Restoring early-phase insulin secretion - the new goal in type 2 diabetes management

Exploring the relationship between pancreatic fat and insulin secretion in overweight or obese women without type 2 diabetes mellitus: A preliminary investigation of the TOFI_Asia cohort

OBJECTIVE

While there is an emerging role of pancreatic fat in the aetiology of type 2 diabetes mellitus (T2DM), its impact on the associated decrease in insulin secretion remains controversial. We aimed to determine whether pancreatic fat negatively affects β-cell function and insulin secretion in women with overweight or obesity but without T2DM.

METHODS

20 women, with normo- or dysglycaemia based on fasting plasma glucose levels, and low (< 4.5%) vs high (≥ 4.5%) magnetic resonance (MR) quantified pancreatic fat, completed a 1-hr intravenous glucose tolerance test (ivGTT) which included two consecutive 30-min square-wave steps of hyperglycaemia generated by using 25% dextrose. Plasma glucose, insulin and C-peptide were measured, and insulin secretion rate (ISR) calculated using regularisation deconvolution method from C-peptide kinetics. Repeated measures linear mixed models, adjusted for ethnicity and baseline analyte concentrations, were used to compare changes during the ivGTT between high and low percentage pancreatic fat (PPF) groups.

RESULTS

No ethnic differences in anthropomorphic variables, body composition, visceral adipose tissue (MR-VAT) or PPF were measured and hence data were combined. Nine women (47%) were identified as having high PPF values. PPF was significantly associated with baseline C-peptide (p = 0.04) and ISR (p = 0.04) in all. During the 1-hr ivGTT, plasma glucose (p<0.0001), insulin (p<0.0001) and ISR (p = 0.02) increased significantly from baseline in both high and low PPF groups but did not differ between the two groups at any given time during the test (PPF x time, p > 0.05). Notably, the incremental areas under the curves for both first and second phase ISR were 0.04 units lower in the high than low PPF groups, but this was not significant (p > 0.05).

CONCLUSION

In women with overweight or obesity but without T2DM, PPF did not modify β-cell function as determined by ivGTT-assessed ISR. However, the salient feature in biphasic insulin secretion in those with ≥4.5% PPF may be of clinical importance, particularly in early stages of dysglycaemia may warrant further investigation.

Prenatal Dexamethasone Exposure Programs the Development of the Pancreas and the Secretion of Insulin in Rats

BACKGROUND

There is increasing epidemiological evidence indicating that many chronic diseases originate during early life, even before birth, through what are termed fetal programming effects. Prenatal glucocorticoid is frequently used clinically to accelerate the maturation of the lung, but its long-term effects remain unclear.

METHODS

We gave pregnant Sprague-Dawley rats either intraperitoneal dexamethasone (0.1 mg/kg body weight) or vehicle at Gestational Days 14-20 and assessed the effects to pancreas at Postnatal Days 7 and 120.

RESULTS

We found fewer pancreatic β cell fractions (0.31±0.05 % vs. 0.49±0.05 %, p=0.013) and tissues (0.0017±0.0002 % vs. 0.0025±0.0002 %, p=0.042) and decreased secretion of insulin in response to a glucose challenge at Postnatal Day 105 (1.00±0.19 ng/mL vs. 1.57±0.17 ng/mL at the 15-minute time-point, p=0.046) in rats treated prenatally with dexamethasone. At Postnatal Day 7 in rats treated prenatally with dexamethasone, the expression of pancreatic duodenal homeobox gene-1 and V-maf avian musculoaponeurotic fibrosarcoma oncogene homolog A was lower than that in the rats in the Vehicle group (0.22±0.07 vs. 1.00±0.41 fold, p=0.01, 0.20±0.12 vs. 1.00±0.35 fold, p=0.01) while the histone deacetylases activity (54.2±3.7 ng/h/mL vs. 37.6±3.5 ng/h/mL, p=0.012) and 8-hydroxy-2-deoxyguanosine staining (1.34±0.01 vs. 1.00±0.02 fold, p<0.01) were higher.

CONCLUSION

Prenatal dexamethasone exposure affects early postnatal gene expression related to pancreas development and may exert an effect on β-cell development at 120 postnatal days.