Apo-12'-lycopenal, a Lycopene Metabolite, Promotes Adipocyte Differentiation via Peroxisome Proliferator-Activated Receptor γ Activation

Metabolome analysis reveals that cyclic adenosine diphosphate ribose contributes to the regulation of differentiation in mice adipocyte

Adipocytes play a key role in energy storage and homeostasis. Although the role of transcription factors in adipocyte differentiation is known, the effect of endogenous metabolites of low molecular weight remains unclear. Here, we analyzed time-dependent changes in the levels of these metabolites throughout adipocyte differentiation, using metabolome analysis, and demonstrated that there is a positive correlation between cyclic adenosine diphosphate ribose (cADPR) and Pparγ mRNA expression used as a marker of differentiation. We also found that the treatment of C3H10T1/2 adipocytes with cADPR increased the mRNA expression of those marker genes and the accumulation of triglycerides. Furthermore, inhibition of ryanodine receptors (RyR), which are activated by cADPR, caused a significant reduction in mRNA expression levels of the marker genes and triglyceride accumulation in adipocytes. Our findings show that cADPR accelerates adipocytic differentiation via RyR pathway.

Valerenic Acid Promotes Adipocyte Differentiation, Adiponectin Production, and Glucose Uptake via Its PPARγ Ligand Activity

Although valerenic acid (VA) is an important marker compound for quantitative assessment of Valeriana officinalis products, little is known about its potential effects on adipocytes. We investigated the effects of VA on adipocyte differentiation, adiponectin production, and glucose uptake using 3T3-L1 adipocytes. The results showed that VA promoted adipocyte differentiation and increased the gene expression of adipogenesis and glucose uptake-related proteins, including peroxisome proliferator-activated receptor gamma (PPARγ), cytosine-cytosine-adenosine-adenosine-thymidine enhancer binding protein alpha (C/EBPα), adiponectin, and glucose transporter 4 (GLUT4). Additionally, cell cultures treated with VA had elevated adiponectin secretion and glucose uptake. The PPARγ luciferase assay indicated VA as a partial agonist of PPARγ, while the analysis using its antagonist, GW9662, and a docking simulation between PPARγ and VA revealed the binding site of VA as likely adjacent to the Ω loop pocket of PPARγ. Taken together, these results demonstrate that VA acts as a PPARγ partial agonist to promote adipocyte differentiation, adiponectin production, and glucose uptake.

Preparation of Apoastaxanthinals and Evaluation of Their Anti-inflammatory Action against Lipopolysaccharide-Stimulated Macrophages and Adipocytes

Apocarotenoids are carotenoid derivatives in which the polyene chain is cleaved via enzymatic or nonenzymatic action. They are found in animal tissues and carotenoid-containing foods. However, limited information on the biological functions of apocarotenoids is available. Here, we prepared apocarotenoids from astaxanthin via chemical oxidation and evaluated their anti-inflammatory action against macrophages and adipocytes. A series of astaxanthin-derived apoastaxanthinals, apo-11-, apo-15-, apo-14'-, apo-12'-, apo-10'-, and apo-8'-astaxanthinals, were successfully characterized by chromatography and spectroscopic analysis. The apoastaxanthinals inhibited inflammatory cytokine production and mRNA expression against lipopolysaccharide-stimulated RAW 264.7 macrophages. Apoastaxanthinals suppressed interleukin-6 overexpression in an in vitro model with macrophages and adipocytes in the following cultures: (1) contact coculture of 3T3-L1 adipocytes and RAW264.7 macrophages and (2) 3T3-L1 adipocytes in a RAW264.7-derived conditioned media. These results indicate that the apoastaxanthinals have the potential for regulation of adipose tissue inflammation observed in obesity.

Integration of bioassay and non-target metabolite analysis of tomato reveals that β-carotene and lycopene activate the adiponectin signaling pathway, including AMPK phosphorylation

Adiponectin, an adipokine, regulates glucose metabolism and insulin sensitivity through the adiponectin receptor (AdipoR). In this study, we searched for metabolites that activate the adiponectin signaling pathway from tomato (Solanum lycopersicu). Metabolites of mature tomato were separated into 55 fractions by liquid chromatography, and then each fraction was examined using the phosphorylation assay of AMP-protein kinase (AMPK) in C2C12 myotubes and in AdipoR-knockdown cells by small interfering RNA (siRNA). Several fractions showed AMPK phosphorylation in C2C12 myotubes and siRNA-mediated abrogation of the effect. Non-targeted metabolite analysis revealed the presence of 721 diverse metabolites in tomato. By integrating the activity of fractions on AMPK phosphorylation and the 721 metabolites based on their retention times of liquid chromatography, we performed a comprehensive screen for metabolites that possess adiponectin-like activity. As the screening suggested that the active fractions contained four carotenoids, we further analyzed β-carotene and lycopene, the major carotenoids of food. They induced AMPK phosphorylation via the AdipoR, Ca²⁺/calmodulin-dependent protein kinase kinase and Ca²⁺ influx, in addition to activating glucose uptake via AdipoR in C2C12 myotubes. All these events were characteristic adiponectin actions. These results indicated that the food-derived carotenoids, β-carotene and lycopene, activate the adiponectin signaling pathway, including AMPK phosphorylation.

Tomatoes, Lycopene, and Prostate Cancer: What Have We Learned from Experimental Models?

Human epidemiology suggests a protective effect of tomatoes or tomato phytochemicals, such as lycopene, on prostate cancer risk. However, human epidemiology alone cannot reveal causal relations. Laboratory animal models of prostate cancer provide opportunities to investigate hypotheses regarding dietary components in precisely controlled, experimental systems, contributing to our understanding of diet and cancer risk relations. We review the published studies evaluating the impact of tomatoes and/or lycopene in preclinical models of prostate carcinogenesis and tumorigenesis. The feeding of tomatoes or tomato components demonstrates anti-prostate cancer activity in both transplantable xenograft models of tumorigenesis and models of chemically- and genetically-driven carcinogenesis. Feeding pure lycopene shows anticancer activity in most studies, although outcomes vary by model system, suggesting that the impact of pure lycopene can depend on dose, duration, and specific carcinogenic processes represented in different models. Nonetheless, studies with the transgenic adenocarcinoma of the mouse prostate (TRAMP) model of carcinogenesis typically demonstrate similar bioactivity to that of tomato feeding. In general, interventions that commence earlier in carcinogenesis and are sustained tend to be more efficacious. Accumulated data suggest that lycopene is one, but perhaps not the only, anticancer bioactive compound in tomatoes. Although it is clear that tomatoes and lycopene have anti-prostate cancer activity in rodent models, major knowledge gaps remain in understanding dose-response relations and molecular mechanisms of action. Published and future findings from rodent studies can provide guidance for translational scientists to design and execute informative human clinical trials of prostate cancer prevention or in support of therapy.

In Vitro Imaging of Lycopene Delivery to Prostate Cancer Cells

The ability to monitor the uptake and distribution of food nutrients in in vitro cell culture models is key to understanding the efficacy of these nutraceuticals to treat and prevent disease. Lycopene is a carotenoid found in chloroplasts and chromoplasts of tomatoes, providing the familiar red color, and a bioactive that inhibits prostate carcinogenesis. We employed live-cell Raman microscopy to visualize lycopene delivery from tween 80 micelles into PC-3 prostate cancer cells. The tween 80 micelle provides a mimic of natural lipoprotein complexes that deliver lycopene in vivo, overcomes the low aqueous solubility of lycopene and challenges replicating physiological uptake to cells, and provides a stable signal to assess cellular uptake of the nutraceutical formulation. The Raman images indicate subcellular localization of the lycopene within the cells. The lycopene Raman signal is resonantly enhanced at an excitation wavelength of 532 nm, providing a convenient, sensitive, and label-free technique to detect and quantify lycopene uptake in living cells. Analysis of the acquired Raman spectra in the maps determines the concentration of lycopene at each point in the cell. In addition to the expected lycopene Raman signal, Raman scattering from the tween 80 vehicle is also mapped in the cells. The Raman data correlates with scattering features observed in darkfield microscopy images of the cells, which display the cell membrane and other features for reference. Overall, the Raman maps indicate lycopene likely accumulates in lipid membranes of cytoplasmic organelles.

Neoxanthin in young vegetable leaves prevents fat accumulation in differentiated adipocytes

The present study aimed to investigate the effect of young leaves on fat accumulation in differentiated 3T3-L1 adipocytes. A potent preventive effect on fat accumulation was observed in fractions of young leaves of spinach, beet, and arugula extracted with a low-polarity solvent (hexane: acetone: ethanol: toluene = 10:6:7:6). This effect was seemingly associated with the leaf carotenoid content, including lutein, β-carotene, and neoxanthin. Among these, only neoxanthin, with the characteristic structure of 5,6-monoepoxide and an allenic bond, significantly prevented fat accumulation in a dose-dependent manner. The preventive effect and carotenoid content, including neoxanthin, of these young leaves did not differ from those of the corresponding adult leaves. Therefore, our study demonstrated that young vegetable leaves, such as spinach, beet, and arugula leaves, contained neoxanthin, which prevented fat accumulation in adipocytes in vitro. In the future, the effectiveness of such young leaves and neoxanthin should be investigated in vivo.

Lycopene corrects metabolic syndrome and liver injury induced by high fat diet in obese rats through antioxidant, anti-inflammatory, antifibrotic pathways

Obesity is a global epidemic disease that is closely associated with various health problems as Diabetes mellitus, cardiovascular, and metabolic disorders. Lycopene (LYC), a red-colored carotenoid, has demonstrated various promising therapeutic effects. Hence, the potential of LYC was studied against high fat diet (HFD)-induced obesity and metabolic disturbances in rats. Animals fed on HFD and orally supplemented with LYC (25 and 50 mg/kg) or simvastatin (10 mg/kg) every day for 3 months. The results revealed that long-term consumption of HFD significantly increased weight gain, liver weight, cholesterol, triglycerides (TG), apolipoprotein-B (Apo-B), low-density lipoprotein-cholesterol (LDL-c) levels, as well as decreasing the high-density lipoprotein-cholesterol (HDL-c) levels. Moreover, high blood glucose and insulin levels accompanied by low peroxisome proliferator activated receptor gamma (PPAR-γ) were recorded in HFD group. Further, HFD rats displayed lower levels of antioxidant biomarkers (SOD, CAT, GPx, GR and GSH), in addition to higher levels of MDA, NO and inflammatory mediators (IL-1β, TNF-α, and MPO). Marked increases were observed in atherogenic index, lactate dehydrogenase and creatine kinase together with fibrosis markers (TGF-β1 and α-SMA) in rats fed on HFD. Comparing to model group, LYC was able to effectively reverse HFD-mediated alterations at dose dependent manner. Altogether, dietary supplementation of LYC successfully reversed HFD-induced alterations through its antioxidant, anti-inflammatory, and anti-fibrotic properties. Hence, LYC displayed a therapeutic potential to manage obesity and its associated pathologies.

Carotenoids and carotenoid conversion products in adipose tissue biology and obesity: Pre-clinical and human studies

Antiobesity activities of carotenoids and carotenoid conversion products (CCPs) have been demonstrated in pre-clinical studies, and mechanisms behind have begun to be unveiled, thus suggesting these compounds may help obesity prevention and management. The antiobesity action of carotenoids and CCPs can be traced to effects in multiple tissues, notably the adipose tissues. Key aspects of the biology of adipose tissues appear to be affected by carotenoid and CCPs, including adipogenesis, metabolic capacities for energy storage, release and inefficient oxidation, secretory function, and modulation of oxidative stress and inflammatory pathways. Here, we review the connections of carotenoids and CCPs with adipose tissue biology and obesity as revealed by cell and animal intervention studies, studies addressing the role of endogenous retinoid metabolism, and human epidemiological and intervention studies. We also consider human genetic variability influencing carotenoid and vitamin A metabolism, particularly in adipose tissues, as a potentially relevant aspect towards personalization of dietary recommendations to prevent or manage obesity and optimize metabolic health. This article is part of a Special Issue entitled Carotenoids recent advances in cell and molecular biology edited by Johannes von Lintig and Loredana Quadro.