This study investigated the hypoglycemic, hypolipidemic, and antioxidant effects of dietary quercetin in an animal model of type 2 diabetes mellitus. Four-week-old C57BL/KsJ-db/db mice (n = 18) were offered an AIN-93G diet or a diet containing quercetin at 0.04% (low quercetin, LQE) or 0.08% of the diet (high quercetin, HQE) for 6 weeks after 1 week of adaptation. Plasma glucose, insulin, adiponectin, and lipid profiles, and lipid peroxidation of the liver were determined. Plasma glucose levels were significantly lower in the LQE group than in the control group, and those in the HQE group were even further reduced compared with the LQE group. The homeostasis model assessment for insulin resistance (HOMA-IR) showed lower values for LQE and HQE than for the control group without significant influence on insulin levels. High quercetin increased plasma adiponectin compared with the control group. Plasma triglycerides in the LQE and HQE groups were lower than those in the control group. Supplementation with high quercetin decreased plasma total cholesterol and increased HDL-cholesterol compared with the control group. Consumption of low and high quercetin reduced thiobarbituric acid reactive substances (TBARS) levels and elevated activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) in the liver. Thus, quercetin could be effective in improving hyperglycemia, dyslipidemia, and antioxidant status in type 2 diabetes.

Vestibular neuritis is the most common cause of acute spontaneous vertigo. Vestibular neuritis is ascribed to acute unilateral loss of vestibular function, probably due to reactivation of herpes simplex virus in the vestibular ganglia. The diagnostic hallmarks of vestibular neuritis are spontaneous horizontal-torsional nystagmus beating away from the lesion side, abnormal head impulse test for the involved semicircular canals, ipsilesional caloric paresis, decreased responses of vestibular-evoked myogenic potentials during stimulation of the affected ear, and unsteadiness with a falling tendency toward the lesion side. Vestibular neuritis preferentially involves the superior vestibular labyrinth and its afferents. Accordingly, the function of the posterior semicircular canal and saccule, which constitute the inferior vestibular labyrinth, is mostly spared in vestibular neuritis. However, because the rare subtype of inferior vestibular neuritis lacks the typical features of vestibular neuritis, it may be misdiagnosed as a central vestibular disorder. Even in the patient with the typical pattern of spontaneous nystagmus observed in vestibular neuritis, brain imaging is indicated when the patient has unprecedented headache, negative head impulse test, severe unsteadiness, or no recovery within 1 to 2 days. Symptomatic medication is indicated only during the acute phase to relieve the vertigo and nausea/vomiting. Vestibular rehabilitation hastens the recovery. The efficacy of topical and systemic steroids requires further validation.

Previous studies have demonstrated an association of osteopenia/osteoporosis with idiopathic benign paroxysmal positional vertigo (BPPV). Since vitamin D takes part in the regulation of calcium and phosphorus found in the body and plays an important role in maintaining proper bone structure, decreased bone mineral density in patients with BPPV may be related to decreased serum vitamin D. We measured the serum levels of 25-hydroxyvitamin D in 100 patients (63 women and 37 men, mean age ± SD = 61.8 ± 11.6) with idiopathic BPPV and compared the data with those of 192 controls (101 women and 91 men, mean age ± SD = 60.3 ± 11.3) who had lived in the same community without dizziness or imbalance during the preceding year. The selection of the controls and acquisition of clinical information were done using the data from the Fourth Korean National Health and Nutrition Examination Survey, 2008. The serum level of 25-hydroxyvitamin D was lower in the patients with BPPV than in the controls (mean ± SD = 14.4 ± 8.4 versus 19.1 ± 6.8 ng/ml, p = 0.001). Furthermore, patients with BPPV showed a higher prevalence of decreased serum vitamin D (<20 ng/ml, 80.0 vs. 60.1 %, p < 0.001) than the controls. Multiple logistic regression analyses adjusted for age, sex, body mass index, hypertension, diabetes, proteinuria, regular exercise and the existence of decreased bone mineral density demonstrated that vitamin D insufficiency (10-20 ng/ml) and deficiency (<10 ng/ml) were associated with BPPV with the odds ratios of 3.8 (95 % confidence interval = 1.51-9.38, p = 0.004) and 23.0 (95 % confidence interval = 6.88-77.05, p < 0.001). Our study demonstrated an association between idiopathic BPPV and decreased serum vitamin D. Decreased serum vitamin D may be a risk factor of BPPV.

Osteopenia/osteoporosis may be associated with idiopathic benign positional vertigo (BPV). The effectiveness of measuring bone mineral densitometry and restoring normal calcium metabolism for preventing recurrences of BPV requires further validation.

NCT00810641.