3-HPMA is the main urinary metabolite of acrolein. Acrolein is an environmental pollutant, commonly used as an herbicide and in many different chemical industries. Acrolein is also present in the burning of cigarettes, gasoline, and oil. Certain bacteria produce acrolein, such as Clostridium. Acrolein metabolites are associated with diabetes and insulin resistance.

3-Hydroxyvaleric acid may be products of the condensation of propionyl-CoA with acetyl-CoA catalyzed by 3-oxoacyl-CoA thiolases. An increase amount of 3-hydroxyvaleric acid can be found in methylmalonic acidemia and propionic acidemia. 

Indoleacetic acid (IAA), or indole-3-acetate, is produced by the bacterial fermentation of the amino acid tryptophan.

IAA can be formed from several common gut microbes such as Clostridia species, Escherichia coli, and Saccharomyces species.

3-Indoleacetic is a Tryptophan byproduct of Clostria: C. stricklandii, C. litusburense, C. subterminale, and C. putrefaciens.

3-Indoleacetic is a Tryptophan byproduct of Clostria: C. stricklandii, C. litusburense, C. subterminale, and C. putrefaciens.

Both 1-methylhistidine and 3-methylhistidine are histidine metabolites which have been proposed as markers of meat intake. Note that some confusion exists in the literature regarding the numbering of atoms in the imidazole ring of histidine – 1 versus 3 – and thus, there is caution with interpretation and clinical significance of these two markers.

3-methylhistidine is a constituent of actin and myosin, the contractile proteins of skeletal muscles. Urinary excretion of 3-methylhistidine may be a result of muscle breakdown or consumption of meat fibers. Unlike 1-methylhistidine, 3-methylhistidine has been shown to increase in fasting states indicating catabolism of muscle tissue. Therefore, this marker is more variable with regards to animal protein consumption.

3-Methyl-2-oxovaleric acid is an abnormal metabolite that arises from the incomplete breakdown of branched-chain amino acids. 

Moderate increase may result from lactic acidosis, episodic ketosis, or thiamine/lipoic acid deficiency. Significant elevations are associated with genetic issues, MSUD, and pyruvate dehydrogenase deficiency.

- Slight elevations may be due to deficiencies of the vitamins thiamine or lipoic acid.

- Elevated values are also associated with the genetic diseases maple syrup urine disease or pyruvate dehydrogenase deficiency.

3-Methyl-2-oxovaleric acid is an abnormal metabolite that arises from the incomplete breakdown of branched-chain amino acids. 

Moderate increase may result from lactic acidosis, episodic ketosis, or thiamine/lipoic acid deficiency. Significant elevations are associated with genetic issues, MSUD, and pyruvate dehydrogenase deficiency.

- Slight elevations may be due to deficiencies of the vitamins thiamine or lipoic acid.

- Elevated values are also associated with the genetic diseases maple syrup urine disease or pyruvate dehydrogenase deficiency.

3-Methyl-2-oxovaleric acid is an abnormal metabolite that arises from the incomplete breakdown of branched-chain amino acids. 

Moderate increase may result from lactic acidosis, episodic ketosis, or thiamine/lipoic acid deficiency. Significant elevations are associated with genetic issues, MSUD, and pyruvate dehydrogenase deficiency.

- Slight elevations may be due to deficiencies of the vitamins thiamine or lipoic acid.

- Elevated values are also associated with the genetic diseases maple syrup urine disease or pyruvate dehydrogenase deficiency.

3-Methyl-2-oxovaleric acid is an abnormal metabolite that arises from the incomplete breakdown of branched-chain amino acids. 

Moderate increase may result from lactic acidosis, episodic ketosis, or thiamine/lipoic acid deficiency. Significant elevations are associated with genetic issues, MSUD, and pyruvate dehydrogenase deficiency.

- Slight elevations may be due to deficiencies of the vitamins thiamine or lipoic acid.

- Elevated values are also associated with the genetic diseases maple syrup urine disease or pyruvate dehydrogenase deficiency.

3-Methyl-4-OH-Phenylglycol (MHPG) is a byproduct of the central nervous system’s norepinephrine (NE) metabolism. MHPG metabolizes to vanilmandelic acid (VMA) in the liver using the enzymes alcohol dehydrogenase and aldehyde dehydrogenase. Urinary MHPG was originally thought to represent CNS sympathetic output, but is now known to be principally derived from peripheral neuronal NE metabolism.

MHPG has been widely studied as a marker to predict response to medications used in mood disorders or as a biomarker to monitor pharmacotherapies.

3-Methyl-4-OH-Phenylglycol (MHPG) is a byproduct of the central nervous system’s norepinephrine (NE) metabolism. MHPG metabolizes to vanilmandelic acid (VMA) in the liver using the enzymes alcohol dehydrogenase and aldehyde dehydrogenase. Urinary MHPG was originally thought to represent CNS sympathetic output, but is now known to be principally derived from peripheral neuronal NE metabolism.

MHPG has been widely studied as a marker to predict response to medications used in mood disorders or as a biomarker to monitor pharmacotherapies.

3-Methyl-4-OH-phenylglycol is the breakdown product from norepinephrine, but it may also be produced from epinephrine to a lesser extent.

The marker, 3-methylglutaconic acid in high values indicates a reduced ability to metabolize the amino acid, leucine. This abnormality is found in the genetic disease, methylglutaconic aciduria and in mitochondrial disorders.