Dietary Advanced Glycation End Products Consumption as a Direct Modulator of Insulin Sensitivity in Overweight Humans: A Study Protocol for a Double-Blind, Randomized, Two Period Cross-Over Trial

The Human Microbiome as a Therapeutic Target for Metabolic Diseases

The human microbiome functions as a separate organ in a symbiotic relationship with the host. Disruption of this host-microbe symbiosis can lead to serious health problems. Modifications to the composition and function of the microbiome have been linked to changes in host metabolic outcomes. Industrial lifestyles with high consumption of processed foods, alcoholic beverages and antibiotic use have significantly altered the gut microbiome in unfavorable ways. Therefore, understanding the causal relationship between the human microbiome and host metabolism will provide important insights into how we can better intervene in metabolic health. In this review, I will discuss the potential use of the human microbiome as a therapeutic target to improve host metabolism.

Effect of dietary advanced glycation end products on inflammation and cardiovascular risks in healthy overweight adults: a randomised crossover trial

Diets high in advanced glycation end products (AGEs) are thought to be detrimental to cardiovascular health. However, there remains uncertainty about the beneficial effect of a low AGE diet on cardiovascular risk factors and inflammatory markers in overweight individuals. We thus performed a randomised, double blind, crossover trial to determine whether consumption of low AGE diets reduce inflammation and cardiovascular risks in overweight and obese otherwise healthy adults. All participants (n = 20) consumed low and high AGE diets alternately for two weeks and separated by a four week washout period. Low AGE diets did not change systolic (p = 0.2) and diastolic blood pressure (p = 0.3), mean arterial pressure (p = 0.8) and pulse pressure (p = 0.2) compared to high AGE diets. Change in total cholesterol (p = 0.3), low-density lipoprotein (p = 0.7), high-density lipoprotein (p = 0.2), and triglycerides (p = 0.4) also did not differ and there was no difference in inflammatory markers: interleukin-6 (p = 0.6), monocyte chemoattractant protein-1 (p = 0.9), tumour necrosis factor α (p = 0.2), C-reactive protein (p = 0.6) and nuclear factor kappa beta (p = 0.2). These findings indicate that consumption of low AGE diets for two weeks did not improve the inflammatory and cardiovascular profiles of overweight and obese adults.

Diet low in advanced glycation end products increases insulin sensitivity in healthy overweight individuals: a double-blind, randomized, crossover trial

BACKGROUND

The consumption of advanced glycation end products (AGEs) has increased because of modern food processing and has been linked to the development of type 2 diabetes in rodents.

OBJECTIVE

We determined whether changing dietary AGE intake could modulate insulin sensitivity and secretion in healthy, overweight individuals.

DESIGN

We performed a double-blind, randomized, crossover trial of diets in 20 participants [6 women and 14 men; mean ± SD body mass index (in kg/m(2)): 29.8 ± 3.7]. Isoenergetic- and macronutrient-matched diets that were high or low in AGE content were alternately consumed for 2 wk and separated by a 4-wk washout period. At the beginning and end of each dietary period, a hyperinsulinemic-euglycemic clamp and an intravenous glucose tolerance test were performed. Dietary, plasma and urinary AGEs N(€)-(carboxymethyl)lysine (CML), N(€)-(carboxyethyl)lysin (CEL), and methylglyoxal-derived hydroimadazolidine (MG-H1) were measured with the use of mass spectrometry.

RESULTS

Participants consumed less CML, CEL, and MG-H1 during the low-AGE dietary period than during the high-AGE period (all P < 0.05), which was confirmed by changes in urinary AGE excretion. There was an overall difference in insulin sensitivity of -2.1 mg · kg(-1) · min(-1) between diets (P = 0.001). Insulin sensitivity increased by 1.3 mg · kg(-1) · min(-1) after the low-AGE diet (P = 0.004), whereas it showed a tendency to decrease by 0.8 mg · kg(-1) · min(-1) after the high-AGE diet (P = 0.086). There was no difference in body weight or insulin secretion between diets (P = NS).

CONCLUSIONS

A diet that is low in AGEs may reduce the risk of type 2 diabetes by increasing insulin sensitivity. Hence, a restriction in dietary AGE content may be an effective strategy to decrease diabetes and cardiovascular disease risks in overweight individuals. This trial was registered at clinicaltrials.gov as NCT00422253.

Analysis of advanced glycation end products in the DHS Mind Study

AIMS

Human studies of links between advanced glycation end-products (AGEs) and disease phenotypes are less common than studies of animal and cell models. Here, we examined the association of total AGEs with diabetes risk factors in a predominately type 2 diabetes (T2D) affected cohort.

METHODS

AGEs were measured using an enzyme linked immunosorbant assay in 816 individuals from the DHS Mind Study (n=709 T2D affected), and association analyses were completed.

RESULTS

Total AGEs were associated with estimated glomerular filtration rate (p=0.0054; β=-0.1291) and coronary artery calcification (p=0.0352; β=1.1489) in the entire cohort. No significant associations were observed when individuals with T2D were analyzed separately. In individuals without T2D, increased circulating AGEs were associated with increased BMI (p=0.02, β=0.138), low density lipoproteins (p=0.046, β=17.07) and triglycerides (p=0.0004, β=0.125), and decreased carotid artery calcification (p=0.0004, β=-1.2632) and estimated glomerular filtration rate (p=0.0018, β=-0.1405). Strong trends were also observed for an association between AGEs and poorer cognitive performance on the digit symbol substitution test (p=0.046, β=-6.64) and decreased grey matter volume (p=0.037, β=-14.87).

CONCLUSIONS

AGEs may play an important role in a number of phenotypes and diseases, although not necessarily in interindividual variation in people with T2D. Further evaluation of specific AGE molecules may shed more light on these relationships.