Eicosapentaenoic acid stimulates AMP-activated protein kinase and increases visfatin secretion in cultured murine adipocytes

Abstract

Visfatin is an adipokine highly expressed in visceral AT (adipose tissue) of humans and rodents, the production of which seems to be dysregulated in excessive fat accumulation and conditions of insulin resistance. EPA (eicosapentaenoic acid), an n-3 PUFA (polyunsaturated fatty acid), has been demonstrated to exert beneficial effects in obesity and insulin resistance conditions, which have been further linked to its reported ability to modulate adipokine production by adipocytes. TNF-alpha (tumour necrosis factor-alpha) is a pro-inflammatory cytokine whose production is increased in obesity and is involved in the development of insulin resistance. Control of adipokine production by some insulin-sensitizing compounds has been associated with the stimulation of AMPK (AMP-activated protein kinase). The aim of the present study was to examine in vitro the effects of EPA on visfatin production and the potential involvement of AMPK both in the absence or presence of TNF-alpha. Treatment with the pro-inflammatory cytokine TNF-alpha (1 ng/ml) did not modify visfatin gene expression and protein secretion in primary cultured rat adipocytes. However, treatment of these primary adipocytes with EPA (200 mumol/l) for 24 h significantly increased visfatin secretion (P<0.001) and mRNA gene expression (P<0.05). Moreover, the stimulatory effect of EPA on visfatin secretion was prevented by treatment with the AMPK inhibitor Compound C, but not with the PI3K (phosphoinositide 3-kinase) inhibitor LY294002. Similar results were observed in 3T3-L1 adipocytes. Moreover, EPA strongly stimulated AMPK phosphorylation alone or in combination with TNF-alpha in 3T3-L1 adipocytes and pre-adipocytes. The results of the present study suggest that the stimulatory action of EPA on visfatin production involves AMPK activation in adipocytes.

Lipoic acid inhibits leptin secretion and Sp1 activity in adipocytes

“…Adipocytes were isolated under sterile conditions from epididymal fat depots of eightweek-old male Wistar rats (250-280 g) fed a pelleted chow diet and given deionised water ad libitum [25]. Briefly, adipose tissue fragments were digested with type I collagenase at 37 ºC with gentle shaking for 30 min.…”

“…3T3-L1 adipocytes were cultured and induced to differentiate as described [25]. Cells were serum-starved overnight and then incubated with the appropriate treatment.…”

“…Leptin mRNA levels were determined using predesigned TaqMan® Assays-on-Demand (Rn00565158_m1* and Mm00434759_m1*, Applied Biosystems, Foster City, CA, USA). Quantitative realtime PCR was performed using the ABI PRISM 7000HT and ABI PRISM 7900HT Fast System Sequence Detection System (Applied Biosystems, Foster City, CA, USA) Sequence as described previously [25]. Leptin mRNA levels were normalized by two different housekeeping genes Cyclophilin (Rn00690933_m1*, Mm02342430_g1) and/or Ubiquitin C (Rn01789812_g1, Applied Biosytems).…”

Vitamin C inhibits leptin secretion and some glucose/lipid metabolic pathways in primary rat adipocytes

“…Primary cultures were performed according to protocols described elsewhere (Lorente-Cebrian et al 2009 WAT fragments were digested in the same buffer with type I collagenase (1 . 25 mg/ml per 0 .…”

Studies on Mechanistic Role of Natural Bioactive Compounds in the Management of Obesity An Overview

“…Moreover, EPA has been shown to decrease the TNF-α-induced activation of lipolysis and NF-kB and ERK1/2 signalling pathways in 3T3-L1 adipocytes [93]. The beneficial metabolic effects of DHA and EPA have also been related to their ability to promote AMPK activation and to regulate adipokine secretion [94][95][96].…”