Variation in the gene encoding Krüppel-like factor 7 influences body fat: studies of 14 818 Danes

Analysis of KLF7 and KLF5 transcription factors gene variants in coronary artery disease

INTRODUCTION AND OBJECTIVE

Genetic susceptibility has a key role in the pathogenesis of coronary artery disease (CAD). KLF5 and KLF7 are transcriptional factors essential to cell development and differentiation. Their genetic variants have been associated with the risk of metabolic disorders. The present study aimed to evaluate the possible correlation of KLF5 (rs3812852) and KLF7 (rs2302870) single nucleotide polymorphisms (SNPs) with the risk of CAD for the first time in the world.

METHODS

The clinical trial study comprised 150 patients with CAD and 150 control subjects without CAD from the Iranian population. After blood sampling, deoxyribonucleic acid was extracted and genotyped using the Tetra Primer ARMS-PCR method and confirmed by Sanger sequencing.

RESULTS

The KLF7 A/C genotypes and C allele frequency were meaningfully higher in the control group compared to the CAD+ group (p<0.05). No obvious association has been observed between KLF5 variants and CAD risk. However, the distribution of the AG genotype of KLF5 was statistically lower in CAD+ patients with diabetes than in CAD+ patients without diabetes (p<0.05).

CONCLUSION

This study identified KLF7 SNP as a causative gene contributing to CAD, which presents novel insight into the molecular pathogenesis of the disease. It is, however, unlikely that KLF5 SNP has an essential role in the risk of CAD in the studied population.

KLF7 promotes adipocyte inflammation and glucose metabolism disorder by activating the PKCζ/NF-κB pathway

In the obesity context, inflammatory cytokines secreted by adipocytes lead to insulin resistance and are key to metabolic syndrome development. In our previous study, we found that the transcription factor KLF7 promoted the expression of p-p65 and IL-6 in adipocytes. However, the specific molecular mechanism remained unclear. In the present study, we found that the expression of KLF7, PKCζ, p-IκB, p-p65, and IL-6 in epididymal white adipose tissue (Epi WAT) in mice fed a high-fat diet (HFD) was significantly increased. In contrast, the expression of PKCζ, p-IκB, p-p65, and IL-6 was significantly decreased in Epi WAT of KLF7 fat conditional knockout mice. In 3T3-L1 adipocytes, KLF7 promoted the expression of IL-6 via the PKCζ/NF-κB pathway. In addition, we performed luciferase reporter and chromatin immunoprecipitation assays, which confirmed that KLF7 upregulated the expression of PKCζ transcripts in HEK-293T cells. Collectively, our results show that KLF7 promotes the expression of IL-6 by upregulating PKCζ expression and activating the NF-κB signaling pathway in adipocytes.

Long noncoding RNA PVT1 regulates the proliferation and apoptosis of ARPE-19 cells in vitro via the miR-1301-3p/KLF7 axis

Diabetic retinopathy (DR) as a frequent diabetic microvascular complication shows signs in one-third of diabetic patients. Long non-coding RNAs (lncRNAs) have drawn increasing attention because of their regulatory roles in DR. LncRNA plasmacytoma variant translocation 1 (PVT1) is documented to be upregulated in diabetes-related diseases, while its effects in DR remains unexplored. ARPE-19 cells under the treatment of high-glucose (HG) were used as DR cell models. The gene expression in ARPE-19 cells was examined using RT-qPCR. The viability and apoptosis of ARPE-19 cells were determined by MTT and TUNEL assays. The levels of inflammation-associated proteins or mRNA were measured using western blot. Luciferase reporter assay and RNA pull down assay were conducted for the exploration of the underlying mechanism of PVT1. PVT1 was revealed to be upregulated in DR cell models. Silencing of PVT1 promoted the viability and inhibited apoptosis of HG-stimulated ARPE-19 cells. The results revealed that PVT1 can bind with miR-1301-3p. PVT1 negatively modulated miR-1301-3p expression. Additionally, KLF7 was targeted by miR-1301-3p. PVT1 upregulated KLF7 expression by binding with miR-1301-3p. The silenced PVT1-mediated influence on cell viability and cell apoptosis was rescued by overexpression of KLF7. PVT1 suppresses proliferation and promotes apoptosis of ARPE-19 cells treated with HG in vitro by binding with miR-1301-3p to upregulate KLF7.

Transcriptional control of chicken KLF7 promoter in preadipocytes

Krüppel-like factor 7 (KLF7) has been reported to inhibit adipogenesis and regulate the development of the nervous system. However, transcription regulation of KLF7 remains poorly understood. In the current study, a 2196-bp-long 5'-flanking sequence of chicken KLF7 (-2286 bp to -91 bp, upstream of the translation start site) was studied for promoter activity, and there was a remarkable promoter activity in this sequence (P<0.05). The 5'-truncated mutation analysis showed that a minimal promoter was on the sequence from -241 bp to -91 bp. In addition, GATA2 overexpression facilitated the promoter activity of pGL3-KLF7(-2286/-91), pGL3-KLF7(-1215/-91), pGL3-KLF7(-521/-91), and pGL3-KLF7(-241/-91), and GATA3 overexpression inhibited the promoter activity of pGL3-KLF7(-1845/-91), pGL3-KLF7(-1215/-91), pGL3-KLF7(-521/-91), and pGL3-KLF7(-241/-91) in chicken preadipocytes (P<0.05). Knockdown of GATA2 expression inhibited the promoter activity of pGL3-KLF7(-1215/-91) and pGL3-KLF7(-241/-91), and knockdown of GATA3 expression facilitated the promoter activity of pGL3-KLF7(-521/-91) and pGL3-KLF7(-241/-91) (P<0.05). Additionally, overexpression and knockdown analyses showed that GATA3 inhibited KLF7 mRNA expression (P<0.05), and both overexpression and knockdown of GATA2 resulted in the downregulation of KLF7 mRNA expression in chicken preadipocytes (P<0.05). Western blot analysis in chicken preadipocytes showed that GATA2 facilitated KLF7 expression and GATA3 inhibited KLF7 expression. Mutation analysis showed that the motif of 'GGATCTATCA' (-107 bp/-98 bp) might be a cis-regulation element, which is involved in the KLF7 expression regulation by GATA3 in chicken preadipocytes. These results provided some details of KLF7 transcription regulation in chicken adipose tissue.

DNA methylation of CpG sites in the chicken KLF7 promoter and Exon 2 in association with mRNA expression in abdominal adipose tissue and blood metabolic indicators

BACKGROUND

Our previous study found that chicken KLF7 was an important regulator in formation of adipose tissue. In the present study, we analyzed the association for DNA methylation in chicken KLF7 with its transcripts of abdominal adipose tissue and blood metabolic indicators.

RESULTS

The KLF7 transcripts of the adipose tissue of Chinese yellow broilers were associated with age (F = 6.67, P = 0.0035). In addition, the KLF7 transcripts were negatively correlated with blood glucose levels (r = - 0.61841, P = 0.0140). The DNA methylation levels of 26 CpG loci in the chicken KLF7 promoter and Exon 2 were studied by Sequenom MassArray. A total of 22 valid datasets were obtained. None of them was significantly different in relation to age (P > 0.05). However, the DNA methylation levels in the promoter were lower than those in Exon 2 (T = 40.74, P < 0.01). Correlation analysis showed that the DNA methylation levels of PCpG6 and E2CpG9 were significantly correlated with KLF7 transcripts and blood high-density lipoprotein levels, respectively, and many CpG loci were correlated with each other (P < 0.05). The methylation data were subjected to principal component analysis and factor analysis. The six principal components (z1-z6) were extracted and named Factors 1-6, respectively. Factor analysis showed that Factor 1 had a higher load on the loci in the promoter, and Factors 2-6 loaded highly on quite different loci in Exon 2. Correlation analysis showed that only z1 was significantly correlated to KLF7 transcripts (P < 0.05). In addition, an established regression equation between z1 and KLF7 transcripts was built, and the contribution of z1 to the variation on KLF7 transcripts was 34.29%.

CONCLUSIONS

In conclusion, the KLF7 transcripts of chicken abdominal adipose tissue might be inhibited by DNA methylation in the promoter, and it might be related to the DNA methylation level of PCpG6.

GATA Binding Protein 3 Is a Direct Target of Kruppel-Like Transcription Factor 7 and Inhibits Chicken Adipogenesis

Kruppel-like transcription factor 7 (KLF7) is a negative regulator of adipogenesis, however, its precise mechanism is poorly understood. Our previous KLF7 ChIP-seq analysis showed that one of the KLF7 binding peaks was present upstream of GATA binding protein 3 (GATA3) in chicken preadipocytes. In the present study, we identified GATA3 as a target of KLF7. Overexpression analysis showed KLF7 markedly enhanced the endogenous expression of GATA3 in the immortalized chicken preadipcyte cell line (ICP2), and the luciferase reporter assay showed that KLF7 overexpression increased the reporter gene activity of the cloned upstream region (-5285/-4336 relative to the translation initiation codon ATG) of GATA3 in ICP2 and DF1 cells, and mutation of the putative KLF7 binding site abolished the promotive effect of KLF7 overexpression on the reporter gene activity of the cloned GATA3 upstream region. ChIP-qPCR further demonstrated that KLF7 directly bound to the GATA3 upstream region. Gene expression analysis showed that GATA3 mRNA expression in abdominal adipose tissue was significantly higher in lean chicken line than in the fat line at 2, 3, and 6 weeks of age. In addition, GATA3 mRNA expression markedly decreased during the preadipocyte differentiation. Furthermore, a functional study showed that GATA3 overexpression inhibited the differentiation of the ICP2 cells. Taken together, our results demonstrated that KLF7 inhibits chicken adipogenesis, at least in part through direct upregulation of GATA3.

Loss of the third C2H2 zinc finger of chicken KLF7 affects its transcriptional regulation activities in adipose tissue

KLF7, one of candidate genes in neurotherapy and metabolic syndrome, has been studied in adipogenesis of mammalian species and birds. However, the effect of the third C2H2 zinc finger of KLF7 for its transcriptional regulation in adipogenesis has not been well understood. Here, the wild-type chicken KLF7 (KLF7) overexpression plasmid, pCMV-myc-KLF7, and two plasmids of chicken KLF7 mutants, i.e. pCMV-myc-KLF7m1 with half of the third zinc finger (KLF7m1) and pCMV-myc-KLF7m2 without the third zinc finger (KLF7m2), were constructed. Luciferase reporter assay in DF1 cells showed that the effect of chicken KLF7 overexpression on the promoter activity of LPL was greater than those of KLF7m1 and KLF7m2 (P < 0.05). There was no significant difference among the overexpression of KLF7, KLF7m1 and KLF7m2 on the promoter activities of FASN, C/EBPα and FABP4 (P > 0.05). Additionally, the effects of KLF7, KLF7m1 and KLF7m2 overexpression on the promoter activity of PPARγ were different. KLF7 overexpression had no significant effect on the PPARγ promoter activity (P > 0.05), KLF7m1 overexpression suppressed PPARγ promoter activity (P < 0.05), while KLF7m2 overexpression facilitated the promoter activity of PPARγ (P < 0.05), consistent with the results of western blot analysis. Our results suggested that the third zinc finger of chicken KLF7 may play a role in its transcriptional regulation of LPL and PPARγ but has no effect on its regulation of C/EBPα, FASN and FABP4. The third zinc finger of KLF7 might be a target for the treatment of metabolic disorder in chicken.

The Krüppel-Like Factors and Control of Energy Homeostasis

Nutrient handling by higher organisms is a complex process that is regulated at the transcriptional level. Studies over the past 15 years have highlighted the critical importance of a family of transcriptional regulators termed the Krüppel-like factors (KLFs) in metabolism. Within an organ, distinct KLFs direct networks of metabolic gene targets to achieve specialized functions. This regulation is often orchestrated in concert with recruitment of tissue-specific transcriptional regulators, particularly members of the nuclear receptor family. Upon nutrient entry into the intestine, gut, and liver, KLFs control a range of functions from bile synthesis to intestinal stem cell maintenance to effect nutrient acquisition. Subsequently, coordinated KLF activity across multiple organs distributes nutrients to sites of storage or liberates them for use in response to changes in nutrient status. Finally, in energy-consuming organs like cardiac and skeletal muscle, KLFs tune local metabolic programs to precisely match substrate uptake, flux, and use, particularly via mitochondrial function, with energetic demand; this is achieved in part via circulating mediators, including glucocorticoids and insulin. Here, we summarize current understanding of KLFs in regulation of nutrient absorption, interorgan circulation, and tissue-specific use.

Molecular genetic contributions to self-rated health

Background: Poorer self-rated health (SRH) predicts worse health outcomes, even when adjusted for objective measures of disease at time of rating. Twin studies indicate SRH has a heritability of up to 60% and that its genetic architecture may overlap with that of personality and cognition.

Methods: We carried out a genome-wide association study (GWAS) of SRH on 111 749 members of the UK Biobank sample. Univariate genome-wide complex trait analysis (GCTA)-GREML analyses were used to estimate the proportion of variance explained by all common autosomal single nucleotide polymorphisms (SNPs) for SRH. Linkage disequilibrium (LD) score regression and polygenic risk scoring, two complementary methods, were used to investigate pleiotropy between SRH in the UK Biobank and up to 21 health-related and personality and cognitive traits from published GWAS consortia.

Results: The GWAS identified 13 independent signals associated with SRH, including several in regions previously associated with diseases or disease-related traits. The strongest signal was on chromosome 2 (rs2360675, P = 1.77 x 10^-10) close to KLF7. A second strong peak was identified on chromosome 6 in the major histocompatibility region (rs76380179, P = 6.15 x 10^-10). The proportion of variance in SRH that was explained by all common genetic variants was 13%. Polygenic scores for the following traits and disorders were associated with SRH: cognitive ability, education, neuroticism, body mass index (BMI), longevity, attention-deficit hyperactivity disorder (ADHD), major depressive disorder, schizophrenia, lung function, blood pressure, coronary artery disease, large vessel disease stroke and type 2 diabetes.

Conclusions: Individual differences in how people respond to a single item on SRH are partly explained by their genetic propensity to many common psychiatric and physical disorders and psychological traits.

Secretome analysis of breast cancer-associated adipose tissue to identify paracrine regulators of breast cancer growth

Adipose tissue secretes a plethora of adipokines as evidenced by characterization of subcutaneous and visceral adipose tissue secretomes. However, adipose tissue composition and secretion pattern is depot and disease dependent, influencing the adipose tissue secretome. We investigated the secretome of cancer-associated adipose tissue (CAAT) explants from breast cancer patients and explored its role in breast cancer proliferation. CAAT proteins were identified by LC-MS/MS and human protein antibody arrays and stimulated proliferation of three breast cancer cell lines. Kinomics and transcriptomics of MCF-7 breast cancer cells treated with the secretome of CAAT revealed activation of Akt-, ERK- and JNK-pathways and differential expression of activator protein 1 (AP-1) and cAMP responsive element-binding protein (CREB) target genes. The cyclin-dependent kinase (CDK)4/6-inhibitor palbociclib significantly abrogated CAAT-enhanced breast cancer cell proliferation. Our work characterizes the specific breast CAAT protein secretome and reveals its pro-proliferative potency in breast cancer.

Krüppel-like factors: Crippling and un-crippling metabolic pathways

Krüppel-like factors (KLFs) are DNA-binding transcriptional factors that regulate various pathways that control metabolism and other cellular mechanisms. Various KLF isoforms have been associated with cellular, organ or systemic metabolism. Altered expression or activation of KLFs has been linked to metabolic abnormalities, such as obesity and diabetes, as well as with heart failure. In this review article we summarize the metabolic functions of KLFs, as well as the networks of different KLF isoforms that jointly regulate metabolism in health and disease.

Krüppel-like factors in mammalian stem cells and development

Krüppel-like factors (KLFs) are a family of zinc-finger transcription factors that are found in many species. Recent studies have shown that KLFs play a fundamental role in regulating diverse biological processes such as cell proliferation, differentiation, development and regeneration. Of note, several KLFs are also crucial for maintaining pluripotency and, hence, have been linked to reprogramming and regenerative medicine approaches. Here, we review the crucial functions of KLFs in mammalian embryogenesis, stem cell biology and regeneration, as revealed by studies of animal models. We also highlight how KLFs have been implicated in human diseases and outline potential avenues for future research.

Maternal obesity programs mitochondrial and lipid metabolism gene expression in infant umbilical vein endothelial cells

BACKGROUND/OBJECTIVES

Maternal obesity increases risk for childhood obesity, but molecular mechanisms are not well understood. We hypothesized that primary umbilical vein endothelial cells (HUVEC) from infants of overweight and obese mothers would harbor transcriptional patterns reflecting offspring obesity risk.

SUBJECTS/METHODS

In this observational cohort study, we recruited 13 lean (pre-pregnancy body mass index (BMI) <25.0 kg m^-2) and 24 overweight-obese ('ov-ob', BMI⩾25.0 kg m^-2) women. We isolated primary HUVEC, and analyzed both gene expression (Primeview, Affymetrix) and cord blood levels of hormones and adipokines.

RESULTS

A total of 142 transcripts were differentially expressed in HUVEC from infants of overweight-obese mothers (false discovery rate, FDR<0.05). Pathway analysis revealed that genes involved in mitochondrial and lipid metabolism were negatively correlated with maternal BMI (FDR<0.05). To test whether these transcriptomic patterns were associated with distinct nutrient exposures in the setting of maternal obesity, we analyzed the cord blood lipidome and noted significant increases in the levels of total free fatty acids (lean: 95.5±37.1 μg ml^-1, ov-ob: 124.1±46.0 μg ml^-1, P=0.049), palmitate (lean: 34.5±12.7 μg ml^-1, ov-ob: 46.3±18.4 μg ml^-1, P=0.03) and stearate (lean: 20.8±8.2 μg ml^-1, ov-ob: 29.7±17.2 μg ml^-1, P=0.04), in infants of overweight-obese mothers.

CONCLUSIONS

Prenatal exposure to maternal obesity alters HUVEC expression of genes involved in mitochondrial and lipid metabolism, potentially reflecting developmentally programmed differences in oxidative and lipid metabolism.

Investigation of susceptibility genes triggering lachrymal/salivary gland lesion complications in Japanese patients with type 1 autoimmune pancreatitis

Autoimmune pancreatitis (AIP) is a unique form of chronic pancreatitis characterized by high serum IgG4 concentration and a variety of complicating extra-pancreatic lesions. In particular, lachrymal/salivary gland lesions tend to manifest in a highly active AIP disease state, and several genes are speculated to be associated with the onset of this complication. We therefore searched for candidate susceptibility genes related to lachrymal/salivary gland lesions in a genome-wide association study (GWAS) with the GeneChip Human Mapping 500k Array Set (Affymetrix, CA) that was followed by fine mapping of additional single nucleotide polymorphisms (SNPs) in strongly significant genes with TaqMan assays. Venous blood samples were obtained from 50 type 1 AIP patients with lachrymal/salivary gland lesions (A group) and 53 type 1 AIP patients without (B group). The mean values of IgG and IG4 were both significantly different (P<0.05) between the groups. SNPs that showed a significant association with the A group at the genome-wide level (P<0.0001) were identified and subsequently used in fine SNP mapping of candidate genes. In total, five SNPs had a positive association with complicated AIP (most notably rs2284932 [P=0.0000021]) and five SNPs possessed a negative association (particularly rs9371942 [P=0.00000039]). Among them, KLF7, FRMD4B, LOC101928923, and MPPED2 were further examined for complication susceptibility using additional SNPs that were not included in the GWAS. Individual genotyping of KLF7 rs2284932 revealed that the frequency of the minor C allele was significantly increased (P=0.00062, Pc=0.0018, OR=2.98, 95%CI=1.58-5.65) in group A. The minor T allele of rs4473559 in FRMD4 demonstrated a significant association in the A group (P=0.00015, OR=3.38, 95%CI=1.77-7.65). In the LOC101928923 gene, the frequency of the minor C allele of rs4379306 was significantly decreased in group A in both TaqMan and GWAS analyses. Lastly, the minor C allele of MPPED2 rs514644 carried a significantly increased risk of complications. These four genes may be linked with the onset of lachrymal/salivary gland lesions in type 1 AIP patients and require further study.

MiR-146b is a regulator of human visceral preadipocyte proliferation and differentiation and its expression is altered in human obesity

Visceral obesity is an independent risk factor for metabolic syndrome, and abnormal fat accumulation is linked to increases in the number and size of adipocytes. MiR-146b was a miRNA highly expressed in mature adipocytes while very lowly expressed in human mesenchymal stem cells (hMSCs) and human visceral preadipocytes (vHPA). In this paper, we mainly focused on the roles of miR-146b in adipogenesis. We found miR-146b could inhibit the proliferation of visceral preadipocytes and promote their differentiation. MiR-146b in human visceral adipocytes inhibited the expression of KLF7, a member of the Kruppel-like transcription factors, as demonstrated by a firefly luciferase reporter assay, indicating that KLF7 is a direct target of the endogenous miR-146b. MiR-146b expression was significantly altered in visceral and subcutaneous adipose tissues in human overweight and obese subjects, and in the epididymal fat tissues and brown fat tissues of diet-induced obese mice. Our data indicates that miR-146b may be a new therapeutic target against human visceral obesity and metabolic dysfunction.

Hypoxia induces a HIF-1α dependent signaling cascade to make a complex metabolic switch in SGBS-adipocytes

To elucidate the complex impact of hypoxia on adipose tissue, resulting in biased metabolism, insulin resistance and finally diabetes we used mature adipocytes derived from a Simpson-Golabi-Behmel syndrome patient for microarray analysis. We found a significantly increased transcription rate of genes involved in glycolysis and a striking association between the pattern of upregulated genes and disease biomarkers for diabetes mellitus and insulin resistance. Although their upregulation turned out to be HIF-1α-dependent, we identified further transcription factors mainly AP-1 components to play also an important role in hypoxia response. Analyzing the regulatory network of mentioned transcription factors and glycolysis targets we revealed a clear hint for directing glycolysis to glutathione and glycogen synthesis. This metabolic switch in adipocytes enables the cell to prevent oxidative damage in the short term but might induce lipogenesis and establish systemic metabolic disorders in the long run.

TT Mutant Homozygote of Kruppel-like Factor 5 Is a Key Factor for Increasing Basal Metabolic Rate and Resting Metabolic Rate in Korean Elementary School Children

We investigated the contribution of genetic variations of KLF5 to basal metabolic rate (BMR) and resting metabolic rate (RMR) and the inhibition of obesity in Korean children. A variation of KLF5 (rs3782933) was genotyped in 62 Korean children. Using multiple linear regression analysis, we developed a model to predict BMR in children. We divided them into several groups; normal versus overweight by body mass index (BMI) and low BMR versus high BMR by BMR. There were no differences in the distributions of alleles and genotypes between each group. The genetic variation of KLF5 gene showed a significant correlation with several clinical factors, such as BMR, muscle, low-density lipoprotein cholesterol, and insulin. Children with the TT had significantly higher BMR than those with CC (p = 0.030). The highest muscle was observed in the children with TT compared with CC (p = 0.032). The insulin and C-peptide values were higher in children with TT than those with CC (p= 0.029 vs. p = 0.004, respectively). In linear regression analysis, BMI and muscle mass were correlated with BMR, whereas insulin and C-peptide were not associated with BMR. In the high-BMR group, we observed that higher muscle, fat mass, and C-peptide affect the increase of BMR in children with TT (p < 0.001, p < 0.001, and p = 0.018, respectively), while Rohrer's index could explain the usual decrease in BMR (adjust r(2) = 1.000, p < 0.001, respectively). We identified a novel association between TT of KLF5 rs3782933 and BMR in Korean children. We could make better use of the variation within KLF5 in a future clinical intervention study of obesity.

Loss of Krüppel-like factor 3 (KLF3/BKLF) leads to upregulation of the insulin-sensitizing factor adipolin (FAM132A/CTRP12/C1qdc2)

Krüppel-like factor 3 (KLF3) is a transcriptional regulator that we have shown to be involved in the regulation of adipogenesis in vitro. Here, we report that KLF3-null mice are lean and protected from diet-induced obesity and glucose intolerance. On a chow diet, plasma levels of leptin are decreased, and adiponectin is increased. Despite significant reductions in body weight and adiposity, wild-type and knockout animals show equivalent energy intake, expenditure, and excretion. To investigate the molecular events underlying these observations, we used microarray analysis to compare gene expression in Klf3(+/+) and Klf3(-/-) tissues. We found that mRNA expression of Fam132a, which encodes a newly identified insulin-sensitizing adipokine, adipolin, is significantly upregulated in the absence of KLF3. We confirmed that KLF3 binds the Fam132a promoter in vitro and in vivo and that this leads to repression of promoter activity. Further, plasma adipolin levels were significantly increased in Klf3(-/-) mice compared with wild-type littermates. Boosting levels of adipolin via targeting of KLF3 offers a novel potential therapeutic strategy for the treatment of insulin resistance.

Klf7 modulates the differentiation and proliferation of chicken preadipocyte

Krüppel-like factor 7 (Klf7) has been extensively studied in the mammalian species, but its function in avian species is unclear. The objective of this study was to reveal the function of chicken Klf7 (Gallus gallus Klf7, gKlf7) in adipogenesis. The results of real-time reverse transcription polymerase chain reaction demonstrated that the relative mRNA level of chicken Klf7 (gKlf7/gβ-Actin) in the abdominal adipose tissue was significantly associated with the abdominal fat content and the age of broilers (P < 0.05), and gKlf7 was more highly expressed in preadipocytes than in mature adipocytes (P < 0.05). In addition, Oil red O staining showed that gKlf7 inhibited chicken preadipocyte differentiation, and MTT assay indicated that gKlf7 overexpression promoted preadipocyte proliferation. Additionally, luciferase assays showed that gKlf7 overexpression suppressed the chicken CCAAT/enhancer-binding protein α (C/ebpα), fatty acid synthase (Fasn), and lipoprotein lipase (Lpl) promoter activities (P < 0.05), and gKlf7 knockdown increased the chicken peroxisome proliferator-activated receptor γ (Pparγ), C/ebpα and fatty acid-binding protein 4 (Fabp4) promoter activities (P < 0.05). Together, our study demonstrated that chicken Klf7 inhibits preadipocyte differentiation and promotes preadipocyte proliferation.

Cloning, tissue expression and polymorphisms of chicken Krüppel-like factor 7 gene

Krüppel-like factor 7 (KLF7) has been extensively studied in mammalian species, but its role in birds is still unclear. In the current study, cloning and sequencing showed that the full-length coding region of chicken KLF7 (Gallus gallus KLF7, gKLF7) was 891 bp long, encoding 296 amino acids. In addition, real-time RT-PCR analysis showed that gKLF7 was broadly expressed in all 15 chicken tissues selected, and its expression was significantly different in spleen, proventriculus, abdominal fat, brain, leg muscle, gizzard and heart between fat and lean broilers at 7 weeks of age. Additionally, one novel single nucleotide polymorphism (SNP), XM_426569.3: c. A141G, was identified in the second exon of gKLF7. Association analysis showed that this locus was significantly associated with fatness traits in Arbor Acres broiler random population and the eighth generation of Northeast Agricultural University broiler lines divergently selected for abdominal fat content (NEAUHLF) population (P < 0.05). These results suggest that gKLF7 might be a candidate gene for chicken fatness traits.

Common variants at CDKAL1 and KLF9 are associated with body mass index in east Asian populations

Obesity is a disorder with a complex genetic etiology, and its epidemic is a worldwide problem. Although multiple genetic loci associated with body mass index, the most common measure of obesity, have been identified in European populations, few studies have focused on Asian populations. Here we report a genome-wide association study and replication studies with 62,245 east Asian subjects, which identified two new body mass index-associated loci in the CDKAL1 locus at 6p22 (rs2206734, P = 1.4 × 10(-11)) and the KLF9 locus at 9q21 (rs11142387, P = 1.3 × 10(-9)), as well as several previously reported loci (the SEC16B, BDNF, FTO, MC4R and GIPR loci, P < 5.0 × 10(-8)). We subsequently performed gene-gene interaction analyses and identified an interaction (P = 2.0 × 10(-8)) between a SNP in the KLF9 locus (rs11142387) and one in the MSTN (also known as GDF8) locus at 2q32 (rs13034723). These findings should provide useful insights into the etiology of obesity.

Genetics of adipose tissue biology

Adipose tissue morphology and release of free fatty acids, as well as peptide hormones, are believed to contribute to obesity and related metabolic disorders. These adipose tissue phenotypes are influenced by adiposity, but there is also a strong hereditary impact. Polymorphisms in numerous adipose-expressed genes have been evaluated for association with adipocyte and clinical phenotypes. In our opinion, some results are convincing. Thus ADRB2 and GPR74 genes are associated with adipocyte lipolysis, GPR74 also with BMI; PPARG and SREBP1, which promote adipogenesis and lipid storage, are associated with T2D and possible adiposity; ADIPOQ and ARL15 are associated with circulating levels of adiponectin, ARL15 also with coronary heart disease. We anticipate that the use of complementary approaches such as expression profiling and RNAi screening, and studies of additional levels of gene regulation, that is, miRNA and epigenetics, will be important to unravel the genetics of adipose tissue function.

Mammalian Krüppel-like factors in health and diseases

The Krüppel-like factor (KLF) family of transcription factors regulates diverse biological processes that include proliferation, differentiation, growth, development, survival, and responses to external stress. Seventeen mammalian KLFs have been identified, and numerous studies have been published that describe their basic biology and contribution to human diseases. KLF proteins have received much attention because of their involvement in the development and homeostasis of numerous organ systems. KLFs are critical regulators of physiological systems that include the cardiovascular, digestive, respiratory, hematological, and immune systems and are involved in disorders such as obesity, cardiovascular disease, cancer, and inflammatory conditions. Furthermore, KLFs play an important role in reprogramming somatic cells into induced pluripotent stem (iPS) cells and maintaining the pluripotent state of embryonic stem cells. As research on KLF proteins progresses, additional KLF functions and associations with disease are likely to be discovered. Here, we review the current knowledge of KLF proteins and describe common attributes of their biochemical and physiological functions and their pathophysiological roles.

Recent progress in the genetics of common obesity

The genetic contribution to interindividual variation in common obesity has been estimated at 40-70%. Yet, despite a relatively high heritability, the search for obesity susceptibility genes has been an arduous task. This paper reviews recent progress made in the obesity genetics field with an emphasis on established obesity susceptibility loci identified through candidate gene as well as genome-wide studies. For the last 15 years, candidate gene and genome-wide linkage studies have been the two main genetic epidemiological approaches to identify genetic loci for common traits, yet progress has been slow and success limited. Only recently have candidate gene studies started to succeed; by means of large-scale studies and meta-analyses at least five variants in four candidate genes have been found to be robustly associated with obesity-related traits. Genome-wide linkage studies, however, have so far not been able to pinpoint genetic loci for common obesity. The genome-wide association approach, which has become available in recent years, has dramatically changed the pace of gene discoveries for common disease, including obesity. Three waves of large-scale high-density genome-wide association studies have already discovered at least 15 previously unanticipated genetic loci incontrovertibly associated with body mass index and extreme obesity risk. Although the combined contribution of these loci to the variation in obesity risk at the population level is small and their predictive value is typically low, these recently discovered loci are set to improve fundamentally our insights into the pathophysiology of obesity.

The genetic contribution to non-syndromic human obesity

The last few years have seen major advances in common non-syndromic obesity research, much of it the result of genetic studies. This Review outlines the competing hypotheses about the mechanisms underlying the genetic and physiological basis of obesity, and then examines the recent explosion of genetic association studies that have yielded insights into obesity, both at the candidate gene level and the genome-wide level. With obesity genetics now entering the post-genome-wide association scan era, the obvious question is how to improve the results obtained so far using single nucleotide polymorphism markers and how to move successfully into the other areas of genomic variation that may be associated with common obesity.