incretin raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
This page was last updated on 2026-05-21 and is reviewed periodically as new material appears.
Three structural changes define the molecule. At position 8 an alpha-aminoisobutyric acid residue replaces alanine, which blocks dipeptidyl peptidase-4 cleavage. At position 34 arginine replaces lysine, and at position 26 a lysine carries a C18 fatty diacid attached through a short linker. The fatty chain binds serum albumin, and this albumin association reduces renal filtration and enzymatic attack. The unchanged backbone retains the receptor contacts that produce signalling. The free base has the formula C187H291N45O59 and a molecular weight near 4114 daltons.
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.
Reverse-phase high-performance liquid chromatography is the standard method for purity assessment, separating the peptide from truncated or oxidized variants. Mass spectrometry confirms molecular mass and detects modifications, while ultraviolet absorbance near 280 nanometers supports concentration measurement through tryptophan and tyrosine residues. Circular dichroism can indicate secondary structure, though the peptide is largely helical in solution, and ion-exchange chromatography resolves charge variants. Purity values above 95 percent are typical for research-grade material. Stability studies track degradation over time under defined conditions.
Lyophilized semaglutide is typically stored at temperatures between minus 20 and minus 80 degrees Celsius for long-term preservation. Short-term storage at 2 to 8 degrees Celsius is common for working aliquots. Repeated freeze-thaw cycles can degrade the peptide and are usually avoided. The molecule is hygroscopic in its solid form, so containers should remain sealed with desiccant. Solutions are less stable than powders and are generally prepared fresh. Light exposure is limited because aromatic residues can undergo photo-oxidation.
| 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 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.
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。
Large randomised trials in adults with type 2 diabetes and in adults with obesity have reported reductions in body weight and improvements in several cardiovascular risk markers. One outcome trial found a lower incidence of major adverse cardiovascular events in participants with diabetes and established cardiovascular disease. Gastrointestinal effects such as nausea and vomiting are the most frequently reported adverse events and often diminish over time. Changes in lean body mass during weight loss are an area of ongoing investigation. Effects in adolescents and in pregnancy are less well characterised, and current labelling advises against use during pregnancy.
Semaglutide is a synthetic peptide analogue of glucagon-like peptide-1, a gut hormone released after nutrient intake. The molecule contains 31 amino acid residues and differs from the native sequence at several positions. A non-natural residue at position eight resists the enzyme that normally truncates the hormone, while a lysine-linked fatty diacid side chain promotes binding to serum albumin. These two modifications extend the circulating half-life from minutes to roughly one week. The peptide is produced by solid-phase synthesis followed by selective acylation, and its identity and purity are confirmed by spectrometric and chromatographic techniques.
=== China === In China, Pizza Hut (simplified Chinese: 必胜客; traditional Chinese: 必勝客; pinyin: Bìshèng Kè) used an altered business model, offering a fine-dining atmosphere with knives and forks and using an expanded menu catering to Chinese tastes. Its first location in the Chinese market opened in Beijing in 1990. By 2008, Pizza Hut operated restaurants and delivery locations. That year, the company introduced "Pizza Hut Express", opening locations in Shanghai, Shenzhen, and Hangzhou. The 160 restaurants were in 40 Chinese cities in 2005. As of 2015, Pizza Hut had 1,903 restaurants in China. By June 2023, there were 3,000 stores. As of the end of September 2025, Pizza Hut has over 4,000 outlets in over 1,000 cities. Savio S. Chan (陳少宏, Pinyin: Chén Shàohóng) and Michael Zakkour, authors of China's Super Consumers: What 1 Billion Customers Want and How to Sell it to Them, stated middle-class Chinese perceive Pizza Hut as "akin to fine dining", though Pizza Hut was "China's largest and most successful foreign casual-dining chain".
== Clinical significance == Increased and supraphysiological ER stress in pancreatic β cells disrupts normal insulin secretion, leading to hyperinsulinemia and consequently peripheral insulin resistance associated with obesity in humans. Human clinical trials also suggested a causal link between obesity-induced increase in insulin secretion and peripheral insulin resistance. Abnormalities in XBP1 lead to a heightened endoplasmic reticulum stress response and subsequently causes a higher susceptibility for inflammatory processes that may even contribute to Alzheimer's disease. In the colon, XBP1 anomalies have been linked to the inflammatory bowel diseases including Crohn's disease. The unfolded protein response (UPR) is a cellular stress response related to the endoplasmic reticulum. The UPR is activated in response to an accumulation of unfolded or misfolded proteins in the lumen of the endoplasmic reticulum. The UPR functions to restore normal function of the cell by halting protein translation, degrading misfolded proteins, and activating the signaling pathways that lead to increasing the production of molecular chaperones involved in protein folding. Sustained overactivation of the UPR has been implicated in prion diseases as well as several other neurodegenerative diseases and the inhibition of the UPR could become a treatment for those diseases.
Epidemiological studies have shown a clear association between breathing high concentrations of radon and incidence of lung cancer. Radon is a contaminant that affects indoor air quality worldwide. Because radon is denser than air it accumulates in basements and crawlspaces under dwellings. According to the United States Environmental Protection Agency (EPA), radon is the second most frequent cause of lung cancer, after cigarette smoking, causing 21,000 lung cancer deaths per year in the United States. About 2,900 of these deaths occur among people who have never smoked. While radon is the second most frequent cause of lung cancer, it is the number one cause among non-smokers, according to EPA policy-oriented estimates. Significant uncertainties exist for the health effects of low-dose exposures. Due to local differences in geology, the level of exposure to radon gas differs by location.
== History == The concept of residence time originated in models of chemical reactors. The first such model was an axial dispersion model by Irving Langmuir in 1908. This received little attention for 45 years; other models were developed such as the plug flow reactor model and the continuous stirred-tank reactor, and the concept of a washout function (representing the response to a sudden change in the input) was introduced. Then, in 1953, Peter Danckwerts resurrected the axial dispersion model and formulated the modern concept of residence time.
Has written for The Guardian London Review of Books, Red Pepper (magazine), Novara Media, Radical Philosophy, and has worked with Jews for Justice for Palestinians, Independent Jewish Voices and Faculty for Israeli–Palestinian Peace (FFIPP) engaged in efforts to end the Israeli occupation of Palestinian land and create a just peace between Israel and Palestine. Anthony Seldon (born 2 August 1953); educator, contemporary historian, journalist, broadcaster, academic, author, wrote biographies of British Prime Ministers, John Major, Tony Blair, Gordon Brown, David Cameron, Theresa May and Boris Johnson; was master (headmaster) of Wellington College, one of Britain's co-educational independent boarding schools, and is current Head Master of Epsom College; is author or editor of more than 45 books on contemporary history, politics and education; was co-founder and first director of Centre for Contemporary British History; co-founder of Action for Happiness, is a governor of the Royal Shakespeare Company, and is on board of a number of charities and educational bodies; is honorary historical adviser to 10 Downing Street and member of the First World War Centenary Culture Committee; was knighted in the 2014 Birthday Honours for services to education and modern political history.
Sources: en.wikipedia.org
== Early life == Markin was born and raised in Lincoln, Nebraska. He received a Bachelor of Science degree in 1977 from Nebraska Wesleyan University, where he majored in chemistry with minors in mathematics and physics. He received a Ph.D. in chemistry from the University of Nebraska–Lincoln in 1980; he earned his medical degree from the University of Nebraska Medical Center (UNMC) in 1983; he completed his residency in pathology and laboratory medicine at UNMC in 1986. He has been on the UNMC faculty since 1986. His professional and academic research interests have focused on clinical laboratory automation including robotics, information systems, medical utilization management, business efficiency modeling, adult and pediatric pathology, liver/gastrointestinal pathology, telehealth, telemedicine, technology development and mobile health.
== See also == Loperamide - an μ-opioid receptor agonist that doesn't cross the BBB in significant amounts, and treats diarrhea (in contrast to methynaltrexone, a Mu-opioid receptor antagonist that doesn't cross the BBB, avoiding opiate withdrawal effects in patients, while treating constipation) Naloxegol (trade names Movantik and Moventig) - another peripherally selective opioid antagonist used to treat opioid-induced constipation (+)-Naloxone - a non-opioid drug which also reduces some side effects of opioids without significantly affecting analgesia when used in small oral doses 6β-Naltrexol (6α-hydroxynaltrexone) - another naltrexone derivative that is also a peripherally selective opioid antagonist
It appears that (cancer-mediated) upregulation of PD-L1 on the cell surface may inhibit T cells that might otherwise attack. PD-L1 on cancer cells also inhibits FAS- and interferon-dependent apoptosis, protecting cells from cytotoxic molecules produced by T cells. Antibodies that bind to either PD-1 or PD-L1 and therefore block the interaction may allow the T-cells to attack the tumor.
=== Starships and warp drives === Starships are living spaces, vehicles and ambassadors of the Culture. A proper Culture starship (as defined by hyperspace capability and the presence of a Mind to inhabit it) may range from several hundreds of metres to hundreds of kilometres. The latter may be inhabited by billions of beings and are artificial worlds in their own right, including whole ecosystems, and are considered to be self-contained representations of all aspects of Culture life and capability. The Culture (and most other space-faring species in its universe) use a form of Hyperspace-drive to achieve faster-than-light speeds. Banks has evolved a (self-confessedly) technobabble system of theoretical physics to describe the ships' acceleration and travel, using such concepts as "infraspace" and "ultraspace" and an "energy grid" between universes (from which the warp engines "push off" to achieve momentum). An "induced singularity" is used to access infra or ultra space from real space; once there, "engine fields" reach down to the Grid and gain power and traction from it as they travel at high speeds. These hyperspace engines do not use reaction mass and hence do not need to be mounted on the surface of the ship. They are described as very dense exotic matter, which only reveals its complexity under a powerful microscope. Acceleration and maximum speed depend on the ratio of the mass of the ship to its engine mass. As with any other matter aboard, ships can gradually manufacture extra engine volume or break it down as needed.
=== Later career === During World War II, Mester worked as a surgeon at Saint John's Hospital and in the "Rock Hospital", located in the tunnels underneath Castle Hill in Budapest. Mester chaired the Surgery Department of the Bajcsy Zsilinszky Teaching Hospital in Budapest from 1947 until 1963. He publicly welcomed the 1956 Hungarian uprising against Communism yet, when it failed, he was not persecuted because of his important medical work. In 1963, he became Professor and Department Chair at the Semmelweis Medical University in Budapest, and worked there until his retirement in 1973. In 1971, he received the "Doctor of Sciences" title from the Hungarian Academy of Sciences.
Sources: en.wikipedia.org
Chain brake A chain brake activator is located forward of the upper handle and is activated by a kickback event. When triggered, it tensions a band around the clutch drum, stopping the chain within milliseconds. A chain catcher is located between the saw body and the clutch cover. In most cases, it resembles a hook made of aluminum. It is used to stop the chain when it derails from the bar and shortens the length of the chain. When derailing, the chain swings from underneath the saw towards the operator. This prevents the chain from hitting the operator, which hits the rear handle guard instead. A rear handle guard protects the hand of the operator when the chain derails. Some chains have safety links, as on micro chisel saws. These links keep the saw close to the gap between two cutting links and lift the chain when the space at the safety link is full with saw chips, which lifts the chain and lets it cut slower. Nonprofessional chains have less aggressive teeth, by having shallower depth gauges.
Atmosphere of the Sun: in detectable trace amounts Atmosphere of Mercury: 3.4%, and large amounts of water in Mercury's exosphere Atmosphere of Venus: 0.002% Earth's atmosphere: ≈0.40% over full atmosphere, typically 1–4% at surface Atmosphere of the Moon: in trace amounts Atmosphere of Mars: 0.03% Atmosphere of Ceres Atmosphere of Jupiter: 0.0004% – in ices only; and that of its moon Europa Atmosphere of Saturn – in ices only; Enceladus: 91% and Dione (subsurface ocean) Atmosphere of Uranus – in trace amounts below 50 bar Atmosphere of Neptune – found in the deeper layers Extrasolar planet atmospheres: including those of HD 189733 b and HD 209458 b, Tau Boötis b, HAT-P-11b, XO-1b, WASP-12b, WASP-17b, and WASP-19b. Stellar atmospheres: not limited to cooler stars and even detected in giant hot stars such as Betelgeuse, Mu Cephei, Antares and Arcturus. Circumstellar disks: including those of more than half of T Tauri stars such as AA Tauri as well as TW Hydrae, IRC +10216 and APM 08279+5255, VY Canis Majoris and S Persei.
The enzyme characterised from Escherichia coli combines adenosine triphosphate and nicotinate mononucleotide to give deamido-NAD, a precursor to the coenzyme, nicotinamide adenine dinucleotide (NAD). Pyrophosphate (PPi) is a byproduct. In organisms which use this biosynthetic pathway to NAD, the final step is an amidation reaction. This enzyme belongs to the family of transferases, specifically those transferring phosphorus-containing nucleotide groups (nucleotidyltransferases). The systematic name of this enzyme class is ATP:nicotinate-ribonucleotide adenylyltransferase. Other names in common use include deamido-NAD+ pyrophosphorylase, nicotinate mononucleotide adenylyltransferase, deamidonicotinamide adenine dinucleotide pyrophosphorylase, NaMN-ATase, and nicotinic acid mononucleotide adenylyltransferase.
vector Any DNA molecule used as a vehicle to artificially transport foreign genetic material into another cell, where it can be replicated and/or expressed. Vectors are typically engineered recombinant DNA sequences consisting of an insert (often a transgene) and a longer "backbone" sequence containing an origin of replication, a multiple cloning site, and a selectable marker. Vectors are widely used in molecular biology laboratories to isolate, clone, or express the insert in the target cell.
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.
Long-term storage is usually at minus 20 to minus 80 degrees Celsius in a sealed, desiccated container. Working aliquots can be held briefly at 2 to 8 degrees Celsius.