Selenomethionine induces polyamine biosynthesis in regenerating rat liver tissue

Plasma Polyamines Decrease in Patients with Obstructive Cholecystitis

Polyamines (PAs), endogenous metabolites with a wide range of biological activities, are synthesized at a high rate in liver supporting hepatocyte proliferation and survival. The liver appears as an important regulator of plasma PAs; however, the perspective to exploit plasma PA measurements as indicators for liver function was not explored. This study aimed to evaluate the value of the plasma levels of PAs as a biomarker of pathological changes in the liver in patients with obstructive cholecystitis. The levels of polyamines and their acetylated forms were measured using HPLC/UV in the plasma of patients with obstructive cholecystitis and in healthy subjects. PA turnover was assessed by the ratio between an acetylated form of PA and PA. An effect of diet preference of cheese or meat, the major exogenous sources of PAs, smoking, and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in anamnesis was also evaluated in healthy subjects. We found that the plasma levels of spermine and acetylated spermidine decreased in patients with obstructive cholecystitis without a concurring increase in the total plasma bilirubin and amylase levels. The turnover of spermine and spermidine was also changed, suggesting a decrease in the rate of PA degradation in the liver. In healthy subjects, the PA levels tended to mirror chronic smoking and recent SARS-CoV-2 infection but were not relevant to diet factors. A number of observations indicated the role of physical exercise in the regulation of the plasma pool of PA. The decrease in plasma PA levels and index of PA turnover in the cholestasis syndrome indicate the liver’s metabolic function reduction. A conceivable effect of lung-related conditions on plasma PA, while indicating low specificity, nonetheless, speaks favorably about the high sensitivity of plasma PA measurement as an early diagnostic test in the clinic.

Selenium and anticarcinogenesis: underlying mechanisms

PURPOSE OF REVIEW

To discuss recent research related to anticarcinogenic mechanisms of selenium action in light of the underlying chemical/biochemical functions of the selenium species, likely to be executors of those effects.

RECENT FINDINGS

Recent studies in a variety of model systems have increased the understanding of the anticarcinogenic mechanisms of selenium compounds. These include effects on gene expression, DNA damage and repair, signaling pathways, regulation of cell cycle and apoptosis, metastasis and angiogenesis. These effects would appear to be related to the production of reactive oxygen species produced by the redox cycling, modification of protein-thiols and methionine mimicry. Three principle selenium metabolites appear to execute these effects: hydrogen selenide, methylselenol and selenomethionine. The fact that various selenium compounds can be metabolized to one or more of these species but differ in anticarcinogenic activity indicates competing pathways of their metabolic and chemical/biochemical disposition. Increasing knowledge of selenoprotein polymorphisms has shown that at least some are related to cancer risk and may affect carcinogenesis indirectly by influencing selenium metabolism.

SUMMARY

The anticarcinogenic effects of selenium compounds constitute intermediate mechanisms with several underlying chemical/biochemical mechanisms such as redox cycling, alteration of protein-thiol redox status and methionine mimicry.