GABA gene knockdown alters counterregulatory responses in female rats

Targeting GABA synthesis in the ventromedial hypothalamic nucleus altered gene-expression profiles in growth hormone-releasing hormone neurons and reduced some hormonal responses to low blood glucose in female rats, according to an experimental study in Molecular Biology Reports. The researchers used targeted GAD2 knockdown to examine how local GABAergic signaling influences the dorsomedial division of the ventromedial hypothalamus, a region previously identified in male rats as a potential regulator of counterregulatory hormone secretion. The findings provide evidence of a female-specific response in this rat model, but they do not establish that the same mechanism operates in humans.

The investigators administered a small interfering RNA targeting glutamate decarboxylase 2, also called GAD2 or GAD65, within the ventromedial hypothalamic nucleus of female rats. They then isolated growth hormone-releasing hormone, or Ghrh, neurons by laser-catapult microdissection and analyzed their transcriptomic profiles. Females received either vehicle or insulin before this procedure, creating euglycemic, or normal-glucose, and insulin-induced hypoglycemic conditions for comparison. The study combined gene knockdown, neuronal transcript profiling and measurements of circulating hormones in rats; it was not a human clinical trial.

GAD2 knockdown increased transcripts encoding Ghrh in neurons collected from both vehicle- and insulin-treated females. It also amplified messenger RNA profiles for proteins characterized by the authors as counterregulatory-enhancing markers, including glutaminase and neuronal nitric oxide synthase. In the opposite direction, the intervention down-regulated GAD1 messenger RNA profiles in both euglycemic and hypoglycemic females. Steroidogenic factor-1 transcripts were unaffected in vehicle-treated animals and inhibited in insulin-treated animals following GAD2 knockdown. These results describe changes in gene expression rather than direct measurements of how much each corresponding protein was produced or how strongly each protein changed neuronal activity.

The molecular response also varied with glucose status. Knockdown of GAD2 increased expression of the 5’-AMP-activated protein kinase alpha 1 and alpha 2 genes in Ghrh neurons under euglycemic and hypoglycemic conditions. Lactate and estrogen receptor messenger RNA profiles showed a different pattern: the intervention inhibited these profiles in euglycemic females but amplified them during hypoglycemia. The authors interpret the combined findings as evidence that GABA-dependent input to ventromedial hypothalamic Ghrh neurons is involved in metabolic signal reception, energy monitoring and counterregulatory transmitter regulation in females, with some responses differing according to glucose availability. Because the experiment involved rats, it does not determine whether these molecular effects have direct relevance to human glucose regulation.

At the endocrine level, GAD2 knockdown attenuated the hypoglycemia-associated increases in corticosterone and glucagon. It also reversed the down-regulation of growth hormone secretion observed during hypoglycemia. These measured outcomes support a causal role for GABA synthesis within the targeted hypothalamic region in at least part of the counterregulatory response to low glucose in female rats. The reported scope remains limited to the animal model, the targeted VMN intervention and the hormones examined; the study did not test a treatment in people or establish a complete downstream pathway. The authors said ongoing work aims to clarify how GABA-dependent input from these distinctive neurons may affect counterregulation within female glucostatic neural networks.

Subject of Research: Effects of hypothalamic GAD2 knockdown on counterregulatory gene expression and hormone secretion in female rats

Article Title: Effects of ventromedial hypothalamic nucleus GAD gene knockdown on growth hormone-releasing hormone neuron transcriptomic profile in female rats

Article References: Sapkota, S., Pasula, M. B., Yadav, R., & Briski, K. P. (2026). Effects of ventromedial hypothalamic nucleus GAD gene knockdown on growth hormone-releasing hormone neuron transcriptomic profile in female rats. Molecular Biology Reports, 53(1), Article 1772. https://doi.org/10.1007/s11033-026-12946-w

Image Credits: AI Generated

DOI: 10.1007/s11033-026-12946-w

Keywords: GAD2 knockdown, GABA, ventromedial hypothalamus, hypoglycemia, growth hormone, corticosterone, glucagon, female rats, neuronal transcriptomics, counterregulation, Effects, ventromedial