Plasma enzymic changes in insulin-induced hypoglycemia in experimental rabbits

Characterization of metabolic alterations in the lean metabolically unhealthy alpha defensin transgenic mice

Inflammation is consistently linked to dysmetabolism. In transgenic mice (Def+/+) model the neutrophilic peptide, alpha defensin, proved atherogenic. This phenotype occurred despite favorable cholesterol and glucose levels, and lower body weight and blood pressure. In this study, integration of metabolic&behavioral phenotyping system, endocrine, biochemical and mitochondrial assessment, pathological and immunohistochemical tests, and multiple challenge tests was established to explore the metabolic impact of alpha defensin. Compared to the control group, Def+/+ mice exhibited lower total energy expenditure and carbohydrate utilization, and higher fat oxidation. Their ACTH-cortisol and thyroid profiles were intact. Intriguingly, they had low levels of glucagon, with high ammonia, uric acid, triglyceride, and lactate. Mitochondrial evaluations were normal. Overall, defensin-induced hypoglucagonemia is associated with lipolysis, restricted glucose oxidation, and enhanced wasting. Def+/+ mice may be a useful model for studying the category of lean, apparently metabolically healthy, and atherosclerotic phenotype, with insight into a potential inflammatory-metabolic link.

Establishment of a reperfusion model in rabbits with acute myocardial infarction

Clinically effective cardioprotection under acute myocardial infarction (AMI) can only be achieved by establishing the mechanisms of reperfusion-induced cardiac cell death. In spite of the numerous earlier studies on the prevention of ischemia-reperfusion injury of myocardium, the problem of cardiac cell death upon reperfusion is not yet resolved. Even though animal models provide an immense opportunity in the understanding of the mechanisms of ischemia-reperfusion injury, clinically relevant animal models through which translation of this knowledge into clinic are lacking. In this work, we have established a reperfusion model in rabbits with induced AMI by obstructing and releasing the left anterior ventricular branch of left circumflex coronary artery, which is clinically more relevant. This was achieved by cutting the two left ribs of the rabbit followed by obstructing and releasing the artery unlike the traditional approach, which involves incision through sternum and blocking the anterior descending coronary artery. This animal model of ischemia-reperfusion more closely mimics the physiological condition and also the trauma the animal suffers is much smaller with higher survival rate and thus is a potentially better model for studying the pathology related to ischemia-reperfusion injury.

Glutathione suppresses increase of serum creatine kinase in experimental hypoglycemia

Inhibitory effects of reduced glutathione (GSH) on serum enzymes including alanine aminotransferase (AST), lactate dehydrogenase (LDH) and creatine kinase (CK) were investigated in the hypoglycemic rabbits. Hypoglycemia lasting for 60 min was induced by intravenous injection of insulin (10U/kg) and then recovered by intravenous glucose injection. Serum levels of ALT, AST, LDH and CK increased significantly (p<0.05) at 6h after the induction of hypoglycemia. Plasma GSH, oxidized glutathione (GSSG) and total glutathione (TGSH) began to increase significantly (p<0.05) at 1h after the insulin injection, and GSSG/TGSH ratio rose significantly (p<0.05) at 6h after the induction of hypoglycemia. GSSG contents and GSSG/TGSH ratio in quadriceps significantly increased during hypoglycemia. Administration of GSH significantly decreased plasma GSSG levels, GSSG/TGSH ratio (p<0.05) and suppressed the rise of serum enzymes induced by hypoglycemia. These results suggest that GSH administration may play a preventive role for increases of serum enzymes by experimental hypoglycemia.

Influence of handling procedures on rat plasma creatine kinase activity

Ten-week-old Sprague-Dawley rats were held behind the front legs before and during anesthetic injection of sodium pentobarbital (group 1, 12 rats), or lifted by the base of the tail before and during injection (group 2, 12 rats). Creatine kinase (CK) values were higher (P = 0.004) in group 1 (median 564 IU/L) than in group 2 (median 272 IU/L). Handling rats by holding them behind the front legs may reduce the usefulness of CK activity as a measure of muscular disorders.

Rise in plasma oxidized glutathione by experimental hypoglycemia

Changes in plasma glutathione were investigated under hypoglycemic status. Twelve rabbits were randomly divided into hypoglycemic group (n=6) and saline-injected control group (n=6). Hypoglycemia was induced by intravenous injection of insulin as 10 U/kg and recovered by intravenous glucose injection after 60 minutes. In the control group, saline was intravenously injected in stead of insulin. Plasma levels of oxidized glutathione (GSSG) rose significantly (p<0.01) and remarkably decrease in plasma GSH/GSSG ratio (p<0.05) accompanying increase in serum enzymes in the hypoglycemic group. These results suggest that hypoglycemia might cause change in plasma GSSG which is related to increase of serum enzymes by hypoglycemia.

Muscle damage induced by experimental hypoglycemia

To determine organ damage due to hypoglycemia, we studied the effects of insulin dose and hypoglycemia duration on serum enzyme activity in rabbits. Thirty rabbits were randomly divided into five groups according to hypoglycemia duration and insulin dose: A2, hypoglycemia for 30 minutes with 2 U/kg insulin; A10, hypoglycemia for 30 minutes with 10 U/kg insulin; B2, hypoglycemia for 60 minutes with 2 U/kg insulin; B10, hypoglycemia for 60 minutes with 10 U/kg insulin; and C, no hypoglycemia with 10 U/kg insulin and 50% glucose. Insulin-induced hypoglycemia was reversed by intravenous injection of glucose. Alterations in serum enzyme activity and creatine kinase (CK) isoenzyme distribution were determined before and after insulin injection. Serum CK activity increased significantly in all hypoglycemic groups compared with preinjection values, and tended to remain high for 24 hours in both groups A10 and B10. Serum activity of alanine aminotransferase (ALT), aspartate aminotransferase (AST), and lactate dehydrogenase (LDH) increased only in group B10. In addition, the level of band 4 of serum CK isoenzymes, which exists predominantly in skeletal muscle and myocardium, increased significantly in group B10. These results suggest that the increase in both serum enzyme and CK band 4 isoenzyme activities during hypoglycemia is primarily due to damage in muscle rather than liver, and that the hypoglycemia duration and insulin dosage may influence the extent of organ damage.