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Open AccessArticle

Species-Specific Glucose-6-Phosphatase Activity in the Small Intestine—Studies in Three Different Mammalian Models

1
Institute of Translational Medicine, Semmelweis University, 1094 Budapest, Hungary
2
Department of Medical Chemistry, Molecular Biology and Pathobiochemistry, Semmelweis University, 1094 Budapest, Hungary
3
Department of Molecular and Developmental Medicine, University of Siena, 53100 Siena, Italy
4
Pathobiochemistry Research Group of Hungarian Academy of Sciences & Semmelweis University, 1094 Budapest, Hungary
*
Author to whom correspondence should be addressed.
Int. J. Mol. Sci. 2019, 20(20), 5039; https://doi.org/10.3390/ijms20205039
Received: 23 July 2019 / Revised: 4 October 2019 / Accepted: 9 October 2019 / Published: 11 October 2019
(This article belongs to the Special Issue Channels and Transporters in Cells and Tissues)
Besides the liver, which has always been considered the major source of endogenous glucose production in all post-absorptive situations, kidneys and intestines can also produce glucose in blood, particularly during fasting and under protein feeding. However, observations gained in different experimental animals have given ambiguous results concerning the presence of the glucose-6-phosphatase system in the small intestine. The aim of this study was to better define the species-related differences of this putative gluconeogenic organ in glucose homeostasis. The components of the glucose-6-phosphatase system (i.e., glucose-6-phosphate transporter and glucose-6-phosphatase itself) were analyzed in homogenates or microsomal fractions prepared from the small intestine mucosae and liver of rats, guinea pigs, and humans. Protein and mRNA levels, as well as glucose-6-phosphatase activities, were detected. The results showed that the glucose-6-phosphatase system is poorly represented in the small intestine of rats; on the other hand, significant expressions of glucose-6-phosphate transporter and of the glucose-6-phosphatase were found in the small intestine of guinea pigs and homo sapiens. The activity of the recently described fructose-6-phosphate transporter–intraluminal hexose isomerase pathway was also present in intestinal microsomes from these two species. The results demonstrate that the gluconeogenic role of the small intestine is highly species-specific and presumably dependent on feeding behavior (e.g., fructose consumption) and the actual state of metabolism. View Full-Text
Keywords: glucose-6-phosphatase; glucose-6-phosphate transporter; small intestine; endoplasmic reticulum; fructose glucose-6-phosphatase; glucose-6-phosphate transporter; small intestine; endoplasmic reticulum; fructose
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Varga, V.; Murányi, Z.; Kurucz, A.; Marcolongo, P.; Benedetti, A.; Bánhegyi, G.; Margittai, É. Species-Specific Glucose-6-Phosphatase Activity in the Small Intestine—Studies in Three Different Mammalian Models. Int. J. Mol. Sci. 2019, 20, 5039.

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