HDL (High-Density Lipoprotein) and ApoA-1 (Apolipoprotein A-1) Potentially Modulate Pancreatic α-Cell Glucagon Secretion

Glucagon kinetics assessed by mathematical modelling during oral glucose administration in people spanning from normal glucose tolerance to type 2 diabetes

Background/Objectives

Glucagon is important in the maintenance of glucose homeostasis, with also effects on lipids. In this study, we aimed to apply a recently developed model of glucagon kinetics to determine the sensitivity of glucagon variations (especially, glucagon inhibition) to insulin levels ("alpha-cell insulin sensitivity"), during oral glucose administration.

Subjects/Methods

We studied 50 participants (spanning from normal glucose tolerance to type 2 diabetes) undergoing frequently sampled 5-hr oral glucose tolerance test (OGTT). The alpha-cell insulin sensitivity and the glucagon kinetics were assessed by a mathematical model that we developed previously.

Results

The alpha-cell insulin sensitivity parameter (named SGLUCA; "GLUCA": "glucagon") was remarkably variable among participants (CV=221%). SGLUCA was found inversely correlated with the mean glycemic values, as well as with 2-hr glycemia of the OGTT. When stratifying participants into two groups (normal glucose tolerance, NGT, N=28, and impaired glucose regulation/type 2 diabetes, IGR_T2D, N=22), we found that SGLUCA was lower in the latter (1.50 ± 0.50·10-2 vs. 0.26 ± 0.14·10-2 ng·L-1 GLUCA/pmol·L-1 INS, in NGT and IGR_T2D, respectively, p=0.009; "INS": "insulin").

Conclusions

The alpha-cell insulin sensitivity is highly variable among subjects, and it is different in groups at different glucose tolerance. This may be relevant for defining personalized treatment schemes, in terms of dietary prescriptions but also for treatments with glucagon-related agents.

Vascular endothelial growth factor B improves impaired glucose tolerance through insulin-mediated inhibition of glucagon secretion

BACKGROUND

Impaired glucose tolerance (IGT) is a homeostatic state between euglycemia and hyperglycemia and is considered an early high-risk state of diabetes. When IGT occurs, insulin sensitivity decreases, causing a reduction in insulin secretion and an increase in glucagon secretion. Recently, vascular endothelial growth factor B (VEGFB) has been demonstrated to play a positive role in improving glucose metabolism and insulin sensitivity. Therefore, we constructed a mouse model of IGT through high-fat diet feeding and speculated that VEGFB can regulate hyperglycemia in IGT by influencing insulin-mediated glucagon secretion, thus contributing to the prevention and cure of prediabetes.

AIM

To explore the potential molecular mechanism and regulatory effects of VEGFB on insulin-mediated glucagon in mice with IGT.

METHODS

We conducted in vivo experiments through systematic VEGFB knockout and pancreatic-specific VEGFB overexpression. Insulin and glucagon secretions were detected via enzyme-linked immunosorbent assay, and the protein expression of phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) was determined using western blot. Further, mRNA expression of forkhead box protein O1, phosphoenolpyruvate carboxykinase, and glucose-6 phosphatase was detected via quantitative polymerase chain reaction, and the correlation between the expression of proteins was analyzed via bioinformatics.

RESULTS

In mice with IGT and VEGFB knockout, glucagon secretion increased, and the protein expression of PI3K/AKT decreased dramatically. Further, in mice with VEGFB overexpression, glucagon levels declined, with the activation of the PI3K/AKT signaling pathway.

CONCLUSION

VEGFB/vascular endothelial growth factor receptor 1 can promote insulin-mediated glucagon secretion by activating the PI3K/AKT signaling pathway to regulate glucose metabolism disorders in mice with IGT.

Correlation between Serum 25-Hydroxyvitamin D Concentration, Monocyte-to-HDL Ratio and Acute Coronary Syndrome in Men with Chronic Coronary Syndrome-An Observational Study

Cardiovascular disease (CVD) continues to be the leading cause of death in European men. Atherosclerosis and its clinical consequence, chronic coronary syndrome (CCS), comprise two main elements: dysfunction of lipoprotein metabolism and an important inflammatory component that contributes to the development of complications, including acute coronary syndrome (ACS). Measures of both components are combined in a composite marker called monocyte-to-HDL ratio (MHR). Vitamin D was previously described to influence inflammation processes, and its deficiency influences CVD risk factors. This research describes the differences in MHR and total serum 25-hydroxyvitamin D (25(OH)D) concentration between male patients with different diagnoses of CCS and the correlation between 25(OH)D and MHR in this group. Significant differences were observed between ACS and CCS patients in 25(OH)D and MHR-the highest HDL and serum 25(OH)D concentrations were observed in patients with CCS, whereas the highest value of MHR was observed in patients with STEMI. A significant correlation was observed between 25(OH)D, HDL, and MHR. Due to the significant but small nominal difference in MHR values between groups of patients diagnosed with ACS and CCS, and the possible influence of age and hyperlipidemia status on the differences in vitamin D levels in these groups, this subject requires further well-designed research. The suggested bidirectional relationship between MHR and 25(OH)D and the role of MHR as a predictor of vitamin D status in the body also needs to be verified.

Association between high-density lipoprotein cholesterol to apolipoprotein A ratio and diabetic retinopathy: A cross-sectional study

AIMS

Our study is aimed to investigate the relationship between high-density lipoprotein cholesterol to apolipoprotein A ratio (HDL-C/ApoA) and diabetic retinopathy (DR) in subjects with type 2 diabetes mellitus (T2DM).

METHODS

We retrospect the consecutive medical files of 1058 subjects with T2DM and recorded their clinical information and laboratory findings. Subjects with T2DM were divided into DR group (n = 522) and non-DR group (n = 536). We compared the lipids values of the two groups. Meanwhile we also observed the prevalence of DR at different HDL-C/ApoA levels. Binary logistic regression was used to correct confounding factors. Smooth curve fitting model and subgroup analysis were used to determine the correlation, non-linear relationship and threshold effect between HDL/ApoA and DR.

RESULTS

HDL-C/ApoA value of DR group was significantly higher than non-DR group (0.88 ± 0.17 vs 0.84 ± 0.13, P < 0.05). The prevalence of DR significantly increased as HDL-C/ApoA level increased. There was association between HDL/ApoA levels and DR in the adjusted models (OR 1.55, 95%CI 0.60 to 4.02). After full adjustments for other relevant clinical covariates, patients with HDL/ApoA values in quartile 3 (Q3) had 1.50 times (95 % CI 1.00 to 2.17) and in Q4 had 2.39 times (95%CI 1.65 to 3.47) as high as the risk of DR compared with patients in Q1. HDL/ApoA showed a non-linear relationship with DR, with an inflection point value of 0.759. When HDL/ApoA>0.759, HDL/ApoA was significantly positively associated with DR (HR = 26.508, 95 % CI 7.623-92.174; P < 0.0001). Compared to patients with age < 60, HDL/ApoA was obviously associated with DR when age ≥ 60 (OR = 38.05, 95 % CI 8.06-179.69; P < 0.001).

CONCLUSIONS

HDL-C/ApoA was found to be associated with the incidence of DR in patients with T2DM. After adjusting potential related factors HDL-C/ApoA OR value was 1.55 (95%CI 0.60 to 4.02). A non-linear association between HDL/ApoA and DR was observed in T2DM. Subgroup analysis showed that age could alter the relationship between HDL/ApoA and DR.

Improved HDL Cholesterol through Vitamin D Status Correction Substantially Lowers 10-Year Atherosclerotic Cardiovascular Disease Risk Score in Vitamin D-Deficient Arab Adults

This interventional study aimed to determine whether correcting vitamin D status in deficient Arab adults [25(OH)D <50 nmol/L] improves their 10-year risk of Atherosclerotic Cardiovascular Disease (ASCVD) risk scores. Saudi adults (58 males 62 females) with baseline vitamin D deficiency (<50 nmol/L) were given 50,000 IU cholecalciferol weekly for 2 months, then twice a month, followed by daily 1000 IU until month 6. Fasting blood samples were collected pre- and post-intervention and assessed for glucose, lipids, and 25(OH)D levels. The predicted 10-year ASCVD risk scores were calculated at baseline and after intervention. At baseline, significantly higher 10-year ASCDV risk scores were observed in males than females (9% vs. 3%, p < 0.001). After 6 months, only 21% (25 out of 120) achieved 25(OH)D levels above optimal level (≥75 nmol/L). While modest improvements were seen in glucose and lipid profiles, only HDL cholesterol showed favorable significant changes in all participants, which translated to significantly improved 10-year ASCVD risk scores independent of whether they achieved optimum vitamin D status. Still, those who achieved optimal vitamin D levels had a modestly larger decrease in ASCVD risk scores than those with less optimal 25(OH)D levels (-23% versus -18%) and this improvement was slightly more pronounced in males (-26% versus -10%, or 16% improvement) than females (-47% versus -32%, or 15% improvement). In conclusion, vitamin D status correction significantly enhances HDL cholesterol which prospectively reduces 10-year ASCVD risk as vitamin D levels approach optimum status among adult Arabs with baseline vitamin D deficiency. This improvement appears to be slightly more apparent in males than females.

Chemical Compounds and Ambient Factors Affecting Pancreatic Alpha-Cells Mass and Function: What Evidence?

The exposure to different substances present in the environment can affect the ability of the human body to maintain glucose homeostasis. Some review studies summarized the current evidence about the relationships between environment and insulin resistance or beta-cell dysfunction. Instead, no reviews focused on the relationships between the environment and the alpha cell, although in recent years clear indications have emerged for the pivotal role of the alpha cell in glucose regulation. Thus, the aim of this review was to analyze the studies about the effects of chemical, biological, and physical environmental factors on the alpha cell. Notably, we found studies focusing on the effects of different categories of compounds, including air pollutants, compounds of known toxicity present in common objects, pharmacological agents, and compounds possibly present in food, plus studies on the effects of physical factors (mainly heat exposure). However, the overall number of relevant studies was limited, especially when compared to studies related to the environment and insulin sensitivity or beta-cell function. In our opinion, this was likely due to the underestimation of the alpha-cell role in glucose homeostasis, but since such a role has recently emerged with increasing strength, we expect several new studies about the environment and alpha-cell in the near future.

Uncertainty quantification in variable selection for genetic fine-mapping using bayesian neural networks

In this paper, we propose a new approach for variable selection using a collection of Bayesian neural networks with a focus on quantifying uncertainty over which variables are selected. Motivated by fine-mapping applications in statistical genetics, we refer to our framework as an "ensemble of single-effect neural networks" (ESNN) which generalizes the "sum of single effects" regression framework by both accounting for nonlinear structure in genotypic data (e.g., dominance effects) and having the capability to model discrete phenotypes (e.g., case-control studies). Through extensive simulations, we demonstrate our method's ability to produce calibrated posterior summaries such as credible sets and posterior inclusion probabilities, particularly for traits with genetic architectures that have significant proportions of non-additive variation driven by correlated variants. Lastly, we use real data to demonstrate that the ESNN framework improves upon the state of the art for identifying true effect variables underlying various complex traits.

HDL Cholesterol and Non-Cardiovascular Disease: A Narrative Review

High density lipoprotein (HDL) cholesterol has traditionally been considered the “good cholesterol”, and most of the research regarding HDL cholesterol has for decades revolved around the possible role of HDL in atherosclerosis and its therapeutic potential within atherosclerotic cardiovascular disease. Randomized trials aiming at increasing HDL cholesterol have, however, failed and left questions to what role HDL cholesterol plays in human health and disease. Recent observational studies involving non-cardiovascular diseases have shown that high levels of HDL cholesterol are not necessarily associated with beneficial outcomes as observed for age-related macular degeneration, type II diabetes, dementia, infection, and mortality. In this narrative review, we discuss these interesting associations between HDL cholesterol and non-cardiovascular diseases, covering observational studies, human genetics, and plausible mechanisms.

High Density Lipoproteins and Diabetes

Epidemiological studies have established that a high plasma high density lipoprotein cholesterol (HDL-C) level is associated with reduced cardiovascular risk. However, recent randomised clinical trials of interventions that increase HDL-C levels have failed to establish a causal basis for this relationship. This has led to a shift in HDL research efforts towards developing strategies that improve the cardioprotective functions of HDLs, rather than simply increasing HDL-C levels. These efforts are also leading to the discovery of novel HDL functions that are unrelated to cardiovascular disease. One of the most recently identified functions of HDLs is their potent antidiabetic properties. The antidiabetic functions of HDLs, and recent key advances in this area are the subject of this review. Given that all forms of diabetes are increasing at an alarming rate globally, there is a clear unmet need to identify and develop new approaches that will complement existing therapies and reduce disease progression as well as reverse established disease. Exploration of a potential role for HDLs and their constituent lipids and apolipoproteins in this area is clearly warranted. This review highlights focus areas that have yet to be investigated and potential strategies for exploiting the antidiabetic functions of HDLs.