Mitochondrial, but not peroxisomal, beta-oxidation of fatty acids is conserved in coenzyme A-deficient rat liver

Severe pantothenic acid deficiency induces alterations in the intestinal mucosal proteome of starter Pekin ducks

BACKGROUND

Pantothenic acid deficiency (PAD) results in growth depression and intestinal hypofunction of animals. However, the underlying molecular mechanisms remain to be elucidated. Mucosal proteome might reflect dietary influences on physiological processes.

RESULTS

A total of 128 white Pekin ducks of one-day-old were randomly assigned to two groups, fed either a PAD or a pantothenic acid adequate (control, CON) diet. After a 16-day feeding period, two ducks from each replicate were sampled to measure plasma parameters, intestinal morphology, and mucosal proteome. Compared to the CON group, high mortality, growth retardation, fasting hypoglycemia, reduced plasma insulin, and oxidative stress were observed in the PAD group. Furthermore, PAD induced morphological alterations of the small intestine indicated by reduced villus height and villus surface area of duodenum, jejunum, and ileum. The duodenum mucosal proteome of ducks showed that 198 proteins were up-regulated and 223 proteins were down-regulated (> 1.5-fold change) in the PAD group compared to those in the CON group. Selected proteins were confirmed by Western blotting. Pathway analysis of these proteins exhibited the suppression of glycolysis and gluconeogenesis, fatty acid beta oxidation, tricarboxylic acid cycle, oxidative phosphorylation, oxidative stress, and intestinal absorption in the PAD group, indicating impaired energy generation and abnormal intestinal absorption. We also show that nine out of eleven proteins involved in regulation of actin cytoskeleton were up-regulated by PAD, probably indicates reduced intestinal integrity.

CONCLUSION

PAD leads to growth depression and intestinal hypofunction of ducks, which are associated with impaired energy generation, abnormal intestinal absorption, and regulation of actin cytoskeleton processes. These findings provide insights into the mechanisms of intestinal hypofunction induced by PAD.

Comparative Analysis of Metabolites in the Liver of Muscovy Ducks at Different Egg-Laying Stages Using Nontargeted Ultra-High-Performance Liquid Chromatography-Electrospray Mass Spectrometry-Based Metabolomics

Liver plays an important physiological function in the synthesis of yolk materials during egg laying in birds. Liver metabolite profiles of Muscovy ducks at different egg-laying stages from the perspective of nontargeted metabolomics were analyzed in this study. Twelve Muscovy ducks were selected at pre-laying (22 weeks, TT group), laying (40 weeks, FT group), and post-laying (60 weeks, ST group) stages, resulting in 36 hepatic metabolite profiles by using ultra-high-performance liquid chromatography-electrospray mass spectrometry. A total of 324 differential metabolites (156 increased and 168 decreased) in FT as compared to the TT (FT/TT) group and 332 differential metabolites (120 increased and 212 decreased) in ST as compared to the FT (ST/FT) group were screened out. Metabolic pathways enriched in FT/TT and ST/FT groups were mainly amino acid metabolism, glycerophospholipid metabolism, nucleotide metabolism, and vitamin metabolism. The amino acid metabolism pathways were upregulated in the FT/TT group and downregulated in the ST/FT group (P < 0.05). The glutathione and ascorbic acid abundances were downregulated, and the choline abundance was upregulated during egg laying (P < 0.05). The liver provides amino acids, lipids, nucleotides, vitamins, and choline, and so on, which are essential materials for yolk precursor synthesis. The decrease in the abundance of glutathione and ascorbic acid indicates that Muscovy ducks might be in a relatively stable physiological state during egg laying.

In Vitro Monitoring of the Mitochondrial Beta-Oxidation Flux of Palmitic Acid and Investigation of Its Pharmacological Alteration by Therapeutics

BACKGROUND AND OBJECTIVE

The present study was designed to validate the functional assay that enables rapid screening of therapeutic candidates for their effect on mitochondrial fatty acid oxidation.

METHODS

The two whole-cell systems (tissue homogenates and hepatocytes) have been evaluated to monitor the total beta-oxidation flux of physiologically important ³H-palmitic acid by measurement of tritiated water enrichment in incubations using UPLC coupled on-line to radioactivity monitoring and mass spectrometry.

RESULTS

Our results with several known inhibitors of fatty acid oxidation showed that this simple assay could correctly predict a potential in alteration of mitochondrial function by drug candidates. Since the beta-oxidation of palmitic acid takes place almost exclusively in mitochondria of human hepatocytes, this model can be also utilized to distinguish between the mitochondrial and peroxisomal routes of this essential metabolic pathway in some cases.

CONCLUSIONS

The present work offers a new in vitro screen of changes in mitochondrial beta-oxidation by xenobiotics as well as a model to study the mechanism of this pathway.

Metabonomic analysis of toxic action of long-term low-level exposure to acrylamide in rat serum

This study assessed the effects of long-term, low-dose acrylamide (AA) administration in rats using ultra-performance liquid chromatography–mass spectrometry. Forty male Wistar rats were randomly divided into the following four groups: control, low-dose AA (0.2 mg/kg BW), middle-dose AA (1 mg/kg BW), and high-dose AA (5 mg/kg BW). AA was administered to rats via drinking water ad libitum. After 16-week treatment, rat serum was collected for metabonomic analysis. Biochemical tests were further conducted to verify metabolic alterations. Eleven metabolites were identified with significant changes in intensities (increased or reduced) as a result of treatment. These metabolites included citric acid, pantothenic acid, isobutyryl-l-carnitine, eicosapentaenoic acid, docosahexaenoic acid, sphingosine 1-phosphate, LysoPC(20:4), LysoPC(22:6), LysoPE(20:3), undecanedioic acid, and dodecanedioic acid. Results indicate that chronic exposure to AA at no observed adverse effect level does not exert a toxic effect on rats at the body metabolism level. AA disturbed the metabolism of lipids and energy, affected the nervous system of rats, and induced oxidative stress and liver dysfunction.

Biochemistry and genetics of inherited disorders of peroxisomal fatty acid metabolism

In humans, peroxisomes harbor a complex set of enzymes acting on various lipophilic carboxylic acids, organized in two basic pathways, alpha-oxidation and beta-oxidation; the latter pathway can also handle omega-oxidized compounds. Some oxidation products are crucial to human health (primary bile acids and polyunsaturated FAs), whereas other substrates have to be degraded in order to avoid neuropathology at a later age (very long-chain FAs and xenobiotic phytanic acid and pristanic acid). Whereas total absence of peroxisomes is lethal, single peroxisomal protein deficiencies can present with a mild or severe phenotype and are more informative to understand the pathogenic factors. The currently known single protein deficiencies equal about one-fourth of the number of proteins involved in peroxisomal FA metabolism. The biochemical properties of these proteins are highlighted, followed by an overview of the known diseases.

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.

Control of mitochondrial beta-oxidation flux

The control of mitochondrial beta-oxidation, including the delivery of acyl moieties from the plasma membrane to the mitochondrion, is reviewed. Control of beta-oxidation flux appears to be largely at the level of entry of acyl groups to mitochondria, but is also dependent on substrate supply. CPTI has much of the control of hepatic beta-oxidation flux, and probably exerts high control in intact muscle because of the high concentration of malonyl-CoA in vivo. beta-Oxidation flux can also be controlled by the redox state of NAD/NADH and ETF/ETFH(2). Control by [acetyl-CoA]/[CoASH] may also be significant, but it is probably via export of acyl groups by carnitine acylcarnitine translocase and CPT II rather than via accumulation of 3-ketoacyl-CoA esters. The sharing of control between CPTI and other enzymes allows for flexible regulation of metabolism and the ability to rapidly adapt beta-oxidation flux to differing requirements in different tissues.