Hepatic Uptake Of Insulin Research Articles

Fasting Insulin is Better Partitioned according to Family History of Type 2 Diabetes Mellitus than Post Glucose Load Insulin of Oral Glucose Tolerance Test in Young Adults.

Hyperinsulinemia is contributed by insulin resistance, hepatic insulin uptake, insulin secretion and rate of insulin degradation. Family history of type 2 diabetes mellitus has been reported to cause hyperinsulinemia. Correlation of fasting insulin with post glucose load Oral Glucose Tolerance Test (OGTT) insulin in young adults and their partitioning according to family history of type 2 diabetes. In this observational cross-sectional study, clinical evaluation and biochemical assays of insulin and diabetes related parameters, and secondary clinical influences on type 2 diabetes in volunteers were done for inclusion as participants (n=90) or their exclusion. Cut off levels of quantitative biochemical variables were fixed such that they included the effects of insulin resistance, but excluded other secondary clinical influences. Distribution was analysed by Shapiro-Wilk test; equality of variances by Levene's test; Log10 transformations for conversion of groups to Gaussian distribution and for equality of variances in the groups compared. When the groups compared had Gaussian distribution and there was equality of variance, parametric methods were used. Otherwise, non parametric methods were used. Fasting insulin was correlating significantly with 30, 60 and 120 minute OGTT insulin showing that hyperinsulinemia in the fasting state was related to hyperinsulinemia in the post glucose load states. When fasting and post glucose load OGTT insulin were partitioned into those without and with family history of type 2 diabetes, maximum difference was seen in fasting insulin (p<0.001), followed by 120 (p=0.001) and 60 (p= 0.002) minute OGTT insulin. The 30 minute insulin could not be partitioned (p=0.574). Fasting, 60 and 120 minute OGTT insulin can be partitioned according to family history of type 2 diabetes, demonstrating stratification and heterogeneity in the insulin sample. Of these, fasting insulin was better partitioned and could be used for baseline reference interval calculations.

First test effect in intravenous glucose tolerance testing

Intravenous glucose tolerance testing (IVGTT) is a common test of β-cell function in which a glucose load is administered and insulin and/or C-peptide responses are monitored. Since the first IVGTT may be more stressful and stress may alter β-cell secretion or hepatic insulin extraction, we asked whether there was a first test effect. Insulin and C-peptide responses were compared from two sequential IVGTTs performed within 6 months during staging for the Diabetes Prevention Trial-Type 1 (DPT-1) in 368 people at high risk for type 1 diabetes. Insulin data (1+3 min) were used because the first phase insulin response (and peak insulin concentration) occurs within this time frame. Areas under the curve (AUC) calculations represent early insulin or C-peptide responses from 0 through 10 min post-glucose challenge. More than half of all subjects were found to have first test values lower than the second. This was true for all measures of both insulin and C-peptide but the frequency was significantly different only for insulin measures corrected for basal and for insulin AUC (p < 0.05). However, for subjects (n = 99) whose 1+3 min insulin response was <10th percentile on the first test, there was a significant increase on the second test (p < 0.05). The C-peptide: insulin ratio did not change significantly between tests, indicating that differences are due to changes in β-cell secretion rather than hepatic insulin uptake. A statistically significant first test effect occurs during the IVGTT attributable to variations in insulin secretion rather than hepatic uptake.

Glycemic Control in the ICU

The human body is programmed to maintain constant homeostasis of all body systems through a complex neuroendocrine and autonomic network. Critical illness alters this homeostasis through various exaggerated autonomic and cytokine responses. The mechanisms that are impaired include glucose cellular transport and peripheral and hepatic insulin uptake. Over the past decade, numerous reports have described the deleterious effects of hyperglycemia. In 2001, in a randomized prospective study of critically ill patients, Van den Berghe [1] first reported that intensive glucose control (110 mg/dL) significantly decreased morbidity and mortality. This study was a catalyst for a multitude of subsequent reports evaluating the effects of glycemic control in other patient populations. This article first describes the pathophysiology of hyperglycemia in critical illness, and then summarizes the recent literature on the benefits of decreasing glucose levels and potential harmful effects of hypoglycemia (Table 1).

Impaired Insulin Sensitivity as an Underlying Mechanism Linking Hepatitis C and Posttransplant Diabetes Mellitus in Kidney Recipients

Aim of this study was to investigate the mechanism/s associating hepatitis C virus (HCV) infection and posttransplant diabetes mellitus in kidney recipients. Twenty HCV-positive and 22 HCV-negative kidney recipients, 14 HCV-positive nontransplant patients and 24 HCV-negative nontransplant (healthy) subjects were analyzed. A 3-h intravenous glucose tolerance test was performed; peripheral insulin sensitivity was assessed by minimal modeling. Pancreatic insulin secretion, hepatic insulin uptake, pancreatic antibodies and proinflammatory cytokines in serum (tumor necrosis factor-alpha, intereukin-6, high-sensitive C-reactive protein) were also assessed. HCV-positive recipients showed a significantly lower insulin sensitivity as compared to HCV-negative recipients (3.0 +/- 2.1 vs. 4.9 +/- 3.0 min(-1).microU.mL(- 1).10(4), p = 0.02), however, insulin secretion and hepatic insulin uptake were not significantly different. Pancreatic antibodies were negative in all. HCV status was an independent predictor of impaired insulin sensitivity (multivariate analysis, p = 0.008). The decrease of insulin sensitivity due to HCV was comparable for transplant and non-transplant subjects. No significant correlation was found between any of the cytokines and insulin sensitivity. Our results suggest that impaired peripheral insulin sensitivity is associated with HCV infection irrespective of the transplant status, and is the most likely pathogenic mechanism involved in the development of type 2 diabetes mellitus associated with HCV infection.

Effects of oral and transdermal 17β-estradiol with cyclical oral norethindrone acetate on insulin sensitivity, secretion, and elimination in postmenopausal women

Few studies have examined the effects of 17beta-estradiol on parameters of insulin and glucose metabolism. We studied 42 healthy, untreated postmenopausal women seeking relief from menopausal symptoms. They were randomized to receive either oral 17beta-estradiol 2 mg daily combined with sequential oral norethindrone acetate (NETA) 1 mg daily from days 12 to 22, or transdermal 17beta-estradiol 0.05 mg daily combined with sequential oral NETA 1 mg daily from days 17 to 28. Intravenous glucose tolerance tests (IVGTTs) were performed at baseline and after 46 weeks (estrogen-alone phase) and 48 weeks (combined phase) of completed therapy. Mathematical modeling analysis of plasma glucose, insulin, and C-peptide concentration profiles provided measures of insulin resistance, secretion, and elimination. Both types of therapy were associated with a decrease in fasting insulin and glucose levels. Insulin sensitivity was increased by oral estradiol during the estrogen-alone phase but was reversed by the addition of NETA. Transdermal estradiol did not affect insulin sensitivity. Hepatic insulin uptake and insulin secretion were increased with both types of treatment. The oral regimen of estradiol therapy was favorable to both insulin elimination and sensitivity. Transdermal estradiol therapy had relatively few effects on insulin metabolism.

Effects of oleate and fatty acids from omental adipocytes on insulin uptake in rat liver cells.

Hyperinsulinemia in central type (upper body) obesity has been related to reduced hepatic insulin uptake caused by fatty acids reaching the portal vein directly from the omental (visceral) fat depot. We investigated the effect of sodium oleate and fatty acid-rich buffer recovered from incubation of omental adipocytes with 10(-7) M epinephrine on specific [125I]insulin uptake (at 37 C) in freshly prepared and cultured hepatocytes and nonparenchymal liver cells isolated from 200-250 g rats. In hepatocytes, insulin uptake was studied after standard cell isolation and washing and after additional repeated 30-min washings at 37 C. In the vigorously washed hepatocytes, both fatty acid rich buffer (from 0.08-1.3 mM) and sodium oleate (from 0.0125-1.2 mM) decreased insulin uptake maximally by approximately 30% and approximately 40%, respectively (P < 0.005); a biphasic effect of fatty acids was observed, with maximal inhibition occurring at 0.08-0.1 mM. Without vigorous washing, oleate had no effect on insulin uptake in either freshly prepared or cultured hepatocytes and nonparenchymal cells. The reason for the observed inhibitory effect of fatty acids on insulin uptake in vigorously washed cells remains unknown, but the effect is unlikely to be physiologically important. Thus, our data do not support the hypothesis that the increased concentration of fatty acids in the portal vein is responsible for reduced hepatic insulin uptake and hyperinsulinemia in upper body obesity.

Insulin resistance, secretion, and elimination in postmenopausal women receiving oral or transdermal hormone replacement therapy

Estrogen/progestin steroid combinations adversely affect glucose tolerance and insulin resistance, but their effects in combined hormone replacement therapy (HRT) have rarely been evaluated. We studied 61 untreated symptomatic postmenopausal women randomized to receive oral (conjugated equine estrogens, 0.625 mg/d continuous + levonorgestrel, 0.075 mg/d for 12 days of each 28-day cycle) or transdermal therapy (estradiol 17β, 0.05 mg/d continuous + norethindrone acetate, 0.25 mg/d for 14 days of each 28-day cycle). An untreated control group of 30 postmenopausal women not seeking HRT was also studied. Intravenous glucose tolerance tests (IVGTT) were performed at baseline and 3, 6, and 18 months later. Mathematical modeling analysis of plasma glucose, insulin, and C-peptide concentration profiles provided measures of insulin resistance, secretion, and elimination. There were no changes in glucose or insulin concentrations with transdermal therapy. Oral therapy caused a deterioration of glucose tolerance and an increased overall plasma insulin response, apparently due to a reduction in the immediate plasma insulin response to glucose. This may have resulted from increased hepatic insulin uptake, uncompensated for by an increase in first-phase pancreatic insulin secretion. Neither treatment caused significant insulin resistance compared with baseline, but with the oral treatment insulin resistance was greater during the combined phase compared with the estrogen-only phase. Thus the oral regimen affected both insulin delivery and insulin resistance. The transdermal regimen had relatively few effects on insulin metabolism.

An apparently anomalous relationship between insulin and C-peptide concentrations in their initial response to intravenous glucose

Intravenous glucose tolerance tests (IVGTTs) with determination of plasma glucose, insulin, and C-peptide concentrations were performed in 136 men and 154 women. It was found that in 4% of men and 12% of women the plasma concentration of insulin exceeded that of C-peptide during the initial response to glucose. Subjects exhibiting this phenomenon had lower fasting and post-glucose C-peptide concentrations than those who did not; however, there were no statistically significant differences in glucose or insulin concentrations. The phenomenon was age-related, being absent from individuals aged 35 years and under, while in older age groups it appeared to be more prevalent in women than in men, suggesting an additional effect of menopause. However, in three follow-up IVGTTs performed in a subgroup of postmenopausal women over a period of 18 months, the phenomenon failed to recur in any of the individuals who first exhibited it, although it did occur in others. Our observations suggest the existence of an age-related but intermittent decrease in pancreatic insulin secretion, which does not lead to any significant change in plasma insulin concentrations, possibly as a result of reduced hepatic uptake of insulin. One consequence appears to be an excess of insulin over C-peptide during the early part of the IVGTT, which is probably related to the different distributional kinetics of the two peptides.

Evaluation of four mathematical models of glucose and insulin dynamics with analysis of effects of age and obesity.

Despite there being a number of mathematical models of glucose and insulin dynamics, there have been no evaluations of their operation in large groups of subjects. We have carried out intravenous glucose tolerance tests on a group of 182 healthy males, with determination of plasma glucose, insulin, and C-peptide concentrations. Parameters of glucose and insulin dynamics were determined using the minimal model of glucose disappearance, a minimal model of peripheral insulin delivery, and two different models of pancreatic insulin secretion (models I and II). Successful identifications were obtained in 96, 95, 76, and 100% of cases, respectively. The models were evaluated in terms of their ability to recover effects of obesity and aging on carbohydrate metabolism. The glucose disappearance model successfully detected the insulin resistance of both obesity and aging, whereas the peripheral insulin delivery model indicated an increased responsiveness of insulin delivery to glucose in obesity but detected no significant change associated with age. No parameter of pancreatic secretion model I exhibited a significant association with either age or obesity. Insulin secretion model II indicated that the hyperinsulinemia accompanying obesity resulted from both increased pancreatic secretion and decreased hepatic insulin uptake.

Fatty acids in the portal vein of the rat regulate hepatic insulin clearance.

The effects of FFA on hepatic insulin clearance were studied in the in situ perfused rat liver. Clearance decreased with increasing body weight (age) of the rats. When FFA were added to the perfusate a 40% reduction of hepatic removal of insulin was found over the normal, physiological range (less than 1,000 mumol/liter), less pronounced in heavier rats. When perfusion was started with high concentrations of FFA, inhibition was rapidly reversible, a phenomenon again blunted in heavier rats. In contrast to FFA, different glucose concentrations in the perfusate did not affect the hepatic insulin uptake in the presence of FFA within physiological concentrations. Thus, hepatic clearance of insulin is proportional to rat weight (age) and portal FFA concentrations. Other studies have recently shown that fatty acids inhibit insulin binding, degradation, and function in isolated rat hepatocytes, and that hepatic clearance is inversely dependent on hepatic triglyceride concentrations, both inhibitions reversible by prevention of fatty acid oxidation. It is suggested that the diminished hepatic clearance of insulin in heavier (older) rats is at least partly due to their relative obesity and increased hepatic triglyceride contents. This effect as well as that of portal FFA is probably mediated via fatty acid oxidation in the liver. This mechanism may have implications for the regulation of hepatic metabolism, and peripheral insulin concentrations.

The effect of glipizide on extraction of insulin by the human cirrhotic and noncirrhotic liver

The effect of glipizide on hepatic uptake of insulin was studied in five patients with liver cirrhosis and five patients with varying diseases in the biliary system and pancreas. All patients had portal catheters for diagnostic purposes. The hepatic uptake of insulin was estimated from the clearance rate for insulin obtained after a constant rate infusion into a peripheral vein and the portal vein. Each patient was examined on two consecutive mornings, the second investigation carried out one hour after oral glipizide administration. The fractional hepatic uptake was significantly lower in cirrhotic patients (17% ± 6%) than in the other patients (52% ± 7%; P < .01). After glipizide, an increase in the estimated uptake of insulin occurred in cirrhotic patients (from 17% ± 6% to 39% ± 6%; P < .01), whereas an insignificant decrease was observed in the other patients (from 52% ± 7% to 43% ± 11%).

Altered basal C-peptide/insulin molar ratios in obese patients with fatty liver.

To elucidate if the presence of fatty liver in obesity influences hepatic insulin extraction under basal conditions, serum immunoreactive insulin (IRI) and C-peptide immunoreactivity (CPR) were measured in 20 obese patients with normal glucose tolerance and in 8 normal subjects. The obese patients were subdivided into two groups matched for age and body weight according to the presence or absence of fatty liver: 8 obese patients without fatty liver (OBN) and 14 with fatty liver (OBF). Basal levels of IRI and CPR were significantly greater in the obese patients than in the normals, but were similar in the two obese groups. In the OBF group, the CPR/IRI molar ratios, a relative measure of hepatic insulin uptake, were significantly lower than in the other two groups, while the ratios of the normal and OBN groups were similar. The CPR/IRI molar ratios in all obese patients correlated well with the degree of fatty liver (r = 0.785, p less than 0.001). These results suggest that hepatic insulin extraction in a subgroup of obese patients is either reduced or indistinguishable from that of non-obese subjects, and that basal CPR/IRI molar ratio may serve as a useful indicator of the presence of fatty liver in simple obesity.

Insulin action and dynamics modelled in patients taking the anabolic steroid methandienone (Dianabol).

Plasma glucose and insulin concentrations were measured during oral (OGTT) and intravenous (IVGTT) glucose tolerance tests in nine patients off- and on-treatment with the anabolic steroid, methandienone (Dianabol). On-treatment, the tolerance tests showed a markedly increased insulin response accompanied by impairment of glucose tolerance, characteristics normally attributed to insulin resistance. However, fasting plasma glucose (FPG) and insulin (FPI) concentrations were significantly reduced, whereas the pattern normally associated with insulin resistance is for both to be raised. IVGTT glucose and insulin profiles were analysed using an algorithm derived from the minimal models of glucose and insulin dynamics originally proposed by R. Bergman and co-workers. Measures for the following parameters were thus obtained: Si, the sensitivity of glucose disposal to insulin; Sg, net insulin independent glucose disposal; phi 1, the integral concentration of insulin delivered during the first phase of insulin secretion relative to the initial increase in glucose concentration above a model-derived threshold; phi 2, the sensitivity of the rate of rise of insulin concentration in the second phase of insulin secretion to the concentration of glucose above a model-derived threshold; kappa, the fractional clearance rate of insulin; and tau 1/2, the insulin half-life. S1 was significantly reduced on treatment by a factor of 4. Sg, phi 1, phi 2 and tau 1/2 were all significantly increased, and kappa was significantly reduced. The increases in Sg and phi 1 both showed significant correlations with the increase in weight on-treatment. The reduction in FPG and FPI can be explained by the combined effects of the increase in Sg and Dianabol-induced resistance to glucagon.(ABSTRACT TRUNCATED AT 250 WORDS)

Insulin uptake by the human alcoholic cirrhotic liver

Insulin uptake by the human cirrhotic liver was studied in six patients with Laennec's cirrhosis, and the result was compared with that found in ten control patients with varying diseases affecting the biliary system. All patients had protal catheters for diagnostic purposes. The fractional hepatic uptake of insulin was calculated from the clearance rates for insulin obtained after a constant rate infusion into a peripheral vein and the portal vein in each patient. The fractional hepatic extraction of insulin was 13% ± 5 in cirrhotic patients and differed significantly from the fractional hepatic extraction found in controls (51% ± 5; P < 0.001).

The effects of cyproterone acetate and ethinyl oestradiol on carbohydrate metabolism.

Carbohydrate metabolism was studied in a group of 66 women, taking cyproterone acetate (CA) and ethinyloestradiol (EO) as anti-androgen therapy for the treatment of hirsutism and/or acne. A reverse sequential treatment cycle was used and women were studied in two groups: the first when taking the combination of CA and EO during the first 12 days of the treatment cycle, and the second taking EO alone during days 13 to 22. The combination reduced fasting plasma glucose and raised fasting plasma insulin concentrations. There was deterioration of glucose tolerance with increased plasma insulin concentrations and these effects were progressive with time. The plasma insulin response to intravenous tolbutamide was increased by 50% but there was no accompanying change in the glucose nadir as compared with controls. These results show that the combination of CA and EO causes insulin resistance. Plasma C-peptide concentrations following oral glucose were unchanged compared with controls. This shows that the observed hyperinsulinaemia was due to a reduction of hepatic uptake of insulin rather than its increased secretion. We propose that these effects are due to a CA-induced elevation of fasting plasma insulin resulting in downregulation of hepatic insulin receptors with subsequent induction of insulin resistance and impairment of hepatic insulin uptake. C-peptide concentrations following i.v. tolbutamide were significantly higher on treatment with CA and EO than in controls indicating increased pancreatic secretion of insulin. Tests carried out while patients were taking EO alone showed impairment of glucose tolerance only with no change in insulin levels. There was an increase in plasma insulin in response to tolbutamide but this was not significant. We conclude that these results are explained by a reduced but persisting effect of CA.

Hepatic disposal of biosynthetic human insulin and porcine C-peptide in humans

To examine the fate of insulin across the liver bed, biosynthetic human insulin was infused in increasing amounts in six healthy men. Trapping of insulin by the liver was determined by means of the hepatic venous catheter technique. To minimize any possible error in the estimation of insulin removal as a result of endogenous insulin, pancreatic insulin secretion was suppressed by intravenous administration of somatostatin (500 μg/h). Infusion rates of human insulin were 30, 60, and 150 pmol/m 2 · min (corresponding to 0.25, 0.5, and 1.25 U/m 2 · h) for 70 minutes each. Steady-state insulin levels were within the physiologic range, ie, 69 ± 2, 135 ± 3, and 342 ± 10 pmol/L, respectively. Euglycemia was maintained throughout the study by a variable glucose infusion. The output of C-peptide from the splanchnic bed was reduced by somatostatin by about 90%, indicating that endogenous insulin production only minimally contributed to total insulin levels achieved during infusion of exogenous human insulin. Fractional extraction of insulin by the liver (63 ± 6%, 71 ± 4%, and 74 ± 5%) and hepatic insulin clearance (201 ± 19, 235 ± 23, and 245 ± 29 mL/m 2 · min) did not differ significantly during the three insulin infusion studies. The hepatic uptake of insulin rose with increasing insulin infusion rates, constituting 40% to 60% of total-body insulin removal. No change in the total metabolic clearance rate of insulin was observed between the groups (451 ± 8 mL/m 2 · min). To study the extraction rate of C-peptide by the liver, porcine C-peptide was also infused at the same increasing rates. The failure to detect any concentration gradient of the porcine C-peptide across the splanchnic bed indicates that C-peptide is not extracted by the liver in humans. The results obtained in both studies validate our previously reported data on endogenous secretion and hepatic handling of insulin derived from calculations of splanchnic output of C-peptide and insulin.

Feedback inhibition by biosynthetic human insulin of insulin release in healthy human subjects.

To determine the impact of biosynthetic human insulin (BHI) on endogenous insulin release, splanchnic output and arterial concentrations of C-peptide were measured in eight healthy men after intravenous administration of 0, 0.5, 1.25, U BHI . m-2 . h-1 for 70 min each. Euglycemia was maintained by a variable glucose infusion. Arterial levels of serum insulin were 48 +/- 6 pmol/liter before and 135 +/- 12, 265 +/- 18, and 593 +/- 47 pmol/liter after BHI infusion. Splanchnic C-peptide output was reduced by BHI infusion from 88 +/- 10 pmol/min before to 50 +/- 9, 28 +/- 10, and 18 +/- 16 pmol/min (P less than 0.0025). Simultaneously, arterial concentrations of C-peptide fell from 539 +/- 54 pmol/liter by 29 and 43% when 1.25 and 2.5 U . m-2 . h-1 of BHI were administered. Hepatic insulin uptake was directly related with BHI infusion rate (r = 0.88) and rose during BHI administration from a basal value of 58 +/- 7 to an uptake of 265 +/- 31 pmol/min when 2.5 U . m-2 . h-1 were infused (P less than 0.0005). Basal hepatic insulin clearance was 4.75 +/- 0.60 ml . kg-1 . min-1 and remained unchanged after BHI infusion as did hepatic fractional extraction of insulin, which was 61 +/- 4% in the basal state. Metabolic clearance rate of immunoreactive insulin (MCRi) was dose-dependently reduced by BHI infusion, whereas the relative share of hepatic insulin clearance in total MCRi rose simultaneously (P less than 0.01). We conclude that feedback inhibition of endogenous insulin release may play an important role in vivo. Furthermore, it appears that nonhepatic insulin degradation is a saturable phenomenon as total MCRi fell in the presence of its unchanged hepatic clearance rate after the infusion of large amounts of BHI.

Effect of physical training on insulin uptake by the perfused rat liver

Hepatic uptake of insulin by the in situ perfused rat liver has been measured in rats subjected for 9 wk to physical training (T rats) on a treadmill. Three sedentary groups, one food-restricted (FR) to have the same weight as T rats, one freely-eating (FE), and one sucrose-fed (SF) were also studied. Each liver was cyclically perfused for 30 min with three different insulin concentrations in the medium (∼80, ∼500, and ∼2000 μU/ml). Plasma insulin concentrations in T rats were 50 and 17, in FR 55 and 20, in FE 71 and 30 and in SF 84 and 42 μU/ml in portal and peripheral venous plasma, respectively. Insulin decay curves followed first order kinetics. Taking FE rats as controls physical training enhanced hepatic clearance (expressed in ml/g/min) by 37%–60% whereas sucrose feeding reduced it by 15%–31% during the three perfusion periods. Food restriction in the FR rats caused only minor changes. Similar results were obtained with respect to hepatic extraction ratio and insulin removal. There was a significant negative correlation between portal insulin concentration and hepatic clearance rate. The results indicate that the hepatic extraction of insulin depends on portal insulin concentration. The mean net insulin uptake of the liver was similar in the groups, utilizing portal insulin concentrations and the hepatic clearance rate for calculations. As previously shown, the low peripheral plasma insulin levels after physical training are due mainly to a decreased insulin secretion from the pancreas. This is thus magnified by the efficient trapping of insulin in the liver.

Yucatan miniature swine as a model for the study of human diabetes mellitus.

Two lines of Yucatan miniature swine have been developed by genetic selection for decreased and increased glucose clearance during an i.v. glucose tolerance test. The decreased glucose clearance is due to low peripheral insulin levels usually from a decrease in insulin secretion. In two pigs the decreased peripheral insulin resulted from increased hepatic uptake of insulin. During gestation and lactation, an increased insulin resistance and a diabetic-like state occurs in some animals. When fed a low fiber diet that contains 40% of calories from saturated fat (a typical American diet), Yucatan swine become more glucose intolerant. Seven to ten animals on the diet from the glucose intolerant line showed a glucose tolerance curve that would have been classified as diabetic if they were humans utilizing both intravenous and oral glucose tolerance tests. Miniature swine from this line are available to interested researchers.

Hepatic uptake of insulin in man.

The hepatic uptake of unlabeled insulin (5--50 mU/kg) was determined in 45 nondiabetic patients without hepatic disease. Thirty patients were studied at normoglycemia and 15 at moderate steady hyperglycemia, induced by intraportal infusion of 80 or 200 mg glucose per h and per kg. The first pass fractional hepatic uptake of insulin (FH) was estimated by comparing the results after a portal and a peripheral infusion of unlabeled insulin in each patient. It varied negatively with the amount of insulin given, decreasing about 50% after a tenfold increase in dose. FH was markedly smaller during steady hyperglycemia than at normoglycemia, regardless of insulin dose. For low doses (5--10 mU/kg), giving insulin concentrations within the physiological range, FH was 0.43 (5 mU/kg) and 0.40 (10 mU/kg) at normoglycemia and 0.16 (10 mU/kg) at hyperglycemia. FH did not vary with the fasting or the glucose-stimulated, endogenous insulin levels recorded before insulin infusion. It is suggested that glucose is more important than insulin in modulating the fractional hepatic uptake of insulin.