Malnutrition impairs interferon signaling through mTOR and FoxO pathways in patients with chronic hepatitis C.

BACKGROUND & AIMS: Patients with advanced chronic hepatitis C (CH-C) often are malnourished, but the effects of malnutrition on interferon (IFN) signaling and response to treatment have not been determined. We assessed the importance of the nutritional state of the liver on IFN signaling and treatment response. METHODS: We studied data from 168 patients with CH-C who were treated with the combination of pegylated-IFN and ribavirin. Plasma concentrations of amino acids were measured by mass spectrometry. Liver gene expression profiles were obtained from 91 patients. Huh-7 cells were used to evaluate the IFN signaling pathway, mammalian target of rapamycin complex 1 (mTORC1), and forkhead box O (FoxO). Antiviral signaling induced by branched-chain amino acids (BCAAs) was determined using the in vitro hepatitis C virus replication system. RESULTS: Multivariate logistic regression analysis showed that Fischer's ratio was associated significantly with nonresponders, independent of interleukin-28B polymorphisms or the histologic stage of the liver. Fischer's ratio was correlated inversely with the expression of BCAA transaminase 1, and was affected by hepatic mTORC1 signaling. IFN stimulation was impaired substantially in Huh-7 cells grown in medium that was low in amino acid concentration, through repressed mTORC1 signaling, and increased Socs3 expression, which was regulated by Foxo3a. BCAA could restore impaired IFN signaling and inhibit hepatitis C virus replication under conditions of malnutrition. CONCLUSIONS: Malnutrition impaired IFN signaling by inhibiting mTORC1 and activating Socs3 signaling through Foxo3a. Increasing BCAAs to up-regulate IFN signaling might be used as a new therapeutic approach for patients with advanced CH-C.

Effects of Five Amino Acids (Serine, Alanine, Glutamate, Aspartate, and Tyrosine) on Mental Health in Healthy Office Workers: A Randomized, Double-Blind, Placebo-Controlled Exploratory Trial.

BACKGROUND: The importance of maintaining good mental health with overall well-being has recently drawn attention from various spheres of academics and the working population. Amino acid intake has been reported to reduce depression symptoms and other mental health problems. However, the effectiveness of amino acid intake (i.e., single or combined) remains unknown. In this study, we assessed a combination of five amino acids (serine, alanine, glutamate, aspartate, and tyrosine; SAGAT) reported to regulate mental health. METHODS: A randomized, double-blind, placebo-controlled exploratory trial was conducted. Participants, aged between 20 and 65 years with fatigue sensation, were randomized to receive either SAGAT or the placebo and ingested them for four weeks. A transient mental work was loaded at day 0 and after four weeks of intervention. As the primary outcomes, the fatigue sensation was assessed. The mood status, cognitive function, work efficiency, and blood marker were also measured as secondary outcomes. RESULTS: The number of participants analyzed for the efficacy evaluation were 20 in SAGAT and 22 in the placebo. There were no significant differences in the primary outcomes. However, as the secondary outcomes, the SAGAT group showed a significant improvement in motivation and cognitive function in the recovery period after mental work loaded in a four-week intervention compared to the placebo. CONCLUSION: The current findings suggest that SAGAT contributes to maintaining proper motivation and cognitive function. CLINICAL TRIAL REGISTRATION: University Hospital Medical Information Network Clinical Trial Registry (ID: UMIN 000041221).

Oral administration of branched-chain amino acids activates the mTOR signal in cirrhotic rat liver.

BCAA granules (a mixture of branched-chain amino acids) have been used to reverse the hypoalbuminemia of decompensated liver cirrhotic patients in Japan. Our previous studies showed that BCAA promoted albumin secretion through the mTOR signal transduction pathway in rat primary hepatocyte culture [Ijichi C, Matsumura T, Tsuji T, Eto Y. Branched-chain amino acids promote albumin synthesis in rat primary hepatocytes through the mTOR signal transduction system. Biochem Biophys Res Commun 2003;303:59-64]. However, the mTOR-activating effect of BCAA in the experimental cirrhotic animals presenting with hypoalbuminemia has not yet been examined. The purpose of this study is to assess whether oral administration of BCAA induces mTOR activity in the livers of normal rats and CCl(4)-induced cirrhotic rats (CCl(4) rats). Biochemical analysis of liver extracts isolated from several rats showed that oral administration of BCAA (0.75g/kg body weight (BW)) induced phosphorylation of 4E-BP1 and stimulated the enzymatic activity of p70 S6K. Both of these molecules act downstream of mTOR. From the results, we conclude that orally administrated BCAA augments albumin synthesis in the liver, not only by supplementation of material substrates for protein synthesis, but also by induction of an mTOR signal that is critical for translational initiation. Furthermore, we conclude that induction of mTOR signaling is one of the major pharmacological mechanisms by which BCAA granules reverse the hypoalbuminemia of cirrhotic patients.

Pharmacological activities of branched-chain amino acids: augmentation of albumin synthesis in liver and improvement of glucose metabolism in skeletal muscle.

LIVACT granules, which is a branched-chain amino acid (BCAA) preparation, was developed for the purpose of improving hypoalbuminemia in patients with uncompensated liver cirrhosis in Japan. Recent clinical studies have shown that BCAA supplementation not only improves hypoalbuminemia, but also reduces the occurrence frequency of various complications of liver cirrhosis, which considerably affect mortality. In order to comprehend the significance of BCAA supplementation in patients with liver cirrhosis and to suggest better treatments, we conducted basic non-clinical studies mainly using animal models, clarified the molecular mechanism of the curative effect on hypoalbuminemia and emphasized the importance of mTOR signal transduction. Moreover, we found a new pharmacological action of BCAA, which improves glucose metabolism in skeletal muscles.

Branched chain amino acid suppresses hepatocellular cancer stem cells through the activation of mammalian target of rapamycin.

Differentiation of cancer stem cells (CSCs) into cancer cells causes increased sensitivity to chemotherapeutic agents. Although inhibition of mammalian target of rapamycin (mTOR) leads to CSC survival, the effect of branched chain amino acids (BCAAs), an mTOR complex 1 (mTORC1) activator remains unknown. In this study, we examined the effects of BCAA on hepatocellular carcinoma (HCC) cells expressing a hepatic CSC marker, EpCAM. We examined the effects of BCAA and/or 5-fluorouracil (FU) on expression of EpCAM and other CSC-related markers, as well as cell proliferation in HCC cells and in a xenograft mouse model. We also characterized CSC-related and mTOR signal-related molecule expression and tumorigenicity in HCC cells with knockdown of Rictor or Raptor, or overexpression of constitutively active rheb (caRheb). mTOR signal-related molecule expression was also examined in BCAA-treated HCC cells. In-vitro BCAA reduced the frequency of EpCAM-positive cells and improved sensitivity to the anti-proliferative effect of 5-FU. Combined 5-FU and BCAA provided better antitumor efficacy than 5-FU alone in the xenograft model. Stimulation with high doses of BCAA activated mTORC1. Knockdown and overexpression experiments revealed that inhibition of mTOR complex 2 (mTORC2) or activation of mTORC1 led to decreased EpCAM expression and little or no tumorigenicity. BCAA may enhance the sensitivity to chemotherapy by reducing the population of cscs via the mTOR pathway. This result suggests the utility of BCAA in liver cancer therapy.

Crosstalk between glucocorticoid receptor and nutritional sensor mTOR in skeletal muscle.

Maintenance of skeletal muscle mass relies on the dynamic balance between anabolic and catabolic processes and is important for motility, systemic energy homeostasis, and viability. We identified direct target genes of the glucocorticoid receptor (GR) in skeletal muscle, i.e., REDD1 and KLF15. As well as REDD1, KLF15 inhibits mTOR activity, but via a distinct mechanism involving BCAT2 gene activation. Moreover, KLF15 upregulates the expression of the E3 ubiquitin ligases atrogin-1 and MuRF1 genes and negatively modulates myofiber size. Thus, GR is a liaison involving a variety of downstream molecular cascades toward muscle atrophy. Notably, mTOR activation inhibits GR transcription function and efficiently counteracts the catabolic processes provoked by glucocorticoids. This mutually exclusive crosstalk between GR and mTOR, a highly coordinated interaction between the catabolic hormone signal and the anabolic machinery, may be a rational mechanism for fine-tuning of muscle volume and a potential therapeutic target for muscle wasting.

Branched-chain amino acids improve glucose metabolism in rats with liver cirrhosis.

It is well established that impaired glucose metabolism is a frequent complication in patients with hepatic cirrhosis. We previously showed that leucine, one of the branched-chain amino acids (BCAA), promotes glucose uptake under insulin-free conditions in isolated skeletal muscle from normal rats. The aim of the present study was to evaluate the effects of BCAA on glucose metabolism in a rat model of CCl(4)-induced cirrhosis (CCl(4) rats). Oral glucose tolerance tests were performed on BCAA-treated CCl(4) rats. In the CCl(4) rats, treatment with leucine or isoleucine, but not valine, improved glucose tolerance significantly, with the effect of isoleucine being greater than the effect of leucine. Glucose uptake experiments using isolated soleus muscle from the CCl(4) rats revealed that leucine and isoleucine, but not valine, promoted glucose uptake under insulin-free conditions. To clarify the mechanism of the blood glucose-lowering effects of BCAA, we collected soleus muscles from BCAA-treated CCl(4) rats with or without a glucose load. These samples were used to determine the subcellular location of glucose transporter proteins and glycogen synthase (GS) activity. Oral administration of leucine or isoleucine without a glucose load induced GLUT4 and GLUT1 translocation to the plasma membrane. GS activity was augmented only in leucine-treated rats and was completely inhibited by rapamycin, an inhibitor of mammalian target of rapamycin. In summary, we found that leucine and isoleucine improved glucose metabolism in CCl(4) rats by promoting glucose uptake in skeletal muscle. This effect occurred as a result of upregulation of GLUT4 and GLUT1 and also by mammalian target of rapamycin-dependent activation of GS in skeletal muscle. From these results, we consider that BCAA treatment may have beneficial effects on glucose metabolism in cirrhotic patients.

Pharmacological activities of branched-chain amino acids: specificity of tissue and signal transduction.

Branched-chain amino acid (BCAA: Leu, Ile, and Val) mixture has been used for treatment of hypoalbuminemia in patients with decompensated liver cirrhosis in Japan. It has been known that BCAA, especially leucine, activates mTOR signals and inhibition of protein degradation results in promoting protein synthesis in vitro. Furthermore, leucine activates glycogen synthase via mTOR signals in L6 cell, but not hepatocyte, and it has been shown that leucine improved glucose metabolism in normal and cirrhosis model rats. In this review, it will be proposed about the pharmacological activity of branched-chain amino acids, mainly leucine, on tissue specificity of cirrhotic disease.

Leucine promotes glucose uptake in skeletal muscles of rats.

Soleus muscles isolated from normal rats were incubated to evaluate whether or not leucine promotes glucose uptake under insulin-free conditions, using a labeled 2-deoxyglucose uptake assay. Glucose uptake was promoted by 2mM leucine. A metabolite of leucine, alpha-ketoisocaproic acid (alpha-KIC), also exhibited a similar stimulatory effect, although this was not as potent as leucine. Stimulation of glucose uptake by leucine was completely canceled by pre-treatment with either 10 microM LY294002, a specific inhibitor of phosphatidylinositol 3-kinase (PI3-kinase), or 6 microM GF109203X, a specific inhibitor of protein kinase C (PKC). No significant change was observed by pre-treatment with 1 microM rapamycin, a specific inhibitor of mammalian target of rapamycin (mTOR). These results suggest that leucine stimulates glucose transport in skeletal muscle via PI3-kinase and PKC pathways independently of the mammalian target of mTOR. They also suggest that leucine stimulates glucose transport by an insulin-independent mechanism.