Habitual physical exercise improves macrophage IL-6 and TNF-α deregulated release in the obese zucker rat model of the metabolic syndrome.

OBJECTIVES: The first objective was to evaluate whether the metabolic syndrome (MS) involves deregulation of TNF-α and IL-6 release by non-infiltrated peritoneal macrophages, using obese Zucker rats as the experimental model of MS and lean Zucker rats as a reference for healthy control values. The second purpose was to evaluate in the obese rats the effects of habitual exercise and of a bout of acute exercise on the observed MS-associated deregulation in the release of TNF-α and IL-6 by peritoneal macrophages. METHODS: The habitual exercise consisted of treadmill running: 5 days/week for 14 weeks and 35 cm/s for 35 min in the last month. The acute exercise consisted of a single session of 25-35 min at 35 cm/s. The constitutive or lipopolysaccharide (LPS)-induced release of TNF-α and IL-6 by cultured (24 h, 5% CO2, 100% relative humidity) peritoneal macrophages was determined by ELISA. RESULTS: Macrophages from the obese rats released more IL-6 than those from the lean healthy rats, both spontaneously and after LPS stimulation. However, both spontaneous and LPS-induced release of TNF-α was lower in the obese rats. This deregulated balance in the release of IL-6 and TNF-α in the obese rats was clearly improved following adherence to the program of habitual exercise, reflected by a decrease in the spontaneous release of IL-6 together with a better regulation between the spontaneous and LPS-induced release of TNF-α, approaching the behavior of the lean healthy rats. In addition, an acute bout of exercise decreased the spontaneous release of IL-6 and increased the spontaneous release of TNF-α in the sedentary, but not in the exercise-adapted obese rats. CONCLUSION: MS involves a deregulation of TNF-α and IL-6 release by non-infiltrated peritoneal macrophages, which is improved by habitual physical activity.

Slow- and fast-twitch rat hind limb skeletal muscle phenotypes 8 months after spinal cord transection and olfactory ensheathing glia transplantation.

Paralysed skeletal muscle of rats with spinal cord injury (SCI) undergoes atrophy and a switch in gene expression pattern which leads to faster, more fatigable phenotypes. Olfactory ensheathing glia (OEG) transplants have been reported to promote axonal regeneration and to restore sensory-motor function in animals with SCI. We hypothesized that OEG transplants could attenuate skeletal muscle phenotypic deterioration and that this effect could underlie the functional recovery observed in behavioural tests. A variety of morphological, metabolic and molecular markers were assessed in soleus (SOL) and extensor digitorum longus (EDL) muscles of spinal cord transected (SCT), OEG-transplanted rats 8 months after the intervention and compared with non-transplanted SCT rats and sham-operated (without SCT) controls (C). A multivariate analysis encompassing all the parameters indicated that OEG-transplanted rats displayed skeletal muscle phenotypes intermediate between non-transplanted and sham-operated controls, but different from both. A high correlation was observed between behaviourally tested sensory-motor functional capacity and expression level of slow- and fast-twitch hind limb skeletal muscle phenotypic markers, particularly the histochemical glycerol-3-phosphate dehydrogenase activity (-0.843, P < 0.0001) and the fraction of variant 2s of the slow regulatory myosin light chain isoform (0.848, P < 0.0001) in SOL. Despite the mean overall effect of OEG transplants in patterning skeletal muscle protein expression towards normal, in 6 out of 9 animals they appeared insufficient to overcome fibre type switching and to support a consistent and generalized long-term maintenance of normal skeletal muscle characteristics. The interplay of OEG and exercise-mediated neurotrophic actions is a plausible mechanism underlying OEG transplantation effects on paralysed skeletal muscle.

Induction, modification and accumulation of HSP70s in the rat liver after acute exercise: early and late responses.

Liver cells synthesize HSP72, the cytosolic highly stress-inducible member of the 70 kDa family of heat-shock proteins (HSP70s), in response to acute exercise. This study was aimed at obtaining further insight into the physiological relevance of the hepatic stress response to exercise by investigating the induction and long-term maintenance of increased levels of HSP70s of the HSP and glucose-regulated protein (GRP) families, their post-translational modifications during or after exercise and the possible relation of HSP induction to oxidative stress. In a running rat model, acute exercise activated the synthesis and accumulation of HSP72, GRP75 and GRP78 in liver cells, pointing towards a multifactorial origin of this response. A peak HSP72 accumulation was observed shortly after exercise as a result of transcriptional activation. HSP72 was reduced shortly after exercise preceding the disappearance of its mRNA. Two further waves of HSP72 accumulation peaked 8 and 48 h after exercise without transcriptional activation. A transient increase in the proportion of acidic variants of HSP72 and HSP73 was also observed shortly after exercise as a result, at least in part, of protein phosphorylation. Free and protein-bound lipid peroxidation derivatives (TBARS) showed a tendency to increase in the early post-exercise and the free-to-protein-bound TBARS ratio decreased significantly after 2 h. During the early post-exercise period, protein-bound TBARS correlated positively with HSP72 and 73, but not with GRP75 or GRP78. Altogether, the reported results indicate that the early induction and post-translational modification of HSP70s in liver cells following exercise is a preliminary step of a series of long-lasting HSP70-related events, possibly designed to preserve liver cell homeostasis and to help provide a concerted response of the whole organism to physical stress.