Effect of pioglitazone and its combination with statins in coronary artery disease patients with hyperinsulinemia

The objective of the study was to demonstrate the effect of pioglitazone and pioglitazone in combination with statin on East Indian patients with hyperinsulinemia and hyperlipidemia. It was a randomized, placebo-controlled, double-blind study with a parallel-group design comprising 83 patients. Patients of either sex with cardiac complications, including hyperlipidemia and (or) diabetes mellitus with or without hyperinsulinemia, were enrolled. Patients over 70 years of age, with renal or hepatic failure, or with severe diabetes mellitus (total glucose >400 mg/dL) were excluded from the study. Enrolled patients were randomly assigned to 4 groups that received placebo, pioglitazone, atorvastatin, or both. Blood samples were collected before and after treatment for analysis of serum glucose, insulin, lipid profile, apolipoprotein (apo) A1, apo B, and fibrinogen. Data were compared with that of patients with normal insulin or hyperinsulinemia. The patients with hyperinsulinemia receiving only pioglitazone showed a significant decrease in insulin levels compared with those with normal insulin levels. These patients also showed a significant increase in HDL levels. However, no significant change was observed in patients treated with both atorvastatin and pioglitazone. Pioglitazone was also found to increase significantly the apo A1 levels in patients with hyperinsulinemia, but there was no significant increase in patients given both atorvastatin and pioglitazone. Our data suggests that pioglitazone should be given preferably to the patients with hyperinsulinemia and statin should not be coadministered.     

Role of obesity and hyperinsulinemia in the insulin resistance of obese subjects with the clinical triad of polycystic ovaries, hirsutism and acanthosis nigricans

The insulin resistance of 4 nonobese and 8 obese patients with polycystic ovaries, hirsutism and benign acanthosis nigricans, and of 6 'obese normal' apart from obesity and 10 normal female subjects was evaluated by means of an intravenous insulin tolerance test and by measuring basal and insulin responses to an oral glucose load. The patients with polycystic ovaries, hirsutism and acanthosis had a decreased hypoglycemic response to exogenous insulin. The subjects with polycystic ovaries presented a significantly greater mean glucose response area for the same or greater mean insulin response area than the obese or nonobese normal subjects. The insulin resistance in the patient with polycystic ovaries, hirsutism and acanthosis nigricans could not be exclusively ascribed to a reduced receptor number, but also appeared to be due to a simultaneous postbinding defect probably related to the high insulin levels in patients with polycystic ovaries be they obese or not. The elevated plasma androgens and the presence of acanthosis found in these patients are likely also related to the hyperinsulinemia. To evaluate the influence of obesity, obese and nonobese patients with acanthosis nigricans and polycystic ovaries were compared. Higher insulin levels were found in the thin subjects, which could explain their greater insulin resistance and more severe hyperandrogenism. The comparison between obese patients with and those without acanthosis nigricans and polycystic ovaries suggested that, despite similar insulin levels, the greater known duration of obesity (probably also of the hyperinsulinemia) of the former was a possible explanation for their more intense insulin resistance and higher testosterone levels.     

Effects of fructose and glucose on plasma leptin, insulin, and insulin resistance in lean and VMH-lesioned obese rats

To determine the influence of dietary fructose and glucose on circulating leptin levels in lean and obese rats, plasma leptin concentrations were measured in ventromedial hypothalamic (VMH)-lesioned obese and sham-operated lean rats fed either normal chow or fructose- or glucose-enriched diets (60% by calories) for 2 wk. Insulin resistance was evaluated by the steady-state plasma glucose method and intravenous glucose tolerance test. In lean rats, glucose-enriched diet significantly increased plasma leptin with enlarged parametrial fat pad, whereas neither leptin nor fat-pad weight was altered by fructose. Two weeks after the lesions, the rats fed normal chow had marked greater body weight gain, enlarged fat pads, and higher insulin and leptin compared with sham-operated rats. Despite a marked adiposity and hyperinsulinemia, insulin resistance was not increased in VMH-lesioned rats. Fructose brought about substantial insulin resistance and hyperinsulinemia in both lean and obese rats, whereas glucose led to rather enhanced insulin sensitivity. Leptin, body weight, and fat pad were not significantly altered by either fructose or glucose in the obese rats. These results suggest that dietary glucose stimulates leptin production by increasing adipose tissue or stimulating glucose metabolism in lean rats. Hyperleptinemia in VMH-lesioned rats is associated with both increased adiposity and hyperinsulinemia but not with insulin resistance. Dietary fructose does not alter leptin levels, although this sugar brings about hyperinsulinemia and insulin resistance, suggesting that hyperinsulinemia compensated for insulin resistance does not stimulate leptin production.     

Hyperinsulinemia, insulin resistance and essential hypertension.

Glucose intolerance and noninsulin-dependent diabetes are commonly associated with hypertension. Epidemiological data suggest that this association is independent of age and obesity. Much evidence indicates that the link between diabetes and essential hypertension is hyperinsulinemia. When hypertensive patients whether obese or of normal weight are compared with matched normotensive control subjects, an increased plasma insulin response to a glucose challenge is consistently observed. Studies using insulin glucose clamp techniques in combination with tracer glucose infusion and indirect calorimetry have demonstrated that the insulin resistance in hypertensive subjects is located in muscles and restricted to glycogen synthesis. The relations between hyperinsulinemia and blood pressure do not prove that the relationship is a causal one. However, at least four mechanisms may link hyperinsulinemia with hypertension: Na+ retention, sympathetic nervous system overactivity, disturbed membrane ion transport and proliferation of vascular smooth muscle cells. Diuretics and beta-blockers may enhance insulin resistance, which is not affected by calcium antagonists, but decreased by the ACE inhibitor captopril. Weight reduction and regular physical exercise can improve insulin sensitivity and decrease blood pressure values. These nonpharmacological interventions should be more strongly recommended to diabetic and nondiabetic hypertensive patients.     

Weight-dependent differential contribution of insulin secretion and clearance to hyperinsulinemia of obesity

Obesity is associated with insulin resistance and the resulting hyperinsulinemia has been attributed to an increase of insulin secretion and a reduction of insulin clearance. The present study was intended to further characterize the relative contribution of secretion and clearance especially in the postprandial state. In relation to WHO body weight classes 291 subjects were divided in 5 subgroups Basal insulin concentrations rose stepwise and significantly with increasing BMI. This was paralleled by C-peptide concentrations and insulin secretion, while the reduction of insulin clearance was less stringent in relation to BMI. Basal glucose was unchanged in the BMI25 group and 8% higher in the obese groups (BMI 30, 35, 40) compared to normal weight (NW). Although postprandial insulin concentrations were significantly higher in the overweight and obese groups compared to NW the correlation was not as tight as in the basal state. Furthermore, the present data demonstrate for the first time that insulin secretion only increased in the overweight group without further augmentation in the obese groups. Further hyperinsulinemia of the latter was due to weight-dependent reduction of insulin clearance. The postprandial glucose response was 38–82% higher with increasing weight compared to NW. In summary basal hyperinsulinemia is mainly due to weight related increase of insulin secretion with moderate contribution of reduced insulin clearance. Postprandially, hyperinsulinemia of overweight is predominantly due to secretion while further postprandial hyperinsulinemia of obese subjects is mainly due to reduced clearance. Thus, postprandial insulin secretion cannot respond adequately to the challenge of weight-dependent insulin resistance already in non-diabetic obese subjects.     

The pancreatic glucagon and C-peptide secretion during hyperinsulinemia in euglycemic glucose clamp with or without somatostatin infusion in normal man

6 normal subjects received two times of 2 hr euglycemic glucose clamp studies (insulin infusion rate 40 mU/M2/min) one with and the other without somatostatin (SRIF) infusion (500 microgram/hr). Serum C-peptide and glucagon levels were measured during clamp to study the sensitivity of pancreatic alpha and beta cells to the suppressive effects of exogenous hyperinsulinemia during normoglycemia in normal subjects and to find whether SRIF had any modulative effects on endocrine pancreas secretion at the status of hyperinsulinemia. The results showed that in normal man the degree of suppression of pancreatic glucagon secretion by hyperinsulinemia (approximately 100 uU/ml) during euglycemic glucose clamp without SRIF infusion was less than that of C-peptide with mean value of 62 +/- 4% of basal glucagon remained at the end of clamp study; while only about 30 +/- 2% of basal C-peptide concentrations remained. But during SRIF infused glucose clamp studies (SRIF was infused from 60 to 120 min), 32 +/- 2% of mean basal C-peptide concentrations and 38 +/- 6% of mean basal glucagon concentrations left at the end of 2 hr clamp studies when serum insulin level was about 100 uU/ml. For the glucose infusion rate (M value), it was significantly greater in our normal subjects in response to insulin + SRIF as compared to insulin alone (12.0 + 0.9 vs 8.8 +/- 1.4; P less than 0.01). We concluded: during hyperinsulinemia (100 uU/ml), the sensitivity of pancreatic alpha cells to insulin seems less than that of beta cells in normal man at normoglycemia.(ABSTRACT TRUNCATED AT 250 WORDS)     

Decreased Hepatic Insulin Extraction Precedes Overt Noninsulin Dependent (Type II) Diabetes in Obese Monkeys

Many obese middle-aged rhesus monkeys (Macaca mulatta) spontaneously develop noninsulin dependent diabetes mellitus (NIDDM). Basal hyperinsulinemia and increased stimulated plasma insulin levels are associated with this obesity and precede the onset of overt diabetes. The present studies sought to determine the relative contributions of enhanced insulin secretion and of reduced insulin clearance to this early obesity-associated hyperinsulinemia. Direct simultaneous measurement of portal and jugular vein insulin levels in two normal monkeys showed a constant rate of hepatic insulin extraction of 56±3% over the range of peripheral insulin levels from 351±113 to 625±118 pmol/L. In 33 additional monkeys ranging from normal to diabetic, basal C-peptide levels were examined as an indicator of β-cell secretion and the molar ratio of plasma C-peptide to insulin (C/I ratio) under basal steady state conditions calculated as an index of hepatic insulin extraction. Well in advance of overt diabetes, there was a progressive decline of 67% in the apparent hepatic insulin extraction rate in association with increased obesity and plasma insulin levels. Basal insulin levels and hepatic insulin extraction returned toward normal in monkeys with impaired glucose tolerance and in those with overt diabetes. We conclude that reduced insulin disposal, probably due to reduced hepatic extraction of insulin, in addition to increased β-cell activity, contributes to the development of basal hyperinsulinemia in obese rhesus monkeys progressing toward NIDDM. In addition, in overt diabetes, normal hepatic insulin extraction in the presence of limited β-cell secretion may exacerbate the hypoinsulinemic state. (OBESITY RESEARCH 1993; 1:252–260)     

Development of hyperinsulinemia and insulin resistance during the early stage of weight gain

Obesity is associated with insulin resistance and hyperinsulinemia, which is considered to be a core component in the pathophysiology of obesity-related comorbidities. As yet it is unknown whether insulin resistance and hyperinsulinemia already develop during weight gain within the normal range. In 10 healthy male subjects the effect of intentional weight gain by 2 BMI points was examined on insulin. C-peptide and glucose levels following a meal, 75 g of glucose, and a two-step hyperglycemic clamp increased plasma glucose by 1.38 and 2.75 mmol/l, respectively. Baseline insulin, C-peptide, and glucose concentrations were significantly higher after weight gain from 21.8 to 23.8 kg/m(2) BMI within 4(1/2) mo. Calculations of insulin secretion and clearance indicate that reduced insulin clearance contributes more to post-weight gain basal hyperinsulinemia than insulin secretion. Following oral or intravenous stimulation insulin concentrations were significantly higher post-weight gain during all three test conditions, whereas C-peptide and glucose levels did not differ. Calculations of insulin secretion and clearance demonstrated that higher stimulated insulin concentrations are entirely due to clearance but not secretion. Despite significantly higher insulin levels, the rate of intravenous glucose required to maintain the defined elevation of glucose levels was either identical (1.38 mmol/l) or even significantly lower (2.75 mmol/l) following weight gain. The present study demonstrates for the first time that insulin resistance already develops during weight gain within the normal range of body weight. The associated basal and stimulated hyperinsulinemia is the result of differentiated changes of insulin secretion and clearance, respectively.     

Nocturnal free fatty acids are uniquely elevated in the longitudinal development of diet-induced insulin resistance and hyperinsulinemia

Obesity is strongly associated with hyperinsulinemia and insulin resistance, both primary risk factors for type 2 diabetes. It has been thought that increased fasting free fatty acids (FFA) may be responsible for the development of insulin resistance during obesity, causing an increase in plasma glucose levels, which would then signal for compensatory hyperinsulinemia. But when obesity is induced by fat feeding in the dog model, there is development of insulin resistance and a marked increase in fasting insulin despite constant fasting FFA and glucose. We examined the 24-h plasma profiles of FFA, glucose, and other hormones to observe any potential longitudinal postprandial or nocturnal alterations that could lead to both insulin resistance and compensatory hyperinsulinemia induced by a high-fat diet in eight normal dogs. We found that after 6 wk of a high-fat, hypercaloric diet, there was development of significant insulin resistance and hyperinsulinemia as well as accumulation of both subcutaneous and visceral fat without a change in either fasting glucose or postprandial glucose. Moreover, although there was no change in fasting FFA, there was a highly significant increase in the nocturnal levels of FFA that occurred as a result of fat feeding. Thus enhanced nocturnal FFA, but not glucose, may be responsible for development of insulin resistance and fasting hyperinsulinemia in the fat-fed dog model.     

Insulin responses to mixed meals: comparison of an artificial beta cell and normal beta cells.

The peripheral glucose and free insulin levels seen following a mixed meal in six insulin-dependent diabetic patients whose insulin was administered by a glucose-controlled insulin infusion system (GCIIS) were compared to those of normal subjects who received the same mixed meal or who were given separately carbohydrate, protein, or fat in amounts equivalent to those contained in the mixed meal. Patients treated with the GCIIS achieved nearly normal glucose levels immediately after the mixed meal, but this was accompanied by marked hyperinsulinemia. In the period from 120 to 240 minutes after the start of the mixed meal, the GCIIS duplicates the insulin levels produced by the normal pancreas after a glucose meal and, with appropriate algorithm constants, closely approximates those seen after a mixed meal.     

Familial type C syndrome of insulin resistance and short stature with possible autosomal dominant transmission

We describe a 17-yr-old girl with insulin resistant diabetes, acanthosis nigricans, hirsutism and short stature. At the age of 14 she was found to have glycosuria and diagnosed as diabetes mellitus. No endocrinological abnormality except transient amenorrhea and exaggerated LH response to LHRH was found. Insulin resistance was demonstrated by fasting hyperinsulinemia, insulin tolerance test and euglycemic glucose clamp test, and large doses of insulin with CSII were not effective in controlling blood glucose. Insulin binding to erythrocytes was normal, suggesting a postbinding defect. The same phenotype of insulin resistant diabetes and short stature was found in her mother who was diagnosed as diabetes mellitus at the age of 31 and died of diabetic nephropathy at the age of 41. Her maternal grandfather and uncle were reportedly affected with the same phenotype. Her father had impaired glucose tolerance, but no hyperinsulinemia. Two sisters had essentially normal glucose tolerance. Insulin binding to erythrocytes of her father and mother was also in the normal range. These results suggest that the present case may be a rare syndrome present together with type C syndrome of insulin resistance, and with short stature which was inherited autosomal dominantly.     

Extremity hyperinsulinemia stimulates muscle protein synthesis in severely injured patients

Insulin has a well-recognized anabolic effect on muscle protein, yet critically ill, severely injured patients are often considered "resistant" to the action of insulin. The purpose of this study was to assess the in vivo effects of hyperinsulinemia on human skeletal muscle in severely injured patients. To accomplish this goal, 14 patients with burns encompassing >40% of their body surface area underwent metabolic evaluation utilizing isotopic dilution of phenylalanine, femoral artery and vein blood sampling, and sequential muscle biopsies of the leg. After baseline metabolic measurements were taken, insulin was infused into the femoral artery at 0.45 mIU.min(-1).100 ml leg volume(-1) to create a local hyperinsulinemia but with minimal systemic perturbations. Insulin administration increased femoral venous concentration of insulin (P < 0.01) but with only a 4% (insignificant) decrease in the arterial glucose concentration and a 7% (insignificant) decrease in the arterial concentration of phenylalanine. Extremity hyperinsulinemia significantly increased leg blood flow (P < 0.05) and the rate of muscle protein synthesis (P < 0.05). Neither the rate of muscle protein breakdown nor the rate of transmembrane transport of phenylalanine was significantly altered with extremity hyperinsulinemia. In conclusion, this study demonstrates that insulin directly stimulates muscle protein synthesis in severely injured patients.     

Type A-insulin resistance with lipopexia on extremities: a case report.

We present the unusual case of a 17-year-old female with insulin-resistant diabetes, acanthosis nigricans, hirsutism, amenorrhea, dental dysplasia and lipopexia on the extremities. She had been diagnosed as having border line diabetes with hyperinsulinemia at age 12 when she was not obese and diabetes mellitus at age 13. On admission, she was obese and had lipopexia only on the extremities. The presence of hyperinsulinemia and poor response to exogenous insulin suggested severe insulin resistance. Insulin binding to transformed B-lymphoblasts derived from her was extremely low compared to the normal control, showing decreased receptor affinity. Her parents and sister exhibited hypersecretion of insulin in response to a 75 g oral glucose tolerance test. Her mother was diabetic, and her father and sister had border line diabetes, whereas her brother had a normal response. These findings support strongly the diagnosis of a type A syndrome with severe insulin resistance associated with lipopexia on the extremities. A genetic defect in the insulin receptor gene may be responsible.     

Rho-kinase inhibition improves vasodilator responsiveness during hyperinsulinemia in the metabolic syndrome

In patients with the metabolic syndrome (MetS), the facilitatory effect of insulin on forearm vasodilator responsiveness to different stimuli is impaired. Whether the RhoA/Rho kinase (ROCK) pathway is involved in this abnormality is unknown. We tested the hypotheses that, in MetS patients, ROCK inhibition with fasudil restores insulin-stimulated vasodilator reactivity and that oxidative stress plays a role in this mechanism. Endothelium-dependent and -independent forearm blood flow responses to acetylcholine (ACh) and sodium nitroprusside (SNP), respectively, were assessed in MetS patients (n = 8) and healthy controls (n = 5) before and after the addition of fasudil (200 μg/min) to an intra-arterial infusion of insulin (0.1 mU/kg/min). In MetS patients (n = 5), fasudil was also infused without hyperinsulinemia. The possible involvement of oxidative stress in the effect of fasudil during hyperinsulinemia was investigated in MetS patients (n = 5) by infusing vitamin C (25 mg/min). In MetS patients, compared with saline, fasudil enhanced endothelium-dependent and -independent vasodilator responses during insulin infusion (P < 0.001 and P = 0.008, respectively), but not in the absence of hyperinsulinemia (P = 0.25 and P = 0.13, respectively). By contrast, fasudil did not affect vasoreactivity to ACh and SNP during hyperinsulinemia in controls (P = 0.11 and P = 0.56, respectively). In MetS patients, fasudil added to insulin and vitamin C did not further enhance vasodilation to ACh and SNP (P = 0.15 and P = 0.43, respectively). In the forearm circulation of patients with the MetS, ROCK inhibition by fasudil improves endothelium-dependent and -independent vasodilator responsiveness during hyperinsulinemia; increased oxidative stress seems to be involved in the pathophysiology of this phenomenon.     

Hyperinsulinemia is associated with increasing insulin secretion but not with decreasing insulin clearance in an age-related metabolic dysfunction mice model

Human life expectancy is increasing faster lately and, consequently, the number of patients with age-related diseases such as type 2 diabetes (T2D) is rising every year. Cases of hyperinsulinemia have been extensively reported in elderly subjects and this alteration in blood insulin concentration is postulated to be a cause of insulin resistance, which in some cases triggers T2D onset. Thus, it is important to know the underlying mechanisms of age-dependent hyperinsulinemia to find new strategies to prevent T2D in elderly subjects. Two processes control blood insulin concentration: Insulin secretion by the endocrine portion of the pancreas and insulin clearance, which occurs mainly in the liver by the action of the insulin-degrading enzyme (IDE). Here, we demonstrated that 10-month-old mice (old) display increased body and fat pad weight, compared with 3-month-old mice (control), and these alterations were accompanied by glucose and insulin intolerance. We also confirm hyperinsulinemia in the old mice, which was related to increased insulin secretion but not to reduced insulin clearance. Although no changes in insulin clearance were observed, IDE activity was lower in the liver of old compared with the control mice. However, this decreased IDE activity was compensated by increased expression of IDE protein in the liver, thus explaining the similar insulin clearance observed in both groups. In conclusion, at the beginning of aging, 10-month-old mice do not display any alterations in insulin clearance. Therefore, hyperinsulinemia is initiated primarily due to a higher insulin secretion in the age-related metabolic dysfunction in mice.     

Insulin secretion and sensitivity in acromegaly

To examine the effect of excess growth hormones on carbohydrate metabolism, we studied glucose-stimulated insulin secretion and glucose utilization in 6 patients with acromegaly and 6 age-, sex- and weight-matched normal subjects. The levels of plasma glucose and serum insulin were determined during fasting and every 30 min up to 180 min after 75 g of oral glucose loading. In addition, plasma glucose, serum insulin and serum C-peptide were measured during euglycemic glucose clamp with insulin infusion of 40 mU/m2,min-1. The acromegalic patients had significantly higher mean levels of fasting plasma glucose (p less than 0.05) and insulin (p less than 0.01). After glucose loading for 3 h, the acromegalic patients also had a higher incremental area under the curve of plasma glucose (p less than 0.05) and serum insulin (p less than 0.05). However, no significant difference in the fasting molar ratio of C-peptide/IRI was noted between these two groups. During euglycemic clamp studies, the steady-state serum insulin levels were identical between the two groups. The glucose disposal rate was lower in acromegalics than in normal subjects (p less than 0.01). The results demonstrated that glucose intolerance, hyperinsulinemia and insulin resistance are present in acromegalic patients.     

Hyperinsulinemic hypoglycemia: effect of epinephrine suppression.

The inhibitory effect of epinephrine on basal and tolbutamide-stimulated insulin release was studied in 5 patients with hyperinsulinemic hypoglycemia. Epinephrine inhibited both basal and tolbutamide-induced insulin release in patients with beta-cell adenoma and hyperplasia, but failed to inhibit insulin release in a patient with beta-cell carcinoma. The inhibition of basal insulin with epinephrine was maximum in patients with beta-cell hyperplasia. This differential inhibitory effect of epinephrine on insulin release may prove to be a useful screening test in the preoperative diagnosis of the nature of the lesion producing hyperinsulinemia.     

Diminution of hypertriglyceridemia-induced pressor effect under hyperinsulinemic condition in normal and fructose-induced insulin resistant rats

This study aimed to evaluate the effect of hyperinsulinemia on hypertriglyceridemia-induced pressor response in normal and fructose-induced insulin resistant rats. The rats were divided into six groups of eight rats and were fed a fructose-enriched diet (FINs, F(INS+TG)) or a regular chow diet (C, C(TG), C(INS), C(INS+TG)) for 8 wks. The acute experiment was conducted at the end of wk 8 and consisted of a 30-min basal period and followed by a 120-min test period. After the basal period, somatostatin (1.3 microg/kg/ min) combined with regular insulin (0.6 or 4 mU/kg/min) and variable glucose infusion were given to clamp euglycemia and euinsulinemia in C and C(TG) or euglycemia and hyperinsulinemia in CINs, C(INS+TG), F(INS) and F(INS+TG). During test period, lipofundin (a triglyceride emulsion) was infused into CTG, C(INS+TG), F(INS+TG) and saline instead was infused into C, C(INS), FINS. Plasma insulin and triglyceride levels were significantly higher in fructose-fed rats than in normal rats. During the test period, the lipofundin infusion (1.2 ml/kg/hr) increased plasma triglyceride levels by 368 +/- 39, 351 +/- 71 and 489 +/- 38 mg/dl compared with their baseline levels in lipid-infused groups. During the test period, low-dose insulin infusion kept plasma insulin at basal levels in C and C(TG) and high-dose insulin infusion increased plasma insulin levels about 6 times the baseline insulin level in C. Glucose infusion rate (GIR) was significantly higher in rats with high insulin infusion than those with low insulin infusion. The increase in GIR was lower in fructose-fed groups than in control groups under similar hyperinsulinemia. Rats with or without lipofundin infusion did not alter GIR during the test period. The present results demonstrated that hypertriglyceridemia-induced pressor response was diminished under hyperinsulinemic condition in both normal and fructose-induced insulin resistant rats.     

Portal systemic shunting of insulin does not lead to insulin resistance in patients with extrahepatic portal vein obstruction.

There is no clear relation between portal systemic shunting, reduced hepatic insulin extraction leading to an increased systemic delivery of insulin, and, resultant peripheral hyperinsulinemia and insulin resistance. Extrahepatic portal vein obstruction is a natural human model of portal systemic shunting with essentially normal liver function. To investigate the role of portal systemic shunting of insulin in creating systemic hyperinsulinemia and insulin resistance, we studied nine subjects with portal systemic shunting and nine controls matched for age (+/- 2 years), body weight (+/- 2 kg) and height (+/- 5 cm). We carried out an oral glucose tolerance test and hyperinsulinemic euglycemic clamp study at insulin infusion rate of 40 mU/m2/ min. Comparable (p = 0.61) basal insulin concentrations in the two groups (Mean (SE): 21.0 (3.98) vs. 24.1 (4.28) mU/L) demonstrated a lack of hyperinsulinemia in the presence of portal systemic shunting. The lower (p = 0.03) insulin area under curve on oral glucose tolerance test in presence of portal systemic shunting (7.40 (0.95) vs. 10.83 (1.15) U/L-min) indicated that lower extraction of insulin by the liver leads to a lower requirements in the periphery. The coefficient of variation for plasma glucose between 60 and 120 min of the clamps was 4.44 (0.55)%. Comparable (p = 0.82) M-values (6.21 (0.67) vs. 6.38 (0.45) mg/kg/min) in the two groups proved a lack of significant insulin resistance in the presence of portal systemic shunting. We conclude that isolated portal systemic shunting leads to neither hyperinsulinemia nor insulin resistance.