Serum Immunoreactive Insulin Concentrations Research Articles

Primary insulin autoimmune syndrome in an Italian woman: a case report

Insulin autoimmune syndrome (IAS) is a rare syndrome characterized by fasting or postprandial hypoglycemia, high levels of anti-insulin antibodies and high concentration of total serum immunoreactive insulin. It is relatively known in Japan, rare in remaining Asia and it is extremely uncommon in Western countries, being characterized by a different race-related incidence and associated with HLADR4 alleles. Usually IAS is related to particular drugs, or to autoimmune, rheumatologic or hematological diseases, while it is very rare as a primary form. Here we described a case of an Italian woman affected by a primary form of Hirata syndrome.

Effects of Moxifloxacin on Serum Glucose Concentrations in Rats

Moxifloxacin, a fluoroquinolone antimicrobial agent, has been reported to cause serum glucose abnormalities such as hyper- and hypoglycemia. The purpose of the present study was to investigate the effect of moxifloxacin on serum glucose concentrations in rats. Rats were intravenously injected with moxifloxacin and samples of their arterial blood were collected periodically. Serum glucose concentrations increased with moxifloxacin at 100 mg/kg, and temporal elevations were observed in serum epinephrine and histamine concentrations. On the other hand, intravenous injection of moxifloxacin at 75 mg/kg did not affect serum glucose, epinephrine, or histamine concentrations. Serum immunoreactive insulin concentrations remained unchanged by moxifloxacin both at 75 and 100 mg/kg. In conclusion, moxifloxacin can induce histamine release, leading to an increase in serum epinephrine concentrations and hyperglycemia.

Circulating insulin-like growth factors may contribute substantially to insulin receptor isoform A and insulin receptor isoform B signalling

BackgroundOnly a fraction of circulating insulin-like activity is due to insulin itself. The aim of this study was to determine total serum insulin-like activity mediated via the insulin receptor isoform A (IR-A) and isoform B (IR-B) by using kinase receptor activation (KIRA) assays specific for the IR-A and IR-B. MethodsThe IR-A and IR-B KIRA assays use human embryonic kidney cells which have been transfected with the human IR-A or IR-B gene and quantify serum-mediated phosphorylation of the IR. ResultsBoth IR KIRA assays were sensitive (detection limit 32pmol/L) and precise (intra- and inter assay CV: <12% and <15%). The EC50s of insulin, IGF-I and IGF-II were 1.4, 11.2 and 6.7nmol/L for the IR-A KIRA assay, and 1.3, 31.0 and 15.7nmol/L for the IR-B KIRA assay.The operational range of both assays allowed for determination of total insulin-like activity in human serum. Analysis of serum samples showed that there was a significant positive correlation between serum insulin-like and immunoreactive insulin concentrations (IR-A: r=0.56, p=0.01, IR-B: r=0.68, p=0.001). Importantly, addition of IGF-I or IGF-II antibodies to human serum samples could substantially decrease the endpoint signal in both KIRA assays. ConclusionsWe showed that serum IGF-I and IGF-II may substantially contribute to IR signalling. Since IR isoform specific KIRA assays also take into account the contribution of IGFs present in serum on IR signalling, they may help to gain more insight into the roles of IGF mediated IR-A and IR-B activation in health and disease.

Effects of daily mechanical horseback riding on insulin sensitivity and resting metabolism in middle-aged type 2 diabetes mellitus patients.

The present study was conducted to investigate the effect of daily passive exercise using a horseback riding machine (Joba) on insulin sensitivity and resting metabolism in middle-aged, diabetic patients. Participants were 24 type 2 diabetes mellitus patients aged 59 +/- 8 years (mean +/- SD; range from 43 to 75 years of age). Patients were randomly divided into control (normal lifestyle) and Joba exercise groups. The latter group was instructed to perform one 30-min session of Joba riding per day, 7 times per week, for 3 months. Compared with baseline values, serum immunoreactive insulin (IRI) concentrations decreased and HOMA-IR was improved by Joba training. In addition, exercise duration per day significantly correlated (r = -0.65) with changes in serum IRI, and 3-month mechanical horseback riding significantly increased the resting metabolic rate of the patients. These results suggest that daily Joba passive exercise is potentially useful as a means to improve insulin sensitivity and resting metabolism in diabetic patients. The Joba fitness equipment can prove especially useful as an alternative exercise therapy for aged individuals incapable of performing independent exercise or for those who suffer from knee-joint disorders.

Gatifloxacin-induced histamine release and hyperglycemia in rats

Gatifloxacin, a fluoroquinolone antimicrobial agent, has been reported to cause both hypoglycemia and hyperglycemia in diabetic and non-diabetic patients. The purpose of the present study was to investigate the mechanism of gatifloxacin-induced hyperglycemia in normal and diabetic rats. Rats received a single intravenous injection of gatifloxacin and samples of their arterial blood were collected periodically. Diabetic rats were produced by the injection of streptozotocin and nicotinamide. In normal rats, the concentration of serum glucose decreased after the injection of gatifloxacin at 50 mg/kg, while it increased with gatifloxacin at 100 mg/kg. The concentrations of serum epinephrine and histamine increased after the injection of gatifloxacin at 100 mg/kg. The increases in serum glucose and epinephrine concentrations were reduced by pretreatment with diphenhydramine at 1 mg/kg. In diabetic rats, the concentration of serum glucose actually increased after the injection of gatifloxacin at 50 mg/kg, concomitant with increases in the serum epinephrine and histamine concentrations. The concentration of serum immunoreactive insulin slightly increased after the injection of gatifloxacin at 50 mg/kg. In addition, repeated oral administration of gatifloxacin to rats at 300 mg/kg twice a day for 7 days did not change glucose tolerance. In conclusion, gatifloxacin-induced release of histamine can contribute to an increase in the serum epinephrine concentration and hyperglycemia in normal rats. In diabetic rats, lower doses of gatifloxacin can induce hyperglycemia owing to the low level of insulin secretion that they exhibit compared with normal animals.

Glucose metabolism in five septic neonatal foals

AbstractObjective: Glucose metabolism is often deranged in septic animals. Bacteremia and sepsis are common in foals and clinical experience suggests that glucose metabolism is abnormal in some of these animals. The purpose of this study was to provide initial estimates of rates of glucose appearance, disappearance, and metabolic clearance rate in septic foals.Series Summary: Rates of glucose entry, and exit from blood were determined by use of infusion of isotopically labeled glucose in 5 foals with confirmed sepsis. Serum concentrations of glucose, insulin, glucagon, and cortisol were measured concurrent with measurement of rates of glucose turnover. Median glucose turnover rate was 24 μmol/kg/min (range 17–53 μmol/kg/min), and median glucose metabolic clearance rate was 3.2 mL/kg/min (range 1.7–6.7 mL/kg/min). Median concentration of serum immunoreactive insulin was 55 pmol/L (range 36–190 pmol/L), median serum immunoreactive glucagon was 65 pmol/L (range 19–120 pmol/L), and median serum cortisol was 207 nmol/L (range 100–333 nmol/L).New or unique information provided: These data, although limited in scope and by the lack of data in healthy foals, demonstrate the magnitude and variation in glucose appearance, disappearance, and metabolic clearance rate in septic foals, provide an estimate of rates of glucose utilization in sick foals, and will be useful in guiding future studies of energy metabolism in healthy and ill foals.

Lack of Relationship between Blood Glucose-lowering Activity of Colestimide and Serum Cholecystokinin (CCK) Concentrations in Patients with Type 2 Diabetes

Colestimide has been reported to lower blood glucose levels in patients with type 2 diabetes and hypercholesterolemia. We investigated the mechanism of the hypoglycemic activity of colestimide by examining changes in serum cholecystokinin (CCK) and insulin concentrations before and after its 2-week oral administration. A total of seven type 2 diabetes inpatients with hypercholesterolemia received colestimide after their blood glucose levels had stabilized. We daily measured plasma glucose levels and serum lipid concentrations, calculated Body Mass Index (BMI), and determined whole-day changes in serum immunoreactive insulin (IRI) and CCK concentrations in all study subjects. We daily measured plasma glucose levels, as well as serum IRI and CCK concentrations at 10 time points for measurement. Plasma glucose levels, as well as serum IRI and CCK concentrations before and after the 2-week oral administration of colestimide were compared. The means of total cholesterol levels and BMI decreased significantly after administration. At time points for measurement (10 : 00 and 12 : 00), plasma glucose levels decreased significantly after administration (P=0.026 and P=0.009, respectively). Diurnal changes in serum IRI and CCK concentrations were not observed after administration, except for the IRI concentration at 20: 00. The effect of colestimide on CCK may not explain the mechanism of its blood glucose-lowering activity in patients with type 2 diabetes and hypercholesterolemia.

Effect of levofloxacin on serum glucose concentration in rats

To clarify the mechanism of fluoroquinolone-induced abnormalities in blood glucose, the effect of levofloxacin on serum glucose concentration was investigated in rats. Rats received an intravenous injection of levofloxacin and their arterial blood was sampled periodically. The serum glucose concentration decreased after an injection of 100 mg/kg of levofloxacin, while it increased at levofloxacin 300 mg/kg. The serum immunoreactive insulin concentration increased as the dose of levofloxacin increased. The serum epinephrine concentration was rapidly elevated by levofloxacin at 300 mg/kg. The serum histamine concentration increased after injections of levofloxacin, 200 and 300 mg/kg. Diphenhydramine (1 mg/kg) antagonized the hyperglycemia induced by 300 mg/kg of levofloxacin. In an in vitro study, the release of epinephrine from the adrenal medulla in the presence of levofloxacin was determined. Levofloxacin (300 μg/ml) did not affect epinephrine release from the adrenal medulla. Levofloxacin can induce hypoglycemia and hyperglycemia in rats. Levofloxacin can promote histamine release, leading to an increased serum epinephrine concentration and hyperglycemia.

Dose Response of Inhaled Dry-Powder Insulin and Dose Equivalence to Subcutaneous Insulin Lispro

To determine the pharmacokinetic (PK) and glucodynamic (GD) dose response of human insulin inhalation powder (HIIP) delivered via AIR particle technology and dose equivalence to subcutaneous (SC) insulin lispro. Twenty healthy, nonsmoking, male or female subjects (aged 29.6 +/- 6.9 years, BMI 23.2 +/- 2.3 kg/m2, means +/- SD) with normal forced vital capacity and forced expiratory volume were enrolled in an open-label, randomized, seven-period, euglycemic glucose clamp, cross-over trial. Each subject received up to four single doses of HIIP (2.6, 3.6, 5.2, or 7.8 mg) and three doses of SC lispro (6, 12, or 18 units) from 5 to 18 days apart. HIIP demonstrated a similar rapid onset but an extended time exposure and a prolonged duration of effect (late t(50%) 412 vs. 236 min, P < 0.001) compared with SC lispro. The HIIP versus SC lispro doses of 2.6 mg vs. 6 units, 5.2 mg vs. 12 units, and 7.8 mg vs. 18 units achieved similar PK area under the serum immunoreactive insulin (IRI) concentration-versus-time curve from time zero until the serum IRI concentrations returned to the predose baseline value [AUC(0-t')] and GD (G(tot)) responses. The median insulin (t(max)) was not different between HIIP and SC lispro (45 min for both), although the median time of return to baseline for PK was apparently longer for HIIP compared with SC lispro (480 vs. 360 min). Relative bioavailability and relative biopotency of HIIP were consistent across doses (8 and 9%). While the time-action profile was longer for HIIP than for SC lispro, both treatments showed rapid initial absorption and similar overall PK exposure and GD effect. HIIP was as well tolerated as SC lispro, thereby offering a promising alternative to injectable insulin therapy.

Glycemic index of cracked corn, oat groats and rolled barley in horses.

Muscle glycogen synthesis depends on glucose availability. This study was undertaken to determine the glycemic and insulinemic response of horses to equal amounts of hydrolyzable carbohydrates (starch and sugar) in the form of one of three grain meals or intragastric administration of a glucose solution. In a randomized crossover design, seven horses were fed each of three grain meals (cracked corn, steamed oat groats, or rolled barley) or were infused intragastrically with glucose solution at 2 g of hydrolyzable carbohydrate (starch plus sugar) per kilogram of BW. The quantity of hydrolyzable carbohydrate ingested was not different among all treatments (P = 0.70). Plasma glucose concentration peaked in all four treatments by 1.5 to 2 h after feeding. Plasma glucose concentration remained higher than baseline in oat groats or barley-fed horses throughout 8 h, whereas plasma glucose returned to baseline by 5 to 6 h in corn-fed horses or after glucose administration. Meal consumption was slower in oat groats-fed horses than in corn-fed ones, which may confound the glycemic and insulinemic responses observed after grain feeding. Plasma glucose area under the curve (AUC) was 63% both in corn and oat groats and 57% in barley-fed horses compared with that of horses administered glucose (P = 0.13). Serum immunoreactive insulin concentration peaked between 2 and 3 h after feeding or glucose administration, and barley-fed horses had lower serum immunoreactive insulin concentration by 3 to 4 h than corn-fed horses or after glucose administration (P < 0.05). We conclude, in horses, ingestion of oat groats, corn, and barley result in similar plasma glucose AUC and, compared with the glycemic index of 100 as the glucose reference, corn, oat groats, and barley had a glycemic index of approximately 60.

Insulin resistance in uremia: effect of dialysis modality.

Insulin sensitivity was studied before and after 3 mo of continuous cycling peritoneal dialysis (CCPD) in seven uremic patients, before and after 3 mo of hemodialysis (HD) in another seven uremic patients, and in seven healthy controls. There were no significant differences in the height, weight, anthropometric measures, or intakes of protein and total calories between the CCPD and the HD groups before and after the 3 mo of dialysis therapy. There were no differences in other biochemical parameters between patients on CCPD and patients on HD either at the initiation of dialysis or at the end of 3 mo of dialysis therapy. Residual renal function was not different between the two groups. Mean Kt/Vurea in the CCPD group was 2.10/wk and that for the HD group was 1.20/session. The CCPD group and the HD group both had higher fasting glucose concentrations (p < 0.02), but normal fasting serum immunoreactive insulin concentrations compared with controls. The hyperinsulinemic euglycemic clamp technique was used to measure insulin sensitivity. Before dialysis, insulin sensitivity was low in both patient groups (CCPD 128 +/- 11 mg/m2/min; HD 130 +/- 11) compared with controls (320 +/- 26) (p < 0.01 in both cases) but not different between the patient groups. After 3 mo of dialysis therapy, insulin sensitivity increased by 80 +/- 7% in the CCPD group and by 38 +/- 4% in the HD group (p < 0.01 compared with predialysis values in both groups). Insulin sensitivity in both groups after 3 mo of dialysis was still lower than in the control group (p < 0.01 in both cases). However, both the percentage increase as well as the final insulin sensitivity were significantly higher in the CCPD group (230 +/- 19 mg/m2/min) than the HD groups (179 +/- 16) (p < 0.01 in both cases).

Effects of changes in acid base and calcium concentration on fasting serum insulin, proinsulin, and glucose concentrations.

To test the hypothesis that alterations in acid base or calcium concentration may affect proinsulin processing or the insulin secretion mechanism. Changes in proinsulin secretion or cleavage were assessed by measuring serum intact proinsulin and immunoreactive insulin concentrations in three models of acid base and calcium disturbance: (1) subacute changes in acid base status in six volunteers who received oral placebo, ammonium chloride, or sodium bicarbonate for three five day periods; (2) acute changes in calcium concentration in eight subjects who received 25 mmol oral calcium; (3) chronic changes in calcium concentration in seven patients with primary hyperparathyroidism and five with pseudohypoparathyroidism. Acid base changes were confirmed by rises in serum bicarbonate concentrations (p < 0.01). No changes in serum insulin, intact proinsulin, or the proinsulin:insulin molar ratio were found. Serum calcium concentrations increased (2.49 v 2.38 mmol/l; p < 0.05) and parathyroid hormone concentrations decreased (1.1 v 1.9 pmol/l; p < 0.01) two hours after acute calcium loading. There were no significant differences in serum glucose, insulin, or intact proinsulin concentrations. Fasting proinsulin concentrations were significantly lower in the hyperparathyroid group (1.1 v 2.1 pmol/l; p < 0.05) and increased significantly after parathyroidectomy (2.1 v 1.1 pmol/l; p < 0.05). The results indicate that subacute acid base changes do not affect proinsulin cleavage. Although acute calcium loading has no demonstrable effect, chronic hypercalcaemia may influence the mechanism of insulin secretion.

The high prevalence of diabetes mellitus and hyperinsulinemia among the Japanese-Americans living in Hawaii and Los Angeles

A comparative epidemiologic investigation was conducted among Japanese immigrants and their offspring living in Hawaii and the Los Angeles area, and among Japanese living in Hiroshima. All subjects received an oral glucose tolerance test and the diagnosis of diabetes was made on the basis of WHO criteria. In the subjects aged 40 years or older, the age, sex, and obesity-specific prevalence of diabetes was 2–3 times higher among Japanese living in America than those in Hiroshima. The fasting and post-glucose load serum immunoreactive insulin concentrations were higher in the Japanese-Americans compared to the Hiroshima inhabitants with the same degree of obesity and glucose tolerance. We suggest that a westernized lifestyle induces peripheral insulin resistance and promotes the development of diabetes among Japanese.

Blood sugar, serum insulin and serum non-esterified fatty acid levels during thiopentone anaesthesia in dogs

The purpose of this study was to determine the effect of thiopentone anaesthesia on glucose metabolism. Blood sugar (BS), serum immunoreactive insulin (IRI) and serum non-esterified fatty acid (NEFA) concentrations were measured during the course of (1) an intravenous glucose tolerance test (IVGTT), and (2) an intravenous insulin test (ITT), in conscious and anaesthetized fasted dogs. The IVGTTs were repeated in dogs under alpha- or beta-adrenergic blockade, induced by phentolamine or propranolol. During the IVGTT, the anaesthetized dogs showed glucose intolerance (blood sugar levels were higher than in the control group) and little serum IRI response to hyperglycaemia was detected. An attenuated initial decrease and a slower rebound of NEFA concentration was observed in anaesthetized animals than in controls. Phentolamine administration (5 mg.kg-1 iv) partly restored the IRI response without affecting the BS levels; propanolol (1 mg.kg-1 iv) had no effect. Anaesthetized dogs showed a moderate resistance to insulin induced hypoglycaemic action and a lack of serum NEFA response during counter-regulation of hypoglycaemia, while in conscious controls an intense rebound was observed. Hyperinsulinaemia after iv insulin administration was longer in anaesthetized dogs than in controls. The insulin distribution space was 78% of body weight and insulin t1/2 in blood group compared with 54% and 16 min, in controls. We conclude that thiopentone provokes disturbances in glucose and serum NEFA metabolisms and abolishes the serum IRI response to hyperglycaemia. These effects are influenced by extrapancreatic factors regulating serum IRI levels and by an alpha-adrenergic mechanism, via the inhibition of insulin secretion.

Unresponsiveness of Insulinoma Cells to Secretin

It is well known that B cells in the pancreas release insulin when stimulated by secretin, but there have been few reports on the response of insulinoma cells to secretin. In five patients with insulinoma, changes in serum immunoreactive insulin (IRI) concentration were measured after the intravenous injection of secretin into the peripheral vein before and after extirpation of the insulinoma. The extirpated insulinomas were cultured and tested for their response to secretin. The rise in serum IRI in response to secretin in patients with insulinoma was significantly slower and smaller than in normal volunteers. After removal of the insulinoma, the response to secretin became prompt and increased with time. Cultured insulinoma cells did not release insulin when stimulated by secretin. Therefore, it is concluded that the response of insulinoma cells to secretin is quite different from that of normal beta cells, and that the function of beta cells in the insulinoma-bearing pancreas is suppressed by the autonomous hypersecretion of insulin by the insulinoma. The extent of the decrease in function of the beta cells in patients with insulinoma can be estimated by the intravenous secretin test. Thus, the secretin test is sometimes useful in the differentiation of hypoglycemia due to insulinoma from that due to beta cell hyperplasia or alimentary hyperinsulinemia.

Preferential release of proinsulin relative to insulin in non-insulin-dependent diabetes mellitus.

A radioimmunoassay, using an antiserum that is specific for human proinsulin, has been used to study the response of serum proinsulin to low (25 g) and high (75 g) oral glucose loads in non-obese patients with non-insulin-dependent diabetes mellitus (NIDDM). Diabetic patients were treated by diet only (N = 8) or were receiving oral anti-hyperglycemic agents (N = 8) and therapy was not interrupted during the study. In the fasted state, proinsulin concentrations were higher (P less than 0.05) in the drug-treated patients (31 +/- 3 pmol/l (SEM)) compared with age- and weight-matched healthy subjects (22 +/- 2 pmol/l; N = 10), but concentrations in the diet-treated patients 25 +/- 3 pmol/l) were not significantly different. Following 25 g and 75 g glucose loads, the rises in serum immunoreactive insulin and C-peptide concentrations in both groups of diabetic patients were impaired and delayed relative to those in the control subjects. The responses of serum proinsulin, however, were not significantly different in the NIDDM patients compared with controls at any time point up to 180 min except in the case of drug-treated patients receiving 25 g of glucose who had elevated (P less than 0.05) proinsulin concentrations at 150 min and 180 min after ingestion. It is concluded that NIDDM is not associated with an exaggerated release of proinsulin in response to glucose compared with healthy subjects, but the islets have maintained the ability to release proinsulin better than the ability to release insulin.

Role of the adrenal medulla in stress-induced hyperinsulinaemia in normal mice and in mice infected with Bordetella pertussis or treated with pertussis toxin.

Intranasal infection of mice with a sublethal dose of Bordetella pertussis or the intravenous administration of purified pertussis toxin resulted in a marked increase in the serum immunoreactive insulin concentration following ether stress. This stress-induced hyperinsulinaemia was not modified significantly by blockade of alpha 2-adrenoceptors with idazoxan, beta-adrenoceptors with propranolol, autonomic ganglia with hexamethonium, opioid receptors with naloxone, muscarinic cholinoceptors with atropine or by adrenal demedullation. The effect of pertussis in promoting stress-induced hyperinsulinaemia was mimicked qualitatively by alpha 2-adrenoceptor blockade, adrenal demedullation or ganglionic blockade. However, the serum immunoreactive insulin response to ether stress was smaller in animals subjected to these procedures compared with the response seen in mice infected with B. pertussis or treated with pertussis toxin. Thus, in the mouse, acute stress produces hyperinsulinaemia under conditions in which the release of adrenal medullary catecholamines is prevented, or the inhibitory action on insulin secretion is blocked by alpha 2-adrenoceptor antagonists or by pertussis toxin.

Transient Glucose Intolerance during Attacks of Thyrotoxic Periodic Paralysis

In a 19-year-old Japanese male (case 1) with thyrotoxic periodic paralysis (TPP), an increase of plasma glucose concentration together with abnormally high levels of serum immunoreactive insulin (IRI) was observed preceding a spontaneous attack of paralysis. Therefore, the plasma glucose, glucagon, epinephrine, norepinephrine, serum IRI, growth hormone and cortisol levels, and the erythrocyte insulin receptors were measured in case 1 and a 40-year-old Japanese male (case 2) with TPP during attacks of paralysis induced by prolonged glucose loading. In case 1, the serum IRI concentration was elevated to the extraordinarily high level of 655.0 microU/ml at the beginning of paralysis, and at that time, the plasma glucose concentration was 147 mg/dl. However, when paralysis was not induced by a similar glucose loading during methimazole treatment, the serum IRI and plasma glucose levels at the corresponding time after glucose loading were 20.9 microU/ml and 87 mg/dl, respectively. Furthermore, the affinity of the erythrocyte insulin receptors was decreased during the attack. In case 2, plasma glucose and serum IRI concentrations were increased in accordance with the initiation of paralysis although the blood levels of hormones counteracting insulin were not significantly changed. These findings suggest that there is something interacting with the normal action of the insulin in the early phase of paralysis.

Insulin in the rat fetus. A new form of circulating insulin.

The apparent hyperinsulinemia seen in the fetal rat in late gestation (day 20) is shown to be due to an immunoreactive insulin (IRI) species peculiar to the fetal rat, and not monomeric insulin. This species disappears within 12 h after birth and only insulin as found in the adult can then be detected. The fetal serum IRI has a molecular weight of approximately 11,000 and differs from monomeric insulin and proinsulin in its behavior on gel filtration and anion-exchange chromatography. The activity of fetal serum in an insulin bioassay based on the incorporation of glucose into lipid was half that expected on the basis of the serum IRI concentration. The addition of fetal serum to purified insulin or proinsulin caused an increase in the apparent molecular weight of both hormones by 2000. In the case of insulin, the generated species of mol wt 8000 was clearly differentiated from the endogenous species (11,000) on Sephadex G50. The fetal pancreas at this age was found to contain predominantly monomeric insulin that had full biologic activity in the insulin bioassay. It is postulated that the fetal pancreas secretes monomeric insulin, which is then modified in the circulation to a complex with reduced biologic activity. This process appears to have two steps in that in vitro fetal serum increases the apparent molecular weight of added insulin to 8000, whereas in vivo an additional component of approximately 3000 mol wt is involved to produce the endogenous insulin complex.

Effect of high fructose diet. VI. Effect of fructose on lipoprotein lipase activity of adipose tissue in rats.

A study was made of rats fed a high fructose diet to determine whether males and females responded differently to lipoprotein lipase activity and how this response was affected by sex. The rats were meal-fed with a high fructose or a high glucose diet for two weeks. After two days of starvation, each diet-group was divided into three subgroups: (a) fasted, (b) injected with physiological saline solution, and (c) injected with mannoheptulose solution. Subgroups (b) and (c) were then immediately refed their respective meals of the high fructose or the high glucose diet for three hours and then sacrificed. The weights of the liver and adipose tissues, amounts of liver lipids, lipoprotein lipase activities in the adipose tissues and serum immunoreactive insulin concentrations were determined. Males fed the high fructose diet had a significantly higher hepatic lipid content than those fed the high glucose diet. The weight of adipose tissues of females fed the high fructose diet was less than that of those fed ...