Skeletal muscle FOXO1 (FKHR) transgenic mice have less skeletal muscle mass, down-regulated Type I (slow twitch/red muscle) fiber genes, and impaired glycemic control.
FOXO1, a member of the FOXO forkhead type transcription factors, is markedly up-regulated in skeletal muscle in energy-deprived states such as fasting and severe diabetes, but its functions in skeletal muscle have remained poorly understood. In this study, we created transgenic mice specifically overexpressing FOXO1 in skeletal muscle. These mice weighed less than the wild-type control mice, had a reduced skeletal muscle mass, and the muscle was paler in color. Microarray analysis revealed that the expression of many genes related to the structural proteins of type I muscles (slow twitch, red muscle) was decreased. Histological analyses showed a marked decrease in size of both type I and type II fibers and a significant decrease in the number of type I fibers in the skeletal muscle of FOXO1 mice. Enhanced gene expression of a lysosomal proteinase, cathepsin L, which is known to be up-regulated during skeletal muscle atrophy, suggested increased protein degradation in the skeletal muscle of FOXO1 mice. Running wheel activity (spontaneous locomotive activity) was significantly reduced in FOXO1 mice compared with control mice. Moreover, the FOXO1 mice showed impaired glycemic control after oral glucose and intraperitoneal insulin administration. These results suggest that FOXO1 negatively regulates skeletal muscle mass and type I fiber gene expression and leads to impaired skeletal muscle function. Activation of FOXO1 may be involved in the pathogenesis of sarcopenia, the age-related decline in muscle mass in humans, which leads to obesity and diabetes.
Kamei
Yasutomi
Y
PRESTO, Japan Science and Technology Agency, National Institute of Health and Nutrition, 1-23-1 Toyama, Shinjuku-ku, Tokyo 162-8636, Japan. ykamei@nih.go.jp
Miura
Shinji
S
Suzuki
Miki
M
Kai
Yuko
Y
Mizukami
Junko
J
Taniguchi
Tomoyasu
T
Mochida
Keiji
K
Hata
Tomoko
T
Matsuda
Junichiro
J
Aburatani
Hiroyuki
H
Nishino
Ichizo
I
Ezaki
Osamu
O
D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D001823:Body Composition; D001835:Body Weight; D056668:Cathepsin L; D002403:Cathepsins / Q000096:biosynthesis; D003546:Cysteine Endopeptidases; D015536:Down-Regulation; D005260:Female; D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors; D005947:Glucose / Q000378:metabolism; D005951:Glucose Tolerance Test; D006801:Humans; D015151:Immunoblotting; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D008957:Models, Genetic; D018657:Muscle Fibers, Slow-Twitch / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000473:pathology; D020411:Oligonucleotide Array Sequence Analysis; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; D012313:RNA / Q000737:chemistry / Q000378:metabolism; D013997:Time Factors; D014018:Tissue Distribution; D015534:Trans-Activators / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics* / Q000502:physiology*; D015854:Up-Regulation
D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors; C467200:Foxo1 protein, mouse; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; C485290:Ppargc1a protein, mouse; D015534:Trans-Activators; D014157:Transcription Factors; D012313:RNA; D002403:Cathepsins; D003546:Cysteine Endopeptidases; C534281:CTSL protein, human; D056668:Cathepsin L; C534278:Ctsl protein, mouse; D000251:Adenosine Triphosphatases; D005947:Glucose