Metabolic fate of plasma glucose during hyperglycemia in impaired glucose tolerance: evidence for further early defects in the pathogenesis of type 2 diabetes

LACTATE CAN BE A MARKER OF METABOLIC SYNDROME IN SEVERE OBESITY?

Background:

In the last decades, numerous studies have confirmed the importance of lactate - by-product to the nutrient signal of the intracellular redox state - to regulatory functions in energy metabolism.

Aim:

To evaluate changes in blood lactate in patients with severe obesity and its correlation with body composition and metabolic profile.

Methods:

Twenty-four people with severe obesity (BMI=40 kg/m²) were evaluated in a prospective case-control study before and six months after Roux-in-Y gastric bypass. The blood lactate, total cholesterol, and fractions, C-reactive protein and HOMA-IR were analyzed after 12 h fasting. Body mass composition was evaluated by bioelectrical impedance and respiratory quotient was measured by indirect calorimetry.

Results:

The initial lactate level was 2.5±1.1 mmol/l and returned to normal level (1.9±3.6 mmol/l, p=0.0018) after surgery. This reduction was positively correlated with a decrease in BMI (p=0.0001), % free fat mass (p=0,001), % fat mass (p=0.001) and HOMA-IR (p=0.01). There was normalization of lactatemia in 70% of patients. There was no correlation between lactatemia and C-reactive protein.

Conclusions:

There was a significant improvement of metabolic parameters, normalization of blood lactate, fat mass loss, although these individuals remained with a high BMI.

Role of Altered Venous Blood Lactate and HbA1c in Women with Gestational Diabetes Mellitus

INTRODUCTION

Being a mirror image of metabolic syndrome, Gestational Diabetes Mellitus (GDM) is associated with significant maternal and fetal morbidity. Increased blood lactate concentration and alterations of substrate utilization are partly involved in development of insulin resistance in GDM. Fetuses born to such mothers have shown low umbilical vein oxygen saturation and low oxygen content and increased lactate concentrations. These changes may certainly reflect enhanced fetal metabolism as a result of hyperglycaemia and hyperinsulinemia and therefore, these fetuses deserve intense surveillance at term and during delivery. Ideally, HbA1c should be maintained below 5% during their first trimesters and below 6% during third trimester. We planned to investigate GDM women for their HbA1c levels too.

AIM

To know if there is any alteration in blood lactate and/or HbA1c levels and to know if there is any correlation between these two parameters in GDM pregnancies, in comparison with the previous studies which measured lactate in cord blood and placental vessels of GDM women.

MATERIALS AND METHODS

It was a hospital based prospective study on 40 women with gestational diabetes and 40 age-matched normal pregnant women. We analysed the biochemical and metabolic mileau in these women by estimating venous blood lactate and HbA1c levels. We paid special attention to follow them up regarding maternal complications if any and perinatal outcomes. The independent samples t-test and Pearson's correlation test were applied.

RESULTS

GDM mothers showed significantly higher lactate and HbA1c levels than normal pregnant women, both with p<0.001. Blood pressure and fetal birth weight were also significantly higher in GDM group than Normal Pregnant (NP) group, both with p-values of <0.001. Further, this increased lactate levels showed significant positive correlation with HbA1c, blood pressure and fetal birth weight.

CONCLUSION

Maternal blood lactate and HbA1c levels have a significant role to play in determining the metabolic mileau of both mother and fetus and thus, their obstetric and general health outcomes.

Lactate, a Neglected Factor for Diabetes and Cancer Interaction

Increasing body of evidence suggests that there exists a connection between diabetes and cancer. Nevertheless, to date, the potential reasons for this association are still poorly understood and currently there is no clinical evidence available to direct the proper management of patients presenting with these two diseases concomitantly. Both cancer and diabetes have been associated with abnormal lactate metabolism and high level of lactate production is the key biological property of these diseases. Conversely, high lactate contribute to a higher insulin resistant status and a more malignant phenotype of cancer cells, promoting diabetes and cancer development and progression. In view of associations between diabetes and cancers, the role of high lactate production in diabetes and cancer interaction should not be neglected. Here, we review the available evidence of lactate's role in different biological characteristics of diabetes and cancer and interactive relationship between them. Understanding the molecular mechanisms behind metabolic remodeling of diabetes- and cancer-related signaling would endow novel preventive and therapeutic approaches for diabetes and cancer treatment.

Glucose counterregulation in advanced type 2 diabetes: effect of β-adrenergic blockade

OBJECTIVE

To examine counterregulatory glucose kinetics and test the hypothesis that β-adrenergic blockade impairs these in patients with type 2 diabetes mellitus (T2DM) and advanced β-failure.

RESEARCH DESIGN AND METHODS

Nine insulin-requiring T2DM subjects and six matched nondiabetic control subjects were studied. β-Cell function was assessed by the C-peptide response to arginine stimulation. Counterregulatory hormonal responses and glucose kinetics were assessed by hyperinsulinemic euglycemic-hypoglycemic clamps with [3-(3)H]glucose infusion. T2DM subjects underwent two clamp experiments in a randomized crossover fashion: once with infusion of the β-adrenergic antagonist propranolol and once with infusion of normal saline.

RESULTS

Compared with the control subjects, T2DM subjects had threefold reduced C-peptide responses to arginine stimulation. During the hypoglycemic clamp, glucagon responses were markedly diminished (16.0 ± 4.2 vs. 48.6 ± 6.0 ng/L, P < 0.05), but other hormonal responses and the decrement in the required exogenous glucose infusion rate (GIR) from the euglycemic clamp were normal (-10.4 ± 1.1 vs. -7.8 ± 1.9 µmol · kg(-1) · min(-1) in control subjects); however, endogenous glucose production (EGP) did not increase (-0.8 ± 1.0 vs. 2.2 ± 0.7 µmol · kg(-1) · min(-1) in control subjects, P < 0.05), whereas systemic glucose disposal decreased normally. β-Adrenergic blockade in the T2DM subjects increased GIR ∼20% during the euglycemic clamp (P < 0.01), but neither increased GIR during the hypoglycemic clamp or decreased its decrement from the euglycemic clamp to the hypoglycemic clamp.

CONCLUSIONS

Overall glucose counterregulation is preserved in advanced T2DM, but the contribution of EGP is diminished. β-Adrenergic blockade may increase insulin sensitivity at normoglycemia but does not impair glucose counterregulation in T2DM patients, even those with advanced β-cell failure.

Comprehensive review on lactate metabolism in human health

Metabolic pathways involved in lactate metabolism are important to understand the physiological response to exercise and the pathogenesis of prevalent diseases such as diabetes and cancer. Monocarboxylate transporters are being investigated as potential targets for diagnosis and therapy of these and other disorders. Glucose and alanine produce pyruvate which is reduced to lactate by lactate dehydrogenase in the cytoplasm without oxygen consumption. Lactate removal takes place via its oxidation to pyruvate by lactate dehydrogenase. Pyruvate may be either oxidized to carbon dioxide producing energy or transformed into glucose. Pyruvate oxidation requires oxygen supply and the cooperation of pyruvate dehydrogenase, the tricarboxylic acid cycle, and the mitochondrial respiratory chain. Enzymes of the gluconeogenesis pathway sequentially convert pyruvate into glucose. Congenital or acquired deficiency on gluconeogenesis or pyruvate oxidation, including tissue hypoxia, may induce lactate accumulation. Both obese individuals and patients with diabetes show elevated plasma lactate concentration compared to healthy subjects, but there is no conclusive evidence of hyperlactatemia causing insulin resistance. Available evidence suggests an association between defective mitochondrial oxidative capacity in the pancreatic β-cells and diminished insulin secretion that may trigger the development of diabetes in patients already affected with insulin resistance. Several mutations in the mitochondrial DNA are associated with diabetes mellitus, although the pathogenesis remains unsettled. Mitochondrial DNA mutations have been detected in a number of human cancers. d-lactate is a lactate enantiomer normally formed during glycolysis. Excess d-lactate is generated in diabetes, particularly during diabetic ketoacidosis. d-lactic acidosis is typically associated with small bowel resection.

Antiischemic effects of metoprolol and the risk of carbohydrate metabolism disturbances in angina patients

Aim. To study the association between antiischemic effects (AIE) of metoprolol (MP), glucose tolerance, and insulin sensitivity in patients with stable angina (SA). Material and methods. The study included 28 male patients, aged 46-68 years, with stable effort angina, Functional Class II-III, and positive exercise stress test (EST). The time of the ST segment depression by ≥1 mm defined the threshold exercise stress time. MP in a selected dose was administered twice a day, for one month. Its hemodynamic effects were assessed by the dynamics of heart rate (HR), blood pressure (BP), and double product (DP). Glucose tolerance test (GTT) was performed at baseline (before MP administration) and after one month of MP treatment. Tissue insulin sensitivity and insulin resistance (IR) were assessed by ISI0.120 and HOMA-IR parameters, respectively. Results. AIE was registered in 57% of the patients, while 43% failed to demonstrate it. Both groups did not differ by the extent of MP impact on the levels of HR, BP, and DP. The presence or absence of AIE was linked to selected parameters of glucose metabolism. In patients with AIE, the pre-treatment levels of glucose and insulin 2 hours after glucose load were higher (p=0,028 and 0,043, respectively) and ISI1,120 values lower than in patients without AIE (p=0,023). Among participants with AIE, impaired glucose tolerance (IGT) was observed in 4 at baseline and in 8 one month later; among patients without AIE, IGT was not registered. Conclusion. For the first time, the presence of AIE during MP therapy of SA patients was linked to the decreased insulin sensitivity of peripheral tissues (ISI0.120). Paired EST with a single MP dose at baseline provides an opportunity to identify the patients with a higher risk of metabolic disturbances during the longer-term MP treatment.