Effect of various glucagon/insulin molar ratios on blood ketone body levels in rats by use of osmotic minipumps

Malignant somatostatinoma presenting with diabetic ketoacidosis and inhibitory syndrome: pathophysiologic considerations

OBJECTIVE

To describe a patient with diabetic ketoacidosis secondary to a malignant somatostatinoma.

METHODS

We present the clinical, laboratory, radiologic, and pathologic findings of a patient with diabetic ketoacidosis secondary to a malignant somatostatinoma. We also review the potential effects of somatostatin on glucose homeostasis and discuss the underlying pathophysiologic mechanisms.

RESULTS

A 30-year-old woman presented with diabetic ketoacidosis and had a malignant somatostatinoma with hepatic, bone, and lymph node metastasis. She exhibited features of somatostatinoma "inhibitory syndrome" characterized by mild nonketotic hyperglycemia, hypochlorhydria, cholelithiasis, steatorrhea, anemia, and weight loss. In these tumors, the absence of ketoacidosis is thought to arise from the somatostatin-induced simultaneous suppression of the secretion of insulin and glucagon. The patient's primary tumor could not be located.

CONCLUSIONS

Diabetic ketoacidosis may occur in somatostatinomas. The secretion of larger molecular weight forms of somatostatin from the tumor may contribute to the ketogenesis.

Plasma glucagon and free fatty acid responses to a glucose load in the obese spontaneous hypertensive rat (SHROB) model of metabolic syndrome X

Metabolic Syndrome X is a cluster of abnormalities including insulin resistance, hyperlipidemia, hypertension, and obesity. We sought to determine if excess plasma glucagon and free fatty acids (FFA) might contribute to the insulin resistance in the obese spontaneous hypertensive rat (SHROB), a unique animal model of leptin resistance and metabolic Syndrome X. SHROB were extremely hyperinsulinemic and mildly glucose intolerant compared with lean SHR. SHROB had elevated fasting plasma glucagon and FFA, and showed paradoxical responses to an oral glucose challenge, with increased glucagon at 30 and 60 min postchallenge (200% plus minus 45% and 91% plus minus 13%, respectively; n = 9). In lean SHR, glucagon was nearly unchanged by glucose loading (<30% increase, P > 0.05; n = 5). Plasma FFA were not affected by a glucose load in SHROB, whereas SHR showed a decrease of 40% plus minus 6% (n = 5--9). The I/G molar ratio changed in opposite directions in the two genotypes, with a decrease in SHROB at 30 and 60 min, in contrast to the appropriate increase at 30 and 60 min postchallenge in the lean SHR (P < 0.01; n = 5--9). Administration of 500 ng/kg exogenous glucagon to SHR raised glucagon 56% plus minus 5% to a level that was similar to fasting SHROB. This level of circulating glucagon was sufficient to elevate glucose and insulin during the 7 hr of observation (n = 9). Based on these results, we suggest that fasting hyperglucagonemia and impaired suppression of glucagon secretion and FFA in response to an oral glucose load may contribute to insulin resistance and glucose intolerance in the SHROB model of metabolic Syndrome X.

Carbohydrate metabolism in temporal and persistent hypoglycemic chickens induced by insulin infusion

In order to elucidate the regulatory mechanism of blood glucose concentrations specific to chickens, carbohydrate metabolism in the liver, muscle and kidney and metabolite concentrations in the blood were investigated in chickens with acute and persistent hypoglycemia. Acute and persistent hypoglycemia were experimentally induced by a single injection of insulin (8 U/kg BW) or by continuous infusion of insulin (22.5 U/kg BW/day) for 4 days. Non-esterified fatty acid (NEFA) concentration in plasma and D-3-hydroxybutyrate (3HB) concentrations in liver and muscle increased in the acute hypoglycemia. Plasma NEFA concentration and 3HB concentration in the blood and liver were not changed at day 3 of persistent hypoglycemia, while 3HB concentration in the muscle was decreased. Phosphofructokinase (PFK) activity in the liver tended to increase but PFK and pyruvate kinase (PK) activities were unchanged in acute hypoglycemia. In persistent hypoglycemia, increase of hepatic PFK activity at day 1 in which it was reversed at day 3, and a small increase of muscle PK activity were observed, while PK and phosphoenolpyruvate carboxykinase (PEPCK) activities in the liver and kidney were not significantly changed. These results show that in the persistent hypoglycemic chickens, hepatic glycolysis transiently increases, which is followed by a small decrease, while glycolysis in muscles and gluconeogenesis in the liver and kidney are not significantly changed.