Type 2 diabetes (T2D), one of the most prevalent noncommunicable diseases, is often preceded by insulin resistance (IR), which underlies the inability of tissues to respond to insulin and leads to disturbed metabolic homeostasis. Mitochondria, as a central player in the cellular energy metabolism, are involved in the mechanisms of IR and T2D. Mitochondrial function is affected by insulin resistance in different tissues, among which skeletal muscle and liver have the highest impact on whole-body glucose homeostasis. This review focuses on human studies that assess mitochondrial function in liver, muscle and blood cells in the context of T2D. Furthermore, different interventions targeting mitochondria in IR and T2D are listed, with a selection of studies using respirometry as a measure of mitochondrial function, for better data comparison. Altogether, mitochondrial respiratory capacity appears to be a metabolic indicator since it decreases as the disease progresses but increases after lifestyle (exercise) and pharmacological interventions, together with the improvement in metabolic health. Finally, novel therapeutics developed to target mitochondria have potential for a more integrative therapeutic approach, treating both causative and secondary defects of diabetes.

Increased body weight as well as type 2 diabetes (T2D) are found to be associated with increased incidence of hypertension, although the mechanisms facilitating hypertension in T2D or nondiabetic individuals are not clear. Therefore, in this study we compared the levels of insulin resistance (IR:OGIS), plasma insulin (PI:RIA) levels, and pro-inflammatory cytokines (IL-6 and TNF-α: ELISA), being risk factors previously found to be associated with hypertension, in T2D patients showing increased body weight (obese and overweight, BMI ≥ 25 kg/m²) with hypertension (group A, N = 30), or without hypertension (group B, N = 30), and in nonobese (BMI < 25 kg/m²), normotensive controls (group C, N = 15). We found that OGIS index was the lowest (A: 267 ± 35.42 vs. B: 342.89 ± 32.0, p < 0.01) and PI levels were the highest (A: 31.05 ± 8.24 vs. B: 17.23 ± 3.23, p < 0.01) in group A. In addition, IL-6 levels were higher in group A (A: 15.46 ± 5.15 vs. B: 11.77 ± 6.09; p < 0.05) while there was no difference in TNF-α levels. Our results have shown that appearance of hypertension in T2D patients with increased body weight was dependent on further increase in IR which was associated with the rise in pro-inflammatory IL-6 cytokine. The results imply that lifestyle intervention aimed to decrease IR might be beneficial in reducing the risk for hypertension in those T2D individuals.

Background/Objectives: Previous studies reported impairments in insulin secretion during different stages of type 1 diabetes (T1D), while data regarding insulin sensitivity and immunological changes are still controversial. We analyzed the following: (a) insulin secretion, (b) insulin sensitivity, and (c) pro-inflammatory interleukin-17 (IL-17) levels in peripheral blood in 17 healthy first-degree relatives in stage 1 (FDRs1) (GAD⁺, IA2⁺), 34 FDRs in stage 0 (FDRs0) (GAD⁻, IA2A⁻), 24 recent-onset T1D (R-T1D) patients in the insulin-requiring state (IRS), 10 in clinical remission (CR), and 18 healthy unrelated controls (HC). Methods: Insulin secretion was evaluated by an IVGTT and a glucagon stimulation test, expressed as a first-phase insulin response (FPIR) and a basal/stimulated C-peptide. Insulin sensitivity was tested by the euglycemic hyperinsulinemic clamp, expressed as an M value. Results: FDRs1 had a lower FPIR than FDRs0 (p < 0.05) and HC (p < 0.001) but higher than RT1D-IRS (p < 0.001) and RT1D-CR (p < 0.01). Moreover, FDRs1 had lower basal/stimulated C-peptide than FDRs0 (p < 0.01/p < 0.05) and HC (p < 0.001/p = 0.001) but higher levels than RT1D-IRS (p < 0.001/p < 0.001). However, the M value was similar among FDRs1, FDRs0, and HC (p = 1.0) but higher than RT1D-IRS (p < 0.001) and RT1D-CR (p < 0.01), while RT1D-IRS and RT1D-CR had lower M than HC (p < 0.001; p < 0.001; respectively). FDRs1 had higher IL-17 than FDRs0 (p < 0.001) and HC (p < 0.05). RT1D-IRS had higher IL-17 than FDRs0 (p < 0.001) and HC (p < 0.001), which was similar to RT1D-CR vs. FDRs0 (p < 0.001) and HC (p < 0.05). Conclusions: Early changes in pre-T1D might involve an initial decline of insulin secretion associated with a pro-inflammatory attack, which does not influence insulin sensitivity, whereas later, insulin sensitivity deterioration seems to be associated with the prominent reduction in insulin secretion.

Nogo (RTN4) proteins and their receptors have emerged as candidate mediators of metabolic regulation and vascular pathology relevant to type 2 diabetes (T2D). The primary objective of this PRISMA-guided systematic review was to evaluate the clinical and cohort evidence for RTN4/RTN4R as potential biomarkers of T2D progression and vascular complications. A secondary objective was to synthesize preclinical mechanistic evidence on the effects of Nogo axis modulation on pathways relevant to the pathogenesis of T2D. We performed a PRISMA-guided systematic review. The protocol was not prospectively registered in PROSPERO. To ensure reproducibility, we provide complete search keywords, the screening log and the full-text exclusion table. PubMed/MEDLINE, EMBASE and Web of Science were searched for studies published 2000–2025; full search keywords are provided in the main text. The search strategy combined and free-text terms with Boolean operators. We included original preclinical and clinical studies, cohort/proteomic analyses, meta-analyses, and mechanistic papers reporting expression, function, signaling, or clinical associations of Nogo proteins/receptors in metabolic or vascular outcomes. Exclusion criteria: non-English articles, unclear methods, studies outside 2000–2025, and studies lacking primary data. Two reviewers independently screened records; conflicts were resolved by consensus. Study quality was appraised using established tools (SYRCLE for animal studies, Newcastle–Ottawa Scale for cohort/case-control studies). Preclinical evidence supports tissue-specific roles for RTN4 isoforms and receptors in the regulation of insulin secretion, proGCG → GLP-1 processing, ER homeostasis, and vascular permeability through the Src/PI3K/Akt and RhoA/ROCK axes. Cohort and proteomic analyses report associations between RTN4/RTN4R or serum NogoB and faster progression of T2D or vascular complications, but genetic assessment of causality (Mendelian randomization) has so far provided limited support in available data sets. Findings are heterogeneous with respect to directionality and tissue localization. RTN4 signaling exhibits tissue-specific mechanisms relevant to glucose regulation and vascular biology and warrants further translational study. However, heterogeneity across studies and limited genetic support for causality indicate that isoform-specific quantitative validation, longitudinal cohorts and integrated genetic–functional analyses are required before RTN4/RTN4R can be considered as clinical biomarkers.

Background/Objectives: Gestational diabetes (GD) is a well known risk factor for future metabolic diseases. However, the long-term time-dependent risk of non-alcoholic fatty liver disease (NAFLD) remains unexplored. The aim of this meta-analysis was to quantify the long-term risk of NAFLD in women with previous GD and evaluate if the risk persists beyond the postpartum period. Methods: A systematic search was performed in PubMed using appropriate medical subject headings to identify trials evaluating the incidence of NAFLD among women with previous GD compared to those with normal glucose tolerance (NGT). Studies reporting adjusted risk estimates with a follow-up duration beyond pregnancy were included. Data were extracted and analyzed using relevant statistical methods, with the level of significance at p < 0.05. Results: A total of four studies (N = 2873) were included in the meta-analysis. Women with previous GD had a 2.46-fold higher odds of NAFLD compared to those with NGT (95% CI 1.88–3.23, p < 0.001). The slope for years since delivery was not significant (β = 0.001 per year, 95% CI −0.037 to 0.040, p = 0.901), indicating that the likelihood of NAFLD in women with prior GD did not change over time. Conclusions: GD is associated with a substantially increased and sustained risk of NAFLD, persisting decades beyond pregnancy. These findings identified GD as a potential early risk marker of future liver outcomes and highlight the need for long-term metabolic screening and preventive strategies for this high-risk population.