The first ever study on the demographical effects of life extension has been conducted . The paper investigates 5 different scenarios ranging from negligible senescence after age 60 to continuous rejuvenation. Even the most radical scenario only resulted in a 22% increase in population size over a 100 year period. Another, for most people totally unexpected result, was the finding that even a population of immortal persons with less than two children per family resulted in a finite population growth and the final population is only 1/ 1 – r time larger than the original population. However, I had already noticed in 2008 that population growth is limited (see green and red graph) .
 Gavrilov L. A., and Gavrilova N. S. Demographic Consequences of Defeating Aging. Rejuvenation Research, 2010 [Epub ahead of print].
In a new paper DePinho and colleagues investigate the effect of telomere shortening on mitochondrial function. When telomeres get shorter the tumor-suppressor p53 gets activated. In fast dividing cells (e.g. stem cells) this leads to cell cycle arrest and thus stem cell depletion. However, until now the effect of telomere shortening on post-mitotic cells was neglected. In this new study it is shown that telomere shortening in post-mitotic cells inhibits the transcription of PGC-1alpha and PGC-1beta, two master regulators of gene expression of mitochondrial proteins. This leads to mitochondrial dysfunction as evidenced by reduced mitochondrial DNA content and density, reduced oxygen consumption during state III respiration, decreased ATP synthesis, and increased ROS levels. The mice with short telomeres also exhibited heart problems such as age-progressive dilated cardiomyopathy with left ventricular wall thinning, increased left ventricular diameter, and reduced fractional shortening.
Sahin et al. Telomere dysfunction induces metabolic and mitochondrial compromise. Nature, 2011 [e-pub before print].