Aib substitution is one of those subjects where the details matter more than the headlines. This page pulls together the background, the mechanisms, and the practical points readers ask about most.
Updated 2026-08-01. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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。
该分子作为 GLP-1 受体的选择性激动剂发挥作用，受体属于 B 类 G 蛋白偶联受体家族，激活后经 Gs 通路提升细胞内环腺苷酸水平。在胰腺 β 细胞，信号促进葡萄糖依赖性的胰岛素释放，血糖偏低时该作用明显减弱。在胰岛 α 细胞，胰高血糖素分泌受到抑制。中枢神经系统与胃肠道同样存在受体表达，相应信号参与食欲调节以及胃排空速率的降低。
| Property | Value | Notes |
|---|---|---|
| Molecular class | 31-amino-acid peptide | Modified glucagon-like peptide-1 analogue |
| Molecular mass | approximately 4114 Da | Calculated for the free peptide backbone |
| Appearance | white to off-white powder | Typical of purified lyophilised peptide batches |
| Solubility class | freely soluble in water | Aqueous solubility improves at slightly alkaline pH |
| Typical storage | -20 degrees Celsius, dry, dark | Protect from repeated freeze-thaw cycles |
The primary target is the GLP-1 receptor, a class B G protein-coupled receptor expressed on pancreatic beta cells, in the gut, and in several brain regions. Receptor activation raises intracellular cyclic AMP, which potentiates glucose-dependent insulin secretion and lowers glucagon release when blood glucose is elevated. Signalling in the hypothalamus and brainstem is associated with reduced appetite and slower gastric emptying. Because the insulinotropic effect depends on prevailing glucose levels, the hypoglycaemic risk of the peptide alone is described as low in most study settings. The relative contribution of peripheral and central actions remains an active research question.
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.
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.
Activation of the GLP-1 receptor couples to Gs signalling and raises intracellular cyclic AMP in pancreatic beta cells. The resulting insulin release depends on prevailing glucose concentrations, so the effect is greater when glucose is elevated. Receptor engagement also suppresses glucagon secretion and slows gastric emptying, which flattens post-meal glucose excursions. In the central nervous system, signalling in hypothalamic and brainstem regions is associated with reduced appetite and lower energy intake. Studies continue to examine effects on cardiac, renal and hepatic endpoints; whether those benefits are independent of weight change remains an open question.
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.
The Irish Free State (6 December 1922 – 29 December 1937), also known by its Irish name Saorstát Éireann, was the Irish state established in December 1922 under the Anglo-Irish Treaty of December 1921, initially as a Dominion. The treaty ended the three-year Irish War of Independence between the forces of the Irish Republic—the Irish Republican Army (IRA)—and British Crown forces. As per the 6 December 1922 Constitution of the Irish Free State, the new state was called the Irish Free State and became a Dominion of the British Empire. It comprised 26 of the 32 counties of Ireland. Northern Ireland, which was made up of the remaining six counties, exercised its right under the Treaty to opt out of the new state. The Free State government consisted of the governor-general—the representative of the king—and the Executive Council (cabinet), which replaced both the revolutionary Dáil Government and the Provisional Government set up under the Treaty. W. T. Cosgrave, who had led both of these administrations since August 1922, became the first president of the Executive Council (prime minister). The Oireachtas or legislature consisted of Dáil Éireann (the lower house) and Seanad Éireann (the upper house), also known as the Senate. Members of the Dáil were required to take an Oath of Allegiance to the Constitution of the Free State and to declare fidelity to the king. The oath was a key issue for opponents of the Treaty, who refused to take it and therefore did not take their seats.
Vitamin K is distributed differently within animals depending on its specific homologue. Vitamin K1 is mainly present in the liver, heart and pancreas, while MK-4 is better represented in the kidneys, brain and pancreas. The liver also contains longer chain homologues MK-7 to MK-13. The function of vitamin K2 in the animal cell is to add a carboxylic acid functional group to a glutamate (Glu) amino acid residue in a protein, to form a gamma-carboxyglutamate (Gla) residue. This is a somewhat uncommon posttranslational modification of the protein, which is then known as a "Gla protein". The presence of two −COOH (carboxylic acid) groups on the same carbon in the gamma-carboxyglutamate residue allows it to chelate calcium ions. The binding of calcium ions in this way very often triggers the function or binding of Gla-protein enzymes, such as the so-called vitamin K–dependent clotting factors discussed below. Within the cell, vitamin K participates in a cyclic process. The vitamin undergoes electron reduction to a reduced form called vitamin K hydroquinone (quinol), catalyzed by the enzyme vitamin K epoxide reductase (VKOR). Another enzyme then oxidizes vitamin K hydroquinone to allow carboxylation of Glu to Gla; this enzyme is called gamma-glutamyl carboxylase or the vitamin K–dependent carboxylase. The carboxylation reaction only proceeds if the carboxylase enzyme is able to oxidize vitamin K hydroquinone to vitamin K epoxide at the same time. The carboxylation and epoxidation reactions are said to be coupled. Vitamin K epoxide is then restored to vitamin K by VKOR.
=== Earlier capitals === Bath, the oldest town in North Carolina, was the first nominal capital of the colony from 1705 until 1722, when Edenton took over the role. The colony had no permanent institutions of government until the new capital, New Bern, was established in 1743.
Sources: en.wikipedia.org
== Ductal network == The ductal pancreas network originates from the central pancreatic duct—this main duct with the bile duct opens into the duodenum. The ductal cells of the main pancreatic duct are bound by connective tissue and produce a columnar epithelium. Interlobular ducts originate from the main pancreatic duct and connect the various pancreatic lobes. In these lobes, the intercalated ducts expel acini. Meanwhile, the ductal cells of these intercalated ducts create a simple squamous epithelium that rapidly converts into simple cuboidal epithelium, and connective tissue also surrounds them. As the ducts grow larger, the epithelium becomes cuboidal or columnar (when large in diameter, the ducts become stratified cuboidal), and connective tissue surrounds them. Pancreatic ductal cells are very similar to ductal cells of other exocrine glands (liver, bile duct, salivary glands). Because of this, a common diagnosis affects these cells: cystic fibrosis.
=== Formation of four bonds === This is a general method that is able to give good yields for substituted imidazoles. In essence, it is an adaptation of the Debus method called the Debus-Radziszewski imidazole synthesis. The starting materials are substituted glyoxal, aldehyde, amine, and ammonia or an ammonium salt.
Hans von Euler-Chelpin, together with Arthur Harden, received the 1929 Nobel Prize in Chemistry "for their research on sugar fermentation and the role of enzymes in this process." In 1947, both Bernardo Houssay for his discovery of the role of the pituitary gland in carbohydrate metabolism and Carl and Gerty Cori for their discovery of the conversion of glycogen received the Nobel Prize in Physiology or Medicine. For the discovery of sugar nucleotides in carbohydrate biosynthesis, Luis Leloir received the 1970 Nobel Prize in Chemistry. The term glycobiology was coined in 1988 by Raymond Dwek to recognize the coming together of the traditional disciplines of carbohydrate chemistry and biochemistry. This coming together was as a result of a much greater understanding of the cellular and molecular biology of glycans. "Glycoscience" is a field that explores the structures and functions of glycans.
Nonetheless, ECB Vice President Luis de Guindos stated that central bank liquidity swap lines between the Federal Reserve and the ECB remained "business as usual". International Monetary Fund Director Kristalina Georgieva also spoke in defense of Powell and the Federal Reserve's independence given the role of the United States dollar as the world's reserve currency.
Sources: en.wikipedia.org
DNP raises energy expenditure by 30 to 40 percent and causes a weight loss of 0.7–0.9 kilograms (1.5–2.0 lb) per week. Although DNP is no longer in clinical use as a weight loss drug due to its dangerous side effects, its mechanism of action remains under investigation as a potential approach for treating obesity and non-alcoholic fatty liver disease. Researchers developed a prodrug, HU6, which is metabolized to DNP in the liver to provide more stable blood concentrations. HU6 completed a phase II trial in which it produced significant reductions in liver fat and body weight in overweight people with elevated liver fat, without serious adverse effects. DNP is used by bodybuilders, fitness enthusiasts, and people with an eating disorder to lose weight. The user profile is similar to that of anabolic steroids; many perceive it to be effective and with manageable risks. Despite health warnings from regulators, DNP is readily available online sometimes under other names such as Dinosan, Dnoc, Solfo Black, Nitrophen, Aldifen, and Chemox. DNP is often sold in tablets containing 100 to 200 mg and may be sold alongside other substances such as anabolic steroids and thyroxine. It may also be found as a contaminant in other bodybuilding supplements not advertised as containing DNP. Online message boards provide information on dosage and regimens for DNP use, and describe the risks of taking the compound and provide advice on how to mitigate hyperthermia. According to a study published in 2023, the most commonly reported doses were between 150 to 300 mg/d.
=== Fermentation === Possibly the world's oldest fermented beverage, dating from 9,000 years ago, mead ("honey wine") is the alcoholic product made by adding yeast to honey-water must and fermenting it for weeks or months. The yeast Saccharomyces cerevisiae is commonly used in modern mead production. Mead varieties include drinks called metheglin (with spices or herbs), melomel (with fruit juices, such as grape, specifically called pyment), hippocras (with cinnamon), and sack mead (high concentration of honey), many of which have been developed as commercial products numbering in the hundreds in the United States. Honey is also used to make mead beer, called "braggot".
Indulgence in sexual activity is healthy for stronger individuals, but in weaker people it weakens them further, and is sought to be alleviated by abstinence as it restores shukra, which is always produced as a result of the digestion of food one eats. Ayurveda makes no preference for a celibate or monastic lifestyle, nor does it stress on morality being a part of human sexuality. The health of an individual's shukra and their dharma decides the degree of their sexual activity; for a householder sexual expression is common, while it is not so for a renunciate monk.
Sources: en.wikipedia.org
It is a glucagon-like peptide-1 receptor agonist, often grouped with the incretin mimetics. Its backbone is modified from the human hormone to resist enzymatic degradation and to bind albumin. These two features distinguish it from the native peptide.
No. It shares high sequence identity but carries non-natural modifications that alter its stability and clearance. The naturally occurring hormone is broken down within minutes, while the synthetic analogue circulates far longer.
Attachment to serum albumin reduces renal filtration of the peptide and shields it from enzymatic breakdown. The consequence is a much longer interval between administrations than unmodified peptides allow. The precise contribution of binding affinity to overall duration is still being quantified.
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。