215 Exogenous leptin controls the development of the small intestine in neonatal piglets

J Wolin´ ski, M Biernat, P Guilloteau1, B R Weström2 and R Zabielski The Kielanowski Institute of Animal Physiology and Nutrition, Polish Academy of Sciences, 05-110 Jabłonna, Instytucka 3, Poland 1Unité Mixte de Recherches sur le Veau et le Porc, INRA, 35590 Rennes, France 2Institute of Cell and Organism Biology, Lund University, Lund, Sweden (Requests for offprints should be addressed to R Zabielski; Email: [email protected])

Abstract Leptin, a hormone produced and secreted by adipose absorption in vivo. Feeding milk formula slowed the tissue, muscles and stomach, is involved in the regulation maturation of small intestinal mucosa compared with of adipose tissue mass, food intake and body weight in feeding sow’s milk. However, after leptin treatment the neonatal animals. It is also produced in the mammary length of the small intestine was increased, and intestinal glands and secreted into the colostrum and milk. Since villi length, but not crypt size, was reduced compared with leptin receptors are widely distributed in the small intes- controls. The mitotic index was increased and the per- tine mucosa, the aim of the present study was to investi- centage of vacuolated enterocytes was reduced in the gate the effect of exogenous leptin on the development of entire small intestine. Enterocyte brush border protease the small intestine in neonatal piglets. Male neonatal and lactase activities were reduced in the jejunum. Na- piglets were fed with sow’s milk or artificial milk formula. fluorescein marker molecule absorption did not change but Every 8 h the latter received either vehicle or leptin (2 or that of BSA was reduced 3·8-fold. In conclusion, exogen- 10 µg/kg body weight). The animals were either killed ous leptin administered in physiological doses reversed the after 6 days of treatment and the small intestine sampled maturation of the small intestinal mucosa to the range for histology and brush border enzyme activities or were found in sow-reared piglets. tested for marker molecule (Na-fluorescein and BSA) Journal of Endocrinology (2003) 177, 215–222

Introduction leptin concentrations. Silva and co-workers (1999) showed that leptin is synthesized in the mammary gland and Leptin is a 167 amino acid protein, first discovered in excreted with milk. In contrast, Casabiell and co-workers adipose tissue (Zhang et al. 1994) and after that in a wide (1997) demonstrated that leptin is transferred from the variety of tissues, including the mammary gland (Smith- circulation to the mammary gland, then without loss of Kirwin et al. 1998, Aoki et al. 1999, Silva & VandeHaar biological activity, to the milk and after that to the infant’s 1999, Bonnet et al. 2002). Smith-Kirwin and co-workers stomach and general blood circulation. The biologically (1998) demonstrated the biosynthesis of leptin in human active form of the leptin receptor (OB-Rb) (Cioffi et al. placenta and suggested a plausible role of the hormone in 1996, Lee et al. 1996) is widespread, and has been localized foetal growth. After birth, colostrum and milk take over in the entire length of the small intestine (Morton et al. some of the placenta’s functions, especially in regard to the 1998). Using immunostaining, Barrenetxe et al. (2002) delivery of maternal hormones and growth factors to the demonstrated the leptin receptor within the cytoplasm of neonate. This is true also for leptin, which has been enterocytes located on both intestinal villi and crypts in the identified in human, mouse, rat and pig colostrum and human, rat and mouse small intestine. In human entero- milk (Casabiell et al. 1997, Houseknecht et al. 1997, Aoki cytes, the OB-Rb receptor (long form of the leptin et al. 1999, Estienne et al. 2000, Ucar et al. 2000). It is receptor) was also found in the brush border plasma noteworthy that in humans, leptin is present in whole membrane (Barrenetxe et al. 2002). breast milk at 30- to 150-fold higher concentrations than These studies suggest that ‘milk-borne’ leptin may play in milk formula (Houseknecht et al. 1997, Smith-Kirwin aroleintheoffspring, although its effect on the develop- et al. 1998), and its concentration in breast milk is ment of the neonatal gastrointestinal tract has never been positively correlated with maternal and/or infant plasma experimentally verified. The aim of the present study was

Journal of Endocrinology (2003) 177, 215–222 Online version via http://www.endocrinology.org 0022–0795/03/0177–215  2003 Society for Endocrinology Printed in Great Britain

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to investigate the role of exogenous leptin in the develop- (Leptin Mouse Recombinant; Sigma, St Louis, MO, USA) ment of the small intestine of neonatal piglets fed artificial at a dose of 2 µg/kg body weight – group L2 (n=6), or milk formula. Development was evaluated in regard to the 10 µg/kg body weight – group L10 (n=6) every 8 h via a microscopic structure of the intestinal mucosa, brush stomach tube. The pH of the vehicle was 5·8, which is border-specific enzyme activities and in vivo intestinal optimal for leptin bioactivity and similar to that of the absorption of marker molecules. ingested milk replacer. After 6 days of vehicle or leptin treatment the animals were killed by pentobarbiturate (Vetbutal; Biowet, Poland) overdose, and the gastro- Materials and Methods intestinal tract was removed for morphometric analysis and tissue sampling. The stomach and pancreas were weighed Animal experiments and the small intestine’s weight and length determined. The experiments and treatments were conducted in com- Whole-thickness samples of the duodenum, proximal pliance with the European Union regulations concerning (25%), middle (50%) and distal (75%) jejunum and ileum the protection of experimental animals. The Local Ethics were harvested and fixed in Bouin’s solution for histologi- Committee approved the study protocol. A total of 44 cal analysis. The corresponding 15 cm long intestine male neonatal piglets (Polish LandracePietrain) from segments were gently scraped to collect the mucosa for nine different litters were purchased from a commercial enzyme activity analysis. In the second series, eight piglets pig farm. The average birth weight was 1·600·15 kg. were divided into two groups receiving saline (CM, n=4) The piglets were delivered healthy and without compli- or leptin at a dose of 10 µg/kg body weight (LM, n=4) cations, and were kept with their sows for 24 h, except six using an identical schedule as in the first series. On day 6 of them that were kept with their sows for 7 days (control they were implanted with Silastic catheters in the left group of sow-reared piglets (CSR)). Six animals were jugular vein under general halothane anaesthesia, and on killed by pentobarbiturate overdose 24 h after birth, and the day after, a test of in vivo intestinal absorptive capacity another six were killed 7 days after birth (CSR), and was performed. In the morning, the CM and LM groups sampled like those described below. The other 26 animals received a marker molecule cocktail by a stomach tube. were installed (initially in groups of four piglets) in the The cocktail contained: 500 mg/kg BSA (67 kDa, Cat. laboratory in a special cage equipped with an ‘artificial No. A-4503; Sigma) and 9·4 mg/kg Na-fluorescein sow’. The laboratory provided a 12 h light:12 h darkness (376 Da; Merck, Darmstadt, Germany). The components cycle and an ambient temperature that was decreased from were dissolved in 0·9% NaCl immediately before admin- 32 Cto28C over the 6 days of the experiment to ensure istration and given to the pigs in a volume of 4 ml/kg body a comfortable environment for neonatal piglets. At the weight. For marker molecule analysis, 4 ml venous blood beginning of each trial, four piglets were kept together for samples were taken just before administration (0 h) and an approximately 12 h period of adaptation. After that, the after 0·5, 1, 2, 4, 8 and 24 h. After the last blood sample piglets were housed individually in a manner providing was taken, the animals were killed by pentobarbiturate social contact with each other. Milk-replacer formula for overdose. The blood samples were centrifuged at 3000 g piglets (protein 19·8%; fat 19·7%; ash 8·2%; Milky Farm, (4 C) for 15 min and the plasma harvested and stored Nukamel Olen, Belgium) was distributed to each piglet frozen (20 C) until analysis. every 75 min (20 times per 24 h) in equal amounts by means of an artificial sow (Research Centre Foulum- Mucosa histology and laser scanning cytometry (LSC) model, Pig’s oline; Boss’ Produkter a/s, Denmark). The daily amount of milk replacer was calculated on the basis of Serial histological sections of 5 µm thickness were cut and daily body weight gain and protein intake. Body weight stained with haematoxylin and eosin for morphometric was recorded every morning. Protein intake in neonatal analysis under a light microscope. After staining, the depth pigs rose gradually from 11·0 to 11·3 g/kg body weight of crypts, length of villi and thickness of the tunica mucosa during the first 7 days of life. The concentration of protein were measured in the small intestine preparations at a low in milk formula was 20% of dry matter (V Lesniewska & magnification with a Nikon type 104 (Nikon Corporation, M Hedemann, unpublished observations). Sow colostrum Yokohama, Japan) optical binocular microscope coupled and milk, artificial milk formula and plasma blood samples via a camera to a computer. In each slide, 30 well-oriented collected from pig neonates were measured for leptin villi and crypts were measured using Lucia G v4·60 concentration using an RIA kit (Leptin Multi-Species; software (Laboratory Imaging Ltd, Prague, Czech Linco Research Inc., St Louis, MO, USA). The assay was Republic). In each slide from the jejunum and ileum, all performed in one run. of the enterocytes in 30 well-oriented villi were analysed Two series of experiments were performed in the for the presence of ‘lysosomal vacuoles’ (LV) and the laboratory. In the first series, 18 animals were randomly percentage of vacuolated enterocytes was calculated divided into three groups that received either vehicle (Biernat et al. 1999). In each villi, 20 vacuolated entero- alone (5 ml 0·9% NaCl) – control group (n=6), leptin cytes were measured for the area of LVs (µm2) using a

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Downloaded from Bioscientifica.com at 09/28/2021 04:44:30PM via free access Leptin controls small intestinal development · J WOLINuSKI and others 217 planimetry feature of the Lucia G v.4·60 software. The Statistical analyses mitotic index was estimated in the jejunal crypts by The data are expressed as meansS.E.M. One-way calculating the percentage of mitotic cells in 1000–1200 ANOVA followed by the Tukey post-ANOVA test was counted cells (Biernat et al. 1999). used to indicate the statistical differences between the The rate of apoptosis in the mid-jejunum was estimated groups in the first series, and the unpaired Student’s t-test on the basis of chromatin condensation and DNA content or non-parametric Mann–Whitney test was used to indi- in the nuclei following 7-aminoactinomycin D (7-AAD) cate the statistical differences between the groups in the staining using LSC (CompuCyte Corp., Cambridge, MA, second series (Graph Pad Software v.3·03). In all statistical USA). The fluorescence excitation was provided by a analysis P<0·05 was taken as the level of significance. 488 nm, 10 mW argon laser beam. The far-red fluor- escence of 7-AAD was measured using a combination of dichroic mirrors and filters transmitting at >650 nm (de- Results tector offset 2000 and gain 30). For chromatin conden- After transporting from the farm, four pig neonates were sation another parameter was acquired, corresponding to kept together in one cage for 12 h; at that time (usually the highest value of DNA-related fluorescence in the cell within 5–6 h) one of them had taught himself how to eat – the DNA maximal pixel. In the mid-jejunum, the from the artificial sow. The other piglets soon followed the mitotic index to apoptosis ratio was measured. leader; thus, after separating them into individual cages all piglets ate milk formula distributed by the artificial sow. ff Brush border enzyme activity No di erences in appetite between the milk formula-fed (control, CM) and leptin-supplemented (L2, L10, LM) Brush border enzyme activity was measured in the mucosa piglets were observed, and all piglets ate all of the milk scrapings from the proximal, middle and distal parts of the formula dosed by the artificial sow at once. The concen- jejunum. The mucosa was scraped off with a microscope tration of leptin in colostrum was 53·715·2 ng/ml in the slide, and deep-frozen in liquid nitrogen (–80 C). After first portions, 71·713·0 ng/ml 24 h after that, and in thawing, the intestinal mucosa was homogenized in cold milk collected on day 7 postpartum it was 25·52·5 ng/ distilled water (1 g intestinal mucosa/5 ml distilled water) ml. In the milk formula samples the concentration of leptin and centrifuged for 5 min at 1000 g at 4 C. The protein was 20·32·5 ng/ml. In the milk formula-fed piglets the content was then determined as described by Hartree concentration of leptin in the blood plasma was reduced by (1972), using BSA as the standard. The activities of about 25% with respect to sow-reared piglets. Intragastric aminopeptidase A and N were assayed with -glutamyl- administration of leptin had no effect on plasma leptin p-nitroanilide and -leucyl-p-nitroanilide as substrates concentration, which in control and L10 piglets equalled respectively (Maroux et al. 1973), and that of dipepti- respectively 1·810·44 and 1·410·13 ng/ml. dase IV was assayed with glycyl--prolyl-p-nitroanilide (Nagatsu et al. 1976). The resulting enzymatic units Body and organ weights (IU) are expressed as µmol p-nitroanilide released/min  Neonatal piglets, fed with sow’s milk (CSR) between days at 37 C. Lactase, maltase and sucrase were determined  as described earlier (Dahlquist 1964) with minor 1 and 7 of life gained on average 270 81 g daily; modifications. however, no data on their daily food intake are available. In milk formula-fed piglets the food intake was 9613 g dry matter per day. Milk formula-fed piglets gained Marker macromolecule analysis less, 8415 g daily, and had a shorter small intestine (jejunum) and lighter pancreas compared with CSR The concentrations of marker molecules in the plasma ff samples from the second series of experiments were (Table 1). Six days of leptin treatment had no e ect on the analysed according to Nejdfors et al. (2000). The fluor- body weight of the investigated neonatal piglets or on the escence of Na-fluorescein was measured in a 96-microwell stomach, liver, or pancreas weights relative to the body plate (Nunc, Roskilde, Denmark) by spectrophotofluor- weight compared with the control group (Table 1). The ometry (CytoFluor 2300; Millipore, Bedford, MA, USA), length of the jejunum showed a significant increase and using a filter set-up of 485 nm for excitation and 530 nm that of the ileum a significant reduction in the piglets for emission. The standards for Na-fluorescein were dis- treated with 10 µg/kg body weight of leptin. The length of the entire small intestine in leptin-treated piglets (L10) solved in PBS. BSA was quantified by electroimmunoassay ff (Laurell 1966), using purified BSA diluted in swine serum was not di erent from that found in piglets fed with sow’s as a standard and rabbit anti-BSA antibodies (Dako, milk (Table 1). Glostrup, Denmark). Analysis of the area under the curve (Graph Pad Software v.2·0, San Diego, CA, USA) was Small intestine morphometry performed to compare the marker molecule absorption The results of histometry analysis are shown in Table 2. between CM and LM groups. Feeding with milk formula (control) reduced the crypt www.endocrinology.org Journal of Endocrinology (2003) 177, 215–222

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Table 1 Body weight, intestine length and organ weight in sow-reared (CSR), control (C) and leptin-treated (L2, L10) piglets on day 7 of life. Values are meansS.E.M. (n=6)

CSR C L2 L10 P

Body weight (kg) 3·40·5a 2·10·1b 2·10·1b 2·20·1b 0·0003 Small intestine (cm) 499·232·0a 417·515·2b 431·721·5b 459·822·0ab 0·0060 Duodenum (cm) 7·70·6 8·501·2 6·71·5 7·00·7 0·0333 Jejunum (cm) 485·032·0a 401·415·4b 418·420·8b 448·821·8ab 0·0050 Ileum (cm) 6·20·9a 7·40·8a 6·61·4a 4·10·4b 0·0003 Stomach/body weight (g/kg) 5·30·7 5·40·4 5·10·4 5·20·4 0·4660 Liver/body weight (g/kg) 32·02·7 33·85·1 30·02·3 34·02·2 0·3934 Pancreas/body weight (g/kg) 1·520·2a 1·90·2ab 2·00·1b 1·80·2ab 0·0129

Different letters in a row indicate statistical significance (one-way ANOVA followed by Tukey post-ANOVA test).

depth in the duodenum, reduced the length of villi leptin (L10) groups it was respectively 23·23·0 and and thickness of mucosa in the proximal jejunum and 19·71·2% (P=0·069). The mitotic index to apoptosis increased the length of villi and thickness of mucosa in ratio calculated for this segment of the jejunum in the the ileum compared with natural milk feeding (CSR). leptin-supplemented group was, however, 1·9-fold higher Exogenous leptin caused a significant reduction of villi compared with the control group, and only 1·16-fold length and correspondingly a reduction in mucosa thick- higher compared with the CSR group. ness in the middle and distal jejunum and ileum compared In sow-reared piglets (CSR) large LVs were present with milk formula-fed control piglets. Although the size of in the enterocytes only in the distal jejunum and ileum, intestinal crypts did not change, the mitotic index was the whereas in the milk formula-fed and leptin-supplemented lowest in the jejunum and ileum in the milk formula-fed piglets they were also in the mid-jejunum. However, in group, and the highest in the leptin-supplemented group the leptin-supplemented group (L10) there were only a (Table 2). The apoptotic index analysed using LSC in few LVs in the jejunum and ileum, and of smaller size the mid-jejunum in the sow-reared group (CSR) was compared with the CSR and control groups (Table 2 and 21·15·0%. In the milk formula-fed (control) and Fig. 1).

Table 2 Histological parameters (
m), mitotic index (%), cross-section area of LV (
m2) and percentage of vacuolated enterocytes (%) in sow-reared (CSR), control (C) and leptin-treated (L10) piglets on day 7 of life. Values are meansS.E.M. (n=6)

Crypt depth Villi length Tunica mucosa Mitotic index LV area % LV

Duodenum CSR 15424a 65567 84894 3·80·2a —0 C 11610b 534105 712107 4·20·1b —0 L10 1337ab 52873 673141 5·70·2c —0 Jejunum (25%) CSR 13935 83172a 101079a 4·20·2a —0 C 1099 50965b 63829b 3·70·1b —0 L10 1166 46822b 62424b 5·60·1c —0 Jejunum (50%) CSR 12421 96788a 1108116a 5·20·3a —0 C 1158 865235a 972224a 3·50·2b 8011 432 L10 1187 44375b 60364b 5·80·2c 636* 21*** Jejunum (75%) CSR 11414 84292a 992103a 3·60·2a 8530 723a C 1038 886107a 939157a 3·00·1b 8813 723a L10 11411 477100b 658128b 6·00·1c 70651b Ileum CSR 11820 56489a 71394a 3·30·1a 7911ab 961a C 11310 798106b 926113b 3·00·1b 11433a 984a L10 1188 37147a 51945a 5·70·2c 548b 212b

Different letters in columns indicate statistical significance (one-way ANOVA followed by Tukey post-ANOVA test). *P<0·05, ***P<0·001 (Student’s t-test followed by Mann–Whitney test).

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Figure 1 Representative photographs of the villi in the ileum of milk formula-fed (A) and leptin-supplemented (B) piglets. Note that the villi in the milk formula-fed piglets are much longer than those in the leptin group, and almost all enterocytes in the milk formula-fed piglets contain large LVs in contrast to the leptin-treated group. Haematoxylin and eosin staining. Scale bars=100
m.

Brush border enzyme activities jejunum in leptin-treated piglets compared with the ff In sow-reared piglets, the activity of the examined brush controls. Sucrase activity did not show any di erences border enzymes (aminopeptidase A and N, dipeptidase IV, between the leptin-treated animals and controls. lactase, maltase and sucrase), showed normal dynamic Marker molecule absorption changes during the first week of life (data not shown) related to development. Compared with sow’s milk, After administration of marker molecules, the blood levels feeding milk formula resulted in elevation in aminopepti- of the markers increased in both groups (P<0·01). The dase A and N, dipeptidase IV and lactase activity and peak blood plasma concentration differed between the reduction in lactase, maltase and sucrase in the respective marker molecules in a size-dependent manner, and the segments of the jejunum (Table 3). Notably, in leptin- peaks were seen after 30 min for Na-fluorescein and after treated piglets there was a general trend towards recovery 8 h for BSA (Fig. 2). Area under the curve analysis of aminopeptidase A and N and dipeptidase IV activity to revealed that plasma levels for Na-fluorescein did not differ levels observed in sow-reared piglets, the activity of lactase significantly between the two groups whilst that of BSA in the mid- and distal jejunum was further decreased was 3·8-fold reduced (P=0·016) in the leptin group below the activity present in sow-reared piglets (Table 3). compared with the control. This indicates less intestinal The activity of maltase and lactase in the proximal and absorption of large-size molecules in the leptin-treated distal jejunum of leptin-supplemented piglets was not piglets. different from that in piglets receiving sow’s milk (CSR) or milk formula (controls) whereas in the mid-jejunum it Discussion was as low as in the milk formula-fed group (Table 3). The effects of leptin were dose-dependent (data not shown). Our studies demonstrate for the first time that leptin The activity of maltase was reduced only in the distal present in colostrum and milk may be important for www.endocrinology.org Journal of Endocrinology (2003) 177, 215–222

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Table 3 Brush border enzyme activity (
mol/min per g mucosa) in sow-reared (CSR), control (C) and leptin-treated (L10) piglets on day 7 of life. Values are meansS.E.M. (n=6)

Aminopeptidase A Aminopeptidase N Dipeptidase IV Lactase Maltase Sucrase

Jejunum (25%) CSR 10·01·9ab 2·10·4 0·60·1a 10·81·6 7·92·1 4·01·1 C 11·02·2a 3·61·1 2·00·6b 10·64·3 9·43·0 2·61·1 L10 6·61·4b 3·81·0 1·00·3a 8·00·8 7·41·4 2·51·1 Jejunum (50%) CSR 10·41·4a 1·70·4a 1·90·4a 10·61·8a 7·42·2a 2·60·8a C 23·95·5b 11·62·5b 5·90·9b 16·73·6b 3·20·6b 0·60·3b L10 6·70·8a 3·91·3a 1·10·3a 5·00·3c 3·80·8b 0·30·1b Jejunum (75%) CSR 13·82·6a 10·42·3ab 4·61·3 12·11·0a 1·90·3 1·80·3a C 27·65·3b 15·43·4a 6·30·7 6·21·6b 3·30·8 0·40·3b L10 15·43·5a 6·51·2b 4·10·9 3·61·1c 1·90·5 0·70·2ab

Different letters in columns indicate statistical significance (one-way ANOVA followed by Tukey post-ANOVA test).

controlling the development of small intestine structure sampling to get more precise kinetics of the leptin con- and function in neonatal piglets. Importantly, the clear-cut centration in colostrum and milk. In milk formula-fed effects of leptin supplementation on intestinal mucosa piglets, plasma leptin did not increase in response to morphometry, presence of LVs in the enterocytes, pro- enteral administration of leptin, which may suggest that: (i) liferation of mucosa epithelial cells, enterocyte brush leptin is not transferred from the gut into the circulation, border enzyme activities and marker molecule absorption which is in contrast to the findings in suckling rats by were observed following doses of leptin that can be Casabiell et al. (1997), and (ii) the effects observed in the considered physiological. present study depend on leptin receptors localized in the The concentrations of leptin in sow’s milk, and in the intestinal mucosa (Morton et al. 1998, Barrenetxe et al. blood plasma in piglets, correspond to those previously 2002). reported (Estienne et al. 2000), although no data on leptin We observed a reduction in the body weight of arti- in sow colostrum and milk at the very beginning of ficially reared vs sow-reared piglets; however, in contrast lactation are available. In our study, the concentration of to previous studies in neonatal rats (Yuan et al. 2000), we leptin in milk formula, being roughly one-third of that in did not observe body weight reduction following leptin the colostrum and four-fifths of that in milk, was much treatment. This can be related to either the much higher higher than previously reported for human milk formula doses of leptin applied and/or different route of leptin (Houseknecht et al. 1997, Resto et al. 2001). The differ- administration (i.p.) in the rat study. Possibly, the lack of ence is most probably related to the applied technologies of differences in the body weight between milk formula-fed producing milk formula (Resto et al. 2001). Thus, the and leptin-supplemented piglets in our study could also be higher dose of leptin in our study was sufficient to related to similar intake of milk formula in both groups. supplement the neonates in the colostrum period, and the Nevertheless, we postulate that body weight regulation lower dose was sufficient thereafter. Unfortunately, we did is rather not a direct target for milk leptin. Earlier not have a chance to access the sows for additional studies suggested that leptin can restrict body energy

Figure 2 Mean blood plasma levels of marker molecules, Na-fluorescein and BSA during 24 h after marker gavage feeding to milk formula-fed (•; n=4) and leptin-treated ( ; n=4) neonatal piglets.

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Downloaded from Bioscientifica.com at 09/28/2021 04:44:30PM via free access Leptin controls small intestinal development · J WOLINuSKI and others 221 accumulation indirectly through a local mechanism in the In conclusion, feeding neonatal piglets with milk for- small intestine controlling the absorption of nutrients mula slows the maturation of the small intestinal mucosa, (Lostao et al. 1998, Morton et al. 1998) or intestinal and exogenous leptin given into the stomach (in a range motility (Wolin´ski et al. 2001). Lostao et al. (1998) that is present in colostrum and milk) may reverse the demonstrated that leptin has a rapid inhibitory effect on process as evidenced by morphological and functional -galactose uptake in the rat intestinal mucosa in vitro.In studies. the same year, Morton et al. (1998) showed that leptin can reduce the transcription of genes responsible for apolipo- protein biosynthesis (APO-AIV) in the enterocytes in Acknowledgements mouse jejunum in response to olive oil administration. Correspondingly, in the present in vivo study we observed We thank Maria BTbelewska, Véronique Romé, Inger marked activity reduction of all examined brush border Matson, Małgorzatau Switon´ska and Marta Jurkowska for enzymes (except sucrase) in leptin-supplemented piglets. technical assistance. This work was supported by grants It should be borne in mind, however, that in contrast to from the State Committee for Scientific Research (KBN, natural feeding, milk formula enhances the activity of Poland, grant No. 3 P06D 047 22), POLONIUM aminopeptidases and dipeptidase IV, and leptin sup- program (Poland and France) and PECO-NEI (France). plementation depressed their activity to the level seen in the sow-reared piglets. Recently, we have shown that repetitive intragastric administration of leptin influences in vitro small intestine contractile activity (Wolin´ski References et al. 2001) thus revealing a possible effect of leptin on digesta passage. Leptin increased the spontaneous and Aoki N, Kawamura M & Matsuda T 1999 Lactation-dependent down acetylcholine-stimulated activity of the duodenum and regulation of leptin production in mouse mammary gland. Biochimica et Biophysica Acta 1427 298–306. reduced the activity of the jejunum (Wolin´ski et al. 2001). Baintner K 1994 Demonstration of acidity in intestinal vacuoles of the Replacement of sow’s milk with milk formula inhibits suckling rat and pig. Journal of Histochemistry and Cytochemistry 42 the growth of the small intestine as well as slows the 231–238. maturation of the intestinal mucosa as evidenced by low Barrenetxe J, Villaro AC, Guembe L, Pascual I, Muñoz-Navas M, mitotic index, abundance of vacuolated enterocytes in the BarberA&Lostao MP 2002 Distribution of the long leptin receptor isoform in brush border, basolateral membrane, and mid-jejunum and high lactase and peptidase activities. cytoplasm of enterocytes. Gut 50 797–802. Enteral supplementation with leptin in part reverses these Biernat M, Zabielski R, Sysa P, Sosak-Suwiderska B, Le Huerou-Luron I effects. Namely, leptin selectively and dose-dependently & Guilloteau P 1999 Small intestinal and pancreatic microstructures increases the length of the small intestine, reduces the are modified by an intraduodenal CCK-A receptor antagonist thickness of intestinal mucosa by decreasing the height of administration in neonatal calves. Regulatory Peptides 85 77–85. Bonnet M, Gourdou I, Leroux C, ChilliardY&Djiane J 2002 Leptin villi, and significantly reduces the activity of brush border expression in the ovine mammary gland: putative sequential lactase and proteases, regarded as enzymatic markers of gut involvement of adipose, epithelial and myoepithelial cells during maturation (Henning 1987, Klein 1989). Stem cell pro- pregnancy and lactation. Journal of Animal Sciences 80 723–728. liferation in the intestinal crypts is enhanced and simul- Casabiell X, Pineiro V, Tome MA, Peino R, Dieguez C & taneously cell apoptosis slightly reduced, thereby the Casanueva FF 1997 Presence of leptin in colostrum and/or breast milk from lactating mothers: a potential role in the regulation of mitotic index to apoptosis ratio becomes similar to that in neonatal food intake. Journal of Clinical Endocrinology and Metabolism sow-reared piglets. These effects are consistent with pre- 82 4270–4273. vious immunocytochemical studies (Barrenetxe et al. Cioffi JA, Shafer AW, Zupancic TJ, Smith-Gbur J, Mikhail A, Platika 2002) showing the presence of leptin receptors in the D & Snodgrass HR 1996 Novel B219/OB receptor isoforms: possible role of leptin in hematopoiesis and reproduction. Nature mucosa on the entire length of the small intestine. Small Medicine 2 585–589. numbers of LVs in the jejunum and ileum following Dahlquist A 1964 Assay of intestinal disaccharidases. Scandinavian leptin-supplementation together with an increased mitotic Journal of Laboratory Investigation 44 169–172. index imply that the irreversible process of replacing Estienne MJ, Harper AF, Barb CR & Azain MJ 2000 Concentrations foetal-type enterocytes with adult-type ones (Baintner of leptin in serum and milk collected from lactating sows differing 1994) has been accelerated (Biernat et al. 1999, Radberg in body condition. Domestic Animal Endocrinology 19 275–280. Hartree EF 1972 Determination of protein: a modification of the et al. 2001). The decrease in the endocytosis rate due to Lowry method that gives a linear photometric response. Annals of the presence of adult-type enterocytes may explain the Biochemistry 48 422–427. sharp reduction in BSA absorption in leptin-supplemented Henning SJ 1987 Functional development of the gastrointestinal tract. piglets in the present study (Smith & Peacock 1980). No In Physiology of the Gastrointestinal Tract, edn 2, pp 285–300. Ed. difference in the absorption of the inert and passively LR Johnson. New York: Raven Press. Houseknecht KL, McGuire MK, Portocarrero CP, McGuire MA & transported small-size molecule (Na-fluorescein) suggests Beerman K 1997 Leptin is present in human milk and is related to that functionally the intestinal absorptive area is not maternal plasma leptin concentration and adiposity. Biochemical and restricted following leptin supplementation. Biophysical Research Communications 240 742–747. www.endocrinology.org Journal of Endocrinology (2003) 177, 215–222

Downloaded from Bioscientifica.com at 09/28/2021 04:44:30PM via free access 222 J WOLINuSKI and others · Leptin controls small intestinal development

Klein RM 1989 Small intestine cell proliferation during development. Silva LFP & VandeHaar MJ 1999 Role of leptin in mammary In Human Gastrointestinal Development, pp 367–394. Ed. E cell proliferation. South African Journal of Animal Science 29 Lebendhal. New York: Raven Press. 300–301. Laurell CB 1966 Quantitative estimation of proteins by electrophoresis Smith MW & Peacock MA 1980 Anomalous replacement of foetal in agarose gel containing antibodies. Annals of Biochemistry 15 enterocytes in the neonatal pig. Proceedings of the Royal Society of 45–52. London. Series B 206 411–420. Lee GH, Proenca R, Montez JM, Carroll KM, Darvishzaded JG, Lee Smith-Kirwin SM, O’Connor DM, De Johnston J, Lancey ED, JI & Friedman JM 1996 Abnormal splicing of the leptin receptor in Hassink SG & Funanage VL 1998 Leptin expression in human diabetic mice. Nature 379 632–635. mammary epithelial cells and breast milk. Journal of Clinical Lostao MP, Urdaneta E, Martinez-Anso E, BarberA&Martinez JA Endocrinology and Metabolism 83 1810–1813. 1998 Presence of leptin receptors in rat small intestine and leptin Ucar B, Kirel B, Bor O, Kilic FS, Dogruel N, Aydogdu SD & Tekin effect on sugar absorption. FEBS Letters 423 302–306. N 2000 Breast milk leptin concentrations in initial and terminal MarouxS,LouvardD&Baratti J 1973 The aminopeptidase from hog milk samples: relationships to maternal and infant plasma leptin intestinal brush border. Biochimica et Biophysica Acta 321 282–295. concentrations, adiposity, serum glucose, insulin, lipid and Morton NM, Emilsson V, Liu YL & Cawthorne MA 1998 Leptin lipoprotein levels. Journal of Pediatric Endocrinology and Metabolism 13 action in intestinal cells. Journal of Biological Chemistry 273 149–156. 26194–26201. Nagatsu T, Hino M, Fuyamada H, Hayakawa H, Sakakibara T, Wolin´ski J,u Seniewska V, Biernat M, BTbelewska M, Korczyn´ski W NakagawaY&TakemotoT1976 New chromogenic substrates for & Zabielski R 2001 Exogenous leptin influences gastrointestinal X-prolyl dipeptidyl-aminopeptidase. Annals of Biochemistry 74 growth and in vitro small intestinal motility in neonatal piglets – 466–476. preliminary results. Journal of Animal Feed Science 10 (Suppl 2) Nejdfors P, Ekelund M, JeppssonB&Weström BR 2000 Mucosal 249–254. in vitro permeability in the intestinal tract of the pig, the rat, and Yuan CS, Attele AS, Zhang L, Lynch JP, Xie JT & Shi ZQ 2000 man: species and region related differences. Scandinavian Journal of Leptin reduces body weight gain in neonatal rats. Journal of Pediatric Gastroenterology 35 501–507. Research 48 380–383. Radberg K, Biernat M, Linderoth A, Zabielski R, Pierzynowski SG & Zhang Y, Proenca R, Maffei M, Barone M, Leopold I & Friedman Westrom BR 2001 Enteral exposure to crude red kidney bean JM 1994 Positional cloning of the mouse obese gene and its human lectin induces maturation of the gut in suckling pigs. Journal of homologue. Nature 372 425–432. Animal Science 79 2669–2678. Resto M, O’Connor D, Leef K, Funange V, Spear M & Locke R 2001 Leptin levels in preterm human breast milk and infant Received 12 November 2002 formula. Pediatrics 108 E15. Accepted 28 January 2003

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