Podocytes are highly-specialized epithelial cells essentially required for the generation and the maintenance of the kidney filtration barrier. This elementary function is directly based on an ...elaborated cytoskeletal apparatus establishing a complex network of primary and secondary processes. Here, we identify the actin-bundling protein allograft-inflammatory-inhibitor 1 like (AIF1L) as a selectively expressed podocyte protein in vivo. We describe the distinct subcellular localization of AIF1L to actin stress fibers, focal adhesion complexes and the nuclear compartment of podocytes in vitro. Genetic deletion of AIF1L in immortalized human podocytes resulted in an increased formation of filopodial extensions and decreased actomyosin contractility. By the use of SILAC based quantitative proteomics analysis we describe the podocyte specific AIF1L interactome and identify several components of the actomyosin machinery such as MYL9 and UNC45A as potential AIF1L interaction partners. Together, these findings indicate an involvement of AIF1L in the stabilization of podocyte morphology by titrating actomyosin contractility and membrane dynamics.
Autophagy is a major catabolic pathway by which mammalian cells degrade and recycle macromolecules and organelles. It plays a critical role in removing protein aggregates, as well as damaged or ...excess organelles, to maintain intracellular homeostasis and to keep cells healthy. The accumulation of damaged proteins and organelles induced by hyperglycemia and other metabolic alterations is strongly associated with the development of diabetic nephropathy. Autophagy is up-regulated under conditions of calorie restriction and environmental stress, such as oxidative stress and hypoxia in proximal tubular cells, and occurs even under normal conditions in podocytes. These findings have led to our hypothesis that autophagy is involved in the pathogenesis of diabetic nephropathy, a hypothesis increasingly supported by experimental evidence. To date, however, the exact role of autophagy in diabetic nephropathy has not been fully revealed. This article therefore reviews recent findings and provides perspectives on the involvement of autophagy in diabetic nephropathy.
Vascular endothelial growth factor A (VEGFA) secretion from podocytes is crucial for maintaining endothelial integrity within the glomerular filtration barrier. However, until now, the molecular ...mechanisms underlying podocyte secretory function remained unclear. Through podocyte-specific deletion of BECLIN1 (
or
), a key protein in autophagy initiation, we identified a major role for this molecule in anterograde Golgi trafficking. The
-deficient podocytes displayed aberrant vesicle formation in the
Golgi network (TGN), leading to dramatic vesicle accumulation and complex disrupted patterns of intracellular vesicle trafficking and membrane dynamics. Phenotypically, podocyte-specific deletion of
resulted in early-onset glomerulosclerosis, which rapidly progressed and dramatically reduced mouse life span. Further, in vivo and in vitro studies clearly showed that VEGFA secretion, and thereby endothelial integrity, greatly depended on BECLIN1 availability and function. Being the first to demonstrate the importance of a secretory pathway for podocyte integrity and function, we identified BECLIN1 as a key component in this complex cellular process. Functionally, by promoting VEGFA secretion, a specific secretory pathway emerged as an essential component for the podocyte-endothelial crosstalk that maintains the glomerular filtration barrier.
Renal artery stenosis-induced chronic renal ischemia is an important cause of renal dysfunction, especially in older adults, and its incidence is currently increasing. To elucidate the mechanisms ...underlying chronic renal hypoperfusion-induced kidney damage, we developed a novel mouse model of renal artery coiling-based chronic hypoperfusion-related kidney injury. This model exhibits decreased renal blood flow and function, atrophy, and parenchymal injury in the coiled kidney, along with compensatory hypertrophy in the non-coiled kidney, without chronic hypertension. The availability of this mouse model, which can develop renal ischemia without genetic modification, will enhance kidney disease research by serving as a new tool to investigate the effects of acquired factors (e.g., obesity and aging) and genetic factors on renal artery stenosis-related renal parenchymal damage.
•A mouse model of chronic renal ischemia was established by renal artery coiling.•Renal artery coiling caused renal injury without chronic hypertension.•This model can help to elucidate mechanisms of ischemia-induced renal injury.
Diabetic nephropathy is a leading cause of end-stage renal disease worldwide. The multipronged drug approach targeting blood pressure and serum levels of glucose, insulin, and lipids fails to fully ...prevent the onset and progression of diabetic nephropathy. Therefore, a new therapeutic target to combat diabetic nephropathy is required. Autophagy is a catabolic process that degrades damaged proteins and organelles in mammalian cells and plays a critical role in maintaining cellular homeostasis. The accumulation of proteins and organelles damaged by hyperglycemia and other diabetes-related metabolic changes is highly associated with the development of diabetic nephropathy. Recent studies have suggested that autophagy activity is altered in both podocytes and proximal tubular cells under diabetic conditions. Autophagy activity is regulated by both nutrient state and intracellular stresses. Under diabetic conditions, an altered nutritional state due to nutrient excess may interfere with the autophagic response stimulated by intracellular stresses, leading to exacerbation of organelle dysfunction and diabetic nephropathy. In this review, we discuss new findings showing the relationships between autophagy and diabetic nephropathy and suggest the therapeutic potential of autophagy in diabetic nephropathy.
The prevalence of chronic kidney disease (CKD) is increasing worldwide, making the disease an urgent clinical challenge. Caloric restriction has various anti-aging and organ-protective effects, and ...unraveling its molecular mechanisms may provide insight into the pathophysiology of CKD. In response to changes in nutritional status, intracellular nutrient signaling pathways show adaptive changes. When nutrients are abundant, signals such as mechanistic target of rapamycin complex 1 (mTORC1) are activated, driving cell proliferation and other processes. Conversely, others, such as sirtuins and AMP-activated protein kinase, are activated during energy scarcity, in an attempt to compensate. Autophagy, a cellular self-maintenance mechanism that is regulated by such signals, has also been reported to contribute to the progression of various kidney diseases. Furthermore, in recent years, ketone bodies, which have long been considered to be detrimental, have been reported to play a role as starvation signals, and thereby to have renoprotective effects, via the inhibition of mTORC1. Therefore, in this review, we discuss the role of mTORC1, which is one of the most extensively studied nutrient-related signals associated with kidney diseases, autophagy, and ketone body metabolism; and kidney energy metabolism as a novel therapeutic target for CKD.
The discovery of insulin approximately a century ago greatly improved the management of diabetes, including many of its life-threatening acute complications like ketoacidosis. This breakthrough saved ...many lives and extended the healthy lifespan of many patients with diabetes. However, there is still a negative perception of ketone bodies stemming from ketoacidosis. Originally, ketone bodies were thought of as a vital source of energy during fasting and exercise. Furthermore, in recent years, research on calorie restriction and its potential impact on extending healthy lifespans, as well as studies on ketone bodies, have gradually led to a reevaluation of the significance of ketone bodies in promoting longevity. Thus, in this review, we discuss the emerging and hidden roles of ketone bodies in various organs, including the heart, kidneys, skeletal muscles, and brain, as well as their potential impact on malignancies and lifespan.
Background
Because oral nonsteroidal anti-inflammatory drugs (NSAIDs) have adverse effects on kidney function, patients with kidney diseases are administered these drugs as transdermal patches. ...Little is known about the effects of NSAID patches on renal function. We therefore assessed the effects of topical loxoprofen sodium on kidney function in type 2 diabetic patients with overt nephropathy.
Methods
Twenty patients with type 2 diabetes and overt proteinuria and with knee and/or low back pain were treated with skin patches containing 100 mg loxoprofen on the knee or back for 24 h per day for 5 consecutive days. The degree of pain was assessed using a visual analogue scale (VAS). Blood and 24-h urine samples were obtained at baseline and at the end of the study. Glomerular filtration rate (GFR) was estimated from serum creatinine and cystatin C concentrations.
Results
The 20 patients consisted of 11 males and 9 females, of mean age 61.6 ± 13.9 years. Loxoprofen-containing patches significantly reduced VAS pain without affecting blood pressure, GFR or urinary prostaglandin E
2
concentration. Serum concentrations of loxoprofen and its active trans-OH metabolite did not correlate with GFR.
Conclusions
Loxoprofen-containing patches do not affect renal function in type 2 diabetic patients with overt nephropathy over a short-term period. Long-term studies are needed to clarify the safety of loxoprofen-containing patches in patients with chronic kidney diseases.
For the advancement of DKD treatment, identifying unrecognized residual risk factors is essential. We explored the impact of obesity diversity derived from different carbohydrate qualities, with an ...emphasis on the increasing trend of excessive fructose consumption and its effect on DKD progression. In this study, we utilized db/db mice to establish a novel diabetic model characterized by fructose overconsumption, aiming to uncover the underlying mechanisms of renal damage. Compared to the control diet group, the fructose-fed db/db mice exhibited more pronounced obesity yet demonstrated milder glucose intolerance. Plasma cystatin C levels were elevated in the fructose model compared to the control, and this elevation was accompanied by enhanced glomerular sclerosis, even though albuminuria levels and tubular lesions were comparable. Single-cell RNA sequencing of the whole kidney highlighted an increase in Lrg1 in glomerular endothelial cells (GECs) in the fructose model, which appeared to drive mesangial fibrosis through enhanced TGF-β1 signaling. Our findings suggest that excessive fructose intake exacerbates diabetic kidney disease progression, mediated by aberrant Lrg1-driven crosstalk between GECs and mesangial cells.
•The role of fructose overconsumption in the progression of DKD is to be elucidated.•Fructose overconsumption is a risk for DKD progression independent of hyperglycemia.•Fructose overconsumption increases Lrg1 expression in glomerular endothelial cells.•Secreted Lrg1 from glomerular endothelial cells leads to mesangial cell activation.
Accumulating evidence suggests health benefits of ketone bodies, and especially for longevity. However, the precise role of endogenous ketogenesis in mammalian life span, and the safety and efficacy ...of the long‐term exogenous supplementation of ketone bodies remain unclear. In the present study, we show that a deficiency in endogenous ketogenesis, induced by whole‐body Hmgcs2 deletion, shortens life span in mice, and that this is prevented by daily ketone body supplementation using a diet containing 1,3‐butanediol, a precursor of β‐hydroxybutyrate. Furthermore, feeding the 1,3‐butanediol‐containing diet from early in life increases midlife mortality in normal mice, but in aged mice it extends life span and prevents the high mortality associated with atherosclerosis in ApoE‐deficient mice. By contrast, an ad libitum low‐carbohydrate ketogenic diet markedly increases mortality. In conclusion, endogenous ketogenesis affects mammalian survival, and ketone body supplementation may represent a double‐edged sword with respect to survival, depending on the method of administration and health status.
The present study demonstrates that endogenous ketogenesis is essential for long‐term mammalian survival, which was revealed by a study using Hmgcs2−/− mice, and that dietary administration of 1,3‐butanediol (1,3‐BD), a precursor of β‐OHB, increases midlife mortality in normal mice, but extends life span in aged mice or atherosclerotic mice. By contrast, ad libitum low‐carbohydrate ketogenic diet increases mortality in any mouse models. Thus, ketone bodies represent a double‐edged sword for mammalian survival.
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