25-hydroxy vitamin D levels are associated with childhood asthma in a population-based study in Peru

BACKGROUND

Vitamin D deficiency may be associated with an increased risk of asthma.

OBJECTIVE

We studied the association between 25-hydroxy (25-OH) vitamin D deficiency and asthma prevalence in two Peruvian populations close to the equator but with disparate degrees of urbanization.

METHODS

We conducted a population-based study in 1441 children in two communities in Peru, of which 1134 (79%) provided a blood sample for 25-OH vitamin D analysis.

RESULTS

In these 1134 children, mean age was 14.8 years; 52% were boys; asthma and atopy prevalence was 12% in Lima vs. 3% in Tumbes (P < 0.001) and 59% in Lima vs. 41% in Tumbes (P < 0.001), respectively; and, mean 25-OH vitamin D level was 20.8 ng/mL in Lima vs. 30.1 ng/mL in Tumbes (P < 0.001). Prevalence of 25-OH vitamin D deficiency (< 20 ng/mL) was 47% in Lima vs. 7% in Tumbes (P < 0.001). In multi-variable logistic regression, we found that lower 25-OH vitamin D levels were associated with an increased odds of asthma (OR = 1.7 per each 10 ng/mL decrease in 25-OH vitamin D levels, 95% CI 1.2-2.6; P < 0.01). In stratified analyses, the association between lower 25-OH vitamin D levels and asthma was limited to children with atopy (OR = 2.2, 95% CI 1.3-3.6) and not in those without atopy (OR = 0.9, 95% CI 0.5-2.0). We did not find associations between 25-OH vitamin D levels and other clinical biomarkers for asthma, including exhaled nitric oxide, total serum IgE and pulmonary function.

CONCLUSION AND CLINICAL RELEVANCE

Both asthma and 25-OH vitamin D deficiency were common among children living in Lima (latitude = 12.0 °S) but not among those in Tumbes (3.6 °S). The relationship between 25-OH vitamin D deficiency and asthma was similar in both sites and was limited among children with atopy. Future supplementation trials may need to consider stratification by atopy at the time of design.

Evidence for 14 homeobox gene clusters in human genome ancestry

The arrangement of Hox genes into physical clusters is fundamental to the patterning of animal body plans. Other homeobox genes are often described as dispersed, with only occasional examples of linkage reported, such as the amphioxus ParaHox and Drosophila 93D/E clusters. This clustering is unlikely to be the derived condition, as the genes of the ParaHox and 93D/E clusters are phylogenetically widespread. To assess whether clustering is retained in mammals, and to infer its history, we considered the distribution of ANTP superclass homeobox genes in human and mouse genomes. We postulate four ancient arrays of ANTP superclass genes in animal genomes, denoted 'extended Hox' (Hox, Evx and Mox), NKL (including NK1, NK3, NK4, Lbx, Tlx, Emx, Vax, Hmx, NK6, Msx), ParaHox (Cdx, Xlox, Gsx) and EHGbox (En, HB9, Gbx). Each of these duplicated in the ancestry of the human genome to yield four Hox, four NKL, four ParaHox and at least two EHGbox clusters or arrays. Two of the human NKL clusters (four in mouse) have subsequently been split by chromosome rearrangement, as has one human EHGbox array. We date all cluster duplications to early chordate evolution and infer that three clusters (Hox, NKL, EHGbox) resided on the same chromosome before duplication.

Neuromuscular transmission in the murine mutants "motor end-plate disease" and "jolting"

Mice with the inherited disorder "motor end-plate disease" suffered from a progressive neuromuscular weakness and muscular wasting. The weakness resulted from a failure of evoked transmitter release from the motor nerve terminals. The failure in transmission was all-or-nothing in nature. The numbers of muscle fibres in skeletal muscle and myelinated axons in several major nerve trunks were no different from normal. The loss in muscle bulk was caused by the neuromuscular defect and not from a loss of motor units or muscle fibres. The inherited murine disorder "jolting" was allelic with "motor end-plate disease". Affected "jolting" mice suffered no detectable morphological abnormality in skeletal muscle or peripheral nerve. The physiological properties of skeletal muscle and the characteristics of neuromuscular transmission were indistinguishable from normal.

Reversal of paralysis in nerve-muscle preparations isolated from animals with hereditary motor endplate disease

Motor endplate disease (med) in the mouse is an hereditary disorder of the skeletal neuromuscular system. Affected animals suffer a 'functional denervation' of skeletal muscle (Duchen & Stefani, 1971). Muscle fibres do not respond to indirect excitation, but motor nerve terminals release transmitter spontaneously. Spontaneous transmitter release can be enhanced by raising [K+]o or by exposing muscles to red-back spider venom and functional transmission following indirect stimulation may be restored by 4-aminopyridine.