Serum Levels of Soluble CD26/Dipeptidyl Peptidase-IV in Type 2 Diabetes Mellitus and Its Association with Metabolic Syndrome and Therapy with Antidiabetic Agents in Malaysian Subjects

Metformin in COVID-19: Is There a Role Beyond Glycemic Control?

Context

The coronavirus disease 2019 (COVID-19) pandemic is still a cause of worldwide health concern. Diabetes and its associated comorbidities are risk factors for mortality and morbidity in COVID-19. Selecting the right antidiabetic drug to achieve optimal glycemic control might mitigate some of the negative impacts of diabetes. Metformin continues to be the most widely administered antidiabetic agent. There is evidence of its beneficial outcome in COVID-19 independent of its glucose-lowering effect.

Evidence Acquisition

A thorough literature search was conducted in PubMed, Google Scholar, Scopus, and Web of Science to identify studies investigating metformin in COVID-19.

Results

Several overlapping mechanisms have been proposed to explain its antiviral properties. It could bring about conformational changes in the angiotensin-converting enzyme-2 receptor and decrease viral entry. The effects on the mammalian target of the rapamycin pathway and cellular pH have been proposed to reduce viral protein synthesis and replication. The immunomodulatory effects of metformin might counter the detrimental effects of hyperinflammation associated with COVID-19.

Conclusions

These findings call for broader metformin usage to manage hyperglycemia in COVID-19.

Genetic variation in DPP-IV gene linked to predisposition of T2DM: A case control study

Purpose

DPP-IV is a ubiquitously expressed cell surface protein that can be presented in soluble forms. It has recently gained medical importance as its inhibitors are widely being used as treatment of T2DM. The present research aims to resolve whether genetic variants of DPP-IV have association with susceptibility to T2DM.

Method

Two variants of DPP-IV were detected in 100 controls and 100 T2DM by PCR–RFLP technique. Demographic characteristics were recorded. Clinical characteristics were analyzed by enzymatic method. Statistical analysis was performed using SPSS-21.

Results

Demographic and clinical characteristics differ significantly between two groups. The genetic variation in SNP rs3788979 and SNP rs7608798, both in case and control, were in accordance with Hardy–Weinberg Equilibrium (p value > 0.05). Both SNPs rs3788979 and rs7608798 were significantly related to T2DM (p- < 0.05). Minor G allele of rs3788979 was linked with the susceptibility of T2DM (p-value-0.000; OR- 4.235). T allele of SNP rs7608798 conferred the risk of diabetes with OR-2.235.

Conclusion

This is the first attempt to investigate the association of DPP-IV gene with T2DM in Indian population. The finding of study concludes that genetic variation in DPP-IV gene may considerably increase the risk of developing T2DM.

A haplotype in the dipeptidyl peptidase 4 gene impacts glycemic-related traits of Brazilian older adults

Dipeptidyl peptidase 4 (DPP4) regulates various physiological pathways and has a pivotal role in glucose homeostasis. The objective of this study was to verify the association of a haplotype constituted by two single nucleotide polymorphisms (rs2268894 and rs6741949) in the DPP4 gene with type 2 diabetes mellitus (T2DM) and fasting glycemia-related variables in a sample of Brazilian older adults, taking serum levels and enzymatic activity of DPP4 into account. Clinical, biochemical, and anthropometric characteristics as well as DPP4 serum levels and enzymatic activity were determined in 800 elderly (≥60 years old) individuals. Assessment of polymorphic sites was performed by real-time PCR whereas haplotypes were inferred from genotypic frequencies. Statistical analyses compared measures and proportions according to T2DM diagnosis and DPP4 haplotypic groups. The most common haplotype consisted of the T-rs2268894/G-rs6741949 string, which was 20% more frequent among non-diabetics. Considering non-diabetic patients alone, carriers of the T/G haplotype had significantly lower levels of blood glucose, insulin, HOMA-IR index, and DPP4 activity. Among diabetic patients, the T/G haplotype was associated with lower DPP4 levels whereas glycemic scores were not affected by allelic variants. Our results suggested that the genetic architecture of DPP4 affects the glycemic profile and DPP4 serum levels and activity among elderly individuals according to the presence or absence of T2DM, with a possible implication of the T/G haplotype to the risk of T2DM onset.

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.

Fasting and stimulated glucagon-like peptide-1 exhibit a compensatory adaptive response in diabetes and pre-diabetes states: A multi-ethnic comparative study

BACKGROUND

Impaired secretion of glucagon-like peptide-1 (GLP-1) among Caucasians contributes to reduced incretin effect in type 2 diabetes mellitus (T2DM) patients. However, studies emanating from East Asia suggested preserved GLP-1 levels in pre-diabetes (pre-DM) and T2DM. We aimed to resolve these conflicting findings by investigating GLP-1 levels during oral glucose tolerance test (OGTT) among Malay, Chinese, and Indian ethnicities with normal glucose tolerance (NGT), pre-DM, and T2DM. The association between total GLP-1 levels, insulin resistance, and insulin sensitivity, and GLP-1 predictors were also analyzed.

METHODS

A total of 174 subjects were divided into NGT (n=58), pre-DM (n=54), and T2DM (n=62). Plasma total GLP-1 concentrations were measured at 0, 30, and 120 min during a 75-g OGTT. Homeostasis model assessment of insulin resistance (HOMA-IR), HOMA of insulin sensitivity (HOMA-IS), and triglyceride-glucose index (TyG) were calculated.

RESULTS

Total GLP-1 levels at fasting and 30 min were significantly higher in T2DM compared with pre-DM and NGT (27.18 ± 11.56 pmol/L vs. 21.99 ± 10.16 pmol/L vs. 16.24 ± 7.79 pmol/L, p=0.001; and 50.22 ± 18.03 pmol/L vs. 41.05 ± 17.68 pmol/L vs. 31.44 ± 22.59 pmol/L, p<0.001; respectively). Ethnicity was a significant determinant of AUC_GLP-1, with the Indians exhibiting higher GLP-1 responses than Chinese and Malays. Indians were the most insulin resistant, whereas Chinese were the most insulin sensitive. The GLP-1 levels were positively correlated with HOMA-IR and TyG but negatively correlated with HOMA-IS. This relationship was evident among Indians who exhibited augmented GLP-1 responses proportionately to their high insulin-resistant states.

CONCLUSION

This is the first study that showed GLP-1 responses are augmented as IR states increase. Fasting and post-OGTT GLP-1 levels are raised in T2DM and pre-DM compared to that in NGT. This raises a possibility of an adaptive compensatory response that has not been reported before. Among the three ethnic groups, the Indians has the highest IR and GLP-1 levels supporting the notion of an adaptive compensatory secretion of GLP-1.

Repurposing metformin for covid-19 complications in patients with type 2 diabetes and insulin resistance

Understanding the exact role of current drugs in Covid-19 disease is essential in the era of global pandemics. Metformin which prescribed as the first-line treatment of type 2 diabetes has beneficial effects on Sars-cov2 infection. These effects are including regulation of immune system, Renin-Angiotensin System and Dipeptidyl Peptidase 4 function in Covid-19 infection. It also activates ACE2, the main receptor of Sars-cov2, in the epithelial cells of respiratory tissue through AMPK signaling and subsequently decreases the rate of viral adhesion. Metformin also declines the adherence of Sars-cov2 to DPP4 (the other receptor of the virus) on T cells. Hence, regulatory effects of metformin on membranous ACE2, and DPP4 can modulate immune reaction against Sars-cov2. Also, immunometabolic effects of metformin on inflammatory cells impair hyper-reactive immune response against the virus through reduction of glycolysis and propagation of mitochondrial oxidation. Metformin also decreases platelet aggravation and risk of thrombosis. In this article, we argue that metformin has beneficial effects on Covid-19 infection in patients with type 2 diabetes and insulin resistance. This opinion should be investigated in future clinical trials.

Circulating dipeptidyl peptidase-4 is independently associated with the presence and severity of NAFLD/NASH in individuals with and without obesity and metabolic disease

INTRODUCTION

Dipeptidyl peptidase 4 (DPP4) levels are associated to metabolic and cardiovascular diseases in humans; initial evidence reported a relationship between DPP4 and chronic liver diseases. Aim of this study was to investigate hepatic and systemic DPP4 levels/activity in relation to NAFLD/NASH in individuals with and without metabolic disease.

METHODS

We recruited fifty-two obese individuals undergoing bariatric surgery and intra-operative liver biopsy at Sapienza University, Rome, Italy. The association between DPP4 levels/activity and NAFLD was also evaluated in 126 non-obese individuals recruited in the same setting.

RESULTS

NAFLD patients had significantly higher circulating DPP4 activity than no-NAFLD in both the obese and non-obese cohorts; plasma DPP4 activity and levels linearly correlated with steatosis grade and inflammation at the liver biopsy. Hepatic DPP4 mRNA was not associated to either its circulating levels/activity or NAFLD. In the multivariate logistic regression analysis on all the study participants (n = 178), higher circulating DPP4 activity was associated with NAFLD independently of potential confounders with OR (95% CI): 3.5 (1.2-10.21), p = 0.022.

CONCLUSIONS

This study demonstrates the coexistence of increased plasma DPP4 levels and activity in NAFLD. Circulating DPP4 measurement may represent a novel cost-effective strategy for NAFLD/NASH risk stratification and a potential tool for monitoring disease's progression in established NAFLD.

Effect of stevia aqueous extract on the antidiabetic activity of saxagliptin in diabetic rats

ETHNOPHARMACOLOGICAL RELEVANCE

Stevia rebaudiana Bertoni is a perennial herb that belongs to the Asteraceae family. It is a natural sweetener plant known as "Sweet Leaf", "Sweet Herbs" and "Honey Leaf", which is estimated to be 300 times more sweetening than sugar cane. Stevia has been used as a traditional treatment for diabetes in many countries for hundreds of years. Several animal studies referred to the antihyperglycemic activity of stevia. However, the combined use of stevia with saxagliptin has not been studied so far, so this study has been done. The aim of the present study was to evaluate the antihyperglycemic effect of stevia alone and in combination with saxagliptin.

MATERIALS AND METHODS

Diabetes was induced in rats by i.p. injection of streptozotocin and nicotinamide. Animals were divided into five groups, each contains eight rats. Group I: included negative controland group II: included diabetic control that received saline. Group III: included diabetic rats that received 400 mg/kg/day stevia aqueous extract. Group IV: included diabetic rats that received saxagliptin 10 mg/kg/day. Group V: included diabetic rats that received stevia 400 mg/kg + saxagliptin 10 mg/kg. Food and water intake were measured daily while body weight was measured weekly. After 3 weeks animals were sacrificed and blood and tissue samples were collected. Fasting blood glucose (FBG), serum insulin, serum dipeptidylepeptidase-4 (DPP-4), TC, TGs, LDL, HDL, GSH and MDA were measured in treated and control rats by colorimetric and ELISA methods.

RESULTS

Both stevia and saxagliptin significantly reduced food, water intake, body weight and FBG. Stevia with saxagliptin produced more significant decrease in FBG. While serum insulin increased significantly in stevia, saxagliptin treated groups and their combination. Serum DPP-4 decreased significantly in all treated groups, concerning lipid profile, stevia and saxagliptin notably lowered TC, TGs, and LDL and increased HDL. Both stevia and saxagliptin remarkably decreased MDA and increased GSH compared to diabetic rats. In addition, stevia significantly improved the antidiabetic effects of saxagliptin.

CONCLUSION

Stevia has an antihyperglycemic effect and could enhance the antidiabetic activity of saxagliptin. DPP-4 attenuation, antihyperlipidemic and antioxidant activity as well as improvement of insulin sensitivity may be involved in the antidiabetic action of stevia.

Plasma levels of DPP4 activity and sDPP4 are dissociated from inflammation in mice and humans

Dipeptidyl peptidase-4 (DPP4) modulates inflammation by enzymatic cleavage of immunoregulatory peptides and through its soluble form (sDPP4) that directly engages immune cells. Here we examine whether reduction of DPP4 activity alters inflammation. Prolonged DPP4 inhibition increases plasma levels of sDPP4, and induces sDPP4 expression in lymphocyte-enriched organs in mice. Bone marrow transplantation experiments identify hematopoietic cells as the predominant source of plasma sDPP4 following catalytic DPP4 inhibition. Surprisingly, systemic DPP4 inhibition increases plasma levels of inflammatory markers in regular chow-fed but not in high fat-fed mice. Plasma levels of sDPP4 and biomarkers of inflammation are lower in metformin-treated subjects with type 2 diabetes (T2D) and cardiovascular disease, yet exhibit considerable inter-individual variation. Sitagliptin therapy for 12 months reduces DPP4 activity yet does not increase markers of inflammation or levels of sDPP4. Collectively our findings dissociate levels of DPP4 enzyme activity, sDPP4 and biomarkers of inflammation in mice and humans.

A Physiologically-Based Quantitative Systems Pharmacology Model of the Incretin Hormones GLP-1 and GIP and the DPP4 Inhibitor Sitagliptin

Incretin hormones glucagon‐like peptide‐1 (GLP‐1) and glucose‐dependent insulinotropic polypeptide (GIP) play a major role in regulation of postprandial glucose and the development of type 2 diabetes mellitus. The incretins are rapidly metabolized, primarily by the enzyme dipeptidyl‐peptidase 4 (DPP4), and the neutral endopeptidase (NEP), although the exact metabolization pathways are unknown. We developed a physiologically‐based (PB) quantitative systems pharmacology model of GLP‐1 and GIP and their metabolites that describes the secretion of the incretins in response to intraduodenal glucose infusions and their degradation by DPP4 and NEP. The model describes the observed data and suggests that NEP significantly contributes to the metabolization of GLP‐1, and the traditional assays for the total GLP‐1 and GIP forms measure yet unknown entities produced by NEP. We further extended the model with a PB pharmacokinetics/pharmacodynamics model of the DPP4 inhibitor sitagliptin that allows predictions of the effects of this medication class on incretin concentrations.

Quercetin and Coumarin Inhibit Dipeptidyl Peptidase-IV and Exhibits Antioxidant Properties: In Silico, In Vitro, Ex Vivo

Quercetin and coumarin, two naturally occurring phytochemicals of plant origin, are known to regulate hyperglycemia and oxidative stress. The present study was designed to evaluate the inhibitory activity of quercetin and coumarin on dipeptidyl peptidase-IV (DPP-IV) and their antioxidant potential. DPP-IV inhibition assays were performed, and evaluated IC₅₀ values of diprotin A, quercetin, coumarin, and sitagliptin were found to be 0.653, 4.02, 54.83, and 5.49 nmol/mL, respectively. Furthermore, in silico studies such as the drug-likeliness and docking efficiency of quercetin and coumarin to the DPP-IV protein were performed; the ex vivo antiperoxidative potential of quercetin and coumarin were also evaluated. The results of the present study showed that the DPP-IV inhibitory potential of quercetin was slightly higher than that of sitagliptin. Virtual docking revealed the tight binding of quercetin with DPP-IV protein. Quercetin and coumarin reduced oxidative stress in vitro and ex vivo systems. We report for the first time that both compounds inhibited the DPP-IV along with antioxidant activity and thus may be use as function food ingredients in the prevention of diabetes.

Diagnostic and prognostic significance of serum CD26 level in Asian women with high-grade serous ovarian carcinoma

Aim: The aim of this study was to reveal the diagnostic and prognostic significance of serum CD26 level in high-grade serous ovarian carcinoma women in China. Methods: There were 229 high-grade serous ovarian carcinoma women and 365 controls. Baseline serum CD26 level was measured using ELISA. A 36-month post-operation follow-up was performed. Results: Baseline serum CD26 level ≤601.5 pg/ml was associated with the increased risk of ovarian carcinoma (OR: 1.67; 95% CI: 1.20-2.32). Baseline serum level of CD26 ≤589.7 pg/ml was related to the elevated risk of cancer death (HR: 1.33; 95% CI: 1.04-1.69). Conclusion: Baseline serum CD26 level might be an independent diagnostic and prognostic marker for high-grade serous ovarian carcinoma.

Circulating Levels of Soluble Dipeptidyl Peptidase-4 Are Dissociated from Inflammation and Induced by Enzymatic DPP4 Inhibition

Dipeptidyl peptidase-4 (DPP-4) controls glucose homeostasis through enzymatic termination of incretin action. We report that plasma DPP-4 activity correlates with body weight and fat mass, but not glucose control, in mice. Genetic disruption of adipocyte Dpp4 expression reduced plasma DPP-4 activity in older mice but did not perturb incretin levels or glucose homeostasis. Knockdown of hepatocyte Dpp4 completely abrogated the obesity-associated increase in plasma DPP-4 activity, reduced liver cytokine expression, and partially attenuated inflammation in adipose tissue without changes in incretin levels or glucose homeostasis. In contrast, circulating levels of soluble DPP4 (sDPP4) were dissociated from inflammation in mice with endothelial-selective or global genetic inactivation of Dpp4. Remarkably, inhibition of DPP-4 enzymatic activity upregulated circulating levels of sDPP4 originating from endothelial or hematopoietic cells without inducing systemic or localized inflammation. Collectively, these findings reveal unexpected complexity in regulation of soluble versus enzymatic DPP-4 and control of inflammation and glucose homeostasis.

Renoprotective Effects of the Dipeptidyl Peptidase-4 Inhibitor Sitagliptin: A Review in Type 2 Diabetes

Diabetic nephropathy (DN) is now the single commonest cause of end-stage renal disease (ESRD) worldwide and one of the main causes of death in diabetic patients. It is also acknowledged as an independent risk factor for cardiovascular disease (CVD). Since sitagliptin was approved, many studies have been carried out revealing its ability to not only improve metabolic control but also ameliorate dysfunction in various diabetes-targeted organs, especially the kidney, due to putative underlying cytoprotective properties, namely, its antiapoptotic, antioxidant, anti-inflammatory, and antifibrotic properties. Despite overall recommendations, many patients spend a long time well outside the recommended glycaemic range and, therefore, have an increased risk for developing micro- and macrovascular complications. Currently, it is becoming clearer that type 2 diabetes mellitus (T2DM) management must envision not only the improvement in glycaemic control but also, and particularly, the prevention of pancreatic deterioration and the evolution of complications, such as DN. This review aims to provide an overview of the current knowledge in the field of renoprotective actions of sitagliptin, namely, improvement in diabetic dysmetabolism, hemodynamic factors, renal function, diabetic kidney lesions, and cytoprotective properties.

Improved glycaemia in high-fat-fed neprilysin-deficient mice is associated with reduced DPP-4 activity and increased active GLP-1 levels

AIM/HYPOTHESIS

Neprilysin, a widely expressed peptidase, is upregulated in metabolically altered states such as obesity and type 2 diabetes. Like dipeptidyl peptidase-4 (DPP-4), neprilysin can degrade and inactivate the insulinotropic peptide glucagon-like peptide-1 (GLP-1). Thus, we investigated whether neprilysin deficiency enhances active GLP-1 levels and improves glycaemia in a mouse model of high fat feeding.

METHODS

Nep ^+/+ and Nep ^-/- mice were fed a 60% fat diet for 16 weeks, after which active GLP-1 and DPP-4 activity levels were measured, as were glucose, insulin and C-peptide levels during an OGTT. Insulin sensitivity was assessed using an insulin tolerance test.

RESULTS

High-fat-fed Nep ^-/- mice exhibited elevated active GLP-1 levels (5.8 ± 1.1 vs 3.5 ± 0.8 pmol/l, p < 0.05) in association with improved glucose tolerance, insulin sensitivity and beta cell function compared with high-fat-fed Nep ^+/+ mice. In addition, plasma DPP-4 activity was lower in high-fat-fed Nep ^-/- mice (7.4 ± 1.0 vs 10.7 ± 1.3 nmol ml^-1 min^-1, p < 0.05). No difference in insulin:C-peptide ratio was observed between Nep ^-/- and Nep ^+/+ mice, suggesting that improved glycaemia does not result from changes in insulin clearance.

CONCLUSIONS/INTERPRETATION

Under conditions of increased dietary fat, an improved glycaemic status in neprilysin-deficient mice is associated with elevated active GLP-1 levels, reduced plasma DPP-4 activity and improved beta cell function. Thus, neprilysin inhibition may be a novel treatment strategy for type 2 diabetes.

Altered circulating concentrations of active glucagon-like peptide (GLP-1) and dipeptidyl peptidase 4 (DPP4) in obese subjects and their association with insulin resistance

OBJECTIVES

Soluble DPP4 (sDPP4) is a novel adipokine that degrades glucagon-like peptide (GLP-1). We evaluated the fasting serum levels of active GLP-1 and sDPP4 in obese, overweight and normal weight subjects to assess the association between sDPP4 levels, active GLP-1 levels and insulin resistance in obese subjects.

METHODS

The study involved 235 Malaysian subjects who were randomly selected (66 normal weight subjects, 97 overweight, 59 obese subjects, and 13 subjects who were underweight). Serum sDPP4 and active GLP-1 levels were examined by enzyme-linked immunosorbent assay (ELISA). Also, body mass index kg/m² (BMI), lipid profiles, insulin and glucose levels were evaluated. Insulin resistance (IR) was estimated via the homeostasis model assessment for insulin resistance (HOMA-IR).

RESULTS

Serum sDPP4 levels were significantly higher in obese subjects compared to normal weight subjects (p=0.034), whereas serum levels of active GLP-1 were lower (p=0.021). In obese subjects, sDPP4 levels correlated negatively with active GLP-1 levels (r²=-0.326, p=0.015). Furthermore, linear regression showed that sDPP4 levels were positively associated with insulin resistance (B=82.28, p=0.023) in obese subjects.

CONCLUSION

Elevated serum sDPP4 levels and reduced GLP-1 levels were observed in obese subjects. In addition, sDPP4 levels correlated negatively with active GLP-1 levels but was positively associated with insulin resistance. This finding provides evidence that sDPP4 and GLP-1 may play an important role in the pathogenesis of obesity, suggesting that sDPP4 may be valuable as an early marker for the augmented risk of obesity and insulin resistance.

Dipeptidyl peptidase-4 activity might be a link between tumour necrosis factor alpha and insulin resistance in type 1 diabetes

Tumour necrosis factor alpha (TNF α) leads to β cell damage in type 1 diabetes (T1DM) but also causes insulin resistance (IR). It modulates dipeptidyl peptidase-4 (DPP-4) activity, adipokine linked with both IR and T1DM. We were interested if there is an association of TNF α in conjunction with DPP-4 and IR in T1DM. DPP-4 activity, TNF α concentration measurements, and insulin sensitivity calculation using estimated glucose disposal rate (eGDR) equation were performed in 70 T1DM patients. They were divided into two groups according to eGDR median. The group with higher IR had higher value of DPP-4 activity (27.57 ± 1.77 vs. 18.33 ± 1.14, p < 0.001) and TNF α concentration (12.91 ± 0.83 vs. 6.72 ± 0.36, p < 0.001). TNF α concentration and DPP-4 activity negatively correlated with eGDR (r = -0.616, p < 0.001 and r = -0.643, p < 0.001) while correlating positively with each other (r = 0.422; p = 0.001). The linear regression showed that eGDR decreases for 0.166 mg kg(-1) min(-1) by TNF α concentration increase of 1 pg/mL (p < 0.001) and for 0.090 mg kg(-1) min(-1) by DPP-4 activity increase of 1 U/L (p = 0.001) when adjusted for age, gender disease duration, glycated haemoglobin, body mass index and waist-to-hip ratio. eGDR decreased by additional 0.60 mg kg(-1) min(-1) (B = -0.150, p < 0.001) when DPP-4 activity was additionally adjusted for TNF α. TNF α concentration is associated with IR, correlates with its severity and increases the drop in insulin sensitivity modulated by DPP-4 activity. Whether TNF α involvement in the insulin signalling pathway is mediated by DPP-4 activity needs to be further evaluated.

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.