© 1995 American Heart Association, Inc.
Articles |
Mutations in the Gene for Lipoprotein Lipase
A Cause for Low HDL Cholesterol Levels in Individuals Heterozygous for Familial Hypercholesterolemia
From the Department of Medical Genetics, University of British Columbia, Vancouver (S.N.P., S.E.G., M.R.H.), and the Lipid Research Centre, Laval University, Ste-Foy, Quebec (C.G., P.J.L., D.G., S.M.), Canada; the University of Utah, Cardiovascular Genetics, Salt Lake City (R.R.W.); the Department of Human Genetics, University of Stellenbosch, Tygerberg, South Africa (M.K.); and the Lipid Research Group, Department of Vascular Medicine, University of Amsterdam (Netherlands) (P.W.A.R., J.C.D., J.J.P.K.).
Correspondence to Dr Michael R. Hayden, Department of Medical Genetics, University of British Columbia, Rm 416-2125 East Mall, Vancouver, British Columbia V6T 1Z4, Canada.
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Abstract |
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Abstract Familial hypercholesterolemia (FH) is characterized by elevated plasma concentrations of LDL cholesterol resulting from mutations in the gene for the LDL receptor. Low HDL cholesterol levels are seen frequently in patients both heterozygous and homozygous for mutations in this gene. Suggested mechanisms for reduced HDL levels in FH patients have been altered apolipoprotein A-1 metabolism and elevated cholesteryl ester transfer protein activity, but the molecular basis for hypoalphalipoproteinemia in any of these patients has not yet been identified. We investigated four large families in which individuals were found to be double heterozygotes for both FH and lipoprotein lipase (LPL) deficiency. These double heterozygotes have significantly less HDL cholesterol than persons with FH or LPL heterozygosity alone. In the double heterozygotes, HDL particle composition is not significantly different from FH heterozygotes, suggesting a quantitative rather than qualitative defect in HDL metabolism in these persons. We propose that mutations in the LPL gene may be a cause of low HDL cholesterol levels in some individuals heterozygous for FH.
Key Words: HDL • lipoprotein lipase • familial hypercholesterolemia
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Introduction |
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Familial hypercholesterolemia results from many different defects in the gene for the LDL receptor and is inherited as an autosomal dominant trait.1 Heterozygosity for FH occurs with a frequency of approximately 1 in 500 in the western world and is characterized by elevated levels of LDL cholesterol, tendon xanthomas, and premature coronary artery disease. Plasma levels of HDL cholesterol are significantly reduced in many FH families,2 3 4 5 although the precise frequency with which this occurs is unknown.
Currently, no clear understanding for hypoalphalipoproteinemia in patients with FH has been obtained. Kinetic studies in an FH homozygote suggest both an increased apoA-1 fractional catabolic rate and a decreased apoA-1 production rate as the mechanisms for reduced HDL cholesterol in this subject.6 It has also been suggested that enhanced activity of CETP seen in FH heterozygotes may underlie the reduced levels of HDL cholesterol in some individuals.4 Because of the large contribution (approximately 75%) made by CE to HDL cholesterol,7 any factor resulting in a decrease in the CE content of HDL could consequently reduce the plasma HDL cholesterol level. Animal models of FH (in particular, the Watanabe heritable hyperlipidemic rabbit), which also have low HDL cholesterol, have been shown to have enhanced CETP activity.8 However, the molecular basis for low HDL cholesterol levels in any patients with FH has not yet been reported.
Other genetic variants and environmental factors are known to alter the lipid phenotype and clinical outcome of FH.9 Recently, a patient homozygous for LPL deficiency and heterozygous for FH was described. A markedly reduced LDL cholesterol was noted, confirming in vivo the major role played by LPL in the conversion of TG-rich lipoproteins to LDL in human plasma.10 Here we have studied four families with individuals who were double heterozygotes for both FH and LPL deficiency. We show that double heterozygotes confirmed by molecular analysis present with alterations in their lipid profile, characterized by more marked reduction in HDL cholesterol levels, but no significant alteration in HDL particle composition when compared with family members who are heterozygotes for FH alone. Heterozygosity for partial LPL deficiency is common and may occur in approximately 5% of the general population.11 It may therefore be predicted that heterozygosity for mutations in the LPL gene might occur in approximately 5% of FH families and may represent an important cause of low HDL in some FH families.
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Methods |
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Study Subjects
Assessment of families for LPL mutations resulted in the serendipitous finding of four families containing individuals who were double heterozygotes for both FH and LPL deficiency (families A, B, C, and D). In all four families, mutational analysis was performed to identify the defects underlying both the LDL receptor and LPL mutations (see Table 1
). Individuals in each family were screened for
the specific LPL and LDL receptor mutation found in the proband in all
families. In family C, FH was diagnosed by mutational analysis
in one affected relative and in other relatives by using DNA-validated
clinical criteria that were published previously.12 This
family is a large FH pedigree that was reported together with a formal
segregation analysis that revealed dominant transmission of
elevated LDL cholesterol levels and early coronary
artery disease maximum likelihood complex segregation
analysis.13 In particular, all FH heterozygotes in
this family had elevated total and LDL cholesterol levels
for age and sex, no evidence of secondary
hyperlipidemia, at least one pediatric relative with
very high cholesterol, or a relative with very high
cholesterol and tendon xanthomas. Dominant expression was
also clearly evident in this family.
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The 10-kb deletion and Trp66Gly mutation in the LDL receptor in families A and B were detected by Southern blot and dot blot oligonucleotide hybridization, respectively, as described previously.14 15 In family C, a change in exon 17 of the LDL receptor gene was detected by single-strand conformational polymorphism analysis (R.R.W., unpublished data, 1994). The LDL receptor defect in family D, Val408Met, was detected by Nla III restriction endonuclease digestion after polymerase chain reaction amplification as previously described.16 The LPL mutations in family A (Asn291Ser), B (Pro207Leu), C (Glu188Gly), and D (Asn291Ser) were detected by polymerase chain reaction methods described previously11 17 18 after DNA was extracted by standard procedures.19
None of the subjects included in the study were taking any lipid-lowering drugs or any other medication known to affect lipid metabolism, including hormonal therapy. No study subject had clinical or biochemical evidence of diabetes mellitus or thyroid, hepatic, or renal disease. All individuals known to ingest more than two alcoholic drinks per day were also excluded from the study.
Laboratory Analysis
Lipid levels were measured at the same laboratory for all
subjects within a family. Because no interfamilial comparison was being
made, standardizing laboratories between families was unnecessary. In
all four families, venous blood samples were collected after a 12-hour
overnight fast according to Lipid Research Clinics Program
guidelines.20 Immediately after collection, plasma and
cells were separated by centrifugation in a desktop
centrifuge at 3000g for 20 minutes at room
temperature. Plasma total cholesterol and TG were
analyzed by standard enzymatic methods in families A, B, and
D.21 22 23 In families A and B, HDL cholesterol
was measured after heparin manganese precipitation of VLDL and
LDL.24 In family D, HDL cholesterol was
determined after precipitation of VLDL cholesterol and LDL
cholesterol with phosphotungstate and magnesium chloride as
described previously.25 In family C, plasma lipids were
determined by a microprocedure described elsewhere,26 and
HDL cholesterol was measured after a
MgCl2–dextran sulphate precipitation.27 The
same methods of analysis were used for all family members in
each family.
Detailed lipoprotein analysis was performed in family B. Lipoprotein fractions (VLDL=d<1.006 g/L; IDL=1.006<d<1.019 g/L; LDL=1.019<d<1.063 g/L; and HDL=1.063<d<1.21 g/L) were isolated by sequential ultracentrifugation using a Beckman 50.4 rotor.28 Recovery of lipids averaged 96% (range, 92% to 102%) of the values in plasma. Lipid measurements in lipoprotein fractions were performed on automated Technicon RA-1000 with enzymatic methods; reagents for cholesterol and TG were purchased from Miles Diagnostics, for UC from Boehringer Mannheim, and for PL from Wako Pure Chemicals. ApoA-I and apoB were measured in families A and B by electroimmunoassay as described previously.29 30 Heights and weights were recorded, and body mass index was calculated.
Statistics
In this study, assumptions of normality and homoscedasticity
(and possibly sample independence) were not met. Therefore, a
nonparametric statistical procedure was used to determine
differences in lipid, lipoprotein, and demographic data of groups
within families. A Kruskal-Wallis one-way ANOVA with ranks was
used. If the overall associations for a variable proved
statistically significant (P
.05), pairwise comparisons by
Mann-Whitney two-sample test of association were used. Because of
the known effect of sex differences in HDL values, all four families
were analyzed as males and females separately. Within mutation
groups, no significant sex differences were noted in the lipid values
under investigation in families A, B, and D. For this reason,
statistical results for these families are presented as males
and females combined. Sex differences in HDL, however, were noted
within FH heterozygotes in family C. The statistical analyses
for this family were therefore performed separately for males and
females, and the results are shown accordingly. Within all four
families, mutation groups were age matched; therefore, analyses
were performed without need to correct for age.
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Results |
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DNA Analysis
The molecular basis of FH and LPL deficiency in all four families is shown in Table 1
together with the number
of FH/LPL double heterozygotes, single heterozygotes for LPL
deficiency and FH, and the relatives with neither mutation. Family A,
of French Canadian ancestry, consisted of 25 individuals who were
assessed for mutations in the genes for the LDL receptor and LPL (Fig 1). Mutational analysis revealed the 10-kb
deletion as the underlying LDL receptor defect and the exon 6 Asn291Ser
mutation as a cause for partial LPL deficiency in this family. Four
individuals in the family were found to be double heterozygotes for
both FH and LPL (2 males and 2 females; Table 2). Nine
FH heterozygotes were defined (2 males and 7 females; Table 2), and 4
LPL heterozygotes (1 male and 3 females; Table 2) were studied. The
control group in family A consisted of 8 related individuals (5 males
and 3 females; Table 2).
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Family B (Fig 2), also of French Canadian ancestry,
consisted of 145 individuals of which 8 were found to be double
heterozygote for FH and LPL deficiency (3 males and 5 females; Table 3). Of these 8 double heterozygotes, 4 were not directly
related to the family but had the same mutations, the same ancestry,
and lived in the same isolated geographic area. For these reasons, they
were included in this family study. Fourteen FH heterozygotes (7 males
and 7 females; Table 3) and 21 LPL heterozygotes (12 males and 9
females; Table 3) were studied. A total of 102 relatives without either
mutation (46 males and 56 females; Table 3) were assessed. The LPL
heterozygotes have been analyzed further in detail to assess
age and sex influences on heterozygosity for mutations in the LPL gene
(manuscript in preparation). DNA analysis in this family
revealed the Trp66Gly mutation as the basis for the LDL receptor defect
and the Pro207Leu mutation as the molecular basis for LPL
deficiency.
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Family C, of mixed European ancestry, consisted of 54 individuals (Fig 3) including 4 double heterozygotes (1 male and 3
females; Table 4). Thirteen FH heterozygotes (6 males
and 7 females; Table 4) and 14 LPL heterozygotes (5 males and 9
females; Table 4) were also studied. A total of 23 related individuals
(14 males and 9 females) had neither mutation (Table 4). The LPL
mutation in this family was the Glu188Gly in exon 5 of the LPL
gene; single-strand conformational polymorphism
analysis revealed a new, unpublished variant in exon 17
of the LDL receptor gene, which segregated with the phenotype
of FH in all 13 members of this family and was not found in individuals
without the clinical phenotype in the family. The exact nature
of this mutation remains unknown.
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Family D consisted of 29 individuals, all of Dutch ancestry (Fig 4). Four double heterozygotes were identified (2 males
and 2 females; Table 5). Ten FH heterozygotes (7 males
and 3 females; Table 5) and 2 LPL heterozygotes (2 males; Table 5) were
also studied. A control group consisting of 13 related individuals (1
male and 12 females; Table 5) had neither mutation. DNA
analysis in this family revealed the Val408Met mutation as the
basis for the LDL receptor defect and the Asn291Ser mutation as the
molecular basis for partial LPL deficiency.
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Within each family, age and body mass index did not differ
significantly among the groups (Tables 2 through 5). In addition,
physical activity and smoking habits were recorded in families A,
B, and D; no significant difference was seen among the groups in each
family (data not shown).
Lipid Levels
In all four families, double heterozygotes for both FH and LPL
deficiency had reduced HDL cholesterol levels compared with
those individuals heterozygous for FH. Despite the small numbers
of double heterozygotes, statistical significance was reached in
families A, B, and D (A, P=.037; B, P=.009; D,
P=.048). A similar trend was seen for family C even when
separated into males and females (Table 4), but this did not reach
significance. HDL cholesterol levels were also
consistently lower in the double heterozygotes when compared
with those in individuals heterozygous for LPL deficiency alone in the
same family. Although these results did not reach statistical
significance, a trend was noted in all four families (Tables 2 through 5).
In the four families, the ratio of total cholesterol to HDL
was increased in double heterozygotes for FH and LPL deficiency when
compared with individuals with FH or LPL deficiency alone, although
this reached statistical significance in family B only (see Tables 2 through 5). A trend to higher TG was also noted in FH/LPL double
heterozygotes in all four families when compared with individuals in
the families with FH alone (A, P=.14; B, P=.11;
C, P=.046; D, P=.09).
Lipoprotein Assessment
HDL Lipids
Detailed lipoprotein analysis was undertaken in family B,
chosen for its extensive size. The results, illustrated in Table 6, indicate significant reductions in HDL lipids in
FH/LPL double heterozygotes compared with FH heterozygotes alone.
HDL-UC and HDL-PL were both significantly reduced in these double
heterozygotes (P=.05, respectively). HDL-CE and HDL-TG were
also decreased in the FH/LPL double heterozygotes compared with FH
heterozygotes alone (Table 6), but this did not reach significance. The
lipid concentrations in HDL in FH/LPL double heterozygotes were also
lower than those seen in LPL heterozygotes. Both HDL-TG and HDL-PL were
significantly reduced (P=.008 and P=.01,
respectively). HDL-CE and HDL-UC were also lower in double
heterozygotes compared with LPL heterozygotes, although significance
was not reached (P=.09 and P=.10,
respectively).
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VLDL Lipids
Lipid concentrations in VLDL particles in FH/LPL double
heterozygotes were similar to those of FH heterozygotes alone.
Increased VLDL-TG was noted, but significance was not reached
(P=.154; Table 6). VLDL lipid concentrations were not
different between FH/LPL double heterozygotes and LPL heterozygotes
alone.
LDL Lipids
No significant difference was seen in lipid concentration in LDL
particles between FH/LPL double heterozygotes and FH
heterozygotes alone. However, significantly increased levels of LDL-CE,
LDL-UC, and LDL-PL were seen in FH/LPL double heterozygotes compared
with LPL heterozygotes alone (P=.007 for all measurements,
respectively).
Lipoprotein Particle Composition
Despite the differences noted in lipid concentrations in the
various lipoprotein particles, no significant differences in
lipoprotein particle composition was evident in FH/LPL double
heterozygotes compared with FH heterozygotes alone (Table 7). Differences were seen, however, in FH/LPL double
heterozygotes when compared with LPL heterozygotes alone. These
differences were evident in both LDL and HDL particles. LDL-CE and
LDL-UC made up a significantly greater percentage of the LDL particles
in FH/LPL double heterozygotes compared with LPL heterozygotes
(P=.044 and P=.025, respectively; Table 7). This
increase in LDL cholesterol in FH/LPL double heterozygotes
resulted in a significantly lower percentage of TG in LDL particles
(P=.034) when compared with findings in LPL
heterozygotes.
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HDL particle composition was also significantly different in FH/LPL
double heterozygotes when compared with that in LPL heterozygotes
alone. HDL-CE was significantly greater in double heterozygotes
(P=.014; Table 7), probably because of the larger load of
cholesterol in the lipoprotein fractions due to the
coexisting LDL receptor defect. PL, on the other hand, made up
significantly fewer of the HDL particles in FH/LPL double heterozygotes
compared with LPL heterozygotes alone (P=.019).
Another mechanism by which to assess LPL functional significance is to identify ratios of lipoprotein surface to core in the lipoprotein fractions. UC and PL constitute the surface component and CE and TG the core component of the various lipoproteins. Surface-core ratios of HDL were lower in FH/LPL double heterozygotes compared with FH heterozygotes, LPL heterozygotes, and control subjects, although significance was only reached when compared with control (0.92±0.09 versus 0.96±0.07, P=.028). This significance, however, is expected in that FH heterozygotes alone had significantly lower surface-core ratios when compared with control subjects (0.96±0.07 versus 1.07±0.09, P=.006), as did LPL heterozygotes (1±0.05 versus 1.07±0.09, P=.011). In FH/LPL double heterozygotes, no significant differences in surface-core ratios were seen in both LDL and VLDL particles when compared with either FH or LPL heterozygotes (data not shown).
Apolipoprotein Assessment
In family B, apoA-1 was significantly decreased in the double
heterozygotes when compared with that in FH heterozygotes alone
(P=.028; Table 3); it was decreased, but not significantly,
when compared with that in LPL heterozygotes alone (Table 3). In family
A, nonsignificant decreases in apoA-1 were seen in FH/LPL double
heterozygotes when compared with FH (P=.10) and LPL
heterozygotes (P=.11) within the family (Table 2). ApoA-1
levels were not available for families C or D.
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Discussion |
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We studied four families in which individuals heterozygous for both FH and LPL deficiency present with significantly reduced HDL cholesterol levels and an elevated ratio of TC to HDL when compared with persons in the same family who are heterozygotes for either FH or LPL deficiency alone. We suggest that the various metabolic alterations seen in FH or LPL deficiency alone are additive and may account for either enhanced catabolism and/or decreased production of HDL particles, resulting in reduced HDL cholesterol levels in FH/LPL double heterozygotes.
The families in this study provided a unique opportunity to determine phenotypic expression of gene-gene interaction. In most instances, family members were living in a similar environment with similar diets; for example, all members of families B and D lived in a small town in Eastern Quebec and Holland, respectively. Within each town, family members followed similar diets. Therefore, changes in lipoprotein values within these families are unlikely to be due to environmental differences but rather reflect different genotypes for FH and LPL deficiency.
The heterozygous state for FH is clearly associated with an increased predisposition to coronary artery disease.5 31 32 Within this population, reduced levels of HDL cholesterol are seen, although the precise frequency is unknown.2 3 4 5 33 34 However, no molecular basis for this finding has been proposed. FH heterozygotes with reduced HDL levels are also prone to develop more severe premature artery disease when compared with FH heterozygotes with normal HDL cholesterol levels.34
The mechanism for hypoalphalipoproteinemia in FH alone is poorly understood. Recently Schaefer et al35 described a patient with homozygous FH in whom the fractional catabolic rate was increased and production rate of apoA-1 was decreased when compared with two normal control subjects.35 Similar results have been seen in Watanabe heritable hyperlipidemic rabbits.36 The detailed mechanism of apoA-1 catabolism in the liver and kidney is uncertain. It has been suggested that the increased HDL apoE mass seen in FH individuals37 38 may be more rapidly cleared by an LDL receptor–dependent mechanism, possibly through the remnant receptor, resulting in an enhanced fractional catabolic rate of apoA-1.35 Decreased apoA-1 would therefore be available as a cofactor for lecithin:cholesterol acyltransferase, an enzyme crucial for the generation of plasma HDL-CE formation.39
HDL metabolism is also closely linked to CE transfer. In CETP deficiency, delayed clearance of apoA-1 and elevated levels of HDL have been described.40 In contrast, enhanced CETP activity resulting in CETP-mediated transfer of CE from HDL to apoB-containing lipoproteins is reflected by reductions in plasma HDL levels.41 Different studies have reported increased CETP activity and/or hepatic CETP mRNA levels in FH individuals6 and in animal models for FH,8 possibly providing an explanation for reduced HDL levels in some patients with FH. CE transfer from HDL to apoB-containing lipoproteins is mediated not only by enhanced CETP activity but also by the size of the acceptor lipoprotein pool and by the lipid content of the respective donor and acceptor particles. In FH individuals, both enhanced CETP activity and greatly increased LDL pool size may therefore contribute to the transfer of CE from HDL particles.
Mutations in the LPL gene affecting the catalytic activity of the protein also result in expansion of the pool of apoB- and apoE-containing lipoproteins, namely, VLDL and chylomicron particles. The increased concentrations and delayed clearance of these particles in LPL-deficient subjects allow additional time for TG/CE exchange between these lipoproteins and HDL, resulting in enhanced acceptance of HDL cholesterol by these particles. Despite reported normal CETP activity in LPL heterozygotes,42 the CETP-mediated transfer of CE or exchange of CE and TG may be more efficient. Goldberg et al43 have shown that acute antibody inhibition of LPL resulted not only in marked hypertriglyceridemia but also in marked reduction in HDL-CE and a secondary increase in apoA-1 catabolism. This increased catabolism may be to be due to enhanced renal apoA-1 catabolism as a result of smaller HDL particles.
Defective HDL particle production may be another important mechanism for reduced HDL cholesterol levels in LPL deficiency. The surface coat of TG-rich lipoproteins is an important source of HDL precursors.44 45 46 Defective lipolysis of both chylomicron and VLDL particles may therefore play an important role in defective HDL production.
Increased CETP activity and apoA-1 catabolic rates and reduced apoA-1 production rates seen in FH individuals4 6 are likely to be further aggravated by the coexistence of decreased nascent HDL particle production and the accelerated catabolism of apoA-1 particles in LPL deficiency. As is evidenced by our lipoprotein particle studies in family B, no obvious significant difference is seen in lipoprotein particle composition or lipoprotein particle surface-core ratios in HDL particles, suggesting a quantitative rather than qualitative defect in HDL metabolism in FH/LPL double heterozygotes compared with FH heterozygotes in the family. Supporting this may be the finding of reduced apoA-1 levels in double heterozygotes compared with FH heterozygotes, as is seen in both families A and B in whom apoA-1 was measured. Because of the significant disturbances seen in lipoprotein metabolism in the heterozygous state for FH, the addition of partial LPL deficiency may not be enough to significantly alter lipid exchange between lipoprotein particles but may play a role in further enhancing HDL catabolism and decreasing HDL production.
The enhanced hypoalphalipoproteinemia seen in these double heterozygotes results in elevated TC-HDL ratios in these individuals. This finding has previously been associated with an increased risk for coronary artery disease.47
The trend for higher TG levels in double heterozygotes for FH and partial LPL deficiency compared with FH heterozygotes alone can be explained by the decreased lipolysis of TG-rich lipoprotein particles, an expected finding in these individuals.
LPL activity is not altered in FH, but in our laboratory all three LPL mutations described have been found to be associated with decreased LPL activity both in vivo and in vitro.11 48 49 To further highlight the functional effect of heterozygosity for LPL deficiency, it is noteworthy that HDL cholesterol was reduced in LPL heterozygotes compared with control subjects in all four families, with statistical significance being reached in families B and C (P<.001 and P=.048, respectively).
Another suggested role for LPL is the enhanced uptake of LDL particles by a receptor-dependent and/or -independent mechanism, facilitated by LPL bridging of proteoglycans present on the plasma membrane and circulating lipoproteins containing LPL.50 Studies have shown reduced uptake of lipoproteins in LDL receptor–negative fibroblasts, suggesting a role for the LDL receptor in the metabolism of LPL-lipoprotein complexes.51 In FH/LPL double heterozygotes, one might then expect to find elevated plasma levels of LDL cholesterol as a result of decreased LPL-lipoprotein complex formation and decreased complex internalization. We do not find evidence for increased LDL cholesterol levels in double heterozygotes for FH and LPL deficiency compared with FH heterozygotes alone, suggesting that, in the heterozygous state, LPL deficiency does not reduce LPL-lipoprotein complex formation sufficiently to impair its binding and that the heterozygous state for FH does not reduce the internalization of LPL-lipoprotein complexes sufficiently to result in further elevation of plasma LDL cholesterol. The uptake of these complexes is probably maintained by the functioning LDL receptors and/or by a receptor-independent mechanism.
The high frequency of LPL mutations in the general population (such as the change Asn291Ser) would suggest that these LPL mutations and other less common LPL defects (such as the Pro207Leu and the Glu188Gly described here) may be found in at least one in every 20 to 30 FH families and possibly with higher frequency in areas where LPL carrier rates are high. These LPL defects decrease HDL cholesterol levels and apoA-1 levels in these FH individuals and therefore may alter the prognosis in such persons with both FH and partial LPL deficiency, although this remains to be proven. Underlying LPL mutations may also account for the variability of HDL and TG values within families with FH, since the LPL mutations segregate independently of the mutation in the gene for the LDL receptor.
In summary, we present four families in which individuals were found to be double heterozygotes for both LDL receptor defects and mutations in the LPL gene. Such individuals present with an altered lipid phenotype characterized by significant hypoalphalipoproteinemia and an increased TC-HDL ratio. A nonsignificant trend for higher TG levels was also noted in these individuals. Further studies are needed to see whether these changes in lipoproteins predict an increased susceptibility to atherosclerosis.
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Acknowledgments |
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This work was supported by the MRC Canada and the Heart and Stroke Foundation of British Columbia and the Yukon. Most (3 of the 4) of the families were identified by the International MED-PED collaboration, and we thank all the investigators participating in this project. Thanks also go to Drs Jiri Frohlich and Haydn Pritchard of the Atherosclerosis Specialty Unit, St Pauls' Hospital, Vancouver, BC, for their valuable comments and criticisms. Dr Hayden is an established investigator of the British Columbia Children's Hospital.
Received May 18, 1995; accepted August 2, 1995.
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References |
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TopAbstractIntroductionMethodsResultsDiscussionReferences |
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1. Goldstein J, Hobbs HH, Brown MS. Familial hypercholesterolemia. In: The Metabolic Basis of Inherited Disease. 7th ed. Scriver CR, Beaudet AC, Sly WS, Valle D, eds. New York, NY: McGraw Hill Book Co; 1995:1981-2030.
2. Seftel HC, Baker SG, Sandler MP, Forman MB, Joffe HI, Mendelsohn D, Jenkins T, Mieny CJ. A host of hypercholesterolaemic homozygotes in South Africa. BMJ. 1980;281:633-636.
3. Kwiterovitch PO. Familial hypercholesterolemia (one form of familial type II hyperlipoproteinaemia): a study of its biochemical, genetic and clinical presentation in childhood. J Clin Invest. 1973;53:1237-1249.
4. Inazu A, Koizumi J, Mabuchi H, Kajinami K, Takeda R. Enhanced cholesteryl ester transfer protein activities and abnormalities of high density lipoproteins in familial hypercholesterolemia. Horm Metab Res. 1992;24:284-288. [Medline] [Order article via Infotrieve]
5. Gagné C, Moorjani S, Brun D, Toussaint M, Lupien P-J. Heterozygous familial hypercholesterolemia: relationship between plasma lipids, lipoproteins, clinical manifestations and ischemic heart disease in men and women. Atherosclerosis. 1979;34:13-24. [Medline] [Order article via Infotrieve]
6.
Schaefer JR, Rader DJ, Ikewaki K, Fairwell T, Zech LA,
Kindt MR, Davignon J, Gregg RE, Brewer HB Jr. In vivo
metabolism of apolipoprotein A-1 in a patient with
homozygous familial
hypercholesterolemia.
Arterioscler Thromb. 1992;12:843-848.
7.
Kunz F, Pechlaner C, Erhart R, Fend F, Muhlberger V.
HDL and plasma phospholipids in coronary artery
disease. Arterioscler Thromb. 1994;14:1146-1150.
8.
Son Y-SC, Zilversmit DB. Increased lipid
transfer activities in hyperlipidemic rabbit plasma.
Arteriosclerosis. 1986;6:345-351.
9.
Hill JS, Hayden MR, Frohlich J, Pritchard PH.
Genetic and environmental factors affecting the incidence of
coronary artery disease in heterozygous familial
hypercholesterolemia.
Arterioscler Thromb. 1991;11:290-297.
10. Zambon A, Torres A, Bijvoet S, Gagné C, Moorjani S, Lupien PJ, Hayden MR, Brunzell JD. Prevention of raised low-density lipoprotein cholesterol in a patient with familial hypercholesterolemia and lipoprotein lipase deficiency. Lancet. 1993;341:1119-1121. [Medline] [Order article via Infotrieve]
11. Reymer P, Groenemeyer BE, Gagné E, Forsyth IJ, Jansen H, Seidell JC, Lie KE, Zhang H, Kastelein JJP, Hayden MR. A lipoprotein lipase mutation (Asn291Ser) is associated with reduced HDL cholesterol levels in premature atherosclerosis. Nature Genet. 1995;10:28-34. [Medline] [Order article via Infotrieve]
12. Williams RR, Hunt SC, Schumacher MC, Hegele RA, Leppert MF, Ludwig EH, Hopkins PN. Diagnosing heterozygous familial hypercholesterolemia using new practical criteria validated by molecular genetics. Am J Cardiol. 1993;72:171-176. [Medline] [Order article via Infotrieve]
13.
Williams RR, Hasstedt SJ, Wilson DE, Ash KO, Yanowitz
FF, Reiber GE, Kuida H. Evidence that men with familial
hypercholesterolaemia can avoid early coronary
death. JAMA. 1986;255:219-224.
14. Ma Y, Betard C, Roy M, Davignon J, Kessling AM. Identification of a second "French Canadian" LDL receptor gene deletion and development of a rapid method to detect both deletions. Clin Genet. 1989;36:219-228. [Medline] [Order article via Infotrieve]
15. Leitersdorf E, Tobin EJ, Davignon J, Hobbs HM. Carrier low-density lipoprotein receptor mutations in the French Canadian population. J Clin Invest. 1990;85:1014-1023.
16. Leitersdorf E, Van der Westhuizen DR, Coetzee GA, Hobbs HH. Two common low density lipoprotein receptor gene mutations cause familial hypercholesterolemia in Afrikaners. J Clin Invest. 1989;84:954-961.
17.
Bijvoet SM, Hayden MR. Mismatch PCR: a rapid
method to screen for the Pro207
Leu mutation in the lipoprotein
lipase (LPL) gene. Hum Mol Genet. 1992;1:541.
18. Wilson DE, Emi M, Iverius PH, Hata A, Wu LL, Hillas E, Williams RR, Lalouel J-M. Phenotypic expression of heterozygous lipoprotein lipase deficiency in the extended pedigree of a proband homozygous for a missense mutation. J Clin Invest. 1990;87:735-750.
19. Technical Tips. An efficient salt-chloroform extraction of DNA from blood and tissue. Trends Genet. 1989;5:391. [Medline] [Order article via Infotrieve]
20. Manual of Laboratory Operations. Washington, DC: Lipid Research Clinics Program; 1974. US Dept of Health, Education, and Welfare publication NIH 75-628.
21. Allain CC, Poon LS, Chan CSG, Richmond W, Fu PC. Enzymatic determination of total serum cholesterol. Clin Chem. 1974;20:470-475. [Abstract]
22.
Siedel J, Hegele EO, Ziegenhorn J, Wahlefeld AW.
Reagent for the enzymatic determination in serum total
cholesterol with improved lipolytic efficiency.
Clin Chem. 1983;29:1075-1080.
23. Buccolo G, David H. Quantitative determination of serum triglycerides by the use of enzymes. Clin Chem. 1993;19:476-482. [Abstract]
24.
Warnick GR, Albers JJ. Heparin-Mn2+ quantitation
of high density lipoprotein cholesterol: an ultrafiltration
procedure for lipaemic samples. Clin Chem. 1978;24:900-904.
25. Steele BW, Koehler DF, Azar MM, Blaszkowski TP, Kuba K, Dempsey ME. Enzymatic determination of cholesterol in high density lipoprotein fractions prepared by a precipitation technique. Clin Chem. 1976;22:98-101. [Abstract]
26.
Wu LL, Warnick GR, Wu JT, Williams RR, Lalouel J-M.
A rapid micro-scale procedure for determination of the total
lipid profile. Clin Chem. 1989;35:1486-1491.
27.
Warnick GR, Benderson J, Albers JJ. Dextran
sulphate-Mg2+ precipitation procedure for quantitation of
high-density lipoprotein cholesterol.
Clin Chem. 1982;28:1379-1388.
28. Havel RJ, Eder H, Bragdon HF. The distribution and chemical composition ultracentrifugally separated lipoproteins in human serum. J Clin Invest. 1955;34:1345-1353.
29.
Curry MD, Alaupovic P, Suenram CA. Determination
of apolipoprotein A and its constitutive AI and AII polypeptides by
separate electroimmunoassays. Clin Chem. 1976;22:315-322.
30.
Curry MD, Alaupovic P, Suenram CA.
Electroimmunoassay, radioimmunoassay and radial immunodiffusion
assay evaluated for quantification of human apolipoprotein B.
Clin Chem. 1978;24:280-286.
31. Mouratidis B, Vaughan-Neil EF, Gilday DL, Ash JM, Cullen-Dean G, McIntyre S, MacMillan JH, Rose V. Detection of silent coronary artery disease in young adults with familial hypercholesterolemia by single-photon emission computed tomography-thallium-201 scanning. Am J Cardiol. 1992;70:1109-1112. [Medline] [Order article via Infotrieve]
32.
Mabuchi H, Koizumi J, Shimizu M, Takeda R, for the
Hokuriku FH-CHD Study Group. Development of coronary
heart disease in familial
hypercholesterolemia.
Circulation. 1989;79:225-232.
33. Moorjani S, Gagné C, Lupien J-P, Brun D. Plasma triglycerides related decrease in high-density lipoprotein cholesterol and its association with myocardial infarction in heterozygous familial hypercholesterolemia. Metabolism. 1986;35:311-316. [Medline] [Order article via Infotrieve]
34. Streja D, Steiner G, Kwiterovitch PO. Plasma high density lipoproteins and ischaemic heart disease: studies in a large kindred with familial hypercholesterolemia. Ann Intern Med. 1978;89:871-880.
35. Schaefer JR, Rader DJ, Ikewaki K, Fairwell T, Zech LA, Kindt MR, Davignon J, Gregg RE, Brewer HB Jr. In vivo metabolism of apolipoprotein A-1 in a patient with homozygous familial hypercholesterolemia. Arterioscler Thromb. 1992;12:843-848.
36. Saku Y, Yamamoto K, Sakai T, Yanagida T, Hidaka K, Sasaki J, Arakawa K. Kinetics of HDL-apo A-1 in the WHHL rabbit, an animal model of familial hypercholesterolemia. Atherosclerosis. 1989;79:225-230. [Medline] [Order article via Infotrieve]
37.
Gibson JC, Goldberg RB, Rubinstein A, Ginsburg HN,
Brown WV, Baker S, Joffee BF, Seftel HC. Plasma lipoprotein
distribution of apolipoprotein E in familial
hypercholesterolemia.
Arteriosclerosis. 1987;7:401-407.
38. Keider S, Ostlund RE Jr, Schonfeld G. Apolipoprotein E-rich HDL in patients with homozygous familial hypercholesterolemia. Atherosclerosis. 1990;84:155-163. [Medline] [Order article via Infotrieve]
39. Tall AR. Metabolic and genetic control of HDL cholesterol levels. J Intern Med. 1992;231:661-668. [Medline] [Order article via Infotrieve]
40. Ikewaki K, Sakamoto T, Rader DJ, Schaefer JR, Fairwell T, Kindt M, Ishikawa T, Nagano M, Brewer HB Jr. Cholesteryl ester transfer protein deficiency: delayed catabolism of apo A-1 leading to elevated plasma HDL levels. Circulation. 1991;84(suppl II):II-139. Abstract.
41. Tall A, Sammett D, Granot E. Mechanism of enhanced cholesteryl ester transfer from high density lipoproteins to apolipoprotein B-containing lipoproteins during alimentary lipaemia. J Clin Invest. 1986;77:1163-1172.
42. Miesenbock G, Holzl B, Foger B, Brandstatter E, Paulweber B, Sanhofer F, Patsch JR. Heterozygous lipoprotein lipase deficiency due to a missense mutation as the cause of impaired triglyceride tolerance with multiple lipoprotein abnormalities. J Clin Invest. 1993;91:448-455.
43. Goldberg I, Blaner WS, Vanni TM, Moukides M, Ramakrishan R. Role of lipoprotein apolipoprotein metabolism: studies in normal and lipoprotein lipase-inhibited monkeys. J Clin Invest. 1990;86:463-473.
44. Eisenberg S, Chajek T, Deckelbaum R. Mode of formation of HDL: hypothesis. J Am Chem Soc. 1978;55:A256.
45. Tall AR, Small DM. Plasma high-density lipoproteins. N Engl J Med. 1978;299:1232-1236. [Medline] [Order article via Infotrieve]
46. Eisenberg S. High density lipoprotein metabolism. J Lipid Res. 1984;25:1017-1058. [Medline] [Order article via Infotrieve]
47. International Task Force for Prevention of Coronary Heart Disease. Prevention of coronary heart disease: scientific background and new clinical guidelines. Recommendations of the European Atherosclerosis Society. Nutr Metab Cardiovasc Dis. 1992;2:113-156.
48. Monsalve MV, Henderson H, Roederer G, Julien P, Deeb S, Kastelein JJP, Peritz L, Devlin R, Bruin T, Murthy MRV, Gagné C, Davignon J, Lupien PJ, Brunzell JD, Hayden MR. A missense mutation at codon 188 of the human lipoprotein lipase gene is a frequent cause of lipoprotein lipase deficiency in persons of different ancestries. J Clin Invest. 1990;86:728-734.
49. Ma Y, Henderson H. Ven Murthy MR, Roederer G, Monsalve MV, Clarke LA, Normand T, Julien P, Gagné C, Lambert M, Davignon J, Lupien PJ, Brunzell J, Hayden MR. A mutation in the human lipoprotein lipase gene as the most common cause of familial hyperchylomicronemia in French Canadians. N Engl J Med. 1991;324:1761-1766. [Abstract]
50.
Mulder M, Lombardi P, Jansen H, Van Berkel TJC, Frants
RR, Havekes LM. Low density lipoprotein receptor internalizes
low density and very low density lipoproteins that are bound to heparin
sulfate proteoglycans via lipoprotein lipase. J
Biol Chem. 1993;268:9369-9375.
51. Rumsey C, Obunike JC, Arad Y, Deckelbaum RH, Goldberg IJ. Lipoprotein lipase-mediated uptake and degradation of low density lipoproteins by fibroblasts and macrophages. J Clin Invest. 1992;90:1504-1512.
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