Branched-chain amino acids attenuate early kidney injury in diabetic rats

Study on the potential mechanism of Qingxin Lianzi Yin Decoction on renoprotection in db/db mice via network pharmacology and metabolomics

BACKGROUND

Diabetic nephropathy (DN) was one of the most popular and most significant microvascular complications of diabetes mellitus. Qingxin Lianzi Yin Decoction (QXLZY) was a traditional Chinese classical formula, suitable for chronic urinary system diseases. QXLZY had good clinical efficacy in early DN, but the underlying molecular mechanism remained unrevealed.

PURPOSE

This study aimed to establish the content determination method of QXLZY index components and explore the mechanism of QXLZY on DN by network pharmacology and metabolomics studies.

METHODS

Firstly, the content determination methods of QXLZY were established with calycosin-7-O-β-d-glucoside, acteoside, baicalin and glycyrrhizic acid as index components. Secondly, pharmacological experiments of QXLZY were evaluated using db/db mice. UHPLC-LTQ-Orbitrap MS was used to carry out untargeted urine metabolomics, serum metabolomics, and kidney metabolomics studies. Thirdly, employing network pharmacology, key components and targets were analyzed. Finally, targeted metabolomics studies were performed on the endogenous constituents in biological samples for validation based on untargeted metabolomics results.

RESULTS

A method for the simultaneous determination of multiple index components in QXLZY was established, which passed the comprehensive methodological verification. It was simple, feasible, and scientific. The QXLZY treatment alleviated kidney injury of db/db mice, included the degree of histopathological damage and the level of urinary microalbumin/creatinine ratio. Untargeted metabolomics studies had identified metabolic dysfunction in pathways associated with amino acid metabolism in db/db mice. Treatment with QXLZY could reverse metabolite abnormalities and influence the pathways related to energy metabolism and amino acid metabolism. It had been found that pathways with a high degree were involved in signal transduction, prominently on amino acids metabolism and lipid metabolism, analyzed by network pharmacology. Disorders of amino acid metabolism did occur in db/db mice. QXLZY could revert the levels of metabolites, such as quinolinic acid, arginine, and asparagine.

CONCLUSION

This study was the first time to demonstrate that QXLZY alleviated diabetes-induced pathological changes in the kidneys of db/db mice by correcting disturbances in amino acid metabolism. This work could provide a new experimental basis and theoretical guidance for the rational application of QXLZY on DN, exploring the new pharmacological effect of traditional Chinese medicine, and promoting in-depth research and development.

The association between dietary intake of branched-chain amino acids and odds and severity of rheumatoid arthritis

This case-control study investigated the link between dietary branched-chain amino acids (BCAAs) and the risk and severity of rheumatoid arthritis (RA). We assessed dietary BCAA intake in 95 RA patients and 190 matched controls using a food frequency questionnaire. We also assessed the disease severity using the disease activity score 28 (DAS-28), ESR, VAS, morning stiffness, and tender and swollen joints. Higher BCAA intake, expressed as a percentage of total protein, was significantly associated with increased risk of RA for total BCAAs (OR 2.14, 95% CI 1.53-3.00, P < 0.001), leucine (OR 2.40, 95% CI 1.70-3.38, P < 0.001), isoleucine (OR 2.04, 95% CI 1.46-2.85, P < 0.001), and valine (OR 1.87, 95% CI 1.35-2.59, P < 0.001). These associations remained significant even after adjusting for potential confounders (P < 0.001). However, BCAA intake did not show any significant association with RA severity in either crude or multivariate models (P > 0.05). Our findings suggest that higher dietary BCAA intake may contribute to the development of RA, but further research is needed to confirm these observations and explore the underlying mechanisms.

Role of Gut Microbiota, Immune Imbalance, and Allostatic Load in the Occurrence and Development of Diabetic Kidney Disease

Diabetic kidney disease (DKD) is a prevailing complication arising from diabetes mellitus. Unfortunately, there are no trustworthy and efficacious treatment modalities currently available. In recent times, compelling evidence has emerged regarding the intricate correlation between the kidney and the gut microbiota, which is considered the largest immune organ within the human physique. Various investigations have demonstrated that the perturbation of the gut microbiota and its associated metabolites potentially underlie the etiology and progression of DKD. This phenomenon may transpire through perturbation of both the innate and the adaptive immunity, leading to a burdensome allostatic load on the body and ultimately culminating in the development of DKD. Within this literature review, we aim to delve into the intricate interplay between the gut microbiota, its metabolites, and the immune system in the context of DKD. Furthermore, we strive to explore and elucidate potential chemical interventions that could hold promise for the treatment of DKD, thereby offering invaluable insights and directions for future research endeavors.

GLP-1 Receptor Agonist Improves Mitochondrial Energy Status and Attenuates Nephrotoxicity In Vivo and In Vitro

High-sugar and high-fat diets cause significant harm to health, especially via metabolic diseases. In this study, the protective effects of the antidiabetic drug exenatide (synthetic exendin-4), a glucagon-like peptide 1 (GLP-1) receptor agonist, on high-fat and high-glucose (HFHG)-induced renal injuries were investigated in vivo and in vitro. In vivo and in vitro renal injury models were established. Metabolomic analysis based on 1H-nuclear magnetic resonance was performed to examine whether exenatide treatment exerts a protective effect against kidney injury in diabetic rats and to explore its potential molecular mechanism. In vivo, 8 weeks of exenatide treatment resulted in the regulation of most metabolites in the diabetes mellitus group. In vitro results showed that exendin-4 restored the mitochondrial functions of mesangial cells, which were perturbed by HFHG. The effects of exendin-4 included the improved antioxidant capacity of mesangial cells, increased the Bcl-2/Bax ratio, and reduced protein expression of cyt-c and caspase-3 activation. In addition, exendin-4 restored mesangial cell energy metabolism by increasing succinate dehydrogenase and phosphofructokinase activities and glucose consumption while inhibiting pyruvate dehydrogenase E1 activity. In conclusion, GLP-1 agonists improve renal injury in diabetic rats by ameliorating metabolic disorders. This mechanism could be partially related to mitochondrial functions and energy metabolism.

Depiction of Branched-Chain Amino Acids (BCAAs) in Diabetes with a Focus on Diabetic Microvascular Complications

Type 2 diabetes mellitus (T2DM) still holds the title as one of the most debilitating chronic diseases with rising prevalence and incidence, including its complications such as retinal, renal, and peripheral nerve disease. In order to develop novel molecules for diagnosis and treatment, a deep understanding of the complex molecular pathways is imperative. Currently, the existing agents for T2DM treatment target only blood glucose levels. Over the past decades, specific building blocks of proteins-branched-chain amino acids (BCAAs) including leucine, isoleucine, and valine-have gained attention because they are linked with insulin resistance, pre-diabetes, and diabetes development. In this review, we discuss the hypothetical link between BCAA metabolism, insulin resistance, T2DM, and its microvascular complications including diabetic retinopathy and diabetic nephropathy. Further research on these amino acids and their derivates may eventually pave the way to novel biomarkers or therapeutic concepts for the treatment of diabetes and its accompanied complications.

Metabolic Homeostasis of Amino Acids and Diabetic Kidney Disease

Diabetic kidney disease (DKD) occurs in 25-40% of patients with diabetes. Individuals with DKD are at a significant risk of progression to end-stage kidney disease morbidity and mortality. At present, although renal function-decline can be retarded by intensive glucose lowering and strict blood pressure control, these current treatments have shown no beneficial impact on preventing progression to kidney failure. Recently, in addition to control of blood sugar and pressure, a dietary approach has been recommended for management of DKD. Amino acids (AAs) are both biomarkers and causal factors of DKD progression. AA homeostasis contributes to renal hemodynamic response and glomerular hyperfiltration alteration in diabetic patients. This review discusses the links between progressive kidney dysfunction and the metabolic homeostasis of histidine, tryptophan, methionine, glutamine, tyrosine, and branched-chain AAs. In addition, we emphasize the regulation effects of special metabolites on DKD progression, with a focus on causality and potential mechanisms. This paper may offer an optimized protein diet strategy with concomitant management of AA homeostasis to reduce the risks of DKD in a setting of hyperglycemia.

Aminoaciduria and metabolic dysregulation during diabetic ketoacidosis: Results from the diabetic kidney alarm (DKA) study

OBJECTIVE

We examined changes in the excretion of various amino acids and in glycolysis and ketogenesis-related metabolites, during and after diabetic ketoacidosis (DKA) diagnosis, in youth with known or new onset type 1 diabetes (T1D).

METHODS

Urine samples were collected from 40 youth with DKA (52% boys, mean age 11 ± 4 years, venous pH 7.2 ± 0.1, blood glucose 451 ± 163 mg/dL) at 3 time points: 0-8 h and 12-24 h after starting an insulin infusion, and 3 months after hospital discharge. Mixed-effects models evaluated the changes in amino acids and other metabolites in the urine.

RESULTS

Concentrations of urine histidine, threonine, tryptophan, and leucine per creatinine were highest at 0-8 h (148.8 ± 23.5, 59.5 ± 12.3, 15.4 ± 1.4, and 24.5 ± 2.4% of urine creatinine, respectively), and significantly decreased over 3 months (p = 0.028, p = 0.027, p = 0.019, and p < 0.0001, respectively). Urine histidine, threonine, tryptophan, and leucine per urine creatinine decreased by 10.6 ± 19.2, 0.7 ± 0.9, 1.3 ± 0.9, and 0.5 ± 0.3-fold, respectively, between 0 and 8 h and 3 months.

CONCLUSIONS

In our study, DKA was associated with profound aminoaciduria, suggestive of proximal tubular dysfunction analogous to Fanconi syndrome.

High L-Valine Concentrations Associate with Increased Oxidative Stress and Newly-Diagnosed Type 2 Diabetes Mellitus: A Cross-Sectional Study

OBJECTIVE

Branched-chain amino acids (BCAAs) are essential AAs which are widely used as antioxidants in patients with liver and kidney dysfunction. However, BCAAs are strongly correlated with insulin resistance (IR) and diabetes. This study aimed to evaluate the relationship among BCAAs, oxidative stress, and type 2 diabetes mellitus (T2DM) in a Chinese population.

METHODS

Anthropometric and biochemical examinations were performed in 816 individuals who participated in the Huai'an Diabetes Prevention Program. Serum BCAAs concentrations were measured by hydrophilic interaction chromatography-tandem mass spectrometric method. Oxidative stress was evaluated by malondialdehyde (MDA) as an index of lipid peroxidation and the superoxide dismutase (SOD) activity.

RESULTS

A total of 816 participants were divided into three groups: normal glucose metabolism (NGM), prediabetes, and newly-diagnosed diabetes mellitus (NDM). Subjects in NDM group show higher MDA and lower SOD levels than subjects in other groups. L-Val levels positively correlated with MDA levels and negatively with SOD in NDM groups. After adjusting for T2DM risk factors, high L-Val levels were significantly associated with higher BMI, WC, FPG, increased LnTG and decreased HDL-C. L-Val was also independently associated with NDM (OR 1.06, 95% CI 1.02-1.10; P = 0.005). Furthermore, the odds ratios for NDM among participants with high L-Val (≥35.25μg/mL) levels showed a 2.25-fold (95% CI 1.11-4.57; P = 0.024) increase compared to participants with low L-Val (<27.26 μg/mL) levels after adjusting for MDA and confounding factors.

CONCLUSION

High serum L-Val levels are independently associated with oxidative stress, thus promoting IR and NDM. Further study should be done to clarify the mechanism.

Matrix metalloproteinases and tissue inhibitors of matrix metalloproteinases in kidney disease

Matrix metalloproteinases (MMPs) are a group of zinc and calcium endopeptidases which cleave extracellular matrix (ECM) proteins. They are also involved in the degradation of cell surface components and regulate multiple cellular processes, cell to cell interactions, cell proliferation, and cell signaling pathways. MMPs function in close interaction with the endogenous tissue inhibitors of matrix metalloproteinases (TIMPs), both of which regulate cell turnover, modulate various growth factors, and participate in the progression of tissue fibrosis and apoptosis. The multiple roles of MMPs and TIMPs are continuously elucidated in kidney development and repair, as well as in a number of kidney diseases. This chapter focuses on the current findings of the significance of MMPs and TIMPs in a wide range of kidney diseases, whether they result from kidney tissue changes, hemodynamic alterations, tubular epithelial cell apoptosis, inflammation, or fibrosis. In addition, the potential use of these endopeptidases as biomarkers of renal dysfunction and as targets for therapeutic interventions to attenuate kidney disease are also explored in this review.

Dietary Amino Acid Patterns Are Associated With Incidence of Chronic Kidney Disease

OBJECTIVES

No findings are available regarding the association of the dietary amino acid (AA) intakes with the risk of chronic kidney disease (CKD) in adults. We aimed to assess the association between dietary AA patterns and incidence of CKD in adults.

DESIGN AND METHODS

This study was conducted within the framework of Tehran Lipid and Glucose Study on 4,233 adults, who were free of CKD at baseline (2009-2011) and were followed for 3.1 years (2011-2014). The principal component analysis was used based on 8 AA groups to characterize major AA patterns. Multivariable logistic regression models were used to estimate the risk of CKD across quartiles of dietary AA pattern scores.

RESULTS

Three major AA patterns were extracted: (1) higher loads of branched-chain, alcoholic, and aromatic AAs; (2) higher loads of acidic AAs, proline, and lower load of alkaline AAs and small AAs; and (3) higher loads of sulfuric AAs and small AAs. The mean ± standard deviation age of participants (45.9% male) was 39.4 ± 11.7 at baseline and the incidence of CKD was 12.1% (513 cases) after 3.1 years of follow-up. The highest score of first dietary AA pattern tended to be associated with an increased risk of CKD (odds ratio = 1.43, 95% confidence interval1.06-1.93); however, the second pattern was related to a decreased risk of CKD (odds ratio = 0.71, 95% confidence interval: 0.52-0.97) in the multivariable model.

CONCLUSION

These novel findings suggest that the dietary AA patterns may modify risk of CKD.

Roles of Gut Microbial Metabolites in Diabetic Kidney Disease

Diabetes is a highly prevalent metabolic disease that has emerged as a global challenge due to its increasing prevalence and lack of sustainable treatment. Diabetic kidney disease (DKD), which is one of the most frequent and severe microvascular complications of diabetes, is difficult to treat with contemporary glucose-lowering medications. The gut microbiota plays an important role in human health and disease, and its metabolites have both beneficial and harmful effects on vital physiological processes. In this review, we summarize the current findings regarding the role of gut microbial metabolites in the development and progression of DKD, which will help us better understand the possible mechanisms of DKD and explore potential therapeutic approaches for DKD.

The Association Between Leucine and Diabetic Nephropathy in Different Gender: A Cross-Sectional Study in Chinese Patients With Type 2 Diabetes

OBJECTIVE

This study aimed to evaluate how leucine are associated with diabetic nephropathy (DN) in type 2 diabetes (T2D) patients and the gender difference of this association.

METHODS

We retrieved 1,031 consecutive patients with T2D who meet the inclusion and exclusion criteria from the same tertiary care center and extracted clinical information from electronic medical record. Plasma leucine was measured by liquid chromatography-mass spectrometer. Restricted cubic spline (RCS) was conducted to examine potential non-linear relationship between leucine and the risk of DN. Logistic regression was used to obtain odds ratio (OR) and confidence interval (CI). Additive interaction was used to estimate the interaction effect between leucine and gender for DN.

RESULTS

We found there was a negative correlation between leucine and the risk of DN. After stratifying all patients by gender, this relationship only remained significant in women (OR:0.57, CI:0.41-0.79).

CONCLUSIONS

In conclusion, T2D patients with high levels of leucine have a lower risk of developing DN in female.

Branched Chain Amino Acids Protects Rat Mesangial Cells from High Glucose by Modulating TGF-β1 and BMP-7

AIM

Branched-chain amino acids (BCAAs) have been reported owning curative effects in early diabetic nephropathy. However, the mechanisms of its action have not been elucidated. The aim of this study is to investigate the effect of possible mechanism(s) of BCAAs on cultured rat mesangial cells (RMCs).

METHODS

RMCs were treated with high glucose (30 mmol/L) and BCAAs (10 mmol/L) respectively. Cell proliferation was detected using an MTT assay. Expression of transforming growth factor (TGF)-β1 and gremlin mRNA was detected by semiquantitative reverse-transcription (RT) PCR. TGF-β1 and fibronectin (FN) protein levels were measured using enzyme-linked immunosorbent assays (ELISAs). Gremlin, bone morphogenic protein (BMP)-7, and Smad2/3 proteins were detected by immunofluorescence. Smad1/5/8 and phosphorylated (p)-Smad1/5/8 were detected by Western blotting.

RESULTS

The proliferation rate of the RMCs in the high glucose group alone was 1.45-times of cells in the CON group, and it was reduced by 32% upon co-treatment with BCAAs. The expression of TGF-β1, gremlin, p-Smd2/3 and FN mRNA or protein in the HG group was higher than that in the CON group. In the BCAAs group, the corresponding levels were lower than that in HG group. The expression of BMP-7 and p-Smad1/5/8 were significantly lower in the HG group than in the CON group. Moreover, the expression of BMP-7 and p-Smad1/5/8 were higher in the BCAAs group than in the HG group.

CONCLUSION

BCAAs showed an antidiabetic effect via reducing TGF-β1-Smad2/3 pathway and Gremlin expression and upregulating BMP-7-Smad1/5/8 pathway in rat mesangial cells, consequently lessening ECM deposition in renal tissue.

The aldose reductase inhibitor epalrestat exerts nephritic protection on diabetic nephropathy in db/db mice through metabolic modulation

Epalrestat is an inhibitor of aldose reductase in the polyol pathway and is used for the management of diabetic neuropathy clinically. Our pilot experiments and accumulated evidences showed that epalrestat inhibited polyol pathway and reduced sorbitol production, and suggested the potential renal protection effects of epalrestat on diabetic nephropathy (DN). To evaluate the protective effect of epalrestat, the db/db mice were used and exposed to epalrestat for 8 weeks, both the physiopathological condition and function of kidney were examined. For the first time, we showed that epalrestat markedly reduced albuminuria and alleviated the podocyte foot process fusion and interstitial fibrosis of db/db mice. Metabolomics was employed, and metabolites in the plasma, renal cortex, and urine were profiled using a gas chromatography-mass spectrometry (GC/MS)-based metabolomic platform. We observed an elevation of sorbitol and fructose, and a decrease of myo-inositol in the renal cortex of db/db mice. Epalrestat reversed the renal accumulation of the polyol pathway metabolites of sorbitol and fructose, and increased myo-inositol level. Moreover, the upregulation of aldose reductase, fibronectin, collagen III, and TGF-β1 in renal cortex of db/db mice was downregulated by epalrestat. The data suggested that epalrestat has protective effects on DN, and the inhibition of aldose reductase and the modulation of polyol pathway in nephritic cells be a potentially therapeutic strategy for DN.