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Normal release of glucagon from pancreatic islet α-cells promotes glucose mobilization, which counteracts the hypoglycemic actions of insulin, thereby ensuring glucose homeostasis. In treatment of diabetes aimed at rigorously reducing hyperglycemia to avoid chronic complications, the resulting hypoglycemia triggering glucagon release from α-cells is frequently impaired, with ensuing hypoglycemic complications. This review integrates the physiology of glucagon secretion regulating glucose homeostasis in vivo to single α-cell signaling, and how both become perturbed in diabetes. α-cells within the social milieu of the islet microorgan are regulated not only by α-cellular intrinsic signaling events but also by paracrine regulation, particularly by adjacent insulin-secreting b-cell and somatostatin-secreting β-cells. We discuss the intrinsic α-cell signaling events, including glucose sensing and ion channel regulation leading to glucagon secretion. We then discuss the complex crosstalk between the islet cells and the breakdown of this crosstalk in diabetes contributing to the dysregulated glucagon secretion. Whereas there are many secretory products released by β- and δ-cells that become deficient or excess in diabetes, we discuss the major ones, including the better known insulin and lesser known somatostatin, which act as putative paracrine on/off switches that very finely regulate α- cell secretory responses in health and diabetes. Of note in several type 1 diabetes rodent models, blockade of excess somatostatin actions on α-cell could normalize glucagon secretion sufficient to attain normoglycemia in response to hypoglycemic assaults. There has been slow progress in fully elucidating the pathophysiology of α-cell in diabetes because of the small number of α- cells within an islet and the islet mass becomes severely reduced and inflamed in diabetes. These limitations are just now being surmounted by new approaches. [ABSTRACT FROM AUTHOR]

Objective: Type 2 diabetes is characterized by diminished pancreatic β-cell mass and function. Insulin signaling within the β-cells has been shown to play a critical role in maintaining the essential function of the β-cells. Under basal conditions, enhanced insulin-PI3K signaling via deletion of phosphatase with tensin homology (PTEN), a negative regulator of this pathway, leads to increased β-cell mass and function. In this study, we investigated the effects of prolonged β-cell-specific PTEN deletion in models of type 2 diabetes.Research Design and Methods: Two models of type 2 diabetes were employed: a high-fat diet (HFD) model and a db/db model that harbors a global leptin-signaling defect. A Cre-loxP system driven by the rat insulin promoter (RIP) was employed to obtain mice with β-cell-specific PTEN deletion (RIPcre(+) Pten(fl/fl)).Results: PTEN expression in islets was upregulated in both models of type 2 diabetes. RIPcre(+) Pten(fl/fl) mice were completely protected against diabetes in both models of type 2 diabetes. The islets of RIPcre(+) Pten(fl/fl) mice already exhibited increased β-cell mass under basal conditions, and there was no further increase under diabetic conditions. Their β-cell function and islet PI3K signaling remained intact, in contrast to HFD-fed wild-type and db/db islets that exhibited diminished β-cell function and attenuated PI3K signaling. These protective effects in β-cells occurred in the absence of compromised response to DNA-damaging stimuli.Conclusions: PTEN exerts a critical negative effect on both β-cell mass and function. Thus PTEN inhibition in β-cells can be a novel therapeutic intervention to prevent the decline of β-cell mass and function in type 2 diabetes. [ABSTRACT FROM AUTHOR]

Muscle from the proximal smooth muscle (SM) oesophagus of the cat demonstrates contractions of greater amplitude and greater sensitivity to cholinergic stimulation than muscle from the distal SM oesophagus. In the light of the central role of calcium influx in SM contractility, we hypothesized that regional differences in oesophageal contractility may be associated with differential expression of L-type calcium channels (LCa) along the SM oesophagus. LCa expression was compared between proximal and distal regions of the circular SM oesophagus by Western blots. Patch clamp technique was utilized to study LCa currents. Muscle strip studies assessed LCa contribution to contractile activity. The protein expression of LCa and LCa current density was greater in the proximal than distal region. LCa voltage and time-dependent activation and inactivation curves were similar in cells from both regions. Stimulation of muscle strips with acetylcholine (ACh) in the presence of tetrodotoxin resulted in contractions of greater amplitude in the proximal region. The LCa agonist Bay K 8644 caused a greater increase in ACh-induced contraction amplitude in muscle strips from the proximal region. Therefore, regional myogenic differences in LCa expression along the circular SM oesophageal body exist and may contribute to the nature of oesophageal contractions. [ABSTRACT FROM AUTHOR]

Background: To examine whether the different patterns of post-load insulin secretion can identify the heterogeneity of type 2 diabetes mellitus (T2DM)., Methods: Six hundred twenty-five inpatients with T2DM at Jining No. 1 People's Hospital were recruited from January 2019 to October 2021. The 140 g steamed bread meal test (SBMT) was conducted on patients with T2DM, and glucose, insulin, and C-peptide levels were recorded at 0, 60, 120, and 180 min. To avoid the effect of exogenous insulin, patients were categorized into three different classes by latent class trajectory analysis based on the post-load secretion patterns of C-peptide. The difference in short- and long-term glycemic status and prevalence of complications distributed among the three classes were compared by multiple linear regression and multiple logistic regression, respectively., Results: There were significant differences in long-term glycemic status (e. g., HbA1c) and short-term glycemic status (e. g., mean blood glucose, time in range) among the three classes. The difference in short-term glycemic status was similar in terms of the whole day, daytime, and nighttime. The prevalence of severe diabetic retinopathy and atherosclerosis showed a decreasing trend among the three classes., Conclusions: The post-load insulin secretion patterns could well identify the heterogeneity of patients with T2DM in short- and long-term glycemic status and prevalence of complications, providing recommendations for the timely adjustment in treatment regimes of patients with T2DM and promotion of personalized treatment., Competing Interests: The authors declare that they have no conflict of interest., (Thieme. All rights reserved.)

Precision-cut-tissues (PCTs), which preserve many aspects of a tissue's microenvironment, are typically imaged using conventional sample dishes and chambers. These can require large amounts of reagent and, when used for flow-through experiments, the shear forces applied on the tissues are often ill-defined. Their physical design also makes it difficult to image large volumes and repetitively image smaller regions of interest in the living slice. We report here on the design of a versatile microfluidic device capable of holding mouse or human pancreas PCTs for 3D fluorescence imaging using confocal and selective plane illumination microscopy (SPIM). Our design positions PCTs within a 5 × 5 mm × 140 µ m deep chamber fitted with 150 µ m tall channels to facilitate media exchange. Shear stress in the device is localized to small regions on the surface of the tissue and can be easily controlled. This design allows for media exchange at flowrates ∼10-fold lower than those required for conventional chambers. Finally, this design allows for imaging the same immunofluorescently labeled PCT with high resolution on a confocal and with large field of view on a SPIM, without adversely affecting image quality., (Creative Commons Attribution license.)

Purpose: To investigate whether non-high-density lipoprotein cholesterol (Non-HDL-C), remnant cholesterol (RC), and the ratios of lipid indexes are more closely associated with early progression of kidney dysfunction than traditional lipid indexes; and to explore the association between changes in serum lipids during follow-up and annual decline rate in estimated glomerular filtration rate (eGFR)., Methods: In this prospective cohort study, 3909 participants with normal eGFR and age≥40 years at baseline were followed for 3.3 years. Progression of kidney dysfunction was assessed as annual decline rate in eGFR. Spearman correlation analysis, linear correlation models, and multiple logistic regression were used to assess the associations between lipid indexes at baseline/both baseline and follow-up and the annual decline rate in eGFR., Results: Compared with ΔLDL-C (β = 0.412), other lipid indexes such as ΔLDL-C/HDL-C (β = 0.565), ΔTC/HDL-C (β = 0.448), and ΔNon-HDL-C/HDL-C (β = 0.448) were more closely associated with annual decline rate in eGFR. High TG/HDL-C (OR = 1.699(1.177-2.454)) and TC/HDL-C (OR = 1.567(1.095-2.243)) at baseline, as well as high TC/HDL-C (OR = 1.478 (1.003-2.177)) and TG/HDL-C (OR = 1.53(1.044-2.244)) at both baseline and follow-up were associated with the annual decline rate in eGFR <0.5. High Non-HDL-C (OR = 1.633(1.025-2.602)) and LCI (OR = 1.631(1.010-2.416)) at both baseline and follow-up resulted in a 63% increase in risk of annual decline rate in eGFR >1., Conclusion: High Non-HDL-C, RC and the ratios of lipid indexes were more closely associated with early progression of kidney injury than the increase of traditional lipid indexes. These lipid indexes should be monitored, even in participants with normal traditional serum lipid levels., (© 2022. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Adjacent membrane receptors can show different cellular responses to ligand stimulation. Here, we describe a super-resolution microscopy imaging protocol for tracking the dynamics of two different membrane-bound receptors in single cells. We describe the transfection protocol by electroporation. We detail the imaging procedure for receptors in a single cell. We then outline the data analysis pipeline. We have applied this protocol to imaging of endocytosis of the LOX-1 and AT1 in CHO-K1 cells, but the protocol can be applied to a variety of membrane receptors in other cell lines. For complete details on the use and execution of this protocol, please refer to Takahashi et al. (2021)., Competing Interests: The authors declare no competing interests., (© 2022 The Author(s).)

Introduction: Glomerular hyperfiltration (GHF) is an early kidney injury. We investigated whether GHF is associated with arterial stiffness expressed by increase of brachial-ankle pulse wave velocity (baPWV) and pulse pressure (PP), and whether the coexistence of GHF and abnormal metabolism increases the risk of arterial stiffness. Methods: In this prospective cohort study, 2,133 non-chronic kidney disease (CKD) participants aged ≥40 years were followed for a mean period of 3.3 years. The extent of arterial stiffness was expressed by measures of baPWV and PP. GHF was defined as eGFR exceeding the age- and sex-specific 90th percentile. Multivariate logistic regression models were used to assess the association between GHF/abnormal metabolism and increased baPWV/PP. The interaction indexes of GHF and abnormal metabolism on arterial stiffness were calculated based on the OR in a multivariate logistic regression model. Results: GHF alone was not associated with increased baPWV or PP in all participants in this study. However, when GHF coexisted with abnormal metabolism, the risk of increased PP increased 3.23-fold [OR = 3.23(1.47-7.13)] compared with participants with normal filtration and normal metabolism, in which the interaction accounted for 55.1% of the total effect and 79.8% of the effect from GHF and abnormal metabolism. After subtracting the independent effects of GHF and abnormal metabolism, their combined effect still resulted in a 1.78-fold increase in PP. Conclusion: GHF could interact with abnormal metabolism to significantly enhance arterial stiffness. Since abnormal metabolism commonly exists in the general population, even slight changes in renal function should be distinguished to prevent arterial stiffness risk., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Zhai, Wen, Wang, Zuo, Su, Zhang, Gaisano and He.)

Objectives: Fibrosing pancreatitis (FP) shares clinical features with autoimmune pancreatitis (AIP), although both entities have not been definitely linked. This study aimed to assess the presence of AIP criteria in an historic FP patient cohort and investigate the clinical features, management, and long-term outcomes of pediatric FP (P-FP)., Methods: Clinical data of 14 P-FP patients from Toronto and 42 P-FP cases from a literature review were collected and compared to pediatric AIP (P-AIP). Toronto P-FP patients were recontacted to assess their current health status using a brief questionnaire., Results: Jaundice and abdominal pain were the symptoms at presentation in 44 of 56 (79%) and 50 of 56 (89%) P-FP patients, respectively. Common findings on cross sectional imaging were an enlarged pancreas head with narrowing of the distal common bile duct (51/54, 94%). Histopathology mainly showed gland fibrosis (39/39, 100%). Three of twelve (25%) P-FP patients had elevated IgG4 in serum. None of the patients were treated with corticosteroids, but some underwent surgical or endoscopic intervention. Toronto patients were followed for a median of 13.6 years (interquartile range: 2.9-22.8). Complications during follow-up included exocrine pancreatic insufficiency (3/14, 21%) and pancreatic gland atrophy (5/13, 38%); but none of the patients had disease relapse or developed diabetes type 3c. Five (5/14, 36%) patients developed other immune-mediated diseases over time., Conclusions: Clinical features of patients with P-FP resembled those recently described in a subgroup of P-AIP presenting with jaundice. Long-term outcome of these patients is generally good, with or without invasive interventions. As some patients may develop exocrine pancreatic insufficiency and/or other immune-mediated diseases, ongoing clinical monitoring is recommended.

Aims: This study aimed to examine the association of different anatomical forms of obesity with adipose tissue insulin resistance and to assess the diagnostic value and contribution of obesity to adipose tissue insulin resistance., Methods: This cross-sectional study included a total of 499 subjects aged 50 years or over. Multivariate regression analysis was conducted to clarify the association of different forms of obesity with adipose tissue insulin resistance (calculated as fasting insulin level×fasting free fatty acids level). Receiver operating characteristic cure analyses were used to assess the diagnostic value of each anthropometric indicator for adipose tissue insulin resistance. Attributable risk per cent and population attributable risk per cent were calculated to assess the contribution of obesity to adipose tissue insulin resistance., Results: After adjustment for potential confounders, we showed that anthropometric indicators were all positively associated with adipose tissue insulin resistance. In males, waist circumference (WC) was the strongest associated factor (OR, 3.43 (95% CI 2.03 to 5.82)) and indicator (area under the curve (AUC): 0.79) of adipose tissue insulin resistance among those indicators. Here, abdominal obesity (WC≥90 cm) accounted for 64.9% of adipose tissue insulin resistance in the abdominal obese males. Accordingly, body mass index (BMI) was the strongest associated factor (OR,3.08 (95% CI 2.04 to 4.66)) and indicator (AUC: 0.78) of adipose tissue insulin resistance in females. Here, general obesity of BMI≥25 kg/m 2 accounted for 66.2% of the adipose tissue insulin resistance in the general obese females. We further demonstrated that adipose tissue insulin resistance was associated or trended to be associated with the metabolic diseases of cardiovascular disease, type 2 diabetes and fatty liver in subjects with normal BMI and WC., Conclusions: Maintaining WC in males and BMI in females to a normal range could be an important strategy to significantly reduce the occurrence of adipose tissue insulin resistance and the subsequent metabolic diseases., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2020. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Objective: We aimed to investigate the effects of prediabetes and its phenotypes of impaired fasting glucose (IFG), impaired glucose tolerance (IGT) and elevated glycated hemoglobin A 1 c (EHbA 1c ) on chronic kidney disease (CKD) occurrence, and define the cut-off point of each glycemic index that significantly increases the risk of CKD., Research Design and Methods: In this prospective cohort study, 6446 non-diabetic subjects aged 40 years and over were followed over a period of 3 years to track the new onset of CKD. Cox regression was used to assess the association of prediabetes and its phenotypes with CKD. Receiver operating characteristic curves were used to define the cut-off point of each glycemic index that significantly increases the occurrence of CKD. Population attributable risk percent was calculated to estimate the contribution of prediabetes to CKD., Results: Compared to subjects with normal glucose tolerance, patients with prediabetes significantly increased the risk of development of CKD (HR=2.33 (1.19-4.55)). Specifically, this increased risk of CKD development was observed in patients with IFG, IGT and EHbA 1c . The cut-off points shown to significantly increase the risk of CKD are fasting plasma glucose of 5.63 mmol/L, 2-hour plasma glucose of 6.80 mmol/L and HbA 1c of 5.6%. The contribution of prediabetes to CKD occurrence in the study population was 60.6%., Conclusions: This result suggests that the stricter criteria might be needed to define normal plasma glucose level in China that would not be predisposed to diabetic complications, particularly CKD., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2020. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

The mucus layer is the first line of innate host defense in the gut that protects the epithelium by spatially separating commensal bacteria. MUC2 mucin is produced and stored by goblet cells that is constitutively exocytosed or hyper secreted upon sensing a threat. How coordinated mucus exocytosis maintains homeostasis in the intestinal epithelium and modulates the immunological landscape remains elusive. Here we describe how the vesicle SNARE protein VAMP8 coordinates mucin exocytosis from goblet cells. Vamp8 -/- exhibit a mild pro-inflammatory state basally due to an altered mucus layer and increased encounters with microbial antigens. Microbial diversity shifts to a detrimental microbiota with an increase abundance of pathogenic and mucolytic bacteria. To alleviate the heavy microbial burden and inflammatory state basally, Vamp8 -/- skews towards tolerance. Despite this, Vamp8 -/- is highly susceptible to both chemical and infectious colitis demonstrating the fragility of the intestinal mucosa without proper mucus exocytosis mechanisms.

The intestinal immune system is emerging as an important contributor to obesity-related insulin resistance, but the role of intestinal B cells in this context is unclear. Here, we show that high fat diet (HFD) feeding alters intestinal IgA + immune cells and that IgA is a critical immune regulator of glucose homeostasis. Obese mice have fewer IgA + immune cells and less secretory IgA and IgA-promoting immune mediators. HFD-fed IgA-deficient mice have dysfunctional glucose metabolism, a phenotype that can be recapitulated by adoptive transfer of intestinal-associated pan-B cells. Mechanistically, IgA is a crucial link that controls intestinal and adipose tissue inflammation, intestinal permeability, microbial encroachment and the composition of the intestinal microbiome during HFD. Current glucose-lowering therapies, including metformin, affect intestinal-related IgA + B cell populations in mice, while bariatric surgery regimen alters the level of fecal secretory IgA in humans. These findings identify intestinal IgA + immune cells as mucosal mediators of whole-body glucose regulation in diet-induced metabolic disease.

Background: Basal and premixed insulin have been widely used for insulin therapy of type 2 diabetes mellitus (T2DM) in China. The aim of this study is to compare the sustained efficacy of basal and premixed insulin therapies in T2DM outpatients with insulin monotherapy. Materials and Methods: The survey was conducted in 602 hospitals across China from April to June in 2013. The participants included outpatients who were receiving basal or premixed insulin monotherapy for more than 3 months, and the outcome was attaining a glycated hemoglobin A1C (HbA1c) of <7.0% as a measure of sustained glycemic control. Results: A total of 49,119 T2DM outpatients on basal ( n = 11,967) or premixed insulin ( n = 37,152) monotherapy were included in the final analyses. Using multivariable model analysis, patients using premixed insulin exhibited a better glycemic control, with more outpatients achieving the target HbA1c level than those using basal insulin (model 1, OR 0.695, 95%CI 0.664-0.728; model 2, OR 0.708, 95%CI 0.676-0.742; model 3, OR 0.717, 95%CI 0.684-0.752; model 4, OR 0.750, 95%CI 0.715-0.787). Using subgroup analysis stratified by age, sex, duration of diabetes, duration of insulin treatment, and complications, still more outpatients in every subgroup treated with premixed insulin achieved the target HbA1c (HbA1c < 7%) than those receiving basal insulin. Conclusions: Premixed insulin monotherapy had a better glycemic control (HbA1c < 7.0%) than basal insulin monotherapy for Chinese T2DM outpatients in daily.

Background: Absolute handgrip strength has been correlated with metabolic profile and metabolic disease. Whether relative handgrip strength is also associated with metabolic disease has not been assessed. This study aimed at assessing the association of relative handgrip strength with metabolic profile and metabolic disease in the general population in China. Methods: Data were derived from an ongoing cross-sectional survey of the 2013 National Physical and Health in Shanxi Province, which involved 5520 participants. Multiple linear regression or multiple logistic regression analysis were used to assess the association of absolute/relative handgrip strength with the metabolic profile, preclinical, and established stages of metabolic diseases. Results: This study revealed that relative handgrip strength, that is when normalized to BMI, was associated with: (1) in both genders for more favorable blood lipid levels of high-density lipoprotein cholesterol [males: b = 0.19 (0.15, 0.23); females: b = 0.22 (0.17, 0.28)], low-density lipoprotein cholesterol [males: b = -0.14 (-0.23, -0.05); females: b = -0.19 (-0.31, -0.18)], triglycerides [males: b = -0.58 (-0.74, -0.43); females: b = -0.55 (-0.74, -0.36)] and total cholesterol [males: b = -0.20 (-0.31, -0.10); females: b = -0.19 (-0.32, -0.06)]; and better serum glucose levels in males [ b = -0.30 (-0.46, -0.15)]. (2) lower risk of impaired fasting glucose in males {third quartile [OR = 0.66 (0.45-0.95)] and fourth quartile [OR = 0.46 (0.30-0.71)] vs. first quartile} and dyslipidemia in both genders {third quartile [males: OR = 0.65 (0.48-0.87); females: OR = 0.68 (0.53-0.86)] and fourth quartile [males: OR = 0.47 (0.35-0.64); females: OR = 0.47(0.36-0.61)] vs. first quartile}. (3) lower risk of hyperlipidemia in both genders third quartile [males: OR = 0.66 (0.50-0.87); females: OR = 0.57 (0.43-0.75)] and fourth quartile [males: OR = 0.35 (0.26-0.47); females: OR = 0.51 (0.38-0.70)] vs. first quartile. However, contrary to relative handgrip strength, higher absolute handgrip strength was associated with unfavorable metabolic profiles and higher risk of metabolic diseases. These paradoxical associations were retained even after adjusted for BMI by employed a multivariate analysis. Conclusion: We conclude that measurement of relative handgrip strength can be used as a reasonable clinical predictor of metabolic health and disease.

Background: Waist circumference has been correlated with the risk of hyperuricemia. Whether neck circumference is also associated with hyperuricemia has not been assessed. This study aimed to investigate whether neck circumference is associated with hyperuricemia. Methods: This study population from Beijing is part of the larger China-wide Risk Evaluation of Cancers in Chinese Diabetic Individuals: a lONgitudinal (REACTION) study. For this Beijing sub-center cross-sectional study, a total of 8971 subjects were recruited. Gender-specific multivariable-adjusted regression analyses were conducted to analyze the association of neck circumference and waist circumference with hyperuricemia and the association of neck circumference with serum uric acid levels in the non-hyperuricemia population. Results: After adjusting for confounding variables, regression analyses showed that neck circumference was positively associated with hyperuricemia [OR, 2.61 (1.86-3.67) for males and 3.27 (2.53-4.22) for females] in both genders; further, neck circumference was also positively associated with serum uric acid levels in non-hyperuricemia subjects [b, 2.58 (1.76-3.39) for males and 4.27 (3.70-4.84) for females] in both genders. Additionally, we demonstrated that neck circumference was similar to waist circumference in terms of the strength of association (OR, 3.03 for waist circumference vs. 2.61 for neck circumference in males, and 3.50 vs. 3.27 for females) with hyperuricemia and the ability to predict hyperuricemia (AUC, 0.63 for waist circumference vs. 0.61 for neck circumference in males, and 0.66 vs. 0.66 in females). Conclusion: Neck circumference is positively and independently associated with hyperuricemia in both genders and is also associated with serum uric acid levels in the non-hyperuricemia population.

Insulin secretion plays a central role in glucose homeostasis under normal physiological conditions as well as in disease. Current approaches to study insulin granule exocytosis either use electrophysiology or microscopy coupled to the expression of fluorescent reporters. However most of these techniques have been optimized for clonal cell lines or require dissociating pancreatic islets. In contrast, the method presented here allows for real time visualization of insulin granule exocytosis in intact pancreatic islets. In this protocol, we first describe the viral infection of isolated pancreatic islets with adenovirus that encodes a pH-sensitive green fluorescent protein (GFP), pHluorin, coupled to neuropeptide Y (NPY). Second, we describe the confocal imaging of islets five days after viral infection and how to monitor the insulin granule secretion. Briefly, the infected islets are placed on a coverslip on an imaging chamber and imaged under an upright laser-scanning confocal microscope while being continuously perfused with extracellular solution containing various stimuli. Confocal images spanning 50 µm of the islet are acquired as time-lapse recordings using a fast-resonant scanner. The fusion of insulin granules with the plasma membrane can be followed over time. This procedure also allows for testing a battery of stimuli in a single experiment, is compatible with both mouse and human islets, and can be combined with various dyes for functional imaging (e.g., membrane potential or cytosolic calcium dyes).

We aimed to determine the association of indices of body composition with abnormal metabolic phenotype, and to examine whether the strength of association was differentially distributed in different age groups in normal-weight Chinese adults. A total of 3015 normal-weight adults from a survey of Chinese people encompassing health and basic physiological parameters was included in this cross-sectional study. We investigated the association of body composition measured by bioelectrical impedance analysis and conventional body indices with metabolically unhealthy normal-weight (MUHNW) adults, divided by age groups and gender. Associations were assessed by multiple logistic regression analysis. We found abnormal metabolism in lean Chinese adults to be associated with higher adiposity indices (body mass index, BMI), waist circumference, and percentage body fat), lower skeletal muscle %, and body water %. Body composition was differentially distributed in age groups within the metabolically healthy normal weight (MHNW)/MUHNW groups. The impact of factors related to MUHNW shows a decreasing trend with advancing age in females and disparities of factors (BMI, body fat %, skeletal muscle %, and body water %) associated with the MUHNW phenotype in the elderly was noticed. Those factors remained unchanged in males throughout the age range, while the association of BMI, body fat %, skeletal muscle %, and body water % to MUHNW attenuated and grip strength emerged as a protective factor in elderly females. These results suggest that increased adiposity and decreased skeletal muscle mass are associated with unfavorable metabolic traits in normal-weight Chinese adults, and that MUHNW is independent of BMI, while increased waist circumference appears to be indicative of an abnormal metabolic phenotype in elderly females.

GLP1 activates its receptor, GLP1R, to enhance insulin secretion. The activation and transduction of GLP1R requires complex interactions with a host of accessory proteins, most of which remain largely unknown. In this study, we used membrane-based split ubiquitin yeast two-hybrid assays to identify novel GLP1R interactors in both mouse and human islets. Among these, ATP6ap2 (ATPase H(+)-transporting lysosomal accessory protein 2) was identified in both mouse and human islet screens. ATP6ap2 was shown to be abundant in islets including both alpha and beta cells. When GLP1R and ATP6ap2 were co-expressed in beta cells, GLP1R was shown to directly interact with ATP6ap2, as assessed by co-immunoprecipitation. In INS-1 cells, overexpression of ATP6ap2 did not affect insulin secretion; however, siRNA knockdown decreased both glucose-stimulated and GLP1-induced insulin secretion. Decreases in GLP1-induced insulin secretion were accompanied by attenuated GLP1 stimulated cAMP accumulation. Because ATP6ap2 is a subunit required for V-ATPase assembly of insulin granules, it has been reported to be involved in granule acidification. In accordance with this, we observed impaired insulin granule acidification upon ATP6ap2 knockdown but paradoxically increased proinsulin secretion. Importantly, as a GLP1R interactor, ATP6ap2 was required for GLP1-induced Ca(2+) influx, in part explaining decreased insulin secretion in ATP6ap2 knockdown cells. Taken together, our findings identify a group of proteins that interact with the GLP1R. We further show that one interactor, ATP6ap2, plays a novel dual role in beta cells, modulating both GLP1R signaling and insulin processing to affect insulin secretion., (© 2015 by The American Society for Biochemistry and Molecular Biology, Inc.)

Zinc plays an essential role in the regulation of pancreatic β cell function, affecting important processes including insulin biosynthesis, glucose-stimulated insulin secretion, and cell viability. Mutations in the zinc efflux transport protein ZnT8 have been linked with both type 1 and type 2 diabetes, further supporting an important role for zinc in glucose homeostasis. However, very little is known about how cytosolic zinc is controlled by zinc influx transporters (ZIPs). In this study, we examined the β cell and islet ZIP transcriptome and show consistent high expression of ZIP6 (Slc39a6) and ZIP7 (Slc39a7) genes across human and mouse islets and MIN6 β cells. Modulation of ZIP6 and ZIP7 expression significantly altered cytosolic zinc influx in pancreatic β cells, indicating an important role for ZIP6 and ZIP7 in regulating cellular zinc homeostasis. Functionally, this dysregulated cytosolic zinc homeostasis led to impaired insulin secretion. In parallel studies, we identified both ZIP6 and ZIP7 as potential interacting proteins with GLP-1R by a membrane yeast two-hybrid assay. Knock-down of ZIP6 but not ZIP7 in MIN6 β cells impaired the protective effects of GLP-1 on fatty acid-induced cell apoptosis, possibly via reduced activation of the p-ERK pathway. Therefore, our data suggest that ZIP6 and ZIP7 function as two important zinc influx transporters to regulate cytosolic zinc concentrations and insulin secretion in β cells. In particular, ZIP6 is also capable of directly interacting with GLP-1R to facilitate the protective effect of GLP-1 on β cell survival., (© 2015 by The American Society for Biochemistry and Molecular Biology, Inc.)

Objective: Disruption of TCF7L2 in mouse pancreatic β-cells has generated different outcomes in several investigations. Here we aim to clarify role of β-cell TCF7L2 and Wnt signaling using a functional-knockdown approach., Methods: Adenovirus-mediated dominant negative TCF7L2 (TCF7L2DN) expression was conducted in Ins-1 cells. The fusion gene in which TCF7L2DN expression is driven by P TRE3G was utilized to generate the transgenic mouse line TCF7L2DN Tet . The double transgenic line was created by mating TCF7L2DN Tet with Ins2-rtTA, designated as βTCFDN. β-cell specific TCF7L2DN expression was induced in βTCFDN by doxycycline feeding., Results: TCF7L2DN expression in Ins-1 cells reduced GSIS, cell proliferation and expression of a battery of genes including incretin receptors and β-cell transcription factors. Inducing TCF7L2DN expression in βTCFDN during adulthood or immediately after weaning generated no or very modest metabolic defect, while its expression during embryonic development by doxycycline feeding in pregnant mothers resulted in significant glucose intolerance associated with altered β-cell gene expression and reduced β-cell mass., Conclusions: Our observations support a cell autonomous role for TCF7L2 in pancreatic β-cells suggested by most, though not all, investigations. βTCFDN is a novel model for further exploring the role of TCF7L2 in β-cell genesis and metabolic homeostasis.

Aims/hypothesis: Diabetes mellitus represents a significant burden on the health of the global population. Both type 1 and type 2 diabetes share a common feature of a reduction in functional beta cell mass. A newly discovered ubiquitination molecule HECT, UBA and WWE domain containing 1, E3 ubiquitin protein ligase (HUWE1 [also known as MULE or ARF-BP1]) is a critical regulator of p53-dependent apoptosis. However, its role in islet homeostasis is not entirely clear., Methods: We generated mice with pancreas-specific deletion of Huwe1 using a Cre-loxP recombination system driven by the Pdx1 promoter (Pdx1cre (+) Huwe1 (fl/fl)) to assess the in vivo role of HUWE1 in the pancreas., Results: Targeted deletion of Huwe1 in the pancreas preferentially activated p53-mediated beta cell apoptosis, leading to reduced beta cell mass and diminished insulin exocytosis. These defects were aggravated by ageing, with progressive further decline in insulin secretion and glucose homeostasis in older mice. Intriguingly, Huwe1 deletion provided protection against genotoxicity, such that Pdx1cre (+) Huwe1 (fl/fl) mice were resistant to multiple-low-dose-streptozotocin-induced beta cell apoptosis and diabetes., Conclusion/interpretation: HUWE1 expression in the pancreas is essential in determining beta cell mass. Furthermore, HUWE1 demonstrated divergent roles in regulating beta cell apoptosis depending on physiological or genotoxic conditions.