Identification of cysteinylated transthyretin, a predictive biomarker of treatment response to partially hydrolyzed guar gum in type 2 diabetes rats, by surface-enhanced laser desorption/ionization time-of-flight mass spectrometry

Effect of partially hydrolyzed guar gum on the expression of aquaporin-3 in the colon

In recent years, the development of functional foods targeting gastrointestinal disorders has been in progress. Partially hydrolyzed guar gum (PHGG), which is a water-soluble dietary fiber, is known to have a constipation-improving effect. However, many aspects of the mechanism remain unclear. In this study, we investigated the role of aquaporin-3 (AQP3), which regulates the water content of feces in ameliorative effect of PHGG on constipation. Rats were allowed to freely consume a normal diet or a diet containing 5% PHGG for 14 days, and defecation parameters were measured. We also analyzed the expression levels of genes involved in water transport in the colon. The defecation frequency and volume of rats treated with PHGG were not different from those from the control group, but the fecal water content was significantly increased, and soft stools were observed. The expressions of claudin-1, tight junction protein-1, and cadherin-1, which are involved in tight junctions or adherens junctions, were almost the same in the PHGG-treated group and the control group. The expression level of AQP3 in the colon was significantly decreased in the PHGG-treated group. In this study, PHGG decreased the colonic AQP3 expression, thereby suppressing water transport from the luminal side to the vascular side and improving constipation.

Early diagnosis of type 2 diabetes based on multiple biomarkers and non-invasive indices

We previously reported that type 2 diabetes risk, early impaired glucose tolerance and insulin resistance can be predicted by measuring the fasting levels of certain biomarkers. Here we validated these findings in randomly recruited healthy volunteers (n = 101) based on biomarker expression as well as various non-invasive indices. Weight, body mass index, waist circumference and visceral fat differed between individuals with impaired fasting glucose and/or impaired glucose tolerance, and normal subjects. Fasting plasma levels of glycated hemoglobin, leptin, pro-insulin and retinol binding protein 4 differed between impaired fasting glucose/impaired glucose tolerance and normal subjects group and between newly detected diabetes and normal subjects group. Insulin resistance was correlated with fasting levels of insulin and leptin/adiponectin (r = 0.913); of insulin, retinol binding protein 4 and leptin/adiponectin (r = 0.903); and of insulin, glycated albumin, and leptin/adiponectin (r = 0.913). Type 2 diabetes risk, early impaired glucose tolerance and insulin resistance were predicted with >98% specificity and sensitivity by comparing fasting glucose levels to the estimated Matsuda Index based on fasting levels of insulin, adiponectin and leptin with or without oxidative lineolate metabolites. Non-invasive indices are slightly correlated with glucose tolerance and insulin resistance but do not increase the accuracy of predicting type 2 diabetes risk.

Cysteinylated transthyretin as a discriminator of cardiovascular risk in patients with diabetes mellitus

BACKGROUND

The cysteine residue on transthyretin (TTR) is susceptible to be oxidized, and serum cysteinylated TTR (Cys-TTR) level is thought to reflect oxidative stress. The purpose of this study was to elucidate the relationship between Cys-TTR and arterial stiffness, a known predictor of cardiovascular disease, in patients with type 2 diabetes.

METHODS

The subjects were 105 male outpatients with type 2 diabetes. Arterial stiffness was evaluated by measuring cardio-ankle vascular index (CAVI). The relationship between CAVI and ratio of Cys-TTR to total TTR (Cys-TTR ratio) was analyzed.

RESULTS

Cys-TTR ratio was significantly correlated with CAVI (Pearson's correlation coefficient: 0.316, p<0.01), and CAVI was significantly higher in the 3rd tertile group for Cys-TTR ratio than in its 1st tertile group. These relationships were also significant after adjusting for age, smoking, alcohol drinking, body mass index, mean arterial pressure, hemoglobin A1c, LDL cholesterol-to-HDL cholesterol ratio and eGFR. Prevalence of high CAVI (≥10.0) was significantly higher in the 3rd tertile for Cys-TTR ratio than in its 1st tertile and tended to be higher with an increase in tertile (28.6% in the 1st tertile, 42.9% in the 2nd tertile and 60.0% in the 3rd tertile). Odds ratio (OR) for high CAVI of the 3rd vs. 1st tertile groups for Cys-TTR ratio was significantly higher than the reference level of 1.00 both before and after adjustment for the above cardiovascular risk factors (crude OR, 3.75 [1.38-10.17]; adjusted OR, 5.09 [1.39-18.64]).

CONCLUSIONS

Cys-TTR ratio is associated with arterial stiffness in patients with diabetes and is proposed as a new discriminator of cardiovascular risk.

Biomarkers of stress-mediated metabolic deregulation in diabetes mellitus

This review illustrates the relationship of oxidative and nitrative stress to diabetes mellitus and its complications. This is of considerable interest because diabetes mellitus is a lifetime systemic metabolic disease that may have childhood or adult onset and affects not only a triad of pancreatic islet cell insulin, pituitary insulin-like growth hormone, and liver steatosis, it has a long-term association with adiposity, atherosclerosis, coronary vascular disease, kidney disease of the nature afferent arteriolar sclerosis and nodular glomerulosclerosis, cerebrovascular disease, and amyloid deposition in the pancreas and kidney. Only at the end of the 20th century do we gain insight into oxidative and nitrative stress and their consequences. Of special interest here is the fact that reactive oxygen and nitrogen radicals are with us generated throughout the life cycle, and the roles for glutathione and Fe³⁺ are key elements in the metabolic picture, which brings into the picture dietary factors. More research is required to demonstrate the clinical relivance of naturally-occuring whole-food antioxidants in ameliorating human diabetic complications in vivo.