The Micro-Managing Fat: Exosomes as a New Messenger

Brown fat secretes endocrine factors and exerts metabolic effects beyond thermogenesis. In addition to protein factors and bioactive lipids, recent work has revealed brown fat-derived miRNAs carried by exosomes as a new means of interorgan crosstalk, with potentially important implications for metabolic physiology and disease.

Beraprost sodium, a prostacyclin analogue, reduces fructose-induced hepatocellular steatosis in mice and in vitro via the microRNA-200a and SIRT1 signaling pathway

PURPOSE

To determine whether beraprost sodium, a prostacyclin analogue, could reduce hepatic lipid accumulation induced by fructose in mice and cultured human hepatocytes, and to investigate the expression of microRNAs and the sirtuin 1 (SIRT1) pathway.

METHODS

Male C57BL/6JNju mice were divided into three groups and fed one of the following diets: a normal diet, a high fructose diet, or a high fructose diet with beraprost sodium treatment. In addition, human-derived HepG2 cells were cultured and treated with fructose (25mmol/L) with or without beraprost sodium (10μmol/L) for 24h, and transfected with small interfering RNA (siRNA) against SIRT1, miR-200a mimic, or miR-200a inhibitor for 48h. The miRNA microarray analysis was performed on the HepG2 cells, and the expression profiles of miRNAs were analyzed using Gene Cluster 3.0 and verified using qPCR.

RESULTS

Beraprost sodium treatment attenuated hepatic steatosis, induced the transcription of genes involved in lipid metabolism in C57BL/6 mice (P<0.05), and increased the expression of hepatic SIRT1 and peroxisome proliferator activated receptor α (PPARα) in the cells treated with fructose. These effects were blocked in HepG2 cells after transfection with siRNA against SIRT1. MiR-200a was highly expressed during fructose treatment and was down regulated by beraprost sodium (P<0.05). A luciferase assay showed that miR-200a regulated SIRT1 by binding to the 3' UTR. Overexpression of miR-200a inhibited expression of hepatic SIRT1.

CONCLUSIONS

Our study demonstrated that SIRT1 pathway mediated the effects of beraprost sodium on attenuation of hepatic lipid disorders induced by fructose and revealed the primary role of miR-200a in the regulation of hepatic SIRT1 by beraprost sodium. Our findings suggested that SIRT1 might be a therapeutic target of fructose-related metabolism disorders.

Induced Pluripotent Stem Cell Differentiation Enables Functional Validation of GWAS Variants in Metabolic Disease

Genome-wide association studies (GWAS) have highlighted a large number of genetic variants with potential disease association, but functional analysis remains a challenge. Here we describe an approach to functionally validate identified variants through differentiation of induced pluripotent stem cells (iPSCs) to study cellular pathophysiology. We collected peripheral blood cells from Framingham Heart Study participants and reprogrammed them to iPSCs. We then differentiated 68 iPSC lines into hepatocytes and adipocytes to investigate the effect of the 1p13 rs12740374 variant on cardiometabolic disease phenotypes via transcriptomics and metabolomic signatures. We observed a clear association between rs12740374 and lipid accumulation and gene expression in differentiated hepatocytes, in particular, expression of SORT1, CELSR2, and PSRC1, consistent with previous analyses of this variant using other approaches. Initial investigation of additional SNPs also highlighted correlations with gene expression. These findings suggest that iPSC-based population studies hold promise as tools for the functional validation of GWAS variants.

Hemin Improves Insulin Sensitivity and Lipid Metabolism in Cultured Hepatocytes and Mice Fed a High-Fat Diet

Hemin is a breakdown product of hemoglobin. It has been reported that the injection of hemin improves lipid metabolism and insulin sensitivity in various genetic models. However, the effect of hemin supplementation in food on lipid metabolism and insulin sensitivity is still unclear, and whether hemin directly affects cellular insulin sensitivity is yet to be elucidated. Here we show that hemin enhances insulin-induced phosphorylation of insulin receptors, Akt, Gsk3β, FoxO1 and cytoplasmic translocation of FoxO1 in cultured primary hepatocytes under insulin-resistant conditions. Furthermore, hemin diminishes the accumulation of triglyceride and increases in free fatty acid content in primary hepatocytes induced by palmitate. Oral administration of hemin decreases body weight, energy intake, blood glucose and triglyceride levels, and improves insulin and glucose tolerance as well as hepatic insulin signaling and hepatic steatosis in male mice fed a high-fat diet. In addition, hemin treatment decreases the mRNA and protein levels of some hepatic genes involved in lipogenic regulation, fatty acid synthesis and storage, and increases the mRNA level and enzyme activity of CPT1 involved in fatty acid oxidation. These data demonstrate that hemin can improve lipid metabolism and insulin sensitivity in both cultured hepatocytes and mice fed a high-fat diet, and show the potential beneficial effects of hemin from food on lipid and glucose metabolism.

Resveratrol ameliorates diet-induced dysregulation of lipid metabolism in zebrafish (Danio rerio)

Defective lipid metabolism is associated with increased risk of various chronic diseases, such as obesity, cardiovascular diseases, and diabetes. Resveratrol (RSV), a natural polyphenol, has been shown the potential of ameliorating disregulations of lipid metabolism. The objective of this study was to investigate the effects of feed intake and RSV on lipid metabolism in zebrafish (Danio rerio). The adult males were randomly allocated to 6 groups: control (Con, 8 mg cysts/fish/day), control with 20 μmol/L RSV (Con+RSV), calorie restriction (CR, 5 mg cysts/fish/day), calorie restriction with RSV (CR+RSV), overfeed (OF, 60 mg cysts/fish/day), and overfeed with RSV (OF+RSV) groups. The treatment period was 8 weeks. Results showed that CR reduced body length, body weight, and condition factor of zebrafish. CR reduced levels of plasma triglyceride (TG) and induced protein expression of phosphorylated AMP-activated protein kinase-α (pAMPKα), silent information regulator 2 homolog 1 (Sirt1), and peroxisome proliferator activated receptor gamma coactivator-1α (PGC1α). RSV attenuated CR-induced pAMPKα/AMPKαincreases. RSV increased levels of Sirt1 protein in the OF zebrafish, and decreased OF-induced increase in peroxisome proliferator-activated receptor-γ (PPARγ) protein level. Additionally, RSV down-regulated caveolin-1 and up-regulated microtubule-associated protein 1 light chain 3 -II (LC3-II) protein levels in OF zebrafish. In conclusion, these results suggest that 1) CR reduces plasma TG level through activation of the AMPKα-Sirt1- PGC1α pathway; 2) under different dietary stress conditions RSV might regulate AMPK phosphorylation bi-directionally; 3) RSV might regulate lipid metabolism through the AMPKα-Sirt1-PPARγ pathway in OF zebrafish.

Detection of Lipid and Amphiphilic Biomarkers for Disease Diagnostics

Rapid diagnosis is crucial to effectively treating any disease. Biological markers, or biomarkers, have been widely used to diagnose a variety of infectious and non-infectious diseases. The detection of biomarkers in patient samples can also provide valuable information regarding progression and prognosis. Interestingly, many such biomarkers are composed of lipids, and are amphiphilic in biochemistry, which leads them to be often sequestered by host carriers. Such sequestration enhances the difficulty of developing sensitive and accurate sensors for these targets. Many of the physiologically relevant molecules involved in pathogenesis and disease are indeed amphiphilic. This chemical property is likely essential for their biological function, but also makes them challenging to detect and quantify in vitro. In order to understand pathogenesis and disease progression while developing effective diagnostics, it is important to account for the biochemistry of lipid and amphiphilic biomarkers when creating novel techniques for the quantitative measurement of these targets. Here, we review techniques and methods used to detect lipid and amphiphilic biomarkers associated with disease, as well as their feasibility for use as diagnostic targets, highlighting the significance of their biochemical properties in the design and execution of laboratory and diagnostic strategies. The biochemistry of biological molecules is clearly relevant to their physiological function, and calling out the need for consideration of this feature in their study, and use as vaccine, diagnostic and therapeutic targets is the overarching motivation for this review.

Lipid management in India: a nationwide, cross-sectional physician survey

BACKGROUND

Current international guidelines on dyslipidemia are not concordant on various aspects of management. Also, there are no uniformly accepted Indian guidelines. We, therefore, performed a physician survey to understand lipid management practices in India.

METHODS

An anonymous survey questionnaire was administered to gauge physicians' self-reported behavior regarding lipid management aspects. Results were expressed in terms of percentages based on the number of responses obtained.

RESULTS

A total of 404 physicians participated in the survey. Eighty-eight percent respondents ordered a lipid profile before starting statin therapy, and 80% preferred to set lipid targets, though the tools used for calculating cardiovascular risk varied. Atorvastatin was preferred over rosuvastatin in primary prevention (72.9 vs. 32.4%), secondary prevention (54.6 vs. 46.7%), diabetic patients (56.3 vs. 40.3%) and post-ACS (78.3 vs. 34%). High-intensity statins were preferred by 73.7% of respondents in post-ACS cases. Fifty percent doctors chose not to use a statin in diabetic patients, irrespective of their LDL-C levels. The most preferred drug option for managing atherogenic dyslipidemia and moderate hypertriglyceridemia was statin-fibrate combination (55.1%) and fibrates (35.4%), respectively. Sixty-three percent doctors preferred to prescribe statins in patients with moderately high LDL-C and normal triglycerides, without CHD or CHD risk equivalents. Around 28% of doctors preferred not to use pharmacotherapy for managing isolated low HDL. Of the participants, 73% used fibrates in ≤20% of their dyslipidemic patients, with fenofibrate being the most preferred (90.5%). Ezetimibe was mainly used in patients with uncontrolled LDL-C despite statin therapy (52.4% respondents). Most preferred approaches to manage statin intolerance included reducing statin dose (39%) and stopping and restarting statins at a lower dose (34.5%). Fifty-two percent of doctors chose not to alter pre-existing therapy in patients who had LDL-C levels at goal but elevated non-HDL-C levels.

CONCLUSION

This is the first survey in India that provides useful insights into Indian physicians' self-reported perspectives on managing dyslipidemia in routine clinical practice. Despite concordance with the currently available guidelines in certain aspects, there is incongruence in managing specific dyslipidemia problems. Further continuing medical education and the development of evidence-based, India-specific lipid guidelines can help reduce some of these differences.

Skeletal Muscle PGC1α -1 Nucleosome Position and -260 nt DNA Methylation Determine Exercise Response and Prevent Ectopic Lipid Accumulation in Men

Endurance exercise has been shown to improve lipid oxidation and increase mitochondrial content in skeletal muscle, two features that have shown dependence on increased expression of the peroxisome proliferator-activated receptor-γ coactivator 1α (PGC1α). It is also hypothesized that exercise-related alterations in PGC1α expression occur through epigenetic regulation of nucleosome positioning in association with differential DNA methylation status within the PGC1α promoter. In this study, we show that when primary human myotubes from obese patients with type 2 diabetes are exposed to lipolytic stimulus (palmitate, forskolin, inomycin) in vitro, nucleosome occupancy surrounding the -260 nucleotide (nt) region, a known regulatory DNA methylation site, is reduced. This finding is reproduced in vivo in the vastus lateralis from 11 healthy males after a single, long endurance exercise bout in which participants expended 650 kcal. Additionally, we show a significant positive correlation between fold change of PGC1α messenger RNA expression and -1 nucleosome repositioning away from the -260 nt methylation site in skeletal muscle tissue following exercise. Finally, we found that when exercise participants are divided into high and low responders based on the -260 nt methylation status, the -1 nucleosome is repositioned away from the regulatory -260 nt methylation site in high responders, those exhibiting a significant decrease in -260 nt methylation, but not in low responders. Additionally, high but not low responders showed a significant decrease in intramyocellular lipid content after exercise. These findings suggest a potential target for epigenetic modification of the PGC1α promoter to stimulate the therapeutic effects of endurance exercise in skeletal muscle.

Hypothalamic Regulation of Liver and Muscle Nutrient Partitioning by Brain-Specific Carnitine Palmitoyltransferase 1C in Male Mice

Carnitine palmitoyltransferase (CPT) 1C, a brain-specific protein localized in the endoplasmic reticulum of neurons, is expressed in almost all brain regions. Based on global knockout (KO) models, CPT1C has demonstrated relevance in hippocampus-dependent spatial learning and in hypothalamic regulation of energy balance. Specifically, it has been shown that CPT1C is protective against high-fat diet-induced obesity (DIO), and that CPT1C KO mice show reduced peripheral fatty acid oxidation (FAO) during both fasting and DIO. However, the mechanisms mediating CPT1C-dependent regulation of energy homeostasis remain unclear. Here, we focus on the mechanistic understanding of hypothalamic CPT1C on the regulation of fuel selection in liver and muscle of male mice during energy deprivation situations, such as fasting. In CPT1C-deficient mice, modulation of the main hypothalamic energy sensors (5' adenosine monophosphate-activated protein kinase, Sirtuin 1, and mammalian target of rapamycin) was impaired and plasma catecholamine levels were decreased. Consequently, CPT1C-deficient mice presented defective fasting-induced FAO in liver, leading to higher triacylglycerol accumulation and lower glycogen levels. Moreover, muscle pyruvate dehydrogenase activity was increased, which was indicative of glycolysis enhancement. The respiratory quotient did not decrease in CPT1C KO mice after 48 hours of fasting, confirming a defective switch on fuel substrate selection under hypoglycemia. Phenotype reversion studies identified the mediobasal hypothalamus (MBH) as the main area mediating CPT1C effects on fuel selection. Overall, our data demonstrate that CPT1C in the MBH is necessary for proper hypothalamic sensing of a negative energy balance and fuel partitioning in liver and muscle.

Altered miR-29 Expression in Type 2 Diabetes Influences Glucose and Lipid Metabolism in Skeletal Muscle

MicroRNAs have emerged as important regulators of glucose and lipid metabolism in several tissues; however, their role in skeletal muscle remains poorly characterized. We determined the effects of the miR-29 family on glucose metabolism, lipid metabolism, and insulin responsiveness in skeletal muscle. We provide evidence that miR-29a and miR-29c are increased in skeletal muscle from patients with type 2 diabetes and are decreased following endurance training in healthy young men and in rats. In primary human skeletal muscle cells, inhibition and overexpression strategies demonstrate that miR-29a and miR-29c regulate glucose uptake and insulin-stimulated glucose metabolism. We identified that miR-29 overexpression attenuates insulin signaling and expression of insulin receptor substrate 1 and phosphoinositide 3-kinase. Moreover, miR-29 overexpression reduces hexokinase 2 expression and activity. Conversely, overexpression of miR-29 by electroporation of mouse tibialis anterior muscle decreased glucose uptake and glycogen content in vivo, concomitant with decreased abundance of GLUT4. We also provide evidence that fatty acid oxidation is negatively regulated by miR-29 overexpression, potentially through the regulation of peroxisome proliferator-activated receptor γ coactivator-1α expression. Collectively, we reveal that miR-29 acts as an important regulator of insulin-stimulated glucose metabolism and lipid oxidation, with relevance to human physiology and type 2 diabetes.

Deactivating Fatty Acids: Acyl-CoA Thioesterase-Mediated Control of Lipid Metabolism

The cellular uptake of free fatty acids (FFA) is followed by esterification to coenzyme A (CoA), generating fatty acyl-CoAs that are substrates for oxidation or incorporation into complex lipids. Acyl-CoA thioesterases (ACOTs) constitute a family of enzymes that hydrolyze fatty acyl-CoAs to form FFA and CoA. Although biochemically and biophysically well characterized, the metabolic functions of these enzymes remain incompletely understood. Existing evidence suggests regulatory roles in controlling rates of peroxisomal and mitochondrial fatty acyl-CoA oxidation, as well as in the subcellular trafficking of fatty acids. Emerging data implicate ACOTs in the pathogenesis of metabolic diseases, suggesting that better understanding their pathobiology could reveal unique targets in the management of obesity, diabetes, and nonalcoholic fatty liver disease.

Tumor Necrosis Factor-α Promotes Phosphoinositide 3-Kinase Enhancer A and AMP-Activated Protein Kinase Interaction to Suppress Lipid Oxidation in Skeletal Muscle

Tumor necrosis factor-α (TNF-α) is an inflammatory cytokine that plays a central role in obesity-induced insulin resistance. It also controls cellular lipid metabolism, but the underlining mechanism is poorly understood. We report in this study that phosphoinositide 3-kinase enhancer A (PIKE-A) is a novel effector of TNF-α to facilitate its metabolic modulation in the skeletal muscle. Depletion of PIKE-A in C2C12 myotubes diminished the inhibitory activities of TNF-α on mitochondrial respiration and lipid oxidation, whereas PIKE-A overexpression exacerbated these cellular responses. We also found that TNF-α promoted the interaction between PIKE-A and AMP-activated protein kinase (AMPK) to suppress its kinase activity in vitro and in vivo. As a result, animals with PIKE ablation in the skeletal muscle per se display an upregulation of AMPK phosphorylation and a higher preference to use lipid as the energy production substrate under high-fat diet feeding, which mitigates the development of diet-induced hyperlipidemia, ectopic lipid accumulation, and muscle insulin resistance. Hence, our data reveal PIKE-A as a new signaling factor that is important for TNF-α-initiated metabolic changes in skeletal muscle.

Elovl6 Deficiency Improves Glycemic Control in Diabetic db/db Mice by Expanding β-Cell Mass and Increasing Insulin Secretory Capacity

Dysfunctional fatty acid (FA) metabolism plays an important role in the pathogenesis of β-cell dysfunction and loss of β-cell mass in type 2 diabetes (T2D). Elovl6 is a microsomal enzyme that is responsible for converting C16 saturated and monounsaturated FAs into C18 species. We previously showed that Elovl6 played a critical role in the development of obesity-induced insulin resistance by modifying FA composition. To further define its role in T2D development, we assessed the effects of Elovl6 deletion in leptin receptor-deficient C57BL/KsJ db/db mice, a model of T2D. The db/db;Elovl6^-/- mice had a markedly increased β-cell mass with increased proliferation and decreased apoptosis, an adaptive increase in insulin, and improved glycemic control. db/db islets were characterized by a prominent elevation of oleate (C18:1n-9), cell stress, and inflammation, which was completely suppressed by Elovl6 deletion. As a mechanistic ex vivo experiment, isolated islets from Elovl6^-/- mice exhibited reduced susceptibility to palmitate-induced inflammation, endoplasmic reticulum stress, and β-cell apoptosis. In contrast, oleate-treated islets resulted in impaired glucose-stimulated insulin secretion with suppressed related genes irrespective of the Elovl6 gene. Taken together, Elovl6 is a fundamental factor linking dysregulated lipid metabolism to β-cell dysfunction, islet inflammation, and β-cell apoptosis in T2D, highlighting oleate as the potential culprit of β-cell lipotoxicity.

Rice No Pollen 1 (NP1) is required for anther cuticle formation and pollen exine patterning

Angiosperm male reproductive organs (anthers and pollen grains) have complex and interesting morphological features, but mechanisms that underlie their patterning are poorly understood. Here we report the isolation and characterization of a male sterile mutant of No Pollen 1 (NP1) in rice (Oryza sativa). The np1-4 mutant exhibited smaller anthers with a smooth cuticle surface, abnormal Ubisch bodies, and aborted pollen grains covered with irregular exine. Wild-type exine has two continuous layers; but np1-4 exine showed a discontinuous structure with large granules of varying size. Chemical analysis revealed reduction in most of the cutin monomers in np1-4 anthers, and less cuticular wax. Map-based cloning suggested that NP1 encodes a putative glucose-methanol-choline oxidoreductase; and expression analyses found NP1 preferentially expressed in the tapetal layer from stage 8 to stage 10 of anther development. Additionally, the expression of several genes involved in biosynthesis and in the transport of lipid monomers of sporopollenin and cutin was decreased in np1-4 mutant anthers. Taken together, these observations suggest that NP1 is required for anther cuticle formation, and for patterning of Ubisch bodies and the exine. We propose that products of NP1 are likely important metabolites in the development of Ubisch bodies and pollen exine, necessary for polymerization, assembly, or both.

Whole transcriptomic and proteomic analyses of an isogenic M. tuberculosis clinical strain with a naturally occurring 15 Kb genomic deletion

Tuberculosis remains one of the most difficult to control infectious diseases in the world. Many different factors contribute to the complexity of this disease. These include the ability of the host to control the infection which may directly relate to nutritional status, presence of co-morbidities and genetic predisposition. Pathogen factors, in particular the ability of different Mycobacterium tuberculosis strains to respond to the harsh environment of the host granuloma, which includes low oxygen and nutrient availability and the presence of damaging radical oxygen and nitrogen species, also play an important role in the success of different strains to cause disease. In this study we evaluated the impact of a naturally occurring 12 gene 15 Kb genomic deletion on the physiology and virulence of M. tuberculosis. The strains denominated ON-A WT (wild type) and ON-A NM (natural mutant) were isolated from a previously reported TB outbreak in an inner city under-housed population in Toronto, Canada. Here we subjected these isogenic strains to transcriptomic (via RNA-seq) and proteomic analyses and identified several gene clusters with differential expression in the natural mutant, including the DosR regulon and the molybdenum cofactor biosynthesis genes, both of which were found in lower abundance in the natural mutant. We also demonstrated lesser virulence of the natural mutant in the guinea pig animal model. Overall, our findings suggest that the ON-A natural mutant is less fit to cause disease, but nevertheless has the potential to cause extended transmission in at-risk populations.

[Genetic determination of dyslipidemia - What tell us the results of genome-wide association studies?]

Dyslipidemia (high levels of plasma triglycerides and total cholesterol/LDL-cholesterol and low HDL-cholesterol) is considered as one of the major factors in the development of atherosclerosis and subsequent myocardial infarction. The final value of lipid parameters results from joint action of genetic predispositions and lifestyle factors (primarily smoking status, physical activity and in lower extent also diet). It is estimated that genetic factors are responsible for 40-80 % of the variability of plasma lipid values. Currently are as predictors DL analyzed mainly single nucleotide polymorphisms (SNPs). A fundamental shift in knowledge of genetic determination DL bring genome-wide association studies (GWAs). These revealed several dozen major polymorphisms in a DNA sequence related to lipid levels. Rather surprisingly, these variants are usually not substitutions of the amino acids, or causing a premature stop codon, but substitutions outside the genes. GWAS also found a number of variants within the genes whose function in lipid metabolism was completely unknown (e.g. gene for sortilin). Polymorphisms in genes for APOE, SORT1, LDLR (affect levels of total cholesterol and LDL-cholesterol), CETP, APOA1, ABCA-1, GALNT-2 (influence HDL-cholesterol) and finally in genes for APOA5, LPL or TRIB1 (affect the levels of triglycerides) but explains max. 30 % of the variability of plasma lipids. It is supposed, that rare polymorphisms/mutations and genetic factors unrelated directly to alterations in the DNA sequence (DNA methylation, histone modifications, regulatory RNA molecules) are responsible for the remaining proportion of DL determination.Key words: gene - cholesterol - interaction - mutation - polymorphism - triglycerides.

Differential gene expression at different stages of mesocarp development in high- and low-yielding oil palm

BACKGROUND

The oil yield trait of oil palm is expected to involve multiple genes, environmental influences and interactions. Many of the underlying mechanisms that contribute to oil yield are still poorly understood. In this study, we used a microarray approach to study the gene expression profiles of mesocarp tissue at different developmental stages, comparing genetically related high- and low- oil yielding palms to identify genes that contributed to the higher oil-yielding palm and might contribute to the wider genetic improvement of oil palm breeding populations.

RESULTS

A total of 3412 (2001 annotated) gene candidates were found to be significantly differentially expressed between high- and low-yielding palms at at least one of the different stages of mesocarp development evaluated. Gene Ontologies (GO) enrichment analysis identified 28 significantly enriched GO terms, including regulation of transcription, fatty acid biosynthesis and metabolic processes. These differentially expressed genes comprise several transcription factors, such as, bHLH, Dof zinc finger proteins and MADS box proteins. Several genes involved in glycolysis, TCA, and fatty acid biosynthesis pathways were also found up-regulated in high-yielding oil palm, among them; pyruvate dehydrogenase E1 component Subunit Beta (PDH), ATP-citrate lyase, β- ketoacyl-ACP synthases I (KAS I), β- ketoacyl-ACP synthases III (KAS III) and ketoacyl-ACP reductase (KAR). Sucrose metabolism-related genes such as Invertase, Sucrose Synthase 2 and Sucrose Phosphatase 2 were found to be down-regulated in high-yielding oil palms, compared to the lower yield palms.

CONCLUSIONS

Our findings indicate that a higher carbon flux (channeled through down-regulation of the Sucrose Synthase 2 pathway) was being utilized by up-regulated genes involved in glycolysis, TCA and fatty acid biosynthesis leading to enhanced oil production in the high-yielding oil palm. These findings are an important stepping stone to understand the processes that lead to production of high-yielding oil palms and have implications for breeding to maximize oil production.

Subspecies and diet affect the expression of genes involved in lipid metabolism and chemical composition of muscle in beef cattle

Fourteen Nellore and 14 Angus young bulls with BW of 381±11.8kg were randomly assigned into 2 feeding groups (whole shelled corn without forage (WSC) or corn silage and ground corn (GC)) to evaluate chemical composition and expression of genes involved in lipid metabolism in the longissimus thoracis (LT). We hypothesized that bulls fed the WSC diet have greater amounts of intramuscular fat and Angus have higher expression levels of PPAR and SREBF. Meat from Angus bulls had greater ether extract compared to Nellore (P<0.05). Muscle from bulls fed the WSC diet had greater expression of PPARA (P<0.05) and lower levels of SREBF1 expression (P<0.01). The LT of Nellore fed GC had greater expression of FABP4, ACACA and SCD genes (P<0.01). In conclusion, the greater concentration of starch in the WSC diet did not increase marbling in the beef of bulls fed this diet due to the reduced expression of SREBF1.

Exercise differentially affects metabolic functions and white adipose tissue in female letrozole- and dihydrotestosterone-induced mouse models of polycystic ovary syndrome

Here we hypothesized that exercise in dihydrotestosterone (DHT) or letrozole (LET)-induced polycystic ovary syndrome mouse models improves impaired insulin and glucose metabolism, adipose tissue morphology, and expression of genes related to adipogenesis, lipid metabolism, Notch pathway and browning in inguinal and mesenteric fat. DHT-exposed mice had increased body weight, increased number of large mesenteric adipocytes. LET-exposed mice displayed increased body weight and fat mass, decreased insulin sensitivity, increased frequency of small adipocytes and increased expression of genes related to lipolysis in mesenteric fat. In both models, exercise decreased fat mass and inguinal and mesenteric adipose tissue expression of Notch pathway genes, and restored altered mesenteric adipocytes morphology. In conclusion, exercise restored mesenteric adipocytes morphology in DHT- and LET-exposed mice, and insulin sensitivity and mesenteric expression of lipolysis-related genes in LET-exposed mice. Benefits could be explained by downregulation of Notch, and modulation of browning and lipolysis pathways in the adipose tissue.

Rapid Communication: Cholesterol deficiency-associated APOB mutation impacts lipid metabolism in Holstein calves and breeding bulls

During the last months, the number of reports on Holstein calves suffering from incurable idiopathic diarrhea dramatically increased. Affected calves showed severe hypocholesterolemia and mostly died within days up to a few months after birth. This new autosomal monogenic recessive inherited fat metabolism disorder, termed cholesterol deficiency (CD), is caused by a loss of function mutation of the bovine gene. The objective of the present study was to investigate specific components of lipid metabolism in 6 homozygous for the mutation (CDS) and 6 normal Holstein calves with different genotypes. Independent of sex, CDS had significantly lower plasma concentrations of total cholesterol (TC), free cholesterol (FC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), very-low-density lipoprotein cholesterol (VLDL-C), triacylglycerides (TAG), and phospholipids (PL) compared with homozygous wild-type calves ( < 0.05). Furthermore, we studied the effect of the genotype on cholesterol metabolism in adult Holstein breeding bulls of Swissgenetics. Among a total of 254 adult males, the homozygous mutant genotype was absent, 36 bulls were heterozygous carriers (CDC), and 218 bulls were homozygous wild-type (CDF). In CDC bulls, plasma concentrations of TC, FC, HDL-C, LDL-C, VLDL-C, TAG, and PL were lower compared with CDF bulls ( < 0.05). The ratios of FC:cholesteryl esters (CE) and FC:TC were higher in CDC bulls compared with CDF bulls, whereas the ratio of CE:TC was lower in CDC bulls compared with CDF bulls ( < 0.01). In conclusion, the CD-associated mutation was shown to affect lipid metabolism in affected Holstein calves and adult breeding bulls. Besides cholesterol, the concentrations of PL, TAG, and lipoproteins also were distinctly reduced in homozygous and heterozygous carriers of the mutation. Beyond malabsorption of dietary lipids, deleterious effects of apolipoprotein B deficiency on hepatic lipid metabolism, steroid biosynthesis, and cell membrane function can be expected, which may result in unspecific symptoms of reduced fertility, growth, and health.

Long-chain base kinase1 affects freezing tolerance in Arabidopsis thaliana

Long-chain base kinases (LCBKs) phosphorylate sphingolipid-derived long-chain base lipids and participate in the regulation of stress responses in plants. Here, we isolated a novel Arabidopsis thaliana mutant, lcbk1-2, which was extremely sensitive to freezing temperatures with or without cold acclimation. Physiological assays revealed that concentrations of osmolytes (proline and soluble sugars) and the activity of superoxide dismutase were significantly decreased in the lcbk1-2 mutant, compared with wild type. Also, the balance of reactive oxygen species (ROS) was disrupted in the lcbk1-2 mutant with or without cold treatment and, consistent with this, gene expression profiling analysis showed that the expression of cold-responsive ROS-scavenging genes was substantially decreased in the lcbk1-2 mutant. The expression of membrane lipid-related genes, which are linked to freezing tolerance in plants, was also impaired in the lcbk1-2 mutant. Furthermore, transgenic lines overexpressing LCBK1 showed enhanced freezing tolerance with over-accumulation of osmolytes. Collectively, our results suggested that LCBK1 functions as a novel positive regulator of freezing tolerance in Arabidopsis and may participate in the accumulation of osmolytes, the regulation of ROS homeostasis and lipid metabolism.

Impact of gain-of-function mutations in the low-density lipoprotein receptor-related protein 5 (LRP5) on glucose and lipid homeostasis

LRP5 loss-of-function mutations have been shown to cause profound osteoporosis and have been associated with impaired insulin sensitivity and dysregulated lipid metabolism. We hypothesized that gain-of-function mutations in LRP5 would also affect these parameters. We therefore studied individuals with LRP5 gain-of-function mutations exhibiting high bone mass (HBM) phenotypes and found that while there was no detected change in insulin sensitivity, there was a significant reduction in serum LDL.

INTRODUCTION

Wnt signaling through LRP5 represents a newly appreciated metabolic pathway, which potentially represents a target for drug discovery in type 2 diabetes and hyperlipidemia. Studies in animal models suggest a physiologic link between LRP5 and glucose and lipid homeostasis; however, whether it plays a similar role in humans is unclear. As current literature links loss-of-function LRP5 to impaired glucose and lipid metabolism, we hypothesized that individuals with an HBM-causing mutation in LRP5 would exhibit improved glucose and lipid homeostasis. Since studies in animal models have suggested that Wnt signaling augments insulin secretion, we also examined the effect of Wnt signaling on glucose-stimulated insulin secretion on human pancreatic islets.

METHODS

This was a matched case-control study. We used several methods to assess glucose and lipid metabolism in 11 individuals with HBM-causing mutations in LRP5. Affected study participants were recruited from previously identified kindreds with HBM-causing LRP5 mutations and included 9 males and 2 females. Two subjects that were being treated with insulin for type 2 diabetes were excluded from our analysis, as this would have obscured our ability to determine the impact of gain-of-function LRP5 mutations on glucose metabolism. The mean age of the evaluated study subjects was 55 ± 7 with a mean BMI of 27.2 ± 2.0. Control subjects were matched and recruited from the general community at an equivalent ratio, with 18 males and 4 females (mean age 56 ± 4; mean BMI 27.2 ± 1.0). Study testing was conducted at an academic medical center.

RESULTS

There were no statistically significant differences between affected and matched control populations for HbA1c (p = 0.06), eAG (p = 0.06), insulin (p = 0.82), HOMA-B (p = 0.34), or HOMA-IR (p = 0.66). The mean Insulin Sensitivity Index (ISI) was also similar between control and affected individuals. Total cholesterol (p = 0.43), triglycerides (TG) (p = 0.56), and HDL (p = 0.32) were not different between the same two groups. In a small subset of studied subjects, intramyocellular and hepatic lipid content were similar in the affected individuals and controls when quantified by proton magnetic resonance spectroscopy (MRS). However, the mean value for serum LDL was significantly lower (p = 0.04) in affected individuals. In primary human islets, there were no differences between control and Wnt treatment groups for insulin secretion measured as area under the curve (AUC) for first phase (p = 0.17) or second phase (p = 0.33) insulin secretion.

CONCLUSIONS

Although our sample size was small, our data do not support the hypothesis that HBM-causing LRP5 mutations, associated with increased Wnt signaling, improve glucose metabolism in humans. However, it does appear that LRP5 variants may affect LDL metabolism, a major risk factor for coronary artery disease. The molecular mechanisms underpinning this effect warrant further study.

MicroRNAs and lipid metabolism

PURPOSE OF REVIEW

Work over the past decade has identified the important role of microRNAs (miRNAS) in regulating lipoprotein metabolism and associated disorders including metabolic syndrome, obesity, and atherosclerosis. This review summarizes the most recent findings in the field, highlighting the contribution of miRNAs in controlling LDL-cholesterol (LDL-C) and HDL-cholesterol (HDL-C) metabolism.

RECENT FINDINGS

A number of miRNAs have emerged as important regulators of lipid metabolism, including miR-122 and miR-33. Work over the past 2 years has identified additional functions of miR-33 including the regulation of macrophage activation and mitochondrial metabolism. Moreover, it has recently been shown that miR-33 regulates vascular homeostasis and cardiac adaptation in response to pressure overload. In addition to miR-33 and miR-122, recent GWAS have identified single-nucleotide polymorphisms in the proximity of miRNA genes associated with abnormal levels of circulating lipids in humans. Several of these miRNAs, such as miR-148a and miR-128-1, target important proteins that regulate cellular cholesterol metabolism, including the LDL receptor (LDLR) and the ATP-binding cassette A1 (ABCA1).

SUMMARY

MicroRNAs have emerged as critical regulators of cholesterol metabolism and promising therapeutic targets for treating cardiometabolic disorders including atherosclerosis. Here, we discuss the recent findings in the field, highlighting the novel mechanisms by which miR-33 controls lipid metabolism and atherogenesis, and the identification of novel miRNAs that regulate LDL metabolism. Finally, we summarize the recent findings that identified miR-33 as an important noncoding RNA that controls cardiovascular homeostasis independent of its role in regulating lipid metabolism.

Central action of xenin affects the expression of lipid metabolism-related genes and proteins in mouse white adipose tissue

Xenin is a gastrointestinal hormone that reduces food intake when administered centrally and it has been hypothesized that central action of xenin participates in the regulation of whole-body metabolism. The present study was performed to address this hypothesis by investigating the central effect of xenin on the expression of genes and proteins that are involved in the regulation of lipid metabolism in white adipose tissue (WAT). Male obese ob/ob mice received intracerebroventricular (i.c.v.) injections of xenin (5μg) twice 12h apart. Food intake and body weight change during a 24-h period after the first injection were measured. Epididymal WAT was collected at the end of the 24-h treatment period and levels of lipid metabolism-related genes and proteins were measured. Xenin treatment caused significant reductions in food intake and body weight compared to control vehicle treatment. Levels of fatty acid synthase (FASN) protein were significantly reduced by xenin treatment, while levels of adipose triglyceride lipase (Atgl) and beta-3 adrenergic receptor (Adrb3) mRNA and phosphorylated hormone sensitive lipase (Ser⁶⁶⁰-pHSL and Ser⁵⁶³-pHSL) were significantly increased by xenin treatment. These findings suggest that central action of xenin causes alterations in lipid metabolism in adipose tissue toward reduced lipogenesis and increased lipolysis, possibly contributing to xenin-induced body weight reduction. Thus, enhancing central action of xenin and its downstream targets may be possible targets for the treatment of obesity by reducing the amount of stored fat in adipose tissue.

Molecular effect of fenofibrate on PBMC gene transcription related to lipid metabolism in patients with metabolic syndrome

BACKGROUND

Both fasting and postprandial hypertriglyceridaemia are considered independent risk factors for atherosclerosis. Treatment of hypertriglyceridaemia is based on fibrates, which activate the peroxisome proliferator-activated receptor alpha (PPARα). However, the metabolic pathways that activate or inhibit fibrates, and how the postprandial triglyceride levels are modified, have not yet been fully described. Accordingly, the aim of this study was to determine the feasibility of peripheral blood mononuclear cells (PBMC) to study the effects of fenofibrate in patients with the metabolic syndrome.

MATERIALS AND METHODS

A fat overload was given to 50 patients before and after treatment with fenofibrate for 3 months. Anthropometric and biochemical variables as well as gene expression in PBMC were analysed.

RESULTS

After treatment with fenofibrate, we observed a decrease in both baseline and postprandial (3 h after the fat overload) levels of serum triglycerides, cholesterol and uric acid and an increase in HDL cholesterol and apolipoprotein AI levels. After treatment, there was also a rise in PPARα and RXRα expression and changes in genes regulated by PPARα, both baseline and postprandial. Furthermore, in vitro experiments showed that a PPARα agonist changed the expression of genes related with lipid metabolism.

CONCLUSION

Treatment with fenofibrate reduced fasting and postprandial serum triglyceride levels, possibly through a mechanism related with an increase in the expression of RXRα and PPARα, by activating the pathways involved in the uptake and degradation of triglycerides and increasing the synthesis of apolipoprotein. These results suggest that PBMC may be useful for the easy study of fenofibrate actions.