Their premise was that acute hypoxia, lasting hours to days, acts as a profound physiological stressor that rapidly alters organ perfusion and enzyme activity, whereas chronic hypoxia lasting weeks or longer triggers acclimatization mechanisms that partially offset the initial disruption. If true, the pharmacokinetic consequences of altitude exposure should shrink as the body adapts, a pattern with direct implications for the significant number of people with type 2 diabetes who live in or travel to mountainous regions above 2,500 meters. To build the model, the researchers induced type 2 diabetes in male Wistar rats using a standard two-step protocol: four weeks on a high-calorie, high-sugar diet to promote insulin resistance, followed by a single low-dose injection of streptozotocin.

Only rats with fasting blood glucose persistently at or above 11.1 mmol/L across three consecutive measurements entered the pharmacokinetic experiments. The animals were then split into four groups of eight, comparing acute normoxia with acute hypoxia and chronic normoxia with chronic hypoxia. The hypoxic groups lived in a hypobaric chamber simulating 6,000 meters of altitude, a setting chosen to represent the extreme end of high-altitude exposure. In the acute arm, rats received a single oral dose of dapagliflozin at 1 mg/kg after three days in the chamber or under normal conditions. The results were striking. Compared with the acute normoxia group, the area under the plasma concentration-time curve, a measure of total drug exposure, rose 6.58-fold, and the peak plasma concentration climbed 5.06-fold, with all differences statistically significant.

Apparent oral clearance and apparent volume of distribution collapsed by roughly 84 percent. Concentrations in the hypoxic group exceeded those of the normoxic controls as early as half an hour after dosing, indicating that the perturbation begins almost immediately. The chronic arm told a different story. Rats dosed daily for 14 days at simulated altitude showed a 2.11-fold increase in total exposure and a 1.69-fold increase in peak concentration relative to their normoxic counterparts, with clearance and volume of distribution reduced by about 53 to 59 percent. Expressed as fold-change relative to duration-matched controls, the hypoxia-induced rise in exposure was approximately 70 percent smaller under chronic than under acute exposure. A two-way analysis of variance confirmed that the interaction between hypoxic treatment and exposure duration was significant for total exposure, apparent volume, and apparent clearance, formally validating that the hypoxic effect on drug disposition is duration-dependent rather than a fixed perturbation.

Interpreting these numbers mechanistically requires caution, and the authors are explicit about the limits. Because dapagliflozin was given orally, the apparent clearance and volume parameters cannot distinguish changes in oral bioavailability from true changes in distribution or elimination. The parallel reductions in both parameters, alongside an unchanged terminal half-life, suggest that increased oral bioavailability, possibly through altered first-pass metabolism, may contribute substantially to the exposure rise. Dapagliflozin is primarily cleared by glucuronidation via the enzyme UGT1A9, and the researchers speculate that acute hemodynamic redistribution and altered UGT1A9 activity could be involved, but they did not measure enzyme expression directly, leaving that mechanism speculative. The partial restoration of apparent clearance during chronic exposure is consistent with known acclimatization processes, including erythropoiesis, cardiac output recovery, and hypoxia-inducible factor-mediated transcriptional reprogramming, though again, no direct molecular evidence was gathered.

The pharmacodynamic side of the study added an unexpected wrinkle. Over the 14-day chronic protocol, fasting blood glucose was monitored serially at days 0, 1, 4, 7, 10, and 14. The chronically hypoxic rats showed a significantly blunted early glycemic reduction at days 4 and 7 compared with normoxic controls, differences that remained significant even after Bonferroni correction. Yet by days 10 and 14, glucose levels in the two groups had converged, suggesting that compensatory homeostatic mechanisms gradually offset the initial pharmacodynamic impairment. At the study endpoint, the researchers measured renal cortical SGLT2 protein by ELISA and found it significantly downregulated in the hypoxic group, at 283.30 ng/L versus 348.48 ng/L in normoxic controls.

That combination, lower SGLT2 abundance coexisting with higher early blood glucose, is counterintuitive from a purely pharmacological standpoint, since reduced transporter expression should theoretically enhance glucose lowering by diminishing renal glucose reabsorption. The authors resist a causal interpretation, and for good reason: the glycemic differences emerged on days 4 through 7, whereas SGLT2 was measured only at day 14, so the protein change may be a consequence rather than a cause of the early metabolic disruption. They also note that total SGLT2 protein in whole-tissue homogenates may not reflect functional activity at the apical membrane, that hepatic glucose production and peripheral insulin sensitivity are themselves altered under chronic hypoxia, and that dapagliflozin’s inhibitory effect depends on membrane target occupancy rather than total tissue abundance. Direct measurements of 24-hour urinary glucose excretion and SGLT2 membrane localization will be needed to resolve the paradox.

An individual-level exposure-response analysis sharpened the picture of what the authors describe as a hypoxia-induced dissociation between drug exposure and glycemic response. When data from both chronic groups were pooled, no correlation emerged between dapagliflozin exposure and day-14 fasting glucose. But within the normoxic group alone, total exposure was significantly and negatively correlated with day-14 glucose, exactly the relationship expected if more drug means lower glucose. In the chronically hypoxic group, that relationship vanished entirely. The authors draw a parallel to human evidence: a post hoc analysis of the OMAN trial found that hypertensive patients living at roughly 3,000 meters on the Tibetan Plateau showed attenuated blood pressure responses to olmesartan and amlodipine despite verified adherence, and earlier work showed losartan failing to lower blood pressure at 5,035 meters. Chronic hypoxia, it appears, can blunt end-organ responsiveness across drug classes.

The translational message is framed carefully rather than prescriptively. For people with type 2 diabetes ascending rapidly to altitude, the sixfold exposure increase seen in rats suggests a heightened risk of dose-dependent adverse effects and warrants enhanced clinical vigilance, though no human dapagliflozin data exist yet and the authors stop short of recommending dose changes. For long-term high-altitude residents, the picture is more complex: sustained exposure elevation coexists with renal target downregulation and delayed early glycemic response, raising the possibility that standard doses may provide suboptimal control while simultaneously posing a safety concern. The study has clear limitations, including the confounding of hypoxia duration with dosing regimen, since the acute arm used a single dose while the chronic arm used daily dosing; the use of only male rats; the absence of a formal power analysis; and the exploratory nature of the exposure-response correlations, which relied on pharmacokinetic measurements taken only at day 14.

The authors emphasize that their findings in chemically induced diabetic rats are hypothesis-generating and require confirmation in human studies, particularly given documented species-specific responses to hypoxia. They argue that dedicated clinical pharmacokinetic-pharmacodynamic studies in high-altitude populations are urgently needed to determine whether and how SGLT2 inhibitor therapy should be optimized for people who live at or travel to altitude, a question that current evidence cannot yet answer but that the present rat model now frames in quantitative, testable terms.

Subject of Research: Time-dependent effects of high-altitude hypoxia on dapagliflozin pharmacokinetics, renal SGLT2 expression, and glycemic response in diabetic rats

Article Title: Time-dependent pharmacokinetic changes and renal SGLT2 expression alterations of dapagliflozin under high-altitude hypoxia in diabetic rats

Article References: Tong, Y., Wang, C., Sun, Y., Zhang, X., Fang, H., Xie, Y., Xiao, Y., Ma, S., Li, W., & Wang, R. (2026). Time-dependent pharmacokinetic changes and renal SGLT2 expression alterations of dapagliflozin under high-altitude hypoxia in diabetic rats. Frontiers in Pharmacology, 17, Article 1931102. https://doi.org/10.3389/fphar.2026.1931102

Image Credits: AI Generated

DOI: 10.3389/fphar.2026.1931102

Keywords: dapagliflozin, SGLT2 inhibitors, high-altitude hypoxia, pharmacokinetics, type 2 diabetes, renal glucose reabsorption, drug metabolism, hypobaric chamber, pharmacodynamics, acclimatization, UGT1A9, preclinical study