Mice deficient in mitochondrial glycerol-3-phosphate acyltransferase-1 have diminished myocardial triacylglycerol accumulation during lipogenic diet and altered phospholipid fatty acid composition.

Glycerol-3-phosphate acyltransferase-1 (GPAT1), which is located on the outer mitochondrial membrane comprises up to 30% of total GPAT activity in the heart. It is one of at least four mammalian GPAT isoforms known to catalyze the initial, committed, and rate-limiting step of glycerolipid synthesis. Because excess triacylglycerol (TAG) accumulates in cardiomyocytes in obesity and type 2 diabetes, we determined whether lack of GPAT1 would alter the synthesis of heart TAG and phospholipids after a 2-week high-sucrose diet or a 3-month high-fat diet. Even in the absence of hypertriglyceridemia, TAG increased 2-fold with both diets in hearts from wildtype mice. In contrast, hearts from Gpat1(-/-) mice contained 20-80% less TAG than the wildtype controls. In addition, hearts from Gpat1(-/-) mice fed the high-sucrose diet incorporate 60% less [(14)C]palmitate into heart TAG as compared to wildtype mice. Because GPAT1 prefers 16:0-CoA to other long-chain acyl-CoA substrates, we determined the fatty acid composition of heart phospholipids. Compared to wildtype littermate controls, hearts from Gpat1(-/-)(-/-) mice contained a lower amount of 16:0 in phosphatidylcholine, phosphatidylethanolamine, and phosphatidylserine/phosphatidylinositol and significantly more C20:4n6. Phosphatidylcholine and phosphatidylethanolamine from Gpat1(-/-)(-/-) hearts also contained higher amounts of 18:0 and 18:1. Although at least three other GPAT isoforms are expressed in the heart, our data suggest that GPAT1 contributes significantly to cardiomyocyte TAG synthesis during lipogenic or high-fat diets and influences the incorporation of 20:4n6 into heart phospholipids.

Ontogeny of mRNA expression and activity of long-chain acyl-CoA synthetase (ACSL) isoforms in Mus musculus heart.

Long-chain acyl-CoA synthetases (ACSL) activate fatty acids (FA) and provide substrates for virtually every metabolic pathway that catabolizes FA or synthesizes complex lipids. We have hypothesized that each of the five cloned ACSL isoforms partitions FA towards specific downstream pathways. Adult heart expresses all five cloned ACSL isoforms, but their independent functional roles have not been elucidated. Studies implicate ACSL1 in both oxidative and lipid synthetic pathways. To clarify the functional role of ACSL1 and the other ACSL isoforms (3-6), we examined ACS specific activity and Acsl mRNA expression in the developing mouse heart which increases FA oxidative pathways for energy production after birth. Compared to the embryonic heart, ACS specific activity was 14-fold higher on post-natal day 1 (P1). On P1, as compared to the fetus, only Acsl1 mRNA increased, whereas transcripts for the other Acsl isoforms remained the same, suggesting that ACSL1 is the major isoform responsible for activating long-chain FA for myocardial oxidation after birth. In contrast, the mRNA abundance of Acsl3 was highest on E16, and decreased dramatically by P7, suggesting that ACSL3 may play a critical role during the development of the fetal heart. Our data support the hypothesis that each ACSL has a specific role in the channeling of FA towards distinct metabolic fates.

Differential changes in QTc duration during in-hospital haloperidol use.

AIMS: To evaluate changes in QT duration during low-dose haloperidol use, and determine associations between clinical variables and potentially dangerous QT prolongation. METHODS: In a retrospective cohort study in a tertiary university teaching hospital in The Netherlands, all 1788 patients receiving haloperidol between 2005 and 2007 were studied; ninety-seven were suitable for final analysis. Rate-corrected QT duration (QTc) was measured before, during and after haloperidol use. Clinical variables before haloperidol use and at the time of each ECG recording were retrieved from hospital charts. Mixed model analysis was used to estimate changes in QT duration. Risk factors for potentially dangerous QT prolongation were estimated by logistic regression analysis. RESULTS: Patients with normal before-haloperidol QTc duration (male ≤430 ms, female ≤450 ms) had a significant increase in QTc duration of 23 ms during haloperidol use; twenty-three percent of patients rose to abnormal levels (male ≥450 ms, female ≥470 ms). In contrast, a significant decrease occurred in patients with borderline (male 430-450 ms, female 450-470 ms) or abnormal before-haloperidol QTc duration (15 ms and 46 ms, respectively); twenty-three percent of patients in the borderline group, and only 9% of patients in the abnormal group obtained abnormal levels. Potentially dangerous QTc prolongation was independently associated with surgery before haloperidol use (OR(adj) 34.9, p = 0.009) and before-haloperidol QTc duration (OR(adj) 0.94, p = 0.004). CONCLUSION: QTc duration during haloperidol use changes differentially, increasing in patients with normal before-haloperidol QTc duration, but decreasing in patients with prolonged before-haloperidol QTc duration. Shorter before-haloperidol QTc duration and surgery before haloperidol use predict potentially dangerous QTc prolongation.

Enteric salmonella infection inhibits Paneth cell antimicrobial peptide expression.

Paneth cells, highly secretory epithelial cells found at the bases of small intestinal crypts, release a variety of microbicidal molecules, including alpha-defensins and lysozyme. The secretion of antimicrobials by Paneth cells is thought to be important in mucosal host defense against invasion by enteric pathogens. We explored whether enteric pathogens can interfere with this arm of defense. We found that oral inoculation of mice with wild-type Salmonella enterica serovar Typhimurium decreases the expression of alpha-defensins (called cryptdins in mice) and lysozyme. Oral inoculation with Salmonella serovar Typhimurium strains that are heat killed, lack the PhoP regulon, and lack the SPI1 type III secretion system or with Listeria monocytogenes does not have this effect. Salmonella may gain a specific survival advantage in the intestinal lumen by decreasing the expression of microbicidal peptides in Paneth cells through direct interactions between Salmonella and the small intestinal epithelium.

Analysis of 16S libraries of mouse gastrointestinal microflora reveals a large new group of mouse intestinal bacteria.

Total genomic DNA from samples of intact mouse small intestine, large intestine, caecum and faeces was used as template for PCR amplification of 16S rRNA gene sequences with conserved bacterial primers. Phylogenetic analysis of the amplification products revealed 40 unique 16S rDNA sequences. Of these sequences, 25% (10/40) corresponded to described intestinal organisms of the mouse, including Lactobacillus spp., Helicobacter spp., segmented filamentous bacteria and members of the altered Schaedler flora (ASF360, ASF361, ASF502 and ASF519); 75% (30/40) represented novel sequences. A large number (11/40) of the novel sequences revealed a new operational taxonomic unit (OTU) belonging to the Cytophaga-Flavobacter-Bacteroides phylum, which the authors named 'mouse intestinal bacteria'. 16S rRNA probes were developed for this new OTU. Upon analysis of the novel sequences, eight were found to cluster within the Eubacterium rectale-Clostridium coccoides group and three clustered within the Bacteroides group. One of the novel sequences was distantly related to Verrucomicrobium spinosum and one was distantly related to Bacillus mycoides. Oligonucleotide probes specific for the 16S rRNA of these novel clones were generated. Using a combination of four previously described and four newly designed probes, approximately 80% of bacteria recovered from the murine large intestine and 71% of bacteria recovered from the murine caecum could be identified by fluorescence in situ hybridization (FISH).