Background and Aims Kidney is a high energy-consuming organ depending on fatty acid β-oxidation (FAO) to fulfil energy supply. During various biological stresses in AKI, FAO shuts down, and the aerobic glycolysis is enhanced. In this study, we aimed to investigate the effect of aerobic glycolysis and local lactate production in AKI. Methods & Results A maleic acid (MA) induced AKI model (MA-AKI) was established by MA intraperitoneally (i.p.) in C57BL/6J mice and sacrificed after 24h. The renal function in MA-AKI mice was damaged, accompanied by proximal tubular injury and mitochondrial dysfunction. RNA sequencing revealed a relative increase in glycolytic enzymes (HK1, PKM and PFKP) mRNA levels in the AKI phase. The protein level of glycolysis-related enzymes was also elevated with increased urinary lactate significantly (0.25±0.10 versus 8.60±0.74 mmol/L, P<0.0001) in MA-AKI. Furthermore, glycolysis inhibitor 2-DG was administrated after 2h of MA injection, which improved the renal function (indicated by decreased serum creatinine (Scr), 33.52±2.78 versus 57.15±4.81 μmol/L, P<0.001), proximal tubular histopathological injuries and mitochondrial dysfunction in MA-AKI. Mechanistically, we observed a significant positive correlation between the Scr and urinary lactate levels (R2 = 0.78, P < 0.0001). In order to examine the role of lactate in AKI, the mice were pretreated with oxamate, an inhibitor of lactate dehydrogenase A (LDHA), and the level of Scr (59.18±5.83 versus 28.82±3.41 μmol/L, P<0.0001) was mitigated, with the reduction of urinary lactate (8.60±0.74 versus 4.90±0.98 mmol/L, P<0.01). Conclusion Our study demonstrated that inhibition of aerobic glycolysis to protect kidney function in MA-AKI might be via reducing lactate accumulation.
Study question How does the androgen receptor splice variant (ARSV) contribute to insulin resistance in polycystic ovary syndrome (PCOS) patients? Summary answer ARSV inhibited the intracellular signaling pathway of insulin, resulting in decreased glucose transporter type 4 (GLUT4) translocation, impaired cellular glucose uptake, and insulin resistance. What is known already PCOS is the most common endocrine disorder in women of reproductive age and characterized by hyperandrogenism, ovulation dysfunction, and ovarian polycystic changes. In addition, a significant proportion of PCOS patients will experience insulin resistance. Our previous study identified an ARSV in granulosa cells from PCOS patients, which may be associated with higher insulin levels in follicular fluid. Study design, size, duration / Participants/materials, setting, methods Glucose metabolism of a mouse model presenting ARSV by CRISPR-Cas9 was measured by glucose tolerance test and insulin tolerance test. Body composition was measured by a nuclear magnetic resonance system. KGN cell lines stably overexpressing wild type androgen receptor (AR group) or ARSV (ARSV group) were successfully constructed by lentivirus infection. The process of glucose uptake by GLUT4, and the expression of target genes in the glucose uptake pathway were detected in cells. Main results and the role of chance The mice expressing ARSV had higher body weight and body fat content than the wild type mice, while the muscle content was equivalent.ARSV mice displayed diabetes with impaired glucose tolerance and insulin tolerance at 48 week-age. The levels of fasting glucose and insulin levels were significantly higher in ARSV mice. The basal and insulin-stimulated glucose uptake capacity were also found impaired in ARSV group. Immunofluorescence demonstrated that under insulin stimulation, GLUT4 protein was less expressed in the membrane and more expressed in the cytoplasm in ARSV group. Similar results were obtained by detecting the expression of GLUT4 protein after separating the cell membrane and cytoplasmic proteins. Further detection of the upstream signaling molecules of GLUT4 revealed that the phosphorylation levels of insulin receptor substrate 1 (IRS1) at Ser1101 were slightly increased in ARSV group, after stimulation with insulin and DHT. Besides, the phosphorylation levels of protein kinase B (AKT) were also found significantly decreased at Thr308 and slightly decreased at Ser473 in ARSV group. ARSV inhibited the intracellular signaling pathway of insulin by altering the phosphorylation level of IRS1/AKT signaling, resulting in decreased GLUT4 translocation, impaired cellular glucose uptake, and insulin resistance. Limitations, reasons for caution In this study, we failed to obtain clinical samples of PCOS to prospectively verify the association between ARSV and glucose uptake, insulin resistance, and subsequent onset diabetes. Wider implications of the findings This transgenic animal model can simulate the reproductive and metabolic phenotypes of PCOS patients, providing a model for future PCOS research. PCOS patients with ARSV should delay the onset of insulin resistance through lifestyle intervention, exercise, and drug therapy as early as possible. Trial registration number NA
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