Glioblastomas and brain metastases are highly proliferative brain tumors with short survival times. Previously, using 13C-NMR analysis of brain tumors resected from patients during infusion of 13C-glucose, we demonstrated that there is robust oxidation of glucose in the citric acid cycle, yet glucose contributes less than 50% of the carbons to the acetyl-CoA pool. Here we show that primary and metastatic mouse orthotopic brain tumors have the capacity to oxidize [1,2-13C]acetate and can do so simultaneously with [1,6-13C]glucose oxidation. The tumors do not oxidize [U-13C]glutamine. In vivo oxidation of [1,2-13C]acetate was validated in brain tumor patients and was correlated with expression of acetyl-CoA synthetase enzyme 2, ACSS2. Together the data demonstrate a strikingly common metabolic phenotype in diverse brain tumors that includes the ability to oxidize acetate in the citric acid cycle. This adaptation may be important for meeting the high biosynthetic and bioenergetic demands of malignant growth.

The frontotemporal dementias (FTDs) are a clinically, genetically, and neuropathologically heterogeneous group of diseases accounting for up to 20% of presenile dementia cases. FTD is characterized by behavioral and/or language dysfunction and may co-occur with motor neuron disease (MND).1,2 Frontotemporal lobar degeneration (FTLD) with ubiquitin-positive, tau-negative inclusions (FTLD-U) is the most common underlying pathology in FTD with and without MND.

Primary age-related tauopathy (PART) is a neurodegenerative entity defined as Alzheimer-type neurofibrillary degeneration primarily affecting the medial temporal lobe with minimal to absent amyloid-β (Aβ) plaque deposition. The extent to which PART can be differentiated pathoanatomically from Alzheimer disease (AD) is unclear. Here, we examined the regional distribution of tau pathology in a large cohort of postmortem brains (n = 914). We found an early vulnerability of the CA2 subregion of the hippocampus to neurofibrillary degeneration in PART, and semiquantitative assessment of neurofibrillary degeneration in CA2 was significantly greater than in CA1 in PART. In contrast, subjects harboring intermediate-to-high AD neuropathologic change (ADNC) displayed relative sparing of CA2 until later stages of their disease course. In addition, the CA2/CA1 ratio of neurofibrillary degeneration in PART was significantly higher than in subjects with intermediate-to-high ADNC burden. Furthermore, the distribution of tau pathology in PART diverges from the Braak NFT staging system and Braak stage does not correlate with cognitive function in PART as it does in individuals with intermediate-to-high ADNC. These findings highlight the need for a better understanding of the contribution of PART to cognitive impairment and how neurofibrillary degeneration interacts with Aβ pathology in AD and PART.

Adult brainstem gliomas are difficult to classify based on radiologic and histologic features. A K27M mutation in histone 3 has been described to identify high-grade midline gliomas associated with a particularly unfavorable prognosis. While initially considered a pediatric entity, it is now known that H3K27M-mutant brainstem gliomas occur in all age groups, but they are less well understood in adults. We studied clinical, radiologic, and pathologic features of 25 brainstem gliomas diagnosed at our institution between 1994 and 2017 in subjects at least 18 years old. Seven tumors (28%) were positive for the H3K27M mutation, and their median overall survival was significantly shorter than in the H3-wildtype group (p = 0.004). Although the mutation was invariably associated with a poor prognosis, our study also illustrates the radiologic and pathologic heterogeneity in this molecular tumor subtype. The results showed that H3K27M-mutant status and clinically aggressive course cannot be ruled out based on low-grade histology on the initial biopsy, exophytic growth, only focal or minimal enhancement or an extrapontine location, such as midbrain or medulla. These results favor an integrated approach employing a combination of clinical, radiologic, histologic features as well as H3K27M immunohistochemistry for the diagnostic subclassification of adult brainstem gliomas.

Severe neuronal loss in the hippocampus, that is, hippocampal sclerosis (HS), can be seen in 3 main clinical contexts: dementia (particularly frontotemporal lobar degeneration [FTLD]), temporal lobe epilepsy (TLE), and hippocampal ischemic injury (H–I). It has been suggested that shared pathogenetic mechanisms may underlie selective vulnerability of the hippocampal subfields such as the CA1 in these conditions. We determined the extent of neuronal loss in cases of HS-FTLD (n = 14), HS-TLE (n = 35), and H–I (n = 20). Immunohistochemistry for zinc transporter 3 was used to help define the CA3/CA2 border in the routinely processed human autopsy tissue samples. The subiculum was involved in 57% of HS-FTLD, 10% of H–I, and 0% of HS-TLE cases (p < 0.0001). The CA regions other than CA1 were involved in 57% of HS-TLE, 30% of H–I, and 0% of HS-FTLD cases (p= 0.0003). The distal third of CA1 was involved in 79% of HS-FTLD, 35% of H–I, and 37% of HS-TLE cases (p = 0.02). The distal third of CA1 was the only area involved in 29% of HS-FTLD, 3% of HS-TLE, and 0% of H–I cases (p = 0.019). The proximal-middle CA1 was the only area affected in 50% of H–I, 29% of HS-TLE, and 0% of HS-FTLD cases (p = 0.004). These findings support heterogeneity in the pathogenesis of HS.