Comparative effects of weight loss and incretin-based therapies on vascular endothelial function, fibrinolysis and inflammation in individuals with obesity and prediabetes: A randomized controlled trial
- Design
- Randomized, parallel-group, quadruple-blind (drug arms), placebo-controlled trial; 3 arms (liraglutide, hypocaloric diet, sitagliptin) in 2:1:1 ratio; 14 weeks; measurements at baseline, 2 weeks (pre-weight-loss), and 14 weeks. · 88 participants · Biomarker outcome
- Match to healthy normal-weight adults aged 55–75
- Different populationObesity with prediabetes; but the design (drug vs matched diet-induced weight loss, with measurements before weight loss) directly addresses weight-independence, which is the target question.
- Could weight loss explain it?
- Specifically testedmethod: Both a weight-matched active comparator and a temporal (pre-weight-loss) measurement are present in this trial's design, and the task asks that both be named: (1) weight-matched comparator — the hypocaloric diet arm was explicitly designed to produce weight loss similar to that expected on liraglutide, so a liraglutide-vs-diet comparison at matched weight loss tests whether liraglutide's biomarker effect exceeds what equivalent weight loss alone produces; (2) temporal/pre-weight-loss measurement — the trial measured outcomes at baseline, 2 weeks (explicitly "prior to significant weight loss"), and 14 weeks, so an effect already present at 2 weeks would be attributable to a weight-independent (e.g., direct GLP-1 receptor) mechanism. However, the abstract's MCP-1 sentence does not specify which timepoint(s) the reported MCP-1 reduction refers to, so it cannot be confirmed from the given sources that the temporal design was actually invoked for the MCP-1 result specifically (see key_limitation).
; prespecified: NI; key limitation: The abstract does not state which timepoint(s) (2-week pre-weight-loss vs. 14-week) the reported MCP-1 reduction was measured/analyzed at, and MCP-1 is not a registered outcome at all (no timeFrame is specified for it in NCT03101930.json, unlike FMD and PAI-1, which are explicitly registered with a "Baseline to 2 and 14 weeks" timeFrame). This means the weight-independence claim for MCP-1 cannot be verified against either of the trial's two mediation strategies from the sources available — it is not possible to confirm the 2-week (pre-weight-loss) result was actually where the MCP-1 effect was seen, as opposed to only the 14-week (post-weight-loss) comparison, where a weight-matched-diet difference would still leave open a non-weight mechanism but not a strictly "before weight loss" one.
Adjusted for: weight-matched diet comparator - Study tier
- Study tier 3Small mechanistic RCT with mostly null primary endpoints; one exploratory biomarker supports weight-independence.
- Assessment
- Version 3 · ai:two-pass · Sep 13, 2026
Study facts come from the paper. Population match, weight-loss explanation and study tier are our judgments, made against the reference group of healthy normal-weight adults aged 55–75.
A small NIH-funded trial compared liraglutide, a low-calorie diet and sitagliptin in 88 adults with obesity and prediabetes. Neither drug nor diet improved blood-vessel function; liraglutide alone lowered the inflammatory chemokine MCP-1, suggesting a weight-independent effect on one marker. Mostly null, but methodologically the right kind of study.
01Findings
What the study reported
- Drugs
- Liraglutide
- Dose
- 1.8 mg daily (full text)
- Route
- subcutaneous
- Treatment duration
- 14 weeks
- Comparator
- hypocaloric diet; sitagliptin (double-blind placebo-controlled for drugs)
- Primary outcome
- Flow-mediated vasodilation, PAI-1, urine albumin-creatinine ratio
- Effect
- No treatment effect on FMD or UACR; liraglutide and diet reduced weight, insulin resistance and PAI-1; only liraglutide reduced MCP-1
- 95% confidence interval
- Not extracted
- Follow-up
- 14 weeks
- Adverse events
- Not extracted
- Limitations
- Auto-classified from abstract only; effect estimates, adverse events and limitations not extracted. Requires manual review.
Who was studied
- Condition
- Obesity and prediabetes
- Mean age
- not reported in abstract; registry total (all randomized, N=93): 50.3 years (SD 10.6)
- Sex
- not reported in abstract; registry total (all randomized, N=93): 63 female / 30 male
- Diabetes status
- Prediabetes (by FPG, IGT, or HbA1c criteria per registry eligibility; not established type 1/2 diabetes)
Study quality details
- Study design
- Randomized controlled trial
- Sample size
- not extracted
- Randomization
- yes
- Blinding
- double-blind for drug vs placebo; diet open
- Comparator
- placebo
- Follow up duration
- 14 weeks
- Outcome type
- biomarker
- Replication
- not assessed (auto)
- Consistency with other evidence
- not assessed (auto)
- Population applicability
- INDIRECT
- Statistical precision
- n=88; single biomarker positive
- Funding conflicts
- no
- Peer review status
- yes
- Rob2
- O4: {"D1":{"judgment":"Some concerns","rationale":"This is a small, single-center, investigator-initiated academic trial (Vanderbilt; N=93 randomized), not a large industry registration trial with a described central randomization/IVRS system, so per the collection's D1 rule allocation concealment requires an explicit description of method — none is given. Sequence generation is likewise undescribed in both sources. No clear baseline imbalance is "},"D2":{"judgment":"Some concerns","rationale":"Drug arms were double-blind/placebo-controlled (registry: quadruple masking of participant, care provider, investigator, outcomes assessor), but the diet arm cannot be blinded by nature of the intervention, and GI adverse events differ markedly between arms (nausea 8/46 liraglutide vs. 0/23 sitagliptin vs. 1/24 diet; diarrhea 3/46 vs. 0/23 vs. 0/24) — per the collection's D2 rule this supports \"aw"},"D3":{"judgment":"Some concerns","rationale":"MCP-1 is not a registered outcome measure at all (see D5), so neither source reports the number of participants with MCP-1 data available or missingness by arm — this specific signaling question is NI. As context (not direct evidence for MCP-1 itself), the registry's comparable plasma biomarker measured from the same blood draws, PAI-1, shows differential and at times substantial missingness by 14"},"D4":{"judgment":"Low","rationale":"MCP-1 is a plasma chemokine assay, the same category (objective central-lab biomarker) that the collection's D4 rule treats as Low risk of measurement bias absent evidence the assay changed or differed between arms. No such evidence is present in either source, and outcome assessors were specified as masked in the registry.\n"},"D5":{"judgment":"High","rationale":"The abstract's own stated primary outcomes are FMD, PAI-1 and UACR; MCP-1 is not among them. Checking the registration's full outcome list (primary, secondary, and \"other\" outcomes) for MCP-1 or any inflammation-related measure finds none at all — not even as a registered secondary or exploratory outcome — despite the trial's brief summary explicitly naming \"inflammation\" as one of its three hypot"},"overall":{"judgment":"High"},"result":"Change in MCP-1 (monocyte chemoattractant protein-1), liraglutide vs. sitagliptin and vs. hypocaloric diet. The abstract does not attach a specific timepoint (2-week pre-weight-loss vs. 14-week) to the MCP-1 finding, does not report a table/figure (no numeric values, only direction), and MCP-1 is not a registered outcome measure at all (see D5 and mediation block). Location: abstract Results/Conclusion sentences only (\"Finally, liraglutide, but not sitagliptin or diet, reduced the chemokine monocyte chemoattractant protein-1 (MCP-1)\"; \"Liraglutide alone lowers the pro-inflammatory and pro-atherosclerotic chemokine MCP-1, indicating that this beneficial effect is independent of weight loss.\").\n","passes":[{"pass":"A","model":"claude-sonnet"},{"pass":"B","model":"claude-opus"}],"guide_version":"rob2-guide v1 + v1.1 calibration rulings (2026-09-13)","label":"AI: two passes agreed","resolution":"agreed domains accepted; disagreements decided by the owner 2026-09-13 (IN-009)"}
Methodological notes
Calibration two-pass assessment 2026-09-13 (drafts in data/assessments/36306151/); sources: abstract, registry, public protocol/SAP where available; no paper full text.
01bRisk of bias
How much the result can be relied on
Risk of bias is judged per result, not per paper: the same study can report one marker at low risk and another at high. Two reviewers assess each result independently against a written guide, and every domain judgment below carries its reasoning and the sentences it rests on.
These words are not quality scores. On the RoB 2 scale, High risk of bias is the worst rating a result can receive and Low risk of bias is the best — the opposite of how the same words read on some other scales. Levels are always written out in full here for that reason.
O4
High risk of bias · RoB 2 · Two reviewers agreed on every domain
How the overall was reached: RoB 2 algorithm: overall judgment takes the worst domain. D5 is High (outcome not prespecified in the registry at all, narrative-only reporting with no numbers), which alone sets the overall judgment to High; this is reinforced by Some concerns in D1, D2 and D3 (uninformative randomization/concealment description, ITT/attrition handling not addressed, and unverifiable/likely differential missingness for this specific biomarker).
| Domain | Judgment and reasoning |
|---|---|
| D1 · Randomisation process Some concerns about risk of bias | This is a small, single-center, investigator-initiated academic trial (Vanderbilt; N=93 randomized), not a large industry registration trial with a described central randomization/IVRS system, so per the collection's D1 rule allocation concealment requires an explicit description of method — none is given. Sequence generation is likewise undescribed in both sources. No clear baseline imbalance is evident on the variables reported (age, sex distribution) but BMI is not reported at baseline, so imbalance on a key prognostic variable cannot be ruled out. NI on both sequence generation and allocation concealment with no evidence of a problem -> Some concerns rather than Low or High.NI NI |
| D2 · Deviations from intended interventions Some concerns about risk of bias | Drug arms were double-blind/placebo-controlled (registry: quadruple masking of participant, care provider, investigator, outcomes assessor), but the diet arm cannot be blinded by nature of the intervention, and GI adverse events differ markedly between arms (nausea 8/46 liraglutide vs. 0/23 sitagliptin vs. 1/24 diet; diarrhea 3/46 vs. 0/23 vs. 0/24) — per the collection's D2 rule this supports "aware of assignment" = PY for at least the liraglutide arm. Per the same rule, for a lab biomarker like MCP-1 this awareness alone is judged not to bias the result, so the domain turns on discontinuation imbalance and ITT handling instead. Discontinuation was modest and roughly balanced (liraglutide 2/46 [4.3%], sitagliptin 1/23 [4.3%], diet 2/24 [8.3%]), but the abstract's analyzed sample (N=88) is the completer set, not the full randomized cohort (N=93), with no stated ITT analysis or sensitivity analysis addressing the excluded participants. This deviation from a stated ITT approach, without described handling, is enough for Some concerns rather than Low."masking": "QUADRUPLE", "maskingDescription": "Treatment with liraglutide or sitagliptin will be masked using matching placebo." numEvents: 8, numAffected: 8, numAtRisk: 46 |
| D3 · Missing outcome data Some concerns about risk of bias | MCP-1 is not a registered outcome measure at all (see D5), so neither source reports the number of participants with MCP-1 data available or missingness by arm — this specific signaling question is NI. As context (not direct evidence for MCP-1 itself), the registry's comparable plasma biomarker measured from the same blood draws, PAI-1, shows differential and at times substantial missingness by 14 weeks (diet 6/22 missing = 27.3% vs. liraglutide 3/44 = 6.8%), i.e., a difference well over the collection's 5-point/20% thresholds for a related biomarker in the same substudy. Given NI on the direct question, plus this analogous signal that biomarker missingness in this trial can be differential by arm, and given that dropout for GI reasons plausibly correlates with liraglutide exposure, the guide's default — "NI on key questions usually means Some concerns, not Low" — is applied here.NI "title": "Baseline to 14 weeks" ... groupId OG002 value "16" (denominator, of 22 randomized to diet) |
| D4 · Measurement of the outcome Low risk of bias | MCP-1 is a plasma chemokine assay, the same category (objective central-lab biomarker) that the collection's D4 rule treats as Low risk of measurement bias absent evidence the assay changed or differed between arms. No such evidence is present in either source, and outcome assessors were specified as masked in the registry.the chemokine monocyte chemoattractant protein-1 (MCP-1) "whoMasked": ["PARTICIPANT", "CARE_PROVIDER", "INVESTIGATOR", "OUTCOMES_ASSESSOR"] |
| D5 · Selection of the reported result High risk of bias | The abstract's own stated primary outcomes are FMD, PAI-1 and UACR; MCP-1 is not among them. Checking the registration's full outcome list (primary, secondary, and "other" outcomes) for MCP-1 or any inflammation-related measure finds none at all — not even as a registered secondary or exploratory outcome — despite the trial's brief summary explicitly naming "inflammation" as one of its three hypothesized domains (alongside endothelial function and fibrinolysis) and despite FMD, PAI-1, UACR, blood pressure, heart rate, fasting glucose, fasting insulin and weight all being individually registered. MCP-1 is introduced only in the abstract's results/conclusion as a late, narrative ("Finally...") addition with no numeric estimate, no p-value, no stated timepoint, and no denominator — a pattern consistent with a result selected for reporting from a larger untabulated inflammatory panel (the "inflammation" domain implies other markers such as CRP, IL-6, or TNF-alpha may also have been measured but are not mentioned). Per the collection's D5 rule, an outcome/analysis with unverifiable or absent prespecification is "at least Some concerns"; the complete absence from an otherwise detailed registry outcome list, combined with the narrative-only, no-numbers presentation, supports High rather than the floor of Some concerns.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). "primaryOutcomes": [{"measure": "Change in Flow-mediated Dilation"...},{"measure": "Urine Albumin-to-creatinine Ratio"...},{"measure": "Change in Plasminogen Activator Inhibitor-1"...}] |
02Funding
Funding and conflicts
- Funding
- Vanderbilt University Medical Center (lead sponsor); American Heart Association (collaborator)
- Industry funded
- N
- Manufacturer
- None identified
- Sponsor role
- Investigator-initiated (responsible party is the Principal Investigator, not the sponsor institution or a company)
- Author conflicts
- Multiple authors report industry ties, though none identify the study-drug manufacturers (Novo Nordisk for liraglutide, Merck for sitagliptin) as trial funders. Notably J.R. Koethe reports both consulting for and research support from Merck, which manufactures sitagliptin, one of the study's comparator arms.
- Independent replication
- no
Funding is shown on every study and never used to score it.
03Claims
Claims this study bears on
- GLP-1 receptor agonist treatment reduces systemic inflammatory markers beyond what can be explained by treatment-associated weight loss.Mixed
Liraglutide lowered MCP-1 independent of weight loss vs diet; no effect on FMD or UACR; n=88 with obesity and prediabetes; NIH funded.
04Source
The source, as retrieved
Abstract
[AIM] To test the hypothesis that glucagon-like peptide-1 receptor (GLP-1R) agonists have beneficial effects on vascular endothelial function, fibrinolysis and inflammation through weight loss-independent mechanisms. [MATERIALS AND METHODS] Individuals with obesity and prediabetes were randomized to 14 weeks of the GLP-1R agonist liraglutide, hypocaloric diet or the dipeptidyl peptidase-4 inhibitor sitagliptin in a 2:1:1 ratio. Treatment with drug was double blind and placebo-controlled. Measurements were made at baseline, after 2 weeks prior to significant weight loss and after 14 weeks. 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] Eighty-eight individuals were studied (liraglutide N = 44, diet N = 22, sitagliptin N = 22). Liraglutide and diet reduced weight, insulin resistance and PAI-1, while sitagliptin did not. There was no significant effect of any treatment on endothelial vasodilator function measured by FMD. Post hoc subgroup analyses in individuals with baseline FMD below the median, indicative of greater endothelial dysfunction, showed an improvement in FMD by all three treatments. GLP-1R antagonism with exendin (9-39) increased fasting blood glucose but did not change FMD or PAI-1. There was no effect of treatment on UACR. Finally, liraglutide, but not sitagliptin or diet, reduced the chemokine monocyte chemoattractant protein-1 (MCP-1). [CONCLUSION] Liraglutide and diet reduce weight, insulin resistance and PAI-1. Liraglutide, sitagliptin and diet do not change FMD in obese individuals with prediabetes with normal endothelial function. Liraglutide alone lowers the pro-inflammatory and pro-atherosclerotic chemokine MCP-1, indicating that this beneficial effect is independent of weight loss.
Where this record came from
| Source | Retrieved | Identifier |
|---|---|---|
| pubmed | Sep 13, 2026 | 36306151 first ingestion |