Obesity effect on newly diagnosed and recurrent post-ablation atrial fibrillation: a systematic review and meta-analysis

BACKGROUND AND AIMS

The role of overweight and obesity in the development of atrial fibrillation (AF) is well established; however, the differential effect on the occurrence and recurrence of AF remains uncertain. The aim of this review is to compare the effect of underweight and varying degrees of obesity on onset of AF and in recurrent post-ablation AF, and, when possible, in relation to sex.

METHODS

A systematic literature search was conducted in PubMed, Embase, and Cochrane Library from inception to January 31, 2023. Studies reporting frequency of newly-diagnosed AF and of recurrent post-ablation AF in different BMI categories, were included. 3400 records were screened and 50 met the inclusion criteria. Standardized data search and abstraction were performed following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) Statement. Data were extracted from the manuscripts and were analyzed using a random effect model. The outcome was the occurrence of AF in population studies and in patients undergoing ablation.

RESULTS

Data from 50 studies were collected, of which 27 for newly-diagnosed AF and 23 for recurrent post-ablation AF, for a total of 15,134,939 patients, of which 15,115,181 in studies on newly-diagnosed AF and 19,758 in studies on recurrent post-ablation AF. Compared to normal weight, the increase in AF was significant (p < 0.01) for overweight, obese, and morbidly obese patients for newly-diagnosed AF, and for obese and morbidly obese patients for recurrent post-ablation AF. Newly-diagnosed AF was more frequent in obese female than obese male patients.

CONCLUSION

The effect of increased BMI was greater on the onset of AF, and obese women were more affected than men.

Multiple beneficial effects of 1-year nutritional-behavioral intervention on anthropometric and metabolic parameters in overweight and obese boys

PURPOSE

Childhood obesity is on the rise worldwide increasing the risk for metabolic, cardiovascular and liver diseases in children. Eating habits and lifestyle changes are currently the standard of care for treating pediatric obesity. Our study aimed to determine the impact of a dietary intervention based on the Mediterranean Diet (MD) and the Health Eating Plate, on anthropometric and metabolic parameters in obese and overweight boys.

METHODS

We studied 126 overweight/obese boys with anthropometric measurements, blood biochemistry and nutrient intakes evaluation by means of Food Frequency Questionnaire (FFQ) at baseline, at 6 and 12 months after a nutritional-behavioral intervention.

RESULTS

We observed a significant reduction in energy, macronutrients and micronutrients intakes. BMI-SDS significantly decreased after 1 year with the proportion of obese boys decreasing by 33% and of overweight boys by 41%, while also all fat mass measures decreased both in obese and overweight individuals. In obese boys, ALT decreased significantly after 1-year nutritional intervention and these changes correlated with BMI-SDS reduction. Insulin-resistance and secretion indexes correlated with fat mass and BMI-SDS. In obese boys, significant changes were observed at 6 months for insulin concentrations, 1/HOMA-IR and QUICKI. With regard to the lipid profile, significant decreases were observed for total and LDL cholesterol in obese boys.

CONCLUSION

Metabolic and anthropometric risk factors in overweight and obese boys can be improved by a nutritional-behavioral intervention of 1-year duration.

Blood pressure control in type 2 diabetes mellitus with arterial hypertension. The important ancillary role of SGLT2-inhibitors and GLP1-receptor agonists

Type 2 diabetes mellitus and arterial hypertension are major cardiovascular risks factors which shares metabolic and haemodynamic abnormalities as well as pathophysiological mechanisms. The simultaneous presence of diabetes and arterial hypertension increases the risk of left ventricular hypertrophy, congestive heart failure, and stroke, as compared to either condition alone. A number of guidelines recommend lifestyle measures such as salt restriction, weight reduction and ideal body weight mainteinance, regular physical activity and smoking cessation, together with moderation of alcohol consumption and high intake of vegetables and fruits, as the basis for reduction of blood pressure and prevention of CV diseases. Despite the availability of multiple drugs effective for hypertension, BP targets are reached in only 50 % of patients, with even fewer individuals with T2DM-achieving goals. It is established that new emerging classes of type 2 diabetes mellitus treatment, SGLT2 inhibitors and GLP1-receptor agonists, are efficacious on glucose control, and safe in reducing HbA1c significantly, without increasing hypoglycemic episodes. Furthermore, in recent years, many CVOT trials have demonstrated, using GLP1-RA or SGLT2-inihibitors compared to placebo (in combination with the usual diabetes medications) important benefits on reducing MACE (cardio-cerebral vascular events) in the diabetic population. In this hypothesis-driven review, we have examined the anti-hypertensive effects of these novel molecules of the two different classes, in the diabetic population, and suggest that they could have an interesting ancillary role in controlling blood pressure in type 2 diabetic patients.

Pioglitazone treatment increases food intake and decreases energy expenditure partially via hypothalamic adiponectin/adipoR1/AMPK pathway

INTRODUCTION

Thiazolidinediones (TZDs) enhanced body weight (BW) partially by increased adipogenesis and hyperphagia. Neuronal PPARγ knockout mice on high-fat diet (HFD) are leaner because of enhanced leptin response, although it could be secondary to their leanness. Thus, it still is an open question how TZDs may alter energy balance. Multiple factors regulate food intake (FI) and energy expenditure (EE), including anorexigenic hormones as insulin and leptin. Nonetheless, elevated hypothalamic AMPK activity increases FI and TZDs increase AMPK activity in muscle cells. Thus, the aim of the present study was to investigate whether Pioglitazone (PIO) treatment alters hypothalamic insulin and leptin action/signaling, AMPK phosphorylation, and whether these alterations may be implicated in the regulation of FI and EE.

METHODS

Swiss mice on HFD (2 months) received PIO (25 mg kg(-1) per day-gavage) or vehicle for 14 days. AMPK and AdipoR1 were inhibited via Intracerebroventricular injections using Compound C (CompC) and small interference RNA (siRNA), respectively. Western blot, real-time PCR and CLAMS were done.

RESULTS

PIO treatment increased BW, adiposity, FI, NPY mRNA and decreased POMC mRNA expression and EE in HFD mice. Despite higher adiposity, PIO treatment improved insulin sensitivity, glucose tolerance, decreased insulin and increased adiponectin serum levels. This result was associated with, improved insulin and leptin action/signaling, decreased α2AMPK(Ser491) phosphorylation and elevated Acetyl-CoA carboxylase and AMPK(Thr172) phosphorylation in hypothalamus. The inhibition of hypothalamic AMPK with CompC was associated with decreased adiposity, FI, NPY mRNA and EE in PIO-treated mice. The reduced expression of hypothalamic AdipoR1 with siRNA concomitantly with PIO treatment reverted PIO induced obesity development, suggesting that adiponectin may be involved in this effect.

CONCLUSIONS

These results demonstrated that PIO, despite improving insulin/leptin action in hypothalamus, increases FI and decreases EE, partially, by activating hypothalamic adiponectin/AdipoR1/AMPK axis. Suggesting a novel mechanism in the hypothalamus by which TZDs increase BW.

The inflammatory status score including IL-6, TNF-α, osteopontin, fractalkine, MCP-1 and adiponectin underlies whole-body insulin resistance and hyperglycemia in type 2 diabetes mellitus

A state of subclinical systemic inflammation is characteristically present in obesity/insulin resistance and type 2 diabetes mellitus (T2DM). The aim of the study was to develop an integrated measure of the circulating cytokines involved in the subclinical systemic inflammation and evaluate its relation with whole-body insulin sensitivity and glucose metabolism in T2DM. T2DM patients (n = 17, M/F 13/4, age = 55.0 ± 1.7 years, BMI = 33.5 ± 1.5 kg/m(2), HbA(1c) = 7.7 ± 0.3%) and normal glucose-tolerant (NGT) subjects (n = 15, M/F 7/8, age = 49.1 ± 2.5 years, BMI = 31.8 ± 1.2 kg/m(2), HbA(1c) = 5.6 ± 0.1%) were studied in a cross-sectional design. Whole-body insulin sensitivity was quantified by the euglycemic clamp. Beta-cell function [disposition index (DI)] was calculated using insulin and glucose values derived from an oral glucose tolerance test and the euglycemic clamp. Body fat mass was evaluated by dual-energy X-ray absorptiometry. Plasma cytokine [TNF-α, IL-6, MCP-1, osteopontin, fractalkine and adiponectin] values were divided into quintiles. A score ranging from 0 (lowest quintile) to 4 (highest quintile) was assigned. The inflammatory score (IS) was the sum of each cytokine score from which adiponectin score was subtracted in each study subject. Inflammatory cytokine levels were all higher in T2DM. IS was higher in T2DM as compared to NGT (10.0 ± 1.1 vs. 4.8 ± 0.8; p < 0.001). IS positively correlated with fasting plasma glucose (r = 0.638, p < 0.001), 1-h plasma glucose (r = 0.483, p = 0.005), 2-h plasma glucose (r = 0.611, p < 0.001) and HbA1c (r = 0.469, p = 0.007). IS was inversely correlated with insulin sensitivity (r = -0.478, p = 0.006) and DI (r = -0.523, p = 0.002). IS did not correlate with BMI and body fat mass. IS was an independent predictor of fasting plasma glucose and had a high sensibility and sensitivity to predict insulin resistance (M/I < 4). A state of subclinical inflammation defined and quantifiable by inflammatory score including TNF-α, IL-6, MCP-1, osteopontin, fractalkine and adiponectin is associated with both hyperglycemia and whole-body insulin resistance in T2DM.

Increased carotid intima-media thickness in the physiologic range is associated with impaired postprandial glucose metabolism, insulin resistance and beta cell dysfunction

BACKGROUND

Carotid Intima-Media Thickness (C-IMT) is a reliable predictor of cardiovascular events. We examined if increased C-IMT was associated with defects in glucose metabolism in non-diabetic subjects independently of age.

METHODS

In 366 Caucasian non-diabetic subjects of the CARAMERIS study, we measured glucose response during a 75 g-Oral Glucose Tolerance Test (OGTT), insulin sensitivity index (ISI, by Matsuda Index), Liver Insulin Resistance Index (Liver-IR), insulin secretion by ΔAUC Ins0-120/Glu0-120 (ΔI/ΔG) and beta cell function (Disposition Index, DI).

RESULTS

Subjects were divided in two groups according to the median age (AGE1 ≤ 45 y; AGE2 > 45 y). Only 5 subjects in AGE1 and 32 in AGE2 had C-IMT > 0.9 mm. Compared to AGE1, AGE2 had a worse cardio-metabolic profile, increased cholesterol, glucose and insulin concentrations, blood pressure and C-IMT. Both ΔI/ΔG ratio and DI were significantly reduced in AGE2. By considering tertiles of C-IMT in each AGE group (G1-G3, where G3 comprised the highest C-IMT), we found that G3 showed increased OGTT glucose profiles and Liver IR, decreased ISI and DI, compared to G1 in each AGE group.

CONCLUSIONS

Increased C-IMT, but within normal ranges, is associated independently of age with altered postprandial glucose profile, increased peripheral and hepatic insulin resistance, decreased b-cell function. C-IMT measurement should become a routine analysis even in younger subjects to predict the risk of cardio-metabolic disease.

A probabilistic method for computing quantitative risk indexes from medical injuries compensation claims

BACKGROUND

The increasing demand of health care services and the complexity of health care delivery require Health Care Organizations (HCOs) to approach clinical risk management through proper methods and tools. An important aspect of risk management is to exploit the analysis of medical injuries compensation claims in order to reduce adverse events and, at the same time, to optimize the costs of health insurance policies.

OBJECTIVES

This work provides a probabilistic method to estimate the risk level of a HCO by computing quantitative risk indexes from medical injury compensation claims.

METHODS

Our method is based on the estimate of a loss probability distribution from compensation claims data through parametric and non-parametric modeling and Monte Carlo simulations. The loss distribution can be estimated both on the whole dataset and, thanks to the application of a Bayesian hierarchical model, on stratified data. The approach allows to quantitatively assessing the risk structure of the HCO by analyzing the loss distribution and deriving its expected value and percentiles.

RESULTS

We applied the proposed method to 206 cases of injuries with compensation requests collected from 1999 to the first semester of 2007 by the HCO of Lodi, in the Northern part of Italy. We computed the risk indexes taking into account the different clinical departments and the different hospitals involved.

CONCLUSIONS

The approach proved to be useful to understand the HCO risk structure in terms of frequency, severity, expected and unexpected loss related to adverse events.

Impact of obesity severity and duration on pancreatic β- and α-cell dynamics in normoglycemic non-human primates

Objective

Obesity is associated to high insulin and glucagon plasma levels. Enhanced β–cell function and β–cell expansion are responsible for insulin hypersecretion. It is unknown whether hyperglucagonemia is due to α-cell hypersecretion or to an increase in α-cell mass. In this study, we investigated the dynamics of the β-cell and α-cell function and mass in pancreas of obese normoglycemic baboons.

Methods

Pancreatic β- and α-cell volumes were measured in 51 normoglycemic baboons divided into 6 groups according to overweight severity or duration. Islets morphometric parameters were correlated to overweight and to diverse metabolic and laboratory parameters.

Results

Relative α-cell volume (RαV) and relative islet α-cell volume (RIαV) increased significantly with both overweight duration and severity. Conversely, in spite of the induction of insulin resistance, overweight produced only modest effects on relative β-cell volume (RβV) and relative islet β-cell volume (RIβV). Of note, RIβV did not increase neither with overweight duration nor with overweight severity, supposedly because of the concomitant, greater, increase in RIαV. Baboons' body weights correlated with serum levels of Interleukin-6 and Tumour Necrosis Factor-α soluble Receptors (IL-6sR and sTNF-R1), demonstrating that overweight induces abnormal activation of the signaling of two cytokines known to impact differently β- and α-cell viability and replication.

Conclusion

In conclusion, overweight and insulin resistance induce in baboons a significant increase in α-cell volumes (RαV, RIαV) while have minimal effects on the β-cells. This study suggests that an increase in the α-cell mass may precede the loss of β-cells and the transition to overt hyperglycemia and diabetes.

Increased levels of the Akt-specific phosphatase PH domain leucine-rich repeat protein phosphatase (PHLPP)-1 in obese participants are associated with insulin resistance

AIMS/HYPOTHESIS

We determined the contribution to insulin resistance of the PH domain leucine-rich repeat protein phosphatase (PHLPP), which dephosphorylates Akt at Ser473, inhibiting its activity. We measured the abundance of PHLPP in fat and skeletal muscle from obese participants. To study the effect of PHLPP on insulin signalling, PHLPP (also known as PHLPP1) was overexpressed in HepG2 and L6 cells.

METHODS

Subcutaneous fat samples were obtained from 82 morbidly obese and ten non-obese participants. Skeletal muscle samples were obtained from 12 obese and eight non-obese participants. Quantification of PHLPP-1 in human tissues was performed by immunoblotting. The functional consequences of recombinant PHLPP1 overexpression in hepatoma HepG2 cells and L6 myoblasts were investigated.

RESULTS

Of the 82 obese participants, 31 had normal fasting glucose, 33 impaired fasting glucose and 18 type 2 diabetes. PHLPP-1 abundance was twofold higher in the three obese groups than in non-obese participants (p = 0.004). No differences were observed between obese participants with normal fasting glucose, impaired fasting glucose or type 2 diabetes. PHLPP-1 abundance was correlated with basal Akt Ser473 phosphorylation (r = -0.48; p = 0.001), BMI (r = 0.44; p < 0.0001), insulin (r = 0.35; p < 0.0001) and HOMA (r = 0.38; p < 0.0001). PHLPP-1 abundance was twofold higher in the skeletal muscle of 12 obese participants than in that of eight non-obese participants (p < 0.0001). Insulin treatment of HepG2 cells resulted in a dose- and time-dependent upregulation of PHLPP-1. Overexpression of PHLPP1 in HepG2 cells and L6 myoblasts resulted in impaired insulin signalling involving Akt/glycogen synthase kinase 3, glycogen synthesis and glucose transport.

CONCLUSIONS/INTERPRETATION

Increased abundance of PHLPP-1, production of which is regulated by insulin, may represent a new molecular defect in insulin-resistant states such as obesity.

Impaired regulation of the TNF-alpha converting enzyme/tissue inhibitor of metalloproteinase 3 proteolytic system in skeletal muscle of obese type 2 diabetic patients: a new mechanism of insulin resistance in humans

AIMS/HYPOTHESIS

TNF-alpha levels are increased in obesity and type 2 diabetes. The regulation of TNF-alpha converting enzyme (TACE) and its inhibitor, tissue inhibitor of metalloproteinase 3 (TIMP3), in human type 2 diabetes is unknown.

METHODS

We examined TACE/TIMP3 regulation: (1) in lean and obese normal glucose tolerant (NGT) individuals and in type 2 diabetes patients; (2) following 6 h of lipid/saline infusion in NGT individuals; and (3) in cultured human myotubes from lean NGT individuals incubated with palmitate. Insulin sensitivity was assessed by a euglycaemic clamp and TACE/TIMP3 was evaluated by confocal microscopy, RT-PCR, western blotting and an in vitro activity assay. Circulating TNF-alpha, TNF-alpha-receptor 1 (TNFR1), TNF-alpha-receptor 2 (TNFR2), IL-6 receptor (IL-6R), vascular cell adhesion molecule (VCAM) and intercellular adhesion molecule (ICAM) levels were evaluated.

RESULTS

TIMP3 levels were reduced and TACE enzymatic activity was increased in type 2 diabetes skeletal muscle. TACE expression, and TACE, TNF-alpha, TNFR1 and IL-6R levels were increased in type 2 diabetes, and positively correlated with insulin resistance. A 6 h lipid infusion into NGT individuals decreased insulin-stimulated glucose metabolism by 25% with increased TACE, decreased expression of the gene encoding TIMP3 and increased IL-6R release. Palmitate induced a dramatic reduction of TIMP3 and increased the TACE/TIMP3 ratio in cultured myotubes.

CONCLUSIONS/INTERPRETATION

TACE activity was increased in skeletal muscle of obese type 2 diabetes patients and in lipid-induced insulin resistance. We propose that dysregulation of membrane proteolysis by TACE/TIMP3 of TNF-alpha and IL-6R is an important factor for the development of skeletal muscle insulin resistance in obese type 2 diabetes patients by a novel autocrine/paracrine mechanism.

Spontaneous pathology of the baboon endocrine system

BACKGROUND

Study of endocrine pathology in animal models is critical to understanding endocrine pathology in humans.

METHODS

We evaluated 434 endocrine-related diagnoses from 4619 baboon necropsies, established the incidence of spontaneous endocrine pathology, and analyzed the clinical and biochemical data associated with the individual cases.

RESULTS

The most common diagnoses in descending order, were pancreatic islet cell amyloidosis (n = 259), ovarian cysts (n = 50), pituitary adenoma (n = 37), pancreatic islet cell adenoma (n = 20), granulosa cell tumor (n = 15), thyroid adenoma (n = 11), adrenal hyperplasia (n = 10), thyroid carcinoma (n = 8), and pheochromocytoma (n = 6). The incidence of pancreatic islet cell amyloidosis progressively increased with age. Pheochromocytomas were associated with renal and heart failure. The incidence of pancreatic islet cell amyloidosis and adrenal pathology was similar to humans; the incidence of pituitary adenoma and thyroid pathology was lower than in humans.

CONCLUSIONS

Endocrine disease in baboons is common and shares clinical and biochemical characteristics with endocrine disease in humans.

Bariatric surgery in obesity: changes of glucose and lipid metabolism correlate with changes of fat mass

BACKGROUND AND AIM

Bariatric surgery induces significant weight loss and improves glucose metabolism in obese patients (BMI>35 kg/m(2)). Our aim was to compare restrictive (LAGB, laparoscopic gastric banding) and malabsorptive approaches (BIBP, biliary-intestinal bypass) on the loss of fat-free mass (FFM), fat mass (FM), and on changes of glucose and lipid metabolism.

METHODS AND RESULTS

Body composition (bio-impedance analysis, BIA), blood glucose (BG), insulin, triglycerides, total- and HDL-cholesterol, liver enzymes (AST and ALT) were measured at baseline and 1 year after surgery in patients undergoing LAGB, BIBP, and in diet-treated control patients. In the main study, with patients matched for initial BMI (43-55 kg/m(2), LAGB=24, BIBP=12, controls=6), decreases of BMI, FM, BG and cholesterol were greater in patients with BIBP than with LAGB (p<0.01), while decreases of FFM, insulin, HOMA-IR and triglycerides were similar. No effects on BMI, FM, FFM, BG, insulin, HOMA-IR or cholesterol were observed in the control patients. Decreases of BG, insulin, HOMA-IR, cholesterol and triglycerides correlated with FM but not with FFM decrease. Similar results were obtained in an additional study in patients with a different initial BMI (LAGB=25, BIBP=6, controls=24) and when considering all subjects together. A decrease of liver enzymes (ALT) was greater with LAGB than with BIBP, and HDL-cholesterol increased with LAGB and decreased with BIBP.

CONCLUSION

BMI, FM, BG and cholesterol decrease more with malabsorptive than with restrictive surgery, while FFM, insulin, HOMA-IR and triglycerides decrease in a similar way. FFM loss is of low entity. Changes of glucose and lipid metabolism are proportional to a decrease of fat mass but not of fat-free mass.

Effect of weight loss through laparoscopic gastric banding on blood pressure, plasma renin activity and aldosterone levels in morbid obesity

BACKGROUND AND AIMS

Several mechanisms are probably involved in obesity-related hypertension. This study was aimed to investigate the effect of significant weight loss on blood pressure and plasma renin activity (PRA) and aldosterone levels, other then on metabolic profile, in normotensive and hypertensive obese subjects.

METHODS AND RESULTS

Forty hypertensive and 55 normotensive obese subjects were studied under basal conditions and again 1 year after significant weight loss obtained through laparoscopic adjustable gastric banding (LAGB). Weight, waist circumference, blood glucose, insulin, electrolytes (Na and K), lipids and supine and upright PRA and aldosterone were evaluated. All parameters evaluated improved, except for total cholesterol, and electrolytes that did not change. Blood pressure decreased in hypertensive subjects, with a concordant decrease in PRA and supine aldosterone levels, not observed in normotensive patients.

CONCLUSION

Weight loss is associated with reduction of blood pressure and of PRA and aldosterone levels in obese hypertensive subjects.

Regulation of insulin signalling by hyperinsulinaemia: role of IRS-1/2 serine phosphorylation and the mTOR/p70 S6K pathway

AIM/HYPOTHESIS

Several epidemiological studies have suggested an association between chronic hyperinsulinaemia and insulin resistance. However, the causality of this relationship remains uncertain.

METHODS

We performed chronic hyperinsulinaemic-euglycaemic clamps and delineated, by western blotting, an IR/IRSs/phosphatidylinositol 3-kinase(PI[3]K)/Akt pathway in insulin-responsive tissues of hyperinsulinaemic rats. IRS-1/2 serine phosphorylation, IR/protein tyrosine phosphatase 1B (PTP1B) association, and mammalian target of rapamycin (mTOR)/p70 ribosomal S6 kinase (p70 S6K) activity were also evaluated in the liver, skeletal muscle and white adipose tissue of hyperinsulinaemic animals.

RESULTS

We found that chronic hyperinsulinaemic rats have insulin resistance and reduced levels of glycogen content in liver and muscle. In addition, we demonstrated an impairment of the insulin-induced IR/IRSs/PI3K/Akt pathway in liver and muscle of chronic hyperinsulinaemic rats that parallels increases in IRS1/2 serine phosphorylation, IR/PTP1B association and mTOR activity. Despite a higher association of IR/PTP1B, there was an increase in white adipose tissue of chronic hyperinsulinaemic rats in IRS-1/2 protein levels, tyrosine phosphorylation and IRSs/PI3K association, which led to an increase in basal Akt serine phosphorylation. No increases in IRS-1/2 serine phosphorylation and mTOR activity were observed in white adipose tissue. Rapamycin reversed the insulin resistance and the changes induced by hyperinsulinaemia in the three tissues studied.

CONCLUSIONS/INTERPRETATION

Our data provide evidence that chronic hyperinsulinaemia itself, imposed on normal rats, appears to have a dual effect, stimulating insulin signalling in white adipose tissue, whilst decreasing it in liver and muscle. The underlying mechanism of these differential effects may be related to the ability of hyperinsulinaemia to increase mTOR/p70 S6K pathway activity and IRS-1/2 serine phosphorylation in a tissue-specific fashion. In addition, we demonstrated that inhibition of the mTOR pathway with rapamycin can prevent insulin resistance caused by chronic hyperinsulinaemia in liver and muscle. These findings support the hypothesis that defective and tissue-selective insulin action contributes to the insulin resistance observed in hyperinsulinaemic states.

Ultrasound measurement of visceral and subcutaneous fat in morbidly obese patients before and after laparoscopic adjustable gastric banding: comparison with computerized tomography and with anthropometric measurements

BACKGROUND

There are now a variety of methods to assess body fat distribution, anthropometric (waist circumference and waist/hip W/H ratio), computed tomography (CT), and ultrasound (US) measurements, with CT considered as the reference method. Bariatric surgery leads to a significant and usually durable weight loss in morbidly obese patients; when assessing its results, it is of interest to measure changes of total fat tissue and of body fat distribution.

METHODS

In this study, we compared anthropometric, US, and CT measurements of body fat distribution under basal conditions and 1 year after laparoscopic adjustable gastric banding (LAGB); 120 morbidly obese patients were considered at baseline, and 40 patients were re-evaluated 1 year after LAGB.

RESULTS

Thickness of visceral and subcutaneous fat measured through CT and US methods was superimposable both under basal conditions and 1 year after LAGB, and the highest correlation was found between CT and US data on visceral fat, followed by CT and US data on subcutaneous fat; a fair correlation was also found between CT and US data on visceral fat and waist circumference.

CONCLUSION

We suggest that evaluation of body fat distribution is accomplished by US instead of CT measurement, because of its lower cost and low exposure risk. Waist circumference stands as a reasonable surrogate of both methods, while W/H ratio is poorly correlated with other measures of body fat distribution.

Autoantibodies against a 72-kDa ductal cell membrane glycoprotein in a patient affected by Sjögren's syndrome and gastric MALT lymphoma

Sjögren's syndrome is a chronic autoimmune disease affecting exocrine glands, resulting in xerostomia and xerophthalmia. Lymphocytic infiltration and fibrosis of exocrine glands as well as the presence of autoantibodies against organ-specific and non-organ-specific antigens are the hallmarks of the disease. We investigated whether some patients affected by Sjögren's syndrome might have autoantibodies directed against epithelial duct cell membrane proteins. We screened sera from patients affected by Sjögren's syndrome by indirect immunofluorescence on monkey salivary gland sections and FG-Met-2 cells (a pancreatic carcinoma cell line with ductal features) for the presence of antisalivary duct antibodies. Positive sera were employed in immunoprecipitation experiments on (35)S-methionine in vivo labeled and surface-biotinylated FG-Met-2 cells. The serum of a patient affected by Sjögren's syndrome and gastric mucosa-associated lymphoid tissue (MALT) lymphoma gave positive and distinct membrane immunostaining on FG-Met-2 cells. Immunoprecipitation with the patient's serum from (35)S-methionine-labeled cell extracts followed by sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis (PAGE) and autoradiography showed the presence of autoantibodies against a 72-kDa protein. After biotin-surface labeling of FG-Met-2 cells, a band with identical electrophoretic mobility was immunoprecipitated by the serum, demonstrating that the 72-kDa band is a membrane glycoprotein. We demonstrated by three complementary approaches, i.e., immunocytochemistry, (35)S-methionine in vivo labeling, and cell surface biotinylation, the presence of autoantibodies directed against a duct cell membrane protein of 72-kDa in a patient affected by Sjögren's syndrome and gastric MALT lymphoma. Autoantibodies directed against this novel membrane autoantigen may be an additional serological marker in some cases of Sjögren's syndrome.

Autoantibodies to amphiphysin I and amphiphysin II in a patient with sensory-motor neuropathy

A proportion of patients with peripheral neuropathies has circulating autoantibodies directed against neural antigens. In some cases, autoantibodies may play a pathogenic role. We studied a patient with a progressive sensory-motor axonal neuropathy of unknown etiology, looking for circulating autoantibodies against neural antigens and we showed that the patient's serum contained anti-amphiphysin I (AMP I) and amphiphysin II (AMP II) autoantibodies. A sural nerve biopsy revealed an axonal neuropathy. Indirect immunofluorescence experiments with the patient's serum showed a staining of rat axons due to alpha-AMP I autoantibodies and a specific labelling of cytoplasm and Schmidt-Lanterman incisures of Schwann cells due to alpha-AMP II autoantibodies. In conclusion we identified a patient affected by a sensory-motor neuropathy with autoantibodies against both AMP I and AMP II.

Alfa and beta estrogen receptors and the biliary tree

This manuscript summarizes recent data showing that estrogens and their receptors play an important role in modulating cholangiocyte proliferation. We have recently demonstrated that rat cholangiocytes express both estrogen receptors (ER)-alpha and -beta subtypes, while hepatocytes only express ER-alpha. ER and especially the ER-beta subtype, are overexpressed in cholangiocytes proliferating after bile duct ligation (BDL) in the rat, in association with enlarged bile duct mass and with enhanced estradiol serum levels. Cholangiocyte proliferation, during BDL, is impaired by estrogen antagonists (tamoxifen, ICI 182,780) which furthermore, induce the overexpression of Fas antigen and activate apoptosis of proliferating cholangiocytes. 17beta-estradiol stimulates, in vitro cholangiocyte proliferation, and this effect is individually blocked by tamoxifen or ICI 182,780. Cholangiocyte proliferation during BDL was associated with an enhanced protein expression of phosphorylated extracellular regulated kinases (ERK)1/2 which is, in contrast, negatively modulated by tamoxifen in association with its antiproliferative effect. This indicates a major involvement of the ERK system in the estrogen modulation of cholangiocyte proliferation.

High glucose causes apoptosis in cultured human pancreatic islets of Langerhans: a potential role for regulation of specific Bcl family genes toward an apoptotic cell death program

Type 2 diabetes is characterized by insulin resistance and inadequate insulin secretion. In the advanced stages of the disease, beta-cell dysfunction worsens and insulin therapy may be necessary to achieve satisfactory metabolic control. Studies in autopsies found decreased beta-cell mass in pancreas of people with type 2 diabetes. Apoptosis, a constitutive program of cell death modulated by the Bcl family genes, has been implicated in loss of beta-cells in animal models of type 2 diabetes. In this study, we compared the effect of 5 days' culture in high glucose concentration (16.7 mmol/l) versus normal glucose levels (5.5 mmol/l) or hyperosmolar control (mannitol 11 mmol/l plus glucose 5 mmol/l) on the survival of human pancreatic islets. Apoptosis, analyzed by flow cytometry and electron and immunofluorescence microscopy, was increased in islets cultured in high glucose (HG5) as compared with normal glucose (NG5) or hyperosmolar control (NG5+MAN5). We also analyzed by reverse transcriptase-polymerase chain reaction and Western blotting the expression of the Bcl family genes in human islets cultured in normal glucose or high glucose. The antiapoptotic gene Bcl-2 was unaffected by glucose change, whereas Bcl-xl was reduced upon treatment with HG5. On the other hand, proapoptotic genes Bad, Bid, and Bik were overexpressed in the islets maintained in HG5. To define the pancreatic localization of Bcl proteins, we performed confocal immunofluorescence analysis on human pancreas. Bad and Bid were specifically expressed in beta-cells, and Bid was also expressed, although at low levels, in the exocrine pancreas. Bik and Bcl-xl were expressed in other endocrine islet cells as well as in the exocrine pancreas. These data suggest that in human islets, high glucose may modulate the balance of proapoptotic and antiapoptotic Bcl proteins toward apoptosis, thus favoring beta-cell death.

Evidence for the involvement of phosphatidylinositol 3-kinase in fMLP-stimulated neutrophil adhesion to ICAM-1-transfected cells

Phosphatidylinositol 3-kinase (PI-3K) controls important intracellular steps involved in inflammation, immunity, and cell growth. PI-3K also modulates leukocyte integrin adhesiveness. In this study we evaluated the role of PI-3K on neutrophil adhesion to intercellular adhesion molecule-1 (ICAM-1)-transfected cells. N-formyl-methionyl-leucyl-phenylalanine (fMLP)-stimulated neutrophil adhesion was inhibited by wortmannin and LY294002, two unrelated PI-3K inhibitors, whereas phorbol myristate acetate (PMA)-induced neutrophil adhesion was not inhibited by them. After fMLP stimulation, a rapid activation of AKT and ERK was observed. However, only activation of AKT was reversed by the PI-3K inhibitors. Neutrophil expression of the beta2-integrins Mac-1, lymphocyte function-associated antigen-1(LFA-1), and gp150.95 was not affected by wortmannin, nor was expression of the activation epitope recognized by MAB24. We conclude that (a) PI-3K is involved in fMLP-activated neutrophil adhesion to ICAM-1-transfected cells, (b) the mechanism involved is not mediated by the modulation of beta2-integrin expression or activation, and (c) another mechanism seems to involve the adhesion to ICAM-1 when a cellular system of adhesion is used.

Estrogens stimulate proliferation of intrahepatic biliary epithelium in rats

BACKGROUND & AIMS

We investigated the expression of estrogen receptor (ER) alpha and beta subtypes in cholangiocytes of normal and bile duct-ligated (BDL) rats and evaluated the role and mechanisms of estrogens in the modulation of cholangiocyte proliferation.

METHODS

ER-alpha and ER-beta were analyzed by immunohistochemistry, reverse-transcription polymerase chain reaction, and Western blotting in normal and BDL rats. The effects of the ER antagonists tamoxifen and ICI 182,780 on cholangiocyte proliferation were evaluated.

RESULTS

Cholangiocytes expressed both ER-alpha and ER-beta subtypes, whereas hepatocytes expressed only ER-alpha. In association with a marked cholangiocyte proliferation and with enhanced estradiol serum levels, the immunoreactivity for ER-alpha involved a 3-fold higher percentage of cholangiocytes in 3-week BDL than in normal rats; immunoreactivity for ER-beta showed a 30-fold increase. Western blot analysis showed that during BDL, the total amount of ER-beta in cholangiocytes was markedly increased (5-fold), whereas that of ER-alpha decreased slightly (-25%). Treatment with tamoxifen or ICI 182,780 of 3-week BDL rats inhibited cholangiocyte proliferation and induced overexpression of Fas antigen and apoptosis in cholangiocytes. In vitro, 17 beta estradiol stimulated proliferation of cholangiocyte, an effect blocked to the same extent by tamoxifen or ICI 182,780.

CONCLUSIONS

This study suggests that estrogens and their receptors play a role in the modulation of cholangiocyte proliferation.

Insulin-secreting pituitary GH3 cells: a potential beta-cell surrogate for diabetes cell therapy

In a companion article, we describe the engineering and characterization of pituitary GH3 cell clones stably transfected with a furin-cleavable human insulin cDNA (InsGH3 cells). This article describes the performance of InsGH3 (clones 1 and 7) cell grafts into streptozotocin (STZ)-induced diabetic nude mice. Subcutaneous implantation of 2 x 10(6) InsGH3 cells resulted in the progressive reversal of hyperglycemia and diabetic symptoms, even though the progressive growth of the transplanted cells (clone 7) eventually led to glycemic levels below the normal mouse range. Proinsulin transgene expression was maintained in harvested InsGH3 grafts that, conversely, lose the expression of the prolactin (PRL) gene. Elevated concentrations of circulating mature human insulin were detected in graft recipients, demonstrating that proinsulin processing by InsGH3 cells did occur in vivo. Histologic analysis showed that transplanted InsGH3 grew in forms of encapsulated tumors composed of cells with small cytoplasms weakly stained for the presence of insulin. Conversely, intense insulin immunoreactivity was detected in graft-draining venules. Compared to pancreatic betaTC3 cells, InsGH3 cells showed in vitro a higher rate of replication, an elevate resistance to apoptosis induced by serum deprivation and proinflammatory cytokines, and significantly higher antiapoptotic Bcl-2 protein levels. Moreover, InsGH3 cells were resistant to the streptozotocin toxicity that, in contrast, reduced betaTC3 cell viability to 50-60% of controls. In conclusion, proinsulin gene expression and mature insulin secretion persisted in transplanted InsGH3 cells that reversed hyperglycemia in vivo. InsGH3 cells might represent a potential beta-cell surrogate because they are more resistant than pancreatic beta cells to different apoptotic insults and might therefore be particularly suitable for encapsulation.

Development and characterization of pituitary GH3 cell clones stably transfected with a human proinsulin cDNA

Successful beta-cell replacement therapy in insulin-dependent (type I) diabetes is hindered by the scarcity of human donor tissue and by the recurrence of autoimmune destruction of transplanted beta cells. Availability of non-beta cells, capable of releasing insulin and escaping autoimmune recognition, would therefore be important for diabetes cell therapy. We developed rat pituitary GH3 cells stably transfected with a furin-cleavable human proinsulin cDNA linked to the rat PRL promoter. Two clones (InsGH3/clone 1 and 7) were characterized in vitro with regard to basal and stimulated insulin release and proinsulin transgene expression. Mature insulin secretion was obtained in both clones, accounting for about 40% of total released (pro)insulin-like products. Immunocytochemistry of InsGH3 cells showed a cytoplasmic granular insulin staining that colocalized with secretogranin II (SGII) immunoreactivity. InsGH3 cells/clone 7 contained and released in vitro significantly more insulin than clone 1. Secretagogue-stimulated insulin secretion was observed in both InsGH3 clones either under static or dynamic conditions, indicating that insulin was targeted also to the regulated secretory pathway. Proinsulin mRNA levels were elevated in InsGH3 cells, being significantly higher than in betaTC3 cells. Moreover, proinsulin gene expression increased in response to various stimuli, thereby showing the regulation of the transfected gene at the transcriptional level. In conclusion, these data point to InsGH3 cells as a potential beta-cell surrogate even though additional engineering is required to instruct them to release insulin in response to physiologic stimulations.

Insulin and insulin-like growth factor-1 stimulate proliferation and type I collagen accumulation by human hepatic stellate cells: differential effects on signal transduction pathways

Insulin and insulin-like growth factor (IGF-1) are mitogenic for fibroblasts and smooth muscle cells. IGF-1 increases in inflamed and fibrotic tissues and induces proliferation of rat hepatic stellate cells (HSC). This study evaluates the potential roles of these hormones in the development of liver fibrosis. Insulin and IGF-1 receptor expression was evaluated by immunohistochemistry in both cultured human HSC and human liver tissue. Phosphorylation of both 70-kd S6 kinase and extracellular-regulated kinase (ERK), cell proliferation, type I collagen gene expression, and accumulation in HSC culture media were evaluated by Western blot, immunohistochemistry for bromodeoxyuridine (BrdU), Northern blot, and enzyme-linked immunosorbent assay, respectively. Insulin and IGF-1 receptors were detected in HSC in vitro and in liver sections from patients with chronic active hepatitis. Insulin and IGF-1 induced 70-kd S6 kinase phosphorylation in HSC, whereas IGF-1 only induced ERK phosphorylation. Insulin and IGF-1 stimulated HSC proliferation in a dose-dependent fashion, with IGF-1 being four to five times more potent than insulin. Cell exposure to specific inhibitors showed that both phosphatidylinositol 3-kinase (PI3-K) and ERK are involved in IGF-1-induced mitogenesis, whereas insulin stimulated mitogenesis through a PI3-K-dependent ERK-independent pathway. IGF-1 increased type I collagen gene expression and accumulation in HSC culture media through a PI3-K- and ERK-dependent mechanism. In conclusion, insulin and IGF-1, which stimulate HSC mitogenesis and collagen synthesis, may act in concert to promote liver fibrosis in vivo by a differential activation of PI3-K- and ERK1-dependent pathways.

Nitric oxide inhibits thrombin receptor-activating peptide-induced phosphoinositide 3-kinase activity in human platelets

Although nitric oxide (NO) has potent antiplatelet actions, the signaling pathways affected by NO in the platelet are poorly understood. Since NO can induce platelet disaggregation and phosphoinositide 3-kinase (PI3-kinase) activation renders aggregation irreversible, we tested the hypothesis that NO exerts its antiplatelet effects at least in part by inhibiting PI3-kinase. The results demonstrate that the NO donor S-nitrosoglutathione (S-NO-glutathione) inhibits the stimulation of PI3-kinase associated with tyrosine-phosphorylated proteins and of p85/PI3-kinase associated with the SRC family kinase member LYN following the exposure of platelets to thrombin receptor-activating peptide. The activation of LYN-associated PI3-kinase was unrelated to changes in the amount of PI3-kinase physically associated with LYN signaling complexes but did require the activation of LYN and other tyrosine kinases. The cyclic GMP-dependent kinase activator 8-bromo-cyclic GMP had similar effects on PI3-kinase activity, consistent with a model in which the cyclic nucleotide mediates the effects of NO. Additional studies showed that wortmannin and S-NO-glutathione have additive inhibitory effects on thrombin receptor-activating peptide-induced platelet aggregation and the surface expression of platelet activation markers. These data provide evidence of a distinct and novel mechanism for the inhibitory effects of NO on platelet function.

Crosstalk between insulin and angiotensin II signalling systems

Insulin resistance and hypertension commonly occur together. Pharmacological inhibition of the renin-angiotensin system has been found to reduce not only hypertension, but also insulin resistance. This raises the possibility that the renin-angiotensin system may interact with insulin signalling. We have investigated the relationship between insulin and angiotensin II (AII) intracellular signalling in vivo using an intact rat heart model, and in vitro using rat aorta smooth muscle cells (RASMC). Results generated in the in vivo studies indicate that, like insulin, AII stimulates tyrosine phosphorylation of the insulin receptor substrates IRS-1 and IRS-2. This leads to binding of IRS-1 and IRS-2 to PI3-kinase. However, in contrast to the effect of insulin. IRS-1- and IRS-2-associated PI3-kinase activity is inhibited by AII in a dose-dependent manner. Moreover, AII inhibits insulin-stimulated IRS-1/IRS-2-associated PI3-kinase activity. The in vivo effects of AII are mediated via the AT1 receptor. The results of the in vitro studies indicate that AII inhibits insulin-stimulated, IRS-1-associated PI3-kinase activity by interfering with the docking of IRS-1 with the p85 regulatory subunit of PI3-kinase. It appears that AII achieves this effect by stimulating serine phosphorylation of the insulin receptor beta-subunit IRS-1, and the p85 regulatory subunit of PI3-kinase. These actions result in the inhibition of normal interactions between the insulin signalling pathway components. Thus, we believe that AII negatively modulates insulin signalling by stimulating multiple serine phosphorylation events in the early components of the insulin signalling cascade. Overactivity of the renin-angiotensin system is likely to impair insulin signalling and contribute to insulin resistance observed in essential hypertension.

Insulin signalling in heart involves insulin receptor substrates-1 and -2, activation of phosphatidylinositol 3-kinase and the JAK 2-growth related pathway

OBJECTIVE

Hyperinsulinemia is a common feature of obesity and hypertension and may be associated with abnormal metabolism and growth of heart muscle and vascular wall. Most of the known actions of insulin were characterised in muscle, adipose tissue and liver. In this study we investigate the initial steps of insulin signalling in rat heart.

METHODS

After insulin infusion in the cava vein of male Wistar rats, the insulin receptor, insulin receptor substrates-1 and -2, phosphatidylinositol 3-kinase activity and Janus kinase (JAK) 2 engagement were studied by immunoprecipitation and immunoblot of heart extracts.

RESULTS

An insulin load induces rapid autophosphorylation of the insulin receptor which is followed by the phosphorylation of insulin receptor substrates-1 and -2. The phosphorylation of these early intracellular substrates leads to the association of the p85 subunit of phosphatidylinositol 3-kinase and subsequent activation of its catalytic p110 subunit. Besides activation of the lipid metabolising enzyme phosphatidylinositol 3-kinase, the phosphorylation of insulin receptor substrates-1 and -2 engages the intracellular kinase JAK 2 and induces JAK 2-STAT 1 complex formation.

CONCLUSIONS

We demonstrate that the early steps of insulin signalling in heart include the phosphorylation-activation of the insulin receptor, engagement of insulin receptor substrates-1 and -2 with the consequent activation of phosphatidylinositol 3-kinase and the involvement of the recently discovered growth related pathway--JAK 2-STAT 1.

Neurotransmitter-hormonal responses to psychological stress in peripubertal subjects: relationship to aggressive behavior

The relationship between different degrees of normal aggressiveness (low, medium, high) and neurotransmitter-neuroendocrine responses to the administration of psychologically stressful tests (Mental Arithmetic, Stroop Color Word Interference task, Trial Social Stress test) was examined in thirty male peripubertal junior school adolescents. Plasma concentrations of norepinephrine (NE), epinephrine (EPI), ACTH, cortisol (CORT), growth hormone (GH), prolactin (PRL) and testosterone (T) were measured immediately before the beginning of the tests and at their end, 30 min later. High-normal aggressiveness have been found associated with significantly higher basal concentrations of NE, ACTH, PRL, and T and with a significant increase of GH responses to the stressful stimuli.

Erythrocytosis in a patient with chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) can be accompanied by compensatory secondary erythrocytosis. However, the exact prevalence of secondary erythrocytosis in COPD is unknown. Although diagnostic criteria for polycythemia vera versus secondary erythrocytosis are mutually exclusive, we describe here the coexistence of polycythemia vera and COPD in the same patient.

Angiotensin II inhibits insulin signaling in aortic smooth muscle cells at multiple levels. A potential role for serine phosphorylation in insulin/angiotensin II crosstalk

To investigate potential interactions between angiotensin II (AII) and the insulin signaling system in the vasculature, insulin and AII regulation of insulin receptor substrate-1 (IRS-1) phosphorylation and phosphatidylinositol (PI) 3-kinase activation were examined in rat aortic smooth muscle cells. Pretreatment of cells with AII inhibited insulin-stimulated PI 3-kinase activity associated with IRS-1 by 60%. While AII did not impair insulin-stimulated tyrosine phosphorylation of the insulin receptor (IR) beta-subunit, it decreased insulin-stimulated tyrosine phosphorylation of IRS-1 by 50%. AII inhibited the insulin-stimulated association between IRS-1 and the p85 subunit of PI 3-kinase by 30-50% in a dose-dependent manner. This inhibitory effect of AII on IRS-1/PI 3-kinase association was blocked by the AII receptor antagonist saralasin, but not by AT1 antagonist losartan or AT2 antagonist PD123319. AII increased the serine phosphorylation of both the IR beta-subunit and IRS-1. In vitro binding experiments showed that autophosphorylation increased IR binding to IRS-1 from control cells by 2.5-fold versus 1.2-fold for IRS-1 from AII-stimulated cells, suggesting that AII stimulation reduces IRS-1's ability to associate with activated IR. In addition, AII increased p85 serine phosphorylation, inhibited the total pool of p85 associated PI 3-kinase activity, and decreased levels of the p50/p55 regulatory subunit of PI 3-kinase. These results suggest that activation of the renin-angiotensin system may lead to insulin resistance in the vasculature.

Regulation of endocytic-transcytotic pathways and bile secretion by phosphatidylinositol 3-kinase in rats

BACKGROUND & AIMS

Phosphatidylinositol 3-kinases (PI3-K) are a family of enzymes that play key roles in control of cell growth, membrane recycling, and vesicular endoexocytotic processes. The aim of this study was to investigate the effect of a specific PI3-K inhibitor, wortmannin, on bile secretion, cytoskeleton organization, and endotranscytotic pathways in rats.

METHODS

Isolated perfused rat liver (IPRL) and isolated rat hepatocyte couplets (IRHCs) were used.

RESULTS

Wortmannin induced a 25% inhibition of basal bile flow in IPRL (P < 0.01). Horseradish peroxidase biliary excretion in the IPRL was markedly decreased by wortmanin. In IRHC incubated with 25 nmol/L wortmannin for 10 minutes at 37 degrees C, morphological studies showed early significant dilatation of bite canalicular lumen (P < 0.001). At short intervals (3 minutes), uptake of the fluid-phase marker, Lucifer yellow, was markedly decreased by exposure to wortmannin (P < 0.001). At longer times (20 minutes), Lucifer yellow was retained in basolateral area of IRHC as compared with control cells, where the marker was rapidly transported to the pericanalicular area. In IRHC, wortmannin induced a marked disorganization of microfilaments.

CONCLUSIONS

Wortmannin inhibits basal bile flow, endocytosis, and transcytotic transport of fluid-phase markers in the liver, and causes an early dilatation of the canalicular lumen and disorganization of microfilaments. These findings suggest that PI3-K is involved in the regulation of vesicle trafficking, cytoskeleton organization, and the process of bile formation.

Cross-talk between the insulin and angiotensin signaling systems

Angiotensin II (AII), acting via its G-protein linked receptor, is an important regulator of cardiac, vascular, and renal function. Following injection of AII into rats, we find that there is also a rapid tyrosine phosphorylation of the major insulin receptor substrates 1 and 2 (IRS-1 and IRS-2) in the heart. This phenomenon appears to involve JAK2 tyrosine kinase, which associates with the AT1 receptor and IRS-1/IRS-2 after AII stimulation. AII-induced phosphorylation leads to binding of phosphatidylinositol 3-kinase (PI 3-kinase) to IRS-1 and IRS-2; however, in contrast to other ligands, AII injection results in an acute inhibition of both basal and insulin-stimulated PI 3-kinase activity. The latter occurs without any reduction in insulin receptor or IRS phosphorylation or in the interaction of the p85 and p110 subunits of PI 3-kinase with each other or with IRS-1/IRS-2. These effects of AII are inhibited by AT1 receptor antagonists. Thus, there is direct cross-talk between insulin and AII signaling pathways at the level of both tyrosine phosphorylation and PI 3-kinase activation. These interactions may play an important role in the association of insulin resistance, hypertension, and cardiovascular disease.

The early intracellular signaling pathway for the insulin/insulin-like growth factor receptor family in the mammalian central nervous system

Several studies support the idea that the polypeptides belonging to the family of insulin and insulin-like growth factors (IGFs) play an important role in brain development and continue to be produced in discrete areas of the adult brain. In numerous neuronal populations within the olfactory bulb, the cerebral and cerebellar cortex, the hippocampus, some diencephalic and brainstem nuclei, the spinal cord and the retina, specific insulin and IGF receptors, as well as crucial components of the intracellular receptor signaling pathway have been demonstrated. Thus, mature neurons are endowed with the cellular machinery to respond to insulin and IGF stimulation. Studies in vitro and in vivo, using normal and transgenic animals, have led to the hypothesis that, in the adult brain, IGF-I not only acts as a trophic factor, but also as a neuromodulator of some higher brain functions, such as long-term potentiation and depression. Furthermore, a trophic effect on certain neuronal populations becomes clearly evident in the ischemic brain or neurodegenerative disorders. Thus, the analysis of the early intracellular signaling pathway for the insulin/IGF receptor family in the brain is providing us with new intriguing findings on the way the mammalian brain is sculpted and operates.

Deranged platelet calcium homeostasis in diabetic patients with end-stage renal failure. A possible link to increased cardiovascular mortality?

OBJECTIVE

Platelet hyperfunction is a typical feature of the prothrombotic state that frequently complicates the natural history of diabetes. In uremia, a bleeding diathesis is present, which principally involves the primary phase of hemostasis. Thus, in patients with uremia of diabetic origin, the infrequent coexistence of two opposite alterations of hemostasis takes place. In patients with uremia, an increased incidence of cardiovascular events and related mortality is observed. This phenomenon is greatly amplified in uremia of diabetic origin. Calcium homeostasis is a critical aspect of platelet function, which has recently become available in human diseases. The aim of this study was to evaluate calcium homeostasis in platelets from patients with uremia of diabetic and nondiabetic origin.

RESEARCH DESIGN AND METHODS

We evaluated, by means of Fura 2, the intracellular concentration of ionized calcium ([Ca2+]i) in platelets from 18 patients with uremia of diabetic origin, 12 patients with uremia of nondiabetic origin and 16 healthy control subjects [Ca2+]i was evaluated in resting conditions and after stimulation with 0.05, 0.1, 0.5 U/ml thrombin.

RESULTS

Platelets from uremic patients with diabetes had higher resting [Ca2+]i than both control subjects (P = 0.01) and uremic patients without diabetes (P = 0.001). Similarly, after stimulation with thrombin, the absolute increase of [Ca2+]i was higher (P < 0.05) in platelets from uremic patients with diabetes compared with both control subjects and uremic patients without diabetes. The relative increase of [Ca2+]i was higher (P < 0.05) than normal in platelets from uremic patients after weak or intermediate strength thrombin. No correlation were present between [Ca2+]i values and other clinical and laboratory variables potentially associated with platelet hyperfunction.

CONCLUSIONS

Diabetes and uremia in combination further deteriorate the abnormal platelet calcium homeostasis observed in uremia.

In vivo and in vitro studies of vanadate in human and rodent diabetes mellitus

In vivo vanadate and vanadyl have been shown to mimic the action of insulin and to be effective treatment for animal models of both Type I and Type II diabetes. The molecular mechanism of action of the vanadium salts on insulin sensitivity remains uncertain, and several potential sites proposed for the insulin-like effects are reviewed. In human trials, insulin sensitivity improved in patients with NIDDM, as well as in some patients with IDDM after two weeks of treatment with sodium metavanadate. This increase in insulin sensitivity was primarily due to an increase in non-oxidative glucose disposal, whereas oxidative glucose disposal and both basal and insulin stimulated suppression of hepatic glucose output (HGP) were unchanged. Clinically, oral vanadate was associated with a small decrease in insulin requirements in IDDM subjects. Of additional benefit, there was a decrease in total cholesterol levels in both IDDM and NIDDM subjects. Furthermore, there was an increase in the basal activities of MAP and S6 kinases to levels similar to the insulin-stimulated levels in controls, but there was little or no further stimulation with insulin was seen. Further understanding of the mechanism of vanadium action may ultimately be useful in the design of drugs that improve glucose tolerance.

Metabolic effects of sodium metavanadate in humans with insulin-dependent and noninsulin-dependent diabetes mellitus in vivo and in vitro studies

To investigate the efficacy and mechanism of action of sodium metavanadate as an oral hypoglycemic agent, five insulin-dependent diabetes mellitus (IDDM) and five noninsulin-dependent diabetes mellitus (NIDDM) patients were studied before and after 2 weeks of oral sodium metavanadate (NaVO3; 125 mg/day). Glucose metabolism measured during a two-step euglycemic insulin clamp was not significantly increased by vanadate therapy in patients with IDDM, but was improved by 29% during the low dose (0.5 mU/kg.min) insulin infusion and 39% during the high dose (1.0 mU/kg.min) in patients with NIDDM. The changes in glucose metabolism were largely accounted for by an increase in nonoxidative glucose disposal, as measured by indirect calorimetry. Basal hepatic glucose production and suppression of hepatic glucose production by insulin were unchanged by vanadate therapy. There was a significant decrease in insulin requirements in the patients with IDDM (39.1 +/- 6.6 to 33.8 +/- 4.7 U/day; P < 0.05). Cholesterol levels significantly decreased in both IDDM (4.53 +/- 0.16 vs. 4.27 +/- 0.22 mmol/L; P = 0.06) and NIDDM (6.92 +/- 0.75 vs. 5.28 +/- 0.46 mmol/L; P < 0.05). After NaVO3 therapy, there was a 1.7- to 3.9-fold increase in basal mitogen-activated protein and S6 kinase activities in mononuclear cells from patients with IDDM and NIDDM that mimicked the effect of insulin stimulation in controls. The most common adverse effect of oral NaVO3 was mild gastrointestinal intolerance. These data suggest that vanadate or related agents may have a potential role as adjunctive therapy in patients with diabetes mellitus.

Insulin and dexamethasone regulate insulin receptors, insulin receptor substrate-1, and phosphatidylinositol 3-kinase in Fao hepatoma cells

Insulin rapidly stimulates tyrosine kinase activity of its receptor, resulting in phosphorylation of the cytosolic substrate, insulin receptor substrate-1 (IRS-1), which, in turn, associates with phosphatidylinositol 3-kinase (PI 3-kinase), thus activating the enzyme. In the present study we have examined these three early postreceptor components of the insulin action pathway in rat hepatoma (Fao) cells and have determined the effects of two hormones that can induce insulin resistance, dexamethasone and insulin. Dexamethasone (1 microM) induced a time- and dose-dependent increase in insulin receptor levels in Fao cells, reaching 135 +/- 3% of basal levels after 24 h (P < 0.05). There was a simultaneous increase in IRS-1 protein to 255 +/- 66% of the control value (P < 0.05) and a parallel increase in IRS-1 phosphorylation. Insulin stimulation of IRS-1-associated PI 3-kinase was also increased by 70% in cells treated with dexamethasone despite only a minimal increase in PI 3-kinase protein, as determined by immunoblotting. Prolonged insulin treatment induced a time- and dose-dependent decrease in insulin receptor and IRS-1 protein levels, reaching nadirs of 40 +/- 4% (P < 0.01) and 15 +/- 6% (P < 0.005) of control levels, respectively, after 24 h with 100 nM insulin. There was also a decrease in the phosphorylation of insulin receptors and IRS-1, a marked decrease in the association between IRS-1 and PI 3-kinase, and an 82% decrease in insulin-stimulated PI 3-kinase activity without a significant change in PI 3-kinase protein levels. When cells were exposed to both insulin and dexamethasone, the effect of insulin to reduce insulin receptor and IRS-1 levels and insulin-stimulated IRS-1 phosphorylation dominated. These data suggest that regulation of the insulin receptor, IRS-1, and PI 3-kinase contributes significantly to the insulin resistance induced by chronic hyperinsulinemia, but that glucocorticoid-induced insulin resistance is located beyond these early steps in insulin action.

Insulin receptor substrate-1 (IRS-1) distribution in the rat central nervous system

Insulin receptor substrate 1 (IRS-1) is the primary cytosolic substrate of the insulin and insulin-like growth factor-I (IGF-I) receptors. Following tyrosine phosphorylation IRS-1 binds to and activates specific proteins containing SH2 domains. Using biochemical and immunocytochemical techniques, we have mapped the distribution of IRS-1 in the CNS of the adult rat and compared it with that of insulin and IGF-I receptors and phosphatidylinositol 3-kinase (PI-3 kinase), a signaling molecule functionally related to IRS-1. Immunoprecipitation and Western blotting experiments demonstrate the presence of substantial amounts of IRS-1, insulin receptor, and PI-3 kinase in the brain. IRS-1 immunoreactivity is widely distributed in neurons from several areas of the brain and spinal cord. The cerebral cortex, the hippocampus, many hypothalamic and thalamic nuclei, the basal ganglia, the cerebellar cortex, the brainstem nuclei, and the lamina X of the spinal cord are particularly rich of immunopositive nerve cells. In these areas most of the neurons immunoreactive for IRS-1 are also stained by either anti-insulin receptor or anti-IGF-I receptor antibodies as well as PI-3 kinase antiserum. IRS-1 immunostaining was very weak or totally absent in neurons of the olfactory bulb, the supraoptic and paraventricular nuclei, the mesencephalic trigeminal nucleus, and the granule cell layer of the cerebellum, despite the fact that these areas were immunolabeled with antibodies against insulin or IGF-I receptors and/or PI-3 kinase. These results show that neurons in the adult rat CNS are endowed with some of the components of the early signaling pathway for growth factors of the insulin/IGF-I family, although IRS-1 has a distribution distinct from that of the two receptors.

Platelet calcium homeostasis is abnormal in patients with severe arteriosclerosis

To evaluate platelet calcium homeostasis in a typical thrombosis-prone clinical condition, 14 patients with severe arteriosclerosis and 11 healthy control subjects were studied. Platelet intracellular free calcium concentration ([Ca2+]i) was evaluated by means of the fluorescent probe fura 2 under resting conditions and after challenge with 0.05, 0.1, and 0.5 U/mL thrombin (final concentrations). Three different concentrations of extracellular ionized calcium ([Ca2+]e) were used: 1 mmol/L, 1 mumol/L, and < 1 nmol/L. Resting platelet [Ca2+]i was significantly higher (P < .001) in patients than in control subjects. After addition of 0.05 U/mL thrombin, the relative increase of [Ca2+]i was lower in patients than in control subjects in each of the three [Ca2+]e conditions (P = .05 at 1 mmol/L, P = .02 at 1 mumol/L, and P = .04 at < 1 nmol/L). After addition of 0.1 U/mL thrombin, the relative increase of [Ca2+]i was lower in patients than in control subjects under two [Ca2+]e conditions, 1 mumol/L and < 1 nmol/L (P = .04 and P = .03 respectively). With 0.5 U/mL thrombin, a trend toward lower values in patients than in control subjects was observed, reaching statistical significance (P = .03) only at < 1 nmol/L [Ca2+]e. These results suggest that calcium homeostasis is abnormal in platelets from patients with severe arteriosclerosis and probably reflects a chronic activation.

Regulation of insulin receptor, insulin receptor substrate-1 and phosphatidylinositol 3-kinase in 3T3-F442A adipocytes. Effects of differentiation, insulin, and dexamethasone

Insulin rapidly stimulates tyrosine kinase activity of its receptor resulting in phosphorylation of its cytosolic substrate insulin receptor substrate 1 (IRS-1), which in turn associates with and activates the enzyme phosphatidylinositol 3-kinase (PI 3-kinase). In the present study we have examined these three initial steps in insulin action during the differentiation of 3T3-F442A adipocytes and after treatment with dexamethasone or insulin. The differentiation of 3T3-F442A cells was characterized by a 13-fold increase in insulin receptor protein, a 9-fold increase in IRS-1, and a 10- and 4.5-fold increase in their insulin-stimulated phosphorylation, respectively. The mRNA expression of these two proteins showed a similar 8-fold increase during differentiation. In addition there was a 3.5-fold increase in PI 3-kinase protein [85 kilodalton (kDa) subunit] and a 16-fold increase in IRS-1-associated PI 3-kinase activity between day 0 and day 8 of differentiation. Dexamethasone (1 microM) treatment of differentiated cells induced a further 48% (P < 0.05) increase in insulin receptor level, but the autophosphorylation of the receptor was decreased by 31 +/- 1% (P < 0.02). At the same time there was a decrease by 56 +/- 4% (P < 0.005) in IRS-1 protein and by 31 +/- 1% (P < 0.001) in IRS-1 phosphorylation. The expression of insulin receptor mRNA was unchanged, but the expression of IRS-1 mRNA was decreased by approximately 75% after dexamethasone. By contrast, dexamethasone induced a 69% increase in the level of PI 3-kinase as determined by immunoblotting. The combined effect of decreased IRS-1 phosphorylation and increased PI 3-kinase protein was a minimal change (15% decrease) in the association/activation between IRS-1 and PI 3-kinase. Chronic treatment with 100 nM insulin induced a time- and dose-dependent decrease in insulin receptor and IRS-1 protein levels reaching a nadir of 34 +/- 5% (P < 0.005) and 39 +/- 5% (P < 0.01) of control levels after 24 h, respectively. There was an even more marked decrease in the phosphorylation level of these proteins. Chronic insulin treatment also produced a 30% decrease in PI 3-kinase protein levels and a approximately 50% decrease in the association/activation between IRS-1/PI 3-kinase. The expression of insulin receptor and IRS-1 mRNA was unchanged during chronic insulin treatment.(ABSTRACT TRUNCATED AT 400 WORDS)