sq-23377 and Obesity

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

We investigated the effects of a diet containing EPAX-7010, rich in PUFAs such as eicosapentaenoic acid [20:5(n-3)] and docosahexaenoic acid [22:6(n-3)], i.e., a PUFA/EPAX regimen, on T-cell activation in diabetic pregnant rats and their obese pups.. Mild hyperglycemia in pregnant rats was induced by intraperitoneal injection of streptozotocin on Day 5 of gestation. T-cell blastogenesis was assayed by using (3)H-thymidine, whereas intracellular free calcium concentrations ([Ca(2+)]i) were measured by using Fura-2 in diabetic pregnant rats and their obese offspring.. Concavalin-A-stimulated T-cell proliferation was decreased in both pregnant diabetic rats and their obese pups as compared with control animals. Feeding the PUFA/EPAX diet restored T-cell proliferation in both groups of animals. We also employed ionomycin, which at 50 nM opens calcium channels, and thapsigargin (TG), which recruits [Ca(2+)]i from endoplasmic reticulum pool. We observed that ionomycin-induced increases in [Ca(2+)]i in T-cells of diabetic mothers and obese offspring were greater than in those of control rats. Furthermore, feeding PUFA/EPAX diet diminished significantly the ionomycin-evoked rise in [Ca(2+)]i in diabetic and obese animals. TG-induced increases in [Ca(2+)]i in T-cells of diabetic pregnant rats and their obese offspring were greater than in those of control rats. The feeding of the experimental diet significantly curtailed the TG-evoked increases in [Ca(2+)]i in both diabetic and obese rats.. Together, these observations provide evidence that T-cell activation and T-cell calcium signaling are altered during gestational diabetes and macrosomia. Hence, dietary fish oils, particularly eicosapentaenoic acid and docosahexaenoic acid, may restore these T-cell abnormalities.

Topics: Animals; Calcium; Concanavalin A; Diabetes Mellitus, Experimental; Dietary Fats, Unsaturated; Fatty Acids, Omega-3; Female; Fetal Macrosomia; Gestational Age; Ionomycin; Lymphocyte Activation; Obesity; Pregnancy; Pregnancy in Diabetics; Rats; Rats, Wistar; Signal Transduction; Spleen; T-Lymphocytes; Thapsigargin