Counter-regulatory responses to postprandial hypoglycaemia in patients with post-bariatric hypoglycaemia vs surgical and non-surgical control individuals.

AIMS/HYPOTHESIS: Post-bariatric hypoglycaemia is an increasingly recognised complication of bariatric surgery, manifesting particularly after Roux-en-Y gastric bypass. While hyperinsulinaemia is an established pathophysiological feature, the role of counter-regulation remains unclear. We aimed to assess counter-regulatory hormones and glucose fluxes during insulin-induced postprandial hypoglycaemia in patients with post-bariatric hypoglycaemia after Roux-en-Y gastric bypass vs surgical and non-surgical control individuals. METHODS: In this case-control study, 32 adults belonging to four groups with comparable age, sex and BMI (patients with post-bariatric hypoglycaemia, Roux-en-Y gastric bypass, sleeve gastrectomy and non-surgical control individuals) underwent a postprandial hypoglycaemic clamp in our clinical research unit to reach the glycaemic target of 2.5 mmol/l 150-170 min after ingesting 15 g of glucose. Glucose fluxes were assessed during the postprandial and hypoglycaemic period using a dual-tracer approach. The primary outcome was the incremental AUC of glucagon during hypoglycaemia. Catecholamines, cortisol, growth hormone, pancreatic polypeptide and endogenous glucose production were also analysed during hypoglycaemia. RESULTS: The rate of glucose appearance after oral administration, as well as the rates of total glucose appearance and glucose disappearance, were higher in both Roux-en-Y gastric bypass groups vs the non-surgical control group in the early postprandial period (all p<0.05). During hypoglycaemia, glucagon exposure was significantly lower in all surgical groups vs the non-surgical control group (all p<0.01). Pancreatic polypeptide levels were significantly lower in patients with post-bariatric hypoglycaemia vs the non-surgical control group (median [IQR]: 24.7 [10.9, 38.7] pmol/l vs 238.7 [186.3, 288.9] pmol/l) (p=0.005). Other hormonal responses to hypoglycaemia and endogenous glucose production did not significantly differ between the groups. CONCLUSIONS/INTERPRETATION: The glucagon response to insulin-induced postprandial hypoglycaemia is lower in post-bariatric surgery individuals compared with non-surgical control individuals, irrespective of the surgical modality. No significant differences were found between patients with post-bariatric hypoglycaemia and surgical control individuals, suggesting that impaired counter-regulation is not a root cause of post-bariatric hypoglycaemia. TRIAL REGISTRATION: ClinicalTrials.gov NCT04334161.

Pancreatic polypeptide revisited: Potential therapeutic effects in obesity-diabetes.

Pancreatic polypeptide (PP), a member of the neuropeptide Y (NPY) family of peptides, is a hormone secreted from the endocrine pancreas with established actions on appetite regulation. Thus, through activation of hypothalamic neuropeptide Y4 (NPY4R or Y4) receptors PP induces satiety in animals and humans, suggesting potential anti-obesity actions. In addition, despite being actively secreted from pancreatic islets and evidence of local Y4 receptor expression, PP mediated effects on the endocrine pancreas have not been fully elucidated. To date, it appears that PP possesses an acute insulinostatic effect, similar to the impact of other peptides from the NPY family. However, it is interesting that prolonged activation of pancreatic Y1 receptors leads to established benefits on beta-cell turnover, preservation of beta-cell identity and improved insulin secretory responsiveness. This may hint towards possible similar anti-diabetic actions of sustained Y4 receptor modulation, since the Y1 and Y4 receptors trigger comparable cell signalling pathways. In terms of exploiting the prospective therapeutic promise of PP, this is severely restricted by a short circulating half-life as is the case for many regulatory peptide hormones. It follows that long-acting, enzyme resistant, forms of PP will be required to determine viability of the Y4 receptor as an anti-obesity and -diabetes drug target. The current review aims to refocus interest on the biology of PP and highlight opportunities for therapeutic development.

Assessing the Pathophysiology of Hyperglycemia in the Diabetes RElated to Acute Pancreatitis and Its Mechanisms Study: From the Type 1 Diabetes in Acute Pancreatitis Consortium.

OBJECTIVES: The metabolic abnormalities that lead to diabetes mellitus (DM) after an episode of acute pancreatitis (AP) have not been extensively studied. This article describes the objectives, hypotheses, and methods of mechanistic studies of glucose metabolism that comprise secondary outcomes of the DREAM (Diabetes RElated to Acute pancreatitis and its Mechanisms) Study. METHODS: Three months after an index episode of AP, participants without preexisting DM will undergo baseline testing with an oral glucose tolerance test. Participants will be followed longitudinally in three subcohorts with distinct metabolic tests. In the first and largest subcohort, oral glucose tolerance tests will be repeated 12 months after AP and annually to assess changes in ß-cell function, insulin secretion, and insulin sensitivity. In the second, mixed meal tolerance tests will be performed at 3 and 12 months, then annually, and following incident DM to assess incretin and pancreatic polypeptide responses. In the third, frequently sampled intravenous glucose tolerance tests will be performed at 3 months and 12 months to assess the first-phase insulin response and more precisely measure ß-cell function and insulin sensitivity. CONCLUSIONS: The DREAM study will comprehensively assess the metabolic and endocrine changes that precede and lead to the development of DM after AP.

Functional Insulinomas in a Rhesus Macaque (Macaca mulatta).

We report a rare case of functional insulinomas in a 16.7-year-old female Rhesus macaque (Macaca mulatta) that was presented with neuroglycopenic signs to the breeding colony hospital at the Tulane National Primate Research Center. At initial and follow-up examinations, the animal was consistently hypoglycaemic and was clinically maintained with additional fruits, other high-sugar food items and dextrose supplementation. Occasional episodes of seizure and collapse resolved quickly on administration of high-sugar food items. At necropsy, the uncinate process of the pancreas had a 2.2 cm diameter, red, round, firm neoplastic mass, and another neoplasm was identified on histological examination of the head of pancreas. Histologically, neoplastic cells exhibited neuroendocrine packeting, resembled pancreatic islet cells and immunolabelled for chromogranin A, synaptophysin and insulin but not for somatostatin, gastrin or pancreatic polypeptide. A few cells immunolabelled for glucagon. The clinical signs and gross and histological findings were consistent with functional insulinomas.

Establishment of an enzyme-linked immunosorbent assay for mouse pancreatic polypeptide clarifies the regulatory mechanism of its secretion from pancreatic γ cells.

Pancreatic polypeptide (PP), secreted from γ cells of the islets of Langerhans, is a 36 amino-acid peptide encoded by the Ppy gene. Although previous studies have reported that PP causes a decrease in appetite, the molecular mechanism that regulates PP secretion has not been fully elucidated. Lack of understanding of the regulatory mechanism of PP secretion may be partially owing to the lack of assay systems that can specifically detect PP. We recently developed the mouse monoclonal antibody 23-2D3 that specifically recognizes PP. In the present study, we developed a sandwich enzyme-linked immunosorbent assay for the measurement of mouse PP, and directly monitored intracellular Ca2+ concentrations in Ppy-expressing cells from a newly developed reporter mouse. Using these systems, we identified agonists, such as carbachol and glucose-dependent insulinotropic polypeptide (GIP), which stimulate PP secretion. We further demonstrated that, unlike the case of GIP-induced insulin secretion from ß cells, there is a unique mechanism by which PP secretion is triggered by an increase in intracellular Ca2+ concentrations via voltage-dependent calcium channels even in low-glucose conditions.

Impaired glucose tolerance is associated with enhanced postprandial pancreatic polypeptide secretion.

BACKGROUND: The purpose of this study is to compare serum pancreatic polypeptide (PP), insulin, C-peptide, and glucagon in different glucose tolerance stages; analyze the influencing factors of PP secretion; and further explore the role of PP in the pathogenesis of diabetes mellitus. METHODS: Data were collected from 100 subjects from hospital. According to the results of oral glucose tolerance test (OGTT), the subjects were divided into a normal glucose tolerance (NGT) group, an impaired glucose regulation (IGR) group, and a newly diagnosed type 2 diabetes mellitus (T2DM) group. PP and the related parameters were measured, and the area under the curve (AUC) 120 min after OGTT was calculated. AUCpp (AUC of PP) was used as the dependent variable and the potentially influencing factors were used as the independent variable for multiple linear regression analysis. RESULTS: Postprandial 60 min PP in the IGR group was higher than those in the NGT group (2973.80 [±547.49] pg·h/mL vs 2663.55 [±594.89] pg·h/mL, p < 0.05). AUCpp was significantly higher in the IGR group (428.76 pg·h/mL, 95% confidence interval [CI] [41.06 -816.46], p = 0.031) and newly diagnosed T2DM group (404.35 pg·h/mL, 95% CI [5.37-803.33], p = 0.047) than in the NGT group. AUCpp was negatively correlated with body mass index (BMI) (r = -0.235, p = 0.038) and positively correlated with postprandial 60 min blood glucose (r = 0.370, p = 0.001) and AUCbg (AUC of blood glucose) (r = 0.323, p = 0.007). Multiple linear regression analysis indicated that there was a linear correlation between BMI, AUCbg , and AUCpp (p = 0.004, p = 0.001), and the regression equation was calculated as: AUCpp  = 6592.272 + 86.275 × AUCbg -95.291 × BMI (R2  = 12.7%, p < 0.05). CONCLUSIONS: Compared with NGT subjects, IGR and T2DM patients have an enhanced postprandial PP secretion. In T2DMs, the secretion of PP is mainly affected by BMI and blood glucose.

Crystal structures of human neuropeptide Y (NPY) and peptide YY (PYY).

Neuropeptide Y (NPY), peptide YY (PYY) and pancreatic polypeptide (PP) form the evolutionarily conserved pancreatic polypeptide family. While the fold is widely utilized in nature, crystal structures remain elusive, particularly for the human forms, with only the structure of a distant avian form of PP reported. Here we utilize a crystallization chaperone (antibody Fab fragment), specifically recognizing the amidated peptide termini, to solve the structures of human NPY and human PYY. Intriguingly, and despite limited sequence identity (~50%), the structure of human PYY closely resembles that of avian PP, highlighting the broad structural conservation of the fold throughout evolution. Specifically, the PYY structure is characterized by a C-terminal amidated α-helix, preceded by a backfolded poly-proline N-terminus, with the termini in close proximity to each other. In contrast, in the structure of human NPY the N-terminal component is disordered, while the helical component of the peptide is observed in a four-helix bundle type arrangement, consistent with a propensity for multimerization suggested by NMR studies.

Multiplexed Assay to Quantify the PP-Fold Family of Peptides in Human Plasma Using Microflow Liquid Chromatography-Tandem Mass Spectrometry.

BACKGROUND: Peptide Tyr-Tyr (PYY1-36), pancreatic polypeptide (PP1-36) and neuropeptide Y (NPY1-36) constitute the PP-fold family of peptides that is involved in metabolic regulation. Very low plasma concentrations and cleavage into active 3-36 fragments challenge bioanalytical assays used for the quantification of these peptides. METHODS: We developed a multiplexed isotopic dilution assay to quantify PYY1-36, PP1-36, and NPY1-36 and their dipeptidyl peptidase-4 (DPP4)-derived metabolites PYY3-36, PP3-36 and NPY3-36. All peptides were immunocaptured from plasma using a monoclonal antibody and quantified by micro-ultra-HPLC-MS/MS. Blood samples from healthy volunteers were collected fasting and 30 min after nutrient stimulation. Method comparison was performed with commercial immunoassays. RESULTS: Linearity was shown in the measured intervals (r2 > 0.99). The lower limit of quantification (LLOQ) with a CV at 20% was 1.5 pM for PYY1-36 and PYY3-36, 3.0 pM for PP1-36 and PP3-36, 0.8 pM for NPY1-36 and 0.5 pM for NPY3-36. In all cases, intra- and inter-assay bias and imprecision were <21%. Pre-analytical stability required addition of a protease inhibitor cocktail. Physiological concentrations of PYY3-36, NPY3-36, PP1-36 and PP3-36 were above the LLOQ in 43% to 100% of the samples. PYY1-36 and NPY1-36 were above the LLOQ in 9% and 0% of the samples, respectively. Immunoassays showed higher concentrations of measurands and poor agreement when compared with micro-UHPLC-MS/MS. CONCLUSIONS: The assay allowed for specific multiplexed analysis of the PP-fold family of peptides and their DPP4-cleaved fragments in a single sample, thereby offering new perspectives to study the role and therapeutic potential of these essential peptide hormones in health and metabolic disease.

Peptides in the regulation of glucagon secretion.

Glucose homeostasis is maintained by the glucoregulatory hormones, glucagon, insulin and somatostatin, secreted from the islets of Langerhans. Glucagon is the body's most important anti-hypoglycemic hormone, mobilizing glucose from glycogen stores in the liver in response to fasting, thus maintaining plasma glucose levels within healthy limits. Glucagon secretion is regulated by both circulating nutrients, hormones and neuronal inputs. Hormones that may regulate glucagon secretion include locally produced insulin and somatostatin, but also urocortin-3, amylin and pancreatic polypeptide, and from outside the pancreas glucagon-like peptide-1 and 2, peptide tyrosine tyrosine and oxyntomodulin, glucose-dependent insulinotropic polypeptide, neurotensin and ghrelin, as well as the hypothalamic hormones arginine-vasopressin and oxytocin, and calcitonin from the thyroid. Each of these hormones have distinct effects, ranging from regulating blood glucose, to regulating appetite, stomach emptying rate and intestinal motility, which makes them interesting targets for treating metabolic diseases. Awareness regarding the potential effects of the hormones on glucagon secretion is important since secretory abnormalities could manifest as hyperglycemia or even lethal hypoglycemia. Here, we review the effects of each individual hormone on glucagon secretion, their interplay, and how treatments aimed at modulating the plasma levels of these hormones may also influence glucagon secretion and glycemic control.

Gastrointestinal Hormones in Healthy Adults: Reliability of Repeated Assessments and Interrelations with Eating Habits and Physical Activity.

Background: Gastrointestinal hormones (GIHs) are crucial for the regulation of a variety of physiological functions and have been linked to hunger, satiety, and appetite control. Thus, they might constitute meaningful biomarkers in longitudinal and interventional studies on eating behavior and body weight control. However, little is known about the physiological levels of GIHs, their intra-individual stability over time, and their interaction with other metabolic and lifestyle-related parameters. Therefore, the aim of this pilot study is to investigate the intra-individual stability of GIHs in normal-weight adults over time. Methods: Plasma concentrations of ghrelin, leptin, GLP-1 (glucagon-like-peptide), and PP (pancreatic polypeptide) were assessed by enzyme-linked immunosorbent assay (ELISA) in 17 normal-weight, healthy adults in a longitudinal design at baseline and at follow-up six months later. The reliability of the measurements was estimated using intra-class correlation (ICC). In a second step, we considered the stability of GIH levels after controlling for changes in blood glucose and hemoglobin A1 (HbA1c) as well as self-reported physical activity and dietary habits. Results: We found excellent reliability for ghrelin, good reliability for GLP1 and PP, and moderate reliability for leptin. After considering glucose, HbA1c, physical activity, and dietary habits as co-variates, the reliability of ghrelin, GLP1, and PP did not change significantly; the reliability of leptin changed to poor reliability. Conclusions: The GIHs ghrelin, GLP1, and PP demonstrated good to excellent test-retest reliability in healthy individuals, a finding that was not modified after adjusting for glucose control, physical activity, or dietary habits. Leptin showed only moderate to poor reliability, which might be linked to weight fluctuations, albeit small, between baseline and follow-up assessment in our study sample. Together, these findings support that ghrelin, GLP1, and PP might be further examined as biomarkers in studies on weight control, with GLP1 and PP serving as anorexic markers and ghrelin as an orexigenic marker. Additional reliability studies in obese individuals are necessary to verify or refute our findings for this cohort.

Supraphysiological effects of pancreatic polypeptide on gastric motor function and nutrient tolerance in humans.

Pancreatic polypeptide (PP) is known to affect food intake. In this exploratory study, we set out to investigate its supraphysiological effect on food tolerance, gastric accommodation, and emptying. In 12 healthy volunteers, 0, 3, or 10 pmol*kg-1 *min-1 PP was administered intravenously (PP0, PP3 or PP10). Thirty minutes thereafter, nutrient drink infusion (60 ml*min-1 ) through a nasogastric feeding tube was started until maximum satiation. Gastric accommodation was assessed by measuring the intragastric pressure (IGP; nasogastric manometry). In a separate test, the effect of PP0 or PP10 on gastric emptying was tested in 10 healthy volunteers and assessed using the 13 C breath test. Results are presented as mean ± SEM, and p < 0.05 was considered significant. For the IGP test, PP increased ingested nutrient volume: 886 ± 93, 1059 ± 124, and 1025 ± 125 ml for PP0, PP3, and PP10, respectively (p = 0.048). In all groups, Nadir IGP values were reached upon food intake (transformed values: 1.5 ± 0.2, 1.7 ± 0.3, and 1.6 ± 0.3 mmHg for PP0, PP3, and PP10, respectively; NS) to return to baseline thereafter. For the gastric emptying study, volunteers ingested a similar nutrient volume: 802 ± 119 and 1089 ± 128 ml (p = 0.016), and gastric half-emptying time was 281 ± 52 and 249 ± 37 min for PP0 and PP10, respectively (NS). No significant correlation between tolerated nutrient volume and IGP drop (R² < 0.01; p = 0.88 for PP0 vs. PP3 and R² =0.07; p = 0.40 for PP0 vs. PP10, respectively) or gastric half-emptying time (R² = 0.12; p = 0.32) was found. A supraphysiological PP dose enhances food tolerance; however, this effect is not mediated through gastric motility. CLINICAL TRIAL REGISTRY NUMBER: NCT03854708 is obtained from clinicaltrials.gov.

Pancreatic Ppy-expressing γ-cells display mixed phenotypic traits and the adaptive plasticity to engage insulin production.

The cellular identity of pancreatic polypeptide (Ppy)-expressing γ-cells, one of the rarest pancreatic islet cell-type, remains elusive. Within islets, glucagon and somatostatin, released respectively from α- and δ-cells, modulate the secretion of insulin by ß-cells. Dysregulation of insulin production raises blood glucose levels, leading to diabetes onset. Here, we present the genetic signature of human and mouse γ-cells. Using different approaches, we identified a set of genes and pathways defining their functional identity. We found that the γ-cell population is heterogeneous, with subsets of cells producing another hormone in addition to Ppy. These bihormonal cells share identity markers typical of the other islet cell-types. In mice, Ppy gene inactivation or conditional γ-cell ablation did not alter glycemia nor body weight. Interestingly, upon ß-cell injury induction, γ-cells exhibited gene expression changes and some of them engaged insulin production, like α- and δ-cells. In conclusion, we provide a comprehensive characterization of γ-cells and highlight their plasticity and therapeutic potential.

High Coexpression of the Ghrelin and LEAP2 Receptor GHSR With Pancreatic Polypeptide in Mouse and Human Islets.

Islets represent an important site of direct action of the hormone ghrelin, with expression of the ghrelin receptor (growth hormone secretagogue receptor; GHSR) having been localized variably to alpha cells, beta cells, and/or somatostatin (SST)-secreting delta cells. To our knowledge, GHSR expression by pancreatic polypeptide (PP)-expressing gamma cells has not been specifically investigated. Here, histochemical analyses of Ghsr-IRES-Cre × Cre-dependent ROSA26-yellow fluorescent protein (YFP) reporter mice showed 85% of GHSR-expressing islet cells coexpress PP, 50% coexpress SST, and 47% coexpress PP + SST. Analysis of single-cell transcriptomic data from mouse pancreas revealed 95% of Ghsr-expressing cells coexpress Ppy, 100% coexpress Sst, and 95% coexpress Ppy + Sst. This expression was restricted to gamma-cell and delta-cell clusters. Analysis of several single-cell human pancreatic transcriptome data sets revealed 59% of GHSR-expressing cells coexpress PPY, 95% coexpress SST, and 57% coexpress PPY + SST. This expression was prominent in delta-cell and beta-cell clusters, also occurring in other clusters including gamma cells and alpha cells. GHSR expression levels were upregulated by type 2 diabetes mellitus in beta cells. In mice, plasma PP positively correlated with fat mass and with plasma levels of the endogenous GHSR antagonist/inverse agonist LEAP2. Plasma PP also elevated on LEAP2 and synthetic GHSR antagonist administration. These data suggest that in addition to delta cells, beta cells, and alpha cells, PP-expressing pancreatic cells likely represent important direct targets for LEAP2 and/or ghrelin both in mice and humans.

Urinary Dopamine Excretion Rate Decreases during Acute Dietary Protein Deprivation and Is Associated with Increased Plasma Pancreatic Polypeptide Concentration.

Background: Dopamine, a key neurotransmitter in the autonomic nervous system participating in the homeostatic balance between sympathetic and parasympathetic divisions, is involved in food intake regulation. Objective: We investigated whether dopamine is altered by acute fasting or overfeeding diets with varying macronutrient content. Design: Ninety-nine healthy subjects underwent 24-h dietary interventions including eucaloric feeding, fasting, and five different overfeeding diets in a crossover design. Overfeeding diets (200% of eucaloric requirements) included one diet with 3%-protein (low-protein high-fat overfeeding-LPF: 46%-fat), three diets with 20%-protein, and a diet with 30%-protein (44%-fat). Urine was collected for 24 h and urinary dopamine concentration was quantified by high-performance liquid chromatography. Plasma pancreatic polypeptide (PP) concentration, an indirect marker of parasympathetic activity, was measured prior to and after each diet after an overnight fast. Results: During 24-h of fasting, dopamine decreased on average by ~14% compared to eucaloric conditions, whereas PP increased by two-fold (both p < 0.001). Lower dopamine during 24-h fasting correlated with increased PP (r = -0.40, p < 0.001). Similarly, on average urinary dopamine decreased during LPF by 14% (p < 0.001) and lower dopamine correlated with increased PP (r = -0.31, p = 0.01). No changes in dopamine and PP concentrations were observed during other overfeeding diets (all p > 0.05). Conclusions: Dopamine concentrations decrease during short-term fasting and overfeeding with a low-protein diet. As both dietary conditions have in common protein deficit, the correlation between dopamine and PP suggests a compensatory mechanism underlying the shift from sympathetic to parasympathetic drive during dietary protein deprivation.

Gut Hormones in Health and Obesity: The Upcoming Role of Short Chain Fatty Acids.

We are currently facing an obesity pandemic, with worldwide obesity rates having tripled since 1975. Obesity is one of the main risk factors for the development of non-communicable diseases, which are now the leading cause of death worldwide. This calls for urgent action towards understanding the underlying mechanisms behind the development of obesity as well as developing more effective treatments and interventions. Appetite is carefully regulated in humans via the interaction between the central nervous system and peripheral hormones. This involves a delicate balance in external stimuli, circulating satiating and appetite stimulating hormones, and correct functioning of neuronal signals. Any changes in this equilibrium can lead to an imbalance in energy intake versus expenditure, which often leads to overeating, and potentially weight gain resulting in overweight or obesity. Several lines of research have shown imbalances in gut hormones are found in those who are overweight or obese, which may be contributing to their condition. Therefore, this review examines the evidence for targeting gut hormones in the treatment of obesity by discussing how their dysregulation influences food intake, the potential possibility of altering the circulating levels of these hormones for treating obesity, as well as the role of short chain fatty acids and protein as novel treatments.

Effect of Acute Sprint Exercise on Myokines and Food Intake Hormones in Young Healthy Men.

Physical exercise is known to influence hormonal mediators of appetite, but the effect of short-term maximal intensity exercise on plasma levels of appetite hormones and cytokines has been little studied. We investigated the effect of a 30 s Wingate Test, followed by a postprandial period, on appetite sensations, food intake, and appetite hormones. Twenty-six physically active young males rated their subjective feelings of hunger, prospective food consumption, and fatigue on visual analogue scales at baseline, after exercise was completed, and during the postprandial period. Blood samples were obtained for the measurement of nesfatin-1, ghrelin, leptin, insulin, pancreatic polypeptide (PP), human growth factor (hGH) and cytokine interleukin-6 (IL-6), irisin and plasma lactate concentrations, at 30 min before exercise, immediately (210 s) after exercise, and 30 min following a meal and at corresponding times in control sedentary males without ad libitum meal intake, respectively. Appetite perceptions and food intake were decreased in response to exercise. Plasma levels of irisin, IL-6, lactate, nesfatin-1 and ghrelin was increased after exercise and then it was returned to postprandial/control period in both groups. A significant rise in plasma insulin, hGH and PP levels after exercise was observed while meal intake potentiated this response. In conclusion, an acute short-term fatiguing exercise can transiently suppress hunger sensations and food intake in humans. We postulate that this physiological response involves exercise-induced alterations in plasma hormones and the release of myokines such as irisin and IL-6, and supports the notion of existence of the skeletal muscle-brain-gut axis. Nevertheless, the detailed relationship between acute exercise releasing myokines, appetite sensations and impairment of this axis leading to several diseases should be further examined.

Co-impairment of autonomic and glucagon responses to insulin-induced hypoglycemia in dogs with naturally occurring insulin-dependent diabetes mellitus.

This study aimed to investigate the contributions of two factors potentially impairing glucagon response to insulin-induced hypoglycemia (IIH) in insulin-deficient diabetes: 1) loss of paracrine disinhibition by intra-islet insulin and 2) defects in the activation of the autonomic inputs to the islet. Plasma glucagon responses during hyperinsulinemic-hypoglycemic clamps ([Formula: see text]40 mg/dL) were assessed in dogs with spontaneous diabetes (n = 13) and in healthy nondiabetic dogs (n = 6). Plasma C-peptide responses to intravenous glucagon were measured to assess endogenous insulin secretion. Plasma pancreatic polypeptide, epinephrine, and norepinephrine were measured as indices of parasympathetic and sympathoadrenal autonomic responses to IIH. In 8 of the 13 diabetic dogs, glucagon did not increase during IIH (diabetic nonresponder [DMN]; ∆ = -6 ± 12 pg/mL). In five other diabetic dogs (diabetic responder [DMR]), glucagon responses (∆ = +26 ± 12) were within the range of nondiabetic control dogs (∆ = +27 ± 16 pg/mL). C-peptide responses to intravenous glucagon were absent in diabetic dogs. Activation of all three autonomic responses were impaired in DMN dogs but remained intact in DMR dogs. Each of the three autonomic responses to IIH was positively correlated with glucagon responses across the three groups. The study conclusions are as follows: 1) Impairment of glucagon responses in DMN dogs is not due to generalized impairment of α-cell function. 2) Loss of tonic inhibition of glucagon secretion by insulin is not sufficient to produce loss of the glucagon response; impairment of autonomic activation is also required. 3) In dogs with major ß-cell function loss, activation of the autonomic inputs is sufficient to mediate an intact glucagon response to IIH.NEW & NOTEWORTHY In dogs with naturally occurring, insulin-dependent (C-peptide negative) diabetes mellitus, impairment of glucagon responses is not due to generalized impairment of α-cell function. Loss of tonic inhibition of glucagon secretion by insulin is not sufficient, by itself, to produce loss of the glucagon response. Rather, impaired activation of the parasympathetic and sympathoadrenal autonomic inputs to the pancreas is also required. Activation of the autonomic inputs to the pancreas is sufficient to mediate an intact glucagon response to insulin-induced hypoglycemia in dogs with naturally occurring diabetes mellitus. These results have important implications that include leading to a greater understanding and insight into the pathophysiology, prevention, and treatment of hypoglycemia during insulin treatment of diabetes in companion dogs and in human patients.

GPR120 Regulates Pancreatic Polypeptide Secretion From Male Mouse Islets via PLC-Mediated Calcium Mobilization.

The free fatty acid receptor G protein-coupled receptor 120 (GPR120) is expressed in pancreatic islets, but its specific cell distribution and function have not been fully established. In this study, a GPR120-IRES-EGFP knockin (KI) mouse was generated to identify GPR120-expressing cells with enhanced green fluorescence proteins (EGFP). EGFP-positive cells collected from KI mouse islets by flow cytometry had a significantly higher expression of pancreatic polypeptide (PP) evidenced by reverse transcriptase (RT)-quantitative polymerase chain reaction (qPCR). Single-cell RT-PCR and immunocytochemical double staining also demonstrated the coexpression of GPR120 with PP in mouse islets. The GPR120-specific agonist TUG-891 significantly increased plasma PP levels in mice. TUG-891 significantly increased PP levels in islet medium in vitro, which was markedly attenuated by GPR120 small interfering RNA treatment. TUG-891-stimulated PP secretion in islets was fully blocked by pretreatment with YM-254890 (a Gq protein inhibitor), U73122 (a phospholipase C inhibitor), or thapsigargin (an inducer of endoplasmic reticulum Ca2+ depletion), respectively. TUG-891 triggered the increase in intracellular free Ca2+ concentrations ([Ca2+]i) in PP cells, which was also eliminated by YM-254890, U73122, or thapsigargin. GPR120 gene expression was significantly reduced in islets of high-fat diet (HFD)-induced obese mice. TUG-891-stimulated PP secretion was also significantly diminished in vivo and in vitro in HFD-induced obese mice compared with that in normal-chow diet control mice. In summary, this study demonstrated that GPR120 is expressed in mouse islet PP cells and GPR120 activation stimulated PP secretion via the Gq/PLC-Ca2+ signaling pathway in normal-chow diet mice but with diminished effects in HFD-induced obese mice.

Plasma Protein Panels for Mild Cognitive Impairment Among Elderly Chinese Individuals with Different Educational Backgrounds.

To explore plasma protein panels as potential biomarkers to screen for mild cognitive impairment (MCI) among elderly Chinese individuals with different educational backgrounds. Forty-four illiterate, 36 lower education (1-6 years), and 55 higher education (7 years or more) elderly individuals were included in the present study. Among all subjects, 67 were healthy individuals and 68 were diagnosed with MCI. Fifty plasma proteins in blood samples collected from these subjects were analyzed via the Luminex assay. Binary logistic regression was utilized to explore diagnostic models for MCI among the three educational subgroups. Then, receiver operating characteristic (ROC) curves were conducted for the clinical validity of the MCI models. Among the analyzed proteins, clusterin was used in the model of MCI among the total sample with a sensitivity (se) of 67.6%, a specificity (sp) of 59.7%, and a classification rate of 63.68%. The MCI model for the illiterate group included cystatin C, plasminogen activator inhibitor-1, and apolipoprotein A-I (se: 71.4%, sp.: 82.6%, accuracy: 77.25%). The sensitivity, specificity, and classification rate of the diagnostic model of MCI in elderly adults with lower education (human serum albumin) were each 75.0%. Additionally, the sensitivity, specificity, and accuracy rate of the diagnostic model for MCI elderly individuals with higher education (alpha-acid glycoprotein + soluble intercellular adhesion molecule-1 + pancreatic polypeptide) were 77.8%, 89.3%, and 83.60%, respectively. The performance of diagnostic models for MCI based on different educational levels is superior to that of diagnostic models for MCI without grouping by educational level.