Importance of Lp(a) lipoprotein and HLA genotypes in atherosclerosis and diabetes

The prevention and management of stroke in sickle cell anaemia

Perhaps the most important clinical complication of sickle cell anaemia is stroke, an event that occurs in approximately 5-10% of children who inherit this disorder. To prevent recurrent or progressive CNS damage, the institution of regular red blood cell (RBC) transfusions is the standard of care. In addition, children at high risk of developing stroke, as screened by transcranial Doppler, also benefit from regular RBC transfusions for stroke prevention. In this review, standard and novel techniques of RBC transfusion, and also alternative therapies to treat children with or at risk for stroke are considered. In addition, haematopoietic cell transplantation, the only curative option for sickle cell anaemia, is considered, and speculation about its present and future application in this clinical setting is discussed.

Ethnicity may be a reason for lipid changes and high Lp(a) levels in rheumatoid arthritis

There are so many studies that suggest the changes in lipid profiles and lipoprotein (a) [Lp(a)] are associated with early atherosclerosis in rheumatoid arthritis (RA). But there are some opposite studies also. Because of marked ethnicity differences in the distribution of Lp(a), we aimed to investigate the associations of Lp(a) levels and lipid changes in Turkish RA patients. There were 30 women and 20 men, a total of 50 patients with RA (mean age 47.6 +/- 13.2 years), included and 21 healthy women and 14 healthy men (mean age 45.7 +/- 14.5 years) were recruited as a control (C) group. Serum Lp(a), total cholesterol (TC), triglyceride (TG), HDL cholesterol (HDL-C) and LDL cholesterol (LDL-C) levels were analysed for each group. Analysis of six different studies was performed. In the RA and C groups, mean serum Lp(a) levels were 39.7 +/- 64.4 and 10.5 +/- 13.4 mg/dl, respectively (P=0.001). Mean TC levels were 189.2 +/- 142.5 and 174.0 +/- 29.3 mg/dl (P=0.294), mean TG levels were 121.4 +/- 65.4 and 106.5 +/- 80.0 mg/dl (P=0.030), mean HDL-C levels were 44.5 +/- 10.0 and 47.7 +/- 4.8 mg/dl (P=0.014) and mean LDL-C levels were 94.3 +/- 35.3 and 102.0 +/- 24.6 mg/dl (P=0.98), respectively. Analysis of the six studies showed Lp(a) level was higher and HDL level was lower in RA patients than in healthy controls. Patients with RA may have altered lipid profiles from one country to another one. Especially in Turkey, higher serum Lp(a), lower HDL-C and higher TG levels may be found in RA patients instead of some findings of other countries showing different results. Ethnicity may be a reason for these findings.

Bruch's membrane and the vascular intima: is there a common basis for age-related changes and disease?

Several clinical and epidemiological studies have concurrently illuminated established cardiovascular risk factors in age-related macular degeneration (AMD), raising the possibility that cardiovascular disease and AMD may share a similar pathogenic process. The vascular intima and the Bruch's membrane share several age-related changes and are the seat of many common molecules. Diseases of these structures may represent parallel responses to the tissue injury induced by multiple intercalated factors such as genetic variations, oxidative stress, inappropriately directed immune response or inflammatory disease complex. However, there are marked differences in the age-related changes in these two structures. The strategic location of the Bruch's membrane between the retinal pigment epithelium and the choriocapillaris can at least partially explain the differential susceptibility of AMD to cardiovascular risk factors. Unlike the vascular wall that is exposed to changes from the endothelium, the Bruch's membrane is subject to changes from both the endothelium (choriocapillaris) and epithelium (retinal pigment epithelium). Moreover, although both the vascular wall and Bruch's membrane become lipid laden with age, the lipid composition is characteristically different. This review examines the morphological and biochemical alterations in the senescent Bruch's membrane and its analogy to the vascular wall to evaluate the concurrence of atherosclerosis and AMD.

Effect of antiepileptic drugs on plasma lipids, lipoprotein (a), and liver enzymes

We conducted a study to assess the effect of phenobarbital, carbamazepine, and valproate on serum lipid profiles and lipoprotein (a) in 64 children with epilepsy (aged between 1 and 15 years) admitted to the child neurology outpatient clinic between July 2000 and July 2002. The children were separated as group 1 (18 children), treated with phenobarbital, 5 mg/kg/day; group 2 (22 children), treated with carbamazepine, 10 to 15 mg/kg/day; and group 3 (24 children), treated with sodium valproate, 20 mg/kg/day. Plasma lipoprotein (a), total cholesterol, triglycerides, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, apolipoprotein A and apolipoprotein B levels, and liver enzymes alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, and gamma-glutamyltransferase were determined before the initiation of the treatment and at 3, 6, and 12 months of the treatment period. The mean age of children in group 1 was significantly low compared with those in groups 2 and 3 (P <.05). The mean pretreatment lipid levels among the groups were not significantly increased. The mean lipoprotein (a) levels were significantly increased in all groups at 3, 6, and 12 months of the treatment period (P <.05). The increase in alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, total cholesterol, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol at 3, 6, and 12 months was statistically significant in group 1 (P <.05). The higher levels in lipoprotein (a) (mean > 30 mg/dL) were observed only in carbamazepine-treated patients at 6 and 12 months. The percentage of children with lipoprotein (a) levels over 30 mg/dL was 44%, 63%, and 33% in the phenobarbital-, carbamazepine-, and valproate-treated children, respectively. Antiepileptic drugs significantly increase the level of lipoprotein (a), which is a major risk factor for atherosclerosis, and also have variable effects on other lipid parameters. Lipoprotein (a) levels should be closely followed in patients receiving antiepileptic drugs. (J Child Neurol 2006;21:70-74).

HLA-DRB1 alleles in Hb SS patients with avascular necrosis of the femoral head

Strong associations have been established between various HLA alleles and different complications of sickle cell disease (SCD). Recently, the HLA-DRB1*03 allele was shown to be associated with susceptibility to stroke while the HLA-DRB1*02 allele may be protective. While stroke and silent brain infarcts (SBI) are unusual in Kuwaiti children with SCD, avascular necrosis of the femoral head (AVNFH) is quite common. The modulatory association factors must still be elucidated. An investigation of HLA-DRB1 alleles was carried out in a group of 68 Kuwaiti SS patients, of age 7-44 years, of whom 20 (29.4%) had AVNFH, confirmed by magnetic resonance imaging. A group of 167 apparently healthy age- and sex-matched individuals served as controls. Comparison of the HLA alleles between the whole SS group and the controls showed a significant over-representation of DRB1*01 (P < 0.01) and DRB1*10 (P < 0.05) in the patient group. No significant differences in the allele frequencies in the SS patients with or without AVNFH were observed. It therefore appears that the HLA-DRB1 locus does not play a significant role in the pathogenesis of AVNFH Kuwaiti patients.

Distinct HLA associations by stroke subtype in children with sickle cell anemia

Children with sickle cell anemia (SCA) carry a 200-fold increased risk for cerebral infarction. Stroke can be the result of small-vessel (SV) or large-vessel (LV) disease. However, it is unknown whether these subtypes result from the same pathophysiologic processes. Complete HLA genotyping was performed on 231 eligible children previously enrolled in the Cooperative Study of Sickle Cell Disease (CSSCD). Cerebral infarction on magnetic resonance imaging (MRI) was documented in 71 patients, and 160 patients had negative findings on MRI. Based on MRI/magnetic resonance angiography (MRA) findings, infarct size, and location, 36 patients were classified as having LV stroke and 35 as having SV stroke. When comparing the total MRI+ group with the MRI- group, HLA DPB1*0401 was associated with increased stroke risk (P =.01), whereas DPB1*1701 (P =.02) conferred protection from stroke. These DPB1 associations with stroke were attributed to the SV stroke group, in whom DPB1*0401 was associated with susceptibility (P =.003) and DPB1*1701 with protection from stroke (P =.06). In the LV stroke subgroup, HLA-A*0102 (P =.02) and -A*2612 (P =.007) conferred susceptibility, whereas -A*3301(P =.04) protected from stroke. These results suggest that specific HLA alleles influence stroke risk and appear to contribute differently to SV and LV stroke subtypes. The distinct HLA associations with SV and LV stroke suggest that different pathologic processes may be involved in the development of stroke in children with SCA. If these results are confirmed in a larger study, HLA type may serve as a useful marker for the early identification of SCA patients at high risk for stroke.

Evidence for HLA-related susceptibility for stroke in children with sickle cell disease

Cerebral infarction occurs in one quarter of all children with sickle cell anemia (SCA). There is an increased risk of stroke in siblings with SCA, suggesting genetic factors may influence risk of stroke. The authors investigated whether HLA type was associated with risk of stroke in children with SCA. Fifty-three patients with SCA underwent complete HLA typing at both HLA class I (HLA-A, B) and HLA class II (HLA-DR, DQ, DP) loci. Of the 53 patients, 22 had magnetic resonance imagining (MRI)–documented evidence of cerebral infarction, and the remaining 31 patients had negative MRI scans. Comparison of the results of HLA typing between the SCA patients with a positive and those with a negative MRI documented that the 2 groups differed with respect to the class I HLA-B (P = .012), and the class II HLA-DRB1 (P = .0008) and DQB1 (P = .029). Susceptibility associations at the HLA-DRB1 locus included both DR3 alleles, where DRB1*0301 and *0302 were both associated with an increased risk of stroke. Protective associations were found in the DR2 group, where DRB1*1501 was protective for stroke. DQB1*0201, which is in linkage disequilibrium with DRB1*0301, was also associated with stroke. Similarly, DQB1*0602, in linkage disequilibrium with DRB1*1501, was protective. Specific HLA alleles may influence the risk of stroke in children with SCA. HLA typing may prove useful in identifying SCA patients at higher risk for stroke.

Evidence for HLA-related susceptibility for stroke in children with sickle cell disease

Cerebral infarction occurs in one quarter of all children with sickle cell anemia (SCA). There is an increased risk of stroke in siblings with SCA, suggesting genetic factors may influence risk of stroke. The authors investigated whether HLA type was associated with risk of stroke in children with SCA. Fifty-three patients with SCA underwent complete HLA typing at both HLA class I (HLA-A, B) and HLA class II (HLA-DR, DQ, DP) loci. Of the 53 patients, 22 had magnetic resonance imagining (MRI)–documented evidence of cerebral infarction, and the remaining 31 patients had negative MRI scans. Comparison of the results of HLA typing between the SCA patients with a positive and those with a negative MRI documented that the 2 groups differed with respect to the class I HLA-B (P = .012), and the class II HLA-DRB1 (P = .0008) and DQB1 (P = .029). Susceptibility associations at the HLA-DRB1 locus included both DR3 alleles, where DRB1*0301 and *0302 were both associated with an increased risk of stroke. Protective associations were found in the DR2 group, where DRB1*1501 was protective for stroke. DQB1*0201, which is in linkage disequilibrium with DRB1*0301, was also associated with stroke. Similarly, DQB1*0602, in linkage disequilibrium with DRB1*1501, was protective. Specific HLA alleles may influence the risk of stroke in children with SCA. HLA typing may prove useful in identifying SCA patients at higher risk for stroke.

Inflammation, infection and atherosclerosis: do antibacterials have a role in the therapy of coronary artery disease?

Since the recent publication of 3 studies on the use of antibacterials in patients with coronary artery disease (CAD), there has been a phenomenal interest in the role of infection in the genesis of CAD. It is now generally accepted that inflammation accompanies atherosclerosis from its initiation to the evolution of end-events. Inflammation may occur in response to traditional risk factors, such as hyperlipidaemia, smoking and diabetes mellitus. There is a recent resurgence of the concept that inflammation may have an infectious basis. This concept is based on the identification of microorganisms in the atherosclerotic plaque and seropositivity. The data on eradication of the offending organism with antibiotics and prevention of atherosclerosis-related events have, however, been inconsistent. This may reflect lack of precise understanding of steps leading to atherosclerosis and the evolution of acute ischaemic events. Further work in this area may help identify subsets of patient populations within which infection may play a causative role in the genesis of CAD. Targeted therapy then may be considered logical.

The relation between bone mineral density, insulin-like growth factor I, lipoprotein (a), body composition, and muscle strength in adolescent males

Osteoporosis is the most common metabolic bone disease. A low peak bone mass is regarded a risk factor for osteoporosis. Heredity, physical activity, and nutrition are regarded important measures for the observed variance in peak bone mass. Lp(a) lipoprotein is a well-known risk factor for atherosclerosis. Serum insulin-like growth factor I (IGF-I) has been found to be increased in males with early cardiovascular disease. In this study, we evaluated the association between bone mass, body constitution, muscle strength, Lp(a), and IGF-I in 47 Caucasian male adolescents (mean age, 16.9 yr). Bone mineral density (BMD) and body composition were measured by dual x-ray absorptiometry, muscle strength of thigh using an isokinetic dynamometer, IGF-I by RIA, and Lp(a) by enzyme-linked immunosorbent assay. IGF-I was only associated with Lp(a) (r = 0.38, P < 0.01). Lp(a) was related to total body (r = 0.40, P < 0.01), skull (r = 0.45, P < 0.01), and femoral neck BMD (r = 0.44, P < 0.01). Lp(a) was also related to fat mass (r = 0.34, P < 0.05) and muscle strength (r = 0.30-0.42, P < 0.05). After multiple regression and principal component (PC) analysis, the so-called PC body size (weight, fat mass, lean body mass, and muscle strength) was the most significant predictor of BMD (beta = 0.28-0.51, P < 0.05-0.01), followed by the so-called PC physical activity (beta = 0.28-0.38, P < 0.05-0.01, weight-bearing locations). However, the PC analysis confirmed that Lp(a) was an independent predictor of total body, skull, and femoral neck BMD (beta = 0.33-0.36, P < 0.01). The present investigation confirms that BMD, body size, and muscle strength are closely related and that the level of physical activity is a major determinant of BMD. However, the positive relation of Lp(a), a major risk factor for cardiovascular disease, to BMD has not previously been described. The importance of this observation has to be further investigated.

Interactive role of infection, inflammation and traditional risk factors in atherosclerosis and coronary artery disease

Although first suggested at the turn of the 20th century, there is a renewed interest in the infectious theory of atherosclerosis. Studies done in many laboratories around the world over the past several years have shown an association between markers of inflammation and coronary atherosclerosis with an exacerbation of the inflammatory process during acute myocardial ischemia, particularly in the early stages of reperfusion. It is also being recognized that the traditional risk factors, such as smoking, dyslipidemia, hypertension and diabetes mellitus, do not explain the presence of coronary atherosclerosis in a large proportion of patients. We believe that in certain genetically susceptible people, infection with very common organisms, such as Chlamydia pneumoniae or cytomegalovirus, may lead to a localized infection and a chronic inflammatory reaction. Persistence of infection may relate to the degree of inflammation and severity of atherosclerosis. Early trials with appropriate antibiotic agents in some patients with a recent history of acute myocardial infarction have led to very salutary results. If patients with an infectious basis of atherosclerosis can be identified, a therapy directed at eradication of the offending organism may be appropriate.

Lp(a) lipoprotein is a major risk factor for cardiovascular disease: pathogenic mechanisms and clinical significance

The results of two previous and two recent studies of middle-aged males and females are presented to exemplify the clinical importance of lipoprotein(a) (Lp(a)) as a risk factor for atherosclerosis and coronary heart disease. In these studies various conventional and recently suggested risk factors were included and different methods for Lp(a) quantification were used. Lp(a) was a significant risk factor in all four studies. In the recent prospective case-control study, Lp(a) and cholesterol were found to act synergistically and predict primary acute myocardial infarction in Swedish males. A cholesterol level above 6.5 mmol/l increased the risk of acute myocardial infarction if the Lp(a) level was above 200 mg/l. The plasma apo A-I level was a protective factor. In the other recent case-control study, an Lp(a) level above 500 mg/l was a highly significant risk factor in Black and White US women with myocardial infarction or advanced coronary artery disease in addition to low density lipoprotein cholesterol levels above 130 mg/dl. A high apo A-I level was a protective factor. In these studies no other factors tested reached significance in multivariate logistic regression analysis. A hypothetical association between high Lp(a) levels and intracellular infection with Chlamydia pneumoniae is discussed. The results suggest that the Lp(a) level is useful in identifying high-risk individuals. Lowering low density lipoprotein cholesterol below 100 mg/dl (<2.6 mmol/l) seems to be most important in both males and females with high-risk Lp(a) levels.

Two weeks of daily injections and continuous infusion of recombinant human growth hormone (GH) in GH-deficient adults. II. Effects on serum lipoproteins and lipoprotein and hepatic lipase activity

Recombinant human growth hormone (GH) administered as daily subcutaneous (SC) injections has been shown to affect serum lipoproteins in GH-deficient subjects. However, the effects of continuous infusion of GH on serum lipoproteins have not been investigated in GH-deficient adults. The aim of the present study was to compare effects of daily injections and continuous infusion of GH on lipoprotein metabolism. Recombinant human GH (0.25 U/kg/wk) was administered to nine GH-deficient adult men during a period of 14 days in two different ways, ie, as a daily SC injection at 8:00 PM and as a continuous SC infusion, with 1 month of washout between the treatments. Blood samples and tests were performed in the morning after an overnight fast before the start of GH treatment (day 0) and on day 2 and day 14 of treatment. Abdominal SC adipose tissue lipoprotein lipase (LPL), postheparin plasma LPL, and hepatic lipase (HL) activity were measured 120 minutes after the intake of 100 g glucose. Adipose tissue LPL activity decreased and postheparin plasma HL activity increased after 14 days of GH treatment irrespective of the mode of GH administration, whereas GH treatment had no effect on postheparin plasma LPL activity. Serum triglyceride and very-low-density lipoprotein (VLDL) triglyceride concentrations increased during GH treatment. However, VLDL triglyceride concentrations increased to a greater degree during treatment with daily GH injections than during continuous infusion of GH. Serum apolipoprotein (apo) B and low-density lipoprotein (LDL) cholesterol concentrations decreased during treatment with daily GH injections, but were not significantly affected by continuous GH infusion. Thus, apo B and LDL cholesterol concentrations were lower after daily GH injections versus continuous GH infusion. Serum lipoprotein(a) [Lp(a)] and apo E concentrations increased during both modes of GH treatment. However, continuous infusion of GH resulted in a more marked increase in Lp(a) and apo E concentrations than daily GH injections. Minor effects were observed on serum apo A-I concentrations but high-density lipoprotein (HDL) cholesterol concentrations were not affected. In conclusion, GH treatment of GH-deficient men influenced adipose tissue LPL and postheparin plasma HL activity, as well as serum lipoprotein concentrations. Moreover, continuous GH infusion and daily GH injections differed with respect to the magnitude of effects on several lipoprotein fractions including VLDL triglycerides, LDL cholesterol, apo B, apo E, and Lp(a) concentrations.

Lp(a) lipoprotein, IgG, IgA and IgM antibodies to Chlamydia pneumoniae and HLA class II genotype in early coronary artery disease

The associations previously found between lipoprotein(a) (Lp(a)) levels and atherosclerotic disorders, diabetes, rheumatoid arthritis and renal diseases suggest that Lp(a) may be involved in autoimmune reactions. The relation found between Lp(a) levels and the HLA class II genotype in males with early coronary artery disease (CAD) further support that assumption. It was suggested that an autoimmune process, perhaps triggered by a concomitant intracellular infection may occur especially in patients with inherited high Lp(a) levels in combination with certain inherited HLA class II genotypes. In this study a Chlamydia pneumoniae IgG titer > or = 32 was significantly more common (P = 0.036) in CAD patients than in matched controls. This is in agreement with previous reports by other investigators. In addition, an IgG titer > or = 256 in combination with an Lp(a) level > or = 120 mg/l was found to occur significantly more often (P = 0.011) in male patients than in male controls. Certain HLA class II DR genotypes in combination with high Lp(a) levels and C. pneumoniae titers occurred more frequently in both male and female patients than in controls. Some combinations were very common in male patients, and the difference in comparison with male controls was highly significant.

Lp(a) lipoprotein in cardiovascular disease

The article summarizes the increased knowledge about the enigmatic Lp(a) lipoprotein and its clinical importance over the past 20 years. The mode of inheritance, the unique features of Lp(a) composition and structure and the unusual distribution of the mainly genetically determined plasma Lp(a) levels are discussed. The main factors that can significantly change the inherited plasma Lp(a) levels are endocrine disorders and hormone treatment. It seems possible that sex hormones protect females to a large extent from the potentially deleterious effects of inherited high Lp(a) levels until menopause. The exceptionally strong independent association found in most studies between Lp(a) lipoprotein levels and atherosclerotic disorders indicates that Lp(a) is a factor of outstanding importance in the pathogenesis of atherosclerosis. Probable pathogenetic mechanisms are reviewed. The associations found between LP(a) and insulin release, rheumatoid arthritis and renal diseases suggest that Lp(a) may be involved in immunological mechanisms. In a new hypothesis it is suggested that an autoimmune process might especially occur in individuals with inherited high Lp(a) levels and certain HLA class II genotypes, triggered by a concurrent infection.