Evaluation of the interaction between ketone bodies and obesity-associated proteins: an in silico approach

Introduction

Obesity has always been a pre-existing problem and has been recognized as a global pandemic in the 21^st century (Ryan et al., 2021). It is described as the anomalous, irregular or disproportionate gain of weight as a result of fat buildup in the body, which adversely leads to the risk of several health-related problems such as hypertension, type 2 diabetes, cardiovascular diseases and certain cancer types, amongst others (Aronne, 2002; Natalia et al., 2021).

Obesity calculation is based on body mass index ≥30 kg/m², which is the measurement of fat buildup calculated by dividing body mass (kg) by the square of the body height (m²). In 2016, the World Health Organization (WHO) acknowledged that nearly 2-billion adults worldwide were considered to be overweight and 650 million of that population were found to be obese. The WHO also estimated that 50% of the population found in Europe had a preeminent body weight which could lead to obesity over time (https://www.who.int/news-room/fact-sheets/detail/obesity-and-overweight).

Furthermore, in 2002, certain rural areas in Nigeria were recorded to have a high rate of obesity, at 33.7% (Ogah et al., 2013). Obesity involves a complex process, and certain physical and biochemical factors have been found to induce this condition some of which include unhealthy diets and eating habits, high calorie food consumption, and genetic, epigenetic, and ecological factors. All these factors combined together with the lack of physical activity to burn excess body weight then lead to energy disproportion and fat deposition (Williams et al., 2015; Lin et al., 2017). Due to obesity prevalence over time, several solutions and control measures have been brought up to ameliorate as well as control the condition. Some of these measures include physical activity programmes, behavioural lifestyle programmes, pharmacotherapy, diet management, and in severe obese conditions bariatric surgery is recommended (Gonzalez-Muniesa et al., 2017).

Caloric inhibition, a diet management scheme and a nutritional strategy are the commonly used weight loss mechanisms as far as diet management is concerned, and this research focuses on the use of a ketogenic diet, which has been used successfully in the therapeutic treatment of epilepsy, as a control measure for obesity (Anton et al., 2017; Ułamek-Koziol et al., 2019).

A ketogenic diet is made up of a high fat content, very minimal carbohydrate (not exceeding 4 percent) and a sufficient amount of protein. As a result of the proportionate amount of nutrients in the diet composition, there is reduced metabolism of carbohydrate and protein but increased metabolism of fat (Kayode et al., 2020a, 2020b, 2021). Consequent fat breakdown and reduced carbohydrate and protein breakdown then leads to reduced blood glucose levels and the stimulation of ketogenesis in the liver, which produces increased levels of ketone bodies and fatty acids (Kulak and Polotsky, 2013). The resulting ketone bodies are then transported to the blood–brain barrier to make available energy for the brain, and increased levels of the ketone bodies lead to increased levels of substrates such as creatine, adenine triphosphate, and phosphocreatine that are essential in the brain (Kayode et al., 2021). This study aims at exploring the efficiency of ketogenic-diet-generated ketone bodies in the prevention and amelioration of obesity using in silico simulations.

Methods

Results and discussion

Leptin aids hunger inhibition and energy intake-energy output balance. In the docking analysis results collated from the molecular docking of the protein, leptin was shown to exhibit a positive binding interaction with the ketogenic diet by-products (see Figures 1, 2 and 3 (β-hydroxybutyrate -3.7, acetoacetate -3.3, acetone -2.5)), as well as the standard drugs orlistat, -4.7, and cetilistat, -5 (Figures 4 and 5) used during this research study, although interactions were higher with standard drugs than with the ketone bodies. Therefore, the interaction between the standard drugs and ketone bodies with leptin indicates that greater levels of hunger inhibition, which will culminate in weight reduction, may emanate from standard drug and ketone bodies treatment since leptin’s function of inhibiting hunger and inducing starvation is highly effective in obesity treatment.

Figure 1. 2D and 3D molecular docking complexes of leptin and acetone.

Figure 2. 2D and 3D molecular docking complexes of leptin and acetoacetate.

Figure 3. 2D and 3D molecular docking complexes of leptin and beta-hydroxybutyrate.

Figure 4. 2D and 3D molecular docking complexes of leptin and orlistat.

Figure 5. 2D and 3D molecular docking complexes of leptin and cetilistat.

Stimulation of appetite through the hypothalamic arcuate nucleus, which controls food input and output, is achieved by the ghrelin protein (Kojima and Kangawa, 2005), as shown in the docking analysis results in Figures 6–10. The standard drugs (orlistat, -5.2, and cetilistat, -6.3) and ketone bodies (β-hydroxybutyrate -3.1, acetoacetate -3, acetone -2.3) exhibited positive binding interactions with the ghrelin protein, with the standard drugs having an increased interaction compared with the ketone bodies, which had minimal binding interaction. This connotes that the ghrelin function in the presence of these ligands (standard drugs and ketone bodies) might be inhibited and thus results in the lowering of appetite and thus food consumption, leading to weight loss in individuals.

Figure 6. 3D molecular docking complexes of ghrelin and acetone.

Figure 7. 2D and 3D molecular docking complexes of ghrelin and acetoacetate.

Figure 8. 2D and 3D molecular docking complexes of ghrelin and beta-hydroxybutyrate.

Figure 9. 2D and 3D molecular docking complexes of ghrelin and orlistat.

Figure 10. 2D and 3D molecular docking complexes of ghrelin and cetilistat.

The docking analysis of catalase interaction with standard drugs and ketone bodies (Figures 11–15) revealed the catalase exhibited a positive binding interaction with standard drugs at a higher level than ketone bodies, thereby showing that the catalase function of catalysing the disproportionate amounts of hydrogen peroxide synthesised in cells by certain enzymes and oxidases into a single oxygen (O₂) molecule and water (H₂O) molecule, and maintaining optimal compound levels which induce cell signalling by deactivating hydrogen peroxide are activated by the ketone bodies. This will enhance the anti-oxidative role of the diet and, since oxidative stress has been implicated in obesity progression, an enhanced cell anti-oxidative status by the ketone bodies will lead to the amelioration of obesity (Everse, 2013).

Figure 11. 3D molecular docking complexes of catalase and acetone.

Figure 12. 2D and 3D molecular docking complexes of catalase and acetoacetate.

Figure 13. 2D and 3D molecular docking complexes of catalase and beta-hydroxybutyrate.

Figure 14. 2D and 3D molecular docking complexes of catalase and orlistat.

Figure 15. 2D and 3D molecular docking complexes of catalase and cetilistat.

The docking analysis result of superoxide dismutase (SOD) (Figures 16–20), which is similar to that of catalase, showed positive binding interactions with both standard drugs (orlistat, -5.0, and cetilistat, -5.7) and ketone bodies (β-hydroxybutyrate -3.7, acetoacetate -3.6, and acetone -2.5), hence the SOD function of promoting the defence mechanism of cells against Reactive Oxygen Species (ROS) by catalysing the oxidative deamination of superoxide radicals (O₂) into oxygen molecules (O₂) and hydroxyl radicals (H₂O₂) are activated in vivo by the standard drugs and ketone bodies. This will also enhance the reduction of oxidative stress thus promoting amelioration of metabolic syndromes associated with obesity.

Figure 16. 2D and 3D molecular docking complexes of superoxide dismutase and acetone.

Figure 17. 2D and 3D molecular docking complexes of superoxide dismutase and acetoacetate.

Figure 18. 2D and 3D molecular docking complexes of superoxide dismutase and beta-hydroxybutyrate.

Figure 19. 2D and 3D molecular docking complexes of superoxide dismutase and orlistat.

Figure 20. 2D and 3D molecular docking complexes of superoxide dismutase and cetilistat.

The docking analysis result collated for the FTO interaction with standard drugs (orlistat, 1, and cetilistat, 0.3) and ketone bodies (β-hydroxybutyrate -4.7, acetoacetate -4.5, acetone -3.2), shown in Figures 21–25, showed minimal binding interactions with the standard drugs but showed increased binding interactions with the ketone bodies ligands. This indicates that orlistat and cetilistat in the biological system may have minimal inhibitory action against FTO, while the ketone bodies exhibit greater inhibition of FTO. which can lead to the downregulation of fatty acid synthesis and storage, leading to significant reduction in body fat and obesity.

Figure 21. 3D molecular docking complexes of FTO gene protein and acetone.

Figure 22. 2D and 3D molecular docking complexes of FTO gene protein and acetoacetate.

Figure 23. 2D and 3D molecular docking complexes of FTO gene protein and beta-hydroxybutyrate.

Figure 24. 2D and 3D molecular docking complexes of FTO gene protein and orlistat.

Figure 25. 2D and 3D molecular docking complexes of FTO gene protein and cetilistat.

The docking analysis for the 3-hydroxyl-3-methylgluatarate Co-A (HMG-CoA) reductase interaction with the standard drugs (orlistat, -4.7, and cetilistat, -4.7) and ketone bodies (β-hydroxybutyrate -3.4, acetoacetate -3.4, acetone -2.5) is shown in Figures 26–30. HMG-CoA exhibited binding interactions with the standard drugs and ketone bodies. The interactions may result in inhibition of HMG-CoA reductase, hence leading to reduction in the levels of mevalonate and cholesterol synthesised in vivo This will consequently result in body fat reduction over a period of time.

Figure 26. 3D molecular docking complexes of HMG-CoA reductase interaction with acetone.

Figure 27. 2D and 3D molecular docking complexes of HMG-CoA reductase interaction with acetoacetate.

Figure 28. 2D and 3D molecular docking complexes of HMG-CoA reductase interaction with beta-hydroxybutyrate.

Figure 29. 2D and 3D molecular docking complexes of HMG-CoA reductase interaction with orlistat.

Figure 30. 2D and 3D molecular docking complexes of HMG-CoA reductase reductase interaction with cetilistat.

Conclusions

The ketone bodies exhibited varied positive interactions with the obesity-associated proteins and thus, sequel to further in vivo studies, the ketogenic diet may emerge as a therapeutic remedy for weight maintenance and obesity inhibition, which works via the ketone bodies’ interaction with obesity-associated proteins besides other mechanisms.