## 1 Introduction  
Diabetes mellitus is a type of metabolic disorder that is considered a serious health problem worldwide. Diabetes is caused either as a result of insufficient insulin secretion (type-1 diabetes) or failure of insulin action (type-2 diabetes). It is characterized by a high glucose level in the blood (hyperglycemia) [1], and proinflammatory cytokines such as interleukin (IL)-1\(\beta\), IL-6, and IL-2 are increased in the hyperglycemia condition [2]. Dysregulation of tumor necrosis factor-\(\alpha\) production is also associated with diabetes [3]. Additionally, hyperglycemia causes an increase in oxidative stress and has a positive association with cell dysfunction in diabetic patients [4, 5]. This disease also causes an adverse effect on some organs such as the testis, kidney, liver, and pancreas [6, 7]. Reduced levels of some essential hormones, such as luteinizing hormone, follicle-stimulating hormone, and testosterone, as well as low sperm count and motility, have also been seen in diabetic patients [8, 9].  
Several therapeutic agents have been used to treat diabetes, such as inhibitors of alpha-glucosidase and dipeptidyl peptidase-4, insulin secretagogues, and thiazoltionedine [10]. Unfortunately, some of these agents promote the increased prevalence of cardiovascular disease, gastrointestinal disease, headaches, and nausea [11]. Therefore, studies on novel antidiabetic compounds with less adverse effects is an interesting field and a major challenge for future research in the term of functional foods or natural products.  
Marine algae or seaweeds have been widely used for antidiabetic treatments [12]. Seaweeds contain certain bioactive compounds, such as polysaccharides, carotenoids, polyphenols, and phlorotannin, and have been recognized for their beneficial effects on human health [13,14]. _Caulerpa lentitillifera_ is a type of green seaweed (also known as sea grapes) widely found in the Indo-Pacific region [15]. Previous studies have reported that _C. lentitillifera_ has antioxidant, antibacterial, and anticancer properties [16,17]. Additionally, _C. lentitillifera_ also possesses antidiabetic effects by reducing \(\alpha\)-glucosidase and dipeptidyl peptidase-IV enzyme activities, while enhancing glucose uptake in adipocytes [18]. Furthermore, the hypoglycemic effects of seaweed extracts such as _Sargassum ringgoldianum_, _Sargassum polycystum_, and _Ishige okamurae_ have been reported [19, 20, 21], and fucoxanthin-rich extract from _Laminaria japonica_ and dietary supplementation of _Ulva lactuca_ and _Sargassum angustifolium_ have exhibited ameliorative effects on reproductive dysfunction [22, 23, 24]. However, no studies have yet reported on the ameliorative effects of _C. lentitillifera_ extract on male reproductive dysfunction under diabetic conditions. We hypothesized that this seaweed extract possesses the ability to reduce reproductive dysfunction under diabetic conditions, and this study aims to evaluate the ameliorative effects of the polysaccharides-rich extract from _Caulerpa lentitillifera_ on oxidative stress and proinflammatory cytokines related to reproductive dysfunction using a male diabetic mouse model.