Mechanisms of recovery from type 2 diabetes after malabsorptive bariatric surgery

Metabolic or bariatric surgery? Long-term effects of malabsorptive vs restrictive bariatric techniques on body composition and cardiometabolic risk factors

BACKGROUND

Obesity is an increasing health problem and surgery seems to be the only treatment effective in achieving weight loss without relapse. Among bariatric techniques, many differences exist in terms of weight loss and resolution of comorbidities. Up to now, there are no prospective studies comparing long-term effects of malabsorptive vs restrictive techniques.

OBJECTIVE

In this study, cardiometabolic risk factors and body composition changes after malabsorptive biliointestinal bypass (BIBP) and restrictive laparoscopic adjustable gastric banding (LAGB) were compared during a 4-year follow-up.

DESIGN

Prospective, case-control and cohort study.

PATIENTS

In all, 80 obese subjects, matched for weight and age. Altogether, 40 patients underwent BIBP and 40 underwent LAGB.

MEASUREMENTS

Weight, body composition, fasting and post-loading plasma glucose and insulin, homeostatic model assessment index (HOMA-I), lipid profile, blood pressure (BP), erythrocyte sedimentation rate and fibrinogen were monitored at baseline, 12 and 48 months.

RESULTS

At 12 months after surgery, a significant reduction in body mass index, total fat mass (FM), trunk FM (trFM), trFM/legs FM (lFM) ratio (trFM/lFM), triglycerides, BP and inflammation markers was observed in both groups. BIBP patients showed a significant reduction in total cholesterol (Tot-C), low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C), whereas the LAGB group showed a significant increase of HDL-C. A further improvement of all the parameters evaluated was seen in the BIBP group at 48 months after surgery.

CONCLUSIONS

Both bariatric procedures exerted positive effects on cardiometabolic risk factors and on weight loss in the population studied, but on the long-term period, HOMA-I, Tot-C/HDL-C ratio and body composition improvements were more evident after BIBP. We conclude that malabsorptive BIBP seems to be more effective than LAGB in treating visceral obesity and its metabolic complications.

Bariatric surgery and the gut-brain communication--the state of the art three years later

OBJECTIVE

This review analyzes the literature concerning gut peptides and bariatric surgery, from 2005 to July 2009. In particular, we are interested in whether, and how, gastrointestinal peptide alterations following surgery interfere with appetite/satiety, and what role they might play in the resolution of comorbidities.

RESEARCH METHODS AND PROCEDURE

PubMed/MEDLINE and ISI Web of Knowledge were used to search for human studies concerning gut peptides profiles after any bariatric operation technique.

RESULTS

Most of the studies reviewed had longitudinal design, short follow-up, and low statistical power. The diversity of study results may be partially explained by methodological aspects. Glucagon-like peptide-1, gastric inhibitory peptide, and peptide YY alterations may contribute to the excellent results in glycemic control of diabetics. Results do vary depending on bariatric operation technique; this is particularly evident in the case of ghrelin, which has been much studied in recent years. Ghrelin suppression has been linked to increased satiety, alterations in energy homeostasis, and better glucose metabolism.

CONCLUSIONS

There is a lack of long-term data on gastrointestinal hormone profiles after bariatric surgery and the studies have many methodological pitfalls. We still need prospective, long-term, good methodological studies in this area.

Mechanisms of early improvement/resolution of type 2 diabetes after bariatric surgery

Bariatric surgery represents the main option for obtaining substantial and long-term weight loss in morbidly obese subjects. In addition, malabsorptive (biliopancreatic diversion, BPD) and restrictive (roux-en-Y gastric bypass, RYGB) surgery, originally devised to treat obesity, has also been shown to help diabetes. Indeed, type 2 diabetes is improved or even reversed soon after these operations and well before significant weight loss occurs. Two hypotheses have been proposed to explain the early effects of bariatric surgery on diabetes--namely, the hindgut hypothesis and the foregut hypothesis. The former states that diabetes control results from the more rapid delivery of nutrients to the distal small intestine, thereby enhancing the release of hormones such as glucagon-like peptide-1 (GLP-1). The latter theory contends that exclusion of the proximal small intestine reduces or suppresses the secretion of anti-incretin hormones, leading to improvement of blood glucose control as a consequence. In fact, increased GLP-1 plasma levels stimulate insulin secretion and suppress glucagon secretion, thereby improving glucose metabolism. Recent studies have shown that improved intestinal gluconeogenesis may also be involved in the amelioration of glucose homoeostasis following RYGB. Although no large trials have specifically addressed the effects of bariatric surgery on the remission or reversal of type 2 diabetes independent of weight loss and/or caloric restriction, there are sufficient data in the literature to support the idea that this type of surgery--specifically, RYGB and BPD--can lead to early improvement of glucose control independent of weight loss.

Acute effects of gastric bypass versus gastric restrictive surgery on beta-cell function and insulinotropic hormones in severely obese patients with type 2 diabetes

CONTEXT

Hyperglycemia resolves quickly after bariatric surgery, but the underlying mechanism and the most effective type of surgery remains unclear.

OBJECTIVE

To examine glucose metabolism and beta-cell function in patients with type 2 diabetes mellitus (T2DM) after two types of bariatric intervention; Roux-en-Y gastric bypass (RYGB) and gastric restrictive (GR) surgery.

DESIGN

Prospective, nonrandomized, repeated-measures, 4-week, longitudinal clinical trial.

PATIENTS

In all, 16 T2DM patients (9 males and 7 females, 52+/-14 years, 47+/-9 kg m(-2), HbA1c 7.2+/-1.1%) undergoing either RYGB (N=9) or GR (N=7) surgery.

OUTCOME MEASURES

Glucose, insulin secretion, insulin sensitivity at baseline, and 1 and 4 weeks post-surgery, using hyperglycemic clamps and C-peptide modeling kinetics; glucose, insulin secretion and gut-peptide responses to mixed meal tolerance test (MMTT) at baseline and 4 weeks post-surgery.

RESULTS

At 1 week post-surgery, both groups experienced a similar weight loss and reduction in fasting glucose (P<0.01). However, insulin sensitivity increased only after RYGB, (P<0.05). At 4 weeks post-surgery, weight loss remained similar for both groups, but fasting glucose was normalized only after RYGB (95+/-3 mg 100 ml(-1)). Insulin sensitivity improved after RYGB (P<0.01) and did not change with GR, whereas the disposition index remained unchanged after RYGB and increased 30% after GR (P=0.10). The MMTT elicited a robust increase in insulin secretion, glucagon-like peptide-1 (GLP-1) levels and beta-cell sensitivity to glucose only after RYGB (P<0.05).

CONCLUSION

RYGB provides a more rapid improvement in glucose regulation compared with GR. This improvement is accompanied by enhanced insulin sensitivity and beta-cell responsiveness to glucose, in part because of an incretin effect.

Study of the effects of transoral gastroplasty on insulin sensitivity and secretion in obese subjects

BACKGROUND AND AIMS

Transoral gastroplasty (TOGA) recently emerged as a new, feasible and relatively safe technique for the surgical treatment of obesity. However, so far there are no data on the effects on insulin sensitivity in the literature. Our aim is to evaluate the effect of TOGA on insulin sensitivity and secretion.

METHODS AND RESULTS

Nine glucose normo-tolerant obese subjects (age:41+/-6 years; BMI:42.49+/-1.03 kg/m(2)) were studied. Fat-free mass (FM) and fat mass (FM) were assessed by bioelectrical impedance; plasma glucose, insulin, and C-peptide were measured during an oral glucose tolerance test (OGTT) before and 3 months after the operation. Insulin sensitivity was calculated using the oral-glucose insulin-sensitivity index, and insulin secretion by C-peptide deconvolution. Three months after surgery, a significant (P=0.008) reduction of BMI to 35.65+/-0.65 kg/m(2), with a decrease of FM and FFM from 57.22+/-2.19 to 41.46+/-3.02 kg (P=0.008) and from 59.52+/-1.36 to 56.67+/-1.10 kg (P=0.048) respectively, was observed. Insulinemia was significantly reduced at fast and at 120 min after OGTT; in contrast, no significant change in glucose concentration was observed. Insulin sensitivity significantly increased (348.45+/-20.08 vs. 421.18+/-20.84 ml/min/m(2), P=0.038) and the incremental area of insulin secretion rate (total ISR) significantly decreased (from 235.05+/-27.50 to 124.77+/-14.50 nmol/min/m(2), P=0.021). Total ISR correlated with weight, BMI and FM (r=0.522, P=0.028; r=0.541, P=0.020; r=0.463, P=0.049, respectively). BMI represented the most powerful predictor of ISR decrease (R(2)=0.541, P=0.020).

CONCLUSION

Transoral gastroplasty allows a significant weight loss 3 months after the intervention as well as an amelioration of insulin sensitivity with subsequent reduction of the insulin secretion.

Plasma nonesterified Fatty Acid intolerance and hyperglycemia are associated with intravenous lipid-induced impairment of insulin sensitivity and disposition index

CONTEXT

It is currently unclear why susceptibility to lipid-induced impairment of beta-cell function varies in different populations.

OBJECTIVE

The aim of the study was to determine whether mild hyperglycemia may be associated with nonesterified fatty acid (NEFA) intolerance and increased iv lipid-induced lipotoxic effect on the beta-cell.

DESIGN AND SETTING

The study consisted of an experimental design with control group conducted at an academic clinical research center.

PARTICIPANTS

Twenty-six overweight or obese individuals (12 with normal glucose tolerance, nine with impaired glucose tolerance or type 2 diabetes, and five subjects who previously had impaired glucose tolerance or type 2 diabetes but at the time of study had normal glucose tolerance after biliopancreatic diversion).

INTERVENTIONS

We assessed insulin sensitivity (S(I)) and beta-cell function [insulin disposition index (DI)] after an overnight iv infusion of heparin + Intralipid (HI) vs. normal saline for 16 h using a stepwise, incremental iv glucose infusion followed by a hyperglycemic clamp.

MAIN OUTCOME MEASURES

We measured S(I), DI, HI-induced change in plasma NEFA, and its association with HI-induced change in S(I) and DI.

RESULTS

HI resulted in significant reduction in S(I) and DI across the three groups of participants. HI-induced elevation of plasma NEFA was higher in hyperglycemic vs. normoglycemic groups. Both fasting glucose level and the magnitude of HI-induced NEFA elevation were associated with the reduction in S(I) (P = 0.007 and P = 0.01, respectively) and DI (P = 0.001 and P = 0.007, respectively).

CONCLUSION

Mild hyperglycemia and NEFA intolerance to iv lipid are associated with susceptibility to lipid-induced reduction in S(I) and DI.

The effect of duodenal-jejunal bypass on glucose-dependent insulinotropic polypeptide secretion in Wistar rats

BACKGROUND

Enteroendocrine K cells secrete the incretin hormone glucose-dependent insulinotropic peptide (GIP) and are predominately located in the duodenum. GIP levels should decrease after gastric bypass due to duodenal exclusion; however, studies have found conflicting data regarding the changes in GIP secretion after gastric bypass and duodenal-jejunal bypass (DJB).

METHODS

We performed a DJB or Sham surgery on Wistar rats followed by an oral glucose tolerance test on postoperative (post-op) day 12 and superior mesenteric lymphatic cannulation on post-op day 14. We measured meal-stimulated GIP concentrations and small bowel GIP and GLP-1 protein content after DJB or Sham surgery.

RESULTS

There was no difference in glucose tolerance by 12 days post-op. We found no difference in lymphatic GIP concentration area under the curve between DJB and Sham rats (15,240 pg/ml min +/- 2,651 vs. 17,201 pg/ml min +/- 2,763, respectively, p = 0.62). GIP and GLP-1 protein contents were both significantly increased only in the midjejunum in DJB rats compared to Sham rats (p = 0.009 and p = 0.01, respectively).

CONCLUSIONS

Plasma and lymphatic GIP concentrations did not significantly change after DJB in Wistar rats. DJB increased GIP protein content in the midjejunum at the new site of nutrient absorption, but this was surprisingly not countered by a decrease in GIP protein content in the bypassed duodenum. Further studies are needed to determine the mechanisms that account for the discrepancy in GIP production and subsequent secretion after DJB as well as what role GIP plays in the effect of gastrointestinal surgery on glucose homeostasis.

Alterations in the mitochondrial regulatory pathways constituted by the nuclear co-factors PGC-1alpha or PGC-1beta and mitofusin 2 in skeletal muscle in type 2 diabetes

Muscle mitochondrial metabolism is regulated by a number of factors, many of which are responsible for the transcription of nuclear genes encoding mitochondrial proteins such as PPARdelta, PGC-1alpha or PGC-1beta. Recent evidence indicates that proteins participating in mitochondrial dynamics also regulate mitochondrial metabolism. Thus, in cultured cells the mitochondrial fusion protein mitofusin 2 (Mfn2) stimulates respiration, substrate oxidation and the expression of subunits involved in respiratory complexes. Mitochondrial dysfunction has been reported in skeletal muscle of type 2 diabetic patients. Reduced mitochondrial mass and defective activity has been proposed to explain this dysfunction. Alterations in mitochondrial metabolism may be crucial to account for some of the pathophysiological traits that characterize type 2 diabetes. Skeletal muscle of type 2 diabetic patients shows reduced expression of PGC-1alpha, PGC-1beta, and Mfn2. In addition, a differential response to bilio-pancreatic diversion-induced weight loss in non-diabetic and type 2 diabetic patients has been reported. While non-diabetic morbidly obese subjects showed an increased expression of genes encoding Mfn2, PGC-1alpha, PGC-1beta, PPARdelta or SIRT1 in response to bariatric surgery-induced weight loss, no effect was detected in type 2 diabetic patients. These observations suggest the existence of a heritable component responsible for the abnormal control of the expression of genes encoding for modulators of mitochondrial biogenesis/metabolism, and which may participate in the development of the disease.

Early effects of gastric banding (LGB) and of biliopancreatic diversion (BPD) on insulin sensitivity and on glucose and insulin response after OGTT

BACKGROUND

Bariatric surgery improves glucose metabolism.

METHODS

To assess the direct role of surgery (i.e., independently of significant weight loss) on insulin sensitivity (homeostasis model assessment (HOMA) insulin resistance (IR) and oral glucose insulin sensitivity (OGIS)), on glucose and insulin response (area under the curve (AUC) blood glucose (BG) and AUC insulin (Ins)) to oral glucose tolerance test (OGTT), and on glucose tolerance, 11 subjects underwent OGTT (75 g, p.o.) before and 5 days after laparoscopic gastric banding (LGB; no change of initial body mass index (BMI), 46.7 +/- 2.21 kg/m(2)), and ten subjects underwent OGTT before and 7 days after biliopancreatic diversion (BPD; BMI decreased from 54.5 +/- 3.75 to 52.1 +/- 4.03 kg/m(2)). As controls, we considered OGTT performed twice over a 30-45-day period in two groups of subjects [BMI 43.0 +/- 0.41 (n = 13, matched with LGB subjects for BMI) and 48.2 +/- 0.49 kg/m(2) (n = 14, matched with BPD subjects for BMI), respectively] with stable weight (+/-1.5 kg); a further control group was made of 11 subjects with a spontaneous weight loss similar to BPD subjects (BMI from 55.5 +/- 1.27 to 52.2 +/- 1.35 kg/m(2)).

RESULTS

Fasting BG and OGIS improved in BPD subjects and in subjects with spontaneous weight loss, not in LGB subjects or in weight-stable controls; HOMA-IR, AUC BG, and AUC Ins only decreased in BPD subjects. Glucose tolerance was not affected in a different way in the various groups of subjects.

CONCLUSIONS

These data indicate an early effect of BPD different from LGB on insulin sensitivity and on glucose and on insulin response to OGTT, mostly independent of weight loss.

Improvement in peripheral glucose uptake after gastric bypass surgery is observed only after substantial weight loss has occurred and correlates with the magnitude of weight lost

INTRODUCTION

Altered gut and pancreatic hormone secretion may bolster resolution of insulin resistance after Roux-en-Y gastric bypass (RYGB), but the independent effects of weight loss and hormonal secretion on peripheral glucose disposal are unknown.

METHODS

Two groups of nondiabetic morbidly obese patients were studied: RYGB followed by standardized caloric restriction (RYGB, n = 12) or caloric restriction alone (diet, n = 10). Metabolic evaluations (euglycemic-hyperinsulinemic clamp, meal tolerance test) were done at baseline and 14 days (both groups) and 6 months after RYGB.

RESULTS

At baseline, body composition, fasting insulin, and glucose and peripheral glucose disposal did not differ between groups. At 14 days, excess weight loss (EWL) was similar (RYGB, 12.7% vs. diet, 10.9%; p = 0.12), fasting insulin and glucose decreased to a similar extent, and RYGB subjects had altered postmeal patterns of gut and pancreatic hormone secretion. However, peripheral glucose uptake (M value) was unchanged in both groups. Six months after RYGB, EWL was 49.7%. The changes in fasting glucose and insulin levels and gut hormone secretion persisted. M values improved significantly, and changes in M values correlated with the % EWL (r = 0.68, p = 0.02).

CONCLUSIONS

Improvement in peripheral glucose uptake following RYGB was observed only after substantial weight loss had occurred and correlated with the magnitude of weight lost.

Early insulin sensitivity after restrictive bariatric surgery, inconsistency between HOMA-IR and steady-state plasma glucose levels

BACKGROUND

The low-grade inflammatory condition present in morbid obesity is thought to play a causative role in the pathophysiology of insulin resistance (IR). Bariatric surgery fails to improve this inflammatory condition during the first months after surgery. Considering the close relation between inflammation and IR, we conducted a study in which insulin sensitivity was measured during the first months after bariatric surgery. Different methods to measure IR shortly after bariatric surgery have given inconsistent data. For example, the Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) levels have been reported to decrease rapidly after bariatric surgery, although clamp techniques have shown sustained insulin resistance. In the present study, we evaluated the use of steady-state plasma glucose (SSPG) levels to assess insulin sensitivity 2 months after bariatric surgery.

METHODS

Insulin sensitivity was measured using HOMA-IR and SSPG levels in 11 subjects before surgery and at 26% excess weight loss (approximately 2 months after restrictive bariatric surgery).

RESULTS

The SSPG levels after 26% excess weight loss did not differ from the SSPG levels before surgery (14.3 +/- 5.4 versus 14.4 +/- 2.7 mmol/L). In contrast, the HOMA-IR values had decreased significantly (3.59 +/- 1.99 versus 2.09 +/- 1.02).

CONCLUSION

During the first months after restrictive bariatric surgery, we observed a discrepancy between the HOMA-IR and SSPG levels. In contrast to the HOMA-IR values, the SSPG levels had not improved, which could be explained by the ongoing inflammatory state after bariatric surgery. These results suggest that during the first months after restrictive bariatric surgery, HOMA-IR might not be an adequate marker of insulin sensitivity.

Resolution of type 2 diabetes following gastric bypass surgery: involvement of gut-derived glucagon and glucagonotropic signalling?

Certain types of bariatric surgical procedures have proved not only to be effective with regard to treating obesity, but they also seem to be associated with endocrine changes which independently of weight loss give rise to remission of type 2 diabetes. Currently, it is speculated that surgical re-routing of nutrients triggers changes in the release of gastrointestine-derived hormones, which in turn cause amelioration of the diabetic state. The 'hindgut hypothesis' states that surgical re-routing of nutrients to the distal part of the small intestine results in increased secretion and concomitant glucose-lowering effects of glucagon-like peptide-1, whereas the 'foregut hypothesis' emphasises that surgical bypass of the foregut prevents the release of a hitherto unidentified nutrient-induced diabetogenic signal in susceptible individuals. Recent studies have shown that in patients with type 2 diabetes, glucagon is differentially secreted in response to oral and i.v. glucose, respectively, with lack of suppression (and initial net secretion) during oral glucose administration and a perfectly normal suppression during isoglycaemic i.v. glucose administration. These findings could point towards a role for glucagon or gut-derived glucagonotropic signalling as putative diabetogenic signals of the foregut hypothesis. In the present paper the hypotheses describing the glucose-lowering mechanisms of bariatric surgical procedures sharing the common feature of a bypass of the duodenum and the proximal jejunum are outlined and a possible role for glucagon in these is proposed.

Bariatric surgery: unstressing or boosting the beta-cell?

Bariatric surgery is the most effective therapy for severe obesity in terms of reduction of morbidity and mortality and quality of life improvement. Different bariatric procedures distinctly differ with regard to their effectiveness to reduce body weight and to improve morbidities, such as type 2 diabetes. In this regard, the most effective procedures are bilio-pancreatic diversion (BPD) and duodenal switch procedure curing 98.9% of the diabetes patients, followed by Roux-en-Y gastric bypass (RYGB) with 83.7% success rate, by gastroplasty with 71.6% and by gastric banding with 47.9%. Interestingly, a net improvement up to resolution of type 2 diabetes has been consistently reported few days after RYGB and BPD. RYGB promotes incretin secretion which, in turn, stimulates insulin secretion while insulin sensitivity is slightly improved. Rarely, the long-term effect of incretin hypersecretion might result in hypertrophy and hyperplasia of the islets of Langerhans, otherwise known as nesidioblastosis, associated with hyperinsulinaemia and severe postprandial hypoglycaemia. In contrast, BDP improves insulin resistance to a greater extent and results, in the long run, in supra-normal values of insulin sensitivity with subsequent reduction of insulin secretion. The mechanism allowing diabetes resolution after surgical intestinal manipulation is extremely interesting but only partially understood.

Serum bile acid along with plasma incretins and serum high-molecular weight adiponectin levels are increased after bariatric surgery

Bariatric surgery has been shown to improve glucose tolerance, although the mechanism has not been fully elucidated. Animal studies have suggested important roles of bile acid (BA) as a regulator of energy homeostasis and glucose metabolism. However, little is known about its role in humans. We investigated the longitudinal changes of BA, incretins, and adipokines after significant weight reduction in 34 Japanese adults with morbid obesity who underwent laparoscopic bariatric surgery. In subjects who underwent malabsorptive or restrictive surgery, body mass index had markedly decreased from 43.0 +/- 6.5 (SD) to 37.8 +/- 5.7 kg/m(2) and from 45.3 +/- 11.2 to 41.5 +/- 10.5 kg/m(2), respectively, at 1 month after surgery. Glycated hemoglobin decreased from 6.1% +/- 1.5% to 5.2% +/- 0.4% and from 6.2% +/- 1.3% to 5.4% +/- 0.7%, and total BA level increased from 3.1 +/- 3.5 to 7.2 +/- 5.3 mumol/L and from 3.2 +/- 2.6 to 9.4 +/- 10.0 mumol/L, respectively. At baseline, serum concentration of primary BA was positively correlated with plasma gastric inhibitory polypeptide level (r = 0.548, P = .001); and change in primary BA level was positively correlated with changes in plasma gastric inhibitory polypeptide (r = 0.626, P = .001) and serum immunoreactive insulin level (r = 0.592, P = .002) at 1 month after surgery. Furthermore, plasma glucagon-like peptide-1 and serum high-molecular weight adiponectin levels increased in both surgeries. These hormonal changes might explain the mechanism(s) of improved glucose tolerance after bariatric surgery in morbidly obese subjects.

Evidence for beneficial effects of compromised gastric inhibitory polypeptide action in obesity-related diabetes and possible therapeutic implications

Gastric inhibitory polypeptide (GIP) is a physiological gut peptide secreted from the intestinal K-cells with well documented insulin-releasing actions. However, the GIP receptor is widely distributed in peripheral organs, including the pancreas, gut, adipose tissue, heart, adrenal cortex and brain, suggesting that it may have other functions. The presence of functional GIP receptors on adipocytes and the key role played by GIP in lipid metabolism and fat deposition suggest a possible beneficial effect of compromised GIP action in obesity and insulin resistance. Several key observations in animal models of obesity-related diabetes with chemically or genetically mediated biological GIP deficiency support this concept. Thus, obese diabetic animals with compromised GIP action due to peptide-based GIP receptor antagonists, small molecular weight GIP receptor antagonists, vaccination against GIP, genetic knockout of GIP receptor or targeted K-cell destruction are protected against obesity and associated metabolic disturbances. In addition, by causing preferential oxidation of fat, blockade of GIP signalling clears triacylglycerol deposits from liver and muscle, thereby restoring mechanisms for suppression of hepatic glucose output and improving insulin sensitivity. Emerging evidence also suggests that rapid cure of diabetes in grossly obese patients undergoing bypass surgery is mediated, in part, by surgical removal of GIP-secreting K-cells in the upper small intestine.

Mitochondrial dynamics in mammalian health and disease

The meaning of the word mitochondrion (from the Greek mitos, meaning thread, and chondros, grain) illustrates that the heterogeneity of mitochondrial morphology has been known since the first descriptions of this organelle. Such a heterogeneous morphology is explained by the dynamic nature of mitochondria. Mitochondrial dynamics is a concept that includes the movement of mitochondria along the cytoskeleton, the regulation of mitochondrial architecture (morphology and distribution), and connectivity mediated by tethering and fusion/fission events. The relevance of these events in mitochondrial and cell physiology has been partially unraveled after the identification of the genes responsible for mitochondrial fusion and fission. Furthermore, during the last decade, it has been identified that mutations in two mitochondrial fusion genes (MFN2 and OPA1) cause prevalent neurodegenerative diseases (Charcot-Marie Tooth type 2A and Kjer disease/autosomal dominant optic atrophy). In addition, other diseases such as type 2 diabetes or vascular proliferative disorders show impaired MFN2 expression. Altogether, these findings have established mitochondrial dynamics as a consolidated area in cellular physiology. Here we review the most significant findings in the field of mitochondrial dynamics in mammalian cells and their implication in human pathologies.

Genes involved in mitochondrial biogenesis/function are induced in response to bilio-pancreatic diversion in morbidly obese individuals with normal glucose tolerance but not in type 2 diabetic patients

AIMS/HYPOTHESIS

The mechanisms allowing normalisation of insulin sensitivity and reversal of type 2 diabetes after bilio-pancreatic diversion (BPD) have not been elucidated. We studied whether the expression of genes relevant to mitochondrial biogenesis/function is induced in response to BPD and whether the response differs between morbidly obese patients with normal glucose tolerance (NGT) and patients with type 2 diabetes.

METHODS

The effect of stable weight reduction after BPD on metabolic variables and expression of nuclear genes encoding for mitochondrial proteins or regulators of mitochondrial function was investigated in skeletal muscle. Insulin sensitivity was assessed by euglycaemic-hyperinsulinaemic clamp and substrate oxidation by indirect calorimetry.

RESULTS

Both NGT and type 2 diabetic patients showed a net improvement of insulin sensitivity, with the latter also showing blood glucose normalisation. NGT patients had a large increase in glucose oxidation and substantial reduction in lipid oxidation. In contrast, type 2 diabetic patients had a blunted response to BPD in terms of glucose oxidation. NGT patients showed increased expression of genes encoding mitofusin 2, porin or citrate synthase; no significant changes were detected in diabetic patients. The expression of genes regulating mitochondrial activity (PGC-1beta [also known as PPARGC1B], PGC-1alpha [also known as PPARGC1A], PPARdelta [also known as PPARD], SIRT1) was induced only in NGT patients.

CONCLUSIONS/INTERPRETATION

These findings indicate that weight loss after BPD exerts a beneficial effect on insulin sensitivity via mechanisms that are independent of the expression of genes involved in mitochondrial biogenesis/activity. Furthermore, the observation that gene expression is not altered with weight loss in type 2 diabetic patients while it is induced in NGT patients suggests a heritable component.

The effect of bilio-pancreatic diversion on type 2 diabetes in patients with BMI <35 kg/m2

AIMS/HYPOTHESIS

To aim of the study was to investigate the effect of bilio-pancreatic diversion (BPD) on type 2 diabetes in patients with BMI <35 kg/m(2).

METHODS

OGTTs were performed and anthropometric data were compared between five diabetes patients (BMI 27-33 kg/m(2)) following BPD and seven diabetes patients after a low-energy diet. Insulin secretion was computed by C-peptide deconvolution. A euglycaemic-hyperinsulinaemic clamp was performed only in the BPD group and the M value measured.

RESULTS

One month after BPD, fasting and 2 h post-OGTT glycaemia decreased from 15.22 +/- 3.22 to 6.22 +/- 0.51 mmol/l (p = 0.043), while insulin sensitivity increased significantly. No significant changes were observed in the low-energy diet group. Insulin secretion did not differ significantly after either intervention. Diabetes amelioration (change in HbA(1c) level) was observed up to 18 months after BPD without pharmacological therapy.

CONCLUSIONS/INTERPRETATION

BPD can achieve adequate control of type 2 diabetes also in patients with BMI <35 kg/m(2). The rapid postoperative remission of diabetes is primarily related to an improvement in insulin sensitivity.

Surgery for nonobese type 2 diabetic patients: an interventional study with duodenal-jejunal exclusion

BACKGROUND

A 24-week interventional prospective trial was performed to compare the benefits of open duodenal-jejunal exclusion surgery (GJB) with a matched control group on standard medical care.

METHODS

One-hundred eighty patients were screened for the surgical approach. Twelve patients accepted to be operated and presented the full eligibility criteria for surgery that includes overweight BMI (25-29.9 kg/m2), T2DM diagnosis for less than 15 years, insulin-treated patients, no history of major complications, preserved beta-cell function, and absence of autoimmunity. A matched control group (CG) of patients whom refused surgical treatment was placed to receive standard care. Patients had age of 50 (5) years, time of diagnosis 9 years (range, 3 to 15 years), time of insulin usage 6 months (range, 3 to 48 months), fasting glucose (FG), 9.8 (2.5) mg/dL, and glycated hemoglobin (A1C) 8.90 (2.12)%.

RESULTS

At 24 weeks after surgery, patients experienced greater reductions on FG (14% vs. 7% on CG), A1C (from 8.78 to 7.84 in GJB-p<0.01 and 8.93 to 8.71 in CG; p<0.05 between groups) and reductions on average daily insulin requirement (93% vs. 29%, p<0.01). Ten patients stopped insulin usage in GJB but they remain taking oral medications. No differences were observed in both groups regarding BMI, body distribution and composition, blood pressure, and lipids.

CONCLUSIONS

In conclusion, duodenal-jejunal exclusion was an effective treatment for nonobese T2DM subjects. GJB was superior to standard care in achieving better glycemic control along with reduction in insulin requirements.

Circadian rhythms of GIP and GLP1 in glucose-tolerant and in type 2 diabetic patients after biliopancreatic diversion

AIMS/HYPOTHESIS

We tested the hypothesis that the reversibility of insulin resistance and diabetes observed after biliopancreatic diversion (BPD) is related to changes in circadian rhythms of gastrointestinal hormones.

METHODS

Ten morbidly obese participants, five with normal glucose tolerance (NGT) and five with type 2 diabetes, were studied before and within 2 weeks after BPD. Within-day variations in glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide 1 (GLP1) levels were assessed using a single cosinor model. Insulin sensitivity was assessed by euglycaemic-hyperinsulinaemic clamp.

RESULTS

Basal GLP1 relative amplitude (amplitude/mesor x 100) was 25.82-4.06% in NGT; it increased to 41.38-4.32% after BPD but was unchanged in diabetic patients. GLP1 and GIP mesor were shifted in time after surgery in diabetic patients but not in NGT participants. After BPD, the GLP1 AUC significantly increased from 775 +/- 94 to 846 +/- 161 pmol l(-1) min in NGT, whereas GIP AUC decreased significantly from 1,373 +/- 565 to 513 +/- 186 pmol l(-1) min in diabetic patients. Two-way ANOVA showed a strong influence of BPD on both GIP (p = 0.010) and GLP1 AUCs (p = 0.033), which was potentiated by the presence of diabetes, particularly for GIP (BPD x diabetes, p = 0.003). Insulin sensitivity was markedly improved (p < 0.01) in NGT (from 9.14 +/- 3.63 to 36.04 +/- 8.55 micromol [kg fat-free mass](-1) min(-1)) and diabetic patients (from 9.49 +/- 3.56 to 38.57 +/- 4.62 micromol [kg fat-free mass](-1) min(-1)).

CONCLUSIONS/INTERPRETATION

An incretin circadian rhythm was shown for the first time in morbid obesity. The effect of BPD on the 24 h pattern of incretin differed between NGT and diabetic patients. GLP1 secretion impairment was reversed in NGT and could not be overcome by surgery in diabetes. On the other hand, GIP secretion was blunted after the operation only in diabetic patients, suggesting a role in insulin resistance and diabetes.

O-glycoside biomarker of apolipoprotein C3: responsiveness to obesity, bariatric surgery, and therapy with metformin, to chronic or severe liver disease and to mortality in severe sepsis and graft vs host disease

The glyco-isoforms of intact apolipoprotein C3 (ApoC3) were used to probe glycomic changes associated with obesity and recovery following bariatric surgery, liver diseases such as chronic hepatitis C (CHC) and alcoholic liver cirrhosis, as well as severe, multiorgan diseases such as sepsis and graft vs host disease (GVHD). ApoC3 glyco-isoform ratios responded to unique stimuli that did not correlate with serum lipids or with other blood components measured in either a control population or a group of extremely obese individuals. However, glyco-isoform ratios correlated with obesity with a 1.8-fold change among subjects eligible for bariatric surgery relative to a nonobese control population. Bariatric surgery resulted in rapid change of isoform distribution to that of nonobese individuals, after which the distribution was stable in each individual. Although multiple simultaneous factors complicated effector attribution, the isoform ratios of very obese individuals were nearly normal for diabetic individuals on metformin therapy. Glyco-isoform ratios were sensitive to liver diseases such as chronic hepatitis C and alcoholic liver cirrhosis. The correlation coefficient with fibrosis was superior to that of current assays of serum enzyme levels. Diseases of pregnancy that can result in liver damage, HELLP syndrome and pre-eclampsia, did not alter ApoC3 glyco-isoform ratios. Early after umbilical cord blood transplantation the isoform ratios changed and returned to normal in long-term survivors. Larger changes were observed in persons who died. GVHD had little effect. Persons with severe sepsis showed altered ratios. Similar cut-points for mortality (3.5-fold difference from controls) were found for UCBT and sepsis. Similar values characterized liver cirrhosis. Overall, while changes of glyco-isoform ratios occurred in many situations, individual stability of isoform distribution was evident and large changes were limited to high-level disease. If ratio changes associated with obesity are found to document a risk factor for long-term outcomes, the information provided by glyco-isoform ratio changes may provide important, novel information for diagnostic, prognostic and therapy response to metabolic conditions.

Metabolic surgery and gut hormones - a review of bariatric entero-humoral modulation

The global pandemic of obesity is increasing. Inappropriate food intake relative to energy expenditure results in increased adiposity. These factors are partly regulated by signals through the gut-brain and adipose-brain axes. Metabolic operations (otherwise known as Bariatric surgery) offer the most effective results for sustained metabolic improvement and weight loss. They modulate a number of gut hormones that constitute the gut-brain axis. This review summarizes the literature to-date reporting the gut hormone changes associated with these operations and their subsequent effects on appetite. Understanding the anatomical differences between each operation and how these can differentially regulate gut hormonal release can provide new treatments and targets for obesity, appetite and metabolic disorders.

Bariatric surgery in obesity: changes of glucose and lipid metabolism correlate with changes of fat mass

BACKGROUND AND AIM

Bariatric surgery induces significant weight loss and improves glucose metabolism in obese patients (BMI>35 kg/m(2)). Our aim was to compare restrictive (LAGB, laparoscopic gastric banding) and malabsorptive approaches (BIBP, biliary-intestinal bypass) on the loss of fat-free mass (FFM), fat mass (FM), and on changes of glucose and lipid metabolism.

METHODS AND RESULTS

Body composition (bio-impedance analysis, BIA), blood glucose (BG), insulin, triglycerides, total- and HDL-cholesterol, liver enzymes (AST and ALT) were measured at baseline and 1 year after surgery in patients undergoing LAGB, BIBP, and in diet-treated control patients. In the main study, with patients matched for initial BMI (43-55 kg/m(2), LAGB=24, BIBP=12, controls=6), decreases of BMI, FM, BG and cholesterol were greater in patients with BIBP than with LAGB (p<0.01), while decreases of FFM, insulin, HOMA-IR and triglycerides were similar. No effects on BMI, FM, FFM, BG, insulin, HOMA-IR or cholesterol were observed in the control patients. Decreases of BG, insulin, HOMA-IR, cholesterol and triglycerides correlated with FM but not with FFM decrease. Similar results were obtained in an additional study in patients with a different initial BMI (LAGB=25, BIBP=6, controls=24) and when considering all subjects together. A decrease of liver enzymes (ALT) was greater with LAGB than with BIBP, and HDL-cholesterol increased with LAGB and decreased with BIBP.

CONCLUSION

BMI, FM, BG and cholesterol decrease more with malabsorptive than with restrictive surgery, while FFM, insulin, HOMA-IR and triglycerides decrease in a similar way. FFM loss is of low entity. Changes of glucose and lipid metabolism are proportional to a decrease of fat mass but not of fat-free mass.

First-phase insulin secretion restoration and differential response to glucose load depending on the route of administration in type 2 diabetic subjects after bariatric surgery

OBJECTIVE

The purpose of this study was to elucidate the mechanisms of diabetes reversibility after malabsorptive bariatric surgery.

RESEARCH DESIGN AND METHODS

Peripheral insulin sensitivity and beta-cell function after either intravenous (IVGTT) or oral glucose tolerance (OGTT) tests and minimal model analysis were assessed in nine obese, type 2 diabetic subjects before and 1 month after biliopancreatic diversion and compared with those in six normal-weight control subjects. Insulin-dependent whole-body glucose disposal was measured by the euglycemic clamp, and glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) were also measured.

RESULTS

The first phase of insulin secretion after the IVGTT was fully normalized after the operation. The disposition index from OGTT data was increased about 10-fold and became similar to the values found in control subjects, and the disposition index from IVGTT data increased about 3.5-fold, similarly to what happened after the euglycemic clamp. The area under the curve (AUC) for GIP decreased about four times (from 3,000 +/- 816 to 577 +/- 155 pmol x l(-1) x min, P < 0.05). On the contrary, the AUC for GLP1 almost tripled (from 150.4 +/- 24.4 to 424.4 +/- 64.3 pmol x l(-1) . min, P < 0.001). No significant correlation was found between GIP or GLP1 percent changes and modification of the sensitivity indexes independently of the route of glucose administration.

CONCLUSIONS

Restoration of the first-phase insulin secretion and normalization of insulin sensitivity in type 2 diabetic subjects after malabsorptive bariatric surgery seem to be related to the reduction of the effect of some intestinal factor(s) resulting from intestinal bypass.

Do Incretins play a role in the remission of type 2 diabetes after gastric bypass surgery: What are the evidence?

Gastric bypass surgery (GBP), in addition to weight loss, results in dramatic remission of type 2 diabetes (T2DM). The mechanisms by which this remission occurs are unclear. Besides weight loss and caloric restriction, the changes in gut hormones that occur after GBP are increasingly gaining recognition as key players in glucose control. Incretins are gut peptides that stimulate insulin secretion postprandially; the levels of these hormones, particularly glucagon-like peptide-1, increase after GBP in response to nutrient stimulation. Whether these changes are causal to changes in glucose homeostasis remain to be determined. The purpose of this review is to assess the evidence on incretin changes and T2DM remission after GBP, and the possible mechanisms by which these changes occur. Our goals are to provide a thorough update on this field of research so that recommendations for future research and criteria for bariatric surgery can be evaluated.

Role of the incretin system in the remission of type 2 diabetes following bariatric surgery

AIMS

It has been observed, as a collateral outcome of bariatric surgery, that morbidly obese patients with frank type 2 diabetes mellitus or impaired glucose tolerance undergone Roux-en-Y Gastric Bypass (RYGB) or bilio-pancreatic diversion (BPD) became and remained euglycemic since surgery. But, most interestingly, the conversion to euglycemia happened within few days from the operation, long before a significant weight loss could intervene. The purpose of this viewpoint is to try to elucidate the mechanisms involved in the resolution/remission of diabetes after bariatric surgery, in particular highlighting the role played by the modifications in incretin secretion.

DATA SYNTHESIS

The effect of purely restrictive procedures in improving glucose control is directly proportional to the degree of weight loss. In contrast, either RYGB or BPD, the first a mainly restrictive and the second a quite purely malabsorptive bariatric technique, operate through a different mechanism, as a probable consequence of the small intestine bypass. The bypass of different intestinal portions covers a central role in the mechanisms of action of these two surgical procedures. In fact, while RYGB does not affect insulin resistance but increases insulin secretion via the stimulation of nutrient-mediated incretin secretion, BPD induces a full normalization of insulin resistance and, consequently, a significant reduction of insulin secretion. The insulin resistance reversion is only partially explained by the incretin level changes after BPD.

CONCLUSION

A role of incretins in type 2 diabetes improvement or resolution is ascertained although it is possible that other, not yet identified, hormone(s) can cooperate with them.

Pathogenesis of type 2 diabetes: tracing the reverse route from cure to cause

The metabolic abnormalities of type 2 diabetes can be reversed reproducibly by bariatric surgery. By quantifying the major pathophysiological abnormalities in insulin secretion and insulin action after surgery, the sequence of events leading to restoration of normal metabolism can be defined. Liver fat levels fall within days and normal hepatic insulin sensitivity is restored. Simultaneously, plasma glucose levels return towards normal. Insulin sensitivity of muscle remains abnormal, at least over the weeks and months after bariatric surgery. The effect of the surgery is explicable solely in terms of energy restriction. By combining this information with prospective observation of the changes immediately preceding the onset of type 2 diabetes, a clear picture emerges. Insulin resistance in muscle, caused by inherited and environmental factors, facilitates the development of fatty liver during positive energy balance. Once established, the increased insulin secretion required to maintain plasma glucose levels will further increase liver fat deposition. Fatty liver causes resistance to insulin suppression of hepatic glucose output as well as raised plasma triacylglycerol. Exposure of beta cells to increased levels of fatty acids, derived from circulating and locally deposited triacylglycerol, suppresses glucose-mediated insulin secretion. This is reversible initially, but eventually becomes permanent. The essential time sequence of the pathogenesis of type 2 diabetes is now evident. Muscle insulin resistance determines the rate at which fatty liver progresses, and ectopic fat deposition in liver and islet underlies the related dynamic defects of hepatic insulin resistance and beta cell dysfunction. These defects are capable of dramatic reversal under hypoenergetic feeding conditions, completely in early diabetes and to a worthwhile extent in more established disease.

Papel da cirurgia bariátrica no controle do diabete melito tipo II

RACIONAL: Sabe-se que hoje um dos grandes problemas de saúde pública refere-se a diabete melito com projeção de atingir 366 milhões de pacientes até 2030, entre indivíduos insulino (DM tipo I) e não-insulino (DM tipo II) dependentes. OBJETIVOS: Avaliar por meio de revisão ampla da literatura os resultados encontrados no controle do DM tipo II com diferentes modalidades de tratamento cirúrgico disponíveis em nosso meio. MÉTODO: A partir de 2004 foram levantados 73 trabalhos, sendo que destes 22 versavam especificamente sobre o tema nas bases de dados LiIacs, Medline, Pubmed cruzando os descritores diabete melito e cirurgia. RESULTADOS: Dentre as operações avaliadas obtiveram resultados satisfatórios em 98,9% a derivação biliopancreática ou duodenal, em 83,7% bypass gástrico, em 71,6% gastroplastia e em 47,9% bandas gástricas. Quanto às complicações, encontram-se descritas as mais diversas, desde as da ferida operatória até casos de insuficiência hepática aguda após cirurgia bariátrica que evoluíram com necessidade de transplante ou mesmo óbito, demonstrando que a decisão pelo tratamento operatório deve ser feita de maneira criteriosa ponderando-se o custo benefício. CONCLUSÃO: As técnicas cirúrgicas bariátricas, exercem melhora do diabete tipo II e as derivações biliopancreática, duodenal switch, Scopinaro e bypass gástrico com Y de Roux são as mais indicadas.

In morbid obesity, metabolic abnormalities and adhesion molecules correlate with visceral fat, not with subcutaneous fat: effect of weight loss through surgery

BACKGROUND

Decrease of both visceral fat (surgery, physical exercise) and subcutaneous fat (liposuction) is accompanied by improvement of insulin sensitivity.

METHODS

In this study, metabolic variables (glucose, insulin, high-density lipoprotein-cholesterol, triglycerides, aspartate aminotransferase, alanine aminotransferase, uric acid, ferritin) and adhesion molecules (ICAM-1, entothelin-1, E-selectin) were determined in 126 morbidly obese subjects before and 1 year after bariatric restrictive surgery (laparoscopic gastric banding) and correlated with anthropometric measures, i.e., body mass index (BMI) and waist circumference (waist), and with echographic measures of thickness of visceral (usVT) and subcutaneous (usST) abdominal fat.

RESULTS

Under basal conditions and after 1 year, metabolic variables correlated with BMI and waist (r from 0.157 to 0.507, p from 0.0182 to 0.0001) and with usVT (r from 0.211 to 0.512, p from 0.05 to 0.0001); insulin also correlated with usST, and adhesion molecules only correlated with BMI and usVT (r from 0.341 to 0.502, p from 0.0066 to 0.0001). Changes of metabolic variables correlated with changes of BMI and waist (r from 0.163 to 0.356, p from 0.0328 to 0.0001) and with usVT changes (r from 0.211 to 0.361, p from 0.0339 to 0.0002); changes of adhesion molecules only correlated with BMI and usVT changes (r from 0.227 to 0.361, p from 0.0444 to 0.0108). Changes of metabolic variables and of adhesion molecules virtually never correlated with changes of usST.

CONCLUSION

These data indicate that in morbid obesity, most metabolic abnormalities are associated with visceral fat and that their improvements after weight loss are associated with decrease of visceral fat.

Dorothy Hodgkin Lecture 2008. Gastric inhibitory polypeptide (GIP) revisited: a new therapeutic target for obesity-diabetes?

There is increasing realization that gastric inhibitory polypeptide (GIP) has actions outside of the pancreas and gastrointestinal tract. Most significant is the presence of functional GIP receptors on adipocytes and the appreciation that GIP, secreted strongly in response to fat ingestion, plays a role in the translation of excessive amounts of dietary fat into adipocyte tissue stores. Such effects open up the possibility of exploiting GIP receptor antagonism for the treatment of obesity and insulin resistance. This is borne out by studies in high-fat-fed mice or ob/ob mice with either genetic knockout of GIP receptor or chemical ablation of GIP action using the GIP receptor antagonist, (Pro3)GIP. By causing preferential oxidation of fat, blockade of GIP signalling clears triglyceride deposits from liver and muscle, thereby respectively restoring mechanisms for suppression of hepatic glucose output and cellular glucose uptake. Further studies are needed to determine the applicability of this research to human obesity-diabetes. However, proof of concept is provided by emerging evidence that rapid cure of diabetes in grossly obese subjects undergoing Roux-en-Y bypass surgery is mediated in part by surgical bypass of GIP-secreting K-cells in the upper small intestine.

Twenty-four hour insulin secretion and beta cell NEFA oxidation in type 2 diabetic, morbidly obese patients before and after bariatric surgery

AIMS/HYPOTHESIS

We have previously demonstrated that type 2 diabetes resolves after bariatric surgery. To study the role of NEFA in the prompt normalisation of beta cell glucose sensitivity, insulin secretion and beta cell glucose and lipid metabolism were investigated by a model of nutrient-stimulated insulin secretion using a multiple-meal test.

METHODS

Hourly glucose, C-peptide and NEFA were measured in nine morbidly obese, type 2 diabetic patients before and 1 week after bariatric surgery and in six matched healthy volunteers over 24 h. A mathematical model of glucose-NEFA comodulation of insulin secretion rate (ISR) was used to compute ISR and beta-oxidation. Insulin sensitivity was measured by an OGTT minimal model.

RESULTS

Beta cell sensitivity to glucose and NEFA was doubled after surgery, while the 24 h insulin secretion decreased from 277.1 +/- 144.4 to 198.0 +/- 107.6 nmol/m(2) (p < 0.02). Insulin sensitivity was restored. The beta-oxidation rate of beta cells was completely normalised (from 0.032 +/- 0.012 x 10(-12) to 0.103 +/- 0.031 x 10(-12) mmol/min per cell, p < 0.005). The best predictor of beta cell function improvement was the duration of diabetes.

CONCLUSIONS/INTERPRETATION

Bariatric surgery in type 2 diabetes restores beta-oxidation in beta cells, doubles glucose-NEFA sensitivity and reverses diabetes. It is likely that ISR is reduced to match insulin-sensitivity normalisation, in spite of no significant reduction in NEFA levels. We hypothesise that insulin sensitivity normalisation might appear as a consequence of nutrient exclusion from proximal intestinal transit, and that secondarily the need for insulin secretion diminishes. The insulin sensitivity increase is much higher than usually obtained by insulin-sensitising agents and is independent of weight changes.

A comparison of a personal series of biliopancreatic diversion and literature data on gastric bypass help to explain the mechanisms of resolution of type 2 diabetes by the two operations

BACKGROUND

Roux-en-Y gastric bypass (RYGBP) and biliopancreatic diversion (BPD) are highly beneficial operations for type 2 diabetes mellitus (T2DM) in obese patients, leading to complete T2DM resolution in 75-90 and 97-99% of cases, respectively. In both RYGBP and BPD, the foregut is excluded from the food stream and the distal small bowel receives the food stimulation, while following BPD fat intestinal absorption is also extremely limited. This study was carried out to identify clinical features that could give insight on the different mechanisms of action on diabetes resolution.

METHODS

The files of 443 severely obese patients with T2DM undergoing BPD from May 1976 to May 2007 were examined, and the presence of T2DM (fasting serum glucose >125 mg/ml) at 1-2 months, at 1 year, at 10 years, and at > or =20 years following the operation was recorded.

RESULTS

The percentage of patients cured (fasting serum glucose reduced to < or =110 mg/dl, on free diet and with no therapy) was 74% at 1 month, 97% at 1 and 10 years, and 91% at > or =20 years, the 26% of uncured patients at 1 month being those with most severe preoperative T2DM.

CONCLUSIONS

As the early results after BPD resemble those reported after RYGBP, it can be hypothesized that the duodenal exclusion and the distal small bowel stimulation are the first mechanisms acting in BPD, immediately after the operation, that only subsequently the myocellular fat depletion, which cannot be immediate, takes over, and that the minimal fat absorption is the mechanism accounting for the long-term results of BPD.

Lipid mobilization following Roux-en-Y gastric bypass examined by magnetic resonance imaging and spectroscopy

BACKGROUND

Recent developments of magnetic resonance imaging (MRI) and spectroscopy have made it possible to quantify lipid deposited in different tissues. To what extent an improvement of glucose tolerance shortly after Roux-en-Y gastric bypass surgery (RYGBP) is reflected in lipid levels in liver and skeletal muscle, markers of insulin resistance, has not been clarified.

METHODS

Whole-body MRI and MR spectroscopy (MRS) of liver and muscle and measurements of biochemical markers of glucose and lipid metabolism were performed at baseline and 1, 6, and 12 months following surgery in seven morbidly obese women. Volumes of adipose tissue depots and liver and muscle lipids were assessed from the MRI/MRS data.

RESULTS

At 1 month postoperatively, body mass index and visceral and subcutaneous adipose tissues were reduced by 9%, 26%, and 10%, respectively, whereas no reductions in intrahepatocellular or skeletal intramyocellular lipid concentrations were found. Free fatty acid and beta-hydroxybutyrate levels were elevated two- and sixfold, respectively; glucose and insulin levels were lowered, indicating increased insulin sensitivity. Further weight loss up to 1 year was associated with reductions in all investigated lipid depots investigated, with the exception of the intramyocellular compartment.

CONCLUSION

RYGBP causes rapid lipid mobilization from visceral and subcutaneous adipose depots and enhanced free fatty acid flux to the liver. An exceptional disconnection between liver fat and insulin sensitivity occurs in the early dynamic phase after surgery. However, in the late phase, the energy restriction imposed by the surgical procedure also reduces the liver lipids, but not the intramyocellular lipids.

Hypoadiponectinemia as a marker of adipocyte dysfunction--part II: the functional significance of low adiponectin secretion

Low adiponectin expression is common in obesity and is tightly linked to insulin resistance and fat mass expansion. Whereas normal adipocytes offer effective metabolic buffering through well-controlled release and uptake of free fatty acids on demand, adipocyte expansion induced by caloric excess and modulated by genetic, regional, and systemic factors elicits major unfavorable changes in fat cell phenotypes. Large, dysfunctional adipocytes show increased lipolysis and enhanced expression and secretion of proinflammatory and pro-oxidative cytokines. Low adiponectin secretion is a hallmark of impaired adipocyte function; its secretion is inhibited by cytokines such as tumor necrosis factor alpha, interleukin 6 and plasminogen activator inhibitor 1 and by high oxidative stress induced by increased fatty acids that activate nicotinamide adenine dinucleotide phosphate-oxidase. The ensuing hypoadiponectinemia may aggravate insulin resistance and facilitate the evolution of type 2 diabetes. Only massive weight loss allows true and sustained recovery of normal fat cell function as reflected by adiponectin secretion.

Short-term overfeeding induces insulin resistance in weight-stable patients after bariatric surgery

BACKGROUND

Short time overfeeding of rats rapidly leads to insulin resistance (IR). A study with healthy human volunteers, which we suggest are less susceptible for developing IR after short time overfeeding, did not show these effects on IR. Therefore a study population of weight-stable, former morbidly obese subjects (BMI 31.3 kg/m2), which were treated with bariatric surgery approximately 3 years ago was selected.

METHODS

Eleven subjects were submitted to a 7-day overfeeding study, resulting in a 53% increase in caloric intake (1,227 +/- 394.4 to 1,879.2 +/- 298.4 kcal/day). During normal diet and after overfeeding, insulin sensitivity was measured using steady state plasma glucose (SSPG) levels. At these time points, BMI and waist/hip ratio together with plasma levels of inflammatory markers (CRP, AGP, LBP, and TNF-alpha receptors) and plasma leptin values were also measured.

RESULTS

SSPG levels after overfeeding increased from 8.2 +/- 3.2 to 10.6 +/- 2.6 mmol/l (P < 0.05), indicating decreased insulin sensitivity after overfeeding. Fasting plasma insulin, glucose, circulating levels of inflammatory markers, BMI, and waist/hip ratio remained unchanged.

CONCLUSIONS

This study shows that overfeeding in a group of weight-stable, former morbidly obese subjects 3 years after bariatric surgery results in decreased insulin sensitivity. The mechanisms behind decreased insulin sensitivity induced by overfeeding are poorly understood, but the present results reveal that a unique human model is available to study these mechanisms, leading to a better understanding of the pathophysiology of IR.

Does biliopancreatic diversion carry increased risk for colorectal cancer? A cohort study

BACKGROUND

Because of the rearrangement of the gastrointestinal tract, biliopancreatic diversion (BPD) could lead to an increased risk of colorectal cancer caused by possible carcinogenetic action of the unabsorbed food and bile acid on colonic mucosa.

METHODS

The incidence of colorectal cancer in 1,898 obese subjects submitted to BPD from May 76 to July 2002 with a minimum follow-up of 5 years was retrospectively evaluated.

RESULTS

Among 28,811 person-years, seven cases of colorectal cancer were detected, for an overall incidence of 29.4 per 100,000, which is not different from that observed in the general Italian population, and lower than that reported for obese and type 2 diabetes patients. Logistic regression model suggests that occurrence of colorectal cancer is positively related to the time elapsed from BPD.

CONCLUSION

This study indicates that BPD does not carry any increased risk for colorectal cancer. The complete postoperative restoration of insulin sensibility could exert a valuable protective action.

Restoration of acute insulin response in T2DM subjects 1 month after biliopancreatic diversion

OBJECTIVE

Biliopancreatic diversion (BPD) restores normal glucose tolerance in a few weeks in morbid obese subjects with type 2 diabetes, improving insulin sensitivity. However, there is less known about the effects of BPD on insulin secretion. We tested the early effects of BPD on insulin secretion in obese subjects with and without type 2 diabetes.

METHODS AND PROCEDURES

Twenty-one consecutive morbid obese subjects, 9 with type 2 diabetes (T2DM) and 12 with normal fasting glucose (NFG) were evaluated, just before and 1 month after BPD, by measuring body weight (BW), glucose, adipocitokines, homeostasis model assessment of insulin resistance (HOMA-IR), acute insulin response (AIR) to e.v. glucose and the insulinogenic index adjusted for insulin resistance ([DeltaI5/DeltaG5]/HOMA-IR).

RESULTS

Preoperatively, those with T2DM differed from those with NFG in showing higher levels of fasting glucose, reduced AIR (57.9 +/- 29.5 vs. 644.9 +/- 143.1 pmol/l, P < 0.01) and reduced adjusted insulinogenic index (1.0 +/- 0.5 vs. 17.6 +/- 3.9 1/mmol(2), P < 0.001). One month following BPD, in both groups BW was reduced (by approximately 11%), but all subjects were still severely obese; HOMA-IR and leptin decreased significanlty, while high-molecular weight (HMW) adiponectin and adjusted insulinogenic index increased. In the T2DM group, fasting glucose returned to non-diabetic values. AIR did not change in the NFG group, while in the T2DM group it showed a significant increase (from 58.0 +/- 29.5 to 273.8 +/- 47.2 pmol/l, P < 0.01). In the T2DM group, the AIR percentage variation from baseline was significantly related to changes in fasting glucose (r = 0.70, P = 0.02), suggesting an important relationship exists between impaired AIR and hyperglycaemia.

DISCUSSION

BPD is able to restore AIR in T2DM even just 1 month after surgery. AIR restoration is associated with normalization of fasting glucose concentrations.

GIP receptor antagonism reverses obesity, insulin resistance, and associated metabolic disturbances induced in mice by prolonged consumption of high-fat diet

The gut hormone gastric inhibitory polypeptide (GIP) plays a key role in glucose homeostasis and lipid metabolism. This study investigated the effects of administration of a stable and specific GIP receptor antagonist, (Pro(3))GIP, in mice previously fed a high-fat diet for 160 days to induce obesity and related diabetes. Daily intraperitoneal injection of (Pro(3))GIP over 50 days significantly decreased body weight compared with saline-treated controls, with a modest increase in locomotor activity but no change of high-fat diet intake. Plasma glucose, glycated hemoglobin, and pancreatic insulin were restored to levels of chow-fed mice, and circulating triglyceride and cholesterol were significantly decreased. (Pro(3))GIP treatment also significantly decreased circulating glucagon and corticosterone, but concentrations of GLP-1, GIP, resistin, and adiponectin were unchanged. Adipose tissue mass, adipocyte hypertrophy, and deposition of triglyceride in liver and muscle were significantly decreased. These changes were accompanied by significant improvement of insulin sensitivity, meal tolerance, and normalization of glucose tolerance in (Pro(3))GIP-treated high-fat-fed mice. (Pro(3))GIP concentrations peaked rapidly and remained elevated 24 h after injection. These data indicate that GIP receptor antagonism using (Pro(3))GIP provides an effective means of countering obesity and related diabetes induced by consumption of a high-fat, energy-rich diet.

Incretin hormone mimetics and analogues in diabetes therapeutics

The incretin hormones glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) are physiological gut peptides with insulin-releasing and extrapancreatic glucoregulatory actions. Incretin analogues/mimetics activate GLP-1 or GIP receptors whilst avoiding physiological inactivation by dipeptidyl peptidase 4 (DPP-4), and they represent one of the newest classes of antidiabetic drug. The first clinically approved GLP-1 mimetic for the treatment of type-2 diabetes is exenatide (Byetta/exendin) which is administered subcutaneously twice daily. Clinical trials of liraglutide, a GLP-1 analogue suitable for once-daily administration, are ongoing. A number of other incretin molecules are at earlier stages of development. This review discusses the various attributes of GLP-1 and GIP for diabetes treatment and summarises current clinical data. Additionally, it explores the therapeutic possibilities offered by preclinical agents, such as non-peptide GLP-1 mimetics, GLP-1/glucagon hybrid peptides, and specific GIP receptor antagonists.

Metabolic and nutritional status changes after 10% weight loss in severely obese patients treated with laparoscopic surgery vs integrated medical treatment

BACKGROUND

Bariatric surgery is considered the most effective treatment for reducing excess body weight and maintaining weight loss (WL) in severely obese patients. There are limited data evaluating metabolic and body composition changes after different treatments in type III obese (body mass index [BMI] > 40 kg/m(2)).

METHODS

Twenty patients (9 males, 11 females; 37.6 +/- 8 years; BMI = 50.1 +/- 8 kg/m(2)) treated with dietary therapy and lifestyle correction (group 1) have been compared with 20 matched patients (41.8 +/- 6 years; BMI = 50.4 +/- 6 kg/m(2)) treated with laparoscopic gastric bypass (LGBP; group 2). Patients have been evaluated before treatment and after >10% WL obtained on average 6 weeks after LGBP and 30 weeks after integrated medical treatment. Metabolic syndrome (MS) was evaluated using the Adult Treatment Panel III/America Heart Association (ATP III/AHA) criteria. Resting metabolic rate (RMR) and respiratory quotient (RQ) was assessed with indirect calorimetry; body composition with bioimpedance analysis.

RESULTS

At entry, RMR/fat-free mass (FFM) was 34.2 +/- 7 kcal/24 h.kg in group 1 and 35.1 +/- 8 kcal/24 h.kg in group 2 and did not decrease in both groups after 10% WL (31.8 +/- 6 vs 34.0 +/- 6). Percent FFM and fat mass (FM) was 50.7 +/- 7% and 49.3 +/- 7% in group 1 and 52.1 +/- 6% and 47.9 +/- 6% in group 2, respectively (p = n.s.). After WL, body composition significantly changed only in group 1 (% FFM increased to 55.9 +/- 6 and % FM decreased to 44.1 +/- 6; p = 0.002).

CONCLUSION

After >10% WL, MS prevalence decreases precociously in surgically treated patients; some improvements in body composition are observed in nonsurgically treated patients only. Further investigations are needed to evaluate long-term effects of bariatric surgery on body composition and RMR after stable WL.

The physiology of glucagon-like peptide 1

Glucagon-like peptide 1 (GLP-1) is a 30-amino acid peptide hormone produced in the intestinal epithelial endocrine L-cells by differential processing of proglucagon, the gene which is expressed in these cells. The current knowledge regarding regulation of proglucagon gene expression in the gut and in the brain and mechanisms responsible for the posttranslational processing are reviewed. GLP-1 is released in response to meal intake, and the stimuli and molecular mechanisms involved are discussed. GLP-1 is extremely rapidly metabolized and inactivated by the enzyme dipeptidyl peptidase IV even before the hormone has left the gut, raising the possibility that the actions of GLP-1 are transmitted via sensory neurons in the intestine and the liver expressing the GLP-1 receptor. Because of this, it is important to distinguish between measurements of the intact hormone (responsible for endocrine actions) or the sum of the intact hormone and its metabolites, reflecting the total L-cell secretion and therefore also the possible neural actions. The main actions of GLP-1 are to stimulate insulin secretion (i.e., to act as an incretin hormone) and to inhibit glucagon secretion, thereby contributing to limit postprandial glucose excursions. It also inhibits gastrointestinal motility and secretion and thus acts as an enterogastrone and part of the "ileal brake" mechanism. GLP-1 also appears to be a physiological regulator of appetite and food intake. Because of these actions, GLP-1 or GLP-1 receptor agonists are currently being evaluated for the therapy of type 2 diabetes. Decreased secretion of GLP-1 may contribute to the development of obesity, and exaggerated secretion may be responsible for postprandial reactive hypoglycemia.

Exaggerated glucagon-like peptide-1 and blunted glucose-dependent insulinotropic peptide secretion are associated with Roux-en-Y gastric bypass but not adjustable gastric banding

BACKGROUND

The aim of this study was to measure the circulating levels of glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic peptide (GIP), and glucagon in patients who had undergone adjustable gastric banding (BND) or Roux-en-Y gastric bypass (RYGB) to understand the differences in glucose and insulin regulation after these procedures.

METHODS

This was a cross-sectional study of 3 groups of women matched for age and body mass index: group 1, overweight controls (n = 13); group 2, BND (n = 10); and group 3, RYGB (n = 13). Venous blood was drawn with the patient in the fasted state and throughout a 3-hour period after a liquid meal.

RESULTS

The fasting glucose level was similar between the 2 surgery groups; however, the fasting insulin concentrations were greater in the BND (10.0 microU/mL) than in the RYGB (6.2 microU/mL; P <0.05) group. The glucose level at 60 minutes was significantly lower in the RYGB group (70 mg/dL, range 38-82) than in the BND group (83 mg/dL, range 63-98). The GLP-1 levels at 30 minutes were more than threefold greater in the RYGB group (96 pmol/L) compared with the BND and overweight control (28 pmol/L) groups. The GLP-1 and insulin concentrations correlated at 30 minutes only in the RYGB group (r = .66; P = .013). The glucose-dependent insulinotropic peptide levels at 30 minutes were lower in the RYGB group (20 pmol/L) than in the BND group (31 pmol/L) or overweight control group (33 pmol/L). The peak glucagon levels were similar among the 3 groups.

CONCLUSION

Exaggerated postprandial GLP-1 and blunted glucose-dependent insulinotropic peptide secretion after RYGB might contribute to the greater weight loss and improved glucose homeostasis compared with BND.

Chemical gastric inhibitory polypeptide receptor antagonism protects against obesity, insulin resistance, glucose intolerance and associated disturbances in mice fed high-fat and cafeteria diets

AIMS/HYPOTHESIS

Gastric inhibitory polypeptide (GIP) receptor antagonism with (Pro(3))GIP improves glucose tolerance and ameliorates insulin resistance and abnormalities of islet structure/function in ob/ob mice. This study examined the ability of (Pro(3))GIP to counter the development of obesity, insulin resistance and diabetes in mice fed high-fat and cafeteria diets.

MATERIALS AND METHODS

Young Swiss TO mice on standard chow or high-fat, cafeteria or high-carbohydrate diets received daily injections of either saline or (Pro(3))GIP (25 nmol kg(-1)day(-1)) over 16 weeks. Food intake, body weight, and circulating glucose and insulin were measured frequently. At 16 weeks, glucose tolerance, insulin sensitivity, HbA(1c), circulating hormones and plasma lipids were assessed. Adipose tissue, liver and muscle were excised and weighed, and their histology and triacylglycerol content were further examined.

RESULTS

(Pro(3))GIP significantly reduced body weight, enhanced locomotor activity, and improved HbA(1c), glucose tolerance, beta cell responsiveness and insulin sensitivity in mice fed high-fat and cafeteria diets (p < 0.05 to p < 0.01). Similarly, (Pro(3))GIP significantly reduced plasma corticosterone and triacylglycerols (p < 0.05 to p < 0.001), while glucagon, resistin and adiponectin were unchanged. (Pro(3))GIP decreased adipose tissue mass (p < 0.01) and the triacylglycerol content of liver, muscle and adipose tissue (p < 0.01 to p < 0.001). Adipocyte size and liver morphology were partially normalised. (Pro(3))GIP did not significantly affect any of these parameters in mice fed a high-carbohydrate diet.

CONCLUSIONS/INTERPRETATION

(Pro(3))GIP protects against obesity, insulin resistance, glucose intolerance and associated disturbances in mice fed high-fat and cafeteria diets. This highlights chemical GIP receptor antagonism as a new possibility for the treatment of obesity and associated metabolic disturbances.