Effects of gender, hepatic lipase gene polymorphism and type 2 diabetes mellitus on hepatic lipase activity in Chinese.

Genetic variation in the hepatic lipase (HL) gene (LIPC) promoter is an important determinant of HL activity in Caucasians. As HL activity is increased in patients with type 2 diabetes mellitus, we have investigated whether the -514 C-to-T polymorphism acted independently of type 2 diabetes to regulate HL activity. The frequency of this polymorphism and its effect on plasma HL activity and lipids were examined in 203 Chinese patients with type 2 diabetes and 205 controls. The frequency of the T allele was 0.343 and 0.376 in male and female diabetic patients, respectively, compared with 0.371 and 0.372 in male and female controls. The effect of LIPC genotype on HL activity was similar between men and women, and between diabetic patients and non-diabetic controls, with the lowest HL activity being found in those subjects with the TT genotype. On multivariate analysis, gender, LIPC genotype, the presence of type 2 diabetes and body mass index were independent predictors of HL activity, accounting for 22, 9, 5 and 3%, respectively, of the variance in HL activity (whole model adjusted R(2)=0.39, P<0.0001). The T allele was associated with higher high-density lipoprotein in the controls but not in the diabetic patients, and no associations were found between LIPC genotype and low-density lipoprotein subfractions in either groups. In conclusion, despite the higher frequency of the T allele in Chinese than in Caucasians, gender was the best predictor for HL activity, with LIPC gene polymorphism and type 2 diabetes making relatively smaller contributions to the variation in HL activity.

Natural abundance heteronuclear NMR studies of the T3 mini-loop hairpin in the terminal repeat of the adenoassociated virus 2.

A DNA hairpin containing a T3 loop, as occurs in the terminal repeat of a popular gene therapy vector (Adenoassociated Virus 2, AAV2), has been extensively studied using homo- and heteronuclear NMR experiments. Almost complete assignment of the proton and carbon resonances, including H5'(Pro-S) and H5'(Pro-R) protons, has been accomplished at natural abundance. NOESY spectra in H2O and D2O have revealed many unusual NOEs, which, when combined with the epsilon, beta, gamma, and chi torsion angles determined from heteronuclear 1H-13C, 1H-31P, and 13C-31P coupling constants, have allowed for a more detailed picture of the T3 mini-loop hairpin. The three loop thymidines are all unpaired, yet are highly structured when bracketed by a 5'-GC...GC-3' stem sequence. The structure determined in this manuscript is considerably different from several other structures reported so far. Contrary to an RNA oligomer with a central U3 sequence that has the tendency to form a duplex with three U*U mismatches, the d(GAAGC-TTT-GCTTC) sequence exists mostly as a hairpin under millimolar NMR conditions. Since T3 triloop was found to be an essential element for the site-specific non-homologous integration of the AAV2 virus, and modification of the T3 loop residue abolishes such capability, the structure we report here may be of biological significance.

Stable formation of a pyrimidine-rich loop hairpin in a cruciform promoter.

We have determined the solution structure of a TCC-loop hairpin in the cruciform promoter for the bacteriophage N4 virion RNA polymerase (N4 vRNAP). This hairpin and its complementary GGA-loop hairpin are extruded at physiological superhelical density and are required for vRNAP recognition. Contrary to its complementary GGA-loop, the three pyrimidines in the TCC-loop are all unpaired. However, with the help of two juxtaposed stem Watson-Crick G.C base-pairs, each nucleotide in the loop employs a special method to stabilize the hairpin structure. The resulting structures display extensive loop base-stacking rearrangement yet minor backbone distortion, which is largely accomplished through some loop zeta and alpha torsional angle changes. Consistent with the structural studies, UV melting of the GAAGCTCCGCTTC hairpin revealed a higher melting temperature (66 degrees C) than that of the GAACGTCCCGTTC hairpin (58 degrees C) with reversed stem G.C base-pairs, indicating significant contribution from the extra three loop-stem H-bonds. Thermodynamic parameters DeltaG degrees 25of the GAAGCTCCGCTTC hairpin and its complementary GAAGCGGAGCTTC hairpin are -4.1 and -4. 3 kcal/mol respectively, indicating approximately equal contribution of each hairpin to the cruciform formation of the N4 virion RNA polymerase promoter. No significant loop dynamics in the microsecond to millisecond NMR time-scale was observed, and the abundant well-defined exchangeable and non-exchangeable proton NOEs allowed us to efficiently determine a well-converged family for the final structures of the TCC-loop hairpin.

Roles of hepatic lipase and cholesteryl ester transfer protein in determining low density lipoprotein subfraction distribution in Chinese patients with non-insulin-dependent diabetes mellitus.

Patients with non-insulin-dependent diabetes mellitus (NIDDM) are known to have abnormalities in their low density lipoprotein (LDL) subclass pattern with a preponderance of small dense LDL. The present study was performed to define the roles of lipolytic enzymes (hepatic and lipoprotein lipase) and cholesteryl ester transfer protein (CETP) in determining the distribution of LDL subfractions in these patients. LDL subfractions were measured by density gradient ultracentrifugation in 137 patients with NIDDM (75 male, 62 female) and 140 matched controls (80 male, 60 female). The male diabetic patients had a lower concentration of LDL-I (P < 0.01) and a higher concentration of LDL-III than the controls (P < 0.01). In the female diabetic patients, both LDL-I (P < 0.001) and LDL-II concentrations (P < 0.05) were significantly lower than the controls whereas LDL-III was increased (P < 0.001). Hepatic lipase (HL) was significantly increased in both the male and female diabetic patients (P < 0.01, P < 0.05, respectively) compared to their controls. No significant changes were seen in plasma lipoprotein lipase (LPL) and CETP activity. On multivariate analysis, plasma triglyceride (TG), CETP and HL accounted for 10, 5 and 3% of the variability in LDL-III, respectively, in the diabetic patients (adjusted R2 = 0.18, P = 0.0003). Our findings would support the hypothesis that plasma triglyceride influences LDL particles through a cycle of lipid exchange via the action of CETP. LDL become enriched in triglyceride and are then acted on by HL to produce a population of small dense lipid-poor LDL.