Gut-Brain Endocrine Axes in Weight Regulation and Obesity Pharmacotherapy

Association of Uroguanylin, Body Mass Index, and Waist Circumference: Sex Differences and Obesity Implications among a Sample of Iraqi Adults in Baghdad City

This research investigates the gender-specific associations of uroguanylin levels with various health-related parameters in Iraqi adults. The results revealed significant differences between genders in food style preferences and waist circumference (WC) risk. Notably, uroguanylin exhibited distinct correlations with low density lipoprotein (LDL) cholesterol, glycated hemoglobin (HbA1c), body mass index (BMI), and WC in females and males, indicating potential gender-specific effects on lipid metabolism, glucose regulation, and adiposity. A total of 140 Iraqi adults (73 females and 67 males) were recruited into the study. Physical activity levels, food style preferences, WC risk, and BMI subgroups, were compared between genders. Additionally, participants' characteristics, including age, height, weight, BMI, blood pressure, cholesterol levels, and uroguanylin concentrations, were analyzed. Significant gender differences were observed in food style preferences, with a higher proportion of males preferring fast food, with a greater percentage of females classified as having a high risk, females exhibited lower height and weight compared to males. HbA1c levels were significantly lower in females, whereas high density lipoprotein (HDL) cholesterol levels were significantly higher in females than in males. Uroguanylin concentrations were also significantly lower in females compared to males. Uroguanylin shows a moderately negative correlation with LDL cholesterol in females but not in males. Furthermore, a strong negative association between uroguanylin and HbA1c in females indicated improved glycemic control with higher uroguanylin levels, whereas an opposite trend was observed in males. No significant association was observed between uroguanylin and BMI in females, a significant positive correlation was found in males. For WC, a weak negative correlation was noted in females, whereas a moderately negative correlation was observed in males. These contrasting correlations imply potential gender-specific effects of uroguanylin on adiposity and body fat distribution.

Role of Somatostatin in the Regulation of Central and Peripheral Factors of Satiety and Obesity

Obesity is one of the major social and health problems globally and often associated with various other pathological conditions. In addition to unregulated eating behaviour, circulating peptide-mediated hormonal secretion and signaling pathways play a critical role in food intake induced obesity. Amongst the many peptides involved in the regulation of food-seeking behaviour, somatostatin (SST) is the one which plays a determinant role in the complex process of appetite. SST is involved in the regulation of release and secretion of other peptides, neuronal integrity, and hormonal regulation. Based on past and recent studies, SST might serve as a bridge between central and peripheral tissues with a significant impact on obesity-associated with food intake behaviour and energy expenditure. Here, we present a comprehensive review describing the role of SST in the modulation of multiple central and peripheral signaling molecules. In addition, we highlight recent progress and contribution of SST and its receptors in food-seeking behaviour, obesity (orexigenic), and satiety (anorexigenic) associated pathways and mechanism.

The effect of taste and taste perception on satiation/satiety: a review

As the prevalence of being overweight and obesity has increased worldwide, there is an increasing concern about satiation/satiety that can be achieved by eating. The ability of an individual to perceive tastes in the mouth is believed to be one of the many factors that influence food intake; the taste may affect appetite regulation and energy intake, playing an important role in promoting satiation/satiety. Satiation/satiety is actually induced by food and may be related to physiological and psychological factors such as several basic tastes, the exposure time of the taste and the cognition of different groups and individuals. This paper reviews the mechanism by which taste regulates satiation/satiety and demonstrates how taste and the taste perception of food prompt the brain to send satiation/satiety signals. Existing problems in taste and satiation/satiety and the prospective application of related research in the food industry are addressed, providing a scientific basis and theoretical guidance for the development and utilization of satiation/satiety from the perspective of taste.

Amylin Acts in the Lateral Dorsal Tegmental Nucleus to Regulate Energy Balance Through Gamma-Aminobutyric Acid Signaling

BACKGROUND

The pancreatic- and brain-derived hormone amylin promotes negative energy balance and is receiving increasing attention as a promising obesity therapeutic. However, the neurobiological substrates mediating amylin's effects are not fully characterized. We postulated that amylin acts in the lateral dorsal tegmental nucleus (LDTg), an understudied neural processing hub for reward and homeostatic feeding signals.

METHODS

We used immunohistochemical and quantitative polymerase chain reaction analyses to examine expression of the amylin receptor complex in rat LDTg tissue. Behavioral experiments were performed to examine the mechanisms underlying the hypophagic effects of amylin receptor activation in the LDTg.

RESULTS

Immunohistochemical and quantitative polymerase chain reaction analyses show expression of the amylin receptor complex in the LDTg. Activation of LDTg amylin receptors by the agonist salmon calcitonin dose-dependently reduces body weight, food intake, and motivated feeding behaviors. Acute pharmacological studies and longer-term adeno-associated viral knockdown experiments indicate that LDTg amylin receptor signaling is physiologically and potentially preclinically relevant for energy balance control. Finally, immunohistochemical data indicate that LDTg amylin receptors are expressed on gamma-aminobutyric acidergic neurons, and behavioral results suggest that local gamma-aminobutyric acid receptor signaling mediates the hypophagia after LDTg amylin receptor activation.

CONCLUSIONS

These findings identify the LDTg as a novel nucleus with therapeutic potential in mediating amylin's effects on energy balance through gamma-aminobutyric acid receptor signaling.

Molecular Physiology of Membrane Guanylyl Cyclase Receptors

cGMP controls many cellular functions ranging from growth, viability, and differentiation to contractility, secretion, and ion transport. The mammalian genome encodes seven transmembrane guanylyl cyclases (GCs), GC-A to GC-G, which mainly modulate submembrane cGMP microdomains. These GCs share a unique topology comprising an extracellular domain, a short transmembrane region, and an intracellular COOH-terminal catalytic (cGMP synthesizing) region. GC-A mediates the endocrine effects of atrial and B-type natriuretic peptides regulating arterial blood pressure/volume and energy balance. GC-B is activated by C-type natriuretic peptide, stimulating endochondral ossification in autocrine way. GC-C mediates the paracrine effects of guanylins on intestinal ion transport and epithelial turnover. GC-E and GC-F are expressed in photoreceptor cells of the retina, and their activation by intracellular Ca(2+)-regulated proteins is essential for vision. Finally, in the rodent system two olfactorial GCs, GC-D and GC-G, are activated by low concentrations of CO2and by peptidergic (guanylins) and nonpeptidergic odorants as well as by coolness, which has implications for social behaviors. In the past years advances in human and mouse genetics as well as the development of sensitive biosensors monitoring the spatiotemporal dynamics of cGMP in living cells have provided novel relevant information about this receptor family. This increased our understanding of the mechanisms of signal transduction, regulation, and (dys)function of the membrane GCs, clarified their relevance for genetic and acquired diseases and, importantly, has revealed novel targets for therapies. The present review aims to illustrate these different features of membrane GCs and the main open questions in this field.

Regulation of food intake and the development of anti-obesity drugs

As the most significant cause of death worldwide, obesity has become one of the world's most important public health problems, but approved anti-obesity drugs are extremely limited. This article summarizes the feeding control circuits and regulators involved in obesity development, highlight the hypothalamus, melanocortin system and brain-gut peptide actions in this process, and the five US FDA approved anti-obesity medications in long term use, namely phentermine/topiramate, lorcaserin, naltrexone/bupropion, liraglutide and orlistat.