Layman's summary of caloric restriction study by Ma et al. Cell, 2020 March 5

HC Lee

2020 March 5

I find this comprehensive study by a mostly Beijing group on the effect of a mild caloric restriction (CR) regimen on rats after they reached middle age very interesting. Here's what I think are the key points in layman's terms. First, some abbreviations: AL, eat your full; CR, 70% feeding, BAT (brown fat), WAT (white fat). [Note, brown fat is "good", it is "live" and its main function is energy generation for insulation. White fat is "dead" fat in hard-to-get storage] .

The key experiments¶

The study compared the morphological and molecular (DNA) in a number of tissues including aorta, liver, kidney, BAT, WAT, skin, and bone marrow of three groups of rats:
  - Y-AL, 5-month old rats (16 y human) fed AL
  - O-AL, fed AL to 18 m old, then random selected and continued on AL, test done on surviving samples at 27 m (70 y human)
  - O-CR, fed AL to 18 m old, then random selected and fed 70%, test done on surviving samples at 27 m.

Then they compared O-AL vs Y-AL (the only difference is age) and O-CR vs O-AL (the only difference is diet).

In what follows, effect of aging refers to O-AL vs Y-AL, and effect of CR refers to O-CR vs O-AL.

Results¶

Here are what I think the important results:
1. CR reduces body weight on average by one-third
2. CR extended mean lifespan by 22% (23 m to 28 m).
3. CR significantly reverses these aging-associated morphological changes:
  - In WAT, increase in size of fat droplets (hence larger WAT)
  - In BAT, fewer small droplets and more large droplets (hence larger BAT)
  - Accumulation of old cells in BAT, WAT, live, and kidney
4. CR significantly reverses these aging-associated cellular changes:
  - Increased stiffness of blood vessels
  - increase of immune cells in WAT, BAT, kidney, liver, skin
5. CR boosts a number of anti-aging pathways, including anti-inflammatory pathway

Take home¶

CR extended lifespan by 22%, reduced body weight by 1/3, had big beneficial effects on aorta, BAT, WAT and inflammatory response

Reference¶

[1] Ma et al. (2020). "Caloric Restriction Reprograms the Single-Cell Transcriptional Landscape of Rattus Norvegicus Aging". Cell, March 5, 2020.