Prospective study of HDR brachytherapy (BT), external beam radiotherapy (EBRT) and androgen deprivation therapy (ADT): 10-years experience of an MRI-guided approach

OBJECTIVES

To evaluate the predictive factors for biochemical failure and distant metastases in a prospective cohort of patients with localized prostate cancer treated with the combination of HDR BT and EBRT.

METHODS AND MATERIALS

Patients with intermediate (IR) or high-risk (HR) prostate adenocarcinoma received a single fraction of HDR of 15 Gy combined with RT of 37.5 Gy in 15 fractions. ADT duration was used depending on risk-group. Descriptive analyses were performed. Univariate and multivariate Hazard Ratios were obtained. Finally, the Kaplan-Meier model was used to describe the survival of the events of interest.

RESULTS

309 patients were treated prospectively (199 were IR and 110 HR). Median age was 72 years; 58.3 % were MRI stage ≤ T2c, 34.1 % T3a and 7.6 % T3b; ISUP-grade 1-3 in 78.9 % and ISUP 4-5 in 21.1 %. 71.8 % of patients had ≤ 50 % positive-cores in biopsy and 28.2 % had > 50 %. Median pre-treatment PSA was 9.9 ng/mL. After a median follow-up of 88 months, 41 patients presented biochemical failure and 18 developed distant metastases. Multivariate cox-regression analyses found that MR-T3b Stage (HR 3.88, p = 0.001) and ADT use (HR 3.99, p = 0.03) were the only predictive factors for biochemical failure and the number of positive cores (>50 %) the only independent predictive factor of distant metastases (HR 4.36, p = 0.002).

CONCLUSIONS

Patients with mpMRI evidence of invasion of the SV and involvement of more than 50% of the cores in the prostate biopsy are patients with a higher risk of presenting a biochemical recurrence or developing metastasis due to their prostate cancer, respectively.

Cohort profile: the Spanish Early-onset Colorectal Cancer (SECOC) cohort: a multicentre cohort study on the molecular basis of colorectal cancer among young individuals in Spain

Purpose

The Spanish Early-onset Colorectal Cancer (SECOC) study is a multicentre prospective cohort established in Spain to investigate the molecular basis of early-onset colorectal cancer (EOCRC), including metabolic alterations.

Participants

220 patients with EOCRC have been enrolled since January 2019 through 18 centres across Spain. Individual-level data were collected by questionnaire, including lifestyle and other colorectal cancer-related factors. Medical record review was performed to capture clinical, histopathological and familial cancer history data. Biospecimen collection (blood, stool, tissue) at diagnosis and at various time points across treatment, as applicable, is also completed.

Findings to date

Participants had a median age of 44 years (range 14–49), and the majority are men (60%), with individuals age 40–49 years at EOCRC diagnosis being over-represented. Forty-three per cent of participants were diagnosed with a tumour in the rectosigmoid junction/rectum. Nearly two-thirds of EOCRC cases (64%) were diagnosed with advanced stage (III–IV) disease, and 28% of cases had no reported familial history of cancer.

Future plans

We are actively recruiting and observing participants; we plan to administer follow-up questionnaires and perform additional biospecimen collection. This prospective cohort offers a unique, rich resource for research on EOCRC aetiologies and will contribute to larger international efforts to disentangle the rising disease burden.

P1730 Multimodality assessment of complex ventricular septal defect

Conclusions

The key issue in this case is which of the muscular structures positioned at the ventricular apex is considered to be the true ventricular septum as this determines whether on not there is straddle of the tricuspid valve. In addition the complex and multiple nature of the chordal attachments below the valve made accessing and closing the defect not feasible.

Even in the present era with wide availability of advanced, multimodality imaging techniques demonstrating anatomy can still prove challenging in planning surgical repair, especially within the setting of complex congenital heart disease. Many aspects of such cases still only become apparent at the time of surgery and this remains a key issue when counselling parents.

Abstract P1730 Figure.

Cell therapy with autologous mesenchymal stromal cells in post-traumatic syringomyelia

BACKGROUND AIMS

Recently, clinical studies show that cell therapy with mesenchymal stromal cells (MSCs) improves the sequelae chronically established in paraplegic patients, being necessary to know which of them can obtain better benefit.

METHODS

We present here a phase 2 clinical trial that includes six paraplegic patients with post-traumatic syringomyelia who received 300 million MSCs inside the syrinx and who were followed up for 6 months. Clinical scales, urodynamic, neurophysiological, magnetic resonance (MR) and studies of ano-rectal manometry were performed to assess possible improvements.

RESULTS

In all the cases, MR at the end of the study showed a clear reduction of the syrinx, and, at this time, signs of improvement in the urodynamic studies were found. Moreover, four patients improved in ano-rectal manometry. Four patients improved in neurophysiological studies, with signs of improvement in evoked potentials in three patients. In the American Spinal Injury Association (ASIA) assessment, only two patients improved in sensitivity, but clinical improvement in neurogenic bowel dysfunction was observed in four patients and three patients described improvement in bladder dysfunction. Spasms reduced in two of the five patients who had them previous to cell therapy, and spasticity was improved in the other two patients. Three patients had neuropathic pain before treatment, and it was reduced or disappeared completely during the study. Only two adverse events ocurred, without relation to the cell therapy.

CONCLUSIONS

Cell therapy can be considered as a new alternative to the treatment of post-traumatic syringomyelia, achieving reduction of syrinx and clinical improvements in individual patients.

A systematic review of image segmentation methodology, used in the additive manufacture of patient-specific 3D printed models of the cardiovascular system

Background

Shortcomings in existing methods of image segmentation preclude the widespread adoption of patient-specific 3D printing as a routine decision-making tool in the care of those with congenital heart disease. We sought to determine the range of cardiovascular segmentation methods and how long each of these methods takes.

Methods

A systematic review of literature was undertaken. Medical imaging modality, segmentation methods, segmentation time, segmentation descriptive quality (SDQ) and segmentation software were recorded.

Results

Totally 136 studies met the inclusion criteria (1 clinical trial; 80 journal articles; 55 conference, technical and case reports). The most frequently used image segmentation methods were brightness thresholding, region growing and manual editing, as supported by the most popular piece of proprietary software: Mimics (Materialise NV, Leuven, Belgium, 1992–2015). The use of bespoke software developed by individual authors was not uncommon. SDQ indicated that reporting of image segmentation methods was generally poor with only one in three accounts providing sufficient detail for their procedure to be reproduced.

Conclusions and implication of key findings

Predominantly anecdotal and case reporting precluded rigorous assessment of risk of bias and strength of evidence. This review finds a reliance on manual and semi-automated segmentation methods which demand a high level of expertise and a significant time commitment on the part of the operator. In light of the findings, we have made recommendations regarding reporting of 3D printing studies. We anticipate that these findings will encourage the development of advanced image segmentation methods.

Generating anatomical models of the heart and the aorta from medical images for personalized physiological simulations

The anatomy and motion of the heart and the aorta are essential for patient-specific simulations of cardiac electrophysiology, wall mechanics and hemodynamics. Within the European integrated project euHeart, algorithms have been developed that allow to efficiently generate patient-specific anatomical models from medical images from multiple imaging modalities. These models, for instance, account for myocardial deformation, cardiac wall motion, and patient-specific tissue information like myocardial scar location. Furthermore, integration of algorithms for anatomy extraction and physiological simulations has been brought forward. Physiological simulations are linked closer to anatomical models by encoding tissue properties, like the muscle fibers, into segmentation meshes. Biophysical constraints are also utilized in combination with image analysis to assess tissue properties. Both examples show directions of how physiological simulations could provide new challenges and stimuli for image analysis research in the future.

Amylin effect in extrapancreatic tissues participating in glucose homeostasis, in normal, insulin-resistant and type 2 diabetic state

Amylin is co-secreted with insulin, responds to the same stimuli, is anorectic, lowers body weight by reducing fat mass, and is proposed for diabetes treatment. We examined the effect of a 3-day constant infusion of close to physiological doses of amylin in Wistar rats, on glucotransporter expression, glycogen content (G), glycogen synthase a activity (GSa) and glucose transport (GT), in liver, muscle and fat from insulin resistant (IR) and type 2 diabetic (T2D) models, compared to normal (N) animals; plasma glucose and insulin were measured. Plasma insulin in IR was higher than in N or T2D, and amylin normalized the value. In both, IR and T2D, liver G was lower than normal, accompanied by GLUT-2, mRNA and protein, higher and lower, respectively, than in N; amylin normalized G in both groups, without changes in GLUT-2, except for an mRNA increase in T2D. In IR and T2D, muscle GSa was reduced, together with respective over- and under-GLUT-4 expression; amylin induced only a trend toward GSa normalization in both groups. In isolated adipocytes, GT and GLUT-4 in IR and T2D were lower and higher, respectively, than in N; after amylin, not only GT was normalized in both groups but also the response to insulin was much more pronounced, including that in N, without major changes in GLUT-4. This suggests that the beneficial effect of amylin in states running with altered glucose homeostasis could occur by partially acting on the hexose metabolism of the liver and mainly on that of the adipose tissue.

Induction and reversibility of insulin resistance in rats exposed to exogenous D-fructose

Long-term exposure of normal rats to a fructose-enriched diet or drinking water is currently used as an animal model for experimental insulin resistance. The present study deals with a comparison between rats given access to either a fructose-enriched diet or fructose-enriched drinking water. In both situations, a decrease in food intake and body weight gain, and the induction of insulin resistance with intolerance to D-glucose despite increased secretory response to the aldohexose of insulin-producing cells were documented. Moreover, the rats exposed to exogenous D-fructose displayed a lesser sensitivity to overnight fasting than control animals, in terms of the alteration of glucose homeostasis and reduction of the ratio between plasma insulin and D-glucose concentration. It is also shown that the fructose-induced insulin resistance, as assessed in a hyperinsulinemic-euglycemic clamp, represents a phenomenon reversed within 15-30 days after removal of the keto-hexose from the drinking water.

In vitro approaches to evaluate palytoxin-induced toxicity and cell death in intestinal cells

Palytoxin isolated from the genus Palythoa is the most potent marine toxin known. The aim of the present study was to quantify palytoxin-induced cellular injury in the human intestinal cell line Caco-2. Cellular damage was measured by evaluating cell proliferation, cell membrane permeability, cell morphology and apoptotic markers. Furthermore, changes in F-actin were studied after exposure of cells to increasing amounts of palytoxin. The results show that cell proliferation decreased in a concentration-dependent manner with a mean IC(50) value of about 0.1 nM. A noticeable increase of cell detachment correlated with cell rounding and F-actin depolymerization was observed in palytoxin-treated cells. Moreover LDH was released from the cells in a dose and time dependent manner, although under these conditions there was no propidium iodide uptake. On the other hand, palytoxin impaired mitochondrial activity but other apoptotic markers, such as DNA fragmentation or caspases activation, were not observed. The results obtained in this paper suggest that the effects of palytoxin in Caco-2 cells were very potent and unspecific, since a primary necrosis and a secondary apoptosis seem to occur under these conditions.

Characteristics of palytoxin-induced cytotoxicity in neuroblastoma cells

Cation fluxes appear to play a key role in palytoxin-induced signal. There are other cellular targets that have not been described as well as the biochemical signaling cascades that transmit palytoxin-stimulated signals remain to be clarified. Since modifications of cations, mainly calcium, are generally associated to cell death or apoptosis, we wanted to further evaluate the effect of palytoxin on cell death. Then, in vitro cytotoxic effects of palytoxin were characterized on human neuroblastoma cells. By using several techniques, we studied markers of cell death and apoptosis, such as cell detachment, mitochondrial membrane potential, caspases, DNA damage, LDH leakage, propidium iodide uptake, F-actin depolymerization and inhibition of cellular proliferation. Results show that palytoxin triggers a series of toxic responses; it inhibits cell proliferation, induces cell rounding, detachment from the substratum and F-actin disruption. Among the apoptotic markers studied we only detected fall in mitochondrial membrane potential. Neither caspases activation nor chromatin condensation or DNA fragmentation were observed in palytoxin-treated cells.

Glucose intolerance associated to insulin resistance and increased insulin secretion in rats depleted in long-chain omega3 fatty acids

An intragastric D-glucose tolerance test was performed, after overnight starvation, in female rats depleted in long-chain polyunsaturated omega3 fatty acids (omega3D rats) and control rats of same age and gender. The plasma D-glucose and insulin concentrations, insulinogenic index, and HOMA for insulin resistance were all higher, after overnight starvation, in omega3D rats than in control animals. Over the 120-minute period following the intragastric administration of D-glucose, the area under the curve for the same four variables was also higher in omega3D rats than in control animals. In addition to visceral obesity, liver steatosis, hypertension, and cardiac hypertrophy, the omega3D rats thus display further features of the metabolic syndrome, namely glucose intolerance and insulin resistance, despite hyperinsulinemia.

Effects of diet supplementation with olive oil and guar upon fructose-induced insulin resistance in normal rats

Exposure of normal rats to fructose-containing drinking water represents a current model of insulin resistance. The major aim of the present study was to assess the possible effect of diet supplementation with either olive oil or guar upon the metabolic consequences of exposure to exogenous fructose. For this purpose, the changes in body weight, plasma D-glucose and insulin concentrations, and D-glucose infusion rate during a hyperinsulinemic-euglycemic clamp were measured after 65 days exposure to exogenous fructose and either olive oil- or guar-enriched diet. The results were compared to those previously collected in control animals exposed for the same period to either tap water or the fructose-containing drinking water and a standard diet. Diet supplementation with olive oil or guar failed to affect the increase in the insulinogenic index and the decrease in insulin sensitivity and fasted/fed ratio for plasma insulin concentration caused by exogenous fructose. In the rats exposed to exogenous fructose, the olive oil-fed rats differed from other animals by the absence of a decrease in food intake and body weight gain, whilst the guar-fed rats differed from other animals in a lower plasma D-glucose concentration in fed state and an absence, at day 65, of a higher plasma D-glucose concentration than that at day 0 measured in after overnight fasting state. These findings argue in favour of guar, rather than olive oil, to oppose the effect of exogenous fructose on glucose homeostasis.

High-speed gel microelectrophoresis, a new and easy approach for detection of PCR-amplified microbial DNA from environmental and clinical samples in microgels using conventional equipment

AIMS

Microelectrophoresis allows the detection of DNA bands using minimal amounts of sample in a short time, but commonly requires the use of special equipment which is not available in all laboratories. This fact has limited the application of this technique in microbiology despite its advantages. In this work, we describe a new approach to perform gel microelectrophoresis, named high-speed gel microelectrophoresis (HSGME), and its application for rapid detection of bacteria, protozoa and viruses in clinical, vegetal and environmental samples.

METHODS AND RESULTS

Aliquots of 0.4-1 microl of PCR product were loaded in 2 cm 1% agarose microgels and electrophoresed at high voltage (125 V cm(-1)) in conventional submarine horizontal mini-slabs. By using HSGME, single-DNA bands obtained after specific-PCR useful in diagnosis of different diseases caused by micro-organisms were detected in 5 min.

CONCLUSIONS

HSGME is a rapid and easy procedure applicable to detection of microbial genes, which is carried out using conventional equipment and thus can be performed in any research and diagnostic laboratory.

SIGNIFICANCE AND IMPACT OF THE STUDY

The performance of HSGME saves up to 90% time, material and energy costs, as well as laboratory hazardous wastes including carcinogenic agents used for visualizing DNA bands.

Short-term and long-term effects of guar on postprandial plasma glucose, insulin and glucagon-like peptide 1 concentration in healthy rats

Ingestion of guar gum decreases postprandial glycemia and insulinemia and improves sensitivity to insulin in diabetic patients and several animal models of diabetes. The aim of the present study was to compare the short-term and long-term effects of guar on plasma insulin and glucagon-like peptide 1 concentration in healthy rats. In the short-term experiments, the concomitant intragastric administration of glucose and guar reduced the early increment in plasma glucose, insulin and glucagon-like peptide 1 concentration otherwise induced by glucose alone. Comparable findings were made after twelve days of meal training exposing the rats to either a control or guar-enriched diet for fifteen minutes. Mean plasma glucose concentrations were lower while mean insulin concentrations were higher in the guar group than in the controls according to intragastric glucose tolerance tests conducted in overnight fasted rats maintained for 19 to 36 days on either the control or guar-enriched diet. The intestinal content of glucagon-like peptide 1 at the end of the experiments was also lower in the guar group. Changes in body weight over 62 days of observation were comparable in the control and guar rats. Thus, long-term intake of guar improves glucose tolerance and insulin response to glucose absorption, without improving insulin sensitivity, in healthy rats.

Effects of an olive oil-enriched diet on glucagon-like peptide 1 release and intestinal content, plasma insulin concentration, glucose tolerance and pancreatic insulin content in an animal model of type 2 diabetes

In the light of a recent study conducted in normal rats, the present investigations were aimed at exploring the immediate and long-term effects of an olive oil-enriched diet (OO diet) on GLP-1 release and intestinal content, plasma insulin concentration, glucose tolerance and pancreatic insulin content in adult rats that had been injected with streptozotocin during the neonatal period (STZ rats). The OO diet, when compared to a standard diet, increased the immediate GLP-1 response in meal-trained rats, but decreased GLP-1 content in the intestinal tract after 50 days. Over 50 days, the body weight gain was lower in the rats fed the OO diet compared to standard diet. In the former, however, no improvement of glucose tolerance or insulin response during an oral glucose tolerance test was observed. Thus, a paradoxical lowering of the insulinogenic index, i. e. the paired ratio between plasma insulin and glucose concentration, was recorded during the oral glucose tolerance test in rats fed either standard or OO diet. Moreover, the insulin content of the pancreas was equally low in the STZ rats fed either standard or OO diet. These findings will be discussed in the framework of possible differences in the pathophysiology of B-cell dysfunction in most patients with type-2 diabetes and the present animal model of non-insulin-dependent diabetes.

Plasma malonaldehyde (MDA) and total antioxidant status (TAS) during lactation in dairy cows

Metabolic profiles are widely used to monitor health, reproductive status and nutritional status. In the last few years, the evaluation of oxidative stress has contributed increasingly to our knowledge of the fundamental mechanisms involved in metabolic disorders, especially important in dairy cows, in which lactation imposes great physiological demands on the body's homeostatic mechanisms. The aim of the present study was to evaluate oxidative status in healthy cows during lactation (from lactation onset to peak lactation) using two parameters: (i) plasma levels of malondialdehyde (MDA) and (ii) total antioxidant status (TAS). Our results confirm that nutrition can influence the characteristic metabolic changes occurring between lactation onset and peak lactation. In addition, the combination of MDA and TAS can provide complementary information about the metabolic status of the cow. Thus, the proper metabolic adaptation to the onset of lactation, showed by metabolic profiles, contrasts with the high levels of free radicals which cause lipid peroxidation and high MDA values (68.99+/-33.64 microm/L) which is maintained only for a short period of time. In this moment, the antioxidant system can cope efficiently with lipoperoxide production. The most remarkable fact was the great inter-individual variations observed in MDA that might be studied in further investigations. When the animal reaches peak lactation, metabolic status is stabilized, and this is reflected by antioxidant status with mean values of 28.87+/-5.33 microm/L for MDA and 0.154+/-0.002 mmol/L for TAS values.

Participation of protein kinases in the stimulant action of GLP-1 on 2-deoxy-D-glucose uptake by normal rat skeletal muscle

Several protein kinases were recently proposed for involvement in GLP-1-stimulated D-glucose transport in skeletal muscle from both normal subjects and type 2 diabetic patients. This study was mainly aimed at investigating the effect of potential inhibitors of distinct protein kinases and protein phosphatase-1 upon insulin- and GLP-1-stimulated 2-deoxy-D-glucose net uptake by normal rat skeletal muscle. The basal uptake of the D-glucose analog was decreased by wortmannin--a phosphatidylinositol-3-kinase inhibitor--, PD98059--a mitogen-activated protein kinases inhibitor--, and TNFalpha--a protein phosphatase-1 inhibitor--, but not by either rapamycin--a p70s6 kinase inhibitor--, or H-7--, a protein kinase C inhibitor--. The enhancing action of both insulin and GLP-1 upon 2-deoxy-D-glucose transport was abolished by PD98059 and H-7, but largely unaffected by TNFalpha. Wortmannin and rapamycin preferentially affected the response to GLP-1 and insulin, respectively. These findings thus document both analogies and dissimilarities in the participation of the concerned enzymes in the stimulant action of insulin versus GLP-1 upon D-glucose transport in normal rat skeletal muscle.

Cell signalling of glucagon-like peptide-1 action in rat skeletal muscle

Glucagon-like peptide-1 (GLP-1), an incretin with glucose-dependent insulinotropic and insulin-independent antidiabetic properties, has insulin-like effects on glucose metabolism in extrapancreatic tissues participating in overall glucose homeostasis. These effects are exerted through specific receptors not associated with cAMP, an inositol phosphoglycan being a possible second messenger. In rat hepatocytes, activation of phosphatidylinositol 3-kinase (PI3K)/protein kinase B (PKB), protein kinase C (PKC) and protein phosphatase 1 (PP-1) has been shown to be involved in the GLP-1-induced stimulation of glycogen synthase. We have investigated the role of enzymes known or suggested to mediate the actions of insulin in the GLP-1-induced increase in glycogen synthase a activity in rat skeletal muscle strips. We first explored the effect of GLP-1, compared with that of insulin, on the activation of PI3K, PKB, p70s6 kinase (p70s6k) and p44/42 mitogen-activated protein kinases (MAPKs) and the action of specific inhibitors of these kinases on the insulin- and GLP-1-induced increment in glycogen synthase a activity. The study showed that GLP-1, like insulin, activated PI3K/PKB, p70s6k and p44/42. Wortmannin (a PI3K inhibitor) reduced the stimulatory action of insulin on glycogen synthase a activity and blocked that of GLP-1, rapamycin (a 70s6k inhibitor) did not affect the action of GLP-1 but abolished that of insulin, PD98059 (MAPK inhibitor) was ineffective on insulin but blocked the action of GLP-1, okadaic acid (a PP-2A inhibitor) and tumour necrosis factor-alpha (a PP-1 inhibitor) were both ineffective on GLP-1 but abolished the action of insulin, and Ro 31-8220 (an inhibitor of some PKC isoforms) reduced the effect of GLP-1 while completely preventing that of insulin. It was concluded that activation of PI3K/PKB and MAPKs is required for the GLP-1-induced increment in glycogen synthase a activity, while PKC, although apparently participating, does not seem to play an essential role; unlike in insulin signaling, p70s6k, PP-1 and PP-2A do not seem to be needed in the action of GLP-1 upon glycogen synthase a activity in rat muscle.

Cell signalling of the GLP-1 action in rat liver

GLP-1, incretin with insulin-independent antidiabetic properties, is insulinomimetic upon glucose metabolism in extrapancreatic tissues, acting through specific receptors not associated to adenylate cyclase activation. We investigated the role of enzymes mediating insulin actions, in the GLP-1-induced glycogen synthase a activation in rat hepatocytes. GLP-1, like insulin, activates PI3K/PKB, p70s6k, p44 and p42 MAP-kinase. Wortmannin (PI3K/PKB inhibitor) blocked the stimulatory action of insulin on glycogen synthase a and reduced that of GLP-1; rapamycin (p70s6k inhibitor) was ineffective and PD98059 (MEK/MAPK inhibitor) decreased only the insulin effect; okadaic acid (PP-2A inhibitor) was ineffective, while TNFalpha (PP-1 inhibitor) blocked the action of insulin and reduced that of GLP-1; H-7 or Ro 31-8220 (PKC inhibitors) decreased the GLP-1 effect, while only H-7 reduced that of insulin. The activation of PI3K/PKB, PKC and PP-1, but not PP-2A, seems to mediate the GLP-1 stimulatory action on glycogen synthase a in rat hepatocytes, while MAPKs and p70s6k could participate in other GLP-1 effects.

Pancreatic and extrapancreatic effects of GLP-1

Glucagon-like peptide-1 (GLP-1), an incretin hormone which helps to regulate plasma glucose levels, is considered a potential agent for the treatment of type-2 diabetes mellitus, because of its insulinotropic capacity and insulinomimetic actions. In normal conditions, the beta-cell secretory response to GLP-1 is modulated by the extracellular concentration of D-glucose; however, the recognition of D-glucose by the beta-cell is often impaired in type-2 diabetes, and this could impede the full GLP-1 insulinotropic action. Non-glucidic substrates, such as the dimethyl ester of succinic acid, restore the effect of GLP-1 in the isolated perfused rat pancreas of normal or diabetic rats, in the absence of any other exogenous nutrient; likewise, the dimethyl ester of succinic or L-glutamic acid, and the monomethyl ester of pyruvic acid, potentiate the in vivo beta-cell secretory response to GLP-1 in normal and diabetic rats. Therefore, it was proposed that nutrients susceptible to bypass the site-specific defects of the diabetic beta-cell, could be used to potentiate and/or prolong the insulinotropic action of antidiabetic agents such as GLP-1. In vitro, GLP-1 insulin-like effects on glucose metabolism have been documented in normal and diabetic rat liver, and in rat and human skeletal muscle. In rat and human adipocytes, GLP-1 is lipolytic and/or lipogenic, and also stimulates parameters involved in the glucose metabolism. In liver, muscle and fat, GLP-1 seems to act through specific receptors, apparently different--at least in liver and muscle--in structure or signaling pathway from the pancreatic one. It is proposed that an inositolphosphoglycan might be a second messenger of GLP-1 action in extrapancreatic tissues.

Glucagon-like peptide-1 (GLP-1) and glucose metabolism in human myocytes

Glucagon-like peptide-1 (GLP-1) has been shown to have insulin-like effects upon the metabolism of glucose in rat liver, muscle and fat, and on that of lipids in rat and human adipocytes. These actions seem to be exerted through specific receptors which, unlike that of the pancreas, are not - at least in liver and muscle - cAMP-associated. Here we have investigated the effect, its characteristics, and possible second messengers of GLP-1 on the glucose metabolism of human skeletal muscle, in tissue strips and primary cultured myocytes. In muscle strips, GLP-1, like insulin, stimulated glycogen synthesis, glycogen synthase a activity, and glucose oxidation and utilization, and inhibited glycogen phosphorylase a activity, all of this at physiological concentrations of the peptide. In cultured myotubes, GLP-1 exerted, from 10(-13) mol/l, a dose-related increase of the D-[U-(14)C]glucose incorporation into glycogen, with the same potency as insulin, together with an activation of glycogen synthase a; the effect of 10(-11) mol/l GLP-1 on both parameters was additive to that induced by the equimolar amount of insulin. Synthase a was still activated in cells after 2 days of exposure to GLP-1, as compared with myotubes maintained in the absence of peptide. In human muscle cells, exendin-4 and its truncated form 9-39 amide (Ex-9) are both agonists of the GLP-1 effect on glycogen synthesis and synthase a activity; but while neither GLP-1 nor exendin-4 affected the cellular cAMP content after 5-min incubation in the absence of 3-isobutyl-1-methylxantine (IBMX), an increase was detected with Ex-9. GLP-1, exendin-4, Ex-9 and insulin all induced the prompt hydrolysis of glycosylphosphatidylinositols (GPIs). This work shows a potent stimulatory effect of GLP-1 on the glucose metabolism of human skeletal muscle, and supports the long-term therapeutic value of the peptide. Further evidence for a GLP-1 receptor in this tissue, different from that of the pancreas, is also illustrated, suggesting a role for an inositolphosphoglycan (IPG) as at least one of the possible second messengers of the GLP-1 action in human muscle.

Resistance of succinic acid dimethyl ester insulinotropic action to exendin (9-39) amide

Exendin (9-39) amide (Ex [9-39]) was recently proposed for use in the treatment of alimentary or reactive hypoglycaemia. It was indeed found to antagonise the insulinotropic action of GLP-1 in rats infused with the dimethyl ester of succinic acid (SAD). We have now investigated whether, under comparable experimental conditions, Ex (9-39) also opposes the insulin-releasing action of SAD itself. Since this was not the case, Ex (9-39) could be safely used to abolish the incretin effect of GLP-1 without interfering with the control of insulin secretion by circulating nutrients.

Potentiation and prolongation of the insulinotropic action of glucagon-like peptide 1 by methyl pyruvate or dimethyl ester of L-glutamic acid in a type 2 diabetes animal model

Methyl pyruvate and the dimethyl ester of L-glutamic acid were administered intravenously, as a primed constant infusion (1.0-2.0 micromol followed by 0.5-1.0 micromol/min, both expressed per gram of body wt), in adult rats that had been injected with streptozotocin during the neonatal period. Each ester augmented plasma insulin concentration and potentiated and/or prolonged the insulinotropic action of glucagon-like peptide 1 (GLP-1) injected intravenously (5 pmol/g of body wt) at min 5 of the test. It is proposed, therefore, that suitable nonglucidic nutrients, susceptible to bypassing the site-specific defects of D-glucose transport and metabolism responsible for the preferential impairment of the B-cell secretory response to D-glucose in non-insulin-dependent diabetes, could be used to optimize the insulinotropic action of GLP-1.

Potentiation by glutamic acid dimethyl ester of GLP-1 insulinotropic action in fed anaesthetized rats

The dimethyl ester of L-glutamic acid (DMG) stimulates insulin release and was proposed as a possible insulinotropic tool in the treatment of non-insulin-dependent diabetes. In such a perspective, it was investigated whether DMG enhances the B-cell secretory response to GLP-1 in fed anaesthetized rats. The primed constant infusion of DMG (1.0 micromol and then 0.5 micromol/min, both per g body wt.) provoked a rapid and sustained increase in plasma insulin concentration and augmented the release of insulin caused by GLP-1. Thus, DMG indeed appears as a suitable tool to potentiate the insulinotropic action of GLP-1.

Pancreatic and hepatic glycogen content in normoglycemic and hyperglycemic rats

As judged from morphological criteria, glycogen accumulates to a larger extent in insulin-producing B-cells than in acinar cells of the pancreas in situations of sustained hyperglycemia. In the present study, the glycogen content of the pancreatic gland and liver was measured in either euglycemic or glucose-infused hyperglycemic control rats, as well as in streptozotocin-induced diabetic rats. Whilst the glycogen content of the pancreas was significantly higher in STZ rats than in control euglycemic rats, it was further enhanced in glucose-infused control rats, despite the fact that the latter animals were not more severely hyperglycemic and for a shorter time than STZ rats. From these measurements, it was estimated that, relative to wet weight, the glycogen content was, under the present experimental conditions, about 75 times higher in insulin-producing than other pancreatic cells. Moreover, it is proposed that the intravenous administration of glucagon may help in distinguishing between the glycogen present in the endocrine and exocrine moieties of the pancreatic gland, this hormone being apparently unable to provoke glycogenolysis in the exocrine pancreas, at variance with the situation prevailing in isolated pancreatic islets.

Involvement of nitric oxide in the regulation of growth hormone secretion in dogs

Nitric oxide (NO) is a highly reactive gas that has been suggested to function as a neurotransmitter in the neuroendocrine system. In this work, we have evaluated the role of NO pathways in growth hormone (GH) secretion by assessing the effect of L-arginine infusion, a precursor of NO formation, and L-NAME, a nitric oxide synthase (NOS) inhibitor. The experiments were carried out on 7 adult beagle dogs. A saline infusion was carried out on all the dogs as a control test. L-arginine (infusion i.v. 10 g in 100 ml of saline, from t = 0 to 30 min) and L-nitro-arginine-methyl ester, L-NAME (infusion of 300 microg/kg in 120 ml of saline, from t = -30 to 45 min) were administered alone and together with growth hormone-releasing hormone (GHRH) (i.v. bolus at 0 min, at a dose of 100 microg), the synthetic GH secretagogue GHRP-6 (i.v. bolus at 0 min, at a dose of 90 microg), and the 5-HT1D serotonin receptor agonist sumatriptan, SUM (s.c. injection at the dose of 3 mg). Plasma cGH was determined by RIA. Results were evaluated by one-way analysis of variance, followed by the Newman-Keuls test for multiple comparisons. L-arginine administration resulted in a slight increase in plasma cGH in comparison with saline controls. Combined administration of L-arginine and GHRH enhanced cGH release in comparison with GHRH alone. L-NAME alone did not modify baseline cGH levels, but completely suppressed the GH release induced by GHRH or GHRP-6. It also strongly reduced, but did not abolish the effect of the two peptides (GHRH plus GHRP-6) administered together. Finally, administration of the 5-HT1D agonist SUM induced a significant cGH secretion in all dogs, a response which was not modified when L-NAME was administered in combination with SUM. In conclusion, our data show that inhibition of NO blunts both GHRH or GHRP-6-induced cGH release, and are compatible with the hypothesis that it acts by decreasing hypothalamic somatostatin release.

Degradation of a stilbene-type fluorescent whitening agent with hypochlorite: identification of the degradation products by capillary electrophoresis

The E,E-(4,4'-bis[2-sulfostyryl]biphenyl) (DSBP) is a fluorescent whitening agent widely used by the textile and detergent industries to whiten fabrics. Hypochlorite used to bleach fabrics oxidizes DSBP slowly at room temperature and in a higher rate at 60 degrees C. The ions of metals such as Fe, Cu, and Mn accelerate the process considerably. At ambient temperature, the oxidation results from cleavage of the stilbene bonds and involves the formation of various intermediates that evolve to end products. The intermediates form within minutes to hours and the end products within months. At 60 degrees C or in presence of the previously mentioned transition metals, intermediates form within minutes and the end products within days. The end products of the oxidation are 4-sulfobenzaldehyde and 4,4'-bisaldehyde biphenyl; in the presence of excess of hypochlorite, however, the process yields their corresponding oxidized derivatives 4-sulfobenzoic acid and 4,4'-biphenyldicarboxylic acid. Despite the chlorinating ability of hypochlorite, the major degradation products formed contain no chlorine.

Synergistic insulinotropic effects of succinic acid dimethyl ester and exendin-4 in anaesthetized rats

It was recently proposed that suitable succinic acid esters could be used to potentiate the insulinotropic action of glucagon-like peptide 1 (GLP-1) in the treatment of type-2 diabetes mellitus. In such a perspective, the present study aimed mainly at investigating whether exendin-4 (Ex-4), a peptide structurally related to GLP-1(7-36)amide, and succinic acid dimethyl ester (SAD) also act synergistically upon insulin secretion in anaesthetized rats. Despite a higher plasma insulin concentration in SAD-infused rats (5.5+/-1.1 ng/ml) than in saline-infused animals (1.9+/-0.7 ng/ml), the intravenous injection of Ex-4 augmented to a greater extent the plasma concentration of insulin in the former rats (+7.4+/-2.5 ng/ml) than in the latter animals (+2.8+/-0.6 ng/ml). These findings document that the insulinotropic actions of Ex-4 and GLP-1 display comparable nutrient dependency, being both potentiated by a non-glucidic nutrient secretagogue such as SAD.

Suppression by exendin(9-39)amide of glucagon-like peptide-1 insulinotropic action in rats infused with dimethyl ester of succinic acid

Glucagon-like peptide-1 (GLP-1) acts as a nutrient-dependent insulin-releasing agent, and its insulinotropic action is enhanced by nutrient secretagogues, such as the dimethyl ester of succinic acid (SAD). In the present study, a primed constant infusion of SAD (0.5 micromol followed by 0.25 micromol/min both per g of body wt) was found to increase plasma insulin concentration in fed anesthetized rats, to potentiate the B-cell secretory response to GLP-1 (0.5 pmol/g of body wt), and to unmask the hypoglycemic potential of the gastrointestinal hormone. In the SAD-infused rats, the infusion of exendin(9-39)amide (5.0 pmol/min per g of body wt), 1 min before and 3 min after GLP-1 injection, decreased plasma insulin concentration before GLP-1 injection, suppressed the B-cell secretory response to GLP-1, and both delayed and minimized its hypoglycemic action. It is proposed, therefore, that exendin (9-39)amide could represent a tool in the treatment of alimentary or reactive hypoglycemia.

Effect of GLP-1 treatment on GLUT2 and GLUT4 expression in type 1 and type 2 rat diabetic models

Glucagon-like peptide-1 (G LP-1) is an incretin with glucose-dependent insulinotropic and insulin-independent antidiabetic properties that exerts insulin-like effects on glucose metabolism in rat liver, skeletal muscle, and fat. This study aimed to search for the effect of a prolonged treatment, 3 ds, with GLP-1 on glucotransporter GLUT2 expression in liver, and on that of GLUT4 in skeletal muscle and fat, in rats. Normal rats and streptozotocin-induced type 1 and type 2 diabetic models were used; diabetic rats were also treated with insulin for comparison. In normal rats, GLP-1 treatment reduced in the three tissues the corresponding glucotransporter protein level, without modifying their mRNA. In the type 2 diabetic model, GLP-1, like insulin, stimulated in liver and fat only the glucotransporter translational process, while in the muscle an effect at the GLUT4 transcriptional level was also observed. In the type 1 diabetic model, GLP-1 apparently exerted in the liver only a posttranslational effect on GLUT2 expression; in muscle and fat, while insulin was shown to have an action on GLUT4 at both transcriptional and translational levels, the effect of GLP-1 was restricted to glucotransporter translation. In normal and diabetic rats, exogenous GLP-1 controlled the glucotransporter expression in extrapancreatic tissues participating in the overall glucose homeostasis-liver, muscle, and fat-where the effect of the peptide seems to be exerted only at the translational and/or posttranslational level; in muscle and fat, the presence of insulin seems to be required for GLP-1 to activate the transcriptional process. The stimulating action of GLP-1 on GLUT2 and GLUT4 expression, mRNA or protein, could be a mechanism by which, at least in part, the peptide exerts its lowering effect on blood glucose.

Potentiation by methyl pyruvate of GLP-1 insulinotropic action in normal rats

Methyl pyruvate (MP) stimulates insulin release both in vivo and in vitro. The present study aims at investigating whether MP is also able to enhance the B-cell secretory response to glucagon-like peptide 1 (GLP-1). In anaesthetized rats receiving a primed constant infusion of MP, the ester augmented plasma insulin concentration before GLP-1 injection and potentiated the insulinotropic action of the intestinal hormone. MP infusion also augmented plasma D-glucose concentration, whether in the absence or presence of GLP-1. A further rise in plasma D-glucose concentration was observed when the infusion of MP was halted, this coinciding with a fall in plasma insulin concentration. Whilst documenting that MP indeed enhances the B-cell secretory response to GLP-1, these findings do not suggest that MP is an appropriate tool for optimizing the hypoglycaemic action of the enteric hormone in the treatment of type-2 diabetes mellitus.

Effect of GLP-1 on lipid metabolism in human adipocytes

We have studied the effect of several doses of GLP-1, compared to that of insulin and glucagons, on lipogenesis, lipolysis and cAMP cellular content, in human adipocytes isolated from normal subjects. In human adipocytes, GLP-1 exerts a dual action, depending upon the dose, on lipid metabolism, being lipogenic at low concentrations of the peptide (ED50, 10(-12) M), and lipolytic only at doses 10-100 times higher (ED50, 10(-10) M); both effects are time- and GLP-1 concentration-dependent. The GLP-1 lipogenic effect is equal in magnitude to that of equimolar amounts of insulin; both hormones apparently act synergically, and their respective action is abolished by glucagon. The lipolytic effect of GLP-1 is comparable to that of glucagon, apparently additive to it, and the stimulated value induced by either one is neutralized by the presence of insulin. In the absence of IBMX, GLP-1, at 10(-13) and 10(-12) M, only lipogenic doses, does not modify the cellular content of cAMP, while from 10(-11) M to 10(-9) M, also lipolytic concentrations, it has an increasing effect; in the presence of IBMX, GLP-1 at already 10(-12) M increased the cellular cAMP content. In human adipocytes, GLP-1 shows glucagon- and also insulin-like effects on lipid metabolism, suggesting the possibility of GLP-1 activating two distinct receptors, one of them similar or equal to the pancreatic one, accounting cAMP as a second messenger only for the lipolytic action of the peptide.

Prolongation of the insulinotropic action of glucagon-like peptide 1 by the dimethyl ester of succinic acid in an animal model of type-2 diabetes

Adult rats, that had been injected with streptozotocin during the neonatal period, received a primed constant infusion of succinic acid dimethyl ester (SAD; 0.5 micromol followed by 0.25 micromol x min(-1), both per g body wt.) in saline for 15 min and, at the 5th min of such an infusion, an intravenous injection of GLP-1 (5 pmol per g body wt.). Within 2 min, the ester increased the plasma insulin concentration by 0.33+/-0.05 nM. Likewise, within 2 min, GLP-1 provoked a marked increase in plasma insulin concentration; such an increase was comparable in rats infused with either saline or SAD, with an overall mean value of 0.93+/-0.07 nM. In the rats infused with SAD, however, the secretory response to GLP-1 appeared more sustained than in the saline-infused animals. For instance, the paired ratio for the insulinogenic index at 10/2 min after GLP-1 injection averaged 30.5+/-4.0% in SAD-infused rats, as compared (P<0.025) to only 17.0+/-2.5% in saline-infused animals. These findings suggest that succinic acid esters could be used to prolong the insulinotropic action of GLP-1 in the treatment of type-2 diabetes.

Potentiation of the insulinotropic action of GLP-1 by succinic acid dimethyl ester in fed anaesthetized rats

The insulinotropic action of GLP-1 is modulated by the nutritional environment of islet B-cells. This study explores whether an ester of succinic acid could be used to potentiate the insulin secretory response to GLP-1 in vivo. Fed anaesthetized male rats received a primed constant infusion (0.5 micromol followed by 0.25 micromol x min(-1) both per g body wt) of succinic acid dimethyl ester (SAD) in saline for 15 min and, at the 5th min of such an infusion, an intravenous injection of GLP-1 (5 pmol/g body wt). The ester provoked a rapid, sustained and reversible increase in plasma insulin concentration. In the SAD-infused rats, the increment in plasma insulin concentration caused by GLP-1 was more pronounced and more sustained than in saline-infused rats. It is proposed, therefore, that suitable succinic acid esters could be used to potentiate the insulinotropic action of GLP-1 in Type II (non-insulin-dependent) diabetes.