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LSG mechanisms

LSG involved in the GLP-1 secretion mechanism

Study offers novel insights into the effects of LSG on intestinal motility using the novel cine MRI method

Laparoscopic sleeve gastrectomy accelerates intestinal motility and reduces intestinal transit time, which may be involved in the mechanism underlying enhanced glucagon-like peptide-1 (GLP-1) secretion during oral glucose tolerance test (OGTT) after the procedure, according to paper by researchers from Shiga University of Medical Science, Otsu, Shiga, Japan.

The study, ‘Enhanced Intestinal Motility during Oral Glucose Tolerance Test after Laparoscopic Sleeve Gastrectomy: Preliminary Results Using Cine Magnetic Resonance Imaging’, published online in the journal Plos One, showed that GLP-1 secretion during OGTT was enhanced and cine magnetic resonance imaging (MRI) showed markedly increased intestinal motility at 15 and 30 min during OGTT after laparoscopic sleeve gastrectomy.

Although enhanced secretion of GLP-1 has been suggested as a possible mechanism underlying the improvement in type 2 diabetes mellitus (T2DM) after sleeve gastrectomy, the reason for enhanced GLP-1 secretion during glucose challenge after the procedure remains unclear because the procedure does not include intestinal bypass.

Study

Therefore, the study authors focused on the effects of the procedure on GLP-1 secretion and intestinal motility during the OGTT using cine MRI before and three months after LSG. They used this specific imaging modality as it “provides direct visualisation of intestinal contraction and peristalsis”.

Twelve obese patients with a BMI>35 were recruited into the study; six patients had T2DM and two diabetic patients had haemoglobin A1c (HbA1c) levels >7.8%.

Sleeve gastrectomy was performed using a standard five-port laparoscopic technique with a 45-Fr gastric tube to calibrate the sleeve, and dissection of the greater curvature began approximately 5–6 cm from the pylorus.

MRI examinations were performed for each patient one week before and three months after the surgery and MRI was conducted after eight hours of fasting before as well as 15 and 30 minutes after oral intake of 225mL of fluid containing 7 g of glucose.

Imaging was performed using a 1.5T MR scanner (Signa HDxt 1.5T; GE Healthcare,) with an 8-channel body array coil. Before real cine MRI, coronal images of the entire abdomen were obtained to determine the optimal image plane covering the maximum length of the small bowel loops. A serial coronal scan consisting of 50 images was obtained at the selected plane with the patient in a supine position in 25 seconds during breath holding.

Based on the cine MRI, 2 bowel segments, one located in the left upper quadrant as representative of the jejunal loops and the other located in the right lower quadrant as representative of the ileal loops, were chosen for assessment of contraction

In this process, bowel loops with a degree of distension similar to the rest of the loops in the same quadrant as well as remaining in the image plane during the sequential imaging without displacement out of the image plane were chosen for assessment. Frequencies of bowel contractions were counted visually on a monitor using cine MRI.

Arrival of the orally administered fluid to the jejunum, ileum, and terminal ileum was assessed within each sequence (15 and 30 minutes after glucose intake) by the presence or absence of bowel distension and high signal fluid. The presence or absence of distension of the jejunal and ileal loops was also judged, and contraction frequencies were compared between distended and collapsed bowel loops after surgery.

Results

The outcomes showed that the percentage of excess weight loss (%EWL) at three months after the surgery was 48% ±22% . All six diabetic patients discontinued all diabetic medications immediately after the surgery, and their HbA1c levels significantly decreased. In both the non-diabetic and diabetic patients, GLP-17–36 secretion during OGTT was significantly enhanced (Table 1).

Parameters

         Patient

       Before surgery

        3mths after   surgery

      p value

Body weight

All

109.7 ± 26.4

89.5 ± 25.4

0.000

EWL%

All

 

48 ± 22

 

HbA1C (%)

T2DM

8.0 ± 1.4

6.0 ± 0.8

0.006

 

Non-T2DM

5.2 ± 0.4

5.1 ± 0.4

0.2

Table 1: Changes in body weight and HbA1C 3 months after surgery (T2DM: type 2 diabetes mellitus; EWL: excess weight loss; HbA1C: hemoglobin A1C. Data were shown as mean ± standard deviation.

Cine MRI scans before and three months after LSG were obtained in nine of the 12 patients because of three patients refused examination, including two diabetic patients and one non-diabetic patient. There was no significant difference in mean frequencies of contractions of the jejunum and ileum prior to glucose intake between before and after LSG. However, their contractions significantly increased at 15 and 30 minutes after glucose intake after the procedure, compared with those before (Table 2).

Parameters

      Before surgery

         3mths after surgery  

     p value

Contraction of jejunum at 0min  (frequency/min)

0.4 ± 0.8

0.5 ± 1.1

0.7

Contraction of the jejunum at 15min (frequency/min)

2.4 ± 2.8

6.1 ± 0.7

0.01

Contraction of the jejunum at 30min (frequency/min)

3.2 ± 2.0

5.7 ± 1.4

0.02

Contraction of the ileum at 0min (frequency/min)

1.3 ± 1.7

1.2 ± 1.7

0.8

Contraction of the ileum at 15min (frequency/min)

2.4 ± 2.7

7.0 ± 2.4

0.009

Contraction of the ileum at 30min (frequency/min)

3.4 ± 2.7

7.4 ± 1.4

0.002

Table 2: Changes in contraction of the jejunum and ileum during OGTT 3 months after surgery (data are presented as mean ± standard deviation).

The percentage of patients whose glucose fluid reached the jejunum, ileum, and ileum terminal at 15 and 30 minutes after fluid intake was markedly increased after LSG. Before LSG, 33%, 11%, and 0% of patients showed the presence of fluid in the jejunum, ileum, and ileum terminal at 15 min after fluid intake, respectively. After LSG, 100%, 89%, and 89% of patients showed the presence of fluid in the jejunum, ileum, and ileum terminal, respectively. Moreover, all patients showed the presence of fluid in the jejunum, ileum, and ileum terminal at 30 minutes after fluid intake following LSG compared with 41%, 33%, and 22% before LSG, respectively (Table 3).

Parameters

      Before surgery

         3mths after surgery

Presence of glucose fluid in the jejunum at 15 min (%)

33.3

100

Presence of glucose fluid in the jejunum at 30 min (%)

41.7

100

Presence of glucose fluid in the ileum at 15 min (%)

11.1

 88.9

Presence of glucose fluid in the ileum at 30 min (%)

33.3

100

Presence of glucose fluid in the ileum  terminal at 15 min   (%)

                 0

                     88.9

Presence of glucose fluid in the ileum terminal at 30min (%)

22.2

100

Table 3: Changes in frequency of the presence of glucose fluid in the jejunum, ileum, and ileum terminal during OGTT 3 months after surgery.

In addition, the mean frequency of contractions of fluid-distended jejunum and ileum loops (6.1/min and 7.4/min, respectively) was significantly higher than that of contractions of collapsed jejunum and ileum loops (0.5/min and 1.4/min, respectively) (Table 4).

Parameters

Collapsed

Fluid- distended

p value

Contraction of the jejunum loops (frequency/min)

0.5 ± 1.0

6.1 ± 0.7

0.000

Contraction of the ileum loops (frequency/min)

1.4 ± 1.6

7.4 ± 1.7

0.000

Table 4: Differences in contraction frequencies between collapsed and fluid-distended bowel loops during OGTT 3 months after surgery.

Conclusion

“Our study offers novel insights into the effects of LSG on intestinal motility using the novel cine MRI method,” the authors write. “Using this novel method, we showed that intestinal motility was markedly accelerated and small bowel transit time was reduced after glucose intake in all patients following LSG”

“This acceleration of contraction was concurrently observed with faster arrival of the intake fluid and intestinal distension. The arrival of the glucose fluid might have changed the patterns of bowel contraction from a fasting pattern to a postprandial pattern, distended loops contract more frequently than collapsed loops, as was also observed in the present study,” they conclude. “For the first time, we clearly demonstrated that intestinal motility was markedly accelerated and bowel transit time reduced after LSG using a novel method.”

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