Does lipoprotein particle size play a direct biological role in successful ag- ing and the longevity phenotype, or are these measures simply markers of the longevity phenotype? Although our

where P is the prevalence of VV homo- zygosity in the population and OR is the odds ratio associating VV homozygos- ity with longevity. This estimation for- mula is valid so long as the outcome (longevity) is rare in the population (ap- proximately 1 of 5000-10000). In our data, the OR (combining men and women) is 3.56. We do not have a di- rect observation of population preva- lence of VV homozygosity in our data. However, it is reasonable to take the control groups as a proxy for the popu- lation as a whole because the number of people who will ultimately survive to longevity is a very small proportion of the population. Our estimate of the prevalence of VV homozygosity is 0.09, and applying the formula, population attributable risk fraction is 18.1.

Figure 4. Genotype Frequencies of I405V CETP in Long-Lived Probands, Their Offspring, and Ashkenazi Controls

Women Men 70 70 Probands 60 Offspring 60 Askenazi Controls 50 50 40 40 § 30 30 ∗ ‡ 20 20 † 10 10 0 0 II IV VV II IV VV Genotype Genotype % ,ycneuqerF % ,ycneuqerF

We also assessed the relationship be- tween CETP I405V genotype and lipo- protein particle sizes and CETP activ- ityinthecontrol,offspring,andproband groups, respectively. The VV pheno- type was associated with significantly larger LDL and HDL particle sizes (TABLE 3). Furthermore, participants with the VV genotype had 17% lower CETP concentrations compared with those with II or IV genotype, and HDL level and CETP levels were negatively correlated (r=–0.29; P=.03; Spearman p) ). These findings suggest a survival ad- vantage for individuals with the VV genotype,perhapsmediatedthroughde- creased levels of CETP and its effects on lipoproteins and their particle sizes.

The frequency of homozygosity for the codon 405 isoleucine to valine (I405V) allele of cholesteryl ester trans- ferprotein(CETP)infemaleandmaleprobands(n=156),offspring(n=163),andAshkenazicontrols(n=129). ThefrequencyoftheVVgenotypeis2.4-and2.9-foldincreasedinoffspringandprobands,respectively,com- pared with Ashkenazi controls. *P=.001; †P=.20; ‡P=.004; §P(cid:1).001, indicating differences between pro- bands and offspring vs Ashkenazi controls for women and men.

Table 3. CETP I405V Genotype and Lipoprotein Characteristic and Plasma CETP Levels in Families With Exceptional Longevity and Control Groups

CETP I405V Genotype, Mean (SD) P Value (VV vs Variable VV IV II II Genotypes) HDL Concentration, mg/dL 57 (18) 55 (16) 55 (16) .53 Large particle size, % of total 56 (16) 60 (14) 60 (15) .10 Particle size, nm 9.28 (0.56) 9.09 (0.52) 9.07 (0.48) .02 LDL Concentration, mg/dL 114 (35) 120 (30) 123 (34) .16 Large particle size, % of total 67 (25) 58 (24) 56 (28) .02 Particle size, nm 21.29 (0.67) 20.98 (0.63) 20.88 (0.81) .002 CETP concentration, µg/mL 1.65 (0.59) 1.92 (0.65) 1.99 (0.72) (cid:1).001

COMMENT

Abbreviations: CETP, cholesteryl ester transfer protein; HDL, high-density lipoprotein; I405V, codon 405 valine; LDL, low-density lipoprotein. SI conversion factor: To convert HDL and LDL concentrations to mmol/L, multiply by 0.0259.

(Reprinted) JAMA, October 15, 2003—Vol 290, No. 15 2037

©2003 American Medical Association. All rights reserved.

Because it has been shown that lipo- protein sizes are genetically deter- mined,33 we were interested in finding potential pathways involved in this phe- notype. The biology of rare forms of CETP deficiency may be relevant to our observation of a marked increase in the frequency of homozygosity for the com- moncodon405valineCETPalleleinour families with longevity. Although ho- mozygosity for this variant was ob- served in 24.8% of our probands, it was present at a frequency of only 8.6% in Ashkenazi Jewish control participants. Offspring of long-lived individuals also had a much higher frequency of the VV genotypecomparedwithcontrolgroups. With analyses of 30 different single nucleotide polymorphisms, it could be arguedthatourpositivefindingforI405V CETP is the result of multiple compari- sons.However,thelevelofstatisticalsig- P<. nificance of this association (P .001) maintainsstatisticalsignificanceevenaf- terrigorouscorrectionformultiplecom- parisons. Furthermore, investigation of this variant was hypothesis driven based on known pathways of lipoprotein me- tabolism. Correction for multiple com- parisons would be considered by many as overly conservative. To our knowl- edge,thereisnootherexampleofapoly- morphic allele whose frequency was demonstrated to be so dramatically in- creased in centenarians and for which there is plausible biological mechanism to explain the association. Although the effectofthevaline405alleleonthestruc- ture and function of the CETP protein has not been studied, homozygosity for the valine allele has been shown to re- sultinsignificantlydecreasedCETPcon- centrations,34-36 aswedemonstrated;and significantly decreased CETP activ- ity,37-39 as confirmed by Boekholdt and Thompson.40 Furthermore, in 2 popu- lations, each with more than 1000 par- ticipants, valine 405 homozygosity was associated with a 6.5-mg/dL or approxi- mately 13% increase41 and approxi- mately 4% increase42 in HDL choles- terol. Although this VV homozygosity ap- pears in less than 20% of the offspring,

plexity emphasizes that changes in the functionality of HDL, some through changes in mass or size, may have pleio- tropic antiaging effects.