title: Effects of type 1 diabetes, sprint training and sex on skeletal muscle sarcoplasmic reticulum Ca2+ uptake and Ca2+-ATPase activity.
abstract: Calcium cycling is integral to muscle performance during the rapid muscle contraction and relaxation of high-intensity exercise. Ca(2+) handling is altered by diabetes mellitus, but has not previously been investigated in human skeletal muscle. We investigated effects of high-intensity exercise and sprint training on skeletal muscle Ca(2+) regulation among men and women with type 1 diabetes (T1D, n = 8, 3F, 5M) and matched non-diabetic controls (CON, n = 8, 3F, 5M). Secondarily, we examined sex differences in Ca(2+) regulation. Subjects undertook 7 weeks of three times-weekly cycle sprint training. Before and after training, performance was measured, and blood and muscle were sampled at rest and after high-intensity exercise. In T1D, higher Ca(2+)-ATPase activity (+28%) and Ca(2+) uptake (+21%) than in CON were evident across both times and days (P < 0.05), but performance was similar. In T1D, resting Ca(2+)-ATPase activity correlated with work performed until exhaustion (r = 0.7, P < 0.01). Ca(2+)-ATPase activity, but not Ca(2+) uptake, was lower (-24%, P < 0.05) among the women across both times and days. Intense exercise did not alter Ca(2+)-ATPase activity in T1D or CON. However, sex differences were evident: Ca(2+)-ATPase was reduced with exercise among men but increased among women across both days (time × sex interaction, P < 0.05). Sprint training reduced Ca(2+)-ATPase (-8%, P < 0.05), but not Ca(2+) uptake, in T1D and CON. In summary, skeletal muscle Ca(2+) resequestration capacity was increased in T1D, but performance was not greater than CON. Sprint training reduced Ca(2+)-ATPase in T1D and CON. Sex differences in Ca(2+)-ATPase activity were evident and may be linked with fibre type proportion differences.
authors.affiliation: Clinical and Rehabilitation Sciences Research Group, Faculty of Health Sciences, The University of Sydney, PO Box 170, Lidcombe, NSW 1825, Australia.   alison.harmer@sydney.edu.au.
authors.forename: A R
authors.initials: AR
authors.lastname: Harmer
authors.forename: P A
authors.initials: PA
authors.lastname: Ruell
authors.forename: S K
authors.initials: SK
authors.lastname: Hunter
authors.forename: M J
authors.initials: MJ
authors.lastname: McKenna
authors.forename: J M
authors.initials: JM
authors.lastname: Thom
authors.forename: D J
authors.initials: DJ
authors.lastname: Chisholm
authors.forename: J R
authors.initials: JR
authors.lastname: Flack
mesh_terms: D000328:Adult; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D016022:Case-Control Studies; D003922:Diabetes Mellitus, Type 1 / Q000378:metabolism*; D015444:Exercise; D005260:Female; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000502:physiology; D012519:Sarcoplasmic Reticulum / Q000378:metabolism*; D012737:Sex Factors
chemical_list: D000252:Calcium-Transporting ATPases; D002118:Calcium