FIG. 2.

Diagram depicts shows the key components of the Krebs (citric acid) cycle. The Krebs cycle is a series of enzyme-catalyzed chemical reactions within the matrix of mitochondria that, in conjunction with the electron transport chain (ETC), generates the energy that can be utilized by the cell. Acetyl-L-carnitine (ALC) can serve as an alternate energy source by promoting the formation of acetyl coenzyme A (CoA) in the absence of optimal pyruvate dehydrogenase (PDH) activity, leading to the reduction of nicotinamide adenine dinucleotide (NAD⁺) and flavin adenine dinucleotide (FAD). The reduced forms of FAD (FADH₂) and NAD⁺ (NADH) serve as electron carriers to promote function of the ETC and the production of ATP. Other substances, such as amino acids (e.g., glutamate), ketones, and fatty acids may also potentially serve as alternative energy sources, entering the Krebs cycle at different points than ALC, but their efficacies have not been evaluated in spinal cord injury.