By Cocer Peptides 
25 days ago
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Definition of AOD9604
AOD9604 is a peptide derived from the C-terminal fragment of human growth hormone (hGH). It consists of amino acids 177–191 of hGH, with an additional tyrosine residue (Tyr) added at the N-terminal end of the peptide, i.e., Tyr-hGH 177–191. The amino acid sequence of AOD9604 determines its spatial conformation, which in turn influences its interactions with various receptors and molecules in the body. The tyrosine residue added at the N-terminus may affect the stability of the peptide in the body, cell uptake efficiency, and binding affinity with specific receptors. AOD9604 belongs to the class of peptide compounds, which participate in various physiological processes in the body, such as signal transduction and metabolic regulation. Due to its specific origin and structure, AOD9604 possesses unique physiological functions, particularly exhibiting significant effects in lipid metabolism regulation.
Mechanism of AOD9604 in Regulating Lipid Metabolism
(1) Association with the β-adrenergic pathway
Regulation of β-adrenergic receptor expression: AOD9604 may influence lipid metabolism by interacting with the β-adrenergic pathway, particularly through the regulation of the β(3)-adrenergic receptor (β(3)-AR). In an obese mouse model, after 14 consecutive days of intraperitoneal injection of AOD9604, the expression level of β(3)-AR RNA in adipocytes increased. The β(3)-AR is the primary lipolytic receptor in adipocytes, and its increased expression promotes lipolysis. AOD9604 may enhance the expression of the β(3)-AR gene by activating related signaling pathways, thereby increasing its surface expression in cells. It may influence the binding of certain transcription factors to the promoter region of the β(3)-AR gene, thereby enhancing the efficiency of gene transcription initiation.
The cascading reactions of β-adrenergic pathway activation: When β(3)-AR expression increases, it binds to ligands to activate downstream signaling pathways. Activated β(3)-AR couples with G proteins, leading to the activation of adenylate cyclase, which in turn increases the intracellular levels of the second messenger cyclic adenosine monophosphate (cAMP). cAMP activates protein kinase A (PKA), which phosphorylates and activates hormone-sensitive lipase (HSL), a key enzyme in lipolysis that catalyzes the hydrolysis of triglycerides into fatty acids and glycerol, thereby promoting lipolysis and regulating lipid metabolism.
(2) Direct effects independent of β(3)-AR
Acute experimental findings: In acute experiments with β(3)-AR gene-knockout mice, AOD9604 still increased energy expenditure and fat oxidation. This suggests that AOD9604's regulatory effect on lipid metabolism is not entirely dependent on β(3)-AR. Although the specific mechanism is not yet fully understood, alternative pathways or direct action targets may exist. AOD9604 may directly act on mitochondria, influencing mitochondrial function and enhancing the β-oxidation of fatty acids. Mitochondria are the central hubs of cellular energy metabolism, and fatty acid β-oxidation occurs within mitochondria. AOD9604 can promote fatty acid entry into mitochondria and facilitate oxidative degradation by regulating the activity of transport proteins or related enzymes on the mitochondrial membrane, thereby increasing energy expenditure and fatty acid oxidation.
Potential additional signaling pathways: AOD9604 is also involved in regulating other signaling pathways. It can influence the activity of the peroxisome proliferator-activated receptor (PPAR) family. PPARs are a class of nuclear receptors that play a crucial regulatory role in lipid metabolism, energy balance, and inflammatory responses. AOD9604 can interact with PPARs to regulate the expression of their target genes, thereby affecting the transcription and translation of lipid metabolism-related genes, thereby regulating lipid metabolism. It may also participate in the regulation of the insulin signaling pathway. Although AOD9604 does not have the diabetes-inducing side effects associated with hGH, it may indirectly influence lipid metabolism processes by fine-tuning the insulin signaling pathway.
The Effects of AOD9604
(1) Effects on Body Weight and Fat
Animal experimental evidence: In an obese mouse model, long-term intraperitoneal injection of AOD9604 (14 days of chronic administration) significantly reduced body weight and body fat content. This reduction in body weight and fat was associated with increased β(3)-AR RNA expression levels, indicating that AOD9604 promotes lipolysis by regulating β(3)-AR expression, thereby achieving reductions in body weight and body fat. Specifically, there was a reduction in subcutaneous and visceral fat weight, along with overall weight loss. During the experiment, regular measurements of mouse weight and precise post-mortem measurements of fat tissue weight revealed that AOD9604-treated mice exhibited significantly reduced body weight and fat weight compared to the control group, with this reduction showing a dose-dependent trend.
Figure 2 Current and Future Drug Targets in Weight Management
For the treatment of human obesity, the effects of AOD9604 hold potential application value. Obesity is an important risk factor for many chronic diseases such as cardiovascular disease and diabetes, and reducing body weight and fat is crucial for improving the health status of obese patients.
(2) Effects on Energy Metabolism
Increased Energy Expenditure: AOD9604 increases energy expenditure in both normal mice and β(3)-AR gene knockout mice. In normal mice, indirect calorimetry was used to measure oxygen consumption and carbon dioxide production, revealing that AOD9604 significantly increased energy metabolism rates. This effect is attributed to AOD9604 promoting lipolysis, with the released fatty acids serving as energy substrates for oxidation and utilization, thereby increasing energy expenditure. In β(3)-AR knockout mice, although its mechanism of action does not depend on β(3)-AR, an increase in energy expenditure was still observed, further demonstrating that AOD9604 has an energy metabolism regulation pathway independent of β(3)-AR.
Regulation of fat oxidation: AOD9604 enhances the fat oxidation process. In cellular experiments, using radioactively labeled fatty acids to track their oxidative metabolism, it was found that the rate of fatty acid oxidation was accelerated in cells treated with AOD9604. This not only helps reduce fat storage but also provides the body with more energy. AOD9604 may enhance fatty acid oxidation efficiency by regulating mitochondrial function, increasing mitochondrial biogenesis and activity. It promotes the expression and activity of enzymes related to fatty acid oxidation in mitochondria, including carnitine palmitoyltransferase I (CPT-I), which is the key rate-limiting enzyme for fatty acids entering mitochondria for oxidation. AOD9604 may promote fatty acid entry into mitochondria for oxidative decomposition by upregulating CPT-I expression.
(3) Effects on hepatic lipid metabolism
Hepatic lipid metabolism animal experiment study: In a mouse fatty liver model, the effects of AOD9604 on hepatic lipid metabolism were investigated. Mice were divided into a control group, an exercise group, an exercise + AOD9604 group, and an AOD9604 alone treatment group. The results showed that the alanine aminotransferase (ALT) levels in the AOD9604 alone group and the exercise + AOD9604 group were significantly lower than those in the control group, indicating that AOD9604 has a certain protective effect on liver damage. This can be attributed to AOD9604 regulating lipid metabolism in the liver, reducing fat accumulation in the liver, thereby alleviating hepatic steatosis and inflammatory responses.
Effects on liver enzymes and cytokeratin-18 (CK18): Cytokeratin-18 is a biomarker reflecting hepatocyte apoptosis. In the experiment, although the AOD9604 monotherapy group did not significantly reduce CK18 levels, it also did not produce negative effects. This suggests that AOD9604 may indirectly influence the apoptosis process of liver cells by regulating hepatic lipid metabolism, thereby protecting liver cells from damage to some extent. AOD9604 may maintain the balance of hepatic lipid metabolism by regulating the expression of genes related to lipid synthesis, transport, and degradation in the liver, thereby reducing abnormal fat accumulation in the liver.
Applications of AOD9604
(1) Potential Applications in Obesity Treatment
Advantages and Prospects: Compared to traditional weight-loss drugs, AOD9604 has several potential advantages. It does not have the diabetes-related side effects associated with hGH. hGH may cause adverse reactions such as insulin resistance and elevated blood glucose levels when used to treat obesity. AOD9604 avoids these side effects through its unique structural design. AOD9604 can specifically regulate lipid metabolism, promote fat breakdown, and increase energy expenditure, offering promising treatment prospects for patients with simple obesity. Its mechanism of action involves multiple levels, not only through regulation of the β-adrenergic pathway but also through a mechanism independent of β(3)-AR, providing a more comprehensive intervention approach for obesity treatment.
(2) Potential applications in the treatment of liver diseases
Potential for treating non-alcoholic fatty liver disease (NAFLD): NAFLD is a common liver disease characterized by excessive fat accumulation in the liver. In a mouse model of fatty liver disease, AOD9604 can regulate hepatic lipid metabolism, reduce liver fat content, and improve liver function markers. AOD9604 has certain application value for the treatment of NAFLD. It can reduce fat accumulation in the liver by promoting the breakdown and transport of fat within the liver, thereby alleviating hepatic steatosis and inflammatory responses. AOD9604 can also regulate oxidative stress and inflammatory signaling pathways within the liver, further protecting liver cells from damage.
Conclusion
As a peptide derived from the C-terminal region of human growth hormone, AOD9604's mechanism of action in regulating lipid metabolism involves interactions with the β-adrenergic pathway and direct effects independent of β(3)-AR. Through these mechanisms, AOD9604 effectively reduces body weight and body fat, increases energy expenditure, regulates fat oxidation, and improves hepatic lipid metabolism. In terms of applications, AOD9604 holds significant promise in the treatment of obesity, sports medicine, and liver disease.
Sources
[1] Dehbashi M, Fathi M, Attarzadeh Hosseini S R, et al. The Effect of Eight Weeks Endurance Training, Somatropin Injection, and Its Lipolytic Fragment (AOD9604) on Cytokeratin-18 and Liver Enzymes of Mice Induced Liver Damage Due to a High-Fat Diet[J]. Quarterly of the Horizon of Medical Sciences, 2021,27:502-517.DOI:10.32598/hms.27.4.3513.1.
[2] Cox H D, Smeal S J, Hughes C M, et al. Detection and in vitro metabolism of AOD9604[J]. Drug Testing and Analysis, 2015,7(1):31-38.DOI:10.1002/dta.1715.
[3] Stier H, Vos E, Kenley D L. Safety and Tolerability of the Hexadecapeptide AOD9604 in Humans[J]. Journal of Endocrinology and Metabolism, 2013,3:7-15.
https://api.semanticscholar.org/CorpusID:56559133
[4] Witkamp R F. Current and Future Drug Targets in Weight Management[J]. Pharmaceutical Research, 2011,28(8):1792-1818.DOI:10.1007/s11095-010-0341-1.
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