Effect of different bariatric surgery type on the leukocyte formula

1 2 3 Surgery for Obesity and Related Diseases ] (2016) 00–00 4 5 6 Original article 7 8 Q3 9 10 Filipe M. Cunha, M.D.a,b,*, Ana Saavedra, M.D.a,b, José Barbosa, M.D., Ph.D.c, 11 Q1 Paula Freitas, M.D., Ph.D.a,b, Davide Carvalho, M.D., Ph.D.a,b,d, Ana Varela, M.D.a,b 12 a Serviço de Endocrinologia, Diabetes e Metabolismo, Centro Hospitalar de São João, Porto, Portugal 13 b Faculdade de Medicina da Universidade do Porto, Porto, Portugal c 14 Serviço de Cirurgia Geral, Centro Hospitalar de São João, Porto, Portugal d Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal 15 Received December 6, 2015; revised January 29, 2016; accepted February 2, 2016 16 17 18 Abstract Background: Obesity is associated with higher leukocyte counts, whereas weight loss decreases 19 these counts. It is unknown if different bariatric surgery (BS) types have different effects on 20 leukocytes. 21 Objectives: The aim of the study was to determine predictors of leukocyte and their subset count 22 variation in patients submitted to BS. 23 Setting: Tertiary care university hospital, Porto, Portugal. 24 Methods: This was a retrospective analysis of patients submitted to Roux-en-Y gastric bypass 25 (RYGB), laparoscopic adjustable gastric banding (LAGB), or sleeve gastrectomy (SG). Leukocyte 26 and subset counts were compared between baseline and 1-year postsurgery and between BS types. 27 A multivariate linear regression model was built to study determinants of leukocyte and subset 28 variation. Results: We analyzed 764 patients: 238 submitted to LAGB; 452 to RYGB, and 74 to SG. 29 Mean age was 42 years and 86.6% were women. All BS types were associated with a decrease in 30 leukocyte and neutrophil counts but the variation in body mass index and homeostatic model 31 assessment (HOMA-IR) were the only variables independently associated with a decrease 1-year 32 postsurgery. Monocytes increased in patients submitted to LAGB and decreased in those who 33 underwent RYGB and SG. The BS type was independently associated with monocyte variation. 34 Patients who underwent RYGB and SG had a decrease in monocyte counts of 77/mL and 62/mL, 35 respectively, compared with LAGB. 36 Conclusion: Weight and insulin resistance are the main predictors of leukocyte and neutrophil 37 variation after BS. The specific type of BS is a determinant of monocyte count variation independent 38 of the amount of weight loss or the degree of insulin resistance improvement. (Surg Obes Relat Dis 39 2016;]:00–00.) r 2016 American Society for Metabolic and Bariatric Surgery. All rights reserved. 40 41 Keywords: Obesity; Bariatric surgery; Leukocytes 42 43 44 Adipose tissue is no longer regarded solely as a storage state associated with increased cardiovascular burden [2]. 45 organ but as a highly active endocrine and immunologic Proinflammatory cytokines produced by the adipose 46 organ [1,2]. Obesity is a chronic low-grade inflammatory tissue can contribute to the development of obesity-related 47 co-morbidities including insulin resistance and atheroscle48 rosis [2]. Obese patients also seem to have an increased risk * 49 Correspondence: Filipe M. Cunha, M.D., Serviço de Endocrinologia, of some infections and cancer, suggesting that adipose 50 Diabetes e Metabolismo do Centro Hospitalar de São João, Alameda tissue may be associated with immune system deregulation Professor Hernâni Monteiro, 4202-451 Porto, Portugal. 51 [3,4]. E-mail: fi[email protected] 52 53 http://dx.doi.org/10.1016/j.soard.2016.02.002 54 1550-7289/r 2016 American Society for Metabolic and Bariatric Surgery. All rights reserved. 55

Effect of different bariatric surgery type on the leukocyte formula

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Leukocytes are important players in inflammation. They abound in the adipose tissue and their numbers and functions seem to differ according to weight status [1,2]. In obesity, macrophages accumulate in the adipose tissue and their phenotype changes to a more pro-inflammatory type, being responsible for an important part of adipokine secretion [1,2]. Higher leukocytes counts are seen in obesity, and weight loss decreases the leukocyte count [5–10]. Monocytes were also reported to be increased in obese patients [9,11]. Bariatric surgery is an important weapon against obesity, capable of inducing significant, sustained weight loss as well as improving many of the obesity-related complications independently of weight loss, like diabetes [12]. We aimed to study the effect of different types of bariatric surgery on the differential leukocyte counts 1 year after surgery, and to study determinants of leukocyte variation. Methods This was a retrospective analysis of patients submitted to bariatric surgery—Roux-en-Y gastric bypass (RYGB), laparoscopic adjustable gastric banding (LAGB), or sleeve gastrectomy (SG)—between 2010 and 2013 in Centro Hospitalar São João, Porto, Portugal. All patients considered for bariatric surgery were evaluated by a bariatric surgeon, an endocrinologist, a nutritionist, and a psychiatrist. Candidates for bariatric surgery must be 18 to 65 years, have a body mass index (BMI) 4 40 kg/m2 (or 4 35 kg/m2 and at least 1 obesity-related co-morbidity) and be compliant with a dietary plan for 1 year. After surgery, all patients have medical appointments at 1, 3, and 6 months, and then every 6 months for up to 3 years. Before each appointment, a fasting venous blood sample was collected. Band calibrations were performed at the discretion of the attending surgeon. Medical records were reviewed. We included all patients with a complete leukocyte count before and 1 year after surgery. Patients submitted to revision weight loss surgery and those with incomplete data on weight at baseline or 1 year after surgery were excluded. Surgeries were performed by laparoscopy according to the standard technique. Leukocyte counts were obtained using an automated blood counter, the Sysmex XE-5000. BMI ¼ weight (kg) / height2 (m); ideal weight ¼ weight correspondent to a BMI of 25 kg/m2; and excess weight ¼ presurgical weight  ideal weight. Excess weight loss (EWL) ¼ ([excess weight  weight lost 1 year after surgery]/excess weight)  100. Percentage of total weight loss (%TBWL) ¼ ([initial weight  weight 1 year after surgery]/initial weight)  100. BMI variation (ΔBMI) ¼ BMI at 1 year  BMI at baseline. Variation (Δ) and percentage of variation (%Δ) for each lineage of leukocytes

were calculated as: Δ ¼ value at 1 year  value at baseline and %Δ ¼ (Δ/value at baseline)  100. Patients were considered to have type 2 diabetes (T2D) if there was a medical registry of the condition, if patients had a fasting plasma glucose Z126 mg/dL, a 2-hour plasma glucose Z200 mg/dL during a 75 g oral glucose tolerance test, a glycated hemoglobin (A1C) Z6.5%, or was using an oral hypoglycemic agent (other than metformin) or insulin. Insulin resistance was estimated using the homeostasis model assessment (HOMA-IR) available at: https:// www.dtu.ox.ac.uk. HOMA-IR variation (ΔHOMA-IR) ¼ HOMA-IR at 1 year  HOMA-IR at baseline. Statistical analysis Baseline characteristics of patients submitted to RYGB, SG, and LAGB were compared: χ2 for categorical variables, One-way analysis of variance (ANOVA) and Mann– Whitney U test for continuous variables as appropriate. We used a Wilcoxon test to compare baseline and 1-year counts for each leukocyte lineage. Linear regression analysis was used to access determinants of leukocyte counts variation. A multivariable linear regression model was built. Variables included in the model were those with an association in the univariate approach; gender and smoking status were also included. Data was stored and analyzed using SPSS software (IBM Corp., Armonk, New York, version 20.0). Results We analyzed 764 patients. RYGB patients were younger, had lower BMI at 1 year, and lost more excess weight and total weight (see Table 1). LAGB patients had lower initial BMI, lost less excess and total weight, and had higher BMI at 1 year. Lipid profile and glucose metabolism at baseline were similar between patients who underwent different bariatric surgeries. Groups were also similar concerning hypertension, diabetes, and smoking status. At 1 year, LAGB patients had worse glucose homeostasis, whereas RYGB patients had a better lipid profile. Table 2 shows the leukocyte differential counts at baseline and at 1 year. Patients submitted to LAGB had higher monocyte counts compared with patients who underwent other bariatric surgeries. They also had lower leukocyte, neutrophil, and eosinophil counts compared with those submitted to RYGB. All bariatric surgeries decreased leukocyte and neutrophil counts at 1 year, but LAGB to a lower extent. Patients submitted to LAGB showed an increase in the monocyte counts, and both RYGB and SG presented a decrease. In a univariate approach (Table 3) both RYGB and SG predicted a decrease in leukocyte, neutrophil, monocyte, and eosinophil counts compared with LAGB. Higher A1C

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Table 1 Baseline and 1-year characteristics of patients submitted to bariatric surgery

Age, years Male sex, n (%) BMI at surgery, kg/m2 BMI at 1 year, kg/m2 ΔBMI EWL, % TBWL, % Smoker, n (%) T2D, n (%) Hypertension, n (%) Baseline laboratory parameters Total cholesterol, mg/dL HDL, mg/dL LDL, mg/dL Triglycerides, mg/dL A1C, % Glycemia, mg/dL Insulin, mU/mL HOMA-IR 1-year laboratory parameters Total cholesterol, mg/dL HDL, mg/dL LDL, mg/dL Triglycerides, mg/dL A1C, % Glycemia, mg/dL Insulin, mU/mL HOMA-IR ΔHOMA-IR

All (n ¼ 764)

LAGB (n ¼ 238)

RYGB (n ¼ 452)

SG (n ¼ 74)

P value

42 ⫾ 11 102 (13.4) 44.5 ⫾ 5.1 32.0 ⫾ 5.4 12.5 ⫾ 5.5 64.7 ⫾ 26.5 27.8 ⫾ 11.2 95 (13.5) 186 (24.3) 326 (42.7)

45 ⫾ 10 35 (14.7) 43.2 ⫾ 4.7 36.1 ⫾ 5.0 7.0 ⫾ 4.1 39.2 ⫾ 22.7 16.1 ⫾ 9.1 29 (12.9) 69 (29.0) 114 (47.9)

40 ⫾ 10 53 (11.7) 45.1 ⫾ 5.0 29.7 ⫾ 4.0 15.4 ⫾ 3.8 78.4 ⫾ 17.7 34.0 ⫾ 6.7 55 (13.4) 103 (22.8) 177 (39.2)

45 ⫾ 12 14 (18.9) 45.2 ⫾ 6.1 33.0 ⫾ 5.4 12.2 ⫾ 4.4 62.5 ⫾ 20.8 26.9 ⫾ 8.6 11 (15.5) 14 (18.9) 35 (47.3)

o.001 .18 o.001 o.001 o.001 o.001 o.001 .86 .10 .06

202 ⫾ 40 50 ⫾ 13 128 ⫾ 33 139 ⫾ 70 5.9 ⫾ 1.0 99 ⫾ 31 29.0 ⫾ 13.5 2.54 ⫾ 1.65

204 ⫾ 43 50 ⫾ 15 127 ⫾ 32 137 ⫾ 67 6.0 ⫾ 1.0 99 ⫾ 32 20.7 ⫾ 14.2 2.35 ⫾ 1.62

201⫾ 38 50 ⫾ 15 127 ⫾ 32 137 ⫾ 67 5.9 ⫾ 1.0 98 ⫾ 32 20.7 ⫾ 14.2 2.61 ⫾ 1.71

205 ⫾ 44 49 ⫾ 10 129 ⫾ 32 144 ⫾ 69 5.7 ⫾ .6 93 ⫾ 15 20.8 ⫾ 11.4 2.62 ⫾ 1.36

.50 .73 .61 .65 .08 .40 .15 .18

186 ⫾ 38 57 ⫾ 11 110 ⫾ 32 97 ⫾ 42 5.4 ⫾ .5 87 ⫾ 17 9.0 ⫾ 6.3 1.32 ⫾ .92 1.18 ⫾ 1.69

199 ⫾ 42 55 ⫾ 10 122 ⫾ 37 112 ⫾ 52 5.6 ⫾ .6 94 ⫾ 24 12.8 ⫾ 8.5 1.90 ⫾1.23 .50 ⫾ 1.68

156 ⫾ 32 58 ⫾ 12 101 ⫾ 25 88 ⫾ 34 5.3 ⫾ .4 84 ⫾ 11 6.8 ⫾ 3.1 .99 ⫾ .45 1.54 ⫾ 1.61

204 ⫾ 42 57 ⫾ 12 127 ⫾ 36 102 ⫾ 44 5.3 ⫾ .4 86 ⫾ 9 8.7 ⫾ 4.7 1.27 ⫾ .70 1.49 ⫾ 1.38

o.001 .006 o.001 o.001 .08 o.001 o.001 o.001 o.001

A1C ¼ glycated hemoglobin; BMI ¼ body mass index; Δ BMI ¼ body mass index variation; EWL ¼ excess weight loss; HDL ¼ high-density lipoprotein cholesterol; HOMA-IR ¼ homeostatic model assessment – insulin resistance; Δ HOMA-IR ¼ HOMA variation between surgery and 1 year; LAGB ¼ laparoscopic adjustable gastric banding; LDL ¼ low-density lipoprotein cholesterol; RYGB ¼ Roux-en-Y gastric bypass; SG ¼ sleeve gastrectomy; T2D ¼ type 2 diabetes; TBWL ¼ percentage of total weight loss.

was associated with an increase in leukocyte counts. Less weight loss or less insulin resistance decrease also predicted an increase in leukocyte counts. In a multivariate linear regression analysis (Table 3), the only independent predictors of leukocyte and neutrophil counts variation were ΔBMI and ΔHOMA-IR. The less the decrease in BMI and insulin resistance the more leukocyte and neutrophil counts would increase over the first year. The type of bariatric surgery was not an independent predictor of leukocyte and neutrophil counts variation but it was an independent predictor of the monocyte count variation over the first year postsurgery. If patients were submitted to RYGB or SG their monocyte counts decreased significantly compared with those who underwent LAGB.

Discussion Our results show that patients submitted to different types of bariatric surgery have different “behavior” of leukocyte

counts over the first year postsurgery. Both RYGB and SG are associated with a greater change in leukocyte and neutrophil counts compared with LAGB. Patients submitted to LAGB were the only ones that showed an increase in monocyte counts at 1 year. Previous studies reported an association between obesity and elevated leukocyte and monocyte counts [5–11]. Weight loss seems to be capable of reducing leukocyte counts [6,13]. The pathophysiology of this obesityassociated leukocytosis appears to be multifactorial. Fat accumulation courses with adipose cell hypoxia and necrosis and this turns the resident macrophages into a more proinflammatory phenotype [2,14]. These cells are responsible for the production of inflammatory cytokines that were shown to stimulate bone marrow myelopoiesis, increasing the number of monocytes that are recruited into the adipose tissue where they differentiate into macrophages and increase cytokine production even further [2,14,15]. Leptin, a hormone that is upregulated in obesity, has been shown to stimulate myeloid and lymphoid differentiation from bone marrow progenitor cells [5,6,16–18]. Other

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Table 2 Comparisons of counts, variation, and percentage of variation of leukocytes and their subtypes between types of surgery All (n ¼ 764) Leukocytes (cell/μL) Leukocytes 1 yr (cell/μL) Δ Leukocytes (cells/μL) % Δ Leukocytes (%) Neutrophils (cell/μL) Neutrophils 1 yr (cell/μL) Δ Neutrophils (cells/μL) %Δ Neutrophils (%) Monocytes (cell/μL) Monocytes 1 yr (cell/μL) Δ Monocytes (cells/μL) %Δ Monocytes (%) Eosinophils (cell/μL) Eosinophils 1 yr (cell/μL) Δ Eosinophils (cells/μL) %Δ Eosinophils (%) Lymphocytes (cell/μL) Lymphocytes 1 yr (cell/μL) Δ Lymphocytes (cells/μL) %Δ Lymphocytes (%) Basophils (cell/μL) Basophils 1 yr (cell/μL) Δ Basophils (cells/μL) %Δ Basophils (%)

7620 6650 965 13.0 4485 3520 880 20.8 510 480 20 4.7 160 150 10 8.2 2345 2350 0 0 20 20 0 0

(6475; 9100) (5630; 7928)§ (2050; 100) (24.7; 1.6) (3612; 5500) (2810; 4520)§ (1710; 80) (34.1; 1.7) (412; 630) (400; 590)§ (120; 70) (21.5; 15.9) (110; 230) (90; 220)§ (60; 30) (35.3; 25.0) (1930; 2900) (1930; 2828) (370; 330) (14.8; 15.2) (20; 30) (20; 30) (10; 10) (33.3; 33.3)

LAGB (n ¼ 238) 7440 7120 395 5.3 4375 3890 450 12.2 460 500 45 10.9 150 150 0 0 2310 2385 75 3.5 20 30 0 0

(6402; 8748) (5890; 8242)§ (1388; 548) (17.8; 8.2) (3500; 5175) (3130; 4810)§ (1190; 215) (25.3; 3.1) (380; 580) (400; 660)§ (40; 140) (8.6; 29.6) (100; 220) (100; 242) (40; 50) (25.0; 50.0) (1807; 2878) (1898; 2780) (290; 360) (11.8; 16.2) (20; 40) (20; 40) (10; 10) (27.7; 33.3)

P* .01 .001 o.001 o.001 .02 o.001 o.001 o.001 o.001 .007 o.001 o.001 .02 .16 o.001 o.001 .07 .44 .10 .11 .36 .11 .50 .51

RYGB (n ¼ 452)

P†

7805 6500 1175 16.2 4590 3340 1055 25.5 520 470 50 10.6 170 150 20 14.3 2385 2350 25 1.0 20 20 0 0

.42 .67 .79 .68 .34 .96 .38 .28 .62 .46 .82 .94 .39 .23 .65 .86 .50 .37 .39 .34 .65 .91 .50 .79

(6602; 9300) (5470; 7718)§ (2355; 212) (26.7; 3.0) (3750; 5648) (2668; 4398)§ (1960; 302) (38.4; 8.3) (430; 640) (390; 570)§ (140; 38) (25.4; 7.1) (110; 240) (90; 210)§ (70; 30) (39.6; 20.8) (1980; 2928) (1980; 2870) (400; 320) (15.6; 15.2) (20; 30) (20; 30) (10; 10) (33.3; 42.5)

SG (n ¼ 74) 7600 6440 1235 15.1 4420 3430 1055 22.4 520 470 50 9.3 155 135 20 9.4 2375 2350 50 2.3 20 20 0 0

(5810; 9155) (5505; 7868)§ (2065; 352) (25.7; 4.0) (3432; 5460) (2730; 4258)§ (1650; 310) (34.9; 5.8) (430; 665) (400; 622)¶ (142; 52) (22.6; 9.0) (108; 242) (90; 202)|| (70; 10) (39.3; 9.6) (1818; 2878) (1808; 2710) (402; 170) (16.0; 8.1) (20; 40) (20; 30) (10; 10) (33.3; 33.3)

P‡ .56 .02 o.001 o.001 .67 .006 o.001 o.001 .002 .39 o.001 o.001 .50 .04 .001 o.001 .65 .65 .04 .04 .38 .35 .82 .89

LAGB ¼ laparoscopic adjustable gastric banding; RYGB ¼ Roux-en-Y gastric bypass; SG ¼ sleeve gastrectomy. Data presented as median (interquartile range). * P for comparison between LAGB and RYGB. † P for comparison between RYGB and SG. ‡ P for comparison between LAGB and SG. § P o .001 for comparison between baseline and 1-year count. ¶ P ¼ .005 for comparison between baseline and 1-year count. || P ¼ .001 for comparison between baseline and 1-year count.

possible explanation for leukocytosis in obesity might be the presence of subclinical atherosclerosis [11]. Obese patients have an increased risk of atherosclerosis, and elevated neutrophil and monocyte counts have been reported to be associated with subclinical and clinical atherosclerotic disease [19–21]. All bariatric surgeries course with a decrease in leukocyte and neutrophil counts 1 year after the procedure, but RYGB and SG to a greater extent than LAGB. In our population, BMI and insulin resistance variation were independently associated with leukocyte and neutrophil variation. Per each kg/m2 nondecrease in BMI there was an increase of 58/mL leukocyte count at 1 year after surgery and the increase in neutrophil count was 50/mL. Per each unit of HOMA-IR nondecrease, there was an increase of 124/mL and 74/mL in leukocyte and neutrophil count, respectively. Bariatric surgery type was not independently associated with leukocyte and neutrophil variation at 1 year. This could mean that the amount of weight loss induced by the surgery is more important than the procedure type per se in the reduction of leukocyte and neutrophil count. Weight loss and adipose tissue reduction would course with diminished secretion of proinflammatory cytokines and leptin, and consequent

decrease in bone marrow stimuli to myelopoiesis [2,15, 16,22]. In our study population, those patients submitted to RYGB and SG lost more weight than those who underwent LAGB, and this could explain the greater leukocyte and neutrophil variation in those procedures compared with LAGB. Inflammation is one of the pathways by which obesity induces insulin resistance [1]. In our patient population, we observed an independent association between decreasing insulin sensitivity and leukocyte count increase. One could argue that insulin resistance represents a marker of underlying inflammation. On the other hand, Talukdar et al. reported that neutrophils might themselves mediate insulin resistance through elastase secretion in mice [23], suggesting that this relation could be the other way around. In our study, monocyte counts increased in the LAGB group, while they decreased in the RYGB and SG groups. LAGB patients also had lower baseline monocyte counts compared with the other 2 groups. A reason for this difference may also be related to weight. Monocytes were reported to be associated with BMI [9,11]. In our population, patients who underwent LAGB were less obese at baseline, and this could explain the lower monocyte count

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Table 3 Determinants of white blood cell count variation 1 year after bariatric surgery: linear regression analysis Univariate approach

*

RYGB SG* Female sex Age Smoker T2D A1C ΔBMI, kg/m2 ΔHOMA-IR

Δ Leukocytes β coefficient (95% CI)

P

Δ Neutrophils β coefficient (95% CI)

P

Δ Monocytes β coefficient (95% CI)

P

Δ Eosinophils β coefficient (95% CI)

P

888 807 206 12 221 283 337 77 218

o.001 .001 .29 .05 .26 .06 .007 o.001 o.001

768 629 162 7 118 190 269 62 166

o.001 .001 .31 .15 .47 .13 .009 o.001 o.001

100 97 1 1 4 8 60 6 18

o.001 o.001 .97 .24 .81 .56 o.001 o.001 o.001

34 42 0 1 16 7 5 2 7

o.001 .006 .97 .05 .22 .49 .53 .001 .01

(1166; 610) (1269; 345) (584; 173) (0; 24) (166; 609) (582; 17) (94; 580) (54; 100) (135; 302)

(998; 538) (1011; 246) (476; 152) (3; 17) (199; 435) (438; 59) (68; 469) (43; 81) (96; 238)

(125; 74) (139; 56) (35; 34) (0; 2) (31; 40) (36; 19) (38; 82) (4; 8) (10; 26)

(52; 16) (72; 12) (24; 23) (0; 2) (40; 9) (12; 26) (11; 21) (1; 4) (2; 13)

Multivariate approach Δ Leukocytes β coefficient (95% CI) RYGB* SG* Female sex Smoker A1C ΔBMI, kg/m2 ΔHOMA-IR

223 151 208 246 162 58 124

(653; 208) (736; 433) (663; 246) (171; 662) (508; 184) (21; 94) (35; 212)

P .31 .61 .37 .25 .36 .002 .006

Δ Neutrophils β coefficient (95% CI) 244 138 144 96 139 50 74

(600; 111) (620; 345) (520; 231) (248; 440) (424; 147) (19; 80) (2; 147)

Δ Monocytes β coefficient (95% CI)

P .18 .58 .45 .58 .34 .001 .04

77 62 27 10 21 1 10

(118; 36) (117; 7) (70; 16) (29; 49) (12; 54) (2; 5) (2; 18)

P .001 .03 .21 .62 .21 .45 .02

Δ Eosinophils β coefficient (95% CI) 25 27 3 19 10 0 6

(58; 8) (71; 17) (37; 32) (50; 13) (16; 36) (2; 3) (1; 12)

P .13 .23 .88 .24 .47 .79 .09

A1C ¼ glycated hemoglobin; ΔBMI ¼ body mass index variation; CI ¼ confidence interval; ΔHOMA-IR ¼ HOMA variation between surgery and 1 year; RYGB ¼ Roux-en-Y gastric bypass; SG ¼ sleeve gastrectomy; T2D ¼ type 2 diabetes. * In comparison with adjustable gastric bypass.

before surgery. However, this does not explain why monocyte counts increased in the LAGB group because patients still lost weight, even if in a lesser amount than those submitted to RYGB or SG. RYGB and SG were independently associated with monocyte variation whereas BMI variation was not. Patients who underwent RYGB and SG had a decrease in monocyte counts of 77/mL and 62/mL, respectively, compared with LAGB. This suggests that the type of bariatric surgery has a role in monocyte variation. It has been previously reported that the gastric band can cause some degree of inflammatory reaction in the gastric wall [24,25]. It could be possible that this inflammatory reaction to a foreign body is responsible for the increase in monocytes at 1 year in patients submitted to LAGB. The effect of bariatric surgery in leukocyte counts may have clinical interest as they appear to be associated with cardiovascular morbidity and mortality [20,26–29]. Neutrophils were found to be independent predictors of cardiovascular events after acute coronary syndromes and cardiac revascularization [20,26,27,29] and monocytes appear to independently predict novel plaque formation and cardiovascular disease in some [19–21] but not all studies [27,29]. Since obesity is a well-recognized cardiovascular risk factor, leukocyte counts and their variation in such a patient population may be an important factor to also consider in risk prediction.

As far as we are aware, this is the first study to directly compare the effect of the 3 more common bariatric surgeries on the leukocyte formula. Nevertheless, our study has shortcomings that should be noted. It is a retrospective study with all its inherent limitations. We do not know if patients were infected or if they were taking any medication that could have altered the leukocyte count. Chronic inflammatory conditions were not considered. We also did not analyze different subpopulations of monocytes and lymphocytes that are known to be altered in obesity [1,2]. Nevertheless, we think that the absolute leukocyte counts that are easily obtained and well known to be associated with cardiovascular risk are probably more clinically relevant in the everyday clinical practice. Conclusion Weight and insulin resistance are the main predictors of leukocyte and neutrophil variation after bariatric surgery. The specific type of bariatric surgery is a determinant of monocyte count variation independent of the amount of weight loss or the degree of insulin resistance improvement. Disclosures The authors have no commercial associations that might be a conflict of interest in relation to this article.

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