Biochemical Foundations of Health and Energy Conservation in Hibernating Free-ranging Subadult Brown Bear Ursus arctos.

Brown bears (Ursus arctos) hibernate for 5-7 months without eating, drinking, urinating, and defecating at a metabolic rate of only 25% of the summer activity rate. Nonetheless, they emerge healthy and alert in spring. We quantified the biochemical adaptations for hibernation by comparing the proteome, metabolome, and hematological features of blood from hibernating and active free-ranging subadult brown bears with a focus on conservation of health and energy. We found that total plasma protein concentration increased during hibernation, even though the concentrations of most individual plasma proteins decreased, as did the white blood cell types. Strikingly, antimicrobial defense proteins increased in concentration. Central functions in hibernation involving the coagulation response and protease inhibition, as well as lipid transport and metabolism, were upheld by increased levels of very few key or broad specificity proteins. The changes in coagulation factor levels matched the changes in activity measurements. A dramatic 45-fold increase in sex hormone-binding globulin levels during hibernation draws, for the first time, attention to its significant but unknown role in maintaining hibernation physiology. We propose that energy for the costly protein synthesis is reduced by three mechanisms as follows: (i) dehydration, which increases protein concentration without de novo synthesis; (ii) reduced protein degradation rates due to a 6 °C reduction in body temperature and decreased protease activity; and (iii) a marked redistribution of energy resources only increasing de novo synthesis of a few key proteins. The comprehensive global data identified novel biochemical strategies for bear adaptations to the extreme condition of hibernation and have implications for our understanding of physiology in general.

Downregulation of platelet activation markers during long-term immobilization.

Immobilization and sedentary lifestyle are risk factors for venous thromboembolism and cardiovascular disease, yet little is known about platelet function during long-term physical inactivity. Our aim was to investigate platelet activation markers and their coupling to standardized immobilization: platelet-derived growth factor (PDGF-BB) and P-selectin. We studied 15 healthy females participating in the Women International Space simulation for Exploration study. Following a 20-day ambulatory control period, the subjects underwent 60 days of bed rest in head-down tilt position (-6°) 24 hours a day, finalized by 20 days of recovery. The subjects were randomized into two groups during bed rest: a control group (n = 8) that remained physically inactive and an exercise group (n = 7) that participated in both supine resistance and aerobic exercise training. Blood samples for the analysis of platelet activation markers were collected at baseline (5 days before bed rest), after 44 days of bed rest and 8 days into the recovery period. Compared to baseline, the levels of P-selectin and PDGF-BB decreased after bed rest (by 55%, p = 0.01 and 73%, p < 0.03, respectively) and remained decreased in the recovery period (by 76%, p < 0.001 and 78%, p < 0.02, respectively, compared to baseline). Platelet count (baseline value for the exercise group 260 000/µl ± 34 000 and baseline value for the control group 210 000/µl ± 30 000) did not change during the bed rest study (two-way repeated measurements ANOVA, p = ns). There were no statistical differences between the physically inactive and the exercise group. During long-term immobilization, a known risk factor for thrombosis, the levels of P-selectin and PDGF-BB decreased. Our findings indicate downregulation of platelet activation during immobilization.

Angiographic morphology impacts outcomes in STEMI patients with LAD occlusion.

OBJECTIVES AND BACKGROUND: Acute proximal occlusion of the left anterior descendent coronary artery (LAD) is a critical medical condition often leading to heart failure and death. Our objective was to investigate how additional angiographic findings might influence prognosis. METHODS: In a single center setting by using consecutive data from the Swedish angiography and angioplasty registry (SCAAR), we identified all patients with acute myocardial infarction (AMI) related to the proximal LAD referred for primary coronary angioplasty. Clinical and angiographic data were collected from January 2004 to December 2008. RESULTS: In the study period, 359 patients (mean age 67.9 ± 12.3 years, 111 women) were identified as having proximal LAD-related culprit lesion. Follow-up was up to 5.5 years. Compared to patients with LAD occlusion only, having both a small conus branch (<0.5 mm in diameter) and an occluded first septal perforator was associated with increased risk of death after adjustment for age, diabetes mellitus and prior AMI (hazard ratio 4.5, 95% CI; 1.1-18, P = 0.033). A small conus branch in itself was not important. Multivessel coronary artery disease in addition to occlusion of the first septal perforator branch and having a small conus branch was also associated with increased risk of death (hazard ratio 5.2, 95% CI; 1.3-20), P = 0.018). CONCLUSIONS: In patients with STEMI because of a proximal LAD lesion treated by primary PCI, the combination of a small conus branch and an occluded first septal perforator branch is associated with a poorer outcome. Additional presence of multivessel coronary artery disease further aggravates outcome.

Effect of prolonged standardized bed rest on cystatin C and other markers of cardiovascular risk.

BACKGROUND: Sedentary lifestyle is associated with coronary artery disease but even shorter periods of physical inactivity may increase cardiovascular risk. Cystatin C is independently associated with cardiovascular disease and our objective was to investigate the relation between this novel biomarker and standardized bed rest. Research of immobilization physiology in humans is challenging because good biological models are in short supply. From the Women International Space simulation for Exploration study (WISE) we studied markers of atherosclerosis and kidney function, including cystatin C, in a standardized bed rest study on healthy volunteers. Fifteen healthy female volunteers participated in a 20-day ambulatory control period followed by 60 days of bed rest in head-down tilt position (-6°) 24 h a day, finalized by 20 days of recovery. The subjects were randomized into two groups during bed rest: a control group (n = 8) that remained physically inactive and an exercise group (n = 7) that participated in both supine resistance and aerobic exercise training. RESULTS: Compared to baseline values there was a statistically significant increase in cystatin C in both groups after bed rest (P < 0.001). Glomerular filtration rate (GFR), calculated by both cystatin C and Cockcroft-Gault equation, decreased after bed rest while there were no differences in creatinine or creatine kinase levels. CRP did not change during bed rest in the exercise group, but there was an increase of CRP in the control group during recovery compared to both the baseline and the bed rest periods. The apo-B/apo-Ai ratio increased during bed rest and decreased again in the recovery period. Subjects experienced a small but statistically significant reduction in weight during bed rest and compared to baseline weights remained lower at day 8 of recovery. CONCLUSION: During and following prolonged standardized bed rest the concentrations of several clinically relevant cardiovascular risk markers change.

Brown bears (Ursus arctos) seem resistant to atherosclerosis despite highly elevated plasma lipids during hibernation and active state.

Hibernation is an extreme physiological challenge for the brown bear (Ursus arctos) in which metabolism is based mainly on lipids. The study objective was to compare plasma lipids in hibernating and active free-ranging brown bears and relate them to arterial histopathology. Blood was drawn from seven immobilized free-ranging brown bears (three females, 2-3 years old) during hibernation in February and from the same bears while active in June and analyzed by enzymatic and automated hematology methods within 48 hours of sampling. Left anterior descending coronary arteries and aortic arches from 12 bears (six females, 1.5-12 years old) killed in hunting were examined by histopathology. Total plasma cholesterol decreased from hibernation to the active period (11.08 ± 1.04 mmol/L vs. 7.89 ± 1.96 mmol/L, P= 0.0028) as did triglyceride (3.16 ± 0.62 mmol/L vs. 1.44 ± 0.27 mmol/L, P= 0.00012) and LDL cholesterol (4.30 ± 0.71 mmol/L vs. 2.02 ± 1.03 mmol/L, P= 0.0075), whereas HDL cholesterol was unchanged. No atherosclerosis, fatty streaks, foam cell infiltration, or inflammation were seen in any arterial samples. Brown bears tolerate elevated cholesterol levels, obesity, physical inactivity, and circulatory slow flow during hibernation without signs of -atherosclerosis. This species might serve as a reverse translational model for atherosclerosis resistance.