Viscosity of gums in vitro and their ability to reduce postprandial hyperglycemia in normal subjects

Experiments were carried out in vitro with three viscous polysaccharides (guar gum, pectin, and carboxymethylcellulose (CMC) of similar initial viscosity submitted to conditions that mimic events occurring in the stomach and duodenum, and their viscosity in these situations was compared to their actions on postprandial hyperglycemia in normal human subjects. Guar gum showed greater viscosity than the other gums during acidification and/or alkalinization and also showed larger effects on plasma glucose levels (35 per cent reduction in maximum rise in plasma glucose) and on the total area under the curve of plasma glucose (control: 20,314 + 1007 mg dl(-1) 180 min (-1) vs guar gum: 18,277 + 699 mg dl(-1) 180 min (-1), P<0.01). Pectin, which showed a marked reduction in viscosity at 37 degrees Celsius and after events mimicking those that occur in the stomach and duodenum, did not have a significant effect on postprandial hyperglycemia. The performance of viscosity and the glycemia response to CMC were at an intermediate level between guar gum and pectin. In conclusion, these data suggest that temperature, the process of acidification, alkalinization and exposure to intestinal ions induce different viscosity changes in gums having similar initial viscosity, establishing a direct relationship between a minor decrease of gum viscosity in vitro and a reduction of postprandial hyperglycemia.

Tissue-specific regulation of IRS-1 in unilaterally nephrectomized rats

Insulin stimulates the tyrosine kinase activity of its receptor, resulting in the phosphorylation of its cytosolic substrate, insulin receptor substrate 1 (IRS-1). IRS-1 is also a substrate for different peptides and growth factors, and a transgenic mouse "knockout" for this protein does not have normal growth. However, the role of IRS-1 in kidney hypertrophy and/or hyperplasia was not investigated. In the present study we investigated IRS-1 protein and tyrosine phosphorylation levels in the remnant kidney after unilateral nephrectomy (UNX) in 6-week-old male Wistar ratas. After insulin stimulation the levels of insulin receptor and IRS-1 tyrosine phosphorylation were reduced to 79 + 5 percent (P<0.005) and 58 + 6 percent (P<0.0001), respectively, of the control (C) levels, in the remnant kidney. It is possible that a circulating factor and/or a local (paracrine) factor playing a role in kidney growth can influence the early steps of insulin action in parallel. To investigate the hypothesis of a circulating factor, we studied the early steps of insulin action in liver and muscle of unilateral nephrectomized rats. There was no change in pp185 tyrosine phosphorylation levels in liver (C 100 + 12 percent vs UNX 89 + 9 percent, NS) and muscle (C 100 + 22 percent vs UNX 91 + 17 percent, NS), and also there was no change in IRS-1 phosphorylation levels in both tissues. These data demonstrate that after unilateral nephrectomy there is a decrease in insulin-induced insulin receptor and IRS-1 tyrosine phosphorylation levels in kidney but not in liver and muscle. It will be of interest to investigate which factors, probably paracrine ones, regulate these early steps of insulin action in the contralateral kidney of unilaterally nephrectomized rats.

Insulin resistance in psoriasis

The oral glucose tolerance test (OGTT) and intravenous insulin tolerance test (15-min ITT) were applied to ten patients with psoriasis and to 11 control subjects. No significant differences in mean plasma glucose levels were detected between psoriatic patients and normal individuals. In contrasts, serum insulin levels were significantly higher for the psoriatic patients as compared to the controls at 30, 60 and 120 min during the OGTT (P<0.05). The glucose disappearance rate during the 15-min ITT was lower in patients with psoriasis than in controls (5.1 + or - 0.5 percent min vs 7.5 + or - 0.4 percent/min, P<0.05), demonstrating a state of insulin resistance. Interestingly, the reduction in serum potassium levels during the ITT was also lower in the patients than in the controls (0.6 + or - 0.06 mEq/l vs 1.06 + or - 0.07 mEq/l,P<0.05), suggesting that the insulin resistance observed in psoriasis is not only related to glucose metabolism, but also to another important action of insulin, namely extrarenal potassium homeostasis