Ghrelin and insulin secretion in humans: not a tale of two hormones?

Evaluation of the effects of bredemolic acid on selected markers of glucose homeostasis in diet-induced prediabetic rats

CONTEXT

Pentacyclic triterpenes (such as maslinic acid) are natural anti-diabetic agents that ameliorate glucose metabolism in diet-induced prediabetes. However, the effects of bredemolic acid (BA), maslinic acid isomer, is yet unknown in prediabetic (PD) conditions.

OBJECTIVES

To investigate the effects of BA on some glucose homeostasis parameters in high-fat high-carbohydrate (HFHC) diet-induced PD rats.

METHODS

Thirty-six (36) male rats (150-180 g) were divided into two groups, the normal diet (ND) non-prediabetic, NPD (n = 6) and the HFHC diet PD groups (n = 30). The PD animals were further sub-divided into five groups (n = 6) where they were treated with BA for 12 weeks while monitoring changes in blood glucose, caloric intake, and body weight.

RESULTS

Diet-induced prediabetes resulted in increased body weight, caloric intake, glycated haemoglobin, and glucose tolerance. BA treatment ameliorated glucose tolerance, lowered plasma insulin and increased expression of glucose transporter 4 (GLUT 4) in rats.

CONCLUSIONS

BA administration restored glucose homeostasis in diet-induced prediabetes regardless of diet intervention.

From gut microbiota dysfunction to obesity: could short-chain fatty acids stop this dangerous course?

Study of the interactions between the gut microbiota and brain-gut axis represents a very appealing approach to increasing our knowledge about the mechanisms leading to obesity and obesity-related diseases. The aim of this review is to focus on the effects of short-chain fatty acids (SCFAs), which are the main products of gut microbial fermentation from non-digestible carbohydrates in the colon, on the gut-brain axis. Evidence is accumulating regarding the role of SCFAs in the fine-tuning of the gut-brain axis, a feedback system which is vital not only for the proper maintenance of gastrointestinal and metabolic functions, but also for the regulation of food intake and energy expenditure. SCFAs are thought to play a key role in increasing the host capacity to harvest excess energy from the diet. SCFAs, however, can exert their effects on the host metabolism via multiple complementary pathways. Metabolic, inflammatory, and neural pathways can be regulated by SCFAs, which can act by sensing nutritional status, thereby maintaining body energy homeostasis. SCFA production from prebiotic consumption is the rationale for targeting intestinal mechanisms to increase energy expenditure and thereby reduce obesity risk.

Unacylated Ghrelin: A Novel Regulator of Muscle Intermediate Metabolism With Potential Beneficial Effects in Chronic Kidney Disease

In patients with chronic kidney disease (CKD), malnutrition with loss of skeletal muscle mass has a negative impact on morbidity and mortality. Emerging evidence indicates that a cluster of oxidative stress, inflammation, and insulin resistance directly contributes to skeletal muscle catabolism by favoring protein breakdown over synthesis. Ghrelin is a gastric hormone discovered and initially studied in its acylated orexigenic form. More recently, a role of unacylated ghrelin (UnAG) has been described to reduce skeletal muscle mitochondrial reactive oxygen species generation, inflammation, and insulin resistance both in experimental models and in clinical studies. UnAG administration could therefore represent a potential comprehensive therapeutic approach for CKD-related metabolic and nutritional complications. Studies of UnAG administration in experimental and clinical CKD are needed to test the hypothesis that UnAG may chronically improve nutritional status and outcome in CKD patients.

A closed-loop multi-level model of glucose homeostasis

BACKGROUND

The pathophysiologic processes underlying the regulation of glucose homeostasis are considerably complex at both cellular and systemic level. A comprehensive and structured specification for the several layers of abstraction of glucose metabolism is often elusive, an issue currently solvable with the hierarchical description provided by multi-level models. In this study we propose a multi-level closed-loop model of whole-body glucose homeostasis, coupled with the molecular specifications of the insulin signaling cascade in adipocytes, under the experimental conditions of normal glucose regulation and type 2 diabetes.

METHODOLOGY/PRINCIPAL FINDINGS

The ordinary differential equations of the model, describing the dynamics of glucose and key regulatory hormones and their reciprocal interactions among gut, liver, muscle and adipose tissue, were designed for being embedded in a modular, hierarchical structure. The closed-loop model structure allowed self-sustained simulations to represent an ideal in silico subject that adjusts its own metabolism to the fasting and feeding states, depending on the hormonal context and invariant to circadian fluctuations. The cellular level of the model provided a seamless dynamic description of the molecular mechanisms downstream the insulin receptor in the adipocytes by accounting for variations in the surrounding metabolic context.

CONCLUSIONS/SIGNIFICANCE

The combination of a multi-level and closed-loop modeling approach provided a fair dynamic description of the core determinants of glucose homeostasis at both cellular and systemic scales. This model architecture is intrinsically open to incorporate supplementary layers of specifications describing further individual components influencing glucose metabolism.

Does H2 Alter Mitochondrial Bioenergetics via GHS-R1α Activation?

More than 400 original articles have been published from 2007 onwards evaluating therapeutic potential of molecular hydrogen (H₂), the youngest member of medical gases family with selective anti-oxidative properties. However, recent studies suggest that H₂ may tackle other mitochondrial processes besides oxidative stress, including metabolic pathways that drive cellular energy.

The effects of auricular acupuncture on weight reduction and feeding-related cytokines: a pilot study

OBJECTIVE

Auricular acupuncture is a common therapy used to control appetite; however, the underlying mechanism(s) of action is unclear. The present study examined changes in feeding behaviour and in the levels of several appetite-related hormones in response to auricular acupuncture, and attempted to identify the mechanism(s) by which this traditional medical treatment exerts its effects.

METHODS

Ten healthy adult volunteers (nine female and one male) were recruited by the KOSAI Oriental Healthcare Center. The participants were randomly assigned to one of two groups (n=5 per group): an acupuncture group and a placebo group. Each received detention needle stimulus on a weekly basis for 1 month. Changes in diet, body weight, blood pressure and blood biochemistry were evaluated before treatment and at 1 week after the start of treatment.

RESULTS

The difference in weight before treatment and after 1 week of treatment was significant for all participants in the acupuncture group (p=0.02). The percentage changes in active ghrelin in the acupuncture group were no significant changes observed in active ghrelin levels at 1 week after acupuncture in any individual participant (p=0.89). By contrast, the percentage changes in active ghrelin levels in the placebo group at 1 week after the start of acupuncture were significant (p=0.04). The insulin, adrenocorticotropic hormone, leptin and adiponectin levels did not change significantly in either group.

CONCLUSIONS

There was a statistically significant difference in the percentage change in body weight and active ghrelin levels in each individual participant in auricular acupuncture groups. This is a pilot study and the sample number is small; however, auricular acupuncture may reduce appetite by suppressing ghrelin production.