Beta cell mass and growth after syngeneic islet cell transplantation in normal and streptozocin diabetic C57BL/6 mice

In islet transplantation, nonimmunological factors such as limited growth capacity or increased death rate could reduce the beta cell mass in the graft and lead to failure of the transplant. We studied the evolution of beta cell replication and mass after transplantation of insufficient, minimally sufficient, or excessive islet tissue. Streptozocin diabetic C57BL/6 mice received 150 or 300 syngeneic islets under the kidney capsule and normal mice received 300 islets. In streptozocin diabetic mice 300 islets restored normoglycemia; beta cell replication in transplanted islets was similar to replication in normal pancreas and beta cell mass in the graft remained constant. In contrast, 150 islets were insufficient to achieve normoglycemia; beta cell replication was increased initially but not by 18 or 30 d despite persistent hyperglycemia, and beta cell mass fell progressively. When islets were transplanted into normal recipients, beta cell replication remained normal but beta cells underwent atrophy and mass in the graft was substantially reduced. Therefore, with a successful islet transplant, in diabetic mice beta cell replication and mass remain constant. In contrast, when insufficient islet tissue is transplanted an initial increase in beta cell replication can not compensate for a decline in beta cell mass. When excessive islet tissue is transplanted, beta cell mass is reduced despite normal beta cell replication.

The amphioxus genome illuminates vertebrate origins and cephalochordate biology.

Cephalochordates, urochordates, and vertebrates evolved from a common ancestor over 520 million years ago. To improve our understanding of chordate evolution and the origin of vertebrates, we intensively searched for particular genes, gene families, and conserved noncoding elements in the sequenced genome of the cephalochordate Branchiostoma floridae, commonly called amphioxus or lancelets. Special attention was given to homeobox genes, opsin genes, genes involved in neural crest development, nuclear receptor genes, genes encoding components of the endocrine and immune systems, and conserved cis-regulatory enhancers. The amphioxus genome contains a basic set of chordate genes involved in development and cell signaling, including a fifteenth Hox gene. This set includes many genes that were co-opted in vertebrates for new roles in neural crest development and adaptive immunity. However, where amphioxus has a single gene, vertebrates often have two, three, or four paralogs derived from two whole-genome duplication events. In addition, several transcriptional enhancers are conserved between amphioxus and vertebrates--a very wide phylogenetic distance. In contrast, urochordate genomes have lost many genes, including a diversity of homeobox families and genes involved in steroid hormone function. The amphioxus genome also exhibits derived features, including duplications of opsins and genes proposed to function in innate immunity and endocrine systems. Our results indicate that the amphioxus genome is elemental to an understanding of the biology and evolution of nonchordate deuterostomes, invertebrate chordates, and vertebrates.

Neural regulation of pancreatic islet cell mass and function.

Intracellular glucose signalling pathways control the secretion of glucagon and insulin by pancreatic islet α- and β-cells, respectively. However, glucose also indirectly controls the secretion of these hormones through regulation of the autonomic nervous system that richly innervates this endocrine organ. Both parasympathetic and sympathetic nervous systems also impact endocrine pancreas postnatal development and plasticity in adult animals. Defects in these autonomic regulations impair β-cell mass expansion during the weaning period and β-cell mass adaptation in adult life. Both branches of the autonomic nervous system also regulate glucagon secretion. In type 2 diabetes, impaired glucose-dependent autonomic activity causes the loss of cephalic and first phases of insulin secretion, and impaired suppression of glucagon secretion in the postabsorptive phase; in diabetic patients treated with insulin, it causes a progressive failure of hypoglycaemia to trigger the secretion of glucagon and other counterregulatory hormones. Therefore, identification of the glucose-sensing cells that control the autonomic innervation of the endocrine pancreatic and insulin and glucagon secretion is an important goal of research. This is required for a better understanding of the physiological control of glucose homeostasis and its deregulation in diabetes. This review will discuss recent advances in this field of investigation.

Assessment of letrozole and tamoxifen alone and in sequence for postmenopausal women with steroid hormone receptor-positive breast cancer: the BIG 1-98 randomised clinical trial at 8·1 years median follow-up.

BACKGROUND: Postmenopausal women with hormone receptor-positive early breast cancer have persistent, long-term risk of breast-cancer recurrence and death. Therefore, trials assessing endocrine therapies for this patient population need extended follow-up. We present an update of efficacy outcomes in the Breast International Group (BIG) 1-98 study at 8·1 years median follow-up. METHODS: BIG 1-98 is a randomised, phase 3, double-blind trial of postmenopausal women with hormone receptor-positive early breast cancer that compares 5 years of tamoxifen or letrozole monotherapy, or sequential treatment with 2 years of one of these drugs followed by 3 years of the other. Randomisation was done with permuted blocks, and stratified according to the two-arm or four-arm randomisation option, participating institution, and chemotherapy use. Patients, investigators, data managers, and medical reviewers were masked. The primary efficacy endpoint was disease-free survival (events were invasive breast cancer relapse, second primaries [contralateral breast and non-breast], or death without previous cancer event). Secondary endpoints were overall survival, distant recurrence-free interval (DRFI), and breast cancer-free interval (BCFI). The monotherapy comparison included patients randomly assigned to tamoxifen or letrozole for 5 years. In 2005, after a significant disease-free survival benefit was reported for letrozole as compared with tamoxifen, a protocol amendment facilitated the crossover to letrozole of patients who were still receiving tamoxifen alone; Cox models and Kaplan-Meier estimates with inverse probability of censoring weighting (IPCW) are used to account for selective crossover to letrozole of patients (n=619) in the tamoxifen arm. Comparison of sequential treatments to letrozole monotherapy included patients enrolled and randomly assigned to letrozole for 5 years, letrozole for 2 years followed by tamoxifen for 3 years, or tamoxifen for 2 years followed by letrozole for 3 years. Treatment has ended for all patients and detailed safety results for adverse events that occurred during the 5 years of treatment have been reported elsewhere. Follow-up is continuing for those enrolled in the four-arm option. BIG 1-98 is registered at clinicaltrials.govNCT00004205. FINDINGS: 8010 patients were included in the trial, with a median follow-up of 8·1 years (range 0-12·4). 2459 were randomly assigned to monotherapy with tamoxifen for 5 years and 2463 to monotherapy with letrozole for 5 years. In the four-arm option of the trial, 1546 were randomly assigned to letrozole for 5 years, 1548 to tamoxifen for 5 years, 1540 to letrozole for 2 years followed by tamoxifen for 3 years, and 1548 to tamoxifen for 2 years followed by letrozole for 3 years. At a median follow-up of 8·7 years from randomisation (range 0-12·4), letrozole monotherapy was significantly better than tamoxifen, whether by IPCW or intention-to-treat analysis (IPCW disease-free survival HR 0·82 [95% CI 0·74-0·92], overall survival HR 0·79 [0·69-0·90], DRFI HR 0·79 [0·68-0·92], BCFI HR 0·80 [0·70-0·92]; intention-to-treat disease-free survival HR 0·86 [0·78-0·96], overall survival HR 0·87 [0·77-0·999], DRFI HR 0·86 [0·74-0·998], BCFI HR 0·86 [0·76-0·98]). At a median follow-up of 8·0 years from randomisation (range 0-11·2) for the comparison of the sequential groups with letrozole monotherapy, there were no statistically significant differences in any of the four endpoints for either sequence. 8-year intention-to-treat estimates (each with SE ≤1·1%) for letrozole monotherapy, letrozole followed by tamoxifen, and tamoxifen followed by letrozole were 78·6%, 77·8%, 77·3% for disease-free survival; 87·5%, 87·7%, 85·9% for overall survival; 89·9%, 88·7%, 88·1% for DRFI; and 86·1%, 85·3%, 84·3% for BCFI. INTERPRETATION: For postmenopausal women with endocrine-responsive early breast cancer, a reduction in breast cancer recurrence and mortality is obtained by letrozole monotherapy when compared with tamoxifen montherapy. Sequential treatments involving tamoxifen and letrozole do not improve outcome compared with letrozole monotherapy, but might be useful strategies when considering an individual patient's risk of recurrence and treatment tolerability. FUNDING: Novartis, United States National Cancer Institute, International Breast Cancer Study Group.

Environmental sex reversal, Trojan sex genes, and sex ratio adjustment: conditions and population consequences.

Abstract The great diversity of sex determination mechanisms in animals and plants ranges from genetic sex determination (GSD, e.g. mammals, birds, and most dioecious plants) to environmental sex determination (ESD, e.g. many reptiles) and includes a mixture of both, for example when an individual's genetically determined sex is environmentally reversed during ontogeny (ESR, environmental sex reversal, e.g. many fish and amphibia). ESD and ESR can lead to widely varying and unstable population sex ratios. Populations exposed to conditions such as endocrine-active substances or temperature shifts may decline over time due to skewed sex ratios, a scenario that may become increasingly relevant with greater anthropogenic interference on watercourses. Continuous exposure of populations to factors causing ESR could lead to the extinction of genetic sex factors and may render a population dependent on the environmental factors that induce the sex change. However, ESR also presents opportunities for population management, especially if the Y or W chromosome is not, or not severely, degenerated. This seems to be the case in many amphibians and fish. Population growth or decline in such species can potentially be controlled through the introduction of so-called Trojan sex genes carriers, individuals that possess sex chromosomes or genes opposite from what their phenotype predicts. Here, we review the conditions for ESR, its prevalence in natural populations, the resulting physiological and reproductive consequences, and how these may become instrumental for population management.

Effets extra-rénaux du facteur natriurétique auriculaire [Extrarenal effects of the atrial natriuretic factor]

The synthesis of peptides which have the natriuretic and vasodilator properties of the atrial natriuretic factor has made it possible to study the physiological role of this recently discovered hormonal system. In addition to renal effects, atrial natriuretic peptides exert vascular, hemodynamic and endocrine actions which may participate in the regulation of plasma and interstitial volume as well as arterial blood pressure. Its acute hypotensive effect, which was observed in normal volunteers and in patients with cardiac failure or hypertension, is not entirely explained by its direct vasodilator effect. The complexity of its role is demonstrated by its inhibiting action on the synthesis and/or the activity of other vasoactive hormones. The observed increase in hematocrit suggests that vascular permeability may be enhanced; the resulting consequences, e.g. on blood viscosity, still need to be elucidated. When infusing atrial natriuretic peptides, there exists a clear delay between the moment steady-state plasma levels are achieved and peak effect occurs. This renders the interpretation of the results very difficult. At this moment, the physiological role of atrial natriuretic peptides as well as their potential future use as therapeutic agents cannot yet be fully appreciated.

Hyponatrémie: une histoire en deux temps... [Hyponatremia: an unusual case report]

Hyponatremia is a frequent finding and asks for a rapid diagnostic evaluation. We report a case of recurrent hyponatremia secondary to an adrenal insufficiency of medicamentous and tuberculous origin. This case illustrates the importance of a rapid etiologic diagnosis of hyponatremia and allows us to review adrenal insufficiency of tuberculous origin. It also stresses the danger of potential drug interactions in case of corticosteroid substitution.

Jonctions communicantes et sécrétion [Gap junctions and secretion]

The emergence of multicellular organisms has necessitated the development of mechanisms for interactions between adjacent and distant cells. A consistent feature of this network is the expression of gap junction channels between the secretory cells of all glands so far investigated in vertebrates. Here, we reviewed the distribution of the gap junctions proteins, named connexins, in a few mammalian glands, and discussed the recent evidence pointing to the participation of these proteins in the functioning of endocrine and exocrine cells. Specifically, available data indicate the importance of gap junctions for the proper control of glucose-induced insulin secretion. Understanding the functions of beta-cell connexins are crucial for the engineering of surrogate cells, which is necessary for implementation of a replacement cell therapy in diabetic patients.

The role of microRNAs in the development of type 2 diabets

Pancreatic ß cells are highly specialized endocrine cells located within the islets of Langerhans in the pancreas. Their main role is to produce and secrete insulin, the hormone essential for the regulation of glucose homeostasis and body's metabolism. Diabetes mellitus develops when the amount of insulin released by ß cells is not sufficient to cover the metabolic demand. In type 1 diabetes (5-10% of diagnoses) insulin deficiency is caused by the autoimmune destruction of pancreatic ß cells. Type 2 diabetes (90% of diagnoses) results from a genetic predisposition and from the presence of adverse environmental conditions. The combination of these factors reduces insulin sensitivity of peripheral target tissues, causes impairment in ß-cell function and can lead to partial loss of ß cells. The development of novel therapeutic strategies for the treatment of diabetes necessitates the comprehension of the cellular processes involved in dysfunction and loss of ß cells. My thesis was focused on the involvement in the physiopathological processes leading to the development of diabetes of a class of small regulatory RNA molecules, called microRNAs (miRNAs) that post- transcriptionally regulate gene expression. Global miRNA profiling in pancreatic islets of two animal models of diabetes, the db/db mice and mice that were fed a high fat diet (HFD), characterized by obesity and insulin resistance, led us to identify two groups of miRNAs displaying expression changes under pre-diabetic and diabetic conditions. Among the miRNAs already upregulated in pre-diabetic db/db mice and HFD mice, miR- 132 was found to have beneficial effects on pancreatic ß cell function and survival. Indeed, mimicking the upregulation of miR-132 in primary pancreatic islet cells and ß-cell lines improved glucose- induced insulin secretion and favored survival of the cells upon exposure to pro-apoptotic stimuli such as palmitate and cytokines. MiR-132 was found to exert its action by enhancing the expression of MafA, a transcription factor essential for ß-cell function, survival and identity. On the other hand, up-regulation of miR-199a-5p and miR-199a-3p was detectable only in the islets of diabetic db/db mice and resulted in impaired insulin secretion and sensitization of the cells to apoptosis. MiR-199a- 5p was found to decrease insulin secretion by inducing the expression of granuphilin, a potent inhibitor of ß cell exocytosis. In contrast, miR-199a-3p was demonstrated to directly target and reduce the expression of two key ß-cell genes, mTOR and cMET, resulting in impaired ß-cell adaptation to metabolic demands and loss by apoptosis. Our findings suggest that miRNAs are important players in the onset of type 2 diabetes. MiRNA expression is adjusted in pancreatic ß cells exposed to a diabetogenic environment. These changes initially concern miRNAs responsible for adaptive processes aimed at compensating the onset of insulin resistance, but later such changes can be overlapped by modifications in the level of several additional miRNAs that favor ß-cell failure and the onset of type 2 diabetes.

Hirsutisme: que faire [Hirsutism, what can be done?]

Hirsutism is a relatively frequent condition in an ambulatory setting affecting about 4% of women. A rational clinical and biochemical diagnostic approach assures an optimal treatment directed at etiologic and pathogenetic factors. The diagnosis of hyperandrogenism is evaluated considering the pathophysiologic mechanisms responsible for excessive growth of hair. Ovarian and adrenal tumors are the most serious diseases that have to be excluded by clinical and biochemical tests. The other causes for hirsutism are treatable by a great variety of modalities, available drugs can inhibit pituitary gonadotropins, the hypothalamo-pituitary axis and the conversion of testosterone into biologically active substrate. Finally the binding of androgens to its receptor can be blocked. These possibilities for treatment and their indications for the different etiologies of hirsutism are discussed.

Prognostic relevance of Masaoka and Müller-Hermelink classification in patients with thymic tumors.

BACKGROUND: To compare the prognostic relevance of Masaoka and Müller-Hermelink classifications. METHODS: We treated 71 patients with thymic tumors at our institution between 1980 and 1997. Complete follow-up was achieved in 69 patients (97%) with a mean follow up-time of 8.3 years (range, 9 months to 17 years). RESULTS: Masaoka stage I was found in 31 patients (44.9%), stage II in 17 (24.6%), stage III in 19 (27.6%), and stage IV in 2 (2.9%). The 10-year overall survival rate was 83.5% for stage I, 100% for stage IIa, 58% for stage IIb, 44% for stage III, and 0% for stage IV. The disease-free survival rates were 100%, 70%, 40%, 38%, and 0%, respectively. Histologic classification according to Müller-Hermelink found medullary tumors in 7 patients (10.1%), mixed in 18 (26.1%), organoid in 14 (20.3%), cortical in 11 (15.9%), well-differentiated thymic carcinoma in 14 (20.3%), and endocrine carcinoma in 5 (7.3%), with 10-year overall survival rates of 100%, 75%, 92%, 87.5%, 30%, and 0%, respectively, and 10-year disease-free survival rates of 100%, 100%, 77%, 75%, 37%, and 0%, respectively. Medullary, mixed, and well-differentiated organoid tumors were correlated with stage I and II, and well-differentiated thymic carcinoma and endocrine carcinoma with stage III and IV (p < 0.001). Multivariate analysis showed age, gender, myasthenia gravis, and postoperative adjuvant therapy not to be significant predictors of overall and disease-free survival after complete resection, whereas the Müller-Hermelink and Masaoka classifications were independent significant predictors for overall (p < 0.05) and disease-free survival (p < 0.004; p < 0.0001). CONCLUSIONS: The consideration of staging and histology in thymic tumors has the potential to improve recurrence prediction and patient selection for combined treatment modalities.

Insulin modulation of luteinizing hormone secretion in normal female volunteers and lean polycystic ovary syndrome patients.

BACKGROUND/AIMS: Endocrine features of polycystic ovary syndrome (PCOS) include altered ovarian steroidogenesis, hyperinsulinemia and abnormal luteinizing hormone (LH) secretion. This study was undertaken to further evaluate the role of insulin to modulate LH secretion in lean PCOS patients with normal insulin sensitivity and normal volunteers. METHODS: The study was performed in five nonobese patients diagnosed with PCOS on the basis of amenorrhea and a polycystic morphology at ovarian ultrasound, and 5 normal controls in early to mid-follicular phase and matched for weight and age. All subjects were phenotyped, and then admitted for 12 h of frequent (q 10') blood sampling on two separate occasions, once for a baseline study and the other time for a hyperinsulinemic and euglycemic clamp study. LH was measured in samples obtained throughout each admission in order to perform LH pulse analysis. RESULTS: Baseline LH secretion in PCOS subjects was significantly different from controls: they had higher LH levels, higher LH/FSH ratios as well as a faster LH pulse frequency than normal women. Insulin administration did not affect the pattern of LH secretion of PCOS patients, whereas it significantly increased the LH pulse frequency while decreasing the LH interpulse intervals in the controls. CONCLUSIONS: These data confirm that an abnormal pattern of LH secretion characteristic of PCOS can be observed in lean patients, and appears independent of peripheral insulin levels. Furthermore, our results in lean controls provide the first direct evidence that peripheral insulin can modulate the activity of hypothalamic gonadotropin-releasing hormone (GnRH) neurons in the human.

Possible synergism of physical exercise and ghrelin-agonists in patients with cachexia associated with chronic heart failure.

The occurrence of cachexia of multifactorial etiology in chronic heart failure (CHF) is a common and underestimated condition that usually leads to poor outcome and low survival rates, with high direct and indirect costs for the Health Care System. Recently, a consensus definition on cachexia has been reached, leading to a growing interest by the scientific community in this condition, which characterizes the last phase of many chronic diseases (i.e., cancer, acquired immunodeficiency syndrome). The etiology of cachexia is multifactorial and the underlying pathophysiological mechanisms are essentially the following: anorexia and malnourishment; immune overactivity and systemic inflammation; and endocrine disorders (anabolic/catabolic imbalance and resistance to growth hormone). In this paper, we review the main pathophysiological mechanisms underlying CHF cachexia, focusing also on the broad spectrum of actions of ghrelin and ghrelin agonists, and their possible use in combination with physical exercise to contrast CHF cachexia.

Insulin degradation by adipose tissue is increased in human obesity

White adipose tissue samples from obese and lean patients were used for the estimation ofinsulin protease and insulin:glutathione transhydrogenase using 1251-labeled insulin. There was no activity detected in the absence of reduced glutathione, which indicates that insulin is cleaved in human adipose "tissue through reduction of the disulfide bridge between the chains. O bese patients showed higher transhydrogenase activity (per U tissue protein wt, per U tissue wt, and in the total adipose tissue mass) than the lean group. There is a significant correlation between the activity per U tissue wt, and protein and total activity in the whole adipose tissue with respect to body mass index, with a higher activity in obese patients. The potential ofinsulin cleavage by adipose tissue in obese patients was a mean 5.6-fold higher than that in controla. The coexistence of high insulinemia and high cleavage capability implies that insulin secretion and turnover are increased in the o bese. Thus, white adipose tissue may be crucial in the control of energy availability through modulation ofinsulin cleavage.