Intraduodenal calcium enhances the effects of L-tryptophan to stimulate gut hormone secretion and suppress energy intake in healthy males: a randomized, cross-over, clinical trial.

BACKGROUND: In humans, intraduodenal infusion of L-tryptophan (Trp) increases plasma concentrations of gastrointestinal hormones and stimulates pyloric pressures, both key determinants of gastric emptying and associated with potent suppression of energy intake. The stimulation of gastrointestinal hormones by Trp has been shown, in preclinical studies, to be enhanced by extracellular calcium and mediated in part by the calcium-sensing receptor. OBJECTIVE: To determine whether intraduodenal calcium can enhance the effects of Trp to stimulate gastrointestinal hormones and pyloric pressures, and if so, whether it is associated with greater suppression of energy intake, in healthy males. METHODS: Fifteen males with normal weight (mean±SD; age: 26±7 years; body mass index: 22±2 kg/m2), received on three separate occasions, 150-min intraduodenal infusions of 0, 500 or 1000 mg calcium (Ca), each combined with Trp (load: 0.1 kcal/min, with submaximal energy intake-suppressant effects) from t=75-150 min, in a randomized, double-blind, cross-over study. Plasma concentrations of GI hormones (gastrin, cholecystokinin, glucose-dependent insulinotropic polypeptide (GIP), glucagon-like peptide-1 (GLP-1), peptide tyrosine-tyrosine (PYY)), and Trp, and antropyloroduodenal pressures were measured throughout. Immediately post-infusions (t=150-180 min), energy intake at a standardized buffet-style meal was quantified. RESULTS: In response to calcium alone, both 500-mg and 1000-mg doses stimulated PYY, while only the 1000-mg dose stimulated GLP-1 and pyloric pressures (all P<0.05). The 1000-mg dose also enhanced the effects of Trp to stimulate cholecystokinin and GLP-1, and both doses stimulated PYY, but, surprisingly, reduced the stimulation of GIP (all P<0.05). Both doses substantially and dose-dependently enhanced the effects of Trp to suppress energy intake (kcal; Ca-0+Trp: 1108±70, Ca-500+Trp: 961±90, Ca-1000+Trp: 922±96; P<0.05). CONCLUSIONS: Intraduodenal administration of calcium enhances the effect of Trp to stimulate plasma cholecystokinin, GLP-1 and PYY, and suppress energy intake, in health. These findings have potential implications for novel nutrient-based approaches to energy intake regulation in obesity. CLINICAL TRIAL REGISTRY: The trial was registered with the Australian New Zealand Clinical Trial Registry (www.anzctr.org.au; trial number: ACTRN12620001294943).

Exogenous glucagon-like peptide 2 counteracts exogenous cholecystokinin-induced gallbladder contraction in healthy men.

BACKGROUND AND OBJECTIVE: Studies in humans and mice have demonstrated that the gut hormone glucagon-like peptide 2 (GLP-2) promotes gallbladder relaxation and refilling. Here, we assessed the effect of exogenous GLP-2 on gallbladder motility in the fasted state of healthy men with and without infusion of the potent gallbladder-contracting hormone cholecystokinin (CCK). METHODS: In a randomized, double-blind, placebo-controlled, crossover study, 15 male participants (mean [SD]: age 24.7 [3.6] years; body mass index 22.9 [1.6] kg/m2) underwent four experimental days receiving two infusions on each day: either CCK (0.4 pmol × kg-1 × min-1, time 0-180 min) + GLP-2 (10 pmol × kg-1 × min-1, time 30-240 min), CCK + placebo, placebo + GLP-2, or placebo + placebo, respectively. Gallbladder volume was measured at baseline and throughout the 4-hour study day using ultrasonography. RESULTS: Compared to placebo + placebo, GLP-2 + placebo did not affect gallbladder volume, but when infused in combination with CCK, GLP-2 completely abolished the strong gallbladder-contracting effect seen during CCK + placebo infusion, restoring baseline levels of gallbladder volume. CONCLUSION: Exogenous GLP-2 counteracts exogenous CCK-induced gallbladder emptying in healthy men, pointing to a possible therapeutic potential for GLP-2 as a relaxing modulator of gallbladder smooth muscle tone (e.g., as bridge to surgery in biliary colic). The effect may also explain the gallbladder-related adverse events reported for GLP-2 receptor agonists used in the treatment of short bowel syndrome.

Colesevelam has no acute effect on postprandial GLP-1 levels but abolishes gallbladder refilling.

OBJECTIVE: Colesevelam, a bile acid sequestrant approved for the treatment of hypercholesterolaemia, improves glycaemic control in type 2 diabetes. We hypothesised that single-dose colesevelam increases postprandial GLP-1 secretion, thus, reducing postprandial glucose excursions in individuals with type 2 diabetes. Further, we explored the effects of single-dose colesevelam on ultrasonography-assessed postprandial gallbladder motility, paracetamol absorption (proxy for gastric emptying), and circulating factors known to affect gallbladder motility. METHODS: In a randomised, double-blind, placebo-controlled crossover study, 12 individuals with type 2 diabetes (mean ± SD: age 61 ± 8.8 years; body mass index 29.8 ± 3.0 kg/m2) were subjected to 4 mixed meal tests on separate days; 2 with orally administered colesevelam (3.75 g) and 2 with placebo, with intravenous infusion of the GLP-1 receptor antagonist exendin(9-39)NH2 or saline. RESULTS: Single-dose colesevelam had no effect on postprandial concentrations of glucose (P = .786), C-peptide (P = .440), or GLP-1 (P = .729), and exendin(9-39)NH2 administration revealed no GLP-1-mediated effects of colesevelam. Colesevelam did not affect gallbladder emptying but abolished gallbladder refilling (P = .001), increased postprandial cholecystokinin (CCK) secretion (P = .010), and decreased postprandial serum concentrations of fibroblast growth factor 19 (FGF19) (P = .035) and bile acids (P = .043). CONCLUSION: Single-dose colesevelam had no effect on postprandial GLP-1 responses or glucose tolerance but disrupted postprandial gallbladder refilling by increasing CCK secretion and reducing circulating concentrations of FGF19 and bile acids. These findings leave the antidiabetic actions of colesevelam unresolved but provide mechanistic insights into its effect on gallbladder motility.

The cckOMA syndrome and its relation to the Zollinger-Ellison syndrome: a diagnostic challenge.

OBJECTIVE: Among patients with enteropancreatic neuroendocrine tumor syndromes only one case with a cholecystokinin (CCK) secreting tumor has been reported. She had significant hyperCCKemia leading to a specific syndrome of severe diarrheas, weight loss, repeated duodenal ulcers and a permanently contracted gallbladder with gallstones. There are, however, reasons to believe that further CCKomas exist, for instance among Zollinger-Ellison patients with normal plasma gastrin concentrations. The present review is a call to gastroenterologists for awareness of such CCKoma patients. METHOD: After a short case report, the normal endocrine and oncological biology of CCK is described. Subsequently, the CCKoma symptoms are discussed with particular reference to the partly overlapping symptoms of the Zollinger-Ellison syndrome. In this context, the diagnostic use of truly specific CCK and gastrin assays are emphasized. The discussion also entails the problem of access to accurate CCK measurements. CONCLUSION: Obviously, the clinical awareness about the CCKoma syndrome is limited. Moreover, it is also likely that the knowledge about the necessary specificity demands of diagnostic gastrin and CCK assays have obscured proper diagnosis of the CCKoma syndromes in man.

Gastrointestinal hormones: History, biology, and measurement.

This chapter attempts to provide an all-round picture of a dynamic and major branch of modern endocrinology, i.e. the gastrointestinal endocrinology. The advances during the last half century in our understanding of the dimensions and diversity of gut hormone biology - inside as well as outside the digestive tract - are astounding. Among major milestones are the dual brain-gut relationship, i.e. the comprehensive expression of gastrointestinal hormones as potent transmitters in central and peripheral neurons; the hormonal signaling from the enteroendocrine cells to the brain and other extraintestinal targets; the role of gut hormones as growth and fertility factors; and the new era of gut hormone-derived drugs. Accordingly, gastrointestinal hormones have pathogenetic roles in major metabolic disorders (diabetes mellitus and obesity); in tumor development (common cancers, sarcomas, and neuroendocrine tumors); and in cerebral diseases (anxiety, panic attacks, and probably eating disorders). Such clinical aspects require accurate pathogenetic and diagnostic measurements of gastrointestinal hormones - an obvious responsibility for clinical chemistry/biochemistry. In order to obtain a necessary insight into today's gastrointestinal endocrinology, the chapter will first describe the advances in gastrointestinal endocrinology in a historical context. The history provides a background for the subsequent description of the present biology of gastrointestinal hormones, and its biomedical consequences - not least for clinical chemistry/biochemistry with its specific responsibility for selection of appropriate assays and reliable measurements.

Elucidating the glucose-lowering effect of the bile acid sequestrant sevelamer.

AIM: Bile acid sequestrants are cholesterol-lowering drugs, which also improve glycaemic control in people with type 2 diabetes. The mechanism behind the glucose-lowering effect is unknown but has been proposed to be mediated by increased glucagon-like peptide-1 (GLP-1) secretion. Here, we investigated the glucose-lowering effects of sevelamer including any contribution from GLP-1 in people with type 2 diabetes. MATERIALS AND METHODS: In a randomized, double-blind, placebo-controlled, crossover study, 15 people with type 2 diabetes on metformin monotherapy underwent two 17-day treatment periods with the bile acid sequestrant sevelamer and placebo, respectively, in a randomized order and with an interposed wash-out period of minimum 6 weeks. On days 15 and 17 of each treatment period, participants underwent experimental days with 4-h liquid meal tests and application of concomitant infusion of exendin(9-39)NH2 or saline. RESULTS: Compared with placebo, sevelamer improved insulin sensitivity (assessed by homeostatic model assessment of insulin resistance) and beta-cell sensitivity to glucose and lowered fasting and postprandial plasma glucose concentrations. In both treatment periods, exendin(9-39)NH2 increased postprandial glucose excursions compared with saline but without absolute or relative difference between the two treatment periods. In contrast, exendin(9-39)NH2 abolished the sevelamer-induced improvement in beta-cell glucose sensitivity. CONCLUSIONS: The bile acid sequestrant sevelamer improved insulin sensitivity and beta-cell sensitivity to glucose, but using the GLP-1 receptor antagonist exendin(9-39)NH2 we were not able to detect a GLP-1-mediated glucose-lowering effect of sevelamer in individuals with type 2 diabetes. Nevertheless, the sevelamer-induced improvement of beta-cell sensitivity to glucose was shown to be GLP-1-dependent.

Metabolic adaptation is associated with a greater increase in appetite following weight loss: a longitudinal study.

BACKGROUND: Weight loss is associated with a disproportionate reduction in energy expenditure, along with increases in hunger feelings and ghrelin concentrations. These changes are presumed to be homeostatic mechanisms to counteract the energy deficit. The possibility that these 2 components of the energy balance equation are mechanistically linked has never been examined. OBJECTIVE: This study aimed to determine if the disproportionate reduction in resting metabolic rate (RMR) seen with weight loss is associated with changes in the plasma concentration of gastrointestinal hormones involved in appetite regulation and subjective appetite ratings. METHODS: This was a longitudinal study with repeated measurements. Fifty-six individuals with obesity (body mass index [BMI]: 34.5±0.5 kg/m2; age: 47±1 y; 26 males) underwent an 8 wk low-energy diet, followed by 4 wk of refeeding and weight stabilization. The RMR, respiratory quotient (RQ), body composition, plasma concentrations of ghrelin, glucagon-like peptide 1, peptide YY, cholecystokinin, insulin, and appetite ratings in the fasting and postprandial states were measured at baseline, Wk9 and 13. Metabolic adaptation was defined as significantly lower when measured versus the predicted RMR (pRMR) (from own regression model using baseline data). RESULTS: A 14.2±0.6 kg weight loss was seen at Wk9 and maintained at Wk13. RQ was significantly reduced at Wk9 (0.82±0.06 vs. 0.76±0.05, P< 0.001) but returned to baseline at Wk13. Metabolic adaptation was seen at Wk9, but not Wk13 (-341±58, P <0.001 and -75±72 kJ/d, P = 0.305, respectively). The larger the difference between measured and predicted RMR at both timepoints, the greater the increase in hunger, desire to eat, and composite appetite score (fasting and postprandial at Wk9, postprandial only at Wk13), even after adjusting for weight loss and RQ. CONCLUSION: A larger metabolic adaptation during weight loss is accompanied by a greater drive to eat. This might help explain the interindividual differences in weight loss outcomes to dietary interventions.

Effects of levothyroxine substitution therapy on hunger and food intake in individuals with hypothyroidism.

Context: In individuals with hypothyroidism and overweight, levothyroxine substitution therapy is often expected to cause weight loss due to its effect on resting energy expenditure. However, despite levothyroxine-induced enhancement of resting energy expenditure, fat mass loss is rarely seen after levothyroxine substitution therapy. The mechanism behind this conundrum is unknown. Aim: The aim of the study was to assess the effect of levothyroxine therapy on hunger sensations and ad libitum food intake in individuals with hypothyroidism. Design and setting: Prospective cohort study of 18 newly diagnosed hypothyroid women (thyroid-stimulating hormone (TSH) >10 mU/L). Participants were investigated at diagnosis, after normalization of TSH (<4.0 mU/L), and after 6 months of successful treatment. Eighteen age and body mass index-matched healthy controls were also included. Intervention: Hypothyroid individuals were treated with levothyroxine according to European Thyroid Association guidelines. Main outcomes: Changes in hunger sensation were assessed using visual analog scales (cm) before and during a standardized mixed meal test, and food intake was measured during a subsequent ad libitum meal (g). Results: After 6 months of levothyroxine therapy, mean resting energy expenditure was increased by 144 kcal/day (10%) (P < 0.001). Weight loss was comprised of 0.8 kg fat-free mass while fat mass remained unchanged. Fasting hunger sensation increased from a mean of 4.5 (s.d. 2.2) cm to 5.5 (s.d. 2.2) cm (P = 0.047). The numerical increase in ad libitum meal intake did not reach statistical significance. Conclusion: Our data suggest that levothyroxine-induced hunger may be a culprit in the lack of fat mass loss from levothyroxine therapy.

History of key regulatory peptide systems and perspectives for future research.

Throughout the 20th Century, regulatory peptide discovery advanced from the identification of gut hormones to the extraction and characterization of hypothalamic hypophysiotropic factors, and to the isolation and cloning of multiple brain neuropeptides. These discoveries were followed by the discovery of G-protein-coupled and other membrane receptors for these peptides. Subsequently, the systems physiology associated with some of these multiple regulatory peptides and receptors has been comprehensively elucidated and has led to improved therapeutics and diagnostics and their approval by the US Food and Drug Administration. In light of this wealth of information and further potential, it is truly a time of renaissance for regulatory peptides. In this perspective, we review what we have learned from the pioneers in exemplified fields of gut peptides, such as cholecystokinin, enterochromaffin-like-cell peptides, and glucagon, from the trailblazing studies on the key stress hormone, corticotropin-releasing factor, as well as from more recently characterized relaxin-family peptides and receptors. The historical viewpoints are based on our understanding of these topics in light of the earliest phases of research and on subsequent studies and the evolution of knowledge, aiming to sharpen our vision of the current state-of-the-art and those studies that should be prioritized in the future.

Association between Fat-Free Mass Loss, Changes in Appetite, and Weight Regain in Individuals with Obesity.

BACKGROUND: The role of fat-free mass loss (FFML) in modulating weight regain in individuals with obesity, as well as the potential mechanisms involved, remain inconsistent. OBJECTIVES: The aim of this study was to determine if % FFML following weight loss (WL) is a predictor of weight regain and to investigate the association between %FFML and changes in appetite markers. METHODS: Seventy individuals with obesity (BMI: 36 ± 4 kg/m2; age: 44 ± 9 y; 29 males) underwent 8 wk of a very low energy diet (550-660 kcal/d), followed by 4 wk of gradual refeeding and weight stabilization and a 9-mo maintenance program (eucaloric diet). The primary outcomes were body weight and body composition (fat mass and fat-free mass). The secondary outcomes were plasma concentrations of ß-hydroxybutyrate (a marker of ketosis) in fasting and appetite-related hormones (ghrelin, glucagon-like peptide 1, peptide YY, and cholecystokinin) and subjective appetite feelings during fasting and every 30 min after a fixed breakfast for 2.5 h. All were measured at baseline, week 9, and 1 y [week 13 in 35 subjects (25 males)]. The association between FFML, weight regain, and changes in appetite was assessed by linear regression. RESULTS: WL at week 9 was 17.5 ± 4.3kg and %FFML 20.4 ± 10.6%. Weight regain at 1 y was 1.7 ± 8.2 kg (8.8 ± 45.0%). After adjusting for WL and fat mass at baseline, %FFML at week 9 was not a significant predictor of weight regain. Similar results were seen at week 13. The greater the %FFML at week 9, but not 13, the smaller the reduction, or greater the increase in basal ghrelin concentration (ß: -3.2; 95% CI: -5.0, -1.1; P = 0.003), even after adjusting for WL and ß-hydroxybutyrate. CONCLUSIONS: %FFML was not a significant predictor of weight regain at 1 y in individuals with obesity. However, a greater %FFML was accompanied by a greater increase in ghrelin secretion under ketogenic conditions, suggesting a link between fat-free mass and appetite regulation. This trial was registered at clinicaltrials.gov as NCT01834859.

Weight loss by calorie restriction does not alter appetite-regulating gut hormone responses from perfused rat small intestine.

AIM: Postprandial secretion of the appetite-inhibiting hormones, glucagon-like peptide-1 (GLP-1), and peptide YY are reduced with obesity. It is unclear if the reduced secretion persists following weight loss (WL), if other appetite-inhibiting hormones are also reduced, and if so whether reduced secretion results from intrinsic changes in the gut. METHODS: To address whether WL may restore secretion of GLP-1 and other appetite-inhibiting hormones, we performed a gut perfusion study of the small intestine in diet-induced obese (DIO) rats after WL. A 20% weight loss (means ± SEM (g): 916 ± 53 vs. 703 ± 35, p < 0.01, n = 7) was induced by calorie restriction, and maintained stable for ≥7 days prior to gut perfusion to allow for complete renewal of enteroendocrine cells. Age-matched DIO rats were used as comparator. Several gut hormones were analyzed from the venous effluent, and gene expression was performed on gut tissue along the entire length of the intestine. RESULTS: Secretion of cholecystokinin, gastrin, glucose-dependent insulinotropic peptide, GLP-1, neurotensin, and somatostatin was not affected by WL during basal conditions (p ≥ 0.25) or in response to macronutrients and bile acids (p ≥ 0.14). Glucose absorption was indistinguishable following WL. The expression of genes encoding the studied peptides, macronutrient transporters (glucose, fructose, and di-/tripeptides) and bile acid receptors did also not differ between DIO and WL groups. CONCLUSIONS: These data suggest that the attenuated postprandial responses of GLP-1, as well as reduced responses of other appetite-inhibiting gut hormones, in people living with obesity may persist after weight loss and may contribute to their susceptibility for weight regain.

Liraglutide changes postprandial responses of gut hormones involved in the regulation of gallbladder motility.

AIM: Liraglutide treatment is associated with gallbladder-related disorders and has been shown to delay postprandial gallbladder refilling. The gut hormones cholecystokinin (CCK), fibroblast growth factor 19 (FGF19) and glucagon-like peptide 2 (GLP-2), are known to regulate gallbladder motility and may be implicated in gallbladder-related disorders associated with liraglutide treatment. MATERIALS AND METHODS: In a double-blind, 12-week trial, 52 participants [50% male, age 47.6 ± 10.0 years, body mass index 32.6 ± 3.4 kg/m2 (mean ± standard deviation)] with obesity were randomized 1:1 to once-daily subcutaneous liraglutide (escalated from 0.6 mg to 3.0 mg once-daily) or placebo. During liquid meal tests performed at baseline, after the first dose and following 12 weeks of treatment, we evaluated postprandial gallbladder dynamics and plasma responses of CCK, FGF19 and GLP-2. RESULTS: Liraglutide reduced postprandial FGF19 after the first dose [area under the curve (AUC)0-240 min 24.8 vs. 48.0 min × ng/ml, treatment ratio (TR) (95% confidence interval) 0.52 (0.39; 0.69)] and following 12 weeks of treatment [AUC0-240 min 33.7 vs. 48.5 ng/ml × min, TR 0.69 (0.52; 0.93)]. Liraglutide also reduced postprandial GLP-2 responses (AUC0-240 min 3650 vs. 4894 min × pmol/L, TR 0.75 (0.62; 0.90)] following the first dose as well as after 12 weeks [AUC0-240 min 3760 vs. 4882 min × pmol/L, TR 0.77 (0.60; 0.99)]. Liraglutide increased postprandial responses of CCK after the first dose [AUC0-240 min 762 vs. 670 min × pmol/L; TR 1.14 (0.97; 1.33)] and following 12 weeks of treatment [AUC0-240 min 873 vs. 628 min × pmol/L; TR 1.39 (1.12; 1.73)]. CONCLUSION: Compared with placebo, treatment with liraglutide decreased postprandial FGF19 and GLP-2 concentrations and increased postprandial CCK concentrations, which may explain the delayed postprandial gallbladder refilling observed in individuals with obesity treated with liraglutide.

Four sidenotes about glucagon peptides.

Century old glucagon is a classic pancreatic hormone. But today we also know that the glucagon gene is expressed at high levels at extrapancreatic sites - particularly so in the gut. Major hormonal glucagon gene products in the digestive tract are the two glucagon-like peptides (GLP-1 and -2). Of these, truncated GLP-1 has in recent decades attracted massive interest due to its incretin effect, and the subsequent GLP-1 derived design of potent diabetes and obesity drugs. Truncated GLP-1 has consequently become an important contributor to gastrointestinal endocrinology. The gastrointestinal branch of endocrinology today includes more than 100 bioactive peptides encoded by some 30 different hormone genes. Therefore, the gut is the largest endocrine organ in the body. In addition to a general discussion of glucagon peptides in the hierarchy of gut hormones, this review also includes three short notes about glucagon studies from the 1970s. These studies dealt with reactive hypoglycemia, chronic liver disease, and the secretory response of pancreatic glucagon to gastrin/cholecystokinin stimulation. Considering today's possibilities in molecular endocrinology, revisits to the questions raised by these studies might be worthwhile.

Increased Meal Size but Reduced Meal-Stimulated Plasma Cholecystokinin Concentrations in Women With Obesity.

To better understand the physiological basis of obesity in women, we investigated whether obesity or menstrual cycle phase affects laboratory test-meal size or meal-stimulated plasma cholecystokinin (CCK) concentration. Women with healthy weight (body mass index [BMI] of 18.5-24.9 kg/m2, N = 16) or obesity (BMI 30-39.9 kg/m2, N = 20) were tested once in the late-follicular or peri-ovulatory phase (LF/PO) and once in the mid-luteal phase (ML). Meals of ham sandwiches were offered and blood was sampled. Menstrual cycle phases were verified with participants' reports of menses and measurements of progesterone and luteinizing hormone (LH) concentrations. Women with obesity ate significantly larger meals than women with healthy weight, (mean, 711 [95% CI, 402-1013] kJ, P = 0.001, during the LF/PO and 426 [105-734] kJ, P = 0.027, larger during the ML). Women with healthy weight ate smaller meals during LF/PO than ML (decrease, 510 [192-821 kJ], P = 0.008), but women with obesity did not (decrease, 226 [-87-542] kJ, P = 0.15). CCK concentrations 18 to 30 minutes after meal onset were lower in women with obesity than in women with healthy weight during LF/PO (3.6 [3.1-4.1] vs 6.1 [4.5-7.7] pmol/L; P = 0.004), but not during ML, with a significant interaction effect (1.8 [1.2-2.4] pmol/L, P = 0.048). Women with obesity consumed larger meals than women with healthy weight but displayed reduced meal-stimulated plasma CCK concentrations. These data are consistent with the hypothesis that a defect in CCK secretion compromises satiation in obese women and contributes to the development or maintenance of obesity.

Oral Erythritol Reduces Energy Intake during a Subsequent ad libitum Test Meal: A Randomized, Controlled, Crossover Trial in Healthy Humans.

The impact of oral erythritol on subsequent energy intake is unknown. The aim was to assess the effect of oral erythritol compared to sucrose, sucralose, or tap water on energy intake during a subsequent ad libitum test meal and to examine the release of cholecystokinin (CCK) in response to these substances. In this randomized, crossover trial, 20 healthy volunteers received 50 g erythritol, 33.5 g sucrose, or 0.0558 g sucralose dissolved in tap water, or tap water as an oral preload in four different sessions. Fifteen minutes later, a test meal was served and energy intake was assessed. At set time points, blood samples were collected to quantify CCK concentrations. The energy intake (ad libitum test meal) was significantly lower after erythritol compared to sucrose, sucralose, or tap water (p < 0.05). Before the start of the ad libitum test meal, erythritol led to a significant increase in CCK compared to sucrose, sucralose, or tap water (p < 0.001). Oral erythritol given alone induced the release of CCK before the start of the ad libitum test meal and reduced subsequent energy intake compared to sucrose, sucralose, or tap water. These properties make erythritol a useful sugar alternative.

Biochemistry of the Endocrine Heart.

Production and release of natriuretic peptides and other vasoactive peptides are tightly regulated in mammalian physiology and involved in cardiovascular homeostasis. As endocrine cells, the cardiac myocytes seem to possess almost all known chemical necessities for translation, post-translational modifications, and complex peptide proteolysis. In several ways, intracellular granules in the cells contain not only peptides destined for secretion but also important granin molecules involved in maintaining a regulated secretory pathway. In this review, we will highlight the biochemical phenotype of the endocrine heart recapitulating that the cardiac myocytes are capable endocrine cells. Understanding the basal biochemistry of the endocrine heart in producing and secreting peptides to circulation could lead to new discoveries concerning known peptide products as well as hitherto unidentified cardiac peptide products. In perspective, studies on natriuretic peptides in the heart have shown that the post-translational phase of gene expression is not only relevant for human physiology but may prove implicated also in the development and, perhaps one day, cure of human cardiovascular disease.

Weight loss improves ß-cell function independently of dietary carbohydrate restriction in people with type 2 diabetes: A 6-week randomized controlled trial.

Background: Carbohydrate restriction may benefit ß-cell function and glucose metabolism in type 2 diabetes (T2D) but also leads to weight loss which in itself is beneficial. Methods: In order to determine the additional effect of carbohydrate restriction in addition to a fixed body weight loss, we randomly assigned 72 adults with T2D and obesity (mean ± SD HbA1c 7.4 ± 0.7%, BMI 33 ± 5 kg/m2) to a carbohydrate-reduced high-protein diet (CRHP; energy percent from carbohydrate/protein/fat: 30/30/40) or an isocaloric conventional diabetes diet (CD; 50/17/33) for 6 weeks. All foods were provided free of charge and total energy intake was tailored individually, so both groups lost 6% of baseline body weight. Results: Despite significantly greater reductions in HbA1c (mean [95% CI] -1.9 [-3.5, -0.3] mmol/mol) after 6 weeks, the CRHP diet neither improved glucose tolerance, ß-cell response to glucose, insulin sensitivity, during a 4-h oral glucose tolerance test, nor basal proinsulin secretion when compared to the CD diet, but increased C-peptide concentration and insulin secretion rate (area under the curve [AUC] and peak) significantly more (~10%, P ≤ 0.03 for all). Furthermore, compared with the CD diet, the CRHP diet borderline increased basal glucagon concentration (16 [-0.1, 34]%, P = 0.05), but decreased glucagon net AUC (-2.0 [-3.4, -0.6] mmol/L ×240 min, P < 0.01), decreased basal triglyceride and total AUC (~20%, P < 0.01 for both), and increased gastric inhibitory polypeptide total AUC (14%, P = 0.01). Conclusion: A moderately carbohydrate-restricted diet for 6 weeks decreased HbA1c but did not improve ß-cell function or glucose tolerance beyond the effects of weight loss when compared with a conventional diabetes diet in people with T2D. Clinical trials registration: www.Clinicaltrials.gov, Identifier: NCT02472951.

Lipid emulsion interfacial design modulates human in vivo digestion and satiation hormone response.

Lipid emulsions (LEs) with tailored digestibility have the potential to modulate satiation or act as delivery systems for lipophilic nutrients and drugs. The digestion of LEs is governed by their interfacial emulsifier layer which determines their gastric structuring and accessibility for lipases. A plethora of LEs that potentially modulate digestion have been proposed in recent years, however, in vivo validations of altered LE digestion remain scarce. Here, we report on the in vivo digestion and satiation of three novel LEs stabilized by whey protein isolate (WPI), thermo-gelling methylcellulose (MC), or cellulose nanocrystals (CNCs) in comparison to an extensively studied surfactant-stabilized LE. LE digestion and satiation were determined in terms of gastric emptying, postprandial plasma hormone and metabolite levels characteristic for lipid digestion, perceived hunger/fullness sensations, and postprandial food intake. No major variations in gastric fat emptying were observed despite distinct gastric structuring of the LEs. The plasma satiation hormone and metabolite response was fastest and highest for WPI-stabilized LEs, indicating a limited capability of proteins to prevent lipolysis due to fast hydrolysis under gastric conditions and displacement by lipases. MC-stabilized LEs show a similar gastric structuring as surfactant-stabilized LEs but slightly reduced hormone and metabolite responses, suggesting that thermo-gelling MC prevents lipase adsorption more effectively. Ultimately, CNC-stabilized LEs showed a drastic reduction (>70%) in plasma hormone and metabolite responses. This confirms the efficiency of particle (Pickering) stabilized LEs to prevent lipolysis proposed in literature based on in vitro experiments. Subjects reported more hunger and less fullness after consumption of LEs stabilized with MC and CNCs which were able to limit satiation responses. We do not find evidence for the widely postulated ileal brake, i.e. that delivery of undigested nutrients to the ileum triggers increased satiation. On the contrary, we find decreased satiation for LEs that are able to delay lipolysis. No differences in food intake were observed 5 h after LE consumption. In conclusion, LE interfacial design modulates in vivo digestion and satiation response in humans. In particular, Pickering LEs show extraordinary capability to prevent lipolysis and qualify as oral delivery systems for lipophilic nutrients and drugs.

Resting and postpradial serum cholecystokinin concentrations and evaluation of the effect of seeing and/or smelling food on serum cholecystokinin and bile acid concentrations in healthy dogs.

Serum bile acids concentrations rise postprandially. However, some dogs show paradoxical serum bile acids results with higher pre-prandial than post-prandial concentrations. The aim of this study was to evaluate serum cholecystokinin (CCK) concentrations and determine whether they correspond to paradoxical serum bile acids concentrations. In addition, seeing and smelling food was investigated as a possible cause for paradoxical serum bile acids results. Eight healthy dogs owned by volunteers enrolled in this experimental study. Food was withheld from the dogs for 12 h with great care not to expose them to any sight or smell of food. Blood samples were collected at 0, 30, 60, 120, 180, 240, 480 and 720 min after feeding. Food was then withheld again for 24 h, and blood samples were collected at 0, 30, 60, 120, 180, 240, 480 and 720 min after seeing and smelling food. After feeding, serum CCK concentrations increased, but paradoxical serum CCK concentrations were observed in some of dogs, but only one of those had also paradoxical serum bile acids concentrations. After seeing and smelling food, serum CCK and serum bile acids concentrations did not significantly increase. In conclusion, paradoxical serum CCK concentrations can occur in some healthy dogs after feeding. However, no correlation with paradoxical serum bile acids concentrations was found. Seeing or smelling food are unlikely causes for paradoxical serum bile acids concentrations. Additional studies are warranted to further evaluate the relationship of serum CCK and bile acids concentrations in healthy dogs and dogs with gastrointestinal disease.