Maternal Vitamin D Deficiency Impairs the Development of ß Cells in Offspring Rats in a Sex-Dependent Manner.

Recent studies have shown that maternal vitamin D deficiency (VDD) causes long-term metabolic changes in offspring. However, little is known about the impact of maternal VDD on offspring endocrine pancreas development and insulin secretion in the adult life of male and female animals. Female rats (Wistar Hannover) were fed either control (1000 IU Vitamin D3/kg), VDD (0 IU Vitamin D3/kg), or a Ca2+-enriched VDD diet (0 IU Vitamin D3/kg + Ca2+ and P/kg) for 6 weeks and during gestation and lactation. At weaning, VDD status was confirmed based on low serum calcidiol levels in dams and pups. Next, male and female offspring were randomly separated and fed a standard diet for up to 90 days. At this age, serum calcidiol levels were restored to normal levels in all groups, but serum insulin levels were decreased in VDD males without affecting glucagon levels, glycemia, or glucose tolerance. Islets isolated from VDD males showed lower insulin secretion in response to different glucose concentrations, but this effect was not observed in VDD females. Furthermore, VDD males, but not females, showed a smaller total pancreatic islet area and lower ß cell mass, an effect that was accompanied by reduced gene expression of Ins1, Ins2, Pdx1, and SLC2A2. The decrease in Pdx1 expression was not related to the methylation profile of the promoter region of this gene. Most of these effects were observed in the male VDD+Ca2+ group, indicating that the effects were not due to alterations in Ca2+ metabolism. These data show that maternal VDD selectively impairs the morphology and function of ß cells in adult male offspring rats and that female offspring are fully protected from these deleterious effects.

Condensation of the ß-cell secretory granule luminal cargoes pro/insulin and ICA512 RESP18 homology domain.

ICA512/PTPRN is a receptor tyrosine-like phosphatase implicated in the biogenesis and turnover of the insulin secretory granules (SGs) in pancreatic islet beta cells. Previously we found biophysical evidence that its luminal RESP18 homology domain (RESP18HD) forms a biomolecular condensate and interacts with insulin in vitro at close-to-neutral pH, that is, in conditions resembling those present in the early secretory pathway. Here we provide further evidence for the relevance of these findings by showing that at pH 6.8 RESP18HD interacts also with proinsulin-the physiological insulin precursor found in the early secretory pathway and the major luminal cargo of ß-cell nascent SGs. Our light scattering analyses indicate that RESP18HD and proinsulin, but also insulin, populate nanocondensates ranging in size from 15 to 300 nm and 10e2 to 10e6 molecules. Co-condensation of RESP18HD with proinsulin/insulin transforms the initial nanocondensates into microcondensates (size >1 µm). The intrinsic tendency of proinsulin to self-condensate implies that, in the ER, a chaperoning mechanism must arrest its spontaneous intermolecular condensation to allow for proper intramolecular folding. These data further suggest that proinsulin is an early driver of insulin SG biogenesis, in a process in which its co-condensation with RESP18HD participates in their phase separation from other secretory proteins in transit through the same compartments but destined to other routes. Through the cytosolic tail of ICA512, proinsulin co-condensation with RESP18HD may further orchestrate the recruitment of cytosolic factors involved in membrane budding and fission of transport vesicles and nascent SGs.

Treat-to-target HbA1c and lipid profile to prolong ß-cell mass/function and optimize treatment goal attainment.

BACKGROUND: To evaluate the relation between different serum lipid fractions and other known barriers to attain the HbA1c  ≤ 7.0% (53 mmol/mol) target. METHODS: Data on 2719 patients with type 2 diabetes were collected from the five waves of the International Diabetes Mellitus Practice Study implemented in Argentina (2006 to 2012) including demographic/socioeconomic profile, clinical, metabolic (HbA1c and serum lipids) data, and treatment type and also, percentage of treatment goal attainment. Descriptive statistical analyses included ANOVA, χ2 test, and Fisher exact test and univariate and multivariate logistic regression analyses, which identified predictive factors for HbA1c  ≤ 7% (53 mmol/mol). RESULTS: The average age was 63 years, primary/secondary education, health insurance, 10-year type 2 diabetes duration, most associated with cardiovascular risk factors and some microvascular/macrovascular complications; 94.5% received antihyperglycaemic drugs. Percentage of people on target: HbA1c 51.2%, blood pressure 23.5%, total cholesterol 62.6%, low-density lipoprotein (LDL) cholesterol 38.9%, and triglycerides 61.1%. HbA1c on target depended markedly on treatment type: more of those treated with lifestyle changes and significantly fewer of those receiving insulin. Only 4.1% had all parameters simultaneously on target. Multivariate logistic regression analyses showed that achieving HbA1c  ≤ 7.0% (53 mmol/mol) was associated with higher educational level, shorter diabetes duration, and having reached goals for LDL cholesterol and triglycerides, whereas opposite results were obtained with insulin treatment and longer diabetes duration. CONCLUSIONS: High LDL cholesterol and triglyceride levels simultaneously potentiate development/progression of chronic complications, exerting this effect in the long term by decreasing ß-cell mass/function, thereby making it more difficult to reach HbA1c values able to prevent complications.

Amino acid restriction increases ß-cell death under challenging conditions.

Malnutrition programs metabolism, favor dysfunction of ß cells. We aimed to establish an in vitro protocol of malnutrition, assessing the effect of amino acid restriction upon the ß cells. Insulin-producing cells INS-1E and pancreatic islets were maintained in RPMI 1640 medium containing 1× (Ctl) or 0.25× (AaR) of amino acids. We evaluated several markers of ß-cell function and viability. AaR Insulin secretion was reduced, whereas cell viability was unaltered. Calcium oscillations in response to glucose increased in AaR. AaR showed lower Ins1 RNAm, snap 25, and PKC (protein kinase C) protein content, whereas phospho-eIF2α was increased. AaR cells exposed to nutrient or chemical challenges displayed higher apoptosis rates. We showed that amino acid restriction programmed ß cell and induced functional changes. This model might be useful for the study of molecular mechanisms involved with ß-cell programming helping to establish novel therapeutic targets to prevent harmful outcomes of malnutrition.

Coenzyme Q10 protects against ß-cell toxicity induced by pravastatin treatment of hypercholesterolemia.

New onset of diabetes is associated with the use of statins. We have recently demonstrated that pravastatin-treated hypercholesterolemic LDL receptor knockout (LDLr-/- ) mice exhibit reductions in insulin secretion and increased islet cell death and oxidative stress. Here, we hypothesized that these diabetogenic effects of pravastatin could be counteracted by treatment with the antioxidant coenzyme Q 10 (CoQ 10 ), an intermediate generated in the cholesterol synthesis pathway. LDLr -/- mice were treated with pravastatin and/or CoQ 10 for 2 months. Pravastatin treatment resulted in a 75% decrease of liver CoQ 10 content. Dietary CoQ 10 supplementation of pravastatin-treated mice reversed fasting hyperglycemia, improved glucose tolerance (20%) and insulin sensitivity (>2-fold), and fully restored islet glucose-stimulated insulin secretion impaired by pravastatin (40%). Pravastatin had no effect on insulin secretion of wild-type mice. In vitro, insulin-secreting INS1E cells cotreated with CoQ 10 were protected from cell death and oxidative stress induced by pravastatin. Simvastatin and atorvastatin were more potent in inducing dose-dependent INS1E cell death (10-15-fold), which were also attenuated by CoQ 10 cotreatment. Together, these results demonstrate that statins impair ß-cell redox balance, function and viability. However, CoQ 10 supplementation can protect the statins detrimental effects on the endocrine pancreas.

Calcium-sensing receptor inhibits TGF-ß-signaling by decreasing Smad2 phosphorylation.

Calcium-sensing receptor (CaSR) contributes to maintain homeostatic levels of extracellular calcium. In addition, CaSR controls other cellular activities such as proliferation and migration, particularly in cells not related to extracellular calcium homeostasis, potentially by cross-talking with parallel signaling pathways. Here we report that CaSR attenuates transforming growth factor-ß (TGF-ß)-signaling in hepatic C9 cells and in transfected HEK293 cells. Wild type CaSR interferes with TGF-ß-dependent Smad2 phosphorylation and induces its proteasomal degradation, resulting in a decrease of TGF-ß-dependent transcriptional activity, whereas an inactivating CaSR mutant does not transduce an inhibitory effect of extracellular calcium on TGF-ß signaling. Attenuation of TGF-ß signaling in response to extracellular calcium is linked to Rab11-dependent CaSR-trafficking with the intervention of CaSR carboxyl-terminal tail. Our data suggest that CaSR might regulate TGF-ß-dependent cellular responses mediated by TGF-ß signaling inhibition.