, P. miliaceum L. showed the highest anti-adipogenic activity. The effects of P. miliaceum L. on mRNA expression of peroxisome proliferator-activated receptor-γ, sterol regulatory element-binding protein 1, and the CCAAT/enhancer binding protein-α were evaluated, revealing that the extract significantly decreased the expression of these genes in a dose-dependent manner. Moreover, P. miliaceum L. extract changed the ratio of monounsaturated fatty acids to saturated fatty acids in adipocytes, which is related to biological activity and cell characteristics. These results suggest that some cereals efficiently suppress adipogenesis in 3T3-L1 adipocytes. In particular, the effect of P. miliaceum L. on adipocyte differentiation is associated with the downregulation of adipogenic genes and fatty acid accumulation in adipocytes.

Adaptive genetic variation and heart disease risk

PURPOSE OF REVIEW

Obesity, dyslipidemia and cardiovascular disease are complex and determined by both genetic and environmental factors and their inter-relationships. Many associations from genome-wide association studies and candidate gene approaches have described a multitude of polymorphisms associating with lipid and obesity phenotypes but identified genetic variants account for only a small fraction of phenotypic variation.

RECENT FINDINGS

That many genotype-phenotype associations involve variants under positive selection and that those variants respond to environmental cues together suggest prominent roles for both genetic adaptation and their interactions with the environment. Adaptive genetic variations interacting with environment modulate disease susceptibility but the level to which those variants contribute to dyslipidemia and obesity and how environmental factors, especially diet, alter the genetic association is not yet completely known.

SUMMARY

It is evident that genetic variants under positive selection make important contributions to obesity and heart disease risk. Advances in resequencing the entire human genome will enable accurate identification of adaptive variants. Considering interactions between environmental factors and genotypes will empower both genome-wide association studies and characterization of the relationship between positive selection and the obese and dyslipidemic conditions.

Fatty acid interactions with genetic polymorphisms for cardiovascular disease

PURPOSE OF REVIEW

The number of studies investigating interactions between genes and nutrients for cardiovascular disease continues to grow, and holds tremendous potential for reducing disease risk at the level of the individual genotype. However, understanding the limitations and challenges of interaction studies, whether of observational or interventional design, is essential for critical evaluation of these studies.

RECENT FINDINGS

Nutrient-gene interactions for cardiovascular disease both parallel and extend nutrition studies, encompassing both traditional and novel cardiovascular risk factors. Fatty acid quality, lipid metabolism, inflammation, postprandial metabolism, fatty liver and macronutrient-gene interactions for obesity and metabolic syndrome represent a subset of the major areas of recent focus. With few exceptions, however, studies of gene-nutrient interactions are limited to a single population.

SUMMARY

Gene-nutrient research will continue to expand as genome-wide association studies uncover new sources of genetic variability associated with cardiovascular risk. However, in addition to investigation of newly discovered variants, continuing efforts must focus on the confirmation of previously reported genetic associations and interactions in additional populations.

Energy homeostasis regulation in Drosophila: a lipocentric perspective

The fruit fly Drosophila is a centenarian in research service, but a novice as an invertebrate model system for energy homeostasis research. The last couple of years, however, witnessed numerous technical advances driving the rise of this model organism in central areas of energy balance research such as food perception, feeding control, energy flux and lipometabolism. These studies demonstrate an unanticipated evolutionary conservation of genes and mechanisms governing central aspects of energy homeostasis. Accordingly, research on Drosophila promises both, a systems biology view on the regulatory network, which governs lifelong energy control in a complex eukaryotic organism as well as, important insights into the mammalian energy balance control with a potential impact on the diagnostic and therapeutic strategies in the treatment of human lipopathologies such as obesity.