Time filter

Source Type

Suzuki T.,National Institute for Geriatrics and Gerontology
Clinical calcium | Year: 2011

The prevalence of lifestyle-related diseases including hypertension, dyslipidemia (hyperlipidemia) and diabetes increases with aging, and all these conditions are risk factors of arteriosclerotic diseases such as cerebrovascular event (stroke) and myocardial infarction. The term "metabolic domino" has been used to describe the collective concept of the development and progression of these lifestyle-related diseases, the sequence of events, and the progression process of complications. Like the first tile of a domino toppling game, undesirable lifestyle such as overeating and underexercising first triggers obesity, and is followed in succession by onset of an insulin resistance state (underlied by a genetic background indigenous to Japanese) , hypertension, hyperlipidemia, and further postprandial hyperglycemia (the pre-diabetic state) , the so-called metabolic syndrome, at around the same time. On the other hand, apart from the other lifestyle-related diseases, the prevalence of osteoporosis also increases rapidly accompanying aging. Osteoporosis is known to be strongly related to disorders due to the metabolic domino such as arteriosclerosis and vascular calcification, and a new disease category called "osteo-vascular interaction" has attracted attention recently. Regarding "osteo-vascular interaction" , a close relation between bone density loss or osteoporotic changes and vascular lesion-associated lifestyle-related diseases such as hypertension, dyslipidemia and diabetes has been reported. Therefore, as a common preventive factor for bone mass loss or osteoporosis and lifestyle-related diseases including hypertension, dyslipidemia and diabetes (osteo-vascular interaction) , exercise has been recognized anew as an important non-pharmaceutical therapy that should take top priority. This article overviews the evidence of exercise therapy for the prevention of osteoporosis and other lifestyle-related diseases, from the viewpoint of health promotion, especially of the skeletal system (motor system) .

Kim J.H.,Korea University | Lee J.O.,Korea University | Lee S.K.,Korea University | Moon J.W.,Korea University | And 9 more authors.
Journal of Biological Chemistry | Year: 2011

Homocysteine sulfinic acid (HCSA) is a homologue of the amino acid cysteine and a selective metabotropic glutamate receptor (mGluR) agonist. However, the metabolic role of HCSA is poorly understood. In this study, we showed that HCSA and glutamate stimulated glucose uptake in C2C12 mouse myoblast cells and increased AMP-activated protein kinase (AMPK) phosphorylation. RT-PCR and Western blot analysis revealed that C2C12 expresses mGluR5. HCSA transiently increased the intracellular calcium concentration. Although α-methyl-4- carboxyphenylglycine, a metabotropic glutamate receptor antagonist, blocked the action of HCSA in intracellular calcium response and AMPK phosphorylation, 6-cyano-7-nitroquinoxaline-2,3-dione, an AMPA antagonist, did not exhibit such effects. Knockdown of mGluR5 with siRNA blocked HCSA-induced AMPK phosphorylation. Pretreatment of cells with STO-609, a calmodulin-dependent protein kinase kinase (CaMKK) inhibitor, blocked HCSA-induced AMPK phosphorylation, and knockdown of CaMKK blocked HCSA-induced AMPK phosphorylation. In addition, HCSA activated p38 mitogen-activated protein kinase (MAPK). Expression of dominant-negative AMPK suppressed HCSA-mediated phosphorylation of p38 MAPK, and inhibition of AMPK and p38 MAPK blocked HCSA-induced glucose uptake. Phosphorylation of protein kinase C ζ (PKCζ) was also increased by HCSA. Pharmacologic inhibition or knockdown of p38 MAPK blocked HCSA-induced PKCζ phosphorylation, and knockdown of PKCζ suppressed the HCSA-induced increase of cell surface GLUT4. The stimulatory effect of HCSA on cell surface GLUT4 was impaired in FITC-conjugated PKCζ siRNA-transfected cells. Together, the above results suggest that HCSA may have a beneficial role in glucose metabolism in skeletal muscle cells via stimulation of AMPK. © 2011 by The American Society for Biochemistry and Molecular Biology, Inc.

Lee J.O.,Korea University | Lee S.K.,Korea University | Jung J.H.,Korea University | Kim J.H.,Korea University | And 5 more authors.
Journal of Cellular Physiology | Year: 2011

Metformin is a major oral anti-diabetic drug and is known as an insulin sensitizer. However, the mechanism by which metformin acts is unclear. In this study, we found that AICAR, an AMPK activator, and metformin increased the expression of Rab4 mRNA and protein levels in skeletal muscle C2C12 cells. The promoter activity of Rab4 was increased by metformin in an AMPK-dependent manner. Metformin stimulated the phosphorylation of AS160, Akt substrate, and Rab GTPase activating protein (GAP), and also increased the phosphorylation of PKC-zeta, which is a critical molecule for glucose uptake. Knockdown of AMPK blocked the metformin-induced phosphorylation of AS160/PKC-zeta. In addition, a colorimetric absorbance assay showed that insulin-induced translocation of GLUT4 was suppressed in Rab4 knockdown cells. Moreover, Rab4 interacted with PKC-zeta but not with GLUT4. The C-terminal-deleted Rab4 mutant, Rab4ΔCT, showed diffuse sub-cellular localization, while wild-type Rab4 localized exclusively to the perinuclear membrane. Unlike Rab4ΔCT, wild-type Rab4 co-localized with PKC-zeta. Together, these results demonstrate that metformin induces Rab4 expression via AMPK-AS160-PKC-zeta and modulates insulin-mediated GLUT4 translocation. © 2010 Wiley-Liss, Inc.

Lee S.K.,Korea University | Lee J.O.,Korea University | Kim J.H.,Korea University | Kim S.J.,Korea University | And 8 more authors.
Journal of Cellular Biochemistry | Year: 2011

Insulin resistance is the primary cause responsible for type 2 diabetes. Phosphatase and tensin homolog (PTEN) plays a negative role in insulin signaling and its inhibition improves insulin sensitivity. Metformin is a widely used insulin-sensitizing drug; however, the mechanism by which metformin acts is poorly understood. To gain insight into the role of PTEN, we examined the effect of metformin on PTEN expression. Metformin suppressed the expression of PTEN in an AMP-activated protein kinase (AMPK)-dependent manner in preadipocyte 3T3-L1 cells. Knock-down of PTEN potentiated the increase in insulin-mediated phosphorylation of Akt/ERK. Metformin also increased the phosphorylation of c-Jun N-terminal kinase (JNK)-c-Jun and mammalian target of rapamycin (mTOR)-p70S6 kinase pathways. Both pharmacologic inhibition and knock-down of AMPK blocked metformin-induced phosphorylation of JNK and mTOR. Knock-down of AMPK recovered the metformin-induced PTEN down-regulation, suggesting the involvement of AMPK in PTEN regulation. PTEN promoter activity was suppressed by metformin and inhibition of mTOR and JNK by pharmacologic inhibitors blocked metformin-induced PTEN promoter activity suppression. These findings provide evidence for a novel role of AMPK on PTEN expression and thus suggest a possible mechanism by which metformin may contribute to its beneficial effects on insulin signaling. © 2010 Wiley-Liss, Inc.

Maruyama W.,National Institute for Geriatrics and Gerontology | Shaomoto-Nagai M.,National Institute for Geriatrics and Gerontology | Kato Y.,University of Hyogo | Hisaka S.,Meijo University | And 2 more authors.
Sub-Cellular Biochemistry | Year: 2014

Nervous system controls all the organs in the living like a symphony. In this chapter, the mechanism of neuronal death in aged is discussed in relation to oxidative stress. Polyunsaturated fatty acid (PUFA) is known to be rich in the membranous component of the neurons and plays an important role in maintaining the neuronal functions. Recent reports revealed that oxidation of omega-3 and omega-6 PUFAs, such as docosahexaenoic acid (DHA) and arachidonic acid (ARA), are potent antioxidant but simultaneously, their oxidation products are potentially toxic. In this chapter, the existence of early oxidation products of PUFA is examined in the samples from neurodegenerative disorders and the cellular model. Accumulation of proteins with abnormal conformation is suggested to induce neuronal death by disturbance of proteolysis and mitochondrial function. The role of lipid peroxide and lipid-derived aldehyde adduct proteins is discussed in relation to brain ageing and age-related neurodegeneration. © Springer Science+Business Media Dordrecht 2014.

Discover hidden collaborations