Recombinant human insulin-like growth factor-I (IGF-I) therapy decreases plasma leptin concentration in patients with chronic renal insufficiency

The Relationship Between Gene Polymorphism of Leptin and Leptin Receptor and Growth Hormone Deficiency

BACKGROUND Growth hormone deficiency (GHD) is a major cause of congenital short stature. GHD patients have significantly decreased serum leptin levels, which are regulated by gene polymorphism of leptin and leptin receptor. This study thus investigated the relationship between gene polymorphism and susceptibility to GHD. MATERIAL AND METHODS A case-control study was performed using 180 GHD children in addition to 160 healthy controls. After the extraction of whole genomic DNA, the genotypes of leptin and leptin receptor gene loci were analyzed by sequencing for single-nucleotide polymorphism. RESULTS The frequency distribution of all alleles identified in leptin gene (loci rs7799039) and leptin receptor gene (loci rs1137100 and rs1137101) fit Hardy-Weinberg equilibrium. There was a significant difference in allele frequency at loci rs7799039 or rs1137101, as individuals with heterozygous GA allele had lower (rs7799039) or higher (rs1137101) GHD risk. No significant difference in allele frequency was discovered at loci rs1137100 (p>0.05), which was unrelated to GHD susceptibility. CONCLUSIONS Gene polymorphism of leptin (loci rs7799039) and leptin receptor (loci rs1137101) are correlated with GHD susceptibility.

Insuficiência renal crônica e hormônio de crescimento: efeitos no eixo GH-IGF e na leptina

OBJETIVO: Avaliar as alterações de IGF-1, IGFBP-3, leptina e insulina após o uso de doses de reposição de hormônio de crescimento recombinante humano (rhGH) em crianças baixas pré-púberes com insuficiência renal crônica (IRC). CASUÍSTICA E MÉTODOS: Em 11 crianças (3F:8M), com idade média de 9,6 anos, em uso de rhGH (0,23mg/Kg/semana) por 12 meses, foram dosados (antes, 6 e 12 meses após o início do tratamento com rhGH) leptina, insulina, glicemia, IGF-1 e IGFBP-3. RESULTADOS: As concentrações séricas de leptina, insulina e glicemia não variaram significativamente no decorrer do uso do rhGH, sendo observado o padrão de leptina e glicemia normais, com hiperinsulinemia. Houve aumento significativo da IGF-1 e IGFBP-3 durante o uso do rhGH. CONCLUSÕES: O uso de doses de reposição de rhGH durante 12 meses em um grupo selecionado de crianças com IRC propiciou aumento significativo da concentração sérica de IGF-1 e IGFBP-3, com leptinemia normal e resistência insulínica.

Leptin responses to insulin administration in children with short stature

Abstract The aim of the study was to investigate the effect of standard insulin tolerance test on plasma leptin levels in children with idiopathic short stature (ISS) and in children with growth hormone deficiency (GHD). Furthermore, plasma leptin levels were analyzed with regard to age, body mass index (BMI), and plasma levels of human growth hormone and of insulin-like growth factor-1 (IGF-1). Sixty-three patients with a height below the third percentile, an age of 10.24 +/- 0.40 years and a BMI standard deviation score (SDS) of -0.78 +/- 0.13 (weight SDS -0.07 +/- 0.12; height SDS -2.39 +/- 0.10) were investigated (mean +/- SD). Based on responses to insulin tolerance test, the patients were classified as ISS (n = 49) or GHD (n = 14). Plasma leptin levels were significantly lower in all patients 60 minutes ( P < .001) and 120 minutes ( P < .001) after insulin administration. This effect was independent of GHD, and no difference in leptin decrease was found when comparing patients with ISS to those with GHD. A correlation was found when comparing plasma leptin levels of all patients to BMI SDS (r = 0.43; P < .001) and plasma IGF-1 levels (r = 0.31; P < .01). Furthermore, positive correlation was found when BMI SDS was compared to IGF-1 (r = 0.25; P < .05). In summary, we found that insulin administration in children with short stature decreases plasma leptin levels, equally in those with and without GHD.

Age-related femoral bone loss in men: evidence for hyperparathyroidism and insulin-like growth factor-1 deficiency

BACKGROUND

We sought to determine the extent to which the age-related decline of femoral neck (FN) bone mineral density (BMD) might be explained by the age-related change of body composition and biological parameters and the mechanisms by which these factors might influence FN BMD in men.

METHODS

The relationships between FN BMD and anthropometric, hormonal, and biochemical parameters and bone turnover markers were studied in 82 men aged 25-86 years.

RESULTS

Age was associated with a decline of FN BMD and osteocalcin (OC), bone alkaline phosphatase (bALP), and urinary C-telopeptide (p <.05). The significant relationship between FN BMD and OC (p <.01) did not remain after adjustment for age. With use of multiple linear regression and adjusting for all significant variables associated with FN BMD in univariate analysis (p <.01) (age, weight, lean and fat mass, height, and levels of dehydroepiandrosterone sulfate, insulin-like growth factor [IGF-1], testosterone, and parathyroid hormone [PTH]), age accounted for 29.5% of FN BMD variance. When age was excluded from the model, PTH accounted for 19.5% and IGF-1 for 10% of the FN BMD variance. Bone turnover markers were significantly intercorrelated, and levels of IGF-1 were positively associated with those of bALP and OC (p <.05).

CONCLUSIONS

These results show that age is a strong predictor of FN BMD in men, resulting in a decline of bone remodeling, especially of bone formation. The results also show that, after taking into account anthropometric and other biological factors possibly involved in bone aging, the major part of the effect of age on bone is explained by the age-related increase of PTH and decrease of IGF-1 in men, suggesting that all measures taken to limit these age-related changes may be effective in the prevention of the age-related decline of FN BMD in men.

Phenotypic effects of leptin replacement on morbid obesity, diabetes mellitus, hypogonadism, and behavior in leptin-deficient adults

Genetic mutations in the leptin pathway can be a cause of human obesity. It is still unknown whether leptin can be effective in the treatment of fully established morbid obesity and its endocrine and metabolic consequences in adults. To test the hypothesis that leptin has a key role in metabolic and endocrine regulation in adults, we examined the effects of human leptin replacement in the only three adults identified to date who have genetically based leptin deficiency. We treated these three morbidly obese homozygous leptin-deficient adult patients with recombinant human leptin at low, physiological replacement doses in the range of 0.01-0.04 mg/kg for 18 months. Patients were hypogonadal, and one of them also had type 2 diabetes mellitus. We chose the doses of recombinant methionyl human leptin that would achieve normal leptin concentrations and administered them daily in the evening to model the normal circadian variation in endogenous leptin. The mean body mass index dropped from 51.2 +/- 2.5 (mean +/- SEM) at baseline to 26.9 +/- 2.1 kg/m2 after 18 months of treatment, mainly because of loss of fat mass. We document here that leptin replacement therapy in leptin-deficient adults with established morbid obesity results in profound weight loss, increased physical activity, changes in endocrine function and metabolism, including resolution of type 2 diabetes mellitus and hypogonadism, and beneficial effects on ingestive and noningestive behavior. These results highlight the role of the leptin pathway in adults with key effects on the regulation of body weight, gonadal function, and behavior.

Relationship of leptin and insulin-like growth factor I to nutritional status in hemodialyzed children

Malnutrition is prevalent in patients with end-stage renal disease (ESRD). Elevated serum leptin levels were thought to contribute to the anorexia and poor nutrition in renal failure. However, studies of the relationship between nutritional status and leptin concentration in chronic renal failure have yielded conflicting results. Plasma insulin-like growth factor I (IGF-I) level has been used as an indicator of nutritional status in patients with renal failure. The relationship between leptin and IGF-I is controversial. The present study was conducted with the aim of assessing the relationship between nutritional status, hyperleptinemia, and serum IGF-I. Seventeen ESRD patients (8 male, 9 female), aged 8-18 years (mean 15.3+/-3.3 years) and undergoing standard hemodialysis for 58.8+/-23.1 months were enrolled. Nine age-matched healthy children served as controls. In all patients, energy and protein intakes were 40-70 kcal/kg per day and 1-1.54 g/kg per day, respectively. Predialysis serum leptin and IGF-I levels were measured by radioimmunoassay. Body mass index was decreased in 13 (76%) patients. Triceps skinfold thickness (TST) was reduced (below the 5th percentile) in 7 (41%), whereas mid arm circumference and mid arm muscle circumference were reduced in 14 (82.5%) and 13 (76.5%), respectively. The median serum leptin level was significantly higher in patients than in controls [13.7 interquartile range (IQR) 30.50 pg/ml vs. 6.50 IQR 8.65 pg/ml, P=0.01]. The median serum IGF-I level was lower in the patients (205.1 ng/ml IQR 194.4 ng/l) than controls (418.0 ng/l IQR 310.5 ng/ml) ( P=0.01). IGF-I levels were more decreased in patients with severe malnutrition, defined according to TST (145.0 ng/ml IQR 125.5 ng/l) than patients without malnutrition (301.2 ng/l IQR 218.8 ng/ml) ( P=0.03) and healthy children ( P=0.002). Although statistically not significant, IGF-I levels tended to be decreased, while leptin levels were increased. The median plasma insulin concentration was 15 microU/ml (1.63-45.80) and did not correlate with leptin and IGF-I levels. In conclusion, the results of this study confirm the presence of high circulating plasma leptin levels, which may be one of the many factors involved in the pathogenesis of the malnutrition in children on hemodialysis.

Affect of serum leptin on nutritional status in renal disease

Protein-energy malnutrition is a major comorbid condition in persons with renal disease. A variety of interventions have been implemented to supplement protein and energy intake in malnourished patients with renal disease, but the prevalence of protein-energy malnutrition remains high. Leptin, a hormone secreted by adipose tissue, decreases food intake via neuroendocrine systems in the hypothalamus in persons with normal renal function. Serum leptin levels are elevated in patients with chronic renal insufficiency and end-stage renal disease, and experimental evidence suggests a possible role for leptin in the development of protein-energy malnutrition in this population. Release of leptin from adipocytes may be stimulated by cytokines mediating the inflammatory response, which is frequently pronounced in patients with end-stage renal disease receiving hemodialysis and peritoneal dialysis. This article provides an overview of research conducted on serum leptin levels in different stages of renal disease, and the relationship among serum leptin, body composition, biochemical indexes, and markers of inflammation in persons with end-stage renal disease. Effects of intradialytic parenteral nutrition and anabolic factors on leptin levels and nutritional status are briefly reviewed.

Effects of short-term recombinant human growth hormone therapy on plasma leptin concentrations in dialysis patients

BACKGROUND

Hyperleptinaemia is a well-known biochemical feature found in uraemic patients. However, little is known about the hormonal regulation of leptin in chronic renal disease. Recent studies have shown that circulating leptin levels are modified by treatment with recombinant human growth hormone (rhGH), by recombinant insulin-like growth factor I (rhIGF I), or by a combination of rhIGF I plus rhGH in patients with chronic renal failure. We performed a prospective study to assess plasma leptin concentrations in a group of dialysis patients both before and during short-term rhGH therapy.

METHODS

We studied eight dialysis patients (four haemodialysis (HD) and four on continuous ambulatory peritoneal dialysis (CAPD); three female, five male; mean age 63.9 +/- 3.1 years). All patients were instructed to maintain a stable diet (35 kcal/kg/day and 1 g protein/kg/day ideal body weight) and were treated with rhGH (0.2 IU/kg/day s.c.) for 4 weeks. Blood samples were taken at 0, 2, 4, and 8 weeks for determination of leptin, GH, and IGF I. Serum insulin concentrations were assessed at 0 and 4 weeks.

RESULTS

Mean plasma leptin concentrations were elevated (36.2 +/- 12.8 ng/ml) at study outset and increased progressively throughout the 4 weeks of rhGH therapy (43.7 +/- 13.5 ng/ml (2 weeks, NS) and 70.6 +/- 18.4 ng/ml (4 weeks, P<0.0001)). These values returned to baseline levels (38.0 +/- 12.0 ng/ml, NS) at 1 month after rhGH withdrawal. rhGH therapy was accompanied by the development of direct correlations between leptin and IGF I concentrations at 2 weeks (r=0.86, P<0.01), and with correlations between leptin and IGF I (r=0.84, P<0.01) and between leptin and insulin (r=0.88, P<0.01) after 4 weeks of rhGH administration.

CONCLUSION

These results confirm the presence of high circulating plasma leptin in dialysis patients and show that these levels are further increased by exogenous rhGH administration. The increase in plasma leptin after rhGH therapy may be related to the rhGH-induced changes in insulin in these patients.

Alcohol ingestion decreases both diurnal and nocturnal secretion of leptin in healthy individuals

OBJECTIVE

Neuropeptide Y (NPY) stimulates appetite and increases food intake. Leptin inhibits NPY. It is not known whether alcohol influences any of these factors, but it has been suggested that alcohol stimulates appetite in man. The primary objective of this investigation was to determine whether ingestion of ethanol inhibits leptin secretion in normal subjects.

SUBJECTS AND DESIGN

Fourteen healthy, non-obese subjects of both sexes (7 F/7 M) were included. They were divided into two groups (I and II; 8/6). All were investigated on two occasions. On one occasion alcohol was ingested, and on the other drinking water was given. The experiments took place in random order, one week apart. In group I two experiments (A = alcohol; B = water) were performed during the day. In group II the experiments were carried out during the night (C = alcohol; D = water). Each alcoholic drink contained 0.45 g ethanol/kg. The drinks were given at 08.00, 09.30 and 11.00 hours in experiments A and B, and at 18.00, 20.00 and 22.00 hours in experiments C and D. Venous blood samples were collected before, during and after the drinks over periods of 6 h in group I and 14 h in group II.

MEASUREMENTS

Serum concentrations of leptin, insulin-like growth factor 1 (IGF-1), IGF binding protein 1 (IGFBP-1), insulin, cortisol, testosterone, ethanol and plasma glucose were determined. RESULTS Group I serum leptin levels declined during the day in both men and women regardless of whether alcohol or water had been administered in the morning. Since leptin levels in general were markedly higher in women than in men, all leptin changes after water/alcohol were transformed to percentage changes to make them comparable between sexes. When the percentage leptin decline over a 6-h period (08.00-24.00 hours) was expressed by a decremental area under curve (AUC08-14), it became evident that alcohol inhibited leptin secretion, inasmuch as the leptin decremental area, obtained after alcohol, was significantly larger than the one obtained after water (124 +/- 17 vs. 57 +/- 8; P < 0.01). Similar insulin and glucose levels were obtained after alcohol and water. Group II serum leptin levels increased after both alcohol and water during the initial part of the night (18.00-20.00 hours). In this period alcohol inhibited the secretion of leptin as shown by the leptin incremental area (AUC18-24) which was 53 +/- 18 after alcohol and 113 +/- 15 after water (P < 0.01). As the ethanol concentration in serum began to fall, its inhibitory effect on leptin gradually disappeared, and when leptin AUCs representing the entire night were determined after alcohol and water, they were not significantly different. Similar insulin, glucose, testosterone, IGF-1 and cortisol levels were found after alcohol and water. The IGFBP-1 level increased, but not significantly so until 6 h after commencing the alcohol ingestion.

CONCLUSION

Ingestion of moderate amounts of alcohol has an inhibitory effect on leptin secretion in normal subjects. The effect may be direct rather than indirect, since several factors known to affect leptin are not influenced by alcohol. It is tempting to speculate that alcohol might serve as an appetizer by decreasing leptin secretion, but additional studies are necessary to prove that hypothesis since previous studies have shown that leptin has a long-term rather than an acute effect on hunger.

Effects of growth hormone on leptin metabolism and energy expenditure in hemodialysis patients with protein-calorie malnutrition

The relationships among growth hormone (GH), leptin, and resting energy expenditure (REE) are not understood. It has been reported that in malnourished hemodialysis patients, GH increases muscle protein synthesis, a process that requires energy. The present study evaluated the arterial levels and the forearm exchange of leptin, as well as the REE of the same patients during their participation in the same study, in four sequential 6-wk periods: I, baseline; II, GH treatment; III, washout; and IV, GH + intradialytic parenteral nutrition. During periods II and IV, patients received GH (5 mg three times per week). REE rose by 5% in period II, declined during period III, and rose by 7% during period IV. Basal leptin levels were low (2.0 +/- 0.19 ng/L). Insulin and leptin levels, as well as leptin release from the forearm, were unchanged during periods I through III but rose (+ 36%; P: < 0.05) during period IV. Changes in arterial leptin were directly related to changes in forearm leptin release (P: < 0.002), indicating a role of leptin production by peripheral tissues on leptinemia. Changes in leptin release were directly related to insulin (P: < 0.001) and, less consistently, to insulin-like growth factor-binding protein-1 levels (P: < 0.02). Similarly, variations in leptin levels were directly related to insulin (P: < 0.01). Variations in REE were not related to variations in leptin or insulin levels but to changes in muscle protein synthesis (P: < 0.025). The data show that in malnourished hemodialysis patients, treatment with GH is not invariably associated with an increase in leptin production. An increase in leptin release by peripheral tissues and leptin levels occurs only in the setting of hyperinsulinemia. The increase in REE that is induced by treatment with GH is not dependent on changes in leptin but is largely accounted for by the energy cost of the stimulation of muscle protein synthesis.

Integration of metabolism and intake regulation: a review focusing on periparturient animals

There has been great interest in dry matter intake regulation in lactating dairy cattle to enhance performance and improve animal health and welfare. Predicting voluntary dry matter intake (VDMI) is complex and influenced by numerous factors relating to the diet, management, housing, environment and the animal. The objective of this review is to identify and discuss important metabolic factors involved in the regulation of VDMI and their integration with metabolism. We have described the adaptations of intake and metabolism and discussed mechanisms of intake regulation. Furthermore we have reviewed selected metabolic signals involved in intake regulation. A substantial dip in VDMI is initiated in late pregnancy and continues into early lactation. This dip has traditionally been interpreted as caused by physical constraints, but this role is most likely overemphasized. The dip in intake coincides with changes in reproductive status, fat mass, and metabolic changes in support of lactation, and we have described metabolic signals that may play an equally important role in intake regulation. These signals include nutrients, metabolites, reproductive hormones, stress hormones, leptin, insulin, gut peptides, cytokines, and neuropeptides such as neuropeptide Y, galanin, and corticotrophin-releasing factor. The involvement of these signals in the periparturient dip in intake is discussed, and evidence supporting the integration of the regulation of intake and metabolism is presented. Still, much research is needed to clarify the complex regulation of VDMI in lactating dairy cows, particularly in the periparturient animal.

Plasma leptin association with body composition and energy expenditure in sickle cell disease

OBJECTIVE

To examine the association between fasting plasma leptin concentrations and the hypercatabolic state observed in sickle cell disease (SCD).

METHODS

Plasma leptin concentration and resting energy expenditure (REE) were measured in 37 SCD patients (10 men, 12 boys 14 to 18 years-old, seven women, and eight girls 14 to 18 year-old) and in 37 age, gender and fat mass (FM) matched controls. Body composition was measured hydrostatically, REE by whole room-indirect calorimeter, and plasma leptin using an RIA kit.

RESULTS

Plasma leptin concentration and leptin normalized for body fat (ng/dL*kg FM(-1)) were significantly lower in SCD patients than in non-SCD controls (4.00+/-3.23 vs. 9.94+/-14.69, p=0.021 and 0.406+/-0.260 vs. 0.643+/-0.561, p=0.024, respectively). A positive linear association between log plasma leptin and FM was observed in both males and females, adjusting for age and SCD status. The strength of this association was greater in females compared with males (slope=0.699 and 0.382 log ng/mL per 10 kg FM, respectively; p=0.013). SCD patients on average demonstrated a higher REE, adjusting for FFM (p<0.0001). Log plasma leptin and FM were not statistically significant predictors of REE after adjustment for FFM and SCD.

CONCLUSIONS

Once corrected for body composition, mean plasma leptin concentration was significantly lower among female SCD patients than among non-SCD matched controls. Although REE was higher in SCD patients, there is no simple association between leptin and REE in SCD.

Haemodialysis and peritoneal dialysis: metabolic alterations and nutritional status

In dialysis patients, malnutrition is an independent factor causing morbidity and mortality. Both inadequate alimentation and metabolic alterations, which involve nitrogen and energy metabolism, contribute to malnutrition. Future research must address the treatment of anorexia and inflammation-induced catabolism, as well as the evaluation of nutritional supplementation techniques and anabolic drugs.