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Regulation of Serum Response Factor and Adiponectin by PPARγ Agonist Docosahexaenoic Acid.

Johnson C, Williams R, Wei JY, Ranganathan G - J Lipids (2010)

Bottom Line: Recent studies indicate that significant health benefits involving the regulation of signaling proteins result from the consumption of omega-3 polyunsaturated fatty acids (ω-3 PUFAs).Thus, we find that the levels of SRF and adiponectin are inversely related in response to treatment with PPARγ agonist DHA.Decreased levels of SRF along with increase in membrane-associated adiponectin could in part mediate the health benefits of DHA.

View Article: PubMed Central - PubMed

Affiliation: Donald W. Reynolds Institute on Aging University of Arkansas for Medical Sciences, 4301 West Markham Street, Slot no. 748, Little Rock, AR 72205, USA.

ABSTRACT
Recent studies indicate that significant health benefits involving the regulation of signaling proteins result from the consumption of omega-3 polyunsaturated fatty acids (ω-3 PUFAs). Serum response factor (SRF) is involved in transcriptional regulation of muscle growth and differentiation. SRF levels are increased in the aging heart muscle. It has not been examined whether SRF is made by adipocytes and whether SRF secretion by adipocytes is modulated by PPARγ agonist DHA. Adiponectin is made exclusively by adipocytes. We and others have previously reported that PUFAs such as DHA increase adiponectin levels and secretion in adipocytes. Here we show that DHA downregulates SRF with a simultaneous upregulation of adiponectin and that both these responses are reversible by PPARγ antagonist. Furthermore, there appears to be a direct relationship between DHA exposure and increased levels of membrane-associated high-density adiponectin, as well as lower levels of membrane-associated SRF. Thus, we find that the levels of SRF and adiponectin are inversely related in response to treatment with PPARγ agonist DHA. Decreased levels of SRF along with increase in membrane-associated adiponectin could in part mediate the health benefits of DHA.

No MeSH data available.


Related in: MedlinePlus

SRF expression in mouse adipocytes treated with DHA. Equal volumes (1-2 ml) of freshly isolated adipocytes were incubated in DMEM-HEPES supplemented with penicillin-streptomycin, containing 1% BSA. Adipocytes were treated as specified control, 25 μM DHA,  25 μM DHA plus 1.5 μM GW9662, or 1.5 μM GW9662 alone for 16 h.  Cells and medium were separated and analyzed for SRF expression. (a)  Western blots of SRF expression in mouse adipocytes. (d) Data in the adjacent bar graph represents one of two experiments done in duplicate(*P < .03, #P < .05).  (b) The blot from part A was probed with β-actin antibody.  (c) Western blot of SRF expression in adipocyte  conditioned medium.  Densitometric analysis of SRF expression in cells, and medium is expressed as a percent of control.  (e) The bar graph represents means of all replicate experiments (*P < .025, #P < .025).
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fig2: SRF expression in mouse adipocytes treated with DHA. Equal volumes (1-2 ml) of freshly isolated adipocytes were incubated in DMEM-HEPES supplemented with penicillin-streptomycin, containing 1% BSA. Adipocytes were treated as specified control, 25 μM DHA, 25 μM DHA plus 1.5 μM GW9662, or 1.5 μM GW9662 alone for 16 h. Cells and medium were separated and analyzed for SRF expression. (a) Western blots of SRF expression in mouse adipocytes. (d) Data in the adjacent bar graph represents one of two experiments done in duplicate(*P < .03, #P < .05). (b) The blot from part A was probed with β-actin antibody. (c) Western blot of SRF expression in adipocyte conditioned medium. Densitometric analysis of SRF expression in cells, and medium is expressed as a percent of control. (e) The bar graph represents means of all replicate experiments (*P < .025, #P < .025).

Mentions: We examined the effect of DHA on the regulation of SRF protein in freshly isolated primary cultures of mouse adipocytes. Adipocytes were prepared from epididymal fat pads of C57BL6 mice as described in Methods and incubated for 16 h in the presence of DHA (25μM) or DHA + GW9662 (1.5 μM) or GW9662(1.5 μ) alone. Cells and medium were collected separately; cells were extracted in RIPA lysis buffer containing protease inhibitors and analyzed for SRF expression using Western blots. As shown in Figure 2(a), SRF protein was inhibited by 70± 10% by DHA treatment (P < .025). The addition of GW9662 (1.5 μM) along with DHA decreased the inhibition partially to 55 ± 10% of the control (P < .05), and the addition of GW9662 alone increased SRF by 10 ± 5% above the control. The same blot was probed with β-actin antibody to verify equal protein loading; there was no significant change in β-actin (Figure 2(b)). SRF secretion into the medium is inhibited by DHA treatment 80 ± 5% compared to control (P < .025), the addition of GW9662 along with DHA increased SRF levels to 40 ± 5% (P < .05), and addition of GW9662 to adipocytes increased SRF levels in the medium to 125 ± 10% of control (P < .05) (Figure 2(c)); Western blot shown represents one of two experiments done in triplicate. Bar graphs represent means from densitometric analysis of all replicates from two experiments.


Regulation of Serum Response Factor and Adiponectin by PPARγ Agonist Docosahexaenoic Acid.

Johnson C, Williams R, Wei JY, Ranganathan G - J Lipids (2010)

SRF expression in mouse adipocytes treated with DHA. Equal volumes (1-2 ml) of freshly isolated adipocytes were incubated in DMEM-HEPES supplemented with penicillin-streptomycin, containing 1% BSA. Adipocytes were treated as specified control, 25 μM DHA,  25 μM DHA plus 1.5 μM GW9662, or 1.5 μM GW9662 alone for 16 h.  Cells and medium were separated and analyzed for SRF expression. (a)  Western blots of SRF expression in mouse adipocytes. (d) Data in the adjacent bar graph represents one of two experiments done in duplicate(*P < .03, #P < .05).  (b) The blot from part A was probed with β-actin antibody.  (c) Western blot of SRF expression in adipocyte  conditioned medium.  Densitometric analysis of SRF expression in cells, and medium is expressed as a percent of control.  (e) The bar graph represents means of all replicate experiments (*P < .025, #P < .025).
© Copyright Policy - open-access
Related In: Results  -  Collection

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fig2: SRF expression in mouse adipocytes treated with DHA. Equal volumes (1-2 ml) of freshly isolated adipocytes were incubated in DMEM-HEPES supplemented with penicillin-streptomycin, containing 1% BSA. Adipocytes were treated as specified control, 25 μM DHA, 25 μM DHA plus 1.5 μM GW9662, or 1.5 μM GW9662 alone for 16 h. Cells and medium were separated and analyzed for SRF expression. (a) Western blots of SRF expression in mouse adipocytes. (d) Data in the adjacent bar graph represents one of two experiments done in duplicate(*P < .03, #P < .05). (b) The blot from part A was probed with β-actin antibody. (c) Western blot of SRF expression in adipocyte conditioned medium. Densitometric analysis of SRF expression in cells, and medium is expressed as a percent of control. (e) The bar graph represents means of all replicate experiments (*P < .025, #P < .025).
Mentions: We examined the effect of DHA on the regulation of SRF protein in freshly isolated primary cultures of mouse adipocytes. Adipocytes were prepared from epididymal fat pads of C57BL6 mice as described in Methods and incubated for 16 h in the presence of DHA (25μM) or DHA + GW9662 (1.5 μM) or GW9662(1.5 μ) alone. Cells and medium were collected separately; cells were extracted in RIPA lysis buffer containing protease inhibitors and analyzed for SRF expression using Western blots. As shown in Figure 2(a), SRF protein was inhibited by 70± 10% by DHA treatment (P < .025). The addition of GW9662 (1.5 μM) along with DHA decreased the inhibition partially to 55 ± 10% of the control (P < .05), and the addition of GW9662 alone increased SRF by 10 ± 5% above the control. The same blot was probed with β-actin antibody to verify equal protein loading; there was no significant change in β-actin (Figure 2(b)). SRF secretion into the medium is inhibited by DHA treatment 80 ± 5% compared to control (P < .025), the addition of GW9662 along with DHA increased SRF levels to 40 ± 5% (P < .05), and addition of GW9662 to adipocytes increased SRF levels in the medium to 125 ± 10% of control (P < .05) (Figure 2(c)); Western blot shown represents one of two experiments done in triplicate. Bar graphs represent means from densitometric analysis of all replicates from two experiments.

Bottom Line: Recent studies indicate that significant health benefits involving the regulation of signaling proteins result from the consumption of omega-3 polyunsaturated fatty acids (ω-3 PUFAs).Thus, we find that the levels of SRF and adiponectin are inversely related in response to treatment with PPARγ agonist DHA.Decreased levels of SRF along with increase in membrane-associated adiponectin could in part mediate the health benefits of DHA.

View Article: PubMed Central - PubMed

Affiliation: Donald W. Reynolds Institute on Aging University of Arkansas for Medical Sciences, 4301 West Markham Street, Slot no. 748, Little Rock, AR 72205, USA.

ABSTRACT
Recent studies indicate that significant health benefits involving the regulation of signaling proteins result from the consumption of omega-3 polyunsaturated fatty acids (ω-3 PUFAs). Serum response factor (SRF) is involved in transcriptional regulation of muscle growth and differentiation. SRF levels are increased in the aging heart muscle. It has not been examined whether SRF is made by adipocytes and whether SRF secretion by adipocytes is modulated by PPARγ agonist DHA. Adiponectin is made exclusively by adipocytes. We and others have previously reported that PUFAs such as DHA increase adiponectin levels and secretion in adipocytes. Here we show that DHA downregulates SRF with a simultaneous upregulation of adiponectin and that both these responses are reversible by PPARγ antagonist. Furthermore, there appears to be a direct relationship between DHA exposure and increased levels of membrane-associated high-density adiponectin, as well as lower levels of membrane-associated SRF. Thus, we find that the levels of SRF and adiponectin are inversely related in response to treatment with PPARγ agonist DHA. Decreased levels of SRF along with increase in membrane-associated adiponectin could in part mediate the health benefits of DHA.

No MeSH data available.


Related in: MedlinePlus