A combination of exercise and calorie restriction improves the development of obesity-related type 2 diabetes mellitus in KKAy mice.

We observed that exercise and calorie restriction reduced the body weight and blood glucose levels, concurrently improving insulin resistance and glucose tolerance in obese/diabetic model KKAy mice. Analysis of gene expression in the skeletal muscle showed enhanced mRNA levels of GLUT4 (glucose uptake), ATGL (lipolytic enzyme), and slow-twitch myosin heavy chain, which may contribute to the antiobesity and antidiabetic effects.

Vitamin D Activates Various Gene Expressions, Including Lipid Metabolism, in C2C12 Cells.

Vitamin D is a fat-soluble molecule, well known for its role in regulating calcium homeostasis in bone. It has become increasingly clear that it also has important effects in many other organs, including the skeletal muscle. In order to gain insight into the role of vitamin D in the skeletal muscle, we performed microarray analysis using C2C12 myoblasts treated with 1,25-dihydroxyvitamin D (1,25(OH)2D), active form of vitamin D. We found multiple genes upregulated by 1,25(OH)2D. Some of them, i.e., vitamin D receptor (Vdr), diacylglycerol O-acyltransferase (Dgat1 and Dgat2, the rate limiting steps of triacylglycerol acylation), and vascular endothelial growth factor A (Vegfa), were previously reported to be upregulated by 1,25(OH)2D in C2C12 cells. RT-qPCR analysis confirmed increased mRNA levels of Rarres2, Dio2, Tgm2, Lpl, Mdfi, Igfbp3, Dgat1, Crabp2, Gadd45a, Vagfa, Dgat2, C3, Ldhb, Cebpa, Igfbp5, Mrc2, Vdr. Thus, many genes, including lipid metabolism genes as well as genes related to muscle functions, appear to be upregulated by 1,25(OH)2D in muscle cells.

Metabolomic analysis on blood of transgenic mice overexpressing PGC-1α in skeletal muscle.

PGC-1α expression increases in skeletal muscles during exercise and regulates the transcription of many target genes. In this study, we conducted a metabolomic analysis on the blood of transgenic mice overexpressing PGC-1α in its skeletal muscle (PGC-1α-Tg mice) using CE-TOFMS. The blood level of homovanillic acid (dopamine metabolite) and the gene expression of dopamine metabolic enzyme in the skeletal muscle of PGC-1α-Tg mice were high. The blood level of 5-methoxyindoleacetic acid was also high in PGC-1α-Tg mice. The blood levels of branched-chain α-keto acids and ß-alanine were low in PGC-1α-Tg mice. These metabolites in the skeletal muscle were present in low concentration. The changes in these metabolites may reflect the skeletal muscle condition with increasing PGC-1α, such as exercise.

Vitamin D and Sarcopenia: Potential of Vitamin D Supplementation in Sarcopenia Prevention and Treatment.

Skeletal muscle, the largest organ in the human body, accounting for approximately 40% of body weight, plays important roles in exercise and energy expenditure. In the elderly, there is often a progressive decline in skeletal muscle mass and function, a condition known as sarcopenia, which can lead to bedridden conditions, wheelchair confinement as well as reducing the quality of life (QOL). In developed countries with aging populations, the prevention and management of sarcopenia are important for the improvement of health and life expectancy in these populations. Recently, vitamin D, a fat-soluble vitamin, has been attracting attention due to its importance in sarcopenia. This review will focus on the effects of vitamin D deficiency and supplementation on sarcopenia.

Regulation of Skeletal Muscle Function by Amino Acids.

Amino acids are components of proteins that also exist free-form in the body; their functions can be divided into (1) nutritional, (2) sensory, and (3) biological regulatory roles. The skeletal muscle, which is the largest organ in the human body, representing ~40% of the total body weight, plays important roles in exercise, energy expenditure, and glucose/amino acid usage-processes that are modulated by various amino acids and their metabolites. In this review, we address the metabolism and function of amino acids in the skeletal muscle. The expression of PGC1α, a transcriptional coactivator, is increased in the skeletal muscle during exercise. PGC1α activates branched-chain amino acid (BCAA) metabolism and is used for energy in the tricarboxylic acid (TCA) cycle. Leucine, a BCAA, and its metabolite, ß-hydroxy-ß-methylbutyrate (HMB), both activate mammalian target of rapamycin complex 1 (mTORC1) and increase protein synthesis, but the mechanisms of activation appear to be different. The metabolite of valine (another BCAA), ß-aminoisobutyric acid (BAIBA), is increased by exercise, is secreted by the skeletal muscle, and acts on other tissues, such as white adipose tissue, to increase energy expenditure. In addition, several amino acid-related molecules reportedly activate skeletal muscle function. Oral 5-aminolevulinic acid (ALA) supplementation can protect against mild hyperglycemia and help prevent type 2 diabetes. ß-alanine levels are decreased in the skeletal muscles of aged mice. ß-alanine supplementation increased the physical performance and improved the executive function induced by endurance exercise in middle-aged individuals. Further studies focusing on the effects of amino acids and their metabolites on skeletal muscle function will provide data essential for the production of food supplements for older adults, athletes, and individuals with metabolic diseases.

Screening dataset of food components that enhance transcriptional activity of PGC1-beta.

PGC-1ß is a transcriptional co-activator of nuclear receptors, which acts to increase energy expenditure. PGC-1ß fused to GAL4 DNA-binding domain transfected in HEK293T cells showed a reporter luciferase activity. We screened food-derived and natural compounds using a reporter assay system to measure the transcriptional activity of PGC-1ß. We found that soy-derived isoflavones, genistein and daidzein, and several resveratrols activated PGC-1ß, see "Genistein, daidzein, and resveratrols stimulate PGC-1ß-mediated gene expression" [1]. The list of 166 compounds and their reporter activity is shown here.

Metabolomic Analysis of Skeletal Muscle in Aged Mice.

Sarcopenia is the age-induced, progressive loss of skeletal muscle mass and function. To better understand changes in skeletal muscle during sarcopenia, we performed a metabolomic analysis of skeletal muscle in young (8-week-old) and aged (28-month-old) mice by using capillary electrophoresis with electrospray ionization time-of-flight mass spectrometry. Principal component analysis showed clear changes in metabolites between young and aged mice. Glucose metabolism products were decreased in aged mice, specifically fructose 1,6-diphosphate (0.4-fold) and dihydroxyacetone phosphate (0.6-fold), possibly from decreased glycolytic muscle fibers. Multiple metabolic products associated with phospholipid metabolism were significantly changed in aged mice, which may reflect changes in cell membrane phospholipids of skeletal muscle. Products of polyamine metabolism, which are known to increase nucleic acid and protein synthesis, decreased in spermine (0.5-fold) and spermidine (0.6-fold) levels. By contrast, neurotransmitter levels were increased in skeletal muscle of aged mice, including acetylcholine (1.8-fold), histamine (2.6-fold), and serotonin (1.7-fold). The increase in acetylcholine might compensate for age-associated dropout of neuromuscular junctions, whereas the increases in histamine and serotonin might be due to muscle injury associated with aging. Further analysis focusing on the altered metabolites observed in this study will provide essential data for understanding aging muscles.

Metabolomic analysis of C2C12 myoblasts induced by the transcription factor FOXO1.

The transcription factor FOXO1 is considered to play roles in the regulation of energy metabolism in various tissues. To determine the metabolic changes occurring due to FOXO1 activation, we analyzed the metabolic profile of C2C12 myoblasts expressing a FOXO1-estrogen receptor fusion protein using capillary electrophoresis with electrospray ionization time-of-flight mass spectrometry (CE-TOFMS). In FOXO1-activated cells, the metabolite levels during glycolysis are higher and the gene expression of pyruvate dehydrogenase kinase, an enzyme that inhibits glucose utilization, is increased. In addition, the metabolite levels of numerous amino acids are decreased, with increased gene expression of branched chain amino acid metabolism enzymes. Our results suggest that FOXO1 suppresses glucose utilization and promotes the use of proteins/amino acids as energy sources in muscle cells, potentially during starvation.

Effects of long-term physical exercise on skeletal muscles in senescence-accelerated mice (SAMP8).

We examined the effect of long-term exercise on the prevention of sarcopenia using a senescence-accelerated-prone mice (SAMP8) model. Mice were housed in a wheel cage for 25 weeks to increase voluntary exercise. At week 23, endurance running capacity was examined using a treadmill. In a treadmill running test, the wheel cage group had increased endurance running capacity, which suggests that aging-related loss of muscle function was recovered by long-term exercise. Mice were sacrificed and microarray analysis revealed that genes involved in protein synthesis and degradation were upregulated in the skeletal muscles of the wheel cage group, suggesting accelerated protein turnover. Total body and adipose tissue weights decreased following the use of the wheel cage. Thus, long-term, spontaneous physical exercise may assist in recovering from aging-related sarcopenia (loss of muscle function) and obesity.

Genistein, daidzein, and resveratrols stimulate PGC-1ß-mediated gene expression.

PGC-1ß is a transcriptional co-activator of nuclear receptors such as the estrogen receptor-related receptor (ERR). Transgenic overexpression of PGC-1ß in mice increases energy expenditure and suppresses high-fat diet-induced obesity. In this study, we screened various food-derived and natural compounds using a reporter assay system to measure the transcriptional activity of PGC-1ß. Soy-derived isoflavones, genistein and daidzein, and several resveratrols activated PGC-1ß. Genistein, daidzein, and trans-oxyresveratrol activated ERR-responsive element-mediated reporter activity in the presence of PGC-1ß. Stable overexpression of PGC-1ß in C2C12 myoblasts increased the expression of medium-chain acyl-CoA dehydrogenase (MCAD), an important enzyme in fatty acid ß-oxidation. Genistein and daidzein increased MCAD mRNA levels and mitochondrial content in PGC-1ß-expressing C2C12 cells. These compounds activated ERR/PGC-1ß complex-mediated gene expression, and our findings may be a practical foundation for developing functional foods targeting obesity.