Obesity-associated Blunted Subcutaneous Adipose Tissue Blood Flow After Meal Improves After Bariatric Surgery

Abstract

Context: Glucose-dependent insulinotropic peptide (GIP) and meal ingestion increase subcutaneous adipose tissue (SAT) perfusion in healthy individuals. The effects of GIP and a meal on visceral adipose tissue (VAT) perfusion are unclear.

Objective: Our aim was to investigate the effects of meal and GIP on VAT and SAT perfusion in obese individuals with type 2 diabetes mellitus (T2DM) before and after bariatric surgery.

Methods: We recruited 10 obese individuals with T2DM scheduled for bariatric surgery and 10 control individuals. Participants were studied under 2 stimulations: meal ingestion and GIP infusion. SAT and VAT perfusion was measured using 15O-H2O positron emission tomography-magnetic resonance imaging at 3 time points: baseline, 20 minutes, and 50 minutes after the start of stimulation. Obese individuals were studied before and after bariatric surgery.

Results: Before bariatric surgery the responses of SAT perfusion to meal (P = .04) and GIP-infusion (P = .002) were blunted in the obese participants compared to controls. VAT perfusion response did not differ between obese and control individuals after a meal or GIP infusion. After bariatric surgery SAT perfusion response to a meal was similar to that of controls. SAT perfusion response to GIP administration remained lower in the operated-on than control participants. There was no change in VAT perfusion response after bariatric surgery.

Conclusion: The vasodilating effects of GIP and meal are blunted in SAT but not in VAT in obese individuals with T2DM. Bariatric surgery improves the effects of a meal on SAT perfusion, but not the effects of GIP. Postprandial increase in SAT perfusion after bariatric surgery seems to be regulated in a GIP-independent manner.

Trial registration: ClinicalTrials.gov NCT01880827.

Keywords: adipose tissue; bariatric surgery; blood flow; glucose-dependent insulinotropic polypeptide; positron emission tomography; type 2 diabetes.

Figure 1.

Timeline of the study protocol. All participants were scanned after an overnight fast. All participants were first scanned with magnetic resonance imaging (MRI), followed by 3 positron emission tomography (PET) scans using ¹⁵O-H₂O at 3 time points: baseline, 20 minutes, and 50 minutes after stimulation by meal ingestion or glucose-dependent insulinotropic peptide (GIP) infusion. GIP infusion was started at 4 pmol/kg/min and halved after 15 minutes to mimic physiological concentrations of GIP after meal.

Figure 2.

Subcutaneous adipose tissue and visceral adipose tissue blood flow at baseline, 20 minutes, and 50 minutes after a mixed meal or start of glucose-dependent insulinotropic peptide (GIP) infusion. Statistical comparison was performed using linear mixed models, and Tukey-Kramer method was used to adjust the P values of pairwise comparisons. Asterisk indicates a statistically significant difference from baseline (P < .05). Control n = 10, before surgery mixed meal n = 10, after surgery mixed meal n = 9, before surgery GIP infusion n = 9, after surgery GIP-infusion n = 9.

Figure 3.

Changes caused by mixed meal stimulation and glucose-dependent insulinotropic peptide (GIP) infusion on plasma glucose, insulin, GIP, and glucagon-like peptide-1 (GLP-1) concentrations in controls and obese individuals before and after bariatric surgery. Data are presented as mean (SD). Asterisk indicates change from baseline (P < .05).