Taurine supplementation prevents morpho-physiological alterations in high-fat diet mice pancreatic β-cells

Mitigating diabetes-related complications: Empowering metformin with cholecalciferol and taurine supplementation in type 2 diabetic rats

BACKGROUND

Type 2 diabetes is one of the most prevalent chronic diseases worldwide, significantly impacting patients' quality of life. Current treatment options like metformin (MET) effectively counteract hyperglycemia but fail to alleviate diabetes-associated complications such as retinopathy, neuropathy, nephropathy, hepatopathy, and cardiovascular diseases.

AIM

To propose the supplementation of cholecalciferol (CHO) and taurine (TAU) to enhance MET efficacy in controlling diabetes while minimizing the risk of associated complications.

METHODS

The study involved sixty rats, including ten non-diabetic control rats and fifty experimental rats with type 2 diabetes induced by streptozotocin. The experimental rats were further subdivided into positive control and treatment subgroups. The four treatment groups were randomly allocated to a single MET treatment or MET combined with supplements either CHO, TAU, or both.

RESULTS

Diabetic rats exhibited elevated levels of glucose, insulin, Homeostasis Model Assessment of Insulin Resistance (HOMA-IR), glycated hemoglobin%, lipid markers, aspartate aminotransferase, and malondialdehyde, along with reduced levels of antioxidant enzymes (catalase and superoxide dismutase). The administration of CHO and TAU supplements alongside MET in diabetic rats led to a noticeable recovery of islet mass. The antioxidative, anti-inflammatory, and anti-apoptotic properties of the proposed combination therapy significantly ameliorated the aforementioned abnormalities.

CONCLUSION

The supplementation of CHO and TAU with MET showed the potential to significantly improve metabolic parameters and protect against diabetic complications through its antioxidative, anti-inflammatory, and anti-apoptotic effects.

Vertical sleeve gastrectomy improves glucose-insulin homeostasis by enhancing β-cell function and survival via FGF15/19

Vertical sleeve gastrectomy (VSG) restores glucose homeostasis in obese mice and humans. In addition, the increased fibroblast growth factor (FGF)15/19 circulating level postsurgery has been implicated in this effect. However, the impact of FGF15/19 on pancreatic islets remains unclear. Using a diet-induced obese mice model, we demonstrate that VSG attenuates insulin hypersecretion in isolated pancreatic islets, likely due to morphological alterations in the endocrine pancreas such as reduction in islet, β-cell, and α-cell mass. In addition, VSG relieves gene expression of endoplasmic reticulum (ER) stress and inflammation markers in islets from obese mice. Incubation of INS-1E β-cells with serum from obese mice induced dysfunction and cell death, whereas these conditions were not induced with serum from obese mice submitted to VSG, implicating the involvement of a humoral factor. Indeed, VSG increased FGF15 circulating levels in obese mice, as well as the expression of FGF receptor 1 (Fgfr1) and its coreceptor β-klotho (Klb), both in pancreatic islets from VSG mice and in INS-1E cells treated with the serum from these mice. Moreover, exposing INS-1E cells to an FGFR inhibitor abolished the effects of VSG serum on insulin secretion and cell death. Also, recombinant FGF19 prevents INS-1E cells from dysfunction and death induced by serum from obese mice. These findings indicate that the amelioration of glucose-insulin homeostasis promoted by VSG is mediated, at least in part, by FGF15/19. Therefore, approaches promoting FGF15/19 release or action may restore pancreatic islet function in obesity.NEW & NOTEWORTHY Vertical sleeve gastrectomy (VSG) decreases insulin secretion, endoplasmic reticulum (ER) stress, and inflammation in pancreatic islets from obese mice. In addition, VSG increased fibroblast growth factor (FGF)15 circulating levels in obese mice, as well as the expression of FGF receptor 1 (Fgfr1) and its coreceptor β-klotho (Klb), both in pancreatic islets from VSG mice and in INS-1E β-cells treated with the serum from these mice. Serum from operated mice protects INS-1E cells from dysfunction and apoptosis, which was mediated by FGF15/19.

Taurine and N-acetylcysteine treatments prevent memory impairment and metabolite profile alterations in the hippocampus of high-fat diet-fed female mice

Background: Obesity constitutes a risk factor for cognitive impairment. In rodent models, long-term exposure to obesogenic diets leads to hippocampal taurine accumulation. Since taurine has putative cyto-protective effects, hippocampal taurine accumulation in obese and diabetic models might constitute a counteracting response to metabolic stress. Objective: We tested the hypothesis that treatment with taurine or with N-acetylcysteine (NAC), which provides cysteine for the synthesis of taurine and glutathione, prevent high-fat diet (HFD)-associated hippocampal alterations and memory impairment. Methods: Female mice were fed either a regular diet or HFD. Some mice had access to 3%(w/v) taurine or 3%(w/v) NAC in the drinking water. After 2 months, magnetic resonance spectroscopy (MRS) was used to measure metabolite profiles. Memory was assessed in novel object and novel location recognition tests. Results: HFD feeding caused memory impairment in both tests, and reduced concentration of lactate, phosphocreatine-to-creatine ratio, and the neuronal marker N-acetylaspartate in the hippocampus. Taurine and NAC prevented HFD-induced memory impairment and N-acetylaspartate reduction. NAC, but not taurine, prevented the reduction of lactate and phosphocreatine-to-creatine ratio. MRS revealed NAC/taurine-induced increase of hippocampal glutamate and GABA levels. Conclusion: NAC and taurine can prevent memory impairment, while only NAC prevents alterations of metabolite concentrations in HFD-exposed female mice.

Taurine Supplementation for 48-Months Improved Glucose Tolerance and Changed ATP-Related Enzymes in Avians

Avians differ from mammals, especially in brain architecture and metabolism. Taurine, an amino acid basic to metabolism and bioenergetics, has been shown to have remarkable effects on metabolic syndrome and ameliorating oxidative stress reactions across species. However, less is known regarding these metabolic relationships in the avian model. The present study serves as a preliminary report that examined how taurine might affect avian metabolism in an aged model system. Two groups of pigeons (Columba livia) of mixed sex, a control group and a group that received 48 months of taurine supplementation (0.05% w/v) in their drinking water, were compared by using blood panels drawn from their basilic vein by a licensed veterinarian. From the blood panel data, taurine treatment generated higher levels of three ATP-related enzymes: glutamate dehydrogenase (GLDH), lactate dehydrogenase (LDH), and creatine kinase (CK). In this preliminary study, the role that taurine treatment might play in the adult aged pigeon's metabolism on conserved traits such as augmenting insulin production as well as non-conserved traits maintaining high levels of ATP-related enzymes was examined. It was found that taurine treatment influenced the avian glucose metabolism similar to mammals but differentially effected avian ATP-related enzymes in a unique way (i.e., ∼×2 increase in CK and LDH with a nearly ×4 increase in GLDH). Notably, long-term supplementation with taurine had no negative effect on parameters of lipid and protein metabolism nor liver enzymes. The preliminary study suggests that avians may serve as a unique model system for investigating taurine metabolism across aging with long-term health implications (e.g., hyperinsulinemia). However, the suitability of using the model would require researchers to tightly control for age, sex, dietary intake, and exercise conditions as laboratory-housed avian present with very different metabolic panels than free-flight avians, and their metabolic profile may not correlate one-to-one with mammalian data.

The Role of Gut Microbiota in High-Fat-Diet-Induced Diabetes: Lessons from Animal Models and Humans

The number of diabetes mellitus patients is increasing rapidly worldwide. Diet and nutrition are strongly believed to play a significant role in the development of diabetes mellitus. However, the specific dietary factors and detailed mechanisms of its development have not been clearly elucidated. Increasing evidence indicates the intestinal microbiota is becoming abundantly apparent in the progression and prevention of insulin resistance in diabetes. Differences in gut microbiota composition, particularly butyrate-producing bacteria, have been observed in preclinical animal models as well as human patients compared to healthy controls. Gut microbiota dysbiosis may disrupt intestinal barrier functions and alter host metabolic pathways, directly or indirectly relating to insulin resistance. In this article, we focus on dietary fat, diabetes, and gut microbiome characterization. The promising probiotic and prebiotic approaches to diabetes, by favorably modifying the composition of the gut microbial community, warrant further investigation through well-designed human clinical studies.

Beneficial Effects of Taurine on Metabolic Parameters in Animals and Humans

Taurine (2-aminoethanesulfonic acid) is a non-essential amino acid mainly obtained through diet in humans. Despite the lack of research on the health effects of taurine in animals and humans, it is widely used as a dietary supplement. Evidence from human and animal studies indicates that taurine is involved in conjugation of bile acids and regulation of blood pressure and has anti-oxidative, anti-inflammatory, and anti-obesogenic properties. Taurine can benefit both human and non-human animal health in multiple ways. However, few interventional and epidemiological studies regarding the beneficial impacts of taurine in humans and other animals have been conducted. Here, we review the evidence from animal and human studies showing that taurine protects against dyslipidemia, obesity, hypertension, and diabetes mellitus.

Taurine Supplementation as a Neuroprotective Strategy upon Brain Dysfunction in Metabolic Syndrome and Diabetes

Obesity, type 2 diabetes, and their associated comorbidities impact brain metabolism and function and constitute risk factors for cognitive impairment. Alterations to taurine homeostasis can impact a number of biological processes, such as osmolarity control, calcium homeostasis, and inhibitory neurotransmission, and have been reported in both metabolic and neurodegenerative disorders. Models of neurodegenerative disorders show reduced brain taurine concentrations. On the other hand, models of insulin-dependent diabetes, insulin resistance, and diet-induced obesity display taurine accumulation in the hippocampus. Given the possible cytoprotective actions of taurine, such cerebral accumulation of taurine might constitute a compensatory mechanism that attempts to prevent neurodegeneration. The present article provides an overview of brain taurine homeostasis and reviews the mechanisms by which taurine can afford neuroprotection in individuals with obesity and diabetes. We conclude that further research is needed for understanding taurine homeostasis in metabolic disorders with an impact on brain function.

Recent insights into the molecular regulators and mechanisms of taurine to modulate lipid metabolism: a review

Lipid metabolism disorders such as hypertriglyceridemia and hypercholesterolemia are risk factors for cardiovascular diseases and atherosclerosis that are grave public health issues. Taurine, a sulfur-containing non-essential amino acid exerts a wide range of physiological effects that regulate lipid metabolic disorders. Although the effects of taurine on lipid-lowering have been reported in animals and humans, mechanisms elucidating the lipid-lowering action of taurine remain unclear. A series of molecular regulators associated with lipid metabolism have been identified in the past few decades. These include nuclear receptors, transcription factors, and enzymes that undergo important changes during taurine treatment. In this review, we focus on the role of taurine in lipid metabolism and discuss taurine-related interventions in combating lipid disorders.

The Effects of TRX Suspension Training Combined with Taurine Supplementation on Body Composition, Glycemic and Lipid Markers in Women with Type 2 Diabetes

Background: We aimed to investigate the effects of an 8-week total-body resistance exercise (TRX) suspension training intervention combined with taurine supplementation on body composition, blood glucose, and lipid markers in T2D females. Methods: Forty T2D middle-aged females (age: 53 ± 5 years, body mass = 84.3 ± 5.1 kg) were randomly assigned to four groups, TRX suspension training + placebo (TP; n = 10), TRX suspension training + taurine supplementation (TT; n = 10), taurine supplementation (T; n = 10), or control (C; n = 10). Body composition (body mass, body mass index (BMI), body fat percentage (BFP)), blood glucose (fasting blood sugar (FBS)), hemoglobin A1c (HbA1c), Insulin, and Insulin resistance (HOMA-IR), and lipid markers (low-density lipoprotein (LDL), high-density lipoprotein (HDL), triglyceride (TG), and total cholesterol (TC)) were evaluated prior to and after interventions. Results: All three interventions significantly decreased body mass, BMI, and BFP with no changes between them for body mass and BMI; however, BFP changes in the TT group were significantly greater than all other groups. FBS was significantly reduced in TP and TT. Insulin concentrations’ decrement were significantly greater in all experimental groups compared to C; however, no between group differences were observed between TT, TP, and T. In regards to HOMA-IR, decreases in TT were significantly greater than all other groups TG, HbA1c, and LDL were reduced following all interventions. HDL values significantly increased only in the TT group, while TC significantly decreased in TP and TT groups. Changes in HbA1c, TG, HDL, and TC were significantly greater in the TT compared to all other groups. Conclusions: TRX training improved glycemic and lipid profiles, while taurine supplementation alone failed to show hypoglycemic and hypolipidemic properties. Notably, the synergic effects of TRX training and taurine supplementation were shown in HbA1c, HOMA-IR, TG, TC, HDL, and BFP changes. Our outcomes suggest that TRX training + taurine supplementation may be an effective adjuvant therapy in individuals with T2D.

Ameliorative effect of taurine against diabetes and renal-associated disorders (Review)

To develop novel therapeutic methods for both diabetic and renal disorders, scientists had initially focused on elucidating the molecular mechanisms of taurine in established cell lines and mouse models. Although a large amount of data have been revealed, taurine has been confirmed to be the next step of novel promising therapeutic interventions against diabetic disorders. Taurine appears to ameliorate diabetes 1-related complications in various organs through its antioxidant, anti-inflammatory and anti-hormonal actions. In type 2 diabetes, taurine has been positively implicated in glucose homeostasis, exerting potent hypoglycemic, anti-obesity, hypotensive and hypolipidemic effects. Of particular interest is that taurine provides protection against renal dysfunction, including hypertension and proteinuria, specific glomerular and tubular disorders, acute and chronic renal conditions, and diabetic nephropathy. The ameliorative effects of taurine against renal disorders are based on its osmoregulatory properties, its association with signaling pathways and its association with the renin-angiotensin-aldosterone system (RAAS). Further clinical studies are required to ensure the importance of research findings.

Taurine ameliorates axonal damage in sciatic nerve of diabetic rats and high glucose exposed DRG neuron by PI3K/Akt/mTOR-dependent pathway

Diabetic peripheral neuropathy (DPN) is a common complication of diabetes and axonopathy is its main pathological feature. Previous studies suggested an advantage of taurine against diabetes. However, there are few reports which study the effect of taurine against axonopathy. In this study, we confirmed that taurine significantly decreased blood glucose level, mitigated insulin resistance and improved dysfunctional nerve conduction in diabetic rats. Taurine corrected damaged axonal morphology of sciatic nerve in diabetic rats and induced axon outgrowth of Dorsal root ganglion (DRG) neurons exposed to high glucose. Taurine up-regulated phosphorylation levels of PI3K, Akt, and mTOR in sciatic nerve of diabetic rats and DRG neurons exposed to high glucose. However, Akt and mTOR inhibitors (MK-2206 and Rapamycin) blocked the effect of taurine on improving axonal damage. These results indicate that taurine ameliorates axonal damage in sciatic nerve of diabetic rats by activating PI3K/Akt/mTOR signal pathway. Our findings provide taurine as a potential candidate for axonopathy and a new evidence for elucidating protective mechanism of taurine on DPN.

The Influence of Taurine Supplementation on Serum and Tissular Fe, Zn and Cu Levels in Normal and Diet-Induced Insulin-Resistant Rats

Taurine (Tau) is a β-sulphonated amino acid postulated to improve glucose homeostasis in insulin resistance and diabetes. Changes in carbohydrate metabolism are accompanied by oxidative stress, which may disturb the mineral balance. Therefore, the aim of this study was to assess the effect of Tau supplementation on the levels of trace elements in rats fed either a standard (AIN-93M, 4% fat) diet or a modified high-fat diet (30% fat). For 8 weeks, male Wistar rats were fed these diets supplemented with 3% Tau. Taurine supplementation normalized increased serum insulin concentration and insulin resistance index; however, it did not improve serum CRP concentration in high-fat diet fed rats. The high-fat diet supplemented with Tau decreased the renal and splenic Zn levels, but the tissular Fe content did not change. The effect of Tau supplementation on the mineral balance to some extent depended on the fat content in the rats' diet. The high-fat diet supplemented with Tau decreased the rats' splenic Zn levels but increased their femur levels. In the group fed the standard diet, Tau reduced the rats' femur Zn level, whereas their splenic Zn level was comparable. Tau supplementation decreased the renal Cu level and serum ceruloplasmin concentration in the rats fed the standard diet, but this effect was not observed in the rats fed the high-fat diet. In conclusion, supplementary taurine failed to ameliorate disturbances in mineral homeostasis caused by high-fat diet feeding and led to tissular redistribution of Zn and Cu in the rat.

D-Pinitol Increases Insulin Secretion and Regulates Hepatic Lipid Metabolism in Msg-Obese Mice

D-pinitol is one of the major inositol found in plants and studies suggest its potential hypoglycemic and hypolipidemic actions in diabetic rodents. Here, we investigated the actions of D-pinitol on adiposity, and in lipid and glycemic homeostasis in monosodium glutamate (MSG)-obese mice. Swiss mice received daily subcutaneous injections of MSG [(4g/kg of body weight (BW)] or saline [1.25g/kg BW; control (CTL)] during their first five days of life. From 90-120 day-old, half of the MSG and CTL groups received 50 mg D-pinitol/kg BW/day (MPIN and CPIN groups) or vehicle (saline; MSG and CTL groups) by gavage. MSG mice displayed higher abdominal adiposity and hepatic triglycerides (TG) deposition, and increased hepatic expression of lipogenic genes (SREBP-1c, ACC-1 and FASN), but downregulation in AMPKα mRNA. MSG mice also exhibited hyperinsulinemia, islet hypersecretion and hypertrophy, glucose intolerance and insulin resistance. D-pinitol did not change adiposity, glucose intolerance, insulin resistance, but increased hepatic triglycerides (TG) content in MPIN mice, which was associated with increases in gene expressions of SREBP-1c and FASN, but reduction in AMPKα. Furthermore, D-pinitol enhanced insulin secretion in MPIN and CPIN groups. Therefore, D-pinitol enhanced glucose-induced insulin secretion, which may account to enhances hepatic lipogenesis and TG deposition in MPIN mice.

The effects of taurine supplementation on glycemic control and serum lipid profile in patients with type 2 diabetes: a randomized, double-blind, placebo-controlled trial

Previous studies have suggested that taurine has hypoglycemic and hypolipidemic effects on experimental diabetic models. Therefore, this clinical trial was designed to explore the impacts of taurine supplementation on glycemic control and lipid profile in the patients with T2DM. This study was conducted on 45 patients with T2DM in Tabriz Sheikhor-raees Polyclinic and Imam-Reza Hospital Endocrine Center. Subjects were randomly divided into taurine and placebo groups. Accordingly, the taurine group (n = 23) received taurine 3000 mg/daily and the placebo group (n = 22) took crystalline microcellulose/daily for the duration of 8 weeks. At baseline and after the trial completion, fasting blood samples were obtained from the patients to assess the glycemic indicators and lipid profile. Independent t test, paired t test, Pearson's correlation, and analysis of covariance was used for analysis. At the end of the study, levels of FBS (p = 0.01), insulin (p = 0.01), HOMA-IR (p = 0.003), TC (p = 0.013), and LDL-C (p = 0.041) significantly decreased in the taurine group compared to the placebo group. In addition, there was no significant changes in HbA1c, triglyceride, HDL-C, anthropometric indicators or dietary intakes by passing 8 weeks from the intervention. In conclusion, the findings of the current study indicated that taurine supplementation (3000 mg/day) for 8 weeks could improve the glycemic indexes and lipid profiles including TC and LDL-C in the patients with T2DM.

Taurine inhibits neuron apoptosis in hippocampus of diabetic rats and high glucose exposed HT-22 cells via the NGF-Akt/Bad pathway

Type 2 Diabetes causes learning and memory deficits that might be mediated by hippocampus neuron apoptosis. Studies found that taurine might improve cognitive deficits under diabetic condition because of its ability to prevent hippocampus neuron apoptosis. However, the effect and mechanism is not clear. In this study, we explore the effect and mechanism of taurine on inhibiting hippocampus neuron apoptosis. Sixty male Sprague-Dawley rats were randomly divided into control, T2D, taurine treatment (giving 0.5%, 1%, and 2% taurine in drinking water) groups. Streptozotocin was used to establish the diabetes model. HT-22 cell (hippocampus neurons line) was used for in vitro experiments. Morris Water Maze test was used to check the learning and memory ability, TUNEL assay was used to measure apoptosis and nerve growth factor (NGF); Akt/Bad pathway relevant protein was detected by western blot. Taurine improved learning and memory ability and significantly decreased apoptosis of the hippocampus neurons in T2D rats. Moreover, taurine supplement also inhibited high glucose-induced apoptosis in HT-22 cell in vitro. Mechanistically, taurine increased the expression of NGF, phosphorylation of Trka, Akt, and Bad, as well as reduced cytochrome c release from mitochondria to cytosol. However, beneficial effects of taurine were blocked in the presence of anti-NGF antibody or Akt inhibitor. Taurine could inhibit hippocampus neuron apoptosis via NGF-Akt/Bad pathway. These results provide some clues that taurine might be efficient and feasible candidate for improvement of learning and memory ability in T2D rats.

Combined oral contraceptive in female mice causes hyperinsulinemia due to β-cell hypersecretion and reduction in insulin clearance

Oral contraception is the most commonly used interventional method in the world. However, several women employ the continuous use of these hormones to avoid pre- and menstruation discomforts. Some studies indicate that oral contraceptives are associated with disturbances in glycemia and the effects of the use of a continuous regime are poorly elucidated. Herein, we evaluated the effects of the continuous administration of a combined oral contraceptive (COC) composed by ethinyl estradiol (EE) and drospirenone (DRSP) on glucose homeostasis in female mice. Adult Swiss mice received 0.6 μg EE and 60 μg DRSP (COC group) or vehicle [control (CTL)] daily by gavage for 35 days. COC treatment had no effect on body weight or adiposity, but increased uterus weight and induced hepatomegaly. Importantly, COC females displayed normal glycemia and glucose tolerance, but hyperinsulinemia and lower plasma C-peptide/insulin ratio, indicating reduced insulin clearance. Furthermore, COC mice displayed reduced protein content of the β subunit of the insulin receptor (IRβ) in the liver. Additionally, pancreatic islets isolated from COC mice secreted more insulin in response to increasing glucose concentrations. This effect was associated with the activity of steroid hormones, since INS-1E cells incubated with EE plus DRSP also secreted more insulin. Therefore, we provide the first evidence that the continuous administration of EE and DRSP lead to hyperinsulinemia, due to enhancement of insulin secretion and the reduction of insulin degradation, which possibly lead to the down-regulation of hepatic IRβ. These findings suggest that the continuous administration of COC could cause insulin resistance with the prolongation of treatment.

The Relationship between Plasma Taurine Levels and Diabetic Complications in Patients with Type 2 Diabetes Mellitus

Background: Taurine has an active role in providing glucose homeostasis and diabetes causes a decline in taurine levels. This paper investigates the relationship between taurine and diabetic complications, patients' demographic features, and biochemical parameters. Methods: Fifty-nine patients with type 2 diabetes mellitus (T2DM), and 28 healthy control subjects between the ages of 32 and 82 were included in the study. The mean age of subjects was 55.6 ± 10.3 and mean diabetes duration was 10.2 ± 6.0 years. The most commonly accompanying comorbidity was hypertension (HT) (64.5%, n = 38), and the most frequent diabetic complication was neuropathy (50.8%, n = 30). Plasma taurine concentrations were measured by an enzyme-linked immunoassay (ELISA) kit. Results: Plasma taurine concentrations were significantly lower in diabetic patients (0.6 ± 0.1 mmol/L) than controls (0.8 ± 0.2 mmol/L) and in hypertensive (0. 6 ± 0.1 mmol/L) patients (p = 0.000, p = 0.027 respectively). Conclusion: Plasma taurine levels were decreased in patients with T2DM and this was not related to FBG, HbA1c, and microalbuminuria. With regard to complications, we only found a correlation with neuropathy. We suggest that taurine levels may be more important in the development of diabetes; however, it may also have importance for the progression of the disease and the subsequent complications. We further assert that taurine measurement at different times may highlight whether there is a causal relationship in the development of complications.

Taurine supplementation in high-fat diet fed male mice attenuates endocrine pancreatic dysfunction in their male offspring

Obesity in fathers leads to DNA damage and epigenetic changes in sperm that may carry potential risk factors for metabolic diseases to the next generation. Taurine (TAU) supplementation has demonstrated benefits against testicular dysfunction and pancreatic islet impairments induced by obesity, but it is not known if these protective actions prevent the propagation of metabolic disruptions to the next generation; as such, we hypothesized that paternal obesity may increase the probability of endocrine pancreatic dysfunction in offspring, and that this could be prevented by TAU supplementation in male progenitors. To test this, male C57Bl/6 mice were fed on a control diet (CTL) or a high-fat diet (HFD) without or with 5% TAU in their drinking water (CTAU and HTAU) for 4 months. Subsequently, all groups of mice were mated with CTL females, and the F1 offspring were identified as: CTL-F1, CTAU-F1, HFD-F1, and HTAU-F1. HFD-fed mice were normoglycemic, but glucose intolerant and their islets hypersecreted insulin. However, at 90 days of age, HFD-F1 offspring displayed normal glucose homeostasis and adiposity, but reduced glucose-induced insulin release. HFD-F1 islets also exhibited β- and α-cell hypotrophy, and lower δ-cell number per islet. Paternal TAU supplementation prevented the decrease in glucose-induced insulin secretion and normalized β-cell size and δ-cell number, and increased α-cell size/islet in HTAU-F1 mice. In conclusion, HFD consumption by male founders decreases β-cell secretion and islet-cell distribution in their offspring. TAU attenuates the deleterious effects of paternal obesity on insulin secretion and islet-cell morphology in F1 offspring.

Regulation of glucose and lipid metabolism by the pancreatic and extra-pancreatic actions of taurine

The beneficial actions of L-taurine (Tau) against glucose intolerance, obesity, type 2 diabetes (T2D), and non-alcoholic fat liver disease (NAFLD) have been linked to its antioxidant and anti-inflammatory effects, which ameliorate tissue insulin sensitivity. Importantly, there are several lines of evidence that indicate a direct action of Tau on the endocrine pancreas to regulate the secretion and paracrine actions of insulin, glucagon, and somatostatin. Furthermore, Tau can also ameliorate glucose metabolism through the enhancement of insulin signaling. However, some of the benefits of Tau upon intermediary metabolism may manifest via considerable antagonism of the action of insulin. Therefore, this review discusses the mechanisms of action by which Tau may regulate endocrine pancreatic morphofunction, and glucose and lipid homeostasis.

Acute intraperitoneal administration of taurine decreases the glycemia and reduces food intake in type 1 diabetic rats

Taurine, an amino acid with antioxidant and osmoregulatory properties, has been studied for its possible antidiabetic properties in type 1 and type 2 diabetic animals. In type 2 diabetic mice, taurine decreases blood glucose through increased insulin secretion and insulin receptor sensitization. However, insulin is absent in type 1 diabetic individuals. The aim of this study was to evaluate the effects of taurine on parameters related to the energy balance that could explain the metabolic action of this amino acid in type 1 diabetic rats. Control and streptozotocin-induced diabetic rats received saline or taurine (100 mg/kg/day), intraperitoneally, for 30 days. Parameters such as palatable food intake, gastrointestinal transit rate, serum glucose, insulin, leptin, and glucagon levels were measured 60 min after the last taurine administration. Liver, kidneys, heart, and retroperitoneal fat were dissected and weighted. Glycogen levels were measured in the liver and soleus muscle. Our results showed that acute taurine administration decreased glycemia. It also decreased food intake in diabetic rats, without affecting other metabolic parameters. Altogether, our results suggest that in type 1 diabetic rats, taurine decreases blood glucose by a non-insulin-dependent mechanism. Due to the safety profile of taurine, and its effect on glycemia, this amino acid may help to design new drugs to add benefit to insulin therapy in type 1 diabetic individuals.

Diet-induced glucose homeostasis dysregulation is enhanced by taurine supplementation in ovariectomized mice

Low levels of estrogens are associated with obesity-related comorbidities. Mice with lower levels of estrogens are thereby more sensitive to the effects of a high-fat-diet (HFD) for the development of glucose intolerance and insulin resistance. Studies in vivo have demonstrated that taurine (TAU) supplementation prevents glucose and insulin resistance. Thus, we aimed to investigate the potential beneficial effects of TAU supplementation on glucose homeostasis of mice with low levels of estrogens fed with a HFD. 3-month-old female C57BL/6J mice underwent bilateral ovariectomy (OVX). After 1 week of recovery, mice were divided into 4 groups and either received: a standard chow diet (OVXC), chow diet plus drinking water enriched with 3% of TAU (OVXCT), HFD (OVXH), and HFD plus supplementation of TAU (OVXHT) for 14 weeks. Exposure to the HFD increased adiposity and plasma levels of glucose and insulin. Contrary to our prediction, the addition of TAU enhanced the deleterious effects of the HFD. Glucose and insulin tolerance tests (ipGTT and ipITT) indicated that mice maintained on the HFD + TAU had worse glucose intolerance and insulin resistance that was linked to lower insulin signaling in skeletal muscle and liver. Insulin secretion of isolated pancreatic islets of OVXH mice was higher than OVXC, and the addition of TAU associated with a HFD did not modulate insulin secretion, suggesting a failure of pancreatic β cells of OVXHT mice. These results suggest that despite the beneficial reports of TAU, it should be used cautiously in situations where the levels of estrogens are low.

Prophylactic role of taurine and its derivatives against diabetes mellitus and its related complications

Taurine is a conditionally essential amino acid present in the body in free form. Mammalian taurine is synthesized in the pancreas via the cysteine sulfinic acid pathway. Anti-oxidation and anti-inflammation are two main properties through which it exerts its therapeutic effects. Many studies have shown its excellent therapeutic potential against diabetes mellitus and related complications like diabetic neuropathy, retinopathy, nephropathy, hematological dysfunctions, reproductive dysfunctions, liver and pancreas related complications etc. Not only taurine, a number of its derivatives have also been reported to be important in ameliorating diabetic complications. The present review has been aimed to describe the importance of taurine and its derivatives against diabetic metabolic syndrome and related complications.

Protein malnutrition blunts the increment of taurine transporter expression by a high-fat diet and impairs taurine reestablishment of insulin secretion

Taurine (Tau) restores β-cell function in obesity; however, its action is lost in malnourished obese rodents. Here, we investigated the mechanisms involved in the lack of effects of Tau in this model. C57BL/6 mice were fed a control diet (CD) (14% protein) or a protein-restricted diet (RD) (6% protein) for 6 wk. Afterward, mice received a high-fat diet (HFD) for 8 wk [CD + HFD (CH) and RD + HFD (RH)] with or without 5% Tau supplementation after weaning on their drinking water [CH + Tau (CHT) and RH + Tau (RHT)]. The HFD increased insulin secretion through mitochondrial metabolism in CH and RH. Tau prevented all those alterations in CHT only. The expression of the taurine transporter (Tau-T), as well as Tau content in pancreatic islets, was increased in CH but had no effect on RH. Protein malnutrition programs β cells and impairs Tau-induced restoration of mitochondrial metabolism and biogenesis. This may be associated with modulation of the expression of Tau-T in pancreatic islets, which may be responsible for the absence of effect of Tau in protein-malnourished obese mice.-Branco, R. C. S., Camargo, R. L., Batista, T. M., Vettorazzi, J. F., Borck, P. C., dos Santos-Silva, J. C. R., Boschero, A. C., Zoppi, C. C., Carneiro, E. M. Protein malnutrition blunts the increment of taurine transporter expression by a high-fat diet and impairs taurine reestablishment of insulin secretion.

Taurine Treatment Modulates Circadian Rhythms in Mice Fed A High Fat Diet

Close ties have been made among certain nutrients, obesity, type 2 diabetes and circadian clocks. Among nutrients, taurine has been documented as being effective against obesity and type 2 diabetes. However, the impact of taurine on circadian clocks has not been elucidated. We investigated whether taurine can modulate or correct disturbances in daily rhythms caused by a high-fat diet in mice. Male C57BL/6 mice were divided in four groups: control (C), control + taurine (C+T), high-fat diet (HFD) and HFD + taurine (HFD+T). They were administered 2% taurine in their drinking water for 10 weeks. Mice were euthanized at 6:00, 12:00, 18:00, and 24:00. HFD mice increased body weight, visceral fat and food intake, as well as higher levels of glucose, insulin and leptin, throughout the 24 h. Taurine prevented increments in food intake, body weight and visceral fat, improved glucose tolerance and insulin sensitivity and reduced disturbances in the 24 h patterns of plasma insulin and leptin. HFD downregulated the expression of clock genes Rev-erbα, Bmal1, and Per1 in pancreatic islets. Taurine normalized the gene and protein expression of PER1 in beta-cells, which suggests that it could be beneficial for the correction of daily rhythms and the amelioration of obesity and diabetes.

Lacking of estradiol reduces insulin exocytosis from pancreatic β-cells and increases hepatic insulin degradation

Low levels of plasma estrogens are associated with weight-gain, android fat distribution, and a high prevalence of obesity-related comorbidities such as glucose intolerance and type II diabetes. The mechanisms underlying the association between low levels of estrogens and impaired glucose homeostasis are not completely understood. To begin to test this, we used three-month-old female C57BL/6J mice that either underwent ovariectomy (OVX) or received a sham surgery (Sham), and we characterized glucose homeostasis. In a subsequent series of experiments, OVX mice received estradiol treatment (OVX+E₂) or vehicle (OVX) for 6 consecutive days. As has been previously reported, lack of ovarian hormones resulted in dysregulated glucose homeostasis. To begin to explore the mechanisms by which this occurs, we characterized the impact of estrogens on insulin secretion and degradation in these mice. Insulin secretion and plasma insulin levels were lower in OVX mice. OVX mice had lower levels of pancreatic Syntaxin 1-A (Synt-1A) protein, which is involved in insulin extrusion from the pancreas. In the liver, OVX mice had higher levels of insulin-degrading enzyme (IDE) and this was associated with higher insulin clearance. Estradiol treatment improved glucose intolerance in OVX mice and restored insulin secretion, as well as normalized the protein content of pancreatic Synt-1A. The addition of estrogens to OVX mice reduced IDE protein to that of Sham mice. Our data suggest loss of ovarian estradiol following OVX led to impaired glucose homeostasis due to pancreatic β-cell dysfunction in the exocytosis of insulin, and upregulation of hepatic IDE protein content resulting in lower insulinemia, which was normalized by estradiol replacement.

Plasma Taurine, Diabetes Genetic Predisposition, and Changes of Insulin Sensitivity in Response to Weight-Loss Diets

CONTEXT

Taurine metabolism disturbance is closely linked to obesity, insulin resistance, and diabetes. Previous evidence suggested that the preventative effects of taurine on diabetes might be through regulating the expression levels of diabetes-related genes.

OBJECTIVE

We estimated whether blood taurine levels modified the overall genetic susceptibility to diabetes on improvement of insulin sensitivity in a randomized dietary trial.

DESIGN AND SETTING

We genotyped 31 diabetes-associated variants to calculate a genetic risk score (GRS) and measured plasma taurine levels and glycemic traits among participants from the Preventing Overweight Using Novel Dietary Strategies (POUNDS Lost) trial.

PARTICIPANTS

Seven-hundred eleven overweight or obese participants (age 30-70 y; 60% females) had genetic variants genotyped and blood taurine levels measured.

INTERVENTION

Participants went on 2-year weight-loss diets, which were different in macronutrient composition.

MAIN OUTCOME MEASURE

Improvements in glycemic traits were measured.

RESULTS

We found that baseline taurine levels significantly modified the effects of diabetes GRS on changes in fasting glucose, insulin, and homeostatic model assessment of insulin resistance (HOMA-IR) during the 2-year diet intervention (P-interaction = .04, .01, .002, respectively), regardless of weight loss. High baseline taurine levels were associated with a less reduction in both glucose and HOMA-IR among the participants with the lowest tertile of diabetes GRS (both P = .02), and with a greater reduction in both insulin and HOMA-IR among those with the highest tertile of diabetes GRS (both P = .04).

CONCLUSIONS

Our data suggest that blood taurine levels might differentially modulate the effects of diabetes-related genes on improvement of insulin sensitivity among overweight/obese patients on weight-loss diets.

Acute exercise restores insulin clearance in diet-induced obese mice

The aim of this study was to investigate the insulin clearance in diet-induced obese (DIO) mice submitted to acute endurance exercise (3h of treadmill exercise at 60-70% VO2max). Glucose-stimulated insulin secretion in isolated islets; ipGTT; ipITT; ipPTT; in vivo insulin clearance; protein expression in liver, skeletal muscle, and adipose tissue (insulin degrading enzyme (IDE), insulin receptor subunitβ(IRβ), phospho-Akt (p-Akt) and phospho-AMPK (p-AMPK)), and the activity of IDE in the liver and skeletal muscle were accessed. In DIO mice, acute exercise reduced fasting glycemia and insulinemia, improved glucose and insulin tolerance, reduced hepatic glucose production, and increased p-Akt protein levels in liver and skeletal muscle and p-AMPK protein levels in skeletal muscle. In addition, insulin secretion was reduced, whereas insulin clearance and the expression of IDE and IRβ were increased in liver and skeletal muscle. Finally, IDE activity was increased only in skeletal muscle. In conclusion, we propose that the increased insulin clearance and IDE expression and activity, primarily, in skeletal muscle, constitute an additional mechanism, whereby physical exercise reduces insulinemia in DIO mice.

New insights into the architecture of the islet of Langerhans: a focused cross-species assessment

The human genome project and its search for factors underlying human diseases has fostered a major human research effort. Therefore, unsurprisingly, in recent years we have observed an increasing number of studies on human islet cells, including disease approaches focusing on type 1 and type 2 diabetes. Yet, the field of islet and diabetes research relies on the legacy of rodent-based investigations, which have proven difficult to translate to humans, particularly in type 1 diabetes. Whole islet physiology and pathology may differ between rodents and humans, and thus a comprehensive cross-species as well as species-specific view on islet research is much needed. In this review we summarise the current knowledge of interspecies islet cytoarchitecture, and discuss its potential impact on islet function and future perspectives in islet pathophysiology research.

Impact of taurine depletion on glucose control and insulin secretion in mice

Taurine, an endogenous sulfur-containing amino acid, is found in millimolar concentrations in mammalian tissue, and its tissue content is altered by diet, disease and aging. The effectiveness of taurine administration against obesity and its related diseases, including type 2 diabetes, has been well documented. However, the impact of taurine depletion on glucose metabolism and fat deposition has not been elucidated. In this study, we investigated the effect of taurine depletion (in the taurine transporter (TauT) knockout mouse model) on blood glucose control and high fat diet-induced obesity. TauT-knockout (TauTKO) mice exhibited lower body weight and abdominal fat mass when maintained on normal chow than wild-type (WT) mice. Blood glucose disposal after an intraperitoneal glucose injection was faster in TauTKO mice than in WT mice despite lower serum insulin levels. Islet beta-cells (insulin positive area) were also decreased in TauTKO mice compared to WT mice. Meanwhile, overnutrition by high fat (60% fat)-diet could lead to obesity in TauTKO mice despite lower body weight under normal chow diet condition, indicating nutrition in normal diet is not enough for TauTKO mice to maintain body weight comparable to WT mice. In conclusion, taurine depletion causes enhanced glucose disposal despite lowering insulin levels and lower body weight, implying deterioration in tissue energy metabolism.

Taurine supplementation ameliorates glucose homeostasis, prevents insulin and glucagon hypersecretion, and controls β, α, and δ-cell masses in genetic obese mice

Taurine (Tau) regulates β-cell function and glucose homeostasis under normal and diabetic conditions. Here, we assessed the effects of Tau supplementation upon glucose homeostasis and the morphophysiology of endocrine pancreas, in leptin-deficient obese (ob) mice. From weaning until 90-day-old, C57Bl/6 and ob mice received, or not, 5% Tau in drinking water (C, CT, ob and obT). Obese mice were hyperglycemic, glucose intolerant, insulin resistant, and exhibited higher hepatic glucose output. Tau supplementation did not prevent obesity, but ameliorated glucose homeostasis in obT. Islets from ob mice presented a higher glucose-induced intracellular Ca(2+) influx, NAD(P)H production and insulin release. Furthermore, α-cells from ob islets displayed a higher oscillatory Ca(2+) profile at low glucose concentrations, in association with glucagon hypersecretion. In Tau-supplemented ob mice, insulin and glucagon secretion was attenuated, while Ca(2+) influx tended to be normalized in β-cells and Ca(2+) oscillations were increased in α-cells. Tau normalized the inhibitory action of somatostatin (SST) upon insulin release in the obT group. In these islets, expression of the glucagon, GLUT-2 and TRPM5 genes was also restored. Tau also enhanced MafA, Ngn3 and NeuroD mRNA levels in obT islets. Morphometric analysis demonstrated that the hypertrophy of ob islets tends to be normalized by Tau with reductions in islet and β-cell masses, but enhanced δ-cell mass in obT. Our results indicate that Tau improves glucose homeostasis, regulating β-, α-, and δ-cell morphophysiology in ob mice, indicating that Tau may be a potential therapeutic tool for the preservation of endocrine pancreatic function in obesity and diabetes.

Vagotomy ameliorates islet morphofunction and body metabolic homeostasis in MSG-obese rats

The parasympathetic nervous system is important for β-cell secretion and mass regulation. Here, we characterized involvement of the vagus nerve in pancreatic β-cell morphofunctional regulation and body nutrient homeostasis in 90-day-old monosodium glutamate (MSG)-obese rats. Male newborn Wistar rats received MSG (4 g/kg body weight) or saline [control (CTL) group] during the first 5 days of life. At 30 days of age, both groups of rats were submitted to sham-surgery (CTL and MSG groups) or subdiaphragmatic vagotomy (Cvag and Mvag groups). The 90-day-old MSG rats presented obesity, hyperinsulinemia, insulin resistance, and hypertriglyceridemia. Their pancreatic islets hypersecreted insulin in response to glucose but did not increase insulin release upon carbachol (Cch) stimulus, despite a higher intracellular Ca²⁺ mobilization. Furthermore, while the pancreas weight was 34% lower in MSG rats, no alteration in islet and β-cell mass was observed. However, in the MSG pancreas, increases of 51% and 55% were observed in the total islet and β-cell area/pancreas section, respectively. Also, the β-cell number per β-cell area was 19% higher in MSG rat pancreas than in CTL pancreas. Vagotomy prevented obesity, reducing 25% of body fat stores and ameliorated glucose homeostasis in Mvag rats. Mvag islets demonstrated partially reduced insulin secretion in response to 11.1 mM glucose and presented normalization of Cch-induced Ca²⁺ mobilization and insulin release. All morphometric parameters were similar among Mvag and CTL rat pancreases. Therefore, the higher insulin release in MSG rats was associated with greater β-cell/islet numbers and not due to hypertrophy. Vagotomy improved whole body nutrient homeostasis and endocrine pancreatic morphofunction in Mvag rats.

Taurine supplementation increases K(ATP) channel protein content, improving Ca2+ handling and insulin secretion in islets from malnourished mice fed on a high-fat diet

Pancreatic β-cells are highly sensitive to suboptimal or excess nutrients, as occurs in protein-malnutrition and obesity. Taurine (Tau) improves insulin secretion in response to nutrients and depolarizing agents. Here, we assessed the expression and function of Cav and KATP channels in islets from malnourished mice fed on a high-fat diet (HFD) and supplemented with Tau. Weaned mice received a normal (C) or a low-protein diet (R) for 6 weeks. Half of each group were fed a HFD for 8 weeks without (CH, RH) or with 5% Tau since weaning (CHT, RHT). Isolated islets from R mice showed lower insulin release with glucose and depolarizing stimuli. In CH islets, insulin secretion was increased and this was associated with enhanced KATP inhibition and Cav activity. RH islets secreted less insulin at high K(+) concentration and showed enhanced KATP activity. Tau supplementation normalized K(+)-induced secretion and enhanced glucose-induced Ca(2+) influx in RHT islets. R islets presented lower Ca(2+) influx in response to tolbutamide, and higher protein content and activity of the Kir6.2 subunit of the KATP. Tau increased the protein content of the α1.2 subunit of the Cav channels and the SNARE proteins SNAP-25 and Synt-1 in CHT islets, whereas in RHT, Kir6.2 and Synt-1 proteins were increased. In conclusion, impaired islet function in R islets is related to higher content and activity of the KATP channels. Tau treatment enhanced RHT islet secretory capacity by improving the protein expression and inhibition of the KATP channels and enhancing Synt-1 islet content.