Intestinal very low density lipoprotein secretion in insulin-deficient rats

The intestine's contribution to endogenous, triglyceride (TG)-rich lipoprotein production was compared in control and diabetic rats. Male rats were given either streptozotocin (45 mg. per kilogram) or saline. After one week, hyperglycemic animals were divided into a moderately diabetic group (glucose < 300 mg. per deciliter) and a severely diabetic group (glucose > 300 mg. per deciliter). In some animals, mesenteric lymph duct fistulas were prepared, and rats were restrained and given saline intraduodenally. After an overnight fast, lymph was collected in three two-hour periods for quantification of intestinal TG production. Other animals subjected to sham, lymph duct surgery and overnight restraint were injected with Triton WR 1339, and the ensuing increment in plasma TG concentration was used to quantify total body TG secretion. Results in control rats subjected to surgery and restraint showed the mean (± S.E.) intestinal TG secretion rate to be 3.2 ± 0.2 mg. per hour; this value represented 11 per cent of total body TG secretion. Under identical conditions, intestinal TG secretion increased (p < 0.01) by 70 per cent in moderately diabetic rats; this value represented 24 per cent of total TG secretion. In contrast, intestinal TG secretion in severely diabetic rats represented only 11 per cent of the total TG secretion: this value reflected a significant (p < 0.01) reduction in both intestinal and total body TG secretion. Electron microscopy indicated that the lymph lipoprotein particles in all animals studied were of very low density (VLDL) size. Thus, although the intestine contributes a relatively small amount of VLDL-TG to the plasma pool in control and severely diabetic rats, it appears to be a significant source of very low density lipoprotein–triglyceride (VLDL-TG) in animals with moderate insulin deficiency.

Response of plasma triglycerides to dietary change in patients on hemodialysis

The effect of reduction in dietary carbohydrate content of meal formula diets on plasma triglyceride concentrations was studied in 12 patients receiving chronic hemodialysis. Fasting plasma triglycerides decreased over a 10-day period in 11 of 12 patients in response to a decreased proportion of carbohydrate (from 50 to 35% of total daily calories) regardless of the type of fat used. Postprandial insulin responses were also significantly lower in the patients on the diets lower in carbohydrate. In addition, triglyceride kinetics were studied in three groups of patients. Patients with renal failure (dialyzed and undialyzed) had lower triglyceride production rates than those of control subjects, despite higher plasma triglyceride concentrations. Elevated (greater than 150 mg/100 ml) fasting plasma triglycerides are associated with lower triglyceride production rates in patients with chronic renal failure and may not be improved by conventional hemodialysis. A long-term study of the efficacy of reduction in dietary carbohydrate on plasma triglycerides is needed since routine hemodialysis does not appear to correct the lipid abnormality in patients with chronic renal failure.

Dissociation between rate of hepatic lipoprotein secretion and hepatocyte microtubule content

The fact that colchicines inhibits hepatic secretion of very low density lipoprotein (VLDL) particles has been interpreted to mean that microtubules are involved in hepatic VLDL secretion. To further define this relationship, we have attempted to see if changes in hepatic VLDL secretion are associated with changes in hepatocyte microtubule or tubulin content. Accordingly, hepatic secretion of VLDL was increased in rats, and the hepatocyte content of both microtubules (using quantitative morphometric methods) and tubulin (using a time-decay colchicine binding assay) was determined. In acute experiments, VLDL secretion was increased by perfusion of isolated rat livers for 2 h with varying concentrations of free fatty acids (FFA). Results indicate that hepatic VLDL triglyceride (TG) secretion at perfusate FFA levels of 0.7 muEq/ml is threefold greater (P < 0.01) than when livers are perfused without added FFA. However, no differences are observed in the content of microtubules in these livers: specifically, microtubules occupy 0.029 percent of hepatocyte cytoplasm in livers perfused without FFA and 0.030 percent of cytoplasm in livers perfused with FFA. In chronic experiments, rats were fed for 1 wk with either standard rat chow or a hyperlipidemic (sucrose/lard) diet. With the experimental diet, plasma triglyceride levels increase threefold over controls, and liver VLDL-TG production, as determined by [(3)H]glycerol turnover studies, is 55 percent greater (P < 0.01) than controls. However, microtubules occupy 0.027 percent of the cytoplasm of hepatocyte cytoplasm whether rats are on standard or hyperlipidemic diets. Furthermore, the tubulin content of isolated hepatocytes does change, and represents 1 percent of hepatocyte soluble protein, irrespective of diet. These results suggest that increases in hepatic VLDL secretion can occur without any demonstrable change in hepatocyte assembled microtubule or tubulin content, and raise questions as to the role played by microtubules in hepatic VLDL secretion.

The site of insulin resistance in acute uremia

In order to define the mechanism of glucose intolerance in acutely uremic rats, various studies were carried out 24 hours after bilateral nephrectomy. Glucose removal following intravenous glucose was significantly (p is less than 0.001) decreased in uremic rats compared with sham-operated rats (k = 2.1 +/- 0.03 per cent vs. 5.1 +/- 0.2 per cent). This deterioration in glucose tolerance was associated with higher insulin levels in uremic rats from one to 40 minutes after glucose administration, suggesting that insulin resistance accounted for the decrease in glucose removal by uremic rats. To identify the site of the insulin resistance, we compared the ability of insulin to enhance net glucose uptake by isolated perfused liver and muscle (hindlimb) preparations obtained from uremic and sham-operated rats. Insulin suppressed glucose outflow from perfused livers of uremic rats at least as well as it did from livers of sham-operated rats, and suppression occurred at both maximal ( greater than 600 micromicron./ml.) and threshold (75 micromicron./ml.) perfusate insulin levels. In contrast, there was a significant decrease in the ability of insulin (mean perfusate level = 225 micromicron./ml.) to enhance glucose uptake of perfused hindlimbs of uremic as compared with sham-operated rats. These results suggest that the insulin resistance of acute uremia may be due primarily to decreased insulin-mediated uptake of glucose by skeletal muscle without any decrease in sensitivity of the liver to insulin.

Effect of age and sex on triglyceride metabolism in the rat

The effect of age and sex on triglyceride metabolism were investigated in 3-mo- and 1-year-old rats. Although 3-mo-old female rats produce as much triglyceride as comparably aged male rats, their plasma triglyceride levels are lower. This suggests that 3-mo-old female rats remove triglycerides from plasma more efficiently than do similar aged male rats, and this is supported by the observation that the t1/2 of very low density lipoprotein triglyceride removal is somewhat faster in female rats of this age (p less than 0.1 greater than 0.5). As rats grow to 1 year of age, the ability of both sexes to remove triglycerides from plasma deteriorates, resulting in a rise in plasma triglyceride levels. The decrease in efficiency of triglyceride removal from plasma in female rats is coupled with an increase in triglyceride production rate, leading to an even greater increase in triglyceride levels. These results indicate that both age and sex modify triglyceride metabolism in the rat.

Hepatic insulin responsiveness in patients with endogenous hypertriglyceridaemia

Plasma insulin response to oral glucose, insulin resistance, and insulin suppression of hepatic glucose production were studied in 11 normal subjects and 11 hypertriglyceridaemic patients. Patients with hypertriglyceridaemia had a significantly higher insulin response to oral glucose. Insulin resistance was also significantly greater in hypertriglyceridaemic subjects as determined by measuring the steady-state plasma glucose response during a continuous infusion of epinephrine, propranolol, glucose, and exogenous insulin. Insulin suppression of hepatic glucose production was calculated from the results of two studies in which glucose turnover rate was measured by a continuous infusion of 3H-2-glucose. The first study was performed under conditions of basal insulin secretion, and the second carried out at steady state exogenous insulin levels of approximately 100 muU/ml. The results indicated that basal hepatic glucose production was the same in both groups, and was suppressed to an equal degree by physiological levels of insulin. These data demonstrate that hepatic glucose production can be suppressed to an equal degree in normal and hypertriglyceridaemic subjects at comparable circulating insulin levels, at the same time that resistance to insulin-stimulated glucose uptake is observed in the hypertriglyceridaemic individuals.

Intestinal contribution to secretion of very low density lipoproteins into plasma

To resolve the question of the magnitude of the intestine's contribution to circulating very low density lipoproteins (VLDL), measurements of intestinal, hepatic, and total VLDL--triglyceride were made on the same animals or on animals studied under comparable conditions. Animals were examined in the fasted state and during infusion of a fat-free meal. Intestinal VLDL secretion was determined through timed collections of lymph from the mesenteric lymph duct; hepatic and total VLDL secretion rates were estimated by the accumulation of plasma VLDL after injections of Triton WR 1339. Results indicate that the intestine contributes only a minor portion (11%) of the amount of triglyceride entering into the plasma compartment in the fasted state. Although intestinal triglyceride production is increased by 50% (p less than 0.01) in fed rats, the overall contribution of the intestine is not significantly altered in fed rats and represents only 14--17% of total body VLDL secretion. Thus, although intestinal VLDL secretion can be modified experimentally, its total impact on endogenous triglyceride production in normotriglyceridemic rats is small.

Insulin responsiveness of isolated perfused livers from rats with streptozotocin induced diabetes

The ability of insulin to inhibit efflux of potassium (K) and amino acid nitrogen (AAN) from perfused livers of normal and insulin deficient rats was studied. Two groups of rats with different degrees of insulin deficiency were produced by injecting varying amounts of streptozotocin. One group, classified as being moderately diabetic (MD), had fasting plasma glucose levels between 235--425 mg%, while the other group, whose plasma glucose levels greater than 425 mg%, were considered to have severe diabetes (SD). Two other groups of rats were food restricted in order to attain body weights comparable to the two groups of diabetic rats, and livers from these animals were used for control perfusions. The results indicated that the ability of insulin to suppress efflux of K and AAN from perfused livers of rats with MD was comparable to that seen in control perfusions. On the other hand, insulin could not suppress the efflux of either K or AAN from perfused livers of rats with SD. These results indicate that normal hepatic responsiveness to insulin can be lost secondary to the production of insulin deficiency.

Distribution and content of microtubules in relation to the transport of lipid. An ultrastructural quantitative study of the absorptive cell of the small intestine

To determine whether microtubules are linked to intracellular transport in absorptive cells of the proximal intestine, quantitative ultrastructural studies were carried out in which microtubule distribution and content were determined in cells from fasting and fed animals. Rats were given a 1-h meal of standard chow, and tissue was taken from the mid-jejunum before, 1/2 h, and 6 h after the meal. The microtubule content of apical, Golgi, and basal regions of cells was quantitated by point-counting stereology. The results show) that microtubules are localized in intracellular regions of enterocytes (apical and Golgi areas) previously shown to be associated with lipid transport, and that the microtubule content within apical and Golgi regions is significantly (P less than 0.01) reduced during transport of foodstuffs. To determine the effect of inhibition of microtubule assembly on transport, colchicine or vinblastine sulfate was administered to postabsorptive rats, and the lipid and microtubule content of enterocytes determined 1 and 3 h later. After treatment with these agents, lipid was found to accumulate in apical regions of the cells; this event was associated with a significant reduction in microtubule content. In conclusion, the regional distribution of microtubules in enterocytes, the decrease in assembled microtubules after a fat-containing meal, and the accumulation of lipid after the administration of antimicrotubule agents suggest that microtubules are related to lipid transport in enterocytes.

Development of fasting hyperglycemia in uremic rats

Rats which had been fasted for the previous 24 hr were subjected to either sham surgery, bilateral nephrectomy, or bilateral ureterotomy. The fast was continued for another 24 hr before the animals were decapitated and blood was obtained for determination of serum glucose, insulin, and urea nitrogen levels. A moderate but statistically significant (p less than 0.02) fall in serum glucose levels occurred in rats made uremic by bilateral nephrectomy. In contrast, rats made equally uremic by bilateral ureterotomy developed a significant (p less than 0.001) elevation of both serum glucose and insulin levels. The combination of hyperglycemia and hyperinsulinemia suggested that insulin resistance had developed in these rats, and this was confirmed by demonstrating that the hypoglycemic effect of exogenously administered insulin was attenuated in rats following bilateral ureterotomy as compared to sham-operated rats. Unilateral ureterotomy did not lead to the same metabolic response, and the difference in serum glucose levels between sham-operated and bilaterally ureterotomized rats disappeared when a 5% glucose solution was substituted for tap water as the rat's drinking water. It is suggested that the coexistence of fasting and metabolic acidosis led to increased renal gluconeogenesis in rats subjected to bilateral ureterotomy, and the combination of increased renal glucose production and insulin resistance was responsible for the development of fasting hyperglycemia.

Development of insulin resistance in normal dogs following alloxan-induced insulin deficiency

Insulin resistance was measured in 16 normal dogs by a method involving the continuous intravenous infusion of epinephrine, propranolol, glucose and insulin. With this approach, endogenous insulin secretin is inhibited, similar steady state levels of exogenous insulin are achieved in all doags, and the resultant steady state plasma glucose level provides a direct estimate of the ability of insulin to dispose of the infused glucose load. Thus, the higher the steady state plasma glucose level, the more the insulin resistance. Different amounts of alloxan were then administered to these dogs in order to produce insulin deficiency of varying degrees. Insulin resistance was then measured again in each dog. The results indicated that insulin resistance did not develop in dogs with only a moderate degree of insulin deficiency (fasting plasma glucose levels less than 150 mg/100 ml). On the other hand, a significant degree of insulin resistance developed in dogs with severe insulin deficiency (fasting plasma glucose greater than 150 mg/100 ml). Furthermore, the insulin resistance that developed in dogs with severe insulin deficiency could be returned to normal with insulin replacement for one week. These results indicate that insulin resistance can occur as a secondary manifestation of insulin deficiency.

Aging and insulin resistance in a group of nonobese male volunteers

The relationship of age to insulin resistance was determined in 100 nonobese men whose ages ranged from 22 to 69 years. Seventy of the 100 subjects had normal glucose tolerance, and 30 had chemical diabetes. Insulin resistance was estimated by measuring the steady-state plasma glucose response to a continuous infusion of insulin, glucose, epinephrine, and propranolol. This approach permitted inhibition of endogenous insulin release, achievement of a comparable steady-state plasma level of exogenous insulin, and use of the height of the steady-state plasma glucose response as a direct estimate of insulin resistance. With this experimental method, no correlation was found between age and insulin resistance over the age span of the experimental population. Furthermore, there was no correlation between age and the height of the plasma glucose response to an oral glucose challenge in this population of nonobese, healthy ambulatory men.

Does glucagon play a role in the insulin resistance of patients with adult non-ketotic diabetes?

Using a constant intravenous infusion technique we have measured in vivo insulin resistance in 17 normal subjects, five patients with chemical diabetes, and 13 non-ketotic diabetic patients with fasting hyperglycaemia (FBS greater than 120 mg/100 ml). All of the diabetic patients were non-obese. The results demonstrated that the diabetic patients were insulin resistant compared to normals and that the degree of insulin resistance was greater the more severe the diabetes. No differences in plasma glucagon levels were found among the different groups during the infusion studies. These results demonstrate that non-obese, non-ketotic diabetic patients are insulin resistant and that abnormalities in plasma glucagon concentrations do not account for this insulin resistance.

Effect of age and weight on plasma glucose and insulin responses in the rat

Plasma glucose and insulin responses to orally administered glucose were determined in rats of varying ages and weights. The results indicated that glucose tolerance tends to deteriorate as rats grow from 1 month to 9 months of age. This change in glucose tolerance was associated with an increase in the response of plasma insulin to glucose, consistent with the hypothesis that the decline in glucose tolerance is due to a loss of normal insulin sensitivity. The changes in glucose and insulin responses could not be explained entirely on the basis of the associated weight gain. They seemed to be at least partially secondary to either age or an age-related factor other than obesity.

Insulin binding in diabetes. Relationships with plasma insulin levels and insulin sensitivity

Insulin binding to isolated circulating monocytes from normal subjects and adult patients with diabetes was studied. The diabetic subjects were nonketotic, and their degree of glucose intolerance varied from an abnormal oral glucose tolerance test (chemical diabetes) to significant fasting hyperglycemia. The results indicated that patients with chemical diabetes had a 45 per cent decrease in insulin binding to monocytes, and this decrease was secondary to a reduction in the number of receptor sites per cell (normals, 15,000 sites per monocyte versus 8,500 sites per mono-cyte for chemical diabetics). When the individual data from the normal and chemical diabetic subjects were examined, a highly significant inverse correlation was found between the amount of insulin bound and both the fasting plasma insulin level (r = 0.61, P &gt; 0.001) and the incremental insulin area during an oral glucose tolerance test (r = 0.49, P &gt; 0.001). Furthermore, insulin binding was closely and inversely correlated to the degree of insulin resistance (r = 0.65, P &gt; 0.001) among these subjects. Thus, the ability to bind insulin is inversely related to both the plasma insulin level and insulin sensitivity, and chemical diabetics who are insulin-resistant and hyperinsulinemic have a decreased ability to bind insulin. Many patients with fasting hyperglycemia also have decreased insulin binding. However, although as a group these pa tients have fasting hyperinsulinemia, they are hypoinsulinemic in response to a glucose challenge. Thus, inclusion of their data with that of the normal and chemical-diabetic patients enhances the relationship between insulin binding and fasting insulin level (r = 0.68, P &gt; 0.001) but obliterates the relationship between insulin binding and incremental insulin area. Furthermore, in these subjects no significant correlation was found between insulin binding and the degree of insulin resistance (r = 0.19, N.S.), suggesting that all or most of the insulin resistance in these subjects was independent of changes in insulin receptors. In conclusion, (1) if the subjects are taken as a group, in patients with chemical diabetes and in diabetic patients with fasting hyperglycemia, insulin binding to monocytes is decreased; (2) over the entire spectrum of adult, nonketotic diabetes, insulin binding is decreased to monocytes from patients with fasting hyperinsulinemia, while subjects with normal insulin levels have normal insulin binding; (3) the insulin resistance of patients with chemical diabetes may be related to a decrease in insulin receptors, but this does not appear to be the case for patients with fasting hyperglycemia; and (4) plasma insulin levels are inversely related to insulin binding, but it is the basal, not the stimulated levels that are associated with changes in insulin receptors.

Relationship between heterogeneity of insulin responses and insulin resistance in normal subjects and patients with chemical diabetes

Plasma insulin responses and insulin resistance were determined in 75 subjects, defined as having a normal, borderline abnormal, or abnormal oral glucose tolerance test (OGTT). Although considerable heterogeneity of insulin response existed, most patients with abnormal OGTT's had insulin responses greater than normal; none had insulin responses less than normal. The degree of insulin resistance also varied, but most patients with abnormal OGTT's were also abnormally insulin resistant A significant correlation (r=0.64, p+/-0.001) existed between insulin response and the degree of insulin resistance. However, when both variables were taken into consideration, the entire population could be divided into two groups. One group was characterized by both normal insulin responsiveness and sensitivity, the other by increased insulin response, associated with greater insulin resistance. Most patients with abnormal OGTT's fell into the latter group, but some had glucose intolerance without either an exaggerated insulin response or insulin resistance. These results suggest that true heterogeneity exists in patients with abnormal OGTT's.

Reduction of plasma triglycerides by diet in subjects with chronic renal failure

The response of plasma triglyceride levels to changes in the composition of meal formula diets was studied in 12 subjects who had moderate to severe chronic renal failure. Fasting hypertriglyceridemia (greater than 150 mg/100 ml) was present in seven of 12 subjects. Fasting plasma triglyceride levels decreased in all subjects in response to a reduction in the proportion of carbohydrate (from 50 to 35% of total daily calories) and an increase in the poly-unsaturated to saturated fat ratio (from 0.2 to 2.0) in an isocaloric diet. Fasting plasma cholesterol and postprandial triglyceride levels were unchanged. Both the triglyceride production rate and the insulin response were significantly lower on a diet in carbohydrate and higher in polyunsaturated fat. These data indicate that hypertriglyceridemia occurs in subjects with moderate to severe chronic renal failure, and that dietary modification promptly reduces triglycerides levels over an 11 day period. A long term study on a dietary program incorporating these changes is indicated to determine whether this effect is sustained.

Effect of acute uremia on triglyceride kinetics in the rat

Plasma triglyceride (TG) levesl were elevated 24 hr after the production of acute uremia in rats. The effect of acute uremia on TG production rate was estimated by determining the rate of TG accumulation following Triton WR 1339 inhibition of lipoprotein removal, by measuring hepatic TG secretion rate during in situ liver perfusion, and by quantifying hepatocyte very low density lipoprotein content with the electron microscope. The results of all three of these approaches indicated that TG synthesis and secretion were decreased in acute uremia, suggesting that the associated increase in plasma TG levels had to result from a removal defect. This hypothesis was tested directly by injecting pre-labeled very low density lipoprotein TG into acutely uremic and control rats, and measuring its rate of disappearance from plasma. The t1/2 of removal in acutely uremic rats was found to be approximately twice that of control, confirming the hypothesis that the rise in plasma TG levels in acute uremia is due to a defect in removal of TG from plasma.

Treatment of asymptomatic diabetes mellitus

A large number of individuals currently diagnosed as having diabetes mellitus are asymptomatic. In order to provide rational therapy for this patient population, it is necessary to focus upon the differences between these patients and the classic prototypes with polyuria and weight loss, who require insulin for survival. Patients with asymptomatic diabetes do not need insulin for survival, and, by definition, they do not need it to alleviate symptoms. They tend to be middle-aged and overweight, but they can be young and thin. Their degree of hyperglycemia is moderate, often indistinguishable from that of normal individuals in their day-to-day existence. Indeed, they can often be differentiated from normal persons only on the basis of their blood glucose response to the stress of a large dextrose challenge; in this regard, the potential problem of over-diagnosing diabetes has been discussed. Since the major problem facing patients with asymptomatic diabetes is accelerated atherogenesis, the therapeutic approach must be based upon efforts to delay or prevent the onset of vascular disease. It has yet to be shown that any therapeutic intervention helps such patients, but an argument has been made in support of the following goals in subjects with asymptomatic diabetes whose fasting blood glucose level is less than 170 mg/100 ml: (1) stop smoking, (2) control hypertension, (3) attain ideal body weight, and (4) maintain blood triglyceride and cholesterol levels well within normal limits. Attempts to lower blood glucose with either insulin or oral agents do not seem indicated in the majority of patients within this defined diabetic population.

Locating the site(s) of insulin resistance in patients with nonketotic diabetes mellitus

Insulin resistance and the ability of insulin to inhibit hepatic glucose production and to increas efficiency of glucose uptake were determined in 24 nonobese individuals: eight subjects with normal oral glucose tolerance, eight patients with chemical diabetes, and eight nonketotic patients with fasting hyperglycemia (greater than 150 mg. per cent). Insulin resistance was estimated by measuring the steady-state plasma glucose response to a continuous infusion of insulin, glucose, epinephrine, and propranolol. This approach permits us to inhibit levels of exogenous insulin, and use the height of the steady-state plasma glucose response as a direct estimate of insulin resistance. The ability of insulin to inhibit hepatic glucose production and to increase efficiency of glucose uptake was calculated from the results of two studies in which a continuous infusion of 3H-2-glucose was used to measure glucose turnover rate. The first study was performed after an overnight fast, under conditions of basal insulin levels, while the second was conducted during the infusion of insulin, glucose, epinephrine, and propranolol. Hepatic glucose production is equal to glucose turnover rate during the basal study and is equal to glucose turnover rate minus the infusion rate of cold glucose during the second study. Glucose uptake in both studies is equal to glucose turnover rate minus urinary glucose loss, and the efficiency of glucose uptake is calculated by dividing glucose uptake by the plasma glucose pool size. The mean (+/- S.E.) steady-state plasma glucose response was 113 +/- 9 mg. per cent in normal subjects, 205 +/- 14 mg. per cent in chemical diabetics, and 346 +/- 30 mg. per cent in patients with fasting hyperglycemia. Thus, insulin resistance exists in monoketotic diabetes, and the greater the degree of glucose intolerance, the greater the insulin resistance. The resistance to the insulin infusion in patients with chemical diabetes seemed to be mainly a function of the inability of insulin to increase efficiency of glucose uptake, since insulin did retain its ability to inhibit glucose production (although not to normal levels). In contrast, the infusion of insulin neither inhibited hepatic glucose production nor increased efficienty of glucose uptake in patients with fasting hyperglycemia. Thus, the insulin resistance that exists in patients with nonketotic diabetes cannot be considered to be a global phenomenon. Significant differences exist in the responsiveness of various tissues to the two general aspects of insulin's action on glucose homeostasis, and these differences provide a physiologic basis for the variations in degree of over-all insulin resistance that are present in the three groups of subjects.

Insulin binding to monocytes and total mononuclear leukocytes from normal and diabetic patients

Isolated circulating mononuclear leukocyte preparations were obtained from 19 normal and 11 adult diabetic patients. No differences in monocyte, T cell, or B cell content were found when preparations from the two study groups were compared. The amount of insulin bound to cells from the diabetic patients was found to be decreased regardless of the cell type to which the data were normalized. This indicates that the previously reported decrease in the ability of mononuclear cells of diabetic patients to bind insulin was not a result of differences in mononuclear cell subpopulation.