Gènes impliqués dans la conversion des acides gras (de chaines courtes à chaines longues). Du point de vue évolutionnaire, la sélection de tel ou tel gène ou de tel ou tel allèle de ces gènes a probablement été influencé par l’accès plus ou moins direct à des acides gras à chaine longue issus de produits animaux, au gré des périodes glaciaires, puis des évolutions néolithiques.
Une explication originale de la disparition de Néandertal.
Evolution of the Human Brain: the key roles of DHA (omega-3 fatty acid) and D6-desaturase gene [PDF]
Oilseeds and fat crops and lipids, 2018
The polymorphism of this gene appears to have been essential in allowing the Homo genus to adapt to its food, and for its evolution. It provides an undeniable advantage in terms of the productivity of fat synthesis (DHA), and may partly explain positive selection. With the advent of cooking and new mutations producing even more FADS2, the brain reached its maximum size in Homo neanderthalensis, in a food ecosystem that provided favorable quantities of a-Linolenic acid and DHA. However, the Würm glaciation upset this equilibrium, revealing its fragility as regards to the brain and fertility. Homo sapiens, benefiting from new variants of the FADS2 gene, were able to adapt to this harsh environment, whereas Neanderthal man was unable to do so and became extinct.
Dietary adaptation of FADS genes in Europe varied across time and geography [Texte]
Ye et al.
Here we demonstrate, using ancient and modern DNA, that positive selection acted on the same FADS variants both before and after the advent of farming in Europe, but on opposite (that is, alternative) alleles. Recent selection in farmers also varied geographically, with the strongest signal in southern Europe. These varying selection patterns concur with anthropological evidence of varying diets, and with the association of farming-adaptive alleles with higher FADS1expression and thus enhanced LCPUFA biosynthesis. Genome-wide association studies reveal that farming-adaptive alleles not only increase LCPUFAs, but also affect other lipid levels and protect against several inflammatory diseases
Positive Selection on a Regulatory Insertion–Deletion Polymorphism in FADS2 Influences Apparent Endogenous Synthesis of Arachidonic Acid [PDF]
Kumar S. D. Kothapalli et al.
Molecular biology of evolution, 2016
Analysis using 1000 Genomes Project data confirmed our observation, revealing a global I/I genotype of 70% in South Asians, 53% in Africans, 29% in East Asians, and 17% in Europeans. Tests
based on population divergence, site frequency spectrum, and long-range haplotype consistently point to positive selection encompassing rs66698963 in South Asian, African, and some East Asian populations. Basal plasma phospholipid arachidonic acid (ARA) status was 8% greater in I/I compared with D/D individuals. The biochemical pathway product–precursor difference, ARA minus linoleic acid, was 31% and 13% greater for I/I and I/D compared with D/D, respectively. This study is consistent with previous in vitro data suggesting that the insertion allele enhances n-6 LCPUFA synthesis and may confer an adaptive advantage in South Asians because of the traditional plant-based diet practice.
Conversion vers la vitamine A
A review on factors influencing bioaccessibility and bioefficacy of carotenoids
Critical reviews in food science and nutrition, 2017
A review on factors influencing bioaccessibility and bioefficacy of carotenoids
Carotenoids are important as precursors of vitamin A as well as for prevention of cancers, coronary heart diseases, age-related macular degeneration, cataract etc. Bioaccessibility and bioefficacy of carotenoids are known to be influenced by numerous factors including dietary factors such as fat, fiber, dosage of carotenoid, location of carotenoid in the plant tissue, heat treatment, particle size of food, carotenoid species, interactions among carotenoids, isomeric form and molecular linkage and subject characteristics. Therefore even when carotenoids are found in high quantities in plant foods their utilization may be unsatisfactory because some factors are known to interfere as negative effectors.
A Combination of Single-Nucleotide Polymorphisms Is Associated with Interindividual Variability in Dietary b-Carotene Bioavailability in Healthy Men
Borel et al.
Journal of nutrition, 2015
Single nucleotide polymorphisms upstream from the β-carotene 15,15′-monoxygenase gene influence provitamin A conversion efficiency in female volunteers.
Lietz et al.
Journal of nutrition, 2012
β-Carotene, the most abundant provitamin A carotenoid in the diet, is converted to retinal by β-carotene 15,15′-monoxygenase (BCMO1). However, β-carotene absorption and conversion into retinal is extremely variable among individuals, with proportions of low responders to dietary β-carotene as high as 45%. Recently, 2 common nonsynonymous single nucleotide polymorphisms (SNPs) within the BCMO1 coding region (R267S; rs12934922 and A379V; rs7501331) revealed reduced catalytic activity, confirming that genetic variations contribute to the low responder phenotype. Because 4 SNPs 5′ upstream from the BCMO1 gene were recently shown to affect circulating carotenoid concentrations, the current study aimed to investigate the effects of these SNPs on β-carotene conversion efficiency. Three of the 4 polymorphisms (rs6420424, rs11645428, and rs6564851) reduced the catalytic activity of BCMO1 in female volunteers by 59, 51, and 48%, respectively. The TG-rich lipoprotein fraction retinyl palmitate:β-carotene ratio was negatively correlated with the G allele of rs11645428 (r = -0.44; P = 0.018), whereas it was positively correlated with the G allele of rs6420424 (r = 0.53; P = 0.004) and the T allele of rs6564851 (r = 0.41; P = 0.028). Furthermore, large inter-ethnic variations in frequency of affected alleles were detected, with frequencies varying from 43 to 84% (rs6420424), 52 to 100% (rs11645428), and 19 to 67% (rs6564851). In summary, a range of SNPs can influence the effectiveness of using plant-based provitamin A carotenoids to increase vitamin A status in at-risk population groups and this effect may vary depending on ethnic origin.
The challenge to reach nutritional adequacy for vitamin A : b-carotene bioavailability and conversion—evidence in humans
Marjorie J Haskell
American journal of clinical nutrition, 2012
The absorption of b-carotene from plant sources ranges from 5% to 65% in humans. Vitamin A equivalency ratios for b-carotene to vitamin A from plant sources rangefrom 3.8:1 to 28:1, by weight.
β-Carotene Conversion to Vitamin A Decreases As the Dietary Dose Increases in Humans
Novotny et al.
Journal of nutrition, 2010
The plasma AUC for ROH-d4 increased 36% from the 20-mg dose to the 40-mg dose. These results establish that, in humans, β-carotene conversion to vitamin A decreases as the dietary dose increases.
Review. Bioequivalence of β-carotene and retinol
David I Thurnham
Journal of the science of food and agriculture, 2007
One further piece of information was available and that was that there were some very large differences in individual responses to the β-carotene supplement, varying from 0.2 to 1.4μmol L−1 […] There was no change in plasma β-carotene concentrations in response to the carrots but the β-carotene supplied as a supplement was more bioavailable and the six to seven-fold variability in response was a little surprising.
b-Carotene – vitamin A equivalence in Chinese adults assessed byan isotope dilution technique
Zhixu Wang et al.
British journal of nutrition, 2004
The volunteers(nine males and six females) […] Four of the subjects exhibitedb-carotene to vitamin A conversion factors of.29·0:1 on a molar basis and were termed ‘poor converters’. In the eleven normal converters (seven males and fourfemales), the calculated conversion factors ofb-carotene to retinol ranged from 2·0:1 to 12·2:1 with an average of 4·8 (SD2·8):1 on amolar basis, and from 3·8:1 to 22·8:1 with an average of 9·1 (SD5·3):1 on a weight basis.
Variability in conversion of Beta-carotene to vitamin A in men as measured by using a double-tracer study design
Sabrina J Hickenbottom et al.
American journal of clinical nutrition, 2002
We dosed 11 healthy men […] Only 6 of 11men had sufficient plasma concentrations of D6-carotene and D3 retinol that we could measure. The mean absorption of D6-carotene in these 6 subjects was 4.097±1.208%, and the mean conversion ratio was 0.0540±0.0128 mol retinol to 1 mol-carotene. Conclusion: The vitamin A activity of Beta-carotene, even when measured under controlled conditions, can be surprisingly low and variable.
Variability of the conversion of b-carotene to vitamin A in women measured by using a double-tracer study design
Yumei Lin et al.
American journal of clinical nutrition, 2000
Mean (±SE) absorption of D6 β-carotene was 3.3 ± 1.3% for all subjects. The mean conversion ratio was 0.81 ± 0.34 mol D3 retinol to 1 mol D6 β-carotene for all subjects. However, only 6 of the 11 subjects had plasma D6 β-carotene and D3 retinol concentrations that we could measure. The mean absorption of D6 β-carotene in these 6 subjects was 6.1 ± 0.02% and their conversion ratio was 1.47 ± 0.49 mol D3 retinol to 1 mol D6 β-carotene. The remaining 5 subjects were low responders with ≤0.01% absorption and a mean conversion ratio of 0.014 ± 0.004 mol D3 retinol to 1 mol D6 β-carotene.
Low and high responders topharmacological doses of beta-carotene: proportion in the population,mechanisms involved and consequences on beta-carotene metabolism.
Borel et al.
Journal of lipid research, 1998
the ability to respond to b-carotene is highly variable, but there is probably a very small proportion of true non-responders to pharmacological doses of b-carotene in the healthy population. This variability is apparently mainly due to interindividual differences in the efficiency of intestinal absorption of b-carotene and in chylomicron metabolism.
La capacité d’absorption du fer non-héminique est variable selon les populations.
Natural selection on HFE in Asian populations contributes to enhanced non-heme iron absorption
Kaixiong Ye et al.
BMC genetics, 2015
Meat Consumption During Pregnancy and Substance Misuse Among Adolescent Offspring: Stratification of TCN2 Genetic Variants
Joseph R. Hibbeln et al., 2017
Lower meat consumption disproportionally increased the risks of offspring substance misuse among mothers with optimally functional (homozygous) variants (rs1801198) of the gene transcobalamin 2 gene (TCN2) which encodes the vitamin B12 transport protein transcobalamin 2 implicating a causal role for cobalamin deficits.
[…]Lower prenatal meat consumption was associated with increased risks of adolescent substance misuse. Interactions between TCN2 variant status and meat intake implicate cobalamin deficiencies.
Digestion des produits laitiers
Early Mongolians ate dairy, but lacked the gene to digest it
DNA analysis of the same ancient individuals shows that as adults they lacked the ability to digest lactose, a key sugar in milk. The findings present a puzzle, because they suggest dairying and lactose tolerance may be disconnected. That challenges an oft-told tale of how this adaptation evolved and spread in populations in Europe and Africa. Mongolians’ fondness for fermented milk products—using bacteria to help them digest lactose—may help explain the riddle.
Lactase persistence may explain the paradoxical findings of high vitamin D concentrations in Europeans living in areas of low UV-B irradiation
Sorthe & Moghaddam
European journal of clinical nutrition, 2018
In a recent study of adult-type lactase persistence (LP), it was shown that Caucasian of European descent, who carried the C-13910T LP allele, had higher levels of total serum 25-hydroxyvitamin D compared with those who were lactase non-persistent. This was attributed to higher consumption of dairy. We postulated that the distribution of the LP C-13910T allele in Caucasian populations may explain the vitamin D concentration pattern seen in Europe.