Evaluating the efficacy of curcumin derivatives on adipocyte dysfunction and adipocyte differentiation

Abstract

The prevalence of obesity has increased worldwide, necessitating the need to explore novel therapeutic interventions as the existing treatment options may not always be safe and effective over the long term. As such, natural compounds such as curcumin, a natural polyphenol derived from the turmeric plant, have shown promise in combating obesity through its diverse pharmacological properties, including anti-adipogenic, anti-lipolytic, and anti-inflammatory effects. However, the therapeutic efficacy of curcumin is limited due to its poor pharmacokinetic profile. This has prompted the development of synthetic curcumin derivatives to overcome these limitations and enhance the anti-obesity potential of curcumin. Thus, this study aimed to evaluate the effects of iii curcumin and the three synthetic curcumin derivatives on adipocyte dysfunction and adipogenesis using in silico and in vitro experimental approaches. The three synthetic curcumin derivatives, namely two chloro curcumin derivatives (1A6 and 1A8) and an asymmetric curcumin derivative (1B8), were synthesized via a chemical reaction of 3-chloroacetylacetone (1A6 and 1A8) or acetylacetone (1B8) with boric oxide. Three spectroscopic techniques, including high resolution - mass spectrometry - electrospray ionization (HR-MS-ESI), fourier transform - infrared (FT-IR) spectroscopy, and proton nuclear magnetic resonance (1H-NMR) spectroscopy were used for the characterization of the synthesized curcumin derivatives. Thereafter, in silico computational tools such as Protox II and SwissADME were used to predict the toxicity and pharmacokinetic properties of curcumin and the three synthetic curcumin derivatives. Additionally, SwissTargetPrediction and similarity ensemble approach (SEA) online tools were used to identify potential biological targets of curcumin and three synthetic derivatives. Molecular docking and molecular dynamic simulation were also used to predict the binding affinities and molecular interactions of curcumin, 1A6, 1A8, and 1B8 with the selected target proteins involved in adipogenesis, lipid metabolism, and inflammation. In addition, the bioactivity of curcumin, 1A6, 1A8, and 1B8 was assessed in vitro in 3T3-L1 adipocytes induced with tumor necrosis factor alpha (TNFα), lipopolysaccharide (LPS), and palmitic acid (PA) combination treatment. Metabolic activity, lipolysis, and lipid accumulation were assessed using the adenosine triphosphate (ATP), glycerol release, and Oil Red O staining assays, respectively. Adiponectin (ADIPOQ) and interleukin 6 (IL-6) secreted levels were quantified using enzyme-linked immunosorbent assays and the expression of genes involved in lipid metabolism and inflammation was measured using quantitative real-time polymerase chain reaction (qRT-PCR).The three curcumin derivatives (1A6, 1A8, and 1B8) were synthesized with high purity and thermal stability, and their chemical structures were elucidated by HR-MS-ESI, FT-IR, and 1H-NMR spectroscopic techniques. In silico predictive screening showed that curcumin and the three synthetic curcumin derivatives (1A6, 1A8, and 1B8) similarly exhibit low toxicity, improved drug-like attributes, and favorable pharmacokinetic profiles. Molecular docking and molecular dynamic simulations showed that curcumin, 1A6, 1A8, and 1B8 similarly exhibit favorable binding scores to the predicted biological target proteins, with the most stable binding for peroxisome proliferatoractivated receptor gamma (PPARγ), cyclooxygenase 2 (COX2), and fatty acid synthase (FAS), which are key proteins involved in adipogenesis, inflammation, and lipid metabolism. TNFα, LPS, and PA combination treatment induced metabolic dysfunction in 3T3-L1 adipocytes by reducing metabolic activity, increasing iv lipolysis, decreasing lipid accumulation, reducing anti-inflammatory, and increasing pro-inflammatory markers. ATP assay showed that treatment with curcumin, 1A6, and 1A8 at 40 µM reduced metabolic activity, while lower concentrations of these compounds (1.25 - 20 µM) and 1B8 did not affect metabolic activity in 3T3-L1 adipocytes induced with TNFα, LPS, and PA combination.Similarly, lipolysis was attenuated by treatment with curcumin (5 - 20 µM), 1A6 (2.5 - 20 µM), and 1A8 (2.5 and 10 µM), while 1B8 had no effect. In contrast, treatment with curcumin and 1B8 (10 and 20 µM) increased lipid accumulation, while no effects were observed in cells treated with the chloro curcumin derivatives (1A6 and 1A8). The mRNA expression of the lipolytic gene, patatin-like phospholipase domain containing 3 (Pnpla3) was upregulated by treatment with 1B8 (20 µM). In contrast, acetyl-CoA carboxylase alpha (Acaca) mRNA expression was reduced by 1A6 (20 µM), while fatty acid synthase (Fasn) mRNA expression was also decreased by curcumin (10 µM), 1A6 (10 and 20 µM), and 1A8 (10 and 20 µM). Curcumin (10 and 20 µM), 1A6 (10 and 20 µM), 1A8 (20 µM), and 1B8 (10 and 20 µM) reduced cyclooxygenase 2 (Cox2) mRNA expression levels. Surprisingly, the results showed increased monocyte chemoattractant protein 1 (Mcp1) mRNA expression in cells treated with curcumin and 1A8 at 10 µM. In addition, treatment with curcumin (10 and 20 µM), 1A6 (10 and 20 µM), 1A8 (20 µM), and 1B8 (10 and 20 µM) decreased IL-6 secretion levels. This study suggests that curcumin and the three synthetic curcumin derivatives (1A6, 1A8, and 1B8) ameliorate adipocyte dysfunction by modulating lipid metabolism and inflammation and regulate adipogenesis by targeting key adipogenic and lipid metabolism proteins, thus exerting potential anti-obesity effects. Further experimental work is warranted to explore the anti???obesity potential and mechanism of action of the synthetic curcumin derivatives.