The frequency of twinning among women who have already borne twins, the 'repeat frequency', is significantly higher than in the general population. Individual propensity is not necessarily genetic in origin, but pedigree studies (for reviews see refs 1, 2) confirm that twinning is a family trait. Studies based on archives restrict this conclusion to dizygotic (DZ) twinning and the maternal side, while studies based on interviews of relatives of twins find monozygotic (MZ) twinning and the paternal side also to be involved. However, interview studies can overestimate, while archive studies can underestimate, the real frequency of twinning. We have now analysed the incidence of twinning in the families of 950 zygosity-determined, unselected twin pairs under complete ascertainment. Our results indicate that a propensity to MZ twinning, as well as one to DZ twinning, can be inherited through the maternal line, and that the two mechanisms of twinning might be related. We have also found a paternal role in DZ, but not in MZ twinning.

Current recommendations aimed at reducing neuromuscular and functional loss in aged muscle have identified muscle power as a key target for intervention trials, although little is known about the biological and cardiovascular systemic response in the elderly. This study investigated the effects of 12 weeks of low-frequency, moderate-intensity, explosive-type resistance training (EMRT) on muscle strength and power in old community-dwelling people (70-75 years), monitoring functional performance linked to daily living activities (ADL) and cardiovascular response, as well as biomarkers of muscle damage, cardiovascular risk, and cellular stress response. The present study provides the first evidence that EMRT was highly effective in achieving a significant enhancement in muscular strength and power as well as in functional performance without causing any detrimental modification in cardiovascular, inflammatory, and damage parameters. Moreover, trained elderly subjects showed an adaptive response at both systemic and cellular levels by modulation of antioxidant and stress-induced markers such as myeloperoxidase (MPO), heat shock protein 70 (Hsp70) and 27 (Hsp27), and thioredoxin reductase 1 (TrxR1).

These data supported the hypothesis that PBMCs might produce and secrete BDNF isoforms, as well as modulate the proteins p75(NTR) , Bcl-xL, hsp90, hsp27, and αB-crystallin, as part of the physiological stress response induced by acute exercise, offering a novel example of bidirectional interaction between nervous and immune systems.

To better clarify the relationship between physical activity and oxidative stress, we determined the effects of a maximal test in 18 young subjects with different training levels (six professional Athletes and 12 non-agonists (NA)). Redox homeostasis (total antioxidant activity (TAS), vitamin C and glutathione (GSH)), oxidative damage (diene conjugation and hemolysis), lymphocyte cell death and repair systems (apoptosis, micronuclei and Hsp70 expression) were evaluated. We found that agonistic training led to a chronic oxidative insult (high baseline values of oxidized glutathione (GSSG), micronuclei and hemolysis). On the contrary, NA with the lowest level of training frequency showed a well balanced profile at rest, but they were more susceptible to exercise-induced variations (GSSG/GSH and diene increased values), respect to the NA with an higher level of training. As almost all the parameters employed in this study showed inter-individual variations, the GSSG/GSH ratio remains the most sensitive and reliable marker of oxidative stress, accordingly with other data just reported in the literature.

We recently demonstrated that low frequency, moderate intensity, explosive-type resistance training (EMRT) is highly beneficial in elderly subjects towards muscle strength and power, with a systemic adaptive response of anti-oxidant and stress-induced markers. In the present study, we aimed to evaluate the impact of EMRT on oxidative stress biomarkers induced in old people (70–75 years) by a single bout of acute, intense exercise. Sixteen subjects randomly assigned to either a control, not exercising group (n=8) or a trained group performing EMRT protocol for 12-weeks (n=8), were submitted to a graded maximal exercise stress test (GXT) at baseline and after the 12-weeks of EMRT protocol, with blood samples collected before, immediately after, 1 and 24 h post-GXT test. Blood glutathione (GSH, GSSG, GSH/GSSG), plasma malonaldehyde (MDA), protein carbonyls and creatine kinase (CK) levels, as well as PBMCs cellular damage (Comet assay, apoptosis) and stress–protein response (Hsp70 and Hsp27 expression) were evaluated. The use of multiple biomarkers allowed us to confirm that EMRT per se neither affected redox homeostasis nor induced any cellular and oxidative damage. Following the GXT, the EMRT group displayed a higher GSH/GSSG ratio and a less pronounced increase in MDA, protein carbonyls and CK levels compared to control group. Moreover, we found that Hsp70 and Hsp27 proteins were induced after GXT only in EMRT group, while any significant modification within 24 h was detected in untrained group. Apoptosis rates and DNA damage did not show any significant variation in relation to EMRT and/or GXT.In conclusion, the adherence to an EMRT protocol is able to induce a cellular adaptation allowing healthy elderly trained subjects to cope with the oxidative stress induced by an acute exercise more effectively than the aged-matched sedentary subjects.