Effect of self-managed lifestyle treatment on glycemic control in patients with type 2 diabetes.

The lack of effective, scalable solutions for lifestyle treatment is a global clinical problem, causing severe morbidity and mortality. We developed a method for lifestyle treatment that promotes self-reflection and iterative behavioral change, provided as a digital tool, and evaluated its effect in 370 patients with type 2 diabetes (ClinicalTrials.gov identifier: NCT04691973). Users of the tool had reduced blood glucose, both compared with randomized and matched controls (involving 158 and 204 users, respectively), as well as improved systolic blood pressure, body weight and insulin resistance. The improvement was sustained during the entire follow-up (average 730 days). A pathophysiological subgroup of obese insulin-resistant individuals had a pronounced glycemic response, enabling identification of those who would benefit in particular from lifestyle treatment. Natural language processing showed that the metabolic improvement was coupled with the self-reflective element of the tool. The treatment is cost-saving because of improved risk factor control for cardiovascular complications. The findings open an avenue for self-managed lifestyle treatment with long-term metabolic efficacy that is cost-saving and can reach large numbers of people.

Sulforaphane improves disrupted ER-mitochondria interactions and suppresses exaggerated hepatic glucose production.

AIMS: Exaggerated hepatic glucose production is one of the hallmarks of type 2 diabetes. Sulforaphane (SFN) has been suggested as a new potential anti-diabetic compound. However, the effects of SFN in hepatocytes are yet unclear. Accumulating evidence points to the close structural contacts between the ER and mitochondria, known as mitochondria-associated ER membranes (MAMs), as important hubs for hepatic metabolism. We wanted to investigate whether SFN could affect hepatic glucose production and MAMs. MATERIALS AND METHODS: We used proximity ligation assays, analysis of ER stress markers and glucose production assays in hepatoma cell lines, primary mouse hepatocytes and diabetic animal models. RESULTS: SFN counteracted the increase of glucose production in palmitate-treated mouse hepatocytes. SFN also counteracted palmitate-induced MAM disruptions. Moreover, SFN decreased the ER stress markers CHOP and Grp78. In ob/ob mice, SFN improved glucose tolerance and reduced exaggerated glucose production. In livers of these mice, SFN increased MAM protein content, restored impaired VDAC1-IP3R1 interactions and reduced ER stress markers. In mice on HFHSD, SFN improved glucose tolerance, MAM protein content and ER-mitochondria interactions to a similar extent to that of metformin. CONCLUSIONS: The present findings show that MAMs are severely reduced in animal models of glucose intolerance, which reinforces the role of MAMs as a hub for insulin signaling in the liver. We also show that SFN restores MAMs and improves glucose tolerance by a similar magnitude to that of metformin. These data highlight SFN as a new potential anti-diabetic compound.

Sulforaphane reduces hepatic glucose production and improves glucose control in patients with type 2 diabetes.

A potentially useful approach for drug discovery is to connect gene expression profiles of disease-affected tissues ("disease signatures") to drug signatures, but it remains to be shown whether it can be used to identify clinically relevant treatment options. We analyzed coexpression networks and genetic data to identify a disease signature for type 2 diabetes in liver tissue. By interrogating a library of 3800 drug signatures, we identified sulforaphane as a compound that may reverse the disease signature. Sulforaphane suppressed glucose production from hepatic cells by nuclear translocation of nuclear factor erythroid 2-related factor 2 (NRF2) and decreased expression of key enzymes in gluconeogenesis. Moreover, sulforaphane reversed the disease signature in the livers from diabetic animals and attenuated exaggerated glucose production and glucose intolerance by a magnitude similar to that of metformin. Finally, sulforaphane, provided as concentrated broccoli sprout extract, reduced fasting blood glucose and glycated hemoglobin (HbA1c) in obese patients with dysregulated type 2 diabetes.

Thrombin stimulates insulin secretion via protease-activated receptor-3.

The disease mechanisms underlying type 2 diabetes (T2D) remain poorly defined. Here we aimed to explore the pathophysiology of T2D by analyzing gene co-expression networks in human islets. Using partial correlation networks we identified a group of co-expressed genes ('module') including F2RL2 that was associated with glycated hemoglobin. F2Rl2 is a G-protein-coupled receptor (GPCR) that encodes protease-activated receptor-3 (PAR3). PAR3 is cleaved by thrombin, which exposes a 6-amino acid sequence that acts as a 'tethered ligand' to regulate cellular signaling. We have characterized the effect of PAR3 activation on insulin secretion by static insulin secretion measurements, capacitance measurements, studies of diabetic animal models and patient samples. We demonstrate that thrombin stimulates insulin secretion, an effect that was prevented by an antibody that blocks the thrombin cleavage site of PAR3. Treatment with a peptide corresponding to the PAR3 tethered ligand stimulated islet insulin secretion and single ß-cell exocytosis by a mechanism that involves activation of phospholipase C and Ca(2+) release from intracellular stores. Moreover, we observed that the expression of tissue factor, which regulates thrombin generation, was increased in human islets from T2D donors and associated with enhanced ß-cell exocytosis. Finally, we demonstrate that thrombin generation potential in patients with T2D was associated with increased fasting insulin and insulinogenic index. The findings provide a previously unrecognized link between hypercoagulability and hyperinsulinemia and suggest that reducing thrombin activity or blocking PAR3 cleavage could potentially counteract the exaggerated insulin secretion that drives insulin resistance and ß-cell exhaustion in T2D.

Optogenetic control of insulin secretion in intact pancreatic islets with ß-cell-specific expression of Channelrhodopsin-2.

Insulin is secreted from the pancreatic ß-cells in response to elevated glucose. In intact islets the capacity for insulin release is determined by a complex interplay between different cell types. This has made it difficult to specifically assess the role of ß-cell defects to the insulin secretory impairment in type 2 diabetes. Here we describe a new approach, based on optogenetics, that enables specific investigation of ß-cells in intact islets. We used transgenic mice expressing the light-sensitive cation channel Channelrhodopsin-2 (ChR2) under control of the insulin promoter. Glucose tolerance in vivo was assessed using intraperitoneal glucose tolerance tests, and glucose-induced insulin release was measured from static batch incubations. ChR2 localization was determined by fluorescence confocal microscopy. The effect of ChR2 stimulation with blue LED light was assessed using Ca(2+) imaging and static islet incubations. Light stimulation of islets from transgenic ChR2 mice triggered prompt increases in intracellular Ca(2+). Moreover, light stimulation enhanced insulin secretion in batch-incubated islets at low and intermediate but not at high glucose concentrations. Glucagon release was not affected. Beta-cells from mice rendered diabetic on a high-fat diet exhibited a 3.5-fold increase in light-induced Ca(2+) influx compared with mice on a control diet. Furthermore, light enhanced insulin release also at high glucose in these mice, suggesting that high-fat feeding leads to a compensatory potentiation of the Ca(2+) response in ß-cells. The results demonstrate the usefulness and versatility of optogenetics for studying mechanisms of perturbed hormone secretion in diabetes with high time-resolution and cell-specificity.

Genotype-based treatment of type 2 diabetes with an α2A-adrenergic receptor antagonist.

The feasibility of exploiting genomic information for individualized treatment of polygenic diseases remains uncertain. A genetic variant in ADRA2A, which encodes the α(2A)-adrenergic receptor (α(2A)AR), was recently associated with type 2 diabetes. This variant causes receptor overexpression and impaired insulin secretion; thus, we hypothesized that blocking α(2A)AR pharmacologically could improve insulin secretion in patients with the risk genotype. A total of 50 type 2 diabetes patients were recruited on the basis of ADRA2A genotype for a randomized placebo-controlled intervention study with the α(2A)AR antagonist yohimbine. The patients received 0, 10, or 20 mg of yohimbine at three separate visits. The primary endpoint was insulin secretion at 30 min (Ins30) during an oral glucose tolerance test (OGTT). Patients with the risk variant had 25% lower Ins30 than those without risk genotype. After administration of 20 mg of yohimbine, Ins30 was enhanced by 29% in the risk group, making secretion similar to patients carrying the low-risk allele. The corrected insulin response and disposition index in individuals with the high-risk (but not low-risk) allele were improved by 59 ± 18% and 43 ± 14%, respectively. The beneficial effect of yohimbine was not a consequence of improved insulin sensitivity. In summary, the data show that the insulin secretion defect in patients carrying the ADRA2A risk genotype can be corrected by α(2A)AR antagonism. The findings show that knowledge of genetic risk variants can be used to guide therapeutic interventions that directly target the underlying pathophysiology and demonstrate the potential of individualized genotype-specific treatment of type 2 diabetes.

Eukaryotic translation initiation factor 3 subunit e controls intracellular calcium homeostasis by regulation of cav1.2 surface expression.

Inappropriate surface expression of voltage-gated Ca(2+)channels (CaV) in pancreatic ß-cells may contribute to the development of type 2 diabetes. First, failure to increase intracellular Ca(2+) concentrations at the sites of exocytosis impedes insulin release. Furthermore, excessive Ca(2+) influx may trigger cytotoxic effects. The regulation of surface expression of CaV channels in the pancreatic ß-cells remains unknown. Here, we used real-time 3D confocal and TIRFM imaging, immunocytochemistry, cellular fractionation, immunoprecipitation and electrophysiology to study trafficking of L-type CaV1.2 channels upon ß-cell stimulation. We found decreased surface expression of CaV1.2 and a corresponding reduction in L-type whole-cell Ca(2+) currents in insulin-secreting INS-1 832/13 cells upon protracted (15-30 min) stimulation. This internalization occurs by clathrin-dependent endocytosis and could be prevented by microtubule or dynamin inhibitors. eIF3e (Eukaryotic translation initiation factor 3 subunit E) is part of the protein translation initiation complex, but its effect on translation are modest and effects in ion channel trafficking have been suggested. The factor interacted with CaV1.2 and regulated CaV1.2 traffic bidirectionally. eIF3e silencing impaired CaV1.2 internalization, which resulted in an increased intracellular Ca(2+) load upon stimulation. These findings provide a mechanism for regulation of L-type CaV channel surface expression with consequences for ß-cell calcium homeostasis, which will affect pancreatic ß-cell function and insulin production.

Secreted frizzled-related protein 4 reduces insulin secretion and is overexpressed in type 2 diabetes.

A plethora of candidate genes have been identified for complex polygenic disorders, but the underlying disease mechanisms remain largely unknown. We explored the pathophysiology of type 2 diabetes (T2D) by analyzing global gene expression in human pancreatic islets. A group of coexpressed genes (module), enriched for interleukin-1-related genes, was associated with T2D and reduced insulin secretion. One of the module genes that was highly overexpressed in islets from T2D patients is SFRP4, which encodes secreted frizzled-related protein 4. SFRP4 expression correlated with inflammatory markers, and its release from islets was stimulated by interleukin-1ß. Elevated systemic SFRP4 caused reduced glucose tolerance through decreased islet expression of Ca(2+) channels and suppressed insulin exocytosis. SFRP4 thus provides a link between islet inflammation and impaired insulin secretion. Moreover, the protein was increased in serum from T2D patients several years before the diagnosis, suggesting that SFRP4 could be a potential biomarker for islet dysfunction in T2D.

Reduced insulin exocytosis in human pancreatic ß-cells with gene variants linked to type 2 diabetes.

The majority of genetic risk variants for type 2 diabetes (T2D) affect insulin secretion, but the mechanisms through which they influence pancreatic islet function remain largely unknown. We functionally characterized human islets to determine secretory, biophysical, and ultrastructural features in relation to genetic risk profiles in diabetic and nondiabetic donors. Islets from donors with T2D exhibited impaired insulin secretion, which was more pronounced in lean than obese diabetic donors. We assessed the impact of 14 disease susceptibility variants on measures of glucose sensing, exocytosis, and structure. Variants near TCF7L2 and ADRA2A were associated with reduced glucose-induced insulin secretion, whereas susceptibility variants near ADRA2A, KCNJ11, KCNQ1, and TCF7L2 were associated with reduced depolarization-evoked insulin exocytosis. KCNQ1, ADRA2A, KCNJ11, HHEX/IDE, and SLC2A2 variants affected granule docking. We combined our results to create a novel genetic risk score for ß-cell dysfunction that includes aberrant granule docking, decreased Ca(2+) sensitivity of exocytosis, and reduced insulin release. Individuals with a high risk score displayed an impaired response to intravenous glucose and deteriorating insulin secretion over time. Our results underscore the importance of defects in ß-cell exocytosis in T2D and demonstrate the potential of cellular phenotypic characterization in the elucidation of complex genetic disorders.