Corticotropin-induced reduction of plasma lipoprotein(a) concentrations in healthy individuals and hemodialysis patients: relation to apolipoprotein(a) size polymorphism

Short-term administration of ACTH improves plasma lipid profile and renal function in kidney transplant patients

The present study investigated effects of short-term administration of adrenocorticotrophic hormone (ACTH) on blood lipid profile and renal function in kidney transplant patients. Six patients who had kidney transplantations 2 to 10 years earlier received ACTH intramuscularly (1 mg/d) for 4 days. We analyzed serum levels of lipids, lipoproteins, apolipoproteins, blood creatinine, and other parameters. Short-term ACTH treatment significantly decreased serum apolipoprotein B and apolipoprotein AI, whereas it significantly increased plasma high-density lipoproteins (HDL). Interestingly, creatinine level moderately decreased and creatinine clearances moderately increased among five of six patients. Hepatic function and serum concentration of cyclosporine did not change. There were no serious side effects during ACTH treatment. It was concluded that ACTH treatment had beneficial effects on serum lipoprotein profile, potentially improving renal function in kidney transplant patients. Further observations are needed to confirm these effects.

Dyslipidemia and nephrotic syndrome: Recent advances

Patients with nephrotic syndrome (NS) have one of the most pronounced secondary changes in lipoprotein metabolism known, and the magnitude of the changes correlates with the severity of the disease. These changes are of a quantitative as well as a qualitative nature. All apolipoprotein B (apo B)-containing lipoproteins, such as very-low-density lipoproteins (VLDL), intermediate-density lipoproteins (IDL), low-density lipoproteins (LDL), and lipoprotein(a) [Lp(a)], are elevated in nephrotic syndrome. High-density lipoproteins (HDL) are reported to be unchanged or reduced. In addition to these quantitative changes, the lipoprotein composition is markedly changed, with a higher ratio of cholesterol to triglycerides in the apo B-containing lipoproteins and an increase in the proportion of cholesterol, cholesterol ester, and phospholipids compared with proteins. Also apolipoproteins show major changes, with an increase in apolipoprotein A-I, A-IV, B, C, and E. Particularly the changes in apo C-II, which is an activator of the enzyme lipoprotein lipase (LPL), and apo C-III, an inhibitor of LPL, with an increase of the C-III to C-II ratio, might contribute to the impaired lipoprotein catabolism in NS. The mechanisms for these changes in lipoprotein metabolism are discussed in this review as far as they are known. Furthermore, the tremendous elevations of Lp(a) in nephrotic syndrome and its primary and secondary causes are reviewed. Primary causes became recently apparent by a significantly higher frequency of low-molecular-weight apo(a) phenotypes in patients compared with controls. The secondary causes were shown by an increase of Lp(a) in all apo(a) isoform groups. Because Lp(a) is an LDL-like particle that is usually included in the measured or calculated LDL cholesterol fraction, the influence of the extremely high Lp(a) levels in NS on the measurement of LDL cholesterol is discussed.

Epidemiology, pathophysiology and therapeutic implications of lipoprotein(a) in kidney disease

Chronic kidney disease is associated with a tremendously increased risk for cardiovascular disease. Traditional risk factors for cardiovascular disease, however, show a diminished predictive power in these patients compared with the general population. This review provides an overview of lipoprotein(a), which is considered a nontraditional risk factor. The characteristic genetic and nongenetic changes of lipoprotein(a) in kidney disease are discussed and set into the context of risk prediction. In particular, genetically determined apolipoprotein(a) polymorphism is a powerful risk predictor for cardiovascular disease and total mortality in these patients. Finally, the limited interventional strategies available to lower lipoprotein(a) are considered.

Serum lipoprotein(a) concentrations and apolipoprotein(a) phenotypes in hemodialysis, chronic ambulatory peritoneal dialysis and post-transplant patients

Serum lipoprotein(a) [Lp(a)] concentrations and apolipoprotein(a) apo(a) phenotypes were determined in 81 hemodialysis (HD) patients, 37 chronic ambulatory peritoneal dialysis (CAPD) patients, 25 post-transplant patients and 99 healthy subjects as the reference group. The CAPD patients had significantly higher serum Lp(a) concentration than HD patients, but both had significantly increased Lp(a) levels as compared with the reference group and post-transplant patients. When all studied groups were divided into two subgroups with at least one low molecular weight (LMW) isoform and with only one high molecular weight (HMW) isoform, they presented a similar distribution. (Pearson's chi-squared = 2,78; df = 3; p = NS). The median serum Lp(a) levels were significantly increased with HMW class versus the reference group and post-transplant patients. In CAPD patients, the LMW phenotypes showed significantly increased median serum Lp(a) concentrations versus the reference group, but they were not statistically elevated in HD patients. In the post-transplant patients, LMW and HMW phenotypes did not differ as compared to the reference group. The elevated Lp(a) levels in HD and CAPD groups were explained by apo(a) type-specific, but not by differences in, isoform frequencies. We conclude that HD and CAPD patients had increased Lp(a) levels compared with the reference group, whereas elevated Lp(a) concentrations were observed mainly in patients with HMW apo(a) phenotypes. Patients after renal transplantation showed a correction of Lp(a) levels mainly in HMW phenotypes. The LMW status corresponding to high Lp(a) levels and apo(a) isoforms could be used together with Lp(a) levels with other risk factors to assess in uremic patients the predisposition to coronary artery disease.

ACTH decreases the expression and secretion of apolipoprotein B in HepG2 cell cultures

Administration of adrenocorticotropic hormone (ACTH) has been shown to decrease plasma concentrations of apolipoprotein B (apoB) containing lipoproteins, including lipoprotein(a), in man. However, the mechanism behind this hypolipidemic effect is unknown. This study aimed at distinguishing between the main possibilities (increased elimination or decreased production of lipoproteins) using HepG2 cell cultures. Addition of ACTH to the cell culture medium selectively down-regulated apoB mRNA expression and apoB secretion in a dose-dependent manner. At 100 pmol/liter ACTH, the apoB mRNA level was about 40% lower than in the untreated cells, and the secretion of apoB into the medium was decreased to a similar extent. The expression and secretion of other apolipoproteins (apoA-I, apoE, and apoM), however, were not affected by ACTH. Under normal culture conditions the level of secretion of apoB from HepG2 cells is quite low. In the presence of 0.4 mmol/liter oleic acid secretion of apoB increased 3-fold, but this phenomenon was not seen in ACTH-treated cells. Binding and internalization of radiolabeled low density lipoprotein (LDL) by HepG2 cell, as well as LDL-receptor mRNA and scavenger receptor B-I mRNA levels, were not influenced by ACTH. In conclusion, ACTH directly and selectively down-regulated the production and secretion of apoB in HepG2 cell cultures, suggesting that a principal mechanism behind the cholesterol-lowering effect of ACTH in vivo may be a decreased production rate of apoB-containing lipoproteins from the liver.

Beneficial effects of ACTH on the serum lipoprotein profile and glomerular function in patients with membranous nephropathy

BACKGROUND

Previous studies have shown that short-term treatment with adrenocorticotrophic hormone (ACTH) has a strong and rapid lipid-lowering effect. In this long-term study of nephrotic patients with idiopathic membranous nephropathy, the influence of ACTH on the serum lipoprotein profile and glomerular function as well as the dose-effect relationship was investigated.

METHODS

Fourteen patients received ACTH intramuscularly at increasing doses during 56 days. Serum concentrations of lipids, lipoproteins, and apolipoproteins as well as variables of glomerular function were analyzed, and the side-effects were recorded. ACTH treatment, in the estimated optimal dosage, was then continued in five patients with severe steroid-resistant nephrotic syndrome. In these five patients, the total treatment period was 12 months, and the follow-up time after discontinuing treatment was 18 months.

RESULTS

Taking both the statistically significant therapeutic effects and the modest side-effects into consideration, the optimal dosage of ACTH was estimated to be 1 mg twice per week. At that dose, reductions by 30 to 60% in the serum concentrations of cholesterol, triglycerides, apolipoprotein B, and lipoprotein(a) were observed, whereas the serum concentrations of high-density lipoprotein cholesterol and apolipoprotein AI rose by 30 to 40%. In addition, the urinary albumin excretion decreased by 90%, and the glomerular filtration rate increased by 25%. Deterioration was observed in all cases when ACTH was discontinued after a treatment duration of 56 days. However, the five patients in whom ACTH therapy was resumed were still in remission 18 months after discontinuance of treatment.

CONCLUSIONS

In nephrotic patients with idiopathic membranous nephropathy, treatment with ACTH 1 mg twice per week was associated with significant long-term improvements in serum lipoprotein pattern and glomerular function.