Obesity and its associated comorbidities constitute a major and growing health problem worldwide not only involved with people but also dogs and cats. Although few genetic mutations have been associated with obesity in dogs, molecular mechanism remains to be clearly understood. Given the fact that DNA methylation leads to gene expression variability and has plasticity affected by metabolic phenotypes such as obesity in human, the objective of this study is to identify obesity-associated differentially methylated cytosine-phosphate-guanine (CpG) dinucleotide sites in dogs.

With genome-wide DNA methylation analysis using next-generation sequencing for blood samples from fourteen Miniature dachshunds with body condition score (BCS) 4–5 and BCS ≥6, over 100,000 sites could be analysed to identify genomic locations of differentially methylated CpG sites. As a result, 191 differentially methylated CpG sites (89 CpG sites were hypermethylated in BCS ≥6 and 102 were hypermethylated in BCS 4–5) were identified. These sites included promoter regions of Kisspeptin receptor (KISS1R) and Calcyphosine 2 (CAPS2) genes which were subsequently validated by bisulfite-pyrosequencing for another set of 157 dog blood samples. KISS1R methylation levels were found to be higher in BCS ≥6 group than BCS 4–5 in senior (>84 months) dogs. Especially male dogs but not female dogs as well as uncastrated male dogs but not castrated male dogs showed this trend.

DNA methylation of KISS1R gene will be useful for understanding of comprehensive epigenetic change in obese dogs.

肥胖及其相关的合并症构成了世界范围内一个主要且日益严重的健康问题，不仅涉及人，还涉及狗和猫。尽管很少有基因突变与狗的肥胖有关，但分子机制仍有待清楚地了解。鉴于 DNA 甲基化导致基因表达变异并且具有受代谢表型（如人类肥胖）影响的可塑性，本研究的目的是确定狗中与肥胖相关的差异甲基化胞嘧啶 - 磷酸 - 鸟嘌呤（CpG）二核苷酸位点。

通过对身体状况评分 (BCS) 4-5 和 BCS ≥6 的 14 只小型腊肠犬的血液样本使用新一代测序进行全基因组 DNA 甲基化分析，可以分析超过 100,000 个位点，以确定差异甲基化 CpG 位点的基因组位置。结果，鉴定了 191 个差异甲基化的 CpG 位点（89 个 CpG 位点在 BCS ≥6 中高甲基化，102 个在 BCS 4-5 中高甲基化）。这些位点包括 Kisspeptin 受体 (KISS1R) 和 Calcyphosine 2 (CAPS2) 基因的启动子区域，随后通过亚硫酸氢盐焦磷酸测序对另一组 157 个狗血样进行验证。发现 BCS ≥ 6 组的 KISS1R 甲基化水平高于老年（> 84 个月）狗的 BCS 4-5 组。

KISS1R 基因的 DNA 甲基化将有助于了解肥胖狗的综合表观遗传变化。