Giovanni Pigna

Mutations in the ANGPTL3 gene and familial combined hypolipidemia: a clinical and biochemical characterization.

CONTEXT Familial combined hypolipidemia causes a global reduction of plasma lipoproteins. Its clinical correlates and metabolic implications have not been well defined. OBJECTIVE The objective of the study was to investigate the genetic, clinical, and metabolic characteristics of a cohort of subjects with familial combined hypolipidemia. DESIGN The design of the study included candidate gene screening and the comparison of the clinical and metabolic characteristics between carrier and noncarrier individuals. SETTING The study was conducted in a general community. SUBJECTS Participants in the study included individuals belonging to nine families with familial combined hypolipidemia identified in a small town (Campodimele) as well as from other 352 subjects living in the same community. MAIN OUTCOMES MEASURES Serum concentrations of lipoproteins, Angiopoietin-like 3 (Angptl3) proteins, and noncholesterol sterols were measured. RESULTS The ANGPTL3 S17X mutation was found in all probands, 20 affected family members, and 32 individuals of the community. Two additional frame shift mutations, FsE96del and FsS122, were also identified in two hypocholesterolemic individuals. Homozygotes for the ANGPTL3 S17X mutation had no circulating Angptl3 and a marked reduction of all plasma lipids (P < 0.001). Heterozygotes had 42% reduction in Angptl3 level compared with noncarriers (P < 0.0001) but a significant reduction of only total cholesterol and high-density lipoprotein cholesterol. No differences were observed in the plasma noncholesterol sterols between carriers and noncarriers. No association between familial combined hypolipidemia and the risk of hepatic or cardiovascular diseases were detected. CONCLUSIONS Familial combined hypolipidemia segregates as a recessive trait so that apolipoprotein B- and apolipoprotein A-I-containing lipoproteins are comprehensively affected only by the total deficiency of Angptl3. Familial combined hypolipidemia does not perturb whole-body cholesterol homeostasis and is not associated with adverse clinical sequelae.

Mechanisms of Diabetic Dyslipidemia: Relevance for Atherogenesis

Diabetic dyslipidemia is due to a multiple array of metabolic abnormalities determining a typical phenotype characterized by increased plasma triglycerides, reduced HDL and a preponderance of small, dense LDL. This dyslipidemia, defined as atherogenic dyslipidemia, is thought to be highly responsible for the increased cardiovascular risk in diabetes mellitus. Several lines of evidence indicate that the increased liver production of VLDL is the main underlying defect in atherogenic dyslipidemia. This review will recapitulate the pathophysiological aspects of diabetic dyslipidemia with special focus on the molecular mechanism causing increased liver production of VLDL in diabetic patients. The consequences of atherogenic dyslipidemia on mechanisms of atherogenesis will be also reviewed.

Treating statin-intolerant patients

Statins are effective in reducing cardiovascular events and are safe for almost all patients. Nevertheless, intolerance to statins is frequently faced in clinical practice. This is mostly due to muscular symptoms (myalgia with or without increase of plasma creatinine kinase) and/or elevation of hepatic aminotransferases, which overall constitutes approximately two-thirds of reported adverse events during statin therapy. These side effects raise concerns in patients as well as in doctors and are likely to reduce patients’ adherence and, as a consequence, the cardiovascular benefit. Therefore, it is mandatory that clinicians improve their knowledge on the clinical aspects of muscular and hepatic side effects of statin therapy as well as their ability to manage patients with statin intolerance. Besides briefly examining the clinical aspects and the mechanisms that are proposed to be responsible for the most common statin-associated side effects, the main purpose of this article is to review the available approaches to manage statin-intolerant patients. The first step is to determine whether the adverse events are indeed related to statin therapy. If so, lowering the dosage or changing statin, alternate dosing options, or the use of nonstatin compounds may be practical strategies. The cholesterol-lowering potency as well as the usefulness of these different approaches in treating statin-intolerant patients will be examined based on currently available data. However, the cardiovascular benefit of these strategies has not been well established, so their use has to be guided by a careful clinical assessment of each patient.

Clinical characteristics and plasma lipids in subjects with familial combined hypolipidemia: a pooled analysis

Angiopoietin-like 3 (ANGPTL3) regulates lipoprotein metabolism by modulating extracellular lipases. Loss-of function mutations in ANGPTL3 gene cause familial combined hypolipidemia (FHBL2). The mode of inheritance and hepatic and vascular consequences of FHBL2 have not been fully elucidated. To get further insights on these aspects, we reevaluated the clinical and the biochemical characteristics of all reported cases of FHBL2. One hundred fifteen FHBL2 individuals carrying 13 different mutations in the ANGPTL3 gene (14 homozygotes, 8 compound heterozygotes, and 93 heterozygotes) and 402 controls were considered. Carriers of two mutant alleles had undetectable plasma levels of ANGPTL3 protein, whereas heterozygotes showed a reduction ranging from 34% to 88%, according to genotype. Compared with controls, homozygotes as well as heterozygotes showed a significant reduction of all plasma lipoproteins, while no difference in lipoprotein(a) [Lp(a)] levels was detected between groups. The prevalence of fatty liver was not different in FHBL2 subjects compared with controls. Notably, diabetes mellitus and cardiovascular disease were absent among homozygotes. FHBL2 trait is inherited in a codominant manner, and the lipid-lowering effect of two ANGPTL3 mutant alleles was more than four times larger than that of one mutant allele. No changes in Lp(a) were detected in FHBL2. Furthermore, our analysis confirmed that FHBL2 is not associated with adverse clinical sequelae. The possibility that FHBL2 confers lower risk of diabetes and cardiovascular disease warrants more detailed investigation.

Contribution of mutations in low density lipoprotein receptor (LDLR) and lipoprotein lipase (LPL) genes to familial combined hyperlipidemia (FCHL): A reappraisal by using a resequencing approach

BACKGROUND Defective low-density lipoprotein receptor (LDLR) and lipoprotein lipase (LPL) alleles have been implicated in familial combined hyperlipidemia (FCHL). However, their contribution might have been influenced by diagnostic criteria. This study was aimed to reassess the frequency of rare and common variants in LDLR and LPL in FCHL individuals classified with stringent criteria. METHODS LDLR and LPL were resequenced in 208 FHCL and 171 controls. Variants were classified as loss- (LOF) or gain-of-function (GOF) based upon in silico prediction, familial segregation and available functional data. RESULTS Eight LOF variants were detected in LDLR, 6 of which were missense and 2 were predicted to disrupt normal splicing; all were present at heterozygous state. They were found in 10 FCHL but not in controls, thus indicating that 4.8% of FCHL individuals should be reclassified as FH. LDL-C (positive) and BMI (negative) were the strongest predictors of LDLR mutations with LDL-C 181 mg/dl being the best threshold for diagnosing the presence of dysfunctional LDLR alleles. The cumulative prevalence of definite LPL defective alleles (1 rare and 2 common heterozygous missense variants) was comparable between FCHL and controls (10.1% vs. 10.5%). Conversely, the LPL GOF variant p.Ser474* showed a lower frequency in FCHL than in controls (13.5% vs. 24.0%, p = 0.008). Overall, LOF LPL variants did not show a TG-modulating effect. CONCLUSIONS Our findings indicate that, in well characterized FCHL individuals, variants in LDLR and LPL provide a small contribution to this dyslipidemia, thus limiting the need for such genetic testing.

Functional and morphological vascular changes in subjects with familial combined hypolipidemia: an exploratory analysis.

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The relationship between metabolic syndrome, its components, and the whole-body atherosclerotic disease burden as measured by computed tomography angiography

OBJECTIVE Quantify the whole-body atherosclerotic disease in asymptomatic subjects with and without metabolic syndrome (MetS) and to assess the contribution of the syndrome and its components to the atherosclerotic burden. METHODS Sixty-five subjects with and 51 without ATPIII-defined MetS underwent a 64-slice computed tomography angiography (CTA). Plaques causing >0% stenosis in coronary or extra-coronary arteries were classified as positive. RESULTS The prevalence of plaques in coronary, carotid and peripheral arteries as well as their severity did not differ between groups. Conversely, it was seen an almost 3-fold increased likelihood (OR=2.70; 95% CI 1.30-5.57; P<0.001) of atherosclerosis in any district across categories of MetS components (0-1 vs. 2-3 vs. 4-5). Hypertriglyceridemia (P<0.05) and high blood glucose (P<0.05) were independent predictors of the atherosclerotic burden. CONCLUSIONS Atherosclerotic burden as revealed by 64-TCA appears to be more strongly associated with the number of MetS-related factors than to the clinical diagnosis of MetS itself.

Severe coronary and extracoronary atherosclerosis in autosomal recessive hypercholesterolemia detected by whole-body computed tomography angiography

The patient is a 40-year old, premenopausal woman of Sardinian origin who was diagnosed with marked elevation of low density lipoprotein cholesterol (LDL-C ranging 350–450 mg/dL) since the age of 34 years. All causes of secondary hyperlipidemia were ruled out by the standard clinical tests, and the physical examination demonstrated tendon xanthomas and xanthelasma. Before attending our lipid clinic, she received dietary treatment and simvastatin 40 mg/day for 1 year, resulting in minimal reduction in LDL-C levels (-10%). A resting ECG showed a sinus rhythm and nonspecific ST-T wave changes. In the search for the cause of this severe, resistant form of hypercholesterolemia, we performed a family study, which demonstrated that the patient’s 75-year-old father showed a slightly elevated LDL-C (160 mg/dl), and the 74-year-old mother, normal plasma lipids. The parents were first cousins. The 35-year-old brother showed a severe hypercholesterolemia (LDL-C ranging 300–350 mg/dl). The recessive mode of inheritance of elevated LDL-C in the patient’s family excluded the presence of homozygous familial hypercholesterolemia (HoFH), which is transmitted as a dominant disorder and is caused by reduced function of the LDL receptors (LDLR). HoFH was definitively ruled out by the demonstration that the patient’s LDLR activity in cultured skin fibroblasts was within normal range (about 80% of controls), and no mutations were present in the LDLR gene. A recessive form of hypercholesterolemia was posted. Since sitosterolemia may be a cause of recessive hypercholesterolemia, to rule out this possibility, the patient’s plasma concentration of sitosterol was measured and was found to be within the normal ranges. Recently, a new recessive form of severe hypercholesterolemia, defined autosomal recessive hypercholesterolemia (ARH), has been characterized [1] and to confirm the presence of ARH in the patient, the entire coding sequence as well as the splice junctions of the patient’s ARH gene was sequenced following a previously reported procedure [1]. She was noticed to be homozygous for ARH2 allele (W22X) (Fig. 1a). This mutation, which causes the synthesis of an abnormal ARH protein (Fig. 1b), has been demonstrated to be one of the two causing ARH among Sardinians [1]. Therefore, a definitive diagnosis of ARH was confirmed in the patient. At the time of clinical examination, the patient was asymptomatic for coronary symptoms. An exercise treadmill test was performed, and was interpreted as normal. Due to the high prevalence of atherosclerosis in ARH [1], we decided to carry out a vascular examination in the patient by using sixty-four-slice computed tomography angiography (64-CTA) following a previously reported protocol [2]. The whole-body 64-CTA showed extensive coronary arterial involvement with obstruction of the left anterior descending coronary artery as well as of the middle segment of the right coronary artery, which appears reconstituted through a hypertrophic circumflex coronary artery (Fig. 2a, b). The scan of the extracoronary arterial tree demonstrated arterial wall calcifications at the ascending as well as descending tract of the aorta, at the M. Arca F. Quagliarini G. Pigna Atherosclerosis Unit, Department of Internal Medicine and Allied Specialties, Sapienza University of Rome, Rome, Italy

Current challenges in the management of patients with familial hypercholesterolemia

Abstract Familial hypercholesterolemia (FH) is a codominant monogenic disorder of lipoprotein metabolism, characterized by severely elevated levels of LDL cholesterol from birth onwards. Despite the availability of reliable diagnostic strategies, the vast majority of FH patients remain undiagnosed. Treatment of FH is mandatory to prevent premature cardiovascular disease and statins are the drug of choice. However, in some FH individuals, statins alone or in combination do not allow the attainment of therapeutic goals. LDL apheresis may be an option, mainly in homozygous FH. Nevertheless, the new lipid-lowering agents (blockers of apoB synthesis or PCSK9 inhibitors) hold promise for patients with resistant FH. There are still concerns when beginning pharmacological interventions in children with FH and also the management of FH in women of childbearing age or during pregnancy is a clinical dilemma. In the present article, these current challenges in the management of FH will be discussed.