when does l carnitine show a difference Carnitine: Genetic Variants Affecting Mitochondrial Energy and Health L-Carnitine vs Acetyl L-Carnitine: Which
Description
There are 5 kinds of heavy chains termed IgG, IgA, IgM, IgD, and IgE

found that aged rats treated with ALC showed improvement in NGF-binding capacity in brain regions, suggesting that certain forms of LC might enhance neuron responsiveness to neurotrophic factors in older rats [43]

Neurology 1983, 33: 1136-1140

This is called haplotype analysis