In conclusion, our study did not provide evidence for linkage or association of the MTP gene with nonagenarian longevity in the Dutch population. The absence of association in our study and in other European studies suggests that the genetic determinants of longevity may differ among populations. Further studies are needed to identify other genetic determinants of human longevity.each (non-members).

Individuals, and they proactively matched the controls to the long-lived cases using the genotypes of 60 random SNPs. However, moderate levels of stratification may remain undetected when a small number of SNPs (50-100) are investigated (35). This implies that even after proactively matching, residual population stratification may still have been present in the U.S. control dataset (36). Because our meta-analysis including the U.S. proactively matched sample showed that this putative MTP risk haplotype has no effect on human longevity in Caucasian populations, we conclude that it is more likely that the association found by Geesaman and colleagues has its source in the stratification of (especially) the control group of the U.S. population rather than in the genetic effect of the locus on exceptional longevity.

Considering the absence of linkage in our study, we find it unlikely that chromosome 4q25 harbors a gene explaining the familial effects on Dutch nonagenarian longevity. Furthermore, the current evidence does not support the MTP gene at chromosome 4q25 to be the major longevity gene explaining the previously detected linkage to exceptional longevity.

Figure 2. Kaplan-Meier survival curves per genotype in the two combined cohorts of the Leiden 85-Plus Study for the (cid:1)493G/T and Q95H microsomal transfer protein (MTP) gene single-nucleotide proteins (SNPs). Because the first cohort of the Leiden 85-Plus study was followed for 14 years and the second cohort for 7 years, we were also able to analyze the effect of the MTP SNPs prospectively. None of the genotypes of the (cid:1)493G/T or Q95H MTP SNPs showed an effect on either overall mortality or on specific causes of death (such as cardiovascular disease, which would be the most likely cause of death when MTP would have an effect on mortality). This result is in accordance with the Danish longitudinal results (29).

ACKNOWLEDGMENTS

This study is supported by a grant from Innovation Oriented research Program IOP on Genomics (SenterNovem; IGE01014) and by the Centre for Medical Systems Biology (CMSB), a center of excellence approved by The Netherlands Genomics Initiative/Netherlands Organisation for Scientific Research (NWO). We appreciate the great effort of Michiel Leijnen and J. Kate van Duijn in genotyping the microsatellite markers and the MTP SNPs in samples of the Leiden Longevity Study and the two cohorts of the Leiden 85-Plus Study. We thank Bas Heijmans for his inspiring comments.

To deal with the discrepancies reported in the literature, we performed a meta-analysis on all published data on the association of the MTP T-Q haplotype and longevity. The meta-analysis including the first and second tier of the U.S. samples showed significant heterogeneity. When, however, the U.S. proactively matched cases and controls were addressed, correspondence to Marian Beekman, PhD, Leiden University Medical Center, Section of Molecular Epidemiology, P.O. Box 9503, 2300 RA Leiden, The Netherlands. E-mail: M.Beekman@LUMC.nl US proactively matched France Germany Denmark Leiden Longevity Leiden 85-plus Pooled Odds Ratio 0.6T08 1.0 Odds Ratio from http://biomedgerontology.oxfordjournals.org/ by guest on June 6, 2016 Figure 3. Meta-analysis of the effects of the microsomal transfer protein (MTP) gene T-Q haplotype on longevity. The size of the black square indicates the size of the study.

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