Peter R. Baker

Alterations in human milk leptin and insulin are associated with early changes in the infant intestinal microbiome

BACKGROUND Increased maternal body mass index (BMI) is a robust risk factor for later pediatric obesity. Accumulating evidence suggests that human milk (HM) may attenuate the transfer of obesity from mother to offspring, potentially through its effects on early development of the infant microbiome. OBJECTIVES Our objective was to identify early differences in intestinal microbiota in a cohort of breastfeeding infants born to obese compared with normal-weight (NW) mothers. We also investigated relations between HM hormones (leptin and insulin) and both the taxonomic and functional potentials of the infant microbiome. DESIGN Clinical data and infant stool and fasting HM samples were collected from 18 NW [prepregnancy BMI (in kg/m(2)) <24.0] and 12 obese (prepregnancy BMI >30.0) mothers and their exclusively breastfed infants at 2 wk postpartum. Infant body composition at 2 wk was determined by air-displacement plethysmography. Infant gastrointestinal microbes were estimated by using 16S amplicon and whole-genome sequencing. HM insulin and leptin were determined by ELISA; short-chain fatty acids (SCFAs) were measured in stool samples by using gas chromatography. Power was set at 80%. RESULTS Infants born to obese mothers were exposed to 2-fold higher HM insulin and leptin concentrations (P < 0.01) and showed a significant reduction in the early pioneering bacteria Gammaproteobacteria (P = 0.03) and exhibited a trend for elevated total SCFA content (P < 0.06). Independent of maternal prepregnancy BMI, HM insulin was positively associated with both microbial taxonomic diversity (P = 0.03) and Gammaproteobacteria (e.g., Enterobacteriaceae; P = 0.04) and was negatively associated with Lactobacillales (e.g., Streptococcaceae; P = 0.05). Metagenomic analysis showed that HM leptin and insulin were associated with decreased bacterial proteases, which are implicated in intestinal permeability, and reduced concentrations of pyruvate kinase, a biomarker of pediatric gastrointestinal inflammation. CONCLUSION Our results indicate that, although maternal obesity may adversely affect the early infant intestinal microbiome, HM insulin and leptin are independently associated with beneficial microbial metabolic pathways predicted to increase intestinal barrier function and reduce intestinal inflammation. This trial was registered at clinicaltrials.gov as NCT01693406.

Mesenchymal Stem Cells From Infants Born to Obese Mothers Exhibit Greater Potential for Adipogenesis: The Healthy Start BabyBUMP Project

Maternal obesity increases the risk for pediatric obesity; however, the molecular mechanisms in human infants remain poorly understood. We hypothesized that mesenchymal stem cells (MSCs) from infants born to obese mothers would demonstrate greater potential for adipogenesis and less potential for myogenesis, driven by differences in β-catenin, a regulator of MSC commitment. MSCs were cultured from the umbilical cords of infants born to normal-weight (prepregnancy [pp] BMI 21.1 ± 0.3 kg/m2; n = 15; NW-MSCs) and obese mothers (ppBMI 34.6 ± 1.0 kg/m2; n = 14; Ob-MSCs). Upon differentiation, Ob-MSCs exhibit evidence of greater adipogenesis (+30% Oil Red O stain [ORO], +50% peroxisome proliferator–activated receptor (PPAR)-γ protein; P < 0.05) compared with NW-MSCs. In undifferentiated cells, total β-catenin protein content was 10% lower and phosphorylated Thr41Ser45/total β-catenin was 25% higher (P < 0.05) in Ob-MSCs versus NW-MSCs (P < 0.05). Coupled with 25% lower inhibitory phosphorylation of GSK-3β in Ob-MSCs (P < 0.05), these data suggest greater β-catenin degradation in Ob-MSCs. Lithium chloride inhibition of GSK-3β increased nuclear β-catenin content and normalized nuclear PPAR-γ in Ob-MSCs. Last, ORO in adipogenic differentiating cells was positively correlated with the percent fat mass in infants (r = 0.475; P < 0.05). These results suggest that altered GSK-3β/β-catenin signaling in MSCs of infants exposed to maternal obesity may have important consequences for MSC lineage commitment, fetal fat accrual, and offspring obesity risk.

Haplotype Analysis Discriminates Genetic Risk for DR3-Associated Endocrine Autoimmunity and Helps Define Extreme Risk for Addison’s Disease

CONTEXT Multiple autoimmune disorders (e.g. Addisons disease, type 1 diabetes, celiac disease) are associated with HLA-DR3, but it is likely that alleles of additional genes in linkage disequilibrium with HLA-DRB1 contribute to disease. OBJECTIVE The objective of the study was to characterize major histocompatability complex (MHC) haplotypes conferring extreme risk for autoimmune Addisons disease (AD). DESIGN, SETTING, AND PARTICIPANTS Eighty-six 21-hydroxylase autoantibody-positive, nonautoimmune polyendocrine syndrome type 1, Caucasian individuals collected from 1992 to 2009 with clinical AD from 68 families (12 multiplex and 56 simplex) were genotyped for HLA-DRB1, HLA-DQB1, MICA, HLA-B, and HLA-A as well as high density MHC single-nucleotide polymorphism (SNP) analysis for 34. MAIN OUTCOME MEASURES AD and genotype were measured. RESULT Ninety-seven percent of the multiplex individuals had both HLA-DR3 and HLA-B8 vs. 60% of simplex AD patients (P = 9.72 × 10(-4)) and 13% of general population controls (P = 3.00 × 10(-19)). The genotype DR3/DR4 with B8 was present in 85% of AD multiplex patients, 24% of simplex patients, and 1.5% of control individuals (P = 4.92 × 10(-191)). The DR3-B8 haplotype of AD patients had HLA-A1 less often (47%) than controls (81%, P = 7.00 × 10(-5)) and type 1 diabetes patients (73%, P = 1.93 × 10(-3)). Analysis of 1228 SNPs across the MHC for individuals with AD revealed a shorter conserved haplotype (3.8) with the loss of the extended conserved 3.8.1 haplotype approximately halfway between HLA-B and HLA-A. CONCLUSION Extreme risk for AD, especially in multiplex families, is associated with haplotypic DR3 variants, in particular a portion (3.8) but not all of the conserved 3.8.1 haplotype.

Predicting the onset of Addison’s disease: ACTH, renin, cortisol and 21‐hydroxylase autoantibodies

Context  Autoantibodies to 21‐hydroxylase (21OH‐AA) precede onset of autoimmune Addison’s disease (AD). Progression to AD can take months to years, and early detection of metabolic decompensation may prevent morbidity and mortality.

Metabolomic analysis reveals altered skeletal muscle amino acid and fatty acid handling in obese humans

Investigate the effects of obesity and high‐fat diet (HFD) exposure on fatty acid oxidation and TCA cycle intermediates and amino acids in skeletal muscle to better characterize energy metabolism.

The HLA-B*3906 allele imparts a high risk of diabetes only on specific HLA-DR/DQ haplotypes

Aims/hypothesisWe investigated the risk associated with HLA-B*39 alleles in the context of specific HLA-DR/DQ haplotypes.MethodsWe studied a readily available dataset from the Type 1 Diabetes Genetics Consortium that consists of 2,300 affected sibling pair families genotyped for both HLA alleles and 2,837 single nucleotide polymorphisms across the major histocompatibility complex region.ResultsThe B*3906 allele significantly enhanced the risk of type 1 diabetes when present on specific HLA-DR/DQ haplotypes (DRB1*0801-DQB1*0402: p = 1.6 × 10−6, OR 25.4; DRB1*0101-DQB1*0501: p = 4.9 × 10−5, OR 10.3) but did not enhance the risk of DRB1*0401-DQB1*0302 haplotypes. In addition, the B*3901 allele enhanced risk on the DRB1*1601-DQB1*0502 haplotype (p = 3.7 × 10−3, OR 7.2).Conclusions/interpretationThese associations indicate that the B*39 alleles significantly increase risk when present on specific HLA-DR/DQ haplotypes, and HLA-B typing in concert with specific HLA-DR/DQ genotypes should facilitate genetic prediction of type 1 diabetes, particularly in a research setting.

The past, present, and future of genetic associations in type 1 diabetes.

Type 1 diabetes mellitus (T1DM) is an autoimmune disease affecting approximately one in 300 individuals in the United States. The majority of genetic research to date has focused on the heritability that predisposes to islet autoimmunity and T1DM. The evidence so far points to T1DM being a polygenic, common, complex disease with major susceptibility lying in the major histocompatibility complex (MHC) on chromosome 6 with other smaller effects seen in loci outside of the MHC. With recent advances in technology, novel means of exploring the human genome have given way to new information in the development of T1DM. The newest technologies, namely high-throughput polymorphism typing and sequencing, have led to a paradigm shift in studying common diseases such as T1DM. In this review we highlight the advances in genetic associations in T1DM in the last several decades and how they have led to a better understanding of T1DM pathogenesis.

Dominant Suppression of Addison's Disease Associated with HLA-B15

CONTEXT Autoimmune Addisons disease (AD) is the major cause of primary adrenal failure in developed nations. Autoantibodies to 21-hydroxylase (21OH-AA) are associated with increased risk of progression to AD. Highest genetic risk is associated with the Major Histocompatibility region (MHC), specifically human leukocyte antigen (HLA)-DR3 haplotypes (containing HLA-B8) and HLA-DR4. OBJECTIVE The objective of the study was the further characterization of AD risk associated with MHC alleles. DESIGN, SETTING, AND PARTICIPANTS MHC genotypes were determined for HLA-DRB1, DQA1, DQB1, MICA, HLA-B, and HLA-A in 168 total individuals with 21OH-AA (85 with AD at referral and 83 with positive 21OH-AA but without AD at referral). MAIN OUTCOME MEASURE(S) Genotype was evaluated in 21OH-AA-positive individuals. Outcomes were compared with general population controls and type 1 diabetes patients. RESULTS In HLA-DR4+ individuals, HLA-B15 was found in only one of 55 (2%) with AD vs. 24 of 63 (40%) 21OH-AA-positive nonprogressors (P = 2 × 10(-7)) and 518 of 1558 (33%) HLA-DR4 patients with type 1 diabetes (P = 1 × 10(-8)). On prospective follow-up, none of the HLA-B15-positive, 21-hydroxylase-positive individuals progressed to AD vs. 25% non-HLA-B15 autoantibody-positive individuals by life table analysis (P = 0.03). Single nucleotide polymorphism analysis revealed the HLA-DR/DQ region associated with risk and HLA-B15 were separated by multiple intervening single-nucleotide polymorphism haplotypes. CONCLUSIONS HLA-B15 is not associated with protection from 21OH-AA formation but is associated with protection from progression to AD in 21OH-AA-positive individuals. To our knowledge, this is one of the most dramatic examples of genetic disease suppression in individuals who already have developed autoantibodies and of novel dominant suppression of an autoimmune disease by a class I HLA allele.

Novel Association Between Immune-Mediated Susceptibility Loci and Persistent Autoantibody Positivity in Type 1 Diabetes.

Islet autoantibodies detected at disease onset in patients with type 1 diabetes are signs of an autoimmune destruction of the insulin-producing β-cells. To further investigate the genetic determinants of autoantibody positivity, we performed dense immune-focused genotyping on the Immunochip array and tested for association with seven disease-specific autoantibodies in a large cross-sectional cohort of 6,160 type 1 diabetes–affected siblings. The genetic association with positivity for GAD autoantibodies (GADAs), IA2 antigen (IA-2A), zinc transporter 8, thyroid peroxidase, gastric parietal cells (PCAs), tissue transglutaminase, and 21-hydroxylase was tested using a linear mixed-model regression approach to simultaneously control for population structure and family relatedness. Four loci were associated with autoantibody positivity at genome-wide significance. Positivity for GADA was associated with 3q28/LPP, for IA-2A with 1q23/FCRL3 and 11q13/RELA, and for PCAs with 2q24/IFIH1. The 3q28 locus showed association after only 3 years duration and might therefore be a marker of persistent GADA positivity. The 1q23, 11q13, and 2q24 loci were associated with autoantibodies close to diabetes onset and constitute candidates for early screening. Major susceptibility loci for islet autoantibodies are separate from type 1 diabetes risk, which may have consequences for intervention strategies to reduce autoimmunity.

Male with mosaicism for supernumerary ring X chromosome: Analysis of phenotype and characterization of genotype using array comparative genome hybridization

Supernumerary, derivative, and ring X chromosomes are relatively common in Turner syndrome females but have been reported rarely in males. To date, less than 10 cases have been published, of which only 2 have been partially characterized in defining the breakpoints and genetic content of the derivative X chromosome. We describe a male with mosaicism for a supernumerary X chromosome (46,XY/47,XY, r(X)) who has multiple congenital anomalies, including features of craniofrontonasal dysplasia (Mendelian Inheritance in Man 304110) and the presence of ectopic female reproductive organs. Using comparative genomic hybridization array mapping, we determined that the derivative X is composed of a 24-Mb fragment that contains the regions Xp11.3 through Xq13.1 and lacks the XIST gene. This is the first report to describe a detailed molecular characterization of a ring X chromosome in a male by comparative genomic hybridization array analysis. We compare the clinical and molecular findings in this patient to other 46,XY, r(X) patients reported in the literature and discuss the potential role of disomy for known genes contained on the ring X chromosome.