Insufficient glucocorticoid receptor signaling and flattened salivary cortisol profile are associated with metabolic and inflammatory indices in type 2 diabetes.

PURPOSE: Impaired negative feedback and hyperactivation of the hypothalamic-pituitary-adrenal (HPA) axis characterizes type 2 diabetes mellitus (T2DM). The glucocorticoid receptor (GR) is a key mediator of HPA axis negative feedback; however, its role in linking hypercortisolemia and T2DM-associated hyperglycemia, hyperlipidemia and inflammation is not yet known. METHODS: In peripheral mononuclear cells (PBMC) from 31 T2DM patients and 24 healthy controls, we measured various GR-signaling parameters such as phosphorylated GR (pGR-S211), GRα/GRß gene expression and GC-sensitivity [using the basal and dexamethasone (DEX)-induced leucine zipper (GILZ) and FK506 binding-protein (FKBP5) mRNA levels as well as the basal interleukin (IL)-1ß protein levels]. Diurnal salivary cortisol curve parameters such as the cortisol awaking response (CAR) and area under the curve (AUCtotal and AUCi) as well as inflammatory and metabolic indices were also determined. RESULTS: T2DM patients exhibited diminished pGR-S211 protein content, increased GRß, decreased basal GILZ and FKBP5 mRNA levels and increased IL-1ß levels. Flattened DEX-induced GILZ and FKBP5 response curves and a flattened salivary cortisol profile characterized T2DM patients. Significant associations of GR measures and saliva cortisol curve parameters with biochemical and clinical characteristics were found. CONCLUSION: Our novel data implicate an insufficient GR signaling in PBMCs in T2DM patients and HPA axis dysfunction. The significant associations of GR-signaling parameters with inflammatory and metabolic indices implicate that GR may be the critical link between HPA axis dysfunction, hypercortisolemia and diabetes-associated metabolic disturbances. Our findings provide significant insights into the contribution of GR-mediated mechanisms in T2DM aetiopathology and therapy.

The role of acetic acid on glucose uptake and blood flow rates in the skeletal muscle in humans with impaired glucose tolerance.

BACKGROUND/OBJECTIVES: Previous studies support the glucose-lowering effect of vinegar. However, the effect of vinegar on muscle glucose metabolism and endothelial function has not been studied in humans. This open, randomized, crossover, placebo-controlled study aims to investigate the effects of vinegar on muscle glucose metabolism, endothelial function and circulating lipid levels in subjects with impaired glucose tolerance (IGT) using the arteriovenous difference technique. SUBJECTS/METHODS: Eight subjects with IGT (4 males, age 46±10 years, body mass index 30±5) were randomised to consume 0.50 mmol vinegar (6% acetic acid) or placebo before a mixed meal. Plasma samples were taken for 300 min from the radial artery and the forearm vein for measurements of glucose, insulin, triglycerides, non-esterified fatty acids (NEFAs) and glycerol. Muscle blood flow was measured with strain gauge plethysmography. Glucose flux was calculated as the arteriovenous difference of glucose multiplied by the blood flow rates. RESULTS: Vinegar compared with placebo: (1) decreased arterial plasma insulin (Poverall<0.001; P75 min=0.014, ß=-42), (2) increased forearm blood flow (Poverall<0.001; P240 min=0.011, ß=1.53; P300 min=0.023, ß=1.37), (3) increased muscle glucose uptake (Poverall<0.001; P60 min=0.029, ß=2.78) and (4) decreased arterial plasma triglycerides (Poverall=0.005; P240 min<0.001, ß=-344; P300 min<0.001, ß=-373), without changing NEFA and glycerol. CONCLUSIONS: In individuals with IGT, vinegar ingestion before a mixed meal results in an enhancement of muscle blood flow, an improvement of glucose uptake by the forearm muscle and a reduction of postprandial hyperinsulinaemia and hypertriglyceridaemia. From this point of view, vinegar may be considered beneficial for improving insulin resistance and metabolic abnormalities in the atherogenic prediabetic state.

Adipose tissue lipolysis and circulating lipids in acute and subacute critical illness: effects of shock and treatment.

PURPOSE: The purpose of this study is to assess lipid metabolism at the tissue level in critically ill subjects. MATERIALS AND METHODS: We studied 182 patients with systemic inflammatory response syndrome/severe sepsis or shock during the acute (day 1) and subacute phase of critical illness (day 6). All subjects had a tissue microdialysis (MD) catheter placed in femoral adipose tissue upon admission to the intensive care unit (ICU). Plasma cholesterol, high-density lipoprotein, low-density lipoprotein, free fatty acids (FFAs), triglyceride, and MD glycerol (GLYC) were measured on days 1 and 6 in the ICU. RESULTS: On admission, 56% of the patients had increased levels (>200 µmol/L) of MD GLYC. Patients with shock displayed more pronounced subcutaneous tissue lipolysis and more profound derangements of circulating lipids vs patients without shock (but no appreciable differences in FFA levels). Furthermore, in patients with shock during the acute period, there were positive, albeit weak, correlations of subcutaneous tissue lipolysis (MD GLYC), plasma FFAs (r=0.260; P=.01), and norepinephrine's dose (r=0.230; P=.01), whereas during the subacute phase, MD GLY levels were higher in patients receiving glucocorticoids (344.7±276.0 µmol/L vs 252.2±158.4 µmol/L; P=.03). CONCLUSIONS: Subcutaneous tissue lipolysis is only one of the many determinants of plasma FFAs. Routinely applied therapeutic modalities in the ICU interfere with adipose tissue metabolism.

Skeletal muscle insulin resistance in morbid obesity: the role of interleukin-6 and leptin.

BACKGROUND: Although insulin resistance in obesity is established, the link between excess body fat and skeletal muscle insulin resistance is obscure. The aim of this study was to investigate whether cytokines secreted from the subcutaneous adipose tissue are related to the sensitivity of glucose metabolism to insulin in skeletal muscle. METHODS: A meal was given to 14 obese and 10 non-obese women. Plasma samples were taken for 360 min from a forearm vein and from the radial artery for glucose and insulin measurements. Interleukin-6, leptin, TNFα, resistin and adiponectin were measured preprandially from the radial artery and from the superficial epigastric vein. Forearm blood flow was measured with plethysmography. RESULTS: (1) In obese vs non-obese: (a) Glucose uptake by skeletal muscle was decreased (AUC (0-360)369 ± 55 vs. 877 ± 146 µmol/100 g tissue, p=0.001) (b) arterial interleukin-6 (2.5 ± 0.5 vs. 1 ± 0.1 pg/ml, p=0.013) and subcutaneous venous interleukin-6 (5 ± 0.5 vs. 3.4 ± 0.5 pg/ml, p=0.027) were increased (c) arterial leptin (63 ± 7 vs. 5 ± 0.6 ng/ml, p<0.0001) and subcutaneous venous leptin 80 ± 8 vs. 6.5 ± 0.7 ng/ml, p<0.0001) were increased. (2) Arterial interleukin-6 (p=0.002) and subcutaneous venous interleukin-6 (p=0.014) were negatively associated with forearm glucose uptake in obese. (3) No association was found between leptin and forearm glucose uptake, after correcting with fat mass. CONCLUSIONS: In morbid obesity: (1) Subcutaneous adipose tissue releases interleukin-6 which could then mediate insulin resistance in skeletal muscle. (2) Although there is increased secretion of leptin by the subcutaneous adipose tissue, leptin levels are not correlated to the sensitivity of glucose metabolism to insulin in muscle.

Effects of adiponectin in TNF-α, IL-6, and IL-10 cytokine production from coronary artery disease macrophages.

Adiponectin, an adipose tissue secreted protein, exhibits anti-inflammatory and antiatherogenic properties. We examined the effects of the globular and full-length adiponectin on cytokine production in macrophages derived from Coronary Artery Disease (CAD) patients and control individuals. Adiponectin's effects in human macrophages upon lipopolysaccharide (LPS) treatment were also examined. Full length adiponectin acted differently on TNF-α and IL-6 production by upregulating TNF-α and IL-6 protein production, but not their mRNA expression. Additionally, full length adiponectin was unable to abrogate LPS proinflammatory effect in TNF-α and IL-6 mRNA expression in CAD and NON-CAD macrophages. In contrast, globular adiponectin appeared to have proinflammatory properties by potently upregulating TNF-α and IL-6 mRNA and protein secretion in human macrophages while subsequently rendered cells resistant to further proinflammatory stimuli. Moreover, both forms of adiponectin powerfully suppressed scavenger MSR-AI mRNA expression and augmented IL-10 protein release, both occurring independently of the presence of LPS or CAD. These data indicate that adiponectin could potentially protect human macrophages via the elevated IL-10 secretion and the suppression of MSR-AI expression. It can also be protective in CAD patients since the reduced adiponectin-induced IL-6 release in CAD macrophages compared to controls, could be beneficial in the development of inflammation related atherosclerosis.

Effect of hyperthyroidism on clearance and secretion of glucagon in man.

OBJECTIVE: Glucagon has been proposed to contribute to the increased glucose production found in hyperthyroidism. However, fasting plasma glucagon levels are not increased in hyperthyroidism suggesting that the activity of the α-cell is normal. Nevertheless, an increase in the clearance rate of glucagon may mask increased glucagon secretion. This study was designed to examine the effects of hyperthyroidism on the kinetics of glucagon. DESIGN AND METHODS: A primed-continuous infusion of glucagon was administered to 9 euthyroid and 9 hyperthyroid subjects at 3 sequential rates (1,200, 3,000 and 6,000 pg/kg/min, each given for 2 h). Arterialized blood was drawn at 15-30 min intervals for determination of glucagon. RESULTS: Fasting plasma glucagon levels were comparable in euthyroids (195±8 pg/ml) and hyperthyroids (231±16 pg/ml). During infusions (1,200, 3,000 and 6,000 pg/kg/min), plasma glucagon increased to 387±19, 624±44 and 977±51 pg/ml in euthyroids and to 348±23, 597±42 and 938±56 pg/ml in hyperthyroids respectively. At these infusion rates, metabolic clearance of glucagon (ml/kg/min) was 6.6±0.5, 7.4±0.6 and 7.9±0.5 in euthyroids and 12.6±2, 8.9±1 and 8.8±0.6 in hyperthyroids, respectively. Metabolic clearance of glucagon differed between hyperthyroids and euthyroids at 1 200 pg/kg/min infusion rate (p=0.001). The basal delivery rate of glucagon (ng/kg/min) was 1.3±0.1 in euthyroids and 2.9±0.6 in hyperthyroids (p=0.0005). CONCLUSIONS: In hyperthyroidism, the secretion and metabolic clearance rates of glucagon are increased. These effects may explain the changes in plasma glucagon levels observed in hyperthyroidism and support the important role of glucagon in increasing endogenous glucose production in this condition.

Rates of lipid fluxes in adipose tissue in vivo after a mixed meal in morbid obesity.

OBJECTIVE: Although insulin resistance in obesity is established, information on insulin action on lipid fluxes, in morbid obesity, is limited. This study was undertaken in morbidly obese women to investigate insulin action on triacylglycerol fluxes and lipolysis across adipose tissue. SUBJECTS AND DESIGN: A meal was given to 26 obese (age 35+/-1 years, body mass index 46+/-1 kg m(-2)) and 11 non-obese women (age 38+/-2 years, body mass index 24+/-1 kg m(-2)). Plasma samples for glucose, insulin, triglycerides and non-esterified fatty acids (NEFAs) were taken for 360 min from a vein draining the abdominal subcutaneous adipose tissue and from the radial artery. Adipose tissue blood flow was measured with (133)Xe. RESULTS: In obese vs non-obese: (1) Arterial glucose was similar, but insulin was increased (P=0.0001). (2) Adipose tissue blood flow was decreased (P=0.0001). (3) Arterial triglycerides (P=0.0001) and NEFAs (P=0.01) were increased. (4) Lipoprotein lipase was decreased (P=0.0009), although the arteriovenous triglyceride differences were similar. (5) Veno-arterial NEFA differences across the adipose tissue were similar. (6) NEFA fluxes and hormone-sensitive lipase-derived glycerol output from 100 g adipose tissue were not different. (7) Total adipose tissue NEFA release was increased (P=0.02). CONCLUSIONS: In morbid obesity: (a) hypertriglycerinemia could be attributed to a defect in the postprandial dynamic adjustment of triglyceride clearance across the adipose tissue, partly caused by blunted BF; and (b) postprandially, there is an impairment of adipose tissue to buffer NEFA excess, despite hyperinsulinemia.

Normal peak nasal inspiratory flow rate values in Greek children and adolescents.

BACKGROUND AND AIM: Peak Nasal Inspiratory Flow Rate (PNIFR) is a clinical trial that has been instituted in clinical practice in order to determine the extent of nasal airway patency and it is used to assess the degree of nasal obstruction. This study attempts to provide tables referring to normal values of PNIFR in children and adolescents. PATIENTS AND METHODS: Three thousand one hundred and seventy pupils aged between 5-18 years, were selected to enter the study. Children with acute or chronic upper airway obstruction, such as acute obstructive pulmonary disease or allergic rhinitis and children below the 3rd percentile for weight and/or height were excluded from the study. All children that took part in the study were subjected to PNIFR measurements by using a portable Youlten Peak Flow meter. RESULTS: A continuous increase of PNIFR values for boys and girls in relation to age increase was recorded. PNIFR values were higher in boys compared to girls and this difference was statistically significant until the age of 12. CONCLUSION: Normal ranges for PNIFR standards are of great importance for the study of nasal patency, evaluation of the degree of nasal obstruction and application of treatment. This is the first time that a detailed description of PNIFR standards becomes available for the Greek population of children and adolescents.

Glucose transporter expression on the plasma membrane of resting and activated white blood cells.

BACKGROUND: In white blood cells (WBC), the increase in glucose utilization is a prominent feature during immune response and this depends on the function of specific glucose transporter (GLUT) isoforms. The objective was to examine the effects of activation by Phorbol 12-myristate 13-acetate (PMA) or lipopolysaccharide (LPS) and insulin on the expression of GLUT isoforms in all subpopulations of WBC. MATERIALS AND METHODS: Blood was withdrawn from 27 healthy subjects. The expression of GLUT1, GLUT3 and GLUT4 on the plasma membrane of resting and activated monocytes, T- and B-lymphocytes and polymorphonuclear cells (PMNs) was determined in the absence and presence of physiological concentrations of insulin, by flow cytometry. RESULTS: GLUT1 did not respond to insulin in either resting or PMA/LPS activated state. In the resting state, monocytes and B-lymphocytes increased the abundance of GLUT3 and GLUT4 on their plasma membrane in response to insulin; in contrast, T-lymphocytes and PMNs were unresponsive to insulin. In the activated state, monocytes, B- and T- lymphocytes increased the expression of all three GLUT isoforms on their plasma membrane, whilst PMNs increased only GLUT1 and GLUT3; in all WBC, insulin augmented the expression of GLUT4 and GLUT3 isoforms in addition to the stimulation provided by the PMA or LPS treatment alone. CONCLUSION: Activation of WBC leads to increased expression of GLUT1, GLUT3 and GLUT4 isoforms on their plasma membrane; this process was further augmented by insulin. During infection, these mechanisms may help to redistribute glucose as a potential source of energy away from peripheral tissues and direct it towards cells that mediate the immune response and are therefore crucial to survival.

Thyroid hormone excess increases basal and insulin-stimulated recruitment of GLUT3 glucose transporters on cell surface.

BACKGROUND: In hyperthyroidism, tissue glucose disposal is increased to adapt to high energy demand. Our aim was to examine the glucose transporter isoforms involved in this process and their regulation through insulin in monocytes from subjects with hyperthyroidism. METHODS: Blood (20 ml) was withdrawn from 12 healthy and 12 hyperthyroid subjects. The abundance of glucose transporter isoforms (GLUT) on the monocyte surface membrane was determined in the absence and presence of insulin (10-100 mU/l) using flow cytometry. Anti-CD14-PE monoclonal antibody was used for monocyte gating. GLUT isoforms were determined after staining the cells with specific antisera to GLUT1, GLUT3 and GLUT4. RESULTS: Hyperthyroidism increased basal monocyte-surface GLUT1, GLUT3 and GLUT4 transporters. In these cells, insulin had a marginal effect on GLUT4 translocation (25 %, p < 0.02) and a more significant effect on GLUT3 translocation (45 %, p < 0.001) on plasma membrane. CONCLUSIONS: In the hyperthyroid state, (1) basal abundance of GLUT1, GLUT3 and GLUT4 transporters on the cell surface is increased; (2) insulin mainly increases the recruitment of GLUT3 and, to a lesser extent, GLUT4 glucose transporters on the plasma membrane. These findings may provide a mechanism to explain the increment of glucose disposal in peripheral tissues in hyperthyroidism.

Restoration of early insulin secretion after a meal in type 2 diabetes: effects on lipid and glucose metabolism.

BACKGROUND: In type 2 diabetes (T2D) insulin secretion after a meal is delayed; this may have an impact on the development of hyperglycaemia and hyperlipidaemia. DESIGN: To investigate this, a meal was given to 15 T2D (age 52 +/- 2 years, BMI 25 +/- 0.8 kg m(-2)) on three different occasions: (1) without treatment, (2) after 120 mg of nateglinide before the meal (acute treatment), and (3) after 3 months of nateglinide (120 mg t.i.d., chronic treatment). Fifteen healthy subjects (CON, age 48 +/- 2 years, BMI 24 +/- 0.5 kg m(-2)) were also studied. Blood was withdrawn for 360 min from veins draining the anterior abdominal subcutaneous adipose tissue (AD) and from an arterialized hand vein. Blood flow (BF) in AD was measured with (133)Xe. Lipoprotein lipase activity (LPL) was calculated as the triacylglycerol (TAG) flux across AD, and hormone-sensitive lipase (HSL) as the glycerol flux minus LPL. RESULTS: (1) In T2D the increase in prandial insulin secretion was delayed; postprandial nonesterified fatty acid (NEFA) and TAG levels in blood were increased, while BF, LPL and TAG clearance were blunted vs. CON. (2) Acute or chronic nateglinide treatment induced a prompt increase in prandial insulin secretion, resulting in a decrease in blood glucose and NEFA levels owing to suppression of HSL, while BF, LPL and TAG clearance remained suppressed. CONCLUSIONS: In T2D, restoration of early phase insulin secretion improved postprandial hyperglycaemia and suppressed endogenous lipolysis, resulting in suppression of NEFA levels. These results suggest that in nonobese T2D, metabolic defects may result, to a large extent, from the delay in prandial insulin secretion.

An axon pacemaker: diversity in the mechanism of generation and conduction of action potentials in snail neurons.

One of the main principles in neuroscience is that in vertebrate motoneurons and certain interneurons the decision to initiate an action potential is made at the initial segment of the axon, the axon hillock [Kandel E. R. and Schwartz J. H. (1991) In Principles of Neural Science (eds Kandel E. R., Schwartz J. H. and Jessell T. M. ), pp. 166-167. Elsevier, New York]. The situation in invertebrate motoneurons is different. The axon has many arborizations near its soma, in the nearby neuropil, and many branches in the target region. The action potentials are generated in the region of the axon in the neuropil and in some cases the trigger zone can be found more than 1mm apart from the soma [Tauc C. (1962) Aplysia. J. gen. Physiol. 45, 1077-1097]. Thus, it is obvious that, in a neuron, the removal of the trigger zone would cease the spiking activity in the axon. The purpose of this work is to demonstrate that, in snails, there are axons of certain neurons, like neuron B2, which are able to maintain their firing activity after the removal of their cell body and the so-called trigger zone.

Blocking of the axon spikes by pentylenetetrazol in an identified neuron of the snail Helix lucorum, with consequent induction of epileptic activity in the cell body of the same neuron.

In an isolated preparation which consists of the buccal ganglia and the salivary nerve of Helix lucorum, neuron B2 can be identified by simultaneously recording the soma spike intracellularly and the axon spike extracellularly from the peripheral salivary nerve. The convulsant drug pentylenetetrazol (PTZ) eliminates the axon spike of the neuron within 1-5 min after its application while epileptic activity is induced in the soma of the same neuron for hours. It is interesting that almost all nerve activity in the peripheral nerve is blocked by PTZ.

Axonal transport of herpes simplex virus-1 in an in vitro model based on the isolated sciatic nerve of the frog Rana ridibunda.

An in vitro model for the study of the axonal transport of herpes simplex virus-1 (HSV-1) in the nerve fibres of the sciatic nerve of the frog Rana ridibunda, has been developed. The nerve was placed along a three-chambered bath consisting of three isolated chambers arranged in series: the stimulating, perfusion and recording chambers. The HSV-1 inoculum was placed in the stimulating chamber, where the proximal part of the isolated sciatic nerve was immersed. HSV-1 was detected after 24-36 h in the recording chamber, where the distal part of the nerve was immersed in Dulbecco's Modified Eagle Medium (DMEM), indicating an axonal transport speed of 46-60 mm/day. The evoked maximum compound action potentials generated in the stimulating chamber was monitored continuously in the recording chamber as an indication of the viability of the nerve during axonal transport. The in vitro method presented here is a useful tool for the pharmacological study of various parameters, e.g. drugs diluted in the perfusion chamber, ionising radiation and temperature, which may affect the axonal transport or other properties of HSV-1.