Increased circulating levels of betatrophin in individuals with long-standing type 1 diabetes

Brain-acting hepatokines: its impact on energy balance and metabolism

The liver is recognized for its central role in energy metabolism, yet emerging evidence highlights its function as an endocrine organ, secreting a variety of proteins-hepatokines-that influence distant tissues. Hepatokines not only regulate metabolic processes by acting on peripheral tissues but also exert direct effects on brain function. In this mini-review, we discuss the existing literature on the role of "brain-acting" hepatokines including IGF-1, FGF21, LEAP2, GDF15, and ANGPTLs, and their impact on energy balance and metabolism. We review the existing evidence regarding their roles in metabolism through their action in the brain, and their potential implications in metabolic disturbances. By integrating insights from recent studies, we aim to provide a comprehensive understanding of how liver-derived signals can modulate energy balance and metabolism.

Alterations in serum concentrations of visfatin and betatrophin in dogs with diabetes mellitus

Canine diabetes mellitus (DM) is associated with hyperglycemia and hyperlipidemia. Visfatin and betatrophin are adipokines involved in the pathophysiology of insulin resistance and deranged lipid metabolism, and are also altered in obesity. We hypothesized that visfatin and betatrophin serum concentrations are altered in diabetic dogs, irrespective of their body condition. The study included 23 newly-diagnosed DM (NDDM) dogs, 34 insulin-treated DM (ITDM) dogs and 24 healthy dogs. Body condition score was determined and fasted serum samples were collected for measurement of betatrophin, visfatin and insulin serum concentrations. Visfatin concentrations (mean, 95% CI) were lower in overweight NDDM (4.5 ng/mL, 2.5-8.1, P=0.05) and ITDM (2.8 ng/mL 1.8-4.3, P=0.006) than healthy (7.7 ng/mL, 5.0-11.7) dogs, but were not different among lean dogs, and were negatively correlated to betahydroxybutyric acid in ITDM dogs (r=-0.59, P=0.05). Betatrophin concentrations were lower in NDDM (69 pg/mL, 43-112, P<0.001) and ITDM (53 pg/mL, 34-84, P<0.001) than healthy (267 pg/mL, 167-426) dogs. Among NDDM dogs, betatrophin concentrations were higher in those with concurrent liver disease (203 pg/mL, 49-844) than those with no evidence of liver disease (19 pg/mL, 4-90, P=0.007), and were negatively correlated with glucose concentrations (r=-0.44, P=0.04) and creatinine (r=-0.60, P=0.003). Insulin concentrations were not different among NDDM and healthy dogs. Among NDDM dogs, insulin concentrations were negatively correlated to concentrations of betahydroxybutyric acid (r=-0.65, P=0.002) and were lower in dogs with concurrent kidney disease (5.6 mU/L, 2.1-15.3) compared to those with no evidence of kidney disease (20.6 mU/L, 8.0-53.2, P=0.018). In conclusion, DM in dogs is associated with alteration in visfatin and betatrophin concentrations that are not resolved by insulin treatment.

Dyslipidemia and ANGPTL8 evaluation in young females with Type 1 diabetes mellitus

PURPOSE

ANGPTL8, commonly referred to as betatrophin, has demonstrated promise as a dependable marker for the onset of complications associated with diabetes mellitus, such as dyslipidemia. The objective of this study is to evaluate the lipid profile and ANGPTL8 levels in people diagnosed with Type 1 Diabetes Mellitus (T1DM).

METHODS

A retrospective case-control study was performed on a group of 100 adolescent females, aged 13-17 years. This group consisted of individuals diagnosed with T1DM from the Diabetes and Endocrine Department at Medina's King Fahad Hospital in Saudi Arabia. Additionally, 100 healthy adolescent females of the same age range were included as controls. The hospital conducted laboratory studies to evaluate glucose, HbA1c, insulin, and lipid profiles. The ANGPTL8 levels were quantified using Enzyme-Linked Immunosorbent Assay (ELISA).

RESULTS

Patients with T1DM had ANGPTL8 levels that were twice as high as those observed in individuals without any health conditions. The two groups had contrasting levels of fasting blood glucose (FBG), glycated hemoglobin (HbA1c), C-peptides, triacylglycerol (TG), and cholesterol, along with elevated Atherogenic Index of Plasma readings. Diabetes mellitus patients had considerably elevated values compared to the control group. There was a significant correlation between ANGPTL8 concentrations and lipid abnormalities, with P-values less than 0.05. 56% of the 100 patients exhibited dyslipidemia. The research found a correlation between dyslipidemia and elevated levels of ANGPTL8 in diabetic patients. The concentration of ANGPTL8 had a positive correlation with glucose, HbA1c, TG, and C-peptides while displaying a negative correlation with high-density lipoprotein cholesterol (HDL-C).

CONCLUSION

ANGPTL8 levels were found to be elevated in Saudi young women who were diagnosed with TIDM. ANGPTL8 may potentially contribute to dyslipidemia in individuals with T1DM, hence increasing the susceptibility to cardiovascular disease (CVD). Therefore, ANGPTL8 has the potential to impact lipid metabolism, namely Triglycerides, as a biological route. The results highlight the need to analyze lipid profiles and do ANGPTL8 testing in young females diagnosed with T1DM at an early stage to prevent complications.

Metabolic Crosstalk between Liver and Brain: From Diseases to Mechanisms

Multiple organs and tissues coordinate to respond to dietary and environmental challenges. It is interorgan crosstalk that contributes to systemic metabolic homeostasis. The liver and brain, as key metabolic organs, have their unique dialogue to transmit metabolic messages. The interconnected pathogenesis of liver and brain is implicated in numerous metabolic and neurodegenerative disorders. Recent insights have positioned the liver not only as a central metabolic hub but also as an endocrine organ, capable of secreting hepatokines that transmit metabolic signals throughout the body via the bloodstream. Metabolites from the liver or gut microbiota also facilitate a complex dialogue between liver and brain. In parallel to humoral factors, the neural pathways, particularly the hypothalamic nuclei and autonomic nervous system, are pivotal in modulating the bilateral metabolic interplay between the cerebral and hepatic compartments. The term "liver-brain axis" vividly portrays this interaction. At the end of this review, we summarize cutting-edge technical advancements that have enabled the observation and manipulation of these signals, including genetic engineering, molecular tracing, and delivery technologies. These innovations are paving the way for a deeper understanding of the liver-brain axis and its role in metabolic homeostasis.

Overview of the impact of sleep monitoring on optimal performance, immune system function and injury risk reduction in athletes: A narrative review

Sleep is essential for a range of physiological and mental functions in professional athletes. There is proof that athletes may experience lower quality and quantity of sleep. While adequate sleep has been shown to have restorative effects on the immune system and endocrine system, facilitate nervous system recovery and the metabolic cost of wakefulness, and play a significant role in learning, memory, and synaptic plasticity, which can affect sports recovery, injury risk reduction, and performance. Sports performance may suffer significantly from a lack of sleep, especially under maximal and long-term exercise. Due to the potential harm, these factors may do to an athlete's endocrine, metabolic, and nutritional health, sports performance is impacted by reduced sleep quality or quantity. There are several neurotransmitters associated with the sleep-wake cycle that have been discovered. They comprise cholinergic hormone, orexin, melanin, galanin, serotonin, gamma-aminobutyric acid, histamine, and serotonin. Therefore, dietary modifications that affect the neurotransmitters in the brain also may affect sleep; particularly for athletes who require more physical and psychological recovery owing to the tremendous physiological and psychological demands placed on them during training and performance. This review explores the variables that influence the quantity and quality of sleep-in populations of athletes and assesses their possible effects. In addition, several recommendations for improving sleep are presented. Even though there has been much research on variables that impact sleep, future studies may highlight the significance of these aspects for athletes.

Associations of Betatrophin/ANGPTL8 with Septic Dyslipidemia in Human Peritonitis: An Explorative Analysis

Sepsis is defined by life-threatening organ dysfunction mediated by the host’s response to infection. This can result in septic dyslipidemia, which is involved in the neutralization of pathogen-related lipids. Knowledge of the regulatory mechanisms of septic dyslipidemia is incomplete. The cytokine betatrophin/Angiopoietin-like protein 8 (ANGPTL8) plays a role in the regulation of triacylglyceride metabolism, though its function in septic dyslipidemia remains unknown. Sixty-six patients were enrolled in a cross-sectional study. Circulating concentrations and adipose tissue (AT) mRNA expression of betatrophin/ANGPTL8 were studied in patients suffering from peritoneal sepsis. Insulin-resistant individuals and subjects without metabolic derangement/systemic inflammation were enrolled as controls. All underwent open abdominal surgery. Circulating betatrophin/ANGPTL8 was analyzed by an enzyme-linked immunosorbent assay and AT mRNA expression levels were assessed by real-time PCR. Standard laboratory analyses including lipid electrophoresis were evaluated. Sepsis patients showed pronounced septic dyslipidemia (p < 0.05 for all major lipid classes). Despite comparable betatrophin/ANGPTL8 mRNA expression in AT (p = 0.24), we found significantly increased circulating betatrophin/ANGPTL8 with septic dyslipidemia (p = 0.009). Expression levels of betatrophin/ANGPTL8 in AT correlated with circulating concentrations in both control groups (r = 0.61; p = 0.008 and r = 0.43; p = 0.034), while this association was undetectable in sepsis. After stratification, betatrophin/ANGPTL8 remained associated with hypertriacylglyceridemia (p < 0.05).

Effect of physical activity in a weight loss program on circulating total ANGPTL8 concentrations in northern Americans with obesity: A prospective randomized controlled trial

BACKGROUND AND AIMS

The primary goals of this study were to clarify 1) the effect of weight loss by lifestyle intervention on circulating total angiopoietin-like protein 8 (ANGPTL8), and 2) the role of physical activity on serum total ANGPTL8 in northern Americans with obesity but without diabetes.

METHODS AND RESULTS

A total of 130 subjects with body mass index (BMI) ≧ 35 kg/m² but without diabetes were recruited, and 121 subjects completed a weight loss program for data analysis. Abdominal adipose tissue was determined by non-contrast computed tomography (CT). Serum total ANGPTL8 was higher in the group with obesity than in the lean control group. Serum total ANGPTL8 was positively correlated with waist circumference (WC), BMI, fasting insulin, HOMA-IR, HOMA-B, QUICKI, hs-CRP, IL-6, and leptin. Serum total ANGPTL8 did not significantly differ between the two intervention groups at baseline, and it was significantly lower after weight loss, with comparable changes with diet only and diet plus physical activity.

CONCLUSION

Among northern Americans with obesity but without diabetes, a lifestyle modification resulted in significant reduction of circulating total ANGPTL8 concentrations in a 6-month weight-loss period. Although addition of physical activity resulted in greater total and liver fat loss, it did not promote further significant decline of serum total ANGPTL8 beyond diet alone.

How low is really low? Comparison of two C-peptide assays to establish residual C-peptide production in type 1 diabetes

INTRODUCTION

C-peptide is an important marker to assess residual insulin production in individuals with type 1 diabetes (T1D). The accuracy and detection limits of C-peptide assays are important to detect C-peptide microsecretion and to reliably observe changes over time in these people. We compared and verified two commercially available assays able to measure C-peptide in the picomolar range.

METHODS

The ultrasensitive Mercodia enzyme-linked immunosorbent C-peptide assay (ELISA) was compared with the Beckman immunoradiometric assay (IRMA) for C-peptide, assessing reproducibility (coefficient of variation [CV]), limit of blank (LoB), limit of detection (LoD) and limit of quantitation (LoQ).

RESULTS

For both assays within-run and between-run variation were high at the low (around the detection limit) C-peptide concentration range, with CVs of around 40%. LoB values for the ultrasensitive ELISA and the IRMA were 1.3 and 0.16 pmol/L respectively. LoD values were 2.4 and 0.54 pmol/L respectively. LoQ values were 9.7 and 3.8 pmol/L respectively. Only the IRMA met the specifications claimed by the manufacturer.

CONCLUSIONS

The IRMA provided the lowest threshold for quantification of serum C-peptide. LoQ of commercially available assays should be established in-house before applying them in research studies and clinical trials in which low C-peptide levels have clinical or scientific relevance.

ANGPTL8 in metabolic homeostasis: more friend than foe?

ANGPTL8 is an important cytokine, which is significantly increased in type 2 diabetes mellitus (T2DM), obesity and metabolic syndrome. Many studies have shown that ANGPTL8 can be used as a bio-marker of these metabolic disorders related diseases, and the baseline ANGPTL8 level has also been found to be positively correlated with retinopathy and all-cause mortality in patients with T2DM. This may be related to the inhibition of lipoprotein lipase activity and the reduction of circulating triglyceride (TG) clearance by ANGPTL8. Consistently, inhibition of ANGPTL8 seems to prevent or improve atherosclerosis. However, it is puzzling that ANGPTL8 seems to have a directing function for TG uptake in peripheral tissues; that is, ANGPTL8 specifically enhances the reserve and buffering function of white adipose tissue, which may alleviate the ectopic lipid accumulation to a certain extent. Furthermore, ANGPTL8 can improve insulin sensitivity and inhibit hepatic glucose production. These contradictory results lead to different opinions on the role of ANGPTL8 in metabolic disorders. In this paper, the correlation between ANGPTL8 and metabolic diseases, the regulation of ANGPTL8 and the physiological role of ANGPTL8 in the process of glucose and lipid metabolism were summarized, and the physiological/pathological significance of ANGPTL8 in the process of metabolic disorder was discussed.

Down-regulation of betatrophin enhances insulin sensitivity in type 2 diabetes mellitus through activation of the GSK-3β/PGC-1α signaling pathway

OBJECTIVE

The incidence of type 2 diabetes mellitus (T2DM) among children and adolescents has been rising. Accumulating evidences have noted the significant role of betatrophin in the regulation of lipid metabolism and glucose homeostasis. In our study, we tried to figure out the underlying mechanism of betatrophin in insulin resistance (IR) in type 2 diabetes mellitus (T2DM).

METHODS

First, fasting serum betatrophin, fasting blood glucose (FBG), insulin, total cholesterol (TC), triglyceride (TG), and low-density lipoprotein cholesterol (LDL-C) were detected in T2DM children. The homeostasis model assessment of insulin resistance (HOMA-IR), Gutt insulin sensitivity index (ISI_G) and Matsuda insulin sensitivity index (ISI_M) were calculated. A T2DM-IR mouse model was induced by high-fat diet, with the expression of GSK-3β and PGC-1α detected. Besides, HepG2 cells were induced by a high concentration of insulin to establish an IR cell model (HepG2-IR). The cell viability, glucose consumption, liver glycogen content, inflammation, and fluorescence level of GSK-3β and PGC-1α were analyzed.

RESULTS

Betatrophin was highly expressed in serum of T2DM children and was positively correlated with FBG, insulin, TC, TG, LDL-C and HOMA-IR, while negatively correlated with ISI_G and ISI_M. Betatrophin and GSK-3β in the liver tissues of T2DM-IR mice were increased, while the PGC-1α expression was decreased. Betatrophin expression was negatively correlated with PGC-1α and positively correlated with GSK-3β. Silencing of betatrophin enhanced insulin sensitivity through the activation of GSK-3β/PGC-1α signaling pathway. In vitro experiments also found that silencing of betatrophin promoted glucose consumption and glycogen synthesis while inhibited inflammation.

CONCLUSION

Our findings concluded that silencing of betatrophin could enhance insulin sensitivity and improve histopathological morphology through the activation of GSK-3β/PGC-1α signaling pathway.

Betatrophin Levels Are Related to the Early Histological Findings in Nonalcoholic Fatty Liver Disease

Betatrophin, a liver hormone, regulates glucose and lipid metabolism. We investigated the betatrophin levels in nonalcoholic fatty liver disease (NAFLD) and searched for any relationship with histological severity and metabolic parameters. Fifty males with NAFLD [Nonalcoholic Steatohepatitis (NASH) (n = 32); non-NASH (n = 18)] and 30 healthy controls were included. Plasma betatrophin was measured by ELISA method. Insulin sensitivity was assessed by HOMA-IR index. Histological features were scored by the semi quantitative classification and combined as the NAFLD activity score (NAS). Betatrophin levels in the non-NASH group were significantly higher than the controls. Betatrophin was positively correlated to the age, waist circumference, total cholesterol, triglycerides, LDL cholesterol, glucose, insulin, HOMA-IR index and gamma glutamyl transpeptidase levels, and negatively correlated to the steatosis and NAS. In the stepwise linear regression analysis, the triglyceride (β = 0.457, p < 0.001), glucose (β = 0.281, p = 0.02) and NAS (β = -0.260, p = 0.03) were the independent determinants of betatrophin. Betatrophin levels are higher in the early stages of NAFLD and tend to decrease when the disease progresses. This could be an important preliminary mechanistic finding to explain the increased frequency of glucose intolerance during the course of NAFLD.

ANGPTL8 roles in proliferation, metabolic diseases, hypothyroidism, polycystic ovary syndrome, and signaling pathways

A new and atypical member of the ANGPTL family is angiopoietin-like protein 8 (ANGPTL8). This newly discovered hormone is a drug target that can be used to treat diabetes and dyslipidemia. The protein, as a hepatocyte-derived circulating factor, can control the triglyceride level of plasma. ANGPTL8 is significantly associated with inflammation and metabolic syndrome consequences such as obesity, diabetes, hypothyroidism, and PCOS. ANGPTL8 gene has four exons encoding a 22/5 kDa weight of 198 amino acid polypeptides. A highly preserved ANGPTL8 gene among mammals exhibits the essential hormone functions of ANGPTL8. Nevertheless, the physiological function of this hormone in the body is poorly understood. Studies published in PubMed (2008-2020), Google Scholar (2004-2020), and Scopus (2004-2020) databases of clinical trials were reviewed. This analysis is aimed at collecting information on ANGPTL8. The emphasis of this review was on gathering information about the role of ANGPTL8 in the metabolism of glucose and lipids and cell proliferation. It addition to the different roles of ANGPTL8 in diabetes and lipid metabolism, this review emphasized on the protein role in signaling pathways. The study also proposes the signaling pathways that may be considered as a new target for treatment.

The role of serum β-trophin and endostatin in patients with polycystic ovary syndrome: Are they correlated?

Background

It’s necessary to investigate the serum β-trophin and endostatin (ES) level and its influencing factors in patients with newly diagnosed polycystic ovary syndrome (PCOS).

Methods

Newly diagnosed PCOS patients treated in our hospital were selected, and healthy women who took physical examination during the same period as healthy controls. We detected and compared the related serum indicators between two groups, Pearson correlation were conducted to identify the factors associated with β-trophin and ES, and the influencing factors of β-trophin and ES were analyzed by logistic regression.

Results

A total of 62 PCOS patients and 65 healthy controls were included. The BMI, WHI, LH, FSH, TT, FAI, FBG, FINS, HOMA-IR, TC, TG, LDL, ES in PCOS patients were significantly higher than that of healthy controls, while the SHBG and HDL in PCOS patients were significantly lower than that of healthy controls (all p < 0.05). β-trophin was closely associated with BMI (r = 0.427), WHR (r = 0.504), FBG (r = 0.385), TG (r = 0.405) and LDL (r = 0.302, all p < 0.05), and ES was closely associated with BMI (r = 0.358), WHR (r = 0.421), FBG (r = 0.343), TC (r = 0.319), TG (r = 0.404, all p < 0.05). TG, BMI, WHR and FBG were the main factors affecting the serum β-trophin levels (all p < 0.05). FBG, TC and BMI were the main factors affecting the serum ES levels (all p < 0.05). The TG, β-trophin, ES level in PCOS patients with insulin resistance (IR) were significantly higher than that of those without IR (all p < 0.05).

Conclusion

Increased β-trophin is closely associated with increased ES in patients with PCOS, which may be the useful indicators for the management of PCOS.

Circulating micro RNA-223 and angiopoietin-like protein 8 as biomarkers of gestational diabetes mellitus

BACKGROUND

Gestational diabetes mellitus (GDM) is a serious health problem associated with both foetal and maternal complications. New biomarkers that can predict or help in the early diagnosis of GDM are needed to minimize the hazards of hyperglycaemia in pregnant women and their offspring. We hypothesised a link between levels of microRNA-223 (miRNA-223) and Angiopoietin-Like Protein 8 (ANGPTL8) and GDM.

MATERIALS AND METHODS

The study included 109 patients with confirmed early diagnosed GDM and 103 healthy control pregnant women in their second or third trimester. miRNA-223 and ANGPTL8 blood levels were assessed by real-time RT-PCR and sandwich ELISA, respectively, laboratory markers by standard methods.

RESULTS

There was a significant increase in mean [SD] miRNA-223 and ANGPTL8 in GDM (0.31 [0.06] relative units) and (692 [199] pg/ml), respectively, in the GDM women compared to healthy pregnant women (0.17[0.05] relative units) and (261 [127] pg/ml), respectively, P  < 0.001. miRNA-223 and ANGPTL8 correlated significantly with each other (r = 0.38, P  < 0.001) and with fasting, 1-h and 2-h postprandial blood glucose levels (all P ≤ 0.002) HbA1 c (P  < 0.025), total cholesterol (P < 0.01), LDL-C and triglycerides (both P ≤ 0.005). The ROC area under curve (AUC) (95%CI) was 0.94 (0.91-0.97) for ANGPTL8, 0.92 (0.88-0.96) for miRNA-223 and 0.97 (0.95 - 0.99) for their combination.

CONCLUSIONS

These findings support the hypothesis of involvement of both miRNA-223 and ANGPTL8 in the pathogenesis of GDM. The difference between levels in GDM patients and in control pregnant women indicates potential use for early diagnosis or prediction of GDM.

Correlation of serum betatrophin levels with disease severity and the emergence of insulin resistance in cirrhotic patients

Background

Insulin resistance (IR) is frequently associated with chronic liver disease. There has been an increased interest in betatrophin protein and its involvement in the compensatory response to IR. We aimed to investigate the correlation of serum betatrophin levels with disease severity and the emergence of IR in cirrhotic patients. This study included 27 cirrhotic patients and 30 healthy participants who served as a control group. IR was assessed by the Homeostasis Model Assessment (HOMA-IR). Serum insulin and betatrophin levels were measured using Enzyme-Linked Immunosorbent Assay (ELISA).

Results

IR was existing in 74% of cirrhotic patients (p < 0.001). Subjects with IR had higher serum betatrophin levels than those without IR (p = 0.04). Serum betatrophin levels were significantly higher in cirrhotic patients than controls (p < 0.001). In addition, Child-Pugh class C patients had higher serum betatrophin levels than those with Child-Pugh class B cirrhosis (p = 0.01). Moreover, the highest serum betatrophin levels were detected in patients with tense ascites followed by those with moderate and mild ascites (p = 0.01). In the cirrhosis group, serum betatrophin levels correlated positively with fasting blood glucose levels (p < 0.001), fasting insulin levels (p = 0.006), HOMA-IR (p = 0.006), Child-Pugh score (p = 0.023), MELD score (p < 0.001), and INR (p = 0.005), and correlated negatively with platelets count (p = 0.01).

Conclusion

Cirrhotic patients have higher serum betatrophin levels; moreover, these levels are positively correlated with disease severity as well as the emergence of insulin resistance.

Effects of vitamin D on apoptosis and betatrophin in the kidney tissue of experimental diabetic rats

The aim of this study is to investigate the effects of vitamin D on betatrophin and apoptosis in rats kidney tissue using an experimental diabetes model created with streptozotocin (STZ). 41 male Wistar-albino breed rats were assigned to 5 groups, which included 3 groups consisting of 7 animals each and 2 groups consisting of 10 animals each. The control group received no treatments. Single-dose 0.1 M sodium buffer was administered ip to the Buffer group. The Vitamin D group was orally administered 200 IU/day vitamin D. The Diabetes group was injected ip with single-dose 50 mg/kg STZ by dissolving the material in 0.1 M sodium buffer. Subjects with a glucose level exceeding 250 mg/dl were accepted to be diabetic. The Diabetes + Vitamin D group was injected ip with 50 mg/kg single-dose STZ by dissolving the material in 0.1 M sodium buffer. Once diabetes was established, 200 IU/day vitamin D was administered orally. Rats in all groups were decapitated in the end of the experiment, their kidney tissues were promptly extracted and TUNEL stained with immunohistochemistry. Additionally, serum samples acquired from all groups were evaluated with regard to total antioxidant status (TAS) and total oxidant status (TOS) levels. The histological and biochemical analyses of the Control, Buffer, and Vitamin D groups revealed similar serum TOS and TAS levels, and TUNEL positivity and betatrophin immunoreactivity. While the Diabetes group showed significantly higher TOS levels and TUNEL positivity compared to the Control group, their TAS levels and betatrophin immunoreactivity were significantly reduced. The Diabetes+Vitamin group demonstrated significantly lower TOS levels and TUNEL positivity compared to the Diabetic group, and their TAS levels and betatrophin immunoreactivity increased significantly. In conclusion; experimental diabetes was found to increase TOS and apoptotic cells and decrease TAS and betatrophin levels in kidney tissue in experimental diabetes, and that administering VitD as treatment caused a decrease in TOS and apoptotic cells and an increase in TAS and betatrophin levels. It was concluded that future studies needed to investigate various experimental diabetes times so that the role of diabetes in the pathophysiology of its effect on kidney tissue could be uncovered. (www.actabiomedica.it)

Betatrophin is downregulated in pregnant women with a history of RYGB operation and a high risk of postprandial hypoglycaemia

Betatrophin is a liver and adipose tissue-derived protein which has recently been linked to glucose metabolism. So far, no data exist about the role of betatrophin in pregnant women with a history of Roux-En-Y gastric bypass (RYGB) operation with a high risk of postprandial hypoglycaemia. In this prospective clinical study, an oral glucose tolerance test (OGTT) and an intravenous glucose tolerance test (IVGTT) were performed between the 24th and 28th week of pregnancy and 3–6 months post-partum in a cohort of obese and normal-weight pregnant women, as well as in women with a history of RYGB operation. In the cohort of pregnant women with RYGB and exaggerated risk of postprandial hypoglycaemic events, basal and dynamic betatrophin levels during the OGTT were lower than in the obese or normal-weight pregnant women (basal levels: 13.66 ± 5.88 vs. 19.03 ± 4.15 vs. 15.68 ± 6.48, p = 0.016; OGTT 60′: 13.33 ± 5.40 vs. 17.37 ± 3.16 vs. 15.84 ± 4.99, p = 0.030). During the OGTT, basal and dynamic betatrophin levels at 60′ were positively associated with glucose levels at 60 min (r = 0.55, p = 0.01 and r = 0.45, p = 0.039). This positive association was followed by significant hypoglycaemic events in the RYGB group. It was only in the RYGB group that betatrophin was negatively related to the disposition index (rho = -0.53, p = 0.014). After pregnancy there was a decrease in basal and stimulated betatrophin levels during the OGTT in all three patient groups. In comparison to normal-weight and obese pregnant women, women with a history of RYGB operation and a high risk of postprandial hypoglycaemic events have lower levels of betatrophin. This indicate a mechanistic role in order to decrease the risk of postprandial hypoglycaemia in this specific cohort.

The circulating ANGPTL8 levels show differences among novel subgroups of adult patients with diabetes and are associated with mortality in the subsequent 5 years

ANGPTL8, an important regulator of glucose and lipid metabolism, is associated with diabetes, but the role of ANGPTL8 in the outcomes of novel subgroups of diabetes remains unclear. To assess the circulating ANGPTL8 levels in novel subgroups of diabetes and their association with health outcomes, we performed a data-driven cluster analysis (k-means) of patients with newly diagnosed diabetes (741 patients enrolled from 2011 through 2016) from the Risk Evaluation of Cancers in Chinese Diabetic Individuals: a longitudinal (REACTION) study. The primary outcomes were mortality from all causes and cardiovascular diseases (CVD), and the secondary outcome was any cardiovascular event. Comparisons among groups were performed using the Kruskal-Wallis test, and the correlations between variables were assessed using the Pearson correlation test. Logistic regression was used to detect associations between the risk of outcomes and the ANGPTL8 levels. We identified four replicable clusters of patients with diabetes that exhibited significantly different patient characteristics and risks of all-cause mortality. The serum ANGPTL8 levels in the cluster of mild age-related diabetes (MARD), severe insulin-resistant diabetes (SIRD), and severe insulin-deficient diabetes (SIDD) were significantly higher than those in the mild obesity-related diabetes (MOD) cluster (685.01 ± 24.50 vs. 533.5 ± 18.39, p < 0.001; 649.69 ± 55.83 vs. 533.5 ± 18.39, = 0.040; 643.29 ± 30.89 vs. 533.5 ± 18.39, p = 0.001). High circulating ANGPTL8 levels were more highly associated with a greater hazard of all-cause mortality (quartile 4 vs 1: risk ratio [RR] 3.23, 95% CI 1.13-9.22; per unit increase in the Z score: RR 1.53, 95% CI 1.17-2.01) than low circulating ANGPTL8 levels. In conclusion, this 5-year follow-up REACTION study revealed that the circulating ANGPTL8 levels show differences among novel subgroups of adult patients with diabetes and are associated with all-cause mortality in the subsequent 5 years.

Transcriptional Regulation of the Angptl8 Gene by Hepatocyte Nuclear Factor-1 in the Murine Liver

Brief refeeding times (~60 min) enhanced hepatic Angptl8 expression in fasted mice. We cloned the mouse Angptl8 promoter region to characterise this rapid refeeding-induced increase in hepatic Angptl8 expression. Deletion of the −309/−60 promoter region significantly attenuated basal promoter activity in hepatocytes. A computational motif search revealed a potential binding motif for hepatocyte nuclear factor 1α/1β (HNF-1α/β) at −84/−68 bp of the promoter. Mutation of the HNF-1 binding site significantly decreased the promoter activity in hepatocytes, and the promoter carrying the mutated HNF-1 site was not transactivated by co-transfection of HNF-1 in a non-hepatic cell line. Silencing Hnf-1 in hepatoma cells and mouse primary hepatocytes reduced Angptl8 protein levels. Electrophoretic mobility-shift assays confirmed direct binding of Hnf-1 to its Angptl8 promoter binding motif. Hnf-1α expression levels increased after short-term refeeding, paralleling the enhanced in vivo expression of the Angptl8 protein. Chromatin immunoprecipitation (ChIP) confirmed the recruitment of endogenous Hnf-1 to the Angptl8 promoter region. Insulin-treated primary hepatocytes showed increased expression of Angptl8 protein, but knockdown of Hnf-1 completely abolished this enhancement. HNF-1 appears to play essential roles in the rapid refeeding-induced increases in Angptl8 expression. HNF-1α may therefore represent a primary medical target for ANGPTL8-related metabolic abnormalities. The study revealed the transcriptional regulation of the mouse hepatic Angptl8 gene by HNF-1.

Evaluation of second-trimester maternal serum betatrophin levels and lipid and carbohydrate metabolism parameters in patients with gestational diabetes mellitus

Objective:

We investigated the role of betatrophin in the etiopathogenesis of gestational diabetes mellitus (GDM) and its association with lipid and carbohydrate metabolism in patients with GDM and normoglycemic pregnant women.

Materials and Methods:

A total of 60 patients [30 pregnant women with GDM (study group) and 30 healthy age-, body mass index-, and gestational agematched pregnant women (control group)] were included in this study. Serum betatrophin, fasting glucose, insulin, glycated hemoglobin A1c (HbA1c), and C-peptide levels, as well as lipid parameters, were measured.

Results:

Serum betatrophin, fasting glucose, HbA1c, insulin, and C-peptide levels were significantly higher in the GDM group than in the control group (p<0.001, p=0.009, p=0.013, p<0.001, and p<0.001, respectively). Levels of triglycerides and very-low-density lipoprotein cholesterol were significantly higher in the GDM group (p=0.020 and p=0.020, respectively), but total cholesterol and LDL cholesterol levels were similar in the two groups (p=0.810 and p=0.273, respectively). Betatrophin levels in the GDM group were correlated positively with insulin levels (r=0.336, p=0.009) and the homeostatic model assessment of insulin resistance (HOMA-IR) score (r=0.269, p=0.038), and negatively with the C-peptide levels (r=-0.399, p=0.002); they were not correlated with any other glucose or lipid parameters. Multivariate stepwise linear regression analysis demonstrated that insulin levels (β=0.134, p=0.013) and the HOMA-IR score (β=0.112, p=0.017) were associated independently with serum betatrophin levels.

Conclusion:

These results demonstrate that serum betatrophin levels were significantly higher in pregnant women with GDM than in normoglycemic pregnant women. The levels of betatrophin were correlated significantly with insulin resistance parameters, which is a key feature of GDM pathophysiology.

Circulating betatrophin/ANGPTL8 levels correlate with body fat distribution in individuals with normal glucose tolerance but not those with glucose disorders

BACKGROUND

The relationship between betatrophin/ANGPTL8 and obesity has been investigated using body mass index (BMI); however, since BMI reflects overall adiposity rather than body fat distribution, it remains unclear whether fat deposition in different areas of the body affects betatrophin expression. Here, we investigated the correlation between circulating betatrophin levels and body fat distribution in patients with different glucose tolerance.

METHODS

We performed a cross-sectional study in 128 participants with impaired glucose tolerance (IGT; n = 64) or normal glucose tolerance (NGT; n = 64). Circulating betatrophin levels were detected by enzyme-linked immunosorbent assay (ELISA). Body fat distribution (subcutaneous, visceral, and limb fat) was measured by magnetic resonance imaging (MRI) and a body fat meter.

RESULTS

After controlling for age, sex, and BMI, betatrophin was correlated positively with visceral adipose tissue-to-subcutaneous adipose tissue ratio (VAT/SAT ratio; r = 0.339, p = 0.009) and negatively with body fat ratio (BFR; r = - 0.275, p = 0.035), left lower limb fat ratio (LLR; r = - 0.330, p = 0.011), and right lower limb fat ratio (RLR; r = - 0.288, p = 0.027) in the NGT group, with these correlations remaining after controlling for triglycerides. VAT/SAT ratio (standardized β = 0.419, p = 0.001) was independently associated with serum betatrophin levels; however, betatrophin was not associated with body fat distribution variables in the IGT group.

CONCLUSIONS

Circulating betatrophin levels correlated positively with VAT/SAT ratio and negatively with lower limb fat, but not with subcutaneous or upper limb fat, in individuals with normal glucose tolerance. Thus, betatrophin may be a potential biomarker for body fat distribution in individuals without glucose disorders.

Evidences for Expression and Location of ANGPTL8 in Human Adipose Tissue

The metabolism of triglycerides (TGs) is regulated, among others, by the lipoprotein lipase (LPL) that hydrolyses the TGs on endothelial cells. In turn, LPL is inhibited by the ANGPTLs family of proteins, such as ANGPTL3, 4, and, 8; the latter is the least known. In this work, we have tried to establish the expression and localisation of the Angiopoietin-like 8 (ANGPTL8) protein in the visceral adipose tissue (VAT) of morbid-obese and non-obese patients. 109 subjects (66 women and 43 men) undergoing laparoscopic surgery participated in this study. A blood sample and a portion of the VAT were obtained, and the patients were classified according to their Body Mass Index (BMI) as non-obese (19.5–30 kg/m²) and morbid-obese (40–50 kg/m²). No significant changes in ANGPTL8 plasma levels were determined by EIA in obese patients. The immunocytochemistry and Western blotting showed the presence of increased ANGPTL8 in morbid-obese patients (p < 0.05). In-situ hybridisation and a real time polymerase chain reaction (RT-PCR) confirmed that the mRNA that encodes ANGPTL8 was present in adipocytes, without differences in their nutritional state (p = 0.89), and even in the endothelial cells. Our data suggests that ANGPT8 plasmatic levels do not change significantly in patients with morbid obesity, although there is a modest difference related to gender. Besides, we demonstrate that in visceral adipose tissue, ANGPTL8 is well defined in the cytoplasm of adipocytes coexisting with perilipin-1 and its mRNA, also is present in endothelial cells. These findings suggest the possibility that among other functions, ANGPTL8 could perform either a paracrine and/or an endocrine role in the adipose tissue.

Adipose Insulin Resistance and Circulating Betatrophin Levels in Women with PCOS

The role of IR and metabolic disorders has become a crucial topic of study in the pathogenesis of PCOS. Adipose tissue is an important target organ of insulin, and adipose IR plays an important role in the occurrence and development of PCOS. This study seeks to investigate the role of adipose IR in the development of PCOS and to examine its relationship with circulating betatrophin levels in women with PCOS. A cross-sectional analysis of a cohort of women with PCOS and healthy women was performed in this study. Serum betatrophin concentrations were measured by ELISA. Adipose IR was calculated using the product of fasting insulin and FFA concentrations, and the relationship between adipose IR, circulating betatrophin, and other parameters was analyzed. Adipose IR in women with PCOS was significantly higher than that in controls. We found that women with PCOS who have adipose IR (adipose IR ≥ 55) have a higher BMI and higher blood glucose, insulin, PRL, FFA, TG, HOMA-_IR, AUC_glucose, AUC_insulin, VAI_female, and BAI levels than PCOS-afflicted women without adipose IR, while M-values, and SHBG and LH levels were lower. In women with PCOS, serum betatrophin levels were significantly increased compared with controls. Adipose IR negatively correlated with M values and positively with circulating betatrophin levels in the study population. After metformin treatment, circulating betatrophin levels and adipose IR in women with PCOS were significantly decreased compared with pretreatment. Adipose IR is associated with betatrophin levels in women with PCOS. The combination of adipose IR and circulating betatrophin measurements may be significant for screening patients with PCOS.

Regulation of angiopoietin-like protein 8 expression under different nutritional and metabolic status

Type 2 diabetes mellitus (T2DM) is a chronic metabolic disease with increasing prevalence worldwide. Angiopoietin-like protein 8 (ANGPTL8), a member of the angiopoietin-like protein family, is involved in glucose metabolism, lipid metabolism, and energy homeostasis and believed to be associated with T2DM. Expression levels of ANGPTL8 are often significantly altered in metabolic diseases, such as non-alcoholic fatty liver disease (NAFLD) and diabetes mellitus. Studies have shown that ANGPTL8, together with other members of this protein family, such as angiopoietin-like protein 3 (ANGPTL3) and angiopoietin-like protein 4 (ANGPTL4), regulates the activity of lipoprotein lipase (LPL), thereby participating in the regulation of triglyceride related lipoproteins (TRLs). In addition, members of the angiopoietin-like protein family are varyingly expressed among different tissues and respond differently under diverse nutritional and metabolic status. These findings may provide new options for the diagnosis and treatment of diabetes, metabolic syndromes and other diseases. In this review, the interaction between ANGPTL8 and ANGPTL3 or ANGPTL4, and the differential expression of ANGPTL8 responding to different nutritional and metabolic status during the regulation of LPL activity were reviewed.

Recombinant betatrophin (Angptl‑8/lipasin) ameliorates streptozotocin‑induced hyperglycemia and β‑cell destruction in neonatal rats

Betatrophin [also known as lipasin, angiopoietin‑like 8 (ANGPTL8), refeeding induced in fat and liver (RIFL), or hepatocellular carcinoma‑associated gene TD26], a 22‑kDa protein in the angiopoietin‑like family, is a liver‑derived hormone that promotes pancreatic β‑cell proliferation and lipid metabolism. The aim of the present study was to investigate the effect of recombinant betatrophin on β‑cell regeneration in a neonatal streptozotocin (STZ)‑induced diabetic rat model. One‑day‑old Wistar rats were injected with STZ (100 mg/kg), followed by intraperitoneal administration of betatrophin to the STZ‑injected rats for 6 days. Plasma glucose and body weight were monitored. On days 4 and 7, expression levels of pancreatic duodenal homeobox gene‑1 (PDX‑1), the Bax/B‑cell lymphoma‑2 (Bcl‑2) ratio and plasma insulin were assessed, and the β‑cell proliferation rate was determined. Pancreatic islet area and number were determined at 10 weeks. It was found that betatrophin treatment alleviated STZ‑induced hyperglycemia, elevated pancreatic expression levels of Bcl‑2, PDX‑1, plasma insulin levels and the β‑cell proliferation rate on days 4 and 7. Long‑term betatrophin treatment improved glucose tolerance, associated with improved plasma insulin levels and β‑cell mass. These results suggest that early administration of betatrophin promotes β‑cell proliferation in STZ‑induced diabetic neonates and prevents the development of diabetes in adults.

Histology and molecular biology studies on the expression and localization of angiopoietin-like protein 8 in human tissues

Angiopoietin-like protein (ANGPTL) 8 regulates the partitioning of triglycerides by inhibiting lipoprotein lipase in muscle and adipose tissues. ANGPTL8 is expressed in the liver and adipose tissue and secreted into the blood. However, the precise localization of ANGPTL8-expressing cells in these tissues remains unknown. The aim of the present study was to investigate the localization of ANGPTL8-expressing cells in human tissues. Using formalin-fixed paraffin-embedded human tissue specimens, the expression of ANGPTL8 was investigated by reverse transcription-quantitative polymerase chain reaction (RT-qPCR), immunohistochemistry (IHC) and in situ hybridization (ISH). The expression level of ANGPTL8 mRNA was the highest in the liver, followed by lipoma, hibernoma and normal adipose tissue. In the liver, wild type (KF809856) and two splice variants of ANGPTL8 mRNA (KF809857 and KF809858) were found to be expressed. The expression level of the splice variant KF809858, which produces a short form of ANGPTL8, accounted for <1% of ANGPTL8 in the liver. IHC revealed that ANGPTL8 was expressed in hepatocytes in zone 1 of the hepatic acinus in the liver. In the adipose tissue, mature adipocytes weakly expressed ANGPTL8, while immature adipocytes strongly expressed it. ISH confirmed ANGPTL8 mRNA expression in portal hepatocytes and immature adipocytes. ANGPTL8 was expressed in the cells, which actively uptake and metabolize triglycerides. In hibernoma, the ANGPTL8 protein and mRNA were homogeneously expressed in tumor cells. The expression of ANGPTL8 was associated with the differentiation state and activity of lipid metabolism in a subpopulation of cells in the liver and adipose tissue. The association may be helpful for the understanding of local metabolic state in organs and diseases associated with the lipid metabolism.

The potential role of angiopoietin-like protein-8 in type 2 diabetes mellitus: a possibility for predictive diagnosis and targeted preventive measures?

BACKGROUND

Previous studies showed altered angiopoietin-like protein-8 (ANGPTL-8) circulating levels in type 2 diabetes mellitus (DM). Whether or not the alteration in ANGPTL-8 level can be a predictive maker for increased DM risk remains unclear.

AIM

Investigating possible role of ANGPTL-8 as a risk predictor of type2 DM, in addition to a set of factors likely to affect ANGPTL-8 level.

METHODS

One hundred recently diagnosed persons with type 2 DM and 100 sex- and age-matched healthy controls were enrolled. Exclusion criteria included type 1 DM, acute infections, history of chronic kidney disease, malignancy, and blood loss or transfusion. Serum levels of ANGPTL-8, blood pressure, weight, height, glycosylated hemoglobin (HbA1c), fasting blood glucose, cystatin C, lipid profile, liver, and kidney function tests were assessed. The independent relationship between DM and ANGPTL-8 was tested in the unadjusted and multiple-adjusted regression models.

RESULTS

Serum ANGPTL-8 levels showed significant elevation among persons with vs. without DM (p = 0.006), positive correlation with HbA1c (p < 0.001), and negative correlation with estimated GFR (eGFR) (p = 0.003) but no significant correlation to fasting glucose level. In the unadjusted model, patients in the third tertile of ANGPTL-8 had 4 times risk of DM (OR 4.03; 95% CI = 1.37-11.84). Data adjustment for cardiovascular diseases, smoking, body mass index, systolic blood pressure, alanine transaminase (ALT), and low-density lipoprotein (LDL) increased the direct relationship between ANGPTL-8 and DM (OR 6.26; 95% CI = 1.21-32.50). However, the risk significantly decreased after adjustment of Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) eGFR creatinine-cystatin (OR 2.17; 95% CI = 0.10-49.84).

CONCLUSION

This study highlights a possible predictive role of ANGPTL-8 in diabetic complications, particularly nephropathy. Larger prognostic studies are needed to validate the cause-effect relationship between ANGPTL-8 and deteriorated kidney functions.

Angptl8 mediates food-driven resetting of hepatic circadian clock in mice

Diurnal light-dark cycle resets the master clock, while timed food intake is another potent synchronizer of peripheral clocks in mammals. As the largest metabolic organ, the liver sensitively responds to the food signals and secretes hepatokines, leading to the robust regulation of metabolic and clock processes. However, it remains unknown which hepatokine mediates the food-driven resetting of the liver clock independent of the master clock. Here, we identify Angptl8 as a hepatokine that resets diurnal rhythms of hepatic clock and metabolic genes in mice. Mechanistically, the resetting function of Angptl8 is dependent on the signal relay of the membrane receptor PirB, phosphorylation of kinases and transcriptional factors, and consequently transient activation of the central clock gene Per1. Importantly, inhibition of Angptl8 signaling partially blocks food-entrained resetting of liver clock in mice. We have thus identified Angptl8 as a key regulator of the liver clock in response to food.

Partial remission and early stages of pediatric type 1 diabetes display immunoregulatory changes. A pilot study

Type 1 diabetes (T1D) is a chronic metabolic disease of unknown etiology that results from β-cell destruction. The onset of the disease, which arises after a long asymptomatic period of autoimmune attack, may be followed by a relapsing and remitting progression, a phenomenon that is most evident during the partial remission phase (PR). This stage lasts for a few months, shows minor requirements of exogenous insulin and could be explained by a recovery of immunological tolerance. This study aims to identify new biomarkers at early stages of pediatric T1D that reflect immunoregulatory changes. To that end, pediatric patients with T1D (n = 52) and age-related control subjects (n = 30) were recruited. Immune response-related molecules and lymphocyte subsets were determined starting at T1D onset and until the second year of progression. Results showed that circulating TGF-β levels decreased during PR, and that betatrophin concentration was increased in all the considered stages without differing among studied checkpoints. Moreover, an increase of regulatory T, B and NK subsets was found during T1D progression, probably reflecting an attempt to restore self-tolerance. By contrast, a reduction in monocyte levels was observed at the early stages of diabetes. The results reveal significant changes in immunological parameters during the different early stages of T1D in children, which could ultimately serve as potential biomarkers to characterize the progression of T1D.

Circulating ANGPTL8 Is Associated with the Presence of Metabolic Syndrome and Insulin Resistance in Polycystic Ovary Syndrome Young Women

BACKGROUND

ANGPTL8 has been reported to be a regulator of lipid metabolism, and it is associated with insulin resistance (IR) and metabolic syndrome (MetS). We investigated whether ANGPTL8 plays a role in MetS.

METHODS

ANGPTL8 and adiponectin concentrations were measured in PCOS patients with or without MetS and in their corresponding healthy controls. The association of circulating ANGPTL8 with adiponectin and other parameters was also examined.

RESULTS

Circulating ANGPTL8 concentrations were higher in PCOS women with MetS than in those without MetS and in the controls (P < 0.01). ANGPTL8 was positively correlated with age, BMI, FAT%, WHR, SBP, TG, FBG, HbA1c, Fins, and HOMA-IR (all P < 0.01) in the study populations and negatively associated with adiponectin and M-values (P < 0.001). In addition, ANGPTL8 was positively correlated with PRL, LH, TEST, and FAI and negatively correlated with SHBG (all P < 0.01). ROC curve analyses showed that the AUCMetS was 0.87 (P < 0.001), with a sensitivity of 92.4% and specificity of 75.4%, and the AUCIR was 0.82 (P < 0.01), with a sensitivity of 76.4% and specificity of 75.6%.

CONCLUSION

ANGPTL8 levels progressively decrease from PCOS patients with MetS to those without MetS and may be a serum marker associated with the degree of metabolic disorders.

Circulating betatrophin in relation to metabolic, inflammatory parameters, and oxidative stress in patients with type 2 diabetes mellitus

AIMS

Recently, it was suggested that betatrophin has a role in controlling pancreatic β cell proliferation and lipid metabolism, however, its role in human subjects has not been established yet. The predicting role of betatrophin and MDA along with other biochemical indicators in type 2 diabetes mellitus (T2DM) in a sample of the Iraqi population was examined in the present investigation.

METHODS

A total of 31 patients diagnosed with T2DM and 30 adult subjects without diabetes were matched in age and gender in a case-control study. Logistic and linear regression models were performed to examine the role of MDA and betatrophin in T2DM and triglyceride, respectively.

RESULTS

The study confirmed a higher concentration of LDL (124.45 vs. 102.70 mg/dL; P = .001) and TG (191.13 vs. 103.83 mg/dL; P < .0001), insulin (18.40 vs. 10.97 μU/mL; P < .0001), and Hs. CRP (5.39 vs. 2.80 mg/L; P = .033) in diabetic patients compared to the controls. No significant difference in betatrophin and MDA was found between diabetic patients and non-diabetic healthy subjects. The study showed triglyceride as the only predictor of T2DM (P = .028). Similarly, total cholesterol (P < .0001), HDL (P = .001), LDL (P < .0003), and MDA (P = .010) were shown as predictors of triglyceride in diabetic patients.

CONCLUSION

The present study that triglyceride is a direct and MDA is an indirect predictor for T2DM.

Downregulated angiopoietin-like protein 8 production at calving related to changes in lipid metabolism in dairy cows

Acute physiological adaptation of lipid metabolism during the postpartum transition period of cows facilitates peripheral metabolic regulation. Hepatokines, which are hormones secreted from hepatocytes, are presumed to play a critical role in systemic metabolic regulation. Angiopoietin-like protein 8 (ANGPTL8) has been identified as a novel hepatokine associated with circulating triglyceride concentrations in mice and humans. However, regulation of ANGPTL8 and its physiological effects is still unknown in cattle. The present study aimed to reveal changes in ANGPTL8 expression and secretion during the periparturient period, and to investigate its regulatory effect on adipocytes and mammary epithelial cells. In the peripartum period, liver ANGPTL8 mRNA expression was lesser on the day of parturition and 1 wk postpartum than it was 1 wk before parturition (P < 0.05). Moreover, plasma ANGPTL8 concentrations decreased on the day of parturition as compared with that 1 wk before parturition (P < 0.05). In addition, ANGPTL8 expression in cultured bovine hepatocytes was downregulated after oleate and palmitate treatment but upregulated after insulin treatment (P < 0.05). ANGPTL8 decreased hormone-sensitive lipase (HSL) expression in differentiated adipocytes and cluster of differentiation 36 (CD36), fatty acid synthase (FAS), acetyl-coa carboxylase (ACC), and stearoyl-coa desaturase (SCD) in cultured bovine mammary epithelial cells (P < 0.05). These data suggest that hepatic ANGPTL8 production was downregulated postpartum when the cows experienced a negative energy balance. This downregulation was associated with increased concentrations of NEFA and decreased concentrations of insulin in lactating cows, and it facilitated lipid mobilization from adipose tissue to the mammary glands. We speculate that ANGPTL8 might have beneficial effects in reverting or improving the physiological adaptation and pathological processes of lipid metabolism during the peripartum period.

(Re)generating Human Beta Cells: Status, Pitfalls, and Perspectives

Diabetes mellitus results from disturbed glucose homeostasis due to an absolute (type 1) or relative (type 2) deficiency of insulin, a peptide hormone almost exclusively produced by the beta cells of the endocrine pancreas in a tightly regulated manner. Current therapy only delays disease progression through insulin injection and/or oral medications that increase insulin secretion or sensitivity, decrease hepatic glucose production, or promote glucosuria. These drugs have turned diabetes into a chronic disease as they do not solve the underlying beta cell defects or entirely prevent the long-term complications of hyperglycemia. Beta cell replacement through islet transplantation is a more physiological therapeutic alternative but is severely hampered by donor shortage and immune rejection. A curative strategy should combine newer approaches to immunomodulation with beta cell replacement. Success of this approach depends on the development of practical methods for generating beta cells, either in vitro or in situ through beta cell replication or beta cell differentiation. This review provides an overview of human beta cell generation.

GLP-1 receptor agonists stimulate ANGPTL8 production through the PI3K/Akt pathway in a GLP-1 receptor-dependent manner

The level of serum angiopoietin-like protein 8 (ANGPTL8), a novel hepatokine, is associated with obesity and type 2 diabetes mellitus (T2DM). The aims of this study were to investigate whether serum ANGPTL8 level in patients with T2DM was affected by treatment with exenatide, a glucagon-like peptide-1 receptor (GLP-1R) agonist, and to determine whether and how GLP-1R agonists regulated ANGPTL8 production in hepatocytes. A multiple-center trial was conducted in China. Among 240 patients with T2DM enrolled in this trial, 195 patients adhered to a 16-week exenatide treatment and follow-up. Human liver cell line HepG2 cells were incubated for 24 h with either exendin-4 (a native form of exenatide) or liraglutide in the presence or absence of GLP-1R antagonist exendin (9-39) and PI3K inhibitor LY294002. Change of serum ANGPTL8 level in patients with T2DM and regulation of ANGPTL8 production by the GLP-1R agonists in HepG2 cells were evaluated. Results showed that compared with baseline, exenatide treatment significantly increased serum ANGPTL8 level, and lowered body weight, fasting blood glucose (FBG) and glycated hemoglobin A1c (HbA1c) in patients with T2DM (all P <  0.05). The exenatide treatment-mediated upregulation of serum ANGPTL8 level was not associated with the levels of its lowering effects on body weight, FBG and HbA1c stratified by the median. Moreover, exendin-4 or liraglutide dose-dependently upregulated the level of ANGPTL8 expression and secretion in HepG2 cells, which was eliminated by adding exendin (9-39) and LY294002. In conclusion, GLP-1R agonists enhance ANGPTL8 production in vivo and in vitro, which is mediated via the PI3K/Akt pathway in a GLP-1R-dependent manner.

Association between circulating full-length angiopoietin-like protein 8 and non-high-density lipoprotein cholesterol levels in Chinese non-diabetic individuals: a cross-sectional study

Background

Angiopoietin-like protein 8 (ANGPTL8) is a novel hormone involved in the regulation of lipid metabolism and glucose homeostasis. There are inconsistent results regarding the association between ANGPTL8 and lipids in humans. We aimed to investigate the associations between ANGPTL8 and lipids in people without diabetes.

Methods

This was a cross-sectional study of 107 patients with dyslipidemia and 141 patients without. Dyslipidemia diagnosis was based on Chinese guidelines for the prevention and treatment of dyslipidemia in adults. Total cholesterol (TC), triglycerides (TG), low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol (HDL-C) were examined. Non-HDL-C was calculated by subtracting HDL-C from TC. Circulating full-length ANGPTL8 concentrations were measured using enzyme-linked immunosorbent assay. Associations between log-transformed circulating full-length ANGPTL8 and serum lipids were examined using multivariate linear regression analysis.

Results

Circulating ANGPTL8 concentrations were significantly elevated in patients with dyslipidemia compared with patients without dyslipidemia. Circulating full-length ANGPTL8 concentrations were positively associated with non-HDL-C, TG and TC levels after adjusting for age, gender, body mass index, high-sensitivity C-reactive protein, alanine aminotransferase, and creatinine.

Conclusion

In people without diabetes, circulating full-length ANGPTL8 concentrations in patients with dyslipidemia were significantly elevated compared with non-dyslipidemia, and ANGPTL8 was positively associated with serum non-HDL-C levels.

Electronic supplementary material

The online version of this article (10.1186/s12944-018-0802-9) contains supplementary material, which is available to authorized users.

Circulating MOTS-c levels are decreased in obese male children and adolescents and associated with insulin resistance

BACKGROUND AND AIMS

A novel bioactive peptide, mitochondrial-derived peptide (MOTS-c), has recently attracted attention as a potential prevention or therapeutic option for obesity and type 2 diabetes mellitus (T2DM). MOTS-c profiles have not yet been reported in human obesity and T2DM. We aimed to determine circulating MOTS-c levels in obesity and explore the association between MOTS-c levels and various metabolic parameters.

METHODS

In this case-control study, 40 obese children and adolescents (27 males) and 57 controls (40 males) were recruited in the Hubei Province of China in 2017. Circulating MOTS-c levels were measured, clinical data (eg, glucose, insulin, and lipid profile) were recorded, and anthropometric measurements were performed. Finally, we investigated correlations between MOTS-c levels and related variables.

RESULTS

MOTS-c levels were significantly decreased in the obese group compared with the control group (472.61 ±22.83 vs 561.64 ±19.19 ng/mL, P <.01). After classification by sex, MOTS-c levels were significantly decreased in obese male children and adolescents compared to their counterparts (465.26 ±24.53 vs 584.07 ±21.18 ng/mL, P <.001), while they were comparable between the obese and healthy female subjects (487.89 ±49.77 vs 508.85 ±38.76 ng/mL, P >.05). Further, MOTS-c levels were negatively correlated with body mass index (BMI), BMI SD score, waist circumference, waist-to-hip ratio, fasting insulin level, homeostasis model assessment of insulin resistance (HOMA-IR), and glycated hemoglobin (HbA1c) in the male cohort.

CONCLUSIONS

Circulating MOTS-c levels were decreased in obese male children and adolescents and correlated with markers of insulin resistance and obesity.

Cloning, Expression, Purification and CD Analysis of Recombinant Human Betatrophin

BACKGROUND

Betatrophin is a member of the angiopoietin-like (ANGPTL) family that has been implicated in both triglyceride and glucose metabolism. The physiological functions and molecular targets of this protein remain largely unknown; hence, a purified available protein would aid study of the exact role of betatrophin in lipid or glucose metabolism.

METHODS

In this study, we cloned the full-length cDNA of betatrophin from a human liver cDNA library. Betatrophin was expressed in the pET-21b-E. coli Bl21 (DE3) system and purified by immobilized metal-affinity chromatography and ion-exchange chromatography.

RESULTS

Circular dichroism spectroscopy revealed α-helix as the major regular secondary structure in recombinant betatrophin.

CONCLUSION

The production method is based on commonly available resources; therefore, it can be readily implemented.

Increased plasma and adipose tissue levels of ANGPTL8/Betatrophin and ANGPTL4 in people with hypertension

Background

Hypertension is a risk factor for both cardiovascular diseases (CVDs) and type 2 diabetes (T2D). Angiopoietin-like proteins (ANGPTLs), mainly ANGPTL3, ANGPTL4 and ANGPTL8, are associated with increased plasma lipid content due to their role in regulating the activity of lipoprotein lipase, a key enzyme in metabolism of the lipoprotein in circulation. Dyslipidaemia is a risk factor for hypertension development; however, the roles of ANGPTL3, ANGPTL4 and ANGPTL8 in subjects with hypertension have not yet been established. This study compared the plasma and adipose tissue levels of ANGPTL3, ANGPTL4 and ANGPTL8 in age- and body mass index-matched subjects with and without hypertension.

Methods

A total of 119 subjects, including 69 hypertensive and 50 non-hypertensive subjects, were enrolled. ANGPTL3, ANGPTL4 and ANGPTL8 plasma levels were measured by ELISA, whereas their levels in adipose tissue were assessed via real-time PCR.

Results

We found that ANGPTL4 (202.49 ± 17.44 ng/mL vs. 160.64 ± 10.36 ng/mL, p = 0.04) and ANGPTL8 levels (2310.96 ± 194.88 pg/mL vs. 1583.35 ± 138.27 pg/mL, p = 0.001) were higher in hypertensive subjects than non-hypertensive subjects. However, ANGPTL3 levels were not significantly different between the two populations. Similarly, ANGPTL4 and ANGPTL8 levels were also elevated in subjects with T2D and hypertension than in those with T2D but not hypertension. Additionally, people with highest tertiles of ANGPTL8 had higher odds of having hypertension (odd ratio [OR] = 3.8, 95% confidence interval [CI] = (1.5-9.8), p-Value = 0.005. Similar to its plasma levels, ANGPTL4 and ANGPTL8 were higher in adipose tissue.

Conclusions

In conclusion, our data illustrate that ANGPTL4 and ANGPTL8 levels in both plasma and adipose tissues are increased in subjects with hypertension. The elevated levels of ANGPTL4 and ANGPTL8 in hypertensive subjects highlight their potential involvement, their potential role as biomarkers for hypertension and their therapeutic value in hypertension given their roles in regulating lipid metabolism.

Serum Betatrophin Concentrations and the Risk of Incident Diabetes: A Nested Case-Control Study from Chungju Metabolic Disease Cohort

BACKGROUND

Betatrophin is a newly identified hormone derived from the liver and adipose tissue, which has been suggested to regulate glucose and lipid metabolism. Circulating levels of betatrophin are altered in various metabolic diseases, although the results are inconsistent. We aimed to examine whether betatrophin is a useful biomarker in predicting the development of diabetes.

METHODS

A nested case-control study was performed using a prospective Chungju Metabolic disease Cohort Study. During a 4-year follow-up period, we analyzed 167 individuals who converted to diabetes and 167 non-converters, who were matched by age, sex, and body mass index. Serum betatrophin levels were measured by an ELISA (enzyme-linked immunosorbent assay).

RESULTS

Baseline serum betatrophin levels were significantly higher in the converter group compared to the non-converter group (1,315±598 pg/mL vs. 1,072±446 pg/mL, P<0.001). After adjusting for age, sex, body mass index, fasting plasma glucose, systolic blood pressure, total cholesterol, and family history of diabetes, the risk of developing diabetes showed a stepwise increase across the betatrophin quartile groups. Subjects in the highest baseline quartile of betatrophin levels had more than a threefold higher risk of incident diabetes than the subjects in the lowest quartile (relative risk, 3.275; 95% confidence interval, 1.574 to 6.814; P=0.010). However, no significant relationships were observed between serum betatrophin levels and indices of insulin resistance or β-cell function.

CONCLUSION

Circulating levels of betatrophin could be a potential biomarker for predicting new-onset diabetes. Further studies are needed to understand the underlying mechanism of this association.

Increased serum levels of betatrophin in pancreatic cancer-associated diabetes

Long-standing diabetes or glucose intolerance is recognized as a crucial event in the process of pancreatic cancer. Betatrophin, a novel liver-derived hormone, promotes β-cell proliferation and improves glucose intolerance. However, the relationship between betatrophin and PDAC-associated diabetes is not fully understood. To evaluate the serum betatrophin levels in PDAC-associated diabetes, a total 105 Taiwanese subjects including 15 healthy subjects, and 12 patients having PDAC with normal glucose tolerance (PDAC-NGT), 12 patients having PC with impaired glucose tolerance (PDAC-IGT), and 66 patients having PC with diabetes mellitus (PDAC-DM) were enrolled for this study. Serum betatrophin and carbohydrate antigen 19-9 (CA19-9) levels were analyzed by enzyme-linked immunosorbent assay (ELISA). Compared to healthy subjects, PDAC patients had higher levels of betatrophin and CA19-9. Consistently, betatrophin protein was significantly expressed in pancreatic ductal of PDAC-associated DM patients using immunohistochemistry (IHC) method. Furthermore, multivariate regression analysis showed the betatrophin was significantly and positively independent with T category (β= 0.605, P=0.010), serum albumin (β= 0. 423, P=0.021), lipase (β= 0.292, P=0.039), and blood urea nitrogen (BUN) (β= 0.303, P=0.040). Further, the betatrophin was three folds of having PDAC-associated diabetes with the highest odds ratio [OR=3.39; 95% CI (1.20–9.57); P=0.021) and receiver operating characteristic (ROC) curve analysis showed that AUC value of betarophin was 0.853 which is slightly larger than AUC value of CA19-9 (0.792) in PDAC-DM patients. Interestingly, AUC value of betarophin plus CA19-9 was 0.988 in PDAC-DM patients. Therefore, betatrophin combined CA19-9 may serve as a potential biomarker for PDAC-associated diabetes.

Angiopoietin-like protein 8/betatrophin correlates with hepatocellular lipid content independent of insulin resistance in non-alcoholic fatty liver disease patients

Aims/Introduction

To explore angiopoietin‐like protein 8 (ANGPTL‐8) levels, and its association with hepatocellular lipid content (HCL) and insulin resistance in patients with different extents of non‐alcoholic fatty liver disease (NAFLD).

Materials and Methods

In 48 adults were recruited, of which 12 had no NAFLD (HCL < 5.5%; group 1), 18 had mild NAFLD (5.5% ≤ HCL < 10.0%; group 2) and 18 had moderate‐to‐severe NAFLD (HCL ≥ 10.0%; group 3). The peripheral insulin sensitivity of all participants was monitored by a hyperinsulinemic‐euglycemic clamp (M value), as well as the magnetic resonance image of HCL. Serum ANGPTL‐8, blood glucose levels and lipid profiles were also recorded in the study.

Results

Group 3 had a worse metabolic profile, and had the highest ANGPTL‐8 level (1,129 ± 351 pg/mL vs 742 ± 252 pg/mL, 765 ± 301 pg/mL, P = 0.001) compared with those in group 1 and group 2. In all metabolic profiles, HCL positively correlated the strongest with ANGPTL‐8 (r = 0.436, P = 0.042). Multivariate stepwise linear regression analysis showed ANGPTL‐8 and alanine aminotransferase were independent determinants of HCL (P = 0.002, P < 0.001, respectively), and these two indexes explained 67.4% of the variation of HCL (P < 0.001).

Conclusions

ANGPTL‐8 was positively correlated with hepatocellular lipid content independent of obesity and insulin resistance, indicating that ANGPTL‐8 might be a new and important important predictor of the severity of NAFLD.

ANGPTL8: An Important Regulator in Metabolic Disorders

Long-term controversy regarding the role of angiopoietin-like protein 8 (ANGPTL8) in beta-cell proliferation and diabetes progression made it a research spotlight. Recently, the controversy was resolved. Although ANGPTL8 could not control beta-cell expansion and islet function, ANGPTL8 was still considered as a novel but atypical member in the ANGPTL family because of its unique structure and crucial effects on lipid metabolism. Besides, ANGPTL8 also participated in some other disorders such as non-alcoholic fatty liver disease and renal dysfunction. Understanding the features of ANGPTL8 may offer new diagnostic and therapeutic approaches to metabolic-related diseases. Therefore, we reviewed most recent findings about ANGPTL8 and aimed to provide an integrated picture of ANGPTL8.

Association of Serum Angiopoietin-Like Protein 8 With Albuminuria in Type 2 Diabetic Patients: Results From the GDMD Study in China

Background: Hyperglycemia, insulin resistance and hypertriglyceridesmia are risk factors for albuminuria in type 2 diabetes. Angiopoietin-like Protein 8(ANGPTL8) is a newly identified liver-derived hormone related to these risk factors. Hence, we aimed to explore the relationship between ANGPTL8 and albuminuria in type 2 diabetes. Methods: Serum ANGPTL8 levels were determined in groups of control (n = 50) and type 2 diabetic patients with normoalbuminuria (A1, n = 100), microalbuminuria (A2, n = 45), and macroalbuminuria (A3, n = 33). Results: Serum levels of ANGPTL8 and triglycerides were significantly increased in type 2 diabetic patients with albuminuria as compared with controls (P < 0.001). ANGPTL8 levels were positively correlated with triglycerides, duration of diabetes, and urine albumin-to-creatinine ratio (ACR) and negatively correlated with estimated glomerular filtration rate in type 2 diabetic patients with A2 and A3 (all P < 0.05). Logistic regression analysis indicated that ANGPTL8 had higher odds of having A2 (OR = 2.52, 95% CI 1.16-5.48, P = 0.019) and A3 (OR = 4.89, 95% CI 2.10-11.39, P < 0.001) in type 2 diabetes. Mediation analysis indicated that triglycerides might act as a partial mediator in the relationship between ANGPTL8 and ACR. Conclusions: Triglycerides might partially mediate the correlation between ANGPTL8 and ACR. Our data provide the evidence for a strong link between ANGPTL8 and albuminuria, indicating that ANGPTL8 may be a new biomarker for diabetic kidney disease in type 2 diabetes.

TRIAL REGISTRATION NUMBER

ChiCTR-EPC-14005273.

Cloning, expression, and spectral analysis of mouse betatrophin

Background: Betatrophin, a novel secretory protein from liver and fatty tissues, is believed to be involved in lipid and glucose metabolism. However, its precise physiological role remains unclear. Here, we report the cloning, expression, and purification steps of mouse betatrophin in a prokaryotic system, followed by its structural analysis. Methods: Specific cloning primers were used to amplify the coding sequence of mouse liver betatrophin. The product was cloned into pET28 and expressed in E.coli BL21 (DE3) cells. The suitability of the refolding procedure was assessed by determining secondary structures of the initial and refolded proteins using circular dichroism spectroscopy. Results: The polymerase chain reaction resulted in a 549 bp nucleotide sequence, encoding a 183 amino acid polypeptide, with an apparent molecular weight of 21 kDa, which was expressed in an inclusion body. Following an optimization and refolding procedure, the recombinant protein was purified by anion exchange and metal affinity chromatography. CD spectra revealed that the refolded protein has suitable configuration. Conclusion: We believe that the produced betatrophin is suitable for further biochemical studies on glucose and lipid metabolism.

MicroRNA-221-3p Regulates Angiopoietin-Like 8 (ANGPTL8) Expression in Adipocytes

CONTEXT

Angiopoietin-like 8 (ANGPTL8) has been identified as a key regulator of lipid metabolism.

DESIGN

We addressed the correlation between ANGPTL8 messenger RNA (mRNA) with hallmark insulin-regulated and lipogenic genes in human adipose tissue (AT). The regulation of ANGPTL8 expression in adipocytes was studied after inflammatory challenge, and the role of microRNA (miRNA)-221-3p therein was investigated.

RESULTS

ANGPTL8 gene expression in subcutaneous AT (SAT) and visceral AT (VAT) was highly correlated with SLC2A4/GLUT4, ADIPOQ, fatty acyl synthase, and diacylglycerol O-acyltransferase 1. ANGPTL8 mRNA in human adipocytes was suppressed by the inflammatory impact of conditioned medium of lipopolysaccharide-stimulated macrophages, which markedly induced miR-221-3p. MiR-221-3p was shown to target the ANGPTL8 mRNA, and to reduce adipocyte ANGPTL8 protein expression. Analysis of SAT biopsies from 69 subjects ranging from lean to morbidly obese and of VAT of 19 female subjects biopsied during gynecologic surgery demonstrated a trend of negative correlation between ANGPTL8 and miR-221-3p. Significant negative correlation of ANGPTL8 and miR-221-3p was identified in presurgery SAT samples from 22 morbidly obese subjects undergoing bariatric surgery, but vanished after ∼2-year surgery-induced weight loss, which also resulted in a marked reduction of miR-221-3p. ANGPTL8 correlated negatively with the AT inflammatory gene phospholipase A2 G7, whereas miR-221-3p showed a significant positive correlation with this marker. Of note, no correlation was found between AT ANGPTL8 mRNA expression and plasma ANGPTL8.

CONCLUSIONS

The inflammation-induced miR-221-3p regulates ANGPTL8 expression in adipocytes. This miRNA impact may become especially prominent under pathologic conditions such as morbid obesity, putatively contributing to the impaired AT lipid metabolism in metabolic disease.

Circulating betatrophin is associated with insulin resistance in humans: cross-sectional and interventional studies in vivo and in vitro

Betatrophin has a closely relationship with metabolism. However, its effect on metabolism disorder remains unclear. This study was comprised of a series of cross-sectional and interventional studies in vivo and vitro. PCOS women with IR and healthy women were recruited from the general population and outpatients. Plasma betatrophin levels were measured with ELISA. Insulin sensitivity was assessed with EHC. Gene expressions at mRNA and protein levels were determined with RT-PCR and Western blotting. Influences of insulin, metformin, rosiglitazone and over- or knockdown-expression of betatrophin were analyzed ex vivo. Our results indicated that IR women had higher betatrophin levels compared with the controls. Circulating betatrophin was positively correlated with BMI, WHR, Fat%, triglyceride, total cholesterol, LDL-C, AUC_glucose and AUC_insulin, luteinizing Hormone, FAI and HOMA-IR but negatively with M-value. Metformin treatment in PCOS women with IR led to a reduction of betatrophin levels. Insulin stimulation in hepatocytes increased betatrophin expression. Metformin or rosiglitazone led to a reduction of betatrophin expression in insulin-stimulated hepatocytes. In hepatocytes/macrophages co-culture systems, betatrophin expression was significantly increased, whereas this increase was eliminated by rosiglitazone. In hepatocytes, overexpression and knockdown of betatrophin decreased or increased insulin-stimulated insulin receptor, protein kinase B and insulin receptor substrate-1 phosphorylation respectively. Serum from metformin-treated women with IR decreased betatrophin expression and reinforced insulin signals. Thus, the present study provides the in vivo and in vitro evidence, suggesting that there is a cell cross-talking between hepatocytes with macrophages for the regulating betatrophin and it may be a useful marker for IR and metabolic disorders.

Trans-ancestry Fine Mapping and Molecular Assays Identify Regulatory Variants at the ANGPTL8 HDL-C GWAS Locus

Recent genome-wide association studies (GWAS) have identified variants associated with high-density lipoprotein cholesterol (HDL-C) located in or near the ANGPTL8 gene. Given the extensive sharing of GWAS loci across populations, we hypothesized that at least one shared variant at this locus affects HDL-C. The HDL-C–associated variants are coincident with expression quantitative trait loci for ANGPTL8 and DOCK6 in subcutaneous adipose tissue; however, only ANGPTL8 expression levels are associated with HDL-C levels. We identified a 400-bp promoter region of ANGPTL8 and enhancer regions within 5 kb that contribute to regulating expression in liver and adipose. To identify variants functionally responsible for the HDL-C association, we performed fine-mapping analyses and selected 13 candidate variants that overlap putative regulatory regions to test for allelic differences in regulatory function. Of these variants, rs12463177-G increased transcriptional activity (1.5-fold, P = 0.004) and showed differential protein binding. Six additional variants (rs17699089, rs200788077, rs56322906, rs3760782, rs737337, and rs3745683) showed evidence of allelic differences in transcriptional activity and/or protein binding. Taken together, these data suggest a regulatory mechanism at the ANGPTL8 HDL-C GWAS locus involving tissue-selective expression and at least one functional variant.