Roux-en-Y Gastric Bypass Decreases Serum Inflammatory Markers and Cardiovascular Risk Factors in Obese Diabetics

Abstract

Background:

Obesity and type 2 diabetes mellitus (T2DM) are associated with elevated levels of inflammatory markers. This chronic inflammation is known to contribute to increased risk of cardiovascular disease (CVD) in these populations. Laparoscopic Roux-en-Y gastric bypass (LRYGB) is associated with a high rate of diabetes remission. We hypothesize that LRYGB decreases systemic inflammatory markers and CVD risk factors in obese diabetics.

Methods:

Single-institution prospective cohort study of 61 obese patients with T2DM. Thirty underwent LRYGB surgery and 31 underwent standard medical therapy with diabetes support and education. Collected data included pre- and post-operative inflammatory biomarkers and clinical parameters.

Results:

Twelve months after undergoing LRYGB, after controlling for sex and age, there was a significant correlation between change in interleukin-6 (IL-6) and change in systolic blood pressure (SBP) (Spearman’s r=0.41, p=0.03). Similarly, when sex and age were controlled for in the LRYGB group, a statistically significant relationship remained between percent excess weight loss and change in IL6 (p=0.001).

Conclusion:

A significant relationship exists between decreased systemic IL-6 levels and both excess weight loss and lowered SBP after LRYGB in obese diabetics. These correlations may explain the decreased risk of cardiovascular disease after surgical weight reduction in this patient population.

This study reveals a correlation between decreased inflammatory biomarkers and cardiovascular disease risk factors following Roux-en-Y gastric bypass. The importance of this finding is to emphasize the breadth of comorbidity reduction experienced by this post-operative population.

Introduction

Obesity is an important risk factor for cardiovascular disease (CVD) and is associated with the premature development of atherosclerosis, and increased risk of cardiac ischemia and stroke.¹ The increasing prevalence of obesity and with it, type 2 diabetes mellitus (T2DM), is now the greatest threat to efforts aimed at reducing the prevalence of CVD.² Prospective studies have shown that persons with T2DM have twice the risk of myocardial infarction and ischemic stroke and 2 to 4 times the risk of myocardial infarction and stroke mortality compared with their counterparts without diabetes.³ Strong epidemiological evidence indicates that abdominal adiposity poses a greater CVD risk than in other forms of obesity.⁴ Abdominal adiposity contributes importantly to the inflammatory process in patients with obesity in both vascular and nonvascular tissues. This effect is mediated by proinflammatory mediators released by stressed adipose cells. Adipose tissue from obese individuals contains activated macrophages that together with adipocytes produce inflammatory adipokines such as TNF, IL-1 and IL-6.⁵ The chronic state of inflammation is known to contribute to increased risk of CVD in these populations.⁶

It is known that a loss of 5–10% of initial weight is sufficient to produce significant, clinically relevant improvements in CVD risk factors in overweight and obese patients with T2DM. However, greater weight loss is associated with greater improvements in risk factors.⁷ Currently, bariatric surgery procedures appear to be the only interventional modality that results in sustained and significant weight loss along with reversal of T2DM and with improvements in cholesterol biosynthesis, lipoprotein metabolism, and overall decreased CVD risk factors.⁸

We hypothesized that, in an obese diabetic population, LRYGB would lead to reduced inflammatory biomarker levels and decreased CVD risk when compared to a matched control medical intervention group. The hypothesis was tested by determining the relationship between circulating cytokines and CVD risk factors in the interventional and control groups.

Methods

This was a prospective cohort study aimed to enroll class 2 and 3 patients with obesity (body mass index > 35 kg/m2) with T2DM. Patients thus eligible and approved for surgical weight loss treatment by their health insurance carrier were recruited into the LRYGB group (interventional group). Participants who were eligible for RYGB but did not undergo surgery due to insurance coverage denials were enrolled into the Diabetes Support and Education (DSE) Program (control group). The RYGB group was matched with the DSE group using a matching algorithm according to age, sex and body weight. The matching process was verified every 10 enrollments in the RYGB group, to allow targeted recruitment in the DSE group. We collected data and serum samples for analysis before and 12 months after surgical or non-surgical intervention. T2DM was diagnosed based on any one of the following: current regular use of insulin, current regular use of oral hypoglycemic medication, or documented diabetes by ADA criteria. Throughout the study, all patients received the standard medical care and management of T2DM and cardiovascular disease risk factors. The goal for glycemic control was to maintain an HbA1c of 7% or less. Height and weight were used to calculate BMI, percentage of excess weight loss (EWL) was calculated using the following formula: (weight loss/excess weight) x 100. A more detailed study protocol, including the DSE was previously described.⁹

The surgical procedure consisted of a laparoscopic approach with two 10-mm ports and four 5-mm ports. The technique included the creation of an isolated 10–15-ml proximal gastric pouch, an ante-colic Roux-en-Y gastrojejunostomy with linear stapler technique, a 100-cm Roux-limb, a 50-cm biliopancreatic limb, and a stapled end-side enteroenterostomy.

The study was registered at ClinicalTrials.gov with the following identifier: NCT00787670. An institutional review board approved the protocol for the study prior to data collection. Informed consent was obtained from all patients who enrolled in the study.

Serum samples were stored at −80°C until assayed. All samples were analyzed at the same time. Cytokines were assayed by a Milliplex human adipokine panel assay (EMD Millipore, Darmstadt, Germany).

Descriptive statistics were calculated on sex and age. Paired t-test and independent t-tests were used to compare pre- and post- intervention normally distributed quantitative variables to determine significant differences between the two groups. To determine whether there were relationships between predictive variables (change in circulating inflammatory markers) and outcome variables (percent change in SBP over time, change in BMI over time, change in resting heart rate (HR) and percent excess weight loss), nested multiple regressions were created and compared with likelihood ratio tests. All statistical analyses were conducted RStudio Version 1.25 (RStudio, Inc., Boston, MA). All values were given as means ± standard deviation (SD) unless otherwise stated.

Results

The study enrolled 61 obese participants with T2DM. Thirty participants approved for surgical weight loss treatment by their health insurance carrier were recruited for LRYGB. Another 31 participants were enrolled into the DSE group. For the entire cohort, the mean age was 48.5 ± 7.8 years and the mean body weight was 117.2 ± 17.2 Kg. As previously described, patients in the two groups were successfully matched at baseline for age, sex, weight, SBP, serum cholesterol, triglyceride levels, percent on oral anti-diabetic medications, and percent on insulin therapy. 9 Although there was no significant difference in the body weight, participants in the LRYGB group had significantly greater BMI than those in the DSE group (43.4 ± 4.4 vs 40.1 ± 5.0; p=0.006). In the LRYGB group, 27 patients (90%) had diagnosis of hypertension and received antihypertensive medications. Hypertension was present in 26 patients (84%) in the DSE group. After the intervention, the remission rate of hypertension (SBP<150 mmHg, DBP <90mmHg, and off antihypertensive medications) was 70.4% in the LRYGB and 4% in the DSE groups (p=0.001).

Table 1 shows the magnitude change in excess weight, BMI, blood pressure, heart rate, waist circumference, and inflammatory markers from baseline to 12-month follow-up for both groups. Twelve-month longitudinal changes in BMI, EWL, SBP, heart HR, and IL-6 were statistically significant in the LRYGB group; only SBP was significantly changed in the DSE group. In the LRYGB, the mean percent change in IL6 was −46.5% in patients that went into hypertension remission and −27.9% in patients who did not achieve remission (p=0.12).

Table 1.

Measured data at baseline (0 months), and 12 months following the interventions.

	Baseline	12 months	p-value
BMI (Kg/m2)
DSE	40.1±4.8	40.4±5.3	0.332
LRYGB	43.4±4.2	31.2±4.6	<0.001
EWL (%)
DSE	-	0.6±5.6	0.551
LRYGB	-	−33.6±11.0	<0.001
Waist Circumference (cm)
DSE	123.0±12.6	121.9±13.7	0.422
LRYGB	130.3±12.1	103.7±12.8	<0.001
SBP (mmHg)
DSE	135.4±17.1	130.0±16.0	0.020
LRYGB	138.9±18.9	125.6±15.3	<0.001
DBP (mmHg)
DSE	77.1±8.8	76.2±8.4	0.513
LRYGB	76.1±12.1	76.9±9.1	0.693
HR (BPM)
DSE	76.4±12.6	76.4±10.9	0.921
LRYGB	84.8±12.8	67.1±12.2	<0.001
GM-CSF (pg/mL)
DSE	59.4±42.8	67.5±50.1	0.580
LRYGB	63.1±49.9	52.9±29.1	0.781
Interferon-γ (pg/mL)
DSE	1.6±1.4	2.1±1.4	0.175
LRYGB	1.8±1.0	2.2±0.8	0.477
IL-6 (pg/mL)
DSE	1.6±1.0	1.5±0.7	0.580
LRYGB	2.3±3.9	1.2±2.3	0.002
IL-10 (pg/mL)
DSE	4.3±10.1	8.6±20.9	0.337
LRYGB	2.6±3.1	2.5±1.3	0.803
IL-12 (pg/mL)
DSE	3.3±5.3	19.0±76.1	0.278
LRYGB	2.8±4.8	2.2±2.2	0.275
IL-2 (pg/mL)
DSE	0.6±0.3	0.6±0.4	0.731
LRYGB	0.5±0.3	0.5±0.3	0.580
IL-8 (pg/mL)
DSE	10.7±9.8	11.0±10.2	0.901
LRYGB	10.5±7.8	10.9±4.6	0.782
TNF-α (pg/mL)
DSE	6.5±2.3	7.1±1.6	0.163
LRYGB	6.7±2.2	6.7±1.6	0.932

Table 2 shows Spearman’s correlation calculations for percent change in statically significant variables from baseline to 12 months after LRYGB. Using nested multiple regressions, when sex and age were controlled for in the LRYGB group, a statistically significant relationship remained between percent change in SBP and percent change in IL6 (p = 0.03). In contrast, within the DSE group, when sex and age were controlled for, there was no significant relationship between percent change in SBP and percent change in IL6 (p = 0.63). Similarly, when sex and age were controlled for in the LRYGB group, a statistically significant relationship remained between percent excess weight loss (EWL) and change in IL6 (p=0.001).

Table 2.

Spearman’s correlation calculations for change in statically significant variable from baseline to 12 months after LRYGB

Delta Change (%)	Mean	SD	1)	2)	3)	4)	5)
1) 0–12 months BMI	−27.9	9.2
2) 0–12 months EWL	−55.5	15.1	0.89*
3) 0–12 months waist circumference	−20.3	7.7	0.80*	0.70*
4) 0–12 months heart rate	−20.3	12.3	0.15	0.10	0.01
5) 0–12 months SBP	−8.6	12.6	0.10	0.13	−0.20	0.03
6) 0–12 months IL-6	−41.7	26.9	0.13	0.25	0.01	−0.05	0.49*

^*P<0.01

Discussion:

The association of obesity with increased morbidity and mortality is well-documented.¹⁰ The increasing prevalence of T2DM in the obese population has further confounded such negative effects. Obesity and diabetes are both associated with elevated levels of serum inflammatory markers which create a chronic low-grade inflammatory state. Some of the proinflammatory markers that are most commonly associated with elevated BMI are TNF alpha, C Reactive Protein (CRP), leptin, and IL-6.¹¹

It is now known that adipose tissue is metabolically active by secreting many proinflammatory chemokines, as well as the anti-inflammatory marker adiponectin. Our laboratory has previously investigated adiponectin in the context of bariatric surgery.¹² Adiponectin levels are inversely correlated with mass of adipose tissue. Furthermore, adiponectin is associated with increased insulin sensitivity, which is consistent with studies showing that weight loss leads to increased levels measured in obese patients and subsequent T2DM remission.¹²

LRYGB is superior to sleeve gastrectomy in the associated rates of T2DM remission. A recent 5-year follow up of a randomized study confirmed that among patients who underwent bariatric surgery, those who received LRYGB used fewer diabetic medications compared to patients who received a sleeve gastrectomy.⁸

CVD is particularly prevalent in obese patients with T2DM. Countless studies suggest that the pro-inflammatory state and endothelial cell activation increase the risk for cardiovascular disease in this population.^{13, 14} Chronic hyperglycemia, as seen in diabetes, causes non-enzymatic glycation of proteins and is associated with comorbidities. Advanced glycation end-products (AGE) bind to AGE receptors (RAGE) on endothelial cells, which induce the release of pro-inflammatory cytokines.¹⁵ For well over two decades, the correlation between high AGE levels and severity of coronary artery disease in T2DM has been known.¹⁶

IL-6 has also been independently associated with T2DM and cardiovascular disease.⁶ Although the exact role of IL-6 in T2DM is debated, it has been consistently noted that elevated levels of IL-6 precede the development of insulin resistance.¹⁷ Long-term reduction in serum IL-6 has been demonstrated following bariatric surgery.¹⁸ Over the past few years there has been increasing research acknowledging the correlation between IL-6 and blood pressure.¹⁹

Various parameters have been evaluated to determine whether RYGB impacts clinical measurements beyond weight loss. In 2018 the GATEWAY study was published with the primary endpoint focused on the effect of RYGB on hypertension in obese patients (mostly without diabetes). The remission rate was 51% at 12 months for patients who underwent RYGB. This data was reviewed to meet the Systolic Blood Pressure Intervention Trial (SPRINT) levels, which had 22.4% of patients achieving appropriate systolic blood pressure range without antihypertensive medication.²⁰ The STAMPEDE trial involved obese patients with T2DM who underwent RYGB. While this study did not show a significant difference in systolic blood pressure, it did note a significant reduction in total number of cardiovascular medications at 12 months follow-up.⁸

The physical and metabolic benefits of gastric bypass procedures are well-documented. The LRYGB has repeatedly been associated with diabetes remission.^{8, 21–24} Bariatric operations have been shown to alter inflammatory biomarkers and metabolism in both the immediate and long-term postoperative period. As has been previously observed by our group, patients with obesity and T2DM who undergo LRYGB may have a lower incidence of both microvascular and macrovascular complications as compared to those managed medically.²²

We investigated inflammatory cytokines known to be increased in obesity and T2DM in association with increased risk of cardiovascular disease. We hypothesized that in diabetic populations Roux-en-Y gastric bypass will lead to reduced inflammatory biomarker levels and decreased cardiovascular disease risk. A multivariate regression analysis of our data suggests that a significant relationship exists between the change in inflammatory cytokine IL-6 and the reduction in SBP in morbidly obese diabetic patients who undergo LRYGB. Limitations of our study include short duration of follow-up (12 months), lack of randomization, data collection at a single center, and analysis of secondary endpoints. Although the single center trial may limit the external validity of the study, we emphasize that all patients were classified at least class II obesity (BMI 35 or greater), which is the majority of the bariatric surgery population. We feel that this increases its external validity, as many studies reporting on effects of bariatric surgery use BMI of 30 as the sample minimum. Another weakness is that, ideally, baseline levels should also have been measured in additional control groups such as non-obese non-diabetics and obese non-diabetics. In conclusion, LRYGB appears to offer hypertensive control for morbidly obese patients with T2DM. Our study suggests that reduction in the chronic inflammatory state (represented by IL-6 reduction) is associated with sustained reduction in SBP. As a known cardiovascular risk factor, reduction in hypertension may contribute to the overall decline in morbidity and mortality in morbidly obese patients with T2DM who undergo LRYGB. Further trials with larger sample size and longer follow-up are needed to confirm these findings.