73. Which one of the following does NOT characterize aging?

(I) An insulin/IGF-I signaling system plays an important role in controlling lifespan.

(2) Lifespan increases due to resistance to oxidative stress.

(3) Shortening of telomeres.

(4) Female mice with a mutation in the IGF-1 and IGF-2 show reduced lifespan.

 Analysis of the Statements

1. An insulin/IGF-I signaling system plays an important role in controlling lifespan.

   • True. The insulin/IGF-1 signaling (IIS) pathway is evolutionarily conserved and plays a pivotal role in regulating longevity across species, including C. elegans, flies, mice, and humans. Reduced IIS activity is often associated with increased lifespan and stress resistance.

2. Lifespan increases due to resistance to oxidative stress.

   • True. Enhanced resistance to oxidative stress is a well-known factor contributing to increased lifespan. Organisms with better oxidative stress defenses tend to live longer.

3. Shortening of telomeres.

   • True. Telomere shortening is a hallmark of cellular aging and contributes to replicative senescence and organismal aging.

4. Female mice with a mutation in the IGF-1 and IGF-2 show reduced lifespan.

   • False. Studies show that reduced IGF-1 signaling (such as in Igf1r heterozygous knockout mice) actually increases lifespan, especially in females. Reduced IGF signaling is linked to longevity, not decreased lifespan.

Conclusion

The statement that does NOT characterize aging is:

(4) Female mice with a mutation in the IGF-1 and IGF-2 show reduced lifespan.

This is incorrect because mutations that reduce IGF-1 signaling generally increase lifespan in female mice.

Keywords

aging, insulin/IGF-1 signaling, lifespan regulation, oxidative stress resistance, telomere shortening, IGF-1 mutation, mouse longevity, aging pathways

Correct answer:
(4) Female mice with a mutation in the IGF-1 and IGF-2 show reduced lifespan.