Effect of maternal weight, adipokines, glucose intolerance and lipids on infant birth weight among women without gestational diabetes mellitus

Background:

The delivery of excess maternal nutrients to the fetus is known to increase the risk of macrosomia, even among infants of women without gestational diabetes mellitus. With the current obesity epidemic, maternal adiposity and its associated effects on circulating adipokines and inflammatory proteins may now have a greater impact on fetal growth. We sought to evaluate the independent effects of maternal glycemia, lipids, obesity, adipokines and inflammation on infant birth weight.

Methods:

We included 472 women who underwent an oral glucose tolerance test in late pregnancy and were found not to have gestational diabetes; 104 (22.0%) had gestational impaired glucose tolerance. We also measured fasting levels of insulin, low-and high-density lipoprotein cholesterol, triglycerides, leptin, adiponectin and C-reactive protein. Obstetric outcomes were assessed at delivery.

Results:

The mean birth weight was 3481 g (standard deviation 493 g); 68 of the infants were large for gestational age. On multiple linear regression analysis, positive determinants of birth weight were length of gestation, male infant, weight gain during pregnancy up to the time of the oral glucose tolerance test, body mass index (BMI) before pregnancy and impaired glucose tolerance in pregnancy. Leptin, adiponectin and C-reactive protein levels were each negatively associated with birth weight. On logistic regression analysis, the significant metabolic predictors of having a large-for-gestational-age infant were BMI before pregnancy (odds ratio [OR] 1.16, 95% confidence interval [CI] 1.05–1.27, per 1 kg/m² increase), weight gain during pregnancy up to the time of the oral glucose tolerance test (OR 1.12, 95% CI 1.05–1.19, per 1 kg increase) and leptin level (OR 0.50, 95% CI 0.30–0.82, per 1 standard deviation change).

Interpretation:

Among women without gestational diabetes, maternal adiposity and leptin levels were the strongest metabolic determinants of having a large-for-gestational-age infant rather than glucose intolerance and lipid levels.In 1952, Jørgen Pedersen proposed that delivery of excess maternal glucose to the fetus may be responsible for the increased risk of macrosomia among infants of women with diabetes during pregnancy.¹ He postulated that maternal hyperglycemia leads to fetal hyperglycemia, which in turn stimulates insulin secretion in the fetus, the anabolic effects of which result in excessive fetal growth. Since its introduction, the Pedersen hypothesis has been further extended by other investigators and accepted as the pathophysiologic basis for increased risk of macrosomia among infants of women with diabetes during pregnancy.^2,3 Accordingly, for pregnant women with either pre-existing diabetes or gestational diabetes, modern clinical practice focuses on normalizing blood glucose levels to reduce the risk of fetal hyperglycemia and hence the risk of fetal macrosomia and its associated adverse clinical outcomes (e.g., shoulder dystocia, birth injury, need for cesarean delivery).It is now recognized that the association between maternal nutrients and fetal growth is not restricted solely to women with diabetes. Several studies have shown associations linking maternal blood glucose and triglyceride levels with infant birth weight among women without gestational diabetes.^4–7 This awareness has led to recent recommendations to lower the diagnostic thresholds for gestational diabetes on glucose tolerance testing in pregnancy, to optimize the detection of women who may be at risk of having a large-for-gestational-age infant.⁸Another important factor relevant to the risk of macrosomia is maternal adiposity.⁹ Indeed, the past decade has seen a marked increase in the prevalence of pre-existing obesity among pregnant women.¹⁰ In the context of the current obesity epidemic, we hypothesized that, in women without gestational diabetes, maternal adiposity and its associated effects on circulating levels of adipokines (e.g., adiponectin and leptin) and inflammatory proteins (C-reactive protein) may now have a greater impact than glucose and lipid levels on fetal growth. We conducted this study to evaluate the independent effects of maternal glycemia, lipid levels, obesity, adipokine levels and inflammation on the infant birth weight in a cohort of women without gestational diabetes.     

Effect of intensive catchment and in-lake restoration procedures on phosphorus concentrations in a eutrophic lake

Lake Okaro is a small, warm monomictic lake in central North Island, New Zealand, which progressed from oligotrophic to eutrophic through the 1960s. Trends in phosphorus (P) concentrations in the lake are linked to multiple restoration efforts over a 5-year period (2003–2008). The restoration procedures include a 2.3 ha constructed wetland established in February 2006 and riparian margin protection to reduce external loading, as well as an Alum application in December 2003 and sediment capping using modified zeolite in September 2008 to reduce internal loading. The annual average total phosphorus (TP) concentration in the lake decreased by 41% from 2004–2005 to 2007–2008. Two predictive models based on external P loading data generally underestimated the measured TP concentrations in the water column due to internal P loading. The relatively rapid response of TP concentrations after reduction of the internal loading using modified zeolite suggests that this technique can effect a rapid decrease in lake water TP concentrations though the trophic state of Lake Okaro showed high resilience to the reduced P loading. It is concluded that the combined effect of all restoration procedures resulted in a relatively rapid decrease in TP concentrations in Lake Okaro, which may be prolonged by continued external load reduction.     

Ni(II) and Ni(I) forms of pentaalkylamide derivatives of cofactor F430 of Methanobacterium thermoautotrophicum.

A series of pentaalkylamide forms of F430 and of its 12,13-diepimer have been generated and characterized. Carbodiimide-assisted N-hydroxysulfosuccinimide activation of all five peripheral carboxylates of the F430 macrocycle allows nucleophilic attack by a number of primary amines (RNH2, R- = CH3-, CH3CH2-, CF3CH2-, CH3(CH2)3-) generating the pentaalkylamide derivatives. The identity of each derivative has been verified by fast-atom bombardment mass spectrometry (FAB-MS). The solubility of these derivatives in aprotic organic solvents varies as the amine alkyl substituent (R-) is changed. Electrochemical measurements have shown that the Ni(II/I) reduction potentials in N,N-dimethylformamide (DMF) are approximately -1 V (Ag/AgCl). Reduction by sodium amalgam in THF generates the Ni(I) form of the F430 diepimer pentabutylamide. The visible and EPR spectra of this Ni(I) species are very similar to the corresponding spectra of Ni(I) F430M (Jaun, B. and Pfaltz, A. (1986) J. Chem. Soc. Chem. Commun. 1327-1329.).     

Thymineless death is inhibited by CsrA in Escherichia coli lacking the SOS response

Thymineless death (TLD) is the rapid loss of colony-forming ability in bacterial, yeast and human cells starved for thymine, and is the mechanism of action of common chemotherapeutic drugs. In Escherichia coli, significant loss of viability during TLD requires the SOS replication-stress/DNA-damage response, specifically its role in inducing the inhibitor of cell division, SulA. An independent RecQ- and RecJ-dependent TLD pathway accounts for a similarly large additional component of TLD, and a third SOS- and RecQ/J-independent TLD pathway has also been observed. Although two groups have implicated the SOS-response in TLD, an SOS-deficient mutant strain from an earlier study was found to be sensitive to thymine deprivation. We performed whole-genome resequencing on that SOS-deficient strain and find that, compared with the SOS-proficient control strain, it contains five mutations in addition to the SOS-blocking lexA(Ind⁻) mutation. One of the additional mutations, csrA, confers TLD sensitivity specifically in SOS-defective strains. We find that CsrA, a carbon storage regulator, reduces TLD in SOS- or SulA-defective cells, and that the increased TLD that occurs in csrA⁻ SOS-defective cells is dependent on RecQ. We consider a hypothesis in which the modulation of nucleotide pools by CsrA might inhibit TLD specifically in SOS-deficient (SulA-deficient) cells.     

Nascent high density lipoproteins from liver perfusates of orotic acid-fed rats

Uniformly fatty livers from orotic acid-fed rats secreted almost no very low density lipoproteins (VLDL) but normal amounts of nascent high density lipoproteins (HDL) accumulated in perfusates. When lecithin:cholesterol acyltransferase (LCAT) was inhibited, nascent HDL were uniformly discoidal and lacked cholesteryl esters. Lipid and apoprotein compositions of nascent HDL from normal and fatty livers were similar whether LCAT was inhibited or not. Apolipoprotein B-100 was not detected in perfusates of uniformly fatty livers, but small amounts of apolipoprotein B-48 were present in HDL2 fractions. Nascent lipoproteins were not seen in Golgi compartments, but lipid-rich particles were clearly evident in endoplasmic reticulum cisternae adjacent to the cis face of the Golgi complex, suggesting that orotic acid blocks VLDL secretion by preventing translocation of nascent particles from the endoplasmic reticulum to the cis Golgi compartment. The accumulation of normal amounts of discoidal HDL in liver perfusates despite virtual absence of triglyceride-rich lipoproteins in Golgi secretory compartments, the space of Disse, and the perfusate is inconsistent with the concept that nascent HDL are exclusively a product of surface remnants cast off during lipolysis of chylomicrons and VLDL.     

Regulation of IRAK-1 activation by its C-terminal domain

Macrophages are important mediators of the immune response to infection by virtue of their ability to secrete cytokines that trigger inflammation. Toll-like receptors (TLRs) are largely responsible for meditating the activation of macrophages by pathogens. IRAK-1 is a proximal protein kinase in TLR signalling pathways and hence its activation must be tightly regulated. However, the mechanisms which control the activation of IRAK-1 are poorly understood. IRAK-1 contains a death domain at its N-terminus that mediates its interaction with other death domain containing proteins, a central Ser/Thr kinase domain, and a C-terminal domain that contains binding motifs for TRAF6. We show here that deletion of the death domain or the majority of the C-terminal domain markedly enhanced the capacity of IRAK-1 to activate NF-κB in a TLR-independent manner in RAW 264.7 macrophages. Furthermore, the C-terminal truncation mutant spontaneously oligomerised and formed complexes with the negative regulator IRAK-M in the absence of TLR activation. In contrast to the binding of IRAK-M to IRAK-1, the death domain of IRAK-1 was not required for the interaction of IRAK-4 with IRAK-1. On the basis of these results we propose a model in which IRAK-1 is held in a closed, inactive conformation via an intramolecular mechanism involving its C-terminal domain and possibly the death domain. Phosphorylation of IRAK-1 by IRAK-4 in response to TLR activation may then release IRAK-1 from the inhibitory constraint exerted by its C-terminal domain.     

Sequence homology in the amino-terminal and active-site regions of thermolabile glyceraldehyde-3-phosphate dehydrogenase from a thermophile.

The unusual thermolability of glyceraldehyde-3-phosphate dehydrogenase from the facultative thermophile Bacillus coagulans KU (Crabb et al., Biochemistry 16:4840-4847, 1977) has provided the first opportunity to study a homologous enzyme from the same genus that exhibits a marked difference in thermostability. In pursuit of the structural bases for the thermostability of proteins, the sequences of the amino terminus (residues 1 through 27) and the active-site cysteine cyanogen bromide peptide (residues 130 through 167) of this enzyme have been determined and compared with sequences of the enzyme from other sources. The importance of comparing phylogenetically related proteins is evident from the 87% identity found between these sequences in the enzyme from B. coagulans and Bacillus stearothermophilus, versus only 45% identity for all other known sequences. The marked sequence identity of the enzyme from the two Bacillus species drew attention to the variable region (residues 138 through 140a) which is exposed to the exterior of the quaternary structure of this enzyme. Based on the reported crystallographic structures of the enzyme from lobster muscle and B. stearothermophilus and space-filling models of the variable region, the segment Asp-Pro-Lys-Ala in B. stearothermophilus should be more thermostable than the analogous sequence, Asp-Ala-Ala-Asn, from B. coagulans. In addition, the space-filling models suggested that the spatial relationship of an amino acid side chain and its potential for close packing and interactions with neighboring side chains may be more important than the type of amino acid substituted.