Acetyl coenzyme A is a molecule that was first discovered to transfer acetyl groups to the citric acid cycle (Krebs cycle) to be oxidized for energy production. Now it is known to be involved in many different pathways including fatty acid metabolism, steroid synthesis, acetylcholine synthesis, acetylation, and melatonin synthesis.

A chemical produced in the liver via the breakdown of fatty acids. Beta-hydroxybutyrate is a type of ketone body. It can be used to produce energy inside the mitochondria and acts as a signaling molecule that alters gene expression by inhibiting a class of enzymes known as histone deacetylases.

A molecule composed of carboxylic acid with a long hydrocarbon chain that is either saturated or unsaturated. Fatty acids are important components of cell membranes and are key sources of fuel because they yield large quantities of ATP when metabolized. Most cells can use either glucose or fatty acids for this purpose.

A metabolic pathway in which the liver produces glucose from non-carbohydrate substrates including glycogenic amino acids (from protein) and glycerol (from lipids).

A sugar-alcohol compound that is the backbone of the triglycerides.

An immature cell that can develop into all types of blood cells, including white blood cells, red blood cells, and platelets. Hematopoietic stem cells are found in the peripheral blood and the bone marrow and give rise to both the myeloid and lymphoid lineages of blood cells. The process by which blood cells are produced is known as hematopoiesis.

Myeloid cells include monocytes, macrophages, neutrophils, basophils, eosinophils, erythrocytes, and megakaryocytes to platelets. Lymphoid cells include T cells, B cells, and natural killer cells.

A metabolic pathway in which organisms produce ketones. Ketogenesis occurs primarily in the mitochondria of liver cells via the breakdown of fatty acids and ketogenic amino acids. Insulin is the major hormonal regulator of ketogenesis; however, glucagon, cortisol, thyroid hormones, and catecholamines can induce greater breakdown of free fatty acids, thereby increasing the substrates available for use in the ketogenic pathway. The primary ketones used by the body for energy are acetoacetate and beta-hydroxybutyrate.

Molecules (often simply called “ketones”) produced by the liver during the breakdown of fatty acids. Ketone production occurs during periods of low food intake (fasting), carbohydrate restrictive diets, starvation, or prolonged intense exercise. There are three types of ketone bodies: acetoacetate, beta-hydroxybutyrate, and acetone. Ketone bodies are readily used as energy by a diverse array of cell types, including neurons.

Tiny organelles inside cells that produce energy in the presence of oxygen. Mitochondria are referred to as the "powerhouses of the cell" because of their role in the production of ATP (adenosine triphosphate). Mitochondria are continuously undergoing a process of self-renewal known as mitophagy in order to repair damage that occurs during their energy-generating activities.

The process of generating energy that occurs when mitochondria couple oxygen with electrons that have been derived from different food sources including glucose, fatty acids, and amino acids.

Undifferentiated descendants of stem cells. Unlike stem cells, progenitor cells can differentiate into cells of a particular lineage only and they cannot divide and reproduce indefinitely. Progenitor cells show potential in the fields of plastic and reconstructive surgery, ophthalmology, and heart and blood disorders.

In a state or period of inactivity or dormancy.

Oxygen-containing chemically-reactive molecules generated by oxidative phosphorylation and immune activation. ROS can damage cellular components, including lipids, proteins, mitochondria, and DNA. Examples of ROS include: peroxides, superoxide, hydroxyl radical, and singlet oxygen.

A related byproduct, reactive nitrogen species, is also produced naturally by the immune system. Examples of RNS include nitric oxide, peroxynitrite, and nitrogen dioxide.

The two species are often collectively referred to as ROS/RNS. Preventing and efficiently repairing damage from ROS (oxidative stress) and RNS (nitrosative stress) are among the key challenges our cells face in their fight against diseases of aging, including cancer.

A cell that has the potential to develop into different types of cells in the body. Stem cells are undifferentiated, so they cannot do specific functions in the body. Instead, they have the potential to become specialized cells, such as muscle cells, blood cells, and brain cells. As such, they serve as a repair system for the body. Stem cells can divide and renew themselves over a long time. In 2006, scientists reverted somatic cells into stem cells by introducing Oct4, Sox2, Klf4, and cMyc (OSKM), known as Yamanaka factors.^[1]