sq-23377 and Prediabetic-State

Irisin, myokine secreted by skeletal muscle, was suggested to mediate some of exercise health benefits via "browning" of white adipose tissue. However, mounting evidence contradicts the regulatory role of exercise for muscle irisin production/secretion in humans. Thus, we explored the direct effect of exercise-mimicking treatment on irisin in human primary muscle cells in vitro. Human primary muscle cell cultures were established from lean, obese prediabetic and type-2-diabetic individuals. Complex metabolic phenotyping included assessment of insulin sensitivity (euglycemic hyperinsulinemic clamp) and adiposity content&distribution (MRI&MRS). In vitro exercise-mimicking treatment (forskolin+ionomycin) was delivered in 1-h pulse/day during differentiation. Fndc5 mRNA (qRT-PCR) and secreted irisin (ELISA) were determined in cells and media. Exercise-mimicking treatment more than doubled Pgc1α mRNA in differentiated muscle cells. Nevertheless, Fndc5 mRNA was reduced by 18% and irisin in media by 20%. Moreover, Fncd5 mRNA was increased in myotubes derived from individuals with type-2-diabetes, independent on exercise-mimicking treatment. Fndc5 mRNA in cells was positively related to fasting glycemia (p=0.0001) and negatively to whole-body insulin sensitivity (p<0.05). Collectively, our data do not support the role of exercise-related signaling pathways in irisin regulation in human skeletal muscle and confirm our previous observations on increased Fndc5 expression in muscle cells from individuals with type-2-diabetes.

Topics: Cells, Cultured; Colforsin; Diabetes Mellitus, Type 2; Exercise; Fibronectins; Humans; Ionomycin; Muscle Fibers, Skeletal; Muscle, Skeletal; Obesity; Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; Prediabetic State; RNA, Messenger; Transcription Factors

To understand the ability of regulatory T-cells to control diabetes development in clinically relevant situations, we established a new model of accelerated diabetes in young DP-BB rats by transferring purified T-cells from DR-BB rats made acutely diabetic. Transfer of 3, 5, 10, or 23 million pure in vitro-activated T-cells accelerated diabetes onset in >90% of the recipients, with the degree of acceleration being dosage dependent. Cotransfer of unfractionated leukocytes from healthy donors prevented diabetes. Full protection was achieved when protective cells were transferred 3-4 days before diabetogenic cells, whereas transfer 2 days before conferred only partial protection. Protection resided in the CD4(+) fraction, as purified CD4(+) T-cells prevented the accelerated diabetes. When CD25(+) cells were depleted from these cells before they were transferred, their ability to prevent diabetes was impaired. In contrast, two million CD4(+)CD25(+) cells (expressing Foxp3) prevented the accelerated diabetes when transferred both before and simultaneously with the diabetogenic T-cells. In addition, 2 million CD4(+)CD25(+) T-cells prevented spontaneous diabetes, even when given to rats age 42 days, whereas 20 million CD4(+)CD25(-) cells (with low Foxp3 expression) were far less effective. We thus demonstrated that CD4(+)CD25(+) cells exhibit powerful regulatory potential in rat diabetes.

Topics: Adoptive Transfer; Aging; Animals; CD4 Antigens; Diabetes Mellitus, Type 1; DNA-Binding Proteins; Forkhead Transcription Factors; Gene Expression; Ionomycin; Lymphocyte Activation; Prediabetic State; Rats; Receptors, Interleukin-2; T-Lymphocyte Subsets; Tetradecanoylphorbol Acetate; Transcription Factors

Glucose metabolism and respiratory burst were studied in vitro in resident peritoneal macrophages from non-diabetes-prone BB, spontaneously diabetic BB, diabetes-prone BB, and STZ-induced diabetic BBn rats, in the presence or absence of phorbol myristate acetate plus ionomycin. Glycolysis and pentose phosphate pathway activity were increased in BBd compared with BBn cells. PMA plus IONO did not influence glycolysis in BBn macrophages and slightly decreased it in BBd macrophages. In contrast, PMA plus IONO increased the pentose phosphate pathway activity in BBn and BBd macrophages with a much greater increase in BBd cells. The release of O2- was greater in BBd than BBn cells; PMA plus IONO also induced a much greater release of O2- in BBd cells. H2O2 release was undetectable in unstimulated BBn cells, and stimulation by PMA plus IONO caused a small incremental release. In contrast, the release of H2O2 was measurable in unstimulated cells and further increased by 50% in BBd cells with PMA-plus-IONO stimulation. The release of O2- and H2O2 was increased in macrophages from 75-day-old BBdp rats but not in 50-day-old BBdp rats, compared with age-matched BBn rats. No differences were observed in either glucose metabolism or release of O2- and H2O2 between BBn and STZ-BBn cells in the absence or presence of PMA plus IONO. These data suggest that enhanced oxidative metabolism in BBd macrophages is unlikely to be attributable to diabetes per se.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Aging; Analysis of Variance; Animals; Cells, Cultured; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 1; Female; Glucose; Glycolysis; Hydrogen Peroxide; Ionomycin; Lactates; Macrophages; Pentose Phosphate Pathway; Prediabetic State; Pyruvates; Rats; Rats, Inbred BB; Superoxides; Tetradecanoylphorbol Acetate