Immunosuppressive Reagents Reverse Obesity Induced Insulin Resistance

BackgroundOrgan transplant is an important means of treating end stage organ failure at present. In recent years, with the progress of clinical practice and extensive application of new-type immune inhibitors, rejection of transplanted organ has been effectively controlled. The survival rates have been improved greatly. But many kinds of post-operation complications are still threatening the patient's life. Post transplant diabetes mellitus (PTDM) is one of the main complications. A large number of clinical observations indicate that the risk of transplanted organ dysfunction,infection, microvascular complication (retinopathy, neuropathy and nephropathy) and macrovascular complication (myocardial infarction, cerebral apoplexy, coronary artery disease, peripheral angiopathy) in PTDM patients are increasing. Insulin resistance (IR) is one of the common pathophysiological features of type 2 diabetes mellitus and metabolic syndrome after transplantation. Now it is considered that insulin resistance is a chronic systemic inflammation. A few anti-inflammatory treatment such as aspirin can reverse insulin resistance, and decrease blood sugar and incidence of cardiovascular and cerebrovascular disease. The results from clinical practice of IR inflammatory hypothesis are encouraging. The new mechanism will lead to dramatic fundamental change in type 2 diabetes treatment regimes. In this study, we have observed the effects of several irnmunosuppressive drugs including curcumin, parthenolide and rapamycin in the treatment of IR mouse models, and have carried out the preliminary discussion about related mechanisms. It will provide new insights in further intervention of type 2 diabetes pertaining to post-transplantation diabetes and insulin resistance. This paper includes three parts as follows.Section one: Research on Immunodepressant Curcumin to Reverse Insulin ResistanceObjective: Curcumin has physiological and pharmacological functions such as immunoregulation, antioxidation, anti-inflammation, tumor resistance and anti-artherosclerosis. Studies have found that curcumin is a good immunomodulator. It can inhibit host versus graft reaction and improve the survival rate of the recipients (animals). The aim of this study is to investigate the therapeutic action of curcumin and its mechanism on insulin resistance.Methods: To observe the effects of curcumin on FAO cells and obese insulin resistant animal model (obob mouse) (1) The dose/time- dependent effects of Curcumin on NF-κB inhibition; (2)To investigate therapeutic action of curcumin on insulin resistance in obob mice and observe fasting plasma glucose levels,insulin and glucose tolerant tests. (3) Investigate influence of curcumin on the circulating cytokines included IL-1, IL-6 and TNFαlevels and possible mechanism. (4) To analyze insulin stimulated IRS-1, P85 and AKT phosphorylation levels with immuno-co-precipitation, and observe influence of curcumin on insulin sensitivity in obob mice.Results: (1)The dose/time dependent inhibition of curcumin on NF-κB activation. The curative dose of curcumin was 30μM, which had most effective inhibition on NF-κB during 30-60 minutes. (2)The fasting plasma glucose level was not obviously decreased after the treatment of curcumin, but the level of fasting insulin decreased by about 30%. Furthermore, the level of glucose tolerance curve dropped significantly. (3)The level of TNFα(34.5±3.4 Vs31.3±1.1pg/ml) in circulation was not obviously changed, but the level of IL-1 ( 33.9±3.2 Vs 15.6±1.1pg/ml) and IL-6 (72.1±9.8 Vs47.2±5.3 pg/ml) was suppressed dramatically. (4)IRS-1 tyrosine Phosphorylation levels stimulated by insulin obviously increased, but the phosphorylation level of insulin receptor did not change. Being Parallel with Tyrosine phosphorylation levels of IRS-1, the phosphorylation levels of P85 and AKT increased accordingly.Conclusions: Curcumin can improve obob mouse insulin sensitivity, such effects of reversing insulin resistance may relate to its immunomodulating on cytokines and other inflammatory components.Section two : Research on limmunodepressant Parthenolide to Reverse Insulin ResistanceObjectives: Parthenolide is an another good immunomodulator. Its various biological activities are related to inhibit NF-κB, thus, Parthenolide has physiological and pharmacological actions such as anti-inflammation, inhibition of tumor growth and attenuation of artherosclerosis. It can also improve the survival rates of the recipients by inhibiting the host's immunological rejection. The aim of this study is to investigate the therapeutic action of parthenolide and its mechanism on insulin resistance.Methods: To observe the effects of parthenolide on FAO cells and obese insulin resistant animal model (obob mouse). (1) The dose/time dependent effects of parthenolide on NF-κB inhibition; (2) To investigate therapeutic action of parthenolide on insulin resistance in obob mice and observe fasting plasma glucose levels,insulin and glucose tolerant tests. (3) To investigate influence of parthenolide on the circulating cytokines, i.e., IL-1, IL-6 and TNFαlevels and possible mechanism. (4) To analyze insulin stimulated phosphorylation of IRS-1, P85 and AKT levels with immuno-coprecipitation, and observe influence of parthenolide on insulin sensitivity in obob mice.Results: (1) The curative dose ofparthenolide was 10-20mmol/1, which had most effective inhibitory action on the NF-kB at 20 minutes. (2) The homeostasis model assessment (HOMA) indexes, which were calculated with fasting plasma glucose and insulin levels, had obviously decreased after the treatment of parthenolide. The levels of glucose tolerant curve dropped significantly. As to parameters during euglycemic hyperinsulinemic clamps, the basic hepatic glucose production in treatment group was significantly inhibited when compared with those in control group. Glucose uptake and glucose infusion rates under the euglycemic hyperinsulinemic clamped condition increased by 40% respectively as compared to control group. (3) Parthenolide inhibited NF-κB activity in cells and reversed insulin resistance that was induced by high fat diet and obesity. Hepatic glucose production of mice was significantly inhibited with treatment of parthenolide. The utilization rates of glucose were significantly elevated under the euglycemic hyperinsulinemic clamped condition. (4) Parthenolide inhibited circulating levels of TNFα, IL-6 and MCP-1. Consistent with findings in curcumin experiments, the cytokine levels of TNFα, IL-6 in circulation was inhibited by about 50% with treatment of parthenolide. The level of PAI-1 (1.75±0.20 Vs 1.14±0.15 ng/ml) and MCP-1 (1.48±0.18 Vs 0.97±0.14, p=0.03) was obviously attenuated as well. In contrast, the levels of Leptin and Resistin did not changed obviously. (5) The parthenolide inhibited two site-specific phosphorylations of Serine residues S964 and 1148, which are related to insulin resistance. Conclusion: The parthenolide has inhibitory effects on the systemic inflammation. Down-regulating NF-k B related pathways related to improving the insulin sensitiveness and was indicated as potential approach for type 2 diabetes treatments.Section three: Research on New-type Immunodepressant Rapamycin to Reverse Insulin ResistanceObjectives: Rapamycin (RAPA), a member of macrolides developed by Home Products Company in USA, was demonstrated as a new-type immunodepressant as compared to calcineurin inhibitors and antimetabolitas. As a basic immunodepressant it has already been used extensively in clinical to reduce or avoid immuno-pathological nephrotoxicity in post-transplantation patients. The aim of this study is to investigate the therapeutic action of rapamycin and its possible mechanism on insulin resistance in obese and insulin resistant animal model (obob mouse).Methods: To observe the effects of rapamycin on obese and insulin resistant animal model (obob mouse) (1) To investigate therapeutic action of rapamycin on insulin resistance in obob mice and observe its effects on fasting plasma glucose and insulin levels. (2) To investigate influence of rapamycin on the circulatory cytokines of IL-1, IL-6 and TNFαlevels and possible mechanism.Result:(1) The fasting plasma glucose level was obviously decreased after the treatment of rapamycin. As compare with control group, the result was statistically significant. The levels of fasting insulin were showing similar pattern, and the area under curve had remarkable difference as compared with control group (8.90±0.95 Vs 5.27±0.73, p＜0.05). (2) The levels of TNFα(31.7±3.4 Vs37.7±1.1pg/ml) and IL-1 (18.0±3.2 Vs 29.5±1.1pg/ml) in circulation were decreased as well, but they did not reach statistical difference. The level of IL-6 (46.2±9.8 Vs85.6±5.3 pg/ml) was obviously decreased. (p＜0.05).Conclusion: Rapamycin can improve insulin sensitivity in obob mice and the detail mechanism is still not clearly demonstrated.