Synteza nabłonkowego czynnika wzrostu w mleku ludzkim (ang.).pdf

ACTA Acta Sci. Pol., Technol. Aliment. 9(2) 2010, 237-241

ISSN 1644-0730 (print) ISSN 1889-9594 (online)

ACTIVE SYNTHESIS OF EPIDERMAL GROWTH FACTOR

IN HUMAN MAMMARY GLANDS *

Mieczysław Walczak 1 , Beata Pawlus 1,2 , Andrzej Kędzia 3 ,

Jarosław Walkowiak 3,4

1 Pomeranian Medical University in Szczecin

2 Holy Family Clinic of Gynecology and Obstetrics in Warsaw

3 Poznań University of Medical Sciences

4 Poznań University of Life Sciences

Background. Human milk contains considerable number of growth factors, including ep-

idermal growth factor (EGF) and insulin-like growth factor-1 (IGF-1). There are no data

comparing the EGF and IGF-1 levels in the serum and milk of breast-feeding women.

Therefore, the aim of our study was to assess a possible relationship between the concen-

trations of these growth factors.

Material and methods. Thirty-nine women in child-birth were included in the study.

All women provided blood and milk samples during the first six hours after delivery. EGF

(by immunoenzymatic method) and IGF-1 (by radioimmunossay method) concentrations

were measured in both media.

Results. EGF breast milk concentrations ranged from 3.18 to 4.51 ng/ml and on average

were significantly higher (p < 0.0001) than those found in the women’s serum (from 0.02

to 0.13 ng/ml). The opposite distribution was found for IGF-1 levels. Its milk concentra-

tions ranged from 8.8 to 61.9 ng/ml and on average were significantly lower (p < 0.0001)

than the serum concentrations (from 192.6 to 595.3 ng/ml). No correlation was found be-

tween the serum and milk concentrations of both growth factors.

Conclusion. EGF seems to be synthesized locally in mammary glands, whereas IGF-1

probably permeates into the milk from the vascular bed.

Key words: epidermal growth factor, insulin-like growth factor-1, human milk, serum

* Supported by grant number 3 P05E 069 23 from the Polish Committee of Science.

Corresponding author – Adres do korespondencji: Prof. dr hab. Jarosław Walkowiak, Department

of Gastroenterology and Metabolism of Poznań University of Medical Sciences, Szpitalna 27/33,

60-572 Poznań, Poland, e-mail: jarwalk@ump.edu.pl

238

M. Walczak ...

INTRODUCTION

Epidermal growth factor (EGF) and insulin-like growth factor-1 (IGF-1) are trophic

peptides present in human milk. These growth factors stimulate the growth, differentia-

tion and maturation of different human cells. Their action accelerates a number of de-

velopmental processes, e.g. maturation of the lungs and nervous system. So far, the best

known effect of these growth factors is related to the development of the gastrointestinal

tract [Murphy 1998, Wong and Wright 1999, Ziegler et al. 1999, Playford et al. 2000,

Burrin 2002]. A local action of EGF on the gastrointestinal mucosa plays a crucial role

[Thompson 1999 a, b]. An EGF-stimulated increase in mitotic activity has been ob-

served in cultures of human duodenal mucosal cells. An acceleration in the rate of cell

division and accretion of mucosal mass has also been confirmed [Chang and Chao

2002]. In addition to morphological changes, functional adaptation such as an increase

in water, electrolytes and glucose absorption has also been documented [Chang and

Chao 2002, Troyer et al. 2001]. Thompson et al. [1999 b] have shown an inhibiting

action of EGF on the processes of enterocyte apoptosis induced by somatotropin and its

analogues, particularly in intestinal crypts.

IGF-1 not only acts locally, but also systemically. This factor is one of the major

modulators of somatic development [Kornhauser et al. 2002, Yang and Kim 2000].

It has been documented that IGF-1 strongly stimulates DNA synthesis in fetal chondro-

blasts and chondrocytes [Orbak et al. 2001]. IGF-1 increases the production of proteins,

including collagen and sulphate proteins amongst others. It also stimulates the division

of fat cells [Orbak et al. 2001, Vatten et al. 2002]. Clinical trials have confirmed an

important role of IGF-1 in the regulation of fetal and neonatal growth [Kornhauser et al.

2002, Yang and Kim 2000, Ochoa et al. 2001, Cooley et al. 2004].

Several reports on levels of growth factors in human milk have been published

[Playford et al. 2000, Orbak et al. 2001, Cooley et al. 2004, Dvorak et al. 2003]. How-

ever, there are no data comparing EGF and IGF-1 levels in the serum and milk of

breast-feeding women. Therefore, the aim of our study was to assess a possible relation-

ship between the concentrations of these growth factors in human milk and serum on the

first day of lactation.

MATERIAL AND METHODS

Thirty-nine women in child-birth, aged between 18 and 38 (mean ±SEM: 26.0 ±0.8),

were included in the study. The mean gestational age of the infants was 39.6 ±0.2 weeks

and the average birth weight was 3495 ±83 g. Blood samples were taken and milk sam-

ples were collected from all the women.

The inclusion criteria comprised the delivery of a healthy, full term infant; non-

complicated course of the pregnancy; and the possibility of milk and blood collection

during the first six hours after delivery. The exclusion criteria comprised of any compli-

cations in the mother or/and infant revealed within the in-patient period.

Approximately 3 ml of venous blood was taken from the elbow vein. The blood was

centrifuged for 10 min at 5000 r.p.m., and the serum was stored at –20°C until the assay

was performed. 3 ml of breast milk was collected by hand massage into a test-tube.

The milk was spun in a refrigerated centrifuge (at +4°C) for 20 min at 12 000 r.p.m.

After removing the fat, the centrifuged milk was stored at –20°C until the analysis.

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Active synthesis of epidermal growth factor in human mammary glands

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EGF concentrations in the breast milk and blood serum were measured by an immu-

noenzymatic method (ELISA; Biosource, Belgium) [Carpenter and Cohen 1990]. IGF-1

concentrations were measured by a radioimmunossay method (RIA), using Biosource

isotopes (Belgium) [Nagashima et al. 1990].

The statistical differences between serum and breast milk concentrations of the

growth factors (non-paired data) were calculated by the Whitney-Mann test. The rela-

tionship between serum and milk concentrations of the growth factors was assessed

using the Spearman rank correlation. Unless stated otherwise, values are expressed as

mean ±SEM. The level of significance was set at p < 0.05.

RESULTS

EGF breast milk concentrations ranged from 3.18 to 4.51 ng/ml and on average were

significantly higher (p < 0.0001) than those found in the women’s serum (0.02-0.13

ng/ml). The opposite distribution was found for IGF-1 levels. Its milk concentrations

ranged from 8.8 to 61.9 ng/ml and on average were significantly lower (p < 0.0001)

than the serum concentrations (192.6-595.3 ng/ml). The breast milk and serum EGF and

IGF-1 levels are summarized in Table 1. No correlation was found between serum and

milk concentrations of both growth factors.

Table 1. EGF and IGF-1 serum and breast-milk concentrations

Serum

Breast milk

Statistical

significance

Growth factors

mean ±SEM

EGF

0.05 ±0.003

3.94 ±0.06

p < 0.0001

IGF-1

312.2 ±15.5

33.2 ±2.2

p < 0.0001

DISCUSSION

In recent years special attention has been paid to the role of growth factors contained

in human milk in the maturation processes of the gastrointestinal tract [Burrin 2002,

Yang and Kim 2000]. Hirai et al. [2002] documented in vitro a strong trophic action of

peptide growth factors such as EGF, IGF-1, FGF, HGF and TGF-α in human fetal small

intestine cells. Chang and Chao [2002] found an increased number of intestinal Caco-2

cells, as well as higher DNA, RNA and protein content in these cells by applying EGF

stimulation. An EGF-stimulated increase of such intestinal enzymes as saccharase, amy-

lase, lactase, trehalase, alkaline phosphatase, enterokinase and gamma glutamyltrans-

peptidase is documented [Murphy 1998, Troyer et al. 2001]. After a series of animal

studies [Wong and Wright 1999, Ziegler et al. 1999, Thompson 1999 b, Hirano et al.

1995], EGF has also been recognised as a factor in accelerating regeneration of the

gastrointestinal mucosa. The role of IGF-1 in the alimentary tract is less evident than

that of EGF [Ma and Xu 1997, Burrin et al. 2001]. In this study we have documented

that the EGF concentration in breast milk is almost 80 times higher than in serum.

This finding potentially indicates a dominating role of the local synthesis of EGF in

Acta Scientiarum Polonorum, Technologia Alimentaria 9(2) 2010

240

M. Walczak ...

mammary glands. We did not find any correlation between EGF levels in serum and

breast milk. It also points to factors other than serum concentration influencing EGF

levels in human milk. On the other hand, breast milk IGF-1 levels were found to be

almost 10 times lower than those documented in serum. Similarly, no significant corre-

lation was found between serum and breast milk concentrations. These results suggest

that there is little or no synthesis of IGF-1 in the mammary glands.

CONCLUSIONS

EGF seems to be synthesized locally in mammary glands, whereas IGF-1 probably

permeates into the milk from the vascular bed.

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SYNTEZA NABŁONKOWEGO CZYNNIKA WZROSTU W MLEKU LUDZKIM

Wstęp. Ludzkie mleko zawiera znaczącą liczbę czynników wzrostowych, w tym nabłon-

kowy czynnik wzrostu (epidermal growth factor – EGF) oraz insulinopodobny czynnik

wzrostu (insulin-like growth factor-1 – IGF-1). Dotychczas nie porównano poziomów

EGF i IGF-1 w surowicy i mleku karmiących kobiet. Dlatego też celem badania była oce-

na potencjalnego związku pomiędzy stężeniami tych czynników wzrostowych.

Materiał i metody. Badaniami objęto 39 rodzących kobiet, u których próbki krwi oraz

mleka pobrano w okresie 6 godzin od porodu. W obydwu mediach oceniono stężenia EGF

(metoda immunoenzymatyczna) i IGF-1 (metoda radioimmunoenzymatyczna).

Wyniki. Stężenia EGF w mleku kobiecym wynosiły od 3,18 do 4,51 ng/ml i były znaczą-

co większe (p < 0,0001) niż w surowicy (od 0,02 do 0,13 ng/ml). Odwrotny rozkład war-

tości stwierdzono dla IGF-1, stężenia czynnika wzrostowego w mleku wynosiły od 8,8 do

61,9 ng/ml i były znacząco mniejsze (p < 0,0001) niż w surowicy (od 192,6 do 595,3

ng/ml). Nie wykazano występowania żadnych zależności pomiędzy stężeniami badanych

czynników wzrostowych w mleku i surowicy.

Wnioski. Wydaje się, że EGF jest syntetyzowane miejscowo w gruczołach mlecznych,

natomiast IGF-1 najprawdopodobniej przechodzi do mleka z łożyska naczyniowego.

Słowa kluczowe: nabłonkowy czynnik wzrostu, insulinopodobny czynnik wzrostu, mleko

ludzkie, surowica

Accepted for print – Zaakceptowano do druku: 29.04.2010

For citation – Do cytowania: Walczak M., Pawlus B., Kędzia A., Walkowiak J., 2010. Active

synthesis of epidermal growth factor in human mammary glands. Acta Sci. Pol., Technol. Aliment.

9(2), 237-241.

Acta Scientiarum Polonorum, Technologia Alimentaria 9(2) 2010

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