DNA double-strand breaks in incubating female common eiders (Somateria mollissima): Comparison between a low and a high polluted area.

Alterations in the genetic material may have severe consequences for individuals and populations. Hence, genotoxic effects of environmental exposure to pollutants are of great concern. We assessed the impact of blood concentrations of persistent organic pollutants (POPs) and mercury (Hg) on DNA double-strand break (DSB) frequency, in blood cells of a high-exposed Baltic, and lower exposed Arctic population of common eiders (Somateria mollissima). Furthermore, we examined whether the genotoxic response was influenced by antioxidant concentration (plasma total glutathione (tGSH) and total antioxidant capacity) and female body mass. The DNA DSB frequency did not differ between the two populations. We found significant positive relationships between Hg and DNA DSB frequency in Baltic, but not in Arctic eiders. Although both p,p'-DDE and PCB 118 had a lesser effect than Hg, they exhibited a positive association with DNA DSB frequency in Baltic eiders. Antioxidant levels were not important for the genotoxic effect, suggesting alternative mechanisms other than GSH depletion for the relationship between Hg and DNA DSBs. Hence, the Baltic population, which is considered to be endangered and is under the influence of several environmental stressors, may be more susceptible to genotoxic effects of environmental exposure to Hg than the Arctic population.

Antioxidant Responses in Relation to Persistent Organic Pollutants and Metals in a Low- and a High-Exposure Population of Seabirds.

Oxidative stress occurs when there is an imbalance between the production of reactive oxygen species (ROS) and antioxidant defense. Exposure to pollutants may increase ROS and affect antioxidant levels, and the resulting oxidative stress may negatively affect both reproduction and survival. We measured concentrations of 18 persistent organic pollutants (POPs) and 9 toxic elements in blood, as well as total antioxidant capacity (TAC), total glutathione (tGSH), and carotenoids in plasma of Baltic and Arctic female common eiders (Somateria mollissima) (N = 54) at the end of their incubation-related fasting. The more polluted Baltic population had higher TAC and tGSH concentrations compared to the Arctic population. Carotenoid levels did not differ between populations. The effect of mixtures of pollutants on the antioxidants was assessed, and the summed molar blood concentrations of 14 POPs were positively related to TAC. There was no significant relationship between the analyzed pollutants and tGSH concentrations. The adaptive improvement of the antioxidant defense system in the Baltic population may be a consequence of increased oxidative stress. However, both increased oxidative stress and energy allocation toward antioxidant defense may have adverse consequences for Baltic eiders at the incubation stage, when energy resources reach an annual minimum due to incubation-related fasting.

Cancer risk in people with diabetes: Does physical activity and adiposity modify the association? Prospective data from the HUNT Study, Norway.

AIMS: To examine whether physical activity and adiposity modify the increased risk of cancer associated with diabetes. METHODS: We prospectively examined the association of diabetes and risk of cancer among 73,726 persons stratified by physical activity and body mass index (BMI). Adjusted hazard ratios (HRs) with 95% confidence intervals (CI) were estimated from Cox regression. RESULTS: During a median follow-up of 22.0 years, 9572 people were diagnosed with incident cancer. There was no clear association between diabetes and cancer risk in those reporting high levels of physical activity (≥2.0h per week) (HR 0.93; 95% CI: 0.70-1.24) or those with a normal weight (BMI <25kg/m²) (HR 1.02; 95% CI: 0.84-1.25). However, among people with diabetes who reported low levels of physical activity (<2.0h per week), diabetes was associated with an HR of 1.15 (95% CI: 1.01-1.31). Correspondingly, diabetes was associated with an HR of 1.21 (95% CI: 1.07-1.37) among overweight or obese people (BMI ≥25kg/m²). CONCLUSIONS: There was evidence that the increased risk of cancer associated with diabetes was confined to persons who reported low levels of physical activity, or who were overweight or obese.

To breed or not to breed: endocrine response to mercury contamination by an Arctic seabird.

Mercury, a ubiquitous toxic element, is known to alter expression of sex steroids and to impair reproduction across vertebrates but the mechanisms underlying these effects are not clearly identified. We examined whether contamination by mercury predicts the probability to skip reproduction in black-legged kittiwakes (Rissa tridactyla) from Svalbard. We also manipulated the endocrine system to investigate the mechanism underlying this relationship. During the pre-laying period, we injected exogenous GnRH (gonadotropin-releasing hormone) to test the ability of the pituitary to release luteinizing hormone (LH, a key hormone for the release of sex steroids and hence breeding) in relation to mercury burden. Birds that skipped reproduction had significantly higher mercury concentration in blood than breeders. Endocrine profiles of these birds also varied based on breeding status (breeders versus non-breeders), mercury contamination and sex. Specifically, in skippers (birds that did not breed), baseline LH decreased with increasing mercury concentration in males, whereas it increased in females. GnRH-induced LH levels increased with increasing mercury concentration in both sexes. These results suggest that mercury contamination may disrupt GnRH input to the pituitary. Thus, high mercury concentration could affect the ability of long-lived birds to modulate their reproductive effort (skipping or breeding) according to ongoing environmental changes in the Arctic, thereby impacting population dynamics.

Occupational physical activity, metabolic syndrome and risk of death from all causes and cardiovascular disease in the HUNT 2 cohort study.

OBJECTIVES: To prospectively examine the independent and combined effect of occupational physical activity and metabolic syndrome on all-cause and cardiovascular mortality in a large population-based cohort. METHODS: Data on 37 300 men and women participating in the Norwegian HUNT Study (1995-1997) were linked with the Cause of Death Registry at Statistics Norway. Cox proportional HR with 95% CI were estimated. RESULTS: During a median follow-up of 12.4 years, a total of 1168 persons died. Of these, 278 died from cardiovascular disease. Persons with metabolic syndrome and much walking/lifting at work had a HR of 1.79 (95% CI 1.20 to 2.66) for cardiovascular death referencing persons without metabolic syndrome and much walking/lifting. Using the same reference, persons with metabolic syndrome and sedentary work had a HR of 2.74 (95% CI 1.82 to 4.12) while persons with metabolic syndrome and heavy physical work had a HR of 3.02 (95% CI 1.93 to 4.75). Associations with all-cause mortality were somewhat weaker, and were largely due to deaths from cardiovascular disease. CONCLUSIONS: The association between metabolic syndrome and cardiovascular mortality is stronger for persons with sedentary work and with physically heavy work than for persons with much walking/lifting at work.

Food restriction in young Japanese quails: effects on growth, metabolism, plasma thyroid hormones and mRNA species in the thyroid hormone signalling pathway.

Young birds, in their post-natal growth period, may reduce their growth and metabolism when facing a food shortage. To examine how such responses can be mediated by endocrine-related factors, we exposed Japanese quail chicks to food restriction for either 2 days (age 6-8 days) or 5 days (age 6-11 days). We then measured growth and resting metabolic rate (RMR), and circulating 3,3',5-triiodo-l-thyronine (T3) and 3,5,3',5'-tetraiodothyronine (T4) levels as well as expression patterns of genes involved in growth (insulin-like growth factor-I: IGF-I) and thyroid hormone signalling (thyroid-stimulating hormone-beta: TSHbeta, type II iodothyronine deiodinase: D2, thyroid hormone receptors isoforms: TRalpha and TRbeta). The food-restricted chicks receiving a weight-maintenance diet showed reductions in structural growth and RMR. Plasma levels of both T3 and T4 were reduced in the food-restricted birds, and within the 5 days food-restricted group there was a positive correlation between RMR and T3. IGF-I mRNA showed significantly higher abundance in the liver of ad libitum fed birds at day 8 compared with food-restricted birds. In the brain, TSHbeta mRNA level tended to be lower in food-restricted quails on day 8 compared with controls. Furthermore, TRalpha expression was lower in the brain of food-restricted birds at day 8 compared with birds fed ad libitum. Interestingly, brain D2 mRNA was negatively correlated with plasma T3 levels, tending to increase with the length of food restriction. Overall, our results show that food restriction produced significant effects on circulating thyroid hormones and differentially affected mRNA species in the thyroid hormone signalling pathway. Thus, we conclude that the effects of food restriction observed on growth and metabolism were partly mediated by changes in the endocrine-related factors investigated.