A Novel Cellular Defect in Diabetes

Abstract

OBJECTIVESkeletal muscle myopathy is a common diabetes complication. One possible cause of myopathy is myocyte failure to repair contraction-generated plasma membrane injuries. Here, we test the hypothesis that diabetes induces a repair defect in skeletal muscle myocytes.RESEARCH DESIGN AND METHODSMyocytes in intact muscle from type 1 (INS2Akita+/−) and type 2 (db/db) diabetic mice were injured with a laser and dye uptake imaged confocally to test repair efficiency. Membrane repair defects were also assessed in diabetic mice after downhill running, which induces myocyte plasma membrane disruption injuries in vivo. A cell culture model was used to investigate the role of advanced glycation end products (AGEs) and the receptor for AGE (RAGE) in development of this repair defect.RESULTSDiabetic myocytes displayed significantly more dye influx after laser injury than controls, indicating a repair deficiency. Downhill running also resulted in a higher level of repair failure in diabetic mice. This repair defect was mimicked in cultured cells by prolonged exposure to high glucose. Inhibition of the formation of AGE eliminated this glucose-induced repair defect. However, a repair defect could be induced, in the absence of high glucose, by enhancing AGE binding to RAGE, or simply by increasing cell exposure to AGE.CONCLUSIONSBecause one consequence of repair failure is rapid cell death (via necrosis), our demonstration that repair fails in diabetes suggests a new mechanism by which myopathy develops in diabetes.

Cell wounding activates phospholipase D in primary mouse keratinocytes

“…2 ). Because membrane repair occurs rapidly in the presence of calcium [e.g., ( 20,21 ) and see below], this result indicates that upon membrane repair, PLD activity returned to basal levels, suggesting a possible role for this enzyme in the repair process.…”

“…A laser was used to disrupt cell membranes in the presence of a lipid-soluble fl uorescent dye. This dye enters the cell and binds to membrane-delimited cell organelles such that the fl uorescence intensity of the cell continues to increase until the membrane disruption is repaired, thereby halting dye entry ( 20,21 ). Because membrane repair requires calcium with 1,25(OH) 2 D 3 for 24 h before monitoring PLD activation in lifted cells as in Fig.…”

“…Plasma membrane repair following cell wounding was measured as in ( 20,21 ). Keratinocytes were incubated with PLD inhibitors or DMSO (vehicle control) in SFKM or K-SFM prior to washing and addition of PBS with or without calcium.…”

S100 and annexin proteins identify cell membrane damage as the Achilles heel of metastatic cancer cells

“…1,2 Defect in the muscle cell's ability to repair has been shown to result in muscular dystrophy, [3][4][5][6] where poor repair of injured muscle cell membrane leads to cell death and tissue inflammation. Poor plasma membrane repair (PMR) is also associated with NiemannPick type A, 7 diabetes, 8 and ChediakHigashi 9 syndrome and therapies targeting PMR have been shown to be effective in treating muscle and lung injuries. [10][11][12] While much of the focus has been on disease resulting from poor PMR, we have recently identified that improved PMR is an important contributor for cancer metastasis.…”

Plasma membrane repair provides a new strategy for targeting metastatic cancer cells

“…Still, many cells experience plasma membrane ruptures on a recurring basis that they need to cope with to maintain cell and tissue integrity. Disease results from defect in the repair system and is associated with cancer [1] , diabetes [2] , Chediak-Higashi [3] syndrome and muscular dystrophies [4] .…”