| ObjectiveIn order to provide a clinical evidence of avoiding or attenuating diabetic complications by a novel way of anti-nitrition of proteins in type 2 diabetic patients, the present study was done to try to find out a possible correlation between diabetic blood glucose control and protein nitrition, a relationship between 3-NT levels and risk factors of cardiovascular disease in diabetic patients, a relationship between 3-NT levels and different food categories and their intakes of diabetic patients by detecting serum 3-nitrotyrosine levels of type 2 diabetic patients and their matched control subjects patients.MethodsSubjects and measurements:A randomized case-control trial was carried out, in which 109 type 2 diabetic patients (diabetic case group) and 57 non-diabetic patients (control group) were enrolled. Dietary survey, anthropometric measurements, blood biochemical markers and serum 3-NT levels were done in all subjects. Food Frequency Questionnaire (FFQ) was used for the dietary survey, and duration of the diet retrospect was one year. Anthropometric measurements included body height, body weight, body mass index (BMI). Blood biochemicals were fasting blood glucose, glucosylated serum protein (GSP), HbAlc, insulin, total cholesterol (TC), triglyceride (TG) and apolipoproteins.Apparatus: Body weight were carried on a TZ-1 weighing scale and anthropometric measurements were meadsured on a BCA-2 body analyzer manufactured by Zhongti Tongfang Sports Tech, Ltd. Blood biochemicals were measured by Hitachi 7600 automatic biochemical analyzer.3-NT detection: 3-NT in blood was determined by ELISA kit (Hycult biotechnology bv, Lot#:5822k19). Blood samples were freshly-collected serum, diluted by 25 times. Each sample was set by a parallel reference. 450nm absorption spectrum was measured by Unico UV-2000 Spectrophotometer.Quality control: Specific food models were adopted for the subjects as references of dietary survey to estimate daily intakes of foods such as rice, flour, eggs, milk, fruits, oil, alcohol, tea and so on. All researchers were trained uniformly and data was collected by particular persons.Statistical analysis: Data are expressed as means±s.d. SPSS 13.0 Version for Windows was used for statistical analysis. The level of significant difference was set at P<0.05. Different groups were compared by repeated-measures analysis of variance. When significant differences occurred, related means were then compared by Student's t-test between the two groups, and between the initial and final means in the same group.ResultsLevels of 3-NT in diabetic case group were much higher than those in their matched control group, while 3-NT levels were higher in both male and female diabetic patients than those in non-diabetic male and female patients, respectively(p<0.05). In diabetic case group, 3-NT levels increased with elevation of Body Mass Index (BMI). Male patients with BMI>24kg/m2 had much higher 3-NT levels than those with normal BMI(18.5-23.9) (p<0.05). Diabetic patients with blood glucose >6.1mmol/L had much higher 3-NT levels than those with glucose≤6.1mmol/L (p<0.05). Diabetic patients with HDL-c >1.6mmol/L had lower 3-NT levels than those with normal HDL-c concentration(p<0.05). In diabetic case group, patients with TC more than 5.7mmol/L had lower 3-NT level than those with TC less than 5.7mmol/L (p<0.05). The percentage of energy from dietary fat was significantly higher than RNI in both groups, and the dietary patterns were significantly unreasonable. Daily fat intake in diabetic group was much higher than in control group (p<0.05), while the percentage of energy from carbohydrate was lower than RNI;Daily intake of vitamin B1 and B2 were much lower in diabetic group than in control group (p<0.05), however, daily intake of sodium showed the opposite trend. Daily intake of vitamin C, sodium, iron, manganese, copper, phosphorus were higher than RNIs in both groups, as well as daily intake of vitamin A, vitamin B1, calcium in control group were lower than RNIs (p<0.05). Daily intake of staple food were much lower in diabetic group than in control group (p<0.05). However, daily intake of milk, beans and salt were on the contrary (p<0.05). Daily intakes of carotene, ascorbic acid, folic acid were higher in the HDL-c<1.6 mmol/L group than the HDL-c>1.6 mmol/L group. Serum 3-NT levels had a linear regressive relationship to LDL-c, GSP, and HbAlc in diabetic group. ApoA II and ApoC3 had the most relevant to serum 3-NT levels in male diabetic patients. GSP and HbAlc had the the most relevant to serum 3-NT levels in female diabetic patients. Triglyceride and ApoC3 were the most related with serum 3-NT levels in patients with blood glucose higher than 6.1mmol/L.HbAlc, GSP and ApoC3 were the most highly relevant to serum 3-NT levels in diabetic subjects with HDL-c concentration lower than 1.6mmol/L. Daily intakes of Na, K, Fe had accordingly linear regressive relationships to serum 3-NT levels among 3-NT levels and nutrient intakes.Conclusions3-NT levels in type 2 diabetics patients were much higher than those in their non-diabetic control subjects, which demonstrated that nitrosative injury indeed existed in diabetes. This provides the theoretical basis of anti-nitrition for type 2 diabetics and their cardiovascular complications.3-NT levels in type 2 diabetic patients with poorly controlled blood glucose were much higher than those in the corresponding control group. This conclusion further expands the importance of blood glucose control in diabetes. 3-NT levels in overweight and obese diabetic patients were much higher than those in the corresponding control group. This has laid a theoretical basis for dietary intervention for body weight control to reduce complications of diabetes.The relationships of 3-NT levels to risk factors of diabetic cardiovascular complications are as follows: The serum 3-NT levels and LDL-c, TC showed significant negative correlation. In diabetic patients with poor control of blood, the serum 3-NT levels and Apo C3 showed negative correlation. The possible mechanism is that excessive oxidative damages exist in diabetic patients, whose serum 3-NT levels are high, resulting in the peroxidation of lipids. Therefore, reducing oxidation and production of 3-NT might be a great significance to controlling diabetes and their cardiovascular complications.Daily intakes of Na, K, Fe had respective linear regressive relationships to serum 3-NT levels in diabetic patients, while VitB1 and VitB2 had negative relationship to 3-NT. Therefore, increasing dietary intakes of vitamin B and potassium and reducing dietary intakes of sodium and iron may be beneficial to reducing generation of 3-NT and its related diabetic complications. |
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