A cluster of three single nucleotide polymorphisms in the 3'-untranslated region of human glycoprotein PC-1 gene stabilizes PC-1 mRNA and is associated with increased PC-1 protein content and insulin resistance-related abnormalities.

Glycoprotein PC-1 inhibits insulin signaling and, when overexpressed, plays a role in human insulin resistance. Mechanisms of PC-1 overexpression are unknown. We have identified a haplotype in the 3'-untranslated region of the PC-1 gene that may modulate PC-1 expression and confer an increased risk for insulin resistance. Individuals from Sicily, Italy, carrying the "P" haplotype (i.e., a cluster of three single nucleotide polymorphisms: G2897A, G2906C, and C2948T) were at higher risk (P < 0.01) for insulin resistance and had higher (P < 0.05) levels of plasma glucose and insulin during an oral glucose tolerance test and higher levels of cholesterol, HDL cholesterol, and systolic blood pressure. They also had higher (P < 0.05-0.01) PC-1 protein content in both skeletal muscle and cultured skin fibroblasts. In CHO cells transfected with either P or wild-type cDNA, specific PC-1 mRNA half-life was increased for those transfected with P (t/2 = 3.73 +/- 1.0 vs. 1.57 +/- 0.2 h; P < 0.01). In a population of different ethnicity (Gargano, East Coast Italy), patients with type 2 diabetes (the most likely clinical outcome of insulin resistance) had a higher P haplotype frequency than healthy control subjects (7.8 vs. 1.5%, P < 0.01), thus replicating the association between the P allele and the insulin resistance-related abnormalities observed among Sicilians. In conclusion, we have identified a possible molecular mechanism for PC-1 overexpression that confers an increased risk for insulin resistance-related abnormalities.

Absence of mutations in the gene encoding thyroid transcription factor-1 (TTF-1) in patients with thyroid dysgenesis.

Thyroid transription factor-1 (TTF-1) is a homeodomain-containing nuclear transcription factor, important in regulation of the thyroid-specific genes thyroglobulin (Tg), thyroperoxidase (TPO), and thyrotropin receptor (TSHR). TTF-1 is an early biochemical marker of thyroid differentiation, essential for thyroid development and maintenance of the thyroid differentiated state. It is possible that mutations in titf1 gene encoding TTF-1 could result in failure of the thyroid gland to develop. Single strand conformation polymorphism (SSCP) was used to detect the presence of titf1 gene mutation in a group of 15 patients with congenital hypothyroidism. The etiology of the congenital hypothyroidism included thyroid agenesis (9), sublingual ectopic thyroid (4), and severe hypoplasia (2). The analysis did not identify any titf1 gene mutation, among these patients. These results rule out the presence of titf1 mutations, at least in the coding region, in our thyroid dysgenesis patients. Mutations in titf1 coding region may be an extremely rare event, and was not detected in our small sample size or, alternatively, such a mutant might even be viable since TTF-1 plays an important role in lung, brain, and pituitary development.

Screening of thyrotropin receptor mutations by fine-needle aspiration biopsy in autonomous functioning thyroid nodules in multinodular goiters.

Multinodular goiter (MNG) is characterized by nodules of different size and function. Areas of increased function may emerge, appearing as single, or more frequently, multiple autonomously functioning thyroid nodules (AFTN). The molecular mechanism for the autonomous growth and function of these nodules has been related to mutations in the thyrotropin receptor (TSHR) that constitutively activate the adenylyl cyclase. We searched for mutations in a limited area of the TSHR gene, covering the major mutational hotspot, in 38 AFTNs found in 37 patients with MNGs. We used reverse transcriptase-polymerase chain reaction (RT-PCR) and restriction enzyme analysis of fine-needle aspiration biopsy (FNAB) samples to rapidly identify 4 of the more frequently occurring TSHR mutations: D619G, F631C, T632I and D633E. Mutations were identified in 5 nodules (1 D619G mutation and 4 T632I mutations). Subsequently, the entire transmembrane portion of the TSHR gene was sequenced in a random sample of 12 AFTN samples that were free of mutations by RT-PCR and restriction enzyme analysis. By direct sequencing we identified a new mutation, F666L, in the seventh transmembrane domain in a sample from 1 nodule. Analysis of FMA samples of AFTN is an effective approach to identify TSHR gene mutations because individual mutations may be associated with different growth and function in vitro, our approach might, allow correlation of a given mutation with the clinical behavior in vivo.

The Decorin gene 179 allelic variant is associated with a slower progression of renal disease in patients with type 1 diabetes.

UNLABELLED: Background genetic factors may influence the variability in the rate of progression of kidney disease in type 1 diabetes. In diabetes, progressive mesangial matrix expansion and glomerular sclerosis are, to a large extent, mediated by TGF-beta1. Decorin, a proteoglycan which is a component of the extracellular matrix, regulates TGF-beta1 activity and expression. We have examined the relationship between the 179/183/185 polymorphism of the Decorin gene and the progression of diabetic nephropathy. METHODS: From a cohort of 175 European patients with diabetic nephropathy, we studied 79 patients who were selected because they had a follow-up of at least 2 years (average 6.5 years; range: 2.5-15 years), and regular measurements of serum creatinine on 5 or more occasions. Creatinine clearance (CrCl) calculated from serum creatinine concentration was used as a measure of derived glomerular filtration rate (dGFR). All patients were on antihypertensive therapy. RESULTS: The rate of dGFR decline in the whole cohort was [median (range)] 4.6 (-3.8 to 18) ml/min/year. No patient with 185 allele was found. Patients with 179/183 and 179/179 genotype (n = 14), who were considered together and named 179 carriers, had a slower rate of GFR decline [2.1 (0.06-11.7) ml/min/year] as compared to patients with Decorin 183/183 genotype (n = 65) [5.6 (-3.8 to 18) ml/min/year; p < 0.001]. In addition, when considering individual data, patients carrying the 179 allele had a 3.0 (95%CI: 1.8-4.2)-fold higher probability to be slow progressors (i.e. GFR decline below the median). This difference could not be accounted for by differences in duration of disease, type and duration of antihypertensive therapy, albumin excretion rate, blood glucose or blood pressure control. In a multivariate logistic analysis albumin excretion rate (p < 0.001), mean arterial pressure (p = 0.07) and Decorin gene polymorphism (p = 0.036), but not HbA1c, were independently correlated with the rate of dGFR fall. CONCLUSION: The 179 allele variant of the Decorin gene is related to a slower progression of DN in type 1 diabetic patients with albuminuria and receiving antihypertensive therapy.

ACE, PAI-1, decorin and Werner helicase genes are not associated with the development of renal disease in European patients with type 1 diabetes.

BACKGROUND: Genetic factors are involved in the development of diabetic nephropathy in Type 1 diabetes. We have examined the association of four candidate genes, angiotensin converting enzyme (ACE): insertion/deletion (I/D) polymorphism, plasminogen activator inhibitor-1 (PAI-1): 4G/5G polymorphism, decorin: 179/183/185 polymorphism and Werner syndrome helicase: C/R polymorphism, with the presence of diabetic nephropathy in Type 1 diabetic patients. METHODS: 175 Type 1 diabetic patients with albuminuria (59 with microalbuminuria and 116 with macroalbuminuria) were compared with 136 Type 1 diabetic patients with normoalbuminuria and duration of disease longer than 15 years (mean+/-SD: 25+/-8 years). 200 non-diabetic subjects were also studied as background population. RESULTS: We found no association in the polymorphism of the four genes examined between patients with and without diabetic nephropathy and the control subjects. CONCLUSIONS: The genes studied are unlikely to be involved in the susceptibility to nephropathy in Type 1 diabetic patients.