Biology subjects

Knopf, B. A.

Publications and source records attributed to Knopf, B. A..

6 recordsLinked to original sources

bioRxiv2026

Dietary sugar type determines the response to protein restriction in females, but not males

Low protein (LP) diets improve metabolic health in rodents and humans. In rodents, LP diets are typically implemented by replacing protein with carbohydrates like sucrose or cornstarch, keeping diets isocaloric. However, humans can choose from many different types of carbohydrate, and how dietary carbohydrate quality - the precise composition of the dietary sugars - impacts the response to dietary protein remains largely unexplored. Here, mice were fed control (21% protein) or LP (7% protein) diets with four different carbohydrate sources: sucrose, a 1:1 glucose/fructose mixture, glucose, or fructose. While LP diets improved metabolic health across all groups in male mice, carbohydrate quality also significantly altered specific health outcomes, with fructose-fed mice having the lowest body weight and adiposity of all control diets. In female mice, responses to LP diets were influenced by carbohydrate quality, with certain sugars inducing a stronger metabolic response to LP diets than previously seen. Finally, in female APP/PS1 mice, a model of Alzheimer's disease, we find that although LP diets reduce A-beta; plaque burden irrespective of carbohydrate type, dietary sugar type does influence spatial memory. Together, these results demonstrate that while dietary protein is a critical determinant of metabolic and neurological health, carbohydrate quality influences these outcomes in a sex-specific manner.

physiology↗

bioRxiv2026

Female resistance to the metabolic benefits of protein restriction is reversed by ovariectomy in mice

Dietary protein intake mediates healthy aging in diverse species, with consumption of a low protein (LP) diet improving metabolic health in both humans and mice. In mice, the benefits of LP diets are sex-specific, with males exhibiting a stronger response to a LP diet than females. The reason for this sexually dimorphic response is unknown, but we hypothesized that sex hormones might be responsible for this difference. Here, we tested the role of sex hormones in the response to a LP diet by feeding intact and gonadectomized mice of both sexes either a Control (21% of calorie from protein) or LP (7% of calories from protein) diet, and assessing the effects on weight, body composition, glycemic control, and energy balance over the course of three months, followed by molecular and histological analysis of tissues from each group. We confirm that males show a stronger metabolic response to an LP diet than females, but that ovariectomy sensitizes female mice to the metabolic effects of an LP diet, making them respond more similarly to males; conversely, castration does not substantially impact the response of males to an LP diet. Molecularly, we find that gonadectomy and sex are important interactors that mediate the response of mechanistic target of rapamycin (mTOR) signaling, lipid homeostasis, and thermogenesis to an LP diet. Together, this data shows that the resistance of female mice to an LP diet is mediated by ovarian hormones and suggests the possibility that older female humans might receive enhanced benefits from LP diet feeding.

physiology↗

bioRxiv2025

Lifelong restriction of dietary valine has sex-specific benefits for health and lifespan in mice

Dietary protein is a key regulator of metabolic health in humans and rodents. Many of the benefits of protein restriction are mediated by reduced intake of dietary branched-chain amino acids (BCAAs; leucine, valine and isoleucine), and restriction of the BCAAs is sufficient to extend healthspan and lifespan in mice. While the BCAAs have often been considered as a group, it has become apparent that they have distinct metabolic roles, and we recently found that restriction of isoleucine is sufficient to extend the healthspan and lifespan of male and female mice. Here, we test the effect of lifelong restriction of the BCAA valine on healthy aging. We find that valine restriction (Val-R) improves metabolic health in C57BL/6J mice, promotes leanness and glycemic control across ages, and reduces frailty, cancer prevalence, and senescent cell burden in multiple tissues in both sexes. Val-R reduces glial activation in the brain in a male-specific manner, and extends the lifespan of male, but not female, mice by 23%. To investigate the molecular mechanisms engaged by Val-R with aging, we conducted multi-tissue transcriptional profiling and gene network analysis. While Val-R had a greater molecular impact in the liver, muscle, and brown adipose tissue of females, the enrichment of genes associated with phenotypic traits was stronger in males. Assessing novel gene relationships across tissues, we identified a liver gene module enriched in mitochondrial-related pathways as a central hub. Assessing mitochondrial function, we identified a Val-R-induced male-specific increase in mitochondrial respiration. Our results demonstrate for the first time that Val-R improves multiple aspects of healthspan in mice of both sexes and extends lifespan in males, and suggests that interventions that mimic Val-R may have translational potential for aging and age-related diseases.

physiology↗

bioRxiv2025

Restriction of individual branched-chain amino acids has distinct effects on the development and progression of Alzheimers disease in 3xTg mice

Dietary protein is a critical regulator of metabolic health and aging in diverse species. Recent discoveries have determined that many benefits of a low protein diet are the result of reduced consumption of the three branched-chain amino acids (BCAAs), leucine, isoleucine, and valine. Intriguingly, each BCAA has distinct physiological and molecular effects, with restriction of isoleucine alone being sufficient to improve metabolic health and extend the lifespan of mice. While restriction of protein or all three BCAAs improves cognition in mouse models of Alzheimers disease (AD), the impact of restricting each individual BCAA on the progression and development of AD is unknown. Here, we investigate the effect of restricting each individual BCAA on metabolic health, AD pathology, molecular signaling, and cognition in the 3xTg mouse model. We find that restriction of isoleucine and valine, but not leucine, promotes metabolic health. Restriction of each BCAA had distinct effects on AD pathology and molecular signaling, with transcriptomic analysis of the brain revealing both distinct and shared, and highly sex-specific, molecular impacts of restricting each BCAA. Restricting any of the three BCAAs improved short-term memory in males, with isoleucine restriction having the strongest effect, while restricting valine had the greatest cognitive benefits in females. We identify a set of significantly altered pathways strongly associated with reduced AD pathology and improved cognitive performance in males. Our findings suggest that restricting any of the BCAAs, particularly isoleucine or valine, may form the basis of a novel sex-specific approach to prevent or delay the progression of AD.

physiology↗

bioRxiv2025

Ketogenesis is dispensable for the metabolic adaptations to caloric restriction

Caloric restriction (CR) extends the health and lifespan of diverse species. When fed once daily, CR-treated mice rapidly consume their food and endure a prolonged fast between meals. As fasting is associated with a rise in circulating ketone bodies, we investigated the role of ketogenesis in CR using mice with whole-body ablation of Hmgcs2, the rate-limiting enzyme producing the main ketone body {beta}-hydroxybutyrate ({beta}HB). Here, we report that Hmgcs2 is largely dispensable for many metabolic benefits of CR, including CR-driven changes in adiposity, glycemic control, liver autophagy, and energy balance. Although we observed sex-specific effects of Hmgcs2 on insulin sensitivity, fuel selection, and adipocyte gene expression, the overall physiological response to CR remained robust in mice lacking Hmgcs2. To gain insight into why the deletion of Hmgcs2 does not disrupt CR, we measured fasting {beta}HB levels as mice initiated a CR diet. Surprisingly, as mice adapt to CR, they no longer engage high levels of ketogenesis during the daily fast. Our work suggests that the metabolic benefits of long-term CR are not mediated by ketogenesis.

physiology↗

bioRxiv2025

Tissue-specific effects of dietary protein on cellular senescence are mediated by branched-chain amino acids

Dietary protein is a key regulator of healthy aging in both mice and humans. In mice, reducing dietary levels of the branched-chain amino acids (BCAAs) recapitulates many of the benefits of a low protein diet; BCAA-restricted diets extend lifespan, reduce frailty, and improve metabolic health, while BCAA supplementation shortens lifespan, promotes obesity, and impairs glycemic control. Recently, high protein diets have been shown to promote cellular senescence, a hallmark of aging implicated in many age-related diseases, in the liver of mice. Here, we test the hypothesis that the effects of high protein diets on metabolic health and on cell senescence are mediated by BCAAs. We find that reducing dietary levels of BCAAs protects male and female mice from the negative metabolic consequences of both normal and high protein diets. Further, we identify tissue-specific effects of BCAAs on cellular senescence, with restriction of all three BCAAs - but not individual BCAAs - protecting from hepatic cellular senescence while potentiating cell senescence in white adipose tissue. We find that the effects of BCAAs on hepatic cellular senescence are cell-autonomous, with lower levels of BCAAs protecting cultured cells from antimycin-A induced senescence. Our results demonstrate a direct effect of a specific dietary component on a hallmark of aging and suggest that cellular senescence may be highly susceptible to dietary interventions.

physiology↗