Genetic variation at the perilipin locus is associated with changes in serum free fatty acids and abdominal fat following mild weight loss.

OBJECTIVE: Perilipin (PLIN) is a class of protein-coating lipid droplets in adipocytes. We aimed to examine the association between common single-nucleotide polymorphisms (SNPs) at PLIN locus with circulating free fatty acid (FFA) and abdominal fat distribution in response to weight loss. METHODS: Non-diabetic/overweight-obese Koreans (n=177) participated in a 12-week calorie restriction (-300kcal/day) program. Seven SNPs (6209T>C, 10076C>G, 10171A>T, 11482G>A, 13042A>G, 13048C>T and 14995A>T), abdominal fat areas (visceral/subcutaneous fat areas at 1st lumbar and 4th lumbar levels), serum lipids, glucose, insulin, FFA, oxidized low-density lipoprotein (LDL) and urinary 8-epi-prostaglandin F(2alpha) (PGF(2alpha)) were examined. RESULTS: Single-nucleotide polymorphisms 10076C>G/10171A>T showed the strongest positive linkage disequilibrium (LD) (D'=0.923, R (2)=0.839, P<0.001) and SNPs11482G>A/14995A>T showed moderate positive LD (D'=0.824, R (2)=0.578, P<0.001). Calorie restriction induced 4.6% weight loss with significant abdominal fat reduction. In response to weight loss, subjects with nCA/nCA haplotypes at SNPs 10076C>G/10171A>T showed greater reduction in FFA levels than those with CA/CA haplotype (CA/CA: C/C at SNP 10076 and A/A at SNP 10171, nCA: non-CA haplotype carrier). On the other hand, subjects with nGA/nGA haplotype at SNPs 11482G>A/14995A>T had increased FFA levels with a rapid loss in abdominal fat, whereas GA/GA haplotype carriers had reduction in FFA levels. These results still remained significant after adjusting for age, gender and BMI. Prostaglandin F(2alpha) and oxidized LDL were also more reduced in GA/GA haplotype carriers than in nGA haplotype carriers. This effect remained significant after adjusting for baseline level, age, gender and BMI. Paradoxically, nGA haplotype carriers had increased levels of urinary PGF(2alpha) after weight reduction. CONCLUSION: Fasting plasma FFA changes following a modest weight loss in overweight-obese subjects are influenced by the genetic variability at the PLIN locus. Furthermore, circulating FFA changes rather than body fat itself may determine changes in lipid peroxides such as urinary PGF(2alpha) and oxidized LDL.

Growth hormone induces low-density lipoprotein clearance but not bile acid synthesis in humans.

OBJECTIVE: Growth hormone (GH) induces hepatic low-density lipoprotein (LDL) receptors and lowers plasma cholesterol. We characterized the influence of GH treatment on plasma LDL clearance in normal humans and investigated the relative role of LDL receptor (LDLR) activity and stimulation of bile acid synthesis in subjects with different LDLR expression. METHODS AND RESULTS: Plasma clearance of autologous 125I-LDL was measured before and during 3 weeks of treatment with GH (0.1 IU/kg per day) in 9 healthy young males. Plasma LDL cholesterol was reduced by 13% and the fractional catabolic rate of LDL increased by 27%. More marked changes were seen in a patient with hypopituitarism substituted with GH (0.07 IU/kg per day) for 3 months. In a second study, GH dose-dependently reduced LDL cholesterol and increased Lp(a) levels in 3 groups of males: younger and elderly healthy subjects and heterozygous familial hypercholesterolemia (FH). No effect on bile acid synthesis measured by the plasma marker 7alpha-hydroxy-4-cholesten-3-one was observed. In an LDLR-deficient FH homozygote, LDL cholesterol was not affected by GH. CONCLUSIONS: GH treatment reduces plasma LDL cholesterol by inducing LDL clearance. In humans, LDLR expression is a prerequisite for this effect, whereas it is not related to stimulation of bile acid synthesis.

Handling of low-density lipoprotein by the renal tubule: release of fragments due to incomplete degradation.

Because the mechanism by which lipoproteins are processed and modified in the renal tubule in patients with nephrosis is not completely understood, we studied the handling of low-density lipoprotein (LDL) in perfused rat kidneys made permeable by protamine. Protamine pretreatment increased the clearance of 125(I) LDL 25-fold compared to controls, thereby simulating a proteinuric kidney. Similar studies were also conducted in kidneys of rats made proteinuric by the induction of passive Heymann nephritis. Of the perfused iodinated LDL, 5% was localized in the cortex and lesser amounts in the medulla and urine. In the cortex and medulla, iodinated LDL was present mainly in the intact form (90%); just 10% was present in the degraded form. Using horseradish peroxidase conjugated to LDL, we demonstrated specific staining in the proximal tubules, suggesting that specific LDL receptors were present in that location. Although LDL in the tissue was present mostly in the intact form, it was 95% degraded in urine, and the degradation was inhibited by chloroquine, indicating that the lysosomes were the site of LDL metabolism. Gel chromatography and electrophoresis of iodinated LDL in the urine showed the presence of fragments in the range of 5 to 15 kD. We conclude that renal degradation of LDL is incomplete and that the incompletely degraded fragments released into the urine may be toxic to the kidney by virtue of their lipid side-chains.

Susceptibility of LDL to oxidation is not associated with the presence of coronary heart disease or renal dysfunction in NIDDM patients.

Coronary heart disease (CHD) is the leading cause of death among patients with non-insulin-dependent diabetes mellitus (NIDDM) and the oxidation of low-density lipoprotein (LDL) may be an essential factor in the development of atherosclerotic lesions. Therefore, we studied the in vitro susceptibility of LDL to copper-induced oxidation in 72 NIDDM patients and 94 well-matched non-diabetic control subjects. There was no significant difference in the lagtime of LDL oxidation between NIDDM patients and control subjects (68.1+/-8.8 vs. 66.7+/-9.2 min, respectively, P=0.29). The plasma alpha-tocopherol/LDL-ratio was the most significant determinant of the lagtime in multiple regression analysis. High level of serum triglycerides was associated with decreased lagtime in control subjects, but not in NIDDM patients. Blood glucose balance was not associated with LDL susceptibility to oxidation in NIDDM patients. Subjects with CHD did not have LDL susceptibility to oxidation different from that of subjects without CHD in either of the study groups. Urinary albumin excretion or glomerular filtration rate was not associated with the lagtime of LDL oxidation in NIDDM patients. In conclusion, these data suggest that diabetes and hyperglycemia per se do not affect the susceptibility of LDL to oxidation. The presence of CHD or renal dysfunction were not associated with LDL susceptibility to oxidation.

Imaging human atherosclerosis with 99mTc-labeled low density lipoproteins.

The feasibility of localizing human atherosclerotic plaques by gamma scintillation camera external imaging with technetium-99m-labeled low density lipoproteins (99mTc-LDL) was tested in 17 patients who had atherosclerosis. Imaging demonstrated focal accumulation of radiolabel consistent with 99mTc-LDL sequestration by plaques in the carotid, iliac, or femoral vessels of four patients 8 to 21 hours after intravenous injection of the radiopharmaceutical. Focal accumulation of 99mTc-LDL also appeared in the location of coronary lesions in four patients, but this accumulation could not be distinguished with certainty from residual blood pool radioactivity. When carotid endarterectomy specimens from six patients who received 99mTc-LDL 1 day before endarterectomy were examined, the specimens had focal accumulations of radiolabel, with two to four times greater radioactivity in some regions of each specimen than in others; this occurred whether or not the lesions were detected on the gamma camera images. Lesion composition may have determined whether accumulation was quantitatively sufficient to produce an external image. Histologically, the imaged carotid specimen had abundant foam cells and macrophages and poorly organized intramural blood consistent with a plaque hemorrhage; in contrast, nonimaged endarterectomy specimens were mature, fibrocalcific plaques. We conclude that: 1) 99mTc-LDL did accumulate in human atherosclerotic plaques; 2) in some patients, the accumulation of 99mTc-LDL was sufficient for detection by gamma camera imaging; 3) the amount of LDL that accumulated appeared to depend on lesion composition; and 4) the design of new radiopharmaceuticals with reduced residual blood pool activity relative to plaque accumulation should lead to improved external imaging of atherosclerosis.

A case of nephrotic syndrome with urinary excretion of lipoproteins.

A 47-year-old woman with nephrotic syndrome (membranous glomerulonephropathy) who excreted high, low density lipoproteins (HDL, LDL) which are almost similar to serum HDL and LDL, and small amount of slightly deformed very low density lipoprotein (VLDL) in the urine has been presented.

The magnitude of metabolically induced changes in the density of human low-density lipoproteins.

Radiolabelled low-density lipoproteins (LDL), obtained from a patient with heterozygous, familial hypercholesterolaemia and from a normal subject, were injected into the patient and two normal subjects. Two approaches were made to evaluate the kinetics of metabolism of these LDL: (1) by serial measurements of radioactivity in serum, urine and the whole body; (2) by observing the density of the labelled LDL from serum using density-gradient ultracentrifugation. No significant change was seen in the model density of the LDL in either the patient or the normal subjects, but there were changes in the skewness of the radioactivity peaks. This contrasts with previously published findings in the guinea pig, in which LDL radioactivity gradually accumulated in the densest particles. The guinea pig findings suggested that lipoproteins in the LDL region are structurally modified during their intravascular circulation. The present study indicates that modification leading to changes in density does not occur to any significant degree in the human, whose LDL represent the end product of intravascular metabolism of apolipoprotein B-containing lipoproteins.

Non-stedy-state studies of low-density-liproprotein turnover in familial hypercholesterolaemia.

1. The non-steady-state turnover of low-density lipoprotein (LDL), labelled in its apoprotein moiety (apo-B) with 131I, was determined in four patients with familial hypercholesterolaemia, three of them homozygotes. 2. The fractional and absolute catabolic rates (FCR and ACR) of LDL-apo-B were determined by relating the excretion of radioactivity, measured in urine in vitro and by whole-body counter in vivo, to plasma radioactivity and to LDL specific radioactivity respectively. 3. The FCR remained relatively constant, even after marked reduction of LDL pool size by means of plasma exchange. This confirms the existence of an intrinsic defect in LDL catabolism in familial hypercholesterolaemia. 4. LDL-apo-B synthesis, determined by summing the ACR and the daily increment in plasma LDL, was much higher in the three homozygotes than in the one heterozygote, in whom the synthetic rate was normal. 5. These results illustrate the usefulness of combining plasma exchange and whole-body radioactivy counting as a means of examining the relationship between the turnover and pool size of a 131I-labelled protein, such as LDL.

[Disorder of the activity of the cardiovascular system in obesity in children and adolescents]. / Narushenie deiatel'nosti serdechno-sosudistoi sistemy pri ozhirenii u detei i podrostkov.

The author describes the results of study carried out in 171 children aged from 6 to 14 years suffering from adiposity of the constitutional-exogenous and neuro-endocrine form. A complicated character of hemodynamic dicturbances in adiposity (intensified cardiac activity, hyperdynamia replaced by the hypodynamia of the myocardium syndrome in marked degrees of adiposity, incoordination between the central and the peripheral circulation links is noted. All this points to the early involvement of the heart and the vessels in the pathological process.