Introduction: Depression frequently co-occurs with metabolic disorders (MetD), particularly insulin resistance, yet the mechanisms linking these conditions remain insufficiently understood. In our previous work, we established a mouse model of MetD-related depression by feeding 8-week-old C57BL/6N mice with a high-fat diet (HFD) for 12 weeks, which reliably induced both metabolic abnormalities and depressive phenotypes. We further discovered that HFD markedly reduced the expression of the glial glutamate transporters, GLAST and GLT-1, in the ventral hippocampus (vHPC), impairing local glutamate clearance and elevating extracellular glutamate levels. This glutamatergic dysregulation resulted in hyperactivation of vHPC glutamatergic projections to the nucleus accumbens (NAc), contributing to depression-like phenotypes. These findings identify reduced vHPC GLAST and GLT-1 as key determinants of MetD-related depression and highlight the need to elucidate how HFD suppresses these transporters in order to guide therapeutic development. Since insulin upregulates GLT-1 expression in primary astrocytes, our observations raise the possibility that HFD-induced central insulin resistance may drive the loss of vHPC GLAST and GLT-1 and ultimately contribute to depressive outcomes. Objectives: Accordingly, herein, we aimed to test the hypothesis that loss of vHPC astrocytic insulin signaling reduces local GLAST and GLT-1 expression, leading to hyperactivation of vHPC glutamatergic afferents to the NAc and ultimately the manifestation of depressive-like behaviors. Methods: We employed both in vivo and in vitro insulin-resistance models. To specifically interrogate vHPC astrocytic insulin signaling, we selectively deleted the insulin receptor (IR) in vHPC astrocytes using a Cre-loxP strategy. An adeno-associated virus (AAV) expressing Cre recombinase under the GFAP promoter was bilaterally infused into the vHPC of IR-floxed mice. In addition, AAV-mediated astrocytic overexpression of GLAST and GLT-1, as well as chemogenetic inhibition, were used to validate the contributions of vHPC astrocytic GLAST/GLT-1 and the vHPC-NAc glutamatergic pathway to depressive-like behaviors. (local IACUC approval: 112083) Results: Exogenous insulin failed to activate insulin signaling in the vHPC of HFD-fed mice (p = 0.0079; N = 8), which also displayed reduced GLAST and GLT-1 expression compared to controls. In vitro, saturated fatty acid-induced insulin resistance similarly decreased GLAST (p = 0.0012) and GLT-1 (p = 0.0043) in primary astrocytes (N = 9), indicating that loss of insulin signaling contributes to downregulations of GLAST and GLT-1. Selective deletion of vHPC astrocytic IR reduced local GLAST (p = 0.0410) and GLT-1 (p = 0.0007), increased vHPC-NAc glutamatergic activity (p = 0.0002), and induced depressive-like behaviors (SPT: p = 0.0207, FST: p = 0.0116; N = 21-23). Chemogenetic inhibition of the hyperactive vHPC-NAc pathway reversed depressive phenotypes (FST: p = 0.0211; N = 21-23). Overexpression of GLAST and GLT-1 in the vHPC corrected glutamatergic transmission dysregulations (p = 0.0043) and ameliorated depression-like behaviors (SPT: p = 0.0222, FST: p = 0.0093; N = 21-23). Conclusions: These results demonstrate that impaired astrocytic insulin signaling in the vHPC downregulates GLAST and GLT-1, leading to hyperactivity of the vHPC-NAc glutamatergic pathway and the manifestation of depressive-like behaviors. This positions astrocytic insulin signaling as a critical mechanistic driver of depression and a promising therapeutic target for MetD-related depression.