Low-dose UV radiation before running wheel access activates brown adipose tissue

Abstract

In previous preclinical studies, low (non-burning) doses of UV radiation (UVR) limited weight gain and metabolic dysfunction in mice fed with a high-fat diet. Here, we explored the effects of low-dose UVR on physical activity and food intake and mechanistic pathways in interscapular brown adipose tissue (iBAT). Young adult C57Bl/6J male mice, housed as individuals, were fed a high-fat diet and exposed to low-dose UVR (sub-oedemal, 1 kJ/m2 UVB, twice-a-week) or ‘mock’ treatment, with or without running wheel access (2 h, for ‘moderate’ physical activity) immediately after phototherapy. There was no difference in distance run in mice exposed to UVR or mock-treated over 12 weeks of exposure to running wheels (P = 0.14). UVR (alone) did not significantly affect food intake, adiposity, or signs of glucose dysfunction. Access to running wheels increased food intake (after 10 weeks, P ≤ 0.02) and reduced gonadal white adipose tissue and iBAT mass (P ≤ 0.03). Body weight and hepatic steatosis were lowest in mice exposed to UVR with running wheel access. In the iBAT of mice exposed to UVR and running wheels, elevated Atgl, Cd36, Fasn, Igf1, Pparγ, and Ucp1 mRNAs and reduced CD11c on F4-80 + MHC class II+ macrophages were observed, while renal Sglt2 mRNA levels were increased, compared to high-fat diet alone (P ≤ 0.03). Blood levels of 25-hydroxyvitamin D were not increased by exposure to UVR and/or access to running wheels. In conclusion, when combined with physical activity, low-dose UVR may more effectively limit adiposity (specifically, body weight and hepatic steatosis) and modulate metabolic and immune pathways in iBAT.

Investigating the Potential for Ultraviolet Light to Modulate Morbidity and Mortality From COVID-19: A Narrative Review and Update

“…An important consideration here is the potential for outdoor activity to be a confounder in these studies. We have also observed synergistic interactions in the combined effects of physical activity and UV light to improve metabolic health, with reduced liver steatosis and beneficial effects on metabolic and immune pathways observed in brown adipose tissue of mice allowed access to running wheels following exposure to low dose UV light (147). Some commentators also suggest outdoor activity may be a means of improving vitamin D status through the combined effects of physical activity and skin production of vitamin D in response to exposure to UV light (148).…”

Metabolic dysfunction induced by a high‐fat diet modulates hematopoietic stem and myeloid progenitor cells in brown adipose tissue of mice

“…Bone marrow was isolated from long bones (femurs and tibias) and red blood cells lysed 15 . A single‐cell suspension of vascular stromal cells was isolated from minced iBAT (using scissors) digested for 90 min with collagenase IV (3 mg mL –1 ; Worthington, Lakewood NJ, USA) at 37 ºC under gentle agitation 16,37 . We have previously tested the activity of collagenase IV by “digesting” bone marrow with this enzyme, observing no significant effects on extracellular marker expression by DC subsets and precursors 38 .…”

“…15 A single-cell suspension of vascular stromal cells was isolated from minced iBAT (using scissors) digested for 90 min with collagenase IV (3 mg mL -1 ; Worthington, Lakewood NJ, USA) at 37°C under gentle agitation. 16,37 We have previously tested the activity of collagenase IV by "digesting" bone marrow with this enzyme, observing no significant effects on extracellular marker expression by DC subsets and precursors. 38 In adipose tissue, both immune cells and HSPCs reside in the vascular stromal cell fraction (nonadipose cells), 39 including cells such as adipose-derived stem/stromal cells, endothelial precursor cells, endothelial cells, macrophages, smooth muscle cells, lymphocytes, pericytes and preadipocytes (among others).…”

Exposomes and metabolic health through a physical activity lens: a narrative review

“…These exposures modulate metabolic health in differing directions, with harms described for air pollution, and some benefits for lowlevel (non-burning) sun exposure. Similar to physical activity, both exposures affect metabolic processes in a variety of tissues, acting through an array of interacting mediators that affect pro-inflammatory and oxidative stress pathways, in addition to other novel effects on liver lipid turnover and the gut microbiome , Feng et al 2020, Gorman 2020, Vogel et al 2020. How these exposures -and their induced mediators -interplay with physical activity to affect metabolic health is yet to be fully defined, and further research is needed to determine the best conditions in which to undertake the exercise for prevention and treatment of metabolic dysfunction.…”