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Hyperlipidemia in Childhood Radha R. Cohen, M.D., F.A.A.P Pediatric Grand Rounds April 1, 2004 Hyperlipidemia in Childhood Overview Basic lipoprotein structure and metabolism Role of childhood hyperlipidemia in atherosclerosis Classification of hyperlipidemias Pediatric cholesterol screening guidelines Management of hyperlipidemia in children Hyperlipidemia in Childhood Definition Hyperlipidemias = group of metabolic disorders characterized by an abnormal accumulation of various lipids in plasma. This may be due to genetics, diet or other acquired factors. Cholesterol and trigylceride are the primary lipids in plasma. Because they are insoluble in plasma, they are transported within the vascular space as lipoproteins. Hyperlipidemia in Childhood Lipoprotein structure Lipoprotein structure hydrophobic core triglyceride and/or cholesterol ester surface coat phospholipid monolayer interspersed free cholesterol and apolipoproteins Hyperlipidemia in Childhood 4 Major Classes of Lipoproteins •Lipoproteins are divided into several classes based on their density. •Each class appears to have distinct functions and atherogenic risk. Hyperlipidemia in Childhood Classes of Lipoproteins •Total Cholesterol measured in the blood or serum can be viewed as the sum of cholesterol carried in the different major lipoproteins: •LDL-cholesterol •HDL-cholesterol •VLDL-cholesterol Hyperlipidemia in Childhood LDL •LDL-cholesterol makes up the majority (6070%) of cholesterol in the blood. •It has B-100 as its major apolipoprotein; lipoproteins that contain B-100 accumulate in arteries and within atherosclerotic plaques. •It is viewed as the atherogenic lipid; high levels in adults have been correlated with coronary artery disease. Hyperlipidemia in Childhood LDL •LDL-cholesterol receptors are present throughout the body and their metabolism is highly regulated by intracellular cholesterol levels. •Brown and Goldstein received the Noble prize in 1985 for their work elucidating the control and metabolism of LDL-receptors. Hyperlipidemia in Childhood HDL •HDL-cholesterol typically makes up 20-25% of the total cholesterol. •It is involved with transport of surplus cholesterol out of the tissue; this reverse transport may be responsible for its protective action against atherosclerosis. •In populations with elevated LDL, HDL-levels are inversely correlated with coronary atherosclerosis. Hyperlipidemia in Childhood VLDL and Chylomicrons •These are the largest of the lipoproteins and are major carriers of triglycerides (TG). •TG are the main storage form of fatty acids. Long chain fatty acids are absorbed in the intestine and combine to form triglycerides and are transported through the thoracic duct to enter the blood stream as chylomicrons. •Chylomicrons are cleared from the blood stream after fasting by lipoprotein lipase. Hyperlipidemia in Childhood Atherosclerosis •Clear evidence linking abnormalities in lipid and lipoprotein levels to premature atherosclerosis. •Studies in adults show an unequivocal relationship of elevated levels of total cholesterol and LDL-C to premature atherosclerosis. Atherosclerosis and Coronary Artery Disease •Atherosclerosis is a disease of large arteries that causes deposits of yellowish plaques containing lipoid material and cholesterol in the intima of vessel walls. •This is the pathogenic mechanism for coronary and peripheral vascular disease in adults. Atherosclerosis and Coronary Artery Disease •Advanced lesion results from: •proliferation of smooth muscle cells and macrophages •formation of collagen matrix by smooth muscle •accumulation of lipid within the cells and surrounding tissue •FATTY STREAK=>FIBROUS PLAQUE Atherosclerosis Begins in Childhood In 1962, Strong and McGill reported the autopsy findings of >500 subjects ages 1-69 yrs Fatty streaks rare in 1st decade of life but almost universal by age 20 yrs Progression of Atherosclerosis In Strong & McGill’s study, fibrous plaques were 1st observed in the second decade but increased in frequency and extent during the 3rd & 4th decades. Atherosclerosis and CAD Later in life, fibrous plaques may occlude the vessel lumen and potentiate thrombus formation. THIS IS WHAT WE WANT TO PREVENT!!! Hyperlipidemia in Childhood CAD Begins in Childhood Clinical sequelae of atherosclerosis do not generally occur until later in life. However, there is significant evidence that the pathologic changes begin years prior and are linked to childhood cholesterol levels. = Cholesterol Levels in Childhood and Atherosclerosis Bogalusa Heart Study: children who had their coronary risk factors measured sequentially as participants in this study and then died accidentally were studied at autopsy extent of fatty streaks was related to total and LDL cholesterol fatty streaks in coronaries related best to VLDL inverse relationship of fatty streaks to HDL Cholesterol Levels in Adolescence Linked to Atherosclerosis PDAY (Pathological Determinants of Atherosclerosis in Youth) Study- ongoing autopsy study of progression of atherosclerosis in subjects 15-34yrs VLDL and LDL positively and HDL negatively associated with fatty streaks and fibrous plaques Raised lesions were found in those as young as 25yrs Cholesterol Levels in Childhood and CAD in Adulthood Epidemiological investigations provide further evidence of the importance of cholesterol levels in pediatrics Cross-population studies show children from countries with high incidence of CAD in adulthood have higher cholesterol levels than their counterparts in countries with low incidence of CAD Within a population, elevated levels of total and LDL cholesterol in children have been associated with CAD in adult relatives Hyperlipidemia in Childhood Summary of Data Evidence demonstrates that: fatty streaks occur in young people and then progress to atherosclerotic plaques extent of arterial lesions is related to serum lipid (cholesterol) levels manipulation of cholesterol levels can affect development of atherosclerosis therefore... Efforts to prevent the development and progression of atherosclerosis should begin in childhood and adolescence. Hyperlipidemia in Childhood Goal of the Pediatrician Goal of detection / treatment... prevention of premature coronary artery disease Foundation of this goal depends on... coronary artery disease begins in childhood coronary artery disease is related to blood cholesterol levels lowering cholesterol in children will be effective in CAD National Cholesterol Education Program (NCEP) The NCEP was created by the National Heart, Lung, and Blood Institute of the NIH in 1985. Its charge was to reduce the prevalence of hypercholesterolemia in the US population and thereby reduce the morbidity and mortality associated with CAD. Hyperlipidemia in Childhood Definitions Hypercholesterolemia = total-C or LDL-C 95th % for age Hypertriglyceridemia = TG 95th % for age These are working definitions of hyperlipidemia Levels associated with the least risk of developing CAD in adulthood have not been determined Hyperlipidemia in Childhood Normal Values National Cholesterol Education Program (NCEP): Expert Panel on Blood Cholesterol Levels in Children and Adolescents Hyperlipidemia in Childhood Normal Values National Cholesterol Education Program (NCEP): Expert Panel on Blood Cholesterol Levels in Children and Adolescents Hyperlipidemia in Childhood Classification: Primary versus Secondary first consideration - whether the hyperlipidemia is primary (genetic dyslipidemias) or secondary to a metabolic disease or exogenous cause common secondary causes during infancy · glycogen storage disease and biliary atresia · hypothyroidism, diabetes, nephrotic syndrome · oral contraceptives, alcohol, steroids common secondary causes in childhood common exogenous causes Hyperlipidemias Secondary Causes Exogenous Alcohol Contraceptives Steroid therapy Endocrine and Metabolic Acute intermittent prophyria *Diabetes mellitus Hypopituitarism *Hypothyroidism Lipodystrophy Pregnancy Storage disease Cystine storage disease Gaucher disease *Glycogen storage disease Juvenile Tay-Sachs disease Niemann-Pick disease Tay-Sachs disease Renal Chronic renal failure Hemolytic-uremic syndrome *Nephrotic syndrome Hepatic Benign recuurent intrahepatic cholestasis *Congenital biliary atresia Acute and transient Burns Hepatitis Others Anorexia nervosa Idiopathic hypercalcemia Klinefelter syndrome Progeria Systemic lupus erythematosus Werner syndrome KwiterovichP:Disorders of lipid metabolism, in Rudolph AM (ed): Pediatrics, ed 17. Hyperlipidemia in Childhood Frederickson Classification •In Circulation 1965, Frederickson and Lees published a description of 5 phenotypes to categorize people with familial hyperlipidemia according to their pattern of elevation of plasma lipoproteins. •As knowledge progressed, it has become apparent that there may be several different genetic and secondary causes of the same Frederickson phenotype. •This classification system has now fallen out of use. Hyperlipidemias Fredrickson Classification Clinically Important Genetic Dyslipidemias For clinical purposes, the following categories are more useful in determining risk of atherosclerosis, and planning treatment: Hypercholesterolemia Combined hyperlipidemia Hypoalphalipoproteinemia Hypercholesterolemia Defined as total cholesterol >170mg/dL for children ages 2-19 yrs An isolated elevation of cholesterol is nearly always due to increase in LDL-C 2 genetic disorders are assoc. with Total-C & LDL-C = 2-5Xnormal -familial hypercholesterolemia -familial defective apoB-100 Hypercholesterolemia Familial hypercholesterolemia is caused by a mutation in LDL receptor gene on short arm of chromosome 19. Familial defective apoB-100 is due to rare mutations of the apoB gene. In both cases, LDL receptors are unable to interact with apo-B, the protein ligand on LDL particles. Both have autosomal dominant pattern of inheritance. Familial Hypercholesterolemia Most commonly recognized form of familial hyperlipidemia in childhood Incidence of heterozygotes is 1:500 and homozygotes 1: 1 million Homozygotes present in childhood with serum cholesterol between 400-800mg/dL and cutaneous and tendon xanthomas. Angina and MI before adolescence are common, and most have severe CAD by age 30. Aortic stenosis is also seen. Tendon Xanthomas tendon xanthomas of the achilles and elbow Tendon Xanthomas tendon xanthomas of the hand Cutaneous Xanthomas Familial Hypercholesterolemia Findings in Homozygotes left coronary artery narrowing supravalvar lipid deposition Eye Findings in Familial Hypercholesterolemia Early corneal arcus Cholesterol deposits in retinal fundus Familial Hypercholesterolemia Heterozygous Form LDL-C is > 95% at birth. Lipid levels remain markedly elevated throughout childhood and adulthood with total cholesterol ~300-400mg/dL and LDL-C ~200-300mg/dL. Clinical manifestations include tendon xanthomas after age 20, early corneal arcus, and CAD after age 30. This diagnosis should strongly be suspected in anyone with high LDL-C and tendon xanthomas in the patient or 1st degree relatives. Familial Hypercholesterolemia and CAD In heterozygous males, the risk for development of CAD is estimated to be 20% at age 40yrs, 45% at age 50yrs, and 75% at age 60yrs. FH is thought to account for 3% of premature CAD in the US. Familial Hypercholesterolemia Family history and screening of family members should reveal 1/2 of 1st degree relatives with FH Diagnosis can be confirmed by measuring LDL receptor activity in cultured skin fibroblasts or identifying the gene mutation. Prenatal diagnosis is possible by assessing LDL receptor activity in cultured amniotic cells. Genetic counseling is important, especially if partner’s cholesterol is elevated or not known. Combined Hyperlipidemia Familial combined hyperlipidemia was 1st described by Goldstein et al. as dominantly inherited hyperlipidemia and CAD. Affected individuals have either TG or LDL-C >90% or both TG & LDL-C >90%. Phenotype may vary among family members or even from time to time in same individual. Presentation usually delayed until 3rd decade of life. No cutaneous or ocular findings. Thought to affect ~1% of population and account for 10% of premature CAD. Hypoalphalipoproteinemia Defined as HDL-C < 10% for age and sex associated with normal LDL-C and TG levels. Appears to have autosomal dominant pattern of inheritance in that ~1/2 of family members have low HDL-C and premature atherosclerosis. No clinical manifestations other than premature atherosclerosis with CAD common as early as 4th decade. Cholesterol Screening in Children The NCEP recommended selective screening of children and adolescents, targeting those who were likely to become adults with high blood cholesterol and who would thus be at an increased risk for the development of cardiovascular disease. Cholesterol Screening Reasoning for selective screening children and adolescents with elevated blood cholesterol (particularly LDL) frequently come from families in which there is a high incidence of CAD among adult members high blood cholesterol aggregates in families as a result of both shared environments and genetic factors major risk factor for hypercholesterolemia in a child is a family history of premature CAD or hypercholesterolemia Cholesterol Screening NCEP did not recommend universal screening (controversial) Reasons against universal screening: quite a few children with high cholesterol will not have high enough levels as adults to require treatment leads to many young people inappropriately labeled as having “disease” could lead to overuse of cholesterol-lowering drugs in children Cholesterol Screening Reasons for recommending universal screening: ~50% of children with elevated cholesterol levels would be missed universal screening may benefit young parents as well children are more likely to receive regular health care than young adults Cholesterol Screening Selective screening approach · based on detailed family history and assessment of concomitant risk factors · makes it possible to identify a high risk subset while providing a reasonable balance between the number to be tested and the number to be detected Selective Cholesterol Screening Who should be screened? •Children and adolescents with: -family history of premature atherosclerosis (parents or grandparents with MI, angina pectoris, peripheral vascular disease, cerebrovascular disease, or sudden cardiac death at or before age 55yrs) -parent with high cholesterol (>240mg/dL) -unknown family history, especially those with other risk factors (hypertension, diabetes, obesity, smoking) Age for Cholesterol Screening When do you screen? Anytime after 2 years of age · · cholesterol levels relatively stable by this time no treatment recommendations for children less than 2 years old If levels acceptable, repeat after 5 years Cholesterol Screening What do you order? Total Blood Cholesterol · less expensive, random/nonfasting Fasting Lipid Profile · · · 12 hour fast measure total cholesterol, HDL, TG LDL estimated by formula from Lipid Research Clinics: LDL = total cholesterol - (TG/5 + HDL) inaccurate if TG > 400 mg/dl or if not fasting Cholesterol Screening What to measure also depends on reason for screening • parental high cholesterol total cholesterol • family history of CAD fasting lipid profile LDL level determines risk and need for treatment Cholesterol Screening RISK ASSESSMENT other concerning risk factor family history of hypercholesterolemia measure total cholesterol family history of premature CAD obtain lipoprotein analysis acceptable (<170 mg/dl) borderline (170-199 mg/dl) high (>200 mg/dl) repeat in 5 years nutrition education repeat and average obtain lipoprotein analysis acceptable (<170) repeat in 5 years nutrition education >170 obtain lipoprotein analysis Cholesterol Screening If LDL-C <110 mg/dL, no further testing. If LDL-C 110-129 mg/dL,educate family, prescribe “Step One” diet, and recheck in 1 year. If LDL-C >130 mg/dL, evaluate for causes (r/o secondary causes like hypothyroidism, diabetes; if familial suspected, measure lipid profiles of family) and begin treatment. Management of Elevated Cholesterol LDL-C>130 mg/dL Start “Step One” Diet Recheck level in 6 wks. If LDL not <110 mg/dL, intensify “Step One” Diet and recheck in 3 months. If goal still not met, prescribe “Step Two” diet for next 3 months. If goal still not met after 1 yr with diet alone, consider pharmacotherapy. Hyperlipidemia in Childhood Detection and Treatment LDL level (repeat and average) acceptable (<110 mg/dl) education on eating and CAD risk factors repeat lipoprotein analysis within 5 years high (>130 mg/dl) borderline (110-129 mg/dl) evaluate for secondary causes screen all family members intensive clinical intervention CAD risk factor advise "Step One" diet repeat lipoprotein analysis in 1 year initiate "Step One" diet set goal LDL (at least < 130 mg/dl; ideally < 110 mg/dl) repeat lipoprotein analysis in 6 weeks GOAL NOT ACHIEVED intensify "Step One" diet GOAL ACHIEVED continue long term monitoring repeat lipoprotein analysis in 3 months GOAL NOT ACHIEVED initiate "Step 2" diet GOAL NOT ACHEIVED AFTER 6 MONTHS TO 1 YEAR continue "Step 2" diet consider drug therapy GOAL ACHIEVED continue long term monitoring GOAL ACHIEVED continue long term monitoring long term monitoring = recheck lipoprotein analysis 2x / year Diet Therapy Primary approach to treating children and adolescents with elevated cholesterol levels Aim of diet therapy is to reduce elevated blood cholesterol levels while maintaining a nutritionally adequate eating pattern It is prescribed in two steps that progressively reduce the saturated fatty acid (SFA) and cholesterol intake Diet Therapy Step One diet · < 30% total calories from fat · < 10% total calories from SFA · < 300 mg/day cholesterol · adequate calories for growth and development Requires detailed assessment of current eating patterns and instruction by a physician, RD, or other professional Diet Therapy Step Two diet prescribed if careful adherence to Step One diet for at least 3 months fails to achieve the minimal goals of therapy further reduction of SFAs and cholesterol · · · < 30% calories from fat (SAME as Step One) < 7% total calories from SFA < 200 mg/day cholesterol Diet Therapy National Cholesterol Education Program (NCEP): Expert Panel on Blood Cholesterol Levels in Children and Adolescents Mg of Cholesterol in Foods cholesterol ( 300 mg/day) bacon, 3 slices = 16 mg chicken (3.5 oz), lt meat, no skin=75 mg shrimp (3.5 oz) = 195 mg egg, yolk = 213 mg cheddar cheese (1 oz) = 30 mg bread, one slice = 0 mg butter (one TBS) = 31 mg margarine (one TBS) = 0 mg McDonald’s Big Mac = 100 mg McDonald’s Egg McMuffin = 235 mg Pizza Hut Pan Pizza (1 slice) = 25 mg potato chips (1 oz) = 0 mg cola, regular = 0 mg chocolate chip cookies(4) =18mg peanuts (1 oz) = 0 mg Diet Therapy General food guidelines meat, poultry, and fish · · · major sources of high quality protein but also major contributors of SFA, total fat, and cholesterol use LEAN meat, remove skin from poultry eggs · · · good source of high quality protein, iron, vits yolks very high in cholesterol (whites=none) 2 egg whites substituted for 1 egg in recipes Diet Therapy Fats and oils · · · · SATURATED FATTY ACIDS are BAD intake of saturated oils: coconut, palm kernel, palm intake of unsaturated oils: sunflower, corn, canola, olive, peanut margarine instead of butter (with unsaturated oil listed as first ingredient) Diet Therapy Plant stanol esters · · · Are available in low-fat margarine spreads Also available in salad dressings and snack bars Structurally stanol esters are similar to cholesterol and inhibit cholesterol absorption in the gut by competitive mechanisms Plant Sterol Esters • Studies have demonstrated that consumption of low-fat margarine containing stanol esters can lower total and LDL cholesterol by 10-15% in hypercholesterolemic subjects • Have been studied in children with no adverse clinical effects noted • Does not affect HDL-C or TG levels • Effects on Total and LDL-C seen in 4-8 weeks with a daily dose of 2-3 g (~3 Tbsp of the commercially available products) • Examples: Benecol and Take Control Exercise • In addition to diet prescription, don’t forget to recommend regular aerobic exercise • 30-45 minutes, at least 4-5 times a week • Can increase HDL-C • Can help with regards to other risk factors for CAD, such as obesity and hypertension Drug Therapy Only a small proportion of children should be considered for drug treatment because of the potential side effects relative expense of medications lack of definitive, prospective data on the effect of such treatment on children Drug Therapy Consider drug therapy following adequate trial of diet therapy for 6 months to 1 year if · · LDL remains > 190 mg/dl LDL remains > 160 mg/dl and + family history of premature CAD or 2+ other risk factors still exist (HDL<45 mg/dl, obesity, diabetes, hypertension) · LDL > 130 mg/dl but <160 mg/dl, no specific recommendations for drug therapy Drug Therapy Only approved for children older than 10 years of age Diet & exercise therapy must continue Follow up · · · 6 weeks after starting medication every 3 months thereafter until goal is met then every 6 months Drug Therapy Bile-acid binding resins Ezetimibe HMG-CoA reductase inhibitors (“statins”) Niacin (nicotinic acid) Fibric acid derivatives Bile Acid Sequestrants •Primary therapy recommended in children •Cholestyramine (Questran) and colestipol (Cholestid) •Reduce LDL levels by ~20% •Long-term compliance limited, presumably due to unpalatability and GI side effects (nausea, bloating, constipation, flatulence) Bile Acid Sequestrants Mechanism of action: · · · · · · · · anion exchange resins bind (-) bile acids in SI resin/bile complex out via feces prevents enterohepatic circulation of bile acids bile acid concentration in hepatocytes causes an conversion of cholesterol to bile acids causes in intracellular cholesterol activates an increased uptake of LDL cholesterol particles outcome = plasma cholesterol Bile Acid Sequestrants •Overall safe because not absorbed and lack systemic toxicity •However, they can cause malabsorption of fatsoluble vitamins and folic acid so a daily MVI containing folic acid and iron is recommended •Their use is limited in patients who also have elevated TG since they can increase TG levels •Check CBC and LFTs annually in patients Bile Acid Sequestrants cholestyramine and colestipol both are powders that are mixed with water or juice before ingestion; cholestyramine is also available as flavored bars choice of one over the other depends on individual taste preference and side effects dose is not related to body weight but to levels of total and LDL cholesterol · start on lowest dose possible, then one dose at a time until goal achieved Bile Acid Sequestrants cholestyramine and colestipol dosing regimen · · · one dose = 9 g packet of cholestryramine, one bar of cholestyramine, or 5 g colestipol daily doses TC LDL 1 <245 <195 2 245-300 195-235 3 301-345 236-280 4 345 take immediately before, during, or after meals (largest amount of bile acids in intestine) Ezetimibe (Zetia) Relatively new agent Inhibits intestinal absorption of cholesterol Limited study in children 10-18 yrs Lowers LDL-C by up to 15-20% May decrease TG and increase HDL-C Given as a single 10mg dose tablet No major side effects noted In adults has been used in conjunction with statins Statins HMG-CoA reductase inhibitors work by inhibiting the rate-limiting step in cholesterol biosynthesis Have been used in adults >10-15 years with good success and safety Can decrease Total and LDL-C by 20-60% Limited studies in children show efficacy and no significant side effects, but studies were underpowered for safety Statins Must monitor LFTs every 3-6 months as there is a potential for hepatocellular toxicity Also, statins are potentially teratogenic so they should be used with caution in female adolescents. Hyperlipidemia in Childhood Summary CAD is a major cause of significant mortality, morbiditity, and expense It begins in childhood and progresses in severity as we age It results from a combination of interrelated factors such as genetics, hypercholesterolemia, hypertension, obesity, diabetes, and smoking Many of these risk factors are largely preventable and/or modifiable Hyperlipidemia in Childhood Summary Efforts to prevent the development and progression of atherosclerosis should begin in childhood and adolescence Selective cholesterol screening can identify those children at highest risk for hypercholesterolemia For those children with hypercholesterolemia, a diet low in SFAs and cholesterol is the mainstay of therapy Hyperlipidemia in Childhood