Diabetes mellitus is often associated with cardiovascular morbidity and this may partly be explained by the abnormal lipid profile which is sometimes a feature of DM. With heart failure and cerebrovascular disease increasingly becoming prevalent in our population, it is imperative to determine possible risk factors accounting for this scenario. One such risk factor of note is an abnormal lipid profile.
We undertook to study the pattern of lipid abnormalities in a relatively large population of DM subjects with those with types 1 and 2 DM inclusive. Type 1 DM not surprisingly made up 2% of the study population and differed significantly from type 2 DM in age and the presence of hypertension. The percentage of lipid abnormalities occurring singly or in combination at 89% was high and this was comparable to that reported in a recent Nigerian study [21
] which gave a figure of 89%. The magnitude of the detected abnormalities showed that LDL and TCHOL were the parameters that were most affected as they showed the greatest mean differences between the values in those that had abnormal and those with normal lipid profiles. Elevated cholesterol though not usually regarded as highly predictive of cardiovascular disease was noted in 42% of the participants The significance of screening for total cholesterol lies in the fact that is could serve as a valuable screening measure for dyslipidaemia. The aforestated scenario not withstanding, we report elevated LDL-C and reduced HDL as the prevalent lipid abnormalities in our study. Similar findings have been noted in a recent Nigerian report [21
] and that carried out in an African-American population [22
]. A Kenyan report [13
] on the lipid abnormalities in DM had elevated cholesterol and LDL as the commonest lipid abnormalities noted in their study.
Although we report a higher prevalence of lipid abnormalities in type 2 DM than type 1DM this difference was not significant. A Western report[23
] on lipid abnormalities in DM noted a significantly higher prevalence of lipid abnormalities in type 2 DM compared to type 1 DM. The presence of hypertension may however be contributory to the greater prevalence of dyslipidaemia in type 2 DM than in type 1 DM. The relationship between insulin resistance or compensatory hyperinsulinaemia may partly explain the aforestated scenario [24
]. Insulin resistance often leads to increased intracellular hydrolysis of triglycerides and release of fatty acids into the circulation and the resultant inability of fat cells to store triglyceride is the initial step in the development of dyslipidaemia. Other plausible explanations for the contributory effect of hypertension to abnormal lipid profiles in DM include usage of antihypertensive agents [25
]. The beta blockers and diuretic especially the thiazide diuretics have been found to negatively affect not only the lipid profile but glucose tolerance. Of these two blood pressure lowering agents, the thiazide diuretics were commonly used for the purpose of blood pressure control in our study subjects with DM and hypertension. The pattern of lipid abnormalities in types 1 and 2 differed with respect to triglyceride, TCHOL/HDL-C and LDL-C/HDL-C ratio which were all significantly higher in type 2 DM than type 1DM thus implying a higher cardiometabolic risk in subjects with type 2 DM. Although the habits of smoking cigarettes and ingesting alcohol were not widely practiced by our patients, significant alcohol and smoking histories were found to be contributory to the occurrence of dyslipidaemia.
We found that clinical parameters like age, sex, duration of DM, waist circumference, BMI type of DM and glycaemic control were not possible determinants of the presence of an abnormal lipid profile. However, sex was found to be a possible determinant of the pattern of lipid profile levels in diabetes. Other factors that were found to affect the pattern of lipid abnormalities included age and BMI. In this report, we noted that elevated TCHOL and LDL-C were found to be significantly higher in females than in males and HDL differed significantly between subjects who were underweight and all other cadre of BMI. Cook et al [22
] in their report on gender differences in pattern of dyslipdaemia noted that elevated LDL-C and reduced HDL-C were more commonly documented in females than males. Bowden et al [26
] found gender differences in the HDL-C, LDL-C and TG components of the lipid profile in non -diabetic individuals. From the foregoing it is evident that gender differences are consistently noted in LDL-C in individuals with and those without DM. Although the mean values of the atherogenic indices were comparable in both sexes, the proportion of women with abnormal atherogenic indices was significantly higher than men.
Elevated triglyceride was more significantly elevated in the middle and elderly age group than in the younger age group. The prevalent combination of lipid abnormalities was that of elevated TG and reduced HDL, two defining parameters of the metabolic syndrome [16
]. These two lipid abnormalities are the most commonly noted abnormalities of the standard lipid profile in subjects with obesity and insulin-resistance-related cardiometabolic risk.
We have showed that lipid abnormalities are underdiagnosed in our patients with DM as despite a documented high prevalence of dyslipidaemia only 8% of affected individuals were on treatment.