Ghrelin-Mimicking Drug Temporarily Disrupts Insulin and Blood Sugar Control in Cats
The ghrelin receptor agonist capromorelin initially reduced insulin secretion and worsened blood sugar control in healthy cats, but these metabolic effects largely normalized after 30 days of treatment.
Quick Facts
What This Study Found
Capromorelin activates the ghrelin receptor (GHSR), which is found on pancreatic delta cells that produce somatostatin. Activating delta cells was expected to suppress insulin secretion.
On day 1:
- Fasting blood glucose increased by 13 mg/dL (p < 0.0001)
- Insulin decreased (p = 0.03)
- Glucagon was unchanged
- First-phase insulin response (FPIR) during glucose tolerance test dropped by 72% (from 17,437 to 4,931 ng/L/15min, p = 0.004)
Days 2-4:
- Mean interstitial glucose rose by 19 mg/dL (p = 0.03)
- Glycemic variability increased (SD 9.7 vs 5.0, p = 0.02)
By day 30:
- Glucose tolerance returned to baseline
- Glycemic variability normalized
- But FPIR was still partially blunted (9,993 vs 17,437, p = 0.045)
The body appeared to compensate for the initial insulin suppression over time.
Key Numbers
Day 1: fasting glucose +13mg/dL; FPIR dropped 72%; Days 2-4: glucose +19mg/dL; Day 30: glucose tolerance normalized
How They Did This
Seven healthy cats received capromorelin daily for 30 days. Intravenous glucose tolerance tests were performed on days -3 (baseline), 1, and 30 to assess insulin secretion and glucose clearance. Continuous glucose monitoring tracked interstitial glucose levels and glycemic variability. Blood samples measured fasting glucose, insulin, and glucagon at multiple time points.
Why This Research Matters
This study has implications beyond veterinary medicine. Ghrelin receptor agonists like MK-677 (ibutamoren) are widely used in human growth hormone optimization. Understanding that ghrelin receptor activation temporarily impairs insulin secretion and glucose control is important for anyone considering these compounds, particularly people with existing insulin sensitivity concerns. The finding that metabolic effects normalize over 30 days suggests an adaptation mechanism worth understanding.
The Bigger Picture
Ghrelin receptor agonists are of significant interest in both veterinary and human medicine — for appetite stimulation, growth hormone release, and metabolic regulation. This study reveals an important trade-off: activating the ghrelin receptor boosts appetite and growth hormone but temporarily suppresses insulin and raises blood sugar. This has direct relevance to human use of similar compounds like MK-677, where metabolic side effects are a well-known concern.
What This Study Doesn't Tell Us
Only 7 cats were studied, which is a very small sample size. Only healthy cats were tested — diabetic, obese, or insulin-resistant cats might respond differently or not adapt as well. The 30-day treatment period may not reveal longer-term metabolic consequences. The specific mechanism by which the body compensated for insulin suppression was not fully explored. Results from cats may not directly translate to other species.
Questions This Raises
- ?Does the same metabolic adaptation occur in diabetic or pre-diabetic animals, or does the insulin suppression persist?
- ?Do human ghrelin receptor agonists like MK-677 produce similar temporary insulin suppression followed by metabolic normalization?
- ?What is the specific compensatory mechanism that restores glucose tolerance despite continued ghrelin receptor activation?
Trust & Context
- Key Stat:
- 72% drop in first-phase insulin response Capromorelin dramatically blunted initial insulin secretion on day 1, though partial recovery occurred by day 30
- Evidence Grade:
- This is a small animal study with only 7 cats. While the study design includes baseline controls and multiple time points, the very small sample size limits statistical power. The prospective design with continuous glucose monitoring adds strength, but these are preliminary findings that need replication in larger cohorts.
- Study Age:
- Published in 2021, this study remains relevant as ghrelin receptor agonists continue to be widely used in veterinary medicine and studied for human applications. No major subsequent studies have contradicted these metabolic findings.
- Original Title:
- The effect of the ghrelin-receptor agonist capromorelin on glucose metabolism in healthy cats.
- Published In:
- Domestic animal endocrinology, 74, 106484 (2021)
- Authors:
- Pires, J, Greathouse, R L, Quach, N, Huising, M O, Crakes, K R, Miller, M, Gilor, C
- Database ID:
- RPEP-05689
Evidence Hierarchy
Tests effects in animals (usually mice or rats), not humans.
What do these levels mean? →Frequently Asked Questions
Is capromorelin related to MK-677 (ibutamoren)?
Yes, both are ghrelin receptor agonists (growth hormone secretagogues) that work by mimicking the hunger hormone ghrelin. Capromorelin is FDA-approved for veterinary use in cats and dogs, while MK-677 is an investigational compound used in human research. Both activate the same receptor and are expected to have similar metabolic effects, including potential impacts on insulin and blood sugar.
Should I be concerned about blood sugar if my cat takes capromorelin?
For healthy cats, the temporary blood sugar increase appears to resolve within about a month. However, if your cat has diabetes, pre-diabetes, or is overweight, discuss this metabolic effect with your veterinarian before starting capromorelin. Monitoring blood glucose during the first few weeks of treatment may be advisable.
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Cite This Study
https://rethinkpeptides.com/research/RPEP-05689APA
Pires, J; Greathouse, R L; Quach, N; Huising, M O; Crakes, K R; Miller, M; Gilor, C. (2021). The effect of the ghrelin-receptor agonist capromorelin on glucose metabolism in healthy cats.. Domestic animal endocrinology, 74, 106484. https://doi.org/10.1016/j.domaniend.2020.106484
MLA
Pires, J, et al. "The effect of the ghrelin-receptor agonist capromorelin on glucose metabolism in healthy cats.." Domestic animal endocrinology, 2021. https://doi.org/10.1016/j.domaniend.2020.106484
RethinkPeptides
RethinkPeptides Research Database. "The effect of the ghrelin-receptor agonist capromorelin on g..." RPEP-05689. Retrieved from https://rethinkpeptides.com/research/pires-2021-the-effect-of-the
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Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkPeptides research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.