415 Lactate Dehydrogenase: Physiological Roles and Clinical Implications Copyright@ Ahed J Alkhatib --------------------------------------------------------------------------------------------------------------------------------- This work is licensed under Creative Commons Attribution 4.0 License AJBSR.MS.ID.000705 Mini Review Ahed J Alkhatib 1 * and Nawaf Abduallah Mohammad Alrakaf 2 1 Department of Legal Medicine, Jordan University of Science and Technology, Jordan 2 MOH, Saudi Arabia *Corresponding author: Ahed J Alkhatib, Department of Legal Medicine, Toxicology and Forensic Medicine, School of Medicine, Jordan University of Science and Technology, Jordan. To Cite This Article: Ahed J Alkhatib. Lactate Dehydrogenase: Physiological Roles and Clinical Implications. Am J Biomed Sci & Res. 2019 - 3(5). AJBSR.MS.ID.000705. DOI: 10.34297/AJBSR.2019.03.000705 Received: June 10, 2019 | Published: July 03, 2019 American Journal of Biomedical Science & Research ISSN: 2642-1747 www.biomedgrid.com Introduction Importance of lactate dehydrogenase (LDH) The enzyme lactate dehydrogenase (LDH) is widely spread in almost each cell in the body [1,2]. The prime function of LDH is to convert lactate to pyruvate through oxidation process. LDH exists in the cytoplasm of cell and when cell dies it becomes extracellular [3]. The levels of LDH vary according to metabolic needs of each tissue such as development, biological conditions, and pathological aspects [1]. Biochemistry of LDH The molecular weight of LDH is 134 kDa, and it is consisted of a tetramer including two subunits, H and M. there are 5 isoenzymes, LD1 to LD5. Although LDH is considered as a ubiquitous enzyme that exists in the cell cytoplasm of each cell, but its isoenzyme structure varies in different tissues. As an example, LD1 is mainly abundant in cardiac tissue, red blood cells, and renal cells; and on the other hand, LD5 exists mainly in hepatocytes and skeletal muscles [4-6]. Clinical implications of LDH The indications for requesting a serum LDH have become less important with time. For example, the use of LDH for evaluation of liver function is of limited implications because of its involvement in different areas of the body from one side, and from another side the use of transaminases and alkaline phosphatase is more important than LDH [4]. Its implication in the assessment of muscle disease is limited because creatine kinase is more specific and important than LDH [4]. The levels of LDH are highly elevated due to alterations in carcinogenic status that can lower the conversion rate of lactate to pyruvate ending with increased nicotinamide adenine dinucleotide (NAD+) that has the ability to interact with metabolic pathways of carbohydrate. A high glycolytic activity is thought to increase the likely of cancer development [7]. Tissues damaged by tumours release LDH into bloodstream which participates to increased levels of this enzyme [8]. The levels of serum LDH are used to diagnose a variety of cancers including oral, laryngeal and breast cancer [9]. From a clinical point of view, the variation in the levels of lactate with time reflects directly its production changes. Elevated levels of lactate give a clue for circulatory alterations, while its lowered levels pointed to improved circulation [10]. The clearance of lactate is a very important aspect in assessing the clinical status of patients [10]. Although clearance decreases in some cases such as septic Abstract The present study aimed to review the literature about lactate dehydrogenase regarding physiological roles and clinical implications. The enzyme lactate dehydrogenase (LDH) is widely spread in almost each cell in the body, and its prime function is to convert lactate to pyruvate through oxidation process. LDH exists in the cytoplasm of cell and when cell dies it becomes extracellular. The levels of LDH vary according to metabolic needs of each tissue such as development, biological conditions, and pathological aspects. Its levels are increased in a variety of clinical situations from inflammatory conditions to malignancies. The specificity of LDH cannot be taken as a single parameter but helps with other biochemical investigations. Keywords: Lactate dehydrogenase; Inflammation; Malignancy; Metabolism; Specificity; Clinical implication