Alessandra Calcagno

Evidence for osteocalcin production by adipose tissue and its role in human metabolism.

CONTEXT The adipose tissue (AT), which is an endocrine organ, is linked to several metabolic abnormalities. Undercarboxylated osteocalcin (ucOCN) regulates insulin and adiponectin secretion. OBJECTIVE Our objective was to investigate the involvement of OCN in obesity and to evaluate, in vitro and ex vivo, the role of AT in the modulation of this endocrine circuit. DESIGN, PATIENTS, AND SETTING This transversal study involved 83 male subjects, divided according to the World Health Organization body mass index classification, evaluated at Padovas Obesity Outpatient Clinic. METHODS OCN, both undercarboxylated (ucOCN) and carboxylated (cOCN) forms, was measured in serum by ELISA. OCN mRNA expression and protein production were measured by quantitative RT-PCR and immunohistochemistry during in vitro adipogenesis and in sc AT (SAT) and omental AT (OAT) from normal adult men. cOCN and ucOCN release by AT in a simple growth medium was verified by ELISA. RESULTS Overweight and obese patients had a lower ucOCN and ucOC/OCN ratio. In the whole cohort, ucOCN/OCN ratio was negatively correlated to body mass index (rho = -0.233; P < 0.05). OCN mRNA was present in SAT and OAT and during all stages of adipogenesis, with higher expression in the first steps. Immunohistochemistry confirmed the expression of OCN protein. Both SAT and OAT were able to release cOCN and ucOCN. CONCLUSIONS Our data support a pathophysiological link between ucOCN and cOCN balance and obesity. OCN is present in the first phases of adipogenesis but also in human AT ex vivo. AT releases, in vitro, both ucOCN and cOCN, suggesting a possible link between AT and OCN in the regulation of metabolism.

Effects of octreotide exposure during pregnancy in acromegaly

Background  Only six women who were treated with somatostatin analogues (SSAs) throughout their pregnancies have been described so far. The influence of SSAs on the course of pregnancy and newborn outcomes remains largely unknown. Many aspects of SSAs pharmacokinetics in mother and foetus have not yet been defined.

Analysis of insulin sensitivity in adipose tissue of patients with primary aldosteronism

OBJECTIVE The objective of the study was to assess the effect of high aldosterone levels on insulin sensitivity of adipose tissue in humans. METHODS Visceral adipose tissue (VAT) was obtained from patients with aldosterone-producing adenoma (APA; n=14) and, as controls, nonfunctioning adenoma (NFA; n=14) undergoing laparoscopic adrenalectomy. Homeostasis model assessment index was higher and potassium was lower in APA than NFA (P<0.05). Immunohistochemistry, Western blotting, and real-time PCR were used to detect and quantify mineralocorticoid receptor (MR) expression. Transcript levels of peroxisome proliferative-activated receptor-gamma, insulin receptor, glucose transporter 4, insulin receptor substrate-1 and -2, leptin, adiponectin, IL-6, monocyte chemoattractant protein-1, glucocorticoid receptor (GR)-alpha, 11beta-hydroxysteroid dehydrogenase (HSD11B) type 1, and HSD11B2 were quantified. The effect of increasing aldosterone concentrations on 2-deoxy-[3H]d-glucose uptake was tested in human sc abdominal adipocytes. RESULTS Expression of MR was demonstrated in VAT, with no difference between APA and NFA as to mRNA levels of MR, GRalpha, HSD11B1, and glucose metabolism and inflammation factors. In cultured adipocytes, basal and insulin-stimulated glucose uptake were unaffected by 1-100 nM (normal/hyperaldosteronism) and impaired only by much higher, up to 10 microM, aldosterone concentrations. The impairment was prevented by RU486 but not by eplerenone. CONCLUSIONS Gene expression of insulin signaling/inflammatory molecules was similar in VAT of APA and NFA patients, not supporting an effect of aldosterone excess on insulin sensitivity of adipose tissues. Only at pharmacological concentrations and through GR activation, aldosterone reduced glucose uptake in adipocytes. Insulin resistance in primary aldosteronism might occur in compartments other than fat and/or depend on concurrent environmental factors.

Control of the expression of human neuropeptide Y by leptin: in vitro studies.

Neuropeptide Y (NPY) participates in the regulation of reproduction and food intake. The adipose-secreted hormone, leptin, has also been involved in these processes, and has been shown to exert its effects in part by controlling NPY synthesis and release at the hypothalamic level. In the present study, we utilized the SH-SY5Y human neuroblastoma cell line, to study the leptin-NPY interrelationships. SH-SY5Y cells were found to express leptin receptors (RT-PCR and Western blot analyses). A 24-h treatment with leptin at different concentrations did not affect NPY gene expression, but resulted in a stimulation of NPY release. This stimulated secretion was blocked by the combined treatment with leptin and the muscarinic agonist carbachol or the phorbol ester TPA. Leptin and carbachol also caused an increased intracellular content of NPY. In conclusion, the SH-SY5Y human neuroblastoma cell line appears to be a suitable in vitro model for studying the pharmacological effects of leptin on the biosynthesis and secretion of NPY.

Changes in muscle UCP3 expression and serum leptin in food restricted and refed rats

Obesity is a major pathologic condition which represents an important risk factor for Type 2 diabetes and cardiovascular diseases. The discovery of ob gene and its transcript by the group of Friedmann and of the new uncoupling proteins UCP2 and UCP3 widely expressed in different tissues in both animals and humans led us to reconsider the control system of energy balance in obesity. Leptin clearly represents the peripheral satiating factor, signaling to the brain the amount of energy stored in the body according to the lypostatic model. However the role of the new uncouplers on the energy homeostasis is still controversial. In particular, the effect of food restriction and refeeding on UCP3 expression and its relationship with leptin changes are not fully understood. The aim of this study was therefore to investigate the effect of food restriction and refeeding on plasma leptin levels and on the expression of UCP3 in both lean and obese Zucker rats.

Adipogenic potential of skeletal muscle satellite cells

Abstract Satellite cells (SCs) are undifferentiated skeletal muscle cells that allow muscular growth and regeneration. Since their first description, SCs were simply considered myogenic precursors, but now it is widely accepted that SCs are a heterogeneous stem cell population characterized by plasticity and self-renewal. In this report we focus on SCs capacity to undergo adipogenic differentiation both spontaneous and induced by adipogenic factors. Understanding SC behavior is especially important because their adipogenic potential could represent a pathophysiological explanation for the intramuscular fat depots and associated insulin resistance that characterize many metabolic diseases and age-related sarcopenia. Moreover, SC are a therapeutic promise for neuromuscular diseases in the context of tissue engineering, representing an interesting cell source for implantation.

The novel hormone INSL3 is expressed in human testicular Leydig cell tumors: A clinical and immunohistochemical study

Insulin-like 3 (INSL3) is a novel peptidic hormone member of the relaxin-insulin-like family of peptide factors. It is almost exclusively produced by Leydig cells within the testis and participates to the complex mechanisms leading to physiological testicular descent during embryonic development. We performed a retrospective study evaluating clinical and histopathological characteristics of 13 patients surgically treated for testicular tumor and diagnosed to be affected by Leydig cell tumor (LCT). Furthermore, it was possible to retrieve the archived paraffin embedded tumor together with neighboring healthy testicular tissue of all subjects affected by LCT (12 benign and 1 malignant form), that were analyzed for INSL-3 expression. Immunohistochemical analysis of the tumor sections of the 13 patients affected by LCT demonstrated constitutive expression of INSL3 protein in all LCT, irrespective of the histological pattern of each LCT and with no significant differences of staining intensity between all tumors. In particular, no gross differences were evident between the staining for INSL3 in the 12 benign LCTs and the only one showing malignant clinical behavior. The present study shows that LCTs, a very rare form of testicular tumor with no proven specific serum and histological markers, express a novel member of the relaxin-insulin-like family of peptide factors previously identified as a secretory product of Leydig cells and named INSL3. Thus, there could be the possibility to evaluate the expression and secretion of this novel hormone as a marker of this rare testicular tumor.

The FXR agonist obeticholic acid normalizes lipid droplet and triglyceride handling in visceral adipose tissue preadipocytes from a non-genomic rabbit model of metabolic syndrome

E. Maneschi, L. Vignozzi, A. Morelli, T. Mello, S. Filippi, I. Cellai, P. Comeglio, E. Sarchielli, A. Calcagno, R. Vettor, GB. Vannelli, L. Adorini and M. Maggi. Department of Experimental and Clinical Biomedical Sciences, University of Florence, Italy Introduction: Adipose tissue (AT) dysfunction is characterized by ectopic fat deposition in the abdominal viscera and liver, inflammatory and adipokine dysregulation, and insulin resistance and may be a more important mediator than total fat mass of type 2 diabetes, hypertension and dyslipidaemia development, all these features clustering in the metabolic syndrome (MetS). We recently demonstrated that the selective FXR agonist obeticholic acid (OCA) ameliorates the metabolic profile and reduces visceral AT (VAT) in a high-fat diet (HFD)-induced rabbit model of MetS (1).

A Dose-Response Elevation in Hepatic Glucose Uptake is Paralleled by Liver Triglyceride Synthesis and Release

Background and aims. Enhanced release of triglycerides (TG) by the liver is implicated in the pathogenesis of the metabolic syndrome. The aim of the study was to evaluate whether a primary elevation in hepatic glucose utilization (HGU), as induced by an acute rise in circulating glucose values during physiological hyperinsulinemia, promotes TG synthesis in spite of the reduction in free fatty acids (FFA) levels. Methods. Glucose dose–response studies were conducted in anesthetized pigs using positron emission tomography (PET) to quantify HGU during fasting euglycemic conditions (EF), and under two-step hyperglycemic hyperinsulinemia (1st-HH +3.0, 2nd-HH +6.0 mmol/L over EF glucose values). Liver biopsies were obtained in three animals to evaluate the relationship between glucose exposure and hepatic fat content. Results. Plasma glucose levels were progressively increased in the two-step studies, and otherwise stable within every hour of PET scanning. HGU increased almost fivefold with raising glucose levels, from 0.033 ± 0.009 in EF to 0.149 ± 0.043 in 1st-HH, p = 0.02, and to 0.138 ± 0.050 μmol/min/g in 2nd-HH, p = 0.03. Circulating TG concentrations increased by 50 and 100% in the two hyperglycemic conditions (p = 0.03 2nd-HH vs. EF), in spite of a 70% suppression in plasma FFA levels. The hepatic TG content paralleled the glucose loads. Plasma γ-glutamyl transferase (γ-GT) was increased by 17% (p < 0.05). Conclusions. A short-term elevation in circulating glucose levels within the physiological postprandial range was sufficient to increase HGU, resulting in a significant synthesis and release of TG by the liver, which was accompanied by an acute rise in γ-GT and liver fat content.