Habitual intake of dairy products influences serum 1,5-anhydroglucitol levels independently of plasma glucose

https://doi.org/10.1016/j.diabres.2010.06.023Get rights and content

Abstract

1,5-Anhydroglucitol (1,5-AG), a marker of glycemic control state, is reabsorbed via SGLT (sodium glucose cotransporter)-4 (SLC5A9) at renal proximal tubules. SGLT4 is responsible for reabsorption of mannose, fructose, galactose, glucose, and 1,5-AG. Thus, based on our hypothesis that serum 1,5-AG levels are influenced by diet, we investigated whether eating habits influence serum 1,5-AG levels. In total, 330 subjects (158 males and 172 females) with normal glucose tolerance participated. Relationships between serum 1,5-AG levels and eating habits (intake of meats, fish, soybean products, eggs, dairy products, fruit, vegetables, and salt) surveyed by questionnaire were investigated. Stepwise multivariate regression analysis revealed that habitual intake of dairy products was a significant negative explanatory variable for serum 1,5-AG levels. Serum 1,5-AG levels were lower in subjects with habitual intake of dairy products than in those without. On the other hand, HbA1C, glycated albumin, fasting plasma glucose, and OGTT 2-h plasma glucose were not different between the subjects of these two groups.

In conclusion, habitual intake of dairy products was associated with low serum 1,5-AG levels, independently of plasma glucose levels.

Introduction

1,5-Anhydroglucitol (1,5-AG) is a major polyol in human serum. Serum 1,5-AG levels are reduced in diabetic patients, as they reflect urinary glucose excretion [1], [2]. Based on this observation, serum 1,5-AG is used as a clinical marker of glycemic control in diabetic patients. In comparison to HbA1C, serum 1,5-AG level reflects more recent glycemic control, and more sensitively shows changes in plasma glucose levels [3]. Furthermore, it has been shown that 1,5-AG can reflect postprandial hyperglycemia [4].

1,5-AG is actively reabsorbed by 1,5-AG/fructose/mannose selective transporter [SGLT(sodium glucose cotransporter)-4 (SLC5A9)], which is a glucose transporter in renal proximal tubules that exists downstream of SGLT2 (SLC5A2) [5], [6]. As the reabsorption of 1,5-AG is competitively inhibited by urinary glucose, which has similar structure to 1,5-AG, serum 1,5-AG levels are lower in diabetic patients.

In the absence of urinary glucose, this competitive inhibition by glucose does not occur and serum 1,5-AG levels do not correlate with plasma glucose [7]. Under this condition, there is a possibility that reabsorption of 1,5-AG is affected by monosaccharides such as mannose, fructose, and galactose, which are also reabsorbed via SGLT4. The content of these monosaccharides varies among foods. Thus, we conducted the present study based on a hypothesis that eating habit might affect serum 1,5-AG levels.

Section snippets

Subjects studied

We selected subjects with normal glucose tolerance to eliminate effect of urinary glucose levels. We initially screened 558 subjects (333 males and 225 females) who underwent health examinations at Kinki Central Hospital from July to August 2008 (Table 1). In these subjects 75 g oral glucose tolerance test (OGTT) was performed. Among them, 331 subjects (158 males and 173 females) were diagnosed with normal glucose tolerance. Definition of normal glucose tolerance was defined according to ADA

Results

Fasting plasma glucose and OGTT 2-h plasma glucose were significantly higher, but HbA1C and GA were significantly lower in males than in females with normal glucose tolerance in this study (Table 1). Serum 1,5-AG was significantly higher in males than in females (Table 1).

The summary data for the dietary questionnaire are shown in Table 2. Stepwise multivariate regression analysis was conducted using serum 1,5-AG as a response variable, and 8 questionnaire items of eating habits (Table 3), age,

Discussion

The present study showed that serum 1,5-AG levels were significantly lower in the subjects with habitual intake of dairy products than in those without, regardless of sex. However, plasma glucose, HbA1C, and GA levels were not different between the subjects of these two groups, suggesting that plasma glucose levels were not influenced by habitual intake of dairy products. It has been reported that administration of dairy products suppresses elevation of plasma glucose in high fructose-fed rats

Conflicts of interest

There are no conflicts of interest.

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