Human Studies

Type 2 diabetes related polyneuropathy (DPN) is associated with increased vascular events and mortality, but determinants and outcomes of pain in DPN are poorly understood. We sought to examine the effect of neuropathic pain on vascular events and mortality in patients without DPN, DPN with pain (DPN+P), and DPN without pain (DPN-P).

Chronic knee pain (CKP) is a common pain complaint in older adults that is often associated with disability. This study investigated the relationship between 2 components of subjective well-being (depressive symptoms and life satisfaction) and CKP phenotypes based on the presence of knee disability.

Some chronic pain conditions and comorbidities suppress the hypothalamic-pituitary-adrenal (HPA) axis and response to dynamic testing. We measured HPA axis responses to corticotropin-releasing hormone (CRH) administration in relation to chronic pelvic pain and endometriosis. In a cross-sectional study of women (n = 54) with endometriosis-associated chronic pelvic pain (n = 22), chronic pelvic pain alone (n = 12), or healthy volunteers (n = 20), adrenocorticotropic-releasing hormone (ACTH) and cortisol levels were measured at 0, 15, 30, and 45 min after intravenous ovine CRH administration. ACTH and cortisol delta (peak-baseline) and area under the curve (AUC) were compared by study group and assessed for association with race and menstrual and non-menstrual pain severity. HPA axis responses did not differ among the racially diverse groups or in those with pain compared with healthy volunteers. However, when stratified by race, ACTH delta (129.9 ± 130.7 vs. 52.5 ± 66.0 pg/mL; p = 0.003), ACTH AUC (4813 ± 4707 vs. 2290 ± 2900 min*pg/mL; p = 0.013), and cortisol delta (26.3 ± 21.5 vs. 13.2 ± 9.7 μg/mL; p = 0.005) were significantly higher in black (n = 10) than predominately white (non-black) subjects (n = 44; 39/44 white). In analyses among primarily white (non-black) women, greater menstrual pain severity was associated with blunted ACTH delta (p = 0.015) and cortisol delta (p = 0.023), and greater non-menstrual pain severity with blunted cortisol delta (p = 0.017). Neuroendocrine abnormalities in women with chronic pelvic pain may differ by pain manifestations and may vary by race. The higher HPA axis response in black women merits investigation in pelvic pain studies stratified by race. In white (non-black) women experiencing pain, a blunted response was related to pain severity suggesting pain affects women independently of endometriosis lesions.

The transient receptor potential cation channel subfamily V member 3 (TRPV3) channel plays a critical role in skin physiology, and mutations in TRPV3 result in the development of a congenital skin disorder, Olmsted syndrome. Here we describe multiple cryo-electron microscopy structures of human TRPV3 reconstituted into lipid nanodiscs, representing distinct functional states during the gating cycle. The ligand-free, closed conformation reveals well-ordered lipids interacting with the channel and two physical constrictions along the ion-conduction pore involving both the extracellular selectivity filter and intracellular helix bundle crossing. Both the selectivity filter and bundle crossing expand upon activation, accompanied by substantial structural rearrangements at the cytoplasmic intersubunit interface. Transition to the inactivated state involves a secondary structure change of the pore-lining helix, which contains a π-helical segment in the closed and open conformations, but becomes entirely α-helical upon inactivation. Together with electrophysiological characterization, structures of TRPV3 in a lipid membrane environment provide unique insights into channel activation and inactivation mechanisms.

Pain is a growing public health issue worldwide, but there is limited population-based evidence in low- and middle-income country settings. Using nationwide Indonesian Family Life Survey (IFLS) data in 2007 and 2014, this research sets out to investigate the associations between changes in pain status between two time points and its impact on functional health outcomes among middle-aged and older adults in Indonesia. Analyses focused on 7936 adults aged 50 years and older in 2014 who responded to both waves. Functional health was assessed using a composite score of functional limitations (range 20-100), representing difficulty in performing activities of daily living, and grip strength (kilograms). Multivariate linear regression models were used to analyse associations between pain measured in 2007 and 2014 and functional health in 2014. Severe pain in the latest wave of IFLS was associated with older age, female, lower education, having chronic conditions or depressive symptoms. Notably, those who reported 'low-medium' pain in 2007 and 'severe' pain in 2014 belonged to the most vulnerable group with worst functional health outcomes (4.96 points higher limitation scores and 1.17 kg weaker average grip strength). Findings have implications for public health policy in monitoring and management of pain including related co-morbidities as an increasingly critical component of population ageing.