Metabolism of amino acids by cultured rat Sertoli cells Glo ´ria R.R.F. Kaiser, Siomara C. Monteiro, Daniel P. Gelain, Luiz F. Souza, Marcos L.S. Perry, Elena Aida Bernard * Departamento de Bioquı ´mica, Instituto de Cie ˆncias Ba ´sicas da Sau ´de-UFRGS Rua Ramiro Barcelos 2600-anexo Porto Alegre RS-Brazil Received 11 November 2003; revised 6 October 2004; accepted 18 November 2004 Abstract Sertoli cells support spermatogenesis both spatially and energetically; for this reason, these cells have important adaptations. The energetic metabolism of Sertoli cells was adapted to provide lactate and pyruvate to developing germ cells, because these substrates are essential for spermatocytes and spermatids. In this study, we investigated whether Sertoli cells use alanine, leucine, valine, and glycine as energetic substrates and whether the simultaneous addition of other nutrients, such as glucose and glutamine, might affect the metabolism of these amino acids. Alanine, leucine, valine, and glutamine are almost totally oxidized to CO 2 by these cells. In contrast, glycine has been demonstrated to be a poor energetic substrate, being mainly incorporated into proteins, and their metabolism did not change in the presence of palmitic acid, glucose, and/or glutamine. The metabolism of the 3 other amino acids was modified by palmitic acid; besides, glucose changed alanine, leucine, and valine oxidation. Glutamine decreased the oxidation of alanine, leucine, and valine to CO 2 . Conversely, both alanine and leucine decreased the oxidation of glutamine. Our present findings show that Sertoli cells can adapt its energy metabolism to the oxidative substrates available to fulfill their role in spermatogenic energetic supply. D 2005 Elsevier Inc. All rights reserved. 1. Introduction Sertoli cells are the somatic cells of the testis that are essential for testis formation and spermatogenesis. Sertoli cells facilitate the progression of germ cells in spermatozoa via direct contact and by controlling the environmental milieu within the seminiferous tubules [1-3]. It has been demon- strated that Sertoli cells can use glucose aerobically at a high rate and secrete lactate and pyruvate; lactate and pyruvate are essential for the maintenance of germ cells [4-6]. A small percentage of glucose is oxidized to CO 2 and even less is converted to other intermediates. Thus, it seems that glucose is not the major fuel for Sertoli cells. Little is known about the oxidation of energy substrates other than glucose by Sertoli cells. Jutte et al [7] reported that Sertoli cells incubated with palmitic acid oxidized 66% of this substrate to CO 2 , and they suggest that fatty acids seem to be a major energy substrate for Sertoli cells. In other experiments, Sertoli cells were incubated with valine, leucine, and isoleucine; these amino acids were selectively taken up by the cells, but their metabolic pathways were not investigated. Branched chain amino acid aminotransferase activity was found in Sertoli cells, and 15% to 30% of the 4- methyl-2-oxopentanoate formed by transamination of leu- cine was released, taken up by germ cells and converted to 2-hydroxy-4-methylvalerate [8,9]. However, this is not an energy-producing reaction and its physiological significance is unknown. Furthermore, Grootegoed et al [10] have shown that besides glucose and fatty acids, the single oxidation of glutamine and leucine can yield much of the required energy by Sertoli cells. Nevertheless, the relative importance of the endogenous metabolism of these substrates on the bioener- getic balance of Sertoli cells, when more than one fuel is present in the culture medium, has not been investigated. The aim of the present work is to study the use of different amino acids as energy substrates by Sertoli cells and to determine if Sertoli cell metabolism can be influenced by the presence of other exogenous substrates. Thus, we studied the effect of alanine, glycine, leucine, valine, and glutamine on Sertoli cell metabolism. The substrates alanine, glycine, valine, and glutamine were chosen because of energy potential of the citric acid cycle and leucine for lipid formation. There are no 0026-0495/$ – see front matter D 2005 Elsevier Inc. All rights reserved. doi:10.1016/j.metabol.2004.11.005 * Corresponding author. Fax: +55 51 3316 5535. E-mail address: elenbern@vortex.ufrgs.br (E.A. Bernard). Metabolism Clinical and Experimental 54 (2005) 515 – 521 www.elsevier.com/locate/metabol