Oxytocin Receptor Gene Polymorphisms in Patients With Diabetes

The Predisposition for Type 2 Diabetes Mellitus and Metabolic Syndrome

Type 2 diabetes mellitus (T2DM) and metabolic syndrome (MetS) are diseases caused by the interaction of genetic and non-genetic factors. Therefore, the aim of our study was to investigate the association between six common genetic polymorphisms and T2DM and MetS in males. A total of 120 T2DM, 75 MetS, and 120 healthy controls (HC) were included in the study. ACE ID, eNOS 4a/b, ATR1 A1166C, OXTR (A>G), SOD1 +35A/C, CAT-21A/T gene polymorphisms were genotyped by PCR or PCR-RFLP techniques. T2DM was diagnosed at an earlier age compared to MetS (54 vs 55 years old, p=0.0003) and the difference was greater in carriers of the OXTR G allele (54 vs 56 years old, p=0.0002) or both OXTR G and eNOS b alleles (54 vs 56, p=0.00016). The SOD1 AA genotype (O.R.=0.11, p=0.0006) and the presence of both ACE I and OXTR1 A (O.R.=0.39, p=0.0005) alleles revealed to be protective for T2DM. SOD1 AA and AC genotypes were protective factors for triglyceride (p=0.0002 and p=0.0005, respectively) and HDL cholesterol (p=0.0002 and p=0.0004, respectively) levels in T2DM patients. ACE DD was identified more frequently in hypertensive T2DM patients (O.R.=3.77, p=0.0005) and in those who reported drinking alcohol (p=0.0001) comparing to HC and T2DM patients who did not drink alcohol, respectively. We observed that T2DM patients who reported drinking alcohol had an increased frequency of ACE DD and eNOS bb (p<0.0001), or ACE DD and OXTR G (p<0.0001) compared to non-drinkers. No gene polymorphisms were associated with MetS.

Novel Risk Variants in the Oxytocin Receptor Gene (OXTR) Possibly Linked to and Associated with Familial Type 2 Diabetes

The oxytocin system is well-known for its role in social bonding and reproduction. Recently, the oxytocin system was found to play other metabolic roles such as regulation of food intake, peripheral glucose uptake, and insulin sensitivity. Variants in OXTR gene have been associated with overeating, increased cardiovascular risk, and type 2 diabetes (T2D). We tested 20 microarray-derived single nucleotide polymorphisms in the OXTR gene in 212 Italian families with rich family history for T2D and found four novel and one previously reported variant suggestively significant for linkage and association with the risk of T2D. Our study has shed some light into the genetics of susceptibility to T2D at least in Italian families.

Oxytocin receptor gene polymorphism and low serum oxytocin level are associated with hyperphagia and obesity in adolescents

BACKGROUND/OBJECTIVES

In recent years, oxytocin (OXT) and polymorphisms in the oxytocin receptor (OXTR) gene have been reported to play roles in obesity pathogenesis. However, there was no study evaluating OXTR gene variants in childhood obesity. The aim of the study was to investigate the relation of OXTR gene polymorphisms and serum OXT levels with metabolic and anthropometric parameters in obese and healthy adolescents.

SUBJECTS/METHODS

The study was a multi-centered case-control study, which was conducted on obese and healthy adolescents aged between 12 and 17 years. Serum OXT and leptin levels were measured, and OXTR gene variants were studied by qPCR (rs53576) and RFLP (rs2254298) methods.

RESULTS

A total of 250 obese and 250 healthy adolescents were included in this study. In the obese group, serum OXT level was lower and leptin level was higher than the control group. In the obese group, frequencies of homozygous mutant (G/G) and heterozygous (A/G) genotypes for rs53576 polymorphism were higher than the control group. Homozygous mutant(G/G) and heterozygous (A/G) genotypes for rs53576 polymorphism were found to increase the risk of obesity compared to the wild type (A/A) genotype [OR = 6.05 and OR = 3.06; p < 0.001, respectively]. In patients with homozygous mutant (G/G) and heterozygous (A/G) genotype for rs53576 polymorphism, serum OXT levels were lower than the wild type (A/A) genotype. In the obese group, hyperphagia score was higher than the control group and correlated negatively with serum OXT level.

CONCLUSIONS

This study revealed that low serum OXT level, which is associated with hyperphagia may be an underlying cause for obesity in adolescents. For rs53576 polymorphism of the OXTR gene, obesity risk is higher in patients with homozygous mutant(G/G) and heterozygous(A/G)genotypes.

Oxytocin and Vasopressin Systems in Obesity and Metabolic Health: Mechanisms and Perspectives

PURPOSE OF REVIEW

The neurohypophysial endocrine system is identified here as a potential target for therapeutic interventions toward improving obesity-related metabolic dysfunction, given its coinciding pleiotropic effects on psychological, neurological and metabolic systems that are disrupted in obesity.

RECENT FINDINGS

Copeptin, the C-terminal portion of the precursor of arginine-vasopressin, is positively associated with body mass index and risk of type 2 diabetes. Plasma oxytocin is decreased in obesity and several other conditions of abnormal glucose homeostasis. Recent data also show non-classical tissues, such as myocytes, hepatocytes and β-cells, exhibit responses to oxytocin and vasopressin receptor binding that may contribute to alterations in metabolic function. The modulation of anorexigenic and orexigenic pathways appears to be the dominant mechanism underlying the effects of oxytocin and vasopressin on body weight regulation; however, there are apparent limitations associated with their use in direct pharmacological applications. A clearer picture of their wider physiological effects is needed before either system can be considered for therapeutic use.

Association of COL4A3 (rs55703767), MMP-9 (rs17576)and TIMP-1 (rs6609533) gene polymorphisms with susceptibility to type 2 diabetes

Type 2 diabetes (T2D) is defined by high levels of glucose in the blood. The collagen IV level is associated with conditions of hyperglycemia and insulin resistance. Collagen type IV α3 chain (COL4A3) is a structural protein of the extracellular matrix (ECM). Matrix metallopeptidase 9 (MMP-9) is an enzyme that degrades the extracellular matrix and its activity is moderated by TIMP metallopeptidase inhibitor 1 (TIMP-1). The aim of the current study was to examine the association between genetic polymorphisms of COL4A3 (rs55703767), MMP-9 (rs17576) and TIMP-1 (rs6609533) in patients with T2D. This case-control study was performed on 120 Iranian patients with T2D and 120 healthy individuals. Genotypes were analyzed using the amplification refractory mutation system-polymerase chain reaction technique. The findings demonstrated significant differences between genotypic and allelic distributions of COL4A3 (G/T) and MMP-9 (A/G) polymorphisms as follows: COL4A3 (G/T); TT vs. GG, odds ratio (OR)=0.235, 95% confidence interval (CI)=0.063-0.0802 (P=0.013) and T vs. G, OR=0.592, 95% CI=0.371-0.943 (P=0.026); MMP-9 (A/G); AG vs. GG, OR=2.429, 95% CI=1.232-4.820 (P=0.008) and A vs. G, OR=2.176, 95% CI=1.155-4.130 (P=0.013). No significant association was identified between TIMP-1 (A/G) polymorphism and T2D in females and males. Thus, the genotypic and allelic distributions of COL4A3 (G/T) and MMP-9 (A/G) polymorphisms were associated with T2D. In addition, no significant association was identified in the genotypic distribution of the TIMP-1 (A/G) gene in females and in males. Further studies in other ethnic groups are required to confirm these findings.

Evaluation of Transcription Factor 7 like 2 polymorphisms and haplotypes in risk of Type 2 Diabetes

Type 2 diabetes (T2D) is a chronic disorder with different genetics and environmental factors. It is one of growing diseases in the world. Previous studies show association between Transcription Factor 7 Like2 (TCF7L2) and T2D. The current study set to evaluate the relation between TCF7L2 polymorphisms and T2D in Southeast Iran. The present case-control study was done on 250 T2D and 250 healthy controls (HCs). For genotyping polymorphisms TCF7L2 (rs11196205) and (rs4132670) Amplification-Refractory Mutation System-Polymers Chain Reaction (ARMS-PCR) was used. The results showed frequency rates of GC and CC genotypes increased in patients compared to controls (31% vs. 6% and 55% vs. 8%, respectively), showing a statistically significant difference (OR=2.67(1.37-5.21), P<0.05 and OR=3.31(1.92-5.71), P< 0.05, respectively). The C allele was associated with an increased risk of T2D, with the frequency of 28% and 11% in patients and controls, respectively (OR=3.11 (2.22-4.37), P< 0.05). Another Polymorphism of this gene TCF7L2 (rs4132670) was not associated with T2D. Furthermore, the haplotype analysis revealed that rs11196205C/rs4132670C and rs11196205C/rs4132670T are risk factors against T2D (OR=2.08 (1.49-2.86, P<0.05 and OR=1.72 (1.06-2.78) P<0.05, respectively). The findings demonstrated that TCF7L2 (rs11196205) genotypes GC, CC, and allele (C) confer risk for susceptibility to T2D.