Identification of global transcriptional variations in human peripheral blood mononuclear cells two months postheat injury helps categorization heat-tolerant or heat-intolerant phenotypes.

Thermal intolerance may limit activity in hostile environments. After heat illness, two physiologically distinct phenotypes evolve: heat tolerant (HT) and heat intolerant (HI). The recognition that heat illness alters gene expression justified revisiting the established physiological concept of HI. We used a DNA microarray to examine the global transcriptional response in peripheral blood mononuclear cells (PMBCs) from HI and HT phenotypes, categorized 2-mo postheat injury using a functional physiological heat-tolerance test (HTT, 40°C)-Recovery (R, 24°C) protocol. The impact of recurrent heat stress was studied in vitro using peripheral blood mononuclear cells (PBMCs) from controls (participants with no history of heat injury), HI, and HT (categorized by functional HTT) with a customized NanoString array. There were significant differences under basal conditions between the HI and HT. HI were more immunological alerted. Almost no shared genes were found between end-HTT and recovery phases, suggesting vast cellular plasticity. In HI, mitochondrial function was dysregulated, canonical pathways associated with exercise endurance-NRF2 and insulin were downregulated, whereas AMPK and peroxisome proliferator-activated receptor (PPAR) were upregulated. HT exhibited reciprocal responses, suggesting that energy dysregulation found in HI interfered with performance in the heat. The endoplasmic-reticulum stress response was also suppressed in HI. In vitro HTT (43°C) abolished differences between HI and HT PBMCs including the HSPs genes, whereas controls showed profound HSPs upregulation.

Evaluation of fatigue of respiratory and lower limb muscles during prolonged aerobic exercise.

The respiratory muscles may fatigue during prolonged exercises and thereby become a factor that limits extreme physical activity. The aim of the current study was to determine whether respiratory muscle fatigue imposes a limitation on extreme physical activity of well-trained young men. Electromyography (EMG) signals of respiratory (external intercostal and sternomastoid) and calf muscles (gastrocnemius) were measured (N = 8) during 1 hr of treadmill marching at a speed of 8 km/hr with and without a 15 kg backpack. The root mean square (RMS) and the mean power frequency of the EMG signals were evaluated for calculating fatigue indices. The EMG RMS revealed that the respiratory and calf muscles did not fatigue during the marching without a backpack load. The study did show, however, a significant rise in the EMG values when a backpack was carried with respect to the no-load condition (p < .05), which suggests that respiratory muscles should be trained in military recruits who are required to carry loaded backpacks while marching.

[Exercise induced rhabdomyolysis--characteristics, mechanisms and treatment].

Rhabdomyolysis is defined as a syndrome resulting from skeletal muscle injury with release of muscle cell contents into the plasma. One of the main causes of rhabdomyolysis is eccentric exercise against high resistance. There are mechanical as well as metabolic causes in exercise induced rhabdomyolysis. The mechanical aspect includes high physical tension on the muscle fiber and the metabolic causes include lack of available ATP and disturbance in intracellular electrolyte balance, especially calcium. The clinical picture of rhabdomyolysis may include muscle soreness, reduction of the range of motion, decreased muscle strength, black urine and, in severe cases, acute renal failure. Laboratory results may include delayed high levels of muscle enzymes in the plasma, myoglobinemia and myoglobinuria, disturbance in blood electrolyte balance, and in severe cases, disturbance in coagulatory function and DIC. Compartment syndrome may also be part of severe rhabdomyolyis. The main treatment for rhabdomyolysis is fluids administration and maintaining urination, in order to preserve renal function. In severe compartment syndrome fasciotomy may be necessary. There is a wide variability in the severity of rhabdomyolysis. This variability is not completely understood but may be related to the level of physical fitness, morphometrical characteristics and gender. In order to prevent exercise induced rhabdomyolysis, a gradual training program should be maintained providing enough recovery time, preserving fluid balance, and avoiding extreme eccentric exercise and exercise in high heat load.

Physical exercise enhances protein kinase C delta activity and insulin receptor tyrosine phosphorylation in diabetes-prone psammomys obesus.

We recently reported that physical exercise prevents the progression of type 2 diabetes mellitus in Psammomys obesus, an animal model of nutritionally induced type 2 diabetes mellitus. In the present study we characterized the effect of physical exercise on protein kinase C delta (PKC delta) activity, as a mediator of the insulin-signaling cascade in vivo. Three groups of Psammomys obesus were exposed to a 4-week protocol: high-energy diet (HE/C), high-energy diet and exercise (HE/EX), or low-energy diet (LE/C). None of the animals in the HE/EX group became diabetic, whereas all the animals in the HE/C group became diabetic. After overnight fast, intraperitoneal (IP) insulin (1U) caused a greater reduction in blood glucose levels in the HE/EX and LE/C groups compared to the HE/C group. Tyrosine phosphorylation of insulin receptor (IR), insulin receptor substrate-1 (IRS-1), and phosphatidylinositol 3 kinase (PI3 kinase) was significantly higher in the HE/EX and LE/C groups compared with the HE/C group. Finally, IR-associated PKC delta was higher in the HE/EX and LE/C groups compared to the HE/C group. Coprecipitation of PKC delta with IR was higher in the HE/EX and LE/C groups compared to the HE/C group. Thus, we suggest that 4 weeks of physical exercise results in improved insulin-signaling response in Psammomys obesus accompanied by a direct connection between PKC delta and IR. We conclude that this mechanism may be involved in the preventive effect of exercise on type 2 diabetes mellitus in Psammomys obesus.

Physical exercise prevents the development of type 2 diabetes mellitus in Psammomys obesus.

We hypothesized that exercise training might prevent diabetes mellitus in Psammomys obesus. Animals were assigned to three groups: high-energy diet (CH), high-energy diet and exercise (EH), and low-energy diet (CL). The EH group ran on a treadmill 5 days/wk, twice a day. After 4 wk, 93% of the CH group were diabetic compared with only 20% of the EH group. There was no difference in weight gain among the groups. Both EH and CH groups were hyperinsulinemic. Epididymal fat (% of body weight) was higher in the CH group than in either the EH and or the CL group. Protein kinase C (PKC)-delta activity and serine phosphorylation were higher in the EH group. No differences were found in tyrosine phosphorylation of the insulin receptor, insulin receptor substrate-1, and phosphatidylinositol 3-kinase among the groups. We demonstrate for the first time that exercise training effectively prevents the progression of diabetes mellitus type 2 in Psammomys obesus. PKC-delta may be involved in the adaptive effects of exercise in skeletal muscles that lead to the prevention of type 2 diabetes mellitus.