Glucosensing in the gastrointestinal tract: Impact on glucose metabolism

Intestinal gluconeogenesis: A translator of nutritional information needed for glycemic and emotional balance

At the interface between the outside world and the self, the intestine is the first organ receiving nutritional information. One intestinal function, gluconeogenesis, is activated by various nutrients, particularly diets enriched in fiber or protein, and thus results in glucose production in the portal vein in the post-absorptive period. The detection of portal glucose induces a nervous signal controlling the activity of the central nuclei involved in the regulation of metabolism and emotional behavior. Induction of intestinal gluconeogenesis is necessary for the beneficial effects of fiber or protein-enriched diets on metabolism and emotional behavior. Through its ability to translate nutritional information from the diet to the brain's regulatory centers, intestinal gluconeogenesis plays an essential role in maintaining physiological balance.

Should Glucokinase be Given a Chance in Diabetes Therapeutics? A Clinical-Pharmacological Review of Dorzagliatin and Lessons Learned So Far

Despite advances in the management of type 2 diabetes mellitus (T2DM), one-third of patients with diabetes do not achieve the desired glycemic goal. Considering this inadequacy, many agents that activate glucokinase have been investigated over the last two decades but were withdrawn before submission for marketing permission. Dorzagliatin is the first glucokinase activator that has been granted approval for T2DM, only in China. As overstimulation of glucokinase is linked with pathophysiological disturbances such as fatty liver and cardiovascular issues and a loss of therapeutic efficacy with time. This review aims to highlight the benefits of glucokinase activators vis-à-vis the risks associated with chronic enzymatic activation. We discuss the multisystem disturbances expected with chronic activation of the enzyme, the lessons learned with glucokinase activators of the past, the major efficacy and safety findings with dorzagliatin and its pharmacological properties, and the status of other glucokinase activators in the pipeline. The approval of dorzagliatin in China was based on the SEED and the DAWN trials, the major pivotal phase III trials that enrolled patients with T2DM with a mean glycosylated hemoglobin of 8.3-8.4%, and a mean age of 53-54.5 years from multiple sites in China. Patients with uncontrolled diabetes, cardiac diseases, organ dysfunction, and a history of severe hypoglycemia were excluded. Both trials had a randomized double-blind placebo-controlled phase of 24 weeks followed by an open-label phase of 28 weeks with dorzagliatin. Drug-naïve patients with T2DM with a disease duration of 11.7 months were enrolled in the SEED trial while the DAWN trial involved patients with T2DM with a mean duration of 71.5 months and receiving background metformin therapy. Compared with placebo, the decline in glycosylated hemoglobin at 24 weeks was more with dorzagliatin with an estimated treatment difference of - 0.57% in the SEED trial and - 0.66% in the DAWN trial. The desired glycosylated hemoglobin (< 7%) was also attained at more than two times higher rates with dorzagliatin. The glycemic improvement was sustained in the SEED trial but decreased over 52 weeks in the DAWN trial. Hyperlipidemia was observed in 12-14% of patients taking dorzagliatin versus 9-11% of patients receiving a placebo. Additional adverse effects noticed over 52 weeks with dorzagliatin included an elevation in liver enzymes, hyperuricemia, hyperlacticacidemia, renal dysfunction, and cardiovascular disturbances. Considering the statistically significant improvement in glycosylated hemoglobin with dorzagliatin in patients with T2DM, the drug may be given a chance in treatment-naïve patients with a shorter disease history. However, with the waning therapeutic efficacy witnessed in patients with long-standing diabetes, which was also one of the potential concerns with previously tested molecules, extended studies involving patients with chronic and uncontrolled diabetes are needed to comment upon the long-term therapeutic performance of dorzagliatin. Likewise, evidence needs to be generated from other countries, patients with organ dysfunction, a history of severe hypoglycemia, cardiac diseases, and elderly patients before extending the use of dorzagliatin. Apart from monitoring lipid profiles, long-term safety studies of dorzagliatin should involve the assessment of serum uric acid, lactate, renal function, liver function, and cardiovascular parameters.

Current and future therapies to treat impaired awareness of hypoglycemia

In order to achieve optimal glycemic control, intensive insulin regimes are needed for individuals with Type 1 Diabetes (T1D) and insulin-dependent Type 2 Diabetes (T2D). Unfortunately, intensive glycemic control often results in insulin-induced hypoglycemia. Moreover, recurrent episodes of hypoglycemia result in both the loss of the characteristic warning symptoms associated with hypoglycemia and an attenuated counterregulatory hormone responses. The blunting of warning symptoms is known as impaired awareness of hypoglycemia (IAH). Together, IAH and the loss of the hormonal response is termed hypoglycemia associated autonomic failure (HAAF). IAH is prevalent in up to 25% in people with T1D and up to 10% in people with T2D. IAH and HAAF increase the risk of severe hypoglycemia 6-fold and 25-fold, respectively. To reduce this risk for severe hypoglycemia, multiple different therapeutic approaches are being explored that could improve awareness of hypoglycemia. Current therapies to improve awareness of hypoglycemia include patient education and psychoeducation, the use of novel glycemic control technology, pancreas/islet transplantation, and drug therapy. This review examines both existing therapies and potential therapies that are in pre-clinical testing. Novel treatments that improve awareness of hypoglycemia, via improving the counterregulatory hormone responses or improving hypoglycemic symptom recognition, would also shed light on the possible neurological mechanisms that lead to the development of IAH. To reduce the risk of severe hypoglycemia in people with diabetes, elucidating the mechanism behind IAH, as well as developing targeted therapies is currently an unmet need for those that suffer from IAH.

Lycium barbarum Polysaccharides Improved Glucose Metabolism in Prediabetic Mice by Regulating Duodenal Contraction

Lycium barbarum polysaccharides (LBPs) have been shown to exert an antiglycemic effect. Emerging evidence suggests that patients with hyperglycemia have a hypercontractility of duodenum, and targeting duodenal contraction of duodenum can be beneficial to glucose metabolism. However, it is unknown whether LBPs can improve glucose metabolism by regulating the hypercontractility of the duodenum. Our aim was to explore the effect of LBPs on duodenal contraction in prediabetic mice and also preliminarily investigate the mechanism. The results showed that LBPs improved glucose homeostasis by decreasing the duodenal amplitude of contraction rather than frequency. Moreover, LBPs ameliorated the gut microbiota composition and the levels of short-chain fatty acids, especially acetic acid, which might bind to the receptor on neurons to regulate the contraction of the duodenum. Acetic acid was hypothesized to play a key role in the above process. Then, acetic acid was determined to exert an antiglycemic effect as expected. In conclusion, LBPs may rely on acetic acid to regulate duodenal contraction to ameliorate glucose metabolism in prediabetic mice, which provides a new therapeutic strategy to treat dysglycemia.

Mettl14-mediated m6 A modification regulates the abnormal differentiation of small intestinal epithelial stem cells in diabetic state

Diabetes mellitus (DM) and its related complications are a global epidemic characterized by high morbidity and mortality. However, little is known about diabetic enteropathy (DE) and its the potential underlying mechanism. Intestinal epithelial stem cells (IESCs) were harvested from experimental mice, and the levels of dominant N6-methyladenosine (m6 A)-related enzyme were detected by RT-PCR, Western blotting, immunohistochemistry. The role of Mettl14 in the abnormal differentiation of intestinal epithelial cells (IECs) during DM was confirmed by knockdown experiments. RT-PCR, MeRIP, and bioinformatics analysis were carried out to confirm the downstream target of Mettl14. Through bioinformatics analysis, RT-PCR, and Western blotting, we further analyzed the differentiation-related gene in the IECs from mice with DM. In this study, the levels of Mettl14 and m6 A were higher in db/db mice than that in control mice. And abnormal differentiation of IECs in DM was associated with Mettl14 overexpression. Additionally, Mettl14 is a major determinant of IESCs identity and organoid-forming upon DM state. Mechanistically, we revealed that the candidate binding target of Mettl14 was Fzd2 mRNA and affected Fzd2 stability. Moreover, Mettl14 downregulation was observed to attenuate the abnormal differentiation of IECs through modulating Fzd2 m6A modification in DM state. Together, our results provide definitive evidence for the essential role of Mettl14 in differentiation of IESCs in DM state.

Pasteurized Akkermansia muciniphila improves glucose metabolism is linked with increased hypothalamic nitric oxide release

Background and objective

Pasteurized Akkermansia muciniphila cells have shown anti-diabetic effects in rodents and human. Although, its primary site of action consists in maintaining the gut barrier function, there are no study exploring if A. muciniphila controls glycemia via a gut to brain axis. Targeting the gut motility represents an alternative pathway to treat hyperglycemia. Here, we tested the impact of pasteurized A. muciniphila on gut motility, gut-brain axis and glucose metabolism.

Methods

We used mice fed a 45% high-fat (HFD) treated or not with pasteurized A. muciniphila Muc^T during 12 weeks. We measured the effects of the treatment on body weight gain, glucose metabolism (insulin, glycemia, glucose tolerance), gut contraction and enteric neurotransmitter release, and hypothalamic nitric oxide (NO) release.

Results

We show that pasteurized A. muciniphila exerts positive effects on different metabolic parameters such as body weight, fat mass, insulin, glycemia and glucose tolerance. This could be explained by the ability of pasteurized A. muciniphila supplementation to decrease duodenal contraction and to increase hypothalamic NO release in HFD mice.

Conclusion

We demonstrate a novel mode of action of pasteurized A. muciniphila explaining its beneficial impact on the control of glycemia in a preclinical model of type 2 diabetes via gut-brain axis signaling.

Oral administration of Nigella sativa oil attenuates arsenic-induced redox imbalance, DNA damage, metabolic distress, and histopathological alterations in rat intestine

BACKGROUND

Exposure to arsenic, a widespread environmental toxin, produces multiple organ toxicity, including gastrointestinal toxicity. Nigella sativa (NS) has long been revered for its numerous health benefits under normal and pathological states. In view of this, the present study attempts to evaluate the protective efficacy of orally administered Nigella sativa oil (NSO) against arsenic-induced cytotoxic and genotoxic alterations in rat intestine and elucidate the underlying mechanism of its action.

METHODS

Rats were categorized into the control, NaAs, NSO, and NaAs+NSO groups. After pre-treatment of rats in the NaAs+NSO and NSO groups daily with NSO (2 ml/kg bwt, orally) for 14 days, NSO treatment was further continued for 30 days, with and without NaAs treatment (5 mg/kg bwt, orally), respectively. Various biochemical parameters, such as enzymatic and non-enzymatic antioxidants, carbohydrate metabolic and brush border membrane marker enzyme activities were evaluated in the mucosal homogenates of all the groups. Intestinal brush border membrane vesicles (BBMV) were isolated, and the activities of membrane marker enzyme viz. ALP, GGTase, LAP, and sucrase were determined. Further, the effect on kinetic parameters viz K_M (Michaelis-Menten constant) and V_max of these enzymes was assessed. Integrity of enterocyte DNA was examined using the comet assay. Histopathology of the intestines was performed to evaluate the histoarchitectural alterations induced by chronic arsenic exposure and/or NSO supplementation. Arsenic accumulation in the intestine was studied by inductively coupled plasma-mass spectroscopy (ICP-MS).

RESULTS

NaAs treatment caused substantial changes in the activities of brush border membrane (BBM), carbohydrate metabolism, and antioxidant defense enzymes in the intestinal mucosal homogenates. The isolated BBM vesicles (BBMV) also showed marked suppression in the marker enzyme activities. Severe DNA damage and mucosal arsenic accumulation were observed in rats treated with NaAs alone. In contrast, oral NSO supplementation significantly alleviated all the adverse alterations induced by NaAs treatment. Histopathological examination supported the biochemical findings.

CONCLUSION

NSO, by improving the antioxidant status and energy metabolism, could significantly alter the ability of the intestine to protect against free radical-mediated arsenic toxicity in intestine. Thus, NSO may have an excellent scope in managing gastrointestinal distress in arsenic intoxication.

Intestinal gluconeogenesis: metabolic benefits make sense in the light of evolution

The intestine, like the liver and kidney, in various vertebrates and humans is able to carry out gluconeogenesis and release glucose into the blood. In the fed post-absorptive state, intestinal glucose is sensed by the gastrointestinal nervous system. The latter initiates a signal to the brain regions controlling energy homeostasis and stress-related behaviour. Intestinal gluconeogenesis (IGN) is activated by several complementary mechanisms, in particular nutritional situations (for example, when food is enriched in protein or fermentable fibre and after gastric bypass surgery in obesity). In these situations, IGN has several metabolic and behavioural benefits. As IGN is activated by nutrients capable of fuelling systemic gluconeogenesis, IGN could be a signal to the brain that food previously ingested is suitable for maintaining plasma glucose for a while. This process might account for the benefits observed. Finally, in this Perspective, we discuss how the benefits of IGN in fasting and fed states could explain why IGN emerged and was maintained in vertebrates by natural selection.

Reactive Oxygen Species/Reactive Nitrogen Species as Messengers in the Gut: Impact on Physiology and Metabolic Disorders

Significance: The role of reactive oxygen/nitrogen species as "friend" or "foe" messengers in the whole body is well characterized. Depending on the concentration in the tissue considered, these molecular actors exert beneficial or deleterious impacts leading to a pathological state, as observed in metabolic disorders such as type 2 diabetes and obesity. Recent Advances: Among the tissues impacted by oxidation and inflammation in this pathological state, the intestine is a site of dysfunction that can establish diabetic symptoms, such as alterations in the intestinal barrier, gut motility, microbiota composition, and gut/brain axis communication. In the intestine, reactive oxygen/nitrogen species (from the host and/or microbiota) are key factors that modulate the transition from physiological to pathological signaling. Critical Issues: Controlling the levels of intestinal reactive oxygen/nitrogen species is a complicated balance between positive and negative impacts that is in constant equilibrium. Here, we describe the synthesis and degradation of intestinal reactive oxygen/nitrogen species and their interactions with the host. The development of novel redox-based therapeutics that alter these processes could restore intestinal health in patients with metabolic disorders. Future Directions: Deciphering the mode of action of reactive oxygen/nitrogen species in the gut of obese/diabetic patients could result in a future therapeutic strategy that combines nutritional and pharmacological approaches. Consequently, preventive and curative treatments must take into account one of the first sites of oxidative and inflammatory dysfunctions in the body, that is, the intestine. Antioxid. Redox Signal. 37, 394-415.

Glucose Stimulates Gut Motility in Fasted and Fed Conditions: Potential Involvement of a Nitric Oxide Pathway

(1) Background: Type 2 diabetes (T2D) is associated with a duodenal hypermotility in postprandial conditions that favors hyperglycemia and insulin resistance via the gut-brain axis. Enterosynes, molecules produced within the gut with effects on the enteric nervous system, have been recently discovered and pointed to as potential key modulators of the glycemia. Indeed, targeting the enteric nervous system that controls gut motility is now considered as an innovative therapeutic way in T2D to limit intestinal glucose absorption and restore the gut-brain axis to improve insulin sensitivity. So far, little is known about the role of glucose on duodenal contraction in fasted and fed states in normal and diabetic conditions. The aim of the present study was thus to investigate these effects in adult mice. (2) Methods: Gene-expression level of glucose transporters (SGLT-1 and GLUT2) were quantified in the duodenum and jejunum of normal and diabetic mice fed with an HFD. The effect of glucose at different concentrations on duodenal and jejunal motility was studied ex vivo using an isotonic sensor in fasted and fed conditions in both normal chow and HFD mice. (3) Results: Both SGLT1 and GLUT2 expressions were increased in the duodenum (47 and 300%, respectively) and jejunum (75% for GLUT2) of T2D mice. We observed that glucose stimulates intestinal motility in fasted (200%) and fed (400%) control mice via GLUT2 by decreasing enteric nitric oxide release (by 600%), a neurotransmitter that inhibits gut contractions. This effect was not observed in diabetic mice, suggesting that glucose sensing and mechanosensing are altered during T2D. (4) Conclusions: Glucose acts as an enterosyne to control intestinal motility and glucose absorption through the enteric nervous system. Our data demonstrate that GLUT2 and a reduction of NO production could both be involved in this stimulatory contracting effect.

Fecal Microbiota Transplant in a Pre-Clinical Model of Type 2 Diabetes Mellitus, Obesity and Diabetic Kidney Disease

Diabetes mellitus (DM) burden encompasses diabetic kidney disease (DKD), the leading cause of end-stage renal disease worldwide. Despite compelling evidence indicating that pharmacological intervention curtails DKD progression, the search for non-pharmacological strategies can identify novel targets for drug development against metabolic diseases. One of those emergent strategies comprises the modulation of the intestinal microbiota through fecal transplant from healthy donors. This study sought to investigate the benefits of fecal microbiota transplant (FMT) on functional and morphological parameters in a preclinical model of type 2 DM, obesity, and DKD using BTBR^ob/ob mice. These animals develop hyperglycemia and albuminuria in a time-dependent manner, mimicking DKD in humans. Our main findings unveiled that FMT prevented body weight gain, reduced albuminuria and tumor necrosis factor-α (TNF-α) levels within the ileum and ascending colon, and potentially ameliorated insulin resistance in BTBR^ob/ob mice. Intestinal structural integrity was maintained. Notably, FMT was associated with the abundance of the succinate-consuming Odoribacteraceae bacteria family throughout the intestine. Collectively, our data pointed out the safety and efficacy of FMT in a preclinical model of type 2 DM, obesity, and DKD. These findings provide a basis for translational research on intestinal microbiota modulation and testing its therapeutic potential combined with current treatment for DM.

Neuro-immune-metabolism: The tripod system of homeostasis

Homeostatic regulation of cellular and molecular processes is essential for the efficient physiological functioning of body organs. It requires an intricate balance of several networks throughout the body, most notable being the nervous, immune and metabolic systems. Several studies have reported the interactions between neuro-immune, immune-metabolic and neuro-metabolic pathways. Current review aims to integrate the information and show that neuro, immune and metabolic systems form the triumvirate of homeostasis. It focuses on the cellular and molecular interactions occurring in the extremities and intestine, which are innervated by the peripheral nervous system and for the intestine in particular the enteric nervous system. While the interdependence of neuro-immune-metabolic pathways provides a fallback mechanism in case of disruption of homeostasis, in chronic pathologies of continued disequilibrium, the collapse of one system spreads to the other interacting networks as well. Current review illustrates this domino-effect using diabetes as the main example. Together, this review attempts to provide a holistic picture of the integrated network of neuro-immune-metabolism and attempts to broaden the outlook when devising a scientific study or a treatment strategy.

Fluoroquinolones-Associated Disability: It Is Not All in Your Head

Fluoroquinolones (FQs) are a broad class of antibiotics typically prescribed for bacterial infections, including infections for which their use is discouraged. The FDA has proposed the existence of a permanent disability (Fluoroquinolone Associated Disability; FQAD), which is yet to be formally recognized. Previous studies suggest that FQs act as selective GABAA receptor inhibitors, preventing the binding of GABA in the central nervous system. GABA is a key regulator of the vagus nerve, involved in the control of gastrointestinal (GI) function. Indeed, GABA is released from the Nucleus of the Tractus Solitarius (NTS) to the Dorsal Motor Nucleus of the vagus (DMV) to tonically regulate vagal activity. The purpose of this review is to summarize the current knowledge on FQs in the context of the vagus nerve and examine how these drugs could lead to dysregulated signaling to the GI tract. Since there is sufficient evidence to suggest that GABA transmission is hindered by FQs, it is reasonable to postulate that the vagal circuit could be compromised at the NTS-DMV synapse after FQ use, possibly leading to the development of permanent GI disorders in FQAD.

An integrated systematic approach for investigating microcurrent electrical nerve stimulation (MENS) efficacy in STZ-induced diabetes mellitus

Diabetes mellitus (DM) is a major metabolic disorder and an increasing health problem worldwide. Effective non-invasive therapies for DM are still lacking. Here, we have developed Microcurrent electrical nerve stimulation (MENS), a non-invasive therapy, and tested on 46 mice clustered into five groups, such as control, STZ-induced DM, and MENS treatment groups. Experimental results show that MENS treatment is able to improve seven biochemical indexes (e.g., hemoglobin A1c and glucose level). To investigate the mechanisms of MENS treatment on STZ-induced DM, we selected six representative samples to perform microarray experiments for several groups and developed an integrated Hierarchical System Biology Model (HiSBiM) to analyze these omics data. The results indicate that MENS can affect fatty acid metabolism pathways, peroxisome proliferator-activated receptor (PPAR) signaling pathway and cell cycle. Additionally, the DM biochemical indexes and omics data profiles of MENS treatment were found to be consistent. We then compared the therapeutic effects of MENS with anti-diabetic compounds (e.g., quercetin, metformin, and rosiglitazone), using the HiSBiM four-level biological functions and processes of multiple omics data. The results show MENS and these anti-diabetic compounds have similar effect pathways highly correlated to the diabetes processes, such as the PPAR signaling pathway, bile secretion, and insulin signaling pathways. We believe that MENS is an effective and non-invasive therapy for DM and our HiSBiM is an useful method for investigating multiple omics data.

Differences in intestinal microbiota profiling after upper and lower gastrointestinal surgery

BACKGROUND

We aimed to investigate the long-term effects of metabolic profiles and microbiota status in patients after upper gastrointestinal (GI) surgery and lower GI surgery and compared them with a control group.

METHODS

In this cross-sectional study, we analyzed the occurrence of metabolic syndrome (MS) in 10 patients who underwent curative total gastrectomy with Roux-en-Y esophagojejunostomy (RYEJ) anastomosis, 11 patients who underwent curative partial colectomy with right hemicolectomy (RH), and 33 age- and sex-matched controls. Fecal samples were also analyzed by a next-generation sequencing method.

RESULTS

Compared with the control group, the occurrence of MS was significantly lower among patients who underwent total gastrectomy with RYEJ than the controls over the long-term follow-up (>8 years; p < 0.05). Patients who received RH only had a trend of higher serum fasting glucose (p = 0.10). The diversity of the gut microbiota significantly decreased after RH in comparison with the control group and RYEJ group, respectively (p < 0.05). Principal component analysis revealed significant differences between the control, RYEJ, and RH groups (p < 0.001). At the genus level, the ratio of Prevotella to Bacteroides (P/B) was significantly higher in the RYEJ group than in the control group, whereas the P/B ratio was significantly lower in the RH group than in the control group (p < 0.05).

CONCLUSION

Early gastric cancer patients who received total gastrectomy with RYEJ had a lower occurrence of MS than the controls, while early colorectal cancer patients who received RH were associated with a higher serum fasting glucose than the controls during long-term follow-up. In parallel with the metabolic differences, the P/B ratio was also significantly altered in patients after upper and lower GI surgery.

Glycemic variability in patients with gastrointestinal cancer: An integrative review

PURPOSE

Glycemic variability is associated with risks for adverse events in patients with cancer. Several studies have evaluated the presence and impact of hyperglycemia and/or hypoglycemia in patients with cancer; however, few studies have evaluated glycemic variability. The purpose of this integrative review of studies in patients with gastrointestinal cancers was to investigate the presence and methods of reporting glycemic variability during and following treatments.

METHODS

A comprehensive review of the literature was conducted. PubMed, CINAHL, EMBASE, and Cochrane databases were searched for publications between 1/1/1969 and 7/24/2019. Studies of patients with gastrointestinal cancer following surgery, during treatment, and <5 years following treatment were included and evaluated by cancer type and method of glucose and glycemic variability measurement.

RESULTS

Among 1526 patients with gastrointestinal cancer across 19 studies, gastric and pancreatic cancers were most prevalent. Timing of glucose testing and methods of analyzing glycemic variability varied. Most analyses used the standard deviation or interquartile range. Glycemic variability was more prevalent among patients with Type 2 Diabetes and among those with pancreatic cancer. In some patients glycemic variability remained notable > one year following surgery despite improvements in glycemic control.

CONCLUSION

Patients with gastrointestinal cancer experience glycemic variability during and up to one year following treatment. There was heterogeneity in methods related to timing of testing and reporting glycemic variability among the 19 studies in this review. Future investigations need to identify the presence and define the methods of measuring glycemic variability in patients with gastrointestinal cancer.

Expression of asprosin in rat hepatic, renal, heart, gastric, testicular and brain tissues and its changes in a streptozotocin-induced diabetes mellitus model

In this study, we aimed to investigate the presence of asprosin (ASP) in the liver, kidneys, heart, stomach, testicles and brain and to determine the serum and tissue asprosin levels in diabetic rats. A total of 14 male Wistar Albino rats were divided into two groups, each containing 7 rats: (I) control group and (II) experimental diabetes group. Control rats received no treatment and the rats in the experiment group received single-dose of streptozotocin (STZ) (50 mg/kg) dissolved in 0.1 M sodium citrate buffer (pH: 4.5) intraperitoneally. Serum levels of asprosin were measured using ELISA method. The presence of asprosin in hepatic, renal, cardiac, gastric, testicular and brain tissues was investigated using immunohistochemical staining. Asprosin was detected in hepatocytes in the liver, cortical distal tubule cells in the kidney, cardiomyocytes in heart, surface epithelial cells of stomach fundus, interstitial Leydig cells in testes and cortical neurons of the brain. Compared to control group, it was found that diabetic rats had decreased asprosin levels in liver, kidney and heart tissues, increased levels in gastric and testicular tissues and no significant changes in brain tissue. Serum asprosin levels of diabetic rats were found to be decreased compared to the control group. This is the first study in the literature that reports the presence of asprosin in liver, kidney, heart, stomach, testis and brain tissues in rats. The aim of the study is to determine the presence of ASP, a newly discovered adipokine, in various tissues and to examine tissue and serum level changes in STZ-induced diabetes.

Targeting the Enteric Nervous System to Treat Metabolic Disorders? "Enterosynes" as Therapeutic Gut Factors

The gut-brain axis is of crucial importance for controlling glucose homeostasis. Alteration of this axis promotes the type 2 diabetes (T2D) phenotype (hyperglycaemia, insulin resistance). Recently, a new concept has emerged to demonstrate the crucial role of the enteric nervous system in the control of glycaemia via the hypothalamus. In diabetic patients and mice, modification of enteric neurons activity in the proximal part of the intestine generates a duodenal hyper-contractility that generates an aberrant message from the gut to the brain. In turn, the hypothalamus sends an aberrant efferent message that provokes a state of insulin resistance, which is characteristic of a T2D state. Targeting the enteric nervous system of the duodenum is now recognized as an innovative strategy for treatment of diabetes. By acting in the intestine, bioactive gut molecules that we called "enterosynes" can modulate the function of a specific type of neurons of the enteric nervous system to decrease the contraction of intestinal smooth muscle cells. Here, we focus on the origins of enterosynes (hormones, neurotransmitters, nutrients, microbiota, and immune factors), which could be considered therapeutic factors, and we describe their modes of action on enteric neurons. This unsuspected action of enterosynes is proposed for the treatment of T2D, but it could be applied for other therapeutic solutions that implicate communication between the gut and brain.

Recording and Decoding of Vagal Neural Signals Related to Changes in Physiological Parameters and Biomarkers of Disease

Our bodies have built-in neural reflexes that continuously monitor organ function and maintain physiological homeostasis. Whereas the field of bioelectronic medicine has mainly focused on the stimulation of neural circuits to treat various conditions, recent studies have started to investigate the possibility of leveraging the sensory arm of these reflexes to diagnose disease states. To accomplish this, neural signals emanating from the body's built-in biosensors and propagating through peripheral nerves must be recorded and decoded to identify the presence or levels of relevant biomarkers of disease. The process of acquiring these signals poses several technical challenges related to the neural interfaces, surgical techniques, and data-processing framework needed to record and analyze them. However, these challenges can be addressed with a rigorous experimental approach and new advances in implantable electrodes, signal processing, and machine learning methods. Outlined in this review are studies decoding vagus nerve activity as it related to inflammatory, metabolic, and cardiopulmonary biomarkers. Successfully decoding peripheral nerve activity related to disease states will not only enable the development of real-time diagnostic devices, but also help advancing truly closed-loop neuromodulation technologies.

The Gastrointestinal Tract as Prime Site for Cardiometabolic Protection by Dietary Polyphenols

Substantial evidence from nutritional epidemiology links polyphenol-rich diets with reduced incidence of chronic disorders; however, biological mechanisms underlying polyphenol-disease relations remain enigmatic. Emerging evidence is beginning to unmask the contribution of the gastrointestinal tract on whole-body energy homeostasis, suggesting that the intestine may be a prime target for intervention and a fundamental site for the metabolic actions of polyphenols. During their transit through the gastrointestinal tract, polyphenols may activate enteric nutrient sensors ensuing appropriate responses from other peripheral organs to regulate metabolic homeostasis. Furthermore, polyphenols can modulate the absorption of glucose, attenuating exaggerated hormonal responses and metabolic imbalances. Polyphenols that escape absorption are metabolized by the gut microbiota and the resulting catabolites may act locally, activating nuclear receptors that control enteric functions such as intestinal permeability. Finally, polyphenols modulate gut microbial ecology, which can have profound effects on cardiometabolic health.

Moderate intake of aspartame and sucralose with meals, but not fructose, does not exacerbate energy and glucose metabolism in estrogen-deficient rats

Both nutritive and non-nutritive sweeteners may influence energy and glucose metabolism differently. The hypothesis that sucrose, fructose, aspartame, and sucralose intake differently modulate energy and glucose metabolism was tested in an estrogen-deficient animal model. At 30 min after giving aspartame and sucralose (10 mg/kg body weight), an oral glucose tolerance test (OGTT) was conducted with glucose, sucrose, and fructose in ovariectomized (OVX) rats. After OGTT, they were continuously fed high fat diets including either 10% corn starch (Control), 10% sucrose (Sucrose), 10% fructose (Fructose), 0.05% aspartame + 9.95% starch (Aspartame) or 0.05% sucralose + 9.95% starch (Sucralose) for 8 week. During 30 min after acute administration of aspartame and sucralose, serum glucose concentrations increased despite slightly increased serum insulin levels before glucose infusion. However, glucose tolerance was not significantly different among the groups. In chronic study, serum glucose concentrations were lowest and insulin highest at the overnight-fasted state in Aspartame and Sucralose. Postprandial serum glucagon-like peptide-1 (GLP-1) and insulin levels were higher in Aspartame and Sucralose than Control. Hepatic insulin signaling (pAkt → pGSK-3β) and phosphoenolpyruvate carboxykinase (PEPCK) expression were lower in Sucralose and Aspartame than the Fructose. Serum acetate levels produced by gut microbiota were higher were lower in the fructose group than Aspartame and Sucralose groups. In conclusion, aspartame and sucralose with a meal might be preferable sweeteners to fructose and sucrose in estrogen deficient rats, and possibly post-menopausal women; however, this needs to be confirmed in human studies.

Suppression of sweet sensing with glucose, but not aspartame, delays gastric emptying and glycemic response

Previously, we reported that oral stimulation with Gymnema sylvestre (GS), a plant that selectively suppresses sweet taste sensation in humans, delayed gastric emptying and glycemic response during and after oral glucose ingestion. It is unclear whether these responses are triggered by sweet taste sensing per se. We tested the hypothesis that the effects of sweet taste sensing involving a low-energy sweetener, aspartame, alters gastric emptying, blood glucose, and plasma insulin responses during and after the prandial phase. Nine participants rinsed their mouths with either 25 mL of water (control) or a 2.5% GS solution, and then ingested 200 g (50 g × four times) of either 0.09% aspartame or 15% glucose solution containing 100 mg of ¹³C-sodium acetate. Gastric emptying was measured with a ¹³C breath test. Blood glucose and plasma insulin were measured at baseline as well as during and after ingestion of the sweet solutions. Decreased subjective sweet taste intensity was observed in the GS group for both the aspartame and glucose trials. In the aspartame trial, no measurements showed significant differences between either group. In the glucose trial, gastric emptying was delayed in the GS group compared to controls. In the initial phase, both during and after glucose ingestion in the glucose trial, blood glucose and plasma insulin responses were lower in the GS group than the controls. The presence or absence of sweet taste-sensing involving glucose had a significant effect on gastric emptying and glycemic metabolism, both during and after the prandial phase, as opposed to the effects involving aspartame.

Identification of hypoglycemia-specific neural signals by decoding murine vagus nerve activity

BACKGROUND

Glucose is a crucial energy source. In humans, it is the primary sugar for high energy demanding cells in brain, muscle and peripheral neurons. Deviations of blood glucose levels from normal levels for an extended period of time is dangerous or even fatal, so regulation of blood glucose levels is a biological imperative. The vagus nerve, comprised of sensory and motor fibres, provides a major anatomical substrate for regulating metabolism. While prior studies have implicated the vagus nerve in the neurometabolic interface, its specific role in either the afferent or efferent arc of this reflex remains elusive.

METHODS

Here we use recently developed methods to isolate and decode specific neural signals acquired from the surface of the vagus nerve in BALB/c wild type mice to identify those that respond robustly to hypoglycemia. We also attempted to decode neural signals related to hyperglycemia. In addition to wild type mice, we analyzed the responses to acute hypo- and hyperglycemia in transient receptor potential cation channel subfamily V member 1 (TRPV1) cell depleted mice. The decoding algorithm uses neural signals as input and reconstructs blood glucose levels.

RESULTS

Our algorithm was able to reconstruct the blood glucose levels with high accuracy (median error 18.6 mg/dl). Hyperglycemia did not induce robust vagus nerve responses, and deletion of TRPV1 nociceptors attenuated the hypoglycemia-dependent vagus nerve signals.

CONCLUSION

These results provide insight to the sensory vagal signaling that encodes hypoglycemic states and suggest a method to measure blood glucose levels by decoding nerve signals.

TRIAL REGISTRATION

Not applicable.

Inflammation and Gut-Brain Axis During Type 2 Diabetes: Focus on the Crosstalk Between Intestinal Immune Cells and Enteric Nervous System

The gut-brain axis is now considered as a major actor in the control of glycemia. Recent discoveries show that the enteric nervous system (ENS) informs the hypothalamus of the nutritional state in order to control glucose entry in tissues. During type 2 diabetes (T2D), this way of communication is completely disturbed leading to the establishment of hyperglycemia and insulin-resistance. Indeed, the ENS neurons are largely targeted by nutrients (e.g., lipids, peptides) but also by inflammatory factors from different origin (i.e., host cells and gut microbiota). Inflammation, and more particularly in the intestine, contributes to the development of numerous pathologies such as intestinal bowel diseases, Parkinson diseases and T2D. Therefore, targeting the couple ENS/inflammation could represent an attractive therapeutic solution to treat metabolic diseases. In this review, we focus on the role of the crosstalk between intestinal immune cells and ENS neurons in the control of glycemia. In addition, given the growing evidence showing the key role of the gut microbiota in physiology, we will also briefly discuss its potential contribution and role on the immune and neuronal systems.

A pathogen-derived effector modulates host glucose metabolism by arginine GlcNAcylation of HIF-1α protein

The essential role of pathogens in host metabolism is widely recognized, yet the mechanisms by which they affect host physiology remain to be fully defined. Here, we found that NleB, an enteropathogenic Escherichia coli (EPEC) type III secretion system effector known to possess N-acetylglucosamine (GlcNAc) transferase activity, GlcNAcylates HIF-1α, a master regulator of cellular O₂ homeostasis. We determined that NleB-mediated GlcNAcylation at a conserved arginine 18 (Arg18) at the N-terminus of HIF-1α enhanced HIF-1α transcriptional activity, thereby inducing HIF-1α downstream gene expression to alter host glucose metabolism. The arginine transferase activity of NleB was required for its enhancement of HIF-1α transactivity and the subsequent effect on glucose metabolism in a mouse model of EPEC infection. In addition, HIF-1α acted as a mediator to transact NleB-mediated induction of glucose metabolism-associated gene expression under hypoxia. Thus, our results further show a causal link between pathogen infection and host glucose metabolism, and we propose a new mechanism by which this occurs.

Accumulating evidence shows that pathogens can affect host metabolism, resulting in human diseases such as obesity and type 2 diabetes. However, how pathogens influence their hosts is still not clear, and this results in a lack of effective and specific clinical treatments. Further investigations into the causes of pathogen disturbance of host metabolism are urgently needed. In this study, we show that a protein molecule, NleB, secreted by enteropathogenic bacteria (EPEC) can get into host cells and modify the function of a master regulator of cellular O₂ homeostasis, HIF-1α, thereby altering host glucose metabolism. We show that HIF-1α acts as a mediator to transact NleB-mediated induction of glucose metabolism-associated gene expression under hypoxia. Our results reveal a causal link between pathogen infection and host glucose metabolism, which may provide a new explanation for the causes of human diseases related to metabolic disturbance.

Impaired taste sensation in type 2 diabetic patients without chronic complications: a case-control study

PURPOSE

Few and contradictory data suggest changes in taste perception in type 2 diabetes (T2DM), potentially altering food choices. We, therefore, analyzed taste recognition thresholds in T2DM patients with good metabolic control and free of conditions potentially impacting on taste, compared with age-, body mass index-, and sex-matched normoglycemic controls.

METHODS

An ascending-concentration method was used, employing sucrose (sweet), sodium chloride (salty), citric acid (sour), and quinine hydrochloride (bitter), diluted in increasing concentration solutions. The recognition threshold was the lowest concentration of correct taste identification.

RESULTS

The recognition thresholds for the four tastes were higher in T2DM patients. In a multiple regression model, T2DM [β = 0.95; 95% CI 0.32-1.58; p = 0.004 (salty); β = 0.61; 0.19-1.03; p = 0.006 (sweet); β = 0.78; 0.15-1.40; p = 0.016 (sour); β = 0.74; 0.22-1.25; p = 0.006 (bitter)] and waist circumference [β = 0.05; 0.01-0.08; p = 0.012 (salty); β = 0.03; 0.01-0.05; p = 0.020 (sweet); β = 0.04; 0.01-0.08; p = 0.020 (sour); β = 0.04; 0.01-0.07; p = 0.007 (bitter)] were associated with the recognition thresholds. Age was associated with salty (β = 0.06; 0.01-0.12; p = 0.027) and BMI with sweet thresholds (β = 0.06; 0.01-0.11; p = 0.019).

CONCLUSIONS

Taste recognition thresholds were higher in uncomplicated T2DM, and central obesity was significantly associated with this impairment. Hypogeusia may be an early sign of diabetic neuropathy and be implicated in the poor compliance of these patients to dietary recommendations.

Mild diabetes: long-term effects on gastric motility evaluated in rats

Moderate hyperglycaemic levels seem to be related to abnormal gastric motility in diabetes mellitus. However, experimental models designed to evaluate the relationship between motility and diabetes over time are not yet well established. Our objective was to investigate the long-term effects of mild diabetes on gastric motility in rats. Newborn male rats received streptozotocin (mild diabetes groups - MD) or vehicle (control groups - C), and both groups were evaluated after 3 (C3 and MD3) and 6 months (C6 and MD6) postinduction. Mild diabetic animals (MD3 and MD6) showed moderately elevated blood glucose and decreased insulin levels compared with control (C3 and C6). Insulin secretion was enhanced in MD6 compared with MD3, most likely due to partial β-cell regeneration indicated by HOMA-β. In HOMA-IR, it was noticed that MD6 animals had impaired insulin response compared with MD3. Gastric emptying was faster, amplitude of contraction was stronger in MD6 compared with MD3, and in both groups, the differences were significant when compared with control animals. A significant abnormal rhythmic index was calculated for the mild diabetic groups, despite unchanged mean frequency of contraction. In conclusion, despite increased insulin levels over time, constant levels of moderate hyperglycaemia are also related to abnormal gastric motility and impairment of gastric function.

Galanin enhances systemic glucose metabolism through enteric Nitric Oxide Synthase-expressed neurons

Objective

Decreasing duodenal contraction is now considered as a major focus for the treatment of type 2 diabetes. Therefore, identifying bioactive molecules able to target the enteric nervous system, which controls the motility of intestinal smooth muscle cells, represents a new therapeutic avenue. For this reason, we chose to study the impact of oral galanin on this system in diabetic mice.

Methods

Enteric neurotransmission, duodenal contraction, glucose absorption, modification of gut–brain axis, and glucose metabolism (glucose tolerance, insulinemia, glucose entry in tissue, hepatic glucose metabolism) were assessed.

Results

We show that galanin, a neuropeptide expressed in the small intestine, decreases duodenal contraction by stimulating nitric oxide release from enteric neurons. This is associated with modification of hypothalamic nitric oxide release that favors glucose uptake in metabolic tissues such as skeletal muscle, liver, and adipose tissue. Oral chronic gavage with galanin in diabetic mice increases insulin sensitivity, which is associated with an improvement of several metabolic parameters such as glucose tolerance, fasting blood glucose, and insulin.

Conclusion

Here, we demonstrate that oral galanin administration improves glucose homeostasis via the enteric nervous system and could be considered a therapeutic potential for the treatment of T2D.

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Targeting the enteric nervous system (ENS) is an innovative solution to treat diabetes.

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The ENS controls duodenal contractions to modulate glycemia via the gut–brain axis.

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ENS/contractions are targeted by the neuropeptide galanin in the intestine.

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Oral galanin treatment decreases duodenal hyper-contractility in diabetic mice.

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Oral galanin restores the gut–brain axis to improve glycemia in diabetic mice.

Research on the traditional Chinese medicine treating gastrointestinal motility in diabetic rats by improving biomechanical remodeling and neuroendocrine regulation

Previous studies have demonstrated that TWA, a Chinese herbal medicine, could significantly improve the symptoms of patients with diabetic gastrointestinal dysfunction. However, the specific mechanism of regulating intestinal peristalsis has not been found. This study aimed to discover TWA's therapeutic mechanism for regulating intestinal motility. The intestinal propulsion rate of diabetic rats was significantly increased after treatment with TWA for 8 weeks. Aiming at the mechanical structure, biomechanical testing indicated that TWA can significantly decrease the no-load intestinal wall thickness, cross-sectional area, and angular spread in a zero-stress state. Notably, intestinal stress-strain curve shifted to the right, which indicated TWA can inhibit intestinal hyperplasia and hardening and improve biomechanical remodeling. Further study of the mechanism revealed that TWA significantly inhibited the expression of AGE in the villi, crypt, and muscle and RAGE in crypt and upregulated the expression of nerve regulator (PSD95, C-kit and SCF). Radioimmunoassay showed TWA treatment decreased levels of serum somatostatin and vasoactive intestinal peptide. Moreover, associations were found between the intestinal propulsion rate with the morphologic and biomechanical remodeling parameters, changes of nerve factors, and endocrine hormones. Morphologic and biomechanical remodeling of the intestinal wall are the pathologic basis of gastrointestinal dysfunction. TWA can benefit intestinal motility by improving biomechanical and morphologic remodeling and by regulating expression of neuroendocrine factors. The results showed that the effect of TWA was dose-dependent, the higher the dose, the greater is the improvement. Thus, traditional Chinese medicine might be a valuable tool for treating diabetic gastrointestinal dysfunction.

Moderate Hypothermia Provides Better Protection of the Intestinal Barrier than Deep Hypothermia during Circulatory Arrest in a Piglet Model: A Microdialysis Study

INTRODUCTION

This study aimed to assess the effects of different temperature settings of hypothermic circulatory arrest (HCA) on intestinal barrier function in a piglet model.

METHODS

Twenty Wuzhishan piglets were randomly assigned to 40 min of HCA at 18°C (DHCA group, n = 5), 40 min of HCA at 24°C (MHCA group, n = 5), normothermic cardiopulmonary bypass (CPB group, n = 5) or sham operation (SO group, n = 5). Serum D-lactate (SDL) and lipopolysaccharide (LPS) levels were determined. Microdialysis parameters (glucose, lactate, pyruvate and glycerol) in the intestinal dialysate were measured. After 180 min of reperfusion, intestinal samples were harvested for real-time polymerase chain reaction and western blotting measurements for E-cadherin and Claudin-1.

RESULTS

Higher levels of SDL and LPS were detected in the DHCA group than in the MHCA group (P < 0.001). Both MHCA and DHCA groups exhibited lower glucose levels, higher lactate and glycerol levels and a higher lactate to pyruvate (L/P) ratio compared with the CPB group (p<0.05); the DHCA group had higher lactate and glycerol levels and a higher L/P ratio (p<0.05) but similar glucose levels compared to the MHCA group. No significant differences in E-cadherin mRNA or protein levels were noted. Upregulation of claudin-1 mRNA levels was detected in both the DHCA and MHCA animals' intestines (P < 0.01), but only the DHCA group exhibited a decrease in claudin-1 protein expression (P < 0.01).

CONCLUSION

HCA altered the energy metabolism and expression of epithelial junctions in the intestine. Moderate hypothermia (24°C) was less detrimental to the markers of normal functioning of the intestinal barrier than deep hypothermia (18°C).