Effects of Oral IGF-I or IGF-II on Digestive Organ Growth in Newborn Piglets

Abstract

To study whether colostrum-borne growth factors are responsible for the rapid GI tissue growth in naturally suckled newborn animals, newborn unsuckled piglets were bottle-fed for 24 h with infant milk formula with or without addition of 2 μg/ml of recombinant human insulin-like growth factor-I (IGF-I) or insulin-like growth factor-II (IGF-II), a level which approximated that of porcine colostrum. The animals were then sacrificed for measurements of their digestive organ weights and contents of protein, RNA and DNA in the organs. The treatment with IGF-I or IGF-II failed to show any significant effect on the weight of the esophagus, stomach, small intestine, large intestine, mandibular glands, kidneys and the spleen, and had no effects on the contents of protein, RNA and DNA in the small intestinal mucosa, the liver and the spleen. However, piglets fed with infant formula containing IGF-I (n = 7) or IGF-II (n = 7) had a heavier pancreas (p < 0.05) compared to formula-fed controls (n = 7). The DNA content in the stomach and the pancreas were greater in animals treated with IGF-I or IGF-II than in controls. Using a cell labelling technique it was shown that both IGF-I and IGF-II stimulated cell proliferation in the small intestinal crypts. The results indicate that the substantial GI tissue growth reported in newborn animals is unlikely due to colostrum-borne IGF-I or IGF-II alone. On the other hand the study does suggest that oral IGF-I and IGF-II are capable of stimulating cell proliferation in the GI tract.

Intestinal effects of milkborne growth factors in neonates of agricultural importance.

“…Piglets receiving the IGF-I-supplemented formula consumed approximately 200 mg·kg-BW −1 ·d −1 (Houle et al, 1995). Consistent with previous studies, two studies Xu et al, 1994) indicated that weight gain and final BW were unaffected by oral IGF-I administration. Serum IGF-I (Burrin et al, 1995b;Houle et al, 1995), serum IGF-II (Houle et al, 1995), or serum IGFBP profiles (Houle et al, 1995) were also unaffected by oral IGF-I intake, supporting our previous study that suggested that absorbed [ 125 I]IGF-I made a negligible contribution to serum IGF-I (Donovan et al, 1996).…”

“…The lack of effect on overall body weight or tissue weights observed after consumption of colostral levels of IGF-I (500 mg/L) for 14 d suggests that orally administered IGF-I at a high physiological dose is not a major regulator of neonatal growth (Houle et al, 1995). Although a pharmacologic dose of IGF-I or IGF-II (2,000 mg/L) increased pancreatic growth in the first 24 h of life (Xu et al, 1994), the physiological relevance of this finding is questionable. With respect to the intestine, results thus far suggest that the magnitude of the response is affected both by the dose administered and the duration of the exposure.…”

“…have investigated the role of orally administered IGF-I or IGF-II in neonatal calves Baumrucker et al, 1994a,b) or piglets (Xu et al, 1994;Burrin et al, 1995b;Houle et al, 1995) (Table 2). In the first study, three groups of newborn dairy calves were fed 1 ) milk replacer, 2 ) milk replacer containing 750 mg/L of recombinant human IGF-I (milk replacer+IGF-I); or 3 ) pooled bovine colostrum for the first four feedings, then milk replacer for the remainder of the study Baumrucker et al, 1994a,b).…”

“…Three studies in which IGF-I or IGF-II was orally administered to the neonatal piglet have been reported recently (Xu et al, 1994, Burrin et al, 1995bHoule et al, 1995) (Table 2). In the first study, newborn colostrum-deprived piglets were fed a human infant formula supplemented with either 2,000 mg/L recombinant human IGF-I or 2,000 mg/L recombinant human IGF-II for the first 24 h postpartum.…”

Bioactive peptides in young animal nutrition

“…According to Donovan et al (1997) and Hammon and Blum (1997), IGF-I is not absorbed in the small intestine in calves and pigs, even immediately after birth, though colostrum ingestion causes a marked increase of IGF-I in blood plasma (Egli and Blum, 1998). Feeding piglets with an infant formula supplemented with IGF-I and IGF-II leads to a higher DNA content in the stomach tissue and increases cell proliferation in the upper gut as compared with infant formula alone (Xu et al, 1994). In neonatal calves, orally administered recombinant human IGF-I stimulated growth of the intestine as evidenced by [ 3 H]-thymidine incorporation into the enterocyte (Baumrucker et al, 1994), but histological examination of the intestinal mucosa did not reveal any effect (Blum and Hammon, 2000).…”