Leptin and the neural circuit regulation food intake and glucose metabolism

Leptin and the neural circuit regulation food intake and glucose metabolism
IT’S A PLEASURE AND PRIVILEGE TO HOST OUR WALS SPEAKER DR. JEFFREY FRIEDMAN. DR. FRIEDMAN RECEIVED HIS MD FROM ALBANN ALBANY MEDICAL COLLEGE, WHERE HE ALSO COMPLETED MEDICAL RESIDENCY, AND HE RECEIVED HIS PH.D. FROM ROCKEFELLER UNIVERSITY, WHERE NOW HE’S PROFESSOR, DIRECTOR OF THE CENTER FOR HUMAN GENETICS, AND INVESTIGATOR OF THE HOWARD HUGHES MEDICAL INSTITUTE.
DR. FREE FRIEDMAN IS TRULY A GIANT IN MEDICINE AND GIANT IN THE FIELD WITH SUBSTANTIAL CONTRIBUTION TO THE UNDERSTANDING OF THE GENETIC AND MOLECULAR MECHANISMS TO REGULATE METABOLISM, FOOD INTAKE AND BODY WEIGHT. FOR EXAMPLE, HE’S THE DISCOVERER OF THE HORMONE LEPTIN, BODY WEIGHT, REPRESENTING A LANDMARK DISCOVERY THAT HAS SUBSTANTIALLY CONTRIBUTED TO THE UNDERSTANDING OF THE MECHANISM INVOLVED IN THE DEVELOPMENT AND MAINTENANCE OF OBESITY, AND INDEED THE ACHIEVEMENTS IN DR. FRIEDMAN’S LAB HAVE INSPIRED TRANSLATIONAL RESEARCH BEYOND BASICALLY INCLUDING OTHER ENDOCRINE AND METABOLIC DISORDERS AN EVEN ADDICTIVE DISORDERS. DR. FREED PLAN’S LIST OF AWARDS IS IMPRESSIVE. JUST TO NAME A FEW, HE WAS THE RECIPIENT OF THE LAS CAR AWARD IN 2010, IN 5, AND LIFE SCIENCE IN 2009. HE’S A MEMBER OF THE NATIONAL ACADEMY OF SCIENCE, MEMBER OF THE AMERICAN ACADEMY OF ARTS AND SCIENCE, AND MOAM BER OF THE MEMBER OF THE SWEDISH ACADEMY OF SCIENCE. TODAY’S LECTURE IS TITLED LEPTIN AND THE NEURAL CIRCUIT REGULATION FOOD INTAKE AND GLUCOSE METABOLISM. PLEASE HELP ME IN WELCOMING DR. FRIEDMAN. [APPLAUSE]
IT’S TRULY A GREAT PLEASURE TO BE HERE, TO SEE SOME OLD FRIENDS, MAKE SOME NEW ONES. I’M GOING TO GIVE A TALK TODAY WITH A SLIGHTLY REVISED TITLE SHOWN HERE, LEPTIN PHYSIOLOGY, PATHOPHYSIOLOGY AND THE NEURAL CIRCUIT REGULATING BODY WEIGHT. AND THIS REVISION WILL GIVE ME AN OPPORTUNITY IN PART TO ACKNOWLEDGE SOME OF THE PIONEERING WORK THAT’S BEEN DONE HERE BY THE GROUP THAT INCLUDES PHIL GORDON, REBECCA BROWN AND PREVIOUSLY — WHO REALLY CHAMPIONED AND MADE POSSIBLE THE USE OF LEPTIN AT A THERAPEUTIC. THIS AND OTHER INFORMATION IN THE FIRST PART, THEN I’D LIKE TO CONTINUE WITH TWO SEPARATE RESEARCH — I’VE GOT SOME NEW ONGOING RESEARCH IN THE LAB.
WE’LL TALK ABOUT SOME YET UNPUBLISHED DATA ESTABLISHING THE ROLE — A ROLE FOR THE DORSAL RAPHE NUCLEUS TO REGULATE FEEDING AND LOCOMOTION IN FOOD INTAKE, AND I’LL ALSO TALK ABOUT SOME NEW DATA ESTABLISHING THE ROLE FOR THE HYPOTHALAMUS TO REGULATE FEEDING AND PARTICULAR GLUCOSE METABOLISM. THESE STUDIES MAKE USE OF A NEW METHOD WE’VE DEVELOPED THAT ENABLES REMOTE MODULATION OF CELLS USING A MA MAGNETIC FIELD. ONE OF THE CLINICAL MANIFESTATIONS OF THE CIRCUIT THAT WE STUDY PERTAINS TO OBESITY, AND WE’D OF COURSE, AS WOULD OTHERS, LIKE TO UNDERSTAND WHY THERE’S SOME INDIVIDUALS IN THE POPULATION THAT HAVE AN APPEARANCE LIKE THIS AND OTHERS HAVE AN APPEARANCE LIKE THIS.
THERE ARE MANY DIFFERENT VIEWPOINTS AND PUBLIC DISCOURSE ABOUT WHAT MIGHT EXPLAIN THE DIFFERENCE BETWEEN THESE TWO APPEARANCES. THE INDIVIDUAL MIGHT APPEAR ONE WAY OR THE OTHER. THE FIRST WOULD BE TO SUGGEST THAT THE OBESE PERSON LACKS A LEVEL OF WILLPOUR THAT’S EVIDENT IN LEAN PEOPLE. THAT IS HELD MORE BY LEAN PEOPLE. SECOND POSSIBILITY IS THAT OBESITY IS A DISEASE OF MATERNITY, IT’S THE RESULT OF AN ALTERATION IN LIFESTYLE AND THE ENVIRONMENT THAT CREATES A PREDISPOSITION TO OBESITY. THE THIRD POSSIBILITY THAT’S CONSIDERED IS THE DIFFERENCES IN WEIGHT ARE ATTRIBUTED TO BIOLOGICAL OR GENETIC FACTORS. AT VARIOUS TIMES I’VE TAKEN VOTES ABOUT WHAT PEOPLE THINK IS THE MOST IMPORTANT CONTRIBUTOR BEFORE AND AFTER I SPEAK, I STOPPED DOING THAT WHEN FEWER PEOPLE VOTED FOR BIOLOGY WHEN I WAS DONE THAN WHEN I BEGAN.
SO I’M NOT GOING TO DO THAT TODAY. RATHER, I’LL JUST POINT OUT SOMETHING WHICH IS THAT PEOPLE TEND TO THINK OF THE CAUSE OF OBESITY AS BEING ONE OR THE OTHER OF THESE TO THE EXCLUSION OF THE OTHER TWO. AND WHERE I TALK ABOUT ANY OTHER CONDITION, PEOPLE WOULD IMMEDIATELY DPRAF TAT GRAVITATE TO THE IDEA THAT THERE’S A BIOLOGICAL FRAMEWORK ON WHICH BEHAVIORAL AND ENVIRONMENTAL FACTORS ACT. AND SO I THINK ALL CONTRIBUTE, BUT I’D LIKE TO AT LEAST LEAVE YOU WITH THE CONCLUSION IF POSSIBLE IF I’M CAPABLE OF IT THAT THERE IS AN IMPORTANT BIOLOGICAL FRAMEWORK THAT ACTUALLY GIVES YOU AN OPPORTUNITY TO THINK ABOUT HOW BEHAVIORAL AND ENVIRONMENTAL FACTORS MIGHT EXERT THEIR EFFECTS. NOW, THERE’S A LONG LIST OF DATA THAT WOULD SUPPORT THE NOTION THAT BIOLOGICAL FACTORS IN GENES CONTRIBUTE. I WON’T GO THROUGH THAT IN ANY DETAIL OTHER THAN TO SAY THAT SOME OF THE MOST POWERFUL EVIDENCE COMES FROM HERITABILITY STUDIES THAT HAVE ESTABLISHED THAT OBESITY IS AS OR MORE HERITABLE THAN ANY TRAIT THAT’S BEEN STUDIED WITH THE EXCEPTION OF HEIGHT, AND THIS STRONG HERITABILITY OR SOME OF THE VARIANTS THAT CAN BE DESCRIBED IN GENETIC FACTORS IS EVEN IN TWIN STUDIES WHERE THERE’S VERY STRONG EVIDENCE THAT GENETIC FACTORS PLAY A CRITICAL ROLE IN THE DEVELOPMENT OF OBESITY. TO ILLUSTRATE THE POWER OF SUCH GENETIC FACTORS,
I WANT TO TELL YOU BRIEFLY OF A CASE REPORT FROM CAMBRIDGE STUDYING A YOUNG BOY WHOSE IMAGE I BEGAN BY SHOWING, NORMAL WEIGHT AN AT BIRTH, QUICKLY BEGAN TO DEVELOP MORBID OBESITY, PREDIABETIC AT THE AGE OF 4, WHEN HE WEIGHED 90 POUNDS WITH 57% BODY FAT. NOW THIS CHILD CAME FROM A HIGHLY INBRED PEDIGREE, WHICH OFTEN SUGGESTS THAT THE EXTREME PHENOTYPE MIGHT BE THE RESULT OF A — MUTATION. OWE RAHILMUTATION. THIS IS THE OBESE MOUSE, AND THIS ANIMAL HERE WEIGHS THREE TIMES AS MUCH AND HAS FIVE TIMES AS MUCH FAT AS A NORMAL MOUSE, DESPITE THE FACT THAT IT LIVES IN THE SAME CAGE WITH THE SAME ACCESS TO FOOD AS A SIBLING LITTERMATE. NOW, AS I JUST MENTIONED, THIS IS THE RESULT OF A FULLY PE — RESE SENT GENE.
I’M INTERESTED IN THE MOLECULAR BASIS OF BEHAVIOR, WHICH AS YOU’LL SEE WE CONTINUE TO EXPLORE, BECAUSE YOU COULD ALSO LOOK AT THIS ANIMAL AS A BEHAVIORAL MUTE, THE AN MEAL EATS IN AN UNRESTRAINED MANNER. NOW WE HAVE SET OUT TO STUDY THESE ANIMALS AND IDENTIFY THE DEFECTIVE GENE. THE PHENOTYPE OF THESE ANIMALS IS COMPLICATED AND INCLUDES A NUMBER OF OTHER ABNORMALITIES THAT ARE NOT TYPICALLY EVIDENT IN OBESE THANK YOU PLANS. THE ANIMALS ARE HYPOTHERMIC, THEY’RE INFERTILE, THEY HAVE IMMUNE ABNORMALITIES, IN FACT THEY HAVE ABNORMALITIES IN JUST ABOUT EVERY BIOLOGICAL SYSTEM, AND THERE WAS NO READY EXPLANATION FOR THIS CONSTELLATION OF ABNORMALITIES THAT WOULD NOT TYPICALLY BE SEEN IN OBESE PATIENTS. THIS SET OF FINDINGS LED SOME AT LEAST TO QUESTION HOW RELEVANT THIS MIGHT BE TO HUMAN PHYSIOLOGY. AFTER AN EIGHT-YEAR EFFORT, WE IDENTIFIED THE DEFECTIVE GENE AS ENCODING A HORMONE WHICH W — LEPTIN, NEGATIVE FEEDBACK LOOP THAT MAINTAINS HOMEOSTATIC CONTROL OF FAT MASS. SECRETED FROM FAT IN PROPORTION TO ITS MASS, IT CIRCULATES IN BLOOD AND ACTIVATES DISCRETE SETS OF HYPOTHAT MA MIC AND OTHER NEURONS TO CONTROL FOOD INTAKE. IF BODY WEIGHT GOES UP, LEPTIN GOES UP AND SUPPRESSES APPETITE. THE BODY WEIGHT IS LOST, LEPTIN GOES DOWN AND INCREASES APPETITE. AND BY THIS MECHANISM, BODY WEIGHT CAN BE REGULATED WITHIN A RELATIVELY NARROW RANGE.
I DON’T WANT TO LEAVE YOU WITH THE IMPRESSION THAT LEPTIN IS THE ONLY FACTOR THAT REGULATES APPETITE, IT’S NOT, BUT I VIEW IT AS SETTING THE GAME ON THE SYSTEM SO THAT IN A SENSE IT EXERTS A BIOLOGICAL FORCE THAT RESISTS WEIGHT CHANGE IN EITHER DIRECTION. OTHER THINGS — THAT FORCE IS THERE NONETHELESS. THE O.B. MOUSE, THERE’S A MUTATION IN THE LEPTIN GENE. NO — UNRESTRAINED APPETITE DEVELOPS, AND ANIMALS CAN BECOME OBESE. NOW BECAUSE LEPTIN IS A CIRCULATING PE PEPTIDE HORMONE, YOU CAN MAKE IT IN THE LABORATORY, IF YOU MAKE IT IN THE LABORATORY AND GIVE IT TO MICE, THIS IS WHAT HAPPENS. YOU CAN NORMALIZE THE WEIGHT OF THESE ANIMALS WITH INTRAPERITONEAL INJECTIONS OVER THE COURSE OF TWO TO THREE WEEKS. WHY DO THE ANIMALS LOSE WEIGHT? FOR ONE THING, THEY EAT LESS. WHAT’S SHOWN HERE IS AN EXPERIMENT SHOWING FOOD INTAKE GOES DOWN BY ABOUT TWO THIRDS IN O.B. ANIMALS RECEIVING LEPTIN THERAPY, BUT THE ANIMALS ALSO MOVE AROUND MORE. AND I JUST WANT TO BRIEFLY SHOW YOU A VIDEO, THIS IS A LEPTIN-TREATED ANIMAL. YOU’LL NOTE THAT THE O.B. MOUSE EXHIBITS WHAT’S REFERRED TO AS LOCOMOTIVE RETARDATION WHERE IT SITS IN A CORNER AND DOESN’T MOVE.
LEPTIN-TREATED ANIMAL MOVES NORMALLY. THIS ANIMAL HAS BEEN TREATED FOR A WHILE BUT IT TURNS OUT THAT YOU CAN SEE THIS INCREASED LOCOMOTION WITHIN A DAY OF LEPTIN THERAPY, YOU CAN SEE EFFECTS ON LOCOMOTION EVEN BEFORE YOU SEE EFFECTS ON FOOD INTAKE. SO THIS FURTHER SUGGESTS THAT LEPTIN IS DOING MORE THAN REGULATING FOOD INTAKE AND FURTHERMORE SUGGESTS THAT LOCOMOTION IS ALSO UNDER GENETIC AND NEURAL CONTROL. NOW WITH THIS INFORMATION IN HAND, AS I MENTIONED, HE SUGGESTED THAT THE CHILD — MIGHT HAVE A LEPTIN MUTATION, AN AND AND INDEED ON SEQUENCING AT PLASMA LEVEL, THE CHILD HAD A MUTATION, ONE OF THE SAME STRAINS THE MOUSE STRAIN HAS, AND MAKES NO LEPTIN. SO HERE AGAIN, HE USED CLINICALLY APPROPRIATE LEPTIN AND GAVE IT TO THIS CHILD, APPEARS TO RESOLVE IT. THIS IS THE CHILD AT THE AGE OF 3, AND THE CHILD AT THE AGE OF 8, THE USE OF THE SAME — I BEGAN BY SHOWING YOU, AND THESE DATA SUGGEST THAT WHAT’S DRIVING OBESITY AT LEAST WITH THIS CHILD IS NOT A LACK OF WILLPOWER OR MODERN ENVIRONMENT, IT’S A LACK OF THE HORMONE LEPTIN. NOW LEPTIN MUTATIONS AS A CAUSE OF OBESITY IS RARE, THAT’S TO BE EXPECTED FOR HORMONES WHICH ARE POOR TARGETS FOR MUTATION. THERE ARE ONLY A FEW DOZEN SUCH PATIENTS WORLDWIDE. AND SO WHILE WE CAN SAY WITH SOME CONFIDENCE THAT LEPTIN PLAYS A ROLE IN NEUROPHYSICIAN YOJ, IT INEUROPHYSIOLOGY, IT IS NOT A FREQUENT CAUSE FOR OBESITY.
THE MUTATIONS IN THE NEURAL CIRCUIT THAT RESPOND TO LEPTIN ARE ACTUALLY NOT AT ALL UNCOMMON IN MORBID OBESITY, AND THIS PROVIDES A WINDOW INTO THE GENETIC — YOU HEARD FROM LORENZO FOR THE GENETIC AND PHYSIOLOGIC MECHANISMS THAT REGULATE WEIGHT. NOW, I WANT TO EMPHASIZE THAT THESE CHILDREN AND ADULTS WHO ARE LEPTIN DEFICIENT ALSO HAVE A SET OF OTHER PLEIOTROPIC ABNORMALITY, AND ALL THESE OTHER ABNORMALITIES ARE ALSO CORRECTED BY LEPTIN. NOW, HOW MIGHT WE THINK OF IT? WELL, THE ABNORMALITIES INCLUDE INFERTILITY, IMMUNE ALTERATIONS, METABOLIC ALTERATIONS, HEMATOLOGIC ALTERATIONS. IN RETRO SPE RETROSPECT, IT TURNS OUT THESE ABNORMALITIES ARE NORMALLY ASSOCIATED NOT WITH OBESITY BUT WITH STARVATION. SO ONE MIGHT IMAGINE BASED ON WHAT I JUST SAID THAT IF YOU’RE MISSING LEPTIN, THE BRAIN INTERPRETS THAT AS STARVATION, IT STIMULATES FOOD INTAKE, WHICH WHEN FOOD IS AVAILABLE, LEADS TO OBESE PHENOTYPE, BUT IT ALSO ACTIVATES A SET OF DOWNSTREAM PHYSIOLOGIC RESPONSES THAT ARE — IN THE FACE OF STARVATION. THINK OF IT THIS WAY, THIS CHILD IS OBESE BECAUSE HIS BRAIN THINKS HE’S STARVING, AND THIS LINE OF REASONING AS WELL AS SOME EXPERIMENTS CONTRIBUTED BY JEFF’S LAB SUGGESTED THE FOLLOWING. THAT WHEN WEIGHT IS LOST, LEPTIN LEVEL FALLS, IT ACTIVATES WHAT YOU MIGHT CALL THE ADAPTIVE RESPONSE TO STARVATION. SOME OF THE ELEMENTS ARE SHOWN HERE, IMMUNE DYSFUNCTION, THE SO CALLED INSULIN RESISTANCE OF STARVATION, AS WELL AS REDUCED REPRODUCTIVE FUNCTION. IN AGGREGATE, WHAT THESE RESPONSES DO IS REDUCE ENERGY EXPENDITURE IN THE FACE OF THE STAR OFFED CONDITIONS.
NOW, IN ADDITION TO THE PHYSIOLOGIC IMPORTANCE OF THIS SET OF FINDINGS, THIS SET OF RESULTS HAS ALSO SUGGESTED THERAPEUTIC OPPORTUNITIES FOR LEPTIN USAGE. THE IDEA BEING THAT IF ONE REASON OR ANOTHER AN INDIVIDUAL HAS A PATHOLOGICALLY LOW LEPTIN LEVEL AND ONE OR MORE OF THESE ABNORMALITIES, THEN RESTORING LEPTIN LEVELS TO PHYSIOLOGIC LEVELS SHOULD IMPROVE THESE PATHOLOGIES. AND I’M GOING TO TELL YOU VERY QUICKLY TWO VIGNETTES THAT ILLUSTRATE THIS MENTION FIRST HAVING TO DO WITH INSULIN SIGNALING. SO THE QUESTION HERE IS, ARE THERE STATES ASSOCIATED WITH LOW LEPTIN AND METABOLIC ABNORMALITIES SUCH AS INSULIN RESISTANCE. AND THE ANSWER, OF COURSE, IS YES, THIS CONDITION IS KNOWN AS LIPO DYSTROPHY, THE CONGENITAL OR ACQUIRED LOSS OF ADIPOSE TISSUE, THESE INDIVIDUALS HAVE REDUCED FAT MASS OFTENTIMES — THIS IS THEREFORE ASSOCIATED WITH REDUCED LEPTIN LEVEL. THESE PATIENTS DEVELOP SEVERE, OFTEN INTRACTABLE INSULIN RESISTANCE, DIABETES AND WAS FIRST SHOWN THAT LEPTIN REPLACEMENT IN AN ANIMAL MODEL COULD MARKEDLY IMPROVE HIS CONDITION. AND THIS MOTIVATED PHIL AND HIS COLLEAGUES TO GO AHEAD AND TEST LEPTIN FIRST IN THE MOST SEVERE FORM CALLED GENERALIZED LIPODYSTROPHY, SOME OF THE GENE MUTATIONS ARE SHOWN HERE.
THIS PATIENT STUDIED BY PHIL, NO ADIPOSE TISSUE, MASSIVELY ENGORGED FATTY LIVER WITH EE RUMTIONS ALL OVER HER BODY, AND AFTER A YEAR ON LEPTIN, HIS LYMPHOMAS DISAPPEAR AND THE FATTY LIVER HAD MORE OR LESS RESOLVED. GIGANTIC FATTY LIVER BEFORE LEPTIN, CORRECTION AFTER LEPTIN. IN THIS PARTICULAR PATIENT, SOME OF THE OTHER ABNORMALITIES WERE ALSO MARKEDLY APPROVED: THIS WOMAN’S — TRIGLYCERIDES FELL FROM 6300 TO 179. AND HER PROTEINURIA REVOLVED. BASED ON RECEIPT SPONS SHOWN RESPONSE SHOWN HERE, LEPTIN WAS APPROVED TWO YEARS AGO NOW FOR THE TREATMENT OF GENERALIZED LIPODYSTROPHY, THE MOST SEVERE FORM, IT’S NOT APPROVED FOR OTHER FORMS. BUT I DO WANT TO SUGGEST NOW BASED ON EVIDENCE THAT’S ALSO BEEN PROVIDED BY THE NIDDK GROUP THAT LEPTIN MIGHT BE USEFUL IN OTHER SUBGROUPS THAT ARE LESS SEVERE. THESE ARE KNOWN AS PARTIAL LIPODISPROPHY, AND IT’S BEEN FORMED NOW LED BY THESE THREE WOMEN, ALL OF WHOM HAVE LIPODYSTROPHY. I SHOW THE SLIDE BECAUSE IT POINTS OUT THAT YOU WOULDN’T NECESSARILY PICK OUT ANY OF THESE WOMEN AS HAVING LIPODYSTROPHY BASED ON THEIR APPEARANCE, IN CONTRAST TO GENERALIZED PATIENTS WHERE THERE IS A DISTINCTIVE APPEARANCE. ANDRA AND GAIL LOOKED PRETTY LEAN, MARY ALSO IS LIPO DYSTROPHIC, AND SHE SEEMS TO HAVE A SORT OF CA CUSHINOID APPEARANCE. AND THERE’S CERTAINLY EVIDENCE FROM THE NIH GROUP THAT AT LEAST AT THE METABOLIC ABNORMALITIES ARE SEVERE IN PARTIAL LIPODYSTROPHY,
THE LEPTIN TREATMENT CAN HAVE — ILLICIT AN IMPORTANT RESPONSE. THIS BEGINS TO SUGGEST, I THINK, THAT — OR SHOW THAT DIABETES IS HETEROGENEOUS AND MAYBE THAT WE OUGHT TO BE MEASURING LEPTIN LEVELS IN LEAN DIABETIC PATIENTS TO EXCLUDE THE POSSIBILITY THAT THEY’RE LIPODYSTROPHIC. LEPTIN IS NOT APPROVED FOR THIS COHORT OF PATIENTS BUT ON THE OTHER HAND, YOU MIGHT TREAT OR MANAGE THESE PRAISHTS DIFFERENTLY IF YOU KNEW THEY HAD LIPODYSTROPHY AS COMPARED TO OTHER CAUSES OF DIABETES IN LEAN SUBJECTS. NOW ONE OF THE THINGS THAT I HAVE BEEN NOTING FOR A LONG PERIOD OF TIME IS THIS APPEARANCE OF SOMEONE LIKE MARY, BECAUSE SHE’S LIKE A DYSTROPHIC EVEN THOUGH SHE DOESN’T LOOK LEAN, IT TURNS OUT HER ARMS AND LEX ARE RELATIVELY LEAN, AND YOU SEA RAY LOT OYOU SEE A LOT OF PATIENTS IN THE CLINIC THAT LOOK LIKE THIS, COULD THIS APPEARANCE ACTUALLY BE INDICATIVE OF THAT. I’VE BEEN MUSING ABOUT THIS FOR A WHILE TO KNOW GOOD EFFORT, WHEN MORE RECENTLY TWO PAPERS APPEARED THAT ACTUALLY SUGGEST THIS IS THE CASE. I WON’T GO THROUGH IN ANY DETAIL THE EVIDENCE OTHER THAN TO SAY BOTH PAPERS REACHED THE SAME CONCLUSION, WHICH IS THAT AMONG COHORTS OF INSULIN RESISTANT PATIENTS, ABOUT 15% OF THEM ACTUALLY HAVE THE CLINICAL FEATURES OF LIPODYSTROPHY AND A POLYGENIC G SIGNATURE FROM GENOME WIDE ASSOCIATION STUDIES, THAT INDICATE, IN FACT, THAT THERE’S A POLYGENIC FORM OF LIPODYSTROPHY, AND THIS PROBABLY CORRESPONDS TO WHAT HAS LONG BEEN DESCRIBED AS PATIENTS WHO WERE SO-CALLED NORMAL WEIGHT MET METABOLICALLY OBESE. SO I THINK THE EVIDENCE IS EVOLVING THAT LIPODYSTROPHY IS A SPECTRUM DISORDER, AND ONE EXTREME, IT CAN BE MONOGENIC, RECESSIVE OR ACQUIRED AND VERY SEVERE.
IN THE MIDDLE ARE THESE DOMINANT PARTIAL LIPODYSTROPHY FORMS, THEN THE OTHER EXTREME IS PROBABLY A POLYGENIC FORM THAT OVERLAPS SUBSTANTIALLY WITH WHAT ARE REPORTED TO AS THE NORMAL WEIGHT MED BOLGLY OBESE PHENOTYPE. I THINK THIS PROBABLY IS RELEVANT ALSO TO THE HIGH PREVALENCE OF DIABETES AND LOW BMI IN THE ASIAN POPULATIONS. SO THIS DIVERSION BASICALLY WAS MEANT TO SAY THAT I THINK THAT DIABETES AND METABOLIC SYNDROME IS HETEROGENEOUS AND THAT CLEARLY ON THE DIFFERENTIAL OF DIABETES NOW DAYS, ESPECIALLY IN LEAN PATIENTS, I THINK ONE MIGHT WANT TO AT LEAST EXPLORE THE POSSIBILITY OF PARTIAL LIPODYSTROPHY OR A POLYGENIC VERSION OF IT. THESE PATIENTS MIGHT, IN FACT, BE CANDIDATES FOR LEPTIN THERAPY, BUT I WANT TO EMPHASIZE, AGAIN, AS YET THE ONLY APPROVED USE OF LEPTIN IS FOR THIS SEVERE GENERALIZED FORM. SO THAT’S THE FIRST ONE. I WANT TO QUICKLY GO THROUGH ANOTHER ONE, TALKING ABOUT THE LINK BETWEEN LEPTIN AND REPRODUCTIVE FUNCTION. ARE THERE PATIENTS WITH LOW LEPTIN LEVELS WHO ARE INFERTILE, AND THE ANSWER IS YES, THERE ARE. THIS IS A CONDITION KNOWN AS HYPOTHALAMIC AMEN REA, OFTEN DEVELOPS IN WOMEN WHO ARE EXTREME ATHLETES AND EXTREMELY LEAN, IT ACTUALLY ACCOUNTS FOR A THIRD, I’M TOLD, OF VISITS TO AN INFERTILITY CLINIC BY WOMEN AND OF COURSE THESE WOMEN ARE THIN, ATHLETIC WOMEN WITH LOW LEPTIN LEVELS, AND RECENTLY — WELL, A FEW YEARS AGO, CHRIS MALSURO TREATED TWO DIFFERENT COHORTS OF THESE WOMEN WITH LEPTIN AND IN ALMOST EVERY CASE, LEPTIN RESTORED REPRODUCTIVE FUNCTION, AND CORRECTED OTHER ABNORMALITIES IN PLACES ALSO TYPICALLY ASSOCIATED WITH STARVATION.
SO THIS CLEARLY LINKS LEPTIN TO REPRODUCTIVE FUNCTION. SEVERAL OF THE PATIENTS IN THE OTHER STUDY BECAME PREGNANT ON LEPTIN. THE ONE POINT I WANT TO MAKE SEER, THIS IS A BUSY SLIDE, BUT WHAT YOU WOULD SEE IF YOU HAD TIME TO PERUSE IT IN DETAIL IS THAT A NUMBER OF ABNORMALITIES ARE EVIDENT IN THESE WOMEN, THEY’RE THE ABNORMALITIES TYPICALLY ASSOCIATED WITH STARVATION, BUT WHEN YOU GIVE LEPTIN, ALL THESE ABNORMALITIES ARE EITHER CORRECTED OR IMPROVED, DESPITE THE FACT OF WHAT’S SHOWN HERE, WHICH IS THAT THE PATIENTS LOSE WEIGHT. THEY START OUT WITH THIS WEIGHT. THEY DON’T LOSE AN ENORMOUS AMOUNT OF WEIGHT BUT THE POINT I’M TRYING TO MAKE HERE IS, THE SEQUELAE OF THE SO CALLED STAR PHENOTYPE ARE AMELIORATED IN PATIENTS DESPITE THE FACT THAT THEY LOST THE WEIGHT, AND THIS TELLS US THAT IT’S THE LOW LEPTIN THAT’S SIGNALING STARVATION, NOT SOME INTRINSIC ASPECT OF THE FAT TISSUE OR SOME OTHER FACTOR. THE THIRD VIGNETTE HAS TO DO WITH IMMUNE FUNCTION, AND I’LL JUST GO THROUGH
THIS IN A DIDACTIC MANNER IN THE INTEREST OF TIME. STARVATION AND LEPTIN DEFICIENCY BOTH CAUSE THE SAME SET OF IMMUNE CHANGES. IT IP VOFLS A SHIFT FROM TH1 TO TH2 IMMUNITY WITH SUSCEPTIBILITY TO BACTERIA INFECTION. IN FACT THERE’S BEEN A HIGH RATE OF DEATH FROM BACTERIAL PNEUMONIA. LEPTIN TREATMENT IN ANIMALS NORMALIZES THE IMMUNE ABNORMALITIES OF BOTH LEPTIN DEFICIENCY AS WELL AS STARVATION. AND THERE HAS EACH BEEN SOME EVIDENCE PROVIDED THAT LEPTIN CAN EXTEND LIFESPAN IN INFECTED OR STORED IN STAR OFFED ANIMALS. ALL OF THESE ESTABLISH LEPTIN AS A TRUE HORMONE THAT IN MY VIEW IS CHANGING THE NUTRITIONAL STATE TO PHYSIOLOGIC RESPONSES AND OTHER ORDERS. I’VE ALSO DESCRIBED AT LEAST THREE STATES ASSOCIATED — THAT RESPOND TO LEPTIN THERAPY. PATIENTS WITH LEPTIN MUTATIONS, LIPODYSTROPHY AND AMENORRHEA. NOT LISTED HERE HOWEVER IS OBESITY ITSELF, AND THAIS BECAUSE OBESITY IS NOT A LEPTIN DEFICIENCY PROBLEM.
AS PERCENT FAT GOES UP, SO, TOO, GOES UP LEPTIN SUCH THAT OBESE PATIENTS HAVE HIGHER LEPTIN LEVELS THAN LEAN PATIENTS. NOW WHEN YOU SEE A HIGH LEVEL OF A HORMONE I AND THE ABSENCE OF THE HORMONE’S EFFECT IN THIS CASE TO LOSE WEIGHT, IT USUALLY INDICATES INSULIN RESISTANT SYNDROME, OR YOU’LL NOTE ANY BMI, SOME OF THE PATIENTS CAN HAVE QUITE LOW LEPTIN LEVELS AND THEY, AS I’LL TELL YOU IN A MOMENT, MY MIGHT BE CANDIDATES FOR LEPTIN THERAPY IN THE LONG TERM. THE STUDIES OF LEPTIN LEVELS AND OTHER STUDIES I WILL TALK ABOUT SUGGEST INDEED A DROP IN LEPTIN ACTION IF LESS LEPTIN SIGNALING GOES ON, YOU MIGHT EXPECT AN ANIMAL TO EAT MORE, GAIN MORE WEIGHT THAN RESET THEIR WEIGHT AT A HIGHER LEVEL, SO WE THINK THAT’S ONE OF THE PATHOGENIC MECHANISMS THAT CONTRIBUTES TO OBESITY.
A REGTIVE DOWN REGULATION OF LEPTIN SIGNALING. YOU MIGHT THEN ASK, WHAT GOOD WOULD LEPTIN OR HORMONE TREATMENT DO AND THE PRECEDENT FOR OTHER DISORDERS IS THE EFFECTS ARE GOING TO BE MUCH MORE VARIABLE AND THAN IN THE HORMONE DEFICIENT STATE AND THAT’S CERTAINLY TRUE FOR LEPTIN AS WELL. HERE AGAIN JUST AS A REVIEW IN THE INTEREST OF TIME, I’LL GO THROUGH A FEW DI DIDACTIC POINTS OF WHAT’S TO LEARN ABOUT — THE FIRST IS THAT IF THERE’S ABSENT LEPTIN, PATIENTS LOSE WEIGHT. AND THEN IF THERE ARE LOW LEPTIN LEVELS, PATIENTS LOSE WEIGHT. I SHOWED YOU THAT WITH HYPOTHALAMIC AMENORRHEA, AND ALSO TRUE FOR LIPODYSTROPHIC PATIENTS. SO TO SOME EXTENT, A LOW LEPTIN LEVEL PREDICTS RESPONSE TO THERAPY SO MIGHT WHREP TIN BE USED FOR OBESITY, YOU MIGHT ANTICIPATE IF THERE WERE RESPONDERS,
THEY WOULD BE PATIENTS THAT HAD LOW LEPTIN LEVELS. NOW THIS HAS NEVER BEEN TESTED DIRECTLY, BUT THERE IS REASON TO THINK THAT IT’S WORTH TESTING AND THAT’S BECAUSE THERE’S CLEARLY A RESPONDER SUBSET FROM THE AMGEN DATA, 35% OF THE OBESE PATIENTS SHOW A 5% WEIGHT LOSS AND 12% SHOW AN EVEN 10% WEIGHT LOSS, SO IT’S NOT YET BEEN TESTED AS TO WHETHER OR NOT THIS IS THE COHORT THAT HAS LOWER LEPTIN LEVELS. HOWEVER, MORE RECENTLY — TELLS ME SHE’S BEEN STUDYING OBESE PATIENTS THAT STARTED OFF WITH A RELATIVELY LOW LEPTIN LEVEL AND THESE PATIENTS DID INDEED APPEAR TO LOSE WEIGHT AND SHOW SOME METABOLIC IMPROVEMENT, ALTHOUGH THE COHORT SIZE WAS SMALL. IT’S ALSO POSSIBLE THAT LEPTIN COULD BE USED AFTER A VERY LOW CALORIE DIET AND THERE’S UNPUBLISHED DATA THAT WHEN PATIENTS WHO LOSE WEIGHT AND STHOA A REDUCED LEPTIN LEVEL AND GET LEPTIN THERAPY,
IT DOES HAVE AN IMPACT PARTICULARLY ON MEN ON PROAT PENS IT TO GAIN THE WEIGHT BACK. ALSO POTENTIAL AS A COMBINATION THERAPY, LEPTIN COMBINED WITH A NUMBER OF GUT PEPTIDES HAS BEEN SHOWN TO SINNER JIES TO LOSE WEIGHT IN OBESE ANIMALS AND LEPTIN PLUS AMYLIN WAS SHOWN IN A TRIAL TO LEAD TO 13.7% WEIGHT LOSS IN HUMANS. THIS STUDY WAS SUSPENDED AND NOT CONTINUED YET BECAUSE OF POTENTIAL CONCERN ABOUT ANTIBODIES TO LEPTIN. I THINK THEY’VE HAD ISSUE AS TO PARTIALLY BUT NOT COMPLETELY RESOLVED AND SO THESE DATA WANE FA LOW PENDING, I THINK, A GREATER SET OF EXPERIENCES WITH LEPTIN AS A THERAPEUTIC AND A GREATER SENSE OF COMFORT ABOUT ITS SAFETY IF A BROADER POPULATION IS TREATED. SO THIS COMPLETES THE CLINICAL REVIEW.
THAT’S BECAUSE I’M NOT A CLINICIAN ANY LONGER AND WE DON’T DO ANY CLINICAL WORK. IN FACT I DIDN’T DO ANY OF THE WORK I JUST SPOKE ABOUT, HOPEFULLY I ACKNOWLEDGED THE PEOPLE I DID FULLY. WE STUDIED THE NEURAL CIRCUITS THAT RESPOND TO LEPTIN. WHAT WE’D LIKE TO UNDERSTAND AMONG OTHER THINGS IS, WHAT’S DIFFERENT ABOUT THAT — WHAT’S THE ANATOMIC AND MOLECULAR BASIS OF LEPTIN THAT LEADS THESE HORMONES TO HAVE A LOWER EFFECT THAN OTHERS? THIS OF COURSE WILL REQUIRE DELINEATING THE EXOAPTS OF THE NEURAL CIRCUIT THAT REGULATES WEIGHT ON WHICH LEPTIN ACTS, AND THAT’S OCCUPIED MOST OF OUR ATTENTION FOR THE LAST DECADE. NOW WE’VE LEARNED A LOT ABOUT THESE NEURAL CIRCUITS, OUR KNOWLEDGE IS INCOMPLETE BUT IMROAING AND IMPORTANTLY THE LOGIC OF THIS HAS BEEN ELABORATED IN THE FORM OF AT LEAST TWO DIFFERENT NEUROPOPULATIONS THAT RESPOND TO LEPTIN. BOTH OF WHICH EXPRESS
THE LEPTIN RECEPTOR, NONE OF WHICH COEXPRESSES THE NEUROPEPTIDE Y, THE OTHER WHICH EXPRESSES ALPHA NSH. WHEN THESE GREEN NEURONS SPIRE, AN ANIMAL EATS MORE, WHEN THESE RED ONES SPIRE, AN ANIMAL EATS LESS, AND LEPTIN ACTS BY INHIBITING THE OREXOGENIC NEURONS AND ACTIVATING THE AN WRECK OWEGENIC NEURONS. THESE BECOME ACTIVE, THESE GO OFF AND EAT LESS AND THE SYSTEM IS TUNED SO THAT QAWPT TAITIVE CHANGES IN LEPTIN LEVEL CHANGE THE RELATIVE BALANCE OF ACTIVITY BETWEEN THESE TWO CONTROL POPULATIONS. THESE PATHWAYS ATTRACT A GREAT DEAL OF ACTINGS I ACTION IN RECENT YEARS IN LARGE PART BECAUSE MUTATIONS IN IT CAUSE HUMAN OBESITY. SO THE LEPTIN RECEPTOR, MSH AND THE MSH RECEPTOR, THE MC4 RECEPTOR, NOW ARE KNOWN TO ACCOUNT FOR PROBABLY AS MUCH AS 10 TO 15% OF MORBID OBESITY. THIS IS AN ENORMOUS NUMBER, A HIGHER LEVEL OF LOADING THAN FOR ANY OTHER THAT’S BEEN STUDIED. IT DOESN’T FULLY EXPLAIN THE HERITABILITY THAT I MENTIONED A FEW MOMENTS AGO, BUT I SUSPECT WITH INCREASED EXOME SEQUENCING AND GENOMIC APPROACHES, SOME OF WHICH WE’VE ALSO UNDERTAKEN, THE NUMBER WILL GROW.
ALL OF THE GENES THAT CAUSE — MUTATIONS THAT CAUSE OBESITY MAP TO THIS NEURAL CIRCUIT TO DATE AND THE OTHERS ARE NOT SHOWN HERE IN THE INTEREST OF PARSIMONY. NOW ONE STRATEGY WOULD BE TO FOLLOW, IF LEPTIN RESISTANCE IS THE PROBLEM, ONE APPROACH MIGHT TO BE TRY TO IDENTIFY NODES IN THE CIRCUIT DOWNSTREAM OF LEPTIN ACTION IF WE COULD THEN ACTIVATE THAT SET OF NEURONS IN A MANNER THAT REPLICATED LEPTIN’S EFFECTS, WE COULD ESSENTIALLY BYPASS THE BLOCK AND DEVELOP NEW APPROACHES FOR THERAPY.
I WANT TO TELL YOU, A VIGNETTE THAT IDENTIFIES SUCH A NODE THAT WAS IDENTIFIED BY MY GROUP, USING ONE OF THESE NEW BRAIN CLEARING METHODS, IN ONE IS KNOWN AS I DISCO, WHAT THIS DOES, YOU HAVE A SCAFFOLD OF ALL THE PROTEINS AND YOU CAN DO CHEMISTRY OF THE WHOLE BRAIN AT ONCE. HERE IS JUST AN EXAMPLE OF THIS, THIS IS A WHOLE BRAIN STAINED FOR GFP. THIS ISN’T THE PRETTIEST IMAGE BUT YOU CAN SEE EACH NEURON EXPRESSES GFP. WHAT’S POWERFUL ABOUT THIS METHOD IS THAT ONCE YOU HAVE THIS 3D — OF STAINED BRAIN, YOU CAN MAKE OPTICAL SECTIONS AND LOOK AT ANY BRAIN REGION OR ANY MARKER YOU WISH TO LOOK AT. SO WHAT MARK AND ALEX DID IS THE FOLLOWING: THEY FASTED ANIMALS AND THEY STAINED NOT FOR GFP, BUT FOR CFOS FOR NEURAL ACTIVATION. SO WHAT THEY’RE ESSENTIALLY ASKING IS, ARE THERE PARTS IN A BRAIN SPECIFICALLY ACTIVATED IN RESPONSE TO FOOD RESTRICTION, AND IF THERE ARE, WE CAN STUDY THEM.
ONE OF THE VERY USEFUL TOOLS THAT’S AVAILABLE IS SOFTWARE NOW THAT CAN OVERLAY THESE IMAGES, IN THIS CASE, CFOS, ON TOP OF THE BRAIN ATLAS. SO PURELY COMPUTATIONALLY, YOU CAN — WHICH BRAIN REGIONS WERE ACTIVATED. SO THEY GO THROUGH THIS EXERCISE FOR CFOS, HERES AT LEAST SOME OF THE — HERE’S THE ANNOTATION, HERE’S THE CFOS STAINING, HERE’S A HEAT MAP THAT’S GENERATED, THE CONTROL FED STATE, HERE’S THE FASTED STATE. YOU GET STATISTICAL DATA. WHEN WE DO THIS, TWO BRAIN REGIONS LIGHT UP. MOST PROMINENTLY. THE ARCUATE NUCLEUS AND THE DORSAL FA NUCLEUS. SO WHAT’S THE DORSAL FA NUCLEUS? THIS IS A BRAINSTEM NUCLEUS RIGHT BENEATH THE CEREBRAL AQUA DUCT BUT THERE’S CELLULAR HETEROGENEITY SUCH THAT THERE ARE NOT ONLY — BUT ALSO OTHER NEURONS. DEX15LURAMINE INCREASES SEROTONIN LEVELS WAS A COMPONENT OF THE ANTIOBESITY DRUG PHEN-FEN. THIS NUCLEUS HAS BEEN INVOKED AS PLAYING A ROLE IN MANY DIFFERENT BEHAVIORS, INCLUDING — WE ALSO NOTED AND I WON’T SHOW YOU THAT THE GABA — AND — PROJECTED TO THE HYPOTHALAMUS AS WELL AS OTHER RELEVANT AREAS FOR FEEDING SO WE TURNED OUR ATTENTION TO THESE TWO POPULATIONS. THE GABAERGIC AND GLUTAMATERGIC.
WE ASKED IS THERE A ROLE FOR THE NUCLEUS AS A WHOLE TO CONTROL FEEDING, SO ALEX INFUSED MUSCIMOL DORSALLY INTO THE NUCLEUS AND WHAT YOU CAN SEE IS A PRETTY SIGNIFICANT INCREASE IN FEEDING. INCREASES IN FEEDING ARE ALWAYS CONSIDERED TO BE SIGNIFICANT BECAUSE OF A DECREASE IN FEEDING COULD INDICATE NAUSEA OR SOME — BUT AN INCREASE IN FEEDING NEEDS TO BE TAKEN SIRE JUSTLY, AND SERIOUSLY, AND THAT IS A BIG INCREASE IN FEEDING. IN THE FIRST EXPERIMENT, WHAT ALEX DID IS TRY TO — BY NOW OPT GENETICALLY ACTIVATING THE GABAERGIC NEURONS. SO A FIBER IS PLACED, A CHANNEL IS PLACED, THEY’RE ACTIVATED BY THE LASER, AND HERE’S THE RESULT. FOOD CONSUMPTION GOES UP DRAMATICALLY WHEN THESE NEURONS ARE ACTIVATED. THREE FOLD. THAT’S SHOWN HERE, THIS IS ONE THAT SHOWS AN EVEN — THIS SHOWS AN EVEN MORE PROFOUND INCREASE IN FEEDING, AND YOU ACTIVATE THE GABAERGIC NEURONS — I SHOWED YOU EARLIER THAT LEPTIN THERAPY DECREASES FOOD INCREASE AND INCREASES LOCOMOTION, SO WE WANTED TO TEST THE POSSIBLE EFFECT OF LOCOMOTION IN ACTIVATING THESE GABAERGIC NEURONS HAD NO EFFECT ON LOCOMOTION. WE NOW TURN OUR ATTENTION HERE, NOW WE GET THE OPPOSITE RESULT. IN THE WINDOW IN WHICH THE NEURONS ARE ACTIVATED, WE SEE A REDUCTION IN FOOD INTAKE. AGAIN, IT’S PRETTY SIGNIFICANT, A THREE FOLD REDUCTION. BUT IN THIS CASE, LOCOMOTOR ACTIVITY GOES WILD. SHOWING A TREMENDOUS INCREASE IN LOCOMOTOR ACTIVITY. IT SUPPRESSES FOOD INTAKE AND INCREASES LOCOMOTOR ACTIVITY. THAT’S THE SAME THING I SHOWED YOU LEPTIN DOES, SO WE NEXT WANTED TO ASK, WHAT IS THE EFFECT OF ACTIVATING THE NEURONS IN AN O.B. MOUSE? HERE’S THE RESULT. MARKED REDUCTION IN FOOD INTAKE, IF YOU’D REPEAT THE EXPERIMENT IN OB MOUSE, IN FACT, THE FOOD INTAKE OF THESE MICE IS PRETTY MUCH EQUIVALENT TO THAT OF A NORMAL HOUSE WHEN THESE NEURONS ARE ACTIVATED, SO IT’S NOT A SUBTLE EFFECT. IN FACT, I THINK THAT’S OKAY AND THEN YOU DO THE SAME EXPERIMENT AN YOU CA AND YOU CAN ALSO SEE WHEN YOU ACTIVATE THESE NEURONS AN INCREASE IN LOCOMOTION THAT’S SHOWN HERE. AND WHAT I WANT TO POINT OUT HERE IS OB MICE SHOW A MUCH LOWER DISTANCE TRAVELED OR VELOCITY WHICH IS HOW YOU MEASURE LOCOMOTOR ACTIVITY AND COMPLETELY LOCALIZE MOTOR RETARDATION BY ACTIVATING THESE GL. LUTOMANERGIC NEURONS. SO WHAT THE DATA SUGGESTS IS — IN THE DORSAL NUCLEUS RIP SENT ANOTHER NODE WHICH HAS THE SAME LOGIC, IT WOULD APPEAR, THAT WAS DEVELOPED THROUGH THE ARCUATE NUCLEUS. IMPORTANTLY, LEPTIN RECEPTOR IS NOT EXPRESSED ON THESE NEURONS, SO THIS IS A DOWNSTREAM NODE, AND THE QUESTION THEN IS, IF WE CAN ACTIVATE THIS DOWNSTREAM — THIS NODE WHICH IS DOWNSTREAM OF LEPTIN SIGNALING, CAN WE GET A BENEFICIAL OR A THERAPEUTIC EFFECT. SO THE QUESTION IS, DOES PHARMACOLOGIC — ALTER FOOD INTAKE AND REPLICATE LEPTIN’S EFFECTS, AND SO THE APPROACH WAS TO PROFILE THESE NEURONS TO TRY TO IDENTIFY CELL-SPECIFIC MARKERS THAT COU COULD BE TARGETS FOR PHARMACOLOGIC AGENTS THAT WE COULD THEN TEST FOR POSSIBLE EFFECTS ON FEEDING. SO WE PROFILED EACH OF THESE NEURONS USING THE STANDARD TRAP TECHNOLOGY, WE COMPARED THE EXPRESSION PROFILES HERE. HERE ARE THE GENES EXPRESSED IN THE GABA AND GLUTAMATE RGIC NEURONS, THESE ARE ENRICHED IN THE GLUE TA MATTER JIK NEURONS AND THESE ARE ENRICHED IN THE GABANER IM. IC NEURONS. WE TESTED ALL THREE, THIS RECEPTOR IS EXPRESSED ON THE GLUTAMATERGIC NEURONS. THE SEROTONIN — I’M GOING TO SHOW YOU THEM INSTEAD, THE RESULT OF THE NPY2 RECEPTOR, WHICH IS A DIFFERENT ONE. SO THIS IS A GS COUPLED RECEPTOR, THAT MEANS IT WOULD ACTIVATE THE NEURONS SO YOU WOULD EXPECT ACTIVATING THE GLUTAMATERGIC NEURONS TO SUPPRESS INTAKE. LOCALLY INFUSE — Y-Y AND THEN — THAT SHOULD ACTIVATE THESE NEURONS AND INCREASE FOOD INTAKE. HERE’S JUST — SHOWING, IN FACT — PREPARATIONS — INCREASE THE FIRING RATE OF THESE NEURONS, AND SURE ENOUGH, IF YOU INFUSE IT LOCALLY, YOU SEE A REDUCTION OF FOOD INTAKE. WE’VE DONE SIMILAR EXPERIMENTS TO THE TWO OTHER MARKERS AND THEY’RE ALL CONSISTENT, SO THIS REPRESENTS A POTENTIAL OPPORTUNITY NOW FOR DEFINING CHEMICAL EP ENTITYS THAT MODULATE THESE NEURONS AND ALLOW REGULATION OF WEIGHT IN AN INDEPENDENT MANNER. SO THIS, I THINK, REPRESENTS OUR EFFORTS TO FURTHER EXPLORE THE ROLE OF THE DORSAL FA NUCLEUS IN FEEDING AND THE READOUT FOR THIS HAS BEEN THE CONTROL OF FOOD INTAKE. BUT BASED ON THE EFFECTIVE — WE’RE ALSO INTERESTED IN NEURAL CIRCUITS EFFECTS ON METABOLIC PARAMETERS, SPECIFICALLY WE WOULD LIKE TO KNOW HOW IT IS THAT LEPTIN CORRECTS THESE METABOLIC ABNORMALITIES SO WE DON’T KNOW VERY WELL, WE DON’T KNOW YET WHAT THEY ARE, BUT WE DO KNOW THE EFFECTS OF LEPTIN IN THIS SETTING, HOWEVER, ARE CENTRAL, AND THAT’S BASED ON THIS SET OF ANIMAL STUDIES STUDYING AN ANIMAL MODEL LIPODYSTROPHY IN WHICH WE COMPARE THE EFFECTS OF LEPTIN GIVEN EITHER SUBCUTANEOUSLY OR DIRECTLY INTO THE BRAIN ICV. THE SIMPLE POINT I WANT TO MAKE HERE IS THAT ICV LEPTIN IN VERY, VERY LOW DOSES, DOSES THAT HAVE NO EFFECT WHEN GIVEN PERIPHERALLY, HAVE AN EVEN GREATER EFFECT TO LOWER BLOOD GLUCOSE AND PLASMA INSULIN IN THESE AB MALL ANIMALS AND GIVES A HIGHER DOSE GIVEN PERIPHERALLY. SO THE EFFECT OF LEPTIN TO IMPROVE THESE ABNORMALITIES IS ESSENTIAL. WE’VE DONE OTHER STUDIES I DON’T HAVE TIME TO TELL BUT ALSO SHOWING THESE EFFECTS OF LEPTIN ARE INDEPENDENT ON EFFECTS OF FOOD INTAKE AND ADIPOSITY, SO BASED ON THIS, WE SPECULATE THAT LEPTIN ACTS ON BRAIN CIRCUITS THAT THEN WE INITIALLY THOUGHT WOULD AFFECT OTHER GLUCOSE OUTPUT FOR GLUCOSE UTILIZATION. WE’D LIKE TO KNOW MORE ABOUT THOSE CIRCUITS. AND THE SPECIFIC — WE DEVELOPED WAS THAT PERHAPS ICP LEPTIN MOD LATES THE ACTIVITY OF GLUCOSE SENSING NEURONS IN THE HYPE THALAMUS WHICH ARE KNOWN TO EXIST. SO THAT WAS THE MOTIVATION FOR THE EXPERIMENT I’M GOING TO TELL YOU ABOUT NOW, WHICH IS TO ASK WHAT IS THE BIOLOGICAL EFFECT OF LEPTIN OR ACTIVATION OF GLUCOSE SENSING NEURONS IN THE HYPOTHALAMUS. — CONFESS WHAT THE ROLE OF THEE NEURONS IS IN LIPODYSTROPHY OVER SES TESTING. SO TO DO THIS, WE MADE A NEW MOUSE AND THIS IS MATING OF THE GLUCOKINASE CRE MOUSE TO A REPORTER MOUSE. GLUCOKINASE IS AN ENZYME IN THE GLUCOSE SENSING PATHWAY. IT MARKS PANCREATIC BETA CELLS AS WELL AS SUBSTANCE OF NEURONS IN THE HYPOTHALAMUS KNOWN TO BE GLUCOSE SENSING. SO AT THIS POINT NOW, WE WANT TO ASK, WHAT’S THE BIOLOGICAL EFFECT OF ACTIVATING GLUCOSE SENSING NEURONS IN DIFFERENT BRAIN REGIONS, AND I’M GOING TO SHOW YOU THE DATA IN A FEW MOMENTS FOR THE VE — WE COULD HAVE USED OPTOGENETICS. AS I MENTIONED BEFORE, THIS INVOLVES PLACING A LIGHT ACTIVATED CHANNEL OF NEURONS, ACTIVATED BY LIGHT. YOU GET A DEEP POLARIZATION AND NORMAL FIRING. THERE IS ONE FEATURE THAIS THEAS UNDESIRABLE, YOU HAVE TO PUT IN A — CATHETER TO DELIVER THE LIGHT. SO WE STARTED TO MUSE ABOUT WHETHER OR NOT THERE WOULD BE A WAY TO ACHIEVE THE SAME END BUT NOT USING LIGHT BUT RATHER USING ANOTHER SIGNAL THAT DIDN’T REQUIRE A PERMANENT IMPLANT. WE TURNED OUR ATTENTION, WE MEANING SARAH STANLEY AND I, SARAH IS NOW A FACULTY MEMBER AT MOUNT SINAI SCHOOL OF MEDICINE. WE TURNED OUR ATTENTION TO ELECTROMAGNETIC WAVES IN PART BECAUSE THESE ARE USED IN CLINICAL PRACTICE, MRI NNS, COCHLEAR IMPLANTS OR PACEMAKERS. SO HOW CAN WE ENGINEER A CELL TO RESPOND TO AN ELECTROMAGNETICFIELD? WELL, THERE HAVE BEEN SEVERAL ITERATIONS OF THIS, THIS IS VERSION 4.0 THAT BASICALLY MAKES USE OF TWO COMPONENTS. A TARGET FOR CHILI PEPPERS, IN RESPONSE TO HEAT. THE SECOND COMPONENT IS FERRITIN FERRITIN, EVERY CELL USES IRON BUT IT CAN BE TOXIC. SO IT DETOXIFIES IT AND KEEPS IT IN THE CELL. SO THE ORIGINAL IDEA WE HAD WAS IF YOU TETHER FERRETIN DIRECTLY TO THE CHANNEL USING ANTIBODY AND EXPOSE IT TO AN ELECTROMAGNETIC FIELD, IT WILL HAVE TO MAKE A PARTICLE IN SOME WAY AND GAVE THE CHANNEL. GATE THE CHANNEL. SO WE NEEDED A SOURCE OF THE ELECTROMAGNETIC FIELD AND THIS IS THE ORIGINAL SOURCE, WE HAVE MORE SOPHISTICATED ONES NOW. THIS ACTUALLY IS A COMMERCIAL WELDING DEVICE. COMMERCIAL WELDING IS DONE IN PIPES THAT SAY IN THIS COIL, WHERE A FIELD IS GENERATED — SO TEND TO EXPOSE THEMSELVES USING — ELECTROMAGNETIC FIELD, ACTIVATE THE CELLS? WELL, YES IT CAN. IN THIS CASE, IT’S A HIGHLY OSCILLATING FIELD, WE’RE DOING CALCIUM IMAGING. WHAT YOU’LL SEE IN A MOMENT IS SOME CELLS TURNING ON ALL THE TIME AS THEIR EXPOSURE TO THE ELECTROMAGNETIC FIELD. YOU’RE SEEING SOME CELLS TURN ON NOW. WE ALSO FOUND THAT WE COULD USE THE STATIC MAGNET, NOT AN OSCILLATING MAGNETIC FIELD FOR THIS PURPOSE. SARAH WENT TO THE HARDWARE STORE AND BOUGHT FIXED PAG MANET MAGNET. BY PULLING THE MAGNET IN USING A MICRO MANIPULATOR, YOU CAN ALSO CHANGE THEIR ACTIVITY. IN THIS EXPERIMENT, YOU SEE THE WILD TYPE VERSION OF THE CHANNEL. IF YOU APPLY THE MAGNET IN NEURAL SLICE, YOU CAN SEE A MARKED INCREASE IN THE FIRING RATE. AND I’LL TELL YOU IN A MOMENT ABOUT IMMUNE CHANNEL SERENADE, NOW CHLORIDE INSTEAD OF CALCIUM AND SODIUM WHICH THE CHILD TYPE CHANNEL DOES. IF YOU WAVE THE MAGNET OVER THE — CHANNEL MUT CHANNEL, IT STOPS. SO WE CONTINUE TO BE INTERESTED IN WHAT THE MECHANISM IS. I’M NOT GOING TO — I WOULD SAY TO THE MOMENT IT’S UNCERTAIN. BUT WE’RE STUDYING WHAT THE MECHANISM IS OR WHAT THE ACTIVATION MECHANISM IS AND IT APPEARS TO BE AN INTERESTING TOPIC. RATHER, I WANT TO QUICKLY ADVANCE NOW AND TELL YOU ABOUT EXPERIMENTS WHEN WE TEST THE SYSTEM IN VIVO, USING — AFTER THEY INHIBIT — TO THE VENTRAL MEDIAL HYPOTHALAMUS. SO IN THE FIRST EXPERIMENT, SARAH TAKES THE WILD TYPE CHANNEL THAT INDUCES ACTION POTENTIALS, SHE MAKES A CRE-DEPENDENT VIRUS AND INJECTS IT INTO THE GLUCOKINASE MICE. IT’S ACTIVATED ONLY IN THE GLUCOKINASE CRE NEURONS. SHE EXPOSES THE AB MALLS TO ANIMALS TO A RADIO WAVE. HERE’S WHAT HAPPENS. BLOOD GLUCOSE GOES UP BY 75%. THAT’S IN GREEN. IN BLUE IS THE SAME EXPERIMENT WITH OPTOGENETICS, SO IT LOOKS LIKE THIS CAN REPLICATE THE EFFECT OF OPTOGENETICS. GLUCOSE HAS GONE UP. WHY HAS IT GONE UP? THE EASIEST THING, THE MOST LOGICAL THING TO MEASURE WOULD BE PANCREATIC HORMONES. GLUCOSE GOES UP BECAUSE GLUE GLUCAGON GOES UP AND SIGNIFICANT DECREASE IN INSULIN. THEES NEURONS ARINSULIN. THESE ARE GLUCOSE INHIBITED NEURON, THEY SENSE HYPOGLYCEMIA, AND WHEN THESE ARE ACTIVATED, GLUCAGON GOES UP. WE DID OUR EXPERIMENT AND FED ANIMALS WITH THESE NEURONS THAT WOULD NORMALLY BE OFF BUT IF WE MAGNETICALLY ACTIVATE THEM, THE NEURONS ARE ACTIVATED, THE ANIMAL PERCEIVES THAT AS HYPOGLYCEMIA, FLEW KOAS GOES UP, INSULIN IMOAS DOWN. GOES DOWN. WHAT SARAH DID WAS TO MAKE MUTATIONS TO CONVERT IT INTO A CHLORIDE CHANNEL. THIS SHOWS MUTATIONS IN TRPVI CAN CREATE A CHLORIDE CHANNEL. WE NOW REPEAT EXACTLY THE SAME EXPERIMENT I SHOWED YOU A MOMENT AGO. INTRODUCING — NOW WE SEE THE OPPOSITE RESULT. 50% REDUCTION IN BLOOD GLUCOSE. WHAT’S HAPPENING HERE? NOW IN THIS CASE, YOU SEE A MASSIVE RISE IN INSULIN, THREE FOLD, AND GLUE KA GONE FAILS TO RISE DESPITE THE FACT THAT THE ANIMAL HAS BEEN MADE HYPOGLYCEMIC. WHAT THIS FIRST OF ALL TELLS US IS THAT THIS EFFECT IS CHANNEL-DEPENDENT, AND THAT’S BECAUSE WE GET OPPOSITE EFFECTS DEPENDING ON WHETHER OR NOT WE USE THE ACTIVATING NEUROINHIBITORY CHANNEL. SO SORT OF THAT HELPS TO VALIDATE THE METHOD BECAUSE WE GET OPPOSITE RESULTS DEPENDING ON THE FORM OF THE CHANNEL WE USE. I THINK IN A BIOLOGICAL SENSE, WHAT IT SUGGESTS TO US IS THAT THE BRAIN CAN INDEED CONTROL METABOLISM, IT MAY DO SO IN PART THAT AFFECTS ON THE LIVER OR FAT CELLS OR MUSCLE, BUT THE BRAIN ALSO HAS VERY POWERFUL TEESKTS REGULATE THE PRODUCTION OF PANCREATIC HORMONES. IT’S ALMOST AS IF THE BETA CELLS ARE GETTING THEIR INSTRUCTIONS FROM THE BRAIN, THEY CAN ALMOST BE VIEWED AS AN EFFECTOR LIMB AND A CNS CIRCUIT THAT IS DOWN — THAT — GLUCOSE ACTIVATES NEURONS AND ACTIVATES HORMONE PRODUCTION. NOW I ACTUALLY THINK THAT THIS IS PROBABLY THE MAIN WAY IN WHICH BLOOD GLUCOSE IS REGULATED. AND THAT PANCREATIC GLUCOSE SENSING IS A FALL BACK MECHANISM IN CASES WHERE THE BRAIN MECHANISM IS DISORDERED. LET ME TRY TO DEFEND THAT. ALTHOUGH I MAY BE PUSHING IT A LITTLE TOO FAR. THE BRAIN IS THE MAIN CONSUMER OF GLUCOSE, NOT THE BETA CELLS. AND SO THE BRAIN CARES MOST ABOUT HOW GLUCOSE IS REGULATED SO IT SHOULDN’T BE AT ALL SURPRISING IF IT WERE THE PRIMARY GLUCOSE SENSING ORGAN. WHY, THEN, DO YOU NEED GLUCOSE SENSING IN THE BETA CELL OR THE ALPHA CELL? WELL, THE BRAIN DYSFUNCTIONS IF YOUR GLUCOSE IS DISORDERED SO YOU NEED A FALL BACK MECHANISM IN CASE GLUCOSE SENSING IN THE BRAIN LEADS TO AN INDUCTION OF ABNORMAL FUNCTIONING. WHY ELSE? WELL, HERE WE’RE GETTING VERY POWERFUL CHANGES IN GLUCOSE AND PANCREATIC HORMONES JUST BY PICKLING THE BRAIN, ON THE OTHER HAND, IF WE GAVE GLUCAGON OR INSULIN AS AN INJECTION, THE BRAIN WOULD COUNTERREGULATE. SO I THINK A CASE CAN BE MADE THAT ONE OF THE MAIN DRIVERS OF PLASMA GLUCOSE IS BASED ON GLUCOSE SENSING NEURONS IN THE BRAIN, AND I SHOULD SAY THAT THIS CONCLUSION IS CONSISTENT WITH A WHOLE HOST OF PRIOR PHARMACOLOGIC AND ANATOMIC DATA FROM STEVE BLOOM AND MANY OTHER PEOPLE. CHANGES THE WAY I THINK ABOUT GLUCOSE CONTROL. SO WITH THAT, I’M GOING TO STOP AND SUM UP BY SAYING THAT I THINK WE’VE IDENTIFIED A NEW ENDOCRINE CIRCUIT — INTERGRA TRI CENTERS IN BRAIN — THAT REGULATE FOOD IB TAKE IN METABOLISM. THE STUDY I SHOID YOU ADDING PANCREATIC BETA CELLS TO THIS LIST AND I’LL SIMPLY — THE CLONING OF THE OB GENE AND IDENTIFICATION OF LEPTIN HAS UNCOVERED A NEW ENDOCRINE SYSTEM REGULATING BODY WEIGHT. THE SYSTEM PROVIDES A MEANS BY WHICH CHANGES IN NEWER TRITIONAL STATE REGULATE ALL OTHER PHYSIOLOGIC SYSTEMS. THERE ARE A SEVERAL LEPTIN DEFICIENCY SYNDROMES THAT ARE TREATABLE WITH LEPTIN REPLACEMENT. A SUBSTANTIAL FRACTION OF MORBID OBESITY IS THE RESULT OF MENDELIAN DEFECTS IN THE NEURAL CIRCUIT THAT IS MODULATED BY LEPTIN, AND THE DORSAL RAPHE NUCLEUS REGULATES FOOD INTAKE, AND NANOPARTICLE BASED METHOD USED TO SHOW THAT CNS CAN GLUCOSE ME TACK LISM BY REGULATING HORMONES SECRETION BY PANCREATIC ISLETS. LET ME JUST END BY GIVING SOME ACKNOWLEDGMENTS. I’LL STOP HERE AND TAKE ANY QUESTIONS YOU MIGHT HAVE. THANK YOU. [APPLAUSE] >> THANK YOU VERY MUCH. PLEASE GO TO THE MICROPHONE FOR QUESTIONS. >> YOU MENTIONED NASH WHICH IS A TOPIC A LOT OF DRUG COMPANIES ARE GOING AFTER THAT NOW. IN A GENERAL POPULATION OF NON-ALCOHOLICS WHO HAVE HAD HEPATITIS, WHAT PERCENTAGE OF THIS WOULD YOU GUESS YOU MIGHT BE ABLE TO TREAT JUST USING YOUR LEPTIN TYPE THERAPIES? >> — WOULD ONLY BE THOSE PATIENTS WHO HAD A LOW STARTING LEPTIN LEVEL. SO RATHER SMALL SUBSET. >> THANK YOU. >> I WAS WONDERING IF YOU THINK THERE MIGHT BE SOME ASSOCIATION BETWEEN LEPTIN AND THE MUSCULOSKELETAL SYSTEM AS WELL. >> LEPTIN AND THE MUSCULOSKELETAL SYSTEM? YOU KNOW, I THINK THE EVIDENCE I KNOW THAT SORT OF ADDRESSES THIS IS AS FOLLOWS AND IT’S IN THE LEPTIN-DEFICIENT ANIMALS. LEPTIN-DEFICIENT MEIST SHOW MORE PRODUCTION IN LEAN BODY MASS. IT’S ALMOST AS IF ALL THEIR CALORIES GET SHUNTED INTO FAT AT THE EXPENSE OF MUSCLE AND ALSO THE BRAIN WEIGHTS ARE ALSO SMALLER, SO I THINK THERE MAY BE SOME DEVELOPMENTAL ISSUES. TO MY KNOWLEDGE, NO ONE HAS ACTUALLY EVER STUDIED LEPTIN EFFECT ON MUSCLE PERFORMANCE. THERE HAVE BEEN STUDIES OF EFFECTS OF LEPTIN ON MUSCLE GLUCOSE UP TAKE AND I THINK THERE ARE EFFECTS THERE. ALTHOUGH I THINK THEY’RE A BIT CONTROVERSIAL BECAUSE THEY USED SOME SPECIFIC TISSUE-KNOCKOUT TECHNOLOGIES. >> — HORMONE LEVELS OR — >> SO I THINK WHAT YOU’RE ASKING IS, IF YOU WERE TO RAISE LEPTIN LEVELS, WOULD YOU SEE AN ALTERATION IN MUSCULAR PERFORMANCE? >> OR NOT — >> SO IT’S NOT LOOKED AT CAREFULLY. I WOULD JUST MAKE THE FOLLOWING GENERAL POINT. LEPTIN’S POTENCY IS MOST PROMINENT IF YOU GO FROM ZERO TO PHYSIOLOGIC LEVELS, AND IF ONE WERE GOING TO TEST, I WOULD — THE SETTING IN WHICH I WOULD TEST IT. THE EFFECTS ARE MUCH MORE SUBTLE IF YOU GO FROM PHYSIOLOGIC TO SUPER PHYSIOLOGIC LEVELS. I’D BE SURPRISED IF YOU HAD AN EFFECT IN THAT SORT OF EXPERIMENT, BUT IT’S CERTAINLY CONCEIVABLE TO ME THAT THERE MIGHT BE AN EFFECT OF, LET’S SAY, YOU LOOKED AT MUSCLE PR HE FOREMAN’S — IT’S NOT BEEN DONE TO MY KNOWLEDGE. >> THANK YOU. >> ANY OTHER QUESTIONS? I HAD A QUESTION, JEFF. HOW MUCH DO WE KNOW ABOUT — IN THE PATIENTS WITH LIPODYSTROPHY? >> THE QUESTION IS HOW MUCH DO I KNOW, THE ANSWER IS NOTHING. DO YOU KNOW ANYTHING ABOUT — AND MICRO DYSTROPHY PATIENTS? NOTHING? IT’S OFFICIAL. [LAUGHTER] >> OKAY. SO NOW THE WALS SEMINAR IS CONTINUING WITH THE RECEPTION WHICH IS AT THE NIH LIBRARY, AND THANK YOU SO MUCH AGAIN, JEFF, FOR COMING TODAY AND THANK YOU FOR YOUR LECTURE. THANK YOU SO MUCH.