Higher Serum Free Glycerol Levels in a Group of Alcoholics than in Controls

A novel assay for triglycerides using glycerol dehydrogenase and a water-soluble formazan dye, WST-8

Background

The glycerol-3-phosphate (GPO)-peroxidase (POD) chromogenic method is one of the most widely used methods to assay triglycerides. However, it is well known that peroxidase is affected by reducing agents, and recently, it has been reported that some materials affect its activity. Moreover, there is a high possibility of non-specific reaction, as the method uses many enzymes. Against this background, we developed a simpler assay method for triglycerides without using peroxidase.

Methods

Triglycerides were hydrolysed to glycerol and fatty acids by lipoprotein lipase followed by the oxidation of glycerol to dihydroxyacetone with simultaneous production of NADH by glycerol dehydrogenase. To overcome incomplete conversion of glycerol to dihydroxyacetone by glycerol dehydrogenase at equilibrium, we added 2-(2-methoxy-4-nitrophenyl)-3–(4-nitrophenyl)-5–(2,4-disulfophenyl)-2 H-tetrazolium monosodium salt (WST-8) to the reaction mixture to remove NADH, allowing the reaction to complete while showing stoichiometric production of reduced WST-8.

Results

The reaction was linear up to 6.4 mmol/L. The mean intra-assay ( n = 20) and inter-assay ( n = 20) imprecision, as determined by replicate analysis of three pooled human serum samples with different triglyceride concentrations, were 1.1–2.3% and 1.1–1.5% coefficient of variation (%CV), respectively. No interference by 2.5 g/L haemoglobin, 65  μmol/L free bilirubin and 359  μmol/L conjugated bilirubin was observed. The equation obtained in comparison with that by the GPO-POD method including endogenous glycerol-eliminating step was: y = 1.0002x + 0.0395 mmol/L; r = 0.999; Sy/x = 0.049 mmol/L; n = 97.

Conclusion

Our method is an accurate, yet simpler and more sensitive for the quantitative analysis of triglycerides.

Acute liver injury in a patient with alcohol dependence: a case resembling autoimmune hepatitis or drug-induced liver injury

Some patients with alcohol dependence may initially present with atypical laboratory and histological features resembling autoimmune hepatitis (AIH) or drug-induced liver injury (DILI). Even with liver biopsy, it may be difficult to diagnose certain patients with alcohol dependence. However, careful follow-up of our patient and consultations with the attending psychiatrist were successful in diagnosing alcohol dependence and its liver injury. The immune mechanisms of alcoholic liver diseases, AIH and DILI may be overlapping. Certain patients are suffering from AIH with flares on a background of alcohol abuse. Certain patients with alcohol abuse may have a past history of DILI. This might be consistent with the fact that alcohol dependence initially presents with atypical laboratory features of AIH or DILI. With careful observation, the clinician should remind himself that alcohol dependence is not always required for developing liver disease, since many patients with liver disease do not meet the criteria for alcohol dependence.