Intranasal Insulin Attenuates the Long-Term Adverse Effects of Neonatal Hyperglycemia on the Hippocampus in Rats

Hyperglycemia due to relative hypoinsulinism is common in extremely preterm infants and is associated with hippocampus-mediated long-term cognitive impairment. In neonatal rats, hypoinsulinemic hyperglycemia leads to oxidative stress, altered neurochemistry, microgliosis, and abnormal synaptogenesis in the hippocampus. Intranasal insulin (INS) bypasses the blood-brain barrier, targets the brain, and improves synaptogenesis in rodent models, and memory in adult humans with Alzheimer's disease or type 2 diabetes, without altering the blood levels of insulin or glucose. To test whether INS improves hippocampal development in neonatal hyperglycemia, rat pups were subjected to hypoinsulinemic hyperglycemia by injecting streptozotocin (STZ) at a dose of 80 mg/kg i.p. on postnatal day (P) 2 and randomized to INS, 0.3U twice daily from P3-P6 (STZ + INS group), or no treatment (STZ group). The acute effects on hippocampal neurochemical profile and transcript mRNA expression of insulin receptor (Insr), glucose transporters (Glut1, Glut4, and Glut8), and poly(ADP-ribose) polymerase-1 (Parp1, a marker of oxidative stress) were determined on P7 using in vivo 1H MR spectroscopy (MRS) and qPCR. The long-term effects on the neurochemical profile, microgliosis, and synaptogenesis were determined at adulthood using 1H MRS and histochemical analysis. Relative to the control (CONT) group, mean blood glucose concentration was higher from P3 to P6 in the STZ and STZ + INS groups. On P7, MRS showed 10% higher taurine concentration in both STZ groups. qPCR showed 3-folds higher Insr and 5-folds higher Glut8 expression in the two STZ groups. Parp1 expression was 18% higher in the STZ group and normal in the STZ + INS group. At adulthood, blood glucose concentration in the fed state was higher in the STZ and STZ + INS groups. MRS showed 59% higher brain glucose concentration and histochemistry showed microgliosis in the hippocampal subareas in the STZ group. Brain glucose was normal in the STZ + INS group. Compared with the STZ group, phosphocreatine and phosphocreatine/creatine ratio were higher, and microglia in the hippocampal subareas fewer in the STZ + INS group (p < 0.05 for all). Neonatal hyperglycemia was associated with abnormal glucose metabolism and microgliosis in the adult hippocampus. INS administration during hyperglycemia attenuated these adverse effects and improved energy metabolism in the hippocampus.

Use of Intranasal Insulin as Neuroprotection From Hyperglycemia in Rat Model of Extremely Preterm Infants

Background: Hyperglycemia is common in extremely preterm infants (EPI) and is a risk factor for increased mortality and morbidity, including abnormal neurodevelopment. Hippocampus-mediated cognitive deficits are common in this population. In a rat model of insulinopenic hyperglycemia, abnormal neurochemistry in the hippocampus was found, with lactate, glutamate (Glu):glutamine (Gln) ratio lower and Phosphorylated Creatinine (PCr):Creatinine (Cr) higher. Intranasal insulin has been shown to improve cognitive function in animal models of Alzheimer’s disease and type 2 diabetes mellitus, as well as in adult human studies of Alzheimer’s disease. No study has previous investigated the use of intranasal insulin on preventing the long-term effects of hyperglycemia in the EPI population. Objective: To determine whether administration of intranasal insulin during early postnatal days would negate the effects of hyperglycemia on the developing hippocampus in neonatal rat model of streptozotocin (STZ)-induced hyperglycemia. Design/Methods: STZ (80mg/kg IP) was injected on postnatal day (P) 2, and littermates in the control group were injected with an equivalent volume of citrate buffer. STZ pups were randomized to intranasal insulin, 3U twice daily from P3-P6 (STZ + INS) or left untreated (STZ). Neurochemical profile (consisting of 20 metabolites, PCr:Cr and Glu:Gln ratios) of the hippocampus was evaluated using ultra-high-field (9.4 T) magnetic resonance spectroscopy (MRS) on P7 (acute effects) and P56 (long-term effects) compared with the control group (CON)(N=6/group). Results: Mean glucose values from P3-P6 were higher in STZ groups (STZ = 279.0 +/- 132.2 mg/dL, STZ+INS = 274.4 +/- 89.5 mg/dL, CONT = 128.4 +/- 15.1 mg/dL). The neurochemical profile was different at both P7 and P56. On P7, compared with the control, the taurine (Tau) was higher in the STZ groups (p = 0.007. At P56, PCr:Cr was higher in the STZ group compared to CONT and STZ+INS groups (p = 0.04). No difference noted between the STZ+INS and CONT groups. No other metabolites were altered. Conclusion: Neonatal hyperglycemia alters the acute and long-term neurochemical profile in the hippocampus of developing rats. The increase in PCr:Cr ratio in the STZ group indicates lower demand for ATP and PCr, secondary to decreased neuronal activity, which has been demonstrated in previous studies. PCr:Cr ratio of the STZ+INS group was no different than control, indicating that intranasal insulin reverses the negative effect on neuronal activity caused by neonatal hyperglycemia.

Continuous glucose monitoring assessment of metabolic control in east African children and young adults with type 1 diabetes: A pilot and feasibility study

BACKGROUND

For individuals with type 1 diabetes (T1D) in East Africa and other low-income regions, the last decade has seen substantial gains in access to insulin and trained healthcare providers, yet metabolic control remains poor.

METHODS

The objective was to determine the feasibility of continuous glucose monitoring (CGM) and to gather baseline metabolic data for future power analysis in Ugandan and Kenyan youth with T1D using a Freestyle Libre Pro blinded CGM.

RESULTS

Of 78 participants recruited, four sensors fell off and six patients did not return, leaving 68 evaluable subjects. Average age was 16 ± 5 (range 4-26) years, 43% female. Average diabetes duration was 7 ± 5 years, insulin dose 0.9 ± 0.3 U/kg/d, and number of fingerstick glucose levels per day 2.1 ± 1.1. All were on human insulin. Point-of-care HbA1c was 10.9 ± 2.7% (96 ± 30 mmol/mol). Mean number of sensor days was 13 ± 3; >90% wore the sensor for ≥10 days. Mean glucose was 231 ± 86 mg/dL (12.8 ± 4.8 mmol/L). Only 30 ± 19% of time was spent in the target range (70-180 mg/dL; 3.9-10 mmol/L), and 7 ± 8% of time was spent in hypoglycaemia (glucose <55 mg/dL, 3.0 mmol/L). Hypoglycaemia occurred in 81% of participants, averaging five events/wk with an average duration of 140 ± 79 minutes/event.

CONCLUSIONS

Despite significant diabetes care improvements, East African youth with T1D have poor metabolic control with chronic hyper- and hypoglycaemia, placing them at high risk for serious acute and chronic complications. This study demonstrates the feasibility of CGM use in this population and provides baseline metabolic data that will be used to inform a future intervention study.