Satiety and gastrointestinal hormones during a Mixed Meal Tolerance Test after gastric bypass surgery: association with plasma amino acid concentrations

No Evidence That Circulating GLP-1 or PYY Are Associated with Increased Satiety during Low Energy Diet-Induced Weight Loss: Modelling Biomarkers of Appetite

Bariatric surgery and pharmacology treatments increase circulating glucagon-like peptide-1 (GLP-1) and peptide YY (PYY), in turn promoting satiety and body weight (BW) loss. However, the utility of GLP-1 and PYY in predicting appetite response during dietary interventions remains unsubstantiated. This study investigated whether the decrease in hunger observed following low energy diet (LED)-induced weight loss was associated with increased circulating 'satiety peptides', and/or associated changes in glucose, glucoregulatory peptides or amino acids (AAs). In total, 121 women with obesity underwent an 8-week LED intervention, of which 32 completed an appetite assessment via a preload challenge at both Week 0 and Week 8, and are reported here. Visual analogue scales (VAS) were administered to assess appetite-related responses, and blood samples were collected over 210 min post-preload. The area under the curve (AUC_0-210), incremental AUC (iAUC_0-210), and change from Week 0 to Week 8 (∆) were calculated. Multiple linear regression was used to test the association between VAS-appetite responses and blood biomarkers. Mean (±SEM) BW loss was 8.4 ± 0.5 kg (-8%). Unexpectedly, the decrease in ∆AUC_0-210 hunger was best associated with decreased ∆AUC_0-210 GLP-1, GIP, and valine (p < 0.05, all), and increased ∆AUC_0-210 glycine and proline (p < 0.05, both). The majority of associations remained significant after adjusting for BW and fat-free mass loss. There was no evidence that changes in circulating GLP-1 or PYY were predictive of changes in appetite-related responses. The modelling suggested that other putative blood biomarkers of appetite, such as AAs, should be further investigated in future larger longitudinal dietary studies.

Histidine dose-response effects on lactational performance and plasma amino acid concentrations in lactating dairy cows: 1. Metabolizable protein-adequate diet

The objective of this experiment was to determine the effect of increasing digestible His (dHis) doses on milk production, milk composition, and plasma AA concentrations in lactating dairy cows fed diets that meet or exceed their energy and metabolizable protein (MP) requirements. In a companion paper (Räisänen et al., 2021) results are presented on the effect of increasing dHis dose with an MP-deficient basal diet. In this experiment, 16 Holstein cows (72 ± 15 d in milk) were used in a replicated 4 × 4 Latin square design experiment with four 28-d periods. Treatments were as follows: (1) control, total mixed ration (TMR) with 1.8% dHis of MP (TMR1; dHis1.8); (2) a different TMR with 2.2% dHis (TMR2; dHis2.2); (3) TMR2 supplemented with rumen-protected His (RP-His) to supply 2.6% dHis (dHis2.6); and (4) TMR2 supplemented with RP-His to supply 3.0% dHis of MP (dHis3.0). Estimated dHis intakes calculated at the end of the experiment were 46, 58, 69, and 79 g/d for dHis1.8, dHis2.2, dHis2.6, and dHis3.0, respectively. Contrasts were used to compare TMR1 with TMR2 and to test the linear and quadratic effects of RP-His inclusion rate on TMR2. We detected no effects of TMR or dHis dose on dry matter intake or milk yield, whereas energy-corrected milk (ECM) yield was quadratically increased, being greatest for cows on treatment dHis2.6. Milk true protein and lactose concentrations and milk true protein yield were not affected by TMR or dHis dose. Milk fat concentration and yield increased quadratically, and lactose yield tended to increase quadratically with increasing dHis dose. Calculated apparent efficiency of His utilization decreased quadratically with increasing dHis supply. Further, plasma concentration of His was greater for cows on TMR2 compared with TMR1. When an MP-adequate diet was fed to dairy cows, milk true protein concentration and yield were not affected by dHis supply, but milk fat and ECM yields of dairy cows were optimized at dHis supply of 69 g/d or 2.65% of MP.

Histidine dose-response effects on lactational performance and plasma amino acid concentrations in lactating dairy cows: 2. Metabolizable protein-deficient diet

The objective of this experiment was to determine the effect of increasing digestible His (dHis) levels with a rumen-protected (RP) His product on milk production, milk composition, and plasma AA concentrations in lactating dairy cows fed a metabolizable protein (MP)-deficient diet, according to the National Research Council dairy model from 2001. The companion paper presents results on the effect of increasing dHis dose with a MP-adequate basal diet. Twenty Holstein cows, of which 8 were rumen-cannulated, were used in a replicated 4 × 4 Latin square design experiment with four 28-d periods. Treatments were a control diet supplying 1.8% dHis of MP or 37 g/d (dHis1.8) and the control diet supplemented RP-His to provide 2.2, 2.6, or 3.0%, dHis of MP, or 53, 63, and 74 g/d (dHis2.2, dHis2.6, and dHis3.0, respectively). Histidine dose did not affect dry matter intake, but milk yield increased quadratically and energy-corrected milk yield increased linearly with increasing dHis dose. Histidine dose had a quadratic effect on milk fat concentration but did not affect milk fat yield. Lactose concentration decreased linearly, whereas lactose yield increased linearly with increasing dHis dose. There was a tendency for a linear increase in milk true protein concentration, and milk true protein yield increased linearly with dHis dose. Further, plasma His concentration increased linearly with increasing dHis dose and calculated apparent efficiency of His utilization decreased quadratically with increasing dHis supply. Histidine had minor or no effects on rumen fermentation. In the conditions of this experiment, RP-His supplementation of an MP-deficient corn silage-based diet increased milk yield linearly up to a dHis supply of 63 g/d (or 2.6% dHis of MP) and increased feed efficiency, energy-corrected milk yield and milk true protein yield linearly up to a dHis supply of 74 g/d (or 3.0% dHis of MP) in lactating dairy cows.

Effect of a Food for Special Medical Purposes for Muscle Recovery, Consisting of Arginine, Glutamine and Beta-Hydroxy-Beta-Methylbutyrate on Body Composition and Skin Health in Overweight and Obese Class I Sedentary Postmenopausal Women

The consumption of dietary amino acids has been evaluated for therapeutic and safety intervention in obesity. In particular, three molecules have been shown to be effective: arginine, glutamine and leucine (and its metabolite beta-hydroxy-beta-methylbutyrate, HMB). This randomized, double-blinded pilot study in obese postmenopausal patients aimed to evaluate the efficacy of the administration of a specific food for special medical purposes (FSMP) consisting of arginine, glutamine and HMB on body composition, in particular, visceral adipose tissue (VAT), assessed by dual-energy X-ray absorptiometry (DXA), as the primary endpoint. The secondary endpoint was to evaluate the effects on skin health through a validated self-reported questionnaire. A significant improvement on VAT of Δ = -153.600, p = 0.01 was recorded in the intervention group. Skin health showed a significant improvement in the treatment group for the following: bright Δ = 1.400 (0.758; 2.042), elasticity Δ = 0.900 (0.239; 1.561), wrinkles Δ = 0.800 (0.276; 1.324), and on total score, Δ = 3.000 (1.871; 4.129). In the intervention group, the improvement in VAT was associated with an improvement in the bright score (r = -0.58; p = 0.01). In conclusion, this study demonstrated that the intake for 4-weeks of arginine, glutamine and HMB effects a significant reduction in VAT and improves skin condition, while fat free mass (FFM) is maintained, thus achieving "high-quality" weight loss.

Diminished Counterregulatory Responses to Meal-Induced Hypoglycemia 4 Years After RYGB

PURPOSE

Post-bariatric hypoglycemia is a complication of bariatric surgery, especially Roux-en-Y gastric bypass (RYGB). The counterregulatory hormonal and sympathetic neural responses were measured during a previously reported meal test in which 48% had an almost asymptomatic hypoglycemic event.

MATERIALS AND METHODS

Forty-four randomly selected patients 4 years after RYGB. A liquid meal test (MMT) after overnight fasting. Based on the glucose nadir during the MMT, patients were divided in a hypo group (glucose < 3.3 mmol/L) and a non-hypo group (glucose ≥ 3.3 mmol/L). Cortisol, epinephrine, norepinephrine, blood pressure, and heart rate were measured up to 180 min after ingestion of the meal. Incremental areas under the curve (iAUC), peak, and delta hormone responses after the glucose nadir were calculated. Parameters were compared between the hypo and non-hypo groups.

RESULTS

A total of 21/44 (48%) had an almost asymptomatic hypoglycemic event. Cortisol and epinephrine responses in the hypo group were not increased compared to the non-hypo group, and there were no signs of increased sympathetic nerve activity. Peak and delta cortisol were lower in the hypo compared to the non-hypo group. Norepinephrine was higher in the hypo group especially in the time frame 60-120 and 120-180 min after start of the meal.

CONCLUSION

No increase in epinephrine and a lower cortisol response to hypoglycemia were observed compared to normoglycemia during a meal test in patients after RYGB. Norepinephrine levels were higher in the hypo group. These findings may suggest that possible recurrent hypoglycemia after RYGB results in blunting of counterregulatory responses indicative of hypoglycemia-induced autonomic failure.

CLIN TRIAL REGISTER ID

ISRCTN 11738149.

Biomarkers of appetite: is there a potential role for metabolomics?

Knowing the biological signals associated with appetite control is crucial for understanding the regulation of food intake. Biomarkers of appetite have been defined as physiological measures that relate to subjective appetite ratings, measured food intake, or both. Several metabolites including amino acids, lipids and glucose were proposed as key molecules associated with appetite control over 60 years ago, and along with bile acids are all among possible appetite biomarker candidates. Additional metabolites that have been associated with appetite include endocannabinoids, lactate, cortisol and β-hydroxybutyrate. However, although appetite is a complex integrative process, studies often investigated a limited number of markers in isolation. Metabolomics involves the study of small molecules or metabolites present in biological samples such as urine or blood, and may present a powerful approach to further the understanding of appetite control. Using multiple analytical techniques allows the characterisation of molecules, such as carbohydrates, lipids, amino acids, bile acids and fatty acids. Metabolomics has proven successful in identifying markers of consumption of certain foods and biomarkers implicated in several diseases. However, it has been underexploited in appetite control or obesity. The aim of the present narrative review is to: (1) provide an overview of existing metabolites that have been identified in human biofluids and associated with appetite control; and (2) discuss the potential of metabolomics to deepen understanding of appetite control in humans.

Comparison of Diabetes Remission and Micronutrient Deficiency in a Mildly Obese Diabetic Rat Model Undergoing SADI-S Versus RYGB

BACKGROUND

Single-anastomosis duodeno-ileal bypass with sleeve gastrectomy (SADI-S) has launched a huge challenge to classic Roux-en-Y gastric bypass (RYGB). Our objective was to compare diabetes remission and micronutrient deficiency in a mildly obese diabetic rat model undergoing SADI-S versus RYGB.

METHODS

Thirty adult male mildly obese diabetic rats were randomly assigned to sham (S), SADI-S, and RYGB groups. Body weight, food intake, fasting plasma glucose (FPG), oral glucose tolerance test (OGTT), plasma insulin, GLP-1, and ghrelin levels were measured at indicated time points. Meanwhile, insulin sensitivity and pancreatic β cell function were assessed during OGTT. Finally, plasma micronutrient evaluation and islet β cell mass analysis were performed after all animals were sacrificed.

RESULTS

As compared to sham, the SADI-S and RYGB groups achieved almost equivalent efficacy in caloric restriction and FPG control without excessive weight loss. During OGTT, the SADI-S and RYGB groups also provided comparable effects on glycemic excursion, insulin sensitivity, and β cell function; however, only rats in the RYGB group showed significant changes in gut hormones, whereas the three groups were found to exhibit no significant difference in β cell mass. In addition, only vitamin E in the RYGB group was deficient as compared with the SADI-S and S groups.

CONCLUSION

In mildly obese diabetic rat, SADI-S and RYGB procedures have comparable efficacy in diabetes remission and risk of micronutrient deficiency. These data show that each of the surgery accomplishes diabetes improvements through both overlapping and distinct mechanisms requiring further investigation.

The role of calcium sensing receptors in GLP-1 and PYY secretion after acute intraduodenal administration of L-Tryptophan in rats

Objectives: The calcium-sensing receptor (CaSR), the major sensor of extracellular Ca²⁺, is expressed in various tissues, including the gastrointestinal tract. Although the essential ligand of CaSR is calcium, its activity can be regulated by aromatic L-amino acids. The expression of CaSR on enteroendocrine cells suggests that CaSR functions as a physiological amino acid sensor for gut hormone release. Here, we investigated the effects of L-tryptophan (L-Trp) on rat glucagon-like peptide-1 (GLP-1), peptide YY (PYY), and insulin secretion, and the role of CaSR in this mechanism in vivo.Methods: The effects of intraduodenal L-Trp on GLP-1, PYY, and insulin secretion were investigated. A CaSR antagonist, NPS 2143, was administered to determine whether CaSR plays a role in L-Trp-mediated gut hormone release. Male Wistar rats were divided into L-Trp, L-Trp+NPS 2143, and L-Trp+vehicle groups. Blood samples were collected, before and after the intraduodenal infusions, for determining plasma glucose, L-Trp, insulin, GLP-1, and PYY levels.Results: Our study showed a significant increase in plasma GLP-1 and insulin levels, but not plasma PYY and glucose levels, following the acute intraduodenal administration of L-Trp. We demonstrated that CaSR plays a role in L-Trp-mediated GLP-1 secretion due to attenuation of GLP-1 release with the CaSR antagonist NPS 2143.Discussion: We demonstrated that GLP-1, but not PYY, secretion following intraduodenal L-Trp administration was mediated through calcium-sensing receptors. This mechanism underlying protein sensing in the gastrointestinal system may be important for the development of new therapeutic strategies without side effects for obesity and diabetes.

The Neurocognitive Effects of Ghrelin-induced Signaling on the Hippocampus: A Promising Approach to Alzheimer's Disease

The communication between the gastrointestinal tract and the central nervous system (CNS) allows for certain peptide hormones to influence neurocognitive function. Ghrelin, also known as the 'hunger hormone,' has the unique ability to enter the CNS and interact with the growth hormone secretagogue receptor (GHS-R) within the hippocampus. Upon interaction with ghrelin, a conformational change in the receptor causes an increase in transcription factors to foster a wide array of physiologic changes in response to caloric deprivation. With the GHS-R in a relatively high concentration within the hippocampus, ghrelin can promote memory, spatial, learning, and behavioral effects. In fact, ghrelin appears to also have a neuroprotective and neuromodulatory response once active within the hippocampal dentate gyrus. Through the GHS-R, higher levels of ghrelin may alter cognitive circuitry and offer a possible link to the treatment of some pathologies implicated in neurological dysfunction. Alzheimer's disease (AD) is already becoming a significant target for ghrelin neuroreceptor therapy. In such experimental models, ghrelin has been shown to combat this degenerative process by eliciting an ameliorative and regenerative response. Although trials and research are still ongoing, further studies are indicated as early research into this adjuvant therapy is promising. The research team explored the effects of ghrelin by reviewing the downstream signaling modifications of ghrelin's interaction with a specific CNS receptor, the GHS-R. Although the GHS-R is found in multiple locations within the CNS, the team investigated the role of the GHS-R within the hippocampus to focus solely on the neurocognitive implications of ghrelin. The team noted which signaling pathways in particular that ghrelin initiated and used this approach to determine whether ghrelin may have any therapeutic benefits. The team explored the possible therapeutic indications of ghrelin by looking at studies conducted with a specific neurodegenerative disease known to target the hippocampus.