Control Long Lived (n = 470, (n = 207, All (n = 677) 16–83 y) p 85–104 y) Sex (male/female) 289/388 239/231 — 50/157* Age (y) 62 ± 26 48 ± 15 .001 96 ± 4 BMI (kg/m2) 24.5 ± 3.2 25.1 ± 2.9 .001 23.1 ± 3.5 Glucose (mmol/dL) 4.8 ± 0.9 4.9 ± 0.8 .400 4.8 ± 1.1 Insulin (mU/mL) 10.6 ± 4.4 11.6 ± 4.2 .001 8.5 ± 4.3 Triglycerides (mg/dL) 107 ± 45 108 ± 44 .540 105 ± 48 Total cholesterol (mg/dL) 198 ± 42 201 ± 41 .020 191 ± 42 hDL cholesterol (mg/dL) 51.2 ± 10.6 49.6 ± 8.4 .001 54.3 ± 12.0

Discussion

Our study supports the hypothesis that the Gly1057Asp variant of IRS2 is associated with human longevity. Partici- pants with one or two IRS2Asp alleles displayed a greater chance of living between 96 and 104 years of age. These results are consistent with experiments in mice showing that reduced IRS2 signaling increases life span up to 20% (5).

Notes: BMI = body mass index; hDL = high-density lipoprotein. * 2= 41,86; df = 1 p<0.05. All data presented are mean ± SD. χ

frequencies observed were almost similar to those reported in previous studies among Caucasians.

even though our findings provide novel and intriguing evidence for the involvement of the IRS2 in the control of aging and longevity also in humans, the functional effects of the structural variation of the IRS2 due to the gene poly- morphism remain unclear, and mechanism relating such variation with circulating insulin levels and longevity has to be established. however, the finding that IRS2Asp/Asp together with obesity is associated with polycystic ovarian syndrome, reduced beta-cell function, and/or diabetes in certain populations (6,8–11) suggests that IRS2Asp might have reduced function that exacerbates the effects of obe- sity. Without an underlying cause of obesity to promote

In the whole population, homozygous IRS2Asp/Asp participants were more represented among LL versus C participants (16.7% vs 12.0%; p = .04; Table 2). The asso- ciation between IRS2 gene polymorphism with longevity (being LL) was independent of sex, hOMA-IR, hOMA%B, BMI, plasma cholesterol, triglycerides, and hDL levels (odds ratio: 2.07, 95% CI = 1.38–3.12; p = .001).

Categorizing participants into percentiles by age, an ordi- nal logistic regression analysis was performed to determine whether the IRS2Asp/Asp, IRS2Gly/Asp, or the most common IRS2Gly/Gly genotype was associated with extreme longevity

3025201510C(<85) LL(>85)Femaleo180160140HOMA2 %B 120100C(<65) LL>85) C(<85) LLO85) —C(<85)_ LL(>85)Male Female Malec 2&2,6=zC(<85) LLOB5) —C(<85)-_LLO>85)Female Male

Figure 1. (A–C) hOMA2%B, hOMA-IR, and body mass index (BMI) in control (C; n = 239; mean age: 48 ± 16 years, age range: 16–82 years) and long-lived (LL; n = 50; mean age: 93 ± 5 years, age range: 85–102 years) male participants or in control (C; n = 231; mean age: 47 ± 15 years, age range: 16–83 years) and long-lived (LL; n = 157; mean age: 96 ± 4 years, age range: 85–104 years) female participants.

Table 2. Allele and Genotype Distributions of the IRS2 Gene Variant in Control (mean age = 48 ± 15 years, age range = 16–83 years) and Long Lived (mean age = 96 ± 4 years, age range = 85–104 years)

Table 3. Multinomial Regression of Age in Percentiles as the Ordinal Dependent Variable and Cumulative Logit as the Link Function With

hOMA2%B, and BMI and the Serum Concentration of Cholesterol, and hDL at Various Metabolic Parameters as (n = 677, male/female = 289/388, age range: 16–104 years)

Control Long Lived (n = 418) (n = 144) IRS2 Gly/Gly 46.1 34.7 c2 = 6.16; p = .04 Gly/Asp 41.9 48.6 Asp/Asp 12.0 16.7 Allele frequency Gly 88.0 83.3 Asp 12.0 16.7 Asp + participants 53.8 65.3 Fischer’s test: p =

Confidence Interval Parameter* Odds Ratio† Lower Upper p Genotype IRS2Asp/Asp 2.03 1.39 2.99 .0003 IRS2Gly/Asp 1.49 1.15 1.94 .003 IRS2Gly/Gly 1‡ Sex Female 1.49 1.16 1.91 .002 Male 1‡ hOMA2 IR 0.80 0.64 1.00 .051 %B 0.998 0.995 1.000 .034 Metabolic BMI 0.934 0.900 0.970 .0004 Cholesterol 0.998 0.994 1.001 .15 Triglycerides 1.000 0.997 1.003 .88 hDL 1.005 0.993 1.017 .44

Note: IRS2 = insulin receptor substrate-2.

insulin resistance, IRS2Asp people might act like the IRS2+/− mice that have improved glucose tolerance and reduced ß-cell function and live 20% longer than control mice.

As people age, compensatory hyperinsulinemia main- tains euglycemia by opposing the effects of insulin resis- tance (13). hyperinsulinemia/insulin resistance has been found implicated in the development of many diseases, such as hypertension, dyslipidemia, obesity, and atherosclerosis strongly affecting morbidity, disability, and mortality among the elderly participant (18,19). however, chronic hyperin- sulinemia might also affect life span directly by slowly damaging brain function (18,19). Interestingly, in humans, genetically reduced insulin signaling is associated with a lower risk of cognitive impairment and increased survival beyond 85 years (20). Moreover, brain-specific deletion of one or both IRS2 alleles extends mouse life span about 18% (5). These findings suggest that consequences of the local action of insulin within the brain include effects on aging and longevity. We hypothesize that, like brain-specific IRS2 knockout mice, the IRS2Asp variant might protect the aging brain from the negative effects of hyperinsulinemia that ordinarily develop with overweight and advancing age by attenuating, also in humans, IRS2 signaling. In mice, it will be important to compare the phenotype of Thr1049Asp knock-in mouse variant (homologous to the human Gly1057Asp variant) to determine whether IRS2Asp also extends mouse life span.

Notes: BMI = body mass index; hDL = high-density lipoprotein; hOMO = homeostasis model assessment; IRS2 = insulin receptor substrate-2. * Dependent variable is age (percentile). † Odds ratio of reaching the 90% percentile for age (>96 years). ‡ Set to 1 as the reference.