Leptin beyond the lipostat: key component of blood pressure regulation

Effect of Leptin on Chronic Inflammatory Disorders: Insights to Therapeutic Target to Prevent Further Cardiovascular Complication

In response to obesity-associated chronic inflammatory disorders, adipose tissue releases a biologically active peptide known as leptin. Leptin activates the secretion of chemical mediators, which contribute to the pathogenesis of chronic inflammatory disorders, such as rheumatoid arthritis (RA), systemic lupus erythematosus (SLE) and psoriasis. Conversely, adiposity and obesity are the major aggravating risk factors in the pathogenesis of metabolic syndrome (MetS), including type II diabetes mellitus and obesity-associated hypertension. Elevated level of leptin in obesity-associated hypertension causes an increase in the production of aldosterone, which also results in elevation of arterial blood pressure. Hyperleptinemia is associated with the progress of the atherosclerosis through secretion of pro-inflammatory cytokines, like interleukin 6 (IL-6), tumor necrosis factor α (TNF-α), IL-17, and other cytokines to promote inflammation. The release of those cytokines leads to chronic inflammatory disorders and obesity-associated MetS. Thus, the aberrant leptin level in both MetS and chronic inflammatory disorders also leads to the complication of cardiovascular diseases (CVD). Therapeutic target of leptin regarding its pro-inflammatory effect and dysregulated sympathetic nervous system activity may prevent further cardiovascular complication. This review mainly assesses the mechanism of leptin on the pathogenesis and further cardiovascular risk complication of chronic inflammatory disorders.

Serum angiopoietin-like 3 levels are elevated in obese non diabetic men but are unaffected during an oral glucose tolerance test

This study aimed to determine ANGPTL3 serum levels in healthy young lean and obese non-diabetic men during an oral glucose tolerance test (OGTT) and correlate them with anthropometric, biochemical and hormonal parameters. A case-control study was carried out and 30 young obese non-diabetic (23.90 ± 3.84 years and BMI 37.92 ± 4.85 kg/m²) and 28 age-matched healthy lean (24.56 ± 3.50 years and BMI of 22.10 ± 1.72 kg/m²) men were included in this study. The primary outcome measures were serum basal ANGPTL3 and ANGPTL3-area under the curve (AUC) levels. The percentage of body fat was measured by dual-energy X-ray absorptiometry and biochemical, hormonal and insulin resistance indices were determined. Basal ANGPTL3 and ANGPTL3-AUC levels were significantly elevated (p < 0.05) in young obese subjects compared with lean subjects and were positively and significantly associated with different anthropometric measurements. Fasting ANGPTL3 serum levels were positively correlated with fasting insulin, leptin, Leptin/Adiponectin index and triglyceride-glucose index. Moreover, ANGPTL3-AUC was negatively correlated with Matsuda index. In this regard, chronically high ANGPTL3 levels in young obese subjects might favor triglyceride-rich lipoprotein clearance to replenish triglyceride stores by white adipose tissue rather than oxidative tissues.

Nanotechnology-Mediated Drug Delivery for the Treatment of Obesity and Its Related Comorbidities

Obesity is a serious health issue affecting humanity on a global scale. Recognized by the American Medical Association as a chronic disease, the incidence of obesity continues to grow at an accelerating rate and obesity has become one of the major threats to human health. Excessive weight gain is tied to metabolic syndrome, which is shown to increase the risk of chronic diseases, such as heart disease and type 2 diabetes, taxing an already overburdened healthcare system and increasing mortality worldwide. Available treatments such as bariatric surgery and pharmacotherapy are often accompanied by adverse side effects and poor patient compliance. Nanotechnology, an emerging technology with a wide range of biomedical applications, has provided an unprecedented opportunity to improve the treatment of many diseases, including obesity. This review provides an introduction to obesity and obesity-related comorbidities. The most recent developments of nanotechnology-based drug delivery strategies are highlighted and discussed. Additionally, challenges and consideration for the development of nanoformulations with translational potential are discussed. The overall objective of this review is to enhance the understanding of the design and development of nanomedicine for treatments of obesity and related comorbidities.

Astragaloside IV Prevents Obesity-Associated Hypertension by Improving Pro-Inflammatory Reaction and Leptin Resistance

Low-grade pro-inflammatory state and leptin resistance are important underlying mechanisms that contribute to obesity-associated hypertension. We tested the hypothesis that Astragaloside IV (As IV), known to counteract obesity and hypertension, could prevent obesity-associated hypertension by inhibiting pro-inflammatory reaction and leptin resistance. High-fat diet (HFD) induced obese rats were randomly assigned to three groups: the HFD control group (HF con group), As IV group, and the As IV + α-bungaratoxin (α-BGT) group (As IV+α-BGT group). As IV (20 mg·Kg-1·d-1) was administrated to rats for 6 weeks via daily oral gavage. Body weight and blood pressure were continuously measured, and NE levels in the plasma and renal cortex was evaluated to reflect the sympathetic activity. The expressions of leptin receptor (LepRb) mRNA, phosphorylated signal transducer and activator of transcription-3 (p-STAT3), phosphorylated phosphatidylinositol 3-kinase (p-PI3K), suppressor of cytokine signaling 3 (SOCS3) mRNA, and protein-tyrosine phosphatase 1B (PTP1B) mRNA, pro-opiomelanocortin (POMC) mRNA and neuropeptide Y (NPY) mRNA were measured by Western blot or qRT-PCR to evaluate the hypothalamic leptin sensitivity. Additionally, we measured the protein or mRNA levels of α7nAChR, inhibitor of nuclear factor κB kinase subunit β/ nuclear factor κB (IKKβ/NF-KB) and pro-inflammatory cytokines (IL-1β and TNF-α) in hypothalamus and adipose tissue to reflect the anti-inflammatory effects of As IV through upregulating expression of α7nAChR. We found that As IV prevented body weight gain and adipose accumulation, and also improved metabolic disorders in HFD rats. Furthermore, As IV decreased BP and HR, as well as NE levels in blood and renal tissue. In the hypothalamus, As IV alleviated leptin resistance as evidenced by the increased p-STAT3, LepRb mRNA and POMC mRNA, and decreased p-PI3K, SOCS3 mRNA, and PTP1B mRNA. The effects of As IV on leptin sensitivity were related in part to the up-regulated α7nAchR and suppressed IKKβ/NF-KB signaling and pro-inflammatory cytokines in the hypothalamus and adipose tissue, since co-administration of α7nAChR selective antagonist α-BGT could weaken the improved effect of As IV on central leptin resistance. Our study suggested that As IV could efficiently prevent obesity-associated hypertension through inhibiting inflammatory reaction and improving leptin resistance; furthermore, these effects of As IV was partly related to the increased α7nAchR expression.

Pubertal testis volume, age at pubertal onset, and adolescent blood pressure: Evidence from Hong Kong's "Children of 1997" birth cohort

OBJECTIVES

A warning from Health Canada suggests that testosterone increases blood pressure (BP). No evidence from large randomized controlled trials is available, and observational studies are confounded by ill-health lowering serum testosterone. To address the evidence gap, we assessed the association of pubertal testicular volume, as a reflection of testosterone production, with BP.

METHODS

We examined whether testicular volume was associated with sex-, age-, and height-standardized BP z-score at ∼13 years in a population-representative Chinese birth cohort (n = 5195, 63% follow-up). We used age at pubertal onset, determined as the earliest age when Tanner stage II for genitalia, breast, or pubic hair, or testicular volume of 4 mL occurred, as control exposures. These exposures were expected to produce findings different from testicular volume because they are not direct measures of testosterone. They were used to ascertain specificity of exposure and to detect residual confounding.

RESULTS

Greater testicular volume was associated with higher systolic BP by 0.03 z-score, which is equivalent to 1.40 mm Hg per standard deviation of testicular volume (95% CI 0.02-0.04), adjusted for infant characteristics, socioeconomic position, and childhood body mass index. Similarly adjusted, earlier pubertal onset was not associated with higher systolic BP z-score in boys or girls.

CONCLUSIONS

Greater pubertal testicular volume is related to higher BP, consistent with a potential role of androgens in the higher BP in boys than girls that emerges during puberty. Our finding provides preliminary evidence supportive of more definitive studies to clarify the warning on testosterone from Health Canada.

Targeting adipose tissue in the treatment of obesity-associated diabetes

Adipose tissue regulates numerous physiological processes, and its dysfunction in obese humans is associated with disrupted metabolic homeostasis, insulin resistance and type 2 diabetes mellitus (T2DM). Although several US-approved treatments for obesity and T2DM exist, these are limited by adverse effects and a lack of effective long-term glucose control. In this Review, we provide an overview of the role of adipose tissue in metabolic homeostasis and assess emerging novel therapeutic strategies targeting adipose tissue, including adipokine-based strategies, promotion of white adipose tissue beiging as well as reduction of inflammation and fibrosis.