Association between angiopoietin-like 6 (ANGPTL6) gene polymorphisms and metabolic syndrome-related phenotypes in the French MONICA Study

AIM: Although the ANGPTL6 (angiopoietin-like 6) gene product is now known to be involved in the regulation of fat mass and insulin sensitivity in mice, its physiological functions in humans have yet to be determined. METHODS: Subjects from the population-based French MONICA Study (n=3402) were genotyped for single nucleotide polymorphisms (SNPs) in ANGPTL6, and associations with anthropometric or biochemical phenotypes were looked for. RESULTS: On evaluating the frequency of 17 ANGPTL6 SNPs in 100 randomly selected subjects on the basis of linkage disequilibrium mapping, four SNPs (rs6511435, rs8112063, rs11671983 and rs15723) were found to cover more than 95% of the known ANGPTL6 genetic variability. Subjects from the entire MONICA Study were then genotyped for these four SNPs. No significant association was detected for rs11671983 and rs15723. In contrast, the G allele of rs8112063 was associated with lower plasma glucose levels (P=0.009). Also, obese subjects carrying the G allele of rs6511435 had higher plasma insulin levels than AA subjects (P=0.0055). Moreover, the G allele of rs6511435 tended to be associated with a 20% higher risk of the metabolic syndrome (P=0.034). However, when false discovery rate testing (40 tests) was applied, these associations were no longer statistically significant. CONCLUSION: These findings constitute the first study in humans of ANGPTL6 genetic variability. Although there was no evidence that polymorphisms in ANGPTL6 might be significantly associated with the metabolic syndrome-related phenotypes, a weak association of these polymorphisms with these parameters cannot be excluded. Further association studies are needed to arrive at any definite conclusions

Beneficial effect of a high number of copies of salivary amylase AMY1 gene on obesity risk in Mexican children

Aims/hypothesis: Childhood obesity is a major public health problem in Mexico, affecting one in every three children. Genome-wide association studies identified genetic variants associated with childhood obesity, but a large missing heritability remains to be elucidated. We have recently shown a strong association between a highly polymorphic copy number variant encompassing the salivary amylase gene (AMY1 also known as AMY1A) and obesity in European and Asian adults. In the present study, we aimed to evaluate the association between AMY1 copy number and obesity in Mexican children.Methods: We evaluated the number of AMY1 copies in 597 Mexican children (293 obese children and 304 normal weight controls) through highly sensitive digital PCR. The effect of AMY1 copy number on obesity status was assessed using a logistic regression model adjusted for age and sex.Results: We identified a marked effect of AMY1 copy number on reduced risk of obesity (OR per estimated copy 0.84, with the number of copies ranging from one to 16 in this population; p = 4.25 × 10−6). The global association between AMY1 copy number and reduced risk of obesity seemed to be mostly driven by the contribution of the highest AMY1 copy number. Strikingly, all children with >10 AMY1 copies were normal weight controls.Conclusions/interpretation: Salivary amylase initiates the digestion of dietary starch, which is highly consumed in Mexico. Our current study suggests putative benefits of high number of AMY1 copies (and related production of salivary amylase) on energy metabolism in Mexican children

Whole-exome sequencing and high throughput genotyping identified KCNJ11 as the thirteenth MODY gene.

BACKGROUND: Maturity-onset of the young (MODY) is a clinically heterogeneous form of diabetes characterized by an autosomal-dominant mode of inheritance, an onset before the age of 25 years, and a primary defect in the pancreatic beta-cell function. Approximately 30% of MODY families remain genetically unexplained (MODY-X). Here, we aimed to use whole-exome sequencing (WES) in a four-generation MODY-X family to identify a new susceptibility gene for MODY. METHODOLOGY: WES (Agilent-SureSelect capture/Illumina-GAIIx sequencing) was performed in three affected and one non-affected relatives in the MODY-X family. We then performed a high-throughput multiplex genotyping (Illumina-GoldenGate assay) of the putative causal mutations in the whole family and in 406 controls. A linkage analysis was also carried out. PRINCIPAL FINDINGS: By focusing on variants of interest (i.e. gains of stop codon, frameshift, non-synonymous and splice-site variants not reported in dbSNP130) present in the three affected relatives and not present in the control, we found 69 mutations. However, as WES was not uniform between samples, a total of 324 mutations had to be assessed in the whole family and in controls. Only one mutation (p.Glu227Lys in KCNJ11) co-segregated with diabetes in the family (with a LOD-score of 3.68). No KCNJ11 mutation was found in 25 other MODY-X unrelated subjects. CONCLUSIONS/SIGNIFICANCE: Beyond neonatal diabetes mellitus (NDM), KCNJ11 is also a MODY gene ('MODY13'), confirming the wide spectrum of diabetes related phenotypes due to mutations in NDM genes (i.e. KCNJ11, ABCC8 and INS). Therefore, the molecular diagnosis of MODY should include KCNJ11 as affected carriers can be ideally treated with oral sulfonylureas

Multipoint linkage analysis following a dominant parametric model in the French pedigree.

<p>The positions of the genetic markers are ordered from chromosome 11p15.5 to 11q12.2 (chr11∶1,820,211–59,856,421; positions given according to human genome assembly GRCh37/hg19).</p

Clinical and molecular genetic characteristics of all studied members from the French MODY family.

a<p>or last treatment for deceased people;</p><p><b><i>BMI</i></b>, body mass index; <b><i>FPG</i></b>, fasting plasma glucose; <b><i>PG</i></b>, plasma glucose; <b><i>OGTT</i></b>, oral glucose tolerance test; <b><i>HbA1c</i></b>, glycated hemoglobin; <b><i>NA</i></b>, not available; <b><i>NG</i></b>, normoglycaemic; <b><i>IFG</i></b>, impaired fasting glucose; <b><i>IGT</i></b>, impaired glucose tolerance; <b><i>T2D</i></b>, type 2 diabetes (non autoimmune diabetes); <b><i>T1D</i></b>, type 1 diabetes (autoimmune diabetes); <b><i>INS</i></b>, insulin; <b><i>OHA</i></b>, oral hypoglycaemic agents; <b><i>SU</i></b>, sulfonylurea.</p><p>Of note, no member of the family showed NDM.</p

Pedigree of the family showing diabetes status of each member, as well as genetic status, age of diagnosis, treatment and date of birth.

<p>With regard to the genetic status, NM denotes the presence of the heterozygous <i>KCNJ11</i> p.Glu227Lys mutation and NN denotes the absence of mutation at the same locus. Circles represent female participants and squares male participants. A slash through the symbol indicates that the family member is deceased. Black symbols indicate patients with non autoimmune diabetes. The half-filled and quarter-filled symbols indicate individuals with impaired glucose tolerance and impaired fasting glucose, respectively. The black symbols with a white diagonal denote patients with type 1 diabetes. Green arrows point to members for whom the whole-exome was sequenced. <b><i>INS</i></b>, insulin; <b><i>OHA</i></b>, oral hypoglycaemic agents; <b><i>SU</i></b>, sulfonylurea.</p

Estimation of number of variants to be assessed by genotyping in the extended family and in controls.

a<p>Variants of interest are non-synonymous mutations, splice site mutations, gains of STOP codon. No frameshift mutation was found in any of the combinations.</p

Number of variants identified through the WES analysis of the four DNA samples.

a<p>This includes all identified variants (including insertion or deletion) that reach the quality threshold and with depth of coverage ≥8×; <b><i>Novel</i></b> means not present in the public database dbSNP130; <b><i>Indel</i></b>, insertion or deletion.</p