Fuel selection in intestinal cells

The intestinal response to feeding in seawater gulf toadfish, Opsanus beta, includes elevated base secretion and increased epithelial oxygen consumption

“…The high RQ in control tissue suggests the utilization of a carbohydrate-rich (carbohydrate RQ1.0) substrate. This result is in accordance with studies suggesting the intestine metabolizes predominantly carbohydrate and protein (RQ0.83) substrates (Duee et al, 1995) and that these macromolecules are also the predominant fuels for osmoregulation (Tseng and Hwang, 2008), a process in which the marine teleost intestine plays a critical role (Grosell, 2007). Furthermore, the high RQ under control conditions is in agreement with our observations of glucose alone being a sufficient metabolic substrate for toadfish intestinal tissue.…”

“…In mammals, the gastrointestinal (GI) tract is a site of high O 2 uptake that amounts to 20-25% of the whole-body O 2 consumption, even in the post-absorptive or fasting state (Britton and Krehbiel, 1993;Duee et al, 1995). This energy consumption is disproportionate for the size of the tissue (about 6% of body mass in these studies).…”

“…In a 20g toadfish, intestinal O 2 consumption accounts for 3.4molh -1 , or 5.6% of whole-animal O 2 consumption. This is a surprisingly low fraction considering studies suggesting the nonfed, non-osmoregulating mammalian GI tract accounts for 20-25% of whole-animal O 2 consumption (Duee et al, 1995). Peak postprandial intestinal O 2 consumption equates to 6.3molh -1 for a 20g toadfish, and this intestinal SDA response of a 2.9molh -1 increase in O 2 consumption can account for approximately 4.8% of an assumed 60molh -1 increase in metabolic rate of a 20g toadfish as suggested by typical increases in fish O 2 consumption associated with SDA (Jobling, 1981;McCue, 2006;Secor, 2009).…”

“…While salines used in isolated teleost intestine experiments typically include approximately 5mmoll -1 glucose in the serosal saline (Grosell et al, 2005;Grosell and Genz, 2006;Grosell et al, 2009a), literature on substrate utilization in isolated mammalian intestinal epithelia (Duee et al, 1995) led us to investigate the effects of adding 5mmoll -1 glutamate to the 'standard' (Table1) HCO 3 --free serosal saline and also the addition of these two substrates to the 'standard' (Table1) mucosal saline. Furthermore, the impact of a mucosal saline containing a more complete mixture of amino acids, intended to more closely mimic the composition of chyme, was investigated on fasted intestinal tissue using L-15 cell culture media (Sigma, St Louis, MO, USA).…”

Glutamine stimulates translation of uncoupling protein 2mRNA

“…However, in our hands, treatments of cell lines known to promote oxidative stress failed to provide conclusive evidence for stimulation of UCP2 production (not shown). UCP2 is expressed in immune cells as well as in the gut, two sites of glutamine utilization as an energy substrate [8,9]. An analysis of UCP2 expression in the mouse macrophage cell line RAW 264 -7 revealed variations in UCP2 levels that correlated with the changes in the culture medium during the normal growth of this cell line.…”