Immunobiological consequence of regulation of insulin receptor on alloactivated lymphocytes in normal and obese subjects

Potential antiinflammatory role of insulin via the preferential polarization of effector T cells toward a T helper 2 phenotype

Hyperglycemia in critical illness is a common complication and a strong independent risk factor for morbidity and death. Intensive insulin therapy decreases this risk by up to 50%. It is unclear to what extent this benefit is due to reversal of glucotoxicity or to a direct effect of insulin, because antiinflammatory effects of insulin have already been described, but the underlying mechanisms are still poorly understood. The insulin receptor is expressed on resting neutrophils, monocytes, and B cells, but is not detectable on T cells. However, significant up-regulation of insulin receptor expression is observed on activated T cells, which suggests an important role during T cell activation. Exogenous insulin in vitro induced a shift in T cell differentiation toward a T helper type 2 (Th2)-type response, decreasing the T helper type 1 to Th2 ratio by 36%. This result correlated with a corresponding change in cytokine secretion, with the interferon-gamma to IL-4 ratio being decreased by 33%. These changes were associated with increased Th2-promoting ERK phosphorylation in the presence of insulin. Thus, we demonstrate for the first time that insulin treatment influences T cell differentiation promoting a shift toward a Th2-type response. This effect of insulin in changing T cell polarization may contribute to its antiinflammatory role not only in sepsis, but also in chronic inflammation associated with obesity and type 2 diabetes.

The significance of glucose, insulin and potassium for immunology and oncology: a new model of immunity

Background

A recent development in critical care medicine makes it urgent that research into the effect of hormones on immunity be pursued aggressively. Studies have demonstrated a large reduction in mortality as a result of infusion with glucose, insulin and potassium. Our work in the oncology setting has led us to propose that the principal reason for such an effect is that GIK stimulates lymphocytes to proliferate and attack pathogens, sparing the patient the stress of infection. That suggestion is based on a new model of immunity that describes the effect of hormones on lymphocytes. We hypothesized that the application of glucose, insulin, thyroid and potassium would awaken inert tumor infiltrating lymphocytes to destroy the tumor.

Methods

The antitumor effect of a thyroxine, glucose, insulin, and potassium (TGIK) combination was studied in a series of controlled experiments in murine models of tumor progression to assess the biologic activity of the formulation, the effect of route of administration, the effect on tumor type, and the requirement for insulin in the TGIK formulation.

Results

Melanoma and colon tumors inoculated with TGIK were significantly reduced in size or retarded in growth compared to controls injected with saline. I.P. and I.M. injections showed that the formulation had no effect systemically at the doses administered.

Conclusion

We conclude that TGIK has anti-tumor activity when administered intratumorally, probably by stimulating lymphocytes to attack tumors. This is similar to the effect of GIK on reducing sepsis in critical care patients. We suggest that when GIK is administered exogenously, it restores immune competence to the critically ill or cancer patient and causes destruction of pathogens or tumors, while endogenous resources are devoted to repair. This implies that hormonal therapy may be useful in treating various other pathologies involving immune suppression, as well as malignancies. We also propose research that could bring resolution of the controversy over mechanism and point the way to new therapeutic strategies for numerous diseases including chronic infections and auto-immune diseases.

Immunological effects of a hyperinsulinaemic euglycaemic insulin clamp in healthy males

The purpose of this study was to determine the in-vivo and in-vitro effects of insulin, at physiological and supraphysiological concentrations, on the human immune system. Ten healthy young men went through a sequential two-step hyperinsulinaemic euglycaemic clamp. Plasma insulin concentrations were increased from baseline (9.0 microU/ml) to 49.1 microU/ml after 1 h of insulin infusion (step I) and to 1281 microU/ml (step II) after 2 h of infusion. As control experiments infusions of isotonic saline were performed. The unstimulated natural killer (NK) cell activity among blood mononuclear cells (BMNC) increased in response to supraphysiological plasma insulin levels (baseline versus step II: 20.6 +/- 11.3 versus 27.8 +/- 14.4%). The percentages of the D16+ NK cells did not change, indicating an enhanced cytotoxic capability per individual NK cell. Insulin also slightly increased the activity of NK cells in vitro. A decline at step II in the concentrations of monocytes (0.29 +/- 0.09 versus 0.12 +/- 0.03 x 10(9)/L), lymphocytes (1.57 +/- 0.46 versus 1.22 +/- 0.25 x 10(9)/L), and CD16+(24.2 +/- 17.5 versus 16.7 +/- 11.2 x 10(7)/L), CD14+ (20.9 +/- 10.8 versus 8.6 +/- 3.9 x 10(7)/L), HLA-DR+ (37.2 +/- 22.1 versus 19.2 +/- 10.7 x 10(7)/L) and CD45RO+ (91.6 +/- 33.4 versus 61.7 +/- 6.4 x 10(7)/L) cells as well as in the percentages of CD14+ cells (11.2 +/- 4.7 versus 6.4 +/- 2.3%) and CD14+/HLA-DR+ monocytes (9.7 +/- 3.9 versus 4.8 +/- 2.8%) were observed. No changes were found at step I. Hyperinsulinaemia did not change the percentages of the CD3+, CD4+, CD8+, CD19+, CD56+, CD11a+, CD45RO+ and CD45RA+ cells, the numbers of circulating immunoglobulin (Ig)G-, IgA- and IgM- secreting cells, or the proliferative responses of BMNC to phytohaemagglutinin, purified derivative of tuberculin or interleukin (IL)-2. Hyperinsulinaemia did not change the in-vitro sensibility to insulin. In conclusion, supraphysiological insulin levels increased the activity of the individual NK cells, but decreased the numbers of NK cells, lymphocytes and activated monocytes. The findings are presumably of minor clinical relevance but may indicate an insulin-induced immune activation.

Characterization of rat lymphocyte primary culture for the development of an in-vitro mutagenesis assay: effect of interleukin-2 and 2-mercaptoethanol on the activities of intermediary metabolism enzymes and cell proliferation

Efficient energy utilization is essential for cell growth; in an attempt to improve the growth conditions of the rat T-lymphocyte culture model for potential use in studying the mutagenic activity of carcinogens in vitro, we have investigated the effects of phytohemagglutinin (PHA), interleukin-2 (IL-2) and 2-mercaptoethanol (2-ME) on the activities of intermediary metabolism enzymes and cell proliferation. Isolated lymphocytes were cultured in the presence and absence of PHA, IL-2, or 2-ME. The intermediary metabolism enzymes investigated were glutamate dehydrogenase, glutamate-pyruvate transaminase, malate dehydrogenase, isocitrate dehydrogenase, lactate dehydrogenase, pyruvate kinase, and fatty acid synthetase (FAS). Measurable activity of all enzymes investigated, except for FAS, was detected in PHA-stimulated cells cultured with IL-2 or 2-ME. The unstimulated lymphocytes had significantly lower enzyme activity than stimulated cells. The combination of all three agents showed increased enzyme activity. This increase in activity brought about by the combination of the three agents was not reproduced by either agent acting alone. In general, the increase in enzyme activity correlated with cell proliferation as measured by [3H]thymidine uptake in PHA-stimulated cultures containing IL-2 and/or 2-ME. The results suggest that the addition of exogenous IL-2 and 2-ME enhances metabolic function and may be beneficial in in vitro culture of rat lymphocytes.