Cystatin C And The Risk Of Mild Cognitive Impairment In Elderly People With Type 2 Diabetes Mellitus

BACKGROUNDThe increase of prevalence of type 2 diabetes and cognitive impairment, which are very susceptible disorders in elderly people, is becoming a serious medical problem in the world. Epidemiological investigations show that type 2 diabetes can enhance the occurrence of mild cognitive impairment (MCI). Mild cognitive impairment is the middle state of normal aging and dementia. If mild cognitive impairment at early stage is screened and identified, appropriate interventions will be taken. Therefore, dementia should be prevented and delayed. Unforturenately there is no good screening measures available for current use.Cystatin C is associated with neural degeneration through amyloid-beta(Aβ), regeneration and degeneration of neuron, apoptosis and oxidative stress. It is related to diabetic complication closely, especially to atherosclerosis. CST3 is the coding gene of Cystatin C. Most of investigations consider that CST3 B is the risk factor of Alzheimer's disease(AD). CST3 BB is related to the decrease secretion of Cystatin C in system. The current findings of Cystatin C and CST3 are inconsistent with some reports of protective effect of Cystatin C on cognitive function while some reports of accelerative effect of Cystatin C on cognitive function impairment and other reports of no relationship between Cystatin C and the cognitive function. The reason of this contrary is that the researchers used to choose different stage of AD. Cystatin C shows its marked protective effect at the mild cognitive impairment stage, namely at the early stage of AD. Serum Cystatin C can be precisely detected by immunoturbidimetry. However, it is unknown whether the concentration of serum Cystatin C is related to system Cystatin C and to mild cognitive impairment in elderly type 2 diabetes mellitus so far. Participants are recruited from veteran cadre nursing home in shanghai China. It iseasy to put epidemiological survey into practice under the integrated healthcare system with intact clinical data and comprehensive management. Dependable data are warranted and epidemiological survey can be completed with high quality.The molecular epidemiology method was employed in this study to investigate the relation between serum protein which is related to mild cognitive impairment and gene on mild cognitive impairment in elderly type 2 diabetes mellitus. It is of significance on explanation of the mechanism of mild cognitive impairment combined with elderly type 2 diabetes mellitus and mild cognitive impairment, and formulation of relevant protective strategies. So far, there is neither literature reporting the association between polymorphism of CST3 and mild cognitive impairment in elderly type 2 diabetes mellitus nor study on analysis of the relationship between serum Cystatin C concentration and its gene polymorphism and mild cognitive impairment combined with elderly type 2 diabetes mellitus.OBJECTIVETo investigate systematically the relationship between serum Cystatin C, CST3 and mild cognitive impairment in elderly people with type 2 diabetes mellitus from the point of view on serum Cystatin C and its polymorphism. To probe the risk factor of mild cognitive impairment. To describe the characteristic of genotype and allele frequency of CST3AA/BB/AB in elderly type 2 diabetes mellitus of veteran cadre nursing home in shanghai China.PARTICIPANTS AND METHODS1. Participants156 eligible candidate were recruited from veteran cadre nursing home in shanghai China diagnosed as having elderly type 2 diabetes mellitus under according to criterion (diagnostic criteria:1999 WHO). Exclusion criterion: patient with history of hypoglycemia, ketoacidemia coma, other endocrine system diseases, immune diseases, other central nervous system diseases, serious handicap of hearing, seeing and limbs moving affecting cognition function measurement. Referring to the American psychiatric society the diagnostic and statistical manual of mental disorders (the fourth revision of DSM-IV) and 2004 international group proposed generalized MCI diagnostic criteria of MCI: (1) the cognitive dysfunction, but did not reach dementia diagnostic criteria, (2) the cognitive function decline, patients and /or insider confirmed and objective examination confirmed in cognitive damage, (3) ability to remain normal daily life, life ability of manipulating complex tool is normal or minor damaged. Participants were divided into diabetes mild cognitive impairment group (T2DM-MCI) and the diabetes with normal cognitive function group (T2DM-NC).T2DM-MCI group (n=79): complaints of cognitive impairment or the clinical significance of the cognitive decline provided by insider with associated symptoms for 6 six months. Overall cognitive function is basically normal, total score is in the normal range by simple mini-mental state examination (MMSE). M19-25 point in Montreal cognitive assessment scale (MOCA). At least one impairment but mild abnormalty in a cognitive areas by Cognitive function scale examination, (each points boundary value less than 1.5 SD). Activities of Daily living scale (ADL)<26 points; general degenerating scale (GDS) is 2~3 grade. T2DM-NC group (n=77): all the cognitive function test items are in the normal range. No social adaptation ability damagement with ADL < 26 points, grade 1 of GDS.2. Research methodsMMSE was adopted in screening patients with dementia with requirement to stratified according to the education degree by illiteracy(≥20 points ,education time< 1year), the primary school (≥23 points, education time 1~6 years), high school and above (≥27 points, education time≥7 years). Depressive symptoms were exclusive by screening with the self-administrative scale of depression(CES-D), accord with the criterion of CES-D≤15 points. Anxiety symptoms were eliminate with SAS< 50 points using anxiety self rating scale(SAS). Parkinson's disease symptoms were eliminated with SSPD <1 points adopting Parkinson's screening scale(SSPD). daily living skills were assessed with< 26 points adopting ADL. Cognitive damage degrees were evaluated using GDS. MOCA was adopted for evaluation of patients cognitive functions of executive function, visual spatial memory, attention, naming, language, abstract, delayed recall and directional force in MCI group. Latex enhanced immunoturbidimetry was used to detect the serum Cys C protein level. glycated hemoglobin(HbAlc) was measured with HPLC. Triglycerides (TG) and total cholesterol (TC) was determined with enzymatic methods. Polymerase chain reaction- restriction fragment length polymorphism method (PCR-RFLP) was used to detect CST3 gene polymorphism.According to the frequency controlled study requirements to match gender, age and education level on two groups . 3. StatisticsData were analyzed with SPSS17.0 statistics packages for processing. Qualitative data were presented with mean±SD. The independent sample t-test or one-way ANOVA was adapt to describe continuously variable. CST3 genotype and allele frequency were calculated with gene notation calculation. The chi-squareχ2 test was used to compare the research objects and the accord with Hardy-Weinberg balance, between groups and extent genotype and allele frequency. Double continuity normal distribution variables were analyzed by Pearson relation. Rank or half quantitative data and abnormal distribution or general distribution types of continuous variables were analyzed with spearman rank correlation. Single factor and multi-factor unconditional Logistic regression model were used for analysis of risk factors for MCI elderly patients with type 2 diabetes.RESULTS1. Comparison of T2DM-MCI group to T2DM-NC groupParticipants with hypertension significantly increased T2DM-MCI, and MCI significantly increased among hypertension patients. There is significant difference statistically(P<0.001) in the combination of hypertension between two groups. Duration of diabetes and HbA1c were significantly deferent(P<0.001) between these two groups. The duration of diabetes and HbA1c are increased in T2DM-MCI group and the difference in FBG was at the edge of statistical significance(P=0.059). There are not statistically significant differences of BMI mean and distribution, TG, TC and SCr between two groups(P>0.05). Serum Cys C level was obviously increased in T2DM-MCI group with statistically significant difference(P=0.018). MMSE(P=0.049) was statistically significant differences between two groups. There is significant difference statistically in MOCA between two groups(P<0.001). AA, BB, AB genotype frequency (68.3%, 7.6%, 24.1% respectively) in T2DM-MCI and those (83.1%, 1.3%, 15.6% respectively) in T2DM-NC group. The comparisons of two groups:χ2=5.975, P=0.050. A allele frequency in T2DM-MCI group and in T2DM-NC group were 80.4% and 90.9% respectively, B allele frequency in T2DM-MCI group and T2DM-NC group were 19.6% and 9.1%respectively, there is statistically significant differences with comparisons of two groups:χ2=7.005, P=0.008. 2. Comparison among AA/BB/AB genotype of CST3There is no statistically significance between deferent genotypes of hypertension, BMI distribution, MMSE total score, duration of diabetes, HbA1c, FBG, TG and TC (P>0.05). There is statistically difference in SCr among the three groups (F=2.359, P=0.043). There is statistically significant difference in Cys C in three groups (F=49.928, P<0.001) with CST3 BB genotype setting largest value. There is a significant difference of the total score MOCA (F=6.802, P=0.001) with the lowest scored of MOCA in CST3 BB genotype and highest score of MOCA in CST3 AA genotype.3. Correlation analysis of Cystatin C/CST3 and mild cognitive impairmentSerum Cystatin C (r<0, P<0.05) is negative correlated with MMSE (r=-0.304), MOCA (r=-0.593), Visuospatial/Executive (r=-0.306), Naming (r=-0.246), Attention (r=-0.242), Language (r=-0.252), Delayed recall (r=-0.241). There is no statistically significance in Abstraction in MOCA (P=0.646) or Orientation (P=0.907). There is higher correlation of serum Cystatin C and occurrence of T2DM-MCI. The higher level of serum Cystatin C the higher risk of T2DM-MCI. The group of serum Cystatin C=1.16~1.80 mg/L are more likely to cause mild cognitive impairment compare to those <1.16 mg/L (OR 3.205, 95%CI 1.075 to 9.554, P=0.037), and the group of serum Cystatin C>1.80 mg/L are more likely to cause mild cognitive impairment compare to those <1.16 mg/L (OR 4.500, 95%CI 1.390 to 14.568, P=0.012). Diabetes course (OR 3.246, 95%CI 1.706 to 6.176, P<0.001), HbA1c (OR 5.016, 95%CI 2.104 to 11.961, P<0.001), high blood pressure (OR 3.668, 95%CI 1.636 to 8.223, P=0.002), serum Cystatin C (OR 2.272, 95%CI 0.988 to 5.226, P=0.053) and carry with CST3 B allele (OR 2.279, 95%CI 1.064 to 4.882, P=0.034) are all risk factors of mild cognitive impairment in elderly people with type 2 diabetes mellitus.CONCLUSIONMultiple risk factor including longer duration of diabetes, higher blood pressure, higher serum Cystatin C, higher HbA1c and carry with CST3 B allele induce the mild cognitive impairment in elderly people with type 2 diabetes mellitus. The increase of serum Cystatin C level is correlation with multiple symptom of mild cognitive impairment. There is CST3 AA/BB/AB polymorphism in the population of veteran cadre nursing home in shanghai China. The increased level of serum Cystatin C in CST3 BB group suggests that serum Cystatin C level is inconsistent with system Cystatin C level. The detection of serum Cystatin C and CST3 polymorphism must be helpful in early diagnosis of mild cognitive impairment in elderly people with type 2 diabetes mellitus.