Relationship between maternal growth, infant birthweight and nutrient partitioning in teenage pregnancies

OBJECTIVE

Teenagers are susceptible to delivering small-for-gestational-age (SGA) infants. Previous studies suggest that maternal growth may contribute, as a result of preferential nutrient partitioning to the mother. We investigated the impact of maternal growth on birthweight in pregnant teenagers in the UK, and examined endocrine mediators of nutrient partitioning.

DESIGN

A prospective observational multicentre study, About Teenage Eating, conducted between 2004 and 2007.

SETTING

Four hospitals in socially-deprived areas of Manchester and London.

POPULATION

A total of 500 pregnant adolescents (14-18 years of age) with a singleton pregnancy were recruited at 10-21 weeks of gestation, with follow-up studies on 368 subjects. A cohort of 80 pregnant adults (25-40 years of age) provided a control group for determining growth.

METHODS

Skeletal growth, weight gain and skinfold thickness were measured from first to third trimester, together with maternal levels of micronutrients and metabolic hormones: insulin-like growth factor (IGF) system and leptin. Dietary analyses were performed.

MAIN OUTCOME MEASURE

SGA birth.

RESULTS

Maternal growth was not associated with SGA birth: growing mothers delivered more large-for-gestational-age infants (OR 2.51; P < 0.05). Growers had greater weight gain (P < 0.001), fat accrual (P < 0.001) and red cell folate concentrations (P < 0.01) than non-growers. Maternal IGF-I (P < 0.01) and leptin (P < 0.001) were positively associated with maternal and fetal growth, whereas IGF-I (P < 0.001) was negatively associated. Teenagers that were underweight at booking or with low weight gain were at greater risk of SGA birth.

CONCLUSIONS

Maternal growth was not detrimental to fetal growth in this UK population of teenagers. Greater weight gain and higher concentrations of IGF-I in growing teenagers may provide anabolic drive for maternal and fetal growth.

Mice lacking pro-opiomelanocortin are sensitive to high-fat feeding but respond normally to the acute anorectic effects of peptide-YY(3-36)

Inactivating mutations of the pro-opiomelanocortin (POMC) gene in both mice and humans leads to hyperphagia and obesity. To further examine the mechanisms whereby POMC-deficiency leads to disordered energy homeostasis, we have generated mice lacking all POMC-derived peptides. Consistent with a previously reported model, Pomc(-/-) mice were obese and hyperphagic. They also showed reduced resting oxygen consumption associated with lowered serum levels of thyroxine. Hypothalami from Pomc(-/-) mice showed markedly increased expression of melanin-concentrating hormone mRNA in the lateral hypothalamus, but expression of neuropeptide Y mRNA in the arcuate nucleus was not altered. Provision of a 45% fat diet increased energy intake and body weight in both Pomc(-/-) and Pomc(+/-) mice. The effects of leptin on food intake and body weight were blunted in obese Pomc(-/-) mice whereas nonobese Pomc(-/-) mice were sensitive to leptin. Surprisingly, we found that Pomc(-/-) mice maintained their acute anorectic response to peptide-YY(3-36) (PYY(3-36)). However, 7 days of PYY(3-36) administration had no effect on cumulative food intake or body weight in wild-type or Pomc(-/-) mice. Thus, POMC peptides seem to be necessary for the normal response of energy balance to high-fat feeding, but not for the acute anorectic effect of PYY(3-36) or full effects of leptin on feeding. The finding that the loss of only one copy of the Pomc gene is sufficient to render mice susceptible to the effects of high fat feeding emphasizes the potential importance of this locus as a site for gene-environment interactions predisposing to obesity.

Agouti-related protein (83-132) is a competitive antagonist at the human melanocortin-4 receptor: no evidence for differential interactions with pro-opiomelanocortin-derived ligands

Interactions between pro-opiomelanocortin (POMC)-derived peptides, agouti-related protein (AGRP) and the melanocortin-4 receptor (MC4-R) are central to energy homeostasis. In this study we have undertaken comprehensive pharmacological analysis of these interactions using a CHOK1 cell line stably transfected with human MC4-R. Our main objectives were (1) to compare the relative affinities and potencies of POMC-derived peptides endogenously secreted within the hypothalamus, (2) to investigate the potency of AGRP(83-132) antagonism with respect to each POMC-derived peptide and (3) to determine whether AGRP(83-132) and POMC-derived peptides act allosterically or orthosterically. We have found that beta melanocyte-stimulating hormone (betaMSH), desacetyl alpha MSH (da-alphaMSH) and adrenocorticotrophic hormone all have very similar affinities and potencies at the MC4-R compared with the presumed natural ligand, alphaMSH. Moreover, even MSH precursors, such as beta lipotrophic hormone, showed significant binding and functional activity. Therefore, many POMC-derived peptides could have important roles in appetite regulation and it seems unlikely that alphaMSH is the sole physiological ligand. We have shown that AGRP(83-132) acts as a competitive antagonist. There was no significant difference in the potency of inhibition by AGRP(83-132) or agouti(87-132) at the MC4-R, regardless of which POMC peptide was used as an agonist. Furthermore, we have found that AGRP(83-132) has no effect on the dissociation kinetics of radiolabelled Nle4,D-Phe7 MSH from the MC4-R, indicating an absence of allosteric effects. This provides strong pharmacological evidence that AGRP(83-132) acts orthosterically at the MC4-R to inhibit Gs-coupled accumulation of intracellular cAMP.

Structure of a multifunctional protein. Mammalian phosphatidylinositol transfer protein complexed with phosphatidylcholine

Eukaryotic phosphatidylinositol transfer protein is a ubiquitous multifunctional protein that transports phospholipids between membrane surfaces and participates in cellular phospholipid metabolism during signal transduction and vesicular trafficking. The three-dimensional structure of the alpha-isoform of rat phosphatidylinositol transfer protein complexed with one molecule of phosphatidylcholine, one of its physiological ligands, has been determined to 2.2 A resolution by x-ray diffraction techniques. A single beta-sheet and several long alpha-helices define an enclosed internal cavity in which a single molecule of the phospholipid is accommodated with its polar head group in the center of the protein and fatty acyl chains projected toward the surface. Other structural features suggest mechanisms by which cytosolic phosphatidylinositol transfer protein interacts with membranes for lipid exchange and associates with a variety of lipid and protein kinases.

Purification, crystallization and x-ray analysis of crystals of pectate lyase A from Exwinia chrysanthemi

Pectate lyase A is secreted by Erwinia chrysanthemi and is a virulence factor for soft rot diseases in plants. Crystals of pectate lyase A were obtained by vapor-diffusion techniques in the presence of polyethylene glycol. The crystals belong to the monoclinic space group P2(1), with unit-cell parameters a = 48.96, b = 148.86, c = 78.61 A, beta = 97.32 degrees. The crystals contain two protein molecules of 38 kDa per asymmetric unit and diffract to 2.4 A using Cu Kalpha radiation.

Do immunoassays differentially detect different acidity glycoforms of FSH?

OBJECTIVE

The possibility of the carbohydrate residues of glycoproteins affecting their recognition in immunoassays is an important and unresolved issue. This study looked for evidence of differential recognition of FSH glycoform preparations, of variable isoelectric point (pI) and known molarity, using three routine assays employing different antibody configurations.

DESIGN

Seven glycoform preparations with differing pI bands (between 3.8 and 5.5) were produced by isoelectric focusing of recombinant human FSH and the molecular weights determined by mass spectroscopy. Three concentrations of each glycoform were assayed and the results expressed relative to unfractionated material. From the relative responses, recognition differences between the assay methods and between the glycoform preparations were investigated.

MEASUREMENTS

Three routine assays were employed: the commercially available Amerlite(R) enzyme immunoassay and Delfia(R) immunofluorometric assay, together with an in-house competitive two-site radioimmunoassay (RIA).

RESULTS

Overall, the three assays gave the same relative responses for equivalent glycoforms, with the only exceptions involving small differences between some assay pairs for the fractions at the extremes of the pI range investigated. Within each assay type, differences (P < 0.05) of up to 33% existed between glycoforms of different pI, however, these differences showed no patterns or trends across the entire acidity range examined.

CONCLUSIONS

Between the assay methods investigated in this study, few differences exist in the recognition of individual pI bands of FSH when expressed relative to a common unfractionated standard. Differences were apparent in the recognition of the different acidity glycoforms within each assay method, however, these were small and unlikely to be of clinical significance.

X-ray analysis of crystals of rat phosphatidylinositol-transfer protein with bound phosphatidylcholine

Phosphatidylinositol-transfer protein (PITP) is a soluble, ubiquitously expressed, highly conserved protein encoded by two genes in humans, rodents and other mammals. A cDNA encoding the alpha isoform of the rat gene was expressed to high levels in Escherichia coli, the protein purified and the homogeneous protein used for crystallization studies. Crystals of rat PITP-alpha were obtained by vapor-diffusion techniques using the sitting-drop method. Crystals grow within two weeks by vapor-diffusion techniques in the presence of polyethylene glycol 4000. Both crystal forms pack in the monoclinic space group P21. Crystal form I has unit-cell parameters a = 44.75, b = 74.25, c = 48.32 A and beta = 114.14 degrees. Unit-cell parameters for crystal form II are a = 47.86, b = 73.59, c = 80.49 A and beta = 98.54 degrees. Crystal form I has a Vm of 2.295 A3 Da-1 and an estimated solvent content of 46.4% with one molecule per asymmetric unit, while crystal form II has a Vm of 2.196 A3 Da-1 and an estimated solvent content of 44.0%, assuming two molecules per asymmetric unit.

Multiple Genotypes in Individuals of Claytonia virginica

Supernumerary chromosomes are common among plants of Claytonia virginica found in a weedy population near the southwestern edge of its distribution. Roots, stems, and microsporocytes vary in chromosome number within the same plant in 68 percent of the population studied.