Antiobesity and Caecal Microbiome Effects of Dichloromethane – Methanolic Extracts of Solanum Nigrum (Subsp Villosum) in High Fat Fed Sprague Dawley Rats

Abstract

Despite the rapid rise of obesity in Kenya, its treatment and management has remained a challenge due to its high side effects and unaffordability. Locally based remedies may offer cheaper, safer and more cost effective alternatives. Materials and Methods This study sought to evaluate the anti-obesity effects of Solanum nigrum (Subsp villosum) extracts in high fat fed Sprague dawley rats. The study utilized 35 Sprague dawley rats weighing between 160-180g. Experimental rats were divided into seven groups of 5 rats each; normal control group (fed with normal chow rat feed), a negative control group (fed with high fat diet), reference positive control group (orlistat 30mg/kgbw with high fat diet) and experimental groups (treated with Dichloromethane and methanolic leaf dose extracts of Solanum nigrum (Subsp villosum) at concentrations of 150mg/kgbw and 300mg/kg bw respectively plus high fat diet). The body weight and lengths (naso-anal length) were measured once per week for eleven weeks to determine the body mass index. At the end of the experiment, blood samples were obtained through cardiac puncture. They were centrifuged at 2400rpm for 10 minutes and the serum obtained was used for clinical chemistry. In addition, caecum samples were collected for microbiome analysis and molecular identification of Solanum done using internal transcribed spacer 2 (ITS2) and ribulose biphosphate carboxylase large (RBCL) marker. Statistical analysis was conducted using Student’s t-test and one way anova. Results: Leaf extracts of Solanum nigrum (Subsp villosum) at dose of 150mg/kgbw and 300mg/kgbw, showed significant decrease on body mass index (BMI) from week 5-11 compared to the negative control (p<0.05). However, low dose of dichloromethane (150mg/kgbw) and high dose of methanol extracts (300mg/kgbw) showed better decrease in BMI than all the other treatment groups. There was no significant difference on total cholesterol among the treatment groups compared to the negative control (p>0.05) however, a significant difference was seen on triglycerides, low density lipoprotein- cholesterol and high density lipoprotein- cholesterol among the treatment groups compared to the negative control. There was a significance difference on adipose tissue weights and liver weight on rats administered with high fat diet compared to other treatments (p<0.05). The rats on high fat diet (negative control) indicated a significant increase on alanine aminotransferase, gamma- glutamyl transferase and alkaline phosphatase compared to the other treatment groups. Decrease on adipose tissue and liver weights on other treatments compared to the negative control was significant (p<0.05). These extracts showed presence of various phytochemical compounds. Microbiome analysis exhibited that all groups had varying amounts of bacteria phylum. However, Campylobacterota had a significant increase on the DCM and methanolic treatment groups as well the positive control compared to negative and normal control groups. On the other hand, the different sequences of plant markers (ITS2 and rbcl) used to infer phylogeny indicated that the specie with antiobesity effects (Kat_001) is Solanum nigrum (Subsp villosum) specie. Conclusion: Solanum nigrum (Subsp villosum) reduces BMI, has hypolipidemic effect and possess anti-obesity phytochemicals with no adverse effects on liver function suggesting its safe use. High fat diet and Solanum nigrum (Subsp villosum) extracts caused significant changes in the caecum microbial system of the high fat fed diet rats. These results were similar to those of positive control. The agreement between rbcl and the combined set of rbcl and ITS2 sequences, together with morphological data strongly suggests Kat_001 is Solanum nigrum (Subsp villosum). The study recommends consumption of Solanum nigrum (Subsp villosum) as a supplement used to prevent obesity.