Emerging Therapeutic Targets for Metabolic Syndrome: Lessons from Animal Models

Oxidative Stress in Men with Obesity, Metabolic Syndrome and Type 2 Diabetes Mellitus: Mechanisms and Management of Reproductive Dysfunction

Reactive oxygen species (ROS) are critical physiological mediators of cellular function, including male fertility. When ROS exceed antioxidant regulation, oxidative stress occurs which is detrimental to cellular function. Oxidative stress has been found to be a central mediator of obesity, metabolic syndrome (MetS) and type 2 diabetes mellitus (T2DM), as well as with male infertility. Human studies have correlated testicular oxidative stress in obese males, and animal studies have further provided insight into potential mechanisms of action. Management of oxidative stress is not well defined. Appropriate nutrition and exercise can be recommended for all diabetic patients, and weight loss for obese patients with MetS and T2DM. Consideration of dietary supplements including micronutrients, antioxidants or medicinal herbs are recommended. Metformin may also offer benefits on testicular oxidative stress and fertility parameters. Significantly more research on causation, mechanisms, clinical assessments and appropriate management of infertility on obesity, MetS and T2DM is still required.

MH-76, a Novel Non-Quinazoline α1-Adrenoceptor Antagonist, but Not Prazosin Reduces Inflammation and Improves Insulin Signaling in Adipose Tissue of Fructose-Fed Rats

Background: Quinazoline α₁-adrenoceptors antagonists have been shown to exert moderately favorable effects on the metabolic profile in hypertensive patients. However, based on AntiHypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial (ALLHAT) results, they are no longer recommended as a first line therapy of hypertension. Recent studies have shown that quinazoline-based α₁-adrenoceptors antagonists (prazosin, doxazosin) induce the apoptosis and necrosis, which may be responsible for ALLHAT outcomes; however, these effects were proven to be independent of α₁-adrenoceptor blockade and were associated with the presence of quinazoline moiety. MH-76 (1-[3-(2,6-dimethylphenoxy)propyl]-4-(2-methoxyphenyl)piperazine hydrochloride)) is a non-quinazoline α₁-adrenoceptor antagonist which, in fructose-fed rats, exerted antihypertensive effect, and, contrary to prazosin, reduced insulin resistance and abdominal adiposity. In this study we aimed to further investigate and compare the effects of MH-76 and prazosin on inflammation in adipose tissue of fructose-fed rats. Methods: Abdominal adipose tissue was collected from four groups of fructose-fed rats (Control, Fructose, Fructose + MH-76 and Fructose + Prazosin) and subjected to biochemical, histopathological and immunohistochemical studies. Moreover, selected tissue distribution studies were performed. Results: Treatment with MH-76 but not with prazosin improved endothelial integrity, reduced adipose tissue inflammation and infiltration by immune cells, resulting in lowering leptin, MCP-1, IL-6, TNF-α and PAI-1 levels. In adipose tissue from Fructose + MH-76 animals, a higher amount of eosinophils accompanied with higher IL-4 concentration was observed. Treatment with MH-76 but not with prazosin markedly reduced phosphorylation of IRS-1 at Ser307. Conclusion: MH-76 may improve insulin signaling in adipose tissue by reducing the pro-inflammatory cytokine production and inhibiting the inflammatory cells recruitment. In contrast, in adipose tissue from animals treated with prazosin, the inflammatory effect was clearly enhanced.

Obesity and male infertility: Mechanisms and management

Obesity is considered a global health problem affecting more than a third of the population. Complications of obesity include cardiovascular diseases, type 2 diabetes mellitus, malignancy (including prostatic cancer), neurodegeneration and accelerated ageing. In males, these further include erectile dysfunction, poor semen quality and subclinical prostatitis. Although poorly understood, important mediators of obesity that may influence the male reproductive system include hyperinsulinemia, hyperleptinemia, chronic inflammation and oxidative stress. Obesity is known to disrupt male fertility and the reproduction potential, particularly through alteration in the hypothalamic-pituitary-gonadal axis, disruption of testicular steroidogenesis and metabolic dysregulation, including insulin, cytokines and adipokines. Importantly, obesity and its underlying mediators result in a negative impact on semen parameters, including sperm concentration, motility, viability and normal morphology. Moreover, obesity inhibits chromatin condensation, DNA fragmentation, increases apoptosis and epigenetic changes that can be transferred to the offspring. This review discusses the impact of obesity on the male reproductive system and fertility, including associated mechanisms. Furthermore, weight management strategies, lifestyle changes, prescription medication, and complementary and alternative medicine in the management of obesity-induced subfertility is discussed.