Table 2.

Impact of extrahepatic tissues on bilirubin metabolism

Tissue	Observations	Reference
Small intestine	UGT1A1 was highly expressed in small intestine	Nakamura et al., 2008 Tukey and Strassburg, 2000
	Transplantation of normal small intestine to Gunn rat resulted in decreased serum bilirubin levels	Takahashi et al., 1994 Medley et al., 1995
	Developmental expression of intestinal UGT1A1 correlated to serum bilirubin levels in neonatal hUGT1 mice	Fujiwara et al., 2010
	Specific induction of UGT1A1 in small intestine resulted in a decrease in serum bilirubin levels in hUGT1 mice	Fujiwara et al., 2012
	Breast milk suppressed UGT1A1 expression in small intestine of BMJ mice	Fujiwara et al., 2012
	Knockout of liver Ugt1 locus and the Ugt1a1 gene resulted in only a slight increase in TSB levels	Chen et al., 2013
Skin	UGT1A1 was expressed in human skin and human keratinocyte HaCaT cells	Sumida et al., 2013 Peters et al., 1987
	Expression of UGT1A1 was higher in the skin than that in the liver in neonatal hUGT1 mice	Sumida et al., 2013
	UVB induced skin UGT1A1 and decreased serum bilirubin levels in hUGT1 mice	Sumida et al., 2013