Presence of benzodiazepine-like molecules in food and their implication in the nutrition of cirrhotic patients

Natural endogenous ligands for benzodiazepine receptors in hepatic encephalopathy

Benzodiazepines of natural origin (NBZDs) have been found in human blood and brains as well as in medicinal plants and foods. In plasma and brain tissue there are i.e. diazepam and nordiazepam equal to commercial drugs but there are also other benzodiazepine-like compounds termed "endozepines", which act as agonists at the benzodiazepine receptors of central type (CBR). A synthetic pathway for the production of NBZDs has not yet been found, but it has been suggested that micro-organisms may synthesize molecules with benzodiazepine-like structures. Hence NBZDs could be of both endogenous and exogenous source and be considered as natural anxyolitic and sedative. Interestingly there are also natural compounds, such as the polypeptide Diazepam Binding Inhibitor (DBI) acting as an "inversive agonist" implicated in fair and panic disorders. It has been suggested that NBZDs may play a role in the pathogenesis of hepatic encephalopathy (HE). Multidirectional studies evaluated NBZDs levels (1) in the blood of normal subjects, of cirrhotic with or without HE and in commercial benzodiazepine consumers; (2) in the blood of cirrhotic treated or not with a non-absorbable antibiotic; (3) in several constituents of our diet. In conclusion, NBZDs increase sometime in cirrhotics with or without HE but they reach concentrations not higher than those found in commercial benzodiazepines consumers. Hence NBZDs must be considered as occasional precipitating factor of HE and benzodiazepine antagonists only symptomatic drugs. The finding that NBZDs may be in part synthesized by intestinal bacterial flora and in part constituent of our diet underlines the importance to feed cirrhotic patients with selected food.

Endozepines in recurrent stupor

Stupor is a condition from which the subject can be aroused only by vigorous stimuli. Most patients with stupor have a diffuse organic cerebral dysfunction. Rarely stupor is recurrent and no specific causes can be found. Patients with idiopathic recurrent stupor were awakened by i.v. administration of an antagonist (flumazenil) of the benzodiazepine recognition site located in the GABA(A) receptor. Since no exogenous benzodiazepines were detected in plasma and cerebrospinal fluid by high performance liquid chromatography, an excess of endogenous benzodiazepine-like compounds (endozepines) was proposed as the cause of stupor. The existence of endozepines, their widespread distribution in the CNS and their involvement in hepatic encephalopathy are established. However, the origin of these compounds, how biosynthesis occurs and the mechanisms and causes through which they alter brain functions are poorly understood. The fact that a number of synthetic benzodiazepines are difficult to detect using conventional techniques and the discovery that some cases of recurrent stupor were caused by fraudulent administration of lorazepam question whether the concept of endozepine recurrent stupor can be sustained. This review summarizes the state of endozepine physiology and pharmacology and the clinical syndromes attributed to their involvement. A diagnostic work-up to define endozepine-induced recurrent stupor is suggested.

Management of hepatic encephalopathy: role of rifaximin

Hepatic encephalopathy (HE) is a neuropsychiatric syndrome, which develops in patients with acute or chronic liver failure. It is widely accepted to be due to impairment of hepatic clearance of toxic products from the gut such as ammonia. Accumulation of ammonia induces a glutamate neurotoxicity leading to an increased tone of the gamma-aminobutyric acid A (GABA-A) receptor system in the brain which results in HE. Factors either increasing the ammonia levels (protein load, constipation, sepsis, or gastrointestinal bleeding) or potentiating the functional activity of the GABAergic system [natural benzodiazepine-like compounds (NBZDs) or exogenous benzodiazepines] may act as precipitating factors of HE. NBZDs are present in trace amounts in the blood of normal subjects and have been found to be increased in the blood of patients with liver cirrhosis, with or without HE. These compounds may derive either from the diet since they have been found in plants, vegetables and animals or from gut bacteria. The observation that intestinal bacterial flora is involved in the production of both primary agent of HE (ammonia) and precipitating factors (NBZDs) suggests that the use of nonabsorbable antibiotics such as rifaximin may be useful in preventing episodes of HE in patients with liver cirrhosis.

Peripheral benzodiazepine receptors in potatoes (Solanum tuberosum)

The peripheral benzodiazepine receptor (PBR), an internal protein of the mammalian mitochondrial membrane, is involved in several metabolic functions such as steroidogenesis, oxidative phosphorylation, and regulation of cell proliferation. Here we report the presence of PBRs in parenchymal and meristematic tissues of potato (Solanum tuberosum). PBRs are heterogeneously distributed in potato and are highly expressed in meristematic cells. In particular the receptor protein is mainly localised in the meristematic nuclear subcellular preparation. This 30-36 kDa protein, which corresponds to PBR, is increased, indeed, in meristematic compared to the parenchymal tissue. This suggests an involvement of this receptor in the regulation of cell plant growth. In addition, the demonstration that PBRs are also present in vegetables supports the hypothesis of a highly conserved receptor system during phylogenesis.

Extraction and purification from Ceratonia siliqua of compounds acting on central and peripheral benzodiazepine receptors

The presence of molecules with high affinity for central and peripheral benzodiazepine receptors was determined in the pod and leaves of Ceratonia siliqua (carob). The amount of the substances able to selectively bind the central benzodiazepine receptor recovered from carob pods and leaves was respectively 12.17 and 18.7 ng diazepam equivalent/g. The amount of compounds active on peripheral benzodiazepine receptor in both pods and leaves was higher in comparison with the central one, being 49.83 and 40.00 PK 11195 equivalent/g, respectively. In particular the compounds acting on peripheral benzodiazepine receptors were found to be extremely concentrated in the young leaves (2572.57 ng PK 11195 equivalent/g). The presence of substances with central benzodiazepine activity in carob extracts seems of great importance in view of the possibility to use carob extract as potential natural products with anxiolytic-sedative effects. Moreover, the prevalence in leaves of substances acting on peripheral benzodiazepine receptor suggests the possible utilisation of leave extracts as chemopreventive agents.