Homeostatic housecleaning effect of selenium: evidence that noncytotoxic oxidant-induced damage sensitizes prostate cancer cells to organic selenium-triggered apoptosis

Differential Inhibition of Anaplerotic Pyruvate Carboxylation and Glutaminolysis-Fueled Anabolism Underlies Distinct Toxicity of Selenium Agents in Human Lung Cancer

Past chemopreventive human trials on dietary selenium supplements produced controversial outcomes. They largely employed selenomethionine (SeM)-based diets. SeM was less toxic than selenite or methylseleninic acid (MSeA) to lung cancer cells. We thus investigated the toxic action of these Se agents in two non-small cell lung cancer (NSCLC) cell lines and ex vivo organotypic cultures (OTC) of NSCLC patient lung tissues. Stable isotope-resolved metabolomics (SIRM) using 13C6-glucose and 13C5,15N2-glutamine tracers with gene knockdowns were employed to examine metabolic dysregulations associated with cell type- and treatment-dependent phenotypic changes. Inhibition of key anaplerotic processes, pyruvate carboxylation (PyC) and glutaminolysis were elicited by exposure to MSeA and selenite but not by SeM. They were accompanied by distinct anabolic dysregulation and reflected cell type-dependent changes in proliferation/death/cell cycle arrest. NSCLC OTC showed similar responses of PyC and/or glutaminolysis to the three agents, which correlated with tissue damages. Altogether, we found differential perturbations in anaplerosis-fueled anabolic pathways to underlie the distinct anti-cancer actions of the three Se agents, which could also explain the failure of SeM-based chemoprevention trials.

Selenium and Dogs: A Systematic Review

The intent of this review is to summarize the knowledge about selenium and its function in a dog's body. For this purpose, systematic literature search was conducted. For mammals, including dogs, a balanced diet and sufficient intake of selenium are important for correct function of metabolism. As for selenium poisoning, there are no naturally occurring cases known. Nowadays, we do not encounter clinical signs of its deficiency either, but it can be subclinical. For now, the most reliable method of assessing selenium status of a dog is measuring serum or plasma levels. Levels in full blood can be measured too, but there are no reference values. The use of glutathione peroxidase as an indirect assay is questionable in canines. Commercial dog food manufactures follow recommendations for minimal and maximal selenium levels and so dogs fed commercial diets should have balanced intake of selenium. For dogs fed home-made diets, complex data are missing. However, subclinical deficiency seems to affect, for example, male fertility or recovery from parasitical diseases. Very interesting is the role of selenium in prevention and treatment of cancer.

Devising a new dialogue for nutrition science: how life course perspective, U-shaped thinking, whole organism thinking, and language precision contribute to our understanding of biological heterogeneity and forge a fresh advance toward precision medicine

The process of designing and implementing individualized health-promoting interventions, nutritional or otherwise, is fraught with great difficulty owing to the heterogeneity inherent in factors that influence healthy longevity. This article proposes that careful attention to three principles-life course perspective, U-shaped thinking, and whole organism thinking-creates an attitudinal framework that can be used to reframe biological heterogeneity into the clinically relevant question: Who will benefit? The search for tools to cope with the complexity of this heterogeneity has been dominated by technological advances, including state-of-the-art "-omics" approaches and machine-based handling of "big data." Here, it is proposed that language precision and nuanced category usage could provide critical tools for coping with heterogeneity, thereby enabling interventionalists to design and implement strategies to promote healthy longevity with greater precision. The lack of a clear understanding of "Who will benefit?" stands as a major obstacle to the design and implementation of nutritional strategies to optimize healthy longevity. This article opens a new dialogue situating the principles of life course perspective, U-shaped thinking, and whole organism thinking, along with cultivating an attitude of language precision at the very core of accelerating creative discovery and refining practical advance in the field of nutrition science.

Selenium, aging and aging-related diseases

Selenium is an essential trace element in the human body and plays an important role in the body via selenoprotein, which contains selenium. Selenoproteins (glutathione peroxidase, thioredoxin reductase, methionine sulfoxide reductase1 and endoplasmic reticulum-selenoproteins, etc.) have antioxidant effects and are involved in regulating antioxidant activities. Aging is an inevitable process and is always accompanied by aging-related diseases. Reactive oxygen species are important initial factors in aging and aging-related diseases. Selenium contributes to the alleviation of reduced reactive oxygen species-mediated inflammation, reduced DNA damage and prolonged telomere length and thereby plays roles in fighting aging and preventing aging-related diseases. In the elderly, aging-related diseases include neuropsychiatric diseases, tumors, cardiovascular diseases, and skin aging, among others. Selenium supplementation is an important strategy for anti-aging and the prevention of aging-related diseases and is of great significance for the elderly. However, with the accumulation of related research, selenium supplementation does not necessarily contribute to the prevention of aging and aging-related diseases. It is believed that a low level of selenium is beneficial to the human body. Thus, the effect of selenium on human aging and aging-related diseases is still controversial. This paper reviews the research progress and objective role of selenium in aging and aging-related diseases.

Five threads: How U-shaped thinking weaves together dogs, men, selenium, and prostate cancer risk

Prostate cancer is one of the leading causes of cancer-related mortality among men living in developed countries, making the development of safe, practical approaches to prostate cancer risk reduction a high research priority. The relationship between prostate cancer risk and selenium, an essential nutrient required for a number of metabolically important enzymes including glutathione peroxidases, has been investigated, but a satisfactory integration of results has proven elusive. Dogs, like men, naturally develop prostate cancer during aging, providing an appropriate context to study the effects of selenium supplementation on the dysregulation of homeostasis that drives cancer development within the aging prostate. In this paper, we summarize the translational significance of research results gained from dog studies on selenium and prostate cancer risk. Our discovery of a U-shaped dose-response between toenail selenium concentration and prostatic DNA damage in dogs remarkably parallels data on the relationship between selenium status and prostate cancer risk in men. Notably, the dog U-curve provides a plausible explanation for the unanticipated increase in prostate cancer incidence among men with highest baseline selenium who received selenium supplementation in the largest-ever prostate cancer prevention trial (SELECT). Moreover, the dog U-curve guided the discovery of a non-antioxidant, anti-carcinogenic mechanism of organic selenium - the preferential triggering of apoptosis in DNA damaged cells, which we have termed "homeostatic housecleaning". Taken together, the data from dogs and men indicate that increasing selenium status will not necessarily be associated with prostate cancer risk reduction. Landing in the trough of the U - achieving mid-range selenium status - is better than being too low or too high. Personalizing health promotion in a more-is-not-necessarily-better world poses distinctive challenges. Dog studies can be relied upon to contribute important insights into dose-dependent and form-dependent effects - two critical aspects of selenium biology that will have to be disentangled if the burgeoning science of selenium is to be translated into effective strategies for human disease prevention. Beyond contributing to understanding the role of selenium in biology, our work situates the concept of U-shaped thinking at the core of personalized medicine and precision nutrition.

Skeletal muscle atrophy is attenuated in tumor-bearing mice under chemotherapy by treatment with fish oil and selenium

Chemotherapy can cause cachexia, which is manifested by weight loss, inflammation and muscle atrophy. However, the mechanisms of tumor and chemotherapy on skeletal muscle proteolysis, remained unclear. In this report, we demonstrated that tumor-induced myostatin in turn induced TNF-α, thus activating calcium-dependent and proteasomal protein degradation. Chemotherapy activated myostatin-mediated proteolysis and muscle atrophy by elevating IL-6. In tumor-bearing mice under chemotherapy, supplementation with fish oil and selenium prevented a rise in IL-6, TNF-α and myostatin and muscle atrophy. The findings presented here allow us to better understand the molecular basis of cancer cachexia and potentiate nutrition supplementation in future cancer chemotherapy.

Sensitization of cisplatin therapy by a naphthalimide based organoselenium compound through modulation of antioxidant enzymes and p53 mediated apoptosis

The widely used anti-cancer drug cisplatin imparts various toxic manifestations in the host, with nephrotoxicity being the most severe one. The trace element selenium shows antioxidant activity in both human and animals. The present study was designed to assess the chemoprotecting and chemoenhancing efficacy of a naphthalimide based organoselenium compound 2-(5-selenocyanato-pentyl)-benzo[de]isoquinoline 1,3-dione during cisplatin chemotherapy in mice bearing Ehrlich ascites carcinoma cells. Cisplatin (5 mg/kg b.w.) was administered intraperitoneally and the organoselenium compound (3 mg/kg b.w.) was given by oral gavage in concomitant and pretreatment schedule. The effects of the test compound was evaluated by assaying biochemical, hematological, histological, genotoxicity parameters and by investigating induction of apoptosis in tumor cells, and calculating tumor growth response in the host. The organoselenium compound significantly prevented cisplatin induced generation of reactive oxygen species (ROS), reactive nitrogen species, and onset of lipid peroxidation in the kidney tissue of the experimental mice. In addition, the test compound was also substantially restored cisplatin induced depleted activities of the renal antioxidant enzymes and reduced glutathione level; prevented the serum blood urea nitrogen level, creatinine level, chromosomal aberration, DNA damage, histological alterations of kidney, and normalized the hematological profile of the tumor bearing mice. Furthermore, the organoselenium compound alone or during combination therapy induced apoptosis in tumor cells through mitochondria mediated and DNA damage mediated pathway and ultimately increased the life span of the tumor bearing host. Hence, the results showed that the test compound not only reduced the toxicity of cisplatin but also enhanced its anti-tumor efficacy.