Influence of PvuII (intron 6) polymorphism of the lipoprotein lipase gene on cord plasma lipid and apolipoprotein levels in Indian and Chinese newborns of Singapore

Lipoprotein concentrations in newborns are associated with allelic variations in their mothers

BACKGROUND

Factors determining lipoprotein concentrations in the fetus are not yet fully understood. We postulated that an important factor is the genetic make-up of the mother. In the present study, we examined the associations between the cord blood concentrations of lipoproteins of 525 newborns and the polymorphisms present in their mothers on the genes of apolipoprotein E (APOE*E2, *E3, *E4), apolipoprotein C-III (APOC3*C3238G also called APOC3*S2) and lipoprotein lipase (LPL*S447X).

RESULTS

Newborns born of mothers with APOE*E2 allele had significantly lower cord blood LDL-C (P < 0.01) and apoB (P < 0.01) and significantly higher cord blood HDL-C and apoA1 (all P-values < 0.03) compared to those born of mothers with APOE*E3E3 genotype. These associations were independent of the presence of APOE*E2 allele in the newborns. Similarly, APOC3*S2 in mothers was associated with significantly lower (all P < 0.001) cord blood LDL-C, apoB, HDL-C and apoA1. In contrast, LPL*S447X in mothers lowered significantly cord blood LDL-C and apoB only when LPL*S447X was present in newborns. Most of the effects of these maternal polymorphisms on the newborns were independent of the changes of maternal lipoproteins generated by these polymorphisms.

CONCLUSIONS

This is the first evidence that maternal genetic variations influence fetal lipoprotein concentrations, independent of the genetic status of the fetus and of the variations of maternal lipoprotein concentrations generated by these genetic variants. It suggests that proteic components of maternal lipoproteins strongly control the metabolism of maternal lipoproteins carried out at the surface of the placenta to assure the cholesterol delivery to the fetus.

Genes, diet and serum lipid concentrations: lessons from ethnically diverse populations and their relevance to coronary heart disease in Asia

PURPOSE OF REVIEW

The burden of coronary heart disease (CHD) in Asia has risen in tandem with socio-economic development and urbanization. Although all ethnic groups have been affected, some appear to be at particularly high risk. The basis of these ethnic differences remains poorly understood.

RECENT FINDINGS

Differing levels of risk factors for CHD have been observed between ethnic groups. Previous studies, however, may be confounded by a large ethnic variation in socio-economic status and place of residence. Few studies have taken dietary factors into account. Recent studies involving Chinese, Malays and Asian Indians living in Singapore suggest that neither dietary nor genetic factors, taken in isolation, sufficiently explain ethnic differences in serum lipid profiles. Several genetic variants in key candidate genes (apolipoprotein E, APOE, cholesteryl ester transfer protein, CETP and hepatic lipase, LIPC) have recently been found to modulate the association between dietary factors and serum lipid concentrations in these ethnic groups and in other populations.

SUMMARY

To fully evaluate the differences in CHD risk between ethnic groups, environmental exposures, including dietary factors need to be carefully evaluated, and gene-environment interactions that may give rise to these differences need to be taken into account. These are critical steps in the development of targeted strategies to contain the epidemic of coronary heart disease in Asia. An understanding of the basis of these differences may also provide insights into the pathogenesis of disease that one cannot get through the examination of more homogenous populations.

Unique character and metabolism of high density lipoprotein (HDL) in fetus

Lipid and lipoprotein profiles, and enzymes for the lipid metabolism were compared between cord and adult blood. Consistent with previous reports, the major lipoprotein in cord blood was high-density lipoprotein (HDL), and that in adult blood was low-density lipoprotein (LDL). The level of apolipoprotein E (apo E) in cord blood was almost equivalent to that in adult blood, while other apolipoproteins and lipids were all lower than the adult level. In cord blood, apo E-rich HDL cholesterol represented more than 30% of total HDL cholesterol (around 11% in adult), and the concentration was about twice of that in adult blood. This apo E-rich HDL cholesterol was poorly esterified (E/T 56%) compared with that in adults (93%). The lecithin:cholesterol acyltransferase (LCAT) activity in cord blood was extremely low, while the activity and mass of cholesteryl ester transfer protein (CETP) were higher than those in adult blood. The apo E genotype did not show influences on total cholesterol, LDL cholesterol, total HDL cholesterol, and apo E rich HDL cholesterol levels in cord blood, as opposed to those in adult blood. The association of D442G mutation of the CETP gene with the increased HDL cholesterol in adult blood was not seen in cord blood. Rather, the mutation was associated with low total cholesterol and LDL cholesterol levels in cord blood. These results indicate that, in fetus, the character and metabolism of HDL, especially of apo E-rich HDL cholesterol, are distinct from those in adults.

Lipoprotein-genotype associations in Trinidadian neonates

OBJECTIVES

We hypothesized that common variation in the angiotensinogen (AGT), beta-3-adrenergic receptor, intestinal fatty acid-binding protein, serum paraoxonase, paraoxonase-2, hepatic lipase, apolipoprotein E (APOE), and Werner helicase (WRN) genes would be associated with variation in biochemical phenotypes in a previously unstudied neonatal sample.

DESIGN AND METHODS

We examined associations of both nongenetic and genetic variables with plasma lipoprotein traits in neonates from Trinidad.

RESULTS

Among nongenetic variables, we found significant associations between plasma concentrations of: 1) lipoprotein(a) [Lp(a)] and both ethnicity (p = 0.037) and birth weight (p = 0.001); 2) total cholesterol and gender (p = 0.010); 3) triglyceride and birth weight (p = 0.035); and 4) apolipoprotein AI and gender (p = 0.016). Among genetic variables, we found that: 1) common variation on chromosome 1q in AGT codon 235 was significantly associated with variation in plasma apolipoproteins AI (p<0.0001) and B (p = 0.013); 2) common variation in WRN at codon 1367 was significantly associated with variation in plasma Lp(a) (p<0.0001); and 3) common variation in APOE at codons 112 and 158 was significantly associated with variation in plasma triglycerides (p = 0.013).

CONCLUSIONS

The associations with AGT and WRN are novel and may have resulted either from a direct influence of the genetic variants or through linkage disequilibrium with other functional loci, such as the familial combined hyperlipidemia locus on chromosome 1q in the case of AGT. Despite the fact that there are some limitations in making determinations from cord blood, the results suggest that there may be genetic determinants of plasma lipoproteins in neonates.