incretin comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Last reviewed on 2026-01-12. Where a claim depends on a specific study, the study is described rather than over-claimed.
皮下注射后吸收相对缓慢，绝对生物利用度约为百分之八十九，血药浓度峰值通常出现在给药后一到三天。与白蛋白结合使清除减慢，终末半衰期约为一百六十五小时，接近一周。连续给药约四到五周后达到稳态暴露水平。表观分布容积约为每千克零点二五升，血浆蛋白结合率超过百分之九十九。代谢以蛋白水解切割和脂肪二酸侧链的 β-氧化为主，相关产物主要经尿液与粪便排出。
序列层面的改动同时解决了两个问题，即酶解稳定性与肾脏清除速度。天然 GLP-1 在循环中的半衰期仅约两分钟，主要被二肽基肽酶-4 迅速灭活。酰化侧链与白蛋白的可逆结合形成循环储库，使分子缓慢释放并持续激活受体。这种设计思路后来被广泛用于同类长效肽的开发，属于该类药物化学改造的典型范式。
Semaglutide 是一种经结构修饰的胰高血糖素样肽-1 类似物，其主链与内源性 GLP-1(7-36) 约有百分之九十四的序列一致性。第 8 位丙氨酸被 α-氨基异丁酸取代，使二肽基肽酶-4 无法识别原有切割位点。第 34 位赖氨酸换为精氨酸，进一步降低酶解速率。第 26 位赖氨酸经间隔基连接一条含十八个碳的二酸脂肪链，该侧链赋予分子与血浆白蛋白结合的能力。
Stability studies examine how temperature, pH, and moisture influence degradation rates over time. In aqueous solution, hydrolysis and deamidation accelerate as pH moves away from mildly acidic conditions. Light exposure and residual metal ions can also trigger oxidation of susceptible residues. Accelerated aging at elevated temperature is used to estimate shelf life, though extrapolation to room temperature carries uncertainty because individual degradation pathways do not always scale predictably.
Lyophilized semaglutide powder is typically held at minus twenty degrees Celsius for long-term storage. At that temperature, solid-state degradation reactions proceed slowly and the peptide remains intact for extended periods. Repeated freeze-thaw cycles are best avoided because they promote aggregation and can shift the proportion of monomeric peptide present. Working aliquots are often prepared so that each portion is thawed only once, and desiccant is placed inside the vial to limit moisture uptake.
| Property | Value | Notes |
|---|---|---|
| 分子式 | C187H291N45O59 | 按主链与 C18 二酸侧链计算 |
| 分子量 | 约 4113.6 道尔顿 | 游离碱形式，随反离子略有差异 |
| 外观 | 白色至类白色冻干粉末 | 具吸湿性，需干燥保存 |
| 溶解性 | 微溶于水，易溶于碱性缓冲液 | 溶解性随 pH 升高而改善 |
| 等电点 | 约 5.4 | 影响缓冲液选择与聚集倾向 |
Two principal therapeutic variants exist under separate regulatory filings, one indicated for glycemic control in type 2 diabetes and one for chronic weight management. Both use the same active molecule; differences lie in formulation strength, titration schedule, and labeling. Regulatory agencies in the United States and European Union approved injectable forms in 2017 and 2018 respectively. An oral tablet formulation received approval later, using a carrier molecule to enhance absorption across the gastric epithelium. Labeling differs by jurisdiction and by indication.
The distinction between established facts and open questions matters here. That the peptide binds the GLP-1 receptor and stimulates insulin release in a glucose-dependent manner is well documented. How individual variability in receptor density, gastric emptying rate, and gut microbiome composition shapes response remains an active research area. Long-term outcomes beyond five years of continuous use are not yet fully characterized in published trials, and several extension studies are ongoing.
Pharmacological activity arises from agonism at the glucagon-like peptide-1 receptor, a G protein-coupled receptor expressed in the pancreas, the gastrointestinal tract, and the brainstem. Receptor activation raises intracellular cyclic adenosine monophosphate and enhances insulin release in a glucose-dependent manner, an effect that diminishes when blood glucose concentration is low. Other effects include slowed gastric emptying and hypothalamic satiety signalling. These pathways are described well. Receptor desensitisation rates across tissues, relative to the endogenous hormone, are still under investigation, and reported findings differ between laboratories.
The company that developed the compound filed it as a long-acting analogue, and it gained first approval in 2017 for type 2 diabetes. Later authorisations from several regulators extended the indication to chronic weight management, and the World Health Organization added the glucagon-like peptide-1 receptor agonist drug class to its model list of essential medicines in 2023. Production uses solid-phase peptide synthesis followed by side-chain conjugation and chromatographic purification. Supply constraints and cost differences across regions are well documented. Literature on long-term outcomes continues to grow, with many trials reporting surrogate endpoints rather than hard clinical endpoints.
Semaglutide is a synthetic peptide of thirty-one amino acids that shares roughly ninety-four percent sequence identity with human glucagon-like peptide-1. Two substitutions resist enzymatic cleavage by dipeptidyl peptidase-4, and a fatty diacid side chain attached through a linker promotes binding to serum albumin. That albumin binding slows renal clearance and extends the circulating half-life from minutes to approximately one week. The structural changes are well established in the published literature. Whether the same modifications affect receptor signalling bias in ways that matter clinically remains an open question.
Two structural features account for the prolonged half-life of semaglutide. A modified amino acid at position 8 resists cleavage by dipeptidyl peptidase-4, the enzyme that rapidly degrades native GLP-1. A fatty diacid side chain binds serum albumin, which limits renal clearance and protects the peptide from enzymatic breakdown. These modifications yield a plasma half-life of approximately one week in humans, allowing once-weekly administration. The relationship between plasma concentration and clinical effect varies between individuals, and sources of that variability are still being characterized.
Semaglutide is a synthetic peptide analog of glucagon-like peptide-1 (GLP-1), a hormone released from intestinal L-cells after food intake. The compound belongs to the incretin mimetic class and acts at GLP-1 receptors distributed across pancreatic, gastrointestinal, cardiovascular, and central nervous system tissues. Compared with native GLP-1, the molecule carries structural changes that extend its activity from minutes to roughly one week. It is studied for glycemic control in type 2 diabetes and for weight management, and its effects on cardiovascular and other outcomes remain active research areas.
Clinical development of this compound followed earlier short-acting GLP-1 analogues that required frequent injection. Once-weekly subcutaneous formulations entered use after 2017, and an oral formulation using a permeation enhancer later became available. The oral version pairs the peptide with sodium N-(8-[2-hydroxybenzoyl] amino) caprylate, a carrier that improves uptake across the gastric epithelium. Interest has expanded from glycaemic control into weight management and metabolic liver disease. Regulatory status and approved indications differ between countries, and the product remains subject to ongoing safety monitoring.
Semaglutide is a synthetic peptide that acts as an agonist at the glucagon-like peptide-1 receptor. It is a structural analogue of human GLP-1(7-37), modified to resist enzymatic degradation by dipeptidyl peptidase-4. The peptide backbone contains alpha-aminoisobutyric acid at position 8, a substitution that stabilises the helix and slows cleavage. A fatty diacid side chain attached through a linker at lysine 34 promotes binding to serum albumin, which extends the circulating half-life. These two modifications together allow less frequent administration than native GLP-1 requires.
=== Proteins === Proteins present in the hemolymph vary in quantity during the course of development. These proteins are classified by their functions: chroma proteins, protease inhibitors, storage, lipid transport, enzymes, the vitellogenins, and those involved in the immune responses of arthropods. Some hemolymphic proteins incorporate carbohydrates and lipids into the structure.
=== Service with other air forces === After World War II, the P-51 Mustang served in the air arms of more than 25 nations. During the war, a Mustang cost about $51,000, while many hundreds were sold postwar for the nominal price of one dollar to signatories of the Inter-American Treaty of Reciprocal Assistance, ratified in Rio de Janeiro in 1947. These countries used the P-51 Mustang:
Ramelteon has no appreciable affinity for the GABA receptors or for receptors that bind neuropeptides, cytokines, serotonin, dopamine, noradrenaline, acetylcholine, and opioids. Ramelteon also does not interfere with the activity of a number of selected enzymes in a standard panel.
Brainshuttle or brain shuttle is a technology developed by Roche to help molecules such as monoclonal antibodies to cross the blood-brain barrier more than they would otherwise. It has been tested with anti-amyloid monoclonal antibodies such as trontinemab.
==== Neurological diseases ==== RNAi strategies also show potential for treating neurodegenerative diseases. Studies in cells and in mouse have shown that specifically targeting Amyloid beta-producing genes (e.g. BACE1 and APP) by RNAi can significantly reduced the amount of Aβ peptide which is correlated with the cause of Alzheimer's disease. In addition, this silencing-based approaches also provide promising results in treatment of Parkinson's disease and Polyglutamine disease.
Sources: en.wikipedia.org
coli and Salmonella typhimurium and has since been demonstrated in many other bacterial cells. It was found that bacteria use histidine and aspartate phosphorylation as a model for bacterial signaling transduction. Serine, threonine and tyrosine phosphorylation are also present in bacteria. Bacteria carry kinases and phosphatases similar to that of their eukaryotic equivalent and have also developed unique kinases and phosphatases not found in eukaryotes.
The genome of a given organism contains thousands of genes, but not all these genes need to be active at any given moment. A gene is expressed when it is being transcribed into mRNA and there exist many cellular methods of controlling the expression of genes such that proteins are produced only when needed by the cell. Transcription factors are regulatory proteins that bind to DNA, either promoting or inhibiting the transcription of a gene. Within the genome of Escherichia coli bacteria, for example, there exists a series of genes necessary for the synthesis of the amino acid tryptophan. However, when tryptophan is already available to the cell, these genes for tryptophan synthesis are no longer needed. The presence of tryptophan directly affects the activity of the genes—tryptophan molecules bind to the tryptophan repressor (a transcription factor), changing the repressor's structure such that the repressor binds to the genes. The tryptophan repressor blocks the transcription and expression of the genes, thereby creating negative feedback regulation of the tryptophan synthesis process.
And there were more flash points outside of the war. On 6 May 1902 at Holkrantz in the southeastern Transvaal, a Zulu faction had their cattle stolen and their women and children tortured by the Boers as a punishment for assisting the British. The local Boer officer then sent an insulting message to the tribe, challenging them to take back their cattle. The Zulus attacked at night, and in a mutual bloodbath, the Boers lost 56 killed and 3 wounded, while the Indigenous Africans suffered 52 killed and 48 wounded. About 10,000 black men were attached to Boer units where they performed camp duties; a handful unofficially fought in combat. The British Army employed over 14,000 Indigenous Africans as wagon drivers. Even more had combatant roles as spies, guides, and eventually as soldiers. By 1902 there were about 30,000 armed Indigenous Africans in the British Army. Sol Plaatje was the only black person to keep a diary during the war, which later proved to be a valuable source about the black participation in the war.
Cultivation of microorganisms does not require fertile soil and therefore does not compete with agriculture. Thanks to the low water requirements, SCP cultivation can even be done in dry climates with infertile soil and may provide a means of fail-safe food supply in arid countries. Photosynthetic microorganisms can reach a higher solar-energy-conversion efficiency than plants, because in photobioreactors supply of water, CO2 and a balanced light distribution can be tightly controlled. Unlike agricultural products which are processed towards a desired quality, it is easier with microorganisms to direct production towards a desired quality. Instead of extracting amino acids from soy beans and throwing away half of the plant body in the process, microorganisms can be genetically modified to overproduce or even secrete a particular amino acid. However, in order to keep a good consumer acceptance, it is usually easier to obtain similar results by screening for microorganisms which already have the desired trait or train them via selective adaptation. Although SCP shows very attractive features as a nutrient for humans, however there are some problems that deter its adoption on global basis:
These are generally substituted anthraquinones; many have medicinal applications, being used as purgatives, while one, ruberythric acid, yields the valuable dyestuff madder, the base of which is alizarin. Chrysophanic acid, a dioxymethylanthraquinone, occurs in rhubarb, which also contains emodin, a trioxymethylanthraquinone; this substance occurs in combination with rhamnose in Frangula bark. A recent study suggests, that purified anthraquinone glycosides from rhubarb could be a potential therapeutic avenue to treat type 2 diabetes mellitus by modulating the gut microbiota and reducing systematic inflammation. Arguably the most important cyanogenic glucoside is amygdalin, which occurs in bitter almonds. The enzyme maltase decomposes it into glucose and mandelic nitrile glucoside; the latter is broken down by emulsin into glucose, benzaldehyde and prussic acid. Emulsin also decomposes amygdalin directly into these compounds without the intermediate formation of mandelic nitrile glucoside. Several other glucosides of this nature have been isolated. The saponins are a group of substances characterized by forming a lather with water; they occur in soap-bark. Mention may also be made of indican, the glucoside of the indigo plant; this is hydrolysed by the indigo ferment, indimulsiri, to indoxyl and indiglucin.
Sources: en.wikipedia.org
=== First Trump administration (2017–2021) === On August 13, 2018, Section 1051 of the Fiscal Year 2019 John S. McCain National Defense Authorization Act (P.L. 115-232) established the National Security Commission on Artificial Intelligence "to consider the methods and means necessary to advance the development of artificial intelligence, machine learning, and associated technologies to comprehensively address the national security and defense needs of the United States." Steering on regulating security-related AI is provided by the National Security Commission on Artificial Intelligence. The Artificial Intelligence Initiative Act (S.1558) is a proposed bill that would establish a federal initiative designed to accelerate research and development on AI for, inter alia, the economic and national security of the United States. On January 7, 2019, following an Executive Order on Maintaining American Leadership in Artificial Intelligence, the White House's Office of Science and Technology Policy released a draft Guidance for Regulation of Artificial Intelligence Applications, which includes ten principles for United States agencies when deciding whether and how to regulate AI. In response, the National Institute of Standards and Technology (NIST) released a position paper, and the Defense Innovation Board issued recommendations on the ethical use of AI. A year later, the administration called for comments on regulation in another draft of its Guidance for Regulation of Artificial Intelligence Applications.
== Undergraduate Research Program == The College of Science and Technology offers the CST Undergraduate Research Program (URP). Students selected to participate work with a faculty sponsor to perform research in the faculty member's lab. Students may be asked to participate in conferences, author papers or to showcase their research work in the department or at the URP Research Symposium.
== Chemistry == Etifoxine is a nonbenzodiazepine—that is, it is similarly a GABAA receptor positive allosteric modulator but its chemical structure is distinct from that of benzodiazepines. Instead, it is a benzoxazine derivative.
=== Absorption === The oral bioavailability of testosterone is very low. The bioavailability of oral testosterone undecanoate is 3 to 7%. Topical testosterone gels have a bioavailability of about 8 to 14% when administered to recommended skin sites including the abdomen, arms, shoulders, and thighs. The bioavailability of testosterone by subcutaneous implant is virtually 100%. The bioavailability of drugs that are administered intramuscularly is generally almost 95%.
Sources: en.wikipedia.org
差别集中在三处：第 8 位残基被非天然氨基酸取代，第 34 位换成精氨酸，第 26 位增加一条脂肪酸侧链。前两处改动降低酶解速率，侧链则通过白蛋白结合延长循环时间。综合结果是半衰期从约两分钟延长到约一周。
胰岛素释放需要细胞内环腺苷酸与钙信号升高，同时依赖葡萄糖代谢产生的协同信号。血糖水平较低时协同信号不足，分泌增强有限。这一机制在降糖效果与低血糖风险之间提供了缓冲。
白蛋白结合是主要原因，它减少肾小球滤过并保护分子免受蛋白酶降解。序列修饰带来的酶解抵抗同样不可忽略，二者共同作用。脂肪链的疏水性还会影响组织分布，但其对总半衰期的贡献程度仍在研究之中。
Manufacturers commonly state multi-year stability when the powder is kept dry and frozen. Actual shelf life depends on residual moisture, vial sealing, and storage temperature. A re-test by chromatography is the only way to confirm remaining purity.