Clinical Implications of the Molecular Basis of Familial Hypercholesterolemia and Other Inherited Dyslipidemias

The effects of 3-year statin therapy and the achievement of LDL cholesterol target values in familial hypercholesterolemia patients: An experience from Serbia

BACKGROUND AND AIMS

Despite the use of statins, familial hypercholesterolemia (FH) patients often have increased LDL-cholesterol (Ch) and high risk for atherosclerotic cardiovascular disease (ASCVD). This study aimed to analyze the effect of statin therapy on attainment of LDL-Ch treatment targets and appearance of new ASCVD and diabetes in FH patients.

METHODS

This study is a retrospective analysis of data from medical records of 302 FH patients treated continuously with statins during 3 years. At baseline and once yearly, anthropometric measurements, lipids (total Ch, LDL-Ch, HDL-Ch, triglycerides, apoliporotein A1 and B), fasting plasma glucose, and insulin were determined.

RESULTS

In FH patients, high intensity statin was prescribed only in 17.9% of cases. LDL-Ch levels were significantly lower after 3 years of statin treatment (3.61 ± 1.19 mmol/l) vs. baseline (4.51 ± 1.69 mmol/l; p < 0.01), but only 6.9% of FH patients reached the recommended ≥50% LDL-Ch reduction and 16.2% attained the LDL-Ch <2.6 mmol/l target. Simultaneously, 9.6% of FH patients developed new ASCVD, with lower HDL-Ch after 3 years of statin treatment than in those who remained free of ASCVD. In addition, we observed new onset diabetes in 6.4% of FH patients who were more obese, older and with higher fasting glucose at baseline than FH patients free of diabetes, regardless of the type of statin.

CONCLUSIONS

These results imply that only a small proportion of FH patients achieved the recommended LDL-Ch treatment targets, mostly due to the use of low statin dose and infrequent implementation of high-intensity statin treatment, which altogether could not prevent the increase in residual cardiovascular risk.

Universal screening of cholesterol in children

Atherosclerosis begins in childhood, and these early lesions are related to cardiovascular risk factors, including non-high-density lipoprotein cholesterol (HDL-C). Genetic disorders of lipid metabolism, principally familial hypercholesterolemia, have a high frequency in the population (about 1:300-1:500), and cause cardiovascular morbidity beginning in the third decade of life. The current obesity epidemic in children has worsened cardiovascular risk status. Cardiovascular risk factors present in youth often track into adulthood and are more predictive of future subclinical atherosclerosis than risk factors measured in young adulthood. Further, modification of risk factors beginning in childhood and young adulthood can lead to restoration to normal or improvement in measures of subclinical atherosclerosis measures both in those with genetic dyslipidemias and those with dyslipidemia secondary to obesity. Prior recommended selective lipid screening strategies based on family history or presence of other cardiovascular risk factors have failed to capture many with genetic dyslipidemia. Medium-term clinical trials of statin therapy for inherited dyslipidemias are safe and effective in lowering low-density lipoprotein cholesterol (LDL-C). Cholesterol screening in childhood is necessary to prevent cardiovascular morbidity in those with genetic dyslipidemias and to increase awareness of the need for behavioral intervention in those with multiple cardiovascular risk factors, often a result of the obesity epidemic.

Identification of people with heterozygous familial hypercholesterolemia

PURPOSE OF REVIEW

Familial hypercholesterolemia is an underdiagnosed autosomal codominant genetic condition associated with significantly increased risk of early cardiovascular disease when untreated. Early diagnosis and treatment decrease the excess risk, and strategies for identification of affected individuals are being developed worldwide. This review will discuss, from a clinician's perspective, some of the issues involved in identifying people with familial hypercholesterolemia.

RECENT FINDINGS

Several sets of recommendations have been published outlining the strategies for identification of people with familial hypercholesterolemia in various countries and regions. These include Australasia, Europe, and the USA.

SUMMARY

Continuing efforts to find the best methods for identification of people with familial hypercholesterolemia are needed to ensure that this very treatable inherited condition is diagnosed early enough to prevent the development of atherosclerotic vascular disease.

Miscellaneous non-inflammatory musculoskeletal conditions. Rare thesaurismosis and xanthomatosis

The focus will be on xanthomatosis, a tissue danger signal which needs to be recognized by the clinician, and its relationship with monogenetic lipoprotein disorders (cholesterol, triglycerides), bile acid and sterol metabolism, particularly on metabolic pathways and genetics as well as on musculoskeletal and cardiovascular involvement, and their implications for clinical management. The critical question is to assess coronary heart disease risk, requiring correct identification of the pattern of lipoprotein disorders and of the causes (primary or secondary). Familial hypercholesterolemia must be suspected in adults and children with raised total cholesterol, especially when there is a personal or a family history of premature coronary heart disease, usually requiring potent statins to achieve adequate LDL-cholesterol lowering, even if we do not know safety of long-term therapy and whether treatments of dyslipidemia early in life prevent cardiovascular diseases in adulthood. Cerebrotendinous xanthomatosis is a treatable disease and must be suspected if there is a history of infantile chronic diarrhea and/or juvenile cataracts, even in the absence of tendon xanthomas. Current evidence for the prevention and screening, diagnosis, and treatment of dyslipidemia are available for the clinicians.

Molecular pathology of familial hypercholesterolemia, related dyslipidemias and therapies beyond the statins

The development of the statin class of cholesterol-lowering drugs is one of the most significant success stories of modern pharmacotherapy. World-wide there are an estimated 150 million people on statins, with the emerging economies of India and China predicted to contribute significantly to that number. Notwithstanding their success, a significant number of people cannot tolerate statins because of serious side effects; of equal concern, a substantial proportion of high risk patients fail to reach cholesterol-lowering targets. For these subjects there is an urgent need for new cholesterol-lowering agents to be used alone or in combination with statins. The success of statins has been largely underpinned by knowledge of cholesterol homeostasis at a molecular level, knowledge that was first gleaned in the 1980s from Brown and Goldstein's pioneering studies of familial hypercholesterolemia (FH, OMIM 143890). Follow-up work that has identified a number of intracellular and circulating factors, all capable of disrupting LDL clearance, has revealed that the low-density lipoprotein receptor- (LDLR) mediated clearance pathway is substantially more complex than previously thought. These factors were discovered in studies of individuals with very rare inherited conditions that lead to either hypo- or hypercholesterolemia. These investigations, besides providing clearer insight into the molecular mechanisms regulating plasma LDL concentrations, have also revealed a number of novel therapeutic targets independent from statins. Consequently, a number of novel therapeutic approaches that are based on small interfering bio-molecules, including antisense oligonucleotides, are now in clinical development. These are aimed at impairing the assembly, synthesis and secretion of apolipoprotein B-containing lipoproteins and/or accelerating their hepatic catabolism. The aim of this article is to focus on these recent advances in the understanding of the molecular basis of cholesterol metabolism that should herald novel cholesterol-lowering agents beyond the statins.