Autonomic Nervous System in Obesity and Insulin-Resistance-The Complex Interplay between Leptin and Central Nervous System.

The role of the autonomic nervous system in obesity and insulin-resistant conditions has been largely explored. However, the exact mechanisms involved in this relation have not been completely elucidated yet, since most of these mechanisms display a bi-directional effect. Insulin-resistance, for instance, can be caused by sympathetic activation, but, in turn, the associated hyperinsulinemia can activate the sympathetic branch of the autonomic nervous system.

The risk of carotid plaque instability in patients with metabolic syndrome is higher in women with hypertriglyceridemia.

Background: Metabolic syndrome certainly favors growth of carotid plaque; however, it is uncertain if it determines plaque destabilization. Furthermore, it is likely that only some components of metabolic syndrome are associated with increased risk of plaque destabilization. Therefore, we evaluated the effect of different elements of metabolic syndrome, individually and in association, on carotid plaques destabilization.

Natural Bioactive Compounds Useful in Clinical Management of Metabolic Syndrome.

Metabolic syndrome (MetS) is a clinical manifestation characterized by a plethora of comorbidities, including hyperglycemia, abdominal obesity, arterial hypertension, and dyslipidemia. All MetS comorbidities participate to induce a low-grade inflammation state and oxidative stress, typical of this syndrome. MetS is related to an increased risk of cardiovascular diseases and early death, with an important impact on health-care costs.

Functional retinal impairment in type 1 diabetic patients without any signs of retinopathy.

Purpose: To investigate functional and morphological retinal changes in the long-term follow-up in subjects with type 1 diabetes mellitus (DM1) without any signs of retinal vasculopathy.

Methods: Functional testing included Humphrey Matrix perimetry (30-2 threshold program) and white-on-white Humphrey perimetry (HFA, 30-2 SITA standard), while retinal nerve fibre layer (RNFL) thickness was measured by scanning laser polarimetry with variable corneal birefringence compensator.

Results: Data from 20 eyes of 20 subjects with DM1 were analysed.

The role of Humphrey Matrix testing in the early diagnosis of retinopathy in type 1 diabetes.

Aim: The aim of the study was to investigate the role of Humphrey Matrix threshold testing in the detection of early functional retinal impairment in subjects with type 1 diabetes mellitus (DM1) without any signs of retinal vasculopathy, and to investigate the relationship between both functional and structural retinal parameters and metabolic control.

Methods: Thirty eyes of 30 subjects with DM1, with no sign of retinal vasculopathy, and 30 eyes of 30 age- and sex-matched healthy subjects were enrolled in this cross-sectional clinical study. Functional testing included Humphrey Matrix perimetry and white-on-white Humphrey visual field perimetry (HFA), while retinal nerve fibre layer (RNFL) thickness was measured by scanning laser polarimetry with variable corneal birefringence compensator (GDx VCC).

Neurotrophins and neurotrophin receptors mRNAs expression in pancreatic islets and insulinoma cell lines.

Context: It is worth noting that islets and betaTC6-F7 cells share a common pattern of expression of neurotrophins and neurotrophin receptors. Recently, several studies have hypothesized a role for nerve growth factor in pancreatic development and maturation, suggesting that nerve growth factor may be a survival factor for pancreatic beta-cells.

Objective: The aim of the present study was to investigate the pattern of expression of neurotrophins and their relative receptors both in rat pancreatic islets and in a wide panel of insulinoma cell lines.

PKC zeta enhances insulin-like growth factor 1-dependent mitogenic activity in the rat clonal beta cell line RIN 1046-38.

Protein kinase C seems to be linked to the regulation of insulin secretion as well as mitogenic signaling in pancreatic beta cells. To study the impact of different PKC isoforms on insulin secretion and mitogenic activity we stably overexpressed the PKC isoforms alpha, beta2, epsilon, and zeta in the rat clonal beta cell line RIN 1046-38. Under basal conditions PKC alpha, beta2, epsilon, and zeta were identified mainly in the cytosol.

NGF-withdrawal induces apoptosis in pancreatic beta cells in vitro.

Aims/hypothesis: Using primary cultures of human pancreatic islets, purified human pancreatic beta cells and the mouse beta TC6-F7 cell line, we analysed the expression of nerve growth factor, (NGF/NGF) receptors in beta cells. To investigate whether NGF could sub-serve an autocrine antiapoptotic role in beta cells, we studied the effects of NGF withdrawal using a neutralizing monoclonal anti-NGF antibody.

Methods: The expression of NGF and NGF receptors (gp140(Trk-A) and p75(NTR)) were analysed by RT-PCR and immunofluorescence.

Insulin inhibits leptin receptor signalling in HEK293 cells at the level of janus kinase-2: a potential mechanism for hyperinsulinaemia-associated leptin resistance.

Aims/hypothesis: Leptin resistance in obese humans seems to be predominantly caused by signalling abnormalities at the post receptor level. Leptin resistance in obese individuals is frequently associated with insulin resistance and pronounced hyperinsulinaemia indicating a negative crosstalk of the insulin and leptin signalling chain.

Methods: This hypothesis was tested using a cell model of peripheral leptin signalling, i.

The sulfonylurea glimepiride regulates intracellular routing of the insulin-receptor complexes through their interaction with specific protein kinase C isoforms.

Sulfonylureas may stimulate glucose metabolism by protein kinase C (PKC) activation. Because interaction of insulin receptors with PKC plays an important role in controlling the intracellular sorting of the insulin-receptor complex, we investigated the possibility that the sulfonylurea glimepiride may influence intracellular routing of insulin and its receptor through a mechanism involving PKC, and that changes in these processes may be associated with improved insulin action. Using human hepatoma Hep-G2 cells, we found that glimepiride did not affect insulin binding, insulin receptor isoform expression, and insulin-induced receptor internalization.

Insulin receptor substrate (IRS) transduction system: distinct and overlapping signaling potential.

Insulin receptor substrate (IRS) proteins play a central role in maintaining basic cellular functions such as growth and metabolism. They act as an interface between multiple growth factor receptors possessing tyrosine kinase activity, such as the insulin receptor, and a complex network of intracellular signalling molecules containing Src homology 2 (SH2) domains. Four members (IRS-1, IRS-2, IRS-3, IRS-4) of this family have been identified which differ in their subcellular distribution and interaction with SH2 domain proteins.

The common Arg972 polymorphism in insulin receptor substrate-1 causes apoptosis of human pancreatic islets.

Molecular scanning of human IRS-1 gene revealed a common polymorphism causing Gly-->Arg972 change. Diabetic and pre-diabetic carriers of Arg972 IRS-1 are characterized by low fasting levels of insulin and C-peptide. To investigate directly whether the Arg 972 IRS-1 affects human islet cells survival, we took advantage of the unique opportunity to analyze pancreatic islets isolated from three donors heterozygous for the Arg972 and six donors carrying wild-type IRS-1.

The Gly-->Arg972 amino acid polymorphism in insulin receptor substrate-1 affects glucose metabolism in skeletal muscle cells.

Molecular scanning of insulin receptor substrate-1 (IRS-1) revealed several amino acid substitutions. The most common IRS-1 variant, a Gly to Arg972 change, is more prevalent among type 2 diabetic patients. In this study we overexpressed wild-type and Arg972IRS-1 variant in L6 skeletal muscle cells and examined the functional consequences of this polymorphism on insulin metabolic signaling.

Molecular and functional characterization of pituitary adenylate cyclase-activating polypeptide (PACAP-38)/vasoactive intestinal polypeptide receptors in pancreatic beta-cells and effects of PACAP-38 on components of the insulin secretory system.

It has been previously demonstrated that pituitary adenylate cyclase-activating polypeptide (PACAP) regulates insulin secretion. PACAP exerts its biological action by binding to at least three different receptor subtypes coupled to different signal transduction mechanisms. The signaling pathways underlying the insulinotropic effect of PACAP involve mainly the activation of adenylate cyclase to form cAMP, which directly and indirectly, through increased intracellular Ca2+, stimulates insulin exocytosis.

GLUT2 and glucokinase expression is coordinately regulated by sulfonylurea.

In the present study we examined the effect of sulfonylurea on the expression of the glucose transporter GLUT2 and the glucose phosphorylating enzyme Glucokinase (GK) in betaTC6-F7 cells; furthermore, we studied the modifications induced by sulfonylurea on glucose-responsiveness and -sensitivity. Results demonstrate that sulfonylurea increases GLUT2 and GK mRNA expression after 24 h in a dose-dependent manner. On the contrary, after 48 and 72 h a time-dependent reduction of both GLUT2 and GK mRNA occurs.

Expression, processing, and secretion of the neuroendocrine VGF peptides by INS-1 cells.

The neurotropin-inducible gene vgf is expressed in neuronal and endocrine tissues. It encodes a secretory protein that is proteolytically processed in neuronal cells to low molecular mass polypeptides. In the present report, we show that vgf is expressed in different insulinoma cell lines and in normal rat pancreatic islets.

The Gly972-->Arg amino acid polymorphism in IRS-1 impairs insulin secretion in pancreatic beta cells.

Recent studies have identified several polymorphisms in the human insulin receptor substrate-1 (IRS-1) gene. The most prevalent IRS-1 variant, a Gly-->Arg change at the codon 972, has been reported to be increased in prevalence among patients with type 2 diabetes. Carriers of the Arg(972) substitution are characterized by lower fasting insulin and C-peptide levels compared with non-carriers, suggesting that the Arg(972) IRS-1 variant may contribute to impairment of insulin secretion.

Corticosterone treatment differentially affects adrenocorticoid receptors expression and binding in the hippocampus and spinal cord of the rat.

We have studied the immediate and long-term effects of high doses of corticosterone (CORT) on mRNA expression and binding properties of mineralocorticoid receptor and glucocorticoid receptor in the hippocampus and spinal cord of rats. Animals were treated with corticosterone (10 mg/d subcutaneously) for 21 consecutive days, and mineralocorticoid and glucocorticoid receptors were studied either 24 h or 2 wk after the last injection. Major results show that corticosterone treatment reduces mineralocorticoid and glucocorticoid receptor maximum binding capacity (Bmax) in both the hippocampus and spinal cord and that this reduction is partially reversed after cessation of treatment.

Increased abundance of insulin/insulin-like growth factor-I hybrid receptors in skeletal muscle of obese subjects is correlated with in vivo insulin sensitivity.

We reported that in noninsulin-dependent diabetes melitus (NIDDM) patients expression of insulin/insulin-like growth factor I (IGF-I) hybrid receptors is increased in insulin target tissues. Whether this is a defect associated with NIDDM or represents a generalized abnormality associated with insulin resistant states is still unsettled. To address this, we applied a microwell-based immunoassay to measure abundance of insulin receptors, type 1 IGF receptors, and hybrid receptors in muscle of eight normal and eight obese subjects.

Increased abundance of insulin/IGF-I hybrid receptors in adipose tissue from NIDDM patients.

Insulin/IGF-I hybrid receptors composed of an insulin receptor (IR) alphabeta-hemireceptor and a type 1 IGF receptor (IGF-IR) alphabeta-hemireceptor are formed in tissues expressing both molecules. To date there is a limited information about the proportion of hybrids in tissues of normal or diabetic subjects. In this study, we determined the abundance of hybrids in fat from control and NIDDM subjects by using a microwell-based immunoassay.

Dose-dependent effect of octreotide on insulin secretion after OGTT in obesity.

Objective: The present study aimed at evaluating the acute effect of increasing doses of octreotide (OCT), a long-acting somatostatin analogue, on glucose tolerance and insulin secretion.

Methods: A standard and two other oral glucose tolerance tests 30 min after subcutaneous administration of OCT were performed in randomized order in each subject. Obese subjects received 10, 25, or 50 microg of OCT; control subjects received only 10 and 25 microg.

The effects of pregnancy steroids on adaptation of beta cells to pregnancy involve the pancreatic glucose sensor glucokinase.

Pregnancy is associated with adaptive changes including increased number and size of beta cells and enhanced gap-junctional coupling among beta cells, increased glucose-induced insulin response and decreased glucose stimulation threshold. The role exerted by pregnancy steroids and lactogenic hormones in the development of islets upregulation during pregnancy has been widely investigated. In the present study we studied the possibility that pregnancy steroids induce functional modifications of beta cells involving the expression and function of glucokinase.

Distribution of adrenocorticoid receptors in the rat CNS measured by competitive PCR and cytosolic binding.

Combined quantitative polymerase chain reaction (PCR) and cytosolic binding assay techniques are used to measure mineralocorticoid receptor (MR) and glucocorticoid receptor (GR) mRNA, Kd, and Bmax in various rat central nervous system (CNS) regions, namely amygdala, hypothalamus, hippocampus, cortex, pituitary, and cervical, thoracic, and lumbar spinal cord. Two internal standards (i.s.

Distribution of insulin/insulin-like growth factor-I hybrid receptors in human tissues.

Insulin receptors (IR) and type 1 IGF receptors (IGF-IR) have been shown to form insulin/IGF-I hybrid receptors in tissues expressing both molecules. The biological function of hybrid receptors is still undefined. To date there is no information about the distribution of hybrid receptors in human tissues.

Increased expression of insulin/insulin-like growth factor-I hybrid receptors in skeletal muscle of noninsulin-dependent diabetes mellitus subjects.

Insulin receptors (IR) and IGF-I receptors (IGF-IR) have been shown to form hybrid receptors in tissues coexpressing both molecules. To date there is no information about the distribution of hybrids in tissues of normal or diabetic subjects. We developed a microwell-based immunoassay to quantitate hybrids in small human tissues samples.