Effects of diet and phenotype on adipose cellularity and 5'-deiodinase activity of liver and brown adipose tissue of diabetic SHR/N-cp rats

Long-term sucrose-drinking causes increased body weight and glucose intolerance in normal male rats

The current epidemic of diabetes likely reflects marked changes in environmental factors, although genetic susceptibility plays a powerful role in the occurrence of diabetes in certain populations. We investigated whether long-term sucrose-drinking causes hyperglycaemia in male Wistar-Imamichi littermates (n 32), which are not genetically susceptible to diabetes or obesity. Each litter was divided equivalently into two groups, the sucrose group and the control group. The sucrose group received 300 g/l sucrose water and the control group received regular water until 42 weeks of age. Rats were weighed every 1 or 2 weeks. Oral glucose tolerance tests were performed at 28 and 36 weeks of age. Plasma glucose and insulin concentrations were measured. Body weights were significantly greater in the sucrose group than in the control group in 18-week-old rats (P<0·05), and the difference between the two groups reached 163 g by the end of the study (P<0·01). The 120 min post-load plasma glucose concentration in the sucrose group was 11·4 (sd 2·8) mmol/l in 28-week-old rats and 12·7 (sd 2·2) mmol/l in 36-week-old rats, while that of the control group remained approximately 7·3–7·7 mmol/l. In the sucrose group, the plasma insulin peak occurred 30 min post-load at 28 weeks of age; but the peak disappeared and hyperinsulinaemia was prolonged at 36 weeks of age. In conclusion, long-term sucrose-drinking causes increased body weight and glucose intolerance in normal male rats.

GLUT1-mediated glucose transport and its regulation by IGF-I in cultured bovine chromaffin cells

Regulation of glucose transport was studied in primary cultures of bovine chromaffin cells (BCC) using the glucose analogue 2-deoxyglucose (DOG) as a model substrate. The glucose transporter in freshly isolated and cultured BCC was identified as GLUT1 by Western immunoblots. The level of GLUT1 increased by time in culture and was followed by an enhancement in uptake of DOG. The DOG uptake was stimulated by insulin-like growth factor I (IGF-I) with an EC50 of 1 nM and a maximal response (approximately 2-fold) was obtained at 10-100 nM IGF-I. Insulin was at least 100-fold less potent than IGF-I. Exposure to 10(-8) M IGF-I also caused a redistribution of GLUT1 from an intracellular compartment to a plasma membrane-enriched fraction. Our results demonstrate a GLUT1-mediated glucose uptake in adrenomedullary cells. An enhanced glucose transport in response to IGF-I appears to be coupled to activation of IGF receptor type 1 and GLUT1 translocation.

Human pheochromocytoma: different patterns of catecholamines and chromogranins in the intact tumour, urine and serum in clinically unsuspected cases

Clinically unsuspected pheochromocytoma is usually discovered either at autopsy or during surgical intervention for unrelated conditions, despite often enormous neoplastic masses producing and storing catecholamine (CA). In order to assess whether these tumours share some common features we have compiled data for six patients admitted to hospital without previous diagnosis of their pheochromocytoma. The clinical variables and the morphological and immunohistochemical characteristics of the tumours revealed that these cases represented quite different expressions of adrenomedullary neoplasms. They differed not only with respect to nuclear ploidity and overall cytoplasmic morphology but also in catecholamine storage and expression of immunoreactive chromogranin A sequences in the intact tissue. In two of the patients hypertension had been overlooked as a diagnostic indicator of their CA-producing tumours. There was no clear relationship between the mean arterial pressure, the tumour content of CA and the serum levels of CA. Processed chromogranin A dominated in the serum of the two hypertensive cases. The 24-h urine values of CA and its main metabolite (vanillin mandelic acid) were, together with the serum values of chromogranin A and B, proportional to tumour mass and provided the most reliable diagnostic indicators for the non-hypertensive as well as the hypertensive cases.