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Aim of the Study: APOA5 has been linked to metabolic syndrome (MetS) or its traits in several populations. In North Africa, only the Moroccan population was investigated. Our aim is to assess the association between APOA5 gene polymorphisms with the susceptibility to MetS and its components in the Tunisian population., Materials and Methods: A total of 594 participants from the Tunisian population were genotyped for two polymorphisms rs3135506 and rs651821 located in APOA5 gene using KASPar technology. Statistical analyses were performed using R software., Results: The SNP rs651821 increased the risk of MetS under the dominant model (OR=1.91 [1.17-3.12], P=0.008) whereas the variant rs3135506 was not associated with MetS. After stratification of the cohort following the sex, only the variant rs651821 showed a significant association with MetS among the women group. The influence of the geographic origin of the studied population on the genotype distribution of APOA5 variants showed that the variant rs651821 was significantly associated with MetS only for the Northern population. The association analyses of the variants rs651821 and rs3135506 with different quantitative traits of MetS showed a significant association only between the variant rs3135506 and triglycerides levels., Conclusion: This is the first study reporting the association of APOA5 gene variants with MetS in Tunisia. Our study emphasizes the role of APOA5 variants in the regulation of the triglycerides blood levels. Further studies are needed to confirm the clinical relevance of these associations and to better understand the physiopathology of the MetS., (Copyright © 2017 Elsevier Masson SAS. All rights reserved.)

The FTO (Fat mass and obesity associated) locus has recently been associated with obesity and type 2 diabetes (T2D) in humans. To understand the role of the FTO gene in polycystic ovary syndrome (PCOS) we genotyped single nucleotide polymorphism (SNP) rs1421085 (C/T) in women with PCOS (n=207) and controls (n=100) from a Central European population. The homozygous C/C genotype showed increased prevalence in PCOS patients either obese or with metabolic syndrome (MetS) compared to lean PCOS patients or controls (27.6%, 38.9%, 22.3%, and 16.3%, respectively). In logistic regression, this genotype strongly associated with MetS (P<0.0001, OR 3.2, 95% CI 1.8-5.7) and impaired fasting glucose (IFG) with P<0.0007, OR 7.7, 95% CI 2.1-28.6, independently of BMI or age, and to AUC(gluc) during OGTT (P<0.0001, alpha=0.99), indicating an influential role of the FTO gene in the glucose intolerance component of MetS.

To elucidate genetic determinants of insulin resistance, we investigated insulin receptor (IR) and insulin receptor substrate-1 (IRS-1) genes, in vitro IR function and in vivo insulin sensitivity in a family with Type A syndrome. Two missense IR mutations (Asp59Gly and Leu62Pro) found in the proband, resulted in reduction by 90% of insulin binding to erythrocytes, decreased receptor autophosphorylation and a dramatic reduction of insulin sensitivity. The proband and mother were heterozygote for Gly972Arg IRS-1 variant. Asp59Gly mutation, also carried by proband's brother with no consequence on insulin sensitivity, was inherited from the mother who is diabetic and insulin resistant and Leu62Pro was from the father. We conclude that severity of insulin resistance in the proband may be explained by the genetic condition of compound heterozygote for IR mutations while severe insulin resistance in the mother raises the possibility that other genetic factors, like IRS-1 polymorphisms, may contribute to the phenotypic expression of IR mutations.

In order to establish a working cellular model for the study of post-receptor signaling events, insulin-dependent phosphatidylinositol 3' (PtdIns 3')-kinase activity was investigated in circulating mononuclear cells from normal subjects. The p85 alpha regulatory subunit of PtdIns 3'-kinase co-precipitated with activated insulin receptor as revealed by immunoblotting. Whereas insulin receptor substrate-1 was weakly detected, insulin increased 5.5 +/- 1.5-fold (mean +/- SD) PtdIns 3'-kinase activity in receptor immunoprecipitates. We conclude that insulin-stimulated PtdIns 3'-kinase activity is measurable in circulating mononuclear cells which may constitute an easily available cellular model for the detection of post-receptor defects in insulin-resistant states.

To characterize the carbohydrate moieties of the insulin receptor on IM-9 lymphocytes, the cells were surface iodinated and solubilized, and the insulin receptors were precipitated with anti-receptor antibody. The precipitates were resuspended, subjected to either enzymatic digestion or chemical treatment with trifluoromethanesulfonic acid and the relative mobilities of the alpha and beta subunits before and after treatment were analyzed by polyacrylamide gel electrophoresis and autoradiography. The results indicate that the alpha subunit possesses primarily N-linked carbohydrate which is both complex (Endoglycosidase F sensitive) and polymannose (Endoglycosidase H sensitive). The beta subunit also contains polymannose oligosaccharide units and has, in addition, a substantial amount of carbohydrate which is removed by chemical treatment but is not susceptible to Endoglycosidase F, suggesting the presence of O-linked saccharides. The apparent molecular weights of the core protein of the mature alpha and beta subunits as determined by gel electrophoresis following complete deglycosylation are 98 kDa and 80 kDa, respectively.