The pathogenesis of depression is complex, and recent research has focused on the potential relationship between energy metabolism and depression, wrote Qian Yao, MD, of Wuhan University, Hubei, China, and colleagues.
Previous studies have suggested that serum lactate dehydrogenase (LDH) may be a biomarker for Parkinson’s disease, Huntington’s disease, and post-stroke depression, but the link between lactate metabolism and depression remains unclear, they said.
“We hypothesize that LDH may act as a potential biomarker for MDD, considering it represents a reduced energy metabolic status in depressive patients,” they explained.
In a study published in General Hospital Psychiatry, the researchers examined differences in serum LDH in 232 patients with major depressive disorder (MDD) and 110 healthy controls. They also examined whether LDH was predictive of suicide attempts in the MDD patients. Depression was assessed via the 24-item Hamilton Depression Scale (HAMD-24).
The mean age across both groups was 33 years; other clinical characteristics were similar between the groups.
The serum LDH level of the MDD group was significantly lower than the control group was (177.94 U/L vs. 196.50 U/L; P < .001). Analysis of blood lipid levels showed significantly lower levels of total cholesterol in the MDD group compared with controls, but no significant differences were noted in LDL cholesterol, HDL cholesterol, or triglycerides.
In a further analysis of subgroups of depression, the serum LDH in MDD patients who had attempted suicide was significantly lower compared to those without suicide attempts (169.96 vs. 181.25; P = .002), although the LDH level for the non-suicide MDD patients also was significantly lower than controls (181.25 vs. 196.50; P < .001). No significant correlation was noted between HAMD-24 score and suicide attempts.
Some gender differences also appeared. Both male and female MDD patients had significantly lower LDH levels compared with controls. However, in a regression analysis, a correlation between total cholesterol and LDL cholesterol as potential suicide markers was noted in female MDD patients, but not male MDD patients, which suggests an impact of gender on suicide risk in MDD, the researchers wrote in their discussion.
The findings were limited by several factors including the retrospective design, lack of investigation of changes in LDH isozymes in MDD patients, and lack of assessment of changes in LDH in cerebrospinal fluid, the researchers noted. However, the results “provide clear evidence that the concentration of LDH in serum is associated with early onset and clinical prognosis of depressive symptoms,” in MDD, which may inform diagnosis and guide clinical intervention, including early identification of suicide risk, they concluded.
The study was supported by the National Natural Science Foundation of China. The researchers had no financial conflicts to disclose.