How bitter melon seed oil can help fight obesity

Bitter melons contain a lot of health benefits despite its acrid taste. In particular, the anti-obesity properties that bitter melon seed oil may be linked to changes in density in the hypothalamic spine, that is, the region connecting the hypothalamus and the spinal cord. The study, published in the Journal of Nutrition & Intermediary Metabolism, also indicated that bitter melon seeds also affect the mammalian target of rapamycin (mTOR) pathway, which plays a role in protein synthesis.

There are many studies that have extensively discussed the anti-obesity property of bitter melon. However, there are only a few reports available that look at its effects on the central nervous system (CNS). This, despite the fact that obesity-associated inflammation in the hypothalamus occurs at a faster rate than in peripheral tissues. 

Moreover, obesity can affect areas of the brain that are responsible for certain functions. A discrete study led by researchers from the University of Michigan revealed that obesity-induced changes in the structure of the hippocampus – the region of the brain that governs emotions and spatial navigation – resulted in mild cognitive impairment. In the same vein, obesity could compromise the function of the hypothalamus, the area responsible for hunger and thirst, as well as the regulation of whole-body energy. This might result in further weight gain and obesity development.

For this study, researchers sought to understand how bitter melon seed extracts affect neurobiological mechanisms related to obesity. To do this, they first prepared ripe bitter melon seeds. The seeds were then processed using supercritical CO2 to extract oil and stored prior to use.

The team then obtained four-week-old mice that were given a high-fat diet (HFD) consisting of lard oil, egg yolk powder, butter, and peanut butter. These were then grouped into four and given differing amounts of bitter melon seed extracts. Aside from the control group, the amounts given to the others ranged from one gram per kilogram of body weight (one g/kg), five g/kg, and 10 g/kg, respectively. The mice were treated for three weeks, and their brains were collected for analysis. Researchers then used Golgi-Cox staining and western blotting assays to look at hypothalamic spine density. In particular, information on NMDA-2B and P-S6 proteins were observed.

Researchers discovered that mice that were given bitter melon seed oil significantly posted a significant reduction in obese characteristics such as body weight, fat index, and adipose tissue (the medical term for fat) sizes. Regarding obesity-induced inflammation in the hypothalamus, the groups that were fed bitter melon seed extracts had their spine densities restored. This indicated that the oil extract was able to normalize the brain function of the murine hypothalamus.

As for the effects of bitter melon in the mTOR signaling pathway, a high dose of bitter melon seed oil decreased the protein levels in ribosomal protein S6 after phosphorylation, that is, the addition of phosphate to a protein. This process indicated that mTOR signaling, which is activated when there is an imbalance in the energy status of the hypothalamus, is affected by bitter melon seed oil. In particular, researchers proffered that mTOR signaling is a factor in the anti-obesity property of bitter melon. They also add that bitter melon seed oil first acted on the mTOR using available signals, which then resulted in the restoration of inflamed spines and the recovery of neuronal function of the hypothalamus.

One limitation that they noted was that response to NMDA-2B levels in mice was already increased, which researchers believe was not an effect of bitter melon seed oil.

Based on the findings, researchers posited that the plasticity of the hypothalamus could help the fat-reducing property of bitter melon seed oil. "BMSO’s anti-obesity effect was correlated with alterations of hypothalamic spine densities, as well as their causative mTOR pathway," the authors wrote of their findings. "This was a novel demonstration of central regulatory mechanisms of bitter melon seed oil in losing weight, and provided a meaningful step towards the prevention and intervention of the hypothalamic obesity."