Oral glucose tolerance test effects on endothelial inflammation markers in healthy subjects and diabetic patients

The nutrition and immunity (nutrIMM) study: protocol for a non-randomized, four-arm parallel-group, controlled feeding trial investigating immune function in obesity and type 2 diabetes

Introduction

Individuals with obesity and/or type 2 diabetes are at higher risk of infection and have worse prognoses compared to healthy individuals. Several factors may influence immune responses in this population, including high adiposity, hyperglycemia, and unhealthy dietary habits. However, there is insufficient data on the independent or clustered contribution of these factors to obesity-related immune dysfunction, especially accounting for dietary intake. This study aims to establish the independent contribution of obesity and hyperglycemia to immune dysfunction independent of diet in adults with and without obesity with or without type 2 diabetes.

Methods

The Nutrition and Immunity (nutrIMM) study is a single-centre, non-randomized, four-arm, parallel-group, controlled feeding trial. It will enroll adults without obesity (Lean-NG) and with obesity and three metabolic phenotypes of normoglycemia, glucose intolerance, and type 2 diabetes. Participants will be assigned to one of four groups and will consume a standard North American-type diet for 4 weeks. The primary outcomes are plasma concentration of C-reactive protein and concentration of ex-vivo interleukin-2 secreted upon stimulation of T cells with phytohemagglutinin.

Discussion

This will be the first controlled feeding study examining the contribution of obesity, hyperglycemia, and diet on systemic inflammation, immune cell phenotype, and function in adults of both sexes. Results of this clinical trial can ultimately be used to develop personalized dietary strategies to optimize immune function in individuals with obesity with different immune and metabolic profiles.

Clinical trial registration

ClinicalTrials.gov, identifier NCT04291391.

Jabuticaba juice improves postprandial glucagon-like peptide-1 and antioxidant status in healthy adults: a randomized crossover trial

Jabuticaba is a Brazilian berry rich in polyphenols, which may exert beneficial effects on metabolic diseases. This randomized crossover study aimed to determine the effects of jabuticaba juice (250 ml in a portion) on postprandial response. Sixteen healthy subjects (11 women; 5 men; 28.4 ± 3.8 years old; body mass index (BMI) 21.7 ± 2.3 kg m-2) consumed two test products after fasting overnight in a randomized controlled crossover design. Each test product portion had a similar composition of sugar components: 250 mL water with glucose, fructose, colored with artificial non-caloric food colorings (placebo); and 250 mL of jabuticaba juice. Beverages were administered immediately before a carbohydrate meal. Blood samples were collected at 0, 15, 30, 45, 60, 90, and 120 min after each test product to analyze the concentrations of glucose, insulin, C-peptide, antioxidant capacity, plasma glucagon-like peptide-1 (GLP-1), and appetite sensations. Compared to the placebo, the intake of jabuticaba juice resulted in a higher GLP-1 response as the area under the curve (AUC) and peaking at 60 min. Jabuticaba juice also resulted in higher antioxidant capacity. Postprandial glucose, insulin, C-peptide levels, and appetite sensations were not significantly different between tests. In conclusion, 250 mL of jabuticaba juice before a carbohydrate meal was able to improve the antioxidant status and GLP-1 concentrations in healthy subjects.

Metabolic Actions of a Supplement of Ilex Paraguariensis (An Extract of the Leaf Standardized to 2% I-Deoxinojirimcina), White Mulberry and Chromium Picolinate in Nondiabetic Subects with Dysglycemia: A Randomized Trial

Aim: To prove if a nutraceutical containing Ilex paraguariensis (Ilex L. spp. Aquifoliales) (an extract of the leaf standardized to 2% I-deoxinojirimcina), white mulberry (Morus spp., Moraceae), and chromium picolinate can be effective in improving glycemic status in subject with dysglycemia. Methods: We randomized patients to consume placebo or the nutraceutical, self-administered once a day, one tablet at breakfast, for 3 months. Results: A reduction in fasting plasma glucose, postprandial glucose, and glycated hemoglobin was observed with the nutraceutical combination, both compared to baseline and placebo. Data suggested a decrease in the Homeostasis Model Assessment index with the nutraceutical, both compared to baseline and placebo. The M value, an index of insulin sensitivity, obtained after nutraceutical treatment was higher compared to baseline. We recorded a decrease in total cholesterol, low-density lipoprotein-cholesterol, and triglycerides with the nutraceutical combination compared to baseline and placebo. A decrease in high-sensitivity C-reactive protein was observed with the nutraceutical combination compared to baseline and placebo. Conclusions: A nutraceutical containing Ilex paraguariensis, white mulberry, and chromium picolinate can be helpful in improving glycemic status and lipid profile in dysglycemic subjects.

Blackcurrant (Ribes nigrum) lowers sugar-induced postprandial glycaemia independently and in a product with fermented quinoa: a randomised crossover trial

Berries rich in anthocyanins have beneficial effects on postprandial glycaemia. We investigated whether blackcurrant (75 g in a portion) independently and in a product with fermented quinoa induced similar effects on the sugar-induced postprandial glucose metabolism as observed before with 150 g of blackcurrant. Twenty-six healthy subjects (twenty-two females and four males) consumed four test products after fasting overnight in a randomised, controlled crossover design. Each test product portion contained 31 g of available carbohydrates and had similar composition of sugar components: 300 ml water with sucrose, glucose and fructose (SW; reference), blackcurrant purée with added sugars (BC), a product consisting of the blackcurrant purée and a product base with fermented quinoa (BCP) and the product base without blackcurrant (PB). Blood samples were collected at 0, 15, 30, 45, 60, 90, 120 and 180 min after eating each test product to analyse the concentrations of glucose, insulin and NEFA. In comparison with the SW, the intake of both the BC and BCP resulted in reduced glucose and insulin concentrations during the first 30 min, a more balanced decline during the first hour and improved glycaemic profile. The BCP induced more efficient effects than the BC due to the product base with fermented quinoa. A rebound of NEFA after the sugar-induced hypoglycaemic response was attenuated at the late postprandial phase by the BC and BCP. In conclusion, we showed that 75 g of blackcurrant and the product with fermented quinoa were able to lower postprandial glycaemia and insulinaemia.

Nutritional genomics, inflammation and obesity

The Human Genome Project has significantly broadened our understanding of the molecular aspects regulating the homeostasis and the pathophysiology of different clinical conditions. Consequently, the field of nutrition has been strongly influenced by such improvements in knowledge - especially for determining how nutrients act at the molecular level in different conditions, such as obesity, type 2 diabetes, cardiovascular disease, and cancer. In this manner, characterizing how the genome influences the diet and vice-versa provides insights about the molecular mechanisms involved in chronic inflammation-related diseases. Therefore, the present review aims to discuss the potential application of Nutritional Genomics to modulate obesity-related inflammatory responses. Arch Endocrinol Metab. 2020;64(3):205-22.

Current and Future Nutritional Strategies to Modulate Inflammatory Dynamics in Metabolic Disorders

Obesity, type 2 diabetes, and other metabolic disorders have a large impact on global health, especially in Western countries. An important hallmark of metabolic disorders is chronic low-grade inflammation. A key player in chronic low-grade inflammation is dysmetabolism, which is defined as the inability to keep homeostasis resulting in loss of lipid control, oxidative stress, inflammation, and insulin resistance. Although often not yet detectable in the circulation, chronic low-grade inflammation can be present in one or multiple organs. The response to a metabolic challenge containing lipids may magnify dysfunctionalities at the tissue level, causing an overflow of inflammatory markers into the circulation and hence allow detection of early low-grade inflammation. Here, we summarize the evidence of successful application of metabolic challenge tests in type 2 diabetes, metabolic syndrome, obesity, and unhealthy aging. We also review how metabolic challenge tests have been successfully applied to evaluate nutritional intervention effects, including an "anti-inflammatory" mixture, dark chocolate, whole grain wheat and overfeeding. Additionally, we elaborate on future strategies to (re)gain inflammatory flexibility. Through epigenetic and metabolic regulation, the inflammatory response may be trained by regular mild and metabolic triggers, which can be understood from the perspective of trained immunity, hormesis and pro-resolution. New strategies to optimize dynamics of inflammation may become available.

Ascophyllum nodosum and Fucus vesiculosus on glycemic status and on endothelial damage markers in dysglicemic patients

The aim of this study was to evaluate a nutraceutical combination containing polyphenols extracted from Ascophyllum nodosum and Fucus vesiculosus and chromium picolinate on glyemic status; secondary outcomes were considered the changes on endothelial markers. We randomized 65 dysglycemic patients to placebo or the nutraceutical agent for 6 months. We evaluated fasting plasma glucose (FPG), postprandial plasma glucose (PPG), HbA1c , fasting plasma insulin, homeostatic model assessment (HOMA) index, high sensitivity C-reactive protein (Hs-CRP), tumor necrosis factor-α (TNF-α), and adhesion molecules. At baseline and at 3 and 6 months, all patients underwent an oral glucose tolerance test. We recorded a reduction of HbA1c , FPG, PPG, and HOMA-IR compared with placebo (p < 0.05). After 6 months, 18.2% of patients retuned to a normal glycemic status in the nutraceutical group versus 0 patients in placebo group (p < 0.05); 69.7% were classified as impaired fasting glycemia and 12.1% as impaired glucose tolerance in the nutraceutical group versus 17.2% and 82.8 in placebo group (p < 0.01) for both. A reduction of Hs-CRP and TNF-α was recorded with the nutraceutical. The administration of a nutraceutical combination containing A. nodosum and F. vesiculosus can be helpful in improving insulin sensitivity and glycemic status. Larger randomized studies are required to confirm the positive effects of these agents.

An Overall Glance of Evidence Supportive of One-Hour and Two-Hour Postload Plasma Glucose Levels as Predictors of Long-Term Cardiovascular Events

This review summarizes the vast literature describing the long-term epidemiological studies with emphasis on postprandial glucose as a stronger predictor of cardiovascular complications as compared to fasting glucose and HbA1c. Many molecular studies also supported this fact by illustrating that postchallenge hyperglycemia is associated with elevated biomarkers of systemic inflammation in the plasma and thus increasing the chances of vascular damage. Large-scale studies have proved that vascular stiffness, brachial-ankle pulse-wave velocity, carotid intima thickness, and left ventricular hypertrophy have been associated with postprandial glucose as compared to fasting glucose or glycosylated hemoglobin.

Ascophyllum Nodosum, Fucus Vesiculosus and chromium picolinate nutraceutical composition can help to treat type 2 diabetic patients

AIM

To evaluate the actions of a combination of polifenolic composition (extracted from Ascophyllum Nodosum and Fucus Vesiculosus, InSea2^®) and chromium picolinate compared to placebo in addition to previously taken anti-diabetic therapy in patients with type 2 diabetes.

METHODS

175 Caucasian patients with type 2 diabetes were randomized to take nutraceutical combination or placebo for 6 months. One hundred and sixty-four cases completed the study. At baseline and after 6 months, glyco-metabolic control and lipid profile were evaluated.

RESULTS

Glycated hemoglobin was significantly reduced by the nutraceutical combination, but not by placebo, both compared to baseline (p<0.05), and compared to placebo (p<0.05). A similar trend was recorded for fasting plasma glucose (FPG) [-23.5% (p<0.01) vs baseline, and -18.0% (p<0.01) vs placebo] and post-prandial glucose (PPG) [-17.1% (p<0.01) vs baseline, and -11.1% (p<0.05) vs placebo]. No variations of lipid profile were recorded compared to baseline, even if it seems to observe a reduction trend of triglycerides level in the nutraceutical group.

CONCLUSION

In conclusion, a nutraceutical combination of polifenolic composition and chromium picolinate in addition to previously taken anti-diabetic therapy can be helpful in reducing glycated hemoglobin in patients with type 2 diabetes mellitus.

Microcystis bloom containing microcystin-LR induces type 2 diabetes mellitus

Epidemiological data from Lake Taihu showed significantly higher incidences of type 2 diabetes mellitus (T2DM) than in other areas of China. This may be related to the occurrence of a Microcystis bloom in Lake Taihu in the summer and autumn every year. The objective of this study is to investigate whether the contaminated water from the Microcystis bloom and the derivative pollutant microcystin-LR (MC-LR) can explain the higher incidences of T2DM. Healthy male mice were fed with water from different regions of Lake Taihu, and were either acutely or chronically exposed to MC-LR through oral administration or intraperitoneal injection. Serum lipid profiles were determined, and the effects on T2DM-related gene expression and insulin receptor signaling pathway were investigated. Intraperitoneal glucose tolerance (IPGTT) and insulin resistance (IRT) tests were implemented, and the functions of pancreatic islet and β-cell were also evaluated. The results showed that both water sampled from the region with a Microcysis bloom and those containing MC-LR altered the serum glucide and lipid profiles in mice after exposure. The exposure to a Microcysis bloom water affected the expression T2DM-related genes: up-regulated the mRNA levels of FASn, ACACA, G6pc, LPL, and Insig2, and down-regulated the mRNA level of PEPCK and Gsk-3β. Both acute and chronic exposure of MC-LR, even at very low concentrations (1 μg/L), impaired the insulin receptor signalling pathway and induced hyperinsulinemia and insulin resistance in mice. In this study, the most important intracellular target of MC-LR was found to be hetapocellular mitochondria. Thus, exposure to Microcystis bloom water containing microcystin-LR can induce the incidence of T2DM, by impairing the function of mitochondria by microcystin-LR. The study suggests a review of the risk assessment concerning 1 μg/L MC-LR as the reference dose in surface water.

Effects of metformin extended release compared to immediate release formula on glycemic control and glycemic variability in patients with type 2 diabetes

PURPOSE

The purpose of this study is to evaluate, in a randomized clinical trial, the effects of metformin immediate release (IR) compared with metformin extended release (XR) on the gastrointestinal tolerability and glycemic control.

MATERIALS AND METHODS

We enrolled 253 Caucasian patients with type 2 diabetes not well controlled by diet (glycated hemoglobin [HbA_1c] >7.0% and <8.5%). Patients were randomized to metformin IR or metformin XR for a period of 6 months at the maximum tolerated dose. The average dose of metformin IR used was 2,000±1,000 mg/day, while that of metformin XR was 1,000±500 mg/day. We evaluated body weight, HbA_1c, fasting and postprandial glucose, fasting plasma insulin (FPI) and homeostasis model assessment insulin resistance (HOMA-IR), lipid profile, and levels of some adipocytokines, including tumor necrosis factor-α (TNF-α), high-sensitivity C-reactive protein (hs-CRP), visfatin, and vaspin. Moreover, at the baseline and after 6 months, we administered patients some validated questionnaires to assess patients' satisfaction toward treatments.

RESULTS

After 6 months, both formulations gave a similar reduction in body weight and body mass index (BMI); however, metformin XR gave a greater improvement in glycemic control, FPI, and HOMA-IR, compared with both baseline and metformin IR. A reduction in total cholesterol (TC) and low-density lipoprotein (LDL) cholesterol was observed with metformin XR compared with IR. Levels of TNF-α, hs-CRP, and vaspin were reduced by metformin XR but not by the IR formulation. Metformin XR also raised the levels of visfatin.

CONCLUSION

Metformin XR formulation seems to be more effective than metformin IR in improving glyco-metabolic control, lipid profile, and levels of some adipocytokines in patients with type 2 diabetes mellitus.

The role of various peroxisome proliferator-activated receptors and their ligands in clinical practice

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors involved in several physiological processes including modulation of cellular differentiation, development, metabolism of carbohydrates, lipids, proteins, and tumorigenesis. The aim of this review is to examine how different PPAR ligands act, and discuss their use in clinical practice. PPAR ligands have a lot of effects and applications in clinical practice. Some PPAR ligands such as fibrates (PPAR-α ligands) are currently used for the treatment of dyslipidemia, while pioglitazone and rosiglitazone (PPAR-γ ligands) are anti-diabetic and insulin-sensitizing agents. Regarding new generation drugs, acting on both α/γ, β/δ, or α/δ receptors simultaneously, preliminary data on PPAR-α/γ dual agonists revealed a positive effect on lipid profile, blood pressure, atherosclerosis, inflammation, and anti-coagulant effects, while the overexpression of PPAR-β/δ seems to prevent obesity and to decrease lipid storage in cardiac cells. Finally, PPAR-α/δ dual agonist induces resolution of nonalcoholic steatohepatitis without fibrosis worsening.

A review about biomarkers for the investigation of vascular function and impairment in diabetes mellitus

The aim of this review was to analyze the main biomarkers of vascular function and impairment in patients with type 2 diabetes. Medline, SCOPUS, Web of Science, and Google Scholar databases were searched. We concluded that proatherogenic adhesion molecules (soluble intercellular adhesion molecule-1, soluble vascular adhesion molecule-1, and soluble E selectin) and inflammatory cytokines (high-sensitivity C-reactive protein, interleukin-6, and tumor necrosis factor-α) were elevated in type 2 diabetes mellitus. Their increased expression and release contribute to the accelerated atherogenesis typical of these patients. For these reasons, the early identification of high levels of these biomarkers will help to establish new strategies to reduce cardiovascular complications.

A green tea-containing starch confection increases plasma catechins without protecting against postprandial impairments in vascular function in normoglycemic adults

Postprandial hyperglycemia (PPH) increases cardiovascular disease risk regardless of glucose intolerance by transiently impairing vascular endothelial function (VEF) by limiting nitric oxide bioavailability in an oxidative stress-dependent manner. Preclinical studies show that green tea catechins attenuate PPH by inhibiting starch digestion. We hypothesized that a starch-based confection containing catechin-rich green tea extract (GTE) would limit PPH-mediated impairments in VEF in normoglycemic adults. We formulated a unique GTE confection and then conducted a double-blind, randomized, controlled, crossover study in healthy men (n = 15; 25.3 ± 1.0 years; 22.4 ± 1.8 kg m(-2)) in which they ingested starch confections (50 g carbohydrate) formulated with or without GTE (1 g) prior to evaluating sensory characteristics of confections and plasma glucose, biomarkers of lipid peroxidation and nitric oxide homeostasis, and brachial artery flow-mediated dilation (FMD) at 30 min intervals for 3 h. Sensory evaluation of confections indicated acceptable consumer appeal and an inability to distinguish between confections regardless of GTE. Plasma catechins concentrations increased following ingestion of the GTE confection. However, plasma glucose peaked at 60 min (P < 0.05) following confection ingestion and was unaffected throughout the postprandial period by the GTE confection (P > 0.05). FMD was significantly decreased only at 60 min regardless of confections containing GTE. Also at 60 min, both confections similarly increased plasma malondialdehyde while decreasing arginine and increasing asymmetric dimethylarginine/arginine. The successfully formulated GTE-containing confection effectively delivered catechins, but without mitigating PPH-mediated impairments in VEF in association with oxidative stress that likely limits nitric oxide bioavailability.

Short-term high-fat diet alters postprandial glucose metabolism and circulating vascular cell adhesion molecule-1 in healthy males

Short-term intake of a high-fat diet aggravates postprandial glucose metabolism; however, the dose-response relationship has not been investigated. We hypothesized that short-term intake of a eucaloric low-carbohydrate/high-fat diet (LCHF) would aggravate postprandial glucose metabolism and circulating adhesion molecules in healthy males. Seven healthy young males (mean ± SE; age: 26 ± 1 years) consumed either a eucaloric control diet (C, approximately 25% fats), a eucaloric intermediate-carbohydrate/intermediate-fat diet (ICIF, approximately 50% fats), or an LCHF (approximately 70% fats) for 3 days. An oral meal tolerance test (MTT) was performed after the 3-day dietary intervention. The concentrations of plasma glucose, insulin, glucagon-like peptide-1 (GLP-1), intercellular adhesion molecule-1, and vascular cell adhesion molecule-1 (VCAM-1) were determined at rest and during MTT. The incremental area under the curve (iAUC) of plasma glucose concentration during MTT was significantly higher in LCHF than in C (P = 0.009). The first-phase insulin secretion indexes were significantly lower in LCHF than in C (P = 0.04). Moreover, the iAUC of GLP-1 and VCAM-1 concentrations was significantly higher in LCHF than in C (P = 0.014 and P = 0.04, respectively). The metabolites from ICIF and C were not significantly different. In conclusion, short-term intake of eucaloric diet containing a high percentage of fats in healthy males excessively increased postprandial glucose and VCAM-1 concentrations and attenuated first-phase insulin release.

Hypoglycemic agents and potential anti-inflammatory activity

Current literature shows an association of diabetes and secondary complications with chronic inflammation. Evidence of these immunological changes include altered levels of cytokines and chemokines, changes in the numbers and activation states of various leukocyte populations, apoptosis, and fibrosis during diabetes. Therefore, treatment of diabetes and its complications may include pharmacological strategies to reduce inflammation. Apart from anti-inflammatory drugs, various hypoglycemic agents have also been found to reduce inflammation that could contribute to improved outcomes. Extensive studies have been carried out with thiazolidinediones (peroxisome proliferator-activated receptor-γ agonist), dipeptidyl peptidase-4 inhibitors, and metformin (AMP-activated protein kinase activator) with each of these classes of compounds showing moderate-to-strong anti-inflammatory action. Sulfonylureas and alpha glucosidase inhibitors appeared to exert modest effects, while the injectable agents, insulin and glucagon-like peptide-1 receptor agonists, may improve secondary complications due to their anti-inflammatory potential. Currently, there is a lack of clinical data on anti-inflammatory effects of sodium–glucose cotransporter type 2 inhibitors. Nevertheless, for all these glucose-lowering agents, it is essential to distinguish between anti-inflammatory effects resulting from better glucose control and effects related to intrinsic anti-inflammatory actions of the pharmacological class of compounds.

Improvement of plasma adiponectin, leptin and C-reactive protein concentrations by orlistat: a systematic review and meta-analysis

AIMS

To conduct a systematic review and meta-analysis of relevant randomized clinical trials (RCTs) to ascertain the effect size of orlistat in modulating plasma levels of adipokines, ghrelin and C-reactive protein (CRP).

METHODS

Medline, SCOPUS, Web of Science and Google Scholar databases were searched. A random-effects model and the generic inverse variance method were used for quantitative data synthesis. Heterogeneity was quantitatively assessed using I(2) index. Sensitivity analyses were conducted using the one-study remove approach. Random-effects meta-regression was performed using unrestricted maximum likelihood method to evaluate the impact of duration of treatment, percentage change in body mass index (BMI) and baseline BMI values as potential confounders of the estimated effect size.

RESULTS

Meta-analysis suggested a significant increase in plasma levels of adiponectin [weighted mean difference (WMD): 19.18%, 95% confidence interval (CI): 5.80, 32.57, p = 0.005] and significant reductions in plasma levels of leptin (WMD: -13.24%, 95% CI: -20.69, -5.78, p = 0.001) and CRP (WMD: -11.52%, 95% CI: -16.55, -6.49, p < 0.001) following treatment with orlistat. In meta-regression, changes in plasma concentrations of adiponectin, leptin and CRP were associated with duration of treatment, but not with either change in BMI or baseline BMI values.

CONCLUSION

Orlistat is effective in increasing plasma concentrations of adiponectin and decreasing those of leptin and CRP.

Dietary proteins improve endothelial function under fasting conditions but not in the postprandial state, with no effects on markers of low-grade inflammation

Endothelial dysfunction (ED) and low-grade inflammation (LGI) have a role in the development of CVD. The two studies reported here explored the effects of dietary proteins and carbohydrates on markers of ED and LGI in overweight/obese individuals with untreated elevated blood pressure. In the first study, fifty-two participants consumed a protein mix or maltodextrin (3×20 g/d) for 4 weeks. Fasting levels and 12 h postprandial responses of markers of ED (soluble intercellular adhesion molecule 1 (sICAM), soluble vascular cell adhesion molecule 1 (sVCAM), soluble endothelial selectin and von Willebrand factor) and markers of LGI (serum amyloid A, C-reactive protein and sICAM) were evaluated before and after intervention. Biomarkers were also combined into mean Z-scores of ED and LGI. The second study compared 4 h postprandial responses of ED and LGI markers in forty-eight participants after ingestion of 0·6 g/kg pea protein, milk protein and egg-white protein. In addition, postprandial responses after maltodextrin intake were compared with a protein mix and sucrose. The first study showed significantly lower fasting ED Z-scores and sICAM after 4 weeks on the high-protein diet (P≤0·02). The postprandial studies found no clear differences of ED and LGI between test meals. However, postprandial sVCAM decreased more after the protein mix compared with maltodextrin in both studies (P≤0·04). In conclusion, dietary protein is beneficial for fasting ED, but not for fasting LGI, after 4 weeks of supplementation. On the basis of Z-scores, postprandial ED and LGI were not differentially affected by protein sources or carbohydrates.

Phenotypic flexibility as key factor in the human nutrition and health relationship

Metabolic adaptation to a disturbance of homeostasis is determined by a series of interconnected physiological processes and molecular mechanisms that can be followed in space (i.e., different organs or organelles) and in time. The amplitudes of these responses of this "systems flexibility network" determine to what extent the individual can adequately react to external challenges of varying nature and thus determine the individual's health status and disease predisposition. Connected pathways and regulatory networks act as "adaptive response systems" with metabolic and inflammatory processes as a core-but embedded into psycho-neuro-endocrine control mechanisms that in their totality define the phenotypic flexibility in an individual. Optimal metabolic health is thus the orchestration of all mechanisms and processes that maintain this flexibility in an organism as a phenotype. Consequently, onset of many chronic metabolic diseases results from impairment or even loss of flexibility in parts of the system. This also means that metabolic diseases need to be diagnosed and treated from a systems perspective referring to a "systems medicine" approach. This requires a far better understanding of the mechanisms involved in maintaining, optimizing and restoring phenotypic flexibility. Although a loss of flexibility in a specific part of the network may promote pathologies, this not necessarily takes place in the same part because the system compensates. Diagnosis at systems level therefore needs the quantification of the response reactions of all relevant parts of the phenotypic flexibility system. This can be achieved by disturbing the homeostatic system by any challenge from extended fasting, to intensive exercise or a caloric overload.

The acute effects of low-dose TNF-α on glucose metabolism and β-cell function in humans

Type 2 diabetes is characterized by increased insulin resistance and impaired insulin secretion. Type 2 diabetes is also associated with low-grade inflammation and increased levels of proinflammatory cytokines such as TNF-α. TNF-α has been shown to impair peripheral insulin signaling in vitro and in vivo. However, it is unclear whether TNF-α may also affect endogenous glucose production (EGP) during fasting and glucose-stimulated insulin secretion (GSIS) in vivo. We hypothesized that low-dose TNF-α would increase EGP and attenuate GSIS. Recombinant human TNF-α or placebo was infused in healthy, nondiabetic young men (n = 10) during a 4-hour basal period followed by an intravenous glucose tolerance test (IVGTT). TNF-α lowered insulin levels by 12% during the basal period (P < 0.05). In response to the IVGTT, insulin levels increased markedly in both trials, but there was no difference between trials. Compared to placebo, TNF-α did not affect EGP during the basal period. Our results indicate that TNF-α acutely lowers basal plasma insulin levels but does not impair GSIS. The mechanisms behind this are unknown but we suggest that it may be due to TNF-α increasing clearance of insulin from plasma without impairing beta-cell function or hepatic insulin sensitivity.

The role of TNF-α G-308A promoter polymorphism in glycemic control in Type 2 diabetes patients

BACKGROUND

TNF-α polymorphisms were shown to be associated with insulin resistance and diabetes development and complications.

AIM

To investigate the association between glycemic control in Type 2 diabetes patients and TNF-α G-308A single nucleotide polymorphism (SNP).

METHODS

This was a cross-sectional observational study, where diabetes patients from both genders (170 male and 185 female) were enrolled in the study. Patients were divided into two groups: good glycemic control (n = 158) and poor glycemic control (n = 197). Genotyping of TNF-α G-308A SNP was carried out using restriction fragment length polymorphisms-polymerase chain reaction.

RESULTS

The results showed that TNF-α G-308A SNP is strongly associated with glycemic control in type 2 diabetes patients. Patients with the AA and AG genotypes had better glycemic control than those with GG genotype (P < 0.01). Other parameters that impacted glycemic control include duration of the disease (P < 0.01) and response to insulin therapy (P < 0.01). However, no contribution for gender or statins use to glycemic control was observed (P > 0.05).

CONCLUSION

TNF-α G-308A SNP might modulate glycemic control among type 2 diabetes patients.

Assessment of inflammatory resilience in healthy subjects using dietary lipid and glucose challenges

BACKGROUND

Resilience or the ability of our body to cope with daily-life challenges has been proposed as a new definition of health, with restoration of homeostasis as target resultant of various physiological stress responses. Challenge models may thus be a sensitive measure to study the body's health. The objective of this study was to select a dietary challenge model for the assessment of inflammatory resilience. Meals are a challenge to metabolic homeostasis and are suggested to affect inflammatory pathways, yet data in literature are limited and inconsistent.

METHOD

The kinetic responses of three different dietary challenges and a water control challenge were assessed on various metabolic and inflammatory markers in 14 healthy males and females using a full cross-over study design. The dietary challenges included glucose (75 g glucose in 300 ml water), lipids (200 ml whipping cream) and a mix of glucose and lipids (same amounts as above), respectively. Blood samples were collected at baseline and at 0.5, 1, 2, 4, 6, 8 and 10 h after consumption of the treatment products. Inflammation (IFNγ, IL-1β, IL-6, IL-8, IL-10, IL-12p70, TNF-α CRP, ICAM-1, VCAM-1, SAA, E-selectin, P-selectin, thrombomodulin, leukocytes, neutrophils, lymphocytes) and clinical (e.g. glucose, insulin, triglycerides) markers as well as gene expression in blood cells and plasma oxylipin profiles were measured.

RESULTS

All three dietary challenges induced changes related to metabolic control such as increases in glucose and insulin after the glucose challenge and increases in triglycerides after the lipid challenge. In addition, differences between the challenges were observed for precursor oxylipins and some downstream metabolites including DiHETrE's and HODE's. However, none of the dietary challenges induced an acute inflammatory response, except for a modest increase in circulating leukocyte numbers after the glucose and mix challenges. Furthermore, subtle, yet statistically significant increases in vascular inflammatory markers (sICAM-1 and sVCAM-1) were found after the mix challenge, when compared to the water control challenge.

CONCLUSIONS

This study shows that dietary glucose and lipid challenges did not induce a strong acute inflammatory response in healthy subjects, as quantified by an accurate and broad panel of parameters.

The role of oxidative stress in postprandial endothelial dysfunction

Endothelial dysfunction is a turning point in the initiation and development of atherosclerosis and its complications and is predictive of future cardiovascular events. Ingestion of high-carbohydrate or high-fat meals often results in postprandial hyperglycaemia and/or hypertriacylglycerolaemia that may lead to a transient impairment in endothelial function. The present review will discuss human studies evaluating the impact of high-carbohydrate and high-fat challenges on postprandial endothelial function as well as the potential role of oxidative stress in such postprandial metabolic alterations. Moreover, the present review will differentiate the postprandial endothelial and oxidative impact of meals rich in varying fatty acid types.

Relationship of pentraxin 3 with insulin sensitivity in gestational diabetes

BACKGROUND

Pentraxin 3 (PTX3) is a cytokine-inducible molecule expressed in different tissues, the levels of which increase in a response to a variety of inflammatory conditions. Recently, it has been linked to the serum glucose levels and some comorbidities in type 2 diabetes.

MATERIALS AND METHODS

Here, we aimed to investigate the role of PTX3 in gestational diabetes mellitus (GDM), which is considered a forerunner of type 2 diabetes. Fasting PTX3 serum levels were measured in 90 women [45 GDM, 45 normal glucose tolerance (NGT)] during pregnancy. In addition, PTX3 was measured during a 2 h, 75 g oral glucose tolerance test (OGTT) in 20 women (10 GDM, 10 NGT) at 24-28 weeks of gestation and in 16 of them after delivery (10GDM, 6 NGT).

RESULTS

A continuous increase in PTX3 levels was observed during the OGTT and reached in the GDM group a significant difference after 120 min compared with baseline (P < 0·05). Additionally, a rise in the PTX3 concentration was significantly higher in the GDM- compared with the NGT group, 120 min after glucose challenge (P < 0·01). During pregnancy, serum glucose and C-peptide were positively correlated with the PTX3 levels in the whole study group, whereas a negative association was found with the insulin sensitivity parameters QUICKI and OGIS.

CONCLUSIONS

Dependence of PTX3 on serum glucose levels was more pronounced in women with GDM than in the NGT group. This notion together with its inverse relation to the parameters of insulin sensitivity, suggests a potential involvement of PTX3 in GDM pathology.

A consideration of biomarkers to be used for evaluation of inflammation in human nutritional studies

To monitor inflammation in a meaningful way, the markers used must be valid: they must reflect the inflammatory process under study and they must be predictive of future health status. In 2009, the Nutrition and Immunity Task Force of the International Life Sciences Institute, European Branch, organized an expert group to attempt to identify robust and predictive markers, or patterns or clusters of markers, which can be used to assess inflammation in human nutrition studies in the general population. Inflammation is a normal process and there are a number of cells and mediators involved. These markers are involved in, or are produced as a result of, the inflammatory process irrespective of its trigger and its location and are common to all inflammatory situations. Currently, there is no consensus as to which markers of inflammation best represent low-grade inflammation or differentiate between acute and chronic inflammation or between the various phases of inflammatory responses. There are a number of modifying factors that affect the concentration of an inflammatory marker at a given time, including age, diet and body fatness, among others. Measuring the concentration of inflammatory markers in the bloodstream under basal conditions is probably less informative compared with data related to the concentration change in response to a challenge. A number of inflammatory challenges have been described. However, many of these challenges are poorly standardised. Patterns and clusters may be important as robust biomarkers of inflammation. Therefore, it is likely that a combination of multiple inflammatory markers and integrated readouts based upon kinetic analysis following defined challenges will be the most informative biomarker of inflammation.

α-Glucosidase inhibitors and their use in clinical practice

Post-prandial hyperglycemia still remains a problem in the management of type 2 diabetes mellitus. Of all available anti-diabetic drugs, α-glucosidase inhibitors seem to be the most effective in reducing post-prandial hyperglycemia. We conducted a review analyzing the clinical efficacy and safety of α-glucosidase inhibitors, both alone and in combination with other anti-diabetic drugs, with respect to glycemic control, inflammation and atherosclerosis. α-Glucosidase inhibitors proved to be effective and safe both in monotherapy and as an add-on to other anti-diabetic drugs. Compared to miglitol and voglibose, acarbose seems to have some additive effects such as stabling carotid plaques, and reducing inflammation. Acarbose also proved to reverse impaired glucose tolerance to normal glucose tolerance.

Metabolic syndrome and acute hyperglycemia are associated with endoplasmic reticulum stress in human mononuclear cells

Endoplasmic reticulum (ER) stress and the activation of the unfolded protein response (UPR) have been implicated in a number of complications associated with diabetes mellitus including micro- and macrovascular dysfunction. In this study we examine ER stress levels in blood cells isolated from human subjects with metabolic syndrome and in healthy controls. Total RNA and protein were isolated from leukocytes and the levels of specific ER stress markers were quantified by real-time-PCR and immunoblot analysis. Our results indicate that, compared to healthy controls, individuals with metabolic syndrome have elevated mRNA levels of genes indicative of ER stress; including spliced XBP-1 (sXBP-1), Grp78, and CHOP. Induced ER stress levels correlate with blood glucose but not plasma lipid concentration. Furthermore, in healthy individuals, a standard 75 g oral glucose challenge produced a significant elevation in spliced XBP-1 (1.3 fold), Grp78 (2.0 fold), and calreticulin (3.5 fold) mRNA 60 min post challenge and a significant increase in Grp78 (2.0 fold), calreticulin (2.7 fold) protein levels 2 h postchallenge, relative to fasting levels. The UPR was also activated ex vivo, in human leukocytes cultured in the presence of 15 mmol/l glucose, supporting a specific role for glucose. The oral glucose challenge was associated with a significant increase in the expression of inflammatory cytokines, including interleukin (IL)-1α/β, IL-6, and IL-8, that may result from ER stress. These findings suggest that there is an association between both acute and chronic dysglycemia and ER stress in humans.

Acarbose actions on insulin resistance and inflammatory parameters during an oral fat load

The aim of this study was to evaluate the effects of acarbose on inflammatory biomarkers and insulin resistance in diabetic patients before and after a standardized oral fat load (OFL). Ninety six patients were assigned to take acarbose 50mg three times a day and 92 to take placebo; after the first month acarbose was titrated to 100mg three times a day. We evaluated the following parameters at the baseline, and after 1, 2 and 7months: body mass index (BMI), glycemic control, fasting plasma insulin, post-prandial plasma insulin, homeostasis model assessment insulin resistance index (HOMA-IR), blood pressure, lipid profile, soluble intercellular adhesion molecule-1 (sICAM-1), interleukin-6 (IL-6), high-sensitivity C reactive protein (Hs-CRP), soluble vascular cell adhesion molecule-1 (sVCAM-1), and soluble E-selectin (sE-selectin). Furthermore, at the baseline and at the end of the study all patients underwent OFL, and an euglycemic hyperinsulinemic clamp to evaluate M value and total glucose requirement. Acarbose was better than placebo in improving glycemic and lipid profile, and HOMA-IR. Furthermore, acarbose gave a decrease of fasting plasma insulin, post-prandial insulin, s-ICAM-1, sVCAM-1, IL-6, and Hs-CRP, not observed with placebo, even if no significant differences between the two groups were observed. During the second OFL performed after the therapy with acarbose, we observed a significant decrease of all inflammatory parameters' peaks compared to the OFL administered at baseline. Acarbose was more effective than acarbose in reducing the post-OFL peaks of the various parameters included the inflammatory markers, after 7months of therapy.