Session: SAT 1-25-Glucocorticoid Actions & HPA Axis
Poster Board SAT-11
Cryopreserved human hepatocytes were purchased from Celsis in Vitro Technologies (Baltimore, USA). All donors were healthy, male non-diabetic, on no regular medications. Cells were incubated with variable doses of cortisol (0-1000 nM) for 24h in the presence and absence of insulin (5 nM). Insulin signalling gene expression levels were quantified by real-time PCR and western blotting was performed to determine total and phospho PKB/akt protein expression levels. De novo lipogenesis (DNL) was measured by 1-[14C] acetate incorporation in triglyceride.
GC receptor, IRS1/2, Insulin receptor, AKT1/2, ACC1/2, CPT1, DGAT and FAS were all expressed in primary cultures. Incubation with cortisol alone (0-1000 nM) or in combination with insulin did not alter expression of insulin signalling, steroid hormone regulatory genes or those involved in lipid metabolism. However, whilst cortisol treatment did not alter total PKB/akt protein levels, phosphorylation of PKB/akt at serine 473 after insulin stimulation increased following cortisol pre-treatment in a dose dependant manner (1.23-fold [100nM], 1.68-fold [250nM], 2.44-fold [1000nM] vs. control n=4 p<0.05).
Insulin alone (5nM, 24h) had a modest impact upon acetate incorporation into lipid (129.1±13.0%), however, co-incubation with cortisol significantly enhanced insulin stimulated lipogenesis (43.9±12.7% [250nM], 66.13±9.8% [1000nM] vs. control (23.61±10.7%), p<0.05).
We have demonstrated that in primary human hepatocytes GC treatment enhances insulin signalling through increased serine phosphorylation of PKB/akt and that GCs and insulin can act synergistically to promote lipogenesis. Whilst translation to the clinical setting is crucially important, this mechanism may be fundamental in explaining the interaction between GCs and insulin to drive lipogenesis. Furthermore, this may contribute to the pathogenesis of non-alcoholic fatty liver disease with GC excess.
Nothing to Disclose: MN, IB, PMS, LLG, JWT
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