Juan C. Marini, D.V.M., Ph.D.

Assistant Professor of Pediatrics
Baylor College of Medicine

Education:

Research:

Dr. Marini’s research is focused on urea cycle intermediates and their role in supporting ureagenesis and nitric oxide production. Current studies are aimed at increasing our understanding of how the supply of urea cycle intermediates help overcome reduced enzymatic activity found in urea cycle disorder models. We are also investigating the role of genetic background and interorgan transactions of urea cycle intermediates in ornithine transcarbamylase deficiency murine models. In this hypomorphic model, we have shown that the exogenous supply of ornithine is able to restore ureagenesis and mitigate hyperammonemia in C57 mice. However, due to an increase in endogenous ornithine production, mice of different genetic backgrounds harboring the same mutation do not become hyperammonemic.

We are also investigating the role of arginine and intracellular citrulline recycling in sustaining nitric oxide production during basal conditions and LPS challenge in different mouse models. The combination of mouse genetic models and the determination of metabolite fluxes utilizing minimally invasive techniques offers the possibility to study complex pathways and interorgan transaction at the whole organism level in conscious animals.

Representative Publications:

Marini, J.C., M.S. Attene-Ramos. 2007. An improved analytical method for the determination of urea nitrogen isotopomers in biological samples utilizing continuous flow-isotope ratio mass spectrometry. Rapid Commun. Mass Spectrom. (In press).

Marini, J.C., B. Lee, P.J. Garlick. 2006. Non-surgical alternatives to surgical procedures in mice. Lab. Animals 40:275-281.

Marini, J.C., B. Lee, P.J. Garlick. 2006. Ornithine restores ureagenesis capacity and mitigates hyperammonemia in Otcspf-ash mice. J. Nutr. 136:1834-1838.

Imoberdorf, R., P.J. Garlick, M.A. McNurlan, G.A. Casella, J.C. Marini, M Turgay, P Barstsch, P.E. Ballmer. 2006. The effect of acute active or passive ascent to high altitude on human skeletal muscle protein synthesis. Med. Sci. Sports Exerc. 38:1082-1087.

Marini, J.C., S. Broussard. 2006. Hyperammonemia increases sensitivity to LPS. Mol Genet Metab 88:131-137.

Marini, J.C., B. Lee, P.J. Garlick. 2006. Reduced ornithine transcarbamylase activity does not impair ureagenesis in Otcspf-ash mice. J. Nutr. 136:1017-1020.*

Marini, J.C., B. Lee, P.J. Garlick. 2006. In vivo urea kinetic studies in conscious mice. J. Nutr. 136:202-206.

Marini, J.C., J. Sands and M. E. Van Amburgh. 2005. Urea transport systems in relation to recycling. In Ruminant physiology: Digestion, metabolism and impact of nutrition on gene expression, immunology and stress. Edited by K. Sejrsen, T. Hvelplund and M.O. Nielsen. Wageningen Academic Publishers, Wageningen, The Netherlands.

Marini, J.C. and M. E. Van Amburgh. 2005. Partition of nitrogen excretion in the urine and the feces of Holstein replacement heifers. J. Dairy Sci 88:1778-1784.

Scaglia, F., N. Brunetti-Pierri, S. Kleppe, J. Marini, S. Carter, P. Garlick, F. Jahoor, W. O’Brien, and B. Lee. 2003. Clinical consequences of urea cycle enzyme deficiencies and potential links to arginine and nitric oxide metabolism. J. Nutr. 134:2775S-2782S.

Marini, J.C., J.D. Klein, J.M. Sands and M.E. Van Amburgh. 2004. Effect of N intake on N recycling and urea transporter expression in lambs. J. Anim. Sci. 82:1157-1164.

Scaglia, F., J. Marini, J. Rosenberger, J. Henry, P. Garlick, and P. Reeds. 2003. Differential utilization of systemic and enteral ammonia for urea synthesis in control subjects and carriers for ornithine transcarbamylase deficiency. Am. J. Clin. Nutr. 78:749-755.

Marini, J.C., K.W. Simpson , A. Gerold , M.E. Van Amburgh. 2003. The effect of immunization with jackbean urease on antibody response and nitrogen recycling in mature sheep. Livest. Prod. Sci. 81:283-292.

Marini, J.C. and M.E. Van Amburgh. 2003. Nitrogen metabolism and recycling in Holstein heifers. J. Anim. Sci. 81:545-552.