(a) Glucose tolerance test at room temperature (23°C) and cold (4°C) in Mpc1F/F and Mpc1F/F::Ucp1Cre3–4 months old, N = 5. (b) Insulin tolerance test at room temperature (23°C) in Mpc1F/F and Mpc1F/F::Ucp1Cre, 3–4 months old, N = 6. (c). Representative H and E images of BAT, iWAT, eWAT, and liver from Mpc1F/F and Mpc1F/F::Ucp1Cre mice exposed to 4°C for 6 hr. (d) Gene expression in BAT from Mpc1F/F and Mpc1F/F::Ucp1Cre mice exposed to 4°C for 6 hr. N = 6. (e–g) Energy expenditure, RER, and locomotor activity of Mpc1F/F and Mpc1F/F::Ucp1Cre mice at 6°C. N = 4.