3. Results

Clinical characteristics of study group are reported in Table 1. All subjects were old, not obese, in sufficient metabolic control with a greater proportion of female (Table 1).

The allele frequency and genotype distribution of Pro/Ala gene polymorphism did not differ between long- lived and aged subjects (Pro/Pro 82.9 vs 85.6%; Pro/Ala 53.6 vs 46.4%; Ala/Ala 0.5 vs 1.6%; x2 ¼ 2: 77; df ¼ 2; p ¼ 0: 25). Indeed, due to the different male/female proportion in the two age groups, genders were analyzed separately. As shown in Table 2 aged and long-lived men subjects had similar Ala allele frequency, whilst the frequency of Pro/Ala genotype was significantly increased in long-lived men (20%). As shown in Table 3, no differences was found when allele and genotype distribution of Pro/Ala gene polymorphism were analyzed in the two age group of women.

According to gender ratio, female had a significantly ^ ^ higher plasma triglycerides (105 50 vs 94 40 mg/dl; p ¼ 0: 027) and cholesterol (202 ^ 44 vs 183 ^ 36; : p , 0 01) levels compared to male subjects. Indeed, no ^ ^ differences in plasma HDL (56.6 16.0 vs 53.8 15.5 mmol/ml; p ¼ 0: 10) level, BMI (24.2 ^ 3.4 vs 24.7 ^ 2.5; p ¼ 0: 09) and IR (HOMA) index (2.18 ^ 1.40 vs 2.06 ^ 1.13; p ¼ 0: 41) were found.

As far as Pro/Ala gene polymorphism is concerned, the frequency of the Ala allele in the whole population, was 8.4%. The frequency of Pro/Pro, Pro/Ala and Ala/Ala genotypes was 84.3, 14.6 and 1.1%, respectively. The observed genotype and allele distribution were in Hardy– Weinberg equilibrium ðp . 0: 05Þ: The genotypic frequency

The impact of Pro/Ala substitution in exon B of PPARG gene on BMI and insulin resistance degree was also evaluated in a subgroup of the whole of subjects ðn ¼ 414Þ: Comparing insulin resistance degree among the three genotype groups, there was a trend for individuals with Pro/Ala genotype to have lower IR degree

characteristics of study population ðn ¼ 472Þ

All Aged p Long lived ðn ¼ 472Þ ðn ¼ 250Þ ðn ¼ 222Þ Age (yrs) 75 ^ 26 55 ^ 21 0.001 97 ^ 4 Sex (male/female) 165/307 71/179 94/128* BMI (kg/m2) 24.4 ^ 3.2 25.1 ^ 2.6 0.001 23.2 ^ 3.6 Glucose (mmol/dl) 5.4 ^ 1.4 5.6 ^ 1.3 0.001 5.0 ^ 1.5 Insulin (mU/ml) 8.6 ^ 4.0 9.0 ^ 3.6 0.001 7.9 ^ 4.5 Triglycerides (mg/dl) 102 ^ 47 100 ^ 45 NS 103 ^ 50 Total cholesterol 196 ^ 43 198 ^ 42 NS 193 ^ 43 (mg/dl) HDL cholesterol 55.8 ^ 15.9 54.4 ^ 15.7 0.020 58.2 ^ 15.9 (mg/dl) HOMA (IR) 2.1 ^ 1.3 2.3 ^ 1.4 0.001 1.7 ^ 1.1

Table 3

Allele and genotype distribution of the PPARG Pro/Ala polymorphism in women ðn ¼ 307Þ

Aged ðn ¼ 179Þ % Long lived ðn ¼ 128Þ % Pro/Pro 84.4 85.2 Pro/Ala 14.5 14.1 Ala/Ala 1.1 0.8 Allele frequency Pro 91.6 92.2 Ala 8.4 7.8

Data are mean ^ SD. *x2 ¼ 5:69; df ¼ 1; p ¼ 0:017:

x2 ¼ 0:10; df ¼ 2; p ¼ NS for genotype distribution.

M. Barbieri et al. / Experimental Gerontology 39 (2004) 1095–1100

BMI (kg/m’)35302520‘ialPro/Ala Ala/AlaPro/Ala polymorohism of PPARG? aene

et al., 2000; Hasstedt et al., 2001; Mancini et al., 1999; Beamer et al., 1998).

Previous studies, investigating the association of Pro/Ala with BMI and insulin sensitivity have inconsistent findings. In fact, Ala allele has been associated either with a higher BMI (Koch et al., Mancini et al., 1999; Beamer et al., 1998), or with BMI (Fajas et al., 1997; Deeb et al., 1998), while studies have found no association (Rosmond et al., Altshuler et al., 2000). Likewise, a beneficial effect insulin sensitivity is reported in some (Deeb et al., 1998; et al., 2001) but not in all population (Mancini al., 1999). Reasons for such discrepancy might be an statistical power, ethnic differences and genetic Furthermore, it is possible that Pro/Ala variant produces a characteristic phenotype only a certain genetic background.

Pro/Ala polymorphism of PPARG2 gene

1. Body mass index among the three different genotype groups. Variation of the group means: p ¼ 0:039:

In our study, the Pro/Ala genotype has been found to be associated with lower BMI and with a trend towards lower IR (HOMA) degree. Nevertheless, some caution in data interpretation should be kept in mind due to the large SD of BMI in all study groups. Indeed, we demonstrated that the BMI difference as the trend and not as real difference among the group was significant, thus supporting the information that subjects grouped under Ala/Ala genotype were at the higher ‘risk’ to have higher BMI.

^ ^ ^ (1.82 1.0 vs 2.19 1.3 and 2.5 0.6 for pro/pro and ala/ala genotype, respectively); the differences, however, did not reach statistical significance ðp ¼ 0: 12Þ: Indeed, subjects with Pro/Ala polymorphism had significantly lower BMI than Ala/Ala and Pro/Pro polymorphism (Fig. 1). Categoris- ing subject in aged and long-lived subjects the association between Pro/Ala genotype and BMI was significant in men but not in women (data not shown)

It is unclear why a significant association with BMI could be demonstrated only in men, although gender differences in the association of PPARG gene polymorphism with dyslipidemia (Zietz et al., 2002), insulin sensitivity and BMI have been previously documented (Deeb et al., 1998). Interestingly, the greater part of the association studies evaluating the role of PPARG polymorphism have been performed only in men and not in women (Ek et al., 1999; Schneider et al., 2002; Rosmond et al., 2003b).

4. Discussion

Our study demonstrates that genetic variation in peroxi- some proliferator-activated receptor (PPAR)g-2 is associ- ated with human longevity. Such an effect is probably due to the effect of Pro/Ala polymorphism on body composition and appears to be gender specific. In fact, a different Pro/Ala genotype frequency distribution between long-lived and aged men subjects has been found, having long-lived men an increased frequency of Pro/Ala genotype.