Effect of neurotensin in the dumping syndrome

Late-onset rapid gastric emptying: Identification of a new abnormal finding in patients with otherwise normal results on gastric emptying scintigraphy

BACKGROUND

The 4-h gastric emptying (GE) scintigraphy protocol is the gold standard for assessing GE. Rapid gastric emptying (RGE) is >30% emptied by 30 min and >65% emptied at1 h. We observed that some GE studies demonstrated rapid emptying at a later time although interpreted as normal (NGE) at 4 h. We aimed to establish thresholds to characterize this subset of late-onset rapid gastric emptying (LRGE).

METHODS

We retrospectively analyzed 4-h GE studies of 425 patients with upper GI symptoms who fulfilled the criteria for NGE. We recruited 24 normal subjects to establish GE cutoff values (mean +/- 2SD) at 1-2, 2-3, and 3-4 h. These thresholds were applied to the 425 patients with NGE. During every GE study, patients graded their postprandial symptoms on a scale from 0 to 4.

KEY RESULTS

The mean upper threshold decrement limits were calculated from the normal volunteers as 67.6% at 1-2 h, 48.7% at 2-3 h, and 27.9% at 3-4 h. After applying these values to the NGE patients, 19 (4.5%) were classified as having LRGE; 6 patients (1.4%) for the 2- to 3-h; and 13 (3.1%) for the 3- to 4-h period. Patients with LRGE had abdominal pain, bloating, nausea, or diarrhea beginning more than 1-h postprandial.

CONCLUSION

5% of patients classified as "normal" at 4 h had an abnormal GE pattern based on the proposed criteria for LRGE. This highlights the importance of applying these hourly decrement thresholds to identify LRGE as a new diagnostic entity explaining postprandial symptoms.

Modifications at Arg and Ile Give Neurotensin(8-13) Derivatives with High Stability and Retained NTS1 Receptor Affinity

Due to its expression in various malignant tumors, the neurotensin receptor 1 (NTS₁R) has been suggested and explored as a target for tumor diagnosis and therapy. Animal model-based investigations of various radiolabeled NTS₁R ligands derived from the hexapeptide neurotensin(8-13) (NT(8-13)), e.g. ⁶⁸Ga- and ¹⁸F-labeled compounds for PET diagnostics, give rise to optimize such radiotracers for clinical use. As NT(8-13) is rapidly degraded in vivo; structural modifications are required in terms of increased metabolic stability. In this study, the stabilization of the peptide backbone of NT(8-13) against enzymatic degradation was systematically explored by performing an N-methyl scan, replacing Ile¹² by tert-butylglycine¹² (Tle¹²) and N-terminal acylation. N-Methylation of either arginine, Arg⁸, or Arg⁹, combined with the Ile¹²/Tle¹² exchange, proved to be most favorable with respect to NTS₁R affinity (K _i < 2 nM) and stability in human plasma (t _1/2 > 48 h), a valuable result regarding the development of radiopharmaceuticals derived from NT(8-13).

Dumping Syndrome: A Review of the Current Concepts of Pathophysiology, Diagnosis, and Treatment

Gastric surgery has long been known to be a cause of dumping syndrome (DS). However, the increasing incidence of gastric bypass surgery, as well as reports of DS unrelated to previous gastric surgeries, has increased the importance of understanding DS in recent years. DS is due to the gastrointestinal response to voluminous and hyperosmolar chyme that is rapidly expelled from the stomach into the small intestine. This response involves neural and hormonal mechanisms. This review encompasses the symptoms, diagnosis, and treatment approaches of DS and also focuses on the current research status of the pathophysiology of DS.

Dumping syndrome: pathophysiology and treatment

Anatomic and physiologic changes introduced by gastric surgery result in clinically significant dumping syndrome in approximately 10% of patients. Dumping is the effect of alteration in the motor functions of the stomach, including disturbances in the gastric reservoir and transporting function. Gastrointestinal hormones play an important role in dumping by mediating responses to surgical resection. Treatment options of dumping syndrome include diet, medications, and surgical revision. Poor nutrition status can be anticipated in patients who fail conservative therapy. Management of refractory dumping syndrome can be a challenge. This review highlights current knowledge about the mechanisms of dumping syndrome and available therapy.

Octreotide acetate induces fasting small bowel motility in patients with dumping syndrome

The long acting somatostatin analogue octreotide acetate has been effective in the treatment of early dumping syndrome. We hypothesized that this may be related to its effects on inhibiting gastric emptying and delaying intestinal transit. To study the effect of octreotide acetate on intestinal motility in patients we carried out a randomized, double-blinded study using a subcutaneous injection of either octreotide acetate (100 micrograms) or placebo given 20 min prior to ingestion of a high carbohydrate "dumping" meal in six patients with known severe dumping syndrome. Prior to each study a multilumen polyethylene tube was inserted into the efferent limb to study small intestinal contractions using low compliance pneumo-hydraulic water-perfused manometry. Octreotide acetate prevented dumping symptoms in all six patients and induced the appearance of migrating myoelectric complexes (MMC) characteristic of interdigestive motility. After ingestion of the dumping meal the postprandial "fed" motility pattern lasted for 141 +/- 9 min while after octreotide acetate the fed motility lasted for 29 +/- 5 min (P less than 0.03). The vigor of the fed motility pattern as measured by the motility index (MI = loge (sum of amplitudes X No. of contractions + 1] was lower after octreotide acetate than after placebo (15.1 +/- 0.1 vs 13.4 +/- 0.2, P less than 0.03). The induction of fasting MMC motility pattern and reduction in the duration and vigor of fed motility may explain the symptomatic relief these patients obtained with octreotide acetate. It is not known whether the induction of the MMC is a direct effect of octreotide acetate or secondary to the concomitant inhibition of peptide release (neurotensin, insulin, glucagon, pancreatic polypeptide) that has been demonstrated in earlier studies.