Role of a Dual Glucose-Dependent Insulinotropic Peptide (GIP)/Glucagon-like Peptide-1 Receptor Agonist (Twincretin) in Glycemic Control: From Pathophysiology to Treatment

Glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) are two gut hormones, defined incretins, responsible for the amplification of insulin secretion after oral glucose intake. Unlike GLP-1, GIP has little acute effect on insulin secretion and no effect on food intake; instead it seems that the GIP may be an obesity-promoting hormone. In patients with type2 diabetes mellitus (T2DM) some studies found a downregulation of GIP receptors on pancreatic β cells caused by hyperglycemic state, but the glucagonotropic effect persisted. Agonists of the receptor for the GLP-1 have proven successful for the treatment of diabetes, since they reduce the risk for cardiovascular and renal events, but the possible application of GIP as therapy for T2DM is discussed. Moreover, the latest evidence showed a synergetic effect when GIP was combined with GLP-1 in monomolecular co-agonists. In fact, compared with the separate infusion of each hormone, the combination increased both insulin response and glucagonostatic response. In accordance with theseconsiderations, a dual GIP/GLP-1receptor agonist, i.e., Tirzepatide, known as a "twincretin" had been developed. In the pre-clinical trials, as well as Phase 1-3 clinical trials, Tirzepatideshowedpotent glucose lowering and weight loss effects within an acceptable safety.

Efficacy and safety of novel twincretin tirzepatide a dual GIP and GLP-1 receptor agonist in the management of type-2 diabetes: A Cochrane meta-analysis

BACKGROUND

Till date, there is no Cochrane meta-analysis available which has analyzed efficacy and safety of tirzepatide in type-2 diabetes. This meta-analysis was undertaken to address this knowledge gap.

METHODS

Electronic databases were searched for randomized controlled trials (RCTs) involving people with diabetes receiving tirzepatide compared to a placebo/active comparator. Primary outcome was to evaluate changes in HbA1c. Secondary outcomes were to evaluate alterations in blood-glucose, glycemic targets, weight, lipids, and adverse events.

RESULTS

From 34 articles initially screened, data from six RCTs involving 3484 patients were analyzed. Over 12-52 weeks, individuals receiving tirzepatide had significantly greater lowering of HbA1c [mean difference (MD) = -0.75% (95% confidence interval (CI): -1.05 to -0.45); P < 0.01; I ² = 100%], fasting glucose [MD = -0.75 mmol/L (95% CI: -1.05 to- -0.45); P < 0.01; I ² = 100%], 2-h post-prandial-glucose [MD = -0.87 mmol/L (95% CI: -1.12 to -0.61); P < 0.01; I ² = 99%], weight [MD = -8.63 kg (95% CI: -12.89 to -4.36); P < 0.01; I ² = 100%], body mass index [MD = -1.80 kg/m² (95% CI: -2.39 to -1.21); P < 0.01; I ² = 99%], and waist circumference [MD = -4.43 cm (95% CI: -5.31 to -3.55); P < 0.01; I ² = 95%] as compared to dulaglutide, semaglutide, degludec, or glargine. Patients receiving tirzepatide had higher odds of achieving HbA1c <6.5% compared to active controls [odds ratio (OR) = 4.39 (95% CI: 2.44-7.92); P < 0.01; I ² = 90%]. Tirzepatide use had significantly higher odds of weight loss >5% [OR = 19.18 (95% CI: 2.34-157.17); P < 0.01; I ² = 99%], >10% [OR = 21.40 (95% CI: 2.36-193.94); P < 0.01; I ² = 98%], and >15% [OR = 32.84 (95% CI: 2.27-474.33); P = 0.01; I ² = 96%] compared to active-control group. Treatment-emergent adverse events [risk ratio (RR) = 1.43 (95% CI: 1.14-1.80); P < 0.01; I ² = 40%] and severe adverse events [RR = 1.00 (95% CI: 0.64-1.57); P = 1.00; I ² = 49%] were not different. High data heterogeneity and the presence of publication bias limits the grading of current data from "moderate to low."

CONCLUSION

Tirzepatide has impressive glycemic efficacy and weight-loss data over 1-year clinical use. The need for higher grade, long-term efficacy, and safety data remains.

Neuroprotective Effects and Treatment Potential of Incretin Mimetics in a Murine Model of Mild Traumatic Brain Injury

Traumatic brain injury (TBI) is a commonly occurring injury in sports, victims of motor vehicle accidents, and falls. TBI has become a pressing public health concern with no specific therapeutic treatment. Mild TBI (mTBI), which accounts for approximately 90% of all TBI cases, may frequently lead to long-lasting cognitive, behavioral, and emotional impairments. The incretins glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) are gastrointestinal hormones that induce glucose-dependent insulin secretion, promote β-cell proliferation, and enhance resistance to apoptosis. GLP-1 mimetics are marketed as treatments for type 2 diabetes mellitus (T2DM) and are well tolerated. Both GLP-1 and GIP mimetics have shown neuroprotective properties in animal models of Parkinson's and Alzheimer's disease. The aim of this study is to evaluate the potential neuroprotective effects of liraglutide, a GLP-1 analog, and twincretin, a dual GLP-1R/GIPR agonist, in a murine mTBI model. First, we subjected mice to mTBI using a weight-drop device and, thereafter, administered liraglutide or twincretin as a 7-day regimen of subcutaneous (s.c.) injections. We then investigated the effects of these drugs on mTBI-induced cognitive impairments, neurodegeneration, and neuroinflammation. Finally, we assessed their effects on neuroprotective proteins expression that are downstream to GLP-1R/GIPR activation; specifically, PI3K and PKA phosphorylation. Both drugs ameliorated mTBI-induced cognitive impairments evaluated by the novel object recognition (NOR) and the Y-maze paradigms in which neither anxiety nor locomotor activity were confounds, as the latter were unaffected by either mTBI or drugs. Additionally, both drugs significantly mitigated mTBI-induced neurodegeneration and neuroinflammation, as quantified by immunohistochemical staining with Fluoro-Jade/anti-NeuN and anti-Iba-1 antibodies, respectively. mTBI challenge significantly decreased PKA phosphorylation levels in ipsilateral cortex, which was mitigated by both drugs. However, PI3K phosphorylation was not affected by mTBI. These findings offer a new potential therapeutic approach to treat mTBI, and support further investigation of the neuroprotective effects and mechanism of action of incretin-based therapies for neurological disorders.