Vitamin D status positively associates with skeletal muscle mass and function in adolescents. The C-3 alpha epimer of 25-hydroxyvitamin D3 (3-epi-25(OH)D3) is high in infants, yet the potential impacts of 25-hydroxyvitamin D3 (25(OH)D3) and 3-epi-25(OH)D3 on skeletal muscle development are largely unexplored. The objective of this study was (i) to explore how the concentrations of 25(OH)D3 and 3-epi-25(OH)D3 track with body composition (lean mass (LM) and fat mass (FM)) and (ii) to determine the association between 25(OH)D3 and 3-epi-25(OH)D3 in infancy. Healthy breastfed infants (n = 132) were followed from 1 to 12 months of age as part of a vitamin D dose-response study (NCT00381914). Anthropometry and diet were assessed. Body composition was measured with dual-energy X-ray absorptiometry. Plasma 25(OH)D3 and 3-epi-25(OH)D3 concentrations were evaluated using liquid chromatography tandem mass spectrometry. Plasma 25(OH)D3 and 3-epi-25(OH)D3 increased from 1 to 3 months of age and decreased thereafter (p < 0.05). Infants with 25(OH)D3 concentrations above 75 nmol/L did not have a higher LM (g or %; p > 0.273) than those below this cutoff. LM was not associated with 25(OH)D3, whereas LM% was positively associated with 25(OH)D3 (β = 0.03; CI: 0.01 to 0.06; p = 0.006), while accounting for sex, weight-for-age Z-score, protein and fat intake, and age. For FM, the variables accounting for a significant amount of the variation were plasma 25(OH)D3 concentration (β = -2.38; CI: -4.35, -0.41; p = 0.019), weight-for-age Z-score, protein and fat intake, and time. In healthy infants, higher vitamin D status associates with leaner body composition, though the effect is smaller in magnitude relative to growth.

BackgroundCOVID-19 is a new infectious disease with severe disease course and high mortality in some groups. Blood tests on admission to the hospital can be useful for stratification of patients and timely correction. Our study investigated the clinical features of COVID-19 patients in Latvia and differences in blood tests in groups with different disease severity.MethodsThe retrospective study included 100 patients hospitalized in Riga East Clinical University Hospital in Spring 2020. The severity of the disease course was classified by the presence of pneumonia and its combination with respiratory failure. We have assessed blood cells’ count, hemoglobin, hematocrit, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), alanine aminotransferase, lactate dehydrogenase (LDH), troponin T, electrolytes, creatinine, glomerular filtration rate (GFR), D-dimer, prothrombin time, prothrombin index, oxygen saturation, and temperature on admission to the hospital.ResultsPatients were from 18 to 99 (57±18 years, 57% males). Comorbidities were found in 74% of patients. The mild, moderate, and severe groups included 35, 44, and 16 patients, respectively. In the severe group, the mortality rate was 50%. The progression to severe COVID-19 was associated positively with temperature, ESR, CRP, creatinine, LDH, and troponin T and negatively associated with oxygen saturation, eosinophils, and GFR on admission to the hospital.ConclusionsCOVID-19 severity associates with lower renal function and a higher level of inflammation and tissue damage. Eosinophils, CRP, ESR, LDH, troponin T, creatinine, and GFR are blood indicators for monitoring patients’ condition.