Biomedical subjects

Kari Baxter

Publications and source records attributed to Kari Baxter.

6 recordsLinked to original sources

PubMed2006

Obesity does not increase effects of synthetic ghrelin on human gastric motor functions.

BACKGROUND & AIMS: Ghrelin is secreted by the stomach and stimulates food intake. Obese individuals have lower fasting plasma ghrelin levels but increased appetite, suggesting greater responses to endogenous ghrelin in obesity. The aim of this study was to compare effects of exogenous ghrelin (at a dose that stimulates growth hormone [GH] release in the physiologic range) versus placebo on gastric emptying, gastric volume, and postprandial symptoms and determine whether body mass (ranging from normal weight to obesity) influences responses to ghrelin. METHODS: After intravenous bolus synthetic human ghrelin (0.33 mug/kg) or saline, we measured plasma GH, gastric volume, and gastric emptying by combined (99m)Tc-single-photon emission computed tomography and scintigraphy ((111)In egg meal, 300 kcal) and postprandial symptoms using visual analogue scales. RESULTS: In 25 obese subjects (5 men and 20 women; body mass index [BMI], 36 +/- 4 kg/m(2)) and 13 female normal-weight (BMI, 22 +/- 2 kg/m(2)) subjects of similar ages, ghrelin increased GH levels (15.0 +/- 2.4 ng/mL) at 40 minutes postinjection and tended to decrease fasting gastric volumes compared with placebo (P = .059). There were no effects of BMI on treatment response and no differences between ghrelin and saline on postprandial (P = .09) or change in (postprandial minus fasting) gastric volumes, gastric emptying, or aggregate postprandial symptoms. Effects of ghrelin did not differ between obese and normal-weight participants. CONCLUSIONS: At doses that stimulate physiologic GH plasma levels, synthetic ghrelin tended to decrease fasting gastric volumes without altering postprandial volumes or gastric emptying in a predominantly female cohort. The data are not consistent with the hypothesis that higher body mass is associated with increased gastric responsiveness to ghrelin.

Adolescent↗

PubMed2006

Effect of a selective chloride channel activator, lubiprostone, on gastrointestinal transit, gastric sensory, and motor functions in healthy volunteers.

Chloride channels modulate gastrointestinal neuromuscular functions in vitro. Lubiprostone, a selective type 2 chloride channel (ClC-2) activator, induces intestinal secretion and has been shown to relieve constipation in clinical trials; however, the effects of lubiprostone on gastric function and whole gut transit in humans are unclear. Our aim was to compare the effects of the selective ClC-2 activator lubiprostone on maximum tolerated volume (MTV) of a meal, postprandial symptoms, gastric volumes, and gastrointestinal and colonic transit in humans. We performed a randomized, parallel-group, double-blind, placebo-controlled study evaluating the effects of lubiprostone (24 microg bid) in 30 healthy volunteers. Validated methods were used: scintigraphic gastrointestinal and colonic transit, SPECT to measure gastric volumes, and the nutrient drink ("satiation") test to measure MTV and postprandial symptoms. Lubiprostone accelerated small bowel and colonic transit, increased fasting gastric volume, and retarded gastric emptying. MTV values were reduced compared with placebo; however, the MTV was within the normal range for healthy adults in 13 of 14 participants, and there was no significant change compared with baseline measurements. Lubiprostone had no significant effect on postprandial gastric volume or aggregate symptoms but did decrease fullness 30 min after the fully satiating meal. Thus the ClC-2 activator lubiprostone accelerates small intestinal and colonic transit, which confers potential in the treatment of constipation.

Adolescent↗

PubMed2005

Effect of gastric volume or emptying on meal-related symptoms after liquid nutrients in obesity: a pharmacologic study.

BACKGROUND & AIMS: Altered postprandial satiation influences food intake in obesity. The aim of this study was to evaluate the contribution of gastric motor functions to intra- and postprandial symptoms in obese, otherwise healthy, people. METHODS: In a randomized, parallel-group, double-blind design, 40 obese (body mass index>30 kg/m2) healthy volunteers (n=10/group) received intravenous saline (placebo), atropine (.02 mg/kg), or erythromycin (1 or 3 mg/kg) to alter gastric volume and emptying after liquid nutrient meals, measured by validated imaging methods. The nutrient drink test assessed the volume ingested at maximum satiation, and intra- and early postprandial symptoms. Relationships between gastric motor functions, meal size, and symptoms were assessed by using multiple regression. Circulating levels of candidate upper-gut hormones involved in satiation were measured. RESULTS: Relative to placebo, atropine retarded gastric emptying and increased gastric volumes; erythromycin accelerated gastric emptying and reduced gastric volumes during fasting. Although similar maximal tolerated volumes were recorded across treatments, intra- and immediate postprandial symptoms were increased by these perturbations, particularly nausea and bloating. Upper-gut hormonal profiles generally reflected changes in gastric emptying. Regression analysis showed that fasting predrug gastric volume was a significant predictor of intra- and postprandial bloating. Change in gastric volume postdrug or postmeal did not contribute additionally to predicting intra- or postprandial symptoms. There was significant (negative) association between gastric emptying and fullness score, and significant (positive) association with hunger score 30 minutes postprandially. CONCLUSIONS: In obese individuals, fasting gastric volumes and gastric emptying, but not postprandial gastric volumes, were associated with intra- and postprandial symptoms. Understanding the determinants of gastric volume may provide insights on mechanisms controlling satiation.

Adolescent↗

PubMed2005

Effect of alvimopan and codeine on gastrointestinal transit: a randomized controlled study.

UNLABELLED: background & aims: Opiate bowel dysfunction is a significant clinical problem. Our aim was to evaluate the ability of a peripheral mu-opioid antagonist, alvimopan, to reverse the effect of codeine on gastric, small-bowel, and colonic transit time in healthy volunteers. METHODS: Seventy-four healthy participants (43 women) were randomized in a double-blind, placebo-controlled manner to 1 of 4 groups: alvimopan 12 mg twice daily in the presence and absence of codeine sulfate 30 mg 4 times/day, or codeine or placebo alone. Gastric emptying, small-bowel, and colonic transit were measured by scintigraphy using a 99m-labeled technetium egg meal and 111-labeled indium charcoal delivered to the proximal colon via a delayed-release capsule. The primary end points for colonic transit were geometric center of the colonic counts at 24 hours and time for 50% ascending colon emptying. Analysis of covariance was used to assess the significance of the primary and secondary end points. RESULTS: Codeine delayed gastric, small-bowel, proximal, and overall colonic transit (P < .05). Alvimopan reversed codeine's effect on small bowel and colon (ascending colon and overall colonic transit). Alvimopan also accelerated overall colonic transit compared with placebo. Thus, the mean colonic geometric center at 24 hours was 2.33 with placebo/placebo, 3.25 with alvimopan/placebo (P < .05), 1.5 with placebo/codeine (P < .05), and 2.63 with alvimopan/codeine. Alvimopan did not reverse codeine's delay of gastric emptying. CONCLUSIONS: Alvimopan reverses codeine's inhibitory effect on small-bowel and colon transit and has potential for treatment of opiate bowel dysfunction. Alvimopan alone accelerates colonic transit, suggesting that mu-opiate mechanisms participate in the physiologic control of colonic transit.

Adolescent↗

PubMed2005

Effect of somatostatin analog on postprandial satiation in obesity.

OBJECTIVE: Altered satiation may impact postprandial symptoms and potentially change food intake in obesity. Our aim was to compare effects of octreotide and placebo on postprandial symptoms, satiation, and gastric volumes in obesity. RESEARCH METHODS AND PROCEDURES: In a randomized, parallel-group, double-blind, placebo-controlled study, 26 obese but otherwise healthy participants received 100 mug of octreotide or placebo subcutaneously 30 minutes before each study. Studies were performed on 2 separate days and included validated non-invasive techniques: (99m)Tc-single photon emission computed tomography imaging to measure fasting stomach volume and gastric volume changes after 90 mL of water and 240 mL of Ensure and a standardized nutrient drink test to measure the maximum tolerated volume and postprandial symptoms. RESULTS: Relative to placebo, octreotide increased gastric volume after 90 mL of water; however, fasting and gastric volume change post-Ensure and maximum tolerated volume of Ensure were not different. Octreotide decreased sensations of fullness (p = 0.035) and bloating (p = 0.05) and tended to reduce aggregate symptoms (p = 0.07) after the fully satiating meal. DISCUSSION: In obese individuals, somatostatin analog significantly reduced postprandial sensations after a satiating meal without altering maximum tolerated meal volume or postnutrient gastric volume, suggesting an effect on upper gut sensation. The role of somatostatin as a permissive factor in the development of obesity by reducing postprandial sensations deserves further study.

Adult↗

PubMed2004

Effect of renzapride on transit in constipation-predominant irritable bowel syndrome.

BACKGROUND & AIMS: The aim of this study was to evaluate the dose-ranging pharmacodynamic effects of renzapride, a 5-hydroxytryptamine 4 (5-HT4) receptor full agonist/5-HT3 receptor antagonist, on gastrointestinal transit and symptoms in patients with constipation-predominant irritable bowel syndrome (C-IBS). METHODS: Forty-eight patients (46 women) with C-IBS underwent recording of baseline symptoms for 1 week. Twelve patients per group were randomized (double-blind, parallel design) to 11-14 days of renzapride (1, 2, or 4 mg) or placebo, once daily. Daily bowel habits and weekly satisfactory relief of IBS symptoms were recorded. At the end of treatment, gastric emptying (GE), small bowel transit (SBT), and colon transit (CT) were measured by scintigraphy. The relationship between CT and bowel function was evaluated. RESULTS: A statistically significant linear dose response to renzapride was detected for CT (GC8 h, P = 0.004; GC24 h, P = 0.056), and ascending colon (AC) emptying t1/2 (P = 0.019), but not for GE (t1/2, P = 0.088; or SBT, P = 0.41). AC half-time transit (t1/2) for placebo and 4 mg of renzapride were (median) 17.5 vs. 5.0 hours, respectively. Improved bowel function scores (stool form and ease of passage, but not frequency) were significantly (P < 0.05) associated with accelerated CT. Pharmacokinetic analysis showed linear kinetics of renzapride with a mean t1/2 in plasma of 10 hours. Bowel function and satisfactory relief were not significantly altered by renzapride, although a type II error cannot be excluded. No significant adverse clinical, laboratory, or electrocardiogram (ECG) effects were observed. CONCLUSIONS: Renzapride causes clinically significant dose-related acceleration of CT, particularly ascending colonic emptying; this acceleration of transit is associated with improvement of bowel function in female C-IBS patients.

Adult↗