The negative association between plasma ghrelin and IGF-I is modified by obesity, insulin resistance and type 2 diabetes

Molecular and cellular mechanisms underlying the hepatoprotective role of ghrelin against NAFLD progression

The underlying mechanisms for the development and progression of nonalcoholic fatty liver disease (NAFLD) are complex and multifactorial. Within the last years, experimental and clinical evidences support the role of ghrelin in the development of NAFLD. Ghrelin is a gut hormone that plays a major role in the short-term regulation of appetite and long-term regulation of adiposity. The liver constitutes a target for ghrelin, where this gut-derived peptide triggers intracellular pathways regulating lipid metabolism, inflammation, and fibrosis. Interestingly, circulating ghrelin levels are altered in patients with metabolic diseases, such as obesity, type 2 diabetes, and metabolic syndrome, which, in turn, are well-known risk factors for the pathogenesis of NAFLD. This review summarizes the molecular and cellular mechanisms involved in the hepatoprotective action of ghrelin, including the reduction of hepatocyte lipotoxicity via autophagy and fatty acid β-oxidation, mitochondrial dysfunction, endoplasmic reticulum stress and programmed cell death, the reversibility of the proinflammatory phenotype in Kupffer cells, and the inactivation of hepatic stellate cells. Together, the metabolic and inflammatory pathways regulated by ghrelin in the liver support its potential as a therapeutic target to prevent NAFLD in patients with metabolic disorders.

Proteomic biomarkers of Kleine-Levin syndrome

STUDY OBJECTIVES

Kleine-Levin syndrome (KLS) is characterized by relapsing-remitting episodes of hypersomnia, cognitive impairment, and behavioral disturbances. We quantified cerebrospinal fluid (CSF) and serum proteins in KLS cases and controls.

METHODS

SomaScan was used to profile 1133 CSF proteins in 30 KLS cases and 134 controls, while 1109 serum proteins were profiled in serum from 26 cases and 65 controls. CSF and serum proteins were both measured in seven cases. Univariate and multivariate analyses were used to find differentially expressed proteins (DEPs). Pathway and tissue enrichment analyses (TEAs) were performed on DEPs.

RESULTS

Univariate analyses found 28 and 141 proteins differentially expressed in CSF and serum, respectively (false discovery rate <0.1%). Upregulated CSF proteins included IL-34, IL-27, TGF-b, IGF-1, and osteonectin, while DKK4 and vWF were downregulated. Pathway analyses revealed microglial alterations and disrupted blood-brain barrier permeability. Serum profiles show upregulation of Src-family kinases (SFKs), proteins implicated in cellular growth, motility, and activation. TEA analysis of up- and downregulated proteins revealed changes in brain proteins (p < 6 × 10-5), notably from the pons, medulla, and midbrain. A multivariate machine-learning classifier performed robustly, achieving a receiver operating curve area under the curve of 0.90 (95% confidence interval [CI] = 0.78-1.0, p = 0.0006) in CSF and 1.0 (95% CI = 1.0-1.0, p = 0.0002) in serum in validation cohorts, with some commonality across tissues, as the model trained on serum sample also discriminated CSF samples of controls versus KLS cases.

CONCLUSIONS

Our study identifies proteomic KLS biomarkers with diagnostic potential and provides insight into biological mechanisms that will guide future research in KLS.

The Complex World of Regulation of Pituitary Growth Hormone Secretion: The Role of Ghrelin, Klotho, and Nesfatins in It

The classic concept of how pituitary GH is regulated by somatostatin and GHRH has changed in recent years, following the discovery of peripheral hormones involved in the regulation of energy homeostasis and mineral homeostasis. These hormones are ghrelin, nesfatins, and klotho. Ghrelin is an orexigenic hormone, released primarily by the gastric mucosa, although it is widely expressed in many different tissues, including the central nervous system and the pituitary. To be active, ghrelin must bind to an n-octanoyl group (n = 8, generally) on serine 3, forming acyl ghrelin which can then bind and activate a G-protein-coupled receptor leading to phospholipase C activation that induces the formation of inositol 1,4,5-triphosphate and diacylglycerol that produce an increase in cytosolic calcium that allows the release of GH. In addition to its direct action on somatotrophs, ghrelin co-localizes with GHRH in several neurons, facilitating its release by inhibiting somatostatin, and acts synergistically with GHRH stimulating the synthesis and secretion of pituitary GH. Gastric ghrelin production declines with age, as does GH. Klotho is an anti-aging agent, produced mainly in the kidneys, whose soluble circulating form directly induces GH secretion through the activation of ERK1/2 and inhibits the inhibitory effect that IGF-I exerts on GH. Children and adults with untreated GH-deficiency show reduced plasma levels of klotho, but treatment with GH restores them to normal values. Deletions or mutations of the Klotho gene affect GH production. Nesfatins 1 and 2 are satiety hormones, they inhibit food intake. They have been found in GH3 cell cultures where they significantly reduce the expression of gh mRNA and that of pituitary-specific positive transcription factor 1, consequently acting as inhibitors of GH production. This is a consequence of the down-regulation of the cAMP/PKA/CREB signaling pathway. Interestingly, nesfatins eliminate the strong positive effect that ghrelin has on GH synthesis and secretion. Throughout this review, we will attempt to broadly analyze the role of these hormones in the complex world of GH regulation, a world in which these hormones already play a very important role.

Trajectories of Handgrip Strength and Their Associations with Mortality among Older Adults in Korea: Analysis of the Korean Longitudinal Study of Aging

BACKGROUND

Handgrip strength (HGS) is a good predictor of adverse health outcomes in later life. This prospective study aimed to investigate whether HGS trajectory patterns were associated with all-cause mortality among older adults in Korea.

METHODS

This study used the database of the 2006-2016 Korean Longitudinal Study of Aging. Study participants included 3,069 adults aged ≥65 years without a previous history of cancer. The trajectory model was developed to identify different homogeneous trajectory patterns of HGS according to study period. Cox proportional hazards models were then applied to investigate the association between HGS and all-cause mortality.

RESULTS

The survival probability according to HGS during the follow-up period decreased as base HGS weakened. We identified four distinct trajectory groups of HGS among men and three among women. The risk of mortality increased as the HGS of both males and females decreased. Compared with the highest HGS group, the adjusted hazard ratios for all-cause mortality of the lowest, lower-mid, and upper-mid HGS groups among males were 3.46 (95% confidence interval [CI], 2.17-6.69), 2.26 (95% CI, 1.47-3.48), and 1.58 (95% CI, 1.07-2.32). Those of the low and mid HGS groups among females were 2.69 (95% CI, 1.39-5.21) and 1.97 (95% CI, 1.05-3.69).

CONCLUSION

The faster HGS declined over time, the greater the all-cause mortality risk increased compared with the slowly decreasing or maintained HGS groups among men and women. HGS measurement among older adults will be helpful in assessing their health statuses and pre-assessing disease-associated morbidity.

Associations Between Handgrip Strength and Disease-Specific Mortality Including Cancer, Cardiovascular, and Respiratory Diseases in Older Adults: A Meta-Analysis

Several controversial studies linking handgrip strength and health have suggested that low handgrip strength in older adults may be related to health problems and have investigated whether there is a minimum handgrip strength level associated with reduced mortality. Thus, by meta-analysis, the authors identified an association between handgrip strength in older adults and disease-specific mortality and all-cause mortality. Thirty studies with a total of 194,767 older adult participants were included in this meta-analysis. Higher handgrip strength was associated with an 18% decrease in all-cause mortality. Lower handgrip strength was associated with increased all-cause mortality. The minimum handgrip strength in older women that did not increase all-cause mortality was 18.21 kg. Increased handgrip strength showed a decreased all-cause mortality, whereas decreased handgrip strength was associated with increased all-cause mortality. Strengthening the handgrip may help improve disease-specific mortality in older adults.

Role of ghrelin on growth hormone/insulin-like growth factor-1 axis during endotoxemia

OBJECTIVE

To investigate the anti-inflammatory property of ghrelin treatment on the Growth Hormone (GH)/Insulin-like Growth Factor-I (IGF-1) axis in Wistar rats that have undergone endotoxemia.

DESIGN

In this randomized animal study, lipopolysaccharide (LPS) (5 mg/kg; intraperitoneal) was administered to induce endotoxemia, and ghrelin (15 nmol/kg; endovenous) was injected simultaneously. Blood and liver samples were collected 2 h, 6 h and 12 h after LPS administration for analysis.

MEASUREMENTS

Tumor necrosis factor alpha (TNF-α), interleukin (IL)-1, beta (IL-1β), and IL-6 from both blood and liver were determined by ELISA assay. Serum nitrate was determined by chemiluminescense. Growth hormone receptor (GHR) and growth hormone secretagogue receptor 1a (GHSR-1a) were determined by western blotting. GHR mRNA and IGF-1 mRNA were determined by RT-PCR.

RESULTS

LPS administration induced a decrease in IGF-1 and GH serum levels, characterizing GH/IGF-1 axis disruption. Ghrelin treatment attenuated the decrease of serum levels of IGF-1 as well as the increase of TNF-α, IL-1β, IL-6 and nitrate induced by LPS. The increase of induced GHSR-1a protein expression seen in the LPS group after 2 h remained until 6 h after ghrelin treatment. However, attenuation of the circulating IGF-1 decrease by ghrelin treatment was not accompanied by changes in GHR protein expression nor GHR and IGF-1 gene expression.

CONCLUSION

Ghrelin was able to attenuate changes in the GH/IGF-1 axis observed during systemic inflammation, which may be due to the modulation of pro-inflammatory mediators release.

Association of ghrelin with cardiometabolic risk factors in Iranian adolescents: the CASPIAN-III study

Introduction: Current evidence suggests that ghrelin could contribute to the development of metabolic syndrome (MetS) in adults, but limited experience exists in adolescents. This study aims to explore the association of ghrelin levels with the MetS components among Iranian adolescents.

Methods: In this case-control study, 32 adolescents with MetS and 148 healthy controls were selected randomly from the childhood and Adolescence Surveillance and Prevention of Adult Non communicable disease (CASPIAN-III) study. MetS was defined according to the Adult Treatment Panel III (ATP III) criteria modified for children and adolescents. Anthropometric measures (including body mass index [BMI], waist circumference [WC] and waist to height ratio [WHtR]), blood pressure (BP) and biochemical data (including fasting blood sugar [FBS], triglyceride [TG], high-density lipoprotein cholesterol [HDL-C], low-density lipoprotein cholesterol [LDL-C], total cholesterol [TC] and gerlin) were measured.

Results: Total ghrelin level was significantly higher in students without MetS compared to those with MetS (748.89 ± 85.04 vs. 728.72 ± 90.36 [pg/mL]; P < 0.001). Significant negative correlations were seen between ghrelin levels and BMI, WC, WHtR, TG, and TC. Ghrelin had also relatively strong inverse correlations with FBS (r = −0.59, P< 0.001), LDL-C (r = −0.56, P < 0.001), and positive correlation with HDL-C (r = 0.60, P < 0.001). Compared with the children with MetS, in those without MetS, ghrelin was significantly associated with HDL-C and LDL-C. A decreasing trend was observed in the mean ghrelin level across increasing number of MetS components (P for trend <0.001).

Conclusion: We observed a relationship between ghrelin concentration and MetS components in adolescents.

Serum ghrelin and adiponectin levels are increased but serum leptin level is unchanged in low weight Chronic Obstructive Pulmonary Disease patients

BACKGROUND

Weight loss and muscle wasting are common features reported in COPD patients and they are all related with systemic inflammation. In this study, the relationship between pulmonary functions and inflammatory and metabolic parameters in low weight COPD patients were investigated.

METHODS

Fifty male COPD patients were grouped according to the Global Initiative for Chronic Obstructive Lung Disease criteria. Group 1: Mild-moderate COPD patients (n=18; with a mean age of 66.4 ± 9.2 yrs; body mass index (BMI):19.7 ± 1.5 kg/m(2)), group 2: Severe-very severe COPD patients (n=32; with a mean age of 65.9 ± 10.0 yrs; BMI:19.3 ± 1.6 kg/m(2)), group 3: Control group composed of healthy nonsmoking males (n=17; with a mean age of 50.2 ± 8.4 yrs; BMI:21.85 ± 1.5 kg/m(2)). Anthropometric parameters, serum levels of adiponectin (ApN), ghrelin, leptin, hsCRP, IL-6, IL-1β, IL-8, TNF-α and pulmonary functions were compared.

RESULTS

Adiponectin concentration was higher in group 1 (43.3 ± 28.6 ng/mL; p<0.05) and group 2 (59.9 ± 31.8 ng/mL; p<0.001) when compared with the control group (23.5 ± 13.6 ng/mL). Ghrelin concentrations were higher in COPD groups (1281.0 ± 1173.7 and 1840.0 ± 403.6 pg/mL; p<0.05) compared to the control subjects (554.0 ± 281.9 pg/mL). When the groups were compared, no significant difference was found for leptin, IL-1β, TNF-α, and IL-8. Interleukin-6 and hsCRP levels were higher in group 1 than in the control group. ApN was negatively correlated with BMI and FEV1. In all groups, FEV1 showed positive correlation with BMI, skinfold thicknesses, insulin and triglyceride; negative correlation with age, pack/years, HDL-Chol and ApN. Increased SHBG with decreased insulin level and HOMA-IR may indicate increased insulin sensitivity in COPD groups.

CONCLUSION

The anti-inflammatory effect of ApN and ghrelin is more evident in severe-very severe COPD patients.

Midlife and late-life handgrip strength and risk of cause-specific death in a general Japanese population: the Hisayama Study

BACKGROUND

Decreased handgrip strength has been reported to be a risk factor for all-cause death among the elderly. However, it is unclear whether handgrip strength measured in midlife is associated with risk of all-cause and cause-specific death in the general population.

METHODS

We followed, prospectively, a total of 2527 community-dwelling Japanese (1064 men and 1463 women) aged ≥40 years for 19 years. Participants were divided into three groups according to the age-specific and sex-specific tertiles of handgrip strength (T1, lowest; T3, highest).

RESULTS

During the follow-up period, 783 participants died, of whom 235 died of cardiovascular disease, 249 of cancer, 154 of respiratory disease and 145 of other causes. In the middle-aged group (40-64 years), multivariable-adjusted HRs (95% CIs) for all-cause death were 0.75 (0.56 to 0.99) in T2 and 0.49 (0.35 to 0.68) in T3 compared with T1 as a reference. Corresponding HRs (95% CI) in the elderly group (≥65 years) were 0.50 (0.40 to 0.62) and 0.41 (0.32 to 0.51), respectively. As regards the cause of death, higher levels of handgrip strength were significantly associated with decreased risks of cardiovascular death, respiratory death and death from other causes, but not of cancer, in the middle-aged and the elderly.

CONCLUSIONS

Our findings suggest that handgrip strength levels in midlife and late life are inversely associated with the risks of all-cause and non-cancer death in the general Japanese population.

Novel molecular aspects of ghrelin and leptin in the control of adipobiology and the cardiovascular system

Ghrelin and leptin show opposite effects on energy balance. Ghrelin constitutes a gut hormone that is secreted to the bloodstream in two major forms, acylated and desacyl ghrelin. The isoforms of ghrelin not only promote adiposity by the activation of hypothalamic orexigenic neurons but also directly stimulate the expression of several fat storage-related proteins in adipocytes, including ACC, FAS, LPL and perilipin, thereby stimulating intracytoplasmic lipid accumulation. Moreover, both acylated and desacyl ghrelin reduce TNF-α-induced apoptosis and autophagy in adipocytes, suggesting an anti-inflammatory role of ghrelin in human adipose tissue. On the other hand, leptin is an adipokine with lipolytic effects. In this sense, leptin modulates via PI3K/Akt/mTOR the expression of aquaglyceroporins such as AQP3 and AQP7 that facilitate glycerol efflux from adipocytes in response to the lipolytic stimuli via its translocation from the cytosolic fraction (AQP3) or lipid droplets (AQP7) to the plasma membrane. Ghrelin and leptin also participate in the homeostasis of the cardiovascular system. Ghrelin operates as a cardioprotective factor with increased circulating acylated ghrelin concentrations in patients with left ventricular hypertrophy (LVH) causally related to LV remodeling during the progression to LVH. Additionally, leptin induces vasodilation by inducible NO synthase expression (iNOS) in the vascular wall. In this sense, leptin inhibits the angiotensin II-induced Ca(2+) increase, contraction and proliferation of VSMC through NO-dependent mechanisms. Together, dysregulation of circulating ghrelin isoforms and leptin resistance associated to obesity, type 2 diabetes, or the metabolic syndrome contribute to cardiometabolic derangements observed in these pathologies.

Acylated ghrelin and leptin concentrations in patients with type 2 diabetes mellitus, people with prediabetes and first degree relatives of patients with diabetes, a comparative study

Background

Ghrelin is known as a new endocrine component supposed to have an influence in control of feeding behavior and energy balance. Recent studies have shown that ghrelin concentration in the subjects with diabetes mellitus type 2 (DM 2) is lower than normal. To clarify the relationship between ghrelin and insulin resistance and also DM 2, a cross-sectional study was designed.

Methods

In a cross-sectional study, 87 subjects were enrolled in three groups, 29 with DM2, 29 pre-diabetes state and 29 normoglycemic subjects of first-degree relatives of diabetic group. After clinical examination, blood samples were taken to measure fasting blood glucose, HbA1c, lipids, insulin, leptin and acylated ghrelin concentrations.

Results

Mean serum concentrations of acylated ghrelin in all groups (47.4 ± 27.9 pg/ml) were lower than normal values (150.3 ± 56.4 pg/ml) (P: 0.006) without significant difference within groups comparison(P: 0.1). A significant correlation was found between ghrelin concentration with body mass index (BMI) (r: -0.23, p <0.02) and abdominal circumference (AC) (r: -0.28, P < 0.008). Also inverse relationship between ghrelin level and insulin resistance (HOMA-IR) (r: -.032, p: 0.002) was seen in all subjects. Leptin level has a significant correlation with abdominal circumference (AC) and BMI (P < 0.0001) but not with ghrelin.

Conclusion

This study showed that obesity has a strong association with the reduced level of ghrelin concentration. It seems that the process of ghrelin reduction is initiated in earlier stages of insulin resistance prior to the onset of overt DM.

IGF-1 Increases with Hyperbaric Oxygen Therapy and Promotes Wound Healing in Diabetic Foot Ulcers

Objectives. To investigate insulin-like growth factor I (IGF-1) levels in response to hyperbaric oxygen therapy (HBOT) for diabetic foot ulcers and to determine whether IGF-1 is a predictive indicator of wound healing in patients with diabetic foot ulcers. Design and Methods. We treated 48 consecutive patients with diabetic foot ulcers with HBOT. Alterations of IGF-1 levels in patients whose wound healed with HBOT were compared with those in patients who did not benefit from HBOT. Results. There was no significant difference in initial IGF-1 levels between the two groups (P = 0.399). The mean IGF-1 level increased with HBOT (P < 0.05). In the healed group, the mean IGF-1 increase and the final values were significantly higher (P < 0.05). In the nonhealed group, the mean IGF-1 increase was minus and the final values were not significantly different (P < 0.05). The increase in IGF-1 level with HBOT was significantly higher in the healed group (P < 0.001). Conclusions. IGF-1 increased significantly in the healed group. We believe that HBOT is effective in the treatment of diabetic foot ulcers, with an elevation of IGF-1. This alteration seems to be a predictive factor for wound healing in diabetic foot ulcers treated with HBOT.

The ghrelin O-acyltransferase-ghrelin system reduces TNF-α-induced apoptosis and autophagy in human visceral adipocytes

AIMS/HYPOTHESIS

Proinflammatory and proapoptotic cytokines such as TNF-α are upregulated in human obesity. We evaluated the association between ghrelin isoforms (acylated and desacyl ghrelin) and TNF-α in obesity and obesity-associated type 2 diabetes, as well as the potential role of ghrelin in the control of apoptosis and autophagy in human adipocytes.

METHODS

Plasma concentrations of the ghrelin isoforms and TNF-α were measured in 194 participants. Ghrelin and ghrelin O-acyltransferase (GOAT) levels were analysed by western-blot, immunohistochemistry and real-time PCR in 53 biopsies of human omental adipose tissue. We also determined the effect of acylated and desacyl ghrelin (10 to 1,000 pmol/l) on TNF-α-induced apoptosis and autophagy-related molecules in omental adipocytes.

RESULTS

Circulating concentrations of acylated ghrelin and TNF-α were increased, whereas desacyl ghrelin levels were decreased in obesity-associated type 2 diabetes. Ghrelin and GOAT were produced in omental and subcutaneous adipose tissue. Visceral adipose tissue from obese patients with type 2 diabetes showed higher levels of GOAT, increased adipocyte apoptosis and increased expression of the autophagy-related genes ATG5, BECN1 and ATG7. In differentiating human omental adipocytes, incubation with acylated and desacyl ghrelin reduced TNF-α-induced activation of caspase-8 and caspase-3, and cell death. In addition, acylated ghrelin reduced the basal expression of the autophagy-related genes ATG5 and ATG7, while desacyl ghrelin inhibited the TNF-α-induced increase of ATG5, BECN1 and ATG7 expression.

CONCLUSIONS/INTERPRETATION

Apoptosis and autophagy are upregulated in human visceral adipose tissue of patients with type 2 diabetes. Acylated and desacyl ghrelin reduce TNF-α-induced apoptosis and autophagy in human visceral adipocytes.

Comparison of markers of appetite and inflammation between hemodialysis patients with and without failed renal transplants

OBJECTIVE

The survival of patients returning to hemodialysis (HD) following kidney transplant failure is unfavorable. However, the factors responsible for this poor outcome are largely unknown; chronic inflammation due to failed allograft and malnutrition may contribute to morbidity and mortality. We aim to compare the markers of appetite and malnutrition, and their relation with inflammation in HD patients with and without previous kidney transplantation.

METHODS

Fifty-six patients with failed renal allografts at least 3 months on dialysis (31 men, 25 women; mean age, 46 ± 9 years) and 77 HD patients who never underwent a transplant (43 men, 34 women; mean age, 50 ± 15 years) were included in the study. The appetite and diet assessment tool (ADAT) was used to determine the self reported appetite of patients. Serum concentrations of ghrelin, leptin, insulin like growth factor 1 (IGF-1), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and high-sensitivity C-reactive protein (hs-CRP) were measured. Associations among these variables were analyzed.

RESULTS

There were no significant differences considering age, gender or duration of renal replacement therapy between the 2 groups. The scores from Appetite and Diet Assessment Tool were significantly higher in the failed-transplant group. Serum ghrelin levels were significantly higher and serum albumin levels were significantly lower in the failed-transplant group. Serum leptin levels were similar between 2 groups. In addition, hs-CRP, IL-6, and TNF-α levels, which were used as inflammatory parameters, were significantly higher in the failed-transplant group.

CONCLUSIONS

Elevated serum ghrelin levels and inflammation may cause diminished appetite and malnutrition in patients with failed renal allografts, and higher levels of this hormone seem to be associated with inflammation caused by retained failed allografts.

The ghrelin-positive cells number is increased in duodenum in children with celiac disease

Ghrelin is predominately produced in the stomach, but new findings indicate that the intestinal wall is an important source of the hormone. In patients with shortbowel syndrome, reduction in the intestinal tissue resulted in a decrease in the circulating ghrelin levels. Since in celiac disease (CD) intestinal mucosa atrophy is the main finding, alterations in duodenal ghrelin-positive cell population can be expected. The aim of the study was to evaluate the density of ghrelin-positive cells in the duodenum of CD children and its relationship with body mass index (BMI) and clinical presentation. The study included 31 consecutive patients with newly diagnosed CD [BMI SD scores (BMISDS) -0.926+/-1.496]. The control group consisted of 21 children (BMISDS -0.517+/-1.186], diagnosed with growth retardation, anemia or abdominal pain. All the patients underwent endoscopy with biopsy samples taken from distal duodenum. Immunohistochemistry was performed using rabbit anti- ghrelin (human) antiserum. The number of ghrelin-positive cells in the duodenum was significantly higher in children with CD than in controls (14.82+/-11.12 vs 5.69+/-5.02, p<0.0013). The density of ghrelin-positive cells in the duodenum did not correlate with age, pubertal status, BMISDS or clinical presentation. In the duodenum of CD children, the number of ghrelin-positive cells is increased compared with the control patients. The population of ghrelin-positive cells in the duodenum does not simply reflect an altered mucosal morphology or failure to thrive but is under the influence of other conditions.

Plasma adiponectin concentration is associated with ambulatory daytime systolic blood pressure but not with the dipping status

The objective of this study was to analyse the relationship between the ambulatory blood pressure (ABP) measurement and plasma adiponectin levels in a population-based cohort. Non-hypertensive, non-diabetics from the Oulu Project Elucidating Risk of Atherosclerosis cohort aged 40-60 years with ABP measurement available in 226 men and 236 women were analysed. ABP was recorded using the fully automatic SpaceLabs 90207 oscillometric unit. Plasma adiponectin concentrations were assayed using the enzyme-linked immunosorbent assay method. Without adjustment the highest plasma adiponectin tertile was associated with the lowest ABP and office BP measurements (P from 0.025 to P<0.001, respectively). Only the association of plasma adiponectin concentration with systolic ABP was independent of other conventional risk factors (age, body mass index (BMI), waist, gender, insulin sensitivity index, smoking and alcohol consumption) for hypertension (P=0.017). No association was observed between systolic dipping pattern and adiponectin level. The plasma high adiponectin concentration is independently associated with low daytime systolic ABP value. The mechanisms may include effects on endothelial function and the sympathetic nervous system.

Serum ghrelin levels in inflammatory bowel disease with relation to disease activity and nutritional status

Ghrelin possesses various biological activities -- it stimulates growth hormone (GH) release, plays a major role in energy metabolism, and is one of the hormones that affects body composition. It also plays a role in modulating immune response and inflammatory processes. In this study we aimed to determine whether serum ghrelin levels had correlation with markers associated with disease activation. We also investigated any probable relationship between serum ghrelin level and nutritional status. Serum levels of ghrelin and its relationship with disease activity and nutritional status were evaluated in 34 patients with ulcerative colitis (UC), 25 patients with Crohn's disease (CD), and 30 healthy controls. Serum ghrelin levels, serum IGF-1 and GH levels, and markers of disease activity (sedimentation, C-reactive protein, and fibrinogen) were measured in all subjects. Body composition and nutritional status was assessed by both direct (by anthropometry) and indirect (by bioimpedance) methods. Serum ghrelin levels were significantly higher in patients with active UC and CD than in those in remission (108 +/- 11 pg/ml vs. 71 +/- 13 pg/ml for UC patients, P < 0.001; 110 +/- 10 pg/ml vs. 75 +/- 15 pg/ml for CD patients, P < 0.001). Circulating ghrelin levels in UC and CD patients were positively correlated with sedimentation, fibrinogen and CRP and was negatively correlated with IGF-1, BMI, TSFT, MAC, fat mass (%), and fat free mass (%). This study demonstrates that patients with active IBD have higher serum ghrelin levels than patients in remission and high levels of circulating ghrelin correlate with the severity of disease and the activity markers. Ghrelin levels in inflammatory bowel disease (IBD) patients show an appositive correlation with IGF-1 and bioelectrical impedance analysis, body composition, and anthropometric assessments. Finally, we arrived at the conclusion that ghrelin level may be important in determination of the activity in IBD patients and evaluation of nutritional status.

Acute ghrelin response to intravenous dexamethasone administration in idiopathic short stature or isolated idiopathic growth hormone-deficient children

Acylated ghrelin has been originally described for its potent GH-releasing activity mediated by the activation of the GH secretagogue receptor type 1a. More recently, ghrelin has been reported to exert several other GH-independent biological actions, among which in the modulation of metabolic functions. Glucocorticoids are well known to exert important metabolic functions but also to modulate GH secretion, although through mechanisms that have not been fully clarified so far. Interestingly, the existence of a feedback link between glucocorticoids and ghrelin system has already been reported. The aim of our study was to evaluate the acute GH and ghrelin responses to dexamethasone (DEX) administration in children with idiopathic short stature (ISS) or isolated idiopathic GH deficiency (GHD). Eight children with ISS (age: 9.5+/-1.2 yr) and 7 with GHD (12.1+/-1.4 yr) underwent iv DEX administration (0.3 mg/body surface area at 0 min). IGF-I, GH, and ghrelin levels were assayed at baseline and every 30 min from 120 up to 240 min after DEX. Compared to baseline levels DEX decreased ghrelin in ISS at 120 min and 240 min (p<0.04). On the other hand DEX did not modify ghrelin levels in GHD. After DEX, ghrelin was reduced in ISS compared to GHD (p<0.02). DEX increased GH in ISS but not in GHD (peak: 11.1+/-1.2 vs 7.6+/-0.9 microg/l). Basal, as well as after-DEX ghrelin levels negatively correlated with IGF-I in GHD (p<0.03) and with height SD score (HSDS) in ISS (p<0.02). Acute DEX administration is able to decrease ghrelin in ISS, but not in GHD children. Both basal and after-DEX ghrelin levels negatively correlate with IGF-I and HSDS. All these data suggest the existence of a feedback link among ghrelin, glucocorticoids and the GH/IGF-I axis.

Interactions between ghrelin, leptin and IGF-I affect metabolic syndrome and early atherosclerosis

BACKGROUND

High leptin and low ghrelin are associated with the metabolic syndrome (MS).

AIMS AND METHODS

Ghrelin, leptin (RIA kits), and insulin-like growth factor I (IGF-I) (ELISA kit) concentrations of the population-based cohort of 1045 subjects and their interactions with metabolic parameters were analysed. Intima-media thickness (IMT) was measured with carotid ultrasound.

RESULTS

The interaction between leptin and ghrelin on the MS was significant (P = 0.011). An additive effect of high leptin and low ghrelin on metabolic disturbances was observed: low ghrelin concentration (adjusted for age and sex) (P < 0.001) was associated with the MS and type 2 diabetes in the highest but not in the lower leptin quartiles. In the highest leptin quartile, ghrelin concentrations decreased linearly when the number of International Diabetes Federation MS criteria met (P < 0.01) increased. Ghrelin-leptin relation was independently associated with carotid IMT (P < 0.005). The independent positive association (P < 0.01) between the plasma ghrelin quartile and the carotid IMT was evident in the lowest IGF-I quartile.

CONCLUSIONS

Low ghrelin is associated with MS and type 2 diabetes in the presence of insulin and leptin resistance. Ghrelin-leptin relation is associated with early atherosclerosis. The interaction between IGF-I and ghrelin modifies the association of ghrelin with early atherosclerosis.

Growth hormone and somatostatin directly inhibit gastric ghrelin secretion. An in vitro organ culture system

Ghrelin is a 28-amino-acid hormone produced mainly by the stomach which strongly promotes food intake. It is the only known peripheral orexigenic hormone that induces the release of GH. Ghrelin has been proposed as a link between the enteric system and central regulation of energy balance and growth. Although it has recently been the focus of extensive study, the secretion mechanism is not yet well characterized. The aim of this study was to test the direct effect of hormones from the somatotropic axis on ghrelin release directly from the stomach. To this end, an organ culture model of gastric tissue explants from rat donors was used. These stomach explants were incubated in 6 well plates for 1, 2, and 3 h after treatment with either GH, GHRH, SS or IGF-I, all them at 10(-6) M. After incubation, the medium was collected and the amount of ghrelin secreted by the gastric tissue was measured by radioimmunoassay. It was observed that GH and SS significantly decreased gastric ghrelin secretion, while GHRH and IGF-1 had no effect on the present model. These results would confirm the capacity of GH and SS to act directly upon gastric level, inhibiting ghrelin secretion in vitro.

Genome-wide scan for serum ghrelin detects linkage on chromosome 1p36 in Hispanic children: results from the Viva La Familia study

This study was conducted to investigate genetic influence on serum ghrelin and its relationship with adiposity-related phenotypes in Hispanic children (n=1030) from the Viva La Familia study (VFS). Anthropometric measurements and levels of serum ghrelin were estimated and genetic analyses conducted according to standard procedures. Mean age, body mass index (BMI), and serum ghrelin were 11+/-0.13 y, 25+/-0.24 kg/m2 and 38+/-0.5 ng/mL, respectively. Significant heritabilities (p<0.001) were obtained for BMI, weight, fat mass, percent fat, waist circumference, waist-to-height ratio, and ghrelin. Bivariate analyses of ghrelin with adiposity traits showed significant negative genetic correlations (p<0.0001) with weight, BMI, fat mass, percent fat, waist circumference, and waist-to-height ratio. A genome-wide scan for ghrelin detected significant linkage on chromosome 1p36.2 between STR markers D1S2697 and D1S199 (LOD=3.2). The same region on chromosome 1 was the site of linkage for insulin (LOD=3.3), insulinlike growth factor binding protein 1 (IGFBP1) (LOD=3.4), homeostatic model assessment method (HOMA) (LOD=2.9), and C-peptide (LOD=2.0). Several family-based studies have reported linkages for obesity-related phenotypes in the region of 1p36. These results indicate the importance of this region in relation to adiposity in children from the VFS.

Not insulin but insulin sensitivity, leptin, and cortisol are major factors regulating serum acylated ghrelin level in healthy women

It has been suggested that insulin and glucose are the most important factors for ghrelin secretion. Most of these studies were performed using total ghrelin assays, detecting two forms of ghrelin (acylated and desacyl), derived from the same peptide precursor but having different biological effects. This study was therefore designed to characterize associations between serum acylated ghrelin levels (Ghr), selected adipocytokines, hormones, and carbohydrate metabolism parameters in healthy women in stable energy metabolism. The study was performed on 32 healthy, normal-weight, non-pregnant women with normal [body mass index (BMI) 18.9-24.2 kg/m2] and stable (the difference between two measurements performed within 1 month being less than 0.5 kg) body weight, aged 22-47 yr. Leptin, Ghr, GH, IGF-I, cortisol, insulin, and glucose were measured in the early follicular phase of the menstruation cycle. Insulin sensitivity was measured using quantitative insulin sensitivity check index (QUICKI). Body composition was assessed by bioimpedance. We found a positive linear correlation between leptin and Ghr (r=0.375; p=0.034) and negative correlation between insulin and Ghr (r=-0.374; p=0.034). GH, IGF-I, adiponectin, and body composition parameters did not correlate with Ghr. In multiple regression analysis only QUICKI, leptin, glucose, and cortisol (positively) and age (negatively) accounted for 50% variation of Ghr. Insulin and BMI did not contribute significantly to the model. Our results suggest that in healthy women basal Ghr level is regulated by multiple factors, mainly by insulin sensitivity, leptin, and adrenal glands activity. However, further studies are needed to elucidate the physiological mechanisms involved in acylated Ghr secretion.

Low level of IGF-1 in obesity may be related to obstructive sleep apnea syndrome

The aim of this study was to compare serum insulin-like growth factor (IGF-1) levels in patients with obstructive sleep apnea syndrome (OSAS) with those of nonapneic controls and to determine the risk factors of low IGF-1 levels in patients with OSAS. The study included 39 newly diagnosed moderate-to-severe OSAS patients and 36 nonapneic controls. Overnight polysomnography (PSG) was performed in all patients. The circulating levels of IGF-1 in the OSAS group were significantly lower than those of the control group (p < 0.05). There was a significant negative correlation between IGF-1 and logarithmic transformation (Ln) of the apnea-hypopnea index (AHI), duration of apnea-hypopnea, arousal index, average desaturation, and oxygen desaturation index (ODI). The result of stepwise regression analyses showed that OSAS (p = 0.001) was a risk factor for a low IGF-1 level, independent of age, gender, and body mass index (BMI). Our findings demonstrated that there was a significant negative correlation between IGF-1 and Ln AHI and that OSAS reduced the circulating levels of IGF-1.

Ghrelin has novel vascular actions that mimic PI 3-kinase-dependent actions of insulin to stimulate production of NO from endothelial cells

Ghrelin is an orexigenic peptide hormone secreted by the stomach. In patients with metabolic syndrome and low ghrelin levels, intra-arterial ghrelin administration acutely improves their endothelial dysfunction. Therefore, we hypothesized that ghrelin activates endothelial nitric oxide synthase (eNOS) in vascular endothelium, resulting in increased production of nitric oxide (NO) using signaling pathways shared in common with the insulin receptor. Similar to insulin, ghrelin acutely stimulated increased production of NO in bovine aortic endothelial cells (BAEC) in primary culture (assessed using NO-specific fluorescent dye 4,5-diaminofluorescein) in a time- and dose-dependent manner. Production of NO in response to ghrelin (100 nM, 10 min) in human aortic endothelial cells was blocked by pretreatment of cells with NG-nitro-L-arginine methyl ester (nitric oxide synthase inhibitor), wortmannin [phosphatidylinositol (PI) 3-kinase inhibitor], or (D-Lys3)-GHRP-6 (selective antagonist of ghrelin receptor GHSR-1a), as well as by knockdown of GHSR-1a using small-interfering (si) RNA (but not by mitogen/extracellular signal-regulated kinase inhibitor PD-98059). Moreover, ghrelin stimulated increased phosphorylation of Akt (Ser473) and eNOS (Akt phosphorylation site Ser1179) that was inhibitable by knockdown of GHSR-1a using siRNA or by pretreatment of cells with wortmannin but not with PD-98059. Ghrelin also stimulated phosphorylation of mitogen-activated protein (MAP) kinase in BAEC. However, unlike insulin, ghrelin did not stimulate MAP kinase-dependent secretion of the vasoconstrictor endothelin-1 from BAEC. We conclude that ghrelin has novel vascular actions to acutely stimulate production of NO in endothelium using a signaling pathway that involves GHSR-1a, PI 3-kinase, Akt, and eNOS. Our findings may be relevant to developing novel therapeutic strategies to treat diabetes and related diseases characterized by reciprocal relationships between endothelial dysfunction and insulin resistance.

Ghrelin, the peripheral hunger hormone

In the current review we summarize the available data concerning the gastric hormone ghrelin and its receptor. Ghrelin stimulates short-term food intake and long-term body weight regulation via its adipogenic and diabetogenic effects. Ghrelin stimulates gastric emptying, and these effects could be explored from a therapeutic point of view. Ghrelin levels change profoundly in anorexia, in states of insulin resistance, in obesity, and after bariatric surgery, suggesting that this is an important hormone in body weight regulation.

Modulation of the growth hormone-insulin-like growth factor (GH-IGF) axis by pharmaceutical, nutraceutical and environmental xenobiotics: an emerging role for xenobiotic-metabolizing enzymes and the transcription factors regulating their expression. A review

The growth hormone-insulin-like growth factor (GH-IGF) axis has gained considerable focus over recent years. One cause of this increased interest is due to a correlation of age-related decline in plasma GH/IGF levels with age-related degenerative processes, and it has led to the prescribing of GH replacement therapy by some practitioners. On the other hand, however, research has also focused on the pro-carcinogenic effects of high GH-IGF levels, providing strong impetus for finding regimes that reduce its activity. Whereas the effects of GH/IGF activity on the action of xenobiotic-metabolizing enzyme systems is reasonably well appreciated, the effects of xenobiotic exposure on the GH-IGF axis has not received substantial review. Relevant xenobiotics are derived from pharmaceutical, nutraceutical and environmental exposure, and many of the mechanisms involved are highly complex in nature, not easily predictable from existing in vitro tests and do not always predict well from in vivo animal models. After a review of the human and animal in vivo and in vitro literature, a framework for considering the different levels of direct and indirect modulation by xenobiotics is developed herein, and areas that still require further investigation are highlighted, i.e. the actions of common endocrine disruptors such as pesticides and phytoestrogens, as well as the role of xenobiotic-metabolizing enzymes and the transcription factors regulating their expression. It is anticipated that a fuller appreciation of the existing human paradigms for GH-IGF axis modulation gained through this review may help explain some of the variation in levels of plasma IGF-1 and its binding proteins in the population, aid in the prescription of particular dietary regimens to certain individuals such as those with particular medical conditions, guide the direction of long-term drug/nutraceutical safety trials, and stimulate ideas for future research. It also serves to warn athletes that using compounds touted as performance enhancing because they promote short-term GH release could in fact be detrimental to performance in the long-run.

Maternal and Cord Blood Ghrelin in the Pregnancies of Smoking Mothers: Possible Markers of Nutrient Availability for the Fetus

AIMS

To investigate the role of ghrelin in maternal and fetal metabolism, we determined its value in maternal smoking, a specific cause of reduced placenta function and fetal growth.

METHODS

In 85 normal term pregnancies, 42 in smoking and 43 in non-smoking mothers, we measured ghrelin in the maternal blood at the onset of labor and in the cord blood of their 85 singletons immediately after birth. We determined the relationships between ghrelin and placental GH (PGH), pituitary GH (pitGH), and IGF-I.

RESULTS

The newborns of smoking mothers weighed 0.24 kg less (p < 0.05) than those of non-smoking mothers. Cord blood ghrelin was 71% higher and PGH and cord blood IGF-I were 34% and 32% lower, respectively, in the pregnancies of smoking compared with non-smoking mothers (p < 0.05). Cord blood ghrelin was unrelated to pitGH and cord blood IGF-I. Maternal ghrelin was unchanged in smoking mothers, increased with maternal fasting duration (r = 0.26, p < 0.05), showed no correlation with PGH and negative correlation with cord blood IGF-I (r = -0.42, p < 0.01).

CONCLUSION

The decrease in placental function and fetal growth in smoking mothers is associated with an increase in cord blood ghrelin, and no change in maternal ghrelin. Maternal ghrelin concentration increases with fasting, and is negatively correlated with cord blood IGF-I: it may signal a reduction in the level of nutrients available for placental transfer. No correlation supports a role for ghrelin in PGH or pitGH secretion.

Distribution and determinants of adiponectin, resistin and ghrelin in a randomly selected healthy population

OBJECTIVE

Adiponectin, resistin, ghrelin and the IGF-I system seem to play an important role in the regulation of body composition throughout life, but the mechanisms are not well understood. The aim of our study was to analyse the distribution among sexes and all decades of the adult life of adiponectin, resistin and ghrelin and their relationship with anthropometric, body composition parameters and the IGF-I system.

SUBJECTS

One hundred and thirty-four men and 127 healthy women were included in the study.

MEASUREMENTS

Plasma concentration of adiponectin, resistin, ghrelin, total IGF-I, free IGF-I and IGFBP-3 were determined in all subjects. Body composition was evaluated by bioelectrical impedance.

RESULTS

Resistin and ghrelin were not affected by age. Plasma adiponectin correlated negatively with age, body mass index (BMI), waist-to-hip ratio (WHR), waist circumference (WC), fat mass (FM) and body fat (BF) in men. Adiponectin correlated negatively with WHR and positively with free IGF-I in women. Resistin correlated positively with BMI and WC only in men, and ghrelin correlated positively with WC, BMI and FM and negatively with free IGF-I in men. In multiple regression analysis adiponectin remained associated with WHR (beta=-0.19, P=0.01) in women. Resistin was positively associated with BMI (beta=0.30, P=0.003) in women and ghrelin was negatively related to free IGF-I (beta=-0.158, P=0.019) in men.

CONCLUSIONS

Plasma adiponectin declines with age and is negatively associated with FM in men. Our data suggest the existence of a positive correlation of adiponectin and the IGF-I axis in women and of an inverse relationship between ghrelin and the IGF-I system in men.