Pantothenic acid in health and disease

Urine metabolic fingerprinting can be used to predict the risk of metritis and highlight the pathobiology of the disease in dairy cows

INTRODUCTION

Metritis is an uterine pathology that causes economic losses for the dairy industry. It is associated with lower reproductive efficiency, increased culling rates, decreased milk production and increased veterinary costs.

OBJECTIVES

To gain a more detailed view of the urine metabolome and to detect metabolite signature in cows with metritis. In addition, we aimed to identify early metabolites which can help to detect cows at risk to develop metritis in the future.

METHODS

We used nuclear magnetic resonance spectroscopy starting at 8 and 4 weeks prior to the expected day of parturition, during the week of diagnosis of metritis, and at 4 and 8 weeks after diagnosis of metritis in Holstein dairy cows.

RESULTS

At 8 weeks before parturition, pre-metritic cows had a total of 30 altered metabolites. Interestingly, 28 of them increased in urine when compared with control cows (P < 0.05). At 4 weeks before parturition, 34 metabolites were altered. At the week of diagnosis of metritis a total of 20 metabolites were altered (P < 0.05). The alteration continued at 4 and 8 weeks after diagnosis.

CONCLUSIONS

The metabolic fingerprints in the urine of pre-metritic and metritic cows point toward excretion of multiple amino acids, tricarboxylic acid cycle metabolites and monosaccharides. Combination of galactose, leucine, lysine and panthotenate at 8 weeks before parturition might serve as predictive biomarkers for metritis.

Metabolomics and Ionomics of Potato Tuber Reveals an Influence of Cultivar and Market Class on Human Nutrients and Bioactive Compounds

Potato (Solanum tuberosum L.) is an important global food crop that contains phytochemicals with demonstrated effects on human health. Understanding sources of chemical variation of potato tuber can inform breeding for improved health attributes of the cooked food. Here, a comprehensive metabolomics (UPLC- and GC-MS) and ionomics (ICP-MS) analysis of raw and cooked potato tuber was performed on 60 unique potato genotypes that span 5 market classes including russet, red, yellow, chip, and specialty potatoes. The analyses detected 2,656 compounds that included known bioactives (43 compounds), nutrients (42), lipids (76), and 23 metals. Most nutrients and bioactives were partially degraded during cooking (44 out of 85; 52%), however genotypes with high quantities of bioactives remained highest in the cooked tuber. Chemical variation was influenced by genotype and market class. Specifically, ~53% of all detected compounds from cooked potato varied among market class and 40% varied by genotype. The most notable metabolite profiles were observed in yellow-flesh potato which had higher levels of carotenoids and specialty potatoes which had the higher levels of chlorogenic acid as compared to the other market classes. Variation in several molecules with known association to health was observed among market classes and included vitamins (e.g., pyridoxal, ~2-fold variation), bioactives (e.g., chlorogenic acid, ~40-fold variation), medicinals (e.g., kukoamines, ~6-fold variation), and minerals (e.g., calcium, iron, molybdenum, ~2-fold variation). Furthermore, more metabolite variation was observed within market class than among market class (e.g., α-tocopherol, ~1-fold variation among market class vs. ~3-fold variation within market class). Taken together, the analysis characterized significant metabolite and mineral variation in raw and cooked potato tuber, and support the potential to breed new cultivars for improved health traits.

Integrative analysis of indirect calorimetry and metabolomics profiling reveals alterations in energy metabolism between fed and fasted pigs

Background

Fasting is a simple metabolic strategy that is used to estimate the maintenance energy requirement where the energy supply for basic physiological functions is provided by the mobilization of body reserves. However, the underlying metabolic components of maintenance energy expenditure are not clear. This study investigated the differences in heat production (HP), respiratory quotient (RQ) and plasma metabolites in pigs in the fed and fasted state, using the techniques of indirect calorimetry and metabolomics.

Methods

Nine barrows (45.2 ± 1.7 kg BW) were fed corn-soybean based meal diets and were kept in metabolism crates for a period of 14 d. After 7 d adaptation, pigs were transferred to respiratory chambers to determine HP and RQ based on indirect calorimetry. Pigs were fed the diet at 2,400 kJ ME/(kg BW^0.6·d) during d 8 to 12. The last 2 d were divided into 24 h fasting and 48 h fasting treatment, respectively. Plasma samples of each pig were collected from the anterior vena cava during the last 3 d (1 d while pigs were fed and 2 d during which they were fasted). The metabolites of plasma were determined by high-resolution mass spectrometry using a metabolomics approach.

Results

Indirect calorimetry analysis revealed that HP and RQ were no significant difference between 24 h fasting and 48 h fasting, which were lower than those of fed state (P <  0.01). The nitrogen concentration of urine tended to decrease with fasting (P = 0.054). Metabolomics analysis between the fed and fasted state revealed differences in 15 compounds, most of which were not significantly different between 24 h fasting and 48 h fasting. Identified compounds were enriched in metabolic pathways related to linoleic acid metabolism, amino acid metabolism, sphingolipid metabolism, and pantothenate and CoA biosynthesis.

Conclusion

These results suggest that the decreases in HP and RQ of growing pigs under fasting conditions were associated with the alterations of linoleic acid metabolism and amino acid metabolism. The integrative analysis also revealed that growing pigs under a 24-h fasting were more appropriate than a 48-h fasting to investigate the metabolic components of maintenance energy expenditure.

Integration of Transcriptomic and Metabolomic Data Reveals Enhanced Steroid Hormone Biosynthesis in Mouse Uterus During Decidualization

It has been long recognized that decidualization is accompanied by significant changes in metabolic pathways. In the present study, we used the GC-TOF-MS approach to investigate the global metabolite profile changes associated with decidualization of mouse uterus on day 8 of pregnancy. We identified a total of 20 differentially accumulated metabolites, of which nine metabolites were down-regulated and 11 metabolites were up-regulated. As expected, seven differentially accumulated metabolites were involved in carbohydrate metabolism. We observed statistically significant changes in polyamines, putrescine and spermidine. Interestingly, the pantothenic acid, also known as vitamin B₅ , was up-regulated. Finally, by integrating with transcriptomic data obtained by RNA-seq, we revealed enhanced steroid hormone biosynthesis during decidualization. Our study contributes to an increase in the knowledge on the molecular mechanisms of decidualization.

Microbiome-Metabolome Responses to a High-Grain Diet Associated with the Hind-Gut Health of Goats

Studies on the effect of a high-concentrate (HC) diet on the hindgut microbiota and metabolome of ruminants are rarely reported. We used 454 pyrosequencing of 16S rDNA genes and gas chromatography-mass spectrometry to evaluate the effects of long-term feeding (HL) or short-term (HS) feeding of an HC diet on changes in bacterial microbiota and their metabolites in the hindgut, with Guanzhong goat as a ruminant model. Results indicated that an HC diet decreased bacterial diversity and induced metabolic disorder in the hindgut. The levels of lactate, endotoxin (lipopolysaccharide, LPS), and volatile fatty acid concentrations were higher in the intestinal digesta of the HC goats than in those of the LC goats (P < 0.05). The level of beta-alanine decreased, whereas the levels of stigmasterol and quinic acid decreased in the cecal and colonic digesta of the HC goats. At the genus level, the abundance of Clostridium and Turicibacter was significantly increased in both the colonic and cecal digesta of the HC goats. Several potential relationships between metabolites and several microbial species were revealed in this study. The mRNA expression of the genes functionally associated with nutrients transport, including NHE2, NHE3, MCT1, and MCT4 were significantly downregulated in the colonic mucosa by the HC diet (P < 0.05). The expression levels of the genes related to the inflammatory response, including TLR4, MYD88, TNF-α, and IL-1β were markedly upregulated in the cecal mucosa by the HC diet (P < 0.05). Our results indicate that an HC diet induces microbiota dysbiosis, metabolic disorders, and mucosal damage in the hindgut of goats.

An Essential Role for the Tumor-Suppressor Merlin in Regulating Fatty Acid Synthesis

Neurofibromatosis type 2 (NF2) is an autosomal dominant disorder characterized by the development of multiple tumors in the central nervous system, most notably schwannomas, and meningiomas. Mutational inactivation of the NF2 gene encoding the protein Merlin is found in most sporadic and inherited schwannomas, but the molecular mechanisms underlying neoplastic changes in schwannoma cells remain unclear. We report here that Nf2-deficient cells display elevated expression levels of key enzymes involved in lipogenesis and that this upregulation is caused by increased activity of Torc1. Inhibition or knockdown of fatty acid synthase (FASN), the enzyme that catalyzes the formation of palmitic acid from malonyl-CoA, drove NF2-deficient cells into apoptosis. Treatment of NF2-mutant cells with agents that inhibit the production of malonyl-CoA reduced their sensitivity to FASN inhibitors. Collectively, these results suggest that the altered lipid metabolism found in NF2-mutant cells renders them sensitive to elevated levels of malonyl-CoA, as occurs following blockade of FASN, suggesting new targeted strategies in the treatment of NF2-deficient tumors. Cancer Res; 77(18); 5026-38. ©2017 AACR.

miR-103 inhibits proliferation and sensitizes hemopoietic tumor cells for glucocorticoid-induced apoptosis

Glucocorticoid (GC) hormones are an important ingredient of leukemia therapy since they are potent inducers of lymphoid cell apoptosis. However, the development of GC resistance remains an obstacle in GC-based treatment. In the present investigation we found that miR-103 is upregulated in GC-sensitive leukemia cells treated by the hormone. Transfection of GC resistant cells with miR-103 sensitized them to GC induced apoptosis (GCIA), while miR-103 sponging of GC sensitive cells rendered them partially resistant. miR-103 reduced the expression of cyclin dependent kinase (CDK2) and its cyclin E1 target, thereby leading to inhibition of cellular proliferation. miR-103 is encoded within the fifth intron of PANK3 gene. We demonstrate that the GC receptor (GR) upregulates miR-103 by direct interaction with GC response element (GRE) in the PANK3 enhancer. Consequently, miR-103 targets the c-Myc activators c-Myb and DVL1, thereby reducing c-Myc expression. Since c-Myc is a transcription factor of the miR-17~92a poly-cistron, all six miRNAs of the latter are also downregulated. Of these, miR-18a and miR-20a are involved in GCIA, as they target GR and BIM, respectively. Consequently, GR and BIM expression are elevated, thus advancing GCIA. Altogether, this study highlights miR-103 as a useful prognostic biomarker and drug for leukemia management in the future.

Down-regulation of coasy, the gene associated with NBIA-VI, reduces Bmp signaling, perturbs dorso-ventral patterning and alters neuronal development in zebrafish

Mutations in Pantothenate kinase 2 and Coenzyme A (CoA) synthase (COASY), genes involved in CoA biosynthesis, are associated with rare neurodegenerative disorders with brain iron accumulation. We showed that zebrafish pank2 gene plays an essential role in brain and vasculature development. Now we extended our study to coasy. The gene has high level of sequence identity with the human ortholog and is ubiquitously expressed from the earliest stages of development. The abrogation of its expression led to strong reduction of CoA content, high lethality and a phenotype resembling to that of dorsalized mutants. Lower doses of morpholino resulted in a milder phenotype, with evident perturbation in neurogenesis and formation of vascular arborization; the dorso-ventral patterning was severely affected, the expression of bone morphogenetic protein (Bmp) receptors and activity were decreased, while cell death increased. These features specifically correlated with the block in CoA biosynthesis and were rescued by the addition of CoA to fish water and the overexpression of the human wild-type, but not mutant gene. These results confirm the absolute requirement for adequate levels of CoA for proper neural and vascular development in zebrafish and point to the Bmp pathway as a possible molecular connection underlining the observed phenotype.

Vitamin D deficiency changes the intestinal microbiome reducing B vitamin production in the gut. The resulting lack of pantothenic acid adversely affects the immune system, producing a "pro-inflammatory" state associated with atherosclerosis and autoimmunity

STUDY OBJECTIVES

Vitamin D blood levels of 60-80ng/ml promote normal sleep. The present study was undertaken to explore why this beneficial effect waned after 2years as arthritic pain increased. Pantothenic acid becomes coenzyme A, a cofactor necessary for cortisol and acetylcholine production. 1950s experiments suggested a connection between pantothenic acid deficiency, autoimmune arthritis and insomnia. The B vitamins have been shown to have an intestinal bacterial source and a food source, suggesting that the normal intestinal microbiome may have always been the primary source of B vitamins. Review of the scientific literature shows that pantothenic acid does not have a natural food source, it is supplied by the normal intestinal bacteria. In order to test the hypothesis that vitamin D replacement slowly induced a secondary pantothenic acid deficiency, B100 (100mg of all B vitamins except 100mcg of B12 and biotin and 400mcg of folate) was added to vitamin D supplementation.

METHODS

Vitamin D and B100 were recommended to over 1000 neurology patients. Sleep characteristics, pain levels, neurologic symptoms, and bowel complaints were recorded by the author at routine appointments.

RESULTS

Three months of vitamin D plus B100 resulted in improved sleep, reduced pain and unexpected resolution of bowel symptoms. These results suggest that the combination of vitamin D plus B100 creates an intestinal environment that favors the return of the four specific species, Actinobacteria, Bacteroidetes, Firmicutes and Proteobacteria that make up the normal human microbiome.

HYPOTHESES

1) Seasonal fluctuations in vitamin D levels have normally produced changes in the intestinal microbiome that promoted weight gain in winter. Years of vitamin D deficiency, however, results in a permanently altered intestinal environment that no longer favors the "healthy foursome". 2) Humans have always had a commensal relationship with their intestinal microbiome. We supplied them vitamin D, they supplied us B vitamins. 3) The four species that make up the normal microbiome are also commensal, each excretes at least one B vitamin that the other three need but cannot make. 4) Improved sleep and more cellular repairs eventually depletes body stores of pantothenic acid, causing reduced cortisol production, increased arthritic pain and widespread "pro-inflammatory" effects on the immune system. 5) Pantothenic acid deficiency also decreases available acetylcholine, the neurotransmitter used by the parasympathetic nervous system. Unopposed, increased sympathetic tone then produces hypertension, tachycardia, atrial arrhythmias and a "hyper-adrenergic" state known to predispose to heart disease and stroke.

Quantitative Measurement of Histone Tail Acetylation Reveals Stage-Specific Regulation and Response to Environmental Changes during Drosophila Development

Histone modification plays a major role in regulating gene transcription and ensuring the healthy development of an organism. Numerous studies have suggested that histones are dynamically modified during developmental events to control gene expression levels in a temporal and spatial manner. However, the study of histone acetylation dynamics using currently available techniques is hindered by the difficulty of simultaneously measuring acetylation of the numerous potential sites of modification present in histones. Here, we present a methodology that allows us to combine mass spectrometry-based histone analysis with Drosophila developmental genetics. Using this system, we characterized histone acetylation patterns during multiple developmental stages of the fly. Additionally, we utilized this analysis to characterize how treatments with pharmacological agents or environmental changes such as γ-irradiation altered histone acetylation patterns. Strikingly, γ-irradiation dramatically increased the level of acetylation at H3K18, a site linked to DNA repair via nonhomologous end joining. In mutant fly strains deficient in DNA repair proteins, however, this increase in the level of H3K18 acetylation was lost. These results demonstrate the efficacy of our combined mass spectrometry system with a Drosophila model system and provide interesting insight into the changes in histone acetylation during development, as well as the effects of both pharmacological and environmental agents on global histone acetylation.

Vitamin B5 and N-Acetylcysteine in Nonalcoholic Steatohepatitis: A Preclinical Study in a Dietary Mouse Model

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is the number one cause of chronic liver disease and second indication for liver transplantation in the Western world. Effective therapy is still not available. Previously we showed a critical role for caspase-2 in the pathogenesis of nonalcoholic steatohepatitis (NASH), the potentially progressive form of NAFLD. An imbalance between free coenzyme A (CoA) and acyl-CoA ratio is known to induce caspase-2 activation.

OBJECTIVES

We aimed to evaluate CoA metabolism and the effects of supplementation with CoA precursors, pantothenate and cysteine, in mouse models of NASH.

METHODS

CoA metabolism was evaluated in methionine-choline deficient (MCD) and Western diet mouse models of NASH. MCD diet-fed mice were treated with pantothenate and N-acetylcysteine or placebo to determine effects on NASH.

RESULTS

Liver free CoA content was reduced, pantothenate kinase (PANK), the rate-limiting enzyme in the CoA biosynthesis pathway, was down-regulated, and CoA degrading enzymes were increased in mice with NASH. Decreased hepatic free CoA content was associated with increased caspase-2 activity and correlated with worse liver cell apoptosis, inflammation, and fibrosis. Treatment with pantothenate and N-acetylcysteine did not inhibit caspase-2 activation, improve NASH, normalize PANK expression, or restore free CoA levels in MCD diet-fed mice.

CONCLUSION

In mice with NASH, hepatic CoA metabolism is impaired, leading to decreased free CoA content, activation of caspase-2, and increased liver cell apoptosis. Dietary supplementation with CoA precursors did not restore CoA levels or improve NASH, suggesting that alternative approaches are necessary to normalize free CoA during NASH.

Integration of Metabolomics and Transcriptomics Reveals Major Metabolic Pathways and Potential Biomarker Involved in Prostate Cancer

Prostate cancer is a highly prevalent tumor affecting millions of men worldwide, but poor understanding of its pathogenesis has limited effective clinical management of patients. In addition to transcriptional profiling or transcriptomics, metabolomics is being increasingly utilized to discover key molecular changes underlying tumorigenesis. In this study, we integrated transcriptomics and metabolomics to analyze 25 paired human prostate cancer tissues and adjacent noncancerous tissues, followed by further validation of our findings in an additional cohort of 51 prostate cancer patients and 16 benign prostatic hyperplasia patients. We found several altered pathways aberrantly expressed at both metabolic and transcriptional levels, including cysteine and methionine metabolism, nicotinamide adenine dinucleotide metabolism, and hexosamine biosynthesis. Additionally, the metabolite sphingosine demonstrated high specificity and sensitivity for distinguishing prostate cancer from benign prostatic hyperplasia, particularly for patients with low prostate specific antigen level (0-10 ng/ml). We also found impaired sphingosine-1-phosphate receptor 2 signaling, downstream of sphingosine, representing a loss of tumor suppressor gene and a potential key oncogenic pathway for therapeutic targeting. By integrating metabolomics and transcriptomics, we have provided both a broad picture of the molecular perturbations underlying prostate cancer and a preliminary study of a novel metabolic signature, which may help to discriminate prostate cancer from normal tissue and benign prostatic hyperplasia.

Biosynthesis of Pantothenic Acid and Coenzyme A

Pantothenate is vitamin B5 and is the key precursor for the biosynthesis of coenzyme A (CoA), a universal and essential cofactor involved in a myriad of metabolic reactions, including the synthesis of phospholipids, the synthesis and degradation of fatty acids, and the operation of the tricarboxylic acid cycle. CoA is also the only source of the phosphopantetheine prosthetic group for enzymes that shuttle intermediates between the active sites of enzymes involved in fatty acid, nonribosomal peptide, and polyketide synthesis. Pantothenate can be synthesized de novo and/or transported into the cell through a pantothenatepermease. Pantothenate uptake is essential for those organisms that lack the genes to synthesize this vitamin. The intracellular levels of CoA are controlled by the balance between synthesis and degradation. In particular, CoA is assembled in five enzymatic steps, starting from the phosphorylation of pantothenate to phosphopantothenatecatalyzed by pantothenate kinase, the product of the coaA gene. In some bacteria, the production of phosphopantothenate by pantothenate kinase is the rate limiting and most regulated step in the biosynthetic pathway. CoA synthesis additionally networks with other vitamin-associated pathways, such as thiamine and folic acid.

Alteration of the coenzyme A biosynthetic pathway in neurodegeneration with brain iron accumulation syndromes

NBIA (neurodegeneration with brain iron accumulation) comprises a heterogeneous group of neurodegenerative diseases having as a common denominator, iron overload in specific brain areas, mainly basal ganglia and globus pallidus. In the past decade a bunch of disease genes have been identified, but NBIA pathomechanisms are still not completely clear. PKAN (pantothenate kinase-associated neurodegeneration), an autosomal recessive disorder with progressive impairment of movement, vision and cognition, is the most common form of NBIA. It is caused by mutations in the PANK2 (pantothenate kinase 2) gene, coding for a mitochondrial enzyme that phosphorylates vitamin B5 in the first reaction of the CoA (coenzyme A) biosynthetic pathway. A distinct form of NBIA, denominated CoPAN (CoA synthase protein-associated neurodegeneration), is caused by mutations in the CoASY (CoA synthase) gene coding for a bifunctional mitochondrial enzyme, which catalyses the final steps of CoA biosynthesis. These two inborn errors of CoA metabolism further support the concept that dysfunctions in CoA synthesis may play a crucial role in the pathogenesis of NBIA.

The sodium/multivitamin transporter: a multipotent system with therapeutic implications

The Na(+)/multivitamin transporter (SMVT) is a member of the solute:sodium symporter family that catalyzes the Na(+)-dependent uptake of the structurally diverse water-soluble vitamins pantothenic acid (vitamin B5) and biotin (vitamin H), α-lipoic acid-a vitamin-like substance with strong antioxidant properties-and iodide. The organic substrates of SMVT play central roles in the cellular metabolism and are, therefore, essential for normal human health and development. For example, biotin deficiency leads to growth retardation, dermatological disorders, and neurological disorders. Animal studies have shown that biotin deficiency during pregnancy is directly correlated to embryonic growth retardation, congenital malformation, and death of the embryo. This chapter focuses on the structural and functional features of the human isoform of SMVT (hSMVT); the discovery of which was greatly facilitated by the cloning and expression of hSMVT in tractable expression systems. Special emphasis will be given to mechanistic implications of the transport process of hSMVT that will inform our understanding of the molecular determinants of hSMVT-mediated transport in dynamic context to alleviate the development and optimization of hSMVT as a multipotent platform for drug delivery.

Exome sequence reveals mutations in CoA synthase as a cause of neurodegeneration with brain iron accumulation

Neurodegeneration with brain iron accumulation (NBIA) comprises a clinically and genetically heterogeneous group of disorders with progressive extrapyramidal signs and neurological deterioration, characterized by iron accumulation in the basal ganglia. Exome sequencing revealed the presence of recessive missense mutations in COASY, encoding coenzyme A (CoA) synthase in one NBIA-affected subject. A second unrelated individual carrying mutations in COASY was identified by Sanger sequence analysis. CoA synthase is a bifunctional enzyme catalyzing the final steps of CoA biosynthesis by coupling phosphopantetheine with ATP to form dephospho-CoA and its subsequent phosphorylation to generate CoA. We demonstrate alterations in RNA and protein expression levels of CoA synthase, as well as CoA amount, in fibroblasts derived from the two clinical cases and in yeast. This is the second inborn error of coenzyme A biosynthesis to be implicated in NBIA.

Computational sequence analysis of predicted long dsRNA transcriptomes of major crops reveals sequence complementarity with human genes

Long double-stranded RNAs (long dsRNAs) are precursors for the effector molecules of sequence-specific RNA-based gene silencing in eukaryotes. Plant cells can contain numerous endogenous long dsRNAs. This study demonstrates that such endogenous long dsRNAs in plants have sequence complementarity to human genes. Many of these complementary long dsRNAs have perfect sequence complementarity of at least 21 nucleotides to human genes; enough complementarity to potentially trigger gene silencing in targeted human cells if delivered in functional form. However, the number and diversity of long dsRNA molecules in plant tissue from crops such as lettuce, tomato, corn, soy and rice with complementarity to human genes that have a long history of safe consumption supports a conclusion that long dsRNAs do not present a significant dietary risk.

EDC4 interacts with and regulates the dephospho-CoA kinase activity of CoA synthase

Coenzyme A synthase (CoAsy) is a bifunctional enzyme which facilitates the last two steps of Coenzyme A biogenesis in higher eukaryotes. Here we describe that CoAsy forms a complex with enhancer of mRNA-decapping protein 4 (EDC4), a central scaffold component of processing bodies. CoAsy/EDC4 complex formation is regulated by growth factors and is affected by cellular stresses. EDC4 strongly inhibits the dephospho-CoA kinase activity of CoAsy in vitro. Transient overexpression of EDC4 decreases cell proliferation, and further co-expression of CoAsy diminishes this effect. Here we report that EDC4 might contribute to regulation of CoA biosynthesis in addition to its scaffold function in processing bodies.

The role of B vitamins in the management of heart failure

Heart failure (HF) is the leading cause of morbidity and mortality in industrialized countries, creating a significant burden on both the healthcare system and quality of life. Research efforts continue to explore new pharmaceutical or surgically based approaches to HF management, but the role of nutrition as an adjunct therapy has been largely ignored. Elderly age, anorexia, malabsorption, premature satiety, and disease severity are among the factors identified as contributing to reduced nutrient intakes in patients with HF. These factors suggest that patients with HF are at increased risk of multiple-nutrient deficiencies, including B vitamins. B vitamins may be of particular therapeutic interest because of their key roles as cofactors in energy-producing pathways. Recently, impaired stores of high-energy compounds have been linked with myocardial dysfunction and prognosis in patients with HF. Therefore, deficiencies of B vitamins might contribute to reduced energy stores and disease progression. This review summarizes the existing literature both with respect to the prevalence of B vitamin deficiency as well as evidence from supplementation trials in patients with HF. The findings suggest that most of the literature in this area has focused on thiamin deficiency in patients with HF, whereas other B vitamins remain largely unstudied. Although few sporadic trials suggest a role for B vitamins in the management of HF, none are conclusive. Therefore, there is a need for larger, more robust trials to assist in defining the B vitamin requirements as well as the impact of supplementation on both morbidity and mortality in patients with HF.

Acute pantothenic acid and cysteine supplementation does not affect muscle coenzyme A content, fuel selection, or exercise performance in healthy humans

Reduced skeletal muscle free coenzyme A (CoASH) availability may decrease the contribution of fat oxidation to ATP production during high-intensity, submaximal exercise or, alternatively, limit pyruvate dehydrogenase complex (PDC) flux and thereby carbohydrate oxidation. Here we attempted to increase the muscle CoASH pool in humans, via pantothenic acid and cysteine feeding, in order to elucidate the role of CoASH availability on muscle fuel metabolism during exercise. On three occasions, eight healthy male volunteers (age 22.9 ± 1.4 yr, body mass index 24.2 ± 1.5 kg/m(2)) cycled at 75% maximal oxygen uptake (Vo(2max)) to exhaustion, followed by a 15-min work output performance test. Muscle biopsies were obtained at rest, and after 60 min and 91.3 ± 3.1 min of exercise (time to exhaustion on baseline visit) on each occasion. Two weeks following the first visit (baseline), 1 wk of oral supplementation with either 3 g/day of a placebo control (glucose polymer; CON) or 1.5 g/day each of d-pantothenic acid and l-cysteine (CP) was carried out prior to the second and third visits in a randomized, counterbalanced, double-blind manner, leaving a 3-wk gap in total between each visit. Resting muscle CoASH content was not altered by supplementation in any visit. Following 60 min of exercise, muscle CoASH content was reduced by 13% from rest in all three visits (P < 0.05), and similar changes in the respiratory exchange ratio, glycogenolysis (∼235 mmol/kg dry muscle), PCr degradation (∼57 mmol/kg dry muscle), and lactate (∼25 mmol/kg dry muscle) and acetylcarnitine (∼12 mmol(.)kg/dry muscle) accumulation was observed during exercise when comparing visits. Furthermore, no difference in work output was observed when comparing CON and CP. Acute feeding with pantothenic acid and cysteine does not alter muscle CoASH content and consequently does not impact on muscle fuel metabolism or performance during exercise in humans.

Water-soluble vitamin homeostasis in fasting northern elephant seals (Mirounga angustirostris) measured by metabolomics analysis and standard methods

Despite the importance of water-soluble vitamins to metabolism, there is limited knowledge of their serum availability in fasting wildlife. We evaluated changes in water-soluble vitamins in northern elephant seals, a species with an exceptional ability to withstand nutrient deprivation. We used a metabolomics approach to measure vitamins and associated metabolites under extended natural fasts for up to 7 weeks in free-ranging lactating or developing seals. Water-soluble vitamins were not detected with this metabolomics platform, but could be measured with standard assays. Concentrations of measured vitamins varied independently, but all were maintained at detectable levels over extended fasts, suggesting that defense of vitamin levels is a component of fasting adaptation in the seals. Metabolomics was not ideal for generating complete vitamin profiles in this species, but gave novel insights into vitamin metabolism by detecting key related metabolites. For example, niacin level reductions in lactating females were associated with significant reductions in precursors suggesting downregulation of the niacin synthetic pathway. The ability to detect individual vitamins using metabolomics may be impacted by the large number of novel compounds detected. Modifications to the analysis platforms and compound detection algorithms used in this study may be required for improving water-soluble vitamin detection in this and other novel wildlife systems.

microRNA: a master regulator of cellular processes for bioengineering systems

microRNAs (miRNAs) are small RNAs 18 to 24 nucleotides in length that serve the pivotal function of regulating gene expression. Instead of being translated into proteins, the mature single-stranded miRNA binds to messenger RNAs (mRNAs) to interfere with the translational process. It is estimated that whereas only 1% of the genomic transcripts in mammalian cells encode miRNA, nearly one-third of the encoded genes are regulated by miRNA. Various bioinformatics databases, tools, and algorithms have been developed to predict the sequences of miRNAs and their target genes. In combination with the in silico approaches in systems biology, experimental studies on miRNA provide a new bioengineering approach for understanding the mechanism of fine-tuning gene regulation. This review aims to provide state-of-the-art information on this important mechanism of gene regulation for researchers working in biomedical engineering and related fields. Particular emphases are placed on summarizing the current tools and strategies for miRNA study from a bioengineering perspective and the possible applications of miRNAs (such as antagomirs and miRNA sponges) in biomedical engineering research.

The role of UPF0157 in the folding of M. tuberculosis dephosphocoenzyme A kinase and the regulation of the latter by CTP

Background

Targeting the biosynthetic pathway of Coenzyme A (CoA) for drug development will compromise multiple cellular functions of the tubercular pathogen simultaneously. Structural divergence in the organization of the penultimate and final enzymes of CoA biosynthesis in the host and pathogen and the differences in their regulation mark out the final enzyme, dephosphocoenzyme A kinase (CoaE) as a potential drug target.

Methodology/Principal Findings

We report here a complete biochemical and biophysical characterization of the M. tuberculosis CoaE, an enzyme essential for the pathogen's survival, elucidating for the first time the interactions of a dephosphocoenzyme A kinase with its substrates, dephosphocoenzyme A and ATP; its product, CoA and an intrinsic yet novel inhibitor, CTP, which helps modulate the enzyme's kinetic capabilities providing interesting insights into the regulation of CoaE activity. We show that the mycobacterial enzyme is almost 21 times more catalytically proficient than its counterparts in other prokaryotes. ITC measurements illustrate that the enzyme follows an ordered mechanism of substrate addition with DCoA as the leading substrate and ATP following in tow. Kinetic and ITC experiments demonstrate that though CTP binds strongly to the enzyme, it is unable to participate in DCoA phosphorylation. We report that CTP actually inhibits the enzyme by decreasing its Vmax. Not surprisingly, a structural homology search for the modeled mycobacterial CoaE picks up cytidylmonophosphate kinases, deoxycytidine kinases, and cytidylate kinases as close homologs. Docking of DCoA and CTP to CoaE shows that both ligands bind at the same site, their interactions being stabilized by 26 and 28 hydrogen bonds respectively. We have also assigned a role for the universal Unknown Protein Family 0157 (UPF0157) domain in the mycobacterial CoaE in the proper folding of the full length enzyme.

Conclusions/Significance

In view of the evidence presented, it is imperative to assign a greater role to the last enzyme of Coenzyme A biosynthesis in metabolite flow regulation through this critical biosynthetic pathway.

Effects of pantothenic acid supplementation on adrenal steroid secretion from male rats

The effects of pantothenic acid-supplementation on the adrenal secretion of corticosterone and progesterone in male rats were investigated using an in vitro cell culture system. Male rats at 21 d of age were given 0.03% pantothenic acid in their drinking water for 9 weeks. After 9 weeks of treatment, the animals were decapitated, and adrenal cells were cultured in the absence or presence of rat adrenocorticotropic hormone (ACTH; 10(-15) to 10(-10) M) and/or ovine prolactin (oPRL; 10(-9) to 10(-7) M) for 4 h. Adrenal cells in pantothenic acid-treated rats exhibited higher basal levels of corticosterone and progesterone than control rats. The response of ACTH and/or PRL on corticosterone and progesterone release was higher in the pantothenic acid-treated rats than in the control rats. In addition, PRL increased the stimulatory effect of ACTH-induced corticosterone secretion in both normal and pantothenic acid-treated rats. These results clearly demonstrated that pantothenic acid supplementation stimulates the ability of adrenal cells in male rats to secrete corticosterone and progesterone. Additionally, these results also showed that pantothenic acid supplementation induced adrenal hyperresponsiveness to ACTH stimulation, and PRL further stimulated adrenal sensitivity to ACTH.

Hereditary and acquired diseases of acyl-coenzyme A metabolism

Coenzyme A (CoA) sequestration, toxicity or redistribution (CASTOR) is predicted to occur in many hereditary and acquired conditions in which the degradation of organic acyl esters of CoA is impaired. The resulting accumulation of CoA esters and reduction of acetyl-CoA and free CoA (CoASH) will then trigger a cascade of reactions leading to clinical disease. Most conditions detected by expanded neonatal screening are CASTOR diseases. We review acyl-CoA metabolism, including CoASH synthesis, transesterification of acyl-CoAs to glycine, glutamate or l-carnitine and hydrolysis of CoA esters. Because acyl-CoAs do not cross biological membranes, their main toxicity is intracellular, primarily within mitochondria. Treatment measures directed towards removal of circulating metabolites do not address this central problem of intracellular acyl-CoA accumulation. Treatments usually involve the restriction of dietary precursors and administration of agents like l-carnitine and glycine, which can accept the transfer of acyl groups from acyl-CoA, liberating CoASH. Many hereditary CASTOR patients are chronically ill, with persistent symptoms and continuously abnormal metabolites in blood and urine despite good compliance with treatment. Conversely, asymptomatic patients are also common in hereditary CASTOR conditions. Future challenges include the understanding of pathophysiologic mechanisms in CASTOR diseases, the discovery of reliable predictors of outcome in individual patients and the establishment of therapeutic trials with sufficient numbers of patients to permit solid therapeutic conclusions.

The expression of microRNA miR-107 decreases early in Alzheimer's disease and may accelerate disease progression through regulation of beta-site amyloid precursor protein-cleaving enzyme 1

MicroRNAs (miRNAs) are small regulatory RNAs that participate in posttranscriptional gene regulation in a sequence-specific manner. However, little is understood about the role(s) of miRNAs in Alzheimer's disease (AD). We used miRNA expression microarrays on RNA extracted from human brain tissue from the University of Kentucky Alzheimer's Disease Center Brain Bank with near-optimal clinicopathological correlation. Cases were separated into four groups: elderly nondemented with negligible AD-type pathology, nondemented with incipient AD pathology, mild cognitive impairment (MCI) with moderate AD pathology, and AD. Among the AD-related miRNA expression changes, miR-107 was exceptional because miR-107 levels decreased significantly even in patients with the earliest stages of pathology. In situ hybridization with cross-comparison to neuropathology demonstrated that particular cerebral cortical laminas involved by AD pathology exhibit diminished neuronal miR-107 expression. Computational analysis predicted that the 3'-untranslated region (UTR) of beta-site amyloid precursor protein-cleaving enzyme 1 (BACE1) mRNA is targeted multiply by miR-107. From the same RNA material analyzed on miRNA microarrays, mRNA expression profiling was performed using Affymetrix Exon Array microarrays on nondemented, MCI, and AD patients. BACE1 mRNA levels tended to increase as miR-107 levels decreased in the progression of AD. Cell culture reporter assays performed with a subset of the predicted miR-107 binding sites indicate the presence of at least one physiological miR-107 miRNA recognition sequence in the 3'-UTR of BACE1 mRNA. Together, the coordinated application of miRNA profiling, Affymetrix microarrays, new bioinformatics predictions, in situ hybridization, and biochemical validation indicate that miR-107 may be involved in accelerated disease progression through regulation of BACE1.

Nutrigenomics and antioxidants

Since the complete sequencing of the human genome, the era of the ‘omics’ has appeared. Among them, a new discipline called ‘nutrigenomics’ emerged from the interface of nutrition research and genetics. Its aim is to understand how nutrients modulate gene expression. This powerful tool allows determinination of new biomarkers and the molecular pathways by which our diet may have a potential protective effect against degenerative diseases such as cancer. On one hand, cellular metabolism produces continuous oxidative stress and reactive oxygen species with mutagenic and oncogenic effects. On the other hand, diet provides natural antioxidants present in various fruits and vegetables that may prevent diseases. This review first reports the main antioxidants provided by diet and the main results from epidemiological studies of their role in health. Second, we describe how nutrigenomics could provide new insights into nutrition research and innovative developments through neutraceutical products and a personalized medicine.

Energizing miRNA research: a review of the role of miRNAs in lipid metabolism, with a prediction that miR-103/107 regulates human metabolic pathways

MicroRNAs (miRNAs) are powerful regulators of gene expression. Although first discovered in worm larvae, miRNAs play fundamental biological roles-including in humans-well beyond development. MiRNAs participate in the regulation of metabolism (including lipid metabolism) for all animal species studied. A review of the fascinating and fast-growing literature on miRNA regulation of metabolism can be parsed into three main categories: (1) adipocyte biochemistry and cell fate determination; (2) regulation of metabolic biochemistry in invertebrates; and (3) regulation of metabolic biochemistry in mammals. Most research into the 'function' of a given miRNA in metabolic pathways has concentrated on a given miRNA acting upon a particular 'target' mRNA. Whereas in some biological contexts the effects of a given miRNA:mRNA pair may predominate, this might not be the case generally. In order to provide an example of how a single miRNA could regulate multiple 'target' mRNAs or even entire human metabolic pathways, we include a discussion of metabolic pathways that are predicted to be regulated by the miRNA paralogs, miR-103 and miR-107. These miRNAs, which exist in vertebrate genomes within introns of the pantothenate kinase (PANK) genes, are predicted by bioinformatics to affect multiple mRNA targets in pathways that involve cellular Acetyl-CoA and lipid levels. Significantly, PANK enzymes also affect these pathways, so the miRNA and 'host' gene may act synergistically. These predictions require experimental verification. In conclusion, a review of the literature on miRNA regulation of metabolism leads us believe that the future will provide researchers with many additional energizing revelations.

Crystal structure of Escherichia coli ketopantoate reductase in a ternary complex with NADP+ and pantoate bound: substrate recognition, conformational change, and cooperativity

Ketopantoate reductase (KPR, EC 1.1.1.169) catalyzes the NADPH-dependent reduction of ketopantoate to pantoate, an essential step for the biosynthesis of pantothenate (vitamin B5). Inhibitors of the enzymes of this pathway have been proposed as potential antibiotics or herbicides. Here we present the crystal structure of Escherichia coli KPR in a precatalytic ternary complex with NADP+ and pantoate bound, solved to 2.3 A of resolution. The asymmetric unit contains two protein molecules, each in a ternary complex; however, one is in a more closed conformation than the other. A hinge bending between the N- and C-terminal domains is observed, which triggers the switch of the essential Lys176 to form a key hydrogen bond with the C2 hydroxyl of pantoate. Pantoate forms additional interactions with conserved residues Ser244, Asn98, and Asn180 and with two conservatively varied residues, Asn194 and Asn241. The steady-state kinetics of active site mutants R31A, K72A, N98A, K176A, S244A, and E256A implicate Asn98 as well as Lys176 and Glu256 in the catalytic mechanism. Isothermal titration calorimetry studies with these mutants further demonstrate the importance of Ser244 for substrate binding and of Arg31 and Lys72 for cofactor binding. Further calorimetric studies show that KPR discriminates binding of ketopantoate against pantoate only with NADPH bound. This work provides insights into the roles of active site residues and conformational changes in substrate recognition and catalysis, leading to the proposal of a detailed molecular mechanism for KPR activity.

Transdifferentiation of porcine satellite cells to adipoblasts with ciglitizone

Ciglitizone, a class of thiazolidinediones, acts as a potent activator of the adipose differentiation program in established preadipose cell lines. Thiazolidinediones have also been investigated in diabetic patients and have been reported to act as peroxisome proliferator-activated receptor-gamma ligands. Intramuscular adipogenesis or marbling through transdifferentiation of satellite cells in cattle was successfully conducted earlier. In this report, the effects of ciglitizone on the differentiation pathway of porcine myogenic satellite cells was investigated. Semitendinosus muscle was aseptically taken from 10-d-old piglets under general anesthesia, and porcine satellite cells were obtained and grown to near confluence. Postconfluent cells (d 0) were further cultured in differentiation medium containing an adipogenic mixture plus ciglitizone (10 microM) for 48 h. From d 2 onward, the cells were cultured only in the presence of ciglitizone until d 10. Controls were cultured in differentiation medium only. Exposure of porcine satellite cells to the adipogenic mixture plus ciglitizone generated lipid droplets on d 2, and subsequently, exposure of cells to ciglitizone alone helped in cytoplasmic lipid filling, providing them with the acquisition of adipocyte morphology. An increase (P < 0.05) in the fusion (structures containing 2 to 3 nuclei) of satellite cells was observed, and myosin heavy chain appeared with greater intensity (immunohistochemistry) in the control group from d 2 onward. Adipocyte-specific transcriptional factors (i.e., CCAAT/enhancer binding protein-alpha and peroxisome proliferator-activated receptor-gamma) were predominant during transdifferentiation and were observed with immunohistochemistry, Western blot (approximately 47.2 and approximately 60.4 kDa, respectively), and real-time PCR. Ciglitizone appeared to convert the differentiation pathway of satellite cells into that of adipoblasts.

Mitochondrial function and toxicity: role of the B vitamin family on mitochondrial energy metabolism

The B vitamins are water-soluble vitamins required as coenzymes for enzymes essential for cell function. This review focuses on their essential role in maintaining mitochondrial function and on how mitochondria are compromised by a deficiency of any B vitamin. Thiamin (B1) is essential for the oxidative decarboxylation of the multienzyme branched-chain ketoacid dehydrogenase complexes of the citric acid cycle. Riboflavin (B2) is required for the flavoenzymes of the respiratory chain, while NADH is synthesized from niacin (B3) and is required to supply protons for oxidative phosphorylation. Pantothenic acid (B5) is required for coenzyme A formation and is also essential for alpha-ketoglutarate and pyruvate dehydrogenase complexes as well as fatty acid oxidation. Biotin (B7) is the coenzyme of decarboxylases required for gluconeogenesis and fatty acid oxidation. Pyridoxal (B6), folate and cobalamin (B12) properties are reviewed elsewhere in this issue. The experimental animal and clinical evidence that vitamin B therapy alleviates B deficiency symptoms and prevents mitochondrial toxicity is also reviewed. The effectiveness of B vitamins as antioxidants preventing oxidative stress toxicity is also reviewed.

An Arabidopsis mutant impaired in coenzyme A biosynthesis is sugar dependent for seedling establishment

Once the plant coenzyme A (CoA) biosynthetic pathway has been elucidated by comparative genomics, it is feasible to analyze the physiological relevance of CoA biosynthesis in plant life. To this end, we have identified and characterized Arabidopsis (Arabidopsis thaliana) T-DNA knockout mutants of two CoA biosynthetic genes, HAL3A and HAL3B. The HAL3A gene encodes a 4'-phosphopantothenoyl-cysteine decarboxilase that generates 4'-phosphopantetheine. A second gene, HAL3B, whose gene product is 86% identical to that of HAL3A, is present in the Arabidopsis genome. HAL3A appears to have a predominant role over HAL3B according to their respective mRNA expression levels. The hal3a-1, hal3a-2, and hal3b mutants were viable and showed a similar growth rate as that in wild-type plants; in contrast, a hal3a-1 hal3b double mutant was embryo lethal. Unexpectedly, seedlings that were null for HAL3A and heterozygous for HAL3B (aaBb genotype) displayed a sucrose (Suc)-dependent phenotype for seedling establishment, which is in common with mutants defective in beta-oxidation. This phenotype was genetically complemented in aaBB siblings of the progeny and chemically complemented by pantethine. In contrast, seedling establishment of Aabb plants was not Suc dependent, proving a predominant role of HAL3A over HAL3B at this stage. Total fatty acid and acyl-CoA measurements of 5-d-old aaBb seedlings in medium lacking Suc revealed stalled storage lipid catabolism and impaired CoA biosynthesis; in particular, acetyl-CoA levels were reduced by approximately 80%. Taken together, these results provide in vivo evidence for the function of HAL3A and HAL3B, and they point out the critical role of CoA biosynthesis during early postgerminative growth.

Identification of a novel CoA synthase isoform, which is primarily expressed in the brain

CoA and its derivatives Acetyl-CoA and Acyl-CoA are important players in cellular metabolism and signal transduction. CoA synthase is a bifunctional enzyme which mediates the final stages of CoA biosynthesis. In previous studies, we have reported molecular cloning, biochemical characterization, and subcellular localization of CoA synthase (CoASy). Here, we describe the existence of a novel CoA synthase isoform, which is the product of alternative splicing and possesses a 29aa extension at the N-terminus. We termed it CoASy beta and originally identified CoA synthase, CoASy alpha. The transcript specific for CoASy beta was identified by electronic screening and by RT-PCR analysis of various rat tissues. The existence of this novel isoform was further confirmed by immunoblot analysis with antibodies directed to the N-terminal peptide of CoASy beta. In contrast to CoASy alpha, which shows ubiquitous expression, CoASy beta is primarily expressed in the brain. Using confocal microscopy, we demonstrated that both isoforms are localized on mitochondria. The N-terminal extension does not affect the activity of CoA synthase, but possesses a proline-rich sequence which can bring the enzyme into complexes with signalling proteins containing SH3 or WW domains. The role of this novel isoform in CoA biosynthesis, especially in the brain, requires further elucidation.

Biophysical tools to monitor enzyme-ligand interactions of enzymes involved in vitamin biosynthesis

Knowledge of biomolecular interactions is of importance to our understanding of biological processes such as enzyme catalysis and inhibition. Biophysical techniques enable sensitive detection and accurate characterization of binding and are therefore powerful tools in enzymology and rational drug design. The applications of NMR spectroscopy and isothermal titration calorimetry to study enzyme-ligand interactions will be discussed. Recent work on ketopantoate reductase, which catalyses an important step on the biosynthetic pathway to vitamin B5, is used to illustrate the potential of this approach.

Mitochondrial Localization of Human PANK2 and Hypotheses of Secondary Iron Accumulation in Pantothenate Kinase-Associated Neurodegeneration

Mutations in the pantothenate kinase 2 gene (PANK2) lead to pantothenate kinase-associated neurodegeneration (PKAN, formerly Hallervorden-Spatz syndrome). This neurodegenerative disorder is characterized by iron accumulation in the basal ganglia. Pantothenate kinase is the first enzyme in the biosynthesis of coenzyme A from pantothenate (vitamin B(5)). PANK2, one of four human pantothenate kinase genes, is uniquely predicted to be targeted to mitochondria. We demonstrate mitochondrial localization of PANK2 and speculate on mechanisms of secondary iron accumulation in PKAN. Furthermore, PANK2 uses an unconventional translational start codon, CUG, which is polymorphic in the general population. The variant sequence, CAG (allele frequency: 0.05), leads to skipping of the mitochondrial targeting signal and cytosolic localization of PANK2. This common variant may cause mitochondrial dysfunction and impart susceptibility to late-onset neurodegenerative disorders with brain iron accumulation, including Parkinson's disease.

Overexpression of NtHAL3 genes confers increased levels of proline biosynthesis and the enhancement of salt tolerance in cultured tobacco cells

The Hal3 protein of Saccharomyces cerevisiae inhibits the activity of PPZ1 type-1 protein phosphatases and functions as a regulator of salt tolerance and cell cycle control. In plants, two HAL3 homologue genes in Arabidopsis thaliana, AtHAL3a and AtHAl3b, have been isolated and the function of AtHAL3a has been investigated through the use of transgenic plants. Expressions of both AtHAL3 genes are induced by salt stress. AtHAL3a overexpressing transgenic plants exhibit improved salt and sorbitol tolerance. In vitro studies have demonstrated that AtHAL3 protein possessed 4'-phosphopantothenoylcysteine decarboxylase activity. This result suggests that the molecular function of plant HAL3 genes is different from that of yeast HAL3. To understand the function of plant HAL3 genes in salt tolerance more clearly, three tobacco HAL3 genes, NtHAL3a, NtHAL3b, and NtHAL3c, from Nicotiana tabacum were identified. NtHAL3 genes were constitutively expressed in all organs and under all conditions of stress examined. Overexpression of NtHAL3a improved salt, osmotic, and lithium tolerance in cultured tobacco cells. NtHAL3 genes could complement the temperature-sensitive mutation in the E. coli dfp gene encoding 4'-phosphopantothenoyl-cysteine decarboxylase in the coenzyme A biosynthetic pathway. Cells overexpressing NtHAL3a had an increased intracellular ratio of proline. Taken together, these results suggest that NtHAL3 proteins are involved in the coenzyme A biosynthetic pathway in tobacco cells.

PPARalpha controls the intracellular coenzyme A concentration via regulation of PANK1alpha gene expression

Pantothenate kinase (PanK) is thought to catalyze the first rate-limiting step in CoA biosynthesis. The full-length cDNA encoding the human PanK1alpha protein was isolated, and the complete human PANK1 gene structure was determined. Bezafibrate (BF), a hypolipidemic drug and a peroxisome proliferator activator receptor-alpha (PPARalpha) agonist, specifically increased hPANK1alpha mRNA expression in human hepatoblastoma (HepG2) cells as a function of time and dose of the drug, compared with hPANK1beta, hPANK2, and hPANK3, which did not significantly increase. Four putative PPARalpha response elements were identified in the PANKIalpha promoter, and BF stimulated hPANK1alpha promoter activity but did not alter the mRNA half-life. Increased hPANK1alpha mRNA resulted in higher hPanK1 protein, localized in the cytoplasm, and elevated PanK enzyme activity. The enhanced hPANK1alpha gene expression translated into increased activity of the CoA biosynthetic pathway and established a higher steady-state CoA level in HepG2 cells. These data are consistent with a key role for PanK1alpha in the control of cellular CoA content and point to the PPARalpha transcription factor as a major factor governing hepatic CoA levels by specific modulation of PANK1alpha gene expression.

Subcellular localization and regulation of coenzyme A synthase

CoA synthase mediates the last two steps in the sequence of enzymatic reactions, leading to CoA biosynthesis. We have recently identified cDNA for CoA synthase and demonstrated that it encodes a bifunctional enzyme possessing 4'-phosphopantetheine adenylyltransferase and dephospho-CoA kinase activities. Molecular cloning of CoA synthase provided us with necessary tools to study subcellular localization and the regulation of this bifunctional enzyme. Transient expression studies and confocal microscopy allowed us to demonstrate that full-length CoA synthase is associated with the mitochondria, whereas the removal of the N-terminal region relocates the enzyme to the cytosol. In addition, we showed that the N-terminal sequence of CoA synthase (amino acids 1-29) exhibits a hydrophobic profile and targets green fluorescent protein exclusively to mitochondria. Further analysis, involving subcellular fractionation and limited proteolysis, indicated that CoA synthase is localized on the mitochondrial outer membrane. Moreover, we demonstrate for the first time that phosphatidylcholine and phosphatidylethanolamine, which are the main components of the mitochondrial outer membrane, are potent activators of both enzymatic activities of CoA synthase in vitro. Taken together, these data provide the evidence that the final stages of CoA biosynthesis take place on mitochondria and the activity of CoA synthase is regulated by phospholipids.

Synthesis and analysis of potential prodrugs of coenzyme A analogues for the inhibition of the histone acetyltransferase p300

Lys-CoA (1) is a selective inhibitor of p300 histone acetyltransferase (HAT) but shows poor pharmacokinetic properties because of its multiply charged phosphates. In an effort to overcome this limitation, truncated derivatives of 1 were designed, synthesized and tested as p300HAT inhibitors as well as substrates for the CoA biosynthetic bifunctional enzyme phosphopantetheine adenylyltransferase-dephospho-CoA kinase (PPAT/DPCK). Lys-pantetheine (3) and Lys-phosphopantetheine (2) showed no detectable p300HAT inhibition whereas 3'-dephospho-Lys-CoA (5) was a modest p300 inhibitor with IC(50) of 1.6 microM (compared to IC(50) of approximately 50 nM for 1 blocking p300). Compound 2 was shown to be an efficient substrate for PPAT whereas 5 was a very poor DPCK substrate. Further analysis with 3'-dephospho-Me-SCoA (7) indicated that DPCK shows relatively narrow capacity to accept substrates with sulfur substitution. While these results suggest that truncated derivatives of 1 will be of limited value as lead agents for p300 blockade in vivo, they augur well for prodrug versions of CoA analogues that do not require 3'-phosphate substitution for efficient binding to their targets, such as the GCN-5 related N-acetyltransferases.

Molecular cloning of CoA Synthase. The missing link in CoA biosynthesis

Coenzyme A functions as a carrier of acetyl and acyl groups in living cells and is essential for numerous biosynthetic, energy-yielding, and degradative metabolic pathways. There are five enzymatic steps in CoA biosynthesis. To date, molecular cloning of enzymes involved in the CoA biosynthetic pathway in mammals has been only reported for pantothenate kinase. In this study, we present cDNA cloning and functional characterization of CoA synthase. It has an open reading frame of 563 aa and encodes a protein of approximately 60 kDa. Sequence alignments suggested that the protein possesses both phosphopantetheine adenylyltransferase and dephospho-CoA kinase domains. Biochemical assays using wild type recombinant protein confirmed the gene product indeed contained both these enzymatic activities. The presence of intrinsic phosphopantetheine adenylyltransferase activity was further confirmed by site-directed mutagenesis. Therefore, this study describes the first cloning and characterization of a mammalian CoA synthase and confirms this is a bifunctional enzyme containing the last two components of CoA biosynthesis.

Complete reconstitution of the human coenzyme A biosynthetic pathway via comparative genomics

The biosynthesis of CoA from pantothenic acid (vitamin B5) is an essential universal pathway in prokaryotes and eukaryotes. The CoA biosynthetic genes in bacteria have all recently been identified, but their counterparts in humans and other eukaryotes remained mostly unknown. Using comparative genomics, we have identified human genes encoding the last four enzymatic steps in CoA biosynthesis: phosphopantothenoylcysteine synthetase (EC ), phosphopantothenoylcysteine decarboxylase (EC ), phosphopantetheine adenylyltransferase (EC ), and dephospho-CoA kinase (EC ). Biological functions of these human genes were verified using a complementation system in Escherichia coli based on transposon mutagenesis. The individual human enzymes were overexpressed in E. coli and purified, and the corresponding activities were experimentally verified. In addition, the entire pathway from phosphopantothenate to CoA was successfully reconstituted in vitro using a mixture of purified recombinant enzymes. Human recombinant bifunctional phosphopantetheine adenylyltransferase/dephospho-CoA kinase was kinetically characterized. This enzyme was previously suggested as a point of CoA biosynthesis regulation, and we have observed significant differences in mRNA levels of the corresponding human gene in normal and tumor cells by Northern blot analysis.

The murine pantothenate kinase (Pank1) gene encodes two differentially regulated pantothenate kinase isozymes

Pantothenate kinase (PanK) is a rate-determining enzyme in coenzyme A (CoA) biosynthesis. The mouse murine pantothenate kinase (Pank1) gene consists of seven introns and eight exons and is located on chromosome 19 (19C2-3). Two biochemically distinct PanK1 protein isoforms, PanK1 alpha and PanK1 beta, are encoded by the Pank1 gene. Both proteins have the same 363 amino acid catalytic domain encoded by exons 2 through 7. The PanK1 beta transcript begins with exon 1 beta and translates into a ten-residue amino terminus plus the catalytic domain. The PanK1 alpha transcript initiates at an alternate upstream site at exon 1 alpha which is spliced with exon 2, excluding exon 1 beta. Exon 1 alpha encodes a 184-residue regulatory domain at the amino terminus of the PanK1 alpha protein that confers feedback inhibition by free CoA and long-chain acyl-CoA, and increases the regulation of PanK enzyme activity by acetyl-CoA and malonyl-CoA. Differential expression of the PanK1 alpha and PanK1 beta transcripts would alter the amount of CoA produced in cells as a function of the ratio of free CoA to acetyl-CoA, a reflection of the metabolic status of the tissue.