Vitamin D and Healthy Aging: Establishing the Sled Dog Sentinel for the Circumpolar North

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PROJECT SUMMARY Our long-term goal is to establish levels of vitamin D intake and vitamin D sufficiency for humans and canines living in the circumpolar north. Our overall objectives are to (i) define how chronological age impacts vitamin D status and morphological changes in the sled dog model, and (ii) determine the effects of salmon on vitamin D status and markers of metabolic syndrome and insulin signaling in old and young sled dogs. With their shorter lifespan and parallel biochemical pathways, dogs have become an important biomedical research model for both dementia related impairments and insulin signaling. Sled dogs, in particular, are an important human health model in the circumpolar north because they are part of the traditional subsistence lifestyle. Over the past 100 years, societies in North America and elsewhere in the world have transitioned towards the so-called “Western diet,” composed primarily of highly processed “factory foods”. This nutritional transition has been identified as playing a central role in current public health issues in peoples of the far north. Historically, Alaska Natives (AN) were able to consume adequate vitamin D from traditional foods, most notably from salmon, despite living at latitudes that prevent the synthesis of vitamin D in the skin from sunlight for much of the year. This is also true for village sled dogs. With the shift away from traditional foods, peoples of the circumpolar north are experiencing increased prevalence of vitamin D deficiency. Yup’ik children are developing rickets at higher rates while elders consistently exhibit higher serum vitamin D levels; this is a stark contrast to national trends. It is estimated that over 1 billion people worldwide are deficient in vitamin D. Vitamin D deficiency has been implicated in a multitude of diseases, including metabolic disorders, aging, and cognitive impairments. Still, little consensus has been reached on recommended intake to achieve adequate levels in humans and even less so in dogs. Therefore, there is a critical need to develop better understanding of vitamin D intake in the circumpolar north, where there is the highest risk of deficiency, to understand the links between diet, age, vitamin D status, and metabolic health. This study will begin to fill the gaps in knowledge pertaining to vitamin D deficiency with the following specific aims: 1) Correlate markers of brain aging with vitamin D status in an animal model of the circumpolar north and 2) Determine the effects of increased vitamin D from wild Alaska salmon on biomarkers of insulin signaling and metabolic health. Volume and morphology changes in brain gray and white matter will be assessed with magnetic resonance imaging in old and young dogs and correlated with serum vitamin D status. In addition to other markers of metabolic syndrome, the insulin responsive glucose transporter (GLUT4) on peripheral blood mononuclear cells will be measured in response to insulin in sled dogs of varying ages before and after a dietary supplementation with wild Alaskan Salmon. The expected outcomes of this project will lend to the insufficient data pertaining to vitamin D requirements, status, and health outcomes in populations that rely solely on dietary intake to obtain sufficiency.