SGLT2 Inhibitors: A Broad Impact Therapeutic Option for the Nephrologist

The SLC6A15-SLC6A20 Neutral Amino Acid Transporter Subfamily: Functions, Diseases, and Their Therapeutic Relevance

The neutral amino acid transporter subfamily that consists of six members, consecutively SLC6A15-SLC620, also called orphan transporters, represents membrane, sodium-dependent symporter proteins that belong to the family of solute carrier 6 (SLC6). Primarily, they mediate the transport of neutral amino acids from the extracellular milieu toward cell or storage vesicles utilizing an electric membrane potential as the driving force. Orphan transporters are widely distributed throughout the body, covering many systems; for instance, the central nervous, renal, or intestinal system, supplying cells into molecules used in biochemical, signaling, and building pathways afterward. They are responsible for intestinal absorption and renal reabsorption of amino acids. In the central nervous system, orphan transporters constitute a significant medium for the provision of neurotransmitter precursors. Diseases related with aforementioned transporters highlight their significance; SLC6A19 mutations are associated with metabolic Hartnup disorder, whereas altered expression of SLC6A15 has been associated with a depression/stress-related disorders. Mutations of SLC6A18-SLCA20 cause iminoglycinuria and/or hyperglycinuria. SLC6A18-SLC6A20 to reach the cellular membrane require an ancillary unit ACE2 that is a molecular target for the spike protein of the SARS-CoV-2 virus. SLC6A19 has been proposed as a molecular target for the treatment of metabolic disorders resembling gastric surgery bypass. Inhibition of SLC6A15 appears to have a promising outcome in the treatment of psychiatric disorders. SLC6A19 and SLC6A20 have been suggested as potential targets in the treatment of COVID-19. In this review, we gathered recent advances on orphan transporters, their structure, functions, related disorders, and diseases, and in particular their relevance as therapeutic targets. SIGNIFICANCE STATEMENT: The following review systematizes current knowledge about the SLC6A15-SLCA20 neutral amino acid transporter subfamily and their therapeutic relevance in the treatment of different diseases.

Renal and Cardiovascular Metabolic Impact Caused by Ketogenesis of the SGLT2 Inhibitors

Sodium-glucose cotransporter type 2 inhibitors (SGLT2i) are glycosuric drugs that were originally developed for the treatment of type 2 diabetes mellitus (T2DM). There is a hypothesis that SGLT2i are drugs that are capable of increasing ketone bodies and free fatty acids. The idea is that they could serve as the necessary fuel, instead of glucose, for the purposes of cardiac muscle requirements and could explain antihypertensive effects, which are independent of renal function. The adult heart, under normal conditions, consumes around 60% to 90% of the cardiac energy that is derived from the oxidation of free fatty acids. In addition, a small proportion also comes from other available substrates. In order to meet energy demands with respect to achieving adequate cardiac function, the heart is known to possess metabolic flexibility. This allows it to switch between different available substrates in order to obtain the energy molecule adenosine triphosphate (ATP), thereby rendering it highly adaptive. It must be noted that oxidative phosphorylation in aerobic organisms is the main source of ATP, which is a result of reduced cofactors. These cofactors include nicotine adenine dinucleotide (NADH) and flavin adenine dinucleotide (FADH2), which are the result of electron transfer and are used as the enzymatic cofactors that are involved in the respiratory chain. When there is an excessive increase in energy nutrients-such as glucose and fatty acids-which occur in the absence of a parallel increase in demand, a state of nutrient surplus (which is better known as an excess in supply) is created. The use of SGLT2i at the renal level has also been shown to generate beneficial metabolic alterations, which are obtained by reducing the glucotoxicity that is induced by glycosuria. Together with the reduction in perivisceral fat in various organs, such alterations also lead to the use of free fatty acids in the initial stages of the affected heart. Subsequently, this results in an increase in production with respect to ketoacids, which are a more available energy fuel at the cellular level. In addition, even though their mechanism is not fully understood, their vast benefits render them of incredible importance for the purposes of further research.

Clinical Parameters Affecting the Therapeutic Efficacy of SGLT-2—Comparative Effectiveness and Safety of Dapagliflozin and Empagliflozin in Patients with Type 2 Diabetes

(1) Background. We aimed to assess long-term efficacy and safety in inadequately controlled type 2 diabetes (T2DM) of two SGLT-2 inhibitors: empagliflozin (Empa) and dapagliflozin (Dapa), combined with metformin, other oral antidiabetics or insulin, according to the protocols in Romania. (2) Methods. The data of 100 patients treated for T2DM with associated dyslipidemia and/or cardiovascular diseases at the University Hospital and Consultmed Medical Center in Iasi were retrospectively reviewed (2017–2021). In total, 48 patients had received dapagliflozin (10 mg with oral antidiabetics or insulin) and 52 patients received empagliflozin (10 mg /25 mg with oral antidiabetics). (3) Results. In both groups, the lowering of BMI was significant: Dapa group (32.04 ± 4.49 vs. 31.40 ± 4.18 kg/m²; p = 0.006), and Empa group (34.16 ± 5.08 vs. 33.17 ± 4.99 kg/m²; p = 0.002). Blood sugar average levels decreased significantly (170 vs. 136 mg/dL; p = 0.001 for Dapa; 163 vs. 140 mg/dL; p = 0.002 for Empa) and also average levels of HbA1c (7.90% vs. 7.51%; p = 0,01 for Dapa; 7.72% vs. 7.35%; p = 0.004 for Empa). (4) Conclusions. Better results in all variables were observed in younger male patients with a shorter duration of diabetes and threshold BMI levels of 34.1, treated with SGLT2, and more significantly with Empa.