Jamaican vomiting sickness
Encyclopedia
Jamaican vomiting sickness is an acute illness caused by the toxin hypoglycin
A, which is present in unripened fruit of the ackee
tree. Hypoglycin A is present in the unripe arilli at levels of over 1000 ppm, which falls to less than 0.1 ppm in the fully ripened arilli. Hypoglycin B, found only in the inedible seed, is believed to be a derivative of hypoglycin A. Its concentration rises from 0.4 mg/g to 3.3 mg/g as the fruit ripens.
, so that only unsaturated fatty acids can be fully oxidized. Fatty acids accumulate in the liver in a microvesicular pattern that can be seen on biopsy. In the absence of fatty acid metabolism, the body becomes dependent on glucose and glycogen for energy. Octreotide
can be used to reduce secretion of insulin by the pancreas, preventing severe hypoglycemia
.
Inhibition of beta-oxidation of fatty acids, however, also depletes a necessary cofactor for gluconeogenesis
. Once the liver glycogen stores are depleted, the body cannot synthesize glucose, and severe hypoglycemia results.
episode, "Great Expectations", where the symptoms are not recognized by the doctors.
Hypoglycin
Hypoglycin is a naturally occurring organic compound in the species Blighia sapida. It is particularly concentrated in the fruit of the plant. Hypoglycin is toxic if ingested and is the causative agent of Jamaican Vomiting Sickness. It is an amino acid and chemically related to lysine...
A, which is present in unripened fruit of the ackee
Ackee
The ackee, also known as the vegetable brain, achee, akee apple or akee is a member of the Sapindaceae , native to tropical West Africa in Cameroon, Gabon, São Tomé and Príncipe, Benin, Burkina Faso, Côte d'Ivoire, Ghana, Guinea, Guinea-Bissau, Mali, Nigeria, Senegal, Sierra Leone and Togo.It is...
tree. Hypoglycin A is present in the unripe arilli at levels of over 1000 ppm, which falls to less than 0.1 ppm in the fully ripened arilli. Hypoglycin B, found only in the inedible seed, is believed to be a derivative of hypoglycin A. Its concentration rises from 0.4 mg/g to 3.3 mg/g as the fruit ripens.
Pathophysiology
When ingested, hypoglycin A is metabolized to produce methylenecyclopropylacetic acid (MCPA). MCPA acts to inhibit the beta-oxidation of fatty acids in two ways. First, it interferes with the transport of long-chain fatty acids into the mitochondria. Also, it inhibits acyl-CoA dehydrogenasesAcyl CoA dehydrogenase
Acyl-CoA dehydrogenases are a class of enzymes that function to catalyze the initial step in each cycle of fatty acid β -oxidation in the mitochondria of cells. Their action results in the introduction of a trans double-bond between C2 and C3 of the acyl-CoA thioester substrate...
, so that only unsaturated fatty acids can be fully oxidized. Fatty acids accumulate in the liver in a microvesicular pattern that can be seen on biopsy. In the absence of fatty acid metabolism, the body becomes dependent on glucose and glycogen for energy. Octreotide
Octreotide
Octreotide is an octapeptide that mimics natural somatostatin pharmacologically, though it is a more potent inhibitor of growth hormone, glucagon, and insulin than the natural hormone...
can be used to reduce secretion of insulin by the pancreas, preventing severe hypoglycemia
Hypoglycemia
Hypoglycemia or hypoglycæmia is the medical term for a state produced by a lower than normal level of blood glucose. The term literally means "under-sweet blood"...
.
Inhibition of beta-oxidation of fatty acids, however, also depletes a necessary cofactor for gluconeogenesis
Gluconeogenesis
Gluconeogenesis is a metabolic pathway that results in the generation of glucose from non-carbohydrate carbon substrates such as lactate, glycerol, and glucogenic amino acids....
. Once the liver glycogen stores are depleted, the body cannot synthesize glucose, and severe hypoglycemia results.
Disease course
Abdominal discomfort begins two to six hours after eating unripe ackee fruit, followed by sudden onset vomiting. In severe cases, profound dehydration, seizures, coma, and death may ensue. Children and those who are malnourished are more susceptible to the disease.In popular culture
The disease appears in an ERER (TV series)
ER is an American medical drama television series created by novelist Michael Crichton that aired on NBC from September 19, 1994 to April 2, 2009. It was produced by Constant c Productions and Amblin Entertainment, in association with Warner Bros. Television...
episode, "Great Expectations", where the symptoms are not recognized by the doctors.