BST1 regulates nicotinamide riboside metabolism via its glycohydrolase and base-exchange activities.

Nicotinamide riboside (NR) is one of the orally bioavailable NAD+ precursors and has been demonstrated to exhibit beneficial effects against aging and aging-associated diseases. However, the metabolic pathway of NR in vivo is not yet fully understood. Here, we demonstrate that orally administered NR increases NAD+ level via two different pathways. In the early phase, NR was directly absorbed and contributed to NAD+ generation through the NR salvage pathway, while in the late phase, NR was hydrolyzed to nicotinamide (NAM) by bone marrow stromal cell antigen 1 (BST1), and was further metabolized by the gut microbiota to nicotinic acid, contributing to generate NAD+ through the Preiss-Handler pathway. Furthermore, we report BST1 has a base-exchange activity against both NR and nicotinic acid riboside (NAR) to generate NAR and NR, respectively, connecting amidated and deamidated pathways. Thus, we conclude that BST1 plays a dual role as glycohydrolase and base-exchange enzyme during oral NR supplementation.

1'-Acetoxychavicol Acetate Increases Proteasome Activity by Activating cAMP-PKA Signaling.

Protein degradation systems are critical pathways for the maintenance of protein homeostasis. The age-dependent attenuation of the proteasome activity contributes to age-related neurodegenerative processes. The molecule 1'-acetoxychavicol acetate (ACA) is naturally obtained from the rhizomes and seeds of Zingiberaceae plants, such as Languas galangal and Alpinia galangal, and exhibits anti-carcinogenic effects. Recently, we have shown that ACA protected the age-related learning and memory impairments in senescence-accelerated mice and maintained cognitive performance. Therefore, we here examined the effects of ACA on the protein degradation systems and cell protection against neurotoxicity in differentiated PC12 cells. ACA increased proteasome activity in PC12 cells. Increased proteasome activity occurred during the initial stages of ACA treatment and lasted at least 9 h. The activity returned to control levels within 24 h. The increase in proteasome activity by ACA was suppressed by H-89, which is a cAMP-dependent protein kinase A inhibitor. ACA increased the adenylate cyclase activity and therefore the intracellular cAMP levels. Furthermore, ACA recovered the initial cell viability, which was reduced after the addition of the amyloid ß-protein fragment to neuronally differentiated PC12 cells. The effects of ACA on amyloid toxicity were reduced after treatment with MG132, a proteasome inhibitor. These results demonstrated a neuroprotective effect of ACA via activation of cAMP/cAMP-dependent protein kinase A signaling in neuronally differentiated PC12 cells.

1'-Acetoxychavicol acetate ameliorates age-related spatial memory deterioration by increasing serum ketone body production as a complementary energy source for neuronal cells.

1'-Acetoxychavicol acetate (ACA) is naturally obtained from the rhizomes and seeds of Alpinia galangal. Here, we examined the effect of ACA on learning and memory in senescence-accelerated mice prone 8 (SAMP8). In mice that were fed a control diet containing 0.02% ACA for 25 weeks, the learning ability in the Morris water maze test was significantly enhanced in comparison with mice that were fed the control diet alone. In the Y-maze test, SAMP8 mice showed decreased spontaneous alterations in comparison with senescence-accelerated resistant/1 (SAMR1) mice, a homologous control, which was improved by ACA pretreatment. Serum metabolite profiles were obtained by GC-MS analysis, and each metabolic profile was plotted on a 3D score plot. Based upon the diagram, it can be seen that the distribution areas for the three groups were completely separate. Furthermore, the contents of ß-hydroxybutyric acid and palmitic acid in the serum of SAMP8-ACA mice were higher than those of SAMP8-control mice and SAMR1-control mice. We also found that SAMR1 mice did not show histological abnormalities, whereas histological damage in the CA1 region of the hippocampus in SAMP8-control mice was observed. However, SAMP8-ACA mice were observed in a similar manner as SAMR1 mice. These findings confirm that ACA increases the serum concentrations of ß-hydroxybutyric acid and palmitic acid levels and thus these fuels might contribute to the maintenance of the cognitive performance of SAMP8 mice.

1'-acetoxychavicol acetate inhibits adipogenesis in 3T3-L1 adipocytes and in high fat-fed rats.

Alpinia galanga and Languas galanga, which are plants belonging to the ginger family, are frequently used for cooking, especially in Thai and Indonesian cuisine. The compound 1'-acetoxychavicol acetate (ACA), which is naturally obtained from the rhizomes and seeds of these gingers, has antioxidant and anti-inflammatory properties. We investigated the anti-obesity effects of ACA in 3T3-L1 adipocytes and in high fat diet (HFD)-induced rat models of obesity. ACA caused a significant decrease in the activity of GPDH in 3T3-L1 adipocytes without eliciting cell cytotoxicity, and it inhibited cellular lipid accumulation through the down-regulation of transcription factors such as PPARγ and C/EBPα. ACA also induced a dose-dependent phosphorylation of AMP-activated protein kinase (AMPK). In the animal model, rats fed an HFD containing 0.05% ACA gained less weight than rats fed an HFD alone. The visceral fat mass in rats fed an HFD containing 0.05% ACA tended to be lower than that in rats fed an HFD alone. Furthermore, a histological examination of livers from rats fed an HFD showed steatohepatitis. However, rats fed an HFD containing 0.05% ACA showed no histopathological changes in the liver tissue. Our results show that ACA exerts anti-obesity activities both in vitro and in vivo and suggests that ACA may have a novel preventive activity against obesity and possibly other metabolic diseases.

1'-Acetoxychavicol acetate enhances the phase II enzyme activities via the increase in intranuclear Nrf2 level and cytosolic p21 level.

(1'S)-acetoxychavicol acetate ((S)-ACA) exhibits chemopreventive effects on chemically induced tumor formation. It has been shown that ACA inhibited the development of azoxymethane-induced colon carcinogenesis through its suppression of cell proliferation in the colonic mucosa and its induction of glutathione S-transferase and quinone oxidoreductase 1 in vivo. In this study, we investigated how ACA induced these enzymes by using rat intestine epithelial cells (IEC6) in vitro. ACA induced glutathione S-transferase (GST) and NAD (P)H: quinone oxidoreductase 1 (NQO1) activities, increased intracellular glutathione (GSH) level, and upregulated intranuclear Nrf2 and cytosolic p21. It suggested that activation of phase II enzymes via Nrf2 associated with p21 is one of possible mechanisms of ACA to prevent advance of carcinogenesis.