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Affecting an estimated 88 million Americans, prediabetes increases the risk for developing type 2 diabetes mellitus (T2DM), and independently, cardiovascular disease, retinopathy, nephropathy, and neuropathy. Nevertheless, little is known about the use of metformin for diabetes prevention among patients in the Veterans Health Administration, the largest integrated healthcare system in the U.S. This is a retrospective observational cohort study of the proportion of Veterans with incident prediabetes who were prescribed metformin at the Veterans Health Administration from October 2010 to September 2019. Among 1,059,605 Veterans with incident prediabetes, 12,009 (1.1%) were prescribed metformin during an average 3.4 years of observation after diagnosis. Metformin prescribing was marginally higher (1.6%) among those with body mass index (BMI) ≥35 kg/m 2 , age <60 years, HbA 1c ≥6.0%, or those with a history of gestational diabetes, all subgroups at a higher risk for progression to T2DM. In a multivariable model, metformin was more likely to be prescribed for those with BMI ≥35 kg/m 2 incidence rate ratio [IRR] 2.6 [95% confidence intervals (CI): 2.1-3.3], female sex IRR, 2.4 [95% CI: 1.8-3.3], HbA 1c ≥6% IRR, 1.93 [95% CI: 1.5-2.4], age <60 years IRR, 1.7 [95% CI: 1.3-2.3], hypertriglyceridemia IRR, 1.5 [95% CI: 1.2-1.9], hypertension IRR, 1.5 [95% CI: 1.1-2.1], Major Depressive Disorder IRR, 1.5 [95% CI: 1.1-2.0], or schizophrenia IRR, 2.1 [95% CI: 1.2-3.8]. Over 20% of Veterans with prediabetes attended a comprehensive structured lifestyle modification clinic or program. Among Veterans with prediabetes, metformin was prescribed to 1.1% overall, a proportion that marginally increased to 1.6% in the subset of individuals at highest risk for progression to T2DM., Competing Interests: Declaration of conflicting interestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Objective: Pilot-test personalized digital health information to substantiate human-delivered exercise support for adults with type 1 diabetes (T1D)., Design: Single-group, 2-week baseline observation, then 10-week intervention with follow-up observation., Setting: Community-based sample participating remotely with physician oversight., Participants: Volunteers aged 18 to 65 years with T1D screened for medical readiness for exercise intervention offerings. N = 20 enrolled, and N = 17 completed all outcomes with 88% to 91% biosensor adherence., Intervention: Feedback on personalized data from continuous glucose monitoring (CGM), its intersection with other ecological data sets (exercise, mood, and sleep), and other informational and motivational elements (exercise videos, text-based exercise coach, and self-monitoring diary)., Main Outcome Measures: Feasibility (use metrics and assessment completion), safety (mild and severe hypoglycemia, and diabetic ketoacidosis), acceptability (system usability scale, single items, and interview themes), and standard clinical and psychosocial assessments., Results: Participants increased exercise from a median of 0 (Interquartile range, 0-21) to 64 (20-129) minutes per week ( P = 0.001, d = 0.71) with no severe hypoglycemia or ketoacidosis. Body mass index increased (29.5 ± 5.1 to 29.8 ± 5.4 kg/m 2 , P = 0.02, d = 0.57). Highest satisfaction ratings were for CGM use (89%) and data on exercise and its intersection with CGM and sleep (94%). Satisfaction was primarily because of improved exercise management behavioral skills, although derived motivation was transient., Conclusions: The intervention was feasible, safe, and acceptable. However, there is a need for more intensive, sustained support. Future interventions should perform analytics upon the digital health information and molecular biomarkers (eg, genomics) to make exercise support tools that are more personalized, automated, and intensive than our present offerings., Competing Interests: The authors report no conflicts of interest., (Copyright © 2023 Wolters Kluwer Health, Inc. All rights reserved.)

Introduction: Type 2 diabetes mellitus (T2DM) is a powerful risk factor for cardiovascular disease (CVD), conferring a greater relative risk in women than men. We sought to examine sex differences in cardiometabolic risk factors and management in the contemporary cohort represented by the Glycemia Reduction Approaches in Diabetes: A Comparative Effectiveness Study (GRADE)., Research Design and Methods: GRADE enrolled 5047 participants (1837 women, 3210 men) with T2DM on metformin monotherapy at baseline. The current report is a cross-sectional analysis of baseline data collected July 2013 to August 2017., Results: Compared with men, women had a higher mean body mass index (BMI), greater prevalence of severe obesity (BMI≥40 kg/m 2 ), higher mean LDL cholesterol, greater prevalence of low HDL cholesterol, and were less likely to receive statin treatment and achieve target LDL, with a generally greater prevalence of these risk factors in younger women. Women with hypertension were equally likely to achieve blood pressure targets as men; however, women were less likely to receive ACE inhibitors or angiotensin receptor blockers. Women were more likely to be divorced, separated or widowed, and had fewer years of education and lower incomes., Conclusions: This contemporary cohort demonstrates that women with T2DM continue to have a greater burden of cardiometabolic and socioeconomic risk factors than men, particularly younger women. Attention to these persisting disparities is needed to reduce the burden of CVD in women., Trial Registration Number: ClinicalTrials.gov (NCT01794143)., Competing Interests: Competing interests: JBG reports grants from NIDDK during the conduct of the study; and grants and personal fees from Boehringer Ingelheim/Lilly, personal fees from NovoNordisk, grants from Roche, personal fees from Hawthorne Effect/Omada, grants and personal fees from Sanofi/Lexicon, personal fees from Pfizer, grants from Glaxo SmithKline, personal fees from Bayer, grants from Merck, and grants and personal fees from AstraZeneca outside the submitted work. HA reports other from Novo Nordisk during the conduct of the study; and other from Novo Nordisk outside the submitted work. CD reports grants and personal fees from Novo Nordisk, personal fees from Astra Zeneca, grants from Sanofi, grants from the Department of Defense, and consultation for Bayer outside the submitted work. AJA reports personal fees from Novo Nordisk and personal fees from Lilly during the conduct of the study; and personal fees from Medtronic outside the submitted work. DJW reports other from Novo Nordisk outside the submitted work. VRA reports grants and other from Applied Therapeutics, grants and other from Fractyl, grants and other from Novo Nordisk, other from Pfizer, grants and other from Sanofi, other from Eli Lilly, and other from Janssen (Spouse) outside the submitted work. BIG, NMB, JHL, TH, HK-S and CES have nothing to disclose., (© Author(s) (or their employer(s)) 2023. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Background: Our clinical trial of a mobile exercise intervention for adults 18 to 65 years old with type 1 diabetes (T1D) occurred during COVID-19 social distancing restrictions, prompting us to test web-based recruitment methods previously underexplored for this demographic., Objective: Our objectives for this study were to (1) evaluate the effectiveness and cost of using social media news feed advertisements, a clinic-based approach method, and web-based snowball sampling to reach inadequately active adults with T1D and (2) compare characteristics of enrollees against normative data., Methods: Participants were recruited between November 2019 and August 2020. In method #1, Facebook and Instagram news feed advertisements ran for five 1-to-8-day windows targeting adults (18 to 64 years old) in the greater New Haven and Hartford, Connecticut, areas with one or more diabetes-related profile interest. If interested, participants completed a webform so that the research team could contact them for eligibility screening. In method #2, patients 18 to 24 years old with T1D were approached in person at clinical visits in November and December 2019. Those who were interested immediately completed eligibility screening. Older patients could not be approached due to clinic restrictions. In method #3, snowball sampling was conducted by physically active individuals with T1D contacting their peers on Facebook and via email for 48 days, with details to contact the research staff to express interest and complete eligibility screening. Other methods referred participants to the study similarly to snowball sampling., Results: In method #1, advertisements were displayed to 11,738 unique viewers and attracted 274 clickers (2.33%); 20 participants from this group (7.3%) volunteered, of whom 8 (40%) were eligible. Costs averaged US $1.20 per click and US $95.88 per eligible volunteer. Men had lower click rates than women (1.71% vs 3.17%; P<.001), but their responsiveness and eligibility rates did not differ. In method #2, we approached 40 patients; 32 of these patients (80%) inquired about the study, of whom 20 (63%) volunteered, and 2 of these volunteers (10%) were eligible. Costs including personnel for in-person approaches averaged US $21.01 per inquirer and US $479.79 per eligible volunteer. In method #3, snowball sampling generated 13 inquirers; 12 of these inquirers (92%) volunteered, of whom 8 (67%) were eligible. Incremental costs to attract inquirers were negligible, and total costs averaged US $20.59 per eligible volunteer. Other methods yielded 7 inquirers; 5 of these inquirers (71%) volunteered, of whom 2 (40%) were eligible. Incremental costs to attract inquirers were negligible, and total costs averaged US $34.94 per eligible volunteer. Demographic overrepresentations emerged in the overall cohort (ie, optimal glycemic control, obesity, and low exercise), among those recruited by news feed advertisements (ie, obesity and older age), and among those recruited by snowball sampling (ie, optimal glycemic control and low exercise)., Conclusions: Web-based advertising and recruitment strategies are a promising means to attract adults with T1D to clinical trials and exercise interventions, with costs comparing favorably to prior trials despite targeting an uncommon condition (ie, T1D) and commitment to an intervention. These strategies should be tailored in future studies to increase access to higher-risk participants., Trial Registration: ClinicalTrials.gov NCT04204733; https://clinicaltrials.gov/ct2/show/NCT04204733., (©Garrett I Ash, Stephanie Griggs, Laura M Nally, Matthew Stults-Kolehmainen, Sangchoon Jeon, Cynthia Brandt, Barbara I Gulanski, Elias K Spanakis, Julien S Baker, Robin Whittemore, Stuart A Weinzimer, Lisa M Fucito. Originally published in JMIR Diabetes (https://diabetes.jmir.org), 08.07.2021.)

Context: Transgender men (TGM) are persons assigned female gender at birth with a male gender identity and are routinely treated with testosterone. Androgen excess is associated with endothelial dysfunction among cisgender females (CGF) and is an early sign of atherosclerosis and hypertension., Objective: To determine the effect of testosterone treatment on endothelial function in TGM., Setting: The John B. Pierce Laboratory and Yale School of Medicine., Subjects: Eleven TGM (age 27 ± 5 years; BMI 24.4 ± 3.7 kg/m 2 ) receiving testosterone (T) and 20 CGF (28 ± 5 years; BMI 26.0 ± 5.1 kg/m 2 ) during the early follicular phase of their menstrual cycle., Design and Outcome Measures: We evaluated brachial vasodilatory responses following stimuli designed to elicit shear stress using 5-minute occlusion to determine endothelial function (flow-mediated vasodilation, FMD)., Results: Total T was greater in the TGM compared to CGF (484.6 ± 122.5 vs 1.5 ± 0.7 ng/dL), as was free T (83.9 ± 32.4 vs 1.9 ± 0.8 pg/dL). FMD was markedly lower in the TGM (4.5 ± 2.7%) compared to the CGF (8.1 ± 2.9%, P = .002) indicating significantly diminished endothelial function in TGM., Conclusions: We have shown for the first time that in TGM the androgen-dominant hormonal milieu was associated with impaired endothelial function. Endothelial dysfunction precedes clinically detectable atherosclerotic plaque in the coronary arteries, so is an important marker for clinical cardiovascular risk. Therefore, attention to cardiovascular risk factors should be integral to the care of transgender men., (© 2019 John Wiley & Sons Ltd.)

Context: Intensive insulin therapy reduces the risk for long-term complications in patients with type 1 diabetes mellitus (T1DM) but increases the risk for hypoglycemia-associated autonomic failure (HAAF), a syndrome that includes hypoglycemia unawareness and defective glucose counterregulation (reduced epinephrine and glucagon responses to hypoglycemia)., Objective: The objective of the study was to address mechanisms underlying HAAF, we investigated whether nonglucose fuels such as acetate, a monocarboxylic acid (MCA), can support cerebral energetics during hypoglycemia in T1DM individuals with hypoglycemia unawareness., Design: Magnetic resonance spectroscopy was used to measure brain transport and metabolism of [2-(13)C]acetate under hypoglycemic conditions., Setting: The study was conducted at the Yale Center for Clinical Investigation Hospital Research Unit, Yale Magnetic Resonance Research Center., Patients and Other Participants: T1DM participants with moderate to severe hypoglycemia unawareness (n = 7), T1DM controls without hypoglycemia unawareness (n = 5), and healthy nondiabetic controls (n = 10) participated in the study., Main Outcome Measure(s): Brain acetate concentrations, (13)C percent enrichment of glutamine and glutamate, and absolute rates of acetate metabolism were measured., Results: Absolute rates of acetate metabolism in the cerebral cortex were 1.5-fold higher among T1DM/unaware participants compared with both control groups during hypoglycemia (P = .001). Epinephrine levels of T1DM/unaware subjects were significantly lower than both control groups (P < .05). Epinephrine levels were inversely correlated with levels of cerebral acetate use across the entire study population (P < .01), suggesting a relationship between up-regulated brain MCA use and HAAF., Conclusion: Increased MCA transport and metabolism among T1DM individuals with hypoglycemia unawareness may be a mechanism to supply the brain with nonglucose fuels during episodes of acute hypoglycemia and may contribute to the syndrome of hypoglycemia unawareness, independent of diabetes.

When a person consumes ethanol, the body quickly begins to convert it to acetic acid, which circulates in the blood and can serve as a source of energy for the brain and other organs. This study used 13C magnetic resonance spectroscopy to test whether chronic heavy drinking is associated with greater brain uptake and oxidation of acetic acid, providing a potential metabolic reward or adenosinergic effect as a consequence of drinking. Seven heavy drinkers, who regularly consumed at least 8 drinks per week and at least 4 drinks per day at least once per week, and 7 light drinkers, who consumed fewer than 2 drinks per week were recruited. The subjects were administered [2-13C]acetate for 2 hours and scanned throughout that time with magnetic resonance spectroscopy of the brain to observe natural 13C abundance of N-acetylaspartate (NAA) and the appearance of 13C-labeled glutamate, glutamine, and acetate. Heavy drinkers had approximately 2-fold more brain acetate relative to blood and twice as much labeled glutamate and glutamine. The results show that acetate transport and oxidation are faster in heavy drinkers compared with that in light drinkers. Our finding suggests that a new therapeutic approach to supply acetate during alcohol detoxification may be beneficial.

Background: Prior research has indicated an association between insulin resistance and stroke; we sought to determine if this association persists after adjusting for stroke risk factors, including glycemic control., Methods: We used data from the Third National Health and Nutrition Survey (1988-1994), including participants aged > or =40 years. We assessed insulin sensitivity using the homeostasis model assessment (HOMA): HOMA = (FPGSI x FPI)/22.5, where FPGSI refers to fasting plasma glucose (mmol/l) and FPI refers to fasting plasma insulin (microU/l). Increasing HOMA indicates decreasing insulin sensitivity. We used glycosylated hemoglobin (HbA1c) to measure glycemic control. Multivariable logistic regression analysis was used to identify factors that were independently associated with stroke., Results: Among 3,844 participants, 168 (4%) reported a stroke history. Participants with stroke had lower insulin sensitivity than participants without stroke: HOMA mean +/- standard deviation, 4.0 +/- 4.0 vs. 3.3 +/- 3.0; p = 0.022. HOMA was independently associated with stroke (odds ratio 1.06, 95% CI: 1.01-1.12; adjusted for age, hypertension, myocardial infarction, claudication, activity, and HbA1c). The strength of the association between HOMA and stroke was similar to the association between claudication and stroke (index R(2): 0.0032 vs. 0.0036)., Conclusions: Impaired insulin sensitivity is independently associated with stroke, even after adjustment for glycemic control., (Copyright (c) 2005 S. Karger AG, Basel.)

Background and Objective: Two methods for measuring insulin sensitivity, fasting plasma insulin (FPI) and homeostasis model assessment (HOMA) have been proposed for use in large epidemiological research and clinical practice. This project describes the range of observed values of the HOMA and FPI in a large sample of the U.S. population., Methods: We used fasting plasma glucose and insulin values from the Third National Health and Nutrition Survey (NHANES III) to identify the FPI and HOMA values. For both FPI and HOMA, higher values indicate lower insulin sensitivity., Results: Among 6,511 participants without treated diabetes mellitus, FPI ranged from 1.8 to 175.8 microU/mL, with 25th percentile=6.7, median=9.3, 75th percentile=13.3, and mean+/-1 SD=11.2+/-7.5; HOMA ranged from 0.3 to 52.6 (mmol)(microU)/L(2), with 25th percentile=1.5, median=2.2, 75th percentile=3.3, and mean+/-SD=2.8+/-2.4., Conclusion: These findings describe the spectrum of insulin sensitivity and may be useful in helping physicians develop a clinical understanding of the dynamic range of both FPI and HOMA measures.

Most studies of sex hormones and insulin resistance (IR) have focused on androgens; few have examined the association of endogenous estrogens and IR. We determined the cross-sectional association of endogenous levels of total and bioavailable testosterone and estradiol and SHBG with IR among 845 healthy, postmenopausal women aged 45-65 yr. Women were within 10 yr of menopause and not using hormone replacement therapy. Total adiposity was estimated by body mass index, visceral adiposity by waist to hip ratio (WHR), and IR by the homeostasis model assessment. We defined homeostasis model assessment-IR as the highest quartile (cutpoint, 2.1) of the distribution in this cohort. In logistic regression analyses, the odds for IR were significant and increased in a dose-response fashion across each quartile of total estradiol, bioavailable estradiol, and bioavailable testosterone (all P < 0.001 for linear trend). These associations remained significant after adjusting for WHR; adjusted odds ratios were 4.0, 6.1, and 2.7 for total estradiol, bioavailable estradiol, and bioavailable testosterone, respectively, comparing the highest to the lowest quartile (all P < 0.001). Adjusting for body mass index and WHR together eliminated the linear association of IR with total estradiol and bioavailable testosterone, but the association with bioavailable estradiol remained (adjusted odds ratio, 2.7; P < 0.001, comparing the highest to the lowest quartile). IR was not associated with total testosterone before or after adjusting for adiposity. Lower SHBG levels were associated with higher odds of IR, independent of adiposity. These results suggest that estrogen may be equally or more important than testosterone in the pathway to IR in healthy, young postmenopausal women, with differences not entirely explained by body size.

Estrogen-deficient women show increased skeletal sensitivity to the resorbing actions of PTH. The basis for this effect is not known. To examine the influence of estrogen deficiency on PTH-induced proresorptive cytokine production in humans, the response of five young women to a 36-h infusion of (1-34)human PTH (hPTH) was studied. PTH induced significant increases in circulating levels of IL-6 (mean values, T(0)-->T(36 h); 2.2-->19.2 pg/ml), IL-6 soluble receptor (IL-6sR; 29.8-->67.2 ng/ml), urine N-telopeptide of type I collagen (NTX) (38.6-->148 nM bone collagen equivalent/mM creatinine) and serum calcium (2.12-->2.62 mmol/liter). To examine the impact of hormonal status on this response, PTH infusions were next undertaken in seven estrogen-deficient and seven estrogen-treated postmenopausal women. When compared with estrogen-treated women, and correcting for differences in baseline values, estrogen-deficient women demonstrated an exaggerated increase in circulating levels of IL-6 (5.0-->31.7 vs. 3.2-->14.4 pg/ml; P = 0.0001) and IL-6sR (49.2-->102.1 vs. 37.7-->66.7; P = 0.0001). This was accompanied by greater increases in NTX excretion in the estrogen-deficient women (61.2-->201.6 vs. 44.8-->114.8, E(-) vs. E(+), P = 0.0001). Estrogen deficiency was not associated with augmented PTH-induced increases in colony-stimulating factor-1, IL-1beta, IL-11, or TNF-alpha. In a multiple regression model controlling for group, age, years since menopause both IL-6 and IL-6sR were strong predictors of NTX. These data, along with previous animal studies, support the conclusion that the IL-6/IL-6SR cytokine system plays a role in the increased skeletal sensitivity to PTH seen in estrogen-deficient women.

This study was designed to assess the prevalence and severity of low bone mineral density in an institutionalized population of postmenopausal women (n = 79) with developmental disabilities, using quantitative ultrasound of the calcaneus. The results demonstrate that this population has a significantly lower quantitative ultrasound index (QUI) of the calcaneus compared with a referent population of age-matched control subjects without mental disabilities. We used the QUI T-score threshold of <-2.0 standard deviations (SDs) to define individuals at high risk for osteoporosis, and 82% of the study participants met this criterion. Furthermore, approx 43% of the population had a heel QUI that was more than 2 SDs below that of age-matched control subjects, consistent with a severe degree of demineralization.

Background: The objective of this study was to evaluate the efficacy and safety of metrifonate, a long-acting acetylcholinesterase inhibitor, in patients clinically diagnosed with probable Alzheimer's disease of mild-to-moderate severity., Method: This was a prospective, multicenter, 26-week, double-blind, parallel group study. The 264 randomized patients met diagnostic criteria of the National Institute of Neurological and Communicative Diseases and Stroke and the Alzheimer's Disease and Related Disorders Association for probable Alzheimer's disease. Patients had Mini-Mental State Examination (MMSE) scores of 10-26 and ischemic scores (Rosen modification) of <4. Metrifonate-treated patients received a single 50-mg dose once daily. The efficacy of metrifonate was investigated with respect to 3 symptom domains. Cognitive performance was analyzed using the Alzheimer's Disease Assessment Scale-Cognitive Subscale (ADAS-Cog) and the MMSE. Psychiatric and behavioral disturbances were analyzed using the Neuropsychiatric Inventory (NPI) and the ADAS-Noncognitive subscale (ADAS-Noncog). The ability to perform instrumental and basic activities of daily living was evaluated using the Disability Assessment for Dementia (DAD) scale. Additionally, global state was assessed using the Clinician Interview-Based Impression of Change with Caregiver Input (CIBIC-Plus) scale., Results: After 26 weeks of metrifonate therapy, a statistically significant benefit of metrifonate was observed in the cognitive performance of Alzheimer's disease patients (ADAS-Cog, t = 2.55, df = 237, p = .012; MMSE, t = 4.60, df = 237, p = .0001). Metrifonate also significantly attenuated the deterioration in activities of daily living of the patients (DAD total score, t = -2.11, df = 233, p = .036) and relieved patients' psychiatric and behavioral disturbances (NPI total score, t = 2.51, df = 233, p = .013). In addition, metrifonate significantly improved the scores for the global state of the patients (CIBIC-Plus, t = 2.07, df = 232, p = .039). Metrifonate was well tolerated; adverse events were predominantly mild in intensity, and no hepatotoxicity was observed., Conclusion: In this study, metrifonate was safe and well tolerated. It benefited the cognitive decline, psychiatric and behavioral disturbances, impaired ability to perform instrumental and basic activities of daily living, and global state of patients diagnosed with mild-to-moderate Alzheimer's disease.

The role of self-esteem in modulating patterns of neuroendocrine response to challenge at older ages was examined in 16 healthy 70-yr-olds. Responses to two challenges were examined: (1) a driving simulation designed to reflect a 'real life' challenge situation; and (2) a pharmacologic, corticotropin-releasing-hormone (CRH) challenge (1 micrograms/kg). Both challenges evoked significant elevations in cortisol and adrenocorticotropic hormone (ACTH). Levels of self-esteem were significantly and negatively associated with peak elevations in cortisol in response to the driving simulation challenge (r = -0.51, p = 0.04). ACTH responses showed similar trends (r = -0.41, p = 0.12). Self-esteem levels were not correlated with responses to the CRH challenge. These data indicate that psychological characteristics such as self-esteem may play a role in modulating patterns of neuroendocrine response to cognitive/behavioral challenges in everyday life in older individuals.

We examined the cell type-specific expression of the alpha 1, alpha 2, and alpha 3 subunits of the sodium pump in rat brain using in situ hybridization and [3H]ouabain autoradiography. These techniques allowed us to colocalize mRNA and functional alpha 2/alpha 3 pumps on adjacent sections. The perikarya of many neurons possessed high levels of alpha 1 and/or alpha 3 transcripts, while alpha 2 mRNA appeared to be present in only a few neuronal types. [3H]Ouabain binding in general paralleled the distribution of alpha 3 mRNA-positive neurons. The regional variation of alpha 1 and alpha 3 transcripts was complex and varied. Large neurons of the olfactory bulb and piriform cortex expressed high levels of alpha 3 transcripts, but low levels of alpha 1 mRNA. In frontal cortex, neurons of layers II-III were enriched in alpha 1 mRNA, while those in layer V exhibited high levels of alpha 3 transcripts. In the hippocampus, principal neurons expressed all three alpha subunit mRNAs. CA subfield pyramidal neurons exhibited a high alpha 3/alpha 1 ratio, while dentate granule cells and hilar pyramidal neurons expressed approximately equal levels of alpha 1 and alpha 3. In the cerebellum, Purkinje and Golgi cells were rich in alpha 3 mRNA, while the granule cells appeared to express only alpha 1 transcripts. The distribution of functional sodium pump protein, as localized by [3H]ouabain binding, was highest in the neuropil of the hippocampus and cerebral cortex, and lowest over perikarya and white matter. [3H]ouabain did not bind to alpha 1 pump units, as confirmed by the complete absence of labeling over the choroid plexus, a tissue expressing only alpha 1 mRNA. In the cerebellum, regions of dense [3H]ouabain binding were localized to the granule cell layer, the inner third of the molecular layer in the basket region, and the deep cerebellar nuclei. Surprisingly, the dense neuropil in the outer 2/3 of the molecular layer lacked high [3H]ouabain binding. Thus, functional alpha 3 sodium pump units appear distributed to the axon terminals and not to apical dendrites of Purkinje, Golgi and basket cells. A similar pattern of increased [3H]ouabain binding in axonal but not dendritic fields of alpha 3-enriched neurons was present in the cerebral cortex and the hippocampus. Considering that many alpha 3-enriched neurons are of the Golgi I type with long axons, the alpha 3 isoform may be preferentially directed into axons to function in presynaptic membranes.