Insulin Extraction Research Articles

Porcine Insulin Biodegradable Polyester Microspheres: Stability and In Vitro Release Characteristics

The stability of porcine insulin in biodegradable polymers, i.e., poly(dl-lactide-co-glycolide) 50:50 (50:50 DL-PLGA) and poly(l-lactide) (L-PLA) was investigated. Insulin encapsulated microspheres were fabricated from both polymers using double-emulsion–solvent evaporation and emulsion–solvent evaporation techniques and subjected to accelerated stability studies at 40°C and 75% relative humidity. Porcine insulin was found to degrade in all microsphere formulations with an average of <50% of the initial loading amount remaining intact at the end of 4 weeks. The two major degradation products observed in these formulations were determined to be A-21 desamido insulin and covalent insulin dimer with trace amounts of high molecular weight transformation products. In vitro release studies in phosphate buffered saline at 37°C resulted in very slow and incomplete (<30% in 30 days) release kinetics for all microsphere formulations. Extraction and analyses of the unreleased insulin within the microspheres revealed that an average of ∼11% of the encapsulated insulin remained intact. The degradation products observed consisted of ∼15% of three distinct deamidated hydrolysis products including A-21 desamido insulin, ∼22% covalent insulin dimer, and trace amounts of high molecular weight transformation products. The degradation of porcine insulin within biodegradable polyester microspheres during stability and release studies can be attributed to the gradual decrease in the pH within the microspheres due to progressive polymer hydrolysis resulting in the production of dl-lactic and glycolic acids. The encapsulation of an acid–base indicator, bromophenol blue, in 50:50 PLGA microspheres (as a probe to estimate pH within the microspheres during accelerated stability studies) indicated that the pH decreased to ∼3.8 after 3 weeks.

Splanchnic and extrasplanchnic extraction of insulin following oral and intravenous glucose loads

Splanchnic and extrasplanchnic extraction of insulin following oral and intravenous glucose loads

Splanchnic and extrasplanchnic extraction of insulin following oral and intravenous glucose loads

In the basal state, approx. 60-70% of the insulin released from the pancreas is extracted by the liver; the remaining 30-40% is extracted by extrasplanchnic organs. Carbohydrate ingestion is known to stimulate pancreatic insulin release and to inhibit whole-body insulin extraction. The present study was undertaken to obtain a quantitative assessment of the degree to which early postprandial insulinaemia in peripheral blood is due to the inhibition of splanchnic as opposed to extrasplanchnic insulin extraction. By means of catheterization, which allowed frequent analyses of insulin and C-peptide in arterial and hepatic venous blood and estimates of splanchnic plasma flow (indocyanine), insulin extraction by splanchnic and extrasplanchnic tissues was studied in 16 healthy volunteers at timed intervals before and after or during oral (n=8) and intravenous (n=8) isoglycaemic glucose loads. Splanchnic insulin extraction (66+/-2% in the basal state) fell significantly during the 10 min after oral glucose to a minimum of 45+/-8%; during 5-20 min of intravenous glucose administration it rose significantly to a maximum of 72+/-2%. Extrasplanchnic extraction of insulin fell from 90-100% in the basal state to a minimum of 3+/-6% (P<0.001) after oral glucose; during the first 5 min of intravenous glucose infusion it fell in relative but not in absolute terms. It is concluded that the early postprandial increase in peripheral insulinaemia largely (>85% during the first 30 min) reflects a marked inhibition of insulin extraction. It is suggested that intestinal hormones and/or splanchnic blood flow may be involved in the mechanisms governing the postprandial inhibition of insulin extraction.

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.

Effect of different times of administration of a single ethanol dose on insulin action, insulin secretion and redox state.

Ethanol (EtOH) can affect glucose metabolism by altering the redox state, insulin-mediated glucose uptake and insulin secretion. We sought to determine the effects of an acute oral EtOH load on insulin secretion and glucose tolerance and the importance of a different timing of administration relative to a glucose load. Eleven subjects underwent a frequently sampled intravenous glucose tolerance test (FSIGT) on three occasions in random order. In one, EtOH was given 50 min 'before' the FSIGT; on the second, the same amount was administered 6 min after the glucose pulse ('during' study); on the third no EtOH was given. Blood EtOH peaked at 4.43+/-0.24 mmol/l (mean +/- SD) in the 'during' and 4.16+/-0.31 mmol/l in the 'before' study. No differences were noticed in S(I), the index of insulin sensitivity, or in S(G), the glucose effectiveness, between the 'before', 'during' and control studies. There were no differences in the first-phase insulin secretion between the three studies but a significant increase in the sensitivity to glucose of second-phase dynamic insulin response, phi2, in the 'before' (0.062+/-0.036 pmol x min(-2) x (mg(-1) x dl(-1))(-1)) and 'during' (0.063+/-0.059) studies, compared to the control study (0.017+/-0.010, P<0.05) was observed. No differences were observed in the hepatic extraction of insulin. In the 'before' study, there was a significant decline in NEFA (non-esterified fatty acid) concentration from the baseline (mean 602+/-51 micromol/l) to the O min value (mean 353+/-37, P<0.01). During the FSIGT, the mean plasma NEFA concentration was significantly lower in the 'before' and in the 'during' than in the control study. An acute oral EtOH load does not impair glucose metabolism, at least in part because of an increased second-phase insulin secretion. Since this effect is observed irrespective of whether EtOH is consumed either before or during the glucose load, the existence of a priming effect is questioned.

Elaboration of Matrix Metalloproteinase Inhibitors by Human Skin in Organ Culture and by Skin Cells in Monolayer Culture: Relationship to Invasion

Functional and immunochemical approaches were used to assess matrix metalloproteinase (MMP) inhibitors, e.g., tissue inhibitor of metalloproteinases 1 and 2 (TIMP-1 and TIMP-2), in organ cultures of normal human skin maintained under growth factor free conditions or in medium supplemented with a combination of growth factors including epidermal growth factor, insulin, and pituitary extract. It has previously been shown that under growth factor free conditions, normal skin structure and function are maintained for several days, while in the presence of these exogenous growth factors, the epithelial cells invade the stroma [Invasion and Metastasis 1993;13:225–233]. TIMP-1 was detected in equivalent amounts in organ culture fluids under both conditions. TIMP-2 was not detected under either condition. Normal epidermal keratinocytes, normal dermal fibroblasts, and three different epithelial tumor cell lines were also examined for MMP inhibitor expression. Keratinocytes and fibroblasts produced high levels of both TIMP-1 and TIMP-2, but in neither cell type was there a significant difference between growth factor free and growth factor containing conditions. In contrast, the three epithelial tumor cell lines produced low to undetectable levels of both TIMP-1 and TIMP-2. These data suggest that acquisition of local invasive capacity is not dependent on a reduction in MMP inhibitor expression. A reduction in MMP inhibitors may accompany the transition from invasive to metastatic tumors.

Free fatty acids impair hepatic insulin extraction in vivo.

Hyperinsulinemia is a common finding in obesity and results from insulin hypersecretion and impaired hepatic insulin extraction. In vitro studies have shown that free fatty acids (FFAs), which are often elevated in obesity, can impair insulin binding and degradation in isolated rat hepatocytes. To investigate whether FFAs impair hepatic insulin extraction (E(H)) in vivo, either saline (SAL) or 10% Intralipid (0.03 ml x kg(-1) x min(-1)) plus heparin (0.44 U x kg(-1) x min(-1)) (IH) was infused into normal dogs to elevate FFA levels. Insulin was infused intraportally at 18 pmol x kg(-1) x min(-1) for 150 min (period A, high insulin dose), and then at 2.4 pmol x kg(-1) x min(-1) for another 150 min (period B, low insulin dose). After the low portal insulin dose, additional insulin was infused peripherally at 8.4 pmol x kg(-1) x min(-1) for 120 min (period C) to assess the clearance of insulin from the peripheral plasma. In 16 paired experiments, FFA levels were 1,085 +/- 167, 1,491 +/- 240, 1,159 +/- 221 micromol/l (IH) and 221 +/- 44, 329 +/- 72, 176 +/- 44 micromol/l (SAL) in periods A, B, and C, respectively. Peripheral insulin levels were greater with IH (P < 0.001) than with SAL in all periods (1,620 +/- 114, 126 +/- 12, 1,050 +/- 72 pmol/l for IH vs. 1,344 +/- 168, 96 +/- 4.2, 882 +/- 60 pmol/l for SAL). Glucose clearance was impaired by IH in all periods (P < 0.05), whereas glucose production was slightly increased by IH during period B. Peripheral insulin clearance (Cl) and E(H) were calculated from the insulin infusion rate and insulin concentration data in each period by taking into account the nonlinearity of insulin kinetics. Cl was lower (P < 0.01) with IH (9.6 +/- 0.6, 12.0 +/- 0.9, 10.2 +/- 0.6 ml x kg(-1) x min(-1)) than with SAL (11.2 +/- 1, 13.6 +/- 0.7, 11.9 +/- 0.9 ml x kg(-1) x min(-1)) in periods A, B, and C. E(H) was also lower (P < 0.05) with IH (25 +/- 4, 40 +/- 5, 32 +/- 5%) than with SAL (30 +/- 2.8, 47 +/- 3, 38 +/- 3%). We conclude that FFAs can impair hepatic insulin extraction in vivo at high and low insulin levels, an effect that may contribute to the peripheral hyperinsulinemia of obesity.

Counterregulatory response to hypoglycemia differs according to the insulin delivery route, but does not affect glucose production in normal humans.

The magnitude of the counterregulatory response to insulin-induced hypoglycemia is primarily determined by the degree of hypoglycemia. We examined whether the route of acute insulin delivery (portal or peripheral venous) is also important in determining the magnitude of the counterregulatory response to hypoglycemia in nine healthy nondiabetic men. Pancreatic insulin secretion, stimulated by an i.v. tolbutamide infusion (portal insulin study), was matched with an exogenous insulin infusion into the peripheral vein 4-6 weeks later (peripheral insulin study). Each study consisted of a 150-min baseline tracer equilibration period, a 180-min euglycemic hyperinsulinemic (portal or peripheral insulin delivery) period, a 60-min hypoglycemic period in which insulin secretion diminished during tolbutamide or was reduced during exogenous insulin, and a 30-min recovery period. Peripheral venous glucose concentrations were well matched in the portal and peripheral studies during euglycemia and hypoglycemia (glucose nadir, 2.9 +/- 0.1 mmol/L in the portal and 2.7 +/- 0.1 mmol/L in the peripheral; mean +/- SEM; P = NS), and insulin concentrations were about 1.5-fold higher throughout the experiment in the peripheral vs. the portal insulin study due to the first pass extraction of insulin in the portal study. There was a much greater increment (P < 0.0001) in FFA in the portal vs. the peripheral study (area under the curve: portal, 19.5 +/- 3.9 mmol/L x 90 min; peripheral, 3.3 +/- 1.1 mmol/L x 90 min), whereas plasma glucagon and GH were higher in the peripheral study (P = 0.01 for glucagon; P = 0.015 for GH). There was no significant difference between studies in epinephrine and norepinephrine responses to hypoglycemia or stimulation of endogenous glucose production (area under the curve: portal, 636 +/- 103 micromol/kg x 90 min; peripheral, 705 +/- 69 micromol/kg x 90 min; P = NS). In summary, we have shown that the glucagon, GH, and FFA responses to hypoglycemia during insulin dissipation are affected by the route of insulin delivery and are not controlled exclusively by the nadir blood glucose level. The clinical importance of these observations in diabetic subjects as they relate to route of insulin delivery (portal or peripheral) during insulin dissipation remains to be determined.

Differential effect of transdermal estrogen plus progestagen replacement therapy on insulin metabolism in postmenopausal women: relation to their insulinemic secretion.

To evaluate the impact on glucose and insulin metabolism of transdermal estrogen patches before and after the addition of cyclic dydrogesterone in postmenopausal women. We studied 21 postmenopausal women seeking treatment for symptomatic menopause. All patients received transdermal 50 micrograms/day estradiol for 24 weeks. After 12 weeks of treatment, 10 mg/day dydrogesterone were added. During both regimens, insulin and C-peptide plasma concentrations were evaluated after an oral glucose tolerance test (OGTT); insulin sensitivity was evaluated by a hyperinsulinemic euglycemic clamp technique. Insulin and C-peptide response to OGTT were expressed as area under the curve (AUC) and as incremental AUC; insulin sensitivity was expressed as mg/kg body weight. Fractional hepatic insulin extraction (FHIE) was estimated by the difference between the incremental AUC of the C-peptide and insulin divided by the incremental AUC of the C-peptide. Plasma hormone and lipid concentrations were assessed at baseline and at 12 and 24 weeks of treatment. Nine patients proved to be hyperinsulinemic and 12 were normoinsulinemic. Transdermal estrogen treatment significantly decreased the insulin AUC (P < 0.05) and the insulin incremental AUC in hyperinsulinemic patients; addition of dydrogesterone further decreased both the AUC and incremental AUC of insulin. Estrogen alone and combined with dydrogesterone evoked a significant increase in C-peptide AUC in hyperinsulinemic (79.2%) and normoinsulinemic (113%) patients. The treatment increased the values for FHIE and insulin sensitivity in all patients (P < 0.04) and in the hyperinsulinemic group (P < 0.01), whereas it did not affect such parameters in normoinsulinemic patients. Transdermal estrogen substitution alone and combined with cyclical dydrogesterone may ameliorate hyperinsulinemia in a selected population of postmenopausal women.

Stabilization of pH-Induced Degradation of Porcine Insulin in Biodegradable Polyester Microspheres

The purpose of this research project was to stabilize the pH-induced degradation of porcine insulin encapsulated within biodegradable polyester microspheres through the incorporation of a basic additive. Insulin microspheres fabricated using Poly(L-lactide) (L-PLA) and Poly(DL-lactide-co-glycolide) (50:50 DL-PLGA) were subjected to in vitro release studies and the stability of unreleased insulin encapsulated within microspheres was investigated. The intramicrosphere pH was estimated by encapsulating acid-base indicators covering a wide pH transition range within 50:50 DL-PLGA microspheres. Finally, a basic excipient sodium bicarbonate was incorporated in 50:50 DL-PLGA microspheres to minimize acid-induced insulin degradation. The in vitro release was slow and incomplete (<30% in 30 days). Extraction and analyses of the unreleased insulin within the microspheres revealed that an average of ∼11% remained intact. The degradation products observed consisted of ∼15% of three distinct deamidated hydrolysis products including A-21 Desamido insulin, ∼22% Covalent Insulin Dimer and trace amounts of High Molecular Weight Transformation Products. Comparison of the degradation profile of unreleased insulin contained in various microsphere formulations with the in vitro release kinetics indicated that an increase in covalent dimer formation within the microspheres prior to release is associated with a decrease in the cumulative percent insulin released during a 30-day incubation period. In an attempt to correlate insulin degradation with the drop in intra-microsphere pH due to polymer hydrolysis, it was determined that the pH within a degrading microsphere reaches a value of ∼1.8 after 4 weeks. The incorporation of a basic excipient, sodium bicarbonate, in 50:50 DL-PLGA microspheres resulted in an improved in vitro release profile (cumulative release ∼47.3% in 30 days) as well as a significant reduction in covalent dimerization of the unreleased insulin to barely detectable levels. The low pH microenvironment within a degrading microsphere is one of the major factors leading to protein instability, and the degradation of proteins encapsulated within polyester microspheres can be minimized by the incorporation of a basic excipient.

Insulin secretion and hepatic insulin clearance as determinants of hyperinsulinaemia in normotolerant grossly obese adolescents

Obesity is characterized by variable degrees of hyperinsulinaemia, which has been attributed to either β‐cell hypersecretion or reduced hepatic insulin extraction, or both. To investigate this controversial issue, a 4‐h frequently sampled i.v. glucose tolerance test (glucose dose 12.8 g m‐2) was performed in 13 normotolerant, grossly obese adolescents (10 F/3 M; 13 ± 1 y; body mass index 32 ± 0.9; pubertal stage 4–5; obesity duration 7.8 ± 3 y) and in a comparable group of 8 healthy, normal‐weight subjects. Glucose, insulin and C‐peptide time‐course were analysed by the minimal model technique, which estimates β‐cell secretion, insulin sensitivity (Si), glucose effectiveness (SG) and hepatic insulin extraction (HE). Despite similar fasting and after load glucose patterns (SGsimilar in the two groups), obese adolescents showed sustained peripheral hyperinsulinaemia (total insulin area under the concentration curve 67.2 ± 10.8 vs 19.1 ± 1.2 pmol l‐1in 240 min;p&lt; 0:002) and a 71% reduction inSi(2.02 ± 0.33 vs 6.95 ± 1.03±104min‐1(μU ml‐1);p&lt; 0:001). Compared with control subjects, the total amounts of prehepatic insulin secretion and posthepatic insulin delivery were also increased significantly in obese adolescents by 30% and 46%, respectively; HE was reduced by 15% during the first 30 min of the test, but recovered within the normal range during the rest of the test. In conclusion, severely obese adolescents are insulin resistant and their hyperinsulinaemia is primarily caused by β‐cell hypersecretion, whereas the reduction in insulin hepatic extraction is a transient metabolic phenomenon.

Improved assessment of isolated islet tissue volume using digital image analysis

% 1Correspondence should be addressed to: Claudy J.-P. Mullon, Circe Biomedical Inc., 99 Hayden Avenue, Lexington, MA, 02173.\\. Accurate and consistent measurement of tissue volume is critical to performing many types of islet research; however, conventional visual determination of isolated islet yields through a microscope is heavily operator dependent. An improved method of islet volume determination using digital image analysis (DIA) was developed to remove operator bias and automate the islet counting process. A series of 140 porcine islet isolations were used to evaluate the DIA method in three separate stages. In Stage 1 ( n = 29 isolations), the conventional and DIA methods were correlated with two other independent islet quantitation methods: insulin extraction, and DNA extraction. It was found that volumes determined by DIA correlated more closely with insulin content and DNA content than did conventionally determined volumes. In Stages 2 and 3 ( n = 54 and 57 isolations, respectively), it was shown that an increase in the number of fields analyzed by DIA did not significantly improve the quality of the correlations. Inclusion of very small tissue (<50 μm in diameter), which is ignored in the conventional protocol affected yields by less than 10% and did not significantly improve the correlation with insulin or DNA content. Quantitation of isolated islet tissue volume using DIA has been shown to be rapid, consistent, and objective. In the laboratory, use of this method as the standard for islet volume measurement will allow more meaningful comparison of experimental results between centers. In the clinic, its use will allow more accurate dosing of transplanted tissue.

Improved assessment of isolated islet tissue volume using digital image analysis.

Accurate and consistent measurement of tissue volume is critical to performing many types of islet research; however, conventional visual determination of isolated islet yields through a microscope is heavily operator dependent. An improved method of islet volume determination using digital image analysis (DIA) was developed to remove operator bias and automate the islet counting process. A series of 140 porcine islet isolations were used to evaluate the DIA method in three separate stages. In Stage 1 (n = 29 isolations), the conventional and DIA methods were correlated with two other independent islet quantitation methods: insulin extraction, and DNA extraction. It was found that volumes determined by DIA correlated more closely with insulin content and DNA content than did conventionally determined volumes. In Stages 2 and 3 (n = 54 and 57 isolations, respectively), it was shown that an increase in the number of fields analyzed by DIA did not significantly improve the quality of the correlations. Inclusion of very small tissue (<50 microm in diameter), which is ignored in the conventional protocol affected yields by less than 10% and did not significantly improve the correlation with insulin or DNA content. Quantitation of isolated islet tissue volume using DIA has been shown to be rapid, consistent, and objective. In the laboratory, use of this method as the standard for islet volume measurement will allow more meaningful comparison of experimental results between centers. In the clinic, its use will allow more accurate dosing of transplanted tissue.

Age-Related Reduction in Glucose Elimination Is Accompanied by Reduced Glucose Effectiveness and Increased Hepatic Insulin Extraction in Man1

This study examined whether insulin secretion, insulin sensitivity, glucose effectiveness (SG), and hepatic extraction (HE) of insulin are altered by age when glucose tolerance is normal. A frequently sampled i.v. glucose tolerance test was performed in 20 elderly (E, 10/10 male/female, all 63 yr old) and in 20 young subjects (Y, 10/10 male/female, all 27 yr old), who were similar in body mass index and 2-h blood glucose during oral glucose tolerance test. E exhibited impaired glucose elimination (i.v. tolerance index, 1.31 +/- 0.10 vs. 1.70 +/- 0.12% min-1; P = 0.019). First-phase insulin secretion and SI did not differ between the groups, whereas E had lower glucose sensitivity of second-phase insulin secretion (0.40 +/- 0.07 vs. 0.70 +/- 0.08 (pmol/L)min-2/(mmol/L), P = 0.026), lower SG, 0.017 +/- 0.002 vs. 0.025 +/- 0.002 min-1, P = 0.004), and higher HE (81.3 +/- 2.4 vs. 73.2 +/- 2.1%, P = 0.013). Across both groups, SG correlated positively with glucose tolerance index (r = 0.58, P < 0.001) and negatively with HE (r = -0.54, P < 0.001). Plasma leptin and glucagon did not change by age, whereas plasma pancreatic polypeptide (PP) was higher in E (122 +/- 18 vs. 66 +/- 6 pg/mL, P = 0.004). PP did not, however, correlate to any other parameter. We conclude that E subjects with normal oral glucose tolerance have reduced SG, impaired second-phase insulin secretion, and increased HE, whereas SI and first-phase insulin secretion seem normal. SG seems most related to age-dependent impairment of glucose elimination, whereas leptin, glucagon, and PP do not seem to contribute.

Possible Mechanism of Antihyperglycemic Effect of Gymnema sylvestre Leaf Extract, Part I

1. Effect of water soluble fraction of alcoholic extract of G. sylvestre leaves on glycogen content by isolated rat hemidiaphragm was studied in normal and glucose fed hyperglycemic rats. 2. The leaf extract by itself failed to alter the hepatic glycogen content in normal rats. 3. In glucose fed rats, the leaf extract lowered the glycogen content of the tissue significantly ( P<0.05) and this was further lowered when both exogenous insulin and leaf extract was administered. 4. The results are discussed.

Diminished insulin clearance during late pregnancy in patients with Type I diabetes mellitus

1. Intensive insulin treatment of patients with Type I diabetes mellitus during pregnancy is associated with a high frequency of serious hypoglycaemic events. A potential change in insulin metabolism during pregnancy may affect both the frequency and the severity of insulin-induced hypoglycaemia.2. In 10 patients with Type I diabetes, during the third trimester of pregnancy and 5 to 13 months after delivery, hypoglycaemia was induced by the hyperinsulinaemic hypoglycaemic clamp technique. A constant high-dose intravenous insulin infusion was administered for 150 min and arterial blood glucose was clamped at 2.2 mmol/l by counterregulation with intravenous glucose. During the experiment venous samples were collected for later analysis of free plasma insulin, whereby the metabolic clearance rate of insulin could be calculated.3. The desired blood glucose level was approached after approximately 60 min of insulin infusion. After just 30 min the insulin levels were significantly higher during pregnancy compared with after delivery. In addition, the steady-state insulin level from 90 to 150 min was significantly higher during pregnancy.4. From the steady-state insulin levels at 90 to 150 min, the metabolic clearance rate of insulin was calculated, being 24% higher after delivery.5. We conclude that there is a decreased metabolic clearance rate of insulin during pregnancy. This might be due to altered blood-flow distribution, decreased hepatic insulin extraction and relative increase in body fat during pregnancy. A decreased clearance of insulin will contribute to the risk for serious hypoglycaemic events in patients with Type I diabetes during pregnancy.

Diminished insulin clearance during late pregnancy in patients with Type I diabetes mellitus

1.Intensive insulin treatment of patients with Type I diabetes mellitus during pregnancy is associated with a high frequency of serious hypoglycaemic events. A potential change in insulin metabolism during pregnancy may affect both the frequency and the severity of insulin-induced hypoglycaemia.2.In 10 patients with Type I diabetes, during the third trimester of pregnancy and 5 to 13 months after delivery, hypoglycaemia was induced by the hyperinsulinaemic hypoglycaemic clamp technique. A constant high-dose intravenous insulin infusion was administered for 150 ;min and arterial blood glucose was clamped at 2.2 ;mmol/l by counterregulation with intravenous glucose. During the experiment venous samples were collected for later analysis of free plasma insulin, whereby the metabolic clearance rate of insulin could be calculated.3.The desired blood glucose level was approached after approximately 60 ;min of insulin infusion. After just 30 ;min the insulin levels were significantly higher during pregnancy compared with after delivery. In addition, the steady-state insulin level from 90 to 150 ;min was significantly higher during pregnancy.4.From the steady-state insulin levels at 90 to 150 ;min, the metabolic clearance rate of insulin was calculated, being 24% higher after delivery.5.We conclude that there is a decreased metabolic clearance rate of insulin during pregnancy. This might be due to altered blood-flow distribution, decreased hepatic insulin extraction and relative increase in body fat during pregnancy. A decreased clearance of insulin will contribute to the risk for serious hypoglycaemic events in patients with Type I diabetes during pregnancy.

Age-Related Reduction in Glucose Elimination Is Accompanied by Reduced Glucose Effectiveness and Increased Hepatic Insulin Extraction in Man

Age-Related Reduction in Glucose Elimination Is Accompanied by Reduced Glucose Effectiveness and Increased Hepatic Insulin Extraction in Man

Characteristics of young offspring of type 2 diabetic parents in a biracial (black-white) community-based sample: The Bogalusa heart study

The impact of race (black-white) and family history of type 2 diabetes mellitus on metabolic characteristics in early life was examined in a community-based sample from Bogalusa, LA. Study subjects included offpsirng of type 2 diabetics (n = 53, 47%) black) and nondiabetics (n = 52, 40% black), with the mean age of each group ranging from 14.2 to 15.6 years. Offspring were given a 1-hour oral glucose tolerance test. Measures of body fatness such as body weight, body-mass index (BMI; weight/height 2), and triceps and subscapular thicknesses were significantly higher only in white offspring of diabetics versus nondiabetics; measures of abdominal fat (waist circumference and waist-to-hip ratio) were significantly higher among offspring of diabetics of both races. Among the measures of glucose homeostasis, basal glucose, insulin, insulin—to-—C-peptide ratio (a measure of hepatic insulin extraction), insulin resistance index (derived from basal glucose and insulin levels), and glucose response after glucose challenge were higher in the offsprig of diabetics of both races. The differences in insulin—to—C-peptide ratio and glucose response remained significant after adjusting for BMI; further, these two variables were independently associated with parental diabetes in both races. Waist-to-hip ratio, glucose response, C-peptide response (a measure of insulin secretion) were lower, and basal insulin—to—C-peptide ratio and postglucose suppression of free fatty acids greater in blacks versus whites, regardless of status of parental diabetes. Black-white differences in postglucose suppression of free fatty acids disappeared after adjusting for BMI. Thus, blacks and whites with parental type 2 diabetes show multiple abnormalities in parameters governing glucose homeostasis early in life, and some of these traits differ between the races, regardless of status of parental diabetes.

Zinc supplementation improves glucose disposal in patients with cirrhosis

Zinc deficiency is common in cirrhosis, and was proved to affect nitrogen metabolism. In experimental animals, zinc status may also affect glucose disposal, and acute zinc supplementation improves glucose tolerance in healthy subjects. This study was aimed at measuring the effects of long-term oral zinc supplements on glucose tolerance in cirrhosis. The time courses of glucose, insulin, and C-peptide in response to an intravenous (IV) glucose load were analyzed by the minimal-model technique before and after long-term oral zinc supplements (200 mg three times per day for 60 days) in 10 subjects with advanced cirrhosis and impaired glucose tolerance or diabetes. The test was performed using a simplified procedure, based on 20 blood samples collected within 4 hours from the glucose load. Normal values were obtained in 25 age-matched healthy subjects. Zinc levels were low to normal or reduced before treatment, and were normalized by oral zinc. Glucose disappearance improved by greater than 30% in response to treatment. There were no changes in pancreatic insulin secretion and systemic delivery, or in the hepatic extraction of insulin. Insulin sensitivity (S I), which was reduced by 80% before treatment, did not change. Glucose effectiveness (S G) was nearly halved in cirrhosis before treatment (0.013 [SD 0.007] min −1 v. 0.028 [SD 0.009] in controls; P < .001), and increased to 0.017 (SD 0.009) after zinc ( P < .05 v. baseline). The return to normal of plasma zinc levels after long-term zinc treatment in advanced cirrhosis improves glucose tolerance via an increase of the effects of glucose per se on glucose metabolism. Poor zinc status may contribute to the impaired glucose tolerance and diabetes of cirrhosis.