Adaptation of intestinal hydrolases to starvation in rats: effect of thyroid function

Abstract

The effects of long-term starvation on the activities of sucrase, lactase, and aminopeptidase, and on their respective mRNA were determined in the small intestine of thyroidectomized and sham-operated adult rats. Thyroidectomy reduced the protein loss at the level of the intestinal brush border membranes during starvation. Prolonged fasting caused a significant decrease in sucrase activity, but thyroidectomy partly prevented this effect. However, the amount of the corresponding mRNA dropped during long term starvation without incidence of thyroidectomy. Lactase activity in the brush border membranes was increased by starvation, and thyroidectomy caused a further elevation of the enzyme activity. Simultaneously, lactase mRNA content rose only slightly compared to the enzyme activity. Aminopeptidase activity and mRNA content decreased during starvation and thyroidectomy did not prevent this process. These results indicate that intestinal hydrolases respond non-coordinately to long-term food deprivation. In addition, the thyroid status of the animals has a direct influence on the adaptation of several brush border hydrolases to starvation. This suggests that the drop in plasma thyroid hormones during fasting allows a better maintenance of protein content and of hydrolase activities in the brush border membranes of the small intestine. These adaptive processes seemed to be partly controlled at a post-transcriptional level.

Amplitude‐dependent modulation of brush border enzymes and proliferation by cyclic strain in human intestinal Caco‐2 monolayers

“…Profound changes occur in the gut mucosa during ileus, fasting, and starvation (Brown et al, 1960;Eastwood, 1977;Galluser et al, 1991;Goodlad et al, 1988;Gorostiza et al, Steiner et al, 1968) in parallel with complex alterations in gut motility (Telford et al, 1993). Animal and clinical studies have demonstrated that such changes are only partially reversed by parenteral nutrition (Inoue et al, 19931, while one investigator has reported the reversal of atrophic changes in defunctionalized small intestinal loops after luminal perfusion with water (Clarke, 1976).…”

Enhancement of brush border membrane peptidase activity in rat jejunum induced by starvation

“…These findings suggest that common systemic factors might be involved in regulating the expression of these enzymes. Although little is known about the factors regulating the activity of these peptidases, the role of hormonal factors has been well documented, especially in the ontogenetic maturation of the small intestine [9,10,16,24]. It seems worth speculating about the potential role of hormones as systemic regulatory factors.…”

“…From the results of that study, we considered that the absorption of dietary protein might be preserved under conditions of malnourishment. However, studies of the adaptation of intestinal peptidases to starvation have yielded conflicting results [5,10,14,21].…”

Adaptation to Lactose in Lactase Non Persistent People: Effects on Intolerance and the Relationship between Dairy Food Consumption and Evalution of Diseases

“…The reasons for these discrepancies are not clear. In small animal studies, thyroxine increased intestinal lactase in embryogenesis [ 36 ] but later it inhibited intestinal lactase [ 37 ]. The above clinical observations could be explained by inhibition of human intestinal lactase but human studies are scarce [ 36 ].…”