Peptide regulation of intestinal glucose absorption.

Abstract

Terminal hydrolysis of oligosaccharides at the small intestinal brush border yields monomeric glucose, most of which is then absorbed by the transepithelial route. This involves carrier-mediated processes requiring specialized functional proteins situated in the brush border (SGLT1) and basolateral (GLUT2) membranes. Glucose translocation at the enterocyte apical membrane is an active, Na(+)-dependent and saturable process, whereas exit from enterocytes is by facilitated diffusion and is energy-independent. Specific adaptation of glucose active transport occurs in response to changes in the proportion of glucose in the diet. The regulatory signals responsible for transport induction are imprecisely defined, although numerous protein hormones and gut regulatory proteins are implicated. Epidermal growth factor and peptide YY invoke up-regulation of jejunal active glucose transport in vivo. Recently, peptide YY has been shown to stimulate active glucose transport in mice without altering oxygen consumption of jejunal tissue. Several other peptides whose presence in tissues of the small bowel imply that they exert control over epithelial nutrient transport are considered, and the relevance of these physiological manipulations, with various regulatory peptides and hormones, to animal agriculture are discussed.

Regulation of intestinal glucose absorption: A new issue in animal science

“…Martinez-Sapiña et al (1989) report no changes in intestinal glucose transport in hamsters administered somatostatin. Bird et al (1996a) have reported that subcutaneous administration of somatostatin-14 to mice for 3 d had no effect on 3-0-methylglucose uptake by jejunal rings. If somatostatin has an effect on the absorption of glucose and other nutrients, it is likely an indirect effect via inhibition of gastrointestinal motility and exocrine and endocrine secretion (Krejs 1986;Schusdziarra 1988;Del Valle et al 1990;Mulvihill et al 1990) which has been reported to be mediated by the suppression of synthesis and release of several gut peptides (Schusdziarra 1988;Lewin 1992).…”

“…This phenomenon is characterized by slowed gastric emptying and intestinal transit when the distal bowel is exposed to unabsorbed nutrients (Taylor 1993). Bird et al (1996a) have reported that PYY increases jejunal glucose absorption in mice without concomitant increase in tissue respiration. This suggests that PYY increases the apparent energetic efficiency of active intestinal glucose transport (Fig.…”

Apparent energetic efficiency of jejunal glucose uptake in young adult turkeys selected for rapid growth

“…As measured in this study, the energetic component of this term is confounded by the expenditure of ATP for other Na + -dependent transport processes such as amino acids, which are present in the media used in the respiration chambers. In spite of this limitation, previous studies in our laboratory have demonstrated that physiological factors such as age (Bird et al1994b), genotype (Cefalu et al 1998) and exogenous administration of gut peptides such as PYY (Bird et al 1996) can result in changes in this value. Furthermore, studies in our laboratory (Bird et al 1996) and those of others (Schwartz and Storozuk 1988) suggest that induced changes in Na + -dependent carbohydrate transport and Na + -dependent amino acid transport occur in parallel.…”

“…In spite of this limitation, previous studies in our laboratory have demonstrated that physiological factors such as age (Bird et al1994b), genotype (Cefalu et al 1998) and exogenous administration of gut peptides such as PYY (Bird et al 1996) can result in changes in this value. Furthermore, studies in our laboratory (Bird et al 1996) and those of others (Schwartz and Storozuk 1988) suggest that induced changes in Na + -dependent carbohydrate transport and Na + -dependent amino acid transport occur in parallel. However, any change in this ratio may also reflect changes in intracellular metabolism and transport processes of other nutrients.…”

Acute effects of epidermal growth factor on Na+, K+-ATPase-dependent oxygen consumption and the amount of the enzyme units in enterocytes isolated from the jejunum of chickens

“…The effects of EGF include 1) stimulation of glycolysis in cultured hepatocytes (Schneider et al 1978); 2) triggering of cytosolic alkalinization in chicken granulosa cells (Li et al 1991); 3) increased rate of glucose transport in small intestine (Opleta-Madsen et al 1991;Bird et al 1996); 4) inhibition of Na + transport in rabbit cortical collecting ducts (Vehaskari et al 1991); 5) stimulation of rat jejunal Na + , H + -antiport (Ghishan et al, 1992) and tissue and Na + , K + -dependent O 2 uptake in the small intestine of mice (Bird et al 1994;Croom et al 1998). …”