Alteration of Plasma Indoles in Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) is one of the most common endocrinopathies in reproductive-aged women. The occurrence of PCOS was reported to be associated with the alteration of gut microbiota. Microbiota-derived indoles may possibly play a key role in glycemic control. The purpose of this work is to reveal the alteration of plasma indoles in PCOS patients and to investigate the correlation between indoles levels and glucose metabolism. Sixty-five patients with PCOS and twenty-eight age-matched women were enrolled in this work. The concentrations of plasma indoles, including indoxyl sulfate (IS), indole-3-acetic acid (IAA), indole-3-propionate (IPA), indole (IND), and 3-methylindole (3-MI), were measured by HPLC with the fluorescence detection. The plasma levels of IS, IAA, and IND were significantly elevated in patients with PCOS compared to those in the control group (p < 0.05). Furthermore, the plasma levels of IS, IAA, and IND were positively correlated with fasting glucose, fasting insulin, and the homeostatic model of insulin resistance index (HOMA-IR) (p < 0.05). Besides, the 3-MI level in the plasma was positively correlated with the fasting glucose level, whereas plasma levels of IS, IAA, IND, and 3-MI were negatively correlated with glucagon-like peptide 1 (p < 0.05). Moreover, IS and IND were considered to be risk factors for PCOS after age, BMI, T, LH, and HOMA-IR adjustment. The area under the receiver-operating characteristic curve of the combined index of five indoles was 0.867 for PCOS diagnosis. Additionally, plasma indoles altered in PCOS, which was closely associated with the glucose metabolism.

Sodium benzoate attenuates 2,8-dihydroxyadenine nephropathy by inhibiting monocyte/macrophage TNF-α expression

Sodium benzoate (SB), a known D-amino acid oxidase (DAO) enzyme inhibitor, has an anti-inflammatory effect, although its role in renal damage has not been explored. 2,8-dihydroxyadenine crystal induced chronic kidney disease, in which TNF-α is involved in the pathogenesis, was established by oral adenine administration in C57BL/6JJcl mice (AdCKD) with or without SB to investigate its renal protective effects. SB significantly attenuated AdCKD by decreasing serum creatinine and urea nitrogen levels, and kidney interstitial fibrosis and tubular atrophy scores. The survival of AdCKD mice improved 2.6-fold by SB administration. SB significantly decreased the number of infiltrating macrophages observed in the positive F4/80 immunohistochemistry area and reduced the expression of macrophage markers and inflammatory genes, including TNF-α, in the kidneys of AdCKD. Human THP-1 cells stimulated with either lipopolysaccharide or TNF-α showed increased expression of inflammatory genes, although this was significantly reduced by SB, confirming the anti-inflammatory effects of SB. SB exhibited renal protective effects in AdCKD in DAO enzyme deficient mice, suggesting that anti-inflammatory effect of SB was independent of DAO enzyme activity. Moreover, binding to motif DNA sequence, protein level, and mRNA level of NF-κB RelB were significantly inhibited by SB in AdCKD kidneys and lipopolysaccharide treated THP-1 cells, respectively. We report that anti-inflammatory property of SB is independent of DAO enzymatic activity and is associated with down regulated NF-κB RelB as well as its downstream inflammatory genes such as TNF-α in AdCKD.

Alterations of DNA methylation during adipogenesis differentiation of mesenchymal stem cells isolated from adipose tissue of patients with obesity is associated with type 2 diabetes

Adipogenesis regulation is crucial for mature adipocyte function. In obesity, a major driver of type 2 diabetes (T2D), this process is disrupted and remains poorly characterized. Here we identified altered DNA methylation profiles in diabetic obese patients, during three adipocytes differentiation stages. We isolated mesenchymal cells from visceral adipose tissue of obese patients with and without T2D to analyse DNA methylation profiles at 0, 3, and 18 days of ex vivo differentiation and documented their impact on gene expression. Methylation and gene expression were analysed with EPIC and Clarion S arrays, respectively. Patients with T2D had epigenetic alterations in all the analysed stages, and these were mainly observed in genes important in adipogenesis, insulin resistance, cell death programming, and immune effector processes. Importantly, at 3 days, we found six-fold more methylated CpG alterations than in the other stages. This is the first study to document epigenetic markers that persist through all three adipogenesis stages and their impact on gene expression, which could be a cellular metabolic memory involved in T2D. Our data provided evidence that, throughout the adipogenesis process, alterations occur in methylation that might impact mature adipocyte function, cause tissue malfunction, and potentially, lead to the development of T2D.

Contribution of uremic dysbiosis to insulin resistance and sarcopenia

BACKGROUND

Chronic kidney disease (CKD) leads to insulin resistance (IR) and sarcopenia, which are associated with a high mortality risk in CKD patients; however, their pathophysiologies remain unclear. Recently, alterations in gut microbiota have been reported to be associated with CKD. We aimed to determine whether uremic dysbiosis contributes to CKD-associated IR and sarcopenia.

METHODS

CKD was induced in specific pathogen-free mice via an adenine-containing diet; control animals were fed a normal diet. Fecal microbiota transplantation (FMT) was performed by oral gavage in healthy germ-free mice using cecal bacterial samples obtained from either control mice (control-FMT) or CKD mice (CKD-FMT). Vehicle mice were gavaged with sterile phosphate-buffered saline. Two weeks after inoculation, mice phenotypes, including IR and sarcopenia, were evaluated.

RESULTS

IR and sarcopenia were evident in CKD mice compared with control mice. These features were reproduced in CKD-FMT mice compared with control-FMT and vehicle mice with attenuated insulin-induced signal transduction and mitochondrial dysfunction in skeletal muscles. Intestinal tight junction protein expression and adipocyte sizes were lower in CKD-FMT mice than in control-FMT mice. Furthermore, CKD-FMT mice showed systemic microinflammation, increased concentrations of serum uremic solutes, fecal bacterial fermentation products and elevated lipid content in skeletal muscle. The differences in gut microbiota between CKD and control mice were mostly consistent between CKD-FMT and control-FMT mice.

CONCLUSIONS

Uremic dysbiosis induces IR and sarcopenia, leaky gut and lipodystrophy.

Accumulation of natriuretic peptides is associated with protein energy wasting and activation of browning in white adipose tissue in chronic kidney disease

Protein energy wasting is a common feature of patients with chronic kidney disease (CKD) and is associated with poor outcomes. Protein energy wasting and cachexia, a severe form of protein energy wasting, are characterized by increased resting energy expenditure but the underlying mechanisms are unclear. Browning corresponds to the activation of inducible brown adipocytes in white adipose tissue and occurs in states of cachexia associated with hypermetabolic disease such as cancer. Here we tested the hypothesis that CKD-associated protein energy wasting could result from browning activation as a direct effect of the uremic environment on adipocytes. In a murine model of CKD (5/6 nephrectomy), there was increased resting energy expenditure, expression of uncoupling protein 1 (a thermogenic protein uncoupling oxidative phosphorylation in mitochondria) and citrate synthase activity (a proxy of mitochondrial density in white adipose tissue). Mice with CKD also exhibited increased levels of atrial natriuretic peptide, a well known activator of browning. The incubation of primary adipose cells with plasma from patients receiving dialysis treatment and having signs of protein energy wasting led to an increased synthesis of uncoupling protein 1. Similarly, primary adipose cells exposed to atrial natriuretic peptide at concentrations relevant of CKD led to a significant increase of uncoupling protein 1 content. Thus, accumulation of cardiac natriuretic peptides during CKD could contribute to the browning of white adipose tissue and protein energy wasting.

Metabolic Abnormalities in Diabetes and Kidney Disease: Role of Uremic Toxins

PURPOSE OF REVIEW

Chronic kidney disease (CKD) is characterized by the accumulation of uremic retention solutes (URS) and is associated with perturbations of glucose homeostasis even in absence of diabetes. The underlying mechanisms of insulin resistance, β cell failure, and increase risk of diabetes in CKD, however, remain unclear. Metabolomic studies reported that some metabolites are similar in CKD and diabetic kidney disease (DKD) and contribute to the progression to end-stage renal disease. We attempted to discuss the mechanisms involved in the disruption of carbohydrate metabolism in CKD by focusing on the specific role of URS.

RECENT FINDINGS

Recent clinical data have demonstrated a defect of insulin secretion in CKD. Several studies highlighted the direct role of some URS (urea, trimethylamine N-oxide (TMAO), p-cresyl sulfate, 3-carboxylic acid 4-methyl-5-propyl-2-furan propionic (CMPF)) in glucose homeostasis abnormalities and diabetes incidence. Gut dysbiosis has been identified as a potential contributor to diabetes and to the production of URS. The complex interplay between the gut microbiota, kidney, pancreas β cell, and peripheral insulin target tissues has brought out new hypotheses for the pathogenesis of CKD and DKD. The characterization of intestinal microbiota and its associated metabolites are likely to fill fundamental knowledge gaps leading to innovative research, clinical trials, and new treatments for CKD and DKD.

The Role of Gut Microbiota and Diet on Uremic Retention Solutes Production in the Context of Chronic Kidney Disease

Uremic retention solutes (URS) are associated with cardiovascular complications and poor survival in chronic kidney disease. The better understanding of the origin of a certain number of these toxins enabled the development of new strategies to reduce their production. URS can be classified according to their origins (i.e., host, microbial, or exogenous). The discovery of the fundamental role that the intestinal microbiota plays in the production of many URS has reinstated nutrition at the heart of therapeutics to prevent the accumulation of URS and their deleterious effects. The intestinal microbiota is personalized and is strongly influenced by dietary habits, such as the quantity and the quality of dietary protein and fibers. Herein, this review out lines the role of intestinal microbiota on URS production and the recent discoveries on the effect of diet composition on the microbial balance in the host with a focus on the effect on URS production.

Altered microbiome in chronic kidney disease: systemic effects of gut-derived uremic toxins

In chronic kidney disease (CKD), influx of urea and other retained toxins exerts a change in the gut microbiome. There is decreased number of beneficial bacteria that produce short-chain fatty acids, an essential nutrient for the colonic epithelium, concurrent with an increase in bacteria that produce uremic toxins such as indoxyl sulphate, p-cresyl sulphate, and trimethylamine-N-oxide (TMAO). Due to intestinal wall inflammation and degradation of intercellular tight junctions, gut-derived uremic toxins translocate into the bloodstream and exert systemic effects. In this review, we discuss the evidence supporting a role for gut-derived uremic toxins in promoting multiorgan dysfunction via inflammatory, oxidative stress, and apoptosis pathways. End-organ effects include vascular calcification, kidney fibrosis, anemia, impaired immune system, adipocyte dysfunction with insulin resistance, and low turnover bone disease. Higher blood levels of gut-derived uremic toxins are associated with increased cardiovascular events and mortality in the CKD population. Clinical trials that have examined interventions to trap toxic products or reverse gut microbial dysbiosis via oral activated charcoal AST-120, prebiotics and probiotics have not shown impact on cardiovascular or survival outcomes but were limited by sample size and short trials. In summary, the gut microbiome is a major contributor to adverse cardiovascular outcomes and progression of CKD.

Aldosterone and Insulin Resistance: Vicious Combination in Patients on Maintenance Hemodialysis

Recently, we demonstrated that plasma aldosterone contributed to insulin resistance in chronic kidney disease. The aim of this study is the clinical impact of this relationship in hemodialysis patients. In a cross section study using a total of 128 hemodialysis patients, multiple regression analysis revealed that plasma aldosterone levels were independently associated with HOMA-IR, insulin resistance index. This association was found to be more stringent in diabetic patients than in non-diabetic patients. Aldosterone levels were associated with cardiac hypertrophy and carotid artery stenosis. HOMA-IR was associated with cardiac hypertrophy. The patients whose aldosterone and HOMA-IR were above the top tertile of each parameter in this cohort showed more severe cardiac hypertrophy and lower contractile function as compared with the patients whose aldosterone levels and HOMA-IR are below the lowest tertile of each parameter. In conclusion, in hemodialysis patients, aldosterone levels and insulin resistance are closely interrelated and the constellation of the two is related to severe cardiovascular tissue damages.

Differential expression of sirtuin 2 and adipocyte maturation restriction: an adaptation process during hypoxia in fish

Sirtuins have received widespread attention due to their diverse physiological role in metabolism. Among sirtuins, SIRT2 is more abundant in adipocytes and exerts effects on adipocyte differentiation, a process which involves conversion of preadipocytes to mature adipocytes orchestrated by adipokines and adipogenic transcription factors. Grey mullet (Mugil cephalus) was chosen as a study organism due to its excellent service as a biomonitor. Adipocytes isolated from natural field conditions were termed as field-hypoxic (Ennore) and -normoxic (Kovalam) based on dissolved oxygen (DO) level in the estuary. A previous study portrayed the hypoxic instance of Ennore estuary (low DO) and grey mullet [HIF1α in adipocytes, brain endothelial cell (EC) and hepatocytes] inhabiting this estuary ( Padmini et al., 2016a, b; Padmini and Tharani, 2015). In this context, fish adipocytes of both conditions were subjected to in vitro hypoxia for 1 h (in the pre/trigassed incubator with the supply of 1% O₂; 94% N₂; 5% CO₂) and were analysed for the expression of adipokines, adipogenic transcription factors and anti-adipogenic markers in fish adipocytes. Elevation of asymmetric dimethylarginine (ADMA), TNFα and leptin along with decreased adiponectin, adipogenic transcription factors and altering sirtuins were observed in test adipocytes and in control adipocytes on in vitro hypoxia. This suggests that adipocytes may follow internal caloric restriction as portrayed from cytomorphological/ultrastructural analysis, limiting adipocyte maturation process, one of the adaptive mechanisms triggered by adipocyte of fish surviving in Ennore estuary. Prolonged exposure to hypoxia (test on in vitro hypoxia for 1 h) showed a drastic alteration in these components leading to both structural and biological fluctuation when compared to limited hypoxic condition (field-hypoxic and control on in vitro hypoxia). Our study concludes that hypoxia may serve as the chief molecular cue in eliciting adipocyte maturation restriction though metabolic reprogramming and it also shows the significance of adipocyte maturation restriction in imparting survival mechanism.

Summary: Adipocyte maturation restriction is tightly regulated by SIRT2 activation which downregulates preadipocytes from the maturation process as adaptation strategy in fish surviving in the polluted (hypoxic) environment.

Chronic kidney disease promotes chronic inflammation in visceral white adipose tissue

White adipose tissue plays an important role in the development of metabolic disturbance, which is a common feature in patients with chronic kidney disease (CKD). The effect of CKD on white adipose tissue remains poorly appreciated. Here, we evaluated the inflammatory potential of visceral white adipose tissue in a rat model of CKD. The results showed that production of proinflammatory cytokines and infiltration of macrophage in the tissue were increased significantly in CKD rats compared with sham rats. Moreover, the primary adipocytes and stromal vascular fraction under the condition of CKD could trigger the inflammatory response in each other. Free fatty acid induced robust inflammatory response in ex vivo peritoneal-derived macrophages from CKD rats, which was associated with reduced activity of silent information regulator T1 (SIRT1). Improvement of SIRT1 activity by an activator could alleviate free fatty acid-induced inflammatory response in the macrophages and inflammation in the white adipose tissue. Moreover, oxidative stress occurred in the tissue and linked with the reduced activity of SIRT1 in macrophages and enhanced release of free fatty acid in the tissue. We thus identified CKD as a risk factor for chronic inflammation in white adipose tissue. These observations might open up new therapeutic strategies for metabolic disturbance in CKD via the modulation of adipose tissue-related pathways.

Selection of Suitable Reference Genes for Quantitative Real-Time PCR Normalization in Three Types of Rat Adipose Tissue

Quantitative real-time PCR (qRT-PCR) is the most classical technique in the field of gene expression study. This method requires an appropriate reference gene to normalize mRNA levels. In this study, the expression stability of four frequently-used reference genes in epididymal white adipose tissue (eWAT), inguinal beige adipose tissue (iBeAT) and brown adipose tissue (BAT) from obese and lean rats were evaluated by geNorm, NormFinder and BestKeeper. Based on the Minimum Information for Publication of Quantitative Real-Time PCR Experiments (MIQE) guidelines, the two most stable reference genes were recommended in each type of adipose tissue. Two target genes were applied to test the stability of the reference genes. The geNorm and NormFinder results revealed that GAPDH and 36B4 exhibited the highest expression stabilities in eWAT, while 36B4 and β-actin had the highest expression stabilities in iBeAT and BAT. According to the results of the BestKeeper analysis, 36B4 was the most stable gene in eWAT, iBeAT and BAT, in terms of the coefficient of variance. In terms of the coefficient of correlation, GAPDH, 36B4 and β-actin were the most stable genes in eWAT, iBeAT and BAT, respectively. Additionally, expected results and statistical significance were obtained using a combination of two suitable reference genes for data normalization. In conclusion, 36B4 and GAPDH, in combination, are the best reference genes for eWAT, while 36B4 and β-actin are two most suitable reference genes for both iBeAT and BAT. We recommend using these reference genes accordingly.