Traumatic brain injury induces adipokine gene expression in rat brain

Traumatic brain injury (TBI) induces cachexia and neuroinflammation which profoundly impact patient recovery. Adipokine genes such as leptin (ob), resistin (rstn) and fasting-induced adipose factor (fiaf) are implicated in energy metabolism and body weight control and are also associated with chronic low grade inflammation. Since central rstn and fiaf expression was increased following hypoxic/ischemic brain injury, we hypothesized that these genes would also be induced in the rat brain following TBI. Realtime RT-PCR detected a 2-2.5-fold increase in ob mRNA in the ipsilateral cortex and thalamus 12 h following lateral fluid percussion (FP)-induced brain injury. Fiaf mRNA was elevated 5-7.5-fold in cortex, hippocampus and thalamus, and modest increases were also detectable in the contralateral brain. Remarkably, rstn mRNA was elevated in ipsilateral (150-fold) and in contralateral (50-fold) hippocampus. To test whether these changes were part of an inflammatory response to TBI we also examined the effects of an intracerebral injection of lipopolysaccharide (LPS). We determined that central injection of LPS produced some, but not all, of the changes seen after TBI. For example, in contrast to the stimulatory influence of TBI, LPS had no effect on ob expression in any brain region, though fiaf and rstn mRNA levels were significantly elevated in both ipsi- and contralateral cortex. In conclusion: (a) brain-derived adipokines could be involved in the acute pathology of traumatic brain injury partly through modulation of central inflammatory responses, but also via leptin-mediated neuroprotective effects and (b) TBI-induced brain adipokines may induce the metabolic changes observed following neurotrauma.