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Background Hyponatremia, the most common electrolyte disorder, has been reported to be related to increased mortality. However, the association between hyponatremia and prognoses remains unclear in patients with nutrition support team (NST) intervention. This study aimed to determine the prevalence of abnormal serum sodium levels, its relation to patient data, and the impact of hyponatremia on prognosis. Methods Patients who received nutrition support at Tokushima University Hospital for the first time and whose serum sodium levels were measured at the start of NST intervention were enrolled. Patients were classified into three groups according to their serum Na levels at the start of NST intervention: hyponatremia group, normonatremia group, and hypernatremia group. Results In the hyponatremia group compared to the normonatremia group, body weight and body mass index were significantly lower. C-reactive protein levels and urea nitrogen/creatinine ratios were significantly higher. Meanwhile, there was no significant difference in the estimated glomerular filtration rate among the groups. The prevalence of malnutrition and anemia were the highest in the hyponatremia group. The 3-year survival rate was approximately 45% in the hyponatremia group, which was the lowest of all three groups. The mortality risk ratio of the hyponatremia group to the normonatremia group was 2.29. Conclusions Hyponatremia in NST intervention patients is an independent prognostic predictor. Therefore, adding an assessment of serum sodium at the beginning of NST intervention can identify patients at high risk at an early stage and may improve the quality of NST activity.

Decreases in plasma vitamin D concentrations have been reported in diabetes, although the mechanism involved in this decrease is unclear. Here, we investigated the association between Cyp24a1, a vitamin D catabolic enzyme, and abnormalities in vitamin D metabolism in streptozotocin-induced diabetes rats, an animal model of type 1 diabetes. Plasma 1,25-dihydroxyvitamin D [1,25(OH)2D] levels were significantly lower in streptozotocin-induced diabetes rats and renal Cyp24a1 mRNA expression levels were increased. Western blotting analysis of streptozotocin-induced diabetes rats kidney tissues with anti-CYP24A1 antibody showed a strong signal around 40 kDa, which differs from the predicted 50–55 kDa molecular weight for full-length Cyp24a1 and could represent the Cyp24a1-splicing variant that lacks exons 1 and 2. We observed high levels of renal Cyp24a1-splicing variant mRNA expression in streptozotocin-induced diabetes rats. We also confirmed transcriptional up-regulation of endogenous Cyp24a1 mRNA expression through glucocorticoid receptors by glucocorticoid in opossum kidney proximal cells. Taken together, our results indicated that high Cyp24a1 expression levels may play a role in the decrease of plasma 1,25(OH)2D levels in streptozotocin-induced diabetes rats. High plasma corticosterone levels in diabetes may affect transcriptional regulation to promote increases in Cyp24a1 expression.

In this study, we investigated the relationship between age-related changes in renal α-Klotho gene expression, vitamin D metabolism and the responsiveness of dietary phosphate in 1, 2 and 13 month-old mice fed a high phosphate (phosphate 1.2%) diet or low phosphate (phosphate 0.02%) diet for 5 days. We found that 1,25-dihydroxyvitamin D levels in plasma were significantly lower in the high phosphate group than the low phosphate group for 1 and 2 month-old mice, but not 13 month-old mice. In addition, in the high phosphate group plasma 1,25-dihydroxyvitamin D levels were decreased in 2 month-old mice relative to 1 month-old mice, but 13 month-old mice had higher levels than 2 month-old mice. In fact, plasma 1,25-dihydroxyvitamin D levels showed a significant correlation with vitamin D metabolism gene Cyp27b1 and Cyp24a1 mRNA expression in the high phosphate group. Interestingly, renal α-Klotho mRNA and protein levels were significant change with age. Furthermore, α-Klotho mRNA expression showed a significant negative correlation with plasma 1,25-dihydroxyvitamin D levels in the high phosphate group. Our results suggest that age-related alterations in renal α-Klotho expression could affect the responsiveness of dietary phosphate to vitamin D metabolism.

The physiological activity of the steroid derived hormone vitamin D is regulated by several enzymatic steps. Both 25-hydroxy vitamin D