Prostaglandin profiling reveals a role for haematopoietic prostaglandin D synthase in adipose tissue macrophage polarisation in mice and humans.

BACKGROUND/OBJECTIVES: Obesity has been associated with both changes in adipose tissue lipid metabolism and inflammation. A key class of lipid-derived signalling molecules involved in inflammation are the prostaglandins. In this study, we aimed to determine how obesity affects the levels of prostaglandins within white adipose tissue (WAT) and determine which cells within adipose tissue produce them. To avoid the effects of cellular stress on prostaglandin levels, we developed a multivariate statistical approach in which metabolite concentrations and transcriptomic data were integrated, allowing the assignment of metabolites to cell types. SUBJECTS/METHODS: Eicosanoids were measured by liquid chromatography-tandem mass spectrometry and mRNA levels using real-time PCR. Eicosanoid levels and transcriptomic data were combined using principal component analysis and hierarchical clustering in order to associate metabolites with cell types. Samples were obtained from C57Bl/6 mice aged 16 weeks. We studied the ob/ob genetically obese mouse model and diet-induced obesity model. We extended our results in mice to a cohort of morbidly obese humans undergoing bariatric surgery. RESULTS: Using our modelling approach, we determined that prostglandin D2 (PGD2) in adipose tissue was predominantly produced in macrophages by the haematopoietic isoform of prostaglandin D synthase (H-Pgds). Analysis of sub-fractionated WAT confirmed that H-Pgds was expressed in adipose tissue macrophages (ATMs). Furthermore, H-Pgds expression in ATMs isolated from lean and obese mice was consistent with it affecting macrophage polarisation. Functionally, we demonstrated that H-PGDS-produced PGD2 polarised macrophages toward an M2, anti-inflammatory state. In line with a potential anti-inflammatory role, we found that H-PGDS expression in ATMs was positively correlated with both peripheral insulin and adipose tissue insulin sensitivity in humans. CONCLUSIONS: In this study, we have developed a method to determine the cellular source of metabolites within an organ and used it to identify a new role for PGD2 in the control of ATM polarisation.

IS6110 dot blot hybridization for the identification of Mycobacterium tuberculosis complex.

To explore a simple, rapid, and inexpensive way to identify Mycobacterium tuberculosis complex culture, dot blot hybridization using IS6110 as the marker was performed against 2788 known clinical isolates of mycobacteria including M. tuberculosis (n = 721), M. kansasii (177), M. marinum (10), M. avium complex (700), M. terrae complex (203), M. fortuitum (476), M. chelonae (439), and other nonpigmented Runyon's Group IV mycobacteria (62). We found that the sensitivity and specificity of the test were 94.3% and 100%, respectively. When this method was evaluated in a laboratory blind study of 1253 initially unknown clinical isolates, its sensitivity and specificity were 91.2% and 100%, respectively. Because this identification test is technically simple, rapid, and can be done in batches, together with its high sensitivity and specificity, it is a cost-effective method for routine identification of M. tuberculosis complex in laboratories of areas with a high incidence of tuberculosis.

Small-scale multi-residue method for the determination of organochlorine and pyrethroid pesticides in vegetables.

A simple and inexpensive multi-residue method is described for the determination of organochlorine and pyrethroid pesticides in vegetables. Pesticides in vegetables were extracted with ethanol and partitioned into toluene. A mini-column packed with 0.5 g of Florisil was used for further clean-up prior to gas chromatographic determination. The detection limits were 0.02-0.05 microgram/g without concentrating the extract, which are below the maximum residue limits set by the Singapore government. The recoveries of the pesticides from fortified samples were 65-97% at the 0.1 microgram/g level and 87-114% at the 0.5 microgram/g level. The amounts of the reagents required for analysing one sample are only 100 ml of ethanol, 6 ml of toluene and 0.5 g of Florisil. Among fifteen vegetable samples collected from the Singapore local market and were analysed by this method, five were found to contain detectable amount of organochlorine pesticides. One sample contained 22 micrograms/g of endosulfan but the residue levels in other four samples were below 1 microgram/g.