In human adults, adiponectin is the most abundant protein hormone found in plasma. During adulthood, adiponectin mRNA is expressed exclusively in adipose tissue and its plasma concentration is inversely related with body fat mass and insulin sensitivity. Adiponectin plays a variety of roles, including stimulation of vasodilation, oxidation of triglycerides in muscle, and suppression of glucose production in liver.
Far less is known about adiponectin during fetal life, but fetal expression in non-adipose tissues of mesodermal and ectodermal origin was reported recently. The major objective of the present study was to investigate the mRNA expression of adiponectin and its receptors by qRT-PCR in fetal sheep, a recognized model of human fetal life. Adiponectin mRNA levels were found at day 135 of fetal life in perirenal adipose tissue and this expression was 2-fold higher than in adult ewes.
No significant mRNA expression was found at day 50 in muscle or other tissues surveyed (heart, intestine, liver, fetal membrane, brain, kidney, placenta, and lung). Adiponectin Receptor-1 (AdipoR1), whose mRNA is most abundantly found in skeletal muscle in adult humans, was most abundant in placenta, liver and muscle. Its mRNA levels declined by 50% in liver from day 50 to day 135, but remained unchanged in placenta and muscle.
AdipoR1 expression increased 2-fold in muscle from day 135 to adult. Adiponectin Receptor-2 (AdipoR2), whose mRNA is most abundantly expressed in liver in adult humans, was also found in the placenta, liver, and muscle. Its expression declined by 60% in placenta from day 50 to day 135. Skeletal