Hair corticosterone measurement in mouse models of type 1 and type 2 diabetes mellitus

Abstract

In diabetes, glucocorticoid secretion increases secondary to hyperglycemia and is associated with an extensive list of disease complications. Levels of cortisol in humans, or corticosterone in rodents, are usually measured as transitory biomarkers of stress in blood or saliva. Glucocorticoid concentrations accumulate in human or animal hair over weeks and could more accurately measure the cumulative stress burden of diseases like chronic diabetes. In this study, corticosterone levels were measured in hair in verified rodent models of diabetes mellitus. To induce type 1 diabetes, C57BL/6J mice were injected with streptozotocin and blood and hair samples were collected 28days following induction. Leptin receptor deficient (db/db) mice were used as a spontaneous model of type 2 diabetes and blood and hair samples were collected at 8weeks of age, after the development of hyperglycemia and obesity. Corticosterone levels from serum, new growth hair and total growth hair were analyzed using an enzyme immunoassay. Corticosterone levels in new growth hair and serum were significantly elevated in both models of diabetes compared to controls. In contrast, corticosterone levels in old hair growth did not differ significantly between diabetic and non-diabetic animals. Thus, hair removal and sampling of new hair growth was a more sensitive procedure for detecting changes in hair corticosterone levels induced by periods of hyperglycemia lasting for 4weeks in mice. These results validate the use of hair to measure long-term changes in corticosterone induced by diabetes in rodent models. Further studies are now needed to validate the utility of hair cortisol as a tool for measuring the stress burden of individuals with diabetes and for following the effects of long-term medical treatments.

Keywords: Corticosterone; Diabetes; Hair; Mouse; Streptozotocin.

Figure 1

Blood glucose (mg/dl) and body weight over time for diabetic and non-diabetic control mice. Panel A shows glucose levels over days following injection of A) Veh (n = 12) or STZ (n = 11). Panel B shows glucose levels in db/+ non-diabetic (n = 8) and db/db diabetic (n = 8) mice as a function of age. Body weights (mean ± SEM) are shown for the same mice injected with C) Veh (n = 12) or STZ (n = 11), and D) db/+ non-diabetic (n = 8) and db/db diabetic (n = 8) mice. Asterisks indicate significant difference between groups at each timepoint (***p < 0.001, ****p < 0.0001).

Figure 2

Serum corticosterone levels (mean ± SEM) for diabetic and non-diabetic control mice. A) Mice injected with Veh (n = 10) or STZ (n = 9) at 28 days post-injection, and B) db/+ non-diabetic (n = 8) and db/db diabetic (n = 8) mice at 9 weeks of age. Asterisks indicate significant difference between groups (**p < 0.01, ***p < 0.001).

Figure 3

Hair corticosterone (mean ± SEM) for diabetic and non-diabetic control mice. A) Mice injected with Veh or STZ: Day 0 (Veh n = 11, STZ n = 11), Day 28 old hair growth (Veh n = 11, STZ n = 10), Day 28 new hair growth (Veh n = 9, STZ n = 8), and B) db/+ non-diabetic db/db diabetic mice: Day 0 (db/+ n = 7, db/db n = 8), Day 28 old hair growth (db/+ n = 7, db/db n = 7), Day 28 new hair growth (db/+ n = 8, db/db n = 7). Groups (STZ and Veh, db/+ and db/db) were statistically compared by two-way ANOVA. Ampersand indicates significant difference compared to corresponding control group (&&& p < 0.001). Number sign indicates significant difference between new and old hair growth at day 28 (### p < 0.001). Asterisks indicate significant difference between day 0 and day 28 new hair growth (*p < 0.05, ***p < 0.001).