[Protective effect of insulin on burn serum-challenged cardiomyocytes in vitro].
0
Citation
0
Reference
10
Related Paper
Abstract:
To investigate the protective effect of insulin on burn serum-challenged cardiomyocytes in vitro.Primary culture of cardiomyocytes from Sprague-Dawley (SD) 2-day-old neonate rats were divided into sham group, burn group, insulin group, and insulin activation inhibitor LY294002 pretreatment group (LY group). The model of cardiomyocytes injury induced by burn serum of 3-month-old SD rats [the serum of abdominal aortic was collected at 6 hours after modelling 30% total surface area (TBSA) III degree scald rat] was reproduced. In the insulin group, 10% burn serum and insulin (10 U/L) were added into cell culture medium, and in the LY group, LY294002 (50 μmol/L) was pretreated for 30 minutes before the addition of burn serum and insulin. Sham group was only given 10% serum of sham injured rats (sham rats were only placed in 37 centigrade warm water). After the cells were cultured for 12 hours, the release of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and creatine kinase (CK) were determined by enzyme-linked immunosorbent assay (ELISA). The cardiac troponin T (cTnT) protein expression was examined by Western Blot. Apoptosis of cardiomyocytes was observed after Hoechst 33258 staining.Compared with the sham group, the cardiomyocytes were damaged and released inflammatory cytokines after burn serum-challenged. The levels of TNF-α, IL-6 and CK increased [TNF-α (ng/L): 273±48 vs. 21±6, IL-6 (ng/L): 416±83 vs. 44±11, CK (U/L): 1.44±0.24 vs. 0.14±0.08, all P < 0.01], while the expression of cTnT protein decreased (cTnT/β-actin: 0.12±0.04 vs. 0.86±0.34, P < 0.01), and the cardiomyocyte apoptosis increased [(19.1±5.6)% vs. (5.2±1.3)%, P < 0.01]. Insulin could significantly reduce the damage of cardiomyocytes, decrease the release of TNF-α, IL-6 and CK induced by burn serum [TNF-α (ng/L): 105±37 vs. 273±48, IL-6 (ng/L): 176±77 vs. 416±83, CK (U/L): 0.82±0.26 vs. 1.44±0.24, all P < 0.05], the expression of cTnT protein significantly increased (cTnT/β-actin: 0.41±0.16 vs. 0.12±0.04, P < 0.05), and the cells apoptosis rate significantly decreased [(10.7±3.2)% vs. (19.1±5.6)%, P < 0.05]. Further blocking experiments showed that LY294002 could mitigate the protective effects of insulin.For cardiomyocytes challenged by burn serum, insulin may decrease inflammation, apoptosis and then protect the cardiomyocytes.Keywords:
Creatine kinase
To determine whether increments in circulating GH concentrations within the physiological range would exert insulin-like as well as insulin-antagonistic actions in man and, if so, whether both actions would occur in hepatic and extrahepatic tissues, normal volunteers (n = 6) were infused with human GH (hGH; 100 ng/kg-min) for 6 h along with somatostatin (100 jug/ h) to suppress insulin, glucagon, and hGH secretion and also with sufficient insulin (100 μU/kg-min) to maintain a constant plasma insulin level. During the final 2 h, glucose (2 mg/kgmin) was infused. In control studies, saline was infused instead of hGH. Infusion of hGH increased plasma hGH to 35 ng/ml. Plasma glucose decreased to 60 ± 2 mg/dl compared to 67 ± 1 mg/dl observed in control studies (P < 0.05); this greater hypoglycemia was due to both greater suppression of hepatic glucose production (P < 0.05) and greater augmentation of glucose clearance (P < 0.05). These insulin-like effects of hGH were no longer evident after 2 h. Subsequently, when glucose was infused, plasma glucose increased to 133 ± 4 mg/dl compared to the 104 ± 6 mg/dl observed in control studies (P < 0.01). This greater hyperglycemia was due to both impaired suppression of hepatic glucose production (P < 0.001) and decreased glucose clearance (P < 0.01). These results indicate that physiological increments in plasma hGH cause both insulin-like and insulin-antagonistic effects in man and that these actions occur in hepatic as well as extrahepatic tissues. The insulin-like actions of hGH are transient.
Cite
Citations (173)
Cite
Citations (21)
We investigated the specific and associated effects of insulin and glucose on beta-cell growth and function in adult rats. By combining simultaneous infusion either of glucose and/or insulin or glucose and diazoxide, three groups of rats were constituted: hyperglycemic-hyperinsulinemic rats (high glucose-high insulin), hyperglycemic-euinsulinemic rats (high glucose), and euglycemic-hyperinsulinemic rats (high insulin). All the infusions lasted 48 h. Control rats were infused with 0.9% NaCl (saline controls). In all groups, beta-cell mass was significantly increased, compared with controls (by 70% in high glucose-high insulin rats, 65% in high glucose rats, and 50% in high insulin rats). The stimulation of neogenesis was suggested by the high number of islets budding from pancreatic ducts in high glucose-high insulin and high glucose rats and by the presence of numerous clusters of few beta-cells within the exocrine pancreas in high insulin rats. beta-Cell hypertrophy was observed only in high glucose-high insulin rats. The rate of beta-cell proliferation was similar to that of controls in high glucose-high insulin rats after a 48-h glucose infusion, dropped dramatically in high insulin rats, and dropped to a lesser extent in high glucose rats. In high glucose-high insulin and high glucose rats, beta-cell mass increase was related to a higher beta-cell responsiveness to glucose in vitro as measured by islet perifusion studies, whereas in high insulin rats, no significant enhancement of glucose induced insulin secretion could be noticed. The data show that glucose and insulin may have specific stimulating effects on beta-cell growth and function in vivo in adult rats independently of the influence they exert each other on their respective plasma concentration.
Insulin oscillation
Carbohydrate Metabolism
Cite
Citations (134)
In rat pancreatic islets, the effect of old age (24-month-old) on [125I]insulin binding, glucose-induced insulin release and inhibition of insulin secretion by exogenous insulin were studied. The results were compared with corresponding data obtained from young (3-month-old) rats. Specifically bound [125I]insulin in islets of old rats was increased by 40% (P < 0.02) compared to that in young rats. Scatchard plots of displacement studies indicated an increase in receptor number rather than receptor affinity. The insulin-releasing capacity of 16.7 mM glucose did not differ between islets of old and young rats when medium insulin was bound to added antiinsulin serum. In the presence of 16.7 mM glucose (without the addition of antiinsulin serum), insulin secretion was less in islets of old rats compared to that in young rats (283 ± 38 vs. 528 ± 29 μU/ml; P < 0.001). Exogenous insulin inhibited glucose (16.7 mM)-induced insulin release more in islets of old rats than in those of young rats. In conclusion, the present in vitro results may be interpreted to reflect increased insulin binding to islets of aged rats and, consequently, increased inhibition of glucose-mediated insulin secretion due to increased feedback of insulin.
Pancreatic Islets
Insulin oscillation
Cite
Citations (5)
Abstract Circulating plasma insulin and glucose levels are thought to be major regulators of leptin secretion. There is evidence from in vitro and animal experiments that glucose metabolism rather than insulin alone is a main determinant of leptin expression. Here, we tested the hypothesis that in humans also leptin secretion is primarily regulated by glucose uptake and only secondarily by plasma insulin and glucose. In 30 lean and healthy men we induced 4 experimental conditions by using the blood glucose clamp technique. A total of 60 hypoglycemic and euglycemic clamps, lasting 6 h each, were performed. During these clamps insulin was infused at either high (15.0 mU/min·kg) or low (1.5 mU/min·kg) rates, resulting in low-insulin-hypo, high-insulin-hypo, low-insulin-eu, and high-insulin-eu conditions. Serum leptin increased from 0–360 min by 20.5 ± 4.1% in the low-insulin-hypo, 33.6 ± 7.6% in the high-insulin-hypo, 39.6 ± 6.0% in the low-insulin-eu, and 60.4 ± 7.6% in the high-insulin-eu condition. Multiple regression analysis revealed a significant effect of circulating insulin (low vs. high insulin; P = 0.001) and blood glucose (hypoglycemia vs. euglycemia; P = 0.001) on the rise of serum leptin. However, when the total amount of dextrose infused during the clamp (grams of dextrose per kg BW) was included into the regression model, this variable was significantly related to the changes in serum leptin (P = 0.001), whereas circulating insulin and glucose had no additional effect. These findings in humans support previous in vitro data that leptin secretion is mainly related to glucose metabolism.
Glucose clamp technique
Carbohydrate Metabolism
Cite
Citations (123)
We examined the effect of somatostatin (SRIH) infusion on insulin-mediated glucose disposal (Rd) in normal young subjects (n = 8) to determine the influence of SRIH on insulin action. Paired 3-h euglycemic insulin clamp studies were performed in random order employing insulin alone (25 mU/ m2-min) or insulin with SRIH (250 μg/h) and replacement of basal glucagon (0.4 ng/kgmin). Basal plasma glucose, insulin, glucagon (IRG), and GH concentrations, hepatic glucose production, and Rd were similar on each occasion. Steady state (10–180 min) plasma insulin [insulin alone, 283 ± 10 (±sem); insulin IRG, and SRIH, 284 ± 10 pmol/L) and glucagon levels (insulin alone, 84 ± 7; insulin, IRG, and SRIH, 82 ± 7 ng/L) were similar. Hepatic glucose production (insulin alone, 0.66 ± 0.12; insulin, IRG, and SRIH, 0.78 ± 0.48 mg/kg-min) and Rd (insulin alone, 8.16 ± 0.62; insulin, IRG, and SRIH, 8.17 ± 0.61 mg/kg-min) were not different at steady state. We conclude that SRIH infusion with glucagon replacement does not augment insulinmediated glucose disposal in normal young subjects at physiological insulin levels.
Basal (medicine)
Cite
Citations (19)
Insulin-deficient diabetes in humans, as well as in the neonatal streptozocin-induced rat model of non-insulin-dependent diabetes mellitus (NIDDM), are associated with islet β-cell insensitivity to glucose. We hypothesized that the chronic hyperglycemia- -hypoinsulinemia pattern causes this impairment of the glucose influence on insulin secretion. This study was designed to determine whether the glucose defect could be counteracted by normalizing the diabetic state in rats with NIDDM after insulin therapy. Mixte lente insulin (5 U · kg−1 · day−1) was given daily at 1700 h over 24 h or 5 consecutive days. Insulin secretion was studied the morning after the last insulin injection with the isolated perfused pancreas preparation. Fed basal plasma glucose levels decreased in diabetic rats from 183 ± 8 to 136 ± 10 mg/dl after the 1-day insulin treatment and to 135 ± 5 mg/dl after the 5-day insulin treatment (vs. 116 ± 3 mg/dl in control rats). Pancreatic insulin stores were not affected by insulin therapy. Although the 1-day insulin treatment did not modify the lack of glucose response in the diabetic rats, the 5-day insulin treatment improved their glucose-induced insulin secretion. Moreover, insulin therapy improved the priming effect of glucose on a second stimulation with glucose. The return of this glucose effect was hardly detectable after the 1-day insulin therapy but was clearly present after the 5-day treatment. The hyperresponse to arginine, characteristic of the untreated diabetic rat, returned similar to that in controls after a 1-day insulin therapy, and it was again amplified at high glucose levels, although amplification remained lower than that of control rats. This indicates that the potentiating effect of glucose on the response to arginine was regained more precociously than the acute insulin response to glucose after insulin therapy. These data agree with the hypothesis that the chronic hyperglycemia-hypoinsulinemia in the NIDDM rat causes abnormal glucose influence on glucose- and arginine-stimulated insulin release.
Streptozocin
Insulin oscillation
Basal (medicine)
Regular insulin
Cite
Citations (36)
Insulin binding to isolated fat cells from rats rendered hyperthyroid by daily injections of T4 (1 mg/kg) for 5 days was approximately doubled. The Scatchard curves reflected a large increase in receptor number, as well as an elevation in affinity of the high affinity binding sites. The response to insulin of the fat cells, however, was not increased accordingly: glucose incorporation into lipid in the presence of insulin did not differ significantly from that observed in the control group, whereas the effect of insulin on the lipolytic response to isoprenaline (isoproterenol) was even reduced in the T4-treated animals. T4 treatment had thus dissociated insulin binding from the metabolic effects of insulin, since the increase in membrane receptors was not paralleled by an enhanced effect of the hormone. Since levels of serum insulin were increased in the treated animals, the increase in number of insulin receptors was not mediated by reduced exposure to insulin. Propranolol failed to fully antagonize the effect of T4 on insulin binding, and reserpine treatment even enhanced it. It seems unlikely, therefore, that the increase in insulin receptors of adipocytes results from an augmented response to endogenous catecholamines in T4-treated rats.
Isoprenaline
Cite
Citations (31)
The effects of insulin treatment and dietary glucose on the responsiveness of adipose tissue to insulin and GH after hypophysectomy were studied. Male rats, 130–150 g, were hypophysectomized. Glucose metabolism was measured by determining the production of CO2 from [14C]glucose and the incorporation of glucose into lipids in the epididymal fat pad. Basal levels of glucose oxidation as well as the response to insulin were markedly decreased 7 days after hypophysectomy. In hypophysectomized animals given drinking water containing 10% glucose, insulin responsiveness was partially restored, and an enhanced response to the insulin-like effect of GH was observed. Plasma insulin levels decreased after hypophysectomy. Additional glucose caused a significant increase in plasma insulin levels, but these levels were still lower than those in shamoperated animals. To examine the possibility that endogenous insulin levels are important for the capacity of adipose tissue to metabolize glucose and respond to insulin and GH, hypophysectomized rats were injected with different, progressively increasing doses of insulin for 7 days, beginning on the day after the operation. Basal levels of glucose oxidation were decreased in hypophysectomized control animals and gradually increased in a dose-dependent manner in insulin-treated animals. Basal levels were normalized when the total dose of insulin injected was 16.5 U. In these animals, the response to insulin was enhanced, and there was an increase in the magnitude of the response to GH. Similar results were obtained when glucose incorporation into lipids was determined. The decrease in basal and insulin-stimulated glucose oxidation levels after hypophysectomy were most pronounced when measured at a high glucose concentration (50 mm), when glucose transport is not rate limiting. The results indicate that the changes in glucose metabolism and hormonal responsiveness of adipose tissue after hypophysectomy are, at least in part, dependent upon the decrease in endogenous insulin levels. (Endocrinology116: 945–951, 1985)
Hypophysectomy
Basal (medicine)
Carbohydrate Metabolism
Cite
Citations (19)
Insulin secretion after glucose stimulation and residual insulin content was studied in islets of Langerhans isolated from adult female rats which had been treated for 1–2 weeks with progesterone (P),estriol (E3), 17β-estradiol (E2), human chorionic somatomammotropin (HCS), E3 + P, E2 + P, HCS + P, or E3 + HCS + P. An increase in insulin secretion was observed after P treatment which was not further augmented by E3 + P and was reversed by E2 + P treatment. E2 treatment alone led to a smaller than normal insulin secretion response to glucose stimulation. Blunting of P-enhanced glucose-stimulated insulin secretion was also observed after E3 + HCS + P, but not after HCS + P. Residual islet insulin content increased after P and E3 + P, but not after E2 + P administration. These results indicate that these gestational hormones do not produce additive effects on glucosestimulated insulin secretion or on total islet insulin content. (Endocrinology91: 977, 1972)
Insulin oscillation
Cite
Citations (25)