Cachexia is characterized by inexorable muscle wasting that significantly affects patient prognosis and increases mortality. Therefore, understanding the molecular basis of this muscle wasting is of significant importance. Recent work showed that components of the forkhead box O (FoxO) pathway are increased in skeletal muscle during cachexia. In the current study, we tested the physiological significance of FoxO activation in the progression of muscle atrophy associated with cachexia. FoxO‐DNA binding dependent transcription was blocked in the muscles of mice through injection of a dominant negative (DN) FoxO expression plasmid prior to inoculation with Lewis lung carcinoma cells or the induction of sepsis. Expression of DN FoxO inhibited the increased mRNA levels of atrogin‐1, MuRF1, cathepsin L, and/or Bnip3 and inhibited muscle fiber atrophy during cancer cachexia and sepsis. Interestingly, during control conditions, expression of DN FoxO decreased myostatin expression, increased MyoD expression and satellite cell proliferation, and induced fiber hypertrophy, which required de novo protein synthesis. Collectively, these data show that FoxO‐DNA binding‐dependent transcription is necessary for normal muscle fiber atrophy during cancer cachexia and sepsis, and further suggest that basal levels of FoxO play an important role during normal conditions to depress satellite cell activation and limit muscle growth.—Reed, S. A., Sandesara, P. B., Senf, S. F., Judge, A. R. Inhibition of FoxO transcriptional activity prevents muscle fiber atrophy during cachexia and induces hypertrophy. FASEB J. 26, 987‐1000 (2012). www.fasebj.org

The Forkhead Box O (FOXO) transcription factors regulate diverse cellular processes, and in skeletal muscle are both necessary and sufficient for muscle atrophy. Although the regulation of FOXO by Akt is well evidenced in skeletal muscle, the current study demonstrates that FOXO is also regulated in muscle via the histone acetyltransferase (HAT) activities of p300/CREB-binding protein (CBP). Transfection of rat soleus muscle with a dominant-negative p300, which lacks HAT activity and inhibits endogenous p300 HAT activity, increased FOXO reporter activity and induced transcription from the promoter of a bona fide FOXO target gene, atrogin-1. Conversely, increased HAT activity via transfection of either wild-type (WT) p300 or WT CBP repressed FOXO activation in vivo in response to muscle disuse, and in C2C12 cells in response to dexamethasone and acute starvation. Importantly, manipulation of HAT activity differentially regulated the expression of various FOXO target genes. Cotransfection of FOXO1, FOXO3a, or FOXO4 with the p300 constructs further identified p300 HAT activity to also differentially regulate the activity of the FOXO homologues. Markedly, decreased HAT activity strongly increased FOXO3a transcriptional activity, while increased HAT activity repressed FOXO3a activity and prevented its nuclear localization in response to nutrient deprivation. In contrast, p300 increased FOXO1 nuclear localization. In summary, this study provides the first evidence to support the acetyltransferase activities of p300/CBP in regulating FOXO signaling in skeletal muscle and suggests that acetylation may be an important mechanism to differentially regulate the FOXO homologues and dictate which FOXO target genes are activated in response to varying atrophic stimuli.

Mesenchymal stem cells (MSCs) offer promise as therapeutic aids in the repair of tendon, ligament, and bone damage suffered by sport horses. The objective of the study was to identify and characterize stem‐like cells from newborn foal umbilical cord blood (UCB). UCB was collected and MSC isolated using human reagents. The cells exhibit a fibroblast‐like morphology and express the stem cell markers Oct4, SSEA‐1, Tra1‐60 and Tra1‐81. Culture of the cells in tissue‐specific differentiation media leads to the formation of cell types characteristic of mesodermal and endodermal origins. Chondrogenic differentiation reveals proteoglycan and glycosaminoglycan synthesis as measured histochemically and Sox9 and collagen 2A1 gene transcription. Osteocytes capable of mineral deposition, osteonectin and Runx2 transcription were evident. Hepatogenic cells formed from UCBs express albumin and cytokeratin 18. Multinucleated myofibers that express desmin were observed indicating partial differentiation into mature muscle cells. Interestingly, conventional human protocols for UCB differentiation into adipocytes were unsuccessful in foal UCB and adult horse adipose‐derived MSC. These results demonstrate that equine UCB can be induced to form multiple cell types that underlie their value for regenerative medicine in injured horses. In addition, this work suggests that subtle differences exist between equine and human UCB stem cells. J. Cell. Physiol. 215: 329–336, 2008.

Maternal over and restricted nutrition has negative consequences on the muscle of offspring by reducing muscle fiber number and altering regulators of muscle growth. To determine if over and restricted maternal nutrition affected muscle growth and gene and protein expression in offspring, 36 pregnant ewes were fed 60%, 100% or 140% of National Research Council requirements from d 31 ± 1.3 of gestation until parturition. Lambs from control-fed (CON), restricted-fed (RES) or over-fed (OVER) ewes were necropsied within 1 d of birth (n = 18) or maintained on a control diet for 3 mo (n = 15). Semitendinosus muscle was collected for immunohistochemistry, and protein and gene expression analysis.

Poor maternal nutrition during gestation can have immediate and life-long negative effects on offspring growth and health. In livestock, this leads to reduced product quality and increased costs of production. Based on previous evidence that both restricted- and overfeeding during gestation decrease offspring muscle growth and alter metabolism postnatally, we hypothesized that poor maternal nutrition during gestation would reduce the growth and development of offspring muscle prenatally, reduce the number of myogenic progenitor cells, and result in changes in the global expression of genes involved in prenatal muscle development and function. Ewes were fed a control (100% NRC)-, restricted (60% NRC)-, or overfed (140% NRC) diet beginning on day 30 of gestation until days 45, 90, and 135 of gestation or until parturition. At each time point fetuses and offspring (referred to as CON, RES, and OVER) were euthanized and longissimus dorsi (LM), semitendinosus (STN), and triceps brachii (TB) were collected at each time point for histological and RNA-Seq analysis. In fetuses and offspring, we did not observe an effect of diet on cross-sectional area (CSA), but CSA increased over time (P < 0.05). At day 90, RES and OVER had reduced secondary:primary muscle fiber ratios in LM (P < 0.05), but not in STN and TB. However, in STN and TB percent PAX7-positive cells were decreased compared with CON (P < 0.05). Maternal diet altered LM mRNA expression of 20 genes (7 genes downregulated in OVER and 2 downregulated in RES compared with CON; 5 downregulated in OVER compared with RES; false discovery rate (FDR)-adj. P < 0.05). A diet by time interaction was not observed for any genes in the RNA-Seq analysis; however, 2,205 genes were differentially expressed over time between days 90 and 135 and birth (FDR-adj. P < 0.05). Specifically, consistent with increased protein accretion, changes in muscle function, and increased metabolic activity during myogenesis, changes in genes involved in cell cycle, metabolic processes, and protein synthesis were observed during fetal myogenesis. In conclusion, poor maternal nutrition during gestation contributes to altered offspring muscle growth during early fetal development which persists throughout the fetal stage. Based on muscle-type-specific effects of maternal diet, it is important to evaluate more than one type of muscle to fully elucidate the effects of maternal diet on offspring muscle development.