Plasma cholesteryl ester transfer protein and lipoprotein levels during treatment of growth hormone-deficient adult humans

GH Supplementation Effects on Cardiovascular Risk in GH Deficient Adult Patients: A Systematic Review and Meta-analysis

BACKGROUND AND OBJECTIVE

The current meta-analysis aims at evaluating whether the existing clinical evidence may ascertain the effects of growth hormone (GH) replacement therapy on cardiovascular risk, both in isolated GH deficiency (GHD) and in compensated panhypopituitarism including GH deficit.

METHODS

Original articles published from 1991 to 2015 were searched on Medline (Pubmed). Among an overall number of 181 potentially suitable studies, 24 fulfilled the selection criteria and were included in the analysis. Data aggregation was carried out through the calculation of the absolute risk reduction. The meta-analysis was then conducted by means of a fixed-effects model, according to the heterogeneity test (Chi-square statistic).

RESULTS

Fat-free mass (FFM) increase and fat mass (FM) reduction were found, together with a C-LDL reduction, a wide variation in glycaemia and a neutral effect on glycated haemoglobin (HbA1c) and blood pressure. These effects were valid both for isolated GHD patients and for those with compensated panhypopituitarism. The global outcome D showed a nonsignificant reduction of the overall cardiovascular risk (0.53; 95% C.I. -1.23, 2.85).

CONCLUSION

Our meta-analysis shows no signnificatly positive trend in cardiovascular risk after both short and long-term GH supplementation therapy in adult GHD patients. However, a reduction of LDL cholesterol levels has been found. No differences were found between isolated GHD participants and those affected by panhypopituitarism well compensated since at least 3 months.

Reduced growth hormone secretion in obesity is associated with smaller LDL and HDL particle size

OBJECTIVE

Reduced growth hormone (GH) secretion is observed in obesity and may contribute to increases in cardiovascular disease (CVD) risk. Lipoprotein characteristics including increased small dense low-density lipoprotein (LDL) particles are known independent risk factors for CVD. We hypothesized that reduced GH secretion in obesity would be associated with a more atherogenic lipid profile including increased small dense LDL particles.

DESIGN

To evaluate this hypothesis, we studied 102 normal weight and obese men and women using standard GH stimulation testing to assess GH secretory capacity and performed comprehensive lipoprotein analyses including determination of lipoprotein particle size and subclass concentrations using proton NMR spectroscopy.

RESULTS

Obese subjects were stratified into reduced or sufficient GH secretion based on the median peak-stimulated GH (≤6·25 μg/l). Obese subjects with reduced GH secretion (n = 35) demonstrated a smaller mean LDL and HDL particle size in comparison to normal weight subjects (n = 33) or obese subjects with sufficient GH (n = 34) by ANOVA (P < 0·0001). Univariate analyses demonstrated peak-stimulated GH was positively associated with LDL (r = 0·50; P < 0·0001) and HDL (r = 0·57; P < 0·0001), but not VLDL (P = 0·06) particle size. Multivariate regression analysis controlling for age, gender, race, ethnicity, tobacco, use of lipid-lowering medication, BMI and HOMA demonstrated peak-stimulated GH remained significantly associated with LDL particle size (β = 0·01; P = 0·01; R(2) = 0·42; P < 0·0001 for overall model) and HDL particle size (β = 0·008; P = 0·001; R(2) = 0·44; P < 0·0001 for overall model).

CONCLUSIONS

These results suggest reduced peak-stimulated GH in obesity is independently associated with a more atherogenic lipoprotein profile defined in terms of particle size.

Glucocorticoid replacement is associated with hypertriglyceridaemia, elevated glucose and higher non-HDL cholesterol and may diminish the association of HDL cholesterol with the -629C>A CETP promoter polymorphism in GH-receiving hypopituitary patients

OBJECTIVES

The effect of glucocorticoid substitution on the prevalence of metabolic syndrome components (NCEP ATP III criteria) and serum lipid levels was determined in GH-replaced hypopituitary patients. As glucocorticoid replacement is associated with a pronounced decrease in plasma cholesteryl ester transfer protein (CETP) activity, we also tested associations of HDL cholesterol with the -629C>A CETP promoter polymorphism in subjects with and without ACTH deficiency.

DESIGN AND PATIENTS

In a university setting, we retrieved protocolized clinical and laboratory data from 165 adult hypopituitary patients, who had received GH for 1 year.

RESULTS

After adjustment for age, sex and smoking, non-HDL cholesterol (P = 0.05) and triglycerides (P = 0.004) were higher, but HDL cholesterol was not decreased in 117 glucocorticoid (mainly cortisone acetate in two divided doses) receiving subjects compared to 48 ACTH-sufficient subjects. The prevalence of elevated plasma glucose and/or diabetes (P = 0.04) and hypertriglyceridaemia (P = 0.005), but not of other metabolic syndrome components, was higher in glucocorticoid-replaced subjects. HDL cholesterol was higher in -629 A allele carriers compared to -629CC homozygotes in ACTH-sufficient subjects (P = 0.04), but not in glucocorticoid-treated subjects (P = 0.13). Multiple linear regression analysis demonstrated that only in ACTH-sufficient subjects, HDL cholesterol was independently related to this CETP gene variation (P = 0.03).

CONCLUSIONS

In GH- and glucocorticoid-replaced hypopituitary patients, serum non-HDL cholesterol and triglycerides are higher and the prevalence of hyperglycaemia is increased, but HDL cholesterol is not decreased. Conventional glucocorticoid replacement appears to diminish the association of HDL cholesterol with a common CETP gene variation.

Obesity induced during sexual maturation is linked to LDL-triacylglycerols in Yucatan miniature swine

The incidence of childhood obesity is rising dramatically throughout industrialised countries. To evaluate and study the impact of childhood obesity on lipoprotein metabolism, we developed a new animal model of premature obesity. Yucatan mini-pigs aged 4 months were studied over a 12-month period from childhood to adulthood. Animals were divided into two groups: the first group were overfed a Western misbalanced diet; the second group were normally fed a recommended human-type diet. Cholesterol and triacylglycerol concentrations in VLDL-, LDL- and HDL-lipoproteins were followed from baseline to adulthood by fast protein liquid chromatography. At 10 (the end of sexual maturation) and 16 months old (adulthood), liver, visceral and subcutaneous adipose tissues were sampled. Real-time RT-PCR was performed in order to compare apo AI, apo B, apo C-III, PPAR-α, insulin receptor and lipoprotein lipase gene expression between groups and ages. Differences between groups were observed only after sexual maturity. Adult overfed mini-pigs had a higher LDL-cholesterol:HDL-cholesterol ratio (P<0·05; 0·55 (SE 0·06) for overfedv. 0·42 (SE 0·04) for normally fed pigs at the tenth month of the study). In both groups, VLDL-triacylglycerol decreased (P<0·05). VLDL-triacylglycerol evolution in the overfed group was associated with an increase in LDL-triacylglycerol plasma concentrations (P<0·05) after sexual maturation. LDL-triacylglycerol concentration in overfed mini-pigs went from an average of 0·28 mmol/l before sexual maturation to reach an average concentration of 0·56 mmol/l afterwards. This phenomenon has never been observed in similar studies when obesity is induced in adult mini-pigs and may represent a specific hallmark of an obesity induced during sexual maturity.

Pharmacological modulation of cholesteryl ester transfer protein, a new therapeutic target in atherogenic dyslipidemia

In mediating the transfer of cholesteryl esters (CE) from antiatherogenic high density lipoprotein (HDL) to proatherogenic apolipoprotein (apo)-B-containing lipoprotein particles (including very low density lipoprotein [VLDL], VLDL remnants, intermediate density lipoprotein [IDL], and low density lipoprotein [LDL]), the CE transfer protein (CETP) plays a critical role not only in the reverse cholesterol transport (RCT) pathway but also in the intravascular remodeling and recycling of HDL particles. Dyslipidemic states associated with premature atherosclerotic disease and high cardiovascular risk are characterized by a disequilibrium due to an excess of circulating concentrations of atherogenic lipoproteins relative to those of atheroprotective HDL, thereby favoring arterial cholesterol deposition and enhanced atherogenesis. In such states, CETP activity is elevated and contributes significantly to the cholesterol burden in atherogenic apoB-containing lipoproteins. In reducing the numbers of acceptor particles for HDL-derived CE, both statins (VLDL, VLDL remnants, IDL, and LDL) and fibrates (primarily VLDL and VLDL remnants) act to attenuate potentially proatherogenic CETP activity in dyslipidemic states; simultaneously, CE are preferentially retained in HDL and thereby contribute to elevation in HDL-cholesterol content. Mutations in the CETP gene associated with CETP deficiency are characterized by high HDL-cholesterol levels (>60 mg/dL) and reduced cardiovascular risk. Such findings are consistent with studies of pharmacologically mediated inhibition of CETP in the rabbit, which argue strongly in favor of CETP inhibition as a valid therapeutic approach to delay atherogenesis. Consequently, new organic inhibitors of CETP are under development and present a potent tool for elevation of HDL in dyslipidemias involving low HDL levels and premature coronary artery disease, such as the dyslipidemia of type II diabetes and the metabolic syndrome. The results of clinical trials to evaluate the impact of CETP inhibition on premature atherosclerosis are eagerly awaited.