Peptide YY and glucagon-like peptide-1 contribute to decreased food intake after Roux-en-Y gastric bypass surgery.

BACKGROUND/OBJECTIVES: Exaggerated postprandial secretion of glucagon-like peptide-1 (GLP-1) and peptide YY (PYY) may explain appetite reduction and weight loss after Roux-en-Y gastric bypass (RYGB), but causality has not been established. We hypothesized that food intake decreases after surgery through combined actions from GLP-1 and PYY. GLP-1 actions can be blocked using the GLP-1 receptor antagonist Exendin 9-39 (Ex-9), whereas PYY actions can be inhibited by the administration of a dipeptidyl peptidase-4 (DPP-4) inhibitor preventing the formation of PYY3-36. SUBJECTS/METHODS: Appetite-regulating gut hormones and appetite ratings during a standard mixed-meal test and effects on subsequent ad libitum food intake were evaluated in two studies: in study 1, nine patients with type 2 diabetes were examined prospectively before and 3 months after RYGB with and without Ex-9. In study 2, 12 RYGB-operated patients were examined in a randomized, placebo-controlled, crossover design on four experimental days with: (1) placebo, (2) Ex-9, (3) the DPP-4 inhibitor, sitagliptin, to reduce formation of PYY3-36 and (4) Ex-9/sitagliptin combined. RESULTS: In study 1, food intake decreased by 35% following RYGB compared with before surgery. Before surgery, GLP-1 receptor blockage increased food intake but no effect was seen postoperatively, whereas PYY secretion was markedly increased. In study 2, combined GLP-1 receptor blockage and DPP-4 inhibitor mediated lowering of PYY3-36 increased food intake by ~20% in RYGB patients, whereas neither GLP-1 receptor blockage nor DPP-4 inhibition alone affected food intake, perhaps because of concomitant marked increases in the unblocked hormone. CONCLUSIONS: Blockade of actions from only one of the two L-cell hormones, GLP-1 and PYY3-36, resulted in concomitant increased secretion of the other, probably explaining the absent effect on food intake on these experimental days. Combined blockade of GLP-1 and PYY actions increased food intake after RYGB, supporting that these hormones have a role in decreased food intake postoperatively.

Oral 2-oleyl glyceryl ether improves glucose tolerance in mice through the GPR119 receptor.

The intestinal G protein-coupled receptor GPR119 is a novel metabolic target involving glucagon-like peptide-1 (GLP-1)-derived insulin-regulated glucose homeostasis. Endogenous and diet-derived lipids, including N-acylethanolamines and 2-monoacylglycerols (2-MAG) activate GPR119. The purpose of this work is to evaluate whether 2-oleoyl glycerol (2-OG) improves glucose tolerance through GPR119, using wild type (WT) and GPR 119 knock out (KO) mice. We here show that GPR119 is essential for 2-OG-mediated release of GLP-1 and CCK from GLUTag cells, since a GPR119 specific antagonist completely abolished the hormone release. Similarly, in isolated primary colonic crypt cultures from WT mice, GPR119 was required for 2-OG-stimulated GLP-1 release while there was no response in crypts from KO mice. In vivo, gavage with 2-oleyl glyceryl ether ((2-OG ether), a stable 2-OG analog with a potency of 5.3 µM for GPR119 with respect to cAMP formation as compared to 2.3 µM for 2-OG), significantly (P < 0.05) improved glucose clearance in WT littermates, but not in GPR119 KO mice. Finally, deletion of GPR119 in mice resulted in lower glucagon levels, whereas the levels of insulin and GIP were unchanged. In the present study we show that 2-OG stimulates GLP-1 secretion through GPR119 activation in vitro, and that fat-derived 2-MAGs are potent candidates for mediating fat-induced GLP-1 release through GPR119 in vivo. © 2016 BioFactors, 42(6):665-673, 2016.

Effect of chenodeoxycholic acid and the bile acid sequestrant colesevelam on glucagon-like peptide-1 secretion.

AIM: To evaluate the effects of the primary human bile acid, chenodeoxycholic acid (CDCA), and the bile acid sequestrant (BAS) colesevelam, instilled into the stomach, on plasma levels of glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide, glucose, insulin, C-peptide, glucagon, cholecystokinin and gastrin, as well as on gastric emptying, gallbladder volume, appetite and food intake. METHODS: On four separate days, nine patients with type 2 diabetes, and 10 matched healthy control subjects received bolus instillations of (i) CDCA, (ii) colesevelam, (iii) CDCA + colesevelam or (iv) placebo. At baseline and for 180 min after instillation, blood was sampled. RESULTS: In both the type 2 diabetes group and the healthy control group, CDCA elicited an increase in GLP-1 levels compared with colesevelam, CDCA + colesevelam and placebo, respectively (p < 0.05). The interventions did not affect plasma glucose, insulin or C-peptide concentrations in any of the groups. CDCA elicited a small increase in plasma insulin : glucose ratio compared with colesevelam, CDCA + colesevelam and placebo in both groups. Compared with colesevelam, CDCA + colesevelam and placebo, respectively, CDCA increased glucagon and delayed gastric emptying in both groups. CONCLUSIONS: CDCA increased GLP-1 and glucagon secretion, and delayed gastric emptying. We speculate that bile acid-induced activation of TGR5 on L cells increases GLP-1 secretion, which, in turn, may result in amplification of glucose-stimulated insulin secretion. Furthermore our data suggest that colesevelam does not have an acute effect on GLP-1 secretion in humans.

Effects of RYGB on energy expenditure, appetite and glycaemic control: a randomized controlled clinical trial.

OBJECTIVES: Increased energy expenditure (EE) has been proposed as an important mechanism for weight loss following Roux-en-Y gastric bypass (RYGB). However, this has never been investigated in a controlled setting independent of changes in energy balance. Similarly, only few studies have investigated the effect of RYGB on glycaemic control per se. Here, we investigated the effect of RYGB on EE, appetite, glycaemic control and specific signalling molecules compared with a control group in comparable negative energy balance. SUBJECTS/METHODS: Obese normal glucose-tolerant participants were randomized to receive RYGB after 8 (n=14) or 12 weeks (n=14). The protocol included a visit at week 0 and three visits (weeks 7, 11 and 78) where 24-h EE, appetite and blood parameters were assessed. Participants followed a low-calorie diet from weeks 0-11, with those operated at week 12 serving as a control group for those operated at week 8. RESULTS: Compared with controls, RYGB-operated participants had lower body composition-adjusted 24-h EE and basal EE 3 weeks postoperatively (both P<0.05) but EE parameters at week 78 were not different from preoperative values (week 7). Surgery changed the postprandial response of glucagon-like peptide-1 (GLP-1), peptide YY3-36 (PYY), ghrelin, cholecystokinin, fibroblast growth factor-19 and bile acids (all P<0.05). Particularly, increases in GLP-1, PYY and decreases in ghrelin were associated with decreased appetite. None of HOMA-IR (homeostasis model assessment-estimated insulin resistance), Matsuda index, the insulinogenic index, the disposition index and fasting hepatic insulin clearance were different between the groups, but RYGB operated had lower fasting glucose (P<0.05) and the postprandial glucose profile was shifted to the left (P<0.01). CONCLUSIONS: Our data do not support that EE is increased after RYGB. More likely, RYGB promotes weight loss by reducing appetite, partly mediated by changes in gastrointestinal hormone secretion. Furthermore, we found that the early changes in glycaemic control after RYGB is to a large extent mediated by caloric restriction.

Gut hormones, early dumping and resting energy expenditure in patients with good and poor weight loss response after Roux-en-Y gastric bypass.

OBJECTIVE: To identify factors contributing to the variation in weight loss after Roux-en-Y gastric bypass (RYGB). DESIGN: Cross-sectional study of patients with good (excess body mass index lost (EBL) >60%) and poor weight loss response (EBL <50%) >12 months after RYGB and a lean control group matched for age and gender. MATERIALS AND METHODS: Sixteen patients with good weight loss response, 17 patients with poor weight loss response, and eight control subjects were included in the study. Participants underwent dual energy X-ray absorptiometry scan, indirect calorimetry and a 9 h multiple-meal test with measurements of glucose, insulin, total bile acids (TBA), glucagon-like peptide (GLP)-1, peptide YY3-36 (PYY), cholecystokinin (CCK), ghrelin, neurotensin and pancreatic polypeptide (PP) as well as assessment of early dumping and appetite. RESULTS: Suppression of hunger was more pronounced in the good than the poor responders in response to the multiple-meal test (P=0.006). In addition, the good responders had a larger release of GLP-1 (P=0.009) and a greater suppression of ghrelin (P=0.037) during the test, whereas the postprandial secretion of CCK was highest in the poor responders (P=0.005). PYY, neurotensin, PP and TBA release did not differ between the RYGB-operated groups. Compared with control subjects, patients had exaggerated release of GLP-1 (P<0.001), PYY (P=0.008), CCK (P=0.010) and neurotensin (P<0.001). Early dumping was comparable in the good and poor responders, but more pronounced than in controlled subjects. Differences in resting energy expenditure between the three groups were entirely explained by differences in body composition. CONCLUSION: Favorable meal-induced changes in hunger and gut hormone release in patients with good compared with poor weight loss response support the role of gut hormones in the weight loss after RYGB.

Changes in gastrointestinal hormone responses, insulin sensitivity, and beta-cell function within 2 weeks after gastric bypass in non-diabetic subjects.

BACKGROUND: Roux-en-Y gastric bypass (RYGB) surgery causes profound changes in secretion of gastrointestinal hormones and glucose metabolism. We present a detailed analysis of the early hormone changes after RYGB in response to three different oral test meals designed to provide this information without causing side effects (such as dumping). METHODS: We examined eight obese non-diabetic patients before and within 2 weeks after RYGB. On separate days, oral glucose tolerance tests (25 or 50 g glucose dissolved in 200 mL of water) and a liquid mixed meal test (200 mL 300 kcal) were performed. We measured fasting and postprandial glucose, insulin, C-peptide, glucagon, total and intact glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP), glucagon-like peptide-2 (GLP-2), peptide YY(3-36) (PYY), cholecystokinin (CCK), total and active ghrelin, gastrin, somatostatin, pancreatic polypeptide (PP), amylin, leptin, free fatty acids (FFA), and registered postprandial dumping. Insulin sensitivity was measured by homeostasis model assessment of insulin resistance. RESULTS: Fasting glucose, insulin, ghrelin, and PYY were significantly decreased and FFA was elevated postoperatively. Insulin sensitivity increased after surgery. The postprandial response increased for C-peptide, GLP-1, GLP-2, PYY, CCK, and glucagon (in response to the mixed meal) and decreased for total and active ghrelin, leptin, and gastrin, but were unchanged for GIP, amylin, PP, and somatostatin after surgery. Dumping symptoms did not differ before and after the operation or between the tests. CONCLUSIONS: Within 2 weeks after RYGB, we found an increase in insulin secretion and insulin sensitivity. Responses of appetite-regulating intestinal hormones changed dramatically, all in the direction of reducing hunger.

Incretin physiology beyond glucagon-like peptide 1 and glucose-dependent insulinotropic polypeptide: cholecystokinin and gastrin peptides.

Gastrin and cholecystokinin (CCK) are homologous hormone systems known to regulate gastric acid secretion, gallbladder emptying, and cell growth in the pancreas and stomach. They are, however, also involved in the development and secretory functions of pancreatic islet cells. For instance, foetal and neonatal islets express significant amounts of gastrin, and human as well as porcine islet cells express the gastrin/CCK-B receptor abundantly. Therefore, exogenous gastrin and CCK peptides stimulate insulin and glucagon secretion in man. Accordingly, endogenous hypergastrinaemia is accompanied by islet cell hyperplasia and increased insulin secretion. Conventionally, the effect of gastrointestinal hormones on insulin secretion (the incretin effect) has been defined and quantified in relation to oral versus intravenous glucose loadings. Under these unphysiological conditions, the release of gastrin and CCK and, hence, their effect on insulin secretion are modest in comparison with the effects of glucose-dependent insulinotropic polypeptide and glucagon-like peptide 1 (GLP-1). Consequently, the interest of CCK and gastrin in incretin research has for decades been limited. A few years ago, however, it was suggested that gastrin together with epidermal growth factor or later GLP-1 might stimulate beta cell growth and secretion. Recent studies have shown that the combination of gastrin and GLP-1 actually restores normoglycaemia in diabetic mice. Therefore, a short review of the incretin system in a broader functional context that includes gastrin and CCK peptides may be timely.

Basal and postprandial plasma levels of PYY, ghrelin, cholecystokinin, gastrin and insulin in women with moderate and morbid obesity and metabolic syndrome.

Metabolic syndrome (MS), defined as central obesity, hyperinsulinemia, insulin resistance, hypertension, dyslipidemia and glucose intolerance, has been associated with inflammatory biomarkers and cardiovascular diseases. This study was carried out on three groups of women; lean controls, moderately obese with MS (OB-MS) and morbidly obese with MS (MOB-MS). The main objectives were: 1. to analyze the plasma levels of total and acylated ghrelin, peptide YY(3-36) (PYY(3-36)), cholecystokinin (CCK), gastrin and insulin levels under basal conditions and in response to a standard mixed meal, and 2. to elucidate the relationship between the plasma levels of these gut peptides and metabolic syndrome parameters. Plasma levels of the gut hormones were measured by radioimmunoassays at time 0 just before the meal and at 30, 60 and 120 min after a meal ingestion. Traditional lipid profile and high-sensitivity C reactive protein (hs-CRP), the strongest biomarker of inflammation were also determined in OB-MS and MOB-MS. When compared to OB-MS, MOB-MS exhibited much higher anthropometric parameters such as waist circumference, higher fat mass and higher plasma levels of low density lipoprotein-cholesterol (LDL-C) and hs-CRP. Both these obese groups revealed significantly higher values of body mass index (BMI), fat mass, total cholesterol (TC), LDL-C, fasting glucose, fasting insulin, insulin resistance (IR) calculated from homeostatic model assessment (HOMA) and hs-CRP compared to the values recorded in lean subjects. Fasting PYY(3-36) level was lower, while fasting acylated ghrelin was higher in MOB-MS than in OB-MS. Plasma total and acylated ghrelin levels were significantly lower in OB-MS compared to lean women. In MOB-MS women the fasting PYY(3-36) levels were lower compared to lean controls and OB-MS, whilst postprandially in both OB-MS and MOB-MS, it was much lower than in lean women. The fasting plasma levels of total and acylated ghrelin and their postprandial decrease were significantly smaller in both obese groups compared to lean subjects. Plasma hs-CRP levels correlated positively with BMI, waist circumference, fat mass, fasting glucose, HOMA IR and fasting active ghrelin, whilst it negatively correlated with plasma fasting and total ghrelin. Moreover, plasma fasting acylated ghrelin correlated positively with fat mass. Fasting total ghrelin correlated positively with BMI, HDL-C and negatively with HOMA IR. We conclude that MS features of obesity are closely related to fasting and postprandial alterations of concentrations of PYY(3-36), CCK and ghrelin, suggesting that determination of gut hormones controlling food intake might be considered as a valuable tool to assess the progression of MS to comorbidities of obesity.

Basal and postprandial gut peptides affecting food intake in lean and obese pregnant women.

Maternal obesity has been reported as a risk factor for various maternal and fetal complications. The aim of the present study was to examine the patterns of basal and postprandial plasma concentrations of certain gut hormones affecting food intake such as acylated ghrelin, peptide YY(3-36) (PYY(3-36)), cholecystokinin (CCK), insulin and glucose in pregnant women with varying body mass gain during physiological pregnancy. The study included 34 women with singleton pregnancies in the 2(nd) trimester of gestation. The examined pregnant women were divided into 4 groups; I. control pregnancy (CP) with weight gain below 0.5 kg/week; II. overweight low weight gain <1 kg/week (OLWG), III. overweight high weight gain >1 kg/week (OHWG); morbidly obese pregnant with weight gain >1.5 kg/week (MOP). The basal acylated-ghrelin levels in MOP subjects were significantly higher than those in CP and no usual suppression of acylated ghrelin after the meal observed in CP as well as in OLWG and OHWG was found in MOP women. Basal PYY(3-36) plasma levels were similar in CP, OLWG and OHWG but in MOP was significantly reduced and no significant increase in hormone level, typically observed in CP, was detected after a meal in overweight or obese women studied. The fasting CCK and C-reactive protein (CRP) levels in MOP subjects were significantly higher than those in CP and other overweight women. In conclusion, we found that pregnant women with overweight and obesity exhibit significant changes in fasting and postprandial gut hormones affecting food intake such as acylated ghrelin, PYY(3-36) and CCK as well as in CRP and these changes might contribute, at least in part, the development of obesity in pregnancy.

Ghrelin stimulates gastric emptying and hunger in normal-weight humans.

CONTEXT: Ghrelin is produced primarily by enteroendocrine cells in the gastric mucosa and increases gastric emptying in patients with gastroparesis. MAIN OBJECTIVE: The objective of the study was to evaluate the effect of ghrelin on gastric emptying, appetite, and postprandial hormone secretion in normal volunteers. DESIGN: This was a randomized, double-blind, crossover study. SUBJECTS: Subjects included normal human volunteers and patients with GH deficiency. INTERVENTION: Intervention included saline or ghrelin (10 pmol/kg.min) infusion for 180 min after intake of a radioactively labeled omelette (310 kcal) or GH substitution in GH-deficient patients. MAIN OUTCOME MEASURES: Measures consisted of gastric empty-ing parameters and postprandial plasma levels of ghrelin, cholecystokinin, glucagon-like peptide-1, peptide YY, and motilin. RESULTS: The emptying rate was significantly faster for ghrelin (1.26 +/- 0.1% per minute), compared with saline (0.83% per minute) (P < 0.001). The lag phase (16.2 +/- 2.2 and 26.5 +/- 3.8 min) and half-emptying time (49.4 +/- 3.9 and 75.6 +/- 4.9 min) of solid gastric emptying were shorter during ghrelin infusion, compared with infusion of saline (P < 0.001). The postprandial peak in plasma concentration for cholecystokinin and glucagon-like peptide-1 occurred earlier and was higher during ghrelin infusion. There was no significant effect of ghrelin on plasma motilin or peptide YY. There was no difference in gastric emptying before and after GH substitution. CONCLUSION: Our results demonstrate that ghrelin increases the gastric emptying rate in normal humans. The effect does not seem to be mediated via GH or motilin but may be mediated by the vagal nerve or directly on ghrelin receptors in the stomach. Ghrelin receptor agonists may have a role as prokinetic agents.

Different effects of whole milk and a fermented milk with the same fat and lactose content on gastric emptying and postprandial lipaemia, but not on glycaemic response and appetite.

Longitudinal studies indicate that milk and fermented milk products lower basal plasma cholesterol concentrations, despite their high content of saturated fat, and therefore have favourable health effects. However, there have been few studies on the postprandial effects of milk products. The present study compared the effect of whole milk with a fermented milk, A-38, on postprandial carbohydrate and lipid metabolism, gastric emptying and appetite. Eight healthy young men participated. On the two test days, they arrived fasting for collection of baseline values before consuming the meals, which for a 75 kg subject consisted of 1.4 litre milk or fermented milk, plus 165 mg [13C]acetate (for later determination of gastric emptying by a [13C]acetate breath test). Lactose (15 g) was added to the A-38 meal to equalize the lactose content. Postprandially the A-38 meal resulted in a slower gastric emptying rate than milk (P<0.001). Furthermore, the A-38 meal resulted in a greater increase and a quicker decrease of the triacylglycerol content in all lipoprotein fractions (LDL-fraction, P<0.05; other fractions, P<0.001) and of the gastrointestinal hormones (cholecystokinin and peptide YY, P<0.05; gastric inhibitory polypeptide and glucagon-like polypeptide-1, P<0.001). There were no significant differences in appetite sensations (measured by visual analogue scale) or in the glucose and insulin response (P>0.10). The slower emptying rate of the liquid phase after the A-38 meal is probably due to the higher viscosity of A-38. The lower and more prolonged triacylglycerol response after the milk meal might be caused by coagulation of milk in the stomach.

Hereditary spastic paraplegia with cerebellar ataxia: a complex phenotype associated with a new SPG4 gene mutation.

Complex forms of hereditary spastic paraplegia (HSP) are rare and usually transmitted in an autosomal recessive pattern. A family of four generations with autosomal dominant hereditary spastic paraplegia (AD-HSP) and a complex phenotype with variably expressed co-existing ataxia, dysarthria, unipolar depression, epilepsy, migraine, and cognitive impairment was investigated. Genetic linkage analysis and sequencing of the SPG4 gene was performed and electrophysiologic investigations were carried out in six individuals and positron emission tomography (PET) in one patient. The disease was linked to the SPG4 locus on chromosome 2p as previously reported for pure HSP. Sequence analysis of the SPG4 (spastin) gene identified a novel 1593 C > T (GLN490Stop) mutation leading to premature termination of exon 12 with ensuing truncation of the encoded protein. However, the mutation was only identified in those individuals who were clinically affected by a complex phenotype consisting of HSP and cerebellar ataxia. Other features noted in this kindred including epilepsy, cognitive impairment, depression, and migraine did not segregate with the HSP phenotype or mutation, and therefore the significance of these features to SPG4 is unclear. Electrophysiologic investigation showed increased central conduction time at somatosensory evoked potentials measured from the lower limbs as the only abnormal finding in two affected individuals with the SPG4 mutation. Moreover, PET of one patient showed significantly relatively decreased regional cerebral blood flow in most of the cerebellum. We conclude that this kindred demonstrates a considerable overlap between cerebellar ataxia and spastic paraplegia, emphasizing the marked clinical heterogeneity of HSP associated with spastin mutations.

A centenary of gastrointestinal endocrinology.

Gastrointestinal hormones are peptides released to circulation from endocrine cells as well as neurons in the gastrointestinal tract. More than 30 hormone genes are currently known to be expressed in the stomach and intestines, which makes the gut the largest endocrine organ in the body. Moreover, cell and molecular biology now makes it feasible to conceive gastrointestinal endocrinology under five general headings: 1) The structural homology groups the hormones into eight families, each of which is assumed to originate from a common ancestral gene; 2) the individual hormone gene often have multiple phenotypes due to alternative splicing of the primary transcript, tandem organization of the translational product or differentiated maturation of the prohormone. By a combination of these mechanisms, more than 100 different hormonally active peptides are released from the gastrointestinal tract; 3) in addition, gut hormone genes are also widely expressed outside the gut, some only in neurons and/or in endocrine cells, but others also in other extraintestinal cell-types; 4) the different cell types may express different hormonally active fragments of the same prohormone by variation in the cell-specific posttranslational processing. Finally, 5) endocrine cells, neurons, and spermatozoa display different cell-specific release of gut peptides, so the same peptide may act as a metabolic blood-borne hormone, as a neurotransmitter, as a long-acting growth factor, and as an acute fertility factor.

Progastrin and its products from patients with chronic viral hepatitis and liver cirrhosis.

BACKGROUND: Gastrin and its precursor, progastrin, are synthesized in the stomach, particularly when infected with Helicobacter pylori, and they are metabolized, at least in part, in the liver. However, little is known about their levels in various hepatic diseases. METHODS: This study was carried out on 147 patients including chronic hepatitis B (n = 35), hepatitis C (n = 52) and liver cirrhosis (n = 60) of class A (n = 38), class B (n = 15) and class C (n = 7) (Child-Pugh classification) and age- and sex-matched healthy controls (n = 65). The diagnosis of chronic hepatitis was confirmed by liver biopsy in all patients, whereas the diagnosis of liver cirrhosis was based on clinical and laboratory findings. Liver biopsy was done in 38 out of 60 patients. Blood samples were collected under basal conditions and separated plasma samples were kept frozen at -70 degrees C until radioimmunoassay of progastrin and its products, including bioactive amidated gastrins. RESULTS: Median (range) plasma concentrations of total progastrin product and amidated gastrin in control subjects were 147.5 (73-345) pM and 33 (15-65), respectively. These concentrations in hepatitis B and C were not significantly different from those in controls. In cirrhosis (classes A, B and C), the concentrations of the progastrin and of gastrin were significantly (P < 0.05) higher than in controls reaching, respectively, 253.5 (135-683 pM) and 47.5 (17-385) pM. Both progastrin and gastrin levels were significantly higher in H. pylori-positive than in negative cirrhotic patients. Antibodies against H. pylori were present in about 50% of controls, 68% of hepatitis B, 57% of hepatitis C and in 83% in cirrhosis patients. The difference in H. pylori prevalence between cirrhosis and controls was statistically significant. CONCLUSIONS: Plasma levels of progastrin and gastrin are significantly increased in cirrhotic patients and this could be attributed to reduced metabolism of these peptides in liver cirrhosis and to their increased release due to H. pylori infection rate in this disease.

Increased cardiac BNP expression associated with myocardial ischemia.

Congestive heart failure is accompanied by increased cardiac brain natriuretic peptide (BNP) gene expression with elevated plasma concentrations of BNP and its precursor, proBNP. We investigated if myocardial ischemia in the absence of overt heart failure may be another mechanism for increased myocardial BNP expression. The BNP expression was examined in hypoxic myocardium of patients undergoing coronary bypass grafting surgery, in patients with coronary artery disease and normal left ventricular function undergoing percutaneous transluminal intervention therapy, and in heart failure patients without coronary artery disease. BNP mRNA was quantified by real-time PCR, and plasma BNP and proBNP concentrations were measured with radioimmunoassays. Quantitative analysis of BNP mRNA in atrial and ventricular biopsies from coronary bypass grafting patients revealed close associations of plasma BNP and proBNP concentrations to ventricular, but not atrial, BNP mRNA levels. Plasma BNP and proBNP concentrations were markedly increased in patients with coronary artery disease but without concomitant left ventricular dysfunction. These results are compatible with the notion that myocardial ischemia, even in the absence of left ventricular dysfunction, augments cardiac BNP gene expression and increases plasma BNP and proBNP concentrations. Thus, elevated BNP and proBNP concentrations do not necessarily reflect heart failure but may also result from cardiac ischemia.

The posttranslational phase of gene expression: new possibilities in molecular diagnosis.

Proteins in general and secretory proteins in particular undergo posttranslational processes before they reach the structure in which they can fulfill their functional purpose. The protein precursor may undergo a wide variety of proteolytic cleavages, N- and C-terminal trimmings and amino acid derivatizations in cells that express the protein. Occasionally, the same precursor is differently processed in different cell types and, in addition, diseased cells may process a given precursor abnormally. For instance, the translational process is often either increased or decreased in diseased cells, which render the ensuing modifications of the precursor incomplete. As a result, a variable mixture of precursors and processing-intermediates accumulates. Measurement of a single protein or peptide component of the posttranslational processing cascade may not facilitate the diagnosis of a disease, because the pattern of precursors and processing products vary individually among patients. In order to exploit disturbed posttranslational processing for diagnostic use, and--at the same time--provide an accurate measure of the translational product, a simple analytical principle named "processing-independent analysis" (PIA) has been designed. PIA-methods quantitate the total mRNA product irrespective of the degree of precursor processing. PIA-methods have recently been developed for a number of prohormones and neuroendocrine proteins, and their diagnostic potential appears promising in early diagnosis of tumors and cardiovascular diseases. The present review describes posttranslational processing patterns for some neuroendocrine proteins. Second, PIA-measurements of precursor-products are mentioned with indication of problems and pitfalls. Finally, PIA-results obtained in diagnosis of neoplastic and cardiovascular diseases are highlighted. But first general aspects of the posttranslational processing are reviewed as a necessary basis for the understanding of the new diagnostic possibilities.

Inhibition of gastric emptying by acarbose is correlated with GLP-1 response and accompanied by CCK release.

We investigated the effect of acarbose, an alpha-glucosidase and pancreatic alpha-amylase inhibitor, on gastric emptying of solid meals of varying nutrient composition and plasma responses of gut hormones. Gastric emptying was determined with scintigraphy in healthy subjects, and all studies were performed with and without 100 mg of acarbose, in random order, at least 1 wk apart. Acarbose did not alter the emptying of a carbohydrate-free meal, but it delayed emptying of a mixed meal and a carbohydrate-free meal given 2 h after sucrose ingestion. In meal groups with carbohydrates, acarbose attenuated responses of plasma insulin and glucose-dependent insulinotropic polypeptide (GIP) while augmenting responses of CCK, glucagon-like peptide-1 (GLP-1), and peptide YY (PYY). With mixed meal + acarbose, area under the curve (AUC) of gastric emptying was positively correlated with integrated plasma response of GLP-1 (r = 0.68, P < 0.02). With the carbohydrate-free meal after sucrose and acarbose ingestion, AUC of gastric emptying was negatively correlated with integrated plasma response of GIP, implying that prior alteration of carbohydrate absorption modifies gastric emptying of a meal. The results demonstrate that acarbose delays gastric emptying of solid meals and augments release of CCK, GLP-1, and PYY mainly by retarding/inhibiting carbohydrate absorption. Augmented GLP-1 release by acarbose appears to play a major role in the inhibition of gastric emptying of a mixed meal, whereas CCK and PYY may have contributory roles.

The method of administration of cholecystokinin determines the effects evoked in the pancreas.

Earlier studies have shown different effects on cell proliferation and weight characteristics by sulfated cholecystokinin-8 (CCK-8S) in the rat pancreas when the peptide has been administered continuously rather than intermittently. The aim of this study was as follows: (i) to compare the effect of continuous infusion and of intermittent injections of CCK-8S on cell proliferation, weight gain, and induction of apoptosis and (ii) to examine the effect of injections of CCK-8S on CCK-A receptor gene expression in the rat pancreas. Male Sprague-Dawley rats had subcutaneous continuous infusion of CCK-8S in a dose of 5 microg/kg/h or 1% bovine serum albumin (BSA) (vehicle) by implanted osmotic minipumps. The rats were killed after 4 days. Other rats were either injected subcutaneously only once or injected twice daily for 3 days with either 6 microg of CCK dissolved in 0.5 mL BSA or 0.5 mL BSA alone. The rats were killed 1, 3, 6, and 12 hours after the last injection. One hour before death they received 5-bromo-2-deoxyuridine (BrdU) intraperitoneally to localize and quantitate the cell proliferation. Plasma was collected for analysis of CCK. The pancreas was dissected and immunohistochemistry was performed for analysis of the expression of the apoptosis promoting protein bax and the apoptosis inhibiting protein bcl-2, and for BrdU and CCK-A receptor localization. In situ hybridization (ISH) was used for examination and semiquantification of CCK-A receptor mRNA expression. Continuous infusion of CCK-8S led to a sixfold increase in plasma CCK and a 40% increase in pancreatic weight without any effect on BrdU labeling. Immunohistochemistry revealed decreased tissue expression of bax but unaffected expression of bcl-2. Intermittent injections of CCK-8S led to hyper-CCK-emia with increased incorporation of BrdU, indicating increased cell proliferation but no increase in pancreatic weight. Immunohistochemistry showed increased expression of bax, whereas bcl-2 remained unchanged. Immunofluorescence and ISH for the CCK-A receptor and its gene expression, respectively, showed a lowest intensity at 3 hours after CCK-8S injections. The results indicate that decreased apoptosis could explain the increased pancreatic weight during continuous infusion of CCK-8S. An increased apoptosis could explain the lack of pancreatic weight gain upon intermittent injections of CCK-8S despite the stimulation of cell proliferation. Injections of CCK-8S only transiently decreased the tissue levels of its receptor.

A processing enzyme cleaving avian progastrin at post-Phe bonds.

Neuroendocrine peptides mature partly through endoproteolytic processing of long precursor forms. Best characterised is cleavage at mono- and dibasic residues, but additional sites also exist. Among these is post-Phe cleavage, first suggested to participate in the processing of chicken progastrin. In order to characterise this new mechanism, antibodies recognising the processing products of post-Phe cleavage of chicken progastrin were produced for radioimmunoassay measurements and immunocytochemistry. High concentrations of the carboxyamidated C-terminus and the N-terminus of gastrin-53 were measured in extracts of the antrum. In addition, significant amounts were detected using an assay specific for the N-terminus of gastrin-30 and with another assay for the C-terminus of the corresponding peptide, gastrin-53(1-23), obtained after cleavage at the Phe(23)-Ala(24) bond of gastrin-53. Colocalisation in antral G-cells of the N-termini of gastrin-53 and gastrin-30 and of the C-terminus of gastrin-53(1-23) was confirmed by immunohistochemistry. Finally, we identified the intact N-terminal 1-23 fragment of gastrin-53 complementary to gastrin-30, verifying endoproteolytic cleavage at the Phe(23)-Ala(24) bond. Taken together, the results support the existence of vertebrate endoprotease cleaving hormone precursors at post-Phe sites.