Continuous Subcutaneous Insulin Infusion (CSII) is superior to conventional insulin therapy as it improves glycemic control thus reducing the probability of diabetic complications. Notwithstanding CSII's benefits, insulin dependent diabetic patients rarely achieve optimal glucose control. Moreover, CSII is only FDA approved for 3 days and often fails prematurely for reasons that have not been fully elucidated. We hypothesize that phenolic compounds, such as m‐cresol and phenol, which are present in all commercial insulin formulations are responsible for the tissue reaction occurring at the insulin infusion site. This hypothesis was examined with in vitro cell cultures and a mouse air‐pouch model to determine cellular and tissue reactions following infusions with saline, phenolic compounds, (i.e., commercial diluent), and insulin. We demonstrated that diluent and insulin were cytotoxic to cells in culture at sub‐clinical concentrations (e.g., >1:10 of commercial insulin). Air pouch studies demonstrated that infusion of either diluted insulin or diluent itself induced three to five‐fold level of recruited leukocytes as compared to saline. At both 3‐ and 7‐days post infusion, these were predominantly neutrophils and macrophages. We conclude that phenolic compounds in commercial insulin preparations are cell and tissue toxic, which contributes to the failure of effective insulin infusion therapy.

No abstract

Abbreviations:CNS, central nervous system; ARC, arcuate nucleus of the hypothalamus; DMH, dorsomedial hypothalamic nucleus; LHA, lateral hypothalamus; PVH, paraventricular hypothalamic nucleus; AbstractBenzene is a well-known human carcinogen that is one of the major components of air pollution. Sources of benzene in ambient air include cigarette smoke, e-cigarettes vaping and evaporation of benzene containing petrol processes. While carcinogenic effects of benzene exposure have been well studied, less is known about metabolic effects of benzene exposure.We show that chronic exposure to benzene at low levels induces severe metabolic imbalance in a sex-specific manner, which is associated with hypothalamic inflammation and endoplasmic reticulum (ER) stress. Benzene exposure rapidly activates hypothalamic ER stress and neuroinflammatory responses in male mice, while pharmacological inhibition of ER stress response by inhibiting IRE1α-XBP1 pathway significantly alleviates benzene-induced glial inflammatory responses. Additionally, feeding mice with Acarbose, a clinically available anti-diabetes drug, protected against benzene induced central and peripheral metabolic imbalance. Acarbose imitates the slowing of dietary carbohydrate digestion, suggesting that choosing a diet with a low glycemic index might be a potential strategy for reducing the negative metabolic effect of chronic exposure to benzene for smokers or for people living/working in urban environments with high concentrations of exposure to automobile exhausts.

Background: Exogenous insulin therapy requires stabilization of the insulin molecule, which is achieved through the use of excipients (e.g., phenolic preservatives (PP)) that provide protein stability, sterility and prolong insulin shelf life. However, our laboratory recently reported that PP, (e.g., m-creosol and phenol) are also cytotoxic, inducing inflammation and fibrosis. Optimizing PP levels through filtration would balance the need for insulin preservation with PP-induced inflammation. Method: Zeolite Y (Z-Y), a size-exclusion-based resin, was employed to remove PP from commercial insulin formulations (Humalog) before infusion. Results: PP removal significantly decreased cell toxicity in vitro and inflammation in vivo. Infusion site histological analysis after a 3 day study demonstrated that leukocyte accumulation increased with nonfiltered preparations but decreased after filtration. Additional studies demonstrated that a Z-Y fabricated filter effectively removed excess PP such that the filtered insulin solution achieved equivalent glycemic control in diabetic mice when compared to nonfiltered insulin. Conclusion: This approach represents the proof of concept that using Z-Y for in-line PP removal assists in lowering inflammation at the site of insulin infusion and thus could lead to extending the functional lifespan of insulin infusion sets in vivo.

Background: Effective exogenous insulin delivery is the cornerstone of insulin dependent diabetes mellitus management. Recent literature indicates that commercial insulin-induced tissue reaction and cellular cytotoxicity may contribute to variability in blood glucose as well as permanent loss of injection or infusion site architecture and function. It is well accepted that insulin formulations are susceptible to mechanical and chemical stresses that lead to insulin fibril formation. This study aims to characterize in vitro and in vivo toxicity, as well as pro-inflammatory activity of insulin fibrils. Method: In vitro cell culture evaluated cytotoxicity and fibril uptake by macrophages and our modified murine air-pouch model quantified inflammatory activity. The latter employed FLOW cytometry and histopathology to characterize fibril-induced inflammation in vivo, which included fibril uptake by inflammatory phagocytes. Results: These studies demonstrated that insulin derived fibrils are cytotoxic to cells in vitro. Furthermore, inflammation is induced in the murine air-pouch model in vivo and in response, macrophages uptake fibrils both in vitro and in vivo. Conclusions: Administration of insulin fibrils can lead to cytotoxicity in macrophages. In vivo data demonstrate insulin fibrils to be pro-inflammatory which over time can lead to cumulative cell/tissue toxicity, inflammation, and destructive wound healing. Long term, these tissue reactions could contribute to loss of insulin injection site architecture and function.