Biology subjects

Karppinen, J. E.

Publications and source records attributed to Karppinen, J. E..

3 recordsLinked to original sources

bioRxiv2024

Estrogen deficiency reduces maximal running capacity and affects serotonin levels differently in the hippocampus and nucleus accumbens in response to acute exercise

ObjectiveEstrogen deficiency is associated with unfavorable changes in body composition and metabolic health. While physical activity ameliorates several of the negative effects, loss of ovarian function is associated with decreased physical activity levels. It has been proposed that the changes in brain neurochemical levels and /or impaired skeletal muscle function may underlie this phenomenon. MethodsWe studied the effect of estrogen deficiency induced via ovariectomy (OVX) in female Wistar rats (n=64). Rats underwent either sham or OVX surgery and were allocated thereafter into four groups matched for body mass and maximal running capacity: sham/control, sham/max, OVX/control, and OVX/max, of which the max groups had maximal running test before euthanasia to induce acute response to exercise. Metabolism, spontaneous activity, and maximal running capacity were measured before (PRE) and after (POST) the surgeries. Three months following the surgery, rats were euthanized, and blood and tissue samples harvested. Proteins were analyzed from gastrocnemius muscle and retroperitoneal adipose tissue via Western blot. Brain neurochemical markers were measured from nucleus accumbens (NA) and hippocampus (HC) using ultra-high performance liquid chromatography. ResultsOVX had lower basal energy expenditure and higher body mass and retroperitoneal adipose tissue mass compared with sham group (p[≤]0.005). OVX reduced maximal running capacity by 17% (p=0.005) with no changes in muscle mass or phosphorylated form of regulatory light chain (pRLC) in gastrocnemius muscle. OVX was associated with lower serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA) level in the NA compared with sham (p=0.007). In response to acute exercise, OVX was associated with low serotonin level in the HC and high level in the NA (p[≤]0.024). ConclusionsOur results highlight that OVX reduces maximal running capacity and affects the response of brain neurochemical levels to acute exercise in a brain region-specific manner. These results may offer mechanistic insight into why OVX reduces willingness to exercise.

molecular biology↗

bioRxiv2022

Age but not menopausal status is linked to lower resting energy expenditure

ContextIt remains uncertain whether aging before late adulthood and menopause are associated with fat-free mass and fat mass-adjusted resting energy expenditure (REEadj). ObjectivesWe investigated whether REEadj differs between middle-aged and younger women and between middle-aged women with different menopausal statuses. We repeated the age group comparison between middle-aged mothers and their daughters to partially control for genotype. We also explored whether serum estradiol and follicle-stimulating hormone concentrations explain REEadj in midlife. MethodsWe divided 120 women, including 16 mother-daughter pairs, into age groups; group I (n = 26) consisted of participants aged 17-21, group II (n = 35) of those aged 22-38 and group III (n = 59) of those aged 41-58 years. The women in group III were further categorized as pre- or perimenopausal (n = 19), postmenopausal (n = 30) or postmenopausal hormone therapy users (n = 10). REE was assessed using indirect calorimetry, body composition using dual-energy X-ray absorptiometry and hormones using immunoassays. ResultsThe REEadj of group I was 126 kcal/d (95% CI: 93-160) higher than that of group III, and the REEadj of group II was 88 kcal/d (95% CI: 49-127) higher. Furthermore, daughters had a 100 kcal/d (95% CI: 63-138 kcal/d) higher REEadj than their middle-aged mothers (all P < 0.001). In group III, REEadj was not lower in postmenopausal women and did not vary by sex hormone concentrations. ConclusionsWe demonstrated that REEadj declines with age in women before late adulthood, also when controlling partially for genetic background, and that menopause may not contribute to this decline.

physiology↗

bioRxiv2022

Extracellular vesicles and high-density lipoproteins: Exercise and estrogen-responsive small RNA carriers

Decreased systemic estrogen levels (i.e., menopause) affect metabolic health. However, the detailed mechanisms underlying this process remain unclear. Both estrogens and exercise have been shown to improve metabolic health, which may be partly mediated by circulating microRNA (c-miR) signaling. In recent years, extracellular vesicles (EV) have increased interest in the field of tissue crosstalk. However, in many studies on EV-carried miRs, the co-isolation of high-density lipoprotein (HDL) particles with EVs has not been considered, potentially affecting the results. Here, we demonstrate that EV and HDL particles have distinct small RNA (sRNA) content, including both host and nonhost sRNAs. Exercise caused an acute increase in relative miR abundancy in EVs, whereas in HDL particles, it caused an increase in transfer RNA-derived sRNA. Furthermore, we demonstrate that estrogen deficiency caused by menopause blunts acute exercise-induced systemic miR-response in both EV and HDL particles. HIGHLIGHTSO_LIExtracellular vesicles and HDL particles have a distinct sRNA content C_LIO_LIExtracellular vesicles and HDL particles carry both host and nonhost sRNA cargo C_LIO_LIEstrogen deficiency blunts the c-miR-response induced by acute exercise C_LIO_LIExercise responsive miRs in HT users may regulate the choice of energy substrate C_LI

molecular biology↗