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OBJECTIVE--Skeletal muscle protein metabolism is resistant to the anabolic action of insulin in healthy, nondiabetic older adults. This defect is associated with impaired insulin-induced vasodilation and mTORC1 signaling. We hypothesized that, in older subjects, pharmacological restoration of insulin-induced capillary recruitment would improve the response of muscle protein synthesis and anabolism to insulin. RESEARCH DESIGN AND METHODS--Twelve healthy, nondiabetic older subjects (71 ± 2 years) were randomized to two groups. Subjects were studied at baseline and during local infusion in one leg of insulin alone (Control) or insulin plus sodium nitroprusside (SNP) at variable rate to double leg blood flow. We measured leg blood flow by dye dilution; muscle microvascular perfusion with contrast enhanced ultrasound; Akt/mTORC1 signaling by Western blotting; and muscle protein synthesis, amino acid, and glucose kinetics using stable isotope methodologies. RESULTS--There were no baseline differences between groups. Blood flow, muscle perfusion, phenylalanine delivery to the leg, and intracellular availability of phenylalanine increased significantly (P < 0.05) in SNP only. Akt phosphorylation increased in both groups but increased more in SNP (P < 0.05). Muscle protein synthesis and net balance (nmol x [min.sup.-1] x 100 ml x [leg.sup.-1]) increased significantly (P < 0.05) in SNP (synthesis, 43 ± 6 to 129 ± 25; net balance, -16 ± 2 3 to 26 ± 12) but not in Control (synthesis, 41 ± 10 to 53 ± 8; net balance, -17 ± 3 to -2 ± 3). CONCLUSIONS--Pharmacological enhancement of muscle perfusion and amino acid availability during hyperinsulinemia improves the muscle protein anabolic effect of insulin in older adults. Diabetes 59:2764-2771, 2010, Recent studies have highlighted that insulin resistance is one of the potential mechanisms underlying the involuntary loss of skeletal muscle mass, strength, and function with aging (sarcopenia) (1-3). Specifically, it [...]

Muscle wasting increases the morbidity and mortality associated with chronic kidney disease (CKD) and has been attributed to malnutrition. In most patients, this is an incorrect diagnosis because simply feeding more protein aggravates uremia. Instead, there are complex mechanisms that stimulate loss of skeletal muscle, involving activation of mediators that stimulate the ATP-dependent ubiquitin-proteasome system (UPS). Identified mediators of muscle protein breakdown include inflammation, metabolic acidosis, angiotensin II, and neural and hormonal factors that cause defects in insulin/ insulin-like growth factor I (IFG-I) intracellular signaling processes. Abnormalities in insulin/IGF-I signaling activate muscle protein degradation in the UPS and caspase-3, a protease that disrupts the complex structure of muscle proteins to provide substrates for the UPS. During the cleavage of muscle proteins, caspase-3 leaves behind a characteristic 14-kD actin fragment in the insoluble fraction of muscle, and characterization of this fragment identifies the presence of muscle catabolism. Thus, it could become a marker of excessive muscle wasting, providing a method for early detection of muscle wasting. Another consequence of activation of caspase-3 in muscle is stimulation of the activity of the proteasome, which increases the degradation of muscle proteins. Treatment strategies for blocking muscle wasting include correction of metabolic acidosis, which can suppress muscle protein losses in patients with CKD who are or are not being treated by dialysis. Correcting acidosis also improves bone metabolism in CKD and hence should be a goal of therapy. Exercise training is a potentially beneficial approach, but more information is needed to optimize exercise regimens. Replacing testosterone deficits can improve muscle mass in men, but dosing and side effects in women have not been adequately tested. Although insulin resistance occurs early in the course of CKD, there are no effective means of correcting it. Consequently, new therapies that can safely suppress muscle wasting are needed. Am J Clin Nutr 2010;91(suppl):1128S-32S. doi: 10.3945/ajcn.2010.28608B.

OBJECTIVE--Nephrin, an immunoglobulin-like protein essential for the function of the glomerular podocyte and regulated in diabetic nephropathy, is also expressed in pancreatic β-cells, where its function remains unknown. The aim of this study was to investigate whether diabetes modulates nephrin expression in human pancreatic islets and to explore the role of nephrin in β-cell function. RESEARCH DESIGN AND METHODS--Nephrin expression in human pancreas and in MIN6 insulinoma cells was studied by Western blot, PCR, confocal microscopy, subcellular fractionation, and immunogold labeling. Islets from diabetic (n = 5) and nondiabetic (n = 7) patients were compared. Stable transfection and siRNA knockdown in MIN-6 cells/human islets were used to study nephrin function in vitro and in vivo after transplantation in diabetic immunodeficient mice. Live imaging of green fluorescent protein (GFP)-nephrin-transfected cells was used to study nephrin endocytosis. RESULTS--Nephrin was found at the plasma membrane and on insulin vesicles. Nephrin expression was decreased in islets from diabetic patients when compared with nondiabetic control subjects. Nephrin transfection in MIN-6 cells/pseudoislets resulted in higher glucose-stimulated insulin release in vitro and in vivo after transplantation into immunodeficient diabetic mice. Nephrin gene silencing abolished stimulated insulin release. Confocal imaging of GFP-nephrin-transfected cells revealed nephrin endocytosis upon glucose stimulation. Actin stabilization prevented nephrin trafficking as well as nephrin-positive effect on insulin release. CONCLUSIONS--Our data suggest that nephrin is an active component of insulin vesicle machinery that may affect vesicle-actin interaction and mobilization to the plasma membrane. Development of drugs targeting nephrin may represent a novel approach to treat diabetes., In the U.S. alone, diabetes affects >20 million people. Although advances have been made in the clinical care of diabetes, one of the major limitations for finding a cure is [...]

Background: It has been reported that the blunted muscle protein synthetic response to food intake in the elderly can be normalized by increasing the leucine content of a meal. Objective: The objective was to assess the effect of 3 mo of leucine supplementation on muscle mass and strength in healthy elderly men. Design: Thirty healthy elderly men with a mean ([+ or -]SEM) age of 71 [+ or -] 4 y and body mass index (BMI; in kg/[m.sup.2]) of 26.1 [+ or -] 0.5 were randomly assigned to either a placebo-supplemented (n = 15) or leucine-supplemented (n = 15) group. Leucine or placebo (2.5 g) was administered with each main meal during a 3-mo intervention period. Whole-body insulin sensitivity, muscle strength (one-repetition maximum), muscle mass (measured by computed tomography and dual-energy X-ray absorptiometry), myosin heavy chain isoform distribution, and plasma amino acid and lipid profiles were assessed before, during, and/or after the intervention period. Results: No changes in skeletal muscle mass or strength were observed over time in either the leucine- or placebo-supplemented group. No improvements in indexes of whole-body insulin sensitivity (oral glucose insulin sensitivity index and the homeostasis model assessment of insulin resistance), blood glycated hemoglobin content, or the plasma lipid profile were observed. Conclusion: Long-term leucine supplementation (7.5 g/d) does not augment skeletal muscle mass or strength and does not improve glycemic control or the blood lipid profile in healthy elderly men. This trial was registered at clinicaltrials.gov as NCT00807508.

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jtcvs.2008.08.020 Byline: Rajesh G. Katare (a), Motonori Ando (a)(c), Yoshihiko Kakinuma (a), Mikihiko Arikawa (a), Takemi Handa (a), Fumiyasu Yamasaki (b), Takayuki Sato (a) Abbreviations: ACh, acetylcholine; ATP, adenosine triphosphate; CABG, coronary artery bypass grafting; PTP, permeability transition pore; SS, sham stimulation; VS, vagal stimulation Abstract: In spite of recent advances in coronary interventional therapy, reperfusion injury is still considered to be a major problem in patients undergoing surgical procedures, such as bypass grafting. Here we demonstrate a novel therapeutic strategy against ischemia-reperfusion injury: vagally mediated prevention of reperfusion-induced opening of mitochondrial permeability transition pore. Author Affiliation: (a) Department of Cardiovascular Control, Kochi Medical School, Nankoku, Japan (b) Department of Clinical Laboratory, Kochi Medical School, Nankoku, Japan (c) Department of Science and Education, Okayama University, Okayama, Japan Article History: Received 20 September 2007; Revised 16 July 2008; Accepted 8 August 2008 Article Note: (footnote) Supported by a Health and Labor Sciences Research Grant (H14-NANO-002, H16-NANO-005) from the Ministry of Health, Labor, and Welfare of Japan and by a Grant-in-Aid for Scientific Research (15300165, 17790892) from the Ministry of Education, Science, Sports, and Culture of Japan.

Age causes structural and functional changes in skeletal muscle in a wide range of species, including humans. Muscle changes in humans start in the fourth decade of life and cause frailty and disabilities. Associated changes in body composition form the basis of many metabolic disorders, such as insulin resistance, type 2 diabetes, hypertension, and hyperlipidemia, which result in an increased incidence of cardiovascular death. Decreases in the synthesis rates of many muscle proteins, specifically of myosin heavy chain and mitochondrial proteins, occur with age. The underlying causes of the reduction in mitochondrial biogenesis and ATP production seem to be decreases in mitochondrial DNA and messenger RNA. Reduced ATP production could be the basis of reduced muscle protein turnover, which requires energy. Both aerobic exercise and resistance exercise enhance muscle protein synthesis and mitochondrial biogenesis. Insulin and amino acids have also been shown to enhance muscle mitochondrial biogenesis and mitochondrial protein synthesis. However, the insulin-induced increase in muscle mitochondrial ATP production is defective in type 2 diabetic patients with insulin resistance. Moreover, a dissociation between increases in muscle mitochondrial biogenesis and insulin sensitivity after exercise has been noted in older persons. It remains to be determined whether muscle mitochondrial dysfunction causes or results from insulin resistance. Exercise seems to enhance the efficiency of muscle mitochondrial DNA in rodents. Reduced physical activity as a contributor of age-related mitochondrial dysfunction remains to be determined. It is proposed that a reduction in tissue mitochondrial ATP production signals the hypothalamic centers to reduce spontaneous physical activities. Voluntary physical activity is regulated by cognitive centers and could attenuate the progressive decline in mitochondrial functions that occurs with age. KEY WORDS Aging, muscle, proteins, mitochondria, myosin, hypothalamus

Byline: Hajime Otani, Hideyasu Ohmiya, Reiji Hattori, Hirofumi Fujii, Hideki Ninomiya, Masakuni Kido, Hideki Kawaguchi, Motohiko Osako, Hiroji Imamura, Tetsuo Ohta, Shoji Ohkuma Abstract: Objective: Vacuolar H.sup.+-adenosine triphosphatase plays a pivotal role in pH regulation and molecular transport across the vacuolar membranes and is involved in cell proliferation and transformation. In the present study, possible involvement of vacuolar H.sup.+-adenosine triphosphatase in neointimal formation was investigated in an organ culture model of human saphenous vein. Methods and results: Cultured saphenous vein segments developed neointimal formation and marked thickening of the media within 14 days. Neointimal formation and medial thickening were completely inhibited by 10 nmol/L bafilomycin A.sub.1, a selective inhibitor of vacuolar H.sup.+-adenosine triphosphatase, although structurally related macrolide antibiotics FK-506 and erythromycin were without an effect. The neointimal cells were positive for [alpha]-smooth muscle actin and vimentin but negative for desmin, indicative of myofibroblasts. The emergence of myofibroblasts was inhibited, and endothelial cells were preserved in the saphenous vein segments treated with bafilomycin A.sub.1. Uptake of bromodeoxyuridine, a proliferation marker, by myofibroblasts was abrogated in the saphenous vein segments treated with 10 nmol/L bafilomycin A.sub.1. Detection of apoptotic cells by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling concomitant with identification of desmin-expressing smooth muscle cells demonstrated that neointimal myofibroblasts, but not medial smooth muscle cells, that expressed desmin underwent apoptosis by treatment with bafilomycin A.sub.1. Conclusions: These results suggest that vacuolar H.sup.+-adenosine triphosphatase may be involved in myofibroblast growth that contributes to neointimal formation and medial thickening in cultured human saphenous vein. Increased sensitivity of myofibroblasts, but not endothelial cells, and differentiated smooth muscle cells to bafilomycin A.sub.1 may have potential therapeutic implications in the treatment for vein graft disease. (J Thorac Cardiovasc Surg 2000;119:998-1007) Author Affiliation: From the Department of Thoracic and Cardiovascular Surgery,.sup.a Kansai Medical University, Department of Surgery (II),.sup.b School of Medicine, Kanazawa University, and the Laboratory of Biochemistry,.sup.c Department of Molecular and Cell Biology, Faculty of Pharmaceutical Science, Kanazawa University, Kanazawa, Japan Article History: Received 27 July 1999; Revised 7 October 1999; Revised 16 December 1999; Accepted 16 December 1999 Article Note: (footnote) [star] Address for reprints: Hajime Otani, MD, Department of Thoracic and Cardiovascular Surgery, Kansai Medical University, 10-15 Fumizono-cho, Moriguchi City, Osaka 570, Japan (E-mail: otanih@takii.kmu.ac.jp ).

Byline: Akira Koike, Toshiaki Akita, Yoshihiro Hotta, Kazumi Takeya, Itsuo Kodama, Mitsuya Murase, Toshio Abe, Junji Toyama Abstract: The effects of 5-(N,N-dimethyl)amiloride, a potent and specific Na.sup.+-H.sup.+ exchange inhibitor, were investigated in isolated perfused rabbit hearts subjected to ischemia and reperfusion. Phosphorus 31-nuclear magnetic resonance spectroscopy was used to monitor intracellular pH, creatine phosphate, [beta]-adenosine triphosphate, and inorganic phosphate. After cardioplegic arrest with St. Thomas' Hospital solution, normothermic (37A* C) global ischemia was induced for 45 minutes, and the hearts were reperfused for 50 minutes. Dimethyl amiloride at 10 [mu]mol/L, which has minimal inotropic and chronotropic effects on the nonischemic heart, was added to the cardioplegic solution. Treatment with dimethyl amiloride reduced the elevation of left ventricular end-diastolic pressure during and after the ischemia and improved the postischemic recovery of developed pressure from 76% [+ or -] 3.2% at 30 minutes of reperfusion in control hearts (n = 6) up to 99% [+ or -] 1.9% in hearts treated with dimethyl amiloride (n = 8). Dimethyl amiloride did not affect the decline in intracellular pH during ischemia for up to 30 minutes but enhanced the intracellular acidosis thereafter. The intracellular pH at the end of ischemia was 6.21 [+ or -] 0.05 in control hearts compared with 5.24 [+ or -] 0.17 in hearts treated with dimethyl amiloride (p < 0.05). During reperfusion, intracellular pH of hearts treated with dimethyl amiloride was less than control for 5 minutes, but subsequent recovery of intracellular pH was similar to control. Treatment with dimethyl amiloride did not affect creatine phosphate breakdown, inorganic phosphate accumulation, and [beta]-adenosine triphosphate depletion during 45 minutes of ischemia. The creatine phosphate resynthesis and inorganic phosphate reduction during reperfusion were also unaffected. These findings suggest that Na.sup.+-H.sup.+ exchange plays an important role not only during reperfusion but also during ischemia for the development of postischemic cardiac dysfunction most likely by inducing primary Na.sup.+ and secondary Ca.sup.2+ overload. Specific Na.sup.+-H.sup.+ exchange inhibitors like dimethyl amiloride would have a potential therapeutic profile in cardiac surgery, especially if added before ischemia. (J THORAC CARDIOVASC SURG 1996;112:765-75) Article History: Received 24 July 1995; Revised 14 November 1995; Revised 2 April 1996; Accepted 3 April 1996 Article Note: (footnote) [star] From the Department of Thoracic Surgery, School of Medicine, Nagoya University,a Nagoya, Japan; the Department of Pharmacology, Aichi Medical University,b Aichi, Japan; and the Departments of Circulation and Humoral Regulation,c Research Institute of Environmental Medicine, Nagoya University, Nagoya, Japan., [star][star] Address for reprints: Itsuo Kodama, MD, Department of Humoral Regulation, Research Institute of Environmental Medicine, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-01, Japan., a 0022-5223/96 $5.00 + 0, aa 12/1/73914

Byline: Stanley K.C. Tam, Wei Gu, Bernardo Nadal-Ginard Abstract: In this study, we evaluated the feasibility of converting cardiac fibroblasts into skeletal muscle cells by forced expression of the MyoD gene, one of the basic helix-loop-helix myogenic factors. Primary cardiac fibroblasts, isolated from newborn rats, were infected with retrovirus-carrying sense or antisense MyoD gene. Ten days after infection, expression of MyoD protein was demonstrated in 95% of cells infected with sense MyoD virus by intense nuclear immunostaining with a MyoD polyclonal antibody. In contrast, none of the cells infected with antisense MyoD virus showed staining. On withdrawal of serum, 95% of MyoD positive cells became elongated and, in the presence of appropriate cell density, fused to form multinucleated myotubes, morphologically similar to striated muscle cell. Expression of downstream myogenic differentiation markers, myosin heavy chain and myocyte-specific enhancer factor 2, in 95% of these myotubes were detected by intense cytoplasmic and nuclear immunostaining, respectively, with specific antibodies. In contrast, no detectable staining was noted in MyoD negative cells. Spontaneous contractile movements were noted in a few clusters of myotubes. In summary, cardiac fibroblasts were able to be converted into bonafide potentially functional skeletal myocytes as shown by definitive morphologic and biochemical changes. Further studies with in vivo models are needed to explore this unique molecular strategy to treat patients with chronic heart failure. (J THORAC CARDIOVASC SURG 1995;109:918-24) Author Affiliation: Boston, Mass. Article Note: (footnote) [star] Sponsored by Gus J. Vlahakes, MD, Boston, Mass., [star][star] From the Cardiac Surgical Unit, Massachusetts General Hospital, the Department of Cardiology, The Children's Hospital, and the Departments of Surgery and Pediatrics, Harvard Medical School, Boston, Mass., a Read at the Seventy-fourth Annual Meeting of The American Association for Thoracic Surgery, New York, N.Y., April 24-27, 1994., aa Address for reprints: Stanley K.C. Tam, MD, 300 Mount Auburn St. Suite 516, Cambridge, MA 02138, acents 0022-5223/95 $3.00 + 0, acentsacents 12/6/61883

MYOSTATIN & MUSCLES Bodybuilders love training heavy, but make sure you lighten your workload now and then to reduce the effects of myostatin, a protein that limits muscle growth. When [...]

Byline: Men'S Health - Editorial, Men'S Health - Editorial I've heard I should eat before I hit the gym, but doing that makes me sick to my stomach when I [...]

A study aims to determine the effects of conjugated linoleic acid (CLA) supplementation during resistance training. The conclusion is that supplementation with CLA during resistance training results in relatively small changes in body composition accompanied by a lessening of the catabolic effect of training on muscle protein.