Combination therapy with acipimox enhances the effect of growth hormone treatment on linear body growth in the normal and small-for-gestational-age rat

Manipulation of the Growth Hormone-Insulin-Like Growth Factor (GH-IGF) Axis: A Treatment Strategy to Reverse the Effects of Early Life Developmental Programming

Evidence from human clinical, epidemiological, and experimental animal models has clearly highlighted a link between the early life environment and an increased risk for a range of cardiometabolic disorders in later life. In particular, altered maternal nutrition, including both undernutrition and overnutrition, spanning exposure windows that cover the period from preconception through to early infancy, clearly highlight an increased risk for a range of disorders in offspring in later life. This process, preferentially termed “developmental programming” as part of the developmental origins of health and disease (DOHaD) framework, leads to phenotypic outcomes in offspring that closely resemble those of individuals with untreated growth hormone (GH) deficiency, including increased adiposity and cardiovascular disorders. As such, the use of GH as a potential intervention strategy to mitigate the effects of developmental malprogramming has received some attention in the DOHaD field. In particular, experimental animal models have shown that early GH treatment in the setting of poor maternal nutrition can partially rescue the programmed phenotype, albeit in a sex-specific manner. Although the mechanisms remain poorly defined, they include changes to endothelial function, an altered inflammasome, changes in adipogenesis and cardiovascular function, neuroendocrine effects, and changes in the epigenetic regulation of gene expression. Similarly, GH treatment to adult offspring, where an adverse metabolic phenotype is already manifest, has shown efficacy in reversing some of the metabolic disorders arising from a poor early life environment. Components of the GH-insulin-like growth factor (IGF)-IGF binding protein (GH-IGF-IGFBP) system, including insulin-like growth factor 1 (IGF-1), have also shown promise in ameliorating programmed metabolic disorders, potentially acting via epigenetic processes including changes in miRNA profiles and altered DNA methylation. However, as with the use of GH in the clinical setting of short stature and GH-deficiency, the benefits of treatment are also, in some cases, associated with potential unwanted side effects that need to be taken into account before effective translation as an intervention modality in the DOHaD context can be undertaken.

Growth hormone reverses dyslipidemia in adult offspring after maternal undernutrition

The abnormal intrauterine milieu of fetal growth retardation could lead to dyslipidemia in adulthood. Studies have shown that growth hormone (GH) therapy in small for gestational age (SGA) children would be beneficial for metabolic parameters. Here we investigated whether GH treatment introduced at adolescent period in SGA could reverse dyslipidemia during later life. SGA rat model was established by using semi-starvation treatment during the whole pregnancy. SGA or appropriate for gestational age (AGA) offspring were assigned to receive GH or normal saline (NS). Once-daily subcutaneous injections of GH were administered between 21-35 days of age. In adulthood, as compared to AGA, SGA showed: (1) decreased body weight and length; (2) increased serum triglycerides; (3) down-regulated hepatic AMPK-α1 but up-regulated SREBP-1c and ACC-1; (4) a significant reduction in histone H3 acetylation at the promoter of AMPK-α1. Exogenous GH administration led to a restoration of body weight and length and normalized serum triglycerides by reversing expression of AMPK-α1 and its targeted genes SREBP-1c and ACC-1, through increasing H3 acetylation at the promoter of AMPK-α1 in SGA in adult period. These results demonstrated positive effects on lipid metabolism by a short treatment course of GH in SGA adult period.

Acipimox during exercise points to an inhibitory feedback of GH on ghrelin secretion in bulimic and healthy women

OBJECTIVE

Ghrelin is predominantly produced by the stomach and the growth hormone (GH)-ghrelin feedback loop between the stomach and the pituitary gland has recently been suggested. The disruption of the gut-brain axis might be involved in bulimia nervosa (BN).

METHODS

We investigated responses of plasma GH, ghrelin, and neuropeptide Y (NPY) concentrations to exercise or to exercise after the administration of the antilipolytic drug Acipimox (Aci) in seven BN patients and seven healthy women (C). Aci was administered 1h before exercise (45 min, 2 W/kg of lean body mass/LBM/). Ghrelin, GH, NPY, free fatty acids (FFA) and glycerol plasma levels were measured during the test using commercial kits.

RESULTS

The exercise induced an increase in plasma GH, NPY and FFA in both groups and a decrease in plasma ghrelin levels only in BN patients. Exercise after Aci administration resulted in an increase in plasma GH, and a decrease in plasma ghrelin in both groups; NPY increased more in BN patients. Exercise-induced FFA increase was depressed after Aci.

CONCLUSIONS

We conclude that the Aci-induced suppression in plasma ghrelin levels during exercise in both groups suggests a negative feedback of GH on ghrelin secretion. Observed changes in plasma FFA levels were not related to changes in GH and ghrelin levels.

Niacin: a re-emerging pharmaceutical for the treatment of dyslipidaemia

Dyslipidaemias, particularly those characterized by the 'atherogenic profile' of high low-density lipoprotein-cholesterol and triglycerides and low high-density lipoprotein-cholesterol, are the major modifiable risk factor for atherosclerosis. The search for drugs to favourably alter such lipid profiles, reducing the associated morbidity and mortality, remains a major research focus. Niacin (nicotinic acid) is the most effective agent available for increasing high-density lipoprotein-cholesterol, but its use is associated with side effects that negatively affect patient compliance: these appear to arise largely as a result of production of prostaglandin D(2) and its subsequent activation of the DP(1) receptor. Desire to reduce the side effects (and improve pharmacokinetic parameters) has led to the development of a number of agonists that have differing effects, both in terms of clinical potency and the severity of adverse effects. The recent discovery of the niacin G-protein-coupled receptor HM74A (GPR109A) has clarified the distinction between the mechanism whereby niacin exerts its therapeutic effects and the mechanisms responsible for the generation of side effects. This has allowed the development of new drugs that show great potential for the treatment of dyslipidaemia. However, recent advances in understanding of the contribution of prostaglandin metabolism to vascular wall health suggest that some of the beneficial effects of niacin may well result from activation of the same pathways responsible for the adverse reactions. The purpose of this review is to emphasize that the search for agonists that show higher tolerability must take into account all aspects of signalling through this receptor.

Transient growth hormone therapy to rats with low protein-inflicted intrauterine growth restriction does not prevent elevated blood pressure in later life

Intrauterine growth restriction (IUGR) is a risk factor for the development of hypertension in later life. Insulin-like growth factor I and growth hormone (GH) have the potential to improve metabolic syndrome after IUGR in adult animals. The objective of the present study was to examine whether transient GH treatment of pups after weaning can prevent the development of arterial hypertension in adult rats. IUGR was induced in Wistar rats by isocaloric protein restriction in pregnant dams and litter size was reduced to six male neonates after birth. Recombinant human GH was applied by daily subcutaneous injections at a dose of 3 microg/g body weight between days 24 and 60 of life. Control animals received vehicle treatment (VEH) only. Birth weight was significantly lower in low protein (LP) animals than in normal protein (NP) animals (5.1 +/- 0.3 g vs. 5.9 +/- 0.7 g, p < 0.05). Until weaning at day 23, LP animals reached similar body length, but had reduced body weight compared to NP animals. Intraarterially measured mean arterial blood pressure at day 120 was elevated in LP-VEH compared to NP-VEH animals (113 +/- 6 mmHg vs. 101 +/- 6 mmHg, p < 0.01). However, transient GH-treatment did not prevent arterial hypertension in LP animals (112 +/- 5 mmHg). Our data suggest that GH treatment between days 24 and 60 of life does not or at least not permanently reprogram blood pressure elevation after IUGR.

Genetic disorders in the GH IGF-I axis in mouse and man

Animal knockout experiments have offered the opportunity to study genes that play a role in growth and development. In the last few years, reports of patients with genetic defects in GH-IGF-I axis have greatly increased our knowledge of genetically determined causes of short stature. We will present the animal data and human reports of genetic disorders in the GH-IGF-I axis in order to describe the role of the GH-IGF-I axis in intrauterine and postnatal growth. In addition, the effects of the GH-IGF-I axis on the development and function of different organ systems such as brain, inner ear, eye, skeleton, glucose homeostasis, gonadal function, and immune system will be discussed. The number of patients with genetic defects in the GH-IGF-I axis is small, and a systematic diagnostic approach and selective genetic analysis in a patient with short stature are essential to identify more patients. Finally, the implications of a genetic defect in the GH-IGF-I axis for the patient and the therapeutic options will be discussed.