Fig. 1Stress loading on rats. We exposed rats to a cat in an experimental box to produce mental stress. The box was composed of two separate but adjacent compartments into which the cat and the rats were placed. Rats were exposed to the cat for 60 minutes for the stress-loading test. We measured glucose levels with a glucometer at 5-minute intervals during the test.
Fig. 2Variables for analysis of pattern of glucose fluctuation induced by stress. Gpeak, peak glucose level; ΔG, glucose increment caused by stress; ΔGAUC, total amount of hyperglycemic change caused by stress; Tpeak, time to reach peak glucose level; Ttotal, time to return to the baseline glucose level from the beginning of the stressor exposure; Grinc(peak), increasing rate of glucose from beginning to peak (mg/dL/min); Grinc(15 min, 30 min, and 60 min), increasing rate of glucose from beginning to 15, 30 to 60 minutes points, respectively; Grdec, decreasing rate of glucose from peak level to baseline level. aGrinc(15 min), bGrinc(30 min), cGrinc(60 min), dGrinc(peak), eGrdec.
Fig. 3Patterns of glucose fluctuation induced by acute predator stress with cat exposure in type 1 diabetes model (T1D), obese type 2 diabetes model (OT2D), and nonobese type 2 diabetes model (NOT2D). Pattern A, fast & slow, in which glucose was rapidly increased by the acute stress and slowly decreased after reaching peak level; pattern B, fast & fast, in which glucose rapidly increased and also rapidly decreased; and pattern C, slow & slow, in which glucose slowly increased and also slowly decreased. aRM ANOVA, repeated measures analysis of variance test.
Fig. 4(A-D) Comparison of variables associated with pattern of glucose fluctuation induced by acute predator stress. Values are presented as mean±standard deviation. T1D, type 1 diabetes model; OT2D, obese type 2 diabetes model; NOT2D, nonobese type 2 diabetes model; Gpeak, peak glucose level (mg/dL); ΔG, glucose increment caused by stress (mg/dL); ΔGAUC, total amount of hyperglycemic change caused by stress (mg/dL/min); Tpeak, time to reach peak glucose level; Ttotal, time to return to the baseline glucose level from the beginning of the stressor exposure. Independent two-tailed Student t-test. aP<0.05 T1D vs. OT2D, bP<0.01 OT2D vs. NOT2D, cP<0.05, dP<0.05, eP<0.01 T1D vs. NOT2D.
Table 1Characteristics of glucose fluctuation induced by acute predator stress in three diabetes models before and after the development of diabetes