Due to an imbalance between energy intake and expenditure, obesity develops which leads to an increase in adipose tissue mass, which is not a storage site but acts as a hormone-secreting organ that secretes adipokines, free fatty acids, and cytokines that disrupt metabolic homeostasis [11]. Adipose tissue changes to a pro-inflammatory state, especially in visceral adiposity which facilitates systemic metabolic dysfunction and insulin resistance [11]. The metabolic stress is increased by the inflammatory environment across several tissues which disrupt insulin signaling [12]. Endocrine factors are altered by obesity, levels of protective adipokines like adiponectin decrease, whereas leptin resistance, increased resistin, and other adipokine disturbances are involved in reduction of IR [11]. These obesity-related metabolic abnormalities cause metabolic stress, insulin resistance, and chronic inflammation when combined, which increases the development of diabetic kidney disease. Eventually, adaptive hyperinsulinemia is caused by obesity-induced IR, and over time pancreatic β-cell dysfunction ensues, contributing to the progression of overt hyperglycemia and T2DM as metabolic compensation fails [11].

When insulin-target tissues including the liver, adipose tissue, and skeletal muscles are unable to respond properly to normal insulin levels, IR develops, leading to an increase in gluconeogenesis, impaired glucose uptake, and dysregulated lipid metabolism [13]. One primary mechanism includes accumulation of abnormal lipid deposits especially diacylglycerols (DAGs) and ceramides in the liver and muscles, which initiate novel protein kinase C isoforms (e.g., Protein Kinase C (PKC) θ in muscle; PKCϵ in liver) that catalyze phosphorylation of insulin receptor substrate proteins on serine residues, impairing insulin receptor tyrosine kinase signaling [14]. Reduced β-oxidation of fatty acids and increased formation of reactive oxygen species due to mitochondrial dysfunction further facilitate lipotoxicity and oxidative stress, which interfere with insulin signaling cascades and promote inflammation [14]. When nutrient overload occurs (e.g., glucose, excessive free fatty acids), endoplasmic reticulum (ER) stress is induced, triggering the unfolded protein response (UPR) and activating kinases such as Inositol-requiring enzyme1 (IRE1) and Jun N-terminal kinase (JNK), which can transfer a phosphate group to Insulin receptor substrate (IRS) on inhibitory sites, reducing downstream Phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) signaling [14]. Genetic and epigenetic factors (e.g., polymorphisms in IRS, PI3K, insulin receptor genes; alternative splicing; regulation of negative modulators) modulate individual susceptibility to IR [15]. Hyperinsulinemia itself can exacerbate IR by downregulation of insulin receptor expression, induction of receptor internalization, and negative feedback via downstream signaling (e.g., Mammalian Target of Rapamycin (mTOR)/Ribosomal protein S6 kinase (S6K) pathway) that impairs IRS function. Additionally, by creating a chronic state of insulin resistance, the persistence of these defects encourages cellular dysfunction, inflammation, and metabolic stress in insulin-responsive tissues. Together, these mechanisms converge to disrupt the insulin receptor → IRS → PI3K → AKT signaling axis, reduce Glucose transporter type 4 (GLUT4) translocation in muscle and adipose, impair suppression of liver glucose output, and thus chronically elevate blood glucose levels leading to T2DM [14].

Adipose tissue secretes adipokines—such as resistin, leptin, and adiponectin—and inflammatory mediators such as Tumor Necrosis Factor Alpha (TNF-α) and Interleukin 6 (IL-6), which play a central role in metabolic dysfunction in obesity [16]. TNF-α released by adipocytes and infiltrating macrophages induces serine phosphorylation of insulin receptor substrate (IRS) proteins, thereby disrupting insulin signaling and contributing to IR [16]. Reduced levels of anti-inflammatory adipokines like adiponectin further change the balance toward pro-inflammatory states, exacerbating IR and renal hemodynamic alterations [16].

Excessive production of reactive oxygen species (ROS) in endothelial cells is caused by oxidative stress driven by metabolic dysregulation and hyperglycemia, overwhelming antioxidant defenses and damaging cellular components [17]. In individuals with diabetes, excessive production of superoxide in endothelial cells activates detrimental pathways, including advanced glycation end products (AGEs), the polyol pathway, the hexosamine pathway, and PKC activation, each contributing to endothelial injury [17].

Systemic and intrarenal Renin-angiotensin-aldosterone system (RAAS) become inappropriately activated in diabetes and obesity, contributing to renal injury and hypertension [18]. The release of renin is stimulated by increased sympathetic tone, hyperglycemia, and signals from the macula densa, resulting in elevated angiotensin II, which produces vasoconstrictive and pro-fibrotic effects [19]. The progression of DKD is promoted by angiotensin II, through stimulation of renal fibrosis and mesangial growth via Transforming growth factor-beta (TGF-β) signaling [18]. The activation of intrarenal RAAS may precede the progression of clinical kidney disease, making RAAS inhibition Angiotensin converting enzyme (ACE) inhibitors or Angiotensin receptor blockers (ARBs) a key factor in preventive therapy in diabetic kidney disease [18].

The formation of slit diaphragms and maintenance of the filtration barrier are mediated by podocytes, which are highly differentiated glomerular epithelial cells. In DKD, they undergo foot process effacement, loss by apoptosis, hypertrophy, epithelial-mesenchymal transition (EMT), and decreased autophagy, altering structural integrity [20]. Significant causes of podocyte damage that promote apoptosis and structural disruption in DKD include angiotensin II signaling, TGF-β1, Mechanistic/mammalian target of rapamycin complex 1 (mTORC1) activation, and metabolic stress [20]. Experimental studies and clinical research illustrate that podocytes to be one of the initial and most crucial targets of metabolic, inflammatory, and profibrotic attacks in diabetic kidney disease, which resulting in the gradual weakening of glomerular barrier activity. Podocytes are particularly vulnerable to long-term damage in diabetic kidney disease due to these convergent detrimental pathways, which impairs their ability to maintain the integrity of the glomerular filtration barrier. Loss of podocytes is one of the early events in DKD, and correlates with proteinuria and a reduction in GFR. Further, a dysregulation of intracellular calcium (Ca²⁺) signaling has been found to be a major cause of podocyte impairment in diabetic kidney disease. Metabolic and oxidative stressors disrupt calcium ions homeostasis in the podocyte, triggering cytoskeletal changes, slit diaphragm malfunction, and apoptosis. The interaction of these calcium-dependent processes with inflammatory and profibrotic processes further enhances the glomerular damage and increases proteinuria in diabetic kidney disease [21].

One of the earliest hallmarks of DKD is glomerular hyperfiltration which it can be noticed in individuals with T1DM and T2DM, which occurs before the onset of albuminuria and a gradual decline in renal function [22]. The glomerular capillary pressure is increased by prolonged hyperfiltration, leading to mechanical stress on glomerular structures and promoting mesangial expansion, basement membrane thickening, and podocyte injury [22]. According to several studies, individuals with hyperfiltration have faster GFR decline than those who do not have hyperfiltration, especially when hyperfiltration remains despite treatment [23]. The development from microalbuminuria to macroalbuminuria has been linked to hyperfiltration, indicating its role in disease progression [23]. Molecular profiling of kidneys from hyperfiltering diabetic individuals reveals upregulation of endothelial stress response, TGF-β pathways, and inflammatory signatures, suggesting that hyperfiltration not only induces structural stress, but also activates damaging biochemical cascades [24].

Increased body weight canelevate the risk of hypertension through several mechanisms, including sodium retention, overactivation of the sympathetic nervous system, and elevation of RAAS activity, all of which contribute to hypertension in obese people [25]. Obesity also produces structural and functional alterations in the kidney, such as increased GFR hyperfiltration and glomerular capillary wall stress, which predispose to proteinuria [26]. Visceral adipose tissue generates adipokines and cytokines (e.g., leptin, resistin, TNF-α) that promote inflammation, endothelial dysfunction, and increased glomerular permeability [27].

Visceral adipose tissue, which encircles internal structures, is more strongly linked to IR, dyslipidemia, impaired glucose metabolism, metabolic syndrome, and hypertension than subcutaneous adipose tissue (SAT) [28]. SAT, especially in people with lower Visceral adipose tissue (VAT), may have less harmful and potentially protective metabolic effects, partly through better lipid storage and lower secretion of pro-inflammatory cytokines [29]. In longitudinal studies, increases in VAT predict incident metabolic risk factors over time (higher glucose, worse lipid profiles), whereas SAT changes show weaker and less consistent associations after adjusting for VAT [30].

The development of DKD and glomerular damage is accelerated by IR-related hyperinsulinemia, which raises intraglomerular pressure and glomerular hyperfiltration [22]. In animal models and early human studies, chronically increased insulin levels provoke glomerular hypertrophy even before the onset of overt hyperglycemia or diabetes, suggesting that hyperinsulinemia alone may initiate structural glomerular changes [31]. Moreover, insulin can stimulate profibrotic pathways, including TGF-β activation, leading to basement membrane thickening and mesangial matrix expansion, thereby accelerating the decline in glomerular filtration rate over time [32].

Lipolysis in adipose tissue can be increased by IR in DKD, enhancing free fatty acid (FFA) flux to the liver, which elevates Very Low-Density Lipoprotein (VLDL) production [33]. Some of the characteristics of lipid abnormalities in DKD include elevated triglycerides and increased numbers of small dense Low-Density Lipoprotein (LDL) particles, while High-Density Lipoprotein (HDL) cholesterol tends to be reduced [34]. Lipoprotein lipase (LPL) is suppressed and Apolipoprotein C-III (ApoC-III) is increased by IR, which further impairs triglyceride clearance and worsens dyslipidemia [35]. These lipid disturbances are linked to albuminuria and accelerated decline in eGFR, contributing to the progression of DKD [36].

IR is detectable early in CKD, even when glomerular filtration rate is still in the normal or mildly reduced range, and becomes prevalent in most people with severe stages of kidney disease [37]. IR contributes to CKD progression via multiple mechanisms: worsening renal hemodynamics (e.g., increased intraglomerular pressure), sodium retention, and sympathetic nervous system activation [37]. Several cohort studies indicate that higher baseline insulin resistance or hyperinsulinemia is associated with faster progression through CKD stages, greater likelihood of moving from early to moderate and severe CKD [37].

Glycated Hemoglobin (HbA1c) values reflect chronic hyperglycemia and are strongly linked to an increased risk of DKD, and HbA1c variability independently correlates with advanced nephropathy in T2DM [38]. HOMA-IR (Homeostatic Model Assessment for Insulin Resistance (HOMA-IR), an abbreviation of homeostasis model assessment of insulin resistance, is increased in individuals with T2DM who develop DKD, and those in the highest tertile of HOMA-IR have significantly greater odds of DKD compared with those in lower tertiles [39]. High-sensitivity CRP (hs-CRP) is correlated with HbA1c and HOMA-IR, and elevated hs-CRP is seen in DKD, reflecting low-grade inflammation as a contributor to renal damage [39]. Thus, together HbA1c (glycemic control), HOMA-IR (insulin resistance), and CRP (inflammation) form an interlinked triad that serves both as a marker of risk and a potential target for intervention to slow DKD progression [39].

Albumin-to-creatinine ratio (UACR) or urinary albumin excretion (UAE) are the earliest standardclinical indicator of DKD, correlating with the risk of progression to micro- and macroalbuminuria and declining GFR [40]. However, UAE has limitations: some patients develop renal structural damage or decline in eGFR even while normoalbuminuric, suggesting that albuminuria alone may miss early injury [40]. Consequently, other urinary biomarkers of renal injury are currently under investigation: for example, type IV collagen, urinary N-acetyl-β-D-glucosaminidase (NAG), urinary adiponectin (especially high-molecular-weight forms), and tubular injury markers like retinol-binding protein, α1-microglobulin, and β2-microglobulin [41]. These markers may detect glomerular, podocyte, and tubular damage before overt albuminuria, improving early diagnosis and risk stratification in patients with diabetes [40].

Kidney injury molecule-1 (KIM-1) and neutrophil gelatinase-associated lipocalin (NGAL) are elevated in urine in obese children before any decline in GFR or overt proteinuria, indicating early renal tubular injury [42]. In farming communities in Sri Lanka, urinary KIM-1 and NGAL were higher even in apparently healthy individuals in areas with increasing CKD prevalence, suggesting their utility as early detection biomarkers [43]. The adiponectin/leptin ratio and leptin levels have been studied; a higher adiponectin-to-leptin ratio is linked with lower risk of incident CKD, especially in men with lower body mass index [44]. By reflecting early glomerular and tubular injury as well as metabolic and inflammatory abnormalities, these novel biomarkers support their significance in predicting the evolution of diabetic kidney disease and offer insight into disease activity before overt functional deterioration. A recent review of emerging biomarkers in DKD highlights NGAL, KIM-1, adiponectin, and leptin among markers that may improve early risk stratification and potentially guide therapy [45].

A large cross-sectional study of 4079 Chinese T2DM patients found that both higher Body mass index (BMI) (general obesity) and waist-to-hip ratio (abdominal obesity) were each associated with a higher prevalence of DKD, and those with both general, abdominal obesity and multiple metabolic abnormalities carried the greatest risk of DKD [46]. A British cohort of approximately 4.4 million adults who were metabolically healthy but obese still showed increased risk of incident CKD in comparison to normal-weight healthy individuals (Hazard Ratio (HR) ~1.30 for overweight; ~1.66) for metabolically healthy obesity [47]. A study using Mendelian randomization in T1DM (n ≈ 6049) demonstrated that genetic predisposition to higher BMI causally increases the risk of DKD, macroalbuminuria, and End-stage renal disease (ESRD) [48].

A 12-year prospective cohort (n = 5347) found that individuals with elevated HOMA-IR trajectory compared with a stable pattern had more than double the risk of adverse renal outcomes (eGFR <60 or new proteinuria), even after adjusting for baseline HOMA-IR and clinical covariates [49]. In the Tehran lipid and glucose study, over 18 years’ follow-up, individuals in the elevated HOMA-IR trajectory group had a significantly higher incidence of CKD (HR ~1.72 in men, ~1.37 in women) compared with stable trajectories [50]. A three-year longitudinal study among Chinese adults without CKD at baseline showed that higher homeostasis model assessment of IR was associated with faster progression to mildly reduced eGFR and CKD; both IR and metabolic syndrome accelerated CKD onset [51]. In elderly Asians (≥65 years), IR and metabolic syndrome were linked with prevalent CKD and more rapid eGFR decline over ~3 years; each unit increase in HOMA-IR raised the odds of CKD and proteinuria. Although the prevalent finding in epidemiological studies indicates clearly that the metabolic syndrome and insulin resistance are crucial determinants associated with chronic kidney disease, the degree of their association with it differs among populations, age groups, and comorbidities, especially in older adults [52].

In patients with CKD, non-surgical interventions such as dietary modifications, exercise, and anti-obesity medications have been shown to reduce BMI by approximately 3.7 kg/m², and significantly decrease proteinuria (weighted mean difference of approximately 1.31 g/24 h) without accelerating GFR decline [53]. Sustained weight loss with strict metabolic therapies is associated with improvements in renal hemodynamics, reductions in albuminuria, and a reduction in long-term kidney and cardiovascular risk in obese individuals with type 2 diabetes. Bariatric/metabolic surgery (e.g., Roux-en-Y gastric bypass) in obese T2DM patients lowers the incidence of diabetic nephropathy, improves albuminuria, and slows decline of renal function across a range of baseline kidney function levels [54].

SGLT2 inhibitors reduce glucose reabsorption in the proximal tubule, increase natriuresis and glucosuria, thereby reducing hyperfiltration, lowering intraglomerular pressure, and improving renal outcomes in DKD [55]. The combination of SGLT2 inhibitors with RAAS blockade offers additive renoprotective benefit: simultaneous suppression of hemodynamic stress, inflammation, and fibrosis appears greater than either agent alone [56]. By restoring tubuloglomerular feedback and demonstrating anti-inflammatory and antifibrotic effects, SGLT2 inhibitors directly target significant pathophysiological pathways that propel the development of diabetic kidney disease, especially in insulin-resistant and obese phenotypes. Therapeutic trials such as Empagliflozin (EMPA-KIDNEY), Dapagliflozin and Prevention of Adverse Outcomes in Chronic Kidney Disease (DAPA-CKD), and Canagliflozin and Renal Events in Diabetes with Established Nephropathy Clinical Evaluation (CREDENCE) have shown that SGLT2 inhibitors plus background RAAS inhibitor therapy reduce the risk of kidney endpoints (e.g., sustained GFR decline, ESRD), cardiovascular death or mortality in patients with DKD [57].

Lifestyle modification combining diet and exercise in obese CKD patients produced significant weight loss (≈5 kg in 12 weeks), reduced fat mass, IR (assessed via the Matsuda index), adipokine profile (increase adiponectin, decrease leptin), and reduced inflammation markers, though GFR remained stable in short term [58]. Intentional weight loss (IWL) strategies—dietary, surgical, and pharmacological—reviewed in obese people with DKD show slowed progression of kidney disease, improvements in albuminuria, but heterogeneity in outcomes due to differing methods and baseline renal function [59]. Lifestyle changes that specifically target sodium intake are crucial for lowering hemodynamic stress and volume overload in individuals with diabetic kidney disease, which slows the progression of chronic kidney disease. Dietary sodium restriction as part of lifestyle counselling in CKD (many with diabetic nephropathy) attenuated proteinuria, reduced blood pressure, and in one study reduced risk of composite renal outcomes over approximately ~3.5 years [60].

It is now recognized that obesity and insulin resistance play a major role in the development of diabetic kidney disease through interconnected hemodynamic, metabolic, inflammatory, and fibrotic pathways. Even though we now have a much better understanding of these pathways, we still have a long way to go before we can effectively translate mechanistic discoveries into phenotype-specific therapies to stop the progression of renal failure. These gaps need to be filled in order to enhance risk classification and therapeutic targeting in obese individuals with diabetic kidney disease. Human kidney biopsy studies are scarce, especially in early disease, which hampers understanding of which cell types (podocytes, endothelial, mesangial or tubularcells) are first altered in obese individuals [63]. The recent integrative studies of insulin-resistant renal models and the small human sample biopsy datasets suggest cell-type-specific molecular alterations that are typical of diabetic kidney disease; however, the time-dependent dynamics of the disease and its pathophysiology are still limited by the experimental modelsand the cross-sectional analysis of human samples. Moreover, longitudinal mechanistic human studies that track molecular, proteomic, transcriptomic and functional changes over time in individuals with obesity and diabetes are few, limiting understanding of causal ordering and potential reversibility. Biomarker studies (e.g., NGAL, KIM-1) show promise, but their mechanistic underpinnings in obese DKD and whether they reflect upstream processes versus downstream damage require clarification. Ultimately, human mechanistic studies are necessary to bridge from bench to bedside: to validate therapeutic targets, identify early disease signatures, and personalize interventions based on mechanisms in obese DKD [64].

Genetic susceptibility plays a substantial role in DKD: the disease shows familial clustering and heritability in both T1DM and T2DM, suggesting that DNA sequence variation underlies differential risk of developing DKD among individuals exposed to similar metabolic insults. Genome-wide association studies (GWAS) in DKD have detected many genes (e.g., Uromodulin, Engulfment and Cell Motility Protein 1, Carnosine Dipeptidase 1, Apolipoprotein L1, AF4/FMR2 Family Member 3, Advanced Glycosylation End-product Specific Receptor (UMOD, ELMO1, CNDP1, APOL1, AFF3, AGER) whose polymorphisms are associated with susceptibility or resistance to DKD or progression to ESRD. Despite these associations, the effect sizes of individual variants are small, and together they explain only part of the inter-individual variability in DKD risk or progression. Epigenetic modifications such as methylation changes, altered expression of non-coding RNAs, and histone modifications (miRNAs, lncRNAs) mediate how environmental or metabolic exposures (e.g., hyperglycemia, oxidative stress) influence gene expression relevant to DKD progression. For example, epigenome-wide studies (EWAS) have revealed differentially methylated Cytosine-phosphate-Guanine (CpG) sites in kidney-related genes (e.g., Solute Carrier Family 22 Member 12, Transient Receptor Potential Cation Channel Subfamily M Member 6 (SLC22A12, TRPM6) in DKD patients versus controls [65]. Histone methylation modifications (on Histone 3 Lysine 4, Histone 3 Lysine 9, Histone 3 Lysine 27 (H3K4, H3K9, H3K27) have been shown in DKD to contribute to chromatin structural changes that alter transcription of genes driving inflammation, fibrosis, and extracellular matrix deposition [66]. Moreover, the concept of “metabolic memory” depends heavily on epigenetic processes: prior hyperglycemic exposure leaves lasting epigenetic marks that promote DKD progression even after glycemic control is improved [67].

Precision medicine in T2DM has begun to stratify patients by IR, obesity, and triglyceride levels to predict differential drug responses—e.g., individuals with obesity and high triglycerides show reduced HbA1c response to Dipeptidyl Peptidase-4 (DPP-4) inhibitors compared to non-obese individuals, which may influence the choice of therapy in DKD settings [68]. Recent meta-regression analyses of Randomized Controlled Trials (RCTs) indicate that weight-loss therapies show variable effectiveness depending on patient phenotypes (baseline insulin resistance, obesity degree, metabolic health), suggesting that selecting dietary, pharmacologic, or surgical weight-loss options based on individual traits could enhance outcomes [69]. Genetics is increasingly recognized: obesity genetic variants, polygenic risk scores, and gene-environment interactions might help predict who is more likely to develop IR, renal damage, or respond to weight-loss interventions [70].