Noradrenergic stimulation of mitochondriogenesis in brown adipocytes differentiating in culture

Abstract

The ability of adrenergic agents to promote the differentiation and especially the mitochondriogenesis of brown fat precursor cells, grown in culture, was investigated. These cells begin to differentiate during the days preceding confluence. We found here that, already during the early growth phase, the cultures (essentially precursor cells and preadipocytes at this stage) show increased cyclic AMP (cAMP) levels when acutely stimulated with norepinephrine (NE). The cultured cells were therefore chronically treated with NE up to the time of confluence, and their cytochrome-c oxidase activity was measured as an index of mitochondriogenesis. Chronic NE treatment resulted in an increased cytochrome-c oxidase activity of the cells at confluence. This effect was reproduced by selective activation of adenylate cyclase with cholera toxin, suggesting that the NE effect was exerted through an increase in cAMP. Ascorbate (added with NE as an antioxidant) had in itself a positive effect, both on final cell number and on cytochrome-c oxidase activity. It is concluded that NE, working through beta-adrenergic receptors, can stimulate mitochondriogenesis in brown fat cells through a direct effect on the cells, in accordance with the suggestion (based on in vivo experiments) that NE accelerates, rather than initiates, the differentiation process.

β3- and α1-Adrenergic Erk1/2 Activation Is Src- but Not Gi-mediated in Brown Adipocytes

“…the external factor that physiologically influences the processes of proliferation, differentiation, and survival in a specific cell type. As these features are under adrenergic control in brown adipocytes (11,15,17,30,31), it is consequential that in these cells, Erk1/2 activation is also under adrenergic control. That Erk1/2 activation is thus induced via distinct, tissue-specific pathways in cells from different tissues underlines the generality of the Erk1/2 pathway for control of proliferation, differentiation, and survival.…”

Adipose tissue cellularity and apoptosis after intracerebroventricular injections of leptin and 21 days of recovery in rats

“…27 Increasing sympathetic output to BAT by exposure to low temperature increased the Bcl-2/Bax protein ratio 26 and reduced apoptotic cell death of brown adipocytes. [47][48][49] This was also mimicked by the addition of noradrenaline to brown adipocytes in culture. 26,49 The present study similarly suggests that leptin administration increases signals, such as sympathetic outflow, to the RP and EPI white fat pads and BAT to upregulate UCP and/or the Bcl-2/Bax ratio in these tissues.…”

β-Adrenoceptors, but not α-adrenoceptors, stimulate AMP-activated protein kinase in brown adipocytes independently of uncoupling protein-1

“…Cell isolation and cell culture of mouse brown adipocytes Brown fat precursor cells were isolated essentially as described previously [21,22]. Cells were grown in DMEM (4.5 g glucose/l) containing newborn calf serum (10%, v/v), insulin (2.4 nmol/l), HEPES (10 mmol/l), L-glutamine (4 mmol/l), penicillin (50 IU/ml), streptomycin (50 μg/ml) and sodium ascorbate (25 μg/ml) under 8% CO 2 at 37°C.…”

“…Cells were grown in DMEM (4.5 g glucose/l) containing newborn calf serum (10%, v/v), insulin (2.4 nmol/l), HEPES (10 mmol/l), L-glutamine (4 mmol/l), penicillin (50 IU/ml), streptomycin (50 μg/ml) and sodium ascorbate (25 μg/ml) under 8% CO 2 at 37°C. After 5 days in culture, the brown adipocyte precursor cells spontaneously convert from displaying a fibroblast-like morphology to acquiring the typical multilocular lipid droplets seen in mature brown adipocytes; this conversion occurs at the time of cellular confluence [21,22]. In these cells, spontaneous induction of Adrb3 mRNA reaches a steady-state level at day 5 that corresponds with the ability of noradrenaline to induce the expression of Ucp1, the gene encoding the most specific brown adipocyte differentiation marker, UCP1 [17].…”