The improvement effect of L-Lys as a chemical chaperone on STZ-induced diabetic rats, protein structure and function

Ginseng polysaccharide components attenuate obesity and liver lipid accumulation by regulating fecal microbiota and hepatic lysine degradation

The increasing incidence of obesity has led to widespread attention in the exploration of natural ingredients. Ginseng polysaccharides (PGP), the main components from Panax ginseng, have been reported potential effect to attenuate obesity and regulate lipid metabolism. In this study, we found that PGP inhibited the high-fat diet (HFD)-induced weight gain, fat ratio and fat tissue weight after 8-week administration. Serum and liver lipid analysis showed that PGP decreased the levels of triglyceride and total cholesterol, which was mediated by the inhibition of key genes for fatty acid and cholesterol metabolisms. Metabolomics studies showed that the inhibitory effect of PGP on liver lipid accumulation was significantly correlated with its regulation of citric acid cycle and lysine degradation. PGP regulated the expression of genes related to lysine degradation in both liver tissue and hepatocytes. In addition, PGP reshaped the composition of fecal microbiota at the genus and species levels in obese mice. Spearman's correlation analysis demonstrated that Staphylococcus sciuri, Staphylococcus lentus, and Pseudoflavonifractor sp. An85 may be the potential targets that PGP maintains the abundance of l-lysine against obesity. It concluded that PGP can attenuate obesity and liver lipid accumulation by regulating fecal microbiota and hepatic lysine degradation.

Co-administration of "L-Lysine, Vitamin C, and Zinc" increased the antioxidant activity, decreased insulin resistance, and improved lipid profile in streptozotocin-induced diabetic rats

PURPOSE

We previously showed the beneficial effect of L-Lysine (Lys), a chemical chaperone, on reducing diabetic complications in diabetic rats and type 2 diabetic patients. Herein, we evaluated the effect of Lys co-administration with Vitamin C and Zinc (Lys+VC+Zn), in diabetic rats.

METHODS

The streptozotocin (50 mg/Kg) was injected into male adult Wistar rats to induce diabetes. Then, different groups of normal and diabetic rats were treated with Lys and Lys+VC+Zn for five months. So, there were 0.1 % Lys in the drinking water of both groups. The control groups received water alone. During the experiment, the body weight, and various parameters were determined in the blood, serum/plasma, and urine of the rats.

RESULTS

The determination of biochemical indexes confirmed diabetes induction and its complications in rats. Treatment with either Lys or Lys+VC+Zn resulted in reduced blood glucose and protein glycation (decreasing AGEs and HbA1c), increased insulin secretion, alleviated insulin resistance and HOMA-IR, improved lipid profile and HDL functionality (LCAT and PON1), enhanced antioxidant status (FRAP and AOPP), improved kidney function (decreased microalbuminuria, serum urea, and creatinine), and increased chaperone capacity (HSP70). Lys+VC+Zn showed better effects on these parameters than Lys alone.

CONCLUSIONS

The results of this study indicated that co-administration of Lys, a chemical chaperone, with two antioxidants (VC and Zn) potentiates its antidiabetic effects and prevent diabetic complications in rat model of diabetes.

All-potassium channel CRISPR screening reveals a lysine-specific pathway of insulin secretion

OBJECTIVE

Genome-scale CRISPR-Cas9 knockout coupled with single-cell RNA sequencing (scRNA-seq) has been used to identify function-related genes. However, this method may knock out too many genes, leading to low efficiency in finding genes of interest. Insulin secretion is controlled by several electrophysiological events, including fluxes of KATP depolarization and K+ repolarization. It is well known that glucose stimulates insulin secretion from pancreatic β-cells, mainly via the KATP depolarization channel, but whether other nutrients directly regulate the repolarization K+ channel to promote insulin secretion is unknown.

METHODS

We used a system involving CRISPR-Cas9-mediated knockout of all 83 K+ channels and scRNA-seq in a pancreatic β cell line to identify genes associated with insulin secretion.

RESULTS

The expression levels of insulin genes were significantly increased after all-K+ channel knockout. Furthermore, Kcnb1 and Kcnh6 were the two most important repolarization K+ channels for the increase in high-glucose-dependent insulin secretion that occurred upon application of specific inhibitors of the channels. Kcnh6 currents, but not Kcnb1 currents, were reduced by one of the amino acids, lysine, in both transfected cells, primary cells and mice with β-cell-specific deletion of Kcnh6.

CONCLUSIONS

Our function-related CRISPR screen with scRNA-seq identifies Kcnh6 as a lysine-specific channel.

The Vicious Cycle of Type 2 Diabetes Mellitus and Skeletal Muscle Atrophy: Clinical, Biochemical, and Nutritional Bases

Today, type 2 diabetes mellitus (T2DM) and skeletal muscle atrophy (SMA) have become increasingly common occurrences. Whether the onset of T2DM increases the risk of SMA or vice versa has long been under investigation. Both conditions are associated with negative changes in skeletal muscle health, which can, in turn, lead to impaired physical function, a lowered quality of life, and an increased risk of mortality. Poor nutrition can exacerbate both T2DM and SMA. T2DM and SMA are linked by a vicious cycle of events that reinforce and worsen each other. Muscle insulin resistance appears to be the pathophysiological link between T2DM and SMA. To explore this association, our review (i) compiles evidence on the clinical association between T2DM and SMA, (ii) reviews mechanisms underlying biochemical changes in the muscles of people with or at risk of T2DM and SMA, and (iii) examines how nutritional therapy and increased physical activity as muscle-targeted treatments benefit this population. Based on the evidence, we conclude that effective treatment of patients with T2DM-SMA depends on the restoration and maintenance of muscle mass. We thus propose that regular intake of key functional nutrients, along with guidance for physical activity, can help maintain euglycemia and improve muscle status in all patients with T2DM and SMA.

Metabolomics (Non-Targeted) of Induced Type 2 Diabetic Sprague Dawley Rats Comorbid with a Tissue-Dwelling Nematode Parasite

Type 2 diabetes is a non-communicable metabolic syndrome that is characterized by the dysfunction of pancreatic β-cells and insulin resistance. Both animal and human studies have been conducted, demonstrating that helminth infections are associated with a decreased prevalence of type 2 diabetes mellitus (T2DM). However, there is a paucity of information on the impact that helminths have on the metabolome of the host and how the infection ameliorates T2DM or its progression. Therefore, this study aimed at using a non-targeted metabolomics approach to systematically identify differentiating metabolites from serum samples of T2DM-induced Sprague Dawley (SD) rats infected with a tissue-dwelling nematode, Trichinella zimbabwensis, and determine the metabolic pathways impacted during comorbidity. Forty-five male SD rats with a body weight between 160 g and 180 g were used, and these were randomly selected into control (non-diabetic and not infected with T. zimbabwensis) (n = 15) and T2DM rats infected with T. zimbabwensis (TzDM) (n = 30). The results showed metabolic separation between the two groups, where d-mannitol, d-fructose, and glucose were upregulated in the TzDM group, when compared to the control group. L-tyrosine, glycine, diglycerol, L-lysine, and L-hydroxyproline were downregulated in the TzDM group when compared to the control group. Metabolic pathways which were highly impacted in the TzDM group include biotin metabolism, carnitine synthesis, and lactose degradation. We conclude from our study that infecting T2DM rats with a tissue-dwelling nematode, T. zimbabwensis, causes a shift in the metabolome, causing changes in different metabolic pathways. Additionally, the infection showed the potential to regulate or improve diabetes complications by causing a decrease in the amino acid concentration that results in metabolic syndrome.

Identification of blood metabolic biomarkers associated with diabetic distal symmetric sensorimotor polyneuropathy in patients with type 2 diabetes mellitus

BACKGROUND

Distal symmetric sensorimotor polyneuropathy (DSPN) is a common neurologic complication of type 2 diabetes mellitus (T2DM), but the underlying mechanisms and changes in serum metabolites remain largely undefined. This study aimed to characterize the plasma metabolite profiles of participants with T2DM using targeted metabolomics analysis and identify potential biomarkers for DSPN.

METHODS

A combined liquid chromatography MS/MS and direct flow injection were used to quantify plasma metabolite obtained from 63 participants with T2DM, 81 with DSPN, and 33 nondiabetic control participants. A total of 130 metabolites, including amino acids, biogenic amines, sphingomyelins (SM), phosphatidylcholines, carnitines, and hexose, were analyzed.

RESULTS

A total of 16 plasma metabolites and 3 cholesterol-related laboratory parameters were found to have variable importance in the projection score >1.0 and false discovery rate <5.0% between control, T2DM, and DSPN. Among these variables, five serum metabolites, including phenylalanine (AUC = 0.653), alanine (AUC = 0.630), lysine (AUC = 0.622) tryptophan (AUC = 0.620), and SM C16:0 (AUC = 0.630), are potential biomarkers (all p < .05) in distinguishing T2DM with DSPN from those without (AUC = 0.720).

CONCLUSIONS

In this cross-sectional study, derangement of several metabolites in the plasma was observed in T2DM with and without DSPN, and these metabolites may be potential biomarkers for predicting DSPN. Longitudinal studies are warranted.

Arginine and Lysine Supplementation Potentiates the Beneficial β-Hydroxy ß-Methyl Butyrate (HMB) Effects on Skeletal Muscle in a Rat Model of Diabetes

Skeletal muscle is the key tissue for maintaining protein and glucose homeostasis, having a profound impact on the development of diabetes. Diabetes causes deleterious changes in terms of loss of muscle mass, which will contribute to reduced glucose uptake and therefore progression of the disease. Nutritional approaches in diabetes have been directed to increase muscle glucose uptake, and improving protein turnover has been at least partially an oversight. In muscle, β-hydroxy β-methyl butyrate (HMB) promotes net protein synthesis, while arginine and lysine increase glucose uptake, albeit their effects on promoting protein synthesis are limited. This study evaluates if the combination of HMB, lysine, and arginine could prevent the loss of muscle mass and function, reducing the progression of diabetes. Therefore, the combination of these ingredients was tested in vitro and in vivo. In muscle cell cultures, the supplementation enhances glucose uptake and net protein synthesis due to an increase in the amount of GLUT4 transporter and stimulation of the insulin-dependent signaling pathway involving IRS-1 and Akt. In vivo, using a rat model of diabetes, the supplementation increases lean body mass and insulin sensitivity and decreases blood glucose and serum glycosylated hemoglobin. In treated animals, an increase in GLUT4, creatine kinase, and Akt phosphorylation was detected, demonstrating the synergic effects of the three ingredients. Our findings showed that nutritional formulations based on the combination of HMB, lysine, and arginine are effective, not only to control blood glucose levels but also to prevent skeletal muscle atrophy associated with the progression of diabetes.

Lomatogonium rotatum extract alleviates diabetes mellitus induced by a high-fat, high-sugar diet and streptozotocin in rats

BACKGROUND

Lomatogonium rotatum (LR) is traditionally used in Mongolian folk medicine as a hypoglycemic agent, but its evidence-based pharmacological effects and me-chanisms of action have not been fully elucidated.

AIM

To emphasize the hypoglycemic action mechanism of LR in a type 2 diabetic rat model and examine potential biomarkers to obtain mechanistic understanding regarding serum metabolite modifications.

METHODS

A high-fat, high-sugar diet and streptozotocin injection-induced type 2 diabetic rat model was established. The chemical composition of the LR was identified by high performance liquid chromatography. LR extract administrated as oral gavage at 0.5 g/kg, 2.5 g/kg, and 5 g/kg for 4 wk. Anti-diabetic effects of LR extract were evaluated based on histopathological examination as well as the measurement of blood glucose, insulin, glucagon-like peptide 1 (GLP-1), and lipid levels. Serum metabolites were analyzed using an untargeted metabolomics approach.

RESULTS

According to a chemical analysis, swertiamarin, sweroside, hesperetin, coumarin, 1.7-dihydroxy-3,8-dimethoxyl xanthone, and 1-hydroxy-2,3,5 trimethoxanone are the principal active ingredients in LR. An anti-diabetic experiment revealed that the LR treatment significantly increased plasma insulin and GLP-1 levels while effectively lowering blood glucose, total cholesterol, triglycerides, low-density lipoprotein cholesterol, and oral glucose tolerance test compared to the model group. Furthermore, untargeted metabolomic analysis of serum samples detected 236 metabolites, among which 86 were differentially expressed between the model and the LR group. It was also found that LR considerably altered the levels of metabolites such as vitamin B6, mevalonate-5P, D-proline, L-lysine, and taurine, which are involved in the regulation of the vitamin B6 metabolic pathway, selenium amino acid metabolic pathway, pyrimidine metabolic pathway, and arginine and proline metabolic pathways.

CONCLUSION

These findings indicated that LR may have a hypoglycemic impact and that its role may be related to changes in the serum metabolites and to facilitate the release of insulin and GLP-1, which lower blood glucose and lipid profiles.

L-Lysine Ameliorates Diabetic Nephropathy in Rats with Streptozotocin-Induced Diabetes Mellitus

Introduction

Diabetic nephropathy is one of the leading causes of end-stage renal disease worldwide. Uncontrolled hyperglycemia and subsequent production of glycation end-products activate the paths which lead to diabetic nephropathy. The aim of this study was to assess the effects of L-lysine on antioxidant capacity, biochemical factors, kidney function, HSP70 level, and the expression of the TGFβ, VEGF, and RAGE genes in rats with streptozocin-induced diabetes mellitus.

Methods

Thirty-two male Wistar rats were randomly allocated to four eight-rat groups, namely, a healthy group, a diabetic group treated with vehicle (DM + vehicle), a diabetic group treated with L-lysine (DM + Lys), and a healthy group treated with L-lysine (healthy + Lys). Rats in the DM + Lys and the healthy + Lys groups were treated with L-lysine 0.15%. The levels of fasting blood glucose, insulin, HbA_1C, advanced glycation end-products (AGEs), lipid profile, serum creatinine, blood urea nitrogen, glomerular filtration rate, urine microalbumin, oxidative stress parameters, kidney histology and morphology, and TGFβ, VEGF, and RAGE gene expressions were assessed. Findings. An eight-week treatment with L-lysine significantly reduced the levels of fasting blood glucose, AGEs, kidney function parameters, oxidative stress parameters, lipid profile, and the TGFβ, VEGF, and RAGE gene expression and significantly increased the levels of serum insulin and tissue HSP70.

Conclusion

Treatment with L-lysine seems to slow down the progression of diabetic nephropathy.

The Combination Effect of Voluntary Exercise and Crocin on Angiogenic miRNAs in High-Fat Diet/Low-Dose STZ-Induced Type2 Diabetes in Rats: miR-126 and miR-210

Background: As one of the major complications of diabetes, cardiovascular disease might result in early death in people with diabetes. miR-126 and 210 expressions undergo alterations in cardiac disease and cause heart failure. Methods: Animals were divided into the 5 groups of control (Con), diabetes (Dia), diabeticcrocin (Dia-Cro), diabetic-voluntary exercise (Dia-Exe), and diabetic-crocin-voluntary exercise (Dia-Cro-Exe). Type 2 diabetes was induced by the use of a high-fat diet (4 weeks) and injection of streptozotocin (STZ) (i.p, 35 mg/kg). Animals received crocin orally (50 mg/kg), and voluntary exercise was performed alone or together for 8 weeks. QRT–PCR method was used to determine the levels of miR-210 and miR-126 in cardiac tissue. Results: The levels of miR-210 and miR-126 in the cardiac tissue augmented in both the crocin and voluntary exercise groups in comparison with the non-treated group (p<0.001). The use of combination therapy with exercise and crocin magnified their effects on miR-210 and miR-126 levels (p<0.001). Moreover, MiR-210 levels were lower in the crocin group compared to the exercise group (p<0.001). Conclusion: The results indicated that voluntary exercise combined with crocin might provide a novel therapeutic plan for cardiovascular disease through increasing miR-210 and miR-126 expression.

Fungal Enzyme l-Lysine α-Oxidase Affects the Amino Acid Metabolism in the Brain and Decreases the Polyamine Level

The fungal glycoprotein l-lysine α-oxidase (LO) catalyzes the oxidative deamination of l-lysine (l-lys). LO may be internalized in the intestine and shows antitumor, antibacterial, and antiviral effects in vivo. The main mechanisms of its effects have been shown to be depletion of the essential amino acid l-lys and action of reactive oxidative species produced by the reaction. Here, we report that LO penetrates into the brain and is retained there for up to 48 h after intravenous injection, which might be explained by specific pharmacokinetics. LO actively intervenes in amino acid metabolism in the brain. The most significant impact of LO was towards amino acids, which are directly exposed to its action (l-lys, l-orn, l-arg). In addition, the enzyme significantly affected the redistribution of amino acids directly associated with the tricarboxylic acid (TCA) cycle (l-asp and l-glu). We discovered that the depletion of l-orn, the precursor of polyamines (PA), led to a significant and long-term decrease in the concentration of polyamines, which are responsible for regulation of many processes including cell proliferation. Thus, LO may be used to reduce levels of l-lys and PA in the brain.

Effects of the Lysulin™ supplementation on pre-diabetes: A randomized double-blind, placebo-controlled clinical trial

BACKGROUND AND AIMS

Diabetes is a leading cause of morbidity and mortality worldwide. Recent studies have demonstrated that nutraceutical products have beneficial effects in diabetes. Present study aims to investigate whether a product (Lysulin™) containing amino acid lysine, micronutrient zinc and vitamin C will have beneficial effects in pre-diabetes.

METHODS

A randomized, double-blind, placebo-controlled trial was conducted for a period of 6 months. The two parallel groups (1:1) were Lysulin™ (Interventional group-IG) and placebo (control group-CG). Evaluations were done at baseline, 1, 3 and 6 months. Primary outcome was defined as change in glycaemic control measured by HbA1c from baseline. Other outcomes included change in; fasting plasma glucose (FPG), 2-h OGTT plasma glucose and lipid profile from baseline. Three multiple regression analyses were performed, where change in FPG, 2-h OGTT, and HbA1c post intervention from baseline respectively were the continuous dependent variable with other independent variables.

RESULTS

One hundred and ten participants were recruited, 50% (n = 55) were males and mean age (±SD) was 46.7 ± 9.9 years. A significantly higher percentage of participants in CG (25.4%, n = 14) developed diabetes in comparison to IG (7.3%, n = 4) (p = 0.018). FPG, 2-h OGTT and HbA1c significantly reduced in the IG only. Both total cholesterol and LDL cholesterol decreased significantly from baseline only in the IG. In all three regression models the best predictor of respective dependent variable was Lysulin™ treatment.

CONCLUSIONS

Lysulin™ improved glycaemic control, with reduced progression to diabetes, in those with pre-diabetes. Treatment also showed a beneficial reduction in total and LDL cholesterol levels.

TRIAL REGISTRATION

Sri Lanka Clinical Trials Registry, identifier: SLCTR/2018/022 (http://slctr.lk/trials/1290). Registered on 13th July 2018; Study protocol version 2.0 (23rd March 2018).

The effect of cold atmospheric plasma on diabetes-induced enzyme glycation, oxidative stress, and inflammation; in vitro and in vivo

Cold atmospheric plasma (CAP) is known as the versatile tool in different biological, and medical applications. In this study, we investigated the effect of cold plasma on diabetes via in vitro and in vivo assessments. We performed the in vitro assay to evaluate the impact of CAP on glycated glutathione peroxidase (GPx) through enzyme activity measurement as a function index and far- and near-UV circular dichroism (CD) and fluorescence analysis as structure indices. The result of in vitro assessment showed that the exposure of glycated GPx to plasma causes a considerable increase in enzyme activity up to 30%. Also, the evaluation of far- and near-UV CD and fluorescence analysis indicated a modification in the protein structure. According to obtained result from in vitro assessment, in vivo assay evaluated the effect of CAP on diabetic mice through analyzing of blood glucose level (BGL), advanced glycation end products (AGEs), antioxidant activity, oxidative stress biomarkers such as malondialdehyde (MDA), advanced oxidation protein products (AOPP), and oxidized low-density lipoprotein (oxLDL), and inflammation factors including tumor necrosis factor (TNF-α), interleukin-1 (IL-1), and interleukin-6 (IL-6). The result of in vivo experiment also showed a 20% increase in antioxidant activity. Also, the reduction in AGEs, oxidative stress biomarkers, and inflammatory cytokines concentrations was observed. The result of this study revealed that CAP could be useful in diabetes treatment and can be utilized as a complementary method for diabetes therapy.

L-lysine protects C2C12 myotubes and 3T3-L1 adipocytes against high glucose damages and stresses

Hyperglycemia is a hallmark of diabetes, which is associated with protein glycation and misfolding, impaired cell metabolism and altered signaling pathways result in endoplasmic reticulum stress (ERS). We previously showed that L-lysine (Lys) inhibits the nonenzymatic glycation of proteins, and protects diabetic rats and type 2 diabetic patients against diabetic complications. Here, we studied some molecular aspects of the Lys protective role in high glucose (HG)-induced toxicity in C2C12 myotubes and 3T3-L1 adipocytes. C2C12 and 3T3-L1 cell lines were differentiated into myotubes and adipocytes, respectively. Then, they were incubated with normal or high glucose (HG) concentrations in the absence/presence of Lys (1 mM). To investigate the role of HG and/or Lys on cell apoptosis, oxidative status, unfolded protein response (UPR) and autophagy, we used the MTT assay and flow cytometry, spectrophotometry and fluorometry, RT-PCR and Western blotting, respectively. In both cell lines, HG significantly reduced cell viability and induced apoptosis, accompanying with the significant increase in reactive oxygen species (ROS) and nitric oxide (NO). Furthermore, the spliced form of X-box binding protein 1 (XBP1), at both mRNA and protein levels, the phosphorylated eukaryotic translation initiation factor 2α (p-eIf2α), and the Light chain 3 (LC3)II/LC3I ratio was also significantly increased. Lys alone had no significant effects on most of these parameters; but, treatment with HG plus Lys returned them all to, or close to, the normal values. The results indicated the protective role of Lys against glucotoxicity induced by HG in C2C12 myotubes and 3T3-L1 adipocytes.

Prevention of α-crystallin glycation and aggregation using l-lysine results in the inhibition of in vitro catalase heat-induced-aggregation and suppression of cataract formation in the diabetic rat

The principle role of α-crystallin is chaperoning activity that protect s other proteins against different stresses. High glucose concentration induces the osmotic stress and results in biomacromolecules glycation, which is subsequently cause their conformational and functional changes. Here, the roles of l-lysine (Lys) on the prevention of α-crystallin glycation in both in vitro and in vivo conditions are investigated. The catalase (CAT) activity was considered as a marker of α-crystallin functionality in both conditions. Streptozotocin-induced diabetic rats were treated with 0.1% of the Lys in drinking water. The purified α-crystallin was also incubated with glucose, in the presence or absence of the Lys and its structure-function was compared. The results showed that the visual cataract score was significantly lower in the diabetic rats treated with Lys. After Lys treatment, CAT, superoxide dismutase, aldose reductase and other biochemical parameters in the lens and serum of the diabetic rats returned to the normal value. Formation of the advanced glycation endproducts (AGEs), protein cross-linking, and the hydrophobicity of α-crystallin were changed due to glycation, but they were reversed by Lys treatment. The glycated α-crystallin lost its chaperone activity against heat denatured-CAT, but in the presence of Lys, it preserved its activity and prevented CAT aggregation. In conclusion, Lys treatment significantly inhibited the progression of diabetic cataract in rats. These effects were due to the Lys antiglycating and antioxidant effects, in addition to its protective effect against α-crystallin chaperoning activity.

Effects of Lysulin™ supplementation on pre-diabetes: study protocol for a randomized controlled trial

BACKGROUND

Diabetes mellitus is rapidly becoming one of the leading causes of morbidity and mortality worldwide. Preventive measures have become important, especially in the South Asian region and other parts of the world where diabetes is becoming increasingly prevalent. We postulate that a product containing amino acid lysine, micronutrient zinc and vitamin C will have beneficial effects on glycemic control and disease progression in patients with pre-diabetes and we aim to evaluate this hypothesis using a phase II/III randomized double-blind controlled clinical trial design.

METHODS/DESIGN

The study will be conducted as a randomized, double-blind, placebo-controlled clinical trial for a period of 6 months. The study has been approved by the Ethics Review Committee of Faculty of Medicine, University of Colombo, Sri Lanka. A total of 110 adults with pre-diabetes will be recruited for the study. They will be randomly assigned to the test and placebo groups on a 1:1 ratio. The test group will receive two tablets of Lysulin™ three times a day and the control group will receive identical placebo tablets. The study drugs will be double blinded to both investigators and subjects. The visits and the evaluations will be done as follows: screening (visit 0), 1 month (visit 1), 3 months (visit 2) and 6 months (visit 4). The primary outcome will be defined as change in glycemic control measured by HbA1c from baseline. Data will be analyzed using SPSS v16.

DISCUSSION

To our knowledge this is one of the first randomized controlled trials evaluating the effects of Lysulin™ (a combination of lysine, vitamin C and zinc) in pre-diabetes. This study will provide the necessary groundwork for future large-scale multicentered clinical trials. The result, positive or negative, should provide a step change in the evidence guiding current and future policies regarding management of pre-diabetes.

TRIAL REGISTRATION

Sri Lanka Clinical Trials Registry, SLCTR/2018/022 . Registered on 13 July 2018. Study protocol version 2.0 (23 March 2018).

Dietary supplementation with L-lysine affects body weight and blood hematological and biochemical parameters in rats

L-Lysine (Lys) is a popular additive in foods, but the physiological effects of excess Lys supplementation are poorly understood and upper limits of safe intake have not been established. The objectives of this study were to examine the effects of dietary supplementation with increasing amounts of Lys on body weight (BW), food intake, and various blood hematological and biochemical parameters in rats. Male Sprague-Dawley rats at 10 weeks of age were assigned to ten diet groups (eight rats/group) and fed diets containing either 7% or 20% casein and supplemented with either 0% (Control), 1.5%, 3%, 6% Lys, or 6% Lys + 3% arginine for 1 week. Rats fed 7% casein with ≥ 1.5% Lys supplementation had lower serum albumin and leptin and higher LDL cholesterol (LDLC), ratios of total cholesterol (TC):HDL cholesterol (HDLC) and LDLC:HDLC than those fed 7% casein Control diet (P < 0.05). Rats fed 7% casein diet supplemented with 3% Lys diet had lower BW gain, food intake, serum alkaline phosphatase activity, and increased mean corpuscular hemoglobin concentration, blood urea nitrogen and serum pancreatic polypeptide compared to rats fed the Control diet (P < 0.05). Addition of 6% Lys in 7% casein caused significant BW loss (P < 0.001) and altered additional parameters. Addition of 6% Lys in a 20% casein diet reduced BW gain and food intake and altered numerous parameters. Arg supplementation normalized many of the endpoints changed by Lys. Collectively, these results show that Lys supplementation affects BW, food intake and a number of hematological and biochemical parameters. These effects of Lys supplementation were confined primarily in diets with lower levels of dietary protein. In the context of a low protein diet (7% casein), levels of Lys supplementation ≥ 1.5% may exert adverse health effects in rats.

Heat Shock Proteins as a Potential Therapeutic Target in the Treatment of Gestational Diabetes Mellitus: What We Know so Far

Gestational diabetes mellitus (GDM) is a complex condition that involves a variety of pathological mechanisms, including pancreatic β-cell failure, insulin resistance, and inflammation. There is an increasing body of literature suggesting that these interrelated phenomena may arise from the common mechanism of endoplasmic reticulum (ER) stress. Both obesity-associated nutrient excess and hyperglycemia disturb ER function in protein folding and transport. This results in the accumulation of polypeptides in the ER lumen and impairs insulin secretion and signaling. Exercise elicits metabolic adaptive responses, which may help to restore normal chaperone expression in insulin-resistant tissues. Pharmacological induction of chaperones, mimicking the metabolic effect of exercise, is a promising therapeutic tool for preventing GDM by maintaining the body's natural stress response. Metformin, a commonly used diabetes medication, has recently been identified as a modulator of ER-stress-associated inflammation. The results of recent studies suggest the potential use of chemical ER chaperones and antioxidant vitamins as therapeutic interventions that can prevent glucose-induced ER stress in GDM placentas. In this review, we discuss whether chaperones may significantly contribute to the pathogenesis of GDM, as well as whether they can be a potential therapeutic target in GDM treatment.

Effect of Low-Level Laser Irradiation on the Function of Glycated Catalase

Introduction: The aim of this work is to evaluate the effect of low-level laser irradiation (LLLI), by lasers with different wavelengths, on glycated catalase enzyme in vitro experimentally. Methods: This is done by measuring the activity and structure properties of glycated catalase enzyme. The structure properties were evaluated with circular dichroism (CD) and fluoroscopy methods. Three continuous wave (CW) lasers in the visible spectrum (λ =450, 530, 638 nm) and a 100-ns pulsed laser in the infrared spectrum (λ =905 nm) were chosen for comparison. For the infrared laser, same effects have been investigated for different energy doses. The effect of photon energy (hυ) at different wavelengths was measured on activity, CD, and fluoroscopy properties of catalase, and compared with the control group (samples without irradiation). The energy intensity of laser should not exceed 0.1 J/cm² . Experiments were performed on glycated catalase between 2 to 16 weeks after glycation of catalase. The LLLI effect was also investigated on the samples, by comparing the catalase activity, CD and fluoroscopy for different wavelengths. Results: Our results indicated, the decrease in catalase activity as a function of glycation time (weeks) for all samples, and a slight increase on its activity by different laser wavelengths irradiation for any fixed period of glycation time. Finally, the catalase activity has been increased as the laser's photon energy (hυ) intensified. More specifically, the blue laser (λ =450 nm) had the most and the red laser (λ =638 nm) had the least effect, and the green laser (λ =530 nm) had the medium effect on catalase activity as well. Furthermore, pulsed laser had an additional effect by increasing energy dosage. Conclusion: As we expected in all experiments, an increase in the catalase activity was coincident with a decrease in the catalase fluoroscopy and CD parameters.

Heat Shock Proteins and Diabetes

Diabetes is a chronic disease, and its prevalence continues to rise and can increase the risk for the progression of microvascular (such as nephropathy, retinopathy and neuropathy) and also macrovascular complications. Diabetes is a condition in which the oxidative stress and inflammation rise. Heat shock proteins (HSPs) are a highly conserved family of proteins that are expressed by all cells exposed to environmental stress, and they have diverse functions. In patients with diabetes, the expression and levels of HSPs decrease, but these chaperones can aid in improving some complications of diabetes, such as oxidative stress and inflammation. (The suppression of some HSPs is associated with a generalized increase in tissue inflammation.) In this review, we summarize the current understanding of HSPs in diabetes as well as their complications, and we also highlight their potential role as therapeutic targets in diabetes.

Inhibitory Effect of Crocin(s) on Lens α-Crystallin Glycation and Aggregation, Results in the Decrease of the Risk of Diabetic Cataract

The current study investigates the inhibitory effect of crocin(s), also known as saffron apocarotenoids, on protein glycation and aggregation in diabetic rats, and α-crystallin glycation. Thus, crocin(s) were administered by intraperitoneal injection to normal and streptozotocin-induced diabetic rats. The cataract progression was recorded regularly every two weeks and was classified into four stages. After eight weeks, the animals were sacrificed and the parameters involved in the cataract formation were measured in the animal lenses. Some parameters were also determined in the serum and blood of the rats. In addition, the effect of crocin(s) on the structure and chaperone activity of α-crystallin in the presence of glucose was studied by different methods. Crocin(s) lowered serum glucose levels of diabetic rats and effectively maintained plasma total antioxidants, glutathione levels and catalase activity in the lens of the animals. In the in vitro study, crocin(s) inhibited α-crystallin glycation and aggregation. Advanced glycation end products fluorescence, hydrophobicity and protein cross-links were also decreased in the presence of crocin(s). In addition, the decreased chaperone activity of α-crystallin in the presence of glucose changed and became close to the native value by the addition of crocin(s) in the medium. Crocin(s) thus showed a powerful inhibitory effect on α-crystallin glycation and preserved the structure-function of this protein. Crocin(s) also showed the beneficial effects on prevention of diabetic cataract.

Carbonyl scavenging and chemical chaperon like function of essential amino acids attenuates non-enzymatic glycation of albumin

Essential amino acids showed potent antiglycation activity by preventing formation of both early and advanced glycation end products (AGEs).

Role of crystallins in diabetic complications

BACKGROUND

Crystallins are the major structural proteins of vertebrate eye lens responsible for maintaining the refractive index of the lens. However, recent studies suggest that they also have a functional significance in non-lenticular tissues. Prolonged uncontrolled diabetes results in the development of macro and microvascular complications that are the leading causes of morbidity and mortality in diabetic patients all over the world.

SCOPE OF REVIEW

Recent studies have shown that crystallins play an instrumental role in diabetes and its complications. Therefore, this review highlights the current data on the impact of chronic hyperglycemia on expression, distribution, glycation, phosphorylation, chaperone-like function and, anti-apoptotic activity of crystallins. Furthermore, we discussed the insights for developing therapeutic strategies for diabetic complications including natural agents, peptides, and pharmacological chaperones that modulate or mimic chaperone activity of α-crystallins.

MAJOR CONCLUSIONS

Upregulation of crystallins appears to be a common feature of chronic diabetes. Further, chronic hyperglycemia induces the glycation and phosphorylation of crystallins, mainly α-crystallins and thereby alters their properties. The disturbed interaction of αB-crystallin with various apoptotic mediators including Bax and caspases is also an important factor for increased cell death in diabetes. Numerous dietary agents, peptides, and chemical chaperones prevent apoptosis and the loss of chaperone activity in diabetes.

GENERAL SIGNIFICANCE

Understanding the role of crystallins will aid in developing therapeutic strategies for alleviating pathophysiological conditions such as protein aggregation, inflammation, oxidative stress and apoptosis associated with chronic complications of diabetes including cataract, retinopathy, and cardiomyopathy. This article is part of a Special Issue entitled Crystallin Biochemistry in Health and Disease.

Biochemical Studies on Methylglyoxal-Mediated Glycated Histones: Implications for Presence of Serum Antibodies against the Glycated Histones in Patients with Type 1 Diabetes Mellitus

Reactive carbonyl species (RCS) mainly reacts with lysine and arginine residues of proteins to form advanced glycation end products (AGEs). Histone was glycoxidated with glyoxal and methylglyoxal. It was characterized by polyacrylamide gel electrophoresis and quenching studies involving penicillamine and aminoguanidine as carbonyl scavengers. Further characterization of histone modified with methylglyoxal was done by UV, fluorescence, and IR spectrophotometry. Spectral analysis of the protein clearly demonstrates structural perturbation in the histone by methylglyoxal. Methylglyoxal-induces cross-linking in the protein leading to aggregation. Role of methylglyoxal mediated glycoxidation of histone in type 1 diabetes was also undertaken. Antibodies were detected against glycoxidated histone in sera of type 1 diabetes patients by solid-phase enzyme immunoassay. The findings indicate that as a result of structural perturbation in histone by methylglyoxal, the modified histone may be involved in production of serum antibodies in the diabetes patients.

Anticancer effects of crocetin in both human adenocarcinoma gastric cancer cells and rat model of gastric cancer

This study investigated the therapeutic effect of crocetin, a carotenoid derived from saffron, on gastric adenocarcinoma (AGS) cells and 1-methyl-3-nitro-1-nitrosoguanidine (MNNG)-induced gastric cancer in rats. An MTT assay showed a significant dose- and time-dependent inhibition of AGS cell proliferation as a result of crocetin administration. Flow cytometry and caspases activity assays revealed apoptosis had been induced in these cells; RT-PCR and Western blot analyses revealed the suppression of Bcl-2 and up-regulation of Bax expression in AGS cells treated with crocetin. These changes were not observed in normal human fibroblast (HFSF-PI3) cells. Pathological study of the tumor tissue in MNNG-induced gastric cancer in rats indicated the dose-dependent inhibition of tumor progression. In addition, crocetin reversed some changed biochemical parameters, including serum antioxidant activity and lactate dehydrogenase in rat serum. The present study demonstrates the antioxidant, anti-proliferative, and apoptotic activities of crocetin against gastric cancer that may benefit human stomach cancer treatment.

Effect of crocin on the insulin resistance and lipid profile of streptozotocin-induced diabetic rats

Crocin is the only water soluble carotenoid in nature, and it has a known powerful antioxidant activity. The aim of this work was to investigate the hypoglycemic and hypolipidemic effects of crocin in streptozotocin (STZ)-induced type 2 diabetic rats. Neonatal male Wistar rats (2-5 days old) were randomly divided into five groups. Three groups were intraperitoneally injected with STZ (90 mg/kg body weight). Among them, two groups were treated with intraperitoneal injection of crocin (50 or 100 mg/kg), and the third group was treated with vehicle only. Two control groups were also considered, and one of them was treated with crocin. After 5 months, their blood and urine samples were collected, and the animals were sacrified. The results indicate a significant lower body weight (P < 0.001) and abnormal parameters in the diabetic rats compared with the normal group. An administration of both doses of crocin significantly decreased the levels of serum glucose, advanced glycation end products, triglyceride, total cholesterol, and low-density lipoprotein and increased the high-density lipoprotein in the diabetic rats. The treatments were also effective in decreasing HbA1c and microalbuminuria, as well as homeostatic model assessment for insulin resistance as a measure of insulin resistance in the diabetic rats.

Investigation of the mechanism(s) involved in decreasing increased fibrinogen activity in hyperglycemic conditions using L-lysine supplementation

INTRODUCTION

Fibrinogen is a plasma glycoprotein that participates in the hemostasis system. Its malfunction has been reported as a consequence of diabetic complications. In this study, the inhibitory effect of L-Lysine (Lys) on the nonenzymatic glycation of fibrinogen was investigated in both in vitro and in vivo conditions.

MATERIALS AND METHODS

Fibrinogen was incubated with glucose in the presence or absence of Lys. Then, its structure was studied by fluorescence spectroscopy, circular dichroism, and electrophoresis. The Clauss method was used to determine fibrinogen activity. In addition, one of the two groups of type 2 diabetic patients receiving ordinary treatment was additionally treated with Lys for 3 months. Fibrinogen activity and some other parameters were evaluated in their plasma.

RESULTS

The results indicated increases in the activity of glycated fibrinogen in both of the in vivo and in vitro experiments. Advanced glycation end products were increased by time, as shown using fluorometry in both the plasma of the diabetic patients and the incubation medium of protein with glucose. The circular dichroism spectra showed some changes in the fibrinogen secondary and tertiary structures after glycation. The electrophoretic mobility of the glycated fibrinogen changed and the cross-link formation between the fibrinogen subunits due to glycation was observed. Lys inhibited all of the mentioned fibrinogen changes both in the in vitro experiments and after its administration to the diabetic patients.

CONCLUSION

Lys, as an inhibitor of protein glycation, improved fibrinogen's structure and function, both in vitro and in vivo.

Effect of chemical chaperones on glucose-induced lysozyme modifications

Nonenzymatic glycation of biomacromolecules occurs due to the diabetes mellitus and ageing. A number of small molecules, known as chemical chaperones, stabilize protein conformation against thermal and chemically induced denaturation. These compounds are including: polyamines (e.g. spermine and spermidine), amino acids (e.g. lysine) and polyols (e.g. glycerol). In this study the effect of spermidine (Spd), spermine (Spm), and glycerol on glycation, structure and function of lysozyme (LZ), as an extra-cellular protein, by different techniques is investigated. LZ is incubated with or without glucose (50 or 100 mM) in the absence or presence of Spd/Spm/glycerol at 37 °C up to 16 weeks. All the observed changes of glycated-LZ in comparison with the native protein, including: increased fluorescence emission, alteration in the secondary and tertiary structure, and reduced electrophoretic mobility- indicate its structural changes that are accompanied with its reduced activity. Glucose in the presence or absence of Spd induces the protein dimerization, but glucose plus Spm induces its trimmerization. In contrast, glycerol inhibits the LZ glycation and prevents the large changes on its structure and function. Glucose binds lysine residues, decreases the protein positive charges and induces some alterations in its structure and activity. Polyamines also directly bind to LZ, increase its positive charges and hence induce more glycation; more conformational changes, oligomerization and its inactivation in the presence of glucose, but glycerol affect the protein environment and preserve protein from these harmful effects.

The effect of hot-tub therapy on serum Hsp70 level and its benefit on diabetic rats: a preliminary report

PURPOSE

To carry out a preliminary study examining the efficacy of long-term hot-tub therapy (HTT) in the improvement of diabetic complications on streptozotocin-induced diabetic rats.

MATERIALS AND METHODS

Male Wistar rats were immersed mid-sternum in a circulating water bath (42 degrees C for 30 min) to obtain a core body temperature of 41 degrees C; this process was repeated three times a week for 5 months. The blood was collected every month. Multiple parameters were examined for all rats including heat shock protein (Hsp70) level, serum glucose and insulin concentrations, advanced glycation end product (AGE) and glycated haemoglobin (HbA1c) formation, lipid profile and antioxidant defence system. Additionally, the chaperoning capacity of glycated Hsp70 was evaluated based on in vitro studies in which the refolding of denatured luciferase was compared to refolding by native Hsp70.

RESULTS

HTT-treated diabetic rats showed a significant improvement in lipid profile, antioxidant capacity, insulin secretion and serum Hsp70 level and a significant decrease in AGE formation compared to the untreated diabetic rats. However, HTT had a borderline significant effect on weight and fasting blood glucose. Glycated Hsp70 lost its chaperoning ability to reactivate the denatured luciferase.

CONCLUSION

A decrease in complications in diabetic rats after hot-tub therapy is shown here. An increase in the extracellular Hsp70 level due to HTT was observed. This increase may serve to protect the structure of proteins (e.g. preventing AGE formation), and the observed beneficial effects may be related to it.

Effect of spermine on lipid profile and HDL functionality in the streptozotocin-induced diabetic rat model

This study aimed to investigate the effect of spermine (Spm) as a chemical chaperone and glycation inhibitor on the lipid profile and HDL functionality in the short- and long-term treatment of the STZ-induced diabetic rats. Male Wistar rats were divided into 4 groups (control, n=7; diabetic, n=9). Two groups (named 2 and 3) were injected intraperitoneally with streptozotocin. Control rats (named 1 and 4) were injected with vehicle alone. The treatment of diabetic and control animals (groups 3 and 4) with 60 micromol/l of Spm in drinking water was begun. The study continued up to the end of the fifth month. The serum glucose and insulin level, AGE formation, lipid profile, paraoxonase 1 (PON1), and lecithin: cholesterol acyl transferase (LCAT) activities were measured. Significantly lower plasma PON1, and LCAT activities and higher serum AGE, TG, TC and LDL-c, and lower HDL-c were seen in diabetic rats as compared to control groups (P<0.01). The increased AGE, TG, TC and LDL-c levels in diabetic groups decreased gradually after receiving Spm. In addition, due to Spm administration, an increase in the HDL-c level was observed after the first month of the experiment (P<0.01). The increase in the PON1 and LCAT activities in the diabetic group that received Spm was significant after the second and the forth month of the experiment, P<0.02 and P<0.05, respectively. In conclusion, spermine administration attenuated the changed parameters to near normal values in diabetic rats. Spermine, despite a lack of significant changes on glucose metabolism and insulin secretion, was found to improve diabetes complications.