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Metabolism

The switches in our metabolism

Enzymes that switch over when food is scarce, and a long debate

Some enzymes switch the metabolism over as soon as food gets scarce. Their role in ageing has been argued about for twenty years.

What sirtuins do

Sirtuins are a family of enzymes that change proteins inside the cell. In this way, they help decide how the metabolism runs and how the cell's power plants work. They become especially active when little food is available.

To work, they need NAD, the helper from the previous topic. If its amount drops with age, they have less of it too. This links the two topics directly.

The dispute about resveratrol

In 2003, Konrad Howitz described that resveratrol, a substance found in grapes among other things, activates these enzymes. The finding started one of the longest debates in ageing research.

Nine years later, another research group showed that resveratrol first acts at a completely different point, and the sirtuins only switch on as a second step. So the explanation was wrong. The observed effect remained. Anyone who wants to judge this substance should know both.

What the animal studies showed, and what they did not

In mice fed a very high-calorie diet, resveratrol clearly improved health and survival. Five years later came the important limitation: age-related decline set in later, but the maximum lifespan did not get longer. Both belong together.

In humans it is more difficult

Resveratrol is absorbed, but almost all of it is converted before it can act. Even so, two independent reviews of controlled studies found measurable effects on sugar metabolism and related values. Here too, studies with piperine describe higher blood levels.

Astaxanthin, the red pigment of the alga Haematococcus, is studied for a different reason: it tends to settle in the outer layers of the cells and their power plants rather than in the watery interior.

Sources

  1. Howitz 2003 — Nature — resveratrol as a sirtuin activator PMID 12939617
  2. Park 2012 — Cell — phosphodiesterase inhibition as the primary mechanism PMID 22304913
  3. Baur 2006 — Nature — health and survival in an animal model PMID 17086191
  4. Pearson 2008 — Cell Metab — healthspan without extension of maximum lifespan PMID 18599363
  5. Imai & Guarente 2014 — Trends Cell Biol — NAD⁺ and sirtuins PMID 24786309
  6. Houtkooper 2012 — Nat Rev Mol Cell Biol PMID 22395773
  7. Mouchiroud 2013 — Cell — NAD⁺/sirtuin axis PMID 23870130
  8. Walle 2004 — Drug Metab Dispos — bioavailability of resveratrol PMID 15333514
  9. Johnson 2011 — Mol Nutr Food Res — resveratrol with piperine PMID 21714124
  10. Liu 2014 — Am J Clin Nutr — meta-analysis, 11 randomised studies PMID 24695890
  11. Asgary 2019 — Rev Endocr Metab Disord — meta-analysis, metabolic syndrome PMID 31065943
  12. Wolf 2010 — J Nutr Biochem — astaxanthin and mitochondrial redox state PMID 19423317
  13. Yoshida 2010 — Atherosclerosis — human study, lipid parameters PMID 19892350
  14. Park 2010 — Nutr Metab — human study PMID 20205737

Note. These pages reflect the current state of published research. They describe biological processes and studies on substances. They make no statement about products and do not replace medical advice, diagnosis or treatment.