We investigate the health effect of a material on energy metabolism via mammalian cell mode in following four aspects of metabolism:
Cellular reduction potential and Mitochondrial membrane potential Metabolically active cells create a reduction potential that can be quantified and used to indicate cell metabolic activity and cell viability. When measured in a population of cells, cellular reduction potential is proportional to the number of living cells. In the presence of exogenous compounds, decreases in cellular reduction potential can indicate decreased viability. In the meantime, ATP (adenosine triphosphate) generation occurs primarily in mitochondria, and a decrease in mitochondrial membrane potential will lead to a reduced ATP production, and eventually activation of a series of metabolic activities. By assessing cellular and mitochondrial reduction potential in the presence and absence of the test material, we would be able to assess its effects on cellular metabolic activity.
Oxidative phosphorylation: Cellular oxidative consumption rate assay Energy metabolism is the process by which nutrients are converted to ATP. There are two significant pathways of cellular ATP production: oxidative phosphorylation and glycolysis. Oxidative phosphorylation generates the majority of ATP in an organism and is the result of electron transfer from substrates in the mitochondria. This can be investigated via cellular oxidative consumption rate assay.
Glycolysis Glycolysis is another significant pathway of cellular ATP production where glucose is converted into pyruvate and energy is released in the process to form ATP and other high-energy molecules. The degree of glycolysis can be measured by the rate of hexokinase formation (Cellular hexokinase assay) and extracellular acidification (Cellular Extracellular Acidification Assay).
Metabolic enzymatic activity and gene expression Substances that substantially increase energy metabolism may have potent effects on gene expression. For example, caffeine activates AMPK (5’adenosine monophosphate-activated protein kinase), which serves as a “fuel gauge” in cells and is activated under conditions that signify cellular stress. Caffeine also significantly increases expression of an essential precursor to mitochondrial biosynthesis, peroxisome proliferator-activated receptor coactivator 1 alpha (PGC-1α). Along the same approach, we apply Cellular AMPK assay and Cellular metabolic gene expression assay to assess whether a test material has significant effects on proteins associated with energy metabolism.