Low Body Adiposity and High Leptinemia in Breast-fed Infants BornSmall-for-Gestational-Age

Lourdes Ibanez, MD, PhD,* Giorgia Sebastiani, MD,* Marta Diaz, PhD, Maria Dolores Gomez-Roig, MD, PhD,

Abel Lopez-Bermejo, MD, PhD, and Francis de Zegher, MD, PhD

Breast-fed infants born small-for-gestational-age (SGA) (n = 28) were found to develop lower adiposity across earlyinfancy, when compared with appropriate-for-gestational age infants (n = 46). The SGA infants were also found tohave 2-fold higher (P < .001) levels of circulating leptin at 4 months. This paradoxical hyperleptinemia in early infancymay contribute to a program that produces a process from fetal underweight to adult overweight. (J Pediatr2010;156:145-7)

From the Endocrinology Unit (L.I., G.S., M.D.) and Gynecology Department(M.D.G.-R.), Hospital Sant Joan de Deu, University of Barcelona, Barcelona, Spain;CIBER de Diabetes y Enfermedades Metabolicas Asociadas, ISCIII, Madrid, Spain(A.L.-B.); the Department of Pediatrics, Dr. Josep Trueta Hospital, Girona, Spain(A.L.-B.); and the Department of Woman and Child, University of Leuven, Leuven,Belgium (F.Z.)

*Contributed equally to this work.

Supported by the Social Security Research Fund, Health Institute Carlos III, Spain

Circulating leptin levels have long been known toreflect body weight and body adiposity, both beforebirth and beyond late infancy.1-3 Early infancy is

a phase of marked fat expansion and may be a critical windowfor the lifelong settings of weight control, particularly in sub-jects who have had a fetal growth restraint, and who recoverin early infancy from such a restraint.4

Methods

In the absence of longitudinal data on the endocrinology andbody composition of breast-fed appropriate-for-gestational-age (AGA) and small-for-gestational-age (SGA) infants, wereceived approval to assemble a reference cohort prospec-tively. The present study population consists of the first 37girls (23 AGA; 14 SGA) and 37 boys (23 AGA; 14 SGA)who were recruited at birth to these cohorts and who werealso assessed at the age of 4 months.

Inclusion criteria for the present analysis were (1) mater-nally uncomplicated pregnancy (no gestational diabetes; nopreeclampsia; no use of alcohol or drugs) with term delivery(37 to 42 weeks) at Sant Joan Hospital; (2) cord serum avail-able (collection dependent on logistic restraints, especially atnighttime); (3) birth weight within strict limits: Z-scorebetween �1 and +1 for AGA infants; Z-score below �2,and birth weight above 1800 g for SGA infants (5); (4) par-ents with enough Catalan background to allow for writteninformed consent in Catalan; (5) exclusive breast-feedingfor 4 months; (6) prefeeding serum sample available at age4 months; and (7) body composition assessment, by absorp-tiometry, available at age �2 weeks and 4 months.

Exclusion criteria were dysmorphic features and10-minute Apgar score <7. All infants were born after single-ton pregnancies and were of Caucasian origin.

The sample size in AGA infants was estimated from earlierexperience in newborn infants,5 where matched subgroups of

AGA Appropriate-for-gestational age

HMW High-molecular-weight

IGF Insulin-like growth factor

SGA Small-for-gestational age

n = 16 proved informative; the sample size in SGA infants waslimited by recruitment restraints; after enrollment and beforeanalysis, AGA and SGA subgroups were each balanced forsex, the infants being included into the analysis in the sameorder as they were enrolled. The study protocol was approvedby the Institutional Review Board, Sant Joan University Hos-pital; written consent of parents was obtained before enroll-ment of infants.

All infants had supine length measured at birth and at age 4months (mean� SEM; 138� 3 days) by the same investigator(G.S.). Blood glucose and circulating insulin, interleukingrowth factor (IGF)-I, and high-molecular-weight (HMW)adiponectin were measured in prefeeding samples obtainedat age 4 months, in the morning. Blood samples were centri-fuged and serum was frozen until assay. Glucose wasmeasured by glucose oxidase method. Insulin and IGF-Iwere measured by immunochemiluminescence (IMMULITE2000, Diagnostic Products, Los Angeles, California); the lowerdetection limits for insulin and IGF-I were 0.4 mU/mL and 25ng/mL. HMW adiponectin and leptin were assessed with, re-spectively, an ELISA and RIA kit (Linco Research, St Charles,Missouri). Intra-assay and interassay coefficients of variationwere <10%; for leptin; they were 3.5% and 6.7%, respectively.

Body composition was assessed by absorptiometry at age15� 0.6 days and at age 4.5� 0.1 months with a Lunar Prod-igy, coupled to Lunar software (version 3.4/3.5, Lunar Corp.,Madison, Wisconsin), adapted for assessment of infants.5 Allassessments were performed during spontaneous sleep,

(P108/0443). The authors declare no conflicts of interest.

L.I. and M.D. are Clinical Investigators of CIBERDEM (CB07/08/0044, Fondo deInvestigacion Sanitaria, Instituto de Salud Carlos III, Madrid, Spain). A.L.B. is anInvestigator of the Fund for Scientific Research ‘‘I3’’ (Ministry of Education andScience, Spain). F.dZ. is a Clinical Investigator of the Fund for Scientific Research(Flanders, Belgium)

0022-3476/$ - see front matter. Copyright ª 2010 Mosby Inc.

All rights reserved. 10.1016/j.jpeds.2009.06.050

145

Table I. Auxological, body composition, and endocrine indices in AGA infants at age 2 weeks and 4 months

Girlsn = 23

Boysn = 23

At 2 wk* At 4 mo 4-mo change At 2 wk* At 4 mo 4-mo change

Length (cm) 50.4 � 0.4 60.7 � 0.9 10.3 � 1.0 50.7 � 0.3 65.4 � 0.6d 14.7 � 0.7c

Weight (g)† 3409 � 92 6856 � 241 3447 � 209 3478 � 80 7915 � 178 c 4437 � 213c

Bone mineral content (g) 114 � 4 203 � 6 89 � 7 110 � 3 222 � 7a 112 � 8a

Lean mass (g) 2866 � 67 3793 � 149 926 � 141 3176 � 55 4650 � 100 d 1474 � 111b

Fat mass (g) 758 � 70 2860 � 132 2102 � 114 631 � 48 3043 � 123 2412 � 129a

Abdominal fat (g) 50 � 4 175 � 10 125 � 9 33 � 3 183 � 12 150 � 13a

Body fat fraction (%) 20.6 � 1.6 41.5 � 0.8 20.9 � 1.4 16.4 � 1.1 39.2 � 1.4 22.8 � 1.7D Lean mass/D Fat mass 0.45 � 0.08 0.65 � 0.06a

Glucose (mg/dL) 80 � 3 89 � 1b

Insulin (mU/mL) 6.3 � 1.4 5.3 � 0.8IGF-I (ng/mL) 55 � 5 71 � 6a

HMW Adipo (mg/L) 25 � 2 23 � 3Leptin (ng/mL) 1.7 � 0.2 2.0 � 0.3

*Except for length, which was measured at birth.†Estimated from the sum of BMC + lean mass + fat mass.aP # .05,bP < .01,cP # .001,dP # .0001 for comparisons between girls and boys.

THE JOURNAL OF PEDIATRICS � www.jpeds.com Vol. 156, No. 1

without sedation, before a next feeding. All scans were pro-cessed by the same operator. Total body fat, lean mass, andbone mineral content were assessed.5

Statistical analyses were performed with SPSS 12.0 (SPSSInc., Chicago, Illinois). Results from AGA and SGA infantswere compared by 2-sided unpaired t test. Changes over 4months in AGA versus SGA infants were tested by generallinear models for repeated measures. Skewed data were log-transformed before comparison. P < .05 was consideredstatistically significant.

Results

Results of AGA and SGA infants are shown by sex in Tables Iand II, respectively. Table III compares AGA with SGA

Table II. Auxological, body composition, and endocrine indi

Girlsn = 14

At 2 wk* At 4 mo 4-m

Length (cm) 46.6 � 0.7 59.2 � 0.4 12Weight (g)† 2281 � 107 6063 � 142 318Bone mineral content (g) 81 � 4 170 � 6 9Lean mass (g) 2355 � 51 3659 � 128 130Fat mass (g) 446 � 57 2234 � 82 178Abdominal fat (g) 28 � 5 144 � 9 11Body fat fraction (%) 15.4 � 1.4 38.5 � 2.0 20D Lean mass/D Fat mass 0.7Glucose (mg/dL) 86 � 2Insulin (mU/mL) 7.0 � 1.8IGF-I (ng/mL) 61 � 8HMW adipo (mg/L) 25 � 3Leptin (ng/mL) 3.1 � 0.6

*Except for length, which was measured at birth.†Estimated from the sum of BMC + lean mass + fat mass.aP # .05,bP < .01 for comparisons between girls and boys.

146

infants, with the results of both sexes pooled. In early infancy,SGA infants gained more lean mass and less fat mass thanAGA infants, thereby becoming (more) hypo-adipose.Nevertheless, leptin levels were nearly 2-fold higher in4-month-old SGA infants than in AGA infants (P < .001).Prefeeding levels of circulating glucose, insulin, IGF-I, andHMW adiponectin were similar in AGA and SGA infants.No differences in potentially confounding factors, such asmaternal smoking or parity, were observed among groups.

Discussion

The elevated levels of circulating leptin in our SGA infants fitwell with the absolute values that were previously reported in3- and 6-month-old SGA infants but that were difficult to

ces in SGA infants at age 2 weeks and 4 months

Boysn = 14

o change At 2 wk* At 4 mo 4-mo change

.6 � 0.5 48.3 � 0.7 62.0 � 0.5b 13.8 � 0.91 � 150 3107 � 140 7037 � 249b 3930 � 221a

0 � 7 88 � 5 178 � 8 95 � 84 � 132 2621 � 107 4291 � 123b 1671 � 152a

8 � 88 474 � 88 2483 � 138 2009 � 1646 � 10 28 � 4 150 � 12 122 � 12.9 � 1.4 13.7 � 1.4 36.1 � 1.1 22.8 � 1.77 � 0.12 0.91 � 0.11

87 � 24.8 � 1.168 � 733 � 53.6 � 0.5

Ibanez et al

Table III. Auxological, body composition, and endocrine indices in AGA and SGA infants at age 2 weeks and 4 months

AGAn = 46 (23 girls and 23 boys)

SGA28 (14 girls and 14 boys)

At 2 wk* At 4 mo 4-mo change At 2 wk* At 4 mo 4-mo change

Length (cm) 50.5 � 0.3 63.0 � 0.6 12.5 � 0.7 47.5 � 0.5 60.6 � 0.4b 13.2 � 0.5Weight (g)† 3444 � 60 7385 � 168 3942 � 165 3032 � 99 6508 � 155b 3476 � 153Bone mineral content (g) 112 � 2 212 � 5 100 � 5 85 � 3 174 � 5c 90 � 5Lean mass (g) 3021 � 49 4222 � 109 1201 � 98 2488 � 63 3975 � 106 1487 � 104a

Fat mass (g) 695 � 43 2952 � 90 2257 � 88 460 � 52 2358 � 82 c 1899 � 94b

Abdominal fat (g) 41 � 3 179 � 8 138 � 8 28 � 3 147 � 7 119 � 8Body fat fraction (%) 18.5 � 1.0 40.4 � 0.8 20.9 � 1.4 14.6 � 1.0 37.3 � 1.2a 22.8 � 1.7D Lean mass/D Fat mass 0.55 � 0.05 0.84 � 0.08b

Glucose (mg/dL) 85 � 2 86 � 1Insulin (mU/mL) 5.8 � 0.8 5.9 � 1.1IGF-I (ng/mL) 63 � 4 65 � 5HMW adipo (mg/L) 24 � 2 29 � 3Leptin (ng/mL) 1.8 � 0.2 3.4 � 0.4 c

*Except for length, which was measured at birth.†Estimated from the sum of BMC + lean mass + fat mass.aP # .05,bP # .01,cP # .001 for comparisons between AGA and SGA infants.

January 2010 CLINICAL AND LABORATORY OBSERVATIONS

interpret because of the absence of AGA controls in this agerange and because of the absence of data on nutrition and onbody composition.6

The mechanisms underpinning the hyperleptinemia ofSGA infants remain to be elucidated. Several factors shouldbe considered. Leptin may be released more abundantlyinto the circulation and/or be cleared less rapidly from thecirculation in SGA infants than in AGA infants. Breast-fedinfants store fat at a rate of about 12 g/d, and they distributeit in a peripheral fashion, as more than 90% is stored subcu-taneously.7 The expansion of adipose tissue in early infancy isnot only driven by increasing adipocyte size but also by aug-menting adipocyte number; both these increments remainto be further delineated.8 HMW adiponectin is abundantlypresent in the circulation of breast-fed infants, and it ispossible that such physiological hyperadiponectinemiainfluences the link between leptinemia and body adiposity.

Evidence in rats indicates that a transient rise of leptinemiain early life can permanently alter the set-points that controlweight gain, caloric intake, fat mass, and their endocrine cor-relates.9 It remains to be studied to what extent the transienthyperleptinemia of SGA infants contributes to their long-term weight control4,10 and to their tendency to accumulategreater visceral adiposity and be hyperinsulinemic and hypo-adiponectinemic during the first years of childhood.11-14

n

L.I. and M.D. are Clinical Investigators of CIBERDEM (CB07/08/0044, Fondo de Investigacion Sanitaria, Instituto de Salud CarlosIII, Madrid, Spain). A.L.B. is an Investigator of the Fund for ScientificResearch ‘‘I3’’ (Ministry of Education and Science, Spain). F.d.Z. isa Clinical Investigator of the Fund for Scientific Research (Flanders,Belgium).

Submitted for publication Apr 2, 2009; last revision received May 7, 2009;

accepted Jun 24, 2009.

Reprint requests: Dr Lourdes Ibanez, Endocrinology Unit, Hospital Sant Joan

de Deu, University of Barcelona, Passeig de Sant Joan de Deu, 2, 08950

Esplugues, Barcelona, Spain. E-mail: libanez@hsjdbcn.org.

Low Body Adiposity and High Leptinemia in Breast-fed Infants B

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