{'fraction_non_alphanumeric': 0.03288740245261984, 'fraction_numerical': 0.026755852842809364, 'mean_word_length': 4.904605263157895, 'pattern_counts': {'":': 0, '<': 1, '<?xml version=': 0, '>': 2, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Delta-aminolevulinate synthase 2 polymorphism is associated with maximal oxygen uptake after Living-high exercise-high training-low in a male Chinese population.

OBJECTIVE
Each individual shows great variations to hypoxic training, which may be due to individual differences in genotype or gene polymorphism. δ-aminolevulinic acid synthase 2 (ALAS2 ) polymorphism is used as a marker for X-linked sideroblastic anemia. This study assessed the ALAS2 polymorphism for an association with response to Living-high exercise-high training-low (HiHiLo) training in Han Chinese males.


METHODS
A total of 244 healthy young male subjects of Han nationality were recruited from Northern China for detection of the ALAS2 polymorphism, 72 of whom were then selected for undergoing a four-week HiHiLo training program (i.e., subject to 10 h of hypoxia training daily at 14.5-14.8% O2 exposure, three occurrences of hypoxic training every week at 15.4% O2 level, and normal training at sea level). GeneScan and DNA sequencing were used to analyze ALAS2 polymorphism. Before and after training, the maximal oxygen uptake (VO2 max) in each individual was recorded.


RESULTS
A successive cut-point analysis showed that the initial hemoglobin value in individuals with dinucleotide repeats ≤ 166 bp was significantly higher than in individuals with dinucleotide repeats > 166-bp (P = 0.05). The ∆VO2 max and ∆rVO2 max after HiHiLo training were significantly higher in individuals with dinucleotide repeats ≤ 166 bp than in individuals with dinucleotide repeats > 166 bp (P < 0.01).


CONCLUSIONS
The compound dinucleotide repeat polymorphism in ALAS2 intron 7 correlated with response to HiHiLo training. Further study will evaluate this ALAS2 SNP as a genetic marker to predict responses to HiHiLo training.