| 1. |
- Augestad, IL, et al.
(author)
-
Regulation of Glycemia in the Recovery Phase After Stroke Counteracts the Detrimental Effect of Obesity-Induced Type 2 Diabetes on Neurological Recovery
- 2020
-
In: Diabetes. - : American Diabetes Association. - 1939-327X .- 0012-1797. ; 69:9, s. 1961-1973
-
Journal article (peer-reviewed)abstract
- The interplay between obesity and type 2 diabetes (T2D) in poststroke recovery is unclear. Moreover, the impact of glucose control during the chronic phase after stroke is undetermined. We investigated whether obesity-induced T2D impairs neurological recovery after stroke by using a clinically relevant experimental design. We also investigated the potential efficacy of two clinically used T2D drugs: the dipeptidyl peptidase 4 inhibitor linagliptin and the sulfonylurea glimepiride. We induced transient middle cerebral artery occlusion (tMCAO) in T2D/obese mice (after 7 months of high-fat diet [HFD]) and age-matched controls. After stroke, we replaced HFD with standard diet for 8 weeks to mimic the poststroke clinical situation. Linagliptin or glimepiride were administered daily from 3 days after tMCAO for 8 weeks. We assessed neurological recovery weekly by upper-limb grip strength. Brain damage, neuroinflammation, stroke-induced neurogenesis, and atrophy of parvalbumin-positive (PV+) interneurons were quantified by immunohistochemistry. T2D/obesity impaired poststroke neurological recovery in association with hyperglycemia, neuroinflammation, and atrophy of PV+ interneurons. Both drugs counteracted these effects. In nondiabetic mice, only linagliptin accelerated recovery. These findings shed light on the interplay between obesity and T2D in stroke recovery. Moreover, they promote the use of rehabilitative strategies that are based on efficacious glycemia regulation, even if initiated days after stroke.
|
|
| 2. |
- Barker, CJ, et al.
(author)
-
XPR1 Mediates the Pancreatic β-Cell Phosphate Flush
- 2021
-
In: Diabetes. - : American Diabetes Association. - 1939-327X .- 0012-1797. ; 70:1, s. 111-118
-
Journal article (peer-reviewed)abstract
- Glucose-stimulated insulin secretion is the hallmark of the pancreatic β-cell, a critical player in the regulation of blood glucose concentration. In 1974, the remarkable observation was made that an efflux of intracellular inorganic phosphate (Pi) accompanied the events of stimulated insulin secretion. The mechanism behind this “phosphate flush,” its association with insulin secretion, and its regulation have since then remained a mystery. We recapitulated the phosphate flush in the MIN6m9 β-cell line and pseudoislets. We demonstrated that knockdown of XPR1, a phosphate transporter present in MIN6m9 cells and pancreatic islets, prevented this flush. Concomitantly, XPR1 silencing led to intracellular Pi accumulation and a potential impact on Ca2+ signaling. XPR1 knockdown slightly blunted first-phase glucose-stimulated insulin secretion in MIN6m9 cells, but had no significant impact on pseudoislet secretion. In keeping with other cell types, basal Pi efflux was stimulated by inositol pyrophosphates, and basal intracellular Pi accumulated following knockdown of inositol hexakisphosphate kinases. However, the glucose-driven phosphate flush occurred despite inositol pyrophosphate depletion. Finally, while it is unlikely that XPR1 directly affects exocytosis, it may protect Ca2+ signaling. Thus, we have revealed XPR1 as the missing mediator of the phosphate flush, shedding light on a 45-year-old mystery.
|
|
| 3. |
- Jersin, R. A., et al.
(author)
-
Role of the Neutral Amino Acid Transporter SLC7A10 in Adipocyte Lipid Storage, Obesity, and Insulin Resistance
- 2021
-
In: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 70:3, s. 680-695
-
Journal article (peer-reviewed)abstract
- Elucidation of mechanisms that govern lipid storage, oxidative stress, and insulin resistance may lead to improved therapeutic options for type 2 diabetes and other obesity-related diseases. Here, we find that adipose expression of the small neutral amino acid transporter SLC7A10, also known as alanine-serine-cysteine transporter-1 (ASC-1), shows strong inverse correlates with visceral adiposity, insulin resistance, and adipocyte hypertrophy across multiple cohorts. Concordantly, loss of Slc7a10 function in zebrafish in vivo accelerates diet-induced body weight gain and adipocyte enlargement. Mechanistically, SLC7A10 inhibition in human and murine adipocytes decreases adipocyte serine uptake and total glutathione levels and promotes reactive oxygen species (ROS) generation. Conversely, SLC7A10 overexpression decreases ROS generation and increases mitochondrial respiratory capacity. RNA sequencing revealed consistent changes in gene expression between human adipocytes and zebrafish visceral adipose tissue following loss of SLC7A10, e.g., upregulation of SCD (lipid storage) and downregulation of CPT1A (lipid oxidation). Interestingly, ROS scavenger reduced lipid accumulation and attenuated the lipid-storing effect of SLC7A10 inhibition. These data uncover adipocyte SLC7A10 as a novel important regulator of adipocyte resilience to nutrient and oxidative stress, in part by enhancing glutathione levels and mitochondrial respiration, conducive to decreased ROS generation, lipid accumulation, adipocyte hypertrophy, insulin resistance, and type 2 diabetes.
|
|
| 4. |
- Mileti, E, et al.
(author)
-
Human White Adipose Tissue Displays Selective Insulin Resistance in the Obese State
- 2021
-
In: Diabetes. - : American Diabetes Association. - 1939-327X .- 0012-1797. ; 70:7, s. 1486-1497
-
Journal article (peer-reviewed)abstract
- Selective hepatic insulin resistance is a feature of obesity and type 2 diabetes. Whether similar mechanisms operate in white adipose tissue (WAT) of those with obesity and to what extent these are normalized by weight loss are unknown. We determined insulin sensitivity by hyperinsulinemic euglycemic clamp and insulin response in subcutaneous WAT by RNA sequencing in 23 women with obesity before and 2 years after bariatric surgery. To control for effects of surgery, women postsurgery were matched to never-obese women. Multidimensional analyses of 138 samples allowed us to classify the effects of insulin into three distinct expression responses: a common set was present in all three groups and included genes encoding several lipid/cholesterol biosynthesis enzymes; a set of obesity-attenuated genes linked to tissue remodeling and protein translation was selectively regulated in the two nonobese states; and several postobesity-enriched genes encoding proteins involved in, for example, one-carbon metabolism were only responsive to insulin in the women who had lost weight. Altogether, human WAT displays a selective insulin response in the obese state, where most genes are normalized by weight loss. This comprehensive atlas provides insights into the transcriptional effects of insulin in WAT and may identify targets to improve insulin action.
|
|
| 5. |
|
|
| 6. |
- Stone, VM, et al.
(author)
-
Coxsackievirus B Vaccines Prevent Infection-Accelerated Diabetes in NOD Mice and Have No Disease-Inducing Effect
- 2021
-
In: Diabetes. - : American Diabetes Association. - 1939-327X .- 0012-1797. ; 70:12, s. 2871-2878
-
Journal article (peer-reviewed)abstract
- Enteroviruses, including the Coxsackievirus Bs (CVB), have been implicated as causal agents in human type 1 diabetes. Immunization of at-risk individuals with a CVB vaccine provides an attractive strategy for elucidating the role of CVBs in the disease etiology. Previously, we have shown that an inactivated whole-virus vaccine covering all CVB serotypes (CVB1–6) is safe to administer and highly immunogenic in preclinical models, including nonhuman primates. Before initiating clinical trials with this type of vaccine, it was also important to address 1) whether the vaccine itself induces adverse immune reactions, including accelerating diabetes onset in a diabetes-prone host, and 2) whether the vaccine can prevent CVB-induced diabetes in a well-established disease model. Here, we present results from studies in which female NOD mice were left untreated, mock-vaccinated, or vaccinated with CVB1–6 vaccine and monitored for insulitis occurrence or diabetes development. We demonstrate that vaccination induces virus-neutralizing antibodies without altering insulitis scores or the onset of diabetes. We also show that NOD mice vaccinated with a CVB1 vaccine are protected from CVB-induced accelerated disease onset. Taken together, these studies show that CVB vaccines do not alter islet inflammation or accelerate disease progression in an animal model that spontaneously develops autoimmune type 1 diabetes. However, they can prevent CVB-mediated disease progression in the same model.
|
|
| 7. |
- Taddeo, EP, et al.
(author)
-
Mitochondrial Proton Leak Regulated by Cyclophilin D Elevates Insulin Secretion in Islets at Nonstimulatory Glucose Levels
- 2020
-
In: Diabetes. - : American Diabetes Association. - 1939-327X .- 0012-1797. ; 69:2, s. 131-145
-
Journal article (peer-reviewed)abstract
- Fasting hyperinsulinemia precedes the development of type 2 diabetes. However, it is unclear whether fasting insulin hypersecretion is a primary driver of insulin resistance or a consequence of the progressive increase in fasting glycemia induced by insulin resistance in the prediabetic state. Herein, we have discovered a mechanism that specifically regulates non–glucose-stimulated insulin secretion (NGSIS) in pancreatic islets that is activated by nonesterified free fatty acids, the major fuel used by β-cells during fasting. We show that the mitochondrial permeability transition pore regulator cyclophilin D (CypD) promotes NGSIS, but not glucose-stimulated insulin secretion, by increasing mitochondrial proton leak. Islets from prediabetic obese mice show significantly higher CypD-dependent proton leak and NGSIS compared with lean mice. Proton leak–mediated NGSIS is conserved in human islets and is stimulated by exposure to nonesterified free fatty acids at concentrations observed in obese subjects. Mechanistically, proton leak activates islet NGSIS independently of mitochondrial ATP synthesis but ultimately requires closure of the KATP channel. In summary, we have described a novel nonesterified free fatty acid–stimulated pathway that selectively drives pancreatic islet NGSIS, which may be therapeutically exploited as an alternative way to halt fasting hyperinsulinemia and the progression of type 2 diabetes.
|
|
| 8. |
- Yuan, Shuai, et al.
(author)
-
Is Type 2 Diabetes Causally Associated With Cancer Risk? : Evidence From a Two-Sample Mendelian Randomization Study
- 2020
-
In: Diabetes. - : AMER DIABETES ASSOC. - 0012-1797 .- 1939-327X. ; 69:7, s. 1588-1596
-
Journal article (peer-reviewed)abstract
- We conducted a two-sample Mendelian randomization study to investigate the causal associations of type 2 diabetes mellitus (T2DM) with risk of overall cancer and 22 site-specific cancers. Summary-level data for cancer were extracted from the Breast Cancer Association Consortium and UK Biobank. Genetic predisposition to T2DM was associated with higher odds of pancreatic, kidney, uterine, and cervical cancer and lower odds of esophageal cancer and melanoma but not associated with 16 other site-specific cancers or overall cancer. The odds ratios (ORs) were 1.13 (95% CI 1.04, 1.22), 1.08 (1.00, 1.17), 1.08 (1.01, 1.15), 1.07 (1.01, 1.15), 0.89 (0.81, 0.98), and 0.93 (0.89, 0.97) for pancreatic, kidney, uterine, cervical, and esophageal cancer and melanoma, respectively. The association between T2DM and pancreatic cancer was also observed in a meta-analysis of this and a previous Mendelian randomization study (OR 1.08; 95% CI 1.02, 1.14;P= 0.009). There was limited evidence supporting causal associations between fasting glucose and cancer. Genetically predicted fasting insulin levels were positively associated with cancers of the uterus, kidney, pancreas, and lung. The current study found causal detrimental effects of T2DM on several cancers. We suggest reinforcing the cancer screening in T2DM patients to enable the early detection of cancer.
|
|
| 9. |
- Zhao, Lue Ping, et al.
(author)
-
Next-Generation HLA Sequence Analysis Uncovers Seven HLA-DQ Amino Acid Residues and Six Motifs Resistant to Childhood Type 1 Diabetes
- 2020
-
In: Diabetes. - Arlington, VA, United States : AMER DIABETES ASSOC. - 0012-1797 .- 1939-327X. ; 69:11, s. 2523-2535
-
Journal article (peer-reviewed)abstract
- HLA-DQA1 and -DQB1 genes have significant and potentially causal associations with autoimmune type 1 diabetes (T1D). To follow up on the earlier analysis on high-risk HLA-DQ2.5 and DQ8.1, the current analysis uncovers seven residues (alpha a1, alpha 157, alpha 196, beta 9, beta 30, beta 57, and beta 70) that are resistant to T1D among subjects with DQ4-, 5-, 6-, and7-resistant DQ haplotypes. These 7 residues form 13 common motifs: 6 motifs are significantly resistant, 6 motifs have modest or no associations (Pvalues >0.05), and 1 motif has 7 copies observed among control subjects only. The motifs "DAAFYDG," "DAAYHDG," and "DAAYYDR" have significant resistance to T1D (odds ratios [ORs] 0.03, 0.25, and 0.18;P= 6.11 x 10(-24), 3.54 x 10(-15), and 1.03 x 10(-21), respectively). Remarkably, a change of a single residue from the motif "DAAYHDG" to "DAAYHSG" (D to S at beta 57) alters the resistance potential, from resistant motif (OR 0.15;P= 3.54 x 10(-15)) to a neutral motif (P= 0.183), the change of which was significant (FisherPvalue = 0.0065). The extended set of linked residues associated with T1D resistance and unique to each cluster of HLA-DQ haplotypes represents facets of all known features and functions of these molecules: antigenic peptide binding, peptide-MHC class II complex stability, beta 167-169 RGD loop, T-cell receptor binding, formation of homodimer of alpha-beta heterodimers, and cholesterol binding in the cell membrane rafts. Identification of these residues is a novel understanding of resistant DQ associations with T1D. Our analyses endow potential molecular approaches to identify immunological mechanisms that control disease susceptibility or resistance to provide novel targets for immunotherapeutic strategies.
|
|
| 10. |
|
|
