High blood pressure is prevalent in obesity and in diabetes, both conditions with insulin resistance. To test whether hypertension is associated with insulin resistance independently of obesity and glucose intolerance, we measured insulin sensitivity (using the euglycemic insulin-clamp technique), glucose turnover (using [3H]glucose isotope dilution), and whole-body glucose oxidation (using indirect calorimetry) in 13 young subjects (38 +/- 2 years [+/- SEM]) with untreated essential hypertension (165 +/- 6/112 +/- 3 mm Hg), normal body weight, and normal glucose tolerance. In the postabsorptive state, all measures of glucose metabolism were normal. During steady-state euglycemic hyperinsulinemia (about 60 microU per milliliter), hepatic glucose production and lipolysis were effectively suppressed, and glucose oxidation and potassium disposal were normally stimulated. However, total insulin-induced glucose uptake was markedly impaired (3.80 +/- 0.32 vs. 6.31 +/- 0.42 mg per minute per kilogram of body weight in 11 age- and weight-matched controls, P less than 0.001). Thus, reduced nonoxidative glucose disposal (glycogen synthesis and glycolysis) accounted for virtually all the defect in overall glucose uptake (1.19 +/- 0.24 vs. 3.34 +/- 0.44 mg per minute per kilogram, P less than 0.001). Total glucose uptake was inversely related to systolic or mean blood pressure (r = 0.76 for both, P less than 0.001). These results provide preliminary evidence that essential hypertension is an insulin-resistant state. We conclude that this insulin resistance involves glucose but not lipid or potassium metabolism, is located in peripheral tissues but not the liver, is limited to nonoxidative pathways of intracellular glucose disposal, and is directly correlated with the severity of hypertension.

Insulin resistance in essential hypertension

Background Insulin resistance and hyperinsulinemia are features of obesity, non-insulin-dependent diabetes mellitus, and other disorders. Skeletal muscle is a major site of insulin action, and insulin sensitivity may be related to the fatty-acid composition of the phospholipids within the muscle membranes involved in the action of insulin. Methods We determined the relation between the fatty-acid composition of skeletal-muscle phospholipids and insulin sensitivity in two groups of subjects. In one study, we obtained samples of the rectus abdominis muscle from 27 patients undergoing coronary artery surgery; fasting serum insulin levels provided an index of insulin sensitivity. In the second study, a biopsy of the vastus lateralis muscle was performed in 13 normal men, and insulin sensitivity was assessed by euglycemic-clamp studies. Results In the patients undergoing surgery, the fasting serum insulin concentration (a measure of insulin resistance) was negatively correlated with the percentage of individua...

The Relation between Insulin Sensitivity and the Fatty-Acid Composition of Skeletal-Muscle Phospholipids

Insulin resistance, recently recognized as a strong predictor of disease in adults, has become the leading element of the metabolic syndrome and renewed as a focus of research. The condition exists when insulin levels are higher than expected relative to the level of glucose. Thus, insulin resistance is by definition tethered to hyperinsulinemia. The rising prevalence of medical conditions where insulin resistance is common has energized research into the causes. Many causes and consequences have been identified, but the direct contributions of insulin itself in causing or sustaining insulin resistance have received little sustained attention. We examine situations where insulin itself appears to be a proximate and important quantitative contributor to insulin resistance. 1) Mice transfected with extra copies of the insulin gene produce basal and stimulated insulin levels that are two to four times elevated. The mice are of normal weight but show insulin resistance, hyperglycemia, and hypertriglyceridemia. 2) Somogyi described patients with unusually high doses of insulin and hyperglycemia. Episodes of hypoglycemia with release of glucose-raising hormones, postulated as the culprits in early studies, have largely been excluded by studies including continuous glucose monitoring. 3) Rats and humans treated with escalating doses of insulin show both hyperinsulinemia and insulin resistance. 4) The pulsatile administration of insulin (rather than continuous) results in reduced requirements for insulin. 5) Many patients with insulinoma who have elevated basal levels of insulin have reduced (but not absent) responsiveness to administered insulin. In summary, hyperinsulinemia is often both a result and a driver of insulin resistance.

https://care.diabetesjournals.org/content/diacare/31/Supplement_2/S262.full.pdf

Insulin Resistance and Hyperinsulinemia Is hyperinsulinemia the cart or the horse

Background. Insulin resistance and impaired insulin secretion both occur in non-insulin-dependent diabetes (NIDDM), but their relative importance is unclear. Hyperglycemia itself has adverse effects on tissue insulin sensitivity and insulin secretion that make it difficult to distinguish between primary and secondary abnormalities. To avoid this problem we studied subjects with postprandial glucose intolerance but not sustained hyperglycemia. Methods. We compared the rate of systemic appearance and disappearance of glucose, the output of endogenous hepatic glucose, splanchnic and muscle uptake of glucose, and plasma insulin and glucagon responses after the ingestion of 1 g of glucose per kilogram of body weight in 15 subjects with impaired glucose tolerance (8 of them nonobese and 7 obese) and in 16 normal subjects (9 nonobese and 7 obese) who were matched for age and weight. Results. After glucose ingestion the mean (±SE) rate of total systemic appearance of glucose was significantly higher in b...

https://www.nejm.org/doi/pdf/10.1056/NEJM199201023260104

Role of Reduced Suppression of Glucose Production and Diminished Early Insulin Release in Impaired Glucose Tolerance

The factors responsible for fasting hyperglycemia were investigated in 77 normal weight non-insulin-dependent diabetic (NIDD) and 72 age-, sex-, and weight-matched control individuals. In diabetic subjects with mild fasting hyperglycemia (less than 140 mg/dL) hepatic glucose production (1.85 +/- 0.03 mg/kg.min) was similar to controls (1.84 +/- 0.02); the major factor responsible for the elevated basal glucose level in the diabetic group was a decreased efficiency in the tissue uptake of glucose, as reflected by a 30% decline in the rate of glucose clearance (1.56 +/- 0.03 v 2.00 +/- 0.03 mL/kg.min, P less than .001). In contrast, in diabetic subjects with fasting plasma glucose concentrations above 140 mg/dL, basal hepatic glucose production was significantly elevated (2.42 +/- 0.08 mg/kg.min, P less than .001) and correlated closely with the increase in fasting plasma glucose concentration (r = .796, P less than .001). The basal rate of whole body glucose clearance reached a plateau value at fasting glucose levels of 160 to 180 mg/dL and did not contribute to the further rise in fasting plasma glucose concentrations above 160 to 180 mg/dL. Decreased efficiency of tissue glucose uptake is responsible the development of fasting hyperglycemia in patients with mild NIDDM (fasting plasma glucose less than 140 mg/dL). As the diabetic state worsens, an increase in basal hepatic glucose production is the major factor responsible for the progressive rise in fasting glucose levels.

Fasting hyperglycemia in non-insulin-dependent diabetes-mellitus - contributions of excessive hepatic glucose-production and impaired tissue glucose-uptake

It has been proposed that hyperinsulinaemia may cause or exacerbate insulin resistance. The present studies were undertaken to test this hypothesis in man. Glucose utilization, glucose production, and overall glucose metabolism at submaximally and maximally effective plasma insulin concentrations (approximately 80 and approximately 1700 mU/l), and monocyte and adipocyte insulin binding were measured in normal volunteers on two occasions: once after 40 h of hyperinsulinaemia (25-35 mU/l) produced by infusion of insulin and once after infusion of saline (75 mmol/l; plasma insulin approximately 10 mU/l). After 40 h of hyperinsulinaemia, glucose utilization and overall glucose metabolism at submaximally and maximally effective plasma insulin concentrations were both slightly, but significantly, reduced compared with values observed after the infusion of saline (p less than 0.05), whereas glucose production rates were unaffected. Monocyte and adipocyte binding were also unaffected. These results indicate that hyperinsulinaemia of the magnitude observed in insulin resistant states, such as obesity, can produce insulin resistance in man. Assuming that human insulin sensitive tissues possess spare insulin receptors and that monocyte and adipocyte insulin binding accurately reflect insulin binding in insulin-sensitive tissues, the decreased maximal responses to insulin and the lack of change in insulin binding suggest that this insulin resistance occurred at a post-binding site.

/pdf/production-of-insulin-resistance-by-hyperinsulinaemia-in-man-1q412y3lgw.pdf

Production of insulin resistance by hyperinsulinaemia in man.

To determine the effect of thyroid hormone excess on insulin secretion, metabolism and action in humans, we examined intravenous glucose tolerance, glucose-induced insulin secretion, insulin clearance, monocyte insulin receptor binding, and the dose-response characteristics for the effects of insulin on glucose production, uptake, oxidation, and nonoxidative disposal in 10 normal volunteers for 14 days before and after oral administration of triiodothyronine (T3) in doses that increased plasma T3 to levels observed in spontaneous thyrotoxicosis (P less than 0.001). After T3 postabsorptive plasma glucose (P less than 0.05) and insulin (P less than 0.05) both increased; intravenous glucose tolerance was unaffected, but plasma insulin responses were increased (P less than 0.01); basal glucose production, uptake, and oxidation all increased (all P less than 0.05), whereas nonoxidative glucose disposal was unaffected (P = NS); monocyte insulin receptor binding increased (P less than 0.01) due to increased receptor affinity (P less than 0.05); and receptor number was not significantly altered (P = NS). Insulin clearance was increased. Insulin-induced suppression of glucose production was impaired (Km 22 +/- 3 vs. 37 +/- 7 microU/ml, P less than 0.02); maximal insulin-induced glucose uptake (10.7 +/- 0.6 vs. 13.0 +/- 0.9 mg X kg-1 X min-1, P less than 0.001) and oxidation (3.41 +/- 0.30 vs. 5.34 +/- 0.59 mg X kg-1 X min-1, P less than 0.001) were increased without a significant change in Km. However, submaximal rates of nonoxidative glucose disposal and glucose uptake were inappropriately low for the increased insulin receptor binding.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of thyroid hormone excess on action, secretion, and metabolism of insulin in humans.

To determine whether hyperinsulinaemia can cause insulin resistance in man and, if so, whether this occurs at a receptor or post-receptor site, nine normal volunteers were infused with insulin for 6 h at a rate (2 mU·kg-1·min-1) which resulted in steady-state plasma insulin concentrations of 140±13mU/l and four subjects were infused with saline (0.45%). Isolated adipocytes and monocytes were used as models for studying insulin binding, while adipocytes were also used to study insulin action in vitro. Adipocyte insulin binding did not decrease following infusion of insulin (4.6±0.5 versus 4.4±0.4% per 2×105 cells, before and after, respectively), whereas monocyte insulin binding did (7.2±0.6 versus 6.2±0.6% per 107 cells, p<0.05). Initial rates of adipocyte 3-0-methyl glucose transport were decreased in the absence of insulin (basal) and at submaximally effective (33.3pmol/l) but not at maximally effective insulin concentrations. At all insulin concentrations and in the absence of insulin, rates of glucose conversion to lipids were decreased more than 50% (p<0.05), whereas rates of glucose oxidation were unaffected. This decrease in the rates of conversion of glucose to lipids could not be accounted for by the decrease in rates of glucose transport. These results suggest that hyperinsulinaemia can cause insulin resistance in man and that, at least initially, this occurs at a post-receptor site. Furthermore, the discordant effect of hyperinsulinaemia on monocyte and adipocyte insulin binding indicates that monocyte insulin binding may not always reflect insulin binding in insulin-sensitive tissues.

/pdf/infusion-of-insulin-impairs-human-adipocyte-glucose-vz6fm3p794.pdf

Infusion of insulin impairs human adipocyte glucose metabolism in vitro without decreasing adipocyte insulin receptor binding

To determine the influence of insulin infusions used in dose-response studies on monocyte insulin binding, monocyte insulin binding and glucose disposal were measured in six normal subjects before and at the end of each of four sequential 2-h insulin infusions (0.4, 1.0, 2.0, and 10 mU kg−1 min−1). Monocyte insulin binding was unaltered at the end of the first three infusions (plasma insulin, 31 ± 2 (SEM),77 ± 3, and 184 ± 10 μU/ml) but was decreased after the last infusion (plasma insulin, 1730 ± 125 μU/ml) at 0.2 through 10.2 ng/ml insulin concentrations in the binding assay (P < 0.01). Using a one-site model, this could be ascribed to a decrease in insulin receptor affinity (1.54 ± 0.26 vs. 2.27 ± 0.48 × 108 M−1 P < 0.05), whereas in a two-site model this appeared to be due to a decrease in high affinity binding sites (1,868 ± 228 vs. 2,387 ± 207, P < 0.02). Nevertheless, insulin receptor occupancies estimated to occur during the insulin infusions were virtually identical whether preinsulin infusion bi...

B. Baker

Papers

Production of insulin resistance by hyperinsulinaemia in man.

Effect of thyroid hormone excess on action, secretion, and metabolism of insulin in humans.

Infusion of insulin impairs human adipocyte glucose metabolism in vitro without decreasing adipocyte insulin receptor binding

Influence of Changes in Insulin Receptor Binding during Insulin Infusions on the Shape of the Insulin Dose-Response Curve for Glucose Disposal in Man*