Comparative Effects of Weight Loss and Incretin-Based Therapies on Vascular Endothelial Function, Fibrinolysis, and Inflammation: A Randomized, Controlled Trial

Aims/Hypothesis GLP-1 receptor (GLP1R) agonists cause weight loss in obese individuals and decrease cardiovascular events in patients with type 2 diabetes. The objective of this study was to test the hypothesis that GLP1R agonists have beneficial effects on vascular endothelial function, fibrinolysis, and inflammation in obesity through weight loss-independent (GLP1R-dependent) mechanism(s). Methods We conducted a randomized, parallel-group, three-arm double-blinded controlled trial at a single center in the United States. Eligibility criteria were as follows: age 18-65 years, body mass index ≥ 30kg/m2, and pre-diabetes defined by the American Diabetes Association criteria. Participants were randomized in a 2:1:1 ratio to 14 weeks of the GLP1R agonist liraglutide, hypocaloric diet, or the dipeptidyl peptidase 4 inhibitor sitagliptin. Treatment with drug was double blind and placebo controlled. Measurements were made at baseline, after 2 weeks of treatment prior to significant anticipated weight loss, and after 14 weeks of treatment. The primary outcomes were measures of endothelial function: flow-mediated vasodilation (FMD), plasminogen activator inhibitor-1 (PAI-1), and urine albumin-to-creatinine ratio (UACR). Results Ninety-three obese pre-diabetic individuals were randomized, and data from 88 individuals who completed at least a single study day are included in the analysis (liraglutide N=44, diet N=22, sitagliptin N=22). Liraglutide and diet reduced weight and insulin resistance, while sitagliptin did not. There was no significant effect of any treatment on endothelial vasodilator function as measured by FMD (Liraglutide: 2 weeks: difference from baseline +0.70%, 95% CI [-0.71, 2.11], P=0.33, 14 weeks: +1.38% [-0.01, 2.78], P=0.05; Sitagliptin: 2 weeks: +1.92% [-0.05, 3.88], P=0.06, 14 weeks: +1.59% [-0.30, 3.48], P=0.10; Diet: 2 weeks: +1.24% [-0.69, 3.18], P=0.21, 14 weeks: +1.20% [-0.97, 3.38], P=0.28). As baseline endothelial function was normal in the overall cohort, post hoc subgroup analyses were conducted in participants stratified by FMD below or above the median. Individuals with baseline FMD below the median, indicative of endothelial dysfunction, had higher BMI, waist circumference and insulin resistance as compared to those with baseline FMD above the median. All three treatments improved FMD at 2 and 14 weeks in individuals with baseline FMD below the median (P<0.05 for all). Liraglutide reduced PAI-1 at 2 and 14 weeks (2 weeks: -2.3 U/mL [-4.1, -0.6], P<0.01; 14 weeks: -3.7 U/mL [-5.5, -2.0], P<0.001), and diet reduced PAI-1 at 14 weeks (-3.8 U/mL [-6.6, -1.0], P<0.01), but sitagliptin did not change PAI-1 levels. GLP1R antagonism with exendin (9-39) increased fasting blood glucose but did not change FMD or PAI-1 in any treatment group. There was no effect of treatment on UACR. Finally, liraglutide, but not sitagliptin or diet, reduced the chemokine monocyte chemoattractant protein-1 (MCP-1) at 2 and 14 weeks (2 weeks: -10.7 pg/mL [-17.6, -3.7], P<0.01; 14 weeks: -10.7 pg/mL [-17.7, -3.7], P<0.01). Conclusions Liraglutide and diet cause weight loss, improve insulin resistance and reduce PAI-1 concentrations. Liraglutide, sitagliptin and diet do not change FMD in obese pre-diabetic individuals with normal endothelial function after 14 weeks of treatment. Liraglutide alone lowers the pro-inflammatory and pro-atherosclerotic chemokine MCP-1 at 2 and 14 weeks, indicating that this beneficial cardiovascular effect is independent of weight loss. [Clinicaltrials.gov][1] Identifier NCT03101930 What is already known about this subject? What is the key question? What are the new findings? How might this impact on clinical practice in the foreseeable future? ### Competing Interest Statement None unless noted below: J.A.B.: Dr. Beckman is a consultant for JanOne, serves on a DSMB for Janssen and Novartis, and has ownership in EMX and Janacare. J.R.K: Dr. Koethe has served as a consultant to Gilead Sciences, Merck, ViiV Healthcare, Theratechnologies and Janssen. He has also received research support from Gilead Sciences and Merck. J.M.L: Dr. Luther has served on the advisory board for Mineralys. N.J.B.: Dr. Brown serves on the scientific advisory board for Alnylam Pharmaceuticals. She serves as a consultant for Pharvaris Gmbh and eBioStar Tech. Dr. Brown owns equity in Abbvie and J and J Pharmaceuticals. ### Clinical Trial NCT03101930 ### Funding Statement Research reported in this publication was supported by the American Heart Association 17SFRN33520017 (M.M., J.A.B., H.N., D.M., P.W., S.E.H., B.P., D.O., J.R.K., C.Y., H.S., J.M.L, N.J.B), National Center for Advancing Translational Sciences 5UL1TR002243, National Institute of Diabetes and Digestive and Kidney Diseases T32DK007061 (M.M), National Institute of Allergy and Infectious Diseases U19AI095227 (K.N.C), National Heart, Lung and Blood Instituted R01HL146654 (J.D.B). This work utilized the core(s) of the Vanderbilt Diabetes Research and Training Center funded by grant DK020593 from the National Institute of Diabetes and Digestive and Kidney Disease. Novo Nordisk provided liraglutide and matching placebo. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The study was approved by the Vanderbilt Institutional Review Board, registered at [clinicaltrials.gov][2] [NCT03101930][3], and conducted according to the Declaration of Helsinki. All participants provided written informed consent. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors. * DPP4 : Dipeptidyl peptidase 4 FMD : Flow-mediated dilation GLP-1 : Glucagon-like peptide-1 GLP1R : Glucagon-like peptide-1 receptor HbA1c : Hemoglobin A1c HOMA-IR : Homeostatic Model Assessment for Insulin Resistance HOMA2 : Homeostatic Model Assessment 2 MCP-1 : monocyte chemoattractant protein-1 NMD : Nitroglycerin-mediated dilation OGTT : Oral glucose tolerance test PAI-1 : Plasminogen activator inhibitor-1 T2DM : Type 2 diabetes mellitus UACR : Urine albumin-to-creatinine ratio [1]: http://Clinicaltrials.gov [2]: https://clinicaltrials.gov [3]: /lookup/external-ref?link_type=CLINTRIALGOV&access_num=NCT03101930&atom=%2Fmedrxiv%2Fearly%2F2022%2F07%2F18%2F2022.02.23.22271434.atom