Studies on Retatrutide Peptide and Metabolic Processing

Retatrutide, designated as LY3437943, is a synthetic peptide identified as a triple receptor agonist, consisting of 39 amino acids.⁽¹⁾ Designed as an analog of gastric inhibitory polypeptide (GIP), researchers report that this compound exhibits affinity towards the glucagon-like peptide-1 (GLP-1) receptor and the glucagon (GCG) receptor.⁽²⁾ These receptors typically bind their respective endogenous hormones, GIP, GLP-1, and GCG, which are considered to be key regulators within the endocrine system.

The interaction of Retatrutide with these receptors indicates a multifaceted potential on metabolic regulation, which may be significant in the study of glycemic impacts and control. Additionally, Retatrutide has undergone chemical modification with a C20 moiety, purportedly extending its half-life to approximately six days.⁽³⁾

Peptide Mechanism

Fig.1 Diagram Tree – Hypothesized Mechanisms of Retatrutide Peptide

Research suggests that GLP-1 and GIP, acting as incretin hormones, might support insulin secretion from pancreatic beta cells and potentially increase satiety following nutrient intake. Conversely, glucagon is thought to play a compensatory role by potentially elevating blood glucose levels during fasting states.

Furthermore, activation of GLP-1 receptors is proposed to slow gastric emptying, while stimulation of GCG receptors is hypothesized to increase energy expenditure and fat cell metabolism. This influence appears most notable in hepatic processes and the conversion of white adipose tissue to beige adipose tissue, which is believed to possess thermogenic properties akin to brown adipose tissue, potentially enhancing thermogenesis and metabolic rates.

 

Research

Retatrutide Peptide and Caloric Intake

In a 48-week phase 2 study, Retatrutide was evaluated for its potential to significantly reduce total energy intake and promote the maintenance of a caloric deficit. Research indicates that Retatrutide may lead to a substantial reduction in baseline weight, with observed decreases exceeding 24.2%, in contrast to a 2.1% reduction observed in the control group. Additionally, the study reported improvements in several cardiometabolic parameters, including indicators related to cholesterol metabolism, glucose regulation, and insulin sensitivity.⁽⁴⁾

Researchers noted that in models of type 2 diabetes, Retatrutide peptide appeared to exhibit “meaningful improvements in glycaemic control and robust reductions in bodyweight, with a … profile consistent with GLP-1 receptor agonists and GIP and GLP-1 receptor agonists.”

Retatrutide Peptide and Glycated Hemoglobin Levels

Retatrutide has been suggested to exert significant potential in reducing glycated hemoglobin (HbA1c) levels in hyperglycemic models with baseline HbA1c exceeding 7%. Data from phase 2 trials, extending up to 36 weeks, suggest that Retatrutide may decrease HbA1c levels by up to 2.16% (23.59 mmol/mol), indicating a significant reduction in hyperglycemia. The findings also indicated a notable reduction in total weight, with decreases from baseline to 36 weeks reaching a least-squares mean of 16.94% in the Retatrutide-exposed groups.⁽⁵⁾

Retatrutide Peptide and Metabolic Energy Processes

Activation of glucagon (GCG) receptors by Retatrutide, a peptide agonist, may increase energy expenditure and promote fat oxidation, optimizing metabolic efficiency. Research indicates that Retatrutide may activate GCG receptors in hepatocytes, stimulating lipid catabolism and increasing hepatic metabolic rate through mechanisms such as hepatic futile cycling and enhanced mitochondrial function. This activation also triggers the secretion of thermogenic factors, including fibroblast growth factor 21 (FGF21) and bile acids, potentially further amplifying energy expenditure. These metabolic responses are associated with reductions in hepatic steatosis, enhanced metabolic enzyme activity, and elevated mitochondrial biogenesis.

Retatrutide may also induce beiging of white adipose tissue by activating GCG receptors in adipocytes, converting them into metabolically active beige adipocytes. Similar to brown adipocytes, beige adipocytes are believed to contribute to energy dissipation through UCP1-dependent thermogenesis and metabolic futile cycles, such as those involving creatine and succinate. This process may increase caloric expenditure by generating heat and potentially impacts certain metabolic processes.

Furthermore, researchers speculate that Retatrutide may impact the thermogenic capacity of brown adipose tissue (BAT) by activating BAT-specific UCP1, which may dissipate mitochondrial proton gradients as heat. This mechanism utilizes stored lipids and enhances the oxidation of glucose, lipids, and amino acids, thereby contributing to overall energy. Collectively, based on Retatrutide’s modulation of GCG receptors in both hepatic and adipose tissues,  the researchers propose that “the thermogenic activity of GCGR agonism” might reduce weight in laboratory animal models.

Retatrutide Peptide and Metabolic Outcomes

Research suggests that Retatrutide exerts its potential through the activation of glucagon-like peptide-1 (GLP-1) receptors. This peptide appears to interact with GLP-1 receptors in the pancreas, potentially stimulating insulin secretion from pancreatic beta cells and suppressing glucagon production from alpha cells in a glucose-dependent manner. The GLP-1 receptor, belonging to the class B G protein-coupled receptor family, appears to primarily activate the cAMP-PKA signaling pathway in pancreatic cells.

The interaction between GLP-1 and its receptor is believed to initiate adenylate cyclase (AC) activity, converting ATP to cyclic adenosine monophosphate (cAMP), thereby elevating cAMP levels. Elevated cAMP levels activate protein kinase A (PKA) and the guanine nucleotide exchange factor RAPGEF4 (EPAC2). PKA activation may lead to closure of ATP-sensitive K+ channels, membrane depolarization, activation of voltage-dependent Ca2+ channels, and subsequent Ca2+ influx, which may trigger potential action. Additionally, PKA activation may promote Ca2+ release via inositol trisphosphate (IP3). EPAC2 activation might further stimulate Ras-related protein 1 and phospholipase C, potentially enhancing Ca2+ release through IP3 and diacylglycerol (DAG) pathways.

Collectively, these pathways may increase intracellular Ca2+ levels, potentially enhancing mitochondrial ATP synthesis and promoting insulin secretion via exocytosis.⁽⁶⁾

Similar to its potential on GIP receptors, Retatrutide is proposed to influence neurons in the hypothalamic arcuate nucleus, deemed crucial for appetite regulation in animal models, possibly through GLP-1 receptors. These neurons express neuropeptides such as pro-opiomelanocortin (POMC) and cocaine- and amphetamine-regulated transcript (CART). Direct activation of GLP-1 receptors on POMC/CART neurons may induce satiety and indirectly inhibit the release of hunger-stimulating peptides neuropeptide Y (NPY) and agouti-related peptide (AgRP). Additionally, GLP-1 receptor activation by agonists like Retatrutide may help maintain elevated levels of free leptin and peptide YY3-36 (PYY3-36) in states of reduced caloric intake.⁽⁷⁾

Retatrutide Peptide and GIP Receptors Interaction

Retatrutide’s mode of action appears to include the activation of gastric inhibitory polypeptide (GIP) receptors. Extensive research has explored the intricate roles of GIP receptor activation in regulating energy balance. It is hypothesized that Retatrutide may exert its effects through central neural pathways, particularly in key brain regions such as the hypothalamus and brainstem,⁽⁸⁾ which may play pivotal roles in maintaining energy homeostasis and controlling appetite.

GIP receptor agonists are suggested to directly interact with neurons within these regions, potentially modulating neuronal activity to reduce caloric intake and promote a negative energy balance. The hypothalamus, housing nuclei deemed crucial for appetite regulation and energy expenditure like the arcuate, paraventricular, and ventromedial nuclei, might be sites of GIP receptor activation. Activation within these nuclei may suppress appetite or enhance satiety signals. For instance, GIP receptor activation in the arcuate nucleus might influence neuropeptide Y (NPY) and pro-opiomelanocortin (POMC) neurons, associated with appetite stimulation and suppression, respectively, suggesting a role for GIP receptor agonists in modulating these neuropeptide systems to potentially reduce caloric intake.

Furthermore, the study explores the potential impact of GIP receptor agonists on the brain’s emetic centers. By potentially influencing neural circuits in the area postrema and nucleus tractus solitarius of the brainstem—regions involved in nausea and vomiting—GIP receptor agonists may inhibit these responses. Additionally, GIP receptor agonists are proposed to enhance blood-brain barrier (BBB) permeability, potentially improving the delivery and efficacy of agents targeting brain regions involved in energy balance. This modulation might involve altering tight junctions or transport systems within the neurovascular unit, facilitating enhanced access of these agents to the central nervous system (CNS).

 
NOTE: These products are intended for laboratory research use only. This peptide is not intended for personal use. Please review and adhere to our Terms and Conditions before ordering.

 

References:

1. Folli F, Finzi G, Manfrini R, Galli A, Casiraghi F, Centofanti L, Berra C, Fiorina P, Davalli A, La Rosa S, Perego C, Higgins PB. Mechanisms of action of incretin receptor based dual- and tri-agonists in pancreatic islets. Am J Physiol Endocrinol Metab. 2023 Nov 1;325(5):E595-E609. doi: 10.1152/ajpendo.00236.2023. Epub 2023 Sep 20. PMID: 37729025; PMCID: PMC10874655. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10874655/
2. Jakubowska A, Roux CWL, Viljoen A. The Road towards Triple Agonists: Glucagon-Like Peptide 1, Glucose-Dependent Insulinotropic Polypeptide and Glucagon Receptor – An Update. Endocrinol Metab (Seoul). 2024 Feb;39(1):12-22. doi: 10.3803/EnM.2024.1942. Epub 2024 Feb 14. PMID: 38356208; PMCID: PMC10901658. https://pubmed.ncbi.nlm.nih.gov/38356208/
3. Doggrell SA. Is retatrutide (LY3437943), a GLP-1, GIP, and glucagon receptor agonist a step forward in the treatment of diabetes and obesity? Expert Opin Investig Drugs. 2023 May;32(5):355-359. doi: 10.1080/13543784.2023.2206560. Epub 2023 Apr 24. PMID: 37086147. https://pubmed.ncbi.nlm.nih.gov/37086147/
4. Jastreboff AM, Kaplan LM, Frías JP, Wu Q, Du Y, Gurbuz S, Coskun T, Haupt A, Milicevic Z, Hartman ML; Retatrutide Phase 2 Obesity Trial Investigators. Triple-Hormone-Receptor Agonist Retatrutide for Obesity – A Phase 2 Trial. N Engl J Med. 2023 Aug 10;389(6):514-526. doi: 10.1056/NEJMoa2301972. Epub 2023 Jun 26. PMID: 37366315. https://pubmed.ncbi.nlm.nih.gov/37366315/
5. Rosenstock J, Frias J, Jastreboff AM, Du Y, Lou J, Gurbuz S, Thomas MK, Hartman ML, Haupt A, Milicevic Z, Coskun T. Retatrutide, a GIP, GLP-1 and glucagon receptor agonist, for people with type 2 diabetes: a randomised, double-blind, placebo and active-controlled, parallel-group, phase 2 trial conducted in the USA. Lancet. 2023 Aug 12;402(10401):529-544. doi: 10.1016/S0140-6736(23)01053-X Epub 2023 Jun 26. PMID: 37385280. https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(23)01053-X/abstract
6. Zhao X, Wang M, Wen Z, Lu Z, Cui L, Fu C, Xue H, Liu Y, Zhang Y. GLP-1 Receptor Agonists: Beyond Their Pancreatic Effects. Front Endocrinol (Lausanne). 2021 Aug 23;12:721135. doi: 10.3389/fendo.2021.721135. PMID: 34497589; PMCID: PMC8419463. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8419463/
7. Ard J, Fitch A, Fruh S, Herman L. Weight Loss and Maintenance Related to the Mechanism of Action of Glucagon-Like Peptide 1 Receptor Agonists. Adv Ther. 2021 Jun;38(6):2821-2839. doi: 10.1007/s12325-021-01710-0. Epub 2021 May 11. PMID: 33977495; PMCID: PMC8189979. https://pubmed.ncbi.nlm.nih.gov/33977495/
8. Samms RJ, Sloop KW, Gribble FM, Reimann F, Adriaenssens AE. GIPR Function in the Central Nervous System: Implications and Novel Perspectives for GIP-Based Therapies in Treating Metabolic Disorders. Diabetes. 2021 Sep;70(9):1938-1944. doi: 10.2337/dbi21-0002. Epub 2021 Jun 27. PMID: 34176786; PMCID: PMC8576420. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8576420/
9. Image Source: https://www.researchgate.net/figure/Diagram-showing-the-mechanism-of-action-of-retatrutide_fig1_378290658