Search results: Found 4

Listing 1 - 4 of 4
Sort by
Vitamin K and Vitamin K-Dependent Proteins in Relation to Human Health

Authors: ---
ISBN: 9783038428312 9783038428329 Year: Pages: X, 192 Language: English
Publisher: MDPI - Multidisciplinary Digital Publishing Institute
Subject: Nutrition and Food Sciences
Added to DOAB on : 2018-04-17 12:23:54
License:

Loading...
Export citation

Choose an application

Abstract

Vitamin K comprises a group of highly lipophilic molecules that possess a common 2-methyl-1, 4-naphthoquinone nucleus and a variable polyisoprenoid side chain at the 3-position that can vary in both length and degree of saturation. In nature, these forms are found as a single plant form (phylloquinone or vitamin K1) and a series of bacterial forms (menaquinones or vitamin K2). Vitamin K acts as a cofactor for a microsomal enzyme, γ-carboxyglutamyl carboxylase (GGCX), that serves to transform specific peptide-bound glutamate residues found in certain specialized proteins to γ-carboxyglutamate (Gla). This posttranslational protein modification is the only firmly established biochemical function of vitamin K. The resultant vitamin K-dependent (VKD) proteins, or Gla proteins, are diverse in both structure and function and are found in many cell and tissue types. The best-known example of the health role of vitamin K-mediated protein γ-carboxylation is in the synthesis of several VKD blood coagulation proteins, which are essential for the maintenance of extracellular haemostasis. An overt deficiency of vitamin K results in bleeding and although rare in most populations, vitamin K deficiency bleeding (VKDB) in early infancy has potentially devastating and fatal consequences because bleeding commonly occurs within the brain. For this reason it is recommended that all newborn infants should receive vitamin K prophylaxis. On the other hand, the deliberate lowering of circulating VKD-coagulation factors by the therapeutic administration of vitamin K antagonists (VKA) such as warfarin is used to treat and prevent thrombotic disorders. The functions of most non-coagulation Gla proteins remain uncertain, but are suspected to play roles in processes as diverse as bone and cardiovascular mineralization, vascular integrity, energy metabolism, immune response, brain metabolism, and in cellular growth, survival, and signalling. For the most part, extrapolations of the cellular properties of extrahepatic Gla proteins to tangible health benefits are unclear or fuzzy, as are the health consequences of their undercarboxylation. However, there is evidence that higher nutritional intakes of vitamin K are required to enable maximal γ-carboxylation of certain extrahepatic Gla proteins, such as osteocalcin and matrix Gla protein (MGP). Osteocalcin and MGP currently represent the best-studied extrahepatic Gla proteins with respect to their putative roles in bone and cardiovascular health, respectively. In addition, osteocalcin may play a role in regulating energy metabolism. Much current interest focuses on the role of MGP as an inhibitor of vascular mineralization, particularly in renal disease and in patients taking VKA. Interestingly, although VKA have been in clinical use for decades, recent evidence suggests that they may cause unintended health consequences by disrupting the function of MGP resulting in calcification and loss of the functional integrity of the vessel wall. Apart from the role of vitamin K in γ-carboxylation there is evidence that some forms, particularly menaquinone-4 (MK-4), have a direct influence on cellular functions.This Special Issue of Nutrients focuses on advances that extend our knowledge of the biochemical functions and health roles played by both the micronutrient vitamin K and its target Gla proteins. The scope of potential topics is wide and may include studies in population and patient groups, animal models and at the cellular level. Examples include the presentation, diagnosis, incidence, causes, and prevention of deficiency syndromes, of which the most obvious is bleeding in infancy, but also extends to other putative roles of vitamin K such as in bone and cardiovascular health. In trying to define extrahepatic functions of vitamin K it is important to obtain evidence of pathophysiological signatures that may derive from chronic suboptimal vitamin K intakes or as a consequence of vitamin K antagonists. An important related question is whether the pathophysiology can be ameliorated or prevented by judicious vitamin K supplementation. Equally important to our understanding of the human physiology of vitamin K are studies that define the relative functional importance of individual vitamers and how differences in their availability and metabolism affect their biological activity. Recent highlights in metabolism include the delineation of the importance of vitamin K epoxide reductase (VKOR) in maintaining vitamin K status and the intriguing hypothesis that its paralog VKOR-like 1 enzyme (VKORL1) may serve an antioxidant function. Another highlight illustrating the importance of metabolism to vitamin K function is the discovery that the enzyme UbiA prenyltransferase-containing domain 1 (UBIAD1) participates in the cellular conversion of phylloquinone to MK-4 with menadione as a metabolic intermediate. We invite authors to submit reviews or original research on any of the above topics.

Vitamin C: Current Concepts in Human Physiology

Authors: ---
ISBN: 9783038972945 9783038972952 Year: Pages: 148 DOI: 10.3390/books978-3-03897-295-2 Language: English
Publisher: MDPI - Multidisciplinary Digital Publishing Institute
Subject: Therapeutics --- Biology
Added to DOAB on : 2018-11-05 12:11:11
License:

Loading...
Export citation

Choose an application

Abstract

ca. 200 words; this text will present the book in all promotional forms (e.g. flyers). Please describe the book in straightforward and consumer-friendly terms.[Vitamin C is synthesized by almost all animals. However, for humans, it is a vitamin that needs constant replenishment in the diet. While its role as an anti-oxidant and for preventing scurvy have been known for a long time, novel functions and unrecognized associations continue to be identified for this enigmatic molecule. In the past decade, new details have emerged regarding differences in its uptake by oral and intravenous modes. While vitamin C deficiency remains largely unknown and poorly addressed in many segments of the population, novel pharmacological roles for high-dose, intravenous vitamin C in many disease states have now been postulated and investigated. This has shifted its role in health and disease from the long-perceived notion as merely a vitamin and an anti-oxidant to a pleiotropic molecule with a broad anti-inflammatory, epigenetic, and anti-cancer profile.This Special Issue comprises original research papers and reviews on vitamin C metabolism and function that relate to the following topics: understanding its role in the modulation of inflammation and immunity, therapeutic applications and safety of pharmacological ascorbate in disease, and the emerging role of vitamin C as a pleiotropic modulator of critical care illness and cancer.]

Vitamin C in Health and Disease

Authors: ---
ISBN: 9783038970293 9783038970309 Year: Pages: X, 288 Language: english
Publisher: MDPI - Multidisciplinary Digital Publishing Institute
Subject: Cardiovascular
Added to DOAB on : 2018-08-09 11:31:26
License:

Loading...
Export citation

Choose an application

Abstract

Vitamin C is a pivotal water soluble electron donor in nature and an essential nutrient in man. Despite its many years as a research focus, new and increasingly regulatory functions of vitamin C in human health are continually being unravelled. This improved mechanistic insight is starting to provide rationales explaining the extensive epidemiological literature that, for decades, has consistently shown strong associations between poor vitamin C status and increased morbidity and mortality.In this Special Issue, we include original research and literature reviews by experts in the field outlining the roles of vitamin C in early, daily and late life, as well as the roles of deficiency in cardiovascular disease, inflammation and cancer.

Physiology and Pathophysiology of the Extracellular Calcium-Sensing Receptor

Author:
Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889455126 Year: Pages: 189 DOI: 10.3389/978-2-88945-512-6 Language: English
Publisher: Frontiers Media SA
Subject: Science (General) --- Physiology
Added to DOAB on : 2019-01-23 14:53:42
License:

Loading...
Export citation

Choose an application

Abstract

Calcium is vital for human physiology; it mediates multiple signaling cascades, critical for cell survival, differentiation, or death both as first and as second messenger. The role of calcium as first messenger is mediated by the G-protein coupled receptor, the extracellular calcium-sensing receptor (CaSR). The CaSR is a multifaceted molecule that senses changes in the concentration of a wide variety of environmental factors including di- and trivalent cations, amino acids, polyamines, and pH. In calcitropic tissues with obvious roles in calcium homeostasis such as parathyroid, kidney, and bone it regulates circulating calcium concentrations. The germline mutations of the CaSR cause parathyroid disorders demonstrating the importance of the CaSR for the maintenance of serum calcium homeostasis. The CaSR has an important role also in a range of non-calcitropic tissues, such as the intestine, lungs, central and peripheral nervous system, breast, skin and reproductive system, where it regulates molecular and cellular processes such as gene expression, proliferation, differentiation and apoptosis; as well as regulating hormone secretion and lactation.This Research Topic is an overview of the CaSR and its molecular signaling properties together with the various organ systems where it plays an important role. The articles highlight the current knowledge regarding many aspects of the calcitropic and non-calcitropic physiology and pathophysiology of the CaSR.

Listing 1 - 4 of 4
Sort by
Narrow your search

Publisher

MDPI - Multidisciplinary Digital Publishing Institute (3)

Frontiers Media SA (1)


License

CC by-nc-nd (3)

CC by (1)


Language

english (4)


Year
From To Submit

2018 (4)