Comparative Impact of Sleeve Gastrectomy and One Anastomosis Gastric Bypass on Glycemic Control and Abdominal Adiposity:ARandomized Controlled Study

doi:10.21203/rs.3.rs-4638884/v1

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Comparative Impact of Sleeve Gastrectomy and One Anastomosis Gastric Bypass on Glycemic Control and Abdominal Adiposity:ARandomized Controlled Study

https://doi.org/10.21203/rs.3.rs-4638884/v1

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Background

Abdominal subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) depots are implicated in the interplay between obesity and metabolic complications. The present study aimed to compare the impact of sleeve gastrectomy (SG) and one anastomosis gastric bypass (OAGB) on weight loss and glycemic control and to assess the potential role of VAT in type 2 diabetes mellitus (DM) remission.

Patients and methods

Patients with obesity and DM participated in this randomized controlled study were randomly allocated to the SG and OAGB groups. Computed tomography was used to assess VAT and SAT. Patients were followed up one year after surgery.

Results

At the 12-month follow-up, the two groups showed significant weight loss and improvement in the metabolic profile. The OAGB group showed a statistically significant higher percentage reduction in HbA1c. The incidence of complete remission was 76.0% in the SG group and 87.0% in the OAGB group (p = 0.331). The OAGB group showed significantly lower mean VAT/SAT and higher mean reduction rates. DM duration and VAT/SAT still significantly predicted DM remission.

Conclusion

Both SG and OAGB procedures are effective in achieving weight loss and improving metabolic performance at 12 months postoperatively. The OAGB group showed superior glycemic control and a higher reduction in the VAT area relative to abdominal fat.

Sleeve gastrectomy

one anastomosis gastric bypass

Type 2 diabetes mellites

visceral adipose tissue

There has been a continually rising prevalence rate of obesity and its associated medical complications [1]. The pathophysiology of obesity-related complications is multifaceted, involving chronic low-grade inflammation, altered adipokine secretion, and dysregulated lipid metabolism. These mechanisms collectively contribute to metabolic derangements and increased cardiovascular risk [2].

It has been presumed that both abdominal subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) depots are considered a crucial part of the endocrine system, which is implicated in the multifaceted interplay among obesity, metabolic complications, and systemic inflammation [3, 4]. Both fat depots, along with intrahepatic fat, have been described to be involved in metabolic complications [5, 6] through the secretion of bioactive cytokines, leading to resistance to insulin and subsequent type 2 DM [7, 8].

Bariatric surgery has become the definitive management of obesity and its associated complications in patients who could not achieve a healthy weight with lifestyle modifications and medications [9]. Despite traditionally being categorized as restrictive, malabsorptive, or a combination, strong evidence has shown that this classification is improper with the described bariatric surgery effect on endocrine and neural signaling pathways that modulate the weight loss and remission of complications such as type 2 diabetes mellitus (DM) after bariatric surgery [10].

Sleeve gastrectomy (SG) has currently achieved a persistently increased popularity due to its efficacy and being technically simple [11, 12].

Bypass surgeries such as Roux-en-Y gastric bypass (RYGB) have shown a more evident metabolic effect and remission of obesity-associated conditions due to the bypass component of the surgery [10]. One anastomosis gastric bypass (OAGB) is another bypass procedure that was first announced by Rutledge and published in 2001 [13]. Since then, it has gained wide popularity and acceptance, being a relatively simple procedure compared to RYGB and maintaining its effectiveness in weight loss and resolution of obesity-associated medical conditions [14–16]. In addition, it gained recognition as a mainstream bariatric technique by the IFSO in 2018 [11].

The present study aimed to compare the impact of SG and OAGB on weight loss and glycemic control and to assess the potential role of abdominal adipose depots, as measured by computed tomography (CT), in the remission of type 2 DM.

The present study is a prospective randomized controlled trial (RCT) that included patients recruited from the bariatric outpatient clinic to our institution for bariatric surgery during the period from September 2022 to February 2024. The study started after obtaining the institutional Research Ethics Committee (No.: MD-257-2022) and adhering to the Declaration of Helsinki.

All initially included patients received comprehensive assessments by a multidisciplinary team including a bariatric surgeon, endocrinologist, nutritionist, radiologist, and anesthetist. Other specialties were requested when indicated. The patients’ evaluation encompassed history-taking, clinical assessment, and routine laboratory investigations.

Adult patients who were generally fit for laparoscopic surgery and anesthesia and indicated for bariatric surgery as per the criteria proposed by the National Institutes of Health (NIH) Consensus Development Panel in 1991 that were confirmed and updated by the European Association for Endoscopic Surgery (EAES) in 2020, and the American Society for Metabolic and Bariatric Surgery (ASMBS) as well as the International Federation for the Surgery of Obesity and Metabolic Disorders (IFSO) in 2022 [17–19] with a previous diagnosis of type 2 DM as per the American Diabetes Association criteria [20] were eligible for the study.

Patients who had previous bariatric surgery, patients who were relatively not indicated for LSG or OAGB as previously established [21, 22], those who were unfit for the CT examination due to exceeding the upper limit of the physical constraints suitable for the CT equipment as specified by the CT machine's manufacturer, and those who did not accept to participate in the study or were lost during follow-up were excluded from the study.

Written informed consents were obtained from all included patient after discussion with the surgeon regarding each procedure’s benefits and potential drawbacks.

Sample size calculation

In this study, the sample size calculation was done using G*Power 3.1.9.7 software. The used parameters were based on the study by Castro et al. [23], who assessed the short-term glycemic control after SG and OAGB. The alpha error probability was set at 0.05, and the used power was 80%, indicating that the required sample size per group was at least 18 participants. This number was further increased to compensate for the potential dropout.

‎Individualized Metabolic Surgery (IMS) Score calculation

The Individualized Metabolic Surgery (IMS) Score was calculated for every patient included. The score was calculated based on the study of Aminian et al. [24], which takes into account the number of anti-diabetic medications, using insulin, duration of DM, and the glycemic control (glycated hemoglobin A; HbA1c < 7%).

CT assessment of the abdominal fat

The radiological assessment of the study patients included a non-contrast CT examination of the abdomen and pelvis. It was done using 16-detector-row scanners (emition SOMATOM), with a slice thickness of 5 mm. According to the manufacturer’s instructions, patients weighing up to 150 kg with a scanning range of up to 157 cm were suitable to be scanned. Scanning was performed from the lower chest D10 level down to the upper thigh.

To estimate the abdominal adipose tissue, a single slice at the level of the fourth lumbar vertebral body was used. Visceral adipose tissue was traced using a cursor pointer by defining the muscular layer of the abdominal wall [26], and fat was considered when the attenuation value lied within a range of − 190 to − 30 Hounsfield units (HU) [27]. The VAT and total abdominal fat (TAF) areas were measured in cm² (Fig. 1), and the area of the SAT area was calculated by subtracting VAT from the TAF. The relative contribution of VAT to abdominal adiposity was calculated as the VAT/SAT and VAT/TAF ratios [25, 26].

Hepatic and splenic parenchymal density was measured in HU using regions of interest (ROI). Three ROIs were placed on the liver, one on the left lobe and two on the right lobe, and one was placed on the spleen. ROIs were careful not to include vessels or any structure other than the homogenous parenchymal tissue. The ratio between liver and spleen density (L/S ratio) was obtained by dividing the mean density of both hepatic lobes by the splenic density. An L/S ratio of less than 1.0 and/or liver attenuation lower than 40 HU were considered for the diagnosis of increased hepatic parenchymal fat [27]. (Fig. 2)

Randomization

The included patients were equally randomized to the LSG group and the OAGB group. The randomization was done using the closed opaque envelope method that was conducted by an independent hospital employer who randomly distributed the envelopes inside a box and disclosed them to the patients on the night before surgery.

Intervention

The surgery was performed under general anesthesia while patients in the supine position and the surgeon standing in the French position. The patients were firmly secured to the table to permit placing them in the anti-Trendelenburg position, when necessary, with the compressing stockings applied to the patients’ legs. In all cases, pneumoperitoneum was created, and a five-trocar diamond-shaped approach was used.

The surgery in the two groups was performed as previously established. In all patients, early mobilization was encouraged upon return to the surgical ward. Clear oral fluids were allowed on day 0. Patients were discharged home after ensuring hemodynamic stability and gastrointestinal recovery. Patients received the standardized diet regimen and required supplementation protocol and were scheduled for follow-up visits.

At the 12-month follow-up, the study patients were subjected to a complete general examination, including anthropometric measures, laboratory investigations, and pelvi-abdominal assessment, with a comparison of the results to the baseline data.

The percentages of excess BMI loss (EBMIL%) and total weight loss (TWL%) were calculated [28], and remission or improvement of DM was judged per the ASMBS criteria [29]. The percentage reduction of any clinical measure was calculated as (baseline value minus 12-month value) / (baseline value) * 100.

Study outcomes

The primary outcomes of this study were glycemic control 12 months after the two procedures and its association with the abdominal adiposity measures. The secondary outcomes were the 12-month weight loss and other metabolic improvements in the two groups.

Statistical methods

This patient's data were analyzed using the statistical software Jamovi (Jamovi, Version 2.3, Computer Software, Sydney, Australia). The normality of the numerical data was tested, and then the student t-test or the Mann-Whiteney test was used for comparison as appropriate. A paired t-test was used to compare postoperative data to baseline data. Categorical data were analyzed using the Chi-square test, Fisher’s exact test, or Z test for proportion accordingly. Binary logistic regression analysis was performed to assess the predictors for DM remission. Statistical significance was set at 0.05.

This RCT initially included 60 patients who were equally allocated to the SG group (n = 30) and the OAGB group (n = 30). Five patients from the SG group and seven patients from the OAGB group did not complete the study and were excluded. Finally, the SG group consisted of 25 patients, and the OAGB group consisted of 23 patients who were included in the final analysis (Fig. 3).

The mean patients’ age was 39.8 ± 9.5 years in the SG group and 42.3 ± 7.28 years in the OAGB group (p = 0.314). Most of the patients in the two groups were females (68.0% and 82.6%, p = 0.243). The mean baseline weight was 130.9 ± 25.4 kg and 136.2 ± 24.7 kg (p = 0.465), BMI was 50.1 ± 9.61 kg/m2 and 50.5 ± 6.02 kg/m2 (p = 0.879), waist circumference was 130.6 ± 13.31 cm and 131.1 ± 16.58 cm (p = 0.904), waist to hip ratio was 1.54 ± 0.182 and 1.62 ± 0.131 (p = 0.09), in the two groups, respectively (Table 1).

Table 1

Baseline data of the study groups
Parameter	SG Group (n = 25)	OAGB Group (n = 23)	p-value
Age (years)	39.8 ± 9.5	42.3 ± 7.28	0.314
Female: n (%)	17 (68.0%)	19 (82.6%)	0.243
Baseline Weight (kg)	130.9 ± 25.4	136.2 ± 24.7	0.465
BMI (kg/m²)	50.1 ± 9.61	50.5 ± 6.02	0.879
WC (cm)	130.6 ± 13.31	131.1 ± 16.58	0.904
WHR	1.54 ± 0.182	1.62 ± 0.131	0.09
Medical complications n (%)
Dyslipidemia	15 (60.0%)	14 (60.9%)	0.951
Hypertension	11 (44.0%)	11 (47.8%)	0.790
Bronchial Asthma	3 (12.0%)	1 (4.3%)	0.338
Arthritis	1 (4.0%)	0 (0.0%)	0.332
Hypothyroidism	0 (0.0%)	2 (8.7%)	0.132
Positive family history of DM	19 (76.0%)	18 (78.3%)	0.852
Number of anti-diabetic medications: n (%)
1	22 (88.0%)	16 (69.6%)	0.288
2	2 (8.0%)	5 (21.7%)	0.288
3	1 (4.0%)	2 (8.7%)	0.288
Patients Using Insulin: n (%)	5 (20.0%)	8 (34.8%)	0.250
Duration of DM (years)	1 (0.7–6)	5 (0.95–10.5)	0.155
IMS	18.2 (16.6–35)	68.6 (14–109)	0.247
Numerical data were presented as mean ± standard deviation or median (inter-quartile range), BMI: body mass index, WC: waist circumference, WHR: waist to hip ratio, IMS: individualized metabolic score, p < 0.05: statistically significant.

The patients’ obesity-associated complications other than diabetes mellitus were mainly dyslipidemia and hypertension. Others were bronchial asthma, arthritis, and hypothyroidism (Table 1).

Positive family history of diabetes mellitus was predominant in the two groups (76.0% and 78.3%, respectively, p = 0.852). The distribution of patients according to the number of diabetic medications showed that the majority of patients had one antidiabetic medication (88.0% and 69.6%, respectively); two and three medications were taken by 8.0% and 4.0% of the SG group, respectively, p = 0.288. Both groups included patients using insulin (20.0% and 34.8% of the two groups, respectively) (p = 0.250). The median (IQR) duration of DM was 1 (0.7–6) and 5 (0.95–10.5) years in the two groups, respectively (p = 0.155). The median (IQR) duration of IMS was 18.2 (16.6–35) and 68.6 (14.1–109) in the two groups, respectively (p = 0.247) (Table 1).

The mean fasting glucose (FBG) levels were 131.3 ± 24.9 mg/dl in the SG group and 128.4 ± 27.5 mg/dl in the OAGB group (p = 0.704), the mean HBA1c levels were 7.10 ± 1.19 in the SG group and 7.45 ± 1.08 in the OAGB group (p = 0.291), the mean triglycerides levels were 207.7 ± 88.9 mg/dl and 211.3 ± 93.9 mg/dl (p = 0.892), the mean low-density lipoprotein (LDL) levels were 125.6 ± 38.3 mg/dl and 122.2 ± 41.4 mg/dl (p = 0.769), and the mean high-density lipoprotein (HDL) levels were 42.6 ± 11.8 mg/dl and 41.9 ± 12.1 mg/dl (p = 0.840), in the two groups, respectively.

By CT assessment, the mean VAT was 162.2 ± 46.4 cm² in the SG group and 167.2 ± 44.2 cm² in the OAGB group (p = 0.705), the mean SAT was 386.6 ± 80.6 cm² and 396.7 ± 72.9 cm² (p = 0.650), the mean VAT/SAT was 0.419 ± 0.18 and 0.421 ± 0.13 (p = 0.965), the mean VAT/TAF ratios were 0.296 ± 0.06 and 0.297 ± 0.08 (p = 0.961), the mean liver densities were 34.1 ± 11.7 and 34.0 ± 11.7 (p = 0.987), and the mean liver/spleen ratios were 0.83 ± 0.23 and 0.84 ± 0.27 (p = 0.891), in the two groups, respectively.

Follow-up at 12 months

At the 12-month follow-up, the mean BMI was 32.4 ± 5.6 kg/m2 in the SG group and 30.4 ± 6.25 kg/m2 in the OAGB group (p = 0.259), the mean EBMIL% was 70.6 ± 13.8 and 78.8 ± 17.7 (p = 0.082), and the mean TWL% was 30.1 ± 5.4 and 31.9 ± 5.8 (p = 0.270) in the two groups, respectively.

The mean FBG levels were 89.7 ± 15.9 mg/dl in the SG group and 87.4 ± 12.8 mg/dl in the OAGB group (p = 0.582), the mean HBA1c levels were 5.52 ± 0.7 in the SG group and 5.4 ± 0.32 in the OAGB group (p = 0.473), the mean triglycerides levels were 88.5 ± 23.7 mg/dl and 84.6 ± 25.9 mg/dl (p = 0.590), the mean LDL levels were 110.7 ± 23.6 mg/dl and 111.5 ± 24.7 mg/dl (p = 0.909), and the HDL levels were 51.3 ± 12.4 mg/dl and 50.9 ± 13.4 mg/dl (p = 0.915), in the two groups, respectively (Table 2).

Table 2

Laboratory and radiological data of the study patients at the baseline and 12-months after surgery
	Baseline			12-month
Parameter	SG Group	OAGB Group	p-value	SG Group	OAGB Group	p-value
FBG (mg/dl)	131.3 ± 24.9	128.4 ± 27.5	0.704	89.7 ± 15.9	87.4 ± 12.8	0.582
HbA1c (%)	7.10 ± 1.19	7.45 ± 1.08	0.291	5.52 ± 0.7	5.4 ± 0.32	0.473
Triglycerides (mg/dl)	207.7 ± 88.9	211.3 ± 93.9	0.892	88.5 ± 23.7	84.6 ± 25.9	0.590
LDL (mg/dl)	125.6 ± 38.3	122.2 ± 41.4	0.769	110.7 ± 23.6	111.5 ± 24.7	0.909
HDL (mg/dl)	42.6 ± 11.8	41.9 ± 12.1	0.840	51.3 ± 12.4	50.9 ± 13.4	0.915
VAT (cm²)	162.2 ± 46.4	167.2 ± 44.2	0.705	83.2 ± 17.3	73.4 ± 18.6	0.065
SAT (cm²)	386.6 ± 80.6	396.7 ± 72.9	0.650	266.3 ± 25.8	275.9 ± 29.9	0.239
VAT/SAT	0.409 ± 0.18	0.421 ± 0.13	0.965	0.31 ± 0.03	0.266 ± 0.05	< 0.001
VAT/TAF	0.303 ± 0.06	0.297 ± 0.08	0.961	0.24 ± 0.02	0.21 ± 0.03	< 0.001
Liver Density (HU)	34.1 ± 11.7	34.0 ± 11.7	0.987	57.6 ± 10.1	57.2 ± 5.2	0.862
L/S Ratio	0.83 ± 0.23	0.84 ± 0.27	0.891	1.2 ± 0.15	1.3 ± 0.17	0.037
FBG: Fasting blood glucose, HbA1c: glycated hemoglobin, LDL: low-density lipoprotein, HDL: high density lipoprotein, VAT: visceral adipose tissue, SAT: subcutaneous adipose tissue, TAF: total abdominal fat, L/S: Liver/Spleen Ratio, p < 0.05: statistically significant.

Compared to the baseline measures, there was statistically significant improvement in the FBG (p < 0.001 in both groups), HBA1c (p < 0.001 in both groups), triglycerides (p < 0.001 in both groups), LDL (p < 0.001 in the SG group and p = 0.02 in the OAGB group), and HDL (p < 0.001 in both groups).

The OAGB group showed a statistically significant higher percentage reduction in HbA1c (− 27.52 ± 4.31% vs. −22.25 ± 4.68%, p < 0.001). No other statistically significant differences were observed between the two groups in the percentages of changes in other parameters (p > 0.05).

The incidence of complete remission was 76.0% in the SG group and 87.0% in the OAGB group (p = 0.331). All the remaining patients in the two groups had DM improvement.

By CT assessment, the mean VAT in the two groups was 83.2 ± 17.3 cm2 and 73.4 ± 18.6 cm2 (p = 0.065), with mean reduction rates of 48.7% ± 10.1% and 56.1% ± 14.96% (p = 0.052). The mean SAT was 266.3 ± 25.8 cm2 and 275.9 ± 29.9 cm2 (p = 0.239), with mean reduction rates of 31.1% ± 4.79% and 30.5% ± 3.69% (p = 0.628). The mean VAT/SAT were 0.31 ± 0.03 and 0.266 ± 0.05 (p < 0.001), with mean reduction rates of 32.6% ± 7.07% and 36.8% ± 5.4% (p = 0.026). The mean VAT/TAF were 0.24 ± 0.02 and 0.21 ± 0.03 (p < 0.001), with mean reduction rates of 19.6% ± 9.7% and 29.3% ± 9.8% (p < 0.001). The mean liver densities were 57.6 ± 10.1 HU and 57.2 ± 5.2 HU (p = 0.862), with mean increase rates of 68.91% ± 12.01% and 68.24% ± 11.15% (p = 0.842). The mean liver/spleen ratios were 1.2 ± 0.15 and 1.3 ± 0.17 (p = 0.037), with mean increase rates of 44.58% ± 11.51% and 54.8% ± 10.91% in the two groups, respectively (p = 0.003). In all the measured CT parameters, there was statistically significant improvement in the two groups compared to the baseline measures (p < 0.001).

Univariate regression analysis revealed that the patients’ age (β = -1.578, 95% CI: -3.11 to -0.05, OR = 0.206, p = 0.043), duration of DM (β = -0.140, 95% CI: -0.257 to -0.0218, OR = 0.870, p = 0.020), type of surgery (OAGB) (β = 0.024, 95% CI: 0.005 to 0429, OR = 1.025, p = 0.011), and 12-month VAT/SAT ratio (β = -0.0852, 95% CI: -0.1375 to -0.0330, OR = 0.918, p = 0.001) were the statistically significant predictors of DM remission. Adjusting these factors for confounders showed that DM duration (β = -1.422, 95% CI: -2.89 to -0.06, OR = 0.611, p = 0.048) and VAT/SAT (β = -0.0846, 95% CI: -0.139 to -0.0304, OR = 0.919, p = 0.002) were still significantly predicting the DM remission.

Postoperative complications

The postoperative adverse events were gastroesophageal reflux disease (GERD), anemia, vomiting, offensive steatorrhea, and dumping. Nutritional complications were vitamin B, vitamin D, and calcium deficiencies. A statistically significant higher complication rate was associated with OAGB (69.6% vs. 40.0 in the SG group, p = 0.04) (Table 3). All were treated conservatively.

Table 3

Postoperative adverse events
	SG Group (n = 25)	OAGB Group (n = 23)	P-value
Total	10 (40.0%)	16 (69.6%)	0.04
GERD	1 (4.0%)	0 (0.0%)	1
Anemia	2 (8.0%)	2 (8.7%)	1
Vomiting	2 (8.0%)	0 (0.0%)	0.490
Offensive steatorrhea	0 (0.0%)	5 (21.7%)	0.020
Dumping	0 (0.0%)	1 (4.3%)	0.479
Vit D and calcium deficiency	5 (20.0%)	2 (8.7%)	0.419
Vit B deficiency	1 (4.0%)	0 (0.0%)	1
Hair loss	0 (0.0%)	8 (34.8%)	0.001
GERD: gastroesophageal reflux disease, p < 0.05: statistically significant.

Both SG and OAGB have gained prominence in the treatment of obesity and its associated medical problems due to their efficacy and relative safety profiles. However, there is an ongoing debate regarding their comparative outcomes.

In this study, both the SG and OAGB groups demonstrated substantial reductions in weight and BMI, with OAGB showing non-significantly higher EBMIL% and TWL% after 12 months of surgery. Furthermore, both groups experienced significant improvements in their metabolic profiles. However, the OAGB group exhibited a significantly higher percentage reduction in HbA1c, suggesting a superior impact on glycemic control. This was further reflected in a notably higher incidence of DM complete remission in the OAGB group (87.0%) compared to the SG group (76.0%), though this difference did not reach the level of significance.

The lack of statistically significant differences in weight loss and diabetes remission rates between the two groups suggests that both surgical options remain viable for weight loss and metabolic improvement. Nonetheless, potential advantages of OAGB in managing obesity and the associated type 2 DM are highlighted, and a more evident significance could potentially emerge in a larger population.

In line with our study, Lee et al. [30] observed that OAGB was related to better glycemic control than SG. This was also supported by a meta-analysis study by Yang et al. [31], who reported the superiority of bypass surgery over SG in the treatment of DM.

The DM remission rates found in the present study were similar to those of Seetharamaiah et al. [32], who reported that the patients treated with OAGB had a DM remission rate of 83.7%, compared to a respective rate of 76.6% in the SG group. Like our study, this difference lacked statistical significance. Other previous studies, such as those of Wang et al. [33], Magouliotis [34], Akool et al. [35], and Quan et al. [36], also emphasized the better OAGB effect on DM. In a recent meta-analysis study by Ding et al. [37], where four RCTs including more than 200 patients were analyzed, OAGB showed a distinctively higher DM remission rate than SG, with a significant reduction in HbA1c levels despite comparable EBMIL% at the short-term follow-up.

The primary mechanisms contributing to these beneficial effects are weight loss and restricted calories intake. Bariatric surgery induces substantial weight loss, leading to a decrease in adipose tissue mass. This reduction alleviates the inflammatory milieu typically seen in obesity, which is a significant contributor to insulin resistance. As a result, the body's cells become more responsive to insulin, facilitating better glucose uptake by the cells and thereby lowering blood glucose levels [38].

Reduced calorie intake is another critical factor. Bariatric procedures restrict the stomach capacity, resulting in early satiety and decreased overall food intake. This caloric restriction directly impacts blood glucose levels by reducing the amount of glucose entering the bloodstream, aiding in glycemic control [38].

The mechanisms underlying the OAGB superiority in DM remission compared to SG are still unclear. However, it is believed that the additional malabsorptive component of the OAGB largely contributes to this efficiency. In OAGB, the hormonally active foregut is bypassed. It was demonstrated that the response of cholecystokinin after meals was eliminated in OAGB compared to SG [39]. Another mechanism was proposed by Lee et al. [40], who assumed that OAGB results in more rapid recovery of the incretin effect compared to SG. Incretins, such as glucose-dependent insulinotropic polypeptide and glucagon-like peptide-1, are gut hormones that enhance insulin secretion in response to food intake, helping regulate blood glucose levels. The incretin effect is blunted in type 2 DM [41, 42].

Another plausible explanation could emerge from the effect on VAT, which was investigated in this study. In this context, it has been described that SAT and VAT are metabolically distinct and have different hormonal responses [43]. Visceral adipose tissue has been indicated to be particularly involved in the metabolic complications of obesity due to its unique location in adherence with the portal circulation that is characterized by the secretion of diverse bioactive substances [44, 45]. As per the “portal vein hypothesis” [46], increased VAT leads to an increase in the delivery of free fatty acids to the liver and the secretion of inflammatory mediators, resulting in a state of low-grade inflammation and insulin resistance [47]. On the other hand, SAT appeared to have a weaker contribution to metabolic dysfunction when compared with VAT [48].

Our findings highlighted the better OAGB impact on VAT with postoperatively lower VAT area, VAT/SAT, and VAT/TAF ratios seen in patients treated with OAGB. Liver densities and liver/spleen ratios improved significantly in both groups, with the OAGB group showing a significantly greater increase in the liver/spleen ratio. These findings suggest that OAGB not only reduces overall fat but also more effectively targets the visceral component, which is crucial for reducing metabolic risk.

In the current study, the patients’ age, DM duration, type of surgery, and VAT/SAT ratio were identified as significant predictors of DM remission. After adjusting for confounders, DM duration and VAT/SAT ratio remained significant predictors, indicating that these factors play a crucial role in predicting the likelihood of DM remission post-surgery.

Patients with a shorter duration of DM had a higher likelihood of achieving remission. This can be attributed to the fact that a shorter disease duration typically indicates less beta-cell dysfunction. Therefore, these patients have a better capacity for glycemic improvement when substantial weight loss is achieved. The VAT/SAT ratio also emerged as a significant predictor of DM remission, which confirms its mediating role in the OAGB superiority in glycemic control.

While the OAGB group showed superior glycemic control and higher remission rates of DM, it also experienced a higher rate of postoperative complications. All of which, however, were treated conservatively. This demands proper patients’ selection and strict postoperative monitoring.

To our knowledge, this is the first study to compare the short-term effects of OAGB and SG on glycemic control and abdominal adiposity and their associations. The study is strengthened by its prospective design, which is an RCT. However, our work is limited by the relatively small number of patients and the short-term follow-up. Further long-term studies with larger sample sizes are needed to confirm these findings and evaluate the sustainability of the observed effects.

Both SG and OAGB procedures are effective in achieving weight loss and improving metabolic parameters at 12 months postoperatively. The OAGB group showed superior glycemic control and a higher reduction in the VAT area relative to abdominal fat. The duration of DM and VAT/SAT were associated with the DM remission. OAGB posed a higher risk of complications, necessitating careful patient selection and postoperative management.

Statement for informed consent: Informed consent was obtained from all participants in the study.
Statement for conflict of interest: The authors declare no conflict of interest.

Ethical approval:

• This study has been approved by the appropriate institutional research ethics committee.

Funding:

None.

Author Contribution

H.H and M.M wrote the main manuscript text and H.M prepared figures 1-3. All authors reviewed the manuscript."

Acknowledgment:

• None.

Data Availability

Data of this study is available upon editorial request

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Comparative Impact of Sleeve Gastrectomy and One Anastomosis Gastric Bypass on Glycemic Control and Abdominal Adiposity:ARandomized Controlled Study

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