FGF23 suppresses both serum phosphate and 1,25-dihydroxyvitamin D [1,25D] levels in vivo. Because 1,25D itself is a potent regulator of phosphate metabolism, it has remained unclear whether FGF23-induced changes in phosphate metabolism were caused by a 1,25D-independent mechanism. To address this issue, we intravenously administered recombinant FGF23 to vitamin D receptor (VDR) null (KO) mice as a rapid bolus injection and evaluated the early effects of FGF23. Administration of recombinant FGF23 further decreased the serum phosphate level in VDR KO mice, accompanied by a reduction in renal sodium-phosphate cotransporter type IIa (NaPi2a) protein abundance and a reduced renal 25-hydroxyvitamin D-1alpha-hydroxylase (1alphaOHase) mRNA level. Thus FGF23-induced changes in NaPi2a and 1alphaOHase expression are independent of the 1,25D/VDR system. However, 24-hydroxylase (24OHase) mRNA expression remained undetectable by the treatment with FGF23. We also analyzed the regulatory mechanism for FGF23 expression. The serum FGF23 level was almost undetectable in VDR KO mice, whereas dietary calcium supplementation significantly increased circulatory levels of FGF23 and its mRNA abundance in bone. This finding indicates that calcium is another determinant of FGF23 production that occurs independently of the VDR-mediated mechanism. In contrast, dietary phosphate supplementation failed to induce FGF23 expression in the absence of VDR, whereas marked elevation in circulatory FGF23 was observed in wild-type mice fed with a high-phosphate diet. Taken together, FGF23 works, at least in part, in a VDR-independent manner, and FGF23 production is also regulated by multiple mechanisms involving VDR-independent pathways.

An Epstein-Barr virus (EBV)-producer line, designated Akata, was established from a Japanese patient with Burkitt's lymphoma. The Akata line possessed the Burkitt's-type chromosome translocation, t(8q- ; 14q+), and was derived from the tumor cell. Akata cells produced a large quantity of transforming virus upon treatment of cells with anti-immunoglobulin antibodies (Takada, 1984). Southern blot analysis of viral DNA indicated that the Akata EBV is nondefective and more representative of wild-type viruses. Akata cells should be useful as a source of EBV.

Our previous study reported that intramuscular metabolic stress during low-intensity resistance exercise was significantly enhanced by combining blood flow restriction (BFR); however, they did not reach the levels achieved during high-intensity resistance exercise. That study was performed using a single set of exercise; however, usual resistance exercise consists of multiple sets with rest intervals. Therefore, we investigated the intramuscular metabolic stress during multiple-set BFR exercises, and compared the results with those during multiple-set high-intensity resistance exercise. Twelve healthy young subjects performed 3 sets of 1-min unilateral plantar flexion (30 repetitions) with 1-min intervals under 4 different conditions: low intensity (L, 20 % 1 RM) and high intensity (H, 65 % 1 RM) without BFR, and L with intermittent BFR (IBFR, only during exercise) and with continuous BFR (CBFR, during rest intervals as well as exercise). Intramuscular metabolic stress, defined as intramuscular metabolites and pH, and muscle fiber recruitment were evaluated by 31P-magnetic resonance spectroscopy. The changes of intramuscular metabolites and pH during IBFR were significantly greater than those in L but significantly lower than those in H. By contrast, those changes in CBFR were similar to those in H. Moreover, the fast-twitch fiber recruitment, evaluating by a splitting Pi peak, showed a similar level to H. In conclusion, the multiple sets of low-intensity resistance exercise with continuous BFR could achieve with the same metabolic stress as multiple sets of high-intensity resistance exercise.

Skeletal muscle bulk and strength are becoming important therapeutic targets in medicine. To increase muscle mass, however, intensive, long-term mechanical stress must be applied to the muscles, and such stress is often accompanied by orthopedic and cardiovascular problems. We examined the effects of circulatory occlusion in resistance training combined with a very low-intensity mechanical load on enhancing muscular metabolic stress and thereby increasing muscle bulk. Muscular metabolic stress, as indicated by the increases in inorganic phosphate (P(i)) and a decrease in intramuscular pH, was evaluated by (31)P-magnetic resonance spectroscopy during unilateral plantar-flexion at 20% of the one-repetition maximum (1-RM) with circulatory occlusion for 2 min in 14 healthy, male untrained participants (22 yr) at baseline. Participants performed two sets of the same exercise with a 30-s rest between sets, 2 times/day, 3 days/wk, for 4 wk. The muscle cross-sectional area (MCA) of the plantar-flexors and the 1-RM were measured at baseline and after 2 and 4 wk of training. MCA and 1-RM were significantly increased after 2 and 4 wk (P < 0.05, respectively). The increase in MCA at 2 wk was significantly (P < 0.05) correlated with the changes in P(i) (r = 0.876) and intramuscular pH (r = 0.601). Furthermore, the increases in MCA at 4 wk and 1-RM at 2 wk were also correlated with the metabolic stress. Thus enhanced metabolic stress in exercising muscle is a key mechanism for favorable effects by resistance training. Low-intensity resistance exercise provides successful outcomes when performed with circulatory occlusion, even with a short training period.

New findings r What is the central question of this study? Does angiotensin II directly induce skeletal muscle abnormalities? r What is the main finding and its importance?Angiotensin II induces skeletal muscle abnormalities and reduced exercise capacity. Mitochondrial dysfunction and a decreased number of oxidative fibres are manifest early, while muscle atrophy is seen later. Thus, angiotensin II may play an important role in the skeletal muscle abnormalities observed in a wide variety of diseases.Skeletal muscle abnormalities, such as mitochondrial dysfunction, a decreased percentage of oxidative fibres and atrophy, are the main cause of reduced exercise capacity observed in ageing and various diseases, including heart failure. The renin-angiotensin system, particularly angiotensin II (Ang II), is activated in the skeletal muscle in these conditions. Here, we examined whether Ang II could directly induce these skeletal muscle abnormalities and investigated their time course. Angiotensin II (1000 ng kg −1 min −1 ) or vehicle was administered to male C57BL/6J mice (10-12 weeks of age) via subcutaneously implanted osmotic minipumps for 1 or 4 weeks. Angiotensin II significantly decreased body and hindlimb skeletal muscle weights compared with vehicle at 4 weeks. In parallel, muscle cross-sectional area was also decreased in the skeletal muscle at 4 weeks. Muscle RING finger-1 and atrogin-1 were significantly increased in the skeletal muscle from mice treated with Ang II. In addition, cleaved caspase-3 and terminal deoxynucleotidyl trasferase-mediated dUTP nick-positive nuclei were significantly increased in mice treated with Ang II at 1 and 4 weeks, respectively. Mitochondrial oxidative enzymes, such as citrate synthase, complex I and complex III activities were significantly decreased in the skeletal muscle from mice treated Ang II at 1 and 4 weeks. NAD(P)H oxidase-derived superoxide production was increased. NADH staining revealed that type I fibres were decreased and type IIb fibres increased in mice treated with Ang II at 1 week. The work and running distance evaluated by a treadmill test were significantly decreased in mice treated with Ang II at 4 weeks. Thus, Ang II could directly induce the abnormalities in skeletal muscle function and structure.

Fas (APO-1/CD95) and its ligand have been identified as important signal-mediators of apoptosis (1). The structural organization of Fas (APO-1/CD95) indicates that it is a member of the tumor necrosis factor receptor superfamily, which also includes the p75 nerve growth factor receptor (2), the T-cellactivation marker CD27 (3), the Hodgkin-lymphoma-associated antigen CD30 (4), the human B cell antigen CD40 (5), and T cell antigen OX40 (6). Genetic mutations of both Fas and its ligand have been associated with lymphoproliferative and autoimmune disorders in mice (7,8). Furthermore, alterations of Fas expression level have been implicated in the induction of apoptosis in T-cells infected with human immunodeficiency virus (9). Several Fas-interacting signal transducing molecules, have been identified using yeast two-hybrid and biochemical approaches, including Fas-associated phosphatase-1 (FAP-1) 1 (10), FADD/MORT1/CAP-1/CAP-2 (11-13), and RIP (14). All but FAP-1 associate with the functional cell death domain of Fas and overexpression of FADD/MORT1, or RIP induces apoptosis in cells transfected with these proteins. In contrast, FAP-1 is the only protein that associates with a negative regulatory domain (C-terminal 15 amino acids) (15) of Fas and that inhibits Fas-induced apoptosis.FAP-1 (PTPN13) has several alternatively-spliced forms that are identical to PTP-BAS/hPTP1E/PTPL1 (16 -18), and contains a membrane-binding region similar to those found in the cytoskeleton-associated proteins, ezrin (19), radixin (20), moesin (21), neurofibromatosis type II gene product (NFII) (22), and protein 4.1 (23), as well as in the PTPases PTPH1 (24), PTP-MEG (25), and PTPD1 (26). FAP-1 intriguingly contains six PDZ (GLGF/DHR) domains that are thought to mediate intra-and inter-molecular interactions among protein. The third PDZ repeat of FAP-1 was first identified as a domain showing the specific interaction with the C terminus of Fas receptor (10). In the present study, we first demonstrated that the C-terminal three amino acids (SLV) of human Fas were necessary and sufficient for its interaction with the third PDZ domain of FAP-1. More important, we were able to induce Fas-mediated apoptosis in a colon cancer cell line by the direct cytoplasmic microinjection of this tripeptide (Ac-SLV). MATERIALS AND METHODSConstructions of Libraries and Screenings-To create numerous mutations in a restricted DNA sequence, PCR mutagenesis with degenerate oligonucleotides was employed according to a protocol described elsewhere (27). Based on the homology between human and rat, two palindromic sequences were designed for construction of a semi-random library. The two primers used were 5Ј-CGGAATTCNNNNNNNNNAA-CAGCNNNNNNNNNAATGAANNNCAAAGTCTGNNNTGAGGATC-CTCA-3Ј and 5Ј-CGGAATTCGACTCAGAANNNNNNAACTTCAGA-NNNNNNATCNNNNNNNNNGTCTGAGGATCCTCA-3Ј. Briefly, the two primers (200 pmol each), purified by high pressure liquid chromatography, were annealed at 70°C for 5 min and cooled at 23°C for 60 min. A Klenow fragment (5 units) was used for filling in with a ...

Objective: The purpose of this study was to examine whether the activation of iNKT cells might affect the development of LV remodeling and failure. Methods and Results:After creation of MI, mice received the injection of either α-galactosylceramide (αGC; n=27), the activator of iNKT cells, or phosphate-buffered saline (n=31) 1 and 4 days after surgery, and were followed during 28 days. Survival rate was significantly higher in MI+αGC than MI+PBS (59% versus 32%, P<0.05). LV cavity dilatation and dysfunction were significantly attenuated in MI+αGC, despite comparable infarct size, accompanied by a decrease in myocyte hypertrophy, interstitial fibrosis, and apoptosis. The infiltration of iNKT cells were increased during early phase in noninfarcted LV from MI and αGC further enhanced them. It also enhanced LV interleukin (IL)-10 gene expression at 7 days, which persisted until 28 days. AntienIL-10 receptor antibody abrogated these protective effects of αGC on MI remodeling. The administration of αGC into iNKT cell-deficient Jα18 −/− mice had no such effects, suggesting that αGC was a specific activator of iNKT cells. Conclusions: iNKT cells play a protective role against post-MI LV remodeling and failure through the enhanced expression of cardioprotective cytokines such as

A DPP-4 inhibitor may be a novel therapeutic agent against the exercise intolerance seen in HF patients by improving the mitochondrial biogenesis in their skeletal muscle.