Progressive Acceleration of Insulin Exposure Over 7 Days of Infusion Set Wear

Insulin exposure varies over 3 days of insulin infusion set (IIS) wear making day-to-day insulin dosing challenging for people with diabetes (PWD). Here we report insulin pharmacodynamic (PD) and pharmacokinetic (PK) data extending these observations to 7 days of IIS wear. PWD (A1C ≤8.5%, C-peptide <0.6 nmol/L, ≥6 months pump use) were enrolled in a crossover euglycemic clamp pilot study comparing conventional Teflon angled IISs with an investigational extended-wear IIS. PK/PD data from six participants were obtained for 5 h postbolus. Although PD data were unstable, PK profiles (pooled data from both groups) of insulin lispro (0.15 U/kg bolus) showed statistically significant progressive decreases from days 0 to 7 for t_max (P < 0.001), C_max (P < 0.05), and mean residence time (P < 0.0001). Area under the insulin concentration curve (AUC_0-300) declined by ∼24% from days 0 to 7 (P < 0.05). These results confirm/extend previous observations showing progressive acceleration of insulin exposure over IIS wear time. This may have implications for PWD and designers of closed-loop algorithms, although larger studies are necessary to confirm this. The study was registered in clinicaltrials.gov (NCT04398030).

Insulin Replacement Across the Menstrual Cycle in Women with Type 1 Diabetes: An In Silico Assessment of the Need for Ad Hoc Technology

Background: Women with type 1 diabetes (T1D) of fertile age may experience fluctuations in insulin needs across the menstrual cycle. When present, these fluctuations complicate glucose management and oftentimes worsen glycemic control. In this work, an in silico analysis was conducted to assess whether current technology is sufficient to handle changes in insulin needs due to the menstrual cycle in women with T1D. Methods: Euglycemic clamp studies were performed in 16 women with T1D in the follicular phase (FP) and luteal phase (LP) of the menstrual cycle. Interphase insulin sensitivity (IS) variability observed in the data was modeled and introduced in the University of Virginia/Padova T1D Simulator. Open-loop and closed-loop insulin delivery was tested in two in silico studies, without (nominal study) and with (informed study) a priori knowledge on cycle-related IS variability informing insulin therapy. Glycemic metrics were computed on the obtained glucose traces. Results: In the pool of studied women, the glucose infusion rate area under the curve significantly decreased from FP to LP (P = 0.0107), indicating an average decrease of IS in LP. When introduced in the simulator, this pattern led to increased time spent >180 and >250 mg/dL during LP versus FP in the nominal studies, irrespective of the insulin delivery strategy. In the informed studies, glycemic metrics stabilized across the cycle. Conclusion: This work suggests that current insulin delivery technology may benefit from informing the dosing algorithm with knowledge on menstrual cycle related IS changes. Clinical validation of these results is warranted. ClinicalTrials.gov identifier: NCT02693938.

Regulation of circulating CTRP-2/CTRP-9 and GDF-8/GDF-15 by intralipids and insulin in healthy control and polycystic ovary syndrome women following chronic exercise training

Background

Polycystic ovary syndrome (PCOS) is associated with obesity, diabetes, and insulin resistance. The circulating C1Q/TNF-related proteins (CTRP-2, CTRP-9) and growth differentiation factors (GDF-8, GDF-15) contribute to glucose and lipid homeostasis. The effects of intralipids and insulin infusion on CTRP-2, CTRP-9, GDF-8 and GDF-15 in PCOS and control subjects before and after chronic exercise training were examined.

Methods

Ten PCOS and nine healthy subjects were studied at baseline status and after moderate-intensity chronic exercise training (1 h exercise, 3 times per week, 8 weeks). All participants were infused with 1.5 mL/min of saline or intralipids (20%) for 5 h, and during the last 2 h of saline or intralipids infusion hyperinsulinemic-euglycemic clamp (HIEC) was performed. CTRP-2, CTRP-9, GDF-8 and GDF-15 levels were measured at 0, 3 and 5 h.

Results

Intralipids dramatically increased CTRP-2 levels in PCOS (P = 0.02) and control (P = 0.004) subjects, which was not affected by insulin infusion or by exercise. Intralipids alone had no effects on CTRP-9, GDF-8, or GDF-15. Insulin increased the levels of GDF-15 in control subjects (P = 0.05) during the saline study and in PCOS subjects (P = 0.04) during the intralipid infusion. Insulin suppressed CTRP9 levels during the intralipid study in both PCOS (P = 0.04) and control (P = 0.01) subjects. Exercise significantly reduced fasting GDF-8 levels in PCOS (P = 0.03) and control (P = 0.04) subjects; however, intralipids infusion after chronic exercise training increased GDF-8 levels in both PCOS (P = 0.003) and control (P = 0.05) subjects and insulin infusion during intralipid infusion reduced the rise of GDF-8 levels.

Conclusion

This study showed that exogenous lipids modulate CTRP-2, which might have a physiological role in lipid metabolism. Since chronic exercise training reduced fasting GDF-8 levels; GDF-8 might have a role in humoral adaptation to exercise. GDF-15 and CTRP-9 levels are responsive to insulin, and thus they may play a role in insulin responses.

[The Pharmacokinetics, Pharmacodynamics and Bioequivalence of Insulin Aspart Produced by the United Laboratories Evaluated by Euglycemic Clamp Study]

Objective

To investigate the pharmacokinetics (PK) and pharmacodynamics (PD) of a rapid-acting insulin analog-insulin aspart (the tested formulation) which was manufactured by The United Laboratories and to evaluate the bioequiavailability to the reference formulation (NovoRapid ^®) produced by Novo Nordisk in Chinese healthy volunteers.

Methods

A total of 24 male healthy volunteers were recruited from February to April 2016 to participant in this before-after, single dose, and randomized crossover study. And the experimental observation was conducted on 2 test days respectively with a between-period from 7 to10 d. According to a random number table, the volunteers were divided into group A or B, group A was administrated with tested insulin aspart (IAsp) for the first time and reference NovoRapid ^® for the second time and group B had the revered order differed from group A. The PK/PD of these insulin analogs were estimated by euglycemic clamp study.

Results

The relative biological effectiveness (reflecting gloucose-lowing effect) and bioavailability on behalf of plasma-drug concentration were 98.3±18.8% and 97.3%±8.3% respectively. For PK parameters, the 90% confidence interval ( CI) of peak plasma insulin concentration ( C _max) and area under the curve of insulin aspart concentration from 0 to 10 hours ( AUC _{IAsp, 0-10 h}) of IAsp were 88.8%-106% (equivalent range 70%-143%) and 94.0%-100% (equivalent range 80%-125%) respectively; for PD parameters, the 90% CI of the maximum glucose infusion rate ( GIR _max) and AUC _{GIR, 0-10 h} were 95.5%-113% (equivalent range 70%-143%) and 89.9%-104% (equivalent range 80%-125%) respectively, which indicated that IAsp and NovoRapid® was bioequivalent. One of the subjects discovered hyperuricemia without clinical symptoms and the rest had no clinically significant abnormalities in the safety indexes before and after the tests. No hypoglycemic events, allergic reactions, or local injection adverse reaction occurred in this trial.

Conclusion

The tested IAsp has comparable relative bioavailability to the reference NovoRapid ^®.

[Effect of peripheral hyperinsulinemia on assessment of pharmacokinetics and pharmacodynamics of insulin preparations in euglycemic clamp]

Objective: To evaluate the effect of peripheral hyperinsulinemia on assessment of pharmacokinetics (PK) and pharmacodynamics (PD) of insulin preparations in euglycemic clamp. Method: A total of 40 healthy male volunteers aged 18-45 years old in West China Hospital between 2015 and 2017 were divided into euglycemic-hyperinsulinaemic clamp (A) group and euglycemic clamp (B) group. Humulin R (0.2 U/kg) was given subcutaneously at steady state of clamp after infusion of short-acting insulin in A group while in B group Humulin R was given subcutaneously without establishment of artificial hyperinsulinemia. The blood glucose was maintained within target range during the whole clamp. Result: Maximum insulin concentration [(667±141) pmol/L vs (267±68) pmol/L, P<0.01] and area under curve (AUC) of insulin concentration [(152±32) nmol·L(-1)·min vs (57±7) nmol·L(-1)·min, P<0.01] in A group were higher while maximum glucose infusion rate (GIR) [(3.70±0.70) mg·kg(-1)·min(-1) vs (7.66±2.11) mg·kg(-1)·min(-1), P<0.01] and AUC of GIR [(931±272) mg/kg vs (1 920±452) mg/kg, P<0.01] were lower compared to B group. The serum C-peptide levels were lower in both groups after administration of insulin compared with baseline. Conclusion: It is not necessary applying euglycemic-hyperinsulinaemic clamp to evaluate the PK/PD of insulin preparations, which may overestimate the PKparameters and underestimate the PD parameters of insulin preparations.

Investigation of insulin resistance in the popularly used four rat models of type-2 diabetes

Animal models are widely used to develop drugs for treating diabetes mellitus (DM). Insulin resistance (IR) is one of the main problems in type-2 DM (T2DM). Streptozotocin (STZ) is used to damage pancreatic cells for induction of DM. Many rat models were applied in research as T2DM. However, the degree of IR in each model is unknown. In the present study, IR and insulin signaling were compared in four models of type 2 diabetes: rats fed a fructose-rich chow for 8 weeks, rats feed high-fat chow for 4 weeks followed by injection with streptozotocin (35 mg/kg, i.p.), rats injected with a single low dose streptozotocin (45 mg/kg, i.p.), and rats injected with a single dose of nicotinamide followed by a single high dose of streptozotocin (60 mg/kg, i.p.). Values from these determinations in diabetic rats showing the order that insulin resistance is most marked in rats received fructose-rich chow followed by high-fat diet before STZ injection induced model (HFD/STZ rats), and rats injected with low dose of STZ but it is less marked in rats induced by nicotinamide and STZ. Additionally, insulin secretion was reduced in three rat models except the rats receiving fructose-rich chow. Western blots also showed the same changes in phosphorylation of IRS-1 or Akt using soleus muscle from each model. The obtained data suggest a lack of pronounced IR in the rats with acute diabetes induced by nicotinamide and STZ while IR is markedly identified in rats fed fructose-rich chow. However, the increase of plasma glucose levels in fructose-rich chow-fed rats was not so significant as other groups. Therefore, HFD/STZ rats is an appropriate and stable animal model which is analogous to the human T2DM through a combination of high-fat diet with multiple low-dose STZ injections.

High prevalence of insulin resistance assessed by the glucose clamp technique in hormonal and non-hormonal contraceptive users

OBJECTIVE

To assess the prevalence of insulin resistance (IR) and associated factors in contraceptive users.

METHODS

A total of 47 women 18 to 40 years of age with a body mass index (kg/m(2)) < 30, fasting glucose levels < 100 mg/dl and 2-hour glucose level < 140 mg/dl after a 75-g oral glucose load were submitted to a hyperinsulinemic-euglycemic clamp. The women were distributed in tertiles regarding M-values. The analysed variables were use of combined hormonal/non-hormonal contraception, duration of use, body composition, lipid profile, glucose levels and blood pressure.

RESULTS

IR was detected in 19% of the participants. The women with low M-values presented significantly higher body fat mass, waist-to-hip ratio, fasting insulin, HOMA-IR and were nulligravida, showed > 1 year of contraceptive use and higher triglyceride levels. IR was more frequent among combined oral contraceptive users, however no association was observed after regression analysis.

CONCLUSIONS

The prevalence of IR was high among healthy women attending a family planning clinic independent of the contraceptive method used with possible long-term negative consequences regarding their metabolic and cardiovascular health. Although an association between hormonal contraception and IR could not be found this needs further research. Family planning professionals should be proactive counselling healthy women about the importance of healthy habits.

Comparison of insulin sensitivity measures in South Asians

OBJECTIVE

South Asians have increased visceral adiposity, insulin resistance and greater prevalence of type 2 diabetes and cardiovascular disease when compared to Caucasians of European origin. Surrogate markers of insulin resistance such as the composite insulin sensitivity (Matsuda) index correlate with glucose clamps in other populations, but ethnicity can affect these indices. We compared the Matsuda index, homeostasis model assessment (HOMA-IR), quantitative insulin sensitivity check index (QUICKI), and triglyceride/HDL ratio to insulin sensitivity derived from euglycemic clamps in healthy South Asians and Caucasians.

MATERIALS/METHODS

Twenty-three healthy South Asians and 18 Caucasians matched for age (mean±SE=33.6±2.1 vs. 36.0±3.0 years) and BMI (25.2±1.1 vs. 24.6±0.9 kg/m(2)) underwent 75 g oral glucose tolerance test (OGTT), 2-h euglycemic hyperinsulinemic clamp (240 pmol·m(-2)·min(-1)), fasting lipid profile, and anthropometric measures.

RESULTS

South Asians had higher fasting insulin (41±5 vs. 21±2 pmol/l; p=0.002) and lower HDL-C (1.25±0.06 vs. 1.56±0.10 mmol/l; p=0.010), but similar fasting glucose (5.0±0.1 vs. 4.9±0.1 mmol/l) levels vs. Caucasians. South Asians had significantly decreased measures of insulin sensitivity derived from both the euglycemic clamp (24.9±1.3 vs. 41.4±1.9 μmol·kg(-1)·min(-1); p<0.0001) and OGTT (Matsuda Index 7.60±0.99 vs. 13.60±1.79; p=0.004). The Matsuda index correlated highly with clamp insulin sensitivity in South Asians (r=0.50; p=0.014) and Caucasians (r=0.47; p=0.046). HOMA-IR, QUICKI, and triglyceride/HDL ratio correlated with clamp values in South Asians, but not in Caucasians.

CONCLUSIONS

In South Asians, Matsuda index, HOMA-IR, QUICKI, and triglyceride/HDL ratio offer simple and valid surrogate measures of insulin sensitivity that can be employed in larger clinical or epidemiological studies in this ethnic group.