Association of increased renal Cyp24a1 gene expression with low plasma 1,25-dihydroxyvitamin D levels in rats with streptozotocin-induced diabetes

MicroRNA-125b regulates vitamin D resistance by targeting CYP24A1 in the progression of gestational diabetes mellitus

Vitamin D deficiency is prevalent in pregnancy and has been associated with increased occurrences of preeclampsia, cesarean delivery, neonatal bacterial vaginosis, and gestational diabetes. CYP24A1, recognized as a key factor in vitamin D metabolism homeostasis, encodes 24-hydroxylase responsible for converting 25(OH)D3 and 1,25(OH)2D3 into inactive metabolites. Recently, we have reported CYP24A1 overexpression in patients with gestational diabetes mellitus (GDM) and trophoblast cells exposed to hyperglycemia. In this study, we explored miRNA-mediated regulation of CYP24A1 in GDM progression, validating our findings through silencing experiments in a trophoblast cell line. In silico tools identified miR-125b-5p as a putative target of CYP24A1. Expression analysis revealed downregulation of miR-125b-5p in blood samples from early GDM and GDM compared to healthy pregnant women, positively correlating with vitamin D levels. Hyperglycemic exposure in human trophoblastic cell lines (BeWo) decreased miR-125b-5p expression, concomitant with an increase in CYP24A1. To confirm the regulatory role of miR-125b on CYP24A1, we transfected BeWo cells with antimiR-125b or miR-125b mimic. AntimiR-125b transfection heightened CYP24A1 levels, while miR-125b mimic overexpression resulted in decreased CYP24A1 expression. These findings establish miR-125b as a regulator of CYP24A1. To explore the influence of miR-125b on vitamin D metabolism, trophoblast cells overexpressing miR-125b were treated with 0.1 and 1 µM calcitriol. Hyperglycemic conditions exhibited a reduction in CYP24A1 levels. Collectively, our results indicate that miR-125b may regulate vitamin D metabolism by targeting CYP24A1, contributing to GDM progression. These findings may pave the way for understanding vitamin D resistance in concurrent GDM development and identifying novel miRNAs targeting CYP24A1.

Vitamin D and Diabetic Kidney Disease

Vitamin D is a hormone involved in many physiological processes. Its active form, 1,25(OH)₂D₃, modulates serum calcium-phosphate homeostasis and skeletal homeostasis. A growing body of evidence has demonstrated the renoprotective effects of vitamin D. Vitamin D modulates endothelial function, is associated with podocyte preservation, regulates the renin-angiotensin-aldosterone system, and has anti-inflammatory effects. Diabetic kidney disease (DKD) is a leading cause of end-stage kidney disease worldwide. There are numerous studies supporting vitamin D as a renoprotector, potentially delaying the onset of DKD. This review summarizes the findings of current research on vitamin D and its role in DKD.

Streptozotocin-induced Diabetes Represses Hepatic CYP2R1 Expression but Induces Vitamin D 25-Hydroxylation in Male Mice

Vitamin D deficiency [ie, low plasma 25-hydroxyvitamin D (25-OH-D)] associates with the prevalence of metabolic diseases including type 1 diabetes; however, the molecular mechanisms are incompletely understood. Recent studies have indicated that both fasting and metabolic diseases suppress the cytochrome P450 (CYP) 2R1, the major hepatic vitamin D 25-hydroxylase. We specifically studied the effect of a mouse model of type 1 diabetes on the regulation of Cyp2r1 and vitamin D status. We show that streptozotocin-induced diabetes in mice suppresses the expression of the Cyp2r1 in the liver. While insulin therapy normalized the blood glucose levels in the diabetic mice, it did not rescue the diabetes-induced suppression of Cyp2r1. Similar regulation of Cyp2r1 was observed also in the kidney. Plasma 25-OH-D level was not decreased and was, in contrast, higher after 4 and 8 weeks of diabetes. Furthermore, the vitamin D 25-hydroxylase activity was increased in the livers of the diabetic mice, suggesting compensation of the Cyp2r1 repression by other vitamin D 25-hydroxylase enzymes. Cyp27b1, the vitamin D 1α-hydroxylase, expression in the kidney and the plasma 1α,25-dihydroxyvitamin D level were higher after 4 weeks of diabetes, while both were normalized after 13 weeks. In summary, these results indicate that in the mouse model of type 1 diabetes suppression of hepatic Cyp2r1 expression does not result in reduced hepatic vitamin D 25-hydroxylase activity and vitamin D deficiency. This may be due to induction of other vitamin D 25-hydroxylase enzymes in response to diabetes.

Investigating the Effects of Diet-Induced Pre-Diabetes on the Functioning of Calcium-Regulating Organs in Male Sprague Dawley Rats: Effects on Selected Markers

Derangements to the functioning of calcium-regulating organs have been associated with type 2 diabetes mellitus (T2DM), a condition preceded by pre-diabetes. Type 2 diabetes has shown to promote renal calcium wastage, intestinal calcium malabsorption and increased bone resorption. However, the changes to the functioning of calcium-regulating organs in pre-diabetes are not known. Subsequently, the effects of diet-induced pre-diabetes on the functioning of calcium-regulating organs in a rat model for pre-diabetes was investigated in this study. Male Sprague Dawley rats were separated into two groups (n=6, each group): non-pre-diabetic (NPD) group and a diet-induced pre-diabetic (DIPD) group for 20 weeks. After the experimental period, postprandial glucose and HOMA-IR were analysed in addition to plasma and urinary calcium concentrations. Gene expressions of intestinal vitamin D (VDR), intestinal calbindin-D9k, renal 1-alpha hydroxylase and renal transient receptor potential vanilloid 5 (TRPV5) expressions in addition to plasma osteocalcin and urinary deoxypyridinoline concentrations were analysed at week 20. The results demonstrated significantly increased concentrations of postprandial glucose, HOMA-IR and urinary calcium in addition to unchanged plasma calcium levels in the DIPD group by comparison to NPD. Renal TRPV5, renal 1-alpha hydroxylase, intestinal VDR and intestinal calbindin-D9k expressions were increased in the DIPD group by comparison to NPD. Furthermore, plasma osteocalcin levels were increased and urine deoxypyridinoline levels were decreased in the DIPD group by comparison to NPD. These observations may suggest that calcium-regulating organs compensate for the changes to calcium homeostasis by inducing increased renal calcium reabsorption, increased intestinal calcium absorption and decreased bone resorption followed by increased bone formation.

Effect of vitamin D supplementation on glycose homeostasis and islet function in vitamin D deficient or insufficient diabetes and prediabetes: a systematic review and meta-analysis

Objective of the present study was to evaluate the effect of vitamin D supplementation on glycose homeostasis, islet function, and diabetes progress. Literatures were searched via electronic databases, websites, and previous reviews from the earliest available time to the end of May 2020. Randomized controlled trials initially designed for diabetes and prediabetes with 25-dihydroxyvitamin D [25(OH)D]<30 ng/ml were included. All data were analyzed and presented based on the Cochrane guidelines and PRISMA guidelines. In total, 27 articles (n = 1,932) were enrolled in this study. Vitamin D supplementation significantly improved fasting blood glucose, postprandial blood glucose, and quantitative insulin sensitivity check index in diabetes and prediabetes with baseline 25(OH)D<30 ng/ml. Higher percentages regressing from prediabetes to normal glucose status [1.60 (1.19, 2.17), p = 0.002, n = 564] and lower percentage progressing from prediabetes to diabetes [0.68 (0.36, 1.27), p = 0.23, n = 569] were found in the supplementation group. The positive effects of vitamin D supplementation on body mass index, waist, HDL-C, LDL-C, and CRP were also demonstrated. In conclusion, modest improvements in vitamin D supplementation on short-term glycose homeostasis, insulin sensitivity, and disease development in diabetes and prediabetes with 25(OH)D<30 ng/ml were demonstrated, but more research needs to be conducted in the future to support the clinical application. (Register ID: CRD42020186004)

Gender difference in the relationship between anemia and vitamin D in Korean adults: the fifth Korea National Health and Nutrition Examination Survey

This study was conducted to assess the relationship between vitamin D deficiency and anemia, by gender, in Korean adults. The data of 16,060 adults were analyzed (men, 6,840; premenopausal women, 4,916; postmenopausal women, 4,340) from the fifth Korean National Health and Nutrition Examination Survey (KNHANES V) (2010–2012). There were several key findings. First, after adjusting for related variables, the odds ratio (OR) of anemia [hemoglobin (Hb) <13 g/dl in men or Hb <12 g/dl in women] using the vitamin D normal group {25-hydroxyvitamin [25(OH)D] ≥15.0 ng/ml} as reference, was significant for the vitamin D deficient group [25(OH)D <15.0 ng/ml] in the overall population [OR, 1.310; 95% confidence interval (CI), 1.168–1.470]. Second, the OR of anemia, using the vitamin D normal group as reference, was significant for the vitamin D deficient group in premenopausal women (OR, 1.293; 95% CI, 1.105–1.513). However, vitamin D deficiency in the vitamin D normal group in men (OR, 1.093; 95% CI, 0.806–1.484) and postmenopausal women (OR, 1.130; 95% CI, 0.906–1.409) was not significant. In conclusion, Vitamin D deficiency is positively associated with anemia in premenopausal women, but not in men and postmenopausal women.

Molecular mechanisms of developmental toxicities of azoxystrobin and pyraclostrobin toward zebrafish (Danio rerio) embryos: Visualization of abnormal development using two transgenic lines

Azoxystrobin (AZ) and pyraclostrobin (PY) are strobilurin fungicides that inhibit fungal mitochondrial respiration. In this study, a representative model, zebrafish (Danio rerio), was used as a test species for acute and developmental toxicity. Survival and malformation rates were observed only PY-treated embryos, with an LC₅₀ value of 77.75 ppb accompanied by a dramatic decrease in hatching rate, while AZ did not show great mortality. Morphological changes were observed in PY-treated embryos with the occurrence of pericadial edema at 25 ppb. A delay in growth was observed after treatment with pyraclostrobin at 50 ppb. Use of genetically engineered Tg(cmlc:EGFP) allowed fluorescence observation during heart development. PY interfered with normal heart development via upregulation of the nppa gene responsible for the expression of natriuretic peptides. Heart function was dramatically reduced as indicated by reduced heart rates. Increased expression of the nppa gene was also seen in AZ-treated embryos. The expression level of cyp24a1 was also up-regulated, while ugt1a1 and sult1st6 were down-regulated after treatment of zebrafish embryos with AZ or PY. Overall, strobilurin fungicides might inhibit normal heart formation and function within the range of concentrations tested.

Flavonoids Identification and Pancreatic Beta-Cell Protective Effect of Lotus Seedpod

Oxidative stress is highly associated with the development of diabetes mellitus (DM), especially pancreatic beta-cell injury. Flavonoids derived from plants have caused important attention in the prevention or treatment of DM. Lotus seedpod belongs to a traditional Chinese herbal medicine and has been indicated to possess antioxidant, anti-age, anti-glycative, and hepatoprotective activities. The purpose of this study was to demonstrate the pancreatic beta-cell protective effects of lotus seedpod aqueous extracts (LSE) against oxidative injury. According to HPLC/ESI-MS-MS method, LSE was confirmed to have flavonoids derivatives, especially quercetin-3-glucuronide (Q3G). In vitro, LSE dose-dependently improved the survival and function of rat pancreatic beta-cells (RIN-m5F) from hydrogen peroxide (H₂O₂)-mediated loss of cell viability, impairment of insulin secretion, and promotion of oxidative stress. LSE showed potential in decreasing the H₂O₂-induced occurrence of apoptosis. In addition, H₂O₂-triggered acidic vesicular organelle formation and microtubule-associated protein light chain 3 (LC3)-II upregulation, markers of autophagy, were increased by LSE. Molecular data explored that antiapoptotic and autophagic effects of LSE, comparable to that of Q3G, might receptively be mediated via phospho-Bcl-2-associated death promoter (p-Bad)/B-cell lymphoma 2 (Bcl-2) and class III phosphatidylinositol-3 kinase (PI3K)/LC3-II signal pathway. In vivo, LSE improved the DM symptoms and pancreatic cell injury better than metformin, a drug that is routinely prescribed to treat DM. These data implied that LSE induces the autophagic signaling, leading to protect beta-cells from oxidative stress-related apoptosis and injury.