The aim of this cross-sectional case-control study is to investigate the possible presence of vascular/neurodegenerative alterations in the retina of type 1 diabetes mellitus (T1DM) patients without diabetic retinopathy (DR). Thirty-four eyes of 34 consecutive T1DM without DR (mean age 21 ± 2 years) were included. Another cohort of 27 eyes (27 healthy control subjects matched with age and sex) was also recruited. All patients underwent multimodal imaging evaluation using structural optical coherence tomography (OCT), OCT-angiography (OCT-A), dynamic vessel analyzer (DVA) and microperimetry. No significant differences were disclosed comparing diabetics and controls for visual acuity, central macular thickness, and subfoveal choroidal thickness. On retinal nerve fiber layer and ganglion cell complex thickness, no significant differences were disclosed comparing each 3-mm-diameter macular and peripapillary subfield between two groups. Using OCT-A, deep capillary plexus perfusion density (PD) of diabetics was significantly lower compared to control group, whereas PD of other retinal/choriocapillaris plexuses and foveal avascular zone area did not show any significant difference. Using DVA, diabetic eyes revealed a significantly decreased vessel response to flicker light in comparison to controls. No differences were disclosed using microperimetry analysis. Taken together, these results suggest that vascular alterations could be the first detectable retinal change in the development of DR.

Key Points: Comprehensive genome-wide association study of eGFR in diabetes, accounting for diabetes duration, kidney disease, and known modifiers, identified novel genetic effects. Incorporation of various kidney multi-omics data provides supporting evidence for the role of novel genome-wide association study loci in diabetic kidney disease. Background: Diabetic kidney disease (DKD) is a serious diabetes complication caused by both environmental and genetic risk factors. Previous genome-wide association studies (GWAS) have identified several loci associated with kidney function and kidney disease in the general population and, to a lesser extent, in diabetes. Methods: To uncover the genetic factors driving diabetes-induced kidney function, we conducted a series of GWAS meta-analyses of eGFR in 17,267 individuals with type 1 diabetes and 35,264 with type 2 diabetes (52,531 total), using multiple well-characterized cohorts of type 1 diabetes DKD and data from the UK Biobank and SUrrogate markers for Micro- and Macrovascular hard end points for Innovative diabetes Tools (SUMMIT) consortium. We further accounted for DKD case/control status, diabetes duration and subtype, body mass index, glycated hemoglobin levels, and the relationship between eGFR and albuminuria. Results: GWAS identified 13 loci associated with eGFR ( P < 5×10 ⁻⁸ ), with five loci (candidate genes: HIPK3 , TRIM5 , RORA , ERBB4 , and BCL6 / LPP ) not associated with or were in opposite directions as compared with eGFR in the general population. Four candidate genes ( HIPK3 , BCL6, LPP , and RORA ) demonstrated evidence of differential expression in kidney compartments and cells among subgroups with DKD or diabetes versus controls. Lead single-nucleotide polymorphisms rs8027829 ( RORA ) and rs76300256 ( BCL6/LPP ) were methylation quantitative trait loci in whole blood and kidney tissue, respectively, and rs76300256 and its related CpGs all cluster in a kidney enhancer. Conclusions: Our integrated approach identified candidate genes with diabetes-specific effects on kidney function.

Compound 21 (C21), an AT2 receptor agonist, and Angiotensin 1-7 (Ang 1-7), through Mas receptor, play an important role in the modulation of the protective arm of the renin-angiotensin system. The aim of this study was to investigate in an experimental model of angiotensin II-dependent hypertension whether the activation of the potentially protective arm of the renin-angiotensin system, through AT2 or Mas receptor stimulation, counteracts the onset of myocardial fibrosis and hypertrophy, and whether these effects are mediated by inflammatory mechanism and/or sympathetic activation. Sprague Dawley rats (n = 67) were treated for 1 (n = 25) and 4 (n = 42) weeks and divided in the following groups: (a) Angiotensin II (Ang II, 200 ng/kg/min, osmotic minipumps, sub cutis); (b) Ang II+Compound 21 (C21, 0.3 mg/kg/day, intraperitoneal); (c) Ang II+Ang 1-7 (576 µg/kg/day, intraperitoneal); (d) Ang II+Losartan (50 mg/kg/day, per os); (e) control group (physiological saline, sub cutis). Systolic blood pressure was measured by tail cuff method and, at the end of the experimental period, the rats were euthanized and the heart was excised to evaluate myocardial fibrosis, hypertrophy, inflammatory cell infiltration and tyrosine hydroxylase expression, used as marker of sympathetic activity. Ang II caused a significant increase of blood pressure, myocardial interstitial and perivascular fibrosis and myocardial hypertrophy, as compared to control groups. C21 or Ang 1-7 administration did not modify the increase in blood pressure in Ang II treated rats, but both prevented the development of myocardial fibrosis and hypertrophy. Treatment with losartan blocked the onset of hypertension and myocardial fibrosis and hypertrophy in Ang II treated rats. Activation of AT2 receptors or Mas receptors prevents the onset of myocardial fibrosis and hypertrophy in Ang II-dependent hypertension through the reduction of myocardial inflammatory cell infiltration and tyrosine hydroxylase expression. Unlike what happens in case of treatment with losartan, the antifibrotic and antihypertrophic effects that follow the activation of the AT2 or Mas receptors are independent on the modulation of blood pressure.

Diabetic retinopathy is a complication of diabetes characterized by an extremely low rate of progression. It takes several years to move from the onset of diabetes, both type 1 and type 2, to the development of retinal microaneurysms, then leading to proliferative diabetic retinopathy and vision loss. The recent demonstration that retinal microaneurysms are preceded and, possibly, caused by a subclinical neurodegeneration mainly affecting the neurovascular unit has suggested, on one hand, the possible existence of a previously unknown early neurodegenerative stage of diabetic retinopathy and, on the other, that an early “neuroprotective” treatment could end up preventing the development of the microvascular stages. This review summarizes the present situation in the field and focuses on the prevention of diabetic retinopathy, which seems, for the first time, to be within reach.

Specific and effective preventive treatment for diabetic retinopathy (DR) is presently unavailable, mostly because the early stages of the complication have been, until recently, poorly understood. The recent demonstration that the vascular phase of DR is preceded and possibly caused by the neurodegeneration of retinal ganglion cells suggests that DR could, at least theoretically, be prevented through an early neuroprotective approach. The aims of our study were to clarify the natural history of diabetes-driven retinal neurodegeneration and to verify the possibility to prevent DR using topical nerve growth factor (NGF). The results of the study show that retinal neurodegeneration, characterized by the loss of retinal ganglion cells represents a relatively early phenomenon of diabetes (between 5 and 16 weeks of age), which tends to be self-limiting in the long run. Neurodegeneration is followed by the development of DR-related vascular dysfunctions, as confirmed by the development of acellular capillaries and the loss of retinal pericytes. Both retinal neurodegeneration and subsequent vascular dysfunction can be successfully prevented by topical NGF administration. These findings suggest that: 1) The first stage of DR consists in a self-limiting retinal neurodegeneration 2) The demonstrated effectiveness of topical NGF in the prevention of DR could be rapidly translated into clinical practice.