Alterations in L-arginine and inflammatory markers in type 2 diabetic patients with and without microalbuminuria

Kidney tea [Orthosiphon aristatus (Blume) Miq.] improves diabetic nephropathy via regulating gut microbiota and ferroptosis

Introduction

Diabetic nephropathy (DN) is the leading cause of end-stage renal disease. Due to its complex pathogenesis, new therapeutic agents are urgently needed. Orthosiphon aristatus (Blume) Miq., commonly known as kidney tea, is widely used in DN treatment in China. However, the mechanisms have not been fully elucidated.

Methods

We used db/db mice as the DN model and evaluated the efficacy of kidney tea in DN treatment by measuring fasting blood glucose (FBG), serum inflammatory cytokines, renal injury indicators and histopathological changes. Furthermore, 16S rDNA gene sequencing, untargeted serum metabolomics, electron microscope, ELISA, qRT-PCR, and Western blotting were performed to explore the mechanisms by which kidney tea exerted therapeutic effects.

Results

Twelve polyphenols were identified from kidney tea, and its extract ameliorated FBG, inflammation and renal injury in DN mice. Moreover, kidney tea reshaped the gut microbiota, reduced the abundance of Muribaculaceae, Lachnoclostridium, Prevotellaceae_UCG-001, Corynebacterium and Akkermansia, and enriched the abundance of Alloprevotella, Blautia and Lachnospiraceae_NK4A136_group. Kidney tea altered the levels of serum metabolites in pathways such as ferroptosis, arginine biosynthesis and mTOR signaling pathway. Importantly, kidney tea improved mitochondrial damage, increased SOD activity, and decreased the levels of MDA and 4-HNE in the renal tissues of DN mice. Meanwhile, this functional tea upregulated GPX4 and FTH1 expression and downregulated ACSL4 and NCOA4 expression, indicating that it could inhibit ferroptosis in the kidneys.

Conclusion

Our findings imply that kidney tea can attenuate DN development by modulating gut microbiota and ferroptosis, which presents a novel scientific rationale for the clinical application of kidney tea.

Pteridine and tryptophan pathways in children with type 1 diabetes: Isoxanthopterin as an indicator of endothelial dysfunction

AIM

Type 1 diabetes (T1D) and its complications are known to be associated with oxidative stress. Pteridine derivatives and indoleamine 2,3-dioxygenase (IDO) activity can be used as biomarkers in the evaluation of oxidative stress. In this study, our aim is to compare the concentrations of serum and urinary pteridine derivatives, as well as serum IDO activity, in children and adolescents diagnosed with T1D and those in a healthy control group.

METHOD

A cross-sectional study was performed and included 93 patients with T1D and 71 healthy children. Serum and urine biopterin, neopterin, monapterin, pterin, isoxanthopterin, and pterin-6-carboxylic acid (6PTC) and serum tryptophan and kynurenine levels were analyzed and compared with healthy controls. High-performance liquid chromatography was used for the analysis of pteridine derivatives, tryptophan, and kynurenine. Xanthine oxidase (XO) activity, a marker of oxidative stress, was defined by measurement of serum and urine isoxanthopterin. As an indicator of indolamine 2,3-dioxygenase (IDO) activity, the ratio of serum kynurenine/tryptophan was used.

RESULTS

Serum isoxanthopterin and tryptophan concentrations were increased, and serum 6PTC concentration was decreased in children with T1D (p=0.01, p=0.021, p<0.001, respectively). In children with T1D, IDO activity was not different from healthy controls (p>0.05). Serum neopterin level and duration of diabetes were weakly correlated (p=0.045, r=0.209); urine neopterin/creatinine and isoxanthopterin/creatinine levels were weakly correlated with HbA1c levels (p=0.005, r=0.305; p=0.021, r=0.249, respectively). Urine pterin/creatinine level negatively correlated with body mass index-SDS. (p=0.015, r=-0.208).

CONCLUSION

We found for the first time that isoxanthopterin levels increased and 6PTC levels decreased in children and adolescents with T1D. Elevated isoxanthopterin levels suggest that the XO activity is increased in TID. Increased XO activity may be an indicator of vascular complications reflecting T1D-related endothelial dysfunction.

Neopterin in the Evolution from Obesity to Prediabetes and Newly Diagnosed Type 2 Diabetes

Background: Neopterin, marker of cellular immunity and oxidative stress, is mainly produced by activated macrophages. It could play a crucial role in the development of insulin resistance (IR) and type 2 diabetes (T2D). The aim of this study was to investigate the circulating levels of neopterin in different stages of glucose dysregulation from obesity through prediabetes to newly diagnosed diabetes. Methods: Neopterin levels were determined using a commercially available human enzyme-linked immunosorbent assay kit. The homeostasis model assessment of IR was used as an index to assess IR. Results: The sample consisted of 163 subjects with mean age 52.5 ± 11.3 years, divided in three age- and body mass index (BMI)-matched groups-obesity, prediabetes, and diabetes. The control group consisted of 42 healthy individuals. Neopterin levels were significantly higher in patients with obesity and/or prediabetes and newly diagnosed diabetes than those in the control group, respectively (4.14 ± 2.51; 4.04 ± 2.80 and 2.17 ± 1.93 vs. 0.87 ± 0.84; P < 0.05). Correlation analysis showed that the level of neopterin positively correlated with BMI, waist, waist-to-stature ratio, waist-to-hip ratio, fasting glucose, and triglycerides. Receiver operating characteristic analysis established neopterin suitable for distinguishing subjects with obesity [area under the curve (AUC) = 0.83; P < 0.001] and carbohydrate disturbances (AUC = 0.59; P < 0.05) from those without these conditions. Neopterin ≥0.47 ng/mL have an odds ratio (OR) of 2.71 for development of dysglycemia, whereas threshold value of neopterin ≥0.56 ng/mL shows an OR of 5.94 for development of obesity. Conclusion: The levels of neopterin were increased in patients with obesity and carbohydrate disturbances. Further studies will elucidate the role of the biomarker in development of T2D and its complications.

Potential Prognostic Role of Immune System Activation Marker Neopterin in Patients with Type 2 Diabetes

BACKGROUND

An increase in neopterin concentrations is known in some pathologies due to interferon-gamma (INF-γ) activation. These include viral and bacterial infections, auto immune diseases, metabolic diseases, psychiatric disorders, tissue and organ rejections, and different malignancies. The aim of this study was to evaluate the role of neopterin as a prognostic biomarker in type 2 diabetes, which is a metabolic disease with a high worldwide prevalence.

METHODS

The study included a total of one hundred thirtynine individuals including one hundred and six patients admitted to a family medicine outpatient clinic and diagnosed with type 2 diabetes and thirty-three healthy volunteers. Serum neopterin concentrations were measured using the enzyme-linked immunosorbent assay.

RESULTS

Serum neopterin levels significantly increased in type 2 diabetes patients, compared to the control group (p<0.001).

CONCLUSIONS

Early diagnosis of diabetes and determination of the appropriate therapeutic options are of utmost importance, as diabetes is also associated with other systemic diseases. The risk of developing secondary diseases is high in untreated patients. Our study results suggest that serum neopterin may be a useful biomarker in patients with type 2 diabetes.

l-Arginine and allopurinol supplementation attenuates inflammatory mediators in human osteoblasts-osteoarthritis cells

This study investigated the synergistic effects of l-arginine and allopurinol on antioxidant and inflammatory mediators in human osteoblasts-osteoarthritis (HOb-OA) cells. The cells were treated with allopurinol (50-150 mg/kg bwt) and l-arginine (50-150 mg/kg bwt) for 72 h. Cell viability, catalase, superoxide dismutase (SOD), glutathione peroxidase (Gpx), reduced glutathione (GSH), lipid peroxidation, and the inflammatory markers interleukin 6 (IL-6), interleukin 1β (IL-1β), nuclear factor κB (NF-κB) and tumor necrosis factor alpha (TNF-α) were measured. The combined supplementation with allopurinol and l-arginine increased catalase, SOD, GSH, and Gpx, while it decreased lipid peroxidation, IL-6, IL-1β, and TNF-α. While TNF-α, IL-6, IL-1β, and NF-κB mRNA and protein expression were higher in control HOb-OA cells, the combined supplementation with allopurinol and l-arginine substantially reduced their expression in HOb-OA cells by >40%. In summary, combined supplementation with allopurinol and l-arginine might be very effective in osteoarthritis. A search for therapeutic agents that inhibit inflammation could help to prevent and manage osteoarthritis. However, further studies need to determine the biochemical and molecular mechanisms of these agents in osteoarthritis.

Serum asymmetric dimethylarginine and arginine levels predict microvascular and macrovascular complications in type 2 diabetes mellitus

BACKGROUND

Increased oxidative stress in diabetes increases nitric oxide (NO) oxidation and low l-arginine (Arg) could further reduce NO and impair vascular function, thereby accelerating, in the long run, vascular complications. We therefore measured Arg and asymmetric dimethylarginine (ADMA) levels in patients with type 2 diabetes mellitus (T2DM) and healthy controls. Additionally, we observed the diabetic individuals over time to see if Arg and asymmetric dimethylarginine predicted T2DM complications.

METHODS

We examined baseline serum Arg and ADMA levels in a cohort of 105 participants with type 2 diabetes and compared them with an age- and weight-matched nondiabetic group of 137 individuals who served as a reference population. Additionally, we assessed whether Arg and/or ADMA predicted macrovascular and microvascular complications over 6 years of follow-up.

RESULTS

Serum Arg was lower in individuals with T2DM than in controls (64 ± 28 vs 75 ± 31 μmol/L; P = .009) and inversely related to hemoglobin A1c (r = -0.2; P = .002). Over follow-up, we observed that participants with T2DM in the lowest quartile of Arg had increased risk for the subsequent evolution of nephropathy, peripheral neuropathy, and composite microvascular complications (odds ratio [OR] = 5.5; 95% confidence interval [CI] -1.9 to 16; P = .002). The highest ADMA quartile was associated with increased risk for both microvascular (OR = 4.5; 95% CI -1.4 to 14.1; P = .009) and 6.5-year incident macrovascular complications (OR = 8.3; 95% CI 1.9-35.5; P = .004).

CONCLUSION

l-Arginine levels are lower in individuals with T2DM than in matched controls. Both low Arg and high ADMA, independent of each other and adjusted for classical risk factors, predict the incidence of microvascular complications.

Neopterin and hsCRP are not correlated in gestational diabetes mellitus

OBJECTIVE

To determine serum neopterin and high sensitive C-reactive protein (hsCRP) levels in patients with and without gestational diabetes mellitus (GDM).

METHODS

Neopterin and hsCRP levels were quantified in 28 women with GDM and 20 pregnant women with normal glucose tolerance (NGT). Postpartum neopterin and hsCRP levels were measured in a follow-up study.

RESULTS

Neopterin levels were significantly higher in women with GDM than in women with NGT (15.89 ± 8.19 nmol/L versus 10.4 ± 3.8 nmol/L, p < 0.008, respectively), however the levels significantly decreased after delivery in GDM group (15.89 ± 8.19 nmol/L versus 11.63 ± 5.96 nmol/L, p < 0.001). hsCRP levels were not different between women with and without GDM (5.74 ± 3.91 versus 5.73 ± 3.34, p = 0.9, respectively). In contrast, hsCRP levels decreased after delivery in patients with GDM (5.74 ± 3.91 versus 3.78 ± 2.78, p < 0.01). Neopterin levels were correlated with maternal age (r = 0.3, p = 0.02) and fasting glucose (r = 0.4, p = 0.004), postprandial glucose (r = 0.3, p = 0.01), HbA1c (r = 0.3, p = 0.02), whereas hsCRP levels were correlated with pre-pregnancy (r = 0.3, p = 0.04) and pregnancy body mass index (r = 0.4, p = 0.008). No correlation between serum neopterin and hsCRP levels was found (p = 0.9).

CONCLUSION

Neopterin levels increased in patients with GDM; hence, it may be related to inflammation. However, the lack of correlation between neopterin and hsCRP suggests the role of different attitudes of these two parameters in the course of pregnancy and GDM.

Renal endothelial dysfunction in diabetic nephropathy

Endothelial dysfunction has been posited to play an important role in the pathogenesis of diabetic nephropathy (DN). Due to the heterogeneity of endothelial cells (ECs), it is difficult to generalize about endothelial responses to diabetic stimuli. At present, there are limited techniques fordirectly measuring EC function in vivo, so diagnosis of endothelial disorders still largely depends on indirect assessment of mediators arising from EC injury. In the kidney microcirculation, both afferent and efferent arteries, arterioles and glomerular endothelial cells (GEnC) have all been implicated as targets of diabetic injury. Both hyperglycemia per se, as well as the metabolic consequences of glucose dysregulation, are thought to lead to endothelial cell dysfunction. In this regard, endothelial nitric oxide synthase (eNOS) plays a central role in EC dysfunction. Impaired eNOS activity can occur at numerous levels, including enzyme uncoupling, post-translational modifications, internalization and decreased expression. Reduced nitric oxide (NO) bioavailability exacerbates oxidative stress, further promoting endothelial dysfunction and injury. The injured ECs may then function as active signal transducers of metabolic, hemodynamic and inflammatory factors that modify the function and morphology of the vessel wall and interact with adjacent cells, which may activate a cascade of inflammatory and proliferative and profibrotic responses in progressive DN. Both pharmacological approaches and potential regenerative therapies hold promise for restoration of impaired endothelial cells in diabetic nephropathy.

Neopterin is associated with cardiovascular events and all-cause mortality in renal transplant patients

BACKGROUND

Inflammatory markers show significant associations with cardiovascular events and all-cause mortality after kidney transplantation. Neopterin, reflecting interferon-γ-release, may better reflect the proinflammatory state of recipients than less specific markers.

METHODS

Kidney transplant recipients in the Assessment of LEscol in Renal Transplant (ALERT) trial were examined and investigated for an association between serum neopterin and subsequent clinical events: graft loss, major cardiovascular events (MACE) and all-cause mortality.

RESULTS

After adjustment for established and emerging risk factors neopterin expressed as neopterin-to-creatinine ratio was significantly associated with MACE (p = 0.009) and all-cause mortality (p = 0.002). Endpoints were more frequent with increasing quartiles of neopterin-to-creatinine ratio. The incidence rates of MACE and all-cause mortality were significantly increased in the upper quartiles compared with the first.

CONCLUSIONS

This long-term prospective analysis in stable kidney allograft recipients suggests that neopterin is associated with long-term risk of cardiovascular events and all-cause mortality, but not renal outcomes.

Fatigue symptoms relate to systemic inflammation in patients with type 2 diabetes

Fatigue is frequent in patients with diabetes and this symptom appears to be more prominent in type 2 rather than type 1 diabetic subjects. Chronic inflammation represents one characteristic of type 2 diabetes that may contribute to fatigue symptoms. This possibility was assessed in a sample of 20 type 2 diabetic patients relatively to a group of 20 type 1 diabetic subjects. Specific dimensions of fatigue, including general fatigue, physical fatigue, reduced activity, mental fatigue and reduced motivation, were assessed using the Multidimensional-Fatigue-Inventory (MFI). Biological assays comprised the measurement of serum inflammatory markers [high-sensitive C-reactive-protein (hsCRP), high-sensitive interleukin-6 (hsIL-6), high-sensitive tumor-necrosis-factor-α (hsTNF-α) and neopterin]. Clinical parameters including indexes of adiposity were collected. In comparison to type 1 diabetic subjects, patients with type 2 diabetes exhibited higher fatigue scores, notably in the dimensions of general fatigue, physical fatigue and reduced activity, together with greater levels of inflammatory markers that correlated with indexes of adiposity. Regression analyses controlling for diabetes duration, insulin treatment status, glycemic control and fasting status, indicated that levels of inflammatory markers, in particular hsIL-6, hsCRP and neopterin, were associated with MFI fatigue dimensions in type 2 diabetic patients. Mediation analyses revealed that adiposity did not significantly account for the relationship of inflammatory markers with fatigue scores albeit coefficient regressions decreased somewhat when this variable was controlled for in regression models. These findings indicate that systemic low-grade inflammation relates to fatigue symptoms in patients with type 2 diabetes and suggest the involvement of inflammatory processes in the pathophysiology of diabetes-related fatigue.

Systemic and spinal administration of etanercept, a tumor necrosis factor alpha inhibitor, blocks tactile allodynia in diabetic mice

Painful diabetic neuropathy is one of the most common forms of neuropathic pain syndromes. Tumor necrosis factor alpha (TNF-alpha) is a proinflammatory cytokine that has been implicated as a key pain mediator in the development and maintenance of neuropathic pain conditions. Recent studies showed that endogenous TNF-alpha production was also accelerated in neural tissues and spinal cord under chronic hyperglycemia. Thus, in this study, we investigated whether pharmacological inhibition of TNF-alpha by etanercept, a TNF-alpha antagonist, could block behavioral sign of diabetic neuropathic pain. Diabetes was induced by streptozotocin (STZ) (200 mg/kg, i.p.) in Balb-c mice and behavioral tests were performed between 45 and 60 days after STZ administration. Mechanical and thermal sensitivities were measured by a series of calibrated Von Frey filaments and hot plate test, respectively. Etanercept was given by either intravenous (i.v.), intrathecal (i.th.) or intraplantar (i.pl.) routes to the diabetic mice. Tactile allodynia, but not thermal hyperalgesia, developed in diabetic mice. Both i.v. (1, 10 and 20 mg/kg) or i.th. (1, 5 and 10 μg/mouse) treatments with etanercept produced dose dependent reversal of tactile allodynia in diabetic mice. However, etanercept was found to be inactive against allodynia when given i.pl. (1, 5 and 10 μg/mouse). Our results suggest that etanercept has promising effects on diabetic neuropathic pain with antiallodynic effects when given systemically or intrathecally.

Study of coronary artery calcification risk in Egyptian adolescents with type-1 diabetes

The objective of the study is to assess coronary artery calcification (CAC) among adolescents with type-1 diabetes and to determine its relation with high-sensitivity C-reactive protein (hs-CRP), dyslipidaemia, glycaemic control and microvascular complications. The study included sixty patients with type-1 diabetes. Their ages ranged from 12 to 18 years and their diabetes duration ranged between 10 and 15 years. Patients were compared with 60 healthy subjects who served as controls. Clinical examination and laboratory investigations were done for evaluation of glycaemic control and presence of microvascular complications. Lipid profile, hs-CRP and multislice spiral computed tomography were done. Hs-CRP, total cholesterol, triglycerides and low-density lipoproteins levels were significantly higher in patients with diabetes compared to controls (P < 0.001). Twelve patients with diabetes (20%) had positive CAC. The mean calcium score was significantly higher in patients with diabetes compared to controls (P < 0.05). Smoking significantly affects CAC as 50% of smokers with diabetes had evidence of CAC compared to 9.1% of non-smokers with diabetes (P < 0.001). Fifty percent of patients with diabetes on angiotensin-converting enzyme inhibitor (ACEI) had evidence of CAC compared to 0% of patients without history of ACEI therapy (P < 0.001). Diabetics with CAC had significantly elder age, longer disease duration and higher mean glycosylated hemoglobin compared to diabetics without CAC (P < 0.05). Blood pressure percentiles, albumin creatinine ratio and serum lipids were significantly higher in patients with CAC compared to those without CAC (P < 0.001). All diabetics with severe retinopathy had positive CAC compared to 0% with normal Fundus (P < 0.001). All diabetics with overt nephropathy had positive CAC compared to 13.3% and 0% in micro- and normo-albuminuric patients (P < 0.001). Young patients with diabetes have evidence of CAC. Smoking, microvascular complications and dyslipidaemia might contribute to this risk.

Efficacy of combined use of miglitol in Type 2 diabetes patients receiving insulin therapy-placebo-controlled double-blind comparative study

Combination therapy with an α-glucosidase inhibitor and insulin is commonly performed for type 2 diabetes mellitus. We conducted a placebo-controlled double-blind comparative study to investigate the efficacy of combination therapy with miglitol and insulin. The patients with T2DM on insulin therapy were randomly assigned to either a miglitol treatment group (Group M) or a placebo group (Group P) and treated for 12 weeks. Meal tolerance tests were conducted at the observation period, week 0 and week 12 of the treatment period. Mean values of decrease in 1-h- and 2-h postprandial plasma glucose level were significantly larger in Group M than in Group P (60.3 ± 70.1 mg/dl vs. -5.1 ± 68.2 mg/dl (P < 0.001)), as was HbA1c as well (0.36 ± 0.66% vs. -0.03 ± 0.56% (P < 0.001)). Adverse events included abdominal distension and flatulence, which were significantly more frequent in Group M. The frequency of nocturnal hypoglycemia events tended to be reduced in Group M. Combined use of insulin and miglitol is useful for postprandial glucose regulation and improves glycemic control.

Metabolic syndrome is independently associated with microalbuminuria in type 2 diabetes

We opted in this study to evaluate the association between metabolic syndrome (MetS) and microalbuminuria in type 2 diabetes. A total of 800 adults (344 males; age 54.8 +/- 9.6 years) with type 2 diabetes were studied. MetS was defined by the International Diabetes Federation criteria and microalbuminuria by urinary albumin excretion between 30 and 299 mg/day on at least two of three occasions. Patients with macroalbuminuria and those with poor renal function were not included. Microalbuminuria was present in 237 (29.6%) patients with MetS and increased in prevalence with increasing numbers of metabolic abnormalities (P < 0.001). The normo- and micro-albuminuric groups were not significantly different in age, sex, and renal function. However, MetS was significantly more common among patients with (90.3%) than those without (76.6%) microalbuminuria (P < 0.01). In multivariate regression, MetS was the strongest correlate of microalbuminuria (OR = 3.31, 95% CI = 1.91-5.75; P < 0.01). In conclusion, MetS is independently associated with microalbuminuria in type 2 diabetes.

Effect of L-arginine on the microcirculation in the neuropathic diabetic foot in Type 2 diabetes mellitus: a double-blind, placebo-controlled study

OBJECTIVE

To investigate the effect of L-arginine on endothelial function, transcutaneous oxygen and clinical neuropathy in patients with peripheral neuropathy as a result of diabetes.

RESEARCH DESIGN AND METHODS

Thirty diabetic patients with peripheral neuropathy were randomized to receive L-arginine (3 g three times daily) or placebo (3 g three times daily) for 3 months. All patients had foot microcirculation and foot transcutaneous oxygen pressure (TcPO(2)), neuropathy disability score (NDS) and vibration perception threshold (VPT) assessed at baseline and follow-up.

RESULTS

No difference was observed in endothelium-dependent and -independent vasodilation, TcPO(2), NDS and VPT.

CONCLUSIONS

L-arginine has no effect on endothelial dysfunction, TcPO(2) and clinical neuropathy.