Changes in 24-h area-under-the-curve ghrelin values following diet-induced weight loss are associated with loss of fat-free mass, but not with changes in fat mass, insulin levels or insulin sensitivity

Post-weight loss changes in fasting appetite- and energy balance-related hormone concentrations and the effect of the macronutrient content of a weight maintenance diet: a randomised controlled trial

PURPOSE

We investigated the effects of the macronutrient composition of diets with differing satiety values on fasting appetite-related hormone concentrations after weight loss and examined whether the hormone secretion adapted to changes in body fat mass (FM) and fat-free mass (FFM) during the weight maintenance period (WM).

METHODS

Eighty-two men and women with obesity underwent a 7-week very-low-energy diet (VLED) and were then randomised to a higher-satiety food (HSF) group or a lower-satiety food (LSF) group during 24-weeks of the WM. The groups consumed isoenergetic foods with different satiety ratings and macronutrient compositions.

RESULTS

During the WM, the HSF group consumed more protein and dietary fibre and less fat than the LSF group, but the groups showed similar changes in body weight and fasting appetite-related hormones. In the whole study sample, VLED induced 12 kg (p < 0.001) weight loss. At the end of the WM, weight regain was 1.3 kg (p = 0.004), ghrelin concentration increased, whereas leptin, insulin, and glucose concentrations decreased compared to pre-VLED levels (p < 0.001 for all). Peptide YY did not differ from pre-VLED levels. Changes in ghrelin levels were inversely associated with changes in FFM during weeks 0-12 of the WM (p = 0.002), while changes in leptin and insulin levels were positively associated with changes in FM during weeks 0-12 (p = 0.015 and p = 0.038, respectively) and weeks 12-24 (p < 0.001 and p = 0.022) of the WM.

CONCLUSIONS

The macronutrient composition of an isoenergetic WM diet did not affect fasting appetite-related hormone concentrations. Leptin and insulin adjusted to the reduced FM, whereas ghrelin reflected FFM during the first months of the WM.

TRIAL REGISTRATION

isrctn.com, ID 67529475.

The effect of meal frequency in a reduced-energy regimen on the gastrointestinal and appetite hormones in patients with type 2 diabetes: A randomised crossover study

Background

Appetite and gastrointestinal hormones (GIHs) participate in energy homeostasis, feeding behavior and regulation of body weight. We demonstrated previously the superior effect of a hypocaloric diet regimen with lower meal frequency (B2) on body weight, hepatic fat content, insulin sensitivity and feelings of hunger compared to the same diet divided into six smaller meals a day (A6). Studies with isoenergetic diet regimens indicate that lower meal frequency should also have an effect on fasting and postprandial responses of GIHs. The aim of this secondary analysis was to explore the effect of two hypocaloric diet regimens on fasting levels of appetite and GIHs and on their postprandial responses after a standard meal. It was hypothesized that lower meal frequency in a reduced-energy regimen leading to greater body weight reduction and reduced hunger would be associated with decreased plasma concentrations of GIHs: gastric inhibitory peptide (GIP), glucagon-like peptide-1(GLP-1), peptide YY(PYY), pancreatic polypeptide (PP) and leptin and increased plasma concentration of ghrelin. The postprandial response of satiety hormones (GLP-1, PYY and PP) and postprandial suppression of ghrelin will be improved.

Methods

In a randomized crossover study, 54 patients suffering from type 2 diabetes (T2D) underwent both regimens. The concentrations of GLP-1, GIP, PP, PYY, amylin, leptin and ghrelin were determined using multiplex immunoanalyses.

Results

Fasting leptin and GIP decreased in response to both regimens with no difference between the treatments (p = 0.37 and p = 0.83, respectively). Fasting ghrelin decreased in A6 and increased in B2 (with difference between regimens p = 0.023). Fasting PP increased in B2with no significant difference between regimens (p = 0.17). Neither GLP-1 nor PYY did change in either regimen. The decrease in body weight correlated negatively with changes in fasting ghrelin (r = -0.4, p<0.043) and the postprandial reduction of ghrelin correlated positively with its fasting level (r = 0.9, p<0.001). The postprandial responses of GIHs and appetite hormones were similar after both diet regimens.

Conclusions

Both hypocaloric diet regimens reduced fasting leptin and GIP and postprandial response of GIP comparably. The postprandial responses of GIHs and appetite hormones were similar after both diet regimens. Eating only breakfast and lunch increased fasting plasma ghrelin more than the same caloric restriction split into six meals. The changes in fasting ghrelin correlated negatively with the decrease in body weight. These results suggest that for type 2 diabetic patients on a hypocaloric diet, eating larger breakfast and lunch may be more efficient than six smaller meals during the day.

A systematic review and meta-analysis on the effects of exercise training versus hypocaloric diet: distinct effects on body weight and visceral adipose tissue

Exercise training ('exercise') and hypocaloric diet ('diet') are frequently prescribed for weight loss in obesity. Whilst body weight changes are commonly used to evaluate lifestyle interventions, visceral adiposity (VAT) is a more relevant and stronger predictor for morbidity and mortality. A meta-analysis was performed to assess the effects of exercise or diet on VAT (quantified by radiographic imaging). Relevant databases were searched through May 2014. One hundred seventeen studies (n = 4,815) were included. We found that both exercise and diet cause VAT loss (P < 0.0001). When comparing diet versus training, diet caused a larger weight loss (P = 0.04). In contrast, a trend was observed towards a larger VAT decrease in exercise (P = 0.08). Changes in weight and VAT showed a strong correlation after diet (R(2)  = 0.737, P < 0.001), and a modest correlation after exercise (R(2)  = 0.451, P < 0.001). In the absence of weight loss, exercise is related to 6.1% decrease in VAT, whilst diet showed virtually no change (1.1%). In conclusion, both exercise and diet reduce VAT. Despite a larger effect of diet on total body weight loss, exercise tends to have superior effects in reducing VAT. Finally, total body weight loss does not necessarily reflect changes in VAT and may represent a poor marker when evaluating benefits of lifestyle-interventions.

Successful weight loss maintenance includes long-term increased meal responses of GLP-1 and PYY3-36

OBJECTIVE

The hormones glucagon-like peptide 1 (GLP-1), peptide YY3-36 (PYY3-36), ghrelin, glucose-dependent insulinotropic polypeptide (GIP) and glucagon have all been implicated in the pathogenesis of obesity. However, it is unknown whether they exhibit adaptive changes with respect to postprandial secretion to a sustained weight loss.

DESIGN

The study was designed as a longitudinal prospective intervention study with data obtained at baseline, after 8 weeks of weight loss and 1 year after weight loss.

METHODS

Twenty healthy obese individuals obtained a 13% weight loss by adhering to an 8-week very low-calorie diet (800kcal/day). After weight loss, participants entered a 52-week weight maintenance protocol. Plasma levels of GLP-1, PYY3-36, ghrelin, GIP and glucagon during a 600-kcal meal were measured before weight loss, after weight loss and after 1 year of weight maintenance. Area under the curve (AUC) was calculated as total AUC (tAUC) and incremental AUC (iAUC).

RESULTS

Weight loss was successfully maintained for 52 weeks. iAUC for GLP-1 increased by 44% after weight loss (P<0.04) and increased to 72% at week 52 (P=0.0001). iAUC for PYY3-36 increased by 74% after weight loss (P<0.0001) and by 36% at week 52 (P=0.02). tAUC for ghrelin increased by 23% after weight loss (P<0.0001), but at week 52, the increase was reduced to 16% compared with before weight loss (P=0.005). iAUC for GIP increased by 36% after weight loss (P=0.001), but returned to before weight loss levels at week 52. Glucagon levels were unaffected by weight loss.

CONCLUSIONS

Meal responses of GLP-1 and PYY3-36 remained increased 1 year after weight maintenance, whereas ghrelin and GIP reverted toward before-weight loss values. Thus, an increase in appetite inhibitory mechanisms and a partly decrease in appetite-stimulating mechanisms appear to contribute to successful long-term weight loss maintenance.

The effects of separate and combined dietary weight loss and exercise on fasting ghrelin concentrations in overweight and obese women: a randomized controlled trial

OBJECTIVE

Compensatory metabolic changes that accompany weight loss, for example, increased ghrelin, contribute to weight regain and difficulty in long-term weight loss maintenance; however, the separate effects of long-term caloric restriction and exercise on total circulating ghrelin in humans are unknown.

DESIGN

A 12-month randomized controlled trial comparing: i) dietary weight loss with a 10% weight loss goal ('diet'; n = 118); ii) moderate-to-vigorous intensity aerobic exercise for 45 min/day, 5 days/week ('exercise'; n = 117); iii) dietary weight loss and exercise ('diet + exercise'; n = 117); or iv) no-lifestyle-change control (n = 87).

PARTICIPANTS

439 overweight or obese postmenopausal women (50-75 y).

MEASUREMENTS

Fasting total serum ghrelin was measured by radioimmunoassay at baseline and 12 months. Fasting serum leptin, adiponectin and insulin were also measured.

RESULTS

Fasting total ghrelin significantly increased in the diet + exercise arm (+7·4%, P = 0·008) but not in either the diet (+6·5%, P = 0·07) or exercise (+1·0%, P = 0·53) arms compared with control. Greater weight loss was associated with increased ghrelin concentrations, regardless of intervention. Neither baseline ghrelin nor body composition modified the intervention effects on changes in total ghrelin. The 12-month change in total ghrelin was inversely associated with changes in leptin, insulin and insulin resistance, and positively associated with change in adiponectin.

CONCLUSIONS

Greater weight loss, achieved through a reduced calorie diet or exercise, is associated with increased total ghrelin concentrations in overweight or obese postmenopausal women.

Fasting and meal-suppressed ghrelin levels before and after intragastric balloons and balloon-induced weight loss

BACKGROUND

Intragastric balloons may be an option for obese patients with weight loss failure. Its mode of action remains enigmatic. We hypothesised depressed fasting ghrelin concentrations and enhanced meal suppression of ghrelin secretion by the gastric fundus through balloon contact and balloon-induced delayed gastric emptying.

METHODS

Patients were randomised to a 13-week period of sham or balloon treatment, followed by a 13-week period of balloon treatment in everyone. Blood samples for ghrelin measurement were taken in the fasting state and every 15 min for 1 h after a breakfast meal at the start, after 13 weeks and after 26 weeks. Patients filled out scales to assess satiety and kept a food diary.

RESULTS

Forty obese patients (BMI 43.1 kg/m(2)) participated. At the start, fasting ghrelin values were low with a blunted ghrelin response to a test meal. The presence of a balloon had no influence on fasting or meal-suppressed ghrelin concentrations. Despite a weight loss of 10 % after 13 weeks and 15 % after 26 weeks, fasting ghrelin concentrations did not change; neither did the ghrelin response to a meal. No relation was found between ghrelin and insulin, satiety, intermeal interval, the number of meals or subsequent energy intake. Ghrelin concentrations were more suppressed with greater weight loss or with balloons located in the fundus.

CONCLUSIONS

Ghrelin concentrations did not change by balloon treatment after 13 and 26 weeks and, unexpectedly, did not rise despite substantial weight loss and negative energy balance. This suppression might be of benefit in the maintenance of weight loss but could not be ascribed to the balloon treatment.

Structure and physiological actions of ghrelin

Ghrelin is a gastric peptide hormone, discovered as being the endogenous ligand of growth hormone secretagogue receptor. Ghrelin is a 28 amino acid peptide presenting a unique n-octanoylation modification on its serine in position 3, catalyzed by ghrelin O-acyl transferase. Ghrelin is mainly produced by a subset of stomach cells and also by the hypothalamus, the pituitary, and other tissues. Transcriptional, translational, and posttranslational processes generate ghrelin and ghrelin-related peptides. Homo- and heterodimers of growth hormone secretagogue receptor, and as yet unidentified receptors, are assumed to mediate the biological effects of acyl ghrelin and desacyl ghrelin, respectively. Ghrelin exerts wide physiological actions throughout the body, including growth hormone secretion, appetite and food intake, gastric secretion and gastrointestinal motility, glucose homeostasis, cardiovascular functions, anti-inflammatory functions, reproductive functions, and bone formation. This review focuses on presenting the current understanding of ghrelin and growth hormone secretagogue receptor biology, as well as the main physiological effects of ghrelin.

Ghrelin in the regulation of body weight and metabolism

Ghrelin, a peptide hormone predominantly produced by the stomach, was isolated as the endogenous ligand for the growth hormone secretagogue receptor. Ghrelin is a potent stimulator of growth hormone (GH) secretion and is the only circulatory hormone known to potently enhance feeding and weight gain and to regulate energy homeostasis following central and systemic administration. Therapeutic intervention with ghrelin in catabolic situations may induce a combination of enhanced food intake, increased gastric emptying and nutrient storage, coupled with an increase in GH thereby linking nutrient partitioning with growth and repair processes. These qualities have fostered the idea that ghrelin-based compounds may have therapeutic utility in treating malnutrition and wasting induced by various sub-acute and chronic disorders. Conversely, compounds that inhibit ghrelin action may be useful for the prevention or treatment of metabolic syndrome components such as obesity, impaired lipid metabolism or insulin resistance. In recent years, the effects of ghrelin on glucose homeostasis, memory function and gastrointestinal motility have attracted considerable amount of attention and revealed novel therapeutic targets in treating a wide range of pathologic conditions. Furthermore, discovery of ghrelin O-acyltransferase has also opened new research opportunities that could lead to major understanding of ghrelin physiology. This review summarizes the current knowledge on ghrelin synthesis, secretion, mechanism of action and biological functions with an additional focus on potential for ghrelin-based pharmacotherapies.

Anthropometric and leptin changes in women following different dietary approaches to weight loss

Leptin may favorably respond to fat mass (FM) losses induced by a low-carbohydrate (LC) diet, although this is unclear. We examined serum leptin concentrations in women in midlife undergoing different dietary approaches to body weight (BW) loss. Women followed either a LC, high-protein (LCHP; n = 13) or high-carbohydrate, low-fat (HCLF; n = 12) diet for 12 weeks. Changes in anthropometric and soft-tissue mass measurements and leptin concentrations were assessed. Women in both diet groups had reductions in BW, BMI, fat-free soft-tissue mass, FM, body fat percentage, and central abdominal fat (CAF) (P < 0.001 for all variables) over the 12-week intervention. These changes were not significantly different between diet groups. Serum leptin concentrations decreased by 41.8% (P < 0.001) in the LCHP group and by 44.3% (P < 0.001) in the HCLF group from baseline to week 12, with no significant difference between groups. The association of CAF (r = 0.73) and FM (r = 0.83) change with leptin change was strong in the HCLF group. Leptin change did not relate to change in any variable in the LCHP group. Both LCHP and HCLF diets favorably lower FM, CAF, and leptin in women, suggesting that beneficial changes in leptin can be similarly achieved through different dietary approaches to BW loss.

The effect of laparoscopic gastric banding surgery on plasma levels of appetite-control, insulinotropic, and digestive hormones

BACKGROUND

We hypothesized that laparoscopic adjustable gastric banding (LAGB) reduces weight and modulates ghrelin production, but largely spares gastrointestinal endocrine function. To examine this hypothesis, we determined plasma concentrations of appetite-control, insulinotropic, and digestive hormones in relation to LAGB.

METHODS

Twenty-four patients undergoing LAGB were prospectively enrolled. Body mass index (BMI) was measured and blood samples obtained at baseline and 6 and 12 months post-surgery. Plasma concentrations of leptin, acylated and total ghrelin, pancreatic polypeptide (PP), insulin, glucose-dependent insulinotropic peptide (GIP), active glucagon-like peptide-1 (GLP-1), gastrin, and pepsinogens I and II were measured using enzyme-linked immunoassays.

RESULTS

Median percent excess weight loss (%EWL) over 12 months was 45.7% with median BMI decreasing from 43.2 at baseline to 33.8 at 12 months post-surgery (p < 0.001). Median leptin levels decreased from 19.7 ng/ml at baseline to 6.9 ng/ml at 12 months post-surgery (p < 0.001). In contrast, plasma levels of acylated and total ghrelin, PP, insulin, GIP, GLP-1, gastrin, and pepsinogen I did not change in relation to surgery (p > 0.05). Pepsinogen II levels were significantly lower 6 months after LAGB but returned to baseline levels by 12 months.

CONCLUSIONS

LAGB yielded substantial %EWL and a proportional decrease in plasma leptin. Our results support the hypothesis that LAGB works in part by suppressing the rise in ghrelin that normally accompanies weight loss. Unchanged concentrations of insulinotropic and digestive hormones suggest that gastrointestinal endocrine function is largely maintained in the long term.

Expression of ghrelin gene in peripheral blood mononuclear cells and plasma ghrelin concentrations in patients with metabolic syndrome

OBJECTIVE

We examined the expression of ghrelin and ghrelin receptors in peripheral blood mononuclear cells (PBMCs) and evaluated the effect of weight loss or exercise on plasma ghrelin concentrations in subjects with the metabolic syndrome.

DESIGN AND METHODS

Data from 75 overweight/obese subjects randomized to a weight loss, aerobic exercise, resistance exercise or control group for a 33-week intervention period were analysed. The plasma ghrelin concentrations and indices of insulin and glucose metabolism were assessed, and mRNA expression of ghrelin, its receptors and various cytokines in PBMCs was studied using real-time PCR.

RESULTS

Ghrelin and GH secretagogue receptor 1b were expressed in PBMCs of subjects with metabolic syndrome. Ghrelin gene expression correlated positively with the expressions of tumour necrosis factor-alpha (P<0.001), interleukin-1beta (P<0.001) and interleukin-6 (P=0.026) during the study, but was not associated with the plasma ghrelin concentration. Genotype-specific ghrelin gene expression in PBMCs was found for the -604G/A and the -501A/C polymorphisms in the ghrelin gene. At baseline, the plasma ghrelin levels were associated with fasting serum insulin concentrations, insulin sensitivity index and high-density lipoprotein cholesterol. However, longitudinally weight, BMI or waist circumference and acute insulin response in i.v. glucose tolerance test were stronger predictors of the ghrelin concentration. Plasma ghrelin did not change over the study period in the weight reduction group, but it tended to decrease in the control group (P=0.050).

CONCLUSIONS

Ghrelin mRNA expression in PBMCs suggests an autocrine role for ghrelin within an immune microenvironment. Moderate long-term weight loss may prevent a decline in ghrelin concentration over time in individuals with metabolic syndrome.

Interaction of single nucleotide polymorphisms in ADRB2, ADRB3, TNF, IL6, IGF1R, LIPC, LEPR, and GHRL with physical activity on the risk of type 2 diabetes mellitus and changes in characteristics of the metabolic syndrome: The Finnish Diabetes Prevention Study

Single nucleotide polymorphisms (SNPs) in the ADRB2, ADRB3, TNF, IL6, IGF1R, LIPC, LEPR, and GHRL genes were associated with the conversion from impaired glucose tolerance (IGT) to type 2 diabetes mellitus (T2D) in the Finnish Diabetes Prevention Study (DPS). In this study, we determined whether polymorphisms in these genes modified the effect of changes in physical activity (PA) on the risk of T2D in the DPS. Moreover, we assessed whether the polymorphisms modified the effect of changes in PA on changes in measures of body fat, serum lipids, and blood pressure during the first year of the follow-up of the DPS. Overweight subjects with IGT (n = 487) were followed for an average of 4.1 years, and PA was assessed annually with a questionnaire. The interactions of the polymorphisms with changes in total and moderate-to-vigorous PA on the conversion to T2D during the 4.1-year follow-up were assessed using Cox regression with adjustments for the other components of the intervention (dietary changes, weight reduction). Univariate analysis of variance was used to assess interactions on changes in continuous variables during the first year of the follow-up. No interaction between the polymorphisms and PA on the conversion to T2D was found. The Leu72Met (rs696217) polymorphism in GHRL modified the effect of moderate-to-vigorous PA on changes in weight and waist circumference, the -501A/C (rs26802) polymorphism in GHRL modified the effect of total and moderate-to-vigorous PA on change in high-density lipoprotein cholesterol, and the Lys109Arg (rs1137100) polymorphism in LEPR modified the effect of total PA on change in blood pressure. In conclusion, genetic variation may modify the magnitude of the beneficial effects of PA on characteristics of the metabolic syndrome in persons with IGT.

Postprandial ghrelin, cholecystokinin, peptide YY, and appetite before and after weight loss in overweight women with and without polycystic ovary syndrome

BACKGROUND

Polycystic ovary syndrome (PCOS) is a common condition associated with obesity and with reproductive and metabolic dysfunction. Abnormalities in appetite regulation in PCOS patients may contribute to difficulties in weight management.

OBJECTIVE

We aimed to examine appetite, appetite hormones, and ad libitum food consumption before and after weight loss in overweight women with and without PCOS.

DESIGN

Overweight age- and weight-matched women with (n = 14) and without (n = 14) PCOS undertook an 8-wk energy-restricted diet (5185.3 +/- 141.6 kJ/d). At baseline and study end, subjects consumed a test meal (936 kJ; 25% of energy from protein, 9% from fat, and 67% from carbohydrate). Subjective appetite and circulating glucose, insulin, ghrelin, cholecystokinin, and peptide YY were assessed at 0, 15, 30, 45, 60, 90, 120, and 180 min. A mixed buffet lunch was then offered to assess ad libitum food intake.

RESULTS

Weight loss (4.2 +/- 3.9 kg) did not differ significantly between the 2 groups. Women with PCOS had significantly (P = 0.023) lower ghrelin concentrations before and after weight loss than did women without PCOS. The degree of postprandial ghrelin suppression was lower at weeks 0 (P = 0.048) and 8 (P = 0.069) in women with PCOS than in women without PCOS. There were no significant differences between the 2 groups in appetite responses, buffet consumption, or fasting or postprandial peptide YY and cholecystokinin before or after weight loss.

CONCLUSIONS

PCOS was associated with lower fasting ghrelin and a smaller postprandial ghrelin suppression both before and after weight loss but was not associated with other postprandial gut peptides, subjective satiety, or food intake. It is not clear whether appetite regulation is impaired in PCOS.

Ghrelin, obesity and diabetes

The high prevalence of obesity and diabetes will lead to higher rates of morbidity and mortality. The search for drugs to treat these metabolic disorders has, therefore, intensified. The stomach-derived peptide ghrelin regulates food intake and body weight. Recent work suggests that ghrelin also controls glucose metabolism. In addition, current evidence suggests that most of the actions of ghrelin could contribute to the metabolic syndrome. The ghrelin signaling system is, therefore, a promising target for the development of new drugs for the treatment of obesity and diabetes. Agents that block the ghrelin signaling system might be especially useful targets. This Review summarizes the potential and the limitations of ghrelin as a tool to better understand, prevent and treat obesity and diabetes.

Influence of ghrelin on food intake and energy homeostasis

PURPOSE OF REVIEW

The purpose of this review is to provide updated information on the role of ghrelin in food intake and energy homeostasis, and on its mechanism of action. Moreover, the potential of ghrelin as a target for drugs to treat cachexia and obesity will be discussed.

RECENT FINDINGS

Whereas the effects of ghrelin in the regulation of appetite, food intake and energy homeostasis have been fairly well documented, the pathways responsible for the effects of ghrelin are now increasingly being understood. As a consequence, clinical applications of ghrelin are now being developed.

SUMMARY

Ghrelin is an endogenous orexigenic peptide recently discovered in the stomach. Ghrelin is involved in short-term regulation of food intake since its plasma levels increase before meals and decrease strongly postprandially. Ghrelin is also involved in long-term body-weight regulation by inducing adiposity. Ghrelin might be useful for cachexia and obesity treatment.

Emerging results of anticatabolic therapy with ghrelin

PURPOSE OF REVIEW

This review summarizes recent developments in research into anticatabolic therapies with ghrelin. Potential conditions in which ghrelin treatment may be useful include cachexia, anorexia and ageing. We highlight a number of intriguing basic topics related to the anticatabolic effects of ghrelin.

RECENT FINDING

Repeated administration of ghrelin to patients with congestive heart failure or chronic obstructive pulmonary disease improved appetite, body composition, muscle wasting and functional capacity in open-label pilot studies. An acute, randomized, placebo-controlled, crossover clinical trial of cancer patients with anorexia revealed marked increases in energy intake following treatment. The effects of ghrelin treatment in patients with anorexia nervosa are controversial. Basic research studies have extended our understanding of the upstream regulation of neuropeptide Y/agouti-related protein signalling and the central control of adipocyte metabolism. In addition, alterations in fat-free mass may play a role in ghrelin regulation.

SUMMARY

A number of studies are currently evaluating the anticatabolic effects of ghrelin in the treatment of various diseases, including cachexia, anorexia and age-related disorders. These studies will hopefully lead to the development of novel clinical applications for ghrelin treatment. These studies have also facilitated a better understanding of the molecular basis of the anticatabolic effects of ghrelin.