2OG and other 2-monoacylglycerols formed during fat digestion can activate GPR119 and cause incretin release from the human intestine. This mechanism is likely to contribute to the known stimulatory effect of dietary fat on incretin secretion, and it indicates that GPR119 is a fat sensor.

This study was undertaken to investigate the link between dietary fat content and intestinal levels of anorectic N-acylethanolamines (NAEs), including oleoylethanolamide (OEA), palmitoylethanolamide (PEA), and linoleoylethanolamide (LEA). Male rats were fed high-fat diets (HFDs) with variable percentages of fat [20-45% of total energy (E%)] for 1-7 d; afterward, the jejunums were isolated, and jejunal NAE levels were measured by liquid-chromatography mass spectrometry. Enzyme activities and mRNA expression levels were measured for two synthesizing enzymes, N-acylphosphatidylethanolamine-specific phospholipase D (NAPE-PLD) and glycerophosphodiesterase (GDE1), and one degrading enzyme, fatty acid amide hydrolase (FAAH). We found a dose-response relation between the quantity/percentage of dietary fat, irrespective of the energy density, and the reduction of intestinal levels of OEA, PEA, and LEA. The reductions were present after 1 d of 45E% HFD. LEA, the major NAE species, was shown to have an anorectic potency slightly less than that of OEA but higher than PEA. Regulation at the enzyme level seems not to explain the changes in NAE levels. The results suggest the presence of a fat sensor, mediating the reduced intestinal NAE levels. The intestinal NAE levels are reduced in a dose- and time-dependent manner in response to dietary fat intake, and this may contribute to the well-known hyperphagic effect of HFDs.

Coronary artery disease is the main cause of death worldwide and accelerated by increased plasma levels of cholesterol-rich low-density lipoprotein particles (LDL). Circulating PCSK9 contributes to coronary artery disease by inducing lysosomal degradation of the LDL receptor (LDLR) in the liver and thereby reducing LDL clearance. Here, we show that liver heparan sulfate proteoglycans are PCSK9 receptors and essential for PCSK9-induced LDLR degradation. The heparan sulfate-binding site is located in the PCSK9 prodomain and formed by surface-exposed basic residues interacting with trisulfated heparan sulfate disaccharide repeats. Accordingly, heparan sulfate mimetics and monoclonal antibodies directed against the heparan sulfate-binding site are potent PCSK9 inhibitors. We propose that heparan sulfate proteoglycans lining the hepatocyte surface capture PCSK9 and facilitates subsequent PCSK9:LDLR complex formation. Our findings provide new insights into LDL biology and show that targeting PCSK9 using heparan sulfate mimetics is a potential therapeutic strategy in coronary artery disease.

No abstract

Spatial synthesis of N-acyl-phosphatidylethanolamines (NAPEs) and N-acylethanolamines (NAEs) during ischemia-reperfusion in neonatal rats has been investigated and compared to the spatial degradation of other phospholipids. Ischemia was induced in anesthetized Wistar P7 rat pups by left middle cerebral artery electrocoagulation combined with a transient and concomitant occlusion of both common carotid arteries. Pups were sacrificed after 24 and 48 h. Sham-treated animals were sacrificed after 48 h. The frozen brains were sliced and subjected to desorption electrospray ionization imaging mass spectrometry. There was a remarkable increase in the levels of many species of NAPEs in the whole injured area at both time points, and a clear but minor increase in selected NAEs. In the ischemic area, the sodium adducts of phosphatidylcholine and of lyso-phosphatidylcholine accumulated and the potassium adduct of phosphatidylcholine disappeared, indicating breakdown of the Na(+)/K(+) pump. Free fatty acids, e.g., arachidonic and docosahexaenoic acids, tended to be more abundant in the periphery than in the center of the ischemic area and showed different spatial distribution. NAPEs are synthesized in the whole ischemic area where the cells seem to be dead and other phospholipids are degraded. Free fatty acids can be found in the periphery of the ischemic area.

Context: Endocannabinoids (ECs) have a role in obesity by affecting appetite and through peripheral effects. Obesity is associated with a dysregulation of the endocannabinoid system (ECS). Objective: We aimed to determine the ECS in subcutaneous adipose tissue (AT) in obese subject and investigate the influence of diet-induced weight loss on this system. Design: The obese study participants underwent a 12 weeks diet regimen resulting in 10-12% weight loss. All study participants underwent fasting blood samples and AT biopsies from abdomen and gluteal region, the obese subjects both before and after weight loss. Setting and participants: A total of 21 healthy obese individuals (10 men/11 women, age 39.5 ± 1.6 years, body mass index (BMI): 37.5±0.8 kg m À2 ) and 21 age-and gender-matched lean subjects (BMI: 23.8±0.4 kg m À2 ) were studied. Main outcome measures: The activity of ECS in AT was determined by measuring arachidonoyl glycerol (2-AG) and N-arachidonoylethanolamine/anandamide in AT by mass spectrometry and gene expressions of enzymes and receptors involved in the ECS. Results: The EC, 2-AG was reduced in obese individuals in the gluteal AT depot (Po0.01). Moreover, 2-AG increased in both depots in the obese subjects following weight loss (Po0.05). The gene expression of the CB1 was either not affected by the obese state (in the gluteal AT depot) or reduced (in the abdominal depot, Po0.05) and significantly affected by weight loss. The expression of the degrading enzymes FAAH, FAAH2, MGL and MGL2 was differently affected by obesity, AT depot and weight loss. Conclusion: We found reduced levels of 2-AG in subcutaneous AT in obesity, which increased after weight loss. In abdominal AT, the low CB1 expression was normalised after weight loss, whereas in gluteal AT the CB1 expression was reduced after weight loss. These findings support the concept of a dysregulated ECS in AT in association with obesity.

Displaced dual-mode imaging (DDI) is introduced as a method for simultaneous imaging in positive and negative-ion mode on the same sample with desorption electrospray ionization imaging, as well as a method for simultaneous imaging in full-scan and tandem mass spectrometry (MS/MS) mode. DDI is performed by using a smaller row distance in the y-direction than the desired image resolution and recording for example every second row in positive-ion mode and the other half of the rows in negative-ion mode, thus resulting in two separate images. This causes some degree of oversampling, which is thus utilized to obtain complementary mass spectrometric of the sample. Imaging with both polarities is exemplified on an imprint of a Hypericum perforatum leaf containing secondary metabolites which ionize in both polarites and a mouse kidney containing phospholipids which ionize in positive or negative mode only. Simultaneous full-scan and MS/MS imaging was demonstrated on the same mouse kidney, as the mouse had been given a relatively low dose of the antidepressive drug amitriptyline. While the full-scan data allowed imaging of the endogenous phospholipids, the drug and its metabolites were only visible in the MS/MS images. The latter approach is useful, for example in whole-body imaging experiments where the full-scan data gives an overview of the tissue, and the MS/MS mode provides the sensitivity to image trace amounts of drugs and metabolites.

The ADAMTS9 rs4607103 C allele is one of the few gene variants proposed to increase the risk of type 2 diabetes through an impairment of insulin sensitivity. We show that the variant is associated with increased expression of the secreted ADAMTS9 and decreased insulin sensitivity and signaling in human skeletal muscle. In line with this, mice lacking Adamts9 selectively in skeletal muscle have improved insulin sensitivity. The molecular link between ADAMTS9 and insulin signaling was characterized further in a model where ADAMTS9 was overexpressed in skeletal muscle. This selective overexpression resulted in decreased insulin signaling presumably mediated through alterations of the integrin β1 signaling pathway and disruption of the intracellular cytoskeletal organization. Furthermore, this led to impaired mitochondrial function in mouse muscle—an observation found to be of translational character because humans carrying the ADAMTS9 risk allele have decreased expression of mitochondrial markers. Finally, we found that the link between ADAMTS9 overexpression and impaired insulin signaling could be due to accumulation of harmful lipid intermediates. Our findings contribute to the understanding of the molecular mechanisms underlying insulin resistance and type 2 diabetes and point to inhibition of ADAMTS9 as a potential novel mode of treating insulin resistance.