Liver is the source of FGF21 elevation upon dietary restriction and liver damage. The FGF21 expression level was analyzed by quantitative PCR in the indicated mouse tissues under different conditions. A : Increase of FGF21 mRNA levels specifically in mouse livers after prolonged starvation for 48 hrs. mRNA levels are expressed as fold changes relative to the internal β-actin levels in the respective tissues. WAT: white adipose tissue. BAT: brown adipose tissue. Data are shown as mean ± sd, *p (n = 6) <0.05. B : Induction of hepatic FGF21 mRNA in the liver after PHx. mRNA levels at different time lapses after PHx are expressed as fold changes relative to that before PHx. *p <0.05 (n = 3 for each data point). Inset: the corresponding serum FGF21 protein levels were determined by soluble KLB (sKLB) pulldown and western blotting analyses as described in the Method section. C : Changes of hepatic KLB mRNA levels after PHx. D : Changes of hepatic FGFR4 mRNA levels after PHx. Total RNA samples for analyses of KLB and FGFR4 expression are the same as for FGF21 in (B).