A Clinical Evidence of a Correlation Between Insulin Resistance and the ALCAT Food Intolerance Test.

Insulin resistance (IR) is defined as the inability of a known quantity of exogenous or endogenous insulin to increase glucose uptake and utilization. Several mechanisms have been proposed as possible causes underlying the development of IR and the IR syndrome. IR occurs as part of a cluster of cardiovascular-metabolic abnormalities commonly referred to as "The Metabolic Syndrome." This may lead to the development of type 2 diabetes, accelerated atherosclerosis, hypertension, dysmenorrhea, hirsutism, and polycystic ovarian syndrome, depending on the genetic background of the individual developing IR. The aim of this study was to assess, in 123 female and 35 male (mean age, 42 y ± 10.3; range 19-75 y) volunteers) whether IR could be partly related to a dietary sugar intolerance and whether there could be a correlation between the ALCAT intolerance test and a mutation of the TCFTL2 gene (it promotes the trascription of the proglucagone and plays a key role in the development of the Langherans islands). Results evidenced that subjects with an intolerance to sugar, also showed a statistically significant complete or incomplete alteration of the TCFTL2 genetic test. Based upon these findings, our study demonstrated that there is a clinical correlation between the ALCAT food intolerance test and the IR. The positivity to the ALCAT test of one of the sugars tested (fructose, sugar cane, and sugar beet) indicates, in the majority of the subjects, the presence of a mutation of the gene TCF7L2 and could contribute to the prevention and treatment of the IR.

Calcium binding promotes prion protein fragment 90-231 conformational change toward a membrane destabilizing and cytotoxic structure.

The pathological form of prion protein (PrP(Sc)), as other amyloidogenic proteins, causes a marked increase of membrane permeability. PrP(Sc) extracted from infected Syrian hamster brains induces a considerable change in membrane ionic conductance, although the contribution of this interaction to the molecular mechanism of neurodegeneration process is still controversial. We previously showed that the human PrP fragment 90-231 (hPrP90₋231) increases ionic conductance across artificial lipid bilayer, in a calcium-dependent manner, producing an alteration similar to that observed for PrP(Sc). In the present study we demonstrate that hPrP90₋231, pre-incubated with 10 mM Ca⁺⁺ and then re-suspended in physiological external solution increases not only membrane conductance but neurotoxicity as well. Furthermore we show the existence of a direct link between these two effects as demonstrated by a highly statistically significant correlation in several experimental conditions. A similar correlation between increased membrane conductance and cell degeneration has been observed assaying hPrP90₋231 bearing pathogenic mutations (D202N and E200K). We also report that Ca⁺⁺ binding to hPrP90₋231 induces a conformational change based on an alteration of secondary structure characterized by loss of alpha-helix content causing hydrophobic amino acid exposure and proteinase K resistance. These features, either acquired after controlled thermal denaturation or induced by D202N and E200K mutations were previously identified as responsible for hPrP90₋231 cytotoxicity. Finally, by in silico structural analysis, we propose that Ca⁺⁺ binding to hPrP90₋231 modifies amino acid orientation, in the same way induced by E200K mutation, thus suggesting a pathway for the structural alterations responsible of PrP neurotoxicity.