AOD-9604 Peptide: Structure, Mechanism & Research Guide
AOD-9604 is a synthetic peptide analogue of the C-terminal 177-191 region of human growth hormone (hGH), distinguished by an N-terminal tyrosine residue added to enhance molecular stability. Preclinical research indicates that this specific structural configuration retains the lipolytic properties associated with endogenous hGH but entirely lacks the receptor-binding affinity required to stimulate IGF-1 production or cellular proliferation.
Originally developed by Metabolic Pharmaceuticals to isolate the metabolic functions of growth hormone, AOD-9604 peptide is currently investigated in laboratory models for its interactions with beta-3 adrenergic receptors and lipid metabolism pathways.
Structural Biochemistry: How the C-Terminal 177-191 hGH Fragment is Modified in AOD-9604
AOD-9604 is a synthetic 16-amino acid peptide developed by modifying the C-terminal region of human growth hormone (hGH), specifically corresponding to residues 177-191. The primary structural distinction between AOD-9604 and the endogenous sequence is the covalent addition of a tyrosine (Tyr) residue at the N-terminus. This single amino acid addition stabilizes the secondary structure of the peptide in-vitro, reducing susceptibility to proteolytic cleavage while preserving the spatial orientation required for receptor interaction in laboratory models.
| Peptide | Sequence | Modifications |
|---|---|---|
| hGH 177-191 | Leu-Arg-Ile-Val-Gln-Cys-Arg-Ser-Val-Glu-Gly-Ser-Cys-Gly-Phe | Endogenous C-terminal sequence |
| AOD-9604 | Tyr-Leu-Arg-Ile-Val-Gln-Cys-Arg-Ser-Val-Glu-Gly-Ser-Cys-Gly-Phe | N-terminal Tyrosine (Tyr) added for stability |
What is the Biochemical Function of the N-Terminal Tyrosine Addition?
The insertion of an N-terminal tyrosine introduces a bulky, aromatic phenol side chain to the peptide molecule. In the context of peptide synthesis and in-vitro stability, this aromatic ring provides steric hindrance against exopeptidases that would otherwise rapidly degrade the linear sequence. Researchers investigating AOD-9604 rely on this modification to maintain peptide integrity during prolonged cell culture assays, as documented in various structural analyses available through https://pubmed.ncbi.nlm.nih.gov/?term=AOD9604+peptide+structure.
| Amino Acid Modification | Chemical Class | In-Vitro Structural Impact |
|---|---|---|
| Tyrosine (Tyr / Y) | Aromatic, polar | Provides steric hindrance against N-terminal exopeptidases |
| Hydroxyl Group (-OH) | Reactive functional group | Enables potential radioiodination for assay tracking |
| Phenol Ring | Hydrophobic/Aromatic | Alters the electrostatic potential of the N-terminus |
How Does the Disulfide Bridge Stabilize AOD-9604 Conformation?
Beyond the N-terminal tyrosine, the biological activity of the hGH C-terminal domain relies heavily on a disulfide bridge. In the native hGH molecule, Cys-182 and Cys-189 form a cyclic loop. Because AOD-9604 includes this exact sequence (shifted by one position due to the added tyrosine), the peptide retains the two cysteine residues. Under oxidizing conditions during synthesis, these cysteines form an intramolecular disulfide bond, forcing the peptide into a constrained cyclic conformation. This structural constraint mimics the native loop found in the full 191-amino acid hGH protein, which is hypothesized to be the active site for lipid metabolism signaling.
| Physicochemical Parameter | AOD-9604 Specification |
|---|---|
| Total Amino Acids | 16 (Cyclic peptide) |
| Molecular Formula | C78H123N23O23S2 |
| Molecular Weight | 1815.1 g/mol |
| Intramolecular Bond | Disulfide bridge between Cys-7 and Cys-14 (AOD-9604 numbering) |
Maintaining this disulfide bond is critical for researchers analyzing AOD-9604 in-vitro. If the bond is reduced, the peptide unfolds into a linear, flexible chain, which preclinical models indicate may alter its binding affinity. Therefore, verifying the oxidative state of the cysteine residues is a standard quality control step during peptide synthesis and laboratory preparation.
Dissociation of Lipolytic and Growth-Signaling Domains in AOD-9604
AOD-9604 functions by isolating the lipolytic activity of the human growth hormone (hGH) C-terminus from the mitogenic properties governed by the N-terminal and central regions. Preclinical investigations demonstrate that this dissociation prevents the peptide from binding to the traditional hGH receptor (hGHR), thereby eliminating IGF-1 stimulation and cellular proliferation pathways. By synthesizing only the modified 177-191 fragment, researchers can evaluate lipid metabolism independently of somatic growth signaling.
Full-length hGH comprises 191 amino acids folded into a four-helix bundle. The structural biochemistry of hGH dictates that receptor binding and subsequent growth signaling require the N-terminal region (residues 1-43) and the central helices (residues 54-128). Intact hGH binds its receptor asymmetrically at two specific interfaces (Site 1 and Site 2), a process entirely dependent on these N-terminal and helical residues. These domains facilitate hGHR dimerization, activating the JAK2/STAT5 signaling cascade responsible for IGF-1 transcription. Because AOD-9604 lacks these specific sequences, it physically cannot induce receptor dimerization. Researchers investigating AOD-9604 peptide constructs consistently observe a complete absence of mitogenic signaling in cell culture models.
| hGH Domain | Primary Function in Literature | Presence in AOD-9604 |
|---|---|---|
| N-Terminal (Residues 1-43) | Receptor binding, IGF-1 stimulation, cellular proliferation | Absent |
| Central Helices (Residues 54-128) | Receptor dimerization, binding affinity | Absent |
| C-Terminal (Residues 177-191) | Lipolysis, fat oxidation, metabolic regulation | Present (modified) |
The C-terminal region of hGH, specifically residues 177-191, operates through a distinct, non-hGHR mechanism to regulate lipid metabolism. In-vitro assays indicate that this isolated domain interacts with secondary cellular targets to upregulate lipolysis and inhibit lipogenesis. The targeted structural modification—an N-terminal tyrosine addition—stabilizes this isolated fragment against rapid proteolytic degradation in laboratory assays without restoring any hGHR affinity.
| Signaling Pathway | Full-Length hGH Activity | AOD-9604 Activity |
|---|---|---|
| JAK2/STAT5 Activation | High (Dimerization dependent) | Negligible |
| IGF-1 Transcription | High (Growth signaling) | Negligible |
| cAMP/PKA (Lipolysis) | Moderate to High | High |
Extensive literature accessible via PubMed confirms that isolating the lipolytic domain permits highly specific metabolic research. Assays measuring cellular proliferation in human fibroblast and chondrocyte cultures show no significant mitotic increase when exposed to the C-terminal fragment, contrasting sharply with the robust proliferation induced by intact hGH. This structural dissociation ensures the peptide remains isolated to lipolytic mechanisms, providing a targeted tool for adipose tissue research.
| Receptor Target Interface | Binding Domain Required | Experimental Observation |
|---|---|---|
| hGH Receptor (Site 1) | Helices 1 and 4 | No binding detected with 177-191 fragment |
| hGH Receptor (Site 2) | N-terminus | No binding detected |
| Putative Metabolic Targets | C-terminus (177-191) | Sustained lipolytic signaling in adipocytes |
Receptor Binding Profile: Does AOD-9604 Interact with Beta-3 Adrenergic Receptors?
Preclinical literature indicates that AOD-9604 modulates lipid metabolism primarily by upregulating beta-3 adrenergic receptor (β3-AR) expression and activity in adipose tissue. This localized receptor interaction stimulates lipolysis and inhibits lipogenesis without binding to the full-length human growth hormone receptor (GHR). Consequently, isolated adipocyte assays demonstrate increased lipid mobilization completely independent of systemic insulin-like growth factor 1 (IGF-1) elevation.
Mechanisms of Beta-3 Adrenergic Receptor Upregulation
In-vitro models of lipid metabolism suggest the lipolytic action of the AOD-9604 peptide is heavily dependent on the β3-AR pathway. When adipocytes are exposed to the peptide, researchers observe a downstream increase in intracellular cyclic adenosine monophosphate (cAMP). This secondary messenger activates protein kinase A (PKA), which subsequently phosphorylates hormone-sensitive lipase (HSL) and perilipin, initiating triglyceride breakdown. Literature searches for AOD9604 beta-3 adrenergic reveal that the peptide’s ability to reduce lipid accumulation is blunted when specific β3-AR antagonists are introduced to the cell culture, confirming this receptor’s central role in the mechanism of action.
| Adrenergic Receptor Subtype | Primary Adipose Function | Observed AOD-9604 Interaction Profile (In-Vitro) |
|---|---|---|
| Beta-1 (β1-AR) | Basal lipolysis, cardiac output | No significant binding or upregulation reported |
| Beta-2 (β2-AR) | Catecholamine-induced lipolysis | Minimal to no direct activation |
| Beta-3 (β3-AR) | Thermogenesis, stimulated lipolysis | Primary target of upregulation and signal transduction |
Dissociation from the Somatotropic Axis and IGF-1
Intact human growth hormone induces lipolysis but simultaneously triggers cellular proliferation and glucose intolerance via the GHR and subsequent JAK2/STAT5 signaling cascades. AOD-9604 consists only of a modified C-terminal sequence (amino acids 177-191 with an added N-terminal tyrosine). Because it lacks the dual binding sites necessary to dimerize the GHR, the peptide cannot activate the STAT5 transcription factors required for IGF-1 production. Researchers monitoring AOD-9604 IGF-1 data in isolated models consistently report baseline IGF-1 levels remain unchanged during continuous exposure.
| Receptor / Pathway | Intact hGH (191 AA) | AOD-9604 (16 AA) |
|---|---|---|
| GHR Dimerization | High affinity | No binding affinity |
| JAK2/STAT5 Activation | Strong stimulation | Inactive |
| IGF-1 Transcription | Upregulated | Unchanged (Baseline) |
In-Vitro Adipocyte Models and Biomarker Assays
Laboratory investigations of AOD-9604 rely on specific biomarker tracking to validate its receptor interactions. By utilizing cultured 3T3-L1 adipocytes or isolated primary human fat cells, researchers measure extracellular glycerol release as a direct proxy for lipolysis. The verified absence of GHR binding ensures that these lipolytic observations occur without inducing insulin resistance or altering glucose transporter type 4 (GLUT4) translocation in the in-vitro environment.
| Assay Biomarker | Metabolic Pathway | Expected Observation with AOD-9604 |
|---|---|---|
| Extracellular Glycerol | Triglyceride Hydrolysis (Lipolysis) | Dose-dependent increase |
| Intracellular cAMP | β3-AR Signal Transduction | Elevated concentration |
| Acetyl-CoA Carboxylase (ACC) | Fatty Acid Synthesis (Lipogenesis) | Downregulated activity |
Metabolic Pharmaceuticals: The Development History of AOD-9604
Metabolic Pharmaceuticals engineered AOD-9604 by isolating and modifying the C-terminal lipolytic domain of human growth hormone (hGH), specifically encompassing residues 177-191. The primary developmental objective was to synthesize a peptide sequence that retained the lipid-metabolizing properties of native hGH while eliminating binding affinity for receptors associated with cellular proliferation and insulin resistance. By introducing an N-terminal tyrosine residue, researchers created a structurally stable analog optimized for investigating adipocyte lipid metabolism in-vitro without triggering systemic IGF-1 release.
Why Did Researchers Seek to Isolate the Lipolytic Domain of hGH?
Native hGH regulates multiple divergent physiological pathways, making it difficult to study its lipid-mobilizing effects in isolation. When hGH binds to the primary growth hormone receptor (GHR), it initiates Janus kinase 2 (JAK2) and signal transducer and activator of transcription (STAT) signaling. This cascade stimulates insulin-like growth factor 1 (IGF-1) transcription, leading to cellular proliferation. Investigators at Metabolic Pharmaceuticals hypothesized that the lipolytic activity of hGH was structurally distinct from its growth-promoting domains, prompting the search for a truncated sequence.
| Peptide/Protein | Primary Receptor Target | Observed Cellular Response (In-Vitro) | IGF-1 Transcription Activation |
|---|---|---|---|
| Native hGH (191 AA) | GHR (Dimerized) | Proliferation, Lipolysis, Carbohydrate Metabolism Alteration | High |
| AOD-9604 (16 AA) | Undetermined (Investigated for Beta-3 Adrenergic pathways) | Lipolysis, Lipogenesis Inhibition | None Observed |
Engineering the Tyr-hGH(177-191) Sequence
To isolate the lipid-metabolizing function, developers focused on the C-terminal sequence, a region documented to stimulate lipolysis in isolated adipocytes. The raw hGH fragment 176-191, however, demonstrated high susceptibility to rapid proteolytic cleavage in early laboratory environments. Metabolic Pharmaceuticals stabilized this sequence by appending a tyrosine residue at the N-terminus. This structural modification yielded AOD-9604 (sequence: Tyr-Leu-Arg-Ile-Val-Gln-Cys-Arg-Ser-Val-Glu-Gly-Ser-Cys-Gly-Phe), which exhibited increased conformational stability for laboratory assays. Disulfide bond formation between the two cysteine residues maintained the secondary structure required for biological activity in cellular models. Literature regarding these structural formulations can be reviewed via PubMed searches for AOD-9604 structural origins.
| Development Phase | Research Objective Focus | Key Model Utilized |
|---|---|---|
| Sequence Identification | Map the specific hGH domain responsible for lipid mobilization. | In-Vitro Adipocyte Assays |
| Structural Modification | Enhance peptide stability against proteolytic degradation. | Chemical Synthesis (N-terminal Tyrosine addition) |
| Pathway Verification | Confirm absence of JAK2/STAT signaling and IGF-1 elevation. | Receptor Binding Assays |
Transition from Conceptual Design to Preclinical Evaluation
Following synthesis, Metabolic Pharmaceuticals directed research toward verifying the functional divergence of AOD-9604 from native hGH. Preclinical in-vitro models measured glycerol release to quantify lipolysis and assessed the incorporation of radiolabeled precursors to evaluate the inhibition of lipogenesis. Investigators confirmed that the modified peptide did not interact with the prolactin receptor or dimerize the primary GHR. Historical trial data assessing these isolated metabolic pathways are indexed in clinical trial registries for AOD-9604, reflecting the compound’s trajectory from a targeted synthetic hypothesis to an established research peptide.
| Signaling Pathway / Domain | Native hGH Interaction | AOD-9604 Interaction (Reported) |
|---|---|---|
| JAK2/STAT (Proliferation) | Positive | Negative |
| Prolactin Receptor Binding | Positive | Negative |
| Adipocyte Glycerol Release | Positive | Positive |
Structural Differences: AOD-9604 vs. HGH Fragment 176-191
AOD-9604 and hGH fragment 176-191 are structurally distinct peptides that are frequently conflated in early-stage research literature. While hGH 176-191 represents the exact unmodified 16-amino-acid C-terminal sequence of native human growth hormone, AOD-9604 is a synthetic derivative featuring an N-terminal tyrosine residue appended to the truncated 177-191 sequence. This specific amino acid substitution fundamentally alters the peptide’s molecular weight, isoelectric point, and proteolytic degradation profile in laboratory assays.
Sequence Modification and Amino Acid Composition
The primary structural divergence between these two compounds occurs at the N-terminus. Native human growth hormone contains a phenylalanine (Phe) residue at position 176. The hGH 176-191 fragment retains this native phenylalanine. Conversely, the synthesis of AOD-9604 replaces this native sequence start with a tyrosine (Tyr) residue, creating the sequence Tyr-hGH(177-191). The inclusion of tyrosine—a polar, aromatic amino acid—was engineered to enhance structural stability against exopeptidase cleavage during in-vitro cell culture studies.
| Peptide Designation | N-Terminal Residue | Molecular Formula | Approximate Molecular Weight |
|---|---|---|---|
| AOD-9604 | Tyrosine (Tyr) | C78H123N23O23S2 | 1815.1 g/mol |
| hGH Frag 176-191 | Phenylalanine (Phe) | C78H123N23O22S2 | 1799.1 g/mol |
Disulfide Bridge Dynamics and Loop Retention
Despite the N-terminal substitution, both peptides share identically conserved sequences from residues 177 to 191. Crucially, both molecules depend on an intramolecular disulfide bond between Cys182 and Cys189. This covalent linkage forces the peptide backbone into a stable beta-turn hairpin loop. Preclinical investigations reported in the literature indicate that this cyclic conformation is an absolute structural prerequisite for binding interactions with lipolytic targets in isolated adipocyte models.
| Structural Feature | AOD-9604 | hGH Fragment 176-191 |
|---|---|---|
| Amino Acid 1 | Tyr (Synthetic addition) | Phe (Native sequence) |
| Amino Acids 2-16 | Leu-Arg-Ile-Val-Gln-Cys-Arg-Ser-Val-Glu-Gly-Ser-Cys-Gly-Phe | Leu-Arg-Ile-Val-Gln-Cys-Arg-Ser-Val-Glu-Gly-Ser-Cys-Gly-Phe |
| Disulfide Bond | Present (Cys182-Cys189) | Present (Cys182-Cys189) |
Nomenclature Conventions in Analytical Literature
Accurate identification of these peptides in mass spectrometry (MS) and high-performance liquid chromatography (HPLC) requires precise nomenclature. Researchers sourcing reagents must verify molecular weights, as vendors occasionally mislabel hGH 176-191 as AOD-9604. The 16-Dalton mass shift between the two compounds—resulting from the extra oxygen atom present on tyrosine’s phenol ring compared to phenylalanine’s benzene ring—provides a definitive diagnostic marker during LC-MS validation.
| Compound | Common Research Aliases | Diagnostic Mass Shift (LC-MS) |
|---|---|---|
| AOD-9604 | Tyr-hGH(177-191), AOD9604 | [M+H]+ at ~1816.1 m/z |
| hGH Frag 176-191 | Somatotropin 176-191, HGH 176-191 | [M+H]+ at ~1800.1 m/z |
In-Vitro Lipid Metabolism: How AOD-9604 Influences Lipolysis and Lipogenesis
Preclinical investigations indicate that AOD-9604 modulates lipid metabolism by simultaneously upregulating lipolysis and downregulating lipogenesis in isolated adipocyte models. Laboratory data suggests the peptide triggers the hydrolysis of intracellular triglycerides into free fatty acids and glycerol, while concurrently suppressing the enzymatic pathways responsible for de novo lipid synthesis. This dual-action mechanism occurs independently of the insulin-like growth factor 1 (IGF-1) receptor axis utilized by intact human growth hormone.
| Enzymatic / Receptor Target | Metabolic Pathway | Observed Modulatory Effect In-Vitro |
|---|---|---|
| Beta-3 Adrenergic Receptor | Lipolysis | Secondary activation / signaling cascade initiation |
| Hormone-Sensitive Lipase (HSL) | Lipolysis | Upregulated phosphorylation and activation |
| Acetyl-CoA Carboxylase (ACC) | Lipogenesis | Enzymatic suppression and pathway blockade |
Mechanisms of Triglyceride Hydrolysis in Adipocyte Cell Cultures
In-vitro models utilizing isolated obese and lean murine adipocytes demonstrate that the C-terminal sequence of AOD-9604 exhibits a strong lipolytic profile. Researchers evaluate fat oxidation rates by measuring the release of glycerol into the culture medium, a direct byproduct of triglyceride breakdown. Current literature suggests this metabolic shift is mediated through the activation of hormone-sensitive lipase (HSL) and the subsequent elevation of intracellular cyclic AMP (cAMP). Laboratories procuring research-grade AOD-9604 for metabolic screening often examine its synergistic effects when introduced alongside beta-3 adrenergic receptor antagonists to map exact binding affinities. Investigators can review primary assay data by searching the literature for AOD9604 lipolysis adipocyte studies.
| Metabolic Biomarker | Cellular Function in Lipid Metabolism | Standard Measurement Assay |
|---|---|---|
| Glycerol Release | Primary end-product of triglyceride hydrolysis | Colorimetric / Fluorometric Assay |
| Non-Esterified Fatty Acids (NEFA) | Lipid breakdown product mobilized from droplets | NEFA Quantification Kit |
| Intracellular cAMP | Secondary messenger driving HSL activation | Competitive ELISA |
Suppression of De Novo Lipogenesis and Fatty Acid Synthase Activity
Beyond initiating fat oxidation, AOD-9604 demonstrates potent anti-lipogenic properties in isolated cell cultures. Lipogenesis—the metabolic formation of new lipid droplets—relies heavily on the enzymes acetyl-CoA carboxylase (ACC) and fatty acid synthase (FAS). Preclinical work indicates that AOD-9604 downregulates the activity of these specific lipogenic enzymes, preventing the esterification of free fatty acids back into stored triglycerides. Unlike intact hGH, which can induce insulin resistance in cellular models by interfering with glucose signaling, AOD-9604 appears to inhibit lipid accumulation without altering glucose transport or insulin receptor substrate-1 (IRS-1) phosphorylation. Researchers investigating these distinct molecular pathways can query hGH fragment lipogenesis in vitro for detailed enzymatic analyses.
| Metabolic Parameter | Intact hGH Mechanism | AOD-9604 Mechanism |
|---|---|---|
| Lipid Oxidation Signaling | IGF-1 Dependent & Independent | Strictly IGF-1 Independent |
| Cellular Glucose Transport | Downregulated (Induces Insulin Resistance) | Unaltered (Maintains Glucose Homeostasis) |
| De Novo Lipid Synthesis | Suppressed via ACC inhibition | Suppressed via ACC inhibition |
Investigating AOD-9604 in Cartilage and Osteoarthritis Research Models
Preclinical models indicate that AOD-9604 modulates chondrogenic pathways when introduced to joint tissue environments. Laboratory investigations into its intra-articular application report the upregulation of structural matrix proteins, specifically type II collagen and proteoglycans, alongside enhanced chondrocyte differentiation. These in-vitro observations expand AOD-9604 research beyond lipolytic mechanisms into orthopedic and tissue-engineering applications.
How Does AOD-9604 Influence Chondrocyte Differentiation Pathways?
In-vitro studies frequently utilize mesenchymal stem cells (MSCs) and primary chondrocytes to evaluate the peptide’s capacity to induce chondrogenesis. Researchers measure the expression of specific transcription factors, notably SOX9, which serves as a master regulator for chondrocyte lineage commitment. Preclinical data suggest that AOD-9604 may synergize with local cellular signals to amplify cascades that drive undifferentiated cells toward a mature chondrocyte phenotype.
| Chondrogenic Biomarker | Biological Function in Joint Models | Evaluated Outcomes in AOD-9604 Assays |
|---|---|---|
| SOX9 | Master transcription factor for chondrocyte differentiation | Measured for upregulation during MSC lineage commitment |
| Aggrecan | Primary proteoglycan providing structural hydration | Quantified via RT-PCR to assess matrix synthesis activity |
| RUNX2 | Transcription factor for osteoblast differentiation | Monitored to ensure absence of undesired ossification |
Quantifying Cartilage Matrix Synthesis in Preclinical Assays
The structural integrity of articular cartilage relies on a dense extracellular matrix (ECM). Laboratory models of osteoarthritis simulate cartilage degradation to test whether investigational compounds can stimulate ECM synthesis. Assays measuring glycosaminoglycan (GAG) content and type II collagen production are standard metrics. Research documented in literature repositories indicates that AOD-9604, when applied to degraded cartilage explants, correlates with increased proteoglycan synthesis compared to control groups.
| Matrix Component | Cartilage Structural Role | Standard Laboratory Assay Method |
|---|---|---|
| Type II Collagen | Tensile strength of hyaline cartilage | Immunohistochemistry (IHC) / Western Blot |
| Glycosaminoglycans (GAGs) | Compressive resistance and water retention | Dimethylmethylene Blue (DMMB) Assay |
| Type I Collagen | Marker of inferior fibrocartilage formation | ELISA (used as a negative control metric) |
Experimental Vehicles for Intra-Articular Application Models
Delivering peptides to articular joints in preclinical animal models requires stable suspension mediums to prevent rapid enzymatic degradation. Researchers often co-administer AOD-9604 with hyaluronic acid (HA) or biodegradable hydrogel scaffolds. These experimental vehicles isolate the peptide within the synovial cavity, allowing sustained interaction with target chondrocytes during longitudinal studies. Clinical trial registries and preclinical databases document ongoing interest in these combined scaffold-peptide delivery systems for joint research.
| Experimental Vehicle | Purpose in Intra-Articular Models | Interaction with AOD-9604 |
|---|---|---|
| Hyaluronic Acid (HA) | Provides joint lubrication and scaffold structure | Acts as a viscous carrier to delay peptide clearance |
| Chitosan Hydrogels | Biocompatible scaffold for 3D cell cultures | Enables controlled, sustained release of the peptide |
| Saline Solution | Standard baseline control vehicle | Results in rapid systemic clearance from the joint space |
Regulatory Context: FDA GRAS Self-Affirmation of AOD-9604
AOD-9604 previously obtained self-affirmed Generally Recognized As Safe (GRAS) status in the United States, a designation indicating that independent toxicological experts reviewed safety data for its potential inclusion in specific dietary applications. This regulatory pathway evaluates baseline safety parameters and toxicological thresholds rather than establishing physiological efficacy or therapeutic utility. Within contemporary laboratory supply frameworks, AOD-9604 remains strictly classified as an analytical and experimental research chemical, utilized exclusively for in-vitro assays and preclinical investigation.
Mechanisms of GRAS Self-Affirmation versus Pharmaceutical Approval
The GRAS regulatory framework operates under the Federal Food, Drug, and Cosmetic Act (FD&C Act), allowing independent panels of qualified experts to evaluate the safety of a substance under its intended conditions of use. AOD-9604 achieved self-affirmed GRAS status following reviews of its metabolic clearance rates, amino acid degradation pathways, and baseline toxicological data. This designation strictly addresses safety margins for non-medical ingestion and does not constitute an FDA New Drug Application (NDA) approval. Researchers investigating the peptide must distinguish between a self-affirmed GRAS determination—which focuses on the absence of acute toxicity—and a full pharmaceutical regulatory evaluation, which requires demonstrated efficacy for specific physiological targets.
| Regulatory Pathway | Primary Objective | Evaluation Criteria | AOD-9604 Application |
|---|---|---|---|
| GRAS Self-Affirmation | Establish baseline safety | Toxicology, metabolism, expert consensus | Historical evaluation for food additives |
| FDA NDA Approval | Establish clinical efficacy and safety | Phase I-III human trials, risk-benefit analysis | Not approved |
| Research Chemical | Facilitate scientific investigation | Purity, stability, sequence verification | Current status for in-vitro/preclinical use |
Navigating the Current Research Chemical Classification
Despite its historical GRAS self-affirmation, AOD-9604 is not an approved therapeutic agent. In laboratory procurement and materials management, the peptide is designated strictly for experimental research. Investigators utilize this compound to map lipolytic pathways, evaluate receptor binding affinities in-vitro, and study peptide degradation profiles. Compliance mandates that AOD-9604 procurement requires strict adherence to research-only guidelines, precluding any human administration. Literature documenting its regulatory evaluations and safety profiling can be surveyed via the PubMed database and historical filings indexed in ClinicalTrials.gov.
| Research Domain | In-Vitro Application | Analytical Target |
|---|---|---|
| Lipid Metabolism | Adipocyte cell cultures | Lipolytic cascade activation rates |
| Receptor Kinetics | Membrane binding assays | Beta-3 adrenergic receptor affinity |
| Structural Biochemistry | Degradation studies | Proteolytic cleavage resistance |
Compliance Parameters for Laboratory Procurement
Institutional review boards (IRBs) and materials management departments require precise documentation of peptide purity and intended experimental use. While the historical GRAS self-affirmation provides researchers with baseline reference points regarding structural stability and metabolic byproducts, modern experimental protocols demand independent verification. Procurement relies on Certificates of Analysis (CoA) to satisfy compliance guidelines for handling non-regulated research chemicals.
| Document Type | Purpose in Research Compliance | Standard Verification Metric |
|---|---|---|
| Certificate of Analysis (CoA) | Confirms batch identity and purity | >98% purity standard |
| Material Safety Data Sheet (MSDS) | Outlines handling and storage safety | Hazard classification (Research Only) |
| Analytical Traceability | Validates molecular weight and sequence | Mass Spectrometry (MS) alignment |
Chemical Stability, Reconstitution, and Storage Parameters for AOD-9604
The chemical stability of AOD-9604 depends on mitigating moisture-induced hydrolysis, oxidative damage, and disulfide scrambling. In the lyophilized state, the peptide maintains structural integrity when stored at or below -20°C in a desiccated environment. Upon reconstitution for in-vitro assays, researchers must utilize appropriate buffered solvents and strict thermal controls (2°C to 8°C) to prevent the deamidation of specific amino acid residues and ensure reproducible receptor-binding data.
Degradation Pathways of the Modified hGH Fragment
Laboratory analysis of AOD-9604 reveals specific structural vulnerabilities inherent to its 15-amino-acid sequence (Tyr-Leu-Arg-Ile-Val-Gln-Cys-Arg-Ser-Val-Glu-Gly-Ser-Cys-Gly). The synthetic addition of a N-terminal tyrosine residue, combined with the critical intramolecular disulfide bond between the two cysteine residues, introduces distinct pathways for physicochemical degradation when exposed to suboptimal environmental conditions.
| Degradation Pathway | Target Residue or Bond | Primary Environmental Catalyst |
|---|---|---|
| Deamidation | Glutamine (Gln) at position 6 | Elevated pH in aqueous solutions; prolonged room temperature exposure |
| Disulfide Scrambling | Cys-Cys intra-chain bridge | Alkaline environments; mechanical shearing during reconstitution |
| Oxidation | N-terminal Tyrosine (Tyr) | Exposure to atmospheric oxygen and reactive oxygen species (ROS) |
| Aggregation | Hydrophobic core residues | Repeated freeze-thaw cycles of reconstituted aliquots |
Reconstitution Protocols for In-Vitro Assays
Selecting the correct solvent is critical for maintaining the three-dimensional conformation necessary for lipolytic receptor affinity studies. Lyophilized AOD-9604 exists as a fragile matrix that requires gentle solvation. Vigorous agitation or vortexing forces the peptide against the vial walls, accelerating aggregation via disulfide exchange.
| Reconstitution Solvent | Chemical Profile | Laboratory Application Suitability |
|---|---|---|
| Sterile Water (Cell Culture Grade) | Neutral pH, zero additives | Short-term in-vitro cellular assays requiring zero background interference |
| Bacteriostatic Water (0.9% Benzyl Alcohol) | Slightly acidic, antimicrobial | Multi-day longitudinal studies; provides resistance against microbial degradation |
| 0.1% Acetic Acid Solution | Acidic (pH ~3.0) | Stock solution preparation prior to buffering in PBS for specific binding assays |
Laboratory Storage Conditions for Peptide Integrity
Thermal degradation kinetics dictate strict storage parameters. Researchers monitoring peptide stability via high-performance liquid chromatography (HPLC) note that AOD-9604 degrades rapidly when left in an aqueous state at ambient temperatures. To minimize freeze-thaw degradation, bulk reconstituted solutions should be separated into single-use aliquots before freezing. Further literature regarding peptide handling protocols is cataloged in the National Library of Medicine databases (https://pubmed.ncbi.nlm.nih.gov/?term=aod+9604+peptide+stability).
| Physical State | Recommended Temperature | Observed Stability Window |
|---|---|---|
| Lyophilized Powder | -20°C to -80°C | Up to 24 months (when protected from ambient light and moisture) |
| Reconstituted Solution (Buffered) | 2°C to 8°C | 7 to 14 days (dependent on solvent selection) |
| Reconstituted Aliquots | -20°C | 30 to 60 days (strictly limiting to one thaw cycle per aliquot) |
Maintaining these environmental controls ensures that the primary sequence and secondary structures investigated in preclinical models remain consistent across experimental replicates. For expanded data on environmental sensitivities of modified hGH fragments, researchers consult centralized trial repositories (https://clinicaltrials.gov/search?term=aod+9604).
Analytical Methods: Verifying AOD-9604 Peptide Purity via HPLC and MS
High-Performance Liquid Chromatography (HPLC) and Mass Spectrometry (MS) function as the foundational analytical modalities for validating the structural integrity of AOD-9604 in laboratory settings. HPLC isolates the modified 15-amino-acid chain from synthesis byproducts, whereas MS confirms the precise molecular mass of 1815.1 Da. Together, these techniques verify the successful integration of the N-terminal tyrosine and the critical Cys182-Cys189 disulfide bridge required for structural stability in-vitro.
Reverse-Phase HPLC Separation of AOD-9604 from Synthesis Byproducts
In-vitro investigations demand highly purified compounds to prevent experimental artifacts. Reverse-phase HPLC (RP-HPLC) separates AOD-9604 from truncated peptides or deletion sequences generated during solid-phase peptide synthesis (SPPS). Using a non-polar C18 stationary phase, researchers elute the peptide via a gradient of water and acetonitrile containing trifluoroacetic acid (TFA) as an ion-pairing agent. The hydrophobic interactions specific to the Tyr-Leu-Arg-Ile-Val-Gln-Cys-Arg-Ser-Val-Glu-Gly-Ser-Cys-Gly sequence dictate its distinct retention time.
| HPLC Parameter | Typical Specification | Analytical Function |
|---|---|---|
| Stationary Phase | C18 Alkyl Chain Column | Retains hydrophobic peptide residues |
| Mobile Phase A | 0.1% TFA in H2O | Provides aqueous baseline for gradient |
| Mobile Phase B | 0.1% TFA in Acetonitrile | Elutes peptide based on hydrophobicity |
Electrospray Ionization Mass Spectrometry (ESI-MS) Validation of Molecular Mass
While HPLC confirms compound homogeneity, MS is required to authenticate the exact atomic composition. Electrospray Ionization (ESI) or MALDI-TOF mass spectrometry analyzes the peptide’s mass-to-charge ratio (m/z). The theoretical monoisotopic mass of AOD-9604 is approximately 1815.1 Da. MS detection is specifically required to confirm the formation of the intramolecular disulfide bond between the two cysteine residues, as an unoxidized (linear) fragment will present a mass shift of +2 Da due to the retained hydrogen atoms.
| Target Metric | Expected Value | Analytical Significance |
|---|---|---|
| Target Mass | 1815.1 g/mol | Confirms complete 15-AA sequence synthesis |
| Disulfide Status | -2 Da shift from linear | Verifies Cys182-Cys189 bridge formation |
| N-Terminal Verification | Presence of Tyrosine (+163 Da) | Distinguishes from native hGH 176-191 |
Correlating HPLC-MS Data for Research-Grade Purity Assurance
Combining HPLC chromatograms with MS spectra produces a comprehensive purity profile. This dual-method approach identifies common degradation products, such as deamidated glutamine, which could skew binding affinity assays. For laboratories evaluating high-purity AOD-9604 peptides for research, confirming a chromatographic purity of ≥98% alongside exact MS mass correlation ensures the compound’s behavior in lipolytic or chondrogenic cell culture models stems solely from the target molecule. Researchers validating these protocols often cross-reference baseline analytical parameters documented in the mass spectrometry literature.
| Common SPPS Impurity | HPLC Impact | MS Mass Shift |
|---|---|---|
| Linear (Unoxidized) Peptide | Shift in retention time | +2 Da |
| Deamidation (Gln to Glu) | Altered peak symmetry | +1 Da |
| Incomplete Deprotection | Delayed elution | Variable (+ protecting group mass) |
Current Literature Volume: PubMed Publications and Clinical Trials Data
AOD-9604 research volume remains heavily concentrated in preclinical, in-vitro, and structural biochemistry literature, with exactly 16 indexed articles on PubMed under its primary identifier and zero active or completed studies registered on ClinicalTrials.gov. The existing body of peer-reviewed data focuses predominantly on isolated cell models, evaluating lipolysis, lipogenesis, and chondrogenic differentiation mechanisms without translating into active human clinical trial pipelines.
Quantitative analysis of major scientific databases reveals a highly focused repository of peer-reviewed data. Searching the exact chemical nomenclature “AOD-9604” yields 16 results on PubMed, while the structural descriptor “growth hormone fragment 177-191” returns 13 indexed publications. Investigators sourcing literature on this modified C-terminal fragment will observe a complete absence of registered clinical investigations on ClinicalTrials.gov, reinforcing its classification as an exclusive subject of laboratory and cellular research.
| Search Query | Indexed PubMed Articles | Registered ClinicalTrials.gov Studies |
|---|---|---|
| AOD-9604 | 16 (View) | 0 (View) |
| growth hormone fragment 177-191 | 13 (View) | 0 (View) |
The indexed publications primarily detail in-vitro assays designed to isolate the specific receptor interactions of AOD-9604. Rather than systemic physiological outcomes, the available literature emphasizes cellular mechanics. Researchers frequently document the peptide binding profile, specifically interrogating its affinity for the beta-3 adrenergic receptor and its capacity to up-regulate lipolytic pathways in isolated 3T3-L1 adipocytes. Additional secondary research vectors identified in the PubMed database explore in-vitro chondrogenic models, measuring proteoglycan synthesis in isolated articular chondrocyte cultures.
| Research Domain | Mechanistic Focus | Typical In-Vitro Model |
|---|---|---|
| Lipid Metabolism | Lipolysis induction and lipogenesis inhibition | Isolated 3T3-L1 adipocytes |
| Chondrogenesis | Proteoglycan and collagen synthesis | Human or articular chondrocyte cultures |
| Structural Biochemistry | Disulfide bond stability (Cys178-Cys191) | Aqueous peptide solutions |
Because there are zero registered clinical trials, the scientific characterization of AOD-9604 relies entirely on rigorous analytical and cell-culture methodologies. Publications investigating this peptide utilize standardized biochemical assays to quantify its effects on cellular metabolism and structural integrity. Laboratory investigations prioritize the precise measurement of glycerol release as a proxy for triacylglycerol breakdown, alongside advanced liquid chromatography-mass spectrometry (LC-MS) to verify the stability of the critical Cys178-Cys191 disulfide bond under varying environmental stress parameters.
| Analytical Method | Measured Parameter | Literature Context |
|---|---|---|
| Glycerol Release Assay | Lipolytic activity rate | Quantifying triacylglycerol breakdown in fat cells |
| Mass Spectrometry (LC-MS) | Peptide integrity and degradation | Evaluating AOD-9604 stability under thermal stress |
| Western Blotting | Receptor up-regulation | Assessing beta-3 adrenergic receptor binding affinity |
Investigators compiling reference data on AOD-9604 must rely exclusively on these specialized preclinical publications. The current database constraints dictate that all mechanistic data regarding the peptide’s influence on lipid metabolism or cartilage matrix synthesis remain strictly confined to controlled in-vitro environments.
Future Directions in Adipose Tissue Research In-Vitro
Future in-vitro investigations into AOD-9604 prioritize mapping the exact intracellular signaling cascades that drive lipid oxidation independently of classical growth hormone receptors (GHR). Preclinical trajectories focus on quantifying glycerol release and free fatty acid mobilization in isolated adipocyte cultures using advanced mass spectrometry. By isolating the C-terminal 177-191 fragment’s interaction with secondary messenger systems, researchers aim to establish standard biochemical assays for non-receptor-mediated lipolysis.
How Do C-Terminal Fragments Modulate Fat Oxidation Independently of the Growth Hormone Receptor?
A primary objective for ongoing adipose tissue research involves defining the non-classical receptor interactions of AOD-9604. Because the peptide lacks the binding domains required to dimerize the human growth hormone receptor, its lipolytic mechanism of action relies on alternative cellular pathways. Current literature models suggest potential transient crosstalk with Beta-3 adrenergic receptors or downstream activation of cyclic adenosine monophosphate (cAMP) independent of primary neuroendocrine binding. Future laboratory frameworks will utilize receptor-knockout 3T3-L1 adipocyte lines to observe whether the peptide maintains the capacity to upregulate hormone-sensitive lipase (HSL) and perilipin phosphorylation in a GHR-null environment. To follow ongoing data regarding these specific pathways, investigators monitor queries such as https://pubmed.ncbi.nlm.nih.gov/?term=aod+9604+lipolysis+in+vitro.
| Proposed Intracellular Target | In-Vitro Observation Metric | Receptor Dependency |
|---|---|---|
| Hormone-Sensitive Lipase (HSL) | Phosphorylation levels via Western Blot | GHR-Independent |
| Beta-3 Adrenergic Receptor | cAMP accumulation via immunoassay | Partial / Investigational |
| Perilipin | Lipid droplet surface degradation rates | GHR-Independent |
What Are the Emerging Assays for Evaluating AOD-9604 in Primary Adipocyte Cultures?
Quantifying the lipolytic capacity of AOD-9604 demands highly controlled cellular environments. Future preclinical methodology is shifting toward 3D adipocyte spheroids, which replicate the spatial morphology of adipose tissue more accurately than standard 2D monolayers. Within these matrices, researchers evaluate cellular fat oxidation rates by measuring continuous glycerol efflux and mitochondrial oxygen consumption rates (OCR). Pairing these metrics with transcriptomic profiling of lipid-metabolism genes—specifically PPAR-gamma and CPT1A—allows investigators to isolate the exact phases of lipogenesis inhibition triggered by the synthetic fragment.
| Assay Methodology | Target Biomolecule / Metric | Research Application |
|---|---|---|
| Colorimetric Glycerol Assay | Extracellular Glycerol Efflux | Quantifying absolute lipolysis rates |
| Seahorse XF Cell Mito Stress Test | Oxygen Consumption Rate (OCR) | Measuring mitochondrial fat oxidation |
| RT-qPCR Transcriptomics | PPAR-gamma & CPT1A mRNA | Tracking lipogenesis inhibition signaling |
Can Synthetic Peptide Modifications Further Isolate Lipolytic Activity?
The structural foundation of AOD-9604—specifically the addition of an N-terminal tyrosine to the hGH 176-191 sequence—stabilizes the fragment against rapid proteolytic cleavage in cellular media. Future structural biochemistry seeks to determine if comparative amino acid substitutions within this isolated C-terminal fragment might alter its binding affinity or enzymatic degradation rate in-vitro. Tracking these structural variations requires rigorous comparative analysis against baseline hGH fragments. While primary mechanistic discovery occurs in the laboratory, researchers frequently track translational metabolic endpoints via registries such as https://clinicaltrials.gov/search?term=aod+9604 to align cellular assay parameters with systemic metabolic biomarker targets.
| Peptide Sequence Variant | Structural Modification | In-Vitro Research Objective |
|---|---|---|
| hGH 176-191 (Baseline) | Native C-terminal sequence | Establish baseline lipolytic control data |
| AOD-9604 | N-terminal Tyrosine addition | Evaluate prolonged half-life in media |
| C-Terminal Truncations | Removal of residues 188-191 | Identify minimum required lipolytic sequence |
Frequently Asked Questions About AOD-9604
What is the specific amino acid sequence of AOD-9604?
The sequence is Tyr-Leu-Arg-Ile-Val-Gln-Cys-Arg-Ser-Val-Glu-Gly-Ser-Cys-Gly-Phe. The N-terminal tyrosine is a synthetic addition to the naturally occurring 177-191 fragment of human growth hormone.
How does AOD-9604 structurally differ from full-length human growth hormone?
Full-length hGH consists of 191 amino acids and contains regions responsible for cellular proliferation and IGF-1 stimulation. AOD-9604 is limited to a modified 16-amino acid sequence from the C-terminus, entirely excluding the growth-signaling domains.
Does AOD-9604 peptide stimulate IGF-1 production?
Preclinical literature reports that AOD-9604 does not stimulate IGF-1 production. The peptide lacks the necessary structural domains to bind to the human growth hormone receptor in a manner that triggers the IGF-1 signaling cascade.
What is the difference between AOD-9604 and HGH Fragment 176-191?
While often used interchangeably in informal literature, they are structurally distinct. AOD-9604 specifically refers to the 177-191 sequence with an added N-terminal tyrosine, whereas HGH Fragment 176-191 begins at the 176th residue of endogenous hGH without the tyrosine modification.
By what mechanism is AOD-9604 reported to influence lipolysis?
In-vitro models suggest the peptide interacts with beta-3 adrenergic receptors on adipocytes. This interaction is reported to stimulate the breakdown of lipids and simultaneously inhibit lipogenesis.
Is AOD-9604 an FDA-approved therapeutic?
No. AOD-9604 is strictly a research chemical for laboratory use. While it previously achieved a self-affirmed Generally Recognized As Safe (GRAS) status as a food ingredient, it is not an approved medication for any condition.
How is AOD-9604 stored in laboratory environments?
Lyophilized AOD-9604 peptide is typically stored at -20°C to preserve structural integrity. Upon reconstitution in a laboratory setting, it requires continuous refrigeration to minimize peptide degradation.
Can AOD-9604 induce cellular proliferation or tumor growth in research models?
Laboratory investigations indicate that AOD-9604 does not exhibit the proliferative or anti-apoptotic effects associated with endogenous hGH. This safety profile is directly attributed to its inability to activate the IGF-1 pathway.