Propionic acid (PPA) is a ubiquitous short-chain fatty acid, which is a major fermentation product of the enteric microbiome. PPA is a normal intermediate of metabolism and is found in foods, either naturally or as a preservative. PPA and its derivatives have been implicated in both health and disease. Whereas PPA is an energy substrate and has many proposed beneficial effects, it is also associated with human disorders involving mitochondrial dysfunction, including propionic acidemia and autism spectrum disorders (ASDs). We aimed to investigate the dichotomy between the health and disease effects of PPA by measuring mitochondrial function in ASD and age- and gender-matched control lymphoblastoid cell lines (LCLs) following incubation with PPA at several concentrations and durations both with and without an in vitro increase in reactive oxygen species (ROS). Mitochondrial function was optimally increased at particular exposure durations and concentrations of PPA with ASD LCLs, demonstrating a greater enhancement. In contrast, increasing ROS negated the positive PPA effect with the ASD LCLs, showing a greater detriment. These data demonstrate that enteric microbiome metabolites such as PPA can have both beneficial and toxic effects on mitochondrial function, depending on concentration, exposure duration and microenvironment redox state with these effects amplified in LCLs derived from individuals with ASD. As PPA, as well as enteric bacteria, which produce PPA, have been implicated in a wide variety of diseases, including ASD, diabetes, obesity and inflammatory diseases, insight into this metabolic modulator from the host microbiome may have wide applications for both health and disease.

Giant-cell arteritis (GCA) is a systemic autoimmune disease affecting primarily the elderly. Giant cell arteritis can cause sudden and potentially bilateral sequential vision loss in the elderly. Therefore, it is considered a medical emergency in ophthalmology and a significant cause of morbidity in an increasingly aging population. Ophthalmologists need to be able to recognize the classic symptoms and signs of this disease, and then be able to work-up and treat these patients in an efficient manner. An in-depth review of GCA from the literature as well as personal clinical experience follows.

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A 27-year-old pregnant woman reported progressive loss of vision. Brain MRI disclosed an intracranial mass compressing the optic nerves and chiasm with imaging features suggestive of meningioma. Because delivery was imminent, surgical removal was deferred. Within a few days after delivery, the patient noted improvement in vision. Subsequent neuro-ophthalmological evaluations documented almost complete visual recovery within 2 months postpartum. The mass was removed surgically at 10 months postpartum. It was a grade I meningioma with progesterone cell surface receptors. The patient's visual function has remained stable during a follow-up of 14 months. This is the first reported case with full visual function and MRI documentation of spontaneous postpartum visual recovery in a progesterone receptor-positive meningioma compressing the anterior visual pathway.

A 31-year-old woman who had lost 240 lbs following bariatric surgery 3 years ago presented with decreased vision. The patient was found to have deficiencies of folate and vitamin B 1 , and to a lesser degree vitamins B 6 and B 12 . The patient was treated with vitamin supplementation but without improvement. Bariatric surgery is known to cause B vitamin and folate deficiencies, which can lead to both serious ocular and neurological complications. This is important as the incidence of obesity increases and thus the number of bariatric procedures. It is paramount that patients undergoing these procedures and their physicians be made aware of the need for vitamin supplementation to prevent nutritional optic neuropathy.

Idiopathic intracranial hypertension (IIH) is a syndrome characterized by increased intracranial pressure (ICP), the absence of structural lesions on neuroimaging, and normal cerebrospinal fluid composition. Cerebral venous sinus thrombosis (CVST) is a common cause of increased ICP and can be differentiated from IIH with magnetic resonance venography. We describe a young woman with typical IIH who underwent lumbar puncture and was treated with a short course of high-dose corticosteroids followed by acetazolamide. She subsequently developed CVST, subarachnoid hemorrhage, and stroke. Risk factors that may have resulted in CVST are discussed.

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