Dapagliflozin partially restores reproductive function in MC4R KO obese female mice

POMC neurons control fertility through differential signaling of MC4R in Kisspeptin neurons

Inactivating mutations in the melanocortin 4 receptor (MC4R) gene cause monogenic obesity. Interestingly, female patients also display various degrees of reproductive disorders, in line with the subfertile phenotype of MC4RKO female mice. However, the cellular mechanisms by which MC4R regulates reproduction are unknown. Kiss1 neurons directly stimulate gonadotropin-releasing hormone (GnRH) release through two distinct populations; the Kiss1ARH neurons, controlling GnRH pulses, and the sexually dimorphic Kiss1AVPV/PeN neurons controlling the preovulatory LH surge. Here, we show that Mc4r expressed in Kiss1 neurons is required for fertility in females. In vivo, deletion of Mc4r from Kiss1 neurons in female mice replicates the reproductive impairments of MC4RKO mice without inducing obesity. Conversely, reinsertion of Mc4r in Kiss1 neurons of MC4R null mice restores estrous cyclicity and LH pulsatility without reducing their obese phenotype. In vitro, we dissect the specific action of MC4R on Kiss1ARH vs Kiss1AVPV/PeN neurons and show that MC4R activation excites Kiss1ARH neurons through direct synaptic actions. In contrast, Kiss1AVPV/PeN neurons are normally inhibited by MC4R activation except under elevated estradiol levels, thus facilitating the activation of Kiss1AVPV/PeN neurons to induce the LH surge driving ovulation in females. Our findings demonstrate that POMCARH neurons acting through MC4R, directly regulate reproductive function in females by stimulating the "pulse generator" activity of Kiss1ARH neurons and restricting the activation of Kiss1AVPV/PeN neurons to the time of the estradiol-dependent LH surge, and thus unveil a novel pathway of the metabolic regulation of fertility by the melanocortin system.

Novel insights into metabolic-associated steatotic liver disease preclinical models

Metabolic-associated steatotic liver disease (MASLD) encompasses a wide spectrum of metabolic conditions associated with an excess of fat accumulation in the liver, ranging from simple hepatic steatosis to cirrhosis and hepatocellular carcinoma. Finding appropriate tools to study its development and progression is essential to address essential unmet therapeutic and staging needs. This review discusses advantages and shortcomings of different dietary, chemical and genetic factors that can be used to mimic this disease and its progression in mice from a hepatic and metabolic point of view. Also, this review will highlight some additional factors and considerations that could have a strong impact on the outcomes of our model to end up providing recommendations and a checklist to facilitate the selection of the appropriate MASLD preclinical model based on clinical aims.

Sex-dependent effects of canagliflozin and dapagliflozin on hemostasis in normoglycemic and hyperglycemic mice

Sodium-glucose cotransporter 2 inhibitors (SGLT2i) are antihyperglycemic drugs that decrease mortality from cardiovascular diseases. However, their effects on hemostasis in the cardioprotective effects have not been evaluated. Therefore, the effects of canagliflozin (CANA, 100 mg/kg, p.o.) and dapagliflozin (DAPA, 10 mg/kg, p.o.) on the parameters of hemostasis were investigated in female and male normoglycemic and streptozotocin (180 mg/kg, i.p.)-induced diabetic mice. CANA and DAPA reduced platelet activity in thrombus in male and female mice both normoglycemic and diabetic. CANA decreased thrombus formation in diabetic male mice, and platelet activation to ADP in diabetic female and male mice. Activation of fibrinolysis was observed in female mice, both normoglycemic and diabetic. DAPA reduced thrombus formation in diabetic male and female mice, and decreased platelet activation to ADP and fibrin formation in diabetic male mice. DAPA increased fibrin formation in normoglycemic female mice and activated fibrinolysis in diabetic female mice. CANA and DAPA exerted sex-specific effects, which were more pronounced in hyperglycemia. The antithrombotic effect of CANA and DAPA was more noticeable in male mice and could be due to platelet inhibition. The effect on coagulation and fibrinolysis was not clear since an increased coagulation and fibrinolysis were observed only in female mice.

Sodium-glucose cotransporter 2 inhibitor ameliorates high fat diet-induced hypothalamic-pituitary-ovarian axis disorders

High-fat diet (HFD) consumption is known to be associated with ovulatory disorders among women of reproductive age. Previous studies in animal models suggest that HFD-induced microglia activation contributes to hypothalamic inflammation. This causes the dysfunction of the hypothalamic-pituitary-ovarian (HPO) axis, leading to subfertility. Sodium-glucose cotransporter 2 (SGLT2) inhibitors are a novel class of lipid-soluble antidiabetic drugs that target primarily the early proximal tubules in kidney. Recent evidence revealed an additional expression site of SGLT2 in the central nervous system (CNS), indicating a promising role of SGLT2 inhibitors in the CNS. In type 2 diabetes patients and rodent models, SGLT2 inhibitors exhibit neuroprotective properties through reduction of oxidative stress, alleviation of cerebral atherosclerosis and suppression of microglia-induced neuroinflammation. Furthermore, clinical observations in patients with polycystic ovary syndrome (PCOS) demonstrated that SGLT2 inhibitors ameliorated patient anthropometric parameters, body composition and insulin resistance. Therefore, it is of importance to explore the central mechanism of SGLT2 inhibitors in the recovery of reproductive function in patients with PCOS and obesity. Here, we review the hypothalamic inflammatory mechanisms of HFD-induced microglial activation, with a focus on the clinical utility and possible mechanism of SGLT2 inhibitors in promoting reproductive fitness.