The short version of incretin fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-07-31. Anything still debated is marked as such rather than presented as settled.
Identity and purity are usually established with reversed-phase high-performance liquid chromatography for the main peak and with mass spectrometry for the observed molecular mass. Peptide mapping after enzymatic digestion confirms the primary sequence, while amino acid analysis provides a quantitative composition check. Size-exclusion chromatography and ion-exchange chromatography are used to look for aggregates and charge variants. Water content, residual solvents, and counter-ion content are measured separately, since a lyophilised powder is often reported on an as-is basis unless a correction is applied.
Research-grade material circulates through suppliers that differ widely in documentation and testing practice, so a certificate of analysis is a starting point rather than proof of quality. Independent verification typically repeats chromatographic purity and mass confirmation on the received lot, and compares results against a retained reference standard. Regulatory status varies by jurisdiction, and a substance cleared as a medicine is not interchangeable with a research chemical of the same name. Open questions include how closely non-pharmaceutical lots match approved material in impurity profile and in aggregate content.
溶解操作一般使用注射用水或适宜的水性缓冲液，必要时加入少量助溶剂以改善溶解速度，但应避免剧烈涡旋振荡，因为剪切力可能促进聚集。配制后的溶液在冷藏条件下的稳定时间通常短于固体形态，具体时限取决于浓度、缓冲体系与容器材质。是否加入防腐成分，则取决于用途是否为多次取样。
定量分析的主流方法是反相高效液相色谱联用紫外或质谱检测，利用肽在疏水固定相上的保留行为确定纯度与含量。对于生物基质中的浓度测定，常采用液相色谱串联质谱，并配合固相萃取或蛋白沉淀进行样品前处理。免疫分析法也可使用，但可能受到结构相关肽的交叉反应干扰。
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white powder | Lyophilised solid, may form a loose cake |
| Solubility class | Soluble in water | Practically insoluble in nonpolar solvents |
| Storage temperature, solid | -20 °C or below | Desiccated and protected from light |
| Storage temperature, liquid | 2-8 °C | Refrigerated, not frozen |
| Typical identity method | LC-MS | Observed mass compared with calculated mass |
Dual agonism at the GIP and GLP-1 receptors underlies the observed pharmacology. Activation of GLP-1 receptors raises glucose-dependent insulin release, lowers glucagon secretion, slows gastric emptying and reduces appetite. GIP receptor activation contributes additional effects on adipose tissue and on energy balance, and the combined action on appetite appears larger than either pathway alone in animal models. Signalling bias and the relative contribution of each receptor arm to weight-related effects remain areas of active investigation.
Structure-activity work shows that fatty acid length, linker chemistry and the position of acylation all influence albumin affinity and receptor potency. Plasma protein binding exceeds 99 percent, which restricts distribution and slows renal clearance. Degradation proceeds largely through general proteolysis and fatty acid oxidation rather than cytochrome P450 metabolism, so exposure to common oxidative drug interactions is limited. Whether these clearance routes vary meaningfully between individuals is not fully established.
Tirzepatide is a synthetic linear peptide of 39 amino acids that acts as a dual agonist at the glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptors. Its sequence derives from native GIP but incorporates non-natural residues and a C20 fatty diacid moiety linked to a lysine side chain. The lipophilic chain promotes albumin binding, which slows renal clearance and extends circulation time. The unmodified peptide has a molecular formula of C225H348N48O68 and a molecular mass near 4,813 daltons.
Receptor activation by tirzepatide raises intracellular cyclic AMP through Gs-coupled signalling at both targets. At the GLP-1 receptor the downstream effect includes glucose-dependent insulin release, suppressed glucagon secretion, delayed gastric emptying, and reduced appetite signalling in the hypothalamus. GIP receptor engagement adds insulinotropic activity and appears to influence lipid handling in adipose tissue. Because both receptors are stimulated at the same time, the pharmacological profile differs from that of selective GLP-1 receptor agonists, and the relative contribution of each arm remains an area of active investigation.
Tirzepatide is a synthetic peptide that activates both the glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptors. This dual agonist profile distinguishes it from earlier incretin-based compounds that act on a single receptor. The molecule was engineered from the native GIP sequence and carries several non-natural residues that slow enzymatic breakdown. Researchers designed it to combine the insulinotropic effects of GIP signaling with the appetite and gastric-emptying effects associated with GLP-1 activation.
Development of tirzepatide took place under a research program that sought to test whether simultaneous engagement of two incretin receptors would produce greater metabolic effects than single-receptor agonism. Clinical trials were organized into the SURPASS series for type 2 diabetes and the SURMOUNT series for obesity and weight management. Regulatory clearance for type 2 diabetes came in 2022 in the United States, followed by approval for chronic weight management in 2023. The trial programs reported reductions in glycated hemoglobin and body weight relative to comparators, though long-term cardiovascular and durability data continue to accumulate.
The peptide backbone contains 39 amino acids and includes alpha-aminoisobutyric acid residues, which are not among the standard proteinogenic set. A C20 fatty diacid moiety is attached through a linker, allowing the compound to bind serum albumin and extend its circulation time. This albumin binding is the main reason the molecule supports once-weekly administration rather than more frequent dosing. The measured molecular mass is approximately 4,813 daltons, placing it firmly in the peptide rather than small-molecule class.
== Charging and discharging == During discharge, lithium ions (Li+) carry the current within the battery cell from the negative to the positive electrode, through the non-aqueous electrolyte and separator diaphragm. During charging, an external electrical power source applies an over-voltage (a voltage greater than the cell's own voltage) to the cell, forcing electrons to flow from the positive to the negative electrode. The lithium ions also migrate (through the electrolyte) from the positive to the negative electrode where they become embedded in the porous electrode material in a process known as intercalation.
Southern Rhodesia was represented in the Dodecanese Campaign of September–November 1943 by the Long Range Desert Group, which was withdrawn from the North African front in March 1943. After retraining for mountain operations in Lebanon, the LRDG moved in late September to the Dodecanese island of Kalymnos, north-west of Kos and south-east of Leros, off the coast of south-west Turkey. In the fall-out from the Armistice of Cassibile between Italy and the Allies, which had been concluded in the first week of September, the Allies were attempting to capture the Dodecanese so the islands could be used as bases against the German-occupied Balkans. Most of the Italian forces had changed sides; the LRDG found itself in an infantry role, acting as a mobile reserve for Italian troops. The Germans swiftly mobilised to expel the Allied forces and launched heavy air assaults on Kos and Leros. Without fighter support, the islands' defence was soon precarious; the LRDG and the rest of the troops on Kalymnos were withdrawn to Leros on 4 October after the Germans won the Battle of Kos. German air assaults on Leros intensified during late October, and at dawn on 12 November 1943 the Germans attacked Leros by sea and air. During the ensuing Battle of Leros, the LRDG Rhodesians at Point 320, commanded by Rhodesian Captain J R Olivey, spiked their position's guns and withdrew before counter-attacking and retaking the point the next day. They held that position for three more days, during which they learned that the Germans were winning the battle.
During atrial systole, blood flows from the atria to the ventricles down the pressure gradient. Chordae tendineae are relaxed because the atrioventricular (AV) valves are forced open. When the ventricles of the heart contract in ventricular systole, the increased blood pressures in both chambers push the AV valves to close simultaneously, preventing the backflow of blood into the atria. Since the blood pressure in the atria is much lower than that in the ventricles, the flaps attempt to evert to the low pressure regions. The chordae tendineae prevent this prolapse by becoming tense, which pulls on the flaps, holding them in a closed position.
=== Pharmacodynamics === As a glucocorticoid, dexamethasone is an agonist of the glucocorticoid receptor (GR). It is highly selective for the GR over the mineralocorticoid receptor (MR), and in relation to this, has minimal mineralocorticoid activity. This is in contrast to endogenous corticosteroids like cortisol, which bind to and activate both the GR and the MR. Dexamethasone is 25 times more potent than hydrocortisone (cortisol) as a glucocorticoid. Its affinity (Ki) for the GR was about 1.2 nM in one study. The activation of the GR by dexamethasone results in dose-dependent suppression of the hypothalamic–pituitary–adrenal axis (HPA axis) and of production of endogenous corticosteroids by the adrenal glands, thereby reducing circulating endogenous concentrations of corticosteroids like cortisol and corticosterone. Dexamethasone poorly penetrates the blood–brain barrier into the central nervous system due to binding to P-glycoprotein. However, higher doses of dexamethasone override the export capacity of P-glycoprotein and enter the brain to produce central activation of GRs. In conjunction with the suppression of endogenous corticosteroids by dexamethasone, this results in skewed ratios of activation of peripheral versus central GRs as well as skewed ratios of activation of GRs versus MRs when compared to non-synthetic corticosteroids. These differences can have significant clinical relevance.
Rossman (1993), judge on the United States Court of Appeals for the Tenth Circuit Nancy Abudu (1996), lawyer and nominee to the United States Court of Appeals for the Eleventh Circuit Nusrat Jahan Choudhury (1998), lawyer and nominee to the United States District Court for the Eastern District of New York Roy Altman (2004), judge of the United States District Court for the Southern District of Florida Raph Graybill (2010), attorney, chief legal counsel to Steve Bullock and Democratic candidate in the 2020 Montana Attorney General election Shana Knizhnik (2010), lawyer and author known for her book Notorious R.B.G.: The Life and Times of Ruth Bader Ginsburg
Sources: en.wikipedia.org
=== South Africa === In South Africa learnerships to qualify as a Phlebotomy Technician are offered by many public and private educational institutions as well as by private academies owned up by pathology laboratories (such as Ampath Laboratories, Lancet, PathCare) and healthcare service providers (such as Netcare, South African National Blood Service). Some of the larger retail pharmacy chains offering in-store clinical services (such as Clicks, Dis-Chem) also provide training for aspirant phlebotomists. Certification can be obtained from a number of examination and testing institutions. To work as a phlebotomist in South Africa, registration with the Health Professions Council of South Africa (HPCSA) is required.
=== Metabolic disorders === Opioids are primarily metabolized in the liver, before being excreted through urine. Opioids are metabolized by phase 1 and/or phase 2 metabolism, which can lead to the activation or inhibition of these drugs. Phase 1 metabolism is the CYP pathway which consists of different cytochrome P450s – a set of enzymes that catalyze hydrolysis, reduction, and oxidation reactions – to create an active metabolite. In contrast, Phase 2 metabolism causes the opioids to undergo conjugation, with little to no interaction with the CYP pathway. The opioids undergo phase 1 and phase 2 metabolism until they are hydrophilic enough to be renally excreted. Various factors play a role in how an opioid is metabolized. In phase 1 metabolism, the CYP family has several polymorphisms, which can account for the difference in therapeutic responses within each individual. This diversification leads to opioids being modified at varying rates, which can cause the drug to remain in the bloodstream for either a longer or shorter period. Therefore, these polymorphisms control opioid tolerance and facilitate overdose.
Pasteurization is a process for preservation of liquid food. It was originally applied to combat the souring of young local wines. Today, the process is mainly applied to dairy products. In this method, milk is heated at about 70 °C (158 °F) for 15–30 seconds to kill the bacteria present in it and cooling it quickly to 10 °C (50 °F) to prevent the remaining bacteria from growing. The milk is then stored in sterilized bottles or pouches in cold places. This method was invented by Louis Pasteur, a French chemist, in 1862.
Public health care services are available for transgender individuals in Spain, although there has been debate over whether certain procedures should be covered under the public system. The region of Andalusia was the first to approve sex reassignment procedures, including sex reassignment surgery and mastectomies, in 1999, and several other regions have followed their lead in the following years. Multiple interdisciplinary clinics exist in Spain to cater specifically to diagnosing and treating transgender patients, including the Andalusian Gender Team. As of 2013, over 4000 transgender patients had been treated in Spain, including Spaniards and international patients. Beginning in 2007, Spain has begun allowing transgender individuals who are eighteen years or older to change their name and gender identity on public records and documents if they have been receiving hormone replacement therapy for at least two years.
Sources: en.wikipedia.org
Bayesian inference of phylogeny combines the information in the prior and in the data likelihood to create the so-called posterior probability of trees, which is the probability that the tree is correct given the data, the prior and the likelihood model. Bayesian inference was introduced into molecular phylogenetics in the 1990s by three independent groups: Bruce Rannala and Ziheng Yang in Berkeley, Bob Mau in Madison, and Shuying Li in University of Iowa, the last two being PhD students at the time. The approach has become very popular since the release of the MrBayes software in 2001, and is now one of the most popular methods in molecular phylogenetics.
=== Economic vegetarianism === Similar to environmental vegetarianism is the concept of economic vegetarianism. An economic vegetarian is someone who practices vegetarianism from either the philosophical viewpoint concerning issues such as public health and curbing world starvation, the belief that the consumption of meat is economically unsound, part of a conscious simple living strategy or just out of necessity. According to the Worldwatch Institute, "Massive reductions in meat consumption in industrial nations will ease their health care burden while improving public health; declining livestock herds will take pressure off rangelands and grainlands, allowing the agricultural resource base to rejuvenate. As populations grow, lowering meat consumption worldwide will allow more efficient use of declining per capita land and water resources, while at the same time making grain more affordable to the world's chronically hungry." According to estimates in 2016, adoption of vegetarianism would contribute substantially to global healthcare and environmental savings.
== Clinical significance == The enzymes that make and use NAD+ and NADH are important in both pharmacology and the research into future treatments for disease. Drug design and drug development exploits NAD+ in three ways: as a direct target of drugs, by designing enzyme inhibitors or activators based on its structure that change the activity of NAD-dependent enzymes, and by trying to inhibit NAD+ biosynthesis. Because cancer cells utilize increased glycolysis, and because NAD enhances glycolysis, nicotinamide phosphoribosyltransferase (NAD salvage pathway) is often amplified in cancer cells. It has been studied for its potential use in the therapy of neurodegenerative diseases such as Alzheimer's and Parkinson's disease as well as multiple sclerosis. A placebo-controlled clinical trial of NADH (which excluded NADH precursors) in people with Parkinson's failed to show any effect. NAD+ is also a direct target of the drug isoniazid, which is used in the treatment of tuberculosis, an infection caused by Mycobacterium tuberculosis. Isoniazid is a prodrug and once it has entered the bacteria, it is activated by a peroxidase enzyme, which oxidizes the compound into a free radical form. This radical then reacts with NADH, to produce adducts that are very potent inhibitors of the enzymes enoyl-acyl carrier protein reductase, and dihydrofolate reductase. Since many oxidoreductases use NAD+ and NADH as substrates, and bind them using a highly conserved structural motif, the idea that inhibitors based on NAD+ could be specific to one enzyme is surprising.
Sources: en.wikipedia.org
It is normally kept frozen, desiccated, and away from light, with brief warming to room temperature before opening to limit condensation. Repeated freeze-thaw cycles are avoided because they stress the peptide. Once in solution, the material is held cold and used promptly.
Mass spectrometry gives the observed molecular mass, which is compared with the calculated value for the expected sequence. Reversed-phase chromatography shows retention behaviour and main peak purity. Peptide mapping adds sequence-level confirmation when the question requires it.
Typical entries include appearance, chromatographic purity as area percent, observed mass, water or residual solvent content, and the analytical methods used. The document reflects the lot tested and the laboratory that performed the work. It does not by itself establish that the delivered vial matches the tested lot.
建议在低温、避光、干燥环境中密封保存，常见条件为 2 至 8 摄氏度，长期存放可置于更低温度。应避免反复冻融，并尽量减少容器开启次数。