Canine vagus nerve stores cholecystokinin-58 and -8 but releases only cholecystokinin-8 upon electrical vagal stimulation

Effect of Adropin on Pancreas Exocrine Function in a Rat Model: A Preliminary Study

The aim was to investigate the potential effect of adropin (ADR) on pancreatic−biliary juice (PBJ) secretion (volume, protein content, trypsin activity) in a rat model. The animals were divided into control and five experimental groups: adropin, CCK-8 (CCK-8 stimulation), capsaicin (capsaicin deactivation of afferents), vagotomy (vagotomy procedure), and vagal stimulation (vagal nerve stimulation). The experiment consisted of four phases, during which vehicle (0.9% NaCl) and three ADR boluses (5, 10, and 20 µg/kg BW) were administered i.v. every 30 min. PBJ samples were collected from each rat at 15 min intervals after boluses. Exogenous ADR failed to affect the pancreatic responses after vagotomy and the capsaicin pretreatment and reduced the PBJ volume, protein outputs, and trypsin activity in the adropin, CCK-8, and vagal stimulation groups in a dose-dependent manner. In all these groups, volume of PBJ was reduced only by the highest dose of ADR (p < 0.001 for adropin group and p < 0.01 for CCK-8 and vagal stimulation groups), and the protein outputs were reduced by the administration of ADR 10 µg/kg BW (adropin and CCK-8 groups, p < 0.01 in both cases) and 20 µg/kg BW (p < 0.001 for adropin and CCK-8 groups, p < 0.01 for vagal stimulation group). The 10 µg/kg BW dose of ADR reduced the trypsin output in the CCK-8 group (p < 0.01), and the highest ADR dose reduced the trypsin output in the CCK-8 (p < 0.001) and vagal stimulation (p < 0.01) groups. In conclusion, adropin in the analyzed doses exhibits the negative feedback pathway. This mechanism seems to participate in the regulation of pancreatic juice secretion via an indirect vagal mechanism.

Canine hepatobiliary anatomy, physiology and congenital disorders

The biliary system is an integral component of normal physiologic homeostasis and essential for survival. It acts as a conduit for the removal of detoxified and catabolised compounds as well as aids in fat digestion and absorption. Derangements in this system can have dangerous sequela that are associated with varying degrees of morbidity and mortality. Moreover, abnormalities in development of the biliary system can have varied and unpredictable changes on function and long-term outcome. The aims of this article were to review canine hepatobiliary anatomy, physiology and cholestasis as well as summarise congenital biliary disorders including human corollaries.

Life with the pancreas: A personal experience

This review article has primary objective to summarize pancreatic research which has been done in our laboratory since 1965, the first year of the author's registration in the Ph.D. program at the University of Sherbrooke (Canada). It covers the following major topics of pancreatic physiology: controls of pancreatic adaptation to diet, control of pancreatic enzyme secretion, control of pancreatic enzyme synthesis, control of pancreatic growth, intracellular events stimulated during pancreatic growth, pancreas regeneration after pancreatitis and pancreatectomy, the pancreatic cholecystokinin receptor types 1 and 2, growth control and cell signaling in pancreatic cancer cells and finally, cystic fibrosis.

Chronic vagus nerve stimulation decreased weight gain, food consumption and sweet craving in adult obese minipigs

Chronic vagus nerve stimulation (VNS) is known to influence food intake and body weight in animals and humans. The aim of our work was to evaluate the effects of long-term VNS in adult obese minipigs. Eight minipigs were fed ad libitum a Western diet to cause obesity, after which half of the animals were implanted with bilateral vagal electrodes connected to constant current stimulators (2mA, 30Hz, 500-μs pulse, ON 30s, OFF 5min). The other animals were implanted with sham devices. Animals were weighed weekly and their daily consumption was measured. Still 14 weeks after surgery, VNS animals (70.3±3.3kg, P>0.10) did not significantly gain weight compared to sham animals (80.6±8.0kg, P<0.05). Furthermore, food consumption decreased in VNS animals (-18%, P<0.02) compared to sham animals (+1%, P>0.10). When subjected to a three-choice meal test (high-fat vs. high-carbohydrates vs. balanced diet), VNS animals decreased their sweet-food consumption compared to sham animals (P<0.05), and increased their balanced diet consumption in comparison to pre-surgery levels. Our results showed that chronic VNS decreased weight gain, food consumption and sweet craving in adult obese minipigs, which indicates that this therapy might be used to decrease appetite in the context of morbid obesity.

Vagus nerve stimulation does not lead to significant changes in body weight in patients with epilepsy

BACKGROUND

Vagus nerve stimulation (VNS) is an FDA-approved treatment for medically intractable epilepsy. The effect of this therapy on body weight is unclear. VNS could cause weight loss by engaging vagal afferents from the gastrointestinal tract mediating satiety.

METHODS

We performed a retrospective analysis of body weight changes over a period up to 2 years following VNS implantation. We studied 21 patients (13 M/8 F) 35 +/- 12 years old, who received a Cyberonics VNS Therapy System for medically intractable epilepsy between April 1998 and May 2004. The mean +/- SD duration of follow-up was 613.1 +/- 389.1 days. The study had 80% power with a type I error of 0.05 to detect a 5% weight change. Data were analyzed with repeated-measures ANOVA.

RESULTS

Weight changes relative to baseline at 30, 60, 120, 360, 480, and 720 days were -0.17 +/- 2.33, +0.33 +/- 2.64, -0.32 +/- 3.56, +1.09 +/- 5.97, +1.06 +/- 7.47, and +0.33 +/- 3.69%, respectively. At all time points these differences failed to reach statistical significance.

CONCLUSIONS

Vagus nerve stimulation with parameters typically used in the treatment of patients with epilepsy was not associated with clinically significant weight changes. A well-controlled prospective study is necessary for more precise evaluation of the effect of VNS therapy on body weight.

Gastric pacing for morbid obesity: plasma levels of gastrointestinal peptides and leptin

OBJECTIVE

A gastric pacemaker has been developed to treat morbid obesity. Patients experience increased satiety, the ability to reduce food intake, and a resultant weight loss. However, the mechanism behind the changed eating behavior in paced patients is still under investigation.

RESEARCH METHODS AND PROCEDURES

This study was performed on 11 morbidly obese patients (mean BMI, 46.0 kg/m2) treated with gastric pacing. The peripheral blood levels of satiety signals of cholecystokinin (CCK), somatostatin, glucagon-like peptide-1 (GLP-1), and leptin were studied 1 month before gastric pacer implantation, 1 month after implantation, and 6 months after activation of electrical stimulation. Blood samples were drawn 12 hours after fasting and in response to a hypocaloric meal (270 kcal). Patients were followed monthly for vital signs and weight level.

RESULTS

Gastric pacing resulted in a significant weight loss of a mean of 10.4 kg (4.4 BMI units). No negative side effects or complications were observed during the treatment. After activation of the pacemaker, meal-related response of CCK and somatostatin and basal levels of GLP-1 and leptin were significantly reduced (p < 0.05) compared with the tests before gastric pacing. The weight loss correlated significantly with a decrease of leptin levels (R = 0.79, p < 0.01).

DISCUSSION

Gastric pacing is a novel and promising therapy for morbid obesity. Activation of the gastric pacer was associated with a decrease in plasma levels of CCK, somatostatin, GLP-1, and leptin. More studies are necessary to elucidate the correlations between satiety, weight loss, and digestive neuro-hormone changes.

Presence and localization of CCK receptor subtypes in calf pancreas

This study was undertaken to confirm the presence of CCK receptor subtypes in calf pancreas and establish their cellular localization. Using specific antibodies against CCKA and CCKB receptors, somatostatin, glucagon and insulin, we were able to confirm by Western blot the presence of both CCK receptor protein subtypes in the calf pancreas as a 80-85-kDa CCKA receptor and 40-45-kDa CCKB receptor. By immunofluorescence, the CCKB receptor colocalizes with the islets' somatostatin delta cells, confirming what was previously shown in other species, as well as on ductal cells. We could not reproduce in the calf its colocalization with glucagon alpha cells as observed in human and rat. Any specific localization of CCKA receptors with our multiple antibodies failed. Our observation that the CCKB receptor subtype is specifically localized on pancreatic delta cells as well as on ductal cells lets us support the hypothesis that in this species, CCK could be involved in somatostatin metabolism as well as hydrelatic secretion; its effect on enzyme secretion would be indirect.

Neurohormonal control of exocrine pancreas

The exocrine pancreas is regulated by various hormonal factors derived from the gut through hormone-hormonal and neurohormonal interactions. Physiologic stimuli entering the upper small intestine elicit the release of intestinal hormones and activate sensory reflex mechanisms from the intestinal mucosa to stimulate or inhibit exocrine pancreatic secretion. In addition, the endocrine pancreas, intrapancreatic nerves, and some extrapancreatic neural pathways, with or without mediation by the vagus nerve, are known to participate in regulation of exocrine pancreatic secretion. It has been established that two key intestinal hormones, secretin and cholecystokinin (CCK), in physiologic doses, act through the vagal afferent pathway and interact with each other as well as with other gut hormones. The releases of these two hormones are mediated through the corresponding releasing peptides. In the past few years, the roles of secretin- and CCK-releasing peptides have become more clearly defined. The participation of several neurotransmitters and regulatory peptides in the regulation of exocrine pancreatic secretion has also been established. In addition, neurotransmitters and neuropeptides released from the central nervous system may participate in the regulation of pancreatic secretion. It is conceivable that a few neurotransmitters and neuropeptides are involved in each neural regulatory pathway. However, their roles and sites of action in each pathway remain to be determined.