Effects of Diets with Different Proportions of Protein/Carbohydrate on Retinal Manifestations in db Mice

Nutritional Risk Factors in Albuminuria and Retinopathy in Patients Newly Diagnosed With Type 2 Diabetes: A Cross-sectional Case Series Study

BACKGROUND/AIM

Although nutritional risk factors for developing complications in type 2 diabetes mellitus (T2DM) have been examined, the effect of protein intake on nephropathy is debated, and there is little research on retinopathy. This cross-sectional case-series study aimed to examine the risk factors, including nutritional status, for complications in patients newly diagnosed with T2DM.

PATIENTS AND METHODS

Fifty-four patients were recruited, based on the results of examinations of blood glucose and/or glycated hemoglobin level for T2DM. To evaluate nutritional status, blood and urine examinations were performed and the Food Frequency Questionnaire was administered. Two-way analysis of variance, Fisher's exact test and logistic regression analyses were performed.

RESULTS

The patients were categorized into four groups: 24 without albuminuria and without retinopathy, four without albuminuria with retinopathy, 21 with albuminuria without retinopathy, and five with albuminuria with retinopathy. Logistic analysis of albuminuria revealed that estimated sodium intake was significantly independent as the explanatory factors of age, sex, and body mass index. Patients with retinopathy had significantly higher blood urea nitrogen, and significantly lower plasma total protein levels than patients without retinopathy, suggesting that retinopathy is related to a higher catabolic state. Through a questionnaire on food intake, patients with retinopathy had a significantly lower intake of fat and monounsaturated fatty acids and a significantly higher intake of iodine based on intake of seaweed, corrected for energy intake, than patients without retinopathy.

CONCLUSION

The present study may lead to planning a large cohort study for examining nutritional risk factors related to complications in patients newly diagnosed with T2DM in Japan.

Higher Branched-chain Amino Acids and Lower Serine Exist in the Plasma of Nondiabetic Mice: A Comparison Between High- and Low-protein Diet Conditions

BACKGROUND/AIM

The effects of dietary protein and carbohydrate content on the plasma amino acid profile of patients with diabetes are not fully understood. Therefore, we examined whether there are effects of diets with differing proportions of protein and carbohydrate on the plasma amino acid concentrations of control (CT) mice and mice with type 2 diabetes (db).

MATERIALS AND METHODS

We used db mice as an animal model of type 2 diabetes which are genetically deficient in leptin receptor. Diets with differing proportions of protein and carbohydrates (L diet: low protein/carbohydrate ratio, H diet: high protein/carbohydrate ratio) were supplied. db Mice were fed with a restriction on the basis of the consumption by CT-L mice, such that equivalent amounts of energy and fat were consumed. In CT mice fed the L or H diets, there was no significant difference in ad libitum food intake.

RESULTS

There were significant interactions between diet and genotype with respect to water intake, urine volume, urinary glucose concentration, and plasma isoleucine, leucine, valine, branched-chain amino acids, and serine concentrations. db-H mice showed significantly higher water intake, urine volume, and urinary glucose than db-L mice. db Mice fed the L or H diets had similar plasma amino acid profiles, except for valine. In contrast, CT-H mice showed significantly higher valine and branched-chain amino acids and lower serine concentrations than CT-L mice. Thus, the CT-H mice were more similar to db mice fed either of the diets.

CONCLUSION

There were different effects of the dietary protein or carbohydrate content on the plasma amino acid profiles between nondiabetic and diabetic mice. In particular, the profiles in nondiabetic conditions were different between the low- and high-protein diet conditions.

Effects of the amount and type of carbohydrates used in type 2 diabetes diets in animal models: A systematic review

Type 2 diabetes mellitus (T2DM) is among the most prevalent diseases in the world, affecting over 420 million people. The disease is marked by a poor metabolic effect of insulin leading to chronic hyperglycaemia, which can result in microvascular complications. It is widely known that postprandial glycaemia is reliant on the total carbohydrate content of a meal. However, the importance of the amount and the source of these carbohydrates remains controversial due to mechanisms other than insulin secretion. Oxidative stress, inflammation, pyruvate production and the quality of the intestinal microbiota, resulting in plasma lipopolysaccharides and short-chain fatty acids production, play an important role in blood sugar control and consequently in type 2 diabetes. Thus, we systematically reviewed the preclinical evidences on the impact of the amount and type of carbohydrate found in different diets and its influence on blood glucose levels in diabetic animals. We used a comprehensive and structured search in biomedical databases Medline (PubMed), Scopus and Web of Science, recovering and analyzing 27 original studies. Results showed that sucrose-rich diets deteriorated diabetic condition in animal models regardless of the total dietary carbohydrate content. On the other hand, fiber, particularly resistant starch, improved blood glucose parameters through direct and indirect mechanisms, such as delayed gastric emptying and improved gut microbiota. All studies used rodents as animal models and male animals were preferred over females. Improvements in T2DM parameters in animal models were more closely related to the type of dietary carbohydrate than to its content on a diet, i. e., resistant starch seems to be the most beneficial source for maintaining normoglycemia. Results show that current literature is at high risk of bias due to neglecting experimental methods.

Increased Expression of Ecto-NOX Disulfide-thiol Exchanger 1 (ENOX1) in Diabetic Mice Retina and its Involvement in Diabetic Retinopathy Development

BACKGROUND/AIM

Diabetic retinopathy (DR) is a type of retinal damage caused by a complication of diabetes and is a major cause of blindness in working-age adults. Ecto-NOX disulfide-thiol exchanger 1 (ENOX1) is a member of the ecto-NOX family involved in the plasma membrane electron transport pathway. This study aimed to investigate the role of ENOX1 in the development of DR.

MATERIALS AND METHODS

Human retinal endothelial cells (HRECs) and human retinal pigment epithelial cells (HREpiCs) exposed to a high concentration (25 mM) of D-glucose and type 2 diabetes (T2D) mice (+Lepr^db/+Lepr^db, db/db) with retinopathy were used as models to determine the ENOX1 expression levels there.

RESULTS

Our results showed that ENOX1 expression levels did not significantly change in both HRECs and HREpiCs under hyperglycemic conditions for 48 h. Nevertheless, ENOX1 expression increased significantly in T2D mouse retinas, particularly in the photoreceptor layer, compared to the control mouse retinas.

CONCLUSION

Different retinal ENOX1 expression in T2D mice and control mice suggested that ENOX1 may be involved in DR development.