抄録
The Watanabe Heritable Hyperlipidemic (WHHL) rabbit has been reported to be an animal model for familial hypercholesterolemia (FH) because both WHHL rabbits and FH patients show spontaneous hyperlipidemia due to low density lipoprotein (LDL) -receptor deficiency. Rabbits fed on cholesterol-rich chow have been reported to show suppressed level of LDL-receptor. We wished to clarify the resemblances and differences between WHHL rabbits and FH patients by comparing their lipoprotein profiles.
We obtained blood samples after overnight fasting from 16 normal (TC<230 mg/dl, TG<150 mg/dl) human (“NH”), from 15 patients with heterozygous FH, from 8 normal Japanese white rabbits (“NR”) on standard rabbit chow, from 4 Japanese white rabbits fed a 1% cholesterol chow (“CR”), and 8 WHHL rabbits fed on standard chow. We enzymatically measured lipid levels of serum and lipoprotein fractions (VLDL, very low density (d<1.006) lipoprotein; IDL, intermediate density (1.006<d<1.019) lipoprotein; LDL, low density (1.019<d<1.063) lipoprotein; HDL, high density (d>1.063) lipoprotein) . Serum apolipoprotein levels were measured by SRID method. Rabbit VLDL was washed and delipidated by aceton-ethanol and ether. ApoVLDL was electrophoresed in polyacrylamide gels containing 8M urea and 2% ampholine (pH 4-6) . The protein was fixed, stained, and destained, and the gels were scanned at 550 nm. We checked the isoprotein pattern of rabbit apoVLDL by measuring areas under each peaks of scanning chart.
Levels of VLDL-, IDL-, and LDL-TC elevated in FH patients compared with NH subjects, by 1.8, 1.0, and 2.6 times, respectively. WHHL rabbits showed increased levels of these lipoprotein TC compared with NR rabbits, by 26.2, 15.0, and 18.4 times, respectively. CR rabbits also showed elevated levels of lipoprotein TC by 13.4-20.0 times. The triglyceride (TG) levels of VLDL, IDL, and LDL fractions were higher in WHHL rabbits than in NR rabbits, by 8.0-12.8 times. Whereas, the TG levels of CR rabbits and FH patients showed no increase compared with normal controls. The TC/TG ratios of VLDL and IDL fractions were slightly increased in WHHL rabbits to the same degree as in FH patients. The TC/TG ratio of LDL fraction was normal. In CR rabbits. TC/TG ratio of VLDL, IDL, and LDL fraction elevated markedly by above 20 times.
The serum levels of apolipoprotein B (apoB) and apolipoprotein E (apoE) in FH patients were significantly higher than in NH subjects, by 2.0 and 1.5 times, respectively. WHHL rabbits showed higher apoB (1, 420±224 mg/dl) and apoE (52±9mg/dl) levels than NR rabbits (100±27 mg/dl and undetectable level, respectively) .
WHHL rabbits showed very high VLDL-TC level and resembled human type 3 hyperlipidemia, which was known to show elevated level of VLDL and abnormal isoprotein pattern of apoE. Therefore, we checked isoprotein pattern of apoVLDL of WHHL rabbits. There were no changes in isoprotein pattern of apoVLDL in WHHL rabbits compared with NR rabbits. There were some changes of isoprotein pattern in CR rabbits.
We summarized: 1) WHHL rabbits and FH patients showed two common characteristics; increases of slightly TC-rich VLDL and IDL and of LDL: elevated levels of apoB and apoE. 2) The increments of lipoprotein TC levels in WHHL rabbits were above 10 times, whereas those in FH patients were around twice. 3) All WHHL rabbits showed increased levels of VLDL, whereas a few number of patients with FH showed elevation of VLDL. 4) The CR rabbit was different from FH in showing elevation of markedly TC-rich lipoprotein and some changes in isoprotein pattern of apoVLDL. We conclude that the WHHL rabbit is an excellent animal model for FH.
