Portal Venous Metabolite Profiling After RYGB in Male Rats Highlights Changes in Gut-Liver Axis.

After Roux-en-Y gastric bypass (RYGB) surgery, the intestine undergoes structural and metabolic reprogramming and appears to enhance use of energetic fuels including glucose and amino acids (AAs), changes that may be related to the surgery's remarkable metabolic effects. Consistently, RYGB alters serum levels of AAs and other metabolites, perhaps reflecting mechanisms for metabolic improvement. To home in on the intestinal contribution, we performed metabolomic profiling in portal venous (PV) blood from lean, Long Evans rats after RYGB vs sham surgery. We found that one-carbon metabolism (OCM), nitrogen metabolism, and arginine and proline metabolism were significantly enriched in PV blood. Nitrogen, OCM, and sphingolipid metabolism as well as ubiquinone biosynthesis were also overrepresented among metabolites uniquely affected in PV vs peripheral blood in RYGB-operated but not sham-operated animals. Peripheral blood demonstrated changes in AA metabolism, OCM, sphingolipid metabolism, and glycerophospholipid metabolism. Despite enrichment for many of the same pathways, the overall metabolite fingerprint of the 2 compartments did not correlate, highlighting a unique role for PV metabolomic profiling as a window into gut metabolism. AA metabolism and OCM were enriched in peripheral blood both from humans and lean rats after RYGB, demonstrating that these conserved pathways might represent mechanisms for clinical improvement elicited by the surgery in patients. Together, our data provide novel insight into RYGB's effects on the gut-liver axis and highlight a role for OCM as a key metabolic pathway affected by RYGB.

Differential Metabolomic Signatures in Patients with Weight Regain and Sustained Weight Loss After Gastric Bypass Surgery: A Pilot Study.

BACKGROUND: While Roux-en-Y gastric bypass (RYGB) is one of the most effective and durable treatment options for obesity and its comorbidities, it is complicated by long-term weight regain in over 20% of patients. AIMS: We sought to determine the metabolite signatures of serum samples of patients with weight regain (RYGB-WR) after RYGB and features distinguishing these patients from patients with sustained weight loss (RYGB-SWL). METHODS: We prospectively analyzed serum samples from 21 RYGB-WR patients, 14 RYGB-SWL patients, and 11 unoperated controls. The main outcome measure was their serum metabolite profile. RESULTS: Weight regain after RYGB was associated with a unique serum metabolomic fingerprint. Most of the statistically different metabolites were involved in amino acid metabolism, one-carbon metabolism, and related nucleotide metabolism. A principal component analysis identified groups of metabolites that correlate with weight regain. Specifically, weight regain was associated with lower serum levels of metabolites related to the serine, glycine and threonine pathway, phenylalanine metabolism, tricyclic acid cycle, alanine and glutamate metabolism, and higher levels of other amino acids. CONCLUSIONS: Weight regain after RYGB is associated with unique serum metabolite signatures. Metabolite profiling may eventually help us to identify markers that could differentiate the patients who will regain weight versus those who will likely sustain weight loss.

Glycogen storage disease presenting as Cushing syndrome.

Impaired growth is common in patients with glycogen storage disease (GSD), who also may have "cherubic" facies similar to the "moon" facies of Cushing syndrome (CS). An infant presented with moon facies, growth failure, and obesity. Laboratory evaluation of the hypothalamic-pituitary-adrenal (HPA) axis was consistent with CS. He was subsequently found to have liver disease, hypoglycemia, and a pathogenic variant in PHKA2, leading to the diagnosis of GSD type IXa. The cushingoid appearance, poor linear growth and hypercortisolemia improved after treatment to prevent recurrent hypoglycemia. We suspect this child's HPA axis activation was "appropriate" and caused by chronic hypoglycemic stress, leading to increased glucocorticoid secretion that may have contributed to his poor growth and excessive weight gain. This is in contrast to typical CS, which is due to excessive adrenocorticotropic hormone (ACTH) or cortisol secretion from neoplastic pituitary or adrenal glands, ectopic secretion of ACTH or corticotropin-releasing hormone (CRH), or exogenous administration of corticosteroid or ACTH. Pseudo-CS is a third cause of excessive glucocorticoid secretion, has no HPA axis pathology, is most often associated with underlying psychiatric disorders or obesity in children and, by itself, is thought to be benign. We speculate that some diseases, including chronic hypoglycemic disorders such as the GSDs, may have biochemical features and pathologic consequences of CS. We propose that excessive glucocorticoid secretion due to chronic stress be termed "stress-induced Cushing (SIC) syndrome" to distinguish it from the other causes of CS and pseudo-CS, and that evaluation of children with chronic hypoglycemia and poor statural growth include evaluation for CS.

The Feasibility of Examining the Effects of Gastric Bypass Surgery on Intestinal Metabolism: Prospective, Longitudinal Mechanistic Clinical Trial.

BACKGROUND: Bariatric surgery, especially Roux-en-Y gastric bypass (RYGB), is the best treatment for severe obesity and its complications including type 2 diabetes mellitus (T2DM). Understanding the mechanisms responsible for the beneficial metabolic effects will help to engineer ways to improve the procedure or produce these effects without surgery. OBJECTIVE: The aim is to present data on recruitment and feasibility of a translational study designed to collect intestinal samples before and after bariatric surgery. The goal of biobanking is to allow future studies to test the hypothesis that the mechanism of action of RYGB involves specific changes in the postsurgical short- and long-term metabolism and morphology of the jejunum (Roux limb). Specifically, to test whether the intestine enhances its metabolism and activity after RYGB and increases its fuel utilization, we designed a prospective, longitudinal study, which involved the recruitment of candidates for RYGB with and without T2DM. We describe the tissue bank that we have generated, and our experience, hoping to further facilitate the performance of longitudinal mechanistic studies in human patients undergoing bariatric surgery and especially those involving post-RYGB intestinal biology. METHODS: We conducted a trial to characterize the effects of RYGB on intestinal metabolism. Intestinal tissue samples were collected from the jejunum at surgery, 1, 6, and 12 months postoperatively for the analysis of intestinal gene expression and metabolomic and morphologic changes. The target number of patients who completed at least the 6-month follow-up was 26, and we included a 20% attrition rate, increasing the total number to 32. RESULTS: To enroll 26 patients, we had to approach 79 potential participants. A total of 37 agreed to participate and started the study; 33, 30, and 26 active participants completed their 1-month, 6-month, and 12-month studies, respectively. Three participants withdrew, and 30 participants are still active. Altruism and interest in research were the most common reasons for participation. Important factors for feasibility and successful retention included (1) large volume case flow, (2) inclusion and exclusion criteria broad enough to capture a large segment of the patient population but narrow enough to ensure the completion of study aims and protection of safety concerns, (3) accurate assessment of willingness and motivation to participate in a study, (4) seamless integration of the recruitment process into normal clinical flow, (5) financial reimbursement and nonfinancial rewards and gestures of appreciation, and (6) nonburdensome follow-up visits and measures and reasonable time allotted. CONCLUSIONS: Human translational studies of the intestinal mechanisms of metabolic and weight changes after bariatric surgery are important and feasible. A tissue bank with unique samples has been established that could be used by investigators in many research fields, further enabling mechanistic studies on the effects of bariatric surgery. TRIAL REGISTRATION: ClinicalTrials.gov NCT02710370; https://clinicaltrials.gov/ct2/show/NCT02710370 (Archived by WebCite at http://www.webcitation.org/75HrQT8Dl).

Publisher Correction: Inactivating hepatic follistatin alleviates hyperglycemia.

In the version of this article originally published, the y axis labels in Fig. 4b,d were incorrect. In Fig. 4b, the unit on the label was (ng mg-1). This should have been (ng/ml). In Fig. 4d, the y axis label was Serum Fst (ng ml-1). It should have been Serum insulin (ng/ml). The errors have been corrected in the HTML and PDF versions of this article.

Inactivating hepatic follistatin alleviates hyperglycemia.

Unsuppressed hepatic glucose production (HGP) contributes substantially to glucose intolerance and diabetes, which can be modeled by the genetic inactivation of hepatic insulin receptor substrate 1 (Irs1) and Irs2 (LDKO mice). We previously showed that glucose intolerance in LDKO mice is resolved by hepatic inactivation of the transcription factor FoxO1 (that is, LTKO mice)-even though the liver remains insensitive to insulin. Here, we report that insulin sensitivity in the white adipose tissue of LDKO mice is also impaired but is restored in LTKO mice in conjunction with normal suppression of HGP by insulin. To establish the mechanism by which white adipose tissue insulin signaling and HGP was regulated by hepatic FoxO1, we identified putative hepatokines-including excess follistatin (Fst)-that were dysregulated in LDKO mice but normalized in LTKO mice. Knockdown of hepatic Fst in the LDKO mouse liver restored glucose tolerance, white adipose tissue insulin signaling and the suppression of HGP by insulin; however, the expression of Fst in the liver of healthy LTKO mice had the opposite effect. Of potential clinical significance, knockdown of Fst also improved glucose tolerance in high-fat-fed obese mice, and the level of serum Fst was reduced in parallel with glycated hemoglobin in obese individuals with diabetes who underwent therapeutic gastric bypass surgery. We conclude that Fst is a pathological hepatokine that might be targeted for diabetes therapy during hepatic insulin resistance.

A case report of methadone-associated hypoglycemia in an 11-month-old male.

BACKGROUND: Methadone is a synthetic µ-opioid receptor agonist that is used in the management of pain, neonatal abstinence withdrawal syndrome, and opioid dependence. Overdose can cause miosis, respiratory depression, and central nervous system depression. Rarely, hypoglycemia has been reported. We present the case of an 11-month-old male who developed hypoketotic, hyperinsulinemic, hypoglycemia after an acute, unintentional methadone exposure. CASE DETAILS: The patient was a previously healthy 11-month-old male who presented in respiratory failure. He was intubated and transferred to a large tertiary care center where his physical exam was notable for miosis. His labs were notable for a blood glucose of 17 mg/dL, an elevated insulin level, and suppressed serum beta-hydroxybutyrate. The patient was given a dextrose bolus with improvement in blood glucose. Administration of IV naloxone improved his miosis and mental status. A quantitative methadone level was sent upon arrival and was 123 ng/mL. Testing for ethanol, salicylates, sulfonylureas, and metabolic causes of hypoglycemia was negative. A fasting study showed euglycemia with suppression of insulin and appropriate ketosis. Case discussion: We present the case of an 11-month-old male who developed hypoketotic, hyperinsulinemic, hypoglycemia after an acute, unintentional methadone exposure. Alternative explanations for hypoketotic hypoglycemia were rule out. Methadone-induced hypoglycemia has been reported in cancer patients receiving methadone for pain, but a mechanism has not been identified. Based on this case, we believe that the patient's hypoglycemia was the result of methadone-induced insulin secretion. CONCLUSIONS: This case proposes that hyperinsulinism is the mechanism responsible for methadone-associated hypoglycemia. Methadone exposure should be included in the differential diagnosis of new onset hypoglycemia.

Advances in the surgical treatment of morbid obesity.

Due to the rapidly expanding prevalence of obesity, bariatric surgery is becoming an increasingly popular treatment option. Bariatric surgeries including Roux-en-Y gastric bypass (RYGB) and vertical sleeve gastrectomy (VSG) produce long-term weight loss and metabolic improvement, reducing mortality. This review discusses the important benefits and risks of RYGB and VSG, highlighting hypothesized mechanisms for these effects. We present data suggesting that VSG, albeit a newer procedure, may be as effective as RYGB with fewer adverse effects including less surgical risk, reduced nutritional deficiency, and less incidence of dumping syndrome. This may position VSG as an increasingly important procedure, particularly for the treatment of pediatric obesity.

All bariatric surgeries are not created equal: insights from mechanistic comparisons.

Despite considerable scientific progress on the biological systems that regulate energy balance, we have made precious little headway in providing new treatments to curb the obesity epidemic. Diet and exercise are the most popular treatment options for obesity, but rarely are they sufficient to produce long-term weight loss. Bariatric surgery, on the other hand, results in dramatic, sustained weight loss and for this reason has gained increasing popularity as a treatment modality for obesity. At least some surgical approaches also reduce obesity-related comorbidities including type 2 diabetes and hyperlipidemia. This success puts a premium on understanding how these surgeries exert their effects. This review focuses on the growing human and animal model literature addressing the underlying mechanisms. We compare three common procedures: Roux-en-Y Gastric Bypass (RYGB), vertical sleeve gastrectomy (VSG), and adjustable gastric banding (AGB). Although many would group together VSG and AGB as restrictive procedures of the stomach, VSG is more like RYGB than AGB in its effects on a host of endpoints including intake, food choice, glucose regulation, lipids and gut hormone secretion. Our strong belief is that to advance our understanding of these procedures, it is necessary to group bariatric procedures not on the basis of surgical similarity but rather on how they affect key physiological variables. This will allow for greater mechanistic insight into how bariatric surgery works, making it possible to help patients better choose the best possible procedure and to develop new therapeutic strategies that can help a larger portion of the obese population.

The anorectic effect of GLP-1 in rats is nutrient dependent.

GLP-1-induced insulin secretion from the ß-cell is dependent upon glucose availability. The purpose of the current study was to determine whether CNS GLP-1 signaling is also glucose-dependent. We found that fasting blunted the ability of 3(rd) cerebroventricularly (i3vt)-administered GLP-1 to reduce food intake. However, fasted animals maintained the anorexic response to melanotan II, a melanocortin receptor agonist, indicating a specific effect of fasting on GLP-1 action. We also found that i3vt administration of leptin, which is also decreased with fasting, was not able to potentiate GLP-1 action in fasted animals. However, we did find that CNS glucose sensing is important in GLP-1 action. Specifically, we found that i3vt injection of 2DG, a drug that blocks cellular glucose utilization, and AICAR which activates AMPK, both blocked GLP-1-induced reductions in food intake. To examine the role of glucokinase, an important CNS glucose sensor, we studied glucokinase-heterozygous knockout mice, but found that they responded normally to peripherally administered GLP-1 and exendin-4. Interestingly, oral, but not i3vt or IP glucose potentiated GLP-1's anorectic action. Thus, CNS and peripheral fuel sensing are both important in GLP-1-induced reductions in food intake.

Sleeve gastrectomy in rats improves postprandial lipid clearance by reducing intestinal triglyceride secretion.

BACKGROUND & AIMS: Postprandial hyperlipidemia is a risk factor for atherosclerotic heart disease and is associated with the consumption of high-fat diets and obesity. Bariatric surgeries result in superior and more durable weight loss than dieting. These surgeries are also associated with multiple metabolic improvements, including reduced plasma lipid levels. We investigated whether the beneficial effects of vertical sleeve gastrectomy (VSG) on plasma lipid levels are weight independent. METHODS: VSG was performed on Long-Evans rats with diet-induced obesity. Controls were sham-operated animals who were either pair-fed or ad libitum-fed. We measured fasting and postprandial levels of plasma lipid. To determine hepatic and intestinal triglyceride secretion, we injected the lipase inhibitor poloxamer 407 alone or before oral lipid gavage. (13)C-Triolein was used to estimate postprandial uptake of lipid in the intestine. RESULTS: Rats that received VSG and high-fat diets had markedly lower fasting levels of plasma triglyceride, cholesterol, and phospholipid than obese and lean (pair-fed) controls that were fed high-fat diets. Rats that received VSG had a marked, weight-independent reduction in secretion of intestinal triglycerides. VSG did not alter total intestinal triglyceride levels or size of the cholesterol storage pool nor did it affect the expression of genes in the intestine that control triglyceride metabolism and synthesis. VSG did not affect fasting secretion of triglyceride, liver weight, hepatic lipid storage, or transcription of genes that regulate hepatic lipid processing. CONCLUSIONS: VSG reduced postprandial levels of plasma lipid, independently of body weight. This resulted from reduced intestinal secretion of triglycerides following ingestion of a lipid meal and indicates that VSG has important effects on metabolism.

Weight-independent changes in blood glucose homeostasis after gastric bypass or vertical sleeve gastrectomy in rats.

BACKGROUND & AIMS: Roux-en-Y gastric bypass (RYGB) and vertical sleeve gastrectomy (VSG) reduce weight and improve glucose metabolism in obese patients, although it is not clear if metabolic changes are independent of weight loss. We investigated alterations in glucose metabolism in rats following RYGB or VSG. METHODS: Rats underwent RYGB or VSG and were compared to sham-operated rats fed ad lib or pair-fed to animals that received RYGB. Intraperitoneal glucose tolerance and insulin sensitivity tests were performed to assess glycemic function independent of incretin response. A hyperinsulinemic euglycemic clamp was used to compare tissue-specific changes in insulin sensitivity following each procedure. A mixed-meal tolerance test was used to assess the effect of each surgery on postprandial release of glucagon-like peptide 1 (GLP-1)(7-36) and glucose tolerance, and was also performed in rats given GLP-1 receptor antagonist exendin(9-39). RESULTS: Following RYGB or VSG, glucose tolerance and insulin sensitivity improved in proportion to weight loss. Hepatic insulin sensitivity was significantly better in rats that received RYGB or VSG compared with rats fed ad lib or pair-fed, whereas glucose clearance was similar in all groups. During the mixed-meal tolerance test, plasma levels of GLP-1(7-36) and insulin were greatly and comparably increased in rats that received RYGB and VSG compared with those that were pair-fed or fed ad lib. Administration of a GLP-1 receptor antagonist prevented improvements in glucose and insulin responses after a meal among rats that received RYGB or VSG. CONCLUSIONS: In obese rats, VSG is as effective as RYGB for increasing secretion of GLP-1 and insulin and improving hepatic sensitivity to insulin; these effects are independent of weight loss.

Similar effects of roux-en-Y gastric bypass and vertical sleeve gastrectomy on glucose regulation in rats.

Bariatric surgery is the most efficacious procedure for eliciting weight loss in humans, and many patients undergoing the procedure experience significant lessening of their symptoms of type-2 diabetes in addition to losing weight. We have adapted two bariatric surgical procedures commonly employed in humans to a rat model to begin to understand the mechanisms underlying the improvements in energy homeostasis. Young adult male rats received either roux-en-Y gastric bypass (RYGB) or vertical sleeve gastrectomy (VSG) and were assessed for body weight, food intake and parameters of glucose homeostasis over a 28-week period. Control rats received either a sham surgical procedure or else were unoperated. RYGB and VSG had comparable beneficial effects relative to controls. They ate less food and lost more weight, and they both had improved glucose parameters. The most intriguing aspect of the findings is that the two surgical procedures had such similar effects in spite of quite different rearrangements of the gastrointestinal system.

Molecular insights from bariatric surgery.

Bariatric surgical procedures have become important therapeutic options for treatment of morbid obesity in both adults and adolescents co-morbidities of obesity such as glucose intolerance, type 2 diabetes (T2DM), metabolic syndrome, steatohepatitis, hyperlipidemia and cardiovascular disease. These co-morbidities of obesity have significant impacts on the overall quality of life of the individual and our society at large. Roux-en-Y gastric bypass (RYGB) and the relatively newer procedures of gastric banding (GB) and vertical sleeve gastrectomy (VSG) have proven to be efficacious in achieving rapid weight loss and reversing the comorbidities of obesity. Unfortunately, bariatric procedures are not without risks including micronutrient deficiency, failure to maintain lost weight, and mortality. Further, the resolution of T2DM has long been understood to precede weight loss, and this finding provides important clues about the physiologic underpinnings of the observation. In order to design more effective, safe, and widely available therapeutics for obesity, important and highly relevant questions need to be addressed regarding mechanisms behind the weight-loss-independent benefits of bariatric surgical procedures. This review will provide an overview of the molecular changes occurring across all biological systems after bariatric surgery including the changes in hepatic, adipocyte and gut derived signals after surgery. We will also discuss existing literature regarding the weight-loss-independent metabolic benefits including improvement in insulin sensitivity and central nervous system integration of these signals.

Sleeve gastrectomy induces loss of weight and fat mass in obese rats, but does not affect leptin sensitivity.

BACKGROUND & AIMS: Surgical intervention produces sustainable weight loss and metabolic improvement in obese individuals. Vertical sleeve gastrectomy (VSG) produces dramatic, sustained weight loss; we investigated whether these changes result from improved sensitivity to leptin. METHODS: VSG was performed in Long-Evans rats with diet-induced obesity. Naïve or sham-operated rats, fed either ad libitum or pair-fed with the VSG group, were used as controls. Following surgery, body weights and food intake were monitored. We investigated energy expenditure, meal patterns, leptin sensitivity, and expression of pro-opiomelanocortin/agouti-related peptide/neuropeptide Y in the hypothalamus of the rats. RESULTS: We observed sustained losses in weight and body fat in male and female rats after VSG. Weight loss persisted after the disappearance of a transient, postsurgical food intake reduction. Resting energy expenditure was similar between control and VSG rats. VSG rats maintained their reduced body weights. However, they responded to a chronic food restriction challenge by overeating, which resulted in prerestriction, rather than pre-VSG, body weights. Consistent with lower adiposity, VSG decreased plasma leptin levels. Although VSG slightly improved leptin's anorectic action, the response was comparable to that observed in controls matched for adiposity by caloric restriction. Changes in hypothalamic neuropeptide expression were consistent with the lower body weight and lower leptin levels but cannot account for the sustained weight loss. CONCLUSIONS: VSG causes sustained reduction in body weight, which results from loss of fat mass. The maintenance of weight loss observed did not result from changes in sensitivity to leptin.