DPP4 gene DNA methylation in the omentum is associated with its gene expression and plasma lipid profile in severe obesity

Whey protein hydrolysates improve high-fat-diet-induced obesity by modulating the brain-peripheral axis of GLP-1 through inhibition of DPP-4 function in mice

PURPOSE

Obesity is a growing global health concern. Recent literature indicates a prominent role of glucagon-like peptide-1 (GLP-1) in glucose metabolism and food intake. The synergistic action of GLP-1 in the gut and brain is responsible for its satiety-inducing effect, suggesting that upregulation of active GLP-1 levels could be an alternative strategy to combat obesity. Dipeptidyl peptidase-4 (DPP-4) is an exopeptidase known to inactivate GLP-1, suggesting that its inhibition could be a crucial strategy for effectively extending the half-life of endogenous GLP-1. Peptides derived from partial hydrolysis of dietary proteins are gaining traction due to their inhibitory activity on DPP-4.

METHODS

Whey protein hydrolysate from bovine milk (bmWPH) was produced using simulated in situ digestion, purified using RP-HPLC, and characterized for DPP-4 inhibition. The antiadipogenic and antiobesity activity of bmWPH was then studied in 3T3-L1 preadipocytes and high-fat diet-induced obesity (HFD) mice model, respectively.

RESULTS

The dose-dependent inhibitory effect of bmWPH on the catalytic activity of DPP-4 was observed. Additionally, bmWPH suppressed adipogenic transcription factors and DPP-4 protein levels, leading to a negative effect on preadipocyte differentiation. In an HFD mice model, co-administration of WPH for 20 weeks downregulated adipogenic transcription factors, resulting in a concomitant reduction in whole body weight and adipose tissues. Mice fed with bmWPH also showed a marked reduction in DPP-4 levels in WAT, liver, and serum. Furthermore, HFD mice fed with bmWPH exhibited increased serum and brain GLP levels, which led to a significant decrease in food intake.

CONCLUSION

In conclusion, bmWPH reduces body weight in HFD mice by suppressing appetite through GLP-1, a satiety-inducing hormone, in both the brain and peripheral circulation. This effect is achieved through modulation of both the catalytic and non-catalytic activity of DPP-4.

Dipeptidyl Peptidase 4 (DPP4) as A Novel Adipokine: Role in Metabolism and Fat Homeostasis

Dipeptidyl peptidase 4 (DPP4) is a molecule implicated in the regulation of metabolic homeostasis and inflammatory processes, and it exerts its main action through its enzymatic activity. DPP4 represents the enzyme most involved in the catabolism of incretin hormones; thus, its activity impacts appetite, energy balance, and the fine regulation of glucose homeostasis. Indeed, DPP4 inhibitors represent a class of antidiabetic agents widely used for the treatment of Type 2 diabetes mellitus (T2DM). DPP4 also acts as an adipokine and is mainly secreted by the adipose tissue, mostly from mature adipocytes of the visceral compartment, where it exerts autocrine and paracrine activities. DPP4 can disrupt insulin signaling within the adipocyte and in other target cells and tissues, where it also favors the development of a proinflammatory environment. This is likely at the basis of the presence of elevated circulating DPP4 levels in several metabolic diseases. In this review, we summarize the most recent evidence of the role of the DPP4 as an adipokine-regulating glucose/insulin metabolism and fat homeostasis, with a particular focus on clinical outcomes associated with its increased secretion in the presence of adipose tissue accumulation and dysfunction.

Potential Therapeutic Agents That Target ATP Binding Cassette A1 (ABCA1) Gene Expression

The cholesterol efflux protein ATP binding cassette protein A1 (ABCA) and apolipoprotein A1 (apo A1) are key constituents in the process of reverse-cholesterol transport (RCT), whereby excess cholesterol in the periphery is transported to the liver where it can be converted primarily to bile acids for either use in digestion or excreted. Due to their essential roles in RCT, numerous studies have been conducted in cells, mice, and humans to more thoroughly understand the pathways that regulate their expression and activity with the goal of developing therapeutics that enhance RCT to reduce the risk of cardiovascular disease. Many of the drugs and natural compounds examined target several transcription factors critical for ABCA1 expression in both macrophages and the liver. Likewise, several miRNAs target not only ABCA1 but also the same transcription factors that are critical for its high expression. However, after years of research and many preclinical and clinical trials, only a few leads have proven beneficial in this regard. In this review we discuss the various transcription factors that serve as drug targets for ABCA1 and provide an update on some important leads.

Association of the rs17574 DPP4 Polymorphism with Premature Coronary Artery Disease in Diabetic Patients: Results from the Cohort of the GEA Mexican Study

Previously, it has been reported that hypoalphalipoproteinemia (HA) is associated with rs17574 DDP4 polymorphism. Considering that in diabetic patients, HA is often present and is a risk factor for premature coronary artery disease (pCAD), the study aimed to evaluate the association of this polymorphism with pCAD in diabetic individuals. We genotyped the rs17574 polymorphism in 405 pCAD patients with T2DM, 736 without T2DM, and 852 normoglycemic individuals without pCAD and T2DM as controls. Serum DPP4 concentration was available in 818 controls, 669 pCAD without T2DM, and 339 pCAD with T2DM. The rs17574 polymorphism was associated with lower risk of pCAD (padditive = 0.007; pdominant = 0.003, pheterozygote = 0.003, pcodominant1 = 0.003). In pCAD with T2DM patients, DPP4 levels were lower when compared with controls (p < 0.001). In the whole sample, individuals with the rs17574 GG genotype have the lowest protein levels compared with AG and AA (p = 0.039) carriers. However, when the same analysis was repeated separately in all groups, a significant difference was observed in the pCAD with T2DM patients; carriers of the GG genotype had the lowest protein levels compared with AG and AA (p = 0.037) genotypes. Our results suggest that in diabetic patients, the rs17574G DPP4 allele could be considered as a protective genetic marker for pCAD. DPP4 concentrations were lower in the diabetic pCAD patients, and the rs17574GG carriers had the lowest protein levels.

Low levels of soluble DPP4 among Saudis may have constituted a risk factor for MERS endemicity

Most of the cases of Middle East respiratory syndrome coronavirus (MERS-CoV) were reported in Saudi Arabia. Dipeptidyl peptidase-4 (DPP4) was identified as the receptor for the virus. The level of soluble DPP4 (sDPP4) was found to be reduced in MERS-CoV infected patients while high levels of sDPP4 were suggested to be protective against MERS-CoV in animal models. We investigated whether the Saudi population has lower levels of sDPP4 which makes them more susceptible to MERS-CoV infection and, therefore, could explain the larger number of cases from the country. Blood samples were collected from 219 Saudi blood donors and 200 blood donors from other ethnic groups. The plasma level of sDPP4 was measured by ELISA and the following SNPs in the DPP4 gene; rs35128070, rs1861978, rs79700168, and rs17574, were genotyped by TaqMan SNP genotyping assay. The average level of plasma sDDP4 was significantly lower in Saudis than other Arabs and non-Arabs (P value 0.0003 and 0.012, respectively). The genotypes AG of rs35128070 and GT of rs1861978 were significantly associated with lower sDPP4 among Saudis (P value 0.002 for each). While both genotypes AA and AG of rs79700168 and rs17574 were associated with significantly lower average sDPP4 level in Saudis compared to other ethnic groups (P value 0.031 and 0.032, and 0.027 and 0.014, respectively). Herein, we report that the Saudi population has lower levels of plasma sDPP4 than other ethnic groups, which is associated with genetic variants in the DPP4 gene. This may have contributed to increase the susceptibility of the Saudi population to MERS-CoV infection and could be a factor in the long-lasting persistence of the virus in the country.

The Expression of Genes Related to Lipid Metabolism and Metabolic Disorders in Children before and after Hematopoietic Stem Cell Transplantation-A Prospective Observational Study

Metabolic disorders in children after hematopoietic stem cell transplantation (HSCT) are poorly characterized. However, it is known that dyslipidemia and insulin resistance are particularly common in these patients. We conducted a prospective study of 27 patients treated with HSCT to assess the possibility of predicting these abnormalities. We measured gene expressions using a microarray technique to identify differences in expression of genes associated with lipid metabolism before and after HSCT. In patients treated with HSCT, total cholesterol levels were significantly higher after the procedure compared with the values before HSCT. Microarray analysis revealed statistically significant differences in expressions of three genes, DPP4, PLAG1, and SCD, after applying the Benjamini-Hochberg procedure (pBH < 0.05). In multiple logistic regression, the increase of DPP4 gene expression before HCST (as well as its change between pre- and post-HSCT status) was associated with dyslipidemia. In children treated with HSCT, the burden of lipid disorders in short-term follow-up seems to be lower than before the procedure. The expression pattern of DPP4 is linked with dyslipidemia after the transplantation.

The rs12617336 and rs17574 Dipeptidyl Peptidase-4 Polymorphisms Are Associated With Hypoalphalipoproteinemia and Dipeptidyl Peptidase-4 Serum Levels: A Case-Control Study of the Genetics of Atherosclerotic Disease (GEA) Cohort

Dipeptidyl peptidase-4 (DPP4) can influence lipid homeostasis and atherosclerosis progression. We aimed to assess the association of DPP4 gene polymorphisms with hypoalphalipoproteinemia and DPP4 serum levels, in a cohort of Mexican individuals. Five DPP4 polymorphisms (rs12617336, rs12617656, rs1558957, and rs3788979, and rs17574) were genotyped in 748 participants with and 745 without hypoalphalipoproteinemia. The associations were evaluated using logistic regression analyses. Under inheritance models adjusted for confounding variables, the rs12617336 (OR = 0.22, P heterozygote = 0.001) and rs17574 (OR = 0.78, P additive = 0.022; OR = 0.73, P dominant = 0.012; OR = 0.73, P heterozygote = 0.017; OR = 0.72, P codominant 1 = 0.014) minor alleles were associated with a low risk of hypoalphalipoproteinemia. After the correction for multiple comparisons, the associations were marginal except the association of the rs12617336 that remaining significant. Additionally, both DPP4 minor alleles were associated with protection for the presence of insulin resistance (IR) (OR = 0.17, P heterozygote = 0.019 for rs12617336 and OR = 0.75, P additive = 0.049 for rs17574). The rs12617336 minor allele was also associated with a low risk of hyperinsulinemia (OR = 0.11, P heterozygote = 0.006). Differences in DPP4 levels were observed in individuals with rs17574 genotypes, the rs17574 GG genotype individuals had the lowest levels. Our data suggest that rs12617336 and rs17574 DPP4 minor alleles could be envisaged as protective genetic markers for hypoalphalipoproteinemia, IR, and hyperinsulinemia. The rs17574 GG genotype was associated with the lowest DPP4 levels.

Assessment of risk conferred by coding and regulatory variations of TMPRSS2 and CD26 in susceptibility to SARS-CoV-2 infection in human

At present, more than 200 countries and territories are directly affected by the coronavirus disease-19 (COVID-19) pandemic. Incidence and case fatality rate are significantly higher among elderly individuals (age > 60 years), type 2 diabetes and hypertension patients. Cellular receptor ACE2, serine protease TMPRSS2 and exopeptidase CD26 (also known as DPP4) are the three membrane bound proteins potentially implicated in SARS-CoV-2 infection. We hypothesised that common variants from TMPRSS2 and CD26 may play critical role in infection susceptibility of predisposed population or group of individuals. Coding (missense) and regulatory variants from TMPRSS2 and CD26 were studied across 26 global populations. Two missense and five regulatory SNPs were identified to have differential allelic frequency. Significant linkage disequilibrium (LD) signature was observed in different populations. Modelled protein‒protein interaction (PPI) predicted strong molecular interaction between these two receptors and SARS-CoV-2 spike protein (S1 domain). However, two missense SNPs, rs12329760 (TMPRSS2) and rs1129599 (CD26), were not found to be involved physically in the said interaction. Four regulatory variants (rs112657409, rs11910678, rs77675406 and rs713400) from TMPRSS2 were found to influence the expression of TMPRSS2 and pathologically relevant MX1. rs13015258 a 5′ UTR variant from CD26 have significant role in regulation of expression of key regulatory genes that could be involved in SARS-CoV-2 internalization. Overexpression of CD26 through epigenetic modification at rs13015258-C allele was found critical and could explain the higher SARS-CoV-2 infected fatality rate among type 2 diabetes.

More than just an enzyme: Dipeptidyl peptidase-4 (DPP-4) and its association with diabetic kidney remodelling

PURPOSE OF THE REVIEW

This review article discusses recent advances in the mechanism of dipeptidyl peptidase-4 (DPP-4) actions in renal diseases, especially diabetic kidney fibrosis, and summarizes anti-fibrotic functions of various DPP-4 inhibitors in diabetic nephropathy (DN).

RECENT FINDINGS

DN is a common complication of diabetes and is a leading cause of the end-stage renal disease (ESRD). DPP-4 is a member of serine proteases, and more than 30 substrates have been identified that act via several biochemical messengers in a variety of tissues including kidney. Intriguingly, DPP-4 actions on the diabetic kidney is a complex mechanism, and a variety of pathways are involved including increasing GLP-1/SDF-1, disrupting AGE-RAGE pathways, and integrin-β- and TGF-β-Smad-mediated signalling pathways that finally lead to endothelial to mesenchymal transition. Interestingly, an array of DPP-4 inhibitors is well recognized as oral drugs to treat type 2 diabetic (T2D) patients, which promote better glycemic control. Furthermore, recent experimental and preclinical data reveal that DPP-4 inhibitors may also exhibit protective effects in renal disease progression including anti-fibrotic effects in the diabetic kidney by attenuating above signalling cascade(s), either singly or as a combinatorial effect. In this review, we discussed the anti-fibrotic effects of DPP-4 inhibitors based on recent reports along with the possible mechanism of actions and future perspectives to underscore the beneficial effects of DPP-4 inhibitors in DN.

SUMMARY

With recent experimental, preclinical, and clinical evidence, we summarized DPP-4 activities and its mechanism of actions in diabetic kidney diseases. A knowledge gap of DPP-4 inhibition in controlling renal fibrosis in DN has also been postulated in this review for future research perspectives.

Pharmacology of dipeptidyl peptidase-4 inhibitors and its use in the management of metabolic syndrome: a comprehensive review on drug repositioning

OBJECTIVES

Despite advances in our understanding of metabolic syndrome (MetS) and the treatment of each of its components separately, currently there is no single therapy approved to manage it as a single condition. Since multi-drug treatment increases drug interactions, decreases patient compliance and increases health costs, it is important to introduce single therapies that improve all of the MetS components.

EVIDENCE ACQUISITION

We conducted a PubMed, Scopus, Google Scholar, Web of Science, US FDA, utdo.ir and clinicaltrial.gov search, gathered the most relevant preclinical and clinical studies that have been published since 2010, and discussed the beneficial effects of dipeptidyl peptidase (DPP)-4 inhibitors to prevent and treat different constituent of the MetS as a single therapy. Furthermore, the pharmacology of DPP-4 inhibitors, focusing on pharmacodynamics, pharmacokinetics, drug interactions and their side effects are also reviewed.

RESULTS

DPP-4 inhibitors or gliptins are a new class of oral anti-diabetic drugs that seem safe drugs with no severe side effects, commonly GI disturbance, infection and inflammatory bowel disease. They increase mass and function of pancreatic β-cells, and insulin sensitivity in liver, muscle and adipose tissue. It has been noted that gliptin therapy decreases dyslipidemia. DPP-4 inhibitors increase fatty oxidation, and cholesterol efflux, and decrease hepatic triglyceride synthase and de novo lipogenesis. They delay gastric emptying time and lead to satiety. Besides, gliptin therapy has anti-inflammatory and anti-atherogenic impacts, and improves endothelial function and reduces vascular stiffness.

CONCLUSION

The gathered data prove the efficacy of DPP-4 inhibitors in managing MetS in some levels beyond anti-diabetic effects. This review could be a lead for designing new DPP-4 inhibitors with greatest effects on MetS in future. Introducing drugs with polypharmacologic effects could increase the patient's compliance and decrease the health cost that there is not in multi-drug therapy. Graphical abstract ᅟ.

Downregulation of Dipeptidyl Peptidase 4 Accelerates Progression to Castration-Resistant Prostate Cancer

The standard treatment for metastatic prostate cancer, androgen deprivation therapy (ADT), is designed to suppress androgen receptor (AR) activity. However, men invariably progress to castration-resistant prostate cancer (CRPC), and AR reactivation contributes to progression in most cases. To identify mechanisms that may drive CRPC, we examined a VCaP prostate cancer xenograft model as tumors progressed from initial androgen sensitivity prior to castration to castration resistance and then on to relapse after combined therapy with further AR-targeted drugs (abiraterone plus enzalutamide). AR activity persisted in castration-resistant and abiraterone/enzalutamide-resistant xenografts and was associated with increased expression of the AR gene and the AR-V7 splice variant. We then assessed expression of individual AR-regulated genes to identify those that persisted, thereby contributing to tumor growth, versus those that decreased and may therefore exhibit tumor suppressor activities. The most significantly decreased AR target gene was dipeptidyl peptidase 4 (DPP4), which encodes a membrane-anchored protein that cleaves dipeptides from multiple growth factors, resulting in their increased degradation. DPP4 mRNA and protein were also decreased in clinical CRPC cases, and inhibition of DPP4 with sitagliptin enhanced the growth of prostate cancer xenografts following castration. Significantly, DPP4 inhibitors are frequently used to treat type 2 diabetes as they increase insulin secretion. Together, these results implicate DPP4 as an AR-regulated tumor suppressor gene whose loss enhances growth factor activity and suggest that treatment with DPP4 inhibitors may accelerate emergence of resistance to ADT.Significance: These findings identify DPP4 as an AR-stimulated tumor suppressor gene that is downregulated during progression to castration-resistant prostate cancer, warning that treatment with DPP4 inhibitors, commonly used to treat type 2 diabetes, may accelerate prostate cancer progression following androgen deprivation therapy. Cancer Res; 78(22); 6354-62. ©2018 AACR.

Clinical and Physiological Characterization of Elevated Plasma Glucagon-Like Peptide-1 Levels (Hyperglipemia) in a Dipeptidyl Peptidase IV Mutation Carrier

The clinical application of dipeptidyl peptidase IV inhibitors (DPP4i) increasing active glucagon-like peptide-1 (AGLP-1) levels has been linked to pancreatitis, pancreatic tumors, and cardiovascular events. However, DPP4 mutations in humans or the long-term outcomes of high glucagon-like peptide-1 (GLP-1) level exposure have not been reported. A trio family with a proband showing an extremely high AGLP-1 level [defined here as hyperglipemia (hyper-glucagon-like peptide-1-emia)] were conducted whole-exome sequencing for potential pathogenic genetic defects. One novel DPP4 mutation, p.V486M (c.1456 G>A), was identified in the proband and showed damaged enzymatic activity of DPP4. Ex vivo functional study further showed that the serum from the proband markedly enhanced insulin production of primary rat islet cells. Furthermore, V486M variant and another eight DPP4 variants were identified in our in-home database and seven showed decreased enzymatic activities than wild-type DPP4, consistent with their alterations in their protein expression levels. Of note, the levels of glucose, lipids, and tumor markers (especially for CA15-3 and CA125), increased gradually in the proband during a 4-year follow-up period, although no abnormal physical symptoms or imaging results were observed at present. The other two old carriers in the pedigree both had type 2 diabetes, and one of them also had hyperlipidemia and myocarditis. We first identified hyperglipemia in a female subject harboring a loss-of-function DPP4 mutation with decreased DPP4 activity. Other sporadic DPP4 mutations verified the low-frequent occurrence of genetic inhibition of DPP4 activity, at least in the Chinese population studied. These results may provide new evidence for evaluation of the potential long-term effects of DPP4i and GLP-1 analogs.

Dipeptidyl Peptidase-4 and Adolescent Idiopathic Scoliosis: Expression in Osteoblasts

It has been proposed that girls with adolescent idiopathic scoliosis (AIS) tend to have a taller stature and a lower body mass index. Energy homeostasis, that is known to affect bone growth, could contribute to these characteristics. In circulation, dipeptidyl peptidase-4 (DPP-4) inactivates glucagon-like peptide-1 (GLP-1), an incretin that promotes insulin secretion and sensitivity. Our objectives were to investigate DPP-4 status in plasma and in osteoblasts of AIS subjects and controls and to evaluate the regulatory role of metabolic effectors on DPP-4 expression. DPP-4 activity was assessed in plasma of 113 girls and 62 age-matched controls. Osteoblasts were isolated from bone specimens of AIS patients and controls. Human cells were incubated with glucose, insulin, GLP-1 and butyrate. Gene and protein expressions were evaluated by RT-qPCR and Western blot. Our results showed 14% inferior plasma DPP-4 activity in AIS patients when compared to healthy controls (P = 0.0357). Similarly, osteoblasts derived from AIS subjects had lower DPP-4 gene and protein expression than controls by 90.5% and 57.1% respectively (P < 0.009). DPP-4 expression was regulated in a different manner in osteoblasts isolated from AIS participants compared to controls. Our results suggest a role for incretins in AIS development and severity.

Hepatic DPP4 DNA Methylation Associates With Fatty Liver

Hepatic DPP4 expression is elevated in subjects with ectopic fat accumulation in the liver. However, whether increased dipeptidyl peptidase 4 (DPP4) is involved in the pathogenesis or is rather a consequence of metabolic disease is not known. We therefore studied the transcriptional regulation of hepatic Dpp4 in young mice prone to diet-induced obesity. Already at 6 weeks of age, expression of hepatic Dpp4 was increased in mice with high weight gain, independent of liver fat content. In the same animals, methylation of four intronic CpG sites was decreased, amplifying glucose-induced transcription of hepatic Dpp4 In older mice, hepatic triglyceride content was increased only in animals with elevated Dpp4 expression. Expression and release of DPP4 were markedly higher in the liver compared with adipose depots. Analysis of human liver biopsy specimens revealed a correlation of DPP4 expression and DNA methylation to stages of hepatosteatosis and nonalcoholic steatohepatitis. In summary, our results indicate a crucial role of the liver in participation to systemic DPP4 levels. Furthermore, the data show that glucose-induced expression of Dpp4 in the liver is facilitated by demethylation of the Dpp4 gene early in life. This might contribute to early deteriorations in hepatic function, which in turn result in metabolic disease such as hepatosteatosis later in life.

The integration of epigenetics and genetics in nutrition research for CVD risk factors

There is increasing evidence documenting gene-by-environment (G × E) interactions for CVD related traits. However, the underlying mechanisms are still unclear. DNA methylation may represent one of such potential mechanisms. The objective of this review paper is to summarise the current evidence supporting the interplay among DNA methylation, genetic variants, and environmental factors, specifically (1) the association between SNP and DNA methylation; (2) the role that DNA methylation plays in G × E interactions. The current evidence supports the notion that genotype-dependent methylation may account, in part, for the mechanisms underlying observed G × E interactions in loci such asAPOE, IL6and ATP-binding cassette A1. However, these findings should be validated using intervention studies with high level of scientific evidence. The ultimate goal is to apply the knowledge and the technology generated by this research towards genetically based strategies for the development of personalised nutrition and medicine.

Association between DPP4 gene polymorphism and serum lipid levels in Chinese type 2 diabetes individuals

OBJECTIVE

The goal of the genetic investigation was to identify the associations of serum lipid levels and DPP-4 variants in Chinese type 2 diabetes patients.

METHODS

We detected four variants of the DPP4 gene in 190 Chinese individuals with type 2 diabetes and tested for an association with dyslipidemia in 82 selected samples. Data including basic information, HbA1c, FPG, serum lipid parameters were collected. Statistical analysis was performed by SPSS 13.0 through ANOVA and χ² test.

RESULTS

The genetic polymorphism of rs4664443, rs3788979, rs7608798 and rs1558957 in Chinese type 2 diabetes were consistent with Hardy-Weinberg equilibrium. The CT genotype of rs4664443 suffered from higher serum TG (P=0.013), LDL (P=0.044) and ApoB (P=0.006) levels, whereas the TT genotype of rs7608798 exhibited a lower serum TG level (P=0.037). For rs3788979, the serum TG level (P=0.034) and BMI (P=0.04) were significantly different among genotypes. Moreover, serum TG and TC levels and BMI showed a positive correlation with the number unfavorable alleles, and individuals with more than two unfavorable alleles had higher TG (P=0.004), TC (P=0.011), and BMI (P=0.044) values.

CONCLUSIONS

This is the first study to investigate DPP4 allelic distributions and their association with dyslipidemia in Chinese type 2 diabetes patients, which may have clinical significance.

Epigenetics of Lipid Phenotypes

Dyslipidemia is a well-established risk factor for cardiovascular disease, the main cause of death worldwide. Blood lipid profiles are patterned by both genetic and environmental factors. In recent years, epigenetics has emerged as a paradigm that unifies these influences. In this review, we have summarized the latest evidence implicating epigenetic mechanisms-DNA methylation, histone modification, and regulation by RNAs-in lipid homeostasis. Key findings have emerged in a number of novel epigenetic loci located in biologically plausible genes (e.g. CPT1A, ABCG1, SREBF1, and others), as well as microRNA-33a/b. Evidence from animal and cell culture models suggests a complex interplay between different classes of epigenetic processes in the lipid-related genomic regions. While epigenetic findings hold the potential to explain the interindividual variability in lipid profiles as well as the underlying mechanisms, they have yet to be translated into effective therapies for dyslipidemia.

Clinical and genetic predictors of dipeptidyl peptidase-4 inhibitor treatment response in Type 2 diabetes mellitus

AIM

To determine the clinical and genetic predictors of the dipeptidyl peptidase-4 (DPP-4) inhibitor treatment response in Type 2 diabetes mellitus (T2DM) patients.

PATIENTS & METHODS

DPP4, WFS1 and KCNJ11 gene polymorphisms were genotyped in a cohort study of 662 T2DM patients treated with DPP-4 inhibitors sitagliptin, vildagliptin or linagliptin. Genotyping was performed by Applied Biosystems TaqMan SNP genotyping assay.

RESULTS

Patients with triglyceride levels less than 1.7 mmol/l (odds ratio [OR]: 2.2.; 95% CI: 1.031-4.723), diastolic blood pressure (DBP) less than 90 mmHg (OR: 1.7; 95% CI: 1.009-2.892) and KCNJ11 rs2285676 (genotype CC) (OR: 2.0; 95% CI: 1.025-3.767) were more likely to response to DPP-4 inhibitor treatment compared with other patients, as measured by HbA1c levels.

CONCLUSION

Triglycerides, DBP and KCNJ11 rs2285676 are predictors of the DPP-4 inhibitor treatment response in T2DM patients.

Association of DPP4 Gene Polymorphisms with Type 2 Diabetes Mellitus in Malaysian Subjects

Background

Genetic polymorphisms of the Dipeptidyl Peptidase 4 (DPP4) gene may play a role in the etiology of type 2 diabetes mellitus (T2DM). This study aimed to investigate the possible association of single nucleotide polymorphisms (SNPs) of the DPP4 gene in Malaysian subjects with T2DM and evaluated whether they had an effect on the serum levels of soluble dipeptidyl peptidase 4 (sDPP-IV).

Method

Ten DPP4 SNPs were genotyped by TaqMan genotyping assays in 314 subjects with T2DM and 235 controls. Of these, 71 metabolic syndrome (MetS) subjects were excluded from subsequent analysis. The odds ratios (ORs) and their 95% confidence interval (CIs) were calculated using multiple logistic regression for the association between the SNPs of DPP4 and T2DM. In addition, the serum levels of sDPP-IV were investigated to evaluate the association of the SNPs of DPP4 with the sDPP-IV levels.

Results

Dominant, recessive, and additive genetic models were employed to test the association of DPP4 polymorphisms with T2DM, after adjusting for age, race, gender and BMI. The rs12617656 was associated with T2DM in Malaysian subjects in the recessive genetic model (OR = 1.98, p = 0.006), dominant model (OR = 1.95, p = 0.008), and additive model (OR = 1.63, p = 0.001). This association was more pronounced among Malaysian Indians, recessive (OR = 3.21, p = 0.019), dominant OR = 3.72, p = 0.003) and additive model (OR = 2.29, p = 0.0009). The additive genetic model showed that DPP4 rs4664443 and rs7633162 polymorphisms were associated with T2DM (OR = 1.53, p = 0.039), and (OR = 1.42, p = 0.020), respectively. In addition, the rs4664443 G>A polymorphism was associated with increased sDPP-IV levels (p = 0.042) in T2DM subjects.

Conclusions

DPP4 polymorphisms were associated with T2DM in Malaysian subjects, and linked to variations in sDPP-IV levels. In addition, these associations were more pronounced among Malaysian Indian subjects.

Association between CXCL10 and DPP4 Gene Polymorphisms and a Complementary Role for Unfavorable IL28B Genotype in Prediction of Treatment Response in Thai Patients with Chronic Hepatitis C Virus Infection

Pretreatment serum levels of interferon-γ-inducible protein-10 (IP-10, CXCL10) and dipeptidyl peptidase-4 (DPP IV) predict treatment response in chronic hepatitis C (CHC). The association between functional genetic polymorphisms of CXCL10 and DPP4 and treatment outcome has not previously been studied. This study aimed to determine the association between genetic variations of CXCL10 and DPP4 and the outcome of treatment with pegylated interferon-α (PEG-IFN-α) based therapy in Thai patients with CHC. 602 Thai patients with CHC treated using a PEG-IFN-α based regimen were genotyped for CXCL10 rs56061981 G>A and IL28B rs12979860 C>T. In addition, in patients infected with CHC genotype 1, DPP4 (rs13015258 A>C, rs17848916 T>C, rs41268649 G>A, and rs 17574 T>C) were genotyped. Correlations between single nucleotide polymorphisms, genotype, and treatment response were analyzed. The rate of sustained virologic response (SVR) was higher for the CC genotype of IL28B rs12979860 polymorphisms than for non-CC in both genotype 1 (60.6% vs. 29.4%, P < 0.001) and non-genotype 1 (69.4% vs. 49.1%, P < 0.05) CHC. SVR was not associated with the CXCL10 gene variant in all viral genotypes or DPP4 gene polymorphisms in viral genotype1. Multivariate analysis revealed IL28B rs12979860 CC genotype (OR = 3.12; 95% CI, 1.72-5.67; P < 0.001), hepatitis C virus RNA < 400,000 IU/ml (OR = 2.21; 95% CI, 1.22-3.99, P < 0.05), age < 45 years (OR = 2.03; 95% CI, 1.11-3.68; P < 0.05), and liver fibrosis stage 0-1 (OR = 1.64; 95% CI, 1.01-2.65, P < 0.05) were independent factors for SVR. Unfavorable IL28B rs12979860 CT or TT genotypes with the CXCL10 rs56061981 non-GG genotype were associated with a higher SVR than GG genotype (66.7% vs. 33.0%, P = 0.004) in viral genotype 1. In Thai CHC genotype 1 infected patients with an unfavorable IL28B rs12979860 CT/TT genotype, the complementary CXCL10 polymorphism strongly enhances prediction of treatment response.

Incretin-based therapies for obesity treatment

Currently, obesity and its associated complications are considered major public health problems worldwide. Because the causes are multifactorial and complex, different treatment methods are used, which include diet and exercise, as well as the use of drugs, although they can have adverse side effects. A new target for the treatment of obesity may be the incretin system, which consists of hormones that seem to contribute to weight loss. In this sense, some studies have shown a relationship between weight loss and drugs related to incretin system, including glucagon-like peptide-1 (GLP-1) agonists and dipeptidyl peptidase-4 (DPP-4) inhibitors. The objective of this review is to summarize the association between the incretin system and obesity treatment.

DPP4 in Diabetes

Dipeptidyl-peptidase 4 (DPP4) is a glycoprotein of 110 kDa, which is ubiquitously expressed on the surface of a variety of cells. This exopeptidase selectively cleaves N-terminal dipeptides from a variety of substrates, including cytokines, growth factors, neuropeptides, and the incretin hormones. Expression of DPP4 is substantially dysregulated in a variety of disease states including inflammation, cancer, obesity, and diabetes. Since the incretin hormones, glucagon-like peptide-1 and glucose-dependent insulinotropic polypeptide (GIP), are major regulators of post-prandial insulin secretion, inhibition of DPP4 by the gliptin family of drugs has gained considerable interest for the therapy of type 2 diabetic patients. In this review, we summarize the current knowledge on the DPP4–incretin axis and evaluate most recent findings on DPP4 inhibitors. Furthermore, DPP4 as a type II transmembrane protein is also known to be cleaved from the cell membrane involving different metalloproteases in a cell-type-specific manner. Circulating, soluble DPP4 has been identified as a new adipokine, which exerts both para- and endocrine effects. Recently, a novel receptor for soluble DPP4 has been identified, and data are accumulating that the adipokine-related effects of DPP4 may play an important role in the pathogenesis of cardiovascular disease. Importantly, circulating DPP4 is augmented in obese and type 2 diabetic subjects, and it may represent a molecular link between obesity and vascular dysfunction. A critical evaluation of the impact of circulating DPP4 is presented, and the potential role of DPP4 inhibition at this level is also discussed.

Characterization of dedifferentiating human mature adipocytes from the visceral and subcutaneous fat compartments: fibroblast-activation protein alpha and dipeptidyl peptidase 4 as major components of matrix remodeling

Mature adipocytes can reverse their phenotype to become fibroblast-like cells. This is achieved by ceiling culture and the resulting cells, called dedifferentiated fat (DFAT) cells, are multipotent. Beyond the potential value of these cells for regenerative medicine, the dedifferentiation process itself raises many questions about cellular plasticity and the pathways implicated in cell behavior. This work has been performed with the objective of obtaining new information on adipocyte dedifferentiation, especially pertaining to new targets that may be involved in cellular fate changes. To do so, omental and subcutaneous mature adipocytes sampled from severely obese subjects have been dedifferentiated by ceiling culture. An experimental design with various time points along the dedifferentiation process has been utilized to better understand this process. Cell size, gene and protein expression as well as cytokine secretion were investigated. Il-6, IL-8, SerpinE1 and VEGF secretion were increased during dedifferentiation, whereas MIF-1 secretion was transiently increased. A marked decrease in expression of mature adipocyte transcripts (PPARγ2, C/EBPα, LPL and Adiponectin) was detected early in the process. In addition, some matrix remodeling transcripts (FAP, DPP4, MMP1 and TGFβ1) were rapidly and strongly up-regulated. FAP and DPP4 proteins were simultaneously induced in dedifferentiating mature adipocytes supporting a potential role for these enzymes in adipose tissue remodeling and cell plasticity.

An analysis of DNA methylation in human adipose tissue reveals differential modification of obesity genes before and after gastric bypass and weight loss

Background

Environmental factors can influence obesity by epigenetic mechanisms. Adipose tissue plays a key role in obesity-related metabolic dysfunction, and gastric bypass provides a model to investigate obesity and weight loss in humans.

Results

Here, we investigate DNA methylation in adipose tissue from obese women before and after gastric bypass and significant weight loss. In total, 485,577 CpG sites were profiled in matched, before and after weight loss, subcutaneous and omental adipose tissue. A paired analysis revealed significant differential methylation in omental and subcutaneous adipose tissue. A greater proportion of CpGs are hypermethylated before weight loss and increased methylation is observed in the 3′ untranslated region and gene bodies relative to promoter regions. Differential methylation is found within genes associated with obesity, epigenetic regulation and development, such as CETP, FOXP2, HDAC4, DNMT3B, KCNQ1 and HOX clusters. We identify robust correlations between changes in methylation and clinical trait, including associations between fasting glucose and HDAC4, SLC37A3 and DENND1C in subcutaneous adipose. Genes investigated with differential promoter methylation all show significantly different levels of mRNA before and after gastric bypass.

Conclusions

This is the first study reporting global DNA methylation profiling of adipose tissue before and after gastric bypass and associated weight loss. It provides a strong basis for future work and offers additional evidence for the role of DNA methylation of adipose tissue in obesity.

Electronic supplementary material

The online version of this article (doi:10.1186/s13059-014-0569-x) contains supplementary material, which is available to authorized users.

ADRB3 gene promoter DNA methylation in blood and visceral adipose tissue is associated with metabolic disturbances in men

AIM

ADRB3 DNA hypermethylation was recently associated with dyslipidemia in familial hypercholesterolemia (FH). In this study, we verified whether ADRB3 DNA methylation in blood and visceral adipose tissue (VAT) was associated with obesity and its related complications.

METHODS

DNA methylation levels were measured in the blood of 61 FH men, and the blood and VAT of 30 severely obese men. Common ADRB3 polymorphisms were genotyped in all subjects.

RESULTS

Higher ADRB3 DNA methylation levels were significantly associated with lower low-density lipoprotein cholesterol levels (r = -0.40; p = 0.01) in FH, and with a lower waist-to-hip ratio (r = -0.55; p = 0.01) and higher blood pressure (r = 0.43; p = 0.05) in severely obese men. ADRB3 g.-843C>T and p.W64R polymorphisms were found to be strongly associated (p < 0.001) with ADRB3 DNA methylation and mRNA levels.

CONCLUSION

Although further studies are needed, these results suggest that epigenetic changes at the ADRB3 gene locus might be involved in the development of obesity and its related metabolic complications.

A genome-wide association analysis for porcine serum lipid traits reveals the existence of age-specific genetic determinants

Background

The genetic determinism of blood lipid concentrations, the main risk factor for atherosclerosis, is practically unknown in species other than human and mouse. Even in model organisms, little is known about how the genetic determinants of lipid traits are modulated by age-specific factors. To gain new insights into this issue, we have carried out a genome-wide association study (GWAS) for cholesterol (CHOL), triglyceride (TRIG) and low (LDL) and high (HDL) density lipoprotein concentrations measured in Duroc pigs at two time points (45 and 190 days).

Results

Analysis of data with mixed-model methods (EMMAX, GEMMA, GenABEL) and PLINK showed a low positional concordance between trait-associated regions (TARs) for serum lipids at 45 and 190 days. Besides, the proportion of phenotypic variance explained by SNPs at these two time points was also substantially different. The four analyses consistently detected two regions on SSC3 (124 Mb, CHOL and LDL at 190 days) and SSC6 (135 Mb, CHOL and TRIG at 190 days) with highly significant effects on the porcine blood lipid profile. Moreover, we have found that SNP variation within SSC3, SSC6, SSC10, SSC13 and SSC16 TARs is associated with the expression of several genes mapping to other chromosomes and related to lipid metabolism.

Conclusions

Our data demonstrate that the effects of genomic determinants influencing lipid concentrations in pigs, as well as the amount of phenotypic variance they explain, are influenced by age-related factors.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-15-758) contains supplementary material, which is available to authorized users.

Transcriptome analysis of the hippocampus in novel rat model of febrile seizures

Febrile seizures (FS) are the most common type of convulsive events in infants and young children, but the precise underlying genetic mechanism remains to be explored. To investigate the underlying pathogenic factors in FS and subsequent epilepsy, alterations in gene expression between the two new strains of rats (hyperthermia-prone [HP] vs hyperthermia-resistant [HR]), were investigated by using the Whole Rat Genome Oligo Microarray. This process identified 1,140 differentially expressed genes (DEGs; 602 upregulated and 538 downregulated), which were analyzed to determine significant Gene Ontology (GO) categories, signaling pathways and gene networks. Based on the GO analyses, the modified genes are closely related to various FS pathogenesis factors, including immune and inflammatory responses and ion transport. Certain DEGs identified have not been previously examined in relation to FS pathogenesis. Among these genes is dipeptidyl peptidase 4 (DPP4), a gene closely linked to interleukin 6 (IL-6), which played a key role in the gene network analysis. Furthermore, sitagliptin, a DPP4 inhibitor significantly decreased epileptic discharge in rats, observed via electroencephalogram, suggesting an important role for DPP4 in FS. The effectiveness of sitagliptin in reducing seizure activity may occur through a mechanism that stabilizes cellular Ca²⁺ homeostasis. In addition, DPP4 expression may be regulated by DNA methylation. The hippocampal gene expression profiles in novel rat models of FS provides a large database of candidate genes and pathways, which will be useful for researchers interested in disorders of neuronal excitability.

Variation at the DPP4 locus influences apolipoprotein B levels in South Asians and exhibits heterogeneity in Europeans related to BMI

AIMS/HYPOTHESIS

Dyslipidaemia, a common feature of type 2 diabetes, is characterised by an increase in atherogenic particles, quantifiable through apolipoprotein B (ApoB) levels. Genetic studies of lipid levels have focused on Europeans; a study in South Asians could identify novel genes.

METHODS

We tested 31,739 single nucleotide polymorphisms (SNPs) from ∼ 2,000 genes in 2,573 South Asians from the epidemiological arm of the Diabetes Reduction Assessment with Ramipril and Rosiglitazone Medication (DREAM) study (EpiDREAM) for association with ApoB and we tested two novel associations for replication in 1,181 South Asians from the INTERHEART case-control study.

RESULTS

The SNP, rs4664443, within DPP4 was associated with ApoB (p = 7.98 × 10(-5)) in EpiDREAM. The observed association was replicated in the INTERHEART South Asians (one-sided p = 9.65 × 10(-3); combined two-sided p = 4.68 × 10(-6)). The rs4664443 SNP was not associated with ApoB among five other EpiDREAM ethnicities. However, because South Asians had a significantly lower mean BMI compared with other EpiDREAM ethnicities, we tested for and found an interaction between rs4664443 and BMI for ApoB among the Europeans, the largest subgroup in EpiDREAM (p = 4.14 × 10(-3) for interaction), observing an association with ApoB in Europeans with a BMI <25 kg/m(2) (p = 2.35 × 10(-3)), but not with a BMI ≥ 25 kg/m(2) (p = 0.21). The association between rs4664443 and ApoB among all EpiDREAM individuals with BMI <25 kg/m(2) was significant (n = 2,972; p = 1.44 × 10(-5)) compared with those with a BMI ≥ 25 kg/m(2) (n = 11,559; p = 0.81), and there was evidence of association among all genotyped individuals with a BMI <25 kg/m(2), including the INTERHEART South Asians (n = 3,601; p = 9.52 × 10(-7)).

CONCLUSION/INTERPRETATION

Variation at the DPP4 locus is associated with ApoB in South Asians and displays heterogeneity related to BMI in other ethnicities.

Adipose dipeptidyl peptidase-4 and obesity: correlation with insulin resistance and depot-specific release from adipose tissue in vivo and in vitro

OBJECTIVE

To study expression of the recently identified adipokine dipeptidyl peptidase-4 (DPP4) in subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) of patients with various BMIs and insulin sensitivities, as well as to assess circulating DPP4 in relation to obesity and insulin sensitivity.

RESEARCH DESIGN AND METHODS

DPP4 expression was measured in SAT and VAT from 196 subjects with a wide range of BMIs and insulin sensitivities. DPP4 release was measured ex vivo in paired biopsies from SAT and VAT as well as in vivo from SAT of lean and obese patients. Circulating DPP4 was measured in insulin-sensitive and insulin-resistant BMI-matched obese patients.

RESULTS

DPP4 expression was positively correlated with BMI in both SAT and VAT, with VAT consistently displaying higher expression than SAT. Ex vivo release of DPP4 from adipose tissue explants was higher in VAT than in SAT in both lean and obese patients, with obese patients displaying higher DPP4 release than lean controls. Net release of DPP4 from adipose tissue was also demonstrated in vivo with greater release in obese subjects than in lean subjects and in women than in men. Insulin-sensitive obese patients had significantly lower circulating DPP4 than did obesity-matched insulin-resistant patients. In this experiment, DPP4 positively correlated with the amount of VAT, adipocyte size, and adipose tissue inflammation.

CONCLUSIONS

DPP4, a novel adipokine, has a higher release from VAT that is particularly pronounced in obese and insulin-resistant patients. Our data suggest that DPP4 may be a marker for visceral obesity, insulin resistance, and the metabolic syndrome.

Effects of methyl donor diets on incisional pain in mice

Background

Dietary supplementation with methyl donors can influence the programming of epigenetic patterns resulting in persistent alterations in disease susceptibility and behavior. However, the dietary effects of methyl donors on pain have not been explored. In this study, we evaluated the effects of dietary methyl donor content on pain responses in mice.

Methods

Male and female C57BL/6J mice were treated with high or low methyl donor diets either in the perinatal period or after weaning. Mechanical and thermal nociceptive sensitivity were measured before and after incision.

Results

Mice fed high or low methyl donor diets displayed equal weight gain over the course of the experiments. When exposed to these dietary manipulations in the perinatal period, only male offspring of dams fed a high methyl donor diet displayed increased mechanical allodynia. Hindpaw incision in these animals caused enhanced nociceptive sensitization, but dietary history did not affect the duration of sensitization. For mice exposed to high or low methyl donor diets after weaning, no significant differences were observed in mechanical or thermal nociceptive sensitivity either at baseline or in response to hindpaw incision.

Conclusions

Perinatal dietary factors such as methyl donor content may impact pain experiences in later life. These effects, however, may be specific to sex and pain modality.

Epigenome-wide analysis in familial hypercholesterolemia identified new loci associated with high-density lipoprotein cholesterol concentration

AIM

This study aims to assess whether epigenetic changes may account for high-density lipoprotein cholesterol (HDL-C) level variability in familial hypercholesterolemia (FH), a recognized human model to study cardiovascular disease risk modulators.

MATERIALS & METHODS

A genome-wide DNA methylation analysis (Infinium HumanMethylation27 BeadChip, Illumina) was performed on peripheral blood DNA samples obtained from men with FH with low (n = 10) or high (n = 11) HDL-C concentrations. The initial association with one of the top differentially methylated loci located in the promoter of the TNNT1 gene was replicated in a cohort of 276 FH subjects using pyrosequencing.

RESULTS

According to the Ingenuity Pathway Analysis software, the HDL-C differentially methylated loci identified were significantly associated with pathways related to lipid metabolism and cardiovascular disease. TNNT1 DNA methylation levels were positively correlated with mean HDL particle size, HDL-phospholipid, HDL-apolipoprotein AI, HDL-C and TNNT1 expression levels.

CONCLUSION

These results suggest that epigenome-wide changes account for interindividual variations in HDL particle metabolism and that TNNT1 is a new candidate gene for dyslipidemia.

Comparison of the dipeptidyl peptidase-4 gene methylation levels between severely obese subjects with and without the metabolic syndrome

BACKGROUND

The dipeptidyl peptidase-4 (DPP4) enzyme is a novel adipokine potentially involved in the development of the metabolic syndrome (MetS). Previous observations demonstrated higher visceral adipose tissue (VAT) DPP4 gene expression in non-diabetic severely obese men with (MetS+) vs. without (MetS-) MetS. DPP4 mRNA abundance in VAT correlated also with CpG site methylation levels (%Meth) localized within and near its exon 2 (CpG94 to CpG102) in non-diabetic severely obese women, regardless of their MetS status. The actual study tested whether DPP4 %Meth levels in VAT are different between MetS- and MetS+ non-diabetic severely obese subjects, whether variable metabolic and plasma lipid profiles are observed between DPP4 %Meth quartiles, and whether correlation exists in DPP4 %Meth levels between VAT and white blood cells (WBCs).

METHODS

DNA was extracted from the VAT of 26 men (MetS-: n=12, MetS+: n=14) and 79 women (MetS-: n=60; MetS+: n=19), as well as from WBCs in a sub-sample of 17 women (MetS-: n=9; MetS+: n=8). The %Meth levels of CpG94 to CpG102 were assessed by pyrosequencing of sodium bisulfite-treated DNA. ANOVA analyses were used to compare the %Meth of CpGs between MetS- and MetS+ groups, and to compare the metabolic phenotype and plasma lipid levels between methylation quartiles. Pearson correlation coefficient analyses were computed to test the relationship between VAT and WBCs CpG94-102 %Meth levels.

RESULTS

No difference was observed in CpG94-102 %Meth levels between MetS- and MetS+ subjects in VAT (P=0.67), but individuals categorized into CpG94-102 %Meth quartiles had variable plasma total-cholesterol concentrations (P=0.04). The %Meth levels of four CpGs in VAT were significantly correlated with those observed in WBCs (r=0.55-0.59, P≤0.03).

CONCLUSIONS

This study demonstrated that %Meth of CpGs localized within and near the exon 2 of the DPP4 gene in VAT are not associated with MetS status. The actual study also revealed an association between the %Meth of this locus with plasma total-cholesterol in severe obesity, which suggests a link between the DPP4 gene and plasma lipid levels.

Glucagon-like peptide 1 and appetite

Glucagon-like peptide 1 (GLP-1) and GLP-1 analogs have received much recent attention due to the success of GLP-1 mimetics in treating type II diabetes mellitus (T2DM), but these compounds may also have the potential to treat obesity. The satiety effect of GLP-1 may involve both within-meal enteroenteric reflexes, and across-meal central signaling mechanisms, that mediate changes in appetite and promote satiety. Here, we review data supporting the role of both peripheral and central GLP-1 signaling in the control of gastrointestinal motility and food intake. Understanding the mechanisms underlying the appetite-suppressive effects of GLP-1 may help in developing targeted treatments for obesity.

Epigenetic manifestation of metabolic syndrome and dietary management

SIGNIFICANCE

Metabolic syndrome constitutes a group of disorders such as insulin resistance, hypertension, and hypertriglyceridemia, predisposing an individual to risk factors such as cardiovascular disease, diabetes, obesity, and dyslipidemia. A majority of these diseases are influenced by the environmental factors, nutrient uptake, and genetic profile of an individual that together dysregulate gene function. These genetic and nongenetic factors are reported to introduce epigenetic cues that modulate the gene function which is inherited by the offspring.

RECENT ADVANCES

Considering the epigenetic modulation of the metabolic disorders, nutrigenomics has been distinctly categorized as a branch that deals with modulatory effect of nutrients on metabolic disorders and disease progression by supplementing the individuals with key nutrient-enriched diets which are derived from plant and animal sources.

CRITICAL ISSUES

Nutritional components of the diet regulate the metabolic health of an individual either by controlling the expression of some key genes related to metabolic pathways or by modulating the epigenetic events on such genes. The present article discusses various metabolic disorders in detail and the effect of nutrients on the specific genes causing those disorders. We also highlight the molecular mechanisms of some metabolic disorders through epigenetic modifications and possible therapeutic interventions.

FUTURE DIRECTIONS

With the advent of high-throughput technologies and epigenetic modulation of the metabolic disorders, an altered epigenetic code that is programmed due to improper nutrients can be reverted back by supplementing the diet with various plant-derived compounds. The implication of small molecular drugs is also of utmost significance for challenging the metabolic disorders.

LINE-1 methylation in visceral adipose tissue of severely obese individuals is associated with metabolic syndrome status and related phenotypes

Background

Epigenetic mechanisms may be involved in the regulation of genes found to be differentially expressed in the visceral adipose tissue (VAT) of severely obese subjects with (MetS+) versus without (MetS-) metabolic syndrome (MetS). Long interspersed nuclear element 1 (LINE-1) elements DNA methylation levels (%meth) in blood, a marker of global DNA methylation, have recently been associated with fasting glucose, blood lipids, heart diseases and stroke.

Aim

To test whether LINE-1%meth levels in VAT are associated with MetS phenotypes and whether they can predict MetS risk in severely obese individuals.

Methods

DNA was extracted from VAT of 34 men (MetS-: n = 14, MetS+: n = 20) and 152 premenopausal women (MetS-: n = 84; MetS+: n = 68) undergoing biliopancreatic diversion for the treatment of obesity. LINE-1%meth levels were assessed by pyrosequencing of sodium bisulfite-treated DNA.

Results

The mean LINE-1%meth in VAT was of 75.8% (SD = 3.0%). Multiple linear regression analyses revealed that LINE-1%meth was negatively associated with fasting glucose levels (β = -0.04; P = 0.03), diastolic blood pressure (β =  -0.65; P = 0.03) and MetS status (β = -0.04; P = 0.004) after adjustments for the effects of age, sex, waist circumference (except for MetS status) and smoking. While dividing subjects into quartiles based on their LINE-1%meth (Q1 to Q4: lower %meth to higher %meth levels), greater risk were observed in the first (Q1: odds ratio (OR) = 4.37, P = 0.004) and the second (Q2: OR = 4.76, P = 0.002) quartiles compared to Q4 (1.00) when adjusting for age, sex and smoking.

Conclusions

These results suggest that lower global DNA methylation, assessed by LINE-1 repetitive elements methylation analysis, would be associated with a greater risk for MetS in the presence of obesity.

5-Aza-2'-deoxycytidine induced growth inhibition of leukemia cells through modulating endogenous cholesterol biosynthesis

5-Aza-2'-deoxycytidine (5-Aza-CdR), a nucleoside analog that can inhibit DNA cytosine methylation, possesses potent antitumorigenic activities for myeloid disorders. Although 5-Aza-CdR is known to be incorporated into DNA and inhibit DNA (cytosine-5)-methyltransferases, the precise mechanisms underlying the drug's antineoplastic activity remain unclear. Here we utilized a mass spectrometry-based quantitative proteomic method to analyze the 5-Aza-CdR-induced perturbation of protein expression in Jurkat-T cells at the global proteome scale. Among the ≈ 2780 quantified proteins, 188 exhibited significant alteration in expression levels upon a 24-hr treatment with 5 μm 5-Aza-CdR. In particular, we found that drug treatment led to substantially reduced expression of farnesyl diphosphate synthase (FDPS) and farnesyl diphosphate farnesyltransferase (FDFT1), two important enzymes involved in de novo cholesterol synthesis. Consistent with this finding, 5-Aza-CdR treatment of leukemia (Jurkat-T, K562 and HL60) and melanoma (WM-266-4) cells led to a marked decrease in cellular cholesterol content and pronounced growth inhibition, which could be rescued by externally added cholesterol. Exposure of these cells to 5-Aza-CdR also led to epigenetic reactivation of dipeptidyl peptidase 4 (DPP4) gene. Additionally, suppression of DPP4 expression with siRNA induced elevated protein levels of FDPS and FDFT1, and increased cholesterol biosynthesis in WM-266-4 cells. Together, the results from the present study revealed, for the first time, that 5-Aza-CdR exerts its cytotoxic effects in leukemia and melanoma cells through epigenetic reactivation of DPP4 gene and the resultant inhibition of cholesterol biosynthesis in these cells.

The metabolic syndrome influences the response to incretin-based therapies

We hypothesize that type 2 diabetic patients with different phenotypes may show different response to incretin-based therapies. Therefore, we tested whether the presence of metabolic syndrome (MS) influences glycemic response to these drugs. We prospectively followed 211 patients, treated with the GLP-1 analog exenatide (n = 102) or a DPP-4 inhibitor (n = 109) for at least 4 months. Treatment was decided on clinical grounds. We collected baseline data (age, sex, BMI, waist, systolic and diastolic blood pressure, lipid profile, data on diabetic complications and concomitant treatment) and HbA1c at subsequent visits. Patients were divided into groups according to the presence/absence of MS. Compared to patients on exenatide, patients on DPP-4 inhibitors were older and had lower BMI, waist, diastolic blood pressure, fasting plasma glucose, and HbA1c. At means of baseline values, HbA1c reduction was similar in patients treated with exenatide or DPP-4 inhibitors. Patients on exenatide showed significantly higher HbA1c reduction if they had MS (-1.55 ± 0.22%; n = 88) than if they had not (-0.34 ± 0.18%; P = 0.002). Conversely, patients on DPP-4 inhibitors showed significantly lower HbA1c reduction if they had MS (-0.60 ± 0.12%; n = 73) than if they had not (-1.50 ± 0.24%; P < 0.001). Type of MS definition (ATP-III, IDF or WHO) poorly influenced these trends. The interaction between type of therapy (exenatide vs. DPP-4 inhibitors) and MS remained significant after adjusting for age, baseline HbA1c, BMI, and concomitant medications. In conclusion, the presence of MS appears to modify the response to incretin-based therapies. Given the non-randomized nature of this study, these data need to be replicated.