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Proximal tubule fructose metabolism is key to fructose-induced hypertension, but the roles of sex and stress are unclear. We hypothesized that females are resistant to the salt-sensitive hypertension caused by low amounts of dietary fructose compared to males and that the magnitude of the increase in blood pressure (BP) depends, in part, on amplification of the stress response of renal sympathetic nerves. We measured systolic BP (SBP) in rats fed high salt with either no sugar (HS), 20% glucose (GHS) or 20% fructose (FHS) in the drinking water for 7-8 days. FHS increased SBP (p<0.03 vs basal) but neither GHS nor high salt alone raised SBP. FHS increased SBP significantly and similarly in both (male: Δ25±8 mm Hg; female: Δ19±2 mm Hg). FHS increased SBP by 24±5 mm Hg but only by 8±2 mm Hg when measured by plethysmography and telemetry, respectively (p<0.004). When SBP was measured by telemetry under low stress, FHS increased SBP by 8±1 mm Hg; on the contrary, when measured by telemetry under moderate stress conditions (simulating stress of plethysmography), FHS increased SBP by 15±3 mm Hg, a significantly greater increase (p<0.008). Norepinephrine excretion in rats subjected to moderate stress was 63±17 nmole/Kg/day for animals fed FHS but only 19±40 nmole/Kg/day for controls fed HS (p<0.02). We conclude that fructose-induced salt-sensitive hypertension is similar in males and females unlike other forms of hypertension, and the increase in blood pressure depends in part on an augmented response of the sympathetic nervous system to stress.

Proximal tubules (PT) reabsorb fructose via a Na-dependent mechanism. Knocking out the Sodium-Linked Cotransporter 5 (SGLT5, Slc5A10) increases urinary fructose. Elevated dietary fructose increases transport rates in PT, contributing to salt-sensitive hypertension. Whether dietary fructose also elevates transport in other segments of the nephron that do not express known fructose transporters, is a matter of debate. The aldosterone-sensitive distal tubule (ASDT) consists of the late distal convoluted tubule, connecting tubule and collecting duct, and it is essential for regulating fluid volume and blood pressure. We hypothesize that fructose metabolism in PT could affect aldosterone signaling in the distal tubule of rats fed a high-salt diet. We obtained kidney-cortex bulk RNAseq transcriptomes from wild-type and SGLT 5 (-/-) Sprague Dawley rats fed a solid diet containing 4% NaCl and either 20% fructose (FHS) or glucose (GHS). We used Weighted Correlation Network Analysis (WGCNA) to: 1st) create a gene coexpression network of the kidney cortex, and 2nd) identify genes whose expression changes in response to fructose in both wild-type and SGLT5 (-/-). Then, we used open source transcriptomes from mouse ASDT epithelial cells (PMID: 29521601) treated with and without aldosterone to map genes whose expression changes in response to aldosterone to the coexpression modules correlated with dietary fructose. The mouse transcriptome contained 8619 genes that mapped to the rat kidney transcriptome. Of these genes, 454 were significantly changed by aldosterone (ALDO). WGCNA yielded 35 coexpression modules. Five modules were significantly associated with dietary fructose in wild-type. These correlations were blunted in SGLT5 (-/-). Enrichment analysis indicated that 4 of the 35 modules were enriched for ALDO, 2 of which (Paleturquoise: p<5x10-6 and Orange: p<3x10-2) were also correlated with fructose in wild-type (Paleturquoise: p<3x10-2 and Orange: p<4x10-2). Paleturquoise contained 108 genes of which 74 mapped to the mouse transcriptome, and 15 to ALDO. Ontology enrichments in Paleturquoise indicate that it contains genes involved in Na, Cl and HCO3 transport. Importantly, the Amiloride-Sensitive Epithelial Sodium Channel Alpha Subunit (ENaCα; Scnn1a) and the Thiazide-Sensitive Sodium-Chloride Cotransporter (NCC; Slc12a3) belong in this module. Orange contained 148 genes, of which 34 mapped to mouse transcriptomes, and only 5 to ALDO. Orange’s ontology enrichment was largely immune processes, which explain the low number of mapping genes, as ALDO is a tubular epithelial cell signature. We conclude that even on a high-salt diet, kidneys from rats given fructose present higher transcriptional activation of aldosterone-responsive genes than those given glucose. In addition, Orange may be mediating proinflammatory actions of fructose. These effects depend on fructose reabsorption by PTs, as SGLT5 deletion blunts the effects of HSF on ALDO-enriched modules. CWRU-SOM Department of Physiology and Biophysics Pitot grant to A.G-V. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Kidneys of healthy individuals filter 4 to 25 g of fructose (FRU) a day, equivalent to ~10% of the filtered glucose. FRU reabsorbed by proximal tubules (PTs) is mostly used in gluconeogenesis. Elevated dietary FRU alters hormonal signaling in PTs and increases oxidative stress, which overtime, leads to salt-sensitive hypertension, tubulointerstitial injury, and glomerular damage. Four apical transporters could transport FRU at physiological concentrations: SGLT5 (km0.62 mM), NAGLT1 (km4.5 mM), GLUT5 (km12.6 mM) and SGLT4 (undetermined km). We hypothesize that single-cell (sc) transcriptional phenotypes correspond to anatomical features and could inform FRU transport in PTs. We used scRNAseq rat kidney transcriptomes (3 males & 3 females) to measure the expression of FRU transporters in cell clusters corresponding to the S1, S2, and S3 PT segments. We integrated cell transcriptional phenotypes with spatial and structural features using quantitative proteomics and transcriptomics from microdissected PT segments. Clusters S1, S2, and S3 had 1281, 2123 and 1441 cells, respectively. More than 90% of cells in all clusters expressed KHK, the first enzyme in FRU metabolism (expression: S1<S2<S3), showing high correlation with segment-proteomics (PCC (Pearson correlation coefficient) = 0.87) and transcriptomics (PCC = 0.65). In contrast, there were striking imbalances in transporters’ distributions. High-affinity SGLT5 was expressed by 3%, 24%, 75% cells in clusters S1, S2, and S3, with 4, 43, 230 aggregated counts per 100 cells (nCounts), respectively. SGLT5 showed a log2FC > 0.8 in S3 as compared to S1-S2 (p-adj < 1x10-300). SGLT5, PCC was 0.95 for quantitative proteomics and 0.48 for sequencing. Low-affinity NAGLT1 was expressed by 70%, 81%, 47% cells in clusters S1, S2, and S3, with 206, 306, 121 nCounts, respectively. These values were highly correlated with RNAseq in microdissected tubules (PCC = 0.99), but NAGLT1 was absent in the proteomics dataset. GLUT5 was expressed by 9%, 10%, 38% cells in clusters S1, S2 and S3, with 11, 11, 63 nCounts, respectively, and PCC > 0.95 for both quantitative proteomics and sequencing. Finally, SGLT4 was expressed by 4%, 6%, 8% cell in clusters S1, S2 and S3, with 5, 6, 8 nCounts, respectively. Due to the low signal in microdissected segments, we could not conduct a correlation analysis for SGLT4. Our data shows that SGLT5 is most abundant in the straight portion of PTs, particularly S3. GLUT5 and SGLT4 follow a similar distribution. In contrast, low-affinity NAGLT1 is expressed in all segments, most predominantly S1. However, as NAGLT1 affinity for glucose (km3.7 mM) is near that for FRU, it likely reabsorbs glucose in early PT. In the straight portion FRU will be predominantly reabsorbed by the most abundant higher-affinity SGLT5. Our analysis shows a high correlation between scRNAseq clusters and spatial proteomics data and highlights the relevance of SGLT5 as the main FRU transporter in PTs BGT670107 This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.