Enhanced triacylglycerol catabolism by carboxylesterase 1 promotes aggressive colorectal carcinoma.

The ability to adapt to low-nutrient microenvironments is essential for tumor cell survival and progression in solid cancers, such as colorectal carcinoma (CRC). Signaling by the NF-κB transcription factor pathway associates with advanced disease stages and shorter survival in patients with CRC. NF-κB has been shown to drive tumor-promoting inflammation, cancer cell survival, and intestinal epithelial cell (IEC) dedifferentiation in mouse models of CRC. However, whether NF-κB affects the metabolic adaptations that fuel aggressive disease in patients with CRC is unknown. Here, we identified carboxylesterase 1 (CES1) as an essential NF-κB-regulated lipase linking obesity-associated inflammation with fat metabolism and adaptation to energy stress in aggressive CRC. CES1 promoted CRC cell survival via cell-autonomous mechanisms that fuel fatty acid oxidation (FAO) and prevent the toxic build-up of triacylglycerols. We found that elevated CES1 expression correlated with worse outcomes in overweight patients with CRC. Accordingly, NF-κB drove CES1 expression in CRC consensus molecular subtype 4 (CMS4), which is associated with obesity, stemness, and inflammation. CES1 was also upregulated by gene amplifications of its transcriptional regulator HNF4A in CMS2 tumors, reinforcing its clinical relevance as a driver of CRC. This subtype-based distribution and unfavorable prognostic correlation distinguished CES1 from other intracellular triacylglycerol lipases and suggest CES1 could provide a route to treat aggressive CRC.

High glucose alters the DNA methylation pattern of neurodevelopment associated genes in human neural progenitor cells in vitro.

Maternal diabetes alters the global epigenetic mechanisms and expression of genes involved in neural tube development in mouse embryos. Since DNA methylation is a critical epigenetic mechanism that regulates gene functions, gene-specific DNA methylation alterations were estimated in human neural progenitor cells (hNPCs) exposed to high glucose (HG) in the present study. The DNA methylation pattern of genes involved in several signalling pathways including axon guidance (SLIT1-ROBO2 pathway), and Hippo pathway (YAP and TAZ) was altered in hNPCs exposed to HG. The expression levels of SLIT1-ROBO2 pathways genes (including its effectors, SRGAP1 and CDC42) which mediates diverse cellular processes such as proliferation, neurogenesis and axon guidance, and Hippo pathway genes (YAP and TAZ) which regulates proliferation, stemness, differentiation and organ size were downregulated in hNPCs exposed to HG. A recent report suggests a possible cross-talk between SLIT1-ROBO2 and TAZ via CDC42, a mediator of actin dynamics. Consistent with this, SLIT1 knockdown downregulated the expression of its effectors and TAZ in hNPCs, suggesting that HG perturbs the cross-talk between SLIT1-ROBO2 and TAZ in hNPCs. Overall, this study demonstrates that HG epigenetically alters the SLIT1-ROBO2 and Hippo signalling pathways in hNPCs, forming the basis for neurodevelopmental disorders in offspring of diabetic pregnancy.

Changes in Stemness Properties, Differentiation Potential, Oxidative Stress, Senescence and Mitochondrial Function in Wharton's Jelly Stem Cells of Umbilical Cords of Mothers with Gestational Diabetes Mellitus.

Gestational diabetes mellitus (GDM) has been associated with an increased risk of maternal and neonatal morbidity. The Wharton's jelly (WJ) of the umbilical cord (UC) is a useful indicator of the deleterious effects of hyperglycemia on fetal tissues as it represents the fetus embryologically, physiologically and genetically. We studied WJ mesenchymal stem cells (hWJSCs) from UC from mothers without GDM (Normal; n = 3); insulin-controlled GDM mothers (GDMi; n = 3) and diet-controlled GDM mothers (GDMd; n = 3)]. Cell proliferation, stemness markers, telomerase, osteogenic and chondrogenic differentiation, antioxidant enzymes and gene expression for mitochondrial function (ND2, TFAM, PGC1α, and NDUFB9) were significantly lower in GDMi-hWJSCs and GDMd-hWJSCs compared to normal hWJSCs (P < 0.05). On the other hand, cell cycle inhibitors (p16, p21, p27) and p53 were remarkably up-regulated in GDMi-hWJSCs and GDMd-hWJSCs compared to normal hWJSCs. The results from this study confirmed that maternal hyperglycemia even though managed with insulin or diet, induced changes in the properties of the WJ and its cells. These changes may also be observed in fetal tissues and if true, prevention of the onset of gestational diabetes should be a priority over management. Generation of tissues that simulate those of the fetus such as pancreatic and cardiovascular cells from GDM-hWJSCs by direct differentiation or via induced pluripotent stem cell reprogramming provide possible platforms to evaluate the effects of glucose on specific fetal organ.

Ethnicity-Specific Skeletal Muscle Transcriptional Signatures and Their Relevance to Insulin Resistance in Singapore.

Context: Insulin resistance (IR) and obesity differ among ethnic groups in Singapore, with the Malays more obese yet less IR than Asian-Indians. However, the molecular basis underlying these differences is not clear. Objective: As the skeletal muscle (SM) is metabolically relevant to IR, we investigated molecular pathways in SM that are associated with ethnic differences in IR, obesity, and related traits. Design, Setting, and Main Outcome Measures: We integrated transcriptomic, genomic, and phenotypic analyses in 156 healthy subjects representing three major ethnicities in the Singapore Adult Metabolism Study. Patients: This study contains Chinese (n = 63), Malay (n = 51), and Asian-Indian (n = 42) men, aged 21 to 40 years, without systemic diseases. Results: We found remarkable diversity in the SM transcriptome among the three ethnicities, with >8000 differentially expressed genes (40% of all genes expressed in SM). Comparison with blood transcriptome from a separate Singaporean cohort showed that >95% of SM expression differences among ethnicities were unique to SM. We identified a network of 46 genes that were specifically downregulated in Malays, suggesting dysregulation of components of cellular respiration in SM of Malay individuals. We also report 28 differentially expressed gene clusters, four of which were also enriched for genes that were found in genome-wide association studies of metabolic traits and disease and correlated with variation in IR, obesity, and related traits. Conclusion: We identified extensive gene-expression changes in SM among the three Singaporean ethnicities and report specific genes and molecular pathways that might underpin and explain the differences in IR among these ethnic groups.

Metabolic Remodeling during Liver Regeneration.

Liver disease is linked to a decreased capacity of hepatocytes to divide. In addition, cellular metabolism is important for tissue homeostasis and regeneration. Since metabolic changes are a hallmark of liver disease, we investigated the connections between metabolism and cell division. We determined global metabolic changes at different stages of liver regeneration using a combination of integrated transcriptomic and metabolomic analyses with advanced functional redox in vivo imaging. Our data indicate that blocking hepatocyte division during regeneration leads to mitochondrial dysfunction and downregulation of oxidative pathways. This resulted in an increased redox ratio and hyperactivity of alanine transaminase allowing the production of alanine and α-ketoglutarate from pyruvate when mitochondrial functions are impaired. Our data suggests that during liver regeneration, cell division leads to hepatic metabolic remodeling. Moreover, we demonstrate that hepatocytes are equipped with a flexible metabolic machinery able to adapt dynamically to changes during tissue regeneration.

Maternal Factors that Induce Epigenetic Changes Contribute to Neurological Disorders in Offspring.

It is well established that the regulation of epigenetic factors, including chromatic reorganization, histone modifications, DNA methylation, and miRNA regulation, is critical for the normal development and functioning of the human brain. There are a number of maternal factors influencing epigenetic pathways such as lifestyle, including diet, alcohol consumption, and smoking, as well as age and infections (viral or bacterial). Genetic and metabolic alterations such as obesity, gestational diabetes mellitus (GDM), and thyroidism alter epigenetic mechanisms, thereby contributing to neurodevelopmental disorders (NDs) such as embryonic neural tube defects (NTDs), autism, Down's syndrome, Rett syndrome, and later onset of neuropsychological deficits. This review comprehensively describes the recent findings in the epigenetic landscape contributing to altered molecular profiles resulting in NDs. Furthermore, we will discuss potential avenues for future research to identify diagnostic markers and therapeutic epi-drugs to reverse these abnormalities in the brain as epigenetic marks are plastic and reversible in nature.

miRNA-32 Drives Brown Fat Thermogenesis and Trans-activates Subcutaneous White Fat Browning in Mice.

Brown adipose tissue (BAT) activation and subcutaneous white fat browning are essential components of the thermogenic response to cold stimulus in mammals. microRNAs have been shown to regulate both processes in cis. Here, we identify miR-32 as a BAT-specific super-enhancer-associated miRNA in mice that is selectively expressed in BAT and further upregulated during cold exposure. Inhibiting miR-32 in vivo led to impaired cold tolerance, decreased BAT thermogenesis, and compromised white fat browning as a result of reduced serum FGF21 levels. Further examination showed that miR-32 directly represses its target gene Tob1, thereby activating p38 MAP kinase signaling to drive FGF21 expression and secretion from BAT. BAT-specific miR-32 overexpression led to increased BAT thermogenesis and serum FGF21 levels, which further promotes white fat browning in trans. Our results suggested miR-32 and Tob1 as modulators of FGF21 signaling that can be manipulated for therapeutic benefit against obesity and metabolic syndrome.

Gestational Diabetes Alters Functions in Offspring's Umbilical Cord Cells With Implications for Cardiovascular Health.

Because noncommunicable diseases such as type 2 diabetes mellitus have their roots in prenatal development and conditions such as maternal gestational diabetes mellitus (GDM), we aimed to test this hypothesis in primary cells derived from the offspring of mothers with GDM compared with control subjects. We have assessed primary umbilical cord-derived cells such as human umbilical vein endothelial cells (HUVECs) and Wharton's jelly-derived mesenchymal stem cells from the offspring of mothers with and without GDM. We have compared the primary isolates in cell-based assays measuring proliferation, mitochondrial oxygen consumption, and the ability to support blood vessel growth. We conducted gene expression microarray studies with subsequent pathway analysis and candidate gene validation. We observed striking differences between the two groups, such as lower metabolic rates and impairment of endothelial tube formation in cells with GDM background. HUVECs from subjects with maternal GDM have lower expression of the antiapoptotic protein BCL-xL, suggesting compromised angiogenic capabilities. Comparative gene expression analysis revealed blood vessel formation as a major pathway enriched in the GDM-derived HUVECs with the surface marker CD44 as a gene underexpressed in the GDM group. Functional validation of CD44 revealed that it regulates tube formation in HUVECs, thereby providing insights into a pathway imprinted in primary umbilical cord-derived cells from GDM offspring. Our data demonstrate that primary cells isolated from the umbilical cord of offspring born to mothers with GDM maintain metabolic and molecular imprints of maternal hyperglycemia, reflecting an increased risk for cardiovascular disease later in life.

Tissues Derived From Reprogrammed Wharton's Jelly Stem Cells of the Umbilical Cord Provide an Ideal Platform to Study the Effects of Glucose, Zika Virus, and Other Agents on the Fetus.

The infants of mothers with gestational diabetes mellitus (GDM) have an increased risk of metabolic and cardiovascular disease. It has been difficult to study the direct effects of maternal hyperglycemia on the fetus because of inaccessibility of fetal tissues. The development of tissues that simulate the function of fetal organs using stem cell technology provides an unprecedented opportunity to study this disorder. Stem cells in the Wharton's jelly of the umbilical cord (hWJSCs), possess unique properties that are different from other stem cells. They are primitive, present in large numbers, non-tumorigenic, hypoimmunogenic, tumoricidal, and carry a genetic signature that represents the fetus. They are multipotent but their differentiation into functional pancreatic and cardiovascular tissues has been challenging. We have been able to reprogram hWJSCs from normal and GDM cords into induced pluripotent stem cells (iPSCs) from which a variety of functional fetal tissues including insulin-producing and cardiovascular tissues could be derived. Such tissues from reprogrammed hWJSCs of normal and GDM cords that physiologically and genetically mimic the fetus of the diabetic or non-diabetic mother are an ideal platform to study the effects of glucose, the Zika virus, and other harmful agents on the fetus. The immature stemness phenotype of hWJSCs, easy accessibility, availability in large numbers without the need for propagation, and lower risk of accumulation of epigenetic mutations make them the most attractive candidate over other umbilical cord cell types for reprogramming. Additionally, some of their beneficial genes may be retained in memory in the iPSCs derived from them. J. Cell. Biochem. 118: 437-441, 2017. © 2016 Wiley Periodicals, Inc.

E2F1 Orchestrates Transcriptomics and Oxidative Metabolism in Wharton's Jelly-Derived Mesenchymal Stem Cells from Growth-Restricted Infants.

Wharton's jelly-derived Mesenchymal Stem Cells (MSCs) isolated from newborns with intrauterine fetal growth restriction were previously shown to exert anabolic features including insulin hypersensitivity. Here, we extend these observations and demonstrate that MSCs from small for gestational age (SGA) individuals have decreased mitochondrial oxygen consumption rates. Comparing normally grown and SGA MSCs using next generation sequencing studies, we measured global transcriptomic and epigenetic profiles and identified E2F1 as an over-expressed transcription factor regulating oxidative metabolism in the SGA group. We further show that E2F1 regulates the differential transcriptome found in SGA derived MSCs and is associated with the activating histone marks H3K27ac and H3K4me3. One of the key genes regulated by E2F1 was found to be the fatty acid elongase ELOVL2, a gene involved in the endogenous synthesis of docosahexaenoic acid (DHA). Finally, we shed light on how the E2F1-ELOVL2 pathway may alter oxidative respiration in the SGA condition by contributing to the maintenance of cellular metabolic homeostasis.

The transcription factor SOX6 contributes to the developmental origins of obesity by promoting adipogenesis.

An association between impaired fetal growth and the postnatal development of obesity has been established. Here, by comparing adipocytes differentiated from mesenchymal stem cells (MSCs) taken from the umbilical cord and derived from normal and growth-restricted neonates, we identified the transcription factor SOX6 as highly expressed only in growth-restricted individuals. We found that SOX6 regulates adipogenesis in vertebrate species by activating adipogenic regulators including PPARγ, C/EBPα and MEST. We further show that SOX6 interacts with ß-catenin in adipocytes, suggesting an inhibition of WNT/ß-catenin signaling, thereby promoting adipogenesis. The upstream regulatory region of the MEST gene in MSCs from growth-restricted subjects harbors hypomethylated CpGs next to SOX6 binding motifs, and we found that SOX6 binding is impaired by adjacent CpG methylation. In summary, we report that SOX6 is a novel regulator of adipogenesis synergizing with epigenetic mechanisms.

ACSL1 Is Associated With Fetal Programming of Insulin Sensitivity and Cellular Lipid Content.

Individuals who are born small for gestational age (SGA) have a risk to develop various metabolic diseases during their life course. The biological memory of the prenatal state of growth restricted individuals may be reflected in epigenetic alterations in stem cell populations. Mesenchymal stem cells (MSCs) from the Wharton's jelly of umbilical cord tissue are multipotent, and we generated primary umbilical cord MSC isolates from SGA and normal neonates, which were subsequently differentiated into adipocytes. We established chromatin state maps for histone marks H3K27 acetylation and H3K27 trimethylation and tested whether enrichment of these marks was associated with gene expression changes. After validating gene expression levels for 10 significant chromatin immunoprecipitation sequencing candidate genes, we selected acyl-coenzyme A synthetase 1 (ACSL1) for further investigations due to its key roles in lipid metabolism. The ACSL1 gene was found to be highly associated with histone acetylation in adipocytes differentiated from MSCs with SGA background. In SGA-derived adipocytes, the ACSL1 expression level was also found to be associated with increased lipid loading as well as higher insulin sensitivity. ACSL1 depletion led to changes in expression of candidate genes such as proinflammatory chemokines and down-regulated both, the amount of cellular lipids and glucose uptake. Increased ACSL1, as well as modulated downstream candidate gene expression, may reflect the obese state, as detected in mice fed a high-fat diet. In summary, we believe that ACSL1 is a programmable mediator of insulin sensitivity and cellular lipid content and adipocytes differentiated from Wharton's jelly MSCs recapitulate important physiological characteristics of SGA individuals.

Molecular pathways reflecting poor intrauterine growth are found in Wharton's jelly-derived mesenchymal stem cells.

STUDY QUESTION: Are molecular pathways reflecting the biology of small for gestational age (SGA) neonates preserved in umbilical cord-derived mesenchymal stem cells (MSCs)? SUMMARY ANSWER: MSCs from SGA newborns were found to express an altered EGR-1-dependent gene network involved in the regulation of cell proliferation and oxidative stress. WHAT IS KNOWN ALREADY: Individuals with suboptimal intrauterine development are at greater risk of metabolic diseases such as type II diabetes, obesity and cardiovascular disease. STUDY DESIGN, SIZE, DURATION: Umbilical cords (n = 283) from the GUSTO (growing up in Singapore towards healthy outcomes) birth cohort study, and primary MSC isolates established from SGA and matched control cases (n = 6 per group), were subjected to gene expression analysis and candidate genes were studied for functional validation. PARTICIPANTS/MATERIALS, SETTING, METHODS: Umbilical cord specimens were derived from babies born at the National University Hospital (NUH) in Singapore. Local ethical approval was obtained. MSC isolates were established in Wharton's jelly and molecular analysis was conducted by gene expression microarrays and RT-PCR. Cells from SGA and control groups were compared in the presence and absence of insulin and candidate gene function was studied via siRNA-mediated gene knockdown and over-expression experiments in MSCs. MAIN RESULTS AND THE ROLE OF CHANCE: Using repeated measure ANOVAs, proliferation rates of MSCs isolated from SGA neonates were found to be significantly increased (P < 0.01). In the absence of insulin, EGR-1 levels were found to be significantly reduced in the group of SGA-derived MSCs, whereas EGR-1 expression was found to be up-regulated in the same group in the presence of insulin (P < 0.01). EGR-1 was found to induce expression of COX-2 in the SGA group (P < 0.01) and both, EGR-1 and COX-2 stimulated glucose uptake in MSCs (P < 0.01). EGR-1 and COX-2 levels were associated in whole umbilical cords (n = 283, P < 0.01) and EGR-1 positively correlated with abdominal circumference and birthweight (n = 91, P < 0.01 and n = 91, P < 0.01). LIMITATIONS, REASONS FOR CAUTION: Cell models may not entirely reflect the physiology of the host and patient follow-up studies will be necessary for further clinical validation. WIDER IMPLICATIONS OF THE FINDINGS: Our study suggests that Wharton's jelly-derived MSCs are useful in identifying pathways specific for fetal growth restriction. STUDY FUNDING/COMPETING INTERESTS: This work is supported by the Translational Clinical Research (TCR) Flagship Program on Developmental Pathways to Metabolic Disease funded by the National Research Foundation (NRF) and administered by the National Medical Research Council (NMRC), Singapore- NMRC/TCR/004-NUS/2008'. SICS Investigators are supported through the Agency for Science Technology and Research (A*STAR) funding. No potential conflicts of interest relevant to this article were reported.

Alterations to DNA methylation and expression of CXCL14 are associated with suboptimal birth outcomes.

CXCL14 is a chemokine that has previously been implicated in insulin resistance in mice. In humans, the role of CXCL14 in metabolic processes is not well established, and we sought to determine whether CXCL14 is a risk susceptibility gene important in fetal programming of metabolic disease. For this purpose, we investigated whether CXCL14 is differentially regulated in human umbilical cords of infants with varying birth weights. We found an elevated expression of CXCL14 in human low birth weight (LBW) cords, as well as in cords from nutritionally restricted Macaca fascicularis macaques. To further analyze the regulatory mechanisms underlying the expression of CXCL14, we examined CXCL14 in umbilical cord-derived mesenchymal stem cells (MSCs) that provide an in vitro cell-based system amenable to experimental manipulation. Using both whole frozen cords and MSCs, we determined that site-specific CpG methylation in the CXCL14 promoter is associated with altered expression, and that changes in methylation are evident in LBW infant-derived umbilical cords that may indicate future metabolic compromise through CXCL14.

Infinium monkeys: Infinium 450K array for the Cynomolgus macaque (Macaca fascicularis).

The Infinium Human Methylation450 BeadChip Array (Infinium 450K) is a robust and cost-efficient survey of genome-wide DNA methylation patterns. Macaca fascicularis (Cynomolgus macaque) is an important disease model; however, its genome sequence is only recently published, and few tools exist to interrogate the molecular state of Cynomolgus macaque tissues. Although the Infinium 450K is a hybridization array designed to the human genome, the relative conservation between the macaque and human genomes makes its use in macaques feasible. Here, we used the Infinium 450K array to assay DNA methylation in 11 macaque muscle biopsies. We showed that probe hybridization efficiency was related to the degree of sequence identity between the human probes and the macaque genome sequence. Approximately 61% of the Human Infinium 450K probes could be reliably mapped to the Cynomolgus macaque genome and contain a CpG site of interest. We also compared the Infinium 450K data to reduced representation bisulfite sequencing data generated on the same samples and found a high level of concordance between the two independent methodologies, which can be further improved by filtering for probe sequence identity and mismatch location. We conclude that the Infinium 450K array can be used to measure the DNA methylome of Cynomolgus macaque tissues using the provided filters. We also provide a pipeline for validation of the array in other species using a simple BLAST-based sequence identify filter.

The effect of genotype and in utero environment on interindividual variation in neonate DNA methylomes.

Integrating the genotype with epigenetic marks holds the promise of better understanding the biology that underlies the complex interactions of inherited and environmental components that define the developmental origins of a range of disorders. The quality of the in utero environment significantly influences health over the lifecourse. Epigenetics, and in particular DNA methylation marks, have been postulated as a mechanism for the enduring effects of the prenatal environment. Accordingly, neonate methylomes contain molecular memory of the individual in utero experience. However, interindividual variation in methylation can also be a consequence of DNA sequence polymorphisms that result in methylation quantitative trait loci (methQTLs) and, potentially, the interaction between fixed genetic variation and environmental influences. We surveyed the genotypes and DNA methylomes of 237 neonates and found 1423 punctuate regions of the methylome that were highly variable across individuals, termed variably methylated regions (VMRs), against a backdrop of homogeneity. MethQTLs were readily detected in neonatal methylomes, and genotype alone best explained ∼25% of the VMRs. We found that the best explanation for 75% of VMRs was the interaction of genotype with different in utero environments, including maternal smoking, maternal depression, maternal BMI, infant birth weight, gestational age, and birth order. Our study sheds new light on the complex relationship between biological inheritance as represented by genotype and individual prenatal experience and suggests the importance of considering both fixed genetic variation and environmental factors in interpreting epigenetic variation.

Measuring the methylome in clinical samples: improved processing of the Infinium Human Methylation450 BeadChip Array.

The Infinium Human Methylation450 BeadChip Array (TM) (Infinium 450K) is an important tool for studying epigenetic patterns associated with disease. This array offers a high-throughput, low cost alternative to more comprehensive sequencing-based methodologies. Here we compare data generated by interrogation of the same seven clinical samples by Infinium 450K and reduced representation bisulfite sequencing (RRBS). This is the largest data set comparing Infinium 450K array to the comprehensive RRBS methodology reported so far. We show good agreement between the two methodologies. A read depth of four or more reads in the RRBS data was sufficient to achieve good agreement with Infinium 450K. However, we observe that intermediate methylation values (20-80%) are more variable between technologies than values at the extremes of the bimodal methylation distribution. We describe careful processing of Infinium 450K data to correct for known limitations and batch effects. Using methodologies proposed by others and newly implemented and combined in this report, agreement of Infinium 450K data with independent techniques can be vastly improved.

Transcriptome changes affecting Hedgehog and cytokine signalling in the umbilical cord: implications for disease risk.

BACKGROUND: Babies born at lower gestational ages or smaller birthweights have a greater risk of poorer health in later life. Both the causes of these sub-optimal birth outcomes and the mechanism by which the effects are transmitted over decades are the subject of extensive study. We investigated whether a transcriptomic signature of either birthweight or gestational age could be detected in umbilical cord RNA. METHODS: The gene expression patterns of 32 umbilical cords from Singaporean babies of Chinese ethnicity across a range of birthweights (1698-4151 g) and gestational ages (35-41 weeks) were determined. We confirmed the differential expression pattern by gestational age for 12 genes in a series of 127 umbilical cords of Chinese, Malay and Indian ethnicity. RESULTS: We found that the transcriptome is substantially influenced by gestational age; but less so by birthweight. We show that some of the expression changes dependent on gestational age are enriched in signal transduction pathways, such as Hedgehog and in genes with roles in cytokine signalling and angiogenesis. We show that some of the gene expression changes we report are reflected in the epigenome. CONCLUSIONS: We studied the umbilical cord which is peripheral to disease susceptible tissues. The results suggest that soma-wide transcriptome changes, preserved at the epigenetic level, may be a mechanism whereby birth outcomes are linked to the risk of adult metabolic and arthritic disease and suggest that greater attention be given to the association between premature birth and later disease risk.

Sirtuin 1 (SIRT1): the misunderstood HDAC.

The sirtuin family of NAD-dependent histone deacetylases (HDACs) consists of seven mammalian proteins, SIRT1-7. Many of the sirtuin isoforms also deacetylate nonhistone substrates, such as p53 (SIRT1) and α-tubulin (SIRT2). The sirtuin literature focuses on pharmacological activators of SIRT1 (e.g., resveratrol, SRT1720), proposed as therapeutics for diabetes, neurodegeneration, inflammation, and others. However, many of the SIRT1 activator results may have been due to artifacts in the assay methodology (i.e., use of fluorescently tagged substrates). A biological role for SIRT1 in cancer has been given less scrutiny but is no less equivocal. Although proposed initially as an oncogene, we present herein compelling data suggesting that SIRT1 is indeed a context-specific tumor suppressor. For oncology, SIRT1 inhibitors (dual SIRT1/2) are indicated as potential therapeutics. A number of sirtuin inhibitors have been developed but with mixed results in cellular systems and animal models. It is unclear whether this has been due to poorly understood model systems, signalling redundancy, and/or inadequately potent and selective tool compounds. This review provides an overview of recent developments in the field of SIRT1 function. While focusing on oncology, it aims to shed light on new concepts of expanding the selectivity spectrum, including other sirtuins such as SIRT2.