Ceramide is among a number of potential lipotoxic molecules that are thought to modulate cellular energy metabolism. The heart is one of the tissues thought to become dysfunctional due to excess lipid accumulation. Dilated lipotoxic cardiomyopathy, thought to be the result of diabetes and severe obesity, has been modeled in several genetically altered mice, including animals with cardiac-specific overexpression of glycosylphosphatidylinositol (GPI)-anchored human lipoprotein lipase (LpL GPI ). To test whether excess ceramide was implicated in cardiac lipotoxicity, de novo ceramide biosynthesis was inhibited pharmacologically by myriocin and genetically by heterozygous deletion of LCB1, a subunit of serine palmitoyltransferase (SPT). Inhibition of SPT, a rate-limiting enzyme in ceramide biosynthesis, reduced fatty acid and increased glucose oxidation in isolated perfused LpL GPI hearts, improved systolic function, and prolonged survival rates. Our results suggest a critical role for ceramide accumulation in the pathogenesis of lipotoxic cardiomyopathy.-Park, T

Long-chain fatty acids (FAs) are the predominant energy substrate utilized by the adult heart. The heart can utilize unesterified FA bound to albumin or FA obtained from lipolysis of lipoprotein-bound triglyceride (TG). We used heart-specific lipoprotein lipase knock-out mice (hLpL0) to test whether these two sources of FA are interchangeable and necessary for optimal heart function. Hearts unable to obtain FA from lipoprotein TG were able to compensate by increasing glucose uptake, glycolysis, and glucose oxidation. HLpL0 hearts had decreased expression of pyruvate dehydrogenase kinase 4 and increased cardiomyocyte expression of glucose transporter 4. Conversely, FA oxidation rates were reduced in isolated perfused hLpL0 hearts. Following abdominal aortic constriction expression levels of genes regulating FA and glucose metabolism were acutely up-regulated in control and hLpL0 mice, yet all hLpL0 mice died within 48 h of abdominal aortic constriction. Older hLpL0 mice developed cardiac dysfunction characterized by decreased fractional shortening and interstitial and perivascular fibrosis. HLpL0 hearts had increased expression of several genes associated with transforming growth factor-␤ signaling. Thus, long term reduction of lipoprotein FA uptake is associated with impaired cardiac function despite a compensatory increase in glucose utilization.Normal cardiac muscle function requires adequate delivery of oxygen and energy substrates for the production of ATP. In the adult heart, fatty acid (FA) 4 oxidation accounts for 60 -70% of oxygen consumption, with the balance provided by glucose and lactate (1-3). However, during conditions such as ischemia (4, 5) and hypertrophy (4 -6) the heart becomes more dependent on glucose. This initial adaptive response is beneficial in that it maintains ATP levels (7, 8) in the face of diminished mitochondrial oxidative phosphorylation. High rates of FA oxidation inhibit glucose oxidation and impair the recovery of mechanical function during reperfusion of ischemic hearts (9), whereas partial inhibition of FA oxidation during acute ischemia increases glucose oxidation and improves contractile power and efficiency (10 -12). Several pharmacological agents have been developed, including dichloroacetate and ranolazine, which increase glucose oxidation in isolated hearts subjected to ischemia (4, 12). Furthermore, trimetazine, an inhibitor of long-chain 3-ketoacyl-coenzyme A thiolase (the final enzyme in the ␤-oxidation pathway), is cardioprotective in several models of ischemia (13). However, the long term effects of reduced FA oxidation on cardiac energetics and function are unknown.All tissues have several routes through which they may acquire FAs. The heart avidly utilizes FA associated with albumin, and this can be demonstrated both in vivo and in perfused hearts. However, esterified FAs contained in lipoproteins are the major source of cardiac FA (14). These two sources of FA can compete for uptake in perfused hearts (15); this is not surprising, because conversion of TG to ...

TORC2 is a major transcriptional coactivator for hepatic glucose production. Insulin impedes gluconeogenesis by inhibiting TORC2 via SIK2-dependent phosphorylation at Ser171. Interruption of this process greatly perturbs hepatic glucose metabolism, thus promoting hyperglycemia in rodents. Here, we show that hyperactivation of TORC2 would exacerbate insulin resistance by enhancing expression of LIPIN1, a mammalian phosphatidic acid phosphatase for diacylglycerol (DAG) synthesis. Diet-induced or genetic obesity increases LIPIN1 expression in mouse liver, and TORC2 is responsible for its transcriptional activation. While overexpression of LIPIN1 disturbs hepatic insulin signaling, knockdown of LIPIN1 ameliorates hyperglycemia and insulin resistance by reducing DAG and PKCvarepsilon activity in db/db mice. Finally, TORC2-mediated insulin resistance is partially rescued by concomitant knockdown of LIPIN1, confirming the critical role of LIPIN1 in the perturbation of hepatic insulin signaling. These data propose that dysregulation of TORC2 would further exaggerate insulin resistance and promote type 2 diabetes in a LIPIN1-dependent manner.

Background The hepatic endocannabinoid system and cytochrome P450 2E1 (CYP2E1), a key enzyme causing alcohol-induced reactive oxygen species (ROS) generation, are major contributors to the pathogenesis of alcoholic liver disease. The nuclear hormone receptor oestrogen-related receptor γ (ERRγ) is a constitutively active transcriptional activator regulating gene expression. Objective To investigate the role of ERRγ in the alcohol-mediated regulation of CYP2E1 and to examine the possibility to control alcohol-mediated oxidative stress and liver injury through an ERRγ inverse agonist. Design For chronic alcoholic hepatosteatosis study, C57BL/6J wild-type and CB1−/− mice were administered alcohol for 4 weeks. GSK5182 and chlormethiazole (CMZ) were given by oral gavage for the last 2 weeks of alcohol feeding. Gene expression profiles and biochemical assays were performed using the liver or blood of mice. Results Hepatic ERRγ gene expression induced by alcohol-mediated activation of CB1 receptor results in induction of CYP2E1, while liver-specific ablation of ERRγ gene expression blocks alcohol-induced expression of CYP2E1 in mouse liver. An ERRγ inverse agonist significantly ameliorates chronic alcohol-induced liver injury in mice through inhibition of CYP2E1-mediated generation of ROS, while inhibition of CYP2E1 by CMZ abrogates the beneficial effects of the inverse agonist. Finally, chronic alcohol-mediated ERRγ and CYP2E1 gene expression, ROS generation and liver injury in normal mice were nearly abolished in CB1−/− mice. Conclusions ERRγ, as a previously unrecognised transcriptional regulator of hepatic CB1 receptor, controls alcohol-induced oxidative stress and liver injury through CYP2E1 induction, and its inverse agonist could ameliorate oxidative liver injury due to chronic alcohol exposure.

OBJECTIVEDiet-induced obesity (DIO) is linked to peripheral insulin resistance—a major predicament in type 2 diabetes. This study aims to identify the molecular mechanism by which DIO-triggered endoplasmic reticulum (ER) stress promotes hepatic insulin resistance in mouse models.RESEARCH DESIGN AND METHODSC57BL/6 mice and primary hepatocytes were used to evaluate the role of LIPIN2 in ER stress-induced hepatic insulin resistance. Tunicamycin, thapsigargin, and lipopolysaccharide were used to invoke acute ER stress conditions. To promote chronic ER stress, mice were fed with a high-fat diet for 8–12 weeks. To verify the role of LIPIN2 in hepatic insulin signaling, adenoviruses expressing wild-type or mutant LIPIN2, and shRNA for LIPIN2 were used in animal studies. Plasma glucose, insulin levels as well as hepatic free fatty acids, diacylglycerol (DAG), and triacylglycerol were assessed. Additionally, glucose tolerance, insulin tolerance, and pyruvate tolerance tests were performed to evaluate the metabolic phenotype of these mice.RESULTSLIPIN2 expression was enhanced in mouse livers by acute ER stress–inducers or by high-fat feeding. Transcriptional activation of LIPIN2 by ER stress is mediated by activating transcription factor 4, as demonstrated by LIPIN2 promoter assays, Western blot analyses, and chromatin immunoprecipitation assays. Knockdown of hepatic LIPIN2 in DIO mice reduced fasting hyperglycemia and improved hepatic insulin signaling. Conversely, overexpression of LIPIN2 impaired hepatic insulin signaling in a phosphatidic acid phosphatase activity–dependent manner.CONCLUSIONSThese results demonstrate that ER stress–induced LIPIN2 would contribute to the perturbation of hepatic insulin signaling via a DAG-protein kinase C ε–dependent manner in DIO mice.

BackgroundGenetic factors account for the majority of differences in skin color and hair morphology across human populations. Although many studies have been conducted to examine differences in skin color across populations, few studies have examined differences in hair morphology.ObjectiveTo investigate changing of integral hair lipids after ultraviolet (UV) irradiation in three human ethnic groups.MethodsWe studied the UV irradiation induced hair damage in hairs of three human populations. UV irradiation had been performed with self-manufactured phototherapy system. Damaged hair samples were prepared at 12 and 48 hours after UVA (20 J/sec) and UVB (8 J/sec) irradiation. We evaluated the changes of hair lipid using scanning electron microscopy (SEM), transmission electron microscopy (TEM), lipid TEM and HP-TLC. After UV irradiation, hair surface damage was shown.ResultsAfrican hair showed more severe damage on hair surface than others. The lipid compositions across human populations were similar, but Asian hair had more integral hair lipids than other groups as a whole. Especially, free fatty acid contents were higher than other lipids. After UV irradiation, lipid contents were decreased. These patterns were shown in all human populations. Asian hair has more integral hair lipid than European or African hair. After UV irradiation, European and African hair samples exhibited more damage because they have less integral hair lipids. However, Asian hair samples have less damage.ConclusionWe conclude that integral hair lipid may protect the hair against the UV light.

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The Saccharomyces cerevisiae URA7-encoded CTP synthetase is phosphorylated and stimulated by protein kinase C. We examined the hypothesis that Ser 36 , Ser 330 , Ser 354 , and Ser 454 , contained in a protein kinase C sequence motif in CTP synthetase, were target sites for the kinase. Synthetic peptides containing a phosphorylation motif at these serine residues served as substrates for protein kinase C in vitro. Ser 3 Ala (S36A, S330A, S354A, and S454A) mutations in CTP synthetase were constructed by site-directed mutagenesis and expressed normally in a ura7 ura8 double mutant that lacks CTP synthetase activity. The CTP synthetase activity in extracts from cells bearing the S36A, S354A, and S454A mutant enzymes was reduced when compared with cells bearing the wild type enzyme. Kinetic analysis of purified mutant enzymes showed that the S36A and S354A mutations caused a decrease in the V max of the reaction. This regulation could be attributed in part by the effects phosphorylation has on the nucleotide-dependent oligomerization of CTP synthetase. In contrast, CTP synthetase activity in cells bearing the S330A mutant enzyme was elevated, and kinetic analysis of purified enzyme showed that the S330A mutation caused an elevation in the V max of the reaction. In vitro data indicated that phosphorylation of CTP synthetase at Ser 330 affected the phosphorylation of the enzyme at another site. The phosphorylation of CTP synthetase at Ser 36 , Ser 330 , Ser 354 , and Ser 454 residues was physiologically relevant. Cells bearing the S36A, S354A, and S454A mutations had reduced CTP levels, whereas cells with the S330A mutation had elevated CTP levels. The alterations in CTP levels correlated with the regulatory effects CTP has on the pathways responsible for the synthesis of the membrane phospholipid phosphatidylcholine.In the yeast Saccharomyces cerevisiae CTP synthetase catalyzes the ATP-dependent transfer of the amide nitrogen of glutamine to the C-4 position of UTP to form CTP (1, 2). GTP stimulates the reaction by accelerating the formation of a covalent glutaminyl enzyme catalytic intermediate (2-5). URA7 (6) and URA8 (7) are duplicate genes that code for CTP synthetase in S. cerevisiae. The yeast CTP synthetase enzymes (6, 7) contain a conserved glutamine amide transfer domain (see Fig. 1) common to CTP synthetases from other organisms (8 -16). The URA7-encoded CTP synthetase is more abundant than the URA8-encoded enzyme (17) and is responsible for the majority of the CTP synthesized in vivo (7). Neither the URA7 nor the URA8 gene is essential as long as cells possess one functional CTP synthetase gene (6, 7). CTP synthetase is an indispensable enzyme because its reaction product CTP is essential for the synthesis of nucleic acids and membrane phospholipids (18). The importance of understanding the regulation of CTP synthetase is emphasized by the fact that unregulated levels of its activity is a common property of various cancers in humans (19 -26).The yeast CTP synthetase is regulated by genetic and biochemical m...