NAD(P)H:quinone oxidoreductase 1 activity reduces hypertrophy in 3T3-L1 adipocytes

Abstract

The nuclear factor E2-related factor 2 (Nrf2)/Kelch-like ECH-associated protein 1 (Keap1) pathway responds to oxidative stress via control of several antioxidant defense gene expressions. Recent efforts demonstrate that Nrf2 modulates development of adiposity and adipogenesis. One of the major Nrf2-regulated proteins, NAD(P)H:quinone oxidoreductase 1 (NQO1), is implicated in the development of adipose tissue and obesity. However, little is known about in situ disposition of Nrf2, Keap1, and NQO1 during adipogenesis in isolated adipocytes. Based on literature data, we hypothesized that adipocyte differentiation would increase expression of the Nrf2/Keap1 pathway and NQO1. Using murine 3T3-L1 preadipocytes, we mapped an increase in NQO1 protein at limited clonal expansion and postmitotic growth arrest (Days 1-3) stages and a decrease in terminally differentiated (Day 8) adipocytes that lasted for several days afterward. Conversely, NQO1, Nrf2, and Keap1 mRNA expressions were all increased in differentiated adipocytes (Days 11-14), indicating a discrepancy between steady-state mRNA levels and resulting protein. Treatment of differentiated 3T3-L1 adipocytes with glycogen synthase kinase-3β (GSK-3β) inhibitor, LiCl, led to 1.9-fold increase in NQO1 protein. Sulforaphane enhanced NQO1 protein (10.5-fold) and blunted triglyceride and FABP4 accumulation. The decrement in triglyceride content was partially reversed when NQO1 activity was pharmacologically inhibited. These data demonstrate a biphasic response of Nrf2 and NQO1 during adipocyte differentiation that is regulated by Keap1- and GSK-3β-dependent mechanisms, and that hypertrophy is negatively regulated by NQO1 activity.

PPARβ/δ ameliorates fructose-induced insulin resistance in adipocytes by preventing Nrf2 activation

“…This protein is usually detected as a dimer of 90-110 kDa. However, in our 3T3-L1 adipocytes Nrf2 was detected at 56 kDa in agreement with a previous study [29]. In addition, Nrf2 inhibition by trigonelline abolished the increase in CD36 protein levels caused by fructose in adipocytes (Fig.…”

Redox modulation of adipocyte differentiation: hypothesis of “Redox Chain” and novel insights into intervention of adipogenesis and obesity

“…investigated NQO1 expression in the course of adipocyte differentiation [271]. They found an increase of NQO1 protein at limited MCE and postmitotic growth arrest (Days 1-3) stages and a decrease in terminally differentiated (Day 8) adipocytes that lasted for several days afterward [271].…”

“…They found an increase of NQO1 protein at limited MCE and postmitotic growth arrest (Days 1-3) stages and a decrease in terminally differentiated (Day 8) adipocytes that lasted for several days afterward [271]. In contrast to the mapping of protein, NQO1 mRNA expression was increased in differentiated adipocytes (Days11-14), indicating a discrepancy between steady-state of mRNA and resulting protein levels [271].…”

Characterisation of the relationship between Heme-oxygenase-1 and adiponectin

“…Further investigations involving co-treatment with an inhibitor of HO-1 activity or siRNA-mediated HO-1 knockdown, combined with inconsistencies across dose responses, indicate that these effects are HO-1-independent. We propose that they are most-likely mediated by an alternate pathway, possibly involving one or more NRF2 target genes [296]. Collectively, these findings suggest that any beneficial effects following chronic treatment with CoPP or hemin in vivo are unlikely to be mediated by a direct positive effect of HO-1 induction on adipogenesis of preadipocytes.…”

“…These data indicate that chronic treatment with CoPP or hemin interfere with differentiation and adiponectin production from human preadipocytes in a HO-1-independent manner. We propose that induction of other NRF2 target genes, such as NQO1 [296], may underpin the observed inhibitory effects. Finally, these findings do not support the existence of a direct HO-1 -adiponectin axis.…”