GABA dramatically improves glucose tolerance in streptozotocin-induced diabetic rats fed with high-fat diet

The role of GABA in type 1 diabetes

Gamma aminobutyric acid (GABA) is synthesized from glutamate by glutamic decarboxylase (GAD). The entero-pancreatic biology of GABA, which is produced by pancreatic islets, GAD-expressing microbiota, enteric immune cells, or ingested through diet, supports an essential physiologic role of GABA in the health and disease. Outside the central nervous system (CNS), GABA is uniquely concentrated in pancreatic β-cells. They express GAD65, which is a type 1 diabetes (T1D) autoantigen. Glutamate constitutes 10% of the amino acids in dietary protein and is preeminently concentrated in human milk. GABA is enriched in many foods, such as tomato and fermented cheese, and is an over-the-counter supplement. Selected microbiota in the midgut have the enzymatic capacity to produce GABA. Intestinal microbiota interact with gut-associated lymphoid tissue to maintain host defenses and immune tolerance, which are implicated in autoimmune disease. Although GABA is a widely known inhibitory neurotransmitter, oral GABA does not cross the blood brain barrier. Three diabetes-related therapeutic actions are ascribed to GABA, namely, increasing pancreatic β-cell content, attenuating excess glucagon and tamping down T-cell immune destruction. These salutary actions have been observed in numerous rodent diabetes models that usually employed high or near-continuous GABA doses. Clinical studies, to date, have identified positive effects of oral GABA on peripheral blood mononuclear cell cytokine release and plasma glucagon. Going forward, it is reassuring that oral GABA therapy has been well-tolerated and devoid of serious adverse effects.

Fermented Rice Bran Mitigated the Syndromes of Type 2 Diabetes in KK-Ay Mice Model

Background: Diabetes is a devastating disease that causes millions of deaths. Fermented rice bran (FRB), made by fermenting rice bran with Aspergillus kawachii and a mixture of lactic acid bacteria, was hypothesized to b able to improve diabetes-related symptoms. This study aimed to investigate the effects of FRB supplementation in mitigating type 2 diabetes symptoms and identifying FRB bioactive compounds. Methods: In this study, KK-Ay mice (4 w.o. male) were used as a model for type 2 diabetes. Mice were divided into three different groups. The first group received a control diet, the second received a 12.5% non-fermented rice bran (RB) supplemented diet, and the last group was fed a 12.5% FRB-supplemented diet. Supplementation was done for 4 weeks. Results: FRB supplementation lowered the blood glucose level, OGTT, HOMA-IR, total cholesterol, liver RAGE protein, and glucokinase in KK-Ay mice. Metabolome analysis of RB and FRB showed that fermentation increased bioactive compounds in rice bran, such as GABA, L-theanine, and carnitine. It also increased the levels of various free amino acids while converting some amino acids such as arginine, tyrosine, and tryptophan into other metabolites. Conclusions: This research showed the potency of FRB supplementation as a preventive agent against type 2 diabetes.

Long-term GABA Supplementation Regulates Diabetic Gastroenteropathy through GABA Receptor/trypsin-1/PARs/Akt/COX-2 Axis

AIM

Molecular alterations of diabetic gastroenteropathy are poorly identified. This study investigates the effects of prolonged GABA supplementation on key protein expression levels of trypsin-1, PAR-1, PAR-2, PAR-3, PI3K, Akt, COX-2, GABAA, and GABAB receptors in the gastric tissue of type 2 diabetic rats (T2DM).

METHOD

To induce T2DM, a 3-month high-fat diet and 35 mg/kg of streptozotocin was used. Twenty-four male Wistar rats were divided into 4 groups: (1) control, (2) T2DM, (3) insulin-treated (2.5 U/kg), and (4) GABA-treated (1.5 g/kg GABA). Blood glucose was measured weekly. The protein expressions were assessed using western blotting. Histopathological changes were examined by H&E and Masson's staining.

RESULTS

Diabetic rats show reduced NOS1 and elevated COX-2 and trypsin-1 protein expression levels in gastric tissue. Insulin and GABA therapy restored the NOS1 and COX-2 levels to control values. Insulin treatment increased PI3K, Akt, and p-Akt and, decreased trypsin-1, PAR-1, PAR-2, and PAR-3 levels in the diabetic rats. Levels of GABAA and GABAB receptors normalized following insulin and GABA therapy. H&E staining indicated an increase in mucin secretion following GABA treatment.

CONCLUSION

These results suggest that GABA by acting on GABA receptors may regulate the trypsin-1/PARs/Akt/COX-2 pathway and thereby improve complications of diabetic gastroenteropathy.

Long term administration of thiamine disulfide improves FOXO1/PEPCK pathway in liver to reduce insulin resistance in type 1 diabetes rat model

OBJECTIVE

The main objective of this study was to find if thiamine disulfide (TD) lowers blood glucose level and improves insulin resistance (IR) in liver and muscle in rats with chronic type 1 diabetes (T1DM) using euglycemic-hyperinsulinemic clamp technique.

METHODS

A total of fifty male Wistar rats were assigned to five groups consisted of: non-diabetic control (NDC), diabetic control (DC), diabetic treated with thiamine disulfide (D-TD), diabetic treated with insulin (D-insulin), and diabetic treated with both TD and insulin (D-insulin+TD). Diabetes was induced by a 60 mg/kg dose of streptozotocin. Blood glucose levels, pyruvate tolerance test (PTT), intraperitoneal glucose tolerance test (IPGTT), levels of glycosylated hemoglobin (HbA1c), glucose infusion rate (GIR), liver and serum lipid profiles, liver glycogen stores, liver enzymes ([ALT], [AST]), and serum calcium and magnesium levels. were evaluated. Additionally, gene expression levels of phosphoenolpyruvate carboxykinase (Pepck), forkhead box O1 (Foxo1), and glucose transporter type 4 (Glut4) were assessed in liver and skeletal muscle tissues.

RESULTS

Blood glucose level was reduced by TD treatment. In addition, TyG index, HOMA-IR, serum and liver lipid profiles, HbA1c levels, and expressions of Foxo1 and Pepck genes were decreased significantly (P<0.05) in all the treated groups. However, TD did not influence Glut4 gene expression, but GIR as a critical index of IR were 5.0±0.26, 0.29±0.002, 1.5±0.07, 0.9±0.1 and 1.3±0.1 mg.min-1Kg-1 in NDC, DC, D-TD, D-insulin and D-insulin+TD respectively.

CONCLUSIONS

TD improved IR in the liver primarily by suppressing gluconeogenic pathways, implying the potential use of TD as a therapeutic agent in diabetes.

Gamma-Aminobutyric Acid (GABA) Avoids Deterioration of Transport Water Quality, Regulates Plasma Biochemical Indices, Energy Metabolism, and Antioxidant Capacity of Tawny Puffer (Takifugui flavidus) under Transport Stress

Live fish transportation is crucial for managing aquaculture but can pose health risks to fish due to stressors encountered during transportation. Gamma-aminobutyric acid (GABA) is an inhibitory neurotransmitter that plays a crucial role in the central nervous system and is considered to exhibit anti-stress effects. This study aims to investigate the effects of GABA on the transport water quality, plasma biochemical indices, energy metabolism, and antioxidant capacity of tawny puffer (Takifugu flavidus) under transport stress. Tawny puffer were pretreated by immersing in aquariums containing GABA (final concentrations at 0, 5, 50, and 150 mg/L) seawater for 3 days; then, simulated transport was conducted using oxygen-filled polyethylene bags containing the same concentration of GABA seawater as the pretreatment period. Water samples, plasma, and liver were collected after 0, 6, and 12 h of transport. The results revealed that with the prolongation of transportation time, the control group's water quality deteriorated, stress-related plasma biochemical indices increased, glycolytic substrate contents decreased, glycolytic enzyme activities and product contents increased, and aerobic metabolic enzyme activities exhibited initial increases followed by declines, ATPase activities decreased, antioxidant enzyme activities decreased, and the lipid peroxidation marker contents increased. It is noteworthy that GABA treatment could avoid water quality deterioration during transportation, inhibit an elevation in stress-related biochemical indicators, regulate energy metabolism, and reduce oxidative damage in tawny puffer, especially at 50 and 150 mg/L concentrations. In summary, GABA treatment can effectively alleviate the transport stress of tawny puffer.

Impact of NMDA receptors block versus GABA-A receptors modulation on synaptic plasticity and brain electrical activity in metabolic syndrome

PURPOSE

Metabolic syndrome (MetS) is a common disorder associated with disturbed neurotransmitter homeostasis. Memantine, an N-methyl-d-aspartate receptor (NMDAR) antagonist, was first used in Alzheimer's disease. Allopregnanolone (Allo), a potent positive allosteric modulator of the Gamma-Amino-Butyric Acid (GABA)-A receptors, decreases in neurodegenerative diseases. The study investigated the impact of Memantine versus Allo administration on the animal model of MetS to clarify whether the mechanism of abnormalities is related more to excitatory or inhibitory neurotransmitter dysfunction.

MATERIALS AND METHODS

Fifty-six male rats were allocated into 7 groups: 4 control groups, 1 MetS group, and 2 treated MetS groups. They underwent assessment of cognition-related behavior by open field and forced swimming tests, electroencephalogram (EEG) recording, serum markers confirming the establishment of MetS model and hippocampal Glial Fibrillary Acidic Protein (GFAP) and Brain-Derived Neurotrophic Factor (BDNF).

RESULTS

Allo improved anxiety-like behavior and decreased grooming frequency compared to Memantine. Both drugs increased GFAP and BDNF expression, improving synaptic plasticity and cognition-related behaviors. The therapeutic effect of Allo was more beneficial regarding lipid profile and anxiety. We reported progressive slowing of EEG waves in the MetS group with Memantine and Allo treatment with increased relative theta and decreased relative delta rhythms.

CONCLUSIONS

Both Allo and Memantine boosted the outcome parameters in the animal model of MetS. Allo markedly improved the anxiety-like behavior in the form of significantly decreased grooming frequency compared to the Memantine-treated groups. Both drugs were associated with increased hippocampal GFAP and BDNF expression, indicating an improvement in synaptic plasticity and so, cognition-related behaviors.

Effects of dietary supplementation of different levels of gamma-aminobutyric acid on reproductive performance, glucose intolerance, and placental development of gilts

This study aimed to investigate the effects of dietary gamma-aminobutyric acid (GABA) supplementation on reproductive performance, glucose intolerance, and placental development of gilts during mid-late gestation. Based on the principle of backfat thickness consistency, 124 gilts at 65 d of gestation were assigned to three dietary groups: CON (basic diet, n = 41), LGABA (basic diet supplemented with 0.03% GABA, n = 42), and HGABA (basic diet supplemented with 0.06% GABA, n = 41). The litter performance, glucose tolerance, placental angiogenesis, and nutrients transporters were assessed. The LGABA group improved piglet vitality and placental efficiency and decreased area under the curve of glucose tolerance test compared to the CON group (P < 0.05). Meanwhile, the LGABA group enhanced placental vessel density, platelet endothelial cell adhesion molecule-1 levels and gene expression of fibroblast growth factor 18 (P < 0.05). Furthermore, LGABA showed an uptrend in glucose transporter type 1 mRNA level (P = 0.09). Taken together, this study revealed that the dietary supplementation of 0.03% GABA can improve piglet vitality, glucose intolerance, and placental development of gilts.

Gut-joint axis: Oral Probiotic ameliorates Osteoarthritis

Osteoarthritis (OA) etiology is multifactorial, and its prevalence is growing globally. The Gut microbiota shapes our immune system and impacts all aspects of health and disease. The idea of utilizing probiotics to treat different conditions prevails. Concerning musculoskeletal illness and health, current data lack the link to understand the interactions between the host and microbiome. We report that S. thermophilus, L. pentosus (as probiotics), and γ-aminobutyric acid (GABA) harbour against osteoarthritis in vivo and alleviate IL-1β induced changes in chondrocytes in vitro. We examined the increased GABA concentration in mice's serum and small intestine content followed by bacterial treatment. The treatment inhibited the catabolism of cartilage and rescued mice joints from degradation. Furthermore, the anabolic markers upregulated and decreased inflammatory markers in mice knee joints and chondrocytes. This study is the first to represent GABA's chondrogenic and chondroprotective effects on joints and human chondrocytes. This data provides a foundation for future studies to elucidate the role of GABA in regulating chondrocyte cell proliferation. These findings opened future horizons to understanding the gut-joint axis and OA treatment. Thus, probiotic/GABA therapy shields OA joints in mice and could at least serve as adjuvant therapy to treat osteoarthritis.

Diabetes in stiff-person syndrome

Anti-glutamic acid decarboxylase (GAD) autoantibodies are a hallmark of stiff-person syndrome (SPS) and insulin-dependent diabetes mellitus (IDDM). However, patients with concurrent IDDM and SPS often manifest insulin resistance, and SPS-associated IDDM probably has heterogeneous causes. Some patients manifest IDDM associated only with high titers of anti-GAD65 caused by SPS. By contrast, other patients develop IDDM only after being treated with high-dose corticosteroids or they progress to insulin dependency following their treatment with high-dose corticosteroids. The profile of autoantibodies differs markedly between type 1 diabetes mellitus (T1DM), late-onset diabetes mellitus, and SPS-associated IDDM. Therefore, as with new-onset diabetes after transplantation (NODAT), SPS-associated IDDM should be classified as a specific diabetes entity, the pathophysiology of which requires increased attention.

Insights into the cellular, molecular, and epigenetic targets of gamma-aminobutyric acid against diabetes: a comprehensive review on its mechanisms

Diabetes is a metabolic disease due to impaired or defective insulin secretion and is considered one of the most serious chronic diseases worldwide. Gamma-aminobutyric acid (GABA) is a naturally occurring non-protein amino acid commonly present in a wide range of foods. A number of studies documented that GABA has good anti-diabetic potential. This review summarized the available dietary sources of GABA as well as animal and human studies on the anti-diabetic properties of GABA, while also discussing the underlying mechanisms. GABA may modulate diabetes through various pathways such as inhibiting the activities of α-amylase and α-glucosidase, promoting β-cell proliferation, stimulating insulin secretion from β-cells, inhibiting glucagon secretion from α-cells, improving insulin resistance and glucose tolerance, and increasing antioxidant and anti-inflammatory activities. However, further mechanistic studies on animals and human are needed to confirm the therapeutic effects of GABA against diabetes.

Effects of γ-aminobutyric acid supplementation on glucose control in adults with prediabetes: A double-blind, randomized, placebo-controlled trial

BACKGROUND

Gamma-aminobutyric acid (GABA) is mainly known as an endogenously produced neurotransmitter. However, GABA intake from dietary sources like tomatoes and fermented foods can be considerable. Studies in rodent models have shown beneficial effects of oral GABA supplementation on glucose homeostasis and cardiovascular health. Still, it is currently unknown whether oral GABA supplementation produces cardiometabolic benefits in humans.

OBJECTIVES

This study aimed to investigate whether oral GABA supplementation can improve glucose homeostasis in individuals at risk of developing type 2 diabetes.

METHODS

In a randomized, placebo-controlled, double-blind, parallel-arm trial, 52 individuals with prediabetes (classified by impaired glucose tolerance and/or impaired fasting glucose), aged 50 to 70 y with a body mass index ≥25 kg/m2 received either 500 mg GABA 3 times daily or a placebo for 95 days. The primary outcome was the effect of the intervention on glucose response after an OGTT. As exploratory secondary outcomes, markers of glycemic control (glycated hemoglobin, insulin, glucagon, mean amplitude of glycemic excursions, and standard deviation as measured with flash glucose monitoring), cardiovascular health (blood pressure, 24-h blood pressure, circulating triglycerides, cholesterol), and self-reported sleep quality were measured before and after the intervention.

RESULTS

Compared with placebo, GABA supplementation for 95 days did not change the postprandial glucose response (0.21 mmol/L; 95% confidence interval: -0.252, 0.674; P = 0.364). After correction for the false discovery rate, all other outcomes (including fasting plasma GABA concentration) showed no significant effects from GABA intervention at a group level.

CONCLUSIONS

GABA supplementation does not change the postprandial glucose response in individuals at risk of developing type 2 diabetes. However, based on findings in secondary outcome measures, further research is warranted in other study populations. Research could focus on the effects of GABA in individuals with advanced diabetes or other cardiometabolic disorders. This trial was registered at www.

CLINICALTRIALS

gov as NCT04303468.

Bioactive Ingredients in Traditional Fermented Food Condiments: Emerging Products for Prevention and Treatment of Obesity and Type 2 Diabetes

Obesity and type 2 diabetes (T2D) are severe metabolic diseases due to inappropriate lifestyle and genetic factors and their prevention/treatment cause serious problems. Therefore, searching for effective and safe approaches to control obesity and T2D is an essential challenge. This study presents the knowledge regarding the possible use of traditional fermented condiments (TFC), a known major source of bioactive compounds (BACs), as an adjuvant treatment for obesity and T2D. Data on antiobesity, antidiabetic, and different mechanisms of BACs action of TFC were collected using a methodical search in PubMed, Scopus databases, Web of Science, SciELO, and the Cochrane Library. We discuss the mechanisms by which BCs prevent or treat obesity and T2D. The effects of TFC on obesity and T2D have been found both in animal, human, and clinical studies. The findings demonstrated that BACs in TFC confer potential promising antiobesity and antidiabetic effects. Because of the potential therapeutic significance of bioactive ingredients, the consumption of TFC could be recommended as a functional condiment. Nevertheless, further investigation is required in more clinical studies of TFC to support the formulation of functional fermented condiments and nutraceutical and pharmaceutical applications.

Interactive Effect of Dietary Gamma-Aminobutyric Acid (GABA) and Water Temperature on Growth Performance, Blood Plasma Indices, Heat Shock Proteins and GABAergic Gene Expression in Juvenile Olive Flounder Paralichthys olivaceus

Gamma-aminobutyric acid (GABA) is an important inhibitory neurotransmitter in the central nervous system of living organisms and has the ability to reduce the magnitude of stress in humans and animals. In this study, we evaluated the supplemental effects of GABA on normal and high water temperature based on growth, blood plasma composition as well as heat shock proteins and GABA-related gene expression in juvenile olive flounder. For this, a 2 × 2 factorial design of experiment was employed to investigate the dietary effects of GABA at 0 mg/kg of diet (GABA0 diet) and 200 mg/kg of diet (GABA200 diet) in water temperatures of 20 ± 1 °C (normal temperature) and 27 ± 1 °C (high temperature) for 28 days. A total of 180 fish with an average initial weight of 40.1 ± 0.4 g (mean ± SD) were distributed into 12 tanks, of which, each tank contained 15 fish based on the 4 dietary treatment groups in triplicate. At the end of the feeding trial, the results demonstrated that both temperature and GABA had significant effects on the growth performance of the fish. However, fish fed the GABA200 diet had a significantly higher final body weight, weight gain and specific growth rate as well as a significantly lower feed conversion ratio than the fish fed the GABA0 diet at the high water temperature. A significant interactive effect of water temperature and GABA was observed on the growth performance of olive flounder based on the two-way analysis of variance. The plasma GABA levels in fish were increased in a dose-dependent manner at normal or high water temperatures, whereas cortisol and glucose levels were decreased in fish fed GABA-supplemented diets under temperature stress. The GABA-related mRNA expression in the brains of the fish such as GABA type A receptor-associated protein (Gabarap), GABA type B receptor 1 (Gabbr1) and glutamate decarboxylase 1 (Gad1) were not significantly affected by GABA-supplemented diets under normal or temperature stressed conditions. On the other hand, the mRNA expression of heat shock proteins (hsp) in the livers of the fish, such as hsp70 and hsp90, were unchanged in fish fed the GABA diets compared to the control diet at the high water temperature. Collectively, the present study showed that dietary supplementation with GABA could enhance growth performance, and improve the feed utilization, plasma biochemical parameters and heat shock proteins and GABA-related gene expression under the stress of high water temperatures in juvenile olive flounder.

Metabolites, gene expression, and gut microbiota profiles suggest the putative mechanisms via which dietary creatine increases the serum taurine and g-ABA contents in Megalobrama amblycephala

A 90-day experiment was conducted to explore the effects of creatine on growth performance, liver health status, metabolites, and gut microbiota in Megalobrama amblycephala. There were 6 treatments as follows: control (CD, 29.41% carbohydrates), high carbohydrate (HCD, 38.14% carbohydrates), betaine (BET, 1.2% betaine + 39.76% carbohydrates), creatine 1 (CRE1, 0.5% creatine + 1.2% betaine + 39.29% carbohydrates), creatine 2 (CRE2, 1% creatine + 1.2% betaine + 39.50% carbohydrates), and creatine 3 (CRE3, 2% creatine + 1.2% betaine + 39.44% carbohydrates). The results showed that supplementing creatine and betaine together reduced the feed conversion ratio significantly (P < 0.05, compared to CD and HCD) and improved liver health (compared to HCD). Compared with the BET group, dietary creatine significantly increased the abundances of Firmicutes, Bacteroidota, ZOR0006, and Bacteroides and decreased the abundances of Proteobacteria, Fusobacteriota, Vibrio, Crenobacter, and Shewanella in the CRE1 group. Dietary creatine increased the content of taurine, arginine, ornithine, γ-aminobutyric acid (g-ABA), and creatine (CRE1 vs. BET group) and the expression of creatine kinase (ck), sulfinoalanine decarboxylase (csad), guanidinoacetate N-methyltransferase (gamt), glycine amidinotransferase (gatm), agmatinase (agmat), diamine oxidase1 (aoc1), and glutamate decarboxylase (gad) in the CRE1 group. Overall, these results suggested that dietary supplementation of creatine (0.5-2%) did not affect the growth performance, but it altered the gut microbial composition at the phylum and genus levels, which might be beneficial to the gut health of M. amblycephala; dietary creatine also increased the serum content of taurine by enhancing the expressions of ck and csad and increased the serum content of g-ABA by enhancing the arginine content and the expressions of gatm, agmat, gad, and aoc1.

Exosomes Derived from Adipose Stem Cells Enhance Bone Fracture Healing via the Activation of the Wnt3a/β-Catenin Signaling Pathway in Rats with Type 2 Diabetes Mellitus

Nonunion and delayed union are common complications of diabetes mellitus that pose a serious health threat to people. There are many approaches that have been used to improve bone fracture healing. Recently, exosomes have been regarded as promising medical biomaterials for improving fracture healing. However, whether exosomes derived from adipose stem cells can promote bone fracture healing in diabetes mellitus remains unclear. In this study, adipose stem cells (ASCs) and exosomes derived from adipose stem cells (ASCs-exos) are isolated and identified. Additionally, we evaluate the in vitro and in vivo effects of ASCs-exos on the osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) and bone repair and the regeneration in a rat model of nonunion via Western blotting, immunofluorescence assay, ALP staining, alizarin red staining, radiographic examination and histological analysis. Compared with controls, ASCs-exos promoted BMSC osteogenic differentiation. Additionally, the results of Western blotting, radiographic examination and histological analysis show that ASCs-exos improve the ability for fracture repair in the rat model of nonunion bone fracture healing. Moreover, our results further proved that ASCs-exos play a role in activating the Wnt3a/β-catenin signaling pathway, which facilitates the osteogenic differentiation of BMSCs. All these results show that ASCs-exos enhance the osteogenic potential of BMSCs by activating the Wnt/β-catenin signaling pathway, and also facilitate the ability for bone repair and regeneration in vivo, which provides a novel direction for fracture nonunion in diabetes mellitus treatment.

Function of the GABAergic System in Diabetic Encephalopathy

Diabetes is a common metabolic disease characterized by loss of blood sugar control and a high rate of complications. γ-Aminobutyric acid (GABA) functions as the primary inhibitory neurotransmitter in the adult mammalian brain. The normal function of the GABAergic system is affected in diabetes. Herein, we summarize the role of the GABAergic system in diabetic cognitive dysfunction, diabetic blood sugar control disorders, diabetes-induced peripheral neuropathy, diabetic central nervous system damage, maintaining diabetic brain energy homeostasis, helping central control of blood sugar and attenuating neuronal oxidative stress damage. We show the key regulatory role of the GABAergic system in multiple comorbidities in patients with diabetes and hope that further studies elucidating the role of the GABAergic system will yield benefits for the treatment and prevention of comorbidities in patients with diabetes.

Gamma-Aminobutyric Acid Signaling in Damage Response, Metabolism, and Disease

Gamma-aminobutyric acid (GABA) plays a crucial role in signal transduction and can function as a neurotransmitter. Although many studies have been conducted on GABA in brain biology, the cellular function and physiological relevance of GABA in other metabolic organs remain unclear. Here, we will discuss recent advances in understanding GABA metabolism with a focus on its biosynthesis and cellular functions in other organs. The mechanisms of GABA in liver biology and disease have revealed new ways to link the biosynthesis of GABA to its cellular function. By reviewing what is known about the distinct effects of GABA and GABA-mediated metabolites in physiological pathways, we provide a framework for understanding newly identified targets regulating the damage response, with implications for ameliorating metabolic diseases. With this review, we suggest that further research is necessary to develop GABA's beneficial and toxic effects on metabolic disease progression.

Development of Janus Particles as Potential Drug Delivery Systems for Diabetes Treatment and Antimicrobial Applications

Janus particles have emerged as a novel and smart material that could improve pharmaceutical formulation, drug delivery, and theranostics. Janus particles have two distinct compartments that differ in functionality, physicochemical properties, and morphological characteristics, among other conventional particles. Recently, Janus particles have attracted considerable attention as effective particulate drug delivery systems as they can accommodate two opposing pharmaceutical agents that can be engineered at the molecular level to achieve better target affinity, lower drug dosage to achieve a therapeutic effect, and controlled drug release with improved pharmacokinetics and pharmacodynamics. This article discusses the development of Janus particles for tailored and improved delivery of pharmaceutical agents for diabetes treatment and antimicrobial applications. It provides an account of advances in the synthesis of Janus particles from various materials using different approaches. It appraises Janus particles as a promising particulate system with the potential to improve conventional delivery systems, providing a better loading capacity and targeting specificity whilst promoting multi-drugs loading and single-dose-drug administration.

Combined therapy of GABA and sitagliptin prevents high-fat diet impairment of beta-cell function

We recently demonstrated that combined therapy of GABA and sitagliptin promoted beta-cell proliferation, and decreased beta-cell apoptosis in a multiple low-dose streptozotocin (STZ)-induced beta-cell injury mouse model. In this study, we examined whether this combined therapy is effective in ameliorating the impairment of beta-cell function caused by high-fat diet (HFD) feeding in mice. Male C57BL/6J mice were fed normal chow diet, HFD, or HFD combined with GABA, sitagliptin, or both drugs. Oral drug daily administration was initiated one week before HFD and maintained for two weeks. After two weeks of intervention, we found that GABA or sitagliptin administration ameliorated the impairment of glucose tolerance induced by HFD. This was associated with improved insulin secretion in vivo. Notably, combined administration of GABA and sitagliptin significantly enhanced these effects as compared to each of the monotherapies. Combined GABA and sitagliptin was superior at increasing beta-cell mass, and associated Ki67⁺ and PDX-1⁺ beta-cell counts. In addition, we found that HFD-induced compensatory beta-cell proliferation was associated with increased activation of unfolded protein response (UPR), as indicated by BiP expression. This could be an important mechanism of compensatory beta-cell proliferation, and beta cells treated with GABA and sitagliptin showed greater UPR activation. Our results suggest that the combined use of these agents produces superior therapeutic outcomes.

Angiotensin-converting enzyme 2 improves hepatic insulin resistance by regulating GABAergic signaling in the liver

The angiotensin-converting enzyme 2 (ACE2)/angiotensin 1-7/MAS axis and the gamma-aminobutyric acid (GABA)ergic signaling system have both been shown to have the dual potential to improve insulin resistance (IR) and hepatic steatosis associated with obesity in the liver. Recent studies have demonstrated that ACE2 can regulate the GABA signal in various tissues. Notwithstanding this evidence, the functional relationship between ACE2 and GABA signal in the liver under IR remains elusive. Here, we used high-fat diet-induced models of IR in C57BL/6 mice as well as ACE2KO and adeno-associated virus-mediated ACE2 overexpression mouse models to address this knowledge gap. Our analysis showed that glutamate decarboxylase (GAD)67/GABA signaling was weakened in the liver during IR, whereas the expression of GAD67 and GABA decreased significantly in ACE2KO mice. Furthermore, exogenous administration of angiotensin 1-7 and adeno-associated virus- or lentivirus-mediated overexpression of ACE2 significantly increased hepatic GABA signaling in models of IR both in vivo and in vitro. We found that this treatment prevented lipid accumulation and promoted fatty acid β oxidation in hepatocytes as well as inhibited the expression of gluconeogenesis- and inflammation-related genes, which could be reversed by allylglycine, a specific GAD67 inhibitor. Collectively, our findings show that signaling via the ACE2/A1-7/MAS axis can improve hepatic IR by regulating hepatic GABA signaling. We propose that this research might indicate a potential strategy for the management of diabetes.

The influence of a tomato food matrix on the bioavailability and plasma kinetics of oral gamma-aminobutyric acid (GABA) and its precursor glutamate in healthy men

Gamma-aminobutyric acid (GABA) and its precursor glutamate play signaling roles in a range of tissues. Both function as neurotransmitters in the central nervous system, but they also modulate pancreatic and immune functioning, for example. Besides endogenous production, both compounds are found in food products, reaching relatively high levels in tomatoes. Recent studies in rodents suggest beneficial effects of oral GABA on glucose homeostasis and blood pressure. However, the bioavailability from food remains unknown. We studied the bioavailability of GABA and glutamate from tomatoes relative to a solution in water. After a fasting blood sample was taken, eleven healthy men randomly received 1 liter of 4 different drinks in a cross-over design with a one-week interval. The drinks were a solution of 888 mg L^-1 GABA, a solution of 3673 mg L^-1 glutamate, pureed fresh tomatoes and plain water as the control. Following intake, 18 blood samples were taken at intervals for 24 hours. Plasma GABA and glutamate concentrations were determined by ultra-pressure liquid chromatography coupled with tandem mass spectrometry (UPLC-MS/MS). Fasting plasma GABA and glutamate concentrations were found to be 16.71 (SD 2.18) ng mL^-1 and 4626 (SD 1666) ng mL^-1, respectively. Fasting GABA levels were constant (5.8 CV%) between individuals, while fasting glutamate levels varied considerably (23.5 CV%). GABA from pureed tomatoes showed similar bioavailability to that of a solution in water. For glutamate, the absorption from pureed tomatoes occurred more slowly as seen from a longer t_max (0.98 ± 0.14 h vs. 0.41 ± 0.04 h, P = 0.003) and lower C_max (7815 ± 627 ng mL^-1vs. 16 420 ± 2778 ng mL^-1, P = 0.006). These data suggest that GABA is bioavailable from tomatoes, and that food products containing GABA could potentially induce health effects similar to those claimed for GABA supplements. The results merit further studies on the bioavailability of GABA from other food products and the health effects of GABA-rich diets. The clinical trial registry number is NCT04086108 (https://clinicaltrials.gov/ct2/show/NCT04303468).

The role of pancreas to improve hyperglycemia in STZ-induced diabetic rats by thiamine disulfide

Background

The present study investigated the effect of thiamine disulfide (TD) on the pancreas in terms of hyperglycemia improvement and insulin sensitivity increase in diabetic male rats. We also aimed to study the function of Pdx1 (pancreatic and duodenal homeobox 1) and Glut2 (glucose transporter 2) genes in pancreatic tissue.

Methods

Type 1 diabetes was induced through injection of 60 mg/kg streptozotocin (STZ). The diabetic rats were divided into four groups, namely diabetic control (DC), diabetic treated with thiamine disulfide (D-TD), diabetic treated with insulin (D-insulin), and diabetic treated with TD and insulin (D-insulin+TD). The non-diabetic (NDC) and diabetic groups received a normal diet (14 weeks). Blood glucose level and body weight were measured weekly; insulin tolerance test (ITT) and glucagon tolerance test (GTT) were performed in the last month of the study. The level of serum insulin and glucagon were measured monthly and a hyperglycemic clamp (Insulin Infusion rate (IIR)) was done for all the groups. Pancreas tissue was isolated so that Pdx1and Glut2 genes expression could be measured.

Results

We observed that TD therapy decreased blood glucose level, ITT, and serum glucagon levels in comparison with those of the DC group; it also increased serum insulin levels, IIR, and expression of Pdx1 and Glut2 genes in comparison with those of the DC group.

Conclusion

Administration of TD could improve hyperglycemia in type 1 diabetic animals through improved pancreas function. Therefore, not only does TD have a significant effect on controlling and reducing hyperglycemia in diabetes, but it also has the potential to decrease the dose of insulin administration.

Neuronal and Non-Neuronal GABA in COVID-19: Relevance for Psychiatry

Infection with SARS-CoV-2, the causative agent of the COVID-19 pandemic, originated in China and quickly spread across the globe. Despite tremendous economic and healthcare devastation, research on this virus has contributed to a better understanding of numerous molecular pathways, including those involving γ-aminobutyric acid (GABA), that will positively impact medical science, including neuropsychiatry, in the post-pandemic era. SARS-CoV-2 primarily enters the host cells through the renin–angiotensin system’s component named angiotensin-converting enzyme-2 (ACE-2). Among its many functions, this protein upregulates GABA, protecting not only the central nervous system but also the endothelia, the pancreas, and the gut microbiota. SARS-CoV-2 binding to ACE-2 usurps the neuronal and non-neuronal GABAergic systems, contributing to the high comorbidity of neuropsychiatric illness with gut dysbiosis and endothelial and metabolic dysfunctions. In this perspective article, we take a closer look at the pathology emerging from the viral hijacking of non-neuronal GABA and summarize potential interventions for restoring these systems.

Engineered Chimeric Peptides with IGF-1 and Titanium-Binding Functions to Enhance Osteogenic Differentiation In Vitro under T2DM Condition

Due to the complexity of the biomolecules and titanium (Ti) combination, it is a challenge to modify the implant surface with biological cytokines. The study proposed a new method for immobilizing cytokines on implant surface to solve the problem of low osseointegration under type 2 diabetes mellitus (T2DM) condition. This new modified protein that connected Ti-binding artificial aptamer minTBP-1 with Insulin-like growth factor I (IGF-I), had a special strong affinity with Ti and a therapeutic effect on diabetic bone loss. According to the copies of minTBP-1, three proteins were prepared, namely minTBP-1-IGF-1, 2minTBP-1-IGF-1 and 3minTBP-1-IGF-1. Compared with the other modified proteins, 3minTBP-1-IGF-1 adsorbed most on the Ti surface. Additionally, this biointerface demonstrated the most uniform state and the strongest hydrophilicity. In vitro results showed that the 3minTBP-1-IGF-1 significantly increased the adhesion, proliferation, and mineralization activity of osteoblasts under T2DM conditions when compared with the control group and the other modified IGF-1s groups. Real-time PCR assay results confirmed that 3minTBP-1-IGF-1 could effectively promote the expression of osteogenic genes, that is, ALP, BMP-2, OCN, OPG, and Runx2. All these data indicated that the 3minTBP-1-IGF-1 had the most efficacious effect in promoting osteoblasts osteogenesis in diabetic conditions, and may be a promising option for further clinical use.

Long-term GABA administration improves FNDC5, TFAM, and UCP3 mRNA expressions in the skeletal muscle and serum irisin levels in chronic type 2 diabetic rats

In this study, we aimed to investigate whether the anti-diabetic effects of γ-aminobutyric acid (GABA) and insulin can be mediated through the regulation of gene expression related to irisin production and mitochondrial biogenesis in type 2 diabetic mellitus (T2DM) rats. Four groups (n = 6) were used in this study: control, T2DM, T2DM + insulin, and T2DM + GABA groups. After T2DM induction for 3 months (high-fat diet + 35 mg/kg streptozotocin) and treatment with GABA or insulin for 3 months, circulating levels of FBG, triglyceride, LDL, Ox-LDL, and insulin as well as hepatic and serum irisin levels were measured. The mRNA expressions of fibronectin type III domain-containing protein 5 (FNDC5), mitochondrial transcription factor A (TFAM), and mitochondrial uncoupling protein 3 (UCP3) were also evaluated in the skeletal muscle of all groups. GABA therapy improved the FBG and insulin levels in diabetic rats. Insulin treatment significantly reduced FBG and failed to maintain glucose close to the control level. Insulin or GABA therapy significantly decreased the levels of LDL, Ox-LDL, and HOMA-IR index. Circulating irisin levels were markedly decreased in insulin-treated group, while irisin levels did not show significant changes in GABA-treated group compared with control group. GABA or insulin therapy increased mRNA expressions of TFAM and UCP3 in diabetic rats. GABA therapy also led to a significant increase in FNDC5 mRNA. Our findings suggest that the anti-diabetic effect of GABA may be mediated, in part, by a decrease in Ox-LDL levels and an increase in the levels of irisin as well as FNDC5, TFAM, and UCP3 gene expression in T2DM rats.

Revealing the Hypoglycemic Effects and Mechanism of GABA-Rich Germinated Adzuki Beans on T2DM Mice by Untargeted Serum Metabolomics

Type 2 diabetes mellitus (T2DM) is one of the most common metabolic diseases, and exploring strategies to prevent and treat diabetes has become extremely important. In recent decades the search for new therapeutic strategies for T2DM involving dietary interventions has attracted public attention. We established a diabetic mouse model by feeding mice a high-fat diet combined with injection of low-dose streptozotocin, intending to elucidate the effects and possible mechanisms of different dosages of γ-aminobutyric acid (GABA)-rich germinated adzuki beans on the treatment of diabetes in mice. The mice were treated for 6 weeks either with increasing doses of GABA-enriched germinated adzuki beans, with non-germinated adzuki beans, with GABA, or with the positive control drug metformin. Then, the blood glucose levels and blood lipid biochemical indicators of all the mice were measured. At the same time, serum differential metabolite interactions were explored by UPLC-Q/TOF-MS-based serum metabolomic analysis. The results showed that body weight and fasting blood glucose levels were significantly reduced (P < 0.05). We also report improved levels of total cholesterol, triglycerides, aspartate aminotransferase, alanine aminotransferase, urea, and serum creatinine. We observed a significant improvement in the homeostasis model assessment of the beta cell function and insulin resistance (HOMA-β and HOMA-IR) scores (P < 0.05) in the group of mice treated with the highest dose of GABA-enriched germinated adzuki beans. In addition, the metabolic profiles of the serum were analyzed, and 31 differential metabolites including amino acids and lipids were obtained. According to the Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis, this was found to be correlated with nine significantly enriched metabolic pathways involving the up-regulation of levels of L-serine, SM (d18:1/22:1(13Z)), L-histidine, creatine, and 3-indoleacetic acid. Our data suggest that the hypoglycemic effect of GABA-enriched germinated adzuki beans on diabetic mice may be related to improving tryptophan metabolism, glycerol phospholipid metabolism, sphingosline metabolism, and the glycine, serine, and threonine metabolic pathways. This study provides a reference for the application of GABA-enriched germinated foods in type 2 diabetes and could provide a cue for searching biomarkers to be adopted for T2DM diagnosis.

An anthracene-based Hydrogen-bonded Organic Framework as Bifunctional Fluorescent Sensor for the Detection of γ-Aminobutyric Acid and Nitrofurazone

Intelligent fluorescence detection for disease diagnosis has become a research hotspot. In the era of big data, machine learning (ML) for analyzing data and mining will be widely used in...

Combination Therapy with GABA and MgSO4 Improves Insulin Sensitivity in Type 2 Diabetic Rat

BACKGROUND

Gamma-aminobutyric acid (GABA) and magnesium sulfate (MgSO₄) play a crucial role in glycemic control. Therefore, we studied the effect of combination therapy with GABA and MgSO₄ to improve insulin sensitivity in diabetes induced by streptozotocin as well as high-fat diet in a diabetic rat model. Design and Methods. Forty randomly selected rats were assigned to four groups: nondiabetic control group was fed the normal diet, insulin-resistant diabetic rat model was induced by streptozotocin and high-fat diet, GABA + MgSO₄ group received GABA and MgSO₄, and insulin group was treated with insulin. Body weight, abdominal fat, blood glucose, serum insulin, and glucagon concentration were measured. The glucose clamp technique, glucose tolerance test, and insulin tolerance test were performed to study insulin sensitivity. Also, the expressions of glucose 6 phosphatase, glucagon receptor, and phosphoenolpyruvate carboxykinase genes in liver were assessed for the gluconeogenesis pathway. Protein translocation and glucose transporter 4 (Glut4) genes expression in muscle were also assessed.

RESULTS

Combination of GABA + MgSO₄ or insulin therapy enhanced insulin level, glycemic control, glucose and insulin tolerance test, some enzymes expression in the gluconeogenesis pathway, body fat, body weight, and glucagon receptor in diabetic rats. Moreover, an increase was observed in protein and gene expression of Glut4. Insulin sensitivity in combination therapy was more than the insulin group.

CONCLUSIONS

GABA and MgSO₄ enhanced insulin sensitivity via increasing Glut4 and reducing the gluconeogenesis enzyme and glucagon receptor gene expressions.

GABA administration improves liver function and insulin resistance in offspring of type 2 diabetic rats

This study investigated the role of GABA in attenuating liver insulin resistance (IR) in type 2 diabetes parents and reducing its risk in their descendants' liver. Both sexes' rats were divided into four groups of non-diabetic control, diabetic control (DC), GABA-treated (GABA), and insulin-treated (Ins). The study duration lasted for six months and the young animals followed for four months. Consequently, hyperinsulinemic-euglycemic clamp was performed for all animals. Apart from insulin tolerance test (ITT), serum and liver lipid profile were measured in all groups. Glycogen levels, expression of Foxo1, Irs2, Akt2, and Pepck genes in the liver were assessed for all groups. Overall, GABA improved ITT, increased liver glycogen levels and decreased lipid profile, blood glucose level, and HbA1c in parents and their offspring in compared to the DC group. GIR also increased in both parents and their offspring by GABA. Moreover, the expression of Foxo1, Irs2, Akt2, and Pepck genes improved in GABA-treated parents and their descendants in compared to DC group. Results indicated that GABA reduced liver IR in both parents and their offspring via affecting their liver insulin signaling and gluconeogenesis pathways.

Multi-omics of a pre-clinical model of diabetic cardiomyopathy reveals increased fatty acid supply impacts mitochondrial metabolic selectivity

The incidence of type 2 diabetes (T2D) is increasing globally, with long-term implications for human health and longevity. Heart disease is the leading cause of death in T2D patients, who display an elevated risk of an acute cardiovascular event and worse outcomes following such an insult. The underlying mechanisms that predispose the diabetic heart to this poor prognosis remain to be defined. This study developed a pre-clinical model (Rattus norvegicus) that complemented caloric excess from a high-fat diet (HFD) and pancreatic β-cell dysfunction from streptozotocin (STZ) to produce hyperglycaemia, peripheral insulin resistance, hyperlipidaemia and elevated fat mass to mimic the clinical features of T2D. Ex vivo cardiac function was assessed using Langendorff perfusion with systolic and diastolic contractile depression observed in T2D hearts. Cohorts representing untreated, individual HFD- or STZ-treatments and the combined HFD + STZ approach were used to generate ventricular samples (n = 9 per cohort) for sequential and integrated analysis of the proteome, lipidome and metabolome by liquid chromatography-tandem mass spectrometry. This study found that in T2D hearts, HFD treatment primed the metabolome, while STZ treatment was the major driver for changes in the proteome. Both treatments equally impacted the lipidome. Our data suggest that increases in β-oxidation and early TCA cycle intermediates promoted rerouting via 2-oxaloacetate to glutamate, γ-aminobutyric acid and glutathione. Furthermore, we suggest that the T2D heart activates networks to redistribute excess acetyl-CoA towards ketogenesis and incomplete β-oxidation through the formation of short-chain acylcarnitine species. Multi-omics provided a global and comprehensive molecular view of the diabetic heart, which distributes substrates and products from excess β-oxidation, reduces metabolic flexibility and impairs capacity to restore high energy reservoirs needed to respond to and prevent subsequent acute cardiovascular events.

Insulin resistance and the role of gamma-aminobutyric acid

Insulin resistance (IR) is mentioned to be a disorder in insulin ability in insulin-target tissues. Skeletal muscle (SkM) and liver function are more affected by IR than other insulin target cells. SkM is the main site for the consumption of ingested glucose. An effective treatment for IR has two properties: An inhibition of β-cell death and a promotion of β-cell replication. Gamma-aminobutyric acid (GABA) can improve beta-cell mass and function. Multiple studies have shown that GABA decreases IR probably via increase in glucose transporter 4 (GLUT4) gene expression and prevention of gluconeogenesis pathway in the liver. This review focused on the general aspects of IR in skeletal muscle (SkM), liver; the cellular mechanism(s) lead to the development of IR in these organs, and the role of GABA to reduce insulin resistance.

MiR-144-5p, an exosomal miRNA from bone marrow-derived macrophage in type 2 diabetes, impairs bone fracture healing via targeting Smad1

BACKGROUND

Patients with diabetes have an increased risk of nonunion and delayed union of fractures. Macrophages have been shown as a key player in diabetic complications. However, it remains obscure how diabetic milieu affects macrophage-derived exosomes and its implications on osteogenic differentiation of BMSCs. In this study, we aim to define the impact of diabetic milieu on macrophage-derived exosomes, role of extracellular vesicles in intercellular communication with BMSCs, and subsequent effects on osteogenic differentiation and fracture repair.

RESULTS

The osteogenic potential and the ability of fracture repair of exosomes derived from diabetic bone marrow-derived macrophages (dBMDM-exos) were revealed to be lower, as compared with non-diabetic bone marrow-derived macrophages (nBMDM-exos) in vitro and in vivo. Interestingly, miR-144-5p levels were sharply elevated in dBMDM-exos and it could be transferred into BMSCs to regulate bone regeneration by targeting Smad1. In addition, the adverse effects of dBMDM-exos on the osteogenic potential and the ability of fracture repair were reversed through the suppression of miR-144-5p inhibition in vitro and vivo.

CONCLUSIONS

The results demonstrated an important role of exosomal miR-144-5p in bone regeneration, offering insight into developing new strategy for the improvement of fracture healing in patients with diabetes mellitus.

Gamma-aminobutyric acid attenuates insulin resistance in type 2 diabetic patients and reduces the risk of insulin resistance in their offspring

The role of gamma-aminobutyric acid (GABA) in attenuates insulin resistance (IR) in type 2 diabetic (T2D) patients and the reduction of the risk of IR in their offspring, and the function of GLUT4, IRS1 and Akt2 genes expression were investigated. T2D was induced by high fat diet and 35 mg/kg of streptozotocin. The male and female diabetic rats were then divided into three groups: CD, GABA, and insulin. NDC group received a normal diet. All the animals were studied for a six-month. Their offspring were just fed with normal diet for four months. Blood glucose was measured weekly in patients and their offspring. Intraperitoneal glucose tolerance test (IPGTT), urine volume, and water consumption in both patients and their offspring were performed monthly. The hyperinsulinemic euglycemic clamp in both patients and their offspring was done and blood sample collected to measure Hemoglobin A1c (HbA1c). IRS1, Akt and GLUT4 gene expressions in muscle were evaluated in all the groups. GABA or insulin therapy decreased blood glucose, IPGTT, and HbA1c in patients and their offspring compared to DC group. They also increased GIR in patients and their offspring. IRS1, Akt and GLUT4 gene expressions improved in both patients in comparison with DC group. GABA exerts beneficial effects on IRS1 and Akt gene expressions in GABA treated offspring. GABA therapy improved insulin resistance in diabetic patients by increasing the expression of GLUT4. It is also indirectly able to reduce insulin resistance in their offspring possibly through the increased gene expressions of IRS1 and Akt.

Gamma-aminobutyric acid regulates glucose homeostasis and enhances the hepatopancreas health of juvenile Chinese mitten crab (Eriocheir sinensis) under fasting stress

The ability of immune defense and resistance to physiological stress is crucial to animal health and survival. This study investigated the regulation of γ-aminobutyric acid (GABA) on metabolic homeostasis and its enhancement of hepatopancreas health in juvenile Chinese mitten crab (Eriocheir sinensis) under food deprivation. Juvenile crabs of 400 individuals were divided into four treatment groups: a control group without injection, and injections with a phosphate-buffered saline solution, 100 μmol GABA/mL and 1000 μmol GABA/mL, respectively. Hypoglycemia was induced by fasting, whereas the GABA treatment regulated hemolymph glucose homeostasis. The quantitative real-time PCR (qRT-PCR) results showed that the GABA treatment significantly up-regulated the mRNA expression levels of crustacean hyperglycemic hormone (CHH) and pyruvate kinase (PK). In contrast, the expression of E. sinensis insulin-like peptide (EsILP) was significantly down-regulated in the cranial ganglia, thoracic ganglia and hepatopancreas. Moreover, acid phosphatase (ACP), alkaline phosphatase (AKP), aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities were significantly increased in the hepatopancreas by the GABA treatment. Furthermore, the hemocyanin content in serum was significantly increased with the GABA injection, and the glutathione (GSH) content, total superoxide dismutase (T-SOD) activity and catalase (CAT) activity in the hepatopancreas showed a similar increasing trend with the dose elevation of GABA. Therefore, these results indicate that GABA can effectively maintain the hemolymph glucose homeostasis by regulating the levels of glucose metabolism-related hormones and key enzymes to promote the degradation and utilization of hepatopancreas glycogen. Meanwhile, GABA can improve the hepatopancreas function and immune status of juvenile E. sinensis under fasting stress. The treatment with GABA may provide a clue to guide health management in crab farming.

The Potential Role of Pancreatic γ-Aminobutyric Acid (GABA) in Diabetes Mellitus: A Critical Reappraisal

Background

Diabetes mellitus (DM) is an endocrine disorder characterized by hyperglycemia, polyuria, polydipsia, and glucosuria. γ-aminobutyric acid (GABA) is an inhibitory neurotransmitter in the central nervous system (CNS) of humans and other mammals. GABA acts on two different receptors, which are GABA-_A and GABA-_B. Pancreatic β-cells synthesize GABA from glutamic acid by glutamic acid decarboxylase (GAD).

Aim

The objective of this study was to explore the potential role of pancreatic GABA on glycemic indices in DM.

Methods

Evidence from experimental, preclinical, and clinical studies are evaluated for bidirectional relationships between pancreatic GABA and blood glucose disorders. A multiplicity of search strategies took on and assumed included electronic database searches of Medline and Pubmed using MeSH terms, keywords and title words during the search.

Results

The pancreatic GABA signaling system has a role in the regulation of pancreatic hormone secretions, inhibition of immune response, improve β-cells survival, and change α cell into β-cell. Moreover, a GABA agonist improves the antidiabetic effects of metformin. In addition, benzodiazepine receptor agonists improve pancreatic β-cell functions through GABA dependent pathway or through modulation of pancreatic adenosine and glucagon-like peptide (GLP-1).

Conclusions

Pancreatic GABA improves islet cell function, glucose homeostasis, and autoimmunity in DM. Orally administered GABA is safe for humans, and acts on peripheral GABA receptors and represents a new therapeutic modality for both T1DM and T2DM. Besides, GABA-_A receptor agonist like benzodiazepines improves pancreatic β-cell function and insulin sensitivity through activation of GABA-_A receptors.

Physiological Processes Modulated by the Chloride-Sensitive WNK-SPAK/OSR1 Kinase Signaling Pathway and the Cation-Coupled Chloride Cotransporters

The role of Cl- as an intracellular signaling ion has been increasingly recognized in recent years. One of the currently best described roles of Cl- in signaling is the modulation of the With-No-Lysine (K) (WNK) - STE20-Proline Alanine rich Kinase (SPAK)/Oxidative Stress Responsive Kinase 1 (OSR1) - Cation-Coupled Cl- Cotransporters (CCCs) cascade. Binding of a Cl- anion to the active site of WNK kinases directly modulates their activity, promoting their inhibition. WNK activation due to Cl- release from the binding site leads to phosphorylation and activation of SPAK/OSR1, which in turn phosphorylate the CCCs. Phosphorylation by WNKs-SPAK/OSR1 of the Na+-driven CCCs (mediating ions influx) promote their activation, whereas that of the K+-driven CCCs (mediating ions efflux) promote their inhibition. This results in net Cl- influx and feedback inhibition of WNK kinases. A wide variety of alterations to this pathway have been recognized as the cause of several human diseases, with manifestations in different systems. The understanding of WNK kinases as Cl- sensitive proteins has allowed us to better understand the mechanistic details of regulatory processes involved in diverse physiological phenomena that are reviewed here. These include cell volume regulation, potassium sensing and intracellular signaling in the renal distal convoluted tubule, and regulation of the neuronal response to the neurotransmitter GABA.

Exogenous hydrogen sulfide reduces atrial remodeling and atrial fibrillation induced by diabetes mellitus via activation of the PI3K/Akt/eNOS pathway

Diabetes mellitus (DM) facilitates atrial fibrosis and increases the risk of atrial fibrillation (AF). The underlying mechanism of DM in causing AF remains mostly unknown and potential therapeutic targets for DM‑induced AF are rarely reported. Hydrogen sulfide (H2S) has drawn considerable attention in recent years for its potential as a cardiovascular protector. Thus, the aim of the present study was to investigate the effect of H2S on DM‑induced AF and the mechanism of action. Sprague‑Dawley rats were divided into four groups, including the control group, the DM group, the H2S group and the DM+H2S group. The DM group and the DM+H2S group were administered streptozotocin to induce DM, whereas the other two groups were given citrate buffer as a control. The H2S group and the DM+H2S group were administered with an intraperitoneal injection of sodium hydrosulfide (precursor of H2S). AF inducibility, AF duration, atrial fibrosis and vital protein expression of oxidative stress were compared among the four groups. The DM group showed significantly higher AF incidence rates and duration (P<0.05). Histology results demonstrated severe atrial fibrosis in the DM group, and the PI3K/Akt/endothelial nitric oxide synthase (eNOS) pathway was significantly downregulated (P<0.05). However, when H2S was administered, the rats showed lower AF incidence and duration compared with the DM group. Additionally, H2S was able to mitigate the atrial fibrosis induced by DM, as well as the proliferation and migration of cardiac fibroblasts, as demonstrated by an MTT assay and real‑time cell analyzer migration experiment. Western blotting showed that the expression levels of the PI3K/Akt/eNOS pathway in the DM+H2S group were significantly upregulated compared with those of the DM group (P<0.05). In summary, DM status can lead to the structural remodeling of atrial fibrosis, facilitating AF incidence and persistence. Administration of H2S does not affect the glucose level, but can significantly mitigate atrial fibrosis and reduce the incidence of AF induced by DM, probably via activation of the PI3K/Akt/eNOS pathway.

Mechanism underlying starvation-dependent modulation of olfactory behavior in Drosophila larva

Starvation enhances olfactory sensitivity that encourage animals to search for food. The molecular mechanisms that enable sensory neurons to remain flexible and adapt to a particular internal state remain poorly understood. Here, we study the roles of GABA and insulin signaling in starvation-dependent modulation of olfactory sensory neuron (OSN) function in the Drosophila larva. We show that GABAB-receptor and insulin-receptor play important roles during OSN modulation. Using an OSN-specific gene expression analysis, we explore downstream targets of insulin signaling in OSNs. Our results suggest that insulin and GABA signaling pathways interact within OSNs and modulate OSN function by impacting olfactory information processing. We further show that manipulating these signaling pathways specifically in the OSNs impact larval feeding behavior and its body weight. These results challenge the prevailing model of OSN modulation and highlight opportunities to better understand OSN modulation mechanisms and their relationship to animal physiology.

Homotaurine Treatment Enhances CD4+ and CD8+ Regulatory T Cell Responses and Synergizes with Low-Dose Anti-CD3 to Enhance Diabetes Remission in Type 1 Diabetic Mice

Immune cells express γ-aminobutyric acid receptors (GABA-R), and GABA administration can inhibit effector T cell responses in models of autoimmune disease. The pharmacokinetic properties of GABA, however, may be suboptimal for clinical applications. The amino acid homotaurine is a type A GABA-R (GABAA-R) agonist with good pharmacokinetics and appears safe for human consumption. In this study, we show that homotaurine inhibits in vitro T cell proliferation to a similar degree as GABA but at lower concentrations. In vivo, oral homotaurine treatment had a modest ability to reverse hyperglycemia in newly hyperglycemic NOD mice but was ineffective after the onset of severe hyperglycemia. In severely diabetic NOD mice, the combination of homotaurine and low-dose anti-CD3 treatment significantly increased 1) disease remission, 2) the percentages of splenic CD4+and CD8+ regulatory T cells compared with anti-CD3 alone, and 3) the frequencies of CD4+ and CD8+ regulatory T cells in the pancreatic lymph nodes compared with homotaurine monotherapy. Histological examination of their pancreata provided no evidence of the large-scale GABAA-R agonist-mediated replenishment of islet β-cells that has been reported by others. However, we did observe a few functional islets in mice that received combined therapy. Thus, GABAA-R activation enhanced CD4+and CD8+ regulatory T cell responses following the depletion of effector T cells, which was associated with the preservation of some functional islets. Finally, we observed that homotaurine treatment enhanced β-cell replication and survival in a human islet xenograft model. Hence, GABAA-R agonists, such as homotaurine, are attractive candidates for testing in combination with other therapeutic agents in type 1 diabetes clinical trials.

GABAergic regulation of pancreatic islet cells: Physiology and antidiabetic effects

Diabetes occurs when pancreatic β-cell death exceeds β-cell growth, which leads to loss of β-cell mass. An effective therapy must have two actions: promotion of β-cell replication and suppression of β-cell death. Previous studies have established an important role for γ-aminobutyric acid (GABA) in islet-cell hormone homeostasis, as well as the maintenance of the β-cell mass. GABA exerts paracrine actions on α cells in suppressing glucagon secretion, and it has autocrine actions on β cells that increase insulin secretion. Multiple studies have shown that GABA increases the mitotic rate of β cells. In mice, following β-cell depletion with streptozotocin, GABA therapy can restore the β-cell mass. Enhanced β-cell replication appears to depend on growth and survival pathways involving Akt activation. Some studies have also suggested that it induces transdifferentiation of α cells into β cells, but this has been disputed and requires further investigation. In addition to proliferative effects, GABA protects β cells against injury and markedly reduces their apoptosis under a variety of conditions. The antiapoptotic effects depend at least in part on the enhancement of sirtuin-1 and Klotho activity, which both inhibit activation of the NF-κB inflammatory pathway. Importantly, in xenotransplanted human islets, GABA therapy stimulates β-cell replication and insulin secretion. Thus, the intraislet GABAergic system is a target for the amelioration of diabetes therapy, including β-cell survival and regeneration. GABA (or GABAergic drugs) can be combined with other antidiabetic drugs for greater effect.

Effect of oral magnesium sulfate administration on lectin-like oxidized low-density lipoprotein receptor-1 gene expression to prevent atherosclerosis in diabetic rat vessels

AIMS/INTRODUCTION

The purpose of the present study was to investigate the possible effect of oral magnesium sulfate (MgSO4 ) in the reduction of atherosclerosis plaques through inhibition of lectin-like low-density lipoprotein receptor-1 (LOX-1) gene expression in diabetic vessels.

MATERIALS AND METHODS

A total of 50 rats were divided into five groups, including non-diabetic control, Mg-treated non-diabetic control, chronic diabetic, Mg-treated chronic diabetic and insulin-treated chronic diabetic. The induction of diabetes was carried out by streptozotocin. The Mg-treated chronic diabetic and Mg-treated non-diabetic control groups were treated with 10 g/L of MgSO4 added to their drinking water. The insulin-treated chronic diabetic group received 2.5 U/kg of insulin twice per day. The fasting blood glucose level and bodyweight were determined weekly. Blood pressure measurement and the intraperitoneal glucose tolerance test were carried out after 16 weeks, and the plasma levels of Mg, lipid profile and oxidized low-density lipoprotein cholesterol (oxLDL) were determined. The mesenteric bed was isolated and perfused according to the McGregor method. The aorta was isolated for LOX-1 genes and proteins expression, and pathological investigation.

RESULTS

MgSO4 administration improved blood pressure, sensitivity to phenylephrine, intraperitoneal glucose tolerance test, lipid profile and plasma ox-LDL level, and also lowered the blood glucose level to the normal range, and decreased LOX-1 gene and protein expressions. Insulin decreased blood pressure, sensitivity to phenylephrine, blood glucose, lipid profiles and plasma oxLDL level, but it did not decrease LOX-1 gene and protein expressions.

CONCLUSIONS

The present findings suggested that MgSO4 improves blood pressure and vessel structure through decreasing oxLDL, and LOX-1 gene and protein expressions; however, insulin did not repair vessel structure, and LOX-1 gene and protein expressions.

Case Reports of Pre-clinical Replication Studies in Metabolism and Diabetes

Recent articles have highlighted the lack of reproducibility of data from scientific publications. Here we would argue that a better way to describe and also tackle this matter is to use the term "lack of robustness," since it points toward potential solutions. Presenting several case reports, we highlight examples with common underlying issues from Novo Nordisk's experience: animal model variability, reagent quality, and inter-lab variability. We discuss means to prevent these issues and argue for increased collaborative work and transparent manuscript revision procedures. Collectively, we believe these measures will help promote a more rapid and efficient self-corrective process in diabetes drug target research.

Exploratory metabolomics of nascent metabolic syndrome

INTRODUCTION

Metabolic syndrome (MetS) is a disorder defined by having three of five features: increased waist circumference (WC), hypertriglyceridemia, decreased high-density lipoprotein-cholesterol, hypertension and an elevated blood glucose (BG). Metabolic Syndrome ( MetS) affects 35% of American adults and significantly increases risk for Atherosclerotic cardiovascular disease (ASCVD) and type-2 diabetes (T2DM). An understanding of the metabolome will help elucidate the pathogenesis of MetS and lead to better management. We hypothesize that the metabolites, gamma-aminobutyric acid (GABA), d-pyroglutamic acid (PGA) and N-acetyl-d-tryptophan (NAT) will be altered in nascent MetS patients without the confounding of ASCVD or T2DM. We also correlated these metabolites with biomarkers of inflammation.

PATIENTS AND METHODS

This was an exploratory study of 30 patients with nascent MetS and 20 matched controls undertaken in 2018. Metabolites were evaluated from patient's frozen early morning urine samples and were correlated with biomarkers of inflammation and adipokines. They were assayed by the NIH Western Metabolomics Center using liquid chromatography/mass spectrometry and standardized to urinary creatinine. All patients had normal hepatic and renal function.

RESULTS

GABA and PGA levels were significantly increased in MetS patients compared to controls: 2.8-fold and 2.9-fold median increases respectively with p < 0.0001 and p = 0.004, possibly deriving from glutamate. NAT was significantly decreased by 90% in MetS patients compared to controls, p < 0.001. GABA correlates significantly with cardio-metabolic (CM) features including WC, blood pressure systolic (BP-S) while NAT correlated inversely with WC, BP-S, blood glucose (BG) and triglycerides (TG). GABA correlated positively with chemerin, leptin, Fetuin A and endotoxin. NAT correlated inversely with WC, BP-S, BG, TG, high sensitivity C - reactive protein (hsCRP), toll-like receptor-4 (TLR-4), lipopolysaccharide binding protein (LBP), chemerin and retinol binding protein-4 (RBP-4).

CONCLUSIONS

We make the novel observation of increased GABA and PGA with decreased NAT in patients with MetS. While GABA and PGA correlates positively with CM features and biomediators of inflammation, the metabolite NAT correlated inversely. Thus, GABA and PGA could contribute to the pro-inflammatory state of MetS while NAT could mitigate this pro-inflammatory response.

A Clinically Applicable Positive Allosteric Modulator of GABA Receptors Promotes Human β-Cell Replication and Survival as well as GABA's Ability to Inhibit Inflammatory T Cells

A major goal of T1D research is to develop new approaches to increase β-cell mass and control autoreactive T cell responses. GABAA-receptors (GABAA-Rs) are promising drug targets in both those regards due to their abilities to promote β-cell replication and survival, as well as inhibit autoreactive T cell responses. We previously showed that positive allosteric modulators (PAMs) of GABAA-Rs could promote rat β-cell line INS-1 and human islet cell replication in vitro. Here, we assessed whether treatment with alprazolam, a widely prescribed GABAA-R PAM, could promote β-cell survival and replication in human islets after implantation into NOD/scid mice. We observed that alprazolam treatment significantly reduced human islet cell apoptosis following transplantation and increased β-cell replication in the xenografts. Evidently, the GABAA-R PAM works in conjunction with GABA secreted from β-cells to increase β-cell survival and replication. Treatment with both the PAM and GABA further enhanced human β-cell replication. Alprazolam also augmented the ability of suboptimal doses of GABA to inhibit antigen-specific T cell responses in vitro. Thus, combined GABAA-R agonist and PAM treatment may help control inflammatory immune responses using reduced drug dosages. Together, these findings suggest that GABAA-R PAMs represent a promising drug class for safely modulating islet cells toward beneficial outcomes to help prevent or reverse T1D and, together with a GABAA-R agonist, may have broader applications for ameliorating other disorders in which inflammation contributes to the disease process.

GABA promotes β-cell proliferation, but does not overcome impaired glucose homeostasis associated with diet-induced obesity

γ-Aminobutyric acid (GABA) administration has been shown to increase β-cell mass, leading to a reversal of type 1 diabetes in mice. Whether GABA has any effect on β cells of healthy and prediabetic/glucose-intolerant obese mice remains unknown. In the present study, we show that oral GABA administration ( ad libitum) to mice indeed increased pancreatic β-cell mass, which led to a modest enhancement in insulin secretion and glucose tolerance. However, GABA treatment did not further increase insulin-positive islet area in high fat diet-fed mice and was unable to prevent or reverse glucose intolerance and insulin resistance. Mechanistically, whether in vivo or in vitro, GABA treatment increased β-cell proliferation. In vitro, the effect was shown to be mediated via the GABA_A receptor. Single-cell RNA sequencing analysis revealed that GABA preferentially up-regulated pathways linked to β-cell proliferation and simultaneously down-regulated those networks required for other processes, including insulin biosynthesis and metabolism. Interestingly, single-cell differential expression analysis revealed GABA treatment gave rise to a distinct subpopulation of β cells with a unique transcriptional signature, including urocortin 3 ( ucn3), wnt4, and hepacam2. Taken together, this study provides new mechanistic insight into the proliferative nature of GABA but suggests that β-cell compensation associated with prediabetes overlaps with, and negates, its proliferative effects.-Untereiner, A., Abdo, S., Bhattacharjee, A., Gohil, H., Pourasgari, F., Ibeh, N., Lai, M., Batchuluun, B., Wong, A., Khuu, N., Liu, Y., Al Rijjal, D., Winegarden, N., Virtanen, C., Orser, B. A., Cabrera, O., Varga, G., Rocheleau, J., Dai, F. F., Wheeler, M. B. GABA promotes β-cell proliferation, but does not overcome impaired glucose homeostasis associated with diet-induced obesity.

Homotaurine, a safe blood-brain barrier permeable GABAA-R-specific agonist, ameliorates disease in mouse models of multiple sclerosis

There is a need for treatments that can safely promote regulatory lymphocyte responses. T cells express GABA receptors (GABA_A-Rs) and GABA administration can inhibit Th1-mediated processes such as type 1 diabetes and rheumatoid arthritis in mouse models. Whether GABA_A-R agonists can also inhibit Th17-driven processes such as experimental autoimmune encephalomyelitis (EAE), a model of multiple sclerosis (MS), is an open question. GABA does not pass through the blood-brain barrier (BBB) making it ill-suited to inhibit the spreading of autoreactivity within the CNS. Homotaurine is a BBB-permeable amino acid that antagonizes amyloid fibril formation and was found to be safe but ineffective in long-term Alzheimer’s disease clinical trials. Homotaurine also acts as GABA_A-R agonist with better pharmacokinetics than that of GABA. Working with both monophasic and relapsing-remitting mouse models of EAE, we show that oral administration of homotaurine can (1) enhance CD8⁺CD122⁺PD-1⁺ and CD4⁺Foxp3⁺ Treg, but not Breg, responses, (2) inhibit autoreactive Th17 and Th1 responses, and (3) effectively ameliorate ongoing disease. These observations demonstrate the potential of BBB-permeable GABA_A-R agonists as a new class of treatment to enhance CD8⁺ and CD4⁺ Treg responses and limit Th17 and Th1-medaited inflammation in the CNS.