Peripheral mechanisms of sibutramine involving proximal gastric motility in dogs

Acute and chronic effects of desvenlafaxine on gastrointestinal transit and motility in dogs

BACKGROUND

Antidepressants are commonly used for treating functional gastrointestinal (GI) diseases. However, little is known whether antidepressants improve or impair GI motility. This study aimed at exploring possible effects of a serotonin-norepinephrine reuptake inhibitor, desvenlafaxine succinate (DVS), on GI motility in dogs.

METHODS

Eight dogs chronically implanted with a duodenal cannula and a colon cannula were used in the study. Experiments were performed to assess the effects of a single dose of DVS (50 or 100 mg) and DVS given 50 mg once a day for 2 weeks on gastric emptying of solid, small intestinal transit, and colon transit and contractions.

KEY RESULTS

(1) DVS significantly delayed gastric emptying of solid at a single dose of 50 or 100 mg. The inhibitory effect on gastric emptying was completely blocked by guanethidine (an adrenergic blocking agent). (2) DVS at a single dose of 50 or 100 mg accelerated colon transit, but showed no effects on small bowel transit. (3) DVS at a single dose of 50 mg enhanced colon contractions and guanethidine blocked the effect. (4) Surprisingly, DVS given at 50 mg once daily for 2 weeks did not alter gastric emptying, small bowel transit or colon transit.

CONCLUSIONS & INFERENCES

Acute DVS delays gastric emptying of solid and enhances the contractions of the colon, which may be mediated via the sympathetic mechanism. Acute DVS promotes the transit of the colon but not the small intestine. However, chronic administration of DVS does not seem to alter GI motility.

Review article: the role of gastric motility in the control of food intake

BACKGROUND

From a classical point of view, gastric motility acts to clear the stomach between meals, whereas postprandial motility acts to provide a reservoir for food, mixing and grinding the food and to assure a controlled flow of food to the intestines.

AIM

To summarise findings that support the role of gastric motility as a central mediator of hunger, satiation and satiety.

METHODS

A literature review using the search terms 'satiety', 'satiation' and 'food intake' was combined with specific terms corresponding to the sequence of events during and after food intake.

RESULTS

During food intake, when gastric emptying of especially solids is limited, gastric distension and gastric accommodation play an important function in the regulation of satiation. After food intake, when the stomach gradually empties, the role of gastric distension in the determination of appetite decreases and the focus will shift to gastric emptying and intestinal exposure of the nutrients. Finally, we have discussed the role of the empty stomach and the migrating motor complex in the regulation of hunger signals.

CONCLUSIONS

Our findings indicate that gastric motility is a key mediator of hunger, satiation and satiety. More specifically, gastric accommodation and gastric emptying play important roles in the regulation of gastric (dis)tension and intestinal exposure of nutrients and hence control satiation and satiety. Correlations between gastric accommodation, gastric emptying and body weight indicate that gastric motility can also play a role in the long-term regulation of body weight.

A controlled pharmacogenetic trial of sibutramine on weight loss and body composition in obese or overweight adults

BACKGROUND & AIMS

Weight loss in response to sibutramine is highly variable. We assessed the association of specific markers of polymorphisms of candidate alpha2A adrenoreceptor, 5-HT transporter, and GNbeta3 genes and weight loss with sibutramine.

METHODS

We conducted a randomized, double-blind, pharmacogenetic study of behavioral therapy and sibutramine (10 or 15 mg daily) or placebo for 12 weeks in 181 overweight or obese participants. We measured body weight, body mass index, body composition, gastric emptying, and genetic variation (alpha2A C1291G, 5-HTTLPR, and GNbeta3 C825T genotypes). Analysis of covariance was used to assess treatment effects on and associations of the specific markers of candidate genes with weight loss and body composition.

RESULTS

Sibutramine, 10 and 15 mg, caused weight loss (P = .009); there was a statistically significant gene by dose interaction for GNbeta3 genotype. For each candidate gene, significant treatment effects at 12 weeks were observed (P < .017) for all specific genotype variants (Delta weight loss in the 2 sibutramine doses vs placebo): alpha2A CC (Delta, approximately 5 kg), GNbeta3 TC/TT (Delta, approximately 6 kg), and 5-HTTLPR LS/SS (Delta, approximately 4.5 kg). Gene pairs resulted in significantly greater sibutramine treatment effects on weight (both P < .002): in participants with 5-HTTLPR LS/SS with GNbeta3 TC/TT; Delta, approximately 6 kg and those with alpha2A CC with GNbeta3 TC/TT; Delta, approximately 8 kg; however, effects were not synergistic. Treatment with sibutramine also resulted in significantly greater reduction of body fat for specific alpha2A CC and GNbeta3 TC/TT genotype variants individually (both P < .02).

CONCLUSIONS

Patient selection based on candidate genes may enhance response to multidimensional sibutramine and behavioral therapy for obesity.

Effects of sibutramine on gastric emptying, intestinal motility and rectal tone in dogs

The aim of this study was to evaluate the effects of sibutramine on gastric emptying, small-bowel contractions, rectal tone and compliance, and gastrointestinal myoelectrical activity. The study was performed in 14 dogs. It was composed of three separate experiments: gastric emptying of liquids and gastrointestinal slow waves; small-bowel contractions; and rectal tone and rectal compliance. Each experiment included two sessions: a control session and a treatment session with sibutramine (5 mg/kg orally) administrated 2 h before the study. Sibutramine significantly accelerated liquid gastric emptying at 75 and 90 min after the meal but did not alter gastrointestinal slow waves. Gastric emptying at 75 and 90 min was 61.42 +/- 7.71 and 66.32 +/- 7.67% in the control session, and increased to 71.27 +/- 5.14 and 75.93 +/- 5.29% in the session with sibutramine (p < 0.05, vs. control). Sibutramine significantly inhibited postprandial small-bowel contractions. Sibutramine did not alter the rectal tone, but significantly increased rectal compliance. Sibutramine accelerates gastric emptying of liquids but inhibits small-bowel contractions. These findings suggest the peripheral mechanisms of sibutramine in reducing food intake and causing weight loss in obesity patients.

Alteration of gastric functions and candidate genes associated with weight reduction in response to sibutramine

BACKGROUND & AIMS

It is unclear whether weight loss with the noradrenergic (norepinephrine) and serotonergic (5-hydroxytryptamine) reuptake inhibitor, sibutramine, is associated with altered stomach functions and whether genetics influence treatment response.

METHODS

Forty-eight overweight and obese but otherwise healthy participants were randomized to placebo or sibutramine (15 mg/day for 12 weeks). At baseline and posttreatment we measured the following: gastric emptying for solids and liquids by scintigraphy, gastric volumes by single-photon emission computed tomography, maximum tolerated volume and 30-minute postnutrient challenge symptoms, and selected gastrointestinal hormones. All participants received structured behavior therapy for weight management. The influence of candidate gene polymorphisms involved in norepinephrine and 5-hydroxytryptamine or receptor function (phenylethanolamine N-methyltransferase, guanine nucleotide binding protein beta polypeptide 3, alpha2A adrenoreceptor, and solute carrier family 6 [neurotransmitter transporter, serotonin] member 4 [homo sapiens] [SLC6A4]) on weight loss and gastric functions was evaluated.

RESULTS

The overall average weight loss posttreatment was 5.4 +/- 0.8 (SEM) kg with sibutramine and 0.9 +/- 0.9 kg with placebo (P < .001). The sibutramine group showed significant retardation in gastric emptying of solids (P = .03), reduced maximum tolerated volume (P = .03), and increased postprandial peptide YY compared with the placebo group. Obese females showed greater effects of sibutramine on weight loss and gastric emptying of solids and liquids. Gastric volumes and postchallenge symptoms were not significantly different in the 2 treatment groups. The LS/SS genotype of the promoter for SLC6A4 was associated with enhanced weight loss with sibutramine.

CONCLUSIONS

Weight reduction with sibutramine is associated with altered gastric functions and increased peptide YY and is significantly associated with SLC6A4 genotype. The role of genetic variation in SLC6A4 on weight loss in response to sibutramine deserves further study.