Peptide Fraction pOh2 Exerts Antiadipogenic Activity through Inhibition of C/EBP-α and PPAR-γ Expression in 3T3-L1 Adipocytes

Structurally Diverse Bisbenzylisoquinoline Alkaloids with Antiadipogenic Activity through PPARγ Downregulation from the Embryo of Nelumbo nucifera Seeds

Six undescribed and six known bisbenzylisoquinoline alkaloids were isolated from the embryo of Nelumbo nucifera seeds. Their structures were fully characterized by a combination of 1H, 13C NMR, 2D NMR, and HRESIMS analyses, as well as ECD computational calculations. The antiadipogenic activity of 11 alkaloids was observed in a dose-responsive manner, leading to the suppression of lipid accumulation in 3T3-L1 cells. Luciferase assay and Western blot analysis showed that the active alkaloids downregulated peroxisome proliferator-activated receptor gamma (PPARγ, a key antiadipogenic receptor) expression in 3T3-L1 cells. Analysis of the structure-activity relationship unveiled that a 1R,1'S configuration in bisbenzylisoquinoline alkaloids led to a notable enhancement in antiadipogenic activity. The resistance level against lipid accumulation highlighted a consistent pattern with the suppressive effect on the PPARγ expression. These activity results indicate that alkaloids from the embryo of N. nucifera seeds have a potential of antiobesity effects through PPARγ downregulation.

The Inhibitory Effects of Juglanin on Adipogenesis in 3T3-L1 Adipocytes

INTRODUCTION

Deregulation of adipogenesis plays an important role in obesity and other metabolism disorders. PPAR, C/EBP and SREBP1c are key transcriptional factors involved in adipogenesis and lipogenesis. Juglanin is a natural compound belonging to flavonoids, and it has been reported that juglanin has a potent inhibitory effect on inflammation and certain type of cancers. However, the effects of juglanin in adipogenesis have not been reported before.

MATERIALS AND METHODS

3T3-L1 preadipocytes were incubated with differentiation induction medium in the presence or absence of 0.5, 2.5, or 5 µM juglanin for an 8-day differentiation period. The lipid droplets accumulated in the cytoplasm were monitored by Oil Red O staining on days 0, 2, 5, and 8. The regulatory effects of juglanin on adipogenesis-related genes and proteins were investigated by real-time polymerase chain reaction and Western blot analysis.

RESULTS

Juglanin significantly decreased lipid accumulation in differentiated adipocytes. Our findings show that juglanin reduced the expression of C/EBPα, C/EBPβ, and SREBP-1c without affecting PPARα or PPARγ expression. Additionally, juglanin increased the activation of the SIRT1/AMPK signaling pathway through the phosphorylation of AMPKα. Finally, we performed an AMPK inhibitor experiment, which revealed that the inhibitory effects of juglanin on adipogenesis are mediated through AMPK.

DISCUSSION

Juglanin can prevent adipogenesis by suppressing lipid accumulation and the differentiation of preadipocytes. The mechanism of juglanin regulating adipogenesis requires further investigation. Future clinical study in vivo could shed more light on its implication in modulating obesity and metabolic disorders.

Anti-adipogenic 18,19-seco-ursane stereoisomers and oleane-type saponins from Ilex cornuta leaves

Three undescribed seco-ursane stereoisomers, ilexcornutosides A-C, two undescribed triterpenoid saponins, ilexcornutosides D-E, and 11 known triterpenoids were isolated from the leaves of Ilex cornuta Lindl. & Paxton. Ilexcornutosides A-C and F with the same planar structures are unique 13(18)-ene-18,19-seco-ursane skeleton triterpenoids, identified as (3S,12R)-3-O-[β-d-glucopyranosyl-(1 → 2)-α-l-arabinopyranosyl]-12-hydroxyl-19-oxo-18,19-secours-13(18)-en-28,21-lactone. Among them, ilexcornutosides A and F (or ilexcornutosides B and C) are a pair of diastereomers at the C-20 position; ilexcornutosides A and C (or ilexcornutosides B and F) are a pair of diastereomers with epimerization at the C-21. Their structures were established by extensive spectroscopic (IR, 1D and 2D NMR, and HR-ESI-MS) and chemical analyses. The absolute configurations of ilexcornutosides A, B, D and F were determined by a single crystal X-ray diffraction analysis with a Cu Kα radiation. The inhibitory effect of ilexcornutosides A-F on the PPARγ expression was assessed in the 3T3-L1-Lenti-PPARγ-Luc cells using a single luciferase reporter assay. Ilexcornutosides A and C showed a comparable activity in decrease of the PPARγ expression to the positive control (T0070907) at 5 μM.

Structure-based drug design of peroxisome proliferator-activated receptor gamma inhibitors: ferulic acid and derivatives

Peroxisome proliferator-activated receptor gamma (PPARγ), ligand-activated transcription factor, is a key modulator of genes considered in diabetes development as well as treatment. Adipogenesis differentiation through PPARγ, CCAAT-enhancer protein alpha (C/EBPα) is identified as a critical mechanism in fat accumulation and weight gain. Polyphenols studied against adipocyte differentiation is taken up for consistent support and drug discovery. Structure-based drug design found useful to distinguish the underlying mechanism of receptor-ligand interaction and function. In this work, phenolic acids, ferulic acid and its derivatives are used as ligands. Molecular parameters have been set to filter and sort the 34 derivatives from ZINC and PubChem databases. Besides, for affinity and activity identification, troglitazone and resveratrol co-crystallized ligands have been studied. Absorption, distribution, metabolism, elimination and toxicity, density functional theory, highest occupied molecular orbital-lowest unoccupied molecular orbital values and docking scores define the drug candidate as a potential inhibitor. Residues Ser 342 and Arg 280 bind with the ligands by forming hydrogen bonds and hydrophobic contacts. Based on the docking score, pharmacophore properties and functional energy values of the top six compounds are chosen for molecular dynamics and simulation. Consistency and stability maintained throughout the simulation up to 50 ns were observed. Free binding energy values and standard deviation of receptor and ligand calculated using molecular mechanics-generalized Born and surface area solvation method (MM_GBSA) is found significant. Therefore, ferulic acid derivatives and phenolic acids could be a potential inhibitor for adipocyte differentiation and lipid accumulation.Communicated by Ramaswamy H. Sarma.