Ectopic lipid accumulation: A potential cause for metabolic disturbances and a contributor to the alteration of kidney function

VEGF-B signaling impairs endothelial glucose transcytosis by decreasing membrane cholesterol content

Regulation of endothelial nutrient transport is poorly understood. Vascular endothelial growth factor B (VEGF‐B) signaling in endothelial cells promotes uptake and transcytosis of fatty acids from the bloodstream to the underlying tissue, advancing pathological lipid accumulation and lipotoxicity in diabetic complications. Here, we demonstrate that VEGF‐B limits endothelial glucose transport independent of fatty acid uptake. Specifically, VEGF‐B signaling impairs recycling of low‐density lipoprotein receptor (LDLR) to the plasma membrane, leading to reduced cholesterol uptake and membrane cholesterol loading. Reduced cholesterol levels in the membrane leads to a decrease in glucose transporter 1 (GLUT1)‐dependent endothelial glucose uptake. Inhibiting VEGF‐B in vivo reconstitutes membrane cholesterol levels and restores glucose uptake, which is of particular relevance for conditions involving insulin resistance and diabetic complications. In summary, our study reveals a mechanism whereby VEGF‐B regulates endothelial nutrient uptake and highlights the impact of membrane cholesterol for regulation of endothelial glucose transport.

Regulation of TFEB activity and its potential as a therapeutic target against kidney diseases

The transcription factor EB (TFEB) regulates the expression of target genes bearing the Coordinated Lysosomal Expression and Regulation (CLEAR) motif, thereby modulating autophagy and lysosomal biogenesis. Furthermore, TFEB can bind to the promoter of autophagy-associated genes and induce the formation of autophagosomes, autophagosome-lysosome fusion, and lysosomal cargo degradation. An increasing number of studies have shown that TFEB stimulates the intracellular clearance of pathogenic factors by enhancing autophagy and lysosomal function in multiple kidney diseases, such as cystinosis, acute kidney injury, and diabetic nephropathy. Taken together, this highlights the importance of developing novel therapeutic strategies against kidney diseases based on TFEB regulation. In this review, we present an overview of the current data on TFEB and its implication in kidney disease.

Recent Progress on Lipid Intake and Chronic Kidney Disease

The incidence of chronic kidney disease (CKD) is associated with major abnormalities in circulating lipoproteins and renal lipid metabolism. This article elaborates on the mechanisms of CKD and lipid uptake abnormalities. The viewpoint we supported is that lipid abnormalities directly cause CKD, resulting in forming a vicious cycle. On the theoretical and experiment fronts, this inference has been verified by elaborately elucidating the role of lipid intake and accumulation as well as their influences on CKD. Taken together, these findings suggest that further understanding of lipid metabolism in CKD may lead to novel therapeutic approaches.

Podocytes: The Role of Lysosomes in the Development of Nephrotic Syndrome

This commentary highlights the article by Li et al that links ceramide accumulation in podocytes to cellular damage and nephrotic syndrome.

Downregulation of PTEN promotes podocyte endocytosis of lipids aggravating obesity-related glomerulopathy

With the increasing prevalence of obesity in adults worldwide, the incidence of obesity-related glomerulopathy (ORG) has increased yearly, becoming one of the leading causes of end-stage renal disease. Studies have demonstrated significant correlations between hyperlipidemia and impaired renal function in patients with ORG, indicating that hyperlipidemia causes damage in kidney cells. In podocytes, the endocytosis of lipids triggers an intracellular oxidative stress response that disrupts cellular integrity, resulting in proteinuria and glomerular sclerosis. However, the specific molecular mechanisms through which podocytes endocytose lipids remain unclear. Here, we demonstrated the enhanced endocytosis of lipids by podocytes from patients with ORG. This response was associated with decreased expression of phosphatase and tensin homolog (PTEN). In vitro silencing of PTEN promoted the endocytosis of low-density lipoprotein in mouse podocytes. Conversely, overexpression of PTEN inhibited the endocytosis of lipoproteins in podocytes. PTEN directly dephosphorylates and activates the actin-depolymerizing factor cofilin-1, leading to depolymerization of filamentous actin (F-actin), which is necessary for endocytosis. Notably, inhibition of PTEN resulted in the phosphorylation and inactivation of cofilin-1, leading to F-actin formation that enhanced the endocytosis of lipoproteins in podocytes. When hyperlipidemia was induced in mice with podocyte-specific deletion of PTEN, these mice recapitulated the major pathophysiological features of ORG. Thus, PTEN downregulation in podocytes may contribute to the pathogenesis of ORG.

Effect of Sodium Glucose Cotransporter 2 Inhibitors on Renal Function in Patients with Nonalcoholic Fatty Liver Disease and Type 2 Diabetes in Japan

Sodium-glucose cotransporter-2 inhibitors (SGLT2I) have been reported to have renal-protective effects in patients with type 2 diabetes (T2DM). This a retrospective study aimed to evaluate the effect of SGLT2I on renal function in patients with nonalcoholic fatty liver disease (NAFLD) and T2DM. We analyzed 69 consecutive patients with a biopsy-proven NAFLD and T2DM with an estimated glomerular filtration rate (eGFR) >60 mL/min. Of these 69 patients, 22 received SGLT2I and 47 were treated without SGLT2I. Liver function and eGFR were analyzed at baseline and after three years. Body mass index, liver function and HbA1c improved significantly in both groups. In the total population, the median eGFR declined from 80.7 mL/min at the baseline to 74.9 mL/min at the end of follow-up. The median eGFR at the baseline/end of follow-up was 81.2/80.4 mL/min in patients treated with SGLT2I and 80.2/70.8 mL/min in patients treated without SGLT2I. Multivariate analysis identified an increased FIB-4 index with an odds ratio (OR) of 4.721, (p = 0.045) and SGLT2I treatment (OR 0.263, p = 0.033) as predictive factors for decreased eGFR. SGLT2I treatment has a protective effect on the renal function for NAFLD with T2DM. A long-term, randomized, controlled trial is warranted to confirm the renal protective effect of SGLT2I in NAFLD patients with T2DM.

Ipragliflozin Ameliorates Endoplasmic Reticulum Stress and Apoptosis through Preventing Ectopic Lipid Deposition in Renal Tubules

BACKGROUND

Chronic kidney disease (CKD) and non-alcoholic steatohepatitis (NASH) are major health burdens closely related to metabolic syndrome. A link between CKD and NASH has been assumed; however, the underlying mechanism is still unknown. Ectopic lipid deposition (ELD) in the hepatocyte results in endoplasmic reticulum (ER) stress, which plays an important role in the development of steatohepatitis. ELD is also assumed to play a role in the development of kidney injury. We aimed to investigate the role of ELD and ER stress in the development of CKD, and evaluate the efficacy of a sodium glucose cotransporter-2 inhibitor, ipragliflozin.

METHODS

Male FLS-ob/ob mice that closely imitate the pathophysiology of NASH were treated with vehicle or ipragliflozin. Metabolic characteristics, histology of the kidney, ER stress, and apoptotic signals were evaluated.

RESULTS

The serum triglyceride was significantly lower in mice treated with ipragliflozin. Ipragliflozin reduced ELD in renal tubules. Ipragliflozin also reduced the expression levels of GRP78 and CHOP, apoptotic cells, and interstitial fibrosis.

CONCLUSIONS

ELD induced kidney injury through ER stress. Ipragliflozin improved the pathogenesis of CKD by reducing ELD and ER stress in NASH-model mice. Our results suggest ipragliflozin has therapeutic effect on CKD in NASH.

FIB-4 Index and Diabetes Mellitus Are Associated with Chronic Kidney Disease in Japanese Patients with Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is associated with chronic kidney disease (CKD). The aim of this retrospective study was to determine the risk factors for progression of CKD in patients with biopsy-proven NAFLD including patatin-like phospholipase domain containing 3 (PNPLA3) polymorphism. A total of 344 patients with biopsy-proven NAFLD were enrolled consecutively in this study. Multivariate analysis identified males (odds ratio (OR) 5.46), age (per 1 year, OR 1.07), and FIB-4 index (≥1.30, OR 3.85) as factors associated with CKD. Of the 154 patients with a baseline estimated glomerular filtration rate (eGFR) ≥60 mL/min, 30 had a deterioration in CKD stage and 15 developed CKD after 3 years. Multivariate analysis identified diabetes mellitus (OR 2.44) as a risk factor for deterioration in CKD stage, while diabetes mellitus (OR 21.54) and baseline eGFR (per 1 mL/min OR 0.88) were risk factors for development of CKD. PNPLA3 did not affect the change in eGFR. In NAFLD patients, a high FIB-4 index was associated with CKD to increases in the index linked to reductions in eGFR. In order to prevent development of CKD, an appropriate therapy focusing on renal function is needed for NAFLD patients, especially those with diabetes.

Nonalcoholic fatty liver disease increases risk of incident advanced chronic kidney disease: a propensity-matched cohort study

BACKGROUND

As the prevalence of nonalcoholic fatty liver disease (NAFLD) escalates, understanding its potential impact on the development of chronic kidney disease (CKD) is needed.

OBJECTIVE

To determine the longitudinal association of NAFLD with the development of advanced CKD in the United States.

METHODS

A retrospective cohort analysis of the Truven Health MarketScan Database (2006-2015) was conducted. We used Cox proportional hazards models to compare the risk of developing CKD stages 3-5 in patients with NAFLD versus non-NAFLD, identified by ICD-9 codes, after 1:3 propensity score (PS) matching.

RESULTS

In a cohort of 262 619 newly diagnosed patients with NAFLD and 769 878 PS (1:3)-matched non-NAFLD patients, we identified 5766 and 8655 new advanced (stage 3-5) CKD cases, respectively. The crude CKD incidence rate was 8.2 and 5.5 per 1000 person-years in NAFLD and non-NAFLD groups, respectively. In multivariable Cox model, patients with NAFLD had a 41% increased risk of developing advanced CKD compared with non-NAFLD patients [adjusted hazard ratio (aHR), 1.41; 95% confidence interval (CI), 1.36-1.46]. In the sensitivity analysis adjusting for time-varying covariates after NAFLD diagnosis, NAFLD persisted as a significant CKD risk factor (aHR, 1.58; 95% CI, 1.52-1.66) and the association remained significant when stratified by age, gender and pre-existing comorbidities. The risk of CKD increased in NAFLD with compensated cirrhosis (aHR, 1.47; 95% CI, 1.36-1.59) and decompensated cirrhosis (aHR, 2.28; 95% CI, 2.12-2.46).

CONCLUSION

Nonalcoholic fatty liver disease was independently associated with an increased risk of advanced CKD development suggesting renal function screening and regular monitoring are needed in this population.

Flaxseed oil ameliorated high-fat-diet-induced bone loss in rats by promoting osteoblastic function in rat primary osteoblasts

Background

α-Linolenic acid (ALA) is a plant-derived omega-3 unsaturated fatty acid that is rich in flaxseed oil (FO). The effect of FO on bone health is controversial. This study aims to evaluate the effect of FO on bone damage induced by a high-fat diet (HFD) and to explore the possible mechanism.

Methods

Male Sprague-Dawley rats were fed a normal control diet (NC, 10% fat), FO diet (NY, 10% fat), HFD (60% fat), or HFD containing 10% FO (HY, 60% fat) for 22 weeks. Micro CT and three-point bending tests were conducted to evaluate bone microstructure and biomechanics. Serum was collected for the detection of ALP, P1NP, and CTX-1. Rat primary osteoblasts (OBs) were treated with different concentrations of ALA with or without palmitic acid (PA) treatment. The ALP activity, osteogenic-related gene and protein expression were measured.

Results

Rats in the HFD group displayed decreased biomechanical properties, such as maximum load, maximum fracture load, ultimate tensile strength, stiffness, energy absorption, and elastic modulus, compared with the NC group (p < 0.05). However, HY attenuated the HFD-induced decreases in bone biomechanical properties, including maximum load, maximum fracture load, and ultimate tensile strength (p < 0.05). Trabecular bone markers such as trabecular volume bone mineral density (Tb. vBMD), trabecular bone volume/total volume (Tb. BV/TV), trabecular number (Tb. N), trabecular thickness (Tb. Th) were decreased, trabecular separation (Tb. Sp) and the structure model index (SMI) were increased in the HFD group compared with the NC group, and all parameters were remarkably improved in the HY group compared to the HFD group (p < 0.05). However, cortical bone markers such as cortical volume bone mineral density (Ct. vBMD), cortical bone volume/total volume (Ct. BV/TV) and cortical bone thickness (Ct. Th) were not significantly different among all groups. Moreover, the serum bone formation markers ALP and P1NP were higher and the bone resorption marker CTX-1 was lower in the HY group compared with levels in the HFD group. Compared with the NC group, the NY group had no difference in the above indicators. In rat primary OBs, PA treatment significantly decreased ALP activity and osteogenic gene and protein (β-catenin, RUNX2, and osterix) expression, and ALA dose-dependently restored the inhibition induced by PA.

Conclusions

FO might be a potential therapeutic agent for HFD-induced bone loss, most likely by promoting osteogenesis.

Endoplasmic reticulum stress-induced iRhom2 up-regulation promotes macrophage-regulated cardiac inflammation and lipid deposition in high fat diet (HFD)-challenged mice: Intervention of fisetin and metformin

Endoplasmic reticulum stress (ERS) has been implicated in obesity-associated cardiac remodeling and dysfunction. Inactive rhomboid protein 2 (iRhom2), also known as Rhbdf2, is an inactive member of the rhomboid intramembrane proteinase family, playing an essential role in regulating inflammation. Nevertheless, the role of ERS-meditated iRhom2 pathway in metabolic stress-induced cardiomyopathy remains unknown. In the study, we showed that 4-PBA, as an essential ERS inhibitor, significantly alleviated high fat diet (HFD)-induced metabolic disorder and cardiac dysfunction in mice. Additionally, lipid deposition in heart tissues was prevented by 4-PBA in HFD-challenged mice. Moreover, 4-PBA blunted the expression of iRhom2, TACE, TNFR2 and phosphorylated NF-κB to prevent HFD-induced expression of inflammatory factors. Further, 4-PBA restrained HFD-triggered oxidative stress by promoting Nrf-2 signaling. Importantly, 4-PBA markedly suppressed cardiac ERS in HFD mice. The anti-inflammation, anti-ERS and anti-oxidant effects of 4-PBA were verified in palmitate (PAL)-incubated macrophages and cardiomyocytes. In addition, promoting ERS could obviously enhance iRhom2 signaling in vitro. Intriguingly, our data demonstrated that PAL-induced iRhom2 up-regulation apparently promoted macrophage to generate inflammatory factors that could promote cardiomyocyte inflammation and lipid accumulation. Finally, interventions by adding fisetin or metformin significantly abrogated metabolic stress-induced cardiomyopathy through the mechanisms mentioned above. In conclusion, this study provided a novel mechanism for metabolic stress-induced cardiomyopathy pathogenesis. Therapeutic strategy to restrain ROS/ERS/iRhom2 signaling pathway could be developed to prevent myocardial inflammation and lipid deposition, consequently alleviating obesity-induced cardiomyopathy.

Visceral adiposity index and lipid accumulation product as a predictor of type 2 diabetes mellitus: The Bogor cohort study of non-communicable diseases risk factors

OBJECTIVES

Lipid accumulation product (LAP) index and Visceral Adiposity Index (VAI) are simple calculations to measure fat accumulation and visceral fat respectively. We aim to study the use of LAP index and VAI as diagnostic parameter and predictor of T2DM.

METHODS

We analysed the baseline and longitudinal data from the Indonesian Ministry of Health Cohort Study of Non-communicable Diseases Risk Factors in West Java, comprising 846 men and 2437 women aged 25-65 years. At baseline, the odds ratio for the diagnosis of prediabetes and T2DM among subjects with high LAP Index and VAI was analysed using logistic regression analysis. In the longitudinal analysis, LAP index and VAI as predictor of prediabetes and T2DM was analysed with cox regression analysis.

RESULT

Worsening glycemia status was associated with an increased LAP index and VAI (p < 0.001). Subjects with high VAI had an increased OR of having T2DM in both men [OR, 95%CI, 2.29(1.15-4.56), p = 0.018] and women [1.95(1.49-2.54), p < 0.001)]. Association of high LAP with T2DM was found only in women [OR, 95%CI, 2.11(1.16-1.52), p < 0.001]. In terms of T2DM prediction, only women [RR, 95% CI, 2.59 (1.05-6.39), p = 0.038)], with high VAI had an increased risk of T2DM in the future. High LAP index was not associated with an in increased risk of T2DM in the future in both sexes.

CONCLUSION

High LAP index was associated with an increased risk of T2DM diagnosis in women but it could not predict the development of T2DM. High VAI was associated with an increased risk of T2DM diagnosis in both sexes, however, it could only predict the development of T2DM in women.

Sargassum fusiforme Fucoidan SP2 Extends the Lifespan of Drosophila melanogaster by Upregulating the Nrf2-Mediated Antioxidant Signaling Pathway

Damage accumulated in the genome and macromolecules is largely attributed to increased oxidative damage and a lack of damage repair in a cell, and this can eventually trigger the process of aging. Alleviating the extent of oxidative damage is therefore considered as a potential way to promote longevity. SFPS, a heteropolysaccharide extracted from the brown alga Sargassum fusiforme, has previously been shown to alleviate oxidative damage during the aging process in mice, but whether SFPS could extend the lifespan of an organism was not demonstrated. Furthermore, the precise component within SFPS that is responsible for the antioxidant activity and the underlying mechanism of such activity was also not resolved. In this study, SP2, a fucoidan derived from SFPS, was shown to exhibit strong antioxidant activity as measured by in vitro radical-scavenging assays. SP2 also improved the survival rate of D. melanogaster subjected to oxidative stress. The flies that were fed with a diet containing SP2 from the time of eclosion displayed significant enhancement in lifespan and reduced accumulation of triglyceride at the old-age stage. In addition, SP2 markedly improved the activities of the antioxidant enzymes, superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) and reduced the contents of the malondialdehyde (MDA) and oxidized glutathione (GSSG) in old flies. Furthermore, SP2 also upregulated the expression levels of the nuclear factor-erythroid-2-like 2 (nfe2l2 or nrf2) and its downstream target genes, accompanied by a dramatic reduction in the expression of kelch-like ECH-associated protein 1 (keap1, a canonical inhibitor of the Nrf2) in old flies. Additional support linking the crucial role of the Nrf2/ARE pathway to the antioxidant effect of SP2 was the relatively high survival rate under heat stress for D. melanogaster individuals receiving SP2 supplement, an effect that was abolished by the inclusion of inhibitors specific for the Nrf2/ARE pathway. Collectively, the results indicated that SP2, a S. fusiforme fucoidan, could promote longevity in D. melanogaster by enhancing the Nrf2-mediated antioxidant signaling pathway during the aging process.

Filbertone Ameliorates Adiposity in Mice Fed a High-Fat Diet via Activation of cAMP Signaling

The aim of this research was to estimate the preventive effects of filbertone, the main flavor compound in hazelnuts, on lipid accumulation in the adipose tissue of mice fed a high-fat diet (HFD) and to reveal the underlying molecular mechanisms. Male C57BL/6N mice were fed chow, a HFD, or a 0.025% filbertone-supplemented HFD for 14 weeks. We found that filbertone supplementation resulted in significant reductions in body weight gain and lipid accumulation in adipose tissue, with parallel improvements in plasma lipid levels (triglycerides, total cholesterol, and free fatty acids) and proinflammatory cytokines (interleukin 6 (IL-6) and tumor necrosis factor alpha (TNF-α)). Molecular analysis revealed that filbertone treatment led to reprogramming of metabolic signatures in the cyclic adenosine monophosphate (cAMP) pathway. Filbertone supplementation significantly increased the cAMP level and increased downstream protein kinase A catalytic subunit (PKA) signaling in mouse adipose tissue. The mRNA level of adipogenesis-related genes was downregulated in the adipose tissue of filbertone-fed mice compared to control mice fed the HFD alone. Furthermore, filbertone treatment elevated the expression of thermogenic genes in mouse adipose tissue. Filbertone reduced intracellular lipid accumulation and increased the oxygen consumption rate in 3T3-L1 cells and these filbertone-induced changes were abrogated by the adenylate cyclases (ADCY) inhibitor. Taken together, our results suggest that the beneficial effects of filbertone on lipid accumulation may be associated with the activation of cAMP signaling.

Role of TFEB in autophagic modulation of ischemia reperfusion injury in mice kidney and protection by urolithin A

Kidney ischemia reperfusion injury (IRI) is an acute kidney injury associated with high number of mortality. We have examined the molecular mechanism and found that oxidative stress and hypoxia leads to induction of autophagy. In IRI induced autophagy, TFEB translocated to nucleus in response to IRI and induced a number of target genes of Coordinated Lysosomal Expression and Regulation (CLEAR) network. Real-time PCR analyses result showed IRI dependent increase in mRNA level to lysosomal hydrolases (Ctsa, Psap), lysosomal membranes (Lamp1), lysosomal acidification (Atp6ap1) non-lysosomal proteins involved in lysosomal biogenesis (M6pr, Nagpa) and autophagy (Becn1, VPS11). Overall, both lysosomal biogenesis and autophagy pathways were induced. Two key players of TFEB dependent proteins in autophagy, LAMP1 and BECN1 were verified by protein analyses. Pretreatment with urolithin A promoted autophagy and attenuated renal injury in kidney IRI and thus inverse relationship existed between TFEB-CLEAR pathway and kidney injury. Urolithin A also attenuated IRI induced pro-inflammatory cytokines TNFα, IL1β, MIP1α and MIP2 mRNA and associated kidney injury. Overall, our results explored the understanding of autophagy and CLEAR network to kidney IRI and those insights may help to develop new therapeutic strategies to protect against IRI.

Post-weaning Exposure to High-Fat Diet Induces Kidney Lipid Accumulation and Function Impairment in Adult Rats

Aim: We investigated the kidney morphofunctional consequences of high-fat diet intake since post-weaning in adult rats.

Main Methods: Male Wistar rats were divided into two groups: ND (normal diet; n = 10) and HD (high-fat diet; n = 10). The high-fat diet was introduced post-weaned and animals were followed for 8 weeks.

Key Findings: HD group did not change body weight gain even though food consumption has decreased with no changes in caloric consumption. The HD group showed glucose intolerance and insulin resistance. The glomerular filtration rate (GFR) was decreased in vivo (ND: 2.8 ± 1.01; HD: 1.1 ± 0.14 ml/min) and in the isolated perfusion method (34% of decrease). Renal histological analysis showed a retraction in glomeruli and an increase in kidney lipid deposition (ND: 1.5 ± 0.17 HD: 5.9 ± 0.06%). Furthermore, the high-fat diet consumption increased the pro-inflammatory cytokines IL-6 (ND: 1,276 ± 203; HD: 1,982 ± 47 pg/mL/mg) and IL-1b (ND: 97 ± 12 HD: 133 ± 5 pg/mL/mg) without changing anti-inflammatory cytokine IL-10.

Significance: Our study provides evidence that high-fat diet consumption leads to renal lipid accumulation, increases inflammatory cytokines, induces glomeruli retraction, and renal dysfunction. These damages observed in the kidney could be associated with an increased risk to advanced CKD in adulthood suggesting that reduction of high-fat ingestion during an early period of life can prevent metabolic disturbances and renal lipotoxicity.

ER stress contributes to high-fat diet-induced decrease of thyroglobulin and hypothyroidism

Recent studies revealed the emerging role of excess uptake of lipids in the development of hypothyroidism. However, the underlying mechanism is largely unknown. We investigated the effect of high-fat diet (HFD) on thyroid function and the role of endoplasmic reticulum (ER) in HFD-induced hypothyroidism. Male Sprague-Dawley rats were fed with HFD or control diet for 18 wk. HFD rats showed an impaired thyroid function, with decreased thyroglobulin (Tg) level. We found the ER stress was triggered in HFD rat thyroid glands and palmitate-treated thyrocytes. Luminal swelling of ER in thyroid epithelial cells of HFD rats was also observed. The rate of Tg degradation increased in palmitate-treated thyrocytes. In addition, applying 4-phenyl butyric acid to alleviate ER stress in HFD rats improved the decrease of Tg and thyroid function. Withdrawal of the HFD improved thyroid function . In conclusion, we demonstrate that ER stress mediates the HFD-induced hypothyroidism, probably by impairing the production of Tg, and attenuation of ER stress improves thyroid function. Our study provides the understanding of how HFD induces hypothyroidism.

Disulfide-bond A oxidoreductase-like protein protects against ectopic fat deposition and lipid-related kidney damage in diabetic nephropathy

Ectopic fat deposition (EFD) in the kidney has been shown to play a causal role in diabetic nephropathy; however, the mechanism underlying EFD remains elusive. By transcriptome analysis, we found decreased expression levels of disulfide-bond A oxidoreductase-like protein (DsbA-L) in the kidneys of diabetic mice (induced by high-fat diet plus Streptozotocin) compared with control mice. Increased expression of adipocyte differentiation-related protein and abnormal levels of collagen I, fibronectin, and phosphorylated 5'AMP-activated kinase (p-AMPK), adipose triglyceride lipase (p-ATGL), and HMG-CoA reductase (p-HMGCR) were also observed in diabetic mice. These alterations were accompanied by deposition of lipid droplets in the kidney, and were more pronounced in diabetic DsbA-L knockout mice. In vitro, overexpression of DsbA-L ameliorated high glucose-induced intracellular lipid droplet deposition in a human proximal tubular cell line, and DsbA-L siRNA aggravated lipid droplet deposition and reduced the levels of p-AMPK, p-ATGL, and p-HMGCR. High glucose and palmitic acid treatment enhanced the expression of interleukin-1β and interleukin-18; these enhancements were further increased after treatment with DsbA-L siRNA but alleviated by co-treatment with an AMPK activator. In kidney biopsy tissue from patients with diabetic nephropathy, DsbA-L expression was negatively correlated with EFD and tubular damage. Collectively, these results suggest that DsbA-L has a protective role against EFD and lipid-related kidney damage in diabetic nephropathy. Activation of the AMPK pathway is a potential mechanism underlying DsbA-L action in the kidney.

The Effect of Lipotoxicity on Renal Dysfunction in a Nonobese Rat Model of Metabolic Syndrome: A Urinary Proteomic Approach

INTRODUCTION

The development of metabolic syndrome-associated renal dysfunction is exacerbated by a number of factors including dyslipidemia, ectopic deposition of lipids and their toxic metabolites, impairment of lipid metabolism, and insulin resistance. Renal dysfunction is also affected by the production of proinflammatory and profibrotic factors secreted from adipose tissue, which can in turn directly impair kidney cells and potentiate insulin resistance. In this study, we investigated the manifestation of renal lipid accumulation and its effect on renal dysfunction in a model of metabolic syndrome-the hereditary hypertriglyceridemic rat (HHTg)-by assessing microalbuminuria and targeted urinary proteomics. Male Wistar control rats and HHTg rats were fed a standard diet and observed over the course of ageing at 3, 12, and 20 months of age.

RESULTS

Chronically elevated levels of triglycerides in HHTg rats were associated with increased levels of NEFA during OGTT and over a period of 24 hours (+80%, P < 0.01). HHTg animals exhibited qualitative changes in NEFA fatty acid composition, represented by an increased proportion of saturated fatty acids (P < 0.05) and a decreased proportion of n-3 PUFA (P < 0.01). Ectopic lipid deposition in the kidneys of HHTg rats-triglycerides (+30%) and cholesterol (+10%)-was associated with markedly elevated microalbuminuria as ageing increased, despite the absence of microalbuminuria at the young age of 3 months in these animals. According to targeted proteomic analysis, 3-month-old HHTg rats (in comparison to age-matched controls) exhibited increased urinary secretion of proinflammatory parameters (MCP-1, IL-6, IL-8, P < 0.01) and decreased urinary secretion of epidermal growth factor (EGF, P < 0.01) before manifestation of microalbuminuria. Elevation in the urinary secretion of inflammatory cytokines can be affected by increased relative expression of MCP-1 in the renal cortex (P < 0.05).

CONCLUSIONS

Our results confirm dyslipidemia and ectopic lipid accumulation to be key contributors in the development of metabolic syndrome-associated renal dysfunction. Assessing urinary secretion of proinflammatory cytokines and epidermal growth factor can help in detecting early development of metabolic syndrome-associated renal dysfunction.

Ectopic lipid accumulation: potential role in tubular injury and inflammation in diabetic kidney disease

Emerging studies suggest that lipid accumulates in the kidneys during diabetic kidney disease (DKD). However, the correlation between ectopic lipid accumulation with tubular damage has not been thoroughly elucidated to date. Using Oil Red staining, lipid accumulation was observed in the kidneys of type 2 DKD patients (classes II-III) and db/db mice compared with the control and was predominantly located in the proximal tubular compartment. Immunohistochemistry (IHC) staining showed that the intensity of adipose differentiation related protein (ADRP) and sterol regulatory element binding protein-1 (SREBP-1) was clearly up-regulated, which was positively correlated with the tubulointerstitial damage score and inflammation. Furthermore, the urine ADRP content significantly increased in DKD patients compared with the control, which positively correlated with abnormal lipid metabolism, serum creatinine, urine N-acetyl-β-glucosaminidase (NAG), albumin excretion (albumin-to-creatinine ratio (ACR)), and tumor necrosis factor-α (TNF-α) expression. However, there was no significant difference observed in plasma ADRP levels. In addition, the expression of SREBP-1 protein was dramatically increased in peripheral blood mononuclear cells (PBMCs) isolated from DKD patients, which was also tightly correlated with urine NAG, ACR, and TNF-α levels. In vitro studies demonstrated increased ADRP and SREBP-1 expression accompanied by lipid accumulation in HK-2 cells cultured in high glucose (HG). HG induced high levels of TNF-α expression, which was partially blocked by transfection of ADRP siRNA or SREBP-1 siRNA. These data indicated that ADRP and SREBP-1 are crucial factors that mediate lipid accumulation with tubular damage and inflammation in DKD, and ectopic lipid accumulation may serve as a novel therapeutic target for amelioration of tubular injury in DKD.

A new type of familial partial lipodystrophy: distinctive fat distribution and proteinuria

PURPOSE

To describe an interesting subtype of familial partial lipodystrophy (FPLD).

METHODS

The phenotype of this distinctive FPLD subtype was studied in three Turkish female siblings.

RESULTS

Mutation testing was negative for the genes associated with lipodystrophy syndromes. In MRI studies, fat loss was prominent in the posterior aspects of the proximal lower limbs, whilst some fat was preserved in the anterior, medial and lateral aspects. Remarkably, fat tissue was preserved in the distal part of the limbs. Local fat accumulation was observed in the mons pubis area. Asymmetrical fat loss was also remarkable in the upper extremities. All three patients had severe insulin resistance associated with diabetes mellitus, acanthosis nigricans, hypertriglyceridemia and hepatic steatosis. Abnormal amounts of proteinuria were detected in all three subjects. Renal biopsy showed mild tubular atrophy, interstitial fibrosis, irregular thickening and wrinkling of glomerular basal membranes, small areas of segmental sclerosis and pedicel effacement.

CONCLUSIONS

We reported a form of FPLD characterized by a striking pattern of highly selective partial fat loss and proteinuria.

What we need to know about lipid-associated injury in case of renal ischemia-reperfusion

Renal segmental metabolism is reflected by the complex distribution of the main energy pathways along the nephron, with fatty acid oxidation preferentially used in the cortex area. Ischemia/reperfusion injury (IRI) is due to the restriction of renal blood flow, rapidly leading to a metabolic switch toward anaerobic conditions. Subsequent unbalance between energy demand and oxygen/nutrient delivery compromises kidney cell functions, resulting in a complex inflammatory cascade including the production of reactive oxygen species (ROS). Renal IRI especially involves lipid accumulation. Lipid peroxidation is one of the major events of ROS-associated tissue injury. Here, we briefly review the current knowledge of renal cell lipid metabolism in normal and ischemic conditions. Next, we focus on renal lipid-associated injury, with emphasis on its mechanisms and consequences during the course of IRI. Finally, we discuss preclinical observations aiming at preventing and/or attenuating lipid-associated IRI.

Adiponectin receptor agonist AdipoRon decreased ceramide, and lipotoxicity, and ameliorated diabetic nephropathy

BACKGROUND

Adiponectin is known to take part in the regulation of energy metabolism. AdipoRon, an orally-active synthetic adiponectin agonist, binds to both adiponectin receptors (AdipoR)1/R2 and ameliorates diabetic complications. Among the lipid metabolites, the ceramide subspecies of sphingolipids have been linked to features of lipotoxicity, including inflammation, cell death, and insulin resistance. We investigated the role of AdipoRon in the prevention and development of type 2 diabetic nephropathy.

METHODS

AdipoRon (30 mg/kg) was mixed into the standard chow diet and provided to db/db mice (db + AdipoRon, n = 8) and age-matched male db/m mice (dm + AdipoRon, n = 8) from 17 weeks of age for 4 weeks. Control db/db (db cont, n = 8) and db/m mice (dm cont, n = 8) were fed a normal diet of mouse chow.

RESULTS

AdipoRon-fed db/db mice showed a decreased amount of albuminuria and lipid accumulation in the kidney with no significant changes in serum adiponectin, glucose, and body weight. Restoring expression of adiponectin receptor-1 and -2 in the renal cortex was observed in db/db mice with AdipoRon administration. Consistent up-regulation of phospho-Thr¹⁷² AMP-dependent kinase (AMPK), peroxisome proliferative-activated receptor α (PPARα), phospho-Thr⁴⁷³ Akt, phospho-Ser⁷⁹Acetyl-CoA carboxylase (ACC), and phospho-Ser¹¹⁷⁷ endothelial NO synthase (eNOS), and down-regulation of protein phosphatase 2A (PP2A), sterol regulatory element-binding protein-1c (SREBP-1c), and inducible nitric oxide synthase (iNOS) were associated within the same group. AdipoRon lowered cellular ceramide levels by activation of acid ceramidase, which normalized ceramide to sphingosine-1 phosphate (S1P) ratio. In glomerular endothelial cells (GECs) and podocytes, AdipoRon treatment markedly decreased palmitate-induced lipotoxicity, which ultimately ameliorated oxidative stress and apoptosis.

CONCLUSIONS

AdipoRon may prevent lipotoxicity in the kidney particularly in both GECs and podocytes through an improvement in lipid metabolism, as shown by the ratio of ceramide to sphingosines, and further contribute to prevent deterioration of renal function, independent of the systemic effects of adiponectin. The reduction in oxidative stress and apoptosis by AdipoRon provides protection against renal damage, thereby ameliorating endothelial dysfunction in type 2 diabetic nephropathy.

Renal complications of lipodystrophy: A closer look at the natural history of kidney disease

OBJECTIVES

Lipodystrophy syndromes are a group of heterogeneous disorders characterized by adipose tissue loss. Proteinuria is a remarkable finding in previous reports.

STUDY DESIGN

In this multicentre study, prospective follow-up data were collected from 103 subjects with non-HIV-associated lipodystrophy registered in the Turkish Lipodystrophy Study Group database to study renal complications in treatment naïve patients with lipodystrophy.

METHODS

Main outcome measures included ascertainment of chronic kidney disease (CKD) by studying the level of proteinuria and the estimated glomerular filtration rate (eGFR). Kidney volume was measured. Percutaneous renal biopsies were performed in 9 patients.

RESULTS

Seventeen of 37 patients with generalized and 29 of 66 patients with partial lipodystrophy had CKD characterized by proteinuria, of those 12 progressed to renal failure subsequently. The onset of renal complications was significantly earlier in patients with generalized lipodystrophy. Patients with CKD were older and more insulin resistant and had worse metabolic control. Increased kidney volume was associated with poor metabolic control and suppressed leptin levels. Renal biopsies revealed thickening of glomerular basal membranes, mesangial matrix abnormalities, podocyte injury, focal segmental sclerosis, ischaemic changes and tubular abnormalities at various levels. Lipid vacuoles were visualized in electron microscopy images.

CONCLUSIONS

CKD is conspicuously frequent in patients with lipodystrophy which has an early onset. Renal involvement appears multifactorial. While poorly controlled diabetes caused by severe insulin resistance may drive the disease in some cases, inherent underlying genetic defects may also lead to cell autonomous mechanisms contributory to the pathogenesis of kidney disease.

Lipid Deposition in Kidney Diseases: Interplay Among Redox, Lipid Mediators, and Renal Impairment

Significance: The relationship between lipid disturbances and renal diseases has been studied for several decades, and it is well recognized that when the balance of renal lipid uptake, synthesis, oxidation, and outflow is disrupted, lipids will undergo oxidation, be sequestrated as lipid droplets, generate toxic metabolites, and cause nephrotoxicity in diverse renal diseases. Recent Advances: During renal disorders, redox signaling is a pivotal event promoting or resulting from lipid disorders. Accordingly, a vicious cycle of lipid redox dysregulation could be developed, accelerating the renal damage. Critical Issues: The aim of this concise review is to introduce the connection among redox, lipid abnormalities and kidney damage in various conditions. And we summarized current understanding of the lipid redox loop implicated in acute kidney injury, chronic kidney disease, metabolic abnormalities, aging, and genetic pitfalls. Future Directions: Despite recent advances, further investigations are required to clarify the complicated molecular and regulatory mechanisms among redox, lipid mediators and renal disorders. Moreover, exploring an ideal target for potential therapies should be discussed and studied in future. Antioxid. Redox Signal. 28, 1027-1043.

Thyroid hormone status in Ghanaian patients with chronic kidney disease

Introduction

There is limited data on the prevalence of thyroid dysfunction in Ghanaian individuals with chronic kidney disease (CKD). Studies exploring the effect of thyroid hormones on renal function decline are also scanty. Unrecognized thyroid dysfunction in CKD may increase the burden of adverse health outcomes. The aim of this study was to determine thyroid hormone status and lipid profiles in patients with CKD attending the Renal Unit of the Korle-Bu Teaching Hospital.

Methods

60 clinically euthyroid patients with CKD, and 65 clinically euthyroid subjects without CKD were recruited for this study. Estimation of effective glomerular filtration rate (eGFR) was done using the 4-variable Modification of Diet in Renal Disease (MDRD) formula with subsequent staging of CKD (stages 2-4). Collected venous blood samples from all study participants were analyzed for creatinine, free triiodothyronine (FT3), free thyroxine (FT4), thyroid stimulating hormone (TSH), total cholesterol (TC), high density lipoprotein (HDL) cholesterol, low density lipoprotein (LDL) and triglycerides (TG).

Results

Levels of TC, HDL, LDL, and TSH levels did not differ significantly between the two study groups. However, TG, VLDL, FT3 and FT4 levels were significantly higher in CKD patients than in the control group. TC, TG, HDL, LDL, VLDL and TSH levels were not significantly different between stages of CKD in study subjects, although FT4 and FT3 levels were significantly different between all stages of CKD.

Conclusion

Higher levels of FT3 and FT4 but not TSH, are associated with the incidence of CKD and eGFR decline in Ghanaian CKD patients.

Metabolic imaging of fatty kidney in diabesity: validation and dietary intervention

Background

Obesity and type 2 diabetes have not only been linked to fatty liver, but also to fatty kidney and chronic kidney disease. Since non-invasive tools are lacking to study fatty kidney in clinical studies, we explored agreement between proton magnetic resonance spectroscopy (1H-MRS) and enzymatic assessment of renal triglyceride content (without and with dietary intervention). We further studied the correlation between fatty kidney and fatty liver.

Methods

Triglyceride content in the renal cortex was measured by 1H-MRS on a 7-Tesla scanner in 27 pigs, among which 15 minipigs had been randomized to a 7-month control diet, cafeteria diet (CAF) or CAF with low-dose streptozocin (CAF-S) to induce insulin-independent diabetes. Renal biopsies were taken from corresponding MRS-voxel locations. Additionally, liver biopsies were taken and triglyceride content in all biopsies was measured by enzymatic assay.

Results

Renal triglyceride content measured by 1H-MRS and enzymatic assay correlated positively (r = 0.86, P < 0.0001). Compared with control diet-fed minipigs, renal triglyceride content was higher in CAF-S-fed minipigs (137 ± 51 nmol/mg protein, mean ± standard error of the mean, P < 0.05), but not in CAF-fed minipigs (60 ± 10 nmol/mg protein) compared with controls (40 ± 6 nmol/mg protein). Triglyceride contents in liver and kidney biopsies were strongly correlated (r = 0.97, P < 0.001).

Conclusions

Non-invasive measurement of renal triglyceride content by 1H-MRS closely predicts triglyceride content as measured enzymatically in biopsies, and fatty kidney appears to develop parallel to fatty liver. 1H-MRS may be a valuable tool to explore the role of fatty kidney in obesity and type 2 diabetic nephropathy in humans in vivo.

Development of chronic kidney disease in patients with non-alcoholic fatty liver disease: A cohort study

BACKGROUND & AIMS

Non-alcoholic fatty liver disease (NAFLD) has been associated with chronic kidney disease (CKD), but cohort studies are limited. We investigated the longitudinal association of NAFLD and its severity with the development of CKD.

METHODS

We performed a retrospective cohort study of 41,430 adult men and women (average age, 48.9y) without CKD at baseline who underwent repeated health check-up examinations from January 1, 2003, through December 31, 2013. NAFLD status was assessed by ultrasonography, and NAFLD severity was assessed by the NAFLD fibrosis score (NFS).

RESULTS

The outcome was an incident CKD, defined as an estimated glomerular filtration rate less than 60ml/min/1.73m². During 200,790 person-years of follow-up (median follow-up of 4.15years), we identified 691 incident CKD cases. The multivariable-adjusted hazard ratio for CKD comparing participants with and without NAFLD was 1.22 (95% confidence interval [CI] 1.04-1.43). The risk of CKD increased progressively with increased NAFLD severity. The multivariable-adjusted hazard ratios for CKD comparing participants with NFS <-1.455 and those with NFS ≥-1.455 to participants without NAFLD were 1.09 (95% CI 0.91-1.32) and 1.58 (95% CI 1.30-1.92), respectively. The association was consistent across clinically relevant subgroups.

CONCLUSION

In a large cohort of adult men and women without CKD, NAFLD was associated with an increased risk of CKD development. NAFLD may adversely affect renal function and patients may need to be carefully monitored for an increased risk of CKD.

LAY SUMMARY

The presence of fatty liver is associated with the future decline of renal function. Thus, fatty liver patients need to be monitored regularly for renal function.

Hepatic Steatosis Accompanies Pulmonary Alveolar Proteinosis

Maintenance of tissue-specific organ lipid compositions characterizes mammalian lipid homeostasis. The lungs and liver synthesize mixed phosphatidylcholine (PC) molecular species that are subsequently tailored for function. The lungs progressively enrich disaturated PC directed to lamellar body surfactant stores before secretion. The liver accumulates polyunsaturated PC directed to very-low-density lipoprotein assembly and secretion, or to triglyceride stores. In each tissue, selective PC species enrichment mechanisms lie at the heart of effective homeostasis. We tested for potential coordination between these spatially separated but possibly complementary phenomena under a major derangement of lung PC metabolism, pulmonary alveolar proteinosis (PAP), which overwhelms homeostasis and leads to excessive surfactant accumulation. Using static and dynamic lipidomics techniques, we compared (1) tissue PC compositions and contents, and (2) in lungs, the absolute rates of synthesis in both control mice and the granulocyte-macrophage colony-stimulating factor knockout model of PAP. Significant disaturated PC accumulation in bronchoalveolar lavage fluid, alveolar macrophage, and lavaged lung tissue occurred alongside increased PC synthesis, consistent with reported defects in alveolar macrophage surfactant turnover. However, microscopy using oil red O staining, coherent anti-Stokes Raman scattering, second harmonic generation, and transmission electron microscopy also revealed neutral-lipid droplet accumulations in alveolar lipofibroblasts of granular macrophage colony-stimulating factor knockout animals, suggesting that lipid homeostasis deficits extend beyond alveolar macrophages. PAP plasma PC composition was significantly polyunsaturated fatty acid enriched, but the content was unchanged and hepatic polyunsaturated fatty acid-enriched PC content increased by 50% with an accompanying micro/macrovesicular steatosis and a fibrotic damage pattern consistent with nonalcoholic fatty liver disease. These data suggest a hepatopulmonary axis of PC metabolism coordination, with wider implications for understanding and managing lipid pathologies in which compromise of one organ has unexpected consequences for another.

Ameliorative Effect of Ecklonia cava Polyphenol Extract on Renal Inflammation Associated with Aberrant Energy Metabolism and Oxidative Stress in High Fat Diet-Induced Obese Mice

Immoderate fat accumulation causes both oxidative stress and inflammation, which can induce kidney damage in obesity. Previously, Ecklonia cava has shown anti-inflammatory and antioxidative effects. Our group aimed to investigate whether E. cava polyphenol extract (ECPE) improves renal damage in high fat diet (HFD)-induced obese mice through regulation of not only energy metabolism but also oxidative stress and inflammation. After obesity induction by HFD, the mice were treated with different dosages of ECPE (100 or 500 mg/kg/day) by gavage for 12 weeks. ECPE treatment lowered the protein levels related to lipid accumulation (SREBP1c, ACC & FAS), inflammation (NLRP3 inflammasome, NFκB, MCP-1, TNF-α & CRP), and oxidative stress (Nrf2, HO-1, MnSOD, NQO1, GPx, 4-HNE and protein carbonyls) in HFD induced obese mice. Moreover, ECPE supplementation significantly up-regulated renal SIRT1, PGC-1α, and AMPK, which are associated with renal energy metabolism. Consequently, the results provide novel insights into the anti-inflammatory roles of ECPE in obesity-induced renal inflammation.

Hepatocyte Growth Factor Prevented High-Fat Diet-Induced Obesity and Improved Insulin Resistance in Mice

Obesity and its associated chronic inflammation in adipose tissue initiate insulin resistance, which is related to several pathologies including hypertension and atherosclerosis. Previous reports demonstrated that circulating hepatocyte growth factor (HGF) level was associated with obesity and type 2 diabetes. However, its precise role in obesity and related-pathology is unclear. In this experiment, cardiac-specific over-expression of human HGF in mice (HGF-Tg mice) which showed 4–5 times higher serum HGF levels than wild-type mice were used. While body weight in wild-type mice fed with high fat diet (HFD) for 14 weeks was significantly increased accompanied with insulin resistance, HGF-Tg mice prevented body weight gain and insulin resistance. The accumulation of macrophages and elevated levels of inflammatory mediators in adipose tissue were significantly inhibited in HGF-Tg mice as compared to wild-type mice. The HFD-induced obesity in wild-type mice treated with HGF-neutralizing antibody showed an exacerbated response to the glucose tolerance test. These gain-of-function and loss-of-function studies demonstrated that the elevated HGF level induced by HFD have protective role against obesity and insulin resistance.

SGLT2 Protein Expression Is Increased in Human Diabetic Nephropathy: SGLT2 PROTEIN INHIBITION DECREASES RENAL LIPID ACCUMULATION, INFLAMMATION, AND THE DEVELOPMENT OF NEPHROPATHY IN DIABETIC MICE

There is very limited human renal sodium gradient-dependent glucose transporter protein (SGLT2) mRNA and protein expression data reported in the literature. The first aim of this study was to determine SGLT2 mRNA and protein levels in human and animal models of diabetic nephropathy. We have found that the expression of SGLT2 mRNA and protein is increased in renal biopsies from human subjects with diabetic nephropathy. This is in contrast to db-db mice that had no changes in renal SGLT2 protein expression. Furthermore, the effect of SGLT2 inhibition on renal lipid content and inflammation is not known. The second aim of this study was to determine the potential mechanisms of beneficial effects of SGLT2 inhibition in the progression of diabetic renal disease. We treated db/db mice with a selective SGLT2 inhibitor JNJ 39933673. We found that SGLT2 inhibition caused marked decreases in systolic blood pressure, kidney weight/body weight ratio, urinary albumin, and urinary thiobarbituric acid-reacting substances. SGLT2 inhibition prevented renal lipid accumulation via inhibition of carbohydrate-responsive element-binding protein-β, pyruvate kinase L, SCD-1, and DGAT1, key transcriptional factors and enzymes that mediate fatty acid and triglyceride synthesis. SGLT2 inhibition also prevented inflammation via inhibition of CD68 macrophage accumulation and expression of p65, TLR4, MCP-1, and osteopontin. These effects were associated with reduced mesangial expansion, accumulation of the extracellular matrix proteins fibronectin and type IV collagen, and loss of podocyte markers WT1 and synaptopodin, as determined by immunofluorescence microscopy. In summary, our study showed that SGLT2 inhibition modulates renal lipid metabolism and inflammation and prevents the development of nephropathy in db/db mice.

Rutin protects against aging-related metabolic dysfunction

Aging is a complex process which is accompanied by multiple related chronic diseases. Among them, metabolic dysfunction is one of the most important aging-related disorders. In the present study, we aimed to investigate the effect of rutin on aging-related metabolic dysfunction. We found that the increase of fasting blood glucose, insulin levels, blood pressure and HOMA-IR in aged rats was significantly inhibited by rutin. In addition, rutin improved glucose and insulin tolerance in aged rats, as reflected by decreased glucose level in IPGTT and IPITT test. Rutin treatment notably increased Akt and IRS-1 phosphorylation in the livers of old rats. The increase of inflammatory markers, such as IL-1β and TNFα, was prevented by the rutin administration. Moreover, in circulation and livers of old rats, rutin treatment significantly decreased the content of TG. Rutin also inhibited the increase of serum AST and ALT levels. Furthermore, rutin treatment markedly inhibited aging-related mitochondrial dysfunction, ER stress, and oxidative stress, as evidenced by increased oxygen consumption rate and activities of Na(+)/K(+)-ATPase and Ca2(+)-ATPase, decreased expression of ATF3 and GRP78, decreased level of MDA, increased content of GSH and enhanced activity of SOD in aged rats. We show that the administration of rutin could effectively improve aging-related metabolic dysfunction. The amelioration of inflammation, lipid accumulation, mitochondrial dysfunction, ER stress, and oxidative stress may be involved in the effect of rutin on aging-related metabolic dysfunction. These findings provide novel insights into the potential use of rutin in the intervention of aging and its related metabolic diseases.

Integration of ChREBP-Mediated Glucose Sensing into Whole Body Metabolism

Since glucose is the principal energy source for most cells, many organisms have evolved numerous and sophisticated mechanisms to sense glucose and respond to it appropriately. In this context, cloning of the carbohydrate responsive element binding protein has unraveled a critical molecular link between glucose metabolism and transcriptional reprogramming induced by glucose. In this review, we detail major findings that have advanced our knowledge of glucose sensing.

Extracts of Magnolia Species-Induced Prevention of Diabetic Complications: A Brief Review

Diabetic complications are the major cause of mortality for the patients with diabetes. Oxidative stress and inflammation have been recognized as important contributors for the development of many diabetic complications, such as diabetic nephropathy, hepatopathy, cardiomyopathy, and other cardiovascular diseases. Several studies have established the anti-inflammatory and oxidative roles of bioactive constituents in Magnolia bark, which has been widely used in the traditional herbal medicines in Chinese society. These findings have attracted various scientists to investigate the effect of bioactive constituents in Magnolia bark on diabetic complications. The aim of this review is to present a systematic overview of bioactive constituents in Magnolia bark that induce the prevention of obesity, hyperglycemia, hyperlipidemia, and diabetic complications, including cardiovascular, liver, and kidney.

Thioredoxin-interacting protein regulates lipid metabolism via Akt/mTOR pathway in diabetic kidney disease

Abnormal lipid metabolism contributes to the renal lipid accumulation, which is associated with diabetic kidney disease, but its precise mechanism remains unclear. The growing evidence demonstrates that thioredoxin-interacting protein is involved in regulating cellular glucose and lipid metabolism. Here, we investigated the effects of thioredoxin-interacting protein on lipid accumulation in diabetic kidney disease. In contrast to the diabetic wild-type mice, the physical and biochemical parameters were improved in the diabetic thioredoxin-interacting protein knockout mice. The increased renal lipid accumulation, expression of acetyl-CoA carboxylase, fatty acid synthase and sterol regulatory element binding protein-1, and phosphorylated Akt and mTOR associated with diabetes in wild-type mice was attenuated in diabetic thioredoxin-interacting protein knockout mice. Furthermore, thioredoxin-interacting protein knockout significantly increased the expression of peroxisome proliferator-activated receptor-α, acyl-coenzyme A oxidase 1 and carnitine palmitoyltransferaser 1 in diabetic kidneys. In vitro experiments, using HK-2 cells, revealed that knockdown of thioredoxin-interacting protein inhibited high glucose-mediated lipid accumulation, expression of acetyl-CoA carboxylase, fatty acid synthase and sterol regulatory element binding protein-1, as well as activation of Akt and mTOR. Moreover, knockdown of thioredoxin-interacting protein reversed high glucose-induced reduction of peroxisome proliferator-activated receptor-α, acyl-coenzyme A oxidase 1 and carnitine palmitoyltransferaser 1 expression in HK-2 cells. Importantly, blockade of Akt/mTOR signaling pathway with LY294002, a specific PI3K inhibitor, replicated these effects of thioredoxin-interacting protein silencing. Taken together, these data suggest that thioredoxin-interacting protein deficiency alleviates diabetic renal lipid accumulation through regulation of Akt/mTOR pathway, thioredoxin-interacting protein may be a potential therapeutic target for diabetic kidney disease.

Lauric acid-rich medium-chain triglycerides can substitute for other oils in cooking applications and may have limited pathogenicity

Recently, medium-chain triglycerides (MCTs) containing a large fraction of lauric acid (LA) (C12)-about 30%-have been introduced commercially for use in salad oils and in cooking applications. As compared to the long-chain fatty acids found in other cooking oils, the medium-chain fats in MCTs are far less likely to be stored in adipose tissue, do not give rise to 'ectopic fat' metabolites that promote insulin resistance and inflammation, and may be less likely to activate macrophages. When ingested, medium-chain fatty acids are rapidly oxidised in hepatic mitochondria; the resulting glut of acetyl-coenzyme A drives ketone body production and also provokes a thermogenic response. Hence, studies in animals and humans indicate that MCT ingestion is less obesogenic than comparable intakes of longer chain oils. Although LA tends to raise serum cholesterol, it has a more substantial impact on high density lipoprotein (HDL) than low density lipoprotein (LDL) in this regard, such that the ratio of total cholesterol to HDL cholesterol decreases. LA constitutes about 50% of the fatty acid content of coconut oil; south Asian and Oceanic societies which use coconut oil as their primary source of dietary fat tend to be at low cardiovascular risk. Since ketone bodies can exert neuroprotective effects, the moderate ketosis induced by regular MCT ingestion may have neuroprotective potential. As compared to traditional MCTs featuring C6-C10, laurate-rich MCTs are more feasible for use in moderate-temperature frying and tend to produce a lower but more sustained pattern of blood ketone elevation owing to the more gradual hepatic oxidation of ingested laurate.

Obesity-related glomerulopathy: clinical and pathologic characteristics and pathogenesis

The prevalence of obesity-related glomerulopathy is increasing in parallel with the worldwide obesity epidemic. Glomerular hypertrophy and adaptive focal segmental glomerulosclerosis define the condition pathologically. The glomerulus enlarges in response to obesity-induced increases in glomerular filtration rate, renal plasma flow, filtration fraction and tubular sodium reabsorption. Normal insulin/phosphatidylinositol 3-kinase/Akt and mTOR signalling are critical for podocyte hypertrophy and adaptation. Adipokines and ectopic lipid accumulation in the kidney promote insulin resistance of podocytes and maladaptive responses to cope with the mechanical forces of renal hyperfiltration. Although most patients have stable or slowly progressive proteinuria, up to one-third develop progressive renal failure and end-stage renal disease. Renin-angiotensin-aldosterone blockade is effective in the short-term but weight loss by hypocaloric diet or bariatric surgery has induced more consistent and dramatic antiproteinuric effects and reversal of hyperfiltration. Altered fatty acid and cholesterol metabolism are increasingly recognized as key mediators of renal lipid accumulation, inflammation, oxidative stress and fibrosis. Newer therapies directed to lipid metabolism, including SREBP antagonists, PPARα agonists, FXR and TGR5 agonists, and LXR agonists, hold therapeutic promise.

Protective Effects of Curcumin on Renal Oxidative Stress and Lipid Metabolism in a Rat Model of Type 2 Diabetic Nephropathy

PURPOSE

Diabetic nephropathy is a serious complication of type 2 diabetes mellitus, and delaying the development of diabetic nephropathy in patients with diabetes mellitus is very important. In this study, we investigated inflammation, oxidative stress, and lipid metabolism to assess whether curcumin ameliorates diabetic nephropathy.

MATERIALS AND METHODS

Animals were divided into three groups: Long-Evans-Tokushima-Otsuka rats for normal controls, Otsuka-Long-Evans-Tokushima Fatty (OLETF) rats for the diabetic group, and curcumin-treated (100 mg/kg/day) OLETF rats. We measured body and epididymal fat weights, and examined plasma glucose, adiponectin, and lipid profiles at 45 weeks. To confirm renal damage, we measured albumin-creatinine ratio, superoxide dismutase (SOD), and malondialdehyde (MDA) in urine samples. Glomerular basement membrane thickness and slit pore density were evaluated in the renal cortex tissue of rats. Furthermore, we conducted adenosine monophosphate-activated protein kinase (AMPK) signaling and oxidative stress-related nuclear factor (erythroid-derived 2)-like 2 (Nrf2) signaling to investigate mechanisms of lipotoxicity in kidneys.

RESULTS

Curcumin ameliorated albuminuria, pathophysiologic changes on the glomerulus, urinary MDA, and urinary SOD related with elevated Nrf2 signaling, as well as serum lipid-related index and ectopic lipid accumulation through activation of AMPK signaling.

CONCLUSION

Collectively, these findings indicate that curcumin exerts renoprotective effects by inhibiting renal lipid accumulation and oxidative stress through AMPK and Nrf2 signaling pathway.

Nonalcoholic fatty liver is not associated with incident chronic kidney disease: a large histology-based comparison with healthy individuals

BACKGROUND

Nonalcoholic steatohepatitis or fibrosis is associated with the increased prevalence of impaired kidney function. It is not known whether nonalcoholic fatty liver (NAFL), which is steatosis without inflammation or fibrosis, is associated with renal impairment as these individuals are not candidates for liver biopsy.

MATERIALS AND METHODS

The study group included all liver donors who underwent a preoperative liver biopsy for various reasons. NAFL was defined as more than 5% hepatocytes having steatosis and no changes of steatohepatitis and/or fibrosis. Individuals with NAFL were compared with individuals with normal liver histology. Estimated glomerular filtration rate was calculated with the Modification of Diet in Renal Disease and Chronic Kidney Disease Epidemiology Collaboration methods.

RESULTS

The mean age of the study group was 35±10.3 years and the mean BMI was 26±3.2 kg/m. A total of 187 adults having NAFL (80 men) were compared with 186 (88 men) individuals with normal liver histology (controls). Individuals with steatosis had significantly higher BMI (26.8±3.5 vs. 25.5±3.8 kg/m, P<0.001) and serum alanine transaminase levels (33.8±13.3 vs. 27.2±9.8 IU/l, P<0.000). There was no significant difference in the estimated glomerular filtration rate between the normal histology group and the NAFL group with Modification of Diet in Renal Disease (115±21.8 vs. 114.4±23.2 ml/min, P=0.803) and Chronic Kidney Disease Epidemiology Collaboration methods (113.6±14.8 vs. 113±14.7 ml/min, P=0.668). There was no significant difference as regards serum creatinine (0.73±0.16 vs. 0.74±0.16 mg%, P=0.536), proteinuria (P=0.121), diabetes (1 vs. 4, P=0.372), and hypertension (2 vs. 6, P=0.174) in individuals of both groups.

CONCLUSION

Presence of NAFL does not adversely affect renal function.

Imaging Mass Spectrometry Reveals Acyl-Chain- and Region-Specific Sphingolipid Metabolism in the Kidneys of Sphingomyelin Synthase 2-Deficient Mice

Obesity was reported to cause kidney injury by excessive accumulation of sphingolipids such as sphingomyelin and ceramide. Sphingomyelin synthase 2 (SMS2) is an important enzyme for hepatic sphingolipid homeostasis and its dysfunction is considered to result in fatty liver disease. The expression of SMS2 is also high in the kidneys. However, the contribution of SMS2 on renal sphingolipid metabolism remains unclear. Imaging mass spectrometry is a powerful tool to visualize the distribution and provide quantitative data on lipids in tissue sections. Thus, in this study, we analyzed the effects of SMS2 deficiency on the distribution and concentration of sphingomyelins in the liver and kidneys of mice fed with a normal-diet or a high-fat-diet using imaging mass spectrometry and liquid chromatography/electrospray ionization-tandem mass spectrometry. Our study revealed that high-fat-diet increased C18–C22 sphingomyelins, but decreased C24-sphingomyelins, in the liver and kidneys of wild-type mice. By contrast, SMS2 deficiency decreased C18–C24 sphingomyelins in the liver. Although a similar trend was observed in the whole-kidneys, the effects were minor. Interestingly, imaging mass spectrometry revealed that sphingomyelin localization was specific to each acyl-chain length in the kidneys. Further, SMS2 deficiency mainly decreased C22-sphingomyelin in the renal medulla and C24-sphingomyelins in the renal cortex. Thus, imaging mass spectrometry can provide visual assessment of the contribution of SMS2 on acyl-chain- and region-specific sphingomyelin metabolism in the kidneys.

Targeting fatty acid metabolism to improve glucose metabolism

Disturbances in fatty acid metabolism in adipose tissue, liver, skeletal muscle, gut and pancreas play an important role in the development of insulin resistance, impaired glucose metabolism and type 2 diabetes mellitus. Alterations in diet composition may contribute to prevent and/or reverse these disturbances through modulation of fatty acid metabolism. Besides an increased fat mass, adipose tissue dysfunction, characterized by an altered capacity to store lipids and an altered secretion of adipokines, may result in lipid overflow, systemic inflammation and excessive lipid accumulation in non-adipose tissues like liver, skeletal muscle and the pancreas. These impairments together promote the development of impaired glucose metabolism, insulin resistance and type 2 diabetes mellitus. Furthermore, intrinsic functional impairments in either of these organs may contribute to lipotoxicity and insulin resistance. The present review provides an overview of fatty acid metabolism-related pathways in adipose tissue, liver, skeletal muscle, pancreas and gut, which can be targeted by diet or food components, thereby improving glucose metabolism.

Thyroid function modifies the association between ratio of triglyceride to high-density lipoprotein cholesterol and renal function: a multicenter cross-sectional study

Hypothyroidism was confirmed to be associated with both dyslipidemia and renal dysfunction. However, the impact of thyroid function on the relationship between serum lipid levels and renal function has never been given sufficient attention. In this large-scale multicenter cross-sectional study, the ratio of triglyceride to high-density lipoprotein cholesterol (TG/HDL) and the prevalence of hypothyroidism in CKD subjects were significantly higher than those in non-CKD ones (P < 0.001). After adjustment for potential confounding factors, TG/HDL was shown to be significantly associated with serum Cr levels (β = 0.551; 95%CI, 0.394–0.708), and eGFR (β = −0.481; 95%CI, −0.731–−0.230). The risk for CKD was significantly increased as TG/HDL ratio was elevated (adjusted odds ratio = 1.20; 95%CI, 1.11–1.27). These significant associations were found among subjects with euthyroidism and hypothyroidism rather than hyperthyroidism. Furthermore, the associations between TG/HDL and Cr or CKD status were significantly greater in hypothyroidism than those in euthyroidism (P < 0.05). These results suggested that elevated TG/HDL ratio was associated with renal dysfunction; it exhibited a significantly stronger association with Cr and CKD in hypothyroidism than in euthyroidism. Therefore, more attention should be paid on lipid profile to prevent or delay the occurrence and progression of renal dysfunction, especially for those with hypothyroidism.

Obesity, insulin resistance and comorbidities? Mechanisms of association

Overall excess of fat, usually defined by the body mass index, is associated with metabolic (e.g. glucose intolerance, type 2 diabetes mellitus (T2DM), dyslipidemia) and non-metabolic disorders (e.g. neoplasias, polycystic ovary syndrome, non-alcoholic fat liver disease, glomerulopathy, bone fragility etc.). However, more than its total amount, the distribution of adipose tissue throughout the body is a better predictor of the risk to the development of those disorders. Fat accumulation in the abdominal area and in non-adipose tissue (ectopic fat), for example, is associated with increased risk to develop metabolic and non-metabolic derangements. On the other hand, observations suggest that individuals who present peripheral adiposity, characterized by large hip and thigh circumferences, have better glucose tolerance, reduced incidence of T2DM and of metabolic syndrome. Insulin resistance (IR) is one of the main culprits in the association between obesity, particularly visceral, and metabolic as well as non-metabolic diseases. In this review we will highlight the current pathophysiological and molecular mechanisms possibly involved in the link between increased VAT, ectopic fat, IR and comorbidities. We will also provide some insights in the identification of these abnormalities.

Lipotoxicity, a potential risk factor for the increasing prevalence of subclinical hypothyroidism?

CONTEXT

Subclinical hypothyroidism (SCH) is an important public health problem worldwide for its increasing prevalence and potential deleterious effects, whereas its etiology has not been fully elucidated. Lipotoxicity exerts extensive and serious impact on human health, but so far, the potential effect of lipotoxicity on thyroid is unclear.

OBJECTIVE

The objective of the study was to assess the association between serum triglyceride levels and the risk for SCH.

DESIGN, PARTICIPANTS, AND METHODS

We conducted a population-based case-control study. A total of 24 100 subjects with similar and stable iodine nutrition status were recruited from China. Cases of 5033 SCH patients were identified and equal controls were matched by age, gender, and region. Conditional logistic regression was used to analyze the association between serum triglyceride levels and risk for SCH.

RESULTS

Hypertriglyceridemia was associated with an approximately 35% increased risk for SCH in both men (odds ratio 1.325; 95% confidence interval 1.002-1.753) and women (odds ratio 1.397; 95% confidence interval 1.217-1.604), even after adjustment for potential confounders. Notably, the risk for SCH increased progressively following the elevation of serum triglyceride levels. Compared with individuals with serum triglyceride levels less than 0.97 mmol/L, the risk for SCH increased approximately 1.9-fold in men and 1.4-fold in women, respectively, when triglyceride levels were greater than 1.99 mmol/L.

CONCLUSION

Our findings suggested that hypertriglyceridemia was positively associated with the risk for SCH.

Fenofibrate pre-treatment suppressed inflammation by activating phosphoinositide 3 kinase/protein kinase B (PI3K/Akt) signaling in renal ischemia-reperfusion injury

The aim of this study was to investigate the possible beneficial effects of Fenofibrate on renal ischemia-reperfusion injury (IRI) in mice and its potential mechanism. IRI was induced by bilateral renal ischemia for 60 min followed by reperfusion for 24 h. Eighteen male C57BL/6 mice were randomly divided into three groups: sham-operated group (sham), IRI+saline group (IRI group), IRI+Fenofibrate (FEN) group. Normal saline or Fenofibrate (3 mg/kg) was intravenously injected 60 min before renal ischemia in IRI group and FEN group, respectively. Blood samples and renal tissues were collected at the end of reperfusion. The renal function, histopathologic changes, and the expression levels of pro-inflammatory cytokines [interleukin-8 (IL-8), tumor necrosis factor alpha (TNF-α) and IL-6] in serum and renal tissue homogenate were assessed. Moreover, the effects of Fenofibrate on activating phosphoinositide 3 kinase/protein kinase B (PI3K/Akt) signaling and peroxisome proliferator-activated receptor-α (PPAR-α) were also measured in renal IRI. The results showed that plasma levels of blood urea nitrogen and creatinine, histopathologic scores and the expression levels of TNF-α, IL-8 and IL-6 were significantly lower in FEN group than in IRI group. Moreover, Fenofibrate pretreatment could further induce PI3K/Akt signal pathway and PPAR-α activation following renal IRI. These findings indicated PPAR-α activation by Fenofibrate exerts protective effects on renal IRI in mice by suppressing inflammation via PI3K/Akt activation. Thus, Fenofibrate could be a novel therapeutic alternative in renal IRI.