A C-Peptide-Based Model of Pancreatic Insulin Secretion in Extremely Preterm Neonates in Intensive Care

Model-based subcutaneous insulin for glycemic control of pre-term infants in the neonatal intensive care unit

Hyperglycaemia is a common problem in neonatal intensive care units (NICUs). Achieving good control can result in better outcomes for patients. However, good control is difficult, where poor control and resulting hypoglycaemia reduces outcomes and confounds results. Clinically validated models can provide good control, and subcutaneous insulin delivery can provide more options for insulin therapy for clinicians. However, this combination has only been significantly utilised in adult outpatient diabetes, but could hold benefit for treating NICU infants. This research combines a well-validated NICU metabolic model with subcutaneous insulin kinetics models to assess the feasibility of a model-based approach. Clinical data from 12 very/extremely pre-mature infants was collected for an average study duration of 10.1 days. Blood glucose, interstitial and plasma insulin, as well as subcutaneous and local insulin were modelled, and patient-specific insulin sensitivity profiles were identified for each patient. Modelling error was low, where the cohort median [IQR] mean percentage error was 0.8 [0.3 3.4] %. For external validation, insulin sensitivity was compared to previous NICU cohorts using the same metabolic model, where overall levels of insulin sensitivity were similar. Overall, the combined system model accurately captured observed glucose and insulin dynamics, showing the potential for a model-based approach to glycaemic control using subcutaneous insulin in this cohort. The results justify further model validation and clinical trial research to explore a model-based protocol.

Insulin sensitivity in critically ill patients: are women more insulin resistant?

Background

Glycaemic control (GC) in intensive care unit is challenging due to significant inter- and intra-patient variability, leading to increased risk of hypoglycaemia. Recent work showed higher insulin resistance in female preterm neonates. This study aims to determine if there are differences in inter- and intra-patient metabolic variability between sexes in adults, to gain in insight into any differences in metabolic response to injury. Any significant difference would suggest GC and randomised trial design should consider sex differences to personalise care.

Methods

Insulin sensitivity (SI) levels and variability are identified from retrospective clinical data for men and women. Data are divided using 6-h blocks to capture metabolic evolution over time. In total, 91 male and 54 female patient GC episodes of minimum 24 h are analysed. Hypothesis testing is used to determine whether differences are significant (P < 0.05), and equivalence testing is used to assess whether these differences can be considered equivalent at a clinical level. Data are assessed for the raw cohort and in 100 Monte Carlo simulations analyses where the number of men and women are equal.

Results

Demographic data between females and males were all similar, including GC outcomes (safety from hypoglycaemia and high (> 50%) time in target band). Females had consistently significantly lower SI levels than males, and this difference was not clinically equivalent. However, metabolic variability between sexes was never significantly different and always clinically equivalent. Thus, inter-patient variability was significantly different between males and females, but intra-patient variability was equivalent.

Conclusion

Given equivalent intra-patient variability and significantly greater insulin resistance, females can receive the same benefit from safe, effective GC as males, but may require higher insulin doses to achieve the same glycaemia. Clinical trials should consider sex differences in protocol design and outcome analyses.

Insulin sensitivity in critically ill patients: are women more insulin resistant?

BACKGROUND

Glycaemic control (GC) in intensive care unit is challenging due to significant inter- and intra-patient variability, leading to increased risk of hypoglycaemia. Recent work showed higher insulin resistance in female preterm neonates. This study aims to determine if there are differences in inter- and intra-patient metabolic variability between sexes in adults, to gain in insight into any differences in metabolic response to injury. Any significant difference would suggest GC and randomised trial design should consider sex differences to personalise care.

METHODS

Insulin sensitivity (SI) levels and variability are identified from retrospective clinical data for men and women. Data are divided using 6-h blocks to capture metabolic evolution over time. In total, 91 male and 54 female patient GC episodes of minimum 24 h are analysed. Hypothesis testing is used to determine whether differences are significant (P < 0.05), and equivalence testing is used to assess whether these differences can be considered equivalent at a clinical level. Data are assessed for the raw cohort and in 100 Monte Carlo simulations analyses where the number of men and women are equal.

RESULTS

Demographic data between females and males were all similar, including GC outcomes (safety from hypoglycaemia and high (> 50%) time in target band). Females had consistently significantly lower SI levels than males, and this difference was not clinically equivalent. However, metabolic variability between sexes was never significantly different and always clinically equivalent. Thus, inter-patient variability was significantly different between males and females, but intra-patient variability was equivalent.

CONCLUSION

Given equivalent intra-patient variability and significantly greater insulin resistance, females can receive the same benefit from safe, effective GC as males, but may require higher insulin doses to achieve the same glycaemia. Clinical trials should consider sex differences in protocol design and outcome analyses.

Gender diversity of insulin sensitivity markers among patients of type 2 diabetes mellitus in northern India: A cross-sectional analytical study

BACKGROUND

Diabetes mellitus is a worldwide health problem with more than 80% diabetics living in LMIC. Biological and psychosocial factors are also responsible for gender diversity in T2DM which highlights the need for action to combat T2DM in India. The current study was undertaken to evaluate the gender diversity of insulin sensitivity markers among patients of T2DM in northern India and secondly, to assess and compare the quality of life among T2DM patients in northern India.

MATERIAL AND METHODS

It was a cross-sectional analytical study enrolling 78 patients from tertiary care teaching hospital, India. Inclusion criteria was patients within the age group of 18-60 years, diagnosed with T2DM and on insulin therapy. Case reporting form, anthropometric measures, laboratory investigations, and diabetes quality of life (DQoL) instruments were used for data collection for the period of 3 months.

RESULTS

The mean age of T2DM patients for males was 48.00 ± 9.92 years and for females was 49.96 ± 10.39 years. Male and female patients were 50% and 50%, respectively. WHR (P = 0.032), DBP (P = 0.000), body fat % (P = 0.04), and duration of diabetes (P = 0.001) had statistically significant association with insulin resistance (binary logistic regression analysis (P-value <0.05). Results show the statistically significant difference between means of WHR (t value = 4.702, P = 0.000) and body fat % (t value = 3.035, P = 0.000) in male and female T2DM patients (Independent't'-test) (P-value <0.05).

CONCLUSIONS

The study concludes that WHR, DBP, body fat %, and duration of diabetes were significant markers of insulin sensitivity. WHR and body fat % were the differential insulin sensitivity markers in male and female patients of T2DM in northern India. Diabetes adversely affects the quality of life in a nearly similar pattern in both male and female patients.

C-peptide suppression during insulin infusion in the extremely preterm infant is associated with insulin sensitivity

CONTEXT

Little is known about the individual response of glucose-regulating factors to administration of exogenous insulin infusion in extremely preterm infants.

OBJECTIVE

To evaluate longitudinal serum concentrations of insulin, C-peptide, and plasma glucose levels in a high frequency sampling regimen in extremely preterm infants treated with insulin due to hyperglycemia.

DESIGN

Prospective longitudinal cohort study.

SETTING

Two university hospitals in Sweden between December 2015 and September 2016.

PATIENTS AND INTERVENTION

Serum samples were obtained from nine extremely preterm infants, gestational age between 22(+3) and 26(+5) weeks(+days), with hyperglycemia (plasma-glucose >10 mmol/L) at the start of insulin infusion, at 12, 24, and every 24 hours thereafter during ongoing infusion, and 12, 24, and 72 hours after the end of insulin infusion.

MAIN OUTCOME MEASURES

Longitudinal serum concentrations of insulin and C-peptide and plasma glucose levels.

RESULTS

During insulin infusion, the serum C-peptide concentrations decreased compared to at start of infusion (p = 0.036), and then increased after ending the infusion. Individual insulin sensitivity based on the non-fasting plasma glucose/insulin ratio at the start of insulin infusion correlated with the initial decrease in serum ΔC-peptide[After 12h] (p = 0.007) and the degree of lasting decrease in serum ΔC-peptide[After end of infusion] (p = 0.015).

CONCLUSION

Exogenous insulin infusion suppressed the C-peptide concentration to individually different degrees. In addition, the effect of insulin infusion on β-cells may be linked to individual insulin sensitivity, where a low insulin sensitivity resulted in a more pronounced decrease in C-peptide during insulin infusion.

Insulin kinetics and the Neonatal Intensive Care Insulin-Nutrition-Glucose (NICING) model

BACKGROUND

Models of human glucose-insulin physiology have been developed for a range of uses, with similarly different levels of complexity and accuracy. STAR (Stochastic Targeted) is a model-based approach to glycaemic control. Elevated blood glucose concentrations (hyperglycaemia) are a common complication of stress and prematurity in very premature infants, and have been associated with worsened outcomes and higher mortality. This research identifies and validates the model parameters for model-based glycaemic control in neonatal intensive care.

METHODS

C-peptide, plasma insulin, and BG from a cohort of 41 extremely pre-term (median age 27.2 [26.2-28.7] weeks) and very low birth weight infants (median birth weight 839 [735-1000] g) are used alongside C-peptide kinetic models to identify model parameters associated with insulin kinetics in the NICING (Neonatal Intensive Care Insulin-Nutrition-Glucose) model. A literature analysis is used to determine models of kidney clearance and body fluid compartment volumes. The full, final NICING model is validated by fitting the model to a cohort of 160 glucose, insulin, and nutrition data records from extremely premature infants from two different NICUs (neonatal intensive care units).

RESULTS

Six model parameters related to insulin kinetics were identified. The resulting NICING model is more physiologically descriptive than prior model iterations, including clearance pathways of insulin via the liver and kidney, rather than a lumped parameter. In addition, insulin diffusion between plasma and interstitial spaces is evaluated, with differences in distribution volume taken into consideration for each of these spaces. The NICING model was shown to fit clinical data well, with a low model fit error similar to that of previous model iterations.

CONCLUSIONS

Insulin kinetic parameters have been identified, and the NICING model is presented for glycaemic control neonatal intensive care. The resulting NICING model is more complex and physiologically relevant, with no loss in bedside-identifiability or ability to capture and predict metabolic dynamics.