Insulin patterns in equivocal glucose tolerance tests (chemical diabetes)

Polymorphism in the 5' flanking region of the human insulin gene. Relationships with noninsulin-dependent diabetes mellitus, glucose and insulin concentrations, and diabetes treatment in the Pima Indians

Variations in DNA sequences flanking the insulin gene were studied in relation to noninsulin-dependent diabetes mellitus (NIDDM) in 87 unrelated Pima Indians at least 35 yr of age. DNA was isolated from nuclei of peripheral blood leukocytes and digested with restriction endonucleases. Less variation in this region was found in Pima Indians than in other racial groups previously studied. Only two classes of alleles (classes 1 and 3) were found, and there was virtually no variation within classes. At least one class 3 allele was found in 47% of the 38 nondiabetic subjects and in 37% of the 49 with NIDDM (odds ratio = 0.65, P = 0.4, 95% confidence interval for the odds ratio = 0.25 to 1.67). Homozygosity for class 3 alleles, however, was found only in diabetics. There were no differences according to genotype in obesity, fasting or postload glucose or insulin concentrations, or in the relationships between insulin and glucose concentrations. 61% (11/18) of the diabetics with a class 3 allele were receiving drug treatment for diabetes compared with only 26% (8/31) of diabetics without a class 3 allele (P = 0.03). The insulin gene polymorphism probably plays no important role in the genesis of NIDDM in Pima Indians, nor does it influence the glucose or insulin concentrations or their relationship to each other, but the class 3 allele, especially when homozygous in this population, may influence the severity of the disease as indicated by need for drug treatment.

Insulin responsiveness of adipose tissue from normal weight subjects with early diabetes

In normal weight subjects, classified by a 2-h glucose infusion test as having normal (11), borderline (3) or pathological (9) carbohydrate tolerance (CHT), subcutaneous adipose tissue was removed under intracutaneous anesthesia by surgical biopsy. The biological responsiveness of isolated adipocytes as well as adipose tissue fragments measured as incorportion of (1-14C) glucose into CO2 or triglycerides was studied in the absence or presence of different insulin concentrations. In persons with normal CHT the insulin-stimulated (62.5 microU/ml) glucose conversion to CO2 by adipocytes as well as fat pads increased significantly up to 156 +/- 14% and 285 +/- 30%, respectively. Insulin enhanced the glucose incorporation into triglycerides up to 154 +/- 20% (fat cells) and 258 +/- 30% (fat pads) in adipose tissue from subjects displaying a normal CHT. Rates of glucose oxidation and triglyceride synthesis was markedly reduced in adipose tissue obtained from patients with borderline or pathological CHT. A significant positive relationship was found between glucose oxiation to CO2 and triglyceride production of fat cells and fat pads (r = 0.964 and 0.783, respectively). There was no correlation with responsiveness of adipose tissue to insulin and insulin secretion during glucose infusion test. The results indicate that sensitivity to insulin of target cells might be important for the development of carbohydrate intolerance also in normal weight subjects.

Glucose tolerance and erythrocyte insulin receptors in Friedreich's ataxia

Detailed in vivo and in vitro studies of glucose and insulin metabolism in Friedreich's ataxia patients and unaffected family members have further defined the extent of the abnormalities in carbohydrate metabolism. The high incidence of glucose intolerance and a hyperinsulinemic response to a glucose challenge in a high percentage of Friedreich's ataxia patients has been confirmed. An increased incidence of glucose intolerance among heterozygotes is suggested, while the siblings show a more normal distribution of diabetes and a nearly normal insulin response to the glucose tolerance test. Human growth hormone patterns are normal for all groups. Preliminary studies of insulin binding to erythrocytes suggest a difference in the binding characteristics among diabetic Friedreich's ataxia patients, while the binding in the non-diabetic Friedreich's ataxia group is similar to that of non-diabetic controls. Results from a small group of non-diabetic siblings suggest a normal insulin binding, while a tendency toward increased binding at low insulin concentrations among diabetic family members is noted.

Carbohydrate homeostasis in chronic lymphocytic thyroiditis: increased incidence of diabetes mellitus

Twenty-one patients were seen with the diagnosis of chronic lymphocytic thyroiditis in the Endocrine Clinic during 1965-1972. Three patients developed clinical diabetes mellitus at intervals from one month to three years after the diagnosis of thyroiditis was confirmed. An additional patient, a member of the study group reported here, had asymptomatic glucose intolerance initially and developed insulin-dependent diabetes mellitus six months after the diagnosis of thyroiditis was established. Standard glucose tolerance tests were performed on 12 additional patients. One of these patients had unequivocal evidence of chemical diabetes; one other had a borderline abnormal oral glucose tolerance test. The remaining ten patients had normal glucose and insulin values during the OGTT. These studies indicate that children with chronic lymphocytic thyroiditis are at increased risk of developing diabetes mellitus when compared with the normal childhood population.

Demonstration of insulin resistance in untreated adult onset diabetic subjects with fasting hyperglycemia

We have used a continuous intravenous infusion of glucose (6 mg/kg/min), insulin (80 mU/min), epinephrine (6 mug/min), and propranolol (0.08 mg/min) to directly assess insulin resistance in 14 untreated adult onset diabetics with a mean (plus or minus SE) fasting plasma glucose level of 217 plus or minus 17 mg/100 ml. During the infusion endogenous insulin secretion is inhibited and steady-state plasma glucose and insulin levels are achieved after 90 min. Since similar steady-state levels of plasma insulin are achieved in all subjects, the plasma glucose concentration observed during the steady-state period is a measure of an individual's insulin resistance. Under these conditions, the mean (plus or minus SE) steady-state plasma glucose level of the 14 diabetic patients was 350 plus or minus 16 mg/100 ml, while that of 12 normal subjects was 121 plus or minus 4 mg/100 ml. Additional studies were performed in which control subjects and patients with diabetes had their fasting plasma glucose levels acutely raised or lowered to comparable levels before receiving the basic infusion mixture of glucose, insulin, epinephrine, and propranolol. The results of these studies indicated that differences in initial plasma glucose levels could not account for the different glucose responses of the two groups to the basic infusion. Finally, the mean (plus or minus SE) steady-state plasma glucose level of 104 plus or minus 17 mg/100 ml observed during the same basic infusion in five patients with fasting hyperglycemia (mean plus or minus SE, 142 plus or minus 12 mg/100 ml) secondary to chronic pancreatitis suggested that neither chronic hyperglycemia nor hypoinsulinemia per se necessarily lead to insulin resistance. These results demonstrate that marked insulin resistance exists in adult onset diabetics with fasting hyperglycemia. Since previous studies have documented the presence of insulin resistance in patients with chemical diabetes, the possibility exists that insulin resistance may be characteristic of adult onset diabetes mellitus.

Investigation of carbohydrate metabolism and somatomedin in osteosarcoma patients

Altered carbohydrate metabolism associated with fibrosarcomas and chondrosarcomas has been well-documented in past literature. This report describes abnormal carbohydrate metabolism in 2 osteosarcoma patients, and abnormalities in growth hormone and somatomedin serum levels. Experimental evidence is presented showing in vitro suppression of osteosarcoma tumor cell proliferation by 17 beta Estradiol. Estrogen inhibition of linear bone growth, cartilage proliferation, and somatomedin is discussed with reference to possible estrogen therapy in osteosarcoma.