Branched-chain amino acid intake and the risk of diabetes in a Japanese community: the Takayama study

Elevation of branched-chain amino acid levels in diabetes and NAFL and changes with antidiabetic drug treatment

Diabetes mellitus (DM), non-alcoholic fatty liver (NAFL), and obesity are associated with elevated branched-chain amino acid (BCAA) levels, but the mechanism and significance of this has not been elucidated. Eighty-four subjects were enrolled including 43 with DM. Serum BCAA levels were positively correlated with waist-hip ratio and ALT. Serum BCAA levels in subjects with DM were higher than non-DM and those in subjects with NAFL were also higher than non-NAFL. Treatment with pioglitazone and alogliptin (19 of 43 DM subjects) improved serum haemoglobin A1c and decreased BCAA levels. The decrease in BCAAs with improved glucose metabolism suggests that abnormal glucose metabolism is also a factor in elevated BCAA levels.

Plasma levels of lysine, tyrosine, and valine during pregnancy are independent risk factors of insulin resistance and gestational diabetes

BACKGROUND

This study compared plasma concentrations of amino acids in pregnant women with and without gestational diabetes mellitus (GDM) and identified the association between plasma amino acid levels and GDM, insulin resistance, and insulin secretion at 24-28 weeks of pregnancy.

METHODS

Circulating amino acid levels were evaluated using high-performance liquid chromatography at 24-28 weeks of pregnancy in 25 non-GDM and 64 GDM women after adjusting for covariates such as maternal age, body mass index (BMI) before pregnancy, BMI and gestational age at screening GDM, and daily caloric intake. Backward stepwise logistic regression analysis was used to identify the predictors of developing GDM, and homeostatic model assessments for insulin resistance (HOMA-IR) and β-cell function (HOMA-B).

RESULTS

Circulating levels of amino acids except threonine and tyrosine were significantly higher in GDM women than non-GDM women. Along with the intakes of energy, protein, and fat from animal sources, the intakes of each amino acid were significantly higher in the GDM group without a direct correlation to plasma amino acid levels. The variation in GDM development was explained by maternal age, diastolic blood pressure, and plasma lysine levels (R(2)=0.691). Height, BMI before pregnancy, systolic blood pressure, and plasma tyrosine and valine levels accounted for the variation in HOMA-IR (R(2)=0.589). The 53.3% variation of HOMA-B was explained by maternal age, BMI at GDM screening, plasma insulin level at 1 h during the oral glucose tolerance test (OGTT), and plasma valine level.

CONCLUSIONS

Circulating concentrations of lysine, tyrosine, and valine were independently and positively associated with GDM through modifying insulin resistance and secretion.

Negative energy balance affects imprint stability in oocytes recovered from postpartum dairy cows

Ovarian follicle development in post-partum, high-producing dairy cows, occurs in a compromised endogenous metabolic environment (referred to as negative energy balance, NEB). Key events that occur during oocyte/follicle growth, such as the vital process of genomic imprinting, may be detrimentally affected by this altered ovarian environment. Imprinting is crucial for placental function and regulation of fetal growth, therefore failure to establish and maintain imprints during oocyte growth may contribute to early embryonic loss. Using ovum pick-up (OPU), oocytes and follicular fluid samples were recovered from cows between days 20 and 115 post-calving, encompassing the NEB period. In a complimentary study, cumulus oocyte complexes were in vitro matured under high non-esterified fatty acid (NEFA) concentrations and in the presence of the methyl-donor S-adenosylmethionine (SAM). Pyrosequencing revealed the loss of methylation at several imprinted loci in the OPU derived oocytes. The loss of DNA methylation was observed at the PLAGL1 locus in oocytes, following in vitro maturation (IVM) in the presence of elevated NEFAs and SAM. Finally, metabolomic analysis of postpartum follicular fluid samples revealed significant differences in several branched chain amino acids, with fatty acid profiles bearing similarities to those characteristic of lactating dairy cows. These results provide the first evidence that (1) the postpartum ovarian environment may affect maternal imprint acquisition and (2) elevated NEFAs during IVM can lead to the loss of imprinted gene methylation in bovine oocytes.

Dietary protein and blood glucose control

PURPOSE OF REVIEW

This review presents the different pathways by which protein and amino acid impact glucose control. The review more particularly discusses the contradictory effects reported in the literature on the involvement of amino acid on glucose production and in insulin secretion and sensitivity.

RECENT FINDINGS

Some recent findings allow a better understanding of the direct and indirect mechanisms involved in the insulinotropic activity of some amino acids in pancreatic β-cell and in the production of glucose through liver gluconeogenesis that participates to improve the control of glycemia. In contrast, the potential deleterious effects of branched chain amino acid, and particularly leucine, hypothesized in previous publications, have been discussed in some recent publications.

SUMMARY

These processes are of high clinical relevance since the role of protein and amino acid have been repeatedly discussed to improve insulin secretion in type 2 diabetes patients or in weight management strategy in overweight and obese individuals. In addition, whether blood amino acid could be used as biomarkers for the risk of type 2 diabetes needs to be discussed.