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Resistance to thyroid hormone (RTH) is a rare syndrome characterized by reduced sensitivity to thyroid hormone due to thyroid hormone receptor-beta (TRbeta) gene mutations or deletion. RTH has been classified on the basis of clinical features into generalized (GRTH) and pituitary (PRTH) resistance. There is, however, overlap of clinical and biochemical findings in patients with the two forms of resistance, and similar TRbeta gene mutations have been identified in both. The 2 subtypes of RTH, therefore, are considered to be different manifestations of a single genetic entity. We report a mutation of the TRbeta gene, an arginine to leucine substitution at codon 338 (R338L), in 2 unrelated RTH kindreds of northern Italian ancestry. The same mutation was already reported in a single unrelated kindred affected by PRTH. Five individuals, 3 in the first and 2 in the second family, were clinically evaluated and followed for 3-11 years. During the long-term follow-up, the patients manifested symptoms and signs of hyperthyroidism including palpitations, fine tremors, heat intolerance, increased sweating, increased deep tendon reflexes, moist and warm skin, cardiac rhythm abnormalities, reduced body weight, and reduced bone mineral density. The clinical features of these kindreds are consistent with a predominant PRTH phenotype.

IgG associated with Graves' disease bind to the TSH receptor and alter thyroid growth and function, mainly through the stimulation of adenylyl cyclase. In addition, Graves' IgG are able to interact with the phospholipase C (PLC)/Ca2+ and phospholipase A2 (PLA2)/arachidonic acid (AA) cascades. The activation of this latter pathway leads to thyroid cell growth in vitro. The elucidation of additional mechanisms of action of Graves' IgG has made possible the identification of four subgroups of patients, characterized by IgG with different biochemical activities (extent of cAMP and AA release stimulation in in vitro assays). On the basis of these results, a novel therapeutic approach could be proposed based on the inhibition of PLA2 and AA metabolism. To test this hypothesis, the ability of IgG from 56 Graves' patients to stimulate [3H]thymidine incorporation in FRTL5 thyroid cells in the presence and absence of the cyclooxygenase inhibitor indomethacin (2.5 x 10(-6) mol/L) was measured. A significant reduction in [3H]thymidine incorporation was found (33% inhibition; P < 0.0001) upon pretreatment with indomethacin, suggesting that in vitro thyroid cell growth is regulated by cyclooxygenase metabolites. This strengthens the argument for involvement of the PLA2/AA cascade in the pathophysiology of Graves' disease and the proposal for novel selective pharmacological treatments of these patients.

Impaired insulin action plays a major role in the pathogenesis of type 2 diabetes, a chronic metabolic disorder which imposes a tremendous burden to morbidity and mortality worldwide. Unraveling the molecular mechanisms underlying insulin resistance would improve setting up preventive and treatment strategies of type 2 diabetes. Down-regulation of GALNT2, an UDPN-acetyl-alpha-D-galactosamine polypeptideN-acetylgalactosaminyltransferase-2 (ppGalNAc-T2), causes impaired insulin signaling and action in cultured human liver cells. In addition, GALNT2 mRNA levels are down-regulated in liver of spontaneously insulin resistant, diabetic Goto-Kakizaki rats. To investigate the role of GALNT2 in human hyperglycemia, we measured GALNT2 mRNA expression levels in peripheral whole blood cells of 84 non-obese and 46 obese non-diabetic individuals as well as of 98 obese patients with type 2 diabetes. We also measured GALNT2 mRNA expression in human U937 cells cultured under different glucose concentrations. In vivo studies indicated that GALNT2 mRNA levels were significantly reduced from non obese control to obese non diabetic and to obese diabetic individuals (p

Background High serum resistin levels have been associated with kidney dysfunction. Most of these studies have been carried out in individuals with severe kidney impairment, diabetes, cardiovascular disease and related treatments. Thus, the observed association might have been influenced by these confounders. Our aim was to study the relationship between serum resistin, urinary albumin/creatinine ratio (ACR) and glomerular filtration rate (GFR) in a family-based sample, the Gargano Family Study (GFS) of 635 non diabetic, untreated Whites. Methods A linear mixed effects model and bivariate analyses were used to evaluate the phenotypic and genetic relations between serum resistin and both ACR and eGFR. All analyses were adjusted for sex, age, age squared, BMI, systolic blood pressure, smoking habits and physical exercise. Results After adjustments, resistin levels were slightly positively associated with ACR (β±SE = 0.049±0.023, p = 0.035) and inversely related to eGFR (β±SE = −1.43±0.61, p = 0.018) levels. These associations remained significant when either eGFR or ACR were, reciprocally, added as covariates. A genetic correlation (ρg = −0.31±0.12; adjusted p = 0.013) was observed between resistin and eGFR (but not ACR) levels. Conclusion Serum resistin levels are independently associated with ACR and eGFR in untreated non-diabetic individuals. Serum resistin and eGFR share also some common genetic background. Our data strongly suggest that resistin plays a role in modulating kidney function.

OBJECTIVE High molecular weight (HMW) adiponectin is a predominant isoform of circulating adiponectin and has been related to type 2 diabetes. Previous linkage studies suggest that different genetic components might be involved in determining HMW and total adiponectin levels. RESEARCH DESIGN AND METHODS We performed a genome-wide association study (GWAS) of serum HMW adiponectin levels in individuals of European ancestry drawn from the Nurses’ Health Study (NHS) (N = 1,591). The single nucleotide polymorphisms (SNPs) identified in the GWAS analysis were replicated in an independent cohort of Europeans (N = 626). We examined the associations of the identified variations with diabetes risk and metabolic syndrome. RESULTS We identified a novel locus near the FER gene (5q21) at a genome-wide significance level, best represented by SNP rs10447248 (P = 4.69 × 10−8). We also confirmed that variations near the adiponectin-encoding ADIPOQ locus (3q27) were related to serum HMW adiponectin levels. In addition, we found that FER SNP rs10447248 was related to HDL cholesterol levels (P = 0.009); ADIPOQ variation was associated with fasting glucose (P = 0.04), HDL cholesterol (P = 0.04), and a metabolic syndrome score (P = 0.002). CONCLUSIONS Our results suggest that different loci may be involved in regulation of circulating HMW adiponectin levels and provide novel insight into the mechanisms that affect HMW adiponectin homeostasis.

Objective Obesity and cardiovascular disease recognize a common metabolic soil and may therefore share part of their genetic background. Genome-wide association studies have identified variability at the SH2B1 locus as a predictor of obesity. We investigated whether SNP rs4788102, which captures the entire SH2B1 variability, is associated with coronary artery disease (CAD) and/or myocardial infarction (MI) in patients with type 2 diabetes mellitus (T2DM). Design and setting SNP rs4788102 was typed in 2015 White subjects with T2DM from three CAD case–control studies [ n =740 from the Gargano Hearth Study (GHS, Italy); n =818 from the Joslin Hearth Study (JHS, Boston); n =457 from the University of Catanzaro (CZ, Italy)]. Results SNP rs4788102 (G/A) was not associated with CAD (overall allelic OR=1.06, 95% CI=0.93–1.21; p =0.37). On the contrary, it was associated with MI in GHS (1.42, 1.12–1.81; p =0.004) and in the three samples analyzed together (1.21, 1.04–1.41; p =0.016). Insulin stimulated nitric oxide synthase (NOS) activity in human vein endothelial cells from G/G ( n =4, p =0.03) but not the G/A ( n =5, p =0.83) genotype. Of the SNPs in perfect LD with rs4788102, one (rs7498665) affects amino acid polarity (Ala484Thr) and falls into a highly conserved protein segment of SH2B1 containing a class II SH3 domain binding site. Conclusions Variability at the SH2B1 obesity locus is associated with MI in diabetic patients and with reduced insulin-stimulated NOS activity in human endothelial cells. Further studies are needed to replicate this association and dissect the biology underlying this finding.

Objective— Insulin resistance induces increased pulse pressure (PP), endothelial dysfunction (ED), and reduced bioavailability of endothelium-derived nitric oxide (NO). The genetic background of these 3 cardiovascular risk factors might be partly common. The ENPP1 K121Q polymorphism is associated with insulin resistance and cardiovascular risk. Methods and Results— We investigated whether the K121Q polymorphism is associated with increased PP in white Caucasians and with ED in vitro. In 985 individuals, (390 unrelated and 595 from 248 families), the K121Q polymorphism was associated with PP ( P =8.0×10 −4 ). In the families, the Q121 variant accounted for 0.08 of PP heritability ( P =9.4×10 −4 ). This association was formally replicated in a second sample of 475 individuals ( P =2.6×10 −2 ) but not in 2 smaller samples of 289 and 236 individuals ( P =0.49 and 0.21, respectively). In the individual patients’ data meta-analysis, comprising 1985 individuals, PP was associated with the Q121 variant ( P =1.2×10 −3 ). Human endothelial cells carrying the KQ genotype showed, as compared to KK cells, reduced insulin-mediated insulin receptor autophosphorylation ( P =0.03), Ser 473 -Akt phosphorylation ( P =0.03), and NO synthase activity ( P =0.003). Conclusions— Our data suggest that the ENPP1 Q121 variant is associated with increased PP in vivo and reduced insulin signaling and ED in vitro, thus indicating a possible pathogenic mechanism for the increased cardiovascular risk observed in ENPP1 Q121 carriers.

Insulin resistance (IR) is pathogenic for type 2 diabetes and coronary artery disease (CAD). The K121Q polymorphism of the ENPP1/PC-1 gene is associated with IR. Our aim was to investigate the role of the 121Q variant on the risk of type 2 diabetes and CAD. Nondiabetic control subjects (n = 638), type 2 diabetic patients without CAD (n = 535), and type 2 diabetic patients with CAD (n = 434) from Italy and the U.S. were studied. The proportion of 121Q carriers progressively increased in the three groups (27.4, 28.8, and 33.2%, respectively; adjusted P value = 0.027). Among diabetic patients (n = 969), 121Q carriers had an increased risk of developing type 2 diabetes before the age of 65 years (adjusted odds ratio [OR] 2.26, 95% CI 1.26–4.03; P = 0.006) and having a myocardial infarction (MI) (n = 156) by 50 years of age (3.17, 1.46–6.88, P = 0.007). The 121Q variant was also associated with an increased risk for CAD (1.47, 1.01–2.18; P = 0.049) in diabetic patients who did not smoke (n = 546). In conclusion, the ENPP1/PC-1 121Q variant is associated with a progressive deterioration of the IR-atherogenic phenotype; among diabetic individuals, it is also associated with earlier onset of type 2 diabetes and MI.

Adiponectin is a circulating enhancer of insulin action that is secreted by the adipose tissue. In epidemiological studies, serum levels of this protein predict the risk of type 2 diabetes and cardiovascular events. Serum adiponectin levels have been associated with variants at the adiponectin (APM1) and PPARγ2 loci and have also been linked to markers on 5p15 and 14q13. We investigated the role of these four loci in regulating serum adiponectin in a Caucasian population from Italy. Four haplotype-tagging single-nucleotide polymorphisms (ht-SNPs) (−11377 C>G, −4041 A>C, +45 T>G, and +276 G>T) at the APM1 locus and the PPARγ2 Pro12Ala polymorphism were examined for association with serum adiponectin in 413 unrelated, nondiabetic individuals. Of the five SNPs tested, +276G>T was the only one to be associated with serum adiponectin ( P = 0.032), with “TT” individuals having higher adiponectin levels than other subjects. In a variance-components analysis of 737 nondiabetic members of 264 nuclear families, adiponectin heritability was 30%, with a small but significant proportion explained by the +276 genotype ( P = 0.0034). Suggestive evidence of linkage with adiponectin levels was observed on chromosome 14q13, with a LOD of 2.92 ( P = 0.000057) after including the APM1 +276 genotype in the model. No linkage was observed at 5p15. Our data indicate a strong genetic control of serum adiponectin. A small proportion of this can be attributed in our population to variability at the APM1 locus, but an as yet unidentified gene on 14q13 appears to play a much bigger role.

Resistance to thyroid hormone (RTH) is an inherited disease characterized by reduced tissue sensitivity to thyroid hormone. Approximately 90% of subjects with RTH have mutation in the thyroid hormone receptor beta (TRbeta) gene. Approximately 10% of subjects diagnosed as having RTH do not carry mutation in the TRbeta gene. A possible linkage was reported with the retinoid X receptor-gamma (RXR-gamma) gene in two families. The aim of this study is to search for mutation within the RXR-gamma gene in unrelated subjects with diagnosed RTH without mutations in the TRbeta gene. Four subjects with RTH were studied, and sequence variants in the RXR-gamma gene were searched by polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP). Analysis of all the 10 exons of the RXR-gamma gene, including intron-exon boundaries, promoter region and 3' untranslated region (UTR) reveled two variant bands in subjects II and III. Sequencing of these variants showed two single nucleotide polymorphisms (SNPs): 447CT in exon 3 for patients II and IVS9 + 6AG for patient III. Both SNPs were also present at high frequency in a group of normal subjects and in nonaffected relatives of subject III. In conclusion, in patients with RTH we have found two SNPs in the RXR-gamma gene; these SNPS are common in the general population, thus excluding a role for the RXR-gamma gene in these patients.

OBJECTIVE—Two single nucleotide polymorphisms (SNPs) at the adiponectin locus (+45T>G and +276G>T) have been associated with low circulating adiponectin levels, insulin resistance, and type 2 diabetes. We investigated whether these genetic markers are determinants of coronary artery disease (CAD) in type 2 diabetic patients. RESEARCH DESIGN AND METHODS—A total of 376 consecutive type 2 diabetic patients were studied: 142 case subjects with coronary stenosis >50% or previous myocardial infarction and 234 control subjects with no symptoms, no electrocardiogram (ECG) signs of myocardial ischemia, and a normal ECG stress test (n = 189) and/or (n = 45) with coronary stenosis ≤50%. RESULTS—No association with CAD was observed for the +45 SNP (P = 0.48). By contrast, a significant association was observed for the +276 SNP, with T/T homozygotes having a lower risk of CAD than carriers of other genotypes (adjusted odds ratio [OR] 0.13 [95% CI 0.037–0.46], P = 0.002). A similarly protective effect of the +276 T/T genotype was observed in 110 case and 45 control subjects for whom the CAD status had been determined by angiography (0.04 [0.006–0.30], P = 0.002). Serum adiponectin, although clearly related to several features of the proatherogenic/insulin-resistant phenotype, was not different between control subjects and CAD patients (26 ± 17 vs. 25 ± 13 μg/ml). CONCLUSIONS—In conclusion, the +276 G>T polymorphism is a determinant of CAD risk in type 2 diabetic patients. This marker may assist in the identification of diabetic individuals at especially high risk of CAD, so that preventive programs can be targeted at these subjects.

CD36 is a class B scavenger receptor recognizing a variety of ligands including long-chain fatty acids and modified LDL. We investigated whether genetic variability at this locus is a determinant of free fatty acid (FFA) plasma levels and risk of coronary artery disease (CAD) in Caucasians. Typing of 21 polymorphic markers, evenly spanning the CD36 gene, revealed two linkage disequilibrium (LD) blocks that could be tagged by five polymorphisms (-33137A>G, -31118G>A, 25444G>A, 27645del>ins and 30294G>C). In 585 non-diabetic individuals of Caucasian origin, the 30294G>C polymorphism was significantly associated with FFA levels (P = 0.02)--an effect that was especially visible among men (P = 0.009). A similar association was observed in this gender at -33137 (P = 0.008) and -31118 (P = 0.028). When the five tag polymorphisms were considered together, men carrying the AGGIG haplotype had 31% higher FFA (P = 0.0002) and 20% higher triglycerides (P = 0.025) than non-carriers. The same haplotype was associated with increased risk of CAD in 197 type 2 diabetic individuals from the US (OR = 2.3, 95% CI 1.2-4.2). A similar tendency was observed in a group of 321 type 2 diabetic individuals from Italy (OR = 1.4, 0.9-2.3), resulting in an overall relative risk of 1.6 (1.1-2.3, P = 0.015) in the two populations considered together. By targeted resequencing, we identified a common variant in the CD36 promoter that is in strong LD with the AGGIG haplotype and could be partly responsible for these findings. In conclusion, this comprehensive study of CD36 variability indicates that the common polymorphisms at this locus modulate lipid metabolism and cardiovascular risk in Caucasians.