High Intensity Interval Training Improves Glycaemic Control and Pancreatic β Cell Function of Type 2 Diabetes Patients

Physical activity improves the regulation of glucose homeostasis in both type 2 diabetes (T2D) patients and healthy individuals, but the effect on pancreatic β cell function is unknown. We investigated glycaemic control, pancreatic function and total fat mass before and after 8 weeks of low volume high intensity interval training (HIIT) on cycle ergometer in T2D patients and matched healthy control individuals. Study design/method: Elderly (56 yrs±2), non-active T2D patients (n = 10) and matched (52 yrs±2) healthy controls (CON) (n = 13) exercised 3 times (10×60 sec. HIIT) a week over an 8 week period on a cycle ergometer. Participants underwent a 2-hour oral glucose tolerance test (OGTT). On a separate day, resting blood pressure measurement was conducted followed by an incremental maximal oxygen uptake (V˙O_2max) cycle ergometer test. Finally, a whole body dual X-ray absorptiometry (DXA) was performed. After 8 weeks of training, the same measurements were performed. Results: in the T2D-group, glycaemic control as determined by average fasting venous glucose concentration (p = 0.01), end point 2-hour OGTT (p = 0.04) and glycosylated haemoglobin (p = 0.04) were significantly reduced. Pancreatic homeostasis as determined by homeostatic model assessment of insulin resistance (HOMA-IR) and HOMA β cell function (HOMA-%β) were both significantly ameliorated (p = 0.03 and p = 0.03, respectively). Whole body insulin sensitivity as determined by the disposition index (DI) was significantly increased (p = 0.03). During OGTT, the glucose continuum was significantly reduced at -15 (p = 0.03), 30 (p = 0.03) and 120 min (p = 0.03) and at -10 (p = 0.003) and 0 min (p = 0.003) with an additional improvement (p = 0.03) of its 1^st phase (30 min) area under curve (AUC). Significant abdominal fat mass losses were seen in both groups (T2D: p = 0.004 and CON: p = 0.02) corresponding to a percentage change of -17.84%±5.02 and -9.66%±3.07, respectively. Conclusion: these results demonstrate that HIIT improves overall glycaemic control and pancreatic β cell function in T2D patients. Additionally, both groups experienced abdominal fat mass losses. These findings demonstrate that HIIT is a health beneficial exercise strategy in T2D patients.

Trial Registration

ClinicalTrials.gov NCT02333734 http://clinicaltrials.gov/ct2/show/NCT02333734     

Pdx1 Maintains β Cell Identity and Function by Repressing an α Cell Program

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The Furan Fatty Acid Metabolite CMPF Is Elevated in Diabetes and Induces β Cell Dysfunction

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Pancreatic β Cell Dedifferentiation in Diabetes and Redifferentiation following Insulin Therapy

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α Cell Function and Gene Expression Are Compromised in Type 1 Diabetes

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Mutations in SLC2A2 Gene Reveal hGLUT2 Function in Pancreatic β Cell Development

The structure-function relationships of sugar transporter-receptor hGLUT2 coded by SLC2A2 and their impact on insulin secretion and β cell differentiation were investigated through the detailed characterization of a panel of mutations along the protein. We studied naturally occurring SLC2A2 variants or mutants: two single-nucleotide polymorphisms and four proposed inactivating mutations associated to Fanconi-Bickel syndrome. We also engineered mutations based on sequence alignment and conserved amino acids in selected domains. The single-nucleotide polymorphisms P68L and T110I did not impact on sugar transport as assayed in Xenopus oocytes. All the Fanconi-Bickel syndrome-associated mutations invalidated glucose transport by hGLUT2 either through absence of protein at the plasma membrane (G20D and S242R) or through loss of transport capacity despite membrane targeting (P417L and W444R), pointing out crucial amino acids for hGLUT2 transport function. In contrast, engineered mutants were located at the plasma membrane and able to transport sugar, albeit with modified kinetic parameters. Notably, these mutations resulted in gain of function. G20S and L368P mutations increased insulin secretion in the absence of glucose. In addition, these mutants increased insulin-positive cell differentiation when expressed in cultured rat embryonic pancreas. F295Y mutation induced β cell differentiation even in the absence of glucose, suggesting that mutated GLUT2, as a sugar receptor, triggers a signaling pathway independently of glucose transport and metabolism. Our results describe the first gain of function mutations for hGLUT2, revealing the importance of its receptor versus transporter function in pancreatic β cell development and insulin secretion.     

Metformin Plays a Dual Role in MIN6 Pancreatic β Cell Function through AMPK-dependent Autophagy

Metformin improves insulin sensitivity in insulin sensitive tissues such as liver, muscle and fat. However, the functional roles and the underlying mechanism of metformin action in pancreatic β cells remain elusive. Here we show that, under normal growth condition, metformin suppresses MIN6 β cell proliferation and promotes apoptosis via an AMPK-dependent and autophagy-mediated mechanism. On the other hand, metformin protects MIN6 cells against palmitic acid (PA)-induced apoptosis. Our findings indicate that metformin plays a dual role in β cell survival and overdose of this anti-diabetic drug itself may lead to potential β cell toxicity.     

Expansion of Islet-Resident Macrophages Leads to Inflammation Affecting β Cell Proliferation and Function in Obesity

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The Polycomb-Dependent Epigenome Controls β Cell Dysfunction,Dedifferentiation, and Diabetes

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The Role of β Cell Glucagon-like Peptide-1 Signaling in Glucose Regulation and Response to Diabetes Drugs

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Inefficient Translocation of Preproinsulin Contributes to Pancreatic β Cell Failure and Late-onset Diabetes

Among the defects in the early events of insulin biosynthesis, proinsulin misfolding and endoplasmic reticulum (ER) stress have drawn increasing attention as causes of β cell failure. However, no studies have yet addressed potential defects at the cytosolic entry point of preproinsulin into the secretory pathway. Here, we provide the first evidence that inefficient translocation of preproinsulin (caused by loss of a positive charge in the n region of its signal sequence) contributes to β cell failure and diabetes. Specifically, we find that, after targeting to the ER membrane, preproinsulin signal peptide (SP) mutants associated with autosomal dominant late-onset diabetes fail to be fully translocated across the ER membrane. The newly synthesized, untranslocated preproinsulin remains strongly associated with the ER membrane, exposing its proinsulin moiety to the cytosol. Rather than accumulating in the ER and inducing ER stress, untranslocated preproinsulin accumulates in a juxtanuclear compartment distinct from the Golgi complex, induces the expression of heat shock protein 70 (HSP70), and promotes β cell death. Restoring an N-terminal positive charge to the mutant preproinsulin SP significantly improves the translocation defect. These findings not only reveal a novel molecular pathogenesis of β cell failure and diabetes but also provide the first evidence of the physiological and pathological significance of the SP n region positive charge of secretory proteins.     

Multiomic Profiling Identifies cis-Regulatory Networks Underlying Human Pancreatic β Cell Identity and Function

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Liver-Derived Systemic Factors Drive β Cell Hyperplasia in Insulin-Resistant States

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Highlights? Circulating nonneuronal factors drive β cell replication in LIRKO mice ? LIRKO serum increases mouse and human islet β cell replication in vitro ? LIRKO serum induces selective β cell replication in vivo ? Hepatocyte-derived factors stimulate mouse and human β cell replication in vitro     

Arabidopsis OBG-Like GTPase （AtOBGL）Is Localized in Chloroplasts and Has an Essential Function in Embryo Development

OBG-like GTPases, a subfamily of P-loop GTPases, have divers and important functions in bacteria, including initiation of sporulation, DNA replication, and protein translation. Homologs of the Bacillus subtilis spo0B GTP-binding protein （OBG） can be found in plants and algae but their specific function in these organisms has not yet been elucidated. Here, it is shown that ATSG18570 encodes an Arabidopsis thaliana OBG-like protein （AtOBGL） that is localized in chlor- oplasts. In contrast to the bacterial members of this protein family, AtOBGL and other OBG-like proteins from green algae and plants possess an additional N-terminal domain, indicating functional adaptation. Disruption of the gene locus of ATOBGL by TDNA insertion resulted in an embryo-lethal phenotype and light microscopy using Normarski optics revealed that embryo maturation in the atobgl mutant is arrested at the late globular stage before development of a green embryo. Expression of 35S：：ATOBGL within the atobgl mutant background could rescue the mutant phenotype, confirming that embryo-lethality is caused by the loss of AtOBGL. Together, the data show that the bacterial-derived OBG-like GTPases have retained an essential role in chloroplasts of plants and algae. They furthermore corroborate the significance of chloroplast functions for embryo development -- an important stage within the Arabidopsis lifecycle.     

Lymphocyte-Derived Exosomal MicroRNAs Promote Pancreatic β Cell Death and May Contribute to Type 1 Diabetes Development

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