Inter-individual variability in cortical excitability and motor network connectivity following multiple blocks of rTMS

The responsiveness to non-invasive neuromodulation protocols shows high inter-individual variability, the reasons of which remain poorly understood. We here tested whether the response to intermittent theta-burst stimulation (iTBS) - an effective repetitive transcranial magnetic stimulation (rTMS) protocol for increasing cortical excitability - depends on network properties of the cortical motor system. We furthermore investigated whether the responsiveness to iTBS is dose-dependent. To this end, we used a sham-stimulation controlled, single-blinded within-subject design testing for the relationship between iTBS aftereffects and (i) motor-evoked potentials (MEPs) as well as (ii) resting-state functional connectivity (rsFC) in 16 healthy subjects. In each session, three blocks of iTBS were applied, separated by 15min. We found that non-responders (subjects not showing an MEP increase of ≥10% after one iTBS block) featured stronger rsFC between the stimulated primary motor cortex (M1) and premotor areas before stimulation compared to responders. However, only the group of responders showed increases in rsFC and MEPs, while most non-responders remained close to baseline levels after all three blocks of iTBS. Importantly, there was still a large amount of variability in both groups. Our data suggest that responsiveness to iTBS at the local level (i.e., M1 excitability) depends upon the pre-interventional network connectivity of the stimulated region. Of note, increasing iTBS dose did not turn non-responders into responders. The finding that higher levels of pre-interventional connectivity precluded a response to iTBS could reflect a ceiling effect underlying non-responsiveness to iTBS at the systems level.

Dose-dependent effects of antipsychotics on efficacy and adverse effects in schizophrenia

BACKGROUND

Antipsychotics are a cornerstone of pharmacological treatment of schizophrenia. Improved understanding of the dose-response relationship of antipsychotics in terms of efficacy, adverse effects, and mortality can help to optimize the pharmacological treatment of schizophrenia.

METHODS

This narrative literature review summarizes current evidence on the relationship of antipsychotic dose with efficacy, adverse effects, and mortality in patients with schizophrenia.

RESULTS

The efficacy of antipsychotics generally appeared to be highly dose-dependent in the acute phase of schizophrenia, with each antipsychotic having a specific dose-response curve. The presence or absence of dose-dependency and its extent varied according to the type of adverse effect. Parkinsonism, hyperprolactinemia, weight gain, and neurocognitive impairment appeared to be dose-related. The following adverse effects might be at least somewhat dose-dependent: akathisia, tardive dyskinesia, osteoporosis, sexual dysfunction, diabetes mellitus, myocardial infarction, stroke, thromboembolism, QT interval prolongation, anticholinergic adverse effects, somnolence, pneumonia, hip fracture, and neuroleptic malignant syndrome. In contrast, the relationships of antipsychotic dose with dyslipidemia, hypotension, seizure, sialorrhea, and neutropenia and agranulocytosis remained unclear due to mixed findings and/or limited data. Although a higher lifetime cumulative antipsychotic dose might contribute to higher mortality, it is still difficult to conclude whether mortality increases in a dose-dependent manner.

CONCLUSION

These findings could help clinicians to optimize antipsychotic treatment in patients with schizophrenia by balancing risks and benefits in clinical practice. However, further investigations with larger sample sizes and more robust study designs that focus on each antipsychotic agent are needed.

Glucose levels show independent and dose-dependent association with worsening acute pancreatitis outcomes: Post-hoc analysis of a prospective, international cohort of 2250 acute pancreatitis cases

BACKGROUND

Metabolic risk factors, such as obesity, hypertension, and hyperlipidemia are independent risk factors for the development of various complications in acute pancreatitis (AP). Hypertriglyceridemia dose-dependently elicits pancreatotoxicity and worsens the outcomes of AP. The role of hyperglycemia, as a toxic metabolic factor in the clinical course of AP, has not been examined yet.

METHODS

We analyzed a prospective, international cohort of 2250 AP patients, examining associations between (1) glycosylated hemoglobin (HbA1c), (2) on-admission glucose, (3) peak in-hospital glucose and clinically important outcomes (mortality, severity, complications, length of hospitalization (LOH), maximal C-reactive protein (CRP)). We conducted a binary logistic regression accounting for age, gender, etiology, diabetes, and our examined variables. Receiver Operating Characteristic Curve (ROC) was applied to detect the diagnostic accuracy of the three variables.

RESULTS

Both on-admission and peak serum glucose are independently associated with AP severity and mortality, accounting for age, gender, known diabetes and AP etiology. They show a dose-dependent association with severity (p < 0.001 in both), mortality (p < 0.001), LOH (p < 0.001), maximal CRP (p < 0.001), systemic (p < 0.001) and local complications (p < 0.001). Patients with peak glucose >7 mmol/l had a 15 times higher odds for severe AP and a five times higher odds for mortality. We found a trend of increasing HbA1c with increasing LOH (p < 0.001), severity and local complications.

CONCLUSIONS

On-admission and peak in-hospital glucose are independently and dose-dependently associated with increasing AP severity and mortality. In-hospital laboratory control of glucose and adequate treatment of hyperglycemia are crucial in the management of AP.

Simvastatin therapy in higher dosages deteriorates bone quality: Consistent evidence from population-wide patient data and interventional mouse studies

BACKGROUND

Combining mouse experiments with big data analysis of the Austrian population, we investigated the association between high-dose statin treatment and bone quality.

METHODS

The bone microarchitecture of the femur and vertebral body L4 was measured in male and ovariectomized female mice on a high-fat diet containing simvastatin (1.2 g/kg). A sex-specific matched big data analysis of Austrian health insurance claims using multiple logistic regression models was conducted (simvastatin 60-80 mg/day vs. controls; males: n = 138,666; females: n = 155,055).

RESULTS

High-dose simvastatin impaired bone quality in male and ovariectomized mice. In the trabecular femur, simvastatin reduced bone volume (µm³: ♂, 213 ± 15 vs. 131 ± 7, p < 0.0001; ♀, 66 ± 7 vs. 44 ± 5, p = 0.02) and trabecular number (1/mm: ♂, 1.88 ± 0.09 vs. 1.27 ± 0.06, p < 0.0001; ♀, 0.60 ± 0.05 vs. 0.43 ± 0.04, p = 0.01). In the cortical femur, bone volume (mm³: ♂, 1.44 ± 0.03 vs. 1.34 ± 0.03, p = 0.009; ♀, 1.33 ± 0.03 vs. 1.12 ± 0.03, p = 0.0002) and cortical thickness were impaired (µm: ♂, 211 ± 4 vs. 189 ± 4, p = 0.0004; ♀, 193 ± 3 vs. 169 ± 3, p < 0.0001). Similar impairments were found in vertebral body L4. Simvastatin-induced changes in weight or glucose metabolism were excluded as mediators of deteriorations in bone quality. Results from mice were supported by a matched cohort analysis showing an association between high-dose simvastatin and increased risk of osteoporosis in patients (♂, OR: 5.91, CI: 3.17-10.99, p < 0.001; ♀, OR: 4.16, CI: 2.92-5.92, p < 0.001).

CONCLUSION

High-dose simvastatin dramatically reduces bone quality in obese male and ovariectomized female mice, suggesting that direct drug action accounts for the association between high dosage and increased risk of osteoporosis as observed in comparable human cohorts. The underlying pathophysiological mechanisms behind this relationship are presently unknown and require further investigation.