Genetic variation in insulin receptor beta-chain exons among members of familial type 2 (non-insulin-dependent) diabetic pedigrees

Progression of pregnancy induced diabetes mellitus to type two diabetes mellitus, an ambidirectional cohort study

INTRODUCTION

Diabetes mellitus (DM) is a metabolic disorder characterized by elevated level of blood glucose. It affects more than 422 million people globally. In resource limited settings, the progression of gestational diabetes (GDM) to DM was not well investigated and this research work was conducted to estimate the incidence of DM after GDM and their predictors in resource limited settings.

METHODS

A retrospective and prospective cohort studies were used from January 2010 until December 2019. The data were collected using patients chart review, interview and collecting blood sample. Initially, baseline data were collected from GDM and GDM free women and update data were collected every 3 month. Clinical nurses were used to extract the necessary data from medical charts and to collect the data using patient interview. Laboratory technologists were used to measure the blood glucose level of the study participants. The study was conducted in pregnant women presenting themselves in the referral hospitals of Amhara regional state. The sample size was calculated using Epi-info software. Descriptive statistics were used to describe the profile of study participants. Kaplan Meier survival curve and life-table were used to estimate the survivals of study participants. Incidence density was used to estimate the incidence of DM. Cox regression was used to identify the predictors DM.

RESULTS

A total of 4892 women were followed giving for the response rate of 88.62%. The mean age of study participants at the start of the study was 28.34 years with standard deviation [SD] ±7.48 years. DM was associated with gestational diabetes mellitus [AHR (adjusted hazard ratio); 2.53, 95% CI: 2.14-2.99], frequency of breastfeeding [AHR; 0.72, 95% CI: 0.69-0.74], age [AHR; 1.04, 95% CI: 1.03-1.05], parity [AHR; 1.14, 95% CI: 1.07-1.21], regular physical exercise [AHR; 0.45, 95% CI: 0.37-0.55], family history of DM [AHR; 2.04, 95% CI: 1.76-2.37], stillbirth [AHR; 1.67: 95% CI: 1.34-2.07], abortion [AHR; 2.64, 95% CI: 2.25-3.09].

CONCLUSION

The progression of GDM to DM was very high and special follow up should be implemented for women with a history of abortion, stillbirth, and family history of DM.

Genetic variation in exon 17 of INSR is associated with insulin resistance and hyperandrogenemia among lean Indian women with polycystic ovary syndrome

OBJECTIVE

Polycystic ovary syndrome (PCOS) is a multigenic disorder, and insulin resistance is one of its hallmark features. Polymorphisms in exon 17 of insulin receptor (INSR) gene are reported to be associated with PCOS. We investigated this association in Indian women and its putative relationship with PCOS associated traits, which has not been explored so far.

METHODS

In this case control study, the polymorphisms were investigated by direct sequencing in 180 women with PCOS and 144 age matched controls. Clinical, anthropometric, biochemical, and hormonal parameters were also estimated.

RESULTS

The silent C/T polymorphism at His1058 in exon 17 of INSR was found to be present in our study population. The polymorphic genotype (CT+TT) was significantly associated with PCOS in lean women (chi(2)=8.493, df=1, P=0.004). It showed association with higher fasting insulin levels (P=0.02), homeostasis model assessment of insulin resistance (P=0.005), free androgen index (P=0.03), and lower quantitative insulin sensitivity check index (P=0.004) in lean PCOS women. No other novel or known polymorphism was identified in exon 17 in this cohort.

CONCLUSIONS

The study shows significant association of C/T polymorphism at His1058 of INSR with PCOS in the lean rather than obese Indian women. Its association with indices of insulin resistance and hyperandrogenemia is also seen in the same group. The findings strengthen the concept that pathogenesis of PCOS is different in lean and obese women.

SSCP analysis of the tyrosine kinase domain of the insulin receptor gene: polymorphisms detected in South African black and white subjects

The frequency of DNA polymorphisms in the tyrosine kinase domain (exons 17-21) of the insulin receptor gene was assessed in 30 black and 30 white South Africans, using single-stranded conformation polymorphism and direct sequencing analysis. A comparison of the frequencies of the normal versus the combined polymorphic alleles, found only in exon 17, showed a significant difference between black and white groups (P = 0.037).

Genetics of non-insulin-dependent (type-II) diabetes mellitus

Both genetic and environmental factors contribute to the etiology of non-insulin-dependent diabetes. The genetic component is heterogeneous and in some patients is probably complex, involving multiple genes. Specific genetic defects have been identified for rate monogenic forms of NIDDM: maturity-onset diabetes of the young, or MODY (which is due to glucokinase mutations in about 40% of families), syndromes of extreme insulin resistance (which often involve the insulin receptor), and diabetes-deafness syndromes (with defects in mitochondrial genes). In contrast, the genes involved in common forms of NIDDM are still uncertain. Mutations have been extensively searched in genes regulating insulin signaling and secretion. Some evidence of involvement has been produced for insulin-receptor substrate-1, glycogen synthase, the glucagon receptor, a ras-related protein (Rad), histocompatibility antigens, PC-1, and fatty acid binding protein, but the contributions of these genes to NIDDM is probably small. Other candidate genes (e.g. insulin, insulin receptor, glucose transporters) have been excluded as major diabetogenes. New insights are expected in the near future from the systematic scanning of the genome for linkage with NIDDM.

Insulin resistance is mediated by a proteolytic fragment of the insulin receptor

Insulin resistance is a common clinical feature of obesity and non-insulin-dependent diabetes mellitus, and is characterized by elevated serum levels of glucose, insulin, and lipids. The mechanism by which insulin resistance is acquired is unknown. We have previously demonstrated that upon chronic treatment of fibroblasts with insulin, conditions that mimic the hyperinsulinemia associated with insulin resistance, the membrane-associated insulin receptor beta subunit is proteolytically cleaved, resulting in the generation of a cytosolic fragment of the beta subunit, beta', and that the generation of beta' is inhibited by the thiol protease inhibitor E64 (Knutson, V. P. (1991) J. Biol. Chem. 266, 15656-15662). In this report, we demonstrate that in 3T3-L1 adipocytes: 1) cytosolic beta' is generated by chronic insulin administration to the cells, and that E64 inhibits the production of beta'; 2) chronic administration of insulin to the adipocytes leads to an insulin-resistant state, as measured by lipogenesis and glycogen synthesis, and E64 totally prevents the generation of this insulin-induced cellular insulin resistance; 3) E64 has no effect on the insulin-induced down-regulation of insulin receptor substrate-1, and therefore insulin resistance is not mediated by the down-regulation of insulin receptor substrate-1; 4) under in vitro conditions, partially purified beta' stoichiometrically inhibits the insulin-induced autophosphorylation of the insulin receptor beta subunit; and 5) administration of E64 to obese Zucker fatty rats improves the insulin resistance of the rats compared to saline-treated animals. These data indicate that beta' is a mediator of insulin resistance, and the mechanism of action of beta' is the inhibition of the insulin-induced autophosphorylation of the beta subunit of the insulin receptor.

Molecular screening of the glucokinase gene in familial type 2 (non-insulin-dependent) diabetes mellitus

The glucokinase locus has been implicated by linkage studies in several Caucasian pedigrees with early onset, autosomal dominant diabetes, and mutations have been identified in a large number of these pedigrees. Although mutations have been reported in some pedigrees with late onset Type 2 (non-insulin-dependent) diabetes mellitus, linkage studies of typical familial Type 2 diabetes did not suggest a major role for this locus. Nonetheless, linkage studies were consistent with the hypothesis that mutations of the glucokinase gene were responsible for the pathogenesis of Type 2 diabetes in a minority of pedigrees or one gene in a polygenic disorder. To systematically address this hypothesis, we examined 60 diabetic members of 18 pedigrees ascertained for two or more Type 2 diabetic siblings and eight unrelated diabetic spouses. Initially, the coding regions from each of the 11 glucokinase exons were examined by the sensitive technique of single strand conformation polymorphism analysis to screen for single nucleotide substitutions. Subsequently, we also sequenced each exon from an affected member of the single pedigree in which a glucokinase allele was most likely to segregate with diabetes. Single strand conformation polymorphism analysis detected only three variants, none of which altered the amino acid sequence. No coding or splice site mutations were detected. Likewise, no additional mutations were detected upon direct sequence analysis. However, additional screening of promoter and 3' untranslated regions detected a variant pattern in the untranslated region of exon 10 which appeared to segregate with diabetes and impaired glucose tolerance in one pedigree.(ABSTRACT TRUNCATED AT 250 WORDS)

Linkage analysis of the glucokinase locus in familial type 2 (non-insulin-dependent) diabetic pedigrees

Glucokinase is among the few genes which may play a key role in both insulin secretion and insulin action. Glucokinase is present in pancreatic beta cells where it may have a key role in the glucose sensing mechanism, and it is present in hepatocytes, where it may participate in glucose flux. Glucokinase defects have recently been implicated in maturity-onset diabetes of the young. To examine the hypothesis that glucokinase plays a key role in the predisposition to common familial Type 2 (non-insulin-dependent) diabetes mellitus, we typed 399 members of 18 Utah pedigrees with multiple Type 2 diabetic individuals for two markers in the 5' and 3' flanking regions of the glucokinase gene. Linkage analysis was performed under both dominant and recessive models. We also repeated these analyses with individuals with impaired glucose tolerance who were considered affected if their stimulated (2-h) glucose exceeded age-specific normal levels for 95% of the population. Under several dominant models, linkage was significantly excluded, and under recessive models log of the odds (LOD) score was less than -1. We were also unable to demonstrate statistical support for the hypothesis that a small subgroup of pedigrees had glucokinase defects, but the most suggestive pedigree (individual pedigree LOD 1.8-1.9) ranked among the youngest and leanest in our cohort. We can exclude a major role for glucokinase in familial Type 2 diabetes, but our data cannot exclude a role for this locus in a minority of pedigrees.(ABSTRACT TRUNCATED AT 250 WORDS)

Detection of sequence variations in the human insulin-receptor gene by parallel denaturing gradient gel electrophoresis

We developed a parallel denaturing gradient gel electrophoresis (DGGE) protocol to maximize the detection of nucleotide variants in the DNA sequence coding for the mature insulin receptor and in splice site junctions. The melting behaviours of exons 2 to 22 and flanking intronic sequences were computer-simulated using two programs, MELT87 and SQHTX. The data obtained from computer analysis were used to select primers for amplification by polymerase chain reaction and optimal electrophoretic conditions. The ability of this protocol to detect nucleotide changes at the insulin-receptor locus was assessed by studying amplified DNA of a patient with leprechaunism whose insulin-receptor mutations were known and by screening the insulin-receptor gene for polymorphisms in a population of unrelated caucasian individuals. Our results demonstrate that this DGGE protocol is sensitive since it detected (1) sequence variants reported to be undetectable by means of parallel DGGE, (2) previously characterized insulin-receptor nucleotide variants, and (3) unreported polymorphisms at the insulin-receptor locus of caucasian individuals. It is also simple as perpendicular denaturing gradient gels are not required. Application of this protocol will facilitate the search for molecular defects underlying the pathogenesis of insulin resistance observed in genetic syndromes of severe insulin resistance as well as in other metabolic disorders. In addition, its ability to detect several regions of the insulin-receptor gene displaying a number of common polymorphic sites and being multiallelic will contribute to linkage studies in families with diabetic and/or insulin-resistant subjects.