For glioma, a sweet side to diabetes

Causal relationship between type 2 diabetes and glioblastoma: bidirectional Mendelian randomization analysis

As the prevalence of Type 2 Diabetes Mellitus (T2DM) and Glioblastoma (GBM) rises globally, the relationship between T2DM and GBM remains controversial. This study aims to investigate whether genetically predicted T2DM is causally associated with GBM. We performed bidirectional Mendelian randomization (MR) analysis using data from genome-wide studies on T2DM (N = 62,892) and GBM (N = 218,792) in European populations. The results of the inverse-variance weighted (IVW) approach served as the primary outcomes. We applied Cochran's Q test and MR-Egger regression for heterogeneity assessment. Leave-one-out analysis was used to evaluate whether any single SNP significantly influenced the observed effect. Our findings reveal a significant causal association between T2DM and an increased risk of GBM (OR [95% CI] 1.70 [1.09, 2.65], P = 0.019). Conversely, the reverse association between T2DM and GBM was insignificant (OR [95% CI] 1.00 [0.99, 1.01], P = 0.408) (P > 0.40). Furthermore, the results from Cochran's Q-test and funnel plots in the MR-Egger method indicated no evidence of pleiotropy between the SNPs and GBM. Additionally, we mapped causal SNPs to genes and identified 10 genes, including MACF1, C1orf185, PTGFRN, NOTCH2, ABCB10, GCKR, THADA, RBMS1, SPHKAP, and PPARG, located on chromosomes 1, 2, and 3. These genes are involved in key biological processes such as the BMP signaling pathway and various metabolic pathways relevant to both conditions. This study provides robust evidence of a significant causal relationship between T2DM and an increased risk of GBM. The identified SNP-mapped genes highlight potential biological mechanisms underlying this association.

Impact of abdominal obesity on the risk of glioma development in patients with diabetes: A nationwide population-based cohort study in Korea

BACKGROUND

Abdominal obesity has been suggested as a risk factor for glioma; however, it is unclear whether this association applies to people with diabetes. This study examined the association between abdominal obesity and the risk of developing gliomas in diabetic patients.

METHODS

We conducted a retrospective cohort study using the National Health Insurance System of South Korea from 2009 to 2012. The primary outcome was the incidence of newly diagnosed gliomas according to waist circumference (WC), and subgroup analyses were performed according to demographic characteristics and diabetes status including disease duration, number of oral hypoglycemic agents, and insulin use.

RESULTS

Of a total of 1,893,057 participants, 1,846 (0.10%) cases of gliomas occurred. After adjusting for confounding factors, WC ≥90 cm (men)/85 cm (women) was associated with significantly higher risks of gliomas (adjusted HR [95% CI]; 1.279 [1.053, 1.554], 1.317 [1.048, 1.655], and 1.369 [1.037, 1.807] in the WC <95 cm (men)/90 cm (women) group, WC <100 cm (men)/95 cm (women) group, and WC ≥100 cm (men)/95 cm (women) group, respectively). Subgroup analysis showed that patients with larger WC had a consistently higher incidence of glioma than their lean counterparts, except for insulin users (insulin user vs. nonuser, P for interaction = .03).

CONCLUSIONS

Abdominal obesity was associated with the development of gliomas in diabetic patients in a nationwide population-based database. Further study is needed in diabetic patients to stratify the risk for glioma development according to WC and to establish the underlying mechanism of carcinogenesis.

Diabetes Mellitus Management in the Context of Cranial Tumors

The study of the relationship between cancer and diabetes mellitus (DM) has been under investigation for many decades. Particularly in the field of neurology and neurosurgery, increasing emphasis has been put on the examination of comorbid DM in patients with cranial tumors. Namely, as the most common and invasive type of malignant adult brain tumor, glioblastoma (GBS) has been the focus of said research. Several mechanisms have been described in the attempt to elucidate the underlying association between DM and GBS, with the metabolic phenomenon known as the Warburg effect and its consequential downstream effects serving as the resounding culprits in recent literature. Since the effect seen in cancers like GBS exploits an upregulated form of aerobic glycolysis, the role of a sequela of DM, known as hyperglycemia, will be investigated. In particular, in the treatment of GBS, surgical resection and subsequent chemotherapy and/or radiotherapy are used in conjunction with corticosteroid therapy, the latter of which has been linked to hyperglycemia. Unsurprisingly, comorbid DM patients are significantly susceptible to this disposition. Further, this fact is reflected in recent literature that demonstrates the impact of hyperglycemia on cancer advancement and patient outcomes in several preclinical and clinical studies. Thus, this review will aim to underline the significance of diabetes and glycemic control via standard-of-care treatments such as metformin administration, as well as to describe emerging treatments such as the signaling modulation of insulin-like growth factor and the employment of the ketogenic diet.

Clinical Risk and Overall Survival in Patients with Diabetes Mellitus, Hyperglycemia and Glioblastoma Multiforme. A Review of the Current Literature

The relationship between type 2 diabetes mellitus (DM2) and hyperglycemia with cancer patients remains controversial also in the setting of patients with glioblastoma multiforme (GBM), the most common and aggressive form of astrocytoma with a short overall survival (OS) and poor prognosis. A systematic search of two databases was performed for studies published up to 19 August 2020, reporting the OS of patients with DM2 or high blood sugar level and GBM and the clinical risk of diabetic patients for development of GBM. According to PRISMA guidelines, we included a total of 20 papers reporting clinical data of patients with GBM and diabetes and/or hyperglycemia. The aim of this review was to investigate the effect of DM2, hyperglycemia and metformin on OS of patients with GBM. In addition, we evaluated the effect of these factors on the risk of development of GBM. This review supports accumulating evidence that hyperglycemia, rather than DM2, and elevated BMI are independent risk factors for poor outcome and shorter OS in patients with GBM. GBM patients with normal weight compared to obese, and diabetic patients on metformin compared to other therapies, seems to have a longer OS. Further studies are needed to understand better these associations.

Associations between prediagnostic blood glucose levels, diabetes, and glioma

Previous literature indicates that pre-diagnostic diabetes and blood glucose levels are inversely related to glioma risk. To replicate these findings and determine whether they could be attributed to excess glucose consumption by the preclinical tumour, we used data from the Apolipoprotein MOrtality RISk (AMORIS) (n = 528,580) and the Metabolic syndrome and Cancer project (Me-Can) cohorts (n = 269,365). We identified individuals who were followed for a maximum of 15 years after their first blood glucose test until glioma diagnosis, death, emigration or the end of follow-up. Hazard ratios (HRs), 95% confidence intervals (CIs) and their interactions with time were estimated using Cox time-dependent regression. As expected, pre-diagnostic blood glucose levels were inversely related to glioma risk (AMORIS, P_trend = 0.002; Me-Can, P_trend = 0.04) and pre-diagnostic diabetes (AMORIS, HR = 0.30, 95% CI 0.17 to 0.53). During the year before diagnosis, blood glucose was inversely associated with glioma in the AMORIS (HR = 0.78, 95% CI 0.66 to 0.93) but not the Me-Can cohort (HR = 0.99, 95% CI 0.63 to 1.56). This AMORIS result is consistent with our hypothesis that excess glucose consumption by the preclinical tumour accounts for the inverse association between blood glucose and glioma. We discuss additional hypothetical mechanisms that may explain our paradoxical findings.

Inhibitors of GLUT/SLC2A Enhance the Action of BCNU and Temozolomide against High-Grade Gliomas

Glucose transport across glioblastoma membranes plays a crucial role in maintaining the enhanced glycolysis typical of high-grade gliomas and glioblastoma. We tested the ability of two inhibitors of the glucose transporters GLUT/SLC2A superfamily, indinavir (IDV) and ritonavir (RTV), and of one inhibitor of the Na/glucose antiporter type 2 (SGLT2/SLC5A2) superfamily, phlorizin (PHZ), in decreasing glucose consumption and cell proliferation of human and murine glioblastoma cells. We found in vitro that RTV, active on at least three different GLUT/SLC2A transporters, was more effective than IDV, a specific inhibitor of GLUT4/SLC2A4, both in decreasing glucose consumption and lactate production and in inhibiting growth of U87MG and Hu197 human glioblastoma cell lines and primary cultures of human glioblastoma. PHZ was inactive on the same cells. Similar results were obtained when cells were grown in adherence or as 3D multicellular tumor spheroids. RTV treatment but not IDV treatment induced AMP-activated protein kinase (AMPKα) phosphorylation that paralleled the decrease in glycolytic activity and cell growth. IDV, but not RTV, induced an increase in GLUT1/SLC2A1 whose activity could compensate for the inhibition of GLUT4/SLC2A4 by IDV. RTV and IDV pass poorly the blood brain barrier and are unlikely to reach sufficient liquoral concentrations in vivo to inhibit glioblastoma growth as single agents. Isobologram analysis of the association of RTV or IDV and 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) or 4-methyl-5-oxo-2,3,4,6,8-pentazabicyclo[4.3.0]nona-2,7,9-triene-9-carboxamide (TMZ) indicated synergy only with RTV on inhibition of glioblastoma cells. Finally, we tested in vivo the combination of RTV and BCNU on established GL261 tumors. This drug combination increased the overall survival and allowed a five-fold reduction in the dose of BCNU.