A Convergent Functional Genomics Analysis to Identify Biological Regulators Mediating Effects of Creatine Supplementation

Creatine (Cr) and phosphocreatine (PCr) are physiologically essential molecules for life, given they serve as rapid and localized support of energy- and mechanical-dependent processes. This evolutionary advantage is based on the action of creatine kinase (CK) isozymes that connect places of ATP synthesis with sites of ATP consumption (the CK/PCr system). Supplementation with creatine monohydrate (CrM) can enhance this system, resulting in well-known ergogenic effects and potential health or therapeutic benefits. In spite of our vast knowledge about these molecules, no integrative analysis of molecular mechanisms under a systems biology approach has been performed to date; thus, we aimed to perform for the first time a convergent functional genomics analysis to identify biological regulators mediating the effects of Cr supplementation in health and disease. A total of 35 differentially expressed genes were analyzed. We identified top-ranked pathways and biological processes mediating the effects of Cr supplementation. The impact of CrM on miRNAs merits more research. We also cautiously suggest two dose-response functional pathways (kinase- and ubiquitin-driven) for the regulation of the Cr uptake. Our functional enrichment analysis, the knowledge-based pathway reconstruction, and the identification of hub nodes provide meaningful information for future studies. This work contributes to a better understanding of the well-reported benefits of Cr in sports and its potential in health and disease conditions, although further clinical research is needed to validate the proposed mechanisms.

The clinical relevance of antidepressant interaction with neurotransmitter transporters and receptors

This review presents the pharmacology of antidepressants as it relates to their effects on several neurotransmitters and their receptors. A theory about the mechanism of action of these drugs is presented, along with data for their affinities at human transporters for norepinephrine, serotonin, and dopamine, and at several different neurotransmitter receptors. This blockade by antidepressants of transporters and receptors is thought to relate to therapeutic and adverse effects of these compounds. Knowledge of this preclinical pharmacology of antidepressants will help the clinician understand the basis of certain adverse effects and drug interactions that can be avoided or minimized.

Na+ - and Cl- -coupled active transport of nitric oxide synthase inhibitors via amino acid transport system B(0,+)

Nitric oxide synthase (NOS) inhibitors have therapeutic potential in the management of numerous conditions in which NO overproduction plays a critical role. Identification of transport systems in the intestine that can mediate the uptake of NOS inhibitors is important to assess the oral bioavailability and therapeutic efficacy of these potential drugs. Here, we have cloned the Na+ - and Cl- -coupled amino acid transport system B(0,+) (ATB(0,+)) from the mouse colon and investigated its ability to transport NOS inhibitors. When expressed in mammalian cells, ATB(0,+) can transport a variety of zwitterionic and cationic amino acids in a Na+ - and Cl- -coupled manner. Each of the NOS inhibitors tested compete with glycine for uptake through this transport system. Furthermore, using a tritiated analog of the NOS inhibitor N(G)-nitro-L-arginine, we showed that Na+ - and Cl- -coupled transport occurs via ATB(0,+). We then studied transport of a wide variety of NOS inhibitors in Xenopus laevis oocytes expressing the cloned ATB(0,+) and found that ATB(0,+) can transport a broad range of zwitterionic or cationic NOS inhibitors. These data represent the first identification of an ion gradient-driven transport system for NOS inhibitors in the intestinal tract.