Abstract
SummaryThe growth of the intestine requires energy, which is known to be met by catabolism of ingested nutrients. Paradoxically, during whole body energy deficit including calorie restriction, the intestine grows in size. To understand how and why this happens, we reviewed data from several animal models of energetic challenge. These were bariatric surgery, cold exposure, lactation, dietary whey protein intake and calorie restriction. Notably, these challenges all reduced the adipose tissue mass, altered hypothalamic neuropeptide expression and increased intestinal size. Based on these data, we propose that the loss of energy in the adipose tissue promotes the growth of the intestine via a signalling mechanism involving the hypothalamus. We discuss possible candidates in this pathway including data showing a correlative change in intestinal (ileal) expression of the cyclin D1 gene with adipose tissue mass, adipose derived‐hormone leptin and hypothalamic expression of leptin receptor and the pro‐opiomelanocortin gene. The ability of the intestine to grow in size during depletion of energy stores provides a mechanism to maximize assimilation of ingested energy and in turn sustain critical functions of tissues important for survival.
Highlights
SummaryThe growth of the intestine requires energy, which is known to be met by catabolism of ingested nutrients
The intestine is a heterogeneous tissue, containing a number of different cell types including the enterocytes, globlet cells, paneth cells, enteroendocrine cells, M cells and cup cells
Because the bovine form of the proteins has been shown to cause an energy deficit in both humans and rodents [80,81], reflected primarily in reduced white adipose tissue [82], we explored the underlying mechanism and showed that intake of whey protein isolate (WPI) caused a reduction in the ileal expression of fatty acid transport protein 4 (FATP4), glucose transporter 2 (GLUT2) and amino acid transporter (SLC6a19) in mice compared with controls fed casein [83]
Summary
The growth of the intestine requires energy, which is known to be met by catabolism of ingested nutrients. During whole body energy deficit including calorie restriction, the intestine grows in size. To understand how and why this happens, we reviewed data from several animal models of energetic challenge. These were bariatric surgery, cold exposure, lactation, dietary whey protein intake and calorie restriction. These challenges all reduced the adipose tissue mass, altered hypothalamic neuropeptide expression and increased intestinal size. Based on these data, we propose that the loss of energy in the adipose tissue promotes the growth of the intestine via a signalling mechanism involving the hypothalamus.
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