Effect of short- and long-term adrenergic stimulation on the expression of the uncoupling protein thermogenin (UCP) in brown adipocyte precursor cells differentiating in culture

Brown adipose tissue (BAT) is a thermogenic organ present in most mammals. During cold acclimation, BAT recruits (a process involving both the proliferation and differentiation of brown adipocyte precursor cells) and becomes functionally more active. In-vivo and recent in-vitro experiments stongly suggest a central role for the neurotransmittor noradrenaline in the regulation of this cold-induced BAT recruitment. We are currently investigating the effects of noradrenaline on mouse brown adipocyte precursor cells differentiating in culture in order to further investigate this hypothesis. Differentiating mouse brown adipocyte precursor cells were treated from culturing day 7 with noradrenaline (10 μM) in the short-term (24h; acute) or in the longer-term (daily additions for up to 5 days; chronic) and the expression of UCP determined by immunoblotting on culturing days 8 - 12. Acute adrenergic stimulation led to maximal UCP expression on day 8 and thereafter noradrenaline-induced UCP expression declined suggesting a thermogenic dedifferentiation of the cells with time in culture. In clear contrast, chronic adrenergic stimulation led to ever increasing UCP expression up to culturing day 12. Thus, chronic adrenergic stimulation not only prevents but also reverses the apparent thermogenic dedifferentiation which occurs in mouse brown adipocyte cultures.