Elsevier

Life Sciences

Volume 88, Issues 13–14, 28 March 2011, Pages 613-618
Life Sciences

Regulation of adipocytokine secretion and adipocyte hypertrophy by polymethoxyflavonoids, nobiletin and tangeretin

https://doi.org/10.1016/j.lfs.2011.01.024Get rights and content

Abstract

Aims

The polymethoxyflavonoids nobiletin and tangeretin possess several important biological properties such as neuroprotective, antimetastatic, anticancer, and anti-inflammatory properties. The present study was undertaken to examine whether nobiletin and tangeretin could modulate adipocytokine secretion and to evaluate the effects of these flavonoids on the hypertrophy of mature adipocytes.

Main methods

All experiments were performed on the murine preadipocyte cell line 3T3-L1. We studied the formation of intracellular lipid droplets in adipocytes and the apoptosis-inducing activity to evaluate the effects of polymethoxyflavonoids on adipocyte differentiation and hypertrophy, respectively. The secretion of adipocytokines was measured using ELISA.

Key findings

We demonstrated that the combined treatment of differentiation reagents with nobiletin or tangeretin differentiated 3T3-L1 preadipocytes into adipocytes possessing less intracellular triglyceride as compared to vehicle-treated differentiated 3T3-L1 adipocytes. Both flavonoids increased the secretion of an insulin-sensitizing factor, adiponectin, but concomitantly decreased the secretion of an insulin-resistance factor, MCP-1, in 3T3-L1 adipocytes. Furthermore, nobiletin was found to decrease the secretion of resistin, which serves as an insulin-resistance factor. In mature 3T3-L1 adipocytes, nobiletin induced apoptosis; tangeretin, in contrast, did not induce apoptosis, but suppressed further triglyceride accumulation.

Significance

Our results suggest that nobiletin and tangeretin are promising therapeutic candidates for the prevention and treatment of insulin resistance by modulating the adipocytokine secretion balance. We also demonstrated the different effects of nobiletin and tangeretin on mature adipocytes.

Introduction

Obesity is closely associated with insulin resistance, which causes various diseases including type 2 diabetes, hypertension, coronary heart disease, and cancer (Kopelman, 2000). Obesity-related insulin resistance is attributable to an increase in the number and size of adipocytes differentiated from fibroblastic preadipocytes at the cellular level in adipose tissues. Furthermore, such adipocyte hypertrophy subsequently affects the kinetics of the secretion of adipocytokines derived from adipocytes, which are involved in insulin resistance. In obese states, the plasma concentration of the most representative adipocytokine adiponectin is decreased (Maeda et al., 1996, Arita et al., 1999); adiponectin is considered as a physiologically active protein that improves insulin sensitivity (Yamauchi et al., 2001, Díez and Iglesias, 2003). On the other hand, monocyte chemoattractant protein (MCP)-1 or resistin, which is present in high amounts in obese states and in hypertrophic adipocytes, is implicated in the development of insulin resistance and atherosclerosis (Sartipy and Loskutoff, 2003, Haluzik and Haluzikova, 2006, Kim et al., 2006). These results suggest that the modulation of the balance between the secretion of adiponectin and insulin-resistant factors through the regulation of adipocyte hypertrophy is a useful strategy for preventing the development of obesity-related pathologies.

Recently, several flavonoids have been shown to possess antihypertrophic effects against adipocytes through the regulation of multiple actions. Hsu and Yen (2007) have reported that rutin, quercetin, and resveratrol inhibited adipogenesis in 3T3-L1 adipocytes. Furthermore, Hsu and Yen (2008) have reported that epigallocatechin-3-gallate, quercetin, and genistein show anti-obesity effects by inducing apoptosis in adipocytes.

Polymethoxyflavonoids (PMFs) belong to a class of flavones that are commonly found in citrus fruits. The 2 most common PMFs nobiletin and tangeretin exist mainly in the peel of oranges and tangerines (Horowitz and Gentili, 1977). It has been reported that PMFs play important roles in a number of biological functions. They have been reported to possess neuroprotective (Datla et al., 2001), antimetastatic (Sato et al., 2002), anticancer (Silalahi, 2002), and anti-inflammatory properties (Lin et al., 2003). However, the effects of PMFs on adipocyte hypertrophy and adipocytokine secretion remain to be fully elucidated.

In the present study, we examined the effects of nobiletin and tangeretin on the secretion of adiponectin and MCP-1 and hypertrophy of mature adipocytes. We demonstrated that combined treatment of differentiation reagents with nobiletin or tangeretin differentiated 3T3-L1 preadipocytes into adipocytes possessing less intracellular triglyceride as compared to vehicle-treated differentiated 3T3-L1 adipocytes. Both flavonoids increased the secretion of an insulin-sensitizing factor, adiponectin, but concomitantly decreased the secretion of the insulin-resistance factor MCP-1 in 3T3-L1 adipocytes. Furthermore, nobiletin was found to decrease the secretion of resistin, which served as an insulin-resistance factor. In mature 3T3-L1 adipocytes, nobiletin induced apoptosis; tangeretin, in contrast, did not induce apoptosis, but suppressed further triglyceride accumulation.

Section snippets

Materials

Nobiletin (5,6,7,8,3′,4′-hexamethoxyflavone) (Fig. 1A), and tangeretin (5,6,7,8,4′-pentamethoxyflavone) (Fig. 1B) were purchased from Wako Pure Chemical Industries, Ltd. (Osaka, Japan). Pioglitazone was purchased from Sigma (St. Louis, MO). These compounds were soluble in dimethyl sulfoxide (DMSO), and the dissolved concentration of solvent in culture medium was less than 0.4%. The murine preadipocyte cell line 3T3-L1 was obtained from the American Type Culture Collection (Manassas, VA). All

Effects of nobiletin and tangeretin on adipocyte differentiation

After treatment with the differentiation reagents, such as insulin, IBMX, and dexamethasone, in the 2-day differentiation period (day 0–2), the 3T3-L1 preadipocytes were differentiated and had matured into adipocytes with intracellular large lipid droplets by day 8 (Fig. 2A), although there was no lipid accumulation in 3T3-L1 cells without the treatment of the differentiation reagents (data not shown). Combined treatment of the differentiation reagents with nobiletin (Fig. 2B) or tangeretin (

Discussion

In the present study, we demonstrated that both nobiletin and tangeretin modulated the adipocytokine secretion balance by increasing adiponectin secretion and decreasing MCP-1 secretion. Additionally, nobiletin was found to decrease the secretion of resistin. Previous studies (Saito et al., 2007, Kunimasa et al., 2009) have presented similar results, and suggest that nobiletin may have upregulated adiponectin at the mRNA or protein levels. The treatment conditions described in the earlier

Conclusion

In conclusion, we suggest that nobiletin and tangeretin are therapeutic candidates for the prevention and treatment of insulin resistance by modulating the adipocytokine secretion balance. We also found that unlike nobiletin, tangeretin induced suppression of lipid accumulation on mature adipocytes without apoptosis. The effect of tangeretin on lipid metabolism and its mechanism is expected to be very interesting and is deemed worthy of further investigation.

Conflict of interest statement

There are no competing interests.

References (26)

  • K.P. Datla et al.

    Tissue distribution and neuroprotective effects of citrus flavonoid tangeretin in a rat model of Parkinson's disease

    NeuroReport

    (2001)
  • J.J. Díez et al.

    The role of the novel adipocyte-derived hormone adiponectin in human disease

    Eur J Endocrinol

    (2003)
  • M. Haluzik et al.

    The role of resistin in obesity-induced insulin resistance

    Curr Opin Investig Drugs

    (2006)
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