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Exercise‐Induced Increase in Pro‐ and Macroglycogen Content in Hearts from Type 1 Diabetic Mice
Author(s) -
Ross Karen D,
Shearer Jane,
Carley Andrew N,
Chan Carol WY,
Carroll Rogayah,
Severson David L
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.4.a168-b
Subject(s) - glycogen , medicine , endocrinology , sed , diabetes mellitus , diabetic cardiomyopathy , insulin , chemistry , heart failure , cardiomyopathy
Diabetes adversely affects glucose metabolism, resulting in elevated levels of heart glycogen. Exercise training increases glycogen synthesis activity in diabetes; therefore the aim of this study was to examine the effects of exercise on glycogen content in hearts from streptozotocin‐induced (insulin‐deficient for duration of study) type 1 diabetic mice (T1D) mice compared to CD‐1 controls. Mice were exercised by running for 60 min/d, 5 d/wk for 6 wk at low‐moderate intensity. Hearts from T1D and control mice at 12 wk of age were subjected to a 60 min working heart perfusion with glucose and palmitate, prior to glycogen measurements (μmol/g dw) as total glycogen (G t ), proglycogen (PG) and macroglycogen (MG). G t for T1D sedentary (SED) hearts was not significantly different from SED or exercised (EX) non‐diabetic, CD1 controls. In T1D SED hearts, PG contributed 60% of total glycogen, which was significantly elevated compared to EX controls but not to SED controls. EX T1D hearts showed a nearly 2‐fold increase in G t compared to SED diabetic hearts (935±86 vs 584±20) with PG and MG contributing 558±21 and 436±80 glucosyl units respectively. There are intriguing aspects of this data: i) there was no difference in G t between SED T1D and controls implying glycogen synthesis is not impaired in T1D hearts. (ii) Elevated PG levels in T1D hearts reflects a distinct selective process in glycogen formation compared to controls, suggesting T1D hearts form new granules at the expense of MG to maintain G t. (iii) An exercise‐induced improvement in glucose disposal may account for elevated PG and MG levels in EX T1D perfused hearts. Supported by CIHR (DS) and Genome Alberta (JS).