Aerobic training with moderate or high doses of vitamin D improve liver enzymes, LXRα and PGC-1α levels in rats with T2DM

Dysregulation of key transcription factors involved in hepatic energy metabolism, such as peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α) and liver X receptor alpha (LXRα), has been observed in T2DM. The present study aims to investigate the effects of aerobic training and vitamin D supplementation on liver enzyme levels and the levels of PGC-1α and LXRα proteins in hepatocytes, in a rat model of T2DM. The study involved 56 male Wistar rats, divided into two groups: one was non-diabetic and acted as a control group (n = 8), and the other had induced diabetes (n = 48). The diabetic rats were then split into six subgroups: two groups received high or moderate doses of vitamin D and aerobic training (D + AT + HD and D + AT + MD); two groups received high or moderate doses of vitamin D alone (D + HD and D + MD); one group underwent aerobic training with vehicle (sesame oil; D + AT + oil), and one group was a diabetic control receiving only sesame oil (oil-receiving). The D + AT + HD and D + HD groups received 10,000 IU of vitamin D, while the D + AT + MD and D + MD groups received 5000 IU of vitamin D once a week by injection. The D + AT + oil group and the sham group received sesame oil. After eight weeks of treatment, body weight, BMI, food intake, serum insulin, glucose, 25-hydroxyvitamin D, ALT, AST, and visceral fat were measured. The levels of PGC-1α and LXRα proteins in the liver was assessed by western blotting. Statistical analysis was performed using the paired t-test, one-way analysis of variance (ANOVA), and the Tukey post hoc test at a significance level of P < 0.05. Body weight, food intake, and BMI decreased significantly in the D + AT + HD, D + AT + MD, D + AT + oil, D + HD, and D + MD groups with the highest reduction being observed in body weight and BMI in the D + AT + HD group. The D + AT + HD group exhibited the lowest levels of insulin, glucose, and HOMA-IR while the D + C group exhibited the highest levels among the diabetic groups. The D + AT + HD and D + AT + MD groups had lower levels of ALT and AST enzymes compared to the other groups with no significant difference between D + AT + HD and D + AT + MD. D + AT + HD (p = 0.001), D + AT + MD (p = 0.001), D + HD (p = 0.023), D + MD (p = 0.029), and D + AT + oil (p = 0.011) upregulated LXRα compared to D + C. Among these groups, D + AT + HD exhibited a more profound upregulation of LXRα than D + AT + MD, D + AT + oil, D + HD, and D + MD (p = 0.005; p = 0.002, p = 0.001, and p = 0.001, respectively). Similarly, D + AT + HD showed a more notable upregulation of PGC-1α compared to D + AT + oil, D + HD, and D + MD (p = 0.002; p = 0.001, and p = 0.001, respectively). Pearson correlation tests showed significant and negative correlations between serum 25-hydroxyvitamin levels and both visceral fat (r = - 0.365; p = 0.005) and HOMA-IR (r = - 0.118; p = 0.009); while positive and significant correlations between the liver-to-bodyweight ratio with both ALT and AST enzymes and also between QUICKI levels with LXRα (r = 0.578; p = 0.001) and PGC-1α (r = 0.628; p = 0.001). Combined administration of aerobic training and vitamin D supplementation potentially improves liver enzymes in type-2 diabetic rats that were simultaneous with upregulating the levels of PGC-1α and LXRα proteins in hepatocytes. These improvements were more significant when combining exercise with high-dose vitamin D supplementation. This study highlights the potential of this combination therapy as a new diabetes treatment strategy.

Liver X receptor α is targeted by microRNA-1 to inhibit cardiomyocyte apoptosis through a ROS-mediated mitochondrial pathway

Diabetic cardiomyopathy (DCM) is defined as ventricular dysfunction occurring independently of a recognized cause such as hypertension or coronary artery disease. Liver X receptor α (LXRα), a subtype of ligand-activated transcription factors LXRs, has been considered as a potential pharmacological target in the pathogenesis of cardiovascular and metabolic diseases. However, the potential mechanism of how LXRα is regulated in cardiomyocytes is still unclear. This study investigated the effect of activating LXRα with GW3965 on cardiomyocyte apoptosis and its upstream regulator in glucose-induced H9C2 cells. Our data indicated that GW3965 up-regulated the expression of LXRα, inhibited cardiomyocyte apoptosis, and altered the apoptosis-related proteins in glucose-induced H9C2 cells. In addition, GW3965 restored the mitochondrial membrane potential level and decreased the ROS production induced by glucose. Moreover, LXRα was confirmed as a direct target of microRNA-1 (miR-1) that was involved in cardiomyocyte apoptosis of DCM, and overexpression of miR-1 abrogated the inhibiting effect of GW3965 on glucose-induced apoptosis in H9C2 cells. This study highlights an important role of LXRα in the development of DCM and brings new insights into the complex mechanisms involved in the pathogenesis of DCM.