Plasma IL-6 and TNF-a and their Associations with Depression in Severely Obese Women who Undergo Bariatric Surgery
¹Brittni A. Pitts, Moses Washington, Dominique Musselman, Thomas Ziegler, C. Daniel Smith, Edward Lin, Nana Gletsu
¹Emory Endosurgery Unit, Emory University School of Medicine, Atlanta, Georgia;

Abstract

Background: Studies show that morbidly obese patients are commonly diagnosed with depression. Furthermore, elevated concentrations of pro-inflammatory markers such as interleukin-6 (IL-6) and tumor necrosis factor-a (TNF) are typically found in the serum of these patients. This study aims to determine associations between the concentrations of these inflammatory markers and the degree of depression in severely obese patients before and after weight loss surgery.

Methods: Twenty-six morbidly obese women (body mass index [BMI] > 40 kg/m2) between ages 25-50 were evaluated. Concentrations of IL-6 and TNF-a were measured from plasma samples taken before surgery and 1 month and 6 months after surgery. At the same time, patients were asked if they had depression. A subset of 6 patients completed a Zung Depression Self-Rating Scale (ZDS,) a Multidimensional Fatigue Inventory (MFI,) and a Neurotoxicity Rating Scale (NRS) questionnaire each time blood samples were taken. Student t-tests were used to determine significant changes from baseline in inflammatory mediators and depression scores (p<0.05).

Results: Compared to baseline, IL-6 concentrations showed no difference at 1 mo and decreased at 6 mo (4.3, 5.3, and 3.4 pg/mL, respectively). Also, TNF-a concentrations were increased at 1 mo and showed no change at 6 mo (0.63, 0.71, and 0.64 pg/mL, respectively). Compared to baseline, fewer patients tended to feel depressed at 1 mo and 6 mo post-surgery, p>0.05. In the subset of 7 patients assessed with depression scales, depression scores decreased significantly from baseline to 1 month post-surgery.

Conclusions: The self-evaluation survey indicated that patients were less depressed after surgery. According to established questionnaires, depression decreased as early as 1 mo following surgery. The patients also had decreased IL-6 concentrations. Thus, there is a possible relationship between the cytokines and depression.

Introduction

• Depression is the most common psychiatric disorder in adults but the biological and social causes are not fully understood.

• Severely obese patients are commonly diagnosed with depression.

• Previous studies have found elevated concentrations of pro-inflammatory markers in the serum of severely obese patients.

• Weight loss is associated with a reduction in inflammatory markers, including IL-6 and TNF-a.

• IL-6 and other cytokines are increased in patients diagnosed with depression and psychological stress.

• A preliminary study indicated that compared to baseline, patients tended to be less depressed post-surgery, but the values were insignificantly different.

Objective

Determine whether changes in plasma IL-6 and TNF-alpha are associated with changes in clinical depression in severely obese women undergoing bariatic surgery.

Methods and Materials

• Blood was obtained from 26 patients before surgery (baseline), at 1 mo, and at 6 mo post-surgery, and plasma IL-6 and TNF-alpha were determined by enzyme-linked immunoassay (ELISA, R&D Systems, Minneapolis, MN.)

• A subset of 6 patients filled out the Zung Depression Self-Rating Scale (ZDS,) Multidimensional Fatigue Inventory (MFI,) and Neurotoxicity Rating Scale (NRS).

• Changes in plasma cytokine concentrations and depression scores, compared to baseline, were assessed using student t-tests.

Results

Compared to baseline, IL-6 concentrations showed no difference at 1 mo and decreased at 6 month (4.3, 5.3, and 3.4 pg/mL, respectively.) Also, TNF-alpha concentrations were increased at 1 month and showed no change at 6 month (0.63, 0.71, and 0.64 pg/mL, respectively.) Compared to the baseline, fewer patients tended to feel depressed at 1 month and 6 month post-surgery, p>0.05. In the subset of 7 patients assessed with depression scales, depression scores decreased significantly from baseline to 1 month post-surgery.

Conclusions and Future Studies

• IL-6 concentrations decreased 6 mo following Roux-en-Y gastric bypass surgery.

• TNF-alpha concentrations were significantly elevated at 1 mo post-surgery.

• There was a measurable reduction in depression scores as early as 1 mo after surgery.

• Reduced depression may be related to decreased IL-6 levels.

Resources

This material is based upon work supported by the Howard Hughes Medical Institute under Grant No. 52003727, NIH/NIDDK under Grant No. 1 R03 DK067167-01A1, and NIH/NCRR General Clinical Research Center under Grant No. M01 RR00039.

Keywords

ELISA test, depression evaluations