High Quality Proteins Can Impact Circulating Homocysteine Levels.

The amino acid composition of a protein can tell you a lot about it’s health implications. For example a protein source high in sulfur amino acids (methionine and cysteine) can affect methionine metabolism and, ultimately, health. Cysteine is a conditionally essential amino acid, because it can be synthesized endogenously from methionine. Thus, when a dietary protein provides enough methionine beyond the need for cellular protein synthesis, the remaining surplus can be used to synthesize cysteine. Therefore, when a dietary protein has a cysteine concentration in balance with methionine, the need to utilize methionine for its synthesis is reduced. This is often referred to as the methionine-sparing effect of cysteine.This article is published as Schalinske, K.L. (Fall 2010) High quality proteins can impact circulating homocysteine levels. Nutrition Close-Up 27: 4-5. Posted with permission.</p

Advanced Nutrition and Regulation of Metabolism

INTRODUCTION The body, and metabolism in particular, is a very dynamic process that has to respond appropriately to an ever-changing environment, including the supply of nutrients. The vast majority of cells in the body are quite similar with respect to structure; however, not all cells respond the same to nutrients and hormones or produce the same proteins to carry out specific metabolic processes and other protein-driven functions. But before we can discuss nutrition, the first goal is to have a basic understanding of cell biology, as well as some additional biological concepts. Activity Proteins are dynamic and regulated molecules that perform a diverse array of functions. Develop a “real-life” analogy to describe how proteins function and how they are regulated. For example, a transport protein like transferrin, which transports iron in the circulation to cells in the body, is similar to a car using roads to transport people from one place to another. Enzyme kinetics can be difficult to understand—we will have an in-class activity where you, the student, will function as an enzyme as a method to illustrate the concept of maximal velocity, affinity, and how maximal velocity can be altered. Reflection/Discussion Questions Discuss in small groups what happens when a protein is dysfunctional? What could make a protein dysfunctional? Relate this back to the analogy you developed initially. For the car example, if the car cannot accommodate the people, then they cannot get where they need to go; if transferrin cannot bind iron, other cells in the body can become deficient in iron.This book is published as Schalinske, K. (2017) Advanced Nutrition and the Regulation of Metabolism (1st ed.), Cognella, Inc., Academic Publishing (ISBN: 978-1-5165-1468-7). Posted with permission.</p

Homocysteine metabolism and its relation to health and disease.

Homocysteine is a metabolic intermediate in methyl group metabolism that is dependent on a number of nutritional B-vitamin cofactors. An emerging aspect of homocysteine metabolism is its relation to health and disease. Perturbations of homocysteine metabolism, particularly intracellular and subsequently circulating accumulation of homocysteine (i.e., hyperhomocysteinemia), are associated with vascular disease risk, as well as other pathologies. However, intervention with B-vitamin supplementation has been shown to successfully restore normal homocysteine concentrations, but without concomitant reductions in disease risk. Thus, the mechanistic relation between homocysteine balance and disease states, as well as the value of homocysteine management, remains an area of intense investigation.This is the peer reviewed version of the following article from Biofactors, 2010 36(1); 19-24, which has been published in final form at Doi: 10.1002/biof.71. This article may be used for non-commercial purposes in accordance With Wiley Terms and Conditions for self-archiving.</p

Tissue-specific alterations of methyl group metabolism with DNA hypermethylation in the Zucker (type 2) diabetic fatty rat.

BackgroundAltered methyl group and homocysteine metabolism were tissue-specific, persistent, and preceded hepatic DNA hypomethylation in type 1 diabetic rats. Similar metabolic perturbations have been shown in the Zucker (type 2) diabetic fatty (ZDF) rat in the pre-diabetic and early diabetic stages, but tissue specificity and potential impact on epigenetic marks are unknown, particularly during pathogenesis. Methods ZDF (fa/fa) and lean (+/?) control rats were killed at 12 and 21 weeks of age, representing early and advanced diabetic conditions. Blood and tissues were analysed with respect to methyl group and homocysteine metabolism, including DNA methylation. Results At 12 weeks, hepatic glycine N-methyltransferase (GNMT), methionine synthase, and cystathionine β-synthase (CBS) activity and/or abundance were increased in ZDF rats. At 21 weeks, GNMT activity was increased in liver and kidney; however, only hepatic CBS protein abundance (12 weeks) and betaine-homocysteine S-methyltransferase mRNA expression (21 weeks) were significantly elevated (78 and 100%, respectively). Hepatic phosphatidylethanolamine N-methyltransferase expression was also elevated in the ZDF rat. Homocysteine concentrations were decreased in plasma and kidney, but not in liver, at 12 and 21 weeks. In contrast to hepatic DNA hypomethylation in the type 1 diabetic rat, genomic DNA was hypermethylated at 12 and 21 weeks in the liver of ZDF rats, concomitant with an increase in DNA methyltransferase 1 expression at 21 weeks. ConclusionsThe pathogenesis of type 2 diabetes in the ZDF rat was associated with tissue and disease stage-specific aberrations of methyl group and homocysteine metabolism, with persistent hepatic global DNA hypermethylation.This is the peer reviewed version of the following article is from Diabetes / Metabolism Research and Reviews, February 2012, 28(2); 123-131. Which has been published in final form at Doi: 10.1002/dmrr.1281. This article may be used for non-commercial purposes in accordance With Wiley Terms and Conditions for self-archiving.</p