Cytotoxicity and mitochondrial dysfunction caused by the dietary supplement l-norvaline

In addition to the 20 protein amino acids that are encoded for protein synthesis, hundreds of other naturally occurring amino acids, known as non-proteinogenic amino acids (NPAAs) exist. It is well known that some NPAAs are toxic through their ability to mimic protein amino acids, either in protein synthesis or in other metabolic pathways, and this property is utilised by some plants to inhibit the growth of other plants or kill herbivores. L-norvaline is an NPAA readily available for purchase as a dietary supplement. In light of previous evidence of l-norvaline's antifungal, antimicrobial and herbicidal activity, we examined the toxicity of l-norvaline to mammalian cells in vitro and showed that l-norvaline decreased cell viability at concentrations as low as 125 μM, caused necrotic cell death and significant changes to mitochondrial morphology and function. Furthermore, toxicity was reduced in the presence of structurally similar 'protein' amino acids, suggesting l-norvaline's cytotoxicity could be attributed to protein amino acid mimicry.

Selected terpenoids from medicinal plants modulate endoplasmic reticulum stress in metabolic disorders

Objectives

The majority of research performed on cellular stress and apoptosis focuses on mitochondrial dysfunction; however, the importance of the endoplasmic reticulum dysfunction and the link to metabolic diseases has gained a substantial interest. This review focuses on the potential of terpenoids to influence endoplasmic reticulum stress and the possible role terpenoids play as the treatment of metabolic diseases.

Key findings

Metabolic diseases develop as a result of a cascade of cellular pathways. In most cases, cells are able to compensate for the disruption of the cellular homeostasis although the initiation of response pathways; however, chronic stress initiates apoptotic pathways. This reviewed (1) showed the importance of phytoterpenoids to influence endoplasmic reticulum (ER) stress and homeostasis, (2) showed how regulating ER stress affect the cell survival and death, and (3) highlighted some examples of how the progression of metabolic diseases can be influenced by ER.

Summary

Due to the substantial number of terpenoids that have been identified in literature, this review gave examples of 21 terpenoids that have been documented to have an effect on the different proteins associated with ER stress, how these plant terpenoids influence ER dysfunction and metabolic diseases such as diabetes, cancer, liver, and neurological diseases and parasitic infections.