Genetics and diet shape the relationship between islet function and whole body metabolism.

Despite the fact that genes and the environment are known to play a central role in islet function, our knowledge of how these parameters interact to modulate insulin secretory function remains relatively poor. Presently, we performed ex vivo glucose-stimulated insulin secretion and insulin content assays in islets of 213 mice from 13 inbred mouse strains on chow, Western diet (WD), and a high-fat, carbohydrate-free (KETO) diet. Strikingly, among these 13 strains, islets from the commonly used C57BL/6J mouse strain were the least glucose responsive. Using matched metabolic phenotyping data, we performed correlation analyses of isolated islet parameters and found a positive correlation between basal and glucose-stimulated insulin secretion, but no relationship between insulin secretion and insulin content. Using in vivo metabolic measures, we found that glucose tolerance determines the relationship between ex vivo islet insulin secretion and plasma insulin levels. Finally, we showed that islet glucose-stimulated insulin secretion decreased with KETO in almost all strains, concomitant with broader phenotypic changes, such as increased adiposity and glucose intolerance. This is an important finding as it should caution against the application of KETO diet for beta-cell health. Together these data offer key insights into the intersection of diet and genetic background on islet function and whole body glucose metabolism.NEW & NOTEWORTHY Thirteen strains of mice on chow, Western diet, and high-fat, carbohydrate-free (KETO), correlating whole body phenotypes to ex vivo pancreatic islet functional measurements, were used. The study finds a huge spectrum of functional islet responses and insulin phenotypes across all strains and diets, with the ubiquitous C57Bl/6J mouse exhibiting the lowest secretory response of all strains, highlighting the overall importance of considering genetic background when investigating islet function. Ex vivo basal and stimulated insulin secretion are correlated in the islet, and KETO imparts widescale downregulation of islet insulin secretion.

Congenital malformations among offspring of women with type 1 diabetes who use insulin pumps: a prospective cohort study.

AIMS/HYPOTHESIS: Continuous subcutaneous insulin infusion by insulin pump is often superior in improving glycaemic control compared with conventional multiple daily insulin injection (MDI). However, whether pump treatment leads to improved pregnancy outcomes in terms of congenital malformations and perinatal death remains unknown. The present aim was to evaluate the risk of malformations and perinatal and neonatal death in pregnant women with type 1 diabetes treated with pump or MDI. METHODS: We performed a secondary analysis of a prospective multinational cohort of 2088 pregnant women with type 1 diabetes in a real-world setting who were treated by pump (n=750) or MDI (n=1338). ORs for offspring with congenital malformations or perinatal or neonatal death were calculated using crude data and by logistic regression on propensity score-matched data. RESULTS: At enrolment (gestational week 8; 95% CI 4, 14), pump users had a higher educational level (university degree: 37.3% vs 25.1%; p<0.001) and better glycaemic control (mean HbA1c: 51±10 mmol/mol [6.8±0.9%] vs 54±14 mmol/mol [7.1±1.3%], p<0.001) compared with MDI users. Moreover, a greater proportion of pump users had an HbA1c level below 75 mmol/mol (9%) (97.6% vs 91.9%, p<0.001), and more often reported taking folic acid supplementation (86.3% vs 74.8%; p<0.001) compared with MDI users. All clinically important potential confounders were balanced after propensity score matching, and HbA1c remained lower in pump users. The proportion of fetuses with at least one malformation was 13.5% in pump users vs 11.2% in MDI users (crude OR 1.23; 95% CI 0.94, 1.61; p=0.13; propensity score-matched (adjusted) OR 1.11; 95% CI 0.81, 1.52; p=0.52). The proportion of fetuses with at least one major malformation was 2.8% in pump users vs 3.1% in MDI users (crude OR 0.89; 95% CI 0.52, 1.51; p=0.66; adjusted OR 0.78; 95% CI 0.42, 1.45; p=0.43), and the proportions of fetuses carrying one or more minor malformations (but no major malformations) were 10.7% vs 8.1% (crude OR 1.36; 95% CI 1.00, 1.84; p=0.05; adjusted OR 1.23; 95% CI 0.87, 1.75; p=0.25). The proportions of perinatal and neonatal death were 1.6% vs 1.3% (crude OR 1.23; 95% CI 0.57, 2.67; p=0.59; adjusted OR 2.02; 95% CI 0.69, 5.93; p=0.20) and 0.3% vs 0.3% (n=2 vs n=4, p=not applicable), respectively. CONCLUSIONS/INTERPRETATIONS: Insulin pump treatment was not associated with a lower risk of congenital malformations, despite better glycaemic control in early pregnancy compared with MDI. Further studies exploring the efficacy and safety of pump treatment during pregnancy are needed.

Systems-level analysis of insulin action in mouse strains provides insight into tissue- and pathway-specific interactions that drive insulin resistance.

Skeletal muscle and adipose tissue insulin resistance are major drivers of metabolic disease. To uncover pathways involved in insulin resistance, specifically in these tissues, we leveraged the metabolic diversity of different dietary exposures and discrete inbred mouse strains. This revealed that muscle insulin resistance was driven by gene-by-environment interactions and was strongly correlated with hyperinsulinemia and decreased levels of ten key glycolytic enzymes. Remarkably, there was no relationship between muscle and adipose tissue insulin action. Adipocyte size profoundly varied across strains and diets, and this was strongly correlated with adipose tissue insulin resistance. The A/J strain, in particular, exhibited marked adipocyte insulin resistance and hypertrophy despite robust muscle insulin responsiveness, challenging the role of adipocyte hypertrophy per se in systemic insulin resistance. These data demonstrate that muscle and adipose tissue insulin resistance can occur independently and underscore the need for tissue-specific interrogation to understand metabolic disease.

Insulin Tolerance Test under Anaesthesia to Measure Tissue-specific Insulin-stimulated Glucose Disposal.

Insulin resistance is a pathophysiological state defined by impaired responses to insulin and is a risk factor for several metabolic diseases, most notably type 2 diabetes. Insulin resistance occurs in insulin target tissues including liver, adipose and skeletal muscle. Methods such as insulin tolerance tests and hyperinsulinaemic-euglycaemic clamps permit assessment of insulin responses in specific tissues and allow the study of the progression and causes of insulin resistance. Here we detail a protocol for assessing insulin action in adipose and muscle tissues in anesthetized mice administered with insulin intravenously.