Splicing across adipocyte differentiation is highly dynamic and impacted by metabolic phenotype.

Adipose tissue dysfunction underlies many of the metabolic complications associated with obesity. A better understanding of the gene regulation differences present in metabolically unhealthy adipose tissue can provide insights into the mechanisms underlying adipose tissue dysfunction. Here, we used RNA-seq data collected from a differentiation time course of lean, obese, and obese with type 2 diabetes (T2D) individuals to characterize the role of alterative splicing in adipocyte differentiation and function. We found that splicing was highly dynamic across adipocyte differentiation in all three cohorts, and that the dynamics of splicing were significantly impacted by metabolic phenotype. We also found that there was very little overlap between genes that were differentially spliced in adipocyte differentiation and those that were differentially expressed, positioning alternative splicing as a largely independent gene regulatory mechanism whose impact would be missed when looking at gene expression changes alone. To assess the impact of alternative splicing across adipocyte differentiation on genetic risk for metabolic diseases, we integrated the differential splicing results generated here with genome-wide association study results for body mass index and T2D, and found that variants associated with T2D were enriched in regions that were differentially spliced in early differentiation. These findings provide insight into the role of alternative splicing in adipocyte differentiation and can serve as a resource to guide future variant-to-function studies.

Postprandial secretion of follistatin after gastric bypass surgery and sleeve gastrectomy.

Follistatin is secreted from the liver and may regulate muscle growth and insulin sensitivity. Protein intake stimulates follistatin secretion, which may be mediated by increased glucagon in the context of low insulin concentrations. We investigated circulating follistatin after mixed-meals in two cohorts of patients who were part of previously published studies and had undergone bariatric surgery with either simultaneous assessment of amino acid absorption or administration of the GLP-1 receptor antagonist exendin-(9-39), which increased glucagon concentrations and impaired insulin secretion. Study 1 comprised obese matched subjects with previous Roux-en-Y gastric bypass (RYGB) or sleeve gastrectomy (SG) surgery and unoperated controls who underwent 6-hour mixed-meal tests with intravenous and oral tracers including intrinsically labelled caseinate in the meal. Study 2 comprised obese subjects with previous RYGB who underwent two 5-hour mixed-meal tests with concomitant exendin-(9-39) or saline infusion. In study 1, the secretion of follistatin as well as the amino acid absorption was accelerated after RYGB compared with SG and controls, but the glucagon-to-C-peptide ratios did not differ between the groups. In study 2, exendin-(9-39) administration increased postprandial glucagon concentrations and lowered insulin secretion, whereas the concentration of follistatin was unchanged. In conclusion, postprandial follistatin secretion is accelerated in patients after RYGB which might be explained by an accelerated protein absorption rate rather than the glucagon-to-insulin ratio.

The Importance of Endogenously Secreted GLP-1 and GIP for Postprandial Glucose Tolerance and ß-Cell Function After Roux-en-Y Gastric Bypass and Sleeve Gastrectomy Surgery.

Enhanced secretion of glucagon-like peptide 1 (GLP-1) seems to be essential for improved postprandial ß-cell function after Roux-en-Y gastric bypass (RYGB) but is less studied after sleeve gastrectomy (SG). Moreover, the role of the other major incretin hormone, glucose-dependent insulinotropic polypeptide (GIP), is relatively unexplored after bariatric surgery. We studied the effects of separate and combined GLP-1 receptor (GLP-1R) and GIP receptor (GIPR) blockade during mixed-meal tests in unoperated (CON), SG-operated, and RYGB-operated people with no history of diabetes. Postprandial GLP-1 concentrations were highest after RYGB but also higher after SG compared with CON. In contrast, postprandial GIP concentrations were lowest after RYGB. The effect of GLP-1R versus GIPR blockade differed between groups. GLP-1R blockade reduced ß-cell glucose sensitivity and increased or tended to increase postprandial glucose responses in the surgical groups but had no effect in CON. GIPR blockade reduced ß-cell glucose sensitivity and increased or tended to increase postprandial glucose responses in the CON and SG groups but had no effect in the RYGB group. Our results support that GIP is the most important incretin hormone in unoperated people, whereas GLP-1 and GIP are equally important after SG, and GLP-1 is the most important incretin hormone after RYGB.

Effect of Meal Texture on Postprandial Glucose Excursions and Gut Hormones After Roux-en-Y Gastric Bypass and Sleeve Gastrectomy.

Background and aims: The metabolic consequences after Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG) are often studied using a liquid mixed meal. However, liquid meals may not be representative of the patients' everyday diet. We therefore examined postprandial glucose and gut hormone responses using mixed meals differing only with respect to meal texture. Methods: Twelve RYGB-operated, 12 SG-operated, and 12 unoperated individuals (controls) were enrolled in the study. Participants were matched on age, sex, and body mass index. In randomized order, each participant underwent a liquid and a solid 4-h mixed meal test on separate days. The meals were isocaloric (309 kcal), and with identical macronutrient composition (47 E% carbohydrate, 18 E% protein, 32 E% fat, and 3 E% dietary fibers). The liquid meal was blended to create a smooth liquid texture while the other meal retained its solid components. Results: Postprandial glucose concentrations (peak and incremental area under curve, iAUC) did not differ between the two meal textures in any group. In the control group, peak C-peptide was higher after the liquid meal compared with the solid meal (p = 0.04), whereas iAUCs of C-peptide were similar between the two meals in all groups. Peak of glucagon-like peptide-1 (GLP-1) was higher after the liquid meal compared with the solid meal in RYGB- and SG-operated individuals (RYGB p = 0.02; SG p < 0.01), but iAUC of GLP-1 did not differ between meal textures within any group. Peak of glucose-dependent insulin tropic polypeptide (GIP) was higher after the liquid meal in the SG and control groups (SG p = 0.02; controls p < 0.01), but iAUCs of GIP were equal between meals. There were no differences in total AUC of ghrelin between the liquid and solid meals within any of the groups. Conclusion: A liquid and a solid meal with identical macronutrient composition result in similar postprandial glucose responses, both in operated and unoperated individuals. Small differences were observed for the postprandial peaks of C-peptide, GLP-1, and GIP concentrations. Overall, a liquid meal is suitable for evaluating glucose tolerance, ß-cell function, and gut hormones responses, both after RYGB and SG and in unoperated individuals. Clinical Trial Registration: [www.clinicaltrials.gov], identifier [NCT04082923].

Influence of NAFLD and bariatric surgery on hepatic and adipose tissue mitochondrial biogenesis and respiration.

Impaired mitochondrial oxidative phosphorylation (OXPHOS) in liver tissue has been hypothesised to contribute to the development of nonalcoholic steatohepatitis in patients with nonalcoholic fatty liver disease (NAFLD). It is unknown whether OXPHOS capacities in human visceral (VAT) and subcutaneous adipose tissue (SAT) associate with NAFLD severity and how hepatic OXPHOS responds to improvement in NAFLD. In biopsies sampled from 62 patients with obesity undergoing bariatric surgery and nine control subjects without obesity we demonstrate that OXPHOS is reduced in VAT and SAT while increased in the liver in patients with obesity when compared with control subjects without obesity, but this was independent of NAFLD severity. In repeat liver biopsy sampling in 21 patients with obesity 12 months after bariatric surgery we found increased hepatic OXPHOS capacity and mitochondrial DNA/nuclear DNA content compared with baseline. In this work we show that obesity has an opposing association with mitochondrial respiration in adipose- and liver tissue with no overall association with NAFLD severity, however, bariatric surgery increases hepatic OXPHOS and mitochondrial biogenesis.

Roux-en-Y gastric bypass versus sleeve gastrectomy: nationwide data from the Danish quality registry for treatment of severe obesity.

BACKGROUND: Bariatric surgery as treatment of obesity is increasing worldwide. No guidelines exist on which type of bariatric procedure to choose for the individual patient. OBJECTIVES: This study aims to compare Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG) with respect to weight loss, complications, comorbidities, and quality of life. SETTING: A nationwide multi-center register-based cohort study. METHODS: We identified 16,053 patients treated by bariatric surgery from 2008 to 2021 (RYGB, n = 13,075; SG, n = 2978) from the Danish quality registry for treatment of severe obesity (DBSO). We calculated risk ratios (RRs) and prevalence ratios (PRs) comparing surgical complications, weight loss, and medical comorbidities by type of procedure up to 2 years after surgery. RESULTS: Patients treated with RYGB experienced a greater weight loss than patients treated by SG both after 1 year (PR, .53; 95% confidence interval [CI], .48-.58) and 2 years (PR, .46; 95% CI, .39-.54). Compared with RYGB, SG yielded a lower risk of readmission (RR, .71; 95% CI, .60-.85). Likewise, the risk of reoperation between 30 days and 1 year (RR, .40; 95% CI, .30-.53) and 1 and 5 years (RR, .15; 95% CI, .12-.20]) were lower following SG. At 1-year follow-up, 76% of patients treated with RYGB and 63% of patients treated with SG experienced diabetes remission. Ten percent and 61% of patients were lost to follow-up after 1 and 2 years, respectively. CONCLUSION: The DBSO is an important resource in studying treatment of severe obesity. Weight loss is slightly greater after RYGB than after SG, but RYGB is associated with more frequent readmissions and reoperations.

Neurotensin secretion after Roux-en-Y gastric bypass, sleeve gastrectomy, and truncal vagotomy with pyloroplasty.

OBJECTIVE: Neurotensin (NT) is released from enteroendocrine cells and lowers food intake in rodents. We evaluated postprandial NT secretion in humans after surgeries associated with accelerated small intestinal nutrient delivery, and after Roux-en-Y gastric bypass (RYGB) when glucagon-like peptide-1 (GLP-1) signalling and dipeptidyl peptidase 4 (DPP-4) were inhibited, and during pharmacological treatments influencing entero-pancreatic functions. METHODS: We measured NT concentrations in plasma from meal studies: (I) after truncal vagotomy with pyloroplasty (TVP), cardia resection +TVP (CTVP), and matched controls (n = 10); (II) after RYGB, sleeve gastrectomy (SG), and in matched controls (n = 12); (III) after RYGB (n = 11) with antagonism of GLP-1 signalling using exendin(9-39) and DPP-4 inhibition using sitagliptin; (IV) after RYGB (n = 11) during a run-in period and subsequent treatment with, sitagliptin, liraglutide (GLP-1 receptor agonist), verapamil (calcium antagonist), acarbose (alpha glucosidase inhibitor), and pasireotide (somatostatin analogue), respectively. RESULTS: (I) NT secretion was similar after TVP/CTVP (p = 0.9), but increased vs. controls (p < 0.0001). (II) NT secretion was increased after RYGB vs. SG and controls (p < 0.0001). NT responses were similar in SG and controls (p = 0.3), but early postprandial NT concentrations were higher after SG (p < 0.05). (III) Exendin (9-39) and sitagliptin did not change NT responses vs placebo (p > 0.2), but responses were lower during sitagliptin vs. exendin(9-39) (p = 0.03). (IV) Pasireotide suppressed NT secretion (p = 0.004). Sitagliptin tended to lower NT secretion (p = 0.08). Liraglutide, verapamil, and acarbose had no effect (p > 0.9). CONCLUSION: Neurotensin secretion is increased after surgeries associated with accelerated gastric emptying and lowered by pasireotide.

Plasma GDF15 levels are similar between subjects after bariatric surgery and matched controls and are unaffected by meals.

Growth differentiating factor 15 (GDF15) is expressed in the intestine and is one of the most recently identified satiety peptides. The mechanisms controlling its secretion are unclear. The present study investigated whether plasma GDF15 concentrations are meal-related and if potential responses depend on macronutrient type or are affected by previous bariatric surgery. The study included 1) volunteers ingesting rapidly vs. slowly digested carbohydrates (sucrose vs. isomaltose; n = 10), 2) volunteers who had undergone Roux-en-Y gastric bypass (RYGB) or sleeve gastrectomy (SG) surgery and unoperated matched controls ingesting a liquid mixed meal (n = 9-10 in each group), and 3) individuals with previous RYGB compared with unoperated controls ingesting isocaloric glucose, fat, or protein (n = 6 in each group). Plasma was collected after an overnight fast and up to 6 h after ingestion (≥12 time points). In cohort 1, fasting GDF15 concentrations were ∼480 pg/mL. Concentrations after sucrose or isomaltose intake did not differ from baseline (P = 0.26 to P > 0.99) and total area under the curves (tAUCs were similar between groups (P = 0.77). In cohort 2, fasting GDF15 concentrations were as follows (pg/mL): RYGB = 540 ± 41.4, SG = 477 ± 36.4, and controls = 590 ± 41.8, with no between-group differences (P = 0.73). Concentrations did not increase at any postprandial time point (over all time factor: P = 0.10) and tAUCs were similar between groups (P = 0.73). In cohort 3, fasting plasma GDF15 was similar among the groups (P > 0.99) and neither glucose, fat, nor protein intake consistently increased the concentrations. In conclusion, we find that plasma GDF15 was not stimulated by meal intake and that fasting concentrations did not differ between RYGB-, SG-, and body mass index (BMI)-matched controls when investigated during the weight stable phase after RYGB and SG.NEW & NOTEWORTHY Our combined data show that GDF15 does not increase in response to a liquid meal. Moreover, we show for the first time that ingestion of sucrose, isomaltose, glucose, fat, or protein also does not increase plasma GDF15 concentrations, questioning the role of GDF15 in regulation of food source preference. Finally, we find that neither fasting nor postprandial plasma GDF15 concentrations are increased in individuals with previous bariatric surgery compared with unoperated body mass index (BMI)-matched controls.

Effects of Manipulating Circulating Bile Acid Concentrations on Postprandial GLP-1 Secretion and Glucose Metabolism After Roux-en-Y Gastric Bypass.

Background: Altered bile acid (BA) turnover has been suggested to be involved in the improved glucose regulation after Roux-en-Y gastric bypass (RYGB), possibly via stimulation of GLP-1 secretion. We investigated the role of exogenous as well as endogenous BAs for GLP-1 secretion after RYGB by administering chenodeoxycholic acid (CDCA) and the BA sequestrant colesevelam (COL) both in the presence and the absence of a meal stimulus. Methods: Two single-blinded randomized cross-over studies were performed. In study 1, eight RYGB operated participants ingested 200 ml water with 1) CDCA 1.25 g or 2) CDCA 1.25 g + colesevelam 3.75 g on separate days. In study 2, twelve RYGB participants ingested on separate days a mixed meal with addition of 1) CDCA 1.25 g, 2) COL 3.75 g or 3) COL 3.75 g × 2, or 4) no additions. Results: In study 1, oral intake of CDCA increased circulating BAs, GLP-1, C-peptide, glucagon, and neurotensin. Addition of colesevelam reduced all responses. In study 2, addition of CDCA enhanced meal-induced increases in plasma GLP-1, glucagon and FGF-19 and lowered plasma glucose and C-peptide concentrations, while adding colesevelam lowered circulating BAs but did not affect meal-induced changes in plasma glucose or measured gastrointestinal hormones. Conclusion: In RYGB-operated persons, exogenous CDCA enhanced meal-stimulated GLP-1 and glucagon secretion but not insulin secretion, while the BA sequestrant colesevelam decreased CDCA-stimulated GLP-1 secretion but did not affect meal-stimulated GLP-1, C-peptide or glucagon secretion, or glucose tolerance. These findings suggest a limited role for endogenous bile acids in the acute regulation of postprandial gut hormone secretion or glucose metabolism after RYGB.

The effect of acute dual SGLT1/SGLT2 inhibition on incretin release and glucose metabolism after gastric bypass surgery.

Enhanced meal-related enteroendocrine secretion, particularly of glucagon-like peptide-1 (GLP-1), contributes to weight-loss and improved glycemia after Roux-en-Y gastric bypass (RYGB). Dietary glucose drives GLP-1 and glucose-dependent insulinotropic polypeptide (GIP) secretion postoperatively. Understanding how glucose triggers incretin secretion following RYGB could lead to new treatments of diabetes and obesity. In vitro, incretin release depends on glucose absorption via sodium-glucose cotransporter 1 (SGLT1). We investigated the importance of SGLT1/SGLT2 for enteropancreatic hormone concentrations and glucose metabolism after RYGB in a randomized, controlled, crossover study. Ten RYGB-operated patients ingested 50 g of oral glucose with and without acute pretreatment with 600 mg of the SGLT1/SGLT2-inhibitor canagliflozin. Paracetamol and 3-O-methyl-d-glucopyranose (3-OMG) were added to the glucose drink to evaluate rates of intestinal entry and absorption of glucose, respectively. Blood samples were collected for 4 h. The primary outcome was 4-h plasma GLP-1 (incremental area-under the curve, iAUC). Secondary outcomes included glucose, GIP, insulin, and glucagon. Canagliflozin delayed glucose absorption (time-to-peak 3-OMG: 50 vs. 132 min, P < 0.01) but did not reduce iAUC GLP-1 (6,067 vs. 7,273·min·pmol-1·L-1, P = 0.23), although peak GLP-1 concentrations were lowered (-28%, P = 0.03). Canagliflozin reduced GIP (iAUC -28%, P = 0.01; peak concentrations -57%, P < 0.01), insulin, and glucose excursions, whereas plasma glucagon (AUC 3,216 vs. 4,160 min·pmol·L-1, P = 0.02) and amino acids were increased. In conclusion, acute SGLT1/SGLT2-inhibition during glucose ingestion did not reduce 4-h plasma GLP-1 responses in RYGB-patients but attenuated the early rise in GLP-1, GIP, and insulin, whereas late glucagon concentrations were increased. The results suggest that SGLT1-mediated glucose absorption contributes to incretin hormone secretion after RYGB.

Responses of gut and pancreatic hormones, bile acids, and fibroblast growth factor-21 differ to glucose, protein, and fat ingestion after gastric bypass surgery.

Postprandial gut hormone responses change after Roux-en-Y gastric bypass (RYGB), and we investigated the impact of glucose, protein, and fat (with and without pancreas lipase inhibition) on plasma responses of gut and pancreas hormones, bile acids, and fibroblast growth factor 21 (FGF-21) after RYGB and in nonoperated control subjects. In a randomized, crossover study 10 RYGB operated and 8 healthy weight-matched control subjects were administered 4 different 4-h isocaloric (200 kcal) liquid meal tests containing >90 energy (E)% of either glucose, protein (whey protein), or fat (butter with and without orlistat). The primary outcome was glucagon-like peptide-1 (GLP-1) secretion (area under the curve above baseline). Secondary outcomes included responses of peptide YY (PYY), glucose-dependent insulinotropic polypeptide (GIP), cholecystokinin (CCK), glicentin, neurotensin, ghrelin, insulin, glucagon, bile acids, and FGF-21. In the RYGB group the responses of GLP-1, GIP, glicentin, FGF-21, and C-peptide were increased after glucose compared with the other meals. The neurotensin and bile acids responses were greater after fat, while the glucagon and CCK responses were greater after protein ingestion. Furthermore, compared with control subjects, RYGB subjects had greater responses of total PYY after glucose, glucagon after glucose and fat, glicentin after glucose and protein, and GLP-1 and neurotensin after all meals, while GIP and CCK responses were lower after fat. Ghrelin responses did not differ between meals or between groups. Orlistat reduced all hormone responses to fat ingestion, except for ghrelin in the RYGB group. In conclusion, after RYGB glucose is a more potent stimulator of most gut hormones, especially for the marked increased secretion of GLP-1 compared with fat and protein.NEW & NOTEWORTHY We investigated the impact of glucose, protein, and fat meals on intestinal and pancreatic hormones, bile acid, and fibroblast growth factor 21 (FGF-21) secretion in gastric bypass-operated patients compared with matched nonoperated individuals. The fat meal was administered with and without a pancreas lipase inhibitor. We found that the impact of the different meals on gut hormones, bile, and FGF 21 secretion differ and was different from the responses observed in nonoperated control subjects.

Intestinal sensing and handling of dietary lipids in gastric bypass-operated patients and matched controls.

BACKGROUND: Altered meal-related gut hormone secretion seems important for weight loss and diabetes remission after Roux-en-Y gastric bypass (RYGB). Elucidating the responsible meal components and receptors could aid discovery of new treatments of obesity and diabetes. Enteroendocrine cells respond to digestion products of dietary triacylglycerol, especially long-chain fatty acids (LCFAs) and 2-oleoyl-glycerol (2-OG), but not medium-chain fatty acids (MCFAs). OBJECTIVE: We examined the impact of olive oil (20 mL) and its derivates, LCFAs and 2-OG, on enteroendocrine secretions [glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP), cholecystokinin (CCK), peptide YY (PYY), and neurotensin (NT)] and on glucose, lipid, and bile acid metabolism in RYGB-operated and unoperated individuals. METHODS: In an exploratory randomized crossover design, 10 RYGB-operated patients and 10 matched controls ingested 3 equimolar triacylglycerol formulations on separate days: olive oil (digested to 2-OG + LCFAs), C8-dietary oil (2-OG + MCFAs), and tricaprylin (MCFAs; negative control). Hormone responses were calculated as area under the curve (AUC). RESULTS: Independent of group status, olive oil had greater effects than C8-dietary oil on AUCs of plasma GLP-1 (+32%; 95% CI: 23%, 43%; P < 0.01), CCK (+53%, P < 0.01), and NT (+71%, P < 0.01), whereas the effect on GIP differed between groups (+90% in controls, P < 0.01; +24% in RYGB, P = 0.10). Independent of group status, C8-dietary oil had greater effects than tricaprylin on AUCs of plasma CCK (+40%, P < 0.01) and NT (+32%, P < 0.01), but not GLP-1 (+5%; 95% CI: -2.9%, 13%; P = 0.22), whereas the effect on GIP again differed between groups (+78% in controls, P < 0.01; +39% in RYGB, P = 0.01). Distal (GLP-1/PYY/NT), but not proximal (CCK/GIP), enteroendocrine responses were generally greater in RYGB patients than in controls. CONCLUSIONS: The combination of LCFAs plus 2-OG was substantially more effective than 2-OG plus MCFAs in stimulating enteroendocrine secretion in RYGB-operated and matched control individuals. Distal lipid-induced gut hormone release was greater after RYGB.This trial was registered at clinicaltrials.gov as NCT03223389.

Sustained Improvements in Glucose Metabolism Late After Roux-En-Y Gastric Bypass Surgery in Patients with and Without Preoperative Diabetes.

To describe glucose metabolism in the late, weight stable phase after Roux-en-Y Gastric Bypass (RYGB) in patients with and without preoperative type 2 diabetes we invited 55 RYGB-operated persons from two existing cohorts to participate in a late follow-up study. 44 (24 with normal glucose tolerance (NGT)/20 with type 2 diabetes (T2D) before surgery) accepted the invitation (median follow-up 2.7 [Range 2.2-5.0 years]). Subjects were examined during an oral glucose stimulus and results compared to preoperative and 1-year (1 y) post RYGB results. Glucose tolerance, insulin resistance, beta-cell function and incretin hormone secretion were evaluated. 1 y weight loss was maintained late after surgery. Glycemic control, insulin resistance, beta-cell function and GLP-1 remained improved late after surgery in both groups. In NGT subjects, nadir glucose decreased 1 y after RYGB, but did not change further. In T2D patients, relative change in weight from 1 y to late after RYGB correlated with relative change in fasting glucose and HbA1c, whereas relative changes in glucose-stimulated insulin release correlated inversely with relative changes in postprandial glucose excursions. In NGT subjects, relative changes in postprandial nadir glucose correlated with changes in beta-cell glucose sensitivity. Thus, effects of RYGB on weight and glucose metabolism are maintained late after surgery in patients with and without preoperative T2D. Weight loss and improved beta-cell function both contribute to maintenance of long-term glycemic control in patients with type 2 diabetes, and increased glucose stimulated insulin secretion may contribute to postprandial hypoglycemia in NGT subjects.

Afadin is a scaffold protein repressing insulin action via HDAC6 in adipose tissue.

Insulin orchestrates metabolic homeostasis through a complex signaling network for which the precise mechanisms controlling its fine-tuning are not completely understood. Here, we report that Afadin, a scaffold protein, is phosphorylated on S1795 (S1718 in humans) in response to insulin in adipocytes, and this phosphorylation is impaired with obesity and insulin resistance. In turn, loss of Afadin enhances the response to insulin in adipose tissues via upregulation of the insulin receptor protein levels. This happens in a cell-autonomous and phosphorylation-dependent manner. Insulin-stimulated Afadin-S1795 phosphorylation modulates Afadin binding with interaction partners in adipocytes, among which HDAC6 preferentially interacts with phosphorylated Afadin and acts as a key intermediate to suppress insulin receptor protein levels. Adipose tissue-specific Afadin depletion protects against insulin resistance and improves glucose homeostasis in diet-induced obese mice, independently of adiposity. Altogether, we uncover a novel insulin-induced cellular feedback mechanism governed by the interaction of Afadin with HDAC6 to negatively control insulin action in adipocytes, which may offer new strategies to alleviate insulin resistance.

Postprandial Nutrient Handling and Gastrointestinal Hormone Secretion After Roux-en-Y Gastric Bypass vs Sleeve Gastrectomy.

BACKGROUND & AIMS: Sleeve gastrectomy (SG) and Roux-en-Y gastric bypass (RYGB) induce substantial weight loss and improve glycemic control in patients with type 2 diabetes, but it is not clear whether these occur via the same mechanisms. We compared absorption rates of glucose and protein, as well as profiles of gastro-entero-pancreatic hormones, in patients who had undergone SG or RYGB vs controls. METHODS: We performed a cross-sectional study of 12 patients who had undergone sleeve gastrectomy, 12 patients who had undergone RYGB, and 12 individuals who had undergone neither surgery (controls), all in Denmark. Study participants were matched for body mass index, age, sex, and postoperative weight loss, and all had stable weights. They received continuous infusions of stable isotopes of glucose, glycerol, phenylalanine, tyrosine, and urea before and during a mixed meal containing labeled glucose and intrinsically phenylalanine-labeled caseinate. Blood samples were collected for 6 hours, at 10- to 60-minute intervals, and analyzed. RESULTS: The systemic appearance of ingested glucose was faster after RYGB and SG vs controls; the peak glucose appearance rate was 64% higher after RYGB, and 23% higher after SG (both P < .05); the peak phenylalanine appearance rate from ingested casein was 118% higher after RYGB (P < .01), but similar between patients who had undergone SG and controls. Larger, but more transient increases in levels of plasma glucose and amino acids were accompanied by higher secretion of insulin, glucagon-like peptide 1, peptide YY, and cholecystokinin after RYGB, whereas levels of ghrelin were lower after SG, compared with RYGB and controls. Total 6-hour oral recovery of ingested glucose and protein was comparable among groups. CONCLUSIONS: Postprandial glucose and protein absorption and gastro-entero-pancreatic hormone secretions differ after SG and RYGB. RYGB was characterized by accelerated absorption of glucose and amino acids, whereas protein metabolism after SG did not differ significantly from controls, suggesting that different mechanisms explain improved glycemic control and weight loss after these surgical procedures. ClinicalTrials.gov ID NCT03046186.

Preadipocytes from obese humans with type 2 diabetes are epigenetically reprogrammed at genes controlling adipose tissue function.

BACKGROUND: Deterioration of the adipogenic potential of preadipocytes may contribute to adipose tissue dysfunction in obesity and type 2 diabetes (T2D). Here, we hypothesized that extracellular factors in obesity epigenetically reprogram adipogenesis potential and metabolic function of preadipocytes. METHODS: The transcriptomic profile of visceral adipose tissue preadipocytes collected from Lean, Obese and Obese with T2D was assessed throughout in vitro differentiation using RNA sequencing. Reduced Representation Bisulfite Sequencing was used to establish the genome-wide DNA methylation profile of human preadipocytes and 3T3-L1 preadipocytes treated by the inflammatory cytokine Tumour Necrosis Factor-α (TNF-α) or palmitate. RESULTS: While preadipocytes from all obese subjects (Obese+Obese T2D), compared to those of Lean, were transcriptionally different in response to differentiation in culture, preadipocytes from Obese T2D showed impaired insulin signalling and a further transcriptomic shift towards altered adipocyte function. Cultures with a lower expression magnitude of adipogenic genes throughout differentiation (PLIN1, CIDEC, FABP4, ADIPOQ, LPL, PDK4, APOE, LIPE, FABP3, LEP, RBP4 and CD36) were associated with DNA methylation remodelling at genes controlling insulin sensitivity and adipocytokine signalling pathways. Prior incubation of 3T3-L1 preadipocytes with TNF-α or palmitate markedly altered insulin responsiveness and metabolic function in the differentiated adipocytes, and remodelled DNA methylation and gene expression at specific genes, notably related to PPAR signalling. CONCLUSIONS: Our findings that preadipocytes retain the memory of the donor in culture and can be reprogrammed by extracellular factors support a mechanism by which adipocyte precursors are epigenetically reprogrammed in vivo. Epigenetic reprogramming of preadipocytes represents a mechanism by which metabolic function of visceral adipose tissue may be affected in the long term by past exposure to obesity- or T2D-specific factors.

Guanylin and uroguanylin mRNA expression is increased following Roux-en-Y gastric bypass, but guanylins do not play a significant role in body weight regulation and glycemic control.

AIM: To determine whether intestinal expression of guanylate cyclase activator 2A (GUCA2A) and guanylate cyclase activator 2B (GUCA2B) genes is regulated in obese humans following Roux-en-Y gastric bypass (RYGB), and to evaluate the corresponding guanylin (GN) and uroguanylin (UGN) peptides for potentially contributing to the beneficial metabolic effects of RYGB. METHODS: Enteroendocrine cells were harvested peri- and post-RYGB, and GUCA2A/GUCA2B mRNA expression was compared. GN, UGN and their prohormones (proGN, proUGN) were administered subcutaneously in normal-weight mice to evaluate effects on food intake and glucose regulation. The effect of pro-UGN or UGN overexpression, using adeno-associated virus (AAV) vectors, was assessed in diet-induced obese (DIO) mice. Intracerebroventricular administration of GN and UGN was performed in rats for assessment of putative centrally mediated effects on food intake. GN and UGN, as well as their prohormones, were evaluated for effects on glucose-stimulated insulin secretion (GSIS) in rat pancreatic islets and perfused rat pancreas. RESULTS: GUCA2A and GUCA2B mRNA expression was significantly upregulated in enteroendocrine cells after RYGB. Peripheral administration of guanylins or prohormones did not influence food intake, oral glucose tolerance, and GSIS. Central administration of GN and UGN did not affect food intake in rats. Chronic AVV-mediated overexpression of UGN and proUGN had no effect on body weight or glucose homeostasis in DIO mice. CONCLUSION: GN and UGN, as well as their prohormones, do not seem to play a significant role in body weight regulation and glycemic control, suggesting that guanylin-family peptides do not show promise as targets for the treatment of obesity or diabetes.

Chenodeoxycholic acid stimulates glucagon-like peptide-1 secretion in patients after Roux-en-Y gastric bypass.

Postprandial secretion of glucagon-like peptide-1 (GLP-1) is enhanced after Roux-en-Y gastric bypass (RYGB), but the precise molecular mechanisms explaining this remain poorly understood. Plasma concentrations of bile acids (BAs) increase after RYGB, and BAs may act as molecular enhancers of GLP-1 secretion through activation of TGR5-receptors. We aimed to evaluate GLP-1 secretion after oral administration of the primary bile acid chenodeoxycholic acid (CDCA) and the secondary bile acid ursodeoxycholic acid (UDCA) (which are available for oral use) in RYGB-operated participants. Eleven participants (BMI 29.1 ± 1.2, age 37.0 ± 3.2 years, time from RYGB 32.3 ± 1.1 months, weight loss after RYGB 37.0 ± 3.1 kg) were studied in a placebo-controlled, crossover-study. On three different days, participants ingested (1) placebo (water), (2) UDCA 750 mg, (3) CDCA 1250 mg (highest recommended doses). Oral intake of CDCA increased plasma concentrations of GLP-1, C-peptide, glucagon, peptide YY, neurotensin, total bile acids, and fibroblast growth factor 19 significantly compared with placebo (all P < 0.05 for peak and positive incremental area-under-the-curve (piAUC)). All plasma hormone concentrations were unaffected by UDCA Neither UDCA nor CDCA changed glucose, cholecystokinin or glucose-dependent insulinotropic polypeptide (GIP) concentrations. In conclusion, our findings demonstrate that the primary bile acid chenodeoxycholic acid is able to enhance secretion of gut hormones when administered orally in RYGB-operated patients-even in the absence of nutrients.

Gastric bypass surgery reveals independency of obesity and diabetes melitus type 2.

BACKGROUND: Roux-en-Y gastric bypass surgery is widely applied to ameliorate morbid obesity, including diabetes in people with type 2 diabetes. The latter vanish a few days after surgery for many, but not in all patients before any weight reduction has occurred. The explanation for this change in metabolic status is poorly understood, but the observation may suggest that the fate obesity and diabetes is only partly linked after surgery. METHODS: The trajectories of weight reduction measured as reduced body mass index (BMI) in 741obese subjects with and without diabetes were evaluated. Evaluation was performed on three groups: 1) subjects that were non-diabetic before and after surgery; 2) subjects that were diabetics before surgery but non-diabetics after surgery; and 3) subjects that were diabetics before surgery and remained diabetics after surgery. The diabetic state was established at HbA1c above 48 mmol/mol. RESULTS: The trajectories differ significantly between groups and any sub-populations of groups, the latter identified by the distance between individual trajectories using a k-means procedure. The results suggest that different domains in the enormous genetic network governing basic metabolism are perturbed in obesity and diabetes, and in fact some of the patients are affected by two distinct diseases: obesity and diabetes mellitus type 2. CONCLUSION: Although RYGB "normalized" many glycaemic parameters in some of the diabetic subjects apparently converting to a non-diabetics state, other diabetic subjects stay diabetic in the context of the new gut anatomy after surgery. Thus, the obesity part of the glycaemic derangement may have been ameliorated, but some defects of the diabetic state had not.

Effects of endogenous GLP-1 and GIP on glucose tolerance after Roux-en-Y gastric bypass surgery.

Exaggerated secretion of glucagon-like peptide 1 (GLP-1) is important for postprandial glucose tolerance after Roux-en-Y gastric bypass (RYGB), whereas the role of glucose-dependent insulinotropic polypeptide (GIP) remains to be resolved. We aimed to explore the relative importance of endogenously secreted GLP-1 and GIP on glucose tolerance and ß-cell function after RYGB. We used DPP-4 inhibition to enhance concentrations of intact GIP and GLP-1 and the GLP-1 receptor antagonist exendin-(9-39) (Ex-9) for specific blockage of GLP-1 actions. Twelve glucose-tolerant patients were studied after RYGB in a randomized, placebo-controlled, 4-day crossover study with standard mixed-meal tests and concurrent administration of placebo, oral sitagliptin, Ex-9 infusion, or combined Ex-9-sitagliptin. GLP-1 receptor antagonism increased glucose excursions, clearly attenuated ß-cell function, and aggravated postprandial hyperglucagonemia compared with placebo, whereas sitagliptin had no effect despite two- to threefold increased concentrations of intact GLP-1 and GIP. Similarly, sitagliptin did not affect glucose tolerance or ß-cell function during GLP-1R blockage. This study confirms the importance of GLP-1 for glucose tolerance after RYGB via increased insulin and attenuated glucagon secretion in the postprandial state, whereas amplification of the GIP signal (or other DPP-4-sensitive glucose-lowering mechanisms) did not appear to contribute to the improved glucose tolerance seen after RYGB.