Thermoneutrality induces vascular dysfunction and impaired metabolic function in male Wistar rats: a new model of vascular disease

Abstract

Objective: Cardiovascular disease is of paramount importance, yet there are few relevant rat models to investigate its pathology and explore potential therapeutics. Housing at thermoneutral temperature (30 8C) is being employed to humanize metabolic derangements in rodents. We hypothesized that housing rats in thermoneutral conditions would potentiate a highfat diet, resulting in diabetes and dysmetabolism, and deleteriously impact vascular function, in comparison to traditional room temperature housing (22 8C).Methods: Male Wistar rats were housed at either room temperature or thermoneutral temperatures for 16 weeks on either a low or high-fat diet. Glucose and insulin tolerance tests were conducted at the beginning and end of the study. At the study's conclusion, vasoreactivity and mitochondrial respiration of aorta and carotid were conducted. Results:We observed diminished vasodilation in vessels from thermoneutral rats (P < 0.05), whereas high-fat diet had no effect. This effect was also observed in endothelium-denuded aorta in thermoneutral rats (P < 0.05). Vasoconstriction was significantly elevated in aorta of thermoneutral rats (P < 0.05). Diminished nitric oxide synthase activity and nitrotyrosine, and elevated glutathione activity were observed in aorta from rats housed under thermoneutral conditions, indicating a climate of lower nitric oxide and excess reactive oxygen species in aorta. Thermoneutral rat aorta also demonstrated less mitochondrial respiration with lipid substrates compared with the controls (P < 0.05). Conclusion:Our data support that thermoneutrality causes dysfunctional vasoreactivity, decreased lipid mitochondrial metabolism, and modified cellular signaling. These are critical observations as thermoneutrality is becoming prevalent for translational research models. This new model of vascular dysfunction may be useful for dissection of targetable aspects of cardiovascular disease and is a novel and necessary model of disease.

Perivascular adipose tissue remodeling impairs vasoreactivity in thermoneutral-housed rats

“…Some studies show no difference in body weight between rats housed at RT and TN (46), while others show increased diet-dependent adiposity at TN temperatures (47). In our previous study utilizing housing temperature to induce vascular dysfunction, we report that diet had no impact on vascular function (28).…”

“…Sample size per group was determined based on previous data and experimental design (28). Body temperature was taken superficially and elevated temperature was achieved in those housed at thermoneutral conditions as compared with those housed at room temperature (30.4 ± 0.1°C vs. 27.4 ± 0.1°C, p<0.001, data not shown).…”