Chitooligosaccharide induces mitochondrial biogenesis and increases exercise endurance through the activation of Sirt1 and AMPK in rats.

By catabolizing glucose and lipids, mitochondria produce ATPs to meet energy demands. When the number and activity of mitochondria are not sufficient, the human body becomes easily fatigued due to the lack of ATP, thus the control of the quantity and function of mitochondria is important to optimize energy balance. By increasing mitochondrial capacity? it may be possible to enhance energy metabolism and improve exercise endurance. Here, through the screening of various functional food ingredients, we found that chitooligosaccharide (COS) is an effective inducer of mitochondrial biogenesis. In rodents, COS increased the mitochondrial content in skeletal muscle and enhanced exercise endurance. In cultured myocytes, the expression of major regulators of mitochondrial biogenesis and key components of mitochondrial electron transfer chain was increased upon COS treatment. COS-mediated induction of mitochondrial biogenesis was achieved in part by the activation of silent information regulator two ortholog 1 (Sirt1) and AMP-activated protein kinase (AMPK). Taken together, our data suggest that COS could act as an exercise mimetic by inducing mitochondrial biogenesis and enhancing exercise endurance through the activation of Sirt1 and AMPK.

Effects of chitooligosaccharide lactate salt on activity of acetaldehyde dehydrogenase.

Chitooligosaccharides (COS), a kind of oligosaccharide made from chitin or chitosan, have been used a popular remedy for hangovers. In this study we investigated the in vitro effect of COS lactate salt on ethanol-induced cytotoxicity and the in vivo effect of short-term COS lactate salt feeding on ethanol-induced hangover. Pretreatment of HepG2 cells with COS lactate salt significantly reduced ethanol-induced cytotoxicity and suppressed generation of reactive oxygen species. In addition, COS lactate salt dose-dependently increased acetaldehyde dehydrogenase (ALDH) activity in vitro and reversed the ALDH inhibition induced by daidzin. Furthermore, oral administration of COS lactate salt (200 mg/kg) for 5 days significantly decreased the blood levels of alcohol and acetaldehyde in ethanol-treated mice. It was also demonstrated that hepatic mitochondrial ALDH activity was significantly increased in COS lactate salt-treated mice. Taken together, these findings indicate that COS lactate salt may have efficacy for the management of alcoholic hangovers.

Effects of chitooligosaccharide lactate salt on sleep deprivation-induced fatigue in mice.

Chitooligosaccharides (COS), oligosaccharides composed of two to seven glucosamine residues, are known to exhibit various biological activities. In this study, we investigated the effects of COS in an in vivo mouse sleep deprivation-induced fatigue model in an effort to develop a functional food with anti-fatigue efficacy. Male Balb/c mice were orally administered 500 mg (kg d)(-1) of COS lactate or COS HCl for 2 weeks, and severe fatigue was induced by sleep deprivation. To evaluate the extent of fatigue, the swimming time, representing the immobility time, was measured in a forced swim test. As a result, oral intake of COS lactate-manifested anti-fatigue effects could be observed by the attenuation of fatigue-induced body weight loss and shorter immobility period. In addition, COS lactate was shown to alleviate the fatigue-induced increase in cortisol and lipid peroxidation and a decrease in superoxide dismutase (SOD) activity. Of particular note, the oral administration of COS lactate increased the mitochondrial membrane potential and the mitochondrial number significantly, indicating that COS lactate may enhance mitochondrial function. In support of this, COS lactate increased the expression of peroxisome proliferator-activated receptor gamma coactivator-1alpha (PGC-1alpha) and cytochrome c (Cyt C) mRNA, indicating that it may increase mitochondrial biogenesis. These results suggest that COS lactate can be an effective anti-fatigue functional food, and this anti-fatigue effect may result from, at least in part, the enhancement of mitochondrial biogenesis and the inhibition of free radical generation.

Proteomic analysis of mitochondrial proteins of basal and lipolytically (isoproterenol and TNF-alpha)-stimulated adipocytes.

The regulation of adipocyte lipolysis is increasingly believed to influence insulin resistance, in a process that may be associated with mitochondrial dysfunction. However, the molecular basis of the relationship between mitochondrial protein expression, lipolytic responsiveness, and insulin resistance remains unknown. A set of proteins that shows altered abundances in the mitochondria of untreated and treated 3T3-L1 adipocytes with TNF-alpha or isoproterenol was identified. These include the proteins associated with energy production, including fatty acid oxidation, TCA cycle, and oxidative phosphorylation. Proteins associated with oxidative stress dissipation were down-regulated in lipolytically stimulated adipocytes. Lipolytic stimulation with isoproterenol and TNF-alpha, which is also a potent proinflammatory cytokine, showed some noticeable differences in mitochondrial protein expression. For example, isoproterenol markedly enhanced the expression of prohibitin which is involved in the integrity of mitochondria but TNF-alpha did not. These results provide valuable information on mitochondrial dysfunction associated with oxidative stress induced by lipolytic stimulation.

Identification of the domains required for the localization of Prp19p to lipid droplets or the nucleus.

Prp19p is a protein found in the nucleus, cytosol or lipid droplets depending on the cell type. Prp19p participates in pre-mRNA splicing, in neuronal/astroglial cell fate decisions or in adipocyte lipid droplet biogenesis. In this study, the motifs of Prp19p that are necessary for its localization to lipid droplets or the nucleus in 3T3-L1 adipocytes are investigated using a series of truncated mutants of Prp19p that were fused to EGFP and transiently introduced into differentiated 3T3-L1 adipocytes. Immunofluorescence microscopy revealed that a domain of amino acids 167-250 is necessary for the recruitment of Prp19p to lipid droplets and that a domain of amino acids 1-166 is necessary for the recruitment of Prp19p to a nucleus.

(-)-Catechin suppresses expression of Kruppel-like factor 7 and increases expression and secretion of adiponectin protein in 3T3-L1 cells.

Adiponectin is an adipocyte-specific secretory hormone that can increase insulin sensitivity and promote adipocyte differentiation. Administration of adiponectin to obese or diabetic mice reduces plasma glucose and free fatty acid levels. Green tea polyphenols possess many pharmacological activities such as antioxidant, anti-inflammatory, antiobesity, and antidiabetic activities. To investigate whether green tea polyphenols have an effect on the regulation of adiponectin, we measured expression and secretion levels of adiponectin protein after treatment of each green tea polyphenols in 3T3-L1 adipocytes. We found that (-)-catechin enhanced the expression and secretion of adiponectin protein in a dose- and time-dependent manner. Furthermore, treatment of (-)-catechin increased insulin-dependent glucose uptake in differentiated adipocytes and augmented the expression of adipogenic marker genes, including PPARgamma, CEBPalpha, FAS, and SCD-1, when (-)-catechin was treated during adipocyte differentiation. In search of the molecular mechanism responsible for inducible effect of (-)-catechin on adiponectin expression, we found that (-)-catechin markedly suppresses the expression of Kruppel-like factor 7 (KLF7) protein, which has recently been reported to inhibit the expression of adiponectin and other adipogenesis related genes, including leptin, PPARgamma, C/EBPalpha, and aP2 in adipocytes. KLF7 is a transcription factor in adipocyte and plays an important role in the pathogenesis of type 2 diabetes. Taken together, these data suggest that the upregulation of adiponectin protein by (-)-catechin may involve, at least in part, suppression of KLF7 in 3T3-L1 cells.

Identification of mouse Prp19p as a lipid droplet-associated protein and its possible involvement in the biogenesis of lipid droplets.

Prp19p is an integral component of the heteromeric protein complex (the NineTeen complex) in the nucleus, and it is essential for the structural integrity of NineTeen complex and its subsequent activation of the spliceosome. We identified Prp19p, which has never been reported in relation to any function outside of the nucleus, as a member of proteins associated with lipid droplets. Down-regulation of Prp19p expression with RNA interference in 3T3-L1 cells repressed lipid droplet formation with the reduction in the level of expression of perilipin and S3-12. The levels of expression of SCD1 (stearoyl-CoA desaturase-1), DGAT-1 (acyl-CoA diacylglycerol acyltransferase-1), and glycerol-3-phosphate acyltransferase were also reduced in Prp19p down-regulated cells, and a significant decrease in triglycerides was observed. Unlike perilipin, which is one of the most extensively studied lipid droplet-associated proteins, Prp19p is not essential for cAMP- and hormone-sensitive lipase-dependent lipolysis pathways, even though Prp19p is a component of the lipid droplet phospholipid monolayer, and down-regulation of Prp19p represses fat accretion significantly. These results suggest that Prp19p or Prp19-interacting proteins during lipid droplet biogenesis in adipocytes may be considered as another class of potential targets for attacking obesity and obesity-related problems.

Brassinosteroid signals control expression of the AXR3/IAA17 gene in the cross-talk point with auxin in root development.

Transgenic plants overexpressing AXR3/IAA17 were impaired in root growth. Specifically, they exhibited severe defects in lateral root and root hair development similar to the root phenotypes of epi-brassinolide (epiBL)-treated wild-type plants. Here, we investigated the involvement of AXR3/IAA17 gene expression in brassinosteroid (BR)-regulated root development. Exogenous epiBL application significantly induced expression of the AXR3/IAA17 gene as well as several Aux/IAA genes, such as AXR2/IAA7, SLR/IAA14, and IAA28. We analyzed the transcription levels of several Aux/IAA genes related to root development in the BR signaling mutant bri1 and the BR biosynthesis mutant det2. AXR3/IAA17 gene expression was significantly decreased in bri1 plants. In det2 plants, expression of AXR3/IAA17 slightly decreased. This in turn suggests that epiBL induced these Aux/IAA genes, and that these induced gene products might function as factors in root development. Furthermore, AXR3/IAA17 might be involved in the BR signaling pathway, suggesting an intersection node of BR-auxin signaling in root development.