Chronic consumption of an inositol-enriched beverage ameliorates endothelial dysfunction and oxidative stress in type 2 diabetes

Carob: A Sustainable Opportunity for Metabolic Health

Carob (Ceratonia siliqua L.) is an evergreen tree that belongs to the Leguminosae family and grows in the arid and semi-arid regions of the Mediterranean basin. The carob tree is resistant to droughts and salinity, while its deep root systems allow CO₂ to sink, mitigating global warming effects. Traditionally, carob has been used to produce animal feed, but for many years, it was excluded from the human diet. Nowadays, agricultural and industrial sectors exploit carob fruit, also referred to as carob pod, and its primary products (i.e., flour, powder and syrup) to develop a variety of foods and beverages. The nutritional composition varies depending on the carob part but also on genetic, cultivar, seasonal and environmental factors. Despite the high sugar content, the carob pod is rich in insoluble fiber and microconstituents including phenolic compounds, inositols (mainly d-pinitol) and vitamins. In the present review article, we aimed to (a) highlight the role of carob cultivation in addressing climate change challenges and the need for sustainability, and (b) summarize the effects of carob consumption on obesity and related metabolic disorders.

Inositol supplementation and body mass index: A systematic review and meta-analysis of randomized clinical trials

Background

Inositol is a sugar-alcohol and recognized as a key component of cell membrane phospholipids. It has crucial role in the cell signaling pathways and contribute to improving glycemic responses. Although some earlier studies have revealed the effect of inositol mediating glucose uptake by improving insulin sensitivity, the benefit of inositol supplementation in patients with overweight and obesity is not completely understood. This study aimed to assess the impact of inositol supplementation on body mass index (BMI) through a systematic review and meta-analysis of controlled clinical trials.

Methods

A systematic search was performed to August 2021 in the following databases: PubMed-Medline, Embase, Web of Science and Scopus. Fifteen controlled clinical trials investigating the effect of inositol on adult's BMI were finally included in the study. A random-effects model was employed to estimate the effect size. Subgroup analysis was performed by dose, duration, age, type of inositol. Meta-regression was used to investigate presence of any linear relationship. Begg's and Egger's tests were carried out to detect small study effect.

Results

The results of pooled analysis showed that inositol supplementation significantly decreased BMI scores (WMD = -0.41 kg/m2; 95% CI: -0.78, -0.04; p = 0.028). Subgroup analysis was performed to identify the source of heterogeneity among studies (I 2 = 73.9%, p < 0.001), demonstrating supplementation duration, baseline BMI, mean age of participants, type of inositol and dosage were potential sources of heterogeneity. The effect of intervention was more clinically significant in participants with polycystic ovary syndrome (PCOS) and overweight/obesity. Inositol in the form of myo-inositol (MI) had stronger effect on BMI reduction.

Conclusion

The meta-analysis suggests that oral inositol supplementation has positive effect on BMI reduction. Inositol supplementation could be considered as an adjunct treatment to improve body mass index.

Pinitol alleviates systemic inflammatory cytokines in human obesity by a mechanism involving unfolded protein response and sirtuin 1

BACKGROUND & AIMS

It is known that pinitol acts as a mediator of the insulin-signaling pathway, though little is known about its anti-inflammatory effect in human obesity. Therefore, this study aimed to evaluate the effect of pinitol on peripheral blood mononuclear cells (PBMCs) and visceral (VAT) and subcutaneous adipose tissues (SAT), focusing on the involvement of endoplasmic reticulum (ER) stress and sirtuin 1 (SIRT1).

METHODS

In the intervention study, thirteen obese subjects consumed a pinitol-enriched beverage (PEB) for 12 weeks. In the ex vivo study, a biopsy of VAT and SAT was removed from thirty-four obese patients and incubated with D-pinitol for 48 h.

RESULTS

The consumption of a PEB reduced circulating levels of IL6 and TNFα and increased SIRT1 protein expression in PBMCs. Ex vivo experiments showed a decline in gene expression and protein levels of IL6 and TNFα in SAT and a reduction in ER stress parameters (ATF6 and CHOP), while VAT markers remained unaltered. Differential gene expression profiles revealed an up-regulation of SIRT1 and insulin-signaling pathways in SAT with respect to VAT.

CONCLUSIONS

Our results suggests that pinitol down-regulates the inflammatory pathway which may lead to novel treatment options for obesity and its metabolic disorders.

Effects of inositol on glucose homeostasis: Systematic review and meta-analysis of randomized controlled trials

BACKGROUND & AIMS

The effect of inositol on glucose homeostasis is not well characterized. The aim of the present meta-analysis is to synthesize the effects of inositol on glucose homeostasis in different clinical conditions.

METHODS

We performed a systematic review (CRD42017057927) following PRISMA guidelines. Web of Science and Medline were searched for randomized controlled trials (RCTs) that addressed supplementation with compounds of the inositol family in humans and assessed their effects on glucose homeostasis.

RESULTS

We screened 476 abstracts and included 20 RCTs with a total of 1239 subjects. Meta-analysis showed in the treatment arm a reduction in fasting plasma glucose (Mean difference (MD) -0.44 mmol/l, 95% CI -0.65, -0.23), 2 h PG after 75 g OGTT (MD -0.69 mmol/l, 95% CI -1.14, -0.23), abnormal glucose tolerance (Relative risk (RR) 0.28, 95% CI 0.12, 0.66), fasting insulin (MD -38.49 pmol/l, 95% CI -52.63, -24.36), and HOMA-IR (MD -1.96 mmol × mUI/l, 95% CI -2.62, -1.30). No differences were observed in BMI, HbA1c and % of patients requiring insulin treatment. Sensitivity analysis did not change treatment estimates. Mention to adverse events was only present in 13 articles with no sign of seriousness.

CONCLUSIONS

Inositol supplementation decreases blood glucose through an improvement in insulin sensitivity that is independent of weight. Assessment of adverse effects is scarce among published trials and should be fully addressed before considering inositol as a therapeutic agent for glucose-related outcomes. The characterization of the subjects achieving benefit from the intervention and the formulations to be used should also be known.

Effects of a Carob-Pod-Derived Sweetener on Glucose Metabolism

BACKGROUND

Patients with type 2 diabetes mellitus (T2DM) have a higher incidence of cardiovascular (CV) events. The ingestion of high-glycemic index (GI) diets, specially sweetened beverage consumption, has been associated with the development of T2DM and CV disease.

OBJECTIVE

We investigated the effects of the intake of a sweetened beverage, obtained from natural carbohydrates containing pinitol (PEB) compared to a sucrose-enriched beverage (SEB) in the context of impaired glucose tolerance (IGT) and diabetes.

METHODS

The study was divided in three different phases: (1) a discovery phase where the plasma proteomic profile was investigated by 2-DE (two-dimensional electrophoresis) followed by mass spectrometry (matrix-assisted laser desorption/ionization time-of-flight-MALDI-TOF/TOF) in healthy and IGT volunteers; (2) a verification phase where the potential mechanisms behind the observed protein changes were investigated in the discovery cohort and in an additional group of T2DM volunteers; and (3) the results were validated in a proof-of-concept interventional study in an animal model of diabetic rats with complementary methodologies.

RESULTS

Six weeks of pinitol-enriched beverage (PEB) intake induced a significant increase in two proteins involved in the insulin secretion pathway, insulin-like growth factor acid labile subunit (IGF1BP-ALS; 1.3-fold increase; P = 0.200) and complement C4A (1.83-fold increase; P = 0.007) in IGT subjects but not in healthy volunteers. Changes in C4A were also found in the serum samples of Zucker diabetic fatty (ZDF) rats after four weeks of PEB intake compared to basal levels (P = 0.042). In addition, an increased expression of the glucose transporter-2 (GLUT2) gene was observed in the jejunum (P = 0.003) of inositol-supplemented rats when compared to sucrose supplementation. This change was correlated with the observed change in C4A (P = 0.002).

CONCLUSIONS

Our results suggest that the substitution of a common sugar source, such as sucrose, by a naturally-based, pinitol-enriched beverage induces changes in the insulin secretion pathway that could help to reduce blood glucose levels by protecting β-cells and by stimulating the insulin secretion pathway. This mechanism of action could have a relevant role in the prevention of insulin resistance and diabetes progression.

Oxidative stress and reactive oxygen species in endothelial dysfunction associated with cardiovascular and metabolic diseases

Reactive oxygen species (ROS) are reactive intermediates of molecular oxygen that act as important second messengers within the cells; however, an imbalance between generation of reactive ROS and antioxidant defense systems represents the primary cause of endothelial dysfunction, leading to vascular damage in both metabolic and atherosclerotic diseases. Endothelial activation is the first alteration observed, and is characterized by an abnormal pro-inflammatory and pro-thrombotic phenotype of the endothelial cells lining the lumen of blood vessels. This ultimately leads to reduced nitric oxide (NO) bioavailability, impairment of the vascular tone and other endothelial phenotypic changes collectively termed endothelial dysfunction(s). This review will focus on the main mechanisms involved in the onset of endothelial dysfunction, with particular focus on inflammation and aberrant ROS production and on their relationship with classical and non-classical cardiovascular risk factors, such as hypertension, metabolic disorders, and aging. Furthermore, new mediators of vascular damage, such as microRNAs, will be discussed. Understanding mechanisms underlying the development of endothelial dysfunction is an important base of knowledge to prevent vascular damage in metabolic and cardiovascular diseases.

Effect of consumption of a carob pod inositol-enriched beverage on insulin sensitivity and inflammation in middle-aged prediabetic subjects

This study assessed the effects of an inositol-enriched beverage (IEB) on blood glucose levels and inflammation status in subjects with an impaired fasting glucose (IFG) state according to body mass index (BMI). This was a 12 week, double-blind, randomized, controlled trial employing forty-four IFG subjects (fasting glucose levels 100-125 mg dl-1) that were divided into two intervention groups: one receiving a IEB (n = 24) containing mainly pinitol (2.0 g twice a day), and the other a sweetened beverage based on sucrose (SB; n = 20). Anthropometric and biochemical measurements, postprandial and fasting nocturnal glycaemia (continuous glucose monitoring system), and inflammatory parameters (IL-6 and TNF-α) were analyzed at baseline and after intervention according to BMI (non-obese: BMI < 30 kg m-2 or obese: BMI ≥ 30 kg m-2). Non-obese subjects who consumed IEB exhibited a significant decrease in insulin (-14.4%), HOMA-IR index (-15.1%) and percentage of glucose change after postprandial and fasting nocturnal periods (-10.0% and -10.3%, respectively) compared with the SB group (-2.35% and 10.2%, respectively) although they did not show any change in inflammatory cytokine levels. By contrast, obese subjects who consumed IEB showed a smaller variation in glucose levels after nocturnal fasting (-4.34%) and a marked decrease in IL-6 and TNF-α (p < 0.05). These findings support that consumption of IEB in prediabetic subjects produces a response that is dependent on BMI, with a clear improvement of insulin resistance and postprandial and nocturnal glycemia in non-obese subjects and a marked anti-inflammatory response in obese subjects.