Lipoprotein (a) level and other laboratory variables in diabetic patients

Objective: to evaluate the clinical and diagnostic significant of lp (a) levels and other lipid and apolipoprotein profiles in diabetic patients compared with different categorization of diabetic patients. Method: Case control study determined the levels of lp (a), apolipoprotein A1, apolipoprotein B, Total Cholesterol (TC), Triglyceride (TG), Low Density Lipoprotein (LDL), High Density Lipoprotein (HDL) and fibrinogen in 100 diabetic patients with both types (40 were Insulin Dependent Diabetic Mellitus, IDDM and 60 were Non-Insulin Dependent Diabetic Mellitus NIDDM) and compared with normal healthy subjects. Results: lp (a), apolipoprotein B, TC, TG and LDL were significantly higher in patients than control healthy subjects (p<0.05), apolipoprotein A1 and HDL were significantly lower in patients than control healthy subjects (p<0.05). No significant difference found in Fibrinogen between patients and controls. Lp (a) levels in obese patients significantly higher than in normal weight (p<<0.05). lp (a) in patients with Coronary Heart Disease (CHD) was significantly higher than patients without CHD (p<0.05). Lp (a) was significantly higher in NIDDM than in IDDM (p<0.05). Conclusion: The study confirmed that the Lp (a) and other lipid and apolipoprotein parameters were significantly raised (good lipid decreased (apo A1 and HDL)) in diabetic patients compared to healthy subjects, and lp (a) are important diagnostic marker that can be used for early detection of atherosclerotic cardiovascular disease (CVD) in diabetic patients.


INTRODUCTION
Lipoprotein (a) [Lp (a)] is a plasma lipoprotein consisting of a LDL-like particle with a molecule of apolipoprotein B100 covalently linked to a very large additional glycoprotein known as apolipoprotein (a).Elevated Lp (a) levels constitute an independent risk factor for cardiovascular disease in the general population (Nordestgaard et al., 2010).Apolipoprotein (a) is characterized by a high degree of genetic polymorphism, with many isoforms in plasma (Marcovina et al., 1993).Lp (a) has atherogenic and thrombotic properties and is considered to be a major risk factor for the development of atherosclerotic disease.Lp (a) has been considered as an independent risk factor for atherosclerosis.Lp (a) is a variant of LDL and is similar to LDL in lipid composition (Davies etal, 1992).It consists of one or two molecules of apoprotein (a) [apo (a)} linked to apoprotein B-100 by a disulfide bridge (Scanu, 1992).Apo (a) is a distinctive glycoprotein of Lp (a) and is structurally homologous to plasminogen (a key protein) (Scanu, 1992), (Jurgens et al., 1994) and (Ridker et al., 1995) for the fibrinolytic system.Many epidemiologic and prospective studies have revealed elevated levels of Lp (a) in persons with Coronary Heart Disease (CHD) (Bostom, 1996) and (Ramirez et al., 1992) suggesting the importance of Lp (a) in the underlying mechanisms for the development of atherosclerosis in diabetics.But its may has not been determined in these subjects (Khan & Abdul Baseer, 1998).Many studies have shown that Lp (a) levels are closely associated with premature CHD (Garg, 1992).This study was conducted to evaluate the clinical and diagnostic significant of lp (a) levels and other lipid and apolipoprotein profiles in diabetic patients compared with different categorization of patients.

MATERIAL AND METHODS
Subjects: A hundred Sudanese diabetic patients (40 type1 and 60 type 2) (61 male, 39 female), a mean average age of 46±1.6year(ranged from 4 to 78 year), were visiting outpatient clinic of Jabir Abu Alizz Diabetes Centre (Khartoum, Sudan) for treatment and follow up, were enrolled in the study.The patients compared with 50 healthy subjects as a control group of non-diabetic patients randomly selected as relatives of patients and other co-patients.The objectives of this study were verified for all patients and healthy subjects to obtain their consent.Methods: blood samples collected from a subjects (patients and control) when they were fasting, (3ml) in plain containers using disposable syringes.All blood samples were allowed to clot at room temperature and then centrifuged at 4000 R.P.M to obtain the serum.Lipemic samples were cleared by ultracentrifugation.Fibrin formation due to centrifuging of serum samples before a complete formation of clot is avoided to prevent erroneous results.Some samples particularly those from patients receiving anticoagulant therapy, required increased clotting time.Specimens of about (500-600 µl) clear serum were preserved at 2-8C prior to processing.
Glucose (immediately determined), Cholesterol, Triglyceride, HDL, and LDL were measured spectrophotometrically.Apolipoprotein A1 Apolipoprotein B and Lipoprotein (a) were determined by quantitative immunoturbidimetry method.Fibrinogen was determined in plasma spectrophotometrically.Body mass index (BMI): was calculated from standard formula (Kg/m2).Statistical analysis: the data were analyzed SPSS version 19, analysis of variance and t-test used for analysis, and Pearson correlation.The probability P<0.05 consider significant.

RESULTS
Age and gender were matched between groups and Anthropometrics and Biochemical Characteristics of Patients and Control Subjects reported in Table 1.According to biochemical measurements, Lp (a)showed highly significant in patients both groups of diabetes compared to control group (p<0.01), and also showed significant difference in NIDDM compared to IDDM (p<0.05)there were significant difference when compared Total Cholesterol, Triglyceride, LDL, HDL apo A1 and apo B. (p<0.05).Lp (a) in different categorization of patients, showed no significance when compared with gender, but showed significant different when compared in different category of BMI and according to present and absent of hypertension (p<0.05).The Table 2 and.Fig. 1 explain that lp (a) was directly proportional with age.According to data obtained from Table 3, lp (a) was directly correlated with FBG, LDL, and apo B significantly; and correlated inversely with HDL and apo A1 significantly (p<0.05),but no no significant correlation with TC and TG.

DISCUSSION
The major finding of the present study revealed increased level of Lp (a) in patients with diabetes mellitus compared with a healthy subjects; this finding agree with Ramirez et al., 1992 andKhan etal.1998Both reported that uncontrolled diabetes have high Lp (a) level, also suggested that metabolic abnormality contributes to the elevated coronary risk in diabetic subjects.But Taupin et al., 1993 Tseng, 2004 disagree with this finding.Also according to the patients with CHD Lp (a) level showed significant increased.This agrees with Ramirez et al., 1992 andBostom et al., 1996. Lp (a) showed proportion association with the age of patients in this study, this disagree with Boronat et al., 2012.The elevated cardiovascular risk of diabetic patients is only partially explained by the presence of conventional cardiovascular risk factors, such as glycemic control, lipid abnormalities, hypertension and visceral obesity.This has suggested that additional risk factors, such as genetic risk factors, may favor the increased cardiovascular morbidity and mortality observed in diabetic patients (Nathan et al., 2005) Among the genetic risk factors, Lp (a) and apo (a) polymorphism has been evaluated.As the process of atherosclerosis starts in childhood, the risk factors should be assessed and prevention of atherosclerosis should start in childhood (Buscaglia et al., 1995) and(Gazzaruso et al., 1996).Diabetes, the most common non-communicable disease in Sudan, is having an increasing impact on rates of morbidity and mortality.The spread of sedentary lifestyles and adoption of western Dietary habits-high in refined carbohydrates and fat -are driving an increase in the number of people with obesity-related type 2 diabetes (Ahmed & Ahmed, 2001).Physician at primary health care should be motivated to identify the problem and implement necessary remedial and preventive measures focusing on weight control, controlling dyslipidemia and diabetes.

CONCLUSIONS
The study confirmed that the Lp (a) and other lipid and apolipoprotein parameters were significantly raised in diabetic patients compared to healthy subjects, and Lp (a) are important diagnostic marker that can be used for early detection of atherosclerotic cardiovascular disease (CVD) in diabetic patients.

REFERENCES
 a: significant compared to normal weight.b: significant compared to patients without CHD.

Fig. 1 :
Fig. 1: Lp (a) mean levels in different age groups of patients

Table 1 :
Anthropometrics and Biochemical Characteristics of Patients and Control Subjects: significant compare to control.** significant compare to IDDM. The table shows the data as Mean±SD  P-value ≤ 0.05 is considered significant *

Table 2 :
Lp (a) level according to genders, BMI andpresent or absent of CHD in diabetic patients: b  The table shows the data as Mean±SD  BMI: Body Mass Index.CHD: Coronary Heart Disease.

Table 3 :
Pearson correlation between Lp(a) and different biochemical variables in diabetic patients