Lipoprotein(a) is an independent risk factor for coronary artery disease in NIDDM patients in South India

OBJECTIVE: Asian Indians have been reported to have very high prevalence rates of coronary artery disease (CAD) in the absence of traditional risk factors. Recently, elevated levels of lipoprotein(a) [Lp(a)] have been reported to be associated with premature CAD in migrant Asian Indians. However, there are very little data regarding Lp(a) in CAD patients from the Indian subcontinent and virtually none in individuals with NIDDM. The objective of this study was to assess the role of Lp(a) as a marker for CAD in South Indian NIDDM patients. RESEARCH DESIGN AND METHODS: We estimated serum Lp(a) in 100 control subjects, 100 NIDDM patients without CAD, and 100 NIDDM patients with CAD. Lp(a) values were transformed into natural logarithms. Statistical analysis included Student's t test, one-way analysis of variance, and chi2 test. Multiple logistic regression analysis was used to identify associations with CAD. RESULTS: Lp(a) levels were significantly higher in NIDDM patients with CAD compared with NIDDM patients without CAD and control subjects (geometric mean 24.6, 15.1, and 19.4 mg/dl, respectively, P < 0.05). Results of logistic regression analysis showed that Lp(a), age, and HDL were associated with CAD. In NIDDM patients with CAD, there was no correlation between Lp(a) and serum cholesterol, triglyceride, or HDL cholesterol levels, but there was a weak association with LDL cholesterol and systolic blood pressure. CONCLUSIONS: The data suggests that serum Lp(a) is an independent risk factor for CAD in NIDDM patients in South India.     

Lipoprotein (a) and plasminogen in atherosclerosis

The aim of this study was to evaluate plasma levels of lipoprotein (a) [LP(a)] and plasminogen in patients affected with atherosclerotic disease and to understand the mutual relationships. Eighty-four patients affected with atherosclerosis were examined and divided as follows: group I, 24 patients with peripheral arteriopathy; group II, 40 patients with ischemic heart disease (myocardial infarction and/or angina pectoris); group III, 20 patients with multi-infarct dementia; group IV (control group) with 20 healthy young subjects. The results show that Lp(a) plasma levels, in atherosclerotic patients, are higher than 30 mg/dl, while the plasminogen levels are lower than 80 mg/dl. There is an inverse correlation between these two data. Moreover, a different behaviour of Lp(a) and plasminogen rate related to age of patients, to number of atherosclerotic lesions or to acuteness of ischemic heart disease, was observed.     

Lipoprotein(a) in health and disease

Elevated plasma levels of Lp(a) do seem to influence the progression of atherosclerosis. Evidence is emerging that certain apo(a) isoforms may be more atherogenic than others, and in transgenic mice free apo(a) has been shown to be associated with accelerated atherosclerosis. Currently it is not known whether treating elevated Lp(a) levels will reduce progression of atherosclerosis and, as therapeutic options are limited, mass screening of Lp(a) levels in populations is not indicated. The presence of raised Lp(a) levels, however, warrants aggressive treatment to reduce other cardiovascular risk factors. Continuing research to investigate the relationship of the apo(a) gene to other genes, including the plasminogen gene and apo(a)-related genes, will add further information pertaining to the evolution, function, regulation and clinical implications of Lp(a).     

Lipoprotein(a) in health and disease

Lipoprotein(a) [Lp(a)] represents an LDL-like particle to which the Lp(a)-specific apolipoprotein(a) is linked via a disulfide bridge. It has gained considerable interest as a genetically determined risk factor for atherosclerotic vascular disease. Several studies have described a correlation between elevated Lp(a) plasma levels and coronary heart disease, stroke, and peripheral atherosclerosis. In healthy individuals, Lp(a) plasma concentrations are almost exclusively controlled by the apo(a) gene locus on chromosome 6q2.6-q2.7. More than 30 alleles at this highly polymorphic gene locus determine a size polymorphism of apo(a). There exists an inverse correlation between the size (molecular weight) of apo(a) isoforms and Lp(a) plasma concentrations. The standardization of Lp(a) quantification is still an unresolved task due to the large particle size of Lp(a), the presence of two different apoproteins [apoB and apo(a)], and the large size polymorphism of apo(a) and its homology with plasminogen. A working group sponsored by the IFCC is currently establishing a stable reference standard for Lp(a) as well as a reference method for quantitative analysis. Aside from genetic reasons, abnormal Lp(a) plasma concentrations are observed as secondary to various diseases. Lp(a) plasma levels are elevated over controls in patients with nephrotic syndrome and patients with end-stage renal disease. Following renal transplantation, Lp(a) concentrations decrease to values observed in controls matched for apo(a) type. Controversial data on Lp(a) in diabetes mellitus result mainly from insufficient sample sizes of numerous studies. Large studies and those including apo(a) phenotype analysis came to the conclusion that Lp(a) levels are not or only moderately elevated in insulin-dependent patients. In noninsulin-dependent diabetics, Lp(a) is not elevated. Conflicting data also exist from studies in patients with familial hypercholesterolemia. Several case-control studies reported elevated Lp(a) levels in those patients, suggesting a role of the LDL-receptor pathway for degradation of Lp(a). However, recent turnover studies rejected that concept. Moreover, family studies also revealed data arguing against an influence of the LDL receptor for Lp(a) concentrations. Several rare diseases or disorders, such as LCAT- and LPL-deficiency as well as liver diseases, are associated with low plasma levels or lack of Lp(a).     

Lipoprotein(a) and diabetes. An update

On the basis of the available data (much of which is contradictory), I suggest that the following might summarize the role of Lp(a) in diabetes currently. 1. Lp(a) in IDDM: Concentrations are probably elevated. Concentrations are probably related to metabolic control. Concentrations are increased with microalbuminuria. 2. Lp(a) in NIDDM: Concentrations are not elevated. Concentrations do not change with metabolic control. Too few data exist to make an assessment of relation of Lp(a) to microalbuminuria in NIDDM. 3. Lp(a) and CHD in diabetes: Little current evidence shows that Lp(a) is a risk factor for CHD in diabetes. More studies--especially prospective studies with larger numbers of subjects--need to be done.     

Lipoprotein (a): effect of detraining

Plasma levels of lipoprotein (a), total cholesterol, triglycerides, HDL-cholesterol, LDL-cholesterol, apo-protein Al and apoprotein B were evaluated for 8 long-distance runners during the XXIII New York Marathon, with blood samples being taken before and after the race, and after one month of detraining. After detraining lipoprotein (a) increased significantly both with respect to basal values and especially with respect to immediately post-race values. Negligible and predictable modifications of the other metabolic parameters evaluated, were observed. No correlation was found between lipoprotein (a) and the anthropometrical data and metabolic parameters considered.     

Urinary excretion of apo(a) fragments in NIDDM patients

Lp(a), one of the most atherogenic lipoproteins, is believed to contribute significantly to vascular diseases in non-insulin-dependent diabetic (NIDDM) patients. Contradictive data have been published on these patients concerning plasma concentrations of Lp(a) and their relation to renal function. Since apo(a) fragments appear in urine, we measured urinary apo(a) in 134 NIDDM patients and 100 matched controls and related urinary apo(a) concentrations to plasma Lp(a) levels and kidney function. Plasma Lp(a) values were found to be significantly higher in NIDDM patients. NIDDM patients also secreted significantly more apo(a) into their urine as compared to control subjects. There was no correlation between creatinine clearance or albumin excretion and urinary apo(a) concentrations. Patients with macroalbuminuria exhibited a twofold higher apparent fractional excretion of apo(a) in comparison to patients with normal renal function. Urinary apo(a) values in both patients and control subjects were highly correlated to plasma Lp(a), yet no correlation was found with HbA1c or serum lipoproteins. It is concluded that urinary apo(a) excretion is correlated to plasma Lp(a) levels but not to creatinine clearance in patients suffering from NIDDM.     

Lipoprotein (a) concentrations in patients with various dyslipidaemias

The results of operative treatment of 45 flexible flat feet (29 patients) using the sinus tarsi spacer are reported. Although radiological improvement in both the talar declination and the ground-navicular distance was found, our patients suffered from pain and functional impairment for an average period of 5 months. An unacceptably high rate of spacer dislocation was noted. Furthermore, the literature indicates spontaneous improvement as the natural history of flexible flat feet. We therefore no longer advise the sinus tarsi spacer as a routine treatment for flexible flat feet.     

Lipoprotein Lp(a) excess and coronary heart disease

A pharmacokinetic study of all-trans retinoic acid (ATRA) was performed in 8 patients with various types of leukemia and MDS. After oral administration at a dose of 30 mg/m2, the mean peak plasma concentration was 430 ng/ml and was reached at 150 min. In one patient who failed to respond a very low plasma ATRA level was seen. Though the plasma ATRA exposure decreased significantly with daily drug administration, an intermittent schedule of ATRA administration would yield higher plasma drug concentrations. We treated 2 patients with refractory acute promyelocytic leukemia (APL) in a pilot study of ATRA followed by intensive chemotherapy (APL-ATRA protocol). Two patients successfully achieved complete remission with ATRA after failing under conventional chemotherapy. Based on the pharmacokinetic study of ATRA, an intermittent schedule of ATRA in addition to chemotherapy suggests an effective regimen for children with APL. Phase II trials to evaluate the role of intermittent schedules of ATRA are planned in Children's Cancer and Leukemia Study Group.     

Lipoprotein(a)--possible role in the fibrinolysis process

The clinical and epidemiological features of 120 episodes of Streptococcus pyogenes bacteraemia in St. Thomas' Hospital between 1970 and 1997 were analysed. One-third of episodes were nosocomial. M1 was the most common serotype, and 29% of strains were non-typable. There was a variety of presenting features, but nearly half of the patients had cellulitis, 15% were shocked, and 6% had necrotic infections. There was no focus of infection in 13%. 54% of patients had an underlying disease, and 23% of infections were associated with a medical procedure or device. The mortality rate was 19%, and was associated with shock, coma, no focus of infection, and underlying disease. Since 1989, the annual incidence has more than doubled, and M1 strains and necrotic infections have increased, but the mortality rate and the proportion of patients presenting with shock have decreased, and the increase in cases involved many different M-types.     

Apolipoprotein (a) levels and phenotypes in NIDDM patients with microalbuminuria and albuminuria

This study was conducted to determine whether circulating levels of lipoprotein (a), an independent risk factor of macrovascular disease, are increased in non-insulin-dependent diabetes mellitus (NIDDM) patients with microalbuminuria who have an increased risk of cardiovascular mortality. Apolipoprotein (a) [apo(a)] levels and phenotypes, and other circulating lipid levels were determined in 227 Chinese NIDDM patients with varying stages of diabetic nephropathy. None was on lipid-lowering therapy. Apo(a) levels in normoalbuminuric (geometric mean 166 U/L; 95% confidence intervals 137, 200; n = 105) and microalbuminuric patients (162; 132, 209; n = 77) were similar to values in controls (166; 143, 193, n = 168). Albuminuric patients, however, had higher apo(a) levels than both normoalbuminuric patients and controls (242; 184, 317; n = 45; P < 0.05). The overall size range of the apo(a) phenotypes and the frequency of having at least one small isoform, i.e. < 700 kDa, were similar among the four groups of subjects. A positive correlation was found between log apo(a) and log plasma creatinine levels (P < 0.01). Compared to normoalbuminuric patients, both microalbuminuric and albuminuric patients were older (P < 0.01) and had higher HbA1c (P < 0.01), greater BMI (P < 0.05) and longer disease duration (P < 0.05) compared to normoalbuminuric patients. Nevertheless, using multiple linear regression analysis, it was found that the presence of nephropathy conferred an independent influence on increasing total cholesterol (P < 0.001), triglyceride (P < 0.001) and apoB (P < 0.01), and decreasing HDL cholesterol (P < 0.05) levels even when only the normoalbuminuric and microalbuminuric groups were analysed. The prevalence of macrovascular disease was significantly increased in microalbuminuric and albuminuric patients (45.1 and 48.7% respectively vs 20.2% in normoalbuminuric patients, P < 0.01). It is concluded that circulating apo(a) levels were not increased in Chinese NIDDM patients with microalbuminuria. However, atherogenic changes in other lipid and lipoprotein levels may contribute to an increased risk of macrovascular disease in these patients.     

Lipoprotein(a): a link between thrombosis and atherosclerosis?

Lipoprotein(a) (Lp(a)) represents a class of plasma lipoproteins similar to low-density lipoprotein (LDL), but containing an unique apolipoprotein(a) with striking homology to plasminogen. Plasma Lp(a) is inherited as a quantitative genetic trait, with a continuous distribution in Caucasian populations (< 10-2000 mg/l), where high levels are associated with an increased risk of atherosclerotic disease. The physiological role of Lp(a) is unknown, and the metabolism is obscure. Plasma Lp(a) is apparently resistent to diets and drug therapy, and LDL-apheresis is currently the most effective way of reducing plasma Lp(a). However, clinical benefits of lowering plasma Lp(a) have not been demonstrated, and specific therapeutic goals cannot be recommended at present. The structural similarity between apo(a) and plasminogen has generated several experimental observations indicating a prothombogenic and proatherogenic role of Lp(a), but the exact pathophysiological mechanisms have not been determined.     

Lipoprotein (a) and cholesterol in body builders using anabolic androgenic steroids

A 67-year-old Taiwanese woman with multilocular hydatid cysts of the liver presented with a 5-month history of intermittent right upper abdominal discomfort. Abdominal ultrasonography and computed tomography showed multiple cysts in both lobes of the liver. Subsequent selective celiac angiography revealed an avascular space-occupying lesion in the right lobe. She underwent a radical excision of the cyst by total closed (without opening the wall) cystopericystectomy over segments 4, 5 and 6. Histologic study of the lesions showed three structural components: 1) an outer acellular laminated membrane, 2) a thin nucleated germinal membrane and 3) several protoscolices with Echinococcus granulosus suckers. The patient has been well for 5 years since her discharge. Although hydatid cysts of the liver are extremely rare in Taiwan, they may cause life-threatening complications and mortality. Making a preoperative diagnosis is important and is only possible if this rare disease is kept in mind.     

Lipoprotein(a) in patients with carotid atherosclerosis and ischemic cerebrovascular disorders

Two novel peptides, named PACAP (pituitary adenylate cyclase activating polypeptide) containing 38 (PACAP38) and 27 residues (PACAP27) were recently isolated from ovine hypothalami. In order to investigate the pituitary cell type(s) that bear a receptor for PACAP, PACAP38 was biotinylated and used for cytochemical examination of binding. The cells were also identified by immunocytochemical methods using the antisera against each of the rat anterior pituitary hormones or an antiserum against S-100 protein, a marker for pituitary folliculo-stellate (FS) cells. Biotinylated PACAP38 (biot-PACAP) exhibited adenylate cyclase stimulating activity (ACSA) comparable to PACAP38 in rat pituitary cell cultures, and displaced the bound 125I-PACAP27 to the rat pituitary membrane preparation to the same extent as PACAP38. After 2-4 days of culture, dispersed rat pituitary cells were incubated with varying concentrations of biot-PACAP at room temperature or 4 degrees C. The bound biot-PACAP38 was visualized by avidin-biotin-peroxidase complex (ABC) method with nickel intensification. Biot-PACAP-positive and pituitary hormone or S-100-positive cells were counted. More than 90% of S-100-positive cells bound biot-PACAP38. A considerable number of GH and PRL cells and a lesser number of ACTH cells also bound biot-PACAP38, whereas only a few identified LH, FSH, or TSH cells bound biot-PACAP38. These results suggest that FS cells are a major target cell type for PACAP. A recent study from our laboratory demonstrated that PACAP stimulated the release of interleukin (IL)-6 in rat pituitary cell cultures. FS cells are known to produce IL-6.     

Incidence of NIDDM and the effects of gender, obesity and hyperinsulinaemia in Taiwan

Our aim is to determine non-insulin-dependent diabetes mellitus (NIDDM) incidence in Taiwan and examine its relation to obesity and hyperinsulinaemia in Chinese men and women. A total of 995 men and 1195 women aged 35-74 years free from diabetes in two townships in Taiwan were followed up with a second examination. At baseline general and metabolic data were recorded, and detailed anthropometric parameters and plasma glucose and insulin were assessed. World Health Organisation (WHO) criteria of fasting glucose 7.8 mmol/l or greater was utilized for defining diabetes. The age-standardized incidence rate based on the United States population in 1970 was 9.3/1000 (CI 5.8-12.8) in men and 9.3/1000 (CI 6.2-12.4) in women and the based on the WHO population in 1976 was 8.9/1000 (CI .5-12.3) in men and 8.9/1000 (CI 5.9-11.9) in women for the Chinese who had a mean BMI slightly greater than 24 (kg/m2). The predictability of the plasma glucose level was greater than that of the insulin level and the obesity indices. NIDDM incidence increased approximately threefold with each 0.67 mmol/l increase in plasma glucose level in men and women. The present study demonstrated the essential relationship of not only BMI but also central obesity indices (such as subscapular and waist circumference) to the incidence of NIDDM among men and women and a stronger relationship between NIDDM incidence and obesity in women than in men. The predictive effects of obesity indices and fasting plasma insulin values on NIDDM risk were independent of each other in men. Obesity and hyperinsulinaemia each without the presence of the other can lead to an increased risk of NIDDM. In women the NIDDM incidence increased more than additively in those with both obesity and hyperinsulinaemia compared to those with single obesity or hyperinsulinaemia. A slightly higher incidence of NIDDM in Taiwan than in western countries was found. The importance of obesity is indicated for predicting NIDDM in the community. Hyperinsulinaemia was found to play a significant role in predicting NIDDM incidence independent of obesity in men and synergistically with obesity in women.     

Lipoprotein (a) in children with chronic renal failure treated conservatively

The aim of this study was to evaluate serum lipid abnormalities, particularly lipoprotein (a), [Lp(a)] as an independent risk factor for cardiovascular disease in children with mild and moderate renal failure. Study were performed on 14 children of whom serum creatinine levels were above 265.3 mumol/l and 32 patients with serum creatinine levels below 265.3 mumol/l. Control group consisted of 27 healthy age-matched subjects. All children were tested for concentration of serum Lp(a), total cholesterol (TC), triglycerides (TG), low density lipoprotein cholesterol (C-LDL) and high density lipoprotein cholesterol (C-HDL). It was found a significantly increase in Lp(a), TC, C-LDL and significantly decrease in C-HDL in children with more advanced renal insufficiency compared to the control. In children with mild renal failure concentration of serum Lp(a) also increased but not significantly. Patients in this group had elevated serum TC and decreased C-HDL. These results suggest that even in the early stages of renal insufficiency in children abnormalities of lipoprotein are present. Such abnormalities, particularly Lp(a) might contribute to accelerated atherosclerosis in this patients.     

Lipoprotein(a) concentration and molecular weight of apolipoprotein(a) in patients with cerebrovascular disease and diabetes mellitus

Plasma lipoprotein(a) [Lp(a)] concentrations are genetically determined, and hyper-Lp(a)-emia is an independent risk factor for atherosclerosis and thrombosis. To study the implications of Lp(a) in cerebrovascular disease (CVD) and diabetes mellitus (DM), we examined plasma Lp(a) levels and molecular weights of apolipoprotein(a) [apo(a)] in 118 patients with CVD, and 125 cases with DM. Although mean Lp(a) concentrations were higher in those cases with atherothrombotic brain infarction than in those with brain hemorrhage and lacunar infarction, the difference was not statistically significant. Lp(a) levels were significantly higher in the DM cases treated with insulin and in those treated with oral hypoglycemic agents than in those on diet therapy alone, suggesting that insulin and oral agents modulate apo(a) expression. Lp(a) concentrations correlated significantly with the low-molecular-weight isoforms of apo(a) in all CVD and DM groups.     

Appropriate Blood Pressure Control in NIDDM (ABCD) Trial

The ABCD (Appropriate Blood Pressure Control in Diabetes) Trial is a large, prospective, randomized clinical trial of 950 patients with non-insulin-dependent diabetes mellitus (NIDDM) designed to compare the effects of intensive blood pressure control with moderate control on the prevention and progression of diabetic nephropathy, retinopathy, cardiovascular disease, and neuropathy in NIDDM. The secondary objective is to determine equivalency of the effects of a calcium channel blocker (nisoldipine) and an angiotensin-converting-enzyme inhibitor (enalapril) as a first-line antihypertensive agent in the prevention and/or progression of these diabetic vascular complications. The study consists of two study populations aged 40-74 years, 470 hypertensive patients (diastolic blood pressure of > or = 90.0 mmHg at time of randomization) and 480 normotensive patients (diastolic blood pressure of 80.0 mmHg at time of randomization). The study duration is 5 years and is scheduled to end in May of 1998. Patients are randomized to receive either intensive antihypertensive drug therapy or moderate antihypertensive drug therapy. Patients are also randomized to nisoldipine or enalapril, with open-label medications added if further blood pressure control is necessary. The primary outcome measure is glomerular filtration rate as assessed by 24-h creatinine clearance. Secondary outcome measures are urinary albumin excretion, left ventricular hypertrophy, retinopathy, and neuropathy. Cardiovascular morbidity and mortality will also be evaluated. Given the data showing the impact of hypertension on complications in NIDDM, the ABCD Trial is designed to determine if intensive antihypertensive therapy will be more efficacious than moderate antihypertensive therapy on the outcome of diabetic complications in NIDDM.     

Lipoprotein distribution and composition in obesity: their association with central adiposity

OBJECTIVE: To examine the relationships between the distribution and composition of subfractions of very low density (VLDL), low density (LDL) and high density (HDL) lipoproteins and central fat deposition as measured by the waist-to-hip ratio (WHR). DESIGN: Participants (n = 62, 44 women and 18 men; body mass index (BMI) > or = 25.0) were recruited from those consecutively attending the outpatient obesity clinic at the University Hospital, Geneva. MEASUREMENTS: Lipoprotein subfractions were isolated from fasting blood samples by cumulative flotation or density gradient ultracentrifugation. Concentration and composition were analysed as a function of obesity indices. RESULTS: There were significant correlations between the WHR and the profiles of the three major lipoprotein subclasses. Central obesity was associated with larger VLDL, small, dense LDL and lower levels of HDL-2 independently of other indices of obesity and plasma triglycerides. Central obesity was also significantly and independently associated with compositional anomalies, specifically an increased free cholesterol content of VLDL and LDL. CONCLUSIONS: Central body fat was associated with modifications of an atherogenic nature to lipoprotein distribution and composition. The data are consistent with an impact of body fat distribution on cardiovascular disease (CVD) via the agency of modified lipoprotein metabolism independently of raised triglycerides.