Hyperglycaemia induces metabolic dysfunction and glycogen accumulation in pancreatic β-cells

Insulin secretion from pancreatic β-cells is impaired in all forms of diabetes. The resultant hyperglycaemia has deleterious effects on many tissues, including β-cells. Here we use a mouse model of human neonatal diabetes to show that chronic hyperglycemia impairs glucose metabolism and alters expression of metabolic genes in pancreatic islets. This results in marked glycogen accumulation, and increased apoptosis in β-cells. Sulphonylurea therapy rapidly normalizes blood glucose levels, dissipates glycogen stores, increases autophagy, and restores β-cell metabolism. Insulin therapy has the same effect but with slower kinetics. Similar changes are observed in mice expressing an activating glucokinase mutation, in in vitro models of hyperglycaemia, and in islets from type-2 diabetes patients. Altered β-cell metabolism may underlie both the progressive impairment of insulin secretion and reduced β-cell mass in diabetes

FTO Is Expressed in Neurones throughout the Brain and Its Expression Is Unaltered by Fasting

Single-nucleotide polymorphisms in the first intron of the ubiquitously expressed FTO gene are associated with obesity. Although the physiological functions of FTO remain unclear, food intake is often altered when Fto expression levels are manipulated. Furthermore, deletion of FTO from neurones alone has a similar effect on food intake to deletion of FTO in all tissues. These results indicate that FTO expression in the brain is particularly important. Considerable focus has been placed on the dynamic regulation of Fto mRNA expression in the hypothalamus after short-term (16–48 hour) fasting, but results have been controversial. There are no studies that quantify FTO protein levels across the brain, and assess its alteration following short-term fasting. Using immunohistochemistry, we found that FTO protein is widely expressed in mouse brain, and present in the majority of neurones. Using quantitative Western blotting and RT-qPCR we show that FTO protein and mRNA levels in the hypothalamus, cerebellum and rostral brain are relatively uniform, and levels in the brain are higher than in skeletal muscles of the lower limbs. Fasting for 18 hours does not alter the expression pattern, or levels, of FTO protein and mRNA. We further show that the majority of POMC neurones, which are critically involved in food intake regulation, also express FTO, but that the percentage of FTO-positive POMC neurones is not altered by fasting. In summary, we find no evidence that Fto/FTO expression is regulated by short-term (18-hour) fasting. Thus, it is unlikely that the hunger and increased post-fasting food intake caused by such food deprivation is driven by alterations in Fto/FTO expression. The widespread expression of FTO in neurones also suggests that physiological studies of this protein should not be limited to the hypothalamus

Comparison of different therapies for neonatal diabetes – glibenclamide vs insulin

Gain-of-function mutations in the Kir6.2 and SUR subunits of the KATP channel are associated with neonatal diabetes (ND). I used a mouse model selectively expressing the Kir6.2-V59M mutation in pancreatic β-cells (inducible iβ-V59M) to compare the effects of sulphonylurea and insulin therapy on neonatal diabetes. Gene expression was induced in adulthood, which caused severe hyperglycaemia and resulted in a major decrease in insulin content, pancreatic β-cell area, pancreatic islet number, single islet size and total islet area. Insulin secretion and glucose tolerance were also severely impaired. To determine if the preservation of physiological blood glucose levels (~4mM) alone is sufficient to prevent these effects, or if the closure of the KATP channel is also required, induced iβ-V59M mice were implanted with insulin pellets or a high-dose glibenclamide pellet. Insulin therapy restored blood glucose levels but failed to fully preserve pancreatic islet and β-cell morphology and function. Conversely, glibenclamide therapy reduced elevated blood glucose concentrations down to a physiological range and maintained pancreatic islet and β-cell morphology and function. These findings have implications for treatment of human patients suffering from neonatal diabetes.</p

Comparison of different therapies for neonatal diabetes – glibenclamide vs insulin

Gain-of-function mutations in the Kir6.2 and SUR subunits of the KATP channel are associated with neonatal diabetes (ND). I used a mouse model selectively expressing the Kir6.2-V59M mutation in pancreatic β-cells (inducible iβ-V59M) to compare the effects of sulphonylurea and insulin therapy on neonatal diabetes. Gene expression was induced in adulthood, which caused severe hyperglycaemia and resulted in a major decrease in insulin content, pancreatic β-cell area, pancreatic islet number, single islet size and total islet area. Insulin secretion and glucose tolerance were also severely impaired. To determine if the preservation of physiological blood glucose levels (~4mM) alone is sufficient to prevent these effects, or if the closure of the KATP channel is also required, induced iβ-V59M mice were implanted with insulin pellets or a high-dose glibenclamide pellet. Insulin therapy restored blood glucose levels but failed to fully preserve pancreatic islet and β-cell morphology and function. Conversely, glibenclamide therapy reduced elevated blood glucose concentrations down to a physiological range and maintained pancreatic islet and β-cell morphology and function. These findings have implications for treatment of human patients suffering from neonatal diabetes.This thesis is not currently available in ORA

Regulation of IL-10 by chondroitinase ABC promotes a distinct immune response following spinal cord injury

Chondroitinase ABC (ChABC) has striking effects on promoting neuronal plasticity after spinal cord injury (SCI), but little is known about its involvement in other pathological mechanisms. Recent work showed that ChABC might also modulate the immune response by promoting M2 macrophage polarization. Here we investigate in detail the immunoregulatory effects of ChABC after SCI in rats. Initially, we examined the expression profile of 16 M1/M2 macrophage polarization markers at 3 h and 7 d postinjury. ChABC treatment had a clear effect on the immune signature after SCI. More specifically, ChABC increased the expression of the anti-inflammatory cytokine IL-10, accompanied by a reduction in the proinflammatory cytokine IL-12B in injured spinal tissue. These effects were associated with a distinct, IL-10-mediated anti-inflammatory response in ChABC-treated spinal cords. Mechanistically, we show that IL-10 expression is driven by tissue injury and macrophage infiltration, while the p38 MAPK is the central regulator of IL-10 expression in vivo. These findings provide novel insights into the effects of ChABC in the injured spinal cord and explain its immunoregulatory activity