Research into the biological role of the Ca2+-releasing second messenger NAADP (nicotinic acid adenine dinucleotide phosphate) has been hampered by a lack of chemical probes. To find new chemical probes for exploring NAADP signaling, we turned to virtual screening, which can evaluate millions of molecules rapidly and inexpensively. We used NAADP as the query ligand to screen the chemical library ZINC for compounds with 3D-shape and electrostatic similarity. We tested the top-ranking hits in a sea urchin egg bioassay and found that one hit, Ned-19, blocks NAADP signaling at nanomolar concentrations. In intact cells, Ned-19 blocked NAADP signaling and fluorescently labeled NAADP receptors. Moreover, we show the utility of Ned-19 as a chemical probe by using it to demonstrate that NAADP is a key causal link between glucose sensing and Ca2+ increases in mouse pancreatic beta cells.
The accumulation of visceral adipose tissue usually results from an energy imbalance involving the combination of excessive calorie consumption with insufficient energy expenditure. Increased visceral adiposity can induce insulin resistance and lead to type 2 diabetes mellitus, dyslipidemia, hypertension, and cardiovascular disease.1) "Metabolic syndrome" is the combination of multiple cardiovascular risk factors, including visceral obesity, dyslipidemia, glucose intolerance, and hypertension in one individual.2,3) Obesity resulting from an accumulation of visceral adiposity is a primary cause of metabolic syndrome.Propolis is a sticky, resinous substance collected by honey bees (Apis mellifera) from the sap, leaves, and buds of plants, and then mixed with secreted beeswax. The chemical constituents of propolis are mainly flavonoids, phenolic compounds, caffeoylquinic acids, cinnamic acid derivatives, diterpenoic acid, lignan, coumarin acid and other compounds. 4,5) Propolis has been used as a folk medicine in many countries from ancient times especially in Brazil and Eastern Europe. It has been characterized variously as an anti-bacterial, 6,7) anti-viral, 8) anti-inflammatory, 9-11) anti-oxidant, 12) and anti-carcinogenesis agent. 13,14) Obesity is caused by various environmental and genetic factors.15) One of the main environmental factors causing obesity is the intake of a high-fat diet, now common in many populations. A diet-induced obesity animal model has been developed to investigate human obesity, replicating the effects of human obesity more accurately than genetic obesity models.16) Mice that are fed a high-fat diet, develop obesity, hyperglycemia, and hyperlipidemia, and differ from those fed a normal diet in the expression levels of specific genes transcripts.17) Recent studies have reported that propolis prevented and mitigated diabetes and hypertension, [18][19][20][21][22] but it remains unclear whether propolis similarly prevents and mitigates the accumulation of visceral adipose tissues and hyperlipidemia. In this study we examined the effect of propolis on visceral fat and hyperlipidemia induced in a high-fat dietinduced obesity mouse model, and analyzed hepatic gene expression involved in lipid metabolism. MATERIALS AND METHODS Preparation of Propolis ExtractPropolis used in this study was obtained from Apiai, Sao Paulo in Brazil. Propolis (1 kg) was treated with 50% ethanol (3 l) at room temperature for 24 h, and filtered. This extract included 10.8% of solid contents of propolis. Total flavonoids content in the extract was determined as amounts of quercetin by using the aluminum nitrate method as described previously.23) In addition, the extract was subjected to reversed-phase column chromatography using following conditions: column, Shim Pack CLC-ODS (6 mm i.d.ϫ150 mm, Shimadzu, Japan); column temperature, 50°C; gradient system, A solvent (30% MeOH, 70% H 2 O and 1% AcOH) and B solvent (75% MeOH, 25% H 2 O and 1% AcOH), 0-20 min 100% A isocratic, 20-55 min 100% B isocratic, 55-75 min 100% ...
BackgroundTrehalose is hydrolyzed by a specific intestinal brush-border disaccharidase (trehalase) into two glucose molecules. In animal studies, trehalose has been shown to prevent adipocyte hypertrophy and mitigate insulin resistance in mice fed a high-fat diet. Recently, we found that trehalose improved glucose tolerance in human subjects. However, the underlying metabolic responses after trehalose ingestion in humans are not well understood. Therefore, we examined the glycemic, insulinemic and incretin responses after trehalose ingestion in healthy Japanese volunteers.MethodsIn a crossover study, 20 fasted healthy volunteers consumed 25 g trehalose or glucose in 100 mL water. Blood samples were taken frequently over the following 3 h, and blood glucose, insulin, active gastric inhibitory polypeptide (GIP) and active glucagon-like peptide-1 (GLP-1) levels were measured.ResultsTrehalose ingestion did not evoke rapid increases in blood glucose levels, and had a lower stimulatory potency of insulin and active GIP secretion compared with glucose ingestion. Conversely, active GLP-1 showed higher levels from 45 to 180 min after trehalose ingestion as compared with glucose ingestion. Specifically, active GIP secretion, which induces fat accumulation, was markedly lower after trehalose ingestion.ConclusionsOur findings indicate that trehalose may be a useful saccharide for good health because of properties that do not stimulate rapid increases in blood glucose and excessive secretion of insulin and GIP promoting fat accumulation.
Nicotinic acid adenine dinucleotide phosphate (NAADP) is a Ca2؉ -releasing messenger. Biological data suggest that its receptor has two binding sites: one high-affinity locking site and one low-affinity opening site. To directly address the presence and function of these putative binding sites, we synthesized and tested analogues of the NAADP antagonist Ned-19. Ned-19 itself inhibits both NAADP-mediated Ca 2؉ release and NAADP binding. A fluorometry bioassay was used to assess NAADPmediated Ca 2؉ release, whereas a radioreceptor assay was used to assess binding to the NAADP receptor (only at the high-affinity site). In Ned-20, the fluorine is para rather than ortho as in Ned-19. Ned-20 does not inhibit NAADP-mediated Ca 2؉ release but inhibits NAADP binding. Conversely, Ned-19.4 (a methyl ester of Ned-19) inhibits NAADP-mediated Ca 2؉ release but cannot inhibit NAADP binding. Furthermore, Ned-20 prevents the self-desensitization response characteristic of NAADP in sea urchin eggs, confirming that this response is mediated by a high-affinity allosteric site to which NAADP binds in the radioreceptor assay. Collectively, these data provide the first direct evidence for two binding sites (one high-and one lowaffinity) on the NAADP receptor. Ca2ϩ is an extremely versatile and powerful second messenger (1). Three accepted Ca 2ϩ -releasing second messengers that cells utilize to control the spatiotemporal properties of these Ca 2ϩ signals are inositol 1,4,5-trisphosphate (2), cyclic ADPribose (3), and nicotinic acid adenine dinucleotide phosphate (NAADP) 2 (4). Of these three messengers, little is known about the mechanism of action of NAADP. NAADP is the most potent of the three Ca 2ϩ -releasing messengers (5), and its actions are pharmacologically distinct from inositol 1,4,5-trisphosphate and cyclic ADP-ribose (6 -9). Controversy surrounds both the identity of the NAADP-activated channel and its organellar location. There is evidence for the NAADP receptor being the transient receptor potential mucolipin 1 channel (10), the ryanodine receptor (11, 12), or the two-pore channel (Refs. 13-15; for review, see Ref. 16). There is evidence for the Ca 2ϩ store targeted by NAADP being the endoplasmic reticulum (11) or physically distinct (17), acidic, lysosome-related organelles (18).One of the most intriguing features of NAADP is the relationship between concentration, binding, and response (5,9,19). In sea urchin eggs, a subthreshold concentration of NAADP that does not itself release Ca 2ϩ is able to prevent Ca 2ϩ release in response to a second addition of NAADP that would normally be able to release Ca 2ϩ (20,21). This unusual desensitization may relate to the formation of a spatial and temporal "memory" (22,23). This effect is thought to be due to a second high-affinity inhibitory site present on the receptor (24); thus, at low concentrations, NAADP only binds to this site and is able to prevent Ca 2ϩ release via this receptor. In contrast to sea urchin eggs, in mammalian tissue, NAADP has a bell-shaped concentration-r...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.