Bert B. Boyer

MOLECULAR AND METABOLIC ASPECTS OF MAMMALIAN HIBERNATION

713eat seeds from cones and are toolarge to use the subnivian space; forthese animals, winter can be a longseason without foraging opportuni-ties, and they have therefore evolvedthe ability to pass winter by while ina torpid state of lethargy.A highly regulated sequence ofphysiological events beginningmonths in advance of winter coordi-nates entrance into the suspendedstate of animation known as hiber-nation. However, with the exceptionof bears, which become only moder-ately hypothermic, no hibernatingmammal remains deeply hypother-mic for longer than several weeks.Instead, for reasons that are not yetknown, they expend significantamounts of energy to periodicallyrewarm back to normal body tem-peratures for less than a day beforerecooling.The seasonal changes in body tem-perature that occur in an arctic groundsquirrel (

Differential regulation of uncoupling protein gene homologues in multiple tissues of hibernating ground squirrels

Nonshivering thermogenesis in brown adipose tissue (BAT) provides heat through activation of a mitochondrial uncoupling protein (UCP1), which causes futile electron transport cycles without the production of ATP. Recent discovery of two molecular homologues, UCP2, expressed in multiple tissues, and UCP3, expressed in muscle, has resulted in investigation of their roles in thermoregulatory physiology and energy balance. To determine the expression pattern of Ucp homologues in hibernating mammals, we compared relative mRNA levels of Ucp1, -2, and -3 in BAT, white adipose tissue (WAT), and skeletal muscle of arctic ground squirrels (Spermophilus parryii) hibernating at different ambient and body temperatures, with levels determined in tissues from ground squirrels not in hibernation. Here we report significant increases in mRNA levels for Ucp2 in WAT (1. 6-fold) and Ucp3 in skeletal muscle (3-fold) during hibernation. These results indicate the potential for a role of UCP2 and UCP3 in thermal homeostasis during hibernation and indicate that parallel mechanisms and multiple tissues could be important for nonshivering thermoregulation in mammals.Nonshivering thermogenesis in brown adipose tissue (BAT) provides heat through activation of a mitochondrial uncoupling protein (UCP1), which causes futile electron transport cycles without the production of ATP. Recent discovery of two molecular homologues, UCP2, expressed in multiple tissues, and UCP3, expressed in muscle, has resulted in investigation of their roles in thermoregulatory physiology and energy balance. To determine the expression pattern of Ucp homologues in hibernating mammals, we compared relative mRNA levels of Ucp1, -2, and -3 in BAT, white adipose tissue (WAT), and skeletal muscle of arctic ground squirrels ( Spermophilus parryii) hibernating at different ambient and body temperatures, with levels determined in tissues from ground squirrels not in hibernation. Here we report significant increases in mRNA levels for Ucp2 in WAT (1.6-fold) and Ucp3 in skeletal muscle (3-fold) during hibernation. These results indicate the potential for a role of UCP2 and UCP3 in thermal homeostasis during hibernation and indicate that parallel mechanisms and multiple tissues could be important for nonshivering thermoregulation in mammals.

The Center for Alaska Native Health Research Study: a community-based participatory research study of obesity and chronic disease-related protective and risk factors

Objectives. To describe the background, approach and general results of the Center for Alaska Native Health Research (CANHR) study. Study Design. This was a cross-sectional Community-Based Participatory Research (CBPR) study with one tribal group to assess risk and protection for obesity and the risk factors related to chronic disease, diabetes and cardiovascular disease. Methods. A combination of biological, genetic, nutritional and psychosocial measurements were taken on 922 Alaska Native participants in ten communities in Southwestern Alaska. The paper reports on data from 753 adult participants. Results. The prevalence of type 2 diabetes is 3.3% in the sample population. Metabolic syndrome is significantly lower among the males and equal for females when compared with Caucasians in the NHANES III sample. Obesity among adults is now at the national average. Risk factors for chronic disease include a shift to a Westernized diet, stress, obesity and impaired fasting glucose and protective factors include high levels of polyunsaturated fatty acid dietary intake. Articles in this issue present specific results in these areas. Conclusions. The data strongly indicate that, in general, Yup`ik people in our study are metabolically healthy and that diet and life style provide a delicate combination of protective and risk factors. The results strongly indicate that solution focused research utilizing primary and secondary prevention strategies may provide evidence for how to intervene to prevent further increases of chronic diseases. Research that focuses on relating the intrinsic strengths of indigenous worldviews and practices with basic research may contribute to positive transformations in community health. The Center for Alaska Native Health Research Study: a community-based participatory research study of obesity and chronic disease-related protective and risk factors. Mohatt GV, Plaetke R, Klejka J, Luick B, Lardon C, Bersamin A, Hopkins S, Dondanville M, Herron J, Boyer B ABSTRACT [full text] back to issue 66(1)] OBJECTIVES: To describe the background, approach and general results of the Center for Alaska Native Health Research (CANHR) study. Study Design. This was a cross-sectional Community-Based Participatory Research (CBPR) study with one tribal group to assess risk and protection for obesity and the risk factors related to chronic disease, diabetes and cardiovascular disease. Methods. A combination of biological, genetic, nutritional and psychosocial measurements were taken on 922 Alaska Native participants in ten communities in Southwestern Alaska. The paper reports on data from 753 adult participants. Results. The prevalence of type 2 diabetes is 3.3% in the sample population. Metabolic syndrome is significantly lower among the males and equal for females when compared with Caucasians in the NHANES III sample. Obesity among adults is now at the national average. Risk factors for chronic disease include a shift to a Westernized diet, stress, obesity and impaired fasting glucose and protective factors include high levels of polyunsaturated fatty acid dietary intake. Articles in this issue present specific results in these areas. Conclusions. The data strongly indicate that, in general, Yup`ik people in our study are metabolically healthy and that diet and life style provide a delicate combination of protective and risk factors. The results strongly indicate that solution focused research utilizing primary and secondary prevention strategies may provide evidence for how to intervene to prevent further increases of chronic diseases. Research that focuses on relating the intrinsic strengths of indigenous worldviews and practices with basic research may contribute to positive transformations in community health.

mRNA stability and polysome loss in hibernating Arctic ground squirrels (Spermophilus parryii).

ABSTRACT All small mammalian hibernators periodically rewarm from torpor to high, euthermic body temperatures for brief intervals throughout the hibernating season. The functional significance of these arousal episodes is unknown, but one suggestion is that rewarming may be related to replacement of gene products lost during torpor due to degradation of mRNA. To assess the stability of mRNA as a function of the hibernation state, we examined the poly(A) tail lengths of liver mRNA from arctic ground squirrels sacrificed during four hibernation states (early and late during a torpor bout and early and late following arousal from torpor) and from active ground squirrels sacrificed in the summer. Poly(A) tail lengths were not altered during torpor, suggesting either that mRNA is stabilized or that transcription continues during torpor. In mRNA isolated from torpid ground squirrels, we observed a pattern of 12 poly(A) residues at greater densities approximately every 27 nucleotides along the poly(A) tail, which is a pattern consistent with binding of poly(A)-binding protein. The intensity of this pattern was significantly reduced following arousal from torpor and undetectable in mRNA obtained from summer ground squirrels. Analyses of polysome profiles revealed a significant reduction in polyribosomes in torpid animals, indicating that translation is depressed during torpor.

Elevated expression of protein biosynthesis genes in liver and muscle of hibernating black bears (Ursus americanus)

We conducted a large-scale gene expression screen using the 3,200 cDNA probe microarray developed specifically for Ursus americanus to detect expression differences in liver and skeletal muscle that occur during winter hibernation compared with animals sampled during summer. The expression of 12 genes, including RNA binding protein motif 3 (Rbm3), that are mostly involved in protein biosynthesis, was induced during hibernation in both liver and muscle. The Gene Ontology and Gene Set Enrichment analysis consistently showed a highly significant enrichment of the protein biosynthesis category by overexpressed genes in both liver and skeletal muscle during hibernation. Coordinated induction in transcriptional level of genes involved in protein biosynthesis is a distinctive feature of the transcriptome in hibernating black bears. This finding implies induction of translation and suggests an adaptive mechanism that contributes to a unique ability to reduce muscle atrophy over prolonged periods of immobility during hibernation. Comparing expression profiles in bears to small mammalian hibernators shows a general trend during hibernation of transcriptional changes that include induction of genes involved in lipid metabolism and carbohydrate synthesis as well as depression of genes involved in the urea cycle and detoxification function in liver.

Utilizing harmonization and common surveillance methods to consolidate 4 cohorts: the Western Alaska Tribal Collaborative for Health (WATCH) study

Background According to health status reports, chronic disease prevalence appears to be rising in western Alaska Native (AN) people, and accurate population-based data are needed. Four cohort studies of western AN people were conducted in the Norton Sound and Yukon-Kuskokwim regions, but none have been large enough to allow reliable estimates of rates of chronic diseases and evaluate their risk factors. Objective In this article, the methods used to combine 4 major cohort studies of rural western AN people are described and the benefits and challenges encountered in combining data and standardizing surveillance methods for these studies are discussed. Design Tribal permission was obtained for each cohort study and the consolidated study. Data from baseline exams were directly combined or harmonized into new variables. Common surveillance methods were developed and implemented to identify incidence and risk factors for cardiovascular disease (CVD) events and type 2 diabetes. Results A cohort of 4,569 western AN participants (2,116 men and 2,453 women), aged 18–95 years, was established to study CVD and diabetes prevalence. Prospective surveillance data over an average 6.7-year follow-up can now be used to study CVD and diabetes incidence and associated risk factors in a subset of 2,754 western AN participants (1,218 men and 1,536 women) who consented to initial surveillance. Conclusions The combined cohort provides statistical power to examine incidence rates and risk factors for CVD and diabetes and allows for analyses by geographic region. The data can be used to develop intervention programmes in these populations and others.

Leptin Prevents Posthibernation Weight Gain But Does Not Reduce Energy Expenditure in Arctic Ground Squirrels

In mammals, leptin reduces energy intake and may increase energy expenditure as a means to maintain body weight and/or adiposity at an appropriate level. Hibernating mammals seasonally alter body mass, food intake, and body composition and, therefore, represent an attractive model for investigating the physiological regulation of changing body mass and adiposity. Previous experiments in our laboratory demonstrated that administration of mouse recombinant leptin reduces food intake and body weight in arctic ground squirrels during prehibernation fattening. In addition, leptin appeared to reduce metabolic efficiency (weight gain per unit of energy intake). This result suggests that reduced food intake alone may not account for the observed weight loss. Here, we describe the effect of a 3-week constant infusion of leptin given to posthibernation arctic ground squirrels on food consumption and energy expenditure. Mouse recombinant leptin (1 mg/ml) was administered through subcutaneously implanted mini-osmotic pumps (10 microliters/hr flow rate). Resting metabolic rate was monitored before and during the 3-week leptin administration period by indirect calorimetry. Body temperature and locomotory activity were monitored continuously by abdominal radiotransmitters. At the end of the leptin administration period, thermogenic capacity was evaluated by measuring brown fat uncoupling protein-1 mRNA and protein levels. Leptin administration resulted in reduced food intake and prevented posthibernation weight gain, but it did not alter any of the measured parameters of energy expenditure.

Associations of obesity with triglycerides and C-reactive protein are attenuated in adults with high red blood cell eicosapentaenoic and docosahexaenoic acids.

Background:N-3 fatty acids are associated with favorable, and obesity with unfavorable, concentrations of chronic disease risk biomarkers.Objective:We examined whether high eicosapentaenoic (EPA) and docosahexaenoic (DHA) acid intakes, measured as percentages of total red blood cell (RBC) fatty acids, modify associations of obesity with chronic disease risk biomarkers.Methods:In a cross-sectional study of 330 Yup’ik Eskimos, generalized additive models (GAM) and linear and quadratic regression models were used to examine associations of BMI with biomarkers across RBC EPA and DHA categories.Results:Median (5th–95th percentile) RBC EPA and DHA were 2.6% (0.5–5.9%) and 7.3% (3.3–8.9%), respectively. In regression models, associations of BMI with triglycerides, glucose, insulin, C-reactive protein (CRP) and leptin differed significantly by RBC EPA and DHA. The GAM confirmed regression results for triglycerides and CRP: at low RBC EPA and RBC DHA, the predicted increases in triglycerides and CRP concentrations associated with a BMI increase from 25 to 35 were 99.5±45.3 mg/dl (106%) and 137.8±71.0 mg/dl (156%), respectively, for triglycerides and 1.2±0.7 mg/l (61%) and 0.8±1.0 mg/l (35%), respectively, for CRP. At high RBC EPA and RBC DHA, these predicted increases were 13.9±8.1 mg/dl (23%) and 12.0±12.3 mg/dl (18%), respectively, for triglycerides and 0.5±0.5 mg/l (50%) and −0.5±0.6 mg/l (−34%), respectively, for CRP.Conclusions:In this population, high RBC EPA and DHA were associated with attenuated dyslipidemia and low-grade systemic inflammation among overweight and obese persons. This may help inform recommendations for n-3 fatty acid intakes in the reduction of obesity-related disease risk.

Sharing results from complex disease genetics studies: a community based participatory research approach

Objectives. Dissemination of research results to communities builds capacity of the community to understand and utilize the results. The objective of this manuscript was to propose a culturally appropriate approach to disseminate complex disease genetics research findings in small Alaska Native communities. Study Design. The Center for Alaska Native Health Research is a community-based participatory research project (CBPR) directed at understanding the interactions between genetic, nutritional and psychosocial risk factors for obesity, diabetes, and cardiovascular disease in Yup`ik Eskimos. Methods. We have consulted with regional healthcare providers, tribal leaders, and university-, local-, and national-institutional review boards to identify potential mechanisms for sharing population-based genetics research results or progress. Results. We propose a six step CBPR-approach to conducting genetics research in isolated identifiable communities. This CPBR-approach includes generating a common research question, determining community interest, recruitment, capacity building, sharing power and control, avoiding group harm, and development of culturally appropriate dissemination procedures. Conclusions. Research scientists and community members should both benefit from population-based genetics research. Although we are just beginning our discussions with regard to sharing genetics research progress and findings, we believe that it is essential move forward as co-researchers in the CBPR enterprise.

Ethical issues in developing pharmacogenetic research partnerships with American Indigenous communities.

Pharmacogenetic research offers the potential to improve the safety and efficacy of drug prescribing. Assuring that the benefits of this research reach indigenous and other medically underserved people is an important justice concern. First, however, a legacy of mistrust, derived from traditional research practices that disempower communities, must be overcome. Linking pharmacogenetic research to collaborative, power‐sharing research partnerships provides a valuable opportunity to develop new and positive precedents for genetic research in indigenous communities.