title: Augmented pressor and sympathetic responses to skeletal muscle metaboreflex activation in type 2 diabetes patients.
abstract: Previous studies have reported exaggerated increases in arterial blood pressure during exercise in type 2 diabetes (T2D) patients. However, little is known regarding the underlying neural mechanism(s) involved. We hypothesized that T2D patients would exhibit an augmented muscle metaboreflex activation and this contributes to greater pressor and sympathetic responses during exercise. Mean arterial pressure (MAP), heart rate (HR), and muscle sympathetic nerve activity (MSNA) were measured in 16 patients with T2D (8 normotensive and 8 hypertensive) and 10 healthy controls. Graded isolation of the muscle metaboreflex was achieved by postexercise ischemia (PEI) following static handgrip performed at 30% and 40% maximal voluntary contraction (MVC). A cold pressor test (CPT) was also performed as a generalized sympathoexcitatory stimulus. Increases in MAP and MSNA during 30 and 40% MVC handgrip were augmented in T2D patients compared with controls (P < 0.05), and these differences were maintained during PEI (MAP: 30% MVC PEI: T2D, Δ16 ± 2 mmHg vs. controls, Δ8 ± 1 mmHg; 40% MVC PEI: T2D, Δ26 ± 3 mmHg vs. controls, Δ16 ± 2 mmHg, both P < 0.05). MAP and MSNA responses to handgrip and PEI were not different between normotensive and hypertensive T2D patients (P > 0.05). Interestingly, MSNA responses were also greater in T2D patients compared with controls during the CPT (P < 0.05). Collectively, these findings indicate that muscle metaboreflex activation is augmented in T2D patients and this contributes, in part, to augmented pressor and sympathetic responses to exercise in this patient group. Greater CPT responses suggest that a heightened central sympathetic reactivity may be involved.
authors.affiliation: Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, Missouri;
authors.forename: Seth W
authors.initials: SW
authors.lastname: Holwerda
authors.affiliation: Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, Missouri;
authors.forename: Robert M
authors.initials: RM
authors.lastname: Restaino
authors.affiliation: Department of Medicine, University of Missouri, Columbia, Missouri;
authors.forename: Camila
authors.initials: C
authors.lastname: Manrique
authors.affiliation: Department of Medicine, University of Missouri, Columbia, Missouri;
authors.forename: Guido
authors.initials: G
authors.lastname: Lastra
authors.affiliation: School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, United Kingdom.
authors.forename: James P
authors.identifier: http://orcid.org/0000-0001-7851-9222
authors.initials: JP
authors.lastname: Fisher
authors.affiliation: Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, Missouri; Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri; and fadelp@uta.edu.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Fadel
mesh_terms: D000328:Adult; D062186:Arterial Pressure; D001794:Blood Pressure; D003080:Cold Temperature; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism* / Q000503:physiopathology*; D015444:Exercise; D005260:Female; D018737:Hand Strength; D006339:Heart Rate; D006801:Humans; D007511:Ischemia; D007537:Isometric Contraction; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000294:innervation / Q000378:metabolism* / Q000503:physiopathology*; D011312:Pressure; D013564:Sympathetic Nervous System / Q000503:physiopathology*
keywords: blood pressure; exercise; hypertension; muscle sympathetic nerve activity; postexercise ischemia