Nobiletin suppresses monocyte chemoattractant protein-1 (MCP-1) expression by regulating MAPK signaling in 3T3-L1 cells

Time- and glucose-dependent differentiation of 3T3-L1 adipocytes mimics dysfunctional adiposity

The 3T3-L1 murine adipocyte cell line remains one of the most widely used models to study the mechanisms of obesity and related pathologies. Most studies investigate such mechanisms using mature adipocytes that have been chemically induced to differentiate for 7 days in media containing 25 mM glucose. However, the dysfunctional characteristics commonly observed in obesity including adipocyte hypertrophy, increased expression of inflammatory markers, enhanced production of reactive oxygen species (ROS), increased steroidogenic enzyme expression/activity and production of steroid hormones, are not necessarily mimicked in these cells. The aim of this study was to provide an inexpensive model which represents the well-known characteristics of obesity by manipulating the time of adipocyte differentiation and increasing the concentration of glucose in the cell media. Our results showed a glucose- and time-dependent increase in adipocyte hypertrophy, ROS production and gene expression of the pro-inflammatory cytokine interleukin-6 (IL-6), as well as a time-dependent increase in lipolysis and in the gene expression of the chemokine monocyte chemoattractant protein 1 (MCP1). We also showed that gene expression of the steroidogenic enzymes 11-beta-hydroxysteroid dehydrogenase type 1 (11βHSD1), 17βHSD type 7 and 12, as well as CYP19A1 (aromatase), were significantly higher in the hypertrophic model relative to the control adipocytes differentiated using the conventional method. The increase in 11βHSD1 and 17βHSD12 expression was consistent with the enhanced conversion of cortisone and androstenedione to cortisol and testosterone, respectively. As these characteristics reflect those commonly observed in obesity, hypertrophic 3T3-L1 adipocytes are an appropriate in vitro model to study mechanisms of adipocyte dysfunction in an era where the rise in obesity incidence is a global health concern, and where access to adipose tissue from obese patients are limited.

Nobiletin and Derivatives: Functional Compounds from Citrus Fruit Peel for Colon Cancer Chemoprevention

The search for effective methods of cancer treatment and prevention has been a continuous effort since the disease was discovered. Recently, there has been increasing interest in exploring plants and fruits for molecules that may have potential as either adjuvants or as chemopreventive agents against cancer. One of the promising compounds under extensive research is nobiletin (NOB), a polymethoxyflavone (PMF) extracted exclusively from citrus peel. Not only does nobiletin itself exhibit anti-cancer properties, but its derivatives are also promising chemopreventive agents; examples of derivatives with anti-cancer activity include 3'-demethylnobiletin (3'-DMN), 4'-demethylnobiletin (4'-DMN), 3',4'-didemethylnobiletin (3',4'-DMN) and 5-demethylnobiletin (5-DMN). In vitro studies have demonstrated differential efficacies and mechanisms of NOB and its derivatives in inhibiting and killing of colon cancer cells. The chemopreventive potential of NOB has also been well demonstrated in several in vivo colon carcinogenesis animal models. NOB and its derivatives target multiple pathways in cancer progression and inhibit several of the hallmark features of colorectal cancer (CRC) pathophysiology, including arresting the cell cycle, inhibiting cell proliferation, inducing apoptosis, preventing tumour formation, reducing inflammatory effects and limiting angiogenesis. However, these substances have low oral bioavailability that limits their clinical utility, hence there have been numerous efforts exploring better drug delivery strategies for NOB and these are part of this review. We also reviewed data related to patents involving NOB to illustrate the extensiveness of each research area and its direction of commercialisation. Furthermore, this review also provides suggested directions for future research to advance NOB as the next promising candidate in CRC chemoprevention.