Role of different proteolytic pathways in degradation of muscle protein from streptozotocin-diabetic rats

Abstract

In vitro rats of overall proteolysis and the activities of four different proteolytic pathways (lysosomal, Ca2+ dependent, ATP dependent, and ATP independent), as well as rates of protein synthesis, were measured in soleus and extensor digitorum longus (EDL) muscles from streptozotocin-diabetic rats. In the acute phase (1-3 days) of diabetes, there was an increase in overall proteolysis that coincided with an increased activity of the Ca(2+)-dependent pathway in both soleus and EDL and of the ATP-dependent pathway in EDL. After longer periods (5-10 days) of diabetes, the overall rate of protein degradation decreased and reached values similar to or even lower than those of controls as a result of a reduction in the activities of Ca(2+)-dependent and ATP-dependent pathways. No change was detected at any time interval in the activity of the intralysosomal proteolytic system in muscles from diabetic animals. Rates of protein synthesis were already reduced 24 h after diabetes induction and decreased further thereafter. Insulin treatment restored to normal the activities of the proteolytic pathways and rates of protein synthesis.

Assessment of the Antidiabetic Potential of the Ethanolic Extract of Date Palm (Phoenix Dactylifera) Seed in Alloxan-Induced Diabetic Rats

“…Due to destruction of β-cells, the decrease in body weight and increase in food and water intake were commonly observed in diabetes and this may be due to metabolic changes caused by lack or deficiency of insulin [41]. In diabetic rats, reduction in body weight changes observed might be the result of degradation of structural proteins due to deficiency of carbohydrate for the energy metabolism [42]. A slight increase in the body weight of diabetic animals treated with date palm seed extract after 14 days was observed when compared to the diabetic control group which signifies the reversal of gluconeogenesis.…”

Contribution of proteolysis and de novo synthesis to alanine production in diabetic rat skeletal muscle: a 15 N/ 1 H nuclear magnetic resonance study

“…There is strong evidence that diabetes in the acute phase (1-3 days) causes a situation in which protein synthesis is markedly reduced, protein degradation is increased [10,26] and the efflux of amino acids from skeletal muscle studied in vitro [5,7] or in vivo [6,16] is increased. The lack of gain in body weight, the atrophy of EDL muscles (13 %) and the increased total alanine and tyrosine release (20 and 50 % of controls, respectively) from superfused EDL muscles obtained in our experimental STZ-diabetic rats confirm these observations.…”

“…Indeed, Pepato et al [10], in the acute phase (1-3 days) of (2) valine at 2.15 and 1.92 ppm, (3) unknown resonance at 1.75 ppm, (4) free alanine at 1.59 ppm, (5) alanine in a complex structure at 1.43 ppm. Only peaks 1, 2, 4 and 5 were used for the quantification.…”

Participação do estresse oxidativo na disfunção muscular esquelética em ratos diabéticos.

“…, na qual se destacam as calpaínas, quanto pelo sistema ubiquitina-proteassomo (Pepato et al, 1996). Neste período, animais diabéticos também apresentam expressão elevada de atrogina-1 e MURF1 (Lecker et al, 2004).…”

“…Neste período, animais diabéticos também apresentam expressão elevada de atrogina-1 e MURF1 (Lecker et al, 2004). Porém, a degradação proteica volta a valores semelhantes ao controle 5 a 10 dias após indução do diabetes (Pepato et al, 1996), da mesma forma que a expressão de atrogina-1 e MURF1 (Mastrocola et al, 2008).…”