Healthy women show more experimentally induced central sensitization compared with men

Neuropathic pain in diabetic polyneuropathy: a 5-year prospective study

ABSTRACT

There are few prospective studies on neuropathic pain in diabetic polyneuropathy (P-DPN). We aimed to examine the development of P-DPN over time as well as factors associated with both the development of and relief from pain. In this 5-year follow-up study, we included 102 patients with at least probable DPN at baseline, according to the Toronto consensus criteria, recruited from a nationwide Danish cohort of 5514 patients with newly diagnosed type 2 diabetes between 2016 and 2018. All participants underwent detailed phenotyping of both DPN and pain, consisting of a bedside sensory examination, quantitative sensory testing (QST), skin biopsies, and nerve conduction studies at baseline and follow-up. The estimated prevalence (95% CI) of at least probable P-DPN increased from 11.5% (8.2; 14.9) at baseline to 14.8% (9.2; 20.4) at follow-up, with a median (interquartile range) diabetes duration of 11.0 (9.2, 12.2) years. Among 64 patients with baseline nonpainful DPN, 38.2% developed pain at follow-up, while 28.9% of 38 patients with baseline P-DPN did not have pain at follow-up. A higher proportion of patients with baseline dysesthesia developed pain (42.9%), compared with patients without dysesthesia (27.9%, Χ2-test for trend: P < 0.0001). Development of pain was associated with female sex, lower baseline sensitivity to warm stimuli on QST, and lower baseline sural sensory nerve action potential amplitudes. Relief from pain was associated with lower baseline body mass index and cholesterol, as well as higher sensitivity to cold, mechanical, and vibratory stimuli on QST at baseline. This detailed study identified risk factors for neuropathic pain development and cessation.

Sex-related differences in motoneuron firing behavior during typical development

Sex-related differences have been documented for intrinsic motoneuron excitability and firing rates in young adults, with females exhibiting higher excitability than males; however, it is unknown whether these parameters are affected by sex earlier in development. We compared the sex-related differences in firing behavior of single tibialis anterior (TA) motor units decomposed from high-density surface electromyography (EMG) in young (7-17 yr) and older (18-28 yr) developmental males and females during triangular dorsiflexion contractions at 10, 20, and 30% of their maximal voluntary contraction (MVC) torque. The amount of motoneuron self-sustained firing at estimated synaptic inputs below that needed for recruitment was measured [i.e., self-sustained firing (ΔF)], along with start, maximal, and end firing rates and the interspike interval variability across the entire contraction. When taking the recruitment threshold of the motor units into account, both young and older development females had larger ΔF values compared with males, which functionally allows more sustained firing of TA motoneurons in females. Young development females also had faster firing rates compared with males and equivalent firing variability, an effect that disappeared in the older development group, where males exhibited higher start rates and less firing variability. Overall, although female motor unit firing rates became similar to males as they matured, they were more variable, slower at recruitment, and continued to exhibit evidence of greater persistent inward currents that sustained firing (ΔF), the latter indicating that sex-related differences in intrinsic motoneuron excitability are established early during development.NEW & NOTEWORTHY The intrinsic excitability of tibialis anterior (TA) motoneurons was compared between males and females before (7-17 yr) and during (18-28 yr) adulthood. Female motor units exhibited greater self-sustained firing compared with males in both the pre-adult and adult groups, suggesting the intrinsic excitability of motoneurons is established early in life and may not be tightly dependent on the level of sex hormones, unlike the number of decomposed motor units that reflect muscle size.

Clinical Phenotypes, Serological Biomarkers, and Synovial Features Defining Seropositive and Seronegative Rheumatoid Arthritis: A Literature Review

Rheumatoid arthritis (RA) is a chronic autoimmune disorder which can lead to long-term joint damage and significantly reduced quality of life if not promptly diagnosed and adequately treated. Despite significant advances in treatment, about 40% of patients with RA do not respond to individual pharmacological agents and up to 20% do not respond to any of the available medications. To address this large unmet clinical need, several recent studies have focussed on an in-depth histological and molecular characterisation of the synovial tissue to drive the application of precision medicine to RA. Currently, RA patients are clinically divided into "seropositive" or "seronegative" RA, depending on the presence of routinely checked antibodies. Recent work has suggested that over the last two decades, long-term outcomes have improved significantly in seropositive RA but not in seronegative RA. Here, we present up-to-date differences in epidemiology, clinical features, and serological biomarkers in seronegative versus seropositive RA and discuss how histological and molecular synovial signatures, revealed by recent large synovial biopsy-based clinical trials, may be exploited to refine the classification of RA patients, especially in the seronegative group.