New study uncovers effects of beer compound on cartilage cells in osteoarthritis

By Dr. Chinta SidharthanJul 3 2023Reviewed by Benedette Cuffari, M.Sc.

In a recent study published in the journal Nutrients, researchers determined the impact of formononetin (FNT) on the metabolism, viability, and inflammation of chondrocytes to understand the association between beer consumption and osteoarthritis risk.

Study: Formononetin, a Beer Polyphenol with Catabolic Effects on Chondrocytes. Image Credit: Natural Box / Shutterstock.com

What causes osteoarthritis?

Osteoarthritis is a rheumatic disease characterized by the narrowing of the space in the joints due to progressive cartilage degradation. The impact of this narrowing on periarticular tissues leads to the failure of the entire joint, which subsequently causes stiffness, inflammation, pain, and loss of function. The high incidence of osteoarthritis also results in a considerable economic burden.

Although certain factors such as age, ethnicity, sex, genetic profiles, diet, mechanical stress, metabolic diseases, and inflammation can worsen the progression of cartilage degeneration, the etiology of osteoarthritis is not well understood.

Inflammatory cytokines such as tumor necrosis factor (TNF) and various interleukins (ILs) are linked to osteoarthritis progression through the release of reactive oxygen species (ROS) during oxidative stress. Inflammation and oxidative stress degrade chondrocytes and the extracellular matrix, as well as activate matrix metalloproteinases, which further degrade the cartilage extracellular matrix.

Diet is considered a modifiable risk factor for osteoarthritis, with beer consumption believed to worsen osteoarthritis. While flavonoids are some of the most active compounds in beer, the role of isoflavonoids like FNT, also found in various herbs, plants, and coffee, in osteoarthritis progression is poorly understood.

About the study

In the present in vitro study, researchers determine whether FNT impacts chondrocytes through its modulatory effects on estrogenic pathways.

Diets rich in isoflavonoids are believed to increase phytoestrogen levels, which affects the growth plate chondrocytes. FNT has a similar structure as mammalian estrogen and can bind to alpha and beta estrogen receptors (ERα and Erβ, respectively). Furthermore, FNT exerts agonistic action against the aryl hydrocarbon receptor (AhR) present on the growth plate and articular cartilages.

Murine chondrogenic cells were treated with FNT in the presence and absence of IL-1β for 48 hours, after which the cells were subjected to seven days of differentiation. Treated cells were then lysed for ribonucleic acid (RNA) extraction and subjected to a quantitative real-time polymerase chain reaction (RT-PCR).

A colorimetric 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was used to determine cell viability. Additionally, the Griess reaction was used to measure nitrite accumulation in the cells.

The protein structures for AhR, Erα, and Erβ were obtained from the Research Collaboratory for Structural Bioinformatics (RSCB) Protein Data Bank and used for the molecular docking analysis. The results of the molecular docking analysis are expressed in terms of lowest to highest Gibbs free energy for all conformations of the protein.

FNT exposure at low doses does not impair chondrocyte activity

Low concentrations of FNT were not detrimental to cell viability and lowered the expression of genes involved in inflammation. However, high concentrations of FNT can promote catabolic responses and negatively impact chondrocytes. Furthermore, the mechanism of action of FNT on chondrocytes was not mediated through AhR or estrogen receptors.

Low concentrations of FNT between 5 µM and 25 µM, with or without IL-1β, did not impact cell viability. Other studies have reported similar results at concentrations of FNT up to 100 µM. In contrast, some studies have reported that FNT concentrations between 25 µM and 100 µM can cause apoptosis.

The anti-inflammatory activity of FNT was observed at 12.5 µM in combination with IL-1β. However, higher concentrations of FNT starting at 25 µM, with or without IL-1β, did not affect inflammation.

While isoflavonoids mimic estrogen in their modulatory effects, estrogenic pathways were not involved in the action of FNT on chondrocytes. AhR blockade experiments also reported that despite FNT being a known agonist of AhR, their impact on chondrocyte activity did not involve AhR.

Intracellular nitrite concentrations reflected the absence of oxidative stress mechanisms in FNT action, thus indicating that the effect of FNT on chondrocytes is through mechanisms other than those involving AhR, estrogen receptors, or oxidative stress.

Conclusions

Low concentrations of FNT were not detrimental to cell viability and had positive effects on reducing inflammation, with and without the presence of IL-1β. Furthermore, the mechanism of action of FNT on chondrocytes does not appear to involve oxidative stress, AhR, or estrogen receptors. However, high concentrations of FNT could cause catabolic responses and have a negative impact on chondrocyte viability and function.