Adriana Branchi

Accuracy of calculated serum low-density lipoprotein cholesterol for the assessment of coronary heart disease risk in NIDDM patients

OBJECTIVE To evaluate the accuracy of LDL cholesterol calculated with Friedewalds equation in the assessment of cardiovascular risk in NIDDM patients. RESEARCH DESIGN AND METHODS The calculation of LDL cholesterol according to Friedewalds formula was compared with the measurement of LDL cholesterol separated by ultracentrifugation in 151 NIDDM patients with fairly good metabolic control (HbA1c ≤10%) and in 405 nondiabetic subjects. RESULTS Measured and calculated LDL cholesterol was found to be well correlated in both diabetic (r = 0.95) and nondiabetic (r = 0.97) subjects. Compared with measured LDL cholesterol, the calculated LDL cholesterol differed by ≥10% in 34% of samples from diabetic patients and in 26% of samples from nondiabetic subjects (χ2 = 3.885, P < 0.05). The percentage of error increased when the serum triglyceride (TG) level was ≥200 mg/dl (2.26 mmol/l) and when the ratio of VLDL cholesterol to TG was <0.20 or >0.29 in both groups of subjects. Although the percentage of error from calculated LDL cholesterol was greater in diabetic than in nondiabetic subjects because of the greater prevalence of hypertriglyceridemia in the former group, the misclassification of coronary heart disease risk, according to the cutoff points of the National Cholesterol Education Program (NCEP), was similar in the two groups (25% in diabetic and 22% in nondiabetic subjects). In both groups of patients, the misclassification of coronary heart disease risk was higher when calculation of LDL cholesterol produced values near the cutoff points. CONCLUSIONS Although accuracy in the estimation of LDL cholesterol is less than ideal, Friedewalds equation seems to be of value in the correct assignment of coronary heart disease risk classes in the great majority of diabetic as well as nondiabetic subjects. Caution must be exercised for subjects in whom calculated LDL cholesterol is close to the cutoff points of the NCEP guidelines.

Association of alcohol consumption with HDL subpopulations defined by apolipoprotein A-I and apolipoprotein A-II content

Objective: To investigate the relationship between alcohol intake and serum level of high-density lipoprotein (HDL) subfractions defined on the basis of their apolipoprotein A-I and A-II content (LpA-I and LpA-I:A-II). Design: Observational study. Setting: Institute of Internal Medicine and Medical Physiopathology, IRCCS Maggiore Hospital, University of Milan. Subjects: One hundred healthy males with a mean age of 42±11.1 y, selected among blood donors. Results: Both LpA-I and LpA-I:A-II were significantly higher in men drinking more than 30 g a day of alcohol than in non-drinkers (LpA-I: difference between means 6.5 mg/dL, 95% C.I. 1.14–11.9; LpA-I:A-II difference between means 11.5 mg/dL, 95% C.I. 0.52–22.5). The association of alcohol consumption with LpA-I and LpA-I:A-II levels was independent from age, body mass index, physical activity, serum triglycerides and diet composition. Conclusions: Alcohol consumption is associated with an increase of serum levels of both LpA-I and LpA-I:A-II particles and this may, at least in part, explain the reduced cardiovascular morbidity observed in subjects drinking moderate amounts of alcoholic beverages. Sponsorship: Supported by grants from Ricerca Corrente Ospedale Maggiore di Milano IRCCS, Milan Italy.

Changes in Serum Lipids and Blood Glucose in Non Diabetic Patients with Metabolic Syndrome after Mixed Meals of Different Composition

Aims. To investigate the postprandial changes in serum lipoproteins and blood glucose and to verify whether different nutrient composition of the meal elicits different response in patients with (MetS+) and without (MetS−) metabolic syndrome. Research Design and Methods. 50 MetS+ patients and 50 age- and sex-matched MetS− consumed a regular lunch chosen among those more similar to their usual diet. Blood was drawn in the morning after 12-hour fasting and 2 and 4:30 hours after the meal. Results. Serum triglycerides increased more in MetS+ (35%, 4:30 hours after the meal) than in MetS− (29%), HDL-cholesterol decreased 2 hours after the meal in both groups (−4% and −5%, resp.). Blood sugar similarly increased in both groups (19%, 2 hours after the meal in MetS+ and 17% in MetS−) and plasma insulin increased more and remained high longer in MetS+ (73.5 and 52.3 μU/mL, 2 and 4:30 hours after the meal) than in MetS− (46.7 and 21.6 μU/mL). Difference in nutrient composition of the meal (carbohydrate 57%, fat 28% versus carbohydrate 45%, fat 35%) was not associated with differences in postprandial levels of triglycerides, HDL-cholesterol, glucose, and insulin within each group. Conclusions. As compared with MetS−, MetS+ patients show a greater hypertriglyceridemic and hyperinsulinemic response to a regular lunch whatever the carbohydrate or fat content of the meal.

Relationship of serum triglyceride concentration to Lipoprotein composition and concentration in normolipidemic and hyperlipidemic subjects

SummaryIn a series of 438 subjects (184 normolipidemics and 254 hyperlipidemics) the relationship among serum concentration of triglycerides, lipoprotein lipids and apoproteins A-I and B has been evaluated. The results show that as serum triglyceride level increases, VLDL rise and become enriched in triglycerides. The increase of VLDL is associated with a reduction of serum levels of LDL and HDL which appear to be rich in triglycerides and poor in cholesterol. The decrease in serum HDL level is mainly due to a reduction in serum concentration of the HDL, subtraction. The triglyceride content of HDL, and HDL, rises with increasing serum triglycerides. The increase in serum triglyceride concentration seems then to be associated with a complex metabolic derangement which involves all the lipoprotein fractions.

Effects of serum storage on the determination of cholesterol

SummaryCholesterol determined by 4 different enzymatic commercial kits and by the dry chemistry Reflotron system was higher in serum stored at 4 °C and at −20 °C than in fresh serum. The effects of storage seem to be temperature-dependent. In fact, cholesterol values significantly increased only after 2h of freezing. The prolongation of freezing up to 2 weeks was not followed by further significant changes. In serum stored at 4 °C the increase in cholesterol was slower than in frozen serum. Both free and esterified cholesterol underwent an increase after storage. When cholesterol was determined by a chemical method (sulfuric acid-ferric chloride) after extraction with ethyl acetate and ethanol, no difference was observed in fresh and stored serum. Cholesterol, triglycerides and apoproteins A-I and B underwent parallel changes after storage both in whole serum and fractionated lipoproteins. Our findings strongly suggest that in serum stored at positive or negative temperature there is an alteration of the lipoprotein molecules which allows an easier availability of cholesterol for the enzyme-substrate reaction than in fresh serum. Current enzymatic methods underestimate (about 10%) cholesterol when the analysis is performed on fresh serum.

Cholesterol distribution between HDL subfractions. A study of 498 subjects

SummaryIn 498 subjects (205 normolipidemics and 293 hyperlipidemics) of both sexes, the cholesterol content of high density lipoprotein (HDL) subfractions has been determined. The serum concentration of total HDL-cholesterol appears to be more strictly related to the cholesterol content of HDL2 than to that of HDL3. This latter one, however, gives a contribution to the variability of HDL-cholesterol so that the value of HDL-cholesterol cannot be assumed as a reliable estimate of the serum level of the more anti-atherogenic HDL2 subfraction. The cholesterol content of HDL and its subfractions is higher in women than in men and decreases with increasing serum VLDL-cholesterol level and body weight. Both HDL2- and HDL3-cholesterol appear to largely depend from the metabolism of triglyceride-rich lipoproteins in accordance with the data of experimental studies.