Age is not the only risk factor in COVID-19: the role of comorbidities and of long staying in residential care homes.

BACKGROUND: The actual SARS-CoV-2 outbreak caused a highly transmissible disease with a tremendous impact on elderly people. So far, few studies focused on very elderly patients (over 80 years old). In this study we examined the clinical presentation and the outcome of the disease in this group of patients, admitted to our Hospital in Rome. METHODS: This is a single-center, retrospective study performed in the Sant'Andrea University Hospital of Rome. We included patients older than 65 years of age with a diagnosis of COVID-19, from March 2020 to May 2020, divided in two groups according to their age (Elderly: 65-80 years old; Very Elderly > 80 years old). Data extracted from the each patient record included age, sex, comorbidities, symptoms at onset, the Pneumonia Severity Index (PSI), the ratio of the partial pressure of oxygen in arterial blood (PaO2) to the inspired oxygen fraction (FiO2) (P/F) on admission, laboratory tests, radiological findings on computer tomography (CT), length of hospital stay (LOS), mortality rate and the viral shedding. The differences between the two groups were analyzed by the Fisher's exact test or the Wilcoxon signed-rank test for categorical variables and the Mann-Whitney U test for continuous variables. To assess significance among multiple groups of factors, we used the Bonferroni correction. The survival time was estimated by Kaplan-Meier method and Log Rank Test. Univariate and Multivariate logistic regression were performed to estimate associations between age, comorbidities, provenance from long-stay residential care homes (LSRCH) s and clinical outcomes. RESULTS: We found that Very Elderly patients had an increased mortality rate, also due to the frequent occurrence of multiple comorbidities. Moreover, we found that patients coming from LSRCHs appeared to be highly susceptible and vulnerable to develop severe manifestations of the disease. CONCLUSION: We demonstrate that there were considerable differences between Elderly and Very Elderly patients in terms of inflammatory activity, severity of disease, adverse clinical outcomes. To establish a correct risk stratification, comorbidities and information about provenience from LSRCHs should be considered.

Serum interleukin-6 levels are increased in HIV-infected patients that develop autoimmune disease during long-term follow-up.

BACKGROUND: Elevated IL-6 levels have been associated with both autoimmune diseases and treated HIV-seropositive (HIV+) subjects. However, few data on classic and trans-signaling IL-6 in autoimmune thyroid diseases and HIV+ subjects developing autoimmune disorders are currently available. MATERIALS AND METHODS: A total of 102 patients were included in the study. They were subdivided into two groups. Group A consisted in 51 HIV+ patients, who were followed-up for a period of five years in search of possible occurrence of autoimmune diseases. Ten of them, treated with antiretroviral therapy (ART), developed an autoimmune disorder, namely Hashimoto's thyroiditis, and psoriasis. Group B consisted in 51 patients affected by Hashimoto's thyroiditis (HT). Serum levels of the free form of IL-6 were analyzed by ELISA in all patients and for HIV+ patients at the beginning of the follow-up, before initiation of ART. RESULTS: Mean serum levels of IL-6 were similar in Group A and in Group B. In Group B, IL-6 levels showed a 5.8% increase compared with assay minimum detectable dose corresponding to 1% of full serum IL-6 level. However, serum levels of free IL-6 were increased in those HIV+ patients who developed autoimmune disorders (5.8±2.8pg/ml) and in these patients, the highest levels of free IL-6 correlated with age and CD4 cellular counts. CONCLUSIONS: The present study indicates a correlation between serum free IL-6 levels and the occurrence of autoimmune disease in HIV+ population, treated with ART during a long-term follow-up. The increased levels of serum free IL-6 were observed before ART treatment was initiated, indicating that IL-6 measurement in such patients may represent an early predictor of development of autoimmune disease.

Effects of long-term hormone replacement therapy: results from a cohort study.

The positive effects of hormonal replacement therapy (HRT) in protecting the cardiovascular system in women have been supported by several observational studies, while also being questioned by other randomized controlled trials. Today, it is unclear whether HRT plays a crucial role, or even whether there is any role at all, for this therapy in preventing or in lowering cardiovascular disease (CVD). In the present study, we have evaluated the effectiveness of long-term HRT in post-menopausal women on the incidence of cardiovascular events and arterial remodeling, as well as on some metabolic factors. Eighty-four post-menopausal women (mean age: 46.3 ± 5.2; age range: 42-66 yr) underwent HRT for 10.9 ± 1.2 yr (range: 8-12 yr). None of these subjects showed new cardiovascular events, and we found a reduction of the intima-media thickness (baseline: 1.39 ± 0.2, 1.35 ± 0.2, 1.31 ± 0.2 mm) and total cholesterol, LDL and antithrombin III levels were lower, while HDL and fibrinogen levels increased. The study highlights a number of positive effects both on vascular conditions and metabolic and coagulative markers that are usually considered as generic and crucial risk factors for CVD. The relatively low number of patients is perhaps a limitation of this study, however, the long-term period of followup should be considered an interesting and important factor. Furthermore, this study underlines the real-life clinical experience of a Menopause Center.

Serum CA 15-3 is increased in pulmonary fibrosis.

BACKGROUND AND AIM OF THE WORK: Carbohydrate antigen CA 15-3 is a glycoprotein whose expression, aberrant intracellular localization and changes in glycosylation have been associated with a wide range of cancers. Pulmonary fibrosis represents the final evolution of a chronic inflammation and is defined by the overgrowth of fibroblasts and exaggerated extracellular matrix deposition. The aim of the present study was to evaluate the possible diagnostic role of CA 15-3 in fibrosis in different idiopathic interstitial pneumonias. METHODS: CA 15-3 was measured in serum samples from healthy subjects (n=25) and patients affected with idiopathic pulmonary fibrosis (IPF/UIP) (n=20), sarcoidosis (n=22) at different stages (I, II, and III) and systemic sclerosis (n=25). CA 15-3 protein expression was also evaluated by immunohistochemistry in 21 lung biopsies and in 6 primary lung fibroblasts cell lines. RESULTS: The CA 15-3 serum levels were significantly higher in patients with IPF/UIP and with clinically advanced sarcoidosis (stage III). Serum CA 15-3 levels were slightly increased in patients with systemic sclerosis. No difference was observed between serum CA 15-3 levels in patients with sarcoidosis at stages I and II compared with control subjects. In IPF/UIP and in sarcoidosis at stage III elevated CA 15-3 serum levels significantly correlated with decreased total lung capacity, decreased diffusing capacity of carbon monoxide and high resolution computed tomography findings. Immunohistochemical analysis showed an intense specific CA 15-3 staining in fibroblasts within fibroblastic foci, surrounding sarcoid granulomas and in all cell cultures of lung fibroblasts from IPF/UIP lungs. CONCLUSIONS: Our results indicate that increased CA 15-3 levels are associated with pulmonary interstitial damage, fibroblast activity and progression to fibrosis of the lung. Therefore, CA-15-3 may be considered a sensitive marker useful in the identification of patients with advanced fibrosis and more severe prognosis.

Serum hepatocyte growth factor is increased in Hashimoto's thyroiditis whether or not it is associated with nodular goiter as compared with healthy non-goitrous individuals.

BACKGROUND: Some growth factors and cytokines are known to cooperate with TSH in thyroid nodular growth, but few data are available on their circulating levels in Hashimoto's thyroiditis (HT). AIM: To evaluate in HT patients whether thyroid nodules are associated with variations in serum levels of hepatocyte growth factor (HGF) and interleukin-6 (IL-6). SUBJECTS AND METHODS: Serum levels of HGF and IL-6 were measured by enzyme-linked immunosorbent assay in 176 euthyroid subjects, subdivided into 4 groups: A) HT patients with nodular goiter (no.=42); B) non-goitrous HT patients (no.=36); C) non-HT patients with nodular goiter (no.=48), and D) healthy subjects without thyroid disease (no.=50). RESULTS: The highest concentrations of serumHGF were found in patients with nodular goiter, irrespective of the presence of associated HT (groups A and C). Nevertheless, in group A serum HGF levels were significantly higher than in group C (860.8+/-333.6 pg/ml vs 691.5+/-156 pg/ml, p<0.01). Moreover, though serum HGF levels in group B (578.3+/-217 pg/ml) were lower than in group A, they were significantly higher than in healthy controls (group D, 512.7+/-170.4 pg/ml, p<0.001). Serum IL-6 levels were similar in the two HT groups (A and B), and increased with respect to groups C and D. CONCLUSIONS: Serum HGF is increased in HT, especially associated to thyroid nodules, as compared with healthy non-goitrous individuals.

Insulin resistance in postmenopausal women: concurrent effects of hormone replacement therapy and coffee.

BACKGROUND: In postmenopausal women, an increase in insulin resistance is associated with an increased risk of diabetes, cardiovascular disease and breast cancer. Hormone replacement therapy (HRT) can reduce insulin resistance and coffee use is reported to decrease the incidence of diabetes. The aim of our study was to assess possible concurrent effects of HRT and espresso coffee intake on insulin resistance and on interdependent nutritional and clinical features. METHODS: A total of 478 healthy postmenopausal, non-diabetic women (aged 54.5 +/- 4.2 years) were studied: 360 had been on HRT for at least 2 years and 118 were not treated. Insulin resistance was assessed by a conventional homeostasis model (HOMA-IR). RESULTS: Insulin resistance is directly related to body mass index (p < 0.0001), and not with age and blood pressure; hypertensive menopausal women have a slightly higher body mass index but the same degree of insulin resistance as normotensive women. Women on HRT show lower insulin resistance, but not lower prevalence of arterial hypertension. Coffee use is associated with a decrease in insulin resistance in non-obese women receiving HRT, but not in other subsets. CONCLUSIONS: The combination of coffee consumption and HRT could lower insulin resistance in postmenopausal women. In overweight women, greater insulin sensitivity is associated with intake of espresso coffee and not with HRT; in normal weight women, only HRT is associated with lower insulin resistance.

Thyroid fine needle aspiration: how to improve clinicians' confidence and performance with the technique.

Studies from single institutions report an acceptable accuracy rate for thyroid fine needle aspiration (FNA). However, FNA accuracy is much lower in many other centers in Europe and the USA and large multicenter studies indicate that the clinicians' confidence in the FNA technique remains low. One explanation for this is that there is an excess of inadequate and indeterminate findings for a follicular nodule at FNA cytology. In a University Hospital with large and qualified experience on thyroid nodule diagnosis, a review of 320 slides with an FNA diagnosis of indeterminate follicular nodule from different minor Italian Hospitals led to a different diagnosis in 61%. Since ancillary thyroid imaging may be overutilized and only a few authors report a proportion of excised nodules lower than 10%, we suspect that use of the FNA procedure is suboptimal. Several techniques are reported to improve the performance of thyroid FNA. Among these are tumor markers and large needle aspiration biopsy (LNAB). Immunodetection of the tumor marker galectin-3 has been evaluated by large multinational studies. Analysis of LNAB specimens reduces the number of inadequate FNA findings, improves the diagnostic determination of indeterminate follicular FNA findings and represents a better substrate for the determination of galectin-3. Therefore, we propose that clinical practice guidelines reflect these adjuvant techniques to thyroid FNA in order to improve selection criteria for thyroid nodule surgery.

Frizzled-1 is down-regulated in follicular thyroid tumours and modulates growth and invasiveness.

The mechanisms of follicular thyroid carcinoma (FTC) transformation and progression are not well understood. Previously, we detected LOH at 7q21 in all FTCs examined, indicating that loss of genetic material in that region is a common trait in these lesions. To analyse the effects of LOH on gene expression, we performed an analysis of the mRNA expression levels of six different genes, located at 7q21.1-7q21.3. A total of 23 lesions, including eight follicular hyperplasias (FHs), eight follicular adenomas (FAs), two FTCs and five papillary thyroid carcinomas (PTCs) were analysed. The Frizzled-1 (FZD-1) gene, located at 7q21.13, showed the lowest levels of mRNA expression. Down-regulation of FZD-1 expression was also confirmed in an independent series of 69 follicular neoplastic lesions compared to 25 PTCs, analysed by quantitative RT-PCR. In vitro studies showed that FZD-1 expression was also markedly reduced at both protein and mRNA levels in three FTC-derived cell lines (FRO, WRO and FTC-133), while it was normal in the three PTC-derived cell lines (Ca300, Ca301 and K1) examined. We demonstrated that over-expression of FZD-1 in 3 FTC-derived cells decreased invasiveness and proliferation rate, indicating a possible pathogenetic role. In addition, FZD-1 RNA interference in the PTC-derived cell line K1 increased invasiveness. Our data indicated that FZD-1 is involved in growth of follicular tumours and may be considered as a novel marker of this type of tumour.

Expression of hepatocyte growth factor in Hashimoto's thyroiditis with nodular lesions.

Hashimoto's thyroiditis (HT) is an autoimmune thyroid disease frequently associated with hyperplastic nodules (HN)s. Hepatocyte growth factor (HGF) is expressed in benign thyroid nodules and over-expressed in malignant thyroid nodules, particularly in papillary thyroid carcinomas. To elucidate the role of HGF in the development of HNs in association with HT we evaluated, by immunohistochemistry, the expression of HGF in both nodular and extranodular tissues, obtained from 30 HTs and 15 goiter samples. Six normal thyroid glands were used as controls. All normal control tissue samples exhibited no evidence of HGF immunoreaction. HNs showed weak to moderate HGF immunoreaction, which was located exclusively in the cytoplasm of stromal cells (fibroblasts and endothelial cells). However, the percentage of positive cases was higher in HNs arisen in the context of HT, compared to HNs not associated with HT (30/30 or 100% vs 4/15 or 40%; p<0.001). HGF immunoreactivity was also detected in all extranodular tissues from HT specimens (30/30 or 100%), but we found some significant differences. In fact, while in HNs observed in the context of HT lesions HGF was expressed only in stromal cells, in the extranodular tissues from the same thyroid gland affected by HT it was also detected in the cytoplasm of the epithelial follicular cells. Furthermore, HTs showed a much higher HGF staining grade in the extranodular tissue compared to HNs. Finally, a clear positive correlation was observed in HT between the proportion of HGF expressing follicular cells and the grade of lymphoid aggregates of the thyroid gland. In conclusion, HGF is much more frequently and highly expressed in thyroid tissue with HT, compared to goiter. In HT glands HGF can be detected in both follicular thyroid cells and stromal cells, while in HNs, either from goiters or associated with HT, its expression is restricted only to the stromal cells. These data indicate that HGF may play a role in cell proliferation processes occurring in thyroid glands affected by HT, probably under the regulation of the lymphoid infiltrate.

[Hyperhomocysteinemia, oxidative stress, endothelial dysfunction in postmenopausal women]. / Iperomocisteinemia, stress ossidativo, danno endoteliale e menopausa.

AIM: Menopause seems to accelerate the development of atherosclerosis and cardiovascular diseases. Several studies show a significant correlation between elevated homocysteine serum levels and increased cardiovascular risk. Oxidative stress is involved in the pathophysiology of endothelial dysfunction and atherosclerosis. Our study aim was to assess the correlations between intima-media thickness, homocysteine serum levels and oxidative stress both in fertile and postmenopausal women. MATERIALS AND METHODS: We have investigated 34 fertile women (mean age = 42 +/- 2 yrs; BMI = 21 kg/m2 and 34 postmenopausal women (48 +/- 3 yrs; BMI = 22 +/- 2 kg/m2). RESULTS: Results show increased levels of homocysteine, oxidative stress and intima-media tickness (IMT) in postmenopausal women. having a positive correlation with IMT. CONCLUSIONS: The positive correlations between serum levels of homocysteine and IMT in postmenopausal women reinforce the idea that a hyperhomocysteinemia may play a role in the progression of atherosclerosis. The lack of estrogens could be a pathophysiologic risk factor for endothelial damage via an augmented oxidative stress. Clin

Large needle aspiration biopsy and galectin-3 determination in selected thyroid nodules with indeterminate FNA-cytology.

Thyroid fine-needle aspiration biopsy (FNA)-cytology is widely used for the preoperative characterisation of thyroid nodules but this task is difficult for follicular lesions, which often remain undefined. We propose a strategy for improving the preoperative characterisation of selected follicular thyroid proliferations, which is based on large needle aspiration biopsy (LNAB) and galectin-3 expression analysis. Eighty-five thyroid specimens were obtained by LNAB (20-gauge needles) from thyroid nodules with indeterminate follicular FNA-cytology. Aspirated material was processed as a tissue microbiopsy to obtain cell blocks for both cyto/histo-morphological evaluation and galectin-3 expression analysis, by using a purified monoclonal antibody to galectin-3 and a biotin-free immunoperoxidase staining method. Preoperative diagnosis was compared to the final histology. LNAB and cell-block technique allow a preliminary distinction between nodules with a homogeneous microfollicular/trabecular structure, as frequently observed in tumours, and lesions with mixed normo-micro-macrofollicular architecture, as observed in goitre. Furthermore, LNAB provides optimal substrates for galectin-3 expression analysis. Among 85 cases tested, 14 galectin-3-positive cases were discovered preoperatively (11 thyroid cancers and three adenomas confirmed at the final histology), whereas galectin-3-negative cases were 71 (one carcinoma and 70 benign proliferations at the final histology). Sensitivity, specificity and diagnostic accuracy of this integrated morphologic and phenotypic diagnostic approach were 91.6, 97.2 and 95.3%, respectively. In conclusion, LNAB plus galectin-3 expression analysis when applied preoperatively to selected thyroid nodules candidate to surgery can potentially reduce unnecessary thyroid resections.

Immunoexpression of the CD30 ligand/CD30 and IL-6/IL-6R signals in thyroid autoimmune diseases.

To elucidate the role of Th2 cytokines in autoimmune thyroid diseases, we have studied by immunohistochemistry the expression of two Th2 ligand/receptor systems (CD30-L/CD30 and IL-6/IL-6R) in goitrous Graves' disease (GD) and Hashimoto's thyroiditis (HT). A total number of 50 nodular goiters (NG), including 10 GD showing a lymphoid aggregate grade I, 30 HT 8 of which had a lymphoid aggregate of grade I, 12 of grade II and 10 grade III, and 10 colloid goiters have been evaluated. In addition, 5 normal thyroids were included in the study as controls. Reactivity of ligand and cognate receptor of both CD30-L/CD30 and IL-6/IL-6R pathways was observed in a greater proportion of GD, compared to HT (P<0.005). In HT, the expression of CD30-L/CD30 system was detected more frequently than IL-6/IL-6R (P<0.05) and showed an inverse correlation with the grade of lymphoid aggregate, whereas IL-6/IL-6R correlated positively with lymphocyte infiltration (P<0.05). Based on our results concerning a dominance of Th2 cytokines in GD, we postulate that CD30-L/CD30 and IL-6/IL-6R systems could play a major role in the pathogenesis of GD. However, the expression of CD30L/CD30 and IL-6/IL-6R in HT suggests that Th2 mechanisms are involved also in tissue damage of HT. The two systems could contribute to drive the autoimmune response skewing toward a Th2 phenotype and this appears to be correlated with the lymphoid aggregate grade.

Detection and molecular characterisation of thyroid cancer precursor lesions in a specific subset of Hashimoto's thyroiditis.

Hashimoto's thyroiditis (HT) represents the most common cause of hypothyroidism and nonendemic goiter, but its clinical and pathological heterogeneity opens the question if this disease should be more properly considered as a spectrum of different thyroid conditions rather than as a single nosological entity. In this study, we analysed 133 cases of HT for the expression of galectin-3, a lectin molecule involved in malignant transformation, apoptosis and cell cycle control. An unexpected expression of galectin-3 was demonstrated in a subset of HT together with the presence of HBME-1, c-met and cyclin-D1 that are also involved in malignant transformation and deregulated cell growth. Furthermore, a loss of allelic heterozygosity in a specific cancer-related chromosomal region was demonstrated in some HT harbouring galectin-3-positive follicular cells, by using laser capture microdissection. On the basis of the morphological and molecular findings we identified four subsets of HT: (a) HT with classic features of chronic autoimmune thyroiditis; (b) HT associated to hyperplastic/adenomatous lesions; (c) HT harbouring thyroid cancer precursors; (d) HT associated to unequivocal thyroid microcarcinomas. Our findings provide a well-substantiated morphological and molecular demonstration that HT may include a spectrum of different thyroid conditions ranging from chronic autoimmune thyroiditis to thyroiditis triggered by specific immune-response to cancer-related antigens.

Effects of long-term hormone replacement therapy on arterial wall thickness, lipids and lipoproteins, fibrinogen and antithrombin III.

We aimed to study the effects of hormone replacement therapy (HRT) in menopausal women on lipoproteins, blood coagulation, arterial blood pressure and markers of atherosclerosis. A total of 186 postmenopausal women were studied; 98 used HRT (0.625 mg 17 beta-estradiol plus 10 mg progestin) and were followed for 48 months, and were matched with 98 women without therapy. Low-density lipoproteins, high-density lipoproteins, triglycerides, antithrombin III, systolic and diastolic arterial pressure and intima-media thickness were measured at 6, 12, 24, 38 and 48 months. In users of HRT, we found a significant reduction of the lipoproteins, triglycerides, systolic and diastolic pressures and intima-media thickness; however, we found an increase in high-density lipoproteins and anthitrombin III in comparison with non-users. This study has shown a protective effect of HRT on such risk factors and on certain markers of atherosclerosis.

Duration of menopause and behavior of malondialdehyde, lipids, lipoproteins and carotid wall artery intima-media thickness.

AIM: our study assessed whether minor or major hormonal deficiency influenced oxidative status and vascular wall structure in menopausal women. METHODS: the study series was made up of 62 non hypertensive non diabetic menopausal women (mean age 52.3+/-4.7 years) divided into two groups depending on duration of menopause (group 1 duration 0-5 years; group 2 duration over 5 years). Total cholesterol (TC), LDL cholesterol (LDL-C), HDL-cholesterol (HDL-C), triglycerides (TG), malondialdehyde (MDA) and common carotid artery wall intima-media thickness (IMT) were determined in the entire series. RESULTS: mean TC, LDL-C, TG, MDA and IMT values were higher in group 2 than group 1. The intergroup difference between MDA (P<0.007) and IMT values (P<0.006) values was statistically significant. CONCLUSIONS: the study revealed a close temporal correlation between plasma oxidative stress and carotid wall IMT, jeopardizes vascular wall status as menopause proceeds.

Increased c-met expression during ductal beta cell neogenesis in experimental autoimmune diabetes.

C-met immunoreactivity and its co-expression with duct-associated insulin were evaluated in pancreata of non-obese diabetic (NOD) and low-dose streptozotocin (Id-STZ) mice. Diabetic NOD and non-diabetic NOD at the age of 4-8, 15-22 and 30-41 weeks and Balb/c mice at the same age intervals were studied. Ld-STZ mice were studied at day 12 and 24 after STZ administration. A stronger ductal c-met immunoreactivity and a significantly higher number of c-met positive ducts were found in diabetic NOD vs both non-diabetic NOD and Balb/c mice of comparable age. In non-diabetic NOD, the ductal c-met immunoreactivity progressively increased with age and was significantly higher than controls. In 1d-STZ mice a significantly increased ductal c-met immunoreactivity was detected both at day 12 and 24 vs untreated mice. C-met positive ductal cells were also positive for insulin although insulin positive c-met negative ducts were present. This study showed an increased c-met expression and the co-expression of c-met and duct-associated insulin, in both NOD and 1d-STZ mice.

Hyperthyroidism with concurrent thyroid cancer.

The occurrence of thyroid malignancy is considered a rare event in hyperthyroid patients. With the aim of assessing the clinical relevance of this association, we have analyzed the incidence of thyroid cancer in hyperthyroid patients treated by surgery. The incidence of thyroid cancer was retrospectively evaluated in 202 hyperthyroid patients who underwent thyroidectomy during a twenty-year period. A thyroid cancer was diagnosed in 12 cases (5.9 per cent). Histologic examination revealed the presence of papillary carcinoma in 9 cases, follicular carcinoma in 1 case and Hürthle cell carcinoma in 2 cases. The association between thyroid cancer and hyperthyroidism was more frequent in toxic adenomas (17.8 per cent) than in toxic diffuse (5.3 per cent) or multinodular goiters (1.7 per cent). In 8 patients they presented as an occult carcinoma (maximum diameter below 1 cm), but unfavourable histologic features, such as local invasiveness and multifocality, were found in 5 of them. Follow-up data indicate that all 12 patients are currently alive and apparently free of disease. Hyperthyroid patients, particularly those affected by toxic adenomas, should be carefully evaluated to exclude the presence of concurrent malignancy. A special attention should be made moreover to the presence of "occult" lesions that, in our study was characterized in a higher proportion (62.5 per cent) of cases, by unfavourable histologic features.

Disruption of insulin receptor substrate 2 causes type 2 diabetes because of liver insulin resistance and lack of compensatory beta-cell hyperplasia.

To investigate the role of insulin receptor substrate (IRS)-2 in vivo, we generated IRS-2-deficient mice by gene targeting. Although homozygous IRS-2-deficient mice (IRS-2-/- mice) had a body weight similar to wild-type mice, they progressively developed type 2 diabetes at 10 weeks. IRS-2-/- mice showed insulin resistance and a defect in the insulin-stimulated signaling pathway in liver but not in skeletal muscle. Despite insulin resistance, the amount of beta-cells was reduced to 83% of that in wild-type mice, which was in marked contrast to the 85% increase in the amount of beta-cells in IRS-1-deficient mice (IRS-1-/- mice) to compensate for insulin resistance. Thus, IRS-2 plays a crucial role in the regulation of beta-cell mass. On the other hand, insulin secretion by the same number of cells in response to glucose measured ex vivo was significantly increased in IRS-2-/- mice compared with wild-type mice but was decreased in IRS-1-/- mice. These results suggest that IRS-1 and IRS-2 may play different roles in the regulation of beta-cell mass and the function of individual beta-cells.

Mapping a dominant form of multinodular goiter to chromosome Xp22.

Multinodular goiter (MNG) is a common disorder characterized by a nodular enlargement of the thyroid gland and occurring with a female&rcolon;male ratio of 5&rcolon;1. This article reports the analysis of an Italian three-generation pedigree MNG, including 10 affected females and 2 affected males. After linkage to candidate regions previously implicated in various forms of goiter was excluded, a novel MNG locus was searched. Because no male-to-male transmission was present in the study pedigree, an X-linked autosomal dominant pattern of inheritance was hypothesized. Therefore, 18 markers spaced at 10-cM intervals on the X chromosome were examined. A significant LOD score was observed in the Xp22 region, where marker DXS1226 generated a maximum LOD score of 4.73 at a recombination fraction of 0. Analysis of six flanking microsatellites confirmed these data, and haplotype inspection delimited a 9.6-cM interval lying between DXS1052 and DXS8039.

Different subcellular localization and phosphoinositides binding of insulin receptor substrate protein pleckstrin homology domains.

Insulin evokes diverse biological effects through receptor-mediated tyrosine phosphorylation of the insulin receptor substrate (IRS) proteins. Here, we show that, in vitro, the IRS-1, -2 and -3 pleckstrin homology (PH) domains bind with different specificities to the 3-phosphorylated phosphoinositides. In fact, the IRS-1 PH domain binds preferentially to phosphatidylinositol 3,4,5-trisphosphate (PtdIns-3,4,5-P3), the IRS-2 PH domain to phosphatidylinositol 3,4-bisphosphate (PtdIns-3,4-P2), and the IRS-3 PH domain to phosphatidylinositol 3-phosphate. When expressed in NIH-IR fibroblasts and L6 myocytes, the IRS-1 and -2 PH domains tagged with green fluorescent protein (GFP) are localized exclusively in the cytoplasm. Stimulation with insulin causes a translocation of the GFP-IRS-1 and -2 PH domains to the plasma membrane within 3-5 min. This translocation is blocked by the phosphatidylinositol 3-kinase (PI 3-K) inhibitors, wortmannin and LY294002, suggesting that this event is PI 3-K dependent. Interestingly, platelet-derived growth factor (PDGF) did not induce translocation of the IRS-1 and -2 PH domains to the plasma membrane, indicating the existence of specificity for insulin. In contrast, the GFP-IRS-3 PH domain is constitutively localized to the plasma membrane. These results reveal a differential regulation of the IRS PH domains and a novel positive feedback loop in which PI 3-K functions as both an upstream regulator and a downstream effector of IRS-1 and -2 signaling.