Angiopoietin-like protein 6 in patients with obesity, type 2 diabetes mellitus, and anorexia nervosa: The influence of very low-calorie diet, bariatric surgery, and partial realimentation

AMP-activated protein kinase is a key regulator of obesity-associated factors

An imbalance between caloric intake and energy expenditure leads to obesity. Obesity is an important risk factor for the development of several metabolic diseases including insulin resistance, metabolic syndrome, type 2 diabetes mellitus, and cardiovascular disease. So, controlling obesity could be effective in the improvement of obesity-related diseases. Various factors are involved in obesity, such as AMP-activated protein kinases (AMPK), silent information regulators, inflammatory mediators, oxidative stress parameters, gastrointestinal hormones, adipokines, angiopoietin-like proteins, and microRNAs. These factors play an important role in obesity by controlling fat metabolism, energy homeostasis, food intake, and insulin sensitivity. AMPK is a heterotrimeric serine/threonine protein kinase known as a fuel-sensing enzyme. The central role of AMPK in obesity makes it an attractive molecule to target obesity and related metabolic diseases. In this review, the critical role of AMPK in obesity and the interplay between AMPK and obesity-associated factors were elaborated.

Effects of Bariatric Surgeries on Fetuin-A, Selenoprotein P, Angiopoietin-Like Protein 6, and Fibroblast Growth Factor 21 Concentration

Obesity is a civilization disease representing a global health problem. Excessive body weight significantly reduces the quality of life. It is also associated with the leading causes of death, including type 2 diabetes mellitus, cardiovascular diseases, and numerous types of cancer. The mainstay of therapy is a dietary treatment. However, in morbidly obese patients, dietary treatment is often insufficient. In these patients, the most effective procedure is bariatric surgery, but it is still difficult to predict its outcome and metabolic changes. Hepatokines are proteins secreted by hepatocytes. Many of them, including fetuin-A, selenoprotein P, angiopoietin-like protein 6, and fibroblast growth factor 21, have been linked to metabolic dysfunctions. In this context, hepatokines may prove helpful. This review investigates the possible changes in hepatokine profiles after selected bariatric surgery protocols. In this regard, Roux-en-Y gastric bypass is the most studied type of surgery. The overall analysis of published research identified fetuin-A as a potential marker of metabolic alternations in patients after bariatric surgery.

Pathophysiology of growth hormone secretion disorders and their impact on bone microstructure as measured by trabecular bone score

This article is focused on endocrine-mediated osteoporosis caused by growth hormone (GH) disorders; adult GH deficiency and acromegaly. GH and insulin like growth factor-1 (IGF-1) stimulate linear bone growth through complex hormonal interactions and activates epiphyseal prechondrocytes. GH, via receptor activator of nuclear factor-kappaB (RANK), its ligand (RANK-L), and the osteoprotegerin system, stimulates production of osteoprotegerin and its accumulation in bone matrix. Malfunction of this mechanism, could lead to specific bone impairment. However, the primary problem of bone disease in GH secretion disorders is the primary prevention of osteoporotic fractures, so it is important to determine bone quality that better reflects the patient's actual predisposition to fracture. A method estimating bone quality from lumbar spine dual X-ray absorptiometry (DXA) scans is trabecular bone score (TBS). TBS in addition to bone mineral density (BMD) is a promising predictor of the osteoporotic fracture risk in women with postmenopausal osteopenia. In acromegaly TBS better defines risk of fracture because BMD is normal or even increased. TBS helps to monitor the effect of growth hormone therapy. Despite these findings, TBS should not be used alone, but a comprehensive consideration of all fracture risk factors, BMD and bone turnover markers is necessary.

Investigating the Role of Myeloperoxidase and Angiopoietin-like Protein 6 in Obesity and Diabetes

Myeloperoxidase (MPO) is positively associated with obesity and diet-induced insulin resistance. Angiopoietin-like protein 6 (ANGPTL6) regulates metabolic processes and counteract obesity through increased energy expenditure. This study aims to evaluate the plasma MPO and ANGPTL6 levels in obese and diabetic individuals as well as MPO association with biochemical markers of obesity. A total of 238 participants were enrolled, including 137 control and 101 type 2 diabetes (T2D) patients. ANGPTL6 and MPO levels and other biomarkers were measured via ELISA. ANGPTL6 levels were significantly higher in the diabetic population and obese individuals. When the group was stratified based on T2D, ANGPTL6 levels were significantly higher in obese-diabetic participants compared with non-obese-diabetics, but obese-non-diabetic individuals had similar ANGPTL6 levels to their controls. MPO levels were higher in obese compared with non-obese participants but did not differ between T2D and control participants. MPO levels were upregulated in obese compared with non-obese in both diabetics and non-diabetics. MPO was positively associated with ANGPTL6, triglyceride, BMI, TNF-alpha, high-sensitivity C-reactive protein, interleukin-6, and plasminogen activator inhibitor-1. Taken together, our findings suggest that both MPO and ANGPTL6 may regulate obesity, although MPO exerts this effect independent of diabetes while ANGPTL6 may have a modulatory role in diabetes.

Angiopoietin-like proteins as therapeutic targets for cardiovascular disease: focus on lipid disorders

Introduction: Angiopoietin-like (ANGPTL) proteins belong to a family of eight secreted factors that are structurally related to proteins that modulate angiogenesi, commonly known as angiopoietins. Specifically, ANGPTL3, ANGPTL4, and ANGPTL8 (the 'ANGPT L3-4-8 triad'), have surfaced as principal regulators of plasma lipid metabolism by functioning as potent inhibitors of lipoprotein lipase. The targeting of these proteins may open up future therapeutic avenues for metabolic and cardiovascular disease.Areas covered: This article systematically summarizes the compelling literature describing the mechanistic roles of ANGPTL3, 4, and 8 in lipid metabolism, emphasizing their importance in determining the risk of cardiovascular disease. We shed light on population-based studies linking loss-of-function variations in ANGPTL3, 4, and 8 with decreased risk of metabolic conditions and cardiovascular disorders. We also discuss how the strategies aiming at targeting the ANGPT L3-4-8 triad could offer therapeutic benefit in the clinical scenario.Expert opinion: Monoclonal antibodies and antisense oligonucleotides that target ANGPTL3, 4, and 8 are potentially an efficient therapeutic strategy for hypertriglyceridemia and cardiovascular risk reduction, especially in patients with limited treatment options. These innovative therapeutical approaches are at an embryonic stage in development and hence further investigations are necessary for eventual use in humans.

Efficacy of low- and very-low-energy diets in people with type 2 diabetes mellitus: A systematic review and meta-analysis of interventional studies

AIMS

To review systematically and quantify the weight loss achieved through low- (LEDs) and very-low-energy diets (VLEDs) in people with type 2 diabetes mellitus (T2DM).

MATERIALS AND METHODS

Studies reporting the effects of diet-only interventions of up to 1600 kcal/d in people with T2DM were searched in MEDLINE, EMBASE and CINAHL up to July 2018. Changes in the primary (body weight and body mass index [BMI]) and secondary outcomes (glycated haemoglobin, blood lipids) according to energy restriction and duration of diet were modelled using restricted cubic splines.

RESULTS

Forty-four studies (3817 participants) were included. The overall quality of the evidence was moderate and limited to short-term interventions up to 4 months. Baseline mean weight and BMI were 92.1 kg and 36.6 kg/m² . VLEDs of 400 kcal/d led to 5.4% weight loss at 2 weeks, increasing to 17.9% at 3 months. More modest reductions of 7.3% were observed on LEDs of 1200 kcal/d and 2.0% on 1600 kcal/d after 3 months. No clear patterns emerged for secondary outcomes. Publication bias was significant for primary outcomes.

CONCLUSIONS

Through modelling, we were able to describe effective dietary deficit strategies to achieve weight reduction up to 4 months in people with T2DM. High-quality studies are required to further support clinical practice with evidence-based dietary interventions.

The association between dietary antioxidants and adipokines level among obese women

AIM

Adipokines are associated with several oxidative stress-related diseases and pathologic conditions. We aimed to assess the association between antioxidants and adipokines in obese adults.

METHODS AND MATERIALS

In this cross-sectional study, a total of 160 obese women were included. Body composition and anthropometric characteristics were measured. Dietary intakes were assessed by 3-day, 24-h dietary recall. Blood samples were obtained following an overnight fasting. Serum concentrations of adipokines including progranulin, retinol binding protein 4 (RBP4) and Angiopoietin-related growth factor 6 (ANGPTL6) was measured using an enzyme-linked immunosorbent assay. ANCOVA and the linear regression model analysis was performed to assess the relationship between Progranulin, RBP4, AnGPTL6, and antioxidants.

RESULTS

Mean age of included women was 39.31 ± 12.10. Mean and standard deviation for BMI was 35.05 ± 4.26 in this obese population. There was a positive significant association between ANGPTL6 and vitamin D intake (p < 0.001). Also, there was a marginal association between RBP4 and vitamin A (p = 0.063) intake, but after adjustment age, and fat mass, we found a significant association (p = 0.008). However, the associations between dietary antioxidants, progranulin, and ANGPTL6 were not statistically significant.

CONCLUSIONS

ANGPTL6 and RBP4 levels directly associated with dietary vitamins D and A intake, respectively. But, according to the results, the association between ANGPTL6 and vitamin D was bidirectional. The suggested associations probably can be useful in the development of interventional studies for management of chronic diseases.

Leptin regulates the expression of angiopoietin-like 6

Angiopoietin-like 6 (ANGPTL6) is a hepatokine that antagonizes obesity and insulin resistance by increasing energy expenditure. Despite its beneficial effects on metabolism, human studies have shown a paradoxical increase in ANGPTL6 level in the serum of patients with metabolic diseases, which has been interpreted as a compensatory upregulation. However, the regulatory mechanism of ANGPTL6 remains unclear. Since upregulation of ANGPTL6 is induced on metabolic stress, we investigated the hepatic expression of ANGPTL6 by leptin, a representative adipokine of obesity. Mice on a high-fat diet showed increased serum leptin levels and hepatic Angptl6 expression, which were attenuated by exercise training. A single leptin injection also induced hepatic ANGPTL6 expression and increased serum ANGPTL6 levels. In an in vitro model using primary hepatocytes, leptin treatment significantly upregulated ANGPTL6 expression at the mRNA and protein levels, as well as the amount of secreted ANGPTL6 protein in conditioned media. Similarly, exercise training on human participants also showed diminished serum levels of leptin and ANGPTL6. Altogether, these results strongly indicated that hepatic ANGPTL6 expression was determined by leptin.