High-Fat Diet Induces Epigenetic and Metabolic Changes in Kisspeptin Neurons in Association with Obesity and Male Secondary Hypogonadism
Kisspeptin neurons are affected by high-fat diets, which may link obesity and metabolic changes to male reproductive health issues.
Where it sits
this study against the rest of the kisspeptin (kp-10) corpusSummary and findings
This study investigated the effects of a high-fat diet on Kisspeptin neurons in male C57BL6 mice over 16 weeks. The research measured plasma testosterone levels, sperm counts, and gonadotropin responses, finding that high-fat diet induced obesity and metabolic changes associated with male secondary hypogonadism. The study highlights epigenetic alterations in Kiss1 neurons linked to these metabolic disturbances.
Abstract
<h4>Background</h4> Obesity and type 2 diabetes mellitus (T2D) are major risk factors for male hypogonadism, a disorder with multi-system impacts on health. However, the mechanisms underlying obesity-associated male secondary hypogonadism remain poorly understood. Here, we aimed to dissect dysfunction of the hypothalamic–pituitary–testicular (HPT) axis and elucidate underlying epigenetic mechanisms, using a high-fat diet mouse model. <h4>Methods</h4> Male C57BL6 mice were fed standard chow or high-fat diet (HFD, 60% fat) for 16 weeks starting at age 6 weeks. Plasma testosterone levels, sperm counts, and gonadotropin responses to senktide and kisspeptin stimulation were assessed. HFD-induced transcription changes in the hypothalamic arcuate nucleus (ARC) were evaluted using bulk and single-cell RNA-sequencing. Genome-wide changes in 5-hydroxymethylcytosine (5hmC) were analyzed by hydroxymethyl-DNA immunoprecipitation sequencing (hMeDIP-seq). Functional relevance of 5hmC changes was evaluated by ectopic TET expression in an immortalized ARC Kiss1 neuron cell line and RT-qPCR. <h4>Results</h4> HFD-fed mice developed obesity, hyperglycemia, glucose intolerance, and insulin resistance, indicative of the development of a type 2 diabetes-like metabolic disorder. This was accompanied by low testosterone, reduced sperm counts, and unchanged basal luteinizing hormone (LH), consistent with obesity/T2D-associated male secondary hypogonadism, as observed clinically in humans. Impaired LH responses to senktide, a Kiss1 neuron activator, but not to kisspeptin itself, identified suppressed Kiss1 neuron function as a key mechanism underlying secondary hypogonadism. RNA-seq analysis revealed dysregulation of metabolic and neural pathways in Kiss1 neurons. hMeDIP-seq demonstrated widespread 5hmC alterations in the ARC of HFD-induced obese/diabetic mice, correlated with dysregulation of fatty acid metabolism, neuronal activity, and synapse function pathways. Ectopic TET expression ex vivo in Kiss1 neuronal cell lines restored 5hmC levels and upregulated key metabolic and neuronal genes that were repressed in the ARC of DIO mice <h4>Conclusion</h4> Our findings demonstrate that Kiss1 neurons are highly sensitive to diet and metabolic changes, and that obesity/diabetes-induced 5hmC modifications play a key role in dysregulating metabolic and neuronal pathways in Kiss1 neurons. These findings reveal a novel mechanism linking metabolic disturbances to reproductive dysfunction, through direct effects on Kiss1 neurons. <h4>Graphic Abstract</h4>
Background
This paper addresses the relationship between obesity, type 2 diabetes mellitus (T2D), and male secondary hypogonadism, a condition with significant health implications. Previous research has established obesity and T2D as risk factors for hypogonadism, but the underlying mechanisms remain unclear. Understanding the role of Kisspeptin neurons in this context is crucial for elucidating the link between metabolic and reproductive health.
Methods
The study utilized a mouse model, specifically male C57BL6 mice, which were divided into two groups: one fed standard chow and the other a high-fat diet (HFD, 60% fat) for 16 weeks starting at 6 weeks of age. Primary outcomes included plasma testosterone levels, sperm counts, and gonadotropin responses to senktide and kisspeptin stimulation. Secondary outcomes involved RNA-sequencing and hydroxymethyl-DNA immunoprecipitation sequencing to assess transcriptional and epigenetic changes.
Results
HFD-fed mice exhibited obesity, hyperglycemia, glucose intolerance, and insulin resistance. Testosterone levels were low, and sperm counts were reduced, consistent with obesity/T2D-associated male secondary hypogonadism. LH responses to senktide were impaired, while responses to kisspeptin remained unchanged. RNA-seq analysis indicated dysregulation of metabolic and neural pathways in Kiss1 neurons, with hMeDIP-seq revealing widespread 5hmC alterations in the ARC.
Interpretation
The findings suggest that Kiss1 neurons are sensitive to dietary and metabolic changes, with obesity-induced 5hmC modifications contributing to reproductive dysfunction. While the study provides insights into the mechanisms linking metabolic disturbances to reproductive health, the effect sizes observed may not be clinically significant, and the reliance on a mouse model limits direct applicability to human health. Further research is needed to validate these findings in human subjects.
Key findings
- 60% fat diet for 16 weeks led to obesity, hyperglycemia, glucose intolerance, and insulin resistance.
- Low testosterone levels and reduced sperm counts were observed in HFD-fed mice.
- Impaired LH responses to senktide were noted, indicating suppressed Kiss1 neuron function.
- Widespread 5hmC alterations were found in the ARC of HFD-induced obese/diabetic mice.
- Ectopic TET expression restored 5hmC levels and upregulated key metabolic and neuronal genes.
Limitations
- Based on a mouse model, which may not fully translate to humans.
- Single dietary intervention without long-term follow-up.
- Small sample size not reported.
- No clinical data provided.