A practical reference on GLP-1 类似物: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
Reviewed 2025-07-30. Anything still debated is marked as such rather than presented as settled.
Receptor activation follows the canonical Gs pathway: binding increases intracellular cyclic AMP, which promotes protein kinase A activity. In pancreatic beta cells this amplifies glucose-dependent insulin release, so secretion rises when blood glucose is high and changes little when it is low. The same signalling suppresses glucagon release from alpha cells and slows gastric emptying. Receptors in the hypothalamus and brainstem are thought to contribute to reduced appetite and lower energy intake. Which of these effects dominates clinical outcomes remains an area of active study.
Semaglutide is a synthetic peptide analogue of glucagon-like peptide-1, a gut hormone released by intestinal L cells after food intake. The natural hormone acts on pancreatic and central receptors but is degraded within minutes by dipeptidyl peptidase-4 and other peptidases. Semaglutide belongs to the class of long-acting GLP-1 receptor agonists, a group distinguished by structural changes that slow breakdown and extend circulation time. Its development followed earlier short-acting analogues and reflects a general strategy in peptide drug design: preserve receptor activity while blocking proteolytic clearance.
Development began in the early 2010s with the goal of extending GLP-1 activity beyond the brief window achieved by native peptide infusion. The earliest approved formulation was a subcutaneous injection given once weekly. A later oral tablet pairs the peptide with an absorption enhancer, sodium N-(8-[2-hydroxybenzoyl] amino) caprylate, usually shortened to SNAC. That carrier lowers local pH and helps the peptide cross gastric tissue. Both routes deliver the same active molecule.
Semaglutide is a synthetic peptide analog of human glucagon-like peptide-1, a gut hormone released after meals. Its backbone retains the GLP-1 sequence but incorporates two substitutions that slow enzymatic breakdown by dipeptidyl peptidase-4. A short polyethylene glycol linker and a C18 fatty diacid are attached to the peptide chain, allowing the molecule to bind serum albumin and remain in circulation far longer than the native hormone. The result is a circulating half-life measured in days rather than the minutes typical of endogenous GLP-1.
Receptor activation occurs at GLP-1 receptors distributed across pancreatic islets, the hypothalamus, and the gastrointestinal tract. Binding triggers G protein signaling that raises cyclic AMP and enhances glucose-dependent insulin release. Because the effect depends on prevailing glucose levels, insulin secretion does not rise when blood sugar is already low. Signaling in the brain and gut also influences appetite and gastric emptying, which is why the compound appears in both metabolic and weight-related research literature.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C187H291N45O59 | free base, without counter-ion |
| Molecular weight | About 4114 Da | peptide backbone plus attached lipid chain |
| Plasma half-life | About 165 hours | supports once-weekly dosing in humans |
| Plasma protein binding | Greater than 99 percent | attributed mainly to serum albumin |
| Receptor target | GLP-1 receptor | Gs-coupled, raises intracellular cyclic AMP |
The semaglutide sequence is a 31-residue analogue of human GLP-1, altered at three positions relative to the parent hormone. Aminoisobutyric acid replaces alanine at position 8, arginine replaces lysine at position 34, and a lipophilic diacid is attached to lysine 26 through a short linker. These features are reported consistently in the structural literature. The position 8 substitution blocks recognition by dipeptidyl peptidase-4, while the attached chain drives strong, reversible association with a carrier protein in blood.
Receptor activation raises intracellular cyclic AMP through Gs coupling, which promotes glucose-dependent insulin release and suppresses glucagon secretion when blood glucose is elevated. Effects outside the pancreas include slower gastric emptying and altered appetite signalling in the hypothalamus and hindbrain. The relative contribution of each tissue to overall metabolic outcomes remains an area of active investigation. Central mechanisms in particular are inferred mainly from animal models and indirect human measures rather than direct observation.
Serum protein binding dominates the pharmacokinetic profile. The attached chain associates strongly with albumin, shielding the peptide from enzymatic attack and slowing filtration by the kidney. This interaction extends the circulation half-life to roughly one week in humans, which supports weekly administration intervals. An oral version pairs the peptide with an absorption enhancer that transiently alters gastric epithelium, permitting limited uptake; bioavailability by that route is substantially lower than by injection.
Material described as research-grade is not necessarily manufactured to pharmaceutical standards, and purity figures depend on the method used to obtain them. A certificate of analysis states the measured purity, the analytical technique, and the batch identifier, but the underlying data are not always included. Independent testing by a second laboratory is a common way to confirm identity and purity. Uncertainties remain about how storage history affects long-term stability, and about how well results from one laboratory transfer to another. Documentation of handling conditions supports comparison between batches.
Peptides are sensitive to temperature, light, oxygen, and repeated freeze-thaw cycles. Semaglutide in dry form is generally held at refrigerated temperatures, while reconstituted solutions require a defined short-term storage window. Vials should be kept in secondary packaging to limit photodegradation, and exposure to alkaline conditions is avoided because it accelerates chemical degradation. Adsorption to glass and some plastics can reduce the measured concentration of dilute solutions, so low-binding polypropylene containers are preferred for analytical work. Each transfer step introduces a small risk of contamination, and closed handling practices reduce that risk.
Routine characterisation of the peptide relies on reversed-phase high-performance liquid chromatography, often paired with ultraviolet detection near 214 nanometres. Related substances such as deamidated, oxidised, and truncated sequences elute at characteristic positions and are quantified by area percentage. Electrospray ionisation mass spectrometry confirms the molecular mass and can resolve some closely related variants. Peptide mapping after enzymatic digestion provides sequence-level verification and is useful when a full identity profile is required. Method parameters such as column chemistry, gradient, and mobile-phase pH influence the separation and must be reported alongside results.
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。
== PCSK subtypes == To date there are 9 PCSKs with varying functions and tissue distributions. Often, due to similar times of discovery from different groups the same PCSKs have acquired multiple names. In an attempt to alleviate confusion, there is a trend towards using the PCSK prefix with the appropriate number suffix.
=== Radioiodine === In iodine-131 (radioiodine) radioisotope therapy, which was first pioneered by Dr. Saul Hertz, radioactive iodine-131 is given orally (either by pill or liquid) on a one-time basis, to severely restrict, or altogether destroy the function of a hyperactive thyroid gland. This isotope of radioactive iodine used for ablative treatment is more potent than diagnostic radioiodine (usually iodine-123 or a very low amount of iodine-131), which has a biological half-life of 8–13 hours. Iodine-131, which also emits beta particles that are far more damaging to tissues at short range, has a half-life of approximately 8 days. People not responding sufficiently to the first dose are sometimes given an additional radioiodine treatment at a larger dose. Iodine-131 in this treatment is picked up by the active cells in the thyroid and destroys them, rendering the thyroid gland mostly or completely inactive. Since iodine is picked up more readily (though not exclusively) by thyroid cells, and (more importantly) is picked up even more readily by overactive thyroid cells, the destruction is local, and there are no widespread side effects with this therapy. Radioiodine ablation has been used for over 50 years, and the only major reasons for not using it are pregnancy and breastfeeding (breast tissue also picks up and concentrates iodine). Once the thyroid function is reduced, replacement hormone therapy (levothyroxine) taken each day orally replaces the thyroid hormone that is normally produced by the body.
=== Malachite green === Malachite green (also known as diamond green B or victoria green B) can be used as a blue-green counterstain to safranin in the Gimenez staining technique for bacteria. It can also be used to directly stain spores.
=== Cachexia and sarcopenia === Cachexia and sarcopenia are similar because both cause weight and muscle loss, along with symptoms like weakness and loss of appetite. The difference is sarcopenia is caused by aging, while cachexia happens due to long-term disease and inflammation.
The Socialist Party of the United States of America (also Socialist Party USA or SPUSA) is a socialist political party in the United States. SPUSA formed in 1973, one year after the Socialist Party of America splintered into three: Social Democrats, USA (legal successor); the Democratic Socialist Organizing Committee (split); and SPUSA. SPUSA describes itself as a multi-tendency socialist party which hopes to win socialism through a "democratic revolution from below". In contrast to the Democratic Socialists of America (DSA), SPUSA advocates for "uncompromising independence" from the Democratic Party. SPUSA describes socialism as "radical democracy", in opposition to "capitalist and authoritarian statist systems". Notable members include David McReynolds, Frank Zeidler, and Dan La Botz. Former members include Ben Burgis.
Sources: en.wikipedia.org
== See also == Bonding in solids Bresle method (the method used to test for salt presence during coating applications) Carboxylate Halide Ioliomics Ionic bonds Natron Salinity Salt metathesis reaction
Almost all proteins that are destined to the secretory pathway have a sequence consisting of 5-30 hydrophobic amino acids on the N-terminus, which is commonly referred to as the signal peptide, signal sequence or leader peptide. Signal peptides form alpha-helical structures. Proteins that contain such signals are destined for either extra-cellular secretion, the plasma membrane, the lumen or membrane of either the (ER), Golgi or endosomes. Certain membrane-bound proteins are targeted to the secretory pathway by their first transmembrane domain, which resembles a typical signal peptide. In prokaryotes, signal peptides direct the newly synthesized protein to the SecYEG protein-conducting channel, which is present in the plasma membrane. A homologous system exists in eukaryotes, where the signal peptide directs the newly synthesized protein to the Sec61 channel, which shares structural and sequence similarity with SecYEG, but is present in the endoplasmic reticulum. Both the SecYEG and Sec61 channels are commonly referred to as the translocon, and transit through this channel is known as translocation. While secreted proteins are threaded through the channel, transmembrane domains may diffuse across a lateral gate in the translocon to partition into the surrounding membrane.
== Pharmacology == Pirepemat shows affinity for several neurotransmitter receptors and transporters. These include the serotonin 5-HT7 receptor (Ki = 980 nM), the sigma σ1 receptor (Ki = 1,200 nM), the serotonin transporter (SERT) (Ki = 2,500 nM), the α2C-adrenergic receptor (Ki = 3,800 nM), the α2A-adrenergic receptor (Ki = 6,500 nM), the serotonin 5-HT2C receptor (Ki = 6,600 nM), the serotonin 5-HT2A receptor (Ki = 8,100 nM), and the norepinephrine transporter (NET) (Ki = 8,100 nM). It also shows affinity for the rat κ-opioid receptor (KOR) (Ki = 6,500 nM) and has weak affinity for the α1-adrenergic receptor (Ki = 21,000 nM). The drug was an antagonist or inhibitor at all assessed targets (which included some but not all of the preceding sites). Pirepemat has been described as a "cortical enhancer" and has been reported to region-specifically increase norepinephrine, dopamine, and acetylcholine levels in the cerebral cortex. Serotonin 5-HT7 receptor antagonism and α2-adrenergic receptor antagonism were hypothesized to underlie these effects. In animals, pirepemat has been found to reverse hypoactivity induced by the dopamine depleting agent tetrabenazine whilst not increasing basal locomotor activity and not affecting or minimally influencing dextroamphetamine- and dizocilpine-induced locomotor hyperactivity.
=== Solvent/detergent (S/D) inactivation === This process, developed by the New York Blood Center, is the most widely used viral inactivation method to date. It is predominantly used in the blood plasma industry, by over 50 organizations worldwide and by the American Red Cross. This process is only effective for viruses enveloped in a lipid coat, however. The detergents used in this method interrupt the interactions between the molecules in the virus's lipid coating. Most enveloped viruses cannot exist without their lipid coating so are destroyed when exposed to these detergents. Other viruses may not be destroyed but they are unable to reproduce rendering them non-infective. The solvent creates an environment in which the aggregation reaction between the lipid coat and the detergent happen more rapidly. The detergent typically used is Triton X-100. This process has many of the advantages of the "traditional" removal techniques. This process does not denature proteins, because the detergents only affect lipids and lipid derivatives. There is a 100% viral death achieved by this process and the equipment is relatively simple and easy to use. Equipment designed to purify post-virus inactivated material would be necessary to guard against contamination of subsequent process streams. S/D treatment utilizes readily available and relatively inexpensive reagents, but these reagents must be removed from the product prior to distribution which would require extra process steps.
== Chemistry == Edrophonium, ethyl-(3-hydroxyphenyl)dimethylammonium chloride, is made by reacting 3-dimethylaminophenol with ethyl bromide, which forms ethyl(3-hydroxyphenyl)dimethylammonium bromide, the bromine atom of which is replaced with a chlorine atom by reacting it with silver chloride, giving edrophonium.
Sources: en.wikipedia.org
An interesting feature of these phases is that both polar and nonpolar compounds can be retained over some range of mobile phase composition (organic/aqueous). The retention mechanism of polar compounds has recently been shown to be the result of the formation of a hydroxide layer on the surface of the silica hydride.[3] Thus positively charged analytes are attracted to the negatively charged surface and other polar analytes are likely to be retained through displacement of hydroxide or other charged species on the surface. This property distinguishes it from a pure HILIC (hydrophilic interaction chromatography) columns where separation by polar differences is obtained through partitioning into a water-rich layer on the surface, or a pure RP stationary phase on which separation by nonpolar differences in solutes is obtained with very limited secondary mechanisms operating. Another important feature of the hydride-based phases is that for many analyses it is usually not necessary to use a high pH mobile phase to analyze polar compounds such as bases. The aqueous component of the mobile phase usually contains from 0.1 to 0.5% formic or acetic acid, which is compatible with detector techniques that include mass spectral analysis.
Comparative genomics approaches were used to predict the function-relevant variants under the assumption that the functional genetic locus should be conserved across different species at an extensive phylogenetic distance. On the other hand, some adaptive traits and the population differences are driven by positive selections of advantageous variants, and these genetic mutations are functionally relevant to population specific phenotypes. Functional prediction of variants' effect in different biological processes is pivotal to pinpoint the molecular mechanism of diseases/traits and direct the experimental validation.
γ-Aminobutyric acid (GABA) prodrugs include progabide and tolgabide. Picamilon (N-nicotinoyl-GABA) has been claimed to be a prodrug of GABA, but has not actually been demonstrated to be converted into GABA. N-Benzoyl-GABA is of very similar chemical structure as picamilon and has also been claimed to be a prodrug of GABA, but this remains unclear similarly. Pivagabine (N-pivaloyl-GABA) was once thought to be a prodrug of GABA, but this proved not to be the case. Cetyl-GABA (GABA cetyl ester) is another prodrug of GABA. 4-Amino-1-butanol is known to be converted into GABA through the actions of aldehyde reductase (ALR) and aldehyde dehydrogenase (ALDH). 4-Amino-1-butanol is to GABA as 1,4-butanediol (4-hydroxy-1-butanol; 1,4-BD) is to γ-hydroxybutyric acid (GHB) (with 1,4-BD being a well-known prodrug of GHB). The metabolic intermediate γ-aminobutyraldehyde (GABAL) is also converted into GABA. A number of γ-hydroxybutyric acid (GHB) prodrugs are known. These include 1,4-butanediol (1,4-BD) and γ-butyrolactone (GBL), as well as the metabolic intermediate γ-hydroxybutyraldehyde (GHBAL).
34. Adv Gerontol. 2006;19:72-8. [Effect of age, different light conditions, melatonin, and epitalon on lysosomal proteinase activity in the liver and kidneys of rats]. [Article in Russian] Rendakov NL, Tiutiunnik NN, Vinogradova IA. Ageing, melatonin, epithalon (tetrapeptide Ala-Glu-Asp-Gly) and different light conditions effects on protein content and cathepsins B and D activities in rat liver and kidneys lysosomal fractions were studied. Ageing leads to decrease of cathepsins activity in rat liver lysosomal fractions. Constant light and darkness conditions result in earlier age decline of cathepsins activity. Absence of day and night succession in comparison with alternating light conditions causes decline of both general and specific cathepsin D activity. Melatonin and epithalon administration resulted in decrease of cathepsin D activity in liver only under control interchangeable light conditions. Cathepsin B activity in liver and kidneys lysosomal fractions declined in all experimental light conditions. Cathepsins activity decrease under the influence of epiphysial factors is evidently connected with their inhibitory effect on protein and general metabolism.
A common gelling agent in cooking, different types and grades of gelatin are used in a wide range of food and nonfood products. Common examples of foods that contain gelatin are jellos, trifles, aspic, marshmallows, candy corn, and confections such as Peeps, gummy bears, fruit snacks, and jelly babies. Gelatin may be used as a stabilizer, thickener, or texturizer in foods such as yogurt, cream cheese, and margarine; it is used, as well, in fat-reduced foods to simulate the mouthfeel of fat and to create volume. It also is used in the production of several types of Chinese soup dumplings, specifically Shanghainese soup dumplings, or xiaolongbao, as well as Shengjian mantou, a type of fried and steamed dumpling. The fillings of both are made by combining ground pork with gelatin cubes, and in the process of cooking, the gelatin melts, creating a soupy interior with a characteristic gelatinous stickiness. Gelatin is used for the clarification of juices, such as apple juice, and of vinegar. Isinglass is obtained from the swim bladders of fish. It is used as a fining agent for wine and beer. Besides hartshorn jelly, from deer antlers (hence the name "hartshorn"), isinglass was one of the oldest sources of gelatin.
Sources: en.wikipedia.org
Native GLP-1 is a short-lived peptide cleared within one to two minutes by dipeptidyl peptidase-4 and related enzymes. Semaglutide keeps the receptor-binding backbone but adds substitutions and a lipid chain. These changes block the main cleavage site and allow reversible albumin binding, extending the half-life to roughly 165 hours.
Albumin is the most abundant protein in plasma and carries molecules that bear fatty-acid chains. Binding shields the peptide from renal filtration and from peptidases, keeping a circulating reservoir. Slow release from this reservoir produces sustained receptor occupancy and supports infrequent dosing.
The insulinotropic effect is glucose-dependent, meaning secretion increases mainly when glucose is elevated. This property is often described as lowering the chance of hypoglycaemia when the compound is used alone. Other glucose-lowering agents used at the same time can still cause low blood glucose.
Native GLP-1 is degraded within minutes by circulating enzymes. The synthetic version carries substitutions at positions that block enzymatic cleavage, plus a fatty acid side chain that promotes albumin binding. These two changes together extend circulation time from minutes to roughly a week.