[Vitamin supply of patients with type 2 diabetes mellitus complicated by nephropathy]

Insufficient vitamin content in the diet is a risk factor for the development of various diseases and their progression, and drug therapy can also contribute to the development of a deficiency of these micronutrients. Data on vitamin sufficiency of patients with type 2 diabetes mellitus (T2DM) and diabetic nephropathy (DN) are needed to develop measures to improve it. The aim of the research was to compare vitamin status of patients with T2DM without DN and those with T2DM complicated by nephropathy by assessing vitamin blood level and urinary excretion. Material and methods. In a single-stage research, 57 patients with T2DM and concomitant obesity (14 men, 43 women aged 42-75 years) have been examined. The 1st group included 26 patients with T2DM (7 men and 19 women, BMI 41.5±1.7 kg/m²) with glycated hemoglobin (HbA1c) - 8.0±1.4%, blood serum glucose level 8.1±0.6 mmol/l, glomerular filtration rate (GFR) - 86.7±3.0 ml/min per 1.73 m², microalbuminuria - 18.0±2.0 mg/day. The 2nd group included 31 patients with T2DM complicated by DN (7 men and 24 women, BMI 42.5±1.3 kg/m²), with an HbA1c level of 6.4±0.2%, blood serum glucose level 6.8±0.3 mmol/l, GFR - 62.8±2.7 ml/min per 1.73 m², microalbuminuria - 59.5±22.5 mg/day. The determination of vitamins С (ascorbic acid), A (retinol), E (α- and γ-tocopherols), D [25(OH)D], B₂ (riboflavin) and β-carotene in blood serum and vitamins C (ascorbic acid), B₁ (thiamine), B₂ (riboflavin) and B₆ (4-pyridoxic acid) in the morning portion of urine collected on an empty stomach within 40-120 min was carried out. The vitamin status was assessed based on the concentration of vitamins in blood serum and urinary excretion relative to the lower limit of the norm, as well as using the criteria for the optimal supply and 2 molar ratios. Results. Compared to patients with T2DM without nephropathy, patients with DN were better provided with vitamins B₂, A and β-carotene: vitamin B₂ deficiency was found 3.2 fold less often (in 9.7%), β-carotene - 1.8 fold less often (in 35.5%), nonoptimal retinol level occurred twice less often (in 41.9%). At the same time, serum α-tocopherol level below the optimal level was found in 67.7% of individuals versus 50% among patients with T2DM without nephropathy, with a significantly reduced urinary excretion of vitamins B₁ and B₂. With the exception of one man, the rest of the DN patients had a deficiency or lack of vitamin D. The characteristic features of the vitamin status of patients in both groups were the complete absence of individuals who were simultaneously optimally provided with all the studied vitamins and β-carotene (when assessing the vitamin status using both the absolute serum vitamer levels and 2 additional molar ratios), and a high frequency of detection of several simultaneously non-optimal vitamin status indicators. A negative correlation was found between blood serum level of β-carotene and glycemia (ρ=-0.359, p=0.006), as well as GFR (ρ=-0.289, р=0.029) and positive with high-density lipoprotein cholesterol (ρ=0.423, р=0.001), that indicated the need to increase this antioxidant blood level in patients with T2DM. The presence of a negative correlation between the concentration ratio of vitamins C and E and glucosuria (ρ=-0.288, p=0.033) and postprandial glycemia (ρ=-0.313, p=0.031) indicated the need to maintain it at an optimal level. Conclusion. For patients with T2DM and concomitant obesity, vitamin D and β-carotene turned out to be the most problematic, since their reduced levels are detected more often than other vitamins. In addition to the optimal blood level of vitamins C and E, it is extremely important for them to maintain the blood molar ratio of ascorbic acid and α-tocopherol at an optimal level. The purposefully development of specialized vitamin complexes containing effective doses is necessary for patients with DN.