Figure 4.

Conditional STIM1 deficiency alters fuel use and compromises exercise tolerance. (A) Whole-body oxygen consumption, the relationship of energy expenditure to (B) lean mass and (C) whole body weight as well as (D), total activity, (E) food consumption, and (F) respiratory exchange ratio assessed over 48 h in STIM1^−/− v. STIM1^fl/fl fed a chow diet after receiving TMX at 12–15 weeks of age (n = 9–10). (G) Time, and (H) distance to exhaustion, and (I) respiratory exchange ratio in response to a high-intensity exercise test (n = 5–6). (J) Traces of substrate utilization by STIM1^fl/fl (left) and iSTIM1^−/− (right) mice and (K) a bar graph depicting the time to the crossover point where carbohydrate utilization exceeds fat utilization during exercise (n = 5–7). (L) Blood lactate prior to and immediately after 15′ of exercise (n = 5–7). (M) Western blots and (N) quantification of phosphoproteins normalized to total protein in gastrocnemius muscles immediately after 15′ of exercise (n = 5–7). All data represent mean ± SEM. Data in (A, D-I, K, L, and N) were analyzed using Student's two-tailed t-test. ∗p ≤ 0.05, ∗∗p ≤ 0.01, and ∗∗∗p ≤ 0.001. n represents biological replicates.