Effect of thiamine on glucose utilization in hepatic cirrhosis

Influence of innate immune activation on endocrine and metabolic pathways in infancy

Prematurity is the leading cause of neonatal morbidity and mortality worldwide. Premature infants often require extended hospital stays, with increased risk of developing infection compared with term infants. A picture is emerging of wide-ranging deleterious consequences resulting from innate immune system activation in the newborn infant. Those who survive infection have been exposed to a stimulus that can impose long-lasting alterations into later life. In this review, we discuss sepsis-driven alterations in integrated neuroendocrine and metabolic pathways and highlight current knowledge gaps in respect of neonatal sepsis. We review established biomarkers for sepsis and extend the discussion to examine emerging findings from human and animal models of neonatal sepsis that propose novel biomarkers for early identification of sepsis. Future research in this area is required to establish a greater understanding of the distinct neonatal signature of early and late-stage infection, to improve diagnosis, curtail inappropriate antibiotic use, and promote precision medicine through a biomarker-guided empirical and adjunctive treatment approach for neonatal sepsis. There is an unmet clinical need to decrease sepsis-induced morbidity in neonates, to limit and prevent adverse consequences in later life and decrease mortality.

The impact of thiamine supplementation on blood pressure, serum lipids and C-reactive protein in individuals with hyperglycemia: a randomised, double-blind cross-over trial

BACKGROUND

The adverse effects of hyperglycemia may be potentiated when it is accompanied with hypertension and dyslipidemia. This study assessed the effects of high dose thiamine on blood pressure, serum lipids and C-reactive protein (hs-CRP) in individuals with impaired glucose metabolism.

METHODS

This was a double-blind, randomised trial, where 12 hyperglycemic subjects (10 cases of impaired glucose tolerance and 2 new cases of type 2 diabetes mellitus) received both placebo and thiamine capsules (3 × 100 mg/day) for six weeks in a cross-over manner. Anthropometric measurements, systolic and diastolic blood pressure (SBP & DBP), serum cholesterol, triglyceride, HDL-cholesterol, LDL-cholesterol, hs-CRP and thiamine status were evaluated at the start, after three weeks and on the completion of each arm.

RESULTS

DBP was significantly decreased in participants consuming thiamine supplements for six weeks (67.9 ± 5.8 mm Hg) relative to baseline (71.4 ± 7.4 mm Hg, p=0.005) and week 3 (70.9. ± 5.8 mm Hg, p=0.02). This was accompanied with a tendency toward a lower SBP at week six relative to baseline (116.5 ± 11.0 vs. 120.7 ± 15.3 mm Hg, p=0.06). Also, mean arterial pressure (MAP) determined in the supplement arm after six weeks was significantly lower than baseline (84.1 ± 6.5 vs. 87.8 ± 9.0, p=0.005). These variables did not change in the placebo arm. No significant change was detected in the supplement or placebo arms when lipid profile and hs-CRP were assessed.

CONCLUSION/INTERPRETATION

High dose thiamine supplementation may have beneficial effects on the blood pressure of individuals with hyperglycemia at early stages, and may have a role in the prevention of further vascular complications.

TRIAL REGISTRATION

Australian New Zealand Clinical Trials Registry ACTRN12611000051943.

High-dose thiamine supplementation improves glucose tolerance in hyperglycemic individuals: a randomized, double-blind cross-over trial

PURPOSE

To assess the effect of high-dose oral thiamine supplements on glucose tolerance in patients with impaired glucose metabolism.

METHODS

Twelve hyperglycemic subjects (10 cases of impaired glucose tolerance and 2 new cases of type 2 diabetes) completed this randomized, double-blind trial, where all participants received both placebo and thiamine capsules (3 × 100 mg/day) for 6 weeks in a cross-over manner. The main endpoint was changes in 2-h plasma glucose. Fasting plasma glucose and insulin, 2-h plasma insulin, the hemostatic model assessment of insulin resistance (HOMA-IR), renal function measurement and thiamin status were also evaluated at the commencement and completion of each treatment period.

RESULTS

Thiamine supplementation resulted in significant decrease in 2-h plasma glucose relative to baseline (8.78 ± 2.20 vs. 9.89 ± 2.50 mmol/l, p = 0.004), with no significant change in the placebo arm. Fasting plasma glucose and insulin, and HOMA-IR increased significantly from baseline after 6 weeks in the placebo arm (p = 0.003, p = 0.04 and p = 0.02, respectively). These variables did not change with thiamine supplementation. There were no significant changes in 2-h plasma insulin or renal function marker, within or between arms.

CONCLUSION/INTERPRETATION

Supplementation with high-dose thiamine may prevent deterioration in fasting glucose and insulin, and improve glucose tolerance in patients with hyperglycemia. High-dose thiamine supplementation may prevent or slow the progression of hyperglycemia toward diabetes mellitus in individuals with impaired glucose regulation.

Increased protein glycation in cirrhosis and therapeutic strategies to prevent it

Glycation of liver proteins by reactive aldehydes formed from the metabolism of ethanol and lipid peroxidation has been implicated in the development of both alcoholic and nonalcoholic liver cirrhosis. Modified proteins are targeted to the proteasome for proteolysis. Release of glycation-free adducts into the circulation may provide a diagnostic "signature" of hepatic protein damage. We quantitatively screened protein glycation, oxidation, and nitrosation adduct residues and free adducts in portal, hepatic, and peripheral venous blood plasma of cirrhotic patients; we also screened the hepatic and peripheral venous blood plasma of control subjects by liquid chromatography-mass spectrometry. There was a remarkable 14-16-fold increase of glyoxal-derived, hydroimidazolone-free adduct in portal and hepatic venous plasma of cirrhotic patients with respect to normal controls. There was only a twofold increase of glycation adduct residues in plasma proteins in cirrhotic patients, which was attributed mainly to decreased albumin turnover. Therapeutic strategies to decrease dicarbonyl compounds may be beneficial, such as dicarbonyl scavengers, glutathione repleting agents, and high-dose thiamine therapy.

High-dose thiamine therapy counters dyslipidaemia in streptozotocin-induced diabetic rats

AIMS/HYPOTHESIS

Cardiovascular disease in diabetes is linked to increased risk of atherosclerosis, increased levels of triglyceride-rich lipoproteins and enhanced hepatic lipogenesis. The hepatic hexosamine pathway has been implicated in signalling for de novo lipogenesis by the liver. In this study, we assessed if decrease of flux through the hexosamine pathway induced by high-dose thiamine therapy counters diabetic dyslipidaemia.

METHODS

The model of diabetes used was the streptozotocin-induced diabetic rat with maintenance insulin therapy. Normal control and diabetic rats were studied for 24 weeks with and without oral high-dose therapy (7 and 70 mg/kg) with thiamine and benfotiamine. Plasma total cholesterol, HDL cholesterol and triglycerides were determined at 6-week intervals and hepatic metabolites and transketolase activity after death of the rats at 24 weeks.

RESULTS

We found that thiamine therapy (70 mg/kg) prevented diabetes-induced increases in plasma cholesterol and triglycerides in diabetic rats but did not reverse the diabetes-induced decrease of HDL. This was achieved by prevention of thiamine depletion and decreased transketolase activity in the liver of diabetic rats. There was a concomitant decrease in hepatic UDP-N-acetylglucosamine and fatty acid synthase activity. Thiamine also normalised food intake of diabetic rats. A lower dose of thiamine (7 mg/kg) and the thiamine monophosphate prodrug benfotiamine (7 and 70 mg/kg) were ineffective.

CONCLUSIONS/INTERPRETATION

High-dose thiamine therapy prevented diabetic dyslipidaemia in experimental diabetes probably by suppression of food intake and hexosamine pathway signalling but other factors may also be involved. Benfotiamine was ineffective.

Processing of protein glycation, oxidation and nitrosation adducts in the liver and the effect of cirrhosis

BACKGROUND/AIMS

Plasma proteins are modified non-enzymatically in vivo by glycation, oxidation and nitrosation processes. Hepatic extraction of albumin glycated in vitro was reported but it is not clear if plasma proteins glycated in vivo also undergo hepatic extraction. We investigated the hepatic extraction of glycated, oxidised and nitrosated proteins in vivo.

METHODS

Protein glycation, oxidation and nitrosation marker residues and free adducts were determined in portal, hepatic and peripheral venous blood plasma of cirrhotic patients and hepatic and peripheral venous blood plasma (as a surrogate of portal venous blood) of control subjects by liquid chromatography-mass spectrometry.

RESULTS

There was no evidence for extraction of glycated, oxidised or nitrosated proteins or related free adducts by the liver in control subjects. There was limited extraction of methylglyoxal-modified proteins in cirrhotic patients and twofold increases in the concentrations of fructosyl-lysine and advanced glycation endproduct residues of plasma protein, with respect to controls. Remarkably, glyoxal-derived hydroimidazolone free adduct was increased 14-16-fold probably as a consequence of hepatic lipid peroxidation.

CONCLUSIONS

We found no evidence for hepatic extraction of glycated, oxidised and nitrosated proteins or related free adducts in subjects with normal liver function and limited extraction of methylglyoxal-modified protein in cirrhotic subjects.