According to findings published in the FASEB Journal, vitamin A (retinol) may play a role in the synthesis of ATP in mitochondria – the power plant of the cells – and when vitamin A is deficient the production of energy is reduced by 30 per cent.
Researchers led by Ulrich Hammerling from the Institute for Cancer Research, New York found that, when vitamin A supplies are adequate, the preferred energy sources are glycolysis and pyruvate production. On the other hand, when the vitamin is scarce the body turns to fat reserves, preparing the organism to win energy from fat oxidation.
However, when cells are deprived of retinol, the synthesis of ATP decreases as did respiration, but such declines were reversed when retinol levels were restored, and no conversion to other retinoids was observed, showing the effect was related purely to retinol.
View from the market
The research was welcomed by Dr Peter Engel, spokesperson for beta-carotene supplier DSM, who told NutraIngredients that this represents “one of the rare papers containing real fundamental news in the field of vitamin A/beta-carotene research”.
European giants DSM and BASF dominate the world supply of synthetic beta-carotene, which represents the largest part of the carotenoid market. Valued at $247m in 2007, the beta-carotene segment is expected to be worth $285m by 2015, a CAGR of 1.8 per cent, according to BCC Research.
“Bioenergetics is fundamental to all cells,” wrote the researchers. “In view of this tenet, it is puzzling why metabolic regulation by the pathway described in this report depends on retinol that vertebrates cannot synthesize de novo.
“In limiting vitamin A to nutritional sources, there must be an evolutionary advantage of such import as to override the physiological needs for vitamin A in vision and retinoic acid-dependent transcription.
“The answer may lie in the scenario that finite amounts of vitamin A are subject to depletion during periods of severe starvation when an organism is forced to conserve energy. Our observation that in the absence of vitamin A energy generation by respiration adapts downwards appears relevant in this context,” added the researchers.
Data from vitamin A-deficient mice has previously indicated that triglycerides accumulate in the liver, and may signify a switch to fat for energy generation, said the researchers, in order to offset the limited use of glycolysis and pyruvate production.
“It is also predictable that chronic deviations of vitamin A transport will lead to metabolic disease,” added Hammerling and his co-workers.
Triage in action?
The evolutionary aspect of the research is remiscent to the triage theory proposed by Professor Bruce Ames from The University of California, Berkeley and a senior scientist at Children's Hospital Oakland Research Institute (CHORI).
Prof Ames hypothesised that our short-term survival is achieved by prioritising the allocation of scarce micronutrients. The theory was first proposed in 2006 (PNAS, Vol. 103, Pages 17589-94) to explain why age-related diseases like heart disease, cancer, and dementia may be unintended consequences of mechanisms developed during evolution to protect against episodic vitamin/mineral shortages.
Source: FASEB Journal
2010, Volume 24, Pages 627-636
“Control of oxidative phosphorylation by vitamin A illuminates a fundamental role in mitochondrial energy homoeostasis”
Authors: R. Acin-Perez, B. Hoyos, F. Zhao, V. Vinogradov, D.A. Fischman, R.A. Harris, M. Leitges, N. Wongsiriroj, W.S. Blaner, G. Manfredi, U. Hammerling