MicroRNAs are small non-coding RNA (18–24 nt long) that fine-tune gene expression at the post-transcriptional level. With the advent of “multi-omics” analysis and sequencing approaches, they have now been implicated in every facet of basic molecular networks, including metabolism, homeostasis, and cell survival to aid cellular machinery in adapting to changing environmental cues. Many animals must endure harsh environmental conditions in nature, including cold/freezing temperatures, oxygen limitation (anoxia/hypoxia), and food or water scarcity, often requiring them to revamp their metabolic organization, frequently on a seasonal or life stage basis. MicroRNAs are important regulatory molecules in such processes, just as they are now well-known to be involved in many human responses to stress or disease. The present review outlines the role of miRNAs in natural animal models of environmental stress and adaptation including torpor/hibernation, anoxia/hypoxia tolerance, and freeze tolerance. We also discuss putative medical applications of advances in miRNA biology including organ preservation for transplant, inflammation, ageing, metabolic disorders (e.g., obesity), mitochondrial dysfunction (mitoMirs) as well as specialized miRNA subgroups respective to low temperature (CryomiRs) and low oxygen (OxymiRs). The review also covers differential regulation of conserved and novel miRNAs involved at cell, tissue, and stress specific levels across multiple species and their roles in survival. Ultimately, the species-specific comparison and conserved miRNA responses seen in evolutionarily disparate animal species can help us to understand the complex miRNA network involved in regulating and reorganizing metabolism to achieve diverse outcomes, not just in nature, but in human health and disease.
Vitamin D deficiency and insufficiency may further increase fracture risk in patients with decreased bone mineral density. A cross-sectional study on serum vitamin D concentrations in medical inpatients was conducted at Bassetlaw District General Hospital between April 2014 and January 2015 (10 months), and the relationship of serum vitamin D concentrations with calcium and alkaline phosphatase was evaluated. 25-Hydroxyvitamin D immunoassays were used and analyzed in the local laboratory. The total number of patients analyzed was 200, age range 18–99 years, with mean age of 76 years. The most common presentation was found to be fall/collapse. The following cutoff points for serum vitamin D were used: levels ≤30 nmol/L for severe deficiency, >30–50 nmol/L for moderate deficiency, >50–75 nmol/L for mild deficiency, and anything above 75 nmol/L as normal. Of the 209 participants examined, 78 (37.3%) participants had mild vitamin D deficiency, 54 (25.8%) participants had moderate vitamin D deficiency, 68 (32.5%) participants had severe vitamin D deficiency, and 9 (4.3%) participants with low vitamin D levels died during their admission. Of the 122 moderate/severe patients, 70 (57.4%) patients had their vitamin D deficiency treated, according to local Trust guidelines. The study found no relationship between serum calcium levels and vitamin D deficiency, whereas patients’ alkaline phosphatase levels were found to be higher with increased severity of vitamin D deficiency. The study examined the implications of untreated severe/moderate vitamin D deficiency compared to treated deficiency, in terms of the frequency of readmission with similar complaints. It was found that the rate of readmission within one year in patients who were not treated was 57%, compared to 48% in patients whose vitamin D deficiency was treated. Presenting after falls was a recurring theme. It was concluded that even if moderate vitamin D deficiency can be asymptomatic, it is important to correct it as it can have an impact on morbidity and readmission rates in the long term.
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