Plasma ghrelin levels after diet-induced weight loss or gastric bypass surgery

Laparoscopic Roux-en-Y gastric bypass, but not rebanding, should be proposed as rescue procedure for patients with failed laparoscopic gastric banding

OBJECTIVE

To define whether laparoscopic rebanding or Roux-en-Y gastric bypass represents the best approach for failed laparoscopic gastric banding in patients with morbid obesity.

SUMMARY BACKGROUND DATA

Countless laparoscopic gastric bandings have been implanted during the recent years worldwide. Despite excellent short-term results, long-term failures and complications have been reported in more than 20% of patients. Which rescue procedures should be used remains controversial. Therefore, we analyzed our experience with the use of laparoscopic rebanding versus laparoscopic Roux-en-Y gastric bypass after failed gastric banding.

METHODS

Using a prospectively collected database, we analyzed the feasibility, safety, and effectiveness of laparoscopic rebanding versus laparoscopic conversion to Roux-en-Y gastric bypass after failed laparoscopic gastric banding. RESULTS A total of 62 consecutive patients were treated in our institution between May 1995 and December 2002 for failed primary laparoscopic gastric banding, including 30 laparoscopic rebandings and 32 laparoscopic conversions to Roux-en-Y gastric bypass. Rebandings were preferably done during the initial period of the study and Roux-en-Y gastric bypass in the last period. Both groups were comparable before the initial banding procedures. At the time of redo surgery, patients receiving a gastric bypass had more esophageal dysmotility (47% vs. 7%, P = 0.002) and higher body mass index (BMI) than those elected for rebanding procedures (BMI 42.0 vs. 38.4 kg/m2, P = 0.015). Feasibility and safety: Each procedure was performed laparoscopically. Mean operating time was 215 minutes for gastric bypass and 173 minutes for rebanding (P = 0.03). Early complications occurred in one case in the rebanding group and in 2 cases in the bypass group; all underwent a laparoscopic reexploration without the need for open surgery. There was no mortality in this series. Effectiveness: BMI in the gastric bypass group decreased from 42.0 to 31.8 kg/m2 (P = 0.02) within 1 year of surgery, while it remained unchanged in the rebanding group.

CONCLUSIONS

Laparoscopic conversion to a gastric bypass as well as laparoscopic rebanding are feasible and safe. Conversion to gastric bypass offers a significant advantage in terms of further weight loss after surgery. Therefore, this procedure should be considered as the rescue therapy of choice after a failed laparoscopic gastric banding.

The duodenal switch operation for the treatment of morbid obesity

OBJECTIVE

To determine the safety and efficacy of the duodenal switch procedure as surgical treatment of morbid obesity.

SUMMARY BACKGROUND DATA

The longitudinal gastrectomy and duodenal switch procedure as performed for morbid obesity involves a 75% subtotal greater curvature gastrectomy and long limb suprapapillary Roux-en-Y duodenoenterostomy. This results in a restricted caloric intake and diversion of bile and pancreatic secretions to induce fat malabsorption. Broad acceptance of this procedure has been impeded because of concerns that the malabsorptive component may produce serious nutritional complications.

METHODS

Review of data collected prospectively from all patients who underwent duodenal switch as the primary surgical treatment of morbid obesity at a single institution during the 10-year period beginning September 1992. Operative morbidity and mortality, weight loss, volume of food intake, and bowel function were recorded. Sequential measurements of serum albumin, hemoglobin, and calcium levels were obtained to assess metabolic function and nutrient absorption.

RESULTS

Duodenal switch was performed as the primary operation in 701 (81%) of a total 863 patients undergoing bariatric surgery during the period of study. The average body mass index (BMI) was 52.8 (range, 34-95). Perioperative mortality was 1.4%, and morbidity (including leaks, wound dehiscence, splenectomy, and postoperative hemorrhage) occurred in 21 patients (2.9%). Weight loss averaged 127 pounds at 1 year, 131 at 3 years, and 118 at 5 or more years (% EBWL of 69%, 73%, and 66%, respectively). The mean number of bowel movements was fewer than 3 per day. Patients reported and maintained a mean restriction of 63% of their preoperative intake (approximately 1600 calories), with no specific food intolerance, at 3 or more years follow-up. At 3 years, serum albumin remained at normal levels in 98% of patients, hemoglobin in 52%, and calcium in 71%. No patients reported dumping, and marginal ulcers were not seen.

CONCLUSIONS

The longitudinal gastrectomy with duodenal switch is a safe and effective primary procedure for the treatment of morbid obesity. It has the advantage of allowing acceptable alimentation with a minimum of side effects while producing and maintaining significant weight loss. These results are achieved without developing significant dietary restrictions or clinical metabolic or nutritional complications.

Effect of laparoscopic Roux-en Y gastric bypass on type 2 diabetes mellitus

OBJECTIVE

To evaluate pre- and postoperative clinical parameters associated with improvement of diabetes up to 4 years after laparoscopic Roux-en-Y gastric bypass (LRYGBP) in patients with type 2 diabetes mellitus (T2DM).

SUMMARY BACKGROUND DATA

The surgical treatment of morbid obesity leads to dramatic improvement in the comorbidity status of most patients with T2DM. However, little is known concerning what preoperative clinical factors are associated with postoperative long-term improvement in diabetes in the morbidly obese patient with diabetes. METHODS We evaluated pre- and postoperative data, including demographics, duration of diabetes, metabolic parameters, and clinical outcomes, in all patients with impaired fasting glucose (IFG) and type T2DM undergoing LRYGBP from July 1997 to May 2002.

RESULTS

During this 5-year period, 1160 patients underwent LRYGBP and 240 (21%) had IFG or T2DM. Follow up was possible in 191 of 240 patients (80%). There were 144 females (75%) with a mean preoperative age of 48 years (range, 26-67 years). After surgery, weight and body mass index decreased from 308 lbs and 50.1 kg/m2 to 211 lbs and 34 kg/m2 for a mean weight loss of 97 lbs and mean excess weight loss of 60%. Fasting plasma glucose and glycosylated hemoglobin concentrations returned to normal levels (83%) or markedly improved (17%) in all patients. A significant reduction in use of oral antidiabetic agents (80%) and insulin (79%) followed surgical treatment. Patients with the shortest duration (<5 years), the mildest form of T2DM (diet controlled), and the greatest weight loss after surgery were most likely to achieve complete resolution of T2DM.

CONCLUSION

LRYGBP resulted in significant weight loss (60% percent of excess body weight loss) and resolution (83%) of T2DM. Patients with the shortest duration and mildest form of T2DM had a higher rate of T2DM resolution after surgery, suggesting that early surgical intervention is warranted to increase the likelihood of rendering patients euglycemic.

Ghrelin for the gastroenterologist: history and potential

Ghrelin, a novel 28-amino acid orexigenic peptide discovered in 1999, has given us further insights into the control of energy homeostasis and growth hormone secretion. As a natural endogenous ligand of the growth hormone secretagogue receptor, it potently stimulates growth hormone release but is also implicated in many other homeostatic mechanisms. Released from the stomach, it stimulates lactotroph and corticotroph secretion, increases appetite and adiposity, has beneficial hemodynamic effects, has prokinetic and gastric acid secretory functions in the stomach, and may even be implicated in sleep. As advances in the understanding of appetite and obesity are made, it is timely to review the possibly central role of ghrelin in these physiological and pathophysiological states. This review will discuss the recent literature concerning this exciting novel neuropeptide and discuss the possible therapeutic possibilities it may open up to us.

Abnormalities of leptin and ghrelin regulation in obesity-prone juvenile rats

Rats selectively bred to develop diet-induced obesity (DIO) spontaneously gain more body weight between 5 and 7 wk of age than do those bred to be diet resistant (DR). Here, chow-fed DIO rats ate 9% more and gained 19% more body weight from 5 to 6 wk of age than did DR rats but had comparable leptin and insulin levels. However, 6-wk-old DIO rats had 29% lower plasma ghrelin levels at dark onset but equivalent levels 6 h later compared with DR rats. When subsequently fed a high-energy (HE; 31% fat) diet for 10 days, DIO rats ate 70% more, gained more body and adipose depot weight, had higher leptin and insulin levels, and had 22% lower feed efficiency than DR rats fed HE diet. In DIO rats on HE diet, leptin levels increased significantly at 3 days followed by increased insulin levels at 7 days. These altered DIO leptin and ghrelin responses were associated with 10% lower leptin receptor mRNA expression in the arcuate (ARC), dorsomedial (DMN), and ventromedial hypothalamic nuclei and 13 and 15% lower ghrelin receptor (GHS-R) mRNA expression in the ARC and DMN than in the DR rats. These data suggest that increased ghrelin signaling is not a proximate cause of DIO, whereas reduced leptin sensitivity might play a causal role.

Peripheral signals in the control of satiety and hunger

PURPOSE OF REVIEW

Food intake is critical for survival and is a complex behavior with multiple levels of control. Short-term, meal-related signals arise from many sources including the gastrointestinal tract, the environment, and higher centers in the brain. As described in this review, inputs from the gastrointestinal tract can exert potent effects on meal initiation, meal termination, and meal frequency. The complex array of signals generated from the gastrointestinal system and from adipose tissue, which participate in the regulation of food intake, and specifically how these signals relate to satiety and hunger, is the focus of this review.

RECENT FINDINGS

Literature on the role of the well-studied gastrointestinal peptide, cholecystokinin, in satiety, in addition to its interaction with long-term adiposity signals in mediating food intake will be reviewed. In addition, literature on the gastrointestinal hormones glucagon-like-peptide 1, apolipoprotein A-IV and peptide YY, and how they may act to regulate satiety, is described. Finally, the newly discovered hormone, ghrelin, and how it relates to meal initiation and hunger is discussed.

SUMMARY

A better understanding of these systems and how they relate to body adiposity will prove to have important clinical applications. The available data suggest that interventions directed at multiple targets in the energy homeostasis system may be necessary to achieve and maintain weight loss.

Differential effect of protein and fat on plasma ghrelin levels in man

Ghrelin, a gastric hormone that stimulates food intake is decreased after ingestion of carbohydrate-rich meals. The acute effect of fat- and protein-rich meals on plasma ghrelin levels is still unknown. Accordingly, plasma ghrelin levels were determined in 10 healthy volunteers after ingestion of the three macronutrients and during vagal stimulation by modified sham feeding and following gastric distension with a highly viscous guar solution. After a solid carbohydrate-rich test meal ghrelin levels fell from 559+/-59.3 pg/ml to a nadir of 449+/-47.4 pg/ml within 60 min (p<0.05). Following an oral glucose load (75 g in 300 ml water), a similar decrease was observed (p<0.05). A fat-rich meal also decreased plasma ghrelin levels (p<0.05) leading to a nadir towards the end of the study period at 180 min. Protein intake, however, stimulated plasma ghrelin levels from 449+/-68.1 to a plateau of 520 pg/ml (p<0.05). There was no significant change of ghrelin levels after modified sham feeding or gastric distension. In conclusion, the decrease of ghrelin levels after fat ingestion shows a different time pattern compared to carbohydrate, while protein ingestion stimulated ghrelin levels. This suggests that different and as yet unknown mechanisms contribute to the regulation of postprandial ghrelin release in man depending on the ingested macronutrients. Cephalic-vagal and intragastric neural mechanisms most likely do not contribute to the postprandial regulation of ghrelin secretion.

Effects of growth hormone (GH) on ghrelin, leptin, and adiponectin in GH-deficient patients

Ghrelin is a recently discovered gastric peptide that increases appetite, glucose oxidation, and lipogenesis and stimulates the secretion of GH. In contrast to ghrelin, GH promotes lipolysis, glucose production, and insulin secretion. Both ghrelin and GH are suppressed by intake of nutrients, especially glucose. The role of GH in the regulation of ghrelin has not yet been established. We investigated the effect of GH on circulating levels of ghrelin in relation to its effects on glucose, insulin, body composition, and the adipocyte-derived peptides leptin and adiponectin. Thirty-six patients with adult-onset GH deficiency received recombinant human GH for 9 months in a placebo-controlled study. Body composition and fasting serum analytes were assessed at baseline and at the end of the study. The GH treatment was accompanied by increased serum levels of IGF-I, reduced body weight (-2%) and body fat (-27%), and increased serum concentrations of glucose (+10%) and insulin (+48%). Ghrelin levels decreased in 30 of 36 subjects by a mean of -29%, and leptin decreased by a mean of -24%. Adiponectin increased in the women only. The decreases in ghrelin and leptin correlated with changes in fat mass, fat-free mass, and IGF-I. The reductions in ghrelin were predicted independently of the changes in IGF-I and fat mass. It is likely that the reductions in ghrelin and leptin reflect the metabolic effects of GH on lipid mobilization and glucose production. Possibly, a suppression of ghrelin promotes loss of body fat in GH-deficient patients receiving treatment. The observed correlation between the changes in ghrelin and IGF-I may suggest that the GH/IGF-I axis has a negative feedback on ghrelin secretion.

Central nervous determination of food storage—a daily switch from conservation to expenditure: implications for the metabolic syndrome

Here, we present a neuroendocrine concept to review the circularly interacting energy homeostasis system between brain and body. Body-brain interaction is circular because the brain immediately integrates an input to an output, and because part of this response may be that the brain modulates the sensitivity of this perception. First, we describe how the brain senses the body through neurons and blood-borne factors. Direct neuronal connections report the state of various organs. In addition, humoral factors are perceived by the blood-brain barrier and circumventricular organs. We describe how circulating energy carriers are sensed and what signals reach the brain during food intake, exercise and an immune response. We describe that the brain regulates the homeostatic process at two fundamentally different levels during the active and inactive states. The unbalanced output of the brain in the metabolic syndrome is discussed in relation with such circadian rhythms and with regional activity of the autonomic nervous system. In line with the above, we suggest a new approach for the diagnosis and therapy of the metabolic syndrome.

Plasma ghrelin, body fat, insulin resistance, and smoking in clinically healthy men: the atherosclerosis and insulin resistance study

The purpose of the study was to examine whether insulin sensitivity was associated with fasting plasma ghrelin concentrations in a population-based sample of 58-year-old clinically healthy Caucasian men. The methods used were dual-energy x-ray absorptiometry (DXA) for measurement of body composition and a conventional euglycemic hyperinsulinemic clamp, measuring glucose infusion rate (GIR) that was adjusted for fat-free mass. Plasma ghrelin was measured by radioimmunoassay. The results showed that ghrelin was not associated with GIR adjusted for fat-free mass or with GIR adjusted for body mass, and body fat, or waist circumference. Plasma ghrelin correlated negatively to body fat (-0.46, P<.001) and waist circumference (-0.45, P<.001). Ghrelin was also inversely related to systolic and diastolic blood pressure (r=-.29 and r=-0.34, respectively, P<.01) and positively to high-density lipoprotein (HDL) cholesterol (0.33, P<.01), and low-density lipoprotein (LDL) particle size (0.34, P<.001), but these associations did not remain after adjustment for body fat. Plasma ghrelin was associated with current smoking independent of waist circumference. Among current smokers, circulating plasma concentrations were higher in those who had smoked during the hour preceding the blood sample than those who had smoked 2 to 12 hours ago (P=.043). The conclusion is that whole body insulin sensitivity was not associated with plasma ghrelin concentrations. Body fatness was the strongest determinant of circulating ghrelin. It was found that acute smoking may affect ghrelin levels.

Neuroendocrine and metabolic effects of acute ghrelin administration in human obesity

Ghrelin stimulates appetite and plays a role in the neuroendocrine response to energy balance variations. Ghrelin levels are inversely associated with body mass index (BMI), increased by fasting and decreased by food intake, glucose load, insulin, and somatostatin. Ghrelin levels are reduced in obesity, a condition of hyperinsulinism, reduced GH secretion, and hypothalamus-pituitary-adrenal axis hyperactivity. We studied the endocrine and metabolic response to acute ghrelin administration (1.0 microg/kg i.v.) in nine obese women [OB; BMI (mean +/- SD) 36.3 +/- 2.3 kg/m(2)] and seven normal women (NW; BMI 20.3 +/- 1.7 kg/m(2)). Basal ghrelin levels in NW were higher than in OB (P < 0.05). In NW, ghrelin increased (P < 0.05) GH, prolactin (PRL), ACTH, cortisol, and glucose levels but did not modify insulin. In OB, ghrelin increased (P < 0.01) GH, PRL, ACTH, and cortisol levels. The GH response to ghrelin in OB was 55% lower (P < 0.02) than in NW, whereas the PRL, ACTH, and cortisol responses were similar. In OB, ghrelin increased glucose and reduced insulin (P < 0.05). Thus, obesity shows remarkable reduction of the somatotroph responsiveness to ghrelin, suggesting that ghrelin hyposecretion unlikely explains the impairment of somatotroph function in obesity. On the other hand, in obesity ghrelin shows preserved influence on PRL, ACTH, and insulin secretion as well as in glucose levels.

High constitutive signaling of the ghrelin receptor--identification of a potent inverse agonist

Ghrelin is a GH-releasing peptide that also has an important role as an orexigenic hormone-stimulating food intake. By measuring inositol phosphate turnover or by using a reporter assay for transcriptional activity controlled by cAMP-responsive elements, the ghrelin receptor showed strong, ligand-independent signaling in transfected COS-7 or human embryonic kidney 293 cells. Ghrelin and a number of the known nonpeptide GH secretagogues acted as agonists stimulating inositol phosphate turnover further. In contrast, the low potency ghrelin antagonist, [D-Arg1,D-Phe5,D-Trp7,9,Leu11]-substance P was surprisingly found to be a high potency (EC50 = 5.2 nm) full inverse agonist as it decreased the constitutive signaling of the ghrelin receptor down to that observed in untransfected cells. The homologous motilin receptor functioned as a negative control as it did not display any sign of constitutive activity; however, upon agonist stimulation the motilin receptor signaled as strongly as the unstimulated ghrelin receptor. It is concluded that the ghrelin receptor is highly constitutively active and that this activity could be of physiological importance in its role as a regulator of both GH secretion and appetite control. It is suggested that inverse agonists for the ghrelin receptor could be particularly interesting for the treatment of obesity.

Does obesity surgery improve psychosocial functioning? A systematic review

OBJECTIVE

The objective of this study is to present a review of the psychosocial outcome of bariatric surgery with special consideration of psychiatric comorbidity, psychopathology, psychosocial functioning, econometric data, and general quality of life (QoL).

PURPOSE

A review of all (non-) controlled trials of the last two decades both with a retrospective and prospective design and a follow-up period of at least 1 y.

RESEARCH METHODS AND PROCEDURES

The relevant literature was identified by a search of computerized databases. All articles published in English and German since 1980 were reviewed. Based on the requirements of the evidenced-based guidelines of the Agency for Health Care Policy and Research and the Scottish Intercollegiate Guidelines Network, each study was rated by a level of evidence.

RESULTS

In all, 171 publications were reviewed. Using the above inclusion/exclusion criteria, 63 articles including two systematic reviews were identified. A total of 40 studies focused on psychosocial outcome after obesity surgery.

CONCLUSION

Mental health and psychosocial status including social relations and employment opportunities improve for the majority of people after bariatric surgery thus leading to an improved QoL. Psychiatric comorbidity, predominantly affective disorders, and psychopathologic symptoms decrease postsurgically. A substantial percentage of bariatric surgery patients suffer from binge eating disorder or binge eating symptoms. The effect of bariatric surgery on the outcome of binge eating symptoms largely depends on the type of operation. With the exception of patients with a severe psychiatric comorbidity, the concern that obesity surgery will reinforce psychic symptoms and lead to a reduction in the QoL seems to be unfounded.

Ghrelin and the endocrine pancreas

Ghrelin is a 28-amino-acid peptide predominantly produced by the stomach, while substantially lower amounts derive from other tissues including the pancreas. It is a natural ligand of the GH secretagogue (GHS) receptor (GHS-R1a) and strongly stimulates GH secretion, but acylation in serine 3 is needed for its activity. Ghrelin also possesses other endocrine and nonendocrine actions reflecting central and peripheral GHS-R distribution including the pancreas. The wide spectrum of ghrelin activities includes orexigenic effect, control of energy expenditure, and peripheral gastroenteropancreatic actions. Circulating ghrelin levels mostly reflect gastric secretion as indicated by evidence that they are reduced by 80% after gastrectomy and even after gastric by-pass surgery. Ghrelin secretion is increased in anorexia and cachexia but reduced in obesity, a notable exception being Prader-Willi syndrome. The negative association between ghrelin secretion and body weight is emphasized by evidence that weight increase and decrease reduces and augments circulating ghrelin levels in anorexia and obesity, respectively, and agrees with the clear negative association between ghrelin and insulin levels. In fact, ghrelin secretion is increased by fasting whereas it is decreased by glucose load as well as during euglycemic clamp but not after arginine or free fatty acid load in normal subjects; in physiological conditions, however, the most remarkable inhibitory input on ghrelin secretion is represented by somatostatin as well as by its natural analog cortistatin that concomitantly reduce beta-cell secretion. This evidence indicates that the endocrine pancreas plays a role in directly or indirectly modulating ghrelin secretion.

Effect of laparoscopic Roux-en Y gastric bypass on type 2 diabetes mellitus

OBJECTIVE

To evaluate pre- and postoperative clinical parameters associated with improvement of diabetes up to 4 years after laparoscopic Roux-en-Y gastric bypass (LRYGBP) in patients with type 2 diabetes mellitus (T2DM).

SUMMARY BACKGROUND DATA

The surgical treatment of morbid obesity leads to dramatic improvement in the comorbidity status of most patients with T2DM. However, little is known concerning what preoperative clinical factors are associated with postoperative long-term improvement in diabetes in the morbidly obese patient with diabetes. METHODS We evaluated pre- and postoperative data, including demographics, duration of diabetes, metabolic parameters, and clinical outcomes, in all patients with impaired fasting glucose (IFG) and type T2DM undergoing LRYGBP from July 1997 to May 2002.

RESULTS

During this 5-year period, 1160 patients underwent LRYGBP and 240 (21%) had IFG or T2DM. Follow up was possible in 191 of 240 patients (80%). There were 144 females (75%) with a mean preoperative age of 48 years (range, 26-67 years). After surgery, weight and body mass index decreased from 308 lbs and 50.1 kg/m2 to 211 lbs and 34 kg/m2 for a mean weight loss of 97 lbs and mean excess weight loss of 60%. Fasting plasma glucose and glycosylated hemoglobin concentrations returned to normal levels (83%) or markedly improved (17%) in all patients. A significant reduction in use of oral antidiabetic agents (80%) and insulin (79%) followed surgical treatment. Patients with the shortest duration (<5 years), the mildest form of T2DM (diet controlled), and the greatest weight loss after surgery were most likely to achieve complete resolution of T2DM.

CONCLUSION

LRYGBP resulted in significant weight loss (60% percent of excess body weight loss) and resolution (83%) of T2DM. Patients with the shortest duration and mildest form of T2DM had a higher rate of T2DM resolution after surgery, suggesting that early surgical intervention is warranted to increase the likelihood of rendering patients euglycemic.

Effects of 3 months of continuous subcutaneous administration of glucagon-like peptide 1 in elderly patients with type 2 diabetes

OBJECTIVE

Glucagon-like peptide 1 (GLP-1) is an insulinotropic gut hormone that, when given exogenously, may be a useful agent in the treatment of type 2 diabetes. We conducted a 3-month trial to determine the efficacy and safety of GLP-1 in elderly diabetic patients.

RESEARCH DESIGN AND METHODS

A total of 16 patients with type 2 diabetes who were being treated with oral hypoglycemic agents were enrolled. Eight patients (aged 75 +/- 2 years, BMI 27 +/- 1 kg/m(2)) remained on usual glucose-lowering therapy and eight patients (aged 73 +/- 1 years, BMI 27 +/- 1 kg/m(2)), after discontinuing hypoglycemic medications, received GLP-1 delivered by continuous subcutaneous infusion for 12 weeks. The maximum dose was 120 pmol x kg(-1). h(-1). Patients recorded their capillary blood glucose (CBG) levels (four times per day, 3 days per week) and whenever they perceived hypoglycemic symptoms. The primary end points were HbA(1c) and CBG determinations. Additionally, changes in beta-cell sensitivity to glucose, peripheral tissue sensitivity to insulin, and changes in plasma ghrelin levels were examined.

RESULTS

HbA(1c) levels (7.1%) and body weight were equally maintained in both groups. The usual treatment group had a total of 87 CBG measurements of <or=3.6 mmol/l during the study, and only 1 such measurement (3.5 mmol/l) was recorded in the GLP-1 group. Infusion of GLP-1 enhanced glucose-induced insulin secretion (pre: 119 +/- 21; post: 202 +/- 51 pmol/l; P < 0.05) and insulin-mediated glucose disposal (pre: 29.8 +/- 3.3; post: 35.9 +/- 2.3 micromol x kg(-1 x min(-1); P < 0.01). No effect of GLP-1 treatment was seen on the fasting plasma ghrelin levels. Although plasma ghrelin levels decreased during both portions of the clamp, a drug effect was not present.

CONCLUSIONS

A GLP-1 compound is a promising therapeutic option for elderly diabetic patients.

Laparoscopic gastric bypass versus laparoscopic adjustable gastric banding

BACKGROUND

Indications for and results of laparoscopic adjustable gastric banding (LAGB) and laparoscopic gastric bypass (LGB) are still controversial, especially between Europe and the United States. The recent availability of gastric bandings in the United States made it necessary to compare the two techniques.

STUDY DESIGN

We compared a series of 456 LGB to a series of 805 LAGB performed in two different institutions. Body mass index (BMI), complication rate, mortality, and excess weight loss (EWL) after 3, 6, 12, and 18 months were obtained. A Fischer's exact test and a Student t test with covariance analysis were used for statistical analysis.

RESULTS

Results are expressed as a mean +/- standard deviation, comparing LGB with LAGB. Preoperative BMI was 49.4 +/- 8.3 kg/m(2) versus 42.2 +/- 4.9 kg/m(2) (p = 0.0001), respectively. Perioperative major complication rates were 2.0% versus 1.3% (NS), and the early postoperative major complication rates were 4.2% versus 1.7% (p = 0.02), respectively. Mortality rate was 0.4% versus 0% (NS), respectively. The global EWL was 36.3% for LGB versus 14.7% for LAGB at 3 months (p < 0.0001), 51.6% versus 21.9% at 6 months (p < 0.0001), 67.0% versus 33.3% at 12 months (p < 0.0001), and 74.6% versus 40.4% at 18 months (p < 0.0001), respectively. Longterm followup for the LAGB group showed an EWL of 47% at 2 years, 56% at 3 years, and 58% at 4 years. Patients were sorted after their preoperative BMI (30 to 40, 40 to 50, and 50 to 60 kg/m(2)). The EWL at 3, 6, 12, and 18 months was statistically superior in the LGB group, for any BMI ranges.

CONCLUSIONS

These data suggest that LGB provides a higher EWL at 18 months, compared with LAGB, and this was true for any preoperative BMI range. It is associated with a higher early postoperative complication rate.

Inhibition of food intake in obese subjects by peptide YY3-36

BACKGROUND

The gut hormone fragment peptide YY3-36 (PYY) reduces appetite and food intake when infused into subjects of normal weight. In common with the adipocyte hormone leptin, PYY reduces food intake by modulating appetite circuits in the hypothalamus. However, in obesity there is a marked resistance to the action of leptin, which greatly limits its therapeutic effectiveness. We investigated whether obese subjects were also resistant to the anorectic effects of PYY.

METHODS

We compared the effects of PYY infusion on appetite and food intake in 12 obese and 12 lean subjects in a double-blind, placebo-controlled, crossover study. The plasma levels of PYY, ghrelin, leptin, and insulin were also determined.

RESULTS

Caloric intake during a buffet lunch offered two hours after the infusion of PYY was decreased by 30 percent in the obese subjects (P<0.001) and 31 percent in the lean subjects (P<0.001). PYY infusion also caused a significant decrease in the cumulative 24-hour caloric intake in both obese and lean subjects. PYY infusion reduced plasma levels of the appetite-stimulatory hormone ghrelin. Endogenous fasting and postprandial levels of PYY were significantly lower in obese subjects (the mean [+/-SE] fasting PYY levels were 10.2+/-0.7 pmol per liter in the obese group and 16.9+/-0.8 pmol per liter in the lean group, P<0.001). Furthermore, the fasting PYY levels correlated negatively with the body-mass index (r = -0.84, P<0.001).

CONCLUSIONS

We found that obese subjects were not resistant to the anorectic effects of PYY. Endogenous PYY levels were low in the obese subjects, suggesting that PYY deficiency may contribute to the pathogenesis of obesity.

Minireview: From anorexia to obesity--the yin and yang of body weight control

Over the past decade, there has been a tremendous increase in the understanding of the molecular and neural mechanisms that control food intake and body weight. Yet eating disorders and cachexia are still common, and obesity cases are rising at alarming rates. Thus, despite recent progress, an increased understanding of the molecular and neural substrates that control body weight homeostasis is a major public health goal. In this review, we discuss the mechanisms by which metabolic signals interact with key behavioral, neuroendocrine, and autonomic regulatory regions of the central nervous system. Additionally, we offer a model in which hormones such as leptin and ghrelin interact with similar central nervous system circuits and engage them in such a way as to maintain an appropriate and tight regulation of body weight and food intake. Our model predicts that overstimulation or understimulation of these central pathways can result in obesity, anorexia, or cachexia.

Effect of hypocaloric meals with different macronutrient compositions on energy metabolism and lung function in obese women

OBJECTIVE

We investigated the effect of hypocaloric mixed diets with different proportions of carbohydrate, protein, and fat on resting metabolic rate and the thermic effect of food in obese women.

METHODS

Three mixed hypocaloric diets were consumed in random order during separate periods lasting 7 d each. Between each dietary period there was a washout period of 10 d. Diet 1 had a higher proportion of energy from carbohydrate (72%), diet 2 had a higher proportion of energy from protein (43%), and diet 3 had a higher proportion of energy from fat (68%). Indirect calorimetry and lung function tests were done after the completion of each 7-d diet. Seven obese women, ages 22 to 45 y and with body mass indexes of 32 to 59 kg/m(2), participated in the study. Oxygen consumption, carbon dioxide production, resting metabolic rate, and the thermic effect of food by indirect calorimetry were measured. Lung function tests included spirometry in the seated and upright positions, arterial blood gas analysis, and maximal inspiratory and expiratory pressures.

RESULTS

There were no statistically significant differences in the resting metabolic rate and the thermic effect of food resulting from the three diets. The mean resting metabolic rates (kJ/d) were 7453 +/- 1446 for diet 1, 7461 +/- 1965 for diet 2, and 7076 +/- 2048 for diet 3. The mean thermic effects of food (kcal/min) were -0.02 +/- 0.07 for diet 1, -0.01 +/- 0.25 for diet 2, and 0.05 +/- 0.13 for diet 3. Lung function tests were normal before and after the hypocaloic diets: partial pressure of oxygen (mmHg) values were 81 +/- 13, 77 +/- 8, and 78 +/- 11 for diets 1 to 3, respectively; and partial pressure of carbon dioxide (mmHg) were 37 +/- 4, 37 +/- 3, and 37 +/- 4 for diets 1 to 3, respectively.

CONCLUSIONS

Obese women with normal lung function tests and consuming mixed hypocaloric diets showed no alteration in resting metabolic rate and a reduced or absent thermic effect of food independently of the macronutrient composition.

Effects of ghrelin and other neuropeptides (CART, MCH, orexin A and B, and GLP-1) on the release of insulin from isolated rat islets

BACKGROUND AND AIMS

Ghrelin, a neuropeptide containing 28 amino acids, shows a reciprocal diurnal plasma fluctuation to that of plasma insulin. The aim of this study is to clarify the dose and glucose-dependency of ghrelin on the insulin secretion and to compare its effect with that of other neuropeptides-GLP-1, CART (55-102), CART (55-76), CART (62-76), MCH, orexin A, and B.

MATERIALS AND METHODS

Rat islets were incubated with 1 pmol/l-1 micromol/l of ghrelin, CART fragments, MCH, orexin A or B, or GLP-1 (n = 16-32) in the presence of 16.7 mmol/l glucose. Ghrelin (10 nmol/l) was added to islets at glucose concentrations of 3.3, 6.6, 16.7 and 25 mmol/l, respectively (n = 28-32). Also, INS-1E cells were incubated with ghrelin (1 nmol/l) in the presence of glucose (3.3, 6.6, 16.7, and 25 mmol/l). In addition, we measured the mRNA expression of the ghrelin receptor using RT-PCR.

RESULTS

Ghrelin inhibited insulin secretion from islets and INS-1E cells in a dose- and glucose-dependent manner. Neither 10 pmol/l-1 micromol/l of CART fragments, MCH, orexin A, nor orexin B changed the insulin secretion at 16.7 mmol/l glucose, while GLP-1, as expected, stimulated the insulin release from rat islets. Interestingly, ghrelin receptors were expressed both in islets, INS-1E, MIN 6 and alpha cell Tca-9 lines.

CONCLUSIONS

Ghrelin inhibits the insulin secretion in vitro in a dose- and glucose-dependent manner. Beta cells contain ghrelin receptors. CART fragments did not affect the insulin secretion. Ghrelin may play a physiological role for the regulation of insulin secretion.

Ghrelin secretion in severely obese subjects before and after a 3-week integrated body mass reduction program

Ghrelin, the endogenous ligand of GH-secretagogue receptors, has been implicated in the regulation of feeding behavior and energy balance. Aim of the study was to investigate ghrelin levels in fasting conditions and after a standard meal test in obese subjects before and after a 3-week integrated body weight reduction (BWR) program (consisting of energy-restricted diet, exercise training, psychological counselling and nutritional education). Weight, height, fat mass, fat free mass (by impedentiometry), circulating ghrelin, insulin and leptin levels were evaluated in 10 obese subjects (3 male, 7 female; mean age: 35 +/- 9.3 yr; body mass index BMI: 45.2 +/- 10.6 kg/m2) before and after weight reduction. At baseline, obese subjects showed significantly lower ghrelin levels than controls, which were negatively correlated with BMI, weight, insulin and leptin levels. Fasting ghrelin levels were not modified by standard meal test in obese subjects (from 110.8 +/- 69.7 to 91.8 +/- 70.2 pmol/l p=ns), while a significant reduction was observed in controls (from 352.4 +/- 176.7 to 199.0 +/- 105.2 pmol/l; p<0.01). After a 3-week integrated BWR program obese subjects significantly reduced weight, BMI and leptin levels, while no significant changes were found both in fasting ghrelin and in ghrelin response after the meal. In conclusion, 5% weight loss obtained after a short-term period of integrated BWR program is not sufficient to normalize fasting ghrelin levels nor to restore the normal ghrelin suppression after a meal in severely obese subjects.

Serum ghrelin levels in response to glucose load in obese subjects post-gastric bypass surgery

OBJECTIVE

We sought to elucidate further the mechanisms leading to weight loss after gastric bypass (GBP) surgery in morbidly obese individuals. Ghrelin is a gastroenteric appetite-stimulating peptide hormone, fasting levels of which decrease with increasing adiposity and increase with diet-induced weight loss. In addition, ghrelin levels rapidly decline postprandially.

RESEARCH METHODS AND PROCEDURES

We measured serum ghrelin responses to a 75-g oral glucose tolerance test (OGTT) in 6 subjects who had undergone GBP surgery 1.5 +/- 0.7 years before testing and compared these responses with 6 obese subjects about to undergo GBP surgery, 6 obese nonsurgical subjects (matched for BMI to the post-GBP surgical group), and 5 lean subjects.

RESULTS

Despite weight loss induced by the GBP surgery, fasting serum ghrelin levels were significantly lower in the post-GBP surgery group than in the lean subject (by 57%) or pre-GBP surgery (by 45%) group. Serum ghrelin levels during the OGTT were significantly lower in postoperative than in lean, obese pre-GBP surgical, or obese nonsurgical subjects. The magnitude of the decline in serum ghrelin levels between 0 and 120 minutes post-OGTT was significantly smaller in postoperative (by 62%), obese pre-GBP surgical (by 80%), or obese nonsurgical (by 69%) subjects in comparison with lean subjects.

DISCUSSION

Serum ghrelin levels in response to OGTT are lower in subjects post-GBP surgery than in either lean or obese subjects. Tonically low serum ghrelin levels may be involved in the mechanisms inducing sustained weight loss after GBP surgery.

Controle neuroendócrino do peso corporal: implicações na gênese da obesidade

O peso corporal é regulado por uma interação complexa entre hormônios e neuropeptídeos, sob o controle principal de núcleos hipotalâmicos. Mutações nos genes de hormônios e neuropeptídeos, de seus receptores ou de elementos regulatórios, têm sido descritas na espécie humana, mas são tidas como raras, não explicando as formas mais comuns de obesidade. No entanto, o estudo destas mutações tem propiciado um grande avanço nos conhecimentos sobre a base genética e a fisiopatologia da obesidade, possibilitando o estudo e abrindo perspectivas para o desenvolvimento de novas modalidades terapêuticas. Recentemente, demonstrou-se que mutações no receptor 4 da melanocortina podiam ser encontradas em até 5% dos casos de obesidade severa, representando até o presente momento a forma mais prevalente de obesidade monogênica na espécie humana. Nesta revisão, são discutidas as diversas mutações descritas nos seres humanos de elementos da rede neuroendócrina de controle do peso corporal, bem como as implicações dos mesmos na gênese da obesidade.

Obesity Surgery: A Gastroenterologist's Perspective

Obesity is increasing at an alarming rate. Approximately 25% of adult women and 20% of adult men in the United States are obese. Obesity is increasing even more rapidly in children. The incidence of type 2 diabetes mellitus, hypertension, dyslipidemia, and liver disease is significantly increased in obese persons. Traditional methods of diet, exercise, drugs, and behavior modification are unsuccessful in the treatment of patients who are morbidly obese and have a body mass index of 40 kg/m(2) or a body mass index of 35 kg/m(2) with comorbidity. Multiple surgical alternatives to the traditional treatments are available and have been successful. Considerable weight loss may be achieved and maintained. Each procedure is associated with a variety of side effects and complications. The selection of patients for bariatric surgery requires a careful evaluation of their medical condition in addition to multiple psychological and social factors. Postoperative care entails careful medical follow-up and long-term support. Patients may have a difficult time adjusting to their new ability to eat normally.

Ghrelin, a novel growth hormone-releasing peptide, in the treatment of chronic heart failure

Ghrelin is a novel growth hormone (GH)-releasing peptide, isolated from the stomach, which has been identified as an endogenous ligand for growth-hormone secretagogues receptor (GHS-R). This peptide also causes a positive energy balance by stimulating food intake and inducing adiposity through growth hormone-independent mechanisms. In addition, ghrelin has some cardiovascular effects, as indicated by the presence of its receptor in blood vessels and the cardiac ventricles. In vitro, ghrelin inhibits apoptosis of cardiomyocytes and endothelial cells. In humans, infusion of ghrelin decreases systemic vascular resistance and increases cardiac output in patients with heart failure. Repeated administration of ghrelin improves cardiac structure and function and attenuates the development of cardiac cachexia in rats with heart failure. These results suggest that ghrelin has cardiovascular effects and regulates energy metabolism through GH-dependent and -independent mechanisms. Thus, administration of ghrelin may be a new therapeutic strategy for the treatment of severe chronic heart failure (CHF).

Neural regulation of blood pressure by leptin and the related peptides

Recent biological advances make it possible to discover new peptides associated with obesity. Leptin, neuropeptide Y, corticotrophin-releasing factor (CRF), alpha-melanocyte stimulating hormone (alpha-MSH), and cocaine- and amphetamine-regulated transcript (CART) peptides are known to participate in appetite and feeding behavior. Various lines of evidence suggest that these peptides participate not only in feeding behavior but also in cardiovascular and sympathetic regulations. Both leptin and ghrelin are secreted from the peripheral tissue; then they reach the brain to modulate sympathetic activity. These two peptides seem to play important roles to transmit peripheral metabolic information to the brain, and to convert it to cardiovascular and sympathetic information. Leptin activates neurons containing alpha-melanocyte stimulating hormone and cocaine- and amphetamine-regulated transcript peptides, resulting in increases in sympathetic activity and blood pressure. Cardiovascular action of alpha-melanocyte stimulating hormone is mediated through melanocortin-4 receptor, and agouti-related protein (AGRP) plays a role as an endogenous melanocortin-4 receptor antagonist. In contrast, ghrelin and neuropeptide Y in the brain suppress sympathetic activity and decrease blood pressure. Depressor and sympathoinhibitory effects of central neuropeptide Y are inhibited by leptin. Furthermore, central ghrelin modulates baroreflex control of renal sympathetic nerve activity and heart rate. Thus, leptin and the related peptides, which participate in appetite and feeding behavior, seem to function together to regulate cardiovascular system and sympathetic nerve activity, and may play a key role in the association between obesity and hypertension.

Insulin-dependent modulation of plasma ghrelin and leptin concentrations is less pronounced in type 2 diabetic patients

The gastric peptide ghrelin augments and the adipocyte-derived hormone leptin reduces appetite and food intake. In the central nervous system, insulin directly decreases hunger sensation but could also act indirectly by modulating ghrelin and leptin secretion. This study examines dose-dependent effects of insulin on plasma ghrelin and leptin concentrations during hyperinsulinemic (1, 2, and 4 mU x kg(-1) x min(-1))-euglycemic clamp tests in six nondiabetic (control subjects) and six type 2 diabetic patients. Type 2 diabetic patients were studied before and after prolonged (12-h and 67-h) variable intravenous insulin treatment aiming at near-normoglycemia (115 +/- 4 mg/dl). Nondiabetic subjects were also studied during saline infusion, which did not affect ghrelin but decreased leptin by 19 +/- 6% (P < 0.03). In control subjects, plasma ghrelin decreased at all clamp steps (-17 +/- 1, -27 +/- 6, and -33 +/- 4%, respectively; P < 0.006 vs. baseline), whereas leptin increased by 35 +/- 11% (P < 0.05). In type 2 diabetic patients without insulin treatment, ghrelin decreased by 18 +/- 7% (P < 0.05) only after 4 mU x kg(-1) x min(-1) insulin infusion and leptin increased by 19 +/- 6% (P < 0.05). After prolonged insulin treatment and near-normoglycemia, ghrelin and leptin remained unchanged in type 2 diabetic patients during the clamps. In conclusion, insulin reduces plasma ghrelin in nondiabetic patients and, to a lesser extent, in type 2 diabetic patients before insulin therapy. These findings indicate an indirect effect of insulin via ghrelin on the suppression of hunger sensation and appetite.

Nutritional status in the neuroendocrine control of growth hormone secretion: the model of anorexia nervosa

Growth hormone (GH) plays a key role not only in the promotion of linear growth but also in the regulation of intermediary metabolism, body composition, and energy expenditure. On the whole, the hormone appears to direct fuel metabolism towards the preferential oxidation of lipids instead of glucose and proteins, and to convey the energy derived from metabolic processes towards the synthesis of proteins. On the other hand, body energy stores and circulating energetic substrates take an important part in the regulation of somatotropin release. Finally, central and peripheral peptides participating in the control of food intake and energy expenditure (neuropeptide Y, leptin, and ghrelin) are also involved in the regulation of GH secretion. Altogether, nutritional status has to be regarded as a major determinant in the regulation of the somatotropin-somatomedin axis in animals and humans. In these latter, overweight is associated with marked impairment of spontaneous and stimulated GH release, while acute dietary restriction and chronic undernutrition induce an amplification of spontaneous secretion together with a clear-cut decrease in insulin-like growth factor I (IGF-I) plasma levels. Thus, over- and undernutrition represent two conditions connoted by GH hypersensitivity and GH resistance, respectively. Anorexia nervosa (AN) is a psychiatric disorder characterized by peculiar changes of the GH-IGF-I axis. In these patients, low circulating IGF-I levels are associated with enhanced GH production rate, highly disordered mode of somatotropin release, and variability of GH responsiveness to different pharmacological challenges. These abnormalities are likely due not only to the lack of negative IGF-I feedback, but also to a primary hypothalamic alteration with increased frequency of growth hormone releasing hormone discharges and decreased somatostatinergic tone. Given the reversal of the above alterations following weight recovery, these abnormalities can be seen as secondary, and possibly adaptive, to nutritional deprivation. The model of AN may provide important insights into the pathophysiology of GH secretion, in particular as regards the mechanisms whereby nutritional status effects its regulation.

Ghrelin and adipose tissue regulatory peptides: effect of gastric bypass surgery in obese humans

Presently surgery is the most effective way to obtain a controlled weight reduction in morbidly obese patients. Roux-en-Y gastric bypass (RYGBP) surgery is effective and used worldwide, but the exact mechanism of action is unknown. The effect of RYGBP on ghrelin, insulin, adiponectin, and leptin levels was investigated in 66 obese subjects; mean weight 127 kg (range, 96-195 kg) and mean body mass index (BMI) 45 kg/m(2) (range, 33-64) before and after surgery. Ghrelin levels were also compared in 10 nonoperated and 10 operated obese, BMI-matched women. RYGBP resulted in 22% and 30% weight loss at 6 and 12 months, respectively. Ghrelin increased by 44% and 62% and adiponectin by 36% and 98%, but insulin declined by 57% and 62% and leptin by 60% and 64%. The changes were all related to the reduction in BMI. In addition, ghrelin and insulin were inversely correlated at all time points as were changes of the peptides at 12 months (F = 4.9, P = 0.031), independent of the change in BMI. No evidence for RYGBP surgery per se having an effect on ghrelin levels, independent of weight loss, was obtained. The profound changes in the regulatory peptides are likely to reflect the new state of energy balance achieved. A close inverse association between ghrelin and insulin was observed, supporting an important role for ghrelin in glucose homeostasis.

Genetics and pathophysiology of human obesity

Obesity has become a leading public health concern. Over 1 billion people are now overweight or obese, and the prevalence of these conditions is rising rapidly. Remarkable new insights into the mechanisms that control body weight are providing an increasingly detailed framework for a better understanding of obesity pathogenesis. Key peripheral signals, such as leptin, insulin, and ghrelin, have been linked to hypothalamic neuropeptide systems, and the anatomic and functional networks that integrate these systems have begun to be elucidated. This article highlights some of these recent findings and their implications for the future of obesity treatment.

Hypothalamic orexin neurons regulate arousal according to energy balance in mice

Mammals respond to reduced food availability by becoming more wakeful and active, yet the central pathways regulating arousal and instinctual motor programs (such as food seeking) according to homeostatic need are not well understood. We demonstrate that hypothalamic orexin neurons monitor indicators of energy balance and mediate adaptive augmentation of arousal in response to fasting. Activity of isolated orexin neurons is inhibited by glucose and leptin and stimulated by ghrelin. Orexin expression of normal and ob/ob mice correlates negatively with changes in blood glucose, leptin, and food intake. Transgenic mice, in which orexin neurons are ablated, fail to respond to fasting with increased wakefulness and activity. These findings indicate that orexin neurons provide a crucial link between energy balance and arousal.

Electrophysiological actions of peripheral hormones on melanocortin neurons

Neurons of the arcuate nucleus of the hypothalamus (ARH) appear to be sites of convergence of central and peripheral signals of energy stores, and profoundly modulate the activity of the melanocortin circuits, providing a strong rationale for pursuing these circuits as therapeutic targets for disorders of energy homeostasis. Recently, tremendous advances have been made in identifying genes and pathways important to regulating energy homeostasis, particularly the hormone leptin and its receptor. This hormone/receptor pair is expressed at high levels in the so-called satiety centers in the hypothalamus, and at lower levels elsewhere in the body. Recent studies in our lab and those of our collaborators have shown that leptin modulates different populations of hypothalamic cells in different ways, rapidly activating POMC neurons and inhibiting NPY/AgRP neurons. In this report, we outline an integrated model of leptin's action in the arcuate nucleus of the hypothalamus, derived from our electrophysiological studies of brain slice preparations taken from transgenic mice that have been bred to express a variety of fluorescent proteins in specific cell types. We also discuss the recently withdrawn obesity drug fenfluramine, which appears to act on POMC neurons via the serotonin 2C receptor. Nutrient-sensing serotonin neurons may project from the raphe nuclei in the brainstem to the hypothalamus; within the arcuate nucleus, serotonin signals are integrated with others such as leptin, ghrelin, and peptide YY(3-36) from the gut, to produce a coordinated response to nutrient state. Finally, we review the current inquiries into the ability of the hormone ghrelin to stimulate appetite by its action of NPY neurons and inhibition of POMC neurons.

Diabetes and hypertension in severe obesity and effects of gastric bypass-induced weight loss

OBJECTIVE

To evaluate the preoperative relationships of hypertension and diabetes mellitus in severe obesity and the effects of gastric bypass (GBP)-induced weight loss.

SUMMARY BACKGROUND DATA

Severe obesity is associated with multiple comorbidities, particularly hypertension and type 2 diabetes mellitus, that may affect life expectancy.

METHODS

The database of patients who had undergone GBP by one general surgeon at a university hospital between September 1981 and January 2000 was queried as to weight, body mass index (BMI), pre- and postoperative diabetes, hypertension, and other comorbidities, including sleep apnea, hypoventilation, gastroesophageal reflux, degenerative joint disease, urinary incontinence, venous stasis, and pseudotumor cerebri.

RESULTS

Of 1,025 patients treated, 15% had type 2 diabetes mellitus and 51% had hypertension. Of those with diabetes, 75% also had hypertension. There was a progressive increase in age between patients who had neither diabetes nor hypertension, either diabetes or hypertension, or both diabetes and hypertension. At 1 year after GBP (91% follow-up), patients lost 66 +/- 18% excess weight (%EWL) or 35 +/- 9% of their initial weight (%WL). Hypertension resolved in 69% and diabetes in 83%. Patients who resolved their hypertension or diabetes had greater %EWL and %WL than those who did not. African-American patients had a higher risk of hypertension than whites before GBP and were less likely to correct their hypertension after GBP. There was significant resolution of other obesity comorbidity problems. At 5 to 7 years after GBP (50% follow-up), %EWL was 59 +/- 24 and %WL was 31 +/- 13; resolution of hypertension was 66% and diabetes 86%.

CONCLUSIONS

These data suggest that type 2 diabetes mellitus and hypertension may be indirectly related to each other through the effects of obesity, but not directly as to cause and effect. The longer a person remains severely obese, the more likely he or she is to develop diabetes, hypertension, or both. GBP-induced weight loss is effective in correcting diabetes, hypertension, and other comorbidities but is related to the %EWL achieved. Severely obese African-Americans were more likely to have hypertension and respond less well to GBP surgery than whites. These data suggest that GBP surgery for severe obesity should be provided earlier to patients to prevent the development of diabetes and hypertension and their complications.

Ghrelin-induced feeding is dependent on nitric oxide

Ghrelin is a newly discovered gastric peptide, which has orexigenic effects. Ghrelin is the endogenous ligand for the growth hormone secretagogue receptor and stimulates growth hormone and gastrointestinal motility. We have previously shown that nitric oxide (NO) plays an important role as a mediator of feeding induced by a variety of neuropeptides. This raises the question of whether ghrelin's effects are NO dependent. Here, we first determined that intracerebroventricular administration of 100 ng of ghrelin significantly increased food intake in satiated mice. We next examined the effects of N(omega)-nitro-L-arginine methyl ester (L-NAME), a nitric oxide synthase inhibitor, on ghrelin-induced increase in food intake. A subthreshold dose (12.5mg/kg; SC) of L-NAME significantly blocked the ghrelin-induced increase in food intake. Ghrelin administration increased the levels of nitric oxide synthase in the hypothalamus. This supports the hypothesis that nitric oxide is a central regulator of food consumption.

Involvement of cholinergic neurons in the regulation of the ghrelin secretory response to feeding in sheep

We previously demonstrated that a transient surge in plasma levels of ghrelin occurs just prior to a scheduled meal and that this surge is modified by the feeding regimen. This suggests that the ghrelin secretion is regulated by the autonomic nervous system, especially the cholinergic projections to the stomach. To test this hypothesis, we investigated changes in plasma ghrelin levels at feeding time in rams by administering cholinergic blockers (atropine and hexamethonium) and a cholinergic accelerator (metoclopramide). The average food intake in each group infused with atropine, hexamethonium, metoclopramide, and saline was 150+/-28, 137+/-46, 153+/-50, and 1075+/-25g, respectively. Plasma ghrelin concentrations increased (P<0.05) after i.v. infusion of hexamethonium and gradually decreased (P<0.05) after i.v. infusion of metoclopramide. Plasma ghrelin levels in hexamethonium-treated animals were greater (P<0.05) than those of atropine-treated animals. Plasma ghrelin levels were significantly (P<0.05) higher in sheep given i.v. infusions of atropine or hexamethonium than the levels in normal- or pair-fed sheep infused with saline. Plasma ghrelin levels were similar in metoclopramide-treated, pair-fed, and control animals. These results support the possibility that ghrelin secretion is regulated by cholinergic neurons of the vagus and that cholinergic activity suppresses ghrelin secretion in sheep.

Restoration of euglycemia and normal acute insulin response to glucose in obese subjects with type 2 diabetes following bariatric surgery

Insulin resistance and loss of glucose-stimulated acute insulin response (AIR) are the two major and earliest defects in the course of type 2 diabetes. We investigated whether weight loss after bariatric surgery in patients with morbid obesity and type 2 diabetes could restore euglycemia and normal AIR to an intravenous glucose tolerance test (IVGTT). We studied 25 morbidly obese patients-12 with type 2 diabetes, 5 with impaired glucose tolerance, and 8 with normal glucose tolerance (NGT)-before and after a biliopancreatic diversion (BPD) with Roux-en-Y gastric bypass (RYGBP). Twelve individuals with normal BMI served as control subjects. Twelve months after surgery, in the diabetes group, BMI decreased from 53.2 +/- 2.0 to 29.2 +/- 1.7 kg/m(2), fasting glucose decreased from 9.5 +/- 0.83 to 4.5 +/- 0.13 mmol/l, and fasting insulin decreased from 168.4 +/- 25.9 to 37.7 +/- 4.4 pmol/l (mean +/- SE; P < 0.001). AIR, the mean of insulin concentration at 2, 3, and 5 min over basal in the IVGTT, increased by 770 and 935% at 3 and 12 months after surgery, respectively (from 24.0 +/- 22.7 to 209 +/- 43.4 and 248 +/- 33.1 pmol/l, respectively; P < 0,001). Conversely, in the NGT group, the AIR decreased by 40.5% (from 660 +/- 60 to 393 +/- 93 pmol/l; P = 0.027) 12 months after surgery. BPD with RYGBP performed in morbidly obese patients with type 2 diabetes leads to significant weight loss, euglycemia, and normal insulin sensitivity; but most importantly, it restores a normal beta-cell AIR to glucose and a normal relationship of AIR to insulin sensitivity. This is the first study to demonstrate that the lost glucose-induced AIR in patients with type 2 diabetes of mild or moderate severity is a reversible abnormality.

Hyperleptinemia prevents increased plasma ghrelin concentration during short-term moderate caloric restriction in rats

BACKGROUND & AIMS

Ghrelin is an orexigenic hormone secreted by the stomach. Increased plasma ghrelin concentration was reported during diet-induced weight loss in obese humans, suggesting that ghrelin contributes to adaptive increment in appetite associated with caloric restriction. Leptin reduces spontaneous food intake and body weight in rodents. The current study tested the hypothesis that increased plasma leptin prevents the potential increase in plasma ghrelin concentration during moderate caloric restriction in lean rats.

METHODS

Six-month-old male rats (body weight, 367 +/- 9 grams) were randomly assigned to one of the following treatments (8 rats each) for 1 week: (1) leptin subcutaneous infusion to induce moderate hyperleptinemia and moderate caloric restriction (-26% of ad libitum), (2) vehicle infusion and pair feeding, and (3) vehicle infusion and ad libitum feeding.

RESULTS

Leptin-treated (-19 +/- 5 grams) and pair-fed (-19 +/- 2) rats lost weight compared with ad libitum-fed rats (-3 +/- 1, P < 0.05). Compared with control (6.8 +/- 0.7 ng/mL), plasma leptin was higher in leptin-treated (18.6 +/- 0.9 ng/mL, P < 0.01) rats and lower in pair-fed rats (4.3 +/- 0.4 ng/mL, P < 0.05). Plasma ghrelin was substantially higher in calorie-restricted than control rats (2505 +/- 132 pg/mL vs. 1790 +/- 134 pg/mL, P < 0.01), and leptin treatment (1625 +/- 117 pg/mL) completely prevented this change. Plasma ghrelin concentration was negatively correlated with body weight changes in calorie-restricted and control (r = -0.75, P < 0.01) but not in leptin-treated rats (P > 0.8).

CONCLUSIONS

Moderate hyperleptinemia prevents an increase of plasma ghrelin during moderate short-term caloric restriction. Satiety-inducing effects of leptin include suppression of gastric orexigenic signals and disruption of a potential feedback mechanism between body weight changes and plasma ghrelin in lean adult rats.

Roles of leptin and ghrelin in the loss of body weight caused by a low fat, high carbohydrate diet

Loss of body fat by caloric restriction is accompanied by decreased circulating leptin levels, increased ghrelin levels, and increased appetite. In contrast, dietary fat restriction often decreases adiposity without increasing appetite. Substitution of dietary carbohydrate for fat has been shown to increase the area under the plasma leptin vs. time curve (AUC) over the course of 24 h. This effect, if sustained, could explain the absence of a compensatory increase in appetite on a low fat diet. To clarify the effect of dietary fat restriction on leptin and ghrelin, we measured AUC for these hormones in human subjects after each of the following sequential diets: 2 wk on a weight-maintaining 35% fat (F), 45% carbohydrate (C), 20% protein (P) diet (n = 18); 2 wk on an isocaloric 15% F, 65% C, 20% P diet (n = 18); and 12 wk on an ad libitum 15% F, 65% C, 20% P diet (n = 16). AUC for leptin was similar on the isocaloric 15% F and 35% F diets (555 +/- 57 vs. 580 +/- 56 ng/ml.24 h; P = NS). Body weight decreased from 74.6 +/- 2.4 to 70.8 +/- 2.7 kg on the ad libitum 15% F diet (P < 0.001) without compensatory increases in food consumption or AUC for ghrelin. Proportional amplitude of the 24-h leptin profile was increased after 12 wk on the 15% fat diet. We conclude that weight loss early in the course of dietary fat restriction occurs independently of increased plasma leptin levels, but that a later increase in amplitude of the 24-h leptin signal may contribute to ongoing weight loss. Fat restriction avoids the increase in ghrelin levels caused by dietary energy restriction.

Ghrelin in chronic liver disease

BACKGROUND/AIMS

Ghrelin is a novel endogenous ligand for the growth hormone (GH) secretagogue receptor involved in energy metabolism, glucose homeostasis and food intake. We investigated the role of ghrelin and insulin-like growth factor-1 (IGF-1), the mediator of the GH axis, in patients with chronic liver diseases (CLD).

METHODS

Ghrelin and IGF-1 serum levels were determined in 105 CLD patients and 97 healthy controls and correlated with clinical and biochemical parameters.

RESULTS

Ghrelin was significantly elevated and IGF-1 reduced in CLD patients compared with healthy controls. IGF-1 serum levels inversely correlated with Child's classification. Ghrelin levels were significantly elevated in Child C cirrhosis patients independent of the aetiology of liver disease. Ghrelin levels did not correlate with liver function. In contrast, there was a correlation of ghrelin with clinical (gastrointestinal bleeding, ascites, encephalopathy) and biochemical (anaemia, inflammatory markers, hypoglycaemia, renal dysfunction) parameters. In a subgroup of patients with CLD and hepatocellular carcinoma (HCC), we observed a strong inverse correlation between alpha-fetoprotein (AFP) and ghrelin levels.

CONCLUSIONS

Unlike IGF-1, ghrelin is not correlated with liver function, but increases in Child C cirrhosis and with complications of CLD. The inverse correlation with AFP in HCC patients requires further studies on the potential impact of ghrelin on the pathogenesis of anorexia-cachexia syndrome.

Rhythmic, reciprocal ghrelin and leptin signaling: new insight in the development of obesity

The hypothalamus integrates metabolic, neural and hormonal signals to evoke an intermittent appetitive drive in the daily management of energy homeostasis. Three major players identified recently in the feedback communication between the periphery and hypothalamus are leptin, ghrelin and neuropeptide Y (NPY). We propose that reciprocal circadian and ultradian rhythmicities in the afferent humoral signals, anorexigenic leptin from adipocytes and orexigenic ghrelin from stomach, encode a corresponding discharge pattern in the appetite-stimulating neuropeptide Y network in the hypothalamus. An exquisitely intricate temporal relationship among these signaling modalities with varied sites of origin is paramount in sustenance of weight control on a daily basis. Our model envisages that subtle and progressive derangements in temporal communication, imposed by environmental shifts in energy intake, impel a positive energy balance culminating in excessive weight gain and obesity. This conceptual advance provides a new target for designing pharmacologic or gene transfer therapies that would normalize the rhythmic patterns of afferent hormonal and efferent neurochemical messages.

High- versus low-fat diets in human diseases

PURPOSE OF REVIEW

To evaluate the evidence with regard to high-versus low-fat diets in the context of the prevention and management of obesity, type 2 diabetes and coronary heart disease.

RECENT FINDINGS

Despite the increasing prevalence of obesity, there is no evidence to support the view that this is caused by an increased intake of fat. Fat sensors play an important role in regulating energy balance and lipid metabolism, and hypoenergetic diets containing 30-35% energy from fat promote weight loss. High intakes of carbohydrates with a high glycaemic index can result in insulin resistance, but this effect can be modulated by increased physical activity.

SUMMARY

Although arguments to decrease the intake of trans and saturated fatty acids are cogent, the scientific basis for a reduction in the proportion of energy from fat below 30% energy is not supported by experimental evidence. A modest reduction in fat intake to 30-35% energy, with the bulk of carbohydrates being derived from complex carbohydrates from unrefined sources, would appear to be the best option for the prevention of obesity and cardiovascular disease. Increased physical activity appears to be particularly important in modulating the adverse effects associated with high-carbohydrate low-fat diets.

Is the energy homeostasis system inherently biased toward weight gain?

We describe a model of energy homeostasis to better understand neuronal pathways that control energy balance and their regulation by hormonal signals such as insulin and leptin. Catabolic neuronal pathways are those that both reduce food intake and increase energy expenditure (e.g., melanocortin neurons in the hypothalamic arcuate nucleus) and are stimulated by input from insulin and leptin. We propose that in the basal state, catabolic effectors are activated in response to physiological concentrations of leptin and insulin, and that this activation is essential to prevent excessive weight gain. In contrast, anabolic pathways (e.g., neurons containing neuropeptide Y) are those that stimulate food intake and decrease energy expenditure and are strongly inhibited by these same basal concentrations of insulin and leptin. In the basal state, therefore, catabolic effector pathways are activated while anabolic effector pathways are largely inhibited. The response to weight loss includes both activation of anabolic and inhibition of catabolic pathways and is, thus, inherently more vigorous than the response to weight gain (stimulation of already-activated catabolic pathways and inhibition of already-suppressed anabolic pathways). Teleological, molecular, physiological, and clinical aspects of this hypothesis are presented, along with a discussion of currently available supporting evidence.

The influence of insulin on circulating ghrelin

Ghrelin is a novel peptide that acts on the growth hormone (GH) secretagogue receptor in the pituitary and hypothalamus. It may function as a third physiological regulator of GH secretion, along with GH-releasing hormone and somatostatin. In addition to the action of ghrelin on the GH axis, it appears to have a role in the determination of energy homeostasis. Although feeding suppresses ghrelin production and fasting stimulates ghrelin release, the underlying mechanisms controlling this process remain unclear. The purpose of this study was to test the hypotheses, by use of a stepped hyperinsulinemic eu- hypo- hyperglycemic glucose clamp, that either hyperinsulinemia or hypoglycemia may influence ghrelin production. Having been stable in the period before the clamp, ghrelin levels rapidly fell in response to insulin infusion during euglycemia (baseline ghrelin 207 +/- 12 vs. 169 +/- 10 fmol/ml at t = 30 min, P < 0.001). Ghrelin remained suppressed during subsequent periods of hypoglycemia (mean glucose 53 +/- 2 mg/dl) and hyperglycemia (mean glucose 163 +/- 6 mg/dl). Despite suppression of ghrelin, GH showed a significant rise during hypoglycemia (baseline 4.1 +/- 1.3 vs. 28.2 +/- 3.9 microg/l at t = 120 min, P < 0.001). Our data suggest that insulin may suppress circulating ghrelin independently of glucose, although glucose may have an additional effect. We conclude that the GH response seen during hypoglycemia is not regulated by circulating ghrelin.