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.
Updated 2026-04-20. Numbers and descriptions here follow the published literature rather than marketing material.
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。
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.
Receptor binding triggers G protein signaling that raises intracellular cyclic AMP in pancreatic beta cells. Insulin release follows in a glucose-dependent manner, so secretion increases when blood glucose is elevated and diminishes when it is not. The same signaling suppresses glucagon release from alpha cells and slows gastric emptying, which blunts the post-meal glucose rise. In the brain, receptor activation in regions such as the arcuate nucleus is associated with reduced appetite and lower energy intake. How much each of these effects contributes to overall weight change is not fully settled.
| 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 |
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.
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.
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.
Identity and purity are usually assessed by reverse-phase high-performance liquid chromatography coupled to mass spectrometry. Retention time and observed mass are compared against a reference standard run under identical conditions. Impurity profiles reveal deamidation products, oxidized methionine variants, and truncated fragments that arise during synthesis or storage. Peptide mapping through enzymatic digestion confirms the primary sequence, while amino acid analysis offers an independent check on overall composition.
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.
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.
== Pathophysiology == Chronic wounds may affect only the epidermis and dermis, or they may affect tissues all the way to the fascia. They may be formed originally by the same things that cause acute ones, such as surgery or accidental trauma, or they may form as the result of systemic infection, vascular, immune, or nerve insufficiency, or comorbidities such as neoplasias or metabolic disorders. The reason a wound becomes chronic is that the body's ability to deal with the damage is overwhelmed by factors such as repeated trauma, continued pressure, ischemia, or illness. Though much progress has been accomplished in the study of chronic wounds lately, advances in the study of their healing have lagged behind expectations. This is partly because animal studies are difficult because animals do not get chronic wounds, since they usually have loose skin that quickly contracts, and they normally do not get old enough or have contributing diseases such as neuropathy or chronic debilitating illnesses. Nonetheless, current researchers now understand some of the major factors that lead to chronic wounds, among which are ischemia, reperfusion injury, and bacterial colonization.
Qingzhou (Chinese: 轻舟货运飞船; pinyin: Qīngzhōu huòyùn fēichuán) is a class of cargo spacecraft developed by CAS Space, a company founded by the Chinese Academy of Sciences. It is part of the China Manned Space Program's low-cost cargo transportation system designed to support the Tiangong space station. A prototype version of the Qingzhou spacecraft was successfully launched as the primary payload of the maiden flight of the Kinetica-2 (Lijian-2) rocket on 30 March 2026. The first production-standard spacecraft is expected to be ready for flight by late 2026.
=== Malaysia === The Malaysian Armed Forces version of the 24-hour ration pack is intended to provide one man with sufficient food and supplements for one day. Most items are domestically procured and cater to local tastes and religious dietary requirements. The ration makes extensive use of commercially available canned and dehydrated items. Wherever possible, plastic-foil pouches are used instead of cans. The ration is supplemented with precooked or freeze-dried rice. Example menu C: Beef Kurma, Chicken Masak Merah, Fish Curry, and Sambal Shrimp; Bean Curd and Vegetable mix; long bean stew; canned pineapple and canned papaya; 2 packages of quick-cooking porridge (black bean porridge and flour porridge); military biscuits; jam; instant coffee; tea; instant milk powder; sugar; salt; vitamin tablets; matches; and napkins.
While personal and impersonal values often align, they can diverge, for example, if an individual seeks personal gain that is bad from a wider perspective. The exact relation between these two types of value is disputed. According to one proposal, impersonal value is the sum of all personal values. Well-being is typically understood as an intrinsic or final value, meaning that it is good in itself, independent of external factors. Things with instrumental value, by contrast, are only good as means leading to other good things, like the value of money. Well-being is further distinguished from moral, religious, and aesthetic values, which describe what is ethically right, sacred, or beautiful. Well-being may or may not overlap with other values. For instance, donating money to a charity may be morally good, even if it does not increase the donor's well-being. The terms quality of life, good life, welfare, prudential value, personal good, and individual utility are often used as synonyms for well-being. Similarly, the words pleasure, life satisfaction, and happiness are employed in overlapping ways with well-being. However, their precise meanings differ in technical contexts like philosophy and psychology: pleasure refers to individual feelings about what is attractive; life satisfaction is a positive attitude a person has towards their life as a whole; happiness is sometimes identified with life satisfaction or understood as a positive balance of pleasure over pain. Well-being is a crucial goal of many human endeavors on both individual and societal levels.
However, recent medical literature has proposed reclassifying insulin specifically as a reponic hormone (from the Latin repono, meaning "to store") to better distinguish its metabolic role from that of classic anabolic hormones like testosterone or growth hormone. While classic anabolic hormones drive energy-intensive processes to build metabolically active lean tissue, the primary physiological function of a reponic hormone is to conserve and store systemic energy. Insulin achieves this by driving the cellular uptake of glucose and lipids for storage (lipogenesis and glycogenesis) while simultaneously inhibiting the breakdown of stored energy (lipolysis and glycogenolysis). Researchers argue this distinction provides a clearer framework for understanding why hyperinsulinemia is uniquely characterized by central adiposity and metabolic syndrome rather than lean tissue growth.
Sources: en.wikipedia.org
The prescription heroin can be accessed by doctors through Health Canada's Special Access Programme (SAP) for "emergency access to drugs for patients with serious or life-threatening conditions when conventional treatments have failed, are unsuitable, or are unavailable."
==== Monazite compositional mapping ==== Monazite grains which show useful relationships with microtextures or host minerals are selected for compositional mapping. Major elemental and sometimes trace elemental maps are created at high magnification by electron microprobe X-ray mapping to show compositional zonation patterns. Maps of elemental Y, Th, Pb, U have proven useful in identifying compositional domains in monazite.
Clearance is variable in zero-order kinetics because a constant amount of the drug is eliminated per unit time, but it is constant in first-order kinetics, because the amount of drug eliminated per unit time changes with the concentration of drug in the blood. Clearance can refer to the volume of plasma from which the substance is removed (i.e., cleared) per unit time or, in some cases, inter-compartmental clearances can be discussed when referring to redistribution between body compartments such as plasma, muscle, and fat.
Small but significant increases in hemoglobin and hematocrit, and small but significant decreases in fasting blood glucose, insulin levels, and insulin resistance, have been observed with enobosarm at 3 mg/day. In small short-term (3-month) clinical trials in healthy elderly or postmenopausal women, enobosarm at doses ranging from 0.1 to 3 mg/day had mixed effects on sebum production and did not increase body hair growth or cause hirsutism. These effects are measures of androgenic action in skin and hair follicles. In the first study, at doses of 0.1 to 3 mg/day, there were no significant changes relative to placebo in sebum tape scores with enobosarm and there were no consistent increases in Ferriman–Gallwey score, with most women having no change in score or a decreased score and only one having an increase in score. In the second study, which employed 3 mg/day enobosarm, there was a significant 1.25-fold increase in sebum production from baseline and a significant 1.5-fold increase in sebum production relative to placebo. No differences in sebaceous gland volume were apparent upon histological examination in this study. At doses ranging from 0.1 to 18 mg/day in clinical trials, enobosarm has been associated with elevated liver enzymes in subsets of individuals. Rates of elevated liver enzymes or of elevated alanine aminotransferase (ALT) levels have ranged from 0.6% to 33% in these trials. Liver enzyme elevations with enobosarm are often transient and resolve spontaneously.
ABPP can be analyzed using several complementary detection strategies, each suited to different experimental contexts. These methods generally visualize or enrich the enzyme-probe adduct, enabling qualitative assessment, quantitative comparison, or protein identification by mass spectrometry. One of the earliest and most widely used ABPP workflows employs direct visualization on SDS-PAGE gels. Probes with fluorescent reporter tags (e.g. rhodamine) generate distinct bands corresponding to labeled enzymes, allowing rapid assessment of activity across samples or treatment conditions. This approach is commonly used for broad enzyme families such as serine hydrolases or cysteine proteases and is compatible with high-throughput screening for inhibitors. Because the readout is based on in-gel fluorescence rather than protein abundance, gel-based ABPP readily distinguishes active from inactive enzyme species. However, a significant limitation of gel-based detection is lack of resolving ability, preventing the resolution and identification of low-abundance proteins. In recent years ABPP has been combined with tandem mass spectrometry enabling the identification of hundreds of active enzymes from a single sample. This technique, known as ABPP-MudPIT (multidimensional protein identification technology) is especially useful for profiling inhibitor selectivity as the potency of an inhibitor can be tested against hundreds of targets simultaneously. For proteome-wide analysis, ABPs incorporating affinity tags (e.g.
Sources: en.wikipedia.org
Korolev was buoyed by the first successful launches of the R-7 rocket in August and September, which paved the way for the launch of Sputnik 1. Word came that the US was planning to announce a major breakthrough at an International Geophysical Year conference at the National Academy of Sciences in Washington D.C., with a paper titled "Satellite Over the Planet", on October 6, 1957. Korolev anticipated that von Braun might launch a Jupiter-C with a satellite payload on or around October 4 or 5, in conjunction with the paper. He hastened the launch, moving it to October 4. The launch vehicle for PS-1 was a modified R-7 – vehicle 8K71PS number M1-PS – without much of the test equipment and radio gear that was present in the previous launches. It arrived at the Soviet missile base Tyura-Tam in September and was prepared for its mission at launch site number one. The first launch took place on Friday, October 4, 1957, at exactly 10:28:34 pm Moscow time, with the R-7 and the now named Sputnik 1 satellite lifting off the launch pad and placing the artificial "moon" into an orbit a few minutes later. This "fellow traveler", as the name is translated in English, was a small, beeping ball, less than two feet in diameter and weighing less than 200 pounds. But the celebrations were muted at the launch control center until the down-range far east tracking station at Kamchatka received the first distinctive beep ... beep ... beep sounds from Sputnik 1's radio transmitters, indicating that it was on its way to completing its first orbit.
Despite the UN arms embargo on Bosnia, the ISI under General Javed Nasir airlifted anti-tank weapons and missiles to Bosnian mujahideen, shifting the tide in favour of Bosnian Muslims. ISI, under Nasir's leadership, supported Chinese Muslims in Xinjiang, rebel groups in the Philippines, and religious groups in Central Asia. Since 2001, the Pakistan military has been engaged in counterinsurgency and internal security operations in the Khyber Pakhtunkhwa province, primarily targeting Tehrik-e-Taliban Pakistan and associated militant groups. Major military operations conducted during this period include Operation Enduring Freedom, Operation al-Mizan, Operation Zalzala, Operation Sherdil, Operation Rah-e-Haq, Operation Rah-e-Rast, and Operation Rah-e-Nijat.
=== Psychiatric disorders === Serotonin plays an important role in numerous physiological conditions. 5-HT2 receptor antagonists have long been known, but recently 5-HT2 receptor agonists are becoming promising agents in the development for new antipsychotic drugs. Historically, most pharmacological research on antipsychotic drugs have concentrated on the 5-HT2A receptor subtype. However, recent studies show that agonist activity on 5-HT2A receptors can cause hallucination. Comparison of SSRIs and the 5-HT2C receptor agonists showed that the agonists decreased immobility time and increased swimming time in the FST (forced swim test) in rats in a manner comparable to SSRIs. In the 1990s 5-HT2C receptors have received more attention as many studies have shown that selective 5-HT2C receptor agonists may be more suited in the treatment for psychotic indications. A 5-HT2C agonist may be expected to reduce positive symptoms of schizophrenia by reducing dopamine release in the mesolimbic dopamine pathway. Vabicaserin (SCA-136) is a 5-HT2C agonist that has shown promise in preliminary testing for the treatment of schizophrenia.
=== Mitral stenosis === Mitral stenosis is caused almost exclusively by rheumatic heart disease, and has a prevalence of about 0.1% in the United States. Mitral stenosis is the most common valvular heart disease in pregnancy.
=== Formation of one bond === The (1,5) or (3,4) bond can be formed by the reaction of an imidate and an α-aminoaldehyde or α-aminoacetal. The example below applies to imidazole when R1 = R2 = hydrogen.
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。
Native GLP-1 is degraded within minutes by dipeptidyl peptidase-4 and cleared quickly. Semaglutide carries a position 8 substitution that blocks that cleavage and a fatty diacid chain that binds albumin. Together these changes extend its circulating half-life to about one week.