Obesity is a growing global health problem, more and more people die from over-weight than under-weight, so, a multidisciplinary clinic was established for the treatment of severe obesity and its related comorbidities. Current clinical weight loss methods include bariatric surgery, dietary therapy and T2D pharmacological therapy. Those qualifying patients offered bariatric surgery only achieved at average appropriate weight loss (EBWL of 10%).38 Also, those patients after a year of dietary therapy, 46% did not achieve the desired weight loss. However, those patients with diabetes and obesity could benefit from the use of T2D pharmacological treatment as recommended in 2015 by the Endocrine and Obesity Society,39 such as Metformin and Dapagliflozin.
Metformin is the first-line glucose-lowering medication recommended by almost all international guidelines.40 Several studies have demonstrated that Metformin has a positive impact on body weight by reducing appetite with consequent decreased caloric intake. The impact on appetite regulation depends on the directly central effect of the drug and indirectly on its gastrointestinal side effects, such as nausea, bloating, diarrhea and dysgeusia.30,40 Increased secretion of the weight-loss-promoting incretin glucagon-like peptide 1 (GLP-1) and the anorectic hormone peptide YY (PYY) is thought to be an neuropeptides to suppress orexigenic hypothalamic-related (AgRP) neurons.37
The sodium-dependent glucose cotransporter proteins 1 and 2 (SGLT1/2) in the proximal renal tubule of the kidney regulate renal glucose reabsorption. SGLT2 transporter has been reported to induce approximatively the 90% of reabsorption, while the remaining 10% is reabsorbed by SLGT1 transporter.35 Through inhibiting these co-transporters, such as Dapagliflozin, a large amount of glucose, ranging from 50 to 100 g daily, and the corresponding caloric equivalent (200–400 kcal/diet) are pharmacologically forced into urinary excretion, so the whole-body metabolism must undergo adaptive changes involving glucose fluxes, hormonal responses, fuel selection, and energy expenditure. In particular, Dapagliflozin induces an increasing in the glucagon/insulin ratio, resulting in an increased lipid mobilization. Furthermore, Dapagliflozin reduces serum leptin and increases adiponectin concentration, which are mechanisms contributing to lipolysis, weight loss and reduction of adipose accumulation in the myocardium.36 Pharmacological blockade of renal glucose reabsorption reduces fasting and postprandial glycemia both acutely and chronically without causing hypoglycemia, with improvement of both β cell function and insulin sensitivity.47 The long-term deficit of glucose induces an increase in lipid oxidation, thereby maintaining energy balance, with reduction in fat mass.38
So far, there has been seldom discussion related to the dysregulation of brain reward systems in food addiction. In our study, we firstly explored whether T2D medicine treatments could help people with obesity lose weight through modulating the activation of brain reward systems in neural networks. Basing on the functional connectivity and rCBV quantification analysis, our data revealed a trend toward lower functional connectivity and rCBV quantification in Metformin group in prefrontal and limbic regions areas which might be the key for inhibit eating disorder related obesity such as PFC, Hypo, VTA, vHPC, OFC, Thal and NAc. In addition, our results also firstly indicated the effects of T2D medicine on intestinal villus length and intestinal absorption influenced by fructose. In our study, the activity of PKM2 and the abundances of intermediate metabolites associated with glycolysis was increased in Dapagliflozin group which suggesting that the metabolic pattern of IECs has more glycolysis than the control and Metformin groups. Enhanced glycolysis eliminated the longer survival of IECs caused by fructose, as increasing glycolysis inhibited the PPP pathway, which produces anti-ROS to protect IECs. Therefore, Dapagliflozin decreases intestinal villus length and reduce the surface area of the gut for absorbing nutrient and adiposity then mediate the weight-loss.
Even in our study, we have revealed a new mechanism on how Dapagliflozin and Metformin inhibit obesity, there are still no clinical data to support our explorations. Meanwhile, the effects of anesthesia on intrinsic functional connectivity and amplitude were inevitable in our study when process the fMRI.